Constitutive expression and inducibility of CYP1A1 in the H9c2 rat cardiomyoblast cells.

Cardiomyocytes are a valuable tool for studying the drug metabolizing enzymes in the heart. However, isolated cardiomyocytes are rather fragile and difficult to isolate. Therefore, there is an urgent need for an in vitro cell line model. The H9c2 cells are commonly used as an in vitro model for studying the cellular mechanisms and signaling pathways involved in drug-induced cardiotoxicity. These cells maintain many molecular markers of cardiomyocytes and show morphological characteristics of immature embryonic cardiomyocytes. Therefore, in the present study we examined the expression and inducibility of CYP1A1 in the H9c2 rat cardiomyoblast cells. Our results showed that treatment of H9c2 cells with the CYP1A1 inducer, 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) significantly induced CYP1A1 at mRNA, protein, and activity levels in a concentration-dependent manner. The RNA synthesis inhibitor, actinomycin D, completely blocked the CYP1A1 mRNA induction by TCDD, indicating the requirement of de novo RNA synthesis through transcriptional activation. In conclusion, we demonstrated for the first time the constitutive expression and inducibility of CYP1A1 in H9c2 cells. Therefore, this cell line offers a unique in vitro model to study the role of CYP1A1 in the pathogenesis of various cardiovascular diseases.