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

Function Follows Form - A Review of Cardiac Cell Therapy

The investment of nearly 2 decades of clinical investigation into cardiac cell therapy has yet to change cardiovascular practice. Recent insights into the mechanism of cardiac regeneration help explain these results and provide important context in which we can develop next-generation therapies. Non-contractile cells such as bone marrow or adult heart derivatives neither engraft long-term nor induce new muscle formation. Correspondingly, these cells offer little functional benefit to infarct patients. In contrast, preclinical data indicate that transplantation of bona fide cardiomyocytes derived from pluripotent stem cells induces direct remuscularization. This new myocardium beats synchronously with the host heart and induces substantial contractile benefits in macaque monkeys, suggesting that regeneration of contractile myocardium is required to fully recover function. Through a review of the preclinical and clinical trials of cardiac cell therapy, distinguishing the primary mechanism of benefit as either contractile or non-contractile helps appreciate the barriers to cardiac repair and establishes a rational path to optimizing therapeutic benefit.

MiR-484 Protects Rat Myocardial Cells from Ischemia-Reperfusion Injury by Inhibiting Caspase-3 and Caspase-9 during Apoptosis

BACKGROUND AND OBJECTIVES

To reveal the detail mechanism of miR-484 on myocardial ischemia-reperfusion (MI/R) injury.

METHODS

Rats model of MI/R injury was established based on control (Con; sham operate) group, ischemia-reperfusion (I/R) group, miR-484 treatment (miR) group, and I/R-negative control (IR-C) group, followed by pathological and interleukin (IL)-6, tumor necrosis factor (TNF)-α, and IL-1β expression evaluation. Then the myocardial apoptosis, as well as the expression of miR-484, caspase-3, and caspase-9 in myocardium were examined. Finally, the regulatory relation between miR-484 and SMAD family member 7 (SMAD7) was predicated, followed by verification analysis.

RESULTS

Compared with Con group, the expression of miR-484 in I/R and IR-C group was decreased. Compared with I/R and IR-C group, the expression of miR-484 was increased in miR group. Compared with Con group, the expression levels of IL-6, TNF-α, and IL-1β in cardiac myocytes of I/R group and IR-C group were increased. Compared with Con group, the apoptotic index, membrane potential of I/R, and the expression of caspase-3/9 were increased in IR-C group. Compared with the I/R and IR-C groups, the apoptotic index of myocardial cells in the ischemic region was decreased, the membrane potential was increased, and the expression of caspase-3/9 was decreased significantly in the miR group. SMAD7 was the target gene of miR-484.

CONCLUSIONS

MiR-484 protected myocardial cells from I/R injury by suppressing caspase-3 and caspase-9 expression during cardiomyocyte apoptosis. MiR-484 reduced the expression of IL-6, TNF-α, and IL-1β in MI/R. MiR-484 might alleviate the decreasing of mitochondrial membrane potential in MI/R cells.

Roles of Thyroid Hormone-Associated microRNAs Affecting Oxidative Stress in Human Hepatocellular Carcinoma

Oxidative stress occurs as a result of imbalance between the generation of reactive oxygen species (ROS) and antioxidant genes in cells, causing damage to lipids, proteins, and DNA. Accumulating damage of cellular components can trigger various diseases, including metabolic syndrome and cancer. Over the past few years, the physiological significance of microRNAs (miRNA) in cancer has been a focus of comprehensive research. In view of the extensive level of miRNA interference in biological processes, the roles of miRNAs in oxidative stress and their relevance in physiological processes have recently become a subject of interest. In-depth research is underway to specifically address the direct or indirect relationships of oxidative stress-induced miRNAs in liver cancer and the potential involvement of the thyroid hormone in these processes. While studies on thyroid hormone in liver cancer are abundantly documented, no conclusive information on the potential relationships among thyroid hormone, specific miRNAs, and oxidative stress in liver cancer is available. In this review, we discuss the effects of thyroid hormone on oxidative stress-related miRNAs that potentially have a positive or negative impact on liver cancer. Additionally, supporting evidence from clinical and animal experiments is provided.

Molecular mechanisms of heart regeneration

The adult mammalian heart is incapable of clinically relevant regeneration. The regenerative deficit in adult mammalian heart contrasts with the fetal and neonatal heart, which demonstrate substantial regenerative capacity after injury. This deficiency in adult mammals is attributable to the lack of resident stem cells after birth, combined with an inability of pre-existing cardiomyocytes to complete cytokinesis. Studies of neonatal heart regeneration in mammals suggest that latent regenerative potential can be re-activated. Dissecting the cellular and molecular mechanisms that promote cardiomyocyte proliferation is key to stimulating true regeneration in adult humans. Here, we review recent advances in our understanding of cardiomyocyte proliferation that suggest molecular approaches to heart regeneration.

Nanoparticle-Hydrogel System for Post-myocardial Infarction Delivery of MicroRNA

Effective therapies for cardiac repair and regeneration after myocardial infarction (MI) are rather limited. Although microRNAs (miRs) are known to play an important role in improving cardiac function after MI at a cellular level, delivering and retaining miRs at the target site has been challenging. To address this dilemma, several miR carriers have been developed, but these face their own limitations such as immunogenicity and poor targeting to the infarct site. In this Perspective, we summarize different mechanisms for miR administration and localization to cardiac tissue, with a specific focus on the clinically relevant injectable hydrogel and nanoparticle system developed by Yang et al. and reported in this issue of ACS Nano. We also highlight future directions for this field and outline the remaining unanswered questions.

The deficiency of miR-214-3p exacerbates cardiac fibrosis via miR-214-3p/NLRC5 axis

Cardiac fibrosis is a common pathological feature of many cardiovascular diseases. The regulatory mechanisms of miRNAs in cardiac fibrosis are still unknown. Previous studies on miR-214-3p in cardiac fibroblasts reached contradictory conclusions. Thus the role of miR-214-3p in cardiac fibrosis deserves further exploration. Using a combination of in vitro and in vivo studies, we identified miR-214-3p as an important regulator of cardiac fibrosis, and the proliferation and activation of cardiac fibroblasts. We demonstrated that the expression of miR-214-3p is down-regulated in TGF-β1-treated myofibroblasts and transverse aortic constriction (TAC)-induced murine model. Additionally, miR-214-3pflox/flox/FSP1-cre mice and miR-214-3pwt/wt/FSP1-cre mice were subjected to TAC operation or sham operation, and the conditional knockout of miR-214-3p in cardiac fibroblasts aggravates TAC-induced cardiac fibrosis. In vitro, our results indicate that miR-214-3p is an important repressor for fibroblasts proliferation and fibroblast-to-myofibroblast transition by functionally targeting NOD-like receptor family CARD domain containing 5 (NLRC5). In conclusion, our findings show that the deficiency of miR-214-3p exacerbates cardiac fibrosis and reveal a novel miR-214-3p/NLRC5 axis in the regulation of cardiac fibrosis.

Noncoding RNAs in exercise-induced cardio-protection for chronic heart failure

Chronic heart failure (CHF) has long been a major medical care burden on society due to its high morbidity and mortality. Although lots of evidence has demonstrated the beneficial impacts of exercise on CHF, termed exercise-induced cardioprotection (EIC), the underlying mechanisms and applicability of EIC are elusive and controversial, and thus, clinical applications are difficult. Noncoding RNAs (ncRNAs) are potential therapeutic targets for CHF. Increasing number of ncRNAs were found to play a role in EIC and CHF. The purpose of this review is to illustrate the current knowledge of ncRNAs in EIC for CHF as well as their prospective and limitations in clinical application.

