Ischemia/reperfusion injury and cardioprotective mechanisms: Role of mitochondria and reactive oxygen species

MicroRNA-138 attenuates myocardial ischemia reperfusion injury through inhibiting mitochondria-mediated apoptosis by targeting HIF1-α

Myocardial ischemia-reperfusion (I/R) injury is considered to have a detrimental role in coronary heart disease, which is considered to be the leading cause of death worldwide. However, the molecular mechanism involved in the progression of myocardial I/R injury is still unclear. The current study aimed to investigate the expression and function of microRNA (miR)-138 in the process of myocardial I/R injury. First, miR-138 expression levels were analyzed both in myocardium with I/R injury and control myocardium using reverse transcription-quantitative polymerase chain reaction analysis. Then, the relationship between the levels of miR-138 and hypoxia-inducible factor (HIF)1-α was also investigated using a luciferase reporter assay. Assessment of myocardial infarct size, measurements of serum myocardial enzymes and electron microscopy analysis were all utilized to analyse the effect of miR-138 on myocardial I/R injury. The authors of current study also used western blotting to examine the expression levels of the mitochondrial fission-related proteins dynamin-1-like protein and mitochondrial fission 1 protein. It was found that miR-138 is downregulated and HIF1-α is upregulated after myocardial ischemia reperfusion injury. Overexpression of miR-138 reduced myocardial I/R injury-induced infarct sizes and myocardial enzyme levels, and it also inhibited the expression of proteins related to mitochondrial morphology and myocardial I/R-induced mitochondrial apoptosis by targeting HIF1-α. Taken together, these findings provide a novel insight into the molecular mechanism of miR-138 and HIF1-α in the progression of myocardial I/R injury. miR-138 has the potential to become a promising therapeutic target for treating myocardial I/R injury.

Role of reactive oxygen species at reperfusion stage in isoflurane preconditioning-induced neuroprotection

In this in vivo and in vitro study, we aimed to investigate whether isoflurane preconditioning-induced neuronal protection is mediated by reactive oxygen species (ROS) signaling at the reperfusion stage. In the in vivo study, Sprague-Dawley rats were subjected to middle cerebral artery occlusion (MCAO) and in the in vitro study, rat pheochromocytoma (PC12) cells were subjected to oxygen glucose deprivation (OGD). Isoflurane preconditioning was carried out prior to MCAO or OGD and the ROS scavenger, N-2-mercaptopropiopylglycine (2-MPG), was administered at the start of reperfusion. Infarct volume, neurological severity score, and TUNEL staining were analyzed in the in vivo study and cell viability, Bcl-2/Bax ratio, cleaved caspase 3/caspase 3 ratio, and ROS fluorescence intensity were measured in the in vitro study. In the in vivo study, infarct volume, neurological severity score, and TUNEL-positive cell count were significantly decreased with preconditioning but were abrogated by administration of 2-MPG. In the in vitro study, cell viability and Bcl-2/Bax ratio were significantly increased with preconditioning, and cleaved caspase-3/caspase-3 ratio and ROS fluorescence intensity were significantly decreased. Administration of 2-MPG for 10 min abrogated this preconditioning effect, but it did not abolish the protection when administered for 60 min of reperfusion. Isoflurane preconditioning-induced protection was abolished by ROS scavengers at the start of reperfusion, indicating that ROS signaling can mediate the isoflurane preconditioning effect, which suggests that the time window can be important.

Mechanism of nitrite-dependent NO synthesis by human sulfite oxidase

In addition to nitric oxide (NO) synthases, molybdenum-dependent enzymes have been reported to reduce nitrite to produce NO. Here, we report the stoichiometric reduction in nitrite to NO by human sulfite oxidase (SO), a mitochondrial intermembrane space enzyme primarily involved in cysteine catabolism. Kinetic and spectroscopic studies provide evidence for direct nitrite coordination at the molybdenum center followed by an inner shell electron transfer mechanism. In the presence of the physiological electron acceptor cytochrome c, we were able to close the catalytic cycle of sulfite-dependent nitrite reduction thus leading to steady-state NO synthesis, a finding that strongly supports a physiological relevance of SO-dependent NO formation. By engineering SO variants with reduced intramolecular electron transfer rate, we were able to increase NO generation efficacy by one order of magnitude, providing a mechanistic tool to tune NO synthesis by SO.

Investigating and re-evaluating the role of glycogen synthase kinase 3 beta kinase as a molecular target for cardioprotection by using novel pharmacological inhibitors

AIMS

Glycogen synthase kinase 3 beta (GSK3β) link with the mitochondrial Permeability Transition Pore (mPTP) in cardioprotection is debated. We investigated the role of GSK3β in ischaemia (I)/reperfusion (R) injury using pharmacological tools.

METHODS AND RESULTS

Infarct size using the GSK3β inhibitor BIO (6-bromoindirubin-3'-oxime) and several novel analogues (MLS2776-MLS2779) was determined in anaesthetized rabbits and mice. In myocardial tissue GSK3β inhibition and the specificity of the compounds was tested. The mechanism of protection focused on autophagy-related proteins. GSK3β localization was determined in subsarcolemmal (SSM) and interfibrillar mitochondria (IFM) isolated from Langendorff-perfused murine hearts (30'I/10'R or normoxic conditions). Calcium retention capacity (CRC) was determined in mitochondria after administration of the inhibitors in mice and in vitro. The effects of the inhibitors on mitochondrial respiration, reactive oxygen species (ROS) formation, ATP production, or hydrolysis were measured in SSM at baseline. Cyclosporine A (CsA) was co-administered with the inhibitors to address putative additive cardioprotective effects. Rabbits and mice treated with MLS compounds had smaller infarct size compared with control. In rabbits, MLS2776 and MLS2778 possessed greater infarct-sparing effects than BIO. GSK3β inhibition was confirmed at the 10th min and 2 h of reperfusion, while up-regulation of autophagy-related proteins was evident at late reperfusion. The mitochondrial amount of GSK3β was similar in normoxic SSM and IFM and was not altered by I/R. The inhibitors did not affect CRC or respiration, ROS and ATP production/hydrolysis at baseline. The co-administration of CsA ensured that cardioprotection was CypD-independent.

CONCLUSION

Pharmacological inhibition of GSK3β attenuates infarct size beyond mPTP inhibition.

Myocardial Ischemia and Diabetes Mellitus: Role of Oxidative Stress in the Connection between Cardiac Metabolism and Coronary Blood Flow

Ischemic heart disease (IHD) has several risk factors, among which diabetes mellitus represents one of the most important. In diabetic patients, the pathophysiology of myocardial ischemia remains unclear yet: some have atherosclerotic plaque which obstructs coronary blood flow, others show myocardial ischemia due to coronary microvascular dysfunction in the absence of plaques in epicardial vessels. In the cross-talk between myocardial metabolism and coronary blood flow (CBF), ion channels have a main role, and, in diabetic patients, they are involved in the pathophysiology of IHD. The exposition to the different cardiovascular risk factors and the ischemic condition determine an imbalance of the redox state, defined as oxidative stress, which shows itself with oxidant accumulation and antioxidant deficiency. In particular, several products of myocardial metabolism, belonging to oxidative stress, may influence ion channel function, altering their capacity to modulate CBF, in response to myocardial metabolism, and predisposing to myocardial ischemia. For this reason, considering the role of oxidative and ion channels in the pathophysiology of myocardial ischemia, it is allowed to consider new therapeutic perspectives in the treatment of IHD.

Selective mitochondrial superoxide generation in vivo is cardioprotective through hormesis

Reactive oxygen species (ROS) have an equivocal role in myocardial ischaemia reperfusion injury. Within the cardiomyocyte, mitochondria are both a major source and target of ROS. We evaluate the effects of a selective, dose-dependent increase in mitochondrial ROS levels on cardiac physiology using the mitochondria-targeted redox cycler MitoParaquat (MitoPQ). Low levels of ROS decrease the susceptibility of neonatal rat ventricular myocytes (NRVMs) to anoxia/reoxygenation injury and also cause profound protection in an in vivo mouse model of ischaemia/reperfusion. However higher doses of MitoPQ resulted in a progressive alteration of intracellular [Ca²⁺] homeostasis and mitochondrial function in vitro, leading to dysfunction and death at high doses. Our data show that a primary increase in mitochondrial ROS can alter cellular function, and support a hormetic model in which low levels of ROS are cardioprotective while higher levels of ROS are cardiotoxic.

