Notch1 cardioprotection in myocardial ischemia/reperfusion involves reduction of oxidative/nitrative stress

Ectodysplasin-A2 receptor (EDA2R) knockdown alleviates myocardial ischemia/reperfusion injury through inhibiting the activation of the NF-κB signaling pathway

Ischemia/reperfusion (I/R) is a pathological process that occurs in numerous organs and is often associated with severe cellular damage and death. Ectodysplasin-A2 receptor (EDA2R) is a member of the TNF receptor family that has anti-inflammatory and antioxidant effects. However, to the best of our knowledge, its role in the progression of myocardial I/R injury remains unclear. The present study aimed to investigate the role of EDA2R during myocardial I/R injury and the molecular mechanisms involved. In vitro, dexmedetomidine (DEX) exhibited a protective effect on hypoxia/reoxygenation (H/R)-induced cardiomyocyte injury and downregulated EDA2R expression. Subsequently, EDA2R silencing enhanced cell viability and reduced the apoptosis of cardiomyocytes. Furthermore, knockdown of EDA2R led to an elevated mitochondrial membrane potential (MMP), repressed the release of Cytochrome C and upregulated Bcl-2 expression. EDA2R knockdown also resulted in downregulated expression of Bax, and decreased activity of Caspase-3 and Caspase-9 in cardiomyocytes, reversing the effects of H/R on mitochondria-mediated apoptosis. In addition, knockdown of EDA2R suppressed H/R-induced oxidative stress. Mechanistically, EDA2R knockdown inactivated the NF-κB signaling pathway. Additionally, downregulation of EDA2R weakened myocardial I/R injury in mice, as reflected by improved left ventricular function and reduced infarct size, as well as suppressed apoptosis and oxidative stress. Additionally, EDA2R knockdown repressed the activation of NF-κB signal in vivo. Collectively, knockdown of EDA2R exerted anti-apoptotic and antioxidant effects against I/R injury in vivo and in vitro by suppressing the NF-κB signaling pathway.

circMIRIAF aggravates myocardial ischemia-reperfusion injury via targeting miR-544/WDR12 axis

Exploring and discovering novel circRNAs is one of the ways to develop innovative drugs for the diagnosis and treatment of myocardial ischemia-reperfusion injury (MI/RI). In the work, some dysregulated circRNAs were found by microarray screening analysis in AC16 cells, and hsa_circRNA_104852 named circMIRIAF was screened, which was up-regulated in AC16 cells damaged by hypoxia-reoxygenation injury (H/RI). The comprehensive analysis of ceRNA network revealed the potential relationship of circMIRIAF/miR-544/WDR12. Then, the results of interaction research confirmed that circMIRIAF acted as sponge of miR-544 to positively regulate WDR12 protein expression. Further, the validation results indicate that miR-544 silencing increased the expression of WDR12, and WDR12 activated Notch1 signal to aggravate H/RI of AC16 cells and MI/RI of mice via regulating oxidative stress and inflammation. Furthermore, silencing circMIRIAF caused the decreased circMIRIAF levels and the increased miR-544 levels in cardiomyocytes, while excessive miR-544 inhibited WDR12 expression to alleviate the disorder. On the contrary, excessive circMIRIAF increased WDR12 expression by adsorbing miR-544 to exacerbate H/RI in AC16 cells. In addition, circMIRIAF siRNA reversed the aggravation of H/RI in cells caused by WDR12 overexpression. Overall, circMIRIAF can serve as a drug target or treating MI/RI, and circMIRIAF could sponge miR-544 and enhance WDR12 expression to aggravate MI/RI, which may provide a novel therapeutic strategy for MI/RI treatment.

The prognostic potential of long noncoding RNA XIST in cardiovascular diseases: a review

There is a significant mortality rate associated with cardiovascular disease despite advances in treatment. long Non-coding RNAs (lncRNAs) play a critical role in many biological processes and their dysregulation is associated with a wide range of diseases in which their downstream pathways are disrupted. A lncRNA X-inactive specific transcript (XIST) is well known as a factor that regulates the physiological process of chromosome dosage compensation for females. According to recent studies, lncRNA XIST is involved in a variety of cellular processes, including apoptosis, proliferation, invasion, metastasis, oxidative stress and inflammation, through molecular networks with microRNAs and their downstream targets in neoplastic and non-neoplastic diseases. Because these cellular processes play a role in the pathogenesis of cardiovascular diseases, we aim to investigate the role that lncRNA XIST plays in this process. Additionally, we wish to determine whether it is a prognostic factor or a potential therapeutic target in these diseases.

Ischemia-reperfusion injury: molecular mechanisms and therapeutic targets

Ischemia-reperfusion (I/R) injury paradoxically occurs during reperfusion following ischemia, exacerbating the initial tissue damage. The limited understanding of the intricate mechanisms underlying I/R injury hinders the development of effective therapeutic interventions. The Wnt signaling pathway exhibits extensive crosstalk with various other pathways, forming a network system of signaling pathways involved in I/R injury. This review article elucidates the underlying mechanisms involved in Wnt signaling, as well as the complex interplay between Wnt and other pathways, including Notch, phosphatidylinositol 3-kinase/protein kinase B, transforming growth factor-β, nuclear factor kappa, bone morphogenetic protein, N-methyl-D-aspartic acid receptor-Ca2+-Activin A, Hippo-Yes-associated protein, toll-like receptor 4/toll-interleukine-1 receptor domain-containing adapter-inducing interferon-β, and hepatocyte growth factor/mesenchymal-epithelial transition factor. In particular, we delve into their respective contributions to key pathological processes, including apoptosis, the inflammatory response, oxidative stress, extracellular matrix remodeling, angiogenesis, cell hypertrophy, fibrosis, ferroptosis, neurogenesis, and blood-brain barrier damage during I/R injury. Our comprehensive analysis of the mechanisms involved in Wnt signaling during I/R reveals that activation of the canonical Wnt pathway promotes organ recovery, while activation of the non-canonical Wnt pathways exacerbates injury. Moreover, we explore novel therapeutic approaches based on these mechanistic findings, incorporating evidence from animal experiments, current standards, and clinical trials. The objective of this review is to provide deeper insights into the roles of Wnt and its crosstalk signaling pathways in I/R-mediated processes and organ dysfunction, to facilitate the development of innovative therapeutic agents for I/R injury.

Effect of humanine on the Notch signaling pathway in myocardial infarction

Background/aim

By applying humanin (HN) before myocardial infarction (MI), its protection in myocardial injury and the possible roles of its cellular mechanism in the Notch pathway were investigated.

Materials and methods

The study was carried out at Fırat University Experimental Research Center (12/24/2018-12/23/2019). Spraque-Dawley rats were divided into 10 groups: I (control) (n = 6), II (HN 6 h) (n = 6), III (HN 24 h) (n = 6), IV (HN day 7) (n = 6), V (MI 6 h) (n = 7), VI (MI 24 h) (n = 7), VII (MI day 7) (n = 7), VIII (MI+HN 6 h) (n = 7), IX (MI+HN 24 h) (n = 7), and X (MI+HN day 7) (n = 7). To create MI, 200 mg/kg of isoproterenol (ISO) was administered to the rats subcutaneously. Moreover, 252 μg/kg of HN was given intraperitoneally (ip) to the rats on its own and before MI. Molecular parameters Notch1, Notch2, Hes1, Hes2, Jagged1, Jagged2, DLL1, and DLL4 were examined using polymerase chain reaction in the heart tissue, Notch1, Hes1, and DLL4 were examined using western blot, while heart tissue was taken for histochemical examinations.

Results

The mRNA expression levels of the Notch signaling members (Notch1, Notch2, Hes1, Hes2, Jagged1, Jagged2, DLL1, and DLL4) tended to decrease after MI. The Notch signaling members increased more significantly, especially toward day 7 after HN application before MI. In the western blot anylyses, the Notch1, Hes1, and DLL4 protein levels increased significantly toward day 7 in the groups given HN before MI. Moreover, the serum AST, LDH, CK-MB, and troponin I levels tended to decrease with the application of HN before MI and there was a significant decrease in edema, hemorrhage, and mononuclear cells in the heart tissue at 24 h post-MI and fibrosis on day 7 post-MI.

Conclusion

HN administration before MI has a cardioprotective effect on rats via the Notch signaling pathway.

Fine-mapping of retinal vascular complexity loci identifies Notch regulation as a shared mechanism with myocardial infarction outcomes

There is increasing evidence that the complexity of the retinal vasculature measured as fractal dimension, Df, might offer earlier insights into the progression of coronary artery disease (CAD) before traditional biomarkers can be detected. This association could be partly explained by a common genetic basis; however, the genetic component of Df is poorly understood. We present a genome-wide association study (GWAS) of 38,000 individuals with white British ancestry from the UK Biobank aimed to comprehensively study the genetic component of Df and analyse its relationship with CAD. We replicated 5 Df loci and found 4 additional loci with suggestive significance (P < 1e-05) to contribute to Df variation, which previously were reported in retinal tortuosity and complexity, hypertension, and CAD studies. Significant negative genetic correlation estimates support the inverse relationship between Df and CAD, and between Df and myocardial infarction (MI), one of CAD's fatal outcomes. Fine-mapping of Df loci revealed Notch signalling regulatory variants supporting a shared mechanism with MI outcomes. We developed a predictive model for MI incident cases, recorded over a 10-year period following clinical and ophthalmic evaluation, combining clinical information, Df, and a CAD polygenic risk score. Internal cross-validation demonstrated a considerable improvement in the area under the curve (AUC) of our predictive model (AUC = 0.770 ± 0.001) when comparing with an established risk model, SCORE, (AUC = 0.741 ± 0.002) and extensions thereof leveraging the PRS (AUC = 0.728 ± 0.001). This evidences that Df provides risk information beyond demographic, lifestyle, and genetic risk factors. Our findings shed new light on the genetic basis of Df, unveiling a common control with MI, and highlighting the benefits of its application in individualised MI risk prediction.

