Tight junction proteins in gastrointestinal and liver disease

Metabolic Role of Autophagy in the Pathogenesis and Development of NAFLD

Non-alcoholic fatty liver disease (NAFLD) is a spectrum of liver disease, ranging from simple steatosis to hepatitis, fibrosis, cirrhosis, and hepatocellular carcinoma (HCC). Liver fibrosis, which portends a poor prognosis in NAFLD, is characterized by the excessive accumulation of extracellular matrix (ECM) proteins resulting from abnormal wound repair response and metabolic disorders. Various metabolic factors play crucial roles in the progression of NAFLD, including abnormal lipid, bile acid, and endotoxin metabolism, leading to chronic inflammation and hepatic stellate cell (HSC) activation. Autophagy is a conserved process within cells that removes unnecessary or dysfunctional components through a lysosome-dependent regulated mechanism. Accumulating evidence has shown the importance of autophagy in NAFLD and its close relation to NAFLD progression. Thus, regulation of autophagy appears to be beneficial in treating NAFLD and could become an important therapeutic target.

Exploration of the potential mechanism of Baicalin for hepatic fibrosis based on network pharmacology, gut microbiota, and experimental validation

Baicalin (BA) is among the most effective and abundant flavonoids extracted from Scutellaria baicalensis that may be utilized to treat diseases associated with hepatic fibrosis (HF). Through network pharmacology, gut microbiota, and experimental validation, this research intends to elucidate the multi-target mechanism of BA on HF. BA targets were screened using databases and literature. As a result, In the anti-HF mechanism, the BA and 191 HF-associated targets interact, with 9 specific targets indicating that the BA's anti-HF mechanism is closely linked to gut microbiota. Consequently, rat intestinal content samples were obtained and examined using 16S rRNA sequencing. In the BA-treated group, the gut microbiota was positively regulated at the phylum,and genus levels, with Lactobacillus performing significantly. The study concluded that BA has a multi-targeted anti-HF effect and has changed the gut microbial ecosystem.

Colitis aggravated by Mrgprb2 knockout is associated with altered immune response, intestinal barrier function and gut microbiota

NEW FINDINGS

What is the central question of this study? What is the role of mas-related G protein-coupled receptor X2 (MRGPRX2/Mrgprb2) in ulcerative colitis in relation to the intestinal flora, intestinal barrier and immune response? What is the main finding and its importance? Knockout of mouse Mrgprb2 aggravates dextran sulfate sodium (DSS)-induced colitis, which is associated with altered gut microbiota and immune response and disruption of the intestinal barrier. MRGPRB2 may have a protective effect on DSS-induced colitis.

ABSTRACT

Ulcerative colitis (UC) is a chronic immune-related disease, and changes in the intestinal microbiota and damage to the intestinal barrier contribute to its pathogenesis. Mast cells (MCs) are widely distributed in the gastrointestinal tract and are thought to be related to the pathogenesis of UC. Human mas-related G protein-coupled receptor X2 (MRGPRX2) and its mouse homologue, Mrgprb2, are selectively expressed on MCs to recruit immune cells and modulate host defence against microbial infection. To investigate the role of Mrgprb2 in UC in mice, we compared the differences between Mrgprb2 knockout (b2KO) male mice and wild-type (WT) male mice with dextran sulfate sodium (DSS)-induced colitis in the severity of clinical symptoms, inflammatory cell infiltration, degree of intestinal barrier damage and composition of the intestinal flora. The results showed that weight loss, disease activity index score, colon shortening and colonic pathological damage were significantly increased in b2KO mice while MC activation, cytokine and chemokine secretion, and inflammatory cell infiltration were decreased. In addition, the abundance and diversity of the intestinal microbiota were reduced in b2KO mice. B2KO mice also exhibited a reduction of probiotics such as norank_f_Muribaculaceae and Lactobacillus and increase of harmful bacteria like Escherichia-Shigella. Intestinal mucosal barrier damage of b2KO mice was more severe than that of WT mice due to the attenuated expression of mucin-2 and occludin. These results demonstrated that MRGPRB2 may have a protective effect on DSS-induced colitis by altering the intestinal flora, participating in barrier repair and recruiting inflammatory cells to eliminate pathogens.

Curcumin alleviates experimental colitis in mice by suppressing necroptosis of intestinal epithelial cells

Curcumin, the primary bioactive substance in turmeric, exhibits potential therapeutic effects on ulcerative colitis. However, its mechanism for regulating necroptosis in colitis has not been fully elucidated. In this study, the effect of curcumin on experimental colitis-induced necroptosis of intestinal epithelial cells was investigated, and its molecular mechanism was further explored. We found that curcumin blocked necroptosis in a dose-dependent manner by inhibiting the phosphorylation of RIP3 and MLKL instead of RIP1 in HT-29 cells. Co-Immunoprecipitation assay showed that curcumin weakened the interaction between RIP1 and RIP3, possibly due to the direct binding of curcumin to RIP3 as suggested by drug affinity responsive target stability analysis. In a classical in vivo model of TNF-α and pan-caspase inhibitor-induced necroptosis in C57BL/6 mice, curcumin potently inhibited systemic inflammatory responses initiated by the necroptosis signaling pathway. Then, using a dextran sodium sulfate-induced colitis model in C57BL/6 mice, we found that curcumin inhibited the expression of p-RIP3 in the intestinal epithelium, reduced intestinal epithelial cells loss, improved the function of the intestinal tight junction barrier, and reduced local intestinal inflammation. Collectively, our findings suggest that curcumin is a potent targeted RIP3 inhibitor with anti-necroptotic and anti-inflammatory effects, maintains intestinal barrier function, and effectively alleviates colitis injury.

Acupuncture treatment for post-stroke depression: Intestinal microbiota and its role

Stroke-induced depression is a common complication and an important risk factor for disability. Besides psychiatric symptoms, depressed patients may also exhibit a variety of gastrointestinal symptoms, and even take gastrointestinal symptoms as the primary reason for medical treatment. It is well documented that stress may disrupt the balance of the gut microbiome in patients suffering from post-stroke depression (PSD), and that disruption of the gut microbiome is closely related to the severity of the condition in depressed patients. Therefore, maintaining the balance of intestinal microbiota can be the focus of research on the mechanism of acupuncture in the treatment of PSD. Furthermore, stroke can be effectively treated with acupuncture at all stages and it may act as a special microecological regulator by regulating intestinal microbiota as well. In this article, we reviewed the studies on changing intestinal microbiota after acupuncture treatment and examined the existing problems and development prospects of acupuncture, microbiome, and poststroke depression, in order to provide new ideas for future acupuncture research.

A monoclonal antibody targeting nonjunctional claudin-1 inhibits fibrosis in patient-derived models by modulating cell plasticity

Tissue fibrosis is a key driver of end-stage organ failure and cancer, overall accounting for up to 45% of deaths in developed countries. There is a large unmet medical need for antifibrotic therapies. Claudin-1 (CLDN1) is a member of the tight junction protein family. Although the role of CLDN1 incorporated in tight junctions is well established, the function of nonjunctional CLDN1 (njCLDN1) is largely unknown. Using highly specific monoclonal antibodies targeting a conformation-dependent epitope of exposed njCLDN1, we show in patient-derived liver three-dimensional fibrosis and human liver chimeric mouse models that CLDN1 is a mediator and target for liver fibrosis. Targeting CLDN1 reverted inflammation-induced hepatocyte profibrogenic signaling and cell fate and suppressed the myofibroblast differentiation of hepatic stellate cells. Safety studies of a fully humanized antibody in nonhuman primates did not reveal any serious adverse events even at high steady-state concentrations. Our results provide preclinical proof of concept for CLDN1-specific monoclonal antibodies for the treatment of advanced liver fibrosis and cancer prevention. Antifibrotic effects in lung and kidney fibrosis models further indicate a role of CLDN1 as a therapeutic target for tissue fibrosis across organs. In conclusion, our data pave the way for further therapeutic exploration of CLDN1-targeting therapies for fibrotic diseases in patients.

Deoxynivalenol triggers porcine intestinal tight junction disorder: Insights from mitochondrial dynamics and mitophagy

Deoxynivalenol (DON) is universally detected trichothecene in most cereal commodities, which is considered as a major hazardous material for human and animal health. Intestine is the most vulnerable organ with higher concentration of DON than other organs, owing to the first defense barrier function to exogenous substances. However, the underling mechanisms about DON-induced intestinal toxicity remain poorly understood. Here, DON poisoning models of IPEC-J2 cells was established to explore adverse effect and the potential mechanism of DON-induced enterotoxicity. Results showed that DON exposure destroyed IPEC-J2 cells morphology. Results showed that DON exposure destroyed IPEC-J2 cells morphology. Intestinal epithelial barrier injury was caused by DON with increasing LDH release, decreasing cell viability as well decreasing tight junction protein expressions (Occludin, N-Cad, ZO-1, Claudin-1 and Claudin-3). Moreover, DON caused mitochondrial dysfunction by opening mitochondrial permeability transition pore and eliminating mitochondrial membrane potential. DON exposure upregulated protein and mRNA expression of mitochondrial fission factors (Drp1, Fis1, MIEF1 and MFF) and mitophagy factors (PINK1, Parkin and LC3), downregulated mitochondrial fusion factors (Mfn1, Mfn2, except OPA1), resulting in mitochondrial dynamics imbalance and mitophagy. Overall, these findings suggested that DON induced tight junction dysfunction in IPEC-J2 cells was related to mitochondrial dynamics-mediated mitophagy.

