Selective inhibition of PTEN preserves ischaemic post-conditioning cardioprotection in STZ-induced Type 1 diabetic rats: role of the PI3K/Akt and JAK2/STAT3 pathways

Lycorine relieves the CCl4-induced liver fibrosis mainly via the JAK2/STAT3 and PI3K/AKT signaling pathways

Liver fibrosis, a progressive process of fibrous scarring, results from the accumulation of extracellular matrix proteins (ECM). If left untreated, it often progresses to diseases such as cirrhosis and hepatocellular carcinoma. Lycorine, a natural alkaloid derived from medicinal plants, has shown diverse bioactivities by targeting JAK2/STAT3 signaling, but its pharmacological effects and potential molecular mechanisms in liver fibrosis remains largely unexplored. The purpose of this study is to elucidate the pharmacological activity and molecular mechanism of lycorine in anti-hepatic fibrosis. Findings indicate that lycorine significantly inhibited hepatic stellate cells (HSCs) activation by reducing the expression of α-SMA and collagen-1. In vivo, lycorine treatment alleviated carbon tetrachloride (CCl4) -induced mice liver fibrosis, improving liver function, decreasing ECM deposition, and inhibiting fibrosis-related markers' expression. Mechanistically, it was found that lycorine exerts protective activity through the JAK2/STAT3 and PI3K/AKT signaling pathways, as evidenced by transcriptome sequencing technology and small molecule inhibitors. These results underscore lycorine's potential as a therapeutic drug for liver fibrosis.

Cardioprotective role of oleanolic acid in patients with type 2 diabetes mellitus

Background

Patients with type 2 diabetes mellitus (T2DM) experience a decline in cardiac function, resulting in poor prognosis. Therefore, restoration of cardiac function and improvement of myocardial fibrosis is an important treatment goal for patients with T2DM.

Material and methods

The chemical structure of oleanolic acid(OA) was downloaded from PubChem and uploaded to PharmMapper. GeneCards and OMIM databases were searched for genes related to OA and disease and plotted into a Venn diagram. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analyses were performed using R software. Then, a mouse model of diabetes mellitus was established, and ELISA, echocardiographic analysis of cardiac function, TUNEL assay, and reactive oxygen species assay were performed.

Results

Network pharmacology analysis identified the related targets and potential molecular mechanisms underlying the effects of OA in T2DM. ELISA, echocardiographic analysis of cardiac function, and TUNEL assay results showed that OA inhibits apoptosis and improves apoptotic indexes in mice with T2DM-induced myocardial injury.

Conclusion

The results demonstrate the myocardial protective effect of OA in this mouse model.

DJ-1 preserves ischemic postconditioning-induced cardioprotection in STZ-induced type 1 diabetic rats: role of PTEN and DJ-1 subcellular translocation

BACKGROUND

Ischemic postconditioning (IPostC) has been reported as a promising method for protecting against myocardial ischemia-reperfusion (MI/R) injury. Our previous study found that the infarct-limiting effect of IPostC is abolished in the heart of diabetes whose cardiac expression of DJ-1 (also called PARK7, Parkinsonism associated deglycase) is reduced. However, the role and in particular the underlying mechanism of DJ-1 in the loss of sensitivity to IPostC-induced cardioprotection in diabetic hearts remains unclear.

METHODS

Streptozotocin-induced type 1 diabetic rats were subjected to MI/R injury by occluding the left anterior descending artery (LAD) and followed by reperfusion. IPostC was induced by three cycles of 10s of reperfusion and ischemia at the onset of reperfusion. AAV9-CMV-DJ-1, AAV9-CMV-C106S-DJ-1 or AAV9-DJ-1 siRNA were injected via tail vein to either over-express or knock-down DJ-1 three weeks before inducing MI/R.

RESULTS

Diabetic rats subjected to MI/R exhibited larger infarct area, more severe oxidative injury concomitant with significantly reduced cardiac DJ-1 expression and increased PTEN expression as compared to non-diabetic rats. AAV9-mediated cardiac DJ-1 overexpression, but not the cardiac overexpression of DJ-1 mutant C106S, restored IPostC-induced cardioprotection and this effect was accompanied by increased cytoplasmic DJ-1 translocation toward nuclear and mitochondrial, reduced PTEN expression, and increased Nrf-2/HO-1 transcription. Our further study showed that AAV9-mediated targeted DJ-1 gene knockdown aggravated MI/R injury in diabetic hearts, and this exacerbation of MI/R injury was partially reversed by IPostC in the presence of PTEN inhibition or Nrf-2 activation.

CONCLUSIONS

These findings suggest that DJ-1 preserves the cardioprotective effect of IPostC against MI/R injury in diabetic rats through nuclear and mitochondrial DJ-1 translocation and that inhibition of cardiac PTEN and activation of Nrf-2/HO-1 may represent the major downstream mechanisms whereby DJ-1 preserves the cardioprotective effect of IPostC in diabetes.

N-acetylcysteine Protects Against Myocardial Ischemia-Reperfusion Injury Through Anti-ferroptosis in Type 1 Diabetic Mice

The hearts of subjects with diabetes are vulnerable to ischemia-reperfusion injury (IRI). In contrast, experimentally rodent hearts have been shown to be more resistant to IRI at the very early stages of diabetes induction than the heart of the non-diabetic control mice, and the mechanism is largely unclear. Ferroptosis has recently been shown to play an important role in myocardial IRI including that in diabetes, while the specific mechanisms are still unclear. Non-diabetic control (NC) and streptozotocin-induced diabetic (DM) mice were treated with the antioxidant N-acetylcysteine (NAC) in drinking water for 4 week starting at 1 week after diabetes induction. Mice were subjected to myocardial IRI induced by occluding the coronary artery for 30 min followed by 2 h of reperfusion, subsequently at 1, 2, and 5 week of diabetes induction. The post-ischemic myocardial infarct size in the DM mice was smaller than that in NC mice at 1 week of diabetes but greater than that in the NC mice at 2 and 5 week of diabetes, which were associated with a significant increase of ferroptosis at 2 and 5 week but a significant reduction of ferroptosis at 1 week of diabetes. NAC significantly attenuated post-ischemic ferroptosis as well as oxidative stress and reduced infarct size at 2 and 5 week of diabetes. Application of erastin, a ferroptosis inducer, reversed the cardioprotective effects of NAC. It is concluded that increased oxidative stress and ferroptosis are the major factors attributable to the increased vulnerability to myocardial IRI in diabetes and that attenuation of ferroptosis represents a major mechanism whereby NAC confers cardioprotection against myocardial IRI in diabetes.

JAK/STAT3 signaling in cardiac fibrosis: a promising therapeutic target

Cardiac fibrosis is a serious health problem because it is a common pathological change in almost all forms of cardiovascular diseases. Cardiac fibrosis is characterized by the transdifferentiation of cardiac fibroblasts (CFs) into cardiac myofibroblasts and the excessive deposition of extracellular matrix (ECM) components produced by activated myofibroblasts, which leads to fibrotic scar formation and subsequent cardiac dysfunction. However, there are currently few effective therapeutic strategies protecting against fibrogenesis. This lack is largely because the molecular mechanisms of cardiac fibrosis remain unclear despite extensive research. The Janus kinase/signal transducer and activator of transcription (JAK/STAT) signaling cascade is an extensively present intracellular signal transduction pathway and can regulate a wide range of biological processes, including cell proliferation, migration, differentiation, apoptosis, and immune response. Various upstream mediators such as cytokines, growth factors and hormones can initiate signal transmission via this pathway and play corresponding regulatory roles. STAT3 is a crucial player of the JAK/STAT pathway and its activation is related to inflammation, malignant tumors and autoimmune illnesses. Recently, the JAK/STAT3 signaling has been in the spotlight for its role in the occurrence and development of cardiac fibrosis and its activation can promote the proliferation and activation of CFs and the production of ECM proteins, thus leading to cardiac fibrosis. In this manuscript, we discuss the structure, transactivation and regulation of the JAK/STAT3 signaling pathway and review recent progress on the role of this pathway in cardiac fibrosis. Moreover, we summarize the current challenges and opportunities of targeting the JAK/STAT3 signaling for the treatment of fibrosis. In summary, the information presented in this article is critical for comprehending the role of the JAK/STAT3 pathway in cardiac fibrosis, and will also contribute to future research aimed at the development of effective anti-fibrotic therapeutic strategies targeting the JAK/STAT3 signaling.

Salvianolic acids and its potential for cardio-protection against myocardial ischemic reperfusion injury in diabetes

The incidence of diabetes and related mortality rate increase yearly in modern cities. Additionally, elevated glucose levels can result in an increase of reactive oxygen species (ROS), ferroptosis, and the disruption of protective pathways in the heart. These factors collectively heighten the vulnerability of diabetic individuals to myocardial ischemia. Reperfusion therapies have been effectively used in clinical practice. There are limitations to the current clinical methods used to treat myocardial ischemia-reperfusion injury. As a result, reducing post-treatment ischemia/reperfusion injury remains a challenge. Therefore, efforts are underway to provide more efficient therapy. Salvia miltiorrhiza Bunge (Danshen) has been used for centuries in ancient China to treat cardiovascular diseases (CVD) with rare side effects. Salvianolic acid is a water-soluble phenolic compound with potent antioxidant properties and has the greatest hydrophilic property in Danshen. It has recently been discovered that salvianolic acids A (SAA) and B (SAB) are capable of inhibiting apoptosis by targeting the JNK/Akt pathway and the NF-κB pathway, respectively. This review delves into the most recent discoveries regarding the therapeutic and cardioprotective benefits of salvianolic acid for individuals with diabetes. Salvianolic acid shows great potential in myocardial protection in diabetes mellitus. A thorough understanding of the protective mechanism of salvianolic acid could expand its potential uses in developing medicines for treating diabetes mellitus related myocardial ischemia-reperfusion.

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.

Hyperglycemia-Induced Overexpression of PH Domain Leucine-Rich Repeat Protein Phosphatase 1 (PHLPP1) Compromises the Cardioprotective Effect of Ischemic Postconditioning Via Modulation of the Akt/Mst1 Pathway Signaling

PURPOSE

Ischemic postconditioning (IPostC) alleviates myocardial ischemia/reperfusion (IR) injury, but the protective effect is lost during diabetes. PH domain leucine-rich repeat protein phosphatase 1 (PHLPP1) is able to inactivate Akt. Our previous study found that PHLPP1 expression was upregulated in diabetic hearts. We presumed that the attenuation of myocardial injury by IPostC might be hindered by PHLPP1 overexpression in diabetic animals.

