The cellular and molecular origin of reactive oxygen species generation during myocardial ischemia and reperfusion

Interleukin 35 protects cardiomyocytes following ischemia/reperfusion-induced apoptosis via activation of mitochondrial STAT3

Mitochondrial reactive oxygen species (mtROS)-induced apoptosis has been suggested to contribute to myocardial ischemia/reperfusion injury. Interleukin 35 (IL-35), a novel anti-inflammatory cytokine, has been shown to protect the myocardium and inhibit mtROS production. However, its effect on cardiomyocytes upon exposure to hypoxia/reoxygenation (H/R) damage has not yet been elucidated. The present study aimed to investigate the potential protective role and underlying mechanisms of IL-35 in H/R-induced mouse neonatal cardiomyocyte injury. Mouse neonatal cardiomyocytes were challenged to H/R in the presence of IL-35, and we found that IL-35 dose dependently promotes cell viability, diminishes mtROS, maintains mitochondrial membrane potential, and decreases the number of apoptotic cardiomyocytes. Meanwhile, IL-35 remarkably activates mitochondrial STAT3 (mitoSTAT3) signaling, inhibits cytochrome c release, and reduces apoptosis signaling. Furthermore, co-treatment of the cardiomyocytes with the STAT3 inhibitor AG490 abrogates the IL-35-induced cardioprotective effects. Our study identified the protective role of IL-35 in cardiomyocytes following H/R damage and revealed that IL-35 protects cardiomyocytes against mtROS-induced apoptosis through the mitoSTAT3 signaling pathway during H/R.

Lycium barbarum polysaccharides inhibit ischemia/reperfusion-induced myocardial injury via the Nrf2 antioxidant pathway

Oxidative stress is considered to be one of main pathophysiological mechanisms in myocardial ischemia/reperfusion (I/R) injury. Lycium barbarum polysaccharides (LBP), the main ingredient of Lycium barbarum, have potential antioxidant activity. We aimed to investigate the effects of LBP on myocardial I/R injury and explore the underlying mechanisms. Myocardial I/R group was treated with or without LBP to evaluate oxidative stress markers and the role of Nrf2 signal pathway. Our results showed that I/R increased infarct size and the activities of creatine kinase (CK) and lactate dehydrogenase (LDH) when compared with control group. Meanwhile, the levels of reactive oxygen species (ROS), malondialdehyde (MDA), interleukin-6 (IL-6) and tumor necrosis factor-α (TNF-α) were enhanced and the activities of superoxide dismutase (SOD), glutathione peroxidase (GPX) and catalase (CAT) were decreased. These changes were associated with a significant increase in myocardial apoptosis, ultimately leading to cardiac dysfunction. LBP reduced infarct size (38.4 ± 2 % versus 19.4 ± 1.8 %, p < 0.05), CK and LDH activities and myocardial apoptotic index. Meanwhile, LBP suppressed the production of ROS and restored redox status. Additionally, LBP increased protein level of nuclear Nrf2 in vivo (2.1 ± 0.3 versus 3.8 ± 0.4, p < 0.05) and in vitro (1.9 ± 0.2 versus 3.8 ± 0.1, p < 0.05) and subsequently upregulated heme oxygenase 1 and NADPH dehydrogenase quinone 1 compared to I/R group. Interestingly, Nrf2 siRNA abolished the protective effects of LBP. LBP suppressed oxidative stress damage and attenuated cardiac dysfunction induced by I/R via activation of the Nrf2 antioxidant signal pathway.

Electrophysiological and neurochemical evaluation of the adverse effects of REM sleep deprivation and epileptic seizures on rat's brain

AIM

The current study aims to investigate the impact of paradoxical (REM) sleep deprivation and/or epileptic seizures on rat's cortical brain tissues.

MAIN METHODS

Animals were divided into four groups; control, epileptic, REM sleep deprived and epileptic subjected to REM sleep deprivation. Electrocorticogram (ECoG) signals were recorded and quantitatively analyzed for each group. Concentrations of amino acid neurotransmitters; proinflammatory cytokines; and oxidative stress parameters; and acetylcholinesterase activity were determined in the cortex of the animals in different groups.

KEY FINDINGS

Results showed significant variations in the spectral distribution of ECoG waves in the epilepsy model, 24- and 48-hours of REM sleep deprivation and their combined effects indicating a state of cortical hyperexcitability. Significant increases in NO and taurine and significant decrement in glutamine, GABA and glycine were determined. In REM sleep deprived rats significant elevation in glutamate, aspartate, glycine and taurine and a significant lowering in GABA were obtained. This was accompanied by significant reduction in AchE and IL-β. In the cortical tissue of epileptic rats deprived from REM sleep significant increases in lipid peroxidation, TNF-α, IL-1β, IL-6 and aspartate and a significant reduction in AchE were observed.

SIGNIFICANCE

The present data indicate that REM sleep deprivation induces an increase in lipid peroxidation and storming in proinflammatory cytokines in the cortex of rat model of epilepsy during SRS. These changes are associated with a decreased seizure threshold as inferred from the increase in alpha and Beta waves and a decrease in Delta waves of ECoG.

Nanoparticle-induced ferroptosis: detection methods, mechanisms and applications

Although ferroptosis is an iron-dependent cell death mechanism involved in the development of some severe diseases (e.g., Parkinsonian syndrome, stroke and tumours), the combination of nanotechnology with ferroptosis for the treatment of these diseases has attracted substantial research interest. However, it is challenging to differentiate nanoparticle-induced ferroptosis from other types of cell deaths (e.g., apoptosis, pyroptosis, and necrosis), elucidate the detailed mechanisms and identify the key property of nanoparticles responsible for ferroptotic cell deaths. Therefore, a summary of these aspects from current research on nano-ferroptosis is important and timely. In this review, we endeavour to summarize some convincing techniques that can be employed to specifically examine ferroptotic cell deaths. Then, we discuss the molecular initiating events of nanosized ferroptosis inducers and the cascade signals in cells, and therefore elaborate the ferroptosis mechanisms. Besides, the key physicochemical properties of nano-inducers are also discussed to acquire a fundamental understanding of nano-structure-activity relationships (nano-SARs) involved in ferroptosis, which may facilitate the design of nanomaterials to deliberately tune ferroptosis. Finally, future perspectives on the fundamental understanding of nanoparticle-induced ferroptosis and its applications are provided.

Combination of mesenchymal stromal cells and machine perfusion is a novel strategy for organ preservation in solid organ transplantation

Organ preservation is a prerequisite for an urgent increase in the availability of organs for solid organ transplantation (SOT). An increasing amount of expanded criteria donor (ECD) organs are used clinically. Currently, the paradigm of organ preservation is shifting from simple reduction of cellular metabolic activity to maximal simulation of an ex vivo physiological microenvironment. An ideal organ preservation technique should not only preserve isolated organs but also offer the possibility of rehabilitation and evaluation of organ function prior to transplantation. Based on the fact that mesenchymal stromal cells (MSCs) possess strong regeneration properties, the combination of MSCs with machine perfusion (MP) is expected to be superior to conventional preservation methods. In recent years, several studies have attempted to use this strategy for SOT showing promising outcomes. With better organ function during ex vivo preservation and the potential of utilization of organs previously deemed untransplantable, this strategy is meaningful for patients with organ failure to help overcome organ shortage in the field of SOT.

Inonotus obliquus extract alleviates myocardial ischemia/reperfusion injury by suppressing endoplasmic reticulum stress

Inonotus obliquus (IO) is an edible fungus that exerts various biological functions, including anti‑inflammatory, antitumor and immunomodulatory effects. The present study was designed to investigate the role of IO extract (IOE) in myocardial ischemia/reperfusion (MI/R) and determine the exact molecular mechanisms. The left anterior descending coronary artery was ligated to establish the MI/R injury model in rats. IOE exhibited a novel cardioprotective effect, as shown by improvement in cardiac function and decrease in infarct size. Pretreatment with IOE activated antioxidant enzymes in cardiomyocytes, including glutathione peroxidase, superoxide dismutase and catalase. IOE pretreatment also induced the upregulation of NAD‑dependent protein deacetylase sirtuin‑1 (SIRT1) and downregulation of glucose‑regulated protein 78, phosphorylated (p‑) protein kinase R‑like endoplasmic reticulum kinase, p‑eukaryotic translation initiation factor 2 subunit α, C/EBP homologous protein and caspase‑12. Furthermore, IOE alleviated endoplasmic reticulum (ER) stress‑induced apoptosis in cardiomyocytes by decreasing the mRNA levels of caspase‑12. IOE inhibited apoptosis induced by overexpression of pro‑caspase‑9 and pro‑caspase‑3. In summary, IOE pretreatment protects the heart against MI/R injury through attenuating oxidative damage and suppressing ER stress‑induced apoptosis, which may be primarily due to SIRT1 activation.

