1,25-Dihydroxyvitamin D Protects Intestinal Epithelial Barrier by Regulating the Myosin Light Chain Kinase Signaling Pathway

Improvement of chronic metabolic inflammation and regulation of gut homeostasis: Tea as a potential therapy

Chronic metabolic inflammation is a common mechanism linked to the development of metabolic disorders such as obesity, diabetes, and cardiovascular disease (CVD). Chronic metabolic inflammation often related to alterations in gut homeostasis, and pathological processes involve the activation of endotoxin receptors, metabolic reprogramming, mitochondrial dysfunction, and disruption of intestinal nuclear receptor activity. Recent investigations into homeostasis and chronic metabolic inflammation have revealed a novel mechanism which is characterized by a timing interaction involving multiple components and targets. This article explores the positive impact of tea consumption on metabolic health of populations, with a special focus on the improvement of inflammatory indicators and the regulation of gut microbiota. Studies showed that tea consumption is related to the enrichment of gut microbiota. The relative proportion of Firmicutes/Bacteroidetes (F/B) is altered, while the abundance of Lactobacillus, Bifidobacterium, and A. muciniphila increased significantly in most of the studies. Thus, tea consumption could provide potential protection from the development of chronic diseases by improving gut homeostasis and reducing chronic metabolic inflammation. The direct impact of tea on intestinal homeostasis primarily targets lipopolysaccharide (LPS)-related pathways. This includes reducing the synthesis of intestinal LPS, inhibiting LPS translocation, and preventing the binding of LPS to TLR4 receptors to block downstream inflammatory pathways. The TLR4/MyD88/NF-κB p65 pathway is crucial for anti-metaflammatory responses. The antioxidant properties of tea are linked to enhancing mitochondrial function and mitigating mitochondria-related inflammation by eliminating free radicals, inhibiting NLRP3 inflammasomes, and modulating Nrf2/ARE activity. Tea also contributes to safeguarding the intestinal barrier through various mechanisms, such as promoting the synthesis of short-chain fatty acids in the intestine, activating intestinal aryl hydrocarbon receptor (AhR) and farnesoid X receptor (FXR), and improving enteritis. Functional components that improve chronic metabolic inflammation include tea polyphenols, tea pigments, TPS, etc. Tea metabolites such as 4-Hydroxyphenylacetic acid and 3,4-Dihydroxyflavan derivatives, etc., also contribute to anti-chronic metabolic inflammation effects of tea consumption. The raw materials and processing technologies affect the functional component compositions of tea; therefore, consuming different types of tea may result in varying action characteristics and mechanisms. However, there is currently limited elaboration on this aspect. Future research should conduct in-depth studies on the mechanism of tea and its functional components in improving chronic metabolic inflammation. Researchers should pay attention to whether there are interactions between tea and other foods or drugs, explore safe and effective usage and dosage, and investigate whether there are individual differences in the tea-drinking population leading to different effects of tea intervention. Ultimately, the application of tea drinking could be a universal therapy for regulating intestinal homeostasis, anti-chronic metabolic inflammatory responses, and promoting metabolic health.

Elevated SPARC Disrupts the Intestinal Barrier Integrity in Crohn's Disease by Interacting with OTUD4 and Activating the MYD88/NF-κB Pathway

Disruption of the intestinal epithelial barrier results in increased permeability and is a key factor in the onset and progression of Crohn's disease (CD). The protein SPARC is primarily involved in cell interaction and migration, but its specific role in the intestinal epithelial barrier remains unclear. This study demonstrates that SPARC is significantly overexpressed in both CD patients and murine models of colitis. Furthermore, mice deficient in SPARC exhibits resistance to chemically induced colitis, a phenomenon associated with the modulation of barrier-associated proteins. Mechanistically, it is elucidated that SPARC competitively binds to OTUD4 in conjunction with MYD88, facilitating the translocation of p65 from the cytoplasm to the nucleus and subsequent activation of the p65-MLCK/MLC2 pathway, thereby compromising barrier integrity. Additionally, it is identified that the elevated expression of SPARC in CD is regulated via the METTL3-YTHDF1 axis. These findings indicate that SPARC levels are elevated in patients with CD and in colitis-induced mice, leading to intestinal barrier damage through direct interaction with OTUD4 and subsequent activation of the MYD88/p65/MLCK/MLC2 signaling pathway. Consequently, targeting SPARC or the OTUD4/MYD88/p65/MLCK/MLC2 axis may offer novel insights into the molecular mechanisms underlying CD and represent a potential therapeutic strategy.

Exploring Gut Microbiota Imbalance in Irritable Bowel Syndrome: Potential Therapeutic Effects of Probiotics and Their Metabolites

Irritable bowel syndrome is a common functional gastrointestinal disorder characterized by recurrent abdominal discomfort, bloating, cramping, flatulence, and changes in bowel movements. The pathophysiology of IBS involves a complex interaction between motor, sensory, microbiological, immunological, and psychological factors. Diversity, stability, and metabolic activity of the gut microbiota are frequently altered in IBS, thus leading to a situation of gut dysbiosis. Therefore, the use of probiotics and probiotic-derived metabolites may be helpful in balancing the gut microbiota and alleviating irritable bowel syndrome symptoms. This review aimed to report and consolidate recent progress in understanding the role of gut dysbiosis in the pathophysiology of IBS, as well as the current studies that have focused on the use of probiotics and their metabolites, providing a foundation for their potential beneficial effects as a complementary and alternative therapeutic strategy for this condition due to the current absence of effective and safe treatments.

Vitamin D and celiac disease

Celiac disease (CD) is an immune-mediated condition affecting the small intestine. Its reported global prevalence falls within the range of 0.7% to 1.4%. Notably, historically, higher rates, reaching 1% in Western Ireland, have been documented. Recent research has even revealed prevalence rates as elevated as 2% in northern Europe. These findings underscore the urgency for swift and cost-effective diagnosis, especially in individuals identified through screening efforts. At present, the diagnosis of CD relies on a multifaceted approach involving positive serological markers such as IgA anti-tissue transglutaminase (anti-TTG) and anti-endomysial antibodies (anti-EMA). These serological findings are assessed in conjunction with classical histological alterations, as outlined in the Marsh classification. CD is an inflammatory condition triggered by the consumption of gluten, resulting from intricate interactions between genetic, immunological, and environmental factors. CD is linked to malabsorption, leading to nutritional deficiencies. Individuals with CD are required to adhere to a gluten-free diet, which itself can lead to nutrient deficiencies. One such deficiency includes vitamin D, and there is substantial experimental evidence supporting the notion of a bidirectional relationship between CD and vitamin D status. A low level of vitamin D has a detrimental impact on the clinical course of the disease. Here we summarize the key characteristics of CD and explore the prominent roles of vitamin D in individuals with CD.

Sophocarpine alleviates intestinal fibrosis via inhibition of inflammation and fibroblast into myofibroblast transition by targeting the Sirt1/p65 signaling axis

In this study, we used alkaloids from Sophora flavescens to inhibit the SASP, leading to fibroblast-into-myofibroblast transition (FMT) to maintain intestinal mucosal homeostasis in vitro and in vivo. We used western blotting (WB) and immunofluorescence staining (IF) to assess whether five kinds of alkaloids inhibit the major inflammatory pathways and chose the most effective compound (sophocarpine; SPC) to ameliorate colorectal inflammation in a dextran sulfate sodium (DSS)-induced UC mouse model. IF, Immunohistochemistry staining (IHC), WB, disease activity index (DAI), and enzyme-linked immunosorbent assay (ELISA) were conducted to investigate the mechanism of action of this compound. Next, we detected the pharmacological activity of SPC on the senescence-associated secretory phenotypes (SASP) and FMT in interleukin 6 (IL-6)-induced senescence-like fibroblasts and discussed the mucosal protection ability of SPC on a fibroblast-epithelium/organoid coculture system and organ-on-chip system. Taken together, our results provide evidence that SPC alleviates the inflammatory response, improves intestinal fibrosis and maintains intestinal mucosal homeostasis in vivo. Meanwhile, SPC was able to prevent IL-6-induced SASP and FMT in fibroblasts, maintain the expression of TJ proteins, and inhibit inflammation and genomic stability of colonic mucosal epithelial cells by activating SIRT1 in vitro. In conclusion, SPC treatment attenuates intestinal fibrosis by regulating SIRT1/NF-κB p65 signaling, and it might be a promising therapeutic agent for inflammatory bowel disease.

Role of Inflammatory Mechanisms in Major Depressive Disorder: From Etiology to Potential Pharmacological Targets

The involvement of central and peripheral inflammation in the pathogenesis and prognosis of major depressive disorder (MDD) has been demonstrated. The increase of pro-inflammatory cytokines (interleukin (IL)-1β, IL-6, IL-18, and TNF-α) in individuals with depression may elicit neuroinflammatory processes and peripheral inflammation, mechanisms that, in turn, can contribute to gut microbiota dysbiosis. Together, neuroinflammation and gut dysbiosis induce alterations in tryptophan metabolism, culminating in decreased serotonin synthesis, impairments in neuroplasticity-related mechanisms, and glutamate-mediated excitotoxicity. This review aims to highlight the inflammatory mechanisms (neuroinflammation, peripheral inflammation, and gut dysbiosis) involved in the pathophysiology of MDD and to explore novel anti-inflammatory therapeutic approaches for this psychiatric disturbance. Several lines of evidence have indicated that in addition to antidepressants, physical exercise, probiotics, and nutraceuticals (agmatine, ascorbic acid, and vitamin D) possess anti-inflammatory effects that may contribute to their antidepressant properties. Further studies are necessary to explore the therapeutic benefits of these alternative therapies for MDD.