METHODS AND RESULTS

Nondiabetic and diabetic mice were subjected to 45 min of ischemia followed by 2 h of reperfusion with or without IPostC. H9c2 cells were exposed to normal or high glucose and were subjected to 4 h of hypoxia followed by 4 h of reoxygenation with or without hypoxic postconditioning (HPostC). IPostC attenuated postischemic infarction, apoptosis, creatine kinase-MB, and oxidative stress, which were accompanied by increased p-Akt and decreased PHLPP1 expression and p-Mst1 in nondiabetic but not in diabetic mice. PHLPP1 knockdown or an Mst1 inhibitor reduced hypoxia/reoxygenation (HR)-induced cardiomyocyte damage in H9c2 cells exposed to normal glucose, but the effect was abolished by a PI3K/Akt inhibitor. HPostC attenuated HR-induced cardiomyocyte injury and oxidative stress accompanied by increased p-Akt as well as decreased PHLPP1 expression and p-Mst1 in H9c2 cells exposed to normal glucose but not high glucose. In addition, HPostC in combination with PHLPP1 knockdown or PHLPP1 knockdown alone reduced cell death and oxidative stress in H9c2 cells exposed to high glucose, which was hindered by PI3K/Akt inhibitor.

CONCLUSION

IPostC prevented myocardial IR injury partly through PHLPP1/Akt/Mst1 signaling, and abnormalities in this pathway may be responsible for the loss of IPostC cardioprotection in diabetes.

STAT3 Signalling Drives LDH Up-Regulation and Adiponectin Down-Regulation in Cachectic Adipocytes

Cachexia is a devastating pathology that worsens the quality of life and antineoplastic treatment outcomes of oncologic patients. Herein, we report that the secretome from murine colon carcinoma CT26 induces cachectic features in both murine and human adipocytes that are associated with metabolic alterations such as enhanced lactate production and decreased oxygen consumption. The use of oxamate, which inhibits lactate dehydrogenase activity, hinders the effects induced by CT26 secretome. Interestingly, the CT26 secretome elicits an increased level of lactate dehydrogenase and decreased expression of adiponectin. These modifications are driven by the STAT3 signalling cascade since the inhibition of STAT3 with WP1066 impedes the formation of the cachectic condition and the alteration of lactate dehydrogenase and adiponectin levels. Collectively, these findings show that STAT3 is responsible for the altered lactate dehydrogenase and adiponectin levels that, in turn, could participate in the worsening of this pathology and highlight a step forward in the comprehension of the mechanisms underlying the onset of the cachectic condition in adipocytes.

APJ as Promising Therapeutic Target of Peptide Analogues in Myocardial Infarction- and Hypertension-Induced Heart Failure

The widely expressed G protein-coupled apelin receptor (APJ) is activated by two bioactive endogenous peptides, apelin and ELABELA (ELA). The apelin/ELA-APJ-related pathway has been found involved in the regulation of many physiological and pathological cardiovascular processes. Increasing studies are deepening the role of the APJ pathway in limiting hypertension and myocardial ischaemia, thus reducing cardiac fibrosis and adverse tissue remodelling, outlining APJ regulation as a potential therapeutic target for heart failure prevention. However, the low plasma half-life of native apelin and ELABELA isoforms lowered their potential for pharmacological applications. In recent years, many research groups focused their attention on studying how APJ ligand modifications could affect receptor structure and dynamics as well as its downstream signalling. This review summarises the novel insights regarding the role of APJ-related pathways in myocardial infarction and hypertension. Furthermore, recent progress in designing synthetic compounds or analogues of APJ ligands able to fully activate the apelinergic pathway is reported. Determining how to exogenously regulate the APJ activation could help to outline a promising therapy for cardiac diseases.

BNP protects against diabetic cardiomyopathy by promoting Opa1-mediated mitochondrial fusion via activating the PKG-STAT3 pathway

Brain natriuretic peptide (BNP) belongs to the family of natriuretic peptides, which are responsible for a wide range of actions. Diabetic cardiomyopathy (DCM) is often associated with increased BNP levels. This present research intends to explore the role of BNP in the development of DCM and the underlying mechanisms. Diabetes was induced in mice using streptozotocin (STZ). Primary neonatal cardiomyocytes were treated with high glucose. It was found that the levels of plasma BNP started to increase at 8 weeks after diabetes, which preceded the development of DCM. Addition of exogenous BNP promoted Opa1-mediated mitochondrial fusion, inhibited mitochondrial oxidative stress, preserved mitochondrial respiratory capacity and prevented the development of DCM, while knockdown of endogenous BNP exacerbated mitochondrial dysfunction and accelerated DCM. Opa1 knockdown attenuated the aforementioned protective action of BNP both in vivo and in vitro. BNP-induced mitochondrial fusion requires the activation of STAT3, which facilitated Opa1 transcription by binding to its promoter regions. PKG, a crucial signaling biomolecule in the BNP signaling pathway, interacted with STAT3 and induced its activation. Knockdown of NPRA (the receptor of BNP) or PKG blunted the promoting effect of BNP on STAT3 phosphorylation and Opa1-mediated mitochondrial fusion. The results of this study demonstrate for the first time that there is a rise in BNP during the early stages of DCM as a compensatory protection mechanism. BNP is a novel mitochondrial fusion activator in protecting against hyperglycemia-induced mitochondrial oxidative injury and DCM through the activation of NPRA-PKG-STAT3-Opa1 signaling pathway.

Non-responsiveness to cardioprotection by ischaemic preconditioning in Ossabaw minipigs with genetic predisposition to, but without the phenotype of the metabolic syndrome

The translation of successful preclinical and clinical proof-of-concept studies on cardioprotection to the benefit of patients with reperfused acute myocardial infarction has been difficult so far. This difficulty has been attributed to confounders which patients with myocardial infarction typically have but experimental animals usually not have. The metabolic syndrome is a typical confounder. We hypothesised that there may also be a genuine non-responsiveness to cardioprotection and used Ossabaw minipigs which have the genetic predisposition to develop a diet-induced metabolic syndrome, but before they had developed the diseased phenotype. Using a prospective study design, a reperfused acute myocardial infarction was induced in 62 lean Ossabaw minipigs by 60 min coronary occlusion and 180 min reperfusion. Ischaemic preconditioning by 3 cycles of 5 min coronary occlusion and 10 min reperfusion was used as cardioprotective intervention. Ossabaw minipigs were stratified for their single nucleotide polymorphism as homozygous for valine (V/V) or isoleucine (I/I)) in the γ-subunit of adenosine monophosphate-activated protein kinase. Endpoints were infarct size and area of no-reflow. Infarct size (V/V: 54 ± 8, I/I: 54 ± 13% of area at risk, respectively) was not reduced by ischaemic preconditioning (V/V: 55 ± 11, I/I: 46 ± 11%) nor was the area of no-reflow (V/V: 57 ± 18, I/I: 49 ± 21 vs. V/V: 57 ± 21, I/I: 47 ± 21% of infarct size). Bioinformatic comparison of the Ossabaw genome to that of Sus scrofa and Göttingen minipigs identified differences in clusters of genes encoding mitochondrial and inflammatory proteins, including the janus kinase (JAK)-signal transducer and activator of transcription (STAT) pathway. The phosphorylation of STAT3 at early reperfusion was not increased by ischaemic preconditioning, different from the established STAT3 activation by cardioprotective interventions in other pig strains. Ossabaw pigs have not only the genetic predisposition to develop a metabolic syndrome but also are not amenable to cardioprotection by ischaemic preconditioning.

Shenmai Injection Attenuates Myocardial Ischemia/Reperfusion Injury by Targeting Nrf2/GPX4 Signalling-Mediated Ferroptosis

OBJECTIVE

To examine the effect of Shenmai Injection (SMJ) on ferroptosis during myocardial ischemia reperfusion (I/R) injury in rats and the underlying mechanism.

METHODS

A total of 120 SPF-grade adult male SD rats, weighing 220-250 g were randomly divided into different groups according to a random number table. Myocardial I/R model was established by occluding the left anterior descending artery for 30 min followed by 120 min of reperfusion. SMJ was injected intraperitoneally at the onset of 120 min of reperfusion, and erastin (an agonist of ferroptosis), ferrostatin-1 (Fer-1, an inhibitor of ferroptosis) and ML385 (an inhibitor of nuclear factor erythroid-2 related factor 2 (Nrf2)) were administered intraperitoneally separately 30 min before myocardial ischemia as different pretreatments. Cardiac function before ischemia, after ischemia and after reperfusion was analysed. Pathological changes in the myocardium and the ultrastructure of cardiomyocytes were observed, and the myocardial infarction area was measured. Additionally, the concentration of Fe2+ in heart tissues and the levels of creatine kinase-MB (CK-MB), troponin I (cTnl), malondialdehyde (MDA) and superoxide dismutase (SOD) in serum were measured using assay kits, and the expressions of Nrf2, glutathione peroxidase 4 (GPX4) and acyl-CoA synthetase long-chain family member 4 (ACSL4) were examined by Western blot.

RESULTS

Compared with the sham group, I/R significantly injured heart tissues, as evidenced by the disordered, ruptured and oedematous myocardial fibres; the increases in infarct size, serum CK-MB, cTnI and MDA levels, and myocardial Fe2+ concentrations; and the decreases in SOD activity (P<0.05). These results were accompanied by ultrastructural alterations to the mitochondria, increased expression of ACSL4 and inhibited the activation of Nrf2/GPX4 signalling (P<0.05). Compared with I/R group, pretreatment with 9 mL/kg SMJ and 2 mg/kg Fer-1 significantly reduced myocardial I/R injury, Fe2+ concentrations and ACSL4 expression and attenuated mitochondrial impairment, while 14 mg/kg erastin exacerbated myocardial I/R injury (P<0.05). In addition, cardioprotection provided by 9 mL/kg SMJ was completely reversed by ML385, as evidenced by the increased myocardial infarct size, CK-MB, cTnI, MDA and Fe2+ concentrations, and the decreased SOD activity (P<0.05).

