Basic Research
Biology of Myocardial Remodeling and Failure
Dr. Colucci’s laboratory is studying the mechanisms that mediate myocardial remodeling and failure. A major focus is to understand the roles of reactive oxygen species in mediating myocyte phenotype via their effects on cell growth, gene expression and apoptosis. Recently, they have demonstrated that oxidative stress, mechanical deformation and catecholamines can induce both hypertrophic growth and apoptosis in cardiac myocytes. Parallel studies are being performed in vitro and in vivo using cultured cardiac myocytes and genetically-modified mice, respectively in order to determine the relationship between the molecular/cellular events involved in cardiac remodeling and alterations in physiological function that can be assessed at the single myocyte and whole heart level in transgenic and knock-out mice.
Molecular Genetics Unit
Led by Vassillis Zannis, PhD, the laboratory focuses on determining the role apolipoproteins and lipoproteins play in relation to atherosclerosis and Alzheimer’s disease. Investigations in Dr. Zannis’ laboratory are focused in two directions. One is apolipoprotein gene regulation in vivo using antisense and transgenic methodologies, as well as adenovirus-mediated gene transfer. The research focuses on the role of hormone nuclear receptors and factors bound to the apoCIII enhancer and the proximal promoters on the transcriptional regulation of the apoA-I, apoCIII, and apoA-IV gene cluster. The other direction is the elucidation of the structure-function relationship of human apoA-I and apoE and their relevance to cardiovascular disease and Alzheimer’s disease, respectively, using in vitro mutagenesis, transgenic, and gene transfer methodologies. Pertinent questions are the role of apoA-I in the biogenesis of HDL and the reverse transport of cholesterol, the role of apoE in cholesterol and triglyceride homeostasis in the circulation, the role of apoE in lipid homeostasis in the brain, and the pathogenesis of Alzheimer’s disease.
Molecular Genetics of Hypertension and Cardiovascular Disease
Current investigations in the laboratory of Victoria Herrera, MD are focused on the exacerbation of atherosclerosis by hypertension. In particular, Dr. Herrera is dissecting the pathways involved in vulnerable plaque development and destabilization through an integrated approach using histopathology, transcriptomics, proteomics, in vivo pathway testing. In addition, she is involved in the identification of genetic modifiers of hyperlipidemia relevant to gender and genetic background differences through total genome search for putative quantitative trait loci in F2 intercross hybrids and transcription profiling, and the identification of the pathways of salt sensitivity through differential transcription profiling of strategic inbred transgenic rats. The studies’ long-term goal is focused on the development of understanding, at the molecular level, the underlying differential susceptibility to coronary lesion development through gene expression profiling. Ongoing investigations under the leadership of Nelson Ruiz-Opazo, PhD, include the identification f hypertension susceptibility genes in animal models of this disease, currently focusing on the Dahl S/Dahl R hypertensive rat model and in humans. This research has led to the identification of susceptibility genes for hypertension target organ-complications like hypertensive renal disease and cardiac hypertrophy. In addition, both in vitro and in vivo functional analysis of novel AngII, AVP, and ET-1 receptors, including the AngII/AVP dual receptor and the ET-1/AngII dual receptor, have been initiated. Dr. Ruiz-Opazo has begun studies on the determinants of learning and memory in the Dahl S/Dahl R rat model.
Oxidative Protein Modifications in Diabetes, Hypertension, and Atherosclerosis
The Vascular Biology Unit led by Dr. Richard Cohen seeks to understand why oxidants impair function of diseased arteries. His group has found that in diabetes, hypertension, and atherosclerosis, the vasodilator, nitric oxide is inactivated by superoxide, an oxidant produced in diseased blood vessels. As a result of this reaction an even more potent oxidant, peroxynitrite, is formed. Peroxynitrite can be blamed for inactivation of important proteins that normally are responsible for vasodilation. These include the enzymes that make the vasodilators, nitric oxide and prostacyclin, enzymes that scavenge free radicals, and an ion transporter responsible for lowering calcium levels in cells. As part of the new Cardiovascular Proteomics Center, Dr. Cohen and his group are identifying chemical modifications of proteins formed by peroxynitrite that may serve as better markers for disease severity. They have already found such markers in diseased human arteries.
Molecular Genetics of Hypertension
Haralambos Gavras, M.D., is the Director of the Specialized Center of Research (SCOR) on the Molecular Genetics of Hypertension, supported by the NIH. The SCOR comprises one clinical and two basic research projects concerned with various aspects of Genetic Epidemiology, population studies of association and linkage of gene polymorphisms with hypertension or hypotension, as well as studies in animal models of cardiovascular diseases using genetically engineered or inbred animals with alterations in target genes. This research is conducted in collaboration with a number of scientists from various fields, including Lindsay Farrer, Ph.D., a genetic epidemiologist; Clinton Baldwin, Ph.D., a molecular genetcist; Irene Gavras, M.D., a clinical hypertension specialist; Margaret Bresnahan, DSc., a biochemist; Ekaterina Kintsurashvili, Ph.D., a molecular biologist; Faina Schwartz, Ph.D., a molecular biologist, all from the Boston University School of Medicine; as well as Beverly Paigen, Ph.D., and Gary Churchill, both mouse geneticists from the Jackson Laboratories, Bar Harbor, Maine. In parallel, Dr. Gavras is pursuing his research on the pathophysiology and treatment of hypertension and congestive heart failure.
