Discovery of new therapeutic redox targets for cardioprotection against ischemia/reperfusion injury and heart failure

Antioxidative and cardioprotective effects of minocycline in ischemia/reperfusion injury in experimental model of hypertension

Cardiovascular diseases remains leading cause of death and disabilities. Coronary artery occlusion and consequent ischemia leads to acute myocardial infarction, but restoration of blood flow, paradoxically, provokes further myocardial damage known as reperfusion injury. Minocycline is possessing anti-inflammatory and anti-apoptotic activity, immune-modulating and antioxidative properties besides its primary antibacterial effect. Recently it gained significant interest in preventing cardiac damage especially due to myocardial ischemia/reperfusion injury (MI/RI). The aim of this study was to assess the protective ability of pre-treatment and post-treatment of isolated hearts from healthy and spontaneously hypertensive rats with minocycline, on functional recovery and redox status after MI/RI using Langendorff technique. Using sensor in the left ventricle, the cardiodynamic parameters were recorded and in the samples of the coronary venous effluent oxidative stress biomarkers were analyzed. Minocycline was injected directly into the coronary vessels, in pre-treatment 5 min before global ischemia, and in post-treatment during the first 5 min of reperfusion. Changes in redox balance induced by minocycline were more prominent in post-treatment fashion of application. Cardioprotective effects of minocycline due to MI/RI are even more significant in hypertensive hearts. Minocycline showed significant cardioprotective effects, which was more pronounced in hypertensive compared to healthy hearts. Reduction of pro-oxidative biomarkers was more prominent in hypertensive hearts compared to the normotensive, especially if it is applied in the form of post-treatment. Minocycline could be important tool in reduction of heart damage induced by MI/RI due to its antioxidative potential, if these results are confirmed by clinical study.

Diltiazem Hydrochloride Protects Against Myocardial Ischemia/Reperfusion Injury in a BNIP3L/NIX-Mediated Mitophagy Manner

Background

Mitochondrial calcium uptake-induced mitophagy may play an essential role in myocardial ischemia/reperfusion (MI/R) injury. Diltiazem hydrochloride (DIL), a traditional calcium channel blocker, can alleviate MI/R injury by blocking calcium overload. However, whether the protective mechanism of DIL involves mitophagy remains elusive. This study aimed to clarify the underlying molecular mechanism by which DIL ameliorates MI/R injury by downregulating mitophagy in vivo and in vitro.

Methods

Thirty rats were randomized into three groups: the sham, MI/R, and MI/R+DIL (1 mg/kg) groups (n = 10/per group). MI/R injury was induced by ligating the left anterior descending (LAD) artery for 30 min followed by 60 min of reperfusion in vivo. H9C2 cells were selected to establish an oxygen-glucose deprivation/recovery (OGD/R) model to simulate MI/R injury in vitro. The potential mechanism by which DIL alleviates MI/R injury was analyzed based on tissue morphology, mitophagy-related gene transcription, and protein expression.

Results

According to histological and immunohistochemical evaluations, DIL significantly alleviated myocardial damage in vivo. Moreover, DIL significantly increased cell viability, attenuated OGD/R-induced apoptosis, and inhibited mitochondrial autophagy in vitro. Mechanistically, DIL attenuated mitochondrial autophagy through the upregulation of dual-specificity protein phosphatase 1 (DUSP1) and the downregulation of c-Jun N-terminal kinase (JNK) and Bcl2 interacting protein 3-like (BNIP3L, also known as NIX) expression.

Conclusion

Diltiazem hydrochloride protects against myocardial ischemia/reperfusion injury in a BNIP3L/NIX-mediated mitophagy manner in vivo and in vitro.

Mitochondrial Creatine Kinase 2 (Ckmt2) as a Plasma-Based Biomarker for Evaluating Reperfusion Injury in Acute Myocardial Infarction

BACKGROUND/OBJECTIVES

Acute myocardial infarction (AMI), characterized by irreversible heart muscle damage and impaired cardiac function caused by myocardial ischemia, is a leading cause of global mortality. The damage associated with reperfusion, particularly mitochondrial dysfunction and reactive oxygen species (ROS) formation, has emerged as a crucial factor in the pathogenesis of cardiac diseases, leading to the recognition of mitochondrial proteins as potential markers for myocardial damage. This study aimed to identify differentially expressed proteins based on the type of cardiac injury, in particular those with and without reperfusion.

METHODS

Male C57Bl/6J mice were either left untreated, sham-operated, received non-reperfused AMI, or reperfused AMI. Twenty-four hours after the procedures, left ventricular (LV) function and morphological changes including infarct size were determined using echocardiography and triphenyl tetrazolium chloride (TTC) staining, respectively. In addition, plasma was isolated and subjected to untargeted mass spectrometry and, further on, the ELISA-based validation of candidate proteins.

RESULTS

We identified mitochondrial creatine kinase 2 (Ckmt2) as a differentially regulated protein in plasma of mice with reperfused but not non-reperfused AMI. Elevated levels of Ckmt2 were significantly associated with infarct size and impaired LV function following reperfused AMI, suggesting a specific involvement in reperfusion damage.

CONCLUSIONS

Our study highlights the potential of plasma Ckmt2 as a biomarker for assessing reperfusion injury and its impact on cardiac function and morphology in the acute phase of MI.

Cardioprotective potential of oleuropein, hydroxytyrosol, oleocanthal and their combination: Unravelling complementary effects on acute myocardial infarction and metabolic syndrome

Clinical studies have previously established the role of olive products in cardiovascular disease (CVD) prevention, whilst the identification of the responsible constituents for the beneficial effects is still pending. We sought to assess and compare the cardioprotective potential of oleuropein (OL), hydroxytyrosol (HT), oleocanthal (OC) and oleanolic Acid (OA), regarding Ischemia/Reperfusion Injury (IRI) and CVD risk factors alleviation. The scope of the study was to design a potent and safe combinatorial therapy for high-cardiovascular-risk patients on a bench-to-bedside approach. We evaluated the IRI-limiting potential of 6-weeks treatment with OL, HT, OC or OA at nutritional doses, in healthy and metabolic syndrome (MS)-burdened mice. Three combinatorial regimens were designed and the mixture with preponderant benefits (OL-HT-OC, Combo 2), including infarct sparing and antiglycemic potency, compared to the isolated compounds, was further investigated for its anti-atherosclerotic effects. In vivo experiments revealed that the combination regimen of Combo 2 presented the most favorable effects in limiting infarct size and hyperglycemia, which was selected to be further investigated in the clinical setting in Chronic Coronary Artery Syndrome (CCAS) patients. Cardiac function, inflammation markers and oxidative stress were assessed at baseline and after 4 weeks of treatment with the OL-HT-OC supplement in the clinical study. We found that OL, OC and OA significantly reduced infarct size in vivo compared to Controls. OL exhibited antihyperglycemic properties and OA attenuated hypercholesterolemia. OL-HT-OA, OL-HT-OC and OL-HT-OC-OA combination regimens were cardioprotective, whereas only OL-HT-OC mitigated hyperglycemia. Combo 2 cardioprotection was attributed to apoptosis suppression, enhanced antioxidant effects and upregulation of antioxidant enzymes. Additionally, it reduced atherosclerotic plaque extent in vivo. OL-HT-OC supplement ameliorated cardiac, vascular and endothelial function in the small-scale clinical study. Conclusively, OL-HT-OC combination therapy exerts potent cardioprotective, antihyperglycemic and anti-atherosclerotic properties in vivo, with remarkable and clinically translatable cardiovascular benefits in high-risk patients.

The Biology and Biochemistry of Kynurenic Acid, a Potential Nutraceutical with Multiple Biological Effects

Kynurenic acid (KYNA) is an antioxidant degradation product of tryptophan that has been shown to have a variety of cytoprotective, neuroprotective and neuronal signalling properties. However, mammalian transporters and receptors display micromolar binding constants; these are consistent with its typically micromolar tissue concentrations but far above its serum/plasma concentration (normally tens of nanomolar), suggesting large gaps in our knowledge of its transport and mechanisms of action, in that the main influx transporters characterized to date are equilibrative, not concentrative. In addition, it is a substrate of a known anion efflux pump (ABCC4), whose in vivo activity is largely unknown. Exogeneous addition of L-tryptophan or L-kynurenine leads to the production of KYNA but also to that of many other co-metabolites (including some such as 3-hydroxy-L-kynurenine and quinolinic acid that may be toxic). With the exception of chestnut honey, KYNA exists at relatively low levels in natural foodstuffs. However, its bioavailability is reasonable, and as the terminal element of an irreversible reaction of most tryptophan degradation pathways, it might be added exogenously without disturbing upstream metabolism significantly. Many examples, which we review, show that it has valuable bioactivity. Given the above, we review its potential utility as a nutraceutical, finding it significantly worthy of further study and development.