Electrical Conduction System Remodeling in Streptozotocin-Induced Diabetes Mellitus Rat Heart

Cardiovascular complications are common in type 1 diabetes mellitus (TIDM) and there is an increased risk of arrhythmias as a result of dysfunction of the cardiac conduction system (CCS). We have previously shown that, in vivo, there is a decrease in the heart rate and prolongation of the QRS complex in streptozotocin-induced type 1 diabetic rats indicating dysfunction of the CCS. The aim of this study was to investigate the function of the ex vivo CCS and key proteins that are involved in pacemaker mechanisms in TIDM. RR interval, PR interval and QRS complex duration were significantly increased in diabetic rats. The beating rate of the isolated sinoatrial node (SAN) preparation was significantly decreased in diabetic rats. The funny current density and cell capacitance were significantly decreased in diabetic nodal cells. Western blot showed that proteins involved in the function of the CCS were significantly decreased in diabetic rats, namely: HCN4, Ca_v1.3, Ca_v3.1, Cx45, and NCX1 in the SAN; RyR2 and NCX1 in the atrioventricular junction and Cx40, Cx43, Cx45, and RyR2 in the Purkinje network. We conclude that there are complex functional and cellular changes in the CCS in TIDM. The changes in the proteins involved in the function of this electrical system are expected to adversely affect action potential generation and propagation, and these changes are likely to be arrhythmogenic.

Circulating exosomal miRNAs in cardiovascular disease pathogenesis: New emerging hopes

Cardiovascular diseases (CVDs) are one of the leading causes of morbidity and mortality. Standard therapies have failed to significantly increase patients' survival. Moreover, the majority of conventional screening procedures are ineffective for the diagnosis of CVDs at early stages. Accumulating evidence suggests that numerous cell types release a class of nano-sized vesicles named exosomes into the extracellular space. Exosomes are widely distributed in various body fluids and contain a number of diverse biomolecules such as proteins, lipids, and both mRNA and noncoding RNAs which reflect host-cell molecular architecture. MicroRNAs (miRNAs), which can be found in exosomes, could be taken up by both neighboring and distal cells. Not only has recent evidence indicated the regulatory role of exosomal miRNAs in the pathogenesis of CVD, but it has also been shown that differential expression of exosomal miRNAs in CVDs has made them promising biomarkers for early detection of CVDs. Owing to these remarkable features, exosomal miRNAs have emerged as hot spots in research. This review summarizes the role of exosomal miRNAs in the pathogenesis of CVDs and discusses their potential application in the clinical setting as both therapeutic and diagnostic tools.

Cardiomyocytes capture stem cell-derived, anti-apoptotic microRNA-214 via clathrin-mediated endocytosis in acute myocardial infarction

Extracellular vesicles (EVs) have emerged as key mediators of intercellular communication that have the potential to improve cardiac function when used in cell-based therapy. However, the means by which cardiomyocytes respond to EVs remains unclear. Here, we sought to clarify the role of exosomes in improving cardiac function by investigating the effect of cardiomyocyte endocytosis of exosomes from mesenchymal stem cells on acute myocardial infarction (MI). Exposing cardiomyocytes to the culture supernatant of adipose-derived regenerative cells (ADRCs) prevented cardiomyocyte cell damage under hypoxia in vitro. In vivo, the injection of ADRCs into the heart simultaneous with coronary artery ligation decreased overall cardiac infarct area and prevented cardiac rupture after acute MI. Quantitative RT-PCR-based analysis of the expression of 35 known anti-apoptotic and secreted microRNAs (miRNAs) in ADRCs revealed that ADRCs express several of these miRNAs, among which miR-214 was the most abundant. Of note, miR-214 silencing in ADRCs significantly impaired the anti-apoptotic effects of the ADRC treatment on cardiomyocytes in vitro and in vivo To examine cardiomyocyte endocytosis of exosomes, we cultured the cardiomyocytes with ADRC-derived exosomes labeled with the fluorescent dye PKH67 and found that hypoxic culture conditions increased the levels of the labeled exosomes in cardiomyocytes. Chlorpromazine, an inhibitor of clathrin-mediated endocytosis, significantly suppressed the ADRC-induced decrease of hypoxia-damaged cardiomyocytes and also decreased hypoxia-induced cardiomyocyte capture of both labeled EVs and extracellular miR-214 secreted from ADRCs. Our results indicate that clathrin-mediated endocytosis in cardiomyocytes plays a critical role in their uptake of circulating, exosome-associated miRNAs that inhibit apoptosis.

STIM2 knockdown protects against ischemia/reperfusion injury through reducing mitochondrial calcium overload and preserving mitochondrial function

Mitochondrial dysfunction caused by calcium overload is a vital factor for mediating cardiomyocyte death following ischemia/reperfusion (I/R) injury. The stromal interactive molecule 2 (STIM2) is a calcium sensor protein that regulates the store-operated calcium entry (SOCE). Whereas, whether STIM2 is associated with I/R injury remains largely unclear. We report here that STIM2, but not its homologue STIM1, is upregulated in cultured H9c2 cells, a cell model for cardiomyocytes, following I/R injury. In addition, the knockdown of STIM2, but not STIM1, reduces H9c2 cell apoptosis following I/R injury, and similar results were obtained in primary neonatal cardiomyocytes. This anti-apoptotic effect could be attributed to the inhibited activation of mitochondrial apoptosis pathway. Moreover, STIM2 knockdown reduces ER calcium release and simultaneously alleviates mitochondrial calcium overload in H9c2 cells following I/R injury. Furthermore, STIM2 knockdown decreases mitochondrial injury and preserves mitochondrial function following I/R injury. Collectively, these results suggest that the protective role of STIM2 knockdown against I/R injury in cardiomyocytes is associated with the reduced mitochondrial calcium overload and preserved mitochondrial function. Hence, our study may provide a novel insight into the regulation of mitochondrial-mediated cardiomyocyte apoptosis following I/R injury.

Endoplasmic reticulum and the microRNA environment in the cardiovascular system 1

Stress responses are important to human physiology and pathology, and the inability to adapt to cellular stress leads to cell death. To mitigate cellular stress and re-establish homeostasis, cells, including those in the cardiovascular system, activate stress coping response mechanisms. The endoplasmic reticulum, a component of the cellular reticular network in cardiac cells, mobilizes so-called endoplasmic reticulum stress coping responses, such as the unfolded protein response. MicroRNAs play an important part in the maintenance of cellular and tissue homeostasis, perform a central role in the biology of the cardiac myocyte, and are involved in pathological cardiac function and remodeling. In this paper, we review a link between endoplasmic reticulum homeostasis and microRNA with an emphasis on the impact on stress responses in the cardiovascular system.

Upregulation of miR-29b-3p protects cardiomyocytes from hypoxia-induced apoptosis by targeting TRAF5

Background

MicroRNAs (miRNAs) are pivotal regulators in regulating hypoxia-induced cardiomyocyte injury. This study was designed to evaluate the effects of miR-29b-3p on hypoxic cardiomyocytes.

Methods

Human AC16 cells were cultured under normoxic or hypoxic conditions. Hypoxic injury was confirmed based on alterations in cell viability using CCK-8 assay and apoptosis using flow cytometry and Hoechst staining. Bioinformatics analyses and the dual-luciferase reporter assay were performed to predict and validate the target gene of miR-29b-3p.

Results

We found that hypoxia suppressed cell viability and promoted apoptosis. TNF receptor-associated factor 5 (TRAF5) was a potential target gene of miR-29b-3p. Our in vitro experiments revealed that miR-29b-3p overexpression or TRAF6 knockdown significantly protected cardiomyocytes against hypoxia-induced injury. Moreover, knockdown of TRAF5 knockdown potentiated the protective effects of miR-29b-3p against hypoxia-induced cell injury.