Pathophysiology and Treatment of Hypertension and Heart Failure
The Hypertension Section under Dr. Haralambos Gavras, M.D. has a long-standing interest in the neurohormonal aspects of the pathophysiology and treatment of hypertension and heart failure. The Section’s investigators have conducted experimental and clinical studies dissecting the role of various components of the renin-angiotensin system, the sympathetic nervous system, vasopressin, bradykinin, using methodologies ranging from genetic engineering and gene treatment in animals to specific receptor antagonists and inhibitors in animals and humans. These studies, supported by R01 grants from the NIH, have led to several therapeutic applications, including the introduction of angiotensin-converting enzyme inhibition and angiotensin receptor blockade in the treatment of hypertension and heart failure.
Lipoproteins and Atherosclerosis
Dr. Donald Small, G. Graham Shipley, Ph. D., D.Sc., a professor of biophysics and biochemistry, David Atkinson, Ph. D., a professor of biophysics and a research professor of biochemistry, and James Hamilton, Ph.D., a professor of biophysics and a research instructor of biochemistry, study the physical state and molecular interactions of proteins and lipids in living systems to learn how physical state and metabolism affect one another. This work forms a major research area of the program project entitled, “Lipid Physical Chemistry in Biology and Pathology,” directed by Dr. Atkinson. The research includes investigation of the interactions between plasma lipoproteins and arterial cells and the mechanisms determining the deposition and mobilization of lipids from arterial tissue. The size and structure of lipoproteins can be revealed by complex biophysical analysis; molecular biologic techniques in combination with biophysical analysis allow investigators to sequence the proteins and observe how they are folded. The assembly of nascent apoB containing lipoproteins is also under study.
R. Andrew Zoeller Jr., Ph.D., an assistant professor of biophysics, biochemistry and medicine, and Christopher Akey, Ph.D., an assistant professor of biophysics, study fundamental problems relating to the effects of how genetic mutations in lipid genes produce disease and how complex cellular machinery such as the nuclear pore and nuclear spindle are organized.
Human Genome Analysis, Molecular Genetics, and Genetic Engineering
Dr. Cantor’s research is focused on identifying biological problems that are resistant to conventional analytical approaches and then developing new methodologies or techniques for solving these problems. His laboratory has developed methods for separating large DNA molecules, for studying structural relationships in complex assemblies of proteins and nucleic acids, and for sensitive detection of proteins and nucleic acids in a variety of settings. His current interests include the development of new methods for more accurate gene expression analysis, for faster DNA sequencing, and the development of new variations and analogs of the polymerase chain reaction. He is also interested in exploring the possible use of biological molecules for applications in nanoengineering and microrobotics in collaboration with James Collins, and in develop detection schemes for specific single molecules.
Ion Channel Group
Dr.Victoria M.Bolotina’s Ion Channel Group is a part of Vascular Biology Unit headed by Dr. Richard A.Cohen. Dr.Bolotina’s long term goal is to define the role of different ion channels in Ca2+ influx and regulation of physiological and pathological function of smooth muscle cells, cardiac myocytes, platelets and T-lymphocytes. The range of ion channels includes those directly mediating Ca2+ influx (voltage-gated Ca2+ channels and store-operated cation channels), and channels that regulate membrane potential (Ca2+-dependent potassium and chloride channels, delayed rectifier potassium channels, and different types of nonselective cation channels). A variety of techniques (including patch-clamp, high resolution confocal and deconvolution fluorescence imaging, molecular and biochemical approaches) allow us to address many unique questions, and to study major physiological processes at the level of single channel and whole-cell currents, regulation of membrane potential, cation influx, intracellular calcium (both in cytoplasm and in calcium stores), regulation of expression and activity of different elements of the major Ca2+ signaling cascades. All these processes are related to physiological function of normal and diseased blood vessels by measuring corresponding changes in their tension. Such multi-level experimental approach allowed Dr.Victoria M.Bolotina to propose novel ion channel-mediated pathways for regulation of vascular tone by agonists and nitric oxide. Recently this team found and described store-operated cation channels that are responsible for agonist-induced calcium influx and smooth muscle cell contraction, and proposed a novel molecular mechanism for the mysterious store-operated Ca2+ influx pathway. They introduced Ca2+-independent phospholipase A2 as a new molecular determinant in ion channel regulation, Ca2+ signaling and vascular contraction, and unveiled a novel signaling cascade that starts from production of calcium influx factor (CIF) following depletion of intracellular Ca2+ stores, which displaces inhibitory calmodulin from iPLA2, leads to its activation and production of lysophospholipids, that in turn activate specific store-operated Ca2+-conducting channels and Ca2+ influx. They also demonstrated that by activating the sarcoplasmic-endoplasmic reticulum calcium ATPase, and refilling intracellular calcium stores, nitric oxide inhibits these store-operated channels, calcium influx, and contraction which results in smooth muscle cell relaxation. The same mechanism of the store-operated Ca2+ influx pathway has also been recently described by this research team in platelets and T-lymphocytes, as well as other nonexcitable cells. Presently, the studies are on the way to determin the molecular identity of mysterious CIF (its biochemical purification and analysis) and store-operated channels (transgenic mice models and other molecular techniques), and to colocalize all the major parts of the store-operated signaling cascade within the restricted areas in the proximity of the plasma membrane.
