title: Induction of intracellular calcium concentration by environmental benzo(a)pyrene involves a β2-adrenergic receptor/adenylyl cyclase/Epac-1/inositol 1,4,5-trisphosphate pathway in endothelial cells.
abstract: Polycyclic aromatic hydrocarbons (PAHs) such as benzo(a)pyrene (B(a)P) are widely distributed environmental contaminants, known as potent ligands of the aryl hydrocarbon receptor (AhR). These chemicals trigger an early and transient increase of intracellular calcium concentration ([Ca(2+)](i)), required for AhR-related effects of PAHs. The mechanisms involved in this calcium mobilization were investigated in the present study. We demonstrated that B(a)P-mediated [Ca(2+)](i) induction was prevented in endothelial HMEC-1 cells by counteracting β2-adrenoreceptor (β2ADR) activity using pharmacological antagonists, anti-β2ADR antibodies, or siRNA-mediated knockdown of β2ADR expression; by contrast, it was strongly potentiated by β2ADR overexpression in human kidney HEK293 cells. B(a)P was shown, moreover, to directly bind to β2ADR, as assessed by in vitro binding assays and molecular modeling. Pharmacological inhibition and/or siRNA-mediated silencing of various signaling actors acting downstream of β2ADR in a sequential manner, such as G protein, adenylyl cyclase, Epac-1 protein, and inositol 1,4,5-trisphosphate (IP(3))/IP(3) receptor, were next demonstrated to prevent B(a)P-induced calcium signal. Inhibition or knockdown of these signaling elements, as well as the use of chemical β-blockers, were finally shown to counteract B(a)P-mediated induction of cytochrome P-450 1B1, a prototypical AhR target gene. Taken together, our results show that B(a)P binds directly to β2ADR and consequently utilizes β2ADR machinery to mobilize [Ca(2+)](i), through activation of a G protein/adenylyl cyclase/cAMP/Epac-1/IP(3) pathway. This β2ADR-dependent signaling pathway activated by PAHs may likely be crucial for PAH-mediated up-regulation of AhR target genes, thus suggesting a contribution of β2ADR to the health-threatening effects of these environmental pollutants.
authors.affiliation: INSERM U1085/IRSET, IFR140, Université de Rennes 1, 2 Avenue du Pr. L. Bernard, Rennes 35043, France.
authors.forename: Abdullah
authors.initials: A
authors.lastname: Mayati
authors.forename: Nicolas
authors.initials: N
authors.lastname: Levoin
authors.forename: Hervé
authors.initials: H
authors.lastname: Paris
authors.forename: Monique
authors.initials: M
authors.lastname: N'Diaye
authors.forename: Arnaud
authors.initials: A
authors.lastname: Courtois
authors.forename: Philippe
authors.initials: P
authors.lastname: Uriac
authors.forename: Dominique
authors.initials: D
authors.lastname: Lagadic-Gossmann
authors.forename: Olivier
authors.initials: O
authors.lastname: Fardel
authors.forename: Eric
authors.initials: E
authors.lastname: Le Ferrec
mesh_terms: D000262:Adenylyl Cyclases / Q000235:genetics / Q000378:metabolism*; D000393:Air Pollutants / Q000494:pharmacology*; D001189:Aryl Hydrocarbon Hydroxylases / Q000235:genetics / Q000378:metabolism; D001564:Benzo(a)pyrene / Q000494:pharmacology*; D002118:Calcium / Q000378:metabolism*; D020013:Calcium Signaling / Q000187:drug effects* / Q000235:genetics; D065633:Cytochrome P-450 CYP1B1; D042783:Endothelial Cells / Q000378:metabolism*; D055785:Gene Knockdown Techniques; D020662:Guanine Nucleotide Exchange Factors / Q000235:genetics / Q000378:metabolism*; D057809:HEK293 Cells; D006801:Humans; D015544:Inositol 1,4,5-Trisphosphate / Q000235:genetics / Q000378:metabolism*; D011485:Protein Binding; D018343:Receptors, Adrenergic, beta-2 / Q000235:genetics / Q000378:metabolism*; D018336:Receptors, Aryl Hydrocarbon / Q000235:genetics / Q000378:metabolism
chemical_list: D000393:Air Pollutants; D020662:Guanine Nucleotide Exchange Factors; C116122:RAPGEF3 protein, human; D018343:Receptors, Adrenergic, beta-2; D018336:Receptors, Aryl Hydrocarbon; D001564:Benzo(a)pyrene; D015544:Inositol 1,4,5-Trisphosphate; D001189:Aryl Hydrocarbon Hydroxylases; C585496:CYP1B1 protein, human; D065633:Cytochrome P-450 CYP1B1; D000262:Adenylyl Cyclases; D002118:Calcium