The impact of preserved Klotho gene expression on antioxidative stress activity in healthy kidney.

Klotho, which was originally identified as an antiaging gene, forms a complex with fibroblast growth factor 23 receptor in the kidney, with subsequent signaling that regulates mineral metabolism. Other biological activities of Klotho, including antiaging effects such as protection from various types of cellular stress, have been shown; however, the precise mechanism of these effects of Klotho gene in the healthy human kidney is not well understood. In this study, we examined the relationships of Klotho and antioxidative stress gene expression levels in zero-hour biopsy specimens from 44 donors in kidney transplantation and verified them in animal models whose Klotho gene expression levels were varied. The nitrotyrosine expression level in the kidney was evaluated in these animal models. Expression levels of Klotho gene were positively correlated with the p53 gene and antioxidant enzyme genes such as catalase, superoxide dismutase 1 (SOD1), SOD2, peroxiredoxin 3 (PRDX3), and glutathione peroxidase 1 (GPX1) but not clinical parameters such as age and renal function or pathological features such as glomerulosclerosis and interstitial fibrosis tubular atrophy. The expression levels of all genes were significantly higher in mice with Klotho overexpression than in wild-type mice, and those except for catalase, PRDX3, and GPX1 were significantly lower in Klotho-deficient mice than in wild-type littermate mice. Nitrotyrosine-positive bands of various sizes were observed in kidney from Klotho-deficient mice only. The preservation of Klotho gene expression might induce the antioxidative stress mechanism for homeostasis of healthy human kidney independently of its general condition, including age, renal function, and histological findings.