The influence of tamoxifen on growth behavior and cell-cell adhesion in OSCC in vitro

The aim of this study was to evaluate the influence of tamoxifen on the growth and aggregation behavior, focusing on the expression pattern of E-cadherin and beta-catenin, in oral squamous cell carcinoma (OSCC) in vitro. Oral squamous cancer cell lines (UM-SCC-14A, UM-SCC-14B and UM-SCC-14C) were treated with various concentrations of tamoxifen. Growth and aggregation behavior as well as the protein expression and its changes were analysed. All cell lines are estrogen receptor (ER) positive. Tamoxifen induced a significant growth inhibition and induced the ability to form cell aggregates. This phenomena was not accompanied by a change in E-cadherin or beta-catenin expression or due to transcriptional changes. beta-catenin showed isolated membrane staining and nuclear distribution in all cell lines. A defective Ecadherin/beta-catenin complex was seen in UM-SCC-14C with no restoration through tamoxifen treatment. The cell-cell formation is increased in all cell lines without any alterations in the functional and quantitative status of E-cadherin or beta-catenin, indicating that novel cell-cell adhesion complexes not involving the classical E-cadherin/beta-catenin influence cell growth and intercellular adhesion in OSCC.

Paricalcitol attenuates renal interstitial fibrosis in obstructive nephropathy

Deficiency in vitamin D and its active metabolites is a pathologic feature of chronic kidney diseases. Despite that tubular epithelial cells are the major sites of active vitamin D synthesis, little is known about the role of vitamin D in maintaining the structural and functional integrity of tubular epithelium. This study investigated the effects of paricalcitol (19-nor-1,25-hydroxy-vitamin D(2)), a synthetic vitamin D analogue, on obstructive nephropathy, a model that is characterized by predominant tubulointerstitial lesions. Compared with vehicle controls, paricalcitol significantly attenuated renal interstitial fibrosis in mouse kidney after ureteral obstruction, as demonstrated by a reduced interstitial volume, decreased collagen deposition, and repressed mRNA expression of fibronectin and type I and type III collagens. Paricalcitol largely preserved E-cadherin and reduced alpha-smooth muscle actin expression in vivo. In addition, paricalcitol suppressed renal TGF-beta1 and its type I receptor expression, restored vitamin D receptor abundance, and inhibited cell proliferation and apoptosis after obstructive injury. In vitro, paricalcitol abolished TGF-beta1-mediated E-cadherin suppression and alpha-smooth muscle actin and fibronectin induction in tubular epithelial cells, underscoring its ability to block directly the epithelial to mesenchymal transition (EMT). It is interesting that paricalcitol almost completely suppressed renal induction of Snail, a critical transcription factor that is implicated in EMT programming. Furthermore, paricalcitol inhibited the TGF-beta1-mediated Snail induction in vitro, and ectopic expression of Snail repressed E-cadherin promoter activity and downregulated E-cadherin expression in tubular epithelial cells. These studies suggest that paricalcitol is able to ameliorate renal interstitial fibrosis in obstructive nephropathy, possibly by preserving tubular epithelial integrity through suppression of EMT.

Regionalized cadherin-7 expression by radial glia is regulated by Shh and Pax7 during chicken spinal cord development

During development, several genes that specify neuronal subtype identity are expressed in distinct dorsoventral domains of the spinal cord and hindbrain. Cadherin-7 (Cad7), a member of the cadherin family of adhesion molecules, is expressed by radial glia in a dorsal domain of the spinal cord basal plate in chicken. To study the regulation of the Cad7 gene, we ectopically expressed two known dorsoventral patterning genes, Shh and Pax7, in the caudal neural tube and in two brain regions at different stages of development by in vivo electroporation. Results showed that Shh regulated the expression of Cad7 by radial glia in a concentration-dependent manner. Shh induced or repressed the expression of Cad7, at low and high concentrations, respectively. Furthermore, Pax7 inhibited the expression of Cad7. These results are compatible with a role of Shh and Pax7 in regulating endogenous Cad7 expression during spinal cord and hindbrain development. Our data show, for the first time, that Shh can regulate the expression not only of other gene regulatory factors, but also of Cad7, a morphoregulatory molecule that plays a role in axon elongation and neural circuit formation.