Cyclic Hypoxia: An Update on Its Characteristics, Methods to Measure It and Biological Implications in Cancer

Regions of hypoxia occur in most if not all solid cancers. Although the presence of tumor hypoxia is a common occurrence, the levels of hypoxia and proportion of the tumor that are hypoxic vary significantly. Importantly, even within tumors, oxygen levels fluctuate due to changes in red blood cell flux, vascular remodeling and thermoregulation. Together, this leads to cyclic or intermittent hypoxia. Tumor hypoxia predicts for poor patient outcome, in part due to increased resistance to all standard therapies. However, it is less clear how cyclic hypoxia impacts therapy response. Here, we discuss the causes of cyclic hypoxia and, importantly, which imaging modalities are best suited to detecting cyclic vs. chronic hypoxia. In addition, we provide a comparison of the biological response to chronic and cyclic hypoxia, including how the levels of reactive oxygen species and HIF-1 are likely impacted. Together, we highlight the importance of remembering that tumor hypoxia is not a static condition and that the fluctuations in oxygen levels have significant biological consequences.

Modulatory Effect of Myokines on Reactive Oxygen Species in Ischemia/Reperfusion

There is a growing body of evidence showing the importance of physical activity against acute ischemic events in various organs. Ischemia/reperfusion injury (I/R) is characterized by tissue damage as a result of restriction and subsequent restoration of blood supply to an organ. Oxidative stress due to increased reactive oxygen species formation and/or insufficient antioxidant defense is considered to play an important role in I/R. Physical activity not only decreases the general risk factors for ischemia but also confers direct anti-ischemic protection via myokine production. Myokines are skeletal muscle-derived cytokines, representing multifunctional communication channels between the contracting skeletal muscle and other organs through an endocrine manner. In this review, we discuss the most prominent members of the myokines (i.e., brain-derived neurotrophic factor (BDNF), cathepsin B, decorin, fibroblast growth factors-2 and -21, follistatin, follistatin-like, insulin-like growth factor-1; interleukin-6, interleukin-7, interleukin-15, irisin, leukemia inhibitory factor, meteorin-like, myonectin, musclin, myostatin, and osteoglycin) with a particular interest in their potential influence on reactive oxygen and nitrogen species formation or antioxidant capacity. A better understanding of the mechanism of action of myokines and particularly their participation in the regulation of oxidative stress may widen their possible therapeutic use and, thereby, may support the fight against I/R.

Therapeutic effects of histone deacetylase inhibitors on heart disease

A wide range of histone deacetylase (HDAC) inhibitors have been studied for their therapeutic potential because the excessive activity and expression of HDACs have been implicated in the pathogenesis of cardiac diseases. An increasing number of preclinical studies have demonstrated the cardioprotective effects of numerous HDAC inhibitors, suggesting a wide variety of mechanisms by which the inhibitors protect against cardiac stress, such as the suppression of cardiac fibrosis and fetal gene expression, enhancement of angiogenesis and mitochondrial biogenesis, prevention of electrical remodeling, and regulation of apoptosis, autophagy, and cell cycle arrest. For the development of isoform-selective HDAC inhibitors with high efficacy and low toxicity, it is important to identify and understand the mechanisms responsible for the effects of the inhibitors. This review highlights the preclinical effects of HDAC inhibitors that act against Zn²⁺-dependent HDACs and the underlying mechanisms of their protective effects against cardiac hypertrophy, hypertension, myocardial infarction, heart failure, and atrial fibrillation.

Oxidative stress and its association with ST resolution and clinical outcome measures in patients with ST-segment elevation myocardial infarction (STEMI) undergoing primary percutaneous coronary intervention

OBJECTIVE

Reperfusion of ischemic myocardium generates oxidative stress, which itself can mediate myocardial injury. So, in this study, we investigated the level of oxidative stress markers and its association with clinical outcomes in patients with ST-segment elevation myocardial infarction (STEMI) undergoing primary percutaneous coronary intervention.

RESULTS

As indicated in the results, Post MI (Myocardial Infarction) heart failure was significantly higher in the group A (11% vs 4%, p = 0.047). Complete STR (ST-segment resolution) was observed to be significantly higher in the group B (36% vs 17%, p = 0.006). The SOD (Superoxide dismutase) and GPX (Glutathione peroxidase) levels were significantly higher in the group B compared to the other group (1547.51 ± 328.29 vs. 1449.97 ± 246.06, p = 0.019 and 60.62 ± 11.95 vs 57.41 ± 10.14, p = 0.042). The levels of GPX and SOD were shown to be directly related with complete STR and post PCI (Percutaneous coronary intervention)TIMI(Thrombolysis in Myocardial Infarction) flow 3 in the group A (p = 0.002 and p < 0.01, p = 0.005 and p < 0.02, respectively).

Aldehyde dehydrogenase 2 protects against sympathetic excitation-induced cardiac fibrosis

Sympathetic stimulated-cardiac fibrosis imposes great significance on both disease progression and survival in the pathogenesis of many cardiovascular diseases. However, there are few effective therapies targeting it clinically. The cardioprotective effect of aldehyde dehydrogenase 2 (ALDH2) has been explored in many pathological conditions, whether it can exert benefit effects on chronic sympathetic stimulus-induced cardiac fibrosis remains unclear. In this study, we determined to explore the role of ALDH2 on isoproterenol (ISO)-induced cardiac fibroblasts (CF) proliferation and cardiac fibrosis. It was found that ALDH2 enzymatic activity was impaired in ISO-induced HCF proliferation and Aldh2 deficiency promoted mouse CF proliferation. Alda-1, an ALDH2 activator, exerted obvious suppressive effect on ISO-induced HCF proliferation, together with the induction of cell cycle arrest at G₀/G₁ phase and decreased expression of cyclin E1 and cyclin-dependent kinase 2 (CDK2). Mechanistically, the inhibitory role of Alda-1 on HCF proliferation was achieved by decreasing mitochondrial reactive oxygen species (ROS) production, which was partially reversed by rotenone, an inducer of ROS. In addition, wild-type mice treated with Alda-1 manifested with reduced fibrosis and better cardiac function after ISO pump. In summary, Alda-1 alleviates sympathetic excitation-induced cardiac fibrosis via decreasing mitochondrial ROS accumulation, highlighting ALDH2 activity as a promising drug target of cardiac fibrosis.

Cardioprotection of pharmacological postconditioning on myocardial ischemia/reperfusion injury

Acute myocardial infarction is associated with high rates of morbidity and mortality and can cause irreversible myocardial damage. Timely reperfusion is critical to limit infarct size and salvage the ischemic myocardium. However, reperfusion may exacerbate lethal tissue injury, a phenomenon known as myocardial ischemia/reperfusion (I/R) injury. Pharmacological postconditioning (PPC), a strategy involving medication administration before or during the early minutes of reperfusion, is more efficient and flexible than preconditioning or ischemic conditioning. Previous studies have shown that various mechanisms are involved in the effects of PPC. In this review, we summarize the relative effects and potential underlying mechanisms of PPC to provide a foundation for future research attempting to develop novel treatments against myocardial I/R injury.

Roles of Reactive Oxygen Species in Cardiac Differentiation, Reprogramming, and Regenerative Therapies

Reactive oxygen species (ROS) have been implicated in mechanisms of heart development and regenerative therapies such as the use of pluripotent stem cells. The roles of ROS mediating cell fate are dependent on the intensity of stimuli, cellular context, and metabolic status. ROS mainly act through several targets (such as kinases and transcription factors) and have diverse roles in different stages of cardiac differentiation, proliferation, and maturation. Therefore, further detailed investigation and characterization of redox signaling will help the understanding of the molecular mechanisms of ROS during different cellular processes and enable the design of targeted strategies to foster cardiac regeneration and functional recovery. In this review, we focus on the roles of ROS in cardiac differentiation as well as transdifferentiation (direct reprogramming). The potential mechanisms are discussed in regard to ROS generation pathways and regulation of downstream targets. Further methodological optimization is required for translational research in order to robustly enhance the generation efficiency of cardiac myocytes through metabolic modulations. Additionally, we highlight the deleterious effect of the host's ROS on graft (donor) cells in a paracrine manner during stem cell-based implantation. This knowledge is important for the development of antioxidant strategies to enhance cell survival and engraftment of tissue engineering-based technologies. Thus, proper timing and level of ROS generation after a myocardial injury need to be tailored to ensure the maximal efficacy of regenerative therapies and avoid undesired damage.

