Components Of Tight Junctions Research Articles

Selective Inhibition of Hepatocyte Claudin-3 Ameliorates Fibrotic and Cholestatic Liver Damage by Enhancing Bicarbonate Secretion and Bile Dynamics.

Abstract Background Cholestatic-fibrotic liver diseases have a high unmet medical need. Tight junctions, which maintain the blood-biliary-barrier in the liver, have important biological functions that impact cholestatic diseases. A main component of the hepatic tight junction is claudin-3. Aims In this study, we explored the function of claudin-3 and demonstrate its potential as a new drug target in cholestatic-fibrotic liver diseases. Methods Adult C57BL/6 N background Cldn3+/+ or Cldn3-/- mice were subjected to extra- and intrahepatic cholestasis via surgical ligation of the common bile duct (BDL) or chemically, by gavage or feeding alpha-naphthyl isothiocyanate (ANIT). Hepatic necrosis and serum liver injury markers were determined. Bile flow and bicarbonate levels were quantified. Bile acid levels were measured by LC-MS/MS in serum and liver tissue. Claudin-3 was knocked down using liver specific claudin-3 GalNAc-siRNAs. Results Claudin-3 is expressed in normal- and cholestatic liver tissues. Cldn3-/- mice have a higher bile-flow rate, more bicarbonate secretion, and the bile is less concentrated with bile acids and bilirubin. Following bile duct ligation or ANIT, Cldn3-/- mice showed macroscopically less signs of bile acid retention and a different bile color. Hepatic bile acid levels were significantly lower in normal- or cholestasis challenged Cldn3-/- mice. Following BDL, ANIT gavage- or ANIT feeding, liver injury in was remarkably ameliorated in Cldn3-/- mice. Liver specific knockdown of claudin-3 using GalNAc-siRNAs ameliorated cholestasis at a lower success rate compared to the complete knockout. Conclusion Knockout or GalNAc-siRNA mediated inhibition of claudin-3 protected the liver from injury in models of extra- or intrahepatic cholestasis. Further pre-clinical and clinical studies need to be conducted to show whether claudin-3 inhibition is an efficient and safe therapeutic approach for the treatment of cholestatic liver diseases. As next step towards translation of our results, we are currently screening and optimizing human GalNAc conjugated claudin-3 inhibitors.

The barrier-protective effect of β-eudesmol against type 2-inflammatory cytokine-induced tight junction disassembly in airway epithelial cells.

Allergic inflammation, which is the pathogenesis of allergic rhinitis and asthma, is associated with disruption of the airway epithelial barrier due to the effects of type 2 inflammatory cytokines, i.e. interleukin-4 and interleukin-13 (IL-4/13). The anti-allergic inflammatory effect of β-eudesmol (BE) on the tight junction (TJ) of the airway epithelium has not previously been reported. Herein, the barrier protective effect of BE was determined by measurement of transepithelial electrical resistance and by paracellular permeability assay in an IL-4/13-treated 16HBE14o- monolayer. Pre-treatment of BE concentration- and time- dependently inhibited IL-4/13-induced TJ barrier disruption, with the most significant effect observed at 20 μM. Cytotoxicity analyses showed that BE, either alone or in combination with IL-4/13, had no effect on cell viability. Western blot and immunofluorescence analyses showed that BE inhibited IL-4/13-induced mislocalization of TJ components, including occludin and zonula occludens-1 (ZO-1), without affecting the expression of these two proteins. In addition, the mechanism of the TJ-protective effect of BE was mediated by inhibition of IL-4/13-induced STAT6 phosphorylation, in which BE might serve as an antagonist of cytokine receptors. In silico molecular docking analysis demonstrated that BE potentially interacted with the site I pocket of the type 2 IL-4 receptor, likely at Asn-126 and Tyr-127 amino acid residues. It can therefore be concluded that BE is able to prevent IL-4/13-induced TJ disassembly by interfering with cytokine-receptor interaction, leading to suppression of STAT6-induced mislocalization of occludin and ZO-1. BE is a promising candidate for a therapeutic intervention for inflammatory airway epithelial disorders driven by IL-4/13.

State of the art and upcoming trends in claudin-directed therapies in gastrointestinal malignancies.

