Cytochrome P450 1A isoenzymes in brain cells: Expression and inducibility in cultured rat brain neuronal and glial cells

Studies initiated to determine the expression of CYP1A1/1A2 isoenzymes in the primary cultures of rat brain neuronal and glial cells revealed significant activity of CYP1A-dependent 7-ethoxyresorufin-o-dealkylase (EROD) in microsomes prepared from both rat brain neuronal and glial cells. RT-PCR and immunocytochemical studies demonstrated constitutive mRNA and protein expression of CYP1A1 and 1A2 isoenzymes in cultured neuronal and glial cells. Cultured neurons exhibited relatively higher constitutive mRNA and protein expression of CYP1A1 and 1A2 isoenzymes, associated with higher activity of EROD than the glial cells. Induction studies with 3-methylchlorantherene (MC), a known CYP1A-inducer, resulted in significant concentration dependent increase in the activity of EROD in cultured rat brain cells with glial cells exhibiting a greater magnitude of induction than the neuronal cells. This difference in the increase in enzyme activity was also observed with RT-PCR and immunocytochemical studies, indicating relatively higher increase in CYP1A1 and 1A2 mRNA as well as protein expression in the cultured glial cells when compared to the neuronal cells. The greater magnitude of induction of CYP1A1 in glial cells is of significance, as these cells are components of the blood-brain barrier and it is suggested that they have a potential role in the toxication-detoxication mechanism. Our data indicating differences in the expression and sensitivity of CYP1A1 isoenzymes in cultured rat brain cells will not only help in identifying and distinguishing xenobiotic metabolizing capability of these cells but also in understanding the vulnerability of these specific cell types towards neurotoxicants.