KSR1 protects from interleukin-10 deficiency-induced colitis in mice by suppressing T-lymphocyte interferon-γ production

The KSR1/MEK/ERK signaling pathway promotes the progression of intrauterine adhesions

Kinase suppressor of Ras 1 (KSR1) serves as a scaffold protein within the RAS-RAF pathway and plays a role in tumorigenesis, immune regulation, cell proliferation, and apoptosis. However, the specific role of KSR1 in the formation and progression of fibrotic diseases, such as intrauterine adhesions (IUA), remains unclear. This study aims to investigate KSR1 expression in IUA and the mechanisms underlying its role in promoting IUA progression. KSR1 was found to be significantly overexpressed in the endometrium of both IUA model rats and patients with IUA. KSR1 is positively involved in the regulation of proliferation, migration, and fibrosis (FN1, Collagen I, α-SMA) in immortalized human endometrial stromal cells (THESCs). Furthermore, KSR1 knockdown was observed to inhibit the fibrosis, proliferation, and migration of transforming growth factor-β1 (TGF-β1)-induced THESCs. Further studies demonstrated that the key proteins of the MEK/ERK signaling pathway, p-MEK1 and p-ERK1/2, were significantly overexpressed in the uterus of IUA rats. In vitro rescue experiments confirmed that the MEK/ERK pathway inhibitor U0126 (An ERK inhibitor) effectively suppressed the enhanced fibrosis, proliferation, and migration induced by KSR1 overexpression. In conclusion, this study demonstrates that KSR1 promotes IUA by enhancing proliferation, migration, and fibrosis of endometrial stromal cells via the MEK/ERK signaling pathway.

Transient Mild Photothermia Improves Therapeutic Performance of Oral Nanomedicines with Enhanced Accumulation in the Colitis Mucosa

The treatment outcomes of oral medications against ulcerative colitis (UC) have long been restricted by low drug accumulation in the colitis mucosa and subsequent unsatisfactory therapeutic efficacy. Here, high-performance pluronic F127 (P127)-modified gold shell (AuS)-polymeric core nanotherapeutics loading with curcumin (CUR) is constructed. Under near-infrared irradiation, the resultant P127-AuS@CURs generate transient mild photothermia (TMP; ≈42 °C, 10 min), which facilitates their penetration through colonic mucus and favors multiple cellular processes, including cell internalization, lysosomal escape, and controlled CUR release. This strategy relieves intracellular oxidative stress, improves wound healing, and reduces immune responses by polarizing the proinflammatory M1-type macrophages to the anti-inflammatory M2-type. Upon oral administration of hydrogel-encapsulating P127-AuS@CURs plus intestinal intralumen TMP, their therapeutic effects against acute and chronic UC are demonstrated to be superior to those of a widely used clinical drug, dexamethasone. The treatment of P127-AuS@CURs (+ TMP) elevates the proportions of beneficial bacteria (e.g., Lactobacillus and Lachnospiraceae), whose metabolites can also mitigate colitis symptoms by regulating genes associated with antioxidation, anti-inflammation, and wound healing. Overall, the intestinal intralumen TMP offers a promising approach to enhance the therapeutic outcomes of noninvasive medicines against UC.

The inhibitory effect of oral administration of lentinan on DSS-induced inflammation is exerted by the migration of T cells activated in the ileum to the colon

Oral administration of lentinan ameliorated dextran sulfate sodium (DSS)-induced colitis through Dectin-1 receptor on intestinal epithelial cells. However, it is unclear where lentinan affects in the intestine to prevent the inflammation. We found that the administration of lentinan has induced migration of CD4+ cells from the ileum to the colon by using Kikume Green-Red (KikGR) mice in this study. This result suggests that the oral lentinan treatment could accelerate the migration of Th cells in lymphocyte from ileum into the colon during lentinan intake. Then, C57BL/6 mice were administered 2% DSS to induce colitis. The mice were administered lentinan daily via oral or rectal route before DSS administration. Its rectal administration also suppressed DSS-induced colitis, but its suppressive effects were lower compared to when orally administered, indicating that the biological responses to lentinan in the small intestine contributed to the anti-inflammatory effects. In normal mice (without DSS treatment), the expression of Il12b was significantly increased in the ileum by the oral administration of lentinan, but not by rectal one. On the other hand, no change was observed in the colon by either administration method. In addition, Tbx21 was significantly increased in the ileum. These suggested that IL-12 was increased in the ileum and Th1 cells differentiated in dependence on it. Therefore, Th1 predominant condition in the ileum could influence immunity in the colon and improve the colitis.

