Kegg Pathway: Tight junction

Histol Histopathol. 2010 Jan; 25(1): 83-90
Ouban A, Ahmed AA

Claudins are Tight junction proteins that are critical for the sealing of cellular sheets and controlling paracellular ion flux. The claudin family of proteins is composed of at least 24 closely related transmembrane proteins, most of them are well characterized at the gene and protein levels. The claudins are present in variety of normal tissues, hyperplastic conditions, benign neoplasms, and cancers that exhibit epithelial differentiation. Loss of claudins expression has also been reported in several malignancies as well. Differential expression of various members of the claudins family in cancers can be used in confirming the histologic identity of certain cancers and excluding others. Examples include the use of immunohistochemical detection of claudins to differentiate between oncocytoma and chromophobe renal cell carcinoma, endometrial endometrioid carcinoma and seropapillary carcinoma, mesothelioma and metastatic adenocarcinoma, hepatocellular and biliary tract carcinomas, and between intestinal-type and diffuse-type gastric carcinoma. Expression of certain claudins can also be used as markers that can predict patient's prognosis. Thus, it seems that attempts to identify expression claudins in cancers are becoming increasingly useful in histologic diagnosis of tumors as well as means to assess patient's prognosis.

Histol Histopathol. 2010 Jan; 25(1): 55-62
Jakab C, Rusvai M, Gálfi P, Szabó Z, Szabára A, Kulka J

The aim of the present study was to characterise the expression pattern of claudin-1, -3, -4, -5 and -7 Tight junction proteins in canine normal colorectum and in the low-grade, tubulopapillary colorectal carcinoma in canines. Methods and results: The biopsy samples included 10 canine normal colorectal tissues and 20 canine low grade colorectal carcinomas (CLGCCs). The canine normal colorectal mucosa was negative for claudin-1. Claudin-1 was detected as a non-diffuse intense membrane labelling of neoplastic epithelial cells in low grade colorectal cancer in canines. Fifty five per cent of all tumours showed a weak cytoplasmic pattern of staining for claudin-1 protein. The normal colorectal mucosa showed diffuse punctate positivity for claudin-3. Claudin-3 was detected as an intense lateral membrane labelling of tumour cells in CLGCCs. Claudin-4 expression in surface and crypt epithelial cells of the intact colorectal mucosa in canines was punctate. Claudin-4 molecule was detected as a lateral membrane labelling of neoplastic cells in CLGCCs. The epithelium of the CLGCCs and the low grade colorectal carcinoma were negative for claudin-5. The surface and crypt epithlial cells of the canine normal colorectal mucosa showed a diffuse lateral membranous pattern of staining for claudin-7. Claudin-7 molecule was detected as an intense membrane labelling of neoplastic cells in CLGCCs. Seventy per cent of all tumours showed weak cytoplasmic positivity for claudin-7. Conclusion: Consequently, we hypothesize that claudin-1 plays a role in the progression of CLGCCs. Further functional studies are needed to clarify the biological role of the mislocalization of the claudin-1 molecule from cell membrane to the cytoplasm in CLGCCs. Lower claudin-4 expression suggests that reduced expression of claudin-4 molecule may lead to cellular disorientation, detachment and invasion of CLGCCs. Further functional studies are needed to clarify the biological role of overexpression and mislocalisation of claudin-7 in CLGCCs.

J Gen Virol. 2009 Nov 18;
Ludlow M, Rennick LJ, Sarlang S, Skibinski G, McQuaid S, Moore T, de Swart RL, Duprex WP

