HANCE, J.M.; WOHLGEMUTH, S.E.; JULIAN, D.; University of Florida, Gainesville; University of Florida, Gainesville; University of Florida, Gainesville: Survival of coelomocytes from the intertidal polychaete Glycera dibranchiata during exposure to H₂S and the effects of MPTP inhibitors to reduce cytotoxicity

Inhibition of cytochrome c oxidase has traditionally been accepted as the lethal mechanism of hydrogen sulfide (H₂S) toxicity in all animals, including marine invertebrates evolutionarily adapted to H₂S exposure. To test this, we exposed coelomocytes from the sulfide-adapted intertidal polychaete Glycera dibranchiata to H₂S gas in vitro for up to 24 h. We found that cell survival (assayed by neutral red incorporation and by cell count) decreased with increasing H₂S concentration, as expected, with a K_m of 400 �M. Cell death was maximal during the first 3 hours of exposure, and occurred primarily by necrosis, rather than by traditional apoptotic pathways (as indicated by positive propidium iodide labeling and the absence of Annexin V labeling). Addition of 5 mM fructose during H₂S exposure, which would be expected to reduce cell death by providing sufficient ATP via increased glycolysis, had no effect on survival. This suggests toxicity in addition to inhibition of oxidative phosphorylation. Furthermore, addition of 5 mM cyclosporine A and trifluoperazine, which together inhibit opening of the mitochondrial permeability transition pore (MPTP) in mammalian cells, increased cell survival during H₂S exposure by 17% (P = 0.0001, n = 4). This is consistent with the findings of Thompson et al. [Toxicology 188 (2003) 149-159], who exposed rat hepatocytes to Na₂S for up to 4 hours. Our data suggest that H₂S causes cell death at least partially via MPTP opening, and that this mechanism is independent of cytochrome c oxidase inhibition.