miRNAs Regulate hERG

Pacemaker activity and ion channels in the sinoatrial node cells: MicroRNAs and arrhythmia

The primary pacemaking activity of the heart is determined by a spontaneous action potential (AP) within sinoatrial node (SAN) cells. This unique AP generation relies on two mechanisms: membrane clocks and calcium clocks. Nonhomologous arrhythmias are caused by several functional and structural changes in the myocardium. MicroRNAs (miRNAs) are essential regulators of gene expression in cardiomyocytes. These miRNAs play a vital role in regulating the stability of cardiac conduction and in the remodeling process that leads to arrhythmias. Although it remains unclear how miRNAs regulate the expression and function of ion channels in the heart, these regulatory mechanisms may support the development of emerging therapies. This study discusses the spread and generation of AP in the SAN as well as the regulation of miRNAs and individual ion channels. Arrhythmogenicity studies on ion channels will provide a research basis for miRNA modulation as a new therapeutic target.

Non-Coding RNAs in the Cardiac Action Potential and Their Impact on Arrhythmogenic Cardiac Diseases

Cardiac arrhythmias are prevalent among humans across all age ranges, affecting millions of people worldwide. While cardiac arrhythmias vary widely in their clinical presentation, they possess shared complex electrophysiologic properties at cellular level that have not been fully studied. Over the last decade, our current understanding of the functional roles of non-coding RNAs have progressively increased. microRNAs represent the most studied type of small ncRNAs and it has been demonstrated that miRNAs play essential roles in multiple biological contexts, including normal development and diseases. In this review, we provide a comprehensive analysis of the functional contribution of non-coding RNAs, primarily microRNAs, to the normal configuration of the cardiac action potential, as well as their association to distinct types of arrhythmogenic cardiac diseases.

Integrated regulatory network based on lncRNA-miRNA-mRNA-TF reveals key genes and sub-networks associated with dilated cardiomyopathy

Dilated Cardiomyopathy (DCM) is a multifactorial condition often leading to heart failure in many clinical cases. Due to the high number of DCMincidence reported as familial, a gene level network based study was conducted utilizing high throughput next generation sequencing data. We exploited the exome and transcriptome sequencing data in NCBI-SRA database to construct a high confidence scale-free regulatory network consisting of lncRNA, miRNA, mRNA and Transcription Factors (TFs). Analysis of RNA-Seq data revealed 477 differentially expressed coding transcripts and 77 lncRNAs. 268 miRNAs regulated either lncRNAs or mRNAs. Out of the 477 coding transcripts that are deregulated, 82 were TFs. We identified three major hub nodeslncRNA (XIST), miRNA (hsa-miR-195-5p) and mRNA (NOVA1) from the network. We also found putative disease associations of DCM with diabetes and DCM with hypoventillation syndrome. Five highly connected modules were also identified from the network. The hubs showed significant connectivity with the modules.Through this study we were able to gain insights into the underlying lncRNA-miRNA-mRNA-TF network. From a high throughput dataset we have isolated a handful of probable targets that may be utilized for studying the mechanisms of DCM development and progression to heart failure.

HERG channel and cancer: A mechanistic review of carcinogenic processes and therapeutic potential

The human ether-à-go-go related gene (HERG) encodes the alpha subunit of Kv11.1, which is a voltage-gated K⁺ channel protein mainly expressed in heart and brain tissue. HERG plays critical role in cardiac repolarization, and mutations in HERG can cause long QT syndrome. More recently, evidence has emerged that HERG channels are aberrantly expressed in many kinds of cancer cells and play important roles in cancer progression. HERG could therefore be a potential biomarker for cancer and a possible molecular target for anticancer drug design. HERG affects a number of cellular processes, including cell proliferation, apoptosis, angiogenesis and migration, any of which could be affected by dysregulation of HERG. This review provides an overview of available information on HERG channel as it relates to cancer, with focus on the mechanism by which HERG influences cancer progression. Molecular docking attempts suggest two possible protein-protein interactions of HERG with the ß1-integrin receptor and the transcription factor STAT-1 as novel HERG-directed therapeutic targeting which avoids possible cardiotoxicity. The role of epigenetics in regulating HERG channel expression and activity in cancer will also be discussed. Finally, given its inherent extracellular accessibility as an ion channel, we discuss regulatory roles of this molecule in cancer physiology and therapeutic potential. Future research should be directed to explore the possibilities of therapeutic interventions targeting HERG channels while minding possible complications.

