Deoxynivalenol Induces Blood-Testis Barrier Dysfunction through Disrupting p38 Signaling Pathway-Mediated Tight Junction Protein Expression and Distribution in Mice

Deoxynivalenol (DON) is widely present in cereals and processed grains. It can disrupt the blood-testicular barrier (BTB), leading to sterility in males; however, the mechanism is unknown. In this study, 30 Kunming mice and TM4 cells were exposed to 0 or 4.8 mg/kg (28 d) and 0-2.4 μM (24 h) of DON, respectively. Histopathological findings showed that DON increased BTB permeability in mice, leading to tight junction (TJ) structural damage. Immunofluorescence results indicated that DON disrupted the localization of zonula occludens (ZO)-1. The results of protein and mRNA expression showed that the expression of ZO-1, occludin, and claudin-11 was reduced, and that the p38/GSK-3β/snail and p38/ATF-2/MLCK signaling pathways were activated in mouse testes and TM4 cells. Pretreatment with the p38 inhibitor SB203580 maintained TJ integrity in TM4 cells after exposure to DON. Thus, DON induced BTB dysfunction in mice by disrupting p38 pathway-mediated TJ expression and distribution.

Bi-allelic variants in the ESAM tight-junction gene cause a neurodevelopmental disorder associated with fetal intracranial hemorrhage

The blood-brain barrier (BBB) is an essential gatekeeper for the central nervous system and incidence of neurodevelopmental disorders (NDDs) is higher in infants with a history of intracerebral hemorrhage (ICH). We discovered a rare disease trait in thirteen individuals, including four fetuses, from eight unrelated families associated with homozygous loss-of-function variant alleles of ESAM which encodes an endothelial cell adhesion molecule. The c.115del (p.Arg39Glyfs∗33) variant, identified in six individuals from four independent families of Southeastern Anatolia, severely impaired the in vitro tubulogenic process of endothelial colony-forming cells, recapitulating previous evidence in null mice, and caused lack of ESAM expression in the capillary endothelial cells of damaged brain. Affected individuals with bi-allelic ESAM variants showed profound global developmental delay/unspecified intellectual disability, epilepsy, absent or severely delayed speech, varying degrees of spasticity, ventriculomegaly, and ICH/cerebral calcifications, the latter being also observed in the fetuses. Phenotypic traits observed in individuals with bi-allelic ESAM variants overlap very closely with other known conditions characterized by endothelial dysfunction due to mutation of genes encoding tight junction molecules. Our findings emphasize the role of brain endothelial dysfunction in NDDs and contribute to the expansion of an emerging group of diseases that we propose to rename as "tightjunctionopathies."

LncRNA446 Regulates Tight Junctions by Inhibiting the Ubiquitinated Degradation of Alix after Porcine Epidemic Diarrhea Virus Infection

Porcine epidemic diarrhea (PED) is a highly contagious disease, caused by porcine epidemic diarrhea virus (PEDV), which causes huge economic losses. Tight junction-associated proteins play an important role during virus infection; therefore, maintaining their integrity may be a new strategy for the prevention and treatment of PEDV. Long noncoding RNAs (lncRNAs) participate in numerous cellular functional activities, yet whether and how they regulate the intestinal barrier against viral infection remains to be elucidated. Here, we established a standard system for evaluating intestinal barrier integrity and then determined the differentially expressed lncRNAs between PEDV-infected and healthy piglets by lncRNA-seq. A total of 111 differentially expressed lncRNAs were screened, and lncRNA446 was identified due to significantly higher expression after PEDV infection. Using IPEC-J2 cells and intestinal organoids as in vitro models, we demonstrated that knockdown of lncRNA446 resulted in increased replication of PEDV, with further damage to intestinal permeability and tight junctions. Mechanistically, RNA pulldown and an RNA immunoprecipitation (RIP) assay showed that lncRNA446 directly binds to ALG-2-interacting protein X (Alix), and lncRNA446 inhibits ubiquitinated degradation of Alix mediated by TRIM25. Furthermore, Alix could bind to ZO1 and occludin and restore the expression level of the PEDV M gene and TJ proteins after lncRNA446 knockdown. Additionally, Alix knockdown and overexpression affects PEDV infection in IPEC-J2 cells. Collectively, our findings indicate that lncRNA446, by inhibiting the ubiquitinated degradation of Alix after PEDV infection, is involved in tight junction regulation. This study provides new insights into the mechanisms of intestinal barrier resistance and damage repair triggered by coronavirus. IMPORTANCE Porcine epidemic diarrhea is an acute, highly contagious enteric viral disease severely affecting the pig industry, for which current vaccines are inefficient due to the high variability of PEDV. Because PEDV infection can lead to severe injury of the intestinal epithelial barrier, which is the first line of defense, a better understanding of the related mechanisms may facilitate the development of new strategies for the prevention and treatment of PED. Here, we demonstrate that the lncRNA446 directly binds one core component of the actomyosin-tight junction complex named Alix and inhibits its ubiquitinated degradation. Functionally, the lncRNA446/Alix axis can regulate the integrity of tight junctions and potentially repair intestinal barrier injury after PEDV infection.

Identification of the genes encoding candidate septate junction components expressed during early development of the sea urchin, Strongylocentrotus purpuratus, and evidence of a role for Mesh in the formation of the gut barrier

Septate junctions (SJs) evolved as cell-cell junctions that regulate the paracellular barrier and integrity of epithelia in invertebrates. Multiple morphological variants of SJs exist specific to different epithelia and/or phyla but the biological significance of varied SJ morphology is unclear because the knowledge of the SJ associated proteins and their functions in non-insect invertebrates remains largely unknown. Here we report cell-specific expression of nine candidate SJ genes in the early life stages of the sea urchin Strongylocentrotus purpuratus. By use of in situ RNA hybridization and single cell RNA-seq we found that the expression of selected genes encoding putatively SJ associated transmembrane and cytoplasmic scaffold molecules was dynamically regulated during epithelial development in the embryos and larvae with different epithelia expressing different cohorts of SJ genes. We focused a functional analysis on SpMesh, a homolog of the Drosophila smooth SJ component Mesh, which was highly enriched in the endodermal epithelium of the mid- and hindgut. Functional perturbation of SpMesh by both CRISPR/Cas9 mutagenesis and vivo morpholino-mediated knockdown shows that loss of SpMesh does not disrupt the formation of the gut epithelium during gastrulation. However, loss of SpMesh resulted in a severely reduced gut-paracellular barrier as quantitated by increased permeability to 3-5 ​kDa FITC-dextran. Together, these studies provide a first look at the molecular SJ physiology during the development of a marine organism and suggest a shared role for Mesh-homologous proteins in forming an intestinal barrier in invertebrates. Results have implications for consideration of the traits underlying species-specific sensitivity of marine larvae to climate driven ocean change.

Homeostasis effects of fermented Maillard reaction products by Lactobacillus gasseri 4M13 in dextran sulfate sodium-induced colitis mice

BACKGROUND

The incidence of inflammatory bowel disease (IBD) continues to increase worldwide. Multiple factors, including diet, loss of the intestinal barrier function, and imbalance of the immune system can cause IBD. A balanced diet is important for maintaining a healthy bowel and preventing IBD from occurring. The effects of probiotic Lactobacillus gasseri-fermented Maillard reaction products (MRPs) prepared by reacting whey protein with galactose on anti-inflammation and intestinal homeostasis were investigated in this study, which compared MPRs and probiotics separately.

RESULTS

In an animal colitis model induced by 2% dextran sulfate sodium (DSS), FWG administration alleviated colon length loss and maintained intestinal immune system homeostasis as reflected by down-regulated interleukin (IL)-6, IL-10, tumor necrosis factor (TNF)-α output, and metallopeptidase-9, and epithelial barrier balance as reflected by up-regulated occludin, E-cadherin, and zonula occludens-1 production in the colon. Furthermore, the expression of splenic cytokines such as IL-6, TNF-α, and IL-10 was up-regulated in the FWG-treated mice in a comparable amount to the control group to ensure the balance of immune responses.

CONCLUSION

This study showed that the use of FWG protects the intestines from colitis caused by DSS and maintains immune balance. FWG increased antioxidant enzyme activity, increased intestinal permeability, and regulated the balance of pro- and anti-inflammatory cytokines in the intestines and spleen. Continued intake of FWG can alleviate IBD symptoms through the preservation of mucosal immune responses, epithelial junction and homeostasis through the regulated splenic cytokines. © 2021 Society of Chemical Industry.

Selective blood-nerve barrier leakiness with claudin-1 and vessel-associated macrophage loss in diabetic polyneuropathy

Diabetic polyneuropathy (DPN) is the most common complication in diabetes and can be painful in up to 26% of all diabetic patients. Peripheral nerves are shielded by the blood-nerve barrier (BNB) consisting of the perineurium and endoneurial vessels. So far, there are conflicting results regarding the role and function of the BNB in the pathophysiology of DPN. In this study, we analyzed the spatiotemporal tight junction protein profile, barrier permeability, and vessel-associated macrophages in Wistar rats with streptozotocin-induced DPN. In these rats, mechanical hypersensitivity developed after 2 weeks and loss of motor function after 8 weeks, while the BNB and the blood-DRG barrier were leakier for small, but not for large molecules after 8 weeks only. The blood-spinal cord barrier remained sealed throughout the observation period. No gross changes in tight junction protein or cytokine expression were observed in all barriers to blood. However, expression of Cldn1 mRNA in perineurium was specifically downregulated in conjunction with weaker vessel-associated macrophage shielding of the BNB. Our results underline the role of specific tight junction proteins and BNB breakdown in DPN maintenance and differentiate DPN from traumatic nerve injury. Targeting claudins and sealing the BNB could stabilize pain and prevent further nerve damage. KEY MESSAGES: • In diabetic painful neuropathy in rats: • Blood nerve barrier and blood DRG barrier are leaky for micromolecules. • Perineurial Cldn1 sealing the blood nerve barrier is specifically downregulated. • Endoneurial vessel-associated macrophages are also decreased. • These changes occur after onset of hyperalgesia thereby maintaining rather than inducing pain.