CONCLUSIONS

Ferroptosis is involved in myocardial I/R injury. Pretreatment with SMJ alleviated myocardial I/R injury by activating Nrf2/GPX4 signalling-mediated ferroptosis, thereby providing a strategy for the prevention and treatment of ischemic heart diseases.

Overexpression of miR-383-3p protects cardiomyocytes against hypoxia/reoxygenation injury via regulating PTEN/PI3K/AKT signal pathway

MicroRNAs are widely reported as biomarkers and therapeutic targets in cardiovascular diseases. This study is aimed to expound on the regulatory responsibility of miR-383-3p in H/R-induced injury of H9c2 cells. In this study, H9c2 cells were administrated with H/R. MiR-383-3p expression was measured using qRT-PCR. ELISA was used to determine lactate dehydrogenase (LDH), superoxide dismutase (SOD), and malondialdehyde (MDA) levels. Reactive oxygen species (ROS) were detected with 2,7-Dichlorodihydrofluorescein diacetate probe. 3-(4,5)-dimethylthiahiazo (-z-y1)-3,5-di- phenytetrazoliumromide, flow cytometry, and TUNEL experiments were conducted to measure cell viability and apoptosis. Cleaved caspase-3, caspase-3, Bax, Bcl-2, PTEN, PI3K, p-PI3K, Akt, p-AKT expression levels were examined by Western blot. Cleaved caspase-3 expression was also measured by immunofluorescence staining. Dual-luciferase reporter gene assay was applied to validate the binding sites in miR-383-3p and the 3'UTR of PTEN. We reported that, miR-383-3p expression in H9c2 cells treated with H/R was remarkably decreased. MiR-383-3p overexpression ameliorated oxidative stress and apoptosis and promoted cell viability in H9c2 cells treated with H/R, while miR-383-3p inhibitor showed the reverse effects. PTEN was identified as a target gene of miR-383-3p. Additionally, enhancement of PTEN expression abolished the influences of miR-383-3p on H9c2 cells. MiR-383-3p mimics could significantly decrease PTEN expression in H9c2 cells while increasing p-PI3K expression and p-AKT expression, while the miR-383-3p inhibitors showed the opposed effects. In conclusion, miR-383-3p protected H9c2 cells from H/R-induced injury via regulating PTEN/PI3K/AKT signal pathway.

Myocardial ischemia/reperfusion injury: Mechanisms of injury and implications for management (Review)

Myocardial infarction is one of the primary causes of mortality in patients with coronary heart disease worldwide. Early treatment of acute myocardial infarction restores blood supply of ischemic myocardium and decreases the mortality risk. However, when the interrupted myocardial blood supply is recovered within a certain period of time, it causes more serious damage to the original ischemic myocardium; this is known as myocardial ischemia/reperfusion injury (MIRI). The pathophysiological mechanisms leading to MIRI are associated with oxidative stress, intracellular calcium overload, energy metabolism disorder, apoptosis, endoplasmic reticulum stress, autophagy, pyroptosis, necroptosis and ferroptosis. These interplay with one another and directly or indirectly lead to aggravation of the effect. In the past, apoptosis and autophagy have attracted more attention but necroptosis and ferroptosis also serve key roles. However, the mechanism of MIRI has not been fully elucidated. The present study reviews the mechanisms underlying MIRI. Based on current understanding of the pathophysiological mechanisms of MIRI, the association between cell death-associated signaling pathways were elaborated, providing direction for investigation of novel targets in clinical treatment.

Insight into the Role of the PI3K/Akt Pathway in Ischemic Injury and Post-Infarct Left Ventricular Remodeling in Normal and Diabetic Heart

Despite the significant decline in mortality, cardiovascular diseases are still the leading cause of death worldwide. Among them, myocardial infarction (MI) seems to be the most important. A further decline in the death rate may be achieved by the introduction of molecularly targeted drugs. It seems that the components of the PI3K/Akt signaling pathway are good candidates for this. The PI3K/Akt pathway plays a key role in the regulation of the growth and survival of cells, such as cardiomyocytes. In addition, it has been shown that the activation of the PI3K/Akt pathway results in the alleviation of the negative post-infarct changes in the myocardium and is impaired in the state of diabetes. In this article, the role of this pathway was described in each step of ischemia and subsequent left ventricular remodeling. In addition, we point out the most promising substances which need more investigation before introduction into clinical practice. Moreover, we present the impact of diabetes and widely used cardiac and antidiabetic drugs on the PI3K/Akt pathway and discuss the molecular mechanism of its effects on myocardial ischemia and left ventricular remodeling.

Association of Polymorphisms within HOX Transcript Antisense RNA (HOTAIR) with Type 2 Diabetes Mellitus and Laboratory Characteristics: A Preliminary Case-Control Study

Type 2 diabetes mellitus (T2DM) is a complex heterogeneous disease resulting from the environment and genetic interactions. Lately, genetic association studies have shown that polymorphisms in long noncoding RNAs (lncRNAs) are associated with T2DM susceptibility. This preliminary study is aimed at investigating if HOX transcript antisense RNA (HOTAIR) polymorphisms contribute to T2DM development. Five hundred clinically diagnosed T2DM cases and 500 healthy controls were recruited from the southeast Iranian population. Genomic DNA was isolated from nucleated blood cells and genotyped for MspI (C/T) (rs920778) and AluI (A/G) (rs4759314) polymorphisms using the PCR-RFLP technique. For genotyping rs12826786 C/T and rs1899663 G/T variants, ARMS-PCR method was applied. Our findings indicated that HOTAIR rs920778 C/T, rs12826786 C/T, and rs4759314 A/G polymorphisms have a significant positive association with T2DM, while a negative association was observed between rs1899663 G/T T2DM susceptibility. Significant associations were also observed between rs920778 C/T and HDL-C as well as s4759314 A/G and both FBS and LDL-C in T2DM patients. Haplotype analysis indicated that the CGCG, CTTG, TGTA, and TTTG haplotypes of rs920778/rs1899663/rs12826786/rs4759314 significantly enhanced T2DM risk by 1.47, 1.96, 2.81, and 4.80 folds, respectively. No strong linkage disequilibrium was found between the four HOTAIR SNPs. We firstly reported that HOTAIR rs1899663 G/T, rs12826786 C/T, rs4759314 A/G, and rs920778 C/T polymorphisms might influence T2DM susceptibility by modulating different signaling pathways and could be regarded as potential prognostic markers in T2DM patients.

MiRNA-221-5p suppressed the Th17/Treg ratio in asthma via RORγt/Foxp3 by targeting SOCS1

Background

This study was designed to investigate the mechanism and effects of miRNA-221-5p on the T-helper 17 (Th17)/T-regulatory (Treg) ratio in asthma.

Methods

BALB/c mice were intranasally challenged with 100 µg OVA on 14 and 21 day. Mice were rechallenged with 2.5% OVA-PBS on 22 and 28 day. Mice were sacrificed using on day 30 under 35 mg/kg pentobarbital sodium. PBMCs were induced vitro model of asthma using 500 ng of lipopolysaccharides (LPS) for 4 h.

Results

The expression of miRNA-221-5p was reduced in in vivo model, compared sham group. The vitro model of asthma treated with miRNA-221-5p mimic resulted in the reduction of IL-6, IL-17, IL-21 and IL-22 levels, and induction of IL-10, IL-35 and TGF-β levels. In addition, down-regulation of miRNA-221-5p induced the protein expression of suppressor of cytokine signaling 1 (SOCS1) and receptor-related orphan receptor-gamma-t (RORγt) and suppressed that of FOXP3 in in vitro model of asthma. Over-expression of miRNA-221-5p induced the protein expression of FOXP3, and suppressed that of SOCS1 and RORγt in in vitro model of asthma. The inhibition of SOCS1 or RORγt attenuated the effects of anti-miRNA-221-5p on Th17/Treg ratio in asthma.

Conclusion

miRNA-221-5p may play critical roles in driving the differentiation of Th17/Treg ratio via RORγt/Foxp3 by Targeting SOCS1, reduced the function of Th17 cells by directly inhibiting RORγt/SOCS1 and promoted the function of Treg cells via Foxp3/ SOCS1 in asthma.

Impact of the Main Cardiovascular Risk Factors on Plasma Extracellular Vesicles and Their Influence on the Heart's Vulnerability to Ischemia-Reperfusion Injury

The majority of cardiovascular deaths are associated with acute coronary syndrome, especially ST-elevation myocardial infarction. Therapeutic reperfusion alone can contribute up to 40 percent of total infarct size following coronary artery occlusion, which is called ischemia-reperfusion injury (IRI). Its size depends on many factors, including the main risk factors of cardiovascular mortality, such as age, sex, systolic blood pressure, smoking, and total cholesterol level as well as obesity, diabetes, and physical effort. Extracellular vesicles (EVs) are membrane-coated particles released by every type of cell, which can carry content that affects the functioning of other tissues. Their role is essential in the communication between healthy and dysfunctional cells. In this article, data on the variability of the content of EVs in patients with the most prevalent cardiovascular risk factors is presented, and their influence on IRI is discussed.

The Clinical Significance of miR-21 in Guiding Chemotherapy for Patients with Osteosarcoma

Objective

The present study aims to explore the correlation between osteosarcoma (OS) chemosensitivity and the expression levels of serum and tumor tissue micro-ribonucleic acid-21 (miR-21).

Methods

The relevant miR-21 expression levels in 30 patients with OS were detected, and the gender, age, tumor location, pathological type, Enneking stage, and miR-21 expression changes before and after chemotherapy were retrospectively analyzed.

Results

Serum and tumor tissue miR21 expression levels were significantly higher in patients with OS than in control subjects; the serum miR-21 expressions before and after chemotherapy were not related to patient age and gender. The effective chemotherapy group showed significant differences in miR-21 expression levels before and after chemotherapy.

Conclusion

Serum and tumor tissue miR-21 expression levels in patients with OS are closely related to the effects of chemotherapy, making miR-21 a potential biomarker and therapeutic target for the diagnosis and evaluation of chemotherapy effects on patients with OS.

microRNA-26a-5p Prevents Retinal Neuronal Cell Death in Diabetic Mice by Targeting PTEN

AIM

To explore the role of microRNA-26a-5p (miR-26a) in early diabetic retinal neuronal cell death and reveal the underlying mechanism(s).

