Interleukin-8 induction by the environmental contaminant benzo(a)pyrene is aryl hydrocarbon receptor-dependent and leads to lung inflammation

doi:10.1016/j.toxlet.2008.01.006

Toxicology Letters

Volume 177, Issue 2, 15 March 2008, Pages 130-137

https://doi.org/10.1016/j.toxlet.2008.01.006 Get rights and content

Abstract

Benzo(a)pyrene (BP) is an environmental contaminant known to favor airway inflammation likely through up-regulation of pro-inflammatory cytokines. The present study was designed to characterize its effects toward interleukin-8 (IL-8), a well-established pulmonary inflammatory cytokine. In primary human macrophages, BP was shown to induce IL-8 expression at both mRNA and secretion levels in a dose-dependent manner. Such an up-regulation was likely linked to aryl hydrocarbon receptor (AhR)-activation since BP-mediated IL-8 induction was reduced after AhR expression knock-down through RNA interference. Moreover, electrophoretic mobility shift assays (EMSAs) and chromatin immunoprecipitation experiments showed BP-triggered binding of AhR to a consensus xenobiotic responsive element (XRE) found in the human IL-8 promoter. Finally, BP administration to mice led to over-expression of keratinocyte chemoattractant (KC), the murine functional homologue of IL-8, in lung. It also triggered the recruitment of neutrophils in bronchoalveolar lavage (BAL) fluids, which was however fully abolished in the presence of a chemical antagonist of the KC/IL-8 receptors CXCR1/CXCR2, thus supporting the functional and crucial involvement of KC in BP-induced lung inflammation. Overall, these data highlight an AhR-dependent regulation of IL-8 in response to BP that likely contributes to the airway inflammatory effects of this environmental chemical.

Introduction

Polycyclic aromatic hydrocarbons (PAHs) such as benzo(a)pyrene (BP) are ubiquitous environmental contaminants that originate from multiple sources, including diesel exhaust particles, tobacco smoke and air pollution, and to which humans, especially their respiratory tract, are commonly exposed (Hattemer-Frey and Travis, 1991). PAHs exert a wide range of toxic effects, including carcinogenic and pro-inflammatory effects in lung (Borm et al., 1997, Nel et al., 2001, Martey et al., 2005). These deleterious effects of these environmental chemicals have been linked, at least in part, to activation of the aryl hydrocarbon receptor (AhR) and to subsequent interaction of the heterodimer PAHs/AhR/AhR nuclear translocator (ARNT), with specific xenobiotic responsive elements (XREs) found in the 5′-flanking region of PAH-regulated genes, including cytochromes P-450 (CYP) 1A1/2 and CYP1B1 genes (Nebert et al., 2004).

Adverse inflammatory effects due to PAHs towards the respiratory system are well-established (Nel et al., 2001). Stimulations of cytokines/chemokines relevant to airway inflammation are probably involved; the role of AhR in these regulations and their exact contribution to lung inflammation remain however to be precised. To gain insights about these points in the present study, we have studied the regulation of the chemokine interleukin-8 (IL-8) and of its functional mouse homologue keratinocyte chemoattractant (KC) by PAHs since (i) IL-8 is a major target of PAH-containing diesel particles (Kawasaki et al., 2001, Pei et al., 2002) and (ii) IL-8 and KC, via interacting with their receptors CXCR1/CXCR2, play an important role in the pathogenesis of airway inflammation through the chemoattraction of neutrophils (Luster, 1998).

Using primary human macrophages known to mimic alveolar macrophages (Akagawa, 2002), we demonstrated that BP, known as a prototypical PAH, enhanced IL-8 production in an AhR-dependent manner. Moreover intranasal administration (i.n.) of BP to mouse resulted in activated KC expression in lung associated with the development of inflammation, which was, however, fully prevented by using a chemical antagonist of CXCR1/CXCR2. Such data therefore establish IL-8/KC as PAH targets likely contributing in a major way to airway inflammation triggered by exposure to these environmental contaminants.

