|
| ||
|
|
||
Cx43
Terms modified by Cx43 Selected AbstractsCx31 and Cx43 double-deficient mice reveal independent functions in murine placental and skin developmentDEVELOPMENTAL DYNAMICS, Issue 3 2005Mark Kibschull Abstract The overlapping expression of gap junctional connexins in tissues has indicated that the channels may compensate for each other. During development, Cx31 and Cx43 are coexpressed in preimplantation embryos, in the spongiotrophoblast of the placenta and in the epidermis. This study shows that Cx31/Cx43 double-deficient mice exhibit the known phenotypes of the single-knockout strains but no combined effects. Thus, Cx43, coexpressed with Cx31 at midgestation in the spongiotrophoblast of the placenta, cannot be responsible for a partial rescue of the lethal Cx31 knockout phenotype, as assumed before (Plum et al. [ 2001] Dev Biol 231:334,337). It follows that both connexins have unique functions in placental development. Despite an altered expression of other epidermal connexin mRNAs, epidermal differentiation and physiology was unaltered by the absence of Cx31 and Cx43. Therefore, in epidermal and preimplantation development, gap junctional communication can probably be compensated by other isoforms coexpressed with Cx31 and Cx43. Developmental Dynamics 233:853,863, 2005. © 2005 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] Expression of zonula occludens-1 (ZO-1) and the transcription factor ZO-1-associated nucleic acid-binding protein (ZONAB),MsY3 in glial cells and colocalization at oligodendrocyte and astrocyte gap junctions in mouse brainEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 2 2005Mihai C. Penes Abstract The PDZ domain-containing protein zonula occludens-1 (ZO-1) interacts with several members of the connexin (Cx) family of gap junction-forming proteins and has been localized to gap junctions, including those containing Cx47 in oligodendrocytes. We now provide evidence for ZO-1 expression in astrocytes in vivo and association with astrocytic connexins by confocal immunofluorescence demonstration of ZO-1 colocalization with astrocytic Cx30 and Cx43, and by ZO-1 coimmunoprecipitation with Cx30 and Cx43. Evidence for direct interaction of Cx30 with ZO-1 was obtained by pull-down assays that indicated binding of Cx30 to the second of the three PDZ domains in ZO-1. Further, we investigated mouse Y-box transcription factor MsY3, the canine ortholog of which has been termed ZO-1-associated nucleic acid-binding protein (ZONAB) and previously reported to interact with ZO-1. By immunofluorescence using specific antimouse ZONAB antibody, ZONAB was found to be associated with oligodendrocytes throughout mouse brain and spinal cord, and to be colocalized with oligodendrocytic Cx47 and Cx32 as well as with astrocytic Cx43. Our results extend the CNS cell types that express the multifunctional protein ZO-1, demonstrate an additional connexin (Cx30) that directly interacts with ZO-1, and show for the first time the association of a transcription factor (ZONAB) with ZO-1 localized to oligodendrocyte and astrocyte gap junctions. Given previous observations that ZONAB and ZO-1 in combination regulate gene expression, our results suggest roles of glial gap junction-mediated anchoring of signalling molecules in a wide variety of glial homeostatic processes. [source] Mice with astrocyte-directed inactivation of connexin43 exhibit increased exploratory behaviour, impaired motor capacities, and changes in brain acetylcholine levelsEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 8 2003Christian Frisch Abstract Gap junctions mediate communication between many cell types in the brain. Gap junction channels are composed of membrane-spanning connexin (Cx) proteins, allowing the cell-to-cell passage of small ions and metabolites. Cx43 is the main constituent of the brain-spanning astrocytic gap junctional network, controlling activity-related changes in ion and glutamate concentrations as well as metabolic processes. In astrocytes, deletion of Cx43-coding DNA led to attenuated gap junctional coupling and impaired propagation of calcium waves, known to influence neuronal activity. Investigation of the role of Cx43 in behaviour has been impossible so far, due to postnatal lethality of its general deletion. Recently, we have shown that deletion of Cx30, which is also expressed by astrocytes, affects exploration, emotionality, and neurochemistry in the mouse. In the present study, we investigated the effects of the astrocyte-directed inactivation of Cx43 on mouse behaviour and brain neurochemistry. Deletion of Cx43 in astrocytes increased exploratory activity without influencing habituation. In the open field, but not in the elevated plus-maze, an anxiolytic-like effect was observed. Rotarod performance was initially impaired, but reached control level after further training. In the water maze, Cx43 deficient mice showed a steeper learning course, although final performance was similar between groups. Cx43 inactivation in astrocytes increased acetylcholine content in the frontal cortex of water maze-trained animals. Results are discussed in terms of altered communication between astrocytes and neurons, possible compensation processes, and differential effects