Targeting the complex interactions between microbiota, host epithelial and immune cells in inflammatory bowel disease

Bacterial extracellular vesicles: Vital contributors to physiology from bacteria to host

Bacterial extracellular vesicles (bEVs) represent spherical particles with diameters ranging from 20 to 400 nm filled with multiple parental bacteria-derived components, including proteins, nucleic acids, lipids, and other biomolecules. The production of bEVs facilitates bacteria interacting with their environment and exerting biological functions. It is increasingly evident that the bEVs play integral roles in both bacterial and host physiology, contributing to environmental adaptations to functioning as health promoters for their hosts. This review highlights the current state of knowledge on the composition, biogenesis, and diversity of bEVs and the mechanisms by which different bEVs elicit effects on bacterial physiology and host health. We posit that an in-depth exploration of the mechanistic aspects of bEVs activity is essential to elucidate their health-promoting effects on the host and may facilitate the translation of bEVs into applications as novel natural biological nanomaterials.

Causal effects of inflammatory bowel disease on risk of type 2 diabetes: a two-sample multivariable Mendelian randomization study

AIM

This study aimed to explore the causal association between inflammatory bowel disease (IBD) and the risk of type 2 diabetes (T2D) based on a two-sample Mendelian randomization (MR) study.

METHODS

Summary single nucleotide polymorphism (SNP)-phenotype association data were obtained from published two genome-wide association studies (GWAS) including SNPs related to IBD, UC, or CD in European participants (n = 71,997) and East Asian participants (n = 16,805). Two GWAS including SNPs associated with T2D included 655,666 Europeans and 433,540 East Asians. A series of screening processes were performed to select qualified instrumental SNPs strongly related to exposure. We applied the inverse variance weighted (IVW), the MR-Egger regression, and the weighted median to estimate the causal effects of IBD, ulcerative colitis (UC) or Crohn' disease (CD) on T2D. Cochran's Q test was conducted to evaluate the statistical heterogeneity between SNPs in the IVW method. The leave-one-out analysis was employed to assess whether the results were caused by any single SNP associated with IBD, UC, or CD. Odds ratio (OR) and 95% confidence interval (CI) were calculated.

RESULTS

The IVW results demonstrated that IBD could increase the risk of T2D in the European population (OR = 1.0230, 95%CI: 1.0073-1.0390). UC was positively associated with the risk of T2D according to the weighted median (OR = 1.0274, 95%CI: 1.0009-1.0546) and IVW (OR = 1.0244, 95%CI: 1.0071-1.0421) results in the European population. The IVW results indicated that the CD was positively associated with the risk of T2D in the European population (OR = 1.0187, 95%CI: 1.0045-1.0330). In the East Asian population, there are no associations between the IBD, UC, or CD and the risk of T2D (all P > 0.05). MVMR results revealed that the causal effect UC on T2D was still statistically significant after including body mass index (BMI) or low-density lipoprotein (LDL).

CONCLUSION

IBD, UC, or CD had causal effects on the risk of T2D in the European population, which might provide evidence for the prevention of T2D in patients with IBD, UC, or CD.

Therapeutic Effects of Tretinoin and Caffeine-Treated Bone Marrow-Derived Mesenchymal Stem Cell on Immunological Features of Ulcerative Colitis: An Animal Model Study

Background

Ulcerative colitis (UC) is one of the inflammatory gastrointestinal diseases. It causes irritation, inflammation, and ulcers in the digestive tract. UC is distinguished clinically by abdominal and rectal pain and intestinal secretion abnormalities. Mesenchymal stem cell (MSC) therapy could be the underlying treatment for UC. This study aimed to compare the results of MSC therapy with tretinoin and caffeine in an animal model.

Materials and Methods

Sixty male BALB/c mice were randomly divided into six equal groups. Five groups were exposed to acetic acid-induced colitis, and one healthy negative control group was designed. The positive control group was UC-induced mouse model with no treatment. Besides, treatment groups were MSCs (n = 2×106) that received tretinoin and caffeine. The treatment group was given mesalazine orally. The decision to begin treatment was taken after monitoring the symptoms of the UC.

