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PubMed1999

Ethanol modulation of intestinal epithelial tight junction barrier.

Previous studies have shown that high concentrations of ethanol (>/=40%) cause functional damage of the gastrointestinal epithelial barrier by direct cytotoxic effect on the epithelial cells. The effects of lower noncytotoxic doses of ethanol on epithelial barrier function are unknown. A major function of gastrointestinal epithelial cells is to provide a barrier against the hostile substances in the gastrointestinal lumen. The apicolaterally located tight junctions (TJs) form a paracellular seal between the lateral membranes of adjacent cells and act as a paracellular barrier. In this study, we investigated the effects of lower doses of ethanol on intestinal epithelial TJ barrier function using filter-grown Caco-2 intestinal epithelial monolayers. The Caco-2 TJ barrier function was assessed by measuring epithelial resistance or paracellular permeability of the filter-grown monolayers. Ethanol (0, 1, 2.5, 5, 7.5, and 10%) produced a dose-related drop in Caco-2 epithelial resistance and increase in paracellular permeability. Ethanol also produced a progressive disruption of TJ protein (ZO-1) with separation of ZO-1 proteins from the cellular junctions and formation of large gaps between the adjacent cells. Ethanol, at the doses used (</=10%), did not cause cytotoxicity (lactate dehydrogenase release) to the Caco-2 cells. Ethanol produced a disassembly and displacement of perijunctional actin and myosin filaments from the perijunctional areas. On ethanol removal, actin and myosin filaments rapidly reassembled at the cellular borders. Ethanol stimulated the Caco-2 myosin light chain kinase (MLCK) activity but did not affect the MLCK protein levels. Specific MLCK inhibitor ML-7 inhibited both ethanol increases in MLCK activity and TJ permeability without affecting the MLCK protein levels. Consistent with these findings, metabolic inhibitors sodium azide and 2,4-dinitrophenol significantly prevented ethanol-induced increase in Caco-2 TJ permeability, whereas cycloheximide or actinomycin D had no effect. The results of this study indicate that ethanol at low noncytotoxic doses causes a functional and structural opening of the Caco-2 intestinal epithelial TJ barrier by activating MLCK.

Azepines↗
PubMed2000

Quantitative structural and biochemical analyses of tight junction dynamics following exposure of epithelial cells to house dust mite allergen Der p 1.

BACKGROUND: House dust mite allergen Der p 1 is a cysteine peptidase. Previously, we have suggested that the proteolytic activity of this allergen may contribute to asthma by damaging the barrier formed by the airways epithelium. OBJECTIVE: The present study applied novel techniques to compare changes in permeability with quantitative events in tight junctions (TJs) and desmosomes (DMs) of epithelial cells exposed to Der p 1. METHODS: Confluent monolayers of Madin-Darby canine kidney (MDCK) and 16HBE14o-human bronchial epithelial cells were used as experimental models. Permeability was estimated from mannitol clearance. Digital imaging with quantification of TJs and DMs was achieved by fluorescent antibody staining and 2-photon molecular excitation microscopy (2PMEM). Biochemical changes in TJs were studied by immunoblotting, radiolabelling and immunoprecipitation. RESULTS: Der p 1 caused a time-dependent breakage of TJs and reduction in their content of the protein ZO-1. Reduction in ZO-1 immunofluorescence at TJs occurred with a small increase in the amount of diffuse, cytoplasmic immunoreactive ZO-1 staining. Morpho-logical changes in TJs occurred in synchrony with increases in epithelial permeability. DM puncta increased both in size and intensity of staining. Immunoblotting demonstrated that the disruption of TJ morphology was associated with cleavage of ZO-1 and occludin. Cells recovered from allergen exposure by de novo synthesis of occludin. CONCLUSION: Der p 1 could contribute to sensitization and allergic responses by degrading the function of the airway epithelial barrier.

Animals↗
PubMed2005

Correlation of translocation of tight junction protein Zonula occludens-1 and activation of epidermal growth factor receptor in the regulation of invasion of pancreatic cancer cells.

