The Regulatory Mechanism Of Exercise On The Inflammatory Response In The Myocardium Via Mitophagy

Part one The effect of aerobic endurance exercise on the inflammatory response in the aging myocardium via mitophagy regulationBackground and objectiveIt is very important that delaying aging in the cardiac genesis and development is beneficial to improve the life quality of older persons. Inflammaging refers to a low-grade pro-inflammatory status appearing during the aging process, which is a new mechanism in the aging research field. It is generally considered that moderate exercise training is an effective way for anti-myocardial aging, but the exact mechanisms are currently unclear. Therefore, we plan to focus on oxidative stress, inflammatory response, and mitophagy in a model of myocardial aging following the intervention of aerobic endurance exercise, and we plan to investigate the hypothesis:(1)ROS produced by dysfunctional mitochondria in aging myocardium trigger the activation of NLRP3 inflammasome, which serves as platforms for caspase-1 activation and subsequent proteolytic maturation of the potent pro-inflammatory cytokine IL-1β, thereby leading to the initial inflammatory response. Furthermore, this initial inflammatory response stimulates the release of cytokines/chemokines, which recruit and activate inflammatory cells such as monocytes/macrophages and neutrophils to the aging myocardium. Activation of the infiltrated inflammatory cells by the inflammasome enhances the inflammatory response and myocardial injury. Enhanced inflammatory response may increase ROS release from the dysfunctional mitochondria of injured myocardium, thereby creating a vicious cycle and eventually leading to the genesis and development of aging myocardium.(2) Aerobic endurance exercise may reduce the release of ROS from mitochondria by the intervention of mitophagy and subsequently inhibit the NLRP3 inflammasome-mediated inflammatory response of myocardium, resulting in the anti-aging effects on myocardium. The project can provide a theoretical basis for searching the effective targets for prevention and treatment of aging myocardium.Methods80 male C57BL/6 mice were divided into four groups at random including young control group, young training group, aging control group, and aging training group. Mice preconditioning moderate intensity endurance training in the plain, while those in the exercise groups were exercised on a motor-driven rodent treadmill. The cardiac function was evaluated by echocardiography. The mice were killed and the cardiac coefficients were calculated. Myocardium pathologic changes were observed using a light microscope. Myocardium ultrastructure was observed under TEM. Mitochondria state 3 respiration, state 4 respiration, respiratory control ratio, and ROS generation rate in mouse heart mitochondria were detected. The activities of Mn SOD, the contents of MDA and protein carbonyl were detected using UV. Mitochondrial autophagy-related protein(Beclin1、LC3、Bnip3) expressions and inflammatory factors(NLRP3、IL-1β) expressions were measured by Real-time PCR and Western-blot. The concentrations of IL-6, IL-1β and TNF-α in the serum of mice were measured via ELISA.ResultsCompared with young control group, left ventricular function showed progressive decreases in aging control group. Compared with aging control group, left heart function showed progressive increases in aging training group. Compared with young control group, the loose structure of muscle fibers and mitochondria vacuolization were observed in aging control group. Compared with aging control group, the normal arrangement of muscle fibers and a few autophagosomes were observed in aging training group. Compared with young control group, mitochondrial respiration function showed progressive decreases in aging control group. Compared with aging control group, mitochondrial respiration showed progressive increases in aging training group. Compared with young control group, oxidative injury function showed progressive increases in aging control group. Compared with aging control group, oxidative injury showed progressive decreases in aging training group. Compared with young control group, inflammatory response showed progressive increases in aging control group. Compared with aging control group, inflammatory response showed progressive decreases in aging training group. Compared with young control group, mitophagy levels showed progressive decreases in aging control group. Compared with aging control group, mitophagy levels showed progressive increases in aging training group.Conclusions(1) Oxidative stress and NLRP3 inflammasome-induced inflammatory reaction are both involved in the development of aging myocardium.(2) Long time of aerobic endurance exercise can significantly improve the function of aging myocardium.(3) Long time of aerobic endurance exercise has an protective effect angainst aging myocardium via upregulation of mitophagy.(4) Long time of aerobic endurance exercise can allevate the inflammatory response in the aging myocardium via upregulation of mitophagy.Part two Acute exercise-induced mitochondrial stress triggers an inflammatory response in the myocardium via NLRP3 inflammasome activation with mitophagy feedbackBackground and objectiveIncreasing evidence has indicated that acute strenuous exercise can induce a range of adverse reactions including oxidative stress and tissue inflammation. However, little is currently known regarding the mechanisms that underlie the regulation of the inflammatory response in the myocardium during acute heavy exercise. This study evaluated the mitochondrial function, NLRP3 inflammasome activation and mitochondrial autophagy-related proteins to investigate the regulation and mechanism of mitochondrial stress regarding the inflammatory response of the rat myocardium during acute heavy exercise.MethodsAll the male Sprague–Dawley rats were grouped into eight groups at random: resting control group(RC, n=8), exercise training 45 min group(E-45, n=8), exercise training 90 min group(E-90, n=8), exercise training 120min(E-120, n=8, post-exercise recovery 12 h group(R-12, n=8), post-exercise recovery 24 h group(R-24, n=8, post-exercise recovery 36 h group(R-36, n=8), post-exercise recovery 48 h group(R-48, n=8). The training rats were exercised via an acute bout of treadmill running for various durations. Myocardium pathologic changes were observed using a light microscope.The respiration rates of state 3 and state 4, the generation rate of reactive oxygen species(ROS), the mitochondrial membrane potential and the activities of ATP synthase were determined in the rat myocardial mitochondria in each group. With western blotting method to determine the protein expression of myocardial NLRP3,IL-1β、Beclin1、 LC3 and Bnip3. The concentration of IL-1β in the serum of rats was measured via ELISA.ResultsThe results indicated that the mitochondrial function of the myocardium was adaptively regulated to meet the challenge of oxidative stress during acute exercise. The exercise-induced mitochondrial stress also enhanced ROS generation and triggered an inflammatory reaction via NLRP3 inflammasome activation. Moreover, the mitochondrial autophagy-related proteins including Beclin1, LC3 and Bnip3 were all significantly upregulated during acute exercise, which suggests that mitophagy was stimulated to remove the dysfunctional mitochondria in response to the oxidative stress and inflammatory response in the myocardium.ConclusionsTaken together, our study demonstrates that during acute exercise, mitochondrial stress triggers the rat myocardial inflammatory response via NLRP3 inflammasome activation and induces mitophagy via negative feedback regulation.