Reperfusion injury in acute myocardial infarction. From bench to cath lab. Part I: Basic considerations

Impact of various periods of perfusion-pause and reperfusion on the severity of myocardial injury in the langenodorff model

BACKGROUND

To explore impact of various periods of ischemia and reperfusion on the severity of myocardial injury.

METHODS

Langendorff model of isolated cardiac perfusion system was established in 56 rat hearts. They were randomly assigned into four groups with four different ischemia (perfusion-pause) time and reperfusion time. The levels of aspartate aminotransferase (AST), alanine aminotransferase (ALT), lactate dehydrogenase (LDH), and creatine kinase-MB (CK-MB) were measured and the size of myocardial infarction was assessed by 2,3,5-triphenyltetrazolium chloride (TTC) staining.

RESULTS

The levels of AST, ALT, LDH, and CK-MB in the heart tissues and perfusate were lowest in the group I (shortest time of perfusion-pause and reperfusion) followed by the groups II, III, and IV (longest time of perfusion-pause and reperfusion) (p < 0.05). The myocardial infarction size was smallest in the group I (6.63 ± 0.47) followed by group II (15.12 ± 1.03), group III (20.32 ± 2.18), and group IV (32.29 ± 5.42) (p < 0.05). Two-way ANOVA analysis revealed that period of perfusion-pause and reperfusion independently and significantly affected the levels of AST and ALT in both heart tissues and perfusate (p < 0.001). The interaction of pausing period and reperfusion significantly affected the level of AST (p = 0.046) and CK-MB (p = 0.001) in the perfusate. In addition, perfusion-pause period significantly affected levels of LDH and CK-MB only in the perfusate (p < 0.001). Neither perfusate nor heart tissue LDH level was significantly affected by the interaction of perfusion-pause and reperfusion period (p > 0.05).

CONCLUSION

The severity of myocardial injury in the Langendorff model was affected by the period of perfusion-pause and reperfusion. The longer period of perfusion-pause followed by the longer the period of reperfusion, the severe myocardial injury was found.

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

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

Adenosine in Acute Myocardial Infarction-Associated Reperfusion Injury: Does it Still Have a Role?

The mainstay of acute myocardial infarction has long been timely reperfusion of the culprit obstruction. Reperfusion injury resulting from a multitude of pathophysiological processes has been demonstrated to negatively affect myocardial recovery and function post-infarction. Adenosine interacts directly with the sequential pathophysiological processes culminating in reperfusion injury by inhibiting them upstream. The evidence for adenosine’s benefit in acute myocardial infarction has produced mixed results with regards to myocardial salvage and long-term mortality. The heterogenous evidence with regards to benefits on clinical outcomes has resulted in modest uptake of adenosine in the clinical setting. However, it is critical to analyze the variability in study methodologies. The goal of this review is to evaluate how adenosine dose, route of administration, timing of administration, and site of administration play essential roles in the molecule’s efficacy. The benefits of adenosine, as highlighted in the following review, are clear and its role in the treatment of acute myocardial infarction should not be discounted

Proposal of a prediction model for prognosis of patients with acute myocardial infarction after percutaneous coronary intervention based on galectin-3 and soluble growth stimulating expressed gene 2 levels

Background: To study the correlations of serum galectin-3 (Gal-3) and soluble growth stimulating expressed gene 2 (sST2) levels with prognosis of patients with acute myocardial infarction (AMI) after percutaneous coronary intervention (PCI).

Methods: A total of 112 patients diagnosed from August 2015 to October 2017 were selected. They were followed up for 3 years. Based on major adverse cardiovascular events (MACEs) during follow-up, they were divided into MACE and non-MACE groups. Multivariate logistic regression analysis was performed to explore the independent risk factors for MACEs. A nomogram model was established using the factors and validated. The optimal cut-off values of Gal-3 and sST2 levels were determined by receiver operating characteristic curves. Kaplan-Meier method was used for survival analysis.

Results: MACEs occurred in 78 patients during follow-up. Patients in the MACE group were more often hypertensive, had higher total cholesterol, uric acid, sST2 and Gal-3, and lower left ventricular ejection fraction (LVEF) (P<0.05). CK-MB, sST2, Gal-3 and LVEF were the independent risk factors for MACEs (P<0.05). The nomogram model established with these factors had high accuracy for predicting overall survival, and its concordance index (C-index) was 0.768 (95% confidence interval: 0.692-0.865). The prognosis of the patients with Gal-3 ≥12.57 μg/ mL and sST2 ≥18.56 ng/mL was poorer 3 years after PCI.

Conclusions: The levels of serum Gal-3 and sST2 are the independent risk factors for MACEs in AMI patients following PCI, with high prognostic value.

Non-Coding RNAs: Prevention, Diagnosis, and Treatment in Myocardial Ischemia-Reperfusion Injury

Recent knowledge concerning the role of non-coding RNAs (ncRNAs) in myocardial ischemia/reperfusion (I/R) injury provides new insight into their possible roles as specific biomarkers for early diagnosis, prognosis, and treatment. MicroRNAs (miRNAs) have fewer than 200 nucleotides, while long ncRNAs (lncRNAs) have more than 200 nucleotides. The three types of ncRNAs (miRNAs, lncRNAs, and circRNAs) act as signaling molecules strongly involved in cardiovascular disorders (CVD). I/R injury of the heart is the main CVD correlated with acute myocardial infarction (AMI), cardiac surgery, and transplantation. The expression levels of many ncRNAs and miRNAs are highly modified in the plasma of MI patients, and thus they have the potential to diagnose and treat MI. Cardiomyocyte and endothelial cell death is the major trigger for myocardial ischemia–reperfusion syndrome (MIRS). The cardioprotective effect of inflammasome activation in MIRS and the therapeutics targeting the reparative response could prevent progressive post-infarction heart failure. Moreover, the pharmacological and genetic modulation of these ncRNAs has the therapeutic potential to improve clinical outcomes in AMI patients.

