Colon epithelial cell TGFβ signaling modulates the expression of tight junction proteins and barrier function in mice

Unraveling the long-term gastrointestinal impact of perinatal perfluorobutane sulfonate exposure on rat offspring: Intestinal barrier dysfunction and Th17/Treg imbalance

Per- and polyfluoroalkyl substances (PFAS), especially long-chain perfluorooctanoic acid (PFOA) and perfluorooctane sulfonate (PFOS), are increasingly acknowledged as a potential inflammatory bowel diseases (IBD) risk factor. Perfluorobutane sulfonate (PFBS), one kind of shorter chain alternative, has been reported to exhibit similar health hazards to those long-chain PFAS. However, the underlying mechanism underpinning PFBS-induced colonic inflammation has not been sufficiently elucidated. The T-helper-17 (Th17)/regulatory T (Treg) imbalance is a crucial event for the pathogenesis of colonic inflammation. In this study, we aimed to reveal whether and how perinatal PFBS exposure leads to the Th17/Treg imbalance and colonic inflammation in offspring. We firstly demonstrated in vivo that early-life PFBS exposure (0.5 mg/kg, 5 mg/kg) led to increased intestinal permeability and colonic inflammation accompanied by decreased expressions of tight junction protein 1 (Tjp1) and claudin-4 (Cldn4) and increased expressions of interleukin 17A (IL-17A) in colon of rat offspring. Further results indicated that PFBS exposure induces the Th17/Treg imbalance through upregulating the expression of retinoic acid receptor-related orphan receptor gamma t (Ror-γt) and transforming growth factor beta (TGF-β) and downregulating of forkhead box protein 3 (Foxp3) and IL-10 in colon. Moreover, metabolomics analyses indicated that bile secretion metabolism was significantly altered under PFBS exposure. The reduction of lithocholic acid and deoxycholic acid was closely related to the changes of TGF-β and IL-10 in colon, and may contribute to the perturbation of Th17/Treg balance and colonic inflammation. These results provide evidences for the immunotoxicity of PFBS and reveal the potential contribution to colonic inflammation, which raises concern on the health effects and risk assessment of short-chain PFAS.

Trichinellaspiralis C-type lectin mediates larva invasion of gut mucosa via binding to syndecan-1 and damaging epithelial integrity in mice

C-type lectin (CTL) plays a vital role in parasite adhesion, invading host's cells and immune escape. The objective of this research was to explore whether recombinant T. spiralis CTL (rTsCTL) binding with syndecan-1 damages intestine epithelial integrity and mediates T. spiralis intrusion in mice. The results showed that rTsCTL interacted with syndecan-1 and activated STAT3 pathway in gut epithelium, decreased tight junctions (TJs) expressions and damaged gut epithelium integrity, promoted T. spiralis intrusion, and increased expression level of inflammatory cytokine and mucin. The syndecan-1 inhibitor (β-xyloside) and STAT3 phosphorylation inhibitor (Stattic) significantly suppressed syndecan-1 expression and STAT3 pathway activation, reduced the expression levels of TJs, pro-inflammatory cytokines (TNF-α and IL-1β), Muc2 and Muc5ac, and declined intestinal permeability in T. spiralis-infected mice. These results revealed that the inhibitors suppressed T. spiralis invasion and development in gut mucosa, decreased intestinal adult burdens and relieved gut inflammation. These findings further testified that the in vivo binding of TsCTL with syndecan-1 destroyed enteral mucosal epithelial integrity and promoted T. spiralis intrusion of gut mucosa via activating STAT3 pathway and decreasing TJs expression. TsCTL could be deemed as a promising vaccine target to interrupt T. spiralis infection.

Small Molecule Drug C381 Attenuates Brain Vascular Damage Following Repetitive Mild Traumatic Injury

Traumatic brain injury (TBI) remains a significant public health concern, with no effective therapeutic interventions to ameliorate the enduring consequences. The prevailing understanding of TBI pathophysiology indicates a central role for vascular dysfunction. Transforming growth factor-β (TGF-β) is a multifunctional cytokine crucial for vascular development. Aberrant TGF-β signaling is implicated in vascular pathologies associated with various neurological conditions. We recently developed a novel small molecule drug, C381, a TGF-β activator with the ability to restore lysosomal function. Here we used a mouse model of repetitive mild TBI (mTBI) to examine whether C381 would attenuate vascular injury. We first employed RNA-seq analysis to investigate the gene expression patterns associated with mTBI and evaluated the therapeutic potential of C381 in mitigating these changes. Our results demonstrate distinct mTBI-related gene expression signatures, prominently implicating pathways related to vascular integrity and endothelial function. Notably, treatment with C381 reversed these mTBI-induced gene expression changes. Immunohistochemical analysis further corroborated these findings, revealing that C381 treatment attenuated vascular damage in mTBI-affected brain tissue. These findings strongly support the potential clinical usefulness of C381 as a novel therapeutic intervention for mTBI.

Feedback delivery of BMP 7 on the pathological oxidative stress via smart hyaluronic acid hydrogel potentiated the repairing of the gut epithelial integrity

The intestinal barrier integrity was substantially collapsed when colitis flaring up, accompanying by the hallmark of pathological oxidative stress. Bone morphogenetic protein 7 (BMP 7), an endogenous growth factor in gut had the potential to repair the damaged mucosa. Herein, a smart hydrogel (HDP) had been developed by the boronate-ester crosslinked hyaluronic acid to deliver BMP 7. Hydrogel loading BMP 7 (HDP-BMP 7) presented the comparable mechanical strength with that of the naïve gut mucus. HDP-BMP 7 as artificial mucus could specifically adhere to the inflamed colonic mucosa of colitis mice. Importantly, it could apperceive reactive oxygen species at diseased colon to adapt its intrinsic network, enabling the feedback release of BMP 7 on the pathological oxidative stress. Moreover, in vivo animal experiments showed that the disease symptoms of colitis mice were alleviated by HDP-BMP 7. Importantly, both the mucus barrier and the epithelial barriers were obviously recovered by HDP-BMP 7 treatment, which substantially attenuated the immune-inflammation response of colitis mice. Besides, HDP-BMP 7 enriched the diversity of gut flora, increasing the relative abundance of Lactobacillus and decreasing the ratio of Firmicutes/Bacteroidetes. Its therapeutic mechanism was associated with activating TGF-β/Smad signals. Conclusively, this smart hydrogel might potentiate the repairing effect of growth factors on the gut epithelial integrity.