M. fortuitum-induced CNS-pathology: Deciphering the role of canonical Wnt signaling, blood brain barrier components and cytokines

Molecular underpinning of mycobacteria-induced CNS-pathology is not well understood. In the present study, zebrafish were infected with Mycobacterium fortuitum and the prognosis of CNS-pathogenesis studied. We observed M. fortuitum triggers extensive brain-pathology. Evans blue extravasation demonstrated compromised blood-brain barrier (BBB) integrity. Further, decreased expression in tight-junction (TJ) and adherens junction complex (AJC) genes were noted in infected brain. Wnt-signaling has emerged as a major player in host-mycobacterial immunity but its involvement/role in brain-infection is not well studied. Sustained expression of wnt2, wnt3a, fzd5, lrp5/6 and β-catenin, with concordant decline in degradation complex components axin, gsk3β and β-catenin regulator capn2a were observed. The surge in ifng1 and tnfa expression preceding il10 and il4 suggested cytokine-interplay critical in M. fortuitum-induced brain-pathology. Therefore, we suggest adult zebrafish as a viable model for studying CNS-pathology and using the same, conclude that M. fortuitum infection is associated with repressed TJ-AJC gene expression and compromised BBB permeability. Our results implicate Wnt/β-catenin pathway in M. fortuitum-induced CNS-pathology wherein Th1-type signals facilitate bacterial clearance and Th2-type signals prevent the disease sequel.

Potential effect of fish oil to preserve expression of cell cycle and tight junction regulating genes in colon after di-isononyl phthalate ingestion in albino Wistar rats

Di-isononyl phthalate (DIP) is considered a high molecular-weight subtype of phthalates that are commonly used and could easily affect the gastrointestinal tract (GIT). Eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) are the main active components of fish oil (FO), and their anti-inflammatory potential was previously documented. The current study was designed to investigate the protective potential of fish oil against the impacts of DIP exposure on the colon of albino Wistar rats. Sixty albino Wistar rats were divided into Control group received corn oil for ten days. Di-isononyl phthalate treated group received DIP. Di-isononyl phthalate + fish oil treated group received both DIP and FO. FO was found to preserve the histological architecture, tight junction and cell cycle of the colon. In conclusion, the current study provided an evidence that FO has a protective potential against DIP further examinations to be done to fully understand the molecular basis of this potential as a step for further clinical applications.

Loss of Claudin-3 Impairs Hepatic Metabolism, Biliary Barrier Function, and Cell Proliferation in the Murine Liver

BACKGROUND & AIMS

Tight junctions in the liver are essential to maintain the blood-biliary barrier, however, the functional contribution of individual tight junction proteins to barrier and metabolic homeostasis remains largely unexplored. Here, we describe the cell type-specific expression of tight junction genes in the murine liver, and explore the regulation and functional importance of the transmembrane protein claudin-3 in liver metabolism, barrier function, and cell proliferation.

METHODS

The cell type-specific expression of hepatic tight junction genes is described using our mouse liver single-cell sequencing data set. Differential gene expression in Cldn3-/- and Cldn3+/+ livers was assessed in young and aged mice by RNA sequencing (RNA-seq), and hepatic tissue was analyzed for lipid content and bile acid composition. A surgical model of partial hepatectomy was used to induce liver cell proliferation.

RESULTS

Claudin-3 is a highly expressed tight junction protein found in the liver and is expressed predominantly in hepatocytes and cholangiocytes. The histology of Cldn3-/- livers showed no overt phenotype, and the canalicular tight junctions appeared intact. Nevertheless, by RNA-seq we detected a down-regulation of metabolic pathways in the livers of Cldn3-/- young and aged mice, as well as a decrease in lipid content and a weakened biliary barrier for primary bile acids, such as taurocholic acid, taurochenodeoxycholic acid, and taurine-conjugated muricholic acid. Coinciding with defects in the biliary barrier and lower lipid metabolism, there was a diminished hepatocyte proliferative response in Cldn3-/- mice after partial hepatectomy.

CONCLUSIONS

Our data show that, in the liver, claudin-3 is necessary to maintain metabolic homeostasis, retention of bile acids, and optimal hepatocyte proliferation during liver regeneration. The RNA-seq data set can be accessed at: https://www.ncbi.nlm.nih.gov/geo/query/acc.cgi?acc=GSE159914.

Establishment of a novel probe-based RT-qPCR approach for detection and quantification of tight junctions reveals age-related changes in the gut barriers of broiler chickens

Tight junctions (TJs) play a dominant role in gut barrier formation, therefore, resolving the structures of TJs in any animal species is crucial but of major importance in fast growing broilers. They are regulated in molecular composition, ultrastructure and function by intracellular proteins and the cytoskeleton. TJ proteins are classified according to their function into barrier-forming, scaffolding and pore-forming types with deductible consequences for permeability. In spite of their importance for gut health and its integrity limited studies have investigated the TJs in chickens, including the comprehensive evaluation of TJs molecular composition and function in the chicken gut. In the actual study sequence-specific probes to target different TJ genes (claudin 1, 3, 5, 7, 10, 19, zonula occludens 1 (ZO1), occludin (OCLN) and tricellulin (MD2)) were designed and probe-based RT-qPCRs were newly developed. Claudin (CLDN) 1, 5, ZO1 and CLDN 3, 7, MD2 were engulfed in multiplex RT-qPCRs, minimizing the number of separate reactions and enabling robust testing of many samples. All RT-qPCRs were standardized for chicken jejunum and caecum samples, which enabled specific detection and quantification of the gene expression. Furthermore, the newly established protocols were used to investigate the age developmental changes in the TJs of broiler chickens from 1-35 days of age in the same organ samples. Results revealed a significant increase in mRNA expression between 14 and 21days of age of all tested TJs in jejunum. However, in caecum, mRNA expression of some TJs decreased after 1 day of age whereas some TJs mRNA remained constant till 35 days of age. Taken together, determining the segment-specific changes in the expression of TJ- proteins by RT-qPCR provides a deeper understanding of the molecular mechanisms underpinning pathophysiological changes in the gut of broiler chickens with various etiologies.

Indole-3-propionic Acid Improved the Intestinal Barrier by Enhancing Epithelial Barrier and Mucus Barrier

Destruction in intestinal barrier is concomitant with the intestinal diseases. There is growing evidence that tryptophan-derived intestinal bacterial metabolites play a critical role in maintaining the balance of intestinal mucosa. In this study, the Caco-2/HT29 coculture model was used to evaluate the effect of indole-3-propionic acid (IPA) on the intestinal barrier and explore its underlying mechanism. We found that IPA increased transepithelial electrical resistance and decreased paracellular permeability which was consistent with the increase in tight junction proteins (claudin-1, occludin, and ZO-1). Furthermore, IPA strengthened the mucus barrier by increasing mucins (MUC2 and MUC4) and goblet cell secretion products (TFF3 and RELMβ). Additionally, IPA weakened the expression of LPS-induced inflammatory factors. These discoveries provide new views for understanding the improvement of intestinal barrier by gut microbial metabolites of aromatic amino acids.

Enhanced therapeutic efficacy of a novel colon-specific nanosystem loading emodin on DSS-induced experimental colitis

BACKGROUND

Ulcerative colitis (UC) is an intricate enteric disease with a rising incidence that is closely related to mucosa-barrier destruction, gut dysbacteriosis, and immune disorders. Emodin (1,3,8-trihydroxy-6-methyl-9,10-anthraquinone, EMO) is a natural anthraquinone derivative that occurs in many Polygonaceae plants. Its multiple pharmacological effects, including antioxidant, immune-suppressive, and anti-bacteria activities, make it a promising treatment option for UC. However, its poor solubility, extensive absorption, and metabolism in the upper gastrointestinal tract may compromise its anti-colitis effects.

PURPOSE

EMO was loaded in a colon-targeted delivery system using multifunctional biomedical materials and the enhanced anti-colitis effect involving mucosa reconstruction was investigated in this study.

METHODS

EMO-loaded Poly (DL-lactide-co-glycolide)/Eudragit^Ⓡ S100/montmorillonite nanoparticles (EMO/PSM NPs) were prepared by a versatile single-step assembly approach. The colon-specific release behavior was characterized in vitro and in vivo, and the anti-colitis effect was evaluated in dextran sulfate sodium (DSS)-induced acute colitis in mice by weight loss, disease activity index (DAI) score, colon length, histological changes, and colitis biomarkers. The integrity of the intestinal mucosal barrier was evaluated through transwell co-culture model in vitro and serum zonulin-related tight junctions and mucin2 (MUC2) in vivo.

RESULTS

EMO/PSM NPs with a desirable hydrodynamic diameter (~ 235 nm) and negative zeta potential (~ -31 mV) could prevent the premature drug release (< 4% in the first 6 h in vitro) in the upper gastrointestinal tract (GIT) and boost retention in the lower GIT and inflamed colon mucosa in vivo. Compared to free EMO-treatment of different doses in UC mice, the NPs could enhance the remedial efficacy of EMO in DAI decline, histological remission, and regulation of colitis indicators, such as myeloperoxidase (MPO), nitric oxide (NO), and glutathione (GSH). The inflammatory factors including induced nitric oxide synthase (iNOS), cyclooxygenase-2 (COX-2), TNF-α, and IL-1β were suppressed by EMO/PSM NPs at both mRNA and protein levels. The obtained NPs could also promote the regeneration of the mucosal barrier via reduced fluorescein isothiocyanate (FITC)-dextran leakage in the transwell co-culture model and decreased serum zonulin levels, which was demonstrated to be associated with the upregulated tight junctions (TJs)-related proteins (claudin-2, occludin, and zo-1) and MUC2 at mRNA level. Moreover, the NPs could contribute to attenuating the liver injury caused by free EMO under excessive immune inflammation.

