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Signal transduction-mediated CYP1A1 induction by omeprazole in human HepG2 cells
1Department of Molecular Genetics, Institute of Development, Aging and Cancer, Tohoku University, Sendai, Japan.
Abstract:
Benzimidazole compounds, such as omeprazole and thiabendazole, are a different type of CYP1A1-inducer from Ah receptor-ligands, such as 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) and 3-methylcholanthrene. In HepG2 cells, the commonly used tyrosine kinase-inhibitors, herbimycin-A and a series of tyrphostins, inhibited the induction of CYP1A1 produced by treatment with TCDD. Genistein, another type of tyrosine kinase inhibitor, inhibited the induction of CYP 1A1 whether it was produced by omeprazole or TCDD; however, this inhibition was caused by a dual effect of genistein, that is an anti-tyrosine kinase and an anti-topoisomerase I effect. An antagonist of Ah receptor, 3'-methoxy-4'-aminoflavone (1 microM), did not inhibit the induction of CYP1A1 produced in HepG2 cells by omeprazole or alpha-naphthoflavone (50 microM), but this antagonist did inhibit that produced by TCDD. Thus, omeprazole appears to induce CYP1A1 by initiating a protein tyrosine kinase-mediated signal transduction pathway, a different pathway from that initiated by TCDD.
Insights
Omeprazole induces CYP1A1 via a protein tyrosine kinase pathway, distinct from the Ah receptor pathway used by TCDD. This finding clarifies distinct mechanisms of CYP1A1 induction by different compounds.
Area of Science:
- Biochemistry
- Pharmacology
- Cell Biology
Background:
- Cytochrome P450 1A1 (CYP1A1) is induced by various xenobiotics.
- Induction pathways can differ, involving the Aryl hydrocarbon receptor (AhR) or other signaling cascades.
- Understanding these distinct pathways is crucial for predicting drug metabolism and toxicity.
Purpose of the Study:
- To elucidate the signaling pathway by which benzimidazole compounds, specifically omeprazole, induce CYP1A1.
- To compare the induction mechanism of omeprazole with that of known AhR ligands like TCDD.
- To investigate the role of protein tyrosine kinases in CYP1A1 induction.
Main Methods:
- Experiments were conducted using HepG2 cells.
- CYP1A1 induction was assessed following treatment with omeprazole, TCDD, and other compounds.
- Inhibition studies utilized tyrosine kinase inhibitors (herbimycin-A, tyrphostins, genistein) and an AhR antagonist (3'-methoxy-4'-aminoflavone).
Main Results:
- Tyrosine kinase inhibitors (herbimycin-A, tyrphostins) inhibited TCDD-induced CYP1A1.
- Genistein inhibited CYP1A1 induction by both omeprazole and TCDD, exhibiting dual anti-tyrosine kinase and anti-topoisomerase I activity.
- An AhR antagonist blocked TCDD-induced CYP1A1 but not omeprazole-induced CYP1A1.
Conclusions:
- Omeprazole induces CYP1A1 through a protein tyrosine kinase-mediated signal transduction pathway.
- This pathway is distinct from the Ah receptor-dependent pathway initiated by TCDD.
- The findings highlight divergent molecular mechanisms underlying CYP1A1 induction.