Abstract
The cardioprotection of exercise preconditioning (EP) has been well documented. EP can be divided into two phases that are the induction of exercise preconditioning (IEP) and the protection of exercise preconditioning (PEP). PEP is characterized by biphasic protection, including early exercise preconditioning (EEP) and late exercise preconditioning (LEP). LC3 lipidation-mediated autophagy plays a pivotal role in cardioprotection. This study aimed to investigate the alterations of LC3 lipidation-associated proteins during EP-induced cardioprotection against myocardial injury induced by exhaustive exercise (EE) was used in a rat model of EP. These rats were subjected to an intermittent exercise consisting of four periods, with each period including 10 min of running at 30 m/min and 0% grade (approximately 75% VO2max) followed by 10 min of intermittent rest. A model of EE-induced myocardial injury was developed by subjecting rats to a consecutive running (30 m/min, 0% grade) till exhaustion. Following EEP, the colocalization of LC3 with Atg7 was significantly increased, and LC3-I, LC3-II, LC3-II/LC3-I, Atg7, Atg4B, and Atg3 levels were significantly increased. Atg7, Atg4B, and Atg3 mRNAs were all significantly upregulated, and LC3 mRNAs tended to be higher. Following LEP, Atg4B, and Atg3 levels were significantly increased. Atg7, Atg4B, and Atg3 mRNAs were all significantly upregulated, and LC3 mRNAs tended to be higher. A group of rats were subjected to EEP followed by EE, and the co-localization of LC3 with Atg7 was significantly increased, while LC3-I, LC3-II, LC3-II/LC3-I, Atg7, Atg4B, and Atg3 levels were also significantly increased. Moreover, there was a significant increase in the co-localization of LC3 with Atg7, LC3-I, LC3-II, Atg7, and Atg4B levels during LEP followed by EE. The formation of autophagosome during LEP followed by EE may have been weaker than that during EEP followed by EE due to the lower lipidation of LC3. EP may promote autophagy to maintain cell homeostasis and survival, which cooperates for cardioprotection of alleviating exhaustive exercise-induced myocardial injury by increasing LC3 lipidation-associated proteins. There is a difference between EEP and LEP in terms of the mechanisms of cardioprotection afforded by these respective conditions. The positive regulation of transcription and translation level of LC3 lipidation-associated proteins may all be involved in the mechanism of EEP and LEP, while compared with LEP, the regulation of translation level of EEP is more positively to promote autophagy.
Highlights
The belief that physical exercise promotes optimal health and is integral in the prevention and treatment of many medical conditions is burgeoning, but this does not mean that all exercise is good for health
exercise preconditioning (EP) may promote autophagy to maintain cell homeostasis and survival, which cooperates for cardioprotection of alleviating exhaustive exercise-induced myocardial injury by increasing LC3 lipidation-associated proteins
The positive regulation of transcription and translation level of LC3 lipidation-associated proteins may all be involved in the mechanism of exercise preconditioning (EEP) and late exercise preconditioning (LEP), while compared with LEP, the regulation of translation level of EEP is more positively to promote autophagy
Summary
The belief that physical exercise promotes optimal health and is integral in the prevention and treatment of many medical conditions is burgeoning, but this does not mean that all exercise is good for health. Evidence have demonstrated that even a single bout of high-intensity intermittent exercise is capable of forming a “preconditioned” cardioprotective phenotype against myocardial ischemic injury (Domenech et al, 2002; Parra et al, 2015). Exercise preconditioning (EP) refers to repeated high-intensity, intermittent aerobic exercise that can lead to myocardial relative or absolute ischemia-hypoxia, inducing endogenous cardioprotection to protect myocardial tissues against subsequent sustained ischemic-hypoxic injury (Domenech et al, 2002; Kavazis, 2009; Yuan et al, 2018). IEP refers to the process of inducing endogenous cardioprotection through repeated high-intensity, intermittent aerobic exercise, and PEP refers to the process of promoting endogenous cardioprotection after IEP (Li et al, 2019; Liu and Pan, 2019). EEP occurs immediately after the end of IEP and lasts for 1–3 h (Domenech et al, 2002; Kavazis, 2009), while LEP appears 24 h after the end of IEP and lasts for 24–72 h (Domenech et al, 2002; Thijssen et al, 2018)
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