Paracrine nitric oxide induces expression of cardiac sarcomeric proteins in adult progenitor cells through soluble guanylyl cyclase/cyclic-guanosine monophosphate and Wnt/β-catenin inhibition

Regulation and Pharmacology of the Cyclic GMP and Nitric Oxide Pathway in Embryonic and Adult Stem Cells

This review summarizes recent advances in understanding the role of the nitric oxide (NO) and cyclic GMP (cGMP) pathway in stem cells. The levels of expression of various components of the pathway are changed during the differentiation of pluripotent embryonic stem cells. In undifferentiated stem cells, NO regulates self-renewal and survival predominantly through cGMP-independent mechanisms. Natriuretic peptides influence the growth of undifferentiated stem cells by activating particulate isoforms of guanylyl cyclases in a cGMP-mediated manner. The differentiation, recruitment, survival, migration, and homing of partially differentiated precursor cells of various types are sensitive to regulation by endogenous levels of NO and natriuretic peptides produced by stem cells, within surrounding tissues, and by the application of various pharmacological agents known to influence the cGMP pathway. Numerous drugs and formulations target various components of the cGMP pathway to influence the therapeutic efficacy of stem cell-based therapies. Thus, pharmacological manipulation of the cGMP pathway in stem cells can be potentially used to develop novel strategies in regenerative medicine.

Transcriptome Analysis Reveals Enhancement of Cardiogenesis-Related Signaling Pathways by S-Nitroso- N -Pivaloyl- d -Penicillamine: Implications for Improved Diastolic Function and Cardiac Performance

ABSTRACT

We previously reported a novel compound called S-nitroso- N -pivaloyl- d -penicillamine (SNPiP), which was screened from a group of nitric oxide donor compounds with a basic chemical structure of S-nitroso- N -acetylpenicillamine, to activate the nonneuronal acetylcholine system. SNPiP-treated mice exhibited improved cardiac output and enhanced diastolic function, without an increase in heart rate. The nonneuronal acetylcholine-activating effects included increased resilience to ischemia, modulation of energy metabolism preference, and activation of angiogenesis. Here, we performed transcriptome analysis of SNPiP-treated mice ventricles to elucidate how SNPiP exerts beneficial effects on cardiac function. A time-course study (24 and 48 hours after SNPiP administration) revealed that SNPiP initially induced Wnt and cyclic guanosine monophosphate-protein kinase G signaling pathways, along with upregulation of genes involved in cardiac muscle tissue development and oxytocin signaling pathway. We also observed enrichment of glycolysis-related genes in response to SNPiP treatment, resulting in a metabolic shift from oxidative phosphorylation to glycolysis, which was suggested by reduced cardiac glucose contents while maintaining adenosine tri-phosphate levels. In addition, SNPiP significantly upregulated atrial natriuretic peptide and sarcolipin, which play crucial roles in calcium handling and cardiac performance. These findings suggest that SNPiP may have therapeutic potential based on the pleiotropic mechanisms elucidated in this study.

Physical Exercise and Cardiac Repair: The Potential Role of Nitric Oxide in Boosting Stem Cell Regenerative Biology

Over the years strong evidence has been accumulated showing that aerobic physical exercise exerts beneficial effects on the prevention and reduction of cardiovascular risk. Exercise in healthy subjects fosters physiological remodeling of the adult heart. Concurrently, physical training can significantly slow-down or even reverse the maladaptive pathologic cardiac remodeling in cardiac diseases, improving heart function. The underlying cellular and molecular mechanisms of the beneficial effects of physical exercise on the heart are still a subject of intensive study. Aerobic activity increases cardiovascular nitric oxide (NO) released mainly through nitric oxidase synthase 3 activity, promoting endothelium-dependent vasodilation, reducing vascular resistance, and lowering blood pressure. On the reverse, an imbalance between increasing free radical production and decreased NO generation characterizes pathologic remodeling, which has been termed the "nitroso-redox imbalance". Besides these classical evidence on the role of NO in cardiac physiology and pathology, accumulating data show that NO regulate different aspects of stem cell biology, including survival, proliferation, migration, differentiation, and secretion of pro-regenerative factors. Concurrently, it has been shown that physical exercise generates physiological remodeling while antagonizes pathologic remodeling also by fostering cardiac regeneration, including new cardiomyocyte formation. This review is therefore focused on the possible link between physical exercise, NO, and stem cell biology in the cardiac regenerative/reparative response to physiological or pathological load. Cellular and molecular mechanisms that generate an exercise-induced cardioprotective phenotype are discussed in regards with myocardial repair and regeneration. Aerobic training can benefit cells implicated in cardiovascular homeostasis and response to damage by NO-mediated pathways that protect stem cells in the hostile environment, enhance their activation and differentiation and, in turn, translate to more efficient myocardial tissue regeneration. Moreover, stem cell preconditioning by and/or local potentiation of NO signaling can be envisioned as promising approaches to improve the post-transplantation stem cell survival and the efficacy of cardiac stem cell therapy.

