Role Of Cx43 Research Articles

Abstract Tu005: Small Extracellular Vesicles Derived from Bovine Milk Contain an Endogenous Carboxyl Terminal Polypeptide of The Gap Junction Protein Connexin-43

Background: Connexin 43 (Cx43) is the body's most widely expressed gap junctional connexin. Researchers have shown evidence of non-canonical functions of Cx43 and the therapeutic promise of Cx43 mimetic peptides in cardiac pathologies. However, some critical barriers, including in vivo stability and potential immunotoxicity of Cx43 mimetic peptides, hinder clinical translation of these pro-drugs. To address these challenges, we are pioneering bovine milk-derived small extracellular vesicles (mEVs) as delivery vehicles for peptidic drugs. While exploring mEVs as drug delivery tools for αCT1 – a peptide mimicking Cx43 carboxyl terminus (CT) undergoing Phase III testing and known for promoting wound healing and cardioprotection - mEVs without loaded drug cargo exhibited similar bioactivity. This study aimed to test the hypothesis that Cx43, particularly CT fragments of Cx43, are naturally present in mEVs. Methods: mEVs were isolated from bovine milk using a novel protocol developed by our lab based on Tangential Flow Filtration and characterized by Western Blotting (WB), Nanoparticle Tracking Analysis, and Transmission Electron Microscopy. To determine the presence of Cx43 in mEVs, we used WB, immunoprecipitation and Single-Molecule Localization Microscopy (SMLM). Results: Characterization of mEVs confirmed relatively pure and ultrastructurally definitive mEVs isolated from milk at high density. WB for Cx43 in mEVs lysates based on two antibodies - one against the cytoplasmic loop domain and the other against CT-most 20 amino acids of Cx43, showed that full-length Cx43 was present in mEVs. Interestingly, the Cx43 CT antibody also detected a band at around 16 KDa, and this was confirmed by WB by using two more Cx43 CT antibodies. We also immunoprecipitated this Cx43 CT polypeptide from mEVs lysates using the CT antibodies. SMLM suggested that a subpopulation of mEVs contain Cx43 and demonstrated vesicle-to-vesicle heterogeneity to Cx43 immunolabeling. Conclusions: We show for the first time that an endogenous Cx43 CT polypeptide is present in mEVs. Our results provide new insight into the role of Cx43 in mEV bioactivity and potentially offer a path to safe, effective, and orally available therapeutic options based on mEVs.

Inflammation and Connexin 43 profiles in the prefrontal cortex are relevant to stress susceptibility and resilience in mice

Depression is a major chronic mental illness worldwide, characterized by anhedonia and pessimism. Exposed to the same stressful stimuli, some people behave normally, while others exhibit negative behaviors and psychology. The exact molecular mechanisms linking stress-induced depressive susceptibility and resilience remain unclear. Connexin 43 (Cx43) forms gap junction channels between the astrocytes, acting as a crucial role in the pathogenesis of depression. Cx43 dysfunction could lead to depressive behaviors, and depression down-regulates the expression of Cx43 in the prefrontal cortex (PFC). Besides, accumulating evidence indicates that inflammation is one of the most common pathological features of the central nervous system dysfunction. However, the roles of Cx43 and peripheral inflammation in stress-susceptible and stress-resilient individuals have rarely been investigated. Thus, animals were classified into the chronic unpredictable stress (CUS)-susceptible group and the CUS-resilient group based on the performance of behavioral tests following the CUS protocol in this study. The protein expression of Cx43 in the PFC, the Cx43 functional changes in the PFC, and the expression levels including interleukin (IL)-1β, tumor necrosis factor-α, IL-6, IL-2, IL-10, and IL-18 in the peripheral serum were detected. Here, we found that stress exposure triggered a significant reduction in Cx43 protein expression in the CUS-susceptible mice but not in the CUS-resilient mice accompanied by various Cx43 phosphorylation expression and the changes of inflammatory signals. Stress resilience is associated with Cx43 in the PFC and fluctuation in inflammatory signaling, showing that therapeutic targeting of these pathways might promote stress resilience.

Connexin43, A Promising Target to Reduce Cardiac Arrhythmia Burden in Pulmonary Arterial Hypertension.