Long non-coding RNA muscleblind like splicing regulator 1 antisense RNA 1 (LncRNA MBNL1-AS1) promotes the progression of acute myocardial infarction by regulating the microRNA-132-3p/SRY-related high-mobility-group box 4 (SOX4) axis

Long non-coding RNA muscleblind like splicing regulator 1 antisense RNA 1 (LncRNA MBNL1-AS1) exerts vital role in various physiological processes. However, its functions in acute myocardial infarction (AMI) are not elucidated. AMI model was constructed using Wistar rats and it was found that LncRNA MBNL1-AS1 was upregulated in AMI model according to the quantitative real-time polymerase chain reaction (qRT-PCR) results. The left ventricular systolic pressure (LVSP), left ventricular end diastolic pressure (LVEDP) and maximum rate of rise/fall of left ventricle pressure (±dp/dt max) were detected through hemodynamics test, which showed that knockdown of MBNL1-AS1 improved cardiac function in AMI model. Next, the myocardial infarction area was estimated by triphenyltetrazole chloride (TTC) staining, and the levels of cardiac troponin I (cTn-I) and creatine kinase-MB (CK-MB) were detected by enzyme-linked immunosorbent assay (ELISA) kit. The results revealed that silencing MBLN1-AS1 alleviated myocardial injury in AMI model. Additionally, MBNL1-AS1 knockdown inhibited apoptosis of myocardial cells and reduced the expression of apoptotic proteins. According to DIANA database and luciferase reporter assay, miR-132-3p was the direct target of MBNL1-AS1 and was negatively regulated by MBNL1-AS1. Furthermore, Targetscan database predicted that SRY-related high-mobility-group box 4 (SOX4) was the direct target of miR-132-3p and was regulated by MBNL1-AS1 through miR-132-3p. Moreover, overexpression of SOX4 partially eliminated effects of MBNL1-AS1 on myocardial cells. In conclusion, this investigation for the first time revealed that LncRNA MBNL1-AS1 was the potential target for treating AMI and expounded the underlying mechanisms of it.

Reperfusion Cardiac Injury: Receptors and the Signaling Mechanisms

It has been documented that Ca2+ overload and increased production of reactive oxygen species play a significant role in reperfusion injury (RI) of cardiomyocytes. Ischemia/reperfusion induces cell death as a result of necrosis, necroptosis, apoptosis, and possibly autophagy, pyroptosis and ferroptosis. It has also been demonstrated that the NLRP3 inflammasome is involved in RI of the heart. An increase in adrenergic system activity during the restoration of coronary perfusion negatively affected cardiac resistance to RI. Toll-like receptors are involved in RI of the heart. Angiotensin II and endothelin-1 aggravated ischemic/reperfusion injury of the heart. Activation of neutrophils, monocytes, CD4+ T-cells and platelets contributes to cardiac ischemia/reperfusion injury. Our review outlines the role of these factors in reperfusion cardiac injury.

SHP-1/STAT3 Interaction Is Related to Luteolin-Induced Myocardial Ischemia Protection

Prevention and management of myocardial ischemia/reperfusion (I/R) injury is a key step in coronary heart disease surgery. Luteolin is a falconoid compound that has an antioxidant effect, but its mechanism in I/R injury in vivo and in vitro is still under explored. This study attempted to reveal the role of luteolin (Lut) in I/R through mediation of the Src homology 2 domain-containing protein tyrosine phosphatase 1 (SHP-1)/Signal transducer and activator of transcription 3 (STAT3) pathway. To establish I/R rat models, the left anterior descending artery (LAD) was ligated for 30 min and re-perfused for 1 h in Lut-pretreated or nude rats. Comparisons between infarct area, cardiac dysfunction, and myocardial cell death and inflammatory reaction were performed in I/R-induced rats. Hypoxia/reoxygenation (H/R) cell models were established by stimulating H9c2 cells with 95% nitrogen and 5% carbon dioxide. Simultaneously, H/R-related cell death and inflammatory reactions were investigated following Lut treatment. The target protein of Lut was identified using western blotting. Pro-inflammatory cytokines were also measured in serum or Lut-pretreated cell culture medium. The results revealed that compared with the I/R group, Lut treatment could significantly decrease myocardial infarction (MI) area, increase left ventricular ejection fraction (LVEF), and decrease cell death and pro-inflammatory cytokines in the serum. Decreased apoptosis and inflammatory cytokines were also observed in H/R cells after Lut treatment. Lut treatment downregulated SHP-1 expression and subsequently upregulated STAT3 phosphorylation in both I/R rat heart tissue and H9c2 cells. The findings of the current study suggest that Lut can protect the heart and reduce MI area, cell apoptosis rate, and inflammatory level in I/R models.

Protective effects of metformin against myocardial ischemia‑reperfusion injury via AMPK‑dependent suppression of NOX4

Numerous studies have demonstrated that metformin can reduce the incidence of myocardial infarction and improve the prognosis of patients. However, its specific mechanism has not been determined. Using a rat model of myocardial ischemia-reperfusion injury (MIRI), it was observed that metformin significantly reduced infarct size, and decreased the levels of plasma lactate dehydrogenase and creatine kinase-MB form. A TTC-Evans blue staining was used to detect the infarct size and MTT assay was used to evaluate the cell viability. TUNEL assay was performed to evaluate apoptosis. Furthermore, 4-hydroxynonenal was detected by immunohistochemical staining. mRNA expression levels were detected by reverse transcription-quantitative PCR; protein expression levels were detected by immunoblotting. When treated with metformin, the number of TUNEL-positive cells was significantly decreased. Reduced 4HNE immunoreactivity was observed in metformin-treated rats as determined via immunohistochemistry. Furthermore, NADPH oxidase 4 (NOX4) was downregulated by metformin at both the mRNA and protein levels, and adenosine 5′-monophosphate-activated protein kinase (AMPK) phosphorylation was increased by metformin. In a primary myocardial hypoxia-reoxygenation cell model, metformin increased the viability of cardiomyocytes and reduced the content of malondialdehyde. It was also found that metformin upregulated the phosphorylation of AMPK and decreased the expression of NOX4. Furthermore, pre-treatment with AMPK inhibitor compound-C could block the effect of metformin, indicated by increased NOX4 compared with metformin treatment alone. These results suggested that metformin was capable of reducing the oxidative stress injury induced by MIRI. In conclusion, the present study indicated that metformin activated AMPK to inhibit the expression of NOX4, leading to a decrease in myocardial oxidative damage and apoptosis, thus alleviating reperfusion injury.

