Angiotensin-(1-7) upregulates (ATP-binding cassette transporter A1) ABCA1 expression through cyclic AMP signaling pathway in RAW 264.7 macrophages.

OBJECTIVES ATP-binding cassette transporter A1 (ABCA1) plays a crucial role in reverse cholesterol transport and anti-atherosclerosis. Cyclic AMP (cAMP) could increase the ABCA1 expression. Angiotensin (Ang)-(1-7) can protect endothelial cells, inhibit smooth muscle cell growth, ameliorate inflammation and exert anti-atherosclerotic effects. In this study, we attempted to clarify the effect of Ang-(1-7) on expression of ABCA1, and explored the role of cAMP in the regulation of ABCA1 in RAW 264.7 macrophages. MATERIALS AND METHODS RAW 264.7 macrophages were cultured. Then the macro-phages were incubated with different concentration Ang-(1-7) or 10 mM MDL respectively, or 10 mM adenylate cyclase inhibitor MDL-12330A (MDL) plus 1000 nM Ang-(1-7) for 24 h. The expression of ABCA1 was examined by real-time quantitative PCR and western blot analyses. cAMP expression was measured by Enzyme-Linked Immuno Sorbent Assay. Cellar cholesterol efflux from RAW 264.7 macrophages was analyzed using liquid scintillation counting assays. The cellular total cholesterol and free cholesterol were performed to determine by High Performance Liquid Chromatography assays. RESULTS Our results showed that Ang-(1-7) increased ABCA1 expression at both the mRNA and protein levels in a dose-dependent manner. Consequently, the increase in cholesterol efflux was consistent with an ABCA1 expression increase. The cAMP expression was up-regulated by Ang-(1-7). When being treated with MDL and Ang-(1-7), the ABCA1 expression, cellular cholesterol efflux and cholesterol content were partially reversed by MDL. CONCLUSIONS Ang-(1-7) could increase ABCA1 expression partially due to the cAMP pathway.