Abstract 16973: Apolipoprotein A-I Mimetic Peptide, L-4F, Inhibits LPS-Binding to Granulocytes, Monocytes and Lymphocytes to Inhibit Inflammatory Cascade in Human Blood
Atherosclerosis and inflammation are closely related processes. High-Density Lipoprotein (HDL) has anti-atherogenic and anti-inflammatory properties, mainly due to apolipoprotein (apo) A-I component of HDL. L-4F peptide mimics the helical repeating domains of apo A-I. In various animal models, L-4F demonstrates anti-atherosclerotic and anti-inflammatory properties. Here, we tested the hypothesis that L-4F inhibits lipopolysaccharide (LPS)-mediated inflammation in humans. To model inflammation, blood samples were collected from healthy volunteers and incubated with: 1) saline; 2) 1 μg/ml LPS (E. coli); 3) 20 μg/ml L-4F; 4) LPS and L-4F. LPS increased plasma levels of IL-6 and TNF-α and decreased plasma HDL, pre-β-HDL and activity of HDL-associated anti-oxidant enzyme, paraoxonase (PON1). In contrast, L-4F alone increased plasma pre-β-HDL and activity of HDL-associated PON1. Mass Spectrometry confirmed that L-4F was confined in HDL fractions (α-HDL and pre-β HDL) but not in VLDL or LDL. When incubated with LPS, L-4F inhibited LPS-induced cytokine up-regulation, and prevented LPS-induced decrease of plasma HDL, pre-β-HDL, and HDL-associated PON1 activity. L-4F inhibited LPS binding to granulocytes, monocytes and lymphocytes as studied using Bodipy-LPS conjugate and flow cytometry (Figure). L-4F prevented Bodipy-LPS aggregation, which inhibited cytokine up-regulation and decreased endotoxin activity in the Limulus Amebocyte Lysate test. In saline, Bodipy-LPS aggregation was also prevented by direct incubation with L-4F. In conclusion, L-4F inhibits LPS-mediated inflammatory markers in human blood. Two mechanisms are suggested: 1) L-4F directly interacts with LPS decreasing LPS aggregation and biological activity; 2) L-4F modifies HDL properties due to formation of pre-β-HDL-like particles with enhanced LPS scavenging capacity. L-4F therefore may be useful in treatment of gram negative sepsis and sepsis induced cardiovascular disorders.
- © 2010 by American Heart Association, Inc.