Decreased ZO1 expression causes loss of time-dependent tight junction function in the liver of ob/ob mice

Diabetes patients are at a high risk of developing complications related to angiopathy and disruption of the signal transduction system. The liver is one of the multiple organs damaged during diabetes. Few studies have evaluated the morphological effects of adhesion factors in diabetic liver. The influence of diurnal variation has been observed in the expression and functioning of adhesion molecules to maintain tissue homeostasis associated with nutrient uptake. The present study demonstrated that the rhythm-influenced functioning of tight junction was impaired in the liver of ob/ob mice. The tight junctions of hepatocytes were loosened during the dark period in control mice compared to those in ob/ob mice, where the hepatocyte gaps remained open throughout the day. The time-dependent expression of zonula occludens 1 (ZO1, encoded by Tjp1 gene) in the liver plays a vital role in the functioning of the tight junction. The time-dependent expression of ZO1 was nullified and its expression was attenuated in the liver of ob/ob mice. ZO1 expression was inhibited at the mRNA and protein levels. The expression rhythm of ZO1 was found to be regulated by heat shock factor (HSF)1/2, the expression of which was reduced in the liver of ob/ob mice. The DNA-binding ability of HSF1/2 was decreased in the liver of ob/ob mice compared to that in control mice. These findings suggest the involvement of impaired expression and functioning of adhesion factors in diabetic liver complications.

Systematic identification and characterization of lncRNAs and lncRNA-miRNA-mRNA networks in the liver of turbot (Scophthalmus maximus L.) induced with Vibrio anguillarum

Long noncoding RNAs (lncRNAs), can regulate mRNA by targeting miRNA in a competing endogenous RNA network, have become a hot topic in the research of fish immune mechanism recent years. While in turbot (Scophthalmus maximus L.), an economically important marine fish, there are limited researches about the role of lncRNAs in its immune response to bacterial infection. In this study, a total of 184 differentially expressed lncRNAs (DElncRNAs) were systematically identified and characterized using whole-transcriptome sequencing of the liver of turbot challenged with Vibrioanguillarum at 0 h (control) and three different time points post infection (2 h, 12 h and 24 h, respectively). Subsequently, GO and KEGG signaling pathways of differentially expressed lncRNAs were analyzed to predict their function. We found that lncRNAs in our results were significantly enriched in several immune-related signaling pathways, including the NOD-like receptor signaling pathway, Toll-like receptor signaling pathway, Cytokine-cytokine receptor, MAPK signaling pathway, phagosome, PPAR signaling pathway and the regulation of autophagy. In addition, a total of 492 DE lncRNA - DE miRNA -DE mRNA networks were identified at three different time points post infection, which were consisted of 102 networks at 2 h, 122 networks at 12 h and 81 networks at 24 h post infection, respectively. Noticeably, 92 of these regulated networks were immune-related. These observations suggested that lncRNAs can regulate the expression of immune-related genes in the response to bacterial infection in turbot. Moreover, our findings would provide a new insight into the immune response of turbot to pathogen infection and lay a foundation for future study.

New Baitouweng decoction combined with fecal microbiota transplantation alleviates DSS-induced colitis in rats by regulating gut microbiota metabolic homeostasis and the STAT3/NF-κB signaling pathway

AIM OF THE STUDY

We aimed to elucidate the synergistic effect and potential mechanism of New Baitouweng Decoction (NBD) combined with fecal microbiota transplantation (FMT) in rats with DSS-induced ulcerative colitis (UC).

MATERIALS AND METHODS

Colitis was induced by 5% (w/v) dextran sulfate sodium (DSS) in drinking water for 7 days. NBD or NBD combined with FMT were administered to the colitis rats. Body weight and disease activity index were measured, and the colon histological change was imaged to further examine the efficacy of NBD and FMT. The specific effects of NBD on STAT3/NF-κB signaling pathway and gut microbiota in rats with UC were also investigated.

RESULTS

The efficacy of NBD in combination with FMT was demonstrated by the lower disease activity index scores; increased tight junction proteins expression; and a lower expression of macrophage marker (F4/80) in colon tissues. NBD combined with FMT elevated the concentrations of short-chain fatty acids and inhibited activation of the JAK2/STAT3/NF-κB related proteins. Furthermore, 16SrDNA sequencing indicated that the gut microbiota in rats with UC was perturbed, in contrast to that in healthy rats. After treatment with NBD and FMT, the diversity and abundance of intestinal flora showed clear improvements. Spearman correlation analysis indicated a strong correlation between specific microbiota and fecal concentrations of acetate, propionate and butyrate.

CONCLUSIONS

The protective mechanism of NBD combined with FMT may be linked to regulation NF-κB/STAT3 and restoration of the intestinal flora.

Downregulation of zinc finger protein 71 in laryngeal squamous cell carcinoma tissues and its potential molecular mechanism and clinical significance: a study based on immunohistochemistry staining and data mining

Background

The molecular mechanism of laryngeal squamous cell carcinoma (LSCC) is not completely clear, which leads to poor prognosis and treatment difficulties for LSCC patients. To date, no study has reported the exact expression level of zinc finger protein 71 (ZNF71) and its molecular mechanism in LSCC.

Methods

In-house immunohistochemistry (IHC) staining (33 LSCC samples and 29 non-LSCC samples) was utilized in analyzing the protein expression level of ZNF71 in LSCC. Gene chips and high-throughput sequencing data collected from multiple public resources (313 LSCC samples and 192 non-LSCC samples) were utilized in analyzing the exact mRNA expression level of ZNF71 in LSCC. Single-cell RNA sequencing (scRNA-seq) data was used to explore the expression status of ZNF71 in different LSCC subpopulations. Enrichment analysis of ZNF71, its positively and differentially co-expressed genes (PDCEGs), and its downstream target genes was employed to detect the potential molecular mechanism of ZNF71 in LSCC. Moreover, we conducted correlation analysis between ZNF71 expression and immune infiltration.

Results

ZNF71 was downregulated at the protein level (area under the curve [AUC] = 0.93, p < 0.0001) and the mRNA level (AUC = 0.71, p = 0.023) in LSCC tissues. Patients with nodal metastasis had lower protein expression level of ZNF71 than patients without nodal metastasis (p < 0.05), and male LSCC patients had lower mRNA expression level of ZNF71 than female LSCC patients (p < 0.01). ZNF71 was absent in different LSCC subpopulations, including cancer cells, plasma cells, and tumor-infiltrated immune cells, based on scRNA-seq analysis. Enrichment analysis showed that ZNF71 and its PDCEGs may influence the progression of LSCC by regulating downstream target genes of ZNF71. These downstream target genes of ZNF71 were mainly enriched in tight junctions. Moreover, downregulation of ZNF71 may influence the development and even therapy of LSCC by reducing immune infiltration.

Conclusion

Downregulation of ZNF71 may promote the progression of LSCC by reducing tight junctions and immune infiltration; this requires further study.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12957-022-02823-8.

Blood-Brain Barrier Dysfunction in the Pathogenesis of Major Depressive Disorder

Major depression represents a complex and prevalent psychological disease that is characterized by persistent depressed mood, impaired cognitive function and complicated pathophysiological and neuroendocrine alterations. Despite the multifactorial etiology of depression, one of the most recent factors to be identified as playing a critical role in the development of depression is blood-brain barrier (BBB) disruption. The occurrence of BBB integrity disruption contributes to the disturbance of brain homeostasis and leads to complications of neurological diseases, such as stroke, chronic neurodegenerative disorders, neuroinflammatory disorders. Recently, BBB associated tight junction disruption has been shown to implicate in the pathophysiology of depression and contribute to increased susceptibility to depression. However, the underlying mechanisms and importance of BBB damage in depression remains largely unknown. This review highlights how BBB disruption regulates the depression process and the possible molecular mechanisms involved in development of depression-induced BBB dysfunction. Moreover, insight on promising therapeutic targets for treatment of depression with associated BBB dysfunctions are also discussed.

The influence of different proton pump inhibitors and potassium-competitive acid blockers on indomethacin-induced small intestinal injury

BACKGROUND AND AIM

The influence of gastric acid inhibitors (GAIs) on nonsteroidal anti-inflammatory drug (NSAID)-induced enteropathy is controversial. Herein, the influences of different GAIs on NSAID-induced intestinal injury and the underlying mechanisms are clarified.

METHODS

Indomethacin (IND; 10 mg/kg/day) was administered to mice to induce small intestinal injury. Disease activity was examined macroscopically and histologically. The permeability of small intestine was evaluated by measuring plasma lipopolysaccharide levels. 16S rDNA sequencing was performed to determine the composition of intestinal flora.