Claudins, components of tight cell junctions in epithelial and endothelial cells, have emerged as a therapeutic target in gastrointestinal (GI) malignancies, particularly claudin 18.2 (CLDN18.2). Zolbetuximab, a chimeric anti-CLDN18.2 monoclonal antibody (mAb), is currently under FDA review and may emerge as the first claudin targeted therapy approved. Phase 3 trials show that zolbetuximab in combination with front-line fluoropyrimidine plus oxaliplatin improves survival in advanced CLDN18.2 positive (≥75% of tumor cells) gastric adenocarcinoma (GAC) patients. Many other therapies (mAbs; CART; bispecific; ADCs) are under investigation. CLDN18.2 will be an important target in GAC. Early understanding of how to target CLDN18.2 based on the level of expression (high, moderate, low) will be the key to success in this area. Studying these as separate entities should be considered. Resistance patterns, loss of CLDN18.2 expression, role in the refractory setting, and if any role in localized disease are questions that remain. Other targets for claudin that target claudin six and four are under investigation. Their role in GI malignancies will soon be further clarified.

Abstract 5419: Claudin-7 mediates Rab25-induced suppression of colon cancer cell invasion

Abstract Ras-related protein 25 (Rab25) is a member of small GTPase, and growing evidence demonstrates the context-dependent roles of Rab25 in cancer progression. While Rab25 aggravates cancer cell invasion in ER-positive breast, ovarian, and gastric cancers, Rab25 is under-expressed and suppresses colon and triple-negative breast cancer progression. Claudins are major components of tight junctions, and disruption of claudins is implicated in tumorigenesis. Among 27 known members of the claudin family, claudin-7 is suggested to suppress colon cancer progression. Previously, we identified that Rab25 induces endothelial-mesenchymal transition (EMT) and invasiveness of several types of cancer cells through activating the β1 integrin/epidermal growth factor receptor (EGFR)/Snail signaling cascades. However, little is known about the underlying mechanism of Rab25-induced tumor suppression. In the present study, we identify the critical role of claudin-7 in Rab25-induced suppression of colon cancer invasion. 3D Matrigel and modified Boden chamber were used to assess the invasiveness of colon cancer cells. Wound-healing assay was used to analyze colon cancer cell migration. 3D Matrigel was used to analyze tumor growth. Immunoblotting was used to assess the protein expression. Rab25 induced claudin-7 expression in colon cancer cells through protein stabilization. In addition, the enforced expression of claudin-7 not only reduced the EGFR/Ras signaling activity and Snail expression but also attenuated colon cancer cell invasion. However, silencing of claudin-7 expression rescued the tumor suppressive role of Rab25, thereby increasing colon cancer cell invasiveness. Collectively, our data demonstrate for the first time that Rab25 reduces the EGFR/Ras/Snail signaling activity and inhibits colon cancer cell invasion by upregulating claudin-7 expression. Citation Format: Su Jin Cho, Bo Young Jeong, Se-Hee Yoon, Chang Gyo Park, Hoi Young Lee. Claudin-7 mediates Rab25-induced suppression of colon cancer cell invasion [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 5419.

Computational Models of Claudin Assembly in Tight Junctions and Strand Properties.

Claudins are one of the major components of tight junctions (TJs) that polymerize within the cell membrane and form interactions between cells. Some claudins seal the paracellular space, limiting paracellular flux, while others form selectively permeable ion channels that control the paracellular permeability of small ions. Claudin strands are known to be dynamic and reshape within TJs to accommodate large-scale movements and rearrangements of epithelial tissues. Here, we summarize the recent computational and modeling studies on claudin assembly into tetrameric ion channels and their polymerization into μm long strands within the membrane. Computational studies ranging from all-atom molecular dynamics, coarse-grained simulations, and hybrid-resolution simulations elucidate the molecular nature of claudin assembly and function and provide a framework that describes the lateral flexibility of claudin strands.

Antibody-mediated targeting of Claudins in cancer.

