title: N-acetyl-p-benzoquinone imine induces Ca2+ release from mitochondria by stimulating pyridine nucleotide hydrolysis.
abstract: The mechanism of N-acetyl-p-benzoquinone imine (NAPQI)-induced release of Ca2+ from rat liver mitochondria was investigated. The addition of NAPQI or 3,5-Me2-NAPQI (a dimethylated analogue of NAPQI with only oxidizing properties) to mitochondria resulted in the rapid and extensive oxidation of NADH and NADPH. High-performance liquid chromatographic analysis of mitochondrial pyridine nucleotides revealed that the formation of NAD+ and NADP+ was followed by a time-dependent net loss of total pyridine nucleotides as a result of their hydrolysis, with the formation of nicotinamide. Preincubation of the mitochondria with cyclosporin A completely prevented the quinone imine-stimulated release of sequestered Ca2+ from mitochondria. Cyclosporin A did not affect the ability of NAPQI or 3,5-Me2-NAPQI to oxidize NAD(P)H but prevented the quinone imine-induced hydrolysis of the pyridine nucleotides. Although there was no detectable change in total protein-bound ADP-ribose content during quinone imine-induced Ca2+ release from mitochondria, meta-iodobenzylguanidine, a competitive inhibitor of protein mono(ADP-ribosylation), prevented Ca2+ release by NAPQI and 3,5-Me2-NAPQI; meta-iodobenzylguanidine did not inhibit the quinone imine-induced NAD(P)H oxidation and only partially blocked hydrolysis of the oxidized pyridine nucleotides. It is concluded that NAPQI causes the oxidation of mitochondrial NADH and NADPH, and stimulates Ca2+ release as a result of the further hydrolysis of the oxidized pyridine nucleotides and protein mono(ADP-ribosylation).
authors.affiliation: Department of Toxicology, Karolinska Institutet, Stockholm, Sweden.
authors.forename: M
authors.initials: M
authors.lastname: Weis
authors.forename: G E
authors.initials: GE
authors.lastname: Kass
authors.forename: S
authors.initials: S
authors.lastname: Orrenius
authors.forename: P
authors.initials: P
authors.lastname: Moldéus
mesh_terms: D019797:3-Iodobenzylguanidine; D000818:Animals; D016227:Benzoquinones / Q000494:pharmacology*; D002118:Calcium / Q000378:metabolism*; D002463:Cell Membrane Permeability; D016572:Cyclosporine / Q000494:pharmacology; D006868:Hydrolysis; D007097:Imines / Q000494:pharmacology*; D007425:Intracellular Membranes / Q000502:physiology; D007462:Iodobenzenes / Q000494:pharmacology; D008297:Male; D008930:Mitochondria, Liver / Q000187:drug effects / Q000378:metabolism*; D009243:NAD / Q000378:metabolism*; D009249:NADP / Q000378:metabolism*; D010084:Oxidation-Reduction; D051381:Rats; D011919:Rats, Inbred Strains
chemical_list: D016227:Benzoquinones; D007097:Imines; D007462:Iodobenzenes; D009243:NAD; D019797:3-Iodobenzylguanidine; D009249:NADP; D016572:Cyclosporine; C028473:N-acetyl-4-benzoquinoneimine; D002118:Calcium