Leading in Research
Sea squirt’s microbiome offers clues to frontline immune defense, gut health
National Science Foundation research by USF Health’s Larry Dishaw has relevance for debilitating digestive disorders like inflammatory bowel disease
What can we learn about human health from the lowly sea squirt?
More than you may think.
In his laboratory at the USF Children’s Research Institute in St. Petersburg, microbiologist Larry Dishaw, PhD, uses the sea squirt known as Ciona intestinalis to study how the innate immune system interacts with microbes that settle in the gut in ways that seem to facilitate homeostasis (stability) and promote survival and health.
Supported by a four-year, $867,581 grant from the National Science Foundation (NSF), Dr. Dishaw’s immune research explores the populations of microbes living together in the gut – trillions of bacteria, viruses, fungi and even some parasites – collectively known as the gut microbiome. His team is also interested in defining how disruption of a stable gut microbiome relates to the onset of inflammatory bowel disease, an autoimmune disorder affecting 1.6 million Americans.
“Many factors are at play in regulating the microbiome,” said Dr. Dishaw, an associate professor of pediatrics at USF Health Morsani College of Medicine. “And a lot of researchers around the world are interested in how the microbiome colonizes in animals, how this microbial community achieves stability, how it can shift out of balance, and how it is relevant to protecting human health.”
One Of Closest Evolutionary Invertebrate Relatives Of Humans
Ciona intestinalis, an invertebrate marine animal resembling a spongy plant, spends its life attached to underwater structures like boat hulls and pier pilings where it continually siphons in water through one end, filtering out plankton and algae to eat and then squirting water and waste out the other end.
If you look under the microscope at the translucent juvenile sea squirts cultivated by Dr. Dishaw’s lab you can see a gut (with a stomach and intestinal compartment) similar to the digestive tract of vertebrates. Despite its primitive appearance, the sea creature – a protochordate — is considered one of the closest evolutionary invertebrate relatives of humans.
Unlike humans, sea squirts rely their entire lives solely on naturally present innate immunity for host defense. They lack the other more evolved arm of immunity know as adaptive immunity, which differs from one animal species to the next and activates in response to specific foreign invaders.
That, Dr. Dishaw says, is what helps make the sea creature a good model for investigating the evolution of the host immune system and its role in creating and maintaining a well-balanced gut microbiome.
“When humans are born, they do not develop adaptive immunity until ages 3 to 5… so the initial process of colonizing bacteria and other microbes that make up their microbiomes is all mediated by innate immunity,” he said.
With a simpler model system like the sea squirt, the researchers can look at innate immunity in isolation. They can monitor how the immune system responds when encountering microbes for the first time, how microbes initially “choose” where to colonize in the gut, and how the animal maintains homeostasis – that is, a healthy balance of gut microbes needed to digest food and absorb nutrients throughout its life.
Ultimately, the not-so-lowly sea squirt may provide better insight into gut defense evolution and define ways that beneficial (non-pathogenic) bacteria may help prevent the overgrowth of disease-causing (pathogenic) bacteria.
Tipping The “Good” Microbe – “Bad” Microbe Balance
Dr. Dishaw’s NSF grant builds upon the work of his mentor Gary Litman, PhD, USF professor emeritus of pediatrics, whose lab discovered the genes for a family of variable region-containing chitin-binding proteins, or VCBPs, made and secreted by the gut wall in a different protochordate, the ancient fish-like organism amphioxus. These immune proteins appear to help regulate how bacteria and fungi interact and grow such that intestinal barrier function is enhanced, Dr. Dishaw said. The VCBPs also seem to influence the production or release of phages, viruses that infect and destroy specific gut bacteria, he added.
“The goal of our project is to find out what happens when we muck with that system. When the VCBPs don’t bind fungi or bacteria correctly, how is the physiological fitness of the animal affected?” Dr. Dishaw said. “We believe these immune effectors can shape the ecology of the gut microbiome in ways that promote (or deter) health. And we think the sea squirt model can help us understand how that happens.”
The researchers can rear germ-free juvenile Ciona, then introduce into their water whatever microbes they choose. Because the sea squirt filters water constantly, they can quickly track where in this controlled environment the newly introduced gut microbe populations settle and thrive as well as examine the role host-microbe interactions play in developing a frontline immune defense system.
In a series of experiments published last year in Open Biology, the USF researchers induced colitis-like inflammation and damage in sea squirts by exposing their guts to the chemical dextran sulfate sodium (DSS). They showed that DSS altered the production and settlement of the secreted immune molecule that binds bacteria.
Most invertebrates, including sea squirts, defend their gut walls against potential microbial attack and prevent infection with mucous rich in chitin. The researchers found that pretreatment with microparticles of chitin, a fibrous substance prevalent in Ciona’s epithelium-associated gut mucous, protected the animal from the colitis-like effects of subsequent DSS exposure.
Ciona, which permits the study of innate immunity in isolation, “may help us determine how innate immunity modulates recovery from colitis and the re-establishment of (gut microbiome) homeostasis,” the study authors concluded.
Promising Power Of Phages To Treat Drug-Resistant Infections
Dr. Dishaw is also co-investigator for a National Institutes of Health grant led by the USF College of Nursing’s Maureen Groer, PhD. The project is investigating the link between the gut microbiome of premature infants and their health as they age.
“We think early colonization of microbes is critically important in establishing lifelong gut microbiome features,” Dr. Dishaw said. “So, early life events that shape the (evolving) microbiome — like spending 4 to 6 weeks in a neonatal intensive care unit where the infant receives multiple antibiotics to treat or prevent infections — could translate into long-term changes in health.”
The ultimate goal of microbiome research is to come up with effective treatments to reset the equilibrium of a microbial community gone awry – whether by diet, stress, pathogens, or even the medications used to fight disease.
Fecal microbiota transplants, which insert a healthy donor’s fecal matter into a recipient’s colon to reconstitute a stable gut microbiome, have already become a relatively common treatment for Clostridium difficile (C. diff) infection, a debilitating gastrointestinal disease resistant to many antibiotics.
In an age of growing multidrug resistance, Dr. Dishaw believes that phage therapy also offers promise as an alternative or supplement to antibiotics for patients suffering from recurrent, difficult-to-treat infections. In another NSF grant with co-principal investigator Mya Breitbart of the USF College of Marine Sciences, he is colonizing a variety of bacteria in the sea squirts in an effort to test how phages – the viruses that infect bacteria – can be used to selectively eliminate harmful gut bacteria.
Phages, which specifically target single types of bacteria, might be harnessed to chase pathogens out of the microbial community without having to rely on antibiotics, which can wipe out both harmful and beneficial bacteria, Dr. Dishaw said. “In theory, you could use a C diff phage with high precision to target and kill only C. diff bacteria.”
Dr. Dishaw also participates in a clinical study with the USF Health Department of Pediatrics and Johns Hopkins All Children’s Hospital to characterize the gut microbiomes of patients with primary immune deficiencies. The research may provide a better understanding of how different aspects of immunity regulate the gut microbiome.
Written by Anne Delotto Baier, Photos and Video by Torie M. Doll, USF Health Communications and Marketing
Infectious diseases expert looks for new ways to combat resilient parasites
USF Health’s Dr. Kami Kim probes the epigenetics of two global parasitic infections, malaria and toxoplasmosis
While an undergraduate at Harvard University, Kami Kim, MD, participated in a research thesis project exploring leukemia’s resistance to chemotherapy and the effectiveness of combination drugs in combatting it. While she was excited to help figure out (and publish) a mechanism, she recalls that she signed on for this laboratory research primarily “to help in get into medical school.”
Her interest in research intensified in medical school in early 1980s at the beginning of the domestic AIDS era, about the same time tuberculosis cases were exploding and malaria, once considered virtually eliminated as a major public health threat, began to re-emerge globally.
“It was clear that there was much to be done in infectious diseases research — a lot of interesting problems that needed to be solved,” said Dr. Kim, who joined the USF Health Morsani College of Medicine last year as a professor in the Department of Internal Medicine’s Division of Infectious Disease and International Medicine.
Undergraduate laboratory work that sparked a lifelong passion for research
Basic science and clinical infectious diseases expertise
After clinical training as an infectious diseases fellow at the University of California San Francisco (UCSF) – and witnessing firsthand the devastating consequences of acquired immunodeficiency syndrome – Dr. Kim returned to laboratory research, with an emphasis on parasitic infectious diseases. Meanwhile, she continued to see patients as an attending academic physician at some of the nation’s best hospitals in San Francisco and New York City.
That blend of rigorous clinical and basic science expertise makes Dr. Kim one of the first of several high-profile, energetic recruits who will help take USF Health’s global infectious disease research to the next level.