Results

MSCs, tretinoin, and caffeine-treated MSCs significantly decrease inflammatory cytokines (interleukin (IL)-1, IL-6, and tumor necrosis factor (TNF)-α) and inflammatory mediators (myeloperoxidase (MPO) and nitric oxide (NO)) compared with the positive control group. However, the alleviated effects of tretinoin-treated MSCs significantly were more than those of MSCs and caffeine-treated MSCs.

Conclusion

MSC therapy is an effective option for UC and can prevent disease progression. The results represented a high developmental rate and simple cell application of MSC therapy in UC patients. Also, MSC therapy's ability for immunomodulation is strengthened by drugs that improve their microenvironment by binding to their receptors.

Oral Administration of Platinum Nanoparticles with SOD/CAT Cascade Catalytic Activity to Alleviate Ulcerative Colitis

Ulcerative colitis (UC) is a refractory chronic inflammatory disease involving the colon and rectum, falling under the category of inflammatory bowel disease (IBD). The accumulation of reactive oxygen species (ROS) in local tissues has been identified as a crucial contributor to the escalation of inflammatory responses. Therefore, eliminating ROS in the inflamed colon is a promising approach to treating UC. Nanomaterials with intrinsic enzyme-like activities (nanozymes) have shown significant therapeutic potential in UC. In this study, we found that platinum nanoparticles (Pt NPs) exhibited remarkable superoxide dismutase (SOD) and catalase (CAT) cascade catalytic activities, as well as effective hydroxyl radical (•OH) scavenging ability. The in vitro experiments showed that Pt NPs could eliminate excessive ROS to protect cells against oxidative stress. In the colitis model, oral administration of Pt NPs (loaded in chitosan/alginate hydrogel) could significantly alleviate UC, including reducing the colon length, the damaged epithelium, and the infiltration of inflammatory cells. Without appreciable systemic toxicity, Pt NPs represent a novel therapeutic approach to UC and are expected to achieve long-term inflammatory remission.

Life stage-specific glycosylation of extracellular vesicles from Schistosoma mansoni schistosomula and adult worms drives differential interaction with C-type lectin receptors DC-SIGN and MGL

Schistosomes can survive in mammalian hosts for many years, and this is facilitated by released parasite products that modulate the host’s immune system. Many of these products are glycosylated and interact with host cells via C-type lectin receptors (CLRs). We previously reported on specific fucose-containing glycans present on extracellular vesicles (EVs) released by schistosomula, the early juvenile life stage of the schistosome, and the interaction of these EVs with the C-type lectin receptor Dendritic Cell-Specific Intercellular adhesion molecule-3-Grabbing Non-integrin (DC-SIGN or CD209). EVs are membrane vesicles with a size range between 30–1,000 nm that play a role in intercellular and interspecies communication. Here, we studied the glycosylation of EVs released by the adult schistosome worms. Mass spectrometric analysis showed that GalNAcβ1–4GlcNAc (LacDiNAc or LDN) containing N-glycans were the dominant glycan type present on adult worm EVs. Using glycan-specific antibodies, we confirmed that EVs from adult worms were predominantly associated with LDN, while schistosomula EVs displayed a highly fucosylated glycan profile. In contrast to schistosomula EV that bind to DC-SIGN, adult worm EVs are recognized by macrophage galactose-type lectin (MGL or CD301), and not by DC-SIGN, on CLR expressing cell lines. The different glycosylation profiles of adult worm- and schistosomula-derived EVs match with the characteristic glycan profiles of the corresponding life stages and support their distinct roles in schistosome life-stage specific interactions with the host.

