Cyclosporin A protects hepatocytes against prooxidant-induced cell killing. A study on the role of mitochondrial Ca2+ cycling in cytotoxicity.
Cyclosporin A (CsA) is a potent inhibitor of the prooxidant-induced release of Ca2+ from isolated mitochondria. In this investigation, pretreatment of hepatocytes with CsA before exposure to the prooxidants tert-butyl hydroperoxide (tBH), cumene hydroperoxide or 3,5-dimethyl-N-acetyl-p-benzoquinone imine (3,5-Me2-NAPQI) prevented the loss of cell viability. HPLC analysis of adenine and pyridine nucleotide concentrations in hepatocytes treated with 3,5-Me2-NAPQI showed a rapid depletion of ATP prior to the loss of cell viability versus the maintenance of near control levels of ATP in hepatocytes treated with CsA before 3,5-Me2-NAPQI. In 3,5-Me2-NAPQI-exposed hepatocytes there was also a rapid loss of cellular NAD+ which could be accounted for initially by a transient increase in NADP+. Measurement of the intracellular Ca2+ pools showed an early depletion of the mitochondrial Ca2+ pool in hepatocytes exposed to 3,5-Me2-NAPQI, tBH or cumene hydroperoxide; this loss was prevented by CsA. In conclusion, these results show that CsA protected hepatocytes from prooxidant injury by preventing mitochondrial Ca2+ cycling and subsequent mitochondrial dysfunction. This suggests that in prooxidant injury, excessive Ca2+ cycling is an early and important event leading to mitochondrial damage and subsequently to cell death.
Kass
G E
GE
Department of Toxicology, Karolinska Institutet, Stockholm, Sweden.
Juedes
M J
MJ
Orrenius
S
S
D000818:Animals; D001555:Benzene Derivatives / Q000633:toxicity; D016227:Benzoquinones / Q000633:toxicity; D002118:Calcium / Q000378:metabolism*; D016923:Cell Death / Q000187:drug effects; D016572:Cyclosporine / Q000494:pharmacology*; D007097:Imines / Q000633:toxicity; D008099:Liver / Q000187:drug effects*; D008297:Male; D008930:Mitochondria, Liver / Q000187:drug effects / Q000378:metabolism; D010084:Oxidation-Reduction; D010545:Peroxides / Q000633:toxicity; D051381:Rats; D017208:Rats, Wistar; D020122:tert-Butylhydroperoxide
D001555:Benzene Derivatives; D016227:Benzoquinones; D007097:Imines; D010545:Peroxides; C040069:N-acetyl-3,5-dimethyl-4-benzoquinone imine; D016572:Cyclosporine; D020122:tert-Butylhydroperoxide; C007164:cumene hydroperoxide; D002118:Calcium