FICZ

FICZ is a potent aryl hydrocarbon receptor (AhR) agonist with a K_d of 70 pM. In Vitro: FICZ (0.01 nM-1 µM) alone or in combination with 50 nM MNF induces sustained CYP1A1 activity and leads to oxidative stress and activation of apoptosis via a mitochondrial-dependent pathway. In HepG2 cells, FICZ stimulates cell growth at low concentrations but inhibits cell growth at high concentrations^[1]. FICZ (10,000-30,000 nM) significantly decreases CEH viability with an estimated LC₅₀ (95% confidence intervals) of 14,000 nM. FICZ shows concentration-dependent effects on EROD activity in CEH cultures, with the mean EC₅₀ values at 3, 8, and 24 h of 0.016 nM, 0.80 nM, and 11 nM, respectively^[2]. FICZ treatment increases transcript expression of CYP1A1 in a dose-dependent manner in both the parental iPSC line and the CYP1A1 targeted clone^[3]. CYP1 inhibition in the presence of FICZ results in enhanced AHR activation, suggesting that FICZ accumulates in the cell when its metabolism is blocked. CYP1 enzymes plays a role in regulating biological effects of FICZ^[4].
Nuclear export and degradation of the AHR protein are two additional steps in the AHR-mediated signal transduction pathway^[5].
Exposure to AhR agonists causes AhR-expressing cells to downregulate the receptor through the ubiquitin/proteasome degradation pathway^[6].