Fig. 5.

serotonin restores virulence in vivo in P. aeruginosa QSM mutant. (A) SEM images of mice intestines inoculated with (a) JP2 cells and PBS, and (b) JP2 cells and serotonin. Arrows indicate biofilm formation on intestinal tissues. Scale bars represent 10 μm. (B) Intestines were harvested and subjected to histopathological examination after staining with H&E. Uninfected control mice fed with (a) PBS and mice infected with (b) JP2 and fed PBS had no changes to the intestinal tissue. JP2 infected mice treated with (c) serotonin showed loss of villi and some epithelial damage as indicated by the arrows. (C) Intestinal sections were scored for disease severity by a pathologist blinded to specimen. Significant tissue damage was observed in mice infected with bacteria and treated with serotonin (red bars) as compared to mice infected only with the bacteria (blue bars). Tissue damage and oxidative stress markers (D) catalase, (E) MDA, (F) LDH, and (G) GSH were determined in intestinal tissue homogenates both in the absence (blue bars) and presence (red bars) of serotonin. (H) Recruitment of immune cells was examined by MPO activity. (I) The levels of TNFα, IL-1β, IL-12, and IL-6 were determined in intestinal tissues of infected mice in the absence (blue bars) and presence (red bars) of serotonin by ELISA. In all cases, data represents mean ± SD. Results are representative of 2 independent experiments with a minimum of 4 mice per group. **P < 0.001 or ***P < 0.0001 by ANOVA. (For interpretation of the references to color in this figure legend, the reader is referred to the web version of this article.)