miRNAs at the heart of the matter

Cardiovascular disease is among the main causes of morbidity and mortality in developed countries. The pathological process of the heart is associated with altered expression profile of genes that are important for cardiac function. MicroRNAs (miRNAs) have emerged as one of the central players of gene expression regulation. The implications of miRNAs in the pathological process of cardiovascular system have recently been recognized, representing the most rapidly evolving research field. Here, we summarize and analyze the currently available data from our own laboratory and other groups, providing a comprehensive overview of miRNA function in the heart, including a brief introduction of miRNA biology, expression profile of miRNAs in cardiac tissue, role of miRNAs in cardiac hypertrophy and heart failure, the arrhythmogenic potential of miRNAs, the involvement of miRNAs in vascular angiogenesis, and regulation of cardiomyocyte apoptosis by miRNAs. The target genes and signaling pathways linking the miRNAs to cardiovascular disease are highlighted. The applications of miRNA interference technologies for manipulating miRNA expression, stability, and function as new strategies for molecular therapy of human disease are evaluated. Finally, some specific issues related to future directions of the research on miRNAs relevant to cardiovascular disease are pinpointed and speculated

Chemical–Genetic Profiling of Imidazo[1,2-a]pyridines and -Pyrimidines Reveals Target Pathways Conserved between Yeast and Human Cells

Small molecules have been shown to be potent and selective probes to understand cell physiology. Here, we show that imidazo[1,2-a]pyridines and imidazo[1,2-a]pyrimidines compose a class of compounds that target essential, conserved cellular processes. Using validated chemogenomic assays in Saccharomyces cerevisiae, we discovered that two closely related compounds, an imidazo[1,2-a]pyridine and -pyrimidine that differ by a single atom, have distinctly different mechanisms of action in vivo. 2-phenyl-3-nitroso-imidazo[1,2-a]pyridine was toxic to yeast strains with defects in electron transport and mitochondrial functions and caused mitochondrial fragmentation, suggesting that compound 13 acts by disrupting mitochondria. By contrast, 2-phenyl-3-nitroso-imidazo[1,2-a]pyrimidine acted as a DNA poison, causing damage to the nuclear DNA and inducing mutagenesis. We compared compound 15 to known chemotherapeutics and found resistance required intact DNA repair pathways. Thus, subtle changes in the structure of imidazo-pyridines and -pyrimidines dramatically alter both the intracellular targeting of these compounds and their effects in vivo. Of particular interest, these different modes of action were evident in experiments on human cells, suggesting that chemical–genetic profiles obtained in yeast are recapitulated in cultured cells, indicating that our observations in yeast can: (1) be leveraged to determine mechanism of action in mammalian cells and (2) suggest novel structure–activity relationships

Nystatin-Induced Potassium Efflux from <i>Saccharomyces cerevisiae</i> Measured by Flame Photometry: a Potential Bioassay Approach

A potential bioassay method for nystatin has been developed based on the ability of this antibiotic to bring out dose-related potassium ion efflux from susceptible cells of Saccharomyces cerevisiae , such extracellular potassium ion concentration being measured by flame photometry. </jats:p

Ca2+/Calmodulin-Dependent protein kinase II delta and protein kinase D overexpression reinforce the histone deacetylase 5 redistribution in heart failure

Cardiac hypertrophy and heart failure (HF) are associated with reactivation of fetal cardiac genes, and class II histone deacetylases (HDACs) (eg, HDAC5) have been strongly implicated in this process. We have shown previously that inositol trisphosphate, Ca2(+)/calmodulin-dependent protein kinase II ( CaMKII), and protein kinase ( PK)D are involved in HDAC5 phosphorylation and nuclear export in normal adult ventricular myocytes and also that CaMKII delta and inositol trisphosphate receptors are upregulated in HF. Here we tested whether, in our rabbit HF model, nucleocytoplasmic shuttling of HDAC5 was altered either at baseline or in response to endothelin-1, which would indicate HDAC5 phosphorylation and transcription effects. The fusion protein HDAC5 - green fluorescent protein (HDAC5-GFP) was more cytosolic in HF myocytes (F-nuc/F-cyto 3.3 +/- 0.3 vs 7.2 +/- 0.4 in control), and HDAC5 was more phosphorylated. Despite this baseline cytosolic HDAC5 shift, endothelin-1 produced more rapid HDAC5-GFP nuclear export in HF versus control myocytes. We also find that PKD and CaMKII delta(C) expression and activation state are increased in both rabbit and human HF. Inhibition of either CaMKII or PKD in HF myocytes partially restored the HDAC5-GFP F-nuc/F-cyto toward control, and simultaneous inhibition restored F-nuc/F-cyto to that in control myocytes. Moreover, adenovirus-mediated overexpression of PKD, CaMKII delta(B), or CaMKII delta(C) reduced baseline HDAC5 F-nuc/F-cyto in control myocytes (3.4 +/- 0.5, 3.8 +/- 0.5, and 5.2 +/- 0.5, respectively), approaching that seen in HF. We conclude that chronic upregulation and activation of inositol trisphosphate receptors, CaMKII, and PKD in HF shifts HDAC5 out of the nucleus, derepressing transcription of hypertrophic genes. This may directly contribute to the development and/or maintenance of H