Mitogen-activated protein kinase signal transduction pathway was isolated as a potential factor related to cancer cell dissociation in dissociated (PC-1.0 and AsPC-1) and non-dissociated (PC-1 and Capan-2) pancreatic cancer cells in our previous works. On the other hand, changes of structure and function of tight junction (TJ) are reported to be correlated with carcinogenesis and tumor development. In this study, the translocation of TJ protein Zonula occludens-1 (ZO-1) and the activation of epidermal growth factor receptor (EGFR) were examined to demonstrate the involvement and correlation of TJ protein translocation and EGFR activation in the cell dissociation and subsequent invasion of pancreatic cancer. Immunocytochemistry, fluorescence intensity analysis and in vitro invasion assay were performed in dissociated and non-dissociated pancreatic cancer cells. The obvious translocation of cell-cell junction localized ZO-1 protein to the cytoplasm and nucleus, simultaneous activation of EGFR, as well as the dissociation of cell colonies of non-dissociated pancreatic cancer cells were induced by dissociation factor treatment. However, EGFR inhibitor, AG1478, treatment significantly induced the redistribution of ZO-1 protein to the sites of cell-cell junction and the cell aggregation, as well as simultaneous suppression of EGFR activation in both the dissociated and the non-dissociated pancreatic cancer cells. In addition, AG1478 treatment markedly enhanced the in vitro invasion of non-dissociated pancreatic cancer cells. Translocation of TJ protein ZO-1 is closely involved in the induction of invasion through EGFR activation in pancreatic cancer cells.

Animals↗
PubMed2003

Role of nitric oxide, cAMP and cGMP in the radiation induced changes of tight junctions in Madin-Darby canine kidney cells.

Radiation induced inflammatory response is thought to be the consequence of acute and chronic oxidative stress, as well as the increased production of various intercellular mediators. Nitric oxide (NO) originated reactive nitrogen species, cGMP and cAMP are well known regulatory factors of the structure and functions of cell contacts. These data raise the possibility that they may play a role in the radiation induced alterations of tight junctions (TJs) and consequently in the radiation injury of surface tissues. Using immunohistochemical methods on confluent cultures of Madin-Darby canine kidney (MDCK) cells, our goal was to clarify the possible role of NO and its relationship with the cGMP and cAMP second messenger systems in the development of the radiation induced alterations of TJs. We found that increased levels of cAMP and/or inhibition of nitrogen oxide synthase (NOS) activity both tend to strengthen TJ associated cell-to-cell contacts in unirradiated control cells. In contrast increased level of cGMP and/or increased expression of NO-sythase, caused the and irregular staining of TJal complexes, which is commonly observed in irridated cells. Our experiments also indicated the protective role of the experimentally increased cAMP level and of NOS inhibitors against the radiation induced TJ changes. All these results suggest the key role of NO in the early radiation response of TJs.

Animals↗
PubMed2001

Clostridium difficile toxins disrupt epithelial barrier function by altering membrane microdomain localization of tight junction proteins.

The anaerobic bacterium Clostridium difficile is the etiologic agent of pseudomembranous colitis. C. difficile toxins TcdA and TcdB are UDP-glucosyltransferases that monoglucosylate and thereby inactivate the Rho family of GTPases (W. P. Ciesla, Jr., and D. A. Bobak, J. Biol. Chem. 273:16021-16026, 1998). We utilized purified reference toxins of C. difficile, TcdA-10463 (TcdA) and TcdB-10463 (TcdB), and a model intestinal epithelial cell line to characterize their influence on tight-junction (TJ) organization and hence to analyze the mechanisms by which they contribute to the enhanced paracellular permeability and disease pathophysiology of pseudomembranous colitis. The increase in paracellular permeability induced by TcdA and TcdB was associated with disorganization of apical and basal F-actin. F-actin restructuring was paralleled by dissociation of occludin, ZO-1, and ZO-2 from the lateral TJ membrane without influencing the subjacent adherens junction protein, E-cadherin. In addition, we observed decreased association of actin with the TJ cytoplasmic plaque protein ZO-1. Differential detergent extraction and fractionation in sucrose density gradients revealed TcdB-induced redistribution of occludin and ZO-1 from detergent-insoluble fractions constituting "raft-like" membrane microdomains, suggesting an important role of Rho proteins in maintaining the association of TJ proteins with such microdomains. These toxin-mediated effects on actin and TJ structure provide a mechanism for early events in the pathophysiology of pseudomembranous colitis.