Gut Lactococcus garvieae promotes protective immunity to foodborne Clostridium perfringens infection

The gut microbiota, a pivotal component of the intestinal mucosal barrier, is critical for host resistance to enteric pathogen infection. Here, we report a novel function of the potentially probiotic Lactococcus garvieae strain LG1 (L. garvieae strain LG1) in maintaining intestinal mucosal barrier integrity and protecting against foodborne Clostridium perfringens (C. perfringens) infection. L. garvieae was isolated from the intestinal contents of Chinese Mongolian sheep (MS) and exhibited potential probiotic properties. In a C. perfringens enterocolitis model, L. garvieae-pretreated mice were less susceptible to C. perfringens infection compared with Phosphate buffered solution (PBS)-pretreated mice, which manifested as higher survival rates, lower pathogen loads, less weight loss, mild clinical symptoms and intestinal damage, and minor inflammation. Further mechanistic analysis showed that L. garvieae could ameliorate the disruption of intestinal permeability and maintain the integrity of the intestinal mucosal barrier by promoting the expression of tight junction proteins and mucoproteins. Moreover, L. garvieae was also able to facilitate antimicrobial peptide expression and ameliorate dysbiosis of the gut microbiota caused by C. perfringens. Together, these findings highlight the prospect of immunomodulatory potentially probiotic L. garvieae and might offer valuable strategies for prophylaxis and/or treatment of pathogenic C. perfringens mucosal infection.

IMPORTANCE

C. perfringens necrotic enteritis leads to losses of about US $2 billion to the poultry industry worldwide every year. Worse, US Centers for Disease Control and Prevention (CDC) has estimated that C. perfringens causes nearly 1 million foodborne illnesses in the United States annually. Nowadays, the treatment recommendation is a combination of a broad-spectrum synergistic penicillin with clindamycin or a carbapenem, despite growing scientific concern over antibiotic resistance. The global understanding of the gut microbiome for C. perfringens infection may provide important insights into the intervention. L. garvieae originated from Mongolian sheep intestine, exhibited potentially probiotic properties, and was able to limit C. perfringens enterocolitis and pathogenic colonization. Importantly, we found that L. garvieae limits C. perfringens invasion via improving intestinal mucosal barrier function. Also, L. garvieae alleviates C. perfringens-induced gut microbiota dysbiosis. It allowed us to convince that utilization of probiotics to promote protective immunity against pathogens infection is of pivotal importance.

Significance and Possible Biological Mechanism for CLDN8 Downregulation in Kidney Renal Clear Cell Carcinoma Tissues

Background

The clinical role of claudin 8 (CLDN8) in kidney renal clear cell carcinoma (KIRC) remains unclarified. Herein, the expression level and potential molecular mechanisms of CLDN8 underlying KIRC were determined.

Methods

High-throughput datasets of KIRC were collected from GEO, ArrayExpress, SRA, and TCGA databases to determine the mRNA expression level of the CLDN8. In-house tissue microarrays and immunochemistry were performed to examine CLDN8 protein expression. A summary receiver operating characteristic curve (SROC) and standardized mean difference (SMD) forest plot were generated using Stata v16.0. Single-cell analysis was conducted to further prove the expression level of CLDN8. A clustered regularly interspaced short palindromic repeats knockout screen analysis was executed to assess the growth impact of CLDN8. Functional enrichment analysis was conducted using the Metascape database. Additionally, single-sample gene set enrichment analysis was implied to explore immune cell infiltration in KIRC.

Results

A total of 17 mRNA datasets comprising 1,060 KIRC samples and 452 non-cancerous control samples were included in this study. Additionally, 105 KIRC and 16 non-KIRC tissues were analyzed using in-house immunohistochemistry. The combined SMD was -5.25 (95% confidence interval (CI): -6.13 to -4.37), and CLDN8 downregulation yielded an SROC area under the curve (AUC) close to 1.00 (95% CI: 0.99 - 1.00). CLDN8 downregulation was also confirmed at the single-cell level. Knocking out CLDN8 stimulated KIRC cell proliferation. Lower CLDN8 expression was correlated with worse overall survival of KIRC patients (hazard ratio of CLDN8 downregulation = 1.69, 95% CI: 1.2 - 2.4). Functional pathways associated with CLDN8 co-expressed genes were centered on carbon metabolism obstruction, with key hub genes ACADM, ACO2, NDUFS1, PDHB, SDHD, SUCLA2, SUCLG1, and SUCLG2.

Conclusions

CLDN8 is downregulated in KIRC and is considered a potential tumor suppressor. CLDN8 deficiency may promote the initiation and progression of KIRC, potentially in conjunction with metabolic dysfunction.