Protective Effects of Polyphenols against Ischemia/Reperfusion Injury

Myocardial infarction (MI) is a leading cause of morbidity and mortality across the world. It manifests as an imbalance between blood demand and blood delivery in the myocardium, which leads to cardiac ischemia and myocardial necrosis. While it is not easy to identify the first pathogenic cause of MI, the consequences are characterized by ischemia, chronic inflammation, and tissue degeneration. A poor MI prognosis is associated with extensive cardiac remodeling. A loss of viable cardiomyocytes is replaced with fibrosis, which reduces heart contractility and heart function. Recent advances have given rise to the concept of natural polyphenols. These bioactive compounds have been studied for their pharmacological properties and have proven successful in the treatment of cardiovascular diseases. Studies have focused on their various bioactivities, such as their antioxidant and anti-inflammatory effects and free radical scavenging. In this review, we summarized the effects and benefits of polyphenols on the cardiovascular injury, particularly on the treatment of myocardial infarction in animal and human studies.

Ferroptosis and kidney disease

Cell death is a finely regulated process occurring through different pathways. Regulated cell death, either through apoptosis or regulated necrosis offers the possibility of therapeutic intervention. Necroptosis and ferroptosis are among the best studied forms of regulated necrosis in the context of kidney disease. We now review the current evidence supporting a role for ferroptosis in kidney disease and the implications of this knowledge for the design of novel therapeutic strategies. Ferroptosis is defined functionally, as a cell modality characterized by peroxidation of certain lipids, constitutively suppressed by GPX4 and inhibited by iron chelators and lipophilic antioxidants. There is functional evidence of the involvement of ferroptosis in diverse forms of kidneys disease. In a well characterized nephrotoxic acute kidney injury model, ferroptosis caused an initial wave of death, triggering an inflammatory response that in turn promoted necroptotic cell death that perpetuated kidney dysfunction. This suggests that ferroptosis inhibitors may be explored as prophylactic agents in clinical nephrotoxicity or ischemia-reperfusion injury such as during kidney transplantation. Transplantation offers the unique opportunity of using anti-ferroptosis agent ex vivo, thus avoiding bioavailability and in vivo pharmacokinetics and pharmacodynamics issues.

NLRP3 Inflammasome in Acute Myocardial Infarction

Acute myocardial infarction (AMI) is associated with the induction of a sterile inflammatory response that leads to further injury. The NACHT, leucine-rich repeat, and pyrin domain-containing protein 3 (NLRP3) inflammasome is a macromolecular structure responsible for the inflammatory response to injury or infection. NLRP3 can sense intracellular danger signals, such as ischemia and extracellular or intracellular alarmins during tissue injury. The NLRP3 inflammasome is primed and triggered by locally released damage-associated molecular patterns and amplifies the inflammatory response and cell death through caspase-1 activation. Here, we examine the scientific evidence supporting a role for NLRP3 in AMI and the available strategies to inhibit the effects of the inflammasome. Our focus is on the beneficial effects seen in experimental models of AMI in preclinical animal models and the initial results of clinical trials.

Euterpe Oleracea Mart. (Açaí) Reduces Oxidative Stress and Improves Energetic Metabolism in Myocardial Ischemia-Reperfusion Injury in Rats

Background

Euterpe oleracea Mart. (açaí) is a fruit with high antioxidant capacity and could be an adjuvant strategy to attenuate ischemia-reperfusion injury.

Objective

To evaluate the influence of açaí in global ischemia-reperfusion model in rats.

Methods

Wistar rats were assigned to 2 groups: Control (C: receiving standard chow; n = 9) and Açaí (A: receiving standard chow supplemented with 5% açaí; n = 10). After six weeks, the animals were subjected to the global ischemia-reperfusion protocol and an isolated heart study to evaluate left ventricular function. Level of significance adopted: 5%.

Results

There was no difference between the groups in initial body weight, final body weight and daily feed intake. Group A presented lower lipid hydroperoxide myocardial concentration and higher catalase activity, superoxide dismutase and glutathione peroxidase than group C. We also observed increased myocardial activity of b-hydroxyacyl coenzyme-A dehydrogenase, pyruvate dehydrogenase, citrate synthase, complex I, complex II and ATP synthase in the A group as well as lower activity of the lactate dehydrogenase and phosphofructokinase enzymes. The systolic function was similar between the groups, and the A group presented poorer diastolic function than the C group. We did not observe any difference between the groups in relation to myocardial infarction area, total and phosphorylated NF-kB, total and acetylated FOXO1, SIRT1 and Nrf-2 protein expression.

Conclusion

despite improving energy metabolism and attenuating oxidative stress, açai supplementation did not decrease the infarcted area or improve left ventricular function in the global ischemia-reperfusion model.

Juglone as antihypertensive agent acts through multiple vascular mechanisms

Background: Juglone, a natural phenolic compound obtained from the walnut tree, is known for its wide range of biological activities. However, it has yet to be tested for its effects on hypertension and vascular tone. This investigation was aimed to explore the antihypertensive effect and the nature of vascular reactivity of juglone in rat models.Methods: Juglone was tested in in vivo and in vitro experiments in rats. The responses were analyzed and recorded through a PowerLab data acquisition system.Results: Intravenous injection of juglone significantly decreased the mean arterial blood pressure (MAP) in normotensive and hypertensive rats (Max. fall, 43.50 ± 2.96 vs 49.66 ± 3.28 mmHg). In rats pretreated with Nω-Nitro l-arginine methyl ester (_L-NAME), the effect of juglone on MAP was reduced as compared to the control. However, in rats pretreated with atropine the fall in MAP by juglone was not altered. Juglone induced relaxation in the phenylephrine, K⁺ (80 mM), and angiotensin II pretreated isolated rat aortic rings. This vasorelaxant effect was reduced with _L-NAME pretreatment. Atropine pretreatment did not modify the vasorelaxant effect of juglone. Pre-incubation with juglone attenuated the intracellular Ca²⁺ release by suppressing phenylephrine peak formation and also shifted CaCl₂ concentration-response curves (CRCs) to the right. Of note, combined treatment with 4-aminopyridine and barium chloride also reduced juglone-mediated vasorelaxation suggesting a role of K⁺-channels as well.Conclusion: In conclusion, juglone exerts its antihypertensive effect through vasorelaxation, which is mediated by nitric oxide, inhibition of intracellular calcium release and opening of K⁺-channels.

Ischemia Enhances the Acute Stretch-Induced Increase in Calcium Spark Rate in Ventricular Myocytes

Introduction: In ventricular myocytes, spontaneous release of calcium (Ca²⁺) from the sarcoplasmic reticulum via ryanodine receptors (“Ca²⁺ sparks”) is acutely increased by stretch, due to a stretch-induced increase of reactive oxygen species (ROS). In acute regional ischemia there is stretch of ischemic tissue, along with an increase in Ca²⁺ spark rate and ROS production, each of which has been implicated in arrhythmogenesis. Yet, whether there is an impact of ischemia on the stretch-induced increase in Ca²⁺ sparks and ROS has not been investigated. We hypothesized that ischemia would enhance the increase of Ca²⁺ sparks and ROS that occurs with stretch.

Methods: Isolated ventricular myocytes from mice (male, C57BL/6J) were loaded with fluorescent dye to detect Ca²⁺ sparks (4.6 μM Fluo-4, 10 min) or ROS (1 μM DCF, 20 min), exposed to normal Tyrode (NT) or simulated ischemia (SI) solution (hyperkalemia [15 mM potassium], acidosis [6.5 pH], and metabolic inhibition [1 mM sodium cyanide, 20 mM 2-deoxyglucose]), and subjected to sustained stretch by the carbon fiber technique (~10% increase in sarcomere length, 15 s). Ca²⁺ spark rate and rate of ROS production were measured by confocal microscopy.