Actins↗
PubMed1985

Formation of tight junctions in epithelial cells. I. Induction by proteases in a human colon carcinoma cell line.

The experimental modulation of tight junctions (TJ) was studied in the human adenocarcinoma cell line HT 29 by freeze-fracture electron microscopy. The cell line has virtually no TJ when grown in culture. TJ could be induced by mild treatment with a variety of endopeptidases (trypsin, chymotrypsin, collagenase, elastase, plasmin, thrombin, papain, and pronase). Pronase induced the formation of TJ at low (but not at high) concentrations. All exopeptidases studied were unable to induce the formation of TJ. At 0 degree C the trypsin-induced formation of TJ was greatly slowed down although not entirely inhibited. However, when cells were briefly treated with trypsin at 0 degree C and subsequently transferred to 37 degrees C in the presence of protease inhibitors, TJ were rapidly assembled. Thus an induction phase at low temperature and an assembly phase at high temperature could be experimentally separated. When cells were briefly trypsinized at 0 degrees and subsequently kept at 0 degree C without trypsin for several hours, TJ still formed abundantly upon incubation at 37 degrees C. It appears therefore that the effect produced by the protease is retained for long periods in the cold.

Adenocarcinoma↗
PubMed2004

Claudin-1 gene mutations in neonatal sclerosing cholangitis associated with ichthyosis: a tight junction disease.

BACKGROUND AND AIMS: Most human and animal cholestatic disorders are associated with changes in hepatocyte cytoskeleton and tight junctions (TJs). These changes are usually secondary and nonspecific phenomena, both in intra- and extrahepatic cholestasis. Recently, missense mutations in TJ protein 2 (ZO-2) have been identified in patients with familial hypercholanemia. In the liver, TJs separate bile flow from plasma and are composed of strands of claudins and occludin. We previously assigned a syndrome associating ichthyosis and neonatal sclerosing cholangitis (NISCH syndrome) to chromosome 3q27-q28. We considered claudin-1 to be a strong candidate gene based on its mapping to the minimum interval and on the expression pattern of the mouse ortholog. METHODS: The 4 exons and intron-exon junctions of claudin-1 gene were amplified using standard polymerase chain reaction protocols and specific primers. Western blot analysis on cultured fibroblasts and immunohistochemistry on liver tissue section were performed using rabbit anti-claudin-1 antibodies. RESULTS: We described in 4 patients, of 2 inbred kindred of Moroccan origin, a 2-bp deletion (200-201 TT) in exon 1 of the claudin-1 gene arising in a premature stop codon and resulting in total absence of claudin-1 protein in the liver and skin. CONCLUSIONS: Lack of claudin-1 in NISCH syndrome may lead to increased paracellular permeability between epithelial cells. Bile duct injury may be related to the absence of claudin-1 expression in cholangiocytes. Our observation, in conjunction with ZO-2-associated hypercholanemia, emphasizes the role played by TJ components in hereditary cholestasis.

Cholangitis, Sclerosing↗
PubMed1989

Effect of protein synthesis inhibitors on formation and degradation of tight junctions in HT 29 adenocarcinoma cells.

