Loss of Mouse P2Y6 Nucleotide Receptor Is Associated with Physiological Macrocardia and Amplified Pathological Cardiac Hypertrophy.

The study of the mechanisms leading to cardiac hypertrophy is essential to better understand cardiac development and regeneration. Pathological conditions such as ischemia or pressure overload can induce a release of extracellular nucleotides within the heart. We recently investigated the potential role of nucleotide P2Y receptors in cardiac development. We showed that adult P2Y4-null mice displayed microcardia resulting from defective cardiac angiogenesis. Here we show that loss of another P2Y subtype called P2Y6, a UDP receptor, was associated with a macrocardia phenotype and amplified pathological cardiac hypertrophy. Cardiomyocyte proliferation and size were increased in vivo in hearts of P2Y6-null neonates, resulting in enhanced postnatal heart growth. We then observed that loss of P2Y6 receptor enhanced pathological cardiac hypertrophy induced after isoproterenol injection. We identified an inhibitory effect of UDP on in vitro isoproterenol-induced cardiomyocyte hyperplasia and hypertrophy. The present study identifies mouse P2Y6 receptor as a regulator of cardiac development and cardiomyocyte function. P2Y6 receptor could constitute a therapeutic target to regulate cardiac hypertrophy.

Loss of mouse P2Y4 nucleotide receptor protects against myocardial infarction through endothelin-1 downregulation.

Nucleotides are released in the heart under pathological conditions, but little is known about their contribution to cardiac inflammation. The present study defines the P2Y4 nucleotide receptor, expressed on cardiac microvascular endothelial cells and involved in postnatal heart development, as an important regulator of the inflammatory response to cardiac ischemia. P2Y4-null mice displayed smaller infarcts in the left descending artery ligation model, as well as reduced neutrophil infiltration and fibrosis. Gene profiling identified inter alia endothelin-1 (ET-1) as one of the target genes of P2Y4 in ischemic heart. The reduced level of ET-1 was correlated with reduction of microvascular hyperpermeability, neutrophil infiltration, and endothelial adhesion molecule expression, and it could be explained by the decreased number of endothelial cells in P2Y4-null mice. Expression analysis of metalloproteinases and their tissue inhibitors in ischemic heart revealed reduced expression of matrix metalloproteinase (MMP)-9, reported to be potentially regulated by ET-1, and MMP-8, considered as neutrophil collagenase, as well as reduction of tissue inhibitor of MMP-1 and tissue inhibitor of MMP-4 in P2Y4-null mice. Reduction of cardiac permeability and neutrophil infiltration was also observed in P2Y4-null mice in LPS-induced inflammation model. Protection against infarction resulting from loss of P2Y4 brings new therapeutic perspectives for cardiac ischemia and remodeling.

Targeted melanoma prevention intervention: a cluster randomized controlled trial.

PURPOSE: Targeted interventions to reduce the risk and increase the early detection of melanoma have the potential to save lives. We aimed to assess the effect of such an intervention on patient prevention behavior. METHODS: We conducted a pilot clustered randomized controlled trial, comparing a targeted screening and education intervention with a conventional information-based campaign in 20 private surgeries in western France. In the intervention group, 10 general practitioners identified patients at elevated risk for melanoma with a validated assessment tool, the Self-Assessment Melanoma Risk Score (SAMScore), examined their skin, and counseled them using information leaflets. In the control group, 10 general practitioners displayed a poster and the leaflets in their waiting room and examined patients' skin at their own discretion. The main outcome measures were sunbathing and skin self-examinations among patients at elevated risk, assessed 5 months later with a questionnaire. RESULTS: Analyses were based on 173 patients. Compared with control patients, intervention patients were more likely to remember the campaign (81.4% vs 50.0%, P = .0001) and to correctly identify their elevated risk of melanoma (71.1% vs 42.1%, P = .001). Furthermore, intervention patients had higher levels of prevention behaviors: they were less likely to sunbathe in the summer (24.7% vs 40.8%, P = .048) and more likely to have performed skin self-examinations in the past year (52.6% vs 36.8%, P = .029). The intervention was not associated with any clear adverse effects, although there were trends whereby intervention patients were more likely to worry about melanoma and to consult their general practitioner again about the disease. CONCLUSIONS: The combination of use of the SAMScore and general practitioner examination and counseling during consultations is an efficient way to promote patient behaviors that may reduce melanoma risk. Extending the duration of follow-up and demonstrating an impact on morbidity and mortality remain major issues for further research.

P2Y(4) nucleotide receptor: a novel actor in post-natal cardiac development.

Communication between endothelial cells and cardiomyocytes is critical for cardiac development and regeneration. However the mechanisms involved in these endothelial-cardiomyocyte interactions remain poorly understood. Nucleotides are released within the heart, especially under ischemia or pressure overload. The function of P2Y nucleotide receptors in cardiac development has never been investigated. Here we show that adult P2Y(4)-null mice display microcardia. P2Y(4) nucleotide receptor is expressed in cardiac endothelial cells but not in cardiomyocytes. Loss of P2Y(4) in cardiac endothelial cells strongly inhibits their growth, migration and PDGF-B secretion in response to UTP. Proliferation of microvessels and cardiomyocytes is reduced in P2Y(4)-null hearts early after birth, resulting in reduced heart growth. Our study uncovers mouse P2Y(4) receptor as an essential regulator of cardiac endothelial cell function, and illustrates the involvement of endothelial-cardiomyocyte interactions in post-natal heart development. We also detected P2Y(4) expression in human cardiac microvessels. P2Y(4) receptor could constitute a therapeutic target to regulate cardiac remodelling and post-ischemic revascularisation.

Mouse P2Y4 Nucleotide Receptor Is a Negative Regulator of Cardiac Adipose-Derived Stem Cell Differentiation and Cardiac Fat Formation.

Cardiac adipose tissue-derived stem cells (cASCs) have the ability to differentiate into multiple cell lineages giving them a high potential for use in regenerative medicine. Cardiac fat tissue still raises many unsolved questions related to its formation and features. P2Y nucleotide receptors have already been described as regulators of differentiation of bone-marrow derived stem cells, but remain poorly investigated in cASCs. We defined, in this study, the P2Y4 nucleotide receptor as a negative regulator of cardiac fat formation and cASC adipogenic differentiation. Higher expression of P2Y4 receptor in cardiac fat tissue was observed compared to other adipose tissues. P2Y4-null mice displayed a higher mass of cardiac adipose tissue specifically. We therefore examined the role of P2Y4 receptor in cASC adipogenic differentiation. An inhibitory effect of uridine 5'-triphosphate (UTP), ligand of P2Y4, was observed on the maturation state of differentiated cASCs, and on the expression of adipogenesis-linked genes and adiponectin, a cardioprotective adipokine. Higher adiponectin secretion by P2Y4-null adipocytes could be linked with cardioprotection previously observed in the heart of P2Y4-null ischemic mice. We realized here left anterior descending artery ligation on simple and double-knockout mice for P2Y4 and adiponectin. No cardioprotective effect of P2Y4 loss was observed in the absence of adiponectin secretion. In addition, P2Y4 loss was correlated with higher expression of UCP-1 (uncoupling protein-1) and CD137, two markers of brown/beige cardiac adipocytes. Our data highlight the P2Y4 receptor as an inhibitor of cardiac fat formation and cASC adipogenic differentiation, and as a potential therapeutic target in the regulation of cardioprotective function of cardiac fat.