Conclusion

These findings suggest that upregulation of miR-29b-3p could protect cardiomyocytes against hypoxia-induced injury through downregulation of TRAF5. Targeting TRAF5 with miR-29b-3p might be a potential therapeutic method for AMI.

Expression of miRNA-214 in the sera of elderly patients with acute myocardial infarction and its effect on cardiomyocyte apoptosis

The aim of the present study was to investigate the expression of microRNA (miRNA/miR)-214 in the sera of elderly patients with acute myocardial infarction (AMI) and the mechanism of how its expression affects cardiomyocyte apoptosis in these patients. The expression levels of miRNA-214 in elderly patients with AMI, unstable angina (UA) and healthy elderly subjects were detected by reverse transcription-quantitative polymerase chain reaction, and the correlation between the relative expressions of sera miRNA-214 and myocardial enzymes in elderly patients with AMI was examined by Pearson's analysis. Human cardiomyocyte (HCM) cell lines with a high expression miRNA-214 were established. The apoptotic rates of the different groups of cells were detected by flow cytometry and TUNEL assay. The expression of miRNA-214 target genes in the different groups of cells was detected by western blot assay. The relative expression levels of sera miR-214 in elderly AMI patients, UA patients and healthy subjects (as determined by physical examination) were 15.79±4.66, 4.60±2.51 and 2.07±0.99, respectively. The differences between each group were statistically significant (P<0.05). The relative expression of sera miRNA-214 in elderly AMI patients was positively correlated with sera aspartate aminotransferase (r=0.361, P=0.0174), lactate dehydrogenase (r=0.425, P=0.0045), creatine kinase-MB (r=0.835, P<0.001) and cardiac troponin (r=0.770, P<0.001). When compared with normal HCMs, the expressions of p53-upregulated modulator of apoptosis (PUMA), phosphatase and tensin homolog (PTEN), B-cell lymphoma-2-associated X protein (Bax) and caspase 7 proteins was decreased in HCMs overexpressing miRNA-214 following H₂O₂ induction, and the rate of apoptosis decreased by 63.64, 21.95, 46.67 and 50.05%, respectively. miRNA-214 was highly expressed in the sera of elderly patients with AMI, which may inhibit myocardial cell apoptosis by inhibiting the expression of miR-214 target genes including PUMA, PTEN, Bax and caspase 7.

The harmful effects of acute PM2.5 exposure to the heart and a novel preventive and therapeutic function of CEOs

Epidemiological researches have demonstrated the relationship between PM2.5 exposure and increased morbidity and mortality of cardiovascular injury. However, no effective therapeutic method was established. The purpose of this study is to investigate the effect of acute PM2.5 exposure on the mice heart tissue and explore the therapeutic effects of compound essential oils (CEOs) in this model. In this study, after mice were exposed to PM2.5 intratracheally, some obvious histopathological changes as well as some great alterations of proinflammatory cytokines were observed in the heart tissue. The imbalance of oxidative stress, the altered Ca2+ channel related proteins and the increased intracellular free Ca2+ were all involved in the heart impairment and would also be investigated in this model. The CEOs alleviated the heart impairment via its antioxidant effect rather than its anti-inflammatory function because our results revealed that oxidative stress related indicators were restored after CEOs administration. At the same time, increased concentration of intracellular free Ca2+ and ROS induced by PM2.5 were reduced after NAC (N-Acetyl-L-cysteine) administration. These data suggested that the acute PM2.5 exposure would damage heart tissue by inducing the inflammatory response, oxidative stress and intracellular free Ca2+ overload. PM2.5-induced oxidative stress probably increase intracellular free Ca2+ via RYR2 and SERCA2a. CEOs have the potential to be a novel effective and convenient therapeutic method to prevent and treat the acute heart impairment induced by PM2.5 via its antioxidant function.

Effects of ticagrelor on the sodium/calcium exchanger 1 (NCX1) in cardiac derived H9c2 cells

Ticagrelor is a direct acting and reversibly binding P2Y₁₂ antagonist approved for the prevention of thromboembolic events. Clinical effects of ticagrelor cannot be simply accounted for by pure platelet inhibition, and off-target mechanisms can potentially play a role. In particular, recent evidence suggests that ticagrelor may also influence heart function and improve the evolution of myocardial ischemic injury by more direct effects on myocytes. The cardiac sodium/calcium exchanger 1 (NCX1) is a critical player in the generation and control of calcium (Ca²⁺) signals, which orchestrate multiple myocyte activities in health and disease. Altered expression and/or activity of NCX1 can have profound consequences for the function and fate of myocytes. Whether ticagrelor affects cardiac NCX1 has not been investigated yet. To explore this hypothesis, we analyzed the expression, localization and activity of NCX1 in the heart derived H9c2-NCX1 cells following ticagrelor exposure. We found that ticagrelor concentration- and time-dependently reduced the activity of the cardiac NCX1 in H9c2 cells. In particular, the inhibitory effect of ticagrelor on the Ca²⁺-influx mode of NCX1 was evident within 1 h and further developed after 24 h, when NCX1 activity was suppressed by about 55% in cells treated with 1 μM ticagrelor. Ticagrelor-induced inhibition of exchanger activity was reached at clinically relevant concentrations, without affecting the expression levels and subcellular distribution of NCX1. Collectively, these findings suggest that cardiac NCX1 is a new downstream target of ticagrelor, which may contribute to the therapeutic profile of ticagrelor in clinical practice.

Identification of microRNAs related to myocardial ischemic reperfusion injury

Previous studies have suggested that microRNAs (miRNAs) are associated with the progression of myocardial ischemic reperfusion (I/R) injury. However, inconsistent results have been obtained due to the differences in sequencing platform, control selection, and filtering conditions. To explore the key miRNAs in the pathogenesis of myocardial I/R injury and develop miRNA diagnostic biomarkers for myocardial I/R injury prevention, we performed a systematic analysis of publicly available myocardial I/R injury miRNA expression data and investigated the function of the signature miRNA. A total of 17 representative myocardial I/R injury miRNA datasets were extracted from the Google Scholar website and a systematic bioinformatics analysis was done. TargetScan software was used to predict the miRNA target genes, and functional enrichment and transcription factor binding analyses were performed on the target genes using the DAVID and Tfacts databases. In this study, a total of 10 signature miRNAs associated with myocardial I/R injury were identified, which included eight significantly upregulated miRNAs (miR-let-7b-3p, miR-let-7c-3p, miR-15b-3p, miR-195-3p, miR-21-5p, miR-214-5p, miR-24-3p, and miR-320a) and two significantly downregulated miRNAs (miR-126-5p and miR-499a-5p). They had different influences on myocardial I/R injury. The upregulated target gene-expressing signature messenger RNAs (mRNAs) were mainly involved in the transcriptional regulation process of GO: 0000122, negative regulation of transcription from RNA polymerase II promoter, and so on, while downregulated expression of signature mRNAs was mainly involved in GO:0070534, protein K63-linked ubiquitination, and so forth. To summarize, 10 signature miRNAs of myocardial I/R injury pathogenesis were identified and their target genes and transcription factors were revealed, suggesting the potential novel therapeutic targets for myocardial I/R injury.

