Project description:Rationale: Cardiac CITED4 is induced by exercise and is sufficient to cause physiological hypertrophy and mitigate adverse ventricular remodeling after ischemic injury. However, the role of endogenous CITED4 in response to physiological or pathological stress is unknown. Objective: To investigate the role of CITED4 in murine models of exercise and pressure overload. Methods and Results: We generated cardiomyocyte-specific CITED4 knockout mice (C4KO) and subjected them to an intensive swim exercise protocol as well as transverse aortic constriction (TAC). Echocardiography, western blotting, qPCR, immunohistochemistry, immunofluorescence, and transcriptional profiling for mRNA and miRNA expression were performed. Cellular crosstalk was investigated in vitro. CITED4 deletion in cardiomyocytes did not affect baseline cardiac size or function in young adult mice. C4KO mice developed modest cardiac dysfunction and dilation in response to exercise. After TAC, C4KOs developed severe heart failure with left ventricular dilation, impaired cardiomyocyte growth accompanied by reduced mammalian target of rapamycin (mTOR) activity and maladaptive cardiac remodeling with increased apoptosis, autophagy, and impaired mitochondrial signaling. Interstitial fibrosis was markedly increased in C4KO hearts after TAC. RNAseq revealed induction of a pro-fibrotic miRNA network. miR30d was decreased in C4KO hearts after TAC and mediated crosstalk between cardiomyocytes and fibroblasts to modulate fibrosis. miR30d inhibition was sufficient to increase cardiac dysfunction and fibrosis after TAC. Conclusions: CITED4 protects against pathological cardiac remodeling by regulating mTOR activity and a network of miRNAs mediating cardiomyocyte to fibroblast crosstalk. Our findings highlight the importance of CITED4 in response to both physiological and pathological stimuli.
Project description:The heart grows in response to pathological and physiological stimuli, while the former often precedes cardiomyocyte loss and heart failure, the latter paradoxically protects the heart and enhances cardiomyogenesis. Long noncoding RNAs (lncRNAs) are important in cardiac development and disease, less is known about their roles in physiological hypertrophy or cardiomyogenesis. The purpose of this study was to compare transcriptome profilings in exercise-induced physiological cardiac growth and stress-induced pathological cardiac growth. We identified a set of lncRNAs called long noncoding exercise associated cardiac transcripts (lncExACT). One of them, lncExACT1, whose cardiac expression was downregulated after exercise but upregulated after transverse aortic constriction. Inhibition of lncExACT1 induced physiolgoical cardiac growth while overexpression of lncExACT1 induced pathological hypertrophy and heart failure.
Project description:BACKGROUND - MicroRNAs (miRs) are a class of small non-coding RNAs that regulate gene expression. Transgenic models have proved that a single miR can induce pathological cardiac hypertrophy and failure. The roles of miRs in the genesis of physiologic left ventricular hypertrophy (LVH), however, are not well elucidated. OBJECTIVE - To evaluate miRs expression in an experimental model of exercise-induced LVH. METHODS - Male Balb/c mice were divided into sedentary (SED) and exercise (EXE) groups. Voluntary exercise was performed in odometer-monitored metal wheels during 35 days. Analyses were performed after 7 and 35 days of training, and consisted of transthoracic echocardiography, maximal exercise test, miRs microarray (miRBase v.16) and real-time qRT-PCR analysis. RESULTS - Left ventricular weight/body weight ratio increased by 7% in the EXE group at day 7 (p<0.01) and by 11% at 35 days of training (p<0.001) After 7 days of training, microarray identified 35 deregulated miRs: 20 had an increase in their expression and 15 were down-regulated (p=0.01). At day 35 of training, 25 miRs were deregulated: 15 were up-regulated and 10 had decreased their expression compared to the SED group (p<0.01). qRT-PCR confirmed an increase in miR-150 levels at both time points and a decrease in miR-26b, miR-27a and miR-143 after 7 days of voluntary exercise. CONCLUSIONS M-bM-^@M-^S We unraveled new miRs that can modulate physiological cardiac hypertrophy, particularly miR-26b, -150, 27a and -143. Our data also indicate that previously established regulatory gene pathways involved in pathological LVH are not deregulated in physiologic LVH. Experimental model of left ventricular hypertrophy induced by voluntary exercise Male Balb/c mice, 8-10 weeks old, 4 groups analyzed, each group consisted of a pool from 4 animals
