Paari Dominic, MD, PhD
David Krzywanski, PhD
“Nicotinamide nucleotide transhydrogenase regulates redox balance in atherosclerosis.”
Atherosclerosis is one of the leading causes of mortality in the United States. Effective therapeutic options for the treatment and prevention of atherosclerosis are focused on lowering circulating lipids. However, reactive oxygen species have been shown to play a critical role in atherosclerotic plaque development, yet clinical trials utilizing antioxidant therapies have been unsuccessful. We propose that nicotinamide nucleotide transhydrogenase (NNT) significantly impacts the development of atherosclerosis by regulating mitochondrial ROS production and preserving normal endothelial cell function. Our proposed studies will be the first to investigate how NNT expression and activity are impacted by atherosclerosis in human cells and specifically how endothelial NNT contributes to the regulation of plaque development. Results from these studies will highlight the potential of NNT as a novel therapeutic target in the treatment of atherosclerosis.
Hugh Nam, PhD
“Neurogranin Regulation in Cardiovascular Disease”
The goal of this project is to study the role of neurogranin in regulating peripheral nitric oxide and cardiac function. We will characterize for the first time how the neurogranin pathway in the endothelium could regulate the nitric oxide production and cardiovascular function.
Manikandan Panchatcharam, PhD
“Oxidative Stress Mediated Myocardial Lipid Dysfunction”
Acute myocardial infarction and the resulting ischemic heart disease are the single most prevalent cause of morbidity and mortality in the western world. While the bioactive glycerophospholipid lysophosphatidic acid (LPA) plays a well-known role in atherosclerotic disease, its role in myocardial function remains virtually unexplored. Following acute myocardial infarction, serum LPA concentration rises by six-fold over control subjects, suggesting LPA may contribute to the pathogenesis of myocardial infarction. Our preliminary data demonstrate that enhanced cardiac LPA signaling in vivo is due to lack of cardiac lipid phosphate phosphatase-3 (LPP3; an enzyme that breaks down LPA) which leads to severe mitochondrial dysfunction and increased mortality due to myocardial dysfunction. However, the mechanisms regulating LPA signaling in the myocardium remain unknown. LPA production involves hydrolysis of lysophosphatidylcholine by the secreted enzyme autotaxin. In contrast, LPP3 catalyzes LPA dephosphorylation to generate lipid products that are not receptor active. The steady-state of local and circulating LPA is balanced between these opposing pathways of LPA synthesis and degradation. In this application, we present the first evidence that cardiac ischemia/reperfusion (I/R) injury enhances myocardial autotaxin levels and decreases myocardial LPP3 expression, leading to increased serum LPA levels. This data represents the first description of autotaxin and LPP3 regulation in I/R injury in any model system to date. Excess generation of reactive oxygen species plays a significant role in the cellular response to I/R injury, affecting the cell viability and altering the expression of a variety of genes which contribute to the cellular response to I/R. Upon reperfusion, reactive oxygen species production arises as a burst of superoxide from mitochondria, as has been corroborated in a range of tissues and types of I/R injury. Data from our laboratory and others have shown that blocking mitochondrial superoxide reduces complications of post-myocardial infarction. Thus, we hypothesize that I/R injury alters autotaxin and LPP3 expression through mitochondrial superoxide production to drive LPA signaling and cardiomyocyte dysfunction. To address this hypothesis, we propose the following aims. Specific aim 1 will assess the role of myocardial superoxide production in autotaxin expression and LPA production in I/R injury metabolism. Specific aim 2 will determine the role of mitochondrial superoxide production in LPP3 depletion and LPA production in I/R injury. We could identify whether modulation of cellular versus mitochondrial antioxidant status confers a differential protective effect in I/R injury models. These studies will not only extend our understanding of the fundamental mechanism by which oxidative stress regulates cardiac lipid signaling but also identify novel targets for future clinical interventions.
