Lung Inflammation In Rats After Acute Exposure To Cigarette Smoke


Abstract

We have already found that acute exposure of rats to cigarette mainstream smoke induces changes in inflammatory mediators in bronchoalveolar lavage fluid (BALF). Here, we investigate how the changes in inflammatory mediators are reflected in changes in BALF neutrophils after acute and subchronic exposure to cigarette mainstream smoke. Whole smoke (WS), gas-phase depleted particulate phase (PP), and gas phase (GP) were investigated. Sprague Dawley rats (8/group) were exposed either to fresh air (sham) or to smoke from university of Kentucky filtered reference cigarettes. Acute exposure was 2 x 1 hour to WS and PP at concentrations of 300, 600, 900, and 1200 μg total particulate matter (TPM)/L, or to equivalent concentrations for GP. Subchronic exposure was 2 x 1 h/day for 35 days to WS at concentrations of 500 and 750 μg tpm/l, pp at 750 μg tpm/l and an equivalent concentration for GP. Inflammatory mediators (IL-1ß, CINC-1, CINC-3, MCP-1, Fractalkine) and free lung cells (FLC) were quantified in BALF (flow cytometry) and respiratory parameters were measured (plethysmography). Acute exposure to WS and PP resulted in a concentration-related increase of inflammatory mediators. GP had no effect. Effects of PP were more pronounced than those of WS. At 1200 μg TPM/L, FLC consisted of 16% neutrophils in the rats exposed to WS, 25% in rats exposed to PP, and 2% in rats exposed to GP group (equal to sham). After subchronic exposure, neutrophils were concentration-dependently increased. At 750 μg TPM/L, neutrophils were 20% higher in rats exposed to pp than in rats exposed to WS; no differences were seen between GP and sham groups. A reduction of 40% in respiratory minute volume was found during exposure to WS and GP, while no reduction was seen during exposure to PP. This indicates that rats exposed to PP took up more TPM, which causes the inflammatory changes, than was taken up by rats exposed to WS. Effects after acute exposure were qualitatively the same as those observed after subchronic exposure. Acute inhalation exposure of rats may be a useful short-term in vivo assay for the evaluation of the inflammatory effects of cigarette smoke. 

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