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 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.
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.
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.
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.
Dr. Katya Ravid is currently conducting investigations in the area of blood and vascular pathologies. The cells of all blood lineages arise from pluripotent hematopoietic stem cells that reside in the marrow. The bone marrow also contains stem cells of other lineages, including fat, vascular etc. Our research is focused on two interrelated projects that bear on mechanisms associated with the development of blood and vascular pathologies: (1) Studies in the lab center on molecular mechanisms involved in cell cycle control during the development of bone marrow megakaryocytes into platelets, a process that includes cellular polyploidization prior to platelet fragmentation. We also identified mechanisms of polyploidy in vascular smooth muscle cells, and found that the degree of polyploidy serves as an excellent biomarker for aging; (2) Ongoing studies explore the role of vascular and bone marrow cell (mesenchymal stem cells) adenosine receptors in tissue regeneration, and transcriptional mechanisms involved. Transgenic and knockout mouse models are used to assist in exploring mechanisms in vivo.
For a more detailed account of Dr. Ravid’s research, expertise, publications and lab members, please visit:
Run by Dr. Kathleeen Morgan, the Morgan lab works at the intersection of signaling pathways and the cytoskeleton of the contractile vascular smooth muscle cell. We have demonstrated that the nonmuscle cortical cytoskeleton and the adhesion plaques attached to it undergo dynamic rearrangements during stimulus-induced alterations in vascular tone.
Recently we have become especially interested in the possible role of the vascular cytoskeleton, and its connection to matrix proteins through integrins, in the determination of known aging-associated increases aortic stiffness. Aging-associated aortic stiffness is known to be an independent and early predictor for adverse cardiovascular outcomes. We are currently testing the idea that cytoskeletal protein interactions may offer novel therapeutic targets for the regulation of aortic stiffness.
The lab of Dr. Vassilis Zannis conducts research in areas that include:
- Structure and functions and regulation of expression of the human apolipoproteins with emphasis on apoA-I and apoE
- Roles of apoA-I and apoE in cholesterol and triglyceride homeostasis and the biogenesis of HDL
- Role of apoE in Alzheimer’s disease
- Interactions of apoA-I and apoE containing HDL in the arterial wall and in the brain pertinent to protection from atherosclerosis and Alzheimer’s disease.
HDL is synthesized and catabolized through a complex pathway that involves apoA-I, plasma enzymes, lipid transfer proteins, cell receptors and membrane-bound proteins. The pathway of biogenesis of HDL is being probed currently by adenovirus mediated gene transfer of WT and mutant forms of apoA-I. Some mutations disrupt the pathway and generate aberrant phenotypes. Phenotypic markers that indicate defects in the HDL biogenesis include low HDL and apoA-I levels, presence of preβ HDL particles, presence of fast migrating αHDL particles, low number of spherical HDL, presence of discoidal particles, dyslipidemia characterized by high triglyceride and/or cholesterol levels, presence of apoA-I in the VLDL/IDL region. These parameters may be used as markers for diagnosis, prognosis and treatment of low HDL syndromes. In humans, apoE has dual functionality. It clears triglyceride rich lipoproteins via the LDL receptor and participates in the formation of apoE containing HDL (HDL-E). Some apoE mutations are detrimental and may affect either of the two functions. Few other mutations in the 261-269 region were found beneficial due to their ability to promote formation of spherical apoE contained HDL without induction of hypertriglyceridemia. Ongoing research explores the effects of HDL containing WT and variant forms of apoA-I and apoE on the functions of arterial wall cells and the underlying mechanisms that are relevant to atheroprotection.
Dr. Joyce Wong‘s laboratory conducts studies that pertain to cardiovascular disease, the leading cause of death in the United States. While there have been tremendous advances in the development of procedures to remove blockages in blood vessels (e.g. angioplasty, bypass surgery, and stent implantation), unfortunately a large number of these cases result in reformation of the blockage – a process known as restenosis. A major cause of restenosis is migration and growth of vascular smooth muscle cells (VSMCs). A major effort in the laboratory aims to understand how bioscaffold properties (e.g. structural, mechanical, and chemical) affect VSMC migration and growth. By systematically varying these bioscaffold properties, we hope to gain engineering design principles for the fabrication of not only devices to treat restenosis but also tissue-engineered blood vessels. Our laboratory fosters an interdisciplinary environment that integrates materials science and engineering, cell biology, biophysics, colloid and interface science, and micro- and nano-technologies.
