ABSTRACT
Ischemic heart disease is associated with inflammation, interstitial fibrosis and ventricular dysfunction prior to the development of heart failure. Endocannabinoids and the cannabinoid receptor CB2 have been claimed to be involved, but their potential role in cardioprotection is not well understood. We therefore explored the role of the cannabinoid receptor CB2 during the initial phase of ischemic cardiomyopathy development prior to the onset of ventricular dysfunction or infarction. Wild type and CB2-deficient mice underwent daily brief, repetitive ischemia and reperfusion (I/R) episodes leading to ischemic cardiomyopathy. The relevance of the endocannabinoid-CB2 receptor axis was underscored by the finding that CB2 was upregulated in ischemic wild type cardiomyocytes and that anandamide level was transiently increased during I/R. CB2-deficient mice showed an increased rate of apoptosis, irreversible loss of cardiomyocytes and persistent left ventricular dysfunction 60 days after the injury, whereas wild type mice presented neither morphological nor functional defects. These defects were due to lack of cardiomyocyte protection mechanisms, as CB2-deficient hearts were in contrast to controls unable to induce switch in myosin heavy chain isoforms, antioxidative enzymes and chemokine CCL2 during repetitive I/R. In addition, a prolonged inflammatory response and adverse myocardial remodeling were found in CB2-deficient hearts because of postponed activation of the M2a macrophage subpopulation. Therefore, the endocannabinoid-CB2 receptor axis plays a key role in cardioprotection during the initial phase of ischemic cardiomyopathy development.
Subject(s)
Cardiomyopathies/prevention & control , Myocardial Infarction/metabolism , Myocardial Reperfusion Injury/metabolism , Myocytes, Cardiac/metabolism , Receptor, Cannabinoid, CB2/metabolism , Signal Transduction , Animals , Apoptosis , Arachidonic Acids/metabolism , Cardiomyopathies/genetics , Cardiomyopathies/metabolism , Cardiomyopathies/pathology , Cardiomyopathies/physiopathology , Disease Models, Animal , Endocannabinoids/metabolism , Female , Macrophage Activation , Macrophages/metabolism , Male , Mice, Inbred C57BL , Mice, Knockout , Myocardial Infarction/genetics , Myocardial Infarction/pathology , Myocardial Infarction/physiopathology , Myocardial Reperfusion Injury/genetics , Myocardial Reperfusion Injury/pathology , Myocardial Reperfusion Injury/physiopathology , Myocytes, Cardiac/pathology , Polyunsaturated Alkamides/metabolism , Receptor, Cannabinoid, CB2/deficiency , Receptor, Cannabinoid, CB2/genetics , Time Factors , Ventricular Dysfunction, Left/metabolism , Ventricular Dysfunction, Left/physiopathology , Ventricular Dysfunction, Left/prevention & control , Ventricular Function, Left , Ventricular RemodelingABSTRACT
Myocardial infarction is associated with inflammatory reaction leading to tissue remodeling. We compared tissue remodeling between cryoinfarction (cMI) and reperfused myocardial infarction (MI) in order to better understand the local environment where we apply cell therapies. Models of closed-chest one-hour ischemia/reperfusion MI and cMI were used in C57/Bl6-mice. The reperfused MI showed rapid development of granulation tissue and compacted scar formation after 7 days. In contrast, cMI hearts showed persistent cardiomyocyte debris and cellular infiltration after 7 days and partially compacted scar formation accompanied by persistent macrophages and myofibroblasts after 14 days. The mRNA of proinflammatory mediators was transiently induced in MI and persistently upregulated in cMI. Tenascin C and osteopontin-1 showed delayed induction in cMI. In conclusion, the cryoinfarction was associated with prolonged inflammation and active myocardial remodeling when compared to the reperfused MI. These substantial differences in remodeling may influence cellular engraftment and should be considered in cell therapy studies.