of Cx30- and astrocyte-specific Cx43 deletion. [source] Direct integration of cell-free-synthesized connexin-43 into liposomes and hemichannel formationFEBS JOURNAL, Issue 16 2010Yuki Moritani Proteoliposomes were directly prepared by synthesizing membrane proteins with the use of minimal protein synthesis factors isolated from Escherichia coli (the PURE system) in the presence of liposomes. Connexin-43 (Cx43), which is a water-insoluble integral membrane protein that forms a hexameric complex in membranes, was cotranslationally integrated with an essentially uniform orientation in liposomes. The addition of liposomes following protein expression (post-translational presence of liposomes) did not lead to the integration of Cx43 into the liposome membranes. The amount of integrated Cx43 increased as the liposome concentration increased. The presence of liposomes did not influence the total amount of synthesized Cx43. The Cx43 integrated into the liposome membranes formed open membrane pores. These results indicate that the liposomes act in a chaperone-like manner by preventing Cx43 from aggregating in solution, because of integration into the bilayer, and also by functionalization of the integrated Cx43 in the membrane. This is the first report that cell-free-synthesized water-insoluble membrane protein is directly integrated with a uniform orientation as a functional oligomer into liposome membranes. This simple proteoliposome preparation procedure should be a valuable approach for structural and functional studies of membrane proteins. Structured digital abstract ,,MINT-7900670: Cx-43 (uniprotkb:P08050) and Cx-43 (uniprotkb:P08050) bind (MI:0407) by cross-linking study (MI:0030) [source] Normal embryonic development and cardiac morphogenesis in mice with Wnt1-Cre-mediated deletion of connexin43GENESIS: THE JOURNAL OF GENETICS AND DEVELOPMENT, Issue 6 2006M. Kretz Abstract Mice harboring a null mutation in the gap junction protein connexin43 (Cx43) die shortly after birth due to an obstruction of the right ventricular outflow tract of the heart. These hearts exhibit prominent pouches at the base of the pulmonary outlet, i.e., morphological abnormalities that were ascribed to Cx43-deficiency in neural crest cells. In order to examine the Cx43 expression pattern in neural crest cells and derived tissues and to test whether neural crest-specific deletion of Cx43 leads to the conotruncal defects seen in Cx43null mice, we ablated Cx43 using a Wnt1-Cre transgene. Deletion of Cx43 was complete and occurred in neural crest cells as well as in neural crest-derived tissues. Nevertheless, hearts of mice lacking Cx43 specifically in neural crest cells were indistinguishable from controls. Thus, the morphological heart abnormalities of Cx43 null mice are most likely not caused by lack of Cx43 in neural crest cells. genesis 44:269,276, 2006. © 2006 Wiley-Liss, Inc. [source] Modulation of astrocyte P2Y1 receptors by the carboxyl terminal domain of the gap junction protein Cx43GLIA, Issue 2 2008Eliana Scemes Abstract Gap junction proteins, connexins, provide intercellular channels that allow ions and small signaling molecules to be transmitted to adjacent coupled cells. Besides this function, it is becoming apparent that connexins also exert channel-independent effects, which are likely mediated by processes involving protein,protein interactions. Although a number of connexin interacting proteins have been identified, only little is known about the functional consequences of such interactions. We have previously shown that deletion of the astrocytic gap junction protein, connexin43 (Cx43) causes a right-ward shift in the dose-response curve to P2Y1R agonists and decreased P2Y1R expression levels. To evaluate whether these changes were due to reduced gap junctional communication or to protein,protein interactions, Cx43-null astrocytes were transfected with full-length Cx43 and Cx43 domains, and P2Y1R function and expression levels evaluated. Results indicate that restoration of P2Y1R function is independent of gap junctional communication and that the Cx43 carboxyl terminus spanning the SH3 binding domain (260,280) participates in the rescue of P2Y1R pharmacological behavior (shifting to the left the P2Y1R dose-response curve) without affecting its expression levels. These results suggest that the Cx43 carboxyl-terminus domain provides a binding site for an intracellular molecule, most likely a member of the c-Src tyrosine kinase family, which affects P2Y1R-induced calcium mobilization. It is here proposed that a nonchannel function of Cx43 is to serve as a decoy for such kinases. Such modulation of P2Y1R is expected to influence several neural cell functions, especially under inflammation and neurodegenerative disorders where expression levels of Cx43 are decreased. © 2007 Wiley-Liss, Inc. [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] Spatial separation of endothelial small- and intermediate-conductance calcium-activated potassium channels (KCa) and connexins: possible relationship to vasodilator function?JOURNAL OF ANATOMY, Issue 5 2006Shaun L. Sandow Abstract Activation of endothelial cell small- (S) and intermediate- (I) conductance calcium-activated potassium channels (KCa) and