Antioxidant Protects Klotho and FoxO1 and AKT Pathway in Experimental Model of Chronic Cyclosporine Nephropathy

Background: We recently reported that cyclosporine (CsA)-induced oxidative stress suppresses the expression of Klotho, anti-aging gene in kidney. This study was examined the effect of antioxidant, N-acetyl cysterine (NAC), on Klotho expression and its signal pathway in a model of chronic CsA nephropathy. Methods: Mice were divided 4 groups: vehicle (VH, olive oil, 1 ml/kg/day), CsA (30 mg/kg/day), NAC (300 mg/kg/day), and CsA + NAC groups. Under 0.01% sodium diet, mice daily received olive oil or CsA for 4 weeks. Klotho, FoxO1 and AKT protein expression was evaluated with immunohistochemistry and/or immunoblot. Manganese superoxide dismutase (MnSOD) was also evaluated. CsA-induced oxidative stress was evaluated with 8-hydroxy-2'-deoxyguanosine (8-OHdG) excretion in urine and immunohistochemistry. Results: Combined treatment of NAC and CsA significantly decreased the urinary 8-OHdG and restored KLOTHO expression compared with the CsA treatment alone (p < 0.05). The Klotho expression was well correlated with urinary 8-OHdG excretion (r=0.893, P< 0.001). NAC treatment translocates the FoxO1 from cytoplasm into the nucleus, suggesting dephosphorylation of FoxO1, and significantly decreased AKT expression compared with CsA treatment alsone. Decreased MnSOD expression in the CsA group was increased in the CsA+NAC group. Apoptotic cell death caused by CsA was markedly decreased with combined treatment of NAC. Conclusion: Antioxidant protects Klotho expression and its signal pathway. This finding provides a rationale for use of antioxidant in chronic CsA nephropathy.