Regulation of cardiac and renal ischemia-reperfusion injury by microRNAs

Small RNA-big impact: exosomal miRNAs in mitochondrial dysfunction in various diseases

Mitochondria are multitasking organelles involved in maintaining the cell homoeostasis. Beyond its well-established role in cellular bioenergetics, mitochondria also function as signal organelles to propagate various cellular outcomes. However, mitochondria have a self-destructive arsenal of factors driving the development of diseases caused by mitochondrial dysfunction. Extracellular vesicles (EVs), a heterogeneous group of membranous nano-sized vesicles, are present in a variety of bodily fluids. EVs serve as mediators for intercellular interaction. Exosomes are a class of small EVs (30-100 nm) released by most cells. Exosomes carry various cargo including microRNAs (miRNAs), a class of short noncoding RNAs. Recent studies have closely associated exosomal miRNAs with various human diseases, including diseases caused by mitochondrial dysfunction, which are a group of complex multifactorial diseases and have not been comprehensively described. In this review, we first briefly introduce the characteristics of EVs. Then, we focus on possible mechanisms regarding exosome-mitochondria interaction through integrating signalling networks. Moreover, we summarize recent advances in the knowledge of the role of exosomal miRNAs in various diseases, describing how mitochondria are changed in disease status. Finally, we propose future research directions to provide a novel therapeutic strategy that could slow the disease progress mediated by mitochondrial dysfunction.

The mechanism by which miR-494-3p regulates PGC1-α-mediated inhibition of mitophagy in cardiomyocytes and alleviation of myocardial ischemia-reperfusion injury

OBJECTIVE

The purpose of this study was to explore whether miR-494-3p inhibits the occurrence of mitochondrial autophagy in cardiomyocytes by inhibiting the expression of PGC1-α and to supplement the theoretical basis for the role of autophagy in cardiac injury induced by hypoxia/reperfusion (H/R).

METHODS

The expression of miR-494-3p was detected by RT‒qPCR, and the expression of PGC1-α, autophagy-related proteins (LC3, Beclin 1), apoptosis-related proteins (Bax and Bcl-2), PINK1/Parkin signaling pathway-related proteins (PINK1, Parkin) and mitochondrial change-related proteins (Mfn1, Mfn2, OPA1) was detected by Western blotting. The changes in mitochondrial membrane potential were detected by JC-1 staining (ΔΨm). The formation of autophagosomes was observed by transmission electron microscopy. Cell proliferation activity was detected by CCK-8, and cell apoptosis was detected by flow cytometry. A dual-luciferase gene reporter assay identified a targeted binding site between miR-494-3p and PGC1-α.

RESULTS

The results showed that miR-494-3p and PGC1-α were differentially expressed in H/R cardiomyocytes; that is, the expression of miR-494-3p was downregulated, and the expression of PGC1-α was upregulated. In addition, mitochondrial autophagy occurred in H/R cardiomyocytes. That is, LC3-II/LC3-I, Beclin 1, PINK1, and Parkin expression was upregulated, Mfn1, Mfn2, and OPA1 expression was downregulated, and the mitochondrial membrane potential was decreased. The transfection of miR-494-3p mimic can significantly improve the cell proliferation activity of cardiomyocytes and inhibit the occurrence of cardiomyocyte apoptosis and autophagy, while the transfection of miR-494-3p inhibitor has the opposite result. After transfection of the miR-494-3p mimic, treatment with autophagy inhibitors and activators changed the effects of miR-494-3p on cardiomyocyte proliferation and apoptosis. At the same time, the overexpression of PGC1-α reversed the promoting effect of miR-494-3p on cardiomyocyte proliferation and the inhibitory effect on apoptosis and autophagy.

CONCLUSION

MiR-494-3p can target and negatively regulate the expression of PGC1-α to inhibit mitophagy in cardiomyocytes.

Liquid Biopsies Poorly miRror Renal Ischemia-Reperfusion Injury

Acute kidney injury (AKI) is the rapid reduction in renal function. It is often difficult to detect at an early stage. Biofluid microRNAs (miRs) have been proposed as novel biomarkers due to their regulatory role in renal pathophysiology. The goal of this study was to determine the overlap in AKI miRNA profiles in the renal cortex, urine, and plasma samples collected from a rat model of ischemia-reperfusion (IR)-induced AKI. Bilateral renal ischemia was induced by clamping the renal pedicles for 30 min, followed by reperfusion. Urine was then collected over 24 h, followed by terminal blood and tissue collection for small RNA profiling. Differentially expressed (IR vs. sham) miRs within the urine and renal cortex sample types demonstrated a strong correlation in normalized abundance regardless of injury (IR and sham: R2 = 0.8710 and 0.9716, respectively). Relatively few miRs were differentially expressed in multiple samples. Further, there were no differentially expressed miRs with clinically relevant sequence conservation common between renal cortex and urine samples. This project highlights the need for a comprehensive analysis of potential miR biomarkers, including analysis of pathological tissues and biofluids, with the goal of identifying the cellular origin of altered miRs. Analysis at earlier timepoints is needed to further evaluate clinical potential.

MiR-144-5p/CCL12 Signaling Axis Modulates Ischemic Preconditioning-Mediated Cardio-protection by Reducing Cell Viability, Enhancing Cell Apoptosis, Fibrosis, and Pyroptosis

Ischemic postconditioning (IPost) represents short periods of nonlethal ischemia-reperfusion performed at the onset of reperfusion. Studies have shown that IPost involves various biological processes such as cell proliferation, apoptosis, and pyroptosis and can activate complex signaling pathways. CCL12 is a critical mediator in the inflammatory process after tissue injury. In the present study, we examined the potential actions of CCL12-mediated signaling pathways in cardioprotection after IPost using a cardiomyocyte model. By applying the bioinformatics analysis, we found that CCL12 was upregulated in the rat heart tissues after I/R injury, and the expression level of CCL12 was restored in rats with IPost. The in vitro studies showed that CCL12 and CCR2 expression levels were upregulated in the hypoxia/reoxygenation (H/R)-induced H9C2 cells, which was attenuated in the H/R + hypoxia post-conditioning (PostC) group. The functional assays showed that H/R treatment reduced cell viability, increased cell apoptosis, and promoted fibrosis and pyroptosis of H9C2 cells, which was attenuated in the H/R + PostC group. Overexpression of CCL12 impaired the protective action of hypoxia post-conditioning in the H9C2 cells. Further mechanistic studies showed that miR-144-5p could directly target the 3' untranslated region of CCL12. Overexpression of miR-144-5p markedly repressed the expression levels of CCL12 and CCR2 in H9C2 cells, while miR-144-5p inhibition had the opposite effects. Furthermore, the inhibition of miR-144-5p reduced the cell viability, increased cell apoptosis, and enhanced fibrosis and pyroptosis of H9C2 cells after H/R or H/R + PostC treatment. In conclusion, CCL12 was downregulated in cardiomyocytes following ischemic postconditioning, and CCL12 overexpression impaired the cardioprotective actions of ischemic postconditioning by reducing cell viability, enhancing cell apoptosis, fibrosis, and pyroptosis. Further mechanistic evidence revealed that CCL12 was a direct target of miR-144-5p, and miR-144-5p/CCL12/CCR2 signaling may represent a critical pathway in mediating the cardioprotective effects of ischemic postconditioning.