CircBCL2L13 attenuates cardiomyocyte oxidative stress and apoptosis in cardiac ischemia‒reperfusion injury via miR-1246/PEG3 signaling

Ischemia‒reperfusion (I/R) is a common complication in the clinical treatment of acute myocardial infarction (MI), in which cardiomyocytes play a pivotal role in the recovery of cardiac function after reperfusion injury. The expression of numerous circular ribonucleic acids (circRNAs) is disrupted in I/R-induced cardiac damage, but the potential role of circRNAs in I/R damage has not been fully elucidated. The purpose of the present study was to clarify the biological action and molecular mechanism of circRNA 002166 (also termed circCL2L13) in postmyocardial I/R. Oxygen-glucose deprivation/reoxygenation (OGD/R) in an in vivo model was performed to simulate I/R damage. real-time polymerase chain reaction analysis was also conducted to evaluate the relationships of the SOD1, SOD2, NRF2, HO1 and GPX4 indicators with oxidative stress injury. TUNEL immunofluorescence was used to evaluate the degree of cardiomyocyte apoptosis in the different treatment groups. The circBCL2L13 level was markedly upregulated in myocardial tissues from a mouse I/R model. Overexpression of circBCL2L13 markedly attenuated the expression of oxidative stress-related genes and apoptosis in OGD/R-induced cardiomyocytes. A mechanistic study revealed that circBCL2L13 functions as a ceRNA for miR-1246 and modulates paternally expressed gene 3 (PEG3). Eventually, circBCL2L13 was proven to regulate PEG3 by targeting miR-1246, thereby protecting against OGD/R-induced cardiomyocyte oxidative damage and apoptosis. In conclusion, our study confirmed that the circBCL2L13/miR-1246/PEG3 axis suppressed the progression of OGD/R injury in cardiomyocytes, which might lead to new therapeutic strategies for cardiac I/R injury.

Camphene as a Protective Agent in Myocardial Ischemia/Reperfusion Injury

Myocardial ischemia/reperfusion injury (I/R) and the resulting heart failure is one of the main causes of mortality and morbidity worldwide. Camphene has been shown to have anti-inflammatory and hypolipidemic properties; however, its role in the protection of the heart from ischemia and reperfusion has not been investigated. The cardioprotective role of camphene and the mechanism that mediates its action against I/R injury was evaluated in the present study. A single dose of camphene was administered in adult rats prior to ex vivo I/R induction. Infarct size was measured using 2,3,5-triphenyltetrazolium chloride (TTC) staining and cardiomyocyte injury was assessed by determining the release of the enzyme lactate dehydrogenase (LDH). Camphene pretreatment provided significant protection reducing myocardial infarct size and cell death after I/R. The effect was correlated with the reduction in oxidative stress as evidenced by the determination of protein carbonylation, GSH/GSSG ratio, the increase in mitochondrial content as determined by CS activity, and the modulation of antioxidant defense mechanisms (expression of Nrf2 and target genes and activities of CAT, MnSOD, and GR). Furthermore, ferroptosis was decreased, as demonstrated by downregulation of GPx4 expression and reduction in lipid peroxidation. The results suggest that camphene can protect the heart against I/R injury by maintaining redox homeostasis and can hold therapeutic potential for mitigating the detrimental effects of I/R in the heart.

Middle-age abolishes cardioprotection conferred by thioredoxin-1 in mice

Thioredoxin-1 (Trx1) has cardioprotective effects on ischemia/reperfusion (I/R) injury, although its role in ischemic postconditioning (PostC) in middle-aged mice is not understood. This study aimed to evaluate if combining two cardioprotective strategies, such as Trx1 overexpression and PostC, could exert a synergistic effect in reducing infarct size in middle-aged mice. Young or middle-aged wild-type mice (Wt), transgenic mice overexpressing Trx1, and dominant negative (DN-Trx1) mutant of Trx1 mice were used. Mice hearts were subjected to I/R or PostC protocol. Infarct size, hydrogen peroxide (H2O2) production, protein nitration, Trx1 activity, mitochondrial function, and Trx1, pAkt and pGSK3β expression were measured. PostC could not reduce infarct size even in the presence of Trx1 overexpression in middle-aged mice. This finding was accompanied by a lack of Akt and GSK3β phosphorylation, and Trx1 expression (in Wt group). Trx1 activity was diminished and H2O2 production and protein nitration were increased in middle-age. The respiratory control rate dropped after I/R in Wt-Young and PostC restored this value, but not in middle-aged groups. Our results showed that Trx1 plays a key role in the PostC protection mechanism in young but not middle-aged mice, even in the presence of Trx1 overexpression.

Protective effects of Pt-N-C single-atom nanozymes against myocardial ischemia-reperfusion injury

Effective therapeutic strategies for myocardial ischemia/reperfusion (I/R) injury remain elusive. Targeting reactive oxygen species (ROS) provides a practical approach to mitigate myocardial damage following reperfusion. In this study, we synthesize an antioxidant nanozyme, equipped with a single-Platinum (Pt)-atom (PtsaN-C), for protecting against I/R injury. PtsaN-C exhibits multiple enzyme-mimicking activities for ROS scavenging with high efficiency and stability. Mechanistic studies demonstrate that the excellent ROS-elimination performance of the single Pt atom center precedes that of the Pt cluster center, owing to its better synergistic effect and metallic electronic property. Systematic in vitro and in vivo studies confirm that PtsaN-C efficiently counteracts ROS, restores cellular homeostasis and prevents apoptotic progression after I/R injury. PtsaN-C also demonstrates good biocompatibility, making it a promising candidate for clinical applications. Our study expands the scope of single-atom nanozyme in combating ROS-induced damage and offers a promising therapeutic avenue for the treatment of I/R injury.

Almost 50 Years of Monomeric Extracellular Ubiquitin (eUb)

Monomeric ubiquitin (Ub) is a 76-amino-acid highly conserved protein found in eukaryotes. The biological activity of Ub first described in the 1970s was extracellular, but it quickly gained relevance due to its intracellular role, i.e., post-translational modification of intracellular proteins (ubiquitination) that regulate numerous eukaryotic cellular processes. In the following years, the extracellular role of Ub was relegated to the background, until a correlation between higher survival rate and increased serum Ub concentrations in patients with sepsis and burns was observed. Although the mechanism of action (MoA) of extracellular ubiquitin (eUb) is not yet well understood, further studies have shown that it may ameliorate the inflammatory response in tissue injury and multiple sclerosis diseases. These observations, compounded with the high stability and low immunogenicity of eUb due to its high conservation in eukaryotes, have made this small protein a relevant candidate for biotherapeutic development. Here, we review the in vitro and in vivo effects of eUb on immunologic, cardiovascular, and nervous systems, and discuss the potential MoAs of eUb as an anti-inflammatory, antimicrobial, and cardio- and brain-protective agent.

Endothelial Cell Apoptosis but Not Necrosis Is Inhibited by Ischemic Preconditioning

This study aimed to assess the influence of ischemic preconditioning (IP) on hypoxia/reoxygenation (HR)-induced endothelial cell (EC) death. Human umbilical vein endothelial cells (HUVECs) were subjected to 2 or 6 h hypoxia with subsequent reoxygenation. IP was induced by 20 min of hypoxia followed by 20 min of reoxygenation. Necrosis was assessed by the release of lactate dehydrogenase (LDH) and apoptosis by double staining with propidium iodide/annexin V (PI/AV), using TUNEL test, and Bcl-2 and Bax gene expression measured using RT-PCR. In PI/AV staining, after 24 h of reoxygenation, 30-33% of EC were necrotic and 16-21% were apoptotic. In comparison to HR cells, IP reduced membrane apoptosis after 24 h of reoxygenation by 50% but did not influence EC necrosis. Nuclear EC apoptosis affected about 15-17% of EC after 24 h of reoxygenation and was reduced with IP by 55-60%. IP was associated with a significantly higher Bcl-2/Bax ratio, at 8 h 2-4 times and at 24 h 2-3 times as compared to HR. Longer hypoxia was associated with lower values of Bcl-2/Bax ratio in EC subjected to HR or IP. IP delays, without reducing, the extent of HR-induced EC necrosis but significantly inhibits their multi-level evaluated apoptosis.

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.

Xanthine Oxidoreductase in the Pathogenesis of Endothelial Dysfunction: An Update

Xanthine oxidoreductase (XOR) is a rate-limiting enzyme in the formation of uric acid (UA) and is involved in the generation of reactive oxygen species (ROS). Overproduction of ROS has been linked to the pathogenesis of hypertension, atherosclerosis, and cardiovascular disease, with multiple studies over the last 30 years demonstrating that XOR inhibition is beneficial. The involvement of XOR and its constituents in the advancement of chronic inflammation and ROS, which are responsible for endothelial dysfunction, is the focus of this evidence-based review. An overabundance of XOR products and ROS appears to drive the inflammatory response, resulting in significant endothelium damage. It has also been demonstrated that XOR activity and ED are connected. Diabetes, hypertension, and cardiovascular disease are all associated with endothelial dysfunction. ROS mainly modifies the activity of vascular cells and can be important in normal vascular physiology as well as the development of vascular disease. Suppressing XOR activity appears to decrease endothelial dysfunction, probably because it lessens the generation of reactive oxygen species and the oxidative stress brought on by XOR. Although there has long been a link between higher vascular XOR activity and worse clinical outcomes, new research suggests a different picture in which positive results are mediated by XOR enzymatic activity. Here in this study, we aimed to review the association between XOR and vascular endothelial dysfunction. The prevention and treatment approaches against vascular endothelial dysfunction in atherosclerotic disease.

