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Intercellular Communication (intercellular + communication)
Kinds of Intercellular Communication Selected AbstractsDual Mechanism of Intercellular Communication in HOBIT Osteoblastic Cells: A Role for Gap-Junctional HemichannelsJOURNAL OF BONE AND MINERAL RESEARCH, Issue 8 2001Milena Romanello Abstract Intercellular communication allows tissue coordination of cell metabolism and sensitivity to extracellular stimuli. Paracrine stimulation and cell-to-cell coupling through gap junctions induce the formation of complex cellular networks, which favors the intercellular exchange of nutrients and second messengers. Intercellular Ca2+ signaling was investigated in human osteoblast-like initial transfectant (HOBIT) cells, a human osteoblastic cell line in which cells retain most of the osteoblastic differentiation markers. HOBIT cells express connexin43 (Cx43) clustered at the cell-to-cell boundary and display functional intercellular coupling as assessed by the intercellular transfer of Lucifer yellow. Mechanical stimulation of a single cell induced a wave of increased Ca2+ that was radially propagated to surrounding cells. Treatment of cells with thapsigargin blocked mechanically induced signal propagation. Intercellular Ca2+ spreading and dye transfer were inhibited by 18,-glycyrrhetinic acid (18-GA), showing the involvement of gap junctions in signal propagation. Pretreatment of cells with suramin or with apyrase decreased the extent of wave propagation, suggesting that ATP-mediated paracrine stimulation contribute to cell-to-cell signaling. The functional expression of gap-junctional hemichannels was evidenced in experiments of Mn2+ quenching, extracellular dye uptake, and intracellular Ca2+ release, activated by uptake of inositol 1,4,5-trisphosphate (InsP3) from the external medium. Gap-junctional hemichannels were activated by low extracellular Ca2+ concentrations and inhibited by 18-GA. A role for Cx hemichannels in adenosine triphosphate (ATP) release and paracrine stimulation is suggested. [source] Glycobiology: The sweet language of life, complexity, and morphogenesis: Syntax for Intermolecular and Intercellular CommunicationCOMPLEXITY, Issue 6 2007Lokesh Joshi No abstract is available for this article. [source] Dual Mechanism of Intercellular Communication in HOBIT Osteoblastic Cells: A Role for Gap-Junctional HemichannelsJOURNAL OF BONE AND MINERAL RESEARCH, Issue 8 2001Milena Romanello Abstract Intercellular communication allows tissue coordination of cell metabolism and sensitivity to extracellular stimuli. Paracrine stimulation and cell-to-cell coupling through gap junctions induce the formation of complex cellular networks, which favors the intercellular exchange of nutrients and second messengers. Intercellular Ca2+ signaling was investigated in human osteoblast-like initial transfectant (HOBIT) cells, a human osteoblastic cell line in which cells retain most of the osteoblastic differentiation markers. HOBIT cells express connexin43 (Cx43) clustered at the cell-to-cell boundary and display functional intercellular coupling as assessed by the intercellular transfer of Lucifer yellow. Mechanical stimulation of a single cell induced a wave of increased Ca2+ that was radially propagated to surrounding cells. Treatment of cells with thapsigargin blocked mechanically induced signal propagation. Intercellular Ca2+ spreading and dye transfer were inhibited by 18,-glycyrrhetinic acid (18-GA), showing the involvement of gap junctions in signal propagation. Pretreatment of cells with suramin or with apyrase decreased the extent of wave propagation, suggesting that ATP-mediated paracrine stimulation contribute to cell-to-cell signaling. The functional expression of gap-junctional hemichannels was evidenced in experiments of Mn2+ quenching, extracellular dye uptake, and intracellular Ca2+ release, activated by uptake of inositol 1,4,5-trisphosphate (InsP3) from the external medium. Gap-junctional hemichannels were activated by low extracellular Ca2+ concentrations and inhibited by 18-GA. A role for Cx hemichannels in adenosine triphosphate (ATP) release and paracrine stimulation is suggested. [source] Pannexins, distant relatives of the connexin family with specific cellular functions?BIOESSAYS, Issue 9 2009Catheleyne D'hondt Abstract Intercellular communication (IC) is mediated by gap junctions (GJs) and hemichannels, which consist of proteins. This has been particularly well documented for the connexin (Cx) family. Initially, Cxs were thought to be the only proteins capable of GJ formation in vertebrates. About 10 years ago, however, a new GJ-forming protein family related to invertebrate innexins (Inxs) was discovered in vertebrates, and named the pannexin (Panx) family. Panxs, which are structurally similar to Cxs, but evolutionarily distinct, have been shown to be co-expressed with Cxs in vertebrates. Both protein families show distinct properties and have their own particular function. Identification of the mechanisms that control Panx channel gating is a major challenge for future work. In this review, we focus on the specific properties and role of Panxs in normal and pathological conditions. [source] Local Ca2+ influx through CRAC channels activates temporally and spatially distinct cellular responsesACTA PHYSIOLOGICA, Issue 1 2009A. B. Parekh Abstract Ca2+ entry through store-operated Ca2+ release-activated Ca2+ (CRAC) channels controls a disparate array of key cellular responses. In this review, recent work will be described that shows local Ca2+ influx through CRAC channels has important spatial and temporal consequences on cell function. A localized Ca2+ rise below the plasma membrane activates, within tens of seconds, catabolic enzymes resulting in the generation of the intracellular messenger arachidonic acid and the paracrine pro-inflammatory molecule LTC4. In addition, local Ca2+ entry can activate gene expression, which develops over tens of minutes. Local Ca2+ influx through CRAC channels therefore has far-reaching consequences on intra- and intercellular communication. [source] Connexins, cell motility, and the cytoskeletonCYTOSKELETON, Issue 11 2009Stephan Olk Abstract Connexins (Cx) comprise a family of transmembrane proteins, which form intercellular channels between plasma membranes of two adjoining cells, commonly known as gap junctions. Recent reports revealed that Cx proteins interact with diverse cellular components to form a multiprotein complex, which has been termed "Nexus". Potential interaction partners include proteins such as cytoskeletal proteins, scaffolding proteins, protein kinases and phosphatases. These interactions allow correct subcellular localization of Cxs and functional regulation of gap junction-mediated intercellular communication. Evidence is accruing that Cxs might have channel-independent functions, which potentially include regulation of cell migration, cell polarization and growth control. In the current review, we summarize recent knowledge on Cx interactions with cytoskeletal proteins and highlight some aspects of their role in cellular motility. Cell Motil. Cytoskeleton 66: 1000,1016, 2009. © 2009 Wiley-Liss, Inc. [source] Segment-specific expression of connexin31 in the embryonic hindbrain is regulated by Krox20DEVELOPMENTAL DYNAMICS, Issue 4 2002Stefan Jungbluth Abstract Communication and interaction between cells has been shown to be important during the embryonic development of the vertebrate hindbrain, which becomes transiently subdivided into segments called rhombomeres (r). One gene family allowing intercellular communication and possibly being involved in the control of hindbrain development is the connexin family encoding gap junction channels. Here, we have characterized in detail the previously observed (Dahl et al., 1997) expression of one particular connexin gene, connexin31 (Cx31), in the mouse embryonic hindbrain and compared it with that of Cx43 and Cx36. We found transient Cx31 expression from approximately embryonic day (E) E8,E11 in two small lateral/dorsal subgroups of cells in the hindbrain. We could show that these spots of expression corresponded to r3 and r5 and that Cx31 expression in r3 and r5 was controlled by the transcription factor Krox20. In contrast, expression of Cx43 and Cx36 started later (from E9.5 and E10.5, respectively) and was confined to longitudinal stripes of expression. In addition, from E10.5,E11.5, Cx31 was expressed by a column of cells in ventral r4, most likely representing contralateral vestibulo-acoustic efferent neurons, immediately anterior to a ventral column expressing Cx36 at the same stage. From E11.5 onward, another site of Cx31 expression was detected in the boundary cap cells in the entry/exit points of all mixed sensory/motor and in the entry points of pure sensory nerves. This expression was not present in the boundary cap cells of the exit points of pure motor nerves. So far, our analysis of the hindbrain area of Cx31 -deficient embryos in terms of projections of sensory or motor neurons or in the generation or migration of neurons has not yet revealed any obvious defects. © 2002 Wiley-Liss, Inc. [source] Effect of byproducts from the ozonation of pyrene: Biphenyl-2,2,,6,6,-tetracarbaldehyde and biphenyl-2,2,,6,6,-tetracarboxylic acid on gap junction intercellular communication and neutrophil functionENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 3 2005Stephanie L. Luster-Teasley Abstract In this study, biphenyl-2,2,,6,6,-tetracarbaldehyde, an initial by product formed from the ozonation of pyrene, and biphenyl-2,2,,6,6,-tetracarboxylic acid, a subsequent pyrene ozonation byproduct, were evaluated using two toxicology assays to compare the toxicity of ozonation byproducts with that of the parent compound. The first assay measured the potential for the compounds to block gap junctional intercellular communication (GJIC) using the scrape loading/dye transfer technique in normal WB-344 rat liver epithelial cells. The second assay evaluated the ability of the compounds to affect neutrophil function by measuring the production of superoxide in a human cell line (HL-60). Pyrene significantly blocked intercellular communication (f= 0.2,0.5) at 40 ,M and complete inhibition of communication (f < 0.2) occurred at 50 ,M. Gap junctional intercellular communication in cells exposed to biphenyl-2,2,,6,6,-tetracarbaldehyde reached f < 0.5 at a concentration of 15 ,M. At concentrations greater than 20 ,M, biphenyl-2,2,,6,6,-tetracarbaldehyde was cytotoxic and the inhibition of GJIC was caused by cell death. Biphenyl-2,2,,6,6,-tetracarboxylic acid was neither cytotoxic nor inhibitory to GJIC at the concentrations tested (10,500 ,M). Exposure to biphenyl-2,2,,6,6,-tetracarbaldehyde resulted in a concentration-dependent decrease in phorbol 12-myristate 13-acetate,stimulated O12 production. Neither exposure to pyrene nor biphenyl-2,2,,6,6,-tetracarboxylic acid caused a significant toxic effect on neutrophil function. [source] Quorum-sensing in Gram-negative bacteriaFEMS MICROBIOLOGY REVIEWS, Issue 4 2001Neil A Whitehead Abstract It has become increasingly and widely recognised that bacteria do not exist as solitary cells, but are colonial organisms that exploit elaborate systems of intercellular communication to facilitate their adaptation to changing environmental conditions. The languages by which bacteria communicate take the form of chemical signals, excreted from the cells, which can elicit profound physiological changes. Many types of signalling molecules, which regulate diverse phenotypes across distant genera, have been described. The most common signalling molecules found in Gram-negative bacteria are N -acyl derivatives of homoserine lactone (acyl HSLs). Modulation of the physiological processes controlled by acyl HSLs (and, indeed, many of the non-acyl HSL-mediated systems) occurs in a cell density- and growth phase-dependent manner. Therefore, the term ,quorum-sensing' has been coined to describe this ability of bacteria to monitor cell density before expressing a phenotype. In this paper, we review the current state of research concerning acyl HSL-mediated quorum-sensing. We also describe two non-acyl HSL-based systems utilised by the phytopathogens Ralstonia solanacearum and Xanthomonas campestris. [source] A role for Connexin43 during neurodevelopmentGLIA, Issue 7 2007Amy E. Wiencken-Barger Abstract Connexin43 (Cx43) is the predominant gap junction protein expressed in premitotic radial glial cells and mature astrocytes. It is thought to play a role in many aspects of brain development and physiology, including intercellular communication, the release of neuroactive substances, and neural and glial proliferation and migration. To investigate the role of Cx43 in brain physiology, we generated a conditional knockout (cKO) mouse expressing Cre recombinase driven by the human GFAP promoter and a floxed Cx43 gene. The removal of Cx43 from GFAP-expressing cells affects the behavior of the mice and the development of several brain structures; however, the severity of the phenotype varies depending on the mouse background. One mouse subline, hereafter termed Shuffler, exhibits cellular disorganization of the cortex, hippocampus, and cerebellum, accompanied by ataxia and motor deficits. The Shuffler cerebellum is most affected and displays altered distribution and lamination of glia and neurons suggestive of cell migration defects. In all Shuffler mice by postnatal day two (P2), the hippocampus, cortex, and cerebellum are smaller. Disorganization of the ventricular and subventricular zone of the cortex is also evident. Given that these are sites of early progenitor cell proliferation, we suspect production and migration of neural progenitors may be altered. In conclusion, neurodevelopment of Shuffler/Cx43 cKO mice is abnormal, and the observed cellular phenotype may explain behavioral disturbances seen in these animals as well as in humans carrying Cx43 mutations. © 2007 Wiley-Liss, Inc. [source] The TLR3 ligand polyI:C downregulates connexin 43 expression and function in astrocytes by a mechanism involving the NF-,B and PI3 kinase pathwaysGLIA, Issue 8 2006Yongmei Zhao Abstract Toll-like receptor 3 (TLR3) is a component of the innate immune response that responds to dsRNA viruses and virus replication intermediates. In this study we show that activation of astrocytes with the dsRNA mimetic polyinosinic-cytidylic acid (pI:C) results in loss of expression of connexin43 (Cx43) mRNA and protein while upregulating the expression of the ionotropic P2 receptor P2X4R. Analysis of the signaling pathways involved failed to demonstrate a role for the p38 MAP kinase, ERK, or JNK signaling pathways whereas an inhibitor of the PI3 kinase/Akt pathway effectively blocked the action of pI:C. Using adenoviral vectors containing a super-repressor of NF-,B (NF-,B SR) construct or a dominant negative interferon regulatory factor 3 (dnIRF3) construct showed that inhibition of both transcription factors also blocked the effects of pI:C. To explore the functional consequences of pI:C activation we used a pore-forming assay for P2X4R activity and a scrape loading assay for gap junction intercellular communication (GJIC). No pore-forming activity consistent with functional P2X4R expression was detected in either control or activated astrocytes. In contrast, robust Lucifer yellow transfer indicative of GJIC was detected in resting cells that was lost following pI:C activation. The dnIRF3 construct failed to restore GJIC whereas the NF-,B SR or the NF-,B inhibitor BAY11-7082 and the PI3K inhibitor LY294002 all significantly reversed the effect of pI:C on GJ connectivity. We conclude that activation of the innate immune response in astrocytes is associated with functional loss of GJIC through a pathway involving NF-,B and PI3 kinase. © 2006 Wiley-Liss, Inc. [source] Enhanced Connexin 43 immunoreactivity in penumbral areas in the human brain following ischemiaGLIA, Issue 5 2006Taizen Nakase Abstract Astrocytes support neurons not only physically but also chemically by secreting neurotrophic factors and energy substrates. Moreover, astrocytes establish a glial network and communicate through gap junctions in the brain. Connexin 43 (Cx43) is one of major component proteins in astrocytic gap junctions. Heterozygote Cx43 KO mice and astrocyte specific Cx43 KO mice exhibited amplified brain damage after ischemic insults, suggesting a neuroprotective role for astrocytic gap junctions. However, some reports mentioned unfavorable effects of gap junctions in neuronal support. Therefore, the role of astrocytic gap junctions under ischemic condition remains controversial. Since these studies have been performed using animal models, we investigated the Cx43 expression in human brain after stroke. Brain slice sections were prepared from pathological samples in our hospital. Embolic stroke brains sectioned because of the stroke were considered as acute ischemic models. Multiple infarction brains sectioned because of pneumonia or cancer were considered as chronic models. We observed the levels of Cx43 in both lesioned and intact areas, and compared them with acute and chronic models. As the results, astrocytes were strongly activated in penumbral lesions both of acute and chronic ischemic models. The Cx43 immunoreactivity was significantly amplified in the penumbra of chronic model compared to that of the acute model. Neurons were well preserved in chronic model compared to acute model. These findings suggested that the brain may generate neuronal protection by increasing the levels of Cx43 and amplifying the astrocytic gap junctional intercellular communication under hypoxic condition. © 2006 Wiley-Liss, Inc. [source] HuR