TNF-alpha increases tyrosine phosphorylation of vascular endothelial cadherin and opens the paracellular pathway through fyn activation in human lung endothelia

Tumor necrosis factor (TNF)-alpha is a key mediator of sepsis-associated multiorgan failure, including the acute respiratory distress syndrome. We examined the role of protein tyrosine phosphorylation in TNF-alpha-induced pulmonary vascular permeability. Postconfluent human lung microvascular and pulmonary artery endothelial cell (EC) monolayers exposed to human recombinant TNF-alpha displayed a dose- and time-dependent increase in transendothelial [(14)C]albumin flux in the absence of EC injury. TNF-alpha also increased tyrosine phosphorylation of EC proteins, and several substrates were identified as the zonula adherens proteins vascular endothelial (VE)-cadherin, and beta-catenin, gamma-catenin, and p120 catenin (p120(ctn)). Prior protein tyrosine kinase (PTK) inhibition protected against the TNF-alpha effect. TNF-alpha activated multiple PTKs, including src family PTKs. Prior PTK inhibition with the src-selective agents PP1 and PP2 each protected against approximately 60% of the TNF-alpha-induced increment in [(14)C]albumin flux. PP2 also blocked TNF-alpha-induced tyrosine phosphorylation of VE-cadherin, gamma-catenin, and p120(ctn). To identify which src family kinase(s) was required for TNF-alpha-induced vascular permeability, small interfering RNA (siRNA) targeting each of the three src family PTKs expressed in human EC, c-src, fyn, and yes, were introduced into the barrier function assay. Only fyn siRNA protected against the TNF-alpha effect, whereas the c-src and yes siRNAs did not. These combined data suggest that TNF-alpha regulates the pulmonary vascular endothelial paracellular pathway, in part, through fyn activation.

Purification of a novel aminopeptidase from the pollen of Parietaria judaica that alters epithelial integrity and degrades neuropeptides

BACKGROUND

Parietaria judaica pollen is a common cause of pollinosis in the Mediterranean area.

OBJECTIVE

This study sought to purify and characterize the peptidase responsible for the majority of proteolytic activity present in the pollen extract of P judaica, and to investigate its contribution to the allergic response.

METHODS

A serial of chromatographic steps was applied to isolate the peptidase from P judaica's pollen, and its biochemical properties were determined. Bioactive peptides present in the airways were incubated with the peptidase, and their degradation was visualized by direct protein sequencing. In addition, we measured the cellular detachment, by methylene blue binding assay, of an airway-derived epithelial cell line (A549) in the presence of the peptidase, and visualized, by Western blot, the degradation of proteins from intercellular junctions.

RESULTS

We purified a 98-kDa peptidase from the pollen of P judaica that was classified as an aminopeptidase on the basis of its biochemical properties and internal amino acid sequence. The aminopeptidase was able to degrade bioactive peptides. Moreover, the aminopeptidase caused cellular detachment of A549 cell line and degradation of occludin and E-cadherin.

CONCLUSION

Our results suggest that the P judaica aminopeptidase can alter the integrity of the epithelium barrier by degrading occludin as well as E-cadherin. In addition, P judaica aminopeptidase can degrade bioactive peptides, which can exacerbate the overall bronchoconstrictive effect detected in asthmatic lungs.

CLINICAL IMPLICATIONS

The novel aminopeptidase described here could constitute a relevant therapeutic target in the treatment of allergic disorders induced by the pollen of P judaica.

Positional cloning, association analysis and expression studies provide convergent evidence that the cadherin gene FAT contains a bipolar disorder susceptibility allele

A susceptibility locus for bipolar disorder was previously localized to chromosome 4q35 by genetic linkage analysis. We have applied a positional cloning strategy, combined with association analysis and provide evidence that a cadherin gene, FAT, confers susceptibility to bipolar disorder in four independent cohorts (allelic P-values range from 0.003 to 0.024). In two case-control cohorts, association was identified among bipolar cases with a family history of psychiatric illness, whereas in two cohorts of parent-proband trios, association was identified among bipolar cases who had exhibited psychosis. Pooled analysis of the case-control cohort data further supported association (P=0.0002, summary odds ratio=2.31, 95% CI: 1.49-3.59). We localized the bipolar-associated region of the FAT gene to an interval that encodes an intracellular EVH1 domain, a domain that interacts with Ena/VASP proteins, as well as putative beta-catenin binding sites. Expression of Fat, Catnb (beta-catenin), and the three genes (Enah, Evl and Vasp) encoding the Ena/VASP proteins, were investigated in mice following administration of the mood-stabilizing drugs, lithium and valproate. Fat was shown to be significantly downregulated (P=0.027), and Catnb and Enah were significantly upregulated (P=0.0003 and 0.005, respectively), in response to therapeutic doses of lithium. Using a protein interaction map, the expression of genes encoding murine homologs of the FAT (ft)-interacting proteins was investigated. Of 14 interacting molecules that showed expression following microarray analysis (including several members of the Wnt signaling pathway), eight showed significantly altered expression in response to therapeutic doses of lithium (binomial P=0.004). Together, these data provide convergent evidence that FAT and its protein partners may be components of a molecular pathway involved in susceptibility to bipolar disorder.