The research of Dr. David Atkinson focuses on the molecular details of the structure, stability and dynamic properties of the plasma lipoproteins and their constituent apolipoproteins, particularly high density (HDL, “Good Cholesterol”) and low density (LDL, “Bad Cholesterol”). The mechanisms of the well-documented anti-atherogenic role of HDL are clearly related to its involvement in the pathways of reverse cholesterol transport (RCT). A primary focus is on the structure and molecular properties of Apolipoprotein A-1 (apoA-1), the major protein component of HDL. ApoA-1 participates in the entire RCT pathway. ApoA-1 in lipid-poor form interacts with the ABCA1 transporter that plays a pivotal role to mediate the efflux of phospholipids and cholesterol from cells in peripheral tissue. ApoA-1 is a cofactor of the enzyme, LCAT that converts cholesterol into cholesterol ester resulting in the nascent discoidal HDL to mature spherical HDL transformation. Finally, apoA-1 is the ligand for the SR-BI receptor that is responsible for SR-BI mediated selective cholesterol ester uptake from HDL by the liver. A second focus concerns determination of the three-dimensional structure of intact LDL by cryo-electron microscopy and 3D-image reconstruction, with emphasis on the topology and the molecular conformation of the apo-B, protein component of LDL, at the lipoprotein surface. This information is vital to an understanding of the lipid interactions, apoprotein exchanges, lipoprotein cell-surface interactions, receptor-mediated lipoprotein uptake, and lipoprotein inter-conversions that form the basis of lipid transport and metabolism.
Dr. James Hamilton’s laboratory is developing and applying novel physical approaches to study of obesity, metabolic syndrome, and cardiovascular disease. In newer studies, magnetic resonance imaging (MRI) is applied to examine fat tissue and atherosclerosis in animal model systems (mouse and rabbit) and humans. The work emphasizes interactions of different disciplines on translation of basic biophysics to human disease aspects and collaborations with faculty at BUMed. Our study of subjects with metabolic syndrome and obesity explores the hypothesis that a unifying feature of metabolic syndrome is enhanced deposition of lipids throughout the body outside of the normal adipose stores. MR imaging will identify and quantify site-specific abnormalities in obese patients such as cardiac functions. In our animal studies of atherosclerosis, imaging of live mice allows us to follow diseases and therapies in a single animal over a long period of time. A rabbit model of the acute event of atherosclerosis, plaque rupture and thrombosis is being studied to develop MRI for prediction of unstable and high risk plaques. Recent advances are now being translated to human carotid disease with a newly approved IRB protocol. Our MRI of the mouse and rabbit models have led to new imaging protocols that highlight inflammation or the effects of inflammation. We are testing novel therapeutics in both models.
Another major area of focus is the binding and transport of fatty acids by serum album and intracellular fatty acids binding proteins. The major method applied is NMR spectroscopy. Our research efforts focused on fatty acid transport in membranes have now developed fluorescence probes to monitor the adsorption of fatty acids to a membrane, their incorporation within the lipid bilayer, and their diffusion across the lipid bilayer. This combination allows future studies of how membrane proteins and organization/composition of the lipid bilayer might affect fatty acid transport.
An important part of the recent multidisciplinary and translational emphasis of the Hamilton lab has been the training and participation of several MDs, including two cardiologists and a radiologist. They are now actively participating in research projects encompassing atherosclerosis, obesity and fatty liver.
The primary goal of the current research of Dr. Subrata Chakrabarti is to clarify whether redox-mediated CD40-CD40L interactions influence platelet function and platelet-endothelial adhesion and vessel occlusion. For the past several years, we have been studying on the several aspects of the role of platelet and endothelial cells in thrombosis and inflammation. Our studies have indicated a distinct role of reactive oxygen species in the CD40-CD40L mediated processes, involving Akt and p38 MAP kinase signaling and NFkB activation. We are working on projects that will depend heavily on knowledge obtained through animal experiments and novel in vitro studies. The successful outcome of our research plan will have significant contribution to our understanding of the role of platelet-CD40L in thrombosis, atherosclerosis, and acute coronary syndromes; and might therefore create the opportunity for new therapeutic approaches that will prevent cardiovascular mortality. We also plan to extend our studies in the area of aging and inflammatory diseases.
