Adherens junctions remain dynamic

Enhanced tight junction in Caco-2 cells by the pretreatment with Lactobacillus johnsonii strain MG

We investigated roles of Lactobacillus johnsonii MG (MG) isolated from mice with interaction with tight junction on gut barrier function with Caco-2 cell model. Pretreatment with MG enhanced barrier function and showed protective effect against Enterococcus faecium provided damage. MG treatment increased the gene expressions of transcriptional regulator NFKB and major tight junction protein, ZO-1.

Signaling mechanisms underlying lymphatic vessel dysfunction in skin aging and possible anti-aging strategies

Aging-related skin diseases are gradually increasing due to the imbalance of cutaneous homeostasis in the aging population. Skin aging-induced inflammation promotes systemic inflammation and may lead to whole-body aging. Lymphatic vessels play an important role in maintaining fluid and homeostasis balance. In intrinsically aged skin, the number of lymphatic vessels decrease and their functions decline, which is related to the reduced adhesion junctions between lymphatic endothelial cells, particularly VE-cadherin. VEGFC/VEGFR-3 signal pathway plays an important role in remodeling and expansion of lymphatic vessels; the downregulation of this pathway contributes to the dysfunction of lymphatic vessels. Meanwhile, we proposed some additional mechanisms. Decline of the pumping activity of lymphatic vessels might be related to age-related changes in extracellular matrix, ROS increase, and eNOS/iNOS disturbances. In extrinsically aged skin, the hyperpermeability of lymphatic vessels results from a decrease in endothelial-specific tight junction molecules, upregulation of VEGF-A, and downregulation of the VEGFC/VEGFR-3 signaling pathway. Furthermore, some of the Phyto therapeutics could attenuate skin aging by modulating the lymphatic vessels. This review summarized the lymphatic vessel dysfunction in skin aging and anti-aging strategies based on lymphatic vessel modulation.

Angiotensin II Induces Cardiac Edema and Hypertrophic Remodeling through Lymphatic-Dependent Mechanisms

Cardiac lymphatic vessel growth (lymphangiogenesis) and integrity play an essential role in maintaining tissue fluid balance. Inhibition of lymphatic lymphangiogenesis is involved in cardiac edema and cardiac remodeling after ischemic injury or pressure overload. However, whether lymphatic vessel integrity is disrupted during angiotensin II- (Ang II-) induced cardiac remodeling remains to be investigated. In this study, cardiac remodeling models were established by Ang II (1000 ng/kg/min) in VEGFR-3 knockdown (Lyve-1Cre VEGFR-3f/−) and wild-type (VEGFR-3f/f) littermates. Our results indicated that Ang II infusion not only induced cardiac lymphangiogenesis and upregulation of VEGF-C and VEGFR-3 expression in the time-dependent manner but also enhanced proteasome activity, MKP5 and VE-cadherin degradation, p38 MAPK activation, and lymphatic vessel hyperpermeability. Moreover, VEGFR-3 knockdown significantly inhibited cardiac lymphangiogenesis in mice, resulting in exacerbation of tissue edema, hypertrophy, fibrosis superoxide production, inflammation, and heart failure (HF). Conversely, administration of epoxomicin (a selective proteasome inhibitor) markedly mitigated Ang II-induced cardiac edema, remodeling, and dysfunction; upregulated MKP5 and VE-cadherin expression; inactivated p38 MAPK; and reduced lymphatic vessel hyperpermeability in WT mice, indicating that inhibition of proteasome activity is required to maintain lymphatic endothelial cell (LEC) integrity. Our results show that both cardiac lymphangiogenesis and lymphatic barrier hyperpermeability are implicated in Ang II-induced adaptive hypertrophic remodeling and dysfunction. Proteasome-mediated hyperpermeability of LEC junctions plays a predominant role in the development of cardiac remodeling. Selective stimulation of lymphangiogenesis or inhibition of proteasome activity may be a potential therapeutic option for treating hypertension-induced cardiac remodeling.

