Ferroptosis involved in the vulnerability of the proximal tubule S3 region to cisplatin

Abstract

To elucidate the mechanism of renal injury induced by the cisplatin (CDDP), we used immortalized cells (S1, S2, S3 cells) derived from mouse proximal tubule S1, S2, and S3 regions. We found that S3 cells are sensitive to CDDP, and one of the reasons for this is that S3 cells markedly increase the amounts of reactive oxygen species (ROS) by exposure to CDDP. In this study, we aimed to elucidate the mechanisms involved in the vulnerability of S3 cells to CDDP by comparing the cellular responses after the addition of CDDP and paraquat (PQ), a ROS-generating agent. Comparing intracellular free Fe²⁺ levels, S3 cells showed higher values than other cells and CDDP significantly increased the amounts of Fe²⁺ in S3 cells. Intracellular ROS are known to oxidize unsaturated fatty acids contained in cell membrane phospholipids. When we examined the amount of lipid peroxide after exposure to CDDP and PQ, we found that the amounts of lipid peroxide was remarkably high in S3 cells. We next compared the expression levels of glutathione peroxidase 4 (GPX4), which can reduce lipid peroxide. The GPX4 expression levels by exposure to PQ increased in all cells, but decreased only in S3 cells by exposure to CDDP. Ferroptosis, a cell death associated with iron-dependent lipid oxidation, was investigated to determine whether the vulnerability of S3 cells to CDDP. The results showed that ferrostatin-1, an inhibitor of ferroptosis, inhibited CDDP-induced cell death in S3 cells. Taken together, ferroptosis was suggested to be partly responsible for the vulnerability of S3 cells to CDDP.