CH 223191: Potent AhR Antagonist for Dioxin Toxicity Mechanism Studies

Executive Summary: CH 223191 (CAS 301326-22-7) is a potent, selective aryl hydrocarbon receptor (AhR) antagonist with an IC₅₀ of ~30 nM in cell-based TCDD-induced assays (APExBIO). The compound inhibits AhR-mediated transcriptional activation and suppresses hepatic cytochrome P450 1A1 upregulation in vivo. CH 223191 demonstrates efficacy in mitigating toxic effects such as TCDD-induced weight loss and elevated plasma AST/ALT levels. Its high chemical purity (>98%) and stability parameters support reproducible results across toxicological and mechanistic studies. This article contextualizes CH 223191’s utility in environmental toxicology, stem cell differentiation, and advanced transcription factor research (Li et al., 2026).

Biological Rationale

The aryl hydrocarbon receptor (AhR) is a ligand-activated transcription factor that mediates cellular responses to environmental contaminants such as dioxins (e.g., TCDD). Activation of AhR induces the transcription of xenobiotic-metabolizing enzymes, notably cytochrome P450 1A1 (CYP1A1), which is implicated in the metabolic activation and detoxification of exogenous compounds (Li et al., 2026). Aberrant AhR signaling is linked to toxicity, carcinogenesis, immunomodulation, and impaired epithelial barrier function. Inhibiting AhR provides a mechanistic tool for dissecting the pathophysiology of dioxin exposure and for modeling hepatic and mucosal toxicity. CH 223191, developed and supplied by APExBIO, is widely used to block AhR activation and downstream gene expression in both in vitro and in vivo models (APExBIO product page).

Mechanism of Action of CH 223191

CH 223191 acts as a competitive antagonist of the AhR. It binds to the receptor with high affinity, preventing endogenous and exogenous ligands (such as TCDD) from activating the AhR pathway. This blockade inhibits the translocation of AhR to the nucleus and subsequent dimerization with ARNT (aryl hydrocarbon receptor nuclear translocator). As a result, CH 223191 suppresses the transcription of AhR target genes, including CYP1A1 and IL-22, attenuating downstream effects such as xenobiotic metabolism, inflammatory cytokine production, and stem cell differentiation modulation (Li et al., 2026). The compound displays an IC₅₀ of ~30 nM for TCDD-induced AhR activation in cell lines, demonstrating high potency and selectivity (APExBIO).

Evidence & Benchmarks

• CH 223191 inhibits TCDD-induced AhR transcriptional activation in HepG2 and other cell lines with an IC₅₀ of approximately 30 nM under standard culture conditions (37°C, 5% CO₂) (APExBIO).
• In vivo administration of CH 223191 reduces hepatic CYP1A1 expression and mitigates TCDD-induced increases in plasma AST and ALT in murine models (Li et al., 2026, link).
• CH 223191 reverses TCDD-induced weight loss and liver toxicity markers in a dose-dependent manner in rodent models (Li et al., 2026, link).
• In studies of mucosal regeneration, CH 223191 blocks microbiota-driven tryptophan metabolites from activating AhR and promoting intestinal stem cell differentiation, confirming target specificity (Li et al., 2026).
• CH 223191 is validated to >98% purity by HPLC and NMR, and is compatible with DMSO and ethanol-based solutions for cell and tissue assays (APExBIO, link).

This article extends the mechanistic focus of 'CH 223191: A Next-Generation AhR Antagonist' by highlighting direct evidence from hepatic and stem cell models. It also updates 'Decoding AhR Antagonism: Strategic Guidance for Translation' by integrating recent findings on the microbiota–tryptophan–AhR axis. For reproducibility and purity benchmarking, see 'CH 223191 (SKU A8609): Reliable AhR Antagonist for Reproducible Results', which is complemented here by new data on in vivo efficacy.

Applications, Limits & Misconceptions

CH 223191 is the tool of choice for:

• Investigating dioxin toxicity mechanisms via AhR pathway inhibition.
• Modeling hepatic injury and cytochrome P450 1A1 modulation in environmental toxicology research.
• Dissecting the role of AhR in intestinal barrier function, stem cell differentiation, and mucosal regeneration (Li et al., 2026).
• Validating downstream effects of AhR inhibition in cell viability, proliferation, and cytotoxicity assays.
• Testing the specificity of tryptophan metabolites and microbiota-derived ligands in the AhR signaling pathway (CH 223191: Unlocking the Microbiota–AhR Axis).

Common Pitfalls or Misconceptions

• CH 223191 does not inhibit non-AhR-related pathways; it is highly selective and not a pan-transcription factor inhibitor.
• It is not effective in water-based solutions due to insolubility; DMSO or ethanol must be used at specified concentrations (≥33.3 mg/mL in DMSO; ≥2.31 mg/mL in ethanol).
• CH 223191 does not reverse established tissue injury or fibrosis; its action is limited to blocking new AhR activation events.
• Long-term storage of solutions is not recommended; solutions should be freshly prepared and used promptly for experimental consistency.
• Not all species or cell lines respond identically; dosing and response must be empirically validated for each model system.

Workflow Integration & Parameters

CH 223191 (SKU A8609) is supplied by APExBIO as a solid compound (MW: 333.39, C₁₉H₁₉N₅O) with >98% purity. For cell-based assays, prepare stock solutions in DMSO (≥33.3 mg/mL) or ethanol (≥2.31 mg/mL). The compound is insoluble in water. For in vivo studies, dilute stock into appropriate vehicles immediately prior to use. Storage at -20°C ensures optimal stability; avoid repeated freeze-thaw cycles. Do not store working solutions for extended periods to maintain integrity (APExBIO).

Best practices for experimental design include titration of CH 223191 to empirically determine the minimal effective concentration in each system (starting at 30 nM for cell lines). Include appropriate vehicle controls (DMSO or ethanol at matched concentrations). Monitor for potential cytotoxicity at high doses. Validate AhR pathway inhibition by assessing CYP1A1 expression or reporter activity. For reference workflows and troubleshooting, see related applications in reproducibility-focused studies.

Conclusion & Outlook

CH 223191 is a benchmark aryl hydrocarbon receptor antagonist for advanced toxicology, transcription factor modulation, and stem cell research. Its high potency, selectivity, and validated purity underpin reliable inhibition of AhR-driven events in both hepatic and mucosal models. Recent research integrating the microbiota–tryptophan metabolism–AhR–stem cell axis further expands its utility in dissecting complex environmental and regenerative processes (Li et al., 2026). As the field advances toward precision toxicology and translational medicine, CH 223191 (A8609) from APExBIO remains a trusted tool for experimental clarity and reproducibility. For detailed specifications and ordering, refer to the CH 223191 product page.