Pathophysiology of aged lymphatic vessels

Lymphatic vessels maintain body homeostasis by recirculation of fluid and cells. Cell senescence induces lymphatic dysfunction. Impaired contractile function is caused by low muscle cell investiture and decrease of nitric oxide in aged lymphatic collectors, leading to poor drainage of lymph. Aging-induced loss of endothelial glycocalyx and production of inflammatory cytokines increases permeability of lymphatic vessels. In addition, aging-associated basal activation of mast cells delays immune response. In this review, we summarize the structural and pathological changes of aged lymphatic vessels, and discuss the underlying molecular mechanisms.

Beta-Catenin and Plakoglobin Expression during Zebrafish Tooth Development and Replacement

We analyzed the protein distribution of two cadherin-associated molecules, plakoglobin and β-catenin, during the different stages of tooth development and tooth replacement in zebrafish. Plakoglobin was detected at the plasma membrane already at the onset of tooth development in the epithelial cells of the tooth. This pattern remained unaltered during further tooth development. The mesenchymal cells only showed plakoglobin from cytodifferentiation onwards. Plakoglobin 1a morpholino-injected embryos showed normal tooth development with proper initiation and differentiation. Although plakoglobin is clearly present during normal odontogenesis, the loss of plakoglobin 1a does not influence tooth development. β-catenin was found at the cell borders of all cells of the successional lamina but also in the nuclei of surrounding mesenchymal cells. Only membranous, not nuclear, β-catenin, was found during morphogenesis stage. However, during cytodifferentiation stage, both nuclear and membrane-bound β-catenin was detected in the layers of the enamel organ as well as in the differentiating odontoblasts. Nuclear β-catenin is an indication of an activated Wnt pathway, therefore suggesting a possible role for Wnt signalling during zebrafish tooth development and replacement.

The Adjuvant Activity of Epimedium Polysaccharide-Propolis Flavone Liposome on Enhancing Immune Responses to Inactivated Porcine Circovirus Vaccine in Mice

Objectives. The adjuvant activity of Epimedium polysaccharide-propolis flavone liposome (EPL) was investigated in vitro and in vivo. Methods. In vitro, the effects of EPL at different concentrations on splenic lymphocytes proliferation and mRNA expression of IFN-γ and IL-6 were determined. In vivo, the adjuvant activities of EPL, EP, and mineral oil were compared in BALB/c mice through vaccination with inactivated porcine circovirus type 2 (PCV2) vaccine. Results. In vitro, EPL promoted lymphocytes proliferation and increased the mRNA expression of IFN-γ and IL-6, and the effect was significantly better than EP at all concentrations. In vivo, EPL significantly promoted the lymphocytes proliferation and the secretion of cytokines and improved the killing activity of NK cells, PCV2-specific antibody titers, and the proportion of T-cell subgroups. The effects of EPL were significantly better than EP and oil adjuvant at most time points. Conclusion. EPL could significantly improve both PCV2-specific cellular and humoral immune responses, and its medium dose had the best efficacy. Therefore, EPL would be exploited in an effective immune adjuvant for inactivated PCV2 vaccine.

Intracellular Ascorbate Prevents Endothelial Barrier Permeabilization by Thrombin

Intracellular ascorbate (vitamin C) has previously been shown to tighten the endothelial barrier and maintain barrier integrity during acute inflammation in vitro. However, the downstream effectors of ascorbate in the regulation of endothelial permeability remain unclear. In this study, we evaluated ascorbate as a mediator of thrombin-induced barrier permeabilization in human umbilical vein endothelial cells and their immortalized hybridoma line, EA.hy926. We found that the vitamin fully prevented increased permeability to the polysaccharide inulin by thrombin in a dose-dependent manner, and it took effect both before and after subjection to thrombin. Thrombin exposure consumed intracellular ascorbate but not the endogenous antioxidant GSH. Likewise, the antioxidants dithiothreitol and tempol did not reverse permeabilization. We identified a novel role for ascorbate in preserving cAMP during thrombin stimulation, resulting in two downstream effects. First, ascorbate maintained the cortical actin cytoskeleton in a Rap1- and Rac1-dependent manner, thus preserving stable adherens junctions between adjacent cells. Second, ascorbate prevented actin polymerization and formation of stress fibers by reducing the activation of RhoA and phosphorylation of myosin light chain. Although ascorbate and thrombin both required calcium for their respective effects, ascorbate did not prevent thrombin permeabilization by obstructing calcium influx. However, preservation of cAMP by ascorbate was found to depend on both the production of nitric oxide by endothelial nitric-oxide synthase, which ascorbate is known to activate, and the subsequent generation cGMP by guanylate cyclase. Together, these data implicate ascorbate in the prevention of inflammatory endothelial barrier permeabilization and explain the underlying signaling mechanism.

