Primary hepatocytes from mice lacking cysteine dioxygenase show increased cysteine concentrations and higher rates of metabolism of cysteine to hydrogen sulfide and thiosulfate
The oxidation of cysteine in mammalian cells occurs by two routes: a highly regulated direct oxidation pathway in which the first step is catalyzed by cysteine dioxygenase (CDO) and by desulfhydration-oxidation pathways in which the sulfur is released in a reduced oxidation state. To assess the effect of a lack of CDO on production of hydrogen sulfide (H2S) and thiosulfate (an intermediate in the oxidation of H2S to sulfate) and to explore the roles of both cystathionine γ-lyase (CTH) and cystathionine β-synthase (CBS) in cysteine desulfhydration by liver, we investigated the metabolism of cysteine in hepatocytes isolated from Cdo1-null and wild-type mice. Hepatocytes from Cdo1-null mice produced more H2S and thiosulfate than did hepatocytes from wild-type mice. The greater flux of cysteine through the cysteine desulfhydration reactions catalyzed by CTH and CBS in hepatocytes from Cdo1-null mice appeared to be the consequence of their higher cysteine levels, which were due to the lack of CDO and hence lack of catabolism of cysteine by the cysteinesulfinate-dependent pathways. Both CBS and CTH appeared to contribute substantially to cysteine desulfhydration, with estimates of 56 % by CBS and 44 % by CTH in hepatocytes from wild-type mice, and 63 % by CBS and 37 % by CTH in hepatocytes from Cdo1-null mice.
KeywordsCysteine Cysteine dioxygenase Cystathionine γ-lyase Cystathionine β-synthase Hydrogen sulfide Thiosulfate Mice Hepatocytes
The authors thank Dr. John E. Dominy (Department of Cancer Biology, Dana-Farber Cancer Institute, Boston, Massachusetts, USA) for training us in the technique for murine hepatocyte isolation and Dr. Viktor Kožich (Institute of Inherited Metabolic Disorders, Charles University in Prague, First Faculty of Medicine and General University Hospital, Praha, Czech Republic) for facilitating the by LC–MS/MS analyses and reviewing the manuscript. This project was supported by Grant DK-056649 from the National Institute of Diabetes and Digestive and Kidney Diseases. The content is solely the responsibility of the authors and does not necessarily represent the official views of the National Institutes of Health. This study was supported in part by the research program of the Charles University in Prague (PRVOUK-P24/LF1/3) with access to the LC–MS/MS made possible by project OPPK No. CZ.2.16/3.1.00/24012. H.J. was supported by a “Mobility Plus” fellowship from the Ministry of Science and Higher Education (MNISW), Republic of Poland.
Conflict of interest
No conflict of interests, financial or otherwise, are reported by the authors.
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