regulates gap junctional intercellular communication by controlling ,-catenin levels and adherens junction integrity,HEPATOLOGY, Issue 5 2009Niloofar Ale-Agha Gap junctional intercellular communication (GJIC) plays a critical role in the regulation of tissue homeostasis and carcinogenesis and is modulated by the levels, subcellular localization, and posttranslational modification of gap junction proteins, the connexins (Cx). Here, using oval cell-like rat liver epithelial cells, we demonstrate that the RNA-binding protein HuR promotes GJIC through two mechanisms. First, HuR silencing lowered the levels of Cx43 protein and Cx43 messenger RNA (mRNA), and decreased Cx43 mRNA half-life. This regulation was likely due to the direct stabilization of Cx43 mRNA by HuR, because HuR associated directly with Cx43 mRNA, a transcript that bears signature adenylate-uridylate-rich (AU-rich) and uridylate-rich (U-rich) sequences in its 3,-untranslated region. Second, HuR silencing reduced both half-life and the levels of ,-catenin mRNA, also a target of HuR; accordingly, HuR silencing lowered the levels of whole-cell and membrane-associated ,-catenin. Coimmunoprecipitation experiments showed a direct interaction between ,-catenin and Cx43. Small interfering RNA (siRNA)-mediated depletion of ,-catenin recapitulated the effects of decreasing HuR levels: it attenuated GJIC, decreased Cx43 levels, and redistributed Cx43 to the cytoplasm, suggesting that depletion of ,-catenin in HuR-silenced cells contributed to lowering Cx43 levels at the membrane. Finally, HuR was demonstrated to support GJIC after exposure to a genotoxic agent, doxorubicin, or an inducer of differentiation processes, retinoic acid, thus pointing to a crucial role of HuR in the cellular response to stress and in physiological processes modulated by GJIC. Conclusion: HuR promotes gap junctional intercellular communication in rat liver epithelial cells through two related regulatory processes, by enhancing the expression of Cx43 and by increasing the expression of ,-catenin, which, in turn, interacts with Cx43 and is required for proper positioning of Cx43 at the plasma membrane. (HEPATOLOGY 2009.) [source] Gap junction-mediated intercellular communication in a long-term primary mouse hepatocyte culture systemHEPATOLOGY, Issue 5 2003Stephanie A. Stoehr Gap junction-mediated intercellular communication (GJIC) is critical for maintaining integral cellular processes including differentiation and growth control. The disruption of GJIC has been correlated with aberrant function in many cell types, including hepatocytes in vivo; therefore it is imperative that cellular model systems support intercellular communication to simulate normal cellular functions. Functional GJIC has been shown in long-term primary rat hepatocyte cultures, which have been implemented widely to study various aspects of hepatocellular function; however, the onset of transgenic technology in murine species has necessitated the development of a primary mouse hepatocyte system. In this report, we analyze GJIC in a dimethylsulfoxide (DMSO)-containing long-term primary mouse hepatocyte culture system. The cells retain morphologic and biochemical characteristics of differentiated hepatocytes through day 30 post plating, including liver-specific gene expression. We further show that connexin32 and connexin26 expression and gap junction plaque formation increase over time in culture concomitant with an increase in GJIC between adjoining primary mouse hepatocytes. In conclusion, the findings described in this study make it possible to maintain differentiated primary mouse hepatocytes that also show GJIC in long-term culture for 30 days. In addition, this system has the potential to be extended to study primary mouse hepatocytes isolated from genetically engineered mice. [source] Molecular mechanisms of intercellular communication in the hormonal and neural systemsIUBMB LIFE, Issue 5-6 2006Shigetada Nakanishi Abstract This paper reviews our studies that have addressed the molecular mechanisms underlying the biosynthesis and reception of extracellular signaling molecules and integrative mechanisms of extracellular-intracellular signaling transmission in biological systems. We introduced recombinant DNA technology into the neuroendocrine system and established the concept that a single peptide precursor encompasses multiple biologically active peptides and brings about coordinate functions in various biological systems. We then developed a novel functional cloning of membrane receptors and ion channels by combining an oocyte expression system with electrophysiology. We molecularly elucidated not only various peptide receptors, including the first demonstration of the molecular entity of a G protein-coupled peptide receptor (GPCR), substance K receptor, and also diverse members of both G protein-coupled metabotropic type and NMDA type of neurotransmitter glutamate receptors. We demonstrated many novel synaptic mechanisms involving distinct types of glutamate receptors in brain function and dysfunction. These include the mechanisms underlying segregation of light-dark signals in visual transmission, discrimination and memory formation in olfactory transmission, and motor co-ordination in the cerebellum, basal ganglia and the retinal network. iubmb Life, 58: 349-357, 2006 [source] Vesicle traffic through intercellular bridges in DU 145 human prostate cancer cellsJOURNAL OF CELLULAR AND MOLECULAR MEDICINE, Issue 3 2004Cristina Vidulescu Abstract We detected cell-to-cell communication via intercellular bridges in DU 145 human prostate cancer cells by fluorescence microscopy. Since DU 145 cells have deficient gap junctions, intercellular bridges may have a prominent role in the transfer of chemical signals between these cells. In culture, DU 145 cells are contiguous over several cell diameters through filopodial extensions, and directly