Klotho ameliorates hydrogen peroxide-induced oxidative injury in TCMK-1 cells

Defects in Klotho gene expression in mice result in a vulnerability to oxidative injuries. We aimed to identify the expression of Klotho in a mouse tubular epithelial (TCMK-1) cell line, and also to investigate changes in Klotho expression induced by oxidative stress and the potential role of intra- and extracellular Klotho protein.

During exposure to hydrogen peroxide (H₂O₂), an overexpression of the Klotho gene was induced and exogenous Klotho protein was added in TCMK-1 cells. The generation of reactive oxidative species (ROS) was examined by flow cytometry, and cell viability was assessed by Cell Counting Kit-8. Cellular apoptosis was determined by flow cytometry and Hoechst 33258 staining followed by Western blotting to evaluate the expression of Klotho, antioxidant enzymes, and apoptosis-associated proteins.

While H₂O₂ significantly suppressed Klotho expression, cell viability, and the expression of antioxidant enzymes in a concentration-dependent manner, cellular apoptosis was increased and p38/MAPK and JNK/MAPK were activated. Intra- and extracellular Klotho remarkably ameliorated viability inhibition, ROS generation, and cellular apoptosis induced by H₂O₂. Intra- and extracellular Klotho also reversed the loss of antioxidant enzymes, the elevation of cleaved Caspase-3 and Bax/Bcl-2, and the phosphorylation of JNK/MAPK and p38/MAPK.

Klotho has posed antioxidant and anti-apoptotic effects on oxidative injuries in TCMK-1 cells, which might be partially related to its inhibition of JNK/MAPK and p38/MAPK phosphorylation and subsequent elevation of antioxidant enzymes. Increasing Klotho expression has played a protective role against oxidative stress in tubular epithelial cells.