RESULTS

Among the four GAIs, ilaprazole (IPZ) significantly attenuated IND-induced small intestinal injury and maintained the integrity of the mucosal barrier. Omeprazole (OPZ) and vonoprazan (VPZ) ameliorated ulceration without significant differences, while rabeprazole (RPZ) failed to protect against the injury. To explore the potential mechanism, we investigated changes in the gut microbiota mediated by GAIs. After 5-day administration, GAIs significantly altered the composition of the gut microbiota. The IND group had a significant decrease in alpha diversity compared with the control group, and this decrease was reversed by OPZ and IPZ treatment, respectively. After IPZ treatment, the community membership was more assembled in the control group than the IND group. Further, we found that Lactobacillus was significantly increased in the groups of OPZ, IPZ, and VPZ, while Bacteroides was significantly increased in the RPZ group.

CONCLUSION

Our results indicated that GAIs have different influences on the mucosal barrier, possibly by altering the composition of intestinal microbiota, and the impacts mediated by various GAIs in the IND-induced intestinal damage model seem different.

Cold exposure-induced endoplasmic reticulum stress regulates autophagy through the SIRT2/FoxO1 signaling pathway

Cold is a factor affecting health in humans and animals. The liver, a major metabolic center, is highly susceptible to ambient air temperature. Recent studies have shown that endoplasmic reticulum (ER) stress is associated with the liver, and regulates the occurrence and development of liver injury and autophagy. However, the mechanism underlying the relationship between cold exposure and ER stress in the liver is not well understood. In this study, we investigated the effect of ER stress on liver autophagy and its mechanism under cold exposure. AML12 cells were treated with Tg to construct an ER stress model, and the level of autophagy increased. To further explore the mechanism through which ER stress regulates autophagy, we knocked down SIRT2 with shRNA in Tg-treated AML12 cells. Knockdown of SIRT2 significantly increased ER stress and autophagy, increased FoxO1 acetylation, and promoted its entry into the nucleus. To further verify the results of in vitro experiments, we exposed mice to 4°C for 3 h per day for 3 weeks to exacerbate the burden on the liver after cold exposure. Cold exposure damaged the structure and function of the liver and promoted the inflammatory response. It also activated ER stress and promoted autophagy. In addition, cold exposure inhibited the expression of SIRT2, promoted FoxO1 acetylation, and enhanced the interaction with autophagy. Our findings indicated that cold exposure induces liver damage, ER stress, and autophagy through the SIRT2/FoxO1 pathway. These findings suggest that SIRT2 may be a potential target for regulating health under cold exposure.

Evaluation of Caco-2 and human intestinal epithelial cells as in vitro models of colonic and small intestinal integrity

Although the colonic cell line Caco-2 is widely used as a model of the small intestinal barrier function, it has limitations such as overestimated transepithelial electrical resistance (TEER) compared to in vivo conditions. Therefore, we investigated Human Intestinal Epithelial Cells (HIECs) as an alternative in vitro model.

We explored whether cell seeding number of HIEC-6, and the number of incubation days for HIEC and Caco-2 cells had an impact on TEER, and tight junction expression was examined for both cell lines via immunofluorescence in the presence and absence of probiotic bacteria.

We observed no significant difference in TEER readings for either cell lines when cultured for different days. Further, the HIEC TEER readings did not change with increased seeding number and were not significantly different from a control with no cells. HIECs expressed Claudin-1 and Zonula Occludens-1 but not Occludin. Caco-2 co-culture with probiotic bacteria demonstrated a significant increase in TEER, particularly for the lactobacillus strains, whereas HIEC TEER did not respond to bacterial co-incubation.

Our study shows that although HIECs express certain TJ proteins, a significant TEER was not observed, likely due to the embryonic origin of the cells, which limits the application of this cell line as a suitable model for small intestinal barrier function.

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Human embryonic intestinal epithelial cells cannot form a significant barrier.

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Contrary to Caco-2 cells HIECs do not express the tight junction protein occludin.

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Probiotic bacteria induce a tight barrier in Caco-2 cells but not in HIECs.

Influence of Heat Stress on Intestinal Epithelial Barrier Function, Tight Junction Protein, and Immune and Reproductive Physiology

The potential threat of global warming in the 21^st century is on the ecosystem through many aspects, including the negative impact of rising global temperature on the health of humans and animals, especially domestic animals. The damage caused by heat stress to animals has been more and more significant as the worldwide climate continues to rise, along with the breeding industry's expanding scale and stocking density, and it has become the most important stress-causing factor in southern China. In this review, we described the effects of heat stress on animal immune organs and immune system. The much-debated topic is how hyperthermia affects the tight junction barrier. Heat stress also induces inflammation in the body of animals causing low body weight and loss of appetite. This review also discussed that heat stress leads to hepatic disorder, and it also damages the intestine. The small intestine experiences ischemia, and the permeability of the intestine increases. Furthermore, the oxidative stress and mitogen-activated protein kinase (MAPK) pathways have a significant role in stress-induced cellular and organ injury. The study has shown that MAPK activity in the small intestine was increased by heat stress. Heat stress caused extreme small intestine damage, enhanced oxidative stress, and activated MAPK signaling pathways.

A Novel hepatocellular carcinoma specific hypoxic related signature for predicting prognosis and therapeutic responses

Hypoxia is an important feature of the tumor microenvironment(TME) and is closely associated with cancer metastasis, immune evasion, and drug resistance. However, the precise role of hypoxia in hepatocellular carcinoma(HCC), as well as its influence on the TME, and drug sensitivity remains unclear. We found the excellent survival prediction value of Hypoxia_DEGs_Score model. In hypoxic HCC, somatic mutation, copy number variation, and DNA methylation were closely related to hypoxic changes and affected tumorigenesis, progression, metastasis, and drug resistance. In HCC, aggravated hypoxic stress was found to be accompanied by an immune exclusion phenotype and increased infiltration of immunosuppressive cells. In the validation cohort, patients with high Hypoxia_DEGs_Score were found to have worse immunotherapeutic outcomes and prognoses, and may benefit from drugs against cell cycle signaling pathways rather than those inhibiting the PI3K/mTOR pathway. Hypoxia_DEGs_Score has an excellent predictive capability of changes in the TME, the efficacy of immunotherapy, and the response of drugs. Therefore, Hypoxia_DEGs_Score can help develop personalized immunotherapy regimens and improve the prognosis of HCC patients.

Finasteride Alleviates High Fat Associated Protein-Overload Nephropathy by Inhibiting Trimethylamine N-Oxide Synthesis and Regulating Gut Microbiota

Unhealthy diet especially high-fat diet (HFD) is the major cause of hyperlipidemia leading to deterioration of chronic kidney diseases (CKD) in patients. Trimethylamine N-oxide (TMAO) is a gut-derived uremic toxin. Our previous clinical study demonstrated that the elevation of TMAO was positively correlated with CKD progression. Finasteride, a competitive and specific inhibitor of type II 5a-reductase, has been reported recently to be able to downregulate plasma TMAO level thus preventing the onset of atherosclerosis by our research group. In this study, we established a protein-overload nephropathy CKD mouse model by bovine serum albumin (BSA) injection to investigate whether hyperlipidemia could accelerate CKD progression and the underlying mechanisms. Finasteride was administrated to explore its potential therapeutic effects. The results of biochemical analyses and pathological examination showed that HFD-induced hyperlipidemia led to aggravated protein-overload nephropathy in mice along with an elevated level of circulating TMAO, which can be alleviated by finasteride treatment possibly through inhibition of Fmo3 in liver. The 16 S rRNA sequencing results indicated that HFD feeding altered the composition and distribution of gut microbiota in CKD mice contributing to the enhanced level of TMAO precursor TMA, while finasteride could exert beneficial effects via promoting the abundance of Alistipes_senegalensis and Akkermansia_muciniphila. Immunofluorescence staining (IF) and qRT-PCR results demonstrated the disruption of intestinal barrier by decreased expression of tight junction proteins including Claudin-1 and Zo-1 in HFD-fed CKD mice, which can be rescued by finasteride treatment. Cytokine arrays and redox status analyses revealed an upregulated inflammatory level and oxidative stress after HFD feeding in CKO mice, and finasteride-treatment could alleviate these lesions. To summarize, our study suggested that finasteride could alleviate HFD-associated deterioration of protein-overload nephropathy in mice by inhibition of TMAO synthesis and regulation of gut microbiota.

