HMGB1 exacerbates experimental mouse colitis by enhancing innate lymphoid cells 3 inflammatory responses via promoted IL-23 production

Inflammatory Gene Panel Guiding the Study of Genetics in Inflammatory Bowel Disease

Inflammatory bowel disease (IBD) is a complex disease that develops through a sequence of molecular events that are still poorly defined. This process is driven by a multitude of context-dependent genes that play different roles based on their environment. The complexity and multi-faceted nature of these genes make it difficult to study the genetic basis of IBD. The goal of this article is to review the key genes in the pathophysiology of IBD and highlight new technology that can be used in further research. This paper examines Nanostring RNA probe technology, which uses tissue analyzed without the use of enzymes, transcription, or amplification. Nanostring offers several panels of genes to test, including an inflammation panel of 234 genes. This article analyzes this panel and reviews the literature for each gene's effect in IBD for use as a framework to review the pathophysiology of the disease. The panel was narrowed to 26 genes with significant evidence of mechanistic potential in IBD, which were then categorized into specific areas of pathogenesis. These include gut barrier breakdown, inappropriate recognition of commensal bacteria, immune cell activation, proinflammatory cytokine release, and subsequent impairment of the anti-inflammatory response. The eventual goal of this paper is the creation of a customized panel of IBD genes that can be used to better understand the genetic mechanism of IBD and aid in the development of future therapies in IBD.

Inhibition of HMGB1 improves experimental mice colitis by mediating NETs and macrophage polarization

OBJECTIVE

Inflammatory bowel disease (IBD) is listed by the World Health Organization as one of the modern intractable diseases. High mobility histone box 1 (HMGB1), originally described as a non-histone nucleoprotein involved in transcriptional regulation, was later identified as a pro-inflammatory cytokine that may contribute to the pathogenesis of inflammatory diseases such as IBD. Neutrophil extracellular traps (NETs) play an important role in the pathophysiology of IBD The aim of this study was to investigate the role of HMGB1 in experimental colitis mice and its potential mechanisms of action.

METHODS

We first constructed the experimental colitis mouse model. Intervention of mice by rhHMGB1 supplementation or HMGB1 inhibition. The pathological morphology of the colon was observed using HE staining. Apoptosis of colonic tissue intestinal epithelial cells was evaluated using Tunel assay. The expression of HMGB1, ZO-1 and occludin in colon tissue was detected by immunohistochemistry, ELISA and western-blot. We also assessed the effects of HMGB1 on colonic injury, NETs content, macrophage polarization and inflammatory cells in mice. The regulatory effect of HMGB1 inhibition on NETs was assessed by combining DNase I.

RESULTS

Inhibition of HMGB1 significantly reduced the inflammatory model in experimental colitis mice, as evidenced by reduced body weight, increased colonic length, reduced DAI scores and apoptosis, reduced inflammatory response, and improved colonic histopathological morphology and intestinal mucosal barrier function. Meanwhile, inhibition of HMGB1 was able to reduce the expression of CD86, citH3 and MPO and increase the expression of CD206 in the colonic tissue of mice. In addition, DNase I intervention was also able to improve colonic inflammation in mice. And the best effect was observed when DNase I and inhibition of HMGB1 were intervened together.

CONCLUSION

Inhibition of HMGB1 ameliorates IBD by mediating NETs and macrophage polarization.

HMGB1 regulates Th17 cell differentiation and function in patients with psoriasis

BACKGROUND

Psoriasis is an immune-mediated chronic inflammatory skin disease, in which T helper 17 (Th17) cells and its effective cytokine interleukin (IL)-17A play a pivotal pathogenic role. High mobility group box 1 (HMGB1) is an important proinflammatory cytokine, which has been confirmed to be highly expressed in the peripheral circulation and epidermis tissues of psoriasis patients. The regulatory effect of HMGB1 on IL-17A expression and function has been reported in some inflammatory and autoimmune diseases by the HMGB1-Toll-like receptor 4 (TLR4)-interleukin (IL)-23-IL-17A pathway. While, in the pathological environment of psoriasis, whether HMGB1 can exert the regulatory effect on IL-17A is not clear.

OBJECTIVE

We aimed to evaluate the role of HMGB1-TLR4-IL-23-IL-17A pathway in the pathogenesis of psoriasis and explore the possible regulatory mechanism of HMGB1 on Th17 cell differentiation.

METHODS

Serum levels of HMGB1, TLR4, IL-23, and IL-17A were quantified in 50 patients with moderate-to-severe plaque psoriasis and 30 healthy controls. Peripheral blood mononuclear cells  were acquired from 10 severe psoriasis patients and administrated by different concentrations of recombinant-HMGB1 (rHMGB1) to detect the Th17 cell percentage, mRNA and protein levels of TLR4, IL-23, IL-17A and retinoid-related orphan receptor γt (RORγt).

