A review on the effect of Claudin-18 on bronchopulmonary dysplasia in preterm infants / 中国当代儿科杂志

Bronchopulmonary dysplasia (BPD) has the main manifestations of pulmonary edema in the early stage and characteristic alveolar obstruction and microvascular dysplasia in the late stage, which may be caused by structural and functional destruction of the lung epithelial barrier. The Claudin family is the main component of tight junction and plays an important role in regulating the permeability of paracellular ions and solutes. Claudin-18 is the only known tight junction protein solely expressed in the lung. The lack of Claudin-18 can lead to barrier dysfunction and impaired alveolar development, and the knockout of Claudin-18 can cause characteristic histopathological changes of BPD. This article elaborates on the important role of Claudin-18 in the development and progression of BPD from the aspects of lung epithelial permeability, alveolar development, and progenitor cell homeostasis, so as to provide new ideas for the pathogenesis and clinical treatment of BPD.

Expressão de e-caderina e claudina-3 no epitélio cólico após terapia com infliximabe: modelo experimental de colite de exclusão / Expression of e-cadherin and claudin-3 in the colonic epithelium after the infliximab therapy: experimental model of disuse colitis

RESUMO - RACIONAL: A etiopatogenia da colite por desuso (DC) ainda não foi totalmente elucidada. As principais teorias consideram que a doença pode estar relacionada ao aumento de bactérias anaeróbias, falta de suprimento de ácidos graxos de cadeia curta (AGCC) e distúrbios imunológicos que se desenvolvem em segmentos colorretais desprovidos de trânsito fecal. OBJETIVO: Verificar se a aplicação de infliximabe modifica o conteúdo tecidual das proteínas E-caderina e claudina-3 no epitélio cólico de ratos sem trânsito intestinal. MÉTODOS: Vinte dois ratos foram submetidos a derivação do trânsito intestinal pelo procedimento de Hartmann. Eles permaneceram com o ostoma por 12 semanas para permitir o desenvolvimento da colite de exclusão. Em seguida, foram divididos em três grupos experimentais: seis animais receberam 2,0 ml de solução salina/semana, oito infliximabe na dose de 5 mg/Kg/semana e, os demais, infliximabe na dose de 10 mg/Kg/semana por 5 semanas consecutivas. Em seguida, os animais foram eutanasiados e os segmentos cólicos com e sem trânsito intestinal foram removidos. A colite por desuso foi diagnosticada pelas alterações histológicas definidas por uma escala previamente validada. Expressão tecidual de E-caderina e claudina-3 foi avaliada por imuno-histoquímica, e o conteúdo tecidual de ambas as proteínas foi quantificado por análise de imagem assistida por computador. RESULTADOS: Segmentos cólicos exclusos de trânsito fecal apresentaram maior grau de inflamação do que os expostos ao trânsito fecal. Inflamação foi menor nos animais tratados com infliximabe, independente da dose utilizada. Níveis de E-caderina e claudina-3 estavam reduzidos no cólon excluso. O tratamento com infliximabe aumentou os níveis das proteínas em segmentos do cólon sem trânsito intestinal, principalmente nos animais que receberam a dose de 10mg/kg/semana. CONCLUSÃO: Infliximabe reduz inflamação nos segmentos do cólon excluso e aumenta o conteúdo tecidual de E-caderina e claudina-3, especialmente na concentração de 10mg/kg/semana.