GATA2 promotes oxidative stress to aggravate renal ischemia-reperfusion injury by up-regulating Redd1

Renal ischemia-reperfusion injury (RIRI) is a common pathophysiological process, and it is also an important cause of acute renal failure. Therefore, finding an effective therapeutic target for RIRI is extremely urgent. In our study, we constructed hypoxia-reoxygenation (HR) model in vitro and a renal ischemia-reperfusion (IR) model in vivo. Elevated levels of serum creatinine (Cr), blood urea nitrogen (BUN) tumor necrosis factor-α (TNF-α), interleukin-6 (IL-6) and malondialdehyde (MDA) along with the decreased levels of superoxide dismutase (SOD) and glutathione (GSH) proved that kidney function was damaged after IR, and pathological changes of renal tissues were observed using HE staining and TUNEL staining. The protein of Redd1 expression level was detected to be upregulated after IR by western blot (WB). However, transfection of short hairpin RNA of Redd1 (sh-Redd1) alleviated the HR injury on LLC-PK1 cells, as evidenced by increased cell viability, proliferation and decreased cell apoptosis; additionally, the accumulation of ROS was inhibited. Sh-Redd1 also alleviated IR injury in the mouse model. Subsequently, GATA2 was proved to be upregulated in IR and HR models and was the transcription factor of Redd1. Knockdown of GATA2 efficiently mitigated the oxidative stress induced damages in vivo and in vitro, while these mitigations were reversed by transfection of Redd1 overexpression plasmid. In conclusion, our study clarified the possible underlying mechanism of protecting RIRI.

Inhibited HDAC3 or Elevated MicroRNA-494-3p Plays a Protective Role in Myocardial Ischemia-Reperfusion Injury via Suppression of BRD4

Increased histone deacetylase 3 (HDAC3) has been demonstrated to contribute to the pathogenesis of myocardial ischemia-reperfusion injury (MI/RI). Therefore, the goal of this study was to investigate how HDAC3 regulated MI/RI by mediating microRNA (miR)-494-3p/dromodomain-containing protein 4 (BRD4) axis. The MI/RI model was established by ligating the right anterior descending coronary artery. Cardiomyocytes from newborn mice were treated with hypoxia/reoxygenation (H/R). Gain-of-function and loss-of-function approaches were implemented to figure out the roles of miR-494-3p and HDAC3 in MI/RI. miR-494-3p, HDAC3, and BRD4 in myocardial tissues of mice with MI/RI and H/R-treated cardiomyocytes were detected. The relationships between miR-494-3p and HDAC3 and BRD4 were identified. Reduced miR-494-3p and upregulated HDAC3 and BRD4 exhibited in myocardial tissues of mice with MI/RI and H/R-treated cardiomyocytes. Inhibited HDAC3 or elevated miR-494-3p repressed the inflammation and apoptosis, improved cardiac function, and ameliorated myocardial injury in myocardial tissues of mice with MI/RI. Suppression of HDAC3 or elevation of miR-494-3p depressed inflammation and apoptosis and promoted cell viability of primary cardiomyocytes. miR-494-3p targeted BRD4. The study concludes that suppressed HDAC3 plays a protective role in MI/RI by upregulation of miR-494-3p and inhibition of BRD4, which could be helpful for MI/RI therapy.

The protective effects of topiramate on intestinal injury induced with infrarenal aortic occlusion via oxidative stress and apoptosis

Purpose: Prolonged surgical procedures and some clinical conditions such as surgeries of thoracoabdominal aorta, mesenteric ischemia, cardiopulmonary bypass, strangulated hernias and neonatal necrotizing enterocolitis may cause decreased perfusion and injury of relevant organs and tissues. After reperfusion, injuries may get worse, leading to ischemia-reperfusion (I/R) injury. Reperfusion following arterial clamping allows oxygen to ischemic tissues and produce injury by multiple mechanisms, including neutrophilic infiltration, intracellular adhesion molecules, and generation of reactive oxygen radicals. In this study with the analysis of SOD, MDA and Caspase-3 levels, we aimed to investigate the effect of topiramate on the outcome of I/R occured after abdominal aorta clamping on rats.Materials and Methods: Totaly 24 Sprague-Dawley male rats were randomly divided into three experimental groups; the control group (n = 8), I/R (n = 8) and I/R+ topiramate (n = 8). Topiramate (100 mg/kg/day); 50 mg/kg (single dose) was administered intraperitoneally after being diluted with saline 5 days before I/R.Results: The intestinal tissue of the ischemia group displayed hemorrhage, Crypts of Lieberkuhn degeneration, ulceration, vascular congestion and edematous fields as a result of aortic occlusion. We also observed that MDA levels and Caspase-3 positivity increased and SOD levels decreased in the small intestine. However, topiramate administration decreased Crypts of Lieberkuhn degeneration, ulceration, vascular congestion and edematous fields, Caspase-3 positivity, and MDA levels.Conclusion: Our findings suggest that topiramate is effective against aortic occlusion-induced intestinal injury by reducing oxidative stress and apoptosis.

SIRT3 as a potential therapeutic target for heart failure

Heart failure causes significant morbidity and mortality worldwide. The underlying mechanisms and pathological changes associated with heart failure are exceptionally complex. Despite recent advances in heart failure research, treatment outcomes remain poor. The sirtuin family member sirtuin-3 (SIRT3) is involved in several key biological processes, including ATP production, catabolism, and reactive oxygen species detoxification. In addition to its role in metabolism, SIRT3 regulates cell death and survival and has been implicated in the pathogenesis of cardiovascular diseases. Emerging evidence also shows that SIRT3 can protect cardiomyocytes from hypertrophy, ischemia-reperfusion injury, cardiac fibrosis, and impaired angiogenesis. In this review article, we summarize the recent advances in SIRT3 research and discuss the role of SIRT3 in heart failure. We also discuss the potential use of SIRT3 as a therapeutic target in heart failure.