PLGA microspheres carrying miR-20a-5p improved intestinal epithelial barrier function in patients with Crohn's disease through STAT3-mediated inhibition of Th17 differentiation

BACKGROUND

Recent studies have shown that microRNAs (miRNAs) are aberrantly expressed in patients with Crohn's disease (CD). This suggests that the aberrant expression of miRNAs may contribute to the development of CD. Currently, the specific miRNAs involved in CD development have not been clearly identified. Therefore, we aimed to identify CD-associated miRNAs and explore their functions.

METHODS

miRNA microarray analysis was performed to screen for differentially expressed miRNAs in colon tissues from normal controls (NC) and CD patients. The identified miRNAs were validated using quantitative real-time PCR (qPCR). The therapeutic roles of miR-20a-5p mimics via the delivery of poly(lactic-co-glycolic acid) microspheres (PLGA MSs) were further investigated in IL-10^-/- mice with spontaneous chronic colitis that were used as a model of CD. The target genes of miR-20a-5p and the associated signaling pathways were identified through bioinformatic analysis and experimental verification of the interactions between the targets predicted by the algorithms and dysregulated mRNAs.

RESULTS

The analysis showed that miR-20a-5p was the most significantly downregulated miRNA in patients with CD. Treatment with PLGA MSs carrying miR-20a-5p significantly ameliorated the colitis, decreased mucosal inflammation, and improved epithelial barrier function. Bioinformatic analysis and experimental studies showed that miR-20a-5p inhibition enhanced Th17 differentiation and improved intestinal epithelial barrier function by targeting STAT3.

CONCLUSIONS

Downregulation of miR-20a-5p improved the intestinal epithelial barrier function and prevented CD development through the STAT3/IL-17 signaling pathway. Therefore, the delivery of miR-20a-5p by PLGA MSs may serve as a potential therapeutic strategy for CD treatment.

Autophagy induction by rapamycin ameliorates experimental colitis and improves intestinal epithelial barrier function in IL-10 knockout mice

BACKGROUND

An impairment of the intestinal barrier function is one of the major characteristics of Crohn's disease (CD). This study aimed to evaluate the impact of autophagy induction by rapamycin on the intestinal epithelial barrier function in CD model mice.

METHODS

IL-10 knockout (IL-10 KO) mice were used as the human CD models in this study. All the mice were randomly assigned into four groups, (a) wild-type (WT) group; (b) IL-10 KO group; (c) IL-10 KO + rapamycin group and (d) IL-10 KO + 3-methyladenine (3-MA), containing 6 mice in each group. The disease activity index (DAI), histology, pro-inflammatory cytokines and chemotactic factors in colon tissues, intestinal and colonic permeability, distributions and expressions of tight junction (TJ) proteins, epithelial apoptosis of mice in four groups were evaluated and compared.

RESULTS

Autophagy induction by rapamycin treatment ameliorated DAI and histological colitis, decreased pro-inflammatory cytokines (TNF-α, IFN-γ and IL-17) and chemotactic factors (CXCL-1 and CXCL-2), decreased intestinal and colonic permeability, improved the distribution and expression of TJ proteins in IL-10 KO mice.

CONCLUSION

Autophagy induction by rapamycin significantly improved intestinal barrier function and protected IL-10 KO mice from the experimental chronic colitis.

Kinase suppressor of Ras 1 and Exo70 promote fatty acid-stimulated neurotensin secretion through ERK1/2 signaling