Conditional Vitamin D Receptor Deletion Induces Fungal and Archaeal Dysbiosis and Altered Metabolites

A vitamin D receptor (VDR) deficiency leads to the dysbiosis of intestinal bacteria and is associated with various diseases, including cancer, infections, and inflammatory bowel disease. However, the impact of a VDR deficiency on fungi and archaea is unknown. We conditionally deleted the VDR in Paneth cells (VDRΔPC), intestinal epithelial cells (VDRΔIEC), or myeloid cells (VDRΔLyz) in mice and collected feces for shotgun metagenomic sequencing and untargeted metabolomics. We found that fungi were significantly altered in each knockout (KO) group compared to the VDRLoxp control. The VDRΔLyz mice had the most altered fungi species (three depleted and seven enriched), followed by the VDRΔPC mice (six depleted and two enriched), and the VDRΔIEC mice (one depleted and one enriched). The methanogen Methanofollis liminatans was enriched in the VDRΔPC and VDRΔLyz mice and two further archaeal species (Thermococcus piezophilus and Sulfolobus acidocaldarius) were enriched in the VDRΔLyz mice compared to the Loxp group. Significant correlations existed among altered fungi, archaea, bacteria, and viruses in the KO mice. Functional metagenomics showed changes in several biologic functions, including decreased sulfate reduction and increased biosynthesis of cobalamin (vitamin B12) in VDRΔLyz mice relative to VDRLoxp mice. Fecal metabolites were analyzed to examine the involvement of sulfate reduction and other pathways. In conclusion, a VDR deficiency caused the formation of altered fungi and archaea in a tissue- and sex-dependent manner. These results provide a foundation about the impact of a host factor (e.g., VDR deficiency) on fungi and archaea. It opens the door for further studies to determine how mycobiome and cross-kingdom interactions in the microbiome community and metabolites contribute to the risk of certain diseases.

Protective Effect and Mechanism of Aspirin Eugenol Ester on Lipopolysaccharide-Induced Intestinal Barrier Injury

Intestinal inflammation is a complex and recurrent inflammatory disease. Pharmacological and pharmacodynamic experiments showed that aspirin eugenol ester (AEE) has good anti-inflammatory, antipyretic, and analgesic effects. However, the role of AEE in regulating intestinal inflammation has not been explored. This study aimed to investigate whether AEE could have a protective effect on LPS-induced intestinal inflammation and thus help to alleviate the damage to the intestinal barrier. This was assessed with an inflammation model in Caco-2 cells and in rats induced with LPS. The expression of inflammatory mediators, intestinal epithelial barrier-related proteins, and redox-related signals was analyzed using an enzyme-linked immunosorbent assay (ELISA), Western blotting, immunofluorescence staining, and RT-qPCR. Intestinal damage was assessed by histopathological examination. Changes in rat gut microbiota and their functions were detected by the gut microbial metagenome. AEE significantly reduced LPS-induced pro-inflammatory cytokine levels (p < 0.05) and oxidative stress levels in Caco-2 cells and rats. Compared with the LPS group, AEE could increase the relative expression of Occludin, Claudin-1, and zonula occludens-1 (ZO-1) and decrease the relative expression of kappa-B (NF-κB) and matrix metalloproteinase-9. AEE could significantly improve weight loss, diarrhea, reduced intestinal muscle thickness, and intestinal villi damage in rats. Metagenome results showed that AEE could regulate the homeostasis of the gut flora and alter the relative abundance of Firmicutes and Bacteroidetes. Flora enrichment analysis indicated that the regulation of gut flora with AEE may be related to the regulation of glucose metabolism and energy metabolism. AEE could have positive effects on intestinal inflammation-related diseases.

1,25(OH)2D3 alleviates oxidative stress and inflammation through up-regulating HMGCS2 in DSS-induced colitis

BACKGROUND

Previous study found that supplements with active vitamin D3 alleviated experimental colitis. The objective of this study was to investigate the possible role of 3-hydroxy-3-methylglutaryl-CoA synthase 2 (HMGCS2), a ketone synthase, on vitamin D3 protecting against experimental colitis.

METHODS

HMGCS2 and vitamin D receptor (VDR) were measured in UC patients. The effects of vitamin D deficiency (VDD) and exogenous 1,25(OH)2D3 supplementation on experimental colitis were investigated in dextran sulfate sodium (DSS)-treated mice. DSS-induced oxidative stress and inflammation were analyzed in HT-29 cells. HMGCS2 was detected in 1,25(OH)2D3-pretreated HT-29 cells and mouse intestines. HMGCS2 was silenced to investigate the role of HMGCS2 in 1,25(OH)2D3 protecting against experimental colitis.

RESULTS

Intestinal HMGCS2 downregulation was positively correlated with VDR reduction in UC patients. The in vivo experiments showed that VDD exacerbated DSS-induced colitis. By contrast, 1,25(OH)2D3 supplementation ameliorated DSS-induced colon damage, oxidative stress and inflammation. HMGCS2 was up-regulated after 1,25(OH)2D3 supplementation both in vivo and in vitro. Transfection with HMGCS2-siRNA inhibited antioxidant and anti-inflammatory effects of 1,25(OH)2D3 in DSS-treated HT-29 cells.

CONCLUSION

1,25(OH)2D3 supplementation up-regulates HMGCS2, which is responsible for 1,25(OH)2D3-mediated protection against oxidative stress and inflammation in DSS-induced colitis. These findings provide a potential therapeutic strategy for alleviating colitis-associated oxidative stress and inflammation.

Compromised NHE8 Expression Is Responsible for Vitamin D-Deficiency Induced Intestinal Barrier Dysfunction

Objectives: Vitamin D (VitD) and Vitamin D receptor (VDR) are suggested to play protective roles in the intestinal barrier in ulcerative colitis (UC). However, the underlying mechanisms remain elusive. Evidence demonstrates that Na+/H+ exchanger isoform 8 (NHE8, SLC9A8) is essential in maintaining intestinal homeostasis, regarded as a promising target for UC therapy. Thus, this study aims to investigate the effects of VitD/VDR on NHE8 in intestinal protection. Methods: VitD-deficient mice, VDR-/- mice and NHE8-/- mice were employed in this study. Colitis mice were established by supplementing DSS-containing water. Caco-2 cells and 3D-enteroids were used for in vitro studies. VDR siRNA (siVDR), VDR over-expression plasmid (pVDR), TNF-α and NF-κb p65 inhibitor QNZ were used for mechanical studies. The expression of interested proteins was detected by multiple techniques. Results: In colitis mice, paricalcitol upregulated NHE8 expression was accompanied by restoring colonic mucosal injury. In VitD-deficient and VDR-/- colitis mice, NHE8 expression was compromised with more serious mucosal damage. Noteworthily, paricalcitol could not prevent intestinal barrier dysfunction and histological destruction in NHE8-/- mice. In Caco-2 cells and enteroids, siVDR downregulated NHE8 expression, further promoted TNF-α-induced NHE8 downregulation and stimulated TNF-α-induced NF-κb p65 phosphorylation. Conversely, QNZ blocked TNF-α-induced NHE8 downregulation in the absence or presence of siVDR. Conclusions: Our study indicates depressed NHE8 expression is responsible for VitD-deficient-induced colitis aggravation. These findings provide novel insights into the molecular mechanisms of VitD/VDR in intestine protection in UC.

Microbial sensing in the intestine

The gut microbiota plays a key role in host health and disease, particularly through their interactions with the immune system. Intestinal homeostasis is dependent on the symbiotic relationships between the host and the diverse gut microbiota, which is influenced by the highly co-evolved immune-microbiota interactions. The first step of the interaction between the host and the gut microbiota is the sensing of the gut microbes by the host immune system. In this review, we describe the cells of the host immune system and the proteins that sense the components and metabolites of the gut microbes. We further highlight the essential roles of pattern recognition receptors (PRRs), the G protein-coupled receptors (GPCRs), aryl hydrocarbon receptor (AHR) and the nuclear receptors expressed in the intestinal epithelial cells (IECs) and the intestine-resident immune cells. We also discuss the mechanisms by which the disruption of microbial sensing because of genetic or environmental factors causes human diseases such as the inflammatory bowel disease (IBD).

