Functional relevance of intestinal epithelial cells in inflammatory bowel disease

Endoplasmic reticulum stress: A possible connection between intestinal inflammation and neurodegenerative disorders

BACKGROUND

Different studies have shown the key role of endoplasmic reticulum (ER) stress in autoimmune and chronic inflammatory disorders, as well as in neurodegenerative diseases. ER stress leads to the formation of misfolded proteins which affect the secretion of different cell types that are crucial for the intestinal homeostasis.

PURPOSE

In this review, we discuss the role of ER stress and its involvement in the development of inflammatory bowel diseases, chronic conditions that can cause severe damage of the gastrointestinal tract, focusing on the alteration of Paneth cells and goblet cells (the principal secretory phenotypes of the intestinal epithelial cells). ER stress is also discussed in the context of neurodegenerative diseases, in which protein misfolding represents the signature mechanism. ER stress in the bowel and consequent accumulation of misfolded proteins might represent a bridge between bowel inflammation and neurodegeneration along the gut-to-brain axis, affecting intestinal epithelial homeostasis and the equilibrium of the commensal microbiota. Targeting intestinal ER stress could foster future studies for designing new biomarkers and new therapeutic approaches for neurodegenerative disorders.

Epithelial production of elastase is increased in inflammatory bowel disease and causes mucosal inflammation

Imbalance between proteases and their inhibitors plays a crucial role in the development of Inflammatory Bowel Diseases (IBD). Increased elastolytic activity is observed in the colon of patients suffering from IBD. Here, we aimed at identifying the players involved in elastolytic hyperactivity associated with IBD and their contribution to the disease. We revealed that epithelial cells are a major source of elastolytic activity in healthy human colonic tissues and this activity is greatly increased in IBD patients, both in diseased and distant sites of inflammation. This study identified a previously unrevealed production of elastase 2A (ELA2A) by colonic epithelial cells, which was enhanced in IBD patients. We demonstrated that ELA2A hyperactivity is sufficient to lead to a leaky epithelial barrier. Epithelial ELA2A hyperactivity also modified the cytokine gene expression profile with an increase of pro-inflammatory cytokine transcripts, while reducing the expression of pro-resolving and repair factor genes. ELA2A thus appears as a novel actor produced by intestinal epithelial cells, which can drive inflammation and loss of barrier function, two essentials pathophysiological hallmarks of IBD. Targeting ELA2A hyperactivity should thus be considered as a potential target for IBD treatment.

Paneth cells: Maintaining dynamic microbiome-host homeostasis, protecting against inflammation and cancer

The human intestines are constantly under the influence of numerous pathological factors: enteropathogenic microorganisms, food antigens, physico-chemical stress associated with digestion and bacterial metabolism, therefore it must be provided with a system of protection against adverse impact. Recent studies have shown that Paneth cells play a crucial role in maintaining homeostasis of the small intestines. Paneth cells perform many vital functions aimed at maintaining a homeostatic balance between normal microbiota, infectious pathogens and the human body, regulate the qualitative composition and number of intestinal microorganisms, prevent the introduction of potentially pathogenic species, and protect stem cells from damage. Paneth cells take part in adaptive and protective-inflammatory reactions. Paneth cells maintain dynamic balance between microbial populations, and the macroorganism, preventing the development of intestinal infections and cancer. They play a crucial role in gastrointestinal homeostasis and may be key factors in the etiopathological progression of intestinal diseases.

Complex TNF-α B cell epitope MAP vaccine alleviates murine ulcerative colitis

The present study aimed to develop a tumor necrosis factor‑α (TNF‑α) B‑cell epitope/IL‑1β helper T lymphocyte epitope complex MAP vaccine for the alleviation of ulcerative colitis (UC) in mice. The B cell epitopes of murine TNF‑α (mTNF‑α) were predicted in silico and coupled with the universal interleukin 1β (IL‑1β) helper T‑cell epitope peptide VQGEESNDK to synthesize the eight‑branched MAP vaccine. Then, the immunological effects of the MAP vaccine were assessed in vitro and in vivo, as well as its impacts on DAI index, serum DAO levels, colon tissue tight junction protein amounts, ultrastructural changes, and MPO activity in BALB/c mice with UC. The amino acids LTLRSSSQNSSDKPV at positions 78‑92 of mTNF‑α may constitute the dominant B cell epitope. Based on this finding, an eight‑branched peptide structure, the TNF‑α B‑cell epitope/IL‑1β helper T‑cell epitope complex MAP vaccine, was synthesized. Indirect ELISA confirmed that MAP had a high affinity with commercialized mTNF‑α antibodies. Meanwhile, MAP induced high specific antibody titers in vivo, reduced the DAI score, serum MPO activity, colorectal lymph node colony count, ultrastructural injuries, colon tissue histological index score and MPO activity in UC mice, while increasing the expression levels of occludin, claudin1 and ZO1 in colon tissues. The synthetic complex MAP vaccine has good antigenicity and immunogenicity, and can alleviate UC in mouse models.

