Related Experiment Videos
Chlorpyrifos oxon interacts with the mammalian multidrug resistance protein, P-glycoprotein
C L Lanning1, R L Fine, C W Sachs
1Department of Pharmacology, Duke University Medical Center, Durham, North Carolina 27710, USA.
Abstract:
Multidrug resistance (MDR) to chemically unrelated therapeutic anticancer agents in mammalian cells is mediated by the overexpression of an ATP-dependent 150- to 180-kD membrane glycoprotein P-glycoprotein (P-gp). Although the complete physiological role of P-gp is unknown, it is proposed to function in cellular detoxification of xenobiotics. In this study, we investigated whether the organophosphorus insecticide chlorpyrifos (O,O-diethyl O-3,5,6-trichloro-2-pyridinyl phosphorothioate) or its metabolites interact with P-gp. Immunohistochemical analysis of tissues from male Fischer 344 rats administered chlorpyrifos (7.6 mg/kg gavage) showed increased P-gp expression in the kidney, adrenal, liver, jejunum, and stomach (tissues associated with elimination of xenobiotics), compared to control tissues. The most prominent increase was detected in the large bile ducts of the liver and the proximal tubule region of the kidney. P-gp expression was increased throughout the adrenal medulla and cortex, while a moderate increase was detected in the epithelial layers of the stomach and jejunum. To examine further the interaction between chlorpyrifos and P-gp, we evaluated whether chlorpyrifos or its active metabolite, chlorpyrifos oxon, could inhibit [3H]azidopine labeling of P-gp in MDR1 baculovirus-infected insect Sf9 cells. A concentration-dependent inhibition of [3H]azidopine labeling of P-gp was detected with chlorpyrifos oxon, while significant inhibition was not detected with chlorpyrifos. To correlate the binding of chlorpyrifos oxon to P-gp with a biochemical effect, we examined its ability to stimulate P-gp-mediated ATPase activity in these Sf9 cells. Chlorpyrifos oxon stimulated P-gp ATPase activity 1.75 times that of the positive control (10 microM verapamil). Taken together, these results suggest that chlorpyrifos oxon interacts with P-gp, and support the hypothesis that P-gp may play a role in the cellular detoxification of insecticides in mammalian tissues. To our knowledge this is the first report of an organophosphorus insecticide interacting with and increasing the expression of P-gp.
Insights
This study shows the organophosphorus insecticide chlorpyrifos oxon interacts with P-glycoprotein (P-gp), increasing its expression in rat tissues. This suggests P-gp aids in detoxifying insecticides within mammalian cells.
Area of Science:
- Biochemistry
- Toxicology
- Cell Biology
Background:
- Multidrug resistance (MDR) in mammalian cells is often mediated by P-glycoprotein (P-gp), an ATP-dependent membrane glycoprotein.
- P-gp is hypothesized to play a role in cellular detoxification of xenobiotics.
- The interaction of insecticides with P-gp and its effect on P-gp expression is not well understood.
Purpose of the Study:
- To investigate if the organophosphorus insecticide chlorpyrifos or its metabolites interact with P-gp.
- To determine if chlorpyrifos exposure increases P-gp expression in mammalian tissues.
- To assess the functional consequences of chlorpyrifos oxon interaction with P-gp.
Main Methods:
- Immunohistochemical analysis of P-gp expression in tissues of rats treated with chlorpyrifos.
- Inhibition of [3H]azidopine labeling of P-gp by chlorpyrifos and chlorpyrifos oxon in Sf9 cells.
- Measurement of P-gp-mediated ATPase activity in response to chlorpyrifos oxon.
Main Results:
- Chlorpyrifos administration increased P-gp expression in rat kidney, adrenal, liver, jejunum, and stomach, notably in liver bile ducts and kidney proximal tubules.
- Chlorpyrifos oxon, but not chlorpyrifos, inhibited [3H]azidopine labeling of P-gp in a concentration-dependent manner.
- Chlorpyrifos oxon significantly stimulated P-gp-mediated ATPase activity.
Conclusions:
- Chlorpyrifos oxon interacts with P-gp, suggesting a role for P-gp in the cellular detoxification of organophosphorus insecticides.
- Increased P-gp expression following chlorpyrifos exposure supports its involvement in xenobiotic elimination.
- This study provides the first evidence of an organophosphorus insecticide interacting with and upregulating P-gp.