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Connexins (Cxs) are transmembrane proteins involved in the formation of hemichannels and gap junctions (GJs). GJs are involved in various physiological functions, including secretion in glandular tissue. It has been demonstrated that Cx26, Cx32, and Cx43 are mainly expressed in glands, but no data are available in human salivary glands to date. The aim of our study was to investigate the presence and the localization of Cxs in human minor labial salivary glands. Immunofluorescence and immunoelectron microscopy were employed to evaluate the Cx26, Cx32, and Cx43 protein in human labial salivary gland biopsies (hLSGBs). RT-PCR was also used to detect their mRNA expression. Cx expression was found at both the mRNA and protein levels in all hLSGBs analysed. Cxs were observed at the level of the duct and acinar cells, as well as in myoepithelial cells. The localization of the three Cx types was very similar, suggesting colocalization of these Cxs in the same connexons. These results demonstrated the presence of Cxs in human salivary glands for the first time. Moreover, the few samples with primary Sjögren's Syndrome analysed only by immunofluorescence showed an alteration of the Cx expression, indicating that these proteins could be involved in salivary gland dysfunctions.

Connexins are membrane-spanning proteins that form membrane channels and hemichannels. They are involved in the cellular communication and in the maintenance of tissue homeostasis. Recent studies in humans and animals have demonstrated that the expression and distribution of Cx43, the most studied connexin, can change during aging. However, the research on the involvement of the other connexins in cardiac and hepatic aging is, at present, still very poor. Hence, the aim of this study is to evaluate the expression of Cx43 and Cx26 in the heart as well as Cx26 and Cx32 in the liver of a rat model that aged naturally, rather than prematurely because of genetic mutations or age-related diseases. The results obtained in the present study have demonstrated that these connexins decrease in rat cardiomyocytes and in rat hepatocytes as they age. This change was revealed only at protein level, as connexin-mRNAs remained unchanged during aging. Moreover, the aged rats showed an increase in body fat, whose subcutaneous layer tended to be higher. Finally, how these changes could represent signs of physiological adaptation in successful aging was discussed., (Copyright © 2020 Elsevier GmbH. All rights reserved.)

Aims Sodium-glucose cotransporter 2 inhibitors have beneficial effects on heart failure and cardiovascular mortality in diabetic and non-diabetic patients, with unclear mechanisms. Autophagy is a cardioprotective mechanism under acute stress conditions, but excessive autophagy accelerates myocardial cell death leading to autosis. We evaluated the protective role of empagliflozin (EMPA) against cardiac injury in murine diabetic cardiomyopathy. Methods and results Male mice, rendered diabetics by one single intraperitoneal injection of streptozotocin and treated with EMPA (30 mg/kg/day), had fewer apoptotic cells (4.9 ± 2.1 vs. 1 ± 0.5 TUNEL-positive cells %, P < 0.05), less senescence (10.1 ± 2 vs. 7.9 ± 1.2 β-gal positivity/tissue area, P < 0.05), fibrosis (0.2 ± 0.05 vs. 0.15 ± 0.06, P < 0.05 fibrotic area/tissue area), autophagy (7.9 ± 0.05 vs. 2.3 ± 0.6 fluorescence intensity/total area, P < 0.01), and connexin (Cx)-43 lateralization compared with diabetic mice. Proteomic analysis showed a down-regulation of the 5′ adenosine monophosphate-activated protein kinase (AMPK) pathway and upstream activation of sirtuins in the heart of diabetic mice treated with EMPA compared with diabetic mice. Because sirtuin activation leads to the modulation of cardiomyogenic transcription factors, we analysed the DNA binding activity to serum response elements (SRE) of serum response factor (SRF) by electromobility shift assay. Compared with diabetic mice [0.5 ± 0.01 densitometric units (DU)], non-diabetic mice treated with EMPA (2.2 ± 0.01 DU, P < 0.01) and diabetic mice treated with EMPA (2.0 ± 0.1 DU, P < 0.01) significantly increased SRF binding activity to SRE, paralleled by increased cardiac actin expression (4.1 ± 0.1 vs. 2.2 ± 0.01 target protein/β-actin ratio, P < 0.01). EMPA significantly reversed cardiac dysfunction on echocardiography in diabetic mice and inhibited excessive autophagy in high-glucose-treated cardiomyocytes by inhibiting the autophagy inducer glycogen synthase kinase 3 beta (GSK3β), leading to reactivation of cardiomyogenic transcription factors. Conclusion Taken together, our results describe a novel paradigm in which EMPA inhibits hyperactivation of autophagy through the AMPK/GSK3β signalling pathway in the context of diabetes. [ABSTRACT FROM AUTHOR]

