Targeting desmosomal adhesion and signalling for intestinal barrier stabilization in inflammatory bowel diseases-Lessons from experimental models and patients

Christensenella minuta protects and restores intestinal barrier in a colitis mouse model by regulating inflammation

Christensenella minuta DSM 22607 has recently been suggested as a potential microbiome-based therapy for inflammatory bowel disease (IBD) because it displays strong anti-inflammatory effects both in vitro and in vivo. Here, we aimed to decipher the mechanism(s) underlying the DSM 22607-mediated beneficial effects on the host in a mouse model of chemically induced acute colitis. We observed that C. minuta plays a key role in the preservation of the epithelial barrier and the management of DNBS-induced inflammation by inhibiting interleukin (IL)-33 and Tumor necrosis factor receptor superfamily member 8 (Tnfrsf8) gene expression. We also showed that DSM 22607 abundance was positively correlated with Akkermansia sp. and Dubosiella sp. and modulated microbial metabolites in the cecum. These results offer new insights into the biological and molecular mechanisms underlying the beneficial effects of C. minuta DSM 22607 by protecting the intestinal barrier integrity and regulating inflammation.

Formononetin ameliorates dextran sulfate sodium-induced colitis via enhancing antioxidant capacity, promoting tight junction protein expression and reshaping M1/M2 macrophage polarization balance

Ulcerative colitis (UC) is a complex, refractory inflammatory bowel disease characterized impared intestinal mucosal barrier and imbalanced M1/M2 macrophage polarization mediating its progression. Formononetin (FN), a bioactive isoflavone with established anti-inflammatory and immunomodulatory properties, shows promise in mitigating UC, yet its therapeutic and underlying mechanisms remain unclear. In this study, colitis was induced in mice by administering 2.5% (w/v) dextran sulfate sodium (DSS) solution for 7 days. Oral (25, 50, and 100 mg/kg) FN for 10 days significantly ameliorated colitis symptoms in a dose-dependent manner, by mitigating body weight loss, reducing disease activity index (DAI), colonic weight, and colonic weight index, while enhancing survival rates and colonic length. Histological analysis revealed FN remarkably suppressed inflammatory damage in colonic tissues. Furthermore, FN modulated the expression of pro- and anti-inflammatory cytokines and enhanced antioxidant capacity. Notably, FN treatment significantly enhanced the expression of tight junction (TJ) proteins (claudin-1, ZO-1, occludin) at both protein and mRNA levels in the colon tissues, suggesting improved intestinal barrier function. Crucially, FN inhibited macrophage infiltration in colonic tissues and rebalanced M1/M2 macrophage polarization. While, macrophage depletion largely abrogated FN's protective effects against colitis, indicating a crucial role for macrophages in mediating FN's therapeutic response. Overall, FN effectively alleviated colitis primarily via modulating inflammatory cytokine expression, enhancing antioxidant capacity, upregulating TJs proteins expression, and remodeling M1/M2 macrophage polarization equilibrium. These findings suggest that FN could be the next candidate to unlocking UC's treatment challenge.

Miao sour soup alleviates DSS-induced colitis in mice: modulation of gut microbiota and intestinal barrier function

Miao sour soup (MSS), a daily fermented food in Guizhou, China, is rich in microorganisms with various beneficial activities, including anti-inflammatory and antioxidant activities. However, the therapeutic effects of MSS on IBD remain unexplored. This study aimed to investigate the protective effect of MSS against colitis in mice. In this study, we examined the microbial community structure of MSS by metagenomic sequencing and also explored the protective effect of MSS on DSS-induced colitis in mice. We investigated the effects of MSS on intestinal inflammatory response and intestinal barrier function in mice. Finally, the changes in intestinal flora were analyzed based on the 16S rRNA gene sequencing results. Significantly, the experiment result shows that MSS ameliorated the severity of DSS-induced disease in mice by mitigating colitis-associated weight loss, reducing the disease activity index of IBD, alleviating colonic hemorrhagic lesions, increasing colon length, and improving colonic tissue damage. Moreover, MSS preserved intestinal barrier integrity and restored intestinal epithelial function in mice. Additionally, MSS modulated the structure and composition of the intestinal flora. Furthermore, MSS downregulated pro-inflammatory factors and attenuated the NF-κB p65 expression, thereby mitigating the inflammatory response. These findings highlight the protective effect of MSS against DSS-induced colitis, providing substantial scientific support for potential applications of MSS as a functional food.

Peroxisomal cholesterol metabolism regulates yap-signaling, which maintains intestinal epithelial barrier function and is altered in Crohn's disease

Intestinal epithelial cells line the luminal surface to establish the intestinal barrier, where the cells play essential roles in the digestion of food, absorption of nutrients and water, protection from microbial infections, and maintaining symbiotic interactions with the commensal microbial populations. Maintaining and coordinating all these functions requires tight regulatory signaling, which is essential for intestinal homeostasis and organismal health. Dysfunction of intestinal epithelial cells, indeed, is linked to gastrointestinal disorders such as irritable bowel syndrome, inflammatory bowel disease, and gluten-related enteropathies. Emerging evidence suggests that peroxisome metabolic functions are crucial in maintaining intestinal epithelial cell functions and intestinal epithelium regeneration and, therefore, homeostasis. Here, we investigated the molecular mechanisms by which peroxisome metabolism impacts enteric health using the fruit fly Drosophila melanogaster and murine model organisms and clinical samples. We show that peroxisomes control cellular cholesterol, which in turn regulates the conserved yes-associated protein-signaling and contributes to intestinal epithelial structure and epithelial barrier function. Moreover, analysis of intestinal organoid cultures derived from biopsies of patients affected by Crohn's Disease revealed that the dysregulation of peroxisome number, excessive cellular cholesterol, and inhibition of Yap-signaling are markers of disease and could be novel diagnostic and/or therapeutic targets for treating Crohn's Disease. Our studies provided mechanistic insights on peroxisomal signaling in intestinal epithelial cell functions and identified cholesterol as a novel metabolic regulator of yes-associated protein-signaling in tissue homeostasis.

Pig-Derived Probiotic Bacillus tequilensis YB-2 Alleviates Intestinal Inflammation and Intestinal Barrier Damage in Colitis Mice by Suppressing the TLR4/NF-κB Signaling Pathway

The search for new probiotics has been regarded as an important approach to improving intestinal health in animals. Bacillus has many advantages, such as strong resistance to harmful external factors, wide distribution, and easy colonization of the intestine. Hence, this study aims to screen for a probiotic Bacillus strain that improves animal intestinal health and to elucidate its probiotic mechanism so as to provide probiotic resources for the development of feed-using probiotic formulations. In this research, a strain of Bacillus was isolated from adult pig feces and named B. tequilensis YB-2. In vitro probiotic experiments showed that B. tequilensis YB-2 had strong acid and bile salt resistance, indicating that this strain can customize in the intestine. To further explore the effect of B. tequilensis YB-2 upon animal intestinal health, DSS-induced murine colitis models were established, and the body weight, colonic morphology, inflammatory cytokines level, and intestinal-barrier- and TLR4/NF-κB-pathway-related protein were determined. The results showed that mice receiving drinking water with 3% DSS were found to develop colitis symptoms, including body weight loss and increased disease activity index (DAI); colon length and microvilli shedding were shortened; tight junctions were disrupted; goblet cells decreased; anti-inflammatory cytokines were inhibited; and pro-inflammatory cytokines and the TLR4/NF-κB signaling pathway were activated. Notably, orally received B. tequilensis YB-2 alleviated symptoms of DSS-induced colitis in mice. The above results indicated that B. tequilensis YB-2 was capable of improving colitis in mice by weakening inflammation and intestinal barrier damage, and its mechanism may involve the TLR4/NF-κB pathway. Overall, this research suggests that B. tequilensis YB-2 has the potential to serve as an animal feed additive to prevent intestinal inflammation.

Prinsepia utilis Royle polysaccharides promote skin barrier repair through the Claudin family

BACKGROUND

Plant polysaccharides have various biological activities. However, few studies have been conducted on the skin barrier of Prinsepia utilis Royle polysaccharide extract (PURP).

MATERIALS AND METHODS

The proportions of polysaccharides, monosaccharides and proteins were determined by extracting polysaccharides from fruit meal using water. The healing rate was measured by cell scratch assays. SDS-damaged reconstructed human epidermal models, an acetone-ether-induced mouse model and an IL-4-induced cellular inflammation model were used to detect the effects of polysaccharides on the phenotype, HA, TEWL, and TEER, with further characterizations performed using QRT-PCR, Western blotting, immunofluorescence (IF) assays.

