Project description:Zinc dyshomeostasis has been involved in the pathogenesis of cardiac hypertrophy; however, the dynamic regulation of intracellular zinc and its downstream signaling in cardiac hypertrophy remain largely unknown. Here we screened ZIP (SLC39) family members that were responsible for zinc uptake in a phenylephrine (PE)-induced cardiomyocyte hypertrophy model. We found that Slc39a2 was the only member that was altered at mRNA level by PE treatment in neonatal rat ventricular myocytes (NRVMs), but its protein level was not affected. Zincpyr1 staining showed a significant decrease in zinc uptake after PE treatment or after Slc39a2 knockdown in NRVMs, indicating an inhibition of its transport activity during hypertrophy. Slc39a2 deficiency caused spontaneous hypertrophy in NRVMs, and further exacerbated the hypertrophic responses after PE treatment. RNA sequencing analysis confirmed a largely aggravated pro-hypertrophic transcriptome reprogramming after Slc39a2 knockdown. Interestingly, the innate immune pathways, including NOD signaling, TOLL-like receptor, NFB, and IRFs, were substantially enriched after Slc39a2 knockdown. Whereas IRF7, the most sensitive among all IRFs, did not mediate the effect of Slc39a2 in hypertrophy, pro-hypertrophy phosphorylations of NFB and STAT3 were significantly enhanced after Slc39a2 knockdown, in parallel with degradation of IkBα protein. Our data demonstrate that SLC39A2-mediated zinc homeostasis contributes to the remodeling of innate immune signaling in cardiomyocyte hypertrophy, and provide novel insights into the pathogenesis of heart failure and its treatment.
Project description:Pathological growth of cardiomyocytes during hypertrophy is characterized by excess protein synthesis; however, the regulatory mechanism remains largely unknown. Using a neonatal rat ventricular myocyte (NRVMs) model, here we find that the expression of nucleosome assembly protein 1 like 5 (Nap1l5) is upregulated in phenylephrine (PE)-induced hypertrophy. Knockdown of Nap1l5 expression by siRNA significantly blocks cell size enlargement and pathological gene induction after PE treatment. In contrast, Adenovirus-mediated Nap1l5 overexpression significantly aggravates the pro-hypertrophic effects of PE on NRVMs. RNA-seq analysis reveals that Nap1l5 knockdown reverses the pro-hypertrophic transcriptome reprogramming after PE treatment. Whereas immune response is dominantly enriched in the upregulated genes, oxidative phosphorylation, cardiac muscle contraction and ribosome related pathways are remarkably enriched in the down-regulated genes. Although PRC2 and PRC1 are involved in Nap1l5-mediated gene regulation, Nap1l5 does not directly alter the levels of global histone methylations. However, puromycin incorporation assay shows that Nap1l5 is both necessary and sufficient to drive the increased protein synthesis rate in cardiomyocyte hypertrophy. This is attributable to a direct regulation of ribosome assembly by Nap1l5. Our findings demonstrate a previously unrecognized role of Nap1l5 in translation control during cardiac hypertrophy.
Project description:Background: Although myocardial hypertrophy is an essential component of heart’s response to many forms of stress, prolonger excessive hypertrophy contributes importantly to the pathogenesis of heart disease. The pimobendan is a drug that both inhibits phosphodiesterase 3 (PDE3) and acts as a calcium sensitizer, which has been used to treat heart failure. The effects of pimobendan on myocardial hypertrophy is controversial. Objective: This study aims to evaluate the therapeutic effect of pimobendan on myocardial hypertrophy. Methods: Mice were treated with low oral doses of pimobendan (1mg/kg/d) for 4 weeks after transaortic constriction. Heart structure and function was assessed using ultrasound, hemodynamic measurements and histology combined with biochemical assessments of myocardial hypertrophy. We also examined the effects of pimobendan (100 µM) on hypertrophy in cultured neonatal rat cardiomyocytes (NRCMs) induced by 50 µM phenylephrine (PE). Results: The doses pimobendan used in our studies had no effect on baseline contractility. Nevertheless, pimobendan administration of mice subjected to TAC decreased heart weights (normalized to either tibia length or body weight) ventricular wall thickness, cardiomyocyte sizes, myocardial fibrosis and the levels of a number of key myocardial hypertrophy markers (WHICH ONES). In cultured neonatal cardiomyocytes, pimobendan attenuated the PE-induced hypertrophy. In both hypertrophy models pimobendan reduced the phosphorylation levels of several essential proteins in the MAPK pathway, PI3K-AKT pathway, and calcineurin signaling pathway. Conclusion: Low pimobendan may attenuate myocardial hypertrophy. Although the underlying mechanisms remain to be elucidated, the MAPK pathway is likely to play a role.