Changes of Metabolic Phenotype of Cardiac Progenitor Cells During Differentiation: Neutral Effect of Stimulation of AMP-Activated Protein Kinase

Cardiac progenitor cells (CPCs) in the adult mammalian heart, as well as exogenous CPCs injected at the border zone of infarcted tissue, display very low differentiation rate into cardiac myocytes and marginal repair capacity in the injured heart. Emerging evidence supports an obligatory metabolic shift from glycolysis to oxidative phosphorylation (OXPHOS) during stem cells differentiation, suggesting that pharmacological modulation of metabolism may improve CPC differentiation and, potentially, healing properties. In this study, we investigated the metabolic transition underlying CPC differentiation toward cardiac myocytes. In addition, we tested whether activators of adenosine monophosphate-activated protein kinase (AMPK), known to promote mitochondrial biogenesis in other cell types would also improve CPC differentiation. Stem cell antigen 1 (Sca1⁺) CPCs were isolated from adult mouse hearts and their phenotype compared with more mature neonatal rat cardiac myocytes (NRCMs). Under normoxia, glucose consumption and lactate release were significantly higher in CPCs than in NRCMs. Both parameters were increased in hypoxia together with increased abundance of Glut1 (glucose transporter), of the monocarboxylic transporter Mct4 (lactate efflux mediator) and of Pfkfb3 (key regulator of glycolytic rate). CPC proliferation was critically dependent on glucose and glutamine availability in the media. Oxygen consumption analysis indicates that, compared with NRCMs, CPCs exhibited lower basal and maximal respirations with lower Tomm20 protein expression and mitochondrial DNA content. This CPC metabolic phenotype profoundly changed upon in vitro differentiation, with a decrease of glucose consumption and lactate release together with increased abundance of Tnnt2, Pgc-1α, Tomm20, and mitochondrial DNA content. Proliferative CPCs express both alpha1 and -2 catalytic subunits of AMPK that is activated by A769662. However, A769662 or resveratrol (an activator of Pgc-1α and AMPK) did not promote either mitochondrial biogenesis or CPC maturation during their differentiation. We conclude that although CPC differentiation is accompanied with an increase of mitochondrial oxidative metabolism, this is not potentiated by activation of AMPK in these cells.

Dnmt3a-mediated inhibition of Wnt in cardiac progenitor cells improves differentiation and remote remodeling after infarction

Adult cardiac progenitor cells (CPCs) display a low capacity to differentiate into cardiomyocytes in injured hearts, strongly limiting the regenerative capacity of the mammalian myocardium. To identify new mechanisms regulating CPC differentiation, we used primary and clonally expanded Sca-1+ CPCs from murine adult hearts in homotypic culture or coculture with cardiomyocytes. Expression kinetics analysis during homotypic culture differentiation showed downregulation of Wnt target genes concomitant with increased expression of the Wnt antagonist, Wnt inhibitory factor 1 (Wif1), which is necessary to stimulate CPC differentiation. We show that the expression of the Wif1 gene is repressed by DNA methylation and regulated by the de novo DNA methyltransferase Dnmt3a. In addition, miR-29a is upregulated early during CPC differentiation and downregulates Dnmt3a expression, thereby decreasing Wif1 gene methylation and increasing the efficiency of differentiation of Sca-1+ CPCs in vitro. Extending these findings in vivo, transient silencing of Dnmt3a in CPCs subsequently injected in the border zone of infarcted mouse hearts improved CPC differentiation in situ and remote cardiac remodeling. In conclusion, miR-29a and Dnmt3a epigenetically regulate CPC differentiation through Wnt inhibition. Remote effects on cardiac remodeling support paracrine signaling beyond the local injection site, with potential therapeutic interest for cardiac repair.