ATR prevents Ca2+ overload-induced necrotic cell death through phosphorylation-mediated inactivation of PARP1 without DNA damage signaling

Hyperactivation of PARP1 is known to be a major cause of necrotic cell death by depleting NAD⁺/ATP pools during Ca²⁺ overload which is associated with many ischemic diseases. However, little is known about how PARP1 hyperactivity is regulated during calcium overload. In this study we show that ATR kinase, well known for its role in DNA damage responses, suppresses ionomycin, glutamate, or quinolinic acid‐induced necrotic death of cells including SH‐SY5Y neuronal cells. We found that the inhibition of necrosis requires the kinase activity of ATR. Specifically, ATR binds to and phosphorylates PARP1 at Ser179 after the ionophore treatments. This site‐specific phosphorylation inactivates PARP1, inhibiting ionophore‐induced necrosis. Strikingly, all of this occurs in the absence of detectable DNA damage and signaling up to 8 hours after ionophore treatment. Furthermore, little AIF was released from mitochondria/cytoplasm for nuclear import, supporting the necrotic type of cell death in the early period of the treatments. Our results reveal a novel ATR‐mediated anti‐necrotic mechanism in the cellular stress response to calcium influx without DNA damage signaling.

A novel Danshensu/tetramethylpyrazine protects against Myocardial Ischemia Reperfusion Injury in rats

A new Danshensu/tetramethylpyrazine derivative (ADTM) with cardio-protection effects such as antioxidant, arterial relaxation, pro-angiogenesis and antiplatelet activities. Platelet activating factor receptor (PAFR) plays a key role in myocardial ischemia reperfusion (MIR) injury. This study aims to investigate the protective role of ADTM in MIR injury and clarify the potential role of PAFR. We measured the effects of ADTM on MIR injury in rats in vivo and hypoxia re-oxygenation (HR) injury in neonatal rat ventricular myocytes (NRVMs) in vitro. The results show that ADTM can significantly improve the IR-induced decline in heart function as increasing EF and FS, and restore the decreased cardiac hemodynamic parameters (LVSP, ± dp/dt max) and increased the level of LVEDP, decrease the infarct size of damaged myocardium and lactate dehydrogenase (LDH) activity in serum. Additionally, ADTM inhibits cardiomyocytes apoptosis, caspase-3 activity, and inflammatory response as well as down-regulates the MIR-induced IL-1β and TNFα production. Next, PAFR expression was significantly down-regulated in cardiomyocytes of MIR model in vivo and in vitro after treated with ADTM compare to IR group. At the same time, ADTM and PAFR small interfering RNA (siRNA) could inhibit cardiomyocytes apoptosis and inflammation during HR, while PAF presents the opposite effect. Furthermore, the above effects of PAF in HR induced cardiomyocytes were reversed by co-treatment of ADTM. Our findings demonstrate for the first time that ADTM protects against MIR injury through inhibition of PAFR signaling, which provides a new treatment for MIR.

Assessment of effects of methylene blue on intestinal ischemia and reperfusion in a rabbit model: hemodynamic, histological and immunohistochemical study

BACKGROUND

Intestinal ischemia-reperfusion (IR) is an important clinical occurrence seen in common diseases, such as gastric dilatation-volvulus in dogs or colic in horses. Limited data is available on the use of methylene blue in veterinary medicine for intestinal ischemia-reperfusion. The present study aimed to compare the hemodynamic, histopathological, and immunohistochemical effects of two doses of methylene blue in two rabbit model groups In one group, 5 mg/kg IV was administered, and in another, 20 mg/kg IV was administered following a constant rate infusion (CRI) of 2 mg/kg/h that lasted 6 h. All the groups, including a control group had intestinal ischemia-reperfusion. Immunohistochemical analysis was performed using caspase-3.

RESULTS

During ischemia, hemodynamic depression with reduced perfusion and elevated lactate were observed. During reperfusion, methylene blue (MB) infusion generated an increase in cardiac output due to a positive chronotropic effect, an elevation of preload, and an intense positive inotropic effect. The changes in heart rate and blood pressure were significantly greater in the group in which methylene blue 5 mg/kg IV was administered (MB5) than in the group in which methylene blue 20 mg/kg IV dose was administered (MB20). In addition, lactate and stroke volume variations were significantly reduced, and vascular resistance was significantly elevated in the MB5 group compared with the control group and MB20 group. The MB5 group showed a significant decrease in the intensity of histopathological lesion scores in the intestines and a decrease in caspase-3 areas, in comparison with other groups.

CONCLUSIONS

MB infusion produced improvements in hemodynamic parameters in rabbits subjected to intestinal IR, with increased cardiac output and blood pressure. An MB dosage of 5 mg/kg IV administered at a CRI of 2 mg/kg/h exhibited the most protective effect against histopathological damage caused by intestinal ischemia-reperfusion. Further studies with MB in clinical veterinary pathologies are recommended to fully evaluate these findings.

LncRNA TUG1 mediates ischemic myocardial injury by targeting miR-132-3p/HDAC3 axis