Intestinal permeability in patients undergoing stem cell transplantation correlates with systemic acute phase responses and dysbiosis

Intestinal permeability may correlate with adverse outcomes during hematopoietic stem cell transplantation (HSCT), but longitudinal quantification with traditional oral mannitol and lactulose is not feasible in HSCT recipients because of mucositis and diarrhea. A modified lactulose:rhamnose (LR) assay is validated in children with environmental enteritis. Our study objective was to quantify peri-HSCT intestinal permeability changes using the modified LR assay. The LR assay was administered before transplant, at day +7 and +30 to 80 pediatric and young adult patients who received allogeneic HSCT. Lactulose and rhamnose were detected using urine mass spectrometry and expressed as an L:R ratio. Metagenomic shotgun sequencing of stool for microbiome analyses and enzyme-linked immunosorbent assay analyses of plasma lipopolysaccharide binding protein (LBP), ST2, REG3α, claudin1, occludin, and intestinal alkaline phosphatase were performed at the same timepoints. L:R ratios were increased at day +7 but returned to baseline at day +30 in most patients (P = .014). Conditioning regimen intensity did not affect the trajectory of L:R (P = .39). Baseline L:R ratios did not vary with diagnosis. L:R correlated with LBP levels (r2 = 0.208; P = .0014). High L:R ratios were associated with lower microbiome diversity (P = .035), loss of anaerobic organisms (P = .020), and higher plasma LBP (P = .0014). No adverse gastrointestinal effects occurred because of LR. Intestinal permeability as measured through L:R ratios after allogeneic HSCT correlates with intestinal dysbiosis and elevated plasma LBP. The LR assay is well-tolerated and may identify transplant recipients who are more likely to experience adverse outcomes.

NOD-like receptors mediate homeostatic intestinal epithelial barrier function: promising therapeutic targets for inflammatory bowel disease

Inflammatory bowel disease (IBD) is a chronic gastrointestinal inflammatory disease that involves host genetics, the microbiome, and inflammatory responses. The current consensus is that the disruption of the intestinal mucosal barrier is the core pathogenesis of IBD, including intestinal microbial factors, abnormal immune responses, and impaired intestinal mucosal barrier. Cumulative data show that nucleotide-binding and oligomerization domain (NOD)-like receptors (NLRs) are dominant mediators in maintaining the homeostasis of the intestinal mucosal barrier, which play critical roles in sensing the commensal microbiota, maintaining homeostasis, and regulating intestinal inflammation. Blocking NLRs inflammasome activation by botanicals may be a promising way to prevent IBD progression. In this review, we systematically introduce the multiple roles of NLRs in regulating intestinal mucosal barrier homeostasis and focus on summarizing the activities and potential mechanisms of natural products against IBD. Aiming to propose new directions on the pathogenesis and precise treatment of IBD.

Mechanism of Qingchang Suppository on repairing the intestinal mucosal barrier in ulcerative colitis

Ulcerative colitis (UC) is a refractory inflammatory bowel disease, and the outcomes of conventional therapies of UC, including 5-aminosalicylic acid, glucocorticoids, immunosuppressants, and biological agents, are not satisfied with patients and physicians with regard to adverse reactions and financial burden. The abnormality of the intestinal mucosal barrier in the pathogenesis of UC was verified. Qingchang Suppository (QCS) is an herbal preparation and is effective in treating ulcerative proctitis. The mechanism of QCS and its active ingredients have not been concluded especially in mucosal healing. This review elucidated the potential mechanism of QCS from the intestinal mucosal barrier perspective to help exploring future QCS research directions.

Building better barriers: how nutrition and undernutrition impact pediatric intestinal health

Chronic undernutrition is a major cause of death for children under five, leaving survivors at risk for adverse long-term consequences. This review focuses on the role of nutrients in normal intestinal development and function, from the intestinal epithelium, to the closely-associated mucosal immune system and intestinal microbiota. We examine what is known about the impacts of undernutrition on intestinal physiology, with focus again on the same systems. We provide a discussion of existing animal models of undernutrition, and review the evidence demonstrating that correcting undernutrition alone does not fully ameliorate effects on intestinal function, the microbiome, or growth. We review efforts to treat undernutrition that incorporate data indicating that improved recovery is possible with interventions focused not only on delivery of sufficient energy, macronutrients, and micronutrients, but also on efforts to correct the abnormal intestinal microbiome that is a consequence of undernutrition. Understanding of the role of the intestinal microbiome in the undernourished state and correction of the phenotype is both complex and a subject that holds great potential to improve recovery. We conclude with critical unanswered questions in the field, including the need for greater mechanistic research, improved models for the impacts of undernourishment, and new interventions that incorporate recent research gains. This review highlights the importance of understanding the mechanistic effects of undernutrition on the intestinal ecosystem to better treat and improve long-term outcomes for survivors.

Vitamin D and Microbiome: Molecular Interaction in Inflammatory Bowel Disease Pathogenesis

Studies of systemic autoimmune diseases point to characteristic microbial patterns in various diseases, including inflammatory bowel disease (IBD). Autoimmune diseases, and IBD in particular, show a predisposition to vitamin D deficiency, leading to alterations in the microbiome and disruption of intestinal epithelial barrier integrity. This review examines the role of the gut microbiome in IBD and discusses how vitamin D-vitamin D receptor (VDR)-associated molecular signaling pathways contribute to the development and progression of IBD through their effects on gut barrier function, the microbial community, and immune system function. The present data demonstrate that vitamin D promotes the proper function of the innate immune system by acting as an immunomodulator, exerting anti-inflammatory effects, and critically contributing to the maintenance of gut barrier integrity and modulation of the gut microbiota, mechanisms that may influence the IBD development and progression. VDR regulates the biological effects of vitamin D and is related to environmental, genetic, immunologic, and microbial aspects of IBD. Vitamin D influences the distribution of the fecal microbiota, with high vitamin D levels associated with increased levels of beneficial bacterial species and lower levels of pathogenic bacteria. Understanding the cellular functions of vitamin D-VDR signaling in intestinal epithelial cells may pave the way for the development of new treatment strategies for the therapeutic armamentarium of IBD in the near future.

Tobacco Alkaloid Assessment in a DSS-Induced Colitis Mouse Model with a Fully Humanized Immune System

Inflammatory bowel disease (IBD) refers to chronic intestinal immune-mediated diseases including two main disease manifestations: ulcerative colitis (UC) and Crohn’s disease (CD). Epidemiological, clinical, and preclinical evidence has highlighted the potential anti-inflammatory properties of naturally occurring alkaloids. In the present study, we investigated the potential anti-inflammatory activities of the tobacco alkaloids nicotine and anatabine in a dextran sulfate sodium (DSS)-induced UC mouse model with a fully humanized immune system. Our results show that nicotine significantly reduced all acute colitis symptoms and improved colitis-specific endpoints, including histopathologically assessed colon inflammation, tissue damage, and mononuclear cell infiltration. The tobacco alkaloid anatabine showed similar effectiveness trends, although they were generally weaker or not significant. Gene expression analysis in the context of biological network models of IBD further pinpointed a possible mechanism by which nicotine attenuated DSS-induced colitis in humanized mice. The current study enables further investigation of possible molecular mechanisms by which tobacco alkaloids attenuate UC symptoms.

Vitamin D receptor involves in the protection of intestinal epithelial barrier function via up-regulating SLC26A3

BACKGROUND

Vitamin D receptor (VDR) and SLC26A3 (DRA) have been identified as pivotal protective factors in maintaining gut homeostasis in IBD patients. However, the specific mechanism underlying the increased intestinal susceptibility to inflammation induced by the loss of VDR and whether DRA participates in the role of VDR regulating intestinal epithelial barrier function are undefined.

AIM

The current study is undertaken to elucidate the regulatory effects of VDR on DRA and VDR prevents intestinal epithelial barrier dysfunction via up-regulating the expression of DRA.

METHODS

WT and VDR^-/- mice are used as models for intestinal epithelial response. Paracellular permeability is measured by TEER and FD-4 assays. Immunohistochemistry, immunofluorescence, qPCR and immunoblotting are performed to determine the effects of VDR and DRA on gut epithelial barrier function.

RESULTS

VDR^-/- mice exhibits significant hyperpermeability of intestine with greatly decreased levels of ZO-1 and Claudin1 proteins. DRA is located on the intestinal epithelial apical membrane and is tightly modulated by VDR in vivo and in vitro via activating ERK1/2 MAPK signaling pathway. Notably, the current study for the first time demonstrates that VDR maintains intestinal epithelial barrier integrity via up-regulating DRA expression and the lack of DRA induced by VDR knockdown leads to a more susceptive condition for intestine to DSS-induced colitis.

CONCLUSION

Our study provides evidence and deep comprehension regarding the role of VDR in modulating DRA expression in gut homeostasis and makes novel contributions to better generally understanding the links between VDR, DRA and intestinal epithelial barrier function.

The Taq 1 polymorphism of Vitamin D receptor gene is associated with oral cancer and preoral cancer in North Indian population

BACKGROUND

Oral cancer is known as one of the most common cancers, with a poor prognosis, related to delayed clinical diagnosis, either due to the lack of particular biomarkers related to the disease or costly therapeutic alternatives.

AIMS AND OBJECTIVES

In this study association of single nucleotide polymorphism (Taq1, T>C) in Vitamin D receptor gene with oral cancer and pre oral cancer was studied.

MATERIALS AND METHODS

Total 230 patients of precancerous oral lesions (Leukoplakia 70, Oral Sub mucous fibrosis 90, Lichen Planus 70), 72 oral cancer patients and 300 healthy control subjects were genotyped by PCR-RFLP methods. Chi-square test was used for calculation of genotype and allele frequencies.