Ectopic Acsl6 Overexpression Partially Improves Isoproterenol-Induced Cardiac Hypertrophy In Vivo and Cardiomyocyte Hypertrophy In Vitro

ABSTRACT

The increase in cardiac myocyte size is a critical issue in cardiac hypertrophy development. In this study, 61 differentially expressed genes between hypertrophic rats and normal controls were enriched in the positive modulation of fatty acid uptake, fatty acid metabolism and degradation, cardiac conduction, and the oxidation of carbohydrates and other processes. Acsl6 was significantly downregulated in hypertrophic rat and mouse hearts according to online data. Based on the experimental data, Acsl6 was underexpressed in ISO-induced cardiac hypertrophy mouse model and isoproterenol (ISO)-induced cardiomyocyte hypertrophy cell model. In vivo, Acsl6 overexpression partially attenuated ISO-induced increases in the cross-sectional area and cardiac hypertrophy, elevated hypertrophic markers, and caused impairment of cardiac function. In vitro, Acsl6 overexpression partially attenuated ISO-induced cardiomyocyte hypertrophy and increased hypertrophic markers. Conclusively, Ascl6 is downregulated in ISO-induced cardiac hypertrophy mouse model and ISO-induced cardiomyocyte hypertrophy cell model. Acsl6 overexpression could partially improve cardiac hypertrophy in vivo and cardiomyocyte hypertrophy in vitro, possibly through the regulation of HIF-1α/Hippo pathway.

LncRNA-ZFAS1 Promotes Myocardial Ischemia-Reperfusion Injury Through DNA Methylation-Mediated Notch1 Down-Regulation in Mice

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The increase of ZFAS1 expression in MIRI is an important cause of cardiomyocyte apoptosis and ROS production.

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ZFAS1 can directly interact with the promoter region of Notch1, recruit DNMT3b to promote DNA methylation in the promoter region of Notch1, and trigger cardiomyocyte apoptosis and ROS production after MIRI.

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Nicotinamide mononucleotide has the potential to attenuate the apoptosis of cardiomyocytes after MIRI by competitively binding to DNMT3b and inhibiting the DNA methylation of Notch1.

The most devastating and catastrophic deterioration of myocardial ischemia-reperfusion injury (MIRI) is cardiomyocyte death. Here we aimed to evaluate the role of lncRNA-ZFAS1 in MIRI and delineate its mechanism of action. The level of lncRNA-ZFAS1 was elevated in MIRI hearts, and artificial knockdown of lncRNA-ZFAS1 in mice improved cardiac function. Notch1 is a potential target of lncRNA-ZFAS1, and lncRNA-ZFAS1 could bind to the promoter region of Notch1 and recruit DNMT3b to induce Notch1 methylation. Nicotinamide mononucleotide could promote the expression of Notch1 by competitively inhibiting the expression of DNMT3b and improving the apoptosis of cardiomyocytes and cardiac function.

Ischemic preconditioning/ischemic postconditioning alleviates anoxia/reoxygenation injury via the Notch1/Hes1/VDAC1 axis

Ischemic preconditioning (IPC), and ischemic postconditioning (IPost) have a significant protective effect on myocardial ischemia/reperfusion (MI/R) injury by alleviating oxidative stress and mitochondrial disturbances, although the underlying molecular mechanisms are unclear. The study was to demonstrate that cardioprotection against anoxia/reoxygenation (A/R) injury is transduced via the Notch1/Hes1/VDAC1 signaling pathway. Using mass spectrometry and tandem affinity purification (TAP), to screen for differentially expressed proteins associated with Hes1, followed by standard bioinformatics analysis. The co-immunoprecipitation (Co-IP) assay confirmed an interaction between Hes1 and VDAC1 proteins. H9c2 cells were transfected with Hes1 adenoviral N-terminal TAP vector (AD-NTAP/Hes1) and Hes1-short hairpin RNA adenoviral vector (AD-Hes1-shRNA) to establish A/R injury, IPC, and IPost models, respectively. The expression of Hes1 and VDAC1 proteins were measured by western blot analysis, while the levels of reactive oxygen species (ROS), mitochondrial membrane potential (ΔΨm), and apoptosis were evaluated by flow cytometry. AD-NTAP/Hes1 can activate the exogenous protein expression of Hes1, thus decreasing creatine phosphokinase (CPK) and lactate dehydrogenase (LDH) activity and promoting cell viability. The study found that VDAC1 was a potential target protein for Hes1 and the overexpression of Hes1 protein expression downregulated protein expression levels of VDAC1, reduced ROS production, stabilized ΔΨm, and inhibited apoptosis in H9c2 cells. Additionally, downregulation of Hes1 protein expression also upregulated VDAC1 protein expression, increased ROS production, imbalanced ΔΨm, promoted cell apoptosis, and attenuated the cardioprotection afforded by IPC and IPost. The Notch1/Hes1 signaling pathway activated by IPC/IPost can directly downregulate the protein expression of VDAC1 and consequently relieve A/R injury.

The Notch pathway attenuates burn-induced acute lung injury in rats by repressing reactive oxygen species

Background

Acute lung injury (ALI) is a common complication following severe burns. The underlying mechanisms of ALI are incompletely understood; thus, available treatments are not sufficient to repair the lung tissue after ALI.

Methods

To investigate the relationship between the Notch pathway and burn-induced lung injury, we established a rat burn injury model by scalding and verified lung injury via lung injury evaluations, including hematoxylin and eosin (H&E) staining, lung injury scoring, bronchoalveolar lavage fluid and wet/dry ratio analyses, myeloperoxidase immunohistochemical staining and reactive oxygen species (ROS) accumulation analysis. To explore whether burn injury affects Notch1 expression, we detected the expression of Notch1 and Hes1 after burn injury. Then, we extracted pulmonary microvascular endothelial cells (PMVECs) and conducted Notch pathway inhibition and activation experiments, via a γ-secretase inhibitor (GSI) and OP9-DLL1 coculture, respectively, to verify the regulatory effect of the Notch pathway on ROS accumulation and apoptosis in burn-serum-stimulated PMVECs. To investigate the regulatory effect of the Notch pathway on ROS accumulation, we detected the expression of oxidative-stress-related molecules such as superoxide dismutase, nicotinamide adenine dinucleotide phosphate (NADPH) oxidase (NOX) 2, NOX4 and cleaved caspase-3. NOX4-specific small interfering RNA (siRNA) and the inhibitor GKT137831 were used to verify the regulatory effect of the Notch pathway on ROS via NOX4.

Results

We successfully established a burn model and revealed that lung injury, excessive ROS accumulation and an inflammatory response occurred. Notch1 detection showed that the expression of Notch1 was significantly increased after burn injury. In PMVECs challenged with burn serum, ROS and cell death were elevated. Moreover, when the Notch pathway was suppressed by GSI, ROS and cell apoptosis levels were significantly increased. Conversely, these parameters were reduced when the Notch pathway was activated by OP9-DLL1. Mechanistically, the inhibition of NOX4 by siRNA and GKT137831 showed that the Notch pathway reduced ROS production and cell apoptosis by downregulating the expression of NOX4 in PMVECs.

Conclusions

The Notch pathway reduced ROS production and apoptosis by downregulating the expression of NOX4 in burn-stimulated PMVECs. The Notch-NOX4 pathway may be a novel therapeutic target to treat burn-induced ALI.

Activation of the M3AChR and Notch1/HSF1 Signaling Pathway by Choline Alleviates Angiotensin II-Induced Cardiomyocyte Apoptosis

Angiotensin II- (Ang II-) induced cardiac hypertrophy and apoptosis are major characteristics of early-stage heart failure. Choline exerts cardioprotective effects; however, its effects on Ang II-induced cardiomyocyte apoptosis are unclear. In this study, the role and underlying mechanism of choline in regulating Ang II-induced cardiomyocyte apoptosis were investigated using a model of cardiomyocyte apoptosis, which was induced by exposing neonatal rat cardiomyocytes to Ang II (10⁻⁶ M, 48 h). Choline promoted heat shock transcription factor 1 (HSF1) nuclear translocation and the intracellular domain of Notch1 (NICD) expression. Consequently, choline attenuated Ang II-induced increases in mitochondrial reactive oxygen species (mtROS) and promotion of proapoptotic protein release from mitochondria, including cytochrome c, Omi/high-temperature requirement protein A2, and second mitochondrial activator of caspases/direct inhibitor of apoptosis-binding protein with low P. The reversion of these events attenuated Ang II-induced increases in cardiomyocyte size and numbers of terminal deoxynucleotidyl transferase deoxyuridine triphosphate nick end labeling-positive cells, presumably via type 3 muscarinic acetylcholine receptor (M3AChR). Indeed, downregulation of M3AChR or Notch1 blocked choline-mediated upregulation of NICD and nuclear HSF1 expression, as well as inhibited mitochondrial apoptosis pathway and cardiomyocyte apoptosis, indicating that M3AChR and Notch1/HSF1 activation confer the protective effects of choline. In vivo studies were performed in parallel, in which rats were infused with Ang II for 4 weeks to induce cardiac apoptosis. The results showed that choline alleviated cardiac remodeling and apoptosis of Ang II-infused rats in a manner related to activation of the Notch1/HSF1 pathway, consistent with the in vitro findings. Taken together, our results reveal that choline impedes oxidative damage and cardiomyocyte apoptosis by activating M3AChR and Notch1/HSF1 antioxidant signaling, and suggest a novel role for the Notch1/HSF1 signaling pathway in the modulation of cardiomyocyte apoptosis.