CONCLUSION

Our results demonstrated that EMO/PSM NPs could specifically release EMO in the diseased colon, and effectively enhance the anti-colitis effects of EMO related to intestinal barrier improvement. It can be considered as a novel potential alternative for oral colon-targeted UC therapy by increasing therapeutic efficacy and reducing side-effects.

Effect of delayed feeding post-hatch on expression of tight junction- and gut barrier-related genes in the small intestine of broiler chickens during neonatal development

The gut not only plays a key role in digestion and absorption of nutrients but also forms a physical barrier and first line of defense between the host and the luminal environment. A functional gut barrier (mucus and epithelial cells with tight junctions [TJ]) is essential for optimal health and efficient production in poultry. In current broiler system, chicks are deprived of food and water up to 72 h due to uneven hatching, hatchery procedures, and transportation. Post-hatch feed delay results in lower BW, higher FCR and mortality, and delayed post-hatch gut development. Little is known about the effects of early neonatal development and delayed feeding immediately post-hatch on gut barrier function in chickens. Therefore, the aim of the present study was to characterize the expression pattern of gut barrier-related and TJ-related genes in the small intestine of broiler chickens during early development and delay in access to feed. Newly hatched chicks received feed and water immediately after hatch or were subjected to 48 h delayed access to feed to mimic commercial hatchery setting and operations. Birds were sampled (n = 6) at -48, 0, 4, 24, 48, 72, 96, 144, 192, 240, 288, and 336 h post-hatch. Jejunum and ileum were collected, cleaned of digesta, and snap-frozen in liquid nitrogen or fixed in paraformaldehyde. The relative mRNA levels of gut barrier- and TJ-related protein genes were measured by quantitative PCR and analyzed by 2-way ANOVA. In both tissues, changes (P < 0.05) in gene expression pattern of gut barrier-related and TJ-related genes were detected due to delayed access to feed post-hatch and/or development. In general, expression of TJ-related genes was downregulated while mRNA levels of gut barrier-related genes were upregulated during development. Histological differences and changes in mucin staining due to age and treatment were observed. These results suggest that delayed access to feed post-hatch may affect TJ structure and/or function and therefore gut barrier function and overall health of the chicken small intestine.

Cell-cell junctions as sensors and transducers of mechanical forces

Epithelial and endothelial monolayers are multicellular sheets that form barriers between the 'outside' and 'inside' of tissues. Cell-cell junctions, made by adherens junctions, tight junctions and desmosomes, hold together these monolayers. They form intercellular contacts by binding their receptor counterparts on neighboring cells and anchoring these structures intracellularly to the cytoskeleton. During tissue development, maintenance and pathogenesis, monolayers encounter a range of mechanical forces from the cells themselves and from external systemic forces, such as blood pressure or tissue stiffness. The molecular landscape of cell-cell junctions is diverse, containing transmembrane proteins that form intercellular bonds and a variety of cytoplasmic proteins that remodel the junctional connection to the cytoskeleton. Many junction-associated proteins participate in mechanotransduction cascades to confer mechanical cues into cellular responses that allow monolayers to maintain their structural integrity. We will discuss force-dependent junctional molecular events and their role in cell-cell contact organization and remodeling.

Tight junction modulation at the blood-brain barrier: Current and future perspectives

The blood-brain barrier (BBB) is the one of the most robust physical barriers in the body, comprised of tight junction (TJ) proteins in brain microvascular endothelial cells. The need for drugs to treat central nervous systems diseases is ever increasing, however the presence of the BBB significantly hampers the uptake of drugs into the brain. To overcome or circumvent the barrier, many kinds of techniques are being developed. Modulating the paracellular route by disruption of the TJ complex has been proposed as a potential drug delivery system to treat brain diseases, however, it has several limitations and is still in a developmental stage. However, recent significant advance in medical equipment /tools such as targeted ultra-sound technologies may resolve these limitations. In this review, we introduce recent advances in site- or molecular size-selective BBB disruption/modulation technologies and we include details on pharmacological inhibitory molecules against intercellular TJ proteins to modulate the BBB.

The extracellular domain of angulin-1 and palmitoylation of its cytoplasmic region are required for angulin-1 assembly at tricellular contacts

Tricellular tight junctions (tTJs) create paracellular barriers at tricellular contacts (TCs), where the vertices of three polygonal epithelial cells meet. tTJs are marked by the enrichment of two types of membrane proteins, tricellulin and angulin family proteins. However, how TC geometry is recognized for tTJ formation remains unknown. In the present study, we examined the molecular mechanism for the assembly of angulin-1 at the TCs. We found that clusters of cysteine residues in the juxtamembrane region within the cytoplasmic domain of angulin-1 are highly palmitoylated. Mutagenesis analyses of the cysteine residues in this region revealed that palmitoylation is essential for localization of angulin-1 at TCs. Consistently, suppression of Asp-His-His-Cys motif-containing palmitoyltransferases expressed in EpH4 cells significantly impaired the TC localization of angulin-1. Cholesterol depletion from the plasma membrane of cultured epithelial cells hampered the localization of angulin-1 at TCs, suggesting the existence of a lipid membrane microdomain at TCs that attracts highly palmitoylated angulin-1. Furthermore, the extracellular domain of angulin-1 was also required for its TC localization, irrespective of the intracellular palmitoylation. Taken together, our findings suggest that both angulin-1's extracellular domain and palmitoylation of its cytoplasmic region are required for its assembly at TCs.

Claudin-1, A Double-Edged Sword in Cancer

Claudins, a group of membrane proteins involved in the formation of tight junctions, are mainly found in endothelial or epithelial cells. These proteins have attracted much attention in recent years and have been implicated and studied in a multitude of diseases. Claudins not only regulate paracellular transepithelial/transendothelial transport but are also critical for cell growth and differentiation. Not only tissue-specific but the differential expression in malignant tumors is also the focus of claudin-related research. In addition to up- or down-regulation, claudin proteins also undergo delocalization, which plays a vital role in tumor invasion and aggressiveness. Claudin (CLDN)-1 is the most-studied claudin in cancers and to date, its role as either a tumor promoter or suppressor (or both) is not established. In some cancers, lower expression of CLDN-1 is shown to be associated with cancer progression and invasion, while in others, loss of CLDN-1 improves the patient survival. Another topic of discussion regarding the significance of CLDN-1 is its localization (nuclear or cytoplasmic vs perijunctional) in diseased states. This article reviews the evidence regarding CLDN-1 in cancers either as a tumor promoter or suppressor from the literature and we also review the literature regarding the pattern of CLDN-1 distribution in different cancers, focusing on whether this localization is associated with tumor aggressiveness. Furthermore, we utilized expression data from The Cancer Genome Atlas (TCGA) to investigate the association between CLDN-1 expression and overall survival (OS) in different cancer types. We also used TCGA data to compare CLDN-1 expression in normal and tumor tissues. Additionally, a pathway interaction analysis was performed to investigate the interaction of CLDN-1 with other proteins and as a future therapeutic target.

Ophiopogon Saponin C1 Inhibits Lung Tumors by Stabilizing Endothelium Permeability via Inhibition of PKCδ

As the most frequent cause of cancer-related death worldwide, lung cancer is closely related to inflammation. The interaction between tumor cells and inflammatory cells promotes tumor development and metastasis. During tumor development, vascular endothelial cells form the most important barrier to prevent tumor cell migration to the blood and tissue. Increased vascular permeability provides favorable conditions for the migration of tumor cells, and endothelial tight junctions are an important component of the vascular barrier. Protein kinase C δ is involved in the occurrence of non-small cell lung cancer and regulates vascular permeability and tight junction protein expression. Src kinase was reported to play an important role in TNF-α-induced endothelial inflammation. Ophiopogon Saponin C1 is a new chemical compound isolated from Liriope muscari, but its pharmacological activities have not been fully elucidated. Therefore, we tested the protective effects of C1 on endothelial permeability in a model of TNF-α-induced endothelial inflammation by transendothelial electrical resistance and sodium fluorescein assays and verified these results in a nude mouse model of experimental pulmonary adenocarcinoma metastasis. We further elucidated the mechanism of C1, which was based on the PKCδ and Src proteins, by Western blotting. C1 can inhibit lung cancer in vivo, regulate the level of plasma inflammation in tumor-bearing mice, and protect the pulmonary vascular barrier against injury induced by cancer. It was investigated the expression and distribution of the TJ index protein ZO-1 in mouse vascular endothelium and HUVECs and found that C1 could inhibit the degradation and breakage of the ZO-1 protein. Related signaling experiments confirmed that C1 can inhibit TNF-α and activation of PKCδ and Src kinase. This study laid the foundation for further analysis of new drugs with clear mechanisms and independent intellectual property rights of traditional Chinese medicines.

Weighted Gene Co-Expression Network Analysis Reveals Six Hub Genes Involved in and Tight Junction Function in Pancreatic Adenocarcinoma and their Potential Use in Prognosis

Background: Pancreatic adenocarcinoma (PAAD) is an aggressive and invasive tumor with poor prognosis. Identifying prognostic biomarkers of PAAD will provide crucial information for developing treatment plans. Methods: In this analysis, a gene-expression dataset, containing RNA-sequencing data recalculated into transcripts per million, was obtained from the UCSC Xena platform. Three thousand nine hundred and seventy six differentially expressed genes were obtained with analysis of variance. Using these data a co-expression network was constructed using weighted gene co-expression network analysis, from which we obtained eight modules. Results: The blue module included 497 genes and demonstrated significant negative correlation with overall survival. Furthermore, pathway analyses demonstrated the involvement of many of these genes in the tight junction pathway, which plays a critical role in PAAD. In addition, we identified six genes in common (i.e., ANXA2 [annexin A2], EPHA2 [erythropoietin-producing hepatocellular class A2], ITGB4 [integrin beta 4], KRT19 [keratin type I cytoskeletal 19], LGALS3 [galectin-3], and S100A14 [S100 calcium binding protein A14]) between the protein-protein interaction and gene co-expression networks that may have critical functions in PAAD. These hub genes were not only highly expressed at the RNA level but also exhibited high expression in the immunohistological data in the Human Protein Atlas Database. Conclusion: Thus, this research clarified the framework of co-expressed gene modules in PAAD and highlighted potential prognostic biomarkers for the clinical diagnosis of PAAD.