N-n-butyl haloperidol iodide mediates cardioprotection via regulating AMPK/FoxO1 signalling

Derangement of redox condition largely contributes to cardiac ischemia/reperfusion (I/R) injury. FoxO1 is a transcription factor which transcripts a series of antioxidants to antagonize I/R-induced oxidative myocardial damage. N-n-butyl haloperidol iodide (F2 ) is a derivative derived from haloperidol structural modification with potent capacity of inhibiting oxidative stress. This investigation intends to validate whether cardio-protection of F2 is dependent on FoxO1 using an in vivo mouse I/R model and if so, to further elucidate the molecular regulating mechanism. This study initially revealed that F2 preconditioning led to a profound reduction in I/R injury, which was accompanied by attenuated oxidative stress and upregulation of antioxidants (SOD2 and catalase), nuclear FoxO1 and phosphorylation of AMPK. Furthermore, inactivation of FoxO1 with AS1842856 abolished the cardio-protective effect of F2 . Importantly, we identified F2 -mediated nuclear accumulation of FoxO1 is dependent on AMPK, as blockage of AMPK with compound C induced nuclear exit of FoxO1. Collectively, our data uncover that F2 pretreatment exerts significant protection against post ischemic myocardial injury by its regulation of AMPK/FoxO1 pathway, which may provide a new avenue for treating ischemic disease.

Acute heart failure: mechanisms and pre-clinical models-a Scientific Statement of the ESC Working Group on Myocardial Function

While chronic heart failure (CHF) treatment has considerably improved patient prognosis and survival, the therapeutic management of acute heart failure (AHF) has remained virtually unchanged in the last decades. This is partly due to the scarcity of pre-clinical models for the pathophysiological assessment and, consequently, the limited knowledge of molecular mechanisms involved in the different AHF phenotypes. This scientific statement outlines the different trajectories from acute to CHF originating from the interaction between aetiology, genetic and environmental factors, and comorbidities. Furthermore, we discuss the potential molecular targets capable of unveiling new therapeutic perspectives to improve the outcome of the acute phase and counteracting the evolution towards CHF.

Health position paper and redox perspectives on reactive oxygen species as signals and targets of cardioprotection

The present review summarizes the beneficial and detrimental roles of reactive oxygen species in myocardial ischemia/reperfusion injury and cardioprotection. In the first part, the continued need for cardioprotection beyond that by rapid reperfusion of acute myocardial infarction is emphasized. Then, pathomechanisms of myocardial ischemia/reperfusion to the myocardium and the coronary circulation and the different modes of cell death in myocardial infarction are characterized. Different mechanical and pharmacological interventions to protect the ischemic/reperfused myocardium in elective percutaneous coronary interventions and coronary artery bypass grafting, in acute myocardial infarction and in cardiotoxicity from cancer therapy are detailed. The second part keeps the focus on ROS providing a comprehensive overview of molecular and cellular mechanisms involved in ischemia/reperfusion injury. Starting from mitochondria as the main sources and targets of ROS in ischemic/reperfused myocardium, a complex network of cellular and extracellular processes is discussed, including relationships with Ca2+ homeostasis, thiol group redox balance, hydrogen sulfide modulation, cross-talk with NAPDH oxidases, exosomes, cytokines and growth factors. While mechanistic insights are needed to improve our current therapeutic approaches, advancements in knowledge of ROS-mediated processes indicate that detrimental facets of oxidative stress are opposed by ROS requirement for physiological and protective reactions. This inevitable contrast is likely to underlie unsuccessful clinical trials and limits the development of novel cardioprotective interventions simply based upon ROS removal.

Impacts of delta 9-tetrahydrocannabinol against myocardial ischemia/reperfusion injury in diabetic rats: Role of PTEN/PI3K/Akt signaling pathway

Despite the current optimal therapy, patients with myocardial ischemia/reperfusion (IR) injury still experience a high mortality rate, especially when diabetes mellitus is present as a comorbidity. Investigating potential treatments aimed at improving the outcomes of myocardial IR injury in diabetic patients is necessary. Our objective was to ascertain the cardioprotective effect of delta 9-tetrahydrocannabinol (THC) against myocardial IR injury in diabetic rats and examine the role of phosphatase and tensin homolog (PTEN)/phosphatidylinositol 3-kinase (PI3K)/protein kinase B (Akt) signaling pathway in mediating this effect. Diabetes was induced in male Wistar rats (8-10 weeks old, 200-250 g; n = 60) by a single injection of streptozotocin. The duration of the diabetic period was 10 weeks. During the last 4 weeks of diabetic period, rats were treated with THC (1.5 mg/kg/day; intraperitoneally), either alone or in combination with LY294002, and then underwent IR intervention. After 24 h of reperfusion, infarct size, cardiac function, lactate dehydrogenase (LDH) and cardiac-specific isoform of troponin-I (cTn-I) levels, myocardial apoptosis, oxidative stress markers, and expression of PTEN, PI3K, and Akt proteins were evaluated. THC pretreatment resulted in significant improvements in infarct size and cardiac function and decreases in LDH and cTn-I levels (P < 0.05). It also reduced myocardial apoptosis and oxidative stress, accompanied by the downregulation of PTEN expression and activation of the PI3K/Akt signaling pathway (P < 0.05). LY294002 pretreatment abolished the cardioprotective action of THC. This study revealed the cardioprotective effects of THC against IR-induced myocardial injury in diabetic rats and also suggested that the mechanism may be associated with enhanced activity of the PI3K/Akt signaling pathway through the reduction of PTEN phosphorylation.

The role and mechanisms of microvascular damage in the ischemic myocardium

Following myocardial ischemic injury, the most effective clinical intervention is timely restoration of blood perfusion to ischemic but viable myocardium to reduce irreversible myocardial necrosis, limit infarct size, and prevent cardiac insufficiency. However, reperfusion itself may exacerbate cell death and myocardial injury, a process commonly referred to as ischemia/reperfusion (I/R) injury, which primarily involves cardiomyocytes and cardiac microvascular endothelial cells (CMECs) and is characterized by myocardial stunning, microvascular damage (MVD), reperfusion arrhythmia, and lethal reperfusion injury. MVD caused by I/R has been a neglected problem compared to myocardial injury. Clinically, the incidence of microvascular angina and/or no-reflow due to ineffective coronary perfusion accounts for 5-50% in patients after acute revascularization. MVD limiting drug diffusion into injured myocardium, is strongly associated with the development of heart failure. CMECs account for > 60% of the cardiac cellular components, and their role in myocardial I/R injury cannot be ignored. There are many studies on microvascular obstruction, but few studies on microvascular leakage, which may be mainly due to the lack of corresponding detection methods. In this review, we summarize the clinical manifestations, related mechanisms of MVD during myocardial I/R, laboratory and clinical examination means, as well as the research progress on potential therapies for MVD in recent years. Better understanding the characteristics and risk factors of MVD in patients after hemodynamic reconstruction is of great significance for managing MVD, preventing heart failure and improving patient prognosis.

Application of super-resolution microscopy in mitochondria-dynamic diseases

Limited by spatial and temporal resolution, traditional optical microscopy cannot image the delicate ultra-structure organelles and sub-organelles. The emergence of super-resolution microscopy makes it possible. In this review, we focus on mitochondria. We summarize the process of mitochondrial dynamics, the primary proteins that regulate mitochondrial morphology, the diseases related to mitochondrial dynamics. The purpose is to apply super-resolution microscopy developed during recent years to the mitochondrial research. By providing the right research tools, we will help to promote the application of this technique to the in-depth elucidation of the pathogenesis of diseases related to mitochondrial dynamics, assistdiagnosis and develop the therapeutic treatment.

DNAzyme loaded nano-niosomes attenuate myocardial ischemia/reperfusion injury by targeting apoptosis, inflammation in a NF-κB dependent mechanism

Although DNAzymes have been found to reduce injury after myocardial ischemia/reperfusion (MI/R), their efficiency have been limited due to rapid degradation in vivo. Thus, this study was conducted to extend their half-life by encapsulation into nano‑niosomes and examine their cardioprotective effects in a rat model of myocardial infarction (MI). In order to synthesize nano‑niosomes, surface active agent film hydration method was used. Characterization of nano‑niosomes was performed using the atomic force microscopy (AFM). In order to establish MI/R model in rats, left anterior descending coronary artery (LAD) was ligated for 30 min. A single dose (150µL) of drug formulations was injected into the infarcted region. The cardiac function was evaluated using echocardiography. The expression of pro-inflammatory cytokines, apoptotic factors, and nuclear factor-κB (NF-κB) were evaluated using Western blot and immunohistochemistry, respectively. Particle size of only nano-niosomes was in the range of 60-90 nm, while a shift to 70-110 nm was seen after DNAzyme encapsulation. MI rats treated with DNAzyme‑loaded nano‑niosomes could markedly reduce Bax, caspase3, TNF-α, IL-1β, and NF-κB as well as increase Bcl-2 compared to only MI/R group. Collectively, our finding show that nano‑niosomes can be considered excellent drug delivery platforms to extend half-life and stability of DNAzyme, when it is used to reduce myocardial I/R injury.

