The effects of inflammatory cytokines on steroidogenic acute regulatory protein expression in macrophages.

OBJECTIVE

To investigate the expression of steroidogenic acute regulatory protein (StAR) in macrophages and the effects of inflammatory cytokines on StAR expression.

METHODS

The macrophages isolated from ApoE knockout mice and C57BL/6J mice and RAW264.7 cells (a cell line from mouse macrophage. ATCC Number: TIB-71) were cultured in DMEM containing 10% fetal bovine serum. RAW264.7 cells were treated with different inflammatory cytokines (TNF-alpha, IFN-gamma and TGF-beta1) and 8-Br-cAMP, a cAMP analog. RT-PCR and Western blot analysis were applied to evaluate the effects of inflammatory cytokines on StAR expression.

RESULTS

RT-PCR and Western blot analysis demonstrated the expression of StAR in the macrophages isolated from ApoE knockout mice, C57BL/6J mice and RAW264.7 cells. Proinflammatory cytokines TNF-alpha and IFN-gamma significantly decreased StAR mRNA and protein levels in RAW264.7 cells. The inhibition was dose- and time-dependent. In contrast, anti-inflammatory cytokine TGF-beta1 increased StAR mRNA and protein levels. At 1:15 molecular ratio, TGF-beta1 blocked the down-regulation of StAR expression mediated by TNF-alpha. cAMP also induced StAR expression in RAW264.7 cells. When the cells were co-treated with 8-Br-cAMP and TNF-alpha, 8-Br-cAMP failed to induce StAR expression.

CONCLUSION

Our results provide interesting evidence that inflammatory cytokines regulate StAR expression in macrophages.