Section snippets

Chemicals

BP, benzo(e)pyrene (BeP), tricaprylin and N-acetylcysteine (NAC) were provided by Sigma–Aldrich (St Louis, MO) whereas 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) was obtained from Cambridge Isotope Laboratories (Cambridge, MA). Pifithrin-α (PFTα), Bay-11-7082 and NF-κB activation inhibitor were purchased from Calbiochem (La Jolla, CA). 3′-methoxy-4′-nitroflavone (3′M4′NF) was a kind gift from Dr. T. Gasiewicz (University of Rochester Medical Center, Rochester). CXCL8(3–72)K11R/G31P is a potent

BP-induced IL-8 expression and secretion in primary human macrophages

BP was found to trigger up-regulation of IL-8 mRNA expression and IL-8 secretion in primary macrophages in a dose-dependent manner. Its effect started from 1 μM and reached a maximum at 2–10 μM (Fig. 1A and B). Low BP doses such as 0.1 μM had no or only minimal effect on IL-8 expression, at both mRNA and protein levels (Fig. 1A and B). mRNA expression of CYP1B1, a well-known PAH-regulated gene (Nebert et al., 2004), was up-regulated in a dose-dependent manner similar to that observed for IL-8 mRNA

Discussion

The data reported in the present study showed that IL-8 is a target of PAHs such as BP via AhR activation in primary human macrophages and that the increase of secretion of its murine functional homologue KC is crucial to BP-induced lung inflammation. Interestingly, IL-8 induction in macrophages occurred after a relatively low dose (1 μM) and short-time treatment with BP, indicating that acute and transient exposure to PAHs may be sufficient to enhance IL-8 secretion. Such an up-regulation of

Acknowledgements

We wish to thank Dr. L. Vernhet, Dr. D. Lagadic-Gossmann and Dr. S. Corre for helpful comments, and C. Morzadec, C. Le Quément and M. Le Vée for expert technical assistance.

This work was supported by grants from the “Agence Française de Sécurité Sanitaire de l’Environnement et du Travail” (AFSSET), the “Fondation de France” and the “Ligue Nationale contre le Cancer”. N. Podechard is a recipient of a fellowship from the Région Bretagne.

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Interleukin-8 induction by the environmental contaminant benzo(a)pyrene is aryl hydrocarbon receptor-dependent and leads to lung inflammation

Abstract

Introduction

Section snippets

Chemicals

BP-induced IL-8 expression and secretion in primary human macrophages

Discussion

Acknowledgements

J. Allergy Clin. Immunol.

Int. Immunopharmacol.

Immunobiology

Mutat. Res.

FEBS Lett.

Biochem. Biophys. Res. Commun.

J. Biol. Chem.

J. Biol. Chem.

Cytokine

J. Biol. Chem.

Arch. Biochem. Biophys.

Arch. Biochem. Biophys.

Toxicol. Appl. Pharmacol.

Biochem. Biophys. Res. Commun.

Arch. Biochem. Biophys.

Functional heterogeneity of colony-stimulating factor-induced human monocyte-derived macrophages

Int. J. Hematol.

Neutrophils amplify the formation of DNA adducts by benzo[a]pyrene in lung target cells

Environ. Health Perspect.

The selective phosphodiesterase 4 inhibitor RP 73–401 reduced matrix metalloproteinase 9 activity and transforming growth factor-beta release during acute lung injury in mice: the role of the balance between tumor necrosis factor-alpha and interleukin-10

J. Pharmacol. Exp. Ther.

Redox signalling

Mol. Cell Biochem.

The combined CXCR1/CXCR2 antagonist CXCL8(3–74)K11R/G31P blocks neutrophil infiltration, pyrexia, and pulmonary vascular pathology in endotoxemic animals

J. Leukoc. Biol.