Cyclosporine A-loaded apoferritin alleviates myocardial ischemia-reperfusion injury by simultaneously blocking ferroptosis and apoptosis of cardiomyocytes

Myocardial ischemia-reperfusion injury (MI/RI) seriously restricts the therapeutic effect of reperfusion. It is demonstrated that ferroptosis and apoptosis of cardiomyocytes are widely involved in MI/RI. Therefore, simultaneous inhibition of ferroptosis and apoptosis of cardiomyocytes can be a promising strategy to treat MI/RI. Besides, transferrin receptor 1 (TfR1) is highly expressed in ischemic myocardium, and apoferritin (ApoFn) is a ligand of the transferrin receptor. In this study, CsA@ApoFn was prepared by wrapping cyclosporin A (CsA) with ApoFn and actively accumulated in ischemic cardiomyocytes through TfR1 mediated endoctosis in MI/RI mice. After entering cardiomyocytes, ApoFn in CsA@ApoFn inhibited ferroptosis of ischemic cardiomyocytes by increasing the protein expression of GPX4 and reducing the content of labile iron pool and lipid peroxides. At the same time, CsA in CsA@ApoFn attenuated the apoptosis of ischemic cardiomyocytes through recovering mitochondrial membrane potential and reducing the level of reactive oxygen species, which played a synergistic role with ApoFn in the treatment of MI/RI. In conclusion, CsA@ApoFn restored cardiac function of MI/RI mice by simultaneously blocking ferroptosis and apoptosis of cardiomyocytes. ApoFn itself not only served as a safe carrier to specifically deliver CsA to ischemic cardiomyocytes but also played a therapeutic role on MI/RI. CsA@ApoFn is proved as an effective drug delivery platform for the treatment of MI/RI. STATEMENT OF SIGNIFICANCE: Recent studies have shown that ferroptosis is an important mechanism of myocardial ischemia-reperfusion injury (MI/RI). Therefore, simultaneous inhibition of ferroptosis and apoptosis of cardiomyocytes can be a promising strategy to treat MI/RI. Apoferritin, as a delivery carrier, can actively target to ischemic myocardium through binding with highly expressed transferrin receptor on ischemic cardiomyocytes. At the same time, apoferritin plays a protective role on ischemic cardiomyocytes by inhibiting ferroptosis. This strategy of killing two birds with one stone significantly improves the therapeutic effect on MI/RI while does not need more pharmaceutical excipients, which has the prospect of clinical transformation.

The Drp1-Mediated Mitochondrial Fission Protein Interactome as an Emerging Core Player in Mitochondrial Dynamics and Cardiovascular Disease Therapy

Mitochondria, the membrane-bound cell organelles that supply most of the energy needed for cell function, are highly regulated, dynamic organelles bearing the ability to alter both form and functionality rapidly to maintain normal physiological events and challenge stress to the cell. This amazingly vibrant movement and distribution of mitochondria within cells is controlled by the highly coordinated interplay between mitochondrial dynamic processes and fission and fusion events, as well as mitochondrial quality-control processes, mainly mitochondrial autophagy (also known as mitophagy). Fusion connects and unites neighboring depolarized mitochondria to derive a healthy and distinct mitochondrion. In contrast, fission segregates damaged mitochondria from intact and healthy counterparts and is followed by selective clearance of the damaged mitochondria via mitochondrial specific autophagy, i.e., mitophagy. Hence, the mitochondrial processes encompass all coordinated events of fusion, fission, mitophagy, and biogenesis for sustaining mitochondrial homeostasis. Accumulated evidence strongly suggests that mitochondrial impairment has already emerged as a core player in the pathogenesis, progression, and development of various human diseases, including cardiovascular ailments, the leading causes of death globally, which take an estimated 17.9 million lives each year. The crucial factor governing the fission process is the recruitment of dynamin-related protein 1 (Drp1), a GTPase that regulates mitochondrial fission, from the cytosol to the outer mitochondrial membrane in a guanosine triphosphate (GTP)-dependent manner, where it is oligomerized and self-assembles into spiral structures. In this review, we first aim to describe the structural elements, functionality, and regulatory mechanisms of the key mitochondrial fission protein, Drp1, and other mitochondrial fission adaptor proteins, including mitochondrial fission 1 (Fis1), mitochondrial fission factor (Mff), mitochondrial dynamics 49 (Mid49), and mitochondrial dynamics 51 (Mid51). The core area of the review focuses on the recent advances in understanding the role of the Drp1-mediated mitochondrial fission adaptor protein interactome to unravel the missing links of mitochondrial fission events. Lastly, we discuss the promising mitochondria-targeted therapeutic approaches that involve fission, as well as current evidence on Drp1-mediated fission protein interactions and their critical roles in the pathogeneses of cardiovascular diseases (CVDs).

Tingli Dazao Decoction pretreatment ameliorates mitochondrial damage induced by oxidative stress in cardiomyocytes

ETHNOPHARMACOLOGICAL RELEVANCE

Tingli Dazao Decoction (TLDZD) recorded in "Synopsis of Prescriptions of the Golden Chamber" is a classical prescription used for the treatment of heart failure nowadays. The studies of TLDZD were mainly focused on clinical practice where the formula was usually combined with other medicinal herbs. Chemical composition and cardiovascular pharmacological research of TLDZD were still insufficient.

AIM OF THE STUDY

This study aimed to investigate the chemical constituents of TLDZD, evaluate the effects of TLDZD on mitochondria of myocardial cells under oxidative stress, and identify its potential cardioprotective components.

MATERIALS AND METHODS

Chemical composition analysis of TLDZD was performed by ultra-performance liquid chromatography-quadrupole-time of flight-mass spectrometry. An in vitro oxidative stress model of cardiomyocytes was established by treating H9c2 cells with tert-butyl hydroperoxide (tBHP). The impact of TLDZD and its components on the production of cellular reactive oxygen species (ROS) and mitochondrial ROS (mROS), the level of malonaldehyde as well as the structure and function of mitochondria were evaluated. The effect of TLDZD on AKT/Nrf2/HO-1 signaling pathway in cardiomyocytes under oxidative stress were observed.

RESULTS

Seventy-eight compounds were characterized from TLDZD, among which flavonoids, glucosinolates and phenylpropanoids were abundant, and a small number of cardiac glycosides and alkaloids also existed in TLDZD. Pretreatment with TLDZD significantly attenuated cell death, accompanied by decreased ROS and mROS production, reduced malonaldehyde level, lower mitochondrial membrane potential and adenosine triphosphate content in H9c2 cells stimulated with tBHP. The active components were mainly flavonoids of TLZ represented by quercetin-3-O-β-D-glucose-7-O-β-D-gentiobioside. In mechanism, the cardioprotective effect of TLDZD was proved to be associated with the activation of the AKT/Nrf2/HO-1 signaling pathway.

CONCLUSIONS

The chemical profile of TLDZD was comprehensively investigated. Flavonoids with quercetin-3-O-β-D-glucose-7-O-β-D-gentiobioside as the representative, were the main component in TLDZD responsible for attenuating mitochondrial oxidative damage in cardiomyocytes.

Human Plasma Xanthine Oxidoreductase Activity in Cardiovascular Disease: Evidence from a Population-Based Study

Xanthine oxidoreductase (XOR) and its products contribute to the development of chronic inflammation and oxidative stress. Excessive XOR activity is believed to promote inflammatory responses and atherosclerotic plaque formation, which are major cardiovascular risk factors. The mechanisms of XOR activity in the development and progression of cardiovascular disease (CVD), coupled with the complexity of the relationship between XOR activity and the biological effects of uric acid; reactive oxygen species; and nitric oxide, which are the major products of XOR activity, have long been debated, but have not yet been clearly elucidated. Recently, a system for measuring highly sensitive XOR activity in human plasma was established, and there has been progress in the research on the mechanisms of XOR activity. In addition, there are accumulating findings about the relationship between XOR activity and CVD. In this narrative review, we summarize existing knowledge regarding plasma XOR activity and its relationship with CVD and discuss future perspectives.

Recombinant Adenovirus siRNA Knocking Down the Ndufs4 Gene Alleviates Myocardial Apoptosis Induced by Oxidative Stress Injury

Oxidative stress results in myocardial cell apoptosis and even life-threatening heart failure in myocardial ischemia-reperfusion injury. Specific blocking of the complex I could reduce cell apoptosis. Ndufs4 is a nuclear-encoded subunit of the mitochondrial complex I and participates in the electron transport chain. In this study, we designed and synthesized siRNA sequences knocking down the rat Ndufs4 gene, constructed recombinant adenovirus Ndufs4 siRNA (Ad-Ndufs4 siRNA), and primarily verified the role of Ndufs4 in oxidative stress injury. The results showed that the adenovirus infection rate was about 90%, and Ndufs4 mRNA and protein were decreased by 76.7% and 64.9%, respectively. Furthermore, the flow cytometry assay indicated that the cell apoptosis rate of the Ndufs4 siRNA group was significantly decreased as compared with the H₂O₂-treated group. In conclusion, we successfully constructed Ndufs4 siRNA recombinant adenovirus; furthermore, the downexpression of the Ndufs4 gene may alleviate H₂O₂-induced H9c2 cell apoptosis.