RESULTS

Mutant genotype CC as well as C allele were found to significantly decrease the risk of oral disease (P value=0.04, OR=0.60 and P value=0.02, OR=0.75 respectively). In particular, compared to non smokers, smokers with TC & CC genotypes were at decrease risk of oral diseases (P value=0.0001, OR=0.04). The mutant allele genotype CC as well as the mutant allele C showed protective association with leukoplakia (P value=0.01, OR=0.39 & P value=0.009, OR=0.59 respectively). However, individual with CC genotype had developed high cell differentiated grade at diagnosis (OR= 3.78, P value= 0.008).

CONCLUSIONS

This study concludes that VDR (Taq1) polymorphism is associated with oral cancer and pre oral cancer susceptibility in North Indian population.

Enhancing intestinal barrier efficiency: A novel metabolic diseases therapy

Physiologically, the intestinal barrier plays a crucial role in homeostasis and nutrient absorption and prevents pathogenic entry, harmful metabolites, and endotoxin absorption. Recent advances have highlighted the association between severely damaged intestinal barriers and diabetes, obesity, fatty liver, and cardiovascular diseases. Evidence indicates that an abated intestinal barrier leads to endotoxemia associated with systemic inflammation, insulin resistance, diabetes, and lipid accumulation, accelerating obesity and fatty liver diseases. Nonetheless, the specific mechanism of intestinal barrier damage and the effective improvement of the intestinal barrier remain to be explored. Here, we discuss the crosstalk between changes in the intestinal barrier and metabolic disease. This paper also highlights how to improve the gut barrier from the perspective of natural medicine, gut microbiota remodeling, lifestyle interventions, and bariatric surgery. Finally, potential challenges and prospects for the regulation of the gut barrier-metabolic disease axis are discussed, which may provide theoretical guidance for the treatment of metabolic diseases.

GelNB molecular coating as a biophysical barrier to isolate intestinal irritating metabolites and regulate intestinal microbial homeostasis in the treatment of inflammatory bowel disease

Inflammatory bowel disease (IBD) is a chronic, immune-mediated inflammatory disease characterized by the destruction of the structure and function of the intestinal epithelial barrier. Due to the poor remission effect and severe adverse events associated with current clinical medications, IBD remains an incurable disease. Here, we demonstrated a novel treatment strategy with high safety and effective inflammation remission via tissue-adhesive molecular coating. The molecular coating is composed of o-nitrobenzaldehyde (NB)-modified Gelatin (GelNB), which can strongly bond with -NH2 on the intestinal surface of tissue to form a thin biophysical barrier. We found that this molecular coating was able to stay on the surface of the intestine for long periods of time, effectively protecting the damaged intestinal epithelium from irritations of external intestinal metabolites and harmful flora. In addition, our results showed that this coating not only provided a beneficial environment for cell migration and proliferation to promote intestinal repair and regeneration, but also achieved a better outcome of IBD by reducing intestinal inflammation. Moreover, the in vivo experiments showed that the GelNB was better than the classic clinical medication-mesalazine. Therefore, our molecular coating showed potential as a promising strategy for the prevention and treatment of IBD.

HuanglianGanjiang Tang alleviates DSS-induced colitis in mice by inhibiting necroptosis through vitamin D receptor

ETHNOPHARMACOLOGICAL RELEVANCE

HuanglianGanjiang Tang (HGT) is a classic prescription of traditional Chinese medicine (TCM) recorded in Dan Xi Xin Fa, which was used to alleviate manifestations like diarrhea, abdominal pain and hemafecia. In current clinical practices, HGT is adopted for the treatment of ulcerative colitis (UC) and affords good curative effect. However, the underlying mechanism deserves further elucidation.

AIM OF THE STUDY

UC is a hard-to-curable and easy-to-recurrent inflammatory disease. This study is to evaluate the potential therapeutics and explore the molecular mechanism of HGT on UC in the mouse model.

MATERIALS AND METHODS

The components of HGT extracts were identified by HPLC. The colitis of mice was induced by 3% (w./v.) dextran sulfate sodium (DSS). The HGT decoction was prepared through boiling and centrifuging. The mice were given HGT decoction via oral gavage (0.34 g/ml & 0.68 g/ml; 5 ml/kg b.w.). The protective role of HGT on colitis mice was evaluated by body weight change, colon length, disease activity index (DAI) and histological scores. The expressions of necroptosis-related and vitamin D receptor (VDR)-related proteins were measured by Western blot, RT-qPCR and immunofluorescence.

RESULTS

HGT could significantly reduce the loss of body weight and colon length in colitis mice, and alleviated the DAI and histological scores. Mechanically, HGT also promoted the expression of E-cadherin, Occludin, ZO-1 and VDR, and reduced the level of intestinal inflammatory cytokines, such as, IL-6, IL-1β and TNF-α. Besides, HGT downregulated the protein level of p-RIPK3, p-RIPK1 and p-MLKL while upregulated the protein level of Caspase-8 in colon tissue compared to the model group.

CONCLUSION

Our study addressed that HGT can alleviate DSS-induced colitis of mice through inhibiting colonic necroptosis by upregulating the level of VDR.

Pleiotropic Effects of Vitamin D in Patients with Inflammatory Bowel Diseases

The multifaceted activity of vitamin D in patients with inflammatory bowel disease (IBD) presents a challenge for further research in this area. Vitamin D is involved in the regulation of bone mineral metabolism, it participates in the regulation of the immune system, and it is an underlying factor in the pathogenesis of IBD. Additionally, vitamin D affects Th1 and Th2 lymphocytes, influencing the release of cytokines and inhibiting tumor necrosis factor (TNF) expression and the wnt/β-catenin pathway. As far as IBDs are concerned, they are associated with microbiota dysbiosis, abnormal inflammatory response, and micronutrient deficiency, including vitamin D hypovitaminosis. In turn, the biological activity of active vitamin D is regulated by the vitamin D receptor (VDR) which is associated with several processes related to IBD. Therefore, in terms of research on vitamin D supplementation in IBD patients, it is essential to understand the metabolic pathways and genetic determinants of vitamin D, as well as to identify the environmental factors they are subject to, not only in view of osteoporosis prevention and therapy, but primarily concerning modulating the course and supplementation of IBD pharmacotherapy.

N6-adenomethylation of GsdmC is essential for Lgr5+ stem cell survival to maintain normal colonic epithelial morphogenesis

Gut epithelial morphogenesis is maintained by intestinal stem cells. Here, we report that depletion of N6-adenosine methyltransferase subunit Mettl14 from gut epithelial cells in mice impaired colon mucosal morphogenesis, leading to increased mucosal permeability, severe inflammation, growth retardation, and premature death. Mettl14 ablation triggered apoptosis that depleted Lgr5+ stem cells and disrupted colonic organoid growth and differentiation, whereas the inhibition of apoptosis rescued Mettl14-deleted mice and organoids. Mettl14 depletion disrupted N6-adenomethylation on GsdmC transcripts and abolished GsdmC expression. Reconstitution of Mettl14-deleted organoids or mice with GSDMC rescued Lgr5 expression and prevented apoptosis and mouse premature death, whereas GSDMC silence eliminated LGR5 and triggered apoptosis in human colonic organoids and epithelial cells. Mechanistically, Mettl14 depletion eliminated mitochondrial GsdmC, disrupted mitochondrial membrane potential, and triggered cytochrome c release that activates the pro-apoptotic pathway. In conclusion, GsdmC N6-adenomethylation protects mitochondrial homeostasis and is essential for Lgr5+ cell survival to maintain normal colonic epithelial regeneration.

Schisandrin C improves leaky gut conditions in intestinal cell monolayer, organoid, and nematode models by increasing tight junction protein expression

BACKGROUND

Leaky gut symptoms and inflammatory bowel disease (IBD) are associated with damaged intestinal mucosa, intestinal permeability dysfunction by epithelial cell cytoskeleton contraction, disrupted intercellular tight junction (TJ) protein expression, and abnormal immune responses and are intractable diseases.

PURPOSE

We evaluated the effects of schisandrin C, a dibenzocyclooctadiene lignan from Schisandra chinensis, on intestinal inflammation and permeability dysfunction in gut mimetic systems: cultured intestinal cells, intestinal organoids, and a Caenorhabditis elegans model.

METHODS

Schisandrin C was selected from 9 lignan compounds from S. chinensis based on its anti-inflammatory effects in HT-29 human intestinal cells. IL-1β and Pseudomonas aeruginosa supernatants were used to disrupt intestinal barrier formation in vitro and in C. elegans, respectively. The effects of schisandrin C on transepithelial electrical resistance (TEER) and intestinal permeability were evaluated in intestinal cell monolayers, and its effect on intestinal permeability dysfunction was tested in mouse intestinal organoids and C. elegans by measuring fluorescein isothiocyanate (FITC)-dextran efflux. The effect of schisandrin C on TJ protein expression was investigated by western blotting and fluorescence microscopy. The signaling pathway underlying these effects was also elucidated.