Silence of Long Noncoding RNA SNHG14 Alleviates Ischemia/Reperfusion-Induced Acute Kidney Injury by Regulating miR-124-3p/MMP2 Axis

Purpose

Ample evidence has proved that lncRNAs are pivotal regulators in acute kidney injury (AKI). Here, we focus on the role and mechanism of lncRNA SNHG14 in ischemia/reperfusion- (I/R-) caused AKI.

Methods

I/R and hypoxia/reoxygenation (H/R) were applied to induce rats and HK-2 cells to establish AKI models in vivo and in vitro. Relative expression of SNHG14, miR-124-3p, and MMP2 was determined by qRT-PCR. HE staining was used to evaluate pathological changes in renal tissues, and acute tubular necrosis (ATN) score was calculated. Renal function was evaluated by measuring serum creatinine content and blood urea nitrogen content. Levels of IL-1β, IL-6, and TNF-α were measured by ELISA. Cell viability was examined by MTT assay. Oxidative stress was assessed by measuring SOD, MDA, and ROS levels. The target of SNHG14 or miR-124-3p was verified by DLR assay. Protein expression of MMP2 was examined by western blot.

Results

SNHG14 was boosted in renal tissues of I/R-stimulated rats and H/R-induced HK-2 cells, while miR-124-3p was diminished in H/R-stimulated HK-2 cells. Si-SNHG14 or miR-124-3p mimics repressed inflammation and oxidative stress and enhanced cell viability in H/R-stimulated HK-2 cells. Sh-SNHG14 mitigated I/R-induced AKI in rats. MiR-124-3p was targeted by SNHG14, and MMP2 was targeted by miR-124-3p. Inhibition of miR-124-3p or upregulation of MMP2 reversed inhibitory effects of SNHG14 silence on inflammation and oxidative stress as well as the promoting effect of SNHG14 silence on cell viability in H/R-induced HK-2 cells.

Conclusion

Knockdown of SNHG14 alleviated I/R-induced AKI by miR-124-3p-mediated downregulation of MMP2.

Non-coding RNAs and Ischemic Cardiovascular Diseases

The Ischemic Heart Disease (IHD) is considered a clinical condition characterized by myocardial ischemia causing an imbalance between myocardial blood supply and demand, leading to morbidity and mortality across the worldwide. Prompt diagnostic and prognostic represents key factors for the treatment and reduction of the mortality rate. Therefore, one of the newest frontiers in cardiovascular research is related to non-coding RNAs (ncRNAs), which prompted a huge interest in exploring ncRNAs candidates for utilization as potential therapeutic targets for diagnostic and prognostic and/or biomarkers in IHD. However, there are undoubtedly many more functional ncRNAs yet to be discovered and characterized. Here we will discuss our current knowledge and we will provide insight on the roles and effects elicited by some ncRNAs related to IHD.

The Role of Non-coding RNAs in Ischemic Myocardial Reperfusion Injury

MicroRNAs (miRNA) are non-coding RNAs that regulate gene expression in up to 90% of the human genome through interactions with messenger RNA (mRNA). The expression of miRNAs varies and changes in diseased and healthy states, including all stages of myocardial ischemia-reperfusion and subsequent ischemia-reperfusion injury (IRI). These changes in expression make miRNAs an attractive potential therapeutic target. Herein, we review the differences in miRNA expression prior to ischemia (including remote ischemic conditioning and ischemic pre-conditioning), the changes during ischemia-reperfusion, and the changes in miRNA expression after IRI, with an emphasis on inflammatory and fibrotic pathways. Additionally, we review the effects of manipulating the levels of certain miRNAs on changes in infarct size, inflammation, remodeling, angiogenesis, and cardiac function after either ischemia-reperfusion or permanent coronary ligation. Levels of target miRNA can be increased using molecular mimics ("agomirs"), or can be decreased by using "antagomirs" which are antisense molecules that act to bind and thus inactivate the target miRNA sequence. Other non-coding RNAs, including long non-coding RNAs and circular RNAs, also regulate gene expression and have a role in the regulation of IRI pathways. We review the mechanisms and downstream effects of the miRNAs that have been studied as therapy in both permanent coronary ligation and ischemia-reperfusion models.

miR-21, Mediator, and Potential Therapeutic Target in the Cardiorenal Syndrome

Oligonucleotide-based therapies are currently gaining attention as a new treatment option for relatively rare as well as common diseases such as cardiovascular disease. With the remarkable progression of new sequencing technologies, a further step towards personalized precision medicine to target a disease at a molecular level was taken. Such therapies may employ antisense oligonucleotides to modulate the expression of both protein coding and non-coding RNAs, such as microRNAs. The cardiorenal syndrome (CRS) is a complex and severe clinical condition where heart and renal dysfunction mutually affect one another. The underlying mechanisms remain largely unknown and current treatments of CRS are mainly supportive therapies which slow down the progression of the disease, but hardly improve the condition. The small non-coding RNA, microRNA-21 (miR-21), is dysregulated in various heart and kidney diseases and has been repeatedly suggested as therapeutic target for the treatment of CRS. Impressive preclinical results have been achieved by an antisense oligonucleotide-based therapy to effectively block the pro-fibrotic traits of miR-21. Since microRNA-mediated pathways are generally very well-conserved, there is considerable commercial interest with regards to clinical translation. In this review, we will summarize the role of miR-21 within the heart–kidney axis and discuss the advantages and pitfalls of miR-21 targeting therapeutic strategies in CRS.

MicroRNA 3113-5p is a novel marker for early cardiac ischemia/reperfusion injury

BACKGROUND

Ischemia/reperfusion (I/R) injury of heart is one of the major causes of acute cardiac injury, which may result in worsening or even loss of heart function. With novel microRNAs being evolutionarily discovered, numbers of them remained functionally unknown. We aimed to discover novel microRNAs with therapeutic or diagnostic potential in the setting of early cardiac I/R injury.

METHODS

Cardiac electrical activity, biochemical detection and histopathology analysis were performed to reveal early changes of cardiac I/R injury. A microRNA array was performed to screen differential microRNAs in the mouse model of cardiac I/R injury. The differentially expressed microRNAs were validated in cardiac tissues and in serum samples.

