Apoptosis in ischemic and reperfused rat myocardium

Programmed death of cardiomyocytes in cardiovascular disease and new therapeutic approaches

Cardiovascular diseases (CVDs) have a complex pathogenesis and pose a major threat to human health. Cardiomyocytes have a low regenerative capacity, and their death is a key factor in the morbidity and mortality of many CVDs. Cardiomyocyte death can be regulated by specific signaling pathways known as programmed cell death (PCD), including apoptosis, necroptosis, autophagy, pyroptosis, and ferroptosis, etc. Abnormalities in PCD can lead to the development of a variety of cardiovascular diseases, and there are also molecular-level interconnections between different PCD pathways under the same cardiovascular disease model. Currently, the link between programmed cell death in cardiomyocytes and cardiovascular disease is not fully understood. This review describes the molecular mechanisms of programmed death and the impact of cardiomyocyte death on cardiovascular disease development. Emphasis is placed on a summary of drugs and potential therapeutic approaches that can be used to treat cardiovascular disease by targeting and blocking programmed cell death in cardiomyocytes.

L-theanine alleviates myocardial ischemia/reperfusion injury by suppressing oxidative stress and apoptosis through activation of the JAK2/STAT3 pathway in mice

BACKGROUND

L-theanine is a unique non-protein amino acid in tea that is widely used as a safe food additive. We investigated the cardioprotective effects and mechanisms of L-theanine in myocardial ischemia-reperfusion injury (MIRI).

METHODS

The cardioprotective effects and mechanisms of L-theanine and the role of Janus Kinase 2 (JAK2)/signal transducer and activator of transcription 3 (STAT3) signaling were investigated in MIRI mice using measures of cardiac function, oxidative stress, and apoptosis.

RESULTS

Administration of L-theanine (10 mg/kg, once daily) suppressed the MIRI-induced increase in infarct size and serum creatine kinase and lactate dehydrogenase levels, as well as MIRI-induced cardiac apoptosis, as evidenced by an increase in Bcl-2 expression and a decrease in Bax/caspase-3 expression. Administration of L-theanine also decreased the levels of parameters reflecting oxidative stress, such as dihydroethidium, malondialdehyde, and nitric oxide, and increased the levels of parameters reflecting anti-oxidation, such as total antioxidant capacity (T-AOC), glutathione (GSH), and superoxide dismutase (SOD) in ischemic heart tissue. Further analysis showed that L-theanine administration suppressed the MIRI-induced decrease of phospho-JAK2 and phospho-STAT3 in ischemic heart tissue. Inhibition of JAK2 by AG490 (5 mg/kg, once daily) abolished the cardioprotective effect of L-theanine, suggesting that the JAK2/STAT3 signaling pathway may play an essential role in mediating the anti-I/R effect of L-theanine.

CONCLUSIONS

L-theanine administration suppresses cellular apoptosis and oxidative stress in part via the JAK2/STAT3 signaling pathway, thereby attenuating MIRI-induced cardiac injury. L-theanine could be developed as a potential drug to alleviate cardiac damage in MIRI.

Ultrasound-targeted microbubble destruction rapidly improves left ventricular function in rats with ischemic cardiac dysfunction

BACKGROUND

Previous studies have demonstrated the efficacy of ultrasound-targeted microbubble destruction (UTMD) in the treatment of ischemic heart failure (HF). The purpose of this study was to explore the mechanism by which UTMD improves ischemic HF.

METHODS

An ischemic heart failure model was established using Sprague-Dawley rats. Rats were randomly divided into 7 groups: sham group, HF group, HF + MB group, HF + ultrasound (US) group, HF + UTMD group, HF + UTMD+LY294002 group, and HF + LY294002 group. Serum BNP level and echocardiographic parameters were measured to evaluate cardiac function. PI3K/Akt/eNOS signaling pathway protein levels were detected by immunohistochemistry (IHC) and western blotting. The concentrations of nitrous oxide (NO) and ATP were detected by ELISA, and hematoxylin and eosin (HE) staining was used to evaluate myocardial tissue.

RESULTS

UTMD rapidly improved ejection fraction (EF) (HF: 37.16 ± 1.21% vs. HF + UTMD: 46.31 ± 3.00%, P < 0.01) and fractional shortening (FS) (HF: 18.53 ± 0.58% vs. HF + UTMD: 24.05 ± 1.84%, P < 0.01) in rats with ischemic HF. UTMD activated the PI3K/AKT/eNOS signaling pathway (HF vs. HF + UTMD, P < 0.01) and promoted the release of NO and ATP (HF vs. HF + UTMD, both, P < 0.05). Inhibition of the PI3K/AKT/eNOS signaling pathway by LY294002 worsened EF (HF: 37.16 ± 1.21% vs. HF + LY294002: 32.73 ± 3.05%, P < 0.05), and the release of NO and ATP by UTMD (HF + UTMD vs. HF + UTMD+LY294002, P < 0.05).

CONCLUSIONS

UTMD can rapidly improve cardiac function in ischemic HF by activating the PI3K/Akt/eNOS signaling pathway and promoting the release of NO and ATP.

Platelets Induce Cell Apoptosis of Cardiac Cells via FasL after Acute Myocardial Infarction

Acute myocardial infarction (AMI) is one of the leading causes of death worldwide. Cell apoptosis in the myocardium plays an important role in ischemia and reperfusion (I/R) injury, leading to cardiac damage and dysfunction. Platelets are major players in hemostasis and play a crucial role in vessel occlusion, inflammation, and cardiac remodeling after I/R. Here, we studied the impact of platelets on cell apoptosis in the myocardium using a close-chest mouse model of AMI. We found caspase-3-positive resident cardiac cells, while leukocytes were negative for caspase-3. Using two different mouse models of thrombocytopenia, we detected a significant reduction in caspase-3 positive cells in the infarct border zone after I/R injury. Further, we identified platelet FasL to induce cell apoptosis via the extrinsic pathway of Fas receptor activation of target cells. Mechanistically, hypoxia triggers platelet adhesion to FasR, suggesting that platelet-induced apoptosis is elevated after I/R. Platelet-specific FasL knock-out mice showed reduced Bax and Bcl2 expression, suggesting that platelets modulate the intrinsic and extrinsic pathways of apoptosis, leading to reduced infarct size after myocardial I/R injury. Thus, a new mechanism for how platelets contribute to tissue homeostasis after AMI was identified that should be validated in patients soon.

The Flt3-inhibitor quizartinib augments apoptosis and promotes maladaptive remodeling after myocardial infarction in mice

BACKGROUND

Tyrosine kinase inhibitors (TKIs) targeting fms-like tyrosine kinase 3 (Flt3) such as quizartinib were specifically designed for acute myeloid leukemia treatment, but also multi-targeting TKIs applied to solid tumor patients inhibit Flt3. Flt3 is expressed in the heart and its activation is cytoprotective in myocardial infarction (MI) in mice.

OBJECTIVES

We sought to test whether Flt3-targeting TKI treatment aggravates cardiac injury after MI.

METHODS AND RESULTS

Compared to vehicle, quizartinib (10 mg/kg/day, gavage) did not alter cardiac dimensions or function in healthy mice after four weeks of therapy. Pretreated mice were randomly assigned to MI or sham surgery while receiving quizartinib or vehicle for one more week. Quizartinib did not aggravate the decline in ejection fraction, but significantly enhanced ventricular dilatation one week after infarction. In addition, apoptotic cell death was significantly increased in the myocardium of quizartinib-treated compared to vehicle-treated mice. In vitro, quizartinib dose-dependently decreased cell viability in neonatal rat ventricular myocytes and in H9c2 cells, and increased apoptosis as assessed in the latter. Together with H2O2, quizartinib potentiated the phosphorylation of the pro-apoptotic mitogen activated protein kinase p38 and augmented H2O2-induced cell death and apoptosis beyond additive degree. Pretreatment with a p38 inhibitor abolished apoptosis under quizartinib and H2O2.

CONCLUSION

Quizartinib potentiates apoptosis and promotes maladaptive remodeling after MI in mice at least in part via a p38-dependent mechanism. These findings are consistent with the multi-hit hypothesis of cardiotoxicity and make cardiac monitoring in patients with ischemic heart disease under Flt3- or multi-targeting TKIs advisable.