A comprehensive evaluation of pathogenic mutations in primary cutaneous melanomas, including the identification of novel loss-of-function variants

The most common histological subtypes of cutaneous melanoma include superficial spreading and nodular melanoma. However, the spectrum of somatic mutations developed in those lesions and all potential druggable targets have not yet been fully elucidated. We present the results of a sequence capture NGS analysis of 114 primary nodular and superficial spreading melanomas identifying driver mutations using biostatistical, immunohistochemical and/or functional approach. The spectrum and frequency of pathogenic or likely pathogenic variants were identified across 54 evaluated genes, including 59 novel mutations, and the newly identified TP53 loss-of-function mutations p.(L194P) and p.(R280K). Frequently mutated genes most commonly affected the MAPK pathway, followed by chromatin remodeling, and cell cycle regulation. Frequent aberrations were also detected in the genes coding for proteins involved in DNA repair and the regulation and modification of cellular tight junctions. Furthermore, relatively frequent mutations were described in KDR and MET, which represent potential clinically important targets. Those results suggest that with the development of new therapeutic possibilities, not only BRAF testing, but complex molecular testing of cutaneous melanoma may become an integral part of the decision process concerning the treatment of patients with melanoma.

Impaired intestinal barrier function in a mouse model of hyperuricemia

Previous studies have demonstrated the effects of hyperuricemia on the damage to target organs, including the kidneys, joints and the heart. However, it is unclear whether hyperuricemia results in damage to the intestines. The aim of the present study was to investigate intestinal barrier dysfunction in a mouse model of hyperuricemia constructed by knocking out the urate oxidase (Uox) gene. The morphology of the intestine was assessed via hematoxylin and eosin, and alcian blue staining. The serum and intestinal tissue levels of uric acid, tumor necrosis factor (TNF)‑α and interleukin (IL)‑6, in addition to the presence of uremic toxins in the serum, were assessed. The levels of diamine oxidase (DAO), D‑lactate (D‑LAC) and endotoxins in the serum, which are markers of the intestinal permeability, were measured using ELISA. The expression of the intestinal tight junction proteins zona occludens‑1 (ZO‑1) and occludin were detected by reverse transcription‑quantitative polymerase chain reaction, western blotting and immunohistochemical analysis. The Uox‑knockout mice spontaneously developed hyperuricemia. Histopathological analysis indicated notable intestinal defects including sparse villi, mucosal edema and a declining mucus layer in hyperuricemic mice. The expression levels of ZO‑1 and occludin in the intestines were downregulated, and the serum levels of DAO, D‑LAC and endotoxins were higher in the hyperuricemic mice, compared with control mice. The serum and intestinal tissue levels of IL‑6 and TNF‑α were significantly increased. Additionally, the expression levels of the serum uremic toxins, serum creatinine, blood urea nitrogen were significantly increased in hyperuricemic mice compared with the control mice, while only a marked increase in indoxyl sulfate (IS) and p‑cresol sulfate was reported. Collectively, the results of the present study suggested that intestinal barrier dysfunction and subsequent enhanced intestinal permeability may occur as a result of hyperuricemia in mice. Furthermore, we proposed that the loss of intestinal epithelium barrier function may be associated with uric acid‑induced inflammatory responses; however, further investigation is required.

Curcumin Mitigates Immune-Induced Epithelial Barrier Dysfunction by Campylobacter jejuni

Campylobacter jejuni (C. jejuni) is the most common cause of foodborne gastroenteritis worldwide. The bacteria induce diarrhea and inflammation by invading the intestinal epithelium. Curcumin is a natural polyphenol from turmeric rhizome of Curcuma longa, a medical plant, and is commonly used in curry powder. The aim of this study was the investigation of the protective effects of curcumin against immune-induced epithelial barrier dysfunction in C. jejuni infection. The indirect C. jejuni-induced barrier defects and its protection by curcumin were analyzed in co-cultures with HT-29/B6-GR/MR epithelial cells together with differentiated THP-1 immune cells. Electrophysiological measurements revealed a reduction in transepithelial electrical resistance (TER) in infected co-cultures. An increase in fluorescein (332 Da) permeability in co-cultures as well as in the germ-free IL-10^−/− mouse model after C. jejuni infection was shown. Curcumin treatment attenuated the C. jejuni-induced increase in fluorescein permeability in both models. Moreover, apoptosis induction, tight junction redistribution, and an increased inflammatory response—represented by TNF-α, IL-1β, and IL-6 secretion—was observed in co-cultures after infection and reversed by curcumin. In conclusion, curcumin protects against indirect C. jejuni-triggered immune-induced barrier defects and might be a therapeutic and protective agent in patients.

Detailed Clinical Features of Deafness Caused by a Claudin-14 Variant

Tight junctions are cellular junctions that play a major role in the epithelial barrier function. In the inner ear, claudins, occludin, tricellulin, and angulins form the bicellular or tricellular binding of membrane proteins. In these, one type of claudin gene, CLDN14, was reported to be responsible for human hereditary hearing loss, DFNB29. Until now, nine pathogenic variants have been reported, and most phenotypic features remain unclear. In the present study, genetic screening for 68 previously reported deafness causative genes was carried out to identify CLDN14 variants in a large series of Japanese hearing loss patients, and to clarify the prevalence and clinical characteristics of DFNB29 in the Japanese population. One patient had a homozygous novel variant (c.241C>T: p.Arg81Cys) (0.04%: 1/2549). The patient showed progressive bilateral hearing loss, with post-lingual onset. Pure-tone audiograms indicated a high-frequency hearing loss type, and the deterioration gradually spread to other frequencies. The patient showed normal vestibular function. Cochlear implantation improved the patient's sound field threshold levels, but not speech discrimination scores. This report indicated that claudin-14 is essential for maintaining the inner ear environment and suggested the possible phenotypic expansion of DFNB29. This is the first report of a patient with a tight junction variant receiving a cochlear implantation.

Extracellular Vesicles Containing MicroRNA-92a-3p Facilitate Partial Endothelial-Mesenchymal Transition and Angiogenesis in Endothelial Cells

Extracellular vesicles (EVs) are nanometer-sized membranous vesicles used for primitive cell-to-cell communication. We previously reported that colon cancer-derived EVs contain abundant miR-92a-3p and have a pro-angiogenic function. We previously identified Dickkopf-3 (Dkk-3) as a direct target of miR-92a-3p; however, the pro-angiogenic function of miR-92a-3p cannot only be attributed to downregulation of Dkk-3. Therefore, the complete molecular mechanism by which miR-92a-3p exerts pro-angiogenic effects is still unclear. Here, we comprehensively analyzed the gene sets affected by ectopic expression of miR-92a-3p in endothelial cells to elucidate processes underlying EV-induced angiogenesis. We found that the ectopic expression of miR-92a-3p upregulated cell cycle- and mitosis-related gene expression and downregulated adhesion-related gene expression in endothelial cells. We also identified a novel target gene of miR-92a-3p, claudin-11. Claudin-11 belongs to the claudin gene family, which encodes essential components expressed at tight junctions (TJs). Disruption of TJs with a concomitant loss of claudin expression is a significant event in the process of epithelial-to-mesenchymal transition. Our findings have unveiled a new EV-mediated mechanism for tumor angiogenesis through the induction of partial endothelial-to-mesenchymal transition in endothelial cells.

β-Conglycinin-Induced Intestinal Porcine Epithelial Cell Damage via the Nuclear Factor κB/Mitogen-Activated Protein Kinase Signaling Pathway

Soybean allergy is a serious health risk to humans and animals; β-conglycinin is the primary antigenic protein in soybean. Intestinal porcine epithelial (IPEC-J2) cells were used as an in vitro physiological model of the intestinal epithelium to study the effects of different concentrations of soybean antigen protein β-conglycinin to identify the involved signaling pathways. The cells were divided into eight groups and either untreated or treated with different concentrations of β-conglycinin, pyrrolidine dithiocarbamate (PDTC), Nω-nitro-l-arginine methyl ester hydrochloride (l-NAME), SP600125, and SB202190 either alone or in combination. The cells were incubated with 1, 5, and 10 mg·mL-1 β-conglycinin or 5 mg·mL-1 β-conglycinin and 1 μmol·L-1 nuclear factor κB (NF-κB) inhibitor (PDTC), inducible nitric oxide synthase inhibitor (l-NAME), c-Jun N-terminal kinase (JNK) inhibitor (SP600125), and p38 inhibitor (SB202190) for 24 h, separately; controls were left untreated. The mRNA, protein, and phosphorylation levels of NF-κB, p38, and JNK were higher in the treated groups than in the control group. β-Conglycinin decreased tight junction distribution, destroyed the cytoskeleton of IPEC-J2 cells, and caused cell death. After the addition of the inhibitors, β-conglycinin-induced IPEC-J2 cell damage was significantly reduced. β-Conglycinin caused damage to IPEC-J2 cells via the mitogen-activated protein kinase/NF-κB signaling pathway. The results of this study are crucial for exploring the mechanisms underlying allergic reactions caused by soybean antigen proteins.

