Quinone toxicity in hepatocytes: studies on mitochondrial Ca2+ release induced by benzoquinone derivatives.
Hepatocyte cytotoxicity caused by substituted benzoquinones was associated with increased cytosolic Ca2+ concentration. p-Benzoquinone-induced hepatotoxicity was enhanced when the hepatocytes were loaded with Ca2+ by preincubation with ATP. A similar order of potency of the substituted benzoquinones in releasing Ca2+ from isolated mitochondria and inducing hepatocyte cytotoxicity was found; in decreasing order, this was 2-Br-, unsubstituted-, 2-CH3-, 2,6-(CH3O)2-, 2,6-(CH3)2-, 2,5-(CH3)2-, 2,3,5-(CH3)3-, and 2,3,5,6-(CH3)4-benzoquinones (duroquinone). The cellular products of quinone metabolism, hydroquinones and glutathione conjugates, did not cause mitochondrial Ca2+ release. Benzoquinone-induced mitochondrial Ca2+ release was preceded by GSH conjugate formation and NAD(P)H oxidation but followed by mitochondrial swelling. With duroquinone, a slow GSH and NADPH oxidation preceded Ca2+ release, but GSH oxidation did not occur with Se-deficient mitochondria lacking glutathione peroxidase activity. Cyanide-insensitive respiration was also observed with duroquinone but not with benzoquinone, suggesting that duroquinone undergoes redox cycling. GSH was depleted by both arylation and oxidation with 2,6-(CH3O)2-, 2,6-(CH3)2-, 2,5(CH3)2-, and 2,3,5-(CH3)3-benzoquinones. Benzoquinone concentrations that totally depleted GSH did not cause Ca2+ release until intramitochondrial NAD(P)H was oxidized. Ca2+ release was also prevented when NAD(P)H generation was stimulated by the presence of isocitrate or 3-hydroxybutyrate. This suggests that mitochondrial Ca2+ release is associated with NAD(P)H oxidation catalyzed by NADH dehydrogenase with benzoquinone or by the glutathione peroxidase-glutathione reductase system with duroquinone.
Department of Toxicology, Karolinska Institutet, Stockholm, Sweden.
G A
GA
Moore
L
L
Rossi
P
P
Nicotera
S
S
Orrenius
P J
PJ
O'Brien
D000818:Animals; D016227:Benzoquinones; D002118:Calcium / Q000378:metabolism*; D005978:Glutathione / Q000378:metabolism; D005979:Glutathione Peroxidase / Q000378:metabolism; D006706:Homeostasis / Q000187:drug effects; D008297:Male; D008930:Mitochondria, Liver / Q000187:drug effects* / Q000378:metabolism; D009249:NADP / Q000378:metabolism; D010100:Oxygen / Q000378:metabolism; D011809:Quinones / Q000494:pharmacology* / Q000633:toxicity*; D051381:Rats; D011919:Rats, Inbred Strains
D016227:Benzoquinones; D011809:Quinones; C004532:quinone; D009249:NADP; D005979:Glutathione Peroxidase; D005978:Glutathione; D010100:Oxygen; D002118:Calcium; C034257:duroquinone