The Vascular Biology Unit led by Dr. Richard Cohen seeks to understand how nitric oxide and oxidants regulate the function of blood vessels. 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 a potent oxidant, peroxynitrite, is formed. Sustained high levels of peroxynitrite cause irreversible chemical modifications, inducing nitrotyrosine or sulfonic acid cysteine modifications, and thus inactivate important proteins such as manganese superoxide dismutase or the sarcoplasmic reticulum calcium ATPase. At low levels, reactive oxygen and nitrogen species including peroxynitrite and hydrogen peroxide can induce reversible protein modifications such as S-glutathione cysteine adducts that redox regulate the function of many proteins including the sarcoplasmic reticulum calcium ATPase, p21ras, and sirtuin-1, thereby physiologically modulating cell signaling. As part of the BU Cardiovascular Proteomics Center, Dr. Cohen and his group are identifying chemical modifications of proteins formed by oxidants with mass spectrometric and protein tagging strategies. These modifications may serve as biomarkers for abnormal cell signaling and/or metabolic disease. Such markers have been found in diseased human arteries, platelets, and the blood.
Dr. Deborah Siwik is investigating the regulation of the myocardial extracellular matrix cardiac disease. A major focus is to understand the roles of matrix metalloproteinases in cardiac collagen remodeling. We are also looking at the ability of nitric oxide, oxidative stress, and inflammatory cytokines to mediate changes in extracellular matrix either directly or though regulation of matrix metalloproteinases. Changes that are identified are examined in blood samples from patients to determine whether they can be used as biomarkers of heart disease. As part of the Cardiovascular Proteomics Center, we are identifying chemical modifications of cardiac proteins formed by reactive oxygen, nitrogen, and lipid species that may contribute to pathology and that may serve as better markers for disease severity.
One of the areas of study of Dr. Frank Naya focuses on dissecting the in vivo role of the myocyte enhancer factor-2 (MEF2) family of transcription factors in muscle development. The four mammalian mef2 genes, mef2a, mef2b, mef2c, and mef2d are co-expressed in cardiac and skeletal muscle. Loss-of-function studies in mice have revealed important yet distinct functions for the vertebrate mef2 genes in the heart. Inactivation of the mef2c gene results in defective cardiac morphogenesis in developing embryos. In contrast, inactivation of the mef2a and mef2d genes results in perinatal cardiomyopathy and altered stress-dependent cardiac remodeling, respectively. Exploring the downstream cellular pathways controlled by the various mef2 genes will help us understand the genetic pathways in muscle development and disease.
Another area of investigation relates to the role of scaffolding proteins, i.e. proteins that bind signaling enzymes, in muscular dystrophy. Muscular dystrophy is a severe muscle degenerative disease and one form of this disease is the result of a deficiency in dystrophin. Significantly, we have identified a muscle-specific scaffolding protein, myospryn, that interacts with protein kinase A (PKA) and dystrophin. Because the signaling pathways involved in muscular dystrophy are still poorly understood we are looking into the potential role for myospryn in this process.
Dr. Christopher Akey‘s research group studies large macromolecular machines that function in protein translocation (mammalian and bacterial ribosome-channel complexes, the T4b secretion system of Legionella pneumophila, yeast and vertebrate NPCs), apoptosis platforms (apoptosomes) and histone chaperones. We use Molecular Biology, Biochemistry and Biophysical methods to prepare complexes for structural analyses and to characterize their functions. These structural methods include: cryo-electron microscopy and tomography, X-ray crystallography (with Dr. James Head) and, NMR (in collaboration with Drs. James McKnight and Serge Smirnov). Dr. Akeys’ early studies of yeast and vertebrate NPCs revealed a central transport channel, named the central transporter, which gates nucleocytoplasmic transport. His recent research on ribosome-channel complexes showed that a single copy of SecY or Sec61 associates with the ribosome to form the protein conduction channel and also resulted in a pseudo-atomic model of the vertebrate ribosome. His research has also provided insights into the atomic structure of nucleoplasmin family members, which function as histone chaperones. Studies of human and Drosophila apoptosomes have led to structures at 9.5 and 6.9Å resolution respectively, and have provided a model for procaspase activation on these cell death platforms. More recently, a crystal structure of the IcmR-IcmQ complex revealed that IcmR is a co-factor for IcmQ which may function as an ADP ribosyltransferase. Hence, IcmR-IcmQ could regulate the activity of the T4b secretion system of Legionella pneumophila, the causative agent of Legionnaire’s disease.
Dr. Wainford’s laboratory utilizes an integrated physiological, pharmacological, molecular, and gene-targeting approach to investigate the anti-hypertensive role(s) of central, and more specifically hypothalamic paraventricular nucleus (PVN), Gαi2-subunit proteins in the endogenous G-protein coupled receptor (GPCR)-activated pathways that regulate central sympathetic outflow (with particular focus on the renal sympathetic nerves), fluid and electrolyte homeostasis, and systemic blood pressure regulation in salt-resistant and salt-sensitive animal models.