RESULTS

Schisandrin C ameliorated intestinal permeability dysfunction in three IBD model systems and enhanced epithelial barrier formation via upregulation of ZO-1 and occludin in intestinal cell monolayers and intestinal organoids. In Caco-2 cells, schisandrin C restored IL-1β-mediated increases in MLCK and p-MLC expression, in turn blocking cytoskeletal contraction and subsequent intestinal permeabilization. Schisandrin C inhibited NF-ĸB and p38 MAPK signaling, which regulates MLCK expression and structural reorganization of the TJ complex in Caco-2 cells. Schisandrin C significantly improved abnormal FITC-dextran permeabilization in both intestinal organoids and C. elegans.

CONCLUSION

Schisandrin C significantly improves abnormal intestinal permeability and regulates the expression of TJ proteins, long MLCK, p-MLC, and inflammation-related proteins, which are closely related to leaky gut symptoms and IBD development. Therefore, schisandrin C is a candidate to treat leaky gut symptoms and IBDs.

Factors Modulating COVID-19: A Mechanistic Understanding Based on the Adverse Outcome Pathway Framework

Addressing factors modulating COVID-19 is crucial since abundant clinical evidence shows that outcomes are markedly heterogeneous between patients. This requires identifying the factors and understanding how they mechanistically influence COVID-19. Here, we describe how eleven selected factors (age, sex, genetic factors, lipid disorders, heart failure, gut dysbiosis, diet, vitamin D deficiency, air pollution and exposure to chemicals) influence COVID-19 by applying the Adverse Outcome Pathway (AOP), which is well-established in regulatory toxicology. This framework aims to model the sequence of events leading to an adverse health outcome. Several linear AOPs depicting pathways from the binding of the virus to ACE2 up to clinical outcomes observed in COVID-19 have been developed and integrated into a network offering a unique overview of the mechanisms underlying the disease. As SARS-CoV-2 infectibility and ACE2 activity are the major starting points and inflammatory response is central in the development of COVID-19, we evaluated how those eleven intrinsic and extrinsic factors modulate those processes impacting clinical outcomes. Applying this AOP-aligned approach enables the identification of current knowledge gaps orientating for further research and allows to propose biomarkers to identify of high-risk patients. This approach also facilitates expertise synergy from different disciplines to address public health issues.

Effect of oral cholecalciferol in a murine model of celiac disease: A dose ranging study

Previous studies have shown a relationship between vitamin D and celiac disease (CD), however little evidence is available examining the direct effects of vitamin D on pathological features of this disease. In this study we evaluated the effect of oral administration of different doses of native vitamin D3 (cholecalciferol) in enteropathic mice. Female non-obese diabetic (NOD)/ShiLt.J mice were fed standard or gluten-free diet and administered gliadin (5 μg/kg) to induce a celiac pathology. Healthy control (gluten-free diet, without gliadin) and control for pathology (standard diet, with gliadin) were administered olive oil. All other experimental groups received gliadin and standard diet plus oral cholecalciferol (5, 10, 20, 50 and 130 μg/kg). Serum levels of 25(OH)D3, calcium and zonulin and expression of vitamin D receptor (VDR), CD3 and zonula occludens-1 (ZO-1) by immunohistochemistry as well as intestinal histological and histomorphometric analyses were undertaken. Although no difference in serum levels of 25(OH)D3, calcium or zonulin was observed in cholecalciferol-treated mice vs. healthy controls, a significant improvement in intestinal mucosa pathological features in mice administered cholecalciferol was observed by histological analysis. Villi length was also significantly increased by cholecalciferol in a dose-dependent manner. Immunohistochemical staining revealed increased expression of CD3 and ZO-1 in celiac mice compared to mice receiving high dose (130 μg/kg) cholecalciferol. These findings show the effect of oral cholecalciferol on signature features of CD in a mouse model of CD. Further dose-ranging studies to investigate the efficacy of cholecalciferol for the treatment of CD are warranted.

1,25(OH)2 D3 blocks IFNβ production through regulating STING in epithelial layer of oral lichen planus

Stimulator of interferon genes (STING) is reported to exert vital functions in inflammatory responses and autoimmune diseases. Nevertheless, the status and roles of STING in oral lichen planus (OLP) remain elusive. Here, we state that STING and its downstream cytokine interferon‐β (IFNβ) expression is boosted in the oral keratinocytes from patients suffering OLP in comparison with those from healthy participants. Mechanistically, transcription factor GATA‐binding protein 1 (GATA1) which is highly increased in diseased samples specifically interacts with its element in the promoter of STING to enhance STING transcripts. 1,25(OH)₂D₃, the active form of vitamin D, is capable of restricting STING and IFNβ increases in oral keratinocyte models resembling OLP in vitro. Moreover, there is a negative correlation between vitamin D receptor (VDR) and STING or IFNβ in human samples. Using plasmids and small interfering RNA transfection technologies, we find 1,25(OH)₂D₃ regulates STING and IFNβ through a mechanism controlled by the hypoxia‐inducible factor‐1α (HIF‐1α)‐GATA1 axis. Collectively, our findings unveil that 1,25(OH)₂D₃ lowers STING and IFNβ overexpression in the context of OLP.

Macrophage orchestration of epithelial and stromal cell homeostasis in the intestine

The intestinal tract is a complex ecosystem where numerous cell types of epithelial, immune, neuronal, and endothelial origin coexist in an intertwined, highly organized manner. The functional equilibrium of the intestine relies heavily on the proper crosstalk and cooperation among each cell population. Furthermore, macrophages are versatile, innate immune cells that participate widely in the modulation of inflammation and tissue remodeling. Emerging evidence suggest that macrophages are central in orchestrating tissue homeostasis. Herein, we describe how macrophages interact with epithelial cells, neurons, and other types of mesenchymal cells under the context of intestinal inflammation, followed by the therapeutic implications of cellular crosstalk pertaining to the treatment of inflammatory bowel disease.

The efficacy of vitamin D supplementation for irritable bowel syndrome: a systematic review with meta-analysis

BACKGROUND

Irritable bowel syndrome (IBS) is a chronic gastrointestinal disorder involving gut-brain interactions with limited effective treatment options. Vitamin D deficiency is commonly observed in patients with IBS, but whether vitamin D supplementation ameliorates IBS is controversial in randomized controlled trials. The present systematic review and meta-analysis explored the efficacy of vitamin D supplementation in patients with IBS.

METHODS

We performed a systematic search of potentially relevant publications from PubMed, EMBASE, the Cochrane Central Register of Controlled Studies and the Web of Science up until January 2022. We assessed the weighted mean difference (WMD) and 95% confidence interval (95% CI) of the IBS severity scoring system (IBS-SSS), IBS quality of life (IBS-QoL) and IBS total score (IBS-TS) before and after vitamin D supplementation intervention.

RESULTS

We included four randomized, placebo-controlled trials involving 335 participants. The differences in IBS-SSS score between participants in the intervention group and the placebo group increased after intervention (WMD: -55.55, 95% CI: -70.22 to -40.87, I2 = 53.7%, after intervention; WMD: -3.17, 95% CI: -18.15 to 11.81, I2 = 0.0%, before intervention). Participants receiving vitamin D supplementation showed greater improvement in IBS-SSS after intervention than participants receiving placebo treatment (WMD: -84.21, 95% CI: -111.38 to -57.05, I2 = 73.2%; WMD: -28.29, 95% CI: -49.95 to -6.62, I2 = 46.6%, respectively). Vitamin D supplementation was also superior to placebo in IBS-QoL improvement (WMD: 14.98, 95% CI: 12.06 to 17.90, I2 = 0.0%; WMD: 6.55, 95% CI: -2.23 to 15.33, I2 = 82.7%, respectively). Sensitivity analyses revealed an unstable pooled effect on IBS-TS in participants receiving vitamin D supplementation. Therefore, we did not evaluate the efficacy of vitamin D intervention in IBS-TS.

CONCLUSIONS

This systematic review and meta-analysis suggested that vitamin D supplementation was superior to placebo for IBS treatment.

Effects of UV/H2O2 degradation and step gradient ethanol precipitation on Sargassum fusiforme polysaccharides: Physicochemical characterization and protective effects against intestinal epithelial injury

In this study, the degraded purified fraction from Sargassum fusiforme polysaccharides (SFP), named DSFP, was produced by the treatment of ultraviolet/hydrogen peroxide (UV/H2O2) degradation and step gradient ethanol precipitation. Results showed that the treatment significantly reduced the molecular weight of polysaccharides, from 282.83 kDa to 18.54 kDa, and influenced their surface morphology and roughness. SFP and DSFP were typical sulfated polysaccharides, mainly composed of fucose, galacturonic acid, glucuronic acid, galactose, and mannose. Both SFP and DSFP increased cell migration during intestinal epithelial wound healing and stimulated the cell cycle progression by promoting the transition from G0/G1 to S phase in the rat intestine epithelium cells (IEC-6). But DSFP had a stronger positive effect on wound healing and cell migration than SFP. It reinforced the intestinal barrier function and attenuated lipopolysaccharides-induced intestinal inflammation. DSFP significantly downregulated the expression of Toll-like receptor 4, tumor necrosis factor-α, interleukin-6, interleukin-1β, and inducible nitric oxide synthase by 53.14%, 92.41%, 66.01%, 68.24%, and 78.09%, respectively, and upregulated that of interleukin-10 by 2.48 folds when compared to the model. Therefore, the treatment (UV/H2O2 degradation and step gradient ethanol precipitation) could effectively improve the protective effects against intestinal epithelial injury.

