Reserach Interest
The uptake, metabolic activation or inactivation, and elimination of drugs, carcinogens, and environmental toxicants are tightly controlled processes that significantly impact the biological activity of these compounds, including any pathological response. Research in our laboratory is focused on molecular mechanisms controlling the expression of drug and toxicant metabolizing enzymes, including chemical-induced changes in gene expression, genetic variability, and temporal- and tissue-specific control mechanisms. Studies currently being conducted emphasize two major enzymes systems, the cytochrome P450 and flavin-containing monooxygenase gene families.
Cytochrome P450: Although several enzyme systems are known to participate in the metabolic transformation of xenobiotics, the cytochrome P450-dependent monooxygenases are widely recognized as playing a dominant role. The cytochromes P450 are products of a super gene family with 56 distinct functional members in the human. Of these many gene products, members of the CYP3A family represent up to 40% of the total hepatic cytochrome P450 content and account for up to 50% of the oxidative metabolism of clinically relevant drugs. Major changes in hepatic CYP3A expression are observed during development. Thus, CYP3A7 is the dominant form in the fetus while CYP3A4, if present, is expressed at low levels. Within the first one to two years after birth, CYP3A7 expression is extinguished in most individuals and CYP3A4 expression increases such that it represents the dominant enzyme in the adult liver. Studies are underway to identify and characterize the molecular mechanisms controlling this developmental transition.
A second project focuses on genetic variation at the CYP2C9, CYP4F2 and other loci and their impact on the efficacy of warfarin as an anticoagulant in children. The long term goals of this project are to develop and validate a pediatric pharmacogenetic-based algorithm for warfarin dosing that will improve the safety of this drug in children.
Flavin-containing Monooxygenase: Although the cytochrome P450-dependent monooxygenases are perhaps the most important system in the metabolic transformation of xenobiotics, there is increasing awareness of the flavin-containing monooxygenase (FMO) system and its contribution to this process. These enzymes efficiently catalyze the monooxygenation of a variety of nucleophilic nitrogen, sulfur, selenium, and phosphorous containing xenobiotics to their respective oxides.
The FMO enzyme system is encoded by a family of five genes (FMO1-5) that share between 50 and 60% amino acid sequence identity. Each FMO gene product exhibits unique properties, however, due to the nature of the FMO catalytic mechanism, substrate specificity is broad and overlapping. Significant polymorphisms and/or allelic variations have been documented in animal models and humans. We have demonstrated a developmental transition in the expression of the two major FMO hepatic enzymes in the human, FMO1 and FMO3, with FMO1 only be expressed in the fetus while FMO3 is only expressed in the adult. Current studies are focused on identifying mechanisms controlling the FMO1 to FMO3 developmental transition, characterizing the postnatal increase in FMO3 expression in vivo, and determining the impact of common FMO3 genetic variants on interindividual differences in FMO3 expression.
Recent Publications
Nong, A., McCarver, D.G., Hines, R.N. and Krishnan, K. Modeling of interchild differences in pharmacokinetics on the basis of subject-specific data on physiology and hepatic CYP2E1 levels: a case study with toluene. Toxicol. Appl. Pharmacol. 214:78-87, 2006.
Duanmu, Z., Weckle, A., Koukouritaki, S.B., Hines, R.N., Falany, C.N., Kocarek, T.A. and Runge-Morris, M. Developmental expression of aryl, estrogen and hydroxysteroid sulfotransferases in pre- and postnatal human liver. J. Pharmacol. Exptl. Ther. 316:1310-1317, 2006.
Hines, R.N. Developmental and Tissue-Specific Expression of Flavin-Containing Monooxygenase 1 and 3. Expert Opinion Drug Metabol Toxicol 2:41-49, 2006.
Krueger, S.K., VanDyke, J.E., Hines, R.N. and Williams, D.E. The role of flavin-containing monooxygenase (FMO) in the metabolism of tamoxifen and other tertiary amines. Drug Metab. Revs. 38:139-147, 2006.
Cooper, R.L., Lamb, J.C., Barlow, S. M., Bentley, K., Brady, A. M., Doerrer, N.G., Eisenbrandt, D.L., Fenner-Crisp, P.A., Hines, R.N., Irvine, L.F.H., Kimmel, C.A., Koeter, H., Li, A.A., Makris, S.L., Sheets, L.P., Speijers, G.J.A. and Whitby, K.E. A tiered approach to life stage testing for agricultural chemical safety assessment. Crit. Revs. Toxicol. 36:69-98, 2006.
