An ideal treatment for atherosclerosis would involve rapid clearance of plasma cholesterol and inhibition of inflammatory pathways. Recent advances in apoA-I mimetic peptides indicate the possibility of improving HDL functions. This proposal deals with ways of incorporating properties of lowering plasma apolipoprotein B- containing lipoproteins with properties of improving HDL function. Our hypothesis is that such peptides would not only retain properties that improve HDL functions, but also enhance the clearance of apoB-containing lipoproteins, thus lowering plasma cholesterol levels. Thus, we designed novel peptides that possesses the cationic putative receptor binding domain from apoE that is covalently linked to an active apoA-I mimetic peptide domain. We have also designed a single-domain cationic peptide to which we have incorporated the lipid hydroperoxide-scavenging properties of apoA-I mimetics. Preliminary results show that these properties enhance uptake of atherogenic lipoproteins in HepG2 cells and inhibit atherosclerosis in apoE null mice. They also appear to improve HDL function. We have exciting results to show that Ac-hE-18A-NH2 dramatically decreases plasma cholesterol in different dyslipidemic mouse models and WHHL rabbits. Preliminary results also show that the peptide possesses antiinflammatory properties. This occurs through a lowering of plasma lipid hydroperoxide levels concomitant with a significant increase in plasma paraoxonase activity. In the WHHL model, the LDL-R pathway is compromised, thus the peptide-mediated atherogenic lipoprotein clearance is likely via the cell surface heparan sulfate proteoglycan (HSPG)-mediated pathway, as described earlier by us in murine models. In a second rabbit model of atherosclerosis, New Zealand White (NZW) rabbits fed an atherogenic diet, a single intravenous administration (3mg/kg) of the peptide significantly decreased total plasma cholesterol levels for 15 days. En face analysis of the lesions after 50 days showed approximately 50% lesion coverage in the saline administered rabbits (control), while little to no lesion in the peptide-treated animals. We therefore hypothesize that both cholesterol-dependent and -independent properties of these novel peptides contribute to the beneficial effects of the peptides to inhibit atherogenesis. We propose two specific aims to further investigate the mechanism of action of these two types of peptides:
Specific Aim 1 : Effect of peptides on A) uptake of apoB-containing lipoproteins in hepatocytes isolated from different dyslipidemic mouse models and rabbit models and in HepG2 cells. B) Changes in apoA-I and apoE-containing particles and their anti- inflammatory properties.
Specific Aim 2 : Effect of peptides on A) plasma cholesterol levels, B) lesion inhibition in animal models of atherosclerosis, and C) modulation of HDL properties. Research towards the understanding of the antiatherogenic properties of these novel peptides would yield a better understanding of cholesterol homeostasis and could lead to novel therapeutic reagents that would be useful in the treatment of atherosclerosis and its sequelae.
An ideal treatment for atherosclerosis would involve rapid clearance of plasma cholesterol and inhibition of inflammatory pathways. Recent advances in apoA-I mimetic peptides indicate the possibility of improving HDL function. This proposal deals with ways of incorporating properties of lowering plasma apolipoprotein B- containing lipoproteins with properties of improving HDL function. This is hypothesized to preserve both the anti- inflammatory and cholesterol reducing functions in designed peptides in order to obtain a peptide that would be ideal for the treatment of atherosclerosis and related lipid related inflammatory disorders.
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