Carvedilol-responsive microRNAs, miR-199a-3p and -214 protect cardiomyocytes from simulated ischemia-reperfusion injury

Significance of non-coding circular RNAs and micro RNAs in the pathogenesis of cardiovascular diseases

Heart failure, coronary artery disease and myocardial infarction are the most prominent cardiovascular diseases contributing significantly to death worldwide. In the majority of situations, except for surgical interventions and transplantation, there are no reliable therapeutic approaches available to address these health problem. Despite several advances that led to the development of biomarkers and therapies based on the renin–angiotensin system, adrenergic pathways, etc, more definitive and consistent biomarkers and specific target based molecular therapies are still being sought. Recent advances in the field of genomic research has helped in identifying non-coding RNAs, including circular RNAs, piRNAs, micro RNAs, and long non-coding RNAs, that play a significant role in the regulation of gene expression and function and have direct impact on pathophysiological mechanisms. This new knowledge is currently being explored with much hope for the development of novel treatments and biomarkers. Circular RNAs and micro RNAs have been described in myocardium and aortic valves and were shown to be involved in the regulation of pathophysiological processes that potentially contribute to cardiovascular diseases. Approximately 32 000 human exonic circular RNAs have been catalogued and their functions are still being ascertained. In the heart, circular RNAs were shown to bind micro RNAs in a specific manner and regulate the expression of transcription factors and stress response genes, and expression of these non-coding RNAs were found to change in conditions such as cardiac hypertrophy, heart failure and cardiac remodelling, reflecting their significance as diagnostic and prognostic biomarkers. In this review, we address the present state of understanding on the biogenesis, regulation and pathophysiological roles of micro and circular RNAs in cardiovascular diseases, and on the potential future perspectives on their use as biomarkers and therapeutic agents.

miR-145 regulates the proliferation and apoptosis of Y79 human retinoblastoma cells by targeting IGF-1R

PURPOSE

To investigate the effect of miR-145 on the proliferation and apoptosis of human retinoblastoma Y79 cells and to explore the underlying mechanism.

METHOD

The Y79 cells were transfected by miR-145 mimics and IGF-1R siRNA with lipofection, respectively. The expression of miR-145 or IGF-1R was detected after transfection by real time-PCR. Cell proliferation inhibition was measured by Cell Counting Kit-8 (CCK-8) assay. Flow cytometry was used to examine cell cycles. Apoptosis was detected by Annexin/PI double immunofluorescence and flow cytometer. The interaction between miR-145 and IGF-1R was tested by luciferase activity measurement.

RESULTS

The expression of miR-145 in the miR-145 mimics group was significantly increased (P<0.05). The proliferation inhibition rate was higher in the miR-145 mimics group (P<0.01). The results of immunofluorescence and flow cytometry showed that ratios of Annexin or Annexin/PI double positive were increased in the miR-145 mimics group (P<0.05). The OD value of proliferation inhibition was lower in the IGF-1R siRNA group (P<0.05). The ratios of Annexin or Annexin/PI double positive were higher in the IGF-1R siRNA group (P<0.05). Luciferase activity was reduced in miR-145 mimics group (P<0.01).

CONCLUSION

miR-145 inhibited proliferation and induced apoptosis in Y79 cells. Lower expression of IGF-1R suppressed the proliferation of Y79 cells. miR-145 restrained the proliferation of human retinoblastoma Y79 cells by down-regulating the expression of IGF-1R.