RESULTS

The serum levels of HMGB1, TLR4, IL-23, and IL-17A in psoriasis patients were significantly higher than healthy controls, especially in severe patients, and positively correlated with the severity index. There were also positive correlations between every two detected indicators of HMGB1, TLR4, IL-23, and IL-17A. In vitro study, rHMGB1 can promote the elevated expression of Th17 cell percentage as well as TLR4, IL-23, IL-17A, and RORγt in a dose-dependent manner.

CONCLUSION

HMGB1 can contribute to the pathogenesis of psoriasis by regulating Th17 cell differentiation through HMGB1-TLR4-IL-23-RORγt pathway, then promotes IL-17A production and aggravates inflammation process. Targeting HMGB1 may be a possible potential candidate for the immunotherapy of psoriasis.

Toll-like receptor 2 deficiency alleviates acute pancreatitis by inactivating the NF-κB/NLRP3 pathway

The early aseptic immune response is the key factor leading to the aggravation of acute pancreatitis (AP). Toll-like receptor (TLR) 2 is an important member of the TLR family, but the role of TLR2 in AP remains to be investigated. In the present study, we found that TLR2 expression was significantly increased in AP patients. In a mouse model of cerulein-induced AP, TLR2 deficiency resulted in reduced inflammation, reduced infiltration of pancreatic neutrophils and macrophages, and decreased expression of proinflammatory cytokines such as interleukin (IL)-1β, IL-6, IL-17 and IL-18. In addition, transcriptomic analysis revealed that nod-like receptor family pyrin domain-containing 3 (NLRP3) expression was increased in AP, and there was a significant correlation between NLRP3 and TLR2. This study found that TLR2 deficiency can lead to a decrease in the activation of the NF-κB/NLRP3 signalling pathway, and the NLRP3 inhibitor MCC950 can alleviate AP in mice. Therefore, this study confirmed that TLR2 participates in the development of AP by activating the NF-κB/NLRP3 pathway. This study suggested that TLR2 might be a novel therapeutic target for AP.

New insights into ischemia-reperfusion injury signaling pathways in organ transplantation

PURPOSE OF REVIEW

Ischemia-reperfusion injury (IRI) leading to allograft rejection in solid organ transplant recipients is a devastating event that compromises graft and patient survival. As our clinical knowledge regarding its definition and presentation has significantly improved over the last years, adequate biomarkers translating to important therapeutic intervention remains a challenge. This review will summarize recent findings in this area.

RECENT FINDINGS

In the past 18 months, our understanding of organ transplantation IRI has improved. IRI involves a positive amplification feedback loop encompassing damaged cells at the graft site, the activity of redox-sensitive damage-associated molecular patterns, and local sequestration of recipient-derived monocytes, lymphocytes and polymorphonuclear leukocytes, like neutrophils, to sustain the immunological cascade and to enhance the destruction of the foreign tissue. Recent studies have identified critical components leading to IRI, including the oxidation state of high mobility group box 1, a classic danger signal, its role in the Toll-like receptor 4-interleukin (IL)-23-IL-17A signaling axis, and the role of neutrophils and CD321, a marker for transmigration of circulating leukocytes into the inflamed tissue. In addition, recent findings imply that the protective functions mediated by autophagy activation counterbalance the detrimental nucleotide-binding domain-like receptor family, pyrin domain containing 3 inflammasome pathway. Finally, clinical studies reveal the posttransplant variables associated with early allograft dysfunction and IRI.

SUMMARY

The future challenge will be understanding how crosstalk at the molecular and cellular levels integrate prospectively to predict which peri-transplant signals are essential for long-term clinical outcomes.

Dihydromyricetin Improves High-Fat Diet-Induced Hyperglycemia through ILC3 Activation via a SIRT3-Dependent Mechanism

SCOPE

Previous studies indicate that dihydromyricetin (DHM) effectively improved glucose homeostasis and alleviated insulin resistance in population-intervened trials, yet the underlying mechanism remains obscure.

