Regulation Of Intercellular Communication Research Articles

Downregulation of stromal syntenin sustains AMLdevelopment.

The crosstalk between cancer and stromal cells plays a critical role in tumor progression. Syntenin is a small scaffold protein involved in the regulation of intercellular communication that is emerging as a target for cancer therapy. Here, we show that certain aggressive forms of acute myeloid leukemia (AML) reduce the expression of syntenin in bone marrow stromal cells (BMSC). Stromal syntenin deficiency, in turn, generates a pro-tumoral microenvironment. From serial transplantations in mice and co-culture experiments, we conclude that syntenin-deficient BMSC stimulate AML aggressiveness by promoting AML cell survival and protein synthesis. This pro-tumoral activity is supported by increased expression of endoglin, a classical marker of BMSC, which in trans stimulates AML translational activity. In short, our study reveals a vicious signaling loop potentially at the heart of AML-stroma crosstalk and unsuspected tumor-suppressive effects of syntenin that need to beconsidered during systemic targeting of syntenin in cancer therapy.

The Role of Extracellular Vesicles in Colorectal Cancer.

Extracellular vesicles (EVs) are a class of spherical vesicles that are produced by active secretion of cells and encapsulated by phospholipid bilayers. In recent years, numerous studies have shown that EVs play pivotal roles in the regulation of intercellular communication between colorectal cancer (CRC) cells and target cells, and can regulate the proliferation, metastasis, and infiltration of tumor cells by regulating the microenvironment of tumor cells. EVs carry specific molecular substances in source CRC cells and are expected to serve as new molecular markers for the detection of cancers. This review highlights the current state of research and progress of potentially incorporating EVs in the diagnosis and treatment of CRC.

Anchored-PKA regulates connexin-43 gap junction communication in the heart

Cardiac connexin-43 (Cx43) forms gap junction (GJ) channels at the intercalated discs (ID) of cardiomyocytes ensuring anisotropic action potential (AP) propagation. This process is essential for sequential and coordinated contraction of the heart. Stimulation of β-adrenergic receptors activates protein kinase A (PKA), which in turn increases electrical conduction velocity. Myocardial infarction (MI) is characterized by a prolonged ischemia leading to irreversible ventricular cardiomyocytes death and impaired cardiac function. To compensate this loss, chronic activation of PKA signaling is established. In addition, post-MI, Cx43 subcellular localization is altered affecting GJ communication and AP propagation leading to uncoordinated contractions and fatal arrhythmias. Considering the key role of Cx43 and PKA signaling in AP propagation, we investigated the potential regulation of GJ communication by PKA under cardiac physiological condition and post-MI. First, we assessed Cx43 phosphorylation with PKA specific inhibition and with a peptide displacing PKA anchoring from A-Kinase Anchoring Protein (AKAPs). Then, we identified the ezrin as the AKAP mediated the regulation of Cx43 phosphorylation by immunoprecipitation, immunofluorescence and siRNA mediated knockdown experiments. We assessed by functional GAP-FLIP experiments the key role of ezrin-PKA complex in the regulation of intercellular communication. Finally, we generated a left anterior descending coronary artery model of MI in rats to evaluate by proximity ligation assay and western blot experiments the Cx43-ezrin-PKA complex localization and expression. We point that ezrin forms a supramolecular complex with PKA and Cx43 at the ID of cardiomyocytes. Ezrin regulates Cx43 phosphorylation and GJ communication in cardiomyocytes. Interestingly, post-MI we noticed a significant reduction in Cx43 level and phosphorylation associated with a decrease in proximity with ezrin at the ID. Our data identified a cardiac PKA-ezrin-Cx43 complex regulating Cx43 phosphorylation, and therefore, GJ communication. In addition, we reported a loss of proximity between ezrin and Cx43 post-MI. We proposed that this may explain partly an impaired AP propagation leading to uncoordinated contractions post MI.

In Vivo Aniline Blue Staining and Semiautomated Quantification of Callose Deposition at Plasmodesmata.