Project description:<p><strong>OBJECTIVE:</strong> To explore the cardioprotective effects of exercise-derived β-aminoisobutyric (BAIBA) on cardiomyocyte apoptosis and energy metabolism in a rat model of heart failure (HF).</p><p><strong>METHODS:</strong> In male Sprague-Dawley rats (8-week-old), myocardial infarction (MI) was used to induce HF by ligating the left anterior descending branch of the coronary artery. In the Sham group, the coronary artery was threaded but not ligated. After HF development, Sham and HF rats were exercised 60 min daily, 5 days per week on a treadmill for 8 weeks (50-60% maximal intensity) and exercise-induced cardiac remodeling after MI were assessed using echocardiography, hematoxylin and eosin (H&E), Masson’s Trichrome and TUNEL staining for the detection of apoptosis-associated factors in cardiac tissue. High-throughput sequencing and mass spectrometry were used to measure BAIBA production and to explore its cardioprotective effects and molecular actions. To further characterize the cardioprotective effects of BAIBA, an <em>in vitro</em> model of apoptosis was generated by applying H2O2 to H9C2 cells to induce mitochondrial dysfunction. In addition, cells were transfected with either a miR-208b analogue or a miR-208b inhibitor. Apoptosis-related proteins were detected by Western Blotting (WB). ATP production was also assessed by luminometry. After administration of BAIBA and Compound C, the expression of proteins related to apoptosis, mitochondrial function, lipid uptake and β-oxidative were determined. Changes in the levels of reactive oxygen species (ROS) were assessed by fluorescence microscopy. In addition, alterations in membrane potential (δψm) were obtained by confocal microscopy.</p><p><strong>RESULTS:</strong> Rats with HF after MI are accompanied by mitochondrial dysfunction, metabolic stress and apoptosis. Reduced expression of apoptosis-related proteins was observed, together with increased ATP production and reduced mitochondrial dysfunction in the exercised compared with the Sham (non-exercised) HF group. Importantly, exercise increased the production of BAIBA, irrespective of the presence of HF. To assess whether BAIBA had similar effects to exercise in ameliorating HF-induced adverse cardiac remodeling, rats were treated with 75 mg/kg/day of BAIBA and we found BAIBA had a similar cardioprotective effect. Transcriptomic analyses found that the expression of miR-208b was increased after BAIBA administration, and subsequent transfection with an miR-208b analogue ameliorated both the expression of apoptosis-related proteins and energy metabolism in H2O2-treated H9C2 cells. In combining transcriptomic with metabolomic analyses, we identified AMPK as a downstream target for BAIBA in attenuating metabolic stress in HF. Further cell experiments confirmed that BAIBA increased AMPK phosphorylation and had a cardioprotective effect on downstream fatty acid uptake, oxidative efficiency and mitochondrial function, which was prevented by the AMPK inhibitor Compound C.</p><p><strong>CONCLUSION: </strong>Exercise-generated BAIBA can reduce cardiomyocyte metabolic stress and apoptosis induced by mitochondrial dysfunction through the miR-208b/AMPK pathway.</p>
Project description:The mechanistic target of rapamycin (mTOR) is a key regulator of pathological remodeling in the heart by activating ribosomal biogenesis and mRNA translation. Inhibition of mTOR in cardiomyocytes is protective, however, a detailed role of mTOR in translational regulation of specific mRNA networks in the diseased heart is largely unknown. A cardiomyocyte genome-wide sequencing approach was used to define mTOR-dependent post-transcriptional gene expression control at the level of mRNA translation. This approach identified the muscle specific protein Cullin-associated NEDD8-dissociated protein 2 (Cand2) as a translationally upregulated gene dependent on the activity of mTOR. Deletion of Cand2 protects the myocardium against pathological remodeling. Mechanistically, we found that Cand2 links mTOR- signaling to pathological cell growth by increasing Grk5 protein expression. Our data suggest that cell-type specific targeting of mTOR might have therapeutic value for adverse pathological cardiac remodeling.
Project description:Despite some success of pharmacotherapies targeting primarily neurohormonal dysregulation, heart failure is a growing global pandemic with increasing burden. Treatments that improve the disease by reversing heart failure at the cardiomyocyte level are lacking. MicroRNAs (miRNA) are transcriptional regulators of gene expression, acting through complex biological networks, and playing thereby essential roles in disease progression. Adverse structural remodelling of the left ventricle due to myocardial infarction (MI) is a common pathological feature leading to heart failure. We previously demonstrated increased cardiomyocyte expression of the miR-212/132 family during pathological cardiac conditions. Transgenic mice overexpressing the miR-212/132 cluster (miR-212/132-TG) develop pathological cardiac remodelling and die prematurely from progressive HF. Using both knockout and antisense strategies, we have shown miR-132 to be both necessary and sufficient to drive the pathological growth of cardiomyocytes in a murine model of left ventricular pressure overload. Based on the findings, we proposed that miR-132 may serve as a therapeutic target in heart failure therapy. Here we provide novel mechanistic insight and translational evidence for the therapeutic efficacy in small and large animal models (n=135) of heart failure. We demonstrate strong PK/PD relationship, dose-dependent efficacy and high clinical potential of a novel optimized synthetic locked nucleic acid phosphorothioate backbone antisense oligonucleotide inhibitor of miR-132 (antimiR-132) as a next-generation heart failure therapeutic.