Objective
This study tested whether IL-17A is involved in the pathogenesis of mouse myocardial ischemia-reperfusion (I/R) injury and investigated the mechanisms.
Background
Inflammatory processes play a major role in myocardial I/R injury. We recently identified interleukin (IL)-17A as an important cytokine in inflammatory cardiovascular diseases such as atherosclerosis and viral myocarditis. However, its role in myocardial I/R injury remains unknown.
Methods
The involvement of IL-17A was assessed in functional assays in mouse myocardial I/R injury by neutralization/repletion or genetically deficiency of IL-17A, and its mechanism on cardiomyocyte apoptosis and neutrophil infiltration were further studied in vivo and in vitro.
Results
IL-17A was elevated following murine left coronary artery ligation and reperfusion. Intracellular cytokine staining revealed that γδT lymphocytes, but not CD4+ helper T cells, were a major source of IL-17A. Anti-IL-17A mAb treatment or IL-17A knockout markedly ameliorated I/R injury, as demonstrated by reduced infarct size, reduced cardiac troponin T levels and improved cardiac function. This improvement was associated with a reduction in cardiomyocyte apoptosis and neutrophil infiltration. On the contrary, repletion of exogenous IL-17A induced the opposite effect. In vitro study showed that IL-17A mediated cardiomyocyte apoptosis through regulating the Bax/Bcl-2 ratio, induced CXC chemokine-mediated neutrophil migration and promoted neutrophil-endothelial cell adherence through induction of endothelial cell E-selectin and inter-cellular adhesion molecule (ICAM)-1 expression.
Conclusions
IL-17A mainly produced by γδT cells plays a pathogenic role in myocardial I/R injury by inducing cardiomyocyte apoptosis and neutrophil infiltration.
Inflammatory responses play an important role in the pathogenesis of adverse ventricular remodeling after myocardial infarction (MI). We previously demonstrated that interleukin (IL)-17A plays a pathogenic role in myocardial ischemia/reperfusion injury and viral myocarditis. However, the role of IL-17A in post-MI remodeling and the related mechanisms have not been fully elucidated. Acute MI was induced by permanent ligation of the left anterior descending coronary artery in C57BL/6 mice. Repletion of IL-17A significantly aggravated both early- and late-phase ventricular remodeling, as demonstrated by increased infarct size, deteriorated cardiac function, increased myocardial fibrosis, and cardiomyocyte apoptosis. By contrast, genetic IL-17A deficiency had the opposite effect. Additional studies in vitro indicated that IL-17A induces neonatal cardiomyocyte (from C57BL/6 mice) apoptosis through the activation of p38, p53 phosphorylation, and Bax redistribution. These data demonstrate that IL-17A induces cardiomyocyte apoptosis through the p38 mitogen-activated protein kinase (MAPK)-p53-Bax signaling pathway and promotes both early- and late-phase post-MI ventricular remodeling. IL-17A might be an important target in preventing heart failure after MI. Key message: We demonstrated that IL-17A plays a pathogenic role both in the early and late stages of post-MI remodeling. IL-17A induces murine cardiomyocyte apoptosis. IL-17A induces murine cardiomyocyte apoptosis through the p38 MAPK-p53-Bax signaling pathway.
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