MicroRNA-214 protects the mouse heart from ischemic injury by controlling Ca²⁺ overload and cell death

Mitochondrial calcium uniporter, MiRNA and cancer: Live and let die

Mitochondria receive calcium (Ca²⁺) signals from endoplasmic reticulum (ER) and decode them into pro-apoptotic inputs, which lead to cell death. Therefore, mitochondrial Ca²⁺ overload is considered a fundamental trigger of the apoptotic process, and several oncogenes and tumor suppressors modify the activity of protein involved in Ca²⁺ homeostasis to control apoptosis. The identification of the channel responsible for mitochondrial Ca²⁺ entry, the Mitochondrial Ca²⁺Uniporter (MCU), together with its regulatory components, MICU1 and MCUR1, provides new molecular tools to investigate this process. Recent data have also shown that miR-25 decreases mitochondrial Ca²⁺ uptake through selective MCU downregulation, conferring resistance to apoptotic challenges. MCU appears to be downregulated in human colon cancer samples, and accordingly, miR-25 is aberrantly expressed, indicating the importance of mitochondrial Ca²⁺ regulation in cancer cell survival.

Circulating miR-214 is associated with the severity of coronary artery disease

Objective

To study whether miR-214 is regulated in coronary artery disease (CAD) patients and whether placental growth factor (PLGF) is a possible target for miR-214 in atherosclerosis.

Methods

Circulating miR-214 was measured by quantitative PCR using RNA isolated from 40 patients with CAD, including 12 with stable angina pectoris, 16 with unstable angina pectoris and 12 with acute myocardial infarction, and 15 controls without CAD. Plasma level of PLGF was measured by ELISA.

Results

The miR-214 level was significantly lower in CAD patients compared with that in controls (P < 0.01). Compared to controls, patients with unstable angina pectoris (UAP, 38.6±9.1 pg/mL) and acute myocardial infarction (AMI, 46.3±13.4 pg/mL) had significantly higher level of plasma PLGF, but not those with stable angina pectoris (SAP; P = 0.012, UAP vs. Control; P = 0.005, AMI vs. Control). In patients with AMI, the plasma level of miR-214 was positively correlated to that of PLGF.

Conclusions

The results suggest that miR-214 is a beneficial microRNA for CAD patients. Loss of its protection may lead to increased PLGF levels and worsening atherosclerosis. Circulating miR-214 is a promising biomarker for alerting severe CAD.

MicroRNAs and intellectual disability (ID) in Down syndrome, X-linked ID, and Fragile X syndrome

Intellectual disability (ID) is one of the many features manifested in various genetic syndromes leading to deficits in cognitive function among affected individuals. ID is a feature affected by polygenes and multiple environmental factors. It leads to a broad spectrum of affected clinical and behavioral characteristics among patients. Until now, the causative mechanism of ID is unknown and the progression of the condition is poorly understood. Advancement in technology and research had identified various genetic abnormalities and defects as the potential cause of ID. However, the link between these abnormalities with ID is remained inconclusive and the roles of many newly discovered genetic components such as non-coding RNAs have not been thoroughly investigated. In this review, we aim to consolidate and assimilate the latest development and findings on a class of small non-coding RNAs known as microRNAs (miRNAs) involvement in ID development and progression with special focus on Down syndrome (DS) and X-linked ID (XLID) [including Fragile X syndrome (FXS)].

Endothelial cells require miR-214 to secrete exosomes that suppress senescence and induce angiogenesis in human and mouse endothelial cells

Signaling between endothelial cells, endothelial progenitor cells, and stromal cells is crucial for the establishment and maintenance of vascular integrity and involves exosomes, among other signaling pathways. Exosomes are important mediators of intercellular communication in immune signaling, tumor survival, stress responses, and angiogenesis. The ability of exosomes to incorporate and transfer messenger RNAs (mRNAs) encoding for "acquired" proteins or micro RNAs (miRNAs) repressing "resident" mRNA translation suggests that they can influence the physiological behavior of recipient cells. We demonstrate that miR-214, an miRNA that controls endothelial cell function and angiogenesis, plays a dominant role in exosome-mediated signaling between endothelial cells. Endothelial cell-derived exosomes stimulated migration and angiogenesis in recipient cells, whereas exosomes from miR-214-depleted endothelial cells failed to stimulate these processes. Exosomes containing miR-214 repressed the expression of ataxia telangiectasia mutated in recipient cells, thereby preventing senescence and allowing blood vessel formation. Concordantly, specific reduction of miR-214 content in exosome-producing endothelial cells abolishes the angiogenesis stimulatory function of the resulting exosomes. Collectively, our data indicate that endothelial cells release miR-214-containing exosomes to stimulate angiogenesis through the silencing of ataxia telangiectasia mutated in neighboring target cells.