Dr. Kim came to USF Health in November 2017 from Albert Einstein College of Medicine in New York City, where she was a professor of medicine, microbiology and immunology, and pathology. In addition to her laboratory research at USF, she consults monthly on infectious diseases cases at Tampa General Hospital. At Einstein, she directed the infectious diseases section of the Center for Epigenomics and helped launch and led the National Institutes of Health-funded Geographic Medicine and Emerging Infections Training Program, which supports interdisciplinary training in translational research for pre-doctoral students, post-doctoral research fellows and clinical fellows.
Seeking solutions to life-threatening global parasitic diseases
Dr. Kim’s USF Health research team, working out of a laboratory in the university’s research park, focuses on two major areas — malaria and toxoplasmosis. The world’s most dangerous parasitic disease, malaria claims more than 2 million victims and 445,000 deaths yearly, primarily in sub-Saharan Africa. Toxoplasmosis, often asymptomatic, can be life-threatening to babies born to women infected during pregnancy and people with weakened immune systems.
- Toxoplasmosis project: Combining advanced techniques from genetics, cell biology and proteomics, the researchers investigate the ways that epigenetics – the interface of genetics and environmental factors – regulate development of chronic infection by the cat-borne gondii parasite. They seek to understand how this pervasive parasite switches back and forth between a rapidly dividing acute stage destructive to healthy tissue (tachyzoite) and a chronic, or dormant, stage, where bradyzoite forms within pseudocysts remain invisible to the immune system. Dr. Kim collaborates with other leading Toxoplasma experts: Distinguished USF Health Professor Michael White, PhD, a long-time colleague, as well as investigators at Indiana University, Pennsylvania State University and Albert Einstein College of Medicine.
- Malaria project: In the hot, wet regions of Africa, mosquitoes are ubiquitous and children exposed to malaria from birth may contract the infection several time a year. The overwhelming majority of clinical cases are uncomplicated, with flu-like symptoms of fever and malaise that typically resolve. Researchers are trying to determine why a small percentage of individuals, in particular certain children, are more likely to develop severe malaria with coma and death (cerebral malaria) or long-term neurological complications such as seizures and cognitive and behavioral problems. In particular, the USF team is assessing specific biomarkers, or genetic predispositions, and parasite or host factors that may help predict disease development or its outcomes.
Dr. Kim discusses research correlating HIV co-infection with cerebral malaria
Both research initiatives harness the latest genomic technology to better understand how immunity works within the framework of host-parasite interactions – all with the aim of devising better or first-time treatments.
Valuable insights into cerebral malaria, future therapies
With collaborators from the Blantyre Malaria Project, based in Malawi, Africa, Dr. Kim published a high-profile paper in mBIO in 2015 reporting for the first time that children co-infected with HIV were much more likely than those who were not to die from severe malaria. Autopsies of the children who died from cerebral malaria indicated that those with HIV had brain blood vessels more clogged with white blood cells and platelets than those of children with malaria alone. HIV appeared to rev up brain inflammation that could lead to death.
In another study, published in Cell Host & Microbe in 2017, Dr. Kim and colleagues used neuroimaging, parasite transcript profiling and laboratory blood profiles to develop machine-learning models of malarial retinopathy and brain swelling. The researchers found that the interaction of high parasite biomass, low platelet levels and certain parasite protein variants that bind to the endothelial protein C receptor (EPCR) play a pivotal role in fatal cases of malaria. Their findings added strength to the rationale that anti-inflammatory and anticoagulant treatments counteracting the breakdown of endothelium may benefit those with severe malaria.
“We still don’t entirely know why some of these kids get super sick and have complications requiring hospitalization,” Dr. Kim said. “If we could figure that out we could save lives, reduce complications and use limited healthcare dollars more effectively in these under-resourced countries.”
The “Goldilocks” theory of immunity
When it comes to infectious diseases, too much of a good thing may make you sick. Dr. Kim calls it the “Goldilocks” theory of immunity – not too much (overactive immune system) and not too little (under-responsive immune system).
For instance, “for someone with malaria the right amount of immunity might not be just the right amount if they already also have tuberculosis,” Dr. Kim said. “What we’re realizing now with the human immune response to parasites or other foreign invaders (pathogens) is that you have to get the balance just right, so you get rid of the pathogen without damaging the human host.”
Otherwise, she added, even after the pathogen is eliminated, long-term complications like a damaging autoimmune inflammatory condition may linger.
Rigorously studying the dynamics of host-parasite interaction – including how parasites hijack the epigenome, which adjusts specific genes in response to signals from the outside world such as diet and stress — is critical to bridging the gap between discovery and effective treatments for different subgroups of infected patients.
“Both the pathogen and the infected host are duking it out to see which one wins, so figuring out what’s happening on both sides is really important to understanding immunity – how our body fights off disease,” Dr. Kim said. “Using genomic information to tell us who’s most susceptible to certain conditions will likely help us to tailor therapies to the individual, or perhaps to know who needs to be vaccinated.”
Striking the right balance of immunity
Potential applications for other diseases
Within their complex life cycles, both malaria and toxoplasma parasites have dormant forms that the human immune system can’t identify and kill, and antimicrobial drugs can’t touch. For malaria, this silent form lurks in the liver. For Toxoplasma, cysts can settle quietly into the infected person’s brain and muscle tissue without replicating, sometimes for years, until weakened immunity reactivates the disease.
Dr. Kim and other researchers continue to look for new ways to combat chronic infection by parasites.
“Normally when treating a disease you think of killing the form that makes a person clinically symptomatic,” she said, “but with both malaria and Toxoplasma if you can kill the biologically silent form, which is absolutely essential for the disease to continue, you’re accomplishing the same thing.”
Although Dr. Kim’s group targets specific problems underlying malaria and toxoplasmosis, such immune research may have broad applications for understanding and treating other conditions. For instance, atherosclerosis has been linked to the release of molecules from the immune system that can cause inflammation, blood vessel injury and plaque instability leading to heart attacks and stroke.
“Even though drug companies, because of financial return on investment, aren’t necessarily willing to invest in research on malaria host factors,” Dr. Kim said, “they are really interested in stroke and cardiovascular disease. And the big players in the kind of inflammation seen in these two major diseases are platelets and monocytes” – the same inflammatory culprits implicated in cerebral malaria.
While more research is needed, perhaps statin and antiplatelet drugs already approved for another indication could be effective in helping combat malaria,” she said. “It’s entirely possible by better understanding what’s a good immune response to malaria in one situation and bad in another will lead to insights that can be used to develop treatments for other diseases, or insight into what’s protective in another disease.”
Pursuing new approaches to outsmart elusive pathogens
Dr. Kim received her MD degree from the Columbia College of Physicians and Surgeons in New York City. She completed her residency in medicine at Columbia-Presbyterian Medical Center, a clinical fellowship in infectious diseases at UC San Francisco, and two postdoctoral research fellowships – one in parasitology at San Francisco General Hospital and a second in microbiology and immunology at Stanford University.
Dr. Kim is a fellow of the Infectious Diseases Society of America and the American Academy of Microbiology. She is also an elected member of American Society for Clinical Investigation and the Association of American Physicians, national honor societies for physician-scientists. A recipient of the Burroughs Wellcome Fund (BWF) New Investigator Award in Molecular Parasitology early in her career, she has served on the BWF Postdoctoral Research Enrichment Program’s scientific advisory board since 2014. She is a member of the NIH Pathogenic Eukaryotes Study Section.
Throughout much of her career, Dr. Kim’s research has been funded by the National Institute of Allergy and Infectious Diseases. She holds several patents, and was one of the first investigators to develop techniques to genetically manipulate T. gondii. She is the co-editor and currently preparing the third edition of Toxoplasma gondii, the Model Apicomplexan: Perspectives and Methods, a textbook widely considered the seminal source for scientists and physicians working with this parasite.
Dr. Kim said she was attracted to USF because of the university’s upward national trajectory and USF Health leadership’s commitment to building translational research and pursuing innovative approaches and excellence in all its academic missions. She is a member of the USF-wide Genomics Program.
“I enjoy being part of a USF clinical community that excels in the treatment of infectious diseases and working with physicians and scientists who do parasitology research,” she said. “You constantly have to think outside the box and come up with clever strategies – because we’re dealing with pathogens that do not behave like they are supposed to.”
Toxplasma parasite strategy for survival
Some things you might not know about Dr. Kim
- Korean was her first language, and she also speaks Spanish.
- She enjoys food, arts and crafts, and travel. Countries she has visited include Korea, Malawi, South Africa, France, Japan, and Brazil.
- Kim is married to Thomas McDonald, MD, USF Health professor of cardiovascular sciences and director of the new Cardiogenetics Clinic. They have two sons who are both mathematicians, one in a mathematics PhD program and the other in college. They met in the cardiac intensive care unit at Columbia Presbyterian Medical Center when Dr. McDonald was a resident and Dr. Kim was rounding as a medical student.
