title: Mitochondrial toxicity of diclofenac and its metabolites via inhibition of oxidative phosphorylation (ATP synthesis) in rat liver mitochondria: Possible role in drug induced liver injury (DILI).
abstract: Diclofenac is a widely prescribed NSAID, which by itself and its reactive metabolites (Phase-I and Phase-II) may be involved in serious idiosyncratic hepatotoxicity. Mitochondrial injury is one of the mechanisms of drug induced liver injury (DILI). In the present work, an investigation of the inhibitory effects of diclofenac (Dic) and its phase I [4-hydroxy diclofenac (4'-OH-Dic) and 5-hydroxy diclofenac (5-OH-dic)] and Phase-II [diclofenac acyl glucuronide (DicGluA) and diclofenac glutathione thioester (DicSG)] metabolites, on ATP synthesis in rat liver mitochondria was carried out. A mechanism based inhibition of ATP synthesis is exerted by diclofenac and its metabolites. Phase-I metabolite (4'-OH-Dic) and Phase-II metabolites (DicGluA and DicSG) showed potent inhibition (2-5 fold) of ATP synthesis, where as 5-OH-Dic, one of the Phase-I metabolite, was a less potent inhibitor as compared to Dic. The calculated kinetic constants of mechanism based inhibition of ATP synthesis by Dic showed maximal rate of inactivation (Kinact) of 2.64 ± 0.15 min(-1) and half maximal rate of inactivation (KI) of 7.69 ± 2.48 μM with Kinact/KI ratio of 0.343 min(-1) μM(-1). Co-incubation of mitochondria with Dic and reduced GSH exhibited a protective effect on Dic mediated inhibition of ATP synthesis. Our data from this study strongly indicate that Dic as well as its metabolites could be involved in the hepato-toxic action through inhibition of ATP synthesis.
authors.affiliation: Section of Analytical Biosciences, Department of Pharmacy, School of Pharmaceutical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark. Electronic address: muzeeb.syed@sund.ku.dk.
authors.forename: Muzeeb
authors.initials: M
authors.lastname: Syed
authors.affiliation: ADME Department, Discovery Biology and Technology, Novo Nordisk A/S, Måløv, Copenhagen, Denmark.
authors.forename: Christian
authors.initials: C
authors.lastname: Skonberg
authors.affiliation: Section of Analytical Biosciences, Department of Pharmacy, School of Pharmaceutical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark.
authors.forename: Steen Honoré
authors.initials: SH
authors.lastname: Hansen
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D000894:Anti-Inflammatory Agents, Non-Steroidal / Q000633:toxicity*; D056486:Chemical and Drug Induced Liver Injury; D004008:Diclofenac / Q000031:analogs & derivatives* / Q000633:toxicity*; D005978:Glutathione / Q000494:pharmacology; D008297:Male; D008930:Mitochondria, Liver / Q000187:drug effects* / Q000378:metabolism; D010085:Oxidative Phosphorylation / Q000187:drug effects; D017207:Rats, Sprague-Dawley
chemical_list: D000894:Anti-Inflammatory Agents, Non-Steroidal; D004008:Diclofenac; D000255:Adenosine Triphosphate; D005978:Glutathione
keywords: ATP; Diclofenac; Drug induced liver injury; Metabolites; Oxidative phosphorylation; Rat liver mitochondria