Micronutrient Improvement of Epithelial Barrier Function in Various Disease States: A Case for Adjuvant Therapy

The published literature makes a very strong case that a wide range of disease morbidity associates with and may in part be due to epithelial barrier leak. An equally large body of published literature substantiates that a diverse group of micronutrients can reduce barrier leak across a wide array of epithelial tissue types, stemming from both cell culture as well as animal and human tissue models. Conversely, micronutrient deficiencies can exacerbate both barrier leak and morbidity. Focusing on zinc, Vitamin A and Vitamin D, this review shows that at concentrations above RDA levels but well below toxicity limits, these micronutrients can induce cell- and tissue-specific molecular-level changes in tight junctional complexes (and by other mechanisms) that reduce barrier leak. An opportunity now exists in critical care—but also medical prophylactic and therapeutic care in general—to consider implementation of select micronutrients at elevated dosages as adjuvant therapeutics in a variety of disease management. This consideration is particularly pointed amidst the COVID-19 pandemic.

Vitamin D in Inflammatory Bowel Diseases. Mechanisms of Action and Therapeutic Implications

(1) Background: Vitamin D is an immunoregulatory factor influencing intestinal homeostasis. Recent evidence supports a central role of this micronutrient in the course of Inflammatory Bowel Diseases (IBD). This narrative review aims to provide a general overview of the possible biological mechanisms of action of vitamin D and its therapeutic implications in IBD. (2) Methods: A systematic electronic search of the English literature up to October 2021 was performed using Medline and the Cochrane Library. Only papers written in English that analyzed the role of vitamin D in IBD were included. (3) Results: In vitro and animal studies reported that vitamin D signaling improves epithelial barrier integrity regulating the expression of several junctional proteins, defensins, and mucins, modulates the inflammatory response, and affects gut microbiome composition. Recent studies also suggest that vitamin D deficiency is highly prevalent among IBD patients and that low serum levels correlate with disease activity and, less clearly, with disease course. (4) Conclusions: An increasing body of evidence suggests some role of vitamin D in the pathophysiology of IBD, nonetheless the underlying mechanisms have been so far only partially elucidated. A strong correlation with disease activity has been reported but its implication in the treatment is still undefined. Thus, studies focused on this issue, the definition of vitamin D levels responsible for clinical effects, and the potential role of vitamin D as a therapeutic agent are strongly encouraged.

Neuroinflammation as an etiological trigger for depression comorbid with inflammatory bowel disease

Patients with inflammatory bowel disease (IBD) suffer from depression at higher rates than the general population. An etiological trigger of depressive symptoms is theorised to be inflammation within the central nervous system. It is believed that heightened intestinal inflammation and dysfunction of the enteric nervous system (ENS) contribute to impaired intestinal permeability, which facilitates the translocation of intestinal enterotoxins into the blood circulation. Consequently, these may compromise the immunological and physiological functioning of distant non-intestinal tissues such as the brain. In vivo models of colitis provide evidence of increased blood–brain barrier permeability and enhanced central nervous system (CNS) immune activity triggered by intestinal enterotoxins and blood-borne inflammatory mediators. Understanding the immunological, physiological, and structural changes associated with IBD and neuroinflammation may aid in the development of more tailored and suitable pharmaceutical treatment for IBD-associated depression.

Research on the Protective Effect of MiR-185-3p Mediated by Huangqin-Tang Decoction (HQT) on the Epithelial Barrier Function of Ulcerative Colitis

Introduction

It has been reported that the traditional Chinese medicine Huangqin-Tang decoction (HQT) has a protective effect on the epithelial barrier function of ulcerative colitis, but its mechanism has not been fully clarified. This study intends to explore the protective mechanism of HQT in regulating microRNA (miRNA) for the first time.

Methods

Based on the Balb/c mice ulcerative colitis model, the mice were given a gavage of 0.1 mL/10 g HQT every day for 7 days; on the 8th day, the colon of the mice was dissected, the length of the colon for the mice was measured, and the score was given based on this. Analysis of colonic mucosal injury was conducted by hematoxylin-eosin staining. Then, the differential miRNA was screened and sequenced in colon tissue using the HiSeq platform. And the differential miR-185-3p gene was verified by RT-PCR. Finally, the effects of HQT on miR-185-3p, occludin protein expression, and transepithelial electrical resistance (TEER) value were observed in combination with the CaCo₂ intestinal epithelial cell model.

Results

HQT treatment can alleviate the shortening of colon length and reverse the intestinal mucosal injury. miRNA sequencing of colonic tissue showed that miR-185-3p was significantly downregulated in the model group, while HQT could upregulate miR-185-3p, thereby affecting the myosin light chain kinase (MLCK)/myosin light chain phosphorylation (p-MLC) pathway and leading to increased expression of occludin protein, which ultimately protected the intestinal epithelial barrier function.

Conclusion

HQT can protect colon epithelial barrier function by regulating miR-185-3p.

The functional role of miRNAs in inflammatory pathways associated with intestinal epithelial tight junction barrier regulation in IBD

Inflammatory bowel disease – Crohn's disease and ulcerative colitis – is an immune-mediated chronic disorder with still not fully elucidated complex mechanisms of pathogenesis and pathophysiology. Intestinal epithelial barrier (IEB) dysregulation is one of the major underlying mechanisms of inflammatory process induction in IBD. Proper IEB integrity is maintained to a large extent by intercellular tight junctions, the function of which can be modified by many molecules, including miRNAs. MiRNAs belong to noncoding and non-messenger RNAs, which can modulate gene expression by binding predicted mRNAs.

In this review, we summarize and discuss the potential role of miRNAs in the regulation of inflammatory signaling pathways affecting the function of the intestinal epithelial barrier in IBD, with particular emphasis on therapeutic potentials. The aim of the review is also to determine the further development directions of the studies on miRNA in the modulation of the intestinal epithelial barrier in IBD.

Vitamin D Deficiency Exacerbates Colonic Inflammation Due to Activation of the Local Renin-Angiotensin System in the Colon

BACKGROUND

The renin-angiotensin system (RAS) is activated in inflammatory bowel disease (IBD), and vitamin D deficiency aggravates the development of colitis, but the relationship between the local colonic RAS and vitamin D is unclear with regard to the pathogenesis of IBD.

AIMS

To investigate whether vitamin D suppresses the local colonic RAS to prevent colonic mucosal inflammation in a mouse model of experimental colitis.

METHODS

C57BL/6 mice fed vitamin D-deficient (VDD) diet for 8 weeks were induced to colitis by 2,4,6-trinitrobenzenesulfonic acid (TNBS), with mice fed vitamin D-sufficient (VDS) diet as controls. Colitis severity was assessed by histology, and pro-inflammatory cytokines, RAS components, and signaling pathways were quantified by real-time RT-PCR and Western blotting.

RESULTS

C57BL/6 mice fed the VDD diet for 8 weeks exhibited significantly lower serum 25(OH)D₃ concentrations compared to mice fed the VDS diet. When these VDD mice were induced to colitis by TNBS, they exhibited more severe colonic inflammation and developed more severe colitis compared to the VDS counterparts. VDD diet feeding resulted in higher production of mucosal pro-inflammatory cytokines, higher activation of the myosin light chain kinase-tight junction regulatory pathway, and greater increases in mucosal permeability. VDD diet feeding also enhanced colonic RAS activation. Treatment with angiotensin II receptor blocker losartan markedly alleviated colitis in TNBS-induced VDD mice.

CONCLUSION

Vitamin D deficiency promotes colonic inflammation at least in part due to over activation of the local RAS in the colon.

Role of vitamin D in regulating COVID-19 severity-An immunological perspective

Vitamin D, a key nutrient/prohormone classically associated with skeletal health, is also an important immunomodulator, with pleotropic effects on innate and adaptive immune cells. Outcomes of several chronic, autoimmune, and infectious diseases are linked to vitamin D. Emergent correlations of vitamin D insufficiency with coronavirus-induced disease 2019 (COVID-19) severity, alongside empirical and clinical evidence of immunoregulation by vitamin D in other pulmonary diseases, have prompted proposals of vitamin D supplementation to curb the COVID-19 public health toll. In this review paper, we engage an immunological lens to discuss potential mechanisms by which vitamin D signals might regulate respiratory disease severity in severe acute respiratory syndrome coronavirus 2 (SARS-CoV2) infections, vis a vis other pulmonary infections. It is proposed that vitamin D signals temper lung inflammatory cascades during SARS-CoV2 infection, and insufficiency of vitamin D causes increased inflammatory cytokine storm, thus leading to exacerbated respiratory disease. Additionally, analogous to studies of reduced cancer incidence, the dosage of vitamin D compounds administered to patients near the upper limit of safety may serve to maximize immune health benefits and mitigate inflammation and disease severity in SARS-CoV2 infections. We further deliberate on the importance of statistically powered clinical correlative and interventional studies, and the need for in-depth basic research into vitamin D-dependent host determinants of respiratory disease severity.

