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BACKGROUND: Arrhythmia is the most common cardiac complication after ischemic stroke. Connexin 40 is the staple component of gap junctions, which influences the propagation of cardiac electrical signals in the sinoatrial node. However, the role of connexin 40 in post-stroke arrhythmia remains unclear. METHODS: In this study, a permanent middle cerebral artery occlusion model was used to simulate the occurrence of an ischemic stroke. Subsequently, an electrocardiogram was utilized to record and assess variations in electrocardiogram measures. In addition, optical tissue clearing and whole-mount immunofluorescence staining were used to confirm the anatomical localization of the sinoatrial node, and the sinoatrial node tissue was collected for RNA sequencing to screen for potential pathological mechanisms. Lastly, the rAAV9-Gja5 virus was injected with ultrasound guidance into the heart to increase Cx40 expression in the sinoatrial node. RESULTS: We demonstrated that the mice suffering from a permanent middle cerebral artery occlusion displayed significant arrhythmia, including atrial fibrillation, premature ventricular contractions, atrioventricular block, and abnormal electrocardiogram parameters. Of note, we observed a decrease in connexin 40 expression within the sinoatrial node after the ischemic stroke via RNA sequencing and western blot. Furthermore, rAAV9-Gja5 treatment ameliorated the occurrence of arrhythmia following stroke. CONCLUSIONS: In conclusion, decreased connexin 40 expression in the sinoatrial node contributed to the ischemic stroke-induced cardiac arrhythmia. Therefore, enhancing connexin 40 expression holds promise as a potential therapeutic approach for ischemic stroke-induced arrhythmia.

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Systemic sclerosis (SSc) is an autoimmune disease characterized by fibrosis of the skin and internal organs. Although its pathogenesis is not fully understood, connexins (Cxs) and pannexins (Panx) could be involved in the process of fibrosis. We analyzed the protein expression of Cx37, Cx40, Cx43, and Panx1 in the gastric mucosa of patients with SSc and healthy volunteers, using immunofluorescence staining. Protein levels of Cx37 were slightly increased, while the levels of Cx40 were significantly decreased in the lamina propria of the gastric mucosa of SSc patients compared to the controls. The changes were proportional to SSc severity, with the most prominent changes found in patients with severe diffuse cutaneous SSc. No differences in Cx43 or Panx1 levels were found between the analyzed groups of samples. The lack of changes in Cx43 expression, which has been previously associated with fibrosis, could be due to the weak expression of Cx43 in the gastric mucosa in general. Further studies on full-thickness gastric biopsies containing muscle layers and animal SSc models are needed to fully elucidate the role of Cxs and Panxs in SSc-associated fibrosis.

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INTRODUCTION: Atrial fibrillation (AF) is a common cardiac arrhythmia that is associated with heart failure and stroke, leading sometimes to death. But the pathogenesis of AF remains unclear. Numerous studies have investigated whether the connexin 40 (Cx40) polymorphisms influences the risk of AF, but the results are controversial. METHODS: We searched English and Chinese databases and calculated the odds ratio (OR) and 95% confidence interval (CI) to examine the existence of genetic associations between the Cx40 polymorphisms and the risk of AF. All relevant studies were screened and meta-analyzed using Review Manager 5.0. RESULTS: A total of 12 studies, including 10 studies for -44 polymorphism (rs35594137) and 4 studies for -26 polymorphism (rs10465885), were identified for the meta-analysis. For -44 polymorphism, the results showed a significantly increased risk of AF in the five genetic models in the overall analysis. Furthermore, in subgroup analysis, increased AF risks were also observed in Asian and non-Asian populations. For -26 polymorphism, the overall OR revealed an increased risk of AF in dominant model. In subgroup analysis, increased AF risk was only found in recessive genetic model of the Asian population. CONCLUSIONS: The Cx40 polymorphisms were positively associated with AF in both populations, especially on -44 polymorphism.

