Cx43 Protein Research Articles

Abstract 4132820: S-nitrosylation of cardiac Cx43 hemichannels at Cys271 promotes arrhythmogenicity and myocardial injury upon cardiac stress in Duchenne Muscular Dystrophy

Connexin-43 (Cx43) plays a critical role in the propagation of action potentials among cardiomyocytes and proper cardiac contractility. In healthy cardiomyocytes, Cx43 is located at the intercalated disk; however, Cx43 remodeling is observed in cardiac pathologies and is linked with arrhythmogenesis and sudden cardiac death. Utilizing a mouse model of Duchenne muscular dystrophy (DMD mdx ), we have previously demonstrated that cardiac Cx43 is laterally localized, forming undocked hemichannels that activate via S-nitrosylation in response to isoproterenol-evoked cardiac stress. This activation leads to the disruption of cardiac membrane permeability, triggered activity, and deadly arrhythmogenic behaviors. To establish the direct role of S-nitrosylated Cx43 in DMD cardiomyopathy, we developed a specific knock-in mouse line in which the single Cx43 site for S-nitrosylation, cysteine 271 (Cys271), was substituted with a serine (C271S +/- ). Here, we developed a DMD mdx :C271S +/- line (4–6 months old), exhibiting reduced levels of S-nitrosylated Cx43 after crossing DMDmdx mice and C271S +/- mouse lines to assess the effect of β-adrenergic stimulation-induced cardiac stress and heart dysfunction. We show that cardiac Cx43 remodeling was not prevented in DMD mdx :C271S +/- , similar to what was shown in DMD mdx mice via immunofluorescence analysis. In addition, DMD mdx mice displayed an increased number of deadly arrhythmogenic events, increased Ca 2+ signaling, and prolonged action potentials in Langendorff-perfused whole hearts via optical mapping, compared to wild-type and DMD mdx :C271S +/- mice. Similarly, isoproterenol treatment evoked severe myocardial injury, increased levels of plasmatic cardiac troponin I (cTnI), and 40% mortality in DMD mdx mice. Notably, DMD mdx :C271S +/- mice, similar to DMD mdx mice treated with the Cx43 hemichannel blocker Gap19, exhibited cardioprotection compared to the cardiac dysfunction observed in DMD mdx mice. Therefore, these findings strongly suggest that S-nitrosylation of Cx43 proteins at site Cys271 represents a fundamental NO-mediated mechanism involved in the induction of arrhythmias and myocardial injury in DMD mdx after β-adrenergic stress.

Connexin 43 hemichannels and related diseases

Abstract Connexin 43 (Cx43) protein forms hemichannels (connexons) and gap junctions, with hemichannels consisting of six Cx43 molecules and gap junctions formed by two hemichannels. While gap junctions are prevalent in organs like the heart and liver, hemichannels are found in specific cell types, such as astrocytes and osteocytes. They allow the passage of small molecules (<1.5 kDa) between the cytoplasm and extracellular matrix. Cx43 hemichannels have emerged as potential therapeutic targets in various diseases, including central nervous system disorders, bone-related diseases, diabetic complications, wound healing, and cancers. Aberrant hemichannel opening can worsen conditions by releasing inflammatory elements, such as causing gliosis in neuronal cells. Conversely, functional hemichannels may inhibit cancer cell growth and metastasis. Recent studies are revealing new mechanisms of Cx43 hemichannels, broadening their therapeutic applications and highlighting the importance of regulating their activity for improved disease outcomes.