Written by Anne Delotto Baier, Photos and Video by Torie M. Doll, USF Health Communications and Marketing
USF Health cardiologist studies genetic predisposition to sudden cardiac death
In the laboratory and the clinic, Dr. Thomas McDonald focuses on inherited heart diseases that can lead to potentially deadly heart rhythm disturbances.
Sudden cardiac death most often makes the news when athletes in peak physical condition collapse and die while exercising or competing. This spring, Zeke Upshaw, 26, a basketball player for the Grand Rapids Drive, a G-league affiliate of the Detroit Pistons, collapsed face-down on home court during the final minute of a game and later died at the hospital. A medical examiner ruled that he had suffered sudden cardiac death.
“Sudden cardiac death is when someone, usually otherwise healthy and often young, tragically drops dead – without any warning,” said Thomas V. McDonald, MD, a professor in the USF Health Department of Cardiovascular Sciences.
Most of the 200,000 to 450,000 sudden cardiac deaths each year in United Start are caused by heart rhythm disturbances provoked by certain strenuous activities, prescription medications, recreational drugs, or other triggers. “Sometimes it just happens in your sleep. The most severe and earliest form would be sudden infant death, or SIDS,” Dr. McDonald said.
Dr. McDonald was recruited to the USF Health Heart Institute in October 2017 from Albert Einstein College of Medicine in New York City, where he was a professor of both cardiology and molecular pharmacology. He also co-directed the thriving Montefiore-Einstein Clinic for CardioGenetics, the first such interdisciplinary clinic in metropolitan New York for families at risk of sudden cardiac death from arrhythmias.
At USF Health his laboratory continues to focus on the fundamental causes of heart conditions passed from one generation to the next — and what can be done to help prevent disease and its consequences. The hereditary conditions he studies include those affecting the heart’s electrical system to cause arrhythmias, like long QT syndrome and Brugada syndrome, and those affecting heart muscle, such as hypertrophic cardiomyopathy and dilated cardiomyopathy. While rare, these conditions can substantially increase an individual’s risk for sudden cardiac death and devastate families.
Dr. McDonald has also started a USF Health Cardiogenetics Clinic, modeled after the Montefiore-Einstein center he co-founded, to evaluate and treat families in which members succumb to unexplained sudden cardiac death or SIDS, or where suspicion of an underlying, hereditary heart rhythm disturbance exists.
His work bridging the laboratory and clinic has implications for a much larger population than people with relatively rare inherited cardiac disorders. Dr. McDonald points to growing evidence of the interplay between genetics and environmental factors like diet, exercise and stress.
“By studying these rare or uncommon cardiac diseases,” he said, “we may uncover more generalizable biochemical pathways that could be influenced to harm the heart given the wrong environment — even in genetically unaffected families.”
Pinpointing The Meaning Of Genetic Variants Of “Unknown Significance”
Dr. McDonald analyzes genetic changes, or mutations, which may lead to malfunctioning of ion channels that create electrical signals in the heart.
His team has spent the last few years characterizing the function of 1,000 different mutations found in cardiac ion channel genes associated with hereditary rhythm conditions such as long QT syndrome and Brugada syndrome. The researchers recreate the genetic variations in a cellular model and use automated electrophysiology techniques to analyze how the mutations affect the ion channel’s ability to correctly generate each heartbeat. All these variations have been cited in published scientific literature; however, it is still largely unclear which ones truly increase the risk of abnormal rhythms leading to palpitations, seizures, fainting or sudden death – and which are benign.
The research project is supported by a five-year, $1.7 million R01 grant from the NIH’s National Health, Lung and Blood Institute.
“Our ultimate goal is to work with other investigators to create a NIH-curated public database that physicians and genetic counselors could access to find out whether a genetic variant is likely, or unlikely, to cause a potentially life-threatening heart rhythm disturbance in a patient or their family members,” Dr. McDonald said.
As genetic testing is becomes more common, a growing challenge is that lab reports of people referred for DNA sequence testing often come back listing many “variants of unknown significance,” Dr. McDonald said. “That drives physicians and patients crazy because they don’t know what that means… what do they do with that information?”
An important step toward improving the guidance that doctors offer individuals with inherited heart disorders would be the ability to more precisely distinguish between disease-causing mutations and mutations with little or no harmful physiological effects through a resource like a scientifically validated database, he added.
Recommended treatment options for long QT are life-long and vary, including regular cardiac monitoring, taking medication such as beta blockers, restricting strenuous sports activities, or sometimes implanting pacemakers or defibrillators to help control abnormal heartbeats. So, for example, if DNA testing of a child or young adult revealed a long QT genetic variation characterized as having little risk of leading to sudden cardiac death, prescribing beta blockers and routine cardiac monitoring might be the best preventive therapy – avoiding the long-term management and small, but real, lifetime risk of complications from an implantable device.
Opening Tampa Bay Region’s First CardioGenetics Clinic
The twice-monthly Cardiogenetics Clinic, which opened in March, is held at USF Health Cardiology’s Armenia Avenue location. The new clinic is staffed by a team with the expertise to address the diverse medical, psychological, social and ethical issues arising when evaluating genetic heart conditions that predispose patients to sudden cardiac death.
“When I arrived there was no formal cardiogenetics program in the greater metropolitan area of Tampa Bay where 4 million people live — so the prospect of building one from scratch was very attractive,” said Dr. McDonald, who specializes in adult cardiology. He leads the clinic working with USF Health faculty members Christopher Griffith, MD, assistant professor of pediatrics and a clinical geneticist; and Melissa Racobaldo, a genetic counselor; as well as Gary Stapleton, MD, a pediatric interventional cardiologist from Johns Hopkins All Children’s Hospital. USF College of Public Health students specializing in genetic counseling are expected to join the clinic in coming months.
Many with congenital cardiac conditions have no signs or symptoms. Patients and their families referred to the clinic typically have experienced a history of arrhythmias or other cardiac events, or suffered the unexpected death of a loved one.
During the initial visit, families meet with team members for a cardiac history and examination, review of medical records and/or autopsy reports, and baseline tests that include an electrocardiogram and echocardiogram. Based on the family’s medical history, a tree-like chart known as the DNA pedigree is created to identify familial genetic patterns and sudden unexpected deaths linked to cardiac disorders. “The most important genetic test is still a complete family history,” Dr. McDonald said.
DNA testing is usually only recommended when the team discerns that the pattern of cardiac-related events is highly likely to be genetic rather than environmental. For instance, a family history indicating that a few relatives died from heart disease in their 80s might be considered environmental.
If a mutation is found in one of the genes known to be associated with a dangerous cardiac arrhythmia, then the first (affected) patient who got tested receives immediate counseling by a cardiologist, and genetic testing and counseling will be offered to all at-risk relatives. Different heart rhythm genetic mutations have different effects on ion channels, so individualized remedies are required.
“Genetics is still quite complex to most people, so we try to make our explanations understandable and not so scary,” said Dr. McDonald, who has co-authored several articles on how patients are affected by cardiogenetic testing, including in the journals Qualitative Health Research and Personalized Medicine.
“Our dominant message is ‘we’re here to provide information, which gives you knowledge, and knowledge gives you power to manage your life and to help the next generation.”
The Cardiogenetics Clinic will offer patients access to the latest clinical trials for new drugs or devices. Dr. McDonald was recently named USF site lead investigator for a world-wide Phase 3 study testing the effect on walking endurance of an investigational medication for patients with dilated cardiomyopathy caused by a rare genetic mutation. This form of heart disease, in which inadequate pumping of blood causes the heart to become weaker, can lead to heart failure.
“Heart In A Dish” As A Drug Screening Tool
Interested in drug discovery for inherited heart diseases lacking effective medications, Dr. McDonald’s lab has begun collecting blood cells from USF Health cardiomyopathy patients who provide informed consent.
The adult blood cells can be genetically reprogrammed into induced pluripotent stem cells (iPSCs) with the potential to develop into any cell type in the body, including heart cells. The goal is to model the early stages of inherited heart disease with patient-specific cells grown in a petri dish, working out at a molecular level how the disease does its damage to heart muscle.
“Once you do that,” Dr. McDonald said, “you can use the ‘heart disease in a cell culture dish’ to screen any number of drugs or chemical compounds for their potential therapeutic benefit.”
Dr. McDonald is also collaborating with colleagues in the USF Health Department of Neurology to look at rare genetic mutations for nervous system diseases, such as certain types of muscular dystrophy and ataxias, which can lead to severe heart damage,
Dr. McDonald received his bachelor’s degree in zoology from USF in 1977 and MD degree from the University of Florida. He completed a residency in medicine and research fellowship in cardiology at Columbia-Presbyterian Medical Center in New York City. At Stanford University School of Medicine, he conducted fellowships in clinical cardiology and interventional cardiology, as well as a postdoctoral research fellowship. He spent 22 years as a faculty member at Albert Einstein College of Medicine before joining the USF Health Morsani College of Medicine last fall.