Therapeutic Role of Chinese Medicine Targeting Nrf2/HO-1 Signaling Pathway in Myocardial Ischemia/Reperfusion Injury

Acute myocardial infarction (AMI), characterized by high incidence and mortality rates, poses a significant public health threat. Reperfusion therapy, though the preferred treatment for AMI, often exacerbates cardiac damage, leading to myocardial ischemia/reperfusion injury (MI/RI). Consequently, the development of strategies to reduce MI/RI is an urgent priority in cardiovascular therapy. Chinese medicine, recognized for its multi-component, multi-pathway, and multi-target capabilities, provides a novel approach for alleviating MI/RI. A key area of interest is the nuclear factor E2-related factor 2 (Nrf2)/heme oxygenase-1 (HO-1) pathway. This pathway is instrumental in regulating inflammatory responses, oxidative stress, apoptosis, endoplasmic reticulum stress, and ferroptosis in MI/RI. This paper presents a comprehensive overview of the Nrf2/HO-1 signaling pathway's structure and its influence on MI/RI. Additionally, it reviews the latest research on leveraging Chinese medicine to modulate the Nrf2/HO-1 pathway in MI/RI treatment.

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.

Microarray Analysis for Transcriptomic Profiling of Myocardium in Patients with Fatal Myocardial Infarction

Transcriptomic evidence from human myocardium in myocardial infarction (MI) is still not sufficient. Thus, there is a need for studies on human cardiac samples in relation to the clinical data of patients. The purpose of our pilot study was to investigate the transcriptomic profile of myocardium in the infarct zone, in comparison to the remote myocardium, in patients with fatal MI, via microarray analysis. This study included four patients with fatal MI type 1. We selected histologically verified samples from within the infarct area (n = 4) and remote myocardium (n = 4). The whole transcriptome was evaluated using microarray analysis. Differentially expressed genes (DEGs) clustered in the infarct area and in the remote myocardium allowed their differentiation. We identified a total of 1785 DEGs (8.32%) in the infarct area, including 1692 up-regulated (94.79%) and 93 down-regulated (5.21%) genes. The top 10 up-regulated genes were TRAIL, SUCLA2, NAE1, PDCL3, OSBPL5, FCGR2C, SELE, CEP63, ST3GAL3 and C4orf3. In the infarct area, we found up-regulation of seventeen apoptosis-related genes, eleven necroptosis-related, and six necrosis-related genes. Transcriptome profiling of the myocardium in patients with MI remains a relevant area of research for the formation of new scientific hypotheses and a potential way to increase the translational significance of studies into myocardial infarction.

Apoptosis and long non-coding RNAs: Focus on their roles in Heart diseases

Heart disease is one of the principal death reasons around the world and there is a growing requirement to discover novel healing targets that have the potential to avert or manage these illnesses. On the other hand, apoptosis is a strongly controlled, cell removal procedure that has a crucial part in numerous cardiac problems, such as reperfusion injury, MI (myocardial infarction), consecutive heart failure, and inflammation of myocardium. Completely comprehending the managing procedures of cell death signaling is critical as it is the primary factor that influences patient mortality and morbidity, owing to cardiomyocyte damage. Indeed, the prevention of heart cell death appears to be a viable treatment approach for heart illnesses. According to current researches, a number of long non-coding RNAs cause the heart cells death via different methods that are embroiled in controlling the activity of transcription elements, the pathways that signals transmission within cells, small miRNAs, and the constancy of proteins. When there is too much cell death in the heart, it can cause problems like reduced blood flow, heart damage after restoring blood flow, heart disease in diabetics, and changes in the heart after reduced blood flow. Therefore, studying how lncRNAs control apoptosis could help us find new treatments for heart diseases. In this review, we present recent discoveries about how lncRNAs are involved in causing cell death in different cardiovascular diseases.

Beneficial Effects of Halogenated Anesthetics in Cardiomyocytes: The Role of Mitochondria

In the last few years, the use of anesthetic drugs has been related to effects other than those initially related to their fundamental effect, hypnosis. Halogenated anesthetics, mainly sevoflurane, have been used as a therapeutic tool in patients undergoing cardiac surgery, thanks to the beneficial effect of the cardiac protection they generate. This effect has been described in several research studies. The mechanism by which they produce this effect has been associated with the effects generated by anesthetic preconditioning and postconditioning. The mechanisms by which these effects are induced are directly related to the modulation of oxidative stress and the cellular damage generated by the ischemia/reperfusion procedure through the overexpression of different enzymes, most of them included in the Reperfusion Injury Salvage Kinase (RISK) and the Survivor Activating Factor Enhancement (SAFE) pathways. Mitochondria is the final target of the different routes of pre- and post-anesthetic conditioning, and it is preserved from the damage generated in moments of lack of oxygen and after the recovery of the normal oxygen concentration. The final consequence of this effect has been related to better cardiac function in this type of patient, with less myocardial damage, less need for inotropic drugs to achieve normal myocardial function, and a shorter hospital stay in intensive care units. The mechanisms through which mitochondrial homeostasis is maintained and its relationship with the clinical effect are the basis of our review. From a translational perspective, we provide information regarding mitochondrial physiology and physiopathology in cardiac failure and the role of halogenated anesthetics in modulating oxidative stress and inducing myocardial conditioning.

The roles of intracellular proteolysis in cardiac ischemia-reperfusion injury

Ischemic heart disease remains a leading cause of human mortality worldwide. One form of ischemic heart disease is ischemia-reperfusion injury caused by the reintroduction of blood supply to ischemic cardiac muscle. The short and long-term damage that occurs due to ischemia-reperfusion injury is partly due to the proteolysis of diverse protein substrates inside and outside of cardiomyocytes. Ischemia-reperfusion activates several diverse intracellular proteases, including, but not limited to, matrix metalloproteinases, calpains, cathepsins, and caspases. This review will focus on the biological roles, intracellular localization, proteolytic targets, and inhibitors of these proteases in cardiomyocytes following ischemia-reperfusion injury. Recognition of the intracellular function of each of these proteases includes defining their activation, proteolytic targets, and their inhibitors during myocardial ischemia-reperfusion injury. This review is a step toward a better understanding of protease activation and involvement in ischemic heart disease and developing new therapeutic strategies for its treatment.

Mn(III) Porphyrin, MnTnBuOE-2-PyP5+, Commonly Known as a Mimic of Superoxide Dismutase Enzyme, Protects Cardiomyocytes from Hypoxia/Reoxygenation Induced Injury via Reducing Oxidative Stress

Myocardial ischemia-reperfusion injury (I/R) causes damage to cardiomyocytes through oxidative stress and apoptosis. We investigated the cardioprotective effects of MnTnBuOE-2-PyP5+ (BMX-001), a superoxide dismutase mimic, in an in vitro model of I/R injury in H9c2 cardiomyocytes. We found that BMX-001 protected against hypoxia/reoxygenation (H/R)-induced oxidative stress, as evident by a significant reduction in intracellular and mitochondrial superoxide levels. BMX-001 pre-treatment also reduced H/R-induced cardiomyocyte apoptosis, as marked by a reduction in TUNEL-positive cells. We further demonstrated that BMX-001 pre-treatment significantly improved mitochondrial function, particularly O2 consumption, in mouse adult cardiomyocytes subjected to H/R. BMX-001 treatment also attenuated cardiolipin peroxidation, 4-hydroxynonenal (4-HNE) level, and 4-HNE adducted proteins following H/R injury. Finally, the pre-treatment with BMX-001 improved cell viability and lactate dehydrogenase (LDH) activity in H9c2 cells following H/R injury. Our findings suggest that BMX-001 has therapeutic potential as a cardioprotective agent against oxidative stress-induced H/R damage in H9c2 cardiomyocytes.

Tumor Necrosis Factor Family Members and Myocardial Ischemia-Reperfusion Injury: State of the Art and Therapeutic Implications

Ischemic heart disease is the principal cause of death worldwide and clinically manifests as myocardial infarction (MI), stable angina, and ischemic cardiomyopathy. Myocardial infarction is defined as an irreversible injury due to severe and prolonged myocardial ischemia inducing myocardial cell death. Revascularization is helpful in reducing loss of contractile myocardium and improving clinical outcome. Reperfusion rescues myocardium from cell death but also induces an additional injury called ischemia-reperfusion injury. Multiple mechanisms are involved in ischemia-reperfusion injury, such as oxidative stress, intracellular calcium overload, apoptosis, necroptosis, pyroptosis, and inflammation. Various members of the tumor necrosis factor family play a key role in myocardial ischemia-reperfusion injury. In this article, the role of TNFα, CD95L/CD95, TRAIL, and the RANK/RANKL/OPG axis in the regulation of myocardial tissue damage is reviewed together with their potential use as a therapeutic target.