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Approximately 60% of patients with squamous cell carcinoma (LSCC) have regional occult metastatic disease/distant metastases at the time of diagnosis, putting them at higher risk for disease progression. Therefore, biomarkers are needed for early prognostic purpose. The aim of this study was to analyze the expression pattern of connexins (Cx) 37, 40 and 45, pannexin1 (Panx1) and vimentin in LSCC and correlate with tumor grade (G) and outcome. METHODS: Thirty-four patients who underwent (hemi-)laryngectomy and regional lymphadenectomy due to LSCC from 2017 to 2018 in University Hospital Split, Croatia, were studied. Samples of tumor tissue and adjacent normal mucosa embedded in paraffin blocks were stained using the immunofluorescence method and were semi-quantitatively analyzed. RESULTS: The expression of Cx37, Cx40, and Panx1 differed between cancer and adjacent normal mucosa and between histological grades, being the highest in well-differentiated (G1) cancer and low/absent in poorly differentiated (G3) cancer (all p < 0.05). The expression of vimentin was the highest in G3 cancer. Expression of Cx45 was generally weak/absent, with no significant difference between cancer and the controls or between grades. Lower Panx1 and higher vimentin expression were found to be prognostic factors for regional metastatic disease. Lower Cx37 and 40 expressions were present in patients with disease recurrence after the three-year follow-up period. CONCLUSION: Cx37 and Cx40, Panx1, and vimentin have the potential to be used as prognostic biomarkers for LSCC.

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The objective of the study was to investigate the expression levels of potassium voltage-gated channel subfamily A member 5 (KCNA5), connexin 43 (Cx43), and connexin 40 (Cx40) in the left atrial appendage of patients with atrial fibrillation (AF) and the interactions between them. We gathered tissue samples from patients with persistent AF and sinus rhythm and used fluorescence quantitative polymerase chain reaction to evaluate messenger RNA (mRNA) changes of KCNA5, Cx43, and Cx40. Then, we studied the protein levels of KCNA5, Cx43, and Cx40 by immunofluorescence and western blot analysis and the interactions between these proteins were identified by immunoprecipitation and immunofluorescence colocation, respectively. Compared with the control group, the mRNA and protein levels of KCNA5, Cx43, and Cx40 in the AF group were decreased and the positive expression of KCNA5, Cx43, and Cx40 protein was also decreased by immunofluorescence staining in the AF group. In addition, immunoprecipitation and immunofluorescence colocation revealed that KCNA5 was coexpressed with Cx43 and Cx40 proteins. The expressions of KCNA5, Cx43, and Cx40 were substantially downregulated in the myocardium of patients with AF and KCNA5 interacted with Cx43 and Cx40 proteins, respectively.

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The expression pattern of Connexins (Cx) 37, 40, 43, 45 and Pannexin 1 (Pnx1) was analyzed immunohistochemically, as well as semi-quantitatively and quantitatively in histological sections of developing 8th- to 12th-week human eyes and postnatal healthy eye, in retinoblastoma and different uveal melanomas. Expressions of both Cx37 and Cx43 increased during development but diminished in the postnatal period, being higher in the retina than in the choroid. Cx37 was highly expressed in the choroid of retinoblastoma, and Cx43 in epitheloid melanoma, while they were both increasingly expressed in mixoid melanoma. In contrast, mild retinal Cx40 expression during development increased to strong in postnatal period, while it was significantly higher in the choroid of mixoid melanoma. Cx45 showed significantly higher expression in the developing retina compared to other samples, while it became low postnatally and in all types of melanoma. Pnx1 was increasingly expressed in developing choroid but became lower in the postnatal eye. It was strongly expressed in epithelial and spindle melanoma, and particularly in retinoblastoma. Our results indicate importance of Cx37 and Cx40 expression in normal and pathological vascularization, and Cx43 expression in inflammatory response. Whereas Cx45 is involved in early stages of eye development, Pnx1might influence cell metabolism. Additionally, Cx43 might be a potential biomarker of tumor prognosis.

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[This corrects the article DOI: 10.3389/fonc.2019.00595.].

