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.
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