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

BACKGROUND

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

PURPOSE

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

METHODS

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

RESULTS

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

CONCLUSION

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

VEGF-A promotes angiogenesis after acute myocardial infarction through increasing ROS production and enhancing ER stress-mediated autophagy

Proangiogenesis is generally regarded as an effective approach for treating ischemic heart disease. Vascular endothelial growth factor (VEGF)-A is a strong and essential proangiogenic factor. Reactive oxygen species (ROS), endoplasmic reticulum (ER) stress, and autophagy are implicated in the process of angiogenesis. This study is designed to clarify the regulatory mechanisms underlying VEGF-A, ROS, ER stress, autophagy, and angiogenesis in acute myocardial infarction (AMI). A mouse model of AMI was successfully established by occluding the left anterior descending coronary artery. Compared with the sham-operated mice, the microvessel density, VEGF-A content, ROS production, expression of vascular endothelial cadherin, positive expression of 78 kDa glucose-regulated protein/binding immunoglobulin protein (GRP78/Bip), and LC3 puncta in CD31-positive endothelial cells of the ischemic myocardium were overtly elevated. Moreover, VEGF-A exposure predominantly increased the expression of beclin-1, autophagy-related gene (ATG) 4, ATG5, inositol-requiring enzyme-1 (IRE-1), GRP78/Bip, and LC3-II/LC3-I as well as ROS production in the human umbilical vein endothelial cells (HUVECs) in a dose and time-dependent manner. Both beclin-1 small interfering RNA and 3-methyladenine treatment predominantly mitigated VEGF-A-induced tube formation and migration of HUVECs, but they failed to elicit any notable effect on VEGF-A-increased expression of GRP78/Bip. Tauroursodeoxycholic acid not only obviously abolished VEGF-A-induced increase of IRE-1, GRP78/Bip, beclin-1 expression, and LC3-II/LC3-I, but also negated VEGF-A-induced tube formation and migration of HUVECs. Furthermore, N-acetyl- l-cysteine markedly abrogated VEGF-A-increased ROS production, IRE-1, GRP78/Bip, beclin-1 expression, and LC3-II/LC3-I in the HUVECs. Taken together, our data demonstrated that increased spontaneous production of VEGF-A may induce angiogenesis after AMI through initiating ROS-ER stress-autophagy axis in the vascular endothelial cells.

Sphingosine-1-phosphate attenuates hypoxia/reoxygenation-induced cardiomyocyte injury via a mitochondrial pathway

Our previous study showed that Sphingosine-1-phosphate (S1P) could protect cardiomyocytes against hypoxia/reoxygenation (H/R) injury via the JAK-STAT pathway and maintain normal myocardial mitochondria integrity in vivo. However, it is not known yet whether S1P can relieve mitochondrial dysfunction via the mitochondrial apoptotic pathway and its detailed mechanism remains to be investigated. The aim of this study was to demonstrate the mitochondrial protective effects of S1P in a cardiomyocyte H/R injury model. In the present study, we established a H/R model in H9c2 cells. Cell viability was determined by the MTT assay, and apoptosis was evaluated by annexin V-FITC/PI staining. Mitochondrial calcium ion concentration, mitochondrial membrane potential (ΔΨm), opening of the mitochondrial permeability transition pore (mPTP), and release of cytochrome C were detected by laser confocal microscopy. The results showed that S1P inhibited the decrease in cell viability induced by H/R injury and reduced apoptosis. Confocal microscopy showed that S1P prevented loss of ΔΨm, relieved mitochondrial calcium overload, and inhibited opening of the mPTP and release of cytochrome C. The STAT3 inhibitor STATTIC can reverse the antiapoptotic effects of S1P and block the effect of S1P on mitochondria. Taken together, our results indicate that S1P protects cardiomyocytes against H/R injury by relieving mitochondrial dysfunction via the STAT3 pathway.

Imaging assessment of cardioprotection mediated by a dodecafluoropentane oxygen-carrier administered during myocardial infarction

INTRODUCTION

The objective of this study was to investigate the cardioprotective effects of a dodecafluoropentane (DDFP)-based perfluorocarbon emulsion (DDFPe) as an artificial carrier for oxygen delivery to ischemic myocardium, using ^99mTc-duramycin SPECT imaging.

METHODS

Rat hearts with Ischemia-reperfusion (I/R) was prepared by coronary ligation for 45-min followed by reperfusion. The feasibility of ^99mTc-duramycin in detecting myocardial I/R injury and its kinetic profile were first verified in the ischemic hearts with 2-h reperfusion (n = 6). DDFPe (0.6 mL/kg) was intravenously administered at 10 min after coronary ligation in fifteen rats and saline was given in thirteen rats as controls. ^99mTc-duramycin SPECT images were acquired in the DDFPe-treated hearts and saline controls at 2-h (DDFPe-2 h, n = 7 and Saline-2 h, n = 6) or 24-h (DDFPe-24 h, n = 8 and Saline-24 h, n = 7) of reperfusion.

RESULTS

SPECT images, showing "hot-spot" ^99mTc-duramycin uptake in the ischemic myocardium, exhibited significantly lower radioactive retention and smaller hot-spot size in the DDFPe-2 h and DDFPe-24 h hearts compared to controls. The infarcts in the Saline-24 h hearts extended significantly relative to measurements in the Saline-2 h. The extension of infarct size did not reach a statistical difference between the DDFPe-2 h and DDFPe-24 h hearts. Ex vivo measurement of ^99mTc-duramycin activity (%ID/g) was lower in the ischemic area of DDFPe-2 h and DDFPe-24 h than that of the Saline-2 h and Saline-24 h hearts (P < 0.05). The area of injured myocardium, delineated by the uptake of ^99mTc-duramycin, extended more substantially outside the infarct zone in the controls.

CONCLUSIONS

Significant reduction in myocardial I/R injury, as assessed by ^99mTc-duramycin cell death imaging and histopathological analysis, was induced by DDFPe treatment after acute myocardial ischemia. ^99mTc-duramycin imaging can reveal myocardial cell death in ischemic hearts and may provide a tool for the non-invasive assessment of cardioprotective interventions.

GLUT10 maintains the integrity of major arteries through regulation of redox homeostasis and mitochondrial function

Glucose transporter 10 (GLUT10) is a member of the GLUT family of membrane transporters, and mutations in this gene cause arterial tortuosity syndrome (ATS). However, the physiological role and regulation of GLUT10 in arteries remains unclear. To further understand its physiological roles in major arteries, we examined the regulatory mechanisms of GLUT10 in ASMCs and aortic tissues. Interestingly, we find that targeting of GLUT10 to mitochondria is increased in ASMCs under both stress and aging conditions, which enhances dehydroascorbic acid (DHA) uptake and maintains intracellular ascorbic acid (AA) levels. We further demonstrate that the targeting of GLUT10 to mitochondria is important to maintain redox homeostasis, mitochondrial structure and mitochondrial function in ASMCs. A missense mutation of GLUT10 (Glut10G128E) impairs mitochondrial targeting in ASMCs. Consequently, ASMCs isolated from Glut10G128E mice exhibit increased reactive oxygen species (ROS) levels, fragmented mitochondria and impaired mitochondrial function, as well as enhanced cell proliferation and migration. In vivo, mitochondrial structure is altered, and ROS levels are heightened in aortic tissues of Glut10G128E mice. Furthermore, increased number and disorganization of ASMCs, along with progressive arterial wall remodeling were observed in aortic tissues of Glut10G128E mice. These defects were coincident with elevated systolic blood pressure in aged Glut10G128E animals. Our results describe a novel mechanism that GLUT10 targeting to mitochondria under stress and aging condition has a critical role in maintaining AA levels, redox homeostasis and mitochondrial structure and function in ASMCs, which is likely to contribute to the maintenance of healthy vascular tissue.

