Abstract 1046: The ApoA-I Mimetic Peptide, 4F, Inhibits LPS-induced Inflammatory Reactions Through Dysregulation Of The NFkB Activation Pathway.
Background: The apoA-I mimetic peptide 4F possesses potent anti-inflammatory properties. We previously reported that 4F inhibits lipopolysaccharide (LPS)-induced cytokine, chemokine and adhesion molecule expression in vivo and in vitro. Other data show that 4F reduces macrophage content in atheroma in susceptible mice.
Objective: In this study, we explored anti-inflammatory mechanisms of 4F action under basal conditions and in the presence of LPS using THP1 monocytes/macrophages and primary human blood monocytes.
Methods and Results: Blood monocytes isolated by Ficoll and CD14+ MACS separation were analyzed by FACS for CD14, TLR-4 and p-NFκB expression. Cytokines, chemokines and adhesion molecules were measured by the Searchlight multi-analyte analysis (Pierce, MA, USA). 4F treatment (3 days) of both THP-1 and blood monocytes enhanced the secretion of GM-CSF (25-fold), a potent inducer of monocyte to dendritic cell differentiation. 4F also inhibited (by 80%) the PMA-induced phagocytosis of FITC-labeled beads by THP-1 cells. In subsequent studies, effects of 4F on LPS-induced inflammatory responses in monocytes were tested. Pre-treatment with 4F significantly inhibited LPS-induced MCP-1 expression (by 50%) in both THP-1 cells and blood monocytes. Under these conditions, the expression of the anti-inflammatory cytokine IL-10 was increased by 200%. The effects of 4F on the activation of NFκB, a downstream mediator of LPS action, were studied using flow cytometry. 4F pre-treatment significantly inhibited LPS-induced NFκB phosphorylation (NFκBp65) compared to vehicle treatment. Protective effects of 4F in LPS-treated monocytes were associated with a 50% reduction in the expression of TLR-4 and CD14, cell surface receptors for LPS.
Conclusions: These data provide evidence that 4F modulates functional properties of monocytes and show for the first time that 4F inhibits LPS-induced inflammatory responses by inhibiting the expression of CD14, TLR-4 and phosphorylation of NFκB. Enhanced GM-CSF expression and inhibition of monocyte phagocytic activity also suggest that 4F may favor the differentiation of monocytes to a dendritic cell rather than a macrophage phenotype.