Changes in the Expression of Genes Regulating the Response to Hypoxia, Inflammation, Cell Cycle, Apoptosis, and Epithelial Barrier Functioning during Colitis-Associated Colorectal Cancer Depend on Individual Hypoxia Tolerance

One of the factors contributing to colorectal cancer (CRC) development is inflammation, which is mostly hypoxia-associated. This study aimed to characterize the morphological and molecular biological features of colon tumors in mice that were tolerant and susceptible to hypoxia based on colitis-associated CRC (CAC). Hypoxia tolerance was assessed through a gasping time evaluation in a decompression chamber. One month later, the animals were experimentally modeled for colitis-associated CRC by intraperitoneal azoxymethane administration and three dextran sulfate sodium consumption cycles. The incidence of tumor development in the distal colon in the susceptible to hypoxia mice was two times higher and all tumors (100%) were represented by adenocarcinomas, while in the tolerant mice, only 14% were adenocarcinomas and 86% were glandular intraepithelial neoplasia. The tumor area assessed on serially stepped sections was statistically significantly higher in the susceptible animals. The number of macrophages, CD3-CD19+, CD3+CD4+, and NK cells in tumors did not differ between animals; however, the number of CD3+CD8+ and vimentin+ cells was higher in the susceptible mice. Changes in the expression of genes regulating the response to hypoxia, inflammation, cell cycle, apoptosis, and epithelial barrier functioning in tumors and the peritumoral area depended on the initial mouse's hypoxia tolerance, which should be taken into account for new CAC diagnostics and treatment approaches development.

Effects of DNA methylation and its application in inflammatory bowel disease (Review)

Inflammatory bowel disease (IBD) is marked by persistent inflammation, and its development and progression are linked to environmental, genetic, immune system and gut microbial factors. DNA methylation (DNAm), as one of the protein modifications, is a crucial epigenetic process used by cells to control gene transcription. DNAm is one of the most common areas that has drawn increasing attention recently, with studies revealing that the interleukin (IL)‑23/IL‑12, wingless‑related integration site, IL‑6‑associated signal transducer and activator of transcription 3, suppressor of cytokine signaling 3 and apoptosis signaling pathways are involved in DNAm and in the pathogenesis of IBD. It has emerged that DNAm‑associated genes are involved in perpetuating the persistent inflammation that characterizes a number of diseases, including IBD, providing a novel therapeutic strategy for exploring their treatment. The present review discusses DNAm‑associated genes in the pathogenesis of IBD and summarizes their application as possible diagnostic, prognostic and therapeutic biomarkers in IBD. This may provide a reference for the particular form of IBD and its related methylation genes, aiding in clinical decision‑making and encouraging therapeutic alternatives.

Tissue and cellular spatiotemporal dynamics in colon aging

Tissue structure and molecular circuitry in the colon can be profoundly impacted by systemic age-related effects, but many of the underlying molecular cues remain unclear. Here, we built a cellular and spatial atlas of the colon across three anatomical regions and 11 age groups, encompassing ~1,500 mouse gut tissues profiled by spatial transcriptomics and ~400,000 single nucleus RNA-seq profiles. We developed a new computational framework, cSplotch, which learns a hierarchical Bayesian model of spatially resolved cellular expression associated with age, tissue region, and sex, by leveraging histological features to share information across tissue samples and data modalities. Using this model, we identified cellular and molecular gradients along the adult colonic tract and across the main crypt axis, and multicellular programs associated with aging in the large intestine. Our multi-modal framework for the investigation of cell and tissue organization can aid in the understanding of cellular roles in tissue-level pathology.

Challenges and opportunities in inflammatory bowel disease: from current therapeutic strategies to organoid-based models

BACKGROUND

Inflammatory bowel disease (IBD) is an increasingly prevalent global health concern that has garnered substantial attention. However, the underlying mechanisms are still unclear and the current treatments have significant limitations. Intestinal organoids provide an in vitro model to explore the pathogenesis, test the therapeutic effects, and develop regenerative treatments as well as offer the potential to transform drug discovery of IBD.

METHODS

To advance our understanding of the whole story of IBD spanning from the pathogenesis to the current therapeutic strategies and latest advancements, a comprehensive search of major databases including PubMed, Scopus, and Web of Science was conducted to retrieve original articles and reviews related to IBD, organoids, pathogenesis and therapy.

RESULTS

This review deciphers the etiopathogenesis and the current therapeutic approaches in the treatment of IBD. Notably, critical aspects of intestinal organoids in IBD, such as their potential applications, viability, cell renewal ability, and barrier functionality are highlighted. We also discuss the advances, limitations, and prospects of intestinal organoids for precision medicine.

CONCLUSION

The latest strides made in research about intestinal organoids help elucidate intricate aspects of IBD pathogenesis, and pave the prospective avenues for novel therapeutic interventions.

Alkaline Phosphatase Relieves Colitis in Obese Mice Subjected to Forced Exercise via Its Anti-Inflammatory and Intestinal Microbiota-Shaping Properties

Intestinal alkaline phosphatase (IAP) is an enzyme that plays a protective role in the gut. This study investigated the effect of IAP treatment on experimental colitis in mice subjected to forced exercise on a high-fat diet. C57BL/6 mice with TNBS colitis were fed a high-fat diet and subjected to forced treadmill exercise with or without IAP treatment. Disease activity, oxidative stress, inflammatory cytokines, and gut microbiota were assessed. Forced exercise exacerbated colitis in obese mice, as evidenced by increased disease activity index (DAI), oxidative stress markers, and proinflammatory adipokines and cytokines. IAP treatment significantly reduced these effects and promoted the expression of barrier proteins in the colonic mucosa. Additionally, IAP treatment altered the gut microbiota composition, favoring beneficial Verrucomicrobiota and reducing pathogenic Clostridia and Odoribacter. IAP treatment ameliorates the worsening effect of forced exercise on murine colitis by attenuating oxidative stress, downregulating proinflammatory biomarkers, and modulating the gut microbiota. IAP warrants further investigation as a potential therapeutic strategy for ulcerative colitis.

