Pharmacological or genetic inhibition of LTCC promotes cardiomyocyte proliferation through inhibition of calcineurin activity
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ABSTRACT: Cardiomyocytes (CMs) lost during ischemic cardiac injury cannot be replaced due to their limited proliferative capacity. Ca2+ is an important signal transducer that regulates key cellular processes, but its role in regulating CM proliferation is incompletely understood. A drug screen targeting proteins involved in CM Ca2+ cycling in human embryonic stem cell-derived cardiac organoids (hCOs) revealed that only the inhibition of L-Type Calcium Channel (LTCC) using nifedipine induced the CM cell cycle. Overexpression of Ras-related associated with Diabetes (RRAD), an endogenous inhibitor of LTCC, induced CM cell cycle activity in vitro, in human cardiac slices, and in vivo. Mechanistically, LTCC inhibition by RRAD or nifedipine induced CM cell cycle by modulating calcineurin activity and Hoxb13 nuclear translocation. Moreover, ectopic expression of RRAD/CDK4/CCND in combination induced CM proliferation in vitro and in vivo, improved cardiac function and reduced scar size post-myocardial infarction. Together, these findings represent a robust pathway for new Ca2+ signaling-based cardiac regenerative strategies.
Project description:The cardiomyocyte-specific deletion of Ddx5 in mice resulted in heart failure characterized by diminished cardiac function, enlarged heart chambers, and heightened fibrosis. Proteomic analysis unveiled the involvement of DDX5 in RNA splicing within cardiomyocytes. Our study identified DDX5 as a regulator of the abnormal splicing of CamkIIδ, preventing the generation of CaMKIIδA. This isoform activates LTCC through serine phosphorylation of Cacna1c, disrupting Ca2+ homeostasis. Consistently, DDX5-depleted cardiomyocytes exhibited elevated intracellular Ca2+ transients and increased sarcoplasmic reticulum Ca2+ content.
Project description:The cardiomyocyte-specific deletion of Ddx5 in mice resulted in heart failure characterized by diminished cardiac function, enlarged heart chambers, and heightened fibrosis. Proteomic analysis unveiled the involvement of DDX5 in RNA splicing within cardiomyocytes. Our study identified DDX5 as a regulator of the abnormal splicing of CamkIIδ, preventing the generation of CaMKIIδA. This isoform activates LTCC through serine phosphorylation of Cacna1c, disrupting Ca2+ homeostasis. Consistently, DDX5-depleted cardiomyocytes exhibited elevated intracellular Ca2+ transients and increased sarcoplasmic reticulum Ca2+ content.
Project description:Objective: L-type calcium channels (LTCC) homeostatically regulate calcium on a beat by beat basis, but also provide Ca that over long time scales may contribute to transcriptional regulation. We previously showed that sustained LTCC blockade (CCB) elicits LTCC remodeling in ventricular cardiac myocytes (CM). Here we hypothesize that sustained CCB has broad effects on the expression of genes involved in calcium handling. Methods and Results: Therefore, we subjected adult mice to sustained CCB for 24 hours and performed gene expression profiling. In comparison to vehicle-only control animals, 231 genes were up-regulated, and 111 genes were down-regulated by sustained LTCC blockade (p <0.01). Gene ontology analysis suggested that the CaMKIIdelta signaling pathway was up-regulated in these cells. Unexpectedly, phosphorylation of phospholamban (PLN) at threonine17 (Thr17), an index of CaMKIIdelta activity, was not changed by sustained CCB; however, the degree of phosphorylation of the neighboring PLN-Ser16 substrate site for PKA was significantly reduced by sustained CCB compared to control. Gene expression profiling suggested no change in PKA, but it showed that protein phosphatase 2A (PP2A) mRNA increased, and immunoblots demonstrated that PP2Ac-alpha protein was significantly increased by sustained CCB. Consistent with elevated PP2Ac-alpha protein expression LTCC exhibited decreased phosphorylation of the C-terminal Ser1928 PKA substrate site. Conclusions: We conclude that sustained CCB elicits a spectrum of transcriptional events, including compensatory up-regulation of LTCC and PP2Ac-alpha. Although this study is restricted to mouse, these results suggest the new hypothesis that clinically-relevant sustained LTCC blockade in humans results in changes in gene regulation in the heart. Keywords: L-type calcium channel, calcium channel blockade, verapamil
Project description:In this work, we generated a new human induced-pluripotent stem cells derived-cardiomyocytes (hiPSC-CM); in this new hiPSC-CM cell line, Cyclin D2 (CCND2), a cell-cycle activator, was overexpressed, and class I-II of major histocompatibility complex were knocked down. This new cell line (named KO/OEhiPSC-CM) and the wildtype hiPSC-CM (name WThiPSC-CM) were transplanted into pig hearts with ischemic-reperfusion (I/R). The objective is to examine engraftment, cardiac function change, and how the host (pig) heart responded to the transplantation. Surprisingly, while the pig hearts receiving KO/OEhiPSC-CM showed significant cardiac function 4 weeks after I/R, the KO/OEhiPSC-CM grafts were undetectable. Analyzing the single-nuclei RNA sequencing (SnRNAseq) data of these pig hearts showed that 1) the host cardiomyocyte actively reentered cell-cycle, which was among the key factors for cardiac function improvement; 2) this effect was mediated via HIPPO/YAP signaling pathway; and 3) HIPPO/YAP signaling pathway activity was a result of Follistatin (FST) secreted by the transplanted KO/OEhiPSC-CM.