Designer Approaches for G Protein-Coupled Receptor Modulation for Cardiovascular Disease

The new horizon for cardiac therapy may lie beneath the surface, with the downstream mediators of G protein–coupled receptor (GPCR) activity. Targeted approaches have shown that receptor activation may be biased toward signaling through G proteins or through GPCR kinases (GRKs) and β-arrestins, with divergent functional outcomes. In addition to these canonical roles, numerous noncanonical activities of GRKs and β-arrestins have been demonstrated to modulate GPCR signaling at all levels of receptor activation and regulation. Further, research continues to identify novel GRK/effector and β-arrestin/effector complexes with distinct impacts on cardiac function in the normal heart and the diseased heart. Coupled with the identification of once orphan receptors and endogenous ligands with beneficial cardiovascular effects, this expands the repertoire of GPCR targets. Together, this research highlights the potential for focused therapeutic activation of beneficial pathways, with simultaneous exclusion or inhibition of detrimental signaling, and represents a new wave of therapeutic development.

MiR-320 regulates cardiomyocyte apoptosis induced by ischemia-reperfusion injury by targeting AKIP1

Background

MicroRNAs play important roles in regulation of the cardiovascular system. The purpose of this study was to investigate microRNA-320 (miR-320) expression in myocardial ischemia-reperfusion (I/R) injury and the roles of miR-320 in cardiomyocyte apoptosis by targeting AKIP1 (A kinase interacting protein 1).

Methods

The level of miR-320 was detected using quantitative real-time polymerase chain reaction (qRT-PCR), and cardiomyocyte apoptosis was detected via terminal dUTP nick end-labeling assay. Cardiomyocyte apoptosis and the mitochondrial membrane potential were evaluated via flow cytometry. Bioinformatics tools were used to identify the target gene of miR-320. The expression levels of AKIP1 mRNA and protein were detected via qRT-PCR and Western blot, respectively.

Results

Both the level of miR-320 and the rate of cardiomyocyte apoptosis were substantially higher in the I/R group and H9c2 cells subjected to H/R than in the corresponding controls. Overexpression of miR-320 significantly promoted cardiomyocyte apoptosis and increased the loss of the mitochondrial membrane potential, whereas downregulation of miR-320 had an opposite effect. Luciferase reporter assay showed that miR-320 directly targets AKIP1. Moreover, knock down and overexpression of AKIP1 had similar effects on the H9c2 cells subjected to H/R.

Conclusions

miR-320 plays an important role in regulating cardiomyocyte apoptosis induced by I/R injury by targeting AKIP1 and inducing the mitochondrial apoptotic pathway.

Carvedilol Prevents Redox Inactivation of Cardiomyocyte Β1-Adrenergic Receptors

The mechanism that leads to a decrease in β₁-adrenergic receptor (β₁AR) expression in the failing heart remains uncertain. This study shows that cardiomyocyte β₁AR expression and isoproterenol responsiveness decrease in response to oxidative stress. Studies of mechanisms show that the redox-dependent decrease in β₁AR expression is uniquely prevented by carvedilol and not other βAR ligands. Carvedilol also promotes the accumulation of N-terminally truncated β₁ARs that confer protection against doxorubicin-induced apoptosis in association with activation of protein kinase B. The redox-induced molecular controls for cardiomyocyte β₁ARs and pharmacologic properties of carvedilol identified in this study have important clinical and therapeutic implications.

Reduced expression of microRNA-199a-3p is associated with vascular endothelial cell injury induced by type 2 diabetes mellitus

