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Differential effects of diesel exhaust particles on T cell differentiation and autoimmune disease.

ABSTRACT: BACKGROUND:Exposure to particulate matter (PM) has been associated with increased incidence and severity of autoimmune disease. Diesel PM is primarily composed of an elemental carbon core and adsorbed organic compounds such as polycyclic aromatic hydrocarbons (PAHs) and contributes up to 40% of atmospheric PM. The organic fraction (OF) of PM excludes all metals and inorganics and retains most organic compounds, such as PAHs. Both PM and OF increase inflammation in vitro and aggravate autoimmune disease in humans. PAHs are known aryl hydrocarbon receptor (AHR) ligands. The AHR modulates T cell differentiation and effector function in vitro and in experimental autoimmune encephalomyelitis (EAE), a murine model of autoimmune disease. This study aims to identify whether the total mass or active components of PM are responsible for activating pathways associated with exposure to PM and autoimmune disease. This study tests the hypothesis that active components present in diesel PM and their OF enhance effector T cell differentiation and aggravate autoimmune disease. RESULTS:Two different diesel samples, each characterized for their components, were tested for their effects on autoimmunity. Both diesel PM enhanced effector T cell differentiation in an AHR-dose-dependent manner and suppressed regulatory T cell differentiation in vitro. Both diesel PM aggravated EAE in vivo. Fractionated diesel OFs exhibited the same effects as PM in vitro, but unlike PM, only one diesel OF aggravated EAE. Additionally, both synthetic PAH mixtures that represent specific PAHs found in the two diesel PM samples enhanced Th17 differentiation, however one lost this effect after metabolism and only one required the AHR. CONCLUSIONS:These findings suggest that active components of PM and not total mass are driving T cell responses in vitro, but in vivo the PM matrix and complex mixtures adsorbed to the particles, not just the OF, are contributing to the observed EAE effects. This implies that examining OF alone may not be sufficient in vivo. These data further suggest that bioavailability and metabolism of organics, especially PAHs, may have an important role in vivo.

SUBMITTER: O'Driscoll CA

PROVIDER: S-EPMC6109291 | biostudies-literature | 2018 Aug

REPOSITORIES: biostudies-literature

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Differential effects of diesel exhaust particles on T cell differentiation and autoimmune disease.

O'Driscoll Chelsea A CA Owens Leah A LA Gallo Madeline E ME Hoffmann Erica J EJ Afrazi Amin A Han Mei M Fechner John H JH Schauer James J JJ Bradfield Christopher A CA Mezrich Joshua D JD

Particle and fibre toxicology 20180824 1

<h4>Background</h4>Exposure to particulate matter (PM) has been associated with increased incidence and severity of autoimmune disease. Diesel PM is primarily composed of an elemental carbon core and adsorbed organic compounds such as polycyclic aromatic hydrocarbons (PAHs) and contributes up to 40% of atmospheric PM. The organic fraction (OF) of PM excludes all metals and inorganics and retains most organic compounds, such as PAHs. Both PM and OF increase inflammation in vitro and aggravate aut ...[more]

PMID: 30143013

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Project description: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 ?g/ml (~ 30 ?g/cm2). DEP-induced DNA-damage was only apparent at high concentrations (? 200 ?g/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 ?g/ml), compared to the expression of IL-6, IL-8 and COX-2 (50-100 ?g/ml). A CYP1A1 inhibitor (?-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-?B (NF-?B) 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-?B and p38 and are facilitated by CYP1A1. However, the DEP-induced CYP1A1 response does not seem to involve NF-?B and p38 activation. Notably, the present study also indicates that expression of CYP1A1 may represent a particular sensitive biomarker of DEP-exposure.

Dataset Information

Differential effects of diesel exhaust particles on T cell differentiation and autoimmune disease.

Publications

Differential effects of diesel exhaust particles on T cell differentiation and autoimmune disease.

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