Notch signaling is involved in the antiapoptotic effects of liraglutide on rat H9c2 cardiomyocytes exposed to hypoxia followed by reoxygenation

OBJECTIVE

Liraglutide (Lir) protects cardiomyocytes against high glucose-induced myocardial damage. This study investigated whether Notch signaling participated in the antiapoptotic effects of Lir on rat H9c2 cardiomyocytes subjected to hypoxia followed by reoxygenation (H/R).

METHODS

We used H9c2 rat cardiomyocytes as a model of H/R and measured viability, apoptosis, and expression of the apoptotic genes Bax and Bcl-2 and Notch signaling genes Notch1 and Jagged1. Notch1 was depleted by siRNA to test the effect of Notch1 deficiency on the antiapoptotic effects of Lir on H/R-treated H9c2 cardiomyocytes.

RESULTS

After H/R treatment, viability was significantly decreased, and the apoptosis rate was greater in the H/R group than in the control (CT). Lir at 50, 100, and 200 nM significantly increased viability and decreased apoptosis in H/R-treated H9c2 cells. Treatment with 50 nM Lir for 2 hours before H/R significantly increased the expression levels of Notch1, Jagged1, and Bcl-2 compared with the CT levels. Bax was downregulated, which indicated that Lir activated Notch signaling and inhibited apoptosis. Notch1 depletion partially abolished the antiapoptotic effect of Lir on H/R-treated H9c2 cells by altering apoptotic gene expression.

CONCLUSION

Lir activated Notch signaling, which was responsible for the antiapoptotic effect of Lir on H9c2 cardiomyocytes.

Novel PGC-1α/ATF5 Axis Partly Activates UPRmt and Mediates Cardioprotective Role of Tetrahydrocurcumin in Pathological Cardiac Hypertrophy

Mitochondrial unfolding protein response (UPR^mt) effectively resists the pathological cardiac hypertrophy and improves the mitochondrial function. However, the specific activation mechanism and drugs that can effectively activate UPR^mt in the cardiac muscle are yet to be elucidated. The aim of this study was to determine the regulation role of UPR^mt on preventing pathological cardiac hypertrophy by tetrahydrocurcumin (THC) and explore its underlying molecular mechanism. Male C57BL/6J wild-type (WT) mice were divided into a control group and subjected to sham treatment for 4 weeks, and a test group which was subjected to transverse aortic constriction (TAC) surgery. Animals in the control and test group were orally administered THC (50 mg/kg) for 4 weeks after TAC procedure; an equivalent amount of saline was orally administered in the control sham-treated group and the TAC group. Subsequently, oxidative stress and UPR^mt markers were assessed in these mice, and cardiac hypertrophy, fibrosis, and cardiac function were tested. Small interfering RNA (siRNA) targeting proliferator-activated receptor-gamma coactivator (PGC)-1α and activating transcription factor 5 (ATF5) were used to determine the UPR^mt activation mechanism. THC supplement partly upregulated UPR^mt effectors and inhibited TAC-induced oxidative stress compared with TAC-operated WT mice, thereby substantially attenuating contractile dysfunction, cardiac hypertrophy, and fibrosis. Furthermore, PGC-1α knockdown blunted the UPR^mt activation and the cardioprotective role of THC. The interaction between PGC-1α and ATF5 was tested in neonatal rat cardiac myocytes under normal conditions. The results showed that PGC-1α was an upstream effector of ATF5 and partly activated UPR^mt. In vitro, phenylephrine- (PE-) induced cardiomyocyte hypertrophy caused ATF5 upregulating rather than downregulating corresponding to the downregulation of PGC-1α. The PGC-1α/ATF5 axis mediated the UPR^mt activation and stress-resistance role of THC in vitro. Collectively, the present study provides the first evidence that PGC-1 and ATF5 can form a signaling axis to partly activate UPR^mt that mediates the cardioprotective role of THC in pathological cardiac hypertrophy.

Melatonin alleviates angiotensin-II-induced cardiac hypertrophy via activating MICU1 pathway

Mitochondrial calcium uptake 1 (MICU1) is a pivotal molecule in maintaining mitochondrial homeostasis under stress conditions. However, it is unclear whether MICU1 attenuates mitochondrial stress in angiotensin II (Ang-II)-induced cardiac hypertrophy or if it has a role in the function of melatonin. Here, small-interfering RNAs against MICU1 or adenovirus-based plasmids encoding MICU1 were delivered into left ventricles of mice or incubated with neonatal murine ventricular myocytes (NMVMs) for 48 h. MICU1 expression was depressed in hypertrophic myocardia and MICU1 knockdown aggravated Ang-II-induced cardiac hypertrophy in vivo and in vitro. In contrast, MICU1 upregulation decreased cardiomyocyte susceptibility to hypertrophic stress. Ang-II administration, particularly in NMVMs with MICU1 knockdown, led to significantly increased reactive oxygen species (ROS) overload, altered mitochondrial morphology, and suppressed mitochondrial function, all of which were reversed by MICU1 supplementation. Moreover, peroxisome proliferator-activated receptor gamma coactivator 1-α (PGC-1α)/MICU1 expression in hypertrophic myocardia increased with melatonin. Melatonin ameliorated excessive ROS generation, promoted mitochondrial function, and attenuated cardiac hypertrophy in control but not MICU1 knockdown NMVMs or mice. Collectively, our results demonstrate that MICU1 attenuates Ang-II-induced cardiac hypertrophy by inhibiting mitochondria-derived oxidative stress. MICU1 activation may be the mechanism underlying melatonin-induced protection against myocardial hypertrophy.

MiR-21 mediates the protection of kaempferol against hypoxia/reoxygenation-induced cardiomyocyte injury via promoting Notch1/PTEN/AKT signaling pathway

Kaempferol, a natural flavonoid compound, possesses potent myocardial protective property in ischemia/reperfusion (I/R), but the underlying mechanism is not well understood. The present study was aimed to explore whether miR-21 contributes to the cardioprotective effect of kaempferol on hypoxia/reoxygenation (H/R)-induced H9c2 cell injury via regulating Notch/phosphatase and tensin homologue (PTEN)/Akt signaling pathway. Results revealed that kaempferol obviously attenuates H/R-induced the damages of H9c2 cells as evidence by the up-regulation of cell viability, the down-regulation of lactate dehydrogenase (LDH) activity, the reduction of apoptosis rate and pro-apoptotic protein (Bax) expression, and the increases of anti-apoptotic protein (Bcl-2) expression. In addition, kaempferol enhanced miR-21 level in H9c2 cells exposed to H/R, and inhibition of miR-21 induced by transfection with miR-21 inhibitor significantly blocked the protection of kaempferol against H/R-induced H9c2 cell injury. Furthermore, kaempferol eliminated H/R-induced oxidative stress and inflammatory response as illustrated by the decreases in reactive oxygen species generation and malondialdehyde content, the increases in antioxidant enzyme superoxide dismutase and glutathione peroxidase activities, the decreases in pro-inflammatory cytokines interleukin (IL)-1β, IL-8 and tumor necrosis factor-alpha levels, and an increase in anti-inflammatory cytokine IL-10 level, while these effects of kaempferol were all reversed by miR-21 inhibitor. Moreover, results elicited that kaempferol remarkably blocks H/R-induced the down-regulation of Notch1 expression, the up-regulation of PTEN expression, and the reduction of P-Akt/Akt, indicating that kaempferol promotes Notch1/PTEN/AKT signaling pathway, and knockdown of Notch1/PTEN/AKT signaling pathway induced by Notch1 siRNA also abolished the protection of kaempferol against H/R-induced the damage of H9c2 cells. Notably, miR-21 inhibitor alleviated the promotion of kaempferol on Notch/PTEN/Akt signaling pathways in H9c2 cells exposed to H/R. Taken together, these above findings suggested thatmiR-21 mediates the protection of kaempferol against H/R-induced H9c2 cell injuryvia promoting Notch/PTEN/Akt signaling pathway.

COVID-19 in the heart and the lungs: could we "Notch" the inflammatory storm?