METHODS AND RESULTS

Wild-type male mice and recombinase activating gene 1(Rag1)^-/- mice (lacking adaptive immunity lymphocytes) are fed with control, high-fat diet (HFD), or HFD+DHM diets for 8 weeks. DHM effectively protects HFD feeding mice against hyperglycemia by promoting group 3 innate lymphoid cells (ILC3s) cells proliferation and interleukin 22 (IL-22) production. Furthermore, IL-22 secretion induced by DHM increases the expression levels of the tight junction (TJs) molecules to protect the intestinal barrier integrity, thereby decreasing the level of lipopolysaccharides (LPS), an endotoxin that is involved in the regulation of chronic tissue inflammation and insulin resistance. In addition, silent mating-type information regulation 2 homolog 3 (SIRT3) deficiency results in more serious obesity and intestinal barrier damage following HFD feeding and abolished DHM-mediated increase in IL-22 expression levels of ILC3 cells in SIRT3 knockout (SIRT3KO) mice. DHM reduces metabolic stress and enhances mitochondrial respiratory capacity to promote cell proliferation and IL-22 secretion by activating SIRT3 in ILC3 cells CONCLUSIONS: DHM improves IL-22 production of ILC3 cells and subsequently inhibits intestinal barrier dysfunction to alleviate hyperglycemia partially mediated by SIRT3.

Microplastic consumption induces inflammatory signatures in the colon and prolongs a viral arthritis

Global microplastic (MP) contamination and the effects on the environment are well described. However, the potential for MP consumption to affect human health remains controversial. Mice consuming ≈80 μg/kg/day of 1 μm polystyrene MPs via their drinking water showed no weight loss, nor were MPs detected in internal organs. The microbiome was also not significantly changed. MP consumption did lead to small transcriptional changes in the colon suggesting plasma membrane perturbations and mild inflammation. Mice were challenged with the arthritogenic chikungunya virus, with MP consumption leading to a significantly prolonged arthritic foot swelling that was associated with elevated Th1, NK cell and neutrophil signatures. Immunohistochemistry also showed a significant increase in the ratio of neutrophils to monocyte/macrophages. The picture that emerges is reminiscent of enteropathic arthritis, whereby perturbations in the colon are thought to activate innate lymphoid cells that can inter alia migrate to joint tissues to promote inflammation.

Innate (and Innate-like) Lymphoid Cells: Emerging Immune Subsets With Multiple Roles Along Transplant Life

Transplant immunology is currently largely focused on conventional adaptive immunity, particularly T and B lymphocytes, which have long been considered as the only cells capable of allorecognition. In this vision, except for the initial phase of ischemia/reperfusion, during which the role of innate immune effectors is well established, the latter are largely considered as "passive" players, recruited secondarily to amplify graft destruction processes during rejection. Challenging this prevalent dogma, the recent progresses in basic immunology have unraveled the complexity of the innate immune system and identified different subsets of innate (and innate-like) lymphoid cells. As most of these cells are tissue-resident, they are overrepresented among passenger leukocytes. Beyond their role in ischemia/reperfusion, some of these subsets have been shown to be capable of allorecognition and/or of regulating alloreactive adaptive responses, suggesting that these emerging immune players are actively involved in most of the life phases of the grafts and their recipients. Drawing upon the inventory of the literature, this review synthesizes the current state of knowledge of the role of the different innate (and innate-like) lymphoid cell subsets during ischemia/reperfusion, allorecognition, and graft rejection. How these subsets also contribute to graft tolerance and the protection of chronically immunosuppressed patients against infectious and cancerous complications is also examined.

Serum HMGB1 level is correlated with serum I-FABP level in neonatal patients with necrotizing enterocolitis

Background

This study aims to investigate clinical significance of HMGB1 in neonatal patients with necrotizing enterocolitis (NEC).

Methods

This observational study enrolled a total of 106 stage II-III NEC neonatal patients, who were admitted in our hospital from March 2014 to March 2019. In addition, 99 suspected NEC patients and 200 healthy controls were included. The serum levels of HMGB1, I-FABP, and inflammatory factors CRP, IL-1β, IL-6 and TNF-α were determined by enzyme-linked immunosorbent assay (ELISA). Then, the demographic data and clinical characteristics of all patients were collected. Statistical analysis was conducted to determine the correlation between HMGB1 and the clinical characteristics.

Results

No significant difference was found in the basic characteristics of NEC patients and healthy controls, except for birth weight and gestational age. The expression levels of HMGB1, I-FABP, and inflammatory factors IL-1β, IL-6 and TNF-α were significantly higher in NEC patients, when compared to healthy controls. The serum levels of HMGB1, I-FABP, IL-1β and IL-6 markedly increased in stage II-III NEC patients, when compared to stage I NEC patients. The Pearson’s analysis revealed a positive correlation between HMGB1 and I-FABP, HMGB1 and IL-1β, and HMGB1 and IL-6. The ROC curve revealed that both HMGB1 and I-FABP can potentially be used as diagnostic factors for NEC. The logistic multivariate regression revealed that I-FABP, IL-1β and IL-6 are independent risk factors for mortality in neonatal NEC patients.

Conclusions

Serum HMGB1 levels are upregulated in neonatal NEC patients, and these are correlated with the patient’s prognosis.