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Background: TET1 has been implicated in regulating inflammation and cardiovascular disease, but a newly discovered short isoform of TET1 (termed TET1s) exhibits higher expression in adult tissues than full-length TET1. However, the precise role of TET1 in cardiovascular disease remains undefined. Methods and Results: Based on TET1-/- knockout mice (with deletion of both TET1 and TET1s ) and TET1cs/cs mice (with deletion of only TET1), we found that TET1s deletion in TET1-/- mice resulted in more serious atherosclerotic lesions in the whole aorta than TET1cs/cs in the ApoE-/- background mice fed a high-fat diet. Atherosclerotic lesions with Oil red staining were dramatically localized in the aortic arch, abdominal aorta and ligated LCA, where they were exposed to OSS. Furthermore, the OSS-induced depression of TET1s in vitro and in vivo increased inflammatory cell and red blood cell infiltration into the subendothelial layer by impairing the vascular intimal barrier. TET1s upregulation enhanced vascular endothelial barrier function by increasing gap protein connexin 40 (CX40) expression as measured by RNA-seq and was confirmed by CX40 knockdown. TET1s interaction with Sin3a increased the global and CX40 promoter histone H3K27 acetylation levels, but not DNA methylation, to induce CX40 expression. Conclusions: These data demonstrate the unexpected discovery that laminar shear stress induces TET1s expression to protect the vascular endothelial barrier by increasing CX40 expression in ECs and that TET1s overexpression may be the core step for OSS-induced atherosclerosis therapy.

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MicroRNAs (miRNAs) participate in atrial remodeling and atrial fibrillation (AF) promotion. We determined the circulating miRNA profile in patients with AF and heart failure with reduced ejection fraction (HFrEF), and its potential role in promoting the arrhythmia. In plasma of 98 patients with HFrEF (49 with AF and 49 in sinus rhythm, SR), differential miRNA expression was determined by high-throughput microarray analysis followed by replication of selected candidates. Validated miRNAs were determined in human atrial samples, and potential arrhythmogenic mechanisms studied in HL-1 cells. Circulating miR-199a-5p and miR-22-5p were significantly increased in HFrEF patients with AF versus those with HFrEF in SR. Both miRNAs, but particularly miR-199a-5p, were increased in atrial samples of patients with AF. Overexpression of both miRNAs in HL-1 cells resulted in decreased protein levels of L-type Ca2+ channel, NCX and connexin-40, leading to lower basal intracellular Ca2+ levels, fewer inward currents, a moderate reduction in Ca2+ buffering post-caffeine exposure, and a deficient cell-to-cell communication. In conclusion, circulating miR-199a-5p and miR-22-5p are higher in HFrEF patients with AF, with similar findings in human atrial samples of AF patients. Cells exposed to both miRNAs exhibited altered Ca2+ handling and defective cell-to-cell communication, both findings being potential arrhythmogenic mechanisms.

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OBJECTIVE: The present study was performed to elucidate the role of nitric oxide (NO) and connexin 40 (Cx40) in the induction of cerebral vasospasm after subarachnoid hemorrhage (SAH) in vivo. METHODS: A SAH rat model was established using the double-bleed method. A total of 108 Sprague-Dawley rats weighing 250-300 g were randomly divided into 6 groups: SAH; SAH plus diethylenetriamine (DETA)/NO (exogenous NO donor); SAH plus 8-bromoadenosine (8-Br)-cyclic guanosine monophosphate (cGMP; protein kinase G [PKG] activator); SAH plus DETA/NO plus KT5823 (PKG inhibitor); SAH plus DETA/NO plus 40Gap27 (Cx40 inhibitor); and sham. The changes in the diameter of the branch microvessels in the middle cerebral artery were recorded. The neurological score was evaluated using the Garcia scoring system. Basilar artery (BA) tension was measured using the Danish Myo Technology myograph system. Cx40 protein expression was analyzed using immunofluorescence and Western blotting. Endothelial NO synthase, soluble guanylate cyclase, and PKG protein expression were measured by Western blotting. RESULTS: A considerable narrowing of the cerebral vessels was detected in the SAH group compared with that in the sham group. Moreover, compared with the sham group, the SAH group showed a marked decrease in Cx40, endothelial NO synthase, soluble guanylate cyclase, and PKG expression. The expression of Cx40 and PKG were obviously higher in the SAH plus DETA/NO and SAH plus 8-Br-cGMP groups than in the SAH group. However, Cx40 was lower in the SAH plus DETA/NO plus KT5823 and SAH plus DETA/NO plus 40Gap27 groups than in the SAH plus ETA/NO group. The BAs showed significant vasodilation in the SAH plus DETA/NO and SAH plus 8-Br-cGMP groups. However, the vasodilation response of BAs was inhibited in the SAH plus DETA/NO plus KT5823 and SAH plus DETA-NO plus 40Gap27 groups. CONCLUSIONS: The NO-cGMP-PKG pathway alleviated cerebral vasospasm via Cx40 upregulation.