MRTF-A alleviates myocardial ischemia reperfusion injury by inhibiting the inflammatory response and inducing autophagy

Myocardin-related transcription factor A (MRTF-A) has an inhibitory effect on myocardial infarction; however, the mechanism is not clear. This study reveals the mechanism by which MRTF-A regulates autophagy to alleviate myocardial infarct-mediated inflammation, and the effect of silent information regulator 1 (SIRT1) on the myocardial protective effect of MRTF-A was also verified. MRTF-A significantly decreased cardiac damage induced by myocardial ischemia. In addition, MRTF-A decreased NLRP3 inflammasome activity, and significantly increased the expression of autophagy protein in myocardial ischemia tissue. Lipopolysaccharide (LPS) and 3-methyladenine (3-MA) eliminated the protective effects of MRTF-A. Furthermore, simultaneous overexpression of MRTF-A and SIRT1 effectively reduced the injury caused by myocardial ischemia; this was associated with downregulation of inflammatory factor proteins and when upregulation of autophagy-related proteins. Inhibition of SIRT1 activity partially suppressed these MRTF-A-induced cardioprotective effects. SIRT1 has a synergistic effect with MRTF-A to inhibit myocardial ischemia injury through reducing the inflammation response and inducing autophagy.

Progranulin (PGRN) as a regulator of inflammation and a critical factor in the immunopathogenesis of cardiovascular diseases

Immune dysregulation has been identified as a critical cause of the most common types of cardiovascular diseases (CVDs). Notably, the innate and adaptive immune responses under physiological conditions are typically regulated with high sensitivity to avoid the exacerbation of inflammation, but any dysregulation can probably be associated with CVDs. In this respect, progranulin (PGRN) serves as one of the main components of the regulation of inflammatory processes, which significantly contributes to the immunopathogenesis of such disorders. PGRN has been introduced among the secreted growth factors as one related to wound healing, inflammation, and human embryonic development, as well as a wide variety of autoimmune diseases. The relationship between the serum PGRN and TNF-α ratio with the spontaneous bacterial peritonitis constitute one of the independent predictors of these conditions. The full-length PGRN can thus effectively reduce the calcification of valve interstitial cells, and the granulin precursor (GRN), among the degradation products of PGRN, can be beneficial. Moreover, it was observed that, PGRN protects the heart against ischemia-reperfusion injury. Above all, PGRN also provides protection in the initial phase following myocardial ischemia-reperfusion injury. The protective impact of PGRN on this may be associated with the early activation of the PI3K/Akt signaling pathway. PGRN also acts as a protective factor in hyperhomocysteinemia, probably by down-regulating the wingless-related integration site Wnt/β-catenin signaling pathway. Many studies have further demonstrated that SARS-CoV-2 (COVID-19) has dramatically increased the risks of CVDs due to inflammation, so PGRN has drawn much more attention among scholars. Lysosomes play a pivotal role in the inflammation process, and PGRN is one of the key regulators in their functioning, which contributes to the immunomodulatory mechanism in the pathogenesis of CVDs. Therefore, investigation of PGRN actions can help find new prospects in the treatment of CVDs. This review aims to summarize the role of PGRN in the immunopathogenesis of CVD, with an emphasis on its treatment.

Enhancing Techniques for Determining Inflammatory Edema Formation and Neutrophil Accumulation in Murine Skin

Inflammatory edema formation and polymorphonuclear leukocyte (neutrophil) accumulation are common components of cutaneous vascular inflammation, and their assessment is a powerful investigative and drug development tool but typically requires independent cohorts of animals to assess each. We have established the use of a mathematical formula to estimate the ellipsoidal-shaped volume of the edematous wheal or bleb after intradermal injections of substances in mice pretreated intravenously with Evans blue dye (which binds to plasma albumin) to act as an edema marker. Whereas previous extraction of Evans blue dye with formamide is suitable for all strains of mice, we report this quicker and more reliable assessment of edema volume in situ. This therefore allows neutrophil accumulation to be assessed from the same mouse using the myeloperoxidase assay. Importantly, we examined the influence of Evans blue dye on the spectrometry readout at the wavelength at which myeloperoxidase activity is measured. The results indicate that it is feasible to quantify edema formation and neutrophil accumulation in the same mouse skin site. Thus, we show techniques that can assess edema formation and neutrophil accumulation at the same site in the same mouse, allowing paired measurements and reducing the total use of mice by 50%.

miR-1322 protects against the myocardial ischemia via LRP8/PI3K/AKT pathway

INTRODUCTION

Myocardial infarction is a fatal disease that causes millions of deaths worldwide every year. The damage and recovery of cardiomyocytes are closely related to changes in gene expression. miRNA may be a new therapeutic target of myocardial ischemia-reperfusion.

METHODS

The differential expression genes were analyzed based on GSE83500, GSE60993 and GSE154733. miRNA expression profile data and clinical data were downloaded from GSE76591. Bioinformatics analysis including limma package, cluster analysis, WGCNA analysis were performed. H9c2 cell hypoxia model and mouse myocardial ischemia model were established. Q-PCR, Western blot and luciferase assay were carried out.

RESULTS

miR-1322 was identified as a significantly differentially expressed miRNA in myocardial ischemi. Yin Yang 1(YY1) was significantly highly expressed in cells with hypoxia treatment (P < 0.05), and myocardial ischemia mice (P < 0.01), which was identified as the transcription factor of miR-1322. The protein expression of LRP8 was lower in cells with hypoxia treatment and myocardial ischemia mice (P < 0.05) and LRP8 was the target gene of miR-1322. The overexpression of LRP8 could significantly increase the expression of p-PI3K, p-AKT, and P70 S6K (P < 0.05). LRP8 regulated PI3K/AKT/P70 S6K signaling pathway, eventually resulting in cell apoptosis.

CONCLUSION

Our results suggested that miR-1322 can protect against the myocardial ischemia via LRP8/PI3K/AKT pathway.

Role of AMPK in Myocardial Ischemia-Reperfusion Injury-Induced Cell Death in the Presence and Absence of Diabetes

Recent studies indicate cell death is the hallmark of cardiac pathology in myocardial infarction and diabetes. The AMP-activated protein kinase (AMPK) signalling pathway is considered a putative salvaging phenomenon, plays a decisive role in almost all cellular, metabolic, and survival functions, and therefore entails precise regulation of its activity. AMPK regulates various programmed cell death depending on the stimuli and context, including autophagy, apoptosis, necroptosis, and ferroptosis. There is substantial evidence suggesting that AMPK is down-regulated in cardiac tissues of animals and humans with type 2 diabetes or metabolic syndrome compared to non-diabetic control and that stimulation of AMPK (physiological or pharmacological) can ameliorate diabetes-associated cardiovascular complications, such as myocardial ischemia-reperfusion injury. Furthermore, AMPK is an exciting therapeutic target for developing novel drug candidates to treat cell death in diabetes-associated myocardial ischemia-reperfusion injury. Therefore, in this review, we summarized how AMPK regulates autophagic, apoptotic, necroptotic, and ferroptosis pathways in the context of myocardial ischemia-reperfusion injury in the presence and absence of diabetes.

Cytoplasmic sequestration of p53 by lncRNA-CIRPILalleviates myocardial ischemia/reperfusion injury

Myocardial ischemia/reperfusion (MI/R) injury is a pathological process that seriously affects the health of patients with coronary artery disease. Long non-coding RNAs (lncRNAs) represents a new class of regulators of diverse biological processes and disease conditions, the study aims to discover the pivotal lncRNA in MI/R injury. The microarray screening identifies a down-regulated heart-enriched lncRNA-CIRPIL (Cardiac ischemia reperfusion associated p53 interacting lncRNA, lncCIRPIL) from the hearts of I/R mice. LncCIRPIL inhibits apoptosis of cultured cardiomyocytes exposed to anoxia/reoxygenation (A/R). Cardiac-specific transgenic overexpression of lncCIRPIL alleviates I/R injury in mice, while knockout of lncCIRPIL exacerbates cardiac I/R injury. LncCIRPIL locates in the cytoplasm and physically interacts with p53, which leads to the cytoplasmic sequestration and the acceleration of ubiquitin-mediated degradation of p53 triggered by E3 ligases CHIP, COP1 and MDM2. p53 overexpression abrogates the protective effects of lncCIRPIL. Notably, the human fragment of conserved lncCIRPIL mimics the protective effects of the full-length lncCIRPIL on cultured human AC16 cells. Collectively, lncCIRPIL exerts its cardioprotective action via sequestering p53 in the cytoplasm and facilitating its ubiquitin-mediated degradation. The study highlights a unique mechanism in p53 signal pathway and broadens our understanding of the molecular mechanisms of MI/R injury.