Increased production of reactive oxygen species (ROS) significantly contributed to the pathogenesis of acute myocardial infarction (AMI). Recent studies suggest that hypoxia upregulated the long noncoding RNA taurine upregulated gene 1 (TUG1). In this study, we explored the functional significance and molecular mechanisms of TUG1/miR-132-3p axis in ischemia-challenged cardiomyocytes. In primary cardiomyocytes challenged with H2O2, expressions of miR-132-3p, TUG1, and other target proteins were measured by RT quantitative PCR or Western blot analysis; cell viability by 3-(4,5-dimethylthiazolyl-2)-2,5-diphenyltetrazolium bromide assay; apoptosis by annexin V and propidium iodide staining; the abundance of acetylated H3K9 or histone deacetylase 3 (HDAC3) within the promoter of target genes by chromatin immunoprecipitation; the direct interaction between miR-132-3p and HDAC3 or TUG1 by luciferase reporter assay. The biological significance of miR-132-3p, TUG1, and HDAC3 was assessed using miR-132-3p mimic, siRNA-targeting TUG1 and HDAC3 inhibitor RGF966, respectively, in H2O2-challenged cells in vitro or ischemia-reperfusion (I/R)-induced AMI in vivo. miR-132-3p was downregulated, whereas TUG1 upregulated in H2O2-challenged cardiomyocytes. Overexpressing miR-132-3p or knocking down TUG1 significantly improved viability, inhibited apoptosis, and reduced ROS production in H2O2-stressed cardiomyocytes in vitro and alleviated I/R-induced AMI in vivo. Mechanistically, TUG1 sponged miR-132-3p and upregulated HDAC3, which reduced the acetylation of H3K9 and epigenetically inhibited expressions of antioxidative genes, including Bcl-xL, Prdx2, and Hsp70. The TUG1/miR-132-3p/HDAC3 axis critically regulates ROS production and the pathogenic development of AMI. Targeting TUG1, upregulating miR-132-3p, or inhibiting HDAC3 may benefit AMI treatment.NEW & NOTEWORTHY Increased production of reactive oxygen species (ROS) significantly contributed to the pathogenesis of acute myocardial infarction (AMI). Recent studies suggest that hypoxia upregulated the long noncoding RNA taurine upregulated gene 1 (TUG1). However, the underlying mechanisms remain elusive. In the present study, we reported for the first time that H2O2 or ischemia-reperfusion-induced TUG1, by sponging microRNA 132-3p, activated histone deacetylase 3, which in turn targeted multiple protective genes, stimulated intracellular ROS accumulation, and aggravated the injury of AMI. Our findings might provide some insight to seek new targets for AMI treatment.

Ischemia/Reperfusion Injury: Pathophysiology, Current Clinical Management, and Potential Preventive Approaches

Myocardial ischemia reperfusion syndrome is a complex entity where many inflammatory mediators play different roles, both to enhance myocardial infarction-derived damage and to heal injury. In such a setting, the establishment of an effective therapy to treat this condition has been elusive, perhaps because the experimental treatments have been conceived to block just one of the many pathogenic pathways of the disease, or because they thwart the tissue-repairing phase of the syndrome. Either way, we think that a discussion about the pathophysiology of the disease and the mechanisms of action of some drugs may shed some clarity on the topic.

Cell salvage in acute and chronic wounds: a potential treatment strategy. Experimental data and early clinical results

On 9 May 2018, the authors took part in a closed panel discussion on the impact of cell salvage in acute and chronic wounds. The goal was to deliberate the possible use of plurogel micelle matrix (PMM) as a new treatment strategy for wound healing and the authors openly shared their experiences, thoughts, experimental data and early clinical results. The outcome of the panel discussion has been abridged in this paper. The cell membrane consists of a lipid bilayer, which provides a diffusion barrier separating the inside of a cell from its environment. Cell membrane injury can result in acute cellular necrosis when defects are too large and cannot be resealed. There is a potential hazard to the body when these dying cells release endogenous alarm signals referred to as 'damage (or danger) associated molecular patterns' (DAMPs), which trigger the innate immune system and modulate inflammation. Cell salvage by membrane resealing is a promising target to ensure the survival of the individual cell and prevention of further tissue degeneration by inflammatory processes. Non-ionic surfactants such as poloxamers, poloxamines and PMM have the potential to resuscitate cells by inserting themselves into damaged membranes and stabilising the unstable portions of the lipid bilayers. The amphiphilic properties of these molecules are amenable to insertion into cell wall defects and so can play a crucial, reparative role. This new approach to cell rescue or salvage has gained increasing interest as several clinical conditions have been linked to cell membrane injury via oxidative stress-mediated lipid peroxidation or thermal disruption. The repair of the cell membrane is an important step in salvaging cells from necrosis to prevent further tissue degeneration by inflammatory processes. This is applicable to acute burns and chronic wounds such as diabetic foot ulcers (DFUs), chronic venous leg ulcers (VLUs), and pressure ulcers (PUs). Experimental data shows that PMM is biocompatible and able to insert itself into damaged membranes, salvaging their barrier function and aiding cell survival. Moreover, the six case studies presented in this paper reveal the potential of this treatment strategy.

Inhibition of lncRNA TUG1 upregulates miR-142-3p to ameliorate myocardial injury during ischemia and reperfusion via targeting HMGB1- and Rac1-induced autophagy

BACKGROUND

Long non-coding RNAs (lncRNAs) play a central role in regulating heart diseases. In the present study, we examined the effects of lncRNA taurine up-regulated gene 1 (TUG1) in ischemia/reperfusion (I/R)- or hydrogen peroxide-challenged cardiomyocytes, with specific focus on autophagy-induced cell apoptosis.

METHODS

The expressions of miR-142-3p and TUG1 in H2O2-challenged cardiomyocytes and I/R-injured heart tissue were measured by RT-qPCR. Cell death was measured by trypan blue staining assay. Cell apoptosis was determined by Annexin V/PI staining and TUNEL assay. Autophagy was examined by quantifying cells or tissues containing LC3+ autophagic vacuoles by immunofluorescence, or by measuring the expressions of autophagy-related biomarkers by Western blot. The direct interaction between miR-142-3p and TUG1, high mobility group box 1 protein (HMGB1), or Ras-related C3 botulinum toxin substrate 1 (Rac1) was examined using luciferase reporter assay. The significance of miR-142-3p and TUG1 on cell apoptosis or autophagy was examined using both gain-of-function and loss-of-function approaches. The importance of HMGB1 or Rac1 was assessed using siRNA-mediated gene silencing.

RESULTS

miR-142-3p was down-regulated, while TUG1 up-regulated in H2O2-challenged cardiomyocytes in vitro and I/R-injured heart tissues in vivo. Functionally, inhibition of TUG1 and overexpression of miR-142-3p inhibited cell apoptosis and autophagy in cardiomyocytes. The function of TUG1 were achieved by sponging miR-142-3p and releasing the suppression of the putative targets of miR-142-3p, HMGB1 and Rac1. Both HMGB1 and Rac1 essentially mediated cell apoptosis and autophagy induced by TUG1.

CONCLUSIONS

TUG1, by targeting miR-142-3p and up-regulating HMGB1 and Rac1, plays a central role in stimulating autophagic cell apoptosis in ischemia/hypoxia-challenged cardiomyocytes. Down-regulating TUG1 or up-regulating miR-142-3p may ameliorate myocardial injury and protect against acute myocardial infarction.

