SEARCH · Search PubMed

Results for “Tight junctions”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

SourceResearch connectionFrom yearThrough year

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 739 records · Page 41Linked to original sources

PubMed1996

Alterations in cell cholesterol content modulate Ca(2+)-induced tight junction assembly by MDCK cells.

Transepithelial electrical resistance (TER), a measure of tight junction (TJ) barrier function, develops more rapidly and reaches higher values after preincubation of MDCK cells for 24 h with 2 microM Lovastatin (lova), an inhibitor of 3-hydroxy-3-methylglutaryl-CoA reductase. While this effect was attributed to a 30% fall in cholesterol (CH), possible effects of lova on the supply of prenyl group precursors could not be excluded. In the current study, strategies were devised to examine effects on TER of agents that simultaneously lower CH and increase the flux of intermediates through the CH biosynthetic pathway. Zaragozic acid, 20 microM, an inhibitor of squalene synthase known to increase the synthesis of isoprenoids and levels of prenylated proteins, lowered cell CH by 30% after 24 h, while accelerating development of TER in the same manner as lova. TER was also enhanced, despite a 23% increase in the rate of [3H]acetate incorporation into CH, when total CH was reduced by 45% during a 2-h incubation with 2 mM methyl beta-cyclodextrin (MBCD), an agent that stimulates CH efflux from cells. The fact that the rate of TER development was diminished when cell CH content was elevated by incubation with a complex of CH and MBCD is further evidence that this sterol modulates development of the epithelial barrier. Cell associated CH derived from the complex was similar to endogenous CH with respect to its accessibility to cholesterol oxidase. Lova's effect on TER was diminished when 5 micrograms/mL of CH was added to the medium during the last 11 h of incubation with lova.

Animals↗

PubMed1980

The tight junctions of rabbit choroid plexus and ciliary body epithelia. A comparative study using the double replica freeze-fracture technique.

The spatial arrangement of tight junctions in choroid plexus and ciliary body rabbit epithelia has been determined by studying freeze-fracture complementary replicas. In the choroid plexus epithelium, the interruptions of the junctional P-face fibrils were measured to be 14% in their total length. In the ciliary body epithelium, where the fibrils were found to be more fragmented than in the choroid plexus, the P-face fibril interruption accounted for 12% of the total length of the zonulae occludentes sealing the non-pigmented cells and 30% in the focal linear tight junctions connecting the non-pigmented cells at their apices. In both epithelia, the interruptions of the ridges are precisely complemented by particles or short bars of similar length found in the E-face furrows. Consequently, it is possible to conclude that the junctional fibrils are continuous in these two epithelia. For the zonulae occludentes, this continuity appears to be inconsistent with the 'leaky' properties of these epithelia shown by some physiological investigations.

Animals↗

PubMed2003

Regulation of tight junctions during the epithelium-mesenchyme transition: direct repression of the gene expression of claudins/occludin by Snail.

Snail is a transcription repressor that plays a central role in the epithelium-mesenchyme transition (EMT), by which epithelial cells lose their polarity. Claudins and occludin are integral membrane proteins localized at tight junctions, which are responsible for establishing and maintaining epithelial cell polarity. We examined the relationship between Snail and the promoter activity of claudins and occludin. When Snail was overexpressed in cultured mouse epithelial cells, EMT was induced with concomitant repression of the expression of claudins and occludin not only at the protein but also at the mRNA level. We then isolated the promoters of genes encoding claudins and occludin, in which multiple E-boxes were identified. Transfection experiments with various promoter constructs as well as electrophoretic mobility assays revealed that Snail binds directly to the E-boxes of the promoters of claudin/occludin genes, resulting in complete repression of their promoter activity. Because the gene encoding E-cadherin was also reported to be repressed by Snail, we concluded that EMT was associated with the simultaneous repression of the genes encoding E-cadherin and claudins/occludin (i.e. the expression of adherens and tight junction adhesion molecules, respectively).

