Abstract 149: Regulation of Pathogen-Associated Molecular Pattern Recognition by the Apo A-I Mimetic Peptide 4F
The apolipoprotein A-I (apoA-I) mimetic peptide 4F displays prominent anti-inflammatory properties, including the ability to reduce vascular macrophage content. Macrophages are a heterogenous group of cells that are represented by two principal phenotypes, the classically-activated M1 macrophage and an alternatively-activated M2 phenotype. We previously reported that apoA-I and 4F favor the differentiation of human monocytes to an anti-inflammatory phenotype similar to that displayed by M2 macrophages. Further, 4F treatment attenuated LPS-induced inflammatory responses in monocyte-derived macrophages (MDMs). In the current study, we investigated effects of 4F and vehicle on LPS-induced gene expression in human MDMs by microarray analysis. RNA isolation, labeling and hybridization were performed, and the transcriptional profile was examined using the Human Gene ST 1.0 Affymetrix chip. Analysis of MDM gene expression profiles revealed that 4F modulated mRNA expression for 1099 genes (± 2-fold change, p<0.05), of which 149 genes regulated inflammatory responses. LPS treatment of MDMs significantly up-regulated genes encoding Toll-like receptors (TLR1, 2, 4, 6, and 8) compared to vehicle treatment. These responses were attenuated by 4F treatment. MyD88, CD14, IRAK4, TRAF6, TRAF3, MALT1 and IKBKB, genes that modulate NF-κB activation and subsequent cytokine synthesis, were also reduced by 4F. Corroborating this, FACS analyses showed that pre-treatment of MDMs with 4F reduced the LPS-dependent phosphorylation of NF-κB by 70% compared to vehicle treatment. These 4F-induced responses were also associated with a reduction in TNF-α and IL-6 secretion. These data suggest that an important anti-inflammatory mechanism of 4F action may be to down-regulate genes involved in the TLR signaling pathway, thus attenuating the responsiveness of macrophages to LPS and other pathogen-associated molecular patterns (PAMPs).
- © 2012 by American Heart Association, Inc.