Nitrosopersulfide (SSNO−) decomposes in the presence of sulfide, cyanide or glutathione to give HSNO/SNO−: Consequences for the assumed role in cell signalling

Abstract

The emergence of hydrogen sulfide (H2S) as a new signalling molecule able to control vasodilation, neurotransmission and immune response, prompted questions about its possible cross-talk with the other gasontransmitter, nitric oxide (NO). It has been shown that H2S reacts with NO and its metabolites and several potentially biologically active species have been identified. Thionitrous acid (HSNO) was proposed to be an intermediate product of the reaction of S-nitrosothiols with H2S capable of crossing the membranes and causing further trans-nitrosation of proteins. Alternatively, formation of nitrosopersulfide (SSNO−) has been proposed in this reaction. SSNO− was claimed to be particularly stable and inert to H2S, thiols and cyanides. It is suggested that this putative SSNO− slowly decomposes to give NO, HNO and polysulfides. However, the chemical studies with pure SSNO− salts showed some conflicting observations. In this study, we work with pure PNP+SSNO− to show that contrary to everything that is claimed for the yellow reaction product of GSNO with H2S, pure SSNO− decomposes readily in the presence of cyanide, H2S and glutathione to form SNO−. Based on literature overview and chemical data about the structures of HSNO/SNO− and SSNO− we discuss the biological role these two species could have.