The deposition and turnover of callose (beta-1,3 glucan polymer) in the cell wall surrounding the neck regions of plasmodesmata (PD) controls the cell-to-cell diffusion rate of molecules and, therefore, plays an important role in the regulation of intercellular communication in plants.Here we describe a simple and fast in vivo staining procedure for the imaging and quantification of callose at PD. We also introduce calloseQuant, a plug-in for semiautomated image analysis and non-biased quantification of callose levels at PD using ImageJ.

Nitric Oxide and Electrophilic Cyclopentenone Prostaglandins in Redox signaling, Regulation of Cytoskeleton Dynamics and Intercellular Communication.

Nitric oxide (NO) and electrophilic cyclopentenone prostaglandins (CyPG) are local mediators that modulate cellular response to oxidative stress in different pathophysiological processes. In particular, there is increasing evidence about their functional role during inflammation and immune responses. Although the mechanistic details about their relationship and functional interactions are still far from resolved, NO and CyPG share the ability to promote redox-based post-translational modification (PTM) of proteins that play key roles in cellular homeostasis, signal transduction and transcription. NO-induced S-nitrosylation and S-glutathionylation as well as cyclopentenone-mediated adduct formation, are a few of the main PTMs by which intra- and inter-cellular signaling are regulated. There is a growing body of evidence indicating that actin and actin-binding proteins are susceptible to covalent PTM by these agents. It is well known that the actin cytoskeleton is key for the establishment of interactions among leukocytes, endothelial and muscle cells, enabling cellular activation and migration. In this review we analyze the current knowledge about the actions exerted by NO and CyPG electrophilic lipids on the regulation of actin dynamics and cytoskeleton organization, and discuss some open questions regarding their functional relevance in the regulation of intercellular communication.

Extracellular Vesicle miRNAs in the Promotion of Cardiac Neovascularisation.

Cardiovascular disease (CVD) is the leading cause of mortality worldwide claiming almost 17. 9 million deaths annually. A primary cause is atherosclerosis within the coronary arteries, which restricts blood flow to the heart muscle resulting in myocardial infarction (MI) and cardiac cell death. Despite substantial progress in the management of coronary heart disease (CHD), there is still a significant number of patients developing chronic heart failure post-MI. Recent research has been focused on promoting neovascularisation post-MI with the ultimate goal being to reduce the extent of injury and improve function in the failing myocardium. Cardiac cell transplantation studies in pre-clinical models have shown improvement in cardiac function; nonetheless, poor retention of the cells has indicated a paracrine mechanism for the observed improvement. Cell communication in a paracrine manner is controlled by various mechanisms, including extracellular vesicles (EVs). EVs have emerged as novel regulators of intercellular communication, by transferring molecules able to influence molecular pathways in the recipient cell. Several studies have demonstrated the ability of EVs to stimulate angiogenesis by transferring microRNA (miRNA, miR) molecules to endothelial cells (ECs). In this review, we describe the process of neovascularisation and current developments in modulating neovascularisation in the heart using miRNAs and EV-bound miRNAs. Furthermore, we critically evaluate methods used in cell culture, EV isolation and administration.

MicroRNAs As Master Regulators of Atherosclerosis: From Pathogenesis to Novel Therapeutic Options.