Continuously funded throughout his career by the NIH or the American Heart Association (AHA), Dr. McDonald has authored more than 70 peer-reviewed publications. Among his many high-impact papers was a 2013 article published in FASEB. The NIH-supported study was among the first to report that synonymous (silent) changes in DNA traditionally considered neutral may adversely affect the processing speed and efficiency of ion channels associated with the heart arrhythmia syndrome Long QT and alter disease severity.
Dr. McDonald has served on multiple study sections of the NIH and AHA. He was elected in 2011 as an AHA Fellow-Basic Cardiovascular Sciences Council.
Some Things You May Not Know About Dr. McDonald
- During high school, he worked one year as a head cook for a restaurant in Winter Park, Fla., before entering college. “It made me realize that hard work is important, but also motivated me to study so I could make a living by using my head more than my hands.”
- Wife Kami Kim, MD, also a USF Health physician-scientist, is a professor with joint appointments in the Department of Internal Medicine and in the Department of Global Health. They met in the cardiac intensive care unit at Columbia Presbyterian Medical Center when Dr. McDonald was a resident and Dr. Kim was rounding as a medical student. Their two sons, both studying theoretical math, are Clayton, 24, a PhD student at Boston College, and Vaughan, 20, starting his junior year at Harvard University.
- McDonald enjoys bicycling, Japanese cooking, and nearly exclusively reads fiction – “it’s another window on the human condition.” His two favorite books are One Hundred Years of Solitude, an acclaimed novel by Nobel Prize-winning Latin-American author Gabriel García Márquez, and Infinite Jest, a literary bestseller and unconventional comedy by David Foster Wallace.
Written by Anne Delotto Baier, Photos and Video by Torie M. Doll, USF Health Communications and Marketing
USF neuroscientist probes how different states of tau drive brain cell damage
Research by Laura Blair’s team seeking to untangle tau may lead to targeted treatments for Alzheimer’s, Parkinson’s and other neurodegenerative diseases
Both of USF Health neuroscientist Laura Blair’s grandmothers died from ALS, a debilitating neurodenerative disease that progressively weakens muscles and leads to paralysis.
“Seeing that firsthand really put in my heart to do everything I could to help people suffering from these devastating neurodegenerative diseases,” said Blair, PhD, an assistant professor in the Morsani College of Medicine’s Department of Molecular Medicine.
As an USF undergraduate student conducting research in chemist Bill Baker’s laboratory, she had the chance to work at the USF Health Byrd Alzheimer’s Institute with Chad Dickey, PhD, an accomplished and creative NIH-funded neuroscientist who was the first to find that proteins involved in learning and memory were selectively impaired in a mouse model of Alzheimer’s disease.
Blair jumped at the opportunity. Dr. Dickey’s National Institutes of Health (NIH) work was focusing on defects in the removal of damaged proteins from cells, with promising studies of the key role “chaperone proteins” play in regulating brain cell function in Alzheimer’s disease and other neurodegenerative disorders.
“I was excited to be part of the translational work he was doing – seeking to understand how the cell’s natural defense, these chaperone proteins, might be harnessed to regulate (abnormal) misfolding proteins in order to help fix or prevent neurodegenerative disease,” Dr. Blair said.
That was nine years ago.
Carrying on a scientific legacy
Since then, Dr. Blair received her doctorate in medical sciences at USF in 2014 (she also earned bachelor’s and master’s degrees here) and continued to work in Dr. Dickey’s laboratory as a postdoctoral fellow. When Dr. Dickey passed away last year at the age 40 following a courageous battle with cancer, Dr. Blair and colleague John Koren, PhD, assumed the leadership of Dickey’s team with heavy hearts. But they push forward with their mentor’s same dedication to seeking answers and sense of urgency to “publish, publish, publish.”
“Chad was always larger than life and one of the biggest influences in my life, so losing him has been surreal,” said Blair, who keeps Dr. Dickey’s nameplate on the office she now occupies. “It’s hard, but we will continue the work he started and carry on his scientific legacy.”
“He was a tremendous mentor who taught all of us how to think about a problem and ways to come up with solutions.” And she said, smiling at the memory of Dr. Dickey’s unrelenting drive to find solutions, “he taught us there’s no sense in waiting until tomorrow for an experiment that could have been started yesterday.”
Dr. Blair’s laboratory studies how chaperone proteins drive different states of the tau protein associated with Alzheimer’s disease and more than a dozen other tauopathies, including Parkinson’s disease and traumatic brain injury. Just as their name suggests, “chaperone” proteins escort other proteins in the cell to the places they need to be, ensure these proteins do not interact with others that could be bad influences, and see to it that proteins degrade, “or are put to bed, so to speak,” when the time is right, Dr. Blair said. Under normal circumstances, chaperone proteins help ensure tau proteins are properly folded to maintain the healthy structure of nerve cells.
Pursuing how chaperones drive different states of tau
In particular, the USF researchers explore how various chaperone proteins interact, for better or worse, with various forms of tau – ranging from soluble tau protein that can spread from one brain cell to another to the aggregated, misfolded species of tau tangles inside brain cells. (Sticky plaques of B-amyloid protein and toxic tangles of tau protein both accumulate in patients with Alzheimer’s disease, but recent studies suggest that tau deposits may be more closely linked to the actual death of neurons leading to memory loss and dementia.)
“If we can understand which states of tau are worse in terms of driving neurotoxicity,” Dr. Blair said, “maybe we can begin to shift tau into a better state so we can help delay disease progression, if not stop it in its tracks.”
With a support of a new five-year, $1.5-million R01 grant from the National Institute on Aging, Dr. Blair, along with co-principal investigators Paula Bickford, PhD, of the USF Center of Excellence for Aging and Brain Repair, and Vladimir Urvesky of the Department of Molecular Medicine, is looking at a family of energy-independent, small heat shock proteins known to prevent harmful tau aggregation. In an earlier paper published several years ago in the Journal of Neuroscience, Drs. Blair, Dickey and colleagues reported that high levels of one of these chaperone proteins, Hsp27, reduced tau accumulation in neurons and rescued learning and memory in a mouse model for Alzheimer’s disease.
Dr. Blair is also principal investigator of a second, five-year $1.36-million grant from the National Institute of Mental Health (the continuation of a grant originally awarded to Dr. Dickey) to develop a treatment blocking the effect of a stress-related protein genetically linked to depression, anxiety and other behaviors associated with post-traumatic stress disorder (PTSD). The grant builds upon earlier USF research, showing that as levels of this stress-related protein, known as FKBP51, increase in the brain with age it partners with chaperone protein Hsp90 to make tau more deadly to brain cells involved in memory formation. Using a new mouse model genetically engineered to overexpress FKBP51 and exhibit symptoms like those seen in humans with PTSD, Dr. Blair’s team will test various treatments on mice exposed to early-life environmental stresses.
The ultimate goal of all this tau regulation research is to discover and commercialize targeted treatments that work, whether that’s drugs that inhibit or activate chaperone proteins, or gene therapies, or a combination. Currently no FDA-approved medications for Alzheimer’s disease specifically target beta amyloid or tau; they only help improve symptoms for some patients for a limited time.
A single-bullet therapeutic approach to a disease like Alzheimer’s that affects diffuse areas of the brain is unlikely, Dr. Blair said. “The multi-treatment option is probably going to be the most effective, but it’s difficult to address that until we have individual treatments moving forward.”
“Working toward treatments to help slow and prevent these devastating neurodegenerative diseases is what keeps our laboratory so motivated and determined.”
Identifying potential treatments for neurodegenerative diseases
Building on Dr. Dickey’s work with chaperone proteins, the USF researchers continue to make significant progress in identifying potential targets to help slow or prevent neurodegenerative disease progression.
The team recently identified cochaperone protein Aha1, which binds to and stimulates the activity of heat shock protein Hsp90, as one promising therapeutic target. Hsp90 regulates the folding, degradation and accumulation of tau. In a study published this September in Proceedings of the National Academy of Sciences, the researchers demonstrated that Hsp90 cochaperone Aha1 boosted production of toxic tau aggregates in a mouse model of neurodegenerative disease and led to neuron loss and memory impairment.
The researchers also found that inhibiting Aha1 prevented the dramatic accumulation of tau in cultured cells. “We think Aha1 inhibitors offer promise for effects similar to Hsp90 inhibitors with less side effects,” Dr. Blair said.
