Polycyclic aromatic hydrocarbon metabolizing cytochrome P450s in freshly prepared uncultured rat blood lymphocytes

In an attempt to develop blood lymphocyte cytochrome P450 expression profile as a surrogate to monitor tissue enzyme, the present study aimed to identify the expression and regulation of polycyclic aromatic hydrocarbons (PAHs) responsive CYPs in freshly prepared rat blood lymphocytes. Semi-quantitative and RT-PCR studies demonstrated constitutive and inducible mRNA expression of CYP1A1, 1A2, 1B1 isoenzymes and the associated transcription factors, aryl hydrocarbon receptor (AhR) and AhR translocator (ARNT) in blood lymphocytes. Absolute quantification using RT-PCR revealed several fold lower basal expression of CYP1A1, 1A2 and 1B1 in lymphocytes when compared to the liver. However, significant increase in the mRNA expression of these isoenzymes as well as AhR and ARNT in lymphocytes following pretreatment with 3-methylcholanthrene (MC) have demonstrated that responsiveness is retained in the blood lymphocytes, though the magnitude of increase is several fold lower when compared to liver. This increase in the mRNA expression was found to be associated with an increase in the protein expression of CYP1A1 and 1A2 in blood lymphocytes. Further, CYPs expressed in blood lymphocytes catalysed the O-dealkylation of 7-ethoxy- and 7-methoxyresorufins (ER or MR), though the reactivity was several fold lower in lymphocytes when compared to the liver enzyme. Our data providing quantitative evidence for similarities in the regulation of PAH-regulated CYP in uncultured and non-mitogen stimulated blood lymphocytes with the liver enzyme has led us to suggest that blood lymphocytes could be used as a surrogate to monitor tissue expression of CYPs.

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