RESULTS

The abnormality in electrocardiogram and increases in serum cTnI levels suggested the successful establishment of cardiac I/R injury in mice. A total of 1882 microRNAs were identified, of which 11 were significantly down-regulated and 41 were significantly up-regulated at 3 h post reperfusion. microRNA 223-3p and microRNA 3113-5p were among the mostly altered microRNAs and were validated to be up-regulated within the early hours of I/R injury in heart tissues. In the circulating system, cTnI, a sensitive marker of cardiac injury, or microRNA 223-3p only increased within the first 6 h post I/R injury. However, microRNA 3113-5p stably increased in the serum, keeping an increase of 2.5-fold throughout the 24 h. In the human serum samples, microRNA 3113-5p was detected to be significantly upregulated as soon as 3 h after I/R stimuli and kept significantly higher levels within the 48 h.

CONCLUSION

This is the first study that reported the functional roles of microRNA 3113-5p in cardiovascular system. Our data suggested that cardiac microRNA 3113-5p might be a useful target for therapeutic purposes and circulating microRNA 3113-5p might serve as a stable marker for early diagnosis of cardiac I/R injury.

Multi-Omics Approach: New Potential Key Mechanisms Implicated in Cardiorenal Syndromes

Cardiorenal syndromes (CRS) include a scenario of clinical interactions characterized by the heart and kidney dysfunction. The crosstalk between cardiac and renal systems is clearly evidenced but not completely understood. Multi-factorial mechanisms leading to CRS do not involve only hemodynamic parameters. In fact, in recent works on organ crosstalk endothelial injury, the alteration of normal immunologic balance, cell death, inflammatory cascades, cell adhesion molecules, cytokine and chemokine overexpression, neutrophil migration, leukocyte trafficking, caspase-mediated induction of apoptotic mechanisms and oxidative stress has been demonstrated to induce distant organ dysfunction. Furthermore, new alternative mechanisms using the multi-omics approach may be implicated in the pathogenesis of cardiorenal crosstalk. The study of “omics” modifications in the setting of cardiovascular and renal disease represents an emerging area of research. Over the last years, indeed, many studies have elucidated the exact mechanisms involved in gene expression and regulation, cellular communication and organ crosstalk. In this review, we analyze epigenetics, gene expression, small non-coding RNAs, extracellular vesicles, proteomics, and metabolomics in the setting of CRS.

Pretreatment with Cholecalciferol Alleviates Renal Cellular Stress Response during Ischemia/Reperfusion-Induced Acute Kidney Injury

Background

Cellular stress is involved in ischemia/reperfusion- (I/R-) induced acute kidney injury (AKI). This study is aimed at investigating the effects of pretreatment with cholecalciferol on renal oxidative stress and endoplasmic reticulum (ER) stress during I/R-induced AKI.

Methods

I/R-induced AKI was established by cross-clamping renal pedicles for 90 minutes and then reperfusion. In the Chol + I/R group, mice were orally administered with three doses of cholecalciferol (25 μg/kg) at 1, 24, and 48 h before ischemia. Renal cellular stress and kidney injury were measured at different time points after reperfusion.

Results

I/R-induced AKI was alleviated in mice pretreated with cholecalciferol. In addition, I/R-induced renal cell apoptosis, as determined by TUNEL, was suppressed by cholecalciferol. Additional experiment showed that I/R-induced upregulation of renal GRP78 and CHOP was inhibited by cholecalciferol. I/R-induced renal IRE1α and eIF2α phosphorylation was attenuated by cholecalciferol. Moreover, I/R-induced renal GSH depletion, lipid peroxidation, and protein nitration were blocked in mice pretreated with cholecalciferol. I/R-induced upregulation of renal NADPH oxidases, such as p47phox, gp91phox, and nox4, was inhibited by cholecalciferol. I/R-induced upregulation of heme oxygenase- (HO-) 1, gshpx and gshrd, was attenuated in mice pretreated with cholecalciferol.

Conclusions

Pretreatment with cholecalciferol protects against I/R-induced AKI partially through suppressing renal cellular stress response.

LncRNA SNHG14 promotes inflammatory response induced by cerebral ischemia/reperfusion injury through regulating miR-136-5p /ROCK1

Recently, long non-coding RNAs (lncRNAs) are considered as critical regulators in pathogenesis progression of cerebral ischemia. In present study, lncRNA-small nucleolar RNA host gene 14 (SNHG14) was found upregulated in middle cerebral artery occlusion/reperfusion (MCAO/R) treated brain tissues and oxygen-glucose deprivation and reoxygenation (OGD/R) treated PC-12 cells. Interference of SNHG14 by shRNA vector enhanced neuron survival and suppressed inflammation in response to OGD/R insult. SNHG14 positively regulated the expression of Rho-associated coiled-coil-containing protein kinase 1 (ROCK1) via acting as a sponge of microRNA (miR)-136–5p. SNHG14 promoted neurological impairment and inflammatory response through elevating the expression of ROCK1 while decreasing miR-136–5p level in OGD/R induced damage. Collectively, we illustrated that SNHG14 could be a novel strategy for treatment ischemia stoke.

Total Flavonoids from Carya cathayensis Sarg. Leaves Alleviate H9c2 Cells Hypoxia/Reoxygenation Injury via Effects on miR-21 Expression, PTEN/Akt, and the Bcl-2/Bax Pathway

This study aimed to investigate whether the total flavonoids (TFs) from Carya cathayensis Sarg. leaves alleviate hypoxia/reoxygenation (H/R) injury in H9c2 cardiomyocytes and to explore potential mechanisms. H9c2 cells pretreated with TFs for 24h were exposed to H/R treatment. The results indicated that TFs significantly alleviate H/R injury, which include inhibiting apoptosis and enhancing antioxidant capacity. The protective effects of TFs resulted in higher expression of miR-21 in H/R-induced H9c2 cells than that of controls, which in turn upregulated Akt signaling activity via suppressing the expression of PTEN together with decreasing the ratio of Bax/Bcl-2, caspase3, and cleaved-caspase3 expression in H/R-induced H9c2 cells. Conversely, blocking miR-21 expression with miR-21 inhibitor effectively suppressed the protective effects of TFs against H/R-induced injury. Our study suggests that TFs can decrease cell apoptosis, which may be mediated by altering the expression of miR-21, PTEN/Akt, and Bcl/Bax.

MicroRNA-98 attenuates cardiac ischemia-reperfusion injury through inhibiting DAPK1 expression

Cardiovascular ischemic disease is a large class of diseases that are harmful to human health. The significant role of microRNAs (miRNAs) in terms of controlling cardiac injury has been reported in latest studies. MiR-98 is very important in regulating the apoptosis, the differentiation, the growth as well as the metastasis of cells. Nevertheless, the effect of miR-98 in the cardiac ischemia reperfusion (I/R) injury has rarely been investigated. In the current research, we found that the miR-98 expression was down-regulated in the cardiomyocytes subjected to hypoxia/reoxygenation (H/R) and in the myocardium of the I/R rats. In addition, over-expression of miR-98 could significantly reduce the myocardial oxidative stress and ischemic injury as well as cell apoptosis. In agreement, similar findings were demonstrated in H9c2 cells subjected to H/R injury. Bioinformatic analysis using MiRanda and TargetScan and luciferase activity assay confirmed death-associated protein kinase 1 (DAPK1) as a direct target of miR-98. These findings suggest that miR-98 may be exploited as a novel molecular marker or therapeutic target for myocardial I/R injury. © 2018 IUBMB Life, 71(1):166-176, 2019.

