Table 1.

List of major agonists (exogenous and endogenous ligands) and antagonists of the AHR. The table also describes the major target organs and the diseases that are modulated by the AHR.

Source	Examples	Target Organ/Disease
Exogenous	Halogenated aromatic hydrocarbons	Lung cancer [28,73]
	Dibenzofurans	Lung toxicity not confirmed
	Biphenyls	Lung toxicity not confirmed
	Polycyclic aromatic hydrocarbons	Lung cancer [28,73], asthma [74], COPD [75], chronic bronchitis [76,77]
	3-Methylcholanthrene	No severe lung toxicity
	Benzo[a]pyrene	Lung inflammation [78,79], respiratory tract cancer [80]
	Benzanthracenes	No immediate severe lung toxicity
	Benzoflavones	Non-toxic
Dietary Endogenous	Flavonoids	BPD/ARDS [81,82,83]
	Quercetin	BPD [84]
	Indole-3-carbinol	COPD, asthma, ARDS, BPD
	3,3′-Diindolylmethane	Lung cancer chemoprevention [85]
	Indolo[3,2-b]carbazole	No pulmonary therapeutic application reported
Tryptophan metabolites	Kynurenic acid	ALI [86]
	Kynurenine	Lung cancer [87]
	Tryptamine	No pulmonary therapeutic application reported
	6-Formylindolo[3,2-b]carbazole	LPS-induced ALI [88]
	Indoxyl sulfate	No immediate severe lung toxicity
Microbiota	3-Methylindole	May cause lung cancer [89]
	Tryptanthrin	Lung cancer [90]
	1,4-Dihydroxy-2-naphthoic acid	No pulmonary therapeutic application reported
	Indole-3-aldehyde	No immediate severe lung toxicity
	Indole-3-acetate	No pulmonary therapeutic application reported
	Phenazines	No pulmonary therapeutic application reported
	Indirubin	Lung cancer [91], anti-inflammatory [92]
	Malassezin	No pulmonary therapeutic application reported
Xenobiotic	3,4-Dimethoxy-a-naphthoflavone	Lung cancer [93]
	MNF	Lung cancer, COPD, asthma [94]
	CH-223191	Lung cancer, COPD, asthma [74]
Dietary	Resveratrol	Lung cancer, asthma COPD [95]
AHR Active Pharmaceuticals	Tranilast	COPD, Asthma [85]
	Leflunomide	BPD, ARDS [85]
	Omeprazole	BPD, ARDS [85,96,97,98]