The role of reduced glutathione and glutathione reductase in the cytotoxicity of chromium (VI) in osteoblasts.
It is accepted that to exert cytotoxicity and carcinogenicity chromium VI has to be reduced inside cells. The role of reduced glutathione (GSH) and glutathione reductase in the intracellular reduction of Cr VI was investigated using an immortalized rat osteoblast cell line, FFC. Alkaline phosphatase activity was the index of cytotoxicity measured. To investigate the role of GSH in Cr VI toxicity, GSH levels in the cells were elevated by pretreatment with L-cysteine, and depleted using buthionine sulfoximine (BSO), an inhibitor of GSH synthesis. Intracellular GSH levels were not depleted during the metabolism of Cr VI. Depletion of GSH by BSO caused the cells to be more resistant to the toxicity of Cr VI, indicating that GSH is involved in reduction of the Cr VI. Inhibition of glutathione reductase by carmustine (BCNU) partially protected against the cytotoxicity of Cr VI irrespective of the intracellular GSH. The cytotoxic response was similar if cells were pretreated with BCNU plus L-cysteine, or with BCNU plus BSO, although the GSH levels were markedly different. The results indicate that glutathione reductase plays an important role in the intracellular reduction of Cr VI in osteoblasts.
Ning
J
J
Bioengineering Unit, Strathclyde University, Wolfson Centre, G4 0NW, Glasgow, UK.
Grant
M H
MH
D000469:Alkaline Phosphatase / Q000378:metabolism; D000818:Animals; D019328:Buthionine Sulfoximine / Q000494:pharmacology; D002274:Carcinogens, Environmental / Q000633:toxicity*; D002330:Carmustine / Q000494:pharmacology; D002461:Cell Line, Transformed; D002857:Chromium / Q000633:toxicity*; D003545:Cysteine / Q000494:pharmacology; D004347:Drug Interactions; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005978:Glutathione / Q000172:deficiency / Q000378:metabolism*; D005980:Glutathione Reductase / Q000037:antagonists & inhibitors / Q000378:metabolism*; D010006:Osteoblasts / Q000187:drug effects* / Q000378:metabolism / Q000473:pathology; D051381:Rats
D002274:Carcinogens, Environmental; D004791:Enzyme Inhibitors; D002857:Chromium; C074702:chromium hexavalent ion; D019328:Buthionine Sulfoximine; D005980:Glutathione Reductase; D000469:Alkaline Phosphatase; D005978:Glutathione; D003545:Cysteine; D002330:Carmustine