Caffeine 7-N-demethylation and C-8-oxidation mediated by liver microsomal cytochrome P450 enzymes in common marmosets

Abstract

1. 3-N-Demethylation of caffeine (1,3,7-trimethylxanthine) is mediated by human cytochrome P450 1A2, whereas 7-N-demethylation and C-8-hydroxylation are reportedly catalyzed by monkey P450 2C9 and rat P450 1A2, respectively.

2. Roles of marmoset P450 enzymes in caffeine oxidation were investigated using nine marmoset liver microsomes and 14 recombinantly expressed marmoset P450 enzymes.

3. Predominant caffeine 7-N-demethylation and C-8-hydroxylation activities in marmoset liver microsomes were moderately (r = 0.78, p < 0.05) and highly (r = 0.82, p < 0.01) correlated with midazolam 1′-hydroxylation activities, respectively, while the former was not strongly affected by ketoconazole or α-naphthoflavone.

4. Caffeine C-8-hydroxylation in liver microsomes was inhibited by ketoconazole and activated by α-naphthoflavone, suggesting main involvements of P450 3As.

5. Recombinant marmoset P450 3As had high V_max/K_m values for C-8-hydroxylation, comparable to K_m values for marmoset liver microsomes. Marmoset P450 1As efficiently mediated caffeine 3-N-demethylation and C-8-hydroxylation with apparently lower K_m values than those of liver microsomes.

6. These results collectively suggest highly active marmoset P450 3A enzymes toward caffeine 8-hydorxylaiton and involvement of multiple P450 isoforms including P450 1A in caffeine 7-N- and 3-N-demethylations in marmoset livers. Marmoset P450s have slightly different properties to human or monkey P450s regarding caffeine metabolic pathways.

• 8-hydroxylation
• caffeine
• common marmoset
• N-demethylation

Acknowledgements

The authors thank Drs. Makiko Shimizu and Norie Murayama for their technical help.

Declaration of interest

This study was resulted from “Construction of System for Spread of Primate Model Animals” under the Strategic Research Program for Brain Sciences of Japan Agency for Medical Research and Development. This work was also supported by JSPS Grant-in-Aid for Young Scientists (B), Grant Number 15K18934 (SU). The authors are responsible for the content and writing the article and report no declarations of interest.