Impact of cytotoxic agents or apoptosis stimulants on alpha klotho in MDCK, NRK-52E and HK2 kidney cells

alpha Klotho is a transmembrane protein acting as a co-receptor for FGF23, a bone hormone regulating renal phosphate and vitamin D metabolism. alpha Klotho expression is controlled by PPAR gamma. Soluble alpha klotho (sKL) regulates cellular signaling impacting stress resistance and death. alpha Klotho deficiency causes early onset of aging-associated diseases while its overexpression markedly increases lifespan. Cellular stress due to cytotoxic therapeutics or apoptosis induction through caspase activation or serum deficiency may result in cell death. Owing to alpha klotho's role in cellular stress and aging, this study explored the effect of cytotoxic agents or apoptosis stimulants on cellular alpha klotho expression. Experiments were performed in renal MDCK, NRK-52E and HK-2 cells. Gene expression was determined by qRT-PCR, sKL by ELISA, apoptosis and necrosis by annexin V binding and a fluorescent DNA dye, and cell viability by MTT assay. Cytostatic drugs cisplatin, paclitaxel, and doxorubicin as well as apoptosis induction with caspase 3 activator PAC-1 and serum deprivation induced alpha klotho and PPARG gene expression while decreasing viability and proliferation and inducing apoptosis of MDCK and NRK-52E cells to a variable extent. PPAR gamma antagonism attenuated up-regulation of alpha klotho in MDCK cells. In HK-2 cells, alpha klotho gene expression and sKL protein were down-regulated by chemotherapeutics. SKL serum levels in patients following chemotherapy were not significantly changed. In summary, potentially fatal stress results in up-regulation of alpha Klotho gene expression in MDCK and NRK-52E cells and down-regulation in HK-2 cells. These results indicate that different renal cell lines may exhibit completely different regulation of alpha klotho.