Non-coding RNAs and Cardiac Arrhythmias

Cardiac arrhythmias represent wide and heterogenic group of disturbances in the cardiac rhythm. Pathophysiology of individual arrhythmias is highly complex and dysfunction in ion channels/currents involved in generation or spreading of action potential is usually documented. Non-coding RNAs (ncRNAs) represent highly variable group of molecules regulating the heart expression program, including regulation of the expression of individual ion channels and intercellular connection proteins, e.g. connexins.Within this chapter, we will describe basic electrophysiological properties of the myocardium. We will focus on action potential generation and spreading in pacemaker and non-pacemaker cells, including description of individual ion channels (natrium, potassium and calcium) and their ncRNA-mediated regulation. Most of the studies have so far focused on microRNAs, thus, their regulatory function will be described into greater detail. Clinical consequences of altered ncRNA regulatory function will also be described together with potential future directions of the research in the field.

miR-21 promotes non-small cell lung cancer cells growth by regulating fatty acid metabolism

Background

Lung cancer is one of the most common malignant tumors worldwide. CD36 is a receptor for fatty acids and plays an important role in regulating fatty acid metabolism, which is closely related to tumorigenesis and development. The regulation of miR-21 and its role in tumorigenesis have been extensively studied in recent years. However, the relationship between miR-21 and CD36 regulated fatty acid metabolism in human non-small cell lung cancer remains unknown.

Methods

In this study, lentivirus transfection, qRT-PCR, cell migration, immunofluorescence, and western blot were used to examine the relationship between miR-21 and CD36 regulated fatty acid metabolism and the regulation role of miR-21 in human non-small cell lung cancer.

Results

This study demonstrated that up-regulation of miR-21 promoted cell migration and cell growth in human non-small cell lung cancer cells. Moreover, the intracellular contents of lipids including cellular content of phospholipids, neutral lipids content, cellular content of triglycerides were significantly increased following miR-21 mimic treatment compared with control, and the levels of key lipid metabolic enzymes FASN, ACC1 and FABP5 were obviously enhanced in human non-small cell lung cancer cells. Furthermore, down-regulation of CD36 suppressed miR-21 regulated cell growth, migration and intracellular contents of lipids in human non-small cell lung cancer cells, which suggested that miR-21 promoted cell growth and migration of human non-small cell lung cancer cells through CD36 mediated fatty acid metabolism. Inhibition of miR-21 was revealed to inhibit cell growth, migration, intracellular contents of lipids, and CD36 protein expression level in human non-small cell lung cancer cells. In addition, PPARGC1B was a direct target of miR-21, and down-regulation of PPARGC1B reversed the inhibition of CD36 expression induced by miR-21 inhibitor.

Conclusions

These results explored the mechanism of miR-21 promoted non-small cell lung cancer and might provide a novel therapeutic method in treating non-small cell lung cancer in clinic.

MicroRNAs in Cardiac Diseases

Since their discovery 20 years ago, microRNAs have been related to posttranscriptional regulation of gene expression in major cardiac physiological and pathological processes. We know now that cardiac muscle phenotypes are tightly regulated by multiple noncoding RNA species to maintain cardiac homeostasis. Upon stress or various pathological conditions, this class of non-coding RNAs has been found to modulate different cardiac pathological conditions, such as contractility, arrhythmia, myocardial infarction, hypertrophy, and inherited cardiomyopathies. This review summarizes and updates microRNAs playing a role in the different processes underlying the pathogenic phenotypes of cardiac muscle and highlights their potential role as disease biomarkers and therapeutic targets.