A pharmacodynamic study of 5-azacytidine in the P39 cell line

OBJECTIVE

5-azacytidine (azacytidine), a DNA hypomethylating agent, was recently approved as the first therapeutic agent for the treatment of myelodysplastic syndromes. The present subcutaneous dosing schedule, 75 mg/m(2) for 7/28 days, is based on early clinical studies and may constitute a practical problem for patients. The present in vitro study aimed at evaluating the pharmacodynamics of azacytidine, thereby providing a rationale for clinical dose-finding studies.

METHODS

P39 cells were incubated with 0.1, 0.5, and 1 microM azacytidine daily for 24, 48, and 72 hours, followed by 48 hours in drug-free medium. The effects of azacytidine on cell growth, proliferation, apoptosis, cell cycle status, and promoter methylation of E-cadherin, ER, and HIC genes were studied.

RESULTS

Azacytidine decreased cell growth and proliferation, increased apoptosis, and affected cell cycle status in a dose-dependent manner. However, the exposure time, 24 to 72 hours, at doses between 0.5 and 1 microM, did not significantly affect any of these variables. Using first-order exponential pharmacokinetic model, we found that the effect of 1, 2, or 3 microM over 24 hours did not differ from that of 0.5 to 1 microM given over 48 to 72 hours. Induction of promoter hypomethylation was observed already after 24 hours of exposure with >or=0.5 microM azacytidine with no clear dose-effect relationship.

CONCLUSION

Our results indicate that optimal cellular effects of azacytidine might be achieved by shorter exposure times. The model provides information about the relation between azacytidine dose intensity and exposure time on malignant myeloid cells, which could serve as a rationale for further clinical development of practical, safe, and cost-effective dosing schedules.

Matrix metalloproteinase inhibitors suppress transforming growth factor-beta-induced subcapsular cataract formation

The pleotropic morphogen transforming growth factor-beta (TGFbeta) plays an important role in the development of fibrotic pathologies, including anterior subcapsular cataracts (ASCs). ASC formation involves increased proliferation and transition of lens epithelial cells into myofibroblasts, through epithelial-mesenchymal transformation that results in opaque plaques beneath the lens capsule. In this study, we used a previously established TGFbeta-induced rat cataract model to explore the role of matrix metalloproteinases (MMPs) in ASC formation. Treatment of excised rat lenses with TGFbeta resulted in enhanced secretion of MMP-2 and MMP-9. Importantly, co-treatment with two different MMP inhibitors (MMPIs), the broad spectrum inhibitor GM6001 and an MMP-2/9-specific inhibitor, suppressed TGFbeta-induced ASC changes, including the epithelial-mesenchymal transformation of lens epithelial cells. Using an anti-E-cadherin antibody, we revealed that conditioned media from lenses treated with TGFbeta contained a 72-kd E-cadherin fragment, indicative of E-cadherin shedding. This was accompanied by attenuated levels of E-cadherin mRNA. Conditioned media from lenses co-treated with TGFbeta and MMPIs exhibited attenuated levels of the E-cadherin fragment compared with those from TGFbeta-treated lenses. Together, these findings demonstrate that TGFbeta-induced E-cadherin shedding in the lens is mediated by MMPs and that suppression of this phenomenon might explain the mechanism by which MMPIs inhibit ASC plaque formation.