RESULTS

PURP contained 35.73% polysaccharides and 11.1% proteins. PURP promoted cell migration and increased skin thickness in a reconstructed human epidermis model. The TEWL significantly decreased, and the HA content significantly increased. PURP significantly increased the TEER and decreased the permeability of the SDS-damaged reconstructed human epidermis model. Claudin-3, Claudin-4, and Claudin-5 were significantly upregulated. IF and Western blot analysis revealed that the Claudin-4 level significantly increased after treatment with PURP. Claudin-1, Claudin-3, Claudin-4, and Claudin-5 gene expression and IF and immunohistochemical staining were significantly increased in mice treated with acetone-ether. PURP promoted the expression of Claudin-1, Claudin-3, Claudin-4, and Claudin-5 after treatment with 100 ng/mL IL-4. PURP also downregulated the expression of NO, IL6, TNFα and NFκB in Raw 264.7 cells and in a mouse model.

CONCLUSION

We hypothesize that PURP may repair the skin barrier by promoting the expression of the claudin family and can assist in skin therapy.

Gallic acid attenuates LPS-induced inflammation in Caco-2 cells by suppressing the activation of the NF-κB/MAPK signaling pathway

Inflammatory bowel disease (IBD) is a chronic inflammatory disease characterized by intestinal barrier dysfunction, inflammatory synergistic effects and excessive tissue injury. Gallic acid (GA) is renowned for its remarkable biological activity, encompassing anti-inflammatory and antioxidant properties. However, the underlying mechanisms by which GA protects against intestinal inflammation have not been fully elucidated. The aim of this study is to investigate the effect of GA on the inflammation of a lipopolysaccharide (LPS)-stimulated human colon carcinoma cell line (Caco-2) and on the intestinal barrier dysfunction, and explore the underlying molecular mechanism involved. Our findings demonstrate that 5 μg/mL GA restores the downregulation of the mRNA and protein levels of Claudin-1, Occludin, and ZO-1 and decreases the expressions of inflammatory factors such as IL-6, IL-1β and TNF-α induced by LPS. In addition, GA exhibits a protective effect by reducing the LPS-enhanced early and late apoptotic ratios, downregulating the mRNA levels of pro-apoptotic factors ( Bax, Bad, Caspase-3, Caspase-8, and Caspase-9), and upregulating the mRNA levels of anti-apoptotic factor Bcl-2 in Caco-2 cells. GA also reduces the levels of reactive oxygen species increased by LPS and restores the activity of antioxidant enzymes, namely, superoxide dismutase and catalase, as well as the level of glutathione. More importantly, GA exerts its anti-inflammatory effects by inhibiting the LPS-induced phosphorylation of key signaling molecules in the NF-κB/MAPK pathway, including p65, IκB-α, p38, JNK, and ERK, in Caco-2 cells. Overall, our findings show that GA increases the expressions of tight junction proteins, reduces cell apoptosis, relieves oxidative stress and suppresses the activation of the NF-κB/MAPK pathway to reduce LPS-induced intestinal inflammation in Caco-2 cells, indicating that GA has potential as a therapeutic agent for intestinal inflammation.

Intestinal absorption of bioactive oligopeptides: paracellular transport and tight junction modulation

Bioactive oligopeptides have gained increasing attention due to their diverse physiological functions, and these can be transported into the vasculature via transcellular and paracellular pathways. Among these, paracellular transport through the intercellular space is a passive diffusion process without energy consumption. It is currently the most frequently reported absorption route for food-derived bioactive oligopeptides. Previous work has demonstrated that paracellular pathways are mainly controlled by tight junctions, but the mechanism by which they regulate paracellular absorption of bioactive oligopeptides remains unclear. In this review, we summarized the composition of paracellular pathways across the intercellular space and elaborated on the paracellular transport mechanism of bioactive oligopeptides in terms of the interaction between oligopeptides and tight junction proteins, the protein expression level of tight junctions, the signaling pathways regulating intestinal permeability, and the properties of oligopeptides themselves. These findings contribute to a more profound understanding of the paracellular absorption of bioactive oligopeptides.

Research progress in the treatment of inflammatory bowel disease with natural polysaccharides and related structure-activity relationships

Inflammatory bowel disease (IBD) comprises a group of highly prevalent and chronic inflammatory intestinal tract diseases caused by multiple factors. Despite extensive research into the causes of the disease, IBD's pathogenic mechanisms remain unclear. Moreover, side effects of current IBD therapies restrict their long-term clinical use. In contrast, natural polysaccharides exert beneficial anti-IBD effects and offer advantages over current anti-IBD drugs, including enhanced safety and straightforward isolation from abundant and reliable sources, and thus may serve as components of functional foods and health products for use in IBD prevention and treatment. However, few reviews have explored natural polysaccharides with anti-IBD activities or the relationship between polysaccharide conformation and anti-IBD biological activity. Therefore, this review aims to summarize anti-IBD activities and potential clinical applications of polysaccharides isolated from plant, animal, microorganismal, and algal sources, while also exploring the relationship between polysaccharide conformation and anti-IBD bioactivity for the first time. Furthermore, potential mechanisms underlying polysaccharide anti-IBD effects are summarized, including intestinal microbiota modulation, intestinal inflammation alleviation, and intestinal barrier protection from IBD-induced damage. Ultimately, this review provides a theoretical foundation and valuable insights to guide the development of natural polysaccharide-containing functional foods and nutraceuticals for use as dietary IBD therapies.

Oral targeted drug delivery to post-gastrointestinal sites

As an essential branch of targeted drug delivery, oral targeted delivery is attracting growing attention in recent years. In addition to site-specific delivery for the treatment of locoregional diseases in the gastrointestinal tract (GIT), oral targeted delivery to remote sites beyond the GIT emerges as a cutting-edge research topic. This review aims to provide an overview of the fundamental concepts and most recent advances in this field. Owing to the physiological barriers existing in the GIT, carrier systems should be transported across the enteric epithelia to target remote sites. Recently, pioneer investigations have validated the transport of intact micro- or nanocarriers across gastrointestinal barriers and subsequently to various distal organs and tissues. The microfold (M) cell pathway is the leading mechanism underlying the oral absorption of particulates, but the contribution of the transcellular and paracellular pathways should not be neglected either. In addition to well-acknowledged physicochemical and biological factors, the formation of a protein corona may also influence the biological fate of carrier systems. Although in an early stage of conceptualization, oral targeted delivery to remote diseases has demonstrated promising potential for the treatment of inflammation, tumors, and diseases inflicting the lymphatic and mononuclear phagocytosis systems.

Potential effects and mechanism of flavonoids extract of Callicarpa nudiflora Hook on DSS-induced colitis in mice

Callicarpa nudiflora Hook (C. nudiflora) is an anti-inflammatory, antimicrobial, antioxidant, and hemostatic ethnomedicine. To date, little has been reported regarding the activity of C. nudiflora against ulcerative colitis (UC). In this study, we investigated the effect of a flavonoid extract of C. nudiflora on Dextran Sulfate Sodium (DSS)-induced ulcerative colitis in mice. Mice in the treatment group (CNLF+DSS group) and drug-only (CNLF group) groups were administered 400 mg/kg of flavonoid extract of C. nudiflora leaf (CNLF), and drinking water containing 2.5 % DSS was given to the model and treatment groups. The symptoms of colitis were detected, relevant indicators were verified, intestinal barrier function was assessed, and the contents of the cecum were analyzed for intestinal microorganisms. The results showed that CNLF significantly alleviated the clinical symptoms and histological morphology of colitis in mice, inhibited the increase in pro-inflammatory factors (TNF-α, IL-6, IL-1β, and IFN-γ), and increased the level of IL-10. The expression of NF-κB and MAPK inflammatory signal pathway-related proteins (p-p65, p-p38, p-ERK, p-JNK) was regulated. The expression of tight junction proteins (ZO-1, OCLDN, and CLDN1) was increased, while the content of D-LA, DAO, and LPS was decreased. In addition, 16S rRNA sequencing showed that CNLF restored the gut microbial composition, and increased the relative abundance of Prevotellaceae, Intestinimonas butyriciproducens, and Barnesiella_intestinihominis. In conclusion, CNLF alleviated colitis by suppressing inflammation levels, improving intestinal barrier integrity, and modulating the intestinal microbiota, and therefore has promising future applications in the treatment of UC.

Lizhong decoction ameliorates ulcerative colitis by inhibiting ferroptosis of enterocytes via the Nrf2/SLC7A11/GPX4 pathway

ETHNOPHARMACOLOGY RELEVANCE

Traditional herbal medicines have been considered as a novel and effective way to treat many diseases. Lizhong decoction (LZD), a classical prescription composed of Zingiber officinale Rosc., Panax ginseng C. A. Mey., Atractylodes macrocephala Koidz., and Glycyrrhiza uralensis Fisch., has been used to treat gastrointestinal disorders in clinical practices for thousands of years. However, the mechanism of LZD in alleviating ulcerative colitis (UC) is still unclear.

AIM OF THE STUDY

The purpose of this study was to clarify the potential molecular mechanism of LZD in improving UC.

