Tight junction-based epithelial microenvironment and cell proliferation. Oncogene. 2008;27:6930-6938. [PMID: 19029935 DOI: 10.1038/onc.2008.344]

Structural characteristics and anti-photoaging effect of Pyracantha fortuneana fruit polysaccharides in vitro and in vivo

Pyracantha fortuneana is a cultivated pant extensively cultivated worldwide for its ornamental value and ecological benefits. In this study, a polysaccharide with anti-photoaging activity was extracted and purified from P. fortuneana fruit (PPFP). The structural constitution of PPFP was elucidated by molecular weight determination, FT-IR, monosaccharide composition analysis, smith degradation, methylation, and NMR spectroscopy. The results revealed that PPFP is a macromolecular polysaccharide with a weight-average molecular weight of 70,895 Da. The PPFP is predominantly characterized by →3,6)-β-Galp-(1→, →5,3)-α-Araf-(1 → and →4,2)-α-Xylp-(1→, →4)-β-Galp-(1 → and →4)-β-GalpA-(1 → glycosidic linkages, with t-α-Araf-(1 → and t-α-Glcp-(1 → terminal units. The anti-photoaging activity and potential mechanism of action of PPFP was investigated in vitro and in vivo. Results showed that PPFP exerted anti-photoaging effect on UVB-damaged HaCaT cells by ameliorating cell apoptosis, regulating the mitochondrial membrane potential and oxidative stress level, alleviating the phosphorylation level of the proteins in MAPK pathways, and repairing the expression of tight junction proteins. Moreover, PPFP enhanced the lifespan and diminished the oxidative stress in UVB-injured Caenorhabditis elegans. Collectively, this study comprehensively elucidates the anti-photodamaging potential of P. fortuneana fruit polysaccharide and offers a novel plant-derived adjuvant therapy for the treating photodamage.

The activation of adenosine monophosphate-activated protein kinase inhibits the migration of tongue squamous cell carcinoma cells by targeting Claudin-1 via epithelial-mesenchymal transition

BACKGROUND

The role of Claudin-1 in tongue squamous cell carcinoma (TSCC) metastasis needs further clarification, particularly its impact on cell migration. Herein, our study aims to investigate the role of Claudin-1 in TSCC cell migration and its underlying mechanisms.

METHODS

36 TSCC tissue samples underwent immunohistochemical staining for Claudin-1. Western blotting and immunofluorescence analyses were conducted to evaluate Claudin-1 expression and distribution in TSCC cells. Claudin-1 knockdown cell lines were established using short hairpin RNA transfection. Migration effects were assessed through wound healing assays. Furthermore, the expression of EMT-associated molecules was measured via western blotting.

RESULTS

Claudin-1 expression decreased as TSCC malignancy increased. Adenosine monophosphate-activated protein kinase (AMPK) activation led to increased Claudin-1 expression and membrane translocation, inhibiting TSCC cell migration and epithelial-mesenchymal transition (EMT). Conversely, Claudin-1 knockdown reversed these inhibitory effects on migration and EMT caused by AMPK activation.

CONCLUSIONS

Our results indicated that AMPK activation suppresses TSCC cell migration by targeting Claudin-1 and EMT pathways.

Antibody-drug conjugates in gastric cancer: from molecular landscape to clinical strategies

Antibody-drug conjugates (ADCs) represent a crucial component of targeted therapies in gastric cancer, potentially altering traditional treatment paradigms. Many ADCs have entered rigorous clinical trials based on biological theories and preclinical experiments. Modality trials have also been conducted in combination with monoclonal antibody therapies, chemotherapies, immunotherapies, and other treatments to enhance the efficacy of drug coordination effects. However, ADCs exhibit limitations in treating gastric cancer, including resistance triggered by their structure or other factors. Ongoing intensive researches and preclinical experiments are yielding improvements, while enhancements in drug development processes and concomitant diagnostics during the therapeutic period actively boost ADC efficacy. The optimal treatment strategy for gastric cancer patients is continually evolving. This review summarizes the clinical progress of ADCs in treating gastric cancer, analyzes the mechanisms of ADC combination therapies, discusses resistance patterns, and offers a promising outlook for future applications in ADC drug development and companion diagnostics.

Phylogenetic Tracing of Evolutionarily Conserved Zonula Occludens Toxin Reveals a "High Value" Vaccine Candidate Specific for Treating Multi-Strain Pseudomonas aeruginosa Infections

Extensively drug-resistant Pseudomonas aeruginosa infections are emerging as a significant threat associated with adverse patient outcomes. Due to this organism's inherent properties of developing antibiotic resistance, we sought to investigate alternative strategies such as identifying "high value" antigens for immunotherapy-based purposes. Through extensive database mining, we discovered that numerous Gram-negative bacterial (GNB) genomes, many of which are known multidrug-resistant (MDR) pathogens, including P. aeruginosa, horizontally acquired the evolutionarily conserved gene encoding Zonula occludens toxin (Zot) with a substantial degree of homology. The toxin's genomic footprint among so many different GNB stresses its evolutionary importance. By employing in silico techniques such as proteomic-based phylogenetic tracing, in conjunction with comparative structural modeling, we discovered a highly conserved intermembrane associated stretch of 70 amino acids shared among all the GNB strains analyzed. The characterization of our newly identified antigen reveals it to be a "high value" vaccine candidate specific for P. aeruginosa. This newly identified antigen harbors multiple non-overlapping B- and T-cell epitopes exhibiting very high binding affinities and can adopt identical tertiary structures among the least genetically homologous P. aeruginosa strains. Taken together, using proteomic-driven reverse vaccinology techniques, we identified multiple "high value" vaccine candidates capable of eliciting a polarized immune response against all the P. aeruginosa genetic variants tested.

Effect of Porosity on the Colonization of Digital Light-Processed 3D Hydrogel Constructs toward the Development of a Functional Intestinal Model

With the rapid increase of the number of patients with gastrointestinal diseases in modern society, the need for the development of physiologically relevant in vitro intestinal models is key to improve the understanding of intestinal dysfunctions. This involves the development of a scaffold material exhibiting physiological stiffness and anatomical mimicry of the intestinal architecture. The current work focuses on evaluating the scaffold micromorphology of gelatin-methacryloyl-aminoethyl-methacrylate-based nonporous and porous intestinal 3D, intestine-like constructs, fabricated via digital light processing, on the cellular response. To this end, Caco-2 intestinal cells were utilized in combination with the constructs. Both porous and nonporous constructs promoted cell growth and differentiation toward enterocyte-like cells (VIL1, ALPI, SI, and OCLD expression showed via qPCR, ZO-1 via immunostaining). The porous constructs outperformed the nonporous ones regarding cell seeding efficiency and growth rate, confirmed by MTS assay, live/dead staining, and TEER measurements, due to the presence of surface roughness.

Lipid nanoparticles for local delivery of mRNA to the respiratory tract: Effect of PEG-lipid content and administration route

Design of inhalable mRNA therapeutics is promising because local administration in the respiratory tract is minimally invasive and induces a local response. However, several challenges related to administration via inhalation and respiratory tract barriers have so far prevented the progress of inhaled mRNA therapeutics. Here, we investigated factors of importance for lipid nanoparticle (LNP)-mediated delivery of mRNA to the respiratory tract. We hypothesized that: (i) the PEG-lipid content is important for providing colloidal stability during aerosolization and for mucosal delivery, (ii) the PEG-lipid contentinfluences the expression of mRNA-encoded protein in the lungs, and (iii) the route of administration (nasal versus pulmonary) affects mRNA delivery in the lungs. In this study, we aimed to optimize the PEG-lipid content for mucosal delivery and to investigatethe effect of administration route on the kinetics of protein expression. Our results show that increasing the PEG-lipid content improves the colloidal stability during the aerosolization process, but has a negative impact on the transfection efficiencyin vitro. The kinetics of protein expressionin vivois dependent on the route of administration, and we found that pulmonaryadministration of mRNA-LNPs to mice results inmore durable protein expression than nasaladministration. These results demonstrate that the design of the delivery system and the route of administration are importantfor achieving high mRNA transfection efficiency in the respiratory tract.

Clinical effects and mechanisms of a Chinese patent medicine, Tongxinluo capsule, as an adjuvant treatment in coronary heart disease

Coronary heart disease (CHD) is the leading cause of death globally, posing a serious threat to human health. However, the current treatment approaches available for CHD fall short of the ideal results. Tongxinluo (TXL) is a traditional Chinese medicine (TCM) that has been employed in the clinical treatment of cardiovascular and cerebrovascular diseases (such as angina pectoris, stroke, etc.) in China for many years and holds great potential as a prospective treatment. TXL either as a standalone treatment or in combination with interventions recommended in CHD guidelines has been shown to be effective and well tolerated in clinical trials for CHD. Drawing on the evidence from clinical trials and experimental studies, this review will focus on the cardiovascular protective properties and related mechanisms of TXL. By searching 8 Chinese and English databases, more than 4000 articles were retrieved. These articles were categorized, then read, and finally written into this review. In this review, the pharmacological properties of TXL include regulation of blood lipids, improvement of endothelial function, anti-inflammatory, antioxidant, inhibition of apoptosis and regulation of autophagy, anti-fibrosis, promotion of angiogenesis, and modulation of exosome communication. The information provided in this review will help the reader to comprehend better the insights that TCM has developed over time in practice and provide new perspectives for the treatment of CHD.

Unraveling the connection between Hashimoto's Thyroiditis and non-alcoholic fatty liver disease: exploring the role of CD4+central memory T cells through integrated genetic approaches

PURPOSE

Exploring the connection between Hashimoto's thyroiditis (HT) and non-alcoholic fatty liver disease (NAFLD) through integrated genetic approaches.