Vitamin D Reverses Disruption of Gut Epithelial Barrier Function Caused by Campylobacter jejuni

Infections by the zoonotic foodborne bacterium Campylobacter jejuni (C. jejuni) are among the most frequent causes of bacterial gastroenteritis worldwide. The aim was to evaluate the relationship between epithelial barrier disruption, mucosal immune activation, and vitamin D (VD) treatment during C. jejuni infection, using intestinal epithelial cells and mouse models focused on the interaction of C. jejuni with the VD signaling pathway and VD treatment to improve C. jejuni-induced barrier dysfunction. Our RNA-Seq data from campylobacteriosis patients demonstrate inhibition of VD receptor (VDR) downstream targets, consistent with suppression of immune function. Barrier-preserving effects of VD addition were identified in C. jejuni-infected epithelial cells and IL-10^-/- mice. Furthermore, interference of C. jejuni with the VDR pathway was shown via VDR/retinoid X receptor (RXR) interaction. Paracellular leakiness of infected epithelia correlated with tight junction (TJ) protein redistribution off the TJ domain and apoptosis induction. Supplementation with VD reversed barrier impairment and prevented inhibition of the VDR pathway, as shown by restoration of transepithelial electrical resistance and fluorescein (332 Da) permeability. We conclude that VD treatment restores gut epithelial barrier functionality and decreases bacterial transmigration and might, therefore, be a promising compound for C. jejuni treatment in humans and animals.

TNF-α-Induced miR-21-3p Promotes Intestinal Barrier Dysfunction by Inhibiting MTDH Expression

Intestinal barrier dysfunction is characterized by increased intestinal permeability to lumen endotoxin, showing remarkable predisposition to immune enteropathy, and colorectal cancer tumor necrosis factor (TNF)-α is associated with this pathological process, while the mechanism remains unknown. In this study, different doses of TNF-α were used for Caco-2 cell treatment. We discovered that miR-21-3p expression was obviously increased by TNF-α in a dose-dependent manner. Further study demonstrated that TNF-α could upregulate miR-21-3p expression through the NF-κB signaling pathway. Then, TargetScan and miRWalk miRNA-mRNA interaction prediction online tools were introduced, and metadherin (MTDH) was screened out as a potential target of miR-21-3p. We subsequently found that miR-21-3p could directly target the 3'-untranslated region (UTR) of MTDH mRNA and inhibit its expression. Furthermore, it was demonstrated that miR-21-3p could regulate the Wnt signaling pathway by targeting MTDH mRNA, suggesting the effect of miR-21-3p/MTDH/Wnt axis on intestinal barrier dysfunction. Our findings provide a novel potential biomarker and therapeutic target for intestinal barrier dysfunction and related diseases.

ZFP36 promotes VDR mRNA degradation to facilitate cell death in oral and colonic epithelial cells

BACKGROUND

Vitamin D receptor (VDR) plays a vital protective role in oral and colonic epithelial cells. Albeit we know that VDR expression is reduced in the mucosal epithelial layers of autoimmune diseases, the mechanism by which VDR is decreased remains elusive.

METHODS

VDR and zinc finger protein 36 (ZFP36) levels in human samples and cell lines were detected by real-time PCR, western blot and immunostaining. Luciferase report assay was used to test cis-elements in VDR gene promoter, real-time PCR was applied to measure mRNA decay and western blot was performed to evaluate protein degradation. RNA affinity chromatography assay was used to test protein-mRNA interaction. Co-immunoprecipitation was used to detect protein-protein interaction. The role of ZFP36 in AU-rich elements (AREs) in the 3' untranslated region (UTR) of VDR mRNA was also measured by luciferase report assay.

RESULTS

We identify ZFP36 can bind with the AREs in the 3'UTR of VDR mRNA, leading to mRNA degradation in oral and colonic epithelial cells under inflammatory circumstance. Either ZFP36 protein or AREs of VDR mRNA mutation abolishes this protein-mRNA binding process. After the key amino acid's mutation, ZFP36 fails to decrease VDR mRNA expression. We also find that VDR physically binds with Y box-binding protein 1 (YBX-1) to block YBX-1's nuclear translocation and ameliorate cell death in the presence of inflammation.

CONCLUSION

These findings provide insights into the cause of VDR decrease in oral and colonic epithelial cells under inflammatory condition and explain how VDR maintains cell viability in these cells. Video abstract.

Vitamin D Receptor Gene Single Nucleotide Polymorphisms and Association With Vitamin D Levels and Endoscopic Disease Activity in Inflammatory Bowel Disease Patients: A Pilot Study

BACKGROUND

Inflammatory bowel diseases (IBDs) comprise a heterogenous group of chronic gastrointestinal disorders that are multifactorial in etiology. Experimental in vitro and in vivo studies suggest that intestinal vitamin D receptor (VDR) signaling plays a role in modulating the immune response in IBD as a cause and/or a consequence of chronic inflammation.

AIM

The aim of this study is to study the associations between vitamin D receptor gene single nucleotide polymorphisms(SNPs), vitamin D levels, and endoscopic disease activity in IBD.

METHODS

This is a cross-sectional analysis of IBD patients who underwent endoscopic evaluation at a tertiary care hospital. Demographic variables, IBD disease type and location, medical therapies, vitamin D levels, and endoscopic disease activity were collected. Colonic biopsies obtained were investigated for the presence of VDR SNPs: ApaI, TaqI, BsmI, FokI, and Tru9I.

RESULTS

Patients in endoscopic remission had higher vitamin D levels compared with those with inflammation found on endoscopy (P = <0.001). Patients with lower vitamin D levels were homozygous for Fok ancestral alleles (P = 0.0045). With regard to endoscopic disease activity, we found no differences in mutations of any of the VDR SNPs in our sample.

CONCLUSIONS

The association between the presence of the ancestral FokI and lower vitamin D levels suggests a multifactorial etiology for vitamin D deficiency in IBD. Higher vitamin D levels in those in endoscopic remission compared with lower levels in those with active inflammation suggests that the impact of VDR gene SNP on disease activity may be overcome with replacement therapy.

Obesity Promotes Experimental Colitis by Increasing Oxidative Stress and Mitochondrial Dysfunction in the Colon

Although obesity is associated with inflammatory bowel disease (IBD), the underlying molecular mechanism still remains unclear. In this study, we evaluated the effects of high-fat diet (HFD)-induced obesity on the development of experimental colitis in mice. The C57BL/6 mice were fed with a HFD for 12 weeks to develop obesity. The concentrations of free fatty acids (FFA), triglycerides, and cholesterol in plasma were significantly increased in HFD-fed mice compared to low-fat diet (LFD)-fed mice. We found that HFD-induced obesity could exacerbate 2,4,6-trinitro-benzene-sulfonic acid (TNBS)-induced experimental colitis in mice resembling Crohn's disease (CD). HFD-fed mice showed shorter colon length, higher clinical scores and histological scores, more production of mucosal tumor necrosis factor-α (TNF-α), and greater destruction of colonic epithelial barrier than LFD-fed mice after TNBS induction. HFD feeding also promoted reactive oxygen species (ROS) production in colonic epithelial cells, thus activating the pro-apoptotic pathway to damage colonic epithelial barrier induced by TNBS. After HCT116 cells were treated with palmitate acid (PA) and/or TNF-α for 24 h, the combination of PA and TNF-α increased ROS production, promoted mitochondrial dysfunction, and activated the pro-apoptotic pathway, but these effects were markedly attenuated by a ROS inhibitor. Taken together, these observations suggest that HFD-induced obesity promotes experimental colitis by increasing oxidative stress and mitochondrial dysfunction, which triggers the activation of pro-apoptotic pathway in the colon.

HO-1/CO Maintains Intestinal Barrier Integrity through NF-κB/MLCK Pathway in Intestinal HO-1-/- Mice

Background

Intestinal barrier injury is an important contributor to many diseases. We previously found that heme oxygenase-1 (HO-1) and carbon monoxide (CO) protect the intestinal barrier. This study is aimed at elucidating the molecular mechanisms of HO-1/CO in barrier loss.

Materials and Methods

We induced gut leakiness by injecting carbon tetrachloride (CCl₄) to wildtype or intestinal HO-1-deficient mice. In addition, we administrated tumor necrosis factor-α (TNF-α) to cells with gain- or loss-of-HO-1 function. The effects of HO-1/CO maintaining intestinal barrier integrity were investigated in vivo and in vitro.

Results

Cobalt protoporphyrin and CO-releasing molecule-2 alleviated colonic mucosal injury and TNF-α levels; upregulated tight junction (TJ) expression; and inhibited epithelial IκB-α degradation and phosphorylation, NF-κB p65 phosphorylation, long MLCK expression, and MLC-2 phosphorylation after administration of CCl₄. Zinc protoporphyrin completely reversed these effects. These findings were further confirmed in vitro, using Caco-2 cells with gain- or loss-of-HO-1-function after TNF-α. Pretreated with JSH-23 (NF-κB inhibitor) or ML-7 (long MLCK inhibitor), HO-1 overexpression prevented TNF-α-induced TJ disruption, while HO-1 shRNA promoted TJ damage even in the presence of JSH-23 or ML-7, thus suggesting that HO-1 dependently protected intestinal barrier via the NF-κB p65/MLCK/p-MLC-2 pathway. Intestinal HO-1-deficient mice further demonstrated the effects of HO-1 in maintaining intestinal barrier integrity and its relative mechanisms. Alleviated hepatic fibrogenesis and serum ALT levels finally confirmed the clinical significance of HO-1/CO repairing barrier loss in liver injury.