MATERIALS AND METHODS

The amelioration of LZD on dextran sodium sulfate (DSS)-induced UC mice was evaluated by body weight, colon length, pathology of colon tissues, pro-inflammatory cytokines, and intestinal tight junction (TJ) proteins. Moreover, the gene expression profiles of UC patients were extracted to investigate potential pathological mechanisms of UC. The influence of LZD on ferroptosis was analyzed by iron load, malondialdehyde (MDA), and the expression of ferroptosis-associated proteins. Meanwhile, the inhibition of LZD on oxidative stress (OS) was assessed by the superoxide dismutase (SOD) activity, as well as the expression levels of glutathione (GSH) and glutathione disulfide (GSSG). Furthermore, the influence of LZD on ferroptosis was assessed by inhibiting nuclear factor (erythroid-derived-2)-like 2 (Nrf2).

RESULTS

LZD showed significant therapeutic effects in UC mice, including reduction of intestinal injury and inflammation. Moreover, LZD treatment notably upregulated the expression of TJ proteins. Further investigation indicated that LZD significantly inhibited the ferroptosis of enterocytes by decreasing iron load and MDA, and increasing the expression levels of solute carrier family 7 member 11 (SLC7A11) and glutathione peroxidase 4 (GPX4) in colon tissues. Furthermore, the decreased activity of SOD, reduced level of GSH, and increased content of GSSG in UC mice were notably reversed by LZD. Consistent with in vivo results, LZD could markedly inhibit ferroptosis and OS in RSL3-induced Caco-2 cells. Mechanistically, LZD alleviated ferroptosis by suppressing OS through the activation of Nrf2 signaling.

CONCLUSIONS

Collectively, LZD remarkably improved intestinal pathological injury in UC mice, and its potential mechanism was the suppression of ferroptosis in enterocytes by the Nrf2/SLC7A11/GPX4 pathway.

Insights into the effects of chronic combined chromium-nickel exposure on colon damage in mice through transcriptomic analysis and in vitro gastrointestinal digestion assay

Heavy metals interact with each other in a coexisting manner to produce complex combined toxicity to organisms. At present, the toxic effects of chronic co-exposure to heavy metals hexavalent chromium [Cr(VI)] and divalent nickel [Ni(II)] on organisms are seldom studied and the related mechanisms are poorly understood. In this study, we explored the mechanism of the colon injury in mice caused by chronic exposure to Cr or/and Ni. The results showed that, compared with the control group, Cr or/and Ni chronic exposure affected the body weight of mice, and led to infiltration of inflammatory cells in the colon, decreased the number of goblet cells, fusion of intracellular mucus particles and damaged cell structure of intestinal epithelial. In the Cr or/and Ni exposure group, the activity of nitric oxide synthase (iNOS) increased, the expression levels of MUC2 were significantly down-regulated, and those of ZO-1 and Occludin were significantly up-regulated. Interestingly, factorial analysis revealed an interaction between Cr and Ni, which was manifested as antagonistic effects on iNOS activity, ZO-1 and MUC2 mRNA expression levels. Transcriptome sequencing further revealed that the expression of genes-related to inflammation, intestinal mucus and tight junctions changed obviously. Moreover, the relative contents of Cr(VI) and Ni(II) in the Cr, Ni and Cr+Ni groups all changed with in-vitro gastrointestinal （IVG）digestion, especially in the Cr+Ni group. Our results indicated that the chronic exposure to Cr or/and Ni can lead to damage to the mice colon, and the relative content changes of Cr(VI) and Ni(II) might be the main reason for the antagonistic effect of Cr+Ni exposure on the colon damage.

Poria cocos Attenuated DSS-Induced Ulcerative Colitis via NF-κB Signaling Pathway and Regulating Gut Microbiota

Ulcerative colitis (UC), as a chronic inflammatory disease, presents a global public health threat. However, the mechanism of Poria cocos (PC) in treating UC remains unclear. Here, LC-MS/MS was carried out to identify the components of PC. The protective effect of PC against UC was evaluated by disease activity index (DAI), colon length and histological analysis in dextran sulfate sodium (DSS)-induced UC mice. ELISA, qPCR, and Western blot tests were conducted to assess the inflammatory state. Western blotting and immunohistochemistry techniques were employed to evaluate the expression of tight junction proteins. The sequencing of 16S rRNA was utilized for the analysis of gut microbiota regulation. The results showed that a total of fifty-two nutrients and active components were identified in PC. After treatment, PC significantly alleviated UC-associated symptoms including body weight loss, shortened colon, an increase in DAI score, histopathologic lesions. PC also reduced the levels of inflammatory cytokines TNF-α, IL-6, and IL-1β, as evidenced by the suppressed NF-κB pathway, restored the tight junction proteins ZO-1 and Claudin-1 in the colon, and promoted the diversity and abundance of beneficial gut microbiota. Collectively, these findings suggest that PC ameliorates colitis symptoms through the reduction in NF-κB signaling activation to mitigate inflammatory damage, thus repairing the intestinal barrier, and regulating the gut microbiota.

Border Control: The Role of the Microbiome in Regulating Epithelial Barrier Function

The gut mucosal epithelium is one of the largest organs in the body and plays a critical role in regulating the crosstalk between the resident microbiome and the host. To this effect, the tight control of what is permitted through this barrier is of high importance. There should be restricted passage of harmful microorganisms and antigens while at the same time allowing the absorption of nutrients and water. An increased gut permeability, or "leaky gut", has been associated with a variety of diseases ranging from infections, metabolic diseases, and inflammatory and autoimmune diseases to neurological conditions. Several factors can affect gut permeability, including cytokines, dietary components, and the gut microbiome. Here, we discuss how the gut microbiome impacts the permeability of the gut epithelial barrier and how this can be harnessed for therapeutic purposes.

Adenosine in Intestinal Epithelial Barrier Function

At the intestinal front, several lines of defense are in place to resist infection and injury, the mucus layer, gut microbiome and strong epithelial junctions, to name a few. Their collaboration creates a resilient barrier. In intestinal disorders, such as inflammatory bowel disease (IBD), barrier function is compromised, which results in rampant inflammation and tissue injury. In response to the destruction, the intestinal epithelium releases adenosine, a small but powerful nucleoside that functions as an alarm signal. Amidst the chaos of inflammation, adenosine aims to restore order. Within the scope of its effects is the ability to regulate intestinal epithelial barrier integrity. This review aims to define the contributions of adenosine to mucus production, microbiome-dependent barrier protection, tight junction dynamics, chloride secretion and acid-base balance to reinforce its importance in the intestinal epithelial barrier.

The keratin-desmosome scaffold of internal epithelia in health and disease - The plot is thickening

Keratin (K) intermediate filaments are attached to desmosomes and constitute the orchestrators of epithelial cell and tissue architecture. While their relevance in the epidermis is well recognized, our review focuses on their emerging importance in internal epithelia. The significance of keratin-desmosome scaffolds (KDSs) in the intestine is highlighted by transgenic mouse models and individuals with inflammatory bowel disease who display profound KDS alterations. In lung, high K8 expression defines a transitional cell subset during regeneration, and K8 variants are associated with idiopathic pulmonary fibrosis. Inherited variants in desmosomal proteins are overrepresented in idiopathic lung fibrosis, and familiar eosinophilic esophagitis. K18 serum fragments are established hepatocellular injury markers that correlate with the extent of histological inflammation. K17 expression is modified in multiple tumors, and K17 levels might be of prognostic relevance. These data should spur further studies on biological roles of these versatile tissue protectors and efforts on their therapeutic targeting.

Sinomenine regulates the cholinergic anti-inflammatory pathway to inhibit TLR4/NF-κB pathway and protect the homeostasis in brain and gut in scopolamine-induced Alzheimer's disease mice

Sinomenine (SIN), an alkaloid extracted from the Chinese herbal medicine Sinomenium acutum, has great potential in anti-inflammatory, immune regulation, analgesic and sedative, and is already a clinical drug for the treatment of rheumatoid arthritis in China. Our previous studies show SIN inhibits inflammation by regulating ɑ7nAChR, a key receptor of cholinergic anti-inflammatory pathway (CAP), which plays an important role in regulating peripheral and central nervous system inflammation. Growing evidence supports the cholinergic dysregulation and inflammatory responses play the key role in the pathogenesis of AD. The intervention effects of SIN on AD by regulating CAP and homeostasis in brain and gut were analyzed for the first time in the present study using scopolamine-induced AD model mice. Behavioral tests were used to assess the cognitive performance. The neurons loss, cholinergic function, inflammation responses, biological barrier function in the mouse brain and intestinal tissues were evaluated through a variety of techniques, and the gut microbiota was detected using 16SrRNA sequencing. The results showed that SIN significantly inhibited the cognitive decline, dysregulation of cholinergic system, peripheral and central inflammation, biological barrier damage as well as intestinal flora disturbance caused by SCOP in mice. More importantly, SIN effectively regulated CAP to suppress the activation of TLR4/NF-κB and protect the homeostasis in brain and gut to alleviate cognitive impairment.