Sulodexide attenuates endoplasmic reticulum stress induced by myocardial ischaemia/reperfusion by activating the PI3K/Akt pathway

Acute myocardial ischaemia/reperfusion (MI/R) injury causes severe arrhythmias with a high rate of lethality. Extensive research focus on endoplasmic reticulum (ER) stress and its dysfunction which leads to cardiac injury in MI/R Our study evaluated the effects of sulodexide (SDX) on MI/R by establishing MI/R mice models and in vitro oxidative stress models in H9C2 cells. We found that SDX decreases cardiac injury during ischaemia reperfusion and decreased myocardial apoptosis and infarct area, which was paralleled by increased superoxide dismutase and reduced malondialdehyde in mice plasm, increased Bcl‐2 expression, decreased BAX expression in a mouse model of MI/R. In vitro, SDX exerted a protective effect by the suppression of the ER stress which induced by tert‐butyl hydroperoxide (TBHP) treatment. Both of the in vivo and in vitro effects were involved in the phosphatidylinositol 3‐kinase (PI3K)/Akt signalling pathway. Inhibition of PI3K/Akt pathway by specific inhibitor, LY294002, partially reduced the protective effect of SDX. In short, our results suggested that the cardioprotective role of SDX was related to the suppression of ER stress in mice MI/R models and TBHP‐induced H9C2 cell injury which was through the PI3K/Akt signalling pathway.

Editor's Choice- Reperfusion cardiac arrhythmias and their relation to reperfusion-induced cell death

Reperfusion does not only salvage ischaemic myocardium but can also cause additional cell death which is called lethal reperfusion injury. The time of reperfusion is often accompanied by ventricular arrhythmias, i.e. reperfusion arrhythmias. While both conditions are seen as separate processes, recent research has shown that reperfusion arrhythmias are related to larger infarct size. The pathophysiology of fatal reperfusion injury revolves around intracellular calcium overload and reactive oxidative species inducing apoptosis by opening of the mitochondrial protein transition pore. The pathophysiological basis for reperfusion arrhythmias is the same intracellular calcium overload as that causing fatal reperfusion injury. Therefore both conditions should not be seen as separate entities but as one and the same process resulting in two different visible effects. Reperfusion arrhythmias could therefore be seen as a potential marker for fatal reperfusion injury.

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.

Luteolin ameliorates rat myocardial ischaemia-reperfusion injury through activation of peroxiredoxin II

BACKGROUND AND PURPOSE

Antioxidants provide a promising therapeutic effect for the cardiovascular disease. Luteolin, a polyphenolic bioflavonoid, is known to confer cardioprotection, although the underlying mechanisms, especially the role of luteolin on the antioxidant enzymes, such as the peroxiredoxin family, remain unknown.

EXPERIMENTAL APPROACH

We measured the effects of luteolin on myocardial ischaemia/reperfusion (MI/R) injury in vivo (Sprague-Dawley rats) and in vitro, together with the underlying mechanisms, with a focus on signalling by peroxiredoxins. H9c2 cells were used to assess the changes in peroxiredoxins and the other antioxidant enzymes. Oxidative stress, cardiac function, LDH release, ROS and infarct size were also assayed.

KEY RESULTS

Luteolin exerted significant cardioprotective effects in vivo and in vitro via improving cardiac function, increasing the expression of anti-apoptotic protein Bcl-2 and decreasing the pro-apoptotic protein Bax and active caspases 3 and 9, associated with MI/R. Mechanistically, luteolin markedly enhanced expression of peroxiredoxin II, without significant effects on other forms of peroxiredoxin, catalase or SOD1. Molecular docking showed that luteolin could indeed bind to the enzymic active pocket of peroxiredoxin II. Furthermore, down-regulation of peroxiredoxin II by peroxiredoxin II-antisense, administered by adenovirus infection of H9c2 cardiomyocytes, and inhibition of peroxiredoxin II in vivo significantly reversed the cardioprotective effects of luteolin.

CONCLUSIONS AND IMPLICATIONS

Our findings, for the first time, demonstrate that luteolin protects against MI/R injury through promoting signalling through the endogenous antioxidant enzyme, peroxiredoxin II, indicating the important beneficial role of this antioxidant system in the heart.

c-Jun N-Terminal Kinases (JNKs) in Myocardial and Cerebral Ischemia/Reperfusion Injury

In this article, we review the literature regarding the role of c-Jun N-terminal kinases (JNKs) in cerebral and myocardial ischemia/reperfusion injury. Numerous studies demonstrate that JNK-mediated signaling pathways play an essential role in cerebral and myocardial ischemia/reperfusion injury. JNK-associated mechanisms are involved in preconditioning and post-conditioning of the heart and the brain. The literature and our own studies suggest that JNK inhibitors may exert cardioprotective and neuroprotective properties. The effects of modulating the JNK-depending pathways in the brain and the heart are reviewed. Cardioprotective and neuroprotective mechanisms of JNK inhibitors are discussed in detail including synthetic small molecule inhibitors (AS601245, SP600125, IQ-1S, and SR-3306), ion channel inhibitor GsMTx4, JNK-interacting proteins, inhibitors of mixed-lineage kinase (MLK) and MLK-interacting proteins, inhibitors of glutamate receptors, nitric oxide (NO) donors, and anesthetics. The role of JNKs in ischemia/reperfusion injury of the heart in diabetes mellitus is discussed in the context of comorbidities. According to reviewed literature, JNKs represent promising therapeutic targets for protection of the brain and the heart against ischemic stroke and myocardial infarction, respectively. However, different members of the JNK family exert diverse physiological properties which may not allow for systemic administration of non-specific JNK inhibitors for therapeutic purposes. Currently available candidate JNK inhibitors with high therapeutic potential are identified. The further search for selective JNK3 inhibitors remains an important task.