ABSTRACT - BACKGROUND: The etiopathogenesis of disuse colitis (DC) has not yet been fully elucidated. The main theories consider that the disease may be related to an increase in anaerobic bacteria, the lack of short-chain fatty acid (SCFA) supply, and immunological disorders that develop in the colorectal segments devoid of fecal transit. AIM: The aim of this study was to verify whether the application of infliximab modifies the tissue content of E-cadherin and claudin-3 proteins in colonic epithelium of rats devoid of intestinal transit. METHODS: A total of 22 rats underwent intestinal transit bypass using Hartmann's procedure. They remained with the shunt for 12 weeks to allow the development of DC. Later, they were divided into three experimental groups: six animals received 2.0 mL saline solution/week, eight received infliximab at a dose of 5 mg/kg/week, and eight received infliximab at a dose of 10 mg/kg/week for 5 consecutive weeks. At the end of this period, the animals were euthanized, and the colonic segments with and without intestinal transit were removed. DC was diagnosed based on the histological changes defined by a previously validated scale. The tissue expression of E-cadherin and claudin-3 was assessed by immunohistochemistry, and the tissue content of both proteins was quantified by computer-aided image analysis. RESULTS: The colonic segments excluded from fecal transit showed a higher degree of inflammation than those exposed to fecal transit. The degree of inflammation was lower in animals treated with infliximab, regardless of the dose used. The levels of E-cadherin and claudin-3 were reduced in the excluded colon. Treating animals with infliximab increased the levels of both proteins in the colonic segments without intestinal transit, especially in animals receiving a dose of 10 mg/kg/week. CONCLUSION: Infliximab therapy reduces inflammation in the colonic segments excluded from intestinal transit and increases the tissue content of E-cadherin and claudin-3 proteins, especially when used at a concentration of 10 mg/kg/week.

Claudin-1 and Claudin-3 as Molecular Regulators of Myelination in Leukoaraiosis Patients

OBJECTIVES: Leukoaraiosis is described as white matter lesions that are associated with cognitive dysfunction, neurodegenerative disorders, etc. Myelin depletion is a salient pathological feature of, and the loss of oligodendrocytes is one of the most robust alterations evident in, white matter degeneration. Recent studies have revealed that claudin proteins are aberrantly expressed in leukoaraiosis and regulate oligodendrocyte activity. However, the roles of claudin-1 and claudin-3 in oligodendrocytes and leukoaraiosis are still not well-defined. METHODS: Quantitative polymerase chain reaction was used to measure the expression of claudin-1 (CLDN1), claudin-3 (CLDN3), and myelinogenesis-related genes such as myelin basic protein (MBP), proteolipid protein (PLP), oligodendrocyte transcription factor 2 (OLIG2), and SRY-box transcription factor 10 (SOX10) in leukoaraiosis patients (n=122) and healthy controls (n=122). The expression of claudin-1 and claudin-3 was either ectopically silenced or augmented in Oli-neu oligodendrocytes, and colony formation, apoptosis, and migration assays were performed. Finally, the expression of myelin proteins was evaluated by western blotting. RESULTS: Our results revealed that in addition to SOX10, the expression levels of claudin-1, claudin-3, and myelinogenesis-related proteins were prominently downregulated in leukoaraiosis patients, compared to those in healthy controls. Furthermore, the growth and migration of Oli-neu cells were downregulated upon silencing claudin-1 or claudin-3. However, the overexpression of claudin-1 or claudin-3 resulted in the reduction of the degree of apoptosis in Oli-neu cells. In addition, claudin-1 and claudin-3 promoted the expression of MBP, OLIG2, PLP, and SOX10 at the translational level. CONCLUSION: Our data has demonstrated that the abnormal expression of claudin-1 and claudin-3 regulates the pathological progression of leukoaraiosis by governing the viability and myelination of oligodendrocytes. These findings provide novel insights into the regulatory mechanisms underlying the roles of claudin-1 and claudin-3 in leukoaraiosis.

Additive Effects of Rebamipide Plus Proton Pump Inhibitors on the Expression of Tight Junction Proteins in a Rat Model of Gastro-Esophageal Reflux Disease

