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.
Bronchopulmonary Dysplasia/etiology* ; Claudin-3 ; Claudins/genetics* ; Humans ; Infant ; Infant, Newborn ; Infant, Premature ; Lung ; Tight Junctions

BACKGROUNDClaudin-5, claudin-9, and claudin-11 are expressed in endothelial cells to constitute tight junctions, and their deficiency may lead to hyperpermeability, which is the initiating process and pathological basis of cardiovascular disease. Although tongxinluo (TXL) has satisfactory antianginal effects, whether and how it modulates claudin-5, claudin-9, and claudin-11 in hypoxia-stimulated human cardiac microvascular endothelial cells (HCMECs) have not been reported.

METHODSIn this study, HCMECs were stimulated with CoCl2to mimic hypoxia and treated with TXL. First, the messenger RNA (mRNA) expression of claudin-5, claudin-9, and claudin-11 was confirmed. Then, the protein content and distribution of claudin-9, as well as cell morphological changes were evaluated after TXL treatment. Furthermore, the distribution and content histone H3K9 acetylation (H3K9ac) in the claudin-9 gene promoter, which guarantees transcriptional activation, were examined to explore the underlying mechanism, by which TXL up-regulates claudin-9 in hypoxia-stimulated HCMECs.

RESULTSWe found that hypoxia-suppressed claudin-9 gene expression in HCMECs (F = 7.244; P = 0.011) and the hypoxia-suppressed claudin-9 could be reversed by TXL (F = 61.911; P = 0.000), which was verified by its protein content changes (F = 29.142; P = 0.000). Moreover, high-dose TXL promoted the cytomembrane localization of claudin-9 in hypoxia-stimulated HCMECs, with attenuation of cell injury. Furthermore, high-dose TXL elevated the hypoxia-inhibited H3K9ac in the claudin-9 gene promoter (F = 37.766; P = 0.000), activating claudin-9 transcription.

CONCLUSIONSThe results manifested that TXL reversed the hypoxia-suppressed claudin-9 by elevating H3K9ac in its gene promoter, playing protective roles in HCMECs.

Cell Hypoxia ; Cells, Cultured ; Claudins ; analysis ; genetics ; Drugs, Chinese Herbal ; pharmacology ; Endothelial Cells ; drug effects ; metabolism ; Histones ; metabolism ; Humans ; Myocardium ; cytology ; metabolism ; Promoter Regions, Genetic

BACKGROUNDClaudin-6 is a protein component of tight junctions and its expression could downregulate the malignant phenotype of breast carcinoma. Here we investigated the mechanisms of claudin-6 induced human MCF-7 breast cancer cells apoptosis, invasion, and migration.

METHODSTerminal deoxyribonucleotide transferase-mediated nick-end labeling assay and Annexin-V/PI double stain assay were carried out to evaluate apoptosis. Inhibitors of each pathway were used to inactivate the signaling pathways. The expression of claudin-6 and phosphate p38, Erk 1/2 and Akt protein levels was confirmed by Western blotting analysis. Invasive and migratory traits of claudin-6 expressing cells were determined by Boyden chamber invasion assay and monolayer wound-healing assay.

RESULTSCells with high-level expression of claudin-6 had a higher rate of apoptosis than control cells. Western blotting assay showed that by contrast to control groups, p38 pathways were more activated in claudin-6 expressing cells. However, after inhibitor SB203580 treatment, the activation status could be significantly counteracted. Furthermore, by applying inhibitors to the apoptotic rate, invasive and migratory traits were also recovered in cells with claudin-6 expression.

CONCLUSIONClaudin-6 may function through p38 mitogen-activated protein kinase pathway, of which inhibition may reverse claudin-6-induced cell apoptosis, invasion, and migration.