The lymphotropic and myelotropic nature of wild-type measles virus (wt-MV) is well recognised, with dendritic cells and lymphocytes expressing the MV receptor CD150 mediating systemic spread of the virus. Infection of respiratory epithelial cells has long been considered crucial for entry of MV into the body. However, the lack of detectable CD150 on these cells raises the issue of their importance in the pathogenesis of measles. Here we have utilised a combination of in vitro, ex vivo and in vivo model systems to characterise the susceptibility of epithelial cells to wt-MV of proven pathogenicity. Low numbers of MV-infected epithelial cells in close proximity to underlying infected lymphocytes or myeloid cells suggested infection via the basolateral side of the epithelium in the macaque model. In primary cultures of human bronchial epithelial cells foci of MV-infected cells were only observed following infection via the basolateral cell surface. The extent of infection in primary cells was enhanced both in vitro and in ex vivo cornea rim tissue by disrupting the integrity of the cells prior to the application of virus. This demonstrates that whilst epithelial cells may not be the primary target cells for wt-MV, areas of epithelium in which Tight junctions are disrupted can become infected using high multiplicities of infection. The low numbers of MV infected epithelial cells observed in vivo in conjunction with the absence of infectious virus release from infected primary cell cultures suggests that epithelial cells have a peripheral role in MV transmission.

Virology. 2009 Nov 17;
Verma S, Kumar M, Gurjav U, Lum S, Nerurkar VR

Though compromised blood-brain barrier (BBB) is a pathological hallmark of WNV-associated neurological sequelae, underlying mechanisms are unclear. We characterized the expression of matrix metalloproteinases (MMP) in WNV-infected human brain microvascular endothelial cells (HBMVE) and human brain cortical astrocytes (HBCA), components of BBB and their role in BBB disruption. Expression of multiple MMPs was significantly induced in WNV-infected HBCA cells. Naïve HBMVE cells incubated with the supernatant from WNV-infected HBCA cells demonstrated loss of Tight junction proteins, which were rescued in the presence of MMP inhibitor, GM6001. Further, supernatant from WNV-infected HBCA cells compromised the in vitro BBB model integrity. Our data suggest astrocytes as one of the sources of MMP in the brain, which mediates BBB disruption allowing unrestricted entry of immune cells into the brain, thereby contributing to WNV neuropathogenesis. Because of the unavailability of WNV antivirals and vaccines, use of MMP inhibitors as an adjunct therapy to ameliorate WNV disease progression is warranted.

Int J Neurosci. 2009; 119(10): 1881-1904
Kalayci R, Kaya M, Uzun H, Bilgic B, Ahishali B, Arican N, Elmas I, Küçük M

Hypercholesterolemia and/or hypertension impair endothelial function in peripheral vasculature; however, their impact on endothelial cells of brain microvessels is unclear. We investigated the effects of hypercholesterolemia on the integrity of the blood-brain barrier (BBB) and the activity of astrocytes during N(omega)-nitro-L-arginine methyl ester (L-NAME) hypertension followed by angiotensin (ANG) II. We found significant decreases in superoxide dismutase levels with all treatments except ANG II and L-NAME plus ANG II, and in catalase concentrations except ANG II and cholesterol plus L-NAME. Nitric oxide (NO) concentrations were significantly decreased by L-NAME but significantly increased by cholesterol. L-NAME-stimulated plasma malondialdehyde (MDA), Ox-LDL, and cholesterol levels were significantly augmented by cholesterol. Glutathione (GSH) levels significantly decreased, while MDA, TNF-alpha, and Ox-LDL levels significantly increased in cholesterol and/or L-NAME. The increase in BBB permeability by acute hypertension in hypercholesterolemic hypertensive animals was less than that observed in chronically hypertensive animals. Brain vessels of L-NAME-treated animals showed a considerable loss of immunoreactivity for Tight junction proteins, occludin, and ZO-1. Immunoreactivity for occludin and ZO-1 increased in cholesterol plus L-NAME and decreased in cholesterol. Glial fibrillary acidic protein (GFAP) immunoreactivity was seen in few astrocytes in the brain sections of L-NAME-treated animals, but increased in cholesterol plus L-NAME. Positive immunoreactivity for vascular endothelial growth factor (VEGF) was observed in cholesterol and cholesterol plus L-NAME plus ANG II. We suggest that hypercholesterolemia may affect BBB integrity through increasing the expression of Tight junction proteins and GFAP and leading to the production of VEGF, at least partly, via increased NO, TNF-alpha, and catalase in hypertensive conditions.

