Aryl hydrocarbon receptor-dependent induction of the IgA receptor FcαRI by the environmental contaminant benzo(a)pyrene in human macrophages

Polycyclic aromatic hydrocarbons (PAHs), such as benzo(a)pyrene (BaP), are widely distributed toxic environmental contaminants well known to regulate gene expression through activation of the aryl hydrocarbon receptor (AhR). In the present study, we demonstrated that the IgA receptor Fc alpha RI/CD89 constitutes a molecular target for PAHs. Indeed, in vitro exposure to BaP markedly increased mRNA and protein expression of Fc alpha RI in primary human macrophages; intratracheal instillation of BaP to rats also enhanced mRNA expression of Fc alpha RI in alveolar macrophages. BaP concomitantly increased activity of the previously uncharacterized -1734 to -42 fragment of the Fc alpha RI promoter that we sub-cloned in a luciferase reporter vector. Three-methylcholanthrene, a PAH known to activate AhR like BaP, induced Fc alpha RI expression, in contrast to benzo(e)pyrene, a PAH known to poorly interact with AhR. Moreover, Fc alpha RI induction in BaP-exposed human macrophages was fully prevented by down-regulating AhR expression through small interference RNA transfection. In addition, BaP increased nuclear protein binding to a consensus AhR-related xenobiotic-responsive element found in the Fc alpha RI gene promoter, as revealed by electrophoretic mobility shift assay. Overall, these data highlight an AhR-dependent up-regulation of Fc alpha RI in response to BaP, which may contribute to the deleterious effects of environmental PAHs toward the immune/inflammatory response and which also likely emphasizes the role played by AhR in the regulation of genes involved in immunity and inflammation. (C) 2011 Elsevier Ireland Ltd. All rights reserved.