A novel Trichinella spiralis serine proteinase disrupted gut epithelial barrier and mediated larval invasion through binding to RACK1 and activating MAPK/ERK1/2 pathway

BACKGROUND

Gut epithelium is the first natural barrier against Trichinella spiralis larval invasion, but the mechanism by which larval penetration of gut epithelium is not completely elucidated. Previous studies showed that proteases secreted by T. spiralis intestinal infective larvae (IIL) degraded tight junctions (TJs) proteins of gut epithelium and mediated larval invasion. A new T. spiralis serine proteinase (TsSPc) was identified in the IIL surface proteins and ES proteins, rTsSPc bound to the intestinal epithelial cell (IECs) and promoted larval invasion of IECs. The aim of this study was to characterize the interacted proteins of TsSPc and IECs, and to investigate the molecular mechanisms of TsSPc mediating larval invasion of gut mucosa.

METHODOLOGY/PRINCIPAL FINDING

IIFT results showed natural TsSPc was detected in infected murine intestine at 6, 12 hours post infection (hpi) and 3 dpi. The results of GST pull-down, mass spectrometry (MS) and Co-IP indicated that rTsSPc bound and interacted specifically with receptor for activated protein C kinase 1 (RACK1) in Caco-2 cells. rTsSPc did not directly hydrolyze the TJs proteins. qPCR and Western blot showed that rTsSPc up-regulated RACK1 expression, activated MAPK/ERK1/2 pathway, reduced the expression levels of gut TJs (occludin and claudin-1) and adherent protein E-cad, increased the paracellular permeability and damaged the integrity of intestinal epithelial barrier. Moreover, the RACK1 inhibitor HO and ERK1/2 pathway inhibitor PD98059 abolished the rTsSPc activating ERK1/2 pathway, they also inhibited and abrogated the rTsSPc down-regulating expression of occludin, claudin-1 and E-cad in Caco-2 monolayer and infected murine intestine, impeded larval invasion and improved intestinal epithelial integrity and barrier function, reduced intestinal worm burdens and alleviated intestinal inflammation.

CONCLUSIONS

rTsSPc bound to RACK1 receptor in gut epithelium, activated MAPK/ERK1/2 pathway, decreased the expression of gut epithelial TJs proteins and disrupted the epithelial integrity, consequently mediated T. spiralis larval invasion of gut epithelium. The results are valuable to understand T. spiralis invasion mechanism, and TsSPc might be regarded as a vaccine target against T. spiralis invasion and infection.

Traditional Medicine Pien Tze Huang Suppresses Colorectal Tumorigenesis Through Restoring Gut Microbiota and Metabolites

BACKGROUND & AIMS

Pien Tze Huang (PZH) is a well-established traditional medicine with beneficial effects against inflammation and cancer. We aimed to explore the chemopreventive effect of PZH in colorectal cancer (CRC) through modulating gut microbiota.

METHODS

CRC mouse models were established by azoxymethane plus dextran sulfate sodium treatment or in Apcmin/+ mice treated with or without PZH (270 mg/kg and 540 mg/kg). Gut barrier function was determined by means of intestinal permeability assays and transmission electron microscopy. Fecal microbiota and metabolites were analyzed by means of metagenomic sequencing and liquid chromatography mass spectrometry, respectively. Germ-free mice or antibiotic-treated mice were used as models of microbiota depletion.

RESULTS

PZH inhibited colorectal tumorigenesis in azoxymethane plus dextran sulfate sodium-treated mice and in Apcmin/+ mice in a dose-dependent manner. PZH treatment altered the gut microbiota profile, with an increased abundance of probiotics Pseudobutyrivibrio xylanivorans and Eubacterium limosum, while pathogenic bacteria Aeromonas veronii, Campylobacter jejuni, Collinsella aerofaciens, and Peptoniphilus harei were depleted. In addition, PZH increased beneficial metabolites taurine and hypotaurine, bile acids, and unsaturated fatty acids, and significantly restored gut barrier function. Transcriptomic profiling revealed that PZH inhibited PI3K-Akt, interleukin-17, tumor necrosis factor, and cytokine-chemokine signaling. Notably, the chemopreventive effect of PZH involved both microbiota-dependent and -independent mechanisms. Fecal microbiota transplantation from PZH-treated mice to germ-free mice partly recapitulated the chemopreventive effects of PZH. PZH components ginsenoside-F2 and ginsenoside-Re demonstrated inhibitory effects on CRC cells and primary organoids, and PZH also inhibited tumorigenesis in azoxymethane plus dextran sulfate sodium-treated germ-free mice.

CONCLUSIONS

PZH manipulated gut microbiota and metabolites toward a more favorable profile, improved gut barrier function, and suppressed oncogenic and pro-inflammatory pathways, thereby suppressing colorectal carcinogenesis.

The effects of sodium butyrate (NaB) combination with soy saponin dietary supplementation on the growth parameters, intestinal performance and immune-related genes expression of hybrid grouper (Epinephelus fuscoguttatus♀ × E. lanceolatus♂)