J Biomed Biotechnol. 2010; 2010: 460607
Brennan K, Offiah G, McSherry EA, Hopkins AM

Breast cancer is a complex and heterogeneous disease that arises from epithelial cells lining the breast ducts and lobules. Correct adhesion between adjacent epithelial cells is important in determining the normal structure and function of epithelial tissues, and there is accumulating evidence that dysregulated cell-cell adhesion is associated with many cancers. This review will focus on one cell-cell adhesion complex, the Tight junction (TJ), and summarize recent evidence that TJs may participate in breast cancer development or progression. We will first outline the protein composition of TJs and discuss the functions of the TJ complex. Secondly we will examine how alterations in these functions might facilitate breast cancer initiation or progression; by focussing on the regulatory influence of TJs on cell polarity, cell fate and cell migration. Finally we will outline how pharmacological targeting of TJ proteins may be useful in limiting breast cancer progression. Overall we hope to illustrate that the relationship between TJ alterations and breast cancer is a complex one; but that this area offers promise in uncovering fundamental mechanisms linked to breast cancer progression.

PLoS One. 2009; 4(11): e7814
Troy TC, Arabzadeh A, Larivière NM, Enikanolaiye A, Turksen K

The barrier function of the skin protects the mammalian body against infection, dehydration, UV irradiation and temperature fluctuation. Barrier function is reduced with the skin's intrinsic aging process, however the molecular mechanisms involved are unknown. We previously demonstrated that Claudin (Cldn)-containing Tight junctions (TJs) are essential in the development of the epidermis and that transgenic mice overexpressing Cldn6 in the suprabasal layers of the epidermis undergo a perturbed terminal differentiation program characterized in part by reduced barrier function. To dissect further the mechanisms by which Cldn6 acts during epithelial differentiation, we overexpressed a Cldn6 cytoplasmic tail deletion mutant in the suprabasal compartment of the transgenic mouse epidermis. Although there were no gross phenotypic abnormalities at birth, subtle epidermal anomalies were present that disappeared by one month of age, indicative of a robust injury response. However, with aging, epidermal changes with eventual chronic dermatitis appeared with a concomitant barrier dysfunction manifested in increased trans-epidermal water loss. Immunohistochemical analysis revealed aberrant suprabasal Cldn localization with marked down-regulation of Cldn1. Both the proliferative and terminal differentiation compartments were perturbed as evidenced by mislocalization of multiple epidermal markers. These results suggest that the normally robust injury response mechanism of the epidermis is lost in the aging Involucrin-Cldn6-CDelta196 transgenic epidermis, and provide a model for evaluation of aging-related skin changes.

Biochim Biophys Acta. 2009 Nov 12;
Ikari A, Kinjo K, Atomi K, Sasaki Y, Yamazaki Y, Sugatani J

Claudin-16 is involved in the paracellular reabsorption of Mg(2+) in the thick ascending limb of Henle. Little is known about the mechanism regulating the Tight junctional localization of claudin-16. Here, we examined the effect of Mg(2+) deprivation on the distribution and function of claudin-16 using Madin-Darby canine kidney (MDCK) cells expressing FLAG-tagged claudin-16. Mg(2+) deprivation inhibited the localization of claudin-16 at Tight junctions, but did not affect the localization of other claudins. Re-addition of Mg(2+) induced the Tight junctional localization of claudin-16, which was inhibited by U0126, a MEK inhibitor. Transepithelial permeability to Mg(2+) was also inhibited by U0126. The phosphorylation of ERK was reduced by Mg(2+) deprivation, and recovered by re-addition of Mg(2+). These results suggest that the MEK/ERK-dependent phosphorylation of claudin-16 affects the Tight junctional localization and function of claudin-16. Mg(2+) deprivation decreased the phosphothreonine levels of claudin-16. The phosphothreonine levels of T225A and T233A claudin-16 were decreased in the presence of Mg(2+) and these mutants were widely distributed in the plasma membrane. Furthermore, TER and transepithelial Mg(2+) permeability were decreased in the mutants. We suggest that the Tight junctional localization of claudin-16 requires a physiological Mg(2+) concentration and the phosphorylation of threonine residues via a MEK/ERK-dependent pathway.