Baitouweng decoction repairs the intestinal barrier in DSS-induced colitis mice via regulation of AMPK/mTOR-mediated autophagy

ETHNOPHARMACOLOGICAL RELEVANCE

Ulcerative colitis (UC) is one of non-specific inflammatory bowel disease that mainly affects the colon. Recently, UC has become a significant social and economic problem worldwide. Baitouweng decoction (BD), a traditional Chinese medicine described in the "Treatise on Febrile Diseases", has been used for centuries to treat intestinal diseases. However, its underlying mechanism remains largely unexplored.

AIM OF STUDY

In this study, we aimed to investigate the effect of BD on autophagy for repairing the colonic barrier in DSS-induced colitis mice and explored its role in regulating the autophagic signaling pathway AMPK/mTOR.

MATERIALS AND METHODS

Mice with colitis were treated with 3% dextran sulfate sodium (DSS) for 7 days. The effectiveness of BD in treating DSS-induced colitis was evaluated through body weight, disease activity index (DAI), colon length, pathological changes, organ index, and proportion of blood cells. Moreover, intestinal epithelial permeability was analyzed by examining FITC-dextran leakage, the bacterial load of mesenteric lymph nodes (MLNs), and bacterial infiltration of colon tissues. Barrier function was evaluated by assessing the number and proportion of colonic goblet cells and the expression of tight junction proteins, including ZO-1, claudin-1, and occludin. Furthermore, the levels of autophagy were assessed by examining the number of autophagosomes and the expression of the autophagy-related proteins LC3, Beclin1, and P62. Additionally, network pharmacology research was conducted to analyze the potential mechanisms underlying the medicinal effects, as indicated by the role of AMPK/mTOR in regulating the autophagic signaling pathway.

RESULTS

BD improved colitis symptoms in mice by restoring body weight and colon length and reducing inflammatory cell infiltration. Additionally, BD decreased the diffusion of FITC-dextran and bacterial translocation in MLNs, as well as bacterial infiltration of the colonic mucosa. The number and proportion of colonic goblet cells, the expression of ZO-1, Claudin-1, and Occludin, and the levels of autophagy were also increased by BD. Network pharmacology analysis suggested that BD might affect intestinal autophagy through the AMPK signaling pathway, which was confirmed by the activation of AMPK phosphorylation and the downregulation of mTOR expression following BD treatment.

CONCLUSION

Our study demonstrated that BD repaired the intestinal epithelial barrier in DSS-induced colitis mice by activating AMPK phosphorylation and inhibiting mTOR expression to promote autophagy.

Integrated network pharmacology and metabolomics analyses of the mechanism underlying the efficacy of Ma-Mu-Ran Antidiarrheal Capsules against dextran sulfate sodium-induced ulcerative colitis

The current study utilizes a comprehensive network pharmacology and metabolomics analysis to investigate the mechanism of action of Ma-Mu-Ran Antidiarrheal Capsules (MMRAC) for the treatment of ulcerative colitis (UC). In this study, we established a mouse model of UC using dextran sulfate sodium. Colonic tissues were collected from mice and then subjected to hematoxylin and eosin staining, as well as histopathological analysis, to assess the therapeutic effect of MMRAC. Furthermore, we assessed the mechanisms through which MMRAC combats UC by employing integrated metabolomics and network pharmacology strategies. Lastly, we validated the key targets identified through western blot and molecular docking. An integrated network of metabolomics and network pharmacology was constructed using Cytoscape to identify eight endogenous metabolites involved in the therapeutic action of MMRAC on UC. Further comprehensive analyses were focused on four key targets and their associated core metabolites and pathways. The results of western blot and molecular docking demonstrated that MMRAC could modulate key targets and their expression levels. The cumulative results indicated that MMRAC restored intestinal function in UC, reduced inflammatory responses, and alleviated oxidative stress by influencing the methionine and cysteine metabolic pathways, as well as the urea cycle. In addition, it had an impact on arginine, proline, glutamate, aspartate, and asparagine metabolic pathways and their associated targets.

Paeonol alleviates ulcerative colitis in mice by increasing short-chain fatty acids derived from Clostridium butyricum

BACKGROUND

Increasing evidence suggests that repairing the damaged intestinal epithelial barrier and restoring its function is the key to solving the problem of prolonged ulcerative colitis. Previous studies have shown that paeonol (pae) can alleviate colitis by down-regulating inflammatory pathways. In addition, pae also has a certain effect on regulating intestinal flora. However, it remains unclear whether pae can play a role in repairing the intestinal barrier and whether there is a relationship between the therapeutic effect and the gut microbiota.

PURPOSES

The aim of this study is to investigate the effect of pae on intestinal barrier repair in UC mice and how the gut microbiota plays a part in it.

STUDY DESIGN AND METHODS

The therapeutic effect of pae was evaluated in a 3% DSS-induced UC mouse model. The role of pae in repairing the intestinal barrier was evaluated by detecting colonic cupped cells by Alcian blue staining, the expression of colonic epithelial tight junction protein by immunofluorescence and western blot, and the proportion of IL-22+ILC3 cells in the lamina propria lymphocytes by flow cytometry. Subsequently, 16S rRNA sequencing was used to observe the changes in intestinal flora, GC-MS was used to detect the level of SCFAs, and qPCR was used to identify the abundance of Clostridium butyricum in the intestine to evaluate the effect of pae on the gut microbiota. The antibiotic-mediated depletion of the gut flora was then used to verify that pae depends on C. butyricum to play a healing role. Finally, non-targeted metabolomics was employed to investigate the potential pathways of pae regulating C. butyricum.

RESULTS

Pae could improve intestinal microecological imbalance and promote the production of short-chain fatty acids (SCFAs). Most importantly, we identified C. butyricum as a key bacterium responsible for the intestinal barrier repair effect of pae in UC mice. Eradication of intestinal flora by antibiotics abolished the repair of the intestinal barrier and the promotion of SCFAs production by pae, while C. butyricum colonization could restore the therapeutic effects of pae in UC mice, which further confirmed that C. butyricum was indeed the "driver bacterium" of pae in UC treatment. Untargeted metabolomics showed that pae regulated some amino acid metabolism and 2-Oxocarboxylic acid metabolism in C. butyricum.

CONCLUSIONS

Our study showed that the restoration of the impaired intestinal barrier by pae to alleviate colitis is associated with increased C. butyricum and SCFAs production, which may be a promising strategy for the treatment of UC.

Human organoids are superior to cell culture models for intestinal barrier research

Loss of intestinal epithelial barrier function is a hallmark in digestive tract inflammation. The detailed mechanisms remain unclear due to the lack of suitable cell-based models in barrier research. Here we performed a detailed functional characterization of human intestinal organoid cultures under different conditions with the aim to suggest an optimized ex-vivo model to further analyse inflammation-induced intestinal epithelial barrier dysfunction. Differentiated Caco2 cells as a traditional model for intestinal epithelial barrier research displayed mature barrier functions which were reduced after challenge with cytomix (TNFα, IFN-γ, IL-1ß) to mimic inflammatory conditions. Human intestinal organoids grown in culture medium were highly proliferative, displayed high levels of LGR5 with overall low rates of intercellular adhesion and immature barrier function resembling conditions usually found in intestinal crypts. WNT-depletion resulted in the differentiation of intestinal organoids with reduced LGR5 levels and upregulation of markers representing the presence of all cell types present along the crypt-villus axis. This was paralleled by barrier maturation with junctional proteins regularly distributed at the cell borders. Application of cytomix in immature human intestinal organoid cultures resulted in reduced barrier function that was accompanied with cell fragmentation, cell death and overall loss of junctional proteins, demonstrating a high susceptibility of the organoid culture to inflammatory stimuli. In differentiated organoid cultures, cytomix induced a hierarchical sequence of changes beginning with loss of cell adhesion, redistribution of junctional proteins from the cell border, protein degradation which was accompanied by loss of epithelial barrier function. Cell viability was observed to decrease with time but was preserved when initial barrier changes were evident. In summary, differentiated intestinal organoid cultures represent an optimized human ex-vivo model which allows a comprehensive reflection to the situation observed in patients with intestinal inflammation. Our data suggest a hierarchical sequence of inflammation-induced intestinal barrier dysfunction starting with loss of intercellular adhesion, followed by redistribution and loss of junctional proteins resulting in reduced barrier function with consecutive epithelial death.