Poncirin ameliorates cardiac ischemia-reperfusion injury by activating PI3K/AKT/PGC-1α signaling

Poncirin, a flavonoid glycoside derivative extracted from the fruits of Poncirus trifoliata (trifoliate orange or Chinese bitter orange), has a variety of documented bioactivities, including anti-tumor, anti-inflammatory, and antioxidant effects. Oxidative stress is a major underlying factor in the pathogenesis of cardiac ischemia-reperfusion (I/R) injury. Therefore, we investigated the protective efficacy of poncirin on primary cardiomyocytes subjected to anoxia-reoxygenation (A/R) injury in vitro, and on rat hearts subjected to ischemia-reperfusion (I/R) injury in vivo. Poncirin pretreatment enhanced cardiomyocyte survival, inhibited A/R-induced oxidative stress by upregulating cellular antioxidant capacity, suppressed mitochondrial depolarization, and ultimately inhibited apoptosis. Similarly, systemic poncirin treatment significantly reduced cardiomyocyte apoptosis and infarct size in rat hearts. In addition, activity of the PI3K/AKT/PGC-1α pathway was significantly increased by poncirin pretreatment in both A/R and I/R injury models, while PI3K and PGC-1α inhibitors abolished all poncirin related effects, suggesting that this pathway is essential for the cardioprotective effects of poncirin. Pretreatment with the PGC-1α inhibitor reversed effects of poncirin without affecting p-AKT expression, indicating that PGC-1α is downstream of AKT. In conclusion, both in vitro and in vivo studies suggested that poncirin alleviates cardiac ischemia-reperfusion injury by mitigating oxidative stress, which is dependent on activation of the PI3K/AKT/PGC-1α signaling pathway.

Protective effects of syringic acid on inflammation, apoptosis and intestinal barrier function in Caco-2 cells following oxygen-glucose deprivation/reoxygenation-induced injury

Syringic acid (SA) is an abundant phenolic acid compound that has been demonstrated to yield therapeutic benefits in myocardial and renal ischemia/reperfusion (I/R). However, the role of SA in intestinal I/R injury is unclear. Thus, the present study aimed to investigate the protective effect of SA against intestinal I/R injury. Caco-2 cells were incubated with different doses of SA before oxygen-glucose deprivation/reoxygenation (OGD/R) induction. The viability of Caco-2 cells, the activity of lactate dehydrogenase (LDH), the production of pro-inflammatory cytokines and the levels of reactive oxygen species, superoxide dismutase and malondialdehyde were measured. Apoptosis was evaluated using a TUNEL assay and western blotting. Transepithelial electrical resistance and western blotting were performed to evaluate intestinal barrier function in Caco-2 cells. The present study revealed that pretreatment with SA significantly increased cell viability and reduced LDH release in Caco-2 cells subjected to OGD/R treatment. In addition, SA suppressed OGD/R-induced inflammatory responses by reducing pro-inflammatory cytokine levels. Furthermore, the levels of oxidative stress and apoptosis were ameliorated by SA. SA also alleviated the intestinal barrier disruption exhibited by Caco-2 cells after OGD/R injury. Overall, the present study revealed that SA may potentially protect Caco-2 cells from OGD/R injury, and that this effect may be attributed to its anti-inflammatory and anti-apoptotic activities, as well as its ability to protect the function of the intestinal barrier.

Emerging roles of circRNAs in the pathological process of myocardial infarction

Myocardial infarction (MI) is defined as cardiomyocyte death in a clinical context consistent with ischemic insult. MI remains one of the leading causes of morbidity and mortality worldwide. Although there are a number of effective clinical methods for the diagnosis and treatment of MI, further investigation of novel biomarkers and molecular therapeutic targets is required. Circular RNAs (circRNAs), novel non-coding RNAs, have been reported to function mainly by acting as microRNA (miRNA) sponges or binding to RNA-binding proteins (RBPs). The circRNA-miRNA-mRNA (protein) regulatory pathway regulates gene expression and affects the pathological mechanisms of various diseases. Undoubtedly, a more comprehensive understanding of the relationship between MI and circRNA will lay the foundation for the development of circRNA-based diagnostic and therapeutic strategies for MI. Therefore, this review summarizes the pathophysiological process of MI and various approaches to measure circRNA levels in MI patients, tissues, and cells; highlights the significance of circRNAs in the regulation MI pathogenesis and development; and provides potential clinical insight for the diagnosis, prognosis, and treatment of MI.

IL-22 ameliorated cardiomyocyte apoptosis in cardiac ischemia/reperfusion injury by blocking mitochondrial membrane potential decrease, inhibiting ROS and cytochrome C

Irreversible cardiomyocyte death is one of the main reasons of heart failure following cardiac injury. Therefore, controlling cardiomyocyte death is an effective method to delay the progression of cardiac disease after injury. IL-22 plays critical roles in tissue homeostasis and repair, and has become an important bridge between the immune system and specific tissues or organs. However, whether IL-22 can prevent of cardiomyocyte apoptosis from cardiac injury remains unclear. Therefore, the present work would address the above question. Our results showed that, in vitro, IL-22 prevented cardiomyocyte apoptosis induced by Angiotensin II via enhancing the activity of SOD, blocking the decrease of mitochondrial membrane potential, inhibiting ROS production and release of cytochrome C. The similar results were also found in vivo and patients. Our results shed a light on the therapy of cardiac injury.

Ethyl pyruvate: A newly discovered compound against ischemia-reperfusion injury in multiple organs

Ischemia-reperfusion injury (IRI) is a process whereby an initial ischemia injury and subsequent recovery of blood flow, which leads to the propagation of an innate immune response and the changes of structural and functional of multiple organs. Therefore, IRI is considered to be a great challenge in clinical treatment such as organ transplantation or coronary angioplasty. In recent years, ethyl pyruvate (EP), a derivative of pyruvate, has received great attention because of its stability and low toxicity. Previous studies have proved that EP has various pharmacological activities, including anti-inflammation, anti-oxidative stress, anti-apoptosis, and anti-fibrosis. Compelling evidence has indicated EP plays a beneficial role in a variety of acute injury models, such as brain IRI, myocardial IRI, renal IRI, and hepatic IRI. Moreover, EP can not only effectively inhibit multiple IRI-induced pathological processes, but also improve the structural and functional lesion of tissues and organs. In this study, we review the recent progress in the research on EP and discuss their implications for a better understanding of multiple organ IRI, and the prospects of targeting the EP for therapeutic intervention.

Macrophages induce the expression of lncRNA ATB via the secretion of TGF-β to relieve ischemia-reperfusion injury in cardiomyocytes

Cardiac ischemia-reperfusion can cause severe damage to cardiomyocytes. Previous studies have revealed that TGF-β can alleviate ischemia-reperfusion injury in cardiomyocytes by inducing the expression of long non-coding RNA (lncRNA) activated by TGF-β (ATB). However, M2 macrophages can secrete a large amount of TGF-β. However, whether M2 macrophages alleviate the ischemia-reperfusion-induced injury of cardiomyocytes by secreting TGF-β is unclear. In the present study, macrophages and cardiomyocytes were cultured under oxygen-glucose deprivation/reoxygenation (OGD/R) conditions to simulate ischemia-reperfusion injury. M2-type macrophage markers (IL-10, Arginase-1 and IL-13) were validated using reverse transcription-quantitative PCR and western blotting. Subsequently, the culture medium of M2-type macrophages was collected for the treatment of cardiomyocytes, which were cultured under OGD/R conditions. The levels of inflammatory factors and oxidase enzymes were detected with ELISA. The apoptotic rates of cardiomyocytes were detected by flow cytometry. The expression of cell apoptosis-related proteins and the phosphorylation levels of NF-κB were analyzed by western blotting. The expression levels of specific inflammatory cytokines and the levels of malondialdehyde and lactate dehydrogenase were suppressed in cardiomyocytes following treatment with culture medium derived from M2-type macrophages, which were cultured under OGD/R conditions. Furthermore, OGD/R-induced apoptosis of cardiomyocytes was also relieved following treatment of the cells with macrophage medium. It was found that M2-type macrophages could secrete TGF-β and that the culture medium of M2-type macrophages could activate the expression of lncRNA ATB in cardiomyocytes. TGF-β secreted by M2 macrophages relieved the inflammatory response, oxidative stress and apoptosis of cardiomyocytes by inducing the expression of lncRNA ATB.

A nephroprotective iodinated contrast agent with cardioprotective properties: A pilot study

BACKGROUND AND PURPOSE

Evaluation and treatment of acute ischemic syndromes, in the heart and brain, require vessel visualization by iodinated X-ray contrast agents. However, these contrast agents can induce injury, in both the kidneys and target organs themselves. Sulfobutylether beta cyclodextrin (SBECD) added to iohexol (SBECD-iohexol) (Captisol Enabled-iohexol, Ligand Pharmaceuticals, Inc, San Diego, CA) is currently in clinical trials in cardiovascular procedures, to determine its relative renal safety in high-risk patients. Preclinical studies showed that SBECD-iohexol reduced contrast-induced acute kidney injury in rodent models by blocking apoptosis. The current study was undertaken to determine whether SBECD-iohexol is also cardioprotective, in the male rat ischemia-reperfusion model, compared to iohexol alone.

