Abstract
Hydrogen sulfide (H(2)S) functions as a signaling molecule and cytoprotectant. In many tissues, H(2)S is produced from l-cysteine, whereas the kidney also produces H(2)S from d-cysteine by the sequential activities of d-amino acid oxidase (DAO) and 3-mercaptopyruvate sulfurtransferase (3MST). The d-cysteine pathway produces H(2)S more efficiently than the l-cysteine pathway, and d-cysteine significantly reduces ischemia-reperfusion injury in the renal cortex compared with l-cysteine. However, the specific renal cell types responsible for the d-cysteine pathway have not been clearly identified. Here, we show that a subpopulation of MDCK (NBL-2) cells, a renal epithelial cell line, expresses both DAO and 3MST. MDCK cells initially produced H(2)S from d-cysteine, but this activity progressively declined with passage. In contrast, clonal cells expressing DAO and 3MST, established from this subpopulation, maintained stable H(2)S production. The clonal cells exhibited two distinct patterns of DAO expression: one showed increased DAO levels after confluence, whereas the other displayed high DAO expression even before reaching confluence. These findings suggest that the d-cysteine pathway operates in epithelial cells and plays distinct roles depending on cellular state and dynamics. Moreover, the established clonal cells may provide insight into the role of d-cysteine-mediated H(2)S production in the kidney.