Brain cytochrome P450 and testosterone metabolism by rat brain subcellular fractions: Presence of cytochrome P450 3A immunoreactive protein in rat brain mitochondria

Jayyosi, Zaid; Cooper, Kathryn; Thomas, Paul E.

doi:10.1016/0003-9861(92)90122-d

Cited by 46 publications

(25 citation statements)

References 24 publications

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“…This phenytoin-inducible CYP3A is definitely located in microsomes and not in mitochondria as shown by western blotting. In the mitochondrial fraction, a strong CYP3A immunoreactive signal was found in agreement with results of Jayyosi et al (1992), but it was not 346 HOLGER ROSENBROCK et al To identify the isoforms of brain CYP3A we performed RT-PCR experiments using a consensus primer pair which enables the amplification of PCR products of the known murine CYP3A isoforms (published in the nucleotide database of the National Center of Biotechnology Information). Sequencing of five clones of the PCR product of the predicted base pair length evidenced the expression of CYP3A11 and CYP3A13 isoforms in mouse brain.…”

Section: Discussionsupporting

confidence: 63%

Identification, induction and localization of cytochrome P450s of the 3A-subfamily in mouse brain

et al. 2001

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Several cytochrome P450 subfamilies are inducible by specific exogenous compounds like the antiepileptic drug phenytoin. Some of these P450 enzymes are involved in the metabolism of gonadal hormones also contributing to neuronal differentiation. CYP3A enzymes have the capacity to catalyze the hydroxylation of testosterone and a wide variety of therapeutic agents, but little is known about the expression and potential function of this subfamily in mouse brain. Here, we report the identification of mouse CYP3A isoforms, their induction and localization in mouse brain. Western blot analysis with anti-CYP3A1 antibodies revealed the phenytoin-inducible expression of CYP3A in brain microsomes, and also a constitutive expression of members of this subfamily in brain mitochondria. Using RT-PCR with a consensus primer pair for known mouse liver CYP3A-isoforms we could demonstrate the expression of CYP3A11 and 3A13 mRNA in mouse brain. Finally, using double immunofluorescence labeling we analyzed the histoanatomical distribution of CYP3A throughout the brain with confocal laser scanning microscopy. We found strong immunoreactivity in neurons of hippocampus and hypothalamic areas which are sensitive to steroid hormones. CYP3A immunoreactivity was apparent also in neurons of the cerebellum, the thalamus and the olfactory bulb. Non-neuronal expression of CYP3A could be found in some astrocyte populations and in vascular as well as ventricular border lines. The presence of CYP3A predominantly in neurons but also in cells contributing to the blood-brain and blood-liquor barrier suggests important roles of this subfamily in mediation of steroid hormone action in mouse brain as well as in preventing the brain from potentially cytotoxic compounds.

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Section: Discussionsupporting

confidence: 63%

Identification, induction and localization of cytochrome P450s of the 3A-subfamily in mouse brain

et al. 2001

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“…By contrast, CYP3A5 was absent from mitochondrial fractions but present in microsomes of all five regions tested, and in cytosolic fractions of the cortex and hippocampus. CYP3A expression has previously been observed in the mitochondrial fraction of whole rat brain extracts (Jayyosi et al, 1992). However, to our knowledge, human brain CYP3A expression has only previously been assessed and reported in microsomes (Pai et al, 2002).…”

Section: Discussionmentioning

confidence: 93%

Differential Expression of Human Cytochrome P450 Enzymes from the CYP3A Subfamily in the Brains of Alcoholic Subjects and Drug-Free Controls

Depaz

Toselli

Wilce

et al. 2013

Drug Metabolism and Disposition

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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. Nterminal 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.

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“…In brain P450 from control rats, P450 4A and P450 2C were weakly detectable on Western blots and P450 2D and P450 4A were also detected by protein microsequencing. No P450 2E1, 1A, 2B, or 3A was evident in the control rat brain, although these have been detected in the brain by other laboratories (10,11,30,31). It is possible that individual P450S or their mRNAs are localized in a limited number of cells and can be detected by immunohistochemistry or in situ hybridization, even though they are not detectable in P450 prepared from brain regions.…”

Section: Figmentioning

confidence: 86%

Effect of ethanol on cytochrome P450 in the rat brain.

Warner

Gustafsson

1994

Proc. Natl. Acad. Sci. U.S.A.

110

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After a single dose of ethanol (0.8 ml/kg) administered intraperitoneally, the P450 content of the rat brain increased from 62 + 19 to 230 ± 97 pmol/g (wet weight) of tissue (mean ± SD, n = 5). Most of this increase could be accounted for by a 10-to 20-fold increase in the olfactory lobes and hypothalamic preoptic area. The P450s were identified by Western blot analysis and by microsequencing of the N-terminal ends after resolution of the proteins on SDS gels. They were identified as P450 2C7, 2C11, 2E1, 4A3, 4A8, and a member of the P450 2D family. In P450 extracted from the brains of control rats, P450 2C and 4A were also detectable but at a much lower concentration. P450 lA1, 2A1, 2B1, or 3A was not detected in the brains of either control or ethanol-treated rats. Oral administration of the same dose of ethanol resulted in a similar increase in the whole brain but smaller effects in the olfactory lobes. This effect of ethanol on the P450 in the brain has implications for the mechanism of toxicity and the development of tolerance to ethanol and for the effects of other drugs and environmental pollutants that act on the central nervous system.The mechanisms responsible for the intoxication, dependence, and neurotoxicity of ethanol remain largely unknown, and current data on the subject have been extensively reviewed (1-4). Of the many biochemical changes that occur in the body upon ingestion of ethanol, the induction of cytochrome P450 2E1 in the liver (5) has received much attention, not only because of the capacity of this isozyme to metabolize ethanol to acetaldehyde but also because of the potential of this enzyme to cause cellular damage. P450 2E1 can metabolically activate xenobiotics such as halothane and carbon tetrachloride to cytotoxins and nitrosamines to carcinogens (for review, see ref. 6). In addition there is a high production of oxygen radicals during its catalytic cycle, and this leads to lipid peroxidation and destruction of cell membranes (7). P450 2E1 is constitutive in the rat liver and the level ofthe protein, but not its mRNA, is increased by ethanol (8).-The enzyme is also detectable in the kidney and lung at levels that are <10% of that in the liver (9). The presence of P450 2E1 in the brain and its inducibility by ethanol is controversial. Immunohistochemical evidence indicates the presence of P450 2E1 in the brains of untreated rats in some studies (10, 11) but not in others (12), and chronic exposure of rats to ethanol in drinking water was found in one study (12) to increase the level of P450 2E1 in the brain. In the human cDNA libraries, the cDNA of P450 2E1 has been detected (13) but it is not known whether this is constitutive or due to exposure to ethanol or any of the many other organic solvents that induce this enzyme (14).The level of P450 in the brain microsomes, quantitated by its carbon monoxide difference spectrum, has been estimated in several laboratories to be 1-3% of that in the liver (15-18). We have found it impossible to measure P450 in brain microsomal fra...

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Brain cytochrome P450 and testosterone metabolism by rat brain subcellular fractions: Presence of cytochrome P450 3A immunoreactive protein in rat brain mitochondria

Cited by 46 publications

References 24 publications

Identification, induction and localization of cytochrome P450s of the 3A-subfamily in mouse brain

Identification, induction and localization of cytochrome P450s of the 3A-subfamily in mouse brain

Differential Expression of Human Cytochrome P450 Enzymes from the CYP3A Subfamily in the Brains of Alcoholic Subjects and Drug-Free Controls

Effect of ethanol on cytochrome P450 in the rat brain.

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