Plakophilin 2 regulates intestinal barrier function by modulating protein kinase C activity in vitro

Previous data provided evidence for a critical role of desmosomes to stabilize intestinal epithelial barrier (IEB) function. These studies suggest that desmosomes not only contribute to intercellular adhesion but also play a role as signaling hubs. The contribution of desmosomal plaque proteins plakophilins (PKP) in the intestinal epithelium remains unexplored. The intestinal expression of PKP2 and PKP3 was verified in human gut specimens, human intestinal organoids as well as in Caco2 cells whereas PKP1 was not detected. Knock-down of PKP2 using siRNA in Caco2 cells resulted in loss of intercellular adhesion and attenuated epithelial barrier. This was paralleled by changes of the whole desmosomal complex, including loss of desmoglein2, desmocollin2, plakoglobin and desmoplakin. In addition, tight junction proteins claudin1 and claudin4 were reduced following the loss of PKP2. Interestingly, siRNA-induced loss of PKP3 did not change intercellular adhesion and barrier function in Caco2 cells, while siRNA-induced loss of both PKP2 and PKP3 augmented the changes observed for reduced PKP2 alone. Moreover, loss of PKP2 and PKP2/3, but not PKP3, resulted in reduced activity levels of protein kinase C (PKC). Restoration of PKC activity using Phorbol 12-myristate 13-acetate (PMA) rescued loss of intestinal barrier function and attenuated the reduced expression patterns of claudin1 and claudin4. Immunostaining, proximity ligation assays and co-immunoprecipitation revealed a direct interaction between PKP2 and PKC. In summary, our in vitro data suggest that PKP2 plays a critical role for intestinal barrier function by providing a signaling hub for PKC-mediated expression of tight junction proteins claudin1 and claudin4.

Desmoglein-2 and COVID-19 complications: insights into its role as a biomarker, pathogenesis and clinical implications

Desmoglein-2 (DSG2) has emerged as a potential biomarker for coronavirus disease 2019 (COVID-19) complications, particularly cardiac and cardiovascular involvement. The expression of DSG2 in lung tissues has been detected at elevated levels, and circulating DSG2 levels correlate with COVID-19 severity. DSG2 may contribute to myocardial injury, cardiac dysfunction and vascular endothelial dysfunction in COVID-19. Monitoring DSG2 levels could aid in risk stratification, early detection and prognostication of COVID-19 complications. However, further research is required to validate DSG2 as a biomarker. Such research will aim to elucidate its precise role in pathogenesis, establishing standardized assays for its measurement and possibly identifying therapeutic targets.

Glycated Casein by TGase-Type Exerts Protection Potential against DSS-Induced Colitis via Inhibiting TLR4/NF-κB Signaling Pathways in C57BL/6J Mice

Glycation by transglutaminase (TGase)-type could effectively improve the structure and functional properties of proteins. However, the influence on intestinal inflammation or the underlying mechanisms has not been investigated. The goal of this research was to compare the bioactivities between glycated casein generated from the TGase-catalyzed reaction and oligochitosan as well as casein using a mouse model of dextran sulfate sodium (DSS)-induced intestinal inflammation to examine the protective effects and the underlying mechanism of glycated casein on intestinal inflammation. Eight groups of C57BL/6 mice were randomly assigned in this study: Control group: standard diet for 35 days; Model group: standard diet for 28 days and then colitis induction; Pretreated groups: different levels (200, 400, 800 mg/kg BW) of casein or glycated casein for 28 days before colitis induction. The mice were drinking water containing a 3% DSS solution for seven days of mice to cause colitis. The results indicated that glycated casein and casein at 200-800 mg/kg BW all relieved DSS-induced weight loss, reduced disease activity index (DAI) score, alleviated colon length shortening, weakened the destruction of colonic mucosal structure, decreased serum LPS, and MPO, IL-1β, IL-6 and TNF-α levels in serum and colon, as well as regulated the expression of proteins involved in the TLR4/NF-κB signaling pathway in a concentration-dependent manner. Glycated caseinate showed a better protective effect against DSS-induced colitis than casein, highlighting that the TGase-type glycation of proteins as a potential functional food ingredient might be a helpful method for gut health.

Polysaccharides from Armillariella tabescens mycelia mitigate DSS-induced ulcerative colitis via modulating intestinal microbiota in mice

Polysaccharides from Armillariella tabescens mycelia (AT) have a potent anti-inflammatory effect. Nevertheless, the impact of AT on dextran sodium sulfate (DSS)-induced ulcerative colitis (UC) has not yet been illustrated. This study aimed to explore AT's impact on experimental UC mice and investigate its underlying mechanisms. Mice were given DSS, 0.2 g/kg AT or 0.4 g/kg AT for seven days, and the symptoms of UC were observed. The serum and colon samples were harvested to analyze the biochemical indices and inflammasome-related proteins. The feces were collected to analyze short-chain fatty acids (SCFAs) and gut microbiota. The present study found that AT improved the symptoms of UC, colonic oxidative stress, and inflammation. AT treatment elevated SCFAs contents and colonic barrier function. Furthermore, AT improved microbial community structure through the selective enrichment of beneficial bacterial species. In conclusion, these results underlined that AT improved DSS-induced colitis and inhibited colonic inflammation via regulating the intestinal microbial community and enhancing the colonic mucosal barrier.

Storming the gate: New approaches for targeting the dynamic tight junction for improved drug delivery

As biologics used in the clinic outpace the number of new small molecule drugs, an important challenge for their efficacy and widespread use has emerged, namely tissue penetrance. Macromolecular drugs - bulky, high-molecular weight, hydrophilic agents - exhibit low permeability across biological barriers. Epithelial and endothelial layers, for example within the gastrointestinal tract or at the blood-brain barrier, present the most significant obstacle to drug transport. Within epithelium, two subcellular structures are responsible for limiting absorption: cell membranes and intercellular tight junctions. Previously considered impenetrable to macromolecular drugs, tight junctions control paracellular flux and dictate drug transport between cells. Recent work, however, has shown tight junctions to be dynamic, anisotropic structures that can be targeted for delivery. This review aims to summarize new approaches for targeting tight junctions, both directly and indirectly, and to highlight how manipulation of tight junction interactions may help usher in a new era of precision drug delivery.

cCPE Fusion Proteins as Molecular Probes to Detect Claudins and Tight Junction Dysregulation in Gastrointestinal Cell Lines, Tissue Explants and Patient-Derived Organoids

Claudins regulate paracellular permeability, contribute to epithelial polarization and are dysregulated during inflammation and carcinogenesis. Variants of the claudin-binding domain of Clostridium perfringens enterotoxin (cCPE) are highly sensitive protein ligands for generic detection of a broad spectrum of claudins. Here, we investigated the preferential binding of YFP- or GST-cCPE fusion proteins to non-junctional claudin molecules. Plate reader assays, flow cytometry and microscopy were used to assess the binding of YFP- or GST-cCPE to non-junctional claudins in multiple in vitro and ex vivo models of human and rat gastrointestinal epithelia and to monitor formation of a tight junction barrier. Furthermore, YFP-cCPE was used to probe expression, polar localization and dysregulation of claudins in patient-derived organoids generated from gastric dysplasia and gastric cancer. Live-cell imaging and immunocytochemistry revealed cell polarity and presence of tight junctions in glandular organoids (originating from intestinal-type gastric cancer and gastric dysplasia) and, in contrast, a disrupted diffusion barrier for granular organoids (originating from discohesive tumor areas). In sum, we report the use of cCPE fusion proteins as molecular probes to specifically and efficiently detect claudin expression, localization and tight junction dysregulation in cell lines, tissue explants and patient-derived organoids of the gastrointestinal tract.

A spotlight on intestinal permeability and inflammatory bowel diseases

INTRODUCTION

The intestinal barrier is a multi-faced structure lining the surface of the intestinal mucosa of the GI tract. To exert its main functions as a physical and immunological defense barrier, several components of the intestinal barrier act in a concerted and cooperative manner.

AREAS COVERED

Herein, we first introduce to the basic organization of the intestinal barrier and then summarize different methods to assess barrier function in and ex vivo. Finally, we provide an in-depth overview of the relevance of intestinal barrier dysfunction in inflammatory bowel diseases.

EXPERT OPINION

In parallel to a more fundamental understanding of the intestinal barrier as a key component for intestinal integrity is the notion that intestinal barrier defects are associated with a variety of diseases such as inflammatory bowel diseases. Recent research has fueled and perpetuated the concept that barrier defects are critical components of disease development, disease behavior, and potentially also an area of therapeutic intervention in IBD patients. Although being far away from standard, new technologies can be used to easily assess barrier healing in IBD and to derive clinical consequences from these findings such as more accurate forecasting of future disease behavior or the identification of novel therapeutic targets.