HMGB1-TLR4-IL-23-IL-17A axis accelerates renal ischemia-reperfusion injury via the recruitment and migration of neutrophils

Renal ischemia-reperfusion injury (IRI) is an important cause of setting off acute kidney injury. Neutrophil-mediated immunomodulation has a pivotal role in the evolving of IRI. The HMGB1-TLR4-IL-23-IL-17A axis gives rise to neutrophil activation. Therefore, in the study, the role of the HMGB1-TLR4-IL-23-IL-17A axis in IRI was evaluated. Cell viability, inflammation, apoptosis, oxidative stress, survival, renal function and pathology, and the activation of macrophages and neutrophils were measured. Moreover, we evaluated the acetylation, translocation, and secretion of HMGB1 as well as levels of TLR-4, IL-23, IL-17A, and neutrophil chemokines (KC, LIX, and MIP-2). In vivo, anti-HMGB1 antibody decreased the acetylation, translocation, and secretion of HMGB1, reduced the expression of TLR-4, IL-23, IL-17A, KC, LIX, and MIP-2, alleviated the activation of macrophages and neutrophils, improved the survival rate and renal dysfunction, and decreased inflammation, apoptosis, oxidative stress, and pathological injury of the kidney. However, the intervention with recombinant HMGB1(R-HMGB1) significantly abolish the above effect of anti-HMGB1 in IRI. Neutralization IL-23 or IL-17A can alleviated the neutrophils mediated renal dysfunction by suppressing inflammation, apoptosis, and oxidative stress in IRI. In vitro, we confirmed that hypoxic/deoxygenation (H/R) induces the secretion of HMGB1 though acetylation on HK-2 and HMGB1 promotes the secretion of IL-23 in a HMGB1/TLR-4-dependent manner on macrophages. Together, these results implied that the HMGB1-TLR4-IL-23-IL-17A axis regulates inflammation, oxidative stress, apoptosis, and renal injury in IRI by promoting the recruitment and migration of neutrophils.

The Effect and Regulatory Mechanism of High Mobility Group Box-1 Protein on Immune Cells in Inflammatory Diseases

High mobility group box-1 protein (HMGB1), a member of the high mobility group protein superfamily, is an abundant and ubiquitously expressed nuclear protein. Intracellular HMGB1 is released by immune and necrotic cells and secreted HMGB1 activates a range of immune cells, contributing to the excessive release of inflammatory cytokines and promoting processes such as cell migration and adhesion. Moreover, HMGB1 is a typical damage-associated molecular pattern molecule that participates in various inflammatory and immune responses. In these ways, it plays a critical role in the pathophysiology of inflammatory diseases. Herein, we review the effects of HMGB1 on various immune cell types and describe the molecular mechanisms by which it contributes to the development of inflammatory disorders. Finally, we address the therapeutic potential of targeting HMGB1.

Mechanisms of HuR in regulation of epithelial cell apoptosis in rat ulcerative colitis

OBJECTIVE

To investigate the influence of HuR on the apoptosis rate of epithelial cells in rats with ulcerative colitis (UC) and its mechanism.

METHODS

UC cell models were established in LPS induced Caco-2 cells. After transfection of si-HuR, pcDNA3.1-HuR, pcDNA3.1-HMGB1, miR-29a-3p mimic or miR-29a-3p inhibitor and their negative controls, apoptosis rate and apoptosis-related proteins (Bcl-2, Bax and cleaved-caspase-3) were tested by flow cytometry, qRT-PCR and Western blot. Actinomycin D treatment was applied to verify the effect of HuR in Caco-2 cells. The binding of HMGB1 to HuR/miR-29a-3p was measured by RIP and dual luciferase reporter gene assays. Experimental UC rat models were established by rectum administration of TNBS/ethanol. The colonic weight/length ratio was calculated at the day 15. The morphology of colon tissues and the apoptosis of tissues were separately detected by H&E staining and TUNEL staining. qRT-PCR and Western blot were conducted to determine the levels of HuR, miR-29a-3p and HMGB1 in colon tissues.

RESULTS

The apoptosis of LPS-treated Caco-2 cells was inhibited following transfection of si-HuR or miR-29a-3p mimic while facilitated following transfection of pcDNA3.1-HMGB1 or miR-29a-3p inhibitor. RIP and dual luciferase reporter gene assays showed that both HuR and miR-29a-3p can bind HMGB1. Overexpression of HuR in Caco-2 cells results in less HMGB1 that can be bind to miR-29a-3p. The degradation rate of HMGB1 mRNA was increased after transfection of si-HuR in Caco-2 cells. Additionally, miR-29a-3p overexpression can abolish the increases of HMGB1 mRNA induced by HuR, therefore consequently suppress the HMGB1 mRNA that can be bind to HuR. Knockdown of HuR can alleviate TNBS-induced UC in rats and inhibit the apoptosis of colon tissues.

