Canadian Journal of Cardiology
Basic Research| Volume 37, ISSUE 10, P1593-1606, October 2021

A Novel Role of Claudin-5 in Prevention of Mitochondrial Fission Against Ischemic/Hypoxic Stress in Cardiomyocytes

Published:April 07, 2021DOI:



      Downregulation of claudin-5 in the heart is associated with the end-stage heart failure. However, the underlying mechanism ofclaudin-5 is unclear. Here we investigated the molecular actions of claudin-5 in perspective of mitochondria in cardiomyocytes to better understand the role of claudin-5 in cardioprotection during ischemia.


      Myocardial ischemia/reperfusion (I/R; 30 min/24 h) and hypoxia/reoxygenation (H/R; 24 h/4 h) were used in this study. Confocal microscopy and transmission electron microscope (TEM) were used to observe mitochondrial morphology.


      Claudin-5 was detected in murine heart tissue and neonatal rat cardiomyocytes (NRCM). Its protein level was severely decreased after myocardial I/R or H/R. Confocal microscopy showedclaudin-5 presented in the mitochondria of NRCM. H/R-induced claudin-5 downregulation was accompanied by mitochondrial fragmentation. The mitofusin 2 (Mfn2) expressionwas dramatically decreased while the dynamin-related protein (Drp) 1 expression was significantly increased after H/R. The TEM indicatedH/R-induced mitochondrial swelling and fission. Adenoviral claudin-5 overexpression reversed these structural disintegration of mitochondria. The mitochondria-centered intrinsic pathway of apoptosis triggered by H/R and indicated by the cytochrome c and cleaved caspase 3 in the cytoplasm of NRCMs was also reduced by overexpressing claudin-5. Claudin-5 overexpression in mouse heart also significantly decreased cleaved caspase 3 and the infarct size in ischemic heart with improved systolic function.


      We demonstrated for the first time the presence of claudin-5 in the mitochondria in cardiomyocytes and provided the firm evidence for the cardioprotective role of claudin-5 in the preservation of mitochondrial dynamics and cell fate against hypoxia- or ischemia-induced stress.



      Une régulation négative de la claudine-5 dans le cœur est associée à l'insuffisance cardiaque au stade terminal. Cependant, le mécanisme sous-jacent de la claudine-5 n'est pas clair. Nous avons étudié les mécanismes d'actions moléculaires de la claudine-5 dans les mitochondries des cardiomyocytes afin de mieux comprendre le rôle de la claudine-5 dans la cardioprotection pendant l'ischémie.


      L'ischémie/reperfusion (I/R; 30 min/24 h) du myocarde et l'hypoxie/régénération (H/R; 24 h/4 h) ont été appliquées lors de cette étude. La microscopie confocale et la microscopie électronique en transmission (MET) ont été utilisées pour l'observation de la morphologie des mitochondries.


      La claudine-5 a été détectée dans le tissu cardiaque murin et dans les cardiomyocytes néonataux de rat (CNR). Son niveau d'expression protéique était sévérement diminué après une I/R du myocarde ou une H/R. La microscopie confocale a montré que la claudine-5 était présente dans les mitochondries des CNR. La régulation négative de la claudine-5 induite par l'H/R s'est accompagnée d'une fragmentation mitochondriale. Le niveau d'expression de la mitofusine-2 (Mfn2) a considérablement diminué tandis que celui de la protéine de type dynamine-1 (Drp1) a augmenté de manière significative après l'H/R. La MET a mis en èvidence le gonflement et la fission des mitochondries induits par l'H/R. La surexpression de la claudine-5 par infection adénovirale a inversé cette désintégration structurelle des mitochondries. La voie intrinsèque de l'apoptose au niveau mitochondrial, déclenchée par l'H/R et indiquée par l'expression du cytochrome c et de la caspase-3 clivée dans le cytoplasme des CNR, a aussi été réduite lors de la surexpression de la claudine-5. La surexpression de la claudine-5 dans le cœur de souris a également diminué de manière significative la caspase-3 à l'état clivé et la taille de l'infarctus dans le cœur ischémique, avec une amélioration de la fonction systolique.


      Nous avons démontré pour la première fois la présence de la claudine-5 dans les mitochondries des cardiomyocytes et fourni des preuves solides du rôle cardioprotecteur de la claudine-5 dans la préservation de la dynamique mitochondriale et du devenir des cellules opposées au stress induit par l'hypoxie ou l'ischémie.
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