Network-Based Elaboration of the Efficacy of the Dachangshu (BL25) and Tianshu (ST25) Points in the Treatment of Functional Constipation in Children through Inflammation, Adipocytokine, or Leptin Pathways

Constipation commonly occurs during childhood, and more than 95% of cases are classified as functional constipation. If not effectively treated, 20% of patients with childhood constipation can continue to exhibit symptoms into adulthood, which seriously affects their mental health and quality of life. The main feature of acupuncture or acupoint stimulation, a special branch of traditional Chinese medicine, is the selection of different acupoints for different diseases, and many worthy guidelines have been established for matching acupoints. The back-shu and front-mu point combination adheres to an important acupoint compatibility law that has been used since its proposal 2,500 years ago but has not yet been verified by the modern evidence-based experiments. This study focused on the back-shu and front-mu point combination using the Dachangshu (BL25) and Tianshu (ST25) points as examples to explore possible research methods for network acupoint-based stimulation based on existing evidence and to elucidate the mechanisms induced by BL25 and ST25 in the treatment of functional constipation in children (FCC). The study found that BL25 and ST25 have 20 common targets, namely, AQP8, DRD2, VIP, TAC1, IL6R, TNF, FOS, KIT, CHAT, HTR3A, GAS8, SOD3, TRPV1, MPO, CALCA, IL1B, P2RX7, NPY2R, IL10RA, and TPH1, and these targets may provide a strategy for the combined usage of BL25 and ST25. In addition, BL25 and ST25 can affect FCC treatment through inflammation-relatedTh17-cell differentiation, the NF-kappa B signaling pathway, and the Toll-like receptor signaling pathway. Adipocytokines or leptin may also comprise the mechanism through which BL25 and ST25 regulate FCC. In addition, BL25 and ST25 regulate FCC through 13 core targets, namely, NFKBIA, RELA, TNF, IKBKB, IRAK1, TLR4, MYD88, TNFRSF1A, IL1R1, TLR2, IL1B, TRAF6, and TNFRSF1B. In short, this study provides new ideas and methods for studying the mechanism of acupuncture points.

The role of retinoic acid in the production of immunoglobulin A

Vitamin A and its derivative retinoic acid (RA) play important roles in the regulation of mucosal immunity. The effect of vitamin A metabolism on T lymphocyte immunity has been well documented, but its role in mucosal B lymphocyte regulation is less well described. Intestinal immunoglobulin A (IgA) is key in orchestrating a balanced gut microbiota composition. Here, we describe the contribution of RA to IgA class switching in tissues including the lamina propria, mesenteric lymph nodes, Peyer's patches and isolated lymphoid follicles. RA can either indirectly skew T cells or directly affect B cell differentiation. IgA levels in healthy individuals are under the control of the metabolism of vitamin A, providing a steady supply of RA. However, IgA levels are altered in inflammatory bowel disease patients, making control of the metabolism of vitamin A a potential therapeutic target. Thus, dietary vitamin A is a key player in regulating IgA production within the intestine, acting via multiple immunological pathways.

The Main Anthocyanin Monomer from Lycium ruthenicum Murray Fruit Mediates Obesity via Modulating the Gut Microbiota and Improving the Intestinal Barrier

Anthocyanins have been shown to exert certain antiobesity properties, but the specific relationship between anthocyanin-induced beneficial effects and the gut microbiota remains unclear. Petunidin-3-O-[rhamnopyranosyl-(trans-p-coumaroyl)]-5-O-(β-D-glucopyranoside) (P3G) is the main anthocyanin monomer from the fruit of Lycium ruthenicum Murray. Therefore, in this study, we investigated the antiobesity and remodeling effects of P3G on gut microbiota through a high-fat diet (HFD)-induced obesity mouse model and a fecal microbiota transplantation experiment. P3G was found to reduce body weight gain, fat accumulation, and liver steatosis in HFD-induced obese mice. Moreover, supplementation with P3G alleviated the HFD-induced imbalance in gut microbiota composition, and transferring the P3G-regulated gut microbiota to recipient mice provided comparable protection against obesity. This is the first time evidence is provided that P3G has an antiobesity effect by changing the intestinal microbiota. Our present data highlight a link between P3G intervention and enhancement in gut barrier integrity. This may be a promising option for obesity prevention.