MicroRNA-21 ablation exacerbates aldosterone-mediated cardiac injury, remodeling, and dysfunction

Primary aldosteronism is characterized by excess aldosterone secretion by the adrenal gland independent of the renin-angiotensin system and accounts for ~10% of hypertensive patients. Excess aldosterone causes cardiac hypertrophy, fibrosis, inflammation, and hypertension. The molecular mechanisms that trigger the onset and progression of aldosterone-mediated cardiac injury remain incompletely understood. MicroRNAs (miRNAs) are endogenous, small, noncoding RNAs that have been implicated in multiple cardiac pathologies; however, their regulation and role in aldosterone-mediated cardiac injury and dysfunction remains mostly unknown. We previously reported that microRNA-21 (miR-21) is the most upregulated miRNA by excess aldosterone in the left ventricle in a rat experimental model of primary aldosteronism. To elucidate the role of miR-21 in aldosterone-mediated cardiac injury and dysfunction, miR-21 knockout mice and their wild-type littermates were treated with aldosterone infusion and salt in the drinking water for 2 or 8 wk. miR-21 genetic ablation exacerbated aldosterone/salt-mediated cardiac hypertrophy and cardiomyocyte cross-sectional area. Furthermore, miR-21 genetic ablation increased the cardiac expression of fibrosis and inflammation markers and fetal gene program. miR-21 genetic ablation increased aldosterone/salt-mediated cardiac dysfunction but did not affect aldosterone/salt-mediated hypertension. miR-21 target gene Sprouty 2 may be implicated in the cardiac effects of miR-21 genetic ablation. Our study shows that miR-21 genetic ablation exacerbates aldosterone/salt-mediated cardiac hypertrophy, injury, and dysfunction blood pressure independently. These results suggest that miR-21 plays a protective role in the cardiac pathology triggered by excess aldosterone. Furthermore, miR-21 supplementation may be a novel therapeutic approach to abolish or mitigate excess aldosterone-mediated cardiovascular deleterious effects in primary aldosteronism.

FoxO1-miRNA interacting networks as potential targets for mitochondrial diseases

Mitochondrial homeostasis is important for the health and well-being of organ systems and organisms. Mitochondrial dysfunction is known to be the cause and consequence of metabolic diseases, including obesity, diabetes, cancer, neurodegeneration, cerebrovascular, and cardiovascular disease. For cardiovascular tissue, which relies mostly on oxidative phosphorylation, the role of mitochondria is inevitable. Rather than being biomarkers of mitochondrial health, miRNAs are now known as bioregulators of this important feature. Recent studies have shown a close interaction between Forkhead box other 1 (FoxO1) transcription factors and miRNAs in the cardiovascular system. These interactions have also been shown to regulate mitochondrial homeostasis. In this review, I highlight how understanding FoxO1 and miRNA interacting networks could enable us to limit mitochondrial dysfunction and associated pathologies.

MicroRNA-214-3p in the Kidney Contributes to the Development of Hypertension

BACKGROUND

In spite of extensive study, the mechanisms for salt sensitivity of BP in humans and rodent models remain poorly understood. Several microRNAs (miRNAs) have been associated with hypertension, but few have been shown to contribute to its development.

METHODS

We examined miRNA expression profiles in human kidney biopsy samples and rat models using small RNA deep sequencing. To inhibit an miRNA specifically in the kidney in conscious, freely moving rats, we placed indwelling catheters to allow both renal interstitial administration of a specific anti-miR and measurement of BP. A rat with heterozygous disruption of the gene encoding endothelial nitric oxide synthase (eNOS) was developed. We used bioinformatic analysis to evaluate the relationship between 283 BP-associated human single-nucleotide polymorphisms (SNPs) and 1870 human miRNA precursors, as well as other molecular and cellular methods.

RESULTS

Compared with salt-insensitive SS.13BN26 rats, Dahl salt-sensitive (SS) rats showed an upregulation of miR-214-3p, encoded by a gene in the SS.13BN26 congenic region. Kidney-specific inhibition of miR-214-3p significantly attenuated salt-induced hypertension and albuminuria in SS rats. miR-214-3p directly targeted eNOS. The effect of miR-214-3p inhibition on hypertension and albuminuria was abrogated in SS rats with heterozygous loss of eNOS. Human kidney biopsy specimens from patients with hypertension or hypertensive nephrosclerosis showed upregulation of miR-214-3p; the gene encoding miR-214-3p was one of several differentially expressed miRNA genes located in proximity to human BP-associated SNPs.

CONCLUSIONS

Renal miR-214-3p plays a functional and potentially genetic role in the development of hypertension, which might be mediated in part by targeting eNOS.

Therapeutic approaches for cardiac regeneration and repair

Ischaemic heart disease is a leading cause of death worldwide. Injury to the heart is followed by loss of the damaged cardiomyocytes, which are replaced with fibrotic scar tissue. Depletion of cardiomyocytes results in decreased cardiac contraction, which leads to pathological cardiac dilatation, additional cardiomyocyte loss, and mechanical dysfunction, culminating in heart failure. This sequential reaction is defined as cardiac remodelling. Many therapies have focused on preventing the progressive process of cardiac remodelling to heart failure. However, after patients have developed end-stage heart failure, intervention is limited to heart transplantation. One of the main reasons for the dramatic injurious effect of cardiomyocyte loss is that the adult human heart has minimal regenerative capacity. In the past 2 decades, several strategies to repair the injured heart and improve heart function have been pursued, including cellular and noncellular therapies. In this Review, we discuss current therapeutic approaches for cardiac repair and regeneration, describing outcomes, limitations, and future prospects of preclinical and clinical trials of heart regeneration. Substantial progress has been made towards understanding the cellular and molecular mechanisms regulating heart regeneration, offering the potential to control cardiac remodelling and redirect the adult heart to a regenerative state.

The Influence of MicroRNAs on Mitochondrial Calcium

Abnormal mitochondrial calcium ([Ca²⁺]_m) handling and energy deficiency results in cellular dysfunction and cell death. Recent studies suggest that nuclear-encoded microRNAs (miRNA) are able to translocate in to the mitochondrial compartment, and modulate mitochondrial activities, including [Ca²⁺]_m uptake. Apart from this subset of miRNAs, there are several miRNAs that have been reported to target genes that play a role in maintaining [Ca²⁺]_m levels in the cytoplasm. It is imperative to validate miRNAs that alter [Ca²⁺]_m handling, and thereby alter cellular fate. The focus of this review is to highlight the mitochondrial miRNAs (MitomiRs), and other cytosolic miRNAs that target mRNAs which play an important role in [Ca²⁺]_m handling.

miR-214 ameliorates acute kidney injury via targeting DKK3 and activating of Wnt/β-catenin signaling pathway

Background

miR-214 was demonstrated to be upregulated in models of renal disease and promoted fibrosis in renal injury independent of TGF-β signaling in vivo. However, the detailed role of miR-214 in acute kidney injury (AKI) and its underlying mechanism are still largely unknown.

Methods

In this study, an I/R-induced rat AKI model and a hypoxia-induced NRK-52E cell model were used to study AKI. The concentrations of kidney injury markers serum creatinine, blood urea nitrogen, and kidney injury molecule-1 were measured. The expressions of miR-214, tumor necrosis factor-α, interleukin (IL)-1β, IL-6, were detected by RT-qPCR. The protein levels of Bcl-2, Bax, Dickkopf-related protein 3, β-catenin, c-myc, and cyclinD1 were determined by western blot. Cell apoptosis and caspase 3 activity were evaluated by flow cytometry analysis and caspase 3 activity assay, respectively. Luciferase reporter assay was used to confirm the interaction between miR-214 and Dkk3.

