BackgroundEpidemiological studies suggest an association between exposure to volatile organic compounds (VOCs) and adverse allergic and respiratory symptoms. However, whether VOCs exhibit a causal role as adjuvants in asthma development remains unclear.MethodsTo investigate the effect of VOC exposure on the development of allergic airway inflammation Balb/c mice were exposed to VOCs emitted by new polyvinylchloride (PVC) flooring, sensitized with ovalbumin (OVA) and characterized in acute and chronic murine asthma models. Furthermore, prevalent evaporated VOCs were analyzed and mice were exposed to selected single VOCs.ResultsExposure of mice to PVC flooring increased eosinophilic lung inflammation and OVA-specific IgE serum levels compared to un-exposed control mice. The increased inflammation was associated with elevated levels of Th2-cytokines. Long-term exposure to PVC flooring exacerbated chronic airway inflammation. VOCs with the highest concentrations emitted by new PVC flooring were N-methyl-2-pyrrolidone (NMP) and 2,2,4-trimethyl-1,3-pentanediol diisobutyrate (TXIB). Exposure to NMP or TXIB also increased the allergic immune response in OVA-sensitized mice. In vitro or in vivo exposure to NMP or TXIB reduced IL-12 production in maturing dendritic cells (DCs) and enhanced airway inflammation after adoptive DC transfer into Balb/c mice. At higher concentrations both VOCs induced oxidative stress demonstrated by increased isoprostane and glutathione-S-transferase-pi1 protein levels in the lung of non-sensitized mice. Treatment of PVC flooring-exposed mice with N-acetylcysteine prevented the VOC-induced increase of airway inflammation.ConclusionsOur results demonstrate that exposure to VOCs may increase the allergic immune response by interfering with DC function and by inducing oxidative stress and has therefore to be considerate as risk factor for the development of allergic diseases.

Styrene is a volatile organic compound (VOC) that is widely used as an intermediate in many industrial settings. There are known adverse health effects at environmentally significant concentrations, but little is known about the molecular effect of exposure to styrene at subacute toxic concentrations. We exposed human lung epithelial cells, at a wide range of concentrations (1 mg/m3-10 g/m3), to styrene and analyzed the effects on the proteome level by 2-DE, where 1,380 proteins spots were detected and 266 were identified unambiguously by mass spectrometry. A set of 16 protein spots was found to be significantly altered due to exposure to styrene at environmentally significant concentrations of 1-10 mg/m3 (0.2 – 2.3 ppm). Among these, superoxide dismutase [Cu-Zn] as well as biliverdin reductase A could be correlated with the molecular pathway of oxidative stress, while eukaryotic translation initiation factor 5A-1, ezrin, lamin B2 and voltage dependent anion channel 2 have been reported to be involved in apoptosis. Treatment with styrene also caused formation of styrene oxide-protein adducts, specifically for thioredoxin reductase 1. These results underline the relevance of oxidative stress as a primary molecular response mechanism of lung epithelial cells to styrene exposure at indoor-relevant concentrations.

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In industrialized countries, people spend more time indoors and are therefore increasingly exposed to volatile organic compounds that are emitted at working places and from consumer products, paintings, and furniture, with chlorobenzene (CB) and 1,2-dichlorobenzene (DCB) being representatives of the halogenated arenes. To unravel the molecular effects of low concentrations typical for indoor and occupational exposure, we exposed human lung epithelial cells to CB and DCB and analyzed the effects on the proteome level by 2-D DIGE, where 860 protein spots were detected. A set of 25 and 30 proteins were found to be significantly altered due to exposure to environmentally relevant concentrations of 10(-2) g/m(3) of CB or 10(-3) g/m(3) of DCB (2.2 and 0.17 ppm), respectively. The most enriched pathways were cell death signaling, oxidative stress response, protein quality control, and metabolism. The involvement of oxidative stress was validated by ROS measurement. Among the regulated proteins, 28, for example, voltage-dependent anion-selective channel protein 2, PDCD6IP protein, heat shock protein beta-1, proliferating cell nuclear antigen, nucleophosmin, seryl-tRNA synthetase, prohibitin, and protein arginine N-methyltransferase 1, could be correlated with the molecular pathway of cell death signaling. Caspase 3 activation by cleavage was confirmed for both CB and DCB by immunoblotting. Treatment with CB or DCB also caused differential protein phosphorylation, for example, at the proteins HNRNP C1/C2, serine-threonine receptor associated protein, and transaldolase 1. Compared to previous results, where cells were exposed to styrene, for the chlorinated aromatic substances besides oxidative stress, apoptosis was found as the predominant cellular response mechanism.