Selenium-enriched Bifidobacterium longum DD98 effectively ameliorates dextran sulfate sodium-induced ulcerative colitis in mice

The pathogenesis of ulcerative colitis (UC) is complicated with impaired intestinal epithelial barrier and imbalanced gut microbiota. Both selenium and probiotics have shown effects in regulating intestinal flora and ameliorating UC. The objective of this study is to investigate the alleviating effects of Selenium-enriched Bifidobacterium longum DD98 (Se-B. longum DD98) on dextran sulfate sodium (DSS)-induced colitis in mice and explore the underlying mechanism. After treatment of B. longum DD98, Se-B. longum DD98, and sulfasalazine for 3 weeks, the disease severity of UC mice was decreased, with colon lengthened and pathological phenotype improved. The expression of pro-inflammatory cytokines and oxidative stress parameters were also decreased. Thus, Se-B. longum DD98 showed a stronger effect on relieving the aforementioned symptoms caused by DSS-induced colitis. Exploration of the potential mechanism demonstrated that Se-B. longum DD98 showed higher activities to suppress the inflammatory response by inhibiting the activation of the toll-like receptor 4 (TLR4), compared to B. longum DD98 and sulfasalazine. Se-B. longum DD98 also significantly improved the intestinal barrier integrity by increasing the expression of tight junction proteins including ZO-1 and occludin. 16S rDNA sequencing analyses showed that Se-B. longum DD98 improved the diversity of the intestinal flora and promoted the abundance of health-benefiting taxa including Lachnospiraceae, Lactobacillaceae, and Prevotellaceae in family level. In conclusion, compared to B. longum DD98 and sulfasalazine, Se-B. longum DD98 showed stronger therapeutic effects on DSS-induced colitis in mice and might be a promising candidate for the treatment of UC.

Lacticaseibacillus rhamnosus LS8 Ameliorates Azoxymethane/Dextran Sulfate Sodium-Induced Colitis-Associated Tumorigenesis in Mice via Regulating Gut Microbiota and Inhibiting Inflammation

Gut microbiota dysbiosis may promote the process of colorectal cancer (CRC). Lacticaseibacillus rhamnosus LS8 (LRL) is a potential gut microbiota regulating strain because it can produce a novel antimicrobial substance (like cycloalanopine). In addition, this probiotic had an inflammation-ameliorating effect on the dextran sulfate sodium (DSS)-induced colitis mice. However, it is not known whether treatment with this probiotic could ameliorate colitis-associated CRC via regulating gut microbiota. In this study, a CRC mouse model was induced by a single intraperitoneal injection of azoxymethane (AOM, 10 mg/kg) and followed by three 7-day cycles of 2% DSS administration. Results showed that LRL could inhibit tumor formation. Moreover, LRL enhanced the gut barrier by preventing goblet cell loss and promoting the expression of ZO-1, occludin, and claudin-1. Furthermore, LRL ameliorated gut microbiota dysbiosis, which was conducive to the growth of beneficial bacteria (e.g., Faecalibaculum and Akkermansia), and further led to an increase in SCFAs and a decrease in LPS. In addition, LRL alleviated colonic inflammation by inhibiting the overexpression of TLR4/NF-κB, pro-inflammatory cytokines (TNF-α, IL-1β, IL-6, IL-γ, and IL-17a), and chemokines (Cxcl1, Cxcl2, Cxcl3, Cxcl5, and Cxcl7). In conclusion, LRL could alleviate CRC by regulating gut microbiota and preventing gut barrier damage and inflammation.

Relief Effects of Icariin on Inflammation-Induced Decrease of Tight Junctions in Intestinal Epithelial Cells

Inflammatory cytokines including TNF-α and IL-1β impair intestinal barrier function in aging by disrupting intestinal tight junction integrity. Icariin (ICA) has a variety of pharmacological effects. Indeed, ICA produces anti-inflammatory, anti-oxidative stress, and inhibitory effects on microRNA (miRNA) expression. This study was to explore whether ICA could alleviate inflammation-associated intestinal barrier function impairment in aging and its underlying mechanism. Of particular interest, network pharmacology prediction indicated the potential therapeutic impacts of ICA for the treatment of colitis. Then, rats were used to study whether ICA has a protective effect on the reduction of tight junctions caused by inflammatory cytokines. Next, Caco-2 cell monolayers were used to explore the mechanism by which ICA alleviates the down-regulation of tight junctions. Network pharmacology prediction revealed that ICA alleviated colitis via suppressing oxidative stress. After ICA intervention, expressions of inflammatory cytokines were reduced, but tight junctions, antioxidant enzymes in aging rats were up-regulated. ICA reversed the TNF-α-induced decrease in abundance of Occludin protein in Caco-2 cell monolayers. Meanwhile, ICA alleviated the increase in permeability and expression of miR-122a. However, the protective effect of ICA was markedly attenuated after transfection with miR-122a mimics. In conclusion, ICA reduced the expressions of Occludin, Claudin1, and Claudin5 in colon, which were related to the reduction of TNF-α and IL-1β and alleviation of colonic in vivore. And ICA attenuated TNF-α-induced Occludin disruption and epithelial barrier impairment by decreasing miR-122a expression in Caco-2 cell monolayers.

The Anti-Obesity and Anti-Inflammatory Capabilities of Pterostilbene and its Colonic Metabolite Pinostilbene Protect against Tight Junction Disruption from Western Diet Feeding

SCOPE

Tight junctions (TJs) are a member of the intestinal epithelium barrier that provides the first line of protection against external factors. Anti-obesity and protective effects of pterostilbene (PSB) on TJs have previously been reported, but the effect of its colonic metabolite, pinostilbene (PIN), is less understood.

METHODS AND RESULTS

A 16-week animal model fed with western-diet to induced colonic TJs disruption was designed, supplemented with PSB and PIN to evaluate their potent in colonic TJ protection. The results showed that both PSB and PIN exerted suppressive effects on obesity, hepatic steatosis, and chronic inflammation in western-diet-fed mice. Western-diet feeding significantly reduced expression of TJ proteins, including ZO-1, occludin, and claudin-1, while PSB and PIN supplementation effectively protected TJ proteins against disruption. Increment in serum, hepatic, and mesenteric pro-inflammatory cytokines suggest their probable involvement in TJ disruption supported with the findings in macrophage polarization. The adverse were revered by PSB and PIN. The protective effect of PSB and PIN on TJ proteins may stem from their anti-inflammation capabilities.

CONCLUSION

This is the first study suggesting that PIN, the metabolite of PSB, demonstrates a similar protective effect on colonic TJ proteins via its anti-obesity, hepatic protection and anti-inflammatory capabilities. This article is protected by copyright. All rights reserved.

Fufang Zhenzhu Tiaozhi Capsule Prevents Intestinal Inflammation and Barrier Disruption in Mice With Non-Alcoholic Steatohepatitis

Nonalcoholic steatohepatitis (NASH) has become a major cause of liver transplantation and liver-associated death. Targeting the gut-liver axis is a potential therapy for NASH. The Fufang Zhenzhu Tiaozhi (FTZ) capsule, a traditional Chinese medicine commonly used in clinical practice, has recently emerged as a promising drug candidate for metabolic diseases such as NASH. The present study aimed to investigate whether FTZ exerts an anti-NASH effect by targeting the gut-liver axis. Mice were fed with a high-fat diet (HFD) for 20 weeks to induce NASH. HFD-fed mice were daily intragastrically administrated with FTZ at 10 weeks after tbe initiation of HFD feeding. The mRNA levels of genes associated with the intestinal tight junction, lipid metabolism, and inflammation were determined by the q-PCR assay. Hepatic pathology was evaluated by H&E staining. The gut microbiota was analyzed by 16S rRNA gene sequencing. FTZ attenuated HFD-induced obesity, insulin resistance, and hepatic steatosis in mice. FTZ treatment decreased the elevated levels of serum aminotransferases and liver triglyceride in NASH mice. Furthermore, FTZ treatment reduced hepatic inflammatory cell infiltration and fibrosis in mice. In addition, FTZ attenuated the intestinal inflammatory response and improved intestinal barrier function. Mechanistically, FTZ-treated mice showed a different gut microbiota composition compared with that in HFD-fed mice. Finally, we identified eight differential metabolites that may contribute to the improvement of NASH with FTZ treatment. In summary, FTZ ameliorates NASH by inhibiting gut inflammation, improving intestinal barrier function, and modulating intestinal microbiota composition.

EZH2-mediated suppression of CLDN1 leads to barrier dysfunction in PPI-refractory gastroesophageal reflux disease

BACKGROUND

PPI-refractory gastroesophageal reflux disease (RGERD) is characterized as the existence of reflux symptoms resistant to optimized PPI treatment. Alleviated mucosal integrity has been regarded as one of the mechanisms of RGERD.

METHODS

RNA sequencing analysis and GSEA were performed. Human biopsy samples, cell lines, and rat models were recruited. Trans-epithelial electrical resistance (TEER) was tested and a FITC-dextran flux assay was performed to detect barrier permeability. Tissue morphology was evaluated using HE staining, while gene expression was measured by qRT-PCR, western blotting, flow cytometry, immunofluorescence, immunohistochemistry, and chromatin immunoprecipitation (ChIP) analysis.

RESULTS

The tight junction protein Claudin-1 is significantly weakened in the RGERD epithelium, while levels of EZH2-mediated H3K27me3 were increased. Forced EZH2 expression in epithelial cells led to H3K27me3 accumulation and Claudin-1 suppression, which consequently caused epithelial barrier dysfunction. Notably, studies on esophagogastroduodenal anastomosis (EGDA) rat models showed the attenuation of Claudin-1 level and barrier function could be rescued by an Ezh2 inhibitor GSK126. ChIP analysis followed by qPCR (ChIP-qPCR) revealed H3K27me3 suppressed CLDN1 via accumulating at the TSS area.