communicate with adjacent cells across intercellular bridges. These structures range from 100 nm to 5 ,m in diameter, and from a few microns to at least 50,100 ,m in length. Time-lapse imagery revealed that (1) filopodia rapidly move at a rate of microns per minute to contact neighboring cells and (2) intercellular bridges are conduits for transport of membrane vesicles (1,3 ,m in diameter) between adjacent cells. Immunofluorescence detected alpha-tubulin in intercellular bridges and filopodia, indicative of microtubule bundles, greater than a micron in diameter. The functional meaning, interrelationship of these membrane extensions are discussed, along with the significance of these findings for other culture systems such as stem cells. Potential applications of this work include the development of anticancer therapies that target intercellular communication and controlling formation of cancer spheroids for drug testing. [source] Bone morphogenetic protein-2 modulation of chondrogenic differentiation in vitro involves gap junction-mediated intercellular communicationJOURNAL OF CELLULAR PHYSIOLOGY, Issue 2 2002Wei Zhang 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 (18,-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 ,M 18,-GCA decreases chondrogenic differentiation by 50% at 96 h without effects on housekeeping genes. Exposure to 18,-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. 18,-GCA can also block the chondrogenic effects of BMP-2 without effects on cell number or connexin43 expression. These observations demonstrate 18,-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. J. Cell. Physiol. 193: 233,243, 2002. © 2002 Wiley-Liss, Inc. [source] Gene expression profiling of porokeratosisJOURNAL OF CUTANEOUS PATHOLOGY, Issue 11 2008Zheng-Hua Zhang Background:, Porokeratosis (PK) represents a heterogeneous group of disorders of keratinization and has a wide variety of clinical manifestations. PK may exhibit similarities with psoriasis at both clinical and molecular levels. The genetic basis and pathogenesis for PK remain elusive. Methods:, We studied the transcriptional profiles of three pairwise lesional and uninvolved skin biopsies from patients with different subtypes of PK using the Illumina® BeadArrayÔ platform. Results:, A total of 37 upregulated genes were identified in our study, including wound-induced keratins, S100 calcium-binding protein genes involved in epidermal differentiation, as well as genes involved in mediating intercellular communication and the immune response. To our knowledge, this is the first study that characterizes the immune profile of PK lesions. Conclusions:, Here, we report that keratinocytes (KCs)-harboring lesions have activated and overexpressed wound-induced keratin genes, which appear to be coregulated with other genes involved in mediating epidermal differentiation, intercellular communication and immunity. This study, from the perspective of gene profiling, supports that gene misregulation in PK mimics that of psoriasis. Our data indicate that the genes implicated in the T-cell-mediated immune response pathway and activation of KCs play a key role in the pathogenesis of PK. [source] Glucose metabolism and proliferation in glia: role of astrocytic gap junctionsJOURNAL OF NEUROCHEMISTRY, Issue 4 2006Arantxa Tabernero Abstract Astrocytes play a well-established role in brain metabolism, being a key element in the capture of energetic compounds from the circulation and in their delivery to active neurons. Their metabolic status is affected in many pathological situations, such as gliomas, which are the most common brain tumors. This proliferative dysfunction is associated with changes in gap junctional communication, a property strongly developed in normal astrocytes studied both in vitro and in vivo. Here, we summarize and discuss the findings that have lead to the identification of a link between gap junctions, glucose uptake, and proliferation. Indeed, the inhibition of gap junctional communication is associated with an increase in glucose uptake due to a rapid change in the localization of both GLUT-1 and type I hexokinase. This effect persists due to the up-regulation of GLUT-1 and type I hexokinase and to the induction of GLUT-3 and type II hexokinase. In addition, cyclins D1 and D3 have been found to act as sensors of the inhibition of gap junctions and have been proposed to play the role of mediators in the mitogenic effect observed. Conversely, in C6 glioma cells, characterized by a low level of intercellular communication, an increase in gap junctional communication reduces glucose uptake by releasing type I and type II hexokinases from the mitochondria and decreases the exacerbated rate of proliferation due to the up-regulation of the Cdk inhibitors p21 and p27. Identification of the molecular actors involved in these pathways should allow the determination of potential therapeutic targets that could lead to the testing of alternative strategies to prevent, or at least slow down, the proliferation of glioma cells. [source] Insulin-like growth factor-I increases astrocyte intercellular gap junctional communication and connexin43 expression in vitroJOURNAL OF NEUROSCIENCE RESEARCH, Issue 1 2003N. David Åberg Abstract Connexin43 (cx43) forms gap junctions in astrocytes, and these gap junctions mediate intercellular communication by providing transport of low-molecular-weight metabolites and ions. We have recently shown that systemic growth hormone increases cx43 in the brain. One possibility was that local brain insulin-like growth factor-I (IGF-I) could mediate the effect by acting directly on astrocytes. In the present study, we examined the effects of direct application of recombinant human IGF-I (rhIGF-I) on astrocytes in primary culture concerning cx43 protein expression and gap junctional communication (GJC). After 24 hr of stimulation with rhIGF-I under serum-free conditions, the