Diana Cruz-Topete, PhD
"Redox State and Sex Differences in Cardiac miR-34a Expression"
Myocardial infarction (MI) is a leading cause of death and disability in the United States. Growing experimental evidence has demonstrated that microRNA (miRNA) regulation of gene expression after MI determines the progression to heart failure by triggering pathways involved in cardiac cell death and regeneration. In this project, we aim to investigate the sex-specific effects of imbalances in the redox environment (low levels of the primary antioxidant glutathione (GSH)) on miR-34a expression and regulation of the cardioprotective Sirt1 downstream signaling in MI. miR-34a was selected for this study due to its role in regulating cell death and its high expression levels in the heart during cardiac stress. Our goals are 1) to investigate the effects of low GSH on miR-34a levels and its downstream signaling in MI, and 2) to test if the mechanisms controlling these effects are dependent on the sex hormones estrogen (E2) and testosterone (T). We anticipate that our findings will uncover critical differences in how the interplay between sex hormones and the reductive and oxidant cellular environment drive the expression of miR-34a and its deleterious downstream effects in the heart following a heart attack.
Sumitra Miriyala, PhD
“AIFM2: A novel mediator of heart failure development and progression”
Accumulated evidence indicates that oxidative stress in mitochondria plays a vital role in cardiac injury, but how mitochondrial redox mechanisms are involved in cardiac dysfunction remains unclear. A highly toxic aldehyde formed by reactive oxygen species (ROS) is 4-hydroxy-2-nonenal (HNE) through lipid peroxidation following myocardial ischemia/reperfusion (I/R) injury. HNE mediates necrosis, apoptosis, and autophagy within the area rendered ischemic over the first 6 to 24 hours. Several lines of evidence suggest that apoptosis-inducing factor mitochondrion-associated protein (AIFm2), a p53 target gene, a redox-responsive protein that resides in mitochondria and plays a central role in the caspase-independent cell death pathway. We have demonstrated that HNE adduction of AIFm2 shifts the function of AIFm2 from an NADH oxidoreductase to a pro-apoptotic protein. However, the molecular mechanisms involved in AIFm2 translocation that mediates cardiac injury remain unknown. In this application, we present the first evidence that HNE upregulation following cardiac I/R injury activates the translocation of AIFm2 from the mitochondria to the nucleus. Our preliminary data using Tandem mass spectrometric analysis (MS/MS) of the native and oxidatively modified AIFm2 suggest that His174 and Cys 187 are the potential targets for HNE-mediated translocation. Therefore, we hypothesize that HNE adduction to AIFm2 mediates mitochondrial stress signaling through translocation of AIFm2 from mitochondria to the nucleus and contributes to the pathogenesis of heart failure following I/R injury. To address this hypothesis, we propose the following aims. Specific Aim #1: Determine the binding motif that mediates the translocation of AIFm2 from mitochondria following oxidative stress. Specific Aim # 2: Determine the cytosolic transport protein involved in the translocation of the HNE-adducted AIFm2 complex from the cytosol to the nucleus following cardiac injury. These studies will not only extend our understanding of the fundamental mechanism by which these protein adducts are regulated in the myocardium but will also provide a solid rationale towards the specific putative binding sites available on AIFm2 in regulating NADH oxidoreductase activity during I/R injury-induced mitochondrial oxidative stress.
Christopher Pattillo, PhD
“Cellular Reductive State Regulates Arteriogenesis”
The gradual occlusion of blood vessels such as that reported in peripheral artery disease is increasing in frequency, due to a variety of risk factors including several cardiovascular pathologies such as diabetes, obesity, etc. This project addresses the novel relationship between the antioxidant glutathione, its oxidized form (GSSG) and the protein modifications (glutathionylation) that influence the progression of arteriogenesis following the occlusion of conduit arteries. The proposed research will uncover the underlying mechanisms by which levels of glutathione and corresponding protein modification can be manipulated to enhance the progression of arteriogenesis following ischemic insult; providing potential avenues to the development of novel vascular therapeutics.