Apoptosis ; genetics ; physiology ; Blotting, Western ; Cell Movement ; genetics ; physiology ; Claudins ; genetics ; metabolism ; Humans ; In Situ Nick-End Labeling ; MAP Kinase Signaling System ; genetics ; physiology ; MCF-7 Cells ; p38 Mitogen-Activated Protein Kinases ; genetics ; metabolism

ObjectiveTo study the expression of CLAUDIN-11 in the testis tissue of non-obstructive azoospermia (NOA) patients with different severities and investigate its clinical significance.

METHODSSixty-two NOA patients were divided into a hypospermatogenesis (HS) group (n = 30) and a Sertoli cell only syndrome (SCO) group (n =32). The expression of CLAUDIN-11 in the testicular tissue of the patients was detected by immunohistochemistry, that of CLAUDIN-11 mRNA determined by real-time fluorescence quantitative polymerase chain reaction (RT-qPCR), and the levels of serum reproductive hormones measured by chemiluminescent immunoassay.

RESULTSImmunohistochemistry showed that the expression of CLAUDIN-11 was mainly in the cytoplasm of the Sertoli cells around the seminiferous tubule wall in the HS group, but diffusely distributed in the membrane of the Sertoli cells in the SCO group. RT-qPCR revealed a significantly lower expression of CLAUDIN-11 mRNA in the HS than in the SCO group (0.008 ± 0.001 vs 0.013 ± 0.002, t = 10.616, P<0.01). The level of serum luteotropic hormone (LH) was also markedly lower in the HS than in the SCO group (［3.62 ± 1.34］ vs ［4.96 ± 3.10］ IU/L, P<0.05) and so was that of follicle-stimulating hormone (FSH) (［5.36 ± 2.80］ vs ［10.65 ± 9.18］ IU/L, P<0.05).

CONCLUSIONSThe up-regulated expression of CLAUDIN-11 in Sertoli cells may play an important role in the development and progression of spermatogenic dysfunction in NOA patients.

Azoospermia ; genetics ; metabolism ; Claudins ; metabolism ; Follicle Stimulating Hormone ; metabolism ; Humans ; Male ; Oligospermia ; genetics ; metabolism ; RNA, Messenger ; metabolism ; Seminiferous Tubules ; metabolism ; Sertoli Cell-Only Syndrome ; genetics ; metabolism ; Sertoli Cells ; metabolism ; Spermatogenesis ; Testis ; metabolism

Clinical studies reported hypomagnesaemia in long-term omeprazole usage that was probably due to intestinal Mg2+ wasting. Our previous report demonstrated the inhibitory effect of omeprazole on passive Mg2+ transport across Caco-2 monolayers. The present study aimed to identify the underlying mechanism of omeprazole suppression of passive Mg2+ absorption. By using Caco-2 monolayers, we demonstrated a potent inhibitory effect of omeprazole on passive Mg2+, but not Ca2+, transport across Caco-2 monolayers. Omeprazole shifted the %maximum passive Mg2+ transport-Mg2+ concentration curves to the right, and increased the half maximal effective concentration of those dose-response curves, indicating a lower Mg2+ affinity of the paracellular channel. By continually monitoring the apical pH, we showed that omeprazole suppressed apical acid accumulation. Neomycin and spermine had no effect on passive Mg2+ transport of either control or omeprazole treated monolayers, indicating that omeprazole suppressed passive Mg2+ transport in a calcium sensing receptor (CaSR)-independent manner. The results of western blot analysis showed that omeprazole significantly suppressed claudin (Cldn)-7 and -12, but not Cldn-2, expression in Caco-2 cells. By using apical solution of pH 5.5, 6.0, 6.5, and 7.0, we found that apical acidity markedly increased passive Mg2+ transport, Mg2+ affinity of the paracellular channel, and Cldn-7 and -12 expression in Caco-2 monolayers. Apical acidity abolished the inhibitory effect of omeprazole on passive Mg2+ transport and Cldn-7 and -12 expression. Our results provided the evidence for the regulation of intestinal passive Mg2+ absorption by luminal acidity-induced increase in Cldn-7 and -12 expression.
Absorption/drug effects ; Caco-2 Cells ; Calcium/metabolism ; Claudins/genetics/*metabolism ; Dose-Response Relationship, Drug ; Gene Expression/drug effects ; Humans ; Hydrogen-Ion Concentration ; Magnesium/*metabolism ; Omeprazole/*pharmacology ; Proton Pump Inhibitors/*pharmacology ; Receptors, Calcium-Sensing/metabolism

