Diesel exhaust particles induce CYP1A1 and pro-inflammatory responses via differential pathways in human bronchial epithelial cells

Abstract

BackgroundExposure to diesel engine exhaust particles (DEPs) has been associated with several adverse health outcomes in which inflammation seems to play a key role. DEPs contain a range of different inorganic and organic compounds, including polycyclic aromatic hydrocarbons (PAHs). During the metabolic activation of PAHs, CYP1A1 enzymes are known to play a critical role. In the present study we investigated the potential of a characterised sample of DEPs to induce cytotoxicity, to influence the expression of CYP1A1 and inflammation-related genes, and to activate intracellular signalling pathways, in human bronchial epithelial cells. We specifically investigated to what extent DEP-induced expression of interleukin (IL)-6, IL-8 and cyclooxygenase (COX)-2 was regulated differentially from DEP-induced expression of CYP1A1.ResultsThe cytotoxicity of the DEPs was characterised by a marked time- and concentration-dependent increase in necrotic cells at 4 h and above 200 μg/ml (~ 30 μg/cm2). DEP-induced DNA-damage was only apparent at high concentrations (≥ 200 μg/ml). IL-6, IL-8 and COX-2 were the three most up-regulated genes by the DEPs in a screening of 20 selected inflammation-related genes. DEP-induced expression of CYP1A1 was detected at very low concentrations (0.025 μg/ml), compared to the expression of IL-6, IL-8 and COX-2 (50-100 μg/ml). A CYP1A1 inhibitor (α-naphthoflavone), nearly abolished the DEP-induced expression of IL-8 and COX-2. Of the investigated mitogen-activated protein kinases (MAPKs), the DEPs induced activation of p38. A p38 inhibitor (SB202190) strongly reduced DEP-induced expression of IL-6, IL-8 and COX-2, but only moderately affected the expression of CYP1A1. The DEPs also activated the nuclear factor-κB (NF-κB) pathway, and suppression by siRNA tended to reduce the DEP-induced expression of IL-8 and COX-2, but not CYP1A1.ConclusionThe present study indicates that DEPs induce both CYP1A1 and pro-inflammatory responses in vitro, but via differential intracellular pathways. DEP-induced pro-inflammatory responses seem to occur via activation of NF-κB and p38 and are facilitated by CYP1A1. However, the DEP-induced CYP1A1 response does not seem to involve NF-κB and p38 activation. Notably, the present study also indicates that expression of CYP1A1 may represent a particular sensitive biomarker of DEP-exposure.

The occurrence of polycyclic aromatic hydrocarbons and their derivatives and the proinflammatory potential of fractionated extracts of diesel exhaust and wood smoke particles

“…[24] The DEP was collected from the inside of the main exhaust pipe after the diesel engine had been running for 8 weeks, in conjunction with an on-going clinical chamber study. The WSP sample was collected from the interior of a chimney that vented an airtight wood stove burning a mix of hardwoods.…”

“…[24] The percentage of apoptotic and necrotic cells were determined as a fraction of the total number of counted cells.…”

Ultrafine Particles of Diesel Exhaust Induces Cytochrome P450 1A1 Mediated Oxidative Stress and DNA Damage in Cultured Blood and Lung Cells

“…A similar increase, though of a much higher magnitude, was observed in A549 cells and has also been reported after exposure of DEP or organic extracts of DEP 6,38,40,[43][44][45] . A greater magnitude of increase in the expression of CYP1A1 in IM9 or A549 cells exposed to MC prior to DEP have shown that like in the tissues, PAH metabolising CYPs, enriched following exposure of MC, catalyze the metabolic activation of PAHs present in DEPs in the blood cells.…”

Particulate Air Pollutants and Respiratory Diseases

“…After inhalation of PM, phagocytic cells including neutrophils and macrophages are recruited to the foreign particle by cytokines and chemokines, and transported by the mucociliary escalator for removal (Donaldson and Tran, 2002). PM induces the release of inflammatory cytokines, such as IL-6, IL-8, GM-CSF, and TNF- (Stone et al, 2007) from immune cells (e.g., macrophages) as well as structural airway cells (Totlandsdal et al, 2010).…”