METHODS

A streptozotocin (STZ)-induced diabetic mouse model was established using C57BL/6 J mice. Control or miR-26a mimic was intravitreally injected. Hematoxylin-eosin (H&E) and transmission electron microscopy (TEM) were used to observe the morphologic alterations in the retinal structure and ultrastructure, respectively. The expression of miR-26a and phosphatase and tensin homolog (PTEN) was assayed using qRT-PCR and western blotting, respectively. An immunofluorescence assay was used to investigate the distribution of PTEN expression in the retina. The expression of glial fibrillary acidic protein (GFAP) was measured to identify glial cell activation. The mRNA levels of IL-1β, NF-κB, and VEGF were examined to assess diabetic retinal inflammation.

RESULTS

miR-26a expression was decreased in retinal tissues of diabetic mice, and injection of miR-26a mimic restored the miR-26a level. Diabetic mice had significantly reduced neuroretinal thickness and ganglion cell number; miR-26a mimic delayed the thinning of neuroretinal layers and the loss of ganglion numbers. TEM showed damaged ultrastructure of retinal ganglions in diabetic mice, while miR-26a mitigated the damages. PTEN expression was increased mainly in the inner and outer nuclear layer of the retina in diabetic mice; miR-26a mimics lowered PTEN expression. GFAP, IL-1β, NF-κB, and VEGF expression were significantly increased in the diabetic mice, and intravitreal delivery of miR-26a resulted in a down-regulated expression of these factors.

CONCLUSION

miR-26a can protect against retinal neuronal impairment in diabetic mice by down-regulating PTEN, highlighting the potential of miR-26a as a target for DR treatment.

MicroRNA -148 alleviates cardiac dysfunction, immune disorders and myocardial apoptosis in myocardial ischemia-reperfusion (MI/R) injury by targeting pyruvate dehydrogenase kinase (PDK4)

Ischemic heart disease in children may be induced by varied factors, and there is no corresponding systematic treatment up to now. This study aims to investigate the effects of microRNA (miR)-148 on myocardial injury in immature rats with myocardial ischemia-reperfusion (MI/R) injury. In this study, MI/R model was established by ligating the coronary artery of heart. The results showed that miR-148 alleviated myocardial injury and rescued relevant parameters (mean ventricular systolic blood pressure (MAP), left ventricular systolic blood pressure (LVSP), heart rate (HR), creatine kinase-MB (CK-MB), cTn1 and Mb in immature rats with MI/R injury. Besides, miR-148 improved the immune dysfunction induced by MI/R through increasing the number of interleukin (IL)-10⁺ cells and reducing the number of inducible nitric oxide synthase (iNOS)⁺ cells. In addition, miR-148 relieved the apoptosis of cardiomyocytes induced by MI/R through inhibiting the expression of Bax and elevating the expression of Bcl-2. Further molecular mechanism indicated that pyruvate dehydrogenase kinase 4 (PDK4) was the downstream target of miR-148, which was further confirmed by dual luciferase reporter assay and related expression detection. Accordingly, silenced PDK4 attenuated cardiac dysfunction, immune disorder and myocardial apoptosis in immature rats and enhanced the ability of antioxidant enzymes. What is more, activated SMAD pathway induced by MI/R injury was then blocked by silenced PDK4. Taken together, our study demonstrated that overexpressed miR-148 relieved cardiac dysfunction, immune disorder and cardiomyocyte apoptosis in immature MI/R rats by PDK4 inhibition, which provided novel targets for MI/R injury treatment.

Ischemic Postconditioning-Mediated DJ-1 Activation Mitigate Intestinal Mucosa Injury Induced by Myocardial Ischemia Reperfusion in Rats Through Keap1/Nrf2 Pathway

Intestinal mucosal barrier dysfunction induced by myocardial ischemia reperfusion (IR) injury often leads to adverse cardiovascular outcomes after myocardial infarction. Early detection and prevention of remote intestinal injury following myocardial IR may help to estimate and improve prognosis after acute myocardial infarction (AMI). This study investigated the protective effect of myocardial ischemic postconditioning (IPo) on intestinal barrier injury induced by myocardial IR and the underlying cellular signaling mechanisms with a focus on the DJ-1. Adult SD rats were subjected to unilateral myocardial IR with or without ischemic postconditioning. After 30 min of ischemia and 120 min of reperfusion, heart tissue, intestine, and blood were collected for subsequent examination. The outcome measures were (i) intestinal histopathology, (ii) intestinal barrier function and inflammatory responses, (iii) apoptosis and oxidative stress, and (iv) cellular signaling changes. IPo significantly attenuated intestinal injury induced by myocardial IR. Furthermore, IPo significantly increased DJ-1, nuclear Nrf2, NQO1, and HO-1 expression in the intestine and inhibited IR-induced apoptosis and oxidative stress. The protective effect of IPo was abolished by the knockdown of DJ-1. Conversely, the overexpression of DJ-1 provided a protective effect similar to that of IPo. Our data indicate that IPo protects the intestine against myocardial IR, which is likely mediated by the upregulation of DJ-1/Nrf2 pathway.

Inactivation of TOPK Caused by Hyperglycemia Blocks Diabetic Heart Sensitivity to Sevoflurane Postconditioning by Impairing the PTEN/PI3K/Akt Signaling

The cardioprotective effect of sevoflurane postconditioning (SPostC) is lost in diabetes that is associated with cardiac phosphatase and tensin homologue on chromosome 10 (PTEN) activation and phosphoinositide 3-kinase (PI3K)/Akt inactivation. T-LAK cell-originated protein kinase (TOPK), a mitogen-activated protein kinase- (MAPKK-) like serine/threonine kinase, has been shown to inactivate PTEN (phosphorylated status), which in turn activates the PI3K/Akt signaling (phosphorylated status). However, the functions of TOPK and molecular mechanism underlying SPostC cardioprotection in nondiabetes but not in diabetes remain unknown. We presumed that SPostC exerts cardioprotective effects by activating PTEN/PI3K/Akt through TOPK in nondiabetes and that impairment of TOPK/PTEN/Akt blocks diabetic heart sensitivity to SPostC. We found that in the nondiabetic C57BL/6 mice, SPostC significantly attenuated postischemic infarct size, oxidative stress, and myocardial apoptosis that was accompanied with enhanced p-TOPK, p-PTEN, and p-Akt. These beneficial effects of SPostC were abolished by either TOPK kinase inhibitor HI-TOPK-032 or PI3K/Akt inhibitor LY294002. Similarly, SPostC remarkably attenuated hypoxia/reoxygenation-induced cardiomyocyte damage and oxidative stress accompanied with increased p-TOPK, p-PTEN, and p-Akt in H9c2 cells exposed to normal glucose, which were canceled by either TOPK inhibition or Akt inhibition. However, either in streptozotocin-induced diabetic mice or in H9c2 cells exposed to high glucose, the cardioprotective effect of SPostC was canceled, accompanied by increased oxidative stress, decreased TOPK phosphorylation, and impaired PTEN/PI3K/Akt signaling. In addition, TOPK overexpression restored posthypoxic p-PTEN and p-Akt and decreased cell death and oxidative stress in H9c2 cells exposed to high glucose, which was blocked by PI3K/Akt inhibition. In summary, SPostC prevented myocardial ischemia/reperfusion injury possibly through TOPK-mediated PTEN/PI3K/Akt activation and impaired activation of this signaling pathway may be responsible for the loss of SPostC cardioprotection by SPostC in diabetes.

Vanadium Decreases Hepcidin mRNA Gene Expression in STZ-Induced Diabetic Rats, Improving the Anemic State

Diabetes is a disease with an inflammatory component that courses with an anemic state. Vanadium (V) is an antidiabetic agent that acts by stimulating insulin signaling. Hepcidin blocks the intestinal absorption of iron and the release of iron from its deposits. We aim to investigate the effect of V on hepcidin mRNA expression and its consequences on the hematological parameters in streptozotocin-induced diabetic Wistar rats. Control healthy rats, diabetic rats, and diabetic rats treated with 1 mgV/day were examined for five weeks. The mineral levels were measured in diet and serum samples. Hepcidin expression was quantified in liver samples. Inflammatory and hematological parameters were determined in serum or whole blood samples. The inflammatory status was higher in diabetic than in control rats, whereas the hematological parameters were lower in the diabetic rats than in the control rats. Hepcidin mRNA expression was significantly lower in the V-treated diabetic rats than in control and untreated diabetic rats. The inflammatory status remained at a similar level as the untreated diabetic group. However, the hematological profile improved after the V-treatment, reaching similar levels to those found in the control group. Serum iron level was higher in V-treated than in untreated diabetic rats. We conclude that V reduces gene expression of hepcidin in diabetic rats, improving the anemic state caused by diabetes.

Mechanism of N-acetylcysteine in alleviating diabetic myocardial ischemia reperfusion injury by regulating PTEN/Akt pathway through promoting DJ-1

Ischemic heart disease is the main cardiovascular complication of diabetes patients which is mainly caused by oxidative stress. DJ-1 is the key regulator for myocardial protection through inhibiting phosphatase and tensin homolog deleted on chromosome 10 (PTEN) and activating Akt (also known as PKB or protein kinase B). This research is to investigate whether the antioxidant N-acetylcysteine (NAC) could alleviate diabetic myocardial ischemia/reperfusion (I/R) injury by the protective molecule DJ-1. DJ-1 in rat myocardial H9c2 cells and cardiac tissue was respectively knocked down by siRNA and adeno-associated virus (AAV). From the present study, it could be found that compared with high glucose (HG)-normal (N)/DM group, hypoxia/reoxygenation (H/R) or I/R injury can aggravate oxidative stress injury and apoptosis rate of myocardial cells, inhibit the expression of Bcl-2, activate the BAX and cleaved caspase-3 (c-caspase-3) protein and PTEN/Akt pathway. However, in the groups of HG-N, DM, HG-N+I/R and DM+I/R, NAC can significantly reduce oxidative stress injury and apoptosis rate of myocytes, promote the Bcl-2 and DJ-1 molecules, inhibit BAX and c-caspase-3 protein and PTEN/Akt pathway. Compared with HG-N+I/R+NAC and DM+I/R+NAC groups, the oxidative stress injury, apoptosis rate of myocardial cells and heart tissues increased after the knockdown of DJ-1, the expression of Bcl-2 and DJ-1 were inhibited, the BAX and c-caspase-3 expression was increased, and PTEN/Akt pathway was activated. Taken together, the findings suggest that NAC can reduce I/R injury in diabetic myocardium by up-regulating the PTEN/Akt pathway through the level of DJ-1.