OBJECTIVETo investigate the role of claudin-11, a tight junction component of Sertoli cells, in spermatogenic dysfunction induced by oxidative stress in mice exposed to local radiation.

METHODSWe randomly allocated 48 male Kunming mice to a blank control group (A) and three radiation groups (B, C and D) of equal number, the latter three exposed to local radiation of the lower abdomen with 2 Gy, 6 Gy and 10 Gy of 60Co-gamma-ray, respectively, to induce oxidative stress. Four weeks later, we killed the animals, obtained their body and testis weights, observed the histological changes of the testis by HE staining, measured the levels of serum FSH, testosterone and LH by ELISA, and determined the mRNA levels of claudin-11 and inhibin beta B in Sertoli cells by real time quantitative PCR.

RESULTSAfter exposure to 60Co-gamma-ray radiation, the testis weights were (129.4 +/- 10.81), (87.5 +/- 16.83) and (56.1 +/- 12.36) mg in groups B, C and D, significantly decreased as compared with (182.9 +/- 8.43) mg in group A (P < 0.05); the testis indexes were (3.39 +/- 0.57), (2.46 +/- 0.46) and (1.63 +/- 0.44) mg/g in groups B, C and D, remarkably lower than (4.28 +/- 0.31) mg/g in group A (P < 0.01). Histological analysis revealed obviously decreased diameters of seminiferous tubules, reduced seminiferous epithelia and disarranged spermatogenic cells in the three radiation groups. The tubule differentiation indexes (TDI) were markedly lower in groups B, C and D than in A (P < 0.01). The levels of serum FSH were (6.74 +/- 1.95), (8.41 +/- 2.44) and (10.93 +/- 3.16) IU/L in groups B, C and D, 1.9 times higher in D than in A. With increased dose of radiation, the mRNA levels of inhibin beta in the testis tissue were descended, while the transcription levels of claudin-11 elevated, significantly higher in groups C and D than in A (P < 0.01).

CONCLUSIONLocal radiation-induced testicular oxidative stress can decrease the mRNA level of inhibin beta , increase serum FSH, damage Sertoli cells and elevate the expression of claudin-11 in the testis tissue. Increased claudin-11 and serum FSH may delay the cyclical restitution of hemo-testicular barrier and reduce the number of meiotic spermatocytes in the seminiferous epithelium, which consequently leads to male infertility.

Animals ; Claudins ; metabolism ; Male ; Mice ; Mice, Inbred Strains ; Oxidative Stress ; radiation effects ; RNA, Messenger ; genetics ; Seminiferous Tubules ; metabolism ; radiation effects ; Sertoli Cells ; metabolism ; Spermatocytes ; metabolism ; radiation effects ; Spermatogenesis ; Testis ; metabolism ; radiation effects

OBJECTIVEThe 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.

METHODSCLDN-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.

RESULTSQuantitive 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.

CONCLUSIONSThe 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.

ADP Ribose Transferases ; metabolism ; physiology ; Apoptosis ; Bacterial Toxins ; metabolism ; Cell Line, Tumor ; Claudin-3 ; Claudin-4 ; Claudins ; genetics ; metabolism ; Enterotoxins ; metabolism ; physiology ; Exotoxins ; metabolism ; physiology ; Female ; Humans ; Immunotoxins ; metabolism ; Ovarian Neoplasms ; metabolism ; pathology ; RNA, Messenger ; metabolism ; Recombinant Fusion Proteins ; metabolism ; physiology ; Virulence Factors ; metabolism ; physiology