The impact of X-rays on cardiac hydrometabolism and the regulatory role of AS-IV

BackgroundRadiation-induced cardiac injury has emerged as a significant pathological entity, with many studies focusing on the fibrotic changes in myocardial tissue. However, these do not offer solutions for the clinical prevention and treatment of radiation-induced heart disease. Regulating hydrometabolism presents a potential therapeutic target for the management of cardiovascular diseases. This research seeks to explore the impacts of irradiation on cardiac hydrometabolism and its regulatory mechanisms. MethodsThe impact of X-ray radiation on cardiac and cardiomyocyte hydrometabolism was studied through in vivo and in vitro experiments, examining the pharmacological effects and mechanisms of PX-478 and AS-IV interventions in cardiomyocytes. Results28 days after direct chest irradiation with 20 Gy X-rays, C57BL/6 mice exhibited an increased heart wet-to-dry weight ratio, significant enlargement of cardiomyocyte cross-sectional area, and elevated protein expression of HIF-1α, AQP1, AQP4, Cx43, Caspase3, and Bax, with decreased expression of Bcl-2. Irradiation with 6 Gy X-rays induced edema and damage in AC16 and HL-1 cardiomyocytes at 24, 48, and 72 h, with increased expression of HIF-1α, AQP1, AQP4, and Cx43 proteins post-radiation. Inhibition of HIF-1α ameliorated edema and apoptosis in AC16 and HL-1 cardiomyocytes, reducing the expression of HIF-1α, AQP1, AQP4, and Cx43 proteins. AS-IV demonstrated strong binding affinity with HIF-1α, and successfully attenuated the expression levels of HIF-1α, AQP1, AQP4, and Cx43 proteins, alleviating edema, mitochondrial swelling, and apoptosis in AC16 and HL-1 cardiomyocytes. Furthermore, AS-IV improved cardiomyocyte edema by restoring the activity of Na/K-ATPase. ConclusionAberrant activation of the HIF-1α/AQPs/Cx43 axis is a key mechanism in X-ray-induced cardiomyocyte edema and damage. AS-IV can ameliorate X-ray induced cardiac damage by regulating hydrometabolism.

Changes in Cx43 and AQP4 Proteins, and the Capture of 3 kDa Dextran in Subpial Astrocytes of the Rat Medial Prefrontal Cortex after Both Sham Surgery and Sciatic Nerve Injury.

A subpopulation of astrocytes on the brain's surface, known as subpial astrocytes, constitutes the "glia limitans superficialis" (GLS), which is an interface between the brain parenchyma and the cerebrospinal fluid (CSF) in the subpial space. Changes in connexin-43 (Cx43) and aquaporin-4 (AQP4) proteins in subpial astrocytes were examined in the medial prefrontal cortex at postoperative day 1, 3, 7, 14, and 21 after sham operation and sciatic nerve compression (SNC). In addition, we tested the altered uptake of TRITC-conjugated 3 kDa dextran by reactive subpial astrocytes. Cellular immunofluorescence (IF) detection and image analysis were used to examine changes in Cx43 and AQP4 protein levels, as well as TRITC-conjugated 3 kDa dextran, in subpial astrocytes. The intensity of Cx43-IF was significantly increased, but AQP4-IF decreased in subpial astrocytes of sham- and SNC-operated rats during all survival periods compared to naïve controls. Similarly, the uptake of 3 kDa dextran in the GLS was reduced following both sham and SNC operations. The results suggest that both sciatic nerve injury and peripheral tissue injury alone can induce changes in subpial astrocytes related to the spread of their reactivity across the cortical surface mediated by increased amounts of gap junctions. At the same time, water transport and solute uptake were impaired in subpial astrocytes.

Mutations of the Cx43 Gene in Non-Small Cell Lung Cancer: Association with Aberrant Localization of Cx43 Protein Expression and Tumor Progression.

Background and Objectives: The Connexin43 (Cx43) gene is a suspected tumor suppressor gene, as re-expressed wild-type Cx43 genes reduce the malignancy potential of tumor cells. However, the role of Cx43 gene expression in human lung tumorigenesis remains unclear. Materials and Methods: Tumor tissues from 165 primary lung cancer patients were collected to study Cx43 protein expression and gene mutations using immunohistochemistry and direct DNA sequencing. In addition, Cx43 genes with or without mutations were transfected to CL-3 human lung cancer cells to confirm the function of these mutant forms of the Cx43 gene. Results: Aberrant localization of Cx43 protein in the nucleus and cytoplasm of tumor cells was detected in 14 out of 165 non-small cell lung cancer (NSCLC) patients. Mutations in the Cx43 gene were also found in patients with aberrant Cx43 localization, and transfection of these mutant genes into lung cancer cells enhanced their proliferation. Conclusions: To our knowledge, this is the first study to demonstrate Cx43 gene mutations in human lung neoplasm, supporting the hypothesis that Cx43 may function as a tumor suppressor in some lung cancer patients. Additionally, the findings suggest an association between aberrant localization of Cx43 protein expression and tumor progression.

The Role of miRNA-29b1 on the Hypoxia-Induced Apoptosis in Mammalian Cardiomyocytes

A hypoxic stress which causes apoptosis of cardiomyocytes is the main problem in the ischemic heart disease. The present research sought to investigate the role of microRNA-29b1 (miR-29b1) in hypoxia-treated cardiomyocytes and its potential mechanism involved. We replicated an in vitro AC16 and H9C2 cardiomyocytes ischemia model by hypoxia (1% O2, 48 h) treatment. Cell apoptosis was evaluated by flow cytometry using Annexin V FITC-PI staining assay. Moreover, we used western blot and immunofluorescence analysis to determine the expression of Bcl-2, Bax caspase-3 and Cx43 proteins. We found that miR-29b1 protected AC16 and H9C2 cells from hypoxia-induced injury as the evidences that miR-29b1 attenuated the effects of hypoxia treatment on AC16 and H9C2 cell apoptosis after hypoxia treatment. In conclusion, these results revealed the potential cardiovascular protective effects of miR-29b1 in the process of ischemia-related myocardial injury.