Chenodeoxycholic Acid (CDCA) Protects against the Lipopolysaccharide-Induced Impairment of the Intestinal Epithelial Barrier Function via the FXR-MLCK Pathway

Chenodeoxycholic acid (CDCA), a primary bile acid, has been demonstrated to play important roles as a signaling molecule in various physiology functions. However, the role of CDCA in regulating intestinal barrier function remains largely unknown. This study aimed to investigate the effects of CDCA on the lipopolysaccharide (LPS)-impaired intestinal epithelial barrier function and explore the underlying mechanisms. In IPEC-J2 cells, CDCA reversed the LPS-induced increase in transepithelial electrical resistance and decrease in tight junction protein expression. In addition, we found that farnesoid X receptor (FXR) but not Takeda G-protein receptor 5 was responsible for the CDCA-improved epithelial barrier function impaired by LPS. Furthermore, CDCA blocked LPS-induced activation of the myosin light chain kinase (MLCK) pathway in a FXR-dependent manner and elicited similar effects to MLCK inhibition. In mice, CDCA supplementation restored LPS-induced elevation of intestinal permeability and MLCK expression and reduction of tight junction protein expression, thus alleviating LPS-induced intestinal barrier impairment. In conclusion, CDCA protected against the LPS-induced impairment of the intestinal epithelial barrier function via the FXR-MLCK pathway.

Maelstrom regulates spermatogenesis of the silkworm, Bombyx mori

The spermatogenesis of animal is essential for the reproduction and a very large number of genes participate in this procession. The Maelstrom (Mael) is identified essential for spermatogenesis in both Drosophila and mouse, though the mechanisms appear to differ. It was initially found that Mael gene is necessary for axis specification of oocytes in Drosophila, and recent studies suggested that Mael participates in the piRNA pathway. In this study, we obtained Bombyx mori Mael mutants by using a binary transgenic CRISPR/Cas9 system and analyzed the function of Mael in B. mori, a model lepidopteran insect. The results showed that BmMael is not necessary for piRNA pathway in the ovary of silkworm, whereas it might be essential for transposon elements (TEs) repression in testis. The BmMael mutation resulted in male sterility, and further analysis established that BmMael was essential for spermatogenesis. The spermatogenesis defects occurred in the elongation stage and resulted in nuclei concentration arrest. RNA-seq and qRT-PCR analyses demonstrated that spermatogenesis defects were associated with tight junctions and apoptosis. We also found that BmMael was not involved in the silkworm sex determination pathway. Our data provide insights into the biological function of BmMael in male spermatogenesis and might be useful for developing novel methods to control lepidopteron pests.

EspF is crucial for Citrobacter rodentium-induced tight junction disruption and lethality in immunocompromised animals

Attaching/Effacing (A/E) bacteria include human pathogens enteropathogenic Escherichia coli (EPEC), enterohemorrhagic E. coli (EHEC), and their murine equivalent Citrobacter rodentium (CR), of which EPEC and EHEC are important causative agents of foodborne diseases worldwide. While A/E pathogen infections cause mild symptoms in the immunocompetent hosts, an increasing number of studies show that they produce more severe morbidity and mortality in immunocompromised and/or immunodeficient hosts. However, the pathogenic mechanisms and crucial host-pathogen interactions during A/E pathogen infections under immunocompromised conditions remain elusive. We performed a functional screening by infecting interleukin-22 (IL-22) knockout (Il22-/-) mice with a library of randomly mutated CR strains. Our screen reveals that interruption of the espF gene, which encodes the Type III Secretion System effector EspF (E. coli secreted protein F) conserved among A/E pathogens, completely abolishes the high mortality rates in CR-infected Il22-/- mice. Chromosomal deletion of espF in CR recapitulates the avirulent phenotype without impacting colonization and proliferation of CR, and EspF complement in ΔespF strain fully restores the virulence in mice. Moreover, the expression levels of the espF gene are elevated during CR infection and CR induces disruption of the tight junction (TJ) strands in colonic epithelium in an EspF-dependent manner. Distinct from EspF, chromosomal deletion of other known TJ-damaging effector genes espG and map failed to impede CR virulence in Il22-/- mice. Hence our findings unveil a critical pathophysiological function for EspF during CR infection in the immunocompromised host and provide new insights into the complex pathogenic mechanisms of A/E pathogens.

Dietary l-tryptophan alleviated LPS-induced intestinal barrier injury by regulating tight junctions in a Caco-2 cell monolayer model

The intestinal epithelial layer forms a barrier through cell-cell tight junctions and breaking or even slightly disrupting this barrier can lead to serious pathological consequences, including infection and inflammation. Various amino acids have been shown to improve the intestinal tract, but the effect of tryptophan on the intestinal barrier has been controversial. Here, an in vitro Caco-2 cell model was built to investigate the protective and reparative effects of different concentrations of dietary l-Tryptophan (l-Trp) on lipopolysaccharide (LPS)-induced intestinal tight junction injury. Lower concentrations (40 μM) of dietary l-Trp protected and repaired the integrity and permeability injury of the intestinal tight junction induced by LPS, while high concentrations (80 μM) may not have a positive effect. LPS-induced injury led to increased (P < 0.05) mRNA expression of Nuclear factor-kappa B (NFκB) and Myosin light-chain kinase (MLCK), and decreased (P < 0.05) the mRNA expression of extracellular regulated protein kinase 1/2 (ERK1/2) and Mitogen-activated protein (MAP), and the treatment of dietary l-Trp alleviated those regulations in different concentrations, which suggests that dietary l-Trp may attenuate LPS-induced injury to tight junctions via inhibiting the NFκB-MLCK signaling pathway and activating the ERK1/2-MAP signaling pathway. And the mRNA and protein expressions of claudin-1, occludin and ZO-1 in LPS-induced injury were all down-regulated to varying degrees, and dietary l-Trp weakened the down-regulation of claudin-1 (P < 0.05) with no significant regulation of the protein expression of occludin and ZO-1 (P > 0.05).

Defining the role of NG2-expressing cells in experimental models of multiple sclerosis. A biofunctional analysis of the neurovascular unit in wild type and NG2 null mice

During experimental autoimmune encephalomyelitis (EAE), a model for multiple sclerosis associated with blood-brain barrier (BBB) disruption, oligodendrocyte precursor cells (OPCs) overexpress proteoglycan nerve/glial antigen 2 (NG2), proliferate, and make contacts with the microvessel wall. To explore whether OPCs may actually be recruited within the neurovascular unit (NVU), de facto intervening in its cellular and molecular composition, we quantified by immunoconfocal morphometry the presence of OPCs in contact with brain microvessels, during postnatal cerebral cortex vascularization at postnatal day 6, in wild-type (WT) and NG2 knock-out (NG2KO) mice, and in the cortex of adult naïve and EAE-affected WT and NG2KO mice. As observed in WT mice during postnatal development, a higher number of juxtavascular and perivascular OPCs was revealed in adult WT mice during EAE compared to adult naïve WT mice. In EAE-affected mice, OPCs were mostly associated with microvessels that showed altered claudin-5 and occludin tight junction (TJ) staining patterns and barrier leakage. In contrast, EAE-affected NG2KO mice, which did not show any significant increase in vessel-associated OPCs, seemed to retain better preserved TJs and BBB integrity. As expected, absence of NG2, in both OPCs and pericytes, led to a reduced content of vessel basal lamina molecules, laminin, collagen VI, and collagen IV. In addition, analysis of the major ligand/receptor systems known to promote OPC proliferation and migration indicated that vascular endothelial growth factor A (VEGF-A), platelet-derived growth factor-AA (PDGF-AA), and the transforming growth factor-β (TGF-β) were the molecules most likely involved in proliferation and recruitment of vascular OPCs during EAE. These results were confirmed by real time-PCR that showed Fgf2, Pdgfa and Tgfb expression on isolated cerebral cortex microvessels and by dual RNAscope-immunohistochemistry/in situ hybridization (IHC/ISH), which detected Vegfa and Vegfr2 transcripts on cerebral cortex sections. Overall, this study suggests that vascular OPCs, in virtue of their developmental arrangement and response to neuroinflammation and growth factors, could be integrated among the classical NVU cell components. Moreover, the synchronized activation of vascular OPCs and pericytes during both BBB development and dysfunction, points to NG2 as a key regulator of vascular interactions.

TLR3 deficiency exacerbates the loss of epithelial barrier function during genital tract Chlamydia muridarum infection

Problem

Chlamydia trachomatis infections are often associated with acute syndromes including cervicitis, urethritis, and endometritis, which can lead to chronic sequelae such as pelvic inflammatory disease (PID), chronic pelvic pain, ectopic pregnancy, and tubal infertility. As epithelial cells are the primary cell type productively infected during genital tract Chlamydia infections, we investigated whether Chlamydia has any impact on the integrity of the host epithelial barrier as a possible mechanism to facilitate the dissemination of infection, and examined whether TLR3 function modulates its impact.

Method of study

We used wild-type and TLR3-deficient murine oviduct epithelial (OE) cells to ascertain whether C. muridarum infection had any effect on the epithelial barrier integrity of these cells as measured by transepithelial resistance (TER) and cell permeability assays. We next assessed whether infection impacted the transcription and protein function of the cellular tight-junction (TJ) genes for claudins1-4, ZO-1, JAM1 and occludin via quantitative real-time PCR (qPCR) and western blot.

Results

qPCR, immunoblotting, transwell permeability assays, and TER studies show that Chlamydia compromises cellular TJ function throughout infection in murine OE cells and that TLR3 deficiency significantly exacerbates this effect.

Conclusion

Our data show that TLR3 plays a role in modulating epithelial barrier function during Chlamydia infection of epithelial cells lining the genital tract. These findings propose a role for TLR3 signaling in maintaining the integrity of epithelial barrier function during genital tract Chlamydia infection, a function that we hypothesize is important in helping limit the chlamydial spread and subsequent genital tract pathology.