Exercise and Cardioprotection: A Natural Defense Against Lethal Myocardial Ischemia-Reperfusion Injury and Potential Guide to Cardiovascular Prophylaxis

Similar to ischemic preconditioning, high-intensity exercise has been shown to decrease infarct size following myocardial infarction. In this article, we review the literature on beneficial effects of exercise, exercise requirements for cardioprotection, common methods utilized in laboratories to study this phenomenon, and discuss possible mechanisms for exercise-mediated cardioprotection.

Dual role of inorganic polyphosphate in cardiac myocytes: The importance of polyP chain length for energy metabolism and mPTP activation

We have previously demonstrated that inorganic polyphosphate (polyP) is a potent activator of the mitochondrial permeability transition pore (mPTP) in cardiac myocytes. PolyP depletion protected against Ca²⁺-induced mPTP opening, however it did not prevent and even exacerbated cell death during ischemia-reperfusion (I/R). The central goal of this study was to investigate potential molecular mechanisms underlying these dichotomous effects of polyP on mitochondrial function. We utilized a Langendorff-perfused heart model of I/R to monitor changes in polyP size and chain length at baseline, 20 min no-flow ischemia, and 15 min reperfusion. Freshly isolated cardiac myocytes and mitochondria from C57BL/6J (WT) and cyclophilin D knock-out (CypD KO) mice were used to measure polyP uptake, mPTP activity, mitochondrial membrane potential, respiration and ATP generation. We found that I/R induced a significant decrease in polyP chain length. We, therefore, tested, the ability of synthetic polyPs with different chain length to accumulate in mitochondria and induce mPTP. Both short and long chain polyPs accumulated in mitochondria in oligomycin-sensitive manner implicating potential involvement of mitochondrial ATP synthase in polyP transport. Notably, only short-chain polyP activated mPTP in WT myocytes, and this effect was prevented by mPTP inhibitor cyclosprorin A and absent in CypD KO myocytes. To the contrary, long-chain polyP suppressed mPTP activation, and enhanced ADP-linked respiration and ATP production. Our data indicate that 1) effect of polyP on cardiac function strongly depends on polymer chain length; and 2) short-chain polyPs (as increased in ischemia-reperfusion) induce mPTP and mitochondrial uncoupling, while long-chain polyPs contribute to energy generation and cell metabolism.

HMGB1 and repair: focus on the heart

High-mobility group box 1 (HMGB1) is one of the most abundant proteins in eukaryotes and the best characterized damage-associated molecular pattern (DAMP). The biological activities of HMGB1 depend on its subcellular location, context and post-translational modifications. Inside the nucleus, HMGB1 is engaged in many DNA events such as DNA repair, transcription regulation and genome stability; in the cytoplasm, its main function is to regulate the autophagic flux while in the extracellular environment, it possesses more complicated functions and it is involved in a large variety of different processes such as inflammation, migration, invasion, proliferation, differentiation and tissue regeneration. Due to this pleiotropy, the role of HMGB1 has been vastly investigated in various pathological diseases and a large number of studies have explored its function in cardiovascular pathologies. However, in this contest, the precise mechanism of action of HMGB1 and its therapeutic potential are still very controversial since is debated whether HMGB1 is involved in tissue damage or plays a role in tissue repair and regeneration. The main focus of this review is to provide an overview of the effects of HMGB1 in different ischemic heart diseases and to discuss its functions in these pathological conditions.

Potential therapeutic effect of pomegranate seed oil on ovarian ischemia/reperfusion injury in rats

OBJECTIVES

The aim of this study is to determine the therapeutic effects of pomegranate seed oil, which is a powerful antioxidant and anti-inflammatory agent, on ovarian-ischemia and reperfusion injury in rats.

MATERIALS AND METHODS

Fifty-six female albino Wistar rats were divided into 7 equal groups. Group 1; Sham Operation, Group 2; Ischemia, Group 3; Ischemia + Reperfusion, Group 4; Ischemia + Pomegranate 0,32 ml / kg (IP), Group 5; Ischemia + Pomegranate 0.64 ml / kg, Group 6; Ischemia + Pomegranate 0,32 ml / kg + reperfusion, Group 7; Ischemia + Pomegranate 0,64 ml / kg + reperfusion. Three hours after ischemia and 3 hours after reperfusion, the study was terminated.

RESULTS

While NADPH oxidase activity, MDA and TNF-α levels were significantly increased, SOD activity and GSH levels were reduced in ischemia and I/R groups. Low dose pomegranate seed oil application reduced significantly oxidative stress and NADPH oxidase activity in both ischemic and ischemic/reperfusion groups. At the same time, low-dose pomegranate seed oil extract reduced TNF-α levels and significantly increased antioxidant activity.

CONCLUSION

PSO demonstrated an important therapeutic effect in the treatment of ovarian ischemia and reperfusion injury.

Mitoproteomics: Tackling Mitochondrial Dysfunction in Human Disease

Mitochondria are highly dynamic and regulated organelles that historically have been defined based on their crucial role in cell metabolism. However, they are implicated in a variety of other important functions, making mitochondrial dysfunction an important axis in several pathological contexts. Despite that conventional biochemical and molecular biology approaches have provided significant insight into mitochondrial functionality, innovative techniques that provide a global view of the mitochondrion are still necessary. Proteomics fulfils this need by enabling accurate, systems-wide quantitative analysis of protein abundance. More importantly, redox proteomics approaches offer unique opportunities to tackle oxidative stress, a phenomenon that is intimately linked to aging, cardiovascular disease, and cancer. In addition, cutting-edge proteomics approaches reveal how proteins exert their functions in complex interaction networks where even subtle alterations stemming from early pathological states can be monitored. Here, we describe the proteomics approaches that will help to deepen the role of mitochondria in health and disease by assessing not only changes to mitochondrial protein composition but also alterations to their redox state and how protein interaction networks regulate mitochondrial function and dynamics. This review is aimed at showing the reader how the application of proteomics approaches during the last 20 years has revealed crucial mitochondrial roles in the context of aging, neurodegenerative disorders, metabolic disease, and cancer.

Hepatoprotective effects of limb ischemic post-conditioning in hepatic ischemic rat model and liver cancer patients via PI3K/ERK pathways

The most effective way of treating liver cancer is surgical resection, which usually requires blocking the hepatic portal circulation, and may result in hepatic ischemia-reperfusion injury (HIRI). It is of paramount importance to control HIRI for liver cancer surgical resection. In this study, a 70% ischemia-reperfusion (I/R) model of rat liver was established, and the protective effect and mechanism of limb ischemic post-conditioning (LIPOC) on HIRI was investigated. We show that LIPOC has a protective effect on hepatic ischemia-reperfusion injury in rats, which reduces the elimination of superoxide dismutase, thereby increasing oxygen free radical scavenging, decreasing lipid peroxidation, inhibiting neutrophil aggregation, as well as reducing TNFα, IL1β, and other inflammatory cytokines. In addition, LIPOC inhibited the apoptosis of hepatocytes induced by I/R injury, and decreased the Bax/Bcl-2 ratio. Furthermore, LIPOC promoted the phosphorylation of Akt and ERK1/2. The use of PI3K inhibitor LY294002 and ERK1/2 blocker PD98059 inhibited the phosphorylation of Akt and ERK1/2 caused by LIPOC and abolished the injury protection of liver I/R. Moreover, through 16 cases of hepatocellular carcinoma resections, we found that short-term LIPOC treatment significantly suppressed the elevated alanine aminotransferase, aspartic transaminase, and total bilirubin in the early post-operation of liver resection, and reduced reperfusion injury to the ischemic liver. In summary, our study demonstrates that LIPOC could be an effective method for HIRI in the clinical implementation of liver resection and uncovers the potential mechanism of LIPOC in the protective effects of HIRI.

Ginsenoside Rb3 protects cardiomyocytes against hypoxia/reoxygenation injury via activating the antioxidation signaling pathway of PERK/Nrf2/HMOX1

OBJECTIVES

This study aimed to investigate the pharmacological function and underlying regulation mechanisms of Ginsenoside-Rb3 (G-Rb3) in cardioprotection.