current or molecular transfer via myoendothelial gap junctions underlies endothelium-derived hyperpolarization leading to vasodilation. The mechanism underlying the KCa component of vasodilator activity and the characteristics of gap junctions are targets for the selective control of vascular function. In the rat mesenteric artery, where myoendothelial gap junctions and connexin (Cx) 40 are critical for the transmission of the endothelial cell hyperpolarization to the smooth muscle, SKCa and IKCa provide different facets of the endothelium-derived hyperpolarization response, being critical for the hyperpolarization and repolarization phases, respectively. The present study addressed the question of whether this functional separation of responses may be related to the spatial localization of the associated channels? The distribution of endothelial SKCa and IKCa and Cx subtype(s) were examined in the rat mesenteric artery using conventional confocal and high-resolution ultrastructural immunohistochemistry. At the internal elastic lamina,smooth muscle cell interface at internal elastic lamina holes (as potential myoendothelial gap junction sites), strong punctate IKCa, Cx37 and Cx40 expression was present. SKCa, Cx37, Cx40 and Cx43 were localized to adjacent endothelial cell gap junctions. High-resolution immunohistochemistry demonstrated IKCa and Cx37-conjugated gold to myoendothelial gap junction-associated endothelial cell projections. Clear co-localization of KCa and Cxs suggests a causal relationship between their activity and the previously described differential functional activation of SKCa and IKCa. Such precise localizations may represent a selective target for control of vasodilator function and vascular tone. [source] Connexin 43 Is Required for the Anti-Apoptotic Effect of Bisphosphonates on Osteocytes and Osteoblasts In Vivo,JOURNAL OF BONE AND MINERAL RESEARCH, Issue 11 2008Lilian I Plotkin Abstract Connexin (Cx)43 is required for inhibition of osteocyte and osteoblast apoptosis by bisphosphonates in vitro. Herein, we evaluated its requirement for the in vivo actions of bisphosphonates using mice in which Cx43 was deleted specifically from osteocytes and osteoblasts (Cx43,Ob,Ot/, mice). Effective removal of Cx43 was confirmed by the presence of the deleted form of the gene and by reduced mRNA and protein expression in osteoblastic cells and bones obtained from Cx43,Ob,Ot/, mice. The amino-bisphosphonate alendronate (2.3 ,mol/kg/d) was injected daily into 5-mo-old female mice (n = 6,11) for 31 days, starting 3 days before implantation of pellets releasing the glucocorticoid prednisolone (2.1 mg/kg/d). Cx43,Ob,Ot/, mice and their littermates (Cx43fl/,, Cx43,Ob,Ot/+, and Cx43fl/+) gained bone with similar kinetics and exhibited identical bone mass from 2 to 4.5 mo of age, indicating that Cx43 deletion from osteocytes and mature osteoblasts does not impair bone acquisition. In addition, prednisolone induced a similar increase in osteocyte and osteoblast apoptosis in Cx43,Ob,Ot/, or in control Cx43fl/, littermates. However, whereas alendronate prevented prednisolone-induced apoptosis in control Cx43fl/, mice, it was ineffective in Cx43,Ob,Ot/, mice. In contrast, alendronate inhibited glucocorticoid-induced bone loss in both type of animals, suggesting that inhibition of resorption is the predominant effect of alendronate against the early phase of glucocorticoid-induced bone loss. Taken together with earlier in vitro evidence, these findings show that Cx43 is required for the anti-apoptotic effect of bisphosphonates on osteocytes and osteoblasts. [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] Relationship Between Connexins and Atrial Activation During Human Atrial FibrillationJOURNAL OF CARDIOVASCULAR ELECTROPHYSIOLOGY, Issue 2 2004M.R.C.P., PRAPA KANAGARATNAM Ph.D. Introduction: Gap junctional connexin proteins (connexin40 [Cx40], connexin43 [Cx43]) are a determinant of myocardial conduction and are implicated in the development of atrial fibrillation (AF). We hypothesized that atrial activation pattern during AF is related to connexin expression and that this relationship is altered by AF-induced remodeling in the fibrillating atria of chronic AF. Methods and Results: Isochronal activation mapping was performed during cardiac surgery on the right atria of patients in chronic AF (n = 13) using an epicardial electrode array. The atrial activation pattern was categorized using a complexity score based on the number of propagating wavefronts of activation and by grouping atria into those capable of uniform planar activation (simple) and those that were not (complex). The activation pattern was correlated with the levels of Cx43 and Cx40 signal measured by immunoconfocal quantification of biopsies from the mapped region. We studied the impact of electrical remodeling by comparing these findings with the unremodeled atria of patients in sinus rhythm during pacing-induced sustained AF (n = 17). In chronic AF, atria with complex activation had lower Cx40 signal than atria showing simple activation (0.013 ± 0.006 ,m2/,m2 vs 0.027 ± 0.009 ,m2/,m2, P < 0.02), with the relative connexin signal (Cx40/Cx40+Cx43) correlating with complexity score (P = 0.01, r =,0.74). This