CONCLUSION

HuR competitively binds HMGB1 with miR-29a-3p to promote apoptosis of colonic epithelia in rats with UC.

AMPK induces regulatory innate lymphoid cells after traumatic brain injury

The CNS is regarded as an immunoprivileged organ, evading routine immune surveillance; however, the coordinated development of immune responses profoundly influences outcomes after brain injury. Innate lymphoid cells (ILCs) are cytokine-producing cells that are critical for the initiation, modulation, and resolution of inflammation, but the functional relevance and mechanistic regulation of ILCs are unexplored after acute brain injury. We demonstrate increased proliferation of all ILC subtypes within the meninges for up to 1 year after experimental traumatic brain injury (TBI) while ILCs were present within resected dura and elevated within cerebrospinal fluid (CSF) of moderate-to-severe TBI patients. In line with energetic derangements after TBI, inhibition of the metabolic regulator, AMPK, increased meningeal ILC expansion, whereas AMPK activation suppressed proinflammatory ILC1/ILC3 and increased the frequency of IL-10-expressing ILC2 after TBI. Moreover, intracisternal administration of IL-33 activated AMPK, expanded ILC2, and suppressed ILC1 and ILC3 within the meninges of WT and Rag1-/- mice, but not Rag1-/- IL2rg-/- mice. Taken together, we identify AMPK as a brake on the expansion of proinflammatory, CNS-resident ILCs after brain injury. These findings establish a mechanistic framework whereby immunometabolic modulation of ILCs may direct the specificity, timing, and magnitude of cerebral immunity.

Anti-High Mobility Group Box 1 Neutralizing-Antibody Ameliorates Dextran Sodium Sulfate Colitis in Mice

High mobility group box 1 (HMGB1) is a ubiquitous nuclear protein in mammals. When released into the extracellular space, it acts as a damage-associated molecular pattern. This study investigates whether increased HMGB1 levels are found in the intestinal mucosa of ulcerative colitis (UC) patients, and whether an anti-HMGB1 neutralizing-antibody (HnAb) can inhibit the intestinal inflammation elicited by dextran sulfate sodium (DSS) in mice. Because toll-like receptor 4 (TLR4) is implicated in HMGB1-mediated immune cell activation, DSS colitis was also elicited in TLR4-deficient mice in the presence and absence of HnAb. The expression of HMGB1 in UC patients was examined. HnAb was administered via intraperitoneal injection to TLR4 deficient mice and their wild-type littermates, both being induced to colitis with DSS. Finally, the protective effect of HnAb and TLR4 deficiency were evaluated. In UC patients, HMGB1 was up-regulated in the inflamed colon. When administered during DSS application, HnAb alleviated the severity of colitis with a lower disease activity index, limited histological damages, and reduced production of proinflammatory cytokines. This antibody also limited colonic barrier loss, decreased colonic lamina propria macrophages and partially reversed the DSS treatment-associated dysbiosis. The protective effect of this antibody was enhanced in TLR4-deficient mice in some aspects, indicating that both additional HMGB1-mediated as well as TLR4-mediated inflammatory signaling pathways were involved in the induction of colitis by DSS. HnAb ameliorated colitis via macrophages inhibition and colonic barrier protection. It may therefore be a novel treatment option in colitis.

Leucine-rich alpha-2 glycoprotein 1, high mobility group box 1, matrix metalloproteinase 3 and annexin A1 as biomarkers of ulcerative colitis endoscopic and histological activity

OBJECTIVE

The LRG, HMGB1, MMP3 and ANXA1 proteins have been implicated in different inflammatory pathways in ulcerative colitis (UC), but their role as specific biomarkers of both endoscopic and histological activity has yet to be elucidated. In the present study, we aimed to evaluate the LRG1, HMGB1, MMP3 and ANXA1 as potential serum biomarkers for UC endoscopic and histological activity.

METHODS

This cross-sectional study included UC patients under 5-ASA, and healthy controls (HC) undergoing colonoscopy. Blood and biopsy samples were obtained and endoscopic Mayo sub-score (Ms) was recorded for the UC patients. Intramucosal calprotectin as a marker of histologic activity was evaluated in all biopsy samples and serum LRG1, HMGB1, MMP3 and ANXA1 levels were measured in the blood samples.

RESULTS

The HCs ANXA1 level was lower compared to that of the UC group [P = 0.00, area under the curve (AUC) = 0.881] and so was the HCs MMP3 level compared to that of patients (P = 0.00, AUC = 0.835). The HCs ANXA1 levels were also lower compared to these of the independent Ms groups, even to the Ms = 0 (P = 0.00, AUC = 0.913). UC endoscopic activity was associated with MMP3 levels (r = 0.54, P = 0.000) but not with ANXA1, LRG1 and HMGB1 levels CONCLUSION: Serum ANXA1 is a potential diagnostic biomarker of UC and serum MMP3 is a potential biomarker of UC endoscopic and histological activity.

