MALP-2 Downregulated ABCA1 Expression Though The TLR2/NF-?B/ZNF202 Signaling Pathway In THP-1 Macrophages

Objective: ATP-binding cassette transporter A1(ABCA1) is a critical transporter that mediates the transfer of intracellular free cholesterol(FC) and phospholipid to lipid-poor apolipoprotein A-I(apo A-I). It plays an important role in inhibiting intracellular cholesterol accumulation and foam cell formation. Macrophage-activating lipopeptide-2(MALP-2) is a lipopeptide isolated from the cell wall of Mycoplasma fermentans, and can recognize specially Toll-like receptors(TLRs) in the membrane of target cells. It has been reported that MALP-2 is closely associated with atherosclerosis(As). However, it is still unclear whether MALP-2 can regulate the expression of ABCA1. The aim of this study was to observe the effects of MALP-2 on ABCA1 expression in THP-1 macrophages, and to explore the underlying mechanisms.Methods: THP-1 monocytes were incubated with phorbol-12-myristate-13-acetate(PMA) and oxidize low-density lipoprotein(ox-LDL) in turn to convert into THP-1macrophage-derived foam cells. These cells were treated with various concentrations(0, 25,50,100 and 200 m M) of MALP-2 for 24 h or with 100 m M MALP-2 for various time(0, 6, 12, 24 and 48 h). Oil Red O staining was used to observe intracellular lipid accumulation. The contents of total cholesterol(TC), FC and cholesterol ester(CE) within these cells were detected by high performance liquid chromatography(HPLC). Cholesterol efflux was analyzed using liquid scintillator. The expression of ABCA1 m RNA and protein was measured by fluorescence real time quantitative PCR and Western blot, respectively. THP-1macrophage-derived foam cells were pretreated with the inhibitor or small interfering RNA(si RNA) of the TLR2/nuclear factor-?B(NF-?B)/zinc finger protein 202(ZNF202) signaling pathway for 24 h, which was followed by 100 m M MALP-2 for another 24 h. Western blot was used to determine the protein levels of TLR2, ZNF202, ABCA1 and nuclear NF-?B p65. In addition, the expression of ABCA1 m RNA was examined using fluorescence real time quantitative PCR.Results: The amounts of intercellular lipid drops in ox-LDL and MALP-2 treated group were higher than those in ox-LDL treated group(P<0.05). Addition of MALP-2 to THP-1macrophage-derived foam cells significantly increased the contents of intercellular TC, FC and CE but decreased cholesterol efflux and downregulated ABCA1 m RNA and protein expression in a concentration- and time-dependent manner(P<0.05). However, MALP-2–induced downregulation of ABCA1 expression was partially reversed in response to the NF-?B inhibitor pyrrolidine dithiocarbamate(PDTC) or si RNAs for TLR2, NF-?B and ZNF202(P<0.05).Conclusions: MALP-2 decreases the expression of ABCA1 via the TLR2/NF-?B/ZNF202 signaling pathway in THP-1 macrophages, leading to intercellular lipid accumulation and foam cell formation.