METHODS

We utilized integrated genetic approaches, such as single-cell RNA sequencing (scRNA-seq) data analysis, Mendelian Randomization (MR), colocalization analysis, cell communication, and metabolic analyses, to investigate potential correlations between HT and NAFLD.

RESULTS

Through the integrated analysis of scRNA-seq data from individuals with HT, NAFLD, and healthy controls, we observed an upregulation in the proportion of CD4+central memory (CD4+CM) T cells among T cells in both diseases. A total of 63 differentially expressed genes (DEGs) were identified in the CD4+CM cells after the differential analysis. By using MR, 8 DEGs (MAGI3, CSGALNACT1, CAMK4, GRIP1, TRAT1, IL7R, ERN1, and MB21D2) were identified to have a causal relationship with HT, and 4 DEGs (MAGI3, RCAN3, DOCK10, and SAMD12) had a causal relationship with NAFLD. MAGI3 was found to be causally linked to both HT and NAFLD. Therefore, MAGI3 was designated as the marker gene. Reverse MR and Steiger filtering showed no evidence of reverse causality. Colocalization analyses further indicated close links between MAGI3 and HT as well as NAFLD. Finally, based on the expression levels of MAGI3, we stratified CD4+CM cells into two subsets: MAGI3+CD4+CM cells and MAGI3-CD4+CM cells. Functional analyses revealed significant differences between the two subsets, potentially related to the progression of the two diseases.

CONCLUSION

This study delves into the potential connections between HT and NAFLD through integrated genetic methods. Our research reveals an elevated proportion of CD4+CM cells within T cells in both HT and NAFLD. Through MR and colocalization analysis, we identify specific genes causally linked to HT and NAFLD, such as MAGI3. Ultimately, based on MAGI3 expression levels, we categorize CD4+CM cells into MAGI3+CD4+CM cells and MAGI3-CD4+CM cells, uncovering significant differences between them through functional analyses.

Activation of the TGF-β1/EMT signaling pathway by claudin-1 overexpression reduces doxorubicin sensitivity in small cell lung cancer SBC-3 cells

Small-cell lung cancer (SCLC), which accounts for about 15 % of all lung cancers, progresses more rapidly than other histologic types and is rarely detected at an operable early stage. Therefore, chemotherapy, radiation therapy, or their combination are the primary treatments for this type of lung cancer. However, the tendency to acquire resistance to anticancer drugs is a severe problem. Recently, we found that an intercellular adhesion molecule, claudin (CLDN) 1, known to be involved in the migration and invasion of lung cancer cells, is involved in the acquisition of anticancer drug resistance. In the present study, we investigated the effect of CLDN1 on the anticancer-drug sensitivity of SCLC SBC-3 cells. Since epithelial-mesenchymal transition (EMT), which is involved in cancer cell migration and invasion, is well known for its involvement in anticancer-drug sensitivity via inhibition of apoptosis, we also examined EMT involvement in decreased anticancer-drug sensitivity by CLDN1. Sensitivity to doxorubicin (DOX) in SBC-3 cells was significantly decreased by CLDN1 overexpression. CLDN1 overexpression resulted in increased TGF-β1 levels, enhanced EMT induction, and increased migratory potency of SBC-3 cells. The decreased sensitivity of SBC-3 cells to anticancer drugs upon TGF-β1 treatment suggested that activation of the TGF-β1/EMT signaling pathway by CLDN1 causes the decreased sensitivity to anticancer drugs and increased migratory potency. Furthermore, treatments with antiallergic agents tranilast and zoledronic acid, known EMT inhibitors, significantly mitigated the decreased sensitivity of CLDN1-overexpressing SBC-3 cells to DOX. These results suggest that EMT inhibitors might effectively overcome reduced sensitivity to anticancer drugs in CLDN1-overexpressing SCLC cells.

Acute Effects of Systemic Glucocorticoids on the Vocal Folds in a Pre-Clinical Model

OBJECTIVES/HYPOTHESIS

Systemic glucocorticoids (GC)s are employed to treat various voice disorders. However, GCs have varying pharmacodynamic properties with adverse effects ranging from changes in epithelial integrity, skeletal muscle catabolism, and altered body weight. We sought to characterize the acute temporal effects of systemic dexamethasone and methylprednisolone on vocal fold (VF) epithelial glucocorticoid receptor (GR) nuclear translocation, epithelial tight junction (ZO-1) expression, thyroarytenoid (TA) muscle fiber morphology, and body weight using an established pre-clinical model. We hypothesized dexamethasone and methylprednisolone will elicit changes in VF epithelial GR nuclear translocation, epithelial ZO-1 expression, TA muscle morphology, and body weight compared to placebo-treated controls.

METHODS

Forty-five New Zealand white rabbits received intramuscular injections of methylprednisolone (4.5 mg; n = 15), dexamethasone (450 µg; n = 15), or volume matched saline (n = 15) into the iliocostalis/longissimus muscle for 6 consecutive days. Vocal folds from 5 rabbits from each treatment group were harvested at 1-, 3-, or 7 days following the final injection and subjected to immunohistochemistry for ZO-1 and GR as well as TA muscle fiber cross-sectional area (CSA) measures.

RESULTS

Dexamethasone increased epithelial GR nuclear translocation and ZO-1 expression 1-day following injections compared to methylprednisolone (P = .024; P = .012). Dexamethasone and methylprednisolone increased TA CSA 1-day following injections (P = .011). Methylprednisolone decreased body weight 7 days following injections compared to controls (P = .004).

CONCLUSIONS

Systemic dexamethasone may more efficiently activate GR in the VF epithelium with a lower risk of body weight loss, suggesting a role for more refined approaches to GC selection for laryngeal pathology.

Physiological and cognitive changes after treatments of cyclophosphamide, methotrexate, and fluorouracil: implications of the gut microbiome and depressive-like behavior

Introduction

Chemotherapy-induced cognitive impairment colloquially referred to as chemobrain is a poorly understood phenomenon affecting a highly variable proportion of patients with breast cancer. Here we investigate the association between anxiety and despair-like behaviors in mice treated with cyclophosphamide, methotrexate, and fluorouracil (CMF) along with host histological, proteomic, gene expression, and gut microbial responses.

Methods

Forced swim and sociability tests were used to evaluate depression and despair-like behaviors. The tandem mass tag (TMT) proteomics approach was used to assess changes in the neural protein network of the amygdala and hippocampus. The composition of gut microbiota was assessed through 16S rRNA gene sequencing. Finally, quantitative reverse transcription polymerase chain reaction (qRT-PCR) was used to evaluate changes in intestinal gap junction markers.

Results and discussion

We observed that CMF induced social and despair-like behavior in mice 96 hours following treatment. Proteomic analysis identified changes in various proteins related to progressive neurological disease, working memory deficit, primary anxiety disorder, and gene expression revealing increases in NMDA and AMPA receptors in both the hippocampus and the amygdala because of CMF treatment. These changes finally, we observed immediate changes in the microbial population after chemotherapy treatment, with a notable abundance of Muribaculaceae and Romboutsia which may contribute to changes seen in the gut.

Comparing the adult and pre-pubertal testis: Metabolic transitions and the change in the spermatogonial stem cell metabolic microenvironment

BACKGROUND

Survivors of childhood cancer often suffer from infertility. While sperm cryopreservation is not feasible before puberty, the patient's own spermatogonial stem cells could serve as a germ cell reservoir, enabling these patients to father their own children in adulthood through the isolation, in vitro expansion, and subsequent transplantation of spermatogonial stem cells. However, this approach requires large numbers of stem cells, and methods for successfully propagating spermatogonial stem cells in the laboratory are yet to be established for higher mammals and humans. The improvement of spermatogonial stem cell culture requires deeper understanding of their metabolic requirements and the mechanisms that regulate metabolic homeostasis.

AIM

This review gives a summary on our knowledge of spermatogonial stem cell metabolism during maintenance and differentiation and highlights the potential influence of Sertoli cell and stem cell niche maturation on spermatogonial stem cell metabolic requirements during development.

RESULTS AND CONCLUSIONS

Fetal human spermatogonial stem cell precursors, or gonocytes, migrate into the seminiferous cords and supposedly mature to adult stem cells within the first year of human development. However, the spermatogonial stem cell niche does not fully differentiate until puberty, when Sertoli cells dramatically rearrange the architecture and microenvironment within the seminiferous epithelium. Consequently, pre-pubertal and adult spermatogonial stem cells experience two distinct niche environments potentially affecting spermatogonial stem cell metabolism and maturation. Indeed, the metabolic requirements of mouse primordial germ cells and pig gonocytes are distinct from their adult counterparts, and novel single-cell RNA sequencing analysis of human and porcine spermatogonial stem cells during development confirms this metabolic transition. Knowledge of the metabolic requirements and their changes and regulation during spermatogonial stem cell maturation is necessary to implement laboratory-based techniques and enable clinical use of spermatogonial stem cells. Based on the advancement in our understanding of germline metabolism circuits and maturation events of niche cells within the testis, we propose a new definition of spermatogonial stem cell maturation and its amendment in the light of metabolic change.