Effects of ShenLing BaiZhu San Supplementation on Gut Microbiota and Oxidative Stress in Rats with Ulcerative Colitis

The aim of this study was to evaluate the effect of gut microbiota and antioxidation of Shenling Baizhu San (SLBZS) as a supplement in a rat model of ulcerative colitis (UC) induced by 2,4,6-trinitrobenzenesulfonic acid (TNBS). Acute intestinal inflammation was induced in 40 male SD rats aged 4 weeks with 100 mg/kg TNBS, and then three dosages of SLBZS (0.5 g/kg, 1 g/kg, and 1.5 g/kg) were administered for eight days, respectively. Faecal microbiome composition was assessed by 16S rRNA high-throughput sequencing. The result indicated that SLBZS could reduce the diversity of gut microbiota and increased its abundance. At the genus level, the relative abundance of SCFAs producing bacteria including Prevotella and Oscillospira increased, while the relative abundance of opportunistic pathogens including Desulfovibrio and Bilophila decreased. Meanwhile, SLBZS could improve the lesions of colon and significantly reduce the level of MPO, increase the levels of SOD and CAT in rats' serum. These findings revealed that SLBZS was effective and possessed anticolitic activities in a rat model of UC by reducing macroscopical and microscopical colon injury, enhancing antioxidant capacity, and regulating gut microbiota.

Neutrophil extracellular traps in inflammatory bowel diseases: Implications in pathogenesis and therapeutic targets

Crohn's disease (CD) and ulcerative colitis (UC) are the two main forms of inflammatory bowel disease (IBD). Among the various immune cells involved in IBD, neutrophils are the first to infiltrate and appear to contribute to the impairment of the epithelial barrier, destruction of tissues by oxidative and proteolytic damage, as well as to the perpetuation of inflammation by the release of cytokines and chemokines associated with pro-inflammatory effects. In addition to basic effector mechanisms, such as phagocytosis and chemotaxis, neutrophils can also form extracellular traps (NETs), which is made up of a mesh-like structure - which contains its chromatin (DNA + histones) together with granules and enzymes, such as myeloperoxidase (MPO) and neutrophilic elastase (NE) - and that acts as a trap that can result in the death of extracellular pathogens and/or can promote tissue damage. Recent evidence indicates that NETs also play an important and significant role in the pathogenesis of IBD. Previous studies have reported increased levels of NETs in tissue and serum samples from patients with IBD, as well as in experimental colitis. In this review, we discuss current knowledge about the formation of NETs and their role in the pathophysiology of IBD, pointing out potential mechanisms by which NETs promote tissue damage, as well as their involvement in complications associated with IBD. In addition, we propose potential targets for therapy to regulate the production of NETs, making it possible to expand the current spectrum of therapies for IBD.

Long-term and continuous administration of Bacillus subtilis during remission effectively maintains the remission of inflammatory bowel disease by protecting intestinal integrity, regulating epithelial proliferation, and reshaping microbial structure and function