MicroRNA-532-5p Regulates Pericyte Function by Targeting the Transcription Regulator BACH1 and Angiopoietin-1

MicroRNAs regulate endothelial function and angiogenesis, but their implication in pericyte biology remains undetermined. A PCR array, covering a panel of 379 human microRNAs, showed microRNA-532-5p to be one of the most differentially modulated by hypoxia, which was confirmed by qPCR in both skeletal muscle and adventitial pericytes. Furthermore, microRNA-532-5p was upregulated in murine muscular pericytes early after experimentally induced ischemia, decreasing below baseline after reperfusion. Transfection of human pericytes with anti-microRNA, microRNA-mimic, or controls indicates microRNA-532-5p modulates pro-angiogenic activity via transcriptional regulation of angiopoietin-1. Tie-2 blockade abrogated the ability of microRNA-532-5p-overexpressing pericytes to promote endothelial network formation in vitro. However, angiopoietin-1 is not a direct target of microRNA-532-5p. In silico analysis of microRNA-532-5p inhibitory targets associated with angiopoietin-1 transcription indicated three potential candidates, BACH1, HIF1AN, and EGLN1. Binding of microRNA-532-5p to the BACH1 3' UTR was confirmed by luciferase assay. MicroRNA-532-5p silencing increased BACH1, while a microRNA-532-5p mimic decreased expression. Silencing of BACH1 modulated angiopoietin-1 gene and protein expression. ChIP confirmed BACH1 transcriptional regulation of angiopoietin-1 promoter. Finally, microRNA-532-5p overexpression increased pericyte coverage in an in vivo Matrigel assay, suggesting its role in vascular maturation. This study provides a new mechanistic understanding of the transcriptional program orchestrating angiopoietin-1/Tie-2 signaling in human pericytes.

Remote ischemic preconditioning upregulates microRNA-21 to protect the kidney in children with congenital heart disease undergoing cardiopulmonary bypass

BACKGROUND

Acute kidney injury (AKI) is one of the most common emergencies and severe diseases in the clinic. We sought to verify whether remote ischemic preconditioning (RIPC) has a protective effect on the kidney of child with congenital heart disease undergoing cardiopulmonary bypass (CPB) surgery. We hypothesized it may be related to the up-regulation of microRNA-21 (miR-21).

METHODS

We performed a prospective randomized clinical study among children with congenital heart disease undergoing CPB surgery between January and December 2016. Children were randomized to an RIPC or control group. Patients in each group were divided into an AKI and a non-AKI group according to the occurrence of AKI at 48 h after surgery. Remote ischemic preconditioning (RIPC) conducted by blood-pressure cuff was performed 12 h before surgery. Serum creatinine (S_Cr), tumor necrosis factor-α (TNF-α), and miR-21 expression in blood and urine were measured at different time points.

RESULTS

A total of 449 cases (200 RIPC; 249 controls) were enrolled. The male/female ratio was 1.18, with a mean age of 37.50 ± 25.31 months. The incidence of AKI in the RIPC group was significantly lower than that in the control group (19.0% vs. 46.2%, P<0.01). In further analysis, at 6 h, 24 h, and 48 h after CPB operation, blood TNF-α levels were significantly lower in the RIPC group than in the control group (P<0.01); at 24 h, 48 h, and 72 h, urine TNF-α levels were significantly lower in the RIPC group than in the control group (P<0.05). Urine and blood miR-21 expression in the RIPC group increased significantly, while there was no obvious change in the control group.

CONCLUSIONS

Remote ischemic preconditioning has a protective effect on the kidney in children with congenital heart disease, which may be related with the up-regulation of miR-21 and down-regulating the inflammatory mediator, such as TNF-α.

Circulating miR-23b as a Novel Biomarker for Early Risk Stratification After ST-Elevation Myocardial Infarction

Background

miR-23b overexpression can promote cardiomyocyte apoptosis and reduce cell growth under hypoxic conditions, suggesting that miR-23b acts as a biomarker for ST-elevation myocardial infarction (STEMI). The aim of this study was to investigate the effect of miR-23b on STEMI patients.

Material/Methods

We enrolled 80 eligible patients with STEMI and 60 control subjects. Blood samples were obtained at 6 h, 12 h, 24 h, 48 h, 3 days, and 7 days after the onset of symptoms. Another blood sample was collected before and after percutaneous coronary intervention (PCI). The samples were used for real-time quantitative PCR analysis. A Siemens Immulite2000 detector (Germany) was used for cTnI detection, and the serum CK-MB content was detected by electrochemical luminescence method.

Results

The expression level of miR-23b was increased in patients with STEMI (P<0.05). No significance difference was observed among risk factors, although the clinical data was comparable (P>0.05). The level of miR-23b in STEMI patients after PCI was lower (P<0.05). The ROC curve of plasma miR-23b showed a separation, with an AUC of 0.809 (95%CI, 0.737–0.936, P<0.05), compared to CK-MB with an AUC of 0.753 (95%CI, 0.707–0.896) and cTnI with an AUC of 0.783 (95%CI, 0.723–0.917).

Conclusions

The present study reveals that miR-23b is a useful biomarker of STEMI, providing a novel insight for the diagnosis for STEMI.

miR-21 contributes to renal protection by targeting prolyl hydroxylase domain protein 2 in delayed ischaemic preconditioning

AIM

Upregulation of miR-21 in renal ischaemic preconditioning (IPC) was associated with increased hypoxia inducible factor (HIF)-1α expression. Hypoxic induction of HIF-1α is mediated by inhibition of prolyl hydroxylase domain protein 2 (PHD2) .We hypothesized that miR-21 regulated HIF-1α by targeting PHD2 in the renal IPC.

METHODS

Luciferase reporter assay examined if miR-21 target the 3'-untranslated region of PHD2. In vitro, human proximal tubular cell line (HK-2) was incubated in hypoxia or hypoxia/ reoxygenation condition. Kidneys of Mice were respectively subjected to ischaemia/reperfusion injury (IRI) and IPC. Locked nucleic acid (LNA) modified anti-miR-21 was used to knockdown miR-21. Serum creatinine and histological changes estimated the renal injury. Levels of HIF-1α, PHD2, VEGF and miR-21 were examined by western blot or real-time PCR.