Project description:Pathological cardiac hypertrophy is featured by enhanced protein synthesis. Translation inhibition is effective in treating cardiac hypertrophy, yet with systematic side effect. We identified a cardiac-enriched LncRNA CARDINAL, when over-expressed in cardiomyocyte using AAV9 driven by cTNT promoter, ameliorate transaortic constriction (TAC) induced hypertrophy.
Project description:Fibroblasts produce the majority of collagen in the heart and are thought to regulate extracellular matrix (ECM) turnover. However, the in vivo role of fibroblasts in structuring the basal ECM network is poorly understood. To examine the effects of fibroblast loss on the microenvironment in the adult murine heart, we generated mice with reduced fibroblast numbers and evaluated the tissue microenvironment during homeostasis and after injury. We determined that a 60-80% reduction in fibroblasts numbers did not overtly change the fibrillar collagen network but did alter the distribution and abundance of type VI collagen, a microfibrillar collagen that forms an open network with the basement membrane. In fibroblast ablated mice, myocardial infarction did not result in ventricular wall rupture, and heart function was more effectively preserved during angiotensin II/phenylephrine (AngII/PE) induced fibrosis. Analysis of cardiomyocyte contractility demonstrated weaker contractions and slower calcium release and reuptake in uninjured and AngII/PE infused fibroblast ablated animals. Moreover, fibroblast ablated hearts have a similar gene expression prolife to hearts with exercise-induced and physiological hypertrophy after AngII/PE infusion. These results suggest that hearts are resilient to a significant degree of fibroblast loss and that fibroblasts can directly impact cardiomyocyte function. Furthermore, a reduction in fibroblasts may have cardioprotective effects heart after injury suggesting that manipulation of the number of fibroblasts may have therapeutic value.
Project description:Fibroblasts produce the majority of collagen in the heart and are thought to regulate extracellular matrix (ECM) turnover. However, the in vivo role of fibroblasts in structuring the basal ECM network is poorly understood. To examine the effects of fibroblast loss on the microenvironment in the adult murine heart, we generated mice with reduced fibroblast numbers and evaluated the tissue microenvironment during homeostasis and after injury. We determined that a 60-80% reduction in fibroblasts numbers did not overtly change the fibrillar collagen network but did alter the distribution and abundance of type VI collagen, a microfibrillar collagen that forms an open network with the basement membrane. In fibroblast ablated mice, myocardial infarction did not result in ventricular wall rupture, and heart function was more effectively preserved during angiotensin II/phenylephrine (AngII/PE) induced fibrosis. Analysis of cardiomyocyte contractility demonstrated weaker contractions and slower calcium release and reuptake in uninjured and AngII/PE infused fibroblast ablated animals. Moreover, fibroblast ablated hearts have a similar gene expression prolife to hearts with exercise-induced and physiological hypertrophy after AngII/PE infusion. These results suggest that hearts are resilient to a significant degree of fibroblast loss and that fibroblasts can directly impact cardiomyocyte function. Furthermore, a reduction in fibroblasts may have cardioprotective effects heart after injury suggesting that manipulation of the number of fibroblasts may have therapeutic value.