Animals↗

PubMed2003

Protection against hypoxia-induced increase in blood-brain barrier permeability: role of tight junction proteins and NFkappaB.

Co-culture with glial cells and glia-conditioned media can induce blood-brain barrier properties in microvessel endothelial cells and protect against hypoxia-induced blood-brain barrier breakdown. We examined the effect of two types of glia-conditioned media on brain microvessel endothelial cell permeability and tight junction protein expression, and studied potential mechanisms of action. We found that C6-glioma-conditioned media, but not rat astrocyte-conditioned media, protected against an increase in permeability induced by exposure to 1% oxygen for 24 hours. This hypoxic stress caused an increase in the expression of tight junction proteins claudin-1 and actin, particularly in cells treated with C6-conditioned media. We found that C6-conditioned media has a significantly higher level of both basic fibroblast growth factor and vascular endothelial growth factor. Treatment with C6-conditioned media for 1 or 3 days protects against hypoxia-induced permeability increases, and this protective effect may be mediated by signal transduction pathways terminating at the transcription factor NFkappaB.

Actins↗

PubMed2001

Claudin-1 is not restricted to tight junctions in the rat epididymis.

The blood-epididymal barrier creates a unique microenvironment critical for sperm maturation. There is little information on proteins comprising epididymal tight and adhering junctions or on factors regulating their expression. Claudins are a family of transmembrane proteins reported to be exclusively localized to tight junctions. In the present study the expression of claudin-l (Cl-1) was examined with respect to the different cell types of the epididymis and its various regions as well as its expression during postnatal development and regulation by testicular factors, using both immunocytochemistry and Northern blot analysis. RT-PCR of adult epididymal and testicular RNA (positive control) indicated that Cl-1 messenger RNA (mRNA) transcripts were present in all regions of the epididymis. In the adult, Cl-1 was localized immunocytochemically along the entire length of the lateral plasma membranes between adjacent principal cells, including apical areas containing tight junctions, as well as at the interface between principal and basal cells and along the basal plasma membrane of the epithelium in relation to the basement membrane. Northern blot analysis of adult epididymis with a rat Cl-1 complementary DNA indicated the presence of two hybridizing bands of 4.0 and 1.5 kb. Postnatally, in the caput-corpus and cauda epididymidis, mRNA levels for both transcripts were lowest on day 7. In the caput-corpus epididymidis, mRNA levels for the 1.5-kb transcript increased significantly between 7 and 14 days, whereas the levels of the 4.0-kb transcript were significantly higher by day 21. Postnatal studies revealed that in the initial segment and caput epididymidis, Cl-1 immunostaining was present along the entire length of the lateral plasma membranes of undifferentiated epididymal epithelial cells as early as day 7, including apical areas containing tight junctions. By day 21, staining was identical to that of adult animals, but as this is an age when androgen levels are not at their peak, the data would suggest that they are not a prominent factor regulating Cl-1 expression. Orchidectomy and orchidectomy plus testosterone replacement experiments revealed differences in Cl-1 immunostaining in the initial segment, suggesting that localization of Cl-1 in epididymal tight junctions is androgen dependant. Thus, Cl-1 expression in the initial segment appears to be only partially under the control of androgens. However, in all other epididymal regions, orchidectomy with or without testosterone replacement, revealed no changes to the normal staining pattern, suggesting that androgens do not regulate Cl-1 expression in these regions. Taken together, these studies demonstrate that Cl-1 expression in the epididymis is not localized exclusively to tight junctions, but appears along the entire interfaces of adjacent epithelial cells as well as along the basal plasma membrane, suggesting a role for Cl-1 as an adhesion molecule. The data also suggest that the regulation of Cl-1 in the epididymis is complex and multifactorial.

Aging↗

PubMed2006

The role of caspase-3 in lipopolysaccharide-mediated disruption of intestinal epithelial tight junctions.

The mechanisms responsible for microbially induced epithelial apoptosis and increased intestinal permeability remain unclear. This study assessed whether purified bacterial lipopolysaccharide (LPS) increases epithelial apoptosis and permeability and whether these changes are dependent on caspase-3 activation. In nontumorigenic epithelial monolayers, Escherichia coli O26:B6 LPS increased apoptosis, as shown by nuclear breakdown, caspase-3 activation, and PARP cleavage, and induced disruption of tight junctional ZO-1. Apical, but not basolateral, exposure to LPS increased epithelial permeability. Addition of a caspase-3 inhibitor abolished the effects of LPS. The findings describe a novel mechanism whereby apical LPS may disrupt epithelial tight junctional ZO-1 and barrier function in a caspase-3-dependent fashion.

Apoptosis↗

PubMed1994

Modulation of tight junction morphology and permeability by an epithelial factor.

We report evidence of a factor secreted at the apical side of epithelial monolayers which modulates tight junction structure and permeability. This activity was detected within 4-7 days of conditioning of the apical medium by MDCK, A6 or Caco-2 epithelial cell lines cultured on permeable membranes in bipartite chambers. Apical conditioned medium (ACM), applied to the basolateral surface of a confluent monolayer, increased the transepithelial electrical resistance (TER), progressively reaching values 12-22% higher than the baseline within 5-10 min. After 40-60 min, the TER returned slowly to the basal value. This phenomenon was not observed either when using preheated ACM or the ACM filtrate obtained through a 30,000 MW cutoff membrane. The ACM maintained its activity even when applied to cell lines from different organs and species, as demonstrated when ACM from MDCK monolayers promoted an increase of 22% in the TER of Caco-2 cells. The increase of TER induced by the ACM treatment is accompanied by a change in the distribution of the number of tight junction strands, from an initial pattern, dominated mostly by junctions with one or two strands, to a new pattern after treatment dominated by junctions with two or three strands. Our results suggest the existence of a mechanism in epithelial cells that could signal leakage of apically secreted components to the basolateral side, thereby modulating the junction structure and permeability.

Animals↗

PubMed2001

Multi-PDZ domain protein 1 (MUPP1) is concentrated at tight junctions through its possible interaction with claudin-1 and junctional adhesion molecule.

Claudins, most of which end in valine at their COOH termini, constitute tight junction (TJ) strands, suggesting that TJ strands strongly attract PDZ-containing proteins. Indeed, ZO-1, -2, and -3, each of which contains three PDZ domains, were shown to directly bind to claudins. Using the yeast two-hybrid system, we identified ZO-1 and MUPP1 (multi-PDZ domain protein 1) as binding partners for the COOH terminus of claudin-1. MUPP1 has been identified as a protein that contains 13 PDZ domains, but it has not been well characterized. In vitro binding assays with recombinant MUPP1 confirmed the interaction between MUPP1 and claudin-1 and identified PDZ10 as the responsible domain for this interaction. A polyclonal antibody specific for MUPP1 was then generated. Immunofluorescence confocal microscopy as well as immunoelectron microscopy with this antibody revealed that in polarized epithelial cells MUPP1 was exclusively concentrated at TJs. Furthermore, in vitro binding and transfection experiments showed that junctional adhesion molecule, another TJ adhesion molecule, also bound to the PDZ9 domain of MUPP1. These findings suggested that MUPP1 is concentrated at TJs in epithelial cells through its binding to claudin and junctional adhesion molecule and that it may function as a multivalent scaffold protein that recruits various proteins to TJs.

Animals↗

PubMed2004

Loss of tight junction plaque molecules in breast cancer tissues is associated with a poor prognosis in patients with breast cancer.

The aim of this study was to investigate the expression of Zonula Occludens (ZO) proteins ZO-1, ZO-2 and ZO-3, and MUPP-1 (multi-PDZ domain protein 1), peripheral/plaque proteins that function in maintaining tight junction integrity and in transducing regulatory signalling events in patients with primary breast cancer. Breast cancer primary tumours (n=114) and background tissues (n=30) were processed for quantitative-polymerase chain reaction (PCR) analysis, Western blotting and immunostaining. Standardised transcript levels of ZO-1 and MUPP-1 were significantly lower in patients with metastatic disease compared with those remaining disease-free (DF) (median follow-up 72.2 months). Immunohistochemistry confirmed these results, with decreased levels in ZO-1 staining. For both ZO-1 and ZO-3, staining was confined to the intercellular regions in normal tissue, whereas in tumour tissues staining was diffuse and cytosolic. Q-PCR revealed a reduction in the levels of ZO-1 and MUPP-1 in patients with disease recurrence. Prognostic indicators of breast cancer were also inversely correlated with ZO-1 expression. We conclude that low levels of tight junction plaque molecules, such as ZO-1 and MUPP-1, in breast cancer are associated with poor patients prognosis.

Blotting, Western↗

PubMed2001

Dendritic cells express tight junction proteins and penetrate gut epithelial monolayers to sample bacteria.

Penetration of the gut mucosa by pathogens expressing invasion genes is believed to occur mainly through specialized epithelial cells, called M cells, that are located in Peyer's patches. However, Salmonella typhimurium that are deficient in invasion genes encoded by Salmonella pathogenicity island 1 (SPI1) are still able to reach the spleen after oral administration. This suggests the existence of an alternative route for bacterial invasion, one that is independent of M cells. We report here a new mechanism for bacterial uptake in the mucosa tissues that is mediated by dendritic cells (DCs). DCs open the tight junctions between epithelial cells, send dendrites outside the epithelium and directly sample bacteria. In addition, because DCs express tight-junction proteins such as occludin, claudin 1 and zonula occludens 1, the integrity of the epithelial barrier is preserved.

Animals↗

PubMed2001

HGF regulates tight junctions in new nontumorigenic gastric epithelial cell line.

The regulation of intercellular adhesion by hepatocyte growth factor (HGF) was examined on a novel nontumorigenic gastric epithelial cell line (IMGE-5) derived from H-2Kb-tsA58 transgenic mice. IMGE-5 cells constitutively expressed cytokeratin 18 and HGF receptors. Under permissive conditions (33 degrees C + interferon-gamma), IMGE-5 cells proliferated rapidly but did not display membrane expression of adherens and tight junction proteins. Under nonpermissive conditions, their proliferation was decreased and they displayed a strong, localized membrane expression of E-cadherin/beta-catenin and occludin/ZO-1. HGF treatment largely prevented the targeting of ZO-1 to the tight junction and induced a significant decrease of the transepithelial resistance measured across a confluent IMGE-5 cell monolayer. HGF rapidly increased the tyrosine phosphorylation of ZO-1 and decreased its association with occludin in a phosphatidylinositol 3-kinase (PI 3-kinase)-dependent manner. PI 3-kinase was also involved in HGF-induced migration of IMGE-5 cells. Our results demonstrate that 1) HGF prevents the appearance of ZO-1 in the membrane during epithelial cell differentiation; 2) HGF causes partial relocalization of ZO-1 to the cytoplasm and nucleus and concomitantly stimulates cell dissociation and migration; and 3) IMGE-5 cells offer a useful model for the study of gastric epithelial cell differentiation.

Animals↗

PubMed2006

Novel effects of azithromycin on tight junction proteins in human airway epithelia.

The macrolide antibiotic azithromycin improves lung function and prognosis among patients with cystic fibrosis or diffuse panbronchiolitis, independently of bacterial eradication. Anti-inflammatory effects have been implicated, but data from in vivo studies are scarce, and the link between abnormal electrolyte content in airway surface liquid and bronchial infections remains uncertain. In the present study, we treated human airway epithelia on filter supports with azithromycin and monitored transepithelial electrical resistance. We found that azithromycin increased transepithelial electrical resistance of airway epithelia in a dose-dependent manner. Immunocytochemistry and Western blotting showed that addition of azithromycin changed the locations of proteins in cell cultures and induced processing of the tight junction proteins claudin-1 and claudin-4, occludin, and junctional adhesion molecule-A. These effects were reversible, and no effect was seen when cells were treated with penicillin or erythromycin. The data indicate that azithromycin increases the transepithelial electrical resistance of human airway epithelia by changing the processing of tight junction proteins. The results are novel and may help explain the beneficial effects of azithromycin in patients with cystic fibrosis, diffuse panbronchiolitis, and community-acquired pneumonia.

Anti-Bacterial Agents↗

PubMed1989

Phosphorylation of the tight-junction protein ZO-1 in two strains of Madin-Darby canine kidney cells which differ in transepithelial resistance.

A comparison was made of the phosphate content of the tight-junction-specific protein ZO-1 in two strains of Madin-Darby canine kidney cells which differ in transepithelial resistance, a parameter reflective of tight-junctional permeability. Analysis revealed that the ZO-1 from the low-resistance strain contained approximately twice as much phosphate as that from the high-resistance strain.

Animals↗

PubMed2002

Blood-brain barrier tight junctions are altered during a 72-h exposure to lambda-carrageenan-induced inflammatory pain.

In this study, we examined the effect of lambda-carrageenan-induced inflammatory pain on the functional and structural properties of the rat blood-brain barrier (BBB) over a 72-h time period. Systemic inflammation was induced by an intraplantar injection of 3% lambda-carrageenan into the right hind paw of female Sprague-Dawley rats. In situ brain perfusion and Western blot analyses were performed at 1, 3, 6, 12, 24, 48, and 72 h. In situ brain perfusion showed lambda-carrageenan significantly increased brain uptake of [(14)C]sucrose at 1, 3, 6, and 48 h (139 +/- 9%, 166 +/- 19%, 138 +/- 13%, and 146 +/- 7% compared with control, respectively). Capillary depletion analysis insured the increased brain uptake was due to increased BBB permeability and not vascular trapping. Western blot analyses for zonula occludens-1 (ZO-1) and occludin were performed on isolated cerebral microvessels. ZO-1 expression was significantly increased at 1, 3, and 6 h and returned to control expression levels by 12 h. Total occludin expression was significantly reduced at 1, 3, 6, 12, and 48 h. This investigation demonstrated that lambda-carrageenan-induced inflammatory pain elicits a biphasic increase in BBB permeability with the first phase occurring from 1-6 h and the second phase occuring at 48 h. Furthermore, changes in BBB function are correlated with altered tight junctional protein expression of occludin and ZO-1. Changes in the structure of tight junctions may have important clinical ramifications concerning central nervous system homeostasis and therapeutic drug delivery.

Animals↗

PubMed1984

Effect of biliary pressure versus high bile acid flux on the permeability of hepatocellular tight junction.

Creation of a shunt between the common bile duct and vena cava, choledocho-caval shunt (CCS), causes biliary retention without obstruction. This in turn induces a marked choleresis (up to three times the normal bile flow) and increases bile acid output, both of which reach a plateau by 6 hours and remain elevated thereafter. In contrast, bile duct obstruction produces high biliary pressure and stoppage of bile flow and bile acid output. To compare the effect of biliary pressure and bile acid flux on permeability of the hepatocellular tight junction, we examined lanthanum permeation through tight junctions and bile to plasma concentration ratios of 3H-sucrose in these two models. In addition, we examined the effect of biliary pressure further by adjusting biliary pressure to 15 cm of H2O in modified CCS animals. At 6 hours after establishing these experimental models in male Sprague-Dawley rats, we infused lanthanum chloride (5 mM) in physiologic saline through the aorta (120 mm Hg) for 3 minutes, followed by perfusion fixation of the liver. Transmission electron microscopy on 144 bile canaliculi in each group (three rats each) revealed penetration of lanthanum in descending order of pressure rather than bile acid output: bile duct obstruction (50.7%), modified CCS (19.4%), CCS (13.2%), and control (5.6%). Bile to plasma concentration ratios of 3H-sucrose measured at 0, 2, and 6 hours in CCS and modified CCS animals revealed a marked increase of bile to plasma ratios only in the modified CCS group. These data lead us to conclude that biliary pressure is the significant determinant of biliary permeability and that bile acid output is important only insofar as the resultant choleresis elevates pressure.

Animals↗

PubMed1996

The supra-ependymal innervation is not responsible for the repression of tight junctions in the rat cerebral ependyma.

Classically, the contiguous epithelial cells show intercellular tight junctions (TJ) positioned as a continuous belt of cell-cell contacts at the boundary of apical and basolateral plasma membranes. Among the epithelia, the "typical" cerebral ependyma is very peculiar due to the absence of TJ, in contrast to the ependyma of the circumventricular organs (e.g. choroid plexus and the subcommissural organ) which shows well differentiated TJ. Since the "typical" ependyma is covered in the rat with a plexus of intraventricular nervous fibres not present at the surface of the circumventricular organs, we hypothesized local repression of TJ by molecules (serotonin, GABA, etc.) released by the supra-ependymal varicosities. Neither the denervation of the "typical" ependyma nor the ex vivo activation of protein kinase C (which increases the transepithelial resistance as it has been reported in other epithelia) produced junctional fibrils as shown by freeze-fracture. As the protein ZO-1 was not detectable in the "typical" ependyma by immunocytochemistry, there is probably repression of the genes responsible for TJ biosynthesis by unidentified endogenous factors.

5,7-Dihydroxytryptamine↗

PubMedDate not supplied

Peptidase allergen Der p 1 initiates apoptosis of epithelial cells independently of tight junction proteolysis.

Loss of epithelial cell polarity, which can arise following disruption of tight junctions (TJs), is a precursor to the care-fully orchestrated removal of moribund cells from epithelia in apoptosis. Ordinarily, this cycle of events has minimally disruptive effects on the function of the epithelial barrier, but some agents have been identified that induce apoptosis and promote epithelial leakiness. The allergen Der p 1 is a cysteine peptidase that cleaves TJ adhesion proteins and induces apoptosis in epithelial cells. This suggests the possibility that, at least for some inducers of apoptosis, these events might be causally linked. We report here that Der p 1 induces epithelial apoptosis before outright cell detachment and that apoptosis occurs within the same time span as increased paracellular permeability in polarized epithelial monolayers. Whilst TJ-deficient BEAS-2B cells were resistant to Der p 1-induced apoptosis, the cell line 1HAEo-, which was also TJ deficient, was sensitive to Der p 1, providing evidence against TJ proteolysis as a cause of apoptosis. To provide direct evidence, we propagated cells that normally express TJs in low calcium medium that prevented intercellular junction assembly. These cells retained full susceptibility to Der p 1, indicating that Der p 1-induced apoptosis is independent from TJ proteolysis.

Allergens↗

PubMed2004

Immunolocalization of tight junction proteins in the adult and developing human brain.

The formation of endothelial tight junctions (TJs) is crucial in blood-brain barrier (BBB) differentiation, and the expression and targeting of TJ-associated proteins mark the beginning of BBB functions. Using confocal microscopy, this study analyzed endothelial TJs in adult human cerebral cortex and the fetal telencephalon and leptomeninges in order to compare the localization of two TJ-associated transmembrane proteins, occludin and claudin-5. In the arterioles and microvessels of adult brain, occludin and claudin-5 form continuous bands of endothelial immunoreactivity. During fetal development, occludin and claudin-5 immunoreactivity is first detected as a diffuse labeling of endothelial cytoplasm. Later, at 14 weeks, the immunosignal for both proteins shifts from the cytoplasm to the interface of adjacent endothelial cells, forming a linear, widely discontinuous pattern of immunoreactivity that achieves an adult-like appearance within a few weeks. These results demonstrate that occludin and claudin-5 expression is an early event in human brain development, followed shortly by assembly of both proteins at the junctional areas. This incremental process suggests more rapid establishment of the human BBB, consistent with its specific function of creating a suitable environment for neuron differentiation and neurite outgrowth during neocortical histogenesis.

Aged↗