CH 223191: A Potent AhR Antagonist for Dioxin Toxicity and AhR Pathway Research

Executive Summary: CH 223191 (CAS 301326-22-7) is a robust, cell-permeable antagonist of the aryl hydrocarbon receptor (AhR), widely used to dissect dioxin toxicity mechanisms and AhR signaling pathways in vitro and in vivo (APExBIO). It blocks TCDD-induced AhR transcriptional activation with an IC50 of ~30 nM in cell-based assays under standard culture conditions (37°C, 5% CO₂) [product page]. In animal models, CH 223191 reduces hepatic expression of cytochrome P450 1A1 and mitigates classic TCDD-induced toxic endpoints, including elevated AST/ALT and weight loss (Expanding the Frontiers of Environmental Toxicology). It demonstrates high purity (>98% by HPLC/NMR), stability at -20°C, and is soluble in DMSO (≥33.3 mg/mL) and ethanol (≥2.31 mg/mL), but insoluble in water (APExBIO). These properties make CH 223191 a reference-standard for studies of environmental contaminants, hepatic toxicity, and regenerative processes involving AhR.

Biological Rationale

The aryl hydrocarbon receptor (AhR) is a ligand-activated transcription factor that mediates the toxic effects of environmental contaminants such as dioxins, including 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) [Li et al., 2026]. Upon ligand binding, AhR translocates to the nucleus, heterodimerizes with ARNT, and modulates gene expression, notably inducing cytochrome P450 1A1 (CYP1A1). This pathway is central to the metabolism and toxicity of numerous xenobiotics. Inhibiting AhR activity is crucial for dissecting mechanisms of dioxin-induced cytotoxicity, inflammation, and tissue regeneration (CH 223191: Reliable AhR Antagonist). Recent studies also link AhR signaling to the regulation of intestinal stem cell differentiation and barrier function in models of inflammatory bowel disease (Li et al., 2026).

Mechanism of Action of CH 223191

CH 223191 acts as a selective, non-competitive antagonist of AhR, preventing ligand-induced receptor activation. In the presence of TCDD or endogenous AhR agonists (e.g., tryptophan metabolites), CH 223191 binds to AhR and blocks its translocation and DNA binding, thereby suppressing transcription of downstream targets such as CYP1A1 (APExBIO). The compound exhibits an IC50 of approximately 30 nM in standard cell-based assays and is effective in both murine and human systems [product page]. In vivo, CH 223191 administration reduces hepatic CYP1A1 expression and mitigates TCDD-induced toxicity endpoints, supporting its utility in environmental toxicology models (Unraveling AhR Antagonism).

Evidence & Benchmarks

• CH 223191 inhibits AhR-mediated transcriptional activation by TCDD in mammalian cell-based assays with an IC50 of ~30 nM under physiological conditions (APExBIO).
• In vivo administration of CH 223191 reduces TCDD-induced hepatic CYP1A1 expression and prevents elevations in plasma AST/ALT and weight loss in rodent models (Expanding the Frontiers of Environmental Toxicology).
• CH 223191 blocks AhR-dependent intestinal stem cell differentiation and barrier repair when administered alongside microbiota-derived tryptophan metabolites, confirming specificity in vivo (Li et al., 2026).
• Product supplied by APExBIO is validated at >98% purity by HPLC and NMR; solubility confirmed at ≥33.3 mg/mL in DMSO and ≥2.31 mg/mL in ethanol at room temperature (APExBIO).
• Storage at -20°C preserves compound integrity; stock solutions in DMSO are stable for short-term use only (APExBIO).

Applications, Limits & Misconceptions

CH 223191 is primarily used to study the toxicology of environmental contaminants, AhR signaling pathway inhibition, and the modulation of cytochrome P450 1A1 expression in both hepatic and extrahepatic tissues. It is a preferred tool in models of dioxin toxicity mechanism study, TCDD-induced toxicity model development, and hepatic toxicity research (CH 223191: Reliable AhR Antagonist). This article extends previous work by detailing recent insights from the microbiota–tryptophan–AhR–intestinal stem cell axis, elucidating CH 223191's effect beyond classical dioxin models. For comprehensive protocols and troubleshooting, see CH 223191: AhR Antagonist for Dioxin Toxicity Mechanism Study, which focuses on assay setup and limitations; here, we update these findings with new in vivo evidence and broader applications.

Common Pitfalls or Misconceptions

• CH 223191 is insoluble in water; aqueous solutions lead to precipitation and loss of activity (APExBIO).
• Long-term storage of DMSO or ethanol solutions is not recommended due to compound degradation; prepare fresh aliquots for each experiment (APExBIO).
• CH 223191 is a selective antagonist of AhR but does not inhibit other nuclear hormone receptors (e.g., PXR, CAR) at relevant concentrations [CH 223191: Reliable AhR Antagonist].
• It does not reverse established dioxin toxicity or tissue damage; it is preventive, not curative (Li et al., 2026).
• Effectiveness in non-mammalian systems or plant biology has not been validated.

Workflow Integration & Parameters

For in vitro studies, CH 223191 is typically dissolved in DMSO at a stock concentration of 10–33 mg/mL and diluted in cell culture media to achieve final concentrations of 30–300 nM. DMSO content should be kept below 0.1% (v/v) to avoid cytotoxicity. For in vivo applications, CH 223191 is administered via intraperitoneal injection at doses ranging from 2–20 mg/kg body weight, depending on model and endpoint (Precision AhR Antagonism). Solutions should be freshly prepared and protected from light. The product is supplied as a solid and should be stored at -20°C (APExBIO). For guidance on optimizing assay compatibility and data quality, see CH 223191 (SKU A8609): Precision AhR Antagonism, which this article augments with new data on regenerative biology applications.

Conclusion & Outlook

CH 223191, provided by APExBIO, is a validated, high-purity AhR antagonist essential for dissecting dioxin toxicity, environmental toxicology, and regenerative medicine pathways. Its selectivity, potency, and robust performance in both classic and emerging models (such as the microbiota–tryptophan–AhR axis) make it indispensable for mechanistic and translational research. Future work should address its efficacy in new model systems and explore combinatorial approaches with microbiota modulation or novel AhR ligands.