relationship did not occur in the unremodeled atria, and increased heterogeneity of distribution of Cx40 labeling in chronic AF was the only evidence of connexin remodeling that we detected in the overall group. Conclusion: The pattern of atrial activation is related to immunoconfocal connexin signal only in the fully remodeled atria of chronic AF. This suggests that intercellular coupling and pattern of atrial activation are interrelated, but only in conjunction with the remodeling of atrial electrophysiology that occurs in chronic AF. (J Cardiovasc Electrophysiol, Vol. 15, pp. 206-213, February 2004) [source] Cardiac cell therapy: overexpression of connexin43 in skeletal myoblasts and prevention of ventricular arrhythmiasJOURNAL OF CELLULAR AND MOLECULAR MEDICINE, Issue 9b 2009Sarah Fernandes Abstract Cell-based therapies have great potential for the treatment of cardiovascular diseases. Recently, using a transgenic mouse model Roell et al. reported that cardiac engraftment of connexin43 (Cx43)-overexpressing myoblasts in vivo prevents post-infarct arrhythmia, a common cause of death in patients following heart attack. We carried out a similar study but in a clinically relevant context via transplantation of autologous connexin43-overexpressing myoblasts in infarcted rats. Seven days after coronary ligation, rats were randomized into three groups: a control group injected with myoblasts, a null group injected with myoblasts transduced with an empty lentivirus vector (null) and a Cx43 group injected with myoblasts transduced with a lentivirus vector encoding connexin43. In contrast to Roell's report, arrhythmia occurrence was not statistically different between groups (58%, 64% and 48% for the control (n= 12), null (n= 14) and Cx43 (n= 23) groups, respectively, P= 0.92). Using ex vivo intramural monophasic action potential recordings synchronous electrical activity was observed between connexin43-overexpressing myoblasts and host cardiomyocytes, whereas such synchrony did not occur in the null-transduced group. This suggests that ex vivo connexin43 gene transfer and expression in myoblasts improved intercellular electrical coupling between myoblasts and cardiomyocytes. However, in our model such electrical coupling was not sufficient to decrease arrhythmia induction. Therefore, we would suggest a note of caution on the use of combined Cx43 gene and cell therapy to prevent post-infarct arrhythmias in heart failure patients. [source] Impulse conduction and gap junctional remodelling by endothelin-1 in cultured neonatal rat ventricular myocytesJOURNAL OF CELLULAR AND MOLECULAR MEDICINE, Issue 3 2009Y. Reisner Abstract Endothelin-1 (ET-1) is an important contributor to ventricular hypertrophy and failure, which are associated with arrhythmogenesis and sudden death. To elucidate the mechanism(s) underlying the arrhythmogenic effects of ET-1 we tested the hypothesis that long-term (24 hrs) exposure to ET-1 impairs impulse conduction in cultures of neonatal rat ventricular myocytes (NRVM). NRVM were seeded on micro-electrode-arrays (MEAs, Multi Channel Systems, Reutlingen, Germany) and exposed to 50 nM ET-1 for 24 hrs. Hypertrophy was assessed by morphological and molecular methods. Consecutive recordings of paced activation times from the same cultures were conducted at baseline and after 3, 6 and 24 hrs, and activation maps for each time period constructed. Gap junctional Cx43 expression was assessed using Western blot and confocal microscopy of immunofluorescence staining using anti-Cx43 antibodies. ET-1 caused hypertrophy as indicated by a 70% increase in mRNA for atrial natriuretic peptide (P < 0.05), and increased cell areas (P < 0.05) compared to control. ET-1 also caused a time-dependent decrease in conduction velocity that was evident after 3 hrs of exposure to ET-1, and was augmented at 24 hrs, compared to controls (P < 0.01). ET-1 increased total Cx43 protein by ,40% (P < 0.05) without affecting non- phosphorylated Cx43 (NP-Cx43) protein expression. Quantitative confocal microscopy showed a ,30% decrease in the Cx43 immunofluorescence per field in the ET-1 group (P < 0.05) and a reduced field stain intensity (P < 0.05), compared to controls. ET-1-induced hypertrophy was accompanied by reduction in conduction velocity and gap junctional remodelling. The reduction in conduction velocity may play a role in ET-1 induced susceptibility to arrhythmogenesis. [source] Gap junctional communication in human osteoclasts in vitro and in vivoJOURNAL OF CELLULAR AND MOLECULAR MEDICINE, Issue 6a 2008A. F. Schilling Abstract Bone-forming cells are known to be coupled by gap junctions, formed primarily by connexin43 (Cx43). The role of Cx43 in osteoclasts has so far only been studied in rodents, where Cx43 is important for fusion of mononuclear precursors to osteoclasts. Given the potential importance for human diseases with pathologically altered osteoclasts, we asked whether a similar influence of Cx43 can also be observed in osteoclasts of human origin. For this purpose, Cx43 mRNA expression was studied in a time course experiment of human osteoclast differentiation by RT-PCR. Localization of Cx43 in these cells was determined by immunohistochemistry and confocal microscopy. For the