While essential hypertension (HTN) is very prevalent, pulmonary arterial hypertension (PAH) is very rare in the general population. However, due to progressive heart failure, prognoses and survival rates are much worse in PAH. Patients with PAH are at a higher risk of developing supraventricular arrhythmias and malignant ventricular arrhythmias. The latter underlie sudden cardiac death regardless of the mechanical cardiac dysfunction. Systemic chronic inflammation and oxidative stress are causal factors that increase the risk of the occurrence of cardiac arrhythmias in hypertension. These stressful factors contribute to endothelial dysfunction and arterial pressure overload, resulting in the development of cardiac pro-arrhythmic conditions, including myocardial structural, ion channel and connexin43 (Cx43) channel remodeling and their dysfunction. Myocardial fibrosis appears to be a crucial proarrhythmic substrate linked with myocardial electrical instability due to the downregulation and abnormal topology of electrical coupling protein Cx43. Furthermore, these conditions promote ventricular mechanical dysfunction and heart failure. The treatment algorithm in HTN is superior to PAH, likely due to the paucity of comprehensive pathomechanisms and causal factors for a multitargeted approach in PAH. The intention of this review is to provide information regarding the role of Cx43 in the development of cardiac arrhythmias in hypertensive heart disease. Furthermore, information on the progress of therapy in terms of its cardioprotective and potentially antiarrhythmic effects is included. Specifically, the benefits of sodium glucose co-transporter inhibitors (SGLT2i), as well as sotatercept, pirfenidone, ranolazine, nintedanib, mirabegron and melatonin are discussed. Discovering novel therapeutic and antiarrhythmic strategies may be challenging for further research. Undoubtedly, such research should include protection of the heart from inflammation and oxidative stress, as these are primary pro-arrhythmic factors that jeopardize cardiac Cx43 homeostasis, the integrity of intercalated disk and extracellular matrix, and, thereby, heart function.

Interactive mechanism between connexin43 and Cd-induced autophagic flux blockage and gap junctional intercellular communication dysfunction in rat hepatocytes

Cadmium (Cd) is a significant environmental contaminant known for its potential hepatotoxic effects. However, the precise mechanisms underlying Cd-induced hepatotoxicity have yet to be fully understood. Therefore, the purpose of this study was to investigate the dynamic role of connexin 43 (Cx43) in response to Cd exposure, particularly its impact on gap junctional intercellular communication (GJIC) and autophagy in hepatocytes. To establish an in vitro model of Cd-induced hepatocyte injury, the Buffalo rat liver 3A cell line (BRL3A) was utilized.In order to elucidate the mechanism by which Cx43 influences Cd-induced hepatocyte toxic injury, inhibitors of Cx43 (Dynasore) and P-Cx43 (Ro318220) were employed in the model. The findings revealed that inhibiting Cx43 and its phosphorylation further compromised GJIC function, exacerbating the impairment, while also intensifying the blockage of autophagic flux. To gain further insight into the role of Cx43, siRNA was utilized to knock down Cx43 expression, yielding similar results. The down-regulation of Cx43 expression was found to worsen the morphological damage induced by cadmium exposure, diminish the cell proliferation capacity of BRL3A cells, and exacerbate the disruption of GJIC and autophagic flow caused by Cd.These findings suggest that Cx43 may serve as a potential therapeutic target for the treatment of liver damage resulting from Cd exposure. By targeting Cx43, it may be possible to mitigate the adverse effects of Cd on hepatocytes.

Role of Cx43 on the Bone Cell Generation, Function, and Survival.

The presence of gap junction intercellular communication structures in bone cells has been known since the early 1970s, further confirmed by Doty and Marotti at the structural level in the 1980-1990s. Work by Civitelli, Donahue, and others showed the expression of Cx43 at the mRNA and protein levels in all bone cell types: osteoclasts (bone resorbing cells), osteoblasts (bone forming cells), and osteocytes (mature osteoblasts embedded in the bone matrix that regulate the function of both osteoclasts and osteoblasts). While Cx45, Cx46, and Cx37 were also shown to be expressed in bone cells, most studies have focused on Cx43, the most abundant member of the connexin (Cx) family of proteins expressed in bone. The role of Cx43 has been shown to be related to the formation of gap junction intercellular channels, to unopposed hemichannels, and to channel independent functions of the molecule. Cx43 participates in the response of bone cells to pharmacological, hormonal, and mechanical stimuli, and it is involved in the skeletal phenotype with old age. Human and murine studies have shown that mutations of Cx43 lead to oculodentodigital dysplasia and craniometaphyseal dysplasia, both conditions associated with abnormalities in the skeleton. However, whereas substantial advances have been made on the skeletal role of Cx43, further research is needed to understand the basis for the effects of mutated Cx43 and potential ways to prevent the effects of these mutations on bone.

Role of Cx43 in iPSC-CM Damage Induced by Microwave Radiation.

