Abstract 706: HDL and ApoA-I Inhibit Palmitate-induced Lipid Raft Trafficking of TLR4 and Inflammatory Cytokines Expression in Adipocytes
Background: Adipose tissue inflammation induces inflammatory molecules production leading to insulin resistance and increased cardiovascular disease risk. Recently it has become apparent that innate immune system is activated by saturated fatty acids (SFAs) by a process involved in TLR4 signaling. HDL and apoA-I has anti-inflammatory effects, however the mechanisms are not well understood in adipocytes.
Aims: We examined to elucidate the effect of HDL and/or ApoA-I mediated cholesterol efflux on induction of inflammatory gene expression by palmitate in adipocytes via TLR4 dependent immune system.
Methods: 3T3-L1 adipocytes are exposure to 250uM palmitate for periods of up to 24 hours with or without HDL or Apo A-I. Antisense directed to ABCG-1 or ABCA-1 is added 24 hours prior to each reagent challenge. Cells were harvested and estimated for expression of Saa3 gene using real-time PCR or detection of TLR4 in raft or non raft by western blotting. Lipid rafts were purified by ultracentrifugation on discontinuous sucrose gradient, and identified by the presence of caveolin-1.
Results: TLR4 was translocated into lipid raft from non raft within 15 minutes and dislocated by 60 minutes after palmitate exposure. Saa3 gene expression was significantly up-regulated by 24 hours palmitate exposure in adipocytes. TLR4 translocation to raft and Saa3 gene up- regulation induced by palmitate was significantly inhibited by pretreatment of HDL or Apo A-I for 6 hours. Antisense directed to ABCG-1 or SRB1 abrogated these inhibitory effects by HDL, but not ApoA-I whereas antisense to ABCA-1 did by Apo A-I but not HDL.
Conclusions: These findings suggest that TLR4 mediates palmitate-induced Saa3 gene expression in adipocytes. A reduction in membrane cholesterol mediated by ABCG-1, SRB1 or ABCA-1 can account for the ability of HDL or ApoA-I to disrupt stimulation of inflammatory cytokines by palmitate
Author Disclosures: H. Yamada: None. T. Umemoto: None. T. Ohtani: None. H. Fukaya: None. M. Kawano: None. M. Kawakami: None. S. Momomura: None. S. Ishikawa: None.
- © 2015 by American Heart Association, Inc.