CONCLUSION

For the first time, we explored the attenuated tight junction of RGERD, demonstrating a potential underlying mechanism that EZH2-mediated H3K27me3 could impair esophageal epithelial barrier function by suppressing the transcription of CLDN1.

Flavivirus NS1 Triggers Tissue-Specific Disassembly of Intercellular Junctions Leading to Barrier Dysfunction and Vascular Leak in a GSK-3β-Dependent Manner

The flavivirus nonstructural protein 1 (NS1) is secreted from infected cells and contributes to endothelial barrier dysfunction and vascular leak in a tissue-dependent manner. This phenomenon occurs in part via disruption of the endothelial glycocalyx layer (EGL) lining the endothelium. Additionally, we and others have shown that soluble DENV NS1 induces disassembly of intercellular junctions (IJCs), a group of cellular proteins critical for maintaining endothelial homeostasis and regulating vascular permeability; however, the specific mechanisms by which NS1 mediates IJC disruption remain unclear. Here, we investigated the relative contribution of five flavivirus NS1 proteins, from dengue (DENV), Zika (ZIKV), West Nile (WNV), Japanese encephalitis (JEV), and yellow fever (YFV) viruses, to the expression and localization of the intercellular junction proteins β-catenin and VE-cadherin in endothelial cells from human umbilical vein and brain tissues. We found that flavivirus NS1 induced the mislocalization of β-catenin and VE-cadherin in a tissue-dependent manner, reflecting flavivirus disease tropism. Mechanistically, we observed that NS1 treatment of cells triggered internalization of VE-cadherin, likely via clathrin-mediated endocytosis, and phosphorylation of β-catenin, part of a canonical IJC remodeling pathway during breakdown of endothelial barriers that activates glycogen synthase kinase-3β (GSK-3β). Supporting this model, we found that a chemical inhibitor of GSK-3β reduced both NS1-induced permeability of human umbilical vein and brain microvascular endothelial cell monolayers in vitro and vascular leakage in a mouse dorsal intradermal model. These findings provide insight into the molecular mechanisms regulating NS1-mediated endothelial dysfunction and identify GSK-3β as a potential therapeutic target for treatment of vascular leakage during severe dengue disease.

Polystyrene Nanoplastics Toxicity to Zebrafish: Dysregulation of the Brain-Intestine-Microbiota Axis

In animal species, the brain-gut axis is a complex bidirectional network between the gastrointestinal (GI) tract and the central nervous system (CNS) consisting of numerous microbial, immune, neuronal, and hormonal pathways that profoundly impact organism development and health. Although nanoplastics (NPs) have been shown to cause intestinal and neural toxicity in fish, the role of the neurotransmitter and intestinal microbiota interactions in the underlying mechanism of toxicity, particularly at environmentally relevant contaminant concentrations, remains unknown. Here, the effect of 44 nm polystyrene nanoplastics (PS-NPs) on the brain-intestine-microbe axis and embryo-larval development in zebrafish (Danio rerio) was investigated. Exposure to 1, 10, and 100 μg/L PS-NPs for 30 days inhibited growth and adversely affected inflammatory responses and intestinal permeability. Targeted metabolomics analysis revealed an alteration of 42 metabolites involved in neurotransmission. The content of 3,4-dihydroxyphenylacetic acid (DOPAC; dopamine metabolite formed by monoamine oxidase activity) was significantly decreased in a dose-dependent manner after PS-NP exposure. Changes in the 14 metabolites correlated with changes to 3 microbial groups, including Proteobacteria, Firmicutes, and Bacteroidetes, as compared to the control group. A significant relationship between Firmicutes and homovanillic acid (0.466, Pearson correlation coefficient) was evident. Eight altered metabolites (l-glutamine (Gln), 5-hydroxyindoleacetic acid (5-HIAA), serotonin, 5-hydroxytryptophan (5-HTP), l-cysteine (Cys), l-glutamic acid (Glu), norepinephrine (NE), and l-tryptophan (l-Trp)) had a negative relationship with Proteobacteria although histamine (His) and acetylcholine chloride (ACh chloride) levels were positively correlated with Proteobacteria. An Associated Network analysis showed that Firmicutes and Bacteroidetes were highly correlated (0.969). Furthermore, PS-NPs accumulated in the gastrointestinal tract of offspring and impaired development of F1 (2 h post-fertilization) embryos, including reduced spontaneous movements, hatching rate, and length. This demonstration of transgenerational deficits is of particular concern. These findings suggest that PS-NPs cause intestinal inflammation, growth inhibition, and restricted development of zebrafish, which are strongly linked to the disrupted regulation within the brain-intestine-microbiota axis. Our study provides insights into how xenobiotics can disrupt the regulation of brain-intestine-microbiota and suggests that these end points should be taken into account when assessing environmental health risks of PS-NPs to aquatic organisms.

Identification of a protective Bacteroides strain of alcoholic liver disease and its synergistic effect with pectin

The depletion of Bacteroides in the gut is closely correlated with the progression of alcoholic liver disease (ALD). This study aimed to identify Bacteroides strains with protective effects against ALD and evaluate the synergistic effects of Bacteroides and pectin in this disease. Mice were fed Lieber-DeCarli alcohol diet to establish an experimental ALD model and pre-treated with 4 Bacteroides strains. The severity of the liver injury, hepatic steatosis, and inflammation was evaluated through histological and biochemical assays. We found that Bacteroides fragilis ATCC25285 had the best protective effects against ALD strains by alleviating both ethanol-induced liver injury and steatosis. B. fragilis ATCC25285 could counteract inflammatory reactions in ALD by producing short-chain fat acids (SCFAs) and enhancing the intestinal barrier. In the subsequent experiment, the synbiotic combination of B. fragilis ATCC25285 and pectin was evaluated and the underlying mechanisms were investigated by metabolomic and microbiome analyses. The combination elicited superior anti-ALD effects than the individual agents used alone. The synergistic effects of B. fragilis ATCC25285 and pectin were driven by modulating gut microbiota, improving tryptophan metabolism, and regulating intestinal immune function. Based on our findings, the combination of B. fragilis ATCC25285 and pectin can be considered a potential treatment for ALD. KEY POINTS: • B. fragilis ATCC25285 was identified as a protective Bacteroides strain against ALD. • The synbiotic combination of B. fragilis and pectin has better anti-ALD effects. • The synbiotic combination modulates gut microbiota and tryptophan metabolism.

A novel ladderlectin from hybrid crucian carp possesses antimicrobial activity and protects intestinal mucosal barrier against Aeromonas hydrophila infection

Ladderlectin is a pattern recognition receptor (PRR) in fish that is critical for rapid detection of bacteria in vitro, but the immunological function of ladderlectin in vivo is essentially unknown. In this study, we examined the expression and function of a ladderlectin homologue (WR-ladderlectin) from hybrid crucian carp. WR-ladderlectin contains 157 amino acids and possesses the conserved C-type lectin domain. WR-ladderlectin is mainly expressed in the intestine and is upregulated by bacterial infection. Recombinant WR-ladderlectin (rWR-ladderlectin) agglutinated Aeromonas hydrophila and Escherichia coli. rWR-ladderlectin also bound the A. hydrophila and E. coli in a protein dose-dependent manner. As well as its ability to bind bacterial cells, rWR-ladderlectin displayed apparent bactericidal activity against A. hydrophila and E. coli in vitro. When introduced in vivo, rWR-ladderlectin induced significant expression of the antimicrobial molecules and tight junctions in the intestine. In addition, rWR-ladderlectin prevented significant decrease in the length of intestine villus and enhanced the host's resistance to bacterial infection. These results indicate that WR-ladderlectin is a classic pattern recognition molecule that protects intestinal mucosal barrier against bacterial infection.

Extrahepatic manifestations of progressive familial intrahepatic cholestasis syndromes: Presentation of a case series and literature review

BACKGROUND AND AIMS

Progressive familial intrahepatic cholestasis (PFIC) is a collective term for a heterogenous group of rare, inherited cholestasis syndromes. The number of genes underlying the clinical PFIC phenotype is still increasing. While progressive liver disease and its sequelae such as portal hypertension, pruritus and hepatocellular carcinoma determine transplant-free survival, extrahepatic manifestations may cause relevant morbidity.

METHODS

We performed a literature search for extrahepatic manifestations of PFIC associated with pathogenic gene variants in ATP8B1, ABCB11, ABCB4, TJP2, NR1H4 and MYO5B. To illustrate the extrahepatic symptoms described in the literature, PFIC cases from our centres were revisited.

RESULTS

Extrahepatic symptoms are common in PFIC subtypes, where the affected gene is expressed at high levels in other tissues. While most liver-associated complications resolve after successful orthotopic liver transplantation (OLT), some extrahepatic symptoms show no response or even worsen after OLT.

CONCLUSION

The spectrum of extrahepatic manifestations in PFIC highlights essential, non-redundant roles of the affected genes in other organs. Extrahepatic features contribute towards low health-related quality of life (HRQOL) and morbidity in PFIC. While OLT is often the only remaining, curative treatment, potential extrahepatic manifestations need to be carefully monitored and addressed.

