 |
Guy M. Chisolm, III, Ph.D.Staff, Vice Chairman of the Lerner Research Institute
Department of Cell Biology, Lerner Research Institute |
Areas of general research interest:
- Cellular effects of bioactive products of lipoprotein oxidation in inflammation and atherosclerosis
- Intracellular signaling events of apoptosis in vascular cells induced by bioactive lipids
- Genetically altered mouse models of vascular disease
Key words and phrases:
Apoptosis, atherosclerosis, cell signaling, endothelial cells, inflammation, lipoprotein oxidation, lipoprotein-cell interactions, lipoprotein transport into tissue, low density lipoprotein, modified phospholipids, macrophages, oxysterols, phospholipid hydroperoxide glutathione peroxidase (PHGPx or GPx4), smooth muscle cells, Stat1 and Stat3, tissue factor
Investigators:
- Charles A. Kaul, Senior Technologist
- Sudesh Agrawal, Ph.D., Fellow
Brief description and collaborations:
Background-- For over two decades our laboratory has been probing a theory that the oxidative modification of lipoproteins promotes the development of atherosclerotic lesions. Low density lipoprotein (LDL) is the principal cholesterol-carrying molecular complex in normal human plasma and its level correlates strongly with risk of atherosclerosis. Atherosclerotic lesions contain oxidized LDL; however, the mechanisms by which LDL gets oxidized and by which oxidized lipoproteins actually contribute to the disease progression are topics of intense research.
Alterations in cell function induced by oxidized LDL in vitro mimic events in lesion development observed in vivo. Our research focuses on adverse cellular changes brought about by oxidized LDL that are distinct from those resulting from exposure of cells to native, unaltered LDL. We seek to identify constituents of oxidized LDL that are bioactive as well as the cellular mechanisms by which these constituents change cell function.
Oxidized Lipoproteins and Cell Injury-- We have demonstrated that oxidized LDL injures cells in culture. We have shown that the cytotoxicity is independent of the mode of LDL oxidation, that cells are significantly more susceptible during S-phase of the cell cycle, and that the delivery of the toxin does not require lipoprotein receptors. Lipoproteins oxidized in vivo, such as those isolated from diabetic rats, are also cytotoxic to cells in culture; antioxidant treatment of these animals inhibited the development of the toxic products.
We have identified the most potent cytotoxin borne by oxidized LDL to be a hydroperoxide of cholesterol, and we have shown that it accumulates in human lesions. The mechanism of cell death induced by oxidized LDL and the cholesterol hydroperoxide involves peroxidation of cell lipids. Infusion of oxidized LDL can injure vascular endothelial cells in vivo and impair their function.
With Dr. Donna Driscoll, we are currently studying the regulation of a specific selenoprotein antioxidant enzyme (phospholipid hydroperoxide glutathione peroxidase; GPx4) that can reduce toxic lipid peroxides, protect cells from oxidized LDL-induced injury, and potentially protect mammals from atherosclerosis.
Atherosclerotic lesions in animals and humans contain a large number of cells dying by apoptosis (genetically programmed cell death) and we want to know what role this cell death plays in disease progression. GPx4, mentioned above, can inhibit apoptosis induced by many agents. We are studying the role of GPx4 in protecting cells from apoptosis and protecting mice from atherosclerosis progression.
With Drs. Martha Cathcart and George Stark, we are studying mechanisms of apoptosis induced by oxidized LDL constituents, including a variety of oxysterols. We are interested in delineating the apoptotic signaling pathways, and are focused on the roles of the transcription factors, Stat1 (pro-apoptotic) and Stat3 (anti-apoptotic).
We are performing experiments in cell culture and in genetically altered mice to test the hypothesis that the lipoprotein oxidation products kill these cells by an intracellular signaling sequence involving Stat1 and Stat3 regulation. We are using genetically altered, atherosclerosis susceptible mice to test whether atherosclerosis progression is blunted by inhibiting apoptosis of cells in the arterial lesion by altering the gene expression of Stat1 and Stat3.
Procoagulant Actions of Oxidized LDL-- We have also shown that oxidized LDL induces the activity of the clotting cascade initiator, tissue factor, on vascular SMC surfaces. This may be an important contributor to lesion development, since tissue factor induction could lead to the increased local production of thrombin, and thrombin not only enhances coagulation, but is also mitogenic for SMCs. With Dr. Marc Penn we are studying the regulation by oxidized LDL constituents of tissue factor gene expression, protein production and cell surface activity. We have shown that LDL and oxidized LDL can induce the tissue factor gene and lipid hydroperoxide constituents of oxidized LDL can activate the tissue factor pathway.
Selected recent references:
Agrawal S, et al. Signal transducer and activator of transcription 1 is required for optimal foam cell formation and atherosclerotic lesion development. Circulation 2007;115:2939-47.