The heart is one of the major organs affected by microwave radiation, and these effects have been extensively studied. Previous studies have shown that microwave-radiation-induced heart injury might be related to the abnormal expression and distribution of Cx43. In order to make the research model closer to humans, we used iPSC-CMs as the cell injury model to investigate the biological effect and mechanism of iPSC-CM injury after microwave radiation. To model the damage, iPSC-CMs were separated into four groups and exposed to single or composite S-band (2.856 GHz) and X-band (9.375 GHz) microwave radiation sources with an average power density of 30 mW/cm2. After that, FCM was used to detect cell activity, and ELISA was used to detect the contents of myocardial enzymes and injury markers in the culture medium, and it was discovered that cell activity decreased and the contents increased after radiation. TEM and SEM showed that the ultrastructure of the cell membrane, mitochondria, and ID was damaged. Mitochondrial function was aberrant, and glycolytic capacity decreased after exposure. The electrical conduction function of iPSC-CM was abnormal; the conduction velocity was decreased, and the pulsation amplitude was reduced. Wb, qRT-PCR, and IF detections showed that the expression of Cx43 was decreased and the distribution of Cx43 at the gap junction was disordered. Single or composite exposure to S- and X-band microwave radiation caused damage to the structure and function of iPSC-CMs, primarily affecting the cell membrane, mitochondria, and ID. The composite exposure group was more severely harmed than the single exposure group. These abnormalities in structure and function were related to the decreased expression and disordered distribution of Cx43.

ANGIOTENSIN II REDUCES THE EXPRESSION OF CX43 AND INHIBITS THE C-SRC /MAPK/ERK PATHWAY VIA CX43 IN CARDIOMYOCYTES

Objective: Hypertension is associated with abnormal renin angiotensin system (RAS). Angiotensin II (AngII), an important substance in RAS, is closely related to cardiomyocyte injury. Connexin43 (Cx43), a key structural protein in cardiomyocyte membrane, takes part in signal transduction and substance transport. Cx43 may cause extracellular interstitial fibrosis. It is known that Cx43 increases collagen I in heart tissue by regulating nuclear factor kappa B and Mechanistic metalloproteinase. However, the relationship between Ang II and Cx43 has been controversial,and how Ang II affects Cx43-related pathway is unclear. Otherwise, the activation and inhibition of the c-SRC /MAPK/ERK pathway may is related to Cx43, but the fact which is the forward is not sure. Objective:The purpose of this study is to explore whether Ang II affects the expression of Cx43 and inhibits c-Src /MAPK/ERK pathway via Cx43. Design and method: First, we given rat cardiomyocytes (H9C2 cells) different concentrations of Ang II (10-5M,10-6M and 10-7M,for 48h), and establish Ang II groups. There is a contral group, which was given normal culture without Ang II. Second,we given H9C2 cells the Gap26,which is the inhibition of Cx43. Proteins of Cx43 and c-SRC /MAPK/ERK pathway from all groups were detected by Western Blot, and mRNA of these proteins were detected by PCR. SPSS was used for statistical analysis to compare the difference between all the groups. Results: First, compared with the control group, protein of Cx43, c-SRC, ERK2 and ERK1 were significantly decreased in Ang II group, and when the concentration of Ang II was 10-5M, these proteins were the least. mRNA of Cx43, ERK2 and ERK1 also were cut down after giving Ang II (only 10-5M). Second, the Gap26-intervention group had the lower expression protein and mRNA of Cx43, c-SRC, ERK2 and ERK1. Conclusions: We proved that Angiotensin II can reduce the expression of Cx43 and inhibit c-SRC /MAPK/ERK pathway via Cx43 in cardiomyocytes. Based on the role of Cx43 and c-Src /MAPK/ERK pathway, hypertesion may injury the cardiomyocytes via RAS and these pathways.

S-19-3: ANGIOTENSIN II REDUCES THE EXPRESSION OF CX43 AND INHIBITS THE C-SRC /MAPK/ERK PATHWAY VIA CX43 IN CARDIOMYOCYTES