Myocardial Protection and Current Cancer Therapy: Two Opposite Targets with Inevitable Cost

Myocardial protection against ischemia/reperfusion injury (IRI) is mediated by various ligands, activating different cellular signaling cascades. These include classical cytosolic mediators such as cyclic-GMP (c-GMP), various kinases such as Phosphatydilinositol-3- (PI3K), Protein Kinase B (Akt), Mitogen-Activated-Protein- (MAPK) and AMP-activated (AMPK) kinases, transcription factors such as signal transducer and activator of transcription 3 (STAT3) and bioactive molecules such as vascular endothelial growth factor (VEGF). Most of the aforementioned signaling molecules constitute targets of anticancer therapy; as they are also involved in carcinogenesis, most of the current anti-neoplastic drugs lead to concomitant weakening or even complete abrogation of myocardial cell tolerance to ischemic or oxidative stress. Furthermore, many anti-neoplastic drugs may directly induce cardiotoxicity via their pharmacological effects, or indirectly via their cardiovascular side effects. The combination of direct drug cardiotoxicity, indirect cardiovascular side effects and neutralization of the cardioprotective defense mechanisms of the heart by prolonged cancer treatment may induce long-term ventricular dysfunction, or even clinically manifested heart failure. We present a narrative review of three therapeutic interventions, namely VEGF, proteasome and Immune Checkpoint inhibitors, having opposing effects on the same intracellular signal cascades thereby affecting the heart. Moreover, we herein comment on the current guidelines for managing cardiotoxicity in the clinical setting and on the role of cardiovascular confounders in cardiotoxicity.

Biodegradable Redox-Responsive AIEgen-Based-Covalent Organic Framework Nanocarriers for Long-Term Treatment of Myocardial Ischemia/Reperfusion Injury

Timely restoration of blood supply after myocardial ischemia is imperative for the treatment of acute myocardial infarction but causes additional myocardial ischemia/reperfusion (MI/R) injury, which has not been hitherto effectively targeted by interventions for MI/R injury. Hence, the development of advanced nanomedicine that can reduce apoptosis of cardiomyocytes while protecting against MI/R in vivo is of utmost importance. Herein, a redox-responsive and emissive TPE-ss covalent organic framework (COF) nanocarrier by integrating aggregation-induced emission luminogens and redox-responsive disulfide motifs into the COF skeleton is developed. TPE-ss COF allows for efficient loading and delivery of matrine, a renowned anti-cryptosporidial drug, which significantly reduces MI/R-induced functional deterioration and cardiomyocyte injury when injected through the tail vein into MI/R models at 5 min after 30 min of ischemia. Moreover, TPE-ss COF@Matrine shows a drastic reduction in cardiomyocyte apoptosis and improvements in cardiac function and survival rate. The effect of the TPE-ss COF carrier is further elucidated by enhanced cardiomyocyte viability and triphenyltetrazolium chloride staining in vitro. This work demonstrates the cardioprotective effect of TPE-ss COFs for MI/R injury, which unleashes the immense potential of using COFs as smart drug carriers for the peri-reperfusion treatment of ischemic heart disease with low cost, high stability, and single postoperative intervention.

The protective effect of remote ischemic conditioning is lost in patients with hypercholesterolemia

Remote ischemic conditioning (RIC), brief repetitive cycles of ischemia and reperfusion in remote tissues, is known to induce robust protection against myocardial ischemia-reperfusion (I/R) injury in preclinical studies. However, translation of the beneficial effects to the clinical setting has been challenging. A possibility is that comorbidities, including hypercholesterolemia, interfere with the protective mechanisms of RIC. The aim of this study was to test if hypercholesterolemia attenuates the efficacy of RIC in patients with hypercholesterolemia. Patients with familial hypercholesterolemia (FH) with high (≥5.5 mmol/L) low-density lipoprotein cholesterol (LDL-C), FH with low (≤2.5 mmol/L) and healthy control subjects (n = 12 in each group) were included. Flow-mediated vasodilatation (FMD) of the brachial artery was evaluated, before and after a 20-min period of forearm ischemia and 20 min reperfusion (I/R) as a measure of endothelial function. Study subjects were randomized to a RIC protocol consisting of four cycles of 5 min of leg ischemia or sham using a crossover design. Forearm I/R induced significant reduction in FMD in all three groups during the sham procedure. RIC protected from endothelial dysfunction induced by forearm ischemia-reperfusion in healthy controls [FMD baseline 2.8 ± 2.3 vs. FMD after I/R + RIC 4.5 ± 4.0%; means (SD)] and in patients with FH with low LDL-C (4.5 ± 3.5 vs. 4.4 ± 4.2%). By contrast, RIC fails to protect against I/R-induced endothelial dysfunction in patients with FH and high LDL-C (3.9 ± 3.0 vs. 1.1 ± 1.5%; P < 0.01). These findings provide the first evidence in humans that the protective effect of RIC is lost in patients with elevated cholesterol.NEW & NOTEWORTHY We investigated the impact of hypercholesterolemia on the protective effect of RIC on ischemia-reperfusion injury in a well-characterized patient population with isolated hypercholesterolemia. The results show that the protective effect of RIC is absent in patients with hypercholesterolemia but is apparent in patients with hypercholesterolemic following treatment with lipid-lowering drugs. The results are of importance for the understanding of how comorbidities affect the therapeutic potential of RIC.

ROS-triggered endothelial cell death mechanisms: Focus on pyroptosis, parthanatos, and ferroptosis

The endothelium is a single layer of epithelium covering the surface of the vascular system, and it represents a physical barrier between the blood and vessel wall that plays an important role in maintaining intravascular homeostasis. However, endothelial dysfunction or endothelial cell death can cause vascular barrier disruption, vasoconstriction and diastolic dysfunction, vascular smooth muscle cell proliferation and migration, inflammatory responses, and thrombosis, which are closely associated with the progression of several diseases, such as atherosclerosis, hypertension, coronary atherosclerotic heart disease, ischemic stroke, acute lung injury, acute kidney injury, diabetic retinopathy, and Alzheimer's disease. Oxidative stress caused by the overproduction of reactive oxygen species (ROS) is an important mechanism underlying endothelial cell death. Growing evidence suggests that ROS can trigger endothelial cell death in various ways, including pyroptosis, parthanatos, and ferroptosis. Therefore, this review will systematically illustrate the source of ROS in endothelial cells (ECs); reveal the molecular mechanism by which ROS trigger pyroptosis, parthanatos, and ferroptosis in ECs; and provide new ideas for the research and treatment of endothelial dysfunction-related diseases.

The potential role of ischaemia-reperfusion injury in chronic, relapsing diseases such as rheumatoid arthritis, Long COVID, and ME/CFS: evidence, mechanisms, and therapeutic implications

Ischaemia-reperfusion (I-R) injury, initiated via bursts of reactive oxygen species produced during the reoxygenation phase following hypoxia, is well known in a variety of acute circumstances. We argue here that I-R injury also underpins elements of the pathology of a variety of chronic, inflammatory diseases, including rheumatoid arthritis, ME/CFS and, our chief focus and most proximally, Long COVID. Ischaemia may be initiated via fibrin amyloid microclot blockage of capillaries, for instance as exercise is started; reperfusion is a necessary corollary when it finishes. We rehearse the mechanistic evidence for these occurrences here, in terms of their manifestation as oxidative stress, hyperinflammation, mast cell activation, the production of marker metabolites and related activities. Such microclot-based phenomena can explain both the breathlessness/fatigue and the post-exertional malaise that may be observed in these conditions, as well as many other observables. The recognition of these processes implies, mechanistically, that therapeutic benefit is potentially to be had from antioxidants, from anti-inflammatories, from iron chelators, and via suitable, safe fibrinolytics, and/or anti-clotting agents. We review the considerable existing evidence that is consistent with this, and with the biochemical mechanisms involved.

Current Status and Prospects of Research on Ischemia-Reperfusion Injury and Ferroptosis

The pathogenesis of ischemia-reperfusion injury is not fully understood, most of the current clinical treatment methods mainly relieve symptoms, and cannot prevent fundamentally. The mechanism of Ferroptosis has been extensively studied in recent years, but primarily focused on its therapeutic effects on tumors. After careful comparison, it is easy to find that the symptoms of ischemia-reperfusion injury often accompany by increased lipid peroxidation and increased intracellular iron level are the same as the manifestations of iron-dependent non-apoptotic Ferroptosis. Based on this “coincidence”, we launched this survey. After reading a lot of literature, we found that Ferroptosis is the first step of ischemia-reperfusion injury, and cell necrosis and inflammation are the subsequent steps secondary to Ferroptosis. In this review, we have collected and sorted out the current knowledge about the role and targets of Ferroptosis in the process of ischemia-reperfusion injury. And future studies may be biased towards exploring the use of ferroptosis inhibitors in combination with other treatment options.

