Cytochrome P450 (P450) enzymes play crucial roles in the clearance of drugs from the circulation, and therefore changes in their activities can significantly influence the therapeutic and adverse effects of a drug on an individual. In addition some P450 enzymes have crucial roles in metabolism of physiological substrates e.g. CYP2C enzymes in the metabolism of arachidonic acid to bioactive epoxyeicosatrienoic acids. Infectious and inflammatory diseases cause the down-regulation of many P450s and other drug metabolizing enzymes in the liver, causing impairment of drug clearances. Our laboratory has shown that nitric oxide (NO) formed in hepatocyte during an inflammatory response selectively directs the ubiquitin-dependent proteasomal degradation of rat CYP2B1 and CYP3A2, but not CYP2C11. Our preliminary data demonstrate that not only are human CYP2B6 and CYP2C enzymes down-regulated by NO, but they are more sensitive than the rat enzymes to degradation caused by NO-releasing chemicals. Here, we propose to use proteomic methods to define the scope of NO-mediated degradation in human hepatocytes. We will characterize the proteolytic enzymes involved in the NO-mediated degradation of CYP2B6 and 2C9, and elucidate the mechanism whereby NO regulates these processes in an enzyme-specific manner

Public Health Relevance

People with ongoing infections or inflammatory diseases are more susceptible to the undesirable effects of drugs, because their livers cannot break down the drugs efficiently. This project will help us to understand how nitric oxide formed in the liver during inflammation contributes to this change, and so will allow us to predict what patients will need to have their drug doses adjusted to avoid this problem.

National Institute of Health (NIH)
National Institute of General Medical Sciences (NIGMS)
Research Project (R01)
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Xenobiotic and Nutrient Disposition and Action Study Section (XNDA)
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Okita, Richard T
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Emory University
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Lee, Choon-myung; Lee, Bang-sub; Arnold, Samuel L et al. (2014) Nitric oxide and interleukin-1* stimulate the proteasome-independent degradation of the retinoic acid hydroxylase CYP2C22 in primary rat hepatocytes. J Pharmacol Exp Ther 348:141-52
Lee, Choon-Myung; Kumar, Vikas; Riley, Rochelle I et al. (2010) Metabolism and action of proteasome inhibitors in primary human hepatocytes. Drug Metab Dispos 38:2166-72
Morgan, E T (2009) Impact of infectious and inflammatory disease on cytochrome P450-mediated drug metabolism and pharmacokinetics. Clin Pharmacol Ther 85:434-8
Lee, Choon-Myung; Pohl, Jan; Morgan, Edward T (2009) Dual mechanisms of CYP3A protein regulation by proinflammatory cytokine stimulation in primary hepatocyte cultures. Drug Metab Dispos 37:865-72
Aitken, Alison E; Lee, Choon-Myung; Morgan, Edward T (2008) Roles of nitric oxide in inflammatory downregulation of human cytochromes P450. Free Radic Biol Med 44:1161-8
Morgan, Edward T; Goralski, Kerry B; Piquette-Miller, Micheline et al. (2008) Regulation of drug-metabolizing enzymes and transporters in infection, inflammation, and cancer. Drug Metab Dispos 36:205-16
Lee, Choon-Myung; Kim, Bong-Yoon; Li, Lian et al. (2008) Nitric oxide-dependent proteasomal degradation of cytochrome P450 2B proteins. J Biol Chem 283:889-98
Aitken, Alison E; Morgan, Edward T (2007) Gene-specific effects of inflammatory cytokines on cytochrome P450 2C, 2B6 and 3A4 mRNA levels in human hepatocytes. Drug Metab Dispos 35:1687-93
Aitken, Alison E; Richardson, Terrilyn A; Morgan, Edward T (2006) Regulation of drug-metabolizing enzymes and transporters in inflammation. Annu Rev Pharmacol Toxicol 46:123-49