Mechanistic study of mtROS-JNK-SOD2 signaling in bupivacaine-induced neuron oxidative stress

Manganese superoxide dismutase (SOD2) is a key enzyme to scavenge free radical superoxide in the mitochondrion. SOD2 deficiency leads to oxidative injury in cells. Bupivacaine, a local anesthetic commonly used in clinic, could induce neurotoxic injury via oxidative stress. The role and the mechanism of SOD2 regulation in bupivacaine-induced oxidative stress remains unclear. Here, bupivacaine was used to treat Sprague-Dawley rats with intrathecal injection and culture human neuroblastoma cells for developing vivo injury model and vitro injury model. The results showed that bupivacaine caused the over-production of mitochondrial reactive oxygen species (mtROS), the activation of C-Jun N-terminal kinase (JNK), and the elevation of SOD2 transcription. Decrease of mtROS with N-acetyl-L-cysteine attenuated the activation of JNK and the increase of SOD2 transcription. Inhibition of JNK signaling with a small interfering RNA (siRNA) or with sp600125 down-regulated the increase of SOD2 transcription. SOD2 gene knock-down exacerbated bupivacaine-induced mtROS generation and neurotoxic injury but had no effect on JNK phosphorylation. Mito-TEMPO (a mitochondria-targeted antioxidant) could protect neuron against bupivacaine-induced toxic injury. Collectively, our results confirm that mtROS stimulates the transcription of SOD2 via activating JNK signaling in bupivacaine-induced oxidative stress. Enhancing antioxidant ability of SOD2 might be crucial in combating bupivacaine-induced neurotoxic injury.

Empagliflozin and Liraglutide Differentially Modulate Cardiac Metabolism in Diabetic Cardiomyopathy in Rats

Glucagon-like peptide 1 receptor agonists (GLP-1RAs) and sodium-glucose cotransporter-2 inhibitors (SGLT2is) are antihyperglycemic agents with cardioprotective properties against diabetic cardiomyopathy (DCM). However, the distinctive mechanisms underlying GLP-1RAs and SGLT2is in DCM are not fully elucidated. The purpose of this study was to investigate the impacts of GLP1RAs and/or SGLT2is on myocardial energy metabolism, cardiac function, and apoptosis signaling in DCM. Biochemistry and echocardiograms were studied before and after treatment with empagliflozin (10 mg/kg/day, oral gavage), and/or liraglutide (200 μg/kg every 12 h, subcutaneously) for 4 weeks in male Wistar rats with streptozotocin (65 mg/kg intraperitoneally)-induced diabetes. Cardiac fibrosis, apoptosis, and protein expression of metabolic and inflammatory signaling molecules were evaluated by histopathology and Western blotting in ventricular cardiomyocytes of different groups. Empagliflozin and liraglutide normalized myocardial dysfunction in diabetic rats. Upregulation of phosphorylated-acetyl coenzyme A carboxylase, carnitine palmitoyltransferase 1β, cluster of differentiation 36, and peroxisome proliferator-activated receptor-gamma coactivator, and downregulation of glucose transporter 4, the ratio of phosphorylated adenosine monophosphate-activated protein kinase α2 to adenosine monophosphate-activated protein kinase α2, and the ratio of phosphorylated protein kinase B to protein kinase B in diabetic cardiomyocytes were restored by treatment with empagliflozin or liraglutide. Nucleotide-binding oligomerization domain, leucine-rich repeat and pyrin domain-containing 3, interleukin-1β, tumor necrosis factor-α, and cleaved caspase-1 were significantly downregulated in empagliflozin-treated and liraglutide-treated diabetic rats. Both empagliflozin-treated and liraglutide-treated diabetic rats exhibited attenuated myocardial fibrosis and apoptosis. Empagliflozin modulated fatty acid and glucose metabolism, while liraglutide regulated inflammation and apoptosis in DCM. The better effects of combined treatment with GLP-1RAs and SGLT2is may lead to a potential strategy targeting DCM.

Roles of HDAC3-orchestrated circadian clock gene oscillations in diabetic rats following myocardial ischaemia/reperfusion injury

The circadian clock is closely related to the development of diabetes mellitus and cardiovascular disease, and disruption of the circadian clock exacerbates myocardial ischaemia/reperfusion injury (MI/RI). HDAC3 is a key component of the circadian negative feedback loop that controls the expression pattern of the circadian nuclear receptor Rev-erbα to maintain the stability of circadian genes such as BMAL1. However, the mechanism by which the HDAC3-orchestrated Rev-erbα/BMAL1 pathway increases MI/RI in diabetes and its relationship with mitophagy have yet to be elucidated. Here, we observed that the clock genes Rev-erbα, BMAL1, and C/EBPβ oscillations were altered in the hearts of rats with streptozotocin (STZ)-induced diabetes, with upregulated HDAC3 expression. Oscillations of Rev-erbα and BMAL1 were rapidly attenuated in diabetic MI/R hearts versus non-diabetic I/RI hearts, in accordance with impaired and rhythm-disordered circadian-dependent mitophagy that increased injury. Genetic knockdown of HDAC3 significantly attenuated diabetic MI/RI by mediating the Rev-erbα/BMAL1 circadian pathway to recover mitophagy. Primary cardiomyocytes with or without HDAC3 siRNA and Rev-erbα siRNA were exposed to hypoxia/reoxygenation (H/R) in vitro. The expression of HDAC3 and Rev-erbα in cardiomyocytes was increased under high-glucose conditions compared with low-glucose conditions, with decreased BMAL1 expression and mitophagy levels. After H/R stimulation, high glucose aggravated H/R injury, with upregulated HDAC3 and Rev-erbα expression and decreased BMAL1 and mitophagy levels. HDAC3 and Rev-erbα siRNA can alleviate high glucose-induced and H/R-induced injury by upregulating BMAL1 to increase mitophagy. Collectively, these findings suggest that disruption of HDAC3-mediated circadian gene expression oscillations induces mitophagy dysfunction, aggravating diabetic MI/RI. Cardiac-specific HDAC3 knockdown could alleviate diabetic MI/RI by regulating the Rev-erbα/BMAL1 pathway to restore the activation of mitophagy.

Naringin attenuates high glucose-induced injuries and inflammation by modulating the leptin-JAK2/STAT3 pathway in H9c2 cardiac cells

INTRODUCTION

Our previous study showed that naringin (NRG) protects cardiomyocytes against high glucose (HG)-induced injuries by inhibiting p38 mitogen-activated protein kinase (MAPK). Leptin induces hypertrophy in rat cardiomyocytes via p38/MAPK activation. The present study aimed to test the hypothesis that leptin-Janus kinase 2 (JAK2)/signal transducers and activators of transcription 3 (STAT3), which are responsible for leptin's functions, are involved in HG-induced injuries and cardioprotective effects of NRG in cardiomyocytes.

MATERIAL AND METHODS

H9c2 cells were exposed to HG for 24 h to establish a cardiomyocyte injury model. Cells were pretreated with NRG and other drugs before exposure to HG. Protein expression was measured by western blot analysis. Cell viability was detected by Cell Counting Kit-8 assay. Apoptotic cells were assessed by Hoechst 33258 staining assay. Intracellular reactive oxygen species levels were determined by dichlorofluorescein diacetate staining. Mitochondrial membrane potential was evaluated using JC-1. An enzyme-linked immunosorbent assay was performed to determine the inflammatory cytokines.

RESULTS

NRG significantly attenuated HG-induced increases in leptin and Ob-R expression. Pretreatment with either a leptin antagonist (LA) or NRG markedly ameliorated HG-induced elevation of phosphorylated (p)-JAK2 and p-STAT3, respectively. Pretreatment with NRG, LA, Ob-R antagonist, or AG490 clearly alleviated HG-induced injuries and inflammation.

CONCLUSIONS

This study provides new evidence of the NRG protective effects of H9c2 cells against HG-induced injuries possibly via modulation of the leptin-JAK2/STAT3 pathway.

Effect of hyperglycaemia and diabetes on acute myocardial ischaemia-reperfusion injury and cardioprotection by ischaemic conditioning protocols

Diabetic patients are at increased risk of developing coronary artery disease and experience worse clinical outcomes following acute myocardial infarction. Novel therapeutic strategies are required to protect the myocardium against the effects of acute ischaemia-reperfusion injury (IRI). These include one or more brief cycles of non-lethal ischaemia and reperfusion prior to the ischaemic event (ischaemic preconditioning [IPC]) or at the onset of reperfusion (ischaemic postconditioning [IPost]) either to the heart or to extracardiac organs (remote ischaemic conditioning [RIC]). Studies suggest that the diabetic heart is resistant to cardioprotective strategies, although clinical evidence is lacking. We overview the available animal models of diabetes, investigating acute myocardial IRI and cardioprotection, experiments investigating the effects of hyperglycaemia on susceptibility to acute myocardial IRI, the response of the diabetic heart to cardioprotective strategies e.g. IPC, IPost and RIC. Finally we highlight the effects of anti-hyperglycaemic agents on susceptibility to acute myocardial IRI and cardioprotection. LINKED ARTICLES: This article is part of a themed issue on Risk factors, comorbidities, and comedications in cardioprotection. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v177.23/issuetoc.