P163 EMPAGLIFLOZIN AND ITS CARDIOPROTECTIVE EFFECTS IN THE HEART DURING VOLUME OVERLOAD IN AN EXPERIMENTAL MODEL INDUCED BY AORTOCAVAL FISTULA

Mitral regurgitation causes volume overload of the heart, and due to the deregulation of extracellular matrix proteins, the electrical communication between cardiomyocytes provided by connexin channels is disturbed. The aim of this study was to investigate the effect of cardiac volume overload (VO) on its functional parameters, structural remodeling, and connexin43 (Cx43), a protein ensuring electrical synchronization of the heart, and the cardioprotective effect of empagliflozin. Cardiac VO was induced by surgical aortocaval fistula (ACF) in adult, 6-month-old male Wistar rats. Mitral regurgitation and VO developed within four weeks. Subsequently, empagliflozin was administered daily for five weeks at a dose of 10 mg/kg of body weight. Echocardiographic examination showed increased cardiac output and increased Vmax of the aortic valve, decreased ejection fraction and fractional shortening due to ACF-VO. Echocardiographic parameters showed an increase in the diameter of the left ventricle in both systole and diastole, as well as an increase in the volume of the left ventricle at the end of systole and diastole. Empagliflozin normalized the negative parameters in the ACF-VO group. Myocardial protein Cx43 levels were reduced by ACF-VO but normalized by empagliflozin treatment. In addition, empagliflozin suppressed the ACF-VO-induced increase in interstitial collagen detected by van Gieson staining. These findings were consistent with increased protein expression of MMP-2, which is involved in structural remodeling of the extracellular matrix, and was normalized by empagliflozin. Protein kinase C epsilon levels associated with Cx43 and extracellular matrix modulation were reduced by ACF-VO and normalized by empagliflozin. However, protein levels of pro-apoptotic and pro-hypertrophic protein kinase C delta were increased by ACF-VO and normalized by empagliflozin. Protein expression of transforming growth factor beta as well as fibroblast growth factor 21 was increased by ACF-VO and normalized by empagliflozin. The results indicate a cardioprotective effect of empagliflozin due to suppression of myocardial structural remodeling and preservation of Cx43 in an experimental model simulating volume overload. The research was supported by grants APVV-21-0410,VEGA-2/0006/23,VEGA-2/0133/24,VEGA-2/0002/20

Tamoxifen-induced alterations in the expression of connexin 43 in the chicken ovary

Connexin 43 (Cx43) is a gap junction protein that participates in small molecule exchange between adjacent cells. It is a predominant Cx within the mammalian ovary, where is associated with proper follicle development. The expression and regulation of Cx43 in the chicken ovary is largely unknown. The aim of the present study was to examine the expression of the Cx43 gene (GJA1) and protein as well as the immunolocalization of Cx43 in the laying hen ovary in relation to follicle development, and to examine how tamoxifen (TMX; an estrogen receptor modulator) treatment affects these factors. qRT-PCR and western blotting demonstrated differences in Cx43 mRNA transcript and protein abundances in ovarian white follicles, yellowish follicles, small yellow follicles, and the largest yellow preovulatory follicles (F3–F1). In general, Cx43 was more abundant in hierarchical than prehierarchical follicles and in granulosa cells compared with theca cells. Further, the response to TMX treatment depended on the stage of follicle development and the layer of the follicular wall. Ovarian regression following TMX treatment was accompanied by an increase in Cx43 expression in most ovarian tissues, which may impact the formation and function of Cx43 hemichannels. Overall, our results showed, for the first time, the differences in Cx43 mRNA and protein levels between ovarian follicles, suggesting the potential involvement of this gap junction protein in the regulation of ovarian follicle development and function. In addition, the results indicate a possible role for estradiol in regulation of Cx43 transcription and/or translation in the chicken ovary. Understanding the contribution of Cx43 in mechanisms underlying ovarian follicle development may be of considerable importance for poultry egg production.

