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Journal Article 
Catalytic activity and quantitation of CYP2E1 in human embryonic and fetal brain tissues 
Brzezinski, MR; Boutelet-Bochan, H; Person, RE; Juchau, MR 
ISSN: 0731-9193 
CYP2E1 is a P450 enzyme that catalyzes the metabolic oxidation of many low molecular weight xenobiotics. The reactions are often bioactivating resulting in the formation of toxic intermediates. Ethanol is an important substrate and well known teratogen in humans causing profound abnormalities characteristic of fetal alcohol syndrome. The underlying mechanism of the syndrome is currently unknown but may involve this P450 isoform. Reactive oxygen species and free radicals generated during CYP2E1-mediated ethanol oxidation may elicit embryotoxic damage that could be responsible for irreversible effects on the developing brain. A series of experiments were conducted to evaluate the presence of CYP2E1 protein and mRNA in human embryonic (gestational day 50-60) and fetal (gestational day 70-120) brain tissues. The capacity of microsomal fractions to convert the probe substrate p-nitrophenol to 4-nitrocatechol was determined with a high performance liquid chromatography assay. The data suggested that levels of active enzyme increase with gestational age. CYP2E1 was also detected by Western blot analysis using an enhanced chemiluminescent system. Quantitative results indicated that levels of immunoreactive protein were higher than levels of functional enzyme, and the amounts detected in fetal and embryonic tissues were not significantly different. The levels of CYP2E1 mRNA appeared to increase with gestational age based on a ribonuclease protection assay followed by quantitation with phosphor imaging. Collectively, these results suggest that CYP2E1 is present in prenatal human brain tissue and could potentially contribute to the developmental toxicity of ethanol. The low enzyme levels detected may be sufficient to catalyze biotransformation reactions to the extent that teratogenic effects are produced.