Soy saponins are generally known to have negative effects on growth and the intestines of aquatic animals, and appropriate levels of sodium butyrate (NaB) may provide some mitigating effects. We investigated the effects of low and high levels of soy saponin and the protective effects of NaB (based on high level of soy saponin) on growth, serum cytokines, distal intestinal histopathology, and inflammation in hybrid grouper (Epinephelus fuscoguttatus ♀ × E. lanceolatus ♂). The experiment included four groups: fishmeal group (FM, 0.00% saponin and 0.00% NaB), low saponin group (SL, 0.30% saponin and 0.00% NaB), high saponin group (SH, 1.50% saponin and 0.00% NaB) and high saponin with NaB group (SH-NaB, 1.50% saponin and 0.13% NaB). The results showed compared to FM, the final body weight (FBW) and weight gain (WG) were significantly higher and lower in SL and SH, respectively (P < 0.05). Compared to SH, the FBW and WG were significant higher in SH-NaB (P < 0.05). In the serum, compared to FM, the interferon γ (IFN-γ) and interleukin-1β (IL-1β) levels in SH were significantly increased (P < 0.05). Compared to SH, the IFN-γ level was significantly decreased in SH-NaB (P < 0.05). In the distal intestine, based on Alcian Blue-Periodic Acid-Schiff (AB-PAS) observation, the goblet cell/μm was significantly increased and decreased in the SL and SH, respectively, compared to FM. The intestinal diameter/plica height ratio in the SH was significantly higher than those in the FM, SL and SH-NaB (P < 0.05). The NO and ONOO- levels in the SH were significantly higher than that in FM and SL (P < 0.05). At the transcriptional level in the distal intestine, compared to FM, the mRNA levels of tumor necrosis factor (tnfα), il1β, interleukin-8 (il8) and ifnγ were significantly up-regulated in the SH (P < 0.05). Compared to the SH, tnfα, il8 and ifnγ were significantly down-regulated in the SH-NaB (P < 0.05). Compared to the FM, the mRNA levels of claudin3, claudin15, zo2 and zo3 were significantly up-regulated in the SL (P < 0.05). The mRNA levels of occludin, claudin3, claudin12, claudin15, zo1, zo2 and zo3 were significantly down-regulated in the SH compared to the FM (P < 0.05). Additionally, compared to the SH, the mRNA levels of occludin, claudin3, claudin12, claudin15, zo1, zo2 and zo3 were significantly up-regulated in the SH-NaB (P < 0.05). After the 7-day Vibrio parahaemolyticus challenge test, the survival was significantly higher and lower in the SL and SH, respectively, compared to FM (P < 0.05). Overall, low and high levels of soy saponins had positive and negative effects on growth, disease resistance, serum cytokines, and distal intestinal development and anti-inflammation, respectively, in hybrid grouper. NaB effectively increased disease resistance and improved distal intestinal inflammation in hybrid grouper, but the effects of NaB were mainly observed in improving distal intestinal tight junctions.

Rebalancing of mitochondrial homeostasis through an NAD+-SIRT1 pathway preserves intestinal barrier function in severe malnutrition

BACKGROUND

The intestine of children with severe malnutrition (SM) shows structural and functional changes that are linked to increased infection and mortality. SM dysregulates the tryptophan-kynurenine pathway, which may impact processes such as SIRT1- and mTORC1-mediated autophagy and mitochondrial homeostasis. Using a mouse and organoid model of SM, we studied the repercussions of these dysregulations on malnutrition enteropathy and the protective capacity of maintaining autophagy activity and mitochondrial health.

METHODS

SM was induced through feeding male weanling C57BL/6 mice a low protein diet (LPD) for 14-days. Mice were either treated with the NAD+-precursor, nicotinamide; an mTORC1-inhibitor, rapamycin; a SIRT1-activator, resveratrol; or SIRT1-inhibitor, EX-527. Malnutrition enteropathy was induced in enteric organoids through amino-acid deprivation. Features of and pathways to malnutrition enteropathy were examined, including paracellular permeability, nutrient absorption, and autophagic, mitochondrial, and reactive-oxygen-species (ROS) abnormalities.

FINDINGS

LPD-feeding and ensuing low-tryptophan availability led to villus atrophy, nutrient malabsorption, and intestinal barrier dysfunction. In LPD-fed mice, nicotinamide-supplementation was linked to SIRT1-mediated activation of mitophagy, which reduced damaged mitochondria, and improved intestinal barrier function. Inhibition of mTORC1 reduced intestinal barrier dysfunction and nutrient malabsorption. Findings were validated and extended using an organoid model, demonstrating that resolution of mitochondrial ROS resolved barrier dysfunction.

INTERPRETATION

Malnutrition enteropathy arises from a dysregulation of the SIRT1 and mTORC1 pathways, leading to disrupted autophagy, mitochondrial homeostasis, and ROS. Whether nicotinamide-supplementation in children with SM could ameliorate malnutrition enteropathy should be explored in clinical trials.

FUNDING

This work was supported by the Bill and Melinda Gates Foundation, the Sickkids Research Institute, the Canadian Institutes of Health Research, and the University Medical Center Groningen.

1,8-cineole ameliorates colon injury by downregulating macrophage M1 polarization via inhibiting the HSP90-NLRP3-SGT1 complex

Ulcerative colitis (UC) is characterized by chronic relapsing intestinal inflammation. Currently, there is no effective treatment for the disease. According to our preliminary data, 1,8-cineole, which is the main active compound of Amomum compactum Sol. ex Maton volatile oil and an effective drug for the treatment of pneumonia, showed remarkable anti-inflammatory effects on colitis pathogenesis. However, its mechanism of action and direct targets remain unclear. This study investigated the direct targets and mechanism through which 1,8-cineole exerts its anti-inflammatory effects using a dextran sulfate sodium salt-induced colitis mouse model. The effects of 1,8-cineole on macrophage polarization were investigated using activated bone marrow-derived macrophages and RAW264.7 cells. In addition, 1,8-cineole targets were revealed by drug affinity responsive target stability, thermal shift assay, cellular thermal shift assay, and heat shock protein 90 (HSP90) adenosine triphosphatases (ATPase) activity assays. The results showed that 1,8-cineole exhibited powerful anti-inflammatory properties in vitro and in vivo by inhibiting the macrophage M1 polarization and protecting intestinal barrier function. Mechanistically, 1,8-cineole directly interacted with HSP90 and decreased its ATPase activity, also inhibited nucleotide-binding and oligomerization domain-, leucine rich repeat-, and pyrin domain-containing 3 (NLRP3) binding to HSP90 and suppressor of G-two allele of SKP1 (SGT1) and suppressed NLRP3 inflammasome activation in macrophages. These results demonstrated that 1,8-cineole is a potential drug candidate for UC treatment.