Gut microbiota takes part in the pathogenesis of inflammatory bowel disease (IBD). Clinical research has found that probiotics have a beneficial effect on active ulcerative colitis, but to date, significant efficacy has rarely been found in the use of probiotics in the remission phase of ulcerative colitis and Crohn's disease. More studies are needed to assess the utilization of probiotics in IBD remission. In this study, we assessed the administration of Bacillus subtilis in remission and its possible mechanism in mice with IBD. Oral administration of B. subtilis was implemented for 6 weeks (dextran sulfate sodium (DSS)-P6w group), 2 weeks (DSS-P2w group) or 0 weeks (DSS-control(CT) group) in the remission phase in rodents with (DSS)-induced IBD. The body weight, colon length and disease activity index (DAI) were recorded, and colon H&E staining was performed. The expression of tight junction proteins (ZO-1 and occludin) mRNA and epithelium proliferation-related Ki67 was detected. Gut microbiota were tested by 16S rRNA sequencing. Administration of B. subtilis in remission effectively increased the body weight and colon length and decreased DAI in the DSS-P6w group compared with the DSS-CT group, but there is no significant difference between the DSS-P2w and DSS-CT groups. The epithelial integrity was improved, and the expression of ZO-1 and occludin increased due to administration of B. subtilis in remission, which was more evident in the DSS-P6w group. The expression of Ki67 increased in the DSS-CT group compared with that in the CT group. The administration of B. subtilis effectively down-regulated the expression of Ki67 in the DSS-P6w and DSS-P2w groups compared with the DSS-CT group. Furthermore, gut microbial structure was improved, with significantly decreased Escherichia/Shigella and Enterococcus, and increased Akkermansia and corresponding microbial function in the DSS-P6w group. Short-term administration of B. subtilis in the remission phase showed no significant improvement in mice with IBD. Long-term and continuous supplementation of B. subtilis in remission could effectively maintain the remission by protecting epithelial integrity, regulating proliferation of intestinal epithelial cells, and improving gut microbiota and the corresponding microbial function.

Plasma elafin, cathelicidin, and α-defensins are increased in paediatric inflammatory Crohn's disease and reflect disease location

INTRODUCTION

The aim of our study was to assess antimicrobial peptides in children with Crohn's disease (CD).

METHODS

Plasma elafin, cathelicidin, and α- and β-defensins were assessed in 35 children with CD using immunoassays. Phenotype and location of CD were assessed based on the results of endoscopic and radiological studies.

RESULTS

We found increased elafin, cathelicidin, and α-defensins in children with inflammatory phenotype as compared to stricturing and penetrating phenotypes of CD. Additionally, we found increased elafin and cathelicidin in colonic location and α-defensins in ileal CD locations.

CONCLUSIONS

Assessing antimicrobial peptides may be helpful in estimating of phenotype and location of CD lesions.

Cannabinoid Receptor Activation on Haematopoietic Cells and Enterocytes Protects against Colitis

BACKGROUND AND AIMS

Cannabinoid receptor [CB] activation can attenuate inflammatory bowel disease [IBD] in experimental models and human cohorts. However, the roles of the microbiome, metabolome, and the respective contributions of haematopoietic and non-haematopoietic cells in the anti-colitic effects of cannabinoids have yet to be determined.

METHODS

Female C57BL/6 mice were treated with either cannabidiol [CBD], Δ 9-tetrahydrocannabinol [THC], a combination of CBD and THC, or vehicle, in several models of chemically induced colitis. Clinical parameters of colitis were assessed by colonoscopy, histology, flow cytometry, and detection of serum biomarkers; single-cell RNA sequencing and qRT-PCR were used to evaluate the effects of cannabinoids on enterocytes. Immune cell transfer from CB2 knockout mice was used to evaluate the contribution of haematopoietic and non-haematopoietic cells to colitis protection.

RESULTS

We found that THC prevented colitis and that CBD, at the dose tested, provided little benefit to the amelioration of colitis, nor when added synergistically with THC. THC increased colonic barrier integrity by stimulating mucus and tight junction and antimicrobial peptide production, and these effects were specific to the large intestine. THC increased colonic Gram-negative bacteria, but the anti-colitic effects of THC were independent of the microbiome. THC acted both on immune cells via CB2 and on enterocytes, to attenuate colitis.

CONCLUSIONS

Our findings demonstrate how cannabinoid receptor activation on both immune cells and colonocytes is critical to prevent colonic inflammation. These studies also suggest how cannabinoid receptor activation can be used as a preventive and therapeutic modality against colitis.