IL-33 deficiency protects mice from DSS-induced experimental colitis by suppressing ILC2 and Th17 cell responses

BACKGROUND

Recently, IL-33-driven ILC2 response has been shown to participate in a variety of diseases. However, IL-33-driven ILC2 immunity has not been extensively characterized in the context of colitis yet.

MATERIALS AND SUBJECTS

The RAG-2- and IL-33-deficient mice were used to investigate the role and underlying mechanisms of IL-33-driven ILC2 response in the DSS-induced experimental colitis. Body weight, length of colon, and histological analysis were monitored to evaluate the severity of colitis. Proportions of immune cells were examined by flow cytometry. Levels of cytokines were analyzed by ELISA and q-PCR.

RESULTS

Administration of exogenous IL-33 aggravated the DSS-induced colitis, which revealed that IL-33 promoted the generation of ILC2 cells to mediate the inflammation of colon. Consistently, this effect was confirmed in RAG-2-deficient mice without T, B cells. Furthermore, IL-33-deficient mice were used to examine the role of endogenous IL-33 on the pathogenesis of DSS-induced colitis. Interestingly, lack of endogenous IL-33 protected the mice from the DSS-induced colitis. The protective effect is associated with impairments of development of ILC2 as well as Th17 cells. Analysis of their cytokine production profiles revealed that IL-33 deficiency resulted in the reduction of cytokines IL-6 and IL-1β as well as IL-10. These results suggest that IL-33/ILC2 axis is a potential therapeutic target for human colitis.

CONCLUSION

Our findings demonstrate that IL-33 deficiency protects mice from DSS-induced colitis. The protective effect is associated with impairments of ILC2 and Th17 cell development as well as reduction of inflammatory cytokines IL-6 and IL-1β.

Lessons on the Sigma-1 Receptor in TNBS-Induced Rat Colitis: Modulation of the UCHL-1, IL-6 Pathway

Inflammatory Bowel Disease (IBD) is an autoimmune ailment of the gastrointestinal (GI) tract, which is characterized by enhanced activation of proinflammatory cytokines. It is suggested that the sigma-1 receptor (σ1R) confers anti-inflammatory effects. As the exact pathogenesis of IBD is still unknown and treatment options are limited, we aimed to investigate the effects of σ1R in 2,4,6-trinitrobenzenesulfonic acid (TNBS)-induced experimental colitis. To this end, male Wistar-Harlan rats were used to model colitic inflammation through the administration of TNBS. To investigate the effects of σ1R, Fluvoxamine (FLV, σ1R agonist) and BD1063 (σ1R antagonist) were applied via intracolonic administration to the animals once a day for three days. Our radioligand binding studies indicated the existence of σ1Rs as [3H](+)-pentazocine binding sites, and FLV treatment increased the reduced σ1R maximum binding capacity in TNBS-induced colitis. Furthermore, FLV significantly attenuated the colonic damage, the effect of which was abolished by the administration of BD1063. Additionally, FLV potentially increased the expression of ubiquitin C-terminal hydrolase ligase-1 (UCHL-1) and the levels of endothelial nitric oxide synthase (eNOS), and decreased the levels of interleukin-6 (IL-6) and inducible NOS (iNOS) expression. In summary, our study offers evidence for the anti-inflammatory potential of FLV and σ1R in experimental colitis, and our results present a promising approach to the development of new σ1R-targeted treatment options against IBD.

Differential Expression of Soluble Receptor for Advanced Glycation End-products in Mice Susceptible or Resistant to Chronic Colitis

BACKGROUND

Identifying the factors that contribute to chronicity in inflamed colitic tissue is not trivial. However, in mouse models of colitis, we can investigate at preclinical timepoints. We sought to validate murine Trichuris muris infection as a model for identification of factors that promote development of chronic colitis.

METHODS

We compared preclinical changes in mice with a resolving immune response to T. muris (resistant) vs mice that fail to expel the worms and develop chronic colitis (susceptible). Findings were then validated in healthy controls and patients with suspected or confirmed IBD.

RESULTS

The receptor for advanced glycation end products (RAGE) was highly dysregulated between resistant and susceptible mice before the onset of any pathological signs. Increased soluble RAGE (sRAGE) in the serum and feces of resistant mice correlated with reduced colitis scores. Mouse model findings were validated in a preliminary clinical study: fecal sRAGE was differentially expressed in patients with active IBD compared with IBD in remission, patients with IBD excluded, or healthy controls.