Dexmedetomidine protects mice against myocardium ischaemic/reperfusion injury by activating an AMPK/PI3K/Akt/eNOS pathway

Acute myocardial ischaemia/reperfusion (MIR) injury leads to severe arrhythmias and has a high rate of lethality. In the present study, we aim to determine the effect of dexmedetomidine (Dex) on heart injury parameters following MIR surgery. We examined the effects of Dex on heart function parameters and infarct size following MIR surgery. Proinflammatory cytokines, oxidative products and anti-oxidative enzymes in the myocardium were measured to evaluate the anti-inflammatory and anti-oxidative effects of Dex. The role of the adenosine 5'-monophosphate (AMP)-activated protein kinase (AMPK)/phosphatidylino-sitol 3-kinase (PI3k)/Akt/endothelial nitric oxide synthase (eNOS) pathway was investigated using their inhibitors. The alteration of haemodynamic parameters, histopathological results, and infarct size caused by MIR was attenuated by Dex. The interleukine-1 beta (IL-1β), IL-6, tumour necrosis factor-a (TNF-α) and myeloperoxidase (MPO) were all significantly decreased. Anti-oxidative enzymes superoxide dismutase (SOD), catalase and glutathione peroxidase (GPx) were restored by Dex. Oxidative products8-OHdG, MDA and protein carbonyl were all decreased by Dex (P<.05). Dex activated AMPK expression, eNOS and Akt phosphorylation. The influence of Dex on cardiac function was reversed by the inhibitors of the eNOS, AMPK and PI3K/Akt pathways. These results indicate that Dex protected the cardiac functional, histological changes, inflammation and oxidative stress induced by MIR. Our results present a novel signalling mechanism that Dex protects MIR injury by activating an AMPK/PI3K/Akt/eNOS pathway.

Association of the PPARγ/PI3K/Akt pathway with the cardioprotective effects of tacrolimus in myocardial ischemic/reperfusion injury

Myocardial ischemia/reperfusion injury (MIRI) induces severe arrhythmias and has a high risk of mortality. The aim of the present study was to investigate the effect of tacrolimus on arrhythmias, cardiac function, oxidative stress and myocardium apoptosis induced by MIRI, and to elucidate the underlying mechanism. The effects of MIRI and tacrolimus on arrhythmias, cardiac function parameters, myocardial oxidative stress and apoptosis were investigated in a rat model of MIRI. The phosphorylation of peroxisome proliferator‑activated receptor γ (PPARγ) and protein kinase B (Akt) was investigated via western blotting. After rats were treated with inhibitors of PPARγ/phosphoinositide 3‑kinase (PI3K)/Akt, cardiac function parameters were measured. The results demonstrated that the MIRI procedure induced arrhythmias and significant impairment of cardiac function, oxidative stress and apoptosis in cardiomyocytes (P<0.05). Tacrolimus significantly alleviated the arrhythmias and impairment of cardiac function and inhibited the oxidative stress and apoptosis in cardiomyocytes (P<0.05). The phosphorylation of PPARγ and Akt was significantly activated by tacrolimus, whereas inhibitors of PPARγ/PI3K/Akt significantly abolished the effects of tacrolimus (P<0.05). Together, these results suggest that tacrolimus may protect rats from MIRI through activation of the PPARγ/PI3K/Akt pathway.

Signaling mediators modulated by cardioprotective interventions in healthy and diabetic myocardium with ischaemia-reperfusion injury

Ischaemic heart diseases are one of the major causes of death in the world. In most patients, ischaemic heart disease is coincident with other risk factors such as diabetes. Patients with diabetes are more prone to cardiac ischaemic dysfunctions including ischaemia-reperfusion injury. Ischaemic preconditioning, postconditioning and remote conditionings are reliable interventions to protect the myocardium against ischaemia-reperfusion injuries through activating various signaling pathways and intracellular mediators. Diabetes can disrupt the intracellular signaling cascades involved in these myocardial protections, and studies have revealed that cardioprotective effects of the conditioning interventions are diminished in the diabetic condition. The complex pathophysiology and poor prognosis of ischaemic heart disease among people with diabetes necessitate the investigation of the interaction of diabetes with ischaemia-reperfusion injury and cardioprotective mechanisms. Reducing the outcomes of ischaemia-reperfusion injury using targeted strategies would be particularly helpful in this population. In this study, we review the protective interventional signaling pathways and mediators which are activated by ischaemic conditioning strategies in healthy and diabetic myocardium with ischaemia-reperfusion injury.

Administration of the Mitochondrial Permeability Transition Pore Inhibitor, TRO40303, prior to Primary Percutaneous Coronary Intervention, Does Not Affect the Levels of Pro-Inflammatory Cytokines or Acute-Phase Proteins

Objectives: In the MITOCARE study, reperfusion injury was not prevented after administration of the mitochondrial permeability transition pore (mPTP) opening inhibitor, TRO40303, in patients with ST-segment elevation myocardial infarction (STEMI) treated with primary percutaneous coronary intervention (pPCI). The effects of TRO40303 on pro-inflammatory cytokines and acute-phase proteins were assessed. Methods: STEMI patients (n = 163, mean age 62 years) with chest pain within 6 h before admission for pPCI were randomized to intravenous bolus of TRO40303 (n = 83) or placebo (n = 80) prior to reperfusion. We tested whether the groups differed in levels of IL-1β, IL-6, IL-10, TNF, and high-sensitive C-reactive protein at various time points (0, 12, and 72 h) after PCI. Further, potential differences between groups in the change of biomarker levels between 0 and 72 h, 0 and 12 h, and 12 and 72 h were tested. Results: There were no statistically significant differences between the two groups, neither in levels of pro-inflammatory cytokines nor in levels of acute-phase proteins, and there were no statistically significant differences in the change of biomarker levels between the groups considering the time intervals from 0 to 72 h, from 0 to 12 h, and from 12 to 72 h. Conclusion: The administration of the mPTP, TRO40303, prior to reperfusion does not alter the pharmacokinetics of pro-inflammatory cytokines or acute-phase proteins during the first 72 h after PCI.