Results: Baseline Ca²⁺ spark rate was greater in SI (2.54 ± 0.11 sparks·s⁻¹·100 μm⁻²; n = 103 cells, N = 10 mice) than NT (0.29 ± 0.05 sparks·s⁻¹·100 μm⁻²; n = 33 cells, N = 9 mice; p < 0.0001). Stretch resulted in an acute increase in Ca²⁺ spark rate in both SI (3.03 ± 0.13 sparks·s⁻¹·100 μm⁻²; p < 0.0001) and NT (0.49 ± 0.07 sparks·s⁻¹·100 μm⁻²; p < 0.0001), with the increase in SI being greater than NT (+0.49 ± 0.04 vs. +0.20 ± 0.04 sparks·s⁻¹·100 μm⁻²; p < 0.0001). Baseline rate of ROS production was also greater in SI (1.01 ± 0.01 normalized slope; n = 11, N = 8 mice) than NT (0.98 ± 0.01 normalized slope; n = 12, N = 4 mice; p < 0.05), but there was an acute increase with stretch only in SI (+12.5 ± 2.6%; p < 0.001).

Conclusion: Ischemia enhances the stretch-induced increase of Ca²⁺ sparks in ventricular myocytes, with an associated enhancement of stretch-induced ROS production. This effect may be important for premature excitation and/or in the development of an arrhythmogenic substrate in acute regional ischemia.

Sphingosine 1-phosphate signaling in ischemia and reperfusion injury

Ischemia and reperfusion injury is a complex hemodynamic pathological phenomenon that engages the metabolic to inflammatory machinery in development of disease conditions like heart failure, stroke and acute kidney failure. Target specific therapeutic approaches for ischemia reperfusion injury remains critical despite the extensive studies contributing to the understanding of its pathogenesis. Ischemic or pharmacological conditionings have been long established manipulations to harness the endogenous protective mechanisms against ischemia reperfusion injury that fostered the development of potential therapeutic targets such as sphingolipids signaling. Sphingosine 1-phosphate has been emerged as a crucial metabolite of sphingolipids to regulate the cell survival, vascular integrity and inflammatory cascades in ischemia reperfusion injury. Sphingosine 1-phosphate signaling process has been implicated to downgrade the mitochondrial dysfunction, apoptotic assembly along with upregulation of RISK and SAFE pro-survival pathways. It also regulates the endothelial dysfunction and immune cells behavior to control the vascular permeability and immune cells infiltration at ischemia reperfusion injury site. Targeting the signaling of this single moiety holds the vast potential to extensively influence the detrimental signaling of ischemia reperfusion injury. This review highlights the role and significance of S1P signaling that can be therapeutically exploit to treat ischemia reperfusion injury mediated pathological conditions in different organs.

Mitochondrial ROS in myocardial ischemia reperfusion and remodeling

Despite major progress in interventional and medical treatments, myocardial infarction (MI) and subsequent development of heart failure (HF) are still associated with high mortality. Both during ischemia reperfusion (IR) in the acute setting of MI, as well as in the chronic remodeling process following MI, oxidative stress substantially contributes to cardiac damage. Reactive oxygen species (ROS) generated within mitochondria are particular drivers of mechanisms contributing to IR injury, including induction of mitochondrial permeability transition or oxidative damage of intramitochondrial structures and molecules. But even beyond the acute setting, mechanisms like inflammatory signaling, extracellular remodeling, or pro-apoptotic signaling that contribute to post-infarction remodeling are regulated by mitochondrial ROS. In the current review, we discuss both sources and consequences of mitochondrial ROS during IR and in the chronic setting following MI, thereby emphasizing the potential therapeutic value of attenuating mitochondrial ROS to improve outcome and prognosis for patients suffering MI.

MiRNA-Mediated Mechanisms of Cardiac Protection in Ischemic and Remote Ischemic Preconditioning-A Qualitative Systematic Review

BACKGROUND

Ischemic preconditioning (IPC) and remote ischemic preconditioning (RIPC) protect myocardial tissue against subsequent ischemia and reperfusion injury (IRI) and have a high potential to improve patient outcome. The mediators and mechanisms of protection through IPC and RIPC remain largely unknown, but micro-RNAs (miRNAs) are promising candidates.

METHODS

Systematic review of Medline and Embase databases for biomedical scientific literature.

RESULTS

A total of 26 relevant publications (21 full-text original articles and 5 conference abstracts) were identified, 8 describing cell culture experiments, 14 animal experiments, and 4 randomized clinical trials in humans. Most commonly reported miRNAs with differential expression between preconditioned and control groups include miR-1, miR-21, and miR-144. Experimental designs and procedures differ widely, thereby limiting the potential to compare results between studies. Two of the four RCTs did not find any differentially expressed miRNAs.

CONCLUSIONS

Results from RCTs should feed back into basic research and focused studies confirming or rejecting hypotheses generated by these RCTs are needed.

A Review on the Most Important Medicinal Plants Effective in Cardiac Ischemia-Reperfusion Injury

Ischemia, referring to reduction and restriction of perfusion to myocardial tissue which involves coronary artery through the formation of misplaced clots and thrombosis, is one of the most important cardiovascular diseases. Plant-based compounds help to improve or prevent disease by affecting the factors involved in the disease. This review was conducted to report the medicinal plants and factors effective in cardiac ischemiareperfusion (I/R) injury to supplement the knowledge about this disease and its prevention and treatment using certain medicinal plants and their active compounds. For this purpose, medicinal plants and their potential antioxidant activities, effects on lipid levels and plaque formation, atherosclerosis and development of cardiovascular diseases and ischemia were reviewed.

METHODS

To conduct this review, relevant articles published between 1983 and 2018 were retrieved from the Google Scholar, PubMed, Scientific Information Database, Web of Science, and Scopus using search terms antioxidant, ischemia, reperfusion, heart, infarct, inflammation, cholesterol and medicinal plants. Then, the eligible articles were reviewed.

RESULTS

The active compounds of plants, including phenolic compounds, flavonoids, and antioxidant compounds, can be effective on certain pathogenic factors particularly in decreasing cholesterol and blood pressure, preventing an increase in free radicals and ultimately reducing blood clots and vascular resistance to reduce and prevent ischemic disease and its harmful effects.

CONCLUSION

Medicinal plants discussed in this article seem to be able to prevent cardiac damage and the disease progression via affecting the factors that are involved in ischemia.

Nitrite attenuates mitochondrial impairment and vascular permeability induced by ischemia-reperfusion injury in the lung

Primary graft dysfunction (PGD) is directly related to ischemia-reperfusion (I/R) injury and a major obstacle in lung transplantation (LTx). Nitrite (NO2-), which is reduced in vivo to form nitric oxide (NO), has recently emerged as an intrinsic signaling molecule with a prominent role in cytoprotection against I/R injury. Using a murine model, we provide the evidence that nitrite mitigated I/R-induced injury by diminishing infiltration of immune cells in the alveolar space, reducing pulmonary edema, and improving pulmonary function. Ultrastructural studies support severe mitochondrial impairment in the lung undergoing I/R injury, which was significantly protected by nitrite treatment. Nitrite also abrogated the increased pulmonary vascular permeability caused by I/R. In vitro, hypoxia-reoxygenation (H/R) exacerbated cell death in lung epithelial and microvascular endothelial cells. This contributed to mitochondrial dysfunction as characterized by diminished complex I activity and mitochondrial membrane potential but increased mitochondrial reactive oxygen species (mtROS). Pretreatment of cells with nitrite robustly attenuated mtROS production through modulation of complex I activity. These findings illustrate a potential novel mechanism in which nitrite protects the lung against I/R injury by regulating mitochondrial bioenergetics and vascular permeability.