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Despite responses to initial treatment of photodynamic therapy (PDT) being promising, a recurrence rate exists. Thus, finding novel therapeutic targets to enhance PDT efficacy is an urgent need. Reports indicate that connexin (Cx) 40 plays an important role in tumor angiogenesis and growth. However, it is unknown whether Cx40-composed channels have effects on PDT efficacy. The study uniquely demonstrated that Cx40-formed channels could enhance the phototoxicity of PDT to malignant cells in vitro and in vivo. Specifically, Cx40-formed channels at high cell density could increase PDT photocytotoxicity. This action was substantially restricted when Cx40 expression was not induced or Cx40 channels were restrained. Additionally, the presence of Cx40-composed channels enhanced the phototoxicity of PDT in the tumor xenografts. The above results indicate that enhancing the function of Cx40-formed channels increases PDT efficacy. The enhancement of PDT efficacy mediated by Cx40 channels was related with intracellular pathways mediated by ROS and calcium pathways, but not the lipid peroxide-mediated pathway. This work demonstrates the capacity of Cx40-mediated channels to increase PDT efficacy and suggests that therapeutic strategies designed to maintain or enhance Cx40 expression and/or channels composed by Cx40 may increase the therapeutic efficacy of PDT.

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Gap junctions (GJs) are intercellular channels directly linking neighbouring cells and are dodecamers of connexins. In the human heart, connexin40 (Cx40), Cx43, and Cx45 are expressed in different regions of the heart forming GJs ensuring rapid propagation of action potentials in the myocardium. Two of these connexins, Cx40 and Cx45, formed functional GJs with prominent transjunctional voltage-dependent gating (Vj-gating), which can be a mechanism to down regulate coupling conductance (Gj). It is not clear the effects of temperature on Vj-gating properties. We expressed Cx40 or Cx45 in N2A cells to study the Vj-gating extent, the kinetics of deactivation, and the recovery time course from deactivation at 22 °C, 28 °C, and 32 °C. Dynamic uncoupling between cell pairs were evaluated at different temperatures, junctional delays, and/or repeating frequencies. Cx40 or Cx45 GJs showed little changes in the extent of Vj-gating, but in both cases with a faster deactivation kinetics at high temperatures. The recovery from deactivation was faster at higher temperatures for Cx45 GJs, but not for Cx40 GJs. Cx45 GJs, but not Cx40 GJs, were dynamically uncoupled when sufficient junctional delays and/or repeating frequency in all tested temperatures. Gap junction specific dynamic uncoupling could play an important role in regulating action potential propagation speed in Cx45 enriched nodal cells in the heart.