Results

miR-214 expression was induced in ischemia–reperfusion (I/R)-induced AKI rat and hypoxic incubation of NRK-52E cells. Overexpression of miR-214 alleviated hypoxia-induced NRK-52E cell apoptosis while inhibition of miR-214 expression exerted the opposite effect. Dkk3 was identified as a target of miR-214. Anti-miR-214 abolished the inhibitory effects of DKK3 knockdown on hypoxia-induced NRK-52E cell apoptosis by inactivation of Wnt/β-catenin signaling. Moreover, miR-214 ameliorated AKI in vivo by inhibiting apoptosis and fibrosis through targeting Dkk3 and activating Wnt/β-catenin pathway.

Conclusion

miR-214 ameliorates AKI by inhibiting apoptosis through targeting Dkk3 and activating Wnt/β-catenin signaling pathway, offering the possibility of miR-214 in the therapy of ischemic AKI.

Electronic supplementary material

The online version of this article (10.1186/s40659-018-0179-2) contains supplementary material, which is available to authorized users.

Exosomes Derived from miR-214-Enriched Bone Marrow-Derived Mesenchymal Stem Cells Regulate Oxidative Damage in Cardiac Stem Cells by Targeting CaMKII

Cardiac stem cells (CSCs) have emerged as one of the most promising stem cells for cardiac protection. Recently, exosomes from bone marrow-derived mesenchymal stem cells (BMSCs) have been found to facilitate cell proliferation and survival by transporting various bioactive molecules, including microRNAs (miRs). In this study, we found that BMSC-derived exosomes (BMSC-exos) significantly decreased apoptosis rates and reactive oxygen species (ROS) production in CSCs after oxidative stress injury. Moreover, a stronger effect was induced by exosomes collected from BMSCs cultured under hypoxic conditions (Hypoxic-exos) than those collected from BMSCs cultured under normal conditions (Nor-exos). We also observed greater miR-214 enrichment in Hypoxic-exos than in Nor-exos. In addition, a miR-214 inhibitor or mimics added to modulate miR-214 levels in BMSC-exos revealed that exosomes from miR-214-depleted BMSCs partially reversed the effects of hypoxia-induced exosomes on oxidative damage in CSCs. These data further confirmed that miR-214 is the main effector molecule in BMSC-exos that protects CSCs from oxidative damage. miR-214 mimic and inhibitor transfection assays verified that CaMKII is a target gene of miR-214 in CSCs, with exosome-pretreated CSCs exhibiting increased miR-214 levels but decreased CaMKII levels. Therefore, the miR-214/CaMKII axis regulates oxidative stress-related injury in CSCs, such as apoptosis, calcium homeostasis disequilibrium, and excessive ROS accumulation. Collectively, these findings suggest that BMSCs release miR-214-containing exosomes to suppress oxidative stress injury in CSCs through CaMKII silencing.

MiR-214 is an important regulator of the musculoskeletal metabolism and disease

MiR-214 belongs to a family of microRNA (small, highly conserved noncoding RNA molecules) precursors that play a pivotal role in biological functions, such as cellular function, tissue development, tissue homeostasis, and pathogenesis of diseases. Recently, miR-214 emerged as a critical regulator of musculoskeletal metabolism. Specifically, miR-214 can mediate skeletal muscle myogenesis and vascular smooth muscle cell proliferation, migration, and differentiation. MiR-214 also modulates osteoblast function by targeting specific molecular pathways and the expression of various osteoblast-related genes; promotes osteoclast activity by targeting phosphatase and tensin homolog (Pten); and mediates osteoclast-osteoblast intercellular crosstalk via an exosomal miRNA paracrine mechanism. Importantly, dysregulation in miR-214 expression is associated with pathological bone conditions such as osteoporosis, osteosarcoma, multiple myeloma, and osteolytic bone metastasis of breast cancer. This review discusses the cellular targets of miR-214 in bone, the molecular mechanisms governing the activities of miR-214 in the musculoskeletal system, and the putative role of miR-214 in skeletal diseases. Understanding the biology of miR-214 could potentially lead to the development of miR-214 as a possible biomarker and a therapeutic target for musculoskeletal diseases.

Relationship between cardiovascular diseases and circulating cell-free nucleic acids in human plasma

Cardiovascular diseases (CVDs) are the main cause of human morbidity and mortality worldwide. Early diagnosis could improve the efficiency of treatments. New biomarkers are needed for the identification of high-risk populations in order to make accurate diagnosis and therapy monitoring. Circulating cell-free nucleic acids (cf-NAs) offer a promising new noninvasive tool. These have a role in the regulation of normal physiological functions and in the development of pathological alterations. There is extended research on the clinical application and utilization of cell-free genomic DNA, mtDNA, mRNA, miRNA and long noncoding RNA in CVDs. These molecules could serve as components of new generation therapeutics. Our review focuses on the role of cf-NAs in the pathogenesis of CVDs and we are discussing also possible diagnostic applications and therapeutic implications.

MicroRNA-126 accelerates IgE-mediated mast cell degranulation associated with the PI3K/Akt signaling pathway by promoting Ca2+ influx

Mast cells (MCs) have been reported to serve a crucial role in allergic diseases, including asthma, allergic rhinitis and anaphylaxis. A previous study revealed that microRNA-126 (miR-126) was associated with airway hyperresponsiveness induced by house dust mites, however the molecular mechanisms were unclear. The present study aimed to investigate the effect of miR-126 on immunoglobulin E (IgE)-regulated MC degranulation and explore its underlying mechanisms. miR-126 expression was quantified using a rat model in vivo and in rat peritoneal mast cells (RPMCs) in vitro. Overexpression or downregulation of miR-126 was established by transfection with miR-126 mimics or miR-126 inhibitors and MC degranulation was subsequently evaluated. The effect of miR-126 on protein kinase B (Akt) and phosphorylated Akt protein expression was examined by western blot analysis. The phosphoinositide 3-kinase (PI3K) inhibitor (LY294002) was used to determine the role of the PI3K/Akt signaling pathway. In addition, cytosolic calcium (Ca²⁺) levels were measured by a fura-2 assay. The results demonstrated that miR-126 expression was upregulated in the ear tissues of rats with allergic contact dermatitis and IgE-activated MCs. The overexpression of miR-126 in RPMCs was established following miR-126 mimic transfection. The release of β-hexosaminidase and histamine, markers of MC degranulation, were significantly increased in cells with miR-126 overexpression. The phosphorylation of Akt was significantly increased following transfection with miR-126 mimics in stimulated cells, however the signaling activation was abrogated by LY294002. In addition, Ca²⁺ influx was significantly promoted in stimulated RPMCs overexpressing miR-126. These results indicate that miR-126 accelerated IgE-mediated MC degranulation associated with the PI3K/Akt signaling pathway by promoting Ca²⁺ influx. This suggests that miR-126 may be a promising therapeutic target for the treatment of allergic skin diseases.

MicroRNA-532 protects the heart in acute myocardial infarction, and represses prss23, a positive regulator of endothelial-to-mesenchymal transition

Aims

Acute myocardial infarction (MI) leads to cardiac remodelling and development of heart failure. Insufficient myocardial capillary density after MI is considered a critical determinant of this process. MicroRNAs (miRs), negative regulators of gene expression, have emerged as important players in MI. We previously showed that miR-532-5p (miR-532) is up-regulated by the β-arrestin-biased β-adrenergic receptor antagonist (β-blocker) carvedilol, which activates protective pathways in the heart independent of G protein-mediated second messenger signalling. Here, we hypothesize that β2-adrenergic receptor/β-arrestin-responsive miR-532 confers cardioprotection against MI.