Neurotensin is a peptide hormone released from enteroendocrine cells in the small intestine in response to fat ingestion. Although the mechanisms regulating neurotensin secretion are still incompletely understood, our recent findings implicate a role for extracellular signal-regulated kinase 1 and 2 as positive regulators of free fatty acid-stimulated neurotensin secretion. Previous studies have shown that kinase suppressor of Ras 1 acts as a molecular scaffold of the Raf/MEK/extracellular signal-regulated kinase 1 and 2 kinase cascade and regulates intensity and duration of extracellular signal-regulated kinase 1 and 2 signaling. Here, we demonstrate that inhibition of kinase suppressor of Ras 1 attenuates neurotensin secretion and extracellular signal-regulated kinase 1 and 2 signaling in human endocrine cells. Conversely, we show that overexpression of kinase suppressor of Ras 1 enhances neurotensin secretion and extracellular signal-regulated kinase 1 and 2 signaling. We also show that inhibition of extracellular signal-regulated kinase 2 and exocyst complex component 70, a substrate of extracellular signal-regulated kinase 2 and mediator of secretory vesicle exocytosis, potently inhibits basal and docosahexaenoic acid-stimulated neurotensin secretion, whereas overexpression of exocyst complex component 70 enhances basal and docosahexaenoic acid-stimulated neurotensin secretion. Together, our findings demonstrate a role for kinase suppressor of Ras 1 as a positive regulator of neurotensin secretion from human endocrine cells and indicate that this effect is mediated by the extracellular signal-regulated kinase 1 and 2 signaling pathway. Moreover, we reveal a novel role for exocyst complex component 70 in regulation of neurotensin vesicle exocytosis through its interaction with the extracellular signal-regulated kinase 1 and 2 signaling pathway.

Dietary Nondigestible Polysaccharides Ameliorate Colitis by Improving Gut Microbiota and CD4+ Differentiation, as Well as Facilitating M2 Macrophage Polarization

BACKGROUND

The aim of this study was to investigate the therapeutic mechanism of a specific multifiber mix diet (MF) designed to match the fiber content of a healthy diet in interleukin-10 knockout (IL-10^-/- ) mice with spontaneous chronic colitis displaying similar characteristics to those of human Crohn's disease (CD).

METHODS

Sixteen-week-old IL-10^-/- mice were used for the experiments with MF diet for 4 weeks. Severity of colitis, the composition of the fecal microbiota, expression of Th1/Th17 cells, myeloperoxidase (MPO) concentrations, and inflammatory cytokines and chemokines (tumor necrosis factor-α [TNF-α], IL-6, macrophage inflammatory protein [MIP]-2, monocyte chemoattractant protein-1 [MCP-1], and MIP-1α), as well as arginase 1 (Arg1) and signal transducers and activators of transcription 6 (STAT6) proteins, were measured at the end of the experiment. In addition, the corresponding metabolites (short-chain fatty acids) of MF on CD4⁺ CD25⁺ Foxp3⁺ regulatory T cells (Tregs) were also detected in vivo and in vitro.

RESULTS

MF treatment significantly ameliorated colitis associated with decreased lamina propria frequency of Th1/Th17 cells, MPO concentrations, and inflammatory cytokines and chemokines (TNF-α, IL-6, MIP-2, MCP-1, and MIP-1α). An increase in gut microbial diversity was observed after MF treatment compared with IL-10^-/- mice, including a significant increase in bacteria belonging to the Firmicutes phylum and a significant decrease in bacteria belonging to the Proteobacteria phylum. Moreover, MF treatment increased the differentiation of CD4⁺ CD25⁺ Foxp3⁺ Tregs mainly by microbial metabolites butyrate. In addition, Arg1 and STAT6 proteins were also significantly increased after MF treatment.

CONCLUSIONS

These results shed light on the contribution of MF treatment to the CD mouse model and suggest that MF has potential as a therapeutic strategy for enhancing efficacy in inducing remission in patients with active CD.

The class I myosin MYO1D binds to lipid and protects against colitis

Myosin ID (MYO1D) is a member of the class I myosin family. We screened 48,649 third generation (G3) germline mutant mice derived from N-ethyl-N-nitrosourea-mutagenized grandsires for intestinal homeostasis abnormalities after oral administration of dextran sodium sulfate (DSS). We found and validated mutations in Myo1d as a cause of increased susceptibility to DSS-induced colitis. MYO1D is produced in the intestinal epithelium, and the colitis phenotype is dependent on the nonhematopoietic compartment of the mouse. Moreover, MYO1D appears to couple cytoskeletal elements to lipid in an ATP-dependent manner. These findings demonstrate that MYO1D is needed to maintain epithelial integrity and protect against DSS-induced colitis.

Summary: Using random germline mutagenesis and screening of mice, we determined that loss of MYO1D function in nonhematopoietic tissues renders mice susceptible to colitis induced by dextran sodium sulfate challenge.

