Hypotaurine protects against H2S‐induced oxidative stress and cell death in erythrocytes from an H2S‐tolerant marine worm

Abstract

Many marine invertebrates adapted to H2S contain high concentrations of the organic osmolyte hypotaurine (H). In the presence of H2S, H is converted to thiotaurine (Th), and the Th:(H+Th) ratio is higher in animals from environments with higher H2S, suggesting that H can serve as a H2S buffer. However, H and possibly Th are antioxidants and therefore may also protect against free radicals produced by H2S oxidation. We used erythrocytes from the H2S‐tolerant marine polychaete Glycera dibranchiata to determine whether H reduces cell death and oxidative stress caused by H2S exposure in vitro. Greater than 90% of cells were killed by exposure to 0.3% H2S gas (based on calcein‐AM staining) but this death was decreased by 60%, 78%, and 83% with 0.5, 5.0 and 50 mM H, respectively (p<0.001 for each, n=8). Similar trends were observed at both higher and lower H2S concentrations (0.1, 1 and 3% H2S). Oxidative stress (based on H2DCFDA) was increased 67% by H2S (p<0.0001), but this increase was attenuated by H (p=0.0002). In contrast, H did not decrease the effect of H2O2 (0.01–10 mM) on cell death (p=0.001) or oxidative stress (p=0.038), and H that was pre‐converted to Th did not reduce H2S‐induced cell death (p<0.0001). Therefore, hypotaurine protects against cell death and oxidative stress, although it remains unknown whether these effects are due to sulfide buffering or free radical scavenging.