Cytochrome P4502C11 Is a Target of Diclofenac Covalent Binding in Rats

Abstract

Diclofenac antiserum was previously developed and used to detect protein adducts of metabolites of dichlofenac in livers of mice and rats. In this study, the antibody has been used to facilitate the purification of a major 51 kDa microsomal adduct of diclofenac from the liver microsomes of male rats that were treated with diclofenac. The adduct was identified as male-specific cytochrome P4502C11 based on its N-terminal amino acid sequence, reaction with a cytochrome P4502C11 antibody, and by its absence from liver microsomes of diclofenac-treated female rats. When diclofenac was incubated with liver microsomes of control rats in the presence of NADPH, only the 51 kDa adduct was produced. The formation of the adduct was inhibited by a cytochrome P4502C11 monoclonal antibody, but not by reduced glutathione or N-alpha-acetyl-L-lysine. No adduct was detected when diclofenac was incubated with liver microsomes from female rats. Moreover, adduct formation in vivo appeared to lead to a 72% decrease in the activity of cytochrome P4502C11. The results indicate that cytochrome P4502C11 metabolizes diclofenac into a highly reactive product that covalently binds to this enzyme before it can diffuse away and react with other proteins.

The coffee-specific diterpenes cafestol and kahweol protect against aflatoxin B1-induced genotoxicity through a dual mechanism

“…For example, experimental data have indicated that CYP2C11 is involved in the bioactivation of several pro-carcinogens such as styrene (56) and 4-aminobiphenyl (57). Furthermore, 2C11 is known to metabolize the anti-inflamatory drug diclofenac into a highly reactive hepatotoxic product (58). Although the relevance of these data to the human situation remains to be demonstrated, they confirm previous findings (17,42,55) suggesting that these natural coffee-specific components may possess a broad range of promising chemoprotective properties.…”

Pharmacokinetics of diclofenac in rats intoxicated with CCL4, and in the regenerating liver

“…In addition, portalvenous flow could be diminished, due to inflammation caused by necrosis in acute CCl 4 intoxication contributing to a diminution of the absorption of the drug and the total bioavailability. These effects, in addition, to the reduced CYP450 activity during liver regeneration [44], could be why blood concentrations in the oral group were always lower than in the intravenous group. The oral F recovered by day 3, assuming that absorption returned to baseline values too.…”

“…This could be anticipated by the reduction in the activity of hepatic cytochrome P450, since diclofenac is mainly eliminated by CYP2C11 in the rat, during hepatic metabolism [42][43][44] and it is well known that CCl 4 decreases all cytochrome activities [23]. On the other hand, V d did not display alterations between the control group and the groups analysed 1 or 3 days after intoxication with CCl 4, these results are probably associated with the fact that diclofenac binds to plasma proteins (99%) mainly to albumin [5] and that half-life of albumin is 14 days.…”

Mechanism-Based Inactivation of Cytochrome P450 3A4 by Mibefradil through Heme Destruction

“…The observed result is bleaching of the heme chromophore due to fragmentation of the heme moiety. Heme bleaching through destruction of the prosthetic heme has been attributed to compounds such as carbon tetrachloride and N-methyl-N-benzylcyclopropylamine, and phenol-containing compounds such as resveratrol and diclofenac (Guzelian and Swisher, 1979;Macdonald et al, 1982;Davies et al, 1986;Shen et al, 1997;Chang et al, 2001;Ortiz de Montellano and Correia, 2005). Mibefradil seems to fall into this latter category, resulting in a loss of heme with no identifiable heme adducts.…”