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BACKGROUND: Coronary artery development is an intensely studied field. Mice are a popular genetic model for developmental studies, but there is no widely accepted protocol for high-throughput, high-resolution imaging of their developmental and adult coronary artery anatomy. RESULTS: Using tissue-clearing protocols and confocal microscopy, we have analyzed embryonic and juvenile mouse hearts in Cx40:GFP knock-in models with a special focus on septal artery development. We found that the septal artery, which supplies the interventricular septum, was initially formed as an arterial plexus that connected to both the left and right coronary arteries. During development, the plexus was remodeled into a single tube, which then remained connected only to the right coronary artery. Since optical imaging became limited at postnatal stages, it was supplemented with injection techniques using India ink and Microfil; the latter was subsequently analyzed with micro-CT to visualize the anatomy of coronary vessels in 3D. CONCLUSIONS: The techniques described here enable us to study the finer details of coronary artery development in mice and can, therefore, be implemented to study the pathogenesis of coronary malformations in various mouse models. Developmental Dynamics 247:1018-1027, 2018. © 2018 Wiley Periodicals, Inc.

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Atrial fibrillation (AF) is the most common form of cardiac arrhythmia. Recently, four novel heterozygous Cx40 mutations-K107R, L223M, Q236H, and I257L-were identified in 4 of 310 unrelated AF patients and a followup genetic analysis of the mutant carriers' families showed that the mutants were present in all the affected members. To study possible alterations associated with these Cx40 mutants, including their cellular localization and gap junction (GJ) function, we expressed GFP-tagged and untagged mutants in connexin-deficient model cells. All four Cx40 mutants showed clustered localization at cell-cell junctions similar to that observed of wildtype Cx40. However, cell pairs expressing Cx40 Q236H, but not the other individual mutants, displayed a significantly lower GJ coupling conductance (Gj) than wildtype Cx40. Similarly, co-expression of Cx40 Q236H with Cx43 resulted in a significantly lower Gj. Transjunctional voltage-dependent gating (Vj gating) properties were also altered in the GJs formed by Q236H. Reduced GJ function and altered Vj gating may play a role in promoting the Q236H carriers to AF.

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The so-called calcium paradoxon of renin describes the phenomenon that exocytosis of renin from juxtaglomerular cells of the kidney is stimulated by lowering of the extracellular calcium concentration. The yet poorly understood effect of extracellular calcium on renin secretion appears to depend on the function of the gap junction protein connexin 40 (Cx40) in renin-producing cells. This study aimed to elucidate the role of Cx40 for the calcium dependency of renin secretion in more detail by investigating if Cx40 function is really essential for the influence of extracellular calcium on renin secretion, if and how Cx40 affects intracellular calcium dynamics in renin-secreting cells and if Cx40-mediated gap junctional coupling of renin-secreting cells with the mesangial cell area is relevant for the influence of extracellular calcium on renin secretion. Renin secretion was studied in isolated perfused mouse kidneys. Calcium measurements were performed in renin-producing cells of microdissected glomeruli. The ultrastructure of renin-secreting cells was examined by electron microscopy. We found that Cx40 was not essential for stimulation of renin secretion by lowering of the extracellular calcium concentration. Instead, Cx40 increased the sensitivity of renin secretion response towards lowering of the extracellular calcium concentration. In line, the sensitivity and dynamics of intracellular calcium in response to lowering of extracellular calcium were dampened when renin-secreting cells lacked Cx40. Disruption of gap junctional coupling of renin-secreting cells by selective deletion of Cx40 from mesangial cells, however, did not change the stimulation of renin secretion by lowering of the extracellular calcium concentration. Deletion of Cx40 from renin cells but not from mesangial cells was associated with a shift of renin expression from perivascular cells of afferent arterioles to extraglomerular mesangial cells. Our findings suggest that Cx40 is not directly involved in the regulation of renin secretion by extracellular calcium. Instead, it appears that in renin-secreting cells of the kidney lacking Cx40, intracellular calcium dynamics and therefore also renin secretion are desensitized towards changes of extracellular calcium. Whether the dampened calcium response of renin-secreting cells lacking Cx40 function results from a direct involvement of Cx40 in intracellular calcium regulation or from the cell type shift of renin expression from perivascular to mesangial cells remains to be clarified. In any case, Cx40-mediated gap junctional coupling between renin and mesangial cells is not relevant for the calcium paradoxon of renin secretion.