Protective Effect of Naringin on DSS-Induced Ulcerative Colitis in Mice

Peroxisome proliferator-activated receptor γ (PPARγ) is an important member of the nuclear receptor superfamily. Previous studies have shown the satisfactory anti-inflammatory role of PPARγ in experimental colitis models, mainly through negatively regulating several transcription factors such as nuclear factor-κB (NF-κB). Therefore, regulating PPARγ and PPARγ-related pathways has great promise for treating ulcerative colitis (UC). In the present study, our objective was to explore the potential effect of naringin on dextran sulfate sodium (DSS) induced UC in mice and its involved potential mechanism. We found that naringin significantly relieved DSS-induced disease activities index (DAI), colon length shortening, and colonic pathological damage. Exploration of the potential mechanisms demonstrated that naringin significantly activated DSS-induced PPARγ and subsequently suppressed NF-κB activation. PPARγ inhibitor GW9662 largely abrogated the roles of naringin in vitro. Moreover, DSS induced the activation of mitogen-activated protein kinase (MAPK) and (NOD)-like receptor family pyrin domain containing 3 (NLRP3) inflammasome was inhibited by naringin. Tight junction (TJ) architecture in naringin groups was also maintained by regulating zonula occludens-1 (ZO-1) expression. These results suggested that naringin may be a potential natural agent for protecting mice from DSS-induced UC.

Resveratrol Ameliorates Intestinal Barrier Defects and Inflammation in Colitic Mice and Intestinal Cells

This study is aimed to investigate the ameliorative effect of resveratrol in a dextran sodium sulfate (DSS)-induced colitis mouse model and intestinal Caco-2 cells, focusing on neutrophil infiltration and tight junction (TJ) barriers. DSS administration caused body weight loss (day8, control 104 ± 1, DSS 72 ± 2%, p < 0.05), shortening of colon length (control 5.1 ± 0.1, DSS 3.8 ± 0.1 cm, p < 0.05), pro-inflammatory cytokines increase-including interleukin (IL)-1β (control 1.0 ± 0.2, DSS 58.5 ± 29.6 arbitrary unit (AU), p < 0.05), IL-6 (control 1.0 ± 0.3, DSS 312 ± 82 AU, p < 0.05), and chemokine motif ligand 2 (CXCL-2, a murine IL-8 homologue, control 1.0 ± 0.4, DSS 696 ± 262 AU, p < 0.05), decreased TJ proteins (e.g., occludin, control 1.0 ± 0.05, DSS 0.11 ± 0.03 AU, p < 0.05), and neutrophil infiltration (control 1.2 ± 0.2, DSS 25.9 ± 1.1 cells, p < 0.05). Supplemental resveratrol (0.1% (w/w) in the diet) partially or totally reversed these symptoms (body weight change 100 ± 1, colon length 4.6 ± 0.1; IL-1β 5.9 ± 1.8, IL-6 10 ± 3, CXCL-2 14 ± 7, occludin 0.76 ± 0.06, neutrophil infiltration 9.3 ± 0.7, p < 0.05). Pretreatment of intestinal Caco-2 cells with resveratrol suppressed the TNF-α-induced production of IL-8 (control 1.00 ± 0.04, TNFα 3.40 ± 0.16, TNFα+Res 1.81 ± 0.28 AU, p < 0.05) and phosphorylation of the inflammatory signaling molecules including NF-κB, extracellular signal-regulated kinase and stress c-Jun N-terminal protein kinase. Collectively, the reduction of TJ barrier defect and IL-8 in intestinal cells, leading to reduced neutrophil infiltration into colonic tissues, appears to be one of the central mechanisms for the resveratrol-mediated effect.

Selenium (Na2SeO3) Upregulates Expression of Immune Genes and Blood-Testis Barrier Constituent Proteins of Bovine Sertoli Cell In Vitro

Sertoli cells were isolated from newborn calves and cultured in a medium supplemented with 0, 0.25, 0.50, 0.75, and 1.00 mg/L of sodium selenite to study their immune stimulatory effect, influence on cell's viability, and expression of blood-testis barrier proteins (occludin, connexin-43, zonula occluden, E-cadherin) using quantitative PCR and western blot analyses. Results showed that medium supplemented with 0.50 mg/L of selenium significantly (P < 0.05) promoted cell viability, upregulated toll-like receptor gene (TLR4), anti-inflammatory cytokines (IL-4, IL-10, TGFβ1), and expressions of blood-testis barrier proteins, and modulated expressions of pro-inflammatory cytokines (TNF-α, IL-1β, IFN-γ). Sertoli cells grown in culture medium supplemented with 0.25 mg/L of selenium significantly upregulated TLR4, IL-4, IL-10, TGFβ1, and blood-testis barrier proteins compared to the control group. Sodium selenite supplementation at 0.75 and 1.00 mg/L levels was cytotoxic and temporarily downregulated the expression of blood-testis barrier protein within 24 h after culture; however, commencing from 72 h post culture, increased cell viability and upregulation of expression of blood-testis barrier proteins were observed. In conclusion, the results of this study showed that selenium supplementation in the culture medium up to 0.50 mg/L concentration upregulates immune genes and blood-testis barrier constituent proteins of bovine Sertoli cells.

Histology and Transcriptome Profiles of the Mammary Gland across Critical Windows of Development in Sprague Dawley Rats

Breast development occurs through well-defined stages representing 'windows of susceptibility' to adverse environmental exposures that potentially modify breast cancer risk. Systematic characterization of morphology and transcriptome during normal breast development lays the foundation of our understanding of cancer etiology. We examined mammary glands in female Sprague Dawley rats across six developmental stages - pre-pubertal, peri-pubertal, pubertal, lactation, adult parous and adult nulliparous. We investigated histology by Hematoxylin and Eosin and Mallory's Trichrome stain, proliferative and apoptotic rate by immunohistochemistry and whole-transcriptome by microarrays. We identified differentially expressed genes between adjacent developmental stages by linear models, underlying pathways by gene ontology analysis and gene networks and hubs active across developmental stages by coexpression network analysis. Mammary gland development was associated with large-scale changes in the transcriptome; particularly from pre-pubertal to peri-pubertal period and the lactation period were characterized by distinct patterns of gene expression with unique biological functions such as immune processes during pre-pubertal development and cholesterol biosynthesis during lactation. These changes were reflective of the shift in mammary gland histology, from a rudimentary organ during early stages to a secretory organ during lactation followed by regression with age. Hub genes within mammary gene networks included metabolic genes such as Pparg during the pre-pubertal stage and tight junction-related genes claudins and occludins in lactating mammary glands. Transcriptome profile paired with histology enhanced our understanding of mammary development, which is fundamental in understanding the etiologic mechanism of breast cancer, especially pertaining to windows of susceptibility to environmental exposures that may alter breast cancer risk.

Deoxynivalenol decreased the growth performance and impaired intestinal physical barrier in juvenile grass carp (Ctenopharyngodon idella)

Deoxynivalenol (DON) is one of the most common mycotoxin contaminants of animal feed worldwide and brings significant threats to the animal production. However, studies concerning the effect of DON on fish intestine are scarce. This study explored the effects of DON on intestinal physical barrier in juvenile grass carp (Ctenopharyngodon idella). A total of 1440 juvenile grass carp (12.17 ± 0.01 g) were fed six diets containing graded levels of DON (27, 318, 636, 922, 1243 and 1515 μg/kg diet) for 60 days. This study for the first time documented that DON caused body malformation in fish, and histopathological lesions, oxidative damage, declining antioxidant capacity, cell apoptosis and destruction of tight junctions in the intestine of fish. The results indicated that compared with control group (27 μg/kg diet), DON: (1) increased the reactive oxygen species (ROS), malondialdehyde (MDA) and protein carbonyl (PC) content, and up-regulated the mRNA levels of Kelch-like-ECH-associated protein 1 (Keap1: Keap1a but not Keap1b), whereas decreased glutathione (GSH) content and antioxidant enzymes activities, and down-regulated the mRNA levels of antioxidant enzymes (except GSTR in MI) and NF-E2-related factor 2 (Nrf2), as well as the protein levels of Nrf2 in fish intestine. (2) up-regulated cysteinyl aspartic acid-protease (caspase) -3, -7, -8, -9, apoptotic protease activating factor-1 (Apaf-1), Bcl2-associated X protein (Bax), Fas ligand (FasL) and c-Jun N-terminal protein kinase (JNK) mRNA levels, whereas down-regulated B-cell lymphoma-2 (bcl-2) and myeloid cell leukemia-1 (Mcl-1) mRNA levels in fish intestine. (3) down-regulated the mRNA levels of ZO-1, ZO-2b, occludin, claudin-c, -f, -7a, -7b, -11 (except claudin-b and claudin-3c), whereas up-regulated the mRNA levels of claudin-12, -15a (not -15b) and myosin light chain kinase (MLCK) in fish intestine. All above data indicated that DON caused the oxidative damage, apoptosis and the destruction of tight junctions via Nrf2, JNK and MLCK signaling in the intestine of fish, respectively. Finally, based on PWG, FE, PC and MDA, the safe dose of DON for grass carp were all estimated to be 318 μg/kg diet.