Cardioprotective effects and mechanism of Radix Salviae miltiorrhizae and Lignum Dalbergiae odoriferae on rat myocardial ischemia/reperfusion injury

Radix Salviae miltiorrhizae (SM) and Lignum Dalbergiae odoriferae (DO) are traditional Chinese medicinal herbs used to treat ischemic heart disease and other cardiovascular diseases; however, to the best of our knowledge, there are currently few studies regarding their effects. The present study aimed to investigate the cardioprotective effects of SM and DO during myocardial ischemia/reperfusion (MI/R) injury in rats, and explore the molecular mechanisms that underlie their actions. In the present study, Sprague-Dawley rats were pretreated with SM, the aqueous extract of DO (DOA) and the volatile oil of DO (DOO), either as a monotherapy or in combination for 7 days. Subsequently, the rats were subjected to 30 min of ischemia followed by 180 min of reperfusion. Traditional pharmacodynamic evaluation and metabonomics based on gas chromatography/time-of-flight mass spectrometry were used to identify the therapeutic effects of these traditional Chinese medicines. The results revealed that SM, DOA and DOO monotherapies ameliorated cardiac function, and this effect was strengthened further when used in combined therapies. Among the combined treatments, SM + DOO exhibited the greatest potential (P<0.05) to improve electrocardiogram results and heart rate, reduce the heart weight index and myocardial infarct size, and decrease the levels of creatine kinase-MB and lactate dehydrogenase. In addition, metabonomics-based findings, including the principal component analysis and partial least squares discriminant analysis score plot of the metabolic state in rat serum, provided confirmation for the aforementioned results, verifying that SM + DOO exerted synergistic therapeutic efficacies to exhibit a greater effect on rats with MI/R injury when compared with the other pretreatment groups. Furthermore, the most effective duration of SM + DOO treatment was 30 min and the least effective duration was 180 min. Treatment with SM + DOO also significantly (P<0.01) reduced the number of terminal deoxynucleotidyl transferase-mediated dUTP nick end-labeling-positive cells, tumor necrosis factor-α andinterleukin-6 expression, and malondialdehyde content, and increased the serum and tissue activity of superoxide dismutase. These results indicated that the combined effects of SM + DOO may be more effective compared with the single pretreatments against MI/R injury in rats. This effect may be achieved partly through anti-apoptotic, antioxidant and anti-inflammatory activities. Therefore, SM + DOO may be considered an effective and promising novel strategy for the prophylaxis and treatment of ischemic heart disease.

Prospects for Creation of Cardioprotective and Antiarrhythmic Drugs Based on Opioid Receptor Agonists

It has now been demonstrated that the μ, δ1 , δ2 , and κ1 opioid receptor (OR) agonists represent the most promising group of opioids for the creation of drugs enhancing cardiac tolerance to the detrimental effects of ischemia/reperfusion (I/R). Opioids are able to prevent necrosis and apoptosis of cardiomyocytes during I/R and improve cardiac contractility in the reperfusion period. The OR agonists exert an infarct-reducing effect with prophylactic administration and prevent reperfusion-induced cardiomyocyte death when ischemic injury of heart has already occurred; that is, opioids can mimic preconditioning and postconditioning phenomena. Furthermore, opioids are also effective in preventing ischemia-induced arrhythmias.

Association between clinical parameters and ST-segment resolution after primary percutaneous coronary intervention in patients with acute ST-segment elevation myocardial infarction

BACKGROUND AND OBJECTIVE

The aim of this study was to evaluate and compare various parameters between complete and incomplete ST-segment resolution (STR) patients' groups and to identify associates of STR in patients with acute ST-segment elevation myocardial infarction (STEMI) after primary percutaneous coronary intervention (PPCI) (primary outcome).

MATERIALS AND METHODS

A total of 203 consecutive patients were divided into two groups according to the degree of STR: <70% (incomplete) and ≥70% (complete resolution) 5-15min after the PPCI. The cardiovascular risk factors, sex, Killip class, Thrombolysis in Myocardial Infarction (TIMI) flow, symptom-onset-to-balloon time and door-to-balloon time, and adverse cardiovascular events (secondary outcome) were assessed and compared between two groups.

RESULTS

There were 147 patients with incomplete STR and 56 patients with complete STR. Patients with complete STR were younger, had lower Killip class, shorter duration of the chest pain and were less likely to have anterior myocardial infarction (AMI). Patients in the incomplete STR group had longer symptom-onset-to-balloon and door-to-balloon intervals. TIMI3 flow after PPCI was more common in the complete STR group. TIMI flow ≤2 after PCI, AMI and symptom onset-to-balloon time were inversely associated with STR (beta coefficients -28.635, -28.611, and -0.917, respectively). AMI (OR=29.9), symptom onset-to-balloon time (OR=1.7) and patient's age (OR=1.1) were associated with an increased likelihood of having incomplete STR.

CONCLUSIONS

Patients with complete STR were younger, had lower Killip class, shorter duration of STEMI, were less likely to have AMI, were more likely to recover TIMI3 flow. Age, TIMI-flow grade 2 or less after PPCI, AMI and symptom-onset-to-balloon time were associated with STR.

Antiarrhythmic activity in occlusion-reperfusion model of 1-(1H-indol-4-yloxy)-3-{[2-(2-methoxyphenoxy)ethyl]amino} propan-2-ol and its enantiomers

Acute myocardial infarction (AMI) is a leading cause of mortality and morbidity worldwide, especially in developed countries. The most serious problem after myocardial infarction is reperfusion injury that manifests as functional impairment, arrhythmia, and accelerated progression of cell death in certain critically injured myocytes. Subsequently the infarcted myocardium develops features of necrosis and reactive inflammation. To reduce lethal reperfusion injury in patient with AMI antioxidants, anti-inflammatory agents, adenosine, opioids, metabolic modulators (glucose, insulin, and potassium, nicorandil and agents which reduce intracellular Ca(2+) overload and inhibit Na(+)-H(+) exchange) are used. In this study a novel compound (compound 9) 1-(1 h-indol-4-yloxy)-3-{[2-(2-methoxyphenoxy) ethyl]amino}propan-2-ol and its enantiomers are examined in arrhythmia associated with coronary artery occlusion and reperfusion in a rat model. Antioxidant properties are also determined for test compounds using the malondialdehyde (MDA) lipid peroxidation and ferric reducing antioxidant power (FRAP) tests. In summary, the tested compounds, especially the S enantiomer has a strong antiarrhythmic activity in a model of occlusion and reperfusion of the left coronary artery which is probably related to their adrenolytic action. In contrast to carvedilol, none of the test compound reduced the lipid peroxidation but increased ferric reducing antioxidant power. In the antioxidant effect, there was no difference between the optical forms of compound 9.