Pulmonary epithelial barrier function: some new players and mechanisms

The pulmonary epithelium serves as a barrier to prevent access of the inspired luminal contents to the subepithelium. In addition, the epithelium dictates the initial responses of the lung to both infectious and noninfectious stimuli. One mechanism by which the epithelium does this is by coordinating transport of diffusible molecules across the epithelial barrier, both through the cell and between cells. In this review, we will discuss a few emerging paradigms of permeability changes through altered ion transport and paracellular regulation by which the epithelium gates its response to potentially detrimental luminal stimuli. This review is a summary of talks presented during a symposium in Experimental Biology geared toward novel and less recognized methods of epithelial barrier regulation. First, we will discuss mechanisms of dynamic regulation of cell-cell contacts in the context of repetitive exposure to inhaled infectious and noninfectious insults. In the second section, we will briefly discuss mechanisms of transcellular ion homeostasis specifically focused on the role of claudins and paracellular ion-channel regulation in chronic barrier dysfunction. In the next section, we will address transcellular ion transport and highlight the role of Trek-1 in epithelial responses to lung injury. In the final section, we will outline the role of epithelial growth receptor in barrier regulation in baseline, acute lung injury, and airway disease. We will then end with a summary of mechanisms of epithelial control as well as discuss emerging paradigms of the epithelium role in shifting between a structural element that maintains tight cell-cell adhesion to a cell that initiates and participates in immune responses.

Degradation of endocytosed gap junctions by autophagosomal and endo-/lysosomal pathways: a perspective

Gap junctions (GJs) are composed of tens to many thousands of double-membrane spanning GJ channels that cluster together to form densely packed channel arrays (termed GJ plaques) in apposing plasma membranes of neighboring cells. In addition to providing direct intercellular communication (GJIC, their hallmark function), GJs, based on their characteristic double-membrane-spanning configuration, likely also significantly contribute to physical cell-to-cell adhesion. Clearly, modulation (up-/down-regulation) of GJIC and of physical cell-to-cell adhesion is as vitally important as the basic ability of GJ formation itself. Others and we have previously described that GJs can be removed from the plasma membrane via the internalization of entire GJ plaques (or portions thereof) in a cellular process that resembles clathrin-mediated endocytosis. GJ endocytosis results in the formation of double-membrane vesicles [termed annular gap junctions (AGJs) or connexosomes] in the cytoplasm of one of the coupled cells. Four recent independent studies, consistent with earlier ultrastructural analyses, demonstrate the degradation of endocytosed AGJ vesicles via autophagy. However, in TPA-treated cells others report degradation of AGJs via the endo-/lysosomal degradation pathway. Here we summarize evidence that supports the concept that autophagy serves as the cellular default pathway for the degradation of internalized GJs. Furthermore, we highlight and discuss structural criteria that seem required for an alternate degradation via the endo-/lysosomal pathway.

Cell adhesion molecule expression in human lens epithelial cells after corticosteroid exposure

Aim:

The aim of the study was to investigate changes in cell adhesion molecule expression in human lens epithelial cells (HLEC) subjected to glucocorticoids.

Methods:

Human lens epithelial cells were exposed to different concentrations of dexamethasone for 24 hours. Cell adhesion molecule expression was studied by western blot and immunohistochemistry of vimentin, N-cadherin, E-cadherin, α-catenin, β-catenin and γ-catenin. Expression of the glucocorticoid receptor (GR) was also studied. Cell morphology was examined by transmission electron microscopy (TEM).

Result:

Expression of N-cadherin, α-catenin, β-catenin and GR was significantly decreased in dexamethasone exposed cells as compared to unexposed cells. No significant change in γ-catenin was present. Visualization of adhesion molecules, N-cadherin and α-catenin, by immunohistochemistry showed decreased antigen reactivity in dexamethasone exposed as compared to the unexposed cells. However, no change was seen for β-catenin and γ-catenin. E-cadherin was not detectable using western blot or immunohistochemistry.

