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

Abstract

Polycyclic aromatic hydrocarbons (PAHs), such as benzo( a)pyrene (B aP), 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 FcαRI/CD89 constitutes a molecular target for PAHs. Indeed, in vitro exposure to B aP markedly increased mRNA and protein expression of FcαRI in primary human macrophages; intratracheal instillation of B aP to rats also enhanced mRNA expression of FcαRI in alveolar macrophages. B aP concomitantly increased activity of the previously uncharacterized −1734 to −42 fragment of the Fc aRI promoter that we subcloned in a luciferase reporter vector. Three-methylcholanthrene, a PAH known to activate AhR like B aP, induced FcαRI expression, in contrast to benzo( e)pyrene, a PAH known to poorly interact with AhR. Moreover, FcαRI induction in B aP-exposed human macrophages was fully prevented by down-regulating AhR expression through small interference RNA transfection. In addition, B aP increased nuclear protein binding to a consensus AhR-related xenobiotic-responsive element found in the FcαRI gene promoter, as revealed by electrophoretic mobility shift assay. Overall, these data highlight an AhR-dependent up-regulation of FcαRI in response to B aP, 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.