Accumulation of mitochondrial P450MT2, NH2-terminal truncated cytochrome P4501A1 in rat brain during chronic treatment with beta-naphthoflavone - A role in the metabolism of neuroactive drugs

The biochemical and molecular characteristics of cytochrome P4501A1 targete d to rat brain mitochondria was studied to determine the generality of the targeting mechanism previously described for mitochondrial cytochrome P450M T2 (P450MT2) from rat liver. In rat brain and C6 glioma cells chronically e xposed to beta -naphoflavone (BNF), P450MT2 content reached 50 and 95% of t he total cellular pool, respectively. P450MT2 from 10 days of BNF-treated r at brain was purified to over 85% purity using hydrophobic chromatography f ollowed by adrenodoxin affinity binding. Purified brain P450MT2 consisted o f two distinct molecular species with NH2 termini identical to liver mitoch ondrial forms. These results confirm the specificity of endoprotease-proces sing sites. The purified P450MT2 showed a preference for adrenodoxin + adre nodoxin reductase electron donor system and exhibited high erythromycin N-d emethylation activity. Brain mitoplasts from 10-day BNF-treated rats and al so purified P450MT2 exhibited high N-demethylation activities for a number of neuroactive drugs, including trycyclic anti-depressants, anti-convulsant s, and opiates. At 10 days of BNF treatment, the mitochondrial metabolism o f these neuroactive drugs represented about 85% of the total tissue activit y. These results provide new insights on the role of P450MT2 in modulating the pharmacological potencies of different neuroactive drugs in chronically exposed individuals.