Effect of tumor necrosis factor α on cholesterol efflux in adipocytes

BackgroundThe pro-inflammatory cytokine tumor necrosis factor-α (TNF-α) has multiple effects on adipocyte, including cell differentiation, lipolysis and the production of adipokines. It is not known whether TNF-α has effect on cholesterol efflux in adipocyte.MethodsRabbit subcutaneous adipocytes were incubated with 5, 10, 20 ng/ml TNF-α for 24 h. The cholesterol efflux onto apoAI was assessed, and the related peroxisome proliferators-activated receptor (PPAR) γ, liver X receptor (LXR) α and ATP binding cassette transporter A1 (ABCA1) mRNA expression in adipocytes were quantified by reverse transcription polymerase chain reaction.ResultsTreatment of adipocytes with 5 or 10 ng/ml TNF-α for 24 h increased cholesterol efflux, and the effect of 10 ng/ml TNF-α was significant higher than the control group. In contrast, 20 ng/ml TNF-α decreased cholesterol efflux compared with 10 ng/ml TNF-α. The expression of ABCA1 was increased by 5 ng/ml or 10 ng/ml TNF-α compared with control group, and was inhibited by 20 ng/ml TNF-α. The PPARγ and LXRα mRNA were also significantly induced by 10 ng/ml TNF-α and down regulated by higher TNF-α concentration. After pre-treated by GW9662, the expression of PPARγ induced by TNF-α was partially prevented, subsequent to the down-regulation of LXRα and ABCA1.ConclusionsTNF-α affects cholesterol efflux and ABCA1 expression of adipocytes, and the pathway of PPARγ-LXRα-ABCA1 is probably involved.