Empagliflozin mitigates ponatinib-induced cardiotoxicity by restoring the connexin 43-autophagy pathway

BackgroundEmpagliflozin (EMPA), a selective sodium-glucose cotransporter type 2 (SGLT2) inhibitor, has been shown to reduce major adverse cardiovascular events in patients with heart failure of different etiologies, although the underlying mechanism still remains unclear. Ponatinib (PON) is a multi-tyrosine kinase inhibitor successfully used against myeloid leukemia and other human malignancies, but its cardiotoxicity remains worrisome. Cardiac connexins (Cxs) are both substrates and regulators of autophagy and responsible for proper heart function. Alteration in connexin expression and localization have been described in patients with heart failure. AimsTo assess whether EMPA can mitigate PON-induced cardiac dysfunction by restoring the connexin 43-autophagy pathway. Methods and ResultsMale C57BL/6 mice, randomized into four treatment groups (CNTRL, PON, EMPA, PON+EMPA) for 28 days, showed increased autophagy, decreased Cx43 expression as well as Cx43 lateralization, and attenuated systo-diastolic cardiac dysfunction after treatment with EMPA and PON compared with PON alone. Compared with CNTRL (DMSO), cardiomyocyte-differentiated H9c2 (dH9c2) cells treated with PON showed significantly reduced cell viability to approximately 20 %, decreased autophagy, increased cell senescence and reduced DNA binding activity of serum response factor (SRF) to serum response elements (SRE), which were paralleled by reduction in cardiac actin expression. Moreover, PON induced a significant increase of Cx43 protein and its S368-phosphorylated form (pS368-Cx43), as well as their displacement from the plasma membrane to the perinuclear and nuclear cellular region. All these effects were reverted by EMPA. ConclusionEMPA attenuates PON-induced cardiotoxicity by reducing senescence, enhancing the SRE-SRF binding and restoring the connexin 43-autophagy pathway. This effect may pave the way to use of SGLT2 inhibitors in attenuating tyrosine-kinase inhibitor cardiotoxicity.

The effect of intra spinal administration of cerium oxide nanoparticles on central pain mechanism: An experimental study.

This study investigated Cerium oxide nanoparticles (CeONPs) effect on central neuropathic pain (CNP). The compressive method of spinal cord injury (SCI) model was used for pain induction. Three groups were formed by a random allocation of 24 rats. In the treatment group, CeONPs were injected above and below the lesion site immediately after inducing SCI. pain symptoms were evaluated using acetone, Radian Heat, and Von Frey tests weekly for six weeks. Finally, we counted fibroblasts using H&E staining. We evaluated the expression of Cx43, GAD65 and HDAC2 proteins using the western blot method. The analysis of results was done by PRISM software. At the end of the study, we found that CeONPs reduced pain symptoms to levels similar to those observed in normal animals. CeONPs also increased the expression of GAD65 and Cx43 proteins but did not affect HDAC2 inhibition. CeONPs probably have a pain-relieving effect on chronic pain by potentially preserving GAD65 and Cx43 protein expression and hindering fibroblast infiltration.

CX43 and oxidative stress are the targets of BCB staining to predict the developmental potential of buffalo oocytes.

This study used the brilliant cresyl blue (BCB) staining method to group buffalo oocytes (BCB+ and BCB-) and perform invitro maturation, invitro fertilization and embryo culture. At the same time, molecular biology techniques were used to detect gap junction protein expression and oxidative stress-related indicators to explore the molecular mechanism of BCB staining to predict oocyte developmental potential. The techniques of buffalo oocytes to analyse their developmental potential and used immunofluorescence staining to detect the expression level of CX43 protein, DCFH-DA probe staining to detect ROS levels and qPCR to detect the expression levels of the antioxidant-related genes SOD2 and GPX1. Our results showed that the invitro maturation rate, embryo cleavage rate and blastocyst rate of buffalo oocytes in the BCB+ group were significantly higher than those in the BCB- group and the control group (p < .05). The expression level of CX43 protein in the BCB+ group was higher than that in the BCB- group both before and after maturation (p < .05). The intensity of ROS in the BCB+ group was significantly lower than that in the BCB- group (p < .05), and the expression levels of the antioxidant-related genes SOD2 and GPX1 in the BCB+ group were significantly higher than those in the BCB- group (p < .05). Brilliant cresyl blue staining could effectively predict the developmental potential of buffalo oocytes. The results of BCB staining were positively correlated with the expression of gap junction protein and antioxidant-related genes and negatively correlated with the reactive oxygen species level, suggesting that the mechanism of BCB staining in predicting the developmental potential of buffalo oocytes might be closely related to antioxidant activity.

Human coronavirus OC43 infection remodels connexin 43-mediated gap junction intercellular communication in vitro.