Delayed and limited administration of the JAKinib tofacitinib mitigates chronic DSS-induced colitis

In inflammatory bowel disease, dysregulated T cells express pro-inflammatory cytokines. Using a chronic azoxymethane (AOM)/dextran sulfate sodium (DSS)-induced colitis model resembling ulcerative colitis, we evaluated whether and when treatment with the Janus kinase (JAK) inhibitor tofacitinib could be curative. Comparing the treatment with two and three cycles of tofacitinib medication in drinking water - intermittently with DSS induction - revealed that two cycles were not only sufficient but also superior over the 3-x regimen. The two cycles of the 2-x protocol paralleled the second and third cycles of the longer protocol. T cells were less able to express interferon gamma (IFN-γ) and the serum levels of IFN-γ, interleukin (IL)-2, IL-6, IL-17, and tumor necrosis factor (TNF) were significantly reduced in sera, while those of IL-10 and IL-22 increased under the 2-x protocol. Likewise, the frequency and effector phenotype of regulatory T cells (Tregs) increased. This was accompanied by normal weight gain, controlled clinical scores, and restored stool consistency. The general and histologic appearance of the colons revealed healing and tissue intactness. Importantly, two phases of tofacitinib medication completely prevented AOM-incited pseudopolyps and the hyper-proliferation of epithelia, which was in contrast to the 3-x regimen. This implies that the initial IBD-induced cytokine expression is not necessarily harmful as long as inflammatory signaling can later be suppressed and that time-restricted treatment allows for anti-inflammatory and tissue-healing cytokine activities.

Meeting report - Desmosome dysfunction and disease: Alpine desmosome disease meeting

Desmosome diseases are caused by dysfunction of desmosomes, which anchor intermediate filaments (IFs) at sites of cell-cell adhesion. For many decades, the focus of attention has been on the role of actin filament-associated adherens junctions in development and disease, especially cancer. However, interference with the function of desmosomes, their molecular constituents or their attachments to IFs has now emerged as a major contributor to a variety of diseases affecting different tissues and organs including skin, heart and the digestive tract. The first Alpine desmosome disease meeting (ADDM) held in Grainau, Germany, in October 2022 brought together international researchers from the basic sciences with clinical experts from diverse fields to share and discuss their ideas and concepts on desmosome function and dysfunction in the different cell types involved in desmosome diseases. Besides the prototypic desmosomal diseases pemphigus and arrhythmogenic cardiomyopathy, the role of desmosome dysfunction in inflammatory bowel diseases and eosinophilic esophagitis was discussed.

Dahuang Mudan decoction repairs intestinal barrier in chronic colitic mice by regulating the function of ILC3

ETHNOPHARMACOLOGICAL RELEVANCE

Dahuang Mudan decoction (DMD) is a classic prescription for treating intestinal carbuncle from Zhang Zhongjing's "Essentials of the Golden Chamber" in the Han Dynasty. Recent studies also prove that DMD has a therapeutic effect on ulcerative colitis (UC), but its mechanism is still unclear.

AIM OF STUDY

In this study, we aim to assess the therapeutic effect of DMD on DSS-induced chronic colitis in mice and deeply expound its underlying regulative mechanism.

MATERIALS AND METHODS

The efficacy of DMD on mice with 2% DSS-induced chronic colitis was examined by changes in mouse body weight, DAI score, colon length changes, peripheral blood white blood cells (WBC) and red blood cells (RBC) counts, and hemoglobin (HGB) content, using mesalazine as a positive control. A small animal imaging system observed the FITC-Dextran fluorescence distribution in mice, and the contents of IL-22 and IL-17A in colon tissue homogenate supernatant and LPS in peripheral blood were detected by ELISA. Fluorescence in situ molecular hybridization and bacterial culture were used to investigate bacterial infiltration in intestinal mucosa and bacterial translocation in mesenteric lymph nodes and spleen. Mice immune function was further evaluated by analyzing the changes in spleen index, thymus index, and the ratio of peripheral blood granulocytes, monocytes, and lymphocytes. Meanwhile, the proportion of NCR⁺ group 3 innate lymphoid cells (ILC3), NCR^-ILC3, and IL-22⁺ILC3 in colonic lamina propria lymphocytes of mice was detected by flow cytometry. The contents of effectors IL-22, IL-17A, and GM-CSF were detected by RT-PCR. We use cell scratching to determine the effect of DMD conditioned medium on the migration of Caco-2 cells by establishing an in vitro model of MNK-3 conditioned medium (CM) intervening Caco-2 cells. RT-PCR and WB detect the expression of tight junction ZO-1, Occludin, and Claudin-1.

RESULTS

DMD restored the body weight, colon length, peripheral blood RBC numbers, and HGB content of chronic colitis mice and reduced peripheral blood WBC and colon inflammatory cell infiltration. Moreover, DMD decreased LPS content in serum, bacterial infiltration of colonic mucosa, and bacterial translocation in spleen and mesenteric lymph nodes. Simultaneously, DMD intensified the expression of ZO-1, Occludin, and Claudin-1, the ratio of NCR⁺ILC3 and IL-22⁺ILC3, and decreased the proportion of NCR^-ILC3. In vitro studies also confirmed that the conditioned medium of DMD promoted the migration of Caco-2 cells and the expression of tight junction proteins.

CONCLUSION

Our results confirm that DMD improves inflammation and restores intestinal epithelial function in mice with chronic colitis, and the mechanism may be related to regulating ILC3 function.

Differential Response to the Course of Cryptosporidium parvum Infection and Its Impact on Epithelial Integrity in Differentiated versus Undifferentiated Human Intestinal Enteroids

Cryptosporidium is a leading cause of diarrhea and death in young children and untreated AIDS patients and causes waterborne outbreaks. Pathogenic mechanisms underlying diarrhea and intestinal dysfunction are poorly understood. We previously developed stem-cell derived human intestinal enteroid (HIE) models for Cryptosporidium parvum which we used in this study to investigate the course of infection and its effect on intestinal epithelial integrity. By immunofluorescence and confocal microscopy, there was robust infection of undifferentiated and differentiated HIEs in two and three-dimensional (2D, 3D) models. Infection of differentiated HIEs in the 2D model was greater than that of undifferentiated HIEs but lasted only for 3 days, whereas infection persisted for 21 days and resulted in completion of the life cycle in undifferentiated HIEs. Infection of undifferentiated HIE monolayers suggest that C. parvum infects LGR5+ stem cells. Transepithelial electrical resistance measurement of HIEs in the 2D model revealed that infection resulted in decreased epithelial integrity which persisted in differentiated HIEs but recovered in undifferentiated HIEs. Compromised epithelial integrity was reflected in disorganization of the tight and adherens junctions as visualized using the markers ZO-1 and E-cadherin, respectively. Quantitation using the image analysis tools Tight Junction Organizational Rate and Intercellular Junction Organization Quantification, measurement of monolayer height, and RNA transcripts of both proteins by quantitative reverse transcription PCR confirmed that disruption persisted in differentiated HIEs but recovered in undifferentiated HIEs. These models, which more accurately recapitulate human infection, will be useful tools to dissect pathogenic mechanisms underlying diarrhea and intestinal dysfunction in cryptosporidiosis.

A potential therapeutic target in traditional Chinese medicine for ulcerative colitis: Macrophage polarization

Intestinal macrophages are the main participants of intestinal immune homeostasis and intestinal inflammation. Under different environmental stimuli, intestinal macrophages can be polarized into classical activated pro-inflammatory phenotype (M1) and alternative activated anti-inflammatory phenotype (M2). Its different polarization state is the “guide” to promoting the development and regression of inflammation. Under normal circumstances, intestinal macrophages can protect the intestine from inflammatory damage. However, under the influence of some genetic and environmental factors, the polarization imbalance of intestinal M1/M2 macrophages will lead to the imbalance in the regulation of intestinal inflammation and transform the physiological inflammatory response into pathological intestinal injury. In UC patients, the disorder of intestinal inflammation is closely related to the imbalance of intestinal M1/M2 macrophage polarization. Therefore, restoring the balance of M1/M2 macrophage polarization may be a potentially valuable therapeutic strategy for UC. Evidence has shown that traditional Chinese medicine (TCM) has positive therapeutic effects on UC by restoring the balance of M1/M2 macrophage polarization. This review summarizes the clinical evidence of TCM for UC, the vital role of macrophage polarization in the pathophysiology of UC, and the potential mechanism of TCM regulating macrophage polarization in the treatment of UC. We hope this review may provide some new enlightenment for the clinical treatment, fundamental research, and research and development of new Chinese medicine of UC.

Tubular IKKβ Deletion Alleviates Acute Ischemic Kidney Injury and Facilitates Tissue Regeneration

Acute kidney injury (AKI) is a common renal injury leading to relevant morbidity and mortality worldwide. Most of the clinical cases of AKI are caused by ischemia reperfusion (I/R) injury with renal ischemia injury followed by reperfusion injury and activation of the innate immune response converging to NF-ĸB pathway induction. Despite the clear role of NF-ĸB in inflammation, it has recently been acknowledged that NF-ĸB may impact other cell functions. To identify NF-ĸB function with respect to metabolism, vascular function and oxidative stress after I/R injury and to decipher in detail the underlying mechanism, we generated a transgenic mouse model with targeted deletion of IKKβ along the tubule and applied I/R injury followed by its analysis after 2 and 14 days after I/R injury. Tubular IKKβ deletion ameliorated renal function and reduced tissue damage. RNAseq data together with immunohistochemical, biochemical and morphometric analysis demonstrated an ameliorated vascular organization and mRNA expression profile for increased angiogenesis in mice with tubular IKKβ deletion at 2 days after I/R injury. RNAseq and protein analysis indicate an ameliorated metabolism, oxidative species handling and timely-adapted cell proliferation and apoptosis as well as reduced fibrosis in mice with tubular IKKβ deletion at 14 days after I/R injury. In conclusion, mice with tubular IKKβ deletion upon I/R injury display improved renal function and reduced tissue damage and fibrosis in association with improved vascularization, metabolism, reactive species disposal and fine-tuned cell proliferation.