The Probiotic Strain Bifidobacterium animalis ssp. lactis HY8002 Potentially Improves the Mucosal Integrity of an Altered Intestinal Microbial Environment

Intestinal microbiota mediate the development and regulation of the intestinal immune system either directly or indirectly. Particularly, Bifidobacterium spp. play an important role in regulating the intestinal immunity and intestinal barrier. We demonstrated that Bifidobacterium animalis ssp. lactis HY8002, selected from eight Bifidobacterium strains by in vitro experimentation, had exceptional resistance to digestive tract conditions and high adhesion to intestinal epithelial cells and a positive effect on immunoglobulin A (IgA) secretion by Peyer’s patch cells. Moreover, HY8002 restored the expression of tight junction-related genes, initially reduced by lipopolysaccharide treatment, to normal levels in human intestinal epithelial cells. Notably, HY8002 restored kanamycin-induced reduction in Peyer’s patch cell numbers, serum and fecal IgA levels, and zonula occludens 1 and Toll-like receptor 2 levels in the mouse small intestine. In addition, HY8002 restores microbiome composition disturbed by kanamycin, and these microbiome changes have been found to correlate with TLR2 levels in the small intestine. Moreover, the ability of HY8002 to enhance IgA in Peyer’s patch cells and ZO-1 levels in intestinal epithelial cells was significantly inhibited by a TLR2 blocking antibody, which suggests that the HY8002 improve intestinal barrier function via TLR2. Finally, whole-genome sequencing of HY8002 revealed that it did not possess any known virulence factors. Therefore, HY8002 is a promising, functional probiotic supplement to improve intestinal barrier function by improving intestinal immunity and microbiota balance.

Role of zonula occludens in gastrointestinal and liver cancers

A growing body of evidence suggests that tight junction (TJ) proteins play a crucial role in the pathogenesis of various diseases, including gastrointestinal (GI) cancer and hepatocellular carcinoma (HCC). TJ proteins primarily maintain the epithelial and endothelial cells intact together through integral proteins however, recent reports suggest that they also regulate gene expression necessary for cell proliferation, angiogenesis, and metastasis through adapter proteins such as zonula occludens (ZO). ZO proteins are membrane-associated cytosolic scaffolding proteins that modulate cell proliferation by interacting with several transcription factors. Reduced ZO proteins in GI cancer and HCC are correlated with tumor development and poor prognosis. Pubmed has searched for using the keyword ZO and gastric cancer, ZO and cancer, and ZO and HCC for the last ten years to date. This review summarized the role of ZO proteins in cell proliferation and their expression in GI cancer and HCC. Furthermore, therapeutic interventions targeting ZO in GI and liver cancers are reviewed.

Radix Puerariae thomsonii polysaccharide (RPP) improves inflammation and lipid peroxidation in alcohol and high-fat diet mice by regulating gut microbiota

Polysaccharides are the important active constituents of Radix Puerariae thomsonii. Numerous studies have shown that polysaccharides can regulate gut microbiota, repair intestinal barrier, and affect the microbiota-intestine-liver axis, thereby showing therapeutic effects on metabolic disorders. In this study, Radix Puerariae thomsonii polysaccharide (RPP) was extracted from Radix Puerariae thomsonii. The average Mw of RPP was determined to be 1.09 × 10⁵ Da and the monosaccharide composition showed it consisted of glucose. The effects and underlying mechanisms of RPP on fatty liver were studied using C57/BL6J mice induced by alcohol and high-fat diet. The results showed that the oral supplementation of RPP could alleviate alcohol and high-fat diet-induced hepatic injury and steatosis. RPP also promoted intestinal barrier integrity and reduced inflammation through NF-κB signaling pathway. RPP could ameliorate the lipid peroxidation by AMPK/NADPH oxidase signaling pathway. Additionally, these improvements might be related to the enrichment of intestinal bacteria Parabacteroides (promote intestinal barrier integrity) and Prevotellaceae UCG 001 (activation of AMPK signaling pathway). These results demonstrated that RPP could improve inflammation and lipid peroxidation in the alcohol and high-fat diet mouse by restoring the intestinal barrier integrity and regulating the gut microbiota. This suggested that RPP was a potential food supplement for the treatment of fatty liver disease.

Urolithin A attenuates arsenic-induced gut barrier dysfunction

Environmental chemicals such as inorganic arsenic (iAs) significantly contribute to redox toxicity in the human body by enhancing oxidative stress. Imbalanced oxidative stress rapidly interferes with gut homeostasis and affects variety of cellular processes such as proliferation, apoptosis, and maintenance of intestinal barrier integrity. It has been shown that gut microbiota are essential to protect against iAs3+-induced toxicity. However, the effect of microbial metabolites on iAs3+-induced toxicity and loss of gut barrier integrity has not been investigated. The objectives of the study are to investigate impact of iAs on gut barrier function and determine benefits of gut microbial metabolite, urolithin A (UroA) against iAs3+-induced adversaries on gut epithelium. We have utilized both colon epithelial cells and in a human intestinal 3D organoid model system to investigate iAs3+-induced cell toxicity, oxidative stress, and gut barrier dysfunction in the presence or absence of UroA. Here, we report that treatment with UroA attenuated iAs3+-induced cell toxicity, apoptosis, and oxidative stress in colon epithelial cells. Moreover, our data suggest that UroA significantly reduces iAs3+-induced gut barrier permeability and inflammatory markers in both colon epithelial cells and in a human intestinal 3D organoid model system. Mechanistically, UroA protected against iAs3+-induced disruption of tight junctional proteins in intestinal epithelial cells through blockade of oxidative stress and markers of inflammation. Taken together, our studies for the first time suggest that microbial metabolites such as UroA can potentially be used to protect against environmental hazards by reducing intestinal oxidative stress and by enhancing gut barrier function.

5-Hydroxymethylfurfural Exerts Negative Effects on Gastric Mucosal Epithelial Cells by Inducing Oxidative Stress, Apoptosis, and Tight Junction Disruption

5-Hydroxymethylfurfural (5-HMF) is a processing byproduct present in foods that are consumed daily by humans, and the diet is the principal route for human exposure to it. However, its adverse effects on gastric epithelial cells are not fully understood. Based on the half inhibitory concentration value, concentrations of HMF of 2, 4, 8, and 16 mM were selected for this study. After 5-HMF treatment for 24 h, the number of living cells decreased to 89.61 ± 0.48, 77.30 ± 0.57, 58.75 ± 0.36, and 19.61 ± 0.40% of the control, respectively. Apoptosis activated through both the death receptor and mitochondrial pathways was confirmed to be the primary mode of HMF-induced cell death. Further analysis revealed that the reactive oxygen species (ROS) levels in GES-1 cells increased 1.7-6.5 fold after exposure to 5-HMF. Moreover, the inhibition of ROS by N-acetylcysteine blocked HMF-induced apoptosis and cell proliferation suppression, indicating that oxidative stress was important in HMF-induced apoptosis. Besides, after 5-HMF treatment, the gene expressions of occludin and ZO-1 were reduced by 1.1-3.4 fold and 2.0-9.4 fold, respectively. The cell surface morphology and tight junction-related protein expression analysis also revealed the destructive effect of 5-HMF on tight junction integrity. Our research highlights a potential mechanism of HMF-induced toxicity in GES-1 cells and provides additional information on the health risks of 5-HMF exposure to the human gastric epithelium.

Structural characterization of a polysaccharide from bamboo (Phyllostachys edulis) shoot and its prevention effect on colitis mouse

A water-soluble dietary fiber named BSDF-1 (polysaccharide) was isolated from the bamboo (Phyllostachys edulis) shoot. BSDF-1was characterized as a backbone consisting predominately of 1,4-linked Glcp, and the protective effects and mechanisms of the anti-inflammatory activity were investigated using a dextran sulfate sodium (DSS)-induced colitis mouse model. BSDF-1 administration significantly reduced colonic pathological damage, inhibited the activation of inflammatory signaling pathways, including nuclear factor-kappa B and NLR family pyrin domain containing 3 inflammasomes pathways. It restored the mRNA expression of tight junction proteins, including zonula occludens-1, claudin-1, and occludin. Furthermore, BSDF-1 treatment reduced Parabacteroides, Mucispirillum, Helicobacter, Bacteroides, and Streptococcus levels, whereas high-dose BSDF-1 treatment increased Prevotella, Alitipes, Anaerostipes, Odoribacter, Bifidobacterium, Butyricimonas, and Lactobacillus levels. In conclusion, BSDF-1 can inhibit the activation of inflammatory signaling pathways and restore the intestinal barrier function. Thus, BSDF-1 may be a valuable food supplement or nutraceutical to manage and prevent ulcerative colitis.