β-coronaviruses cause acute infection in the upper respiratory tract, resulting in various symptoms and clinical manifestations. OC43 is a human β-coronavirus that induces mild clinical symptoms and can be safely studied in the BSL2 laboratory. Due to its low risk, OC43 can be a valuable and accessible model for understanding β-coronavirus pathogenesis. One potential target for limiting virus infectivity could be gap junction-mediated communication. This study aims to unveil the status of cell-to-cell communications through gap junctions in human β-coronavirus infection. Infection with OC43 leads to reduced expression of Cx43 in A549, a lung epithelial carcinoma cell line. Infection with this virus also shows a significant ER and oxidative stress increase. Internal localization of Cx43 is observed post-OC43 infection in the endoplasmic reticulum-Golgi intermediate compartment (ERGIC) region, which impairs the gap junction communication between two adjacent cells, confirmed by Lucifer yellow dye transfer assay. It also affects hemichannel formation, as depicted by the EtBr uptake assay. Impairment of Cx43 trafficking and the ability to form hemichannels and functional GJIC are hampered by virus-induced Golgi apparatus disruption. Altogether, these results suggest that several physiological changes accompany OC43 infection in A549 cells and can be considered an appropriate model system for understanding the differences in gap junction communication post-viral infections. This model system can provide valuable insights for developing therapies against human β-coronavirus infections.IMPORTANCEThe enduring impact of the recent SARS-CoV-2 pandemic underscores the importance of studying human β-coronaviruses, advancing our preparedness for future coronavirus infections. As SARS-CoV-2 is highly infectious, another human β-coronavirus OC43 can be considered an experimental model. One of the crucial pathways that can be considered is gap junction communication, as it is vital for cellular homeostasis. Our study seeks to understand the changes in Cx43-mediated cell-to-cell communication during human β-coronavirus OC43 infection. In vitro studies showed downregulation of the gap junction protein Cx43 and upregulation of the endoplasmic reticulum and oxidative stress markers post-OC43 infection. Furthermore, HCoV-OC43 infection causes reduced Cx43 trafficking, causing impairment of functional hemichannel and GJIC formation by virus-mediated Golgi apparatus disruption. Overall, this study infers that OC43 infection reshapes intercellular communication, suggesting that this pathway may be a promising target for designing highly effective therapeutics against human coronaviruses by regulating Cx43 expression.

The role of miRNA-29b1 on the hypoxia-induced apoptosis in mammalian cardiomyocytes.

Cardiomyocyte apoptosis is a complex biological process involving the interaction of many factors and signaling pathways. In hypoxic environment, cardiomyocytes may trigger apoptosis due to insufficient energy supply, increased production of oxygen free radicals, and disturbance of intracellular calcium ion balance. The present research aimed to investigate the role of microRNA-29b1 (miR-29b1) in hypoxia-treated cardiomyocytes and its potential mechanism involved. We established an in vitro ischemia model using AC16 and H9C2 cardiomyocytes through hypoxia treatment (1% O2, 48 h). Cell apoptosis was evaluated by flow cytometry using Annexin V FITC-PI staining assay. Moreover, we used Western blot and immunofluorescence analysis to determine the expression of Bcl-2, Bax caspase-3 and Cx43 proteins. We found that miR-29b1 protected AC16 and H9C2 cells from hypoxia-induced injury as evidence that miR-29b1 attenuated the effects of hypoxia treatment on AC16 and H9C2 cell apoptosis after hypoxia treatment. In conclusion, our findings suggest that miR-29b1 may have potential cardiovascular protective effects during ischemia-related myocardial injury.

Deficient Gap Junction Coupling in Two Common Hearing Loss-Related Variants of GJB2.

The aim of this study was to explore the functional consequences of two common variants, p.V37I and c.299-300delAT, in the hearing loss-associated gene GJB2. Connexin 26 expression and gap junctional permeability were studied in HEK 293T cells transfected with plasmids expressing GJB2 wild-type, p.V37I, or c.299-300delAT CX26 proteins tagged with fluorescent markers. Functional analyses of various GJB2 haplotypes were conducted to thoroughly evaluate alterations in ionic and small-molecule coupling. The p.V37I protein was localized at the plasma membrane, but it failed to effectively transport intercellular propidium iodide or Ca2+ efficiently, indicating an impairment in both biochemical and ionic coupling. The presence of GJB2 p.V37I seemed to increase the cells' sensitivity to H2O2 treatment. In contrast, the known variant c.299-300delAT protein was not transported to the cell membrane and was unable to form gap junctions, remaining confined to the cytoplasm. Both ionic and biochemical coupling were defective in cells transfected with c.299-300delAT. The p.V37I and c.299-300delAT GJB2 mutations resulted in deficient gap junction-mediated coupling. Additionally, environmental factors could influence the functional outcomes of the GJB2 p.V37I mutation. These findings could pave the way for the development of molecular therapies targeting GJB2 mutations to treat hearing loss.