Methods and results

Using cultured cardiac endothelial cell (CEC) and in vivo approaches, we show that CECs lacking miR-532 exhibit increased transition to a fibroblast-like phenotype via endothelial-to-mesenchymal transition (EndMT), while CECs over-expressing miR-532 display decreased EndMT. We also demonstrate that knockdown of miR-532 in mice causes abnormalities in cardiac structure and function as well as reduces CEC proliferation and cardiac vascularization after MI. Mechanistically, cardioprotection elicited by miR-532 is in part attributed to direct repression of a positive regulator of maladaptive EndMT, prss23 (a protease serine 23) in CECs.

Conclusions

In conclusion, these findings reveal a pivotal role for miR-532-prss23 axis in regulating CEC function after MI, and this novel axis could be suitable for therapeutic intervention in ischemic heart disease.

Deciphering Non-coding RNAs in Cardiovascular Health and Disease

After being long considered as “junk” in the human genome, non-coding RNAs (ncRNAs) currently represent one of the newest frontiers in cardiovascular disease (CVD) since they have emerged in recent years as potential therapeutic targets. Different types of ncRNAs exist, including small ncRNAs that have fewer than 200 nucleotides, which are mostly known as microRNAs (miRNAs), and long ncRNAs that have more than 200 nucleotides. Recent discoveries on the role of ncRNAs in epigenetic and transcriptional regulation, atherosclerosis, myocardial ischemia/reperfusion (I/R) injury and infarction (MI), adverse cardiac remodeling and hypertrophy, insulin resistance, and diabetic cardiomyopathy prompted vast interest in exploring candidate ncRNAs for utilization as potential therapeutic targets and/or diagnostic/prognostic biomarkers in CVDs. This review will discuss our current knowledge concerning the roles of different types of ncRNAs in cardiovascular health and disease and provide some insight on the cardioprotective signaling pathways elicited by the non-coding genome. We will highlight important basic and clinical breakthroughs that support employing ncRNAs for treatment or early diagnosis of a variety of CVDs, and also depict the most relevant limitations that challenge this novel therapeutic approach.

MicroRNA-214 promotes hepatic stellate cell activation and liver fibrosis by suppressing Sufu expression

MicroRNAs (miRNAs) have been demonstrated to modulate cellular processes in the liver. However, the role of miRNAs in liver fibrosis is poorly understood. Because the activation of hepatic stellate cells (HSCs) is a pivotal event in the initiation and progression of hepatic fibrosis, we investigate the differential expression of miRNAs in activated and quiescent rat HSCs by microarray analysis and find that miR-214 (miR-214-3p) is significantly upregulated during HSC activation. Moreover, the robust induction of miR-214 is correlated with liver fibrogenesis in carbon tetrachloride (CCl4)-treated rats and mice, high-fat diet-induced non-alcoholic steatohepatitis in mice, and cirrhosis in humans. We identify that miR-214 expression is driven by the helix-loop-helix transcription factor Twist1 via the E-box element. The increased miR-214 inhibits the expression of suppressor-of-fused homolog (Sufu), a negative regulator of the Hedgehog signaling pathway, thereby contributing to HSC activation to promote the accumulation of fibrous extracellular matrix and the expression of profibrotic genes in HSCs and LX2 cells. Furthermore, miR-214 expression is inversely correlated with the expression of Sufu in clinical cirrhosis samples. To explore the clinical potential of miR-214, we inject antagomiR-214 oligos into mice to induce hepatic fibrosis. The knockdown of miR-214 in vivo enhances Sufu expression and reduces fibrosis marker expression, which ameliorates liver fibrosis in mice. In conclusions, the Twist1-regulated miR-214 promotes the activation of HSC cells through targeting Sufu involved in the Hedgehog pathway and participates in the development of hepatic fibrosis. Hence, the knockdown of miR-214 expression may be a promising therapeutic strategy for liver fibrosis.

Circadian MicroRNAs in Cardioprotection

The most dramatic feature of life on Earth is our adaptation to the cycle of day and night. Throughout evolutionary time, almost all living organisms developed a molecular clock linked to the light-dark cycles of the sun. In present time, we know that this molecular clock is crucial to maintain metabolic and physiological homeostasis. Indeed, a dysregulated molecular clockwork is a major contributing factor to many metabolic diseases. In fact, the time of onset of acute myocardial infarction exhibits a circadian periodicity and recent studies have found that the light regulated circadian rhythm protein Period 2 (PER2) elicits endogenous cardioprotection from ischemia. Manipulating the molecular clockwork may prove beneficial during myocardial ischemia in humans. MicroRNAs are small non-coding RNA molecules capable of silencing messenger RNA (mRNA) targets. MicroRNA dysregulation has been linked to cancer development, cardiovascular and neurological diseases, lipid metabolism, and impaired immunity. Therefore, microRNAs are gaining interest as putative novel disease biomarkers and therapeutic targets. To identify circadian microRNA-based cardioprotective pathways, a recent study evaluated transcriptional changes of PER2 dependent microRNAs during myocardial ischemia. Out of 352 most abundantly expressed microRNAs, miR-21 was amongst the top PER2 dependent microRNAs and was shown to mediate PER2 elicited cardioprotection. Further analysis suggested circadian entrainment via intense light therapy to be a potential strategy to enhance miR-21 activity in humans. In this review, we will focus on circadian microRNAs in the context of cardioprotection and will highlight new discoveries, which could lead to novel therapeutic concepts to treat myocardial ischemia.

DJ1 and microRNA-214 act synergistically to rescue myoblast cells after ischemia/reperfusion injury

Ischemia/reperfusion injury is a tissue injury occurring post-reperfusion of tissues with pre-existing ischemia. A good blood supply to tissues aids in the survival of ischemic tissue, however, due to prolonged ischemia the levels of ATP decrease and pH declines leading to acidosis. Reduced ATP leads to an increase in the AMP/ATP ratio, causing cessation of intracellular calcium transport, hence calcium overload and cell death. In this study, we demonstrate the synergistic and antagonistic effect of DJ1 and microR-214 (miR-214) in rescuing myoblast C2C12 cells after ischemia/reperfusion in an in vitro model. Both DJ1 and miR-214 were cloned into a hypoxic inducible expression cassette and transfected into the C2C12 cells. We showed that DJ1 and miR-214 have synergistic effects in reducing intracellular lactate dehydrogenase and intracellular transient calcium levels after reoxygenation compared to control cells, in addition to reducing cell death via necrosis. Western blotting revealed a decrease in autophagosome formation in LC3II/I ratio and an increase in AKT expression in cells transfected with DJ1 and miR-214. Using quantitative real-time PCR, we demonstrated that DJ1 and miR-214 significantly reduced the expression of pro-apoptotic factors and autophagy compared to control. The results indicated DJ1 is an endogenous oxidative stress molecule and miR-214 is a potent inhibitor of the sodium calcium exchanger channel. DJ1 had the greatest effect to inhibiting mitochondrial cell death pathways by possibly acting as a modulator of autophagy. Additionally, we have concluded that miR-214 has an inhibitory effect on extrinsic cell death pathways such as necrosis and autophagy.

Decellularized Extracellular Matrix Hydrogels as a Delivery Platform for MicroRNA and Extracellular Vesicle Therapeutics

In the last decade, the use of microRNA (miRNA) and extracellular vesicle (EV) therapies has emerged as an alternative approach to mitigate the negative effects of several disease pathologies ranging from cancer to tissue and organ regeneration; however, delivery approaches towards target tissues have not been optimized. To alleviate these challenges, including rapid diffusion upon injection and susceptibility to degradation, porcine-derived decellularized extracellular matrix (ECM) hydrogels are examined as a potential delivery platform for miRNA and EV therapeutics. The incorporation of EVs and miRNA antagonists, including anti-miR and antago-miR, in ECM hydrogels results in a prolonged release as compared to the biologic agents alone. In addition, individual in vitro assessments confirm the bioactivity of the therapeutics upon release from the ECM hydrogels. This work demonstrates the feasibility of encapsulating miRNA and EV therapeutics in ECM hydrogels to enhance delivery and potentially efficacy in later in vivo applications.