Tight junctions (TJs) are large intercellular adhesion complexes that maintain cell polarity in normal epithelia and endothelia. Claudins are critical components of TJs, forming homo- and heteromeric interaction between adjacent cells, which have emerged as key functional modulators of carcinogenesis and metastasis. Numerous epithelial-derived cancers display altered claudin expression patterns, and these aberrantly expressed claudins have been shown to regulate cancer cell proliferation/growth, metabolism, metastasis and cell stemness. Certain claudins can now be used as biomarkers to predict patient prognosis in a variety of solid cancers. Our understanding of the distinct roles played by claudins during the cancer progression has progressed significantly over the last decade and claudins are now being investigated as possible diagnostic markers and therapeutic targets. In this review, we will summarize recent progress in the use of antibody-based or related strategies for targeting claudins in cancer treatment. We first describe pre-clinical studies that have facilitated the development of neutralizing antibodies and antibody-drug-conjugates targeting Claudins (Claudins-1, -3, -4, -6 and 18.2). Next, we summarize clinical trials assessing the efficacy of antibodies targeting Claudin-6 or Claudin-18.2. Finally, emerging strategies for targeting Claudins, including Chimeric Antigen Receptor (CAR)-T cell therapy and Bi-specific T cell engagers (BiTEs), are also discussed.

Campylobacter jejuni Surface-Bound Protease HtrA, but Not the Secreted Protease nor Protease in Shed Membrane Vesicles, Disrupts Epithelial Cell-to-Cell Junctions.

Fundamental functions of the intestinal epithelium include the digestion of food, absorption of nutrients, and its ability to act as the first barrier against intruding microbes. Campylobacter jejuni is a major zoonotic pathogen accounting for a substantial portion of bacterial foodborne illnesses. The germ colonizes the intestines of birds and is mainly transmitted to humans through the consumption of contaminated poultry meat. In the human gastrointestinal tract, the bacterium triggers campylobacteriosis that can progress to serious secondary disorders, including reactive arthritis, inflammatory bowel disease and Guillain-Barré syndrome. We recently discovered that C. jejuni serine protease HtrA disrupts intestinal epithelial barrier functions via cleavage of the tight and adherens junction components occludin, claudin-8 and E-cadherin. However, it is unknown whether epithelial damage is mediated by the secreted soluble enzyme, by HtrA contained in shed outer-membrane vesicles (OMVs) or by another mechanism that has yet to be identified. In the present study, we investigated whether soluble recombinant HtrA and/or purified OMVs induce junctional damage to polarized intestinal epithelial cells compared to live C. jejuni bacteria. By using electron and confocal immunofluorescence microscopy, we show that HtrA-expressing C. jejuni bacteria trigger efficient junctional cell damage, but not soluble purified HtrA or HtrA-containing OMVs, not even at high concentrations far exceeding physiological levels. Instead, we found that only bacteria with active protein biosynthesis effectively cleave junctional proteins, which is followed by paracellular transmigration of C. jejuni through the epithelial cell layer. These findings shed new light on the pathogenic activities of HtrA and virulence strategies of C. jejuni.

Expression of claudin 18.2 in peritoneal metastasis (PM) of gastric cancer.

403 Background: Prognosis of patients with gastric cancer (GC) with peritoneal metastasis (PM) still remains poor, and new treatment strategies are needed. Claudins (CLDNs) are main components of tight junctions that physiologically mediate cell–cell adhesion and regulate selective permeability in epithelial cellular sheets. Recent clinical trials have demonstrated that monoclonal antibodies (mAb) to CLDN18.2 have been shown to improve the outcome of the patients with unresectable metastatic GC, especially with undifferentiated histology. However, the clinical effects of the anti-CLDN18.2 mAb for patients with PM is unclear. In this study, we evaluated the expression of CLDN18.2 in primary tumor and metastatic nodules in peritoneum of GC using immunohistochemical (IHC) staining. Methods: In 42 patients diagnosed with stage IV GC with PM at our Department from 2014 to 2022, biopsy samples of primary tumor and peritoneal nodules were obtained and the expression of CLDN18.2 in tumor cells by IHC staining using specific antibody for CLDN18.2 (clone: 43-14A, prediluted; Ventana) followed by the incubation with secondary antibody and the primary antibody binding visualized using the DAB IHC Detection Kit. The intensity of the membrane and cytosolic staining was classified as 0 (no reactivity), 1+ (weak), 2+ (moderate), and 3+ (strong). Samples were defined as CLDN18.2-positive when tumor cells showed specific staining with at least 1+ intensity in tumor cells. Percentage of overall CLDN18.2 positive cells was determined by the estimated number of CLDN18.2+ cells divided by the estimated overall number of tumor cells in any fractions. Her2 expression was also examined in parallel. Results: The histology type of primary tumor was differentiated in 7, undifferentiated in 33, and unknown in 2 patients. CLDN18.2-positivity was detected in 31 (74%) of primary tumors, including 5 (71%) differentiated and 26(79%) undifferentiated tumors. CLDN18.2 was positively detected in 15 (35%) disseminated nodules, in 4 (57%) differentiated and 11 (33%) in undifferentiated cases, respectively. All these cases also showed CLDN18.2-positve in primary sites. However, expression of CLDN18.2 in PM was not detected in 16 (52%) cases which showed CLDN18.2-positive for primary tumor. Moderate-to-strong CLDN18.2 expression (≥2+ membrane staining intensity in ≥40% of tumor cells) was observed in 13 (31%) of primary tumor, but only in 2 (5%) of PM. HER2 was positive in 5 (12%) patients, and no correlation was observed between HER2 and CLDN18.2 expression. Conclusions: CLDN18.2 expression did not show significant difference depending on histology. Although the expression of CLDN18.2 in PM showed homology with that in biopsy sample of primary gastric tumor, its expression level generally decreased in PM. Investigation of CLDN18.2 expression in peritoneal nodules might be necessary to predict the clinical response of CLDN18.2 mAb for GC with PM.