Role of connexin 43 in a rat model of periodontitis-induced renal injury.

This study aims to investigate the role of gap junction mediated by connexin 43 (Cx43) in renal injury induced by periodontitis in rats. Twelve SPF-grade Wistar male rats were divided into a control group and a periodontitis group by using a completely random number table method, with six rats in each group. The control group rats were not treated, while the periodontitis group rats were subjected to wire ligation of the neck of their bilateral maxillary first molars to construct a periodontitis model. After 8 weeks of modeling, the rats were examined for clinical indicators of the periodontium. micro-CT scanning of the maxilla reconstructed its 3D structure and analyzed the absorption of alveolar bone. Histopathological changes in periodontal and renal tissues were detected. MitoSOX red reagent was used to determine reactive oxygen species (ROS) content in renal tissues. A biochemical reagent kit was used to detect serum oxidative stress biomarkers. Real-time fluorescent quantitative-polymerase chain reaction (qRT-PCR) was employed to determine Cx43, nuclear factor kappa-B (NF-κB) , interleukin (IL)-1β, IL-6, BCL2-Associated X (Bax), B-lymphomatoma-2 gene (Bcl-2), and Caspase-3 mRNA were determined. Western blot analysis was used to detect Cx43, NF-κB, IL-1β, Bax, Bcl-2 and Caspase-3 protein. micro-CT 3D reconstruction showed significant bone resorption of the first molar alveolar bone in the periodontitis group rats and decreased height of the alveolar ridge. The distance from the enamel cementum boundary to the top of the alveolar ridge in the periodontitis group was significantly higher than that inthe control group. The histopathological results showed a large number of inflammatory cells that infiltrated the periodontal tissue of the periodontitis group, and the alveolar bone was significantly absorbed. Rats in the periodontitis group also exhibited mild thickening of the glomerular basement membrane, dilation of the Bowman's capsule, and destruction of the brush-like edge of the renal tubules in the renal tissue. The MitoSOX red staining results showed a significant increase in ROS content in the renal tissue of the periodontitis group. The biochemical test results showed that the levels of superoxide dismutase and glutathione in the serum of rats with periodontitis decreased, while that of malondialdehyde increased. The results of qRT-PCR and Western blot showed that the expression levels of Cx43, IL-1β, IL-6, Bax, Caspase-3 mRNA and Cx43, IL-1β, NF-κB, Bax, Caspase-3 proteins in the periodontitis group significantly increased compared with those in the control group, while the expression levels of Bcl-2 mRNA and protein decreased. Periodontitis may activate NF-κB signaling molecules by upregulating the expression of Cx43 in rat kidney tissues, leading to increased levels of inflammation and apoptosis and ultimately inducing kidney injury.

New Approach to the Cryopreservation of GV Oocytes and Cumulus Cells through the Lens of Preserving the Intercellular Gap Junctions Based on the Bovine Model.

Differences in structural and functional properties between oocytes and cumulus cells (CCs) may cause low vitrification efficiency for cumulus-oocyte complexes (COCs). We have suggested that the disconnection of CCs and oocytes in order to further cryopreservation in various ways will positively affect the viability after thawing, while further co-culture in vitro will contribute to the restoration of lost intercellular gap junctions. This study aimed to determine the optimal method of cryopreservation of the suspension of CCs to mature GV oocytes in vitro and to determine the level of mRNA expression of the genes (GJA1, GJA4; BCL2, BAX) and gene-specific epigenetic marks (DNMT3A) after cryopreservation and in vitro maturation (IVM) in various culture systems. We have shown that the slow freezing of CCs in microstraws preserved the largest number of viable cells with intact DNA compared with the methods of vitrification and slow freezing in microdroplets. Cryopreservation caused the upregulation of the genes Cx37 and Cx43 in the oocytes to restore gap junctions between cells. In conclusion, the presence of CCs in the co-culture system during IVM of oocytes played an important role in the regulation of the expression of the intercellular proteins Cx37 and Cx43, apoptotic changes, and oocyte methylation. Slow freezing in microstraws was considered to be an optimal method for cryopreservation of CCs.