Deficiency in glutathione synthesis and reduction contributes to the pathogenesis of colitis-related liver injury

OBJECTIVES

Liver disease is the most common extra-intestinal manifestation of ulcerative colitis (UC), but the underlying pathogenesis is still not clarified. It is well accepted that the occurrence of UC-related liver disease has close correlation with immune activation, intestinal bacterial liver translocation, inflammatory cytokine storm, and the disturbance of bile acid circulation. The occurrence of UC-related liver disease makes the therapy difficult, therefor study on the pathogenesis of UC-related liver injury is of great significance for its prevention and treatment. Glutathione (GSH) shows multiple physiological activities, such as free radical scavenging, detoxification metabolism and immune defense. The synthesis and the oxidation-reduction all contribute to GSH antioxidant function. It is reported that the deficiency in hepatic GSH antioxidant function participates in multiple liver diseases, but whether it participates in the pathogenesis of UC-related liver injury is still not clear. This study aims to investigate the feature and underlying mechanism of GSH synthesis and oxidation-reduction function during the development of UC, which will provide useful information for the pathogenesis study on UC-related liver injury.

METHODS

UC model was induced by 2,4,6-trinitrobenzenesulfonic acid (TNBS)-ethanol solution (5 mg/0.8 mL per rat, 50% ethanol) via intra-colonic administration in rats, and the samples of serum, liver, and colon tissue of rats were collected at the 3rd, 5th, and 7th days post TNBS. The severity degree of colitis was evaluated by measuring the disease activity index, colonic myeloperoxidase activity, and histopathological score, and the degree of liver injury was evaluated by histopathological score and the serum content of alanine aminotransferase. Spearman correlation analysis was also conducted between the degree of colonic lesions and index of hepatic histopathological score as well as serum aspartate aminotransferase level to clarify the correlation between liver injury and colitis. To evaluate the hepatic antioxidant function of GSH in UC rats, hepatic GSH content, enzyme activity of GSH peroxidase (GSH-Px), and GSH reductase (GR) were determined in rats at the 3rd, 5th, and 7th days post TNBS, and the protein expressions of glutamine cysteine ligase (GCL), GSH synthase, GSH-Px, and GR in the liver of UC rats were also examined by Western blotting.

RESULTS

Compared with the control, the disease activity index, colonic myeloperoxidase activity, and histopathological score were all significantly increased at the 3rd, 5th, and 7th days post TNBS (all P<0.01), the serum aspartate aminotransferase level and hepatic histopathologic score were also obviously elevated at the 7th day post TNBS (all P<0.05). There was a significant positive correlation between the degree of liver injury and the severity of colonic lesions (P=0.000 1). Moreover, compared with the control, hepatic GSH content and the activity of GSH-Px and GR were all significantly decreased at the 3rd and 5th days post TNBS (P<0.05 or P<0.01), and the protein expressions of GCL, GSH-Px, and GR were all obviously down-regulated at the 3rd, 5th, and 7th days post TNBS (P<0.05 or P<0.01).

CONCLUSIONS

There is a significant positive correlation between the degree of liver injury and the severity of colonic lesions, and the occurrence of reduced hepatic GSH synthesis and decreased GSH reduction function is obviously earlier than that of the liver injury in UC rats. The reduced hepatic expression of enzymes that responsible for GSH synthesis and reduction may contribute to the deficiency of GSH synthesis and oxidation-reduction function, indicating that the deficiency in GSH antioxidant function may participate in the pathogenesis of UC related liver injury.

Disruption of the crypt niche promotes outgrowth of mutated colorectal tumor stem cells

Recent data establish a logarithmic expansion of leucine rich repeat containing G protein coupled receptor 5–positive (Lgr5⁺) colonic epithelial stem cells (CESCs) in human colorectal cancer (CRC). Complementary studies using the murine 2-stage azoxymethane–dextran sulfate sodium (AOM-DSS) colitis-associated tumor model indicate early acquisition of Wnt pathway mutations drives CESC expansion during adenoma progression. Here, subdivision of the AOM-DSS model into in vivo and in vitro stages revealed DSS induced physical separation of CESCs from stem cell niche cells and basal lamina, a source of Wnt signals, within hours, disabling the stem cell program. While AOM delivery in vivo under non-adenoma-forming conditions yielded phenotypically normal mucosa and organoids derived thereof, niche injury ex vivo by progressive DSS dose escalation facilitated outgrowth of Wnt-independent dysplastic organoids. These organoids contained 10-fold increased Lgr5⁺ CESCs with gain-of-function Wnt mutations orthologous to human CRC driver mutations. We posit CRC originates by niche injury–induced outgrowth of normally suppressed mutated stem cells, consistent with models of adaptive oncogenesis.

Role of vitamin D in ulcerative colitis: an update on basic research and therapeutic applications

INTRODUCTION

Vitamin D deficiency is common in patients with ulcerative colitis (UC). Moreover, vitamin D supplementation seems to contribute to disease relief. Nevertheless, the exact etiological link between vitamin D deficiency and UC is far from clear, and an agreement has not been reached on the frequency and dosage of vitamin D supplementation required.

AREAS COVERED

This review will outline the possible role of vitamin D in the pathogenesis of UC and summarize the current state of clinical research on vitamin D. Literature was searched on PUBMED, with 'Vitamin D,' 'Ulcerative colitis,' 'Vitamin D receptor,' and 'disease activity' as MeSH Terms. Relevant information is presented in figures or tables.

EXPERT OPINION

The etiological relationship between vitamin D and the onset of UC is still being researched. More high-quality double-blind randomized clinical studies are needed to determine the efficacy of vitamin D supplementation in the treatment of UC, whether as the main treatment or as an adjuvant treatment. Importantly, determining the dosage and frequency of vitamin D supplementation should be the main research direction in the future, and regional factors should also be fully considered in this respect.

Lactobacillus rhamnosus GG combined with inosine ameliorates alcohol-induced liver injury through regulation of intestinal barrier and Treg/Th1 cells

BACKGROUND

Intestinal epithelial barrier disruption and bacterial translocation exacerbates the progression of alcoholic liver disease. Lactobacillus rhamnosus GG (LGG), a probiotic, has been shown benefits in chronic liver disease and in regulating gut dysbiosis. Previous studies showed the protective roles of LGG in ethanol-disrupted gut barrier functions and liver injury. Inosine, a metabolite produced by intestinal bacteria, has the anti-inflammatory and immunregulatory functions. In this study, the synergistic effect of LGG and inosine was investigated in a mouse model of alcohol-induced liver disease (ALD).

METHODS

Male C57BL/6 mice were fed with a Lieber-DeCarli diet containing 5% alcohol for four weeks to establish a model of alcohol-induced liver injury. LGG or a combination of LGG and inosine were administrated orally to explore a new therapeutic method for alcohol-induced liver disease and to investigate the underlying mechanisms. Liver damage was evaluated by transaminases and pathological changes. Tight junction proteins, composition of the gut microbiome, cytokines, lipopolysaccharides (LPS), glutathione (GSH), superoxide dismutase (SOD), malondialdehyde (MDA), F4/80+ macrophages, as well as p38, Jun N-terminal kinase (JNK), were determined by qRT-PCR, RNAseq, ELISA, IHC and western blot. Regulatory T (Treg) cells were characterized by positive staining of CD4, CD25 and Foxp3 using flow cytometry. IFN-γ-producing CD4⁺ T (Th1) cells were examined by intracellular cytokine staining.

RESULTS

Alcohol consumption induced elevated liver enzymes, steatosis and inflammation, while LGG combined with inosine treatment was more significant to ameliorate these symptoms compared with LGG alone. When LGG combined with inosine were administered to ALD mice, intestinal microecology significantly improved reflected by intestinal villi and tight junction proteins recovery and the restoration of intestinal flora. Combined therapy inhibited phosphorylation of p38 and JNK to alleviate hepatic inflammation. Moreover, flow cytometry analysis showed that long-term excessive alcohol consumption reduced Tregs population while increased Th1 population, which was restored by a combination of LGG and inosine treatment.

CONCLUSIONS

The findings from the study indicate that the combined LGG and inosine treatment ameliorates ALD by improving the gut ecosystem, intestinal barrier function, immune homeostasis and liver injury.

Protective Effects of Companilactobacillus crustorum MN047 against Dextran Sulfate Sodium-Induced Ulcerative Colitis: A Fecal Microbiota Transplantation Study

Gut microbiota dysbiosis could aggravate the development of ulcerative colitis (UC). Companilactobacillus crustorum MN047 (CCMN) is a potential gut microbiota-regulating probiotic that could produce multiple novel bacteriocins. In this study, fecal microbiota transplantation (FMT) was used to verify whether CCMN could alleviate dextran sulfate sodium-induced UC by regulating gut microbiota. Results showed that both CCMN and FMT ameliorated the symptoms of UC, including attenuating the increased disease activity index, shortened colon length, gut barrier damage, and inflammation. Briefly, CCMN and FMT upregulated the expressions of MUCs and tight junctions, downregulated the expressions of proinflammatory cytokines and chemokines, increased fecal short-chain fatty acids, and lowered serum lipopolysaccharides, which were associated with the regulation of gut microbiota (e.g., increased Akkermansia, Blautia, and Ruminococcus levels). These results demonstrated that CCMN could ameliorate UC by modulating gut microbiota and inhibiting the TLR4/NF-κB pathway. Therefore, CCMN could be considered as a potential probiotic supplement for ameliorating UC.