Functional Analysis of Membrane-Associated Scaffolding Tight Junction (TJ) Proteins in Tumorigenic Characteristics of B16-F10 Mouse Melanoma Cells.

Tight junction (TJ) proteins (Tjps), Tjp1 and Tjp2, are tight junction-associated scaffold proteins that bind to the transmembrane proteins of tight junctions and the underlying cytoskeleton. In this study, we first analyzed the tumorigenic characteristics of B16-F10 melanoma cells, including cell proliferation, migration, invasion, metastatic potential, and the expression patterns of related proteins, after the CRISPR-Cas9-mediated knockout (KO) of Tjp genes. The proliferation of Tjp1 and Tjp2 KO cells significantly increased in vitro. Other tumorigenic characteristics, including migration and invasion, were significantly enhanced in Tjp1 and Tjp2 KO cells. Zonula occludens (ZO)-associated protein Claudin-1 (CLDN-1), which is a major component of tight junctions and functions in controlling cell-to-cell adhesion, was decreased in Tjp KO cells. Additionally, Tjp KO significantly stimulated tumor growth and metastasis in an in vivo mouse model. We performed a transcriptome analysis using next-generation sequencing (NGS) to elucidate the key genes involved in the mechanisms of action of Tjp1 and Tjp2. Among the various genes affected by Tjp KO-, cell cycle-, cell migration-, angiogenesis-, and cell-cell adhesion-related genes were significantly altered. In particular, we found that the Ninjurin-1 (Ninj1) and Catenin alpha-1 (Ctnna1) genes, which are known to play fundamental roles in Tjps, were significantly downregulated in Tjp KO cells. In summary, tumorigenic characteristics, including cell proliferation, migration, invasion, tumor growth, and metastatic potential, were significantly increased in Tjp1 and Tjp2 KO cells, and the knockout of Tjp genes significantly affected the expression of related proteins.

Zolbetuximab for Claudin18.2-positive gastric or gastroesophageal junction cancer.

Claudins (CLDNs) are a family of major membrane proteins that form components of tight junctions. In normal tissues, CLDNs seal the intercellular space in the epithelial sheets to regulate tissue permeability, paracellular transport, and signal transduction. Claudin18.2 (CLDN18.2), a member of the CLDN family, is expressed specifically in gastric mucosal cells in normal tissue, and its expression is often retained in gastric cancer cells. CLDN18.2 is ectopically expressed in many cancers other than gastric cancer such as esophageal cancer, pancreatic cancer, biliary tract cancer, non-small-cell lung cancer, and ovarian cancer. Structurally, CLDN18.2 is localized on the apical side of the cell membrane and has extracellular loops capable of binding monoclonal antibodies. Upon malignant transformation, CLDN18.2 is exposed to the cell surface of the whole membrane, which enables the binding of monoclonal antibodies. Based on these characteristics, CLDN18.2 was considered to be optimal for target therapy, and zolbetuximab was developed which is a first-in-class chimeric immunoglobulin G1 monoclonal antibody highly specific for CLDN18.2. It binds to CLDN18.2 on the tumor cell surface and stimulates cellular and soluble immune effectors that activate antibody-dependent cytotoxicity and complement-dependent cytotoxicity. Recently, zolbetuximab combined with chemotherapy demonstrated a survival benefit in patients with CLDN18.2-positive and HER-2-negative gastric or gastroesophageal junction cancers in the global phase III SPOTLIGHT and GLOW trials. From these clinically meaningful results, CLDN18.2-targeting therapy including zolbetuximab has attracted a lot of attention. In this review, we summarize the clinical implications of CLDN18.2-positive gastric or GEJ cancer, and CLDN18.2-targeting therapy, mainly for zolbetuximab.