Sodium Butyrate Improves High-Concentrate-Diet-Induced Impairment of Ruminal Epithelium Barrier Function in Goats

We investigated the effect of sodium butyrate feeding on the disruption of ruminal epithelium barrier function in goats fed a high-concentrate diet. A total of 18 male Boer goats (live weight of 31.75 ± 1.35 kg, aged 1 year) were randomly assigned to three groups, which were fed a low-concentrate diet (LC), a high-concentrate diet (HC), or a high-concentrate diet with 1% sodium butyrate by weight (SH) for 9 weeks. We found that the pH of rumen fluid in the SH and LC groups was higher than that in the HC group. The activity of protein kinase C (PKC) kinase in the rumen epithelium was higher in the HC group than that in the LC and SH groups. The mRNA expression and phosphorylated protein levels of mitogen-activated protein kinases (MAPKs) in the rumen epithelium were lower in the SH and LC groups than those in the HC group. The DNA methylation rate of occludin was higher in the HC group than that in the SH and LC groups. The mRNA and protein expression of claudin-1, claudin-4, occludin, and zona occludin-1 was greater in the SH and LC groups than that in the HC group. In addition, sodium butyrate mitigated damage to the rumen epithelium caused by the HC diet. Together, our results suggest that the supply of sodium butyrate reverses the damage of rumen epithelium tight junction by inhibiting PKC and MAPK signaling pathways and is protective to the rumen epithelium during subacute rumen acidosis.

Biogenic Polyphosphate Nanoparticles from Synechococcus sp. PCC 7002 Exhibit Intestinal Protective Potential in Human Intestinal Epithelial Cells In Vitro and Murine Small Intestine Ex Vivo

Polyphosphates are one of the active compounds from probiotics to maintain gut health. The current research extracted and purified intact biogenic polyphosphate nanoparticles (BPNPs) from Synechococcus sp. PCC 7002 cells. BPNPs were near-spherical anionic particles (56.9 ± 15.1 nm) mainly composed of calcium and magnesium salt of polyphosphate and were colloidally stable at near-neutral and alkaline pH. BPNPs survived gastrointestinal digestion in mice and could be absorbed and transported by polarized Caco-2 cell monolayers. They dose-dependently increased the tightness of intercellular tight junction and the expression of claudin-4, occludin, zonula occludens-1, and heat shock protein 27 in Caco-2 cell monolayers. BPNPs also effectively attenuated H₂O₂-induced cell death, plasma membrane impairment, and intracellular superoxide production in NCM460 cells. In addition, they conferred resistance to H₂O₂-induced barrier disruption in freshly excised mouse small intestine. Our results suggest that BPNPs are a promising postbiotic nanomaterial with potential applications in gut health maintenance.

Cecropin A Modulates Tight Junction-Related Protein Expression and Enhances the Barrier Function of Porcine Intestinal Epithelial Cells by Suppressing the MEK/ERK Pathway

Inflammatory bowel disease (IBD) in humans and animals is associated with bacterial infection and intestinal barrier dysfunction. Cecropin A, an antimicrobial peptide, has antibacterial activity against pathogenic bacteria. However, the effect of cecropin A on intestinal barrier function and its related mechanisms is still unclear. Here, we used porcine jejunum epithelial cells (IPEC-J2) as a model to investigate the effect and mechanism of cecropin A on intestinal barrier function. We found that cecropin A reduced Escherichia coli (E. coli) adherence to IPEC-J2 cells and downregulated mRNA expression of tumor necrosis factor α (TNF-α), interleukin-6 (IL-6), and interleukin-8 (IL-8). Furthermore, cecropin A elevated the transepithelial electrical resistance (TER) value while reducing the paracellular permeability of the IPEC-J2 cell monolayer barrier. Finally, by using Western blotting, immunofluorescence and pathway-specific antagonists, we demonstrated that cecropin A increased ZO-1, claudin-1 and occludin protein expression and regulated membrane distribution and F-actin polymerization by increasing CDX2 expression. We conclude that cecropin A enhances porcine intestinal epithelial cell barrier function by downregulating the mitogen-activated protein kinase (MEK)/extracellular signal-regulated kinase (ERK) pathway. We suggest that cecropin A has the potential to replace antibiotics in the treatment of IBD due to its antibacterial activity on gram-negative bacteria and its enhancement effect on intestinal barrier function.

The effects of hydrocortisone on tight junction genes in an in vitro model of the human fallopian epithelial cells

The tight junction between epithelial cells helps making connections in the fallopian tube and contributes to successful fertilization. Breaking the tight junction complex induces various diseases such as the EP. Previous studies have shown that glucocorticoids are effective in repairing and maintaining intercellular tight junctions in epithelial cells of the fallopian tube, although their mechanism is still unknown. This research is a genomic study of hydrocortisone's effect on epithelial cells of the fallopian tube. Using the human fallopian tube, epithelial cell line (OE-E6/E7) was cultured in four concentrations of hydrocortisone (0 nM, 50 nM, 100 nM and 200 nM) for three durations (24 h, 48 h and 72 h). Glucocorticoids are effective on the expression of Zona occluding-1(ZO-1), Claudin 4, Claudin3, Desmoglein and E-cadherin genes involved in the tight junctions of the fallopian tube. The expression of all genes was up-regulated in the concentrations of 100 nM after 48 h treatment, as compared with the control (0 nM). However, their expression was down-regulated significantly after 72 h treatment (P < 0.05). The present study showed that treatment of epithelial cells of the fallopian tube with glucocorticoid increased the expression of genes involved in tight junctions, including claudin-3, claudin-4, E-cadherin, zona occludin-1 and Desmoglein-1. The obtained data suggests that a new mechanism is developed for glucocorticoid induction of tight junctions by increasing the expression of claudin-3, claudin-4, E-cadherin, zona occludin-1 and Desmoglein-1 genes.

Phosphorylation hotspot in the C-terminal domain of occludin regulates the dynamics of epithelial junctional complexes

The apical junctional complex (AJC), which includes tight junctions (TJs) and adherens junctions (AJs), determines the epithelial polarity, cell-cell adhesion and permeability barrier. An intriguing characteristic of a TJ is the dynamic nature of its multiprotein complex. Occludin is the most mobile TJ protein, but its significance in TJ dynamics is poorly understood. On the basis of phosphorylation sites, we distinguished a sequence in the C-terminal domain of occludin as a regulatory motif (ORM). Deletion of ORM and expression of a deletion mutant of occludin in renal and intestinal epithelia reduced the mobility of occludin at the TJs. ORM deletion attenuated Ca2+ depletion, osmotic stress and hydrogen peroxide-induced disruption of TJs, AJs and the cytoskeleton. The double point mutations T403A/T404A, but not T403D/T404D, in occludin mimicked the effects of ORM deletion on occludin mobility and AJC disruption by Ca2+ depletion. Both Y398A/Y402A and Y398D/Y402D double point mutations partially blocked AJC disruption. Expression of a deletion mutant of occludin attenuated collective cell migration in the renal and intestinal epithelia. Overall, this study reveals the role of ORM and its phosphorylation in occludin mobility, AJC dynamics and epithelial cell migration.

An Ichor-dependent apical extracellular matrix regulates seamless tube shape and integrity

During sprouting angiogenesis in the vertebrate vascular system, and primary branching in the Drosophila tracheal system, specialized tip cells direct branch outgrowth and network formation. When tip cells lumenize, they form subcellular (seamless) tubes. How these seamless tubes are made, shaped and maintained remains poorly understood. Here we characterize a Drosophila mutant called ichor (ich), and show that ich is essential for the integrity and shape of seamless tubes in tracheal terminal cells. We find that Ich regulates seamless tubulogenesis via its role in promoting the formation of a mature apical extracellular matrix (aECM) lining the lumen of the seamless tubes. We determined that ich encodes a zinc finger protein (CG11966) that acts, as a transcriptional activator required for the expression of multiple aECM factors, including a novel membrane-anchored trypsin protease (CG8213). Thus, the integrity and shape of seamless tubes are regulated by the aECM that lines their lumens.

MiR-30a-5p Inhibits Epithelial-to-Mesenchymal Transition and Upregulates Expression of Tight Junction Protein Claudin-5 in Human Upper Tract Urothelial Carcinoma Cells

The involvement of microRNAs (miRNAs) in cancer development and their potential as prognostic biomarkers are becoming increasingly known. However, the signature of miRNAs and their regulatory roles in tumorigenesis of upper tract urothelial carcinoma (UTUC) remain to be elucidated. This study aimed to profile the miRNA expression pattern in UTUC tumor tissues and identify candidate miRNAs with prognostic and/or therapeutic functions. Methods and Results: We collected 22 UTUC tissue and adjacent normal tissues samples from patients who underwent nephroureterectomy. The miRNAs signatures of three selected UTUC samples using next-generation sequencing showed that miR-30a-5p was significantly downregulated in UTUC tumors compared to adjacent normal tissues. The differentially-expressed miRNAs were specifically validated by quantitative real-time polymerase chain reaction. In addition, the miRNA expression signatures were analyzed with the transcriptome profile characterized by microarray. Further in vitro studies indicated that overexpression of miR-30a-5p significantly suppressed proliferation, migration, and epithelial-to-mesenchymal transition (EMT) in cultured BFTC-909 UTUC cells. As a potential target gene of miR-30a-5p in the tight junction pathway suggested by the pathway enrichment analysis, the reduced expression of tight junction protein claudin-5 in UTUC cells was demonstrated to be upregulated by miR-30a-5p genetic delivery. Conclusions: Taken together, our findings demonstrated that miR-30a-5p inhibits proliferation, metastasis, and EMT, and upregulates the expression of tight junction claudin-5 in UTUC cells. Thus, miR-30a-5p may provide a promising therapeutic strategy for UTUC treatment.

[Role of TGF-β1 in Sertoli cells and tight junction]

OBJECTIVE

To explore the role of TGF-β1 in the proliferation and apoptosis of Sertoli cells and its effect on the expressions of tight junction-related proteins and genes in rats.

METHODS

Rat Sertoli cells were isolated in vitro, primarily cultured, and divided into groups A (blank control), B (TGF-β1 receptor blocker), C (TGF-β1), and D (TGF-β1 + receptor blocker). The proliferation and apoptosis of the cells were detected by CCK-8 and flow cytometry, respectively. After establishment of the dual-chamber model for the primary culture of Sertoli cells, the trans-epithelia electrical resistance (TER) value was measured and the relative expressions of Occludin, ZO-1 and Claudin Ⅱ determined by RT-PCR and Western blot.