BACKGROUND/AIMS: The aim of this study was to investigate the effects of rebamipide on tight junction proteins in the esophageal mucosa in a rat model of gastroesophageal reflux disease (GERD). METHODS: GERD was created in rats by tying the proximal stomach. The rats were divided into a control group, a proton pump inhibitor (PPI) group, and a PPI plus rebamipide (PPI+R) group. Pantoprazole (5 mg/kg) was administered intraperitoneally to the PPI and PPI+R groups. An additional dose of rebamipide (100 mg/kg) was administered orally to the PPI+R group. Mucosal erosions, epithelial thickness, and leukocyte infiltration into the esophageal mucosa were measured in isolated esophagi 14 days after the procedure. A Western blot analysis was conducted to measure the expression of claudin-1, -3, and -4. RESULTS: The mean surface area of mucosal erosions, epithelial thickness, and leukocyte infiltration were lower in the PPI group and the PPI+R group than in the control group. Western blot analysis revealed that the expression of claudin-3 and -4 was significantly higher in the PPI+R group than in the control group. CONCLUSIONS: Rebamipide may exert an additive effect in combination with PPI to modify the tight junction proteins of the esophageal mucosa in a rat model of GERD. This treatment might be associated with the relief of GERD symptoms.

Claudin-3 and occludin content in the glands of colonic mucosa devoid from fecal stream submitted to topical intervention with oil extract of Curcuma longa

Abstract Purpose: To evaluate the inflammatory intensity and measure the tissue content of the proteins claudin-3 and occludin in the colonic mucosa without fecal stream submit to intervention with curcumin. Methods: Thirty-six rats were submitted to a proximal colostomy and a distal mucous fistula and divided into two groups according to sacrifice to be performed two or four weeks. Each group was divided into three subgroups according daily application of enemas containing saline, curcumin at 50 mg/kg/day or 200 mg/kg/day. Colitis was diagnosed by histological analysis. Claudin-3 and occludin were determined by immunohistochemistry. The tissue content of claudin-3 and occludin were quantified by computer-assisted image analysis. Mann-Whitney, Student t and ANOVA tests were used to analyze the results establishing the level of significance of 5% for both (p<0.05). Results: Curcumin at both concentrations reduces the inflammation and preserves the tissue content of the proteins claudin-3 and occludin, which was related to the concentration used and to the time of the intervention. Conclusion: The application of enemas with curcumin reduces inflammation and preserves the tissue content of the proteins claudin-3 and occludin in the colonic mucosa devoid from the fecal stream.

A N-glicosilação do EGFR afeta a sinalização intracelular e a estabilidade das Junções Tight em células de câncer colorretal / [ EGFR N-glycosylation affects intracellular signaling and stability of Tight Junctions in Colorectal Cancer Cells]