Rev Neurol (Paris). 2009 Nov 12;
Ghersi-Egea JF, Mönkkönen KS, Schmitt C, Honnorat J, Fèvre-Montange M, Strazielle N

The low cerebral bioavailability of various drugs is a limiting factor in the treatment of neurological diseases. The restricted penetration of active compounds into the brain is the result of the same mechanisms that are central to the maintenance of brain extracellular fluid homeostasis, in particular from the strict control imposed on exchanges across the blood-brain interfaces. Direct drug entry into the brain parenchyma occurs across the cerebral microvessel endothelium that forms the blood-brain barrier. In addition, local drug concentration measurements and cerebral imaging have clearly shown that the choroid plexuses - the main site of the blood-cerebrospinal fluid (CSF) barrier - together with the CSF circulatory system also play a significant role in setting the cerebral bioavailability of drugs and contrast agents. The entry of water-soluble therapeutic compounds into the brain is impeded by the presence of Tight junctions that seal the cerebral endothelium and the choroidal epithelium. The cerebral penetration of many of the more lipid-soluble molecules is also restricted by various classes of efflux transporters that are differently distributed among both blood-brain interfaces, and comprise either multidrug resistance proteins of the ATP-binding cassette superfamily or transporters belonging to several solute carrier families. Expression of these transporters is regulated in various pathophysiological situations, such as epilepsy and inflammation, with pharmacological consequences that have yet to be clearly elucidated. As for brain tumour treatments, their efficacy may be affected not only by the intrinsic resistance of tumour cells, but also by endothelial efflux transporters which exert an even greater impact than the integrity of the endothelial Tight junctions. Relevant to paediatric neurological treatments, both blood-brain interfaces are known to develop a Tight phenotype very early on in postnatal development, but the developmental profile of efflux transporters still needs to be assessed in greater detail. Finally, the exact role of the ependyma and pia-glia limitans in controlling drug exchanges between brain parenchyma and CSF deserves further attention to allow more precise predictions of cerebral drug disposition and therapeutic efficacy.

Cell Microbiol. 2009 Nov 12;
Simovitch M, Sason H, Cohen S, Zahavi EE, Melamed-Book N, Weiss A, Aroeti B, Rosenshine I

Summary Enterohaemorrhagic E. coli (EHEC) and enteropathogenic E. coli (EPEC) are enteropathogens characterized by their ability to induce the host cell to form actin-rich structures, termed pedestals. A type III secretion system (TTSS), through which the pathogens deliver effector proteins into infected host cells, is essential for their virulence and pedestal formation. EHEC encodes two similar effectors, EspM1 and EspM2, which activate the RhoA signaling pathway and induce the formation of stress fibers upon infection of host cells. We confirm these observations and in addition show that EspM inhibits the formation of actin pedestals. Moreover, we show that translocation of EspM into polarized epithelial cells induces dramatic changes in the Tight junction localization and in the morphology and architecture of infected polarized monolayers. These changes are manifested by altered localization of the Tight junctions and 'bulging out' morphology of the cells. Surprisingly, despite the dramatic changes in their architecture, the cells remained alive and the epithelial monolayer maintained a normal barrier function. Taken together, our results show that the EspM effectors inhibit pedestal formation and induce Tight junction mis-localization as well as dramatic changes in the architecture of the polarized monolayer.

Arterioscler Thromb Vasc Biol. 2009 Nov 12;
Burek M, Arias-Loza PA, Roewer N, Förster CY

OBJECTIVE: Estrogens have multiple effects on vascular physiology and function. In the present study, we look for direct estrogen target genes within junctional proteins. METHODS AND RESULTS: We use murine endothelial cell lines of brain and heart origin, which express both subtypes of estrogen receptor, ERalpha and ERbeta. Treatment of these cells with 17beta-estradiol (E2) led to an increase in transendothelial electric resistance and a most prominent upregulation of the Tight junction protein claudin-5 expression. A significant increase of claudin-5 promoter activity, mRNA, and protein levels was detected in cells from both vascular beds. In protein lysates and in immunoreactions on brain sections from ovariectomized E2-treated mice, we noticed an increase in claudin-5 protein and mRNA content. Treatment of cells with a specific ERbeta agonist, diarylpropionitrile, revealed the same effect as E2 stimulation. Moreover, we detected significantly lower claudin-5 mRNA and protein content in ERbeta knockout mice. CONCLUSIONS: We describe claudin-5 as a novel estrogen target in vascular endothelium and show in vivo (brain endothelium) and in vitro (brain and heart endothelium) effects of estrogen on claudin-5 levels. The estrogen-induced increase in junctional protein levels may lead to an improvement in vascular structural integrity and barrier function of vascular endothelium.