METHODS

After anesthesia, the left coronary artery was ligated for 30 min and the ligation released and reperfusion followed for 2 h prior to sacrifice. Groups 1-4 were injected in the tail vein 10 min prior to ischemia with: (1) vehicle; (2) iohexol; (3) SBECD; and (4) SBECD-iohexol. Infarct size, hemodynamics, and serum markers were measured.

RESULTS

An eight-fold increase in serum creatine kinase in the iohexol-alone group was observed, compared with no increase in the SBECD-iohexol group. The mean arterial pressure and rate pressure product were depressed in the iohexol-alone group, but not in the SBECD-iohexol group, or controls. No difference in infarct size or serum creatinine among the groups was observed.

CONCLUSION

The results of this study suggest that SBECD-iohexol is superior to iohexol alone, for both the preservation of cardiomyocyte integrity and preservation of myocardial function in myocardial ischemia.

Cardiac Shock Wave Therapy Alleviates Hypoxia/Reoxygenation-Induced Myocardial Necroptosis by Modulating Autophagy

Regulated necrosis (necroptosis) is crucially involved in cardiac ischaemia-reperfusion injury (MIRI). The aim of our study is to investigate whether shock wave therapy (SWT) is capable of exerting protective effects by inhibiting necroptosis during myocardial ischaemia-reperfusion (I/R) injury and the possible role of autophagy in this process. We established a hypoxia/reoxygenation (H/R) model in vitro using HL-1 cells to simulate MIRI. MTS assays and LDH cytotoxicity assay were performed to measure cell viability and cell damage. Annexin V/PI staining was used to determine apoptosis and necrosis. Western blotting was performed to assess the changes in cell signaling pathways associated with autophagy, necroptosis, and apoptosis. Reactive oxygen species (ROS) production was detected using DHE staining. Autophagosome generation and degradation (autophagic flux) were analysed using GFP and RFP tandemly tagged LC3 (tfLC3). HL-1 cells were then transfected with p62/SQSTM1 siRNA in order to analyse its role in cardioprotection. Our results revealed that SWT increased cell viability in the H/R model and decreased receptor-interacting serine/threonine-protein kinase 1 (RIPK1) and RIPK3 expression. ROS production was also inhibited by SWT. Moreover, SWT decreased Beclin1 expression and the ratio of LC3-II/LC3-I following H/R. Simultaneously, in the tfLC3 assay, the SWT provoked a decrease in the cumulative autophagosome abundance. siRNA-mediated knockdown of p62 attenuated H/R-induced necroptosis, and SWT did not exert additive effects. Taken together, SWT ameliorated H/R injury by inhibiting necroptosis. SWT also relieved the blockade of autophagic flux in response to H/R injury. The restoration of autophagic flux by SWT might contribute to its cardioprotective effect on necroptosis following H/R injury.

Mouse models of atherosclerosis and their suitability for the study of myocardial infarction

Atherosclerotic plaques impair vascular function and can lead to arterial obstruction and tissue ischaemia. Rupture of an atherosclerotic plaque within a coronary artery can result in an acute myocardial infarction, which is responsible for significant morbidity and mortality worldwide. Prompt reperfusion can salvage some of the ischaemic territory, but ischaemia and reperfusion (IR) still causes substantial injury and is, therefore, a therapeutic target for further infarct limitation. Numerous cardioprotective strategies have been identified that can limit IR injury in animal models, but none have yet been translated effectively to patients. This disconnect prompts an urgent re-examination of the experimental models used to study IR. Since coronary atherosclerosis is the most prevalent morbidity in this patient population, and impairs coronary vessel function, it is potentially a major confounder in cardioprotective studies. Surprisingly, most studies suggest that atherosclerosis does not have a major impact on cardioprotection in mouse models. However, a major limitation of atherosclerotic animal models is that the plaques usually manifest in the aorta and proximal great vessels, and rarely in the coronary vessels. In this review, we examine the commonly used mouse models of atherosclerosis and their effect on coronary artery function and infarct size. We conclude that none of the commonly used strains of mice are ideal for this purpose; however, more recently developed mouse models of atherosclerosis fulfil the requirement for coronary artery lesions, plaque rupture and lipoprotein patterns resembling the human profile, and may enable the identification of therapeutic interventions more applicable in the clinical setting.

Etomidate alleviates cardiac dysfunction, fibrosis and oxidative stress in rats with myocardial ischemic reperfusion injury

Background

Etomidate has been shown to reduce ischemia/reperfusion (I/R) injury in several tissues. Here we aimed to investigate the protective effects of etomidate on I/R injury in Sprague-Dawley (SD) rats.

Methods

Thirty rats were randomly divided into 5 groups and pretreated with saline or 0.5/1/2 mg/kg etomidate. I/R injury was induced in all groups except the sham control group. After administration with saline or 0.5/1/2 mg/kg etomidate daily for another 27 days, rats were sacrificed and the effects of etomidate were analyzed.

Results

Treatment with etomidate dose dependently improved echocardiography indexes, ameliorated myocardial histological alterations and reduced serum creatine kinase isoenzyme (CK-MB), myoglobin (Mb) and troponin I (cTnl) levels. Fibrosis markers transforming growth factor beta (TGF-β), alpha-smooth muscle actin (α-SMA) and fibronectin was decreased with etomidate treatment. Etomidate also decreased oxidative stress and inflammation in rats, indicated by increased superoxide dismutase (SOD) and glutathione (GSH), and reduced malondialdehyde (MDA) in myocardial tissues, as well as decreased inducible NO synthase (iNOS) and increased interleukin (IL)-10 in both serum and myocardial tissues.

Conclusions

Altogether, we showed that etomidate alleviated I/R injury in rats through reduced cardiac dysfunction, fibrosis and oxidative stress. These results supported the protective role of etomidate to myocardial I/R injury.

2,6-Diisobornyl-4-Methylphenol Reduces Postishemic Myocardium Remodeling in Delayed Period after Ischemia/Reperfusion in Rats

2,6-Diisobornyl-4-methylphenol (Dibornol, 10 mg/kg intragastrically daily for 5 days after myocardial ischemia/reperfusion) 1.5-fold increased rat survival during the acute post-infarction period in comparison with the control group. In survivors, Dibornol reliably prevented post-ischemic progression of heart failure in the delayed post-infarction period (30 days after ischemia/reperfusion), which was seen from an increase in the left-ventricular developed pressure by 22%, left-ventricular contractility index by 19%, and +dP/dt by 34%. Left-ventricular end-diastolic pressure was by 39% lower than in control animals. Morphological study of heart sections from control group animals showed that Dibornol reduced the area of post-ischemic myocardial damage in the delayed period after ischemia/reperfusion to 3±1% (vs 18±2% in the control group).

The Advances on the Protective Effects of Ginsenosides on Myocardial Ischemia and Ischemia-Reperfusion Injury

Ginseng is a traditional medicine with a complex chemical composition, wide bioactivity and unique pharmacological action. Many studies have confirmed that ginsenosides are the active ingredients of ginseng, and ginsenosides have always been the focus of different researchers. With the development of modern separation and analysis technology, more than 150 kinds of ginsenosides have been isolated. The ginsenosides Rb1, Rb2, Rc, Rg1 and Re account for more than 80% of total ginsenosides, and other saponins, such as Rd, Rg3 and Rh2, which are minor constituents, accounting for only a small portion of the total amount. In recent years, ginsenosides have been found to possess strong pharmacological activities, such as antioxidation, clearing of oxygen free radicals, reducing calcium overload and anti-apoptosis. Ginsenosides play a protective role in ischemia-reperfusion injury. This paper reviews the protective effects of ginsenosides on myocardial ischemia and ischemiareperfusion injury.

Exendin-4 Attenuates Remodeling in the Remote Myocardium of Rats After an Acute Myocardial Infarction by Activating β-Arrestin-2, Protein Phosphatase 2A, and Glycogen Synthase Kinase-3 and Inhibiting β-Catenin

PURPOSE

This study tested if the protective anti-remodeling effect of GLP-1 agonist Exendin-4 after an acute myocardial infarction (MI) in rats involves inhibition of the Wnt1/β-catenin signaling pathway.

METHODS

Rats were divided into sham, sham + Exendin-4 (10 μg/day, i.p), MI, and MI + Exendin-4. MI was introduced to rats by permanent left anterior descending coronary artery (LAD) ligation.