This June, in the journal PLoS Biology, Dr. Blair (principal investigator), Jeremy Baker (lead author) and colleagues reported for the first time that a naturally-occurring human enzyme – called cyclophilin 40 or CyP40 – could break apart clumps of tau in a mouse model of dementia. The USF led study found that CyP40 reduced the amount of aggregated tau, converting it into a more soluble and less toxic form of amyloid. In a mouse model of an Alzheimer’s-like disease, experimental expression of CyP40 preserved brain neurons and rescued cognitive deficits. The same enzyme also disaggregated alpha-synuclein, an aggregate associated with Parkinson’s disease.
Exactly how CyP40 can untangle clumps of tau and alpha-synuclein is not yet clear, but, Blair said “our finding suggests that CyP40, or one of the more than 40 other proteins with similar activity, may have a role to play in treating neurodegenerative diseases.”
Some things you might not know about Dr. Blair:
- Blair and her husband Tom belong to a local swing dancing community, where they enjoy dancing the Lindy Hop and Balboa to ‘40s jazz.
- Blair is a mother to 7-year-old Oliver, and a stepmother to 17-year-old Laney, who is a high school senior. They also have two dogs, a Shih Tzu named Oreo and a Shih Tzu-Yorkshire terrier mix named Pumpkin.
- Participating in the Great American Teach-in two years ago, Dr. Blair spoke to her son’s kindergarten class about her career as a neuroscientist, including working on brain teaser puzzles and discussing a video of a preclinical neurobehavioral test with the young students. But, she said, the kids were particularly impressed with the squishy plastic “stress-reliever brains” she brought along.
–Written by Anne Delotto Baier, Photos by Sandra C. Roa and Eric Younghans, University Communications and Marketing
Genetics research may help tailor more precise therapies for asthma, heart failure
Studies led by USF’s Dr. Stephen Liggett shed light on genetic variability of adrenergic receptors and how they might best be used to treat disease
While significant progress has been made managing asthma over the last two decades, about half of all asthmatics achieve optimal control of this chronic inflammatory disease using currently available medications. Similarly, only about 50 percent of patients with congestive heart failure, which occurs when the heart is too weak to pump enough blood to meet the body’s needs, have an average life expectancy of more than five years.
More still needs to be known at the molecular level about these common diseases to identify potential new targets for drug therapies, said Stephen B. Liggett, MD, associate vice president for research at USF Health, vice dean for research at the Morsani College of Medicine, and professor of internal medicine and molecular pharmacology and physiology.
What ties these two diseases together are the receptors on cardiac muscle and on smooth muscle of the airways. Dr. Liggett’s laboratory helps shed light on the genetic variability of adrenergic receptors and on how these receptors can best be used for treatment. The genetic studies have been particularly useful in developing the concept of pharmacogenetics, a tailoring of therapy based on an individual’s genetic makeup, for heart failure and asthma.
“Twenty years ago we had a handful of medicines for high blood pressure, and today we don’t use any of them. Now, we have a whole new group of more effective (antihypertensive) drugs with much fewer side effects,” he said. “And, I’m sure that one day, we’ll have more tools in our toolbox to better treat heart failure and asthma – drugs that work better for subgroups of people as defined by their genetic makeup and environmental exposures.”
Mining a “superfamily” of receptors for better drug targets
Dr. Liggett leads a USF team that studies the genetic, molecular biology, structure and function of G-coupled protein receptors, or GPCRs, the largest family of human proteins. More than 800 GPCRs have been discovered within cell membranes in the human body, Dr. Liggett said, and one or more of these receptors plays a role in virtually everything the body does, including controlling thoughts in the brain, sight and smell, uterine contraction and relaxation, blood pressure, cardiac, lung and kidney function, to name just a few.
Consequently, malfunctions of GPCR signaling pathways are implicated in many chronic diseases including asthma and cardiovascular diseases. Already this “superfamily” of receptors accounts for nearly half the targets of all prescribed drugs. But, a deeper understanding of the dynamics of the GPCR signaling network and how it maintains a healthy cell or responds to pathogens could lead to the design of drugs that more precisely target diseases with greater effectiveness and fewer side effects.
Dr. Liggett began his work with GPCRs in 1988 as a Howard Hughes Institute postdoctoral research fellow in the Duke University Medical Center laboratory of mentor Robert Lefkowitz, MD. Dr. Lefkowitz was awarded the 2012 Nobel Prize in Chemistry with Brian Kobilka, MD, for groundbreaking discoveries revealing the inner workings of GPCRs.
Building upon his interest and advanced training in pulmonary and critical care medicine, Dr. Liggett began early in his career to concentrate on one of the classes of GPCRs known as adrenergic receptors, which are stimulated by the hormone epinephrine and the neurotransmitter noepinephrine. They are involved in increasing the rate and force of contraction of the heart, as well as constriction and dilation of blood vessels throughout the body and of airways in the lung. For the last 28 years, he has been continuously funded by the National Institutes of Health (NIH) to study the molecular basis of beta-adrenergic receptors in asthma.
Dr. Liggett is the principal investigator of a four-year, $1.12-million R01 grant from the NIH’s National Heart, Blood and Lung Institute (NHBLI) that seeks to understand how beta-adrenergic signaling is regulated to influence the development and treatment of asthma. Over his career, he has also been awarded millions of dollars in NIH funding to explore the role of genetic variations of GPCRs in heart failure, including whether those variations may alter how effectively drugs work in individual patients.
Bitter taste receptors in a new place
Dr. Liggett is also currently a project principal investigator for a five-year, $2-million NHBLI P01 grant examining how airway smooth muscle bitter taste receptors might be applied as new treatments for asthma and chronic obstructive pulmonary disease.
Using a genomics-based method that Dr. Liggett pioneered, his team had previously identified bitter taste receptors, initially thought only to exist on the tongue, deep inside the lung at the airway smooth muscle and demonstrated they act to open the airway. “When activated, they appear far superior to the beta-agonists commonly prescribed to patients to open their airways during an asthma attack,” said Dr. Liggett, who published the discovery and the need for alternatives to current bronchodilators in Nature Medicine and other journals.
Overall, discoveries emerging from Dr. Liggett’s research have yielded more than 250 peer-reviewed papers, many highly cited and appearing in top journals such as Nature Medicine, Science, Proceedings of the National Academy of Sciences, and the New England Journal of Medicine. His work has been cited by other papers more than 26,000 times. He also holds 18 patents detailing potential new targets for drug therapy or genetic variations of known drug targets and how they might be used to predict response to medications and customize treatment.
Among some of his laboratory’s major findings:
– While at the University of Maryland, Dr. Liggett’s team worked with colleagues at the University of Wisconsin-Madison to sequence for the first time the entire genomes (more than 100 different strains) of all known rhinoviruses, a frequent cause of respiratory infections including the common cold. The groundbreaking work, published on the cover of Science, provided a powerful framework for large-scale, genome-based epidemiological studies and the design of antiviral agents or vaccines to combat rhinoviruses. “I originally suggested sequencing 10 strains, and then my collaborator asked why not do them all,” he said. “This made the difference between a mediocre proof-of-concept paper and a full article in Science. I learned that it is important to think big if you want to make a real difference”
– Discovered and characterized genetic variations that may predict which patients with congestive heart failure respond best to a life-saving beta-blocker drug. These landmark studies occurred over several years and were published in Nature Medicine twice, and the Proceedings of the National Academy of Sciences three times. “This is a good example of the progression of an idea over time, where every year or so an unexpected turn of events occurred, and new insight was gained,” he said.
– While at the University of Cincinnati, Dr. Liggett, working with colleagues at Washington University and Thomas Jefferson University, found that a genetic variation of an enzyme, which inhibits beta-adrenergic receptor signaling, confers “genetic beta-blockade” in cardiac muscle and protects against early death in African Americans with heart failure. The findings, published in Nature Medicine, provided insight into individual variations in disease outcomes. Another key study from Cincinnati revealed that a certain combination of genetic variants within a single gene conferred low vs. excellent responses to inhaled beta-agonists in treating asthma. These combinations, called haplotypes, had never been identified in GPCRs. The work was published in Proceedings of the National Academy of Sciences.
Advancing outside his field of study
Dr. Liggett joined USF Health in 2012 from the University of Maryland School of Medicine in Baltimore, where he was associate dean for interdisciplinary research and professor of medicine and physiology. He received his MD degree at the University of Miami and completed both a residency in internal medicine and fellowship in pulmonary diseases and critical care medicine at Washington University School of Medicine and Barnes Hospital in St. Louis, MO.
Within two years, he advanced from a postdoctoral research fellowship in Dr. Lefkowitz’s laboratory at Duke to tenured associate professor and director of pulmonary and critical care medicine at the University of Cincinnati College of Medicine. By the time he left Cincinnati for the University of Maryland in 2005, he held an endowed chair in medicine and directed the university’s Cardiopulmonary Research Center.
Though he had no significant wet-lab experience, Dr. Liggett was fascinated by the emerging science called “molecular biology” and was undeterred from branching into a field of study in which he had no formal training.