METHODS

Cultured H9C2 cells were pre-treated with gradient concentrations of G-Rb3, and subsequently challenged with hypoxia/reoxygenation (H/R) treatment. The generation of intracellular reactive oxygen species (ROS) and cellular antioxidatant capacity were quantified. Cell apoptosis was measured by flow cytometry. Myocardial ischemia reperfusion injury (MIRI) rat models constructed by coronary artery ligation surgery were orally administrated with G-Rb3 for 5 consecutive days, and then infarction area, apoptosis ratio and total antioxidant capacity (T-AOC) of myocardial tissues were measured. PERK phosphorylation inhibitor GSK2656157 and Nrf2 translocation inhibitor ML385 were co-treated with G-Rb3 to further verify the signaling pathway mediated by G-Rb3.

RESULTS

H/R treatment induced prominent ROS deposition and elevated cell apoptosis ratio in H9C2 cells. G-Rb3 pretreatment suppressed intracellular ROS accumulation and enhanced T-AOC, partially rescuing cardiomyocytes from oxidative stress and apoptosis induced by H/R. In vivo, the cardiac infarction area of MIRI model rats was reduced by G-Rb3 treatment via improved total antioxidant levels. In the further functional and mechanistic studies, G-Rb3 was found to induce PERK phosphorylation and nuclear translocation of transcriptional factor Nrf2, promoting the expression of antioxidative genes such as HMOX1. Inhibitors GSK2656157 and ML385 reversed the effects of G-Rb3.

CONCLUSION

Our studies revealed a novel mechanism of G-Rb3 to attenuates oxidative stress via activating the antioxidation signaling pathway of PERK/Nrf2/HMOX1 in vivo and in vitro, which may help us to enrich the theoretical knewledge of Ginsenoside-Rb3 in cardiopretection.

Treating oxidative stress in heart failure: past, present and future

Advances in cardiovascular research have identified oxidative stress as an important pathophysiological pathway in the development and progression of heart failure. Oxidative stress is defined as the imbalance between the production of reactive oxygen species (ROS) and the endogenous antioxidant defence system. Under physiological conditions, small quantities of ROS are produced intracellularly, which function in cell signalling, and can be readily reduced by the antioxidant defence system. However, under pathophysiological conditions, the production of ROS exceeds the buffering capacity of the antioxidant defence system, resulting in cell damage and death. Over the last decades several studies have tried to target oxidative stress with the aim to improve outcome in patients with heart failure, with very limited success. The reasons as to why these studies failed to demonstrate any beneficial effects remain unclear. However, one plausible explanation might be that currently employed strategies, which target oxidative stress by exogenous inhibition of ROS production or supplementation of exogenous antioxidants, are not effective enough, while bolstering the endogenous antioxidant capacity might be a far more potent avenue for therapeutic intervention. In this review, we provide an overview of oxidative stress in the pathophysiology of heart failure and the strategies utilized to date to target this pathway. We provide novel insights into modulation of endogenous antioxidants, which may lead to novel therapeutic strategies to improve outcome in patients with heart failure.

The Role of Platelets in Ischemic Conditioning

Ischemic heart disease (IHD) is one of the leading causes of death and disability worldwide. Platelets, as the main regulators of hemostasis, are major players in acute myocardial ischemia/reperfusion injury (IRI). Additionally, platelets are modified by endogenous cardioprotective strategies such as ischemic preconditioning, postconditioning, and remote ischemic conditioning. In this article, we provide an overview of the functionional role of platelets in acute myocardial IRI, and highlight their potential as targets for cardioprotection to improve health outcomes in patients with IHD.

MicroRNA-140 attenuates myocardial ischemia-reperfusion injury through suppressing mitochondria-mediated apoptosis by targeting YES1

Myocardial ischemia-reperfusion (I/R) injury is thought to have its detrimental role in coronary heart disease (CHD), which is considered as the foremost cause of death all over the world. However, molecular mechanism in the progression of myocardial I/R injury is still unclear. The goal of this study was to investigate the expression and function of microRNA-140 (miR-140) in the process of myocardial I/R injury. The miR-140 expression level was analyzed in the myocardium with I/R injury and control myocardium using quantitative real-time polymerase chain reaction. Then the relation between the level of miR-140 and YES proto-oncogene 1 (YES1) was also investigated via luciferase reporter assay. Assessment of myocardial infarct size measurement of serum myocardial enzymes and electron microscopy analysis were used for analyzing the effect of miR-140 on myocardial I/R injury. We also used Western blot analysis to examine the expression levels of the mitochondrial fission-related proteins, Drp1 and Fis1. miR-140 is downregulated, and YES1 is upregulated after myocardial I/R injury. Overexpression of miR-140 could reduce the increase related to myocardial I/R injury in infarct size and myocardial enzymes, and it also could inhibit the expression of proteins related to mitochondrial morphology and myocardial I/R-induced mitochondrial apoptosis by targeting YES1. Taken together, these findings may provide a novel insight into the molecular mechanism of miR-140 and YES1 in the progression of myocardial I/R injury. MiR-140 might become a promising therapeutic target for treating myocardial I/R injury.

The protective effects of distal ischemic treatment on apoptosis and mitochondrial permeability in the hippocampus after cardiopulmonary resuscitation

Apoptosis and mitochondrial dysfunction are the main cause of neurological injury after cardiopulmonary resuscitation (CPR). However, the effects of distal ischemic treatments on ischemia induced apoptosis are rarely studied, and the mechanism by which mitochondrial dysfunction contributes to CPR still unclear. A rat model of distal ischemia was established by clipping the right femoral artery. Rats were divided into blank, model, pre distal ischemic treatment, per-treatment, and post-treatment groups. Neurological deficit score was scored to evaluate neurologic function after cardiopulmonary resuscitation for 72 hr. We employed TUNEL and flow cytometry to measure the rate of apoptosis of hippocampal neurons, the integrity of mitochondrial membrane and the degree of mitochondrial permeability transition pore (mPTP) opening. The rate of apoptosis rate of hippocampal CA1 neurons in the pre-treatment and post-treatment groups were significantly lower than that of the model group. Moreover, the integrity of the mitochondrial membrane in the pre-treatment and post-treatment groups was higher than that in the model and per- treatment groups. Furthermore, the degree of mPTP opening was lower in the pre-treatment and post-treatment groups than the untreated and per-treatment groups. Taken together, our results show that ischemic preconditioning and post processing can maintain the integrity of mitochondria, perhaps by inhibiting the opening of mPTP, and reducing apoptosis of hippocampal neurons by regulating expression of apoptosis related proteins after CPR, to improve neurological function. This study highlights a novel target pathway for treatment of CPR.

Oxidative burden in familial hypercholesterolemia

Familial hypercholesterolemia (FH) is a genetic disorder characterized by high serum levels of low-density lipoprotein cholesterol (LDL-c). FH is characterized by accelerated development of atherosclerosis and represents the most frequent hereditary cause of premature coronary heart disease. Mutations of the LDL receptor gene are the genetic signature of FH, resulting in abnormal levels of circulating LDLs. Moreover, FH promotes the generation of reactive oxygen species (ROS) which is another key mechanism involved in atherosclerosis development and progression. The aim of this narrative review is to update the current knowledge on the pathophysiological mechanisms linking FH to ROS generation and their detrimental impact on atherosclerotic pathophysiology. With this purpose, we reviewed experimental and clinical data on the association between FH and OS and the functional role of OS as a promoter of inflammation and atherosclerosis. In this regard, oxidant species such as oxidized LDL, malondialdehyde, ROS, and isoprostanes emerged as leading mediators of the oxidative injury in FH. In conclusion, targeting oxidative stress may be a promising therapeutic strategy to reduce atherogenesis in patients with FH.

