Thiosulfate Mediates Cytoprotective Effects of Hydrogen Sulfide Against Neuronal Ischemia

Abstract

BackgroundHydrogen sulfide (H2S) exhibits protective effects in various disease models including cerebral ischemia–reperfusion (I/R) injury. Nonetheless, mechanisms and identity of molecules responsible for neuroprotective effects of H2S remain incompletely defined. In the current study, we observed that thiosulfate, an oxidation product of H2S, mediates protective effects of an H2S donor compound sodium sulfide (Na2S) against neuronal I/R injury.Methods and ResultsWe observed that thiosulfate in cell culture medium is not only required but also sufficient to mediate cytoprotective effects of Na2S against oxygen glucose deprivation and reoxygenation of human neuroblastoma cell line (SH‐SY5Y) and murine primary cortical neurons. Systemic administration of sodium thiosulfate (STS) improved survival and neurological function of mice subjected to global cerebral I/R injury. Beneficial effects of STS, as well as Na2S, were associated with marked increase of thiosulfate, but not H2S, in plasma and brain tissues. These results suggest that thiosulfate is a circulating “carrier” molecule of beneficial effects of H2S. Protective effects of thiosulfate were associated with inhibition of caspase‐3 activity by persulfidation at Cys163 in caspase‐3. We discovered that an SLC13 family protein, sodium sulfate cotransporter 2 (SLC13A4, NaS‐2), facilitates transport of thiosulfate, but not sulfide, across the cell membrane, regulating intracellular concentrations and thus mediating cytoprotective effects of Na2S and STS.ConclusionsThe protective effects of H2S are mediated by thiosulfate that is transported across cell membrane by NaS‐2 and exerts antiapoptotic effects via persulfidation of caspase‐3. Given the established safety track record, thiosulfate may be therapeutic against ischemic brain injury.

Sulfite protects neurons from oxidative stress

“…Marutani et al . () reported that H 2 S is oxidized to thiosulfate, which was proposed as the chemical entity mediating the protective effect on neurons. However, the present study revealed that H 2 S was converted to sulfite before thiosulfate (Figure A), and sulfite exerted protective effects against oxytosis in neurons much more effectively than did thiosulfate (Figures A, E, A and ).…”

“…The cytoprotective effect of H 2 S against oxygen glucose deprivation followed by reoxygenation was reported to be mediated by thiosulfate sequentially produced by the oxidation of H 2 S in culture medium (Marutani et al ., ). We examined whether or not thiosulfate protects neurons from oxytosis.…”

“…Sulfite markedly increased intracellular GSH, while thiosulfate did not (Figures A and E). Thiosulfate was reported to significantly increase the levels of GSH in SH‐SY5Y cells (Marutani et al ., ), but not in primary neuronal cultures in the present study (Figure E). The discrepancy may be caused by the difference between a cell line and primary neuronal cultures.…”

“…Thiosulfate, another oxidized product of H 2 S and H 2 S n , was recently reported to protect neuroblastoma cells and primary neuronal cultures from oxygen glucose deprivation followed by reoxygenation and was proposed as a chemical entity to mediate H 2 S cytoprotection (Marutani et al ., ). Sulfite was a more effective protector of neurons against oxytosis than thiosulfate.…”

Hydrogen Sulfide Protects Renal Grafts Against Prolonged Cold Ischemia–Reperfusion Injury via Specific Mitochondrial Actions

“…Thiosulfate is a naturally occurring intermediate of sulfur metabolism and is currently used as a part of treatment regimens for clinical conditions including calciphylaxis and cyanide poisoning . However, thiosulfate has also recently been shown to produce H 2 S under physiological conditions and mediate protection of neurons from ischemic injury . AGE is known to exert potent antioxidant effects and has a wide variety of clinical applications, including reduction of blood pressure in hypertensive patients and slowing the progression of atherosclerotic plaques .…”