Acrolein suppresses anticancer drug-induced toxicity mediated by activating claudin-1 and Nrf2 axis in a spheroid model of human lung squamous cell carcinoma cells

Tobacco smoke contains various carcinogenic ingredients such as nicotine, acrolein, and benzopyrene; however, their effects on cancer treatment are not fully understood. Claudin-1 (CLDN1), a component of tight junctions, is involved in the increased resistance to anticancer drugs. In this study, we found that acrolein increases the mRNA and protein levels of CLDN1 in RERF-LC-AI cells derived from human lung squamous cell carcinoma (SCC). Acrolein increased the p-extracellular signal-regulated kinase (ERK) 1/2 levels without affecting the p-Akt level. The acrolein-induced elevation of CLDN1 expression was attenuated by U0126, a mitogen-activated protein kinase kinas (MEK) inhibitor. These results indicate that the activation of MEK/ERK pathway is involved in the acrolein-induced elevation of CLDN1 expression. In a spheroid model, acrolein suppressed the accumulation and toxicity of doxorubicin (DXR), which were rescued by CLDN1 silencing. The acrolein-induced effects were also observed in lung SCC-derived EBC-1 and LK-2 cells. Acrolein also increased the expression level of nuclear factor erythroid 2-related factor 2 (Nrf2), a transcription factor that regulates antioxidant and detoxifying genes, which were inhibited by CLDN1 silencing. In spheroid cells, the levels of reactive oxygen species were enhanced by acrolein, which was inhibited by CLDN1 silencing. Taken together, acrolein may reduce the anticancer drug-induced toxicity in human lung SCC cells mediated by high CLDN1 expression followed by the upregulation of Nrf2 signaling pathway.

Claudin-4 Upregulation in Acantholytic and Autoimmune-Mediated Bullous Disorders.

Claudin-4 is a key component of tight junctions, which play an important role in the formation of the epidermal barrier by forming a circumferential network in the granular layer that serves as a gatekeeper of the paracellular pathway. The aim of this study is to illustrate claudin-4 immunohistochemical staining patterns of different blistering disorders. We collected 35 cases, including two Hailey-Hailey disease, one Darier disease, three Grover disease, one acantholytic acanthoma, two warty dyskeratoma, 11 pemphigus vulgaris (PV) including six mucosal PV, and two pemphigus foliaceus. For comparison, we included five cases of normal skin, five eczema, and three bullous pemphigoid cases. Claudin-4 demonstrated weak-to-moderate expression in keratinocytes located in the stratum granulosum, keratinocytes surrounding hair follicles, and adnexal glands. Further, claudin-4 exhibited moderate-to-strong membranous staining in disrupted keratinocytes surrounding and within the acantholytic and bullous areas in 16/22 of the acantholytic cases (not seen in the six cases of mucosal PV) and all three bullous pemphigoids. This finding suggests that claudin-4 is upregulated in these conditions, which may be a compensatory response to the disrupted barrier function. This finding could shed light on the molecular mechanisms underlying disrupted barrier function in blistering disorders, independent of the specific underlying disease mechanism.