MicroRNAs Mediate Beneficial Effects of Exercise in Heart

MicroRNAs (miRNAs, miRs), a group of small non-coding RNAs, repress gene expressions at posttranscriptional level in most cases and are involved in cardiovascular physiology and disease pathogenesis. Increasing evidence has proved that miRNAs are potential regulators of exercise induced cardiac growth and mediate the benefits of exercise in a variety of cardiovascular diseases. In this chapter, we will review the regulatory effects of miRNAs in cardiac adaptations to exercise, and summarize their cardioprotective effects against myocardial infarction, ischemia/reperfusion injury, heart failure, diabetic cardiomyopathy, atherosclerosis, hypertension, and pulmonary hypertension. Also, we will introduce circulating miRNAs in response to acute and chronic exercise. Therefore, miRNAs may serve as novel therapeutic targets and potential biomarkers for cardiovascular diseases.

Fluorescent analysis of bioactive molecules in single cells based on microfluidic chips

Single-cell analysis of bioactive molecules is an essential strategy for a better understanding of cell biology, exploring cell heterogeneity, and improvement of the ability to detect early diseases. In single-cell analysis, highly efficient single-cell manipulation techniques and high-sensitive detection schemes are in urgent need. The rapid development of fluorescent analysis techniques combined with microfluidic chips have offered a widely applicable solution. Thus, in this review, we mainly focus on the application of fluorescence methods in components analysis on microchips at a single-cell level. By targeting different types of biological molecules in cells such as nucleic acids, proteins, and active small molecules, we specially introduce and comment on their corresponding fluorescent probes, fluorescence labelling and sensing strategies, and different fluorescence detection instruments used in single-cell analysis on a microfluidic chip. We hope that through this review, readers will have a better understanding of single-cell fluorescence analysis, especially for single-cell component fluorescence analysis based on microfluidic chips.

β-arrestin-biased agonism of β-adrenergic receptor regulates Dicer-mediated microRNA maturation to promote cardioprotective signaling

RATIONALE

MicroRNAs (miRs) are small, non-coding RNAs that function to post-transcriptionally regulate target genes. First transcribed as primary miR transcripts (pri-miRs), they are enzymatically processed by Drosha into premature miRs (pre-miRs) and further cleaved by Dicer into mature miRs. Initially discovered to desensitize β-adrenergic receptor (βAR) signaling, β-arrestins are now well-appreciated to modulate multiple pathways independent of G protein signaling, a concept known as biased signaling. Using the β-arrestin-biased βAR ligand carvedilol, we previously showed that β-arrestin1 (not β-arrestin2)-biased β1AR (not β2AR) cardioprotective signaling stimulates Drosha-mediated processing of six miRs by forming a multi-protein nuclear complex, which includes β-arrestin1, the Drosha microprocessor complex and a single-stranded RNA binding protein hnRNPA1.

OBJECTIVE

Here, we investigate whether β-arrestin-mediated βAR signaling induced by carvedilol could regulate Dicer-mediated miR maturation in the cytoplasm and whether this novel mechanism promotes cardioprotective signaling.

METHODS AND RESULTS

In mouse hearts, carvedilol indeed upregulates three mature miRs, but not their pre-miRs and pri-miRs, in a β-arrestin 1- or 2-dependent manner. Interestingly, carvedilol-mediated activation of miR-466g or miR-532-5p, and miR-674 is dependent on β2ARs and β1ARs, respectively. Mechanistically, β-arrestin 1 or 2 regulates maturation of three newly identified βAR/β-arrestin-responsive miRs (β-miRs) by associating with the Dicer maturation RNase III enzyme on three pre-miRs of β-miRs. Myocardial cell approaches uncover that despite their distinct roles in different cell types, β-miRs act as gatekeepers of cardiac cell functions by repressing deleterious targets.

CONCLUSIONS

Our findings indicate a novel role for βAR-mediated β-arrestin signaling activated by carvedilol in Dicer-mediated miR maturation, which may be linked to its protective mechanisms.

Metazoan MicroRNAs

MicroRNAs (miRNAs) are ∼22 nt RNAs that direct posttranscriptional repression of mRNA targets in diverse eukaryotic lineages. In humans and other mammals, these small RNAs help sculpt the expression of most mRNAs. This article reviews advances in our understanding of the defining features of metazoan miRNAs and their biogenesis, genomics, and evolution. It then reviews how metazoan miRNAs are regulated, how they recognize and cause repression of their targets, and the biological functions of this repression, with a compilation of knockout phenotypes that shows that important biological functions have been identified for most of the broadly conserved miRNAs of mammals.

MicroRNA-214 protects against hypoxia/reoxygenation induced cell damage and myocardial ischemia/reperfusion injury via suppression of PTEN and Bim1 expression

BACKGROUND

Myocardial apoptosis plays an important role in myocardial ischemia/reperfusion (I/R) injury. Activation of PI3K/Akt signaling protects the myocardium from I/R injury. This study investigated the role of miR-214 in hypoxia/reoxygenation (H/R)-induced cell damage in vitro and myocardial I/R injury in vivo.

METHODS AND RESULTS

H9C2 cardiomyoblasts were transfected with lentivirus expressing miR-214 (LmiR-214) or lentivirus expressing scrambled miR-control (LmiR-control) respectively, to establish cell lines of LmiR-214 and LmiR-control. The cells were subjected to hypoxia for 4 h followed by reoxygenation for 24 h. Transfection of LmiR-214 suppresses PTEN expression, significantly increases the levels of Akt phosphorylation, markedly attenuates LDH release, and enhances the viability of the cells subjected to H/R. In vivo transfection of mouse hearts with LmiR-214 significantly attenuates I/R induced cardiac dysfunction and reduces I/R-induced myocardial infarct size. LmiR-214 transfection significantly attenuates I/R-induced myocardial apoptosis and caspase-3/7 and caspase-8 activity. Increased expression of miR-214 by transfection of LmiR-214 suppresses PTEN expression, increases the levels of phosphorylated Akt, represses Bim1 expression and induces Bad phosphorylation in the myocardium. In addition, in vitro data shows transfection of miR-214 mimics to H9C2 cells suppresses the expression and translocation of Bim1 from cytosol to mitochondria and induces Bad phosphorylation.

CONCLUSIONS

Our in vitro and in vivo data suggests that miR-214 protects cells from H/R induced damage and attenuates I/R induced myocardial injury. The mechanisms involve activation of PI3K/Akt signaling by targeting PTEN expression, induction of Bad phosphorylation, and suppression of Bim1 expression, resulting in decreases in I/R-induced myocardial apoptosis.