GJC and cx43 protein were analyzed. Administration of 30 ng/ml rhIGF-I increased the GJC and the abundance of cx43 protein. Cell proliferation of the astrocytes was not significantly increased by rhIGF-I at this concentration. However, a higher concentration of rhIGF-I (150 ng/ml) had no effect on GJC/cx43 but increased cell proliferation. Because of the important modulatory role of IGF binding proteins (IGFBPs) on IGF-I action, we analyzed IGFBPs in conditioned media. In cultures with a low abundance of IGFBPs (especially IGFBP-2), the GJC response to 30 ng/ml rhIGF-I was 81%, compared with the average of 25%. Finally, as a control, insulin was given in equimolar concentrations. However, GJC was not affected, which suggests that rhIGF-I acted via IGF-I receptors. In summary, the data show that rhIGF-I may increase GJC/cx43, whereas a higher concentration of rhIGF-I,at which stimulation of proliferation occurred,did not affect GJC/cx43. Furthermore, IGFBP-2 appeared to modulate the action of rhIGF-I on GJC in astrocytes by a paracrine mechanism. © 2003 Wiley-Liss, Inc. [source] Zebrafish Cx35: Cloning and characterization of a gap junction gene highly expressed in the retinaJOURNAL OF NEUROSCIENCE RESEARCH, Issue 6 2003Elizabeth McLachlan Abstract The vertebrate connexin gene family encodes protein subunits of gap junction channels, which provide a route for direct intercellular communication. Consequently, gap junctions play a vital role in many developmental and homeostatic processes. Aberrant functioning of gap junctions is implicated in many human diseases. Zebrafish are an ideal vertebrate model to study development of the visual system as they produce transparent embryos that develop rapidly, thereby facilitating morphological and behavioral testing. In this study, zebrafish connexin35 has been cloned from a P1 artificial chromosome (PAC) library. Sequence analysis shows a high degree of similarity to the Cx35/36 orthologous group, which are expressed primarily in nervous tissue, including the retina. The gene encodes a 304-amino acid protein with a predicted molecular weight of approximately 35 kDa. Injection of zebrafish Cx35 RNA into paired Xenopus oocytes elicited intercellular electrical coupling with weak voltage sensitivity. In development, Cx35 is first detectable by Northern analysis and RT-PCR, at 2 days post-fertilization (2 dpf), and in the adult it is expressed in the brain and retina. Immunohistochemical analysis revealed that the Cx35 protein is expressed in two sublaminae of the inner plexiform layer of the adult retina. A similar pattern was seen in the 4 and 5 dpf retina, but no labeling was detected in the retina of earlier embryos. © 2003 Wiley-Liss, Inc. [source] Irsogladine maleate counters the interleukin-1,-induced suppression in gap-junctional intercellular communication but does not affect the interleukin-1,-induced zonula occludens protein-1 levels in human gingival epithelial cellsJOURNAL OF PERIODONTAL RESEARCH, Issue 1 2008T. Fujita Background and Objective:, Irsogladine maleate counters gap junctional intercellular communication reduction induced by interleukin-8 or Actinobacillus actinomycetemcomitans in cultured human gingival epithelial cells. Interleukin-1, is involved in periodontal disease. Little is known, however, about the effect of interleukin-1, on intercellular junctional complexes in human gingival epithelial cells. Furthermore, irsogladine maleate may affect the actions of interleukin-1,. In this study, we examined how interleukin-1, affected gap junctional intercellular communication, connexin 43 and zonula occludens protein-1, and how irsogladine maleate modulated the interleukin-1,-induced changes in the intercellular junctional complexes in human gingival epithelial cells. Material and Methods:, Human gingival epithelial cells were exposed to interleukin-1,, with or without irsogladine maleate. Connexin 43 and zonula occludens protein-1 were examined at mRNA and protein levels by real-time polymerase chain reaction and western blotting, respectively. Gap junctional intercellular communication was determined using the dye transfer method. The expression of zonula occludens protein-1 was also confirmed by immunofluorescence. Results:, Interleukin-1, decreased connexin 43 mRNA levels, but increased zonula occludens protein-1 mRNA levels. Irsogladine maleate countered the interleukin-1,-induced reduction in gap junctional intercellular communication and connexin 43 levels. However, irsogladine maleate did not influence the increased zonula occludens protein-1 levels. Conclusion:, The effect of interleukin-1, on gap junctional intercellular communication and tight junctions of human gingival epithelial cells is different. The recovery of gap junctional intercellular communication by irsogladine maleate in the gingival epithelium may be a normal process in gingival epithelial homeostasis. [source] Expression of gap junction protein connexin 32 in chronic liver diseasesLIVER INTERNATIONAL, Issue 2 2000Kazuaki Yamaoka Abstract:Background: Gap junctions contain intercellular channels through which contacting cells communicate directly. The expression of connexin 32, a major gap junction protein in the liver, during the progression of chronic liver diseases has not yet been clarified. Methods: Immunohistochemical staining was performed using anti-connexin 32 antibody on 6 specimens of normal human liver, 7 of chronic viral hepatitis, and 7 of liver cirrhosis. Results: The number of gap junction plaques in chronic viral hepatitis and liver cirrhosis was significantly smaller than that in normal liver (10350±2180 and 7550±3040 vs 22560±3700 spots/mm2, p<0.01). The number of gap junction plaques tended to be lower in liver cirrhosis than in chronic viral hepatitis. Conclusion: These results suggest that in chronic liver diseases impaired intercellular communication between hepatocytes occurs. [source] Reduced