Mono-methylindoles induce CYP1A genes and inhibit CYP1A1 enzyme activity in human hepatocytes and HepaRG cells

Abstract

Mono-methylindoles (MMI) were described as agonists and/or antagonists of the human aryl hydrocarbon receptor (AhR). Here, we investigated the effects of MMI on AhR-CYP1A pathway in human hepatocytes and HepaRG cells derived from human progenitor hepatic cells. All MMI, except of 2-methylindole, strongly induced CYP1A1 and CYP1A2 mRNAs in HepaRG cells. Induction of CYP1A genes was absent in AhR-knock-out HepaRG cells. Consistently, CYP1A1 and CYP1A2 mRNAs and proteins were induced by all MMIs (except 2-methylindole), in human hepatocytes. The enzyme activity of CYP1A1 was inhibited by MMIs in human hepatocytes and LS180 colon cancer cells in a concentration-dependent manner (IC50 values from 1.2 μM to 23.8 μM and from 3.4 μM to 11.4 μM, respectively). Inhibition of CYP1A1 activity by MMI in human liver microsomes was much weaker as compared to that in intact cells. Incubation of parental MMI with human hepatocytes either diminished (4-methylindole, 6-methylindole) or enhanced (7-methylindole) their agonist effects on AhR in AZ-AHR reporter cells. In conclusion, overall effects of MMI on AhR-CYP1A pathway in human cells comprise the induction of CYP1A genes through AhR, the inhibition of CYP1A catalytic activity and possibly the metabolic transformation causing loss or gain of AhR agonist activity of parental compounds.

Gut Microbial Catabolites of Tryptophan Are Ligands and Agonists of the Aryl Hydrocarbon Receptor: A Detailed Characterization

“…Interestingly, the activation of AhR and the induction of CYP1A1 mRNA was achieved in HepG2 cells by 100 µM IND, but incubation time in this study was only four (4) h [22]. This observation corroborates our findings in the recent studies, where we observed a higher relative efficacy of methylindoles at AhR after four (4) h of incubation as compared to 24 h [24,32]. Fecal concentrations of 3MI vary substantially between healthy subjects (≈40 µM) and in patients with intestinal pathologies (≤750 µM) [29].…”

“…Fecal concentrations of 3MI vary substantially between healthy subjects (≈40 µM) and in patients with intestinal pathologies (≤750 µM) [29]. The activation of the AhR and induction of CYP1A1 by 3MI at concentrations occurring in intestines in vivo is reported here and in several other studies [22][23][24]32], which suggests that the AhR activation could contribute to known physiological and pathophysiological roles of 3MI in gut tissue. The intestinal concentration of TA in humans is largely unknown.…”

Natural Product Skatole Ameliorates Lipotoxicity-Induced Multiple Hepatic Damage under Hyperlipidemic Conditions in Hepatocytes

“…In general, it has been found that skatole can act as a ligand for aryl hydrocarbon receptor (AhR) and regulate the expression of specific genes of the cyp family, the target gene of AhR, in several cell lines and primary human cells [ 51 , 52 , 53 ]. Several reports have indicated that high skatole concentrations are toxic via cyp enzyme activities [ 54 , 55 , 56 ] and cyp-mediated oxidation induced by skatole [ 57 ]. However, in the human colon cancer cell line Caco-2, cell viability decreased with treatment of 250 μM skatole for 72 h, which is a higher dose than was used in our study.…”

In Vitro Safety Signals for Potential Clinical Development of the Anti-Inflammatory Pregnane X Receptor Agonist FKK6

“…FKK6 displayed PXR-dependent protective effects in DSS-induced colitis in mice and human intestinal organoids stimulated with pro-inflammatory cytokines [12,13]. In addition, FKK6 did not activate the aryl hydrocarbon receptor (AhR), which is a good sign of selectivity, given frequent dual agonist effects of indole derivatives, such as methylated indoles [14][15][16], microbial indoles [17,18], substituted tryptamine [19] and imidazolopyridylmodified FKK series [20]. Here, we carried out detailed in vitro pharmacological profiling of FKK6, using complementary sets of non-cellular and cell-based models, to assess FKK6's suitability for potential preclinical development as a therapeutic for IBD.…”