Emerging roles of transmembrane-type tight junction proteins in cancers

Tight junctions (TJs) are the most apical components of the cell-cell adhesion machinery in epithelial and endothelial cells and they play essential roles in homeostasis. Recent studies have revealed that aberrant expression of tight junction proteins (TJPs) is frequently observed in various type of cancers. Here we review cancer-associated aberrant expression of TJPs with focus on transmembrane-type TJPs including claudins, junctional adhesion molecule-A (JAM-A), and occludin. Some transmembrane-type TJPs are upregulated at the early neoplastic stage and their expression persists during dedifferentiation. Aberrant expression of TJPs contributes to proliferation, invasion, and dysregulated signaling of cancer cells. In addition to an increase in their expression level, their localization is altered from a TJ-restricted pattern to distribution throughout the whole cell membrane, making them suitable as therapeutic targets. Extracellular domains of transmembrane-type TJPs can be approached by target drugs not only from the lumen side (apical side) but also from the extracellular matrix side (basal side), including blood vessels. Aberrantly expressed TJPs are potential useful diagnostic markers as well as therapeutic targets for cancers.

Identification of a novel role for TL1A/DR3 deficiency in acute respiratory distress syndrome that exacerbates alveolar epithelial disruption

Alveolar epithelial barrier is a potential therapeutic target for acute respiratory distress syndrome (ARDS). However, an effective intervention against alveolar epithelial barrier has not been developed. Here, based on single-cell RNA and mRNA sequencing results, death receptor 3 (DR3) and its only known ligand tumor necrosis factor ligand-associated molecule 1A (TL1A) were significantly reduced in epithelium from an ARDS mice and cell models. The apparent reduction in the TL1A/DR3 axis in lungs from septic-ARDS patients was correlated with the severity of the disease. The examination of knockout (KO) and alveolar epithelium conditional KO (CKO) mice showed that TL1A deficiency exacerbated alveolar inflammation and permeability in lipopolysaccharide (LPS)-induced ARDS. Mechanistically, TL1A deficiency decreased glycocalyx syndecan-1 and tight junction-associated zonula occludens 3 by increasing cathepsin E level for strengthening cell-to-cell permeability. Additionally, DR3 deletion aggravated barrier dysfunction and pulmonary edema in LPS-induced ARDS through the above mechanisms based on the analyses of DR3 CKO mice and DR3 overexpression cells. Therefore, the TL1A/DR3 axis has a potential value as a key therapeutic signaling for the protection of alveolar epithelial barrier.

Histone demethylase KDM5D upregulation drives sex differences in colon cancer

Sex exerts a profound impact on cancer incidence, spectrum and outcomes, yet the molecular and genetic bases of such sex differences are ill-defined and presumptively ascribed to X-chromosome genes and sex hormones1. Such sex differences are particularly prominent in colorectal cancer (CRC) in which men experience higher metastases and mortality. A murine CRC model, engineered with an inducible transgene encoding oncogenic mutant KRASG12D and conditional null alleles of Apc and Trp53 tumour suppressors (designated iKAP)2, revealed higher metastases and worse outcomes specifically in males with oncogenic mutant KRAS (KRAS*) CRC. Integrated cross-species molecular and transcriptomic analyses identified Y-chromosome gene histone demethylase KDM5D as a transcriptionally upregulated gene driven by KRAS*-mediated activation of the STAT4 transcription factor. KDM5D-dependent chromatin mark and transcriptome changes showed repression of regulators of the epithelial cell tight junction and major histocompatibility complex class I complex components. Deletion of Kdm5d in iKAP cancer cells increased tight junction integrity, decreased cell invasiveness and enhanced cancer cell killing by CD8+ T cells. Conversely, iAP mice engineered with a Kdm5d transgene to provide constitutive Kdm5d expression specifically in iAP cancer cells showed an increased propensity for more invasive tumours in vivo. Thus, KRAS*-STAT4-mediated upregulation of Y chromosome KDM5D contributes substantially to the sex differences in KRAS* CRC by means of its disruption of cancer cell adhesion properties and tumour immunity, providing an actionable therapeutic strategy for metastasis risk reduction for men afflicted with KRAS* CRC.

TJP1 promotes vascular mimicry in bladder cancer by facilitating VEGFA expression and transcriptional activity through TWIST1

Tight junction protein 1 (TJP1) is a recently identified prominent regulator of bladder cancer (BLCA) angiogenesis and tumorigenesis. Vascular mimicry (VM) is a newly described tumor feature and is correlated with an increased risk of tumor metastasis. However, the relationship between TJP1 expression and VM in bladder cancer remains elusive. In the present study, we report a novel function for TJP1 in accommodating VM to promote tumor progression. We found that the elevated TJP1 expression was positively related to VM in patients and xenograft tumor models in bladder cancer. Enforced expression of TJP1 increased VM of BLCA cells in vitro and in vivo by elevating Vascular endothelial growth factor A (VEGFA) levels. Furthermore, VM induced by TJP1 overexpression was significantly blocked by the VEGFA and VEGFR inhibitors (Bevacizumab and Sunitinib). Mechanistically, TJP1 promoted VEGFA transcriptional and protein level in a TWIST1-dependent manner. Taken together, our study reveals that TJP1-regulated VEGFA overexpression may indicate a potential therapeutic target for clinical intervention in the early tumor neovascularization of bladder cancer.

Downregulation of angulin-1/LSR induces malignancy via upregulation of EGF-dependent claudin-2 and TGF-β-dependent cell metabolism in human lung adenocarcinoma A549 cells

Abnormal expression of bicellular tight junction claudins, including claudin-2 are observed during carcinogenesis in human lung adenocarcinoma. However, little is known about the role of tricellular tight junction molecule angulin-1/lipolysis-stimulated lipoprotein receptor (LSR). In the lung adenocarcinoma tissues examined in the present study, expression of claudin-2 was higher than in normal lung tissues, while angulin-1/LSR was poorly or faintly expressed. We investigated how loss of angulin-1/LSR affects the malignancy of lung adenocarcinoma cell line A549 and normal human lung epithelial (HLE) cells. The EGF receptor tyrosine kinase inhibitor AG1478 prevented the increase of claudin-2 expression induced by EGF in A549 cells. Knockdown of LSR induced expression of claudin-2 at the protein and mRNA levels and AG1478 prevented the upregulation of claudin-2 in A549 cells. Knockdown of LSR induced cell proliferation, cell migration and cell metabolism in A549 cells. Knockdown of claudin-2 inhibited the cell proliferation but did not affect the cell migration or cell metabolism of A549 cells. The TGF-β type I receptor inhibitor EW-7197 prevented the decrease of LSR and claudin-2 induced by TGF-β1 in A549 cells and 2D culture of normal HLE cells. EW-7197 prevented the increase of cell migration and cell metabolism induced by TGF-β1 in A549 cells. EW-7197 prevented the increase of epithelial permeability of FITC-4kD dextran induced by TGF-β1 in 2.5D culture of normal HLE cells. In conclusion, downregulation of angulin-1/LSR induces malignancy via EGF-dependent claudin-2 and TGF-β-dependent cell metabolism in human lung adenocarcinoma.

Epidermal growth factor receptor in asthma: A promising therapeutic target?

Activation of the epidermal growth factor receptor (EGFR) pathway is involved in the pathogenesis of asthma. Although decades of intensive research have focused on the role of EGFR in asthma, the specific mechanisms and pathways of EGFR signaling remain unclear. Various reports have indicated that inhibition of EGFR improves the pathological features in asthma models. However, extending these experimental findings to clinical applications is difficult. Several measures can be adopted to promote clinical application of EGFR inhibitors. This review focuses on the role of EGFR in the pathogenesis of asthma and the development of a potentially novel therapeutic target for asthma.

Week-Old Chicks with High Bacteroides Abundance Have Increased Short-Chain Fatty Acids and Reduced Markers of Gut Inflammation

As important commensals in the chicken intestine, Bacteroides are essential complex carbohydrate degraders, and short-chain fatty acid (SCFA) producers that are highly adapted to the distal gut. Previous studies have shown large variation in Bacteroides abundance in young chickens. However, limited information is available regarding how this variation affects the gut microbiome and host immunity. To investigate how elevated or depleted Bacteroides levels affect gut microbial functional capacity and impact host response, we sampled 7-day-old broiler chickens from 14 commercial production flocks. Week-old broiler chickens were screened and birds with low Bacteroides (LB) and high Bacteroides (HB) abundance were identified via 16S rRNA gene amplicon sequencing and quantitative PCR (qPCR) assays. Cecal microbial functionality and SCFA concentration of chickens with distinct cecal Bacteroides abundance were profiled by shotgun metagenomic sequencing and gas chromatography, respectively. The intestinal immune responses of LB and HB chickens were assessed via reverse transcription qPCR. Results showed that the gut microbiota of the LB group had increased abundance of lactic acid bacteria pyruvate fermentation pathway, whereas complex polysaccharide degradation and SCFA production pathways were enriched in the HB group (P < 0.05), which was supported by increased SCFA concentrations in the ceca of HB chickens (P < 0.05). HB chickens also showed decreased expression of interleukin-1β and increased expression of interleukin-10 and tight-junction protein claudin-1 (P < 0.05). Overall, the results indicated that elevated Bacteroides may benefit the 7-day broiler gut and that further work should be done to confirm the causal role of Bacteroides in the observed positive outcomes. IMPORTANCE To date, limited information is available comparing distinct Bacteroides compositions in the chicken gut microbial communities, particularly in the context of microbial functional capacities and host responses. This study showed that possessing a microbiome with elevated Bacteroides in early life may confer beneficial effects to the chicken host, particularly in improving SCFA production and gut health. This study is among the first metagenomic studies focusing on the early life chicken gut microbiota structure, microbial functionality, and host immune responses. We believe that it will offer insights to future studies on broiler gut microbial population and their effects on host health.