Inhibitor 1 of Protein Phosphatase 1 Regulates Ca2+/Calmodulin-Dependent Protein Kinase II to Alleviate Oxidative Stress in Hypoxia-Reoxygenation Injury of Cardiomyocytes

Ca²⁺/calmodulin-dependent protein kinase II (CaMKII), regulated by inhibitor 1 of protein phosphatase 1 (I1PP1), is vital for maintaining cardiovascular homeostasis. However, the role and mechanism of I1PP1 against hypoxia-reoxygenation (H/R) injury in cardiomyocytes remain a question. In our study, after I1PP1 overexpression by adenovirus infection in the neonatal cardiomyocytes followed by hypoxia for 4 h and reoxygenation for 12 h, the CaMKIIδ alternative splicing subtype, ATP content, and lactate dehydrogenase (LDH) release were determined. CaMKII activity was evaluated by phosphoprotein phosphorylation at Thr17 (p-PLB Thr17), CaMKII phosphorylation (p-CaMKII), and CaMKII oxidation (ox-CaMKII). Reactive oxygen species (ROS), mitochondrial membrane potential, dynamin-related protein 1 (DRP1), and optic atrophy 1 (OPA1) expressions were assessed. Our study verified that I1PP1 overexpression attenuated the CaMKIIδ alternative splicing disorder; suppressed PLB phosphorylation at Thr17, p-CaMKII, and ox-CaMKII; decreased cell LDH release; increased ATP content; attenuated ROS production; increased mitochondrial membrane potential; and decreased DRP1 expression but increased OPA1 expression in the cardiomyocytes after H/R. Contrarily, CaMKIIδ alternative splicing disorder, LDH release, ATP reduction, and ROS accumulation were aggravated after H/R injury with the I1PP1 knockdown. Collectively, I1PP1 overexpression corrected disorders of CaMKIIδ alternative splicing, inhibited CaMKII phosphorylation, repressed CaMKII oxidation, suppressed ROS production, and attenuated cardiomyocyte H/R injury.

Isoespintanol, a monoterpene isolated from oxandra cf xylopioides, ameliorates the myocardial ischemia-reperfusion injury by AKT/PKCε/eNOS-dependent pathways

PURPOSE

To determine the actions of isoespintanol (Isoesp) on post-ischemic myocardial and mitochondrial alterations.

METHODS

Hearts removed from Wistar rats were perfused by 20 min. After this period, the coronary flow was interrupted by half an hour and re-established during 1 h. In the treated group, Isoesp was administered at the beginning of reperfusion. To assess the participation of ε isoform of protein kinase C (PKCε), protein kinase B (PKB/Akt), and nitric oxide synthase (NOS), hearts were treated with Isoesp plus the respective inhibitors (chelerythrine, wortmannin, and N-nitro-L-arginine methyl ester). Cell death was determined by triphenyl tetrazolium chloride staining technique. Post-ischemic recovery of contractility, oxidative stress, and content of phosphorylated forms of PKCε, Akt, and eNOS were also examined. Mitochondrial state was assessed through the measurement of calcium-mediated response, calcium retention capacity, and mitochondrial potential.

RESULTS

Isoesp limited cell death, decreased post-ischemic dysfunction and oxidative stress, improved mitochondrial state, and increased the expression of PKCε, Akt, and eNOS phosphorylated. All these beneficial effects achieved by Isoesp were annulled by the inhibitors.

CONCLUSION

These findings suggest that activation of Akt/eNOS and PKCε signaling pathways are involved in the development of Isoesp-induced cardiac and mitochondria tolerance to ischemia-reperfusion.

Myocardial Adaptation in Pseudohypoxia: Signaling and Regulation of mPTP via Mitochondrial Connexin 43 and Cardiolipin

Therapies intended to mitigate cardiovascular complications cannot be applied in practice without detailed knowledge of molecular mechanisms. Mitochondria, as the end-effector of cardioprotection, represent one of the possible therapeutic approaches. The present review provides an overview of factors affecting the regulation processes of mitochondria at the level of mitochondrial permeability transition pores (mPTP) resulting in comprehensive myocardial protection. The regulation of mPTP seems to be an important part of the mechanisms for maintaining the energy equilibrium of the heart under pathological conditions. Mitochondrial connexin 43 is involved in the regulation process by inhibition of mPTP opening. These individual cardioprotective mechanisms can be interconnected in the process of mitochondrial oxidative phosphorylation resulting in the maintenance of adenosine triphosphate (ATP) production. In this context, the degree of mitochondrial membrane fluidity appears to be a key factor in the preservation of ATP synthase rotation required for ATP formation. Moreover, changes in the composition of the cardiolipin’s structure in the mitochondrial membrane can significantly affect the energy system under unfavorable conditions. This review aims to elucidate functional and structural changes of cardiac mitochondria subjected to preconditioning, with an emphasis on signaling pathways leading to mitochondrial energy maintenance during partial oxygen deprivation.

Oxidative Stress in Cell Death and Cardiovascular Diseases

ROS functions as a second messenger and modulates multiple signaling pathways under the physiological conditions. However, excessive intracellular ROS causes damage to the molecular components of the cell, which promotes the pathogenesis of various human diseases. Cardiovascular diseases are serious threats to human health with extremely high rates of morbidity and mortality. Dysregulation of cell death promotes the pathogenesis of cardiovascular diseases and is the clinical target during the disease treatment. Numerous studies show that ROS production is closely linked to the cell death process and promotes the occurrence and development of the cardiovascular diseases. In this review, we summarize the regulation of intracellular ROS, the roles of ROS played in the development of cardiovascular diseases, and the programmed cell death induced by intracellular ROS. We also focus on anti-ROS system and the potential application of anti-ROS strategy in the treatment of cardiovascular diseases.

β-Adrenergic Blocker, Carvedilol, Abolishes Ameliorating Actions of Adipose-Derived Stem Cell Sheets on Cardiac Dysfunction and Remodeling After Myocardial Infarction

BACKGROUND

Treatment of myocardial infarction (MI) includes inhibition of the sympathetic nervous system (SNS). Cell-based therapy using adipose-derived stem cells (ASCs) has emerged as a novel therapeutic approach to treat heart failure in MI. The purpose of this study was to determine whether a combination of ASC transplantation and SNS inhibition synergistically improves cardiac functions after MI.

METHODS AND RESULTS

ASCs were isolated from fat tissues of Lewis rats. In in vitro studies using cultured ASC cells, mRNA levels of angiogenic factors under normoxia or hypoxia, and the effects of norepinephrine and a β-blocker, carvedilol, on the mRNA levels were determined. Hypoxia increased vascular endothelial growth factor (VEGF) mRNA in ASCs. Norepinephrine further increased VEGF mRNA; this effect was unaffected by carvedilol. VEGF promoted VEGF receptor phosphorylation and tube formation of human umbilical vein endothelial cells, which were inhibited by carvedilol. In in vivo studies using a rat MI model, transplanted ASC sheets improved contractile functions of MI hearts; they also facilitated neovascularization and suppressed fibrosis after MI. These beneficial effects of ASC sheets were abolished by carvedilol. The effects of ASC sheets and carvedilol on MI heart functions were confirmed by Langendorff perfusion experiments using isolated hearts.

CONCLUSIONS

ASC sheets prevented cardiac dysfunctions and remodeling after MI in a rat model via VEGF secretion. Inhibition of VEGF effects by carvedilol abolished their beneficial effects.

The TRPA1 Channel in the Cardiovascular System: Promising Features and Challenges

The transient receptor potential ankyrin 1 (TRPA1) channel is a calcium-permeable nonselective cation channel in the plasma membrane that belongs to the transient receptor potential (TRP) channel superfamily. Recent studies have suggested that the TRPA1 channel plays an essential role in the development and progression of several cardiovascular conditions, such as atherosclerosis, heart failure, myocardial ischemia-reperfusion injury, myocardial fibrosis, arrhythmia, vasodilation, and hypertension. Activation of the TRPA1 channel has a protective effect against the development of atherosclerosis. Furthermore, TRPA1 channel activation elicits peripheral vasodilation and induces a biphasic blood pressure response. However, loss of channel expression or blockade of its activation suppressed heart failure, myocardial ischemia-reperfusion injury, myocardial fibrosis, and arrhythmia. In this paper, we review recent research progress on the TRPA1 channel and discuss its potential role in the cardiovascular system.