Background: Hypertension is associated with abnormal renin angiotensin system (RAS). Angiotensin II (AngII), an important substance in RAS, is closely related to cardiomyocyte injury. Connexin43 (Cx43), a key structural protein in cardiomyocyte membrane, takes part in signal transduction and substance transport. Cx43 may cause extracellular interstitial fibrosis.It is known that Cx43 increases collagen I in heart tissue by regulating nuclear factor kappa B and Mechanistic metalloproteinase.However, the relationship between Ang II and Cx43 has been controversial,and how Ang II affects Cx43-related pathway is unclear. Otherwise, the activation and inhibition of the c-SRC /MAPK/ERK pathway may is related to Cx43, but the fact which is the forward is not sure. Objective: The purpose of this study is to explore whether Ang II affects the expression of Cx43 and inhibits c-Src /MAPK/ERK pathway via Cx43. Methods: First,we given rat cardiomyocytes (H9C2 cells) different concentrations of Ang II (10–5 M,10–6 M and 10–7 M,for 48 h), and establish Ang II groups. There is a contral group, which was given normal culture without Ang II. Second,we given H9C2 cells the Gap26,which is the inhibition of Cx43.Proteins of Cx43 and c-SRC /MAPK/ERK pathway from all groups were detected by Western Blot, and mRNA of these proteins were detected by PCR. SPSS was used for statistical analysis to compare the difference between all the groups. Result: First, compared with the control group, protein of Cx43, c-SRC, ERK2 and ERK1 were significantly decreased in Ang II group, and when the concentration of Ang II was 10–5 M, these proteins were the least. mRNA of Cx43, ERK2 and ERK1 also were cut down after giving Ang II (only 10–5 M).Second, the Gap26-intervention group had the lower expression protein and mRNA of Cx43, c-SRC, ERK2 and ERK1. Conclusion: We proved that Angiotensin II can reduce the expression of Cx43 and inhibit c-SRC /MAPK/ERK pathway via Cx43 in cardiomyocytes.Based on the role of Cx43 and c-Src /MAPK/ERK pathway, hypertesion may injury the cardiomyocytes via RAS and these pathways.

Connexin32 regulates expansion of liver cancer stem cells via the PI3K/Akt signaling pathway.

Liver cancer stem cells (LCSCs) are responsible for liver cancer recurrence, metastasis, and drug resistance. Previous studies by the authors demonstrated that upregulated expression of connexin 32 (Cx32) reversed doxorubicin resistance and reduced invasion and metastasis of liver cancer cells. However, the role of Cx32 in expansion of LCSCs remains unclear. A total of 85 patients were enrolled in the present study and followed-up for 5 years. The expression of Cx32 in hepatocellular carcinoma (HCC) tissues and corresponding paracancerous tissues were detected by immunohistochemistry (IHC). Cx32 was silenced in HepG2 cells and overexpressed in HCCLM3 cells and the stemness of liver cells was examined by detecting the expression of LCSC markers (EpCAM, CD133, Nanog, Oct4, Sox9, c-Myc), sphere formation, and xenograft tumorigenesis. Finally, the effect of the phosphoinositide 3-kinase (PI3K)/protein kinase B (Akt) pathway on Cx32-regulated LCSC expansion was investigated. Cx32 was downregulated in LCSCs and HCC tissues, and predicted poor prognosis in patients with HCC. Overexpression of Cx32 in HCCLM3 cells significantly inhibited LCSC expansion, tumorigenesis, and phosphoinositide 3-kinase/protein kinase B (PI3K/Akt) pathway activity. By contrast, silencing of Cx32 in HepG2 cells upregulated expansion of LCSCs and PI3K/Akt pathway activity. Modulating the activity of the PI3K/Akt pathway by SC-79 and LY294002 in HepG2 and HCCLM3 cells, respectively, confirmed that Cx32 could affect the expansion of LCSCs through PI3K/Akt signaling. In conclusion, the present study demonstrated that Cx32 regulated the expansion of LCSCs, and increased expression of Cx32 significantly inhibited the expansion of LCSCs, suggesting that Cx32 may be an optimal target for intervention of HCC.

1395-P: The Role of Adipocyte Connexin-43 in Mediating Adipose Tissue Inflammation and Dysfunction in Obesity

Obesity is a leading global health concern and a major risk factor for type-2 diabetes. Thus, identifying mechanisms linking obesity to insulin resistance is of great importance. Chronic low-grade inflammation of the adipose tissue (AT) observed in obesity has been shown as an important pathophysiological link between obesity and the development of systemic insulin resistance, by various mechanisms. Gap junction (GJ) intercellular-communication, primarily composed of connexin- (Cx) 43, has been recently reported to have immunomodulatory roles in various tissues, and increased Cx43 expression and GJ activity have been implicated in the response of various tissues to chronic stress conditions. We have therefore aimed to study the role of Cx43 in shaping the AT adaptive or maladaptive response to these cellular insults of obesity. In a diet-induced obesity mouse model we demonstrated an increase in Cx43 expression in the intact AT, which could be primarily attributed to increased Cx43 expression in adipocytes. In high fat diet-fed adipocyte-specific Cx43 knock-out mice (AdCx43KO) , we observed increased infiltration of macrophages to the AT as compared to wild-type (WT) mice. This was accompanied by morphologic changes in the AT, with increased variability in adipocyte size. While AdCx43KO mice did not significantly differ from WT mice in body weight, adiposity or food intake, the AdCx43KO mice demonstrated reduced whole-body insulin sensitivity assessed by insulin tolerance test. Mechanistically, we observed that adipocytes can interact directly with neighboring adipocytes as well as with macrophages via Cx43-composed gap junctions, an interaction that is likely to be key in attenuation of the tissue inflammatory response. Our results suggest an immunomodulatory and metabolic role for adipocyte-Cx43 in obesity. Disclosure S.Ron: None. I.Ron: None. M.Rathaus: None. R.Livne: None. A.Tirosh: Advisory Panel; Abbott Diagnostics, AstraZeneca, Boehringer Ingelheim International GmbH, Merck & Co., Inc., Novo Nordisk, Sanofi, Consultant; Bayer AG, DreaMed Diabetes, Ltd., Research Support; Medtronic, Speaker's Bureau; Eli Lilly and Company. Funding Israel Science Foundation (922/17)