Subacute Ruminal Acidosis as a Potential Factor that Induces Endometrium Injury in Sheep

The demand for economic benefits has led to an increase in the proportion of high-concentrate (HC) feed in the ruminant diet, resulting in an increased incidence of subacute ruminal acidosis (SARA). During SARA, a high concentration of lipopolysaccharide (LPS) translocated in the rumen induces a systemic inflammatory response. Inflammatory diseases, such as endometritis and mastitis, are often associated with SARA; however, in sheep, the mechanism of the effect of SARA on the endometrium has rarely been reported. Therefore, the aim of this study was to investigate, for the first time, the influence of LPS translocation on endometrial tight junctions (TJs) during SARA in sheep. The results showed that LPS and TNFα levels in the ruminal fluid, serum, and endometrial tissue supernatant during SARA increased, transcription levels of TLR4, NFκB, and TNFα in the endometrium increased, the protein expression level of claudin-1 in the endometrium increased, and the protein expression level of occludin decreased. 17β-estradiol (E₂) inhibits claudin-1 protein expression and promotes occludin expression, and progesterone (P₄) promotes claudin-1 protein expression and inhibits occludin protein expression. E₂ and P₄ regulate claudin-1 and occludin protein expression through their receptor pathways. Here, we found that LPS hindered the regulatory effect of E₂ and P₄ on endometrial TJs by inhibiting their receptor expression. The results of this study indicate that HC feeding can cause SARA-induced LPS translocation in sheep, increase susceptibility to systemic inflammation, induce the endometrial inflammatory response, and cause endometrial epithelial TJ damage directly and/or by obstructing E₂ and P₄ function. LPS translocation caused by SARA has also been suggested to induce an endometrial inflammatory response, resulting in endometrial epithelial barrier damage and physiological dysfunction, which seriously affects ruminant production. Therefore, this study provides new evidence that SARA is a potential factor that induces systemic inflammation in ruminants. It provides theoretical support for research on the prevention of endometritis in ruminants.

Junctional complexes in epithelial cells: sentinels for extracellular insults and intracellular homeostasis

The cell-cell and cell-ECM junctions within the epithelial tissues are crucial anchoring structures that provide architectural stability, mechanical resistance, and permeability control. Their indispensable role as signaling hubs orchestrating cell shape-related changes such as proliferation, differentiation, migration, and apoptosis has also been well recognized. However, growing amount of evidence now suggests that the multitasking nature of epithelial junctions extends well beyond anchorage-dependent or cell shape change-related biological processes. In this review, we discuss the emerging roles of junctional complexes in regulating innate immune defense, stress resistance, and intracellular proteostasis of the epithelial cells, with emphasis on the upstream regulation of epithelial junctions on various aspects of the epithelial barrier.

Visualization of a novel human monoclonal antibody against Claudin-3 for targeting ovarian cancer

INTRODUCTION

Claudin-3 (CLDN3), a tight junction protein, regulates cell-to-cell interactions in epithelial or endothelial cell sheets. During tumorigenesis, epithelial cells are transformed, and tumor cells proliferate through out-of-plane division, resulting in external exposure of CLDN3. Since alterations of CLDN3 expression are associated with cancer progression and higher CLDN3 expression is observed in most ovarian cancers, we tested the feasibility of using a CLDN3-specific antibody as a novel imaging tracer.

MATERIALS AND METHODS

After reducing the CLDN3-specific antibodies to expose the -SH groups, click chemistry was used to conjugate the radioactive isotope ¹¹¹In or the fluorescent protein FNR648. Human ovarian cancer OVCAR-3 and glioblastoma U87MG cells were used as CLDN3-positive and -negative cells. Flow cytometry was used to determine the CLDN3 IgG1 monoclonal antibody binding to both cell lines. OVCAR-3 cells were injected subcutaneously into mice to establish a xenograft model. ¹¹¹In-labeled CLDN3 antibodies (370 kBq/50 μL) were administered intravenously into mice. After 24 h, organs, including tumors, were excised and measured with a γ-counter. Images were acquired with the IVIS optical imaging system and SPECT/CT.

RESULTS

The labeling efficiency of NOTA-¹¹¹In and antibody-NOTA-¹¹¹In was 98.52% and 100%, respectively. FNR648-labeled CLDN3 antibody bound to the cell surface of OVCAR-3 and U87MG with 83.4% and 5.7% specificity, respectively. In OVCAR-3 tumor xenografted mice, CLDN3 IgG1 antibody showed a 2.5-fold higher tumor uptake (20.4 ± 7.4% ID/g) than human IgG1 (8.8 ± 2.6% ID/g) at 24 h post injection. The CLDN3 antibody fluorescence signal in the tumor peaked at 24 h post injection.

CONCLUSION

We have successfully conjugated a radioisotope and a fluorescent protein with CLDN3-specific antibodies and verified the specific binding of labeled antibodies to OVCAR-3 tumors in a mouse model. Our data suggested that CLDN3-specific human monoclonal antibodies could be used as a useful theranostic tracer.

Effects of dioxins on animal spermatogenesis: A state-of-the-art review

The male reproductive system is especially affected by dioxins, a group of persistent environmental pollutants, resulting in irreversible abnormalities including effects on sexual function and fertility in adult males and possibly on the development of male offspring. The reproductive toxicity caused by dioxins is mostly mediated by an aryl hydrocarbon receptor (AhR). In animals, spermatogenesis is a highly sensitive and dynamic process that includes proliferation and maturation of germ cells. Spermatogenesis is subject to multiple endogenous and exogenous regulatory factors, including a wide range of environmental toxicants such as dioxins. This review discusses the toxicological effects of dioxins on spermatogenesis and their relevance to male infertility. After a detailed categorization of the environmental contaminants affecting the spermatogenesis, the exposure pathways and bioavailability of dioxins in animals was briefly reviewed. The effects of dioxins on spermatogenesis are then outlined in detail. The endocrine-disrupting effects of dioxins in animals and humans are discussed with a particular focus on their effects on the expression of spermatogenesis-related genes. Finally, the impacts of dioxins on the ratio of X and Y chromosomes, the status of serum sex hormones, the quality and fertility of sperm, and the transgenerational effects of dioxins on male reproduction are reviewed.

Atypical Macropinocytosis Contributes to Malignant Progression: A Review of Recent Evidence in Endometrioid Endometrial Cancer Cells

Simple Summary

A novel type of macropinocytosis has been identified as a trigger for the malignant progression of endometrial cancer. Transiently reducing epithelial barrier homeostasis leads to macropinocytosis by splitting between adjacent cells in endometrioid endometrial cancer. Macropinocytosis causes morphological changes in well-differentiated to poorly differentiated cancer cells. Inhibition of macropinocytosis promotes a persistent dormant state in the intrinsic KRAS-mutated cancer cell line Sawano. This review focuses on the mechanisms of atypical macropinocytosis and its effects on cellular function, and it describes the physiological processes involved in inducing resting conditions in endometrioid endometrial cancer cells.

Abstract

Macropinocytosis is an essential mechanism for the non-specific uptake of extracellular fluids and solutes. In recent years, additional functions have been identified in macropinocytosis, such as the intracellular introduction pathway of drugs, bacterial and viral infection pathways, and nutritional supplement pathway of cancer cells. However, little is known about the changes in cell function after macropinocytosis. Recently, it has been reported that macropinocytosis is essential for endometrial cancer cells to initiate malignant progression in a dormant state. Macropinocytosis is formed by a temporary split of adjacent bicellular junctions of epithelial sheets, rather than from the apical surface or basal membrane, as a result of the transient reduction of tight junction homeostasis. This novel type of macropinocytosis has been suggested to be associated with the malignant pathology of endometriosis and endometrioid endometrial carcinoma. This review outlines the induction of malignant progression of endometrial cancer cells by macropinocytosis based on a new mechanism and the potential preventive mechanism of its malignant progression.

Clinical Significance of Claudin Expression in Oral Squamous Cell Carcinoma

A change in claudin expression has been demonstrated in various tumors. The present study specifically compares claudin expression in oral squamous cell carcinoma (OSCC) with healthy oral epithelium from the same individual and analyzes the association between claudin expression and the clinically relevant course parameters. Our study includes tissue samples and clinically relevant follow-up data from 60 patients with primary and untreated OSCC. The oral mucosa was analyzed via Western blot for the expression of claudin-1, -2, -3, -4, -5, and -7. Importantly, the tumor and healthy tissues were obtained pairwise from patients, allowing for intraindividual comparisons. Both the healthy and tumor epithelium from the oral cavity did not express the claudin-3 protein. The intraindividual comparison revealed that, in OSCC, claudin-2 expression was higher, and the expression of claudin-4, -5, and -7 was lower than in healthy epithelium. An association was found between increased claudin-2 expression and shorter relapse-free survival. In addition, the reduced expression of claudin-4 had a negative impact on relapse-free survival. Furthermore, associations between the reduced expression of claudin-7 and the stage of a tumor, or the presence of lymph node metastases, were found. Thus, the expression level of claudin-2, -4, and -7 appears to be predictive of the diagnosis and prognosis of OSCC.

