Response of the Murine Urinary Bladder Microcirculation to Lipopolysaccharide from Escherichia coli and Pseudomonas aeruginosa

There is in vitro evidence demonstrating the inflammatory response to lipopolysaccharide (LPS) differs depending on the bacterial source. The objective of our study was to examine the in vivo inflammatory response to LPS from two common uropathogens, Escherichia coli ( Ec ) and Pseudomonas aeruginosa ( Pa ). LPS or saline was injected transurethrally into bladders of female C57Bl/6 mice at varying doses. The bladder was exteriorized, and the bladder microcirculation examined by intravital microscopy. Leukocyte adhesion at 4 hrs post challenge with 5 mg/kg Pa LPS was 2.9±0.6 cells/field of view and at 7 mg/kg it was 3.9±0.8 cells/field of view, a significant increase from saline control. In contrast, leukocyte adhesion 4 hours post 5 mg/kg Ec LPS challenge was 17.4±3.9 and with 7 mg/kg 19.7±2.9 cells/field of view. However, at 4.5 hours adhesion was similar with either LPS (5 mg/kg) with 18.4±3.0 and 21.2±4.0 cells/field of view, respectively. The flux of rolling leukocytes was significantly increased above baseline levels only after Ec LPS challenge. There was also a significant increase in the number of neutrophils with Ec LPS stimulation. In support of the in vitro observations, these in vivo results demonstrate that Ec LPS is more potent and induces a more rapid inflammatory response than Pa LPS. Supported by a Collaborative Health Research Projects grant from CIHR and NSERC.