Acute colitis chronically alters immune infiltration mechanisms and sensory neuro-immune interactions

- Acute colitis causes a persistent influx of adaptive immune cells in the colon.
- Adaptive immune responses dominate in re-activated colitis.
- Acute colitis chronically alters viscero-sensory neuro-immune pathways.
- Targeting specific pathways would benefit different stages of colitis.

ObjectiveLittle is understood regarding how disease progression alters immune and sensory nerve function in colitis. We investigated how acute colitis chronically alters immune recruitment and the impact this has on re-activated colitis. To understand the impact of disease progress on sensory systems we investigated the mechanisms underlying altered colonic neuro-immune interactions after acute colitis.DesignInflammation was compared in mouse models of health, acute tri-nitrobenzene sulphonic acid (TNBS) colitis, Remission and Reactivated colitis. Cytokine concentrations were compared by ELISA in-situ and in explanted colon tissue. Colonic infiltration by CD11b/F4-80 macrophage, CD4 THELPER (TH) and CD8 TCYTOTOXIC (TC) and α4β7 expression on mesenteric lymph node (MLN) TH and TC was determined by flow cytometry. Cytokine and effector receptor mRNA expression was determined on colo-rectal afferent neurons and the mechanisms underlying cytokinergic effects on high-threshold colo-rectal afferent function were investigated using electrophysiology.ResultsColonic damage, MPO activity, macrophage infiltration, IL-1β and IL-6 concentrations were lower in Reactivated compared to Acute colitis. TH infiltration and α4β7 expression on TH MLN was increased in Remission but not Acute colitis. IFN-γ concentrations, TH infiltration and α4β7 expression on TH and TC MLN increased in Reactivated compared to Acute colitis. Reactivated explants secreted more IL-1β and IL-6 than Acute explants. IL-6 and TNF-α inhibited colo-rectal afferent mechanosensitivity in Remission mice via a BKCa dependent mechanism.ConclusionsAcute colitis persistently alters immune responses and afferent nerve signalling pathways to successive episodes of colitis. These findings highlight the complexity of viscero-sensory neuro-immune interactions in painful remitting and relapsing diseases.