Introdução: O câncer colorretal (CCR) constitui um importante problema de saúde pública no Brasil e no mundo. Durante a progressão de tumores epiteliais, como o CCR, é frequentemente observada uma desestabilização do complexo juncional apical, composto pelas junções tight (JT) e junções aderentes (JA). O aumento dos níveis de expressão das claudinas, principais proteínas transmembranas constituintes das JT, induz a perda da sua função de barreira e aumenta o potencial maligno das células do CCR. Embora cada vez mais estudos estejam focados em compreender melhor os aspectos moleculares que regulam a estabilidade das TJ, o papel desempenhado por N-glicanos neste processo continua sendo pouco explorado. Objetivo: Assim, o objetivo do presente estudo foi investigar o papel dos N-glicanos na regulação da estabilidade das JT em CCR. Materiais e Métodos: Utilizando a linhagem celular HCT-116 (carcinoma colorretal humano), foi avaliado o efeito do tratamento com dois inibidores de biossíntese de N-glicanos, swainsonina (SW) e tunicamicina (Tun), sobre a estabilidade das JT mediante: citometria de fluxo, Western blot, microscopia eletrônica de transmissão, co-imunoprecipitação e imunofluorescência. A expressão de ácido siálico na superfície celular também foi inibida utilizando análogo fluorinado de ácido siálico (Sia-F). Além disso, foram avaliados o grau de N-glicosilação do Receptor do Fator de Crescimento Epidérmico (EGFR) e os níveis de expressão de claudina-3 (cld-3) em tecidos de pacientes com CCR (n = 21) por imunohistoquímica e Western blot (Protocolo-CEP nº: 84/04). Para este estudo foram consultadas bases de dados internacionais (NCBI e TCGA) a fim de identificar os sítios de N-glicosilação (Asn-XSer/Thr) do EGFR e relatos de mutações nestes sítios em CCR. Utilizando um algoritmo classificador de subtipos de CCR foi avaliada também a expressão de glicogenes e de cld-3 em quatro subtipos moleculares de CCR. Ministério da Saúde Instituto Nacional de Câncer Coordenação de Pós-graduação Resultados: Primeiramente, foi avaliado o efeito de SW e Tun na expressão proteica de vários constituintes das TJ. Foi observado que apenas o tratamento com Tun diminuiu os níveis de expressão de cld-3. A Tun também promoveu, concomitantemente, diminuição dos níveis de fosforilação de proteínas na faixa de peso molecular da cld-3 (22kDa) e reorganização da sua localização celular do citoplasma à membrana. Os resultados mostraram que, após o tratamento com Tun, as células HCT-116 desenvolveram contatos celulares mais estabelecidos. Além disso, a deglicosilação do EGFR promoveu redução dos seus níveis de expressão na membrana celular e também diminuiu tanto os seus níveis de ativação quanto a fosforilação das proteínas downstream ERK e AKT. Foi observado que o tratamento com Sia-F diminuiu tanto a ativação de EGFR quanto os níveis de expressão de cld-3. Os resultados mostraram também que tumores de pacientes com CCR, que expressavam maiores níveis proteicos de cld-3 do que os respectivos tecidos normais adjacentes, exibiram também um maior grau de N-glicosilação do EGFR. Finalmente, não foram encontrados relatos de mutações em sítios de N-glicosilação do EGFR em CCR, porém, foram encontradas diferenças na expressão de glicogenes e de cld-3 entre os quatro subtipos moleculares de CCR. Conclusão: Conjuntamente, os resultados demonstram que a N-glicosilação do EGFR desempenha um papel na regulação da cld-3, contribuindo para uma melhor compreensão da biologia do CCR. Estes achados também sugerem um potencial significado clínico de alterações no padrão de N-glicosilação do EGFR.

Changes in tight junction protein expression and permeability of colon mucosa in rats with dextran sulfate sodium-induced inflammatory bowel disease / 中国当代儿科杂志

<p><b>OBJECTIVE</b>To develop an experimental rat model of inflammatory bowel disease (IBD) by administration of dextran sulfate sodium (DSS), and to observe changes in the tight junction protein expression and permeability of colon mucosa.</p><p><b>METHODS</b>Male Sprague-Dawley (SD) rats were randomly divided into control (n=27) and IBD model groups (n=27). In the IBD model group, IBD was induced by 6-day administration of 3% DSS in water followed by 14-day administration of water only. The control group was fed with water only. Pathological changes in colon mucosae were observed on days 7, 14 and 21 after DSS administration. Colon tissue specimens were collected on day 21 for measuring myeloperoxidase (MPO) activity. The transepithelial electric resistance (TEER), transepithelial potential difference (TEPD) and short circuit current (Isc) of the specimens were measured by Ussing chamber. Real-time PCR and Western blot were used to measure the mRNA and protein expression of tight junction proteins in colon epithelia.</p><p><b>RESULTS</b>In the IBD model group, diarrhea, hemafecia and weight loss were seen. Inflammation occurred mainly in the distal colon and was characterized by crypt abscess and inflammatory cell infiltration. The IBD model group showed significantly increased MPO activity (P<0.01), significantly decreased TEER (P<0.01) and TEPD (P<0.01), and significantly increased Isc (P<0.01) compared with the control group. No claudin 2 expression of mRNA and protein was detected in the control group, and they were expressed in the IBD model group. The expression levels of claudin 3, occludin and ZO-1 in the IBD model group were significantly decreased compared with in the control group (P<0.01).</p><p><b>CONCLUSIONS</b>IBD rats show colonic barrier dysfunction and changes in the expression of tight junction proteins. The changes in the expression of tight junction proteins may contribute to colonic barrier dysfunction in cases of IBD in the chronic recovery stage.</p>

Target-specific cytotoxic activity of recombinant fusion toxin C-CPE-ETA' against CLDN-3,4-overexpressing ovarian cancer cells / 中华肿瘤杂志

