Hariom Yadav, PhD, of the USF Center for Microbiome Research, and Ji Li, PhD, of the USF Health Heart Institute  — Photos by Allison Long, USF Health Communications

Two researchers from the USF Health Morsani College of Medicine have received Florida Department of Health (FDOH) grants to help advance discoveries in Alzheimer’s disease and in tobacco-related heart disease.

Hariom Yadav, PhD, an associate professor of neurosurgery and brain repair and director of the USF Center for Microbiome Research, was awarded total expected funds of $743,661 over four years from the FDOH Ed and Ethel Moore Alzheimer’s Disease Research Program. The multidisciplinary consortium project is titled “Role of Microbiome in the Aging of Gut and Brain in Floridian Older Adults.”

Researchers at USF and several other sites across Florida will study how diet affects the gut and oral microbiomes linked to brain health in adults ages 60 and older. Age is a key risk factor for Alzheimer’s disease and related dementias (ADRD); no effective treatment exists, and early risk detection remains a challenge. The FDOH-supported research seeks to determine whether unique microbiome signatures can differentiate older adults suffering cognitive decline and ADRD from their healthy counterparts and predict disease progression. The study will also examine whether abnormalities in microbe-derived metabolites, excessive gut “leakiness” and inflammation definitively contribute to cognitive impairment and ADRD—with the ultimate aim of identifying measures to prevent or delay these devastating conditions.

Ji Li, PhD, professor of surgery and a member of the USF Health Heart Institute, was awarded total expected funds of $583,200 over three years from the FDOH James and Esther King Biomedical Research Program. The grant is titled “Sirtuin 1 and Cardiovascular Impairment by Cigarette Smoking.”

Dr. Li’s laboratory has shown that the anti-aging protein sirtuin 1 (SIRT1) plays a role in cardiovascular disease development, and emerging evidence suggests that SIRT1 is a component of signaling pathways that allow cells to sense and react to cigarette smoking. The FDOH-supported preclinical project will test whether and how SIRT1 signaling helps control the harmful effects of cigarette smoking on the heart’s pumping function in hypertension (abnormally high blood pressure). The study’s outcome could lead to the discovery of SIRT1 agonists or other drugs that may reduce damage and death from hypertensive heart disease associated with chronic smoking.

USF Health research discovers APC limits heart damage by preventing excessive loss of endothelial protein C receptors on the cardiac muscle cell membrane

TAMPA, Fla. (Jan. 31, 2022) — A University of South Florida Health (USF Health) preclinical study offers molecular insight into how activated protein C (APC) may improve aging patients’ tolerance to reperfusion injury – a potentially adverse effect of treatment for ischemic heart disease.

The research, published online Dec. 21 in Circulation Research, suggests that drugs derived from APC may limit ischemia and reperfusion-induced heart damage (reperfusion injury for short) and thereby help preserve cardiac function in older hearts.

Advanced age is a major risk factor for ischemic heart disease, often caused by a buildup of plaques in coronary arteries that narrows the vessels and restricts the supply of oxygenated blood to the heart. This “hardening of the arteries” can eventually trigger a heart attack.

Blood thinners, clot-buster medications, and other drugs, as well as procedures such as coronary artery bypass surgery and balloon angioplasty, are commonly used to restore blood flow to oxygen-starved (ischemic) heart muscle tissue. Paradoxically, especially in older patients, these necessary revascularization treatments can worsen cellular dysfunction and death around the site already damaged by a heart attack, or coronary artery disease. No effective treatments currently exist to prevent age-related reperfusion injury.

“Our research focuses on trying to determine why older hearts are at greater risk for reperfusion injury than younger hearts,” said lead author Di Ren, PhD, a research associate in the Department of Surgery, USF Health Morsani College of Medicine. “Our goal is to find targeted therapeutic strategies to help older people improve their resistance to the pathological condition of ischemia and reperfusion stress.”

“The preliminary evidence in this paper suggests that treatment with activated protein C has the potential to strengthen the cardiac tolerance of aging patients to reperfusion injury from surgery, minimally invasive procedures, or drugs, and (thereby) increase heart attack prevention or survival,” said the study’s principal investigator Ji Li, PhD, a professor of surgery at the USF Health Heart Institute.

Di Ren, PhD, a research associate in the USF Health Department of Sugery, was the Circulation Research paper’s lead author.