Simultaneous Amelioratation of Colitis and Liver Injury in Mice by Bifidobacterium longum LC67 and Lactobacillus plantarum LC27

Disturbances in the gut microbiota composition are associated with chronic inflammatory diseases of the intestine and the liver. In a preliminary study, Lactobacillus plantarum LC27 and Bifidobacterium longum LC67 could inhibit Escherichia coli growth and lipopolysaccharide-induced NF-κB activation linked to gut inflammation. Here, we investigated their effects on 2,4,6-trinitrobenzesulfonic acid (TNBS)-induced colitis and liver damage in mice. First, oral administration of LC27 or LC67 (1 × 10⁹ CFU/mouse) inhibited TNBS-induced colon shortening [F(5,30) = 100.66, P < 0.05] and myeloperoxidase activity [F(5,30) = 56.48, P < 0.05]. These probiotics restored TNBS-induced disturbance of gut microbiota, leading to the suppression of Proteobacteria to Bacteroidetes ratio and fecal and blood lipopolysaccharide levels. Second, LC27 and LC67 inhibited TNBS-induced NF-κB activation, reversed TNBS-suppressed tight junction protein expression, and restored Th17/Treg balance. Also, treatment with LC27 or LC67 significantly decreased TNBS-induced alanine transaminase [ALT, F(5,30) = 3.50, P < 0.05] and aspartate transaminase [AST, F(5,30) = 12.81, P < 0.05] levels in the blood, as well as t-butylhydroperoxide-induced ALT and AST levels. Finally, the mixture of LC27 and LC67 (0.5 × 10⁹ CFU/mouse, respectively) synergistically attenuated TNBS- or t-butylhydroperoxide-induced colitis and liver damage. The capability of LC27 and LC67 to reverse TNBS-mediated microbiota shift and damage signals suggests that these probiotics may synergistically attenuate colitis and liver injury by alleviating gut microbiota imbalance.

GPR120, a potential therapeutic target for experimental colitis in IL-10 deficient mice

It has been proved that interleukin-10-knockout (IL-10 KO) mice display the most similar characteristics to that of human Crohn's disease (CD). Docosahexaenoic acid (DHA) has well established beneficial effects on human and animal models health with potent anti-inflammatory effects with poorly understood mechanisms. This study was aimed at figuring out whether DHA could ameliorate the Crohn's colitis by activating GPR120 and whether GPR120 could be a potential therapeutic target for CD.16 week-old mice included in our present study were divided into three groups, WT group, IL-10 KO group and DHA group(IL-10 KO mice with DHA treatment, i.g., 35.5mg/kg/d), containing 8 mice in each group. The severity of colitis, pro-inflammatory cytokines concentrations, the expression/distribution of protein GPR120 and TAK1/IKK-α/IkB-α/p65 pathway in the proximal colons were evaluated at the end of the experiment. Administration of DHA showed promising results in the experimental chronic colitis (demonstrated by reduced infiltration of inflammatory cells, lowered inflammation scores, decreased pro-inflammatory cytokines) and body weight loss improvement. Moreover, in the DHA-treated mice, enhanced expression and improved distribution integrity of protein GPR120 were observed, which was probably associated with the regulation of TAK1/IKK-α/IkB-α/p65 pathway. Our results indicated that triggering GPR120 via the inhibition of TAK1/IKK-α/IkB-α/p65 pathway might be an important target for Crohn's colitis.

Local level of TGF-β1 determines the effectiveness of dexamethasone through regulating the balance of Treg/Th17 cells in TNBS-induced mouse colitis

Transforming growth factor β1 (TGF-β1) has a crucial role in regulating the balance of type 17 T-helper cells (Th17) and T regulatory cells (Tregs) that are involved in the pathogenesis of inflammatory bowel disease, while the function of local TGF-β1 in this process has remained to be fully elucidated. The present study investigated the effects of different local TGF-β1 levels on the Treg/Th17 balance and on the dexamethasone efficacy in mice with 2,4,6-trinitrobenzenesulfonic acid (TNBS)-induced colitis. Various TGF-β1 levels in colon tissue were achieved by enema delivery of a high, medium or low amount of adenovirus expressing TGF-β1 (10⁷, 10⁸ or 10⁹ pfu, denoted as AdTGF-1, AdTGF-2 and AdTGF-3, respectively). Dexamethasone further decreased colon damage and myeloperoxidase activity in TNBS mice receiving AdTGF-1 and AdTGF-2. When AdTGF-1 was administered, dexamethasone enhanced its effect by reducing interferon (IFN)-γ and increasing interleukin (IL)-10 production. In TNBS mice receiving AdTGF-2, the increase in IFN-γ, tumor necrosis factor-α, IL-6, IL-17 and IL-23 was significantly prevented by dexamethasone treatment. In comparison with the lower doses, AdTGF-3 exerted the opposite effect on regulating the cytokine production in TNBS mice, which was not affected by dexamethasone treatment. In mesenteric lymph nodes, AdTGF-1 prevented the TNBS-induced reduction of Tregs and IL-10, and potentially increased the efficacy of dexamethasone. In addition, dexamethasone further decreased the levels of activated caspase3 in TNBS mice receiving adenoviral TGF-β1, particularly in the AdTGF-1 group. The activation of the p38 mitogen-activated protein kinase/c-Jun N-terminal kinase/c-Jun pathway was significantly inhibited by a low amount of TGF-β1 administered to TNBS-treated mice, which was further decreased by dexamethasone. The present study provided evidence that the therapeutic effect of dexamethasone may depend on the local levels of TGF-β1 in TNBS-induced colitis and may be mediated, at least partially, through promoting the differentiation of Tregs and thus altering the balance of pro- and anti-inflammatory cytokines.