RESULT

miR-21 targeting of PHD2 was confirmed by 3'-untranslated region reporter assay. miR-21 was significantly upregulated by hypoxia/reoxygenation in HK-2 cell, while PHD2 protein level decreased significantly. LNA anti-miR-21 significantly repressed miR-21 levels and increased the abundance of PHD2. In vivo, IPC upregulated miR-21 expression 24 h after the second ischaemia, while PHD2 expression decreased significantly with upregulation of HIF-1α protein and VEGF mRNA. MiR-21 induced by delayed IPC was effectively inhibited by the LNA anti-miR-21. With downregulation of miR-21, the protection of delayed IPC was attenuated and PHD2 protein was increased. Furthermore, upregulation of HIF-1α and VEGF were abolished after the LNA anti-miR-21 treatment.

CONCLUSION

miR-21 could protect kidney against IRI via HIF-1α by inhibiting its target PHD2.The study suggested a new relationship between miR-21 and HIF-1α.

Epigenetics: a potential key mechanism involved in the pathogenesis of cardiorenal syndromes

Epigenetics is defined as the heritable changes in gene expression patterns which are not directly encoded by modifications in the nucleotide DNA sequence of the genome, including higher order chromatin organization, DNA methylation, cytosine modifications, covalent histone tail modifications, and short non-coding RNA molecules. Recently, much attention has been paid to the role and the function of epigenetics and epimutations in the cellular and subcellular pathways and in the regulation of genes in the setting of both kidney and cardiovascular disease. Indeed, deregulation of histone alterations has been highlighted in a large spectrum of renal and cardiac disease, including chronic and acute renal injury, renal and cardiac fibrosis, cardiac hypertrophy and failure, kidney congenital anomalies, renal hypoxia, and diabetic renal complications. Nevertheless, the role of epigenetics in the pathogenesis and pathophysiology of cardiorenal syndromes is currently underexplored. Given the significant clinical relevance of heart-kidney crosstalk, efforts in the research for new action mechanisms concurrently operating in both pathologies are thus of maximum interest. This review focuses on epigenetic mechanisms involved in heart and kidney disease, and their possible role in the setting of cardiorenal syndromes.

Endotoxin Effects on Cardiac and Renal Functions and Cardiorenal Syndromes

Gram-negative sepsis is a major cause of morbidity and mortality in critical ill patients. Recent findings in molecular biology and in signaling pathways have enhanced our understanding of its pathogenesis and opened up opportunities of innovative therapeutic approaches. Endotoxin plays a pivotal role in the pathogenesis of multi-organ dysfunction in the setting of gram-negative sepsis. Indeed, heart and kidney impairments seem to be induced by the release of circulating pro-inflammatory and pro-apoptotic mediators triggered by endotoxin interaction with immune cells. These molecules are responsible for cellular apoptosis, autophagy, cell cycle arrest, and microRNAs activation. Therefore, the early identification of sepsis-associated acute kidney injury and heart dysfunction may improve the patient clinical outcome. In this report, we will consider the role of endotoxin in the pathogenesis of sepsis, its effects on both cardiac and renal functions, and the interactions between these 2 systems in the setting of cardiorenal syndromes (CRS), particularly in CRS type 5. Finally, we will discuss the possible role of extracorporeal therapies in reducing endotoxin levels.

Long non-coding RNA MALAT1 functions as a mediator in cardioprotective effects of fentanyl in myocardial ischemia-reperfusion injury

Long non-coding (lncRNA) MALAT1 can be increased by hypoxia or ischemic limbs. Also, downregulation of MALAT1 contributes to reduction of cardiomyocyte apoptosis. However, the functional involvement of MALAT1 in myocardial ischemia-reperfusion (I/R) injury has not been defined. This study investigated the functional involvement of lncRNA-MALAT1 in cardioprotective effects of fentanyl. HL-1, a cardiac muscle cell line from the AT-1 mouse atrial cardiomyocyte tumor lineage was pre-treated with fentanyl and generated cell model of hypoxia-reoxygenation (H/R). Relative expression of MALAT1, miR-145, and Bnip3 mRNA in cells was determined by quantitative real-time PCR. Cardiomyocyte H/R injury was indicated by lactate dehydrogenase (LDH) release and cell apoptosis. The results showed that fentanyl abrogates expression of responsive gene for H/R and induces downregulation of MALAT1 and Bnip3 and upregulation of miR-145. We found that miR-145/Bnip3 pathway was negatively regulated by MALAT1 in H/R-HL-1 cell with or without fentanyl treatment. Moreover, both MALAT1 overexpression and miR-145 knockdown reverse cardioprotective effects of fentanyl, as indicated by increase in LDH release and cell apoptosis. The reversal effect of MALAT1 for fentanyl is confirmed in cardiac ischemia/reperfusion (I/R) mice. In summary, lncRNA-MALAT1 is sensitive to H/R injury and abrogates cardioprotective effects of Fentanyl by negatively regulating miR-145/Bnip3 pathway.

Mesenchymal Stromal Cells Derived Extracellular Vesicles Ameliorate Acute Renal Ischemia Reperfusion Injury by Inhibition of Mitochondrial Fission through miR-30

Background. The immoderation of mitochondrial fission is one of the main contributors in ischemia reperfusion injury (IRI) and mesenchymal stromal cells (MSCs) derived extracellular vesicles have been regarded as a potential therapy method. Here, we hypothesized that extracellular vesicles (EVs) derived from human Wharton Jelly mesenchymal stromal cells (hWJMSCs) ameliorate acute renal IRI by inhibiting mitochondrial fission through miR-30b/c/d. Methods. EVs isolated from the condition medium of MCS were injected intravenously in rats immediately after monolateral nephrectomy and renal pedicle occlusion for 45 minutes. Animals were sacrificed at 24 h after reperfusion and samples were collected. MitoTracker Red staining was used to see the morphology of the mitochondria. The expression of DRP1 was measured by western blot. miR-30 in EVs and rat tubular epithelial cells was assessed by qRT-PCR. Apoptosis pathway was identified by immunostaining. Results. We found that the expression of miR-30 in injured kidney tissues was declined and mitochondrial dynamics turned to fission. But they were both restored in EVs group in parallel with reduced cell apoptosis. What is more, when the miR-30 antagomirs were used to reduce the miRNA levels, all the related effects of EVs reduced remarkably. Conclusion. A single administration of hWJMSC-EVs could protect the kidney from IRI by inhibition of mitochondrial fission via miR-30.