Connexin43 Overexpression Exacerbates Myocardial Ischemic Reperfusion Injury in Diabetes via Modulating Cardiac Autophagy

BackgroundPatients with diabetes are more vulnerable to myocardial ischemia/reperfusion injury (MIRI). Abnormal increases of cardiac Connexin43 (Cx43) were shown to be associated with a variety of pathological conditions including myocardial ischemia and diabetic cardiomyopathy, concomitant with various degrees of changes in autophagy. However, the role of Cx43 in MIRI in diabetic conditions and in particular its potential interplay with cardiac autophagy in this pathology is unknown. Thus, the present study was aimed to explore the role and mechanism of Cx43 in diabetic MIRI.Methods and ResultsStreptozotocin (STZ)‐induced diabetic and age‐matched control rats were subjected to MIRI by occluding the left coronary artery for 30 minutes followed by 2 hours of reperfusion at 5 weeks of diabetes induction. In vitro, rat origin H9C2 cardiomyocytes (H9C2) were exposed to 35mmol/L high glucose(HG)for 48 hours(h) in the absence or presence of Cx43 gene knockdown with siRNA, followed by hypoxia for 6h and reoxygenation for 12h. Myocardial infarct size was assessed by TTC staining. Cell viability was detected by the CCK‐8 assay, apoptosis by TUNEL assay. Cardiac Cx43 protein, apoptosis‐related proteins and autophagy‐related LC3, p62 and mTOR proteins were assessed by Western blotting. Post‐ischemic myocardial infarct size and cardiac CX43 protein expression were significantly increased in diabetic rats as compared with that in the control (p<0.05), concomitant with increases in the ratio of LC3 II/I and in the protein expression of P62 and mTOR (all p<0.05). In vitro, exposure of H9C2 cells to HG significantly increased cell injury evidenced by increased LDH release and reduced cell viability, and significantly enhanced cell apoptosis and reactive oxygen species(ROS) production that was accompanied by increased cardiomyocyte CX43 overexpression and enhanced autophagy but paradoxically also enhanced mTOR activation, similar to that seen in vivo. All these changes were further exacerbated following H/R under HG. Cx43 Knockdown in H9C2 results in decreased ROS production and decreased apoptosis after H/R under HG leading to increased cell viability (all p<0.05), while Cx43 knockdown attenuated autophagy. Application of the selective mTOR inhibitor rapamycin abolished the abovementioned beneficial effects of Cx43 Knockdown.ConclusionOverexpressed CX43 in the diabetic heart exacerbates MIRI in diabetes through enhanced cardiac autophagy under hyperglycemic condition.

Connexin32 ameliorates epithelial-to-mesenchymal-transition in diabetic renal tubular via inhibiting NOX4

Renal tubulointerstitial fibrosis (RIF), characterized by epithelial-to-mesenchymal transition (EMT) of renal tubular epithelial cells (TECs), is the main cause of diabetic renal fibrosis. Oxidative stress plays a pivotal role in the development of diabetic RIF. Connexin32 (Cx32), prominently expressed in renal TECs, has emerged as an important player in the regulation of oxidative stress. However, the role of Cx32 in diabetic RIF has not been explored yet. Here, we showed that adenovirus-mediated Cx32 overexpression suppressed EMT to ameliorate RIF and renal function in STZ-induced diabetic mice, while knockout (KO) of Cx32 exacerbated RIF in diabetic mice. Moreover, overexpression of Cx32 inhibited EMT and the production of extra cellular matrix (ECM) in high glucose (HG) induced NRK-52E cells, whereas knockdown of Cx32 showed the opposite effects. Furthermore, we showed that NOX4, the main source of ROS in renal tubular, was down-regulated by Cx32. Mechanistically, Cx32 down-regulated the expression of PKC alpha in a carboxyl-terminal-dependent manner, thereby inhibiting the phosphorylation at Thr147 of p22phox triggered by PKC alpha, which ultimately repressed the formation of the p22phox-NOX4 complex to reduce the protein level of NOX4. Thus, we establish Cx32 as a novel target and confirm the protection mechanism in RIF.

