Endotoxin Neutralization by HDL-Mimetic Peptide

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DESCRIPTION (provided by applicant): The objectives of this proposal are to provide the applicant with intensive training in the areas of inflammation and lipidology and to advance applicant's research skills and expertise so as to facilitate his development as an independent investigator. The candidate will be mentored by established investigators and a multidisciplinary advisory committee and will pursue a program of education (coursework, conferences, and seminars) and a research project addressing the protective mechanisms by which an HDLmimetic peptide attenuates lipopolysaccharide (LPS)-mediated sepsis. Sepsis is a major health problem. 25- 30% of all cases of sepsis is due to gram negative bacterial (GNB) infection. LPS, a component of the outer membrane of GNB, mediates many of the toxic effects associated with sepsis. Results indicate that HDL administration may be effective in treating sepsis. However obtaining therapeutic quantities of the HDL is impractical. One mechanism by which HDL neutralizes LPS is thought to occur by insertion and masking of the lipid A domain of LPS into the phospholipid leaflet that covers the surface of HDL. This may occur due to complementary molecular shape of apo A-l (a major protein constituent of HDL) and the lipid A component of LPS. We have developed a novel peptide whose design is based on the structure of apo A-l. This peptide 4F is a class A amphipathic helical molecule that has many of the anti-atherosclerotic properties of apo A-l. Beneficial effects of 4F are thought to be due to its ability to modulate HDL properties including formation of pre-beta HDL like particles. We have observed that the molecular shape of 4F is complementary to that of lipid A. In this application, we demonstrate that administration of 4F significantly reduces LPS-induced activation of inflammatory cytokines and adhesion molecules both in-vitro and in-vivo. We propose the novel hypothesis that the apo A-l mimetic peptide 4F inhibits LPS induced inflammatory processes and will test whether this response is due to : i) Direct physical interaction between lipid A and 4F; ii) Indirect effects of 4F, by promoting the formation of apo A-l rich pre-beta HDL-like particles and thus enhancing the LPS scavenging capacity of HDL. This study will have important implications in understanding the role of apo A-l and HDL in LPS mediated sepsis. It will also provide a rationale for developing HDL-mimetic peptides as effective therapeutic agents against sepsis/inflammation. (End of Abstract)