Targeted suppression of E-cadherin gene expression in bovine preimplantation embryo by RNA interference technology using double-stranded RNA

RNA interference (RNAi) has become acknowledged as an effective and useful tool to study gene function in diverse groups of cells. We aimed to suppress the expression of the E-cadherin gene during in vitro development of bovine preimplantation embryos using RNAi approach. In this experiment the effect of microinjection of E-cadherin and Oct-4 (as control) double-stranded (ds) RNA on the mRNA and protein expression level of the target E-cadherin gene was investigated. For this, a 496 bp long bovine E-cadherin and 341 bp long Oct-4 dsRNA sample were prepared using in vitro transcription. In vitro produced bovine zygotes were categorized into four treatment groups including those injected with E-cadherin dsRNA, Oct-4 dsRNA, RNase-free water, and uninjected controls. While the injection of E-cadherin dsRNA resulted in the reduction of E-cadherin mRNA and protein levels at the morula and blastocyst stage, the transcript and protein product remained unaffected in the Oct-4 dsRNA, water injected and uninjected control groups. The relative abundance of E-cadherin mRNA in the E-cadherin dsRNA injected morula stage embryos was reduced by 80% compared to the control group (P < 0.05). The Western blot analysis also showed a significant decrease in the E-cadherin protein (119 kDa) in E-cadherin dsRNA injected embryos compared to the other three groups. Microinjection of E-cadherin dsRNA has resulted only 22% blastocyst rate compared to 38%-40% in water injected and uninjected controls. In conclusion, our results indicated the suppression of E-cadherin mRNA and protein has resulted in lower blastocyst rate and the RNAi technology is a promising approach to study the function of genes in early bovine embryogenesis.

Rho GTPase activation by cell-cell adhesion

Cell-cell adhesion can occur in a calcium-dependent or calcium-independent manner, depending on the type of receptor involved. Establishment of cell contacts by either type of cell-cell adhesion (calcium-dependent or calcium-independent) has been shown to activate Rho GTPases in different cells. In this chapter, we describe the method used to assess the activation of Rho GTPases by cadherins, the prototype calcium-dependent adhesion receptor in epithelial cells. We cover the optimal cell culture conditions and controls to ensure that the activation of the GTPases is specifically triggered by the formation of cadherin-dependent cell-cell contacts. Controls described herein determine the specificity of activation of Rho proteins with respect to cadherin adhesion and exclude the contribution of other adhesive receptors, calcium-signaling, cell spreading, and migration. Although we focus on cadherin receptors and normal human keratinocytes as our model system, the methods described can be easily adapted to other adhesion receptors and different cell types.

Modulation of E-cadherin by hepatocyte growth factor induces aggressiveness of gastric carcinoma

OBJECTIVE

Hepatocyte growth factor (HGF) is well known as a scatter factor because it can disperse cells. E-cadherin is a protein that plays a main role in the establishment of cell-cell adhesion. This study focused on the role of HGF on the expression and distribution of E-cadherin. Furthermore, we found induction of aggressiveness of gastric carcinoma by modulation of E-cadherin by HGF.

MATERIALS AND METHODS

Tumor tissues from 50 patients with gastric carcinoma were evaluated for the expression of HGF, its receptor c-Met, and E-cadherin. Western blot analysis and invasion assay were performed to confirm the role of HGF on the modulation of E-cadherin using human gastric cancer cell lines.

RESULTS

Seventy-eight percent of the gastric carcinoma tissues showed overexpression of c-Met. E-cadherin expression was found in 86%, which could be further classified as membranous type (52%) or nonmembranous type (48%). The levels of HGF in tumor tissues increased significantly according to the tumor progression. The levels of HGF in tumors with nonmembranous type E-cadherin expression were significantly higher than those in tumors with membranous expression. A striking morphologic change from epithelial shape to fibroblastic shape was observed in SNU-16 cells after 3 days' exposure to HGF, accompanied by down-regulation of functional E-cadherin in the membrane. Treatment of the cells with HGF induced significant invasion into the matrigel.

CONCLUSION

We can conclude that HGF can modulate the expression of E-cadherin in gastric carcinoma, which was accompanied by more aggressive phenotype.

Lithium stimulates proliferation in cultured thyrocytes by activating Wnt/beta-catenin signalling

BACKGROUND

Lithium, clinically used in the treatment of bipolar disorders, is well known to induce thyroid growth. However, the mechanism involved is only incompletely characterized. Although it is conventionally believed that thyroid proliferation depends on the thyroid-stimulating hormone (TSH)/cAMP/cAMP response element binding protein (CREB) pathway, recent data indicate that Wnt/beta-catenin signalling may be of critical importance. In other cell types lithium activates canonical Wnt signalling by GSK-3beta inhibition, which in turn stabilizes cytosolic free beta-catenin. Here we investigated the potential modulation of Wnt/beta-catenin signalling under lithium treatment in primary and neoplastic human thyrocytes.