He secured a position as assistant professor at Duke following his fellowship there, and figured out how to sequence adrenergic receptor genes from a patient’s blood. While routine now, such genetic testing had not been done previously. He unexpectedly kept finding multiple variations (called polymorphisms or mutations) in genes coding for the same receptors, so he sought out the advice of some classic geneticists. At the time, Dr. Liggett said, their traditional thought was modeled after diseases like cystic fibrosis — if a person had the genetic mutation they developed the disease, if the mutation was absent they did not.
“There was no consideration for common genetic variants and how they might affect disease risk, progression, or response to treatment. It simply was not in their thought process,” Dr. Liggett said. He was told “it’s probably nothing and don’t quit your day job.” He did not take their advice.
Instead, he returned to the laboratory to sequence and clone receptors from many different populations with asthma and heart failure, showing that the receptor genes did indeed differ from one individual to another, generally with several common “versions.” His team also created “humanized” mice expressing the human genes for asthma and heart failure so they could begin to understand the physiology of the receptors. They began to find that some genetic alterations increased receptor function, some decreased the drug’s affinity to bind (responsiveness) to a receptor, and still others altered how the receptor was regulated. And, through NIH-supported clinical trials, the researchers correlated outcomes observed in patients undergoing drug therapies with the genetic variations uncovered in the laboratory.
“If there’s a lesson to be learned here by young investigators, I’d say it’s that you can collect information from experts in the field, but you need to use your gut to ultimately decide on whether to pursue a line of research or not,” Dr. Liggett said.
Personalized medicine challenge: Common diseases, multiple genetic variations
Realizing personalized medicine’s full potential will require a better understanding of how environmental variables – including diet, exercise, the gastrointestinal microbiome (gut bacteria) and toxin exposure – combine with genetic variations to affect disease and its treatment, he said. “Personalized medicine faces its greatest challenges in the common diseases like asthma, atherosclerotic heart disease and heart failure, because they involve multiple variations in multiple genes that interact with the environment to give you a disease – and also provide a set-up for unique ways to treat the disease.”
Dr. Liggett was one of the first physicians recruited for what would become the USF Health Heart Institute. He recalls that he still had the letter of offer in his pocket when he stood before the Hillsborough County Commission in 2012 to help USF Health leadership pitch the need for a cardiovascular institute to include a focus on genomics-based personalized medicine. The county joined the state in funding the project, and Dr. Liggett was instrumental in the early planning stages of the Heart Institute before the arrival of its founding director Dr. Samuel Wickline. The institute is now under construction in downtown Tampa as part of the new Morsani College of Medicine facility, a key anchor of Water Street Tampa. Already, 21 of the 31 institute’s biomedical scientists who will investigate the root causes of heart and vascular diseases with the aim of finding new ways to detect, treat and prevent them, have been recruited.
“There’s an excitement here and philosophy of excellence that’s rewarding to see,” Dr. Liggett said. “We have a strategic plan in place, including moving ahead to expand research in cardiovascular disease, infectious disease and the microbiome, and the neurosciences. Our departments are recruiting at a good pace, and the faculty we’re bringing in all have NIH funding and are highly collaborative.”
Dr. Liggett is an elected fellow of the American Association for the Advancement of Science – one of only five Morsani College of Medicine faculty members to receive that prestigious honor. He is also an elected Fellow of the National Academy of Inventors and the American College of Chest Physicians. Last year, he was one of 30 scientists nationwide selected to join The Research Exemplar Project – recognition of his outstanding reputation as a leader whose high-impact, federally-funded research yields novel and reproducible results.
Over his career, he has served on several NIH study sections and on the editorial board of high-impact journals relevant to fundamental biochemistry as well as heart and lung diseases. He is currently editor-in-chief of the Journal of Personalized Medicine.
Some things you may not know about Dr. Liggett:
- He has asthma, which helps motivate his research toward finding better treatments for this common lung disease affecting one in 12 people in the United States.
- Restores vintage cars, primarily DeLoreans. Although he recently finished bringing a funky lime green 1974 Volkswagen Thing back to life, and over the holidays restored a 1973 VW camper.
- Lives with wife Julie on the beach in Treasure Island, where they enjoy surfing, paddle boarding, and photography.
- Has three children – Elliott, an engineer at NASA’s Jet Propulsion Laboratory at Cal Tech in Pasadena, CA; Grace, who recently completed her master’s degree in public health at USF; and Mara, an undergraduate student studying social work at Florida Atlantic University, and two step-children — Madison, an undergraduate at the University of Florida, and Tripp, a senior at St. Petersburg Catholic High School. He also has three grandchildren, ages 2 to 9.
– Written by Anne Delotto Baier, photos by Sandra C. Roa, and audio clips by Eric Younghans, University Communications and Marketing
Dr. Mack Wu studies molecular control of ischemia-reperfusion injury, leaky gut
USF Health researcher Mack Wu, MD, studies what happens when the microvascular endothelial barrier controlling blood-tissue exchange is compromised during ischemia-reperfusion injury, a condition that can lead to irreversible tissue damage. He also investigates the molecular control of gut permeability, also known as “leaky gut,” in tissue injuries caused by trauma and severe burns.
His group’s work has broad implications for a variety of conditions including stroke, heart attack, thrombosis, sepsis, trauma or other inflammatory diseases associated with microvascular injury.
The closely connected endothelial cells lining the interior of blood vessel walls play a critical role in limiting the how much fluid, proteins and small molecules cross the wall of the tiny blood vessels, or microvessels. However when this protective endothelial barrier is damaged, excessive amounts of blood fluid, proteins and molecules leak outside the microvessels into nearby body tissue – a process known as microvascular hyperpermeability. If this breech of endothelial barrier is associated with a body-wide inflammatory response, it can trigger a chain of events leading to edema (swelling), shock from severe blood and fluid loss (hypovolemic shock), and ultimately multiple organ failure.
Pinpointing Potential Solutions For Ischemia-Reperfusion Injury
Previous research by Dr. Wu’s laboratory and other groups discovered that ischemia-reperfusion injury can cause endothelial barrier damage leading to vascular hyperpermeability, or abnormally leaky blood vessels.
Ischemia-reperfusion injury is typically associated with conditions like organ transplantation, stroke, heart attack, or cardiopulmonary bypass where blood supply to a vital organ is temporarily cut off (ischemia), resulting in oxygen deprivation. For instance, a period of ischemia occurs while a donor organ is transported to a recipient in the operating room, or when a clot interrupts blood circulation to the brain. When blood supply is re-established with new blood returned to the previously oxygen-deprived area (reperfusion), tissue injury can worsen because the reperfusion itself causes inflammation and oxidative damage rather than restoring normal function. It its severest form, ischemia-reperfusion injury can result in multiple organ failure, or even death.
“I believe endothelial barrier injury is one of the key elements of ischemia-reperfusion injury, so my group is trying to find out which molecule is ultimately responsible for the endothelial barrier damage,” said Dr. Wu, a professor of surgery and molecular medicine at USF Health Morsani College of Medicine and a research physiologist at James A. Haley Veterans’ Hospital.
With the support of a $1.49-million, four-year R01 grant from the National Heart, Lung and Blood Institute, Dr. Wu’s team is zeroing in on a molecule known as focal adhesion kinase, or FAK, an enzyme that may play a role in weakening the microvascular endothelial barrier during ischemia-reperfusion injury. Using cell models and a newly developed mouse model in which the endothelial-specific gene for FAK is knocked out, the USF researchers are testing whether selectively inhibiting FAK activity can rescue the endothelial barrier from such injury.
The work is critical because no FDA-approved treatment exists to prevent tissue damage following reperfusion. Identifying a new mechanism for the injury would provide potential targets for drug development, Dr. Wu said. So for instance, he said, after an initial stroke a new intravenously administered drug selectively targeting endothelial cells in the brain’s microvessels might stop further harmful swelling of the brain caused by stroke.
Defining Molecular Control Of “Leaky Gut” In Severe Burn Trauma
A second grant from the U.S. Department of Veterans Affairs funds Dr. Wu’s studies to define the underlying molecular mechanisms of leaky guts induced by traumatic injury associated with thermal (fire, scald or chemical) burns. Massive burn trauma is a significant cause of injury and death in American soldiers. With a $960,000 VA Merit Award, Dr. Wu focuses on how intestinal epithelial barrier damage happens during severe burns, with the aim of developing targeted therapies to prevent posttraumatic complications. In particular, he is working to determine the pathways by which the protein palmitoylation in gut epithelial cells are stimulated by burn injury.
Epithelial cells line the interior of the small intestines, and after severe burn injury, this protective epithelial barrier commonly breaks down, causing bacteria and toxins to flow from the intestine into the circulating blood. The result of this abnormal epithelial permeability, or “leaky gut,” can be deadly if sepsis ensues – a bacterial infection in the bloodstream sets up a body-wide inflammatory response leading to multiple organ failure.