Matrine ameliorates spontaneously developed colitis in interleukin-10-deficient mice

Interleukin-10 (IL-10)-deficient mice spontaneously develop T cell-mediated colitis. Previous reports have shown that Matrine may reduce the symptoms of acute colitis induced by trinitrobenzene sulfonic acid (TNBS). However, whether Matrine impacts chronic colitis remains unknown. In this study, we investigated whether Matrine could limit the symptoms of spontaneously developed colitis and its potential molecular mechanisms. IL-10 deficient mice were given Matrine or a PBS control by oral gavage daily for 4weeks and were euthanized at week 2 or week 4. We measured body weight, colon length and weight, and histological scores. We also evaluated the spontaneous secretion of IL-12/23p40, IFN-γ and IL-17 in colon explant cultures as well as IFN-γ and IL-17 secretion in unseparated mesenteric lymph node (MLN) cells, and assessed IFN-γ, IL-17, IL-1β and IL-6 mRNA expression in colon tissue. In addition, we analyzed the proportions of CD4-positive and CD8-positive cells in unseparated MLN cells. Our results show that Matrine-treated mice exhibited better body weight recovery than controls and that histological scores and spontaneously secreted IL-12/23p40, IFN-γ and IL-17 in colon tissue were significantly decreased in treated mice compared with controls. The proportion of CD4-positive cells of MLNs in treated mice was significantly smaller than that in controls at week 4. Both cytokine production and mRNA expression of IFN-γ and IL-17 were significantly reduced in treated mice compared with controls. Taken together, our results indicate that Matrine may ameliorate spontaneously developed chronic colitis and could be considered as a therapeutic alternative for chronic colitis.

SEW2871 protects from experimental colitis through reduced epithelial cell apoptosis and improved barrier function in interleukin-10 gene-deficient mice

Loss of intestinal epithelial barrier function including typical tight junction changes and epithelial cell apoptosis plays an important role in Crohn's disease. SEW2871, a selective sphingosine-1-phosphate type-1 receptor agonist, has been proven to be efficient in protecting against colitis in IL-10(-/-) mice in our previous study. Here we performed additional studies to investigate whether treatment with SEW2871 was associated with an improved epithelial barrier function in IL-10(-/-) mice. SEW2871 was administered by gavage at a dose of 20 mg/kg/day for 2 weeks to IL-10(-/-) mice. Severity of colitis, CD4+ T cells in colon lamina propria and proinflammatory cytokine productions were evaluated. Furthermore, intestinal permeability, tight junction (occludin and ZO-1) expressions and distributions, as well as epithelial cell apoptosis, were also assessed. SEW2871 treatment attenuated established colitis associated with decreased CD4+ T cells in colon lamina propria and reduced TNF-α and IFN-γ levels. Moreover, enhanced barrier function, which resulted from ameliorated tight junction (occludin and ZO-1) expressions and suppressed epithelial cell apoptosis, was found to contribute to the therapeutic effects. SEW2871 treatment protects from colitis in IL-10(-/-) mice through reduced epithelial cell apoptosis and improved barrier function. Thus, targeting sphingosine-1-phosphate may represent a new therapeutic approach in Crohn's disease.