Plasma exosomes induced by remote ischaemic preconditioning attenuate myocardial ischaemia/reperfusion injury by transferring miR-24

Remote ischaemic preconditioning (RIPC) is well known to protect the myocardium against ischaemia/reperfusion injury (IRI). Exosomes are small extracellular vesicles that have become the key mediators of intercellular communication. Various studies have confirmed that circulating exosomes mediate RIPC. However, the underlying mechanisms for RIPC-induced exosome-mediated cardioprotection remain elusive. In our study, we found that the expression level of miR-24 was higher in exosomes derived from the plasma of rats subjected to RIPC than in exosomes derived from the plasma of control rats in vivo. The rat plasma exosomes could be taken up by H9c2 cells. In addition, miR-24 was present in RIPC-induced exosomes and played a role in reducing oxidative stress-mediated injury and decreasing apoptosis by downregulating Bim expression in H₂O₂-treated H9c2 cells in vitro. In vivo, miR-24 in RIPC-induced exosomes reduced cardiomyocyte apoptosis, attenuated the infarct size and improved heart function. Furthermore, the apoptosis-reducing effect of miR-24 was counteracted by miR-24 antagomirs or inhibitors both in vitro and in vivo. Therefore, we provided evidence that RIPC-induced exosomes could reduce apoptosis by transferring miR-24 in a paracrine manner and that miR-24 in the exosomes plays a central role in mediating the protective effects of RIPC.

LncRNA ZFAS1 as a SERCA2a Inhibitor to Cause Intracellular Ca2+ Overload and Contractile Dysfunction in a Mouse Model of Myocardial Infarction

RATIONALE

Ca²⁺ homeostasis-a critical determinant of cardiac contractile function-is critically regulated by SERCA2a (sarcoplasmic reticulum Ca²⁺-ATPase 2a). Our previous study has identified ZFAS1 as a new lncRNA biomarker of acute myocardial infarction (MI).

OBJECTIVE

To evaluate the effects of ZFAS1 on SERCA2a and the associated Ca²⁺ homeostasis and cardiac contractile function in the setting of MI.

METHODS AND RESULTS

ZFAS1 expression was robustly increased in cytoplasm and sarcoplasmic reticulum in a mouse model of MI and a cellular model of hypoxia. Knockdown of endogenous ZFAS1 by virus-mediated silencing shRNA partially abrogated the ischemia-induced contractile dysfunction. Overexpression of ZFAS1 in otherwise normal mice created similar impairment of cardiac function as that observed in MI mice. Moreover, at the cellular level, ZFAS1 overexpression weakened the contractility of cardiac muscles. At the subcellular level, ZFAS1 deleteriously altered the Ca²⁺ transient leading to intracellular Ca²⁺ overload in cardiomyocytes. At the molecular level, ZFAS1 was found to directly bind SERCA2a protein and to limit its activity, as well as to repress its expression. The effects of ZFAS1 were readily reversible on knockdown of this lncRNA. Notably, a sequence domain of ZFAS1 gene that is conserved across species mimicked the effects of the full-length ZFAS1. Mutation of this domain or application of an antisense fragment to this conserved region efficiently canceled out the deleterious actions of ZFAS1. ZFAS1 had no significant effects on other Ca²⁺-handling regulatory proteins.

CONCLUSIONS

ZFAS1 is an endogenous SERCA2a inhibitor, acting by binding to SERCA2a protein to limit its intracellular level and inhibit its activity, and a contributor to the impairment of cardiac contractile function in MI. Therefore, anti-ZFAS1 might be considered as a new therapeutic strategy for preserving SERCA2a activity and cardiac function under pathological conditions of the heart.

Targeting EZH1 and EZH2 contributes to the suppression of fibrosis-associated genes by miR-214-3p in cardiac myofibroblasts

The role of microRNA-214-3p (miR-214-3p) in cardiac fibrosis was not well illustrated. The present study aimed to investigate the expression and potential target of miR-214-3p in angiotensin II (Ang-II)-induced cardiac fibrosis. MiR-214-3p was markedly decreased in the fibrotic myocardium of a mouse Ang-II infusion model, but was upregulated in Ang-II-treated mouse myofibroblasts. Cardiac fibrosis was shown attenuated in Ang-II-infused mice received tail vein injection of miR-214-3p agomir. Consistently, miR-214-3p inhibited the expression of Col1a1 and Col3a1 in mouse myofibroblasts in vitro. MiR-214-3p could bind the 3'-UTRs of enhancer of zeste homolog 1 (EZH1) and -2, and suppressed EZH1 and -2 expressions at the transcriptional level. Functionally, miR-214-3p mimic, in parallel to EZH1 siRNA and EZH2 siRNA, could enhance peroxisome proliferator-activated receptor-γ (PPAR-γ) expression and inhibited the expression of Col1a1 and Col3a1 in myofibroblasts. In addition, enforced expression of EZH1 and -2, and knockdown of PPAR-γ resulted in the increase of Col1a1 and Col3a1 in myofibroblasts. Moreover, the NF-κB signal pathway was verified to mediate Ang-II-induced miR-214-3p expression in myofibroblasts. Taken together, our results revealed that EZH1 and -2 were novel targets of miR-214-3p, and miR-214-3p might be one potential miRNA for the prevention of cardiac fibrosis.

MiR-499-5p protects cardiomyocytes against ischaemic injury via anti-apoptosis by targeting PDCD4

Recent studies have reported that miRNAs might play critical roles in acute myocardial infarction (AMI). The objective of this study is to investigate the role of miR-499-5p in AMI and its potential molecular mechanisms. The expression level of MiR-499-5p was remarkably decreased in the infarcted myocardial tissues and in the cultured neonatal rat cardiomyocytes induced by hypoxia. Overexpression or knockdown of miR-499-5p decreased or increased the apoptotic rates of cultured cardiomyocytes in vitro. In addition, ectopic overexpression of miR-499-5p in the rat AMI models with agomir reduced the myocardial infarct size through decreasing the cardiomyocytes apoptosis in the infarcted area of the rat hearts. PDCD4 (programmed cell death 4) was verified as a direct target of miR-499-5p by luciferase report assay, and ectopic overexpression or inhibition of miR-499-5p could inhibit or increase the PDCD4 expression at both the mRNA and protein levels. Furthermore, we found that ectopic overexpression of PDCD4 without miR-499-5p binding sites reversed miR-499-5p-mediated cardiomyocytes apoptosis. Together, these findings revealed the role of miR-499-5p in protecting the cardiomyocytes against apoptosis induced by AMI via its direct target PDCD4, which providing evidence for the miR-499-5p/PDCD4 pathway as a potential therapeutic target for patients with AMI.

Hypoxia-induced activation of Twist/miR-214/E-cadherin axis promotes renal tubular epithelial cell mesenchymal transition and renal fibrosis

The epithelial-to-mesenchymal transition (EMT) induced by chronic hypoxia is one of the critical causes of renal fibrosis. Previous work reported that the transcription factors Twist plays an important role in hypoxia-induced EMT and renal fibrosis. Recent evidence indicates that miR-214 was regulated by Twist in many fibrotic diseases, but their role in hypoxia-induced EMT and renal fibrosis remains unknown. Here, we found that hypoxia significantly upregulated the expression of miR-214-3p in HK-2 cells, unilateral ureteral obstruction (UUO) nephropathy and patients with chronic kidney disease. Knockdown of miR-214-3p reversed the EMT of renal tubular epithelial cells (TECs) and alleviated fibrosis in the UUO mouse in vivo, while the overexpression of miR-214-3p promoted EMT phenotype and expression of fibrotic factors in TECs under hypoxic condition. In addition, Twist was also observed increased gradually with the prolongation of hypoxia, and it positively correlated with the expression of miR-214-3p in HK-2 cells transfected with Twist-overexpression or Twist-siRNA plasmid. Moreover, miR-214-3p negatively regulated the expression of epithelial cadherin (E-cadherin) by binding the E-cadherin 3' UTR under hypoxic condition. Overall, hypoxia-induced activation of Twist/miR-214/E-cadherin axis is involved in the EMT of TECs, and anti-miR-214 may be an attractive strategy to ameliorate the progression of renal fibrosis.