Significance: Cardiovascular disease (CVD) remains the major cause of morbidity and mortality worldwide. Accumulating evidence indicates that atherosclerosis and its sequelae, coronary artery disease, contribute to the majority of cardiovascular deaths. Atherosclerosis is a chronic inflammatory disease of the arteries in which atherosclerotic plaques form within the vessel wall. Epidemiological studies have identified various risk factors for atherosclerosis, such as diabetes, hyperlipidemia, smoking, genetic predisposition, and sedentary lifestyle. Recent Advances: Through the advancement of genetic manipulation techniques and their use in cardiovascular biology, it was shown that small RNAs, especially microRNAs (miRNAs), are dynamic regulators of disease pathogenesis. They are considered to be central during the regulation of gene expression through numerous mechanisms and provide a means to develop biomarkers and therapeutic tools for the diagnosis and therapy of atherosclerosis. Circulating miRNAs encapsulated within membrane-surrounded vesicles, which originate from diverse subcellular compartments, are now emerging as novel regulators of intercellular communication. The miRNAs, in both freely circulating and vesicle-bound forms, represent a valuable tool for diagnosing and monitoring CVD, recently termed as "liquid biopsy." Critical Issues: However, despite the recent advancements in miRNA-based diagnostics and therapeutics, understanding how miRNAs can regulate atherosclerosis is still crucial to achieving an effective intervention and reducing the disease burden. Future Directions: We provide a landscape of the current developmental progression of RNA therapeutics as a holistic approach for treating CVD in different animal models and clinical trials. Future interrogations are warranted for the development of miRNA-based therapeutics to overcome challenges for the treatment of the disease.

Pancreatic β cell microRNA-26a alleviates type 2 diabetes by improving peripheral insulin sensitivity and preserving β cell function.

Type 2 diabetes (T2D) is characterized by insulin resistance along with pancreatic β cell failure. β cell factors are traditionally thought to control glucose homeostasis by modulating insulin levels, not insulin sensitivity. Exosomes are emerging as new regulators of intercellular communication. However, the role of β-cell–derived exosomes in metabolic homeostasis is poorly understood. Here, we report that microRNA-26a (miR-26a) in β cells not only modulates insulin secretion and β cell replication in an autocrine manner but also regulates peripheral insulin sensitivity in a paracrine manner through circulating exosomes. MiR-26a is reduced in serum exosomes of overweight humans and is inversely correlated with clinical features of T2D. Moreover, miR-26a is down-regulated in serum exosomes and islets of obese mice. Using miR-26a knockin and knockout mouse models, we showed that miR-26a in β cells alleviates obesity-induced insulin resistance and hyperinsulinemia. Mechanistically, miR-26a in β cells enhances peripheral insulin sensitivity via exosomes. Meanwhile, miR-26a prevents hyperinsulinemia through targeting several critical regulators of insulin secretion and β cell proliferation. These findings provide a new paradigm for the far-reaching systemic functions of β cells and offer opportunities for the treatment of T2D.

The Contrasting Role of Extracellular Vesicles in Vascular Inflammation and Tissue Repair.

Extracellular vesicles are a heterogeneous family of vesicles, generated from different subcellular compartments and released into the extracellular space. Composed of a lipid bilayer encompassing both soluble cytosolic material and nuclear components, these organelles have been recently described as novel regulators of intercellular communication between adjacent and remote cells. Due to their diversified composition and biological content, they portray specific signatures of cellular activation and pathological processes, their potential as diagnostic and prognostic biomarkers has raised significant interest in cardiovascular diseases. Circulating vesicles, especially those released from platelets, leukocytes, and endothelial cells are found to play a critical role in activating several fundamental cells within the vasculature, including endothelial cells and vascular smooth muscle cells. Their intrinsic activity and immunomodulatory properties lends them to not only promote vascular inflammation, but also enhance tissue regeneration, vascular repair, and indeed resolution. In this review we aim to recapitulate the recent findings concerning the roles played by EVs that originate from different circulating cells, with particular reference to their action on the endothelium. We focus herein, on the interaction of platelet and leukocyte EVs with the endothelium. In addition, their potential biological function in promoting tissue resolution and vascular repair will also be discussed.