Conclusion

HO-1/CO maintains intestinal barrier integrity through the NF-κB/MLCK pathway. Therefore, the intestinal HO-1/CO-NF-κB/MLCK system is a potential therapeutic target for diseases with a leaky gut.

Potential Mechanisms Mediating the Protective Effects of Tricholoma matsutake-Derived Peptides in Mitigating DSS-Induced Colitis

Intestinal barrier dysfunction and inflammatory cytokine secretion play crucial roles in inflammatory bowel disease (IBD). Herein, we investigated the protective effects of Tricholoma matsutake-derived peptides SDIKHFPF and SDLKHFPF against dextran sulfate sodium-induced colitis. Both peptides alleviated colitis signs, including diarrhea, weight loss, bloody stools, colon shortening, and histopathological changes, while reducing mucus destruction, goblet cell exhaustion, and intestinal permeability. SDIKHFPF and SDLKHFPF protected the barrier function by promoting the expression of tight junction (TJ) zonula occludens-1 and occludin within the colon, as well as attenuating colonic inflammation through myeloperoxidase and pro-inflammatory cytokine suppression. Western blotting indicated that the peptides suppressed myosin light chain kinase (MLCK) and nuclear factor kappa B (NF-κB) levels, inhibiting MLC phosphorylation. SDLKHFPF was more potent than SDIKHFPF. These findings suggest that peptide SDLKHFPF mitigates colitis by regulating TJ protein expression and pro-inflammatory cytokine production via NF-κB/MLCK/p-MLC signaling, improving the barrier function.

Immunomodulatory Effects of Vitamin D Supplementation in a Deficient Population

In addition to its canonical functions, vitamin D has been proposed to be an important mediator of the immune system. Despite ample sunshine, vitamin D deficiency is prevalent (>80%) in the Middle East, resulting in a high rate of supplementation. However, the underlying molecular mechanisms of the specific regimen prescribed and the potential factors affecting an individual's response to vitamin D supplementation are not well characterized. Our objective is to describe the changes in the blood transcriptome and explore the potential mechanisms associated with vitamin D3 supplementation in one hundred vitamin D-deficient women who were given a weekly oral dose (50,000 IU) of vitamin D3 for three months. A high-throughput targeted PCR, composed of 264 genes representing the important blood transcriptomic fingerprints of health and disease states, was performed on pre and post-supplementation blood samples to profile the molecular response to vitamin D3. We identified 54 differentially expressed genes that were strongly modulated by vitamin D3 supplementation. Network analyses showed significant changes in the immune-related pathways such as TLR4/CD14 and IFN receptors, and catabolic processes related to NF-kB, which were subsequently confirmed by gene ontology enrichment analyses. We proposed a model for vitamin D3 response based on the expression changes of molecules involved in the receptor-mediated intra-cellular signaling pathways and the ensuing predicted effects on cytokine production. Overall, vitamin D3 has a strong effect on the immune system, G-coupled protein receptor signaling, and the ubiquitin system. We highlighted the major molecular changes and biological processes induced by vitamin D3, which will help to further investigate the effectiveness of vitamin D3 supplementation among individuals in the Middle East as well as other regions.

Vitamin D/VDR signaling inhibits colitis by suppressing HIF-1α activation in colonic epithelial cells

Vitamin D/vitamin D receptor (VDR) signaling is reported to have a protective effect on the onset or progression of inflammatory bowel diseases (IBD), and hypoxia-inducible factor 1α (HIF-1α) activation is demonstrated to be closely associated with chemical-induced colitis. However, the association between vitamin D/VDR signaling and HIF-1α on IBD development remains a mystery. Here, we showed that HIF-1α expression was largely increased in the colonic epithelial cells of diseased tissues from patients with ulcerative colitis (UC). Consistently, HIF-1α activation was also improved in colonic epithelial cells upon TNFα treatment in a NF-κB pathway-dependent manner. HIF-1α inhibitors treatments ameliorated 2,4,6-trinitrobenzenesulfonic acid (TNBS)- or dextran sulfate sodium (DSS)-induced colitis in animal models. In cell or colitis animal models, vitamin D/VDR signaling suppressed HIF-1α overexpression in colonic epithelial cells via regulating NF-κB pathway, resulting in the inhibition of IFNγ and IL-1β overproductions in these cells. Collectively, these data suggest that vitamin D/VDR signaling relieves colitis development in animal models, at least in part, by suppressing HIF-1α expression in colonic epithelial cells.NEW & NOTEWORTHY This study demonstrates vitamin D/VDR signaling inhibits colitis by suppressing HIF-1α activation in colonic epithelial cells. Since the effect of vitamin D/VDR signaling is only apparent on patients who seem to be vitamin D deficient, the benefits of vitamin D supplementation in patients who are not vitamin D deficient need to be proven.

Adverse Effects of Heat Stress on the Intestinal Integrity and Function of Pigs and the Mitigation Capacity of Dietary Antioxidants: A Review

Heat stress (HS) significantly affects the performance of pigs by its induced stressors such as inflammation, hypoxia and oxidative stress (OS), which mightily strain the intestinal integrity and function of pigs. As heat stress progresses, several mechanisms in the intestinal epithelium involved in the absorption of nutrients and its protective functions are altered. Changes in these mechanisms are mainly driven by cellular oxidative stress, which promotes disruption of intestinal homeostasis, leading to intestinal permeability, emphasizing intestinal histology and morphology with little possibility of recovering even after exposure to HS. Identification and understanding of these altered mechanisms are crucial for providing appropriate intervention strategies. Therefore, it is this papers' objective to review the important components for intestinal integrity that are negatively affected by HS and its induced stressors. With due consideration to the amelioration of such effects through nutritional intervention, this work will also look into the capability of dietary antioxidants in mitigating such adverse effects and maintaining the intestine's integrity and function upon the pigs' exposure to high environmental temperature.

Could there be a role of serum zonulin increase in the development of hypercalcemia in primary hyperparathyroidism

PURPOSE

To evaluate the serum level of zonulin, which is an intestinal permeability (IP) biomarker, in primary hyperparathyroidism (PHPT) and to investigate the relationship between zonulin, calcium, and parathormone (PTH) levels.

METHODS

The study included 34 healthy control (HC) and 39 patients with PHPT. Serum calcium, phosphorus, magnesium, creatinine, albumin, and 24 h urine calcium levels were measured in all groups. Serum levels of zonulin were measured quantitatively by enzyme-linked immunosorbent assay (ELISA). Urinary ultrasonography (to assess the presence of nephrolithiasis) and dual energy X-ray absorptiometry (to assess the presence of osteoporosis) were used to evaluate complications related to PTHP.

RESULTS

Serum zonulin levels were significantly higher in the PHPT group than the HC group (p < 0.001). Zonulin levels were significantly positively correlated with plasma PTH and serum calcium levels (r = 0.600, p < 0.001 and r = 0.610, p < 0.001; respectively). There was no correlation between serum zonulin levels and adenoma volume.

CONCLUSION

Serum zonulin level increases in patients with PHPT. Serum zonulin levels show a moderate/strong positive correlation with serum calcium and plasma PTH levels. This suggests that IP increase may play a role in the development of hypercalcemia in patients with PHPT.

Intestinal Barrier Dysfunction Participates in the Pathophysiology of Ischemic Stroke

The gastrointestinal tract is a major organ for the body to absorb nutrients, water and electrolytes. At the same time, it is a tight barrier to resist the invasion of harmful substances and maintain the homeostasis of the internal environment. Destruction of the intestinal barrier is linked to the digestive system, cardiovascular system, endocrine system and other systemic diseases. Mounting evidence suggests that ischemic stroke not only changes the intestinal microbes, but also increases the permeability of the intestinal barrier, leading to bacterial translocation, infection, and even sepsis. The intestinal barrier, as part of the gut-brain axis, has also been proven to participate in the pathophysiological process of ischemic stroke. However, little attention has been paid to it. Since ischemic stroke is a major public health issue worldwide, there is an urgent need to know more about the disease for better prevention, treatment and prognosis. Therefore, understanding the pathophysiological relationship between ischemic stroke and the intestinal barrier will help researchers further uncover the pathophysiological mechanism of ischemic stroke and provide a novel therapeutic target for the treatment of ischemic stroke. Here, we review the physiology and pathology between ischemic stroke and intestinal barrier based on related articles published in the past ten years about the relationship between ischemic stroke, stroke risk factors and intestinal flora, intestinal barrier, and discuss the following parts: the intestinal barrier; possible mechanisms of intestinal barrier destruction in ischemic stroke; intestinal barrier destruction caused by stroke-related risk factors; intestinal barrier dysfunction in ischemic stroke; targeting the intestinal barrier to improve stroke; conclusions and perspectives.