Differential inhibition of naringenin on human and rat cytochrome P450 2E1 activity.

Cytochrome P450 2E1 (CYP2E1) has been proposed as a molecular target in oxidative stress-associated metabolic diseases. Rats are chosen as model organisms in most experiments studying CYP2E1-related toxicity; however, the human relevance of these results remains unclear. To describe differences in catalysis and inhibition between human and rat CYP2E1, recombinant human and rat CYP2E1 enzymes were treated with different concentrations of naringenin (NAR, 10 nM - 1 mM), and inhibition parameters were calculated. Interspecies differences in the catalytic efficiency for O-demethylation of 7-methoxy-4-(trifluoromethyl)coumarin were revealed (45-fold higher in human CYP2E1 than in the rat enzyme). Additionally, differences in the potency of inhibition of NAR were found (absolute half inhibitory concentration, IC50 = 204 ± 28 and 69 ± 4 µM; inhibition constant, Ki = 9 ± 2 and 161 ± 20 µM in human and rat CYP2E1, respectively). Although NAR exhibited a noncompetitive mechanism of inhibition of both CYP2E1 enzymes, this compound is an irreversible inhibitor of rat CYP2E1 and a reversible inhibitor of the human enzyme. Molecular docking suggested that differences in the potency of inhibition and time dependence between species could be attributable to the differential interactions of NAR with access channels to the CYP2E1 catalytic site. These results highlight the importance of finding the appropriate model to improve the predictability of animal-based assays for human risk assessment.

Effect of [Cu(4,7-dimethyl-1,10-phenanthroline)(acetylacetonato)]NO3, Casiopeína III-Ea, on the activity of cytochrome P450.

Casiopeína III-Ea (Cas III-Ea(1)) is a copper complex with antiproliferative and antitumor activities, designed to act via alternative mechanisms of action different from Cisplatin. This compound has also been well characterized in preclinical test and pharmacokinetic analysis, being a good candidate for clinical phases. Since very little is known about the processes of biotransformation of therapeutic metal based drugs, this paper report the first approach to the study of the interaction between metal complex Cas III-Ea and cytochromes P450 with the aim to find out possible biotransformation pathways for this complexes and feasible drug-drug interactions. Results showed that Cas III-Ea is a strong irreversible competitive inhibitor of CYP1A1 (IC50 = 7.5 ± 1.0 µM; Ki = 240 nM). The magnitude of values indicate that it is necessary to be taken into account such effect when analyzing possible drug interactions with these new drugs in order to prevent adverse reactions derived from this inhibition.