Exploring body weight-influencing gut microbiota by elucidating the association with diet and host gene expression

We aimed to identify gut microbiota that influences body weight by elucidating the association with diets and host genes. Germ-free (GF) mice with and without fecal microbiota transplant (FMT) were fed a normal, high-carbohydrate, or high-fat diet. FMT mice exhibited greater total body weight; adipose tissue and liver weights; blood glucose, insulin, and total cholesterol levels; and oil droplet size than the GF mice, regardless of diet. However, the extent of weight gain and metabolic parameter levels associated with gut microbiota depended on the nutrients ingested. For example, a disaccharide- or polysaccharide-rich diet caused more weight gain than a monosaccharide-rich diet. An unsaturated fatty acid-rich diet had a greater microbial insulin-increasing effect than a saturated fatty acid-rich diet. Perhaps the difference in microbial metabolites produced from substances taken up by the host created metabolic differences. Therefore, we analyzed such dietary influences on gut microbiota, differentially expressed genes between GF and FMT mice, and metabolic factors, including body weight. The results revealed a correlation between increased weight gain, a fat-rich diet, increased Ruminococcaceae abundance, and decreased claudin 22 gene expression. These findings suggest that weight regulation might be possible through the manipulation of the gut microbiota metabolism using the host's diet.

Claudin-4: A New Molecular Target for Epithelial Cancer Therapy

Claudin-4 (CLDN4) is a key component of tight junctions (TJs) in epithelial cells. CLDN4 is overexpressed in many epithelial malignancies and correlates with cancer progression. Changes in CLDN4 expression have been associated with epigenetic factors (such as hypomethylation of promoter DNA), inflammation associated with infection and cytokines, and growth factor signaling. CLDN4 helps to maintain the tumor microenvironment by forming TJs and acts as a barrier to the entry of anticancer drugs into tumors. Decreased expression of CLDN4 is a potential marker of epithelial-mesenchymal transition (EMT), and decreased epithelial differentiation due to reduced CLDN4 activity is involved in EMT induction. Non-TJ CLDN4 also activates integrin beta 1 and YAP to promote proliferation, EMT, and stemness. These roles in cancer have led to investigations of molecular therapies targeting CLDN4 using anti-CLDN4 extracellular domain antibodies, gene knockdown, clostridium perfringens enterotoxin (CPE), and C-terminus domain of CPE (C-CPE), which have demonstrated the experimental efficacy of this approach. CLDN4 is strongly involved in promoting malignant phenotypes in many epithelial cancers and is regarded as a promising molecular therapeutic target.

Smad7 as a positive regulator of intestinal inflammatory diseases

In physiological conditions, the human gut contains more immune cells than the rest of the body, but no overt tissue damage occurs, because several regulatory mechanisms control the activity of such cells thus preventing excessive and detrimental responses. One such mechanism relies on the action of transforming growth factor (TGF)-β1, a cytokine that targets both epithelial cells and many immune cell types. Loss of TGF-β1 function leads to intestinal pathology in both mice and humans. For instance, disruption of TGF-β1 signaling characterizes the destructive immune-inflammatory response in patients with Crohn's disease and patients with ulcerative colitis, the major human inflammatory bowel disease (IBD) entities. In these pathologies, the defective TGF-β1-mediated anti-inflammatory response is associated with elevated intestinal levels of Smad7, an antagonist of TGF-β1 signaling. Consistently, knockdown of Smad7 restores TGF-β1 function thereby attenuating intestinal inflammation in patients with IBD as well as in mice with IBD-like colitis. Up-regulation of Smad7 and reduced TGF-β1 signaling occurs also in necrotizing enterocolitis, environmental enteropathy, refractory celiac disease, and cytomegalovirus-induced colitis. In this article, we review the available data supporting the pathogenic role of Smad7 in the gastrointestinal tract and discuss whether and how targeting Smad7 can help attenuate detrimental immuno-inflammatory responses in the gut.

SMAD4 Suppresses Colitis-associated Carcinoma Through Inhibition of CCL20/CCR6-mediated Inflammation

BACKGROUND & AIMS

We previously reported that colon epithelial cell silencing of Smad4 increased epithelial expression of inflammatory genes, including the chemokine c-c motif chemokine ligand 20 (CCL20), and increased susceptibility to colitis-associated cancer. Here, we examine the role of the chemokine/receptor pair CCL20/c-c motif chemokine receptor 6 (CCR6) in mediating colitis-associated colon carcinogenesis induced by SMAD4 loss.

METHODS

In silico analysis of SMAD4, CCL20, and CCR6 messenger RNA expression was performed on published transcriptomic data from human ulcerative colitis (UC), and colon and rectal cancer samples. Immunohistochemistry for CCL20 and CCR6 was performed on human tissue microarrays comprising human UC-associated cancer specimens, Mice with conditional, epithelial-specific Smad4 loss with and without germline deletion of the Ccr6 gene were subjected to colitis and followed for up to 3 months. Tumors were quantified histologically, and immune cell populations were analyzed by flow cytometry and immunostaining.

RESULTS

In human UC-associated cancers, loss of epithelial SMAD4 was associated with increased CCL20 expression and CCR6+ cells. SMAD4 loss in mouse colon epithelium led to enlarged gut-associated lymphoid tissues and recruitment of immune cells to the mouse colon epithelium and stroma, particularly T regulatory, Th17, and dendritic cells. Loss of CCR6 abrogated these immune responses and significantly reduced the incidence of colitis-associated tumors observed with loss of SMAD4 alone.

CONCLUSIONS

Regulation of mucosal inflammation is central to SMAD4 tumor suppressor function in the colon. A key downstream node in this regulation is suppression of epithelial CCL20 signaling to CCR6 in immune cells. Loss of SMAD4 in the colon epithelium increases CCL20 expression and chemoattraction of CCR6+ immune cells, contributing to greater susceptibility to colon cancer.