ω-3 fish oil fat emulsion preconditioning mitigates myocardial oxidative damage in rats through aldehydes stress

ω-3 fish oil fat emulsions contain a considerable quantity of unsaturated carbon-carbon double bonds, which undergo lipid peroxidation to yield low-dose aldehydes. These aldehydes may stimulate the production of antioxidant enzymes, thereby mitigating myocardial oxidative damage. This study aims to (1) verify the cardioprotective effect of ω-3 fish oil fat emulsion in vivo and in vitro, and (2) determine whether aldehyde stress is a protective mechanism. For modeling purposes, we pretreated rats with 2 ml/kg of a 10% ω-3 fish oil fat emulsion for 5 days in order to generate a sufficient aldehyde stress response to trigger the production of antioxidant enzymes, and we obtained similar response with H9C2 cells that were pretreated with a 0.5% ω-3 fish oil fat emulsion for 24 h. ω-3 fish oil fat emulsion pretreatment in vivo reduced the myocardial infarct size, decreased the incidence of arrhythmias, and promoted the recovery of cardiac function after myocardial ischemia/reperfusion injury. Once the expression of nuclear factor E2-related factor 2 (Nrf2) was silenced in H9C2 cells, aldehydes no longer produced enough antioxidant enzymes to reverse the oxidative damage caused by tert-butyl hydroperoxide (TBHP). Our results demonstrated that ω-3 fish oil fat emulsion enhanced the inhibition of oxidation and production of free radicals, and alleviated myocardial oxidative injury via activation of the Nrf2 signaling pathway.

Preconditioning with endoplasmic reticulum stress alleviated heart ischemia/reperfusion injury via modulating IRE1/ATF6/RACK1/PERK and PGC-1α in diabetes mellitus

The purpose of this study was to observe the functions of preconditioning with endoplasmic reticulum stress (ERS) whether alleviated heart ischemia/reperfusion injury (HI/RI) via modulating IRE1/ATF6/RACK1/PERK and PGC-1α expressions in diabetes mellitus (DM) or not. Diabetic rats were pretreated with 0.6 mg/kg tunicamycin (TM, 0.6 mg/kg tunicamycin was administered via intraperitoneal injection 30 minutes prior to the I/R procedures), and then subjected to 45 minutes of ischemia and 3 hours of reperfusion. Blood and myocardial tissues were collected, myocardial pathological injuries were investigated, serum creatine kinase-MB (CK-MB) and cardiac troponin T (cTnT) levels were measured, left ventricular systolic pressure (LVSP), left ventricular end diastolic pressure (LVEDP), maximum rate of left ventricular pressure rise (+dp/dtmax) and maximum rate of left ventricular pressure drop (-dp/dtmax) were evaluated, reactive oxygen species (ROS) and caspase-3 levels were observed, ΔΨm level and ROS expression were measured, and activated transcript factor 6 (ATF6), receptor for activated C kinase 1 (RACK1), PRK-like ER kinase (PERK), glucose regulated protein 78 (GRP78) and peroxisome proliferator-activated receptor γ co-activator 1-α (PGC-1α) expressions were assessed. The TM ameliorated the pathological damages, reduced myocardial oxidative stress damages, restrained apoptosis, and upregulated the expressions of ATF6, RACK1, PERK, GRP78 and PGC-1α compared with those of the ischemia/reperfusion (I/R) group in DM. This study suggested the preconditioning with endoplasmic reticulum stress (TM) strategy that could enhance protection against HI/RI in DM in clinical myocardial diseases.

The effects of Tel2 on cardiomyocyte survival

AIMS

Overexpression of the mechanistic target of rapamycin (mTOR), a member of the PIKK (phosphoinositide kinase-related kinase) family, protects cardiomyocytes from cell death induced by pathological stimuli such as ischemia. We previously reported that posttranslational modification of mTOR plays an important role in regulating cardiac mTOR expression. The aim of this study was to see if Tel2 (telomere maintenance 2), a protein that regulates the abundance of PIKKs, confers similar cardioprotective effects as mTOR. Tel2 is not well-characterized in cardiomyocytes, therefore we examined the effects of Tel2 on cardiomyocyte viability under ischemic stress conditions.

MATERIALS AND METHODS

We overexpressed Tel2 or silenced Tel2 with siRNA in the HL-1 cardiomyocyte cell line to survey the effects of Tel2 overexpression and downregulation on cell survival during hypoxia. Adult mouse cardiomyocytes transfected with Tel2 adenoviruses were used to test whether Tel2 sufficiently prevented cardiomyocyte cell death against hydrogen peroxide (H₂O₂).

KEY FINDINGS

Overexpressing Tel2 increased mTOR expression with a concomitant increase in mTOR Complex 1 (mTORC1) and mTORC2 activity in HL-1 cells. Tel2 deletion decreased mTOR expression, and mTORC1 and mTORC2 activity accordingly. In both HL-1 cells and adult mouse cardiomyocytes, Tel2 overexpression protected cardiomyocytes under ischemic stress. These effects were mTOR-dependent, as mTOR inhibitors blunted the effects of Tel2. While gene silencing of Tel2 did not affect cell survival under normoxia, Tel2 silencing made cardiomyocytes more vulnerable to cell death under hypoxia.

SIGNIFICANCE

Upregulating Tel2 expression increases mTOR-mediated cardiomyocyte survival and targeting Tel2 could be another therapeutic strategy against ischemic heart disease.

Effect of miR-499a-5p on damage of cardiomyocyte induced by hypoxia-reoxygenation via downregulating CD38 protein

The aim is to investigate the mechanism of miR-499a-5p on the damage of cardiomyocyte induced by hypoxia/reoxygenation. The activity of lactate dehydrogenase (LDH), apoptosis rate and the expression of miR-499a-5p and cluster of differentiation 38 (CD38) in hypoxia-reoxygenation model cells were detected by LDH Cytotoxicity Assay Kit, flow cytometry, real-time polymerase chain reaction, and Western blot analysis, respectively. Apoptosis, the activity of LDH was detected after overexpression of miR-499a-5p or silencing of CD38 in H9c2 cells. The target relationship between miR-499a-5p and CD38 was verified by Targetscan online prediction and dual-luciferase assay. Apoptosis, the activity of LDH was detected after overexpression of miR-499a-5p and CD38. Apoptosis, the activity of LDH and the expression of CD38 were increased (P < .05) while expression of miR-499a-5p was decreased (P < .05) in hypoxia/reoxygenation model cells. Apoptosis and the activity of LDH in H9c2 cells after overexpression of miR-499a-5p or silence of CD38 were decreased (P < .05). The results of Targetscan online prediction and dual-luciferase assay indicated that CD38 was a potential target gene of miR-499a-5p. Overexpression of CD38 could reverse the inhibition of miR-499a-5p on LDH activity and apoptosis in H9c2 cells. miR-499a-5p could relief the injury of cardiomyocytes induced by hypoxia/reoxygenation via targeting CD38.

Cardioprotection of Tetrahedral DNA Nanostructures in Myocardial Ischemia-Reperfusion Injury

Acute myocardial infarction, which can be extremely difficult to treat, is the worst deadly disease around the world. Reperfusion is expedient to reverse myocardial ischemia. However, during reperfusion, reactive oxygen species (ROS) produced by myocardial ischemia-reperfusion injury (MIRI) and further cell apoptosis are the most serious challenges to cardiomyocytes. Therefore, searching for reagents that can simultaneously reduce oxidative damage and MIRI-induced apoptosis is the pivotal strategy to rescue injured cardiomyocytes. Nevertheless, current cardioprotective drugs have some shortcomings, such as cardiotoxicity, inadequate intravenous administration, or immature technology. Previous studies have shown that tetrahedral DNA nanostructures (TDNs) have biological safety with promising anti-inflammatory and antioxidative potential. However, the progress that TDNs have made in the biological behavior of cardiomyocytes has not been explored. In this experiment, a cellular model of MIRI was first established. Then, confirmed by a series of experiments, our study indicates that TDNs can significantly decrease oxidative damage and apoptosis by limiting the overexpression of ROS, along with effecting the expression of apoptosis-related proteins. In addition, Western blot analysis demonstrated that TDNs could activate the Akt/Nrf2 signaling pathway to improve the myocardial injury induced by MIRI. Above all, the antioxidant and antiapoptotic capacities of TDNs make them a potential therapeutic drug for MIRI. This study provides new ideas and directions for more homogeneous diseases induced by oxidative damage.

Edematous Bullae: An Atypical Presentation of Reperfusion Injury. A Discussion of Ischemic-reperfusion Injury and Presentation of an Atypical Case

There is vast literature on the topic of ischemia-reperfusion injury. A summative discussion of the complex pathogenicity will aid practicing physicians in diagnosis and management. We offer a review of this literature as well as a discussion on a rare case of tense edematous bullae as a presentation of ischemia-reperfusion injury. A 65-year-old male underwent a right femoropopliteal bypass for rest pain that had not improved after iliac stent placement. He presented three days after discharge with blistering lesions on the reperfused limb that resembled bullous pemphigoid. This case describes the variability in the presentation of reperfusion injury, as well as the necessity to educate those managing atypical presentations of reperfusion injury.