DHA protects against experimental colitis in IL-10-deficient mice associated with the modulation of intestinal epithelial barrier function

A defect in the intestinal barrier is one of the characteristics of Crohn's disease (CD). The tight junction (TJ) changes and death of epithelial cells caused by intestinal inflammation play an important role in the development of CD. DHA, a long-chain PUFA, has been shown to be helpful in treating inflammatory bowel disease in experimental models by inhibiting the NF-κB pathway. The present study aimed at investigating the specific effect of DHA on the intestinal barrier function in IL-10-deficient mice. IL-10-deficient mice (IL-10(-/-)) at 16 weeks of age with established colitis were treated with DHA (i.g. 35.5 mg/kg per d) for 2 weeks. The severity of their colitis, levels of pro-inflammatory cytokines, epithelial gene expression, the distributions of TJ proteins (occludin and zona occludens (ZO)-1), and epithelial apoptosis in the proximal colon were measured at the end of the experiment. DHA treatment attenuated the established colitis and was associated with reduced infiltration of inflammatory cells in the colonic mucosa, lower mean histological scores and decreased levels of pro-inflammatory cytokines (IL-17, TNF-α and interferon-γ). Moreover, enhanced barrier function was observed in the DHA-treated mice that resulted from attenuated colonic permeability, rescued expression and corrected distributions of occludin and ZO-1. The results of the present study indicate that DHA therapy may ameliorate experimental colitis in IL-10(-/-) mice by improving the intestinal epithelial barrier function.

Tumor Necrosis Factor Receptor 2 Restricts the Pathogenicity of CD8(+) T Cells in Mice With Colitis

BACKGROUND & AIMS

Tumor necrosis factor receptor 2 (TNFR2, Tnfrsf1b) regulates multiple aspects of immune function, but little is known about its role in the immunopathogenesis of inflammatory bowel disease (IBD). We investigated whether TNFR2 restricts the activity of specific immune cell subtypes to protect against the development of colitis in mice.

METHODS

Tnfr2(-/-) mice were crossed with interleukin (Il) 10(-/-) mice, which spontaneously develop colitis, to generate Il10(-/-)Tnfr2(-/-) mice. Colonic tissues were collected from Il10(-/-)Tnfr2(-/-) mice along with Il10(-/-) mice (controls) and analyzed by flow cytometry and histology. Bone marrow was transplanted into Il10(-/-) and Il10(-/-)Tnfr2(-/-) mice from Il10(-/-) or Il10(-/-)Tnfr2(-/-) donors by intravenous injection. CD8(+) T cells were neutralized in Il10(-/-)Tnfr2(-/-) mice by intraperitoneal injection of anti-CD8 or isotype control antibodies. Colitis was induced in Rag2(-/-) mice by intravenous injections of naïve CD8(+) T cells isolated from C57BL/6 or Tnfr2(-/-) mice.

RESULTS

Il10(-/-)Tnfr2(-/-) mice spontaneously developed more severe colitis compared with Il10(-/-) controls, characterized by selective expansion of colonic CD8(+) T cells. Transplantation of TNFR2-deficient bone marrow resulted in significantly increased incidence and severity of colitis. Transcriptome analyses showed that the expression of genes regulated by TNFR2 were specific to CD8(+) T cells and included genes associated with risk for IBD. Depletion of CD8(+) T cells from Il10(-/-)Tnfr2(-/-) mice prevented colonic inflammation. Adoptive transfer of TNFR2-null naïve CD8(+) T cells compared with CD8(+) T cells from control mice increased the severity of colitis that developed in Rag2(-/-) mice.

CONCLUSIONS

TNFR2 protects mice from colitis by inhibiting the expansion of colonic CD8(+) T cells. TNFR2 regulates expression of genes that regulate CD8(+) T cells and have been associated with susceptibility to IBD. Disruption in TNFR2 signaling might therefore be associated with pathogenesis. Strategies to increase levels or activity of TNFR2 and thereby reduce the activity of CD8(+) T cells might be developed to treat IBD patients with CD8(+) T cell dysfunction.

Docosahexaenoic Acid Attenuated Experimental Chronic Colitis in Interleukin 10-Deficient Mice by Enhancing Autophagy Through Inhibition of the mTOR Pathway

BACKGROUND

In the battle against Crohn's disease, autophagy stimulation is a promising therapeutic option-one both new and newly rediscovered. In experimental models, docosahexaenoic acid (DHA)-a long-chain polyunsaturated fatty acid-has been demonstrated to be useful in the treatment of inflammatory bowel disease through inhibition of the nuclear factor-κB pathway. However, the impact of DHA on autophagy in the colon remains unclear.