From January 2020, coronavirus disease (COVID-19) originated in China has spread around the world. The disease is caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). The presence of myocarditis, cardiac arrest, and acute heart failure in COVID-19 patients suggests the existence of a relationship between SARS-CoV-2 infection and cardiac disease. The Notch signalling is a major regulator of cardiovascular function and it is also implicated in several biological processes mediating viral infections. In this report we discuss the possibility to target Notch signalling to prevent SARS-CoV-2 infection and interfere with the progression of COVID-19- associated heart and lungs disease.

PP2Cm overexpression alleviates MI/R injury mediated by a BCAA catabolism defect and oxidative stress in diabetic mice

Diabetic patients are sensitive to myocardial ischemia-reperfusion (MI/R) injury. During diabetes, branched-chain amino acid (BCAA) catabolism is defective and mitochondrial phosphatase 2C (PP2Cm) expression is reduced. This study aims to elucidate the relationship between PP2Cm downregulation and BCAA catabolism defect in diabetic mice against MI/R injury. PP2Cm was significantly downregulated in hearts of diabetic mice. The cardiac function was improved and the myocardial infarct size and apoptosis were decreased in diabetic mice overexpressing PP2Cm after MI/R. In diabetic mice, the cardiac BCAA and its metabolites branched-chain keto-acids (BCKA) levels, and p-BCKDE1α (E1 subunit of BCKA dehydrogenase)/BCKDE1α ratio were increased while the BCKD activity was decreased. Treatment of diabetic mice subjected to MI/R injury with BT2, a BCKD kinase (BDK) inhibitor, alleviated the BCAA catabolism defect, and improved the cardiac function alongside reduced apoptosis. PP2Cm overexpression alleviated the BCAA catabolism defect and MI/R injury. Similarly, MnTBAP ameliorated the oxidative stress and MI/R injury. BCKA treatment of H9C2 cells under simulated ischemia/reperfusion (SI/R) injury significantly decreased cell viability and increased LDH release and apoptosis. These effects were alleviated by BT2 and MnTBAP treatments. These results suggested that PP2Cm directly mediates the BCAA catabolism defect and oxidative stress observed after MI/R in diabetes. Overexpression of PP2Cm alleviates MI/R injury by reducing the catabolism of BCAA and oxidative stress.

Plin5/p-Plin5 Guards Diabetic CMECs by Regulating FFAs Metabolism Bidirectionally

Background

Hyper-free fatty acidemia (HFFA) impairs cardiac capillaries, as well as type 2 diabetes mellitus (T2DM). Perilipin 5 (Plin5) maintains metabolic balance of free fatty acids (FFAs) in high oxidative tissues via the states of nonphosphorylation and phosphorylation. However, when facing to T2DM-HFFA, Plin5's role in cardiac microvascular endothelial cells (CMECs) is not defined.

Methods

In mice of WT or Plin5^−/−, T2DM models were rendered by high-fat diet combined with intraperitoneal injection of streptozocin. CMECs isolated from left ventricles were incubated with high glucose (HG) and high FFAs (HFFAs). Plin5 phosphorylation was stimulated by isoproterenol. Plin5 expression was knocked down by small interfering RNA (siRNA). We determined cardiac function by small animal ultrasound, apoptotic rate by flow cytometry, microvessel quantity by immunohistochemistry, microvascular integrity by scanning electron microscopy, intracellular FFAs by spectrophotometry, lipid droplets (LDs) by Nile red staining, mRNAs by quantitative real-time polymerase chain reaction, proteins by western blots, nitric oxide (NO) and reactive oxygen species (ROS) by fluorescent dye staining and enzyme-linked immunosorbent assay kits.

Results

In CMECs, HFFAs aggravated cell injury induced by HG and activated Plin5 expression. In mice with T2DM-HFFA, Plin5 deficiency reduced number of cardiac capillaries, worsened structural incompleteness, and enhanced diastolic dysfunction. Moreover, in CMECs treated with HG-HFFAs, both ablation and phosphorylation of Plin5 reduced LDs content, increased intracellular FFAs, stimulated mitochondrial β-oxidation, added ROS generation, and reduced the expression and activity of endothelial nitric oxide synthase (eNOS), eventually leading to increased apoptotic rate and decreased NO content, all of which were reversed by N-acetyl-L-cysteine.

Conclusion

Plin5 preserves lipid balance and cell survival in diabetic CMECs by regulating FFAs metabolism bidirectionally via the states of nonphosphorylation and phosphorylation.

Hes1 Knockdown Exacerbates Ischemic Stroke Following tMCAO by Increasing ER Stress-Dependent Apoptosis via the PERK/eIF2α/ATF4/CHOP Signaling Pathway

Apoptosis induced by endoplasmic reticulum (ER) stress plays a crucial role in mediating brain damage after ischemic stroke. Recently, Hes1 (hairy and enhancer of split 1) has been implicated in the regulation of ER stress, but whether it plays a functional role after ischemic stroke and the underlying mechanism remain unclear. In this study, using a mouse model of ischemic stroke via transient middle cerebral artery occlusion (tMCAO), we found that Hes1 was induced following brain injury, and that siRNA-mediated knockdown of Hes1 increased the cerebral infarction and worsened the neurological outcome, suggesting that Hes1 knockdown exacerbates ischemic stroke. In addition, mechanistically, Hes1 knockdown promoted apoptosis and activated the PERK/eIF2α/ATF4/CHOP signaling pathway after tMCAO. These results suggest that Hes1 knockdown promotes ER stress-induced apoptosis. Furthermore, inhibition of PERK with the specific inhibitor GSK2606414 markedly attenuated the Hes1 knockdown-induced apoptosis and the increased cerebral infarction as well as the worsened neurological outcome following tMCAO, implying that the protection of Hes1 against ischemic stroke is associated with the amelioration of ER stress via modulating the PERK/eIF2α/ATF4/CHOP signaling pathway. Taken together, these results unveil the detrimental role of Hes1 knockdown after ischemic stroke and further relate it to the regulation of ER stress-induced apoptosis, thus highlighting the importance of targeting ER stress in the treatment of ischemic stroke.

The Notch pathway: a novel therapeutic target for cardiovascular diseases?

Introduction: The Notch pathway is involved in determining cell fate during development and postnatally in continuously renewing tissues, such as the endothelium, the epithelium, and in the stem cells pool. The dysregulation of the Notch pathway is one of the causes of limited response, or resistance, to available cancer treatments and novel therapeutic strategies based on Notch inhibition are being investigated in preclinical and clinical studies in oncology. A large body of evidence now shows that the dysregulation of the Notch pathway is also involved in the pathophysiology of cardiovascular diseases (CVDs). Areas covered: This review discusses the molecular mechanisms involving Notch which underlie heart failure, aortic valve calcification, and aortic aneurysm. Expert opinion: Despite the existence of preventive, pharmacological and surgical interventions approaches, CVDs are the first causes of mortality worldwide. The Notch pathway is becoming increasingly recognized as being involved in heart failure, aortic aneurysm and aortic valve calcification, which are among the most common global causes of mortality due to CVDs. As already shown in cancer, the dissection of the biological processes and molecular mechanisms involving Notch should pave the way for new strategies to prevent and cure these diseases.

C1q-TNF-related protein-3 attenuates pressure overload-induced cardiac hypertrophy by suppressing the p38/CREB pathway and p38-induced ER stress

C1q-tumor necrosis factor-related protein-3 (CTRP3) is an adipokine, which exerts protective function in ischemic or diabetic heart injury. However, the role of CTRP3 in cardiac hypertrophy remains unclear. The aim of this study was to investigate the pharmacological effects of CTRP3 on pathological cardiac hypertrophy induced by hypertension. Male C57BL/6 J wild-type (WT) mice, Ctrp3 knockout mice, and mice infected with lentivirus overexpressing mouse Ctrp3 underwent sham surgery or transverse aortic constriction (TAC) surgery. After 4 weeks, cardiac hypertrophy, fibrosis, and cardiac function were examined. Compared with WT mice, Ctrp3 deficiency substantially impaired contractile dysfunction, exacerbated the enlargement of cardiomyocytes and myocardial fibrosis, and reprogramed the expression of pathological genes after TAC. Conversely, CTRP3 overexpression played a role in restoring the left ventricular cardiac contractile function, alleviating cardiac hypertrophy and fibrosis, and inhibiting the expression of hypertrophic and fibrotic signaling in mice after TAC. Furthermore, CTRP3 regulated the expression of the p38/CREB pathway and of the primary modulating factors of the endoplasmic reticulum stress, i.e., GRP78 and the downstream molecules eukaryotic translation inhibition factor 2 submit α, C/EBP homologous protein, and inositol-requiring enzyme-1. Further, inhibition of p38 MAPK by SB203580 blunted the ER stress intensified by Ctrp3 deficiency. In vitro, CTRP3 protected neonatal rat cardiac myocytes against phenylephrine-induced cardiomyocyte hypertrophy. We conclude that CTRP3 protects the host against pathological cardiac remodeling and left ventricular dysfunction induced by pressure overload largely by inhibiting the p38/CREB pathway and alleviating p38-induced ER stress.