Diabetes Upregulates Oxidative Stress and Downregulates Cardiac Protection to Exacerbate Myocardial Ischemia/Reperfusion Injury in Rats

Diabetes exacerbates myocardial ischemia/reperfusion (IR) injury by incompletely understood mechanisms. We explored whether diabetes diminished BAG3/Bcl-2/Nrf-2/HO-1-mediated cardioprotection and overproduced oxidative stress contributing to exaggerated IR injury. Streptozotocin-induced diabetes enhanced hyperglycemia, cardiac NADPH oxidase p22/p67 expression, malondialdehyde amount and leukocyte infiltration, altered the mesenteric expression of 4-HNE, CaSR, p-eNOS and BAG3 and impaired microvascular reactivity to the vasoconstrictor/vasodilator by a wire myography. In response to myocardial IR, diabetes further depressed BAG3/Bcl-2/Nrf-2/HO-1 expression, increased cleaved-caspase 3/poly(ADP-ribose) polymerase (PARP)/TUNEL-mediated apoptosis and exacerbated IR-induced left ventricular dysfunction characterized by further depressed microcirculation, heart rate, left ventricular systolic pressure and peak rate of pressure increase/decrease (±dp/dt) and elevated left ventricular end-diastolic pressure (LVEDP) and Evans blue-2,3,5-triphenyltetrazolium chloride-stained infarct size in diabetic hearts. Our results implicated diabetes exacerbated IR-induced myocardial dysfunction through downregulated BAG3/Bcl-2/Nrf-2/HO-1 expression, increased p22/p67/caspase 3/PARP/apoptosis-mediated oxidative injury and impaired microvascular reactivity.

lncRNA Oip5-as1 attenuates myocardial ischaemia/reperfusion injury by sponging miR-29a to activate the SIRT1/AMPK/PGC1α pathway

OBJECTIVES

Myocardial ischaemia/reperfusion (MI/R) injury is associated with adverse cardiovascular outcomes after acute myocardial infarction. However, the molecular mechanisms underlying MI/R injury are unclear. This study investigated the role of long non-coding RNA (lncRNA) Oip5-as1 in regulating mitochondria-mediated apoptosis during MI/R injury.

MATERIALS AND METHODS

Sprague-Dawley rats were subjected to MI/R induced by ligation of the left anterior descending coronary artery followed by reperfusion. H9c2 cells were incubated under oxygen-glucose deprivation/reoxygenation (OGD/R) conditions to mimic in vivo MI/R. RT-qPCR and Western blot were used to evaluate gene and protein levels. CCK-8 assay, biochemical assay and flow cytometric analysis were performed to assess the function of Oip5-as1. The dual-luciferase gene reporter assay and RIP assay were conducted as needed.

RESULTS

Oip5-as1 expression was downregulated in the hearts of rats with MI/R and in H9c2 cells treated with OGD/R. Oip5-as1 overexpression alleviated reactive oxygen species-driven mitochondrial injury and consequently decreased apoptosis in MI/R rats and H9c2 cells exposed to OGD/R. Mechanistically, Oip5-as1 acted as a competing endogenous RNA of miR-29a and thus decreased its expression. Inhibition of miR-29a reduced the oxidative stress and cytotoxicity induced by OGD/R. Overexpression of miR-29a reversed the anti-apoptotic effect of Oip5-as1 in H9c2 cells treated with OGD/R. Further experiments identified SIRT1 as a downstream target of miR-29a. Oip5-as1 upregulated SIRT1 expression and activated the AMPK/PGC1α pathway by targeting miR-29a, thus reducing the apoptosis triggered by OGD/R. However, these effects were reversed by a selective SIRT1 inhibitor, EX527.

CONCLUSIONS

Oip5-as1 suppresses miR-29a leading to activation of the SIRT1/AMPK/PGC1α pathway, which attenuates mitochondria-mediated apoptosis during MI/R injury. Our findings thus provide new insights into the molecular mechanisms of MI/R injury.

Vanadium and insulin: Partners in metabolic regulation

Since the 1970s, the biological role of vanadium compounds has been discussed as insulin-mimetic or insulin-enhancer agents. The action of vanadium compounds has been investigated to determine how they influence the insulin signaling pathway. Khan and coworkers proposed key proteins for the insulin pathway study, introducing the concept "critical nodes". In this review, we also considered critical kinases and phosphatases that participate in this pathway, which will permit a better comprehension of a critical node, where vanadium can act: a) insulin receptor, insulin receptor substrates, and protein tyrosine phosphatases; b) phosphatidylinositol 3'-kinase, 3-phosphoinositide-dependent protein kinase and mammalian target of rapamycin complex, protein kinase B, and phosphatase and tensin homolog; and c) insulin receptor substrates and mitogen-activated protein kinases, each node having specific negative modulators. Additionally, leptin signaling was considered because together with insulin, it modulates glucose and lipid homeostasis. Even in recent literature, the possibility of vanadium acting against metabolic diseases or cancer is confirmed although the mechanisms of action are not well understood because these critical nodes have not been systematically investigated. Through this review, we establish that vanadium compounds mainly act as phosphatase inhibitors and hypothesize on their capacity to affect kinases, which are critical to other hormones that also act on common parts of the insulin pathway.

Role of exosomal miR‑21 in the tumor microenvironment and osteosarcoma tumorigenesis and progression (Review)

Osteosarcoma is the most common bone tumor affecting both adolescents and children. Early detection is critical for the effective treatment of the disease. Derived from cancer cells, miR‑21 contained within exosomes in the tumor microenvironment may act on both cancer cells and the surrounding tumor microenvironment (TME), including immune cells, endothelial cells and fibroblasts. In human serum and plasm, the level of exosomal miR‑21 between osteosarcoma patients and healthy controls differs, supporting the role of miR‑21 as a biomarker for osteosarcoma. The involvement of a number of miR‑21 target genes in tumor progression suggests that miR‑21 may significantly affect the plasticity of cancer cells, leading to tumor progression, metastasis, angiogenesis and immune escape in osteosarcoma. Understanding the biogenesis and functions of exosomal miR‑21 is of great value for the diagnosis and therapy of cancer, including osteosarcoma. The present review discusses the role of miR‑21 in the tumor microenvironment, and in the development and progression of osteosarcoma, with an aim to summarize the functions of this miRNA in cancer.

Deletion of Rap1 protects against myocardial ischemia/reperfusion injury through suppressing cell apoptosis via activation of STAT3 signaling

Ischemic heart disease is a leading cause of morbidity and mortality. Repressor activator protein 1 (Rap1), an established telomere-associated protein, is a novel modulator of hypoxia-induced apoptosis. This study aimed to explore the potential direct role of Rap1 in myocardial ischemia/reperfusion injury (I/RI) and to determine the underlying molecular mechanism. In a mouse model of myocardial I/RI (30-min of left descending coronary artery ligation followed by 2-h reperfusion), Rap1 deficiency significantly reduced myocardial infarct size (IS) and improved cardiac systolic/diastolic function. This was associated with a reduction in apoptosis in the post-ischemic myocardium. In H9C2 and primary cardiomyocytes, Rap1 knockdown or knockout significantly suppressed hypoxia/reoxygenation (H/R)-induced cell injury and apoptosis through increasing the phosphorylation/activation of STAT3 at site Ser⁷²⁷ and translocation of STAT3 to the nucleus. We surmise this since Stattic (selective STAT3 inhibitor) pretreatment canceled the abovementioned protective effect. Furthermore, co-immunoprecipitation assay revealed a direct interaction between Rap1 and STAT3, but not JAK2, suggesting that the association of Rap1 with STAT3 may contribute to the reduced activity of STAT3 (Ser⁷²⁷ ) upon H/R stimulation. In conclusion, Rap1 deficiency protects the heart from ischemic damage through STAT3-dependent reduction of cardiomyocyte apoptosis, which may yield viable target for pharmacological intervention in ischemic heart disease.

GDF11 ameliorated myocardial ischemia reperfusion injury by antioxidant stress and up-regulating autophagy in STZ-induced type 1 diabetic rats

Purpose:

To investigate whether GDF11 ameliorates myocardial ischemia reperfusion (MIR) injury in diabetic rats and explore the underlying mechanisms.

Methods:

Diabetic and non-diabetic rats subjected to MIR (30 min of coronary artery occlusion followed by 120 min of reperfusion) with/without GDF11 pretreatment. Cardiac function, myocardial infarct size, creatine kinase-MB (CK-MB), lactate dehydrogenase (LDH), superoxide dismutase (SOD) 15-F2tisoprostane, autophagosome, LC3II/I ratio and Belcin-1 level were determined to reflect myocardial injury, oxidative stress and autophagy, respectively. In in vitro study, H9c2 cells cultured in high glucose (HG, 30mM) suffered hypoxia reoxygenation (HR) with/without GDF11, hydrogen peroxide (H₂O₂) and autophagy inhibitor 3-methyladenine (3-MA) treatment, cell injury; oxidative stress and autophagy were assessed.

Results:

Pretreatment with GDF11 significantly improved cardiac morphology and function in diabetes, concomitant with decreased arrhythmia severity, infarct size, CK-MB, LDH and 15-F2tisoprostane release, increased SOD activity and autophagy level. In addition, GDF11 notably reduced HR injury in H9c2 cells with HG exposure, accompanied by oxidative stress reduction and autophagy up-regulation. However, those effects were completely reversed by H₂O₂ and 3-MA.

Conclusion:

GDF11 can provide protection against MIR injury in diabetic rats, and is implicated in antioxidant stress and autophagy up-regulation.

Selective Inhibition of PKCβ2 Restores Ischemic Postconditioning-Mediated Cardioprotection by Modulating Autophagy in Diabetic Rats

Diabetic hearts are more susceptible to myocardial ischemia/reperfusion (I/R) injury and less sensitive to ischemic postconditioning (IPostC), but the underlying mechanisms remain unclear. PKCβ2 is preferentially overactivated in diabetic myocardium, in which autophagy status is abnormal. This study determined whether hyperglycemia-induced PKCβ2 activation resulted in autophagy abnormality and compromised IPostC cardioprotection in diabetes. We found that diabetic rats showed higher cardiac PKCβ2 activation and lower autophagy than control at baseline. However, myocardial I/R further increased PKCβ2 activation and promoted autophagy status in diabetic rats. IPostC significantly attenuated postischemic infarct size and CK-MB, accompanied with decreased PKCβ2 activation and autophagy in control but not in diabetic rats. Pretreatment with CGP53353, a selective inhibitor of PKCβ2, attenuated myocardial I/R-induced infarction and autophagy and restored IPostC-mediated cardioprotection in diabetes. Similarly, CGP53353 could restore hypoxic postconditioning (HPostC) protection against hypoxia reoxygenation- (HR-) induced injury evidenced by decreased LDH release and JC-1 monomeric cells and increased cell viability. These beneficial effects of CGP53353 were reversed by autophagy inducer rapamycin, but could be mimicked by autophagy inhibitor 3-MA. It is concluded that selective inhibition of PKCβ2 could attenuate myocardial I/R injury and restore IPostC-mediated cardioprotection possibly through modulating autophagy in diabetes.