Propafenone-induced connexin-43 protein accumulation and intracellular dynamics

Abstract Funding Acknowledgements Type of funding sources: Public grant(s) – National budget only. Main funding source(s): China Scholarship Council Background Connexin-43 (Cx43) plays a pivotal role in intercellular communication through gap junctions. It is instrumental in propagating electrical signals and allowing ions to flow between neighboring cardiomyocytes. This synchronized electrical activity allows the heart to work as a functional syncytium. Any disruption or malfunction of Cx43 can lead to arrhythmias and other cardiac issues. Understanding the functions and regulation of Cx43 is vital in both basic research and clinical contexts. Propafenone, a class Ic antiarrhythmic drug, has shown promise in rhythm control; however, its precise impact on cardiac cellular physiology, particularly regarding Cx43, remains incompletely understood. Purpose To investigate propafenone’s effect on Cx43 expression, physiology, and underlying mechanisms in cell systems. Methods Used cell lines include human embryonic kidney HEK293 cells transfected with Cx43; differentiated murine embryonic carcinoma EPI7 cells with an epithelioid morphology and visceral endoderm-like END2 cells, endogenously expressing high amounts of functional Cx43. Cx43 protein expression levels were determined by Western blot analysis, whereas immunofluorescence (IF) imaged by a Total Internal Reflection Fluorescence (TIRF) microscope was used to assess the subcellular localization of Cx43 proteins. Dye injections were used to gain insight into the effects of propafenone on Cx43 metabolic coupling. Results and Conclusion Full length Cx43 protein levels were increased after treatment with propafenone and IF microscopy showed an intracellular accumulation of Cx43 protein, both on ectopically and endogenously expressed Cx43. Propafenone did not alter Cx43 half-life, in contrast to the lysosomal inhibitor chloroquine. Finally, gap-junctional coupling was decreased by chronic propafenone treatment. We conclude that the class 1c antiarrhythmic drug propanone increases Cx43 protein expression, resulting in its intracellular accumulation, as a side effect.

Cardioprotective effects of Empagliflozin in cardiac volume overload-induced by aortocaval fistula in rats

Abstract Funding Acknowledgements Type of funding sources: Public grant(s) – National budget only. Main funding source(s): Slovak Research and Development Agency under the contract no. 21-0410 VEGA grants no. 2/0006/23 Heart failure is characterized by reduction in cardiac output and the occurrence of malignant arrhythmias, thereby contributing significantly to high morbidity and mortality worldwide. Myocardial structural remodelling is a key factor contributing to the development of these life-threatening events and belongs to unsolved clinical issues challenging to investigate in animal models. The aim of our study was to explore the impact of cardiac volume overload (VO) on structural remodelling and electrical coupling protein, connexin43 (Cx43) in the left and right heart ventricles as well as the efficacy of treatment with SGLT2i, Empagliflozin. Aortocaval fistula (ACF) was surgically induced in 6-month-old Wistar rats, to develop VO during 4 weeks, followed by oral administration of Empagliflozin 10 mg/kg/b.w. daily for 5 weeks. At the end of the experiment, biometric parameters were registered and left and right heart tissue samples were snap-frozen and kept at -80°C for western blot analysis and microscopic examination. Findings revealed an increase of heart, left and right ventricular mass due to ACF-VO versus sham controls, which was associated, with eccentric myocardial hypertrophy. Noteworthy, Empagliflozin reduced heart, left and right ventricular mass. Levels of myocardial protein Cx43, that determine electrical coupling among cardiomyocytes, were reduced by ACF-VO, while normalized by treatment with Empagliflozin. Moreover, treatment attenuated ACF-VO-induced increase of interstitial collagen visualized by van Gieson staining. It was in line with the protein expression of MMP-2, which is involved in structural remodeling. The protein levels of PKCε, concerned/associated with modulation of Cx43 and extracellular matrix, were decreased due to ACV-VO but normalized after treatment with Empagliflozin. On the other hand, protein levels of PKCδ, involved in proapoptotic and prohypertrophic pathways, were increased and normalized by Empagliflozin. The changes were more pronounced in the right ventricle compared to the left heart ventricle. In summary, our pilot results point out the benefit of Empagliflozin due to the suppression of myocardial structural remodelling and preservation of Cx43 in the rat ACF-VO model. Furthermore, this Empagliflozin-induced cardioprotection was associated with the normalization of Cx43, MMP-2, and PKC levels independent of glucose control. However, further analyses are needed to reveal the molecular mechanisms of the cardioprotective effects of Empagliflozin.