Nutritional Preconditioning of Apigenin Alleviates Myocardial Ischemia/Reperfusion Injury via the Mitochondrial Pathway Mediated by Notch1/Hes1

Apigenin (Api), a natural flavone found in high amounts in several herbs, has shown potent cardioprotective effects in clinical studies, although the underlying mechanisms are not clear. We hypothesized that Api protects the myocardium from simulated ischemia/reperfusion (SI/R) injury via nutritional preconditioning (NPC). Rats fed with Api-containing food showed improvement in cardiac functions; lactate dehydrogenase (LDH) and creatine phosphokinase (CPK) activities; infarct size; apoptosis rates; malondialdehyde (MDA) levels; caspase-3, superoxide dismutase (SOD), glutathione peroxidase (GSH-Px), and catalase (CAT) activities; and ferric reducing antioxidant power (FRAP) compared to those fed standard chow following SI/R injury. In addition, Api pretreatment significantly improved the viability, decreased the LDH activity and intracellular reactive oxygen species (ROS) generation, alleviated the loss of mitochondrial membrane potential (MMP), prevented the opening of the mitochondrial permeability transition pore (mPTP), and decreased the caspase-3 activity, cytochrome c (Cyt C) release, and apoptosis induced by SI/R in primary cardiomyocytes. Mechanistically, Api upregulated Hes1 expression and was functionally neutralized by the Notch1 γ-secretase inhibitor GSI, as well as the mPTP opener atractyloside (Atr). Taken together, Api protected the myocardium against SI/R injury via the mitochondrial pathway mediated by the Notch1/Hes1 signaling pathway.

Notch signal pathway - therapeutic target for regulation of reparative processes in the heart

Notch signaling pathway is a universal regulator of cell fate in embryogenesis and in maintaining the cell homeostasis of adult tissue. Through local cell-cell interactions, he controls neighboring cells behavior and determines their capacity for self-renewal, growth, survival, differentiation, and apoptosis. Recent studies have shown that the control of regenerative processes in the heart is also carried out with the participation of Notch system. At the heart of Notch regulates migration bone marrow progenitors and stimulates the proliferation of cardiomyocytes, cardiac progenitor cell activity, limits cardiomyocyte hypertrophy and fibrosis progression and stimulates angiogenesis. Notch signaling pathway may be regarded as a very promising target for the development of drugs for the stimulation of regeneration in the myocardium.

Candidate early predictive plasma protein markers of doxorubicin-induced chronic cardiotoxicity in B6C3F1 mice

Cardiotoxicity is a serious adverse effect of doxorubicin (DOX) treatment in cancer patients. Currently, there is a lack of sensitive biomarkers to predict the risk of DOX-induced cardiotoxicity. Using SOMAmer-based proteomic technology, 1129 proteins were profiled to identify potential early biomarkers of cardiotoxicity in plasma from male B6C3F₁ mice given a weekly intravenous dose of 3 mg/kg DOX or saline (SAL) for 2, 3, 4, 6, or 8 weeks (6, 9, 12, 18, or 24 mg/kg cumulative DOX doses, respectively). Also, a group of mice received the cardio-protectant, dexrazoxane (DXZ; 60 mg/kg; intraperitoneal) 30 min before a weekly DOX or SAL dose. Proteomic analysis in plasma collected a week after the last dose showed a significant ≥1.2-fold change in level of 18 proteins in DOX-treated mice compared to SAL-treated counterparts during 8-week exposure. Of these, neurogenic locus notch homolog protein 1 (NOTCH1), von Willebrand factor (vWF), mitochondrial glutamate carrier 2, Wnt inhibitory factor 1, legumain, and mannan-binding lectin serine protease 1 were increased in plasma at 6 mg/kg cumulative DOX dose, prior to the release of myocardial injury marker, cardiac troponin I at 12 mg/kg and higher cumulative doses. These six proteins also remained significantly elevated following myocardial injury or pathology at 24 mg/kg. Pretreatment of mice with DXZ significantly attenuated DOX-induced elevated levels of only NOTCH1 and vWF with mitigation of cardiotoxicity. This suggests NOTCH1 and vWF as candidate early biomarkers of DOX cardiotoxicity, which may help in addressing a clinically important question of identifying cancer patients at risk for cardiotoxicity.

Protective role of microRNA-374 against myocardial ischemia-reperfusion injury in mice following thoracic epidural anesthesia by downregulating dystrobrevin alpha-mediated Notch1 axis

Ischemia-reperfusion (I/R) injury often leads to myocardial apoptosis and necrosis. Studies have demonstrated the role microRNAs (miRs) played in myocardial I/R injury. Thus, we established a myocardial I/R injury model and a thoracic epidural anesthesia (TEA) model in mice to explore whether microRNA-374 (miR-374) affects myocardial I/R injury. We collected myocardial tissues to evaluate whether TEA exerts a protection effect on myocardial tissues. In addition, the levels of miR-374, dystrobrevin alpha (DTNA), and the statue of the Notch1 axis were detected. Subsequently, cardiomyocytes extracted from TEA mice were treated to regulate their levels of miR-374 and DTNA. After that, cell viability, cell cycle distribution, and apoptosis of cardiomyocytes were assessed. This was followed by the detection of the myocardial infarction area. The mice models of myocardial I/R injury were associated with poorly expressed miR-374 and highly expressed DTNA. TEA was found to protect myocardial tissues against myocardial I/R injury by elevating miR-374 and reducing DTNA. Dual-luciferase reporter assay validated that DTNA was the target gene of miR-374. Cardiomyocytes with overexpressed miR-374 were shown to have downregulated DTNA levels and blocked Notch1 axis. Overexpressed miR-374 was also found to promote the viability and inhibit the apoptosis of cardiomyocytes, as well as to increase the number of cells arrested in the S phase. In accordance with this, the myocardial infarction area was decreased with the upregulated miR-347 and downregulated DTNA. Collectively, these results demonstrated that, by inhibiting the activity of DTNA-mediated Notch1 axis, miR-374 could protect against myocardial I/R injury in mice after TEA.

The protective effects of acupoint gel embedding on rats with myocardial ischemia-reperfusion injury

AIMS

Prevention and treatment of myocardial ischemia-reperfusion (I/R) injury has for many years been a hot topic in treating ischemic heart disease. As one of the most well-known methods of complementary and alternative medicine, acupuncture has attracted increasing interest in preventing myocardial I/R injury due to its remarkable effectiveness and minimal side effect. However, traditional acupuncture approaches are limited by cumbersome execution, high labor costs and inevitable pain caused by frequent stimulation. Therefore, in this work, we aimed to develop a novel acupoint gel embedding approach and investigated its role in protecting against myocardial I/R injury in rats.

MAIN METHODS

Gels were embedded at bilateral Neiguan (PC6) points of rats and their protective effects against myocardial I/R injury evaluated in terms of changes in histomorphology, myocardial enzymology, antioxidant capacity, anti-inflammatory response, and anti-apoptosis of cells.

KEY FINDINGS

We found that the approach of acupoint gel embedding could significantly reduce myocardial infarcted size, repair pathological changes, mitigate oxidative stress damage and inflammatory response, as well as inhibit apoptosis of cardiomyocytes. Such cardioprotective effects were found to be associated with Notch-1/Jagged-1 signaling pathway.

SIGNIFICANCE

The proposed approach of acupoint gel embedding has advantages in continuous acupoint stimulation, dosing controls, and no side effects in the course of treatment, as well as in reducing the pain caused by frequent acupuncture. It can form an alternative therapy to not only protect against myocardial I/R injury but also hold great potential in treating other diseases in the future.

MiR-381 negatively regulates cardiomyocyte survival by suppressing Notch signaling

The mechanisms for cardiomyocyte death in cardiovascular diseases are incompletely understood. The aim of this study is to reveal the function of miR-381 in myocardium infarction (MI)-induced cardiomyocyte apoptosis. We established mouse model of MI and cellular models of apoptosis induced by oxidative stress (H₂O₂ and hypoxia/reoxygenation (H/R)). The expression of miR-381 in these models was assessed by quantitative reverse transcription polymerase chain reaction (qRT-PCR); we employed approaches including cell counting kit-8 (CCK-8) assay and flow cytometry to evaluate the cell viability and apoptosis. Notch signaling was determined by western blot analysis of key signaling components including Notch1 intracellular domain (ICD), Jag1, and Hes1. The predicted binding of miR-381 to Jag1 3' untranslated region (UTR) was validated by luciferase assay. Following MI, miR-381 expression was upregulated time dependently in the border zone of ischemic area but not in the non-ischemic area. MiR-381 expression was also upregulated in cardiomyocytes treated with H₂O₂ and H/R. Overexpression of miR-381 exacerbated H₂O₂- and H/R-induced apoptosis of cardiomyocytes; in contrast, inhibition of miR-381 attenuated apoptosis in these conditions. Importantly, in vivo delivery of miR-381 antagomir significantly reduced infarction size. Moreover, miR-381 negatively regulates the cardioprotective Notch signaling in vivo and in vitro, which might be an effect of targeted inhibition of Jag1 by itself. These data indicate an essential role of miR-381/Jag1 pathway in regulating Notch signaling-mediated cardioprotective effect in cardiomyocytes. Our study also provides a potential therapeutic target for cardiovascular diseases.