While the role gut barrier failure plays in posttraumatic complications is well recognized, its cellular and molecular mechanisms remain poorly understood. Currently, pushing IV fluids to help prevent hypovolemic shock and administering antibiotics and anti-inflammatories are the only therapies, mostly supportive, Dr. Wu said.
“More effective early therapeutic interventions to prevent leaky gut and systemic inflammatory response will be key to preventing sepsis,” he added, whether in soldiers with trauma or VA patients with inflammatory bowel diseases.
From Industry To Academia
Dr. Wu joined USF Health and the Haley VA Hospital in 2011. He came from Sacramento, Calif, where he was an associate professor of surgery at the University of California at Davis School of Medicine and a research physiologist at Sacramento VA Medical Center. Previously, Dr. Wu was a faculty member in the Department of Medical Physiology at Texas A&M University Health Science Center. He screened pharmaceutical compounds as a toxicologist in a biotechnology laboratory before joining Texas A&M, moving from industry to academia in 1995.
Dr. Wu received his MD degree from Second Military Hospital in Shanghai, China, and conducted an internship at Shanghai Second Hospital.
One of his earliest and most highly cited studies, published in the American Journal of Physiology (1996), was first to report nitric oxide’s role in contributing to cardiovascular injury. The study showed an increase in nitric oxide induces vascular endothelial growth factor (VEGF) to promote leakage in tiny coronary veins.
Another more recent study in Shock (2012) provided direct evidence that thermal burn injury causes intestinal barrier disruption and inflammation characterized by intestinal mucosal permeability (leakage) and an infiltration of immune system cells known as neutrophils.
Something You May Not Know About Dr. Wu:
He loves deep-sea fishing. Dr. Wu has fished for sharks off the Golf coast of Texas, rockfish off the Pacific coast of California, and grouper off the west coast of Florida.
– Written by Anne Delotto Baier, photos by Eric Younghans, USF Health Communications and Marketing
USF researcher studies irregular cardiac electrical signals
Seeking to understand how the heart short circuits, Sami Noujaim looks for new drugs to fix atrial fibrillation
Within the last three years, USF biomedical scientist Sami Noujaim, PhD, lost his older brother to sudden cardiac death and his 80-year-old father was diagnosed with atrial fibrillation.
The experiences gave Dr. Noujaim a new appreciation for his research on understanding how normal and abnormal electrical impulses are generated in the heart. The Cardiac Electrophysiology Research Laboratory he directs focuses on finding more effective drugs to treat atrial fibrillation, the most common irregular heart rhythm and a condition for which prevalence rises markedly after age 65.
“When life throws something like that at you, the work you do takes on a more personal tone, a sense of mission. I realized that neither myself nor my loved ones are immune from the cardiovascular diseases I’m studying,” said Dr. Noujaim, an assistant professor in the Morsani College of Medicine’s Department of Molecular Pharmacology and Physiology. “We are all at risk.”
Searching For Noninvasive Solutions To Atrial Fibrillation
Atrial fibrillation is a problem with the cardiac electrical circuitry that controls the rate and rhythm of the heartbeat. The condition affects about 9 percent of the U.S. population age 65 or older, according to the Centers for Disease Control and Prevention, and can lead to potentially deadly complications such as stroke and heart failure. While signs of atrial fibrillation may include heart palpitations, fatigue, lightheadedness, dizziness and shortness of breath, some people experience no noticeable symptoms.
Treatment and management options include lifestyle changes, medications to help control heart rate and rhythm and reduce the risk of blood clots, controlled electrical shock (cardioversion to reset heart rhythm), invasive procedures (catheter ablation) and surgical implantation of pacemakers. However, a major challenge is that atrial fibrillation frequently recurs after normal heart rhythm (sinus rhythm) is restored.
“The existing treatments can be good, but there is a lot of room for improvement, so we are focusing on contributing to noninvasive treatment options,” Dr. Noujaim said. “If we could help physicians get patients with atrial fibrillation to long-term normal sinus rhythm, and perhaps increase the ability to take them off blood thinners, it would be a significant improvement.”
The significance of investigating the relationship between aging and atrial fibrillation.
Designing A “Perfect Plug” Using An Antimalarial Drug Model
“Right now, we are trying to design a perfect plug using the antimalarial drug chloroquine as a model,” Dr. Noujaim said, “We have evidence that if we block that specific type of potassium channels we will be able to stop atrial fibrillation or at least reduce its occurrence.”
Earlier work by Dr. Noujaim and others, including a study reported in the journal FASEB, demonstrated that the antimalarial drug chloroquine was effective in blocking the GIRK potassium channels and suggested a new path for discovering antiarrhythmic drugs.
Dr. Noujaim continues using cellular and animal models to pinpoint how and where the chloroquine molecule interacts with the potassium channel – with the aim of discovering a “plug” that works even better than the antimalarial drug. At the same time, he has reached out to USF Health Department of Cardiovascular Sciences to begin applying the laboratory findings to the clinic.
Working with cardiologists Bengt Herweg, MD, and Dany Sayad, MD, Dr. Noujaim recently gained approval for a pilot study to enroll 40 adults without heart damage whose atrial fibrillation has persisted more than one week and less one year. The team will test the effectiveness of chloroquine in restoring and maintaining normal heart rhythm in patients with atrial fibrillation.
Dr. Noujaim came to USF in 2015 from the Molecular Cardiology Research Institute at Tufts University School of Medicine. He received his PhD in pharmacology, with distinction, from SUNY Upstate Medical University in Syracuse, NY, followed by a year of postdoctoral training there. He then completed a three-year postdoctoral fellowship, supported by the American Heart Association, and the National Institutes of Health, at the Center for Arrhythmia Research, University of Michigan, in Ann Arbor, MI.
Dr. Noujaim said he was attracted to USF by the opportunity to be part of an emerging preeminent university committed to establishing a cardiovascular institute bridging top biomedical research and clinical care.
“The opportunities that the University of South Florida is providing for scientists are equal or greater than those at any other major academic medical center,” he said. “It was also striking to me that, in a place the size of USF, the USF Health leadership is so actively engaged in research, with their own laboratories and grants. That’s not what you would see in a lot of places, and as a biomedical scientist it makes me feel that the leadership here really values research.”
Some Things You May Not Know About Dr. Noujaim:
- Born in Lebanon, he moved to the United States after graduating from high school.
- He routinely swims laps in an indoor pool.
- He enjoys experimenting with cooking, specializing in inventing new dishes by combining ingredients he finds in his refrigerator. “I’ve discovered by trial and error that no matter how bad what I cook really is, adding a tablespoon of soy sauce makes it alright,” he said.
- His first scientific experiment as a college student volunteering in Boston’s Beth Israel Deaconess Medical Center laboratory was unforgettable. He fainted while his blood was being drawn so he could use it to help study blood platelet activation and aggregation. Click on video below to find out more.
– Written by Anne Delotto Baier, Photos by Sandra C. Roa and Eric Younghans
Pioneering nanotechnology research has applications for cardiovascular disease
The founding director of the USF Health Heart Institute has a passion for innovation, translational medicine and entrepreneurship.
Samuel A. Wickline, MD, has parlayed his expertise in harnessing nanotechnology for molecular imaging and targeted treatments into an impressive $1-million portfolio of National Institutes of Health awards, multiple patents and four start-up biotechnology companies.
“We’ve developed nanostructures that can carry drugs or exist as therapeutic agents themselves against various types of inflammatory diseases, including, cancer, cardiovascular disease, arthritis and even infectious diseases like HIV,” said Dr. Wickline, who arrived at USF Health last month from the Washington University School of Medicine in St. Louis.
At Washington University, Dr. Wickline, a cardiologist, most recently was J. Russell Hornsby Professor in Biomedical Sciences and a professor of medicine with additional appointments in biomedical engineering, physics, and cell biology and physiology.
“I like the challenge of building things,” he said.
In St. Louis, he built a 29-year career as an accomplished physician-scientist keenly interested in translating basic science discoveries into practical applications to benefit patients. He served as chief of cardiology at Jewish Hospital, developed one of the first cardiac MRI training and research programs in the country, helped establish Washington University’s first graduate program in biomedical engineering, and led a university consortium that works with academic and industry partners to develop medical applications for nanotechnology.
At USF, there will be no shortage of challenging opportunities to build.
Building the USF Health Heart Institute
A major part of Dr. Wickline’s new job is helping to design, build and equip the Heart Institute. Most importantly, he will staff the state-of-the-art facility with a critical interdisciplinary mix of top biomedical scientists (including immunologists, molecular biologists, cell physiologists and genomics experts), who investigate the root causes of heart and vascular disease with the aim of finding new ways to detect, treat and prevent them. The Heart Institute will be co-located with new Morsani College of Medicine in downtown Tampa; construction on the combined facility is expected to begin later this year.