assessment of the effect of gap junction inhibition on cell fusion, gap junctions were blocked with heptanol during differentiation of the cells and the cells were then evaluated for multinuclearity. Paraffin sections of healthy bone and bone from patients with Paget's disease and giant cell tumour of the bone were used to study Cx43 expression in vivo. We found mRNA and protein expression of Cx43 in fully differentiated osteoclasts as well as in precursor cells. This expression decreased in the course of differentiation. Consistently, we found a lower expression of Cx43 in osteoclasts than in bone marrow precursor cells in the histology of healthy human bone. Blockade of gap junctional communication by heptanol led to a dose-dependent decrease in multinuclearity, suggesting that gap junctional communication precedes cell fusion of human osteoclasts. Indeed, we found a particularly strong expression of Cx43 in the giant osteoclasts of patients with Paget's disease and giant cell tumour of the bone. These results show that gap junctional communication is important for fusion of human mononuclear precursor cells to osteoclasts and that gap junctional Cx43 might play a role in the regulation of size and multinuclearity of human osteoclasts in vivo. [source] TGF-, induces connexin43 gene expression in normal murine mammary gland epithelial cells via activation of p38 and PI3K/AKT signaling pathwaysJOURNAL OF CELLULAR PHYSIOLOGY, Issue 3 2008Charlotte Tacheau One of the shared physiological roles between TGF-, and connexin family members is to inhibit epithelial cell cycle progression and consequently, to provide protection against malignant transformation. Herein, we demonstrated that TGF-,1 induces the expression of connexin43 (Cx43) in normal murine mammary gland (NMuMG) cell lines at the protein and mRNA levels, and transcriptionally. Using overexpression of a truncated dominant-negative form of Cx43, we determined that the modulation of gap junctional communication by TGF-,1 plays a key role in the control of NMuMG cells proliferation by TGF-,1. In addition, using overexpression of truncated dominant-negative forms of either Smad2 or Smad3, and MDA-MB-468 human breast carcinoma cells deficient for Smad4, we determined that the Smad cascade is not implicated in TGF-,1 effect on Cx43 expression. Using specific pharmacologic inhibitors for JNK, ERK, p38, and PI3K/AKT signaling pathways, we demonstrated the cooperative role of p38 and PI3K/AKT signaling in TGF-,1-induced Cx43 expression and gap junctional communication. Furthermore, transfection of a c-jun antisense expression vector significantly prevented TGF-,1-induced Cx43 gene expression demonstrating the involvement of c-Jun/AP-1 pathway together with p38 and PI3K/AKT pathways in mediating TGF-,1-induced Cx43 gene expression. J. Cell. Physiol. 217: 759,768, 2008. © 2008 Wiley-Liss, Inc. [source] Connexin 43 gap junction proteins are up-regulated in remyelinating spinal cordJOURNAL OF NEUROSCIENCE RESEARCH, Issue 5 2007W.A. Roscoe Abstract Alterations in the expression of gap junction proteins have previously been observed in several diseases affecting the central nervous system; however, the status of connexin 43 (Cx43) has not yet been reported in spinal cord remyelination. We studied Cx43 expression in demyelination and remyelination by using a chronic guinea pig model of experimental allergic encephalomyelitis (EAE). Hartley guinea pigs were immunized with homogenized whole CNS and complete Freund's adjuvant. Animals became chronically ill by day 40 postimmunization, and animals with paralysis were entered into the study. Animals were treated on days 40,60 postimmunization with either saline or drugs that promote remyelination: an adenosine amine congener (100 ,g/kg), an anti-,4-integrin blocker (CT301; ELN 69299; 30 mg/kg), or a combination of both drugs. Remyelination was induced in all drug-treated groups. Cx43 expression was virtually absent in demyelinated lesions of saline-treated controls compared with healthy tissue and normal appearing white matter (P < 0.001), whereas Cx43 was considerably increased (300,500%) in remyelinating lesions of all treatment groups (P < 0.001), most notably in CT301-treated animals. These changes in Cx43 expression indicate that Cx43 may beimportant for recovery from neuroinflammation. © 2007 Wiley-Liss, Inc. [source] Differential expression of connexin 43 in the chick tangential vestibular nucleusJOURNAL OF NEUROSCIENCE RESEARCH, Issue 5 2003Anastas Popratiloff Abstract The chick tangential nucleus is a major vestibular nucleus whose principal cells receive convergent inputs from primary vestibular and nonvestibular fibers and participate in the vestibular reflexes. During development, the principal cells gradually acquire the mature firing pattern in part by losing a specific potassium current around hatching (H). Here we focus on characterizing the expression of connexin 43 (Cx43), a gap junction protein found mainly between astrocytes in the mature brain. The astrocytic syncytium plays an important role in maintaining extracellular potassium ion balance in the brain. Accordingly, it is important to characterize the potential of this syncytium to communicate during the critical