The central theme of this program project is based on the hypothesis that antioxidant and anti-inflammatory proteins of HDL and synthetic anti-inflammatory amphipathic helical peptides, due to their common structural features , i.e. presence of p-electron rich aromatic residue clusters that are oxidized lipid binding sites, act on the membrane surface and inhibit formation of reactive oxygen species (ROS). Thus, the apolipoprotein mimetic peptides either modulate the levels or activity of antiatherogenic proteins and enzymes and/or mimic their anti-inflammatory effects directly, thus exerting beneficial effects under inflammatory conditions. The four projects, all of which deal with lipid-mediated inflammatory conditions, address the mechanisms of inhibition of these inflammatory processes. From this we derive the central theme: understanding the mechanism of action of anti-inflammatory and antioxidant apoliprotein-mimetic peptides are fundamental to a full understanding of 1) cause and prevention of inflammatory disorders 2) pathophysiology and mechanisms of inhibition of inflammatory processes.
The objectives of this application are to determine the antioxidant and anti-inflammatory mechanisms of action of apoA-I and apoE mimetic peptides in relation to anti-inflammatory proteins present in HDL and to develop a body of knowledge that will allow translation of this work into potential new diagnostic and therapeutic agent(s), which may include non-peptide anti-inflammatory agents that possess the basic principles in the design of anti-inflammatory and anti-oxidant peptides.
Two mechanisms have been proposed for the progression of atherosclerosis:
It has been shown that both apo E (the protein component of very low-density lipoproteins (VLDL) and apolipoprotein A-I (the major protein component of HDL) are antiatherogenic, but by two distinctly different mechanisms. Using the common structural motif present for the lipid associating domains in apolipoproteins, the amphipathic helix, we have been able to design peptide mimics for 1) the rapid removal of atherogenic lipoproteins from circulation in vivo and inhibition of lesion formation, and 2) inhibit atherosclerosis in atherosclerosis sensitive mice without changing plasma cholesterol profile. Using cell culture studies, we have determined that the peptides that reduce plasma cholesterol levels do so by enhancing their removal by the proteoglycan-mediated pathway. Cell culture studies have also shown that the peptides that inhibit atherosclerosis without altering plasma cholesterol levels do so by "removing the seeding molecules" from atherogenic lipoproteins.
Recently, we have shown in two dyslipidemic rabbit models and in monkeys, the apolipoprotein mimetics reduce atherosclerosis and also in apolipoprotein E knockout mouse model, the peptide mimetics are able to regress already existing atherosclerosis. One of the mechanisms by which both the types of peptides may be functioning is by altering the existing atherogenic lipoproteins. As published recently, the synthetic mimetics are able to modify HDL to a highly active molecule (pre-b-HDL) which is able to enhance the clearance of cellular cholesterol. These active HDL molecules are also able to trap lipid hydroperoxides, the modified inflammatory lipids, thus inhibiting foam cell formation, the hallmark of atherosclerosis. The laboratory is now in the process understanding the mechanism(s) inhibition of atherosclerosis in these two types of molecules. The laboratory uses molecular biology, physical-chemical studies in protein(peptide)-lipid interaction, animal models, peptide synthesis approach and studies of apolipoproteins and lipoproteins to understand the mechanisms involved in inhibiting not only atherosclerosis but also other related diseases related to dyslipidemic and inflammation such as diabetes and bacterial and viral infection, which eventually lead to atherosclerosis. Research toward proving our hypotheses would enable us to better understand not only lipoprotein metabolism but also unique, yet unidentified functional roles of apolipoproteins, other than their known role in cholesterol transport. The research could lead to novel therapeutic reagents that would be useful in the treatment of atherosclerosis and its sequelae.
Dr. G. M. Anantharamaiah is a Professor in the Department of Medicine. He received his B.S. degree in 1967 from Bangalore University, India and his M.S. degree in 1969 from Bangalore University, as well. Dr. Ananth completed his Ph.D. degree in 1978 a Bangalore University. He received his postdoctoral training at Ohio State University in Columbus, OH in 1979. Dr. Ananth joined the UAB faculty in 1982 as an Assistant Professor in Pathology. He is presently the Associate Director of Administration of the Atherosclerosis Research Unit at UA and the Director of the Peptide Laboratory.