P014 Behaviour in mice with chronic DSS colitis mimics fatigue in IBD and is associated with neuroinflammation

Abstract

Background Inflammatory bowel diseases (IBD) are often associated with psychological comorbidities such as fatigue. Up to 47% of patients reports fatigue despite disease remission. The aim of the current study was to assess neurobehavioural changes in a mouse model of extinguished chronic colitis and to explore associated changes along the gut-brain axis. Methods Repeated administration of 2% dextran sulphate sodium (DSS) was used to induce chronic colitis in C57BL/6 mice, followed by a recovery period of 3 weeks to mimic quiescent IBD (Figure 1). Behavioural testing was performed at baseline and after the recovery period and compared with control mice. RNA sequencing was performed of the distal colon and choroid plexus and weighted correlation network analysis (WGCNA) was applied. Next, quantitative polymerase chain reaction (qPCR) was used for the confirmation of the expression levels of genes identified in the WGCNA analysis. The number of microglia and their morphology were assessed by Iba1 immunofluorescence in a second experiment, also including acute colitis (aDSS), which was induced by 1 week of 2% DSS, with sampling at day 7. Results Chronic DSS (cDSS) treatment resulted in chronic inflammation with minimal residual intestinal symptoms (control: median disease activity index (DAI) of 0 IQR [0-0], cDSS: median DAI of 0.5 [0.5-0.88], P <0.0001) after 3 weeks of recovery, which mimics quiescent IBD. At the time of sampling, the mean weight and haematological parameters (including red and white blood cells) in cDSS were comparable to those in control mice. cDSS mice exhibited significantly reduced spontaneous activity compared with their baseline behaviour (P = 0.0084) and with the controls (P = 0.0186). WGCNA on the colon and the choroid plexus expression data revealed a consensus module of 123 co-expressed genes that differed significantly between the control and cDSS mice (P = 0.00001721). These genes were implied in pathways of neutrophil and complement activation and qPCR on different brain regions (frontal cortex, hippocampus and choroid plexus) confirmed upregulation of inflammatory genes Lcn2, TNFa, S100A8 and S100A9 (Figure 2). Acute colitis was associated with activation of microglia in the prefrontal cortex and hippocampus, persisting in the prefrontal cortex of mice that recovered from chronic colitis (Figures 3 and 4). Conclusion In this mouse model of chronic extinguished colitis reduced spontaneous activity was seen, indicating fatigue-like behaviour as observed in patients with IBD. Moreover, mice that recovered from colitis exhibited persisting neuroinflammation.