WS10.3 Monitoring the pro-inflammatory effect of Pseudomonas aeruginosa culture supernatants and the inhibitory effect of azithromycin by in vivo imaging in IL-8 transiently transgenized mice

Abstract

Objectives Airway inflammation is frequently associated with chronic bacterial infections. The IL-8 mediated lung inflammation induced by virulence factors, specifically metalloproteases (MP), secreted by Pseudomonas aeruginosa has been monitored in vivo in a mouse model transiently expressing the luciferase reporter gene under the control of an IL-8 bovine promoter. The model was also used to test the possible anti-inflammatory activity of AZMthromycin (AZM) mediated by its effect on Pseudomonas MP expression. Methods Culture supernatants (SNs) from two P. aeruginosa clinical strains, VR1 and VR2 respectively, were obtained after growth in the absence or presence of a sub-lethal dose of AZM. The MP activity was detectable in the SN from VR1 grown without AZM but was greatly reduced when cells grew with the antibiotic. Results The pro-inflammatory activity of VR1 SN was clearly visible in vivo in the transgenized mice while a significant decrease of the inflammation response was observed with the SN grown in the presence of AZM. Further, VR1 SN stimulated the recruitment of WBC and neutrophils and the expression of a number of cytokines. This later effect was clearly decreased when SN from VR1 grown with AZM was used. Contrarily, SN from VR2 showed neither protease activity or detectable inflammation in the mouse lung. Conclusion The present animal model has revealed useful to the in vivo, long term monitoring of the effect of bacterial virulence factors in the lung tissue and the possible beneficial, anti-inflammatory effect of molecules for therapeutic use. This study was supported by Lega Italiana Fibrosi Cistica and Italian CF Research Foundation (grant #18/2013).