Mitochondrial connexin 43 impacts on respiratory complex I activity and mitochondrial oxygen consumption.

Connexin 43 (Cx43) is present at the sarcolemma and the inner membrane of cardiomyocyte subsarcolemmal mitochondria (SSM). Lack or inhibition of mitochondrial Cx43 is associated with reduced mitochondrial potassium influx, which might affect mitochondrial respiration. Therefore, we analysed the importance of mitochondrial Cx43 for oxygen consumption.

Connexin43 in cardiomyocyte mitochondria contributes to mitochondrial potassium uptake.

Aims: Connexin43 is present at the inner membrane of cardiomyocyte mitochondria (mCx43), but its function remains unknown.

Methods And Results: In this study we verified the presence of mCx43 by a mass spectrometry-based proteomic approach in purified mitochondrial preparations from mouse myocardium and determined by western blot analysis that the C-terminus of mCx43 is oriented towards the intermembrane space. Cross-linking studies with dimethylsuberimidate indicated the presence of Cx43 hexamers in mitochondrial membranes.

Intracoronary acid infusion as an alternative to ischemic postconditioning in pigs.

Previous studies suggested that prolongation of acidosis during reperfusion is protective and may be an important mechanism of postconditioning protection. The aim of this study was to analyze the therapeutic value of this intervention during in vivo coronary reperfusion, and to compare it with ischemic postconditioning. Pigs were submitted to 48 or 60 min of ischemia and 2 h of reperfusion.

Acidic reoxygenation protects against endothelial dysfunction in rat aortic rings submitted to simulated ischemia.

Ischemia-reperfusion causes endothelial dysfunction. Prolongation of acidosis during initial cardiac reperfusion limits infarct size in animal models, but the effects of acidic reperfusion on vascular function are unknown. The present work analyzes the effects of acidic reoxygenation on vascular responses to different agonists in rat aortic rings.

Mitochondrial connexin43 as a new player in the pathophysiology of myocardial ischaemia-reperfusion injury.

Connexins are transmembrane proteins whose best known function is to form gap junction channels. Ventricular cardiomyocytes express the connexin isoform Cx43 and are rich in gap junctions essential for the normal propagation of the action potential. In addition to this physiological role, cardiomyocyte gap junctions contribute to the pathophysiology of ischaemia-reperfusion injury, mainly by synchronizing the onset of rigour contracture during ischaemia and cell-to-cell propagation of hypercontracture during reperfusion.

The modulatory effects of connexin 43 on cell death/survival beyond cell coupling.

Connexins form a diverse and ubiquitous family of integral membrane proteins. Characteristically, connexins are assembled into intercellular channels that aggregate into discrete cell-cell contact areas termed gap junctions (GJ), allowing intercellular chemical communication, and are essential for propagation of electrical impulses in excitable tissues, including, prominently, myocardium, where connexin 43 (Cx43) is the most important isoform. Previous studies have shown that GJ-mediated communication has an important role in the cellular response to stress or ischemia.

Prevention of the ischemia-induced decrease in mitochondrial Tom20 content by ischemic preconditioning.

Preserved mitochondrial function (respiration, calcium handling) and integrity (cytochrome c release) is central for cell survival following ischemia/reperfusion. Mitochondrial function also requires import of proteins from the cytosol via the translocase of the outer and inner membrane (TOM and TIM complexes). Since mitochondrial function following ischemia/reperfusion is better preserved by ischemic preconditioning (IP), we now investigated whether expression of parts of the import machinery is affected by ischemia/reperfusion without or with IP in vivo.

Translocation of connexin 43 to the inner mitochondrial membrane of cardiomyocytes through the heat shock protein 90-dependent TOM pathway and its importance for cardioprotection.

We have previously shown that connexin 43 (Cx43) is present in mitochondria, that its genetic depletion abolishes the protection of ischemia- and diazoxide-induced preconditioning, and that it is involved in reactive oxygen species (ROS) formation in response to diazoxide. Here we investigated the intramitochondrial localization of Cx43, the mechanism of Cx43 translocation to mitochondria and the effect of inhibiting translocation on the protection of preconditioning. Confocal microscopy of mitochondria devoid of the outer membrane and Western blotting on fractionated mitochondria showed that Cx43 is located at the inner mitochondrial membrane, and coimmunoprecipitation of Cx43 with Tom20 (Translocase of the outer membrane 20) and with heat shock protein 90 (Hsp90) indicated that it interacts with the regular mitochondrial protein import machinery.

The end-effectors of preconditioning protection against myocardial cell death secondary to ischemia-reperfusion.

Our understanding of the end-effectors involved in preconditioning protection is still very limited. This is partially due to an incomplete knowledge of the mechanisms responsible for acute sarcolemmal rupture and cell death during the first minutes of reperfusion, including the relative roles of hypercontracture-mediated sarcolemmal rupture and mitochondrial permeability transition pore (MPTP) opening-mediated cell death. In the present article, the role of proposed end-effectors of preconditioning protection, defined as molecules directly involved in cell death that are modified by ischemic preconditioning (IP), is examined.

Connexin 43 in cardiomyocyte mitochondria and its increase by ischemic preconditioning.

Objective: Connexin 43 (Cx43) is involved in infarct size reduction by ischemic preconditioning (IP); the underlying mechanism of protection, however, is unknown. Since mitochondria have been proposed to be involved in IP's protection, the present study analyzed whether Cx43 is localized at mitochondria of cardiomyocytes and whether such localization is affected by IP.

Methods And Results: Western blot analysis on mitochondrial preparations isolated from rat, mouse, pig, and human hearts showed the presence of Cx43.