Melatonin and cardioprotection against ischaemia/reperfusion injury: What's new? A review

Melatonin is a pleiotropic hormone with several functions. It binds to specific receptors and to a number of cytosolic proteins, activating a vast array of signalling pathways. Its potential to protect the heart against ischaemia/reperfusion damage has attracted much attention, particularly in view of its possible clinical applications. This review will focus mainly on the possible signalling pathways involved in melatonin-induced cardioprotection. In particular, the role of the melatonin receptors and events downstream of receptor activation, for example, the reperfusion injury salvage kinase (RISK), survivor activating factor enhancement (SAFE) and Notch pathways, the sirtuins, nuclear factor E2-related factor 2 (Nrf2) and translocases in the outer membrane (TOM70) will be discussed. Particular attention is given to the role of the mitochondrion in melatonin-induced cardioprotection. In addition, a brief overview will be given regarding the status quo of the clinical application of melatonin in humans.

Notch1 Mediates Preconditioning Protection Induced by GPER in Normotensive and Hypertensive Female Rat Hearts

G protein-coupled estrogen receptor (GPER) is an estrogen receptor expressed in the cardiovascular system. G1, a selective GPER ligand, exerts cardiovascular effects through activation of the PI3K-Akt pathway and Notch signaling in normotensive animals. Here, we investigated whether the G1/GPER interaction is involved in the limitation of infarct size, and improvement of post-ischemic contractile function in female spontaneous hypertensive rat (SHR) hearts. In this model, we also studied Notch signaling and key components of survival pathway, namely PI3K-Akt, nitric oxide synthase (NOS) and mitochondrial K⁺-ATP (MitoKATP) channels. Rat hearts isolated from female SHR underwent 30 min of global, normothermic ischemia and 120 min of reperfusion. G1 (10 nM) alone or specific inhibitors of GPER, PI3K/NOS and MitoKATP channels co-infused with G1, just before I/R, were studied. The involvement of Notch1 was studied by Western blotting. Infarct size and left ventricular pressure were measured. To confirm endothelial-independent G1-induced protection by Notch signaling, H9c2 cells were studied with specific inhibitor, N-[N-(3,5 difluorophenacetyl)-L-alanyl]-S-phenylglycine t-butyl ester (DAPT, 5 μM), of this signaling. Using DAPT, we confirmed the involvement of G1/Notch signaling in limiting infarct size in heart of normotensive animals. In the hypertensive model, G1-induced reduction in infarct size and improvement of cardiac function were prevented by the inhibition of GPER, PI3K/NOS, and MitoKATP channels. The involvement of Notch was confirmed by western blot in the hypertensive model and by the specific inhibitor in the normotensive model and cardiac cell line. Our results suggest that GPERs play a pivotal role in mediating preconditioning cardioprotection in normotensive and hypertensive conditions. The G1-induced protection involves Notch1 and is able to activate the survival pathway in the presence of comorbidity. Several pathological conditions, including hypertension, reduce the efficacy of ischemic conditioning strategies. However, G1-induced protection can result in significant reduction of I/R injury also female in hypertensive animals. Further studies may ascertain the clinical translation of the present results.

Fenofibrate protects against acute myocardial I/R injury in rat by suppressing mitochondrial apoptosis as decreasing cleaved caspase-9 activation

BACKGROUND AND AIMS

Peroxisome proliferator-activated receptor-α (PPAR-α) activation has been reported to reduce myocardial ischemia-reperfusion (I/R) injury by inhibiting cell apoptosis. However, the antiapoptotic mechanism of PPAR-α is still unknown. Fenofibrate is a PPAR-α agonist In the present study, we investigate the effects and relevant mechanism of fenofibrate on experimental myocardial ischemia-reperfusion (I/R) injury in rats.

METHODS

Adult male Wistar rats were pretreated with fenofibrate (80 mg/kg) daily for a period of 7 days. After the treatment period, myocardial I/R injury model was made by left anterior descending coronary artery ligation for 45 min and reperfusion for 120 min. Myocardial infarct size, malondialdehyde (MDA) cleaved-caspase-9 protein expression, PPARα and uncoupling protein 2 (UCP2) mRNA levels in myocardial tissue were detected Cell apoptosis was detected by Terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling (TUNEL). Serum lactate dehydrogenase and creatine kinase activities were measured in rats pretreated with fenofibrate The ultrastructure of myocardial tissues was observed.

RESULTS

Significant increases in myocardial cell apoptosis, malondialdehyde (MDA) level and cleaved-caspase-9 protein expression level in myocardial tissue were observed, along with reductions of PPARα and uncoupling protein 2 (UCP2) mRNA levels in myocardial tissue of the experimental myocardial ischemia-reperfusion (I/R) injury in rats. Impaired mitochondria were also observed under electron microscopic. However, pretreatment of ischemia/reperfusion rats with fenofibrate brought the biochemical parameters and related genes expression levels to near normalcy, indicating the protective effect of fenofibrate against myocardial ischemia/reperfusion injury in rats.

CONCLUSIONS

The PPAR-α activator fenofibrate conferred cytoprotective effect against myocardial ischemia-reperfusion (I/R) injury in rats. Associated mechanisms involved decreased cleaved-caspase-9 expression and decreased cell apoptosis.

MicroRNA-30e protects the heart against ischemia and reperfusion injury through autophagy and the Notch1/Hes1/Akt signaling pathway

The aim of the present study was to determine the cardioprotective mechanisms by which micro (mi)RNA-30e protects the heart from myocardial ischemia/reperfusion injury (MI/R) and to explore the signaling pathways that may confer protection for the heart and be potential therapeutic targets. It was demonstrated that miRNA‑30e expression was decreased in patients with MI/R. In H9C2 cells, silencing (si)miRNA‑30e significantly inhibited cellular apoptosis, the expression of apoptosis regulator BAX (Bax) and caspase‑3 activity. It also significantly increased the expression of microtubule‑associated proteins 1A/1B light chain 3B, p62, Beclin‑1, neurogenic locus notch homolog protein‑1 (Notch1), Hes1 and phosphorylated‑protein kinase B (p‑Akt), and decreased the expression of inducible NO synthase (iNOS) and proteins associated with oxidative stress. The inhibition of autophagy following treatment with 3‑methyladenine significantly reversed the effect of si‑miRNA‑30e on apoptosis, Bax, caspase‑3, iNOS and oxidative stress in H9C2 cells. The promotion of Notch1 expression increased the effect of si‑miRNA‑30e on apoptosis, Bax, caspase‑3, iNOS, Notch1, Hes1 and p‑Akt protein expression and oxidative stress in H9C2 cells. Taken together, these results indicate that miRNA‑30e protects the heart from MI/R via autophagy and the Notch1/Hes1/Akt signaling pathway.

The opposite effects of nitric oxide donor, S-nitrosoglutathione, on myocardial ischaemia/reperfusion injury in diabetic and non-diabetic mice

Nitric oxide is a potent anti-apoptotic and cardioprotective molecule in healthy animals. However, recent study demonstrates that overexpression of eNOS exacerbates the liver injury in diabetic animals. whether diabetes may also alter NO's biologic activity in ischaemic/reperfused heart remains unknown. The present experiment was designed to determine whether the nitric oxide donor, S-nitrosoglutathione, may exert different effects on diabetic and non-diabetic myocardial ischaemia/reperfusion (MI/R) injury. Diabetic state was induced in mice by multiple intraperitoneal injections of low-dose streptozotocin (STZ). The control or diabetic mice were subjected to 30 minutes ischaemia and 3 or 24 hours reperfusion. At 10 minutes before reperfusion, diabetic and non-diabetic mice were received an intraperitoneal injection of S-nitrosoglutathione (GSNO, a nitric oxide donor, 1 μmol/kg). GSNO attenuated MI/R injury in non-diabetic mice, as measured by improved cardiac function, reduced infarct size and decreased cardiomyocyte apoptosis. In contrast, GSNO failed to attenuate but, rather, aggravated the MI/R injury in diabetic mice. Mechanically, the diabetic heart exhibited an increased nitrative/oxidative stress level, as measured by peroxynitrite formation, compared with non-diabetic mice. Co-administration of GSNO with EUK134 (a peroxynitrite scavenger) or MnTE-2-PyP5 (a superoxide dismutase mimetic) or Apocynin (a NADPH oxidase inhibitor) 10 minutes before reperfusion significantly decreased the MI/R-induced peroxynitrite formation and the MI/R injury. Collectively, the present study for the first time demonstrated that diabetes may cause superoxide overproduction, increase NO inactivation and peroxynitrite formation, and thus convert GSNO from a cardioprotective molecule to a cardiotoxic molecule.

Effect of the Notch signaling pathway on retinal ganglion cells and its neuroprotection in rats with acute ocular hypertension

AIM

To explore the effect of the Notch signaling pathway on retinal ganglion cells (RGCs) and optic nerve in rats with acute ocular hypertension (OH).

METHODS

Totally 48 Sprague-Dawley (SD) rats were included, among which 36 rats were selected to establish acute OH models. OH rats received a single intravitreal injection of 2 µL phosphate buffered solution (PBS) and another group of OH rats received a single intravitreal injection of 10 µmol/L γ-secretase inhibitor (DAPT). Quantitative real-time polymerase chain reaction (qPCR) and Western blot assay were adopted to determine the mRNA level of Notch and the protein levels of Notch, Bcl-2, Bax, caspase-3, and growth-associated protein 43 (GAP-43). The RGC apoptosis conditions were assessed by TUNEL staining.