RESULTS

On day 7 post-infraction, MI rats showed LV dysfunction with higher serum levels of cardiac markers. Their remote myocardia showed increased mRNA and protein levels of collagen I/III with higher levels of reactive oxygen species (ROS) and inflammatory cytokines, as well as protein levels of Wnt1, phospho-Akt, transforming growth factor (TGF-β1), Smad, phospho-Smad3, α-SMA, caspase-3, and Bax. They also showed higher protein levels of phospho-glycogen synthase kinase-3β (p-GSK3β), as well as total, phosphorylated, and nuclear β-catenin with a concomitant decrease in the levels of cyclic adenosine monophosphate (cAMP), mRNA of manganese superoxide dismutase (MnSOD), and protein levels of Bcl-2, β-arrestin-2, and protein phosphatase-2 (PP2A). Administration of Exendin-4 to MI rats reduced the infarct size and reversed the aforementioned signaling molecules without altering protein levels of TGF-1β and Wnt1 or Akt activation. Interestingly, Exendin-4 increased mRNA levels of MnSOD, protein levels of β-arrestin-2 and PP2A, and β-catenin phosphorylation but reduced the phosphorylation of GSK3β and Smad3, and total β-catenin levels in the LV of control rats.

CONCLUSION

Exendin-4 inhibits the remodeling in the remote myocardium of rats following acute MI by attenuating β-catenin activation and activating β-arrestin-2, PP2A, and GSK3β. Graphical Abstract A graphical abstract that illustrates the mechanisms by which Exendin-4 inhibits cardiac remodeling in remote myocardium of left ventricle MI-induced rats. Mechanisms are assumed to occur in the cardiomyocytes and/or other resident cells such as fibroblast. Β-catenin activation and nuclear translocation are associated with increased synthesis of inflammatory cytokines and transforming growth factor β-1 (TGF-β1). GSK3β is inhibited by phosphorylation at Ser⁹. Under normal conditions, β-catenin is degraded in the cytoplasm by the active GSK3β-dependent degradation complex (un-phosphorylated) which usually phosphorylates β-catenin at Ser^33/37/Thr⁴¹. After MI, TGF-β1, and Wnt 1 levels are significantly increased, the overproduction of Wnt1 induces β-catenin stabilization and nuclear translocation through increasing the phosphorylation of disheveled (DVL) protein which in turn phosphorylates and inhibits GSK3β. TGF-β1 stimulates the phosphorylation of Smad-3 and subsequent nuclear translocation to activate the transcription of collage 1/III and α-smooth muscle actin (α-SMA). Besides, TGF-β1 stabilizes cytoplasmic β-catenin levels indirectly by phosphorylation of Akt at Thr³⁰⁸-induced inhibition of GSK3β by increasing phosphorylation of Ser⁹. Exendin-4, and possibly through G protein-coupled receptors (GPCRs), increases levels of cAMP and upregulates β-arrestin-2 levels. Both can result in a positive inotropic effect. Besides, β-arrestin-2 can stimulate PP2A to dephosphorylation Smad3 (inhibition) and GSK3β (activation), thus reduces fibrosis and prevents the activation of β-catenin and collagen deposition.

Bisoprolol, a β1 antagonist, protects myocardial cells from ischemia-reperfusion injury via PI3K/AKT/GSK3β pathway

The aim of this work was to explore whether bisoprolol plays a protective role in cardiomyocytes against ischemia-reperfusion injury via PI3K/AKT/ GSK3β pathway. We pretreated male Sprague Dawley (SD) rats with bisoprolol by oral administration prior to 0.5 h ischemia/4 h reperfusion. Myocardial infarct size and serum levels of cTnI and CK-MB were measured. In vitro, H9c2 cells were treated with hypoxia and reoxygenation, followed by measurement of cell viability, apoptosis, ROS production, cytometry, activities of AKT, GSK3β, and p-38 in the presence and absence of GSK3β siRNA. We found that bisoprolol reduced infarct size from 44% in I/R group to 31% in treated group (P < 0.05). The levels of cTnI and CK-MB were decreased from 286 ± 7 pg/mL and 32.2 ± 2 ng/mL in I/R group to 196 ± 2 pg/mL and 19.6 ± 0.9 ng/mL in the treated group, respectively (P < 0.05). Bisoprolol also increased cell viability while decreased apoptosis and ROS production in the treatment of hypoxia/ reoxygenation. Furthermore, bisoprolol increased AKT and GSK3β phosphorylation, an effect that was immediately eliminated by LY294002. GSK3β-specific siRNA experiment further confirmed that bisoprolol protected the myocardium against hypoxia/reoxygenation-induced injury via suppressing GSK3β activity. In conclusion, bisoprolol protected myocardium against ischemia-reperfusion injury via the PI3K/AKT/ GSK3β pathway.

TRAF5 protects against myocardial ischemia reperfusion injury via AKT signaling

During the processes of myocardial ischemia reperfusion (I/R) injury, inflammation and apoptosis play an important role. I/R and its induced acute myocardial infarction (AMI) with high morbidity and mortality, and there is no effective treatment for it so far. TRAF5 has been shown to regulate inflammation and apoptosis in atherosclerosis, steatosis and melanoma cells, but its function in myocardial I/R injury is still unclear. This study demonstrates that the expression of TRAF5 is significant up-regulation in heart tissues of I/R injury mice and hypoxia/reoxygenation (H/R)-stimulated cardiomyocytes. TRAF5 knockout mice exhibites heavier heart damage, inflammatory response and cell death after myocardial I/R injury. Further, TRAF5 overexpression inhibites inflammation and apoptosis of H/R-stimulated cardiomyocytes. Mechanistically, we prove that TRAF5 promotes the activation of AKT. Overall, our study indicates that TRAF5 can regulate the processes of myocardial I/R injury. TRAF5 can be a new therapy target for myocardial I/R injury.

Mitochondrial and mitochondrial-independent pathways of myocardial cell death during ischaemia and reperfusion injury

Acute myocardial infarction causes lethal injury to cardiomyocytes during both ischaemia and reperfusion (IR). It is important to define the precise mechanisms by which they die in order to develop strategies to protect the heart from IR injury. Necrosis is known to play a major role in myocardial IR injury. There is also evidence for significant myocardial death by other pathways such as apoptosis, although this has been challenged. Mitochondria play a central role in both of these pathways of cell death, as either a causal mechanism is the case of mitochondrial permeability transition leading to necrosis, or as part of the signalling pathway in mitochondrial cytochrome c release and apoptosis. Autophagy may impact this process by removing dysfunctional proteins or even entire mitochondria through a process called mitophagy. More recently, roles for other programmed mechanisms of cell death such as necroptosis and pyroptosis have been described, and inhibitors of these pathways have been shown to be cardioprotective. In this review, we discuss both mitochondrial and mitochondrial‐independent pathways of the major modes of cell death, their role in IR injury and their potential to be targeted as part of a cardioprotective strategy. This article is part of a special Issue entitled ‘Mitochondria as targets of acute cardioprotection’ and emerged as part of the discussions of the European Union (EU)‐CARDIOPROTECTION Cooperation in Science and Technology (COST) Action, CA16225.

Dexmedetomidine protects H9C2 against hypoxia/reoxygenation injury through miR-208b-3p/Med13/Wnt signaling pathway axis

Dexmedetomidine (Dex) has been reported to be cardioprotective. Differential expression of miR-208b-3p is associated with myocardial injury. But it is unknown that aberrant expression of miR-208b-3p is implicated in myocardial protection of Dex. Hypoxia/reoxygenation (HR) model was established in H9C2 cells. qRT-PCR was performed to detect expression levels of miR-208b-3p in H9C2 undergoing HR, Dex preconditioning, overexpression of miR-208b-3p or inhibition, and to assess expression of Med13 in H9C2 following knockdown of Med13 mRNA. CCK8 and, flow cytometry and Western blot were conducted respectively to examine viability, apoptosis rate and protein expressions of H9C2 subjected to a variety of treatments. Dex preconditioning reduced expression of miR-208b-3p and apoptosis of H9C2 cells caused by HR, while Dex preconditioning increased viability of H9C2. Dex preconditioning increased expression of Med13, which was reduced after knockdown of Med13 mRNA in H9C2. Overexpression of miR-208b-3p attenuated Dex exerted protective effects of myocardial cells, which was reversed by inhibition of miR-208b-3p. Increased expression of Med13 or/and decreased expression of miR-208b-3p decreased expression levels of Wnt/β-catenin signaling pathway-related proteins (Wnt3a, Wnt5a and β-catenin), while knockdown of Med13 mRNA or increased expression of miR-208b-3p increased the expression levels of those proteins. Dex protects H9C2 cells against HR injury through miR-208b-3p/Med13/Wnt/β-catenin signaling pathway axis.