“I have been impressed by the energy and commitment here at the University of South Florida to invest substantial resources in a heart institute,” Dr. Wickline said. “I believe we have a lot to offer in terms of bench-to-bedside research that could solve some of the major cardiovascular problems” like atherosclerosis or heart failure.
“We want to put together a program that supplies the appropriate core facilities to attract the best and brightest researchers to this cardiovascular institute.”
Cardiovascular disease is the leading cause of death in the United States and worldwide, so exploring potential new treatment options is critical. One of the Heart Institute’s driving themes will be advancing concepts and findings that prove promising in the laboratory into projects commercialized for clinical use, Dr. Wickline said.
“Our goal is to make a difference in the lives of patients,” he said. “Innovation is not just about having a new idea, it’s about having a useful idea.”
Dr. Wickline also serves as associate dean for cardiovascular research and a professor of cardiovascular sciences at the Morsani College of Medicine. He holds the Tampa General Endowed Chair for Cardiovascular Research created last year with a gift from USF’s primary teaching hospital.
With Washington University colleague Hua Pan, PhD, a biomedical engineer and expert in molecular biology, Dr. Wickline is re-building his group at USF. Dr. Pan was recently recruited to USF as an assistant professor of medicine to continue her collaborations with Dr. Wickline.
Designing nanoparticles to “kill the messenger”
Dr. Wickline’s lab focuses on building nanoparticles – shaped like spheres or plates, but 10 to 50 times smaller than a red blood cell – to deliver drugs or other therapeutic agents through the bloodstream to specific cell types, or targets. These tiny carrier systems can effectively deliver a sizeable dosage directly to a targeted tissue, yet only require small amounts of the treatment in the circulation to reduce the risk of harmful side effects.
Some types of nanoparticles can carry image-enhancing agents that allow researchers to quantify where the illuminated particles travel, serving as beacons to specific molecules of interest, and enabling one to determine whether a therapeutic agent has penetrated its targeted site, Dr. Wickline said.
Dr. Wickline also is known for designing nanoparticles derived from a component of bee venom called melittin. While bee venom itself is toxic, Dr. Wickline’s laboratory has detoxified the molecule and modified its structure to produce a formula that allows the nanoparticles to carry small interfering (siRNA), also known as “silencing RNA,” or other types of synthetic DNA or RNA strand.
Among other functions, siRNA can be used to inhibit the genes that lead to the production of toxic proteins. Many in the nanotechnology research and development community are working to make siRNA treatment feasible as what Dr. Wickline calls “a message killer,” but the challenges have been daunting.
“The big challenge in the field of siRNA, and many companies have failed at this, is how to get the nanostructure to the cells so that the siRNA can do what it’s supposed – hit its target and kill the messenger — without being destroyed along the way, or having harmful side effects,” Dr. Wickline said. “We figured out how to engineer into a simple peptide all of the complex functionality that allows that to happen.”
Different targets, same delivery vehicle
In a recent series of experiments in mice, Dr. Wickline and colleagues have shown that silencing RNA messages delivered by nanoparticle to a specific type of immune cell known as a macrophage – a “big eater” of fat – actually shrinks plaques that accumulate inside the walls of the arteries during atherosclerosis, one of the main causes of cardiovascular disease. The build-up of atherosclerotic plaques with fat-laden macrophages narrows, weakens and hardens arteries, eventually reducing the amount of oxygen-rich blood delivered to vital organs.
This type of plaque-inhibiting nanotherapy could be useful in aggressive forms of atherosclerosis where patients have intractable chest pain or after an acute heart attack or stroke to prevent a secondary cardiac event, Dr. Wickline said.
In another study, Washington University School of Medicine researchers investigated the potential of the siRNA nanoparticle designed by co-investigators Dr. Pan and Dr. Wickline in treating the inflammation that may lead to osteoarthritis, a degenerative joint disease that is a major cause of disability in the aging population. The nanoparticles — injected directly into injured joints in mice to suppress the activity of the molecule NF-κB — reduced local inflammation immediately following injury and reduced the destruction of cartilage. The findings were reported September 2016 in the Proceedings of the National Academy of Sciences.
Previously, Dr. Wickline said, the Washington University group had shown that nanoparticles delivered through the bloodstream inhibited inflammation in a mouse model of rheumatoid arthritis. And, another laboratory at the University of Kentucky is studying whether locally injected siRNA nanoparticles can quell the bacterial inflammation that can lead to a serious gum disease known as periodontitis. Other collaborating labs are using these nanoparticles in pancreatic, colon, and ovarian cancers with good effects.
“The specific targets in these cases may be different, but the nice thing about this kind of delivery system for RNA interference is that the delivery agent itself, the nanostructures, are the same,” Dr. Wickline said. “All we have to do is change out a little bit of the genetic material that targets the messages and we’re set up to go after another disease. So it’s completely modular and nontoxic.”
The St. Louis-based biotechnology company Trasir Therapeutics is developing these peptide-based nanocarriers for silencing RNA to treat diseases with multiple mechanisms of inflammation. Dr. Wickline co-founded the company in 2014 and continues to serve as its chief scientific officer.
Calming the destructive cycle of inflammation
Dr. Wickline’s work is supported by several NIH RO1 grants, including one from the National Heart, Lung and Blood Institute to develop and test nanotherapies seeking to interrupt inflammatory signaling molecules and reduce the likelihood of thrombosis in acute cardiovascular syndromes.
In essence, Dr. Wickline said, he is interested in suppressing chronic inflammation, without disrupting the beneficial functions of surveillance by which the immune system recognizes and destroys invading pathogens or potential cancer cells.
“If you can inhibit the ongoing inflammation associated with (inappropriate) immune system response, you inhibit the positive feedback cycle of more inflammation, more plaques, more damage and more danger,” he said. “If you can cool off inflammation by using a message killer that says (to macrophages) ‘don’t come here, don’t eat fat, don’t make a blood clot’ – that’s what we think could be a game changer.”
Another NIH grant has funded collaborative work to develop an image-based nanoparticle that detects where in a compromised blood vessel too much blood clotting (hypercoagulation) occurs, and delivers potent anti-clotting agent only to that site. Formation of abnormal blood clots can trigger a heart attack when a clot blocks an artery that leads to heart muscle, or a stroke when a clot obstructs an artery supplying blood to the brain.
Because this site-specific nanotherapy targets only areas of active clotting, it may provide a safer, more effective approach against cardiac conditions like atrial fibrillation and acute heart attack than existing anticoagulant drugs such as warfarin and newer blood thinners like Xarelto® (rivaroxoban) or Eliquis® (apixiban), all which work systemically and come with raised risk for serious bleeding, Dr. Wickline said.
In a study published last year in the journal Arteriosclerosis, Thrombosis, and Vascular Biology, Dr. Wickline and colleagues found that nanoparticles delivering a potent inhibitor of thrombin, a coagulant protein in blood that plays a role in inflammation, not only reduced clotting risk but also rapidly healed blood vessel endothelial barriers damaged during plaque growth.
The preclinical work showed the experimental treatment “is actually an anti-atherosclerotic drug as well as an anti-clotting drug, so there are many potential applications,” Dr. Wickline said.
Dr. Wickline received his MD degree from the University of Hawaii School of Medicine. He completed a residency in internal medicine, followed by clinical and research fellowships in cardiology at Barnes Hospital and Washington University, where he joined the medical school faculty in 1987.
He has authored more than 300 peer-reviewed papers and holds numerous U.S. patents. Dr. Wickline is a fellow of the American College of Cardiology and the American Heart Association, and a 2014 recipient of the Washington University Chancellor’s Award for Innovation and Entrepreneurship.
Some things you may not know about Dr. Wickline
- His first scientific experiment was conducted at age 21, before entering medical school, when he worked in a research laboratory in Hawaii run by a cardiovascular surgeon interested in techniques to best support the heart during cardiopulmonary bypass surgery. Dr. Wickline figured out why one particular way of perfusing blood through the heart pump machine could dangerously compromise oxygenated blood flow to the brain. The results were published in the Annals of Thoracic Surgery. One of Dr. Wickline’s first studies in medical school, published in the prestigious journal Circulation, described a method for determining the size of a heart attack by recording electrical signals, called vector cardiograms.
- He grew up in St. Petersburg, Fla., and did some trick water skiing as a teen. “I learned how to ski backwards.” After being “landlocked” in Missouri for 37 years following medical school in Hawaii, he said he’s glad for the opportunity to get back to get back to the beach and water sports.
- He likes to play the ukulele.
– Story by Anne Delotto Baier, photos and video by Sandra C. Roa