Inflammatory Bowel Disease: A Potential Result from the Collusion between Gut Microbiota and Mucosal Immune System

Host health depends on the intestinal homeostasis between the innate/adaptive immune system and the microbiome. Numerous studies suggest that gut microbiota are constantly monitored by the host mucosal immune system, and any slight disturbance in the microbial communities may contribute to intestinal immune disruption and increased susceptibility to inflammatory bowel disease (IBD), a chronic relapsing inflammatory condition of the gastrointestinal tract. Therefore, maintaining intestinal immune homeostasis between microbiota composition and the mucosal immune system is an effective approach to prevent and control IBD. The overall theme of this review is to summarize the research concerning the pathogenesis of IBD, with particular focus on the factors of gut microbiota-mucosal immune interactions in IBD. This is a comprehensive and in-depth report of the crosstalk between gut microbiota and the mucosal immune system in IBD pathogenesis, which may provide insight into the further evaluation of the therapeutic strategies for IBD.

Construction of a Model Culture System of Human Colonic Microbiota to Detect Decreased Lachnospiraceae Abundance and Butyrogenesis in the Feces of Ulcerative Colitis Patients

Compositional alteration of the gut microbiota is associated with ulcerative colitis (UC). Here, a model culture system is established for the in vitro human colonic microbiota of UC, which will be helpful for determining medical interventions. 16S ribosomal RNA sequencing confirms that UC models are successfully developed from fecal inoculum and retain the bacterial species biodiversity of UC feces. The UC models closely reproduce the microbial components and successfully preserve distinct clusters from the healthy subjects (HS), as observed in the feces. The relative abundance of bacteria belonging to the family Lachnospiraceae significantly decreases in the UC models compared to that in HS, as observed in the feces. The system detects significantly lower butyrogenesis in the UC models than that in HS, correlating with the decreased abundance of Lachnospiraceae. Interestingly, the relative abundance of Lachnospiraceae does not correlate with disease activity (defined as partial Mayo score), suggesting that Lachnospiraceae persists in UC patients at a decreased level, irrespective of the alteration in disease activity. Moreover, the system shows that administration of Clostridium butyricum MIYAIRI restores butyrogenesis in the UC model. Hence, the model detects deregulation in the intestinal environment in UC patients and may be useful for simulating the effect of probiotics.

Absorption of Codonopsis pilosula Saponins by Coexisting Polysaccharides Alleviates Gut Microbial Dysbiosis with Dextran Sulfate Sodium-Induced Colitis in Model Mice

Objectives

Inflammatory Bowel Disease (IBD) is an autoimmune disease, and the gut microbiota has become a new therapeutic target. Herbal medicine (HM) has shown good efficacy in the clinical treatment of IBD; however, the synergistic actions of the dominant chemicals in HM decoctions are unclear.

Methods

In this study, we explored whether the complicated interconnections between HM and the gut microbiota could allow crosstalk between HM ingredients. Saponins and polysaccharides, i.e., the dominant chemicals in the Codonopsis pilosula Nannf (CPN) decoction, were investigated in a dextran sulfate sodium- (DSS-) induced mouse model. Bacterial 16S rRNA sequencing analyzed the change of gut microbiota structure and diversity. Gas chromatography (GC) determined the content of short-chain fatty acids (SCFAs) in feces. ELISA detected the expression of proinflammatory and anti-inflammatory cytokines associated with TH17/Treg balance. UPLC-QTOF-MS technology combined with PKsolver software analyzed the absorption of the highest exposure for monomeric compounds of CPN saponins in serum. The results indicated that CPN polysaccharides showed prebiotic-like effects in mice with DSS-induced colitis by simultaneously stimulating the growth of three important probiotics, i.e., Bifidobacterium spp., Lactobacillus spp., and Akkermansia spp., and inhibiting the growth of pathogenic bacteria, including Desulfovibrio spp., Alistipes spp., and Helicobacter spp. Moreover, CPN polysaccharides improved intestinal metabolism, enhanced the production of short-chain fatty acids, upregulated the expression of anti-inflammatory cytokines and downregulated the secretion of proinflammatory cytokines correlated with Th17/Treg balance, promoted the absorption of certain CPN saponins in the serum, and stimulated recovery of the holistic gut microbiota.

Conclusion

CPN polysaccharides have the good prebiotic properties and shown good application prospects in the prevention and treatment of acute colitis. These findings provide insights into the specific bacteria responsible for active, inactive biotransformation of HM ingredients and those that are altered by HM administration.