RESULTS

The OH rats and PBS-injected rats had increased expression levels of Notch1, Bax, caspase-3, and GAP-43, decreased expression levels of Bcl-2, and increased RGC apoptosis, with severer macular edema and RGCs more loosely aligned, when compared with the normal rats. The DAPT-treated rats displayed increased expression levels of Notch1, Bax, caspase-3, and GAP-43, decreased expression levels of Bcl-2, and increased RGC apoptosis, in comparison with the OH rats and PBS-injected rats. RGCs were hardly observed and macular edema became severe in the DAPT-treated rat.

CONCLUSION

The Notch signaling pathway may suppress the apoptosis of retinal ganglion cells and enhances the regeneration of the damaged optic nerves in rats with acute OH.

Polydatin Protects Diabetic Heart against Ischemia-Reperfusion Injury via Notch1/Hes1-Mediated Activation of Pten/Akt Signaling

Diabetes exacerbates oxidative/nitrative stress during myocardial ischemia-reperfusion (MI/R) injury. Recent studies highlighted the cardioprotective actions of polydatin. However, its effect on diabetic MI/R injury and the underlying mechanisms remain unknown. This work was undertaken to evaluate the effect of polydatin on diabetic MI/R injury with a focus on Notch1/Hes1 signaling and myocardial oxidative/nitrative stress. Streptozotocin- (STZ-) induced diabetic rats were administered with polydatin (20 mg/kg/d) in the absence or presence of DAPT (a γ-secretase inhibitor) or LY294002 (a PI3K/Akt inhibitor) and then subjected to MI/R injury. Polydatin administration preserved cardiac function and reduced myocardial infarct size. Moreover, polydatin ameliorated myocardial oxidative/nitrative stress damage as evidenced by decreased myocardial superoxide generation, malondialdehyde, gp91^phox expression, iNOS expression, NO metabolite level, and nitrotyrosine content and increased eNOS phosphorylation. However, these effects were blocked by DAPT administration. DAPT also inhibited the stimulatory effect of polydatin on the Notch1/Hes1-Pten/Akt signaling pathway in a diabetic myocardium. Additionally, LY294002 not only abolished polydatin's antiapoptotic effect but also reversed its inhibitory effect on myocardial oxidative/nitrative stress. Polydatin effectively reduced MI/R injury and improved left ventricular functional recovery under diabetic condition by ameliorating oxidative/nitrative stress damage. Importantly, Notch1/Hes1-mediated activation of Pten/Akt signaling played a crucial role in this process.

Simulated microgravity hampers Notch signaling in the fight against myocardial ischemia‑reperfusion injury

The gravitational field is an important determinant of cardiovascular function. Exposure to microgravity during spaceflight may lead to a series of maladaptive alterations in the cardiovascular system. The authors have previously demonstrated that microgravity can increase the susceptibility to myocardial ischemia‑reperfusion (IR) injury under simulated microgravity. Although Notch1 signaling protects against myocardial IR injury, whether Notch1 protects against myocardial IR injury under simulated weightlessness remains unknown. The present study is designed to investigate the role of the Notch1 receptor in myocardial IR injury under simulated weightlessness. The differences in Notch signaling expression and myocardial infarct size following myocardial IR were compared between normal rats and tail‑suspended rats that were kept in 30˚ head‑down tilt and hindlimb unloading position. The data revealed low expression levels of Notch1 receptor and its endogenous ligand Jagged1 in normal adult rat hearts. However, significantly higher expression of Notch1 was observed in the border zone compared with the infarcted area and the remote zone following myocardial IR. Notch1 expression was notably reduced in the infarcted hearts of tail‑suspended rats compared with the control group. Conversely, the myocardial infarct size was significantly increased in tail‑suspended rats compared with the control rats. In conclusion, these data suggested that the proper function of Notch signaling may be hampered under simulated microgravity.

MicroRNA-137 regulates hypoxia-induced retinal ganglion cell apoptosis through Notch1

The apoptosis of retinal ganglion cells (RGCs) is a hallmark of several optic neuropathies. MicroRNAs (miRNAs) are recently identified regulators of various biological processes. However, the role of miRNAs in regulating RGC apoptosis remains largely unknown. We herein aimed to demonstrate that miR-137 acts as a hypoxia-responsive gene in RGCs that is downregulated under hypoxic conditions. It was observed that overexpression of miR-137 markedly aggravated hypoxia-induced cell apoptosis, whereas inhibition of miR-137 effectively protected RGCs against hypoxia-induced apoptosis. Hypoxia induced Notch1 expression and signaling activation, while blocking Notch signaling significantly aggravated hypoxia-induced cell apoptosis. Further data revealed that the pro-survival Akt signaling pathway was involved in miR-137-Notch signaling pathway-mediated RGC protection. Knockdown of Notch significantly reversed the effect of anti‑miR-137 on RGC protection and Akt signaling activation. In addition, blocking Akt signaling also significantly abrogated the protective effect of anti-miR-137 on hypoxia-induced cell injury. Overall, the results of the present study demonstrated that miR-137 targets Notch1 expression, revealing a novel link between miR-137 and Notch signaling, and suggesting that a miR-137/Notch1 axis may serve as a potential molecular target for the treatment of hypoxia-induced retinal diseases.

Relaxin ameliorates high glucose-induced cardiomyocyte hypertrophy and apoptosis via the Notch1 pathway

The present study aimed to investigate the role of relaxin (RLX) on high glucose (HG)-induced cardiomyocyte hypertrophy and apoptosis, as well as the possible molecular mechanism. H9c2 cells were exposed to 33 mmol/l HG with or without RLX (100 nmol/ml). Cell viability, apoptosis, oxidative stress, cell hypertrophy and the levels of Notch1, hairy and enhancer of split 1 (hes1), atrial natriuretic polypeptide (ANP), brain natriuretic peptide (BNP), manganese superoxide dismutase (MnSOD), cytochrome C and caspase-3 were assessed in cardiomyocytes. Compared with the HG group, the viability of H9c2 cells was increased by RLX in a time- and dose-dependent manner, and was accompanied with a significant reduction in apoptosis. Furthermore, RLX significantly suppressed the formation of reactive oxygen species and malondialdehyde, and enhanced the activity of SOD. In addition, the levels of ANP, BNP, cytochrome C and caspase-3 were increased and Notch1, hes1 and MnSOD were inhibited in the HG group compared with those in the normal group. However, the Notch inhibitor DAPT almost abolished the protective effects of RLX. These results suggested that RLX protected cardiomyocytes from HG-induced hypertrophy and apoptosis partly through a Notch1-dependent pathway, which may be associated with reducing oxidative stress.

Alginate oligosaccharide alleviates myocardial reperfusion injury by inhibiting nitrative and oxidative stress and endoplasmic reticulum stress-mediated apoptosis

Alginate oligosaccharide (AOS) has recently demonstrated the ability to protect against acute doxorubicin cardiotoxicity and neurodegenerative disorders by inhibiting oxidative stress and endoplasmic reticulum (ER) stress-mediated apoptosis, which are both involved in myocardial ischemia/reperfusion (I/R) injury. In the present study, we investigated whether pretreatment with AOS protects against myocardial I/R injury in mice and explored potential cardioprotective mechanisms. AOS pretreatment significantly decreased the infarct size, reduced the cardiac troponin-I concentration, and ameliorated the cardiac dysfunction. Accompanied with the reduced cardiac injury, AOS pretreatment clearly decreased I/R-induced myocardial apoptosis. With regard to mechanism, AOS pretreatment markedly attenuated nitrative/oxidative stress, as evidenced by decreases in 3-nitrotyrosine content and superoxide generation, and downregulated inducible nitric oxide synthase, NADPH oxidase2, and 4-hydroxynonenal. Moreover, AOS pretreatment decreased myocardial apoptosis by inhibiting the ER stress-mediated apoptosis pathway, which is reflected by the downregulation of C/EBP homologous protein, glucose-regulated protein 78, caspase-12, and Bcl-2-associated X protein, and by the upregulation of the anti-apoptotic protein B-cell lymphoma-2. Collectively, these findings demonstrate that AOS renders the heart resistant to I/R injury, at least in part, by inhibiting nitrative/oxidative stress and ER stress-mediated apoptosis.