Plasma-activated medium ameliorates the chemoresistance of human lung adenocarcinoma cells mediated via downregulation of claudin-2 expression

Plasma-activated medium (PAM) has various biological activities including anticancer and antimicrobial. However, the effect on chemoresistance in cancer cells has not been clarified in detail. Solid cancer cells form a microenvironment in the body and acquire resistance against anticancer drugs. So far, we reported that claudin-2 (CLDN2), a component of tight junctions, suppresses the anticancer drug-induced cytotoxicity of spheroids that mimic in vivo tumors. Here, we found that the protein level of CLDN2 is downregulated by the sublethal concentration of PAM in human lung adenocarcinoma-derived A549 and PC-3 cells. A cycloheximide pulse-chase assay showed that PAM accelerates the degradation of CLDN2 protein. The PAM-induced reduction of CLDN2 protein was inhibited by a lysosome inhibitor, indicating PAM may enhance the lysosomal degradation of CLDN2. The paracellular permeability to doxorubicin (DXR), an anthracycline antitumor drug, was enhanced by PAM. In the spheroids, the accumulation and toxicity of DXR were enhanced by PAM. In addition, oxidative stress and the expression of nuclear factor erythroid 2-related factor 2, one of the key factors for the acquisition of chemoresistance, were attenuated by PAM. The improvement effect of PAM on chemoresistance was suppressed by the exogenous CLDN2 overexpression. These results indicate that PAM has the ability to downregulate CLDN2 expression and may become an adjuvant drug against lung adenocarcinoma.

OGC O02 CLDN18.2 expression in resectable gastroesophageal cancers: associated clinical and molecular signatures and impact of neoadjuvant chemotherapy on intra-tumour heterogeneity

Abstract Background Claudin 18.2 (CLDN18.2), a key component of tight junctions, is overexpressed in up to 40% of oesophagogastric adenocarcinoma (OGA) and is a clinically validated biomarker in the unresectable setting. However, data is required in the resectable stages, including chemotherapy effects, relationship with genomic and immune factors, and measures of heterogeneity. Methods CLDN18.2 (ab222512, Abcam) and PD-L1 (E1L3N, Cell Signaling) were assessed by immunohistochemistry on adjacent FFPE slides in 57 patients with resectable OGA. Positivity was defined as 2+/3+ staining in ≥40% of tumour cells for CLDN18.2 and combined positive score (CPS)≥1 for PD-L1. Twenty-four patients (43%) had additional tumour samples to assess CLDN18.2 intra-tumour heterogeneity. Tumour mutational burden (TMB) and copy number aberrations (CNAs) were estimated from WGS and tumour microenvironment (TME) composition from transcriptomic data. Mann Whitney/t-test was used to compare clinical and molecular characteristics, and log-rank test to compare survival curves. Statistical significance was set at p=0.05. Results Fifty-seven patients with resected OGA (79% after neoadjuvant chemotherapy (nCT)) were evaluated. CLDN18.2 was expressed in 18% and CLDN18.2 expression was not associated with clinicopathological features or survival. CLDN18.2 copy numbers (n=57, p=0.24) and RNA levels (n=20, p=0.48) were not associated with staining intensity. Compared to CLDN18.2-ve, CLDN18.2+ve cases did not differ in PD-L1 expression, TMB, CNAs, or TME composition (all p>0.05). However, exposure to chemotherapy was significantly associated with lack of CLDN18.2 (OR=0.2, 95% CI 0.04-0.79, p=0.03) and, among CLDN18.2+ve cases, CLDN18.2 status concordance between tumour samples was 100% in treatment-naïve but only 29% in cases exposed to chemotherapy. Conclusions CLDN18.2+ve and CLDN18.2-ve tumours had similar clinical, genomic and immune features. However, exposure to chemotherapy substantially contributes to CLDN18.2 intra-tumour heterogeneity. Larger cohorts will need to clarify whether the evaluation of multiple tumour samples is required for an accurate assessment of CLDN18.2 expression.

CLDN6 inhibits colorectal cancer proliferation dependent on restraining p53 ubiquitination via ZO-1/PTEN axis

Colorectal cancer (CRC) is one of the most common cancers in the world. Abnormal proliferation is a chief characteristic of cancer and is the initiation of CRC progression. As an important component of tight junctions, CLDN6 regulates the proliferation of multiple tumors. Our previous study showed that CLDN6 was low expressed in CRC, and CLDN6 overexpression inhibited CRC proliferation. However, the specific mechanism of how CLDN6 works remains unclear. This research aimed to reveal the relationship between CLDN6 and clinical features, as well as the molecular mechanism by which CLDN6 inhibited CRC proliferation. We found that low expression of CLDN6 was associated with pathological grade and prognosis of CRC patients, and confirmed that CLDN6 inhibited CRC proliferation dependent on p53. Mechanically, we elucidated that CLDN6 regulated ubiquitination to enhance p53 stability and nuclear import by PTEN/AKT/MDM2 pathway. Through the PDZ-binding motif (PBM), CLDN6 bound to ZO-1 to interact with PTEN, and regulate AKT/MDM2 pathway. Collectively, our data enriched the theoretical basis for CLDN6 as a potential biomarker for diagnosis, therapy and prognosis of CRC.

