Abstract P372: Serum From Pediatric Dilated Cardiomyopathy Patients Promotes Dysregulation Of Cardiolipin Biosynthesis And Mitochondrial Dysfunction In Primary Cardiomyocytes

Pediatric dilated cardiomyopathy (DCM) is a devastating and poorly understood disease with most clinical treatment paradigms extrapolated from the adult population. Our studies have demonstrated that aspects of metabolism and mitochondrial function are dysregulated in pediatric DCM hearts. Cardiolipin (CL), a unique phospholipid in the inner mitochondrial membrane, is essential for optimal mitochondrial function and was shown to be dysregulated in both the failing adult and pediatric human heart. The objective of this study is to investigate if serum circulating factors from pediatric DCM patients can remodel CL resulting in mitochondrial dysfunction in vitro , similar to what is observed in the failing pediatric heart.

Using a novel in vitro model that consists of treating neonatal rat ventricular myocytes (NRVMs) with serum from pediatric DCM patients or from non-failing (NF) healthy controls, mitochondrial respiration was assessed using the Agilent Seahorse, and reactive oxygen species (ROS) was assessed using Electron Paramagnetic Resonance Spectroscopy. Relative mitochondrial DNA (mtDNA) copy number was determined by qPCR and expression of enzymes involved in CL biosynthesis and remodeling were analyzed using RT-qPCR. Mass-spectrometry was used to quantitate total and specific CL species and to investigate the metabolite composition of NRVMs treated with NF or DCM serum.

While mitochondrial ROS and mtDNA copy number were not significantly altered, we show that DCM serum decreases mitochondrial function, which is associated with alterations in CL content and composition and the downregulation of enzymes implicated in CL biosynthesis and remodeling. Analysis of metabolite content showed an alteration of pathways involved in fatty acid metabolism, mitochondrial biogenesis and regulation of β-oxidation by the transcription factor PPARα.

In conclusion, pediatric DCM serum circulating factors can promote CL remodeling resulting mitochondrial dysfunction in primary cardiomyocytes. These findings suggest that CL could be a novel therapeutic target for this particular population.

Application of microRNA Database Mining in Biomarker Discovery and Identification of Therapeutic Targets for Complex Disease

Over the past two decades, it has become increasingly evident that microRNAs (miRNA) play a major role in human diseases such as cancer and cardiovascular diseases. Moreover, their easy detection in circulation has made them a tantalizing target for biomarkers of disease. This surge in interest has led to the accumulation of a vast amount of miRNA expression data, prediction tools, and repositories. We used the Human microRNA Disease Database (HMDD) to discover miRNAs which shared expression patterns in the related diseases of ischemia/reperfusion injury, coronary artery disease, stroke, and obesity as a model to identify miRNA candidates for biomarker and/or therapeutic intervention in complex human diseases. Our analysis identified a single miRNA, hsa-miR-21, which was casually linked to all four pathologies, and numerous others which have been detected in the circulation in more than one of the diseases. Target analysis revealed that hsa-miR-21 can regulate a number of genes related to inflammation and cell growth/death which are major underlying mechanisms of these related diseases. Our study demonstrates a model for researchers to use HMDD in combination with gene analysis tools to identify miRNAs which could serve as biomarkers and/or therapeutic targets of complex human diseases.

Beyond the genome: challenges and potential for epigenetics-driven therapeutic approaches in pulmonary arterial hypertension

Pulmonary arterial hypertension (PAH) is a devastating disease of the cardiopulmonary system caused by the narrowing of the pulmonary arteries, leading to increased vascular resistance and pressure. This leads to right ventricle remodeling, dysfunction, and eventually, death. While conventional therapies have largely focused on targeting vasodilation, other pathological features of PAH including aberrant inflammation, mitochondrial dynamics, cell proliferation, and migration have not been well explored. Thus, despite some recent improvements in PAH treatment, the life expectancy and quality of life for patients with PAH remains poor. Showing many similarities to cancers, PAH is characterized by increased pulmonary arterial smooth muscle cell proliferation, decreased apoptotic signaling pathways, and changes in metabolism. The recent successes of therapies targeting epigenetic modifiers for the treatment of cancer has prompted epigenetic research in PAH, revealing many new potential therapeutic targets. In this minireview we discuss the emergence of epigenetic dysregulation in PAH and highlight epigenetic-targeting compounds that may be effective for the treatment of PAH.