Inhibition of the SIRT1 signaling pathway exacerbates endoplasmic reticulum stress induced by renal ischemia/reperfusion injury in type 1 diabetic rats

The aim of the present study was to investigate whether the diabetic kidney is more susceptible to ischemia/reperfusion (I/R) injury, and identify the potential mechanisms involved. An animal model of type 1 diabetes was created by treating rats with streptozotocin (STZ). This model was then used, along with healthy controls, to investigate the effect of diabetes mellitus (DM) on renal I/R injury. After 45 min of ischemia and 24 h of reperfusion, kidney and serum samples were acquired and used to evaluate function and histopathological injury in the kidneys. Western blotting was also used to determine the expression levels of key proteins. Rats experiencing renal I/R exhibited significant characteristics of renal dysfunction, reduced levels of Sirtuin 1 (SIRT1) protein (a key signaling protein in the kidneys), increased endoplasmic reticulum stress (ERS) and pyroptosis. Furthermore, diabetic rats exhibited further reductions in the levels of SIRT1 in response to renal I/R injury and an increase in the levels of ERS. These effects were all alleviated by the administration of a SIRT1 agonist. The present analysis revealed that the SIRT1-mediated activation of ER stress and pyroptosis played a pivotal role in diabetic rats subjected to renal I/R injury. Downregulation of the SIRT1 signaling pathway were exacerbated in response to renal I/R injury-induced acute kidney injury (AKI). The present data indicated that DM enhanced ER stress and increased pyroptosis by downregulating the SIRT1 signaling pathway.

Exogenous hydrogen sulfide protects against high glucose-induced apoptosis and oxidative stress by inhibiting the STAT3/HIF-1α pathway in H9c2 cardiomyocytes

Hydrogen sulfide (H2S), an endogenous gasotransmitter, possesses multiple physiological and pharmacological properties including anti-apoptotic, anti-oxidative stress and cardiac protective activities in diabetic cardiomyopathy. An increasing body of evidence has suggested that signal transducer and activator of transcription 3 (STAT3) has beneficial effects in the heart. However, the effect of diabetes on the phosphorylation or activation of cardiac STAT3 appears to be controversial. The present study was designed to investigate the precise function of the STAT3/hypoxia-inducible factor-1α (HIF-1α) signaling pathway in high glucose (HG)-induced H9c2 cardiomyocyte injury and the function of the STAT3/HIF-1α pathway in the cardioprotective action of H2S. The results revealed that GYY4137 pretreatment substantially ameliorated the HG-induced decrease in cell viability and the increase in lactate dehydrogenase (LDH) release in H9c2 cells. Additionally, HG treatment resulted in the upregulation of the phosphorylated (p)-STAT3/STAT3 ratio and HIF-1α protein expression in H9c2 cells, indicating that the activation of the STAT3/HIF-1α pathway was induced by HG. STAT3/HIF-1α pathway inhibition induced by transfection with STAT3 small interfering (si)-RNA attenuated the HG-induced downregulation of cell viability and the upregulation of LDH release. Furthermore, STAT3 siRNA transfection and GYY4137 pretreatment combined attenuated HG-induced apoptosis as illustrated by the decrease in the number of terminal deoxynucleotidyl transferase dUTP nick end labeling-positive cells, caspase-3 activity, apoptosis ratio and BCL2 associated X, apoptosis regulator/BCL2 apoptosis regulator ratio in H9c2 cells. In addition, STAT3 siRNA transfection and GYY4137 blocked HG-induced oxidative stress as evidenced by the decrease in reactive oxygen species generation, malondialdehyde content and NADPH oxidase 2 expression, and the increase in superoxide dismutase activity and glutathione level. Notably, GYY4137 pretreatment was revealed to reduce the p-STAT3/STAT3 ratio and HIF-1α protein expression, resulting in the inhibition of the STAT3/HIF-1α signaling pathway in HG-treated H9c2 cells. Altogether, the present results demonstrated that H2S mitigates HG-induced H9c2 cell damage, and reduces apoptosis and oxidative stress by suppressing the STAT3/HIF-1α signaling pathway.

Chronic type 2 but not type 1 diabetes impairs myocardial ischaemic tolerance and preconditioning in C57Bl/6 mice

NEW FINDINGS

• What is the central question of this study? What is the impact of chronic adult-onset diabetes on cardiac ischaemic outcomes and preconditioning? • What is the main finding and its importance? Chronic adult-onset type 2 but not type 1 diabetes significantly impairs myocardial ischaemic tolerance and ischaemic preconditioning. Preconditioning may be detrimental in type 2 diabetes, exaggerating nitrosative stress and apoptotic protein expression.

ABSTRACT

Effects of diabetes on myocardial responses to ischaemia-reperfusion (I-R) and cardioprotective stimuli remain contentious, potentially reflecting influences of disease duration and time of onset. Chronic adult-onset type 1 diabetes (T1D) and type 2 diabetes (T2D) were modelled non-genetically in male C57Bl/6 mice via 5 × 50 mg kg^-1 daily streptozotocin (STZ) injections + 12 weeks' standard chow or 1 × 75 mg kg^-1 STZ injection + 12 weeks' obesogenic diet (32% calories as fat, 57% carbohydrate, 11% protein), respectively. Systemic outcomes were assessed and myocardial responses to I-R ± ischaemic preconditioning (IPC; 3 × 5 min I-R) determined in Langendorff perfused hearts. Uncontrolled T1D was characterised by pronounced hyperglycaemia (25 mm fasting glucose), glucose intolerance and ∼10% body weight loss, whereas T2D mice exhibited moderate hyperglycaemia (15 mm), hyperinsulinaemia, glucose intolerance and 17% weight gain. Circulating ghrelin, resistin and noradrenaline were unchanged with T1D, while leptin increased and noradrenaline declined in T2D mice. Ischaemic tolerance and IPC were preserved in T1D hearts. In contrast, T2D worsened post-ischaemic function (∼40% greater diastolic and contractile dysfunction) and cell death (100% higher troponin efflux), and abolished IPC protection. Whereas IPC reduced post-ischaemic nitrotyrosine and pro-apoptotic Bak and Bax levels in non-diabetic hearts, these effects were reduced in T1D and IPC augmented Bax and nitrosylation in T2D hearts. The data demonstrate chronic T1D does not inhibit myocardial I-R tolerance or IPC, whereas metabolic and endocrine disruption in T2D is associated with ischaemic intolerance and inhibition of IPC. Indeed, normally protective IPC may exaggerate damage mechanisms in T2D hearts.

Ischemia Reperfusion Injury: Mechanisms of Damage/Protection and Novel Strategies for Cardiac Recovery/Regeneration

Ischemic diseases in an aging population pose a heavy social encumbrance. Moreover, current therapeutic approaches, which aimed to prevent or minimize ischemia-induced damage, are associated with relevant costs for healthcare systems. Early reperfusion by primary percutaneous coronary intervention (PPCI) has undoubtedly improved patient's outcomes; however, the prevention of long-term complications is still an unmet need. To face these hurdles and improve patient's outcomes, novel pharmacological and interventional approaches, alone or in combination, reducing myocardium oxygen consumption or supplying blood flow via collateral vessels have been proposed. A number of clinical trials are ongoing to validate their efficacy on patient's outcomes. Alternative options, including stem cell-based therapies, have been evaluated to improve cardiac regeneration and prevent scar formation. However, due to the lack of long-term engraftment, more recently, great attention has been devoted to their paracrine mediators, including exosomes (Exo) and microvesicles (MV). Indeed, Exo and MV are both currently considered to be one of the most promising therapeutic strategies in regenerative medicine. As a matter of fact, MV and Exo that are released from stem cells of different origin have been evaluated for their healing properties in ischemia reperfusion (I/R) settings. Therefore, this review will first summarize mechanisms of cardiac damage and protection after I/R damage to track the paths through which more appropriate interventional and/or molecular-based targeted therapies should be addressed. Moreover, it will provide insights on novel non-invasive/invasive interventional strategies and on Exo-based therapies as a challenge for improving patient's long-term complications. Finally, approaches for improving Exo healing properties, and topics still unsolved to move towards Exo clinical application will be discussed.

Hyperglycemia-Induced Oxidative Stress Abrogates Remifentanil Preconditioning-Mediated Cardioprotection in Diabetic Rats by Impairing Caveolin-3-Modulated PI3K/Akt and JAK2/STAT3 Signaling

Diabetic hearts are more vulnerable to ischemia/reperfusion (I/R) injury and less responsive to remifentanil preconditioning (RPC), but the underlying mechanisms are incompletely understood. Caveolin-3 (Cav-3), the dominant isoform of cardiomyocyte caveolae, is reduced in diabetic hearts in which oxidative stress is increased. This study determined whether the compromised RPC in diabetes was an independent manifestation of hyperglycemia-induced oxidative stress or linked to impaired Cav-3 expression with associated signaling abnormality. RPC significantly attenuated postischemic infarction, cardiac dysfunction, myocardial apoptosis, and 15-F2t-isoprostane production (a specific marker of oxidative stress), accompanied with increased Cav-3 expression and enhanced Akt and STAT3 activation in control but not in diabetic rats. Pretreatment with the antioxidant N-acetylcysteine (NAC) attenuated hyperglycemia-induced reduction of Cav-3 expression and Akt and STAT3 activation and restored RPC-mediated cardioprotection in diabetes, which was abolished by cardiac-specific knockdown of Cav-3 by AAV9-shRNA-Cav-3, PI3K/Akt inhibitor wortmannin, or JAK2/STAT3 inhibitor AG490, respectively. Similarly, NAC could restore RPC protection from high glucose and hypoxia/reoxygenation-induced injury evidenced by decreased levels of LDH release, 15-F2t-isoprostane, O₂ ^-, and JC-1 monomeric cells, which were reversed by caveolae disrupter methyl-β-cyclodextrin, wortmannin, or AG490 in isolated primary cardiomyocytes or siRNAs of Cav-3, Akt, or STAT3 in H9C2 cells. Either methyl-β-cyclodextrin or Cav-3 knockdown reduced Akt and STAT3 activation. Further, the inhibition of Akt activation by a selective inhibitor or siRNA reduced STAT3 activation and vice versa, but they had no effects on Cav-3 expression. Thus, hyperglycemia-induced oxidative stress abrogates RPC cardioprotection by impairing Cav-3-modulated PI3K/Akt and JAK2/STAT3 signaling. Antioxidant treatment with NAC could restore RPC-induced cardioprotection in diabetes by improving Cav-3-dependent Akt and STAT3 activation and by facilitating the cross talk between PI3K/Akt and JAK2/STAT3 signaling pathways.

