The effect of budesonide on polyIC induced inflammation is altered by exposure to 6 weeks tobacco smoke

Elizabeth Hardaker, Mark Freeman, Rachel Glover, Natalia Kupfer, Katharine Banner, Chris Poll. Novartis Institute for Biomedical Research, Horsham, UK

Acute exacerbations of chronic obstructive pulmonary disease (AECOPD) contribute to increased mortality and a decreased quality of life in COPD patients. Tobacco smoking is the main causative agent for COPD, with the majority of exacerbations being associated with subsequent viral and/or bacterial infection. Inflammation in acute exacerbations is largely resistant to steroids. Our aim was to develop and characterise an in vivo model to mimic aspects of the altered inflammatory response observed in a virus-induced AECOPD. We combined multiple wholebody tobacco smoke (TS) exposures with the administration of polyinosinic:polycytidylic acid (PolyIC) to mimic aspects of virus induced inflammation. For 5 weeks, female Balb/c mice were exposed twice daily to 30 minutes of either TS (450µg/l wet total particulate matter) or room air (RA) on days 1-5 and rested on days 6 and 7. In week 6, the protocol was the same for the first 2 days. On the morning of day 3 PolyIC (3mg/kg) or saline (0.9%w/v) were administered intranasally (i.n) under isoflurane anaesthesia followed 5 hours later by TS or RA exposure. Animals were dosed with budesonide (3mg/kg; i.n) one hour pre and 5 hours post polyIC administration. Twenty four hours after polyIC administration animals were terminally anaesthetised (pentobarbitone i.p, 20mg/kg) and the trachea cannulated. Cell influx was assessed in the bronchoalveolar lavage (BAL) by differential counts and in the lung tissue by histological analysis. Data are expressed as the mean±SEM with n = 9-10 animals per group. In mice exposed to TS and polyIC there was an increase in neutrophils, macrophages and lymphocytes in the BAL fluid compared to those exposed to polyIC alone (table 1). In the lung tissue the total inflammation assessed by haematoxylin and eosin staining was greatest in mice exposed to the combination of TS and polyIC. Budesonide (3mg/kg) reduced neutrophil numbers in the BAL fluid of mice exposed to polyIC alone compared to vehicle controls (63 ± 11 x103 cells vs 138 ± 32 x103 cells). Similarly, budesonide caused a reduction in lymphocytes in the BAL fluid and lung tissue of mice exposed to polyIC alone. In mice exposed to TS for 6 weeks, prior to polyIC administration, the neutrophil numbers in the BAL fluid were elevated by budesonide (3mg/kg) compared to vehicle controls (489 ± 70x103 vs 272 ± 38x103 cells). Total inflammation in the lung tissue of mice exposed to the combination of TS and polyIC was not reduced by budesonide. In contrast, budesonide reduced lymphocytes in the BAL and lung tissue in mice exposed to the combination of TS and polyIC. In conclusion, 6 weeks exposure to TS alters the inflammatory response of mice to polyIC and appears to alter the efficacy of corticosteroids. This in vivo model may therefore be useful to profile compounds that may have beneficial effects in AECOPD.

Table 1: Effect of polyIC and tobacco smoke on cell numbers in the BAL fluid

Data are expressed as mean cells x 103/ml ± sem. (Kruskal-Wallis followed by Dunn’s post test was used # p<0.05, ## p<0.01, ### p<0.001 compared to RA/Saline control.