microRNA-22 attenuates myocardial ischemia-reperfusion injury via an anti-inflammatory mechanism in rats

Previous studies have reported that microRNA-22 (miR-22) may be implicated in ischemia-reperfusion (I/R)-induced myocardial injury. Our previously published data also demonstrated that miR-22 may protect against myocardial I/R injury via anti-apoptosis in rats by targeting cAMP response element-binding protein binding protein (CBP). However, the specific function of miR-22 in myocardial I/R injury is far from fully elucidated. The present study was designed to investigate another cardioprotective signaling mechanism of miR-22 in myocardial I/R injury. A total of 40 adult male Sprague-Dawley rats were randomly divided into four equal groups (n=10): Sham, myocardial I/R, myocardial I/R with adenovirus expressing scramble miRNA (Ad-Scramble) and myocardial I/R with adenovirus expressing miR-22 (Ad-miR-22) groups. Besides the Sham operation group, the remaining three groups were artificially afflicted with coronary occlusion for 30 min and subsequently reperfused for 4 h. A light microscope was used to observe structural changes in the myocardium; reverse transcription polymerase chain reaction was used to measure the miR-22 mRNA expression level; the myocardial infarct size was analyzed by the Evans Blue/triphenyltetrazolium chloride double-staining; and p38 mitogen-activated protein kinase (MAPK), CBP, c-Jun-activator protein (AP)-1 and phospho (p)-c-Jun-AP-1 expression protein levels were detected by a western blot. Furthermore, ELISA was used to measure the levels of TNF-α and IL-6 in the myocardium. The results demonstrated that adenovirus-mediated miR-22 overexpression markedly reduced p38 MAPK, CBP, c-Jun-AP-1, p-c-Jun-AP-1 expression levels concomitant with an improvement in myocardial injury, including smaller infarct size, reduced release of creatine kinase, lactate dehydrogenase and proinflammation mediators (tumor necrosis factor-α and interleukin-6). These findings suggest that miR-22 has a protective effect on myocardial I/R injury. This protection mechanism, at least in part, is due to its anti-inflammatory function via the suppression of the p38 MAPK/CBP/c-Jun-AP-1 signaling pathway.

Hsp90aa1: a novel target gene of miR-1 in cardiac ischemia/reperfusion injury

The role of microRNA-1 (miR-1) in ischemia/reperfusion (I/R)-induced injury is not well illustrated. The present study aimed to investigate the expression and potential target of miR-1 in the myocardium of a rat model of I/R. The apoptosis of cardiomyocytes in the ischemic rat myocardium increased on day 1, then attenuated on day 3 and day 7 post-I/R. Heat shot protein 90 (Hsp90) aa1 mRNA expression was decreased post-I/R, and Hsp90aa1 protein level was decreased on day1 post-I/R, but was reversed on day 3 and day 7 post-I/R. MiR-1 was downregulated post-I/R, and repression of miR-1 in cultured neonatal rat ventricular cells (NRVCs) led to an increase of Bcl-2 and decreases of Bax and active caspase-3. Dual luciferase reporter assays revealed that miR-1 interacted with the 310-315 nt site at the 3'UTR of Hsp90aa1, and miR-1 was verified to inhibit Hsp90aa1 expression at the posttranscriptional level. Over-expression of Hsp90aa1 could attenuate oxygen-glucose deprivation (OGD)-induced apoptosis of NRVCs. Additionally, miR-1 mimic, in parallel to Hsp90aa1 siRNA, could enhance OGD-induced apoptosis of NRVCs. Taken together, our results reveal that Hsp90aa1 is a novel target of miR-1, and repression of miR-1 may contribute to the recovery of Hsp90aa1 during myocardial I/R.

Stress response factors as hub-regulators of microRNA biogenesis: implication to the diseased heart

MicroRNAs (miRNAs) are important regulators of heart function and then an intriguing therapeutic target for plenty of diseases. The problem raised is that many data in this area are contradictory, thus limiting the use of miRNA-based therapy. The goal of this review is to describe the hub-mechanisms regulating the biogenesis and function of miRNAs, which could help in clarifying some contradictions in the miRNA world. With this scope, we analyse an array of factors, including several known agents of stress response, mediators of epigenetic changes, regulators of alternative splicing, RNA editing, protein synthesis and folding and proteolytic systems. All these factors are important in cardiovascular function and most of them regulate miRNA biogenesis, but their influence on miRNAs was shown for non-cardiac cells or some specific cardiac pathologies. Finally, we consider that studying the stress response factors, which are upstream regulators of miRNA biogenesis, in the diseased heart could help in (1) explaining some contradictions concerning miRNAs in heart pathology, (2) making the role of miRNAs in pathogenesis of cardiovascular disease more clear, and therefore, (3) getting powerful targets for its molecular therapy.

MicroRNAs relate to early worsening of renal function in patients with acute heart failure

BACKGROUND

Deregulation of microRNAs (miRNAs) may be involved in the pathogenesis of heart failure (HF) and renal disease. Our aim is to describe miRNA levels related to early worsening renal function in acute HF patients.

METHOD AND RESULTS

We studied the association between 12 circulating miRNAs and Worsening Renal Function (WRF; defined as an increase in the serum creatinine level of 0.3mg per deciliter or more from admission to day 3), absolute change in creatinine and Neutrophil Gelatinase Associated Lipocalin (NGAL) from admission to day 3 in 98 patients hospitalized for acute HF. At baseline, circulating levels of all miRNAs were lower in patients with WRF, with statistically significant decreased levels of miR-199a-3p, miR-423-3p, and miR-let-7i-5p (p-value<0.05). The increase in creatinine during the first 3 days of hospitalization was significantly associated with lower levels of miR-199a-3p, miR-27a-3p, miR-652-3p, miR-423-5p, and miR-let-7i-5p, while the increase in NGAL was significantly associated with lower levels of miR-18a-5p, miR-106a-5p, miR-223-3p, miR-199a-3p and miR-423-3p. MiR-199a-3p was the strongest predictor of WRF, with an Odds Ratio of 1.48 (1.061-2.065; p-value=0.021) and a C-index of 0.701.

CONCLUSIONS

Our results show that the levels of circulating miRNAs at hospital admission for acute HF were consistently lower in patients who developed worsening of renal function. MiR-199a-3p was the best predictor of WRF in these patients.