RESULTS

The OD value of the proliferation of the Sertoli cells was markedly higher in group C than in groups A and D (0.79 ± 0.04 vs 0.66 ± 0.05 and 0.68 ± 0.02, P<0.05), with statistically significant differences among the four groups (F = 5.05, P <0.05). However, no remarkable difference with found among the four groups in the apoptosis rate of the cells (F = 1.13, P >0.05). The TER value was dramatically decreased in group C as compared with groups A and D (［176.37 ± 16.61］ vs ［281.42 ± 9.83］ and ［254.37 ± 13.55］ /cm2, P<0.01), with statistically significant differences among the four groups (F = 38.99, P<0.01). There were no remarkable differences among the four groups in the mRNA expressions of ZO-1 and Claudin Ⅱ (F = 0.49 and 0.93, P>0.05) or their protein expressions (F = 0.28 and 1.31, P>0.05). Both the mRNA and protein expressions of Occludin were markedly lower in group C than in A and D (P<0.01 and P<0.05), with statistically significant differences among the four groups (F = 6.86 and 6.87, P<0.01).

CONCLUSIONS

TGF-β1 can promote the proliferation of Sertoli cells in rats and act on the tight junction of the cells by regulating the expression of Occludin.

Regional astrocyte IFN signaling restricts pathogenesis during neurotropic viral infection

Type I IFNs promote cellular responses to viruses, and IFN receptor (IFNAR) signaling regulates the responses of endothelial cells of the blood-brain barrier (BBB) during neurotropic viral infection. However, the role of astrocytes in innate immune responses of the BBB during viral infection of the CNS remains to be fully elucidated. Here, we have demonstrated that type I IFNAR signaling in astrocytes regulates BBB permeability and protects the cerebellum from infection and immunopathology. Mice with astrocyte-specific loss of IFNAR signaling showed decreased survival after West Nile virus infection. Accelerated mortality was not due to expanded viral tropism or increased replication. Rather, viral entry increased specifically in the hindbrain of IFNAR-deficient mice, suggesting that IFNAR signaling critically regulates BBB permeability in this brain region. Pattern recognition receptors and IFN-stimulated genes had higher basal and IFN-induced expression in human and mouse cerebellar astrocytes than did cerebral cortical astrocytes, suggesting that IFNAR signaling has brain region-specific roles in CNS immune responses. Taken together, our data identify cerebellar astrocytes as key responders to viral infection and highlight the existence of distinct innate immune programs in astrocytes from evolutionarily disparate regions of the CNS.

Drebrin and Spermatogenesis

Drebrin is a family of actin-binding proteins with two known members called drebrin A and E. Apart from the ability to stabilize F-actin microfilaments via their actin-binding domains near the N-terminus, drebrin also regulates multiple cellular functions due to its unique ability to recruit multiple binding partners to a specific cellular domain, such as the seminiferous epithelium during the epithelial cycle of spermatogenesis. Recent studies have illustrated the role of drebrin E in the testis during spermatogenesis in particular via its ability to recruit branched actin polymerization protein known as actin-related protein 3 (Arp3), illustrating its involvement in modifying the organization of actin microfilaments at the ectoplasmic specialization (ES) which includes the testis-specific anchoring junction at the Sertoli-spermatid (apical ES) interface and at the Sertoli cell-cell (basal ES) interface. These data are carefully evaluated in light of other recent findings herein regarding the role of drebrin in actin filament organization at the ES. We also provide the hypothetical model regarding its involvement in germ cell transport during the epithelial cycle in the seminiferous epithelium to support spermatogenesis.

Toll-like receptor 4-mediated lymphocyte influx induces neonatal necrotizing enterocolitis

The nature and role of the intestinal leukocytes in necrotizing enterocolitis (NEC), a severe disease affecting premature infants, remain unknown. We now show that the intestine in mouse and human NEC is rich in lymphocytes that are required for NEC development, as recombination activating gene 1–deficient (Rag1–/–) mice were protected from NEC and transfer of intestinal lymphocytes from NEC mice into naive mice induced intestinal inflammation. The intestinal expression of the lipopolysaccharide receptor TLR4, which is higher in the premature compared with full-term human and mouse intestine, is required for lymphocyte influx through TLR4-mediated upregulation of CCR9/CCL25 signaling. TLR4 also mediates a STAT3-dependent polarization toward increased proinflammatory CD3+CD4+IL-17+ and reduced tolerogenic Foxp3+ Treg lymphocytes (Tregs). Th17 lymphocytes were required for NEC development, as inhibition of STAT3 or IL-17 receptor signaling attenuated NEC in mice, while IL-17 release impaired enterocyte tight junctions, increased enterocyte apoptosis, and reduced enterocyte proliferation, leading to NEC. Importantly, TLR4-dependent Th17 polarization could be reversed by the enteral administration of retinoic acid, which induced Tregs and decreased NEC severity. These findings identify an important role for proinflammatory lymphocytes in NEC development via intestinal epithelial TLR4 that could be reversed through dietary modification.

Activation of classical estrogen receptor subtypes reduces tight junction disruption of brain endothelial cells under ischemia/reperfusion injury

Ischemic stroke, which induces oxidative stress in the brain, disrupts tight junctions (TJs) between brain endothelial cells, resulting in blood-brain barrier (BBB) breakdown and brain edema. Estrogen reduces oxidative stress and protects brain endothelial cells from ischemic insult. The aim of this study was to determine the protective effects of estrogen on TJ disruption and to examine the roles of classical estrogen receptor (ER) subtypes, ERα- and ERβ, in estrogen effects in brain endothelial cells (bEnd.3) exposed to oxygen-glucose deprivation/reperfusion (OGD/R) injury. Estrogen pretreatment prevented OGD/R-induced decreases in cell viability and TJ protein levels. ERα- and ERβ-specific agonists also reduced TJ disruption. Knockdown of ERα or ERβ expression partially inhibited the effects of estrogen, but completely reversed the effects of corresponding ER subtype-specific agonists on the outcomes of OGD/R. During the early reperfusion period, activation of extracellular signal-regulated kinase1/2 and hypoxia-inducible factor 1α/vascular endothelial growth factor was associated with decreased expression of occludin and claudin-5, respectively, and these changes in TJ protein levels were differentially regulated by ER subtype-specific agonists. Our results suggest that ERα and ERβ activation reduce TJ disruption via inhibition of signaling molecules after ischemic injury and that targeting each ER subtype can be a useful strategy for protecting the BBB from ischemic stroke in postmenopausal women.

Formin 1 Regulates Ectoplasmic Specialization in the Rat Testis Through Its Actin Nucleation and Bundling Activity

During spermatogenesis, developing spermatids and preleptotene spermatocytes are transported across the adluminal compartment and the blood-testis barrier (BTB), respectively, so that spermatids line up near the luminal edge to prepare for spermiation, whereas preleptotene spermatocytes enter the adluminal compartment to differentiate into late spermatocytes to prepare for meiosis I/II. These cellular events involve actin microfilament reorganization at the testis-specific, actin-rich Sertoli-spermatid and Sertoli-Sertoli cell junction called apical and basal ectoplasmic specialization (ES). Formin 1, an actin nucleation protein known to promote actin microfilament elongation and bundling, was expressed at the apical ES but limited to stage VII of the epithelial cycle, whereas its expression at the basal ES/BTB stretched from stage III to stage VI, diminished in stage VII, and was undetectable in stage VIII tubules. Using an in vitro model of studying Sertoli cell BTB function by RNA interference and biochemical assays to monitor actin bundling and polymerization activity, a knockdown of formin 1 in Sertoli cells by approximately 70% impeded the tight junction-permeability function. This disruptive effect on the tight junction barrier was mediated by a loss of actin microfilament bundling and actin polymerization capability mediated by changes in the localization of branched actin-inducing protein Arp3 (actin-related protein 3), and actin bundling proteins Eps8 (epidermal growth factor receptor pathway substrate 8) and palladin, thereby disrupting cell adhesion. Formin 1 knockdown in vivo was found to impede spermatid adhesion, transport, and polarity, causing defects in spermiation in which elongated spermatids remained embedded into the epithelium in stage IX tubules, mediated by changes in the spatiotemporal expression of Arp3, Eps8, and palladin. In summary, formin 1 is a regulator of ES dynamics.

Bacterial induction of Snail1 contributes to blood-brain barrier disruption

Bacterial meningitis is a serious infection of the CNS that results when blood-borne bacteria are able to cross the blood-brain barrier (BBB). Group B Streptococcus (GBS) is the leading cause of neonatal meningitis; however, the molecular mechanisms that regulate bacterial BBB disruption and penetration are not well understood. Here, we found that infection of human brain microvascular endothelial cells (hBMECs) with GBS and other meningeal pathogens results in the induction of host transcriptional repressor Snail1, which impedes expression of tight junction genes. Moreover, GBS infection also induced Snail1 expression in murine and zebrafish models. Tight junction components ZO-1, claudin 5, and occludin were decreased at both the transcript and protein levels in hBMECs following GBS infection, and this repression was dependent on Snail1 induction. Bacteria-independent Snail1 expression was sufficient to facilitate tight junction disruption, promoting BBB permeability to allow bacterial passage. GBS induction of Snail1 expression was dependent on the ERK1/2/MAPK signaling cascade and bacterial cell wall components. Finally, overexpression of a dominant-negative Snail1 homolog in zebrafish elevated transcription of tight junction protein-encoding genes and increased zebrafish survival in response to GBS challenge. Taken together, our data support a Snail1-dependent mechanism of BBB disruption and penetration by meningeal pathogens.