Project description:Background Human mutations in the X-linked lysosome-associated membrane protein-2 (LAMP2) gene can cause a multisystem Danon disease or a primary cardiomyopathy characterized by massive hypertrophy, conduction system abnormalities, and malignant ventricular arrhythmias. We introduced an in-frame LAMP2 gene exon 6 deletion mutation (denoted L2Δ6) causing human cardiomyopathy, into mouse LAMP2 gene, to elucidate its consequences on cardiomyocyte biology. This mutation results in in-frame deletion of 41 amino acids, compatible with presence of some defective LAMP2 protein. Methods and Results Left ventricular tissues from L2Δ6 and wild-type mice had equivalent amounts of LAMP2 RNA, but a significantly lower level of LAMP2 protein. By 20 weeks of age male mutant mice developed left ventricular hypertrophy which was followed by left ventricular dilatation and reduced systolic function. Cardiac electrophysiology and isolated cardiomyocyte studies demonstrated ventricular arrhythmia, conduction disturbances, abnormal calcium transients and increased sensitivity to catecholamines. Myocardial fibrosis was strikingly increased in 40-week-old L2Δ6 mice, recapitulating findings of human LAMP2 cardiomyopathy. Immunofluorescence and transmission electron microscopy identified mislocalization of lysosomes and accumulation of autophagosomes between sarcomeres, causing profound morphological changes disrupting the cellular ultrastructure. Transcription profile and protein expression analyses of L2Δ6 hearts showed significantly increased expression of genes encoding activators and protein components of autophagy, hypertrophy, and apoptosis. Conclusions We suggest that impaired autophagy results in cardiac hypertrophy and profound transcriptional reactions that impacted metabolism, calcium homeostasis, and cell survival. These responses define the molecular pathways that underlie the pathology and aberrant electrophysiology in cardiomyopathy of Danon disease.
Project description:End stage heart failure due to ischemic cardiomyopathy (ICM) and dilated cardiomyopathy (DCM) have similar characteristics, enlargement of the ventricles, relatively thin-walled ventricle, which leads to a limited contraction force and blood loading. Nevertheless, the response for present therapeutics is very variable and the prognosis is still very bad for ICM and DCM in general. Thus, the ability to differentiate the etiologies of heart failure based structural and physiological changes of the heart would be a step forward to enhance the specificity and the success of given therapy.
Project description:Mutations in the Hsp70 co-chaperone Bcl2-associated athanogene 3 (Bag3) result in myofibrillar myopathy and pediatric hypertrophic cardiomyopathy (pHCM) in human patients, but the pathological mechanisms underlying Bag3 dysfunction in the developing heart have remained unclear. Here we show that conditional ablation of Bag3 in cardiomyocytes (CMs) results in progressive cardiomyopathy accompanied by increased autophagic flux and autophagosome accumulation in the early post-natal period. Autophagy inhibition via acute administration of chloroquine (CQ) results in transient accumulation of cardiac proteins in the detergent-insoluble fraction, implying a role for autophagy in the degradation of unfolded proteins in the absence of Bag3 co-chaperone activity. Exacerbated autophagy in Bag3 deficient CMs leads to decreased soluble levels of proteins involved in cardiac contraction and conduction, including the gap junction protein connexin 43 (Cx43). Importantly, chronic CQ treatment during the early post-natal period results in a significant amelioration of the pathological phenotype, with recovered contractile performances and restoration of soluble levels of autophagy-targeted proteins. We therefore conclude that loss of Bag3 in CMs leads to autophagic flux exacerbation and that CQ treatment is relevant to therapeutic strategies for Bag3-dependent pHCM patients.
Project description:Activation of the systemic and myocardial rennin-angiotensin-aldosterone system (RAAS) by hyperglycemia plays a critical role in the development of diabetic cardiomyopathy. To test the hypothesis that AngIV protects against diabetic cardiomyopathy via stimulation of AT4R and inhibition of overactive autophagy, diabetic mice were treated with low-, medium- and high-dose AngIV, AT4R antagonist divalinal, forkhead box protein O1 (FoxO1) inhibitor AS1842856 (AS) or their combinations. In vitro, cardiomyocytes were treated with different concentrations of glucose, low-, medium- and high-dose AngIV, divalinal, FoxO1-overexpression plasmid (FoxO1-OE), AS or their combinations. The results showed that AngIV treatment dose-dependently attenuated left ventricular dysfunction, remodeling, fibrosis, and myocyte apoptosis in diabetic mice. Besides, autophagy and FoxO1 protein expression enhanced by diabetes were dose-dependently suppressed by AngIV treatment. However, these cardioprotective effects of AngIV were completely abolished by divalinal administration. Bioinformatic analyses revealed that the differentially expressed genes were enriched in autophagy, apoptosis, and FoxO signaling pathways among control, diabetes, and diabetes+high-dose AngIV groups. Similar to AngIV, AS treatment ameliorated diabetic cardiomyopathy in mice. In vitro, AngIV inhibited collagen expression, apoptosis, overactive autophagy flux, and FoxO1 nuclear translocation induced by high glucose in cardiomyocytes. However, these protective effects of AngIV were completely blocked by the use of divalinal or FoxO1-OE, and these detrimental effects were reversed by the additional administration of AS. In summary, AngIV treatment dose-dependently attenuated left ventricular dysfunction and remodeling in a mouse model of diabetic cardiomyopathy, and the mechanism involved stimulation of AT4R, suppression of FoxO1 nuclear translocation and inhibition of FoxO1-mediated overactive autophagy.
Project description:Characterization of plasma metabolomic profile of 15 patients with advanced heart failure referred for heart transplantation (8 patients with chronic chagasic cardiomyopathy and 7 with idiopathic dilated cardiomyopathy) and 12 heart donor individuals using gas chromatography/quadrupole time-of-flight mass spectrometry.
Project description:Characterization of plasma metabolomic profile of 15 patients with advanced heart failure referred for heart transplantation (8 patients with chronic chagasic cardiomyopathy and 7 with idiopathic dilated cardiomyopathy) and 12 heart donor individuals using gas chromatography/quadrupole time-of-flight mass spectrometry.
Project description:Mutations of the lamin A/C gene (LMNA) cause a variety of diseases including dilated cardiomyopathy (DCM). LMNA-related DCM often leads to severe heart failure, but the underlying pathophysiology is unknown. Here we show that vitamin D receptor (VDR) signaling is critically involved in LMNA-related DCM. We established iPS cells from DCM patients with an LMNA mutation and found that the iPS cell-derived cardiomyocytes (iPSCMs) showed remarkable DNA damage and reduced contractility compared with the isogenic control. Screening of a chemical library revealed that vitamin D2 reduced DNA damage of the mutant iPSCMs. RNA sequencing analysis showed that expression levels of putative downstream genes of VDR including DNA repair factors were downregulated in the mutant iPSCMs, which were upregulated by vitamin D2. Protein-protein interaction screening revealed that the binding of VDR to mutant LMNA was more robust than to wild-type LMNA, resulting in attenuated VDR signaling in the mutant iPSCMs. Vitamin D2 administration reduced DNA damage and improved cardiac function in pressure overload-induced heart failure mice. These results indicate that impaired DNA repair caused by reduced transcriptional activity of VDR induces cardiac dysfunction of LMNA-related DCM and suggest that VDR signaling is a potential therapeutic target for patients with DCM and heart failure.