Long non-coding RNA LOC103222771 promotes infection of porcine reproductive and respiratory syndrome virus in Marc-145 cells by downregulating Claudin-4

Porcine reproductive and respiratory syndrome (PRRS) is an important swine disease caused by infection of porcine reproductive and respiratory syndrome virus (PRRSV), which leads to huge loss in swine industry. How to effectively control PRRS is challenging. Long non-coding RNA (lncRNA) are key regulator of viral infections and anti-virus immunological responses, therefore, further understanding of lncRNAs will aid to identification of novel regulators of viral infections and better design of prevention and control strategies to viral infection related diseases and immune disorders. We demonstrated that PRRSV infection upregulated the expression of lncRNA LOC103222771 in Marc-145 cells and porcine alveolar macrophage cells (PAMs) and that LOC103222771 is mainly located in cytoplasm. Knockdown of LOC103222771 could inhibit the PRRSV infection in Marc-145 cells. RNA-seq analysis and subsequent validation revealed increased expression of Claudin-4 (CLDN4) in Marc-145 when LOC103222771 was specifically downregulated，suggesting that LOC103222771 might be an upstream regulator of CLDN4, an important component of tight junctions for establishment of the paracellular barrier that controls the flow of molecules in the intercellular space between epithelial cells. We and others showed that Downregulation of CLDN4 could boost the infection of PRRSV. Collectively, LOC103222771/CLDN4 signal axis might be a novel mechanism of PRRSV pathogenesis, implying a potential therapeutic target against PRRSV infection.

Increase in Paracellular Leakage of Amino Acids Mediated by Aging-Induced Reduction of Claudin-4 Expression

BackgroundClaudins (CLDNs), major components of tight junctions, control paracellular permeabilities of mineral ions and wastes. The absorption of nutrients including glucose and amino acids (AAs) is regulated by intestinal epithelial cells. However, the role of CLDNs is not fully understood. ObjectivesThe purpose of this study was to clarify the effect of AA deprivation on the expression of AA transporters and CLDNs, as well as the role of CLDNs in the regulation of paracellular AA fluxes. MethodsThe messenger RNA and protein expression of various CLDNs were examined by real-time quantitative polymerase chain reaction and Western blot analyses, respectively. The AA selectivity of CLDNs was estimated using liquid chromatography-tandem mass spectrometry (LC-MS) analysis. ResultsThe expression levels of some AA transporters, CLDN4, and CLDN15 were increased by AA deprivation in normal mouse colon-derived MCE301 cells. The expression of AA transporters and CLDN15 in the mouse colon was positively correlated with aging but the expression of CLDN4 was not. The AA deprivation-induced elevation of CLDN4 expression was inhibited by MHY1485, a mammalian target of rapamycin (mTOR) activator. Furthermore, CLDN4 expression was increased by rapamycin, an mTOR inhibitor. mTOR may be involved in the transcriptional activation of CLDN4. The fluxes of AAs from the basal to apical compartments were decreased and increased by CLDN4 overexpression and silencing, respectively. LC-MS analysis showed that the fluxes of all AAs, especially Lys, His, and Arg, were enhanced by CLDN4 silencing. ConclusionsCLDN4 is suggested to form a paracellular barrier to AAs, especially alkaline AAs, which is attenuated with aging.

Probiotic OMNi-BiOTiC® 10 AAD Reduces Cyclophosphamide-Induced Inflammation and Adipose Tissue Wasting in Mice.