The human colon adenocarcinoma cell line HT 29 grows in DMEM virtually without tight junctions (TJ). Fascia occludens type TJ can be induced in these cells by treatment with a variety of proteases or with hypertonic ammonium sulfate solution. The induced formation of TJ is not affected by pretreatment of the cells with cycloheximide or puromycin. The induced TJ are almost completely degraded within 2 h at 37 degrees C both in the absence and presence of the inhibitors studied. With ammonium sulfate as the initial inducing agent, it was possible to induce a second round of TJ formation as early as 2 h after the initial treatment, i.e., immediately after the degradation of the TJ formed in the first round. The same result was obtained in cells treated with cycloheximide. Similar results were also obtained when TJ were initially induced by a very mild trypsin treatment. However, if the initial induction involved a more rigorous proteolytic treatment, the cells needed a recovery period of several h before TJ could be induced again. Under these conditions, recovery from the protease treatment was impaired by the addition of protein synthesis inhibitors at any time prior to complete recovery. It follows that proteolytic treatment of cells not only induces TJ formation but also destroys cell surface proteins which must be available for the formation of TJ strands. It seems possible that these proteins mediate cell adhesion events which may be a prerequisite for, but not a part of the actual TJ formation.

Adenocarcinoma↗
PubMed2004

Copper treatment alters the barrier functions of human intestinal Caco-2 cells: involving tight junctions and P-glycoprotein.

This study investigated the effects of copper on paracellular permeability and P-glycoprotein (P-gp) in Caco-2 cells. Apical treatment with 100-300 microM CuSO4 in Hanks' balanced salt solution (HBSS, up to 3 hours) induced a time- and concentration-dependent increase in permeability of Caco-2 cell monolayers monitored by transepithelial electrical resistance (TEER). Copper treatment also induced a concentration-dependent reduction of F-actin stain, but not of tight junctional protein ZO-1. In addition, without any adverse effects on TEER, apical treatment with 300 microM CuSO4 in complete medium (for 24 hours) could reduce basolateral-to-apical transport, and increase apical-to-basolateral transport of rhodamine-123 (Rho-123) and accumulation of Rho-123 in Caco-2 cells. Treatment with 10-100 microM CuSO4 in HBSS (up to 3 hours) also induced a time- and concentration-dependent increase in accumulation of Rho-123 in Caco-2 cells. The results indicated that copper treatment increased the paracellular permeability probably by perturbing F-actin skeleton, and inhibited P-gp, thus altering the barrier functions of Caco-2 cells.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed2003

EFA6, exchange factor for ARF6, regulates the actin cytoskeleton and associated tight junction in response to E-cadherin engagement.

We addressed the role of EFA6, exchange factor for ARF6, during the development of epithelial cell polarity in Madin-Darby canine kidney cells. EFA6 is located primarily at the apical pole of polarized cells, including the plasma membrane. After calcium-triggered E-cadherin-mediated cell adhesion, EFA6 is recruited to a Triton X-100-insoluble fraction and its protein level is increased concomitantly to the accelerated formation of a functional tight junction (TJ). The expression of EFA6 results in the selective retention at the cell surface of the TJ protein occludin. This effect is due to EFA6 capacities to promote selectively the stability of the apical actin ring onto which the TJ is anchored, resulting in the exclusion of TJ proteins from endocytosis. Finally, our data suggest that EFA6 effects are achieved by the coordinate action of both its exchange activity and its actin remodeling C-terminal domain. We conclude that EFA6 is a signaling molecule that responds to E-cadherin engagement and is involved in TJ formation and stability.

ADP-Ribosylation Factor 6↗
PubMed2006

Tight junction modulation and its relationship to drug delivery.