Mechanisms Causing Acantholysis in Pemphigus-Lessons from Human Skin

Pemphigus vulgaris (PV) is an autoimmune bullous skin disease caused primarily by autoantibodies (PV-IgG) against the desmosomal adhesion proteins desmoglein (Dsg)1 and Dsg3. PV patient lesions are characterized by flaccid blisters and ultrastructurally by defined hallmarks including a reduction in desmosome number and size, formation of split desmosomes, as well as uncoupling of keratin filaments from desmosomes. The pathophysiology underlying the disease is known to involve several intracellular signaling pathways downstream of PV-IgG binding. Here, we summarize our studies in which we used transmission electron microscopy to characterize the roles of signaling pathways in the pathogenic effects of PV-IgG on desmosome ultrastructure in a human ex vivo skin model. Blister scores revealed inhibition of p38MAPK, ERK and PLC/Ca2+ to be protective in human epidermis. In contrast, inhibition of Src and PKC, which were shown to be protective in cell cultures and murine models, was not effective for human skin explants. The ultrastructural analysis revealed that for preventing skin blistering at least desmosome number (as modulated by ERK) or keratin filament insertion (as modulated by PLC/Ca2+) need to be ameliorated. Other pathways such as p38MAPK regulate desmosome number, size, and keratin insertion indicating that they control desmosome assembly and disassembly on different levels. Taken together, studies in human skin delineate target mechanisms for the treatment of pemphigus patients. In addition, ultrastructural analysis supports defining the specific role of a given signaling molecule in desmosome turnover at ultrastructural level.

Polycatechol-Derived Mesoporous Polydopamine Nanoparticles for Combined ROS Scavenging and Gene Interference Therapy in Inflammatory Bowel Disease

Benefiting from the evolution of nanotechnology, the combination therapy by gene interference and reactive oxygen species (ROS) scavenging are expected, which holds great potential in inflammatory bowel disease (IBD) therapy. However, the functional integration of different therapeutic modules through interface modification of gene vectors for safe and efficient treatment is urgently needed. Herein, we present a catechol chemistry-mediated core-shell nanoplatform for ROS scavenging-mediated oxidative stress alleviation and siRNA-mediated gene interference in a dextran sulfate sodium (DSS)-induced colitis model. The nanoplatform is constructed by employing mesoporous polydopamine nanoparticles (MPDA NPs) with surface modification of amines as the porous core for TNF-α-siRNA loading (31 wt %) and exerts an antioxidant function, while PDA-induced biomineralization of the calcium phosphate (CaP) coating is used as the pH-sensitive protective shell to prevent siRNA from premature release. The CaP layer degraded under weakly acidic subcellular conditions (lysosomes); thus, the synergistic integration of catechol and cation moieties on the exposed surface of MPDA resulted in an efficient lysosomal escape. Subsequently, effective ROS scavenging caused by the electron-donating ability of MPDA and efficient knocking down (40.5%) of tumor necrosis factor-α (TNF-α) via sufficient cytosolic gene delivery resulted in a synergistic anti-inflammation therapeutic effect both in vitro and in vivo. This work establishes the first paradigm of synergistic therapy in IBD by ROS scavenging and gene interference.

Chronic systemic low-grade inflammation and modern lifestyle: the dark role of gut microbiota on related diseases with a focus on pandemic COVID-19

Inflammation is a physiological, beneficial and auto-limiting response of the host to alarming stimuli. Conversely, a chronic systemic low-grade inflammation (CSLGI), known as a long-time persisting condition, causes organs and host tissues' damage, representing a major risk for chronic diseases. Currently, a worldwide a high incidence of inflammatory chronic diseases is observed, often linked to the lifestyle-related changes occurred in the last decade's society. The mains lifestyle-related factors are a proinflammatory diet, psychological stress, tobacco smoking, alcohol abuse, physical inactivity, and finally indoor living and working with its related consequences such as indoor pollution, artificial light exposure and low vitamin D production. Recent scientific evidences found that gut microbiota (GM) has a main role in shaping the host's health, particularly as CSLGI mediator. As a matter of facts, based on the last discoveries regarding the remarkable GM activity, in this manuscript we focused on the elements of actual lifestyle that influence the composition and function of intestinal microbial community, in order to elicit the CSLGI and its correlated pathologies. In this scenario, we provide a broad review of the interplay between modern lifestyle, GM and CSLGI with a special focus on the COVID symptoms and emerging long-COVID syndrome.

When fat meets the gut-focus on intestinal lipid handling in metabolic health and disease

The regular overconsumption of energy‐dense foods (rich in lipids and sugars) results in elevated intestinal nutrient absorption and consequently excessive accumulation of lipids in the liver, adipose tissue, skeletal muscles, and other organs. This can eventually lead to obesity and obesity‐associated diseases such as type 2 diabetes (T2D), non‐alcoholic fatty liver disease (NAFLD), cardiovascular disease, and certain types of cancer, as well as aggravate inflammatory bowel disease (IBD). Therefore, targeting the pathways that regulate intestinal nutrient absorption holds significant therapeutic potential. In this review, we discuss the molecular and cellular mechanisms controlling intestinal lipid handling, their relevance to the development of metabolic diseases, and emerging therapeutic strategies.

Impact of Epithelial Cell Shedding on Intestinal Homeostasis

The gut barrier acts as a first line of defense in the body, and plays a vital role in nutrition and immunoregulation. A layer of epithelial cells bound together via intercellular junction proteins maintains intestinal barrier integrity. Based on a tight equilibrium between cell extrusion and cell restitution, the renewal of the epithelium (epithelial turnover) permits the preservation of cell numbers. As the last step within the epithelial turnover, cell shedding occurs due to the pressure of cell division and migration from the base of the crypt. During this process, redistribution of tight junction proteins enables the sealing of the epithelial gap left by the extruded cell, and thereby maintains barrier function. Disturbance in cell shedding can create transient gaps (leaky gut) or cell accumulation in the epithelial layer. In fact, numerous studies have described the association between dysregulated cell shedding and infection, inflammation, and cancer; thus epithelial cell extrusion is considered a key defense mechanism. In the gastrointestinal tract, altered cell shedding has been observed in mouse models of intestinal inflammation and appears as a potential cause of barrier loss in human inflammatory bowel disease (IBD). Despite the relevance of this process, there are many unanswered questions regarding cell shedding. The investigation of those mechanisms controlling cell extrusion in the gut will definitely contribute to our understanding of intestinal homeostasis. In this review, we summarized the current knowledge about intestinal cell shedding under both physiological and pathological circumstances.

Excessive Apoptosis in Ulcerative Colitis: Crosstalk Between Apoptosis, ROS, ER Stress, and Intestinal Homeostasis

Ulcerative colitis (UC), an etiologically complicated and relapsing gastrointestinal disease, is characterized by the damage of mucosal epithelium and destruction of the intestinal homeostasis, which has caused a huge social and economic burden on the health system all over the world. Its pathogenesis is multifactorial, including environmental factors, genetic susceptibility, epithelial barrier defect, symbiotic flora imbalance, and dysregulated immune response. Thus far, although immune cells have become the focus of most research, it is increasingly clear that intestinal epithelial cells play an important role in the pathogenesis and progression of UC. Notably, apoptosis is a vital catabolic process in cells, which is crucial to maintain the stability of intestinal environment and regulate intestinal ecology. In this review, the mechanism of apoptosis induced by reactive oxygen species and endoplasmic reticulum stress, as well as excessive apoptosis in intestinal epithelial dysfunction and gut microbiology imbalance are systematically and comprehensively summarized. Further understanding the role of apoptosis in the pathogenesis of UC may provide a novel strategy for its therapy in clinical practices and the development of new drugs.