METHODS

Primary (S18) and neoplastic (NPA, FTC133) thyrocytes treated with and without LiCl were analysed using Western blotting, immunoprecipitation, reporter-gene assay, MTT proliferation assay and transfection studies.

RESULTS

LiCl dose-dependently inhibited GSK-3beta, stabilized free beta-catenin and inhibited beta-catenin degradation. Furthermore, LiCl altered the assembly of adherens junction by upregulating the E-cad-herin repressor, Snail, and downregulated E-cadherin expression. At a dose of 5 mM, LiCl significantly increased the proliferative potency of thyrocytes, which appeared to be mediated by beta-catenin, since nuclear beta-catenin stimulated T-cell factor/lymphoid enhancer factor (TCF/LEF)-mediated transcription and upregulated downstream targets like cyclin D1. To characterize the specificity of Wnt/beta-catenin-driven thyrocyte proliferation, we transfected primary thyrocytes and FTC133 cells with dominant negative TCF4 to block Wnt-dependent pathways or with dominant negative CREB to inhibit the TSH/cAMP cascade. In cells transfected with dominant negative CREB lithium-stimulated proliferation was unchanged whereas blocking Wnt/beta-catenin by dominant negative TCF4 reduced proliferation by approx. 50%.

CONCLUSION

Our data indicate that Wnt/beta-catenin signalling is of major importance in the control of lithium-dependent thyrocyte proliferation.

Phosphorylation of ezrin enhances microvillus length via a p38 MAP-kinase pathway in an immortalized mouse hepatic cell line

The apical microvilli are closely related with the development and the maintenance of cell polarization, and the length of microvilli varies in a regular way among cell types. Ezrin, a member of the ezrin/radixin/moesin (ERM) family, seems to be involved in the formation and stabilization of the apical microvilli. We found that phosphorylation of ezrin caused elongation of microvilli via a p38 MAP-kinase signaling pathway in an immortalized mouse hepatic cell line. When, in the oncogenic Raf-1-transfected mouse hepatic cell line, epithelial to mesenchymal transition (EMT) indicated as down-regulation of E-cadherin and up-regulation of Snail occurred, loss of microvilli and down-regulation of ezrin but not radixin and moesin were also observed. In the Raf-1 transfectants treated with the MAP-kinase inhibitor PD98059 and the p38 MAP-kinase inhibitor SB203580, the numbers of microvilli and the expression of ezrin, E-cadherin and Snail were recovered. More interestingly, treatment with SB203580 induced elongation of microvilli and increased phosphorylation of ezrin (at Thr-567 and Tyr-353). Phosphorylated ezrin-positive dots were colocalized with actin-positive dots on the surface of some Raf-1 transfectants treated with SB203580. These results suggested that phosphorylation of ezrin via the p38 MAP-kinase signaling pathway might be involved in the formation of microvilli during development of epithelial cell polarization.

Discrepancy between E-cadherin protein expression and morphology in human gastric carcinoma cells

BACKGROUND/AIMS

The E-cadherin-mediated cell adhesion system is now considered to be an "invasion suppressor system" in cancer cells. The purpose of this study is to examine the effect of E-cadherin on morphogenesis of MKN28 human gastric carcinoma cell line in the course of E-cadherin antisense S-oligodeoxynucleotide (ODN) treatment.

METHODOLOGY

The effect of E-cadherin antisense or random S-ODN treatment on cell growth, morphology in monolayer culture, and E-cadherin protein expression of MKN28 cells were evaluated. Further, immunohistochemical examination was performed.

RESULTS

Cell growth under 3-microM and 6-microM E-cadherin antisense S-ODN treatment did not differ from that under random S-ODN treatment. Although the expression of E-cadherin was decreased assuredly at the time of 6 days after 3-microM E-cadherin antisense S-ODN treatment by immunohistochemical examination, cell-cell adhesion was still observed until Day 10 after the treatment. On Day 15, the cells lost the cell-cell adhesion and showed the detachment and intercellular slits at least. Expression of the insoluble fraction of E-cadherin protein decreased in E-cadherin antisense S-ODN treatment cells at 6 days.

CONCLUSIONS

In this study, we demonstrated that discrepancy between E-cadherin protein expression and morphology exists in MKN28 cells treated with E-cadherin antisense S-ODN treatment.

