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
Kumar, Ramiya; Litoff, Elizabeth J; Boswell, W Tyler et al. (2018) High fat diet induced obesity is mitigated in Cyp3a-null female mice. Chem Biol Interact 289:129-140
Damiri, Basma; Baldwin, William S (2018) Cyp2b-Knockdown Mice Poorly Metabolize Corn Oil and Are Age-Dependent Obese. Lipids 53:871-884
Gissendanner, Chris R; Baldwin, William S; Schaaf, Marcel J M (2018) Non-Mammalian Nuclear Receptors: From Evolution to Human Disease. Nucl Receptor Res 5:
Schmidt, Allison M; Sengupta, Namrata; Saski, Christopher A et al. (2017) RNA sequencing indicates that atrazine induces multiple detoxification genes in Daphnia magna and this is a potential source of its mixture interactions with other chemicals. Chemosphere 189:699-708
Baldwin, William S; Boswell, W Tyler; Ginjupalli, Gautam et al. (2017) Annotation of the Nuclear Receptors in an Estuarine Fish species, Fundulus heteroclitus. Nucl Receptor Res 4:
Sengupta, Namrata; Reardon, Delaney C; Gerard, Patrick D et al. (2017) Exchange of polar lipids from adults to neonates in Daphnia magna: Perturbations in sphingomyelin allocation by dietary lipids and environmental toxicants. PLoS One 12:e0178131
Kumar, Ramiya; Mota, Linda C; Litoff, Elizabeth J et al. (2017) Compensatory changes in CYP expression in three different toxicology mouse models: CAR-null, Cyp3a-null, and Cyp2b9/10/13-null mice. PLoS One 12:e0174355
Sengupta, Namrata; Gerard, Patrick D; Baldwin, William S (2016) Perturbations in polar lipids, starvation survival and reproduction following exposure to unsaturated fatty acids or environmental toxicants in Daphnia magna. Chemosphere 144:2302-11
Sengupta, Namrata; Litoff, Elizabeth J; Baldwin, William S (2015) The HR96 activator, atrazine, reduces sensitivity of D. magna to triclosan and DHA. Chemosphere 128:299-306
Ginjupalli, Gautam K; Gerard, Patrick D; Baldwin, William S (2015) Arachidonic acid enhances reproduction in Daphnia magna and mitigates changes in sex ratios induced by pyriproxyfen. Environ Toxicol Chem 34:527-35

Showing the most recent 10 out of 25 publications