Oxidative stress - Complex pathological issues concerning the hallmark of cardiovascular and metabolic disorders

Oxidative stress is a complex biological process characterized by the excessive production of reactive oxygen species (ROS) that act as destroyers of the REDOX balance in the body and, implicitly, inducing oxidative damage. All the metabolisms are impaired in oxidative stress and even nucleic acid balance is influenced. ROS will promote structural changes of the tissues and organs due to interaction with proteins and phospholipids. The constellation of the cardiovascular risk factors (CVRFs) will usually develop in subjects with predisposition to cardiac disorders. Oxidative stress is usually related with hypertension (HTN), diabetes mellitus (DM), obesity and cardiovascular diseases (CVDs) like coronary artery disease (CAD), cardiomyopathy or heart failure (HF), that can develop in subjects with the above-mentioned diseases. Elements describing the complex relationship between CVD and oxidative stress should be properly explored and described because prevention may be the optimal approach. Our paper aims to expose in detail the complex physiopathology of oxidative stress in CVD occurrence and novelties regarding the phenomenon. Biomarkers assessing oxidative stress or therapy targeting specific pathways represent a major progress that actually change the outcome of subjects with CVD. New antioxidants therapy specific for each CVD represents a captivating and interesting future perspective with tremendous benefits on subject's outcome.

AMPK Activation Alleviates Myocardial Ischemia-Reperfusion Injury by Regulating Drp1-Mediated Mitochondrial Dynamics

Mitochondrial dysfunction is a salient feature of myocardial ischemia/reperfusion injury (MIRI), while the potential mechanism of mitochondrial dynamics disorder remains unclear. This study sought to explore whether activation of Adenosine monophosphate-activated protein kinase (AMPK) could alleviate MIRI by regulating GTPase dynamin-related protein 1 (Drp1)-mediated mitochondrial dynamics. Isolated mouse hearts in a Langendorff perfusion system were subjected to ischemia/reperfusion (I/R) treatment, and H9C2 cells were subjected to hypoxia /reoxygenation (H/R) treatment in vitro. The results showed that AICAR, the AMPK activator, could significantly improve the function of left ventricular, decrease arrhythmia incidence and myocardial infarction area of isolated hearts. Meanwhile, AICAR increased superoxide dismutase (SOD) activity and decreased malondialdehyde (MDA) content in myocardial homogenate. Mechanistically, AICAR inhibited the phosphorylation of Drp1 at Ser 616 while enhanced phosphorylation of Drp1 at Ser 637. In addition, AICAR reduced the expression of inflammatory cytokines including TNF-ɑ, IL-6, and IL-1β, as well as mitochondrial fission genes Mff and Fis1, while improved the expression of mitochondrial fusion genes Mfn1 and Mfn2. Similar results were also observed in H9C2 cells. AICAR improved mitochondrial membrane potential (MMP), reduced reactive oxygen species (ROS) production, and inhibited mitochondrial damage. To further prove if Drp1 regulated mitochondrial dynamics mediated AMPK protection effect, the mitochondrial fission inhibitor Mdivi-1 was utilized. We found that Mdivi-1 significantly improved MMP, inhibited ROS production, reduced the expression of TNF-a, IL-6, IL-1β, Fis1, and Mff, and improved the expression of Mfn1 and Mfn2. However, the protection effect of Mdivi-1 was not reversed by AMPK inhibitor Compound C. In conclusion, this study confirmed that activation of AMPK exerted the protective effects on MIRI, which were largely dependent on the inhibition of Drp1-mediated mitochondrial fission.

Role of Oxidative Stress in Cardiac Dysfunction and Subcellular Defects Due to Ischemia-Reperfusion Injury

Ischemia-reperfusion (I/R) injury is well-known to be associated with impaired cardiac function, massive arrhythmias, marked alterations in cardiac metabolism and irreversible ultrastructural changes in the heart. Two major mechanisms namely oxidative stress and intracellular Ca²⁺-overload are considered to explain I/R-induced injury to the heart. However, it is becoming apparent that oxidative stress is the most critical pathogenic factor because it produces myocardial abnormalities directly or indirectly for the occurrence of cardiac damage. Furthermore, I/R injury has been shown to generate oxidative stress by promoting the formation of different reactive oxygen species due to defects in mitochondrial function and depressions in both endogenous antioxidant levels as well as regulatory antioxidative defense systems. It has also been demonstrated to adversely affect a wide variety of metabolic pathways and targets in cardiomyocytes, various resident structures in myocardial interstitium, as well as circulating neutrophils and leukocytes. These I/R-induced alterations in addition to myocardial inflammation may cause cell death, fibrosis, inflammation, Ca²⁺-handling abnormalities, activation of proteases and phospholipases, as well as subcellular remodeling and depletion of energy stores in the heart. Analysis of results from isolated hearts perfused with or without some antioxidant treatments before subjecting to I/R injury has indicated that cardiac dysfunction is associated with the development of oxidative stress, intracellular Ca²⁺-overload and protease activation. In addition, changes in the sarcolemma and sarcoplasmic reticulum Ca²⁺-handling, mitochondrial oxidative phosphorylation as well as myofibrillar Ca²⁺-ATPase activities in I/R hearts were attenuated by pretreatment with antioxidants. The I/R-induced alterations in cardiac function were simulated upon perfusing the hearts with oxyradical generating system or oxidant. These observations support the view that oxidative stress may be intimately involved in inducing intracellular Ca²⁺-overload, protease activation, subcellular remodeling, and cardiac dysfunction as a consequence of I/R injury to the heart.

Synthesis and in Vivo Evaluation of Triphenylphosphonium Conjugated Trimetazidine with Enhanced Cardioprotection and Ability to Restore Mitochondrial Function

Trimetazidine exhibits great therapeutic potential in cardiovascular diseases and mitochondria-mediated cardioprotection by trimetazidine has been widely reported. In this study, to enhance its cardioprotection, the triphenylphosphonium-based modification of trimetazidine was conducted to deliver it specifically to mitochondria. Fifteen triphenylphosphonium (TPP) conjugated trimetazidine analogs were designed and synthesized. Their protective effects were evaluated in vivo using a tert-butyl hydroperoxide (t-BHP) induced zebrafish injury model. Structure-activity relationship correlations revealed the best way to couple the TPP moiety to trimetazidine, and led to a new conjugate (18a) with enhanced therapeutic properties. Compared to trimetazidine, 18a effectively protects against heart injury in the zebrafish model at a much lower concentration. Further study in t-BHP treated zebrafish and H9c2 cells demonstrated that 18a protects against cardiomyocyte death and damage by inhibiting excessive production of ROS, maintaining mitochondrial morphology, and preventing mitochondrial dysfunction. Consequently, 18a can be regarded as a potential therapeutic agent for cardioprotection.

Empagliflozin attenuates cardiac microvascular ischemia/reperfusion injury through improving mitochondrial homeostasis

BACKGROUND

Empagliflozin has been reported to protect endothelial cell function, regardless of diabetes status. However, the role of empagliflozin in microvascular protection during myocardial ischemia reperfusion injury (I/R) has not been fully understood.

METHODS

Electron microscopy, western blots, immunofluorescence, qPCR, mutant plasmid transfection, co-immunoprecipitation were employed to explore whether empagliflozin could alleviate microvascular damage and endothelial injury during cardiac I/R injury.

RESULTS

In mice, empagliflozin attenuated I/R injury-induced microvascular occlusion and microthrombus formation. In human coronary artery endothelial cells, I/R injury led to adhesive factor upregulation, endothelial nitric oxide synthase inactivation, focal adhesion kinase downregulation, barrier dysfunction, cytoskeletal degradation and cellular apoptosis; however, empagliflozin treatment diminished these effects. Empagliflozin improved mitochondrial oxidative stress, mitochondrial respiration and adenosine triphosphate metabolism in I/R-treated human coronary artery endothelial cells by preventing the phosphorylation of dynamin-related protein 1 (Drp1) and mitochondrial fission 1 protein (Fis1), thus repressing mitochondrial fission. The protective effects of empagliflozin on mitochondrial homeostasis and endothelial function were abrogated by the re-introduction of phosphorylated Fis1, but not phosphorylated Drp1, suggesting that Fis1 dephosphorylation is the predominant mechanism whereby empagliflozin inhibits mitochondrial fission during I/R injury. Besides, I/R injury induced Fis1 phosphorylation primarily by activating the DNA-dependent protein kinase catalytic subunit (DNA-PKcs) pathway, while empagliflozin inactivated this pathway by exerting anti-oxidative effects.

CONCLUSIONS

These results demonstrated that empagliflozin can protect the microvasculature by inhibiting the DNA-PKcs/Fis1/mitochondrial fission pathway during myocardial I/R injury.

Anti-inflammatory effect of trans-anethol in a rat model of myocardial ischemia-reperfusion injury

Myocardial ischemia‑reperfusion injury (MI/R) is considered a main risk factor for global cardiac mortality and morbidity, for which no effective treatment exists. Both inflammation and epigenetic regulation play a pivotal role in the early stage of MI/R. The present study aimed at investigating the prospective anti-inflammatory role of trans-anethole (TNA) in targeting MI/R and its related mechanism in upregulating the expression of the inflammatory and cardiac-related gene (VAV3), and its epigenetic regulators (lncRNA-JRKL-AS1 and miR-1298) that were retrieved from in-silico data analysis in an ischemia/reperfusion (I/R) rat model.