IL-22 regulates endometrial regeneration by enhancing tight junctions and orchestrating extracellular matrix

The uterine endometrium uniquely regenerates after menses, postpartum, or after breaks in the uterine layer integrity throughout women’s lives. Direct cell–cell contacts ensured by tight and adherens junctions play an important role in endometrial integrity. Any changes in these junctions can alter the endometrial permeability of the uterus and have an impact on the regeneration of uterine layers. Interleukin 22 (IL-22) is a cytokine that is recognized for its role in epithelial regeneration. Moreover, it is crucial in controlling the inflammatory response in mucosal tissues. Here, we studied the role of IL-22 in endometrial recovery after inflammation-triggered abortion. Fecundity of mice was studied in consecutive matings of the same animals after lipopolysaccharide (LPS) (10 µg per mouse)-triggered abortion. The fecundity rate after the second mating was substantially different between IL-22 knockout (IL-22^−/−) (9.1%) and wild-type (WT) (71.4%) mice (p < 0.05), while there was no difference between the groups in the initial mating, suggesting that IL-22 deficiency might be associated with secondary infertility. A considerable difference was observed between IL-22^−/− and WT mice in the uterine clearance following LPS-triggered abortion. Gross examination of the uteri of IL-22^−/− mice revealed non-viable fetuses retained inside the horns (delayed clearance). In contrast, all WT mice had completed abortion with total clearance after LPS exposure. We also discovered that IL-22 deficiency is associated with a decreased expression of tight junctions (claudin-2 and claudin-10) and cell surface pathogen protectors (mucin-1). Moreover, IL-22 has a role in the remodeling of the uterine tissue in the inflammatory environment by regulating epithelial–mesenchymal transition markers called E- and N-cadherin. Therefore, IL-22 contributes to the proper regeneration of endometrial layers after inflammation-triggered abortion. Thus, it might have a practical significance to be utilized as a treatment option postpartum (enhanced regeneration function) and in secondary infertility caused by inflammation (enhanced barrier/protector function).

Endogenous Retroviruses and Placental Evolution, Development, and Diversity

The main roles of placentas include physical protection, nutrient and oxygen import, export of gasses and fetal waste products, and endocrinological regulation. In addition to physical protection of the fetus, the placentas must provide immune protection throughout gestation. These basic functions are well-conserved; however, placentas are undoubtedly recent evolving organs with structural and cellular diversities. These differences have been explained for the last two decades through co-opting genes and gene control elements derived from transposable elements, including endogenous retroviruses (ERVs). However, the differences in placental structures have not been explained or characterized. This manuscript addresses the sorting of ERVs and their integration into the mammalian genomes and provides new ways to explain why placental structures have diverged.

EGF-Dependent Activation of ELK1 Contributes to the Induction of CLDND1 Expression Involved in Tight Junction Formation

Claudin proteins are intercellular adhesion molecules. Increased claudin domain-containing 1 (CLDND1) expression is associated with the malignant transformation of estrogen receptor-negative breast cancer cells with low sensitivity to hormone therapy. Abnormal CLDND1 expression is also implicated in vascular diseases. Previously, we investigated the regulatory mechanism underlying CLDND1 expression and identified a strong enhancer region near the promoter. In silico analysis of the sequence showed high homology to the ETS domain-containing protein-1 (ELK1)-binding sequence which is involved in cell growth, differentiation, angiogenesis, and cancer. Transcriptional ELK1 activation is associated with the mitogen-activated protein kinase (MAPK) signaling cascade originating from the epidermal growth factor receptor (EGFR). Here, we evaluated the effect of gefitinib, an EGFR tyrosine kinase inhibitor, on the suppression of CLDND1 expression using ELK1 overexpression in luciferase reporter and chromatin immunoprecipitation assays. ELK1 was found to be an activator of the enhancer region, and its transient expression increased that of CLDND1 at the mRNA and protein levels. CLDND1 expression was increased following EGF-induced ELK1 phosphorylation. Furthermore, this increase in CLDND1 was significantly suppressed by gefitinib. Therefore, EGF-dependent activation of ELK1 contributes to the induction of CLDND1 expression. These findings open avenues for the development of new anticancer agents targeting CLDND1.

LSR antibody promotes apoptosis and disrupts epithelial barriers via signal pathways in endometrial cancer

Lipolysis-stimulated lipoprotein receptor (LSR), a lipid metabolism-related factor localized in tricellular tight junctions (tTJs), plays an important role in maintaining the epithelial barrier. LSR is highly expressed in well-differentiated endometrial endometrioid carcinoma (EEC), and its expression decreases during malignancy. Angubindin-1, a novel LSR ligand peptide, regulates tTJs without cytotoxicity, enhances paracellular permeability, and regulates epithelial barrier via c-Jun N-terminal kinase (JNK)/cofilin. In this study, we investigated the immune-modulatory roles of an anti-LSR antibody in the treatment of EEC in vitro compared to those of angubindin-1. We prepared an antibody against the extracellular N-terminal domain of human LSR (LSR-N-ab) and angubindin-1. EEC cell-line Sawano cells in 2D and 2.5D cultures were treated with 100 μg/ml LSR-N-ab or 2.5 μg/ml angubindin-1 with or without protein tyrosine kinase 2β inhibitor PF431396 (PF43) and JNK inhibitor SP600125 (SP60) at 10 μM. Treatment with LSR-N-ab and angubindin-1 decreased LSR at the membranes of tTJs and the activity of phosphorylated LSR and phosphorylated cofilin in 2D culture. Treatment with LSR-N-ab and angubindin-1 decreased the epithelial barrier measured as TEER values in 2D culture and enhanced the epithelial permeability of FD-4 in 2.5D culture. Treatment with LSR-N-ab, but not angubindin-1, induced apoptosis in 2D culture. Pretreatment with PF43 and SP60 prevented all the changes induced by treatment with LSR-N-ab and angubindin-1. Treatment with LSR-N-ab and angubindin-1 enhanced the cell metabolism measured as the mitochondrial respiration levels in 2D culture. LSR-N-ab and angubindin-1 may be useful for therapy of human EEC via enhanced apoptosis or drug absorption.

Characterization of junctional structures in the gingival epithelium as barriers against bacterial invasion

BACKGROUND AND OBJECTIVE

Adherens junctions (AJs) and tight junctions (TJs) are known to play a crucial role in maintaining the physical barrier function of the epithelium. Here, we aimed to characterize the distribution of AJs and TJs throughout the gingival epithelium and to obtain insights into the physiological importance of these junctional structures.

METHODS

Sections of mouse gingival tissue were examined using transmission electron microscopy (TEM) and bio-high voltage electron microscopy tomography. The gingival sections were stained for E-cadherin and JAM-A as markers of AJs and TJs, respectively, and examined using confocal microscopy and lattice structured illumination microscopy. Bacteria within the gingival epithelium were examined using in situ hybridization.

RESULTS

Junctional structures, including desmosomes, AJs, and TJs, were observed throughout the gingival epithelium. The expression levels of E-cadherin were particularly low in the granular/keratinized layers of the oral epithelium (OE), while extremely low JAM-A levels were detected in the granular/keratinized layers of the sulcular epithelium (SE). The three-dimensional rendering of the junctional structures revealed that both AJs and TJs in the gingival epithelium formed discontinuous short bands or patches. Interestingly, strong bacterial signals were observed at the granular/keratinized layers of both SE and OE, but a few bacteria were detected within the junctional epithelium (JE) and the basal/spinous layers of the SE and OE.

CONCLUSIONS

AJs and TJs form a discontinuous barrier throughout paracellular passage in the gingival epithelium; nevertheless, they seem to play an important role in defending against invading bacteria.

Aberrant expression of claudin-6 contributes to malignant potentials and drug resistance of cervical adenocarcinoma

Recent studies have revealed that aberrant expression of tight junction (TJ) proteins is a hallmark of various solid tumors and it is recognized as a useful therapeutic target. Claudin‐6 (CLDN6), a member of the family of TJ transmembrane proteins, is an ideal therapeutic target because it is not expressed in human adult normal tissues. In this study, we found that CLDN6 is highly expressed in uterine cervical adenocarcinoma (ADC) and that high CLDN6 expression was correlated with lymph node metastasis and lymphovascular infiltration and was an independent prognostic factor. Shotgun proteome analysis revealed that cell‐cell adhesion‐related proteins and drug metabolism‐associated proteins (aldo‐keto reductase [AKR] family proteins) were significantly increased in CLDN6‐overexpressing cells. Furthermore, overexpression of CLDN6 enhanced cell‐cell adhesion properties and attenuated sensitivity to anticancer drugs including doxorubicin, daunorubicin, and cisplatin. Taken together, the results indicate that aberrant expression of CLDN6 enhances malignant potentials and drug resistance of cervical ADC, possibly due to increased cell‐cell adhesion properties and drug metabolism. Our findings provide an insight into a new therapeutic strategy, a CLDN6‐targeting therapy, against cervical ADC.

Dietary supplementation of thiamine enhances colonic integrity and modulates mucosal inflammation injury in goats challenged by lipopolysaccharide and low pH

The current study aimed to investigate the protective effects of dietary thiamine supplementation on the regulation of colonic integrity and mucosal inflammation in goats fed a high-concentrate (HC) diet. Twenty-four Boer goats (live weight of 35·62 (sem 2·4) kg) were allocated to three groups (CON: concentrate/forage = 30:70; HC; concentrate/forage = 70:30 and HCT: concentrate/forage = 70:30 with 200 mg thiamine/kg DMI) for 12 weeks. Results showed that compared with the HC treatment, the HCT group had a significantly higher ruminal pH value from 0 to 12 h after the feeding. The haematoxylin-eosin staining showed that desquamation and severe cellular damage were observed in the colon epithelium of the HC group, whereas the HCT group exhibited more structural integrity of the epithelial cell morphology. Compared with the HC treatment, the HCT group showed a markedly increase in pyruvate dehydrogenase and α-ketoglutarate dehydrogenase enzymes activity. The mRNA expressions in the colonic epithelium of SLC19A2, SLC19A3, SLC25A19, Bcl-2, occludin, claudin-1, claudin-4 and ZO-1 in the HCT group were significantly increased in comparison with the HC diet treatment. Compared with the HC treatment, the HCT diet significantly increased the protein expression of claudin-1 and significantly decreased the protein expression of NF-κB-related proteins p65. The results show that dietary thiamine supplementation could improve the colon epithelial barrier function and alleviate mucosal inflammation injury in goats after lipopolysaccharide and low pH challenge.