1alpha,25-Dihydroxyvitamin D3 regulates the expression of Id1 and Id2 genes and the angiogenic phenotype of human colon carcinoma cells

1alpha,25-Dihydroxyvitamin D3 (1alpha,25(OH)2D3) has antitumor activity in addition to its classical action on calcium metabolism and bone tissue biology. It is thought to regulate the expression of multiple target genes and thus modulate processes critical for tumor growth and metastases. Here we show that 1alpha,25(OH)2D3 differentially regulates the expression of Id1 and Id2 genes, members of a family of transcriptional regulators of cell proliferation and differentiation. 1alpha,25(OH)2D3 induced epithelial differentiation in SW480-ADH human colon carcinoma cell line by promoting expression of the proteins implicated in adherent junction formation, including E-cadherin, and by inhibiting beta-catenin transcriptional activity. 1alpha,25(OH)2D3 activated the human Id1 gene promoter and rapidly induced Id1 RNA and protein. Ectopic overexpression of Id1 was not sufficient to induce E-cadherin, which was critical for the morphological changes induced by 1alpha,25(OH)2D3 in SW480-ADH cells. Conversely, Id2 transcription rate, RNA and protein levels were decreased by 1alpha,25(OH)2D3. Id2 downregulation by 1alpha,25(OH)2D3 mediated the antiproliferative effect of 1alpha,25(OH)2D3 on SW480-ADH cells. In addition, we showed that 1alpha,25(OH)2D3 changed the levels of the inducer of angiogenesis, vascular endothelial growth factor and the potent antiangiogenic factor thrombospondin-1, leading to a balanced change in the angiogenic potential of SW480-ADH human colon carcinoma cells.

Differentiation of circulating endothelial progenitor cells to a cardiomyogenic phenotype depends on E-cadherin

Progenitor cells may contribute to cardiac regeneration. Here, we investigated the role of cadherins and integrins for differentiation of human adult circulating endothelial progenitor cells (EPCs) into cardiomyocytes (CM) in a co-culture system. N- and E-cadherin were expressed in EPCs and were localized at the interface between EPCs and CM. Incubation of a blocking antibody against E-cadherin reduced the expression of CM marker protein in EPCs. Blocking antibodies against N- or P-cadherin or the beta1- and beta2-integrins were not effective. These data suggested that cell-to-cell communication mediated by E-cadherin contributes to the acquirement of a cardiomyogenic phenotype of human endothelial progenitor cells.

Promotion of adenoma growth by dietary inulin is associated with increase in cyclin D1 and decrease in adhesion proteins in Min/+ mice mucosa

We have earlier shown that dietary fructo-oligosaccharide inulin enhances adenoma growth in multiple intestinal neoplasia (Min/+) mice. To further explore inulin-induced early biochemical changes in the normal-appearing mucosa, Min/+ mice were fed from the age of 5 weeks to the ages of 8 and 15 weeks a control diet or an inulin-enriched diet (10% w/w). In addition, the wild-type littermates were fed with the same diets until the age of 8 weeks, in order to determine whether similar changes happen both in the wild-type and Min/+ mice. The mucosa without adenomas was collected and fractionated to nuclear, cytosolic and membrane pools. The protein levels of beta-catenin, cyclin D1 and E-cadherin were determined by Western blotting at both time points, and immunohistochemical stainings were done for 8-week-old mice. The promotion of adenoma growth by inulin (week 15, 1.3-fold increase, P=.0004) was associated with accumulation of cytosolic and nuclear beta-catenin, and increased amount of cytosolic cyclin D1 (1.5-fold increase, P=.003) in the normal-appearing mucosa of the Min/+ mice. Furthermore, inulin feeding reduced the membranous pools of beta-catenin and E-cadherin. Also in the wild-type mice the drop in membranous beta-catenin was clear (P=.015), and, moreover, a subset of crypts had enhanced nuclear beta-catenin staining. These data indicate that dietary inulin can already activate in the normal-appearing mucosa beta-catenin signaling, which in the presence of Apc mutation induces adenoma growth and even in the wild-type mice direction of the changes is similar.

Loss of functional E-cadherin renders cells more resistant to the apoptotic agent taxol in vitro

Experimental evidence supports a role for E-cadherin in suppressing invasion, metastasis, and proliferation. Germline mutations of the E-cadherin represent the genetic cause of hereditary diffuse gastric cancer (HDGC). In this type of tumor, isolated cancer cells permeate the basal membrane and paradoxically survive in the gastric wall in the absence of contact with neighbor epithelial cells or with the extracellular matrix. This suggests that upon E-cadherin deregulation, cells acquired resistance to apoptosis. To test this hypothesis, CHO cells stably expressing either wild-type E-cadherin or the HDGC-related germline mutations T340A and V832M were seeded either on a thin layer of collagen type I or on plastic and then subjected to the apoptotic agent taxol. We found that in vitro functional E-cadherin renders cells more sensitive to the effect of taxol. Our results also indicate that this effect is associated to decreased level of the anti-apoptotic bcl-2 protein.

