IRAK regulates macrophage foam cell formation by modulating genes involved in cholesterol uptake and efflux

Abstract

Interleukin-1 receptor-associated kinase-1 (IRAK1) is linked to the pathogenesis of atherosclerosis; however, its role in macrophage foam cell formation is not known. Therefore, the present study investigated the role of IRAK1 in lipid uptake, biosynthesis, and efflux in THP-1 derived macrophages and human monocyte-derived macrophages (HMDMs). Ox-LDL (40 μg/mL, 15 minutes-48 hours) treatment induced time-dependent increase in IRAK1, IRAK4, and Stat1 activation in THP-1 derived macrophages. IRAK1/4 inhibitor (INH) or IRAK1 siRNA significantly attenuated cholesterol accumulation, DiI-Ox-LDL binding, and uptake while cholesterol efflux to apoAI and HDL was enhanced in THP-1 derived macrophages and HMDMs. Ox-LDL treatment significantly increased the mRNA expression of CD36, LOX-1, SR-A, ABCA1, ABCG1, Caveolin-1, CYP27A1 while that of SR-BI was decreased. IRAK1/4 inhibition or IRAK1 knockdown, however, attenuated Ox-LDL-induced CD36 expression; augmented ABCA1 and ABCG1 expression while expression of others was unaffected in THP-1 derived macrophages and HMDMs. Moreover, IRAK1/4 inhibition had no significant effect on genes involved in lipid biosynthesis. In IRAK1/4 INH pre-treated THP-1 derived macrophages Ox-LDL-induced Stat1 phosphorylation and its binding to CD36 promoter was significantly attenuated while LXRα expression and its binding to the ABCA1/ABCG1 locus, NFATc2 activation and its binding to ABCA1 locus was enhanced. The present study thus demonstrates that IRAK regulates lipid accumulation by modulating CD36-mediated uptake and ABCA1-, ABCG1-dependent cholesterol efflux. Therefore, IRAK1 can be a potential target for preventing macrophage foam cell formation.

Tetramethylpyrazine suppresses lipid accumulation in macrophages via upregulation of the ATP-binding cassette transporters and downregulation of scavenger receptors

“…The expression of ABCA1/ABCG1 was upregulated by the activation of Liver X receptor (LXR) signaling, thus promoting macrophage RCT (30) and decreasing atherosclerosis in mouse models (31). In addition, various antioxidants with anti-atherogenic properties are capable of upregulating the expression of ABCG1 and ABCA1 (32,33). In view of the function of ABCG1 and ABCA1, the increasing effect of TMP on the expression of ABCG1 and ABCA1 observed in the present study may conduce to the inhibition of ox-LDL uptake and subsequent suppression of foam cell formation.…”

Cholesterol uptake and efflux are impaired in human trophoblast cells from pregnancies with maternal supraphysiological hypercholesterolemia

“…Uptake assays. Uptake of increased concentrations of LDL-DiI (0-200 μg/mL, 2 h, 37 °C) and HDL-DiI (0-50 μg/mL, 4 h, 37 °C) was measured in PHT cultured by 72 hours that were pre-incubated (overnight) in DMEM/F12 containing 5% FBS by modification of the protocols previously described [31][32][33][34] . After incubation, the cells were washed with PBS-BSA-free fatty acid (FFA) (2 mg/mL), and fluorescence (λexc/λem: 550/595) was quantified (Infinite M200Pro, Tecan, Austria).…”

Role of pyruvate kinase M2 in oxidized LDL-induced macrophage foam cell formation and inflammation

“…Human LDL (d = 1.019-1.063 g/ml) was isolated from the plasma of healthy volunteers by density gradient ultracentrifugation (31,32). All procedures were approved by the Institutional Human Ethics Committee and were in agreement with Declaration of Helsinki principles.…”

“…BMDMs treated with Ox-LDL were lysed as previously described (32). Pre-adsorption of PKM2 antibody on protein A/G-Sepharose beads was done in the presence of pre-adsorption buffer (16).…”