Inhibition of PKCβ2 overexpression ameliorates myocardial ischaemia/reperfusion injury in diabetic rats via restoring caveolin-3/Akt signaling

Activation of PKCβ (protein kinase Cβ) plays a critical role in myocardial I/R (ischaemia/reperfusion) injury in non-diabetic rodents. In the myocardium of diabetes, PKCβ2 overexpression is associated with increased vulnerability to post-ischaemic I/R injury with concomitantly impaired cardiomyocyte Cav (caveolin)-3 and Akt signalling compared with non-diabetic rats. We hypothesized that myocardial PKCβ overexpression in diabetes exacerbates myocardial I/R injury through impairing Cav-3/Akt signalling. Streptozotocin-induced diabetic rats were treated with the selective PKCβ inhibitor ruboxistaurin (RBX, 1 mg/kg per day) for 4 weeks, starting from 1 week after diabetes induction, before inducing myocardial I/R achieved by occluding the left descending coronary artery followed by reperfusion. Cardiac function was measured using a pressure-volume conductance system. In an in vitro study, cardiac H9C2 cells were exposed to high glucose (30 mmol/l) and subjected to hypoxia followed by reoxygenation (H/R) in the presence or absence of the selective PKCβ2 inhibitor CGP53353 (1 μmol/l), siRNAs of PKCβ2 or Cav-3 or Akt. Cell apoptosis and mitochondrial membrane potential were assessed by TUNEL (terminal deoxynucleotidyltransferase-mediated dUTP nick-end labelling) and JC-1 staining respectively. RBX significantly decreased post-ischaemic myocardial infarct size (35±5% compared with 49±3% in control, P<0.05) and attenuated cardiac dysfunction, and prevented the reduction in cardiac Cav-3 and enhanced phosphorylated/activated Akt (p-Akt) in diabetic rats (P<0.05). H/R increased cardiomyocyte injury under high glucose conditions as was evident by increased TUNEL-positive and increased JC-1 monomeric cells (P<0.05 compared with control), accompanied with increased PKCβ2 phosphorylation/activation and decreased Cav-3 expression. Either CGP53353 or PKCβ2 siRNA significantly attenuated all of these changes and enhanced p-Akt. Cav-3 gene knockdown significantly reduced p-Akt and increased post-hypoxic cellular and mitochondrial injury despite a concomitant reduction in PKCβ2 phosphorylation. PKCβ2 inhibition with RBX protects diabetic hearts from myocardial I/R injury through Cav-3-dependent activation of Akt.

Prognostic value of pentraxin-3 level in patients with STEMI and its relationship with heart failure and markers of oxidative stress

OBJECTIVE

Pentraxin-3 (PTX3) appears to have a cardioprotective effect through a positive influence against postreperfusion damage. This study assesses the prognostic value of PTX3 level and its relationship with clinical parameters and markers of oxidative stress and nitric oxide metabolism in patients with ST-elevation myocardial infarction (STEMI).

METHODS

Plasma/serum levels of several biomarkers of inflammation and oxidative stress and nitrite/nitrate were assessed upon admission and 24 h after STEMI onset in patients treated by primary percutaneous coronary intervention.

RESULTS

ROC analysis showed that plasma PTX3 at 24 h was a strong predictor of 30-day and 1-year mortality and independent predictor of combined end-point of left ventricle dysfunction or mortality in 1 year. The inflammatory response expressed by PTX3 had a significant relationship with age, heart failure, infarct size, impaired flow in the infarct-related artery, and renal function and positively correlated with neopterin, TNF-α, 8-hydroxy-2'-deoxyguanosine, and nitrite/nitrate.

CONCLUSIONS

Plasma PTX3 at 24 h after STEMI onset is a strong predictor of 30-day and 1-year mortality. PTX3 as a single biomarker is comparable with currently used scoring systems (TIMI or GRACE) or B-type natriuretic peptide. PTX3 is also an independent predictor of combined end-point of left ventricle dysfunction or mortality in 1 year.

B-type natriuretic peptide as a predictor of ischemia/reperfusion injury immediately after myocardial reperfusion in patients with ST-segment elevation acute myocardial infarction

BACKGROUND

In animal models of acute myocardial infarction (AMI), B-type natriuretic peptide (BNP) administered before and during coronary occlusion limits infarct size. However, the relation between plasma BNP levels and ischemia/reperfusion injury remains unclear.

METHODS

302 patients with ST-segment elevation AMI (STEMI) received emergency percutaneous coronary intervention within six hours from the onset. The patients were divided into two groups according to the plasma BNP level before angiography: group L (n=151), BNP ≤ 32.2 pg/ml; group H (n=151), BNP >32.2 pg/ml. The Selvester QRS-scoring system was used to estimate infarct size.

RESULTS

The rate of ischemia/reperfusion injury immediately after reperfusion, defined as reperfusion ventricular arrhythmias (26% vs. 11%, p=0.001) and ST-segment re-elevation (44% vs. 22%, p=0.008), was higher in group L than in group H. Group L had a greater increase in the QRS score during percutaneous coronary intervention (3.55 ± 0.17 vs. 2.09 ± 0.17, p<0.001) and a higher QRS score 1 h after percutaneous coronary intervention (5.77 ± 0.28 vs. 4.51 ± 0.28, p=0.002). On multivariate analysis, plasma BNP levels in the lower 50th percentile were an independent predictor of reperfusion injury (odds ratio, 2.620; p<0.001). The odds ratios of reperfusion injury according to decreasing quartiles of BNP level, as compared with the highest quartile, were 1.536, 3.692 and 4.964, respectively (p trend=0.002).

CONCLUSIONS

Plasma BNP level before percutaneous coronary intervention may be a predictor of ischemia/reperfusion injury and the resultant extent of myocardial damage. Our findings suggest that high plasma BNP levels might have a clinically important protective effect on ischemic myocardium in patients with STEMI who receive percutaneous coronary intervention.

The effects of ischemic postconditioning on myocardial function and nitric oxide metabolites following ischemia-reperfusion in hyperthyroid rats

Ischemic postconditioning (IPost) could decrease ischemia-reperfusion (IR) injury. It has not yet reported whether IPost is useful when ischemic heart disease is accompanied with co-morbidities like hyperthyroidism. The aim of this