gap junctional intercellular communication and altered biological effects in mouse osteoblast and rat liver oval cell lines transfected with dominant-negative connexin 43MOLECULAR CARCINOGENESIS, Issue 4 2003Brad L. Upham Abstract Gap junctional intercellular communication (GJIC) maintains normal growth and differentiation of cells in a tissue. The intercellular molecules traversing gap junctions are largely unknown, but the molecular weight (MW) cutoff is normally 1200 Da. No differences in dye transfer were observed in normal or vector controls of WB-F344 rat liver epithelial or mouse osteoblastic MC3T3-E1 cells with either Lucifer Yellow (LY) with a MW of 457 Da (LY-457) or LY with a MW of 649 Da (LY-649). Transfection of a dominant negative-connexin 43 (Cx43) gene decreased GJIC (>50%) when LY-649 was used, however, normal GJIC was observed in both cell lines when LY-457 was used. Therefore, the MW cut off in these clones was considerably less than the wild type. The dominant negative clones of the MC3T3-E1 cells exhibited over 90% less alkaline phosphatase (ALPase) activity and calcium deposition after the induction of differentiation. Similarly, dominant negative Cx43 inhibited gene expression of ALPase and bone sialoprotein but not osteocalcin in MC3T3-E1. WB-F344 cells normally exhibit a biphasic response to 12- O -tetradecanoylphorbol-13-acetate (TPA) where inhibition of GJIC recovers after 2 h, but the dominant negative clones showed no recovery from inhibition of GJIC by TPA. Dominant negative Cx43 also inhibited the formation of network-like structures by WB-F344 cells on Matrigel. These results demonstrate that the dominant negative gene transfected into cell types containing the wild-type connexins result in diminished channel sizes, thus allowing the determination of whether distinct biological endpoints, i.e., differentiation, are dependent upon either small or high MW intercellular signals. © 2003 Wiley-Liss, Inc. [source] Modulation of ABH histo-blood group antigen expression in normal and myasthenic human thymus,APMIS, Issue 10 2006VICTORIA S. SARAFIAN The role of ABH histo-blood group antigens (HBGA) in intercellular communication during normal and pathological processes is still uncertain. The present work investigates the expression of ABH HBGA in epithelial cells and lymphocytes in normal thymus, and characterizes the modulation of their immunoreactivity during myasthenic transformation. Immunohistochemistry and immunoelectron microscopy were applied on normal young thymus and on myasthenia gravis-associated thymomas and thymic hyperplasias. The Hassall's corpuscules in the thymus of young individuals were homogeneously stained for HBGA, while in hyperplastic glands only their central part was positive. Stromal epithelial cells permanently expressed HBGA in all tissue samples. In thymomas, mainly the lymphocytes in close proximity to antigen expressing epithelial cells were positive, while in the hyperplastic gland the most intensely stained lymphocytes were those within Hassall's corpuscules. Novel evidence for modulation of ABH antigen reactivity in normal and myasthenic human thymus is presented. It suggests that HBGA might participate in the regulation of the cross-talk in the thymocyte microenvironment throughout the ontogeny, as well as during the myasthenic transformation. [source] Rotigaptide (ZP123) Improves Atrial Conduction Slowing in Chronic Volume Overload-Induced Dilated AtriaBASIC AND CLINICAL PHARMACOLOGY & TOXICOLOGY, Issue 1 2006Ketil Haugan Rotigaptide (ZP123) is a selective gap junction modifier that increases cardiac gap junctional intercellular communication. We hypothesised that rotigaptide treatment would increase atrial conduction velocity and reduce the inducibility to atrial tachyarrhythmias in a model of chronic volume overload induced chronic atrial dilatation characterized by atrial conduction velocity slowing. Chronic volume overload was created in Japanese white rabbits by arterio-venous shunt formation. Atrial conduction velocity and atrial tachyarrhythmias inducibility were examined in Langendorff-perfused chronic volume overload hearts (n=12) using high-resolution optical mapping before and after treatment with rotigaptide. Moreover, expression levels of atrial gap junction proteins (connexin40 and connexin43) were examined in chronic volume overload hearts (n=6) and compared to sham-operated controls (n=6). Rotigaptide treatment significantly increased atrial conduction velocity in chronic volume overload hearts, however, rotigaptide did not decrease susceptibility to the induction of atrial tachyarrhythmias. Protein expressions of Cx40 and Cx43 were decreased by 32% and 72% (P<0.01), respectively, in chromic volume overload atria compared to control. To conclude, rotigaptide increased atrial conduction velocity in a rabbit model of chromic volume overload induced atrial conduction velocity slowing. The demonstrated effect of rotigaptide on atrial conduction velocity did not prevent atrial tachyarrhythmias inducibility. Whether rotigaptide may possess antiarrhythmic efficacy in other models of atrial fibrillation remains to be determined. [source] Osteoblasts stimulated with pulsed electromagnetic fields increase HUVEC proliferation via a VEGF-A independent mechanism,BIOELECTROMAGNETICS, Issue 3 2009Richard A. Hopper Abstract The clinically beneficial effect of low frequency pulsed electromagnetic fields (ELF-PEMF) on bone healing has been described, but the exact mechanism of action remains unclear. A recent study suggests that there is a direct autocrine mitogenic effect of ELF-PEMF on angiogenesis. The hypothesis of this study is that ELF-PEMF also has an indirect effect on angiogenesis by manipulation of vascular endothelial growth factor (VEGF)-A-based paracrine intercellular communication with neighboring osteoblasts. Conditioned media experiments measured fetal rat calvarial