F — HYPOXIE MYOCARDIQUE, REPERFUSION, ACCIDENT VASCULAIRE CEREBRAL
Intercellular channels formed by connexins (Cx) have been shown to play a critical role in cardiovascular disease. Indeed, connexin-deficient mice showed modifications in cell signalling, that appeared crucial in atherosclerosis and restenosis. In the heart, Cx40 is expressed in atrial myocytes, the conduction system and in endothelial cells. Here, we study the implication of endothelial Cx40 during ischemia and reperfusion in mice. For this purpose, we used the Cre-loxP system to create a mouse line in which Cx40 is deleted from the endothelium only. Immunostainings on TIE2- Cre+Cx40fl/flApoE-/- mice confirmed the absence of Cx40 in the endothelium, whereas the protein was normally expressed in the atria and cardiac conduction system. Moreover, mean arterial pressure and heart rates wehat appeared crucial in atheroscTIE2-Cre-Cx40fl/flApoE-/- and TIE2-Cre+Cx40 wt/wtApoE-/-) and TIE2-Cre+Cx40fl/flApoE-/- animals. Sixteen-week-old mice with or without endothelial-specific deletion of Cx40 were subjected to in vivo left coronary artery occlusion for 30 minutes and sacrificed 24-hours after reperfusion for analysis of infarct size. Myocardial surfaces areas at risk and infracted areas were measured from computed images using NIH Image software. Areas at risk, normalized to total left ventricle surfaces areas, were similar between the experimental groups, i.e controls 29.17±1.19 % (N=11) and TIE2- Cre-Cx40fl/flApoE-/- 29.29±2.37 % (N=7, n.s.). Interestingly, the infarct area, normalized to areas at risk, was significantly increased in TIE2-Cre+Cx40fl/flApoE-/- mice as compared to controls (20.67±4.74 % and 8.47±1.45 %, respectively, P<0.01). We conclude that endothelial Cx40 is implicated in resistance of the heart to ischemia-reperfusion injury. These findings underline once more the importance of connexin-mediated intercellular communication in cardiovascular inflammation, and may point towards novel therapeutic strategies to limit the cardiac injury after coronary interventions.Le texte complet de cet article est disponible en PDF.