<p><b>OBJECTIVE</b>The aim of this study was to explore the possibility of creating a toxin, C-CPE-ETA', by fusing C-terminal high affinity binding domain of CPE (C-CPE) with a truncated form of Pseudomonas aeruginosa exotoxin A (ETA') and to examine whether C-CPE-ETA' could specifically target CLDN-3, 4 molecule and the targeted toxin was cytotoxic against CLDN-3,4-overexpressing ovarian cancer.</p><p><b>METHODS</b>CLDN-3 and CLDN-4 expressions were analyzed at the mRNA level in three ovarian cancer cell lines and epithelial ovarian cancer tissues from 20 patients. After transforming an expression plasmid of C-CPE-ETA' into E. coli BL21 (DE3) plysS strain, the recombinant protein was purified using His-Bind resin chromatography column and analyzed by Western blot and Coomassie blue staining. The specific binding, proapoptotic and cytolytic activities were evaluated by flow cytometry, fluorescence microscopy with the JC-1 probe and MTT assay in CLDN-3,4-overexpressing ovarian cancer cells.</p><p><b>RESULTS</b>Quantitive RT-PCR results showed there existed high levels of CLDN-3 and CLDN-4 in ovarian cancer cells, CAOV3, OVCAR3 and SKOV3. Moreover, high expressions of CLDN-3 and CLDN-4 were observed in 90.0% (18/20) and 60.0% (12/20) of ovarian cancer tissues, with an expression level 10-fold higher than that in the normal ovarian tissue. A 58 000 recombinant protein C-CPE-ETA' was demonstrated by Western blot and Coomassie blue staining. Purified and recombinant C-CPE-ETA' was bound with high affinity to CLDN-3,4-overexpressing ovarian cancer cells, CAOV3, OVCAR3 and SKOV3 cells. C-CPE-ETA' was strongly proapoptotic and cytotoxic towards the CLDN-3,4-overexpressing ovarian cancer cells. The concentration of IC(50) was 7.364 ng/ml for CAOV3 cells, 8.110 ng/ml for OVCAR3 cells and 22.340 ng/ml for SKOV3 cells, respectively. However, control CLDN-3,4-deficient cell line HUVEC was not susceptible to the recombinant C-CPE-ETA' at a concentration up to 10 µg/ml.</p><p><b>CONCLUSIONS</b>The C-CPE-ETA' protein exhibits remarkably specific cytotoxicity for CLDN-3,4-overexpressing ovarian cancer cells. Its therapeutic potential warrants further development for ovarian cancer molecular targeted therapy.</p>

Changes of tight junction claudin-1,-3,-4 protein expression in the intestinal mucosa in patients with irritable bowel syndrome / 南方医科大学学报

<p><b>OBJECTIVE</b>To investigate the changes of intestinal mucosal tight junction proteins claudin-1, -3, -4 in patients with irritable bowel syndrome (IBS), and elucidate its possible role in the bowel evacuation habit changes and formation in these patients.</p><p><b>METHODS</b>Western blotting was employed to determine tight junction protein claudin-1,-3,-4 levels in the intestinal mucosa of patients in the control group, diarrhea-predominant IBS (D-IBS) group and constipation-predominant IBS (C-IBS) group.</p><p><b>RESULTS</b>Compared with the control group, D-IBS patients showed significantly decreased claudin-1 protein levels in both the small intestinal and colonic mucosae (P<0.05), whereas C-IBS patients had significantly elevated claudin-1 protein levels (P<0.05). No significant difference was found in claudin-3 protein expression in the both small intestinal and colonic mucosae between the D-IBS group and the control group (P>0.05), but claudin-3 protein level was shown to increase significantly in C-IBS patients (P<0.05). Claudin-4 protein followed the same pattern of alteration as claudin-1.</p><p><b>CONCLUSION</b>Down-regulated claudin-1 and -4 expressions can be associated with bowel evacuation habit changes and formation in patients with D-IBS, but up-regulated claudin-1, -3 and -4 expressions may relate to such bowel changes in patients with C-IBS.</p>