MATERIALS & METHODS

TNA was administered in 3 doses (50, 100, and 200 mg/kg), 15 min prior to coronary ligation in male Wistar rats. The left ventricular end-diastolic pressure and dP/dtmax were assessed. Histopathological, biochemical, and molecular analyses were performed to assess the effects of TNA pre-treatment on the I/R rats model.

RESULTS

TNA alleviated the I/R-induced cardiac injury pathologically and improved the cardiac function tests and enzymes. At the molecular level, TNA upregulated the expression level of the retrieved RNA-based panel (VAV3 mRNA/miR-1298/lncRNA JRKL-AS1). At the protein level, TNA decreased the cardiac content of the pro-inflammatory cytokine TNF-α.

CONCLUSION

TNA has demonstrated a potential ability to alleviate the cardiac injury and attenuate the inflammatory response following ischemia-reperfusion in the rat model through modulation of the expression of RNA panel (VAV3 mRNA/miR-1298/lncRNA JRKL-AS1) and TNF- α protein.

Beta-Carotene Affects the Effects of Heme Oxygenase-1 in Isolated, Ischemic/Reperfused Rat Hearts: Potential Role of the Iron

Beta-carotene (BC) is a well-known antioxidant. However, increasing evidence shows that under severe oxidative conditions, BC can become pro-oxidant, an effect that may be enhanced in the presence of iron (II). In our earlier studies, we observed that despite increasing heme oxygenase-1 (HO-1) levels in the heart, the protective effects of BC have been lost when it was used at a high concentration. Since iron releases from heme as a consequence of HO-1 activity, we hypothesized that the application of an iron-chelator (IC) would reverse the lost cardiac protection associated with an elevated HO-1 level. Thus, in the present study, we investigated the effects of desferrioxiamine (DFO) in isolated, ischemic/reperfused rat hearts after long-term treatment with vehicle or high-dose (HD) BC. Vehicle or 150 mg/bw kg daily doses of BC were administered to the rats for 4 weeks, and then their hearts were removed and subjected to 30 min of global ischemia (ISA) followed by 120 min of reperfusion (REP). During the experiments, cardiac function was registered, and at the end of the REP period, infarct size (IS) and HO-1 expression were measured. The results show that DFO treatment alone during REP significantly ameliorated postischemic cardiac function and decreased IS, although HO-1 expression was not increased significantly. In hearts isolated from BC-treated rats, no cardioprotective effects, despite an elevated HO-1 level, were observed, while DFO administration after ISA resulted in a mild improvement in heart function and IS. Our results suggest that iron could have a role whether BC exerts antioxidant or pro-oxidant effects in ISA/REP-injured hearts.

The histone demthylase KDM3A protects the myocardium from ischemia/reperfusion injury via promotion of ETS1 expression

Our prior studies have characterized the participation of histone demethylase KDM3A in diabetic vascular remodeling, while its roles in myocardial ischemia/reperfusion (I/R) injury (MIRI) remain to be illustrated. Here we show that KDM3A was significantly downregulated in rat I/R and cellular hypoxia/reoxygenation (H/R) models. Subsequently, gain- and loss-of-function experiments were performed to investigate the effects of KDM3A in the settings of MIRI. KDM3A knockout exacerbated cardiac dysfunction and cardiomyocytes injury both in vivo and in vitro. The deteriorated mitochondrial apoptosis, reactive oxygen species, and inflammation were simultaneously observed. Conversely, KDM3A overexpression developed the ameliorated alternations in MIRI. Mechanistically, the MIRI-alleviating effects of KDM3A were associated with the enhancement of ETS1 expression. ChIP-PCR affirmed that KDM3A bound to the ETS1 promoter and removed dimethylation of histone H3 lysine 9 (H3K9me2), thus promoting ETS1 transcription. Our findings suggest that KDM3A is available for alleviating multi-etiologies of MIRI through the regulation of ETS1.

Prevention of cardiac injury requires a deeper mechanistic understanding of ischemia/reperfusion (I/R) episodes. Here, the authors find that the epigenetic modifier KDM3A plays a crucial role in myocardial I/R injury through its activation of the gene ETS1 and suggest boosting KDM3A expression could be a potential treatment strategy.

JNK-dependent phosphorylation and nuclear translocation of EGR-1 promotes cardiomyocyte apoptosis

Myocardial apoptosis induced by myocardial ischemia and hyperlipemia are the main causes of high mortality of cardiovascular diseases. It is not clear whether there is a common mechanism responsible for these two kinds of cardiomyocyte apoptosis. Previous studies demonstrated that early growth response protein 1 (EGR-1) has a pro-apoptotic effect on cardiomyocytes under various stress conditions. Here, we found that EGR-1 is also involved in cardiomyocyte apoptosis induced by both ischemia and high-fat, but how EGR-1 enters the nucleus and whether nuclear EGR-1 (nEGR-1) has a universal effect on cardiomyocyte apoptosis are still unknown. By analyzing the phosphorylation sites and nucleation information of EGR-1, we constructed different mutant plasmids to confirm that the nucleus location of EGR-1 requires Ser501 phosphorylation and regulated by JNK. Furthermore, the pro-apoptotic effect of nEGR-1 was further explored through genetic methods. The results showed that EGR-1 positively regulates the mRNA levels of apoptosis-related proteins (ATF2, CTCF, HAND2, ELK1), which may be the downstream targets of EGR-1 to promote the cardiomyocyte apoptosis. Our research announced the universal pro-apoptotic function of nEGR-1 and explored the mechanism of its nucleus location in cardiomyocytes, providing a new target for the "homotherapy for heteropathy" to cardiovascular diseases.

Regenerative strategies for the consequences of myocardial infarction: Chronological indication and upcoming visions

Heart muscle injury and an elevated troponin level signify myocardial infarction (MI), which may result in defective and uncoordinated segments, reduced cardiac output, and ultimately, death. Physicians apply thrombolytic therapy, coronary artery bypass graft (CABG) surgery, or percutaneous coronary intervention (PCI) to recanalize and restore blood flow to the coronary arteries, albeit they were not convincingly able to solve the heart problems. Thus, researchers aim to introduce novel substitutional therapies for regenerating and functionalizing damaged cardiac tissue based on engineering concepts. Cell-based engineering approaches, utilizing biomaterials, gene, drug, growth factor delivery systems, and tissue engineering are the most leading studies in the field of heart regeneration. Also, understanding the primary cause of MI and thus selecting the most efficient treatment method can be enhanced by preparing microdevices so-called heart-on-a-chip. In this regard, microfluidic approaches can be used as diagnostic platforms or drug screening in cardiac disease treatment. Additionally, bioprinting technique with whole organ 3D printing of human heart with major vessels, cardiomyocytes and endothelial cells can be an ideal goal for cardiac tissue engineering and remarkable achievement in near future. Consequently, this review discusses the different aspects, advancements, and challenges of the mentioned methods with presenting the advantages and disadvantages, chronological indications, and application prospects of various novel therapeutic approaches.

Effects of Remote Ischaemic Preconditioning on the Internal Thoracic Artery Nitric Oxide Synthase Isoforms in Patients Undergoing Coronary Artery Bypass Grafting

Remote ischaemic preconditioning (RIPC) is a medical procedure that consists of repeated brief periods of transient ischaemia and reperfusion of distant organs (limbs) with the ability to provide internal organ protection from ischaemia. Even though RIPC has been successfully applied in patients with myocardial infarction during coronary revascularization (surgery/percutaneous angioplasty), the underlying molecular mechanisms are yet to be clarified. Thus, our study aimed to determine the role of nitric oxide synthase (NOS) isoforms in RIPC-induced protection (3 × 5 min of forearm ischaemia with 5 min of reperfusion) of arterial graft in patients undergoing urgent coronary artery bypass grafting (CABG). We examined RIPC effects on specific expression and immunolocalization of three NOS isoforms — endothelial (eNOS), inducible (iNOS) and neuronal (nNOS) in patients’ internal thoracic artery (ITA) used as a graft. We found that the application of RIPC protocol leads to an increased protein expression of eNOS, which was further confirmed with strong eNOS immunopositivity, especially in the endothelium and smooth muscle cells of ITA. The same analysis of two other NOS isoforms, iNOS and nNOS, showed no significant differences between patients undergoing CABG with or without RIPC. Our results demonstrate RIPC-induced upregulation of eNOS in human ITA, pointing to its significance in achieving protective phenotype on a systemic level with important implications for graft patency.

