Analysis and characterization of sulfane sulfur

In the late 1970s, sulfane sulfur was defined as sulfur atoms covalently bound only to sulfur atoms. However, this definition was not generally accepted, as it was slightly vague and difficult to comprehend. Thus, in the early 1990s, it was defined as "bound sulfur," which easily converts to hydrogen sulfide upon reduction with a thiol-reducing agent. H2S-related bound sulfur species include persulfides (R-SSH), polysulfides (H2Sn, n ≥ 2 or R-S(S)nS-R, n ≥ 1), and protein-bound elemental sulfur (S0). Many of the biological effects currently associated with H2S may be attributed to persulfides and polysulfides. In the 20th century, quantitative determination of "sulfane sulfur" was conventionally performed using a reaction called cyanolysis. Several methods have been developed over the past 30 years. Current methods used for the detection of H2S and polysulfides include colorimetric assays for methylene blue formation, sulfide ion-selective or polarographic electrodes, gas chromatography with flame photometric or sulfur chemiluminescence detection, high-performance liquid chromatography analysis with fluorescent derivatization of sulfides, liquid chromatography with tandem mass spectrometry, the biotin switch technique, and the use of sulfide or polysulfide-sensitive fluorescent probes. In this review, we discuss the methods reported to date for measuring sulfane sulfur and the results obtained using these methods.

Polysulfide exerts a protective effect against cytotoxicity caused by t-buthylhydroperoxide through Nrf2 signaling in neuroblastoma cells

Polysulfide is a bound sulfur species derived from endogenous H2S. When mouse neuroblastoma, Neuro2A cells were exposed to tert-butyl hydroperoxide after treatment with polysulfide, a significant decline in cell toxicity was observed. Rapid uptake of polysulfides induced translocation of Nrf2 into the nucleus, resulting in acceleration of GSH synthesis and HO-1 expression. We demonstrated that polysulfide reversibly modified Keap1 to form oxidized dimers and induced the translocation of Nrf2. Moreover, polysulfide treatment accelerated Akt phosphorylation, which is a known pathway of Nrf2 phosphorylation. Thus, polysulfide may mediate the activation of Nrf2 signaling, thereby exerting protective effects against oxidative damage in Neuro2A cells.