Functional Analysis of Gastric Tight Junction Proteins in Xenopus laevis Oocytes

The epithelial barrier is crucial for proper gastrointestinal function, preventing the unwanted passage of solutes and therefore representing a prerequisite for vectorial transport. Claudin-4 and claudin-18.2, two critical tight junction proteins of the gastric epithelium, seal neighboring cells in a physically and mechanically challenging environment. As the Xenopus laevis oocyte allows the functional and molecular analyses of claudin interaction, we have addressed the hypothesis that this interaction is not only dependent on mechanical force but also on pH. We expressed human claudin-4 and claudin-18 in Xenopus oocytes, and analyzed them in a two-cell model approach. Cells were clustered in pairs to form contact areas expressing CLDN18 + CLDN18, CLDN4/18 + CLDN4/18, and compared to controls, respectively. Contact areas in cells incubated in medium at pH 5.5 and 7.4 were quantified by employing transmitted light microscopy. After 24 h at pH 5.5, clustering of CLDN18 + CLDN18 and CLDN4/18 + CLDN4/18-expressing oocytes revealed a contact area reduced by 45% and 32%, compared with controls, respectively. A further approach, high-pressure impulse assay, revealed a stronger tight junction interaction at pH 5.5 in oocyte pairs expressing CLDN18 + CLDN18 or CLDN4/18 + CLDN4/18 indicating a protective role of claudin-18 for tight junction integrity during pH challenge. Thus, our current analysis of gastric tight junction proteins further establishes oocytes as an expression and two-cell screening model for tight junction integrity analysis of organ- and tissue-specific claudins by the characterization of homo- and heterophilic trans-interaction dependent on barrier effectors.

TGF-β induces GBM mesenchymal transition through upregulation of CLDN4 and nuclear translocation to activate TNF-α/NF-κB signal pathway

Glioblastoma (GBM) is the most common and aggressive primary malignant brain tumor. The unregulated expression of Claudin-4 (CLDN4) plays an important role in tumor progression. However, the biological role of CLDN4 in GBM is still unknown. This study aimed to determine whether CLDN4 mediates glioma malignant progression, if so, it would further explore the molecular mechanisms of carcinogenesis. Our results revealed that CLDN4 was significantly upregulated in glioma specimens and cells. The inhibition of CLND4 expression could inhibit mesenchymal transformation, cell invasion, cell migration and tumor growth in vitro and in vivo. Moreover, combined with in vitro analysis, we found that CLDN4 can modulate tumor necrosis factor-α (TNF-α) signal pathway. Meanwhile, we also validated that the transforming growth factor-β (TGF-β) signal pathway can upregulate the expression of CLDN4, and promote the invasion ability of GBM cells. Conversely, TGF-β signal pathway inhibitor ITD-1 can downregulate the expression of CLDN4, and inhibit the invasion ability of GBM cells. Furthermore, we found that TGF-β can promote the nuclear translocation of CLDN4. In summary, our findings indicated that the TGF-β/CLDN4/TNF-α/NF-κB signal axis plays a key role in the biological progression of glioma. Disrupting the function of this signal axis may represent a new treatment strategy for patients with GBM.

Berberine represses Wnt/β-catenin pathway activation via modulating the microRNA-103a-3p/Bromodomain-containing protein 4 axis, thereby refraining pyroptosis and reducing the intestinal mucosal barrier defect induced via colitis

Intestinal barrier dysfunction is inflammatory bowel disease’s hallmark. Berberine (BBR) has manifested its anti-inflammatory properties in colitis. For exploring the molecular mechanism of BBR’s impacts on colitis, application of a dextran sodium sulfate-induced mouse colitis in vivo model was with recording the body weight, stool consistency, stool occult blood and general physical symptoms of all groups of mice every day. Behind assessment of intestinal permeability, detection of colon damage’s degree and apoptosis, and inflammatory factors for assessment of pyroptosis was conducted. Application of interleukin-6-stimulated Caco-2 cells was for construction of an in vitro model. Then detection of cell advancement with inflammation and measurement of the barrier’s integrity were put into effect. Verification of microRNA (miR)-103a-3p and Bromodomain-containing protein 4 (BRD4)’s targeting link was conducted. Experiments have clarified BBR, elevated miR-103a-3p or repressive BRD4 was available to alleviate colitis-stimulated pyroptosis and intestinal mucosal barrier defects. BBR elevated miR-103a-3p to target BRD4; Refraining miR-103a-3p or enhancive BRD4 turned around BBR’s therapeutic action on colitis injury. BBR depressed Wnt/β-catenin pathway activation via controlling the miR-103a-3p/BRD4 axis. All in all, BBR represses Wnt/β-catenin pathway activation via modulating the miR-103a-3p/BRD4 axis, thereby mitigating colitis-stimulated pyroptosis and the intestinal mucosal barrier defect. The research suggests BBR is supposed to take on potential in colitis cure.

Aire-dependent transcripts escape Raver2-induced splice-event inclusion in the thymic epithelium

Aire allows medullary thymic epithelial cells (mTECs) to express and present a large number of self-antigens for central tolerance. Although mTECs express a high diversity of self-antigen splice isoforms, the extent and regulation of alternative splicing events (ASEs) in their transcripts, notably in those induced by Aire, is unknown. In contrast to Aire-neutral genes, we find that transcripts of Aire-sensitive genes show only a low number of ASEs in mTECs, with about a quarter present in peripheral tissues excluded from the thymus. We identify Raver2, as a splicing-related factor overexpressed in mTECs and dependent on H3K36me3 marks, that promotes ASEs in transcripts of Aire-neutral genes, leaving Aire-sensitive ones unaffected. H3K36me3 profiling reveals its depletion at Aire-sensitive genes and supports a mechanism that is preceding Aire expression leading to transcripts of Aire-sensitive genes with low ASEs that escape Raver2-induced alternative splicing. The lack of ASEs in Aire-induced transcripts would result in an incomplete Aire-dependent negative selection of autoreactive T cells, thus highlighting the need of complementary tolerance mechanisms to prevent activation of these cells in the periphery.