Extracellular cleavage of E-cadherin by leukocyte elastase during acute experimental pancreatitis in rats

BACKGROUND & AIMS

Cadherins play an important role in cell-cell contact formation at adherens junctions. During the course of acute pancreatitis, adherens junctions are known to dissociate-a requirement for the interstitial accumulation of fluid and inflammatory cells-but the underlying mechanism is unknown.

METHODS

Acute pancreatitis was induced in rats by supramaximal cerulein infusion. The pancreas and lungs were either homogenized for protein analysis or fixed for morphology. Protein sequencing was used to identify proteolytic cleavage sites and freshly prepared acini for ex vivo studies with recombinant proteases. Results were confirmed in vivo by treating experimental pancreatitis animals with specific protease inhibitors.

RESULTS

A 15-kilodalton smaller variant of E-cadherin was detected in the pancreas within 60 minutes of pancreatitis, was found to be the product of E-cadherin cleavage at amino acid 394 in the extracellular domain that controls cell-contact formation, and was consistent with E-cadherin cleavage by leukocyte elastase. Employing cell culture and ex vivo acini leukocyte elastase was confirmed to cleave E-cadherin at the identified position, followed by dissociation of cell contacts and the internalization of cleaved E-cadherin to the cytosol. Inhibition of leukocyte elastase in vivo prevented E-cadherin cleavage during pancreatitis and reduced leukocyte transmigration into the pancreas.

CONCLUSIONS

These data provide evidence that polymorphonuclear leukocyte elastase is involved in, and required for, the dissociation of cell-cell contacts at adherens junctions, the extracellular cleavage of E-cadherin, and, ultimately, the transmigration of leukocytes into the epithelial tissue during the initial phase of experimental pancreatitis.

Anthrax lethal toxin induces endothelial barrier dysfunction

Hemorrhage and pleural effusion are prominent pathological features of systemic anthrax infection. We examined the effect of anthrax lethal toxin (LT), a major virulence factor of Bacillus anthracis, on the barrier function of primary human lung microvascular endothelial cells. We also examined the distribution patterns of cytoskeletal actin and vascular endothelial-cadherin (VE-cadherin), both of which are involved in barrier function regulation. Endothelial monolayers cultured on porous membrane inserts were treated with the LT components lethal factor (LF) and protective antigen (PA) individually, or in combination. LT induced a concentration- and time-dependent decrease in transendothelial electrical resistance that correlated with increased permeability to fluorescently labeled albumin. LT also produced a marked increase in central actin stress fibers and significantly altered VE-cadherin distribution as revealed by immunofluorescence microscopy and cell surface enzyme-linked immunosorbent assay. Treatment with LF, PA, or the combination of an inactive LF mutant and PA did not alter barrier function or the distribution of actin or VE-cadherin. LT-induced barrier dysfunction was not dependent on endothelial apoptosis or necrosis. The present findings support a possible role for LT-induced barrier dysfunction in the vascular permeability changes accompanying systemic anthrax infection.

Characterization of a new allele of Ames waltzer generated by ENU mutagenesis

Mutation in the protocadherin 15 (Pcdh15) gene causes hair cell dysfunction and is associated with abnormal stereocilia development. We have characterized the first allele (Pcdh15(av-nmf19)) of Ames waltzer (av) obtained by N-ethyl-N-nitrosourea (ENU) mutagenesis. Pcdh15(av-nmf19) was generated in the Neuroscience Mutagenesis Facility (NMF) at The Jackson Lab (Bar Habor, USA). Pcdh15(av-nmf19) mutants display circling and abnormal swimming behavior along with lack of auditory-evoked brainstem response at the highest intensities tested. Mutation analysis shows base substitution (A--> G) in the consensus splice donor sequence linked to exon 14 resulting in the skipping of exon 14 and the splicing of exon 13-15. This results in the introduction of a stop codon in the coding sequence of exon 15 due to shift in the reading frame. The effect of nmf19 mutation is expected to be severe since the expressed Pcdh15 protein is predicted to truncate in the 5th cadherin domain. Abnormalities of cochlear hair cell stereocilia are apparent in Pcdh15(av-nmf19) mutants near the time of birth and by about P15 (15 days after birth) there is evidence of sensory cell degeneration. Disorganization of outer hair cell stereocilia is observed as early as P2. Inner hair cell stereocilia are also affected, but less severely than those of the outer hair cells. These results are consistent with characteristics of the mutation in the Pcdh15(av-nmf19) allele and they support our previous finding that Protocadherin 15 plays an important role in hair-bundle morphogenesis.

