Effect of the Exogenous AHR ligand 3MC on CYP2B and CYP1A Gene Expression Sample Clauses

Effect of the Exogenous AHR ligand 3MC on CYP2B and CYP1A Gene Expression. 3-methylcholanthrene (3MC) is a potent activator of AHR and has been shown to significantly induce XXX0X xxxxxx (Xxxxxxxxx & Xxxxxxx, 0000). Primarily used for the formation of murine sarcomas (Xxxxx, 1946) (Mider & Xxxxxx, 1939), 3MC is a planar polycyclic aromatic hydrocarbon typical of many AHR ligands (Figure 1.2b). Here we use 3MC, to see if a structurally different AHR activator would have the same effect on PB-dependent induction of CYP2B. Primary rat hepatocytes were treated with an increasing concentration of 3MC (10 nM-100 µM) with or without the presence of 1 mM PB. RNA was harvested after 24 hrs and in a subsequent experiment protein was harvested after 48 hrs of exposure with a combination of 10 µM 3MC and 1 mM PB. 3MC increased CYP1A2 mRNA expression in a dose- dependent manner with an approximate half maximal induction between 10 µM and 100 µM. Additionally, there was a significant increase in CYP1A2 mRNA expression at the 1µM, 10 µM, and 100 µM concentrations (Figure 3.3d). Interestingly, the fold increase in CYP1A2 caused by 3MC was 10 times greater than by β-NF. For CYP2B, co-treatment with 3MC and PB decreased CYP2B1 mRNA expression at the 10 µM and 100 µM concentration (Figure 3.3e). After 48 hours of exposure to 1 mM PB and 10 µM 3MC, CYP2B protein levels were significantly attenuated with PB and 3MC co-treatment compared to PB alone. Additionally, PB alone significantly increased CYP2B expression when compared to control as expected while 3MC alone decreased CYP2B expression when compared to the control (Figure 3.3.f). CYP1A2 protein levels were also observed after 48 hrs and only the treatments that contain β-NF had an increase in CYP1A2 expression (data not shown). Finally, when comparing the potency of β-NF versus 3MC, 3MC is a less potent inducer of CYP1A2 than β-NF. However, 3MC is more efficacious than β-NF. Both compounds, although structurally different, attenuate the PB-dependent induction of CYP2B at the 10 µM concentration. 140 120 100 80 60 40 20 0 * * Concentration of 3MC log (nM) 1400 1200 1000 800 600 400 200 0 CYP1A2 mRNA Expression * * * Concentration of 3-MC log (nM)