P086 Sphk2 deletion is involved in structural abnormalities and Th17 response but does not aggravate colon immune dysregulation and intestinal permeability in a stress-induced colonic inflammation

Abstract

Background Colon immune dysregulation results in a chronic inflammatory response typical of IBD and mainly driven by T-cell response to microbial antigens. Interestingly, stress can trigger or modulate inflammation and even modify the clinical course of IBD. Sphingosine 1-phosphate (S1P) increase in tissues is involved in T-cell recruitment and different compounds acting on S1P signaling are currently under clinical trials to test their ability to impact IBD progression, including sphingosine kinase 2 (Sphk2) inhibitors. Methods Male C57BL/6NJ and Sphk2-/- mice were randomly assigned to 4 experimental groups: Control WT (n=5), Control Sphk2-/- (n=5), Stress WT (n=8), and Stress Sphk2-/- (n=8). A sub-chronic stress mixed model based on immobilization and ultrasound exposure for 2h during 4 days was used. A set of tissue and biochemical assays was performed to evaluate stress and immune responses, S1P pathways, and epithelial barrier integrity. Results Stress caused weight loss and corticosterone upregulation regardless of the genotype. S1P was increased in the colon of stressed mice due to a decrease in its degradation enzymes and Sphk2, leading to an immune dysregulation reflected by an upregulation of TLR4 pathway, an inhibition of anti-inflammatory mechanisms – 15-lipoxygenase, N-formyl-peptide receptor 2 and Liver X Receptor – a decrease in IgA+ and a decrease in IgM+ B-cells and plasmablasts, and a Th17 polarization. Sphk2 deletion did not affect inflammatory processes but could interfere with Th17 response. Moreover, Sphk2-/- mice showed lower expression levels of claudins 3, 4, 5, 7, and 8 that could be related to structural abnormalities relevant to IBD. Stress exposure also decreased some of these claudins and increased intestinal permeability, but a synergistic effect between stress and genotype for permeability was not detected. Conclusion Sub-chronic stress induced colon S1P increase, immune dysregulation and increased intestinal permeability. Sphk2 deletion is involved in structural abnormalities and Th17 response but did not aggravate the inflammatory processes exerted by stress.