In order for therapeutic agents to exert their pharmacological effects, they have to cross the biological membranes into the systemic circulation and reach the site of action. Drugs cross the membranes by one of two pathways; paracellular or transcellular. Most drugs are transported transcellularly depending on their physiocochemical properties, however the paracellular route is usually the main route of absorption for hydrophilic drugs (proteins, peptides, etc.). The paracellular pathway is governed by the tight junctions (TJs). The modulation of the TJs by absorption enhancers for paracellular drug transport enhancement and hence drug delivery improvement has been hampered for so many years by lack of comprehensive understanding of the structure and function of the TJs. The TJs are a multiple unit structure composed of multiprotein complex that affiliates with the underlying apical actomyosin ring. TJ proteins identified include transmembrane proteins; occludin and claudin, and cytoplasmic plaque proteins; ZO-1, ZO-2, ZO-3, cingulin, and 7H6. Among the new absorption enhancers that evolved in the past few years is Zonula Occludens toxin, Zot. In vivo and in vitro studies have shown that Zot and its biologically active fragment DeltaG could be effectively used to increase the transport/absorption of paracellular markers and low bioavailable drugs across the intestinal epithelium. Above all, the transient opening of the TJs by Zot suggests that it could be used as a novel approach for the safe drug delivery of therapeutic agents.

Animals↗
PubMed2001

The transmembrane protein occludin of epithelial tight junctions is a functional target for serine peptidases from faecal pellets of Dermatophagoides pteronyssinus.

There have been only a few studies of how allergens cross the airway epithelium to cause allergic sensitization. House dust mite fecal pellets (HDMFP) contain several proteolytic enzymes. Group 1 allergens are cysteine peptidases, whilst those of groups 3, 6 and 9 have catalytic sites indicative of enzymes that mechanistically behave as serine peptidases. We have previously shown that the group 1 allergen Der p 1 leads to cleavage of tight junctions (TJs), allowing allergen delivery to antigen presenting cells. In this study we determined whether HDMFP serine peptidases similarly compromise the airway epithelium by attacking TJs, desmosomes and adherens junctions. Experiments were performed in monolayers of MDCK, Calu-3 or 16HBE14o-epithelial cells. Cell junction morphology was examined by 2-photon molecular excitation microscopy and digital image analysis. Barrier function was measured as mannitol permeability. Cleavage of cell adhesion proteins was studied by immunoblotting and mass spectrometry. HDMFP serine peptidases led to a progressive cleavage of TJs and increased epithelial permeability. Desmosomal puncta became more concentrated. Cleavage of TJs involved proteolysis of the TJ proteins, occludin and ZO-1. This was associated with activation of intracellular proteolysis of ZO-1. In contrast to occludin, E-cadherin of adherens junctions was cleaved less extensively. Although Calu-3 and 16HBE14o-cells expressed tethered ligand receptors for serine peptidases, these were not responsible for transducing the changes in TJs. HDMFP serine peptidases cause cleavage of TJs. This study identifies a second general class of HDM peptidase capable of increasing epithelial permeability and thereby creating conditions that would favour transepithelial delivery of allergens.

Amino Acid Sequence↗
PubMed2003

Nitric oxide/nitric oxide synthase, spermatogenesis, and tight junction dynamics.

During spermatogenesis, preleptotene and leptotene spermatocytes, residing in the basal compartment of the seminiferous epithelium, must traverse the blood-testis barrier (BTB) to gain entry to the adluminal compartment for further development at late stage VIII and early stage IX of the epithelial cycle. As such, the timely opening and closing of the BTB is crucial to spermatogenesis. A compromise in this process can lead to infertility. Moreover, the BTB is unique in its relative localization in the seminiferous epithelium compared to the tight junctions (TJs) found in other epithelia. Sertoli cell TJs are situated near the basal lamina in the testis, closest to the basement membrane (a modified form of extracellular matrix [ECM]), unlike TJs found in other epithelia, which are found nearest the apical portion of an epithelium, farthest away from ECM. Needless to say, BTB function in the testis is maintained by intricate regulatory mechanisms. In addition to hormones and cytokines, nitric oxide (NO) was recently shown to be a putative TJ regulator in the testis. Perhaps equally important, TJ dynamics in the testis were shown to be regulated, at least in part, by occludin, a TJ-integral membrane protein, via the NO/soluble guanylate cyclase/cGMP/protein kinase G signaling pathway. This minireview summarizes recent advances in the field regarding the role of NO in testicular function, with special emphasis regarding its role in TJ dynamics and the likely implications of these studies for male contraceptive development.