Protective Effect of Rosamultin against H2O2-Induced Oxidative Stress and Apoptosis in H9c2 Cardiomyocytes

Rosamultin is one of the main active compounds isolated from Potentilla anserina L., which belongs to a triterpene compound. Few studies have examined the effect of rosamultin on oxidative stress and its molecular mechanism. The aim of this present study was to elucidate the protective effect of rosamultin on H₂O₂-induced oxidative damage and apoptosis in H9c2 cardiomyocytes and its mechanism. The results showed that the pretreatment of rosamultin not only increased cell viability but also reduced the release of LDH and CK. Rosamultin inhibited a H₂O₂-induced decrease in SOD, CAT, and GSH-Px activities and an increase in MDA content. Meanwhile, ROS level, intracellular (Ca²⁺) fluorescence intensity, and apoptosis rate in the rosamultin pretreated group were markedly decreased compared with the model group. Rosamultin pretreatment significantly reversed the morphological changes and attenuated H₂O₂-induced apoptosis. Western blot analysis showed that rosamultin enhanced the expression of Bcl-2 and pCryAB and downregulated the expression of Bax, Cyt-c, Caspase-3, and Caspase-9 expression. Additionally, rosamultin might activate PI3K/Akt signal pathways and CryAB relative factors. Therefore, we suggest that rosamultin could have the potential for treating H₂O₂-induced oxidative stress injury through its antioxidant and antiapoptosis effect.

Ultrafine Particulate Matter Increases Cardiac Ischemia/Reperfusion Injury via Mitochondrial Permeability Transition Pore

Ultrafine particulate matter (UFP) has been associated with increased cardiovascular morbidity and mortality. However, the mechanisms that drive PM-associated cardiovascular disease and dysfunction remain unclear. We examined the impact of oropharyngeal aspiration of 100 μg UFP from the Chapel Hill, NC, air shed in Sprague-Dawley rats on cardiac function, arrhythmogenesis, and cardiac ischemia/reperfusion (I/R) injury using a Langendorff working heart model. We found that exposure to UFP was capable of significantly exacerbating cardiac I/R injury without changing overall cardiac function or major changes in arrhythmogenesis. Cardiac I/R injury was attenuable with administration of cyclosporin A (CsA), suggesting a role for the mitochondrial permeability transition pore (mPTP) in UFP-associated cardiovascular toxicity. Isolated cardiac mitochondria displayed decreased Ca²⁺ buffering before opening of the mPTP. These findings suggest that UFP-induced expansion of cardiac I/R injury may be a result of mPTP Ca²⁺ sensitization resulting in increased mitochondrial permeability transition and potential initiation of mPTP-associated cell death pathways.

Anti-arrhythmogenic and anti-inflammatory effects of troxerutin in ischemia/reperfusion injury of diabetic myocardium

INTRODUCTION

Medicinal plants are increasingly used in the treatment of cardiovascular diseases due to their multifaceted properties. This study was designed to investigate anti-arrhythmic and anti-inflammatory potentials of the natural bioflavonoid, troxerutin (TXR) in myocardial ischemia/reperfusion (I/R) injury in diabetic rats.

METHODS

Male Wistar rats were randomly divided into 4 groups (control, control + TXR [150 mg/kg, daily], diabetic, and diabetic + TXR). Type-1 diabetes was induced by an intraperitoneal injection of streptozotocin (50 mg/kg) and lasted for 10 weeks. After mounting on the Langendorff apparatus, isolated hearts in all groups received a normal Krebs-Henseleit solution for 20 min of stabilization period, followed by 30 min of regional ischemia through ligation of the left anterior descending coronary artery, and 60 min of full reperfusion. During the experiment, the electrocardiograms were recorded and the arrhythmias [number, duration and incidence of premature ventricular complexes (PVC), ventricular tachycardia (VT), ventricular fibrillation (VF), and arrhythmia score] during I/R phases were assessed based on the Lambeth Convention. Ischemic left ventricular samples were used to determine the activities of lactate dehydrogenase (LDH), interleukin-1beta (IL-1β), and tumor necrosis factor (TNF-α).

RESULTS

The arrhythmias induced by I/R were not significantly changed in diabetic group as compared to the control group. However, pretreatment with TXR significantly reduced the number of PVC and duration and incidence of VF in ischemic phase in comparison to the untreated animals (P < 0.05). In addition, the duration, and incidence of most arrhythmias during reperfusion phase were significantly declined by TXR administration in both control and diabetic groups (P < 0.05). Pretreatment of rats with TXR significantly reduced myocardial inflammatory cytokines TNF-α and IL-1β levels after I/R insult in diabetic as well as control hearts (P < 0.05).

CONCLUSION

Preconditioning with TXR could provide cardioprotection by anti-arrhythmic and anti-inflammatory effects against I/R injury in rat hearts. This effect of TXR can introduce this material as a protective agent in cardiovascular diseases.

Cyclic Nucleotide-Directed Protein Kinases in Cardiovascular Inflammation and Growth

Cardiovascular disease (CVD), including myocardial infarction (MI) and peripheral or coronary artery disease (PAD, CAD), remains the number one killer of individuals in the United States and worldwide, accounting for nearly 18 million (>30%) global deaths annually. Despite considerable basic science and clinical investigation aimed at identifying key etiologic components of and potential therapeutic targets for CVD, the number of individuals afflicted with these dreaded diseases continues to rise. Of the many biochemical, molecular, and cellular elements and processes characterized to date that have potential to control foundational facets of CVD, the multifaceted cyclic nucleotide pathways continue to be of primary basic science and clinical interest. Cyclic adenosine monophosphate (cyclic AMP) and cyclic guanosine monophosphate (cyclic GMP) and their plethora of downstream protein kinase effectors serve ubiquitous roles not only in cardiovascular homeostasis but also in the pathogenesis of CVD. Already a major target for clinical pharmacotherapy for CVD as well as other pathologies, novel and potentially clinically appealing actions of cyclic nucleotides and their downstream targets are still being discovered. With this in mind, this review article focuses on our current state of knowledge of the cyclic nucleotide-driven serine (Ser)/threonine (Thr) protein kinases in CVD with particular emphasis on cyclic AMP-dependent protein kinase (PKA) and cyclic GMP-dependent protein kinase (PKG). Attention is given to the regulatory interactions of these kinases with inflammatory components including interleukin 6 signals, with G protein-coupled receptor and growth factor signals, and with growth and synthetic transcriptional platforms underlying CVD pathogenesis. This article concludes with a brief discussion of potential future directions and highlights the importance for continued basic science and clinical study of cyclic nucleotide-directed protein kinases as emerging and crucial controllers of cardiac and vascular disease pathologies.

Delta Opioid Receptors and Cardioprotection

The opioid receptor family, with associated endogenous ligands, has numerous roles throughout the body. Moreover, the delta opioid receptor (DORs) has various integrated roles within the physiological systems, including the cardiovascular system. While DORs are important modulators of cardiovascular autonomic balance, they are well-established contributors to cardioprotective mechanisms. Both endogenous and exogenous opioids acting upon DORs have roles in myocardial hibernation and protection against ischaemia-reperfusion (I-R) injury. Downstream signalling mechanisms governing protective responses alternate, depending on the timing and duration of DOR activation. The following review describes models and mechanisms of DOR-mediated cardioprotection, the impact of co-morbidities and challenges for clinical translation.