Evaluation of the Prognostic Relevance of Differential Claudin Gene Expression Highlights Claudin-4 as Being Suppressed by TGFβ1 Inhibitor in Colorectal Cancer

Background: Claudins (CLDNs) are a family of closely related transmembrane proteins that have been linked to oncogenic transformation and metastasis across a range of cancers, suggesting that they may be valuable diagnostic and/or prognostic biomarkers that can be used to evaluate patient outcomes. However, CLDN expression patterns associated with colorectal cancer (CRC) remain to be defined.

Methods: The mRNA levels of 21 different CLDN family genes were assessed across 20 tumor types using the Oncomine database. Correlations between these genes and patient clinical outcomes, immune cell infiltration, clinicopathological staging, lymph node metastasis, and mutational status were analyzed using the GEPIA, UALCAN, Human Protein Atlas, Tumor Immune Estimation Resource, STRING, Genenetwork, cBioportal, and DAVID databases in an effort to clarify the potential functional roles of different CLDN protein in CRC. Molecular docking analyses were used to probe potential interactions between CLDN4 and TGFβ1. Levels of CLDN4 and CLDN11 mRNA expression in clinical CRC patient samples and in the HT29 and HCT116 cell lines were assessed via qPCR. CLDN4 expression levels in these 2 cell lines were additionally assessed following TGFβ1 inhibitor treatment.

Results: These analyses revealed that COAD and READ tissues exhibited the upregulation of CLDN1, CLDN2, CLDN3, CLDN4, CLDN7, and CLDN12 as well as the downregulation of CLDN5 and CLDN11 relative to control tissues. Higher CLDN11 and CLDN14 expression as well as lower CLDN23 mRNA levels were associated with poorer overall survival (OS) outcomes. Moreover, CLDN2 and CLDN3 or CLDN11 mRNA levels were significantly associated with lymph node metastatic progression in COAD or READ lower in COAD and READ tissues. A positive correlation between the expression of CLDN11 and predicted macrophage, dendritic cell, and CD4+ T cell infiltration was identified in CRC, with CLDN12 expression further being positively correlated with CD4+ T cell infiltration whereas a negative correlation was observed between such infiltration and the expression of CLDN3 and CLDN15. A positive correlation between CLDN1, CLDN16, and neutrophil infiltration was additionally detected, whereas neutrophil levels were negatively correlated with the expression of CLDN3 and CLDN15. Molecular docking suggested that CLDN4 was able to directly bind via hydrogen bond with TGFβ1. Relative to paracancerous tissues, clinical CRC tumor tissue samples exhibited CLDN4 and CLDN11 upregulation and downregulation, respectively. LY364947 was able to suppress the expression of CLDN4 in both the HT29 and HCT116 cell lines.

Conclusion: Together, these results suggest that the expression of different CLDN family genes is closely associated with CRC tumor clinicopathological staging and immune cell infiltration. Moreover, CLDN4 expression is closely associated with TGFβ1 in CRC, suggesting that it and other CLDN family members may represent viable targets for antitumor therapeutic intervention.

Hsa_circ_0001021 regulates intestinal epithelial barrier function via sponging miR-224-5p in ulcerative colitis

Aims: Few circRNAs have been thoroughly explored in ulcerative colitis (UC). Materials & methods: Microarrays and qualitative real-time PCRs were used to detect and confirm dysregulated circRNAs associated with UC. Functional analysis was performed to explore the roles. Results: A total of 580 circRNAs and 87 miRNAs were simultaneously dysregulated in both inflamed and noninflamed UC colonic mucosa compared with healthy controls. Accordingly, hsa_circ_0001021 was significantly downregulated in patients with UC and was related to Mayo scores. Clinical samples and cell experiments revealed that hsa_circ_0001021 was expressed in epithelial cells and correlated with ZO-1, occludin and CLDN-2. Moreover, hsa_circ_0001021 sponged miR-224-5p to upregulate smad4 and increased ZO-1 and occludin. Conclusion: Hsa_circ_0001021 is related to UC severity and regulates epithelial barrier function via sponging miR-224-5p.

Involvement of Smad7 in Inflammatory Diseases of the Gut and Colon Cancer

In physiological conditions, the human intestinal mucosa is massively infiltrated with various subsets of immune cells, the activity of which is tightly regulated by several counter-regulatory factors. One of these factors is transforming growth factor-β1 (TGF-β1), a cytokine produced by multiple cell types and targeting virtually all the intestinal mucosal cells. Binding of TGF-β1 to its receptors triggers Smad2/3 signaling, thus culminating in the attenuation/suppression of immune–inflammatory responses. In patients with Crohn’s disease and patients with ulcerative colitis, the major human inflammatory bowel diseases (IBD), and in mice with IBD-like colitis, there is defective TGF-β1/Smad signaling due to high levels of the intracellular inhibitor Smad7. Pharmacological inhibition of Smad7 restores TGF-β1 function, thereby reducing inflammatory pathways in patients with IBD and colitic mice. On the other hand, transgenic over-expression of Smad7 in T cells exacerbates colitis in various mouse models of IBD. Smad7 is also over-expressed in other inflammatory disorders of the gut, such as refractory celiac disease, necrotizing enterocolitis and cytomegalovirus-induced colitis, even though evidence is still scarce and mainly descriptive. Furthermore, Smad7 has been involved in colon carcinogenesis through complex and heterogeneous mechanisms, and Smad7 polymorphisms could influence cancer prognosis. In this article, we review the data about the expression and role of Smad7 in intestinal inflammation and cancer.