Animals↗
PubMed2003

Escherichia coli K1 invasion increases human brain microvascular endothelial cell monolayer permeability by disassembling vascular-endothelial cadherins at tight junctions.

We investigated the permeability changes that occur in the human brain microvascular endothelial cell (HBMEC) monolayer, an in vitro model of the blood-brain barrier, during Escherichia coli K1 infection. An increase in permeability of HBMECs and a decrease in transendothelial electrical resistance were observed. These permeability changes occurred only when HBMECs were infected with E. coli expressing outer membrane protein A (OmpA) and preceded the traversal of bacteria across the monolayer. Activated protein kinase C (PKC)-alpha interacts with vascular-endothelial cadherins (VECs) at the tight junctions of HBMECs, resulting in the dissociation of beta-catenins from VECs and leading to the increased permeability of the HBMEC monolayer. Overexpression of a dominant negative form of PKC-alpha in HBMECs blocked the E. coli-induced increase in permeability of HBMECs. Anti-OmpA and anti-OmpA receptor antibodies exerted inhibition of E. coli-induced permeability of HBMEC monolayers. This inhibition was the result of the absence of PKC-alpha activation in HBMECs treated with the antibodies.

Bacterial Outer Membrane Proteins↗
PubMed2003

Simian virus 40 small tumor antigen induces deregulation of the actin cytoskeleton and tight junctions in kidney epithelial cells.

There is increasing evidence that the transforming DNA tumor virus simian virus 40 (SV40) is associated with human malignancies. SV40 small tumor antigen (small t) interacts with endogenous serine/threonine protein phosphatase 2A (PP2A) and is required for the transforming activity of SV40 in epithelial cells of the lung and kidney. Here, we show that expression of SV40 small t in epithelial MDCK cells induces acute morphological changes and multilayering. Significantly, it also causes severe defects in the biogenesis and barrier properties of tight junctions (TJs) but does not prevent formation of adherens junctions. Small t-induced TJ defects are associated with a loss of PP2A from areas of cell-cell contact; altered distribution and reduced amounts of the TJ proteins ZO-1, occludin, and claudin-1; and marked disorganization of the actin cytoskeleton. Small t-mediated F-actin rearrangements encompass increased Rac-induced membrane ruffling and lamellipodia, Cdc42-initiated filopodia, and loss of Rho-dependent stress fibers. Indeed, these F-actin changes coincide with elevated levels of Rac1 and Cdc42 and decreased amounts of RhoA in small t-expressing cells. Notably, these cellular effects of small t are dependent on its interaction with endogenous PP2A. Thus, our findings provide the first evidence that, in polarized epithelial cells, expression of small t alone is sufficient to induce deregulation of Rho GTPases, F-actin, and intercellular adhesion, through interaction with endogenous PP2A. Because defects in the actin cytoskeleton and TJ disruption have been linked to loss of cell polarity and tumor invasiveness, their deregulation by PP2A and small t likely contributes to the role of SV40 in epithelial cell transformation.

Actins↗
PubMed2002

Tight junction messenger RNA expression levels in bovine embryos are dependent upon the ability to compact and in vitro culture methods.

We have established a transcription map of individual bovine embryos using semiquantitative reverse transcriptase-polymerase chain reaction to detect the levels of six marker genes involved in early embryo differentiation. The critical step of compaction during preimplantation development is often not accomplished or it takes place for only a short period in in vitro generated embryos, which may result in reduced viability. Compaction is accompanied by the assembly of intercellular tight junctions (TJs) as a barrier against the extraembryonic environment and as a prerequisite for blastocele formation. In the present study, we have related the expression of TJ gene mRNA in individual bovine embryos to their developmental stage, their competence to undergo a clear period of compaction before blastocyst formation, and their in vitro or in vivo origin. Our results indicate that embryos that showed a detectable and well-formed compaction period in vitro are of similar quality to their in vivo counterparts. Starting from the same amount of maternal message, in vivo and in vitro development differ most during the critical period of the major switch from maternal to embryonic genomic control before a dramatic increase of TJ mRNAs occurs upon blastocyst formation. Failure to compact in vitro results in significant reduction of specific transcript levels, in a manner that depends on culture conditions, which may contribute to reduced viability. We conclude that TJ mRNA expression levels are sensitive to environmental conditions that may influence the developmental potential of bovine blastocysts.