Mesenchymal stem cell expression of interleukin-35 protects against ulcerative colitis by suppressing mucosal immune responses

BACKGROUND

Interleukin-35 (IL-35) has recently been identified as an immunosuppressive cytokine that has been used as a potential therapy for chronic inflammatory and autoimmune diseases. However, there remains a paucity of data regarding its potential benefits after integration into mesenchymal stem cells (MSCs).

METHODS

We used a dextran sulfate sodium (DSS)-induced colitis mice model and treated them with IL-35-MSCs, MSCs or saline. The body weight was recorded daily and inflammatory processes were determined. Cytokine secretion by lamina propria lymphocytes (LPLs) and percentage of regulatory T cells (Tregs) were also measured.

RESULTS

The data showed that mice in the two treated groups recovered their body weight more rapidly than mice treated with saline in the later stage of colitis. The colon lengths of IL-35-MSC-treated mice were markedly longer than those in the other two groups and the inflammation reduced significantly. Furthermore, the percentage of Foxp3 + Tregs increased significantly and the level of proinflammatory cytokines produced by LPLs decreased significantly in the IL-35-MSC-treated group.

DISCUSSION

The results demonstrate that IL-35-MSCs could ameliorate ulcerative colitis by down-regulating the expression of pro-inflammatory cytokines.

Krill oil, vitamin D and Lactobacillus reuteri cooperate to reduce gut inflammation

Current research into original therapies to treat intestinal inflammation is focusing on no-drug therapies. KLD is a mixture of krill oil (KO), probiotic Lactobacillus reuteri (LR), and vitamin D (VitD3). The aim of this study was to assess in vitro and in vivo the potential cooperative effects of KLD in reducing gut inflammation. Colorectal adenocarcinoma cell lines, CACO2 and HT29, and C57BL/6 mice were used for in vitro and in vivo analyses, respectively. Cells were exposed to cytomix (interferon gamma + tumour necrosis factor alpha (TNF-α)) to induce inflammation or co-exposed to cytomix and KO, LR and VitD3 alone or to cytomix and KLD. Animals were treated for 7 days with dextran sodium sulphate (DSS) to induce colitis or with DSS and KLD. In vitro assays: F-actin expression was analysed by immunofluorescence; scratch test and trans-epithelial electric resistance test were performed to measure wound healing; adhesion/invasion assays of adhesive and invasive Escherichia coli (AIEC) bacteria were made; mRNA expression of TNF-α, interleukin (IL)-8 and vitamin D receptor (VDR) was detected by quantitative PCR. In vivo assays: body weight, clinical score, histological score and large intestine weight and length were estimated; mRNA expression of TNF-α, IL-1β, IL-6, IL-10 by quantitative PCR; VDR expression was detected by quantitative PCR and immunohistochemistry. In vitro: KLD restores epithelial cell-cell adhesion and mucosal healing during inflammation, while decreases the adhesiveness and invasiveness of AIEC bacteria and TNF-α and IL-8 mRNA expression and increases VDR expression. In vivo: KLD significantly improves body weight, clinical score, histological score and large intestine length of mice with DSS-induced colitis and reduces TNF-α, IL-1β and IL-6 mRNA levels, while increases IL-10 mRNA and VDR levels. KLD has significant effects on the intestinal mucosa, strongly decreasing inflammation, increasing epithelial restitution and reducing pathogenicity of harmful commensal bacteria.

