The effect of budesonide in a refined rat model of respiratory infection with Pseudomonas aeruginosa

Ellena Growcott1, Alexander Coulthard1, Richard Amison1,3, Elizabeth Hardaker1, Armelle Grevot2, Chris Poll1, Kathy Banner1. 1Novartis, Horsham, United Kingdom, 2Novartis, Basal, Switzerland, 3University of Bristol, Bristol, United Kingdom.

Anti-inflammatory drugs are used clinically to treat cystic fibrosis (CF). Obtaining sufficient anti-inflammatory activity versus impairment of host defence remains a key challenge. We evaluated if budesonide could attenuate inflammation without modulating bacterial load in a refined rat model of respiratory infection with Pseudomonas aeruginosa (P.a.). P.a. PAO1V strain (University of Colorado) was mixed with molten agar noble and spun into heated mineral oil with 0.01% v/v of the surfactant SPAN® 80 to produce agar beads. Under isofluorane anaesthesia, (day 0), male Sprague Dawley rats (250-300g; n = 16/group) were inoculated (i.t.) with agar beads containing 105 colony forming units (cfu) of P.a. Sham groups were given sterile beads. Rats were dosed prophylactically with 3 mg/kg (p.o.) budesonide or vehicle (1h prior to inoculation), subsequently dosed twice a day and culled on day 2. Cfu counts and ELISAs were performed on lung tissues; cell counts and ELISAs were performed on bronchoalveolar lavage fluid (BALF). Data are expressed as mean ± S.E.M. and analysed using a Kruskal-Wallis test with a Dunn’s post test. Budesonide caused a log increase in bacterial load compared to vehicle-treated rats (Table 1). P.a. elevated total cells counts in BALF of vehicle-treated animals, reflected by an elevated neutrophil count versus sham vehicle-treated animals (P<0.05) (Table 1). Budesonide augmented these responses, elevating BALF total cells and neutrophils compared to vehicle-treated sham (P<0.001) (Table 1). P.a. significantly increased BALF IL-1β and CINC-3 levels (P<0.01 and P<0.05) which, were elevated further by budesonide (Table 1). CINC-1 and CINC-3 levels in budesonide-treated infected animal lung tissue were significantly increased versus sham vehicle (7.2 ± 0.7 and 10.4 ± 2.5 versus 1.6 ± 0.3 and 0.8 ± 0.2 pg/μg protein respectively, P<0.05 and P<0.01, n = 8). In conclusion prophylactic budesonide treatment caused an enhancement in the inflammatory parameters measured as well as increasing bacterial load. It will be of value to establish whether a therapeutic dosing regime, (more akin to the clinical situation), can attenuate inflammation without impairing host defence in this model system.

*, P<0.05; **, P<0.01 and ***, P<0.001 versus vehicle-treated sham, n = 8 animals/group