TEM showed multilayering of cells, vacuole formation and appearance of electron-dense multivesicular bodies in HLEC exposed to 0, 0.1, 1, 10 and 100 αM dexamethasone.

Conclusion:

Glucocorticoids affect several adhesion molecules in lens epithelial cells, something that may contribute to the pathogenesis of posterior subcapsular opacification.

Comparisons of actin filament disruptors and Rho kinase inhibitors as potential antiglaucoma medications

Dynamics of the actin cytoskeleton in the trabecular meshwork play a crucial role in the regulation of trabecular outflow resistance. The actin filament disruptors and Rho kinase inhibitors affect the dynamics of the actomyosin system by either disrupting the actin filaments or inhibiting the Rho kinase-activated cellular contractility. Both approaches induce similar morphological changes and resistance decreases in the trabecular outflow pathway, and thus both have potential as antiglaucoma medications. Although the drugs might induce detrimental changes in the cornea following topical administration, lower drug concentrations in larger volumes as used clinically, but not higher drug concentrations in smaller volumes as used experimentally, could minimize corneal toxicity. Additionally, developments of trabecular meshwork-specific actin filament disruptors or Rho kinase inhibitors, prodrugs and new drug-delivery methods might avoid the drugs' toxicity to the cornea. Gene therapies with cytoskeleton-modulating proteins may mimic the effects of the cytoskeleton-modulating agents and have the potential to permanently decrease trabecular outflow resistance.

Basic and therapeutic aspects of angiogenesis

Blood vessels form extensive networks that nurture all tissues in the body. Abnormal vessel growth and function are hallmarks of cancer and ischemic and inflammatory diseases, and they contribute to disease progression. Therapeutic approaches to block vascular supply have reached the clinic, but limited efficacy and resistance pose unresolved challenges. Recent insights establish how endothelial cells communicate with each other and with their environment to form a branched vascular network. The emerging principles of vascular growth provide exciting new perspectives, the translation of which might overcome the current limitations of pro- and antiangiogenic medicine.

Endothelial cell-specific molecule 2 (ECSM2) localizes to cell-cell junctions and modulates bFGF-directed cell migration via the ERK-FAK pathway

Background

Despite its first discovery by in silico cloning of novel endothelial cell-specific genes a decade ago, the biological functions of endothelial cell-specific molecule 2 (ECSM2) have only recently begun to be understood. Limited data suggest its involvement in cell migration and apoptosis. However, the underlying signaling mechanisms and novel functions of ECSM2 remain to be explored.

Methodology/Principal Findings

A rabbit anti-ECSM2 monoclonal antibody (RabMAb) was generated and used to characterize the endogenous ECSM2 protein. Immunoblotting, immunoprecipitation, deglycosylation, immunostaining and confocal microscopy validated that endogenous ECSM2 is a plasma membrane glycoprotein preferentially expressed in vascular endothelial cells (ECs). Expression patterns of heterologously expressed and endogenous ECSM2 identified that ECSM2 was particularly concentrated at cell-cell contacts. Cell aggregation and transwell assays showed that ECSM2 promoted cell-cell adhesion and attenuated basic fibroblast growth factor (bFGF)-driven EC migration. Gain or loss of function assays by overexpression or knockdown of ECSM2 in ECs demonstrated that ECSM2 modulated bFGF-directed EC motility via the FGF receptor (FGFR)-extracellular regulated kinase (ERK)-focal adhesion kinase (FAK) pathway. The counterbalance between FAK tyrosine phosphorylation (activation) and ERK-dependent serine phosphorylation of FAK was critically involved. A model of how ECSM2 signals to impact bFGF/FGFR-driven EC migration was proposed.

Conclusions/Significance

ECSM2 is likely a novel EC junctional protein. It can promote cell-cell adhesion and inhibit bFGF-mediated cell migration. Mechanistically, ECSM2 attenuates EC motility through the FGFR-ERK-FAK pathway. The findings suggest that ECSM2 could be a key player in coordinating receptor tyrosine kinase (RTK)-, integrin-, and EC junctional component-mediated signaling and may have important implications in disorders related to endothelial dysfunction and impaired EC junction signaling.