Hines, R.N. and McCarver, D.G. Pharmacogenomics and the Future of Drug Therapy. Pediatric Clinics of North America: Scientific Foundations of Clinical Practice Part I (Kliegman, R.M. and Avner, E.D., eds.), pp. 591-619, W.B. Saunders Co., Philadelphia, PA, 2006.
Yang, F., Tong, X., McCarver, D.G., Hines, R.N. and Beard, D.A. Population-based analysis of methadone distribution and metabolism using an age-dependent physiologically based pharmacokinetic model. J. Pharmokinet. Pharmacodyn. 33:485-518, 2006.
Vyas, P.M., Roychowdhury, S., Khan, F.D., Prisinzano, T.E., Lamba, J., Schuetz, E.G., Blaisdell, J., Goldstein, J.A., Munson, K.L., Hines, R.N., Svensson, C.K., Enzyme- mediated protein haptenation of dapsone and sulfamethoxazole in human keratinocytes - 1. Expression and role of cytochromes P450. J. Pharmacol. Exptl. Ther. 319:488-496, 2006.
Vyas, P.M., Roychowdhury, S., Koukouritaki, S.B., Hines, R.N., Krueger, S.K., Williams, D.E., Nauseef, W.M., Svensson, C.K., Enzyme-mediated protein haptenation of dapsone and sulfamethoxazole in human keratinocytes - 2. Expression and role of flavin-containing monooxygenases and peroxidases. J. Pharmacol. Exptl. Ther. 319:497-505, 2006.
Zaya, M.J., Hines, R.N. and Stevens, J.C. Epirubicin glucuronidation and UGT2B7 developmental expression. Drug Metab. Disp. 34:2097-2101, 2006.
Koukouritaki, S.B., Poch, M.T., Henderson, M.C., Siddens, L.K., Krueger, S.B., VanDyke, J.E., Williams, D.E., Pajewski, N.M., Wang, T. and Hines, R.N. Identification and functional analysis of human flavin-containing monooxygenase 3 (FMO3) genetic variants. J . Pharmacol. Exptl. Ther. 320:266-273, 2007.
Shadley JD, Divakaran K, Munson K, Hines RN, Douglas K and McCarver DG. Identification and functional analysis of a CYP2E1 far upstream enhancer. Mol Pharmacol 71(6):1630-1639, 2007.
Klick DE and Hines RN. Mechanisms Regulating Human FMO3 Transcription. Drug Metab Revs 39:419-442, 2007.
Hines, R.N. Ontogeny of Human Hepatic Cytochromes P450. J. Biochem. Mol. Toxicol.21(4):169-175, 2007.
Hines RN, Koukouritaki SB, Poch MT and Stephens MC. Regulatory polymorphisms and their contribution to interindividual differences in the expression of enzymes influencing drug and toxicant disposition. Drug Metab. Revs. 40(2):263-301, 2008.
Hines RN. The ontogeny of drug metabolism enzymes and implications for adverse drug events. Pharmacol. Therapeut., doi: 10.1016/j.pharmthera.2008.02.005.
Hines RN. Ontogeny of drug metabolizing enzymes/pediatric exclusivity. In: Handbook of drug metabolism (Pearson, P.G. and Wienkers, L.C., eds.), 2nd Edition, Vol. 183, Informa Healthcare, New York, NY, 2008.
Kramer MA, Rettie AE, Rieder MJ, Cabacungan ET and Hines RN. Novel CYP2C9 promoter variants and assessment of their impact on gene expression. Mol Pharmacol doi: 10.1124/mol.107.044149.
Klick DE, Shadley JD and Hines RN. Differential regulation of human hepatic flavin-containing monooxygenase 3 (FMO3) by CCAAT/enhancer-binding protein β (C/EBPβ) liver inhibitory and liver activating proteins. Biochem Pharmacol 76(2):268-278, 2008.
Stevens JC, Marsh SA, Zaya MJ, Regina KJ, Le M and Hines RN. Developmental Changes in Human Liver CYP2D6 Expression. Drug Metab Disp 36(8):1587-1593, 2008.