Analysis of miRNAs Involved in Mouse Heart Injury Upon Coxsackievirus A2 Infection

Coxsackievirus A2 (CVA2) has recently been constantly detected, and is associated with viral myocarditis in children. Our previous study demonstrated that CVA2 led to heart damage in a neonatal murine model. However, the molecular mechanism of heart injury caused by CVA2 remains largely unknown. Emerging evidence suggests the significant functions of miRNAs in Coxsackievirus infection. To investigate potential miRNAs involved in heart injury caused by CVA2, our study, for the first time, conducted a RNA-seq in vivo employing infected mice hearts. In total, 87, 101 and 76 differentially expressed miRNAs were identified at 3 days post infection (dpi), 7 dpi and 7 dpi vs 3 dpi. Importantly, above 3 comparison strategies shared 34 differentially expressed miRNAs. These results were confirmed by quantitative PCR (qPCR). Next, we did GO, KEGG, and miRNA-mRNA integrated analysis of differential miRNAs. The dual-luciferase reporter assay confirmed the miRNA-mRNA pairs. To further confirm the above enriched pathways and processes, we did Western blotting and immunofluorescence staining. Our results suggest that inflammatory responses, T cell activation, apoptosis, autophagy, antiviral immunity, NK cell infiltration, and the disruption of tight junctions are involved in the pathogenesis of heart injury caused by CVA2. The dysregulated miRNAs and pathways recognized in the current study can improve the understanding of the intricate interactions between CVA2 and the heart injury, opening a novel avenue for the future study of CVA2 pathogenesis.

Intestinal Claudin-7 deficiency impacts the intestinal microbiota in mice with colitis

BACKGROUND

Intestinal epithelial cells form a physical barrier that protects the intestine against the intestinal microbiota through tight junctions (TJs) and adhesive junctions, while barrier disruption may lead to inflammatory bowel disease (IBD). Claudin-7 (Cldn7) has been implicated in this protection as an important member of TJs. Here, we experimentally study the effect of Cldn7 deletion on intestinal microbiota in colitis.

METHODS

Colitis model was established based on inducible intestinal conditional Cldn7 gene knockout mice (Cldn7fl/fl; villin-CreERT2), by feeding with dextran sodium sulfate (DSS). AB-PAS staining and immunohistochemical staining of Muc2 mucin were used to detect the effect of Cldn7 deficiency on the mucus layer of mice with colitis, and fluorescence in situ hybridization was used to detect how Cldn7 promotes spatial separation of the gut microbiota from the host. The microbiota population was characterized by high-throughput 16S rRNA gene sequencing of DNA extracted from fecal samples.

RESULTS

Compared with the controls, Cldn7 knockout increased susceptibility to colitis, including greater degree of weight loss, colon shortening, and a significantly higher disease activity index score. DSS-treated Cldn7 knockout mice promoted the migration of bacteria to the intestinal epithelium to some extent by damaging the intestinal mucus layer. Sequencing of 16S rRNA showed that DSS-treated Cldn7 knockout mice reduced the gut microbiota diversity and had greater relative abundance of Escherichia coli. LEfSe analysis indicated that Escherichia coli may be the key bacteria in Cldn7 knockout mice during DSS-induced colitis. Furthermore, the Tax4Fun analysis predicted that DSS-treated Cldn7 knockout mice enriched for microbiota impacting infectious diseases, immune system and metabolic functions.

CONCLUSIONS

Our data suggests an association between intestinal Cldn7 knockout and microbiota dysbiosis during inflammatory events.

Construction and imaging of a neurovascular unit model

In 2001, the concept of the neurovascular unit was introduced at the Stroke Progress Review Group meeting. The neurovascular unit is an important element of the health and disease status of blood vessels and nerves in the central nervous system. Since then, the neurovascular unit has attracted increasing interest from research teams, who have contributed greatly to the prevention, treatment, and prognosis of stroke and neurodegenerative diseases. However, additional research is needed to establish an efficient, low-cost, and low-energy in vitro model of the neurovascular unit, as well as enable noninvasive observation of neurovascular units in vivo and in vitro. In this review, we first summarize the composition of neurovascular units, then investigate the efficacy of different types of stem cells and cell culture methods in the construction of neurovascular unit models, and finally assess the progress of imaging methods used to observe neurovascular units in recent years and their positive role in the monitoring and investigation of the mechanisms of a variety of central nervous system diseases.

Claudin-18.2 as a therapeutic target in cancers: cumulative findings from basic research and clinical trials

Claudins are major components of tight junctions that maintain cell polarity and intercellular adhesion. The dynamics of claudins in cancer cells have attracted attention as a therapeutic target. During carcinogenesis, claudin expression is generally downregulated; however, overexpression of claudin-18.2 has been observed in several types of cancers. Upregulated and mislocalized claudin-18.2 expression in cancer cells has been suggested as a therapeutic target. Research on claudin-18.2 has revealed its involvement in carcinogenesis. Clinical trials using zolbetuximab, a monoclonal antibody targeting claudin-18.2, for patients with advanced cancer yielded positive results with few high-grade adverse events; thus, it is expected to be a novel and effective therapeutic. Here, we review current insights into the role that claudin-18.2 plays in basic cancer research and clinical applications. A better understanding of these roles will facilitate the development of new treatment strategies for cancer patients with poor prognoses.

Activating Transcription Factor 3 Protects against Restraint Stress-Induced Gastrointestinal Injury in Mice

Psychological stress increases the risk of gastrointestinal (GI) tract diseases, which involve bidirectional communication of the GI and nerves systems. Acute stress leads to GI ulcers; however, the mechanism of the native cellular protection pathway, which safeguards tissue integrality and maintains GI homeostasis, remains to be investigated. In a mouse model of this study, restraint stress induced GI leakage, abnormal tight junction protein expression, and cell death of gut epithelial cells. The expression of activating transcription factor 3 (ATF3), a stress-responsive transcription factor, is upregulated in the GI tissues of stressed animals. ATF3-deficient mice displayed an exacerbated phenotype of GI injuries. These results suggested that, in response to stress, ATF3 is part of the native cellular protective pathway in the GI system, which could be a molecular target for managing psychological stress-induced GI tract diseases.

Dietary Acrylamide Intake Alters Gut Microbiota in Mice and Increases Its Susceptibility to Salmonella Typhimurium Infection

Acrylamide (AA) has been extensively examined for its potential toxicological effects on humans and animals, but its impacts on gut microbiota and effects on hosts’ susceptibility to enteric infection remain elusive. The present study was designed to evaluate the effect of AA on gut microbiota of mice and susceptibility of mice to S. Typhimurium infection. After four weeks’ intervention, mice fed with AA exhibited significantly decreased body weight. Meanwhile, 16S rRNA gene sequencing showed reduced relative abundance of Firmicutes and increased abundance of Bacteroidetes in AA-treated mice prior to infection. In addition, we observed high relative abundance of Burkholderiales and Erysipelotrichales, more specifically the genus Sutterella and Allobaculum, respectively, in AA-treated mice before infection. Subsequently, the mice were orally infected with S. Typhimurium. The histological changes, systemic dissemination of S. Typhimurium, and inflammatory responses were examined. Compared to mice fed with normal diet, mice fed AA exhibited higher level of bacterial counts in liver, spleen, and ileum, which was consistent with exacerbated tissue damage determined by histological analyses. In addition, higher expression of pro-inflammaroty cytokines, p-IκBα, and p-P65 and lower mRNA expressions of mucin2, occludin, zo-1, claudin-1, and E-cadherin were detected in AA-treated mice. These findings provide novel insights into the potential health impact of AA consumption and the detailed mechanism for its effect on S. Typhimurium infection merit further exploration.

The probiotic Companilactobacillus crustorum MN047 alleviates colitis-associated tumorigenesis via modulating the intestinal microenvironment

Supplementation of probiotics is a promising method to alleviate colorectal cancer (CRC) via modulating the intestinal microenvironment. This study aimed to assess the potential anti-CRC effect of Companilactobacillus crustorum MN047 on an azoxymethane and dextran sulfate sodium-induced colitis-associated (CA)-CRC mouse model. Mice were gavaged with C. crustorum MN047 once daily (∼1 × 10⁹ CFU per mouse). The CA-CRC ameliorating effect of this strain was investigated based on the gut microbiota, inflammation and intestinal barrier integrity. Results showed that C. crustorum MN047 could significantly attenuate tumorigenesis and inflammation via suppressing the TLR4/NF-κB pathway. Moreover, this probiotic could improve the intestinal barrier integrity by increasing the mRNA level of some tight junction-related proteins and reducing goblet cell loss. In addition, C. crustorum MN047 administration led to an increase in beneficial bacteria and a decrease in harmful bacteria, thereby increasing SCFAs and reducing LPS levels. These results suggested that C. crustorum MN047 could partially ameliorate the formation of CA-CRC by modulating the gut microbiota, attenuating inflammation and enhancing the intestinal barrier integrity. Therefore, C. crustorum MN047 was a promising probiotic supplement for attenuating CA-CRC.