Nanotechnologies in Delivery of DNA and mRNA Vaccines to the Nasal and Pulmonary Mucosa

Recent advancements in the field of in vitro transcribed mRNA (IVT-mRNA) vaccination have attracted considerable attention to such vaccination as a cutting-edge technique against infectious diseases including COVID-19 caused by SARS-CoV-2. While numerous pathogens infect the host through the respiratory mucosa, conventional parenterally administered vaccines are unable to induce protective immunity at mucosal surfaces. Mucosal immunization enables the induction of both mucosal and systemic immunity, efficiently removing pathogens from the mucosa before an infection occurs. Although respiratory mucosal vaccination is highly appealing, successful nasal or pulmonary delivery of nucleic acid-based vaccines is challenging because of several physical and biological barriers at the airway mucosal site, such as a variety of protective enzymes and mucociliary clearance, which remove exogenously inhaled substances. Hence, advanced nanotechnologies enabling delivery of DNA and IVT-mRNA to the nasal and pulmonary mucosa are urgently needed. Ideal nanocarriers for nucleic acid vaccines should be able to efficiently load and protect genetic payloads, overcome physical and biological barriers at the airway mucosal site, facilitate transfection in targeted epithelial or antigen-presenting cells, and incorporate adjuvants. In this review, we discuss recent developments in nucleic acid delivery systems that target airway mucosa for vaccination purposes.

The functional role of sulforaphane in intestinal inflammation: a review

Intestinal inflammation represented by inflammatory bowel disease (IBD) has become a global epidemic disease and the number of patients with IBD continues to increase. This digestive tract disease not only affects the absorption of food components by destroying the intestinal epithelial structure, but also can induce diseases in remote organs via the gut-organ axis, seriously harming human health. Nowadays, increasing attention is being paid to the nutritional and medicinal value of food components with increasing awareness among the general public regarding health. As an important member of the isothiocyanates, sulforaphane (SFN) is abundant in cruciferous plants and is famous for its excellent anti-cancer effects. With the development of clinical research, more physiological activities of SFN, such as antidepressant, hypoglycemic and anti-inflammatory activities, have been discovered, supporting the fact that SFN and SFN-rich sources have great potential to be dietary supplements that are beneficial to health. This review summarizes the characteristics of intestinal inflammation, the anti-inflammatory mechanism of SFN and its various protective effects on intestinal inflammation, and the possible future applications of SFN for promoting intestinal health have also been discussed.

The Roles of Tricellular Tight Junction Protein Angulin-1/Lipolysis-Stimulated Lipoprotein Receptor (LSR) in Endometriosis and Endometrioid-Endometrial Carcinoma

Tight junction proteins play roles beyond permeability barriers functions and control cell proliferation and differentiation. The relation between tight junctions and the signal transduction pathways affects cell growth, invasion and migration. Abnormality of tight junction proteins closely contributes to epithelial mesenchymal transition (EMT) and malignancy of various cancers. Angulin-1/lipolysis-stimulated lipoprotein receptor (LSR) forms tricellular contacts that has a barrier function. Downregulation of angulin-1/LSR correlates with the malignancy in various cancers, including endometrioid-endometrial carcinoma (EEC). These alterations have been shown to link to not only multiple signaling pathways such as Hippo/YAP, HDAC, AMPK, but also cell metabolism in ECC cell line Sawano. Moreover, loss of angulin-1/LSR upregulates claudin-1, and loss of apoptosis stimulating p53 protein 2 (ASPP2) downregulates angulin-1/LSR. Angulin-1/LSR and ASPP2 concentrate at both midbody and centrosome in cytokinesis. In EEC tissues, angulin-1/LSR and ASPP2 are reduced and claudin-2 is overexpressed during malignancy, while in the tissues of endometriosis changes in localization of angulin-1/LSR and claudin-2 are seen. This review highlights how downregulation of angulin-1/LSR promotes development of endometriosis and EEC and discusses about the roles of angulin-1/LSR and its related proteins, including claudins and ASPP2.

CLDN6: From Traditional Barrier Function to Emerging Roles in Cancers

Claudins (CLDNs) are the most important tight junction proteins, which are mainly expressed in endothelial cells or epithelial cells in a tissue-specific manner. As a member of the CLDNs family, CLDN6 is highly expressed in fetal tissues such as the stomach, pancreas, lung, and kidney, but is not expressed in corresponding adult tissues. The expression of CLDN6 is regulated by a variety of factors, including but not limited to stimuli and transcription factors, DNA methylation, and post-translational modifications. CLDN6 has been found to have a key role in the formation of barriers, especially the lung epithelial barrier and the epidermal permeability barrier (EPB). Importantly, the roles of CLDN6 in cancers have gained focus and are being investigated in recent years. Strong evidence indicates that the altered expression of CLDN6 is linked to the development of various cancers. Malignant phenotypes of tumors affected by CLDN6 include proliferation and apoptosis, migration and invasion, and drug resistance, which are regulated by CLDN6-mediated key signaling pathways. Given the important role in tumors and its low or no expression in normal tissues, CLDN6 is an ideal target for tumor therapy. This review aims to provide an overview of the structure and regulation of CLDN6, and its traditional barrier function, with a special emphasis on its emerging roles in cancers, including its impact on the malignant phenotypes, signal-modulating effects, the prognosis of tumor patients, and clinical applications in cancers.

Differential Expression of Claudin in Odontogenic Cysts

Objective  This study aimed to analyze claudin-1, -4, and -7 expression in different types of odontogenic cysts (odontogenic keratocysts [OKCs], dentigerous cysts [DCs], calcifying odontogenic cysts [COCs], and radicular cysts [RCs]) as well as its association with OKC recurrence.

Materials and Methods  Seventy samples of odontogenic cysts samples were immunohistochemically stained to detect claudin-1, -4, and -7 expression. Patient information and OKC recurrence data were recorded. The staining was analyzed semiquantitatively and categorized based on the pattern and percentage of positively stained cystic epithelial cells.

Statistical Analysis  Expression of different claudins between groups was analyzed using the Kruskal–Wallis test with Dunn's test, followed by post hoc pairwise comparison. The association between claudin expression and OKC recurrence was analyzed by the Mann–Whitney U test. Correlations among claudin expression were examined with Spearman's correlation coefficient. Level of significance was at p  < 0.005.

Results  Claudin-1 was widely expressed in every odontogenic cyst. Most DCs (50%) expressed claudin-1 in more than 75% of cells, as did RCs (65%), while most OKCs (50%) expressed claudin-1 in 26 to 50% of cells. Most COCs (50%) expressed claudin-1 in 51 to 75% of cells. Every sample of OKC and RC was positive for claudin-4, but no sample showed staining in more than 51% of cells. Every odontogenic cyst was positive for claudin-7. DCs (35%), OKCs (55%), and RCs (40%) mostly showed staining in 26 to 50% of cells. High claudin-1 expression was shown in COCs, DCs, and RCs, while low expression of claudin-4 was shown in every odontogenic cyst. For claudin-7, the expression is high only in COCs. Claudin-1 and -4 was significantly different among each odontogenic cyst. High expression of claudin-1 was correlated with OKC recurrence. The correlations of claudin-1 with claudin-7 expression and claudin-4 with claudin-7 expression were significant in DCs. In COCs, claudin-1 and claudin-7 expression was significantly correlated.

Conclusions  The expression of claudin-1, -4, and -7 was present in every odontogenic cyst, but the proportion of positive staining cells was different. Expression of claudin-1 is associated with OKC recurrence. Dysregulation of claudin expression may play a pathogenic role in cyst pathogenesis.

Innate Immunity in the Middle Ear Mucosa

Otitis media (OM) encompasses a spectrum of clinical presentations ranging from the readily identifiable Acute OM (AOM), which is characterised by otalgia and fever, to chronic otitis media with effusion (COME) where impaired hearing due to middle ear effusion may be the only clinical symptom. Chronic suppurative OM (CSOM) presents as a more severe form of OM, involving perforation of the tympanic membrane. The pathogenesis of OM in these varied clinical presentations is unclear but activation of the innate inflammatory responses to viral and/or bacterial infection of the upper respiratory tract performs an integral role. This localised inflammatory response can persist even after pathogens are cleared from the middle ear, eustachian tubes and, in the case of respiratory viruses, even the nasal compartment. Children prone to OM may experience an over exuberant inflammatory response that underlies the development of chronic forms of OM and their sequelae, including hearing impairment. Treatments for chronic effusive forms of OM are limited, with current therapeutic guidelines recommending a "watch and wait" strategy rather than active treatment with antibiotics, corticosteroids or other anti-inflammatory drugs. Overall, there is a clear need for more targeted and effective treatments that either prevent or reduce the hyper-inflammatory response associated with chronic forms of OM. Improved treatment options rely upon an in-depth understanding of OM pathogenesis, particularly the role of the host innate immune response during acute OM. In this paper, we review the current literature regarding the innate immune response within the middle ear to bacterial and viral otopathogens alone, and as co-infections. This is an important consideration, as the role of respiratory viruses as primary pathogens in OM is not yet fully understood. Furthermore, increased reporting from PCR-based diagnostics, indicates that viral/bacterial co-infections in the middle ear are more common than bacterial infections alone. Increasingly, the mechanisms by which viral/bacterial co-infections may drive or maintain complex innate immune responses and inflammation during OM as a chronic response require investigation. Improved understanding of the pathogenesis of chronic OM, including host innate immune response within the middle ear is vital for development of improved diagnostic and treatment options for our children.