METHODS

Mice were divided into 3 groups: wild type (placebo), the interleukin 10 knockout group (IL-10^-/-, placebo), and the DHA group (IL-10^-/-, DHA). DHA was administered to IL-10^-/- mice by gavage at a dosage of 35.5 mg/kg/d for 2 weeks. The severity of colitis, expression of proinflammatory cytokines, expression/distribution of LC3B, and mTOR signaling pathway were evaluated in the proximal colon tissues collected from all mice at the end of the experiment.

RESULTS

DHA administration ameliorated experimental colitis in the IL-10^-/- mice, as demonstrated by decreased proinflammatory cytokines (TNF-α and IFN-γ), reduced infiltration of inflammatory cells, and lowered histologic scores of the proximal colon mucosa. Moreover, in the DHA-treated mice, enhanced autophagy was observed to be associated with (1) increased expression and restoration of the distribution integrity of LC3B in the colon and (2) inhibition of the mTOR signaling pathway.

CONCLUSION

This study showed that DHA therapy could attenuate experimental chronic colitis in IL-10^-/- mice by triggering autophagy via inhibition of the mTOR pathway.

Anti-mouse CD52 monoclonal antibody ameliorates intestinal epithelial barrier function in interleukin-10 knockout mice with spontaneous chronic colitis

Intestinal inflammation causes tight junction changes and death of epithelial cells, and plays an important role in the development of Crohn's disease (CD). CD52 monoclonal antibody (CD52 mAb) directly targets the cell surface CD52 and is effective in depleting mature lymphocytes by cytolytic effects in vivo, leading to long-lasting changes in adaptive immunity. The aim of this study was to investigate the therapeutic effect of CD52 mAb on epithelial barrier function in animal models of IBD. Interleukin-10 knockout mice (IL-10(-/-) ) of 16 weeks with established colitis were treated with CD52 mAb once a week for 2 weeks. Severity of colitis, CD4(+) lymphocytes and cytokines in the lamina propria, epithelial expression of tight junction proteins, morphology of tight junctions, tumour necrosis factor-α (TNF-α)/TNF receptor 2 (TNFR2) mRNA expression, myosin light chain kinase (MLCK) expression and activity, as well as epithelial apoptosis in proximal colon were measured at the end of the experiment. CD52 mAb treatment effectively attenuated colitis associated with decreased lamina propria CD4(+) lymphocytes and interferon-γ/IL-17 responses in colonic mucosa in IL-10(-/-) mice. After CD52 mAb treatment, attenuation of colonic permeability, increased epithelial expression and correct localization of tight junction proteins (occludin and zona occludens protein-1), as well as ameliorated tight junction morphology were observed in IL-10(-/-) mice. CD52 mAb treatment also effectively suppressed the epithelial apoptosis, mucosa TNF-α mRNA expression, epithelial expression of long MLCK, TNFR2 and phosphorylation of MLC. Our results indicated that anti-CD52 therapy may inhibit TNF-α/TNFR2-mediated epithelial apoptosis and MLCK-dependent tight junction permeability by depleting activated T cells in the gut mucosa.

Celastrol ameliorates experimental colitis in IL-10 deficient mice via the up-regulation of autophagy

BACKGROUND

Celastrol had been proved effective in the treatment for IBD, probably with the modulation of oxidative stress, inflammatory cytokines and intestinal homeostasis. This study was aimed to investigate whether celastrol could ameliorate the inflammation of IL-10 deficient mice, a murine model of Crohn's disease (CD) with the induction of autophagy.

MATERIAL AND METHODS

The mice included were divided into four groups, ##WT group, IL-10(-/-) group, Cel group and Control group (celastrol+3-Methyladenine). Celastrol (2 mg/kg) treatment by gavage was administered to mice daily over one week. 3-Methyladenine (autophagy inhibitors) was administered at a dose of 30 mg/kg by intraperitoneal injection. The histological evaluation of the colon, tissue myeloperoxidase (MPO), and colon inflammation of mice in the four groups was evaluated and compared. Furthermore, the PI3K/Akt/mTOR pathway and the status of autophagy in intestine affected by celastrol were also assessed.