The nonsteroidal anti-inflammatory drug, nabumetone, differentially inhibits beta-catenin signaling in the MIN mouse and azoxymethane-treated rat models of colon carcinogenesis

The mechanisms through which beta-catenin signaling is inhibited during colorectal cancer chemoprevention by nonsteroidal anti-inflammatory agents is incompletely understood. We report that nabumetone decreased uninvolved intestinal mucosal beta-catenin levels in the MIN mouse with a concomitant increase in glycogen synthase kinase (GSK)-3beta levels, an enzyme that targets beta-catenin for destruction. However, in the azoxymethane-treated rat, where beta-catenin is frequently rendered GSK-3beta-insensitive, nabumetone failed to alter beta-catenin levels but did decrease beta-catenin nuclear localization and transcriptional activity as gauged by cyclin D1. In conclusion, we demonstrate that the differential mechanisms for beta-catenin suppression may be determined, at least partly, by GSK-3beta.

Influence of retinoic acid on adhesion complexes in human hepatoma cells: a clue to its antiproliferative effects

Retinoic acid exerts antiproliferative and differentiative effects in normal and transformed in vitro hepatocytes. In order to verify whether these effects are related to a modulation of adhesion molecules, we used Western blot analysis and immunofluorescence microscopy to investigate the E-cadherinl/beta-catenin complex, the main system of adherens junctions, and the occludin/ZO-1 complex present in the tight junctions in HepG2 cells cultured in the presence or absence of retinoic acid. Results showed that retinoic acid treatment increases the amount of beta-catenin bound to E-cadherin by decreasing its tyrosine-phosphorylation level. Similar results were obtained with the tight junction system, in which the amount of occludin/ZO-1 complex is increased by a similar mechanism that reduced the level of ZO-1 phosphorylation on tyrosine. Immunofluorescence images also confirm these results, showing the localization on the cell surface of both adhesion complexes. Their insertion into the plasma membrane could be suggestive of an optimal reassembly and function of adherens and tight junctions in hepatoma cells, indicating that retinoic acid, besides inhibiting cell proliferation, improves cell-cell adhesion, sustaining or inducing the expression of a more differentiated phenotype.

CCL25 Enhances CD103-Mediated Lymphocyte Adhesion to E-Cadherin

Our results demonstrate that (1) CD103 is upregulated on CD8(+) T cells subsequent to their entry into the small intestinal epithelium, and (2) that the chemokine CCL25 enhances CD103-mediated adhesion to E-cadherin. These results suggest a novel role for chemokines in modulating interactions between lymphocytes and epithelial cells at mucosal surfaces.

Expression of cell adhesion molecules in the adriamycin-induced esophageal atresia rat model

Cell adhesion molecules are well-known membrane glycoproteins widely expressed during embryonic development that play a crucial role in cell division, migration and differentiation. We investigated the cell-matrix relationship using N-CAM and pan-cadherin adhesion molecules in the adriamycin-induced esophageal atresia (EA) rat model in the hope of finding a clue to the mechanisms of this unique anomaly.Time-mated pregnant Sprague-Dawley rats were given either saline or adriamycin on days 8 and 9 of gestation. Embryos were harvested on the 18th day of gestation. Esophageal specimens obtained from adriamycin-exposed embryos with (EA+) or without esophageal atresia (EA-) and from saline-exposed embryos were immunostained with N-CAM and pan-cadherin primary antisera. The esophageal specimens from control and EA- groups revealed similar immunostaining properties: weak N-CAM and pan-cadherin immunoreactivity. In contrast, the EA+ group showed intense immunoreactivity. Our study demonstrated an increased synthesis of N-CAM and pan-cadherin in the epithelial cells of the atretic esophagus and trachea. These results suggest that embryonic cell-cell and cell-matrix interactions may play a crucial role in the development of adriamycin-induced EA.