Altered expression of junctional proteins as a potential biomarker in oral precancerous and cancerous patients

Due to a lower survival rate in patients with advanced clinical stages of oral cancer, discovering a biomarker that could diagnose and predict disease progression is vital. Cell-cell junctional proteins play a crucial role in the maintenance of tissue architecture but are often deregulated in different cancer. The present study investigates the expression of cell-cell junctional proteins viz: e-cadherin (E-cad) and zonula occludens-1 (ZO-1) in oral precancerous (OED) and cancerous (OSCC) patients to monitor if they can serve as practicable molecular markers. The ultrastructural junctional complex was studied by transmission electron microscopy, and the expression of proteins was performed by immunohistochemistry. The relationship between the expression of protein and clinicopathological features of the patients was checked by Pearson's correlation test. Furthermore, the survival curve of the follow-up data was estimated by the Kaplan-Meier method. We observed a disrupted junctional complex and a significantly decreased immunoexpression of E-cad and ZO-1 in OED and OSCC when compared to the adjacent non-cancerous tissues. The expression of ZO-1 was associated with TNM stages, whereas E-cad was associated with histological grades as well as TNM stages. A positive correlation was observed between the expression of ZO-1 and E-cad proteins in OED and OSCC. Further, follow-up studies revealed that high ZO-1 and E-cad expressing patients survived longer than their low expressed counterparts. The present study shows disruption of junctional complex and alteration of junctional proteins expression that could draw the attention of health professionals to explore junctional proteins as a possible therapeutic target in oral cancer.

The Disruption of the Endothelial Barrier Contributes to Acute Lung Injury Induced by Coxsackievirus A2 Infection in Mice

Sporadic occurrences and outbreaks of hand, foot, and mouth disease (HFMD) caused by Coxsackievirus A2 (CVA2) have frequently reported worldwide recently, which pose a great challenge to public health. Epidemiological studies have suggested that the main cause of death in critical patients is pulmonary edema. However, the pathogenesis of this underlying comorbidity remains unclear. In this study, we utilized the 5-day-old BALB/c mouse model of lethal CVA2 infection to evaluate lung damage. We found that the permeability of lung microvascular was significantly increased after CVA2 infection. We also observed the direct infection and apoptosis of lung endothelial cells as well as the destruction of tight junctions between endothelial cells. CVA2 infection led to the degradation of tight junction proteins (e.g., ZO-1, claudin-5, and occludin). The gene transcription levels of von Willebrand factor (vWF), endothelin (ET), thrombomodulin (THBD), granular membrane protein 140 (GMP140), and intercellular cell adhesion molecule-1 (ICAM-1) related to endothelial dysfunction were all significantly increased. Additionally, CVA2 infection induced the increased expression of inflammatory cytokines (IL-6, IL-1β, and MCP-1) and the activation of p38 mitogen-activated protein kinase (MAPK). In conclusion, the disruption of the endothelial barrier contributes to acute lung injury induced by CVA2 infection; targeting p38-MAPK signaling may provide a therapeutic approach for pulmonary edema in critical infections of HFMD.

LRRC19 Promotes Permeability of the Gut Epithelial Barrier Through Degrading PKC-ζ and PKCι/λ to Reduce Expression of ZO1, ZO3, and Occludin

BACKGROUND

A dysfunctional gut epithelial barrier allows the augmented permeation of endotoxins, luminal antigens, and bacteria into the bloodstream, causing disease. The maintenance of gut epithelial barrier integrity may be regulated by multiple factors. Herein we analyze the role of leucine-rich repeat-containing protein 19 (LRRC19) in regulating the permeability of the gut epithelial barrier.

METHODS

We utilized Lrrc19 knockout (KO) mice and clinical samples through transmission electron, intestinal permeability assay, Western blot, and immunofluorescence staining to characterize the role of LRRC19 in the permeability of the gut epithelial barrier.

RESULTS

We found that LRRC19, which is expressed in gut epithelial cells, impairs gut barrier function. Transmission electron micrographs revealed a tighter junction and narrower gaps in the colon epithelium cells in LRRC19 KO mice. There were lower levels of serum lipopolysaccharide and 4 kDa-fluorescein isothiocyanate-dextran after gavage in LRRC19 KO mice than in wild-type mice. We found that LRRC19 could reduce the expression of zonula occludens (ZO)-1, ZO-3, and occludin in the colonic epithelial cells. The decreased expression of ZO-1, ZO-3, and occludin was dependent on degrading protein kinase C (PKC) ζ and PKCι/λ through K48 ubiquitination by LRRC19. The expression of LRRC19 was also negatively correlated with ZO-1, ZO-3, occludin, PKCζ, and PKCι/λ in human colorectal cancers.

CONCLUSIONS

The protein LRRC19 can promote the permeability of the gut epithelial barrier through degrading PKC ζ and PKCι/λ to reduce the expression of ZO-1, ZO-3, and occludin.

Super-resolved local recruitment of CLDN5 to filtration slits implicates a direct relationship with podocyte foot process effacement

Under healthy conditions, foot processes of neighbouring podocytes are interdigitating and connected by an electron‐dense slit diaphragm. Besides slit diaphragm proteins, typical adherens junction proteins are also found to be expressed at this cell‐cell junction. It is therefore considered as a highly specialized type of adherens junction. During podocyte injury, podocyte foot processes lose their characteristic 3D structure and the filtration slits typical meandering structure gets linearized. It is still under debate how this change of structure leads to the phenomenon of proteinuria. Using super‐resolution 3D‐structured illumination microscopy, we observed a spatially restricted up‐regulation of the tight junction protein claudin‐5 (CLDN5) in areas where podocyte processes of patients suffering from minimal change disease (MCD), focal and segmental glomerulosclerosis (FSGS) as well as in murine nephrotoxic serum (NTS) nephritis and uninephrectomy DOCA‐salt hypertension models, were locally injured. CLDN5/nephrin ratios in human glomerulopathies and NTS‐treated mice were significantly higher compared to controls. In patients, the CLDN5/nephrin ratio is significantly correlated with the filtration slit density as a foot process effacement marker, confirming a direct association of local CLDN5 up‐regulation in injured foot processes. Moreover, CLDN5 up‐regulation was observed in some areas of high filtration slit density, suggesting that CLND5 up‐regulation preceded the changes of foot processes. Therefore, CLDN5 could serve as a biomarker predicting early foot process effacement.

The blood-brain and gut-vascular barriers: from the perspective of claudins

In some organs, such as the brain, endothelial cells form a robust and highly selective blood-to-tissue barrier. However, in other organs, such as the intestine, endothelial cells provide less stringent permeability, to allow rapid exchange of solutes and nutrients where needed. To maintain the structural and functional integrity of the highly dynamic blood–brain and gut–vascular barriers, endothelial cells form highly specialized cell-cell junctions, known as adherens junctions and tight junctions. Claudins are a family of four-membrane-spanning proteins at tight junctions and they have both barrier-forming and pore-forming properties. Tissue-specific expression of claudins has been linked to different diseases that are characterized by barrier impairment. In this review, we summarize the more recent progress in the field of the claudins, with particular attention to their expression and function in the blood–brain barrier and the recently described gut–vascular barrier, under physiological and pathological conditions.

Abbreviations: 22q11DS 22q11 deletion syndrome; ACKR1 atypical chemokine receptor 1; AD Alzheimer disease; AQP aquaporin; ATP adenosine triphosphate; Aβ amyloid β; BAC bacterial artificial chromosome; BBB blood-brain barrier; C/EBP-α CCAAT/enhancer-binding protein α; cAMP cyclic adenosine monophosphate (or 3ʹ,5ʹ-cyclic adenosine monophosphate); CD cluster of differentiation; CNS central nervous system; DSRED discosoma red; EAE experimental autoimmune encephalomyelitis; ECV304 immortalized endothelial cell line established from the vein of an apparently normal human umbilical cord; EGFP enhanced green fluorescent protein; ESAM endothelial cell-selective adhesion molecule; GLUT-1 glucose transporter 1; GVB gut-vascular barrier; H2B histone H2B; HAPP human amyloid precursor protein; HEK human embryonic kidney; JACOP junction-associated coiled coil protein; JAM junctional adhesion molecules; LYVE1 lymphatic vessel endothelial hyaluronan receptor 1; MADCAM1 mucosal vascular addressin cell adhesion molecule 1; MAPK mitogen-activated protein kinase; MCAO middle cerebral artery occlusion; MMP metalloprotease; MS multiple sclerosis; MUPP multi-PDZ domain protein; PATJ PALS-1-associated tight junction protein; PDGFR-α platelet-derived growth factor receptor α polypeptide; PDGFR-β platelet-derived growth factor receptor β polypeptide; RHO rho-associated protein kinase; ROCK rho-associated, coiled-coil-containing protein kinase; RT-qPCR real time quantitative polymerase chain reactions; PDGFR-β soluble platelet-derived growth factor receptor, β polypeptide; T24 human urinary bladder carcinoma cells; TG2576 transgenic mice expressing the human amyloid precursor protein; TNF-α tumor necrosis factor α; WTwild-type; ZO zonula occludens.