Knockdown of TRIM32 Protects Hippocampal Neurons from Oxygen-Glucose Deprivation-Induced Injury

Tripartite motif 32 (TRIM32) is a member of TRIM family that plays a potential role in neural regeneration. However, the biological function of TRIM32 in cerebral ischemia reperfusion injury has not been investigated. In the present study, we evaluated the expression level of TRIM32 in hippocampal neurons following oxygen-glucose deprivation/reperfusion (OGD/R). The results showed that TRIM32 expression was significantly elevated in hippocampal neurons subjected to OGD/R as compared to the neurons cultured in the normoxia condition. To further evaluate the role of TRIM32, hippocampal neurons were transfected with TRIM32 small interfering RNA (si-TRIM32) to knock down TRIM32. We found that knockdown of TRIM32 improved cell viability of OGD/R-stimulated hippocampal neurons. Generation of reactive oxygen species was decreased, while contents of superoxide dismutase and glutathione peroxidase were increased after si-TRIM32 transfection. Knockdown of TRIM32 suppressed cell apoptosis, as proved by the increased bcl-2 expression along with decreased bax expression and caspase-3 activity. We also found that TRIM32 knockdown enhanced OGD/R-induced activation of Nrf2 signaling pathway in hippocampal neurons. Furthermore, siRNA-Nrf2 was transfected to knock down Nrf2. SiRNA-Nrf2 transfection reversed the protective effects of TRIM32 knockdown on neurons. These data suggested that knockdown of TRIM32 protected hippocampal neurons from OGD/R-induced oxidative injury through activating Nrf2 signaling pathway.

Cardiac Insulin Resistance in Heart Failure: The Role of Mitochondrial Dynamics

Heart failure (HF) frequently coexists with conditions associated with glucose insufficiency, such as insulin resistance and type 2 diabetes mellitus (T2DM), and patients with T2DM have a significantly high incidence of HF. These two closely related diseases cannot be separated on the basis of their treatment. Some antidiabetic drugs failed to improve cardiac outcomes in T2DM patients, despite lowering glucose levels sufficiently. This may be, at least in part, due to a lack of understanding of cardiac insulin resistance. Basic investigations have revealed the significant contribution of cardiac insulin resistance to the pathogenesis and progression of HF; however, there is no clinical evidence of the definition or treatment of cardiac insulin resistance. Mitochondrial dynamics play an important role in cardiac insulin resistance and HF because they maintain cellular homeostasis through energy production, cell survival, and cell proliferation. The innovation of diagnostic tools and/or treatment targeting mitochondrial dynamics is assumed to improve not only the insulin sensitivity of the myocardium and cardiac metabolism, but also the cardiac contraction function. In this review, we summarized the current knowledge on the correlation between cardiac insulin resistance and progression of HF, and discussed the role of mitochondrial dynamics on the pathogenesis of cardiac insulin resistance and HF. We further discuss the possibility of mitochondria-targeted intervention to improve cardiac metabolism and HF.

Genetic Deletion or Pharmacological Inhibition of Soluble Epoxide Hydrolase Ameliorates Cardiac Ischemia/Reperfusion Injury by Attenuating NLRP3 Inflammasome Activation

Activation of the nucleotide-binding oligomerization domain-like receptor (NLR) family pyrin domain containing 3 (NLRP3) inflammasome cascade has a role in the pathogenesis of ischemia/reperfusion (IR) injury. There is growing evidence indicating cytochrome p450 (CYP450)-derived metabolites of n-3 and n-6 polyunsaturated fatty acids (PUFAs) possess both adverse and protective effects in the heart. CYP-derived epoxy metabolites are rapidly hydrolyzed by the soluble epoxide hydrolase (sEH). The current study hypothesized that the cardioprotective effects of inhibiting sEH involves limiting activation of the NLRP3 inflammasome. Isolated hearts from young wild-type (WT) and sEH null mice were perfused in the Langendorff mode with either vehicle or the specific sEH inhibitor t-AUCB. Improved post-ischemic functional recovery and better mitochondrial respiration were observed in both sEH null hearts or WT hearts perfused with t-AUCB. Inhibition of sEH markedly attenuated the activation of the NLRP3 inflammasome complex and limited the mitochondrial localization of the fission protein dynamin-related protein-1 (Drp-1) triggered by IR injury. Cardioprotective effects stemming from the inhibition of sEH included preserved activities of both cytosolic thioredoxin (Trx)-1 and mitochondrial Trx-2 antioxidant enzymes. Together, these data demonstrate that inhibiting sEH imparts cardioprotection against IR injury via maintaining post-ischemic mitochondrial function and attenuating a detrimental innate inflammatory response.

Atrial Infarction-Induced Spontaneous Focal Discharges and Atrial Fibrillation in Sheep: Role of Dantrolene-Sensitive Aberrant Ryanodine Receptor Calcium Release

BACKGROUND

The mechanisms underlying spontaneous atrial fibrillation (AF) associated with atrial ischemia/infarction are incompletely elucidated. Here, we investigate the mechanisms underlying spontaneous AF in an ovine model of left atrial myocardial infarction (LAMI).

METHODS AND RESULTS

LAMI was created by ligating the atrial branch of the left anterior descending coronary artery. ECG loop recorders were implanted to monitor AF episodes. In 7 sheep, dantrolene-a ryanodine receptor blocker-was administered in vivo during the 8-day observation period (LAMI-D, 2.5 mg/kg, IV, BID). LAMI animals experienced numerous spontaneous AF episodes during the 8-day monitoring period that were suppressed by dantrolene (LAMI, 26.1±5.1; sham, 4.3±1.1; LAMI-D, 2.8±0.8; mean±SEM episodes per sheep, P<0.01). Optical mapping showed spontaneous focal discharges (SFDs) originating from the ischemic/normal-zone border. SFDs were calcium driven, rate dependent, and enhanced by isoproterenol (0.03 µmol/L, from 210±87 to 3816±1450, SFDs per sheep) but suppressed by dantrolene (to 55.8±32.8, SFDs per sheep, mean±SEM). SFDs initiated AF-maintaining reentrant rotors anchored by marked conduction delays at the ischemic/normal-zone border. NOS1 (NO synthase-1) protein expression decreased in ischemic zone myocytes, whereas NADPH (nicotinamide adenine dinucleotide phosphate, reduced form) oxidase and xanthine oxidase enzyme activities and reactive oxygen species (DCF [6-carboxy-2',7'-dichlorodihydrofluorescein diacetate]-fluorescence) increased. CaM (calmodulin) aberrantly increased [³H]ryanodine binding to cardiac RyR2 (ryanodine receptors) in the ischemic zone. Dantrolene restored the physiological binding of CaM to RyR2.

CONCLUSIONS

Atrial ischemia causes spontaneous AF episodes in sheep, caused by SFDs that initiate reentry. Nitroso-redox imbalance in the ischemic zone is associated with intense reactive oxygen species production and altered RyR2 responses to CaM. Dantrolene administration normalizes the CaM response, prevents LAMI-related SFDs, and AF initiation. These findings provide novel insights into the mechanisms underlying ischemia-related atrial arrhythmias.

Tyrosine nitration of mitochondrial proteins during myocardial ischemia and reperfusion

Myocardial ischemia reperfusion is associated with mitochondrial dysfunction and increased formation of reactive oxygen/nitrogen species. The main purpose of this study was to assess the role of tyrosine nitration of mitochondrial proteins in postischemic contractile dysfunction known as myocardial stunning. Isolated Langendorff-perfused rat hearts were subjected to 20-min global ischemia followed by 30-min reperfusion. The reperfused hearts showed marked decline in left ventricular developed pressure, maximal rate of contraction (+dP/dt), and maximal rate of relaxation (-dP/dt). Immunofluorescence and ELISA assays demonstrated enhanced protein tyrosine nitration in reperfused hearts. Using two-dimensional gel electrophoresis and MALDI-TOF/TOF mass spectrometry, eight mitochondrial proteins were identified to be nitrated after ischemia reperfusion. These proteins are crucial in mitochondrial electron transport, fatty acid oxidation, tricarboxylic acid cycle, ATP synthesis, and control of high-energy phosphates. The proteome data also indicated reduced abundance in several of nitrated proteins. The results suggest that these changes may contribute to inhibition of aconitase activity but are unlikely to affect electron transport chain activity. Whether tyrosine nitration of mitochondrial proteins can be considered the contributing factor of postischemic contractile dysfunction remains to be explored.