Cardioprotection by exenatide: A novel mechanism via improving mitochondrial function involving the GLP-1 receptor/cAMP/PKA pathway

Accumulating evidence suggests that glucagon-like peptide-1 (GLP-1) and its analogues exert cardioprotective effects via modulating cardiomyocyte metabolism. Mitochondria play a pivotal role in the regulation of cell metabolism. It was hypothesized that treatment with exenatide, a GLP-1 analogue, may exert cardioprotective effects by improving mitochondrial function in an in vitro model of hypoxia/reoxygenation (H/R). H9c2 cells were employed to establish an in vitro model of H/R. Exenatide was added to the cells for 30 min prior to exposure to hypoxia. The GLP-1 receptor antagonist exendin‑(9‑39), the cyclic adenosine monophosphate (cAMP) inhibitor Rp-cAMPS and the protein kinase A (PKA) inhibitor H-89 were added to the cells for 10 min prior to treatment with exenatide. The release of lactate dehydrogenase (LDH) and creatine kinase-MB (CK-MB) and cardiomyocyte apoptosis were evaluated. The characteristics of mitochondrial morphology and functions, including ATP synthesis, membrane potential (ΔΨm), mitochondrial permeability transition pore (mPTP), mitochondrial ATPase activity and oxidative stress, were determined. the mitochondrial uncoupling protein-3 (UCP-3) and nuclear respiratory factor-1 (Nrf-1) were also investigated by western blot analysis. Exenatide pretreatment significantly decreased LDH and CK-MB release and cardiomyocyte apoptosis in H9c2 cells subjected to H/R. More importantly, to the best of our knowledge, this is the first report of exenatide pretreatment decreasing mitochondrial abnormalities and reducing oxidative stress, while enhancing ATP synthesis, mitochondrial ATPase activity and ΔΨm in H9c2 cells subjected to H/R. Exenatide pretreatment also decreased mitochondrial calcium overload and inhibited the opening of mPTP in H9c2 cells subjected to H/R. Furthermore, exenatide pretreatment upregulated UCP-3 and Nrf-1 expression in H9c2 cells subjected to H/R. However, the abovementioned observed effects of exenatide were all abolished when exenatide was co-administered with exendin‑(9‑39), Rp-cAMPS and̸or H-89. Therefore, the GLP-1 analogue exenatide was found to exert cardioprotective effects in an in vitro model of H/R, and this cardioprotection may be attributed to the improvement of mitochondrial function. These effects are most likely associated with the activation of the GLP-1 receptor/cAMP/PKA signaling pathway.

Protective role of STVNa in myocardial ischemia reperfusion injury by inhibiting mitochondrial fission

It has been reported that isosteviol, a widely known sweeteners, can protect against myocardial ischemia-reperfusion (IR) injury in isolated guinea pig heart. Here, we aim to confirm the cardioprotective effect of its sodium salt, isosteviol sodium (STVNa), against IR injury and its potential molecular mechanism in H9c2 cardiomyocytes. STVNa significantly improved cell viability, restored mitochondrial membrane potential, decreased cellular reactive oxygen species generation, and inhibited cell apoptosis. Furthermore, STVNa treatment changed the morphology of mitochondria from fragmented, discontinuous forms to normal elongated, tubular forms. Cyto-immunofluorescence and western blot analysis revealed that STVNa inhibited mitochondrial fission proteins dynamin-related protein 1 (Drp1), and mitochondrial fission 1 (Fis1), thus plays a key role in cardioprotection. These findings, for the first time, suggest that STVNa can protect against myocardial IR injury through reverse mitochondrial fission.

Cytochrome c in patients undergoing coronary artery bypass grafting: A post hoc analysis of a randomized trial

PURPOSE

To establish whether plasma cytochrome c is detectable in patients undergoing cardiac surgery, whether cytochrome c levels are associated with lactate/inflammatory markers/cellular oxygen consumption, and whether cytochrome c levels are associated with clinical outcomes.

MATERIALS AND METHODS

This was an observational sub-study of a randomized trial comparing thiamine to placebo in patients undergoing coronary artery bypass grafting. Patients had blood drawn before, after, and again 6h after surgery. Cytochrome c, inflammatory markers, and cellular oxygen consumption were measured.

RESULTS

64 patients were included. Cytochrome c was detectable in 63 (98%) patients at baseline with a median cytochrome c level of 0.18ng/mL (quartiles: 0.13, 0.55). There was no difference from baseline level to post-surgical level (0.19ng/mL [0.09, 0.51], p=0.36) or between post-surgical level and 6-hour post-surgical level (0.17ng/mL [0.10, 0.57], p=0.61). There was no difference between the thiamine and placebo groups' change in cytochrome c levels from baseline to after surgery (p=0.22). Cytochrome c levels were not associated with lactate, inflammatory markers, cellular oxygen consumption, or clinical outcomes.

CONCLUSIONS

Cytochrome c levels did not increase after cardiac surgery and was not associated with the degree of inflammation or clinical outcomes.

The Slo(w) path to identifying the mitochondrial channels responsible for ischemic protection

Mitochondria play an important role in tissue ischemia and reperfusion (IR) injury, with energetic failure and the opening of the mitochondrial permeability transition pore being the major causes of IR-induced cell death. Thus, mitochondria are an appropriate focus for strategies to protect against IR injury. Two widely studied paradigms of IR protection, particularly in the field of cardiac IR, are ischemic preconditioning (IPC) and volatile anesthetic preconditioning (APC). While the molecular mechanisms recruited by these protective paradigms are not fully elucidated, a commonality is the involvement of mitochondrial K⁺ channel opening. In the case of IPC, research has focused on a mitochondrial ATP-sensitive K⁺ channel (mitoK_ATP), but, despite recent progress, the molecular identity of this channel remains a subject of contention. In the case of APC, early research suggested the existence of a mitochondrial large-conductance K⁺ (BK, big conductance of potassium) channel encoded by the Kcnma1 gene, although more recent work has shown that the channel that underlies APC is in fact encoded by Kcnt2 In this review, we discuss both the pharmacologic and genetic evidence for the existence and identity of mitochondrial K⁺ channels, and the role of these channels both in IR protection and in regulating normal mitochondrial function.

Overexpression of Ubiquinol-Cytochrome c Reductase Core Protein 1 May Protect H9c2 Cardiac Cells by Binding with Zinc

In several recent studies, proteomics analyses suggest that increase of ubiquinol-cytochrome c reductase core protein 1 (UQCRC1) is cardio-protective. However, direct evidence for this effect has not yet been obtained. Thus, the current study aimed to determine this effect and the mechanism underlying this effect. The results showed that overexpression of UQCRC1 protected H9c2 cardiac cells against in vitro simulated ischemia-reperfusion by maintaining mitochondrial membrane potential and suppressing the expression of caspase-3. These protective effects were significantly enhanced by exogenous Zn²⁺ but completely abolished by Zn²⁺-selective chelator TPEN. Furthermore, the upregulation of UQCRC1 reduced the concentration of free Zn²⁺ in mitochondria, whereas the downregulation of UQCRC1 increased the concentration of free Zn²⁺ in mitochondria. In conclusion, the overexpression of UQCRC1 can protect H9c2 cardiac cells against simulated ischemia/reperfusion, and this cardio-protective effect is likely mediated by zinc binding.

Protective role of the novel hybrid 3,5-dipalmitoyl-nifedipine in a cardiomyoblast culture subjected to simulated ischemia/reperfusion

This work investigated the acute effects of the calcium channel blocker nifedipine and its new fatty hybrid derived from palmitic acid, 3,5-dipalmitoyl-nifedipine, compared to endocannabinoid anandamide during the process of inducing ischemia and reperfusion in cardiomyoblast H9c2 heart cells. The cardiomyoblasts were treated in 24 or 96-well plates (according to the test being performed) and maintaining the treatment until the end of hypoxia induction. The molecules were tested at concentrations of 10 and 100μM, cells were treated 24h after assembling the experimental plates and immediately before the I/R. Cell viability, apoptosis and necrosis, and generation of reactive oxygen species were evaluated. Nifedipine and 3,5-dipalmitoyl-nifedipine were used to assess radical scavenging potential and metal chelation. All tested molecules managed to reduce the levels of reactive oxygen species compared to the starvation+vehicle group. In in vitro assays, 3,5-dipalmitoyl-nifedipine showed more antioxidant activity than nifedipine. These results indicate the ability of this molecule to act as a powerful ROS scavenger. Cell viability was highest when cells were induced to I/R by both concentrations of anandamide and the higher concentration of DPN. These treatments also reduced cell death. Therefore, it was demonstrated that the process of hybridization of nifedipine with two palmitic acid chains assigns a greater cardioprotective effect to this molecule, thereby reducing the damage caused by hypoxia and reoxygenation in cardiomyoblast cultures.