The aim of the present study was to investigate the function and mechanism of action of microRNA (miRNA or miR)-199a-3p in vascular endothelial cell injury induced by type 2 diabetes mellitus (T2DM). A total of 36 patients with T2DM (26 males and 10 females; mean age, 52.5±7.0 years) and 20 healthy subjects (10 males and 10 females; mean age, 55.6±4.5 years) were included in the present study. Peripheral blood samples were obtained from all participants and total RNA was extracted Reverse transcription-quantitative polymerase chain reaction was performed to determine the expression of miR-199a-3p. Following the transfection of human umbilical vein endothelial cells (HUVECs) with a negative control (NC) miRNA or miR-199a-3p mimics, cell proliferation was assessed using a Cell Counting kit-8 assay. Cell migration was investigated using Transwell assays and flow cytometry was performed to detect the apoptosis of HUVECs. HUVECs were infected with Ad-GFP-LC3B and laser-scanning confocal microscopy was performed to observe autophagosomes in HUVECs. Western blotting was used to measure the expression of proteins associated with autophagy and the phosphatidylinositol 3-kinase (PI3K)/protein kinase B (AKT)/nuclear factor (NF)-κB signaling pathway. MiR-199a-3p was downregulated in peripheral blood from patients with T2DM compared with healthy subjects. Transfection with miR-199a-3p mimics promoted the proliferation and migration of HUVECs. However, miR-199a-3p overexpression inhibited the apoptosis of HUVECs. MiR-199a-3p facilitated HUVEC autophagy by affecting autophagy-associated signaling pathways. Furthermore, miR-199a-3p regulated the biological functions of HUVECs via the PI3K/AKT/NF-κB signaling pathway. The results of the present study suggest that miR-199a-3p expression was reduced in patients with T2DM compared with healthy subjects and may be associated with vascular endothelial cell injury. In addition, miR-199a-3p promoted the proliferation, migration and autophagy of HUVECs, potentially by regulating the PI3K/AKT/NF-κB signaling pathway. Therefore, miR-199a-3p may function as protector of vascular endothelia.

Circular noncoding RNAs as potential therapies and circulating biomarkers for cardiovascular diseases

Recent advancements in genome-wide analyses and RNA-sequencing technologies led to the discovery of small noncoding RNAs, such as microRNAs (miRs), as well as both linear long noncoding RNAs (lncRNAs) and circular long noncoding RNAs (circRNAs). The importance of miRs and lncRNAs in the treatment, prognosis and diagnosis of cardiovascular diseases (CVDs) has been extensively reported. We also previously reviewed their implications in therapies and as biomarkers for CVDs. More recently, circRNAs have also emerged as important regulators in CVDs. CircRNAs are circular genome products that are generated by back splicing of specific regions of pre-messenger RNAs (pre-mRNAs). Growing interest in circRNAs led to the discovery of a wide array of their pathophysiological functions. CircRNAs have been shown to be key regulators of CVDs such as myocardial infarction, atherosclerosis, cardiomyopathy and cardiac fibrosis. Accordingly, circRNAs have been recently proposed as potential therapeutic targets and biomarkers for CVDs. In this review, we summarize the current state of the literature on circRNAs, starting with their biogenesis and global mechanisms of actions. We then provide a synopsis of their involvement in various CVDs. Lastly, we emphasize the great potential of circRNAs as biomarkers for the early detection of CVDs, and discuss several patents and recent papers that highlight the utilization of circRNAs as promising biomarkers.

G Protein-Coupled Receptor Signaling Through β-Arrestin-Dependent Mechanisms

β-arrestin1 (or arrestin2) and β-arrestin2 (or arrestin3) are ubiquitously expressed cytosolic adaptor proteins that were originally discovered for their inhibitory role in G protein-coupled receptor (GPCR) signaling through heterotrimeric G proteins. However, further biochemical characterization revealed that β-arrestins do not just "block" the activated GPCRs, but trigger endocytosis and kinase activation leading to specific signaling pathways that can be localized on endosomes. The signaling pathways initiated by β-arrestins were also found to be independent of G protein activation by GPCRs. The discovery of ligands that blocked G protein activation but promoted β-arrestin binding, or vice-versa, suggested the exciting possibility of selectively activating intracellular signaling pathways. In addition, it is becoming increasingly evident that β-arrestin-dependent signaling is extremely diverse and provokes distinct cellular responses through different GPCRs even when the same effector kinase is involved. In this review, we summarize various signaling pathways mediated by β-arrestins and highlight the physiologic effects of β-arrestin-dependent signaling.