J Clin Neurosci. 2009 Nov 10;
Tu J, Karunanayaka A, Windsor A, Stoodley MA

This study assessed the blood flow and histological changes of an animal model of arteriovenous malformation (AVM) over 84 days in 71 rats, and compared the histological findings to 17 specimens of human AVM. Carotid-jugular fistula blood flow positively correlated with time. The maximum flow rate occurred at 42 days, at which time the nidus was considered mature and was histologically similar to human AVMs. Morphological similarities between the model and human AVM vessels included heterogeneously thickened walls, splitting of the elastic lamina, thickened endothelial layers, endothelial cushions, lack of Tight junctions, loss of endothelial continuity, endothelial-subendothelial adherent junctions, and luminally directed filopodia. These findings support the theory that vascular changes in human AVMs are secondary to increased flow and provide a basis for using this model in studies of AVMs.

G Ital Dermatol Venereol. 2009 Dec; 144(6): 689-700
Jensen JM, Proksch E

The skin provides an effective barrier between the organism and the environment, preventing the invasion of pathogens and fending off chemical and physical assaults, as well as the unregulated loss of water and solutes. In this review we provide an overview of several components of the physical barrier, as well as how barrier function is regulated and altered in association with dermatoses. The physical barrier localized primarily in the stratum corneum (SC) and consists of protein-enriched cells (corneocytes with cornified envelope and cytoskeletal elements, as well as corneodesmosomes) and lipid-enriched intercellular domains. The nucleated epidermis, with its Tight, gap and adherens junctions, additional desmosomes and cytoskeletal elements, also contributes to the barrier. Lipids are synthesized in the keratinocytes during epidermal differentiation and are then extruded into the extracellular domains, where they form lipid-enriched extracellular layers. The cornified cell envelope, a robust protein/lipid polymer structure, is located below the cytoplasmic membrane on the exterior of the corneocytes. Ceramides A and B, forming the backbone for the subsequent addition of free ceramides, free fatty acids and cholesterol in the SC, are covalently bound to cornified envelope proteins. Filaggrin is cross-linked to the cornified envelope and aggregates keratin filaments into macrofibrils. Cytokines, cAMP and calcium influence the formation and maintenance of barrier function. Changes in lipid composition and epidermal differentiation lead to a disturbed skin barrier, which allows the entry of environmental allergens, immunological reaction and inflammation in atopic dermatitis. A disturbed skin barrier is an important component in the pathogenesis of contact dermatitis, ichthyosis, psoriasis, and atopic dermatitis.

J Biol Chem. 2009 Nov 10;
Kimura J, Abe H, Kamitani S, Toshima H, Fukui A, Miyake M, Kamata Y, Sugita-Konishi Y, Yamamoto S, Horiguchi Y

Clostridium perfringens enterotoxin (CPE), a causative agent of food poisoning, is a pore-forming toxin disrupting the selective permeability of the plasma membrane of target cells, resulting in cell death. We previously identified claudin as the cell surface receptor for CPE. Claudin, a component of Tight junctions, is a tetra-transmembrane protein and constitutes a large family of more than 20 members, not all of which serve as the receptor for CPE. The mechanism by which the toxin distinguishes the sensitive claudins is unknown. In this study, we localized the region of claudin responsible for interaction with CPE to the C-terminal part of the second extracellular loop, and found that the isoelectric point of this region in sensitive claudins was higher than insensitive claudins. Amino-acid substitutions to lower the pI resulted in reduced sensitivity to CPE among sensitive claudins, whereas substitutions to raise the pI endowed CPE-insensitive claudins with sensitivity. The steric structure of the claudin-binding domain of CPE reveals an acidic cleft surrounded by Tyr306, Tyr310, Tyr312, and Leu315, which were reported to be essential for interaction with the sensitive claudins. These results imply that an electrostatic attraction between the basic claudin region and the acidic CPE cleft is involved in their interaction.