developmental age of hatching. Using fluorescence immunocytochemistry, we investigated whether Cx43 staining was concentrated in specific cellular compartments at H1 by applying well-known markers for astrocytes (glial fibrillary acidic protein; GFAP), oligodendrocytes (antimyelin), neurons (microtubule-associated protein 2), and synaptic terminals (synaptotagmin). GFAP-positive astrocytes and GFAP-negative nonneuronal cells around the principal cell bodies were labeled with Cx43, suggesting that Cx43 was expressed exclusively by nonneuronal cells near the neuronal elements. Next, the developmental pattern of expression of Cx43 was studied at embryonic day 16 (E16), H1, and H9. At E16, Cx43 was present weakly as random small clusters in the tangential nucleus, whereas, at H1, overall staining became localized, with increases in size, brightness, and number of immunostained clusters. Finally, at H9, Cx43 staining decreased, but cluster size and location remained unchanged. These results suggest that Cx43 is developmentally regulated with a peak at birth and is associated primarily with astrocytes and nonneuronal cells near the principal cell bodies. © 2003 Wiley-Liss, Inc. [source] Growth and Differentiation of Osteoblast-Like Cells from Calvaria of Connexin43 Deficient MiceMATERIALWISSENSCHAFT UND WERKSTOFFTECHNIK, Issue 12 2004M. Wiemann Osteoblasten-artige Zellen; Connexin43-defiziente Mäuse; gap junctions; Differenzierung Abstract Extensive cell-cell-coupling via gap junctions has been suspected to play an essential role for osteoblast development. Here, osteoblast-like cells (OBL) from connexin(Cx)43 knock out mice were used to explore the role of Cx43 for osteoblast differentiation. Primary cultures of OBL were derived from calvaria of homozygous (Cx43-/-) and heterozygous (Cx43+/,) knock out mice and also from wild type controls (Cx43+/+). In Cx43-/- OBL Lucifer Yellow dye coupling was largely abolished demonstrating that small molecules could no longer be transferred among neighboring cells. Cx43-/- OBL grew out very slowly from calvarial fragments. Nevertheless their cell density around explants was increased 3-fold vs. controls after 3 weeks. Histochemistry showed that in many Cx43-/- OBL there was an increased alkaline phosphatase activity within the cytoplasm and close to the cell membrane. Mineralization was diminished in Cx43-/- cultures. In heterozygous Cx43+/, OBL all aforementioned effects were less pronounced, pointing to a gene-dosage effect. Data suggest that the loss of Cx43 indirectly impairs the osteoblastic phenotype, e.g. by disturbing cellular functions such as motility and/or secretion. If this holds true, all parameters in the interphase of enosseous implants which lower gap junction expression will also affect bone regeneration. Wachstum und Differenzierung von Osteoblasten-artigen Zellen aus Kalvarien Connexin43-defizienter Mäuse Es wurde oft vermutet, dass die ausgeprägte Zell-Zell-Kopplung von Osteoblasten durch gap junctions eine besondere Rolle für die Differenzierung der gekoppelten Zellen spielt. In dieser Arbeit wurden daher Osteoblasten-artige Zellen (OBL) aus Connexin43 (Cx43) knock out Mäusen benutzt, um die Bedeutung von Cx43-gap-junction-Kanälen für die Differenzierung von Osteoblasten zu untersuchen. Die dafür notwendigen OBL-Primärkulturen wurden aus Calvarienfragmenten von homozygoten (Cx43-/-) und heterozygoten (Cx43+/,) knock out Mäusen sowie aus Wildtyp-Mäusen gewonnen. In Cx43-/- OBL war die Lucifer Yellow-Farbstoffkopplung weitgehend aufgehoben. Dieser Befund zeigt, dass Moleküle ,600 D zwischen Cx43-/- Zellen kaum noch ausgetauscht werden können. Cx43-/- Zellen wuchsen vergleichsweise langsam aus ihren Calvarienfragmenten aus. Dennoch erreichten diese Kulturen nach 3 Wochen eine im Vergleich zur Kontrolle 3fach höhere Zelldichte. Histochemisch zeigte sich, dass in Cx43-/- Zellen die alkalische Phosphatase-Aktivität im Zytoplasma und besonders im Bereich der Zellmembran erhöht war. Die Mineralisierung war hingegen herabgesetzt. In heterozygoten Cx43+/, OBL waren alle genannten Effekte intermediär ausgeprägt, was auf einen Gen-Dosis-Effekt deutet. Insgesamt legen die Befunde nahe, dass der Verlust von Cx43 die Ausprägung des osteoblastären Phänotyps, z.,B. durch eine Behinderung der Zellbeweglichkeit und/oder der Sekretion beeinträchtigt. Daher dürften alle Parameter, die die Expression von Cx43 im Interphase eines enossalen Implantats stören, die Knochenregeneration behindern. [source] Independence of Connexin Expression and Vasomotor Conduction from Sympathetic Innervation in Hamster Feed ArteriesMICROCIRCULATION, Issue 5 2004ROBIN C. LOOFT-WILSON ABSTRACT Objective: Vasomotor responses can travel along the wall of resistance microvessels by two distinct mechanisms: cell-to-cell conduction through gap junctions or the release of neurotransmitter along perivascular nerves. It is unknown whether vascular innervation influences the expression of connexin molecules which comprise gap junctions, or the conduction of vasomotor responses. In feed arteries of the hamster retractor muscle (RFA), the authors tested whether sympathetic denervation would alter the expression of connexin isoforms and the conduction of vasomotor responses. Methods: Using intact vessels with sympathetic innervation and those 7,8 days following denervation surgery, mRNA expression was quantified using real-time PCR, cellular localization of Cx protein was characterized using immunohistochemistry, and vasomotor responses to dilator and constrictor stimuli were evaluated in isolated pressurized RFA. Results: Connexin protein localization and mRNA expression were similar between innervated and denervated vessels. mRNA levels were Cx43 = Cx37 > Cx45 , Cx40. Vasodilation to acetylcholine conducted ,2000 , m along innervated and denervated vessels, as did the biphasic conduction of vasoconstriction and vasodilation in response to KCl. Vasoconstriction to phenylephrine conducted < 500 , m and was attenuated (p < .05) in denervated vessels. Conclusions: The profile of connexin expression and the conduction of vasomotor responses are largely independent of sympathetic innervation in feed arteries of the hamster retractor muscle (RFA). [source] ACTH and adrenocortical gap junctionsMICROSCOPY RESEARCH AND TECHNIQUE, Issue 3 2003Sandra A. Murray Abstract Since the initial identification of gap junctions in the adrenal gland, it has been proposed that a system involving direct cell,cell communication might be involved in adrenal cortical functions. Gap junction channels do, in fact, provide pathways for direct intercellular exchange of small molecules (<1,000 Da), many of which have the potential to influence a wide range of cellular activities. Gap junctions are composed of proteins called connexin which, in the adrenal cortex, have proven to be remarkably consistent in both type and zonal distribution with connexin 43 (Cx43) as the predominant component in mammalian adrenal glands thus far evaluated. Only the inner two zones of the cortex (zonae fasciculata and reticularis) exhibit significant amounts of Cx43 and functional coupling. Adrenocorticotropin (ACTH) has been shown to increase Cx43 protein in vivo and in vitro, and a strong correlation has been noted between the presence of gap junctions and certain adrenal cortical functions, especially steroidogenic capacity and cell proliferation. This review summarizes evidence of the Cx43 expression in adrenal cortical cells and the likely role of Cx43 in steroidogenesis and cell proliferation. It is concluded that control of gap junction expression in the adrenal gland is hormonally dependent and is functionally linked to adrenal gland zonation. Microsc. Res. Tech. 61:240,246, 2003. © 2003 Wiley-Liss, Inc. [source] Transcriptional regulation of connexin 43 expression by retinoids and carotenoids: Similarities and differencesMOLECULAR CARCINOGENESIS, Issue 2 2005Alex L. Vine Abstract Gap junctions, connexons, are formed by assembly of trans-membrane connexin proteins and have multiple functions including the coordination of cell responses. Most human tumors are deficient in gap junctional communication (GJC) and restoration of GJC by forced expression of connexins reduces indices of neoplasia. Expression of connexin 43 (Cx43), the most widely-expressed connexin family member, is upregulated by cancer-preventive retinoids and carotenoids in normal and preneoplastic cells; an action considered of mechanistic significance. However, the molecular mechanism for upregulated expression is poorly understood. The retinoic acid receptor antagonist Ro 41-5253 was capable of suppressing retinoid-induction Cx43 luciferase reporter construct in F9 cells, but did not suppress reporter activity induced by the non-pro-vitamin A carotenoids astaxanthin or lycopene, indicating that retinoids have separate mechanisms of gene activation than non-pro-vitamin A carotenoids. Neither class of compound required protein synthesis for induction of Cx43 mRNA, nor was the 5.0 h half-life of Cx43 mRNA altered, indicating direct transcriptional activation. The responsive region was found within ,158 bp and +209 bp of the transcription start site; this contains a Sp1/Sp3 GC-box to which Sp1 and Sp3 were bound, as revealed by electrophoretic mobility shift assays (EMSA), but no retinoic acid response element (RARE). Site directed mutagenesis of this GC-box resulted in increased basal levels of transcription and loss of responsiveness to a synthetic retinoid. In this construct astaxanthin and lycopene produced marginally, but not significantly higher, reporter activity than the control. © 2005 Wiley-Liss, Inc. [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] Nature, significance, and mechanisms of electrical heterogeneities in ventricleTHE ANATOMICAL RECORD : ADVANCES IN INTEGRATIVE ANATOMY AND EVOLUTIONARY BIOLOGY, Issue 2 2004Steven Poelzing Abstract Previously, dispersion of repolarization (DOR) has been extensively linked to the development of arrhythmias and sudden cardiac death. The electrical heterogeneities that cause DOR between transmural myocyte layers have been reported in a wide variety of animals and humans. The underlying causes of transmural electrical heterogeneities are in part due to heterogeneous functional expression of proteins responsible for ion handling. Recently, we found that electrophysiologic heterogeneities between subepicardial and midmyocardial cells can form a substrate for reentrant ventricular