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BACKGROUND: Patch clamping studies using non-cardiomyocytes revealed that the human connexin40 mutations P88S, G38D, and A96S are associated with reduced gap junction conductances compared to wild type connexin40 (wtCx40). Their effects within myocytes however are unclear. We aimed to characterise P88S, G38D, and A96S after expression in rat hearts and primary cardiomyocyte cultures. METHODS: Adult Sprague-Dawley rat atria were transduced with a lentivector containing a transgene encoding wtCx40, P88S, G38D, A96S, or eGFP (n=6 per transgene). Electrophysiology studies (EPS) were performed just prior to and 7 days after surgery. Left atria were assessed for connexin expression, mRNA levels, inflammation and fibrosis. Primary cardiomyocyte cultures were also transduced with the abovementioned vectors (n=6 per transgene) and monolayer conduction velocities (CV) and protein expression were assessed at 96hours. RESULTS: At day 7 EPS, P wave and induced atrial fibrillation (AF) durations were significantly longer in the mutant groups when compared to wtCx40 controls (p<0.05). There were no significant differences in inflammation, fibrosis, or heart to body weight ratios. Monolayer CV's were reduced in the A96S group compared to the wtCx40 group. While similar to wtCx40 controls, P88S velocities were reduced compared to eGFP controls. G38D monolayers possessed spontaneous fibrillatory activity and could not be paced. Immunofluorescence revealed that P88S and G38D reduced native connexin43 myocyte coupling while A96S appeared to co-localise with connexin43 in gap junctions. Connexin43 mRNA levels were similar between groups. CONCLUSIONS: The A96S, G38D, and P88S Cx40 mutations slow conduction and increased the propensity for inducible AF.

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The endotoxin lipopolysaccharide (LPS)-induced pulmonary endothelial barrier disruption is a key pathogenesis of acute lung injury (ALI) and acute respiratory distress syndrome (ARDS). However, the molecular mechanisms underlying LPS-impaired permeability of pulmonary microvascular endothelial cells (PMVECs) are not fully understood. Gap junctions, particularly Connexin40 (Cx40), are necessary for the maintenance of normal vascular function. In this study, we for the first time investigated the role of Cx40 in LPS-impaired permeability of PMVECs and provided potential therapeutic approaches based on mechanistic findings of Cx40 regulation by LPS stimuli. Rat PMVECs were isolated, cultured and identified with cell morphology, specific markers, ultrastructural characteristics and functional tests. Western blot analysis demonstrated that Cx40 is the major connexin highly expressed in PMVECs. Furthermore, by inhibiting Cx40 in a time-dependent manner, LPS impaired gap junction function and induced permeability injury of PMVECs. The key role of Cx40 decline in mediating detrimental effects of LPS was further confirmed in rescue experiments through Cx40 overexpression. Mechanistically, LPS stress on PMVECs inhibited the protein kinase C (PKC) pathway, which may synergize with the inflammatory nuclear factor kappaB (NFκB) signaling activation in suppressing Cx40 expression level and phosphorylation. Moreover, through pharmacological PKC activation or NFκB inhibition, Cx40 activity in PMVECs could be restored, leading to maintained barrier function under LPS stress. Our findings uncover a previously unrecognized role of Cx40 and its regulatory mechanisms in impaired endothelial integrity under endotoxin and inflammation, shedding light on intervention approaches to improve pulmonary endothelial barrier function in ALI and ARDS.

