Lung Exposure to Mineral Dusts Enhances the Capacity of Lung Inflammatory Cells to Release Superoxide

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Abstract
In vitro exposure of macrophages and neutrophils to inorganic dusts can enhance their oxidative metabolism, however the effects of inorganic dust inhalation on lung-inflammatory cell-oxidative metabolism remain unknown. To address this issue, we studied the superoxide anion release from lung inflammatory cells obtained by bronchoalveolar lavage from 19 sheep exposed repeatedly to UICC chrysotile B asbestos (100 mg) over an 18 month period and 10 sheep exposed to a single exposure of quartz (100 mg) over a 6 month period. Exposure to asbestos and quartz did not induce an increase in the spontaneous release of superoxide from inflammatory cells. However lung-inflammatory cells from sheep exposed to asbestos released much higher levels of superoxide in the presence of phorbol myristate acetate (PMA) than did cells of unexposed sheep. In quartz exposed animals, superoxide release with PMA stimulation remained significantly increased up to 2 months after a single quartz infusion. These results suggest that inorganic dust inhalation primes lung inflammatory cells in vivo and markedly enhances their capacity to release toxic oxygen radicals.