Structure and regulation of desmosomes in intercalated discs: Lessons from epithelia

For electromechanical coupling of cardiomyocytes, intercalated discs (ICDs) are pivotal as highly specialized intercellular contact areas. ICD consists of adhesive contacts, such as desmosomes and adherens junctions (AJs) that are partially intermingled and thereby form an area composita to provide mechanical strength, as well as gap junctions (GJ) and sodium channels for excitation propagation. In contrast, in epithelia, mixed junctions with features of desmosomes and AJs are regarded as transitory primarily during the formation of desmosomes. The anatomy of desmosomes is defined by a typical ultrastructure with dense intracellular plaques anchoring the cadherin-type adhesion molecules to the intermediate filament cytoskeleton. Desmosomal diseases characterized by impaired adhesive and signalling functions of desmosomal contacts lead to arrhythmogenic cardiomyopathy when affecting cardiomyocytes and cause pemphigus when manifesting in keratinocytes or present as cardiocutaneous syndromes when both cell types are targeted by the disease, which underscores the high biomedical relevance of these cell contacts. Therefore, comparative analyses regarding the structure and regulation of desmosomal contacts in cardiomyocytes and epithelial cells are helpful to better understand disease pathogenesis. In this brief review, we describe the structural properties of ICD compared to epithelial desmosomes and suggest that mechanisms regulating adhesion may at least in part be comparable. Also, we discuss whether phenomena such as hyperadhesion or the bidirectional regulation of desmosomes to serve as signalling hubs in epithelial cells may also be relevant for ICD.

Desmoglein 2 can undergo Ca2+-dependent interactions with both desmosomal and classical cadherins including E-cadherin and N-cadherin

Desmoglein (Dsg) 2 is a ubiquitously expressed desmosomal cadherin. Particularly, it is present in all cell types forming desmosomes, including epithelial cells and cardiac myocytes and is upregulated in the autoimmune skin disease pemphigus. Thus, we here characterized the binding properties of Dsg2 in more detail using atomic force microscopy (AFM). Dsg2 exhibits homophilic interactions and also heterophilic interactions with the desmosomal cadherin desmocollin (Dsc) 2, and further with the classical cadherins E-cadherin (E-Cad) and N-cadherin (N-Cad), which may be relevant for cross talk between desmosomes and adherens junctions in epithelia and cardiac myocytes. We found that all homo- and heterophilic interactions were Ca²⁺-dependent. All binding forces observed are in the same force range, i.e., 30 to 40 pN, except for the Dsg2/E-Cad unbinding force, which with 45 pN is significantly higher. To further characterize the nature of the interactions, we used tryptophan, a critical amino acid required for trans-interaction, and a tandem peptide (TP) designed to cross-link Dsg isoforms. TP was sufficient to prevent the tryptophan-induced loss of Dsg2 interaction with the desmosomal cadherins Dsg2 and Dsc2; however, not with the classical cadherins E-Cad and N-Cad, indicating that the interaction modes of Dsg2 with desmosomal and classical cadherins differ. TP rescued the tryptophan-induced loss of Dsg2 binding on living enterocytes, suggesting that interaction with desmosomal cadherins may be more relevant. In summary, the data suggest that the ubiquitous desmosomal cadherin Dsg2 enables the cross talk with adherens junctions by interacting with multiple binding partners with implications for proper adhesive function in healthy and diseased states.

Desmosomal Cadherins in Health and Disease

Desmosomal cadherins are a recent evolutionary innovation that make up the adhesive core of highly specialized intercellular junctions called desmosomes. Desmosomal cadherins, which are grouped into desmogleins and desmocollins, are related to the classical cadherins, but their cytoplasmic domains are tailored for anchoring intermediate filaments instead of actin to sites of cell-cell adhesion. The resulting junctions are critical for resisting mechanical stress in tissues such as the skin and heart. Desmosomal cadherins also act as signaling hubs that promote differentiation and facilitate morphogenesis, creating more complex and effective tissue barriers in vertebrate tissues. Interference with desmosomal cadherin adhesive and supra-adhesive functions leads to a variety of autoimmune, hereditary, toxin-mediated, and malignant diseases. We review our current understanding of how desmosomal cadherins contribute to human health and disease, highlight gaps in our knowledge about their regulation and function, and introduce promising new directions toward combatting desmosome-related diseases.

Integrity of the Intestinal Barrier: The Involvement of Epithelial Cells and Microbiota-A Mutual Relationship

Simple Summary

The gastrointestinal tract is a complex organization of various types of epithelial cells forming a single layer of the mucosal barrier, the host mucosal immune system, and microorganisms termed as gut microbiota inhabiting this area. The mucosal barrier, including physical and chemical factors, spatially segregates gut microbiota and the host immune system preventing the development of immune response directed towards non-pathogenic commensals and dietary antigens. However, for the maintenance of the integrity of the mucosal surfaces, cross-talk between epithelial cells and microbiota is required. The microbiome and the intestinal epithelium developed a complex dependence necessary for sustaining intestinal homeostasis. In this review, we highlight the role of specific epithelial cell subtypes and their role in barrier arrangement, the mechanisms employed by them to control intestinal microbiota as well as the mechanisms utilized by the microbiome to regulate intestinal epithelial function. This review will provide information regarding the development of inflammatory disorders dependent on the loss of intestinal barrier function and composition of the intestinal microbiota.

Abstract

The gastrointestinal tract, which is constantly exposed to a multitude of stimuli, is considered responsible for maintaining the homeostasis of the host. It is inhabited by billions of microorganisms, the gut microbiota, which form a mutualistic relationship with the host. Although the microbiota is generally recognized as beneficial, at the same time, together with pathogens, they are a permanent threat to the host. Various populations of epithelial cells provide the first line of chemical and physical defense against external factors acting as the interface between luminal microorganisms and immunocompetent cells in lamina propria. In this review, we focus on some essential, innate mechanisms protecting mucosal integrity, thus responsible for maintaining intestine homeostasis. The characteristics of decisive cell populations involved in maintaining the barrier arrangement, based on mucus secretion, formation of intercellular junctions as well as production of antimicrobial peptides, responsible for shaping the gut microbiota, are presented. We emphasize the importance of cross-talk between gut microbiota and epithelial cells as a factor vital for the maintenance of the homeostasis of the GI tract. Finally, we discuss how the imbalance of these regulations leads to the compromised barrier integrity and dysbiosis considered to contribute to inflammatory disorders and metabolic diseases.

Desmoplakin Maintains Transcellular Keratin Scaffolding and Protects From Intestinal Injury

BACKGROUND & AIMS

Desmosomes are intercellular junctions connecting keratin intermediate filaments of neighboring cells. The cadherins desmoglein 2 (Dsg2) and desmocollin 2 mediate cell-cell adhesion, whereas desmoplakin (Dsp) provides the attachment of desmosomes to keratins. Although the importance of the desmosome-keratin network is well established in mechanically challenged tissues, we aimed to assess the currently understudied function of desmosomal proteins in intestinal epithelia.

METHODS

We analyzed the intestine-specific villin-Cre DSP (DSP^ΔIEC) and the combined intestine-specific DSG2/DSP^ΔIEC (ΔDsg2/Dsp) knockout mice. Cross-breeding with keratin 8-yellow fluorescent protein knock-in mice and generation of organoids was performed to visualize the keratin network. A Dsp-deficient colorectal carcinoma HT29-derived cell line was generated and the role of Dsp in adhesion and mechanical stress was studied in dispase assays, after exposure to uniaxial cell stretching and during scratch assay.

RESULTS

The intestine of DSP^ΔIEC mice was histopathologically inconspicuous. Intestinal epithelial cells, however, showed an accelerated migration along the crypt and an enhanced shedding into the lumen. Increased intestinal permeability and altered levels of desmosomal proteins were detected. An inconspicuous phenotype also was seen in ΔDsg2/Dsp mice. After dextran sodium sulfate treatment, DSP^ΔIEC mice developed more pronounced colitis. A retracted keratin network was seen in the intestinal epithelium of DSP^ΔIEC/keratin 8-yellow fluorescent protein mice and organoids derived from these mice presented a collapsed keratin network. The level, phosphorylation status, and solubility of keratins were not affected. Dsp-deficient HT29 cells had an impaired cell adhesion and suffered from increased cellular damage after stretch.

CONCLUSIONS

Our results show that Dsp is required for proper keratin network architecture in intestinal epithelia, mechanical resilience, and adhesion, thereby protecting from injury.

The Impact of MicroRNAs during Inflammatory Bowel Disease: Effects on the Mucus Layer and Intercellular Junctions for Gut Permeability

Research on inflammatory bowel disease (IBD) has produced mounting evidence for the modulation of microRNAs (miRNAs) during pathogenesis. MiRNAs are small, non-coding RNAs that interfere with the translation of mRNAs. Their high stability in free circulation at various regions of the body allows researchers to utilise miRNAs as biomarkers and as a focus for potential treatments of IBD. Yet, their distinct regulatory roles at the gut epithelial barrier remain elusive due to the fact that there are several external and cellular factors contributing to gut permeability. This review focuses on how miRNAs may compromise two components of the gut epithelium that together form the initial physical barrier: the mucus layer and the intercellular epithelial junctions. Here, we summarise the impact of miRNAs on goblet cell secretion and mucin structure, along with the proper function of various junctional proteins involved in paracellular transport, cell adhesion and communication. Knowledge of how this elaborate network of cells at the gut epithelial barrier becomes compromised as a result of dysregulated miRNA expression, thereby contributing to the development of IBD, will support the generation of miRNA-associated biomarker panels and therapeutic strategies that detect and ameliorate gut permeability.