Effect of TNBS-induced colitis on enteric neuronal subpopulations in adult zebrafish

Abstract

Inflammatory bowel disease (IBD) includes inflammation of the gastrointestinal (GI) tract and is characterized by periods of acute inflammation and remission. Therapeutic management of IBD is still problematic, because of incomplete understanding its pathogenesis. This study focuses on the effect of 2,4,6-trinitrobenzene sulphonic acid (TNBS)-induced colitis on changes in enteric neuronal subpopulations in adult zebrafish. These changes are suggested to be related to the altered neuro-immune interactions and GI motility, and in IBD pathogenesis. New insights into neuroplasticity will be instrumental in finding appropriate therapeutic treatments. TNBS was intraluminally administered in the distal intestine (DI) of anesthetized adult zebrafish. A histological time course of the intestinal inflammatory response was created to establish optimal TNBS concentration and acute inflammation phase. Using double immunolabelling on whole mounts, the effect of inflammation on neuronal populations was analyzed. Based on intestinal wall thickening, epithelial fold disruption, reduced goblet cell number, and eosinophil infiltration, our analysis indicated that the optimal TNBS concentration (320 mM in 25% ethanol) inducing non-lethal inflammation reached a peak at 6 hours post-induction. The inflammatory response returned to baseline values at 3 days post-induction. At the acute inflammation phase, no influence on the distribution or proportion of nitrergic neurons was observed, while only the proportion of cholinergic neurons was significantly reduced in the DI. The proportion of serotonergic neurons was significantly increased in the entire intestine during inflammation. This study describes a method of TNBS-induced colitis in the adult zebrafish. Given that the acute inflammation phase is accompanied by neuroplasticity comparable to changes observed in IBD patients, and the unique and versatile characteristics of the zebrafish, allows this model to be used alongside IBD animal models to unravel IBD pathology and to test new IBD therapies.

Chemically-induced trout model of acute intestinal inflammation using TNBS

“…Other studies with in-depth histological analyses of responses to intrarectal administration of TNBS focused exclusively on zebrafish. These studies consistently observed both immune cell infiltration and thickening of the intestinal folds, as seen in our study, across a variety of dosages and incubation periods [ 17 , 30 ]. Similar thickening of the folds was also observed with administration of oxazolone in place of TNBS [15] .…”

Different wild type strains of zebrafish show divergent susceptibility to TNBS-induced intestinal inflammation displaying distinct immune cell profiles

“…Defects in the intestinal mucosal barrier are a hallmark of IBD ( Lee et al, 2018 ). Uyttebroek et al (2020) showed a decrease in the number of globet cells in adult zebrafish treated with TNBS, and this it was also seen in larvae ( Uyttebroek et al, 2020 ). Accordingly, we observed that the number of mucus-producing cells was remarkably decreased in AB strain upon TNBS-induced colitis, but this was not seen in the TU strain.…”

A review on current advancement in zebrafish models to study chronic inflammatory diseases and their therapeutic targets

“…Chemical inducers activate the inflammatory pathways as well as release of heptanated colonic protein, which leads to the activation of Th1 cells ( Fig. 3 ) TNBS- induced colitis models have been developed to observe the structural changes in the plexuse and enteric ganglia, and it is found that there is an increase in the serotonergic neuron proportion in the complete zebrafish intestine [ 159 ]. Furthermore, the understanding of intestinal injury to study epithelial barrier function and the effect of PGE2 administration leading to improved epithelial barrier function are also studied [ 160 ].…”