Cx43 Promotes Endothelial Cell Migration and Angiogenesis via the Tyrosine Phosphatase SHP-2

The gap junction protein connexin 43 (Cx43) is associated with increased cell migration and to related changes of the actin cytoskeleton, which is mediated via its C-terminal cytoplasmic tail and is independent of its channel function. Cx43 has been shown to possess an angiogenic potential, however, the role of Cx43 in endothelial cell migration has not yet been investigated. Here, we found that the knock-down of Cx43 by siRNA in human microvascular endothelial cells (HMEC) reduces migration, as assessed by a wound assay in vitro and impaired aortic vessel sprouting ex vivo. Immunoprecipitation of Cx43 revealed an interaction with the tyrosine phosphatase SHP-2, which enhanced its phosphatase activity, as observed in Cx43 expressing HeLa cells compared to cells treated with an empty vector. Interestingly, the expression of a dominant negative substrate trapping mutant SHP-2 (CS) in HMEC, via lentiviral transduction, also impaired endothelial migration to a similar extent as Cx43 siRNA compared to SHP-2 WT. Moreover, the reduction in endothelial migration upon Cx43 siRNA could not be rescued by the introduction of a constitutively active SHP-2 construct (EA). Our data demonstrate that Cx43 and SHP-2 mediate endothelial cell migration, revealing a novel interaction between Cx43 and SHP-2, which is essential for this process.

Mechanism of Ca2+-Dependent Pro-Apoptotic Action of Selenium Nanoparticles, Mediated by Activation of Cx43 Hemichannels.

Simple SummaryThe development of new methods of anticancer therapy is an urgent task of modern biology. The use of selenium and its compounds as anticancer drugs have already been shown to be effective. At the same time, the problem of selective delivery of selenium to organs and tissues remains. Nanoparticles are a promising and effective form of selenium delivery. This work is devoted to the study of the molecular and cellular mechanisms of action of selenium nanoparticles on glioblastoma cells. Using fluorescence microscopy and PCR, we were able to show for the first time the complete Ca2+ signaling pathway activated by selenium nanoparticles and the correlation between an increase in Ca2+ ions in the cytosol of cells with the induction of apoptosis. The presented study contributes to understanding the fundamental mechanisms of activation of programmed cell death in cancer tissue.To date, there are practically no data on the mechanisms of the selenium nanoparticles action on calcium homeostasis, intracellular signaling in cancer cells, and on the relationship of signaling pathways activated by an increase in Ca2+ in the cytosol with the induction of apoptosis, which is of great importance. The study of these mechanisms is important for understanding the cytotoxic effect of selenium nanoparticles and the role of this microelement in the regulation of carcinogenesis. The work is devoted to the study of the role of selenium nanoparticles obtained by laser ablation in the activation of the calcium signaling system and the induction of apoptosis in human glioblastoma cells (A-172 cell line). In this work, it was shown for the first time that the generation of Ca2+ signals in A-172 cells occurs in response to the application of various concentrations of selenium nanoparticles. The intracellular mechanism responsible for the generation of these Ca2+ signals has also been established. It was found that nanoparticles promote the mobilization of Ca2+ ions from the endoplasmic reticulum through the IP3-receptor. This leads to the activation of vesicular release of ATP through connexin hemichannels (Cx43) and paracrine cell activation through purinergic receptors (mainly P2Y). In addition, it was shown that the activation of this signaling pathway is accompanied by an increase in the expression of pro-apoptotic genes and the induction of apoptosis. For the first time, the role of Cx43 in the regulation of apoptosis caused by selenium nanoparticles in glioblastoma cells has been shown. It was found that inhibition of Cx43 leads to a significant suppression of the induction of apoptosis in these cells after 24 h treatment of cells with selenium nanoparticles at a concentration of 5 µg/mL.