Tight Junction Protein (Claudin-4) and Inflammatory Regulator (COX-2) Expression in Nasopharyngeal Carcinoma: An Immunohistochemical Study

AbstractBackground: Claudin 4 is one of the tight junction proteins which considered one of the protective barriers that are mostly involved in the regulation of intercellular communication, paracellular transport and apical cell-to-cell adhesion. Over-expression of COX-2 and subsequent increase in prostaglandins (PGs) concentration have emerged in recent years as important players in cancer progression.Aim of Study: To explore immunohisto chemically the expression of both claudin-4 and COX2 in nasopharyngeal carcinoma and correlate their expression with each other and with different clinicopathological parameters.Material and Methods: This retrospective study was done upon formalin fixed, paraffin blocks of 32 nasopharngeal carcinoma cases and 6 non-neoplastic nasopharyngeal epithe-lium. The materials were obtained from archieves of Pathology Departement and Early Cancer Detection Unit (ECDU), Faculty of Medicine, Benha University during the years 2012- 2017. The immunohistochemical stain with Claudin 4 and COX2 was done and evaluated for each case.Results: High expression of claudin 4 was observed in 44% of studied nasopharyngeal cases with statistically signif-icant correlation with tumor stage and distant metastasis (p<0.05). Positive expression of COX2 was detected in 75% of neoplastic group and statistically correlated with depth of tumor invasion, nodal invasion and tumor stage (p<0.05). A statistically significant correlation was detected between overexpression of COX2 and low expression of claudin4 in the studied neoplastic cases (p<0.05).Conclusion: Claudin -4 has different tumorigenic effects besides their known adhesion attributes. Because of that, we believe that claudin 4 with other clinicopahological parameters may be a promising prognostic molecular indicator in na-sopharyngeal cancer cases and can be taken as a novel bi-omarker for the predication of distant metastasis and survival. This work also highlights COX-2 expression's potential as an indicator of cancer progression that can contribute to assess-ment of prognosis and treatment decisions. Therefore, COX-2 inhibitors may have considerable potential as therapeutic agents.

Systemic Immune Response to Traumatic CNS Injuries-Are Extracellular Vesicles the Missing Link?

Inflammation following traumatic injury to the central nervous system (CNS) persists long after the primary insult and is known to exacerbate cell death and worsen functional outcomes. Therapeutic interventions targeting this inflammation have been unsuccessful, which has been attributed to poor bioavailability owing to the presence of blood-CNS barrier. Recent studies have shown that the magnitude of the CNS inflammatory response is dependent on systemic inflammatory events. The acute phase response (APR) to CNS injury presents an alternative strategy to modulating the secondary phase of injury. However, the communication pathways between the CNS and the periphery remain poorly understood. Extracellular vesicles (EVs) are membrane bound nanoparticles that are regulators of intercellular communication. They are shed from cells of the CNS including microglia, astrocytes, neurons and endothelial cells, and are able to cross the blood-CNS barrier, thus providing an attractive candidate for initiating the APR after acute CNS injury. The purpose of this review is to summarize the current evidence that EVs play a critical role in the APR following CNS injuries.

Extracellular Vesicles in Cardiovascular Disease: Potential Applications in Diagnosis, Prognosis, and Epidemiology.

Extracellular vesicles originate from diverse subcellular compartments and are released in the extracellular space. By transferring their cargoes into target cells and tissues, they now emerge as novel regulators of intercellular communication between adjacent and remote cells. Because vesicle composition and biological content are specific signatures of cellular activation and injury, their potential as diagnostic and prognostic biomarkers has raised significant interest in cardiovascular diseases. Characterization of circulating vesicles- or nonvesicles-bound nucleic acids represents a valuable tool for diagnosing and monitoring cardiovascular diseases, recently referred to as a liquid biopsy. Circulating extracellular vesicles offer a noninvasive and almost continuous access to circulating information on the disease state in epidemiological investigations. Finally, genetic engineering and cell-specific application of extracellular vesicles could display a novel therapeutic option for the treatment of cardiovascular diseases. In this review, we summarize the current knowledge about extracellular vesicles as diagnostic and prognostic biomarkers, as well as their potential applications for longitudinal epidemiological studies in cardiovascular diseases.

