Mitochondrial Proteomics In Myocardial Hypertrophic Preconditioning

Background:Myocardial hypertrophy is an adaptive response of the heart to the mechanical stress caused by various factors.In these process,the heart reduces ventricular wall stress by increasing the thickness of the wall to maintain cardiac output.However,when adaptive cardiac hypertrophy gradually transitions to maladaptive cardiac hypertrophy,pathological myocardial hypertrophy occurs,and myocardial hypertrophy cannot continue to meet the energy demand of increased workload,contractile and diastolic function will fall and eventually heart failure will develop.It has been reported that certain cellular and molecular events of adaptive cardiac hypertrophy can be beneficial to the heart.Therefore,identifying relevant molecular mechanisms associated with this process and finding new therapeutic targets is of high clinical significance to attenuate pathological cardiac hypertrophy and prevent its progression to heart failure,thus reducing cardiovascular morbidity and mortality.Objective:To investigate the molecular protective mechanisms of myocardial hypertrophic preconditioning on the murine model of cardiac hypertrophic preconditioning,mitochondrial proteomics and bioinformatics analysis were used to screen significant mitochondrial proteins and explore regulatory mechanisms.Methods:1.C57BL6/J male mice were randomly divided into sham group and cardiac hypertrophic preconditioning group,then myocardial hypertrophic preconditioning group underwent transverse aortic constriction on day 0,while sham operation group underwent sham operation,the aorta constriction of mice were released on day 3,and subsequent experiments were performed on day 7.2.The cardiac function was detected by echocardiography,and mechanical properties of cardiomyocytes were assessed using a SoftEdge Myocam system.3.HE staining and WGA staining were performed to evaluate the degree of myocardial hypertrophy,and myocardial fibrosis was assessed with Masson staining.Heart tissue specimens for electron microscopy were prepared,and mitochondrial ultrastructure was detected by transmission electron microscopy.4.Myocardial mitochondrial proteins were extracted from mice and differentially expressed proteins were screened by label-free quantitative proteomics,and bioinformatics analysis was used to analyze related pathways.5.Western blotting(WB)was used to verify the expression of key proteins.Results:1.Echocardiographic and cardiomyocyte contractile results showed that compared with sham group,there were no significant changes in cardiac function in cardiac hypertrophic preconditioning group.2.Cardiac pathological results showed that compared with sham group,there was no significant difference in cardiomyocyte cross-sectional area and fibrotic area in cardiac hypertrophic preconditioning group.However,electron microscopy analyses showed that the density of mitochondrial cristae was increased in cardiac hypertrophic preconditioning group.3.A total of 20 differentially expressed proteins were screened using mitochondrial proteomics,of which 5 proteins were up-regulated and 15 proteins were down-regulated.Gene ontology analysis revealed that these proteins mainly involved in mitochondrial ribosomal subunit,mitochondrial translation,purine ribonucleotide metabolic process;KEGG Pathway analyses revealed that these proteins mainly involved in ribosome pathway;Protein-protein Interaction analysis indicated mitochondrial ribosomal proteins have strong network interactions between each other.4.WB result showed that the level of key protein Gadd45gipl was increased in cardiac hypertrophic preconditioning group compared with sham group,which was consistent with proteomic analysis.Conclusion:Myocardial hypertrophic preconditioning could promote the energy metabolism of myocardial mitochondria,which may be related to the transcription,processing and transportation of mitochondrial oxidative phosphorylation complex mediated by mitochondrial ribosomal proteins.