Effects of subchronic tobacco smoke exposure and polyinosinic-polycytidylic acid (Poly (I:C)) administration on pulmonary inflammation and lung function in the mouse

Mark Freeman, Elizabeth Hardaker, David Wright, Jennifer Dewhurst, Kathy Banner, Chris Poll. Novartis, Horsham, United Kingdom.

During an acute exacerbation of Chronic Obstructive Pulmonary Disease (AECOPD) an exaggerated inflammatory response in the airways is often observed due to bacterial or viral infections of the lungs. These exacerbations are a major cause of mortality in COPD patients. Our aim was to develop an animal model that would mimic aspects of the hyper-inflammatory response observed in a virally induced AECOPD. We combined multiple wholebody tobacco smoke (TS) exposures with the administration of the viral mimetic synthetic double stranded RNA (Poly (I:C)). Each week for the first 5 weeks female Balb/c mice (n = 9-10 per group) were exposed twice a day to 30 minutes of either TS (750μg/l wet total particulate matter) or room air (RA) on days 1,2, 4 and 5. On the morning of day 3 animals were administered Poly(I:C) (3mg/kg) or saline intranasally under isoflurane anaesthesia, followed by TS or RA 5 hours later. Animals were rested on days 6 and 7. During week six, animals were terminally anaesthetised (Fentanyl citrate 0.8mg/kg, Fluanisone 25mg/kg and Midazolam 12.45mg/kg i.p.) 24 hours after Poly(I:C) administration and lung function measured using a forced oscillations system. Bronchoalveolar lavage (BAL) was then performed to assess cell influx. Total cells and neutrophils were significantly increased in the BAL fluid of animals exposed to TS/Saline and TS/Poly(I:C) when compared to the RA/saline group (Table 1). BAL lymphocytes were significantly elevated in all groups when compared with RA/Saline group (Table 1). Static lung compliance was significantly elevated in the TS/saline and TS/Poly(I:C) groups with 41±3.3% and 42±4.1% (mean±sem) increases respectively when compared to the RA/Saline group (p<0.001 for both groups). Poly(I:C) administration in conjunction with TS exposure produces a pulmonary inflammation greater than that observed with either stimulus alone. However, changes in lung function appeared to be driven by TS exposure rather than by Poly(I:C) or a combination of both.

Table 1: Effect of TS and Poly(I:C) on cell numbers in the BAL

Data are expressed as mean cells x103/ml±sem. (Kruskal-Wallis followed by Dunn’s post test was used **p<0.01, ***p<0.001 compared to RA/Saline control).