Characterization of Maladaptive Processes in Acute, Chronic and Remission Phases of Experimental Colitis in C57BL/6 Mice

Pro-inflammatory macrophages contribute to developing comorbid anxiety-like behaviors through gastrointestinal vagal afferent signaling in experimental colitis mice

Anxiety symptoms are commonly observed in individuals with inflammatory bowel disease (IBD), but the mechanistic link between IBD and comorbid anxiety remains incompletely understood. Our previous study revealed that vagal gut-brain signaling contributes to driving comorbid anxiety-like behaviors in dextran sulfate sodium (DSS)-induced colitis mice, but how vagus nerve senses and transmits information to the brain in response to changes in the colonic microenvironment following DSS treatment remain elusive. Here, we identify a critical contribution of pro-inflammatory CD86+ macrophages to activate gut-innervating vagal afferents and ultimately drive anxiety-like behaviors in DSS-treated mice. An increased number of F4/80+ macrophages accumulated closely with gut-innervating vagal afferent fibers following DSS treatment. Depletion of macrophages alleviated DSS-induced anxiety-like behaviors, whereas peripheral delivery of lipopolysaccharide-activated M1 macrophages promoted anxiety-like behaviors, which were prevented by bilateral vagal afferent ablation. Moreover, differential expression levels of anxiety-like behaviors were positively correlated with neuronal activity changes in the nucleus tractus solitarius, locus coeruleus, and basolateral amygdala. Finally, treatment with either anti-α4β7 integrin antagonist vedolizumab or neutralizing anti-interleukin-1β monoclonal antibody effectively alleviated DSS-induced anxiety-like behaviors. Collectively, these findings unravel a mechanism of macrophage-to-vagus nerve communication via cytokine signaling responsible for comorbid anxiety associated with experimental colitis and suggest that pro-inflammatory CD86+ macrophages may represent a potential therapeutic target for psychological comorbidities in patients with IBD.

Protective Effect of Red Rice Extract Rich in Proanthocyanidins in a Murine Colitis Model

Inflammatory bowel disease (IBD) has become a global concern. Proanthocyanidin-rich red rice extract (PRRE) has been shown to suppress the inflammatory response in cellular cultures. However, the anti-colitis effect of PRRE has never been investigated in animals. This study aimed to examine the protective effect of the PRRE against dextran sulfate sodium (DSS)-induced colitis in mice. Male mice were orally administrated with PRRE of 50, 250 and 500 mg/kg/day for 21 days. Acute colitis was subsequently induced by administrated 2.5% DSS in drinking water for the final seven days. Sulfasalazine-treated mice were the positive group. All doses of PRRE and sulfasalazine significantly ameliorated DSS-induced severity of colitis, as indicated by decreasing daily activity index and restoring colon shortening. Treatments with PRRE, but not sulfasalazine, significantly reduced the histopathological index and infiltration of inflammatory cells. Furthermore, the PRRE treatments effectively improved mucous in colonic goblet cells using PAS staining, and suppressed the production of pro-inflammatory cytokines TNF-α, IL-1β and IL-6 induced by DSS, while sulfasalazine reduced only IL-1β and IL-6. This study suggested that PRRE had a greater anti-colitis effect than sulfasalazine. Thus, PRRE has a potential anti-colitis effect, and should be developed in a clinical trial as a natural active pharmaceutical ingredient for IBD.