Role of ABCA1 in angiotensin II-induced cholesterol accumulation in podocytes

Abstract

Objective To investigate the effects of angiotensinⅡ(AngⅡ) on the expression of ATP-binding cassette transporter A1(ABCA1) in AngⅡ-infused rat model and cultured human podocytes, and to explore the role of ABCA1 in AngⅡ-induced cholesterol accumulation of podocytes. Methods Twelve Wistar rats were randomly subjected to normal saline infusion, or AngⅡ infusion at 400 ng·kg-1·min-1 (via subcutaneous osmotic minipumps) for 8 weeks. The expression of glomerular ABCA1 was analyzed by Western blotting and real-time fluorescent quantitative PCR. In vitro, conditionally immortalized human podocytes were divided into normal group, AngⅡ group, AngⅡ+scrambled siRNA group, AngⅡ+ABCA1 siRNA group. The expression of podocyte ABCA1 was assessed by immunofluorescence, Western blotting and real-time fluorescent quantitative PCR. Oil Red O staining was used to observe the lipid droplets in podocytes and cholesterol efflux assay kit was used to measure the cholesterol efflux rate of podocytes. Fluorescein isothiocyanate (FITC)-conjugated phalloidin was used to observe the podocyte cytoskeleton. Results In vivo, compared with normal group, the protein and mRNA expression of glomerular ABCA1 in AngⅡ-infused rats were decreased (P<0.05). In vitro, ABCA1 was distributed in the cytomembrane of podocytes, and compared with normal group, AngⅡtreatment down-regulated the expression of ABCA1 (P<0.05). Increased lipid droplets, decreased cholesterol efflux and cytoskeletal rearrangement were observed in AngⅡ-treated podocytes. When compared to AngⅡ group, podocytes stimulated by AngⅡand then transfected with ABCA1 siRNA had lower expression level of ABCA1 mRNA and protein (all P<0.05). More lipid droplets and lower cholesterol efflux rate could be observed in AngⅡ+ABCA1 siRNA group (P<0.05). Conclusion The reduced expression of ABCA1 may be involved in AngⅡ-induced cholesterol accumulation in podocytes. Key words: AngiotensinⅡ; Podocytes; ATP binding cassette transporter 1; Cholesterol