Introduction: Connexins (Cxs) are transmembrane proteins involved in the formation of connexons/hemichannels. Two connexons of adjacent cells can dock one each other form- ing an intercellular channel at gap junction (GJ), by which ions and small metabolites can pass between cells. Single hemichannels participate in the exchange of small metabolites between cells and the extracellular space [1]. There are at least 21 isoforms of Cxs expressed in humans and they are localized in almost every tissue. More than one Cx can be expressed in each tissue and connexons can be made by a single Cx or by different types of Cxs. GJ are involved in various physiological functions including secretion in glandular tissue [2-5]. Cx26, Cx32 and Cx43 are the mainly expressed Cxs in glands, but no data are available about their expression in human salivary glands. Aim: The aim of our study is to investigate the presence and the localization of these Cxs in human minor salivary glands. Methods: human minor salivary gland biopsies (hMSGBs) were obtained as part of the routine diagnostic procedures when primary Sjögren’s Syndrome (pSS) was suspected. Samples without pSS were selected for the study. Immunofluorescence and immunoelectron microscopy were employed to evaluated Cx26, Cx32 and Cx43 protein expression while RT-PCR was used to detect their mRNA expression. Results and Conclusions: Cx expression was found at both protein and mRNA level in all hMSGBs analysed. Cxs were observed at level of the duct and acinar cell membranes, as well as in myoepithelial cells. The localization of the three Cx types was very similar, suggesting a colocalization of these Cxs in the same connexons. Further studies are necessary to confirm this hypothesis. However, these preliminary results are important because demonstrate for the first time the presence of Cxs in human salivary glands. Moreover, in the few analysed pSS samples we observed an alteration of Cx expression indicating that these proteins may be involved in salivary gland dysfunctions. [ABSTRACT FROM AUTHOR]

Connexins (Cxs) are a family of membrane-spanning proteins, expressed in vertebrates and named according to their molecular weight. They are involved in tissue homeostasis, and they function by acting at several communication levels. Cardiac Cxs are responsible for regular heart function and, among them, Cx26 and Cx43 are widely expressed throughout the heart. Cx26 is present in vessels, as well as in cardiomyocytes, and its localization is scattered all over the cell aside from at the intercalated discs as is the case for the other cardiac Cxs. However, having been found in cardiomyocytes only recently, both its subcellular localization and its functional characterization in cardiomyocytes remain poorly understood. Therefore, in this study we aimed to obtain further data on the localization of Cx26 at the subcellular level. Our TEM immunogold analyses were performed on rat heart ventricles and differentiated H9c2 cardiac cell sections as well as on differentiated H9c2 derived extracellular vesicles. The results confirmed the absence of Cx26 at intercalated discs and showed the presence of Cx26 at the level of different subcellular compartments. The peculiar localization at the level of extracellular vesicles suggested a specific role for cardiac Cx26 in inter-cellular communication in an independent gap junction manner. [ABSTRACT FROM AUTHOR]

Cardiac connexins (Cxs) are proteins responsible for proper heart function. They form gap junctions that mediate electrical and chemical signalling throughout the cardiac system, and thus enable a synchronized contraction. Connexins can also individually participate in many signal transduction pathways, interacting with intracellular proteins at various cellular compartments. Altered connexin expression and localization have been described in diseased myocardium and the aim of this study is to assess the involvement of Cx43, Cx26, and some related molecules in ponatinib-induced cardiac toxicity. Ponatinib is a new multi-tyrosine kinase inhibitor that has been successfully used against human malignancies, but its cardiotoxicity remains worrisome. Therefore, understanding its signaling mechanism is important to adopt potential anti cardiac damage strategies. Our experiments were performed on hearts from male and female mice treated with ponatinib and with ponatinib plus siRNA-Notch1 by using immunofluorescence, Western blotting, and proteomic analyses. The altered cardiac function and the change in Cxs expression observed in mice after ponatinib treatment, were results dependent on the Notch1 pathway and sex. Females showed a lower susceptibility to ponatinib than males. The downmodulation of cardiac Cx43, Cx26 and miR-122, high pS368-Cx43 phosphorylation, cell viability and survival activation could represent some of the female adaptative/compensatory reactions to ponatinib cardiotoxicity. [ABSTRACT FROM AUTHOR]

The article discusses a study conducted to explore the signaling pathway of Pontine (PON) in a murine model of PON-induced cardiotoxicity focusing on the involvement of Cx43, serine 368 phoshorylated Cx43 (pS368-Cx43) and Cx26 also considering sex-related differences. The study found that c onnexins are involved in mice PON-induced cardiotoxicity, showing a sex related altered expression.