RESULTS

The one-week administration of celastrol ameliorated established colitis in IL-10 deficient mice, associated with a reduction of marked histological inflammation, a decreased colon MPO concentration and suppression of colonic proinflammatory cytokine. Furthermore, the decreased neutrophil infiltration in proximal colon and improvement of inflammation in the Cel group was much more obvious than that in the Control group. The Western blotting analysis of the PI3K/Akt/mTOR pathway and autophagy showed that celastrol treatment up-regulated the autophagy of colon tissue by suppressing the PI3K/Akt/mTOR signaling pathway.

CONCLUSIONS

Celastrol ameliorates experimental colitis in IL-10 deficient mice via the up-regulation of autophagy by suppressing the PI3K/Akt/mTOR signaling pathway.

The dual function of KSR1: a pseudokinase and beyond

Protein kinases play a pivotal role in regulating many aspects of biological processes, including development, differentiation and cell death. Within the kinome, 48 kinases (~10%) are classified as pseudokinases owing to the fact that they lack at least one conserved catalytic residue in their kinase domain. However, emerging evidence suggest that some pseudokinases, even without the ability to phosphorylate substrates, are regulators of multiple cellular signalling pathways. Among these is KSR1 (kinase suppressor of Ras 1), which was initially identified as a novel kinase in the Ras/Raf pathway. Subsequent studies showed that KSR1 mainly functions as a platform to assemble different cellular components thereby facilitating signal transduction. In the present article, we discuss recent findings regarding KSR1, indicating that it has dual activity as an active kinase as well as a pseudokinase/scaffolding protein. Moreover, the biological functions of KSR1 in human disorders, notably in malignancies, are also reviewed.

Overview of molecular pathways in inflammatory bowel disease associated with colorectal cancer development

Patients with long-standing inflammatory bowel disease (IBD) are at a higher risk of developing colorectal cancer (CRC). This risk increases with the longer duration of colitis, greater extent of inflammation, a family history of CRC, severity of bowel inflammation, and a coexistent primary sclerosing cholangitis. The cornerstone for comprehending the development of CRC in IBD and hence early detection is based on the understanding of the molecular pathways of IBD itself. At a molecular level, the pathogenesis of CRC is related to understanding the inflammatory changes and involves multiple inter-related pathways including (i) genetic alterations (e.g. chromosomal and microsatellite instability and hypermethylation), (ii) mucosal inflammatory mediators (e.g. COX-2, interleukin-6, interleukin-23, tumor necrosis factor-α, nuclear factor-κB, and chemokines), (iii) changes in the expression of receptors on the epithelial cells, and (iv) oxidant stress, mucosal breakdown, and intestinal microbiota. The aim of this review is to provide an evidence-based approach for the role of chronic inflammatory mechanisms and the molecular basis of these mechanisms in the development of CRC. Therefore, understanding the molecular basis of CRC is an important step for the identification of new biomarkers that can help in the early detection of CRC in these patients.

Inflamed gut mucosa: downstream of interleukin-10

BACKGROUND

Interleukin-10 is a pleiotropic cytokine, whose main function is limitation and ultimately termination of immune responses. This is especially true for environmental interfaces such as the gastrointestinal tract. IL-10 acts as a key mediator for maintaining gut homeostasis. IL-10 knockout mice are well established as a genetic model for inflammatory bowel disease (IBD), and sequence variants in the IL-10 locus contribute to ulcerative colitis (UC).

DESIGN

This review covers the significance of IL-10 signalling in the intestinal immune response both in health and disease. It explains the biological role of IL-10, its deregulation in IBD and its contribution to intestinal inflammation via endoplasmic reticulum stress response.

RESULTS

Many IBD susceptibility genes have been discovered in the past years, linking fundamental biological systems, like innate and adaptive immunity, stress responses, autophagy and mucosal barrier to the pathogenesis of Crohn's disease (CD) and UC. IL-10 has long been known for its substantial role in regulating gut immunity, but its contribution to IBD was somewhat elusive. A recent study identified mutations in either IL-10 receptor subunits that are associated with early-onset enterocolitis, a severe phenotype of IBD. Other than genetic variants of IL-10 receptors, IL-10 and STAT3 genes are also associated with IBD, emphasizing the involvement of the IL-10 signalling cascade in the pathogenesis of CD and UC.

CONCLUSIONS

  The discovery of inherited deregulations in the IL-10 signalling cascade is not only considered the missing link between IL-10 and intestinal homeostasis, but also demonstrates how findings made in animal models help explaining human disease.