O18 Precision genome editing for targeted correction of pathogenic D50N mutation in keratitis–ichthyosis–deafness syndrome using CRISPR/Cas9 and homology-directed repair

Abstract Introduction and aims Keratitis–ichthyosis–deafness (KID) syndrome is an ectodermal disorder that causes blindness, skin inflammation and deafness. It is caused by autosomal dominant mutations in the gap junction beta 2 (GJB2) gene with 86% being a hotspot mutation on c.148G&amp;gt;A, resulting in the amino acid replacement (D50N) in its coding protein connexin 26 (Cx26). There is currently no curative treatment for KID syndrome. We aim to correct the hotspot mutation D50N using a genome-editing approach. Methods Keratinocytes generated from the patient with KID who had a D50N mutation (KID-KCs) were genetically corrected by homologous-directed repair/CRISPR-Cas9 using an electroporation approach. The correction efficiency was determined and analysed using Sanger sequencing and Synthego Inference of CRISPR Edits analysis. The off-target effects were confirmed by whole-exome sequencing [exome next-generation sequencing (NGS)]. Furthermore, the functional recovery following genome editing was assessed by GJB2 mRNA production, Cx26 protein expression, and trafficking and hemichannel activity. Results The correction efficiencies ranged from 95% to 100% with different doses of CRISPR-Cas9 and 8µg CRISPR-Cas9 was the most optimal concentration with the efficiency of 100% and approximately 0% insertion-deletion (INDEL). Fifty days after gene editing, the INDEL increased to only 2%, indicating a minimum residual CRISPR-Cas9 effect in edited cells. The exome-NGS analysis also showed no off-target effects in the outside target area. Functional studies showed that there was a significant increase in wildtype GJB2 mRNA expression and a reduction of mutant GJB2 expression (n = 5, P &amp;lt; 0.01). Increased Cx26 membranous localization in KID-KCs was also observed (n = 3, P &amp;lt; 0.01). Additionally, Cx26 hemichannel activity assessment using the neurobiotin assay showed a significant decrease in ‘leaky’ hemichannel in gene-edited KID-KCs compared with unedited cells (n = 3, P &amp;lt; 0.05). Conclusions We can genome-correct KID keratinocytes harbouring the mutation D50N with 100% editing efficiency, 0–2% INDEL, and undetectable off-target effects. This result indicates a promising gene therapy for KID syndrome with the hotspot mutation D50N.

Yu Linzhu alleviates primary ovarian insufficiency in a rat model by improving proliferation and energy metabolism of granulosa cells through hif1α/cx43 pathway

BackgroundYu Linzhu (YLZ) is a classical Chinese traditional formula, which has been used for more than 600 years to regulate menstruation to help pregnancy. However, the mechanism of modern scientific action of YLZ needs to be further studied.MethodsThirty SD female rats were divided into three groups to prepare the blank serum and drug-containing serum, and then using UHPLC-QE-MS to identify the ingredients of YLZ and its drug-containing serum. Twenty-four SD female rats were divided into four groups, except the control group, 4-vinylcyclohexene dicycloxide (VCD) was intraperitoneally injected to establish a primary ovarian insufficiency (POI) model of all groups. Using vaginal smear to show that the estrous cycle of rats was disturbed after modeling, indicates that the POI model was successfully established. The ELISA test was used to measure the follicle-stimulating hormone (FSH), estradiol (E2), and anti-Mullerian hormone (AMH) levels in the serum of rats. HE stain was used to assess the morphology of ovarian tissue. The localization and relative expression levels of CX43 protein were detected by tissue immunofluorescence. Primary ovarian granulosa cells (GCs) were identified by cellular immunofluorescence. CCK8 was used to screen time and concentration of drug-containing serum and evaluate the proliferation effect of YLZ on VCD-induced GCs. ATP kit and Seahorse XFe24 were used to detect energy production and real-time glycolytic metabolism rate of GCs. mRNA and protein expression levels of HIF1α, CX43, PEK, LDH, HK1 were detected by RT-PCR and WB.ResultsUHPLC-QE-MS found 1702 ingredients of YLZ and 80 constituents migrating to blood. YLZ reduced the FSH while increasing the AMH and E2 levels. In ovarian tissues, YLZ improved ovarian morphology, follicle development, and the relative expression of CX43. In vitro studies, we found that YLZ increased the proliferative activity of GCs, ATP levels, glycolytic metabolic rate, HIF1α, CX43, PEK, HK1, LDH mRNA, and protein levels.ConclusionsThe study indicated that YLZ increased the proliferation and glycolytic energy metabolism of GCs to improve follicular development further alleviating ovarian function.