Chen Q, Chai Y-C, Mazumder S, Jiang C, Macklis RM, Chisolm GM, Almasan A. The late increase in free radical oxygen species during apoptosis is associated with cytochrome c release, caspase activation and mitochondrial dysfunction. Cell Death & Differentiation 10:323-34, 2003.
Cui M-Z, Zhao G,. Winokur AL, Laag E, Bydash JR, Penn MS, Chisolm GM, Xu X. Lysophosphatidic acid induces tissue factor expression in aortic smooth muscle cells. Arterioscler Thromb Vasc Biol 23:224-30, 2003.
Penn MS, Chisolm GM. Lipoprotein oxidation, inflammation and atherosclerosis. In: "Atherothrombosis and Coronary Artery Disease" 2 nd Ed. Fuster V, Topol EJ, Nabel EG, Eds. Lippincott Williams & Wilkins, Philadelphia, 2003, In Press.
Murugesan GM, Sandhya Rani MR, Gerber CE, Mukhopadyay C, Ransohoff RM, Chisolm GM, Kottke-Marchant K. Lysophosphatidylcholine regulates human microvascular endothelial cell expression of chemokines. J Molec Cellular Cardiol 35:1375-1384, 2003.
Agrawal S, Agarwal ML, Chatterjee-Kishore M, Stark GR, Chisolm GM. Stat1-dependent, p53-independent expression of p21waf1 modulates oxysterol-induced apoptosis. Mol Cell Biol 22:1981-92, 2002.
Chai Y-C, Binion DG, Macklis R, Chisolm GM. Smooth muscle cell proliferation induced by oxidized LDL-borne lysophosphatidylcholine: evidence for FGF-2 release from cells not extracellular matrix. Vascular Pharmacology 38:229-37, 2002.
Yen MH, Pilkington G, Starling RC, Ratliff NB, McCarthy PM, Young JB, Chisolm GM, Penn MS. Increased tissue factor expression predicts development of cardiac allograft vasculopathy. Circulation 106:1379-83, 2002.
Xu X, Shi Y-C, Gao W, Mao G, Zhao G, Agrawal S, Chisolm GM, Sui D, Cui M-Z. The novel presenilin-1-associated protein (PSAP) is a pro-apoptotic mitochondrial protein. J Biol Chem 277:48913-48922, 2002.
Hazen SL, Chisolm GM. Oxidized phosphatidylcholines: pattern recognition ligands for multiple pathways of the innate immune response. Proc Natl Acad Sci USA 99:12515-17, 2002.
Colles SM, Maxson JM, Carlson SG, Chisolm GM. Oxidized LDL-induced injury and apoptosis in atherosclerosis; potential roles for oxysterols. Trends in Cardiovascular Medicine 11:131-8, 2001.
Chisolm GM, Steinberg D. The oxidative modification hypothesis of atherosclerosis: An overview. Free Radical Biology and Medicine 28:1815-26, 2000.
Chisolm GM, Chai Y-C. Regulation of cell growth by oxidized LDL. Free Radical Biology and Medicine 28:1697-707, 2000.
Chai Y-C, Binion DG, Chisolm GM. Relationship of molecular structure to the mechanism of lysophospholipid-induced smooth muscle cell proliferation. Amer J Physiol: Heart and Circ Physiol 279:H1830-8, 2000.
Colles SM, Chisolm GM. Lysophosphatidylcholine-induced cellular injury in cultured fibroblasts involves oxidative events. J Lipid Res 41:1188-98, 2000.
Penn MS, Cui M-Z, Winokur AL, Bethea J, Hamilton TA, DiCorleto PE, Chisolm GM. Smooth muscle cell surface tissue factor pathway activation by oxidized LDL requires cellular lipid peroxidation. Blood 96:3056-63, 2000.
Schmitt D, Shen Z, Zhang R, Colles SM, Wu W, Salomon R, Chen Y, Chisolm GM, Hazen SL. Leukocytes utilize myeloperoxidase-generated nitrating intermediates as physiological catalysts for the generation of biologically active oxidized lipids and sterols in serum. Biochemistry 38:16904-15, 1999.
Penn MS, Patel CV, Cui M-Z, DiCorleto PE, Chisolm GM. LDL increases inactive tissue factor on vascular smooth muscle cell surfaces; hydrogen peroxide activates latent cell surface tissue factor. Circulation 99:1753-9, 1999.
Cui M-Z, Penn MS, Chisolm GM. Native and oxidized low density lipoprotein induction of tissue factor gene expression in smooth muscle cells is mediated by both Egr-1 and Sp1. J Biol Chem 274:32795-802, 1999.
Chisolm GM, Hazen SL, Fox PL, Cathcart MK. The oxidation of lipoproteins by monocytes-macrophages: biochemical and biological mechanisms. J Biol Chem 274:25959-62, 1999.