Exosomic microRNAs as emerging key regulators of intercellular communication in the tumor microenvironment and beyond

AbstractMicroRNAs (miRs) are small non-coding RNAs with key gene regulatory functions. Recent evidence has shown that miRs have a central role in shaping the biology of the Tumor Microenvironment (TME). The discovery that some exosomes contain high levels of miR cargo that shuttle between cells and mediate intercellular cross-talk has shifted the focus of miR research towards understanding the biological role of exosomic miRs. In this review, we highlight the emerging role of exosomic miRs in molding the tumor microenvironment towards pro-tumor conditions by altering intercellular communication. We briefly discuss some mechanisms of selective loading of miRs into exosomes, as well as emerging evidence that exosomic miRs are present in all biological fluids. Furthermore, we describe the differences in the exosomic miR signatures between cancer patients and healthy controls, and the potential role of exosomic miRs as diagnostic, prognostic, and therapeutic biomarkers.

Biology of callose (β-1,3-glucan) turnover at plasmodesmata

The turnover of callose (β-1,3-glucan) within cell walls is an essential process affecting many developmental, physiological and stress related processes in plants. The deposition and degradation of callose at the neck region of plasmodesmata (Pd) is one of the cellular control mechanisms regulating Pd permeability during both abiotic and biotic stresses. Callose accumulation at Pd is controlled by callose synthases (CalS; EC 2.4.1.34), endogenous enzymes mediating callose synthesis, and by β-1,3-glucanases (BG; EC 3.2.1.39), hydrolytic enzymes which specifically degrade callose. Transcriptional and posttranslational regulation of some CalSs and BGs are strongly controlled by stress signaling, such as that resulting from pathogen invasion. We review the role of Pd-associated callose in the regulation of intercellular communication during developmental, physiological, and stress response processes. Special emphasis is placed on the involvement of Pd-callose in viral pathogenicity. Callose accumulation at Pd restricts virus movement in both compatible and incompatible interactions, while its degradation promotes pathogen spread. Hence, studies on mechanisms of callose turnover at Pd during viral cell-to-cell spread are of importance for our understanding of host mechanisms exploited by viruses in order to successfully spread within the infected plant.

Effects of semaphorin 3A overexpression in corneal fibroblasts on the expression of adherens-junction proteins in corneal epithelial cells

Interactions between epithelial cells and fibroblasts play important roles in tissue homeostasis. Semaphorins are a family of glycoproteins that contribute to axon guidance during development. With the use of a coculture system in which human corneal fibroblasts and epithelial cells are cultured on opposite sides of a collagen membrane, we have examined the effects of overexpression of semaphorin 3A in corneal fibroblasts on the expression of junctional proteins in corneal epithelial cells. Reverse transcription-polymerase chain reaction as well as immunoblot and immunofluorescence analyses revealed that the overexpression of semaphorin 3A in corneal fibroblasts increased the expression of E-cadherin and N-cadherin in corneal epithelial cells at both the mRNA and protein levels. These effects of semaphorin 3A were dependent on the presence of extracellular Ca 2+. Our findings indicate that semaphorin 3A released from corneal fibroblasts may play an important role in the regulation of intercellular communication between corneal epithelial cells as well as in the maintenance of corneal structure and function.

TGF-β1 down-regulates connexin 43 expression and gap junction intercellular communication in rat hepatic stellate cells

Intercellular communication is an important tool used by the cells to effectively regulate concerted responses. Hepatic stellate cells (HSCs) communicate to each other through functional gap junctions composed of connexin 43 (Cx43) proteins. We show that exogenous human TGF-β1 (hTGF-β1), a pro-fibrotic stimulus, decreases Cx43 mRNA and protein in a rat HSC cell line and primary HSCs. Furthermore, hTGF-β1 increases the phosphorylation of Cx43 at serine 368. These effects lead to a decrease in the gap junction intercellular communication between the HSCs, as shown by gap-FRAP analysis. We also observe the binding of Snai1, from the nuclear extract of HSCs, to a Snai1 consensus sequence in the Cx43 promoter. In the same context, Snai1 siRNA transfection results in an up-regulation of Cx43 suggesting that TGF-β1 may regulate Cx43 via Snai1. In addition, we demonstrate that the knockdown of Cx43 by siRNA transfection results in a slower proliferation of HSCs. These findings illuminate a new effect of TGF-β1 in HSCs, namely the regulation of intercellular communication by affecting the expression level and the phosphorylation state of Cx43 through Snai1 signaling.