IL-20 promotes hypoxia/reoxygenation-induced mitochondrial dysfunction and apoptosis in cardiomyocytes by upregulating oxidative stress by activating the PKC/NADPH oxidase pathway

Acute myocardial infarction (AMI) is the maximum critical cardiovascular event and causes high morbidity and mortality worldwide. The ischemia and reperfusion that occur in AMI cause apoptosis and cellular dysfunction in cardiomyocytes. IL-20, an IL-10 family member, is involved in various inflammatory diseases. Therefore, we sought to elucidate the role of IL-20 in the infarcted heart following ischemia/reperfusion (I/R) injury. We found that IL-20 and its receptors, IL-20R1 and IL-20R2, were increased in H2C2 cardiomyoblast cells and ventricular tissues subjected to hypoxia/reoxygenation (H/R) stimulation. The presence of IL-20 further inhibited the cell viability of H9C2 cells and primary cardiomyocytes. Our results suggested that IL-20 elicited an increase in Ca²⁺ and activation of the PKC/NADPH oxidase pathway, leading to the elevation of oxidase stress and downregulation of AKT. Furthermore, we demonstrated that IL-20 was able to mediate H/R-induced apoptosis via PKC/NADPH oxidase/AKT signaling. Our findings implied that IL-20 was responsive to H/R stress in vitro and in rat hearts undergoing I/R injury, and this upregulation of IL-20 may contribute to the apoptosis of cardiomyocytes.

Circular RNAs as potential theranostics in the cardiac fibrosis

Circular RNAs (circRNAs) are a type of single-stranded RNA molecules that normally do not encode proteins. circRNAs are involved in many physiological processes as well as the pathogenesis of diseases. Cardiac fibrosis is increasingly recognized as a pathological force in advanced heart diseases. A growing number of studies have reported that the occurrence and development of cardiac fibrosis is closely associated with the regulation of circRNAs. This review summarizes the current understanding of circRNA biogenesis and function and will highlight the recent updates regarding the involvement of circRNAs in cardiac fibrosis, and their potential as emerging biomarkers and therapeutic targets.

The Effect of Ginsenoside RB1, Diazoxide, and 5-Hydroxydecanoate on Hypoxia-Reoxygenation Injury of H9C2 Cardiomyocytes

This study was aimed to investigate whether ginsenoside Rb1 (GS-Rb1) from the cardioprotective Chinese medicine ginseng can reduce hypoxia-reoxygenation (HR)-induced damage to cardiomyocytes by protecting the mitochondria. Mitochondria-mediated apoptosis plays a key role during myocardial ischemia-reperfusion injury (MIRI). When MIRI occurs, the continuous opening of the mitochondrial permeability transition pore (mPTP) causes mitochondrial damage and ultimately leads to apoptosis. We treated H9c2 cells, derived from rat embryonic cardiomyoblasts, with GS-Rb1, diazoxide, and 5-hydroxydecanoate (5-HD), using HR to simulate MIRI. We found that GS-Rb1 can reduce mPTP by stabilizing the mitochondrial membrane potential (MMP) and by reducing reactive oxygen species (ROS) during HR. This protects the mitochondria by reducing the release of cytochrome c and the expression of cleaved-caspase-3 in the cytoplasm, ultimately reducing apoptosis. During this process, GS-Rb1 and diazoxide showed similar effects. These findings provide some evidence for a protective effect of GS-Rb1 treatment on MIRI.

Combination of the ginsenosides Rb3 and Rb2 exerts protective effects against myocardial ischemia reperfusion injury in rats

Ginsenoside Rb3 (G-Rb3) has been demonstrated to alleviate myocardial ischemia reperfusion injury (MIRI); however, it is difficult to separate G-Rb2 from its isomer G-Rb3. The current study aimed to compare the cardioprotective effects of G-Rb3 and the concomitant use of G-Rb3 and G-Rb2 (G-Rb3/Rb2) on MIRI in rats. A rat model of MIRI was established by ligation of the left anterior descending coronary artery and the rats were randomly divided into five groups. Prior to MIRI, G-Rb3/Rb2 (20 mg/kg), G-Rb3 (20 mg/kg) and diltiazem (DLZ; 20 mg/kg, as a positive control) were orally administered to the rats once a day for 3 consecutive days. After 30 min of ischemia and 120 min of reperfusion, cardiac function, infarct size, cardiac marker enzymes, antioxidative parameters, inflammatory factors, histopathological changes, cardiomyocyte apoptosis, and B-cell lymphoma 2 (Bcl-2), Bcl-2-associated X protein and caspase-3 expression were determined using a multi-channel physiological recording system, nitrotetrazolium blue chloride, biochemical kits, radioimmunoassay kits, hematoxylin and eosin, terminal deoxynucleotidyl-transferase-mediated dUTP nick end labeling assay, immunohistochemistry and reverse transcription-quantitative PCR, respectively. The results indicated that treatment with G-Rb3/Rb2 significantly protected rats against MIRI, as shown by improved cardiac function, reduced myocardial ischemic area, decreased serum activities of aspartate aminotransferase, lactate dehydrogenase and creatine kinase MB, decreased serum concentrations of interleukin-6 and tumor necrosis factor-α, decreased malondialdehyde concentration in myocardial tissues, increased activities of superoxide dismutase, glutathione peroxidase and catalase in myocardial tissues, reduced histopathological changes in myocardial tissues, reduced number of apoptotic cardiomyocytes, and changes in the expression levels of caspase-3, Bcl-2 and Bax. In addition, the effects of treatment with G-Rb3/Rb2, G-Rb3 or DLZ were equivalent. The protective effects of G-Rb3/Rb2 on MIRI were similar to those of G-Rb3 in terms of oxidative stress, inflammatory factors and inhibition of cardiomyocyte apoptosis. Therefore, G-Rb3/Rb2 may be developed as a concomitant treatment for MIRI.

The Effects of Progranulin in a Rat Model of Acute Myocardial Ischemia/Reperfusion are Mediated by Activation of the P13K/Akt Signaling Pathway

Background

Progranulin is an adipokine, encoded by the progranulin (GRN) gene. Progranulin is expressed in atherosclerosis, but its effects in cardiac ischemia and reperfusion injury are unknown. Therefore, this study aimed to investigate the effects of progranulin in a rat model of acute myocardial ischemia/reperfusion (MI/R) injury in vivo.

Material/Methods

The model of acute MI/R injury was established in male Wistar rats by ligation of the left anterior descending (LAD) coronary artery for 30 minutes and reperfusion for 60 minutes. Before modeling, one group was treated with progranulin (0.03 μg/kg), and one group was treated with the P13K/Akt inhibitor, LY294002 (3 mg/kg). Left ventricular function (LV) was monitored, including the LV systolic pressure (LVSP), LV end-diastolic pressure (LVEDP), and changes in LV pressure. At the end of the study, blood and myocardial tissue were examined. Cardiac biochemical markers, histopathology, gene expression, and apoptosis were analyzed.

Results

Progranulin improved cardiac function following acute MI/R injury and significantly improved recovery of cardiac contractility and LVSP. Progranulin significantly reduced myocyte apoptosis, inflammation, and tissue edema, and was highly expressed in cardiac tissue following MI/R injury. The cardioprotective effect of progranulin was reduced by blocking the P13K/Akt signaling pathway.

Conclusions

In the rat model of acute MI/R injury, progranulin had a protective effect on cardiac function and morphology, associated with activation of the P13K/Akt signaling pathway. The mechanisms of the anti-apoptotic, anti-inflammatory, and inotropic effects of progranulin in the setting of acute MI/R injury require further in vivo studies.

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

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

Effects of Fimasartan/Amlodipine Fixed-Dose Combination on Left Ventricular Systolic Function and Infarct Size in Rat Myocardial Infarction Model

The aim of this study was to evaluate the effects of fimasartan/amlodipine fixed-dosed combination (F/A) on left ventricle (LV) systolic function and infarct size in the rat myocardial infarction (MI) model. We induced MI in 20 rats by ligation of the left anterior descending coronary artery and they were divided into two groups [MI group (n=10) vs. MI+F/A 10 mg/kg group (n=10)]. F/A was administered for 28 days between day-7 and day-35 in the MI+F/A group and echocardiography was performed at day-7 and at day-35 after the induction of MI. Picrosirius red staining was performed to confirm the fibrotic tissue and infarct size was measured using image analysis program for Image J. At the 35-day follow-up, the LV ejection fraction (EF) was significantly higher (38.10±3.92% vs. 29.86±4.56%, p<0.001) and delta (day-35 minus day-7) EF was significantly higher (0.14±2.66% vs. −8.53±2.66%. p<0.001) in the MI+F/A group than the MI group. Systolic blood pressure was significantly lower in the MI+F/A group than the MI group (103.23±13.35 mmHg vs. 123.43±14.82 mmHg, p<0.01). The MI+F/A group had a smaller infarct size (26.84±5.31% vs. 36.79±3.10%, p<0.01) than the MI group at the 35-day follow-up. Oral administration of F/A 10 mg/kg could improve LV systolic function and reduce infarct size in a rat MI model.

