CA induces expression of AHR-responsive gene <i>Cyp1a1</i>, but with reduced efficacy versus other tryptophan metabolites.

<p>(A) Induction of <i>cyp1a in vivo</i> as measured by qRT-PCR. Zebrafish embryos at 48 or 72 hours post fertilization (hpf) were exposed to CA (100 µM) for 6 hours, and either sampled immediately (54 or 78 hpf; top panel) or placed in clean water and sampled at 96 hpf (24 hours after beginning of exposure; bottom panel). <i>Cyp1a</i> mRNA was normalized to <i>beta-actin</i> and to the average DMSO value. (DMSO values for 78 and 96-hpf embryos were similar). Values represent fold-change in CA-treated versus DMSO control embryos; each panel represents an experiment sampling three replicate groups of twenty embryos per group. (B) Induction of <i>Cyp1a1</i> in wild-type (<i>Ahr</i>^+/+) or <i>Ahr</i>^−/− mouse total lymphocytes incubated with CA (50 µM) in RPMI for 4 hours. <i>Cyp1a1</i> was measured by qRT-PCR and normalized to <i>Hprt</i>. Error bars represent SD. P values were calculated with the Mann-Whitney test from lymphocyte cultures from three individual mice. (C) Induction of <i>CYP1A1</i> PHA-stimulated human total PBMCs after 12–20 hours of incubation with CA (50 µM) in RPMI. <i>CYP1A1</i> was measured by qRT-PCR and normalized to <i>HPRT</i>. Data shown are pooled experiments from six individual donors. Error bars are SD. P values were calculated with the Mann-Whitney test. (D, E) Induction of mouse <i>Cyp1a1</i> (D) and human <i>CYP1A1</i> (E) measured by qRT-PCR relative to <i>Hprt</i> or <i>HPRT</i>. Mouse lymphocytes (D) and PHA-stimulated human PBMCs (E) were incubated with CA, KYA, L-KYN. Values are pooled from at least three independent experiments and represent fold-change versus averaged DMSO control. Metabolite concentrations are in µM. Error bars represent SD.