Thiamine Alleviates High-Concentrate-Diet-Induced Oxidative Stress, Apoptosis, and Protects the Rumen Epithelial Barrier Function in Goats

High-concentrate diets are continually used in ruminants to meet the needs of milk yield, which can lead to the occurrence of subacute rumen acidosis in ruminants. This study investigated the protective effects of dietary thiamine supplementation on the damage of the ruminal epithelium barrier function in goats fed a high-concentrate diet. Twenty-four healthy Boer goats (live weight of 35.62 ± 2.4 kg; age, 1 year) were randomly assigned into three treatments, with eight goats in each treatment, consuming one of three diets: a low-concentrate diet (CON; concentrate/forage, 30:70), a high-concentrate diet (HC; concentrate/forage, 70:30), or a high-concentrate diet with 200 mg of thiamine/kg of dry matter intake (HCT; concentrate/forage, 70:30) for 12 weeks. The additional dose of thiamine was based on our previous study wherein thiamine ameliorates inflammation. Compared with HC treatment, the HCT treatment had markedly higher concentrations of glutathione, superoxide dismutase, and glutathione peroxidase and total antioxidant capacity (P < 0.05) in plasma and rumen epithelium. The results showed that the apoptosis index was lower (P < 0.05) in the HCT treatment than in that of the HC treatment. Compared with the HC treatment, permeability and the electrophysiology parameter short circuit current for ruminal epithelial tissue were significantly decreased (P < 0.05) in the HCT treatment. The immunohistochemical results showed that the expression distribution of tight junctions including claudin-1, claudin-4, occludin, and zonula occludin-1 (ZO-1) was greater (P < 0.05) in the HCT treatments than in the HC treatment. The mRNA expression in the rumen epithelium of ZO-1, occludin, claudin-1, B-cell lymphoma/leukemia 2, nuclear factor erythroid-2 related factor 2 (Nrf2), superoxide dismutase 2 (SOD2), glutathione peroxidase 1, and the phase II metabolizing enzymes quinone oxidoreductase and heme oxygenase in the HCT group was significantly increased in comparison with the HC diet treatment (P < 0.05), whereas the mRNA expression of caspase 3, caspase 8, caspase 9, bcl-2 associated X protein, lipopolysaccharide binding protein, toll-like receptor 4, nuclear factor kappa-B (NFκB), tumor necrosis factor alpha, interleukin-1β, interleukin, and tumor necrosis factor receptor-associated factor 6 decreased significantly in the HCT treatment (P < 0.05). Compared with the HC treatment, the HCT diet significantly increased the protein expression of ZO-1, occludin, claudin-1, NQO1, HO-1, SOD2, serine/threonine kinase, p-Akt, Nrf2, and p-Nrf2; conversely, the expression of NFκB-related proteins p65 and pp65 was significantly decreased (P < 0.05). In addition, thiamine relieved the damage on the ruminal epithelium caused by the HC diet. The results show that dietary thiamine supplementation improves the rumen epithelial barrier function by regulating Nrf2-NFκB signaling pathways during high-concentrate-diet feeding.

EXOC1 plays an integral role in spermatogonia pseudopod elongation and spermatocyte stable syncytium formation in mice

The male germ cells must adopt the correct morphology at each differentiation stage for proper spermatogenesis. The spermatogonia regulates its differentiation state by its own migration. The male germ cells differentiate and mature with the formation of syncytia, failure of forming the appropriate syncytia results in the arrest at the spermatocyte stage. However, the detailed molecular mechanisms of male germ cell morphological regulation are unknown. Here, we found that EXOC1, a member of the Exocyst complex, is important for the pseudopod formation of spermatogonia and spermatocyte syncytia in mice. EXOC1 contributes to the pseudopod formation of spermatogonia by inactivating the Rho family small GTPase Rac1 and also functions in the spermatocyte syncytia with the SNARE proteins STX2 and SNAP23. Since EXOC1 is known to bind to several cell morphogenesis factors, this study is expected to be the starting point for the discovery of many morphological regulators of male germ cells.

Chimeric Claudins: A New Tool to Study Tight Junction Structure and Function

The tight junction (TJ) is a structure composed of multiple proteins, both cytosolic and membranal, responsible for cell–cell adhesion in polarized endothelium and epithelium. The TJ is intimately connected to the cytoskeleton and plays a role in development and homeostasis. Among the TJ’s membrane proteins, claudins (CLDNs) are key to establishing blood–tissue barriers that protect organismal physiology. Recently, several crystal structures have been reported for detergent extracted recombinant CLDNs. These structural advances lack direct evidence to support quaternary structure of CLDNs. In this article, we have employed protein-engineering principles to create detergent-independent chimeric CLDNs, a combination of a 4-helix bundle soluble monomeric protein (PDB ID: 2jua) and the apical—50% of human CLDN1, the extracellular domain that is responsible for cell–cell adhesion. Maltose-binding protein-fused chimeric CLDNs (MBP-CCs) used in this study are soluble proteins that retain structural and functional aspects of native CLDNs. Here, we report the biophysical characterization of the structure and function of MBP-CCs. MBP-fused epithelial cadherin (MBP-eCAD) is used as a control and point of comparison of a well-characterized cell-adhesion molecule. Our synthetic strategy may benefit other families of 4-α-helix membrane proteins, including tetraspanins, connexins, pannexins, innexins, and more.

Environmental contaminant BPA causes intestinal damage by disrupting cellular repair and injury homeostasis in vivo and in vitro

Our previous studies have shown that the environmental contaminant bisphenol A (BPA) exhibits strong intestinal toxicity and can readily cause intestinal barrier dysfunction. However, the causal relationship between adverse biological processes of BPA-induced intestinal tissue and the role of key signaling molecules in it requires further investigation. In this study, we established a mouse and intestinal epithelial cell model of BPA treatment to determine the underlying molecular mechanisms of BPA-induced intestinal injury. The results showed that the BPA treatment increased the intestinal permeability and disrupted the barrier function by increasing the chemical marker content and tight junction expression in intestinal tissues and blood circulation. BPA also altered the oxidative and antioxidant status of intestinal epithelial cells by increasing ROS and RNS contents and decreasing the activity levels of SOD, GPx, CAT, and T-AOC. BPA further induced inflammatory responses by upregulating the gene abundance of key factors of the innate immune system (TLR2, TLR4, MyD88, and NF-κB), the transcriptional activity of NF-kB, and the secretion of pro-inflammatory cytokines (IL-1β, IL-6, IL-8, and TNF-α). Moreover, apoptosis was activated by BPA, whereas cell proliferation was inhibited by BPA. Mechanistically, co-treatment of intestinal epithelial cells with BPA using the oxidative stress scavenger NAC, the NF-κB-specific inhibitor JSH-23, and the apoptosis inhibitor Z-VAD-FMK, respectively, showed that BPA activates the innate immune response by inducing oxidative stress. Consequently, apoptosis is promoted, and cell proliferation is inhibited, ultimately disrupting the intestinal barrier function. Our findings provide insight into the pathogenesis of BPA-induced gut injury.

Differential Splicing of Skipped-exons Predicts Drug Response in Cancer Cell Lines

Alternative splicing of pre-mRNA transcripts is an important regulatory mechanism that increases the diversity of gene products in eukaryotes. Various studies have linked specific transcript isoforms to altered drug response in cancer; however, few algorithms have incorporated splicing information into drug response prediction. In this study, we evaluated whether basal-level splicing information could be used to predict drug sensitivity by constructing doxorubicin-sensitivity classification models with splicing and expression data. We detailed splicing differences between sensitive and resistant cell lines by implementing quasi-binomial generalized linear modeling (QBGLM) and found altered inclusion of 277 skipped exons. We additionally conducted RNA-binding protein (RBP) binding motif enrichment and differential expression analysis to characterize cis- and trans-acting elements that potentially influence doxorubicin response-mediating splicing alterations. Our results showed that a classification model built with skipped exon data exhibited strong predictive power. We discovered an association between differentially spliced events and epithelial-mesenchymal transition (EMT) and observed motif enrichment, as well as differential expression of RBFOX and ELAVL RBP family members. Our work demonstrates the potential of incorporating splicing data into drug response algorithms and the utility of a QBGLM approach for fast, scalable identification of relevant splicing differences between large groups of samples.

Down-Regulation of Claudin-2 Expression by Cyanidin-3-Glucoside Enhances Sensitivity to Anticancer Drugs in the Spheroid of Human Lung Adenocarcinoma A549 Cells

Claudin-2 (CLDN2), an integral membrane protein located at tight junctions, is abnormally expressed in human lung adenocarcinoma tissues, and is linked to drug resistance in human lung adenocarcinoma A549 cells. CLDN2 may be a target for the prevention of lung adenocarcinoma, but there are few compounds which can reduce CLDN2 expression. We found that cyanidin-3-glucoside (C3G), the anthocyanin with two hydroxyl groups on the B-ring, and cyanidin significantly reduce the protein level of CLDN2 in A549 cells. In contrast, pelargonidin-3-glucoside (P3G), the anthocyanin with one hydroxyl group on the B-ring, had no effect. These results suggest that cyanidin and the hydroxyl group at the 3-position on the B-ring play an important role in the reduction of CLDN2 expression. The phosphorylation of Akt, an activator of CLDN2 expression at the transcriptional level, was inhibited by C3G, but not by P3G. The endocytosis and lysosomal degradation are suggested to be involved in the C3G-induced decrease in CLDN2 protein expression. C3G increased the phosphorylation of p38 and the p38 inhibitor SB203580 rescued the C3G-induced decrease in CLDN2 expression. In addition, SB203580 rescued the protein stability of CLDN2. C3G may reduce CLDN2 expression at the transcriptional and post-translational steps mediated by inhibiting Akt and activating p38, respectively. C3G enhanced the accumulation and cytotoxicity of doxorubicin (DXR) in the spheroid models. The percentages of apoptotic and necrotic cells induced by DXR were increased by C3G. Our data suggest that C3G-rich foods can prevent the chemoresistance of lung adenocarcinoma A549 cells through the reduction of CLDN2 expression.