Truong Don H, Eghbal Mohammad A, Hindmarsh Wayne, Roth Sheldon H, O'Brien Peter J
Department of Pharmaceutical Sciences, University of Toronto, Toronto, Ontario, Canada.
Drug Metab Rev. 2006;38(4):733-44. doi: 10.1080/03602530600959607.
The toxicity of H2S has been attributed to its ability to inhibit cytochrome c oxidase in a similar manner to HCN. However, the successful use of methemoglobin for the treatment of HCN poisoning was not successful for H2S poisonings even though the ferric heme group of methemoglobin scavenges H2S. Thus, we speculated that other mechanisms contribute to H2S induced cytotoxicity. Experimental procedure. Hepatocyte isolation and viability and enzyme activities were measured as described by Moldeus et al. (1978), and Steen et al. (2001).
Incubation of isolated hepatocytes with NaHS solutions (a H2S source) resulted in glutathione (GSH) depletion. Moreover, GSH depletion was also observed in TRIS-HCl buffer (pH 6.0) treated with NaHS. Several ferric chelators (desferoxamime and DETAPAC) and antioxidant enzymes (superoxide dismutase [SOD] and catalase) prevented cell-free and hepatocyte GSH depletion. GSH-depleted hepatocytes were very susceptible to NaHS cytotoxicity, indicating that GSH detoxified NaHS or H2S in cells. Cytotoxicity was also partly prevented by desferoxamine and DETAPC, but it was increased by ferric EDTA or EDTA. Cell-free oxygen consumption experiments in TRIS-HCl buffer showed that NaHS autoxidation formed hydrogen peroxide and was prevented by DETAPC but increased by EDTA. We hypothesize that H2S can reduce intracellular bound ferric iron to form unbound ferrous iron, which activates iron. Additionally, H2S can increase the hepatocyte formation of reactive oxygen species (ROS) (known to occur with electron transport chain). H2S cytotoxicity therefore also involves a reactive sulfur species, which depletes GSH and activates oxygen to form ROS.
硫化氢的毒性被认为是由于其能够以与氰化氢类似的方式抑制细胞色素c氧化酶。然而，尽管高铁血红蛋白的铁血红素基团能够清除硫化氢，但使用高铁血红蛋白治疗氰化氢中毒的方法在硫化氢中毒治疗中并不成功。因此，我们推测其他机制也参与了硫化氢诱导的细胞毒性。实验步骤。肝细胞的分离、活力及酶活性的测定方法参照莫尔德斯等人（1978年）以及斯汀等人（2001年）的描述。
用硫氢化钠溶液（一种硫化氢来源）孵育分离的肝细胞会导致谷胱甘肽（GSH）耗竭。此外，在用硫氢化钠处理的TRIS - HCl缓冲液（pH 6.0）中也观察到了谷胱甘肽耗竭。几种铁螯合剂（去铁胺和二乙基三胺五乙酸）以及抗氧化酶（超氧化物歧化酶[SOD]和过氧化氢酶）可防止无细胞体系及肝细胞中的谷胱甘肽耗竭。谷胱甘肽耗竭的肝细胞对硫氢化钠的细胞毒性非常敏感，这表明谷胱甘肽在细胞内可使硫氢化钠或硫化氢解毒。去铁胺和二乙基三胺五乙酸也可部分预防细胞毒性，但乙二胺四乙酸铁或乙二胺四乙酸会使其增加。在TRIS - HCl缓冲液中进行的无细胞耗氧实验表明，硫氢化钠自氧化会生成过氧化氢，二乙基三胺五乙酸可防止其生成，而乙二胺四乙酸会使其增加。我们推测硫化氢可将细胞内结合的三价铁还原为游离的二价铁，从而激活铁。此外，硫化氢可增加肝细胞中活性氧（ROS）的生成（已知这与电子传递链有关）。因此，硫化氢的细胞毒性还涉及一种活性硫物质，它会消耗谷胱甘肽并激活氧以形成活性氧。