STAT3 dictates β-cell apoptosis by modulating PTEN in streptozocin-induced hyperglycemia

Insufficient pancreatic β-cell mass or insulin-producing β-cells are implicated in all forms of diabetes mellitus. However, the molecular mechanisms underlying β-cell destruction are complex and not fully defined. Here we observed that activation of STAT3 is intensely and specifically inhibited in β-cells under hyperglycemic conditions. By knocking out STAT3 specifically in mouse β-cells, we found that the loss of STAT3 sensitized mice to three low doses of STZ stimulation resulting in hyperglycemia. Mechanistically, accumulating PTEN, induced by STAT3 deficiency, directly represses phosphorylation of AKT, which negatively modulates transcription factor activation, dysregulates β-cell function, positively promotes apoptotic signaling, and finally induces β-cell apoptosis. Notably, the defective secretion of insulin and β-cells apoptosis was completely rescued by PTEN ablation in STAT3-null islets or PTEN inhibitor bpv(phen) treatment. Thus our data suggest that STAT3 is a vital modulator of β-cell survival and function, highlighting a critical role for STAT3 in the negative regulation of PTEN-AKT signaling pathway associated with β-cell dysfunction and apoptosis.

Reduction of SIRT1 blunts the protective effects of ischemic post-conditioning in diabetic mice by impairing the Akt signaling pathway

Ischemic post-conditioning (IPO) activates Akt signaling to confer cardioprotection. The responsiveness of diabetic hearts to IPO is impaired. We hypothesized that decreased cardiac SIRT1, a positive regulator of Akt, may be responsible for the impaired responsiveness of diabetic hearts to IPO-mediated cardioprotection. High-fat diet and streptozotocin-induced diabetic mice were subjected to myocardial ischemia/reperfusion (MI/R, 30 min ischemia and 180 min reperfusion) or IPO (three cycles of 10 s of reperfusion and ischemia at the onset of reperfusion). Adenoviral vectors encoding GFP or SIRT1 (Ad-SIRT1) were administered by direct injection into the left ventricular. Our results showed that IPO activated the Akt signaling pathway and reduced MI/R injury in non-diabetic hearts but not in diabetic hearts, in which reduced expression of SIRT1 and increased Akt acetylation were observed. Delivery of Ad-SIRT1 into the diabetic hearts reduced Akt acetylation and restored the cardioprotective effects of IPO by modulating Akt signaling pathway. In contrast, cardiac-specific SIRT1 knockout increased Akt acetylation and blunted the cardioprotective effects of IPO. In in vitro study, transfection with wild-type SIRT1 but not inactive mutant SIRT1 reduced the expression of Akt acetylation and restored the protective effects of hypoxic post-conditioning in high glucose-incubated cardiomyocytes. Moreover, the cardiomyocytes transfected with constitutive Akt acetylation showed repressed Akt phosphorylation and blunted protective effects against hypoxia/reoxygenation injury. These findings demonstrate that the reduction of SIRT1 blunts the protective effects of IPO by impairing Akt signaling pathway and that SIRT1 up-regulation restores IPO-mediated cardioprotection in diabetic mice via deacetylation-dependent activation of Akt signaling pathway.

Melatonin attenuates acute kidney ischemia/reperfusion injury in diabetic rats by activation of the SIRT1/Nrf2/HO-1 signaling pathway

Background and aims: Diabetic kidney is more sensitive to ischemia/reperfusion (I/R) injury, which is associated with increased oxidative stress and impaired nuclear factor erythroid 2-related factor 2 (Nrf2)/heme oxygenase-1 (HO-1) signaling. Melatonin, a hormone that is secreted with the rhythm of the light/dark cycle, has antioxidative effects in reducing acute kidney injury (AKI). However, the molecular mechanism of melatonin protection against kidney I/R injury in the state of diabetes is still unknown. In the present study, we hypothesized that melatonin attenuates renal I/R injury in diabetes by activating silent information regulator 2 associated protein 1 (SIRT1) expression and Nrf2/HO-1 signaling. Methods: Control or streptozotocin (STZ)-induced Type 1 diabetic rats were treated with or without melatonin for 4 weeks. Renal I/R injury was achieved by clamping both left and right renal pedicles for 30 min followed by reperfusion for 48 h. Results: Diabetic rats that were treated with melatonin undergoing I/R injury prevented renal injury from I/R, in aspects of the histopathological score, cell apoptosis, and oxidative stress in kidney, accompanied with decreased expressions of SIRT1, Nrf2, and HO-1 as compared with those in control rats. All these alterations were attenuated or prevented by melatonin treatment; but these beneficial effects of melatonin were abolished by selective inhibition of SIRT1 with EX527. Conclusion: These findings suggest melatonin could attenuate renal I/R injury in diabetes, possibly through improving SIRT1/Nrf2/HO-1 signaling.

Multitarget Strategies to Reduce Myocardial Ischemia/Reperfusion Injury: JACC Review Topic of the Week

Many treatments have been identified that confer robust cardioprotection in experimental animal models of acute ischemia and reperfusion injury. However, translation of these cardioprotective therapies into the clinical setting of acute myocardial infarction (AMI) for patient benefit has been disappointing. One important reason might be that AMI is multifactorial, causing cardiomyocyte death via multiple mechanisms, as well as affecting other cell types, including platelets, fibroblasts, endothelial and smooth muscle cells, and immune cells. Many cardioprotective strategies act through common end-effectors and may be suboptimal in patients with comorbidities. In this regard, emerging data suggest that optimal cardioprotection may require the combination of additive or synergistic multitarget therapies. This review will present an overview of the state of cardioprotection today and provide a roadmap for how we might progress towards successful clinical use of cardioprotective therapies following AMI, focusing on the rational combination of judiciously selected, multitarget therapies. This paper emerged as part of the discussions of the European Union (EU)-CARDIOPROTECTION Cooperation in Science and Technology (COST) Action, CA16225.

Effects of Cardiovascular Risk Factors on Cardiac STAT3

Nuclear, mitochondrial and cytoplasmic signal transducer and activator of transcription 3 (STAT3) regulates many cellular processes, e.g., the transcription or opening of mitochondrial permeability transition pore, and its activity depends on the phosphorylation of Tyr705 and/or Ser727 sites. In the heterogeneous network of cardiac cells, STAT3 promotes cardiac muscle differentiation, vascular element formation and extracellular matrix homeostasis. Overwhelming evidence suggests that STAT3 is beneficial for the heart, plays a role in the prevention of age-related and postpartum heart failure, protects the heart against cardiotoxic doxorubicin or ischaemia/reperfusion injury, and is involved in many cardioprotective strategies (e.g., ischaemic preconditioning, perconditioning, postconditioning, remote or pharmacological conditioning). Ischaemic heart disease is still the leading cause of death worldwide, and many cardiovascular risk factors contribute to the development of the disease. This review focuses on the effects of various cardiovascular risk factors (diabetes, aging, obesity, smoking, alcohol, depression, gender, comedications) on cardiac STAT3 under non-ischaemic baseline conditions, and in settings of ischaemia/reperfusion injury with or without cardioprotective strategies.

Downregulation of PTEN by sodium orthovanadate protects the myocardium against ischemia/reperfusion injury after chronic atorvastatin treatment

Acute statin treatment has been reported to be critical in protecting the cardiac cells against ischemia/reperfusion injury by activating PI3K/Akt signal pathway. In vitro rat myocardial ischemia/reperfusion model, chronic statin treatment led to upregulation of phosphatase and tensin homolog (PTEN). This has been potentially indicated the correlation in PTEN and protective effect of statin on myocardium. In this current study, we evaluated the role of sodium orthovanadate a nonspecific inhibitor to PTEN and its correlation with atorvastatin on protecting myocardium against ischemia/reperfusion injury. We found a long-term statin treatment could increase the PTEN level, and this process was counteracted in the presence of sodium orthovanadate. However, the phosphotyrosine level was not affected by this statin. Besides, this process was mediated by Akt signaling since phosphorylated Akt level was altered by statin and sodium orthovanadate treatment. In a conclusion, this study showed a potential mechanism underlying PTEN-induced attenuation in long-term statin's therapeutic effect, which provided the new insight into the synergic role of PTEN and atorvastatin in protecting cardiac cells against ischemia/reperfusion injury.

Inhibition of HDAC6 Activity Alleviates Myocardial Ischemia/Reperfusion Injury in Diabetic Rats: Potential Role of Peroxiredoxin 1 Acetylation and Redox Regulation

Patients with diabetes are more vulnerable to myocardial ischemia/reperfusion (MI/R) injury, which is associated with excessive reactive oxygen species (ROS) generation and decreased antioxidant defense. Histone deacetylase 6 (HDAC6), a regulator of the antioxidant protein peroxiredoxin 1 (Prdx1), is associated with several pathological conditions in the cardiovascular system. This study investigated whether tubastatin A (TubA), a highly selective HDAC6 inhibitor, could confer a protective effect by modulating Prdx1 acetylation in a rat model of MI/R and an in vitro model of hypoxia/reoxygenation (H/R). Here, we found that diabetic hearts with excessive HDAC6 activity and decreased acetylated-Prdx1 levels were more vulnerable to MI/R injury. TubA treatment robustly improved cardiac function, reduced cardiac infarction, attenuated ROS generation, and increased acetylated-Prdx1 levels in diabetic MI/R rats. These results were further confirmed by an in vitro study using H9c2 cells. Furthermore, a study using Prdx1 acetyl-silencing mutants (K197R) showed that TubA only slightly attenuated H/R-induced cell death and ROS generation in K197R-transfected H9c2 cells exposed to high glucose (HG), but these differences were not statistically significant. Taken together, these findings suggest that HDAC6 inhibition reduces ROS generation and confers a protective effect against MI/R or H/R injury by modulating Prdx1 acetylation at K197.