Xanthine oxidoreductase: A leading actor in cardiovascular disease drama

Cardiovascular diseases (CVD) are the leading cause of global mortality and their pathogenesis lies mainly in the atherosclerotic process. There are close connections linking oxidative stress and inflammation to endothelial dysfunction, atherosclerosis and, consequently, to CVD. This review focuses on the role of xanthine oxidoreductase (XOR) and its products on the development of chronic inflammation and oxidative stress, responsible for atheromatous plaque formation. Evidence is reported that an excessive level of XOR products favors inflammatory response and plaque development, thereby promoting major cardiovascular risk factors. Also, the relationship between hyperuricemia and hypertension as well as between XOR activity and CVD is confirmed. In spite of the increasing number of clinical studies investigating the output of cardiovascular patients treated with urate-lowering therapies (including uricosuric drugs, XOR inhibitors and recombinant uricase) the results are still uncertain. The inhibition of XOR activity appears more promising than just the control of uricemia level in preventing cardiovascular events, possibly because it also reduces the intracellular accumulation of urate, as well as the production of reactive oxygen species. However, XOR inhibition also reduces the availability of the multifaced mediator nitric oxide and, at present, can be recommended only in hyperuricemic patients.

Preconditioning the rat heart with 5-azacytidine attenuates myocardial ischemia/reperfusion injury via PI3K/GSK3β and mitochondrial KATP signaling axis

5-Azacytidine is well known for its clinical usage in cancer treatments. The present study investigates the role of 5-azacytidine as a cardioprotective agent to ameliorate ischemia/reperfusion (I/R) injury. The cardioprotective effect of 5-azacytidine was evaluated in three experimental models: in vitro, ex vivo, and in vivo. The cardioprotective effect was evaluated via cell viability, hemodynamic indices, infarct size measurement, and assessment of histopathology, oxidative stress, and mitochondrial function. The experiments were repeated in the presence of PI3K/GSK3β and mitochondrial K_ATP (mtK_ATP ) cardioprotective signaling pathway inhibitors to understand the underlying mechanism. 5-Azacytidine improved the cell viability by 29% in I/R-challenged H9C2 cells. Both isolated rat heart and LAD ligation model confirmed the infarct sparing effect of 5-azacytidine against I/R. It also provided a beneficial effect by normalizing the altered hemodynamics, reducing the infarct size and cardiac injury markers, reversing the perturbation of mitochondria, reduced oxidative stress, and improved the pPI3K and pAKT protein expression from I/R. In addition, it also augmented the activation of PI3K/AKT and mtK_ATP signaling pathway, confirmed by using wortmannin (PI3K inhibitor), SB216763 (GSK3β inhibitor), and glibenclamide (mtK_ATP channel closer). The effectiveness of 5-azacytidine as a cardioprotective agent is attributed to its activation of the PI3K/GSK3β and mtK_ATP channel signaling axis, thereby preserving mitochondrial function and reducing oxidative stress.

Redox signaling in heart failure and therapeutic implications

Heart failure is a growing health burden worldwide characterized by alterations in excitation-contraction coupling, cardiac energetic deficit and oxidative stress. While current treatments are mostly limited to antagonization of neuroendocrine activation, more recent data suggest that also targeting metabolism may provide substantial prognostic benefit. However, although in a broad spectrum of preclinical models, oxidative stress plays a causal role for the development and progression of heart failure, no treatment that targets reactive oxygen species (ROS) directly has entered the clinical arena yet. In the heart, ROS derive from various sources, such as NADPH oxidases, xanthine oxidase, uncoupled nitric oxide synthase and mitochondria. While mitochondria are the primary source of ROS in the heart, communication between different ROS sources may be relevant for physiological signalling events as well as pathologically elevated ROS that deteriorate excitation-contraction coupling, induce hypertrophy and/or trigger cell death. Here, we review the sources of ROS in the heart, the modes of pathological activation of ROS formation as well as therapeutic approaches that may target ROS specifically in mitochondria.

Inhibition of PI3K/mTOR/KATP channel blunts sodium thiosulphate preconditioning mediated cardioprotection against ischemia-reperfusion injury

Recent studies have shown that pre and postconditioning the heart with sodium thiosulfate (STS) attenuate ischemia-reperfusion (IR) injury. However, the underlying mechanism involved in the cardioprotective signaling pathway is not fully explored. This study examined the existing link of STS mediated protection (as pre and post-conditioning agents) with PI3K, mTOR, and mPTP signaling pathways using its respective inhibitors. STS was administered to the isolated perfused rat heart through Kreb's Heinselit buffer before ischemia (precondition: SIPC) and reperfusion (postcondition: SPOC) in the presence and absence of the PI3K, mTOR, and mPTP signaling pathway inhibitors (wortmannin, rapamycin, and glibenclamide respectively). SIPC failed to improve the IR injury-induced altered cardiac hemodynamics, increased infarct size, and the release of cardiac injury markers in the presence of these inhibitors. On the other hand, the SPOC protocol effectively rendered the cardioprotection even in the PI3K/mTOR/K_ATP inhibitors presence. Interestingly, the SIPC's identified mode of action viz reduction in oxidative stress and the preservation of mitochondrial function were lost in the inhibitors' presence. Based on the above results, we conclude that the underlying mechanism of SIPC mediated cardioprotection works via the PI3K/mTOR/K_ATP signaling pathway axis activation.

Protective Effect of Optic Atrophy 1 on Cardiomyocyte Oxidative Stress: Roles of Mitophagy, Mitochondrial Fission, and MAPK/ERK Signaling

Myocardial infarction is associated with oxidative stress and mitochondrial damage. However, the regulatory mechanisms underlying cardiomyocyte oxidative stress during myocardial infarction are not fully understood. In the present study, we explored the cardioprotective action of optic atrophy 1- (Opa1-) mediated mitochondrial autophagy (mitophagy) in oxidative stress-challenged cardiomyocytes, with a focus on mitochondrial homeostasis and the MAPK/ERK pathway. Our results demonstrated that overexpression of Opa1 in cultured rat H9C2 cardiomyocytes, a procedure that stimulates mitophagy, attenuates oxidative stress and increases cellular antioxidant capacity. Activation of Opa1-mediated mitophagy suppressed cardiomyocyte apoptosis by downregulating Bax, caspase-9, and caspase-12 and upregulating Bcl-2 and c-IAP. Using mitochondrial tracker staining and a reactive oxygen species indicator, our assays showed that Opa1-mediated mitophagy attenuated mitochondrial fission and reduced ROS production in cardiomyocytes. In addition, we found that inhibition of the MAPK/ERK pathway abolished the antioxidant action of Opa1-mediated mitophagy in these cells. Taken together, our data demonstrate that Opa1-mediated mitophagy protects cardiomyocytes against oxidative stress damage through inhibition of mitochondrial fission and activation of MAPK/ERK signaling. These findings reveal a critical role for Opa1 in the modulation of cardiomyocyte redox balance and suggest a potential target for the treatment of myocardial infarction.

Influence of cardiometabolic comorbidities on myocardial function, infarction, and cardioprotection: Role of cardiac redox signaling

The morbidity and mortality from cardiovascular diseases (CVD) remain high. Metabolic diseases such as obesity, hyperlipidemia, diabetes mellitus (DM), non-alcoholic fatty liver disease (NAFLD) and non-alcoholic steatohepatitis (NASH) as well as hypertension are the most common comorbidities in patients with CVD. These comorbidities result in increased myocardial oxidative stress, mainly from increased activity of nicotinamide adenine dinucleotide phosphate oxidases, uncoupled endothelial nitric oxide synthase, mitochondria as well as downregulation of antioxidant defense systems. Oxidative and nitrosative stress play an important role in ischemia/reperfusion injury and may account for increased susceptibility of the myocardium to infarction and myocardial dysfunction in the presence of the comorbidities. Thus, while early reperfusion represents the most favorable therapeutic strategy to prevent ischemia/reperfusion injury, redox therapeutic strategies may provide additive benefits, especially in patients with heart failure. While oxidative and nitrosative stress are harmful, controlled release of reactive oxygen species is however important for cardioprotective signaling. In this review we summarize the current data on the effect of hypertension and major cardiometabolic comorbidities such as obesity, hyperlipidemia, DM, NAFLD/NASH on cardiac redox homeostasis as well as on ischemia/reperfusion injury and cardioprotection. We also review and discuss the therapeutic interventions that may restore the redox imbalance in the diseased myocardium in the presence of these comorbidities.

Energy substrate metabolism and mitochondrial oxidative stress in cardiac ischemia/reperfusion injury

The heart is the most metabolically flexible organ with respect to the use of substrates available in different states of energy metabolism. Cardiac mitochondria sense substrate availability and ensure the efficiency of oxidative phosphorylation and heart function. Mitochondria also play a critical role in cardiac ischemia/reperfusion injury, during which they are directly involved in ROS-producing pathophysiological mechanisms. This review explores the mechanisms of ROS production within the energy metabolism pathways and focuses on the impact of different substrates. We describe the main metabolites accumulating during ischemia in the glucose, fatty acid, and Krebs cycle pathways. Hyperglycemia, often present in the acute stress condition of ischemia/reperfusion, increases cytosolic ROS concentrations through the activation of NADPH oxidase 2 and increases mitochondrial ROS through the metabolic overloading and decreased binding of hexokinase II to mitochondria. Fatty acid-linked ROS production is related to the increased fatty acid flux and corresponding accumulation of long-chain acylcarnitines. Succinate that accumulates during anoxia/ischemia is suggested to be the main source of ROS, and the role of itaconate as an inhibitor of succinate dehydrogenase is emerging. We discuss the strategies to modulate and counteract the accumulation of substrates that yield ROS and the therapeutic implications of this concept.