Parallel Genome-wide Profiling of Coding and Non-coding RNAs to Identify Novel Regulatory Elements in Embryonic and Maturated Heart

Heart development is a complex process, tightly regulated by numerous molecular mechanisms. Key components of the regulatory network underlying heart development are transcription factors (TFs) and microRNAs (miRNAs), yet limited investigation of the role of miRNAs in heart development has taken place. Here, we report the first parallel genome-wide profiling of polyadenylated RNAs and miRNAs in a developing murine heart. These data enable us to identify dynamic activation or repression of numerous biological processes and signaling pathways. More than 200 miRNAs and 25 long non-coding RNAs were differentially expressed during embryonic heart development compared to the mature heart; most of these had not been previously associated with cardiogenesis. Integrative analysis of expression data and potential regulatory interactions suggested 28 miRNAs as novel regulators of embryonic heart development, representing a considerable expansion of the current repertoire of known cardiac miRNAs. To facilitate follow-up investigations, we constructed HeartMiR (http://heartmir.sysbiolab.eu), an open access database and interactive visualization tool for the study of gene regulation by miRNAs during heart development.

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.

Guidelines for experimental models of myocardial ischemia and infarction

Myocardial infarction is a prevalent major cardiovascular event that arises from myocardial ischemia with or without reperfusion, and basic and translational research is needed to better understand its underlying mechanisms and consequences for cardiac structure and function. Ischemia underlies a broad range of clinical scenarios ranging from angina to hibernation to permanent occlusion, and while reperfusion is mandatory for salvage from ischemic injury, reperfusion also inflicts injury on its own. In this consensus statement, we present recommendations for animal models of myocardial ischemia and infarction. With increasing awareness of the need for rigor and reproducibility in designing and performing scientific research to ensure validation of results, the goal of this review is to provide best practice information regarding myocardial ischemia-reperfusion and infarction models.

Listen to this article’s corresponding podcast at ajpheart.podbean.com/e/guidelines-for-experimental-models-of-myocardial-ischemia-and-infarction/.

Dioxygen and Metabolism; Dangerous Liaisons in Cardiac Function and Disease

The heart must consume a significant amount of energy to sustain its contractile activity. Although the fuel demands are huge, the stock remains very low. Thus, in order to supply its daily needs, the heart must have amazing adaptive abilities, which are dependent on dioxygen availability. However, in myriad cardiovascular diseases, “fuel” depletion and hypoxia are common features, leading cardiomyocytes to favor low-dioxygen-consuming glycolysis rather than oxidation of fatty acids. This metabolic switch makes it challenging to distinguish causes from consequences in cardiac pathologies. Finally, despite the progress achieved in the past few decades, medical treatments have not improved substantially, either. In such a situation, it seems clear that much remains to be learned about cardiac diseases. Therefore, in this review, we will discuss how reconciling dioxygen availability and cardiac metabolic adaptations may contribute to develop full and innovative strategies from bench to bedside.

A carvedilol-responsive microRNA, miR-125b-5p protects the heart from acute myocardial infarction by repressing pro-apoptotic bak1 and klf13 in cardiomyocytes

BACKGROUND

Cardiac injury is accompanied by dynamic changes in the expression of microRNAs (miRs), small non-coding RNAs that post-transcriptionally regulate target genes. MiR-125b-5p is downregulated in patients with end-stage dilated and ischemic cardiomyopathy, and has been proposed as a biomarker of heart failure. We previously reported that the β-blocker carvedilol promotes cardioprotection via β-arrestin-biased agonism of β₁-adrenergic receptor while stimulating miR-125b-5p processing in the mouse heart. We hypothesize that β₁-adrenergic receptor/β-arrestin1-responsive miR-125b-5p confers the improvement of cardiac function and structure after acute myocardial infarction.

