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Role of CYP1A2 in hepatic sequestration of dioxin: studies using CYP1A2 knock-out mice
J J Diliberto1, D Burgin, L S Birnbaum
1Experimental Toxicology Division, National Health Effects and Environmental Research Laboratory, United States Environmental Protection Agency, Research Triangle Park, North Carolina 27711, USA. diliberto@herl45.herl.epa.gov
Abstract:
2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD, dioxin), most potent of the polyhalogenated aromatic hydrocarbons, has been studied in a variety of genetically normal species. Transgenic mice lacking a cytochrome P450 1A2 gene were used to study the influence of the CYP1A2 gene on the hepatic sequestration and distribution of TCDD, 4-PeCDF (2,3,4,7,8-pentachlorodibenzofuran; dioxin-like compound), and PCB 153 (2,2',4,4',5,5'-hexachlorobiphenyl; non-dioxin-like PCB (polychlorinated biphenyl)). The knock-out mice were compared to their age-matched lineage strains of C57BL/6N (1A2+/+; Ah(b)) and 129/Sv (1A2+/+; Ah(d)) for each compound. As demonstrated by the liver-to-adipose tissue (L/F) concentration ratios, there was no hepatic sequestering of TCDD and 4-PeCDF in the transgenic knock-out mice.
Insights
Cytochrome P450 1A2 gene absence prevents dioxin sequestration. Transgenic mice lacking this gene showed no hepatic uptake of TCDD and 4-PeCDF, impacting toxic chemical distribution studies.
Area of Science:
- Environmental Toxicology
- Pharmacogenomics
- Biochemistry
Background:
- 2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) is a potent environmental toxicant.
- Polychlorinated aromatic hydrocarbons (PAHs) exhibit varying toxicities and metabolic pathways.
- Cytochrome P450 enzymes play crucial roles in xenobiotic metabolism and distribution.
Purpose of the Study:
- To investigate the role of the Cytochrome P450 1A2 (CYP1A2) gene in the hepatic sequestration and distribution of TCDD, 4-PeCDF, and PCB 153.
- To compare the toxicokinetics of dioxin-like and non-dioxin-like compounds in CYP1A2-deficient mice.
- To elucidate the influence of CYP1A2 on the distribution patterns of persistent organic pollutants.
Main Methods:
- Utilized transgenic mice lacking the CYP1A2 gene (knock-out mice).
- Compared knock-out mice with age-matched wild-type strains (C57BL/6N and 129/Sv).
- Quantified tissue concentrations of TCDD, 4-PeCDF, and PCB 153, calculating liver-to-adipose tissue (L/F) ratios.
Main Results:
- Transgenic mice lacking the CYP1A2 gene demonstrated no significant hepatic sequestration of TCDD and 4-PeCDF.
- The liver-to-adipose tissue (L/F) concentration ratios for TCDD and 4-PeCDF were significantly altered in knock-out mice.
- PCB 153 distribution was not significantly affected by the absence of the CYP1A2 gene.
Conclusions:
- The CYP1A2 gene is critical for the hepatic uptake and sequestration of TCDD and dioxin-like compounds.
- Absence of CYP1A2 influences the distribution of specific persistent organic pollutants, suggesting targeted metabolic pathways.
- Findings provide insights into the toxicokinetics of dioxins and PCBs, relevant for risk assessment and environmental health studies.