Project description:L-type voltage-gated calcium channels (LTCCs) regulate crucial physiological processes in the heart. They are composed of the Cav1 pore-forming subunit and the accessory subunits Cav, Cav2 and Cav. Cav is a cytosolic soluble protein that regulates channel trafficking and activity, but it also exerts other LTCC-independent functions. Cardiac hypertrophy, a relevant risk factor for the development of congestive heart failure, depends on the activation of calcium-dependent pro-hypertrophic signaling cascades; however, the role of LTCCs in this pathology remains controversial. Here, by using shRNA-mediated Cav silencing, we demonstrate that Cav2 downregulation enhances 1-adrenergic receptor agonist-induced cardiomyocyte hypertrophy in an LTCC-independent manner. We report that a pool of Cav2 is targeted to the nucleus in cardiomyocytes and that the expression of this nuclear fraction decreases during in vitro and in vivo induction of cardiac hypertrophy. Moreover, the overexpression of nucleus-targeted Cav2 in cardiomyocytes inhibits in vitro-induced hypertrophy. Quantitative proteomic analyses showed that Cav2 knockdown leads to changes in the expression of diverse myocyte proteins, including reduction of calpastatin, an endogenous inhibitor of the calcium-dependent protease calpain. Accordingly, Cav2-deficient cardiomyocytes had a two-fold increase in calpain activity as compared to control cells. Furthermore, inhibition of calpain activity in Cav2-deficient cells abolished the enhanced 1-adrenergic receptor agonist-induced hypertrophy observed in these cells. Our findings indicate that in cardiomyocytes, a nuclear pool of Cav2 participates in cellular functions that are independent of LTCC activity. They also indicate that a downregulation of nuclear Cav2 during cardiac hypertrophy promotes the activation of calpain-dependent hypertrophic pathways.
Project description:The Mammalian cardiomyocyte (CM) cell cycle is tightly regulated by a complex network of transcription factors; however, the gene regulatory networks depending on their developmental stages are unclear. Here, we report that Tbx6, expressed in the cardiac mesoderm, promote cell cycle re-entry in vitro and in vivo. We performed a gain of function screening for cardiac development regulator genes that promoted neonatal CM proliferation. Tbx6 activate the cell cycle and promote cultured neonatal CM proliferation. Next, we generated recombinant adeno-associated virus serotype 9 vector encoding Tbx6 (AAV9-Tbx6). Injection of AAV9-Tbx6 was shown to promote cell cycle re-entry of CMs in both postnatal and adult mice. Tbx6 overexpression activated cell cycle activators, while repressed cell cycle inhibitor gene. Thus, Tbx6 promotes neonatal CM proliferation in vitro and adult CM cell cycle re-entry in vivo.
Project description:In the heart, metabolic profile switches from glycolysis to fatty acid oxidation (FAO) rapidly after birth accompanied by chromatin reconfiguration, cell cycle exit and cardiomyocyte (CM) maturation, suggesting a synergistic rewiring of transcriptional networks regulated by epigenetic mechanisms in accordance with environmental and metabolic signals. To gain a better insight into the interconnection between epigenetic processes and metabolic pathways during cardiac development, maturation and heart regeneration, we induced a metabolic reprogramming by depleting CPT1b, a crucial enzyme for FAO, specifically in CM. Cpt1b inactivation led to cardiomegaly and attenuated cardiac damage in response to myocardial injury primarily attributed to augmented CM proliferation and enhanced resistance to ischemic injury.
Project description:In the heart, metabolic profile switches from glycolysis to fatty acid oxidation (FAO) rapidly after birth accompanied by chromatin reconfiguration, cell cycle exit and cardiomyocyte (CM) maturation, suggesting a synergistic rewiring of transcriptional networks regulated by epigenetic mechanisms in accordance with environmental and metabolic signals. To gain a better insight into the interconnection between epigenetic processes and metabolic pathways during cardiac development, maturation and heart regeneration, we induced a metabolic reprogramming by depleting CPT1b, a crucial enzyme for FAO, specifically in CM. Cpt1b inactivation led to cardiomegaly and attenuated cardiac damage in response to myocardial injury primarily attributed to augmented CM proliferation and enhanced resistance to ischemic injury.
Project description:In the heart, metabolic profile switches from glycolysis to fatty acid oxidation (FAO) rapidly after birth accompanied by chromatin reconfiguration, cell cycle exit and cardiomyocyte (CM) maturation, suggesting a synergistic rewiring of transcriptional networks regulated by epigenetic mechanisms in accordance with environmental and metabolic signals. To gain a better insight into the interconnection between epigenetic processes and metabolic pathways during cardiac development, maturation and heart regeneration, we induced a metabolic reprogramming by depleting CPT1b, a crucial enzyme for FAO, specifically in CM. Cpt1b inactivation led to cardiomegaly and attenuated cardiac damage in response to myocardial injury primarily attributed to augmented CM proliferation and enhanced resistance to ischemic injury.
Project description:In the heart, metabolic profile switches from glycolysis to fatty acid oxidation (FAO) rapidly after birth accompanied by chromatin reconfiguration, cell cycle exit and cardiomyocyte (CM) maturation, suggesting a synergistic rewiring of transcriptional networks regulated by epigenetic mechanisms in accordance with environmental and metabolic signals. To gain a better insight into the interconnection between epigenetic processes and metabolic pathways during cardiac development, maturation and heart regeneration, we induced a metabolic reprogramming by depleting CPT1b, a crucial enzyme for FAO, specifically in CM. Cpt1b inactivation led to cardiomegaly and attenuated cardiac damage in response to myocardial injury primarily attributed to augmented CM proliferation and enhanced resistance to ischemic injury.