arrhythmias. However, cell-to-cell coupling through gap junctions is expected to attenuate transmural heterogeneities between cell types spanning the ventricular wall. In this article we review a hypothesis that regional uncoupling resulting from expression patterns of gap junctions across the ventricular wall underlies DOR, and DOR can be amplified under disease conditions which remodel gap junctions. We find the principle gap junction protein, connexin43 (Cx43), is selectively reduced in the subepicardium (by 24%) compared to deeper layers of normal canine left ventricle. Additionally, the greatest DOR occurs within the subepicardial-midmyocardial interface, precisely where Cx43 expression is reduced. The present data suggests that ion channel and gap junction heterogeneities act in conjunction to form and maintain transmural DOR. Importantly, both ion channel and gap junction remodeling occurs during many disease states such as heart failure. Importantly, in the absence of ion channel remodeling, pharmacological uncoupling increases transmural DOR, particularly within the epicardial-midmyocardial interface, to values observed in heart failure. Therefore, these data suggest that heterogeneous Cx43 expression produces functionally significant electrophysiologic heterogeneities across the ventricular wall and may be a mechanism for promoting DOR which underlie arrhythmias in heart failure. © 2004 Wiley-Liss, Inc. [source] Charges dispersed over the permeation pathway determine the charge selectivity and conductance of a Cx32 chimeric hemichannelTHE JOURNAL OF PHYSIOLOGY, Issue 10 2008Seunghoon Oh Previous studies have shown that charge substitutions in the amino terminus of a chimeric connexin, Cx32*43E1, which forms unapposed hemichannels in Xenopus oocytes, can result in a threefold difference in unitary conductance and alter the direction and amount of open channel current rectification. Here, we determine the charge selectivity of Cx32*43E1 unapposed hemichannels containing negative and/or positive charge substitutions at the 2nd, 5th and 8th positions in the N-terminus. Unlike Cx32 intercellular channels, which are weakly anion selective, the Cx32*43E1 unapposed hemichannel is moderately cation selective. Cation selectivity is maximal when the extracellular surface of the channel is exposed to low ionic strength solutions implicating a region of negative charge in the first extracellular loop of Cx43 (Cx43E1) in influencing charge selectivity analogous to that reported. Negative charge substitutions at the 2nd, 5th and 8th positions in the intracellular N-terminus substantially increase the unitary conductance and cation selectivity of the chimeric hemichannel. Positive charge substitutions at the 5th position decrease unitary conductance and produce a non-selective channel while the presence of a positive charge at the 5th position and negative charge at the 2nd results in a channel with conductance similar to the parental channel but with greater preference for cations. We demonstrate that a cysteine substitution of the 8th residue in the N-terminus can be modified by a methanthiosulphonate reagent (MTSEA-biotin-X) indicating that this residue lines the aqueous pore at the intracellular entrance of the channel. The results indicate that charge selectivity of the Cx32*43E1 hemichannel can be determined by the combined actions of charges dispersed over the permeation pathway rather than by a defined region that acts as a charge selectivity filter. [source] Connexin abundance in resistance vessels from the renal microcirculation in normo- and hypertensive ratsAPMIS, Issue 4 2009THOMAS HARTIG BRAUNSTEIN The expression of connexins in renal arterioles is believed to have a profound impact on conducted responses, regulation of arteriolar tonus and renal blood flow. We have previously shown that in renal preglomerular arterioles, conducted vasomotor responses are 40% greater in spontaneously hypertensive rats (SHR) than in normotensive Sprague,Dawley (SD) rats. Because conducted vasomotor responses depend on the cell,cell communication mediated through gap junctions, we hypothesized that the increased magnitude of conducted vasomotor response in SHR is associated with an increased amount of connexins in renal arterioles. To test this hypothesis, the amount of connexin 37 (Cx37), Cx40 and Cx43 was assessed in renal arterioles from normo- and hypertensive rats using quantitative immunofluorescence laser confocal miscroscopy. To account for differences in genetic background, we included both normotensive Wistar,Kyoto (WKY) and SD rats in the study. In all three strains of rats, and for all three isoforms, the expression of connexins was predominantly confined to the endothelial cells. We found a significantly increased abundance (240 ± 17.6%, p<0.05) of Cx37 in arterioles from WKY compared with SD and SHR. This high abundance of Cx37 was not related to blood pressure because normotensive SD demonstrated a level of Cx37 similar to that of SHR. Additionally, we found no evidence for an increased abundance of Cx40 and Cx43 in renal arterioles of SHR when compared with normotensive counterparts. [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] | ||||||||||||||||||||||||||||