CSA13 inhibits colitis-associated intestinal fibrosis via a formyl peptide receptor like-1 mediated HMG-CoA reductase pathway

Many Crohn’s disease (CD) patients develop intestinal strictures, which are difficult to prevent and treat. Cationic steroid antimicrobial 13 (CSA13) shares cationic nature and antimicrobial function with antimicrobial peptide cathelicidin. As many functions of cathelicidin are mediated through formyl peptide receptor-like 1 (FPRL1), we hypothesize that CSA13 mediates anti-fibrogenic effects via FPRL1. Human intestinal biopsies were used in clinical data analysis. Chronic trinitrobenzene sulfonic acid (TNBS) colitis-associated intestinal fibrosis mouse model with the administration of CSA13 was used. Colonic FPRL1 mRNA expression was positively correlated with the histology scores of inflammatory bowel disease patients. In CD patients, colonic FPRL1 mRNA was positively correlated with intestinal stricture. CSA13 administration ameliorated intestinal fibrosis without influencing intestinal microbiota. Inhibition of FPRL1, but not suppression of intestinal microbiota, reversed these protective effects of CSA13. Metabolomic analysis indicated increased fecal mevalonate levels in the TNBS-treated mice, which were reduced by the CSA13 administration. CSA13 inhibited colonic HMG-CoA reductase activity in an FPRL1-dependent manner. Mevalonate reversed the anti-fibrogenic effect of CSA13. The increased colonic FPRL1 expression is associated with severe mucosal disease activity and intestinal stricture. CSA13 inhibits intestinal fibrosis via FPRL1-dependent modulation of HMG-CoA reductase pathway.

Runt-related transcription factor 2 (RUNX2) inhibits apoptosis of intestinal epithelial cells in Crohn's disease

Apoptosis in intestinal epithelial cells (IECs) prevents the development of Crohn's disease (CD), a type of inflammatory bowel disease (IBD). Runt-related transcription factor 2 (Runx2) inhibits apoptosis in osteosarcoma-derived U2OS cells via down-regulating the transcriptional activity of p53. However, the expression and function of Runx2 in CD remain unclear. In this study, Runx2 protein levels were decreased in the intestinal epithelial cells (IECs) of CD patients and in a mouse 2, 4,6-trinitrobenzenesulfonic acid (TNBS)-induced colitis model; in contrast, the expression levels of p53 and Bax, a p53-target gene, were increased. In a TNF-α-treated HT29 cell colitis model, the down-regulation of Runx2 was accompanied by the up-regulation of apoptotic markers, including cleaved caspase-3 and Bax. Furthermore, Runx2 overexpression effectively decreased TNF-α-induced Bax and cleaved caspase-3 expression levels. In conclusion, our data indicated that Runx2 might protect IECs from apoptosis in CD, thus revealing a novel molecular target for treating CD.

TGF-β in inflammatory bowel disease: a key regulator of immune cells, epithelium, and the intestinal microbiota

Inflammatory bowel disease (IBD) is defined as chronic intestinal inflammation, and includes ulcerative colitis and Crohn's disease. Multiple factors are involved in the pathogenesis of IBD, and the condition is characterized by aberrant mucosal immune reactions to intestinal microbes in genetically susceptible hosts. Transforming growth factor-β (TGF-β) is an immune-suppressive cytokine produced by many cell types and activated by integrins. Active TGF-β binds to its receptor and regulates mucosal immune reactions through the TGF-β signaling pathway. Dysregulated TGF-β signaling is observed in the intestines of IBD patients. TGF-β signal impairment in specific cell types, such as T-cells and dendritic cells, results in spontaneous colitis in mouse models. In addition, specific intestinal microbes contribute to immune homeostasis by modulating TGF-β production. In this review, we describe the role of TGF-β in intestinal immunity, focusing on immune cells, epithelium, and intestinal microbes. In addition, we present potential therapeutic strategies for IBD that target TGF-β.

Retinoic Acid and Immune Homeostasis: A Balancing Act

In the immune system, the vitamin A metabolite retinoic acid (RA) is known for its role in inducing gut-homing molecules in T and B cells, inducing regulatory T cells (Tregs), and promoting tolerance. However, it was suggested that RA can have a broad spectrum of effector functions depending on the local microenvironment. Under specific conditions, RA can also promote an inflammatory environment. We discuss the dual role of RA in immune responses and how this might be regulated. Furthermore, we focus on the role of RA in autoimmune diseases and whether RA might be used as a therapeutic agent.