The effect of α-melanocyte-stimulating hormone on renal tubular cell apoptosis and tubulointerstitial fibrosis in cyclosporine A nephrotoxicity

Background. The pathogenesis of cyclosporine A (CsA)-induced nephrotoxicity has been known to be secondary to hemodynamic changes, but increasing evidence indicates that CsA has a direct toxicity to renal tubular cells, leading to their apoptosis and tubulointerstitial fibrosis. This study evaluated the mechanism for CsA-induced tubular cell apoptosis, tubulointerstitial fibrosis and its associated proteins, and the therapeutic effects of α-melanocyte- stimulating hormone (MSH) on them. Methods. Male Sprague-Dawley rats fed with a low-sodium diet were divided into three treatment groups: group A (vehicle-injected group), group B (CsA 15 mg/kg-injected group), and group C(CsA+α-MSH-injected group). After 42 days, creatinine clearance; blood CsA level; apoptosis; inflammation and tubulointerstitial fibrosis in renal tissue; and the expression of Bax, Bcl₂, Fas, FasL, and transforming growth factor (TGF)-β protein were determined. Results. CsA-induced tubular cell apoptosis; cellular infiltration; and increase of Fas, Bax, TGF-β protein expression with significant tubulointerstitial fibrosis, and reduced Bcl₂ protein expression. α-MSH treatment prevented the Bax and TGF-β protein increase and induced Bcl₂ protein increase, together with reduction of apoptosis, inflammation, and tubulointerstitial fibrosis. Conclusions. These findings suggest that chronic CsA nephrotoxicity is related to Bax and Bcl₂-related apoptosis pathways, and that α-MSH can attenuate the CsA-induced tubulointerstitial fibrosis as well as tubular cell apoptosis.