NGF induces pulmonary arterial hyperreactivity through Connexin 43 increased expression

Nerve growth factor (NGF) plays a critical role in pathophysiology of pulmonary hypertension (PH) by promoting pulmonary arterial (PA) inflammation, remodelling and hyperreactivity. To determine the mechanisms of NGF-induced PA hyperreactivity, focusing on Connexin 43 (Cx43), a gap junction protein essential for vascular reactivity. Expression of NGF, its TrkA receptor and Cx43 were evaluated by Western blotting in human PA smooth muscle cells (hPASMC) from control donors or from patients suffering from idiopathic pulmonary arterial hypertension (iPAH). Cx43 expression and localisation were evaluated by Western blotting, immunofluorescence and surface biotinylation, after NGF treatment. Gap junction activity was assessed by FRAP microscopy. Contractions of rat PA were induced by phenylephrine (PHE), with or without NGF pre-treatment. The role of Cx43 in NGF-induced rat PA hyperreactivity was evaluated ex vivo by use of 43 Gap26, a Cx43 blocking peptide, or in vivo by use of an anti-Cx43 siRNA. TrkA expression was increased in hPASMC from iPAH patients compared to control hPASMC. NGF increased Cx43 expression, plasma membrane localisation and phosphorylation, with a higher sensitivity in iPAH cells compared to controls. In both cell types, this increase was abolished with K252a, a TrkA kinase inhibitor. Activity of Cx43-dependent GAP junctions was also increased after NGF treatment, with iPAH hPASMC being more sensitive to NGF than control cells. NGF-induced PA hyperreactivity to PHE was inhibited after treatment with 43 Gap26 or with anti-Cx43 siRNA. NGF, through activation of its TrkA receptor, increases Cx43 expression and plasma membrane localisation in hPASMC. This mechanism enhances Cx43-dependent GAP junction activity and contributes to PA hyperreactivity. Moreover, NGF pathway is upregulated in iPAH hPASMC compared to control hPASMC, and iPAH cells are more sensitive to NGF than control cells regarding Cx43 increased expression and Cx43-dependent GAP junction increased activity.

Effects of early crush on aging wild type and Connexin 32 knockout mice: Evidence for a neuroprotective state in CMT1X mouse nerve.

The long-term sequelae of nerve injury as well as age-related neurodegeneration have been documented in numerous studies, however the role of Cx32 in these processes is not well understood. There is a need for better understanding of the molecular mechanisms that underlie long-term suboptimal nerve function and for approaches to prevent or improve it. In this communication we describe our studies using whole animal electrophysiology to examine the long-term sequelae of sciatic nerve crush in both WT and Cx32KO mice, a model of X-linked Charcot Marie Tooth disease, a subtype of inherited peripheral neuropathies. We present results from electrical nerve recordings done 14 to 27 days and 18 to 20 months after a unilateral sciatic nerve crush performed on 35 to 37-day old mice. Contrary to expectations, we find that whereas crush injury leads to a degradation of WT nerve function relative to uninjured nerves at 18 to 20 months, previously crushed Cx32KO nerves perform at the same level as their uninjured counterparts. Thus, 18 to 20 months after injury, WT nerves perform below the level of normal (uninjured) WT nerves in both motor and sensory nerve function. In contrast, measures of nerve function in Cx32KO mice are degraded for sensory axons but exhibit no additional dysfunction in motor axons. Early nerve injury has no negative electrophysiologic effect on the Cx32 KO motor nerves. Based on our prior demonstration that the transcriptomic profile of uninjured Cx32KO and injured WT sciatic nerves are very similar, the lack of an additional effect of crush on Cx32KO motor nerve parameters suggests that Cx32 knockout may implement a form of neuroprotection that limits the effects of subsequent injury.

Down-regulation of the Expression of Senescence Proteins P16 and P21 by Activating Connexin 43 in the Smooth Muscle of Spiral Modiolar Artery of Guinea Pigs

