Differential expression of cytochrome P450 enzymes from the CYP2C subfamily in the human brain.

Cytochrome P450 enzymes from the CYP2C subfamily play a prominent role in the metabolic clearance of many drugs. CYP2C enzymes have also been implicated in the metabolism of arachidonic acid to vasoactive epoxyeicosatrienoic acids. CYP2C8, CYP2C9, and CYP2C19 are expressed in the adult liver at significant levels; however, the expression of CYP2C enzymes in extrahepatic tissues such as the brain is less well characterized. Form-specific antibodies to CYP2C9 and CYP2C19 were prepared by affinity purification of antibodies raised to unique peptides. CYP2C9 and CYP2C19 were located in microsomal fractions of all five human brain regions examined, namely the frontal cortex, hippocampus, basal ganglia, amygdala, and cerebellum. Both CYP2C9 and CYP2C19 were detected predominantly within the neuronal soma but with expression extending down axons and dendrites in certain regions. Finally, a comparison of cortex samples from alcoholics and age-matched controls suggested that CYP2C9 expression was increased in alcoholics.

Expression of CYP2E1 and CYP2U1 proteins in amygdala and prefrontal cortex: influence of alcoholism and smoking.

BACKGROUND: The tissue-specific expression of cytochrome P450 enzymes (CYP, P450) in the human brain may influence the therapeutic response to, and side effects of, neuroactive drugs including alcohol. However, the distribution of many P450s, especially poorly characterized CYP2 forms, within specific regions of the brain remains obscure, partly due to the paucity of available tissue and difficulty in discriminating between related P450s with available antibodies. METHODS: In this study, we analyzed the expression of CYP2A6, CYP2B6, CYP2D6, CYP2E1, CYP2J2, CYP2S1, CYP2U1, and CYP2W1 proteins in human prefrontal cortex (PFC) and amygdala (AMG) by immunoblotting with antibodies for which the P450 form specificity had been enhanced by affinity purification. These brain regions were selected as they mediate the addictive effects of cigarette smoking and alcohol consumption, substances known to modulate P450 expression in other tissues. PFC and AMG samples from alcoholic smokers, alcoholic nonsmokers, nonalcoholic smokers, and nonalcoholic nonsmokers were studied to assess the effect of alcohol use and smoking on the expression of these proteins. RESULTS: Of the P450s studied, CYP2E1 and CYP2U1 were expressed in all samples analyzed (n = 26 and 22 for CYP2E1 and CYP2U1, respectively), and elevated in alcoholics. CYP2U1 expression was also slightly increased in smokers. Expression of both P450s was increased in AMG compared to PFC of the same individuals. CONCLUSIONS: This is the first report of CYP2E1 and CYP2U1 protein expression in human AMG. Our results suggest that CYP2U1 expression may be modulated by alcohol and tobacco, with potential consequent effects on the metabolism of drugs and endogenous chemicals by this enzyme.

Differential expression of human cytochrome P450 enzymes from the CYP3A subfamily in the brains of alcoholic subjects and drug-free controls.

Cytochrome P450 enzymes are responsible for the metabolism of most commonly used drugs. Among these enzymes, CYP3A forms mediate the clearance of around 40-50% of drugs and may also play roles in the biotransformation of endogenous compounds. CYP3A forms are expressed both in the liver and extrahepatically. However, little is known about the expression of CYP3A proteins in specific regions of the human brain. In this study, form-selective antibodies raised to CYP3A4 and CYP3A5 were used to characterize the expression of these forms in the human brain. Both CYP3A4 and CYP3A5 immunoreactivity were found to varying extents in the microsomal fractions of cortex, hippocampus, basal ganglia, amygdala, and cerebellum. However, only CYP3A4 expression was observed in the mitochondrial fractions of these brain regions. N-terminal sequencing confirmed the principal antigen detected by the anti-CYP3A4 antibody in cortical microsomes to be CYP3A4. Immunohistochemical analysis revealed that CYP3A4 and CYP3A5 expression was primarily localized in the soma and axonal hillock of neurons and varied according to cell type and cell layer within brain regions. Finally, analysis of the frontal cortex of chronic alcohol abusers revealed elevated expression of CYP3A4 in microsomal but not mitochondrial fractions; CYP3A5 expression was unchanged. The site-specific expression of CYP3A4 and CYP3A5 in the human brain may have implications for the role of these enzymes in both normal brain physiology and the response to drugs.