Additional NO2 exposure induces a decrease in cytokine specific mRNA expression and cytokine release of particle and fibre exposed human alveolar macrophages.

Soot particles, asbestos fibres and irritant gas are common air pollutants which are able to induce lung and airway pulmonary injury. The aim of this study was to investigate the effect of a simultaneous NO2 and particle or fibre exposure on the proinflammatory specific mRNA expression and protein secretion of human alveolar macrophages (AM) in comparison to only particle or fibre exposed AM. AM were simultaneously exposed to FR 101, P 90, TiO2 or Chrysotile B at a concentration of 100 microg/10(6) cells and to NO2 at a concentration of 1.0 ppm for 30 min. Particle or fibre exposure of the AM was continued in humidified air at 5% CO2 and 37 degrees C for an additional hour (harvesting of total RNA) or additional 7 hrs (harvesting of culture supernatant). The mRNA expression of the proinflammatory cytokines IL-1beta, IL-6, IL-8 and TNF-alpha of NO2-particle/fibre co-exposed AM and only particle or fibre exposed AM was detected using specific RT-PCR. IL-1beta-, IL-6-, IL-8- and TNF-alpha-specific protein secretion was measured by ELISA. Cytotoxicity was detected by lactatedehydrogenase quantification in the culture supernatant. We observed an increased IL-1beta-, IL-6-, IL-8- and TNF-alpha-specific mRNA expression of particle or fibre exposed AM, which was decreased after an additional NO2 exposure. Also the particle or fibre exposure induced significant increase in IL-1beta-, IL-6-, IL-8 and TNF-alpha-release of AM which was decreased after an additional NO2 exposure (p <0.031). The relative cytotoxicity of the NO2-particle/fibre co-exposure was higher than the particle or fibre induced cytotoxicity, but mostly <10%. Therefore it is concluded that particle or fibre exposure may result in an increase in proinflammatory cytokine release by AM, which may be decreased by toxic NO2 due to the oxidative potential (e.g. lipidperoxydation) of this irritant gas. Particle, asbestos fibre and irritant gas exposure may induce airway and pulmonary injury by the activation of AM and consecutive proinflammatory cytokine release.