Project description:We examine the role of G3bp1, a RNA binding protein and site specific endoribonuclease in gene expression in isolated neonatal cardiomyocytes. RNAseq data from cardiomyocytes were infected with adenoviruses expressing shRNA against G3bp1 (ad-siG3bp1) or Luciferase (ad-siLUC, control) showed significant decrease in transcript abudnnace of cardiac-enriched genes involved in Calcium handling, contraction, action potential and sacromere function. On the other hand increase was observed in genes that regulate Hippo, TNF and TGFb signaling. Knockdown of G3bp1 inhibited endothelin-1 induced cardiomyocyte hypertrophy.
Project description:Kinase-catalyzed phosphorylation plays crucial roles in numerous biological processes. CDC-like kinases (CLKs) are a group of evolutionarily conserved dual-specificity kinases that have been implicated in RNA splicing, glucose metabolism, diet-induced thermogenesis and so on. However, it is still largely unknown whether CLKs are involved in pathologic cardiac hypertrophy. This study aimed to investigate the role of CLKs in pathologic cardiac hypertrophy and the underlying mechanisms. Using small RNA interference, we discovered that defects in CLK4, but not CLK1, CLK2 or CLK3, were associated with the pathogenesis of pathological cardiomyocyte hypertrophy, while overexpression of CLK4 exerted resistance to isoproterenol-induced pathological cardiomyocyte hypertrophy. Moreover, the expression of CLK4 was significantly reduced in the failed myocardia of mice subjected to either transverse aortic constriction or isoproterenol infusion. Through the Cre/loxP system, we constructed cardiac-specific Clk4-knockout (Clk4-cKO) mice, which manifested pathological myocardial hypertrophy with progressive left ventricular systolic dysfunction and heart dilation. Phosphoproteomic analysis revealed significant changes in phosphorylation of sarcomere-related proteins in Clk4-cKO mice. Further experiments identified nexilin (NEXN), an F-actin binding protein, as the direct substrate of CLK4, and overexpression of a phosphorylation-mimic mutant of NEXN was sufficient to reverse the hypertrophic growth of cardiomyocytes induced by Clk4 knockdown. Importantly, restoring the phosphorylated NEXN significantly ameliorated the myocardial hypertrophy in Clk4-cKO mice. CLK4 phosphorylates NEXN to regulate the development of pathological cardiac hypertrophy. CLK4 may serve as a potential intervention target for the prevention and treatment of heart failure.
Project description:Aim - Pathological cardiac remodeling is characterized by cardiomyocyte hypertrophy and fibroblast activation, which can ultimately lead to heart failure (HF). Genome-wide expression analysis on heart tissue has been instrumental for the identification of molecular mechanisms at play. However, these data were based on signals derived from all cardiac cell types. Here we aimed for a more detailed view on molecular changes driving cardiomyocyte hypertrophy and failure to aid in the development of therapies to reverse maladaptive remodeling. Methods and results - Utilizing cardiomyocyte-specific reporter mice exposed to pressure overload by transverse aortic banding (TAB), we obtained gene expression profiles of hypertrophic (one-week TAB) and failing (eight-weeks TAB) cardiomyocytes. We identified subsets of genes differentially regulated and specific for either stage. Among these, we found upregulation of known marker genes for HF, such as Nppb and Myh7. Additionally, we identified a set of genes specifically upregulated in failing cardiomyocytes and that so far have not been studied in HF, including the platelet isoform of phosphofructokinase (PFKP). Human cardiomyocytes subjected to 7-day NE/AngII treatment recapitulated the upregulation of the failure-induced genes indicating conservation. RNA-seq on failing and healthy human hearts confirmed increased expression for several failure-induced genes and allowed for expressional correlation to NPPB/MYH7. Finally, suppression of Pfkp in PE-treated primary cardiomyocytes reduced stress-induced gene expression and hypertrophy, suggesting a role in cardiomyocyte failure. Conclusion - Using cardiomyocyte-specific transcriptomic analysis we identified novel failure-induced genes relevant for human HF, and show that PFKP is a conserved failure-induced gene that can modulate cardiomyocyte stress response.