The cytochrome P450s (CYPs) are key enzymes involved in the detoxification of numerous chemicals including steroids, bile acids, pharmaceuticals, and environmental chemicals. Cyp2b is considered the forgotten CYP because not as much is known about its substrate specificity, it is expressed at lower levels in the liver than some other detoxification CYPs, and the FDA does not mandate the use of recombinant Cyp2b in drug metabolism testing. However, Cyp2b is highly inducible, highly polymorphic, gender predominant, and recent work shows it is expressed at higher levels than once thought, especially in hispanics. We will investigate the role of this CYP in the metabolism of environmental toxicants, determine whether individuals with low Cyp2b are sensitive to specific toxicants that are Cyp2b substrates, and evaluate whether CYP inhibition by toxicants could potentially lead to metabolic disorders such as obesity. We have recently developed a Cyp2b-knockdown mouse using RNAi that represses the expression of all five murine Cyp2b members. These mice demonstrate lower Cyp2b protein and activity and TCPOBOP the potent Cyp2b inducer is unable to out-compete the shRNA-mediated repression.
In aim 1, we will use this mouse model to estimate Cyp2b metabolism using microsomes from untreated and TCPOBOP-treated wild-type and Cyp2b-KD mice.
In aim 2, we will test whether Cyp2b-KD mice are susceptible to specific toxicants such as nonylphenol or parathion that are metabolized by Cyp2b. Last, recent preliminary data following ip injections with TCPOBOP or corn oil as a carrier revealed that Cyp2b-KD mice but not wild-type mice are unable to properly depurate the unsaturated fatty acids from the liver. This suggests an important role for Cyp2b in lipid homeostasis.
In aim 3, we will test whether mice with low Cyp2b activity are susceptible to high-fat diet (Western diet) induced hepatic steatosis (fatty liver) and obesity. If Cyp2b-KD mice are susceptible to obesity, this would suggest that Cyp2b inhibitors may act as environmental obesogens. Overall, the purpose of this project is determine the role of Cyp2b in the metabolism, fate, and toxic effects of environmental toxicants in vivo using a novel murine model recently developed in our laboratory.

Public Health Relevance

The cytochrome P450s (CYPs) are key enzymes involved in the detoxification of numerous chemicals including steroids, bile acids, pharmaceuticals, and environmental chemicals. Cyp2b is considered the forgotten CYP because it is expressed at lower levels in the liver than some other detoxification CYPs. However, it is highly inducible and recent work shows it is expressed at higher levels than once thought. We will investigate the role of this CYP in the metabolism of environmental toxicants, determine whether individuals with low Cyp2b are sensitive to specific toxicants, and evaluate whether CYP inhibition by toxicants could potentially lead to metabolic disorders.

Agency
National Institute of Health (NIH)
Institute
National Institute of Environmental Health Sciences (NIEHS)
Type
Academic Research Enhancement Awards (AREA) (R15)
Project #
2R15ES017321-02
Application #
8367031
Study Section
Xenobiotic and Nutrient Disposition and Action Study Section (XNDA)
Program Officer
Thompson, Claudia L
Project Start
2012-09-01
Project End
2015-08-31
Budget Start
2012-09-01
Budget End
2015-08-31
Support Year
2
Fiscal Year
2012
Total Cost
$363,083
Indirect Cost
$113,083
Name
Clemson University
Department
Biology
Type
Schools of Earth Sciences/Natur
DUNS #
042629816
City
Clemson
State
SC
Country
United States
Zip Code
29634
Li, Yangchun; Ginjupalli, Gautam K; Baldwin, William S (2014) The HR97 (NR1L) group of nuclear receptors: a new group of nuclear receptors discovered in Daphnia species. Gen Comp Endocrinol 206:30-42
Litoff, Elizabeth J; Garriott, Travis E; Ginjupalli, Gautam K et al. (2014) Annotation of the Daphnia magna nuclear receptors: comparison to Daphnia pulex. Gene 552:116-25
Ginjupalli, Gautam K; Baldwin, William S (2013) The time- and age-dependent effects of the juvenile hormone analog pesticide, pyriproxyfen on Daphnia magna reproduction. Chemosphere 92:1260-6
Damiri, Basma; Holle, Eric; Yu, Xianzhong et al. (2012) Lentiviral-mediated RNAi knockdown yields a novel mouse model for studying Cyp2b function. Toxicol Sci 125:368-81
Karimullina, Elina; Li, Yangchun; Ginjupalli, Gautam K et al. (2012) Daphnia HR96 is a promiscuous xenobiotic and endobiotic nuclear receptor. Aquat Toxicol 116-117:69-78
Mota, Linda C; Barfield, Christina; Hernandez, Juan P et al. (2011) Nonylphenol-mediated CYP induction is PXR-dependent: The use of humanized mice and human hepatocytes suggests that hPXR is less sensitive than mouse PXR to nonylphenol treatment. Toxicol Appl Pharmacol 252:259-67
Rungta, Parul; Bandera, Yuriy P; Roeder, Ryan D et al. (2011) Selective imaging and killing of cancer cells with protein-activated near-infrared fluorescing nanoparticles. Macromol Biosci 11:927-37
Mota, Linda C; Hernandez, Juan P; Baldwin, William S (2010) Constitutive androstane receptor -null mice are sensitive to the toxic effects of parathion: association with reduced cytochrome p450-mediated parathion metabolism [corrected]. Drug Metab Dispos 38:1582-8
Hernandez, J P; Mota, L C; Baldwin, W S (2009) Activation of CAR and PXR by Dietary, Environmental and Occupational Chemicals Alters Drug Metabolism, Intermediary Metabolism, and Cell Proliferation. Curr Pharmacogenomics Person Med 7:81-105