To analyze the correlation between connexin 43 (Cx43) and the expression of P16 and P21, aging-related proteins, and to investigate the possible role of Cx43 in the development of cell senescence with an aging model prepared by D-galactose (D-gal) intervention in the vascular smooth muscle cells (VSMCs) of guinea pig spiral modiolar artery (SMA). The VSMCs of guinea pig SMA were cultured with the adhesion method, and the markers of VSMCs were detected with immunofluorescence technique. The experiment has a control group, a D-gal group, and a group that received D-gal and gap junction agonist AAP10 intervention, hereafter referred to as the AAP10 group. Cell Counting Kit-8 (CCK-8) was used to check VSMC activity and to determine the concentration and duration of D-gal intervention. The mRNA expression of Cx43 in each group was checked with qRT-PCR. The expression of Cx43, P16 and P21 proteins in each group was examined with the Western blot. The expression and distribution of P16 and P21 proteins were examined with immunofluorescence assay. Immunofluorescence results showed that the positive expression rate of cell actin (α-SM-actin) was over 90%. CCK-8 results showed that the optimal concentration of D-gal intervention was 30 mg/mL and the intervention duration was 48 h. qRT-PCR test showed that the mRNA expression of Cx43 in VSMCs in the D-gal group was significantly lower than that in the control group ( P<0.01), while it is higher in the AAP10 group than that of the D-gal group ( P<0.01); Western blot assay showed that the Cx43 expression level in VSMCs in the D-gal group was significantly lower than that in the control group ( P<0.01) and the expression of P16 and P21 was significantly higher than that in the control group ( P<0.01), the expression of Cx43 protein in AAP10 group was significantly up-regulated compared with that in the D-gal group ( P<0.01), while the expression of P16 and P21 was down-regulated significantly ( P<0.01); The results of immunofluorescence showed that P16 and P21 were mainly expressed in the cell nucleus. Semi-quantitative analysis of fluorescence intensity showed that the level of P16 and P21 protein in the D-gal group was significantly higher than that in the control group, and the fluorescence intensity of AAP10 group was significantly lower than that in the D-gal group ( P<0.01). Up-regulation of Cx43 expression can reverse the D-gal-induced abnormal expression of P16 and P21, two aging-related proteins, in SMA. It is suggested that Cx43 on SMA may be involved in D-gal-induced cell senescence, which provides a theoretical basis and possible intervention target for the delay of cell senescence.

Function of Connexin-43 in Macrophages.

Recent studies have helped to increase the understanding of the function of Connexin-43 (Cx43) in macrophages (Mφ). The various roles of Cx43 in Mφs range from migration, antigen-presentation and some forms of intercellular communication to more delicate processes, such as electrochemical support in the propagation of the heartbeat, immunomodulatory regulation in the lungs and in macrophage-differentiation. Its relevance in pathophysiology becomes evident in inflammatory bowel disease (IBD), tumours and HIV, in which aberrant functioning of Cx43 has been described. However, the involvement of Cx43 in other Mφ functions, such as phagocytosis and polarisation, and its involvement in other types of local and systemic inflammation, are still unclear and need further research.

Importance of Cx43 for Right Ventricular Function.

In the heart, connexins form gap junctions, hemichannels, and are also present within mitochondria, with connexin 43 (Cx43) being the most prominent connexin in the ventricles. Whereas the role of Cx43 is well established for the healthy and diseased left ventricle, less is known about the importance of Cx43 for the development of right ventricular (RV) dysfunction. The present article focusses on the importance of Cx43 for the developing heart. Furthermore, we discuss the expression and localization of Cx43 in the diseased RV, i.e., in the tetralogy of Fallot and in pulmonary hypertension, in which the RV is affected, and RV hypertrophy and failure occur. We will also introduce other Cx molecules that are expressed in RV and surrounding tissues and have been reported to be involved in RV pathophysiology. Finally, we highlight therapeutic strategies aiming to improve RV function in pulmonary hypertension that are associated with alterations of Cx43 expression and function.

Role of connexin 43 in odontoblastic differentiation and structural maintenance in pulp damage repair

Dental pulp can initiate its damage repair after an injury of the pulp–dentin complex by rearrangement of odontoblasts and formation of newly differentiated odontoblast-like cells. Connexin 43 (Cx43) is one of the gap junction proteins that participates in multiple tissue repair processes. However, the role of Cx43 in the repair of the dental pulp remains unclear. This study aimed to determine the function of Cx43 in the odontoblast arrangement patterns and odontoblastic differentiation. Human teeth for in vitro experiments were acquired, and a pulp injury model in Sprague-Dawley rats was used for in vivo analysis. The odontoblast arrangement pattern and the expression of Cx43 and dentin sialophosphoprotein (DSPP) were assessed. To investigate the function of Cx43 in odontoblastic differentiation, we overexpressed or inhibited Cx43. The results indicated that polarized odontoblasts were arranged along the pulp–dentin interface and had high levels of Cx43 expression in the healthy teeth; however, the odontoblast arrangement pattern was slightly changed concomitant to an increase in the Cx43 expression in the carious teeth. Regularly arranged odontoblast-like cells had high levels of the Cx43 expression during the formation of mature dentin, but the odontoblast-like cells were not regularly arranged beneath immature osteodentin in the pulp injury models. Subsequent in vitro experiments demonstrated that Cx43 is upregulated during odontoblastic differentiation of the dental pulp cells, and inhibition or overexpression of Cx43 influence the odontoblastic differentiation. Thus, Cx43 may be involved in the maintenance of odontoblast arrangement patterns, and influence the pulp repair outcomes by the regulation of odontoblastic differentiation.