MicroRNA-494 promotes cyclosporine-induced nephrotoxicity and epithelial to mesenchymal transition by inhibiting PTEN

A major complication associated with cyclosporine (CsA) treatment is nephrotoxicity. In this study, we examined whether microRNAs play a role in cyclosporine-induced nephrotoxicity. Treatment of mice with CsA resulted in nephrotoxicity that was associated with an early increase in expression of microRNA mmu-miR-494 (miR-494). Similarly, tubular epithelial cell epithelial-mesenchymal transition (EMT) induced by CsA toxicity resulted in the upregulation of microRNA-494 and a decrease in PTEN levels in vitro. miR-494 directly targeted Pten and negatively regulated its expression. Preventing Pten targeting by miR-494 was sufficient to prevent CsA induced EMT. Knockdown of miR-494 prevented the downregulation of PTEN in tubular epithelial cells following CsA treatment and also prevented CsA induced EMT. Thus, miR-494 plays a major role in promoting CsA induced nephrotoxicity through its ability to target Pten thereby contributing to EMT. We suggest that manipulating miR-494 expression may represent a novel approach to preventing EMT associated with CsA induced nephrotoxicity.

Vascular and circulating microRNAs in renal ischaemia-reperfusion injury

Ischaemia-reperfusion (I/R) injury of the kidney is a major cause of acute kidney injury. It may result in worsening or even loss of organ function. Transient occlusion of the renal vessel is followed by a reperfusion period, which induces further tissue damage by release of reactive oxygen and nitrogen species. Ischaemia-reperfusion injury of the kidney may be associated with surgical interventions in native kidneys and is also a common and unavoidable phenomenon in kidney transplantation. MicroRNAs are fascinating modulators of gene expression. They are capable of post-transcriptional silencing of genetic information by targeting the 3'-untranslated region of mRNAs, culminating in a suppression of protein synthesis or an increase in mRNA degradation. They might therefore be useful diagnostic and therapeutic entities during renal I/R injury; for instance, miR-21 has been shown to be enriched in kidney tissue in mice and humans with acute kidney injury. Interestingly, most recent literature suggests that modulation of vascular microRNAs might result in the amelioration of kidney function during renal I/R injury. To that end, miR-126 and miR-24, which have been demonstrated to be highly enriched in endothelial cells, were therapeutically modulated and shown to ameliorate renal I/R injury in mice. MicroRNAs in plasma, urine or enriched in microvesicles have been shown to serve as non-invasive tools for disease monitoring and to have potential impact on downstream mechanisms in recipient cells. This review highlights the latest developments regarding the role of microRNAs in renal I/R injury.

The effect of ischemia/reperfusion on the kidney graft

PURPOSE OF REVIEW

Ischemia/reperfusion injury is an unavoidable companion after kidney transplantation and influences short-term as well as long-term graft outcome. Clinically ischemia/reperfusion injury is associated with delayed graft function, graft rejection, and chronic graft dysfunction. Ischemia/reperfusion affects many regulatory systems at the cellular level as well as in the renal tissue that eventually result in a distinct inflammatory reaction of the kidney graft.

RECENT FINDINGS

Underlying factors include energy metabolism, cellular changes of the mitochondria and cellular membranes, initiation of different forms of cell death-like apoptosis and necrosis together with a recently discovered mixed form termed necroptosis. Chemokines and cytokines together with other factors promote the inflammatory response leading to activation of the innate immune system as well as the adaptive immune system. If the inflammatory reaction continues within the graft tissue, a progressive interstitial fibrosis develops that impacts long-term graft outcome.

SUMMARY

It is of particular importance in kidney transplantation to understand the underlying mechanisms and effects of ischemia/reperfusion on the graft as this knowledge also opens strategies to prevent or treat ischemia/reperfusion injury after transplantation in order to improve graft outcome.

Noncoding RNAs and myocardial fibrosis

Cardiac stress leads to remodelling of cardiac tissue, which often progresses to heart failure and death. Part of the remodelling process is the formation of fibrotic tissue, which is caused by exaggerated activity of cardiac fibroblasts leading to excessive extracellular matrix production within the myocardium. Noncoding RNAs (ncRNAs) are a diverse group of endogenous RNA-based molecules, which include short (∼22 nucleotides) microRNAs and long ncRNAs (of >200 nucleotides). These ncRNAs can regulate important functions in many cardiovascular cells types. This Review focuses on the role of ncRNAs in cardiac fibrosis; specifically, ncRNAs as therapeutic targets, factors for direct fibroblast transdifferentation, their use as diagnostic and prognostic markers, and their potential to function as paracrine modulators of cardiac fibrosis and remodelling.

Targeted delivery of miRNA therapeutics for cardiovascular diseases: opportunities and challenges

Dysregulation of miRNA expression has been associated with many cardiovascular diseases in animal models, as well as in patients. In the present review, we summarize recent findings on the role of miRNAs in cardiovascular diseases and discuss the opportunities, possibilities and challenges of using miRNAs as future therapeutic targets. Furthermore, we focus on the different approaches that can be used to deliver these newly developed miRNA therapeutics to their sites of action. Since siRNAs are structurally homologous with the miRNA therapeutics, important lessons learned from siRNA delivery strategies are discussed that might be applicable to targeted delivery of miRNA therapeutics, thereby reducing costs and potential side effects, and improving efficacy.

MicroRNA-92a inhibition attenuates hypoxia/reoxygenation-induced myocardiocyte apoptosis by targeting Smad7

Background

MicroRNAs (miRNAs) regulate a lot of physiological and pathological processes, including myocardial ischemia/reperfusion. Recent studies reported that knockdown of miR-92a could attenuate ischemia/reperfusion-induced myocardial injury. In the present study, we examined the potential anti-apoptotic effects of miR-92a in a rat myocardiocyte cell line, and the possible role of Smad7 in such actions.

Methodology and Results

In a preliminary bioinformatic analysis, we identified SMAD family member 7 (Smad7) as a potential target for miR-92a. A luciferase reporter assay indeed demonstrated that miR-92a could inhibit Smad7 expression. Myocardial ischemia/reperfusion was simulated in rat H9c2 cells with 24-h hypoxia followed by 12-h reoxygenation. Prior to hypoxia/reoxygenation, cells were transfected by miR-92a inhibitor. In some experiments, cells were co-transfected with siRNA-Smad7. The miR-92a inhibitor dramatically reduced the release of lactate dehydrogenase and malonaldehyde, and attenuated cardiomyocyte apoptosis. The miR-92a inhibitor increased SMAD7 protein level and decreased nuclear NF-κB p65 protein. Effects of the miR-92a inhibitor were attenuated by co-transfection with siRNA-Smad7.

Conclusion

Inhibiting miR-92a can attenuate myocardiocyte apoptosis induced by hypoxia/reoxygenation by targeting Smad7.