Cancer therapy is often associated with severe side effects such as drug induced weight loss, also known as chemotherapy-induced cachexia. The aim of this study was to investigate the effects of a multispecies probiotic (OMNi-BiOTiC® 10 AAD) in a chemotherapy mouse model. A total of 24 male BALB/c mice were gavage-fed with the probiotic formulation or water, once a day for 3 weeks. In the third week, the mice received intraperitoneal cyclophosphamide. At euthanasia, the organs were dissected, and serum was sampled for cytokine analysis. Tight junction components, myosin light chain kinase, mucins, and apoptosis markers were detected in the ileum and colon using histological analyses and qRT-PCR. Lipolysis was analyzed by enzymatic activity assay, Western blotting analyses, and qRT-PCR in WAT. The fecal microbiome was measured with 16S-rRNA gene sequencing from stool samples, and fecal volatile organic compounds analysis was performed using gas chromatography/mass spectrometry. The probiotic-fed mice exhibited significantly less body weight loss and adipose tissue wasting associated with a reduced CGI58 mediated lipolysis. They showed significantly fewer pro-inflammatory cytokines and lower gut permeability compared to animals fed without the probiotic. The colons of the probiotic-fed animals showed lower inflammation scores and less goblet cell loss. qRT-PCR revealed no differences in regards to tight junction components, mucins, or apoptosis markers. No differences in microbiome alpha diversity, but differences in beta diversity, were observed between the treatment groups. Taxonomic analysis showed that the probiotic group had a lower relative abundance of Odoribacter and Ruminococcus-UCG014 and a higher abundance of Desulfovibrio. VOC analysis yielded no significant differences. The results of this study indicate that oral administration of the multispecies probiotic OMNi-BiOTiC® 10 AAD could mitigate cyclophosphamide-induced chemotherapy side effects.

Impaired intestinal permeability in patients with multiple sclerosis.

A number of recent studies have shown that the intestinal microbiome, part of the brain-gut axis, is implicated in the pathophysiology of multiple sclerosis. An essential part of this axis, is the intestinal barrier and gastrointestinal disorders with intestinal barrier dysregulation appear to be linked to CNS demyelination, and hence involved in the etiopathogenesis of multiple sclerosis (MS). The aim of this study was to evaluate the integrity of the intestinal barrier in patients with clinically definite multiple sclerosis (CDMS) and clinically isolated syndrome (CIS) using two serum biomarkers, claudin-3 (CLDN3), a component of tight epithelial junctions, and intestinal fatty acid binding protein (I-FABP), a cytosolic protein in enterocytes. Serum levels of CLDN3 in 37 MS patients and 22 controls, and serum levels of I-FABP in 46 MS patients and 51 controls were measured using commercial ELISA kits. Complete laboratory tests excluded the presence of gluten-related disorders in all subjects. Thirty MS patients received either disease-modifying drugs (DMD), immunosuppression (IS) or corticosteroid treatment. CLDN3 levels were only significantly higher in the MS patients treated with DMD or IS compared to the control group (P=0.006). There were no differences in I-FABP serum levels between the groups. Serum CLDN3 levels did not correlate with serum I-FABP levels in CDMS, in CIS patients or controls. In multiple sclerosis patients, the intestinal epithelium may be impaired with increased permeability, but without significant enterocyte damage characterized by intracellular protein leakage. Based on our data, CLDN3 serum levels appear to assess intestinal dysfunction in MS patients but mainly in treated ones.

Discovery, synthesis and biological evaluation of a series of N-(phenylcarbamothioyl)-2-napthamides as inhibitors of Claudin-1

Colorectal cancer (CRC) remains a leading cause of cancer-related deaths worldwide, despite advancements in diagnosis. The main reason for this is that many newly diagnosed CRC patients will suffer from metastasis to other organs. Thus, the development of new therapies is of critical importance. Claudin-1 protein is a component of tight junctions in epithelial cells, including those found in the lining of the colon. It plays a critical role in the formation and maintenance of tight junctions, which are essential for regulating the passage of molecules between cells. In CRC, claudin-1 is often overexpressed, leading to an increase in cell adhesion, which can contribute to the development and progression of the disease. Studies show that high levels of claudin-1 are associated with poor prognosis in CRC patients and targeting claudin-1 may have therapeutic potential for the treatment of CRC. Previously, we have identified a small molecule that inhibits claudin-1 dependent CRC progression. Reported herein are our lead optimization efforts around this scaffold to identify the key SAR components and the discovery of a key new compound that exhibits enhanced potency in SW620 cells.