APC, a protein circulating in blood, has both anticoagulant (blood clot prevention) and anti-inflammatory functions that can help protect cells from disease and injury. Endothelial protein C receptor (EPCR) – located both on cells lining blood vessels and on the surface of cell membranes, including heart muscle cells – is associated with increased APC production and regulates APC’s subsequent cell signaling (or cell communication).

In this mouse model study, the researchers analyzed how APC exerts cardiac protection during ischemia and reperfusion. The groups of mice observed included young and old “wild-type” mice with all their genes intact, and young “knock-in” EPCR R84A/R84A mice genetically modified to make their EPCR receptors incapable of interacting with the APC protein as well as their wild-type littermates without the EPCR R84A/R84A mutation.

Naturally occurring APC or one of two laboratory-engineered APC derivatives were administered to the mice with heart attack-induced ischemia before reperfusion. One derivative (compound APC-2Cys) selectively activated a signaling pathway to promote cell protection without inhibiting blood clotting (coagulation). The other derivative (compound APC-E170A) selectively triggered a signaling pathway promoting only anticoagulation.

Ji Li, PhD, a professor of surgery at the USF Health Heart Institute, was the study’s principal investigator. — Photo by Allison Long, USF Health Communications

Among the team’s key preclinical findings:

— The stress of Ischemia and reperfusion injury induced “shedding” of EPCRs in young and old wild-type mice – that is, a greater number of these receptors were cut from the heart muscle cell membrane and then moved into the bloodstream. This EPCR shortage (deficiency) in the heart can impair activated protein C signaling critical for favorably regulating energy metabolism and anti-inflammatory responses, preventing cell death, and stimulating other activities needed to protect cardiac muscle cells.

— While the hearts of the old and young wild-type mice both showed EPCR shedding, older hearts experienced a more severe EPCR deficiency and decline in APC signaling activity in response to reperfusion injury. No APC signaling was detected in the EPCRR84A/R84A mice, because APC was blocked from binding to the cell membrane receptor.

— Administering APC or its derivatives helped reduce heart damage inflicted by ischemia and reperfusion, particularly in the old mice. Digging deeper, the researchers discovered that by stabilizing (maintaining) EPCR on the cardiac cell membrane, APC strengthens the aging heart’s resistance both to heart attack-related ischemia and to injury associated with restoring coronary artery blood flow.

— Furthermore, APC and the APC-2Cys signaling derivative, but not the APC-E170A anticoagulant-selective signaling (a potential bleeding risk), helped preserve cardiac function. All cardioprotective effects of APC were weaker in young mice in which EPCR was eliminated; their hearts looked and performed like that of older mice.

— The researchers detailed how APC treatments improve cardiac function by regulating both acute (short-term) and chronic (longer-term) metabolic pathways. They demonstrated that enzyme AMPK (AMP-activated protein kinase) mediates an acute adaptive response to cardiac stress immediately following heart attack, while enzyme AKT (protein kinase B) regulates chronic metabolic adjustments to reperfusion stress over time. APC treatment led to better enzyme activity and more efficient energy balance needed to contract cardiac muscle cells and pump blood from the heart to the rest of the body.

“APC is beneficial for ischemia-reperfusion injury both in the acute and chronic stages, so appropriate APC derivatives might be used both as preventive and therapeutic drugs,” Dr. Li said.

Activated protein C (green) interacts with endothelial protein C receptors (red) to form APC/EPCR binding complex (yellow) and stabilize subsequent EPCR-regulated signaling in heart muscle cells under hypoxia-reperfusion stress.  Image courtesy of Ji Li Laboratory, USF Health; first appeared in Circulation Research; DOI: 10.1161/CIRCRESAHA.121.319044

The USF Health Heart Institute researchers collaborated with scientists from Scripps Research Institute, McMaster University (Canada), and the Oklahoma Medical Research Foundation.

Their work was funded by grants from the National Institutes of Health, both the NIGMS and NHLBI.

USF Health preclinical study suggests boosting cardiac SIRT1/SIRT3 levels in older heart attack patients may help protect against ischemia-reperfusion injury

Tampa, FL (Aug. 20, 2021) — Sirtuins are a family of anti-aging proteins that help regulate cellular lifespan, metabolism, and resistance to stress. The potential protective effect of these sirtuin enzymes in age-related diseases, including cardiovascular diseases, remains an area of intense investigation.