MICU1 protects against myocardial ischemia/reperfusion injury and its control by the importer receptor Tom70

Mitochondrial Ca²⁺ overload is a main contributor to mitochondrial damage hence cardiomyocyte death in myocardial ischemia/reperfusion (MI/R) injury. MICU1 has been recently identified as an important regulator of mitochondrial Ca²⁺ homeostasis. Here we try to identify the role of MICU1 in MI/R, and to investigate whether the mitochondrial importer receptor Tom70 possesses critical roles in the mitochondrial translocation of MICU1 and MI/R. Specific small interfering RNA (20 μg) against MICU1 and Tom70, and lentivirus vectors carrying the Tom70a sequences (3.3 × 10⁷ TU) were delivered through intramyocardial injection. Seventy-two hours after injection, mice were subjected to 30 min of MI followed by 3 h (for cell apoptosis and mitochondrial damage assessment) or 24 h (for cardiac function and infarct size determination) of reperfusion. MI/R had no significant effect on total MICU1 expression, but caused significant reduction of MICU1 in mitochondria. Knockdown of MICU1 significantly aggravated MI/R injury, as evidenced by enlarged infarct size, depressed cardiac function and increased myocardial apoptosis. Moreover, MICU1 deficiency resulted in markedly aggravated mitochondrial Ca²⁺ overload, consequently destructed mitochondrial morphology and suppressed mitochondrial function (evidenced by decreased ATP production). Interestingly, mitochondrial Tom70 was also decreased in MI/R. Genetic loss-function study revealed that mitochondrial MICU1 expression was depressed by Tom70 ablation. Furthermore, Tom70 deficiency significantly aggravated MI/R injury and worsened mitochondrial Ca²⁺ overload. However, supplementation of Tom70 significantly attenuated MI/R injury, preserved mitochondrial morphology and function, and inhibited mitochondrial Ca²⁺ overload, all of which were abolished by MICU1 suppression. Mitochondrial Tom70/MICU1 pathway protects against MI/R injury, in which mitochondrial localization of MICU1 is governed by Tom70, and MICU1 serves as an indispensable factor in Tom70’s cardioprotection.

Astragaloside attenuates myocardial injury in a rat model of acute myocardial infarction by upregulating hypoxia inducible factor‑1α and Notch1/Jagged1 signaling

The present study aimed to investigate the mechanisms underlying the cardioprotective effect of Astragaloside against myocardial injury following myocardial infarction (MI) in a rat model. Male Wistar rats were subjected to left anterior descending branch ligation. The rats that survived 24 h (n=18) were randomly and equally assigned to three groups: MI model group, and 2.5 and 10 mg/kg/day Astragaloside group. A further six rats underwent identical surgical procedures without artery ligation, serving as sham controls. Following 28 days of treatment, the left ventricle was harvested for morphological analysis, and mRNA and protein expression levels of hypoxia inducible factor‑1α (HIF‑1α), Notch1 and Jagged1 were measured. Treatment with Astragaloside attenuated pathological changes in the myocardium. Compared with untreated MI rats, rats treated with Astragaloside exhibited significantly increased mRNA expression levels of HIF‑1α, Notch1 and Jagged1 (all P<0.01). HIF‑1α demonstrated a dose‑dependent effect (P<0.05). Astragaloside (10 mg/kg/day) significantly increased HIF‑1α (P<0.05), Notch1 (P<0.01) and Jagged1 (P<0.01) protein expression levels. Additionally, 2.5 mg/kg Astragaloside significantly increased Jagged1 protein expression levels compared with untreated MI rats. Furthermore, there was a dose‑dependent effect of Astragaloside treatment (P<0.01). These findings suggested that the cardioprotective effects of Astragaloside against myocardial injury following MI may involve upregulation of HIF‑α, Notch1 and Jagged1 signaling, implicating these molecules as therapeutic targets for the treatment of MI.

Notch Signaling in Ischemic Damage and Fibrosis: Evidence and Clues from the Heart

Notch signaling is a major intercellular coordination mechanism highly conserved throughout evolution. In vertebrates, Notch signaling is physiologically involved in embryo development, including mesenchymal cell commitment, formation of heart tissues and angiogenesis. In post-natal life, Notch signaling is maintained as a key mechanism of cell–cell communication and its dysregulations have been found in pathological conditions such as ischemic and fibrotic diseases. In the heart, Notch takes part in the protective response to ischemia, being involved in pre- and post-conditioning, reduction of reperfusion-induced oxidative stress and myocardial damage, and cardiomyogenesis. Conceivably, the cardioprotective effects of Notch may depend on neo-angiogenesis, thus blunting lethal myocardial ischemia, as well as on direct stimulation of cardiac cells to increase their resistance to injury. Another post-developmental adaptation of Notch signaling is fibrosis: being involved in the orientation of mesenchymal cell fate, Notch can modulate the differentiation of pro-fibrotic myofibroblasts, e.g., by reducing the effects of the profibrotic cytokine TGF-β. In conclusion, Notch can regulate the interactions between heart muscle and stromal cells and switch cardiac repair from a pro-fibrotic default pathway to a pro-cardiogenic one. These features make Notch signaling a suitable target for new cardiotropic therapies.

2,3,5,4'-Tetrahydroxystilbene-2-O-β-D-glucoside protects murine hearts against ischemia/reperfusion injury by activating Notch1/Hes1 signaling and attenuating endoplasmic reticulum stress

2,3,5,4'-Tetrahydroxystilbene-2-O-β-D-glucoside (TSG) is a water-soluble active component extracted from Polygonum multiflorum Thunb. A number of studies demonstrate that TSG exerts cardioprotective effects. Since endoplasmic reticulum (ER) stress plays a key role in myocardial ischemia/reperfusion (MI/R)-induced cell apoptosis, we sought to determine whether modulation of the ER stress during MI/R injury was involved in the cardioprotective action of TSG. Male mice were treated with TSG (60 mg·kg^-1·d^-1, ig) for 2 weeks and then were subjected to MI/R surgery. Pre-administration of TSG significantly improved post-operative cardiac function, and suppressed MI/R-induced myocardial apoptosis, evidenced by the reduction in the myocardial apoptotic index, serum levels of LDH and CK after 6 h of reperfusion. TSG (0.1-1000 μmol/L) did not affect the viability of cultured H9c2 cardiomyoblasts in vitro, but pretreatment with TSG dose-dependently decreased simulated ischemia/reperfusion (SIR)-induced cell apoptosis. Furthermore, both in vivo and in vitro studies revealed that TSG treatment activated the Notch1/Hes1 signaling pathway and suppressed ER stress, as evidenced by increasing Notch1, Notch1 intracellular domain (NICD), Hes1, and Bcl-2 expression levels and by decreasing p-PERK/PERK ratio, p-eIF2α/eIF2α ratio, and ATF4, CHOP, Bax, and caspase-3 expression levels. Moreover, the protective effects conferred by TSG on SIR-treated H9c2 cardiomyoblasts were abolished by co-administration of DAPT (the Notch1 signaling inhibitor). In summary, TSG ameliorates MI/R injury in vivo and in vitro by activating the Notch1/Hes1 signaling pathway and attenuating ER stress-induced apoptosis.

Melatonin attenuates postmyocardial infarction injury via increasing Tom70 expression

Mitochondrial dysfunction leads to reactive oxygen species (ROS) overload, exacerbating injury in myocardial infarction (MI). As a receptor for translocases in the outer mitochondrial membrane (Tom) complex, Tom70 has an unknown function in MI, including melatonin-induced protection against MI injury. We delivered specific small interfering RNAs against Tom70 or lentivirus vectors carrying Tom70a sequences into the left ventricles of mice or to cultured neonatal murine ventricular myocytes (NMVMs). At 48 h post-transfection, the left anterior descending coronary arteries of mice were permanently ligated, while the NMVMs underwent continuous hypoxia. At 24 h after ischemia/hypoxia, oxidative stress was assessed by dihydroethidium and lucigenin-enhanced luminescence, mitochondrial damage by transmission electron microscopy and ATP content, and cell apoptosis by terminal deoxynucleotidyl transferase dUTP nick-end labeling and caspase-3 assay. At 4 weeks after ischemia, cardiac function and fibrosis were evaluated in mice by echocardiography and Masson's trichrome staining, respectively. Ischemic/hypoxic insult reduced Tom70 expression in cardiomyocytes. Tom70 downregulation aggravated post-MI injury, with increased mitochondrial fragmentation and ROS overload. In contrast, Tom70 upregulation alleviated post-MI injury, with improved mitochondrial integrity and decreased ROS production. PGC-1α/Tom70 expression in ischemic myocardium was increased with melatonin alone, but not when combined with luzindole. Melatonin attenuated post-MI injury in control but not in Tom70-deficient mice. N-acetylcysteine (NAC) reversed the adverse effects of Tom70 deficiency in mitochondria and cardiomyocytes, but at a much higher concentration than melatonin. Our findings showed that Tom70 is essential for melatonin-induced protection against post-MI injury, by breaking the cycle of mitochondrial impairment and ROS generation.

Signaling Pathways in Cardiac Myocyte Apoptosis

Cardiovascular diseases, the number 1 cause of death worldwide, are frequently associated with apoptotic death of cardiac myocytes. Since cardiomyocyte apoptosis is a highly regulated process, pharmacological intervention of apoptosis pathways may represent a promising therapeutic strategy for a number of cardiovascular diseases and disorders including myocardial infarction, ischemia/reperfusion injury, chemotherapy cardiotoxicity, and end-stage heart failure. Despite rapid growth of our knowledge in apoptosis signaling pathways, a clinically applicable treatment targeting this cellular process is currently unavailable. To help identify potential innovative directions for future research, it is necessary to have a full understanding of the apoptotic pathways currently known to be functional in cardiac myocytes. Here, we summarize recent progress in the regulation of cardiomyocyte apoptosis by multiple signaling molecules and pathways, with a focus on the involvement of these pathways in the pathogenesis of heart disease. In addition, we provide an update regarding bench to bedside translation of this knowledge and discuss unanswered questions that need further investigation.