PTPIP51 regulates mouse cardiac ischemia/reperfusion through mediating the mitochondria-SR junction

Protein tyrosine phosphatase interacting protein 51 (PTPIP51) participates in multiple cellular processes, and dysfunction of PTPIP51 is implicated in diseases such as cancer and neurodegenerative disorders. However, there is no functional evidence showing the physiological or pathological roles of PTPIP51 in the heart. We have therefore investigated the role and mechanisms of PTPIP51 in regulating cardiac function. We found that PTPIP51 was markedly upregulated in ischemia/reperfusion heart. Upregulation of PTPIP51 by adenovirus-mediated overexpression markedly increased the contact of mitochondria-sarcoplasmic reticulum (SR), elevated mitochondrial Ca²⁺ uptake from SR release through mitochondrial Ca²⁺uniporter. Inhibition or knockdown of mitochondrial Ca²⁺uniporter reversed PTPIP51-mediated increase of mitochondrial Ca²⁺ and protected cardiomyocytes against PTPIP51-mediated apoptosis. More importantly, cardiac specific knockdown of PTPIP51 largely reduced myocardium infarction size and heart injury after ischemia/reperfusion. Our study defines a novel and essential function of PTPIP51 in the cardiac ischemia/reperfusion process by mediating mitochondria-SR contact. Downregulation of PTPIP51 improves heart function after ischemia/reperfusion injury, suggesting PTPIP51 as a therapeutic target for ischemic heart diseases.

Cardioprotection with halogenated gases: how does it occur?

Numerous studies have studied the effect of halogenated agents on the myocardium, highlighting the beneficial cardiac effect of the pharmacological mechanism (preconditioning and postconditioning) when employed before and after ischemia in patients with ischemic heart disease. Anesthetic preconditioning is related to the dose-dependent signal, while the degree of protection is related to the concentration of the administered drug and the duration of the administration itself. Triggers for postconditioning and preconditioning might have numerous pathways in common; mitochondrial protection and a decrease in inflammatory mediators could be the major biochemical elements. Several pathways have been identified, including attenuation of NFκB activation and reduced expression of TNFα, IL-1, intracellular adhesion molecules, eNOS, the hypercontraction reduction that follows reperfusion, and antiapoptotic activating kinases (Akt, ERK1/2). It appears that the preconditioning and postconditioning triggers have numerous similar paths. The key biochemical elements are protection of the mitochondria and reduction in inflammatory mediators, both of which are developed in various ways. We have studied this issue, and have published several articles on cardioprotection with halogenated gases. Our results confirm greater cardioprotection through myocardial preconditioning in patients anesthetized with sevoflurane compared with propofol, with decreasing levels of troponin and N-terminal brain natriuretic peptide prohormone. The difference between our studies and previous studies lies in the use of sedation with sevoflurane in the postoperative period. The results could be related to a prolonged effect, in addition to preconditioning and postconditioning, which could enhance the cardioprotective effect of sevoflurane in the postoperative period. With this review, we aim to clarify the importance of various mechanisms involved in preconditioning and postconditioning with halogenated gases, as supported by our studies.

Efficacy of gold nanoparticles against isoproterenol induced acute myocardial infarction in adult male albino rats

This study was undertaken to investigate the role of gold nanoparticles (GNPs) of 50 nm diameter on isoproterenol (ISO) induced acute myocardial infarction in adult male albino rats. Forty five adult Wistar male albino rats were equally divided into three groups. Control (group I) was further subdivided into three subgroups. In group II, the rats received ISO subcutaneously at a dose of 100 mg/kg for three days. In group III, rats received ISO as group II and then GNPs (400 μg/kg/day) intravenously for 14 consecutive days. Echocardiography was performed. Left ventricular specimens were prepared for H&E, van Gieson staining, immunohistochemical analysis for (eNOs and Bcl-2), and Electron microscope examination. Energy dispersive X-ray microanalysis was also performed. Cardiac markers such as creatine Kinase-MB (CK-MB), alanine aminotransferase (ALT), aspartate aminotransferase (AST), and cardiac troponin T (cTnT) were measured. Group II revealed cardiomyocytes with deeply stained acidophilic cytoplasm, small dark nuclei, intracellular vacuolations, wide intercellular spaces, and extravasated red blood cells. Increased collagen fibers were observed. Electron microscope examination showed cardiomyocyte with small and irregular outlined nuclei, mitochondria with irregular cristae and others with ruptured mitochondrial membrane, abnormal alignment of myofibrils, dilated cisternae of smooth endoplasmic reticulum, and disorganized intercalated discs. Group III showed that most cardiomyocytes preserved the normal architecture. Increased expression of eNOs immunoreaction and decreased Bcl-2 immunoreaction were detected in group II as compared to the control and GNP-treated groups. These findings suggested that GNPs of 50 nm diameter improved myocardial injury after ISO-induced myocardial infarction in rats.

ABBREVIATIONS

Myocardial infarction (MI), Isoproterenol (ISO), Nitric oxide (NO), Neuronal NOS (nNOs), Endothelial NOs (eNOs), Gold nanoparticle (GNPs), Diamiobenzidine (DAB), Serum Creatine Kinase-MB (CK-MB), Alanine aminotransferase (ALT), Cardiac troponin T (cTnT), Electrochemiluminiscence (ECLIA), Cardiomyocytes (CMC), Peroxisomal proliferator activated receptor (PPARs), Reactive oxygen species (ROS).

Role of Vitamin C in Cardioprotection of Ischemia/Reperfusion Injury by Activation of Mitochondrial KATP Channel

How to provide effective prevention and treatment of myocardial ischemia/reperfusion (I/R) injury and study of the mechanism underlying I/R injury are hotspots of current research. This study aimed to elucidate the effect and cardioprotective mechanism of vitamin C (VC) on myocardial I/R injury. Our study introduced two different I/R models: I/R in vitro and oxygen-glucose deprivation/recovery (OGD/R) in primary neonatal rat cardiac myocytes. We used the mitochondrial permeability transition pore (mPTP) opener lonidamine (LND) and the mitochondrial KATP (mitoKATP) channel inhibitor 5-hydroxydecanoate (5-HD) to analyze the underlying mechanisms. We found that post-treatment with VC decreased I/R injury in our models. Post-treatment with VC significantly decreased I/R-induced injury, attenuated apoptosis, and maintained the functional integrity of mitochondria via alleviation of Ca(2+) overload, reactive oxygen species burst, inhibition of the opening of mPTP, and prevention of mitochondrial membrane potential (ΔΨm) depolarization. VC post-treatment increased the phosphorylation of Akt and glycogen synthase kinase (GSK)-3β. The present results demonstrate that VC might protect the myocardium from I/R-induced injury by inhibiting the mPTP opening via activation of mitoKATP channels. VC mediates cardioprotection via activation of the phosphatidyl inositol 3-kinase (PI3K)-Akt signaling pathway. These findings may contribute toward the development of novel strategies for clinical cardioprotection against I/R injury.

Gelatinases A and B and Antioxidant Enzyme Activity in the Early Phase of Acute Myocardial Infarction

Oxidative stress plays important roles in the pathophysiology of acute myocardial infarction (AMI). The aim of this study was to investigate the correlation of the oxidative stress status and matrix metalloproteinase activity in AMI patients in comparison to controls. This study included 136 subjects: 68 patients with AMI (42 males/26 females; mean age 58.5 ± 10.5 years) and 68 controls (37 males/29 females; mean age 60.2 ± 12.4 years). Gelatinases A and B were assayed using gelatin zymography, enzyme activities were obtained spectrophotometrically. Gelatinase A and B activities were increased in the AMI patients' group compared to the control. Activities of serum superoxide dismutase (SOD) and xanthine oxidase (XO) were significantly higher in AMI patients (106.53 ± 23.45 U/l, P < 0.001 and 158.18 ± 29.59 U/l, P < 0.001) than in the control group (55.99 ± 10.79 U/l and 79.81 ± 7.93 U/l). The activity of catalase (CAT) in the sera of AMI patients was lower (271.31 ± 7.53 U/l, P < 0.005) than in the control group (305.94 ± 97.28 U/l). Plasma glutathione peroxidase (GPx) and glutathione reductase (GR) in AMI patients were significantly higher (582.47 ± 184.81 U/l, P < 0.001 and 59.64 ± 21.88 U/l, P < 0.001) than in the control group (275.32 ± 104.69 U/l and 47.71 ± 20.05 U/l). The present findings demonstrate activation of gelatinases A and B and oxidative stress markers in the early stage of AMI. Gelatinases, detected at high levels in AMI patients only, indicate their noticeable predisposition for becoming additional biomarkers of the early phase of AMI.