METHODS AND RESULTS

Using cultured cardiomyocyte (CM) and in vivo approaches, we show that miR-125b-5p is an ischemic stress-responsive protector against CM apoptosis. CMs lacking miR-125b-5p exhibit increased susceptibility to stress-induced apoptosis, while CMs overexpressing miR-125b-5p have increased phospho-AKT pro-survival signaling. Moreover, we demonstrate that loss-of-function of miR-125b-5p in the mouse heart causes abnormalities in cardiac structure and function after acute myocardial infarction. Mechanistically, the improvement of cardiac function and structure elicited by miR-125b-5p is in part attributed to repression of the pro-apoptotic genes Bak1 and Klf13 in CMs.

CONCLUSIONS

In conclusion, these findings reveal a pivotal role for miR-125b-5p in regulating CM survival during acute myocardial infarction.

Attenuation of miR-34a protects cardiomyocytes against hypoxic stress through maintenance of glycolysis

MiRNAs are a class of endogenous, short, single-stranded, non-coding RNAs, which are tightly linked to cardiac disorders such as myocardial ischemia/reperfusion (I/R) injury. MiR-34a is known to be involved in the hypoxia-induced cardiomyocytes apoptosis. However, the molecular mechanisms are unclear. In the present study, we demonstrate that under low glucose supply, rat cardiomyocytes are susceptible to hypoxia. Under short-time hypoxia, cellular glucose uptake and lactate product are induced but under long-time hypoxia, the cellular glucose metabolism is suppressed. Interestingly, an adaptive up-regulation of miR-34a by long-time hypoxia was observed both in vitro and in vivo, leading to suppression of glycolysis in cardiomyocytes. We identified lactate dehydrogenase-A (LDHA) as a direct target of miR-34a, which binds to the 3′-UTR region of LDHA mRNA in cardiomyocytes. Moreover, inhibition of miR-34a attenuated hypoxia-induced cardiomyocytes dysfunction through restoration of glycolysis. The present study illustrates roles of miR-34a in the hypoxia-induced cardiomyocytes dysfunction and proposes restoration of glycolysis of dysfunctional cardiomyocytes by inhibiting miR-34a during I/R might be an effectively therapeutic approach against I/R injury.

The role of miR-214 in cardiovascular diseases

Cardiovascular disease (CVD) is the leading cause of death throughout the world. The increase in new patients every year leads to a demand for the identification of valid and novel prognostic and diagnostic biomarkers for the prevention and treatment of cardiovascular diseases. MicroRNAs (miRNAs) are critical endogenous small noncoding RNAs that negatively modulate gene expression by regulating its translation. miRNAs are implicated in most physiological processes of the heart and in the pathological progression of cardiovascular diseases. miR-214 is a deregulated miRNA in many pathological conditions, and it contributes to the pathogenesis of multiple human disorders, including cancer and cardiovascular diseases. miR-214 has dual functions in different cardiac pathological circumstances. However, it is considered as a promising marker in the prognosis, diagnosis and treatment of cardiovascular diseases. In this review, we discuss the role of miR-214 in various cardiac disease conditions, including ischaemic heart diseases, cardiac hypertrophy, pulmonary arterial hypertension (PAH), angiogenesis following vascular injury and heart failure.

Insulin and β Adrenergic Receptor Signaling: Crosstalk in Heart

Recent advances show that insulin may affect β adrenergic receptor (βAR) signaling in the heart to modulate cardiac function in clinically relevant states, such as diabetes mellitus (DM) and heart failure (HF). Conversely, activation of βAR regulates cardiac glucose uptake and promotes insulin resistance (IR) in HF. Here, we discuss the recent characterization of the interaction between the cardiac insulin receptor (InsR) and βAR in the myocardium, in which insulin stimulation crosstalks with cardiac βAR via InsR substrate (IRS)-dependent and G-protein receptor kinase 2 (GRK2)-mediated phosphorylation of β₂AR. The insulin-induced phosphorylation promotes β₂AR coupling to G_i and expression of phosphodiesterase 4D, which both inhibit cardiac adrenergic signaling and compromise cardiac contractile function. These recent developments could support new approaches for the effective prevention or treatment of obesity- or DM-related HF.