Betablockers can up-regulate cardiac intercellular communication channels: a new antiarrhythmic mechanism for an old therapy?

Objective: Betablocker therapy is among the antiarrhythmic strategies used in atrial fibrillation and ventricular arrhythmia. Since our previous findings indicated a possible role of alpha- and beta-adrenoreceptors in regulation of intercellular communication via Cx43 gap junction channels, we investigated in cultured rat cardiomyocytes (CRC) and patients with AF the expression of CX40 and CX43 and the influence of beta-adrenergic-agonist treatment on it.

E-Cadherin and Cell Adhesion: a Role in Architecture and Function in the Pancreatic Islet

Background/Aims: The efficient secretion of insulin from β-cells requires extensive intra-islet communication. The cell surface adhesion protein epithelial (E)-cadherin (ECAD) establishes and maintains epithelial tissues such as the islets of Langerhans. In this study, the role of ECAD in regulating insulin secretion from pseudoislets was investigated. Methods: The effect of an immuno-neutralising ECAD on gross morphology, cytosolic calcium signalling, direct cell-to-cell communication and insulin secretion was assessed by fura-2 microfluorimetry, Lucifer Yellow dye injection and insulin ELISA in an insulin-secreting model system. Results: Antibody blockade of ECAD reduces glucose-evoked changes in [Ca²⁺]_i and insulin secretion. Neutralisation of ECAD causes a breakdown in the glucose-stimulated synchronicity of calcium oscillations between discrete regions within the pseudoislet, and the transfer of dye from an individual cell within a cell cluster is attenuated in the absence of ECAD ligation, demonstrating that gap junction communication is disrupted. The functional consequence of neutralising ECAD is a significant reduction in insulin secretion. Conclusion: Cell adhesion via ECAD has distinct roles in the regulation of intercellular communication between β-cells within islets, with potential repercussions for insulin secretion.

Bone morphogenetic protein-2 modulation of chondrogenic differentiation in vitro involves gap junction-mediated intercellular communication.

Undifferentiated mesenchymal cells in the limb bud integrate a complex array of local and systemic signals during the process of cell condensation and chondrogenic differentiation. To address the relationship between bone morphogenetic protein (BMP) signaling and gap junction-mediated intercellular communication, we examined the effects of BMP-2 and a gap junction blocker 18 alpha glycyrrhetinic acid (18alpha-GCA) on mesenchymal cell condensation and chondrogenic differentiation in an in vitro chondrogenic model. We find that connexin43 protein expression significantly correlates with early mesenchymal cellular condensation and chondrogenesis in high-density limb bud cell culture. The level of connexin43 mRNA is maximally upregulated 48 h after treatment with recombinant human BMP-2 with corresponding changes in protein expression. Inhibition of gap junction-mediated intercellular communication with 2.5 microM 18alpha-GCA decreases chondrogenic differentiation by 50% at 96 h without effects on housekeeping genes. Exposure to 18alpha-GCA for only the first 24-48 h after plating does not affect condensation or later chondrogenic differentiation suggesting that gap junction-mediated intercellular communication is not critical for the initial phase of condensation but is important for the onset of differentiation. 18alpha-GCA can also block the chondrogenic effects of BMP-2 without effects on cell number or connexin43 expression. These observations demonstrate 18alpha-GCA-sensitive regulation of intercellular communication in limb mesenchymal cells undergoing chondrogenic differentiation and suggest that BMP-2 induced chondrogenic differentiation may be mediated in part through the modulation of connexin43 expression and gap junction-mediated intercellular communication.

Gap Junctions: Structure, Functions, and Regulation

The review presents data on the role of gap junctions in intercellular communication. The review includes information on history of the appearance of this problem. Data are presented on ultrastructure and function of gap junctions as well as on the mechanisms providing for their activity. A part of the review deals with the problem of regulation of intercellular communication realized by the gap junctions.