Supplementation with psyllium seed husk reduces myocardial damage in a rat model of ischemia/reperfusion

BACKGROUND/OBJECTIVES

Myocardial infarction (MI) is caused by extensive myocardial damage attributed to the occlusion of coronary arteries. Our previous study in a rat model of ischemia/reperfusion (I/R) demonstrated that administration of arabinoxylan (AX), comprising arabinose and xylose, protects against myocardial injury. In this study, we undertook to investigate whether psyllium seed husk (PSH), a safe dietary fiber containing a high level of AX (> 50%), also imparts protection against myocardial injury in the same rat model.

MATERIALS/METHODS

Rats were fed diets supplemented with PSH (1, 10, or 100 mg/kg/d) for 3 d. The rats were then subjected to 30 min ischemia through ligation of the left anterior descending coronary artery, followed by 3 h reperfusion through release of the ligation. The hearts were harvested and cut into four slices. To assess infarct size (IS), an index representing heart damage, the slices were stained with 2,3,5-triphenyltetrazolium chloride (TTC). To elucidate underlying mechanisms, Western blotting was performed for the slices.

RESULTS

Supplementation with 10 or 100 mg/kg/d of PSH significantly reduces the IS. PSH supplementation (100 mg/kg/d) tends to reduce caspase-3 generation and increase BCL-2/BAX ratio. PSH supplementation also upregulates the expression of nuclear factor erythroid 2-related factor 2 (NRF2), and its target genes including antioxidant enzymes such as glutathione S-transferase mu 2 (GSTM2) and superoxide dismutase 2 (SOD2). PSH supplementation upregulates some sirtuins (NAD⁺-dependent deacetylases) including SIRT5 (a mitochondrial sirtuin) and SIRT6 and SIRT7 (nuclear sirtuins). Finally, PSH supplementation upregulates the expression of protein kinase A (PKA), and increases phosphorylated cAMP response element-binding protein (CREB) (pCREB), a target protein of PKA.

CONCLUSIONS

The results from this study indicate that PSH consumption reduces myocardial I/R injury in rats by inhibiting the apoptotic cascades through modulation of gene expression of several genes located upstream of apoptosis. Therefore, we believe that PSH can be developed as a functional food that would be beneficial in the prevention of MI.

Reactive species-induced microvascular dysfunction in ischemia/reperfusion

Vascular endothelial cells line the inner surface of the entire cardiovascular system as a single layer and are involved in an impressive array of functions, ranging from the regulation of vascular tone in resistance arteries and arterioles, modulation of microvascular barrier function in capillaries and postcapillary venules, and control of proinflammatory and prothrombotic processes, which occur in all segments of the vascular tree but can be especially prominent in postcapillary venules. When tissues are subjected to ischemia/reperfusion (I/R), the endothelium of resistance arteries and arterioles, capillaries, and postcapillary venules become dysfunctional, resulting in impaired endothelium-dependent vasodilator and enhanced endothelium-dependent vasoconstrictor responses along with increased vulnerability to thrombus formation, enhanced fluid filtration and protein extravasation, and increased blood-to-interstitium trafficking of leukocytes in these functionally distinct segments of the microcirculation. The number of capillaries open to flow upon reperfusion also declines as a result of I/R, which impairs nutritive perfusion. All of these pathologic microvascular events involve the formation of reactive species (RS) derived from molecular oxygen and/or nitric oxide. In addition to these effects, I/R-induced RS activate NLRP3 inflammasomes, alter connexin/pannexin signaling, provoke mitochondrial fission, and cause release of microvesicles in endothelial cells, resulting in deranged function in arterioles, capillaries, and venules. It is now apparent that this microvascular dysfunction is an important determinant of the severity of injury sustained by parenchymal cells in ischemic tissues, as well as being predictive of clinical outcome after reperfusion therapy. On the other hand, RS production at signaling levels promotes ischemic angiogenesis, mediates flow-induced dilation in patients with coronary artery disease, and instigates the activation of cell survival programs by conditioning stimuli that render tissues resistant to the deleterious effects of prolonged I/R. These topics will be reviewed in this article.

Molecular stressors underlying exercise training-induced improvements in K+ regulation during exercise and Na+ ,K+ -ATPase adaptation in human skeletal muscle

Despite substantial progress made towards a better understanding of the importance of skeletal muscle K⁺ regulation for human physical function and its association with several disease states (eg type-II diabetes and hypertension), the molecular basis underpinning adaptations in K⁺ regulation to various stimuli, including exercise training, remains inadequately explored in humans. In this review, the molecular mechanisms essential for enhancing skeletal muscle K⁺ regulation and its key determinants, including Na⁺ ,K⁺ -ATPase function and expression, by exercise training are examined. Special attention is paid to the following molecular stressors and signaling proteins: oxygenation, redox balance, hypoxia, reactive oxygen species, antioxidant function, Na⁺ ,K⁺ , and Ca²⁺ concentrations, anaerobic ATP turnover, AMPK, lactate, and mRNA expression. On this basis, an update on the effects of different types of exercise training on K⁺ regulation in humans is provided, focusing on recent discoveries about the muscle fibre-type-dependent regulation of Na⁺ ,K⁺ -ATPase-isoform expression. Furthermore, with special emphasis on blood-flow-restricted exercise as an exemplary model to modulate the key molecular mechanisms identified, it is discussed how training interventions may be designed to maximize improvements in K⁺ regulation in humans. The novel insights gained from this review may help us to better understand how exercise training and other strategies, such as pharmacological interventions, may be best designed to enhance K⁺ regulation and thus the physical function in humans.

Possible involvement of alpha B-crystallin in the cardioprotective effect of n-butanol extract of Potentilla anserina L. on myocardial ischemia/reperfusion injury in rat

BACKGROUND

It has been reported that n-butanol extract of Potentilla anserina L (NP) had protective effect against acute myocardial ischemia/reperfusion (I/R) injury in mice. Because of limited phytochemical study on NP, its bioactive compounds and underlying protective mechanisms are largely unclear.

PURPOSE

The purpose of this study was to investigate the major bioactive compounds and possible mechanism for the cardioprotective effect of NP on rat with I/R injury.

METHODS

We analyzed the phytochemical isolation of NP and identified the structure of compounds, which was elucidated by a combination of spectroscopic analyses. An I/R model was established by I-30 min/R-2 h in Sprage-Dawley rats. The rats were given intragastric administration of NP (49.3, 98.6, and 197.2 mg•kg^-1) continuously for 10 days before I/R operation. The morphological changes and apoptosis of cardiomyocytes were observed by H&E staining, Transmission electron microscope and TUNEL staining respectively. The activities or contents of catalase (CAT), superoxide dismutase (SOD), malondialdehyde (MDA) and glutathione (GSH) in plasma were detected. Apoptosis related factors were also measured by RT-PCR and western blot. In order to discover the underlying mechanism of NP on I/R, we performed proteomic analysis using two-dimensional gel electrophoresis (2D-DIGE) and matrix assisted laser desorption/ionization time of flight mass spectrometry (MALDI-TOF/MS) to describe differential proteins expression. Potential target protein resulted from 2D-DIGE coupled to MALDI-TOF/MS analysis were further confirmed by immunohistochemical staining, RT-PCR, and western blot.

RESULTS

We isolated and identified 14 compounds, of which 7 compounds belong to triterpenes. Rats pretreated with NP showed a significant increase on the activities of GSH, SOD and CAT, and remarkable decrease on the content of MDA. NP significantly inhibited the apoptosis of cardiomyocyte and decreased the expression of Cyt C and cleaved-caspase-3. Proteomic analysis revealed that alpha B-crystallin (CryAB) might participate in the NP protective effect against I/R. NP enhanced the level of pCryAB Ser59, whereas the expression of CryAB was decreased.

CONCLUSION

NP was showed to alleviate I/R injury and inhibit myocardial apoptosis, which might be associated with reduction on oxidative stress and apoptosis. CryAB as a possible target involved in the NP protective effect. This study supplied valuable information to develop novel cardioprotective agents from NP extract.