Sulphide quinone reductase contributes to hydrogen sulphide metabolism in murine peripheral tissues but not in the CNS

BACKGROUND AND PURPOSE Hydrogen sulphide (H ₂S) is gaining acceptance as a gaseous signal molecule. However, mechanisms regarding signal termination are not understood. We used stigmatellin and antimycin A, inhibitors of sulphide quinone reductase (SQR), to test the hypothesis that the catabolism of H ₂S involves SQR. EXPERIMENTAL APPROACH H ₂S production and consumption were determined in living and intact mouse brain, liver and colonic muscularis externa using gas chromatography and HPLC. Expressions of SQR, ethylmalonic encephalopathy 1 (Ethe1) and thiosulphate transferase (TST; rhodanese) were determined by RT-PCR and immunohistochemistry. KEY RESULTS In the colonic muscularis externa, H ₂ ³⁵S was catabolized to [ ³⁵S]-thiosulphate and [ ³⁵S]-sulphate, and stigmatellin reduced both the consumption of H ₂ ³⁵S and formation of [ ³⁵S]-thiosulphate. Stigmatellin also enhanced H ₂S release by the colonic muscularis externa. In the brain, catabolism of H ₂ ³⁵S to [ ³⁵S]-thiosulphate and [ ³⁵S]-sulphate, which was stigmatellin-insensitive, partially accounted for H ₂ ³⁵S consumption, while the remainder was captured as unidentified ³⁵S that was probably bound to proteins. Levels of mRNA encoding SQR were higher in the colonic muscularis externa and the liver than in the brain. CONCLUSIONS AND IMPLICATIONS These data support the concept that termination of endogenous H ₂S signalling in the colonic muscularis externa occurs via catabolism to thiosulphate and sulphate partially via a mechanism involving SQR. In the brain, it appears that H ₂S signal termination occurs partially through protein sequestration and partially through catabolism not involving SQR. As H ₂S has beneficial effects in animal models of human disease, we suggest that selective inhibition of SQR is an attractive target for pharmaceutical development.