Animals↗
PubMed2006

Redox regulation of 4-hydroxy-2-nonenal-mediated endothelial barrier dysfunction by focal adhesion, adherens, and tight junction proteins.

4-Hydroxy-2-nonenal (4-HNE), one of the major biologically active aldehydes formed during inflammation and oxidative stress, has been implicated in a number of cardiovascular and pulmonary disorders. 4-HNE has been shown to increase vascular endothelial permeability; however, the underlying mechanisms are unclear. Hence, in the current study, we tested our hypothesis that 4-HNE-induced changes in cellular thiol redox status may contribute to modulation of cell signaling pathways that lead to endothelial barrier dysfunction. Exposure of bovine lung microvascular endothelial cells (BLMVECs) to 4-HNE induced reactive oxygen species generation, depleted intracellular glutathione, and altered cell-cell adhesion as measured by transendothelial electrical resistance. Pretreatment of BLM-VECs with thiol protectants, N-acetylcysteine and mercaptopropionyl glycine, attenuated 4-HNE-induced decrease in transendothelial electrical resistance, reactive oxygen species generation, Michael protein adduct formation, protein tyrosine phosphorylation, activation of ERK, JNK, and p38 MAPK, and actin cytoskeletal rearrangement. Treatment of BLMVECs with 4-HNE resulted in the redistribution of FAK, paxillin, VE-cadherin, beta-catenin, and ZO-1, and intercellular gap formation. Western blot analyses confirmed the formation of 4-HNE-derived Michael adducts with the focal adhesion and adherens junction proteins. Also, 4-HNE decreased tyrosine phosphorylation of FAK without affecting total cellular FAK contents, suggesting the modification of integrins, which are natural FAK receptors. 4-HNE caused a decrease in the surface integrin in a time-dependent manner without altering total alpha5 and beta3 integrins. These results, for the first time, revealed that 4-HNE in redox-dependent fashion affected endothelial cell permeability by modulating cell-cell adhesion through focal adhesion, adherens, and tight junction proteins as well as integrin signal transduction that may lead dramatic alteration in endothelial cell barrier dysfunction during heart infarction, brain stroke, and lung diseases.

Adherens Junctions↗
PubMed2004

Intestinal epithelial tight junctions as targets for enteric bacteria-derived toxins.

The application of a multidisciplinary approach to study bacterial pathogenesis, along with the recent sequencing of entire microbial genomes have made possible discoveries that are changing the way scientists view the bacterium-host interaction. Today, research on the molecular basis of the pathogenesis of infectious diarrheal diseases of necessity transcends established boundaries between microbiology, cell biology, intestinal pathophysiology, and immunology. Novel multidisciplinary approaches led to the discovery of new bacteria-host cell interactions involving signals regulating intestinal permeability through the modulation of cell cytoskeleton and intercellular tight junctions (TJ). A century ago, TJ were conceptualized as a secreted extracellular cement forming an absolute and unregulated barrier within the paracellular space. Biological studies of the past several decades have shown that TJ are dynamic structures subjected to structural changes that dictate their functional status under a variety of developmental, physiological, and pathological circumstances. To meet the many diverse physiological challenges to which the intestinal epithelial barrier is subjected, TJ must be capable of rapid and coordinated responses. This requires the presence of a complex regulatory system that orchestrates the state of assembly of the TJ multiprotein network. Many pathogenic bacteria exploit this system to accomplish their pathogenic strategies by ultimately modulating intestinal permeability.

Animals↗