Differential proteomic analysis of exercise-induced and pathological cardiac hypertrophy models in mice

Abstract

BACKGROUND: Improving outcomes for patients with pathological cardiac hypertrophy by leveraging the mechanisms of exercise-induced cardiac hypertrophy is currently a significant focus in cardiovascular research. However, the molecular mechanisms underlying the differences between exercise-induced and pathological cardiac hypertrophy remain incompletely understood. OBJECTIVE: To identify potential therapeutic targets for pathological cardiac hypertrophy based on cardiac proteomics using mouse models of exercise-induced and pathological cardiac hypertrophy. METHODS: Twenty-one 6-8-week-old male C57BL/6J mice were randomly divided into control, exercise, and isoproterenol groups (n=7 per group). Exercise-induced cardiac hypertrophy was established by 8 weeks of continuous training, while pathological cardiac hypertrophy was induced by subcutaneous injection of isoproterenol for 7 days. After confirming successful modeling via heart mass index, heart-to-tibia ratio, hematoxylin-eosin staining, wheat germ agglutinin staining, and Sirius red staining, tandem mass tag technology was used to reveal differential protein expression and functional characteristics between the two hypertrophy models. RESULTS AND CONCLUSION: Compared with the control group, heart mass index and heart-to-tibia ratio were significantly increased in both exercise and isoproterenol groups (P < 0.001, P < 0.05). Isoproterenol group showed disordered cardiomyocyte arrangement, extensive inflammatory cell infiltration, and obvious cardiomyocyte damage. Cardiomyocyte cross-sectional area was significantly increased in both exercise and isoproterenol groups (P < 0.05, P < 0.01), and myocardial fibrosis area was significantly higher in the isoproterenol group than in the control group (P < 0.01). Compared with the control group, 46 differentially expressed proteins were identified in the exercise group, 302 in the isoproterenol group, and 340 between exercise and isoproterenol groups. Among these, two overlapping proteins were peroxisomal acyl-coenzyme A oxidase 1 (Acox1) and galectin-3 (Gal-3). Gene Ontology and Kyoto Encyclopedia of Genes and Genomes enrichment analyses suggested that exercise may induce physiological cardiac hypertrophy by upregulating Acox1 to promote fatty acid metabolism, while isoproterenol may induce pathological cardiac hypertrophy by downregulating Acox1 leading to peroxisome dysfunction and lipotoxicity. These findings suggest that Acox1 and Gal-3 may serve as potential intervention targets for pathological cardiac hypertrophy.

1. Introduction

Cardiac hypertrophy is the result of the heart's adaptation to various physiological and pathological stimuli. Exercise training and hypertension can cause chronic hemodynamic overload and stimulate the heart to undergo different degrees of hypertrophy [1-2]. Exercise-induced cardiac hypertrophy is a physiological form of cardiac hypertrophy, which is a reversible and beneficial adaptive hypertrophy. It is the result of the heart's good adaptation to the hemodynamic overload caused by exercise, manifested as an 'athlete's heart', with increased heart volume and enhanced cardiac contractile function. After a period of training cessation, the hypertrophied heart can reverse to its original size [3-4]. Pathological cardiac hypertrophy is a pathological compensatory remodeling process that occurs after the onset of many cardiovascular diseases such as hypertension and aortic stenosis. It is an important risk factor for heart failure and increased mortality, characterized by increased heart volume, thickened ventricular wall, and decreased cardiac contractile function [5]. Although both types of cardiac hypertrophy are adaptive responses to stress, there are clear structural, functional, and metabolic differences between them, and the underlying molecular mechanisms have not been fully elucidated.

It has been reported that cellular metabolism, proliferation, non-coding RNAs, immune responses, translational regulation, and epigenetic modifications all have positive or negative regulatory effects on cardiac hypertrophy [6]. Studies have shown that protein kinase A in cardiomyocytes is a major regulator of both physiological and pathological cardiac hypertrophy. Inhibition of protein kinase A can delay postnatal cardiac growth, attenuate exercise-induced physiological cardiac hypertrophy, improve pathological cardiac hypertrophy induced by aortic arch constriction, and reduce cardiomyocyte hypertrophy induced by isoproterenol and phenylephrine [7]. Research has demonstrated that miR-222 expression is increased in the hearts of exercised mice and is an essential molecule for exercise-induced cardiac hypertrophy. It can also inhibit pathological cardiac hypertrophy and heart failure induced by aortic arch constriction [8]. These findings highlight the complexity of the molecular mechanisms underlying cardiac hypertrophy and the need for further proteomic studies to identify novel targets.