CONCLUSIONS

Preclinical changes in mouse models can identify early pathways in the development of chronic inflammation that human studies cannot. We identified the decoy receptor sRAGE as a potential mechanism for protection against chronic inflammation in colitis in mice and humans. We propose that the RAGE pathway is clinically relevant in the onset of chronic colitis and that further study of sRAGE in IBD may provide a novel diagnostic and therapeutic target.

The natural flavonoid galangin ameliorates dextran sulphate sodium-induced ulcerative colitis in mice: Effect on Toll-like receptor 4, inflammation and oxidative stress

This study was carried out to investigate the potential therapeutic effect of galangin, a promising active principle of honeybee propolis, in dextran sulphate sodium (DSS)-induced colitis in mice. We explored the possible underlying mechanisms for galangin action and the therapeutic benefit of adding galangin to the standard therapy sulphasalazine. A galangin dose of 40 mg/kg was selected based on a preliminary dose-selection study for investigation in a 4-week cyclical model of DSS-induced colitis. Mice received 3% DSS in their drinking water during the first and third weeks and were administered the treatments (40 mg/kg galangin, 100 mg/kg sulphasalazine and a combination of 20 mg/kg galangin and 50 mg/kg sulphasalazine) daily starting from the second week. Galangin significantly ameliorated DSS-induced histopathological alterations and tissue injury, down-regulated Toll-like receptor 4 expression, suppressed NF-κB p65 activation, lowered inflammatory cytokine levels and demonstrated antioxidant effects. The combination of galangin and sulphasalazine at half doses yielded comparable results to either drug alone at full dose. This study highlights galangin as a promising therapy for colitis management.

Bifidobacterium longum and VSL#3® amelioration of TNBS-induced colitis associated with reduced HMGB1 and epithelial barrier impairment

Probiotics are a beneficial treatment for inflammatory bowel disease (IBD). However, studies comparing the effects of similar doses of single and mixed probiotics on IBD are scarce. High mobility group box 1 (HMGB1) is an important proinflammatory mediator involved IBD development. The present study assessed fecal HMGB1 levels in IBD patients and compared the effects of similar doses of Bifidobacterium longum (Bif) versus VSL#3^® on HMGB1 levels in 2,4,6-trinitrobenzene sulfonic acid (TNBS)-induced murine colitis. Twenty-four mice were divided into four treatment groups (n = 6 per group): ethanol (control), TNBS, TNBS + Bif, and TNBS + VSL#3^®. Bif and VSL#3^® (4 × 10⁹ CFU/dose) were administered daily by intragastric gavage, beginning 3 d before TNBS treatment, for a total of 7 d. Fecal HMGB1 levels were higher in both active IBD patients and TNBS-induced colitis mice versus their respective controls. Both Bif and VSL#3^® improved intestinal inflammation and fecal microbiota imbalance in TNBS-induced colitis mice. Both treatments also reduced serum and fecal HMGB1 levels as well as increased expression of zonula occludins-1, occludin, and claudin-1 in colon tissues. In Caco-2 cells, HMGB1 reduced transepithelial electrical resistance, zonula occludins-1 protein expression, and increased paracellular permeability of FITC-dextran; the opposite was found with both probiotic treatments. These findings suggest Bif and VSL#3^® have similar beneficial effects on TNBS-induced colitis, possibly through inhibition of HMGB1 release and subsequent HMGB1-mediated gut barrier dysfunction. The present study provides novel insights into probiotic treatment of IBD.

IL-33 ameliorates experimental colitis involving regulation of autophagy of macrophages in mice

Background

Previously, we have demonstrated that IL-33 administration protecting TNBS-induced experimental colitis is associated with facilitation of Th2/Tregs responses in mice. However, whether IL-33 regulates autophagy to ameliorate experimental colitis is unclear.

Results

IL-33 administration (2 μg/day, intraperitoneal injection), while facilitating Th2/Tregs responses, also enhances the autophagy in mice with TNBS-induced colitis as well as macrophages. In the meantime, we observed that inhibition of the autophagy with 3-methyladenine (3-MA) (24 mg/kg, intraperitoneal injection) in mice exacerbates TNBS-induced experimental colitis. On the contrary, administration of rapamycin (2 mg/kg,intragastric administration), an autophagy-enhancer, alleviates the colitis in mice. In vivo, Immunofluorescence analysis revealed that TNBS combined with IL-33 enhanced the autophagy of macrophages in the inflammatory gut tissue. In vitro, treatment with IL-33 promoted the autophagy of macrophages generated from bone marrow cells in dose-dependant manner. Furthermore, the effect of autophagy-enhancement by IL-33 is TLR4 signaling pathway dependant. Our notion was further confirmed by IL-33-deficient bone marrow-derived macrophages cells.