cell (FRC) and human umbilical vein endothelial cell (HUVEC) proliferation using tritiated thymidine uptake. We demonstrate that ELF-PEMF (15 Hz, 1.8 mT, for 8 h) has an indirect effect on the proliferation rate of both endothelial cells and osteoblasts in vitro by altering paracrine mediators. Conditioned media from osteoblast cells stimulated with ELF-PEMF increased endothelial proliferation 54-fold, whereas media from endothelial cells stimulated with ELF-PEMF did not affect osteoblast proliferation. We examined the role of the pro-angiogenic mediator VEGF-A in the mitogenic effect of ELF-PEMF-stimulated osteoblast media on endothelial cells. The production of VEGF-A by FRC as measured by ELISA was not changed by exposure to PEMF, and blocking experiments demonstrated that the ELF-PEMF-induced osteoblast-derived endothelial mitogen observed in these studies was not VEGF-A, but some other soluble angiogenic mediator. Bioelectromagnetics 30:189,197, 2009. © 2008 Wiley-Liss, Inc. [source] Extraction and chromatographic separation of anticarcinogenic fractions from cacao bean huskBIOFACTORS, Issue 3 2005Ki Won Lee Abstract The utilization of cacao bean husk (CBH), a by-product of chocolate manufacture, would be both environmentally and economically beneficial. For this purpose, a process for effectively separating and fractionating CBH fractions having cancer preventive potential was developed in this study. For screening the fractions with potent cancer preventive activity, we examined the effect of extracts and fractions of CBH on the inhibition of gap-junction intercellular communication (GJIC) and the DNA synthesis of cancer cells, both of which are characteristics of the promotion and progression stages in carcinogenesis. The extracts of CBH (especially, the 60% ethanol fraction after extraction with 50% acetone) containing 43 wt.% polyphenol exerted an excellent protective effect on H2O2 -induced inhibition of GJIC in WB-F344 rat liver epithelial cells as determined by the scrape-loading/dye transfer assay. The enhancement of GJIC by the extracts of CBH was approximately 10-fold higher than that of a well-known dietary chemopreventive component, vitamin C. The extracts of CBH (especially, the 60% ethanol fraction) also suppressed DNA synthesis in all liver, stomach, and colon cancer cells as demonstrated by the 3H-thymidine incorporation assay, by approximately four-fold higher than that of vitamin C. These results imply that the polyphenol extracts and fractions of CBH are effective functional materials to be used in either preventing or inhibiting cancer. [source] Disruption of gap junctions attenuates aminoglycoside-elicited renal tubular cell injuryBRITISH JOURNAL OF PHARMACOLOGY, Issue 8 2010Jian Yao BACKGROUND AND PURPOSE Gap junctions play important roles in the regulation of cell phenotype and in determining cell survival after various insults. Here, we investigated the role of gap junctions in aminoglycoside-induced injury to renal tubular cells. EXPERIMENTAL APPROACH Two tubular epithelial cell lines NRK-E52 and LLC-PK1 were compared for gap junction protein expression and function by immunofluorescent staining, Western blot and dye transfer assay. Cell viability after exposure to aminoglycosides was evaluated by WST assay. Gap junctions were modulated by transfection of the gap junction protein, connexin 43 (Cx43), use of Cx43 siRNA and gap junction inhibitors. KEY RESULTS NRK-E52 cells expressed abundant Cx43 and were functionally coupled by gap junctional intercellular communication (GJIC). Exposure of NRK-E52 cells to aminoglycosides, G418 and hygromycin, increased Cx43 phosphorylation and GJIC. The aminoglycosides also decreased cell viability that was prevented by gap junction inhibitors and Cx43 siRNA. LLC-PK1 cells were gap junction-deficient and resistant to aminoglycoside-induced cytotoxicity. Over-expression of a wild-type Cx43 converted LLC-PK1 cells to a drug-sensitive phenotype. The gap junction inhibitor ,-glycyrrhetinic acid (,-GA) activated Akt in NRK-E52 cells. Inhibition of the Akt pathway enhanced cell toxicity to G418 and abolished the protective effects of ,-GA. In addition, gentamycin-elicited cytotoxicity in NRK-E52 cells was also significantly attenuated by ,-GA. CONCLUSION AND IMPLICATIONS Gap junctions contributed to the cytotoxic effects of aminoglycosides. Modulation of gap junctions could be a promising approach for prevention and treatment of aminoglycoside-induced renal tubular cell injury. [source] Heavy-ion-induced bystander killing of human lung cancer cells: Role of gap junctional intercellular communicationCANCER SCIENCE, Issue 4 2009Kosaku Harada The aim of the present study was to clarify the mechanisms of cell death induced by heavy-ion irradiation focusing on the bystander effect in human lung cancer A549 cells. In microbeam irradiation, each of 1, 5, and 25 cells under confluent cell conditions was irradiated with 1, 5, or 10 particles of carbon ions (220 MeV), and then the surviving fraction of the population was measured by a clonogenic assay in order to investigate the bystander effect of heavy-ions. In this experiment, the limited number of cells (0.0001,0.002%, 5,25 cells) under confluent cell conditions irradiated with 5 or 10 carbon ions resulted in an exaggerated 8,14% increase in cell death by clonogenic assay. However, these overshooting responses were not observed under exponentially growing cell conditions. Furthermore, these responses were inhibited in cells treated with an inhibitor of gap junctional intercellular communication (GJIC), whereas they were markedly enhanced by the addition of a stimulator of GJIC. The present results suggest that bystander cell killing by heavy-ions was induced mainly by direct cell-to-cell communication, such as GJIC, which might play important roles in bystander responses. (Cancer Sci 2009; 100: 684,688) [source] | ||||||||||||||||||||||||||||