Role of metallothionein in murine experimental colitis

Abstract

Abstract. Metallothioneins (MTs) are a family of cysteine-rich low molecular-weight proteins that can act as reactive oxygen species scavengers. Although it is known that the induction of MT expression suppresses various inflammatory disorders, the role of MTs in intestinal inflammation remains unclear. In this study, we investigated the effects of dextran sulfate sodium (DSS) administration in mice with targeted deletions of the MT-I/II genes. Acute colitis was induced by 2% DSS in male MT-I/II double knockout (MT-null) and C57BL/6 (wild-type) mice. The disease activity index (DAI) was determined on a daily basis for each animal, and consisted of a calculated score based on changes in body weight, stool consistency and intestinal bleeding. Histology, colon length, myeloperoxidase (MPO) activity and colonic mRNA expression and the concentration of inflammatory cytokines were evaluated by real-time-PCR and enzyme-linked immunosorbent assay (ELISA). The localization of MTs and macrophages was determined by immunohistological and immunofluorescence staining. To investigate the role of MTs in macrophages, peritoneal macrophages were isolated and their responses to lipopolysaccharide were measured. Following DSS administration, the DAI score increased in a time-dependent manner and was significantly enhanced in the MT-I/II knockout mice. Colonic MPO activity levels and inflammatory cytokines [tumor necrosis factor (TNF)-α, interferon (IFN)-γ and interleukin (IL)-17] production increased following DSS administration, and these increases were significantly enhanced in the MT-I/II knockout mice compared with the wild-type mice. MT-positive cells were detected in the lamina propria and submucosal layer by immunohistochemical and immunofluorescence staining, and were mainly co-localized in F4/80-positive macrophages. The production of inflammatory cytokines (TNF-α, IFN-γ and IL-17) from isolated peritoneal macrophages increased following lipopolysaccharide stimulation, and these increases were significantly enhanced in the macrophages obtained from the MT-I/II knockout mice. These data indicate that MTs play an important role in the prevention of colonic mucosal inflammation in a mouse model of DSS-induced colitis, thus suggesting that endogenous MTs play a protective role against intestinal inflammation. IntroductionInflammatory bowel diseases (IBDs) such as ulcerative colitis and Crohn's disease are known as refractory and recurrent diseases of the gastrointestinal tract. Although the features of IBDs suggest a number of possible causes, including genetic, infectious and immunological factors, the precise pathogenesis of IBDs remains unknown (1-3). Recent evidence suggests that oxidative stress caused by reactive oxygen species (ROS) is an important factor involved in the onset and development of intestinal inflammation. Furthermore, it has also been demonstrated that disruptions in the antioxidant defense system are involved in the pathophysiology of IBDs (4,5). Therefore, it is important to investigate the oxidative s...

Smarcad1 mediates microbiota-induced inflammation in mouse and coordinates gene expression in the intestinal epithelium

“…One gene that is highly overexpressed upon Smarcad1-KO in steady state and colitis is Mt1, coding for metallothionein. Metallothionein has been reported to protect against colitis in mouse models, but its role in this process requires further investigation [27,[69][70][71][72][73]. Another gene that is upregulated upon Smarcad1 deletion codes for Bambi.…”

“…These genes include Tlr4, encoding a Toll-like receptor (intestinal stem cells and organoid datasets); Itln1, a lectin receptor; defensins Defa22 and Defa26; Wdfy1 (positively regulates TLR3/4 signaling pathways [25]); and anti-microbial protein genes Ang4 [26], Reg3b, and Lyz1 (lysozyme). Mt1 that is significantly upregulated on Smarcad1 deletion plays an important role in the prevention of colonic mucosal inflammation in the dextran sodium sulfate (DSS)-induced mouse model of colitis [27]. Interestingly, Mt1 is not significantly upregulated in the small intestinal organoid culture upon Smar-cad1-KO, indicating that this upregulation may depend on some external cue, such as niche, microbiota, or immune cells (Fig.…”

Japan’s Practical Guidelines for Zinc Deficiency with a Particular Focus on Taste Disorders, Inflammatory Bowel Disease, and Liver Cirrhosis

“…MTs are a family of low molecular weight proteins containing cysteine residues, which enable high-affinity binding to monovalent and divalent heavy metal atoms. We previously reported that production of several inflammatory cytokines (TNF-α, IFN-γ, and IL-17) was significantly elevated in peritoneal macrophages derived from MT-I/II knockout mice [45], and that dextran sulfate sodium (DSS)-induced colonic inflammation as an animal model of UC was aggravated significantly in knockout mice [45]. Our results also confirmed a significantly higher expression of MT-I/II in the colonic mucosa of the DSS-induced colitis model using the real-time PCR analysis.…”

High‐dose dietary supplementation with zinc prevents gut inflammation: Investigation of the role of metallothioneins and beyond by transcriptomic and metagenomic studies

“…For example, Tsuji et al reported that MTs had a protective effect in dextran sulfate sodium (DSS)-induced colitis. 32 More recently, exosomes enriched in MT-2 were found to be required for the suppression of inflammatory responses and for protection in DSS-induced colitis in mice. 33 In contrast, Tran et al showed that following DSS induction, MT-deficient mice displayed lower levels of inflammation than wild-type mice did.…”

“…An MT-specific monoclonal antibody has been used as a novel therapeutic in murine models of IBD. 34 The disparities regarding the protective or non-protective effects of MTs 19,32,35,36 may be attributed to a variety of factors, including (i) differences in dose levels and dose timing in chemically induced colitis, (ii) differences in the time points at which clinical measurements were made and tissue samples were collected following induction of colitis, and (iii) microbiome heterogeneity in mice strains housed in different animal facilities. 31 Thus, we need to better understanding the nuances of the MTs' complex functions and how these proteins influence the pathogenesis of IBD.…”