Role of Gut Microbiota in a Zebrafish Model with Chemically Induced Enterocolitis Involving Toll-Like Receptor Signaling Pathways

Abstract

Background/Aims: It is believed that inflammatory bowel disease (IBD) involves a breakdown in interactions between the resident commensal microbiota and the host immune response. Recent studies have revealed that gut physiology and pathology relevant to human IBD can be rapidly modeled in zebrafish larvae with a number of advantages compared with murine models. The objective of this study was to evaluate the role of gut microbiota in zebrafish models with IBD-like enterocolitis. Methods: IBD-like enterocolitis was induced by exposing larval zebrafish to 2, 4, 6-trinitrobenzene sulfonic acid (TNBS). Assays were performed using larval zebrafish collected at 8 and 10 days postfertilization (dpf ). Results: In the absence of gut microbiota, the TNBS-induced enterocolitis was less extensive. The expression of toll-like receptor 3 (TLR3) and the TLRs signaling pathway molecules MyD88 and TRIF, the activation of NFjB, and the production of inflammatory cytokine tumor necrosis factor-a were stimulated in TNBS-treated zebrafish but there was no corresponding alteration in germ-free fish. With microbial colonization, all results reverted to a pattern similar to that observed in conventionally reared zebrafish. Conclusion: We described the key role of gut microbiota in the etiology of a chemically induced larval zebrafish IBD-like model, showing an involvement of TLR signaling pathways.

Comparison of Two Chemically-Induced Colitis-Models in Adult Zebrafish, Using Optical Projection Tomography and Novel Transcriptional Markers

“…Previous zebrafish-based studies have reported an increase in gene expression of IL-1β and TNF-α in adult fish few hours after they had been exposed to oxazolone [6] or TNBS [10]. Similar increases have been reported using larval TNBS-models and qPCR/immunofluorescence techniques [7] [9] [11]. The role of IL-6 has not been scrutinized in colitis models using zebrafish until now.…”

“…TLR orthologs as well as MyD88 signalling and NF-κb activation have been described from larval zebrafish [50] [51]. Recently, He et al [11] reported an increase of TLR-3, the signaling proteins MyD88 and TICAM-1(TRIF) and NF-κb in TNBS-treated zebrafish larvae. This is in contrast with the results obtained in the present study in which only TLR-2 and TICAM-1 were significantly down-and up-regulated in the oxazolone group after 72 h and in the TNBS group after 6 hpi, respectively; TLR-3, MYD88 and NF-κb were not significantly affected by the chemical treatment.…”

“…This is in contrast with the results obtained in the present study in which only TLR-2 and TICAM-1 were significantly down-and up-regulated in the oxazolone group after 72 h and in the TNBS group after 6 hpi, respectively; TLR-3, MYD88 and NF-κb were not significantly affected by the chemical treatment. However, He et al [11] used larval zebrafish as opposed to adult fish in this study. It can be speculated that TLR-signaling and associated pathways are different in adult fish, which possess a fully functional adaptive (T-cell based) immune system.…”

Protective and pro-inflammatory roles of intestinal bacteria

“…Although mouse models of IBD have been used for more than 20 years and have been instrumental in defining many of the major immunopathological mechanisms responsible for inflammatory tissue injury in these models, progress as been slow for reasons outlined above [95]. Thus, several groups of investigators have turned to the use of zebrafish to model IBD (see below) [19,47,63,64,216]. The objective of this review is to present our current understanding of the role that the intestinal microbiota play in vertebrate intestinal health and inflammation.…”

Irritable Bowel Syndrome and Its Relationship With Intestinal Microflora

“…Во-первых, имеются доказательства активации кишечной иммунной системы при СРК, которая приводит к микровоспалению, в исследо-ваниях, демонстрирующих повышенные концентрации лимфоцитов в слизистых оболочках [31], тучных клетках [32,33] и 5-гидрокситриптамин-секретирующих энтерох-ромаффинных клетках [34]. Исследования на живот-ных подчеркивают критическую роль микрофлоры кишеч-ника в балансе между иммуносупрессией и воспалением в желудочно-кишечном тракте, включая Toll-подобные рецепторы (TLRs) сигнальных путей [35]. Во-вторых, при-близительно у 10% пациентов с СРК симптомы начались после эпизода инфекционной диареи [36,37], т. н. постин-фекционный СРК (ПИ-СРК).…”