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Structural and electrical remodeling within the atrium mediate the pathogenesis of atrial fibrillation (AF). Two key genes that sever a role in this remodeling are connexin 40 (Cx40) and potassium voltage-gated channel subfamily A member 5 (KCNA5), respectively. Electrical remodeling is considered to induce structural remodeling during AF. In the present study, the left atrial appendage section and atrial myocytes of patients with AF were evaluated. It was observed that Cx40 and KCNA5 mRNA (P<0.05) and protein (P<0.01) expression was significantly downregulated in AF compared with rheumatic heart disease. In addition, a positive correlation between the mRNA expression Cx40 and KCNA5 was observed in the atrial myocytes of patients with AF (P<0.05; r=0.42). The association between Cx40 and KCNA5 expression was subsequently investigated in primary cultured atrial myocytes using siRNA transfection. In atrial myocytes, downregulation of Cx40 inhibited the expression of KCNA5. Similarly, silencing of KCNA5 suppressed the expression of Cx40. These results indicate that synergistic regulation may occur between Cx40 and KCNA5 expression. Furthermore, the combined effects of electrical and structural remodeling in the atrial myocytes of patients with AF may contribute to the pathogenesis of AF.

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Previous studies have demonstrated that connexin40 (Cx40) remolding is involved in atrial fibrillation (AF). GJA5 encoding Cx40 is a potential target mRNA of microRNA-208a-3p (miR-208a-3p), as indicated by preliminary bioinformatics analyses. However, the exact effect of miR-208a-3p on Cx40 in human chronic AF has remained elusive. The present study demonstrated the role of miR-208a-3p in human chronic AF and further investigated the effect of miR-208a-3p on Cx40 expression. A total of 19 patients with AF and 18 patients with sinus rhythm (SR) were enrolled. The AC16 cell line was treated with miR-208a-3p inhibitor or mimics. The miR-208a-3p in right atrial appendage (RAA) tissues of patients was measured by in situ hybridization and reverse-transcription quantitative polymerase chain reaction (RT-qPCR). Furthermore, the expression of Cx40 in the RAA of patients and in AC16 cells treated with miR-208a-3p inhibitor or mimics were detected by RT-qPCR and western blot analysis. A luciferase assay was performed to confirm whether Cx40 was directly targeted by miR-208a-3p. The miR-208a-3p levels in patients with AF were significantly increased compared with those in patients with SR. Conversely, the Cx40 protein levels were significantly decreased and lateralization of Cx40 was observed in patients with AF. miR-208a-3p inhibitor led to a significant upregulation of the protein expression of Cx40 in AC16 cells, while miR-208a-3p mimics led to a significant downregulation. However, the luciferase assay demonstrated that GJA5 was not a direct target gene of miR-208a-3p. The findings still suggested that miR-208a-3p may be involved in human chronic AF by mediating atrial Cx40 remolding, and may represent a potential therapeutic target for AF.

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BACKGROUND: Connexin (Cx) proteins are the building blocks of gap junctions. Among these, Cx37 and Cx40 are expressed on vascular system and reported to have cardioprotective role. Linking polymorphisms in genes coding for Cx and coronary artery disease (CAD) risk showed conflicting results in different populations. None has been studied before in Egyptians. Therefore, the aims of this study were to investigate the influence of Cx37 C1019T and Cx40 A71G polymorphisms on the predisposition of acute myocardial infarction (AMI) in Egyptians, to study linkage disequilibrium (LD) and combined effects of single nucleotide polymorphisms (SNPs) and to correlate the genotypes with sVCAM-1 serum levels. METHODS: Total of 201 Egyptian subjects were recruited for the study. They were divided into 104 AMI patients and 97 healthy controls. Genotypes for each participant were determined using a polymerase chain reaction restriction fragment length polymorphism (PCR-RFLP). Serum sVCAM-1was measured by ELISA. RESULTS: Allele frequencies for both Cx37 and Cx40 were not significantly different between AMI and Controls (p=0.93 and p=0.26 respectively). Moreover, studying the dominant and recessive models concluded that none of the genotypes was a risk factor. Both SNPs were not in LD (R2=0.0027). Serum analysis showed higher levels of sVCAM-1 in AMI patients (p<0.0001). sVCAM-1 levels were not significantly different among SNPs (Cx37; p=0.244 and Cx40; p=0.266). CONCLUSION: This study shows that Cx37 C1019T and Cx40 A71G polymorphisms are not associated with cardioprotective role in Egyptians. Moreover, both SNPs are inherited separately and none of the genotypes were associated with higher sVCAM-1 levels.

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