MicroRNAs in Myocardial Infarction

The complexity of posttranscriptional regulation by noncoding microRNAs (miRNAs, miRs) is still not completely understood. A large fraction of the genome is under the control of miRs via (partial) complementary base pairing within the corresponding mRNA region. Myocardial infarction is characterized by strongly altered gene expression, deregulation of underlying signaling pathways, and crucial participation of several miRs in this context. Mechanistically, miR induction or repression after myocardial infarction triggers downstream events in a cell-type–specific manner, and interference with endogenous miR expression might regulate overall cardiac function. In this brief review, we (1) summarize the current knowledge about the importance of several miRs after myocardial infarction, (2) report about novel miR-based therapeutic approaches to counteract maladaptive remodeling upon cardiac ischemia, and (3) discuss briefly the use of miRs as biomarkers for cardiac ischemia.

MicroRNAs in Cardiovascular Regenerative Medicine: Directing Tissue Repair and Cellular Differentiation

MicroRNAs (miRNAs) are a class of short noncoding RNA molecules, approximately 22 nucleotides in length, which regulate gene expression through inhibition of the translation of target genes. It is now generally accepted that miRNAs guide processes and cellular functions through precise titration of gene dosage, not only for a single gene but also controlling the levels of a large cohort of gene products. miRNA expression is altered in cardiovascular disease and may thereby limit and impair cardiovascular repair responses. Increasing evidence of the essential role of miRNAs in the self-renewal and differentiation of stem cells suggests the opportunity of using the modulation of miRNA levels or their function in directing cell transplantation, cell behavior, and thereby organ healing. In this paper, an overview of miRNA biogenesis and their way of action and different roles that miRNAs play during the myocardial responses to injury and upon cell transplantation will be provided. We focused on cardiomyocyte survival, angiogenesis, extracellular matrix production, and how miRNAs can direct cell plasticity of injected cells and thus drive differentiation for cardiovascular phenotypes, including vascular differentiation and cardiomyocyte differentiation.

MicroRNAs in cardiovascular disease: from pathogenesis to prevention and treatment

The management of cardiovascular risk through lifestyle modification and pharmacotherapy is paramount to the prevention of cardiovascular disease. Epidemiological studies have identified obesity, dyslipidemia, diabetes, and hypertension as interrelated factors that negatively affect cardiovascular health. Recently, genetic and pharmacological evidence in model systems has implicated microRNAs as dynamic modifiers of disease pathogenesis. An expanded understanding of the function of microRNAs in gene regulatory networks associated with cardiovascular risk will enable identification of novel genetic mechanisms of disease and inform the development of innovative therapeutic strategies.

Myofibroblast-mediated mechanisms of pathological remodelling of the heart

The syncytium of cardiomyocytes in the heart is tethered within a matrix composed principally of type I fibrillar collagen. The matrix has diverse mechanical functions that ensure the optimal contractile efficiency of this muscular pump. In the diseased heart, cardiomyocytes are lost to necrotic cell death, and phenotypically transformed fibroblast-like cells-termed 'myofibroblasts'-are activated to initiate a 'reparative' fibrosis. The structural integrity of the myocardium is preserved by this scar tissue, although at the expense of its remodelled architecture, which has increased tissue stiffness and propensity to arrhythmias. A persisting population of activated myofibroblasts turns this fibrous tissue into a living 'secretome' that generates angiotensin II and its type 1 receptor, and fibrogenic growth factors (such as transforming growth factor-β), all of which collectively act as a signal-transducer-effector signalling pathway to type I collagen synthesis and, therefore, fibrosis. Persistent myofibroblasts, and the resultant fibrous tissue they produce, cause progressive adverse myocardial remodelling, a pathological hallmark of the failing heart irrespective of its etiologic origin. Herein, we review relevant cellular, subcellular, and molecular mechanisms integral to cardiac fibrosis and consequent remodelling of atria and ventricles with a heterogeneity in cardiomyocyte size. Signalling pathways that antagonize collagen fibrillogenesis provide novel strategies for cardioprotection.

Ca2+-dependent transcriptional control of Ca2+ homeostasis

Intracellular free Ca(2+) ions regulate many cellular functions, and in turn, the cell devotes many genes/proteins to keep tight control of the level of intracellular free Ca(2+). Here, we review recent work on Ca(2+)-dependent mechanisms and effectors that regulate the transcription of genes encoding proteins involved in the maintenance of the homeostasis of Ca(2+) in the cell.