Flightless I exacerbation of inflammatory responses contributes to increased colonic damage in a mouse model of dextran sulphate sodium-induced ulcerative colitis

Ulcerative colitis (UC) is a chronic inflammatory bowel disease characterized by cytokine driven inflammation that disrupts the mucosa and impedes intestinal structure and functions. Flightless I (Flii) is an immuno-modulatory protein is a member of the gelsolin family of actin-remodelling proteins that regulates cellular and inflammatory processes critical in tissue repair. Here we investigated its involvement in UC and show that Flii is significantly elevated in colonic tissues of patients with inflammatory bowel disease. Using an acute murine model of colitis, we characterised the contribution of Flii to UC using mice with low (Flii+/-), normal (Flii+/+) and high Flii (FliiTg/Tg). High levels of Flii resulted in significantly elevated disease severity index scores, increased rectal bleeding and degree of colon shortening whereas, low Flii expression decreased disease severity, reduced tissue inflammation and improved clinical indicators of UC. Mice with high levels of Flii had significantly increased histological disease severity and elevated mucosal damage with significantly increased inflammatory cell infiltrate and significantly higher levels of TNF-α, IFN-γ, IL-5 and IL-13 pro-inflammatory cytokines. Additionally, Flii overexpression resulted in decreased β-catenin levels, inhibited Wnt/β-catenin signalling and impaired regeneration of colonic crypts. These studies suggest that high levels of Flii, as is observed in patients with UC, may adversely affect mucosal healing via mechanisms involving Th1 and Th2 mediated tissue inflammation and Wnt/β-catenin signalling pathway.

Recombinant expressed vasoactive intestinal peptide analogue ameliorates TNBS-induced colitis in rats

AIM

To investigate the modulatory effect of recombinant-expressed vasoactive intestinal peptide (VIP) analogue (rVIPa) on trinitrobenzene sulfonic acid (TNBS)-induced colitis in rats.

METHODS

Forty-eight rats were randomized into six groups: normal control group (Control), model control group (TNBS), ethanol treatment group (ETOH), and VIP treatment groups with different dosage (rVIPa_1nmol, rVIPa_2nmol, rVIPa_4nmol). Diarrhea and bloody stool were observed. Colonic damage was evaluated histologically. The levels of tumor necrosis factor-α (TNF-α), interleukin-10 (IL-10), myeloperoxidase (MPO) and endotoxin in colonic tissue and serum were determined by enzyme-linked immunosorbent assay (ELISA). The expression of occludin, ZO-1, Toll-like receptor 4 (TLR4), and nuclear factor-kappa B p65 (NF-κB p65), IκBα, and p-IκBα were detected by Western blot.

RESULTS

Administration with 2 nmol rVIPa prevented TNBS-induced necrosis, hyperemia, swelling, inflammation, etc., pathologic changes observed in the inner surface of colon in experimental rats. Moreover, rVIPa significantly decreased colonic TNF-α level (P < 0.001), MPO activity (P < 0.001) and serum endotoxin level (P < 0.01), and remarkably increased colonic IL-10 content (P < 0.001) in rats with TNBS-induced colitis. Furthermore, compared to the TNBS-induced colitis group, 2 nmol rVIPa treatment up-regulated the levels of occludin (P < 0.05) and ZO-1 (P < 0.05), NF-κB p65 (P < 0.01) and IκBα (P < 0.001), and down-regulated the levels of TLR4.

CONCLUSION

rVIPa ameliorates TNBS-induced colonic injury and inflammation and effectively protected the intestinal mucosal barrier function in rats. The mechanism may be related to TLR4/NF-κB-mediated signaling pathway. rVIPa could be used as a new alternative therapy for intestinal inflammatory disorders.