Cardioprotective mechanism of FTY720 in ischemia reperfusion injury

Cardioprotection is a very challenging area in the field of cardiovascular sciences. Myocardial damage accounts for nearly 50% of injury due to reperfusion, yet there is no effective strategy to prevent this to reduce the burden of heart failure. During last couple of decades, by combining genetic and bimolecular studies, many new drugs have been developed to treat hypertension, heart failure, and cancer. The use of percutaneous coronary intervention has reduced the mortality and morbidity of acute coronary syndrome dramatically. However, there is no standard therapy available that can mitigate cardiac reperfusion injury, which contributes to up to half of myocardial infarcts. Literature shows that the activation of sphingosine receptors, which are G protein-coupled receptors, induces cardioprotection both in vitro and in vivo. The exact mechanism of this protection is not clear yet. In this review, we discuss the mechanism of ischemia reperfusion injury and the role of the FDA-approved sphingosine 1 phosphate drug fingolimod in cardioprotection.

PLCE1 promotes myocardial ischemia-reperfusion injury in H/R H9c2 cells and I/R rats by promoting inflammation

Myocardial ischemia–reperfusion (I/R) injury is a major contributor to the morbidity and mortality associated with coronary artery disease. How to ensure the recovery of blood supply to ischemic myocardial tissue while avoiding or reducing I/R injury remains a critical problem in clinical practice. In the present study, we examined the function of phospholipase C ϵ-1 (PLCE1) by an H9c2 H/R (H/R, hypoxia–reoxygenation) model and a rat myocardial I/R injury model. The expression of PLCE1 and its effect on I/R injury-induced inflammatory response as well as its possible underlying mechanism were investigated. Our results have shown that PLCE1 was progressively increased along with the increase in hypoxia time in the H/R H9c2 and HL-1 cells. In myocardial I/R rats, PLCE1 presented a low expression level in the sham group, however, it was increased sharply in the I/R group. Overexpression of PLCE1 promoted the expression of IL-6, TNF-α, and IL-1α, and decreased the expression of IL-10. Knockdown of PLCE1 decreased the expression of IL-6, TNF-α, and IL-1α, and increased the expression of IL-10. Furthermore, overexpression of PLCE1 increased the phosphorylation of p38, ERK1/2, and nuclear factor-κ B (NF-κB) P65 while knockdown of PLCE1 inhibited their phosphorylation. In conclusion, the present study provided evidence that PLCE1 was up-regulated in H/R H9c2 cell and I/R rat. Overexpression of PLCE1 promoted the inflammatoion via activation of the NF-κB signaling pathway.

Hydrogen-rich saline alleviates inflammation and apoptosis in myocardial I/R injury via PINK-mediated autophagy

Ischemia/reperfusion (I/R)-induced inflammatory reaction is one of the most important elements in myocardial I/R injury. In addition, autophagy serves an important role in normal cardiac homeostasis, and obstructions to the autophagy process lead to severe consequences for the heart. Hydrogen exerts an effective therapeutic role in numerous diseases associated with I/R injury via its anti-inflammation, anti-apoptosis and anti-oxidative properties. Therefore, the present study investigated the effect of hydrogen on the myocardial inflammation response and apoptosis in myocardial ischemic/reperfusion (MI/R) injury, and further explored the mechanism of PTEN-induced kinase 1 (PINK1)/Parkin-induced mitophagy in the protection of hydrogen on MI/R injury. MI/R injury was performed by surgical ligation of the left coronary artery in vivo and H9C2 cell injury was performed by hypoxia/reoxygenation (H/R) in vitro. Hydrogen-rich saline was administered twice through intraperitoneal injection at a daily dose of 10 ml/kg following the operation in the in vivo model, and hydrogen-rich medium culture was used for cells instead of normal medium in vitro. The infarction size of hearts, the levels of creati-nine kinase-muscle/brain (CK-MB) and cardiac troponin I (cTnI), cardiac function, cell viability and lactate dehydrogenase (LDH) release, levels of cytokines, apoptosis and the expression of autophagy-associated proteins were detected in the different treatment groups in vivo and in vitro. The results demonstrated that treatment with hydrogen improved the myocardial infarction size of hearts, cardiac function, apoptosis and cytokine release following MI/R in rats. In vitro, hydrogen improved cell viability and LDH release following hypoxia/reoxygenation in myocardial cells. In addition, it was demonstrated that hydrogen exerted an anti-inflammatory and anti-apoptotic effect in myocardial cells induced by H/R via PINK1/Parkin mediated autophagy. These results suggested that hydrogen-rich saline alleviated the inflammation response and apoptosis induced by MI/R or H/R in vivo or in vitro, and that hydrogen-rich saline contributed to the increased expression of proteins associated with autophagy. In summary, the present study indicated that treatment with hydrogen-rich saline improved the inflammatory response and apoptosis in MI/R via PINK1/Parkin-mediated mitophagy.

Value of Serum miR-23a, miR-30d, and miR-146a Biomarkers in ST-Elevation Myocardial Infarction

BACKGROUND The aim of this study was to analyze the relative expression level of miR-30d-5p, miR-23a-3p, and miR-146a-5p, and to comprehensively assess the diagnostic and predictive possibilities of these miRNAs. Their expression changes have not yet been sufficiently investigated during acute myocardial infarction. Therefore, it is important to comprehensively assess the diagnostic and predictive possibilities of these micro-ribonucleic acids (miRNAs). MATERIAL AND METHODS Random patients with ST‑elevated myocardial infarction (STEMI) were enrolled into the study group. The control group was comprised of patients with no inflammation or ischemic heart disease who were hospitalized for minor elective surgery. The relative expression level for each miRNA was determined by reverse transcription quantitative polymerase chain reaction (RT-qPCR)-analysis. RESULTS There were 88 participants enrolled into the study: 62 patients were diagnosed with STEMI and there were 26 healthy controls. Expressions of miR-30d-5p, miR-146a-5p, and miR-23a-3p were respectively 1.581-fold, 4.048-fold, and 4.857-fold lower in patients with STEMI compared to the control group patients (all P values were <0.001). Downregulation of miR-23a-3p was significantly negatively correlated with risk scores of GRACE (Global Registry of Acute Coronary Events) and APACHE II (Acute Physiology and Chronic Health Evaluation II). MiR-23a-3p was a fair predictor for STEMI: area under the curve (AUC)=0.806. Cox regression analysis revealed that expression levels of analyzed miRNAs were not significantly associated with negative endpoints at 1 month after the onset of STEMI. CONCLUSIONS All investigated miRNAs were differentially expressed when comparing patients with STEMI and control group individuals. The evaluation of miR-23a-3p expression levels in serum could be useful to assess the severity of STEMI and as a potential diagnostic biomarker of this condition. In addition, miR-23a-3p may provide limited short-term prognostic value for STEMI patients.

MicroRNA‑21 contributes to the puerarin‑induced cardioprotection via suppression of apoptosis and oxidative stress in a cell model of ischemia/reperfusion injury

Puerarin, a major bioactive constituent of the Radix puerariae, can ameliorate myocardial ischemia/reperfusion (I/R) injury. Emerging evidence supports that microRNA (miR)‑21 functions as a protective factor against I/R and/or hypoxia‑reperfusion (H/R)‑induced myocardial injury. However, the role of miR‑21 in the cardioprotective effect of puerarin remains unclear. Therefore, the purpose of the present study was to demonstrate the involvement of miR‑21 in the cardioprotective mechanisms of puerarin using a cell model of I/R injury, generated by culturing rat H9c2 cardiomyocytes under H/R conditions. The results demonstrated that pre‑treatment with puerarin significantly increased cell viability, decreased lactate dehydrogenase activity and upregulated miR‑21 expression in H/R‑treated H9c2 cells. Transfection of an miR‑21 inhibitor led to an increase in H/R‑induced cytotoxicity and reversed the protective effects of puerarin. Additionally, miR‑21 inhibition attenuated the puerarin‑induced decrease in the rate of apoptosis, caspase‑3 activity and the expression of apoptosis regulator Bax, and increased apoptosis regulator Bcl‑2 expression, under H/R conditions. Furthermore, puerarin mitigated H/R‑induced oxidative stress as evidenced by the decrease in endogenous reactive oxygen species production, malondialdehyde content and NADPH oxidase 2 expression, and enhanced the antioxidative defense system as illustrated by the increase in superoxide dismutase activity, catalase and glutathione peroxidase levels. These effects were all eliminated by miR‑21 inhibitor transfection. Furthermore, the miR‑21 inhibitor exacerbated the H/R‑induced oxidative stress and attenuated the antioxidative defense system in H/R‑treated H9c2 cells. Taken together, the results suggested that miR‑21 mediated the cardioprotective effects of puerarin against myocardial H/R injury by inhibiting apoptosis and oxidative stress.