High-Density Lipoprotein Regulation of Mitochondrial Function

Lipoproteins play a key role in regulating plasma and tissue levels of cholesterol. Apolipoprotein B (apoB)-containing lipoproteins, including chylomicrons, very-low density lipoprotein (VLDL) and low-density lipoprotein (LDL), serve as carriers of triglycerides and cholesterol and deliver these metabolites to peripheral tissues. In contrast, high-density lipoprotein (HDL) mediates Reverse Cholesterol Transport (RCT), a process by which excess cholesterol is removed from the periphery and taken up by hepatocytes where it is metabolized and excreted. Anti-atherogenic properties of HDL have been largely ascribed to apoA-I, the major protein component of the lipoprotein particle. The inflammatory response associated with atherosclerosis and ischemia-reperfusion (I-R) injury has been linked to the development of mitochondrial dysfunction. Under these conditions, an increase in reactive oxygen species (ROS) formation induces damage to mitochondrial structural elements, leading to a reduction in ATP synthesis and initiation of the apoptotic program. Recent studies suggest that HDL-associated apoA-I and lysosphingolipids attenuate mitochondrial injury by multiple mechanisms, including the suppression of ROS formation and induction of autophagy. Other apolipoproteins, however, present in lower abundance in HDL particles may exert opposing effects on mitochondrial function. This chapter examines the role of HDL-associated apolipoproteins and lipids in the regulation of mitochondrial function and bioenergetics.

Roles of MicroRNA-195 in cardiomyocyte apoptosis induced by myocardial ischemia-reperfusion injury

This study aims to investigate microRNA-195 (miR-195) expression in myocardial ischaemia-reperfusion (I/R) injury and the roles of miR-195 in cardiomyocyte apoptosis though targeting Bcl-2. A mouse model of I/R injury was established. MiR- 195 expression levels were detected by real-time quantitative PCR (qPCR), and the cardiomyocyte apoptosis was detected by TUNEL assay. After cardiomyocytes isolated from neonatal rats and transfected with miR-195 mimic or inhibitor, the hypoxia/reoxygenation (H/R) injury model was established. Cardiomyocyte apoptosis and mitochondrial membrane potential were evaluated using flow cytometry. Bcl-2 and Bax mRNA expressions were detected by RT-PCR. Bcl-2, Bax and cytochrome c (Cyt-c) protein levels were determined by Western blot. Caspase-3 and caspase-9 activities were assessed by luciferase assay. Compared with the sham group, miR-195 expression levels and rate of cardiomyocyte apoptosis increased significantly in I/R group (both P < 0.05). Compared to H/R + negative control (NC) group, rate of cardiomyocyte apoptosis increased in H/R + miR-195 mimic group while decreased in H/R + miR-195 inhibitor group (both P <0.05). MiR-195 knockdown alleviated the loss of mitochondrial membrane potential (P <0.05). MiR-195 overexpression decreased Bcl-2 mRNA and protein expression, increased BaxmRNA and protein expression, Cyt-c protein expression and caspase-3 and caspase-9 activities (all P <0.05).While, downregulated MiR-195 increased Bcl-2 mRNA and protein expression, decreased Bax mRNA and protein expression, Cyt-c protein expression and caspase-3 and caspase-9 activities (all P < 0.05). Our study identified that miR-195 expression was upregulated in myocardial I/R injury, and miR-195 overexpression may promote cardiomyocyte apoptosis by targeting Bcl-2 and inducing mitochondrial apoptotic pathway.

Pharmacological Inhibition of NLRP3 Inflammasome Attenuates Myocardial Ischemia/Reperfusion Injury by Activation of RISK and Mitochondrial Pathways

Although the nucleotide-binding oligomerization domain- (NOD-) like receptor pyrin domain containing 3 (NLRP3) inflammasome has been recently detected in the heart, its role in cardiac ischemia/reperfusion (IR) is still controversial. Here, we investigate whether a pharmacological modulation of NLRP3 inflammasome exerted protective effects in an ex vivo model of IR injury. Isolated hearts from male Wistar rats (5-6 months old) underwent ischemia (30 min) followed by reperfusion (20 or 60 min) with and without pretreatment with the recently synthetized NLRP3 inflammasome inhibitor INF4E (50 μM, 20 min before ischemia). INF4E exerted protection against myocardial IR, shown by a significant reduction in infarct size and lactate dehydrogenase release and improvement in postischemic left ventricular pressure. The formation of the NLRP3 inflammasome complex was induced by myocardial IR and attenuated by INF4E in a time-dependent way. Interestingly, the hearts of the INF4E-pretreated animals displayed a marked improvement of the protective RISK pathway and this effect was associated increase in expression of markers of mitochondrial oxidative phosphorylation. Our results demonstrate for the first time that INF4E protected against the IR-induced myocardial injury and dysfunction, by a mechanism that involves inhibition of the NLRP3 inflammasome, resulting in the activation of the prosurvival RISK pathway and improvement in mitochondrial function.

Ischemia/Reperfusion

Ischemic disorders, such as myocardial infarction, stroke, and peripheral vascular disease, are the most common causes of debilitating disease and death in westernized cultures. The extent of tissue injury relates directly to the extent of blood flow reduction and to the length of the ischemic period, which influence the levels to which cellular ATP and intracellular pH are reduced. By impairing ATPase-dependent ion transport, ischemia causes intracellular and mitochondrial calcium levels to increase (calcium overload). Cell volume regulatory mechanisms are also disrupted by the lack of ATP, which can induce lysis of organelle and plasma membranes. Reperfusion, although required to salvage oxygen-starved tissues, produces paradoxical tissue responses that fuel the production of reactive oxygen species (oxygen paradox), sequestration of proinflammatory immunocytes in ischemic tissues, endoplasmic reticulum stress, and development of postischemic capillary no-reflow, which amplify tissue injury. These pathologic events culminate in opening of mitochondrial permeability transition pores as a common end-effector of ischemia/reperfusion (I/R)-induced cell lysis and death. Emerging concepts include the influence of the intestinal microbiome, fetal programming, epigenetic changes, and microparticles in the pathogenesis of I/R. The overall goal of this review is to describe these and other mechanisms that contribute to I/R injury. Because so many different deleterious events participate in I/R, it is clear that therapeutic approaches will be effective only when multiple pathologic processes are targeted. In addition, the translational significance of I/R research will be enhanced by much wider use of animal models that incorporate the complicating effects of risk factors for cardiovascular disease. © 2017 American Physiological Society. Compr Physiol 7:113-170, 2017.

RISK pathway is involved in oxytocin postconditioning in isolated rat heart

The reperfusion injury salvage kinase (RISK) pathway is a fundamental signal transduction cascade in the cardioprotective mechanism of ischemic postconditioning. In the present study, we examined the cardioprotective role of oxytocin as a postconditioning agent via activation of the RISK pathway (PI3K/Akt and ERK1/2). Animals were randomly divided into 6 groups. The hearts were subjected under 30minutes (min) ischemia and 100min reperfusion. OT was perfused 15min at the early phase of reperfusion. RISK pathway inhibitors (Wortmannin; an Akt inhibitor, PD98059; an ERK1/2 inhibitor) and Atosiban (an OT receptor antagonist) were applied either alone 10min before the onset of the ischemia or in the combination with OT during early reperfusion phase. Myocardial infarct size, hemodynamic factors, ventricular arrhythmia, coronary flow and cardiac biochemical marker were measured at the end of reperfusion. OT postconditioning (OTpost), significantly decreased the infarct size, arrhythmia score, incidence of ventricular fibrillation, Lactate dehydrogenase and it increased coronary flow. The cardioprotective effect of OTpos was abrogated by PI3K/Akt, ERK1/2 inhibitors and Atosiban. Our data have shown that OTpost can activate RISK pathway mostly via the PI3K/Akt and ERK1/2 signaling cascades during the early phase of reperfusion.