Principal investigator Ji Li, PhD, is a professor of surgery and member of the USF Health Heart Institute at the USF Health Morsani College of Medicine. | Photo by Allison Long, USF Health Communications

Now, a new preclinical study led by University of South Florida Health (USF Health) researchers has determined that sirtuin 1 (SIRT1) and sirtuin 3 (SIRT3) levels decline in aging hearts, disrupting the ability of cardiac muscle cells (cardiomyocytes) to contract in response to ischemia-reperfusion injury (also known as reperfusion injury). Furthermore, age-related SIRT1 and SIRT3 deficiency can impair cardiac function by altering mitochondrial dynamics, which play an important role in metabolic health and inflammatory response, the researchers report.

The findings were published online July 3 in Aging Cell.

“We discovered that age-related changes in mitochondrial dynamics are caused by SIRT1/SIRT3 deficiency, specifically in the cardiomyocytes,” said principal investigator Ji Li, PhD, professor of surgery in the USF Health Morsani College of Medicine. “You need a strong presence of SIRT1 and SIRT3 to keep mitochondrial dynamics healthy in the heart. Otherwise, the heart’s pumping function becomes weak.”

Diastolic functions assessment of a mouse heart imaged with ultrasound echocardiography | Photo by Allison Long, USF Health Communications

Mitochondria produce the energy needed to drive nearly all processes in living cells. Cardiac muscle cells contain more mitochondria than any other cells, because the heart needs large amounts of energy to constantly pump blood throughout the body. Stabile mitochondrial dynamics maintain a healthy balance between the constant division (fission) and merging (fusion) of mitochondria and help ensure the quality of these specialized structures known as the “powerhouse” of the cell.

Reperfusion, a common treatment following acute heart attack, restores blood flow (and thus oxygen) to a region of the heart damaged by a blood clot blocking the coronary artery. Paradoxically, in some patients this necessary revascularization procedure triggers further injury to heart muscle tissue surrounding the initial heart attack site. No effective therapies currently exist to prevent reperfusion injury.

Research associate Di Ren, PhD (left) works with the heart perfusing system in the Department of Surgery physiology laboratory as USF undergraduate student Julia Fedorova watches. | Photo by Allison Long, USF Health Communications

To help analyze the response of cardiac mitochondria to ischemia-reperfusion stress, the USF Health researchers deleted SIRT1 or SIRT3 in cardiac muscle cells of mouse hearts, and examined the mitochondrial response to ischemic stress by restricted blood flow. They found that the mitochondria in mouse hearts lacking cardiomyocyte SIRT3 were more vulnerable to reperfusion stress than the mouse hearts with SIRT3 intact. The cardiac mitochondrial dynamics (including shape, size, and structure of mitochondria) in these knockout mice physiologically resembled that of aged wildtype (normal) mice retaining cardiac SIRT3.

Furthermore, the young mice with SIRT1 or SIRT3 removed had measurably weaker cardiomyocyte contractions and exhibited aging-like heart dysfunction when ischemia-reperfusion stress was introduced. In essence, without SIRT1/SIRT3 the hearts of these otherwise healthy young mice looked and behaved like old hearts.

“We started this study trying to understand why older people have higher incidences of heart attacks than younger people, and why they die more often even if they receive maximum treatment. Younger people are much more likely to recover from heart attacks and less likely to suffer from ischemia-reperfusion injury,” said Dr. Li, a member of the USF Health Heart Institute. “Our research suggests that one reason could be that both SIRT1 and SIRT3 are downregulated with aging. Younger people have higher levels of these proteins needed to make mitochondrial dynamics healthier.”

Dr. Li’s research team (pictured here) focuses on understanding the molecular mechanisms of coronary artery disease, the most common cause of age-related heart disease. | Photo by Allison Long, USF Health Communications

The study also suggests that, before surgically opening blocked coronary arteries to restore blood flow in older patients, administering a treatment to “rescue” (improve) their diminished SIRT1/ SIRT3 levels may increase tolerance to cardiac muscle reperfusion stress, thereby reducing heart attack complications and deaths, Dr. Li said. Such a cardioprotective treatment might apply a genetic approach to increase SIRT1/SIRT3 production, or an agonist (drug) to activate SIRT1/ SIRT3, he added.

If their mouse model findings translate to human hearts, Dr. Li’s group wants to work with companies interested in developing and testing SIRT1/SIRT3 activators to mitigate heart attack-related reperfusion injury.

“Our ultimate goal is to identify ideal targets for the treatment of heart attack, especially in older patients,” said Dr. Li, whose research is supported by grants from the National Heart, Lung, and Blood Institute, the National Institute on Aging, and the National Institute of General Medical Sciences.