Conclusions

IL-33 regulates the autophagy is a new immunoregulatory property on TNBS-induced experimental colitis in mice.

IL-23 in inflammatory bowel diseases and colon cancer

Studies in recent years have identified a pivotal role of the cytokine IL-23 in the pathogenesis of inflammatory bowel diseases (IBD: Crohn´s disease, ulcerative colitis) and colitis-associated colon cancer. Genetic studies revealed that subgroups of IBD patients have single nucleotide polymorphisms in the IL-23R gene suggesting that IL-23R signaling affects disease susceptibility. Furthermore, increased production of IL-23 by macrophages, dendritic cells or granulocytes has been observed in various mouse models of colitis, colitis-associated cancer and IBD patients. Moreover, in several murine models of colitis, suppression of IL-12/IL-23 p40, IL-23 p19 or IL-23R function led to marked suppression of gut inflammation. This finding was associated with reduced activation of IL-23 target cells such as T helper 17 cells, innate lymphoid cells type 3, granulocytes and natural killer cells as well as with impaired production of proinflammatory cytokines. Based on these findings, targeting of IL-23 emerges as important concept for suppression of gut inflammation and inflammation-associated cancer growth. Consistently, neutralizing antibodies against IL-12/IL-23 p40 and IL-23 p19 have been successfully used in clinical trials for therapy of Crohn´s disease and pilot studies in ulcerative colitis are ongoing. These findings underline the crucial regulatory role of IL-23 in chronic intestinal inflammation and colitis-associated cancer and indicate that therapeutic strategies aiming at IL-23 blockade may be of key relevance for future therapy of IBD patients.

Sigmoid colon mucosal gene expression supports alterations of neuronal signaling in irritable bowel syndrome with constipation

Peripheral factors likely play a role in at least a subset of irritable bowel syndrome (IBS) patients. Few studies have investigated mucosal gene expression using an unbiased approach. Here, we performed mucosal gene profiling in a sex-balanced sample to identify relevant signaling pathways and gene networks and compare with publicly available profiling data from additional cohorts. Twenty Rome III+ IBS patients [10 IBS with constipation (IBS-C), 10 IBS with diarrhea (IBS-D), 5 men/women each), and 10 age-/sex-matched healthy controls (HCs)] underwent sigmoidoscopy with biopsy for gene microarray analysis, including differential expression, weighted gene coexpression network analysis (WGCNA), gene set enrichment analysis, and comparison with publicly available data. Expression levels of 67 genes were validated in an expanded cohort, including the above samples and 18 additional participants (6 each of IBS-C, IBS-D, HCs) using NanoString nCounter technology. There were 1,270 differentially expressed genes (FDR < 0.05) in IBS-C vs. HCs but none in IBS or IBS-D vs. HCs. WGNCA analysis identified activation of the cAMP/protein kinase A signaling pathway. Nine of 67 genes were validated by the NanoString nCounter technology (FDR < 0.05) in the expanded sample. Comparison with publicly available microarray data from the Mayo Clinic and University of Nottingham supports the reproducibility of 17 genes from the microarray analysis and three of nine genes validated by nCounter in IBS-C vs. HCs. This study supports the involvement of peripheral mechanisms in IBS-C, particularly pathways mediating neuronal signaling. NEW & NOTEWORTHY Peripheral factors play a role in the pathophysiology of irritable bowel syndrome (IBS), which, to date, has been mostly evident in IBS with diarrhea. Here, we show that sigmoid colon mucosal gene expression profiles differentiate IBS with constipation from healthy controls. These profiling data and analysis of additional cohorts also support the concept that peripheral neuronal pathways contribute to IBS pathophysiology.

Etiopathogenesis of inflammatory bowel disease: today and tomorrow

PURPOSE OF REVIEW

Crohn's disease and ulcerative colitis, the two major forms of inflammatory bowel disease (IBD), represent chronic diseases of unknown cause, and they are regarded as prototypical complex diseases. Despite all the recent advances, a complete appreciation of the pathogenesis of IBD is still limited. In this review, we present recent information contributing to a better understanding of mechanisms underlying IBD.

RECENT FINDINGS

Here, we attempt to highlight novel environmental triggers, data on the gut microbiota, its interaction with the host, and the potential influence of diet and food components. We discuss recent findings on defective signaling pathways and the potential effects on the immune response, and we present new data on epigenetic changes, inflammasome, and damage-associated molecular patterns associated with IBD.

SUMMARY

The continuing identification of several epigenetic, transcriptomic, proteomic, and metabolomic alterations in patients with IBD reflects the complex nature of the disease and suggests the need for innovative approaches such as systems biology for identifying novel relevant targets in IBD.