Expert Rev Neurother. 2009 Nov; 9(11): 1595-614
Gupta VK

Cortical spreading depression (CSD) has been at the center stage of migraine pathophysiology for approximately six decades. Reanalysis of CSD reveals several major unbridgeable gaps in this experimental neurophysiologic concept for migraine. Key phenotypic and pharmacological features of migraine challenge the assumed pathophysiologic role of CSD. Detection of subclinical infarct-like white matter lesions (WMLs) in the brain of some migraine patients stimulated the concept of CSD-related BBB disruption. Raised plasma levels of matrix metalloproteinases (MMPs) in migraine patients in the headache phase, specifically MMP-9, suggested a pathogenetic role for MMP elevation in the development of both migraine attacks and WMLs. Migraine attacks with or without aura present a unique, profound and protracted vasodilatory challenge to the homeostatic systems of the brain. To accommodate the rather sudden increase in cerebral blood flow, the brain circulatory network must dilate and the BBB must expand considerably. MMPs can influence expansion of the extracellular matrix of the BBB and loosening of the intercellular Tight junctions between endothelial cells through proteolytic degradation during migrainous cerebrovascular dilatation. WMLs most probably reflect transient and discrete breakdown of the BBB consequent to sustained cerebral hyperperfusion rather than hypoperfusion. Systemic elevations of MMPs are not specific to migraine but are found in a variety of neurological and extra-neurological disorders. This perspective presents a conceptual dissociation between the effects of CSD on the brain of experimental animals and the clinical phenomena in migraine patients.

Neurosci Lett. 2009 Nov 10;
Kim YA, Park SL, Kim MY, Lee SH, Baik EJ, Moon CH, Jung YS

Blood-brain barrier (BBB) dysfunction contributes to the pathophysiology of cerebrovascular diseases such as stroke. In the present study, we investigated the role of PKC isoforms in aglycemic hypoxia-induced hyperpermeability using an in vitro model of the BBB consisting of mouse bEnd.3 cells. PKCbetaII and PKCdelta isoforms were activated during aglycemic hypoxia. CGP53353, a specific PKCbetaII inhibitor, significantly attenuated aglycemic hypoxia-induced BBB hyperpermeability and disruption of occludin and zonula occludens-1 (ZO-1), indicating a deleterious role of PKCbetaII in the regulation of BBB permeability during aglycemic hypoxia. Conversely, rottlerin, a specific PKCdelta inhibitor, exacerbated BBB hyperpermeability and Tight junction (TJ) disruption during aglycemic hypoxia, indicating a protective role of PKCdelta against aglycemic hypoxia-induced BBB hyperpermeability. Furthermore, disruption of TJ proteins during aglycemic hypoxia was attenuated by PKCbetaII DN and PKCdelta WT overexpression, and aggravated by PKCbetaII WT and PKCdelta DN overexpression. These results suggest that PKCbetaII and PKCdelta counter-regulate BBB permeability during aglycemic hypoxia.

Anat Rec (Hoboken). 2009 Nov 6;
Kikuchi K, Kawedia J, Menon AG, Hand AR

Salivary gland cells are joined by junctional complexes consisting of a Tight junction (TJ), zonula adherens and one or more desmosomes. TJs regulate paracellular permeability, maintain separate apical and basolateral membrane domains, and serve as signaling centers. We examined TJs of mouse submandibular glands (SMG) in thin sections and freeze-fracture replicas. TJs between acinar cells and between intercalated duct cells had 2-6 parallel strands on the protoplasmic fracture face, with occasional branches, interconnections and free ends, and corresponding grooves on the extracellular face. Granular duct cell TJs had 2-30 strands, a depth of