Possible involvement of the Ah receptor in the induction of cytochrome P-450IA1 under conditions of hydrodynamic shear in microcarrier-attached hepatoma cell lines

Abstract

The exposure of two hepatoma cell lines, Hep G2 and Hepa-1, to moderate hydrodynamic shear, in microcarrier-attached suspension cultures, resulted in the transient induction of cytochrome P450IA1 (CYP1A1). Both cell lines have been characterized with respect to their Ah receptor (AhR) concentrations and induce CYP1A1 in response to exposure to xenobiotics such as 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD). Using an AhR antagonist, alpha-naphthoflavone (alpha-NF) and a protein kinase C (PKC) inhibitor, staurosporine (ST), in the Hep G2 cell line, the induced CYP1A1 activity was modulated in the same manner as when the cells were coexposed to TCDD and either alpha-NF or ST. Exposure of the Hep G2 cell line to TCDD and shear resulted in both enhancement of the induced CYP1A1 activity in addition to a competitive response. Finally, using the wild type and AhR defective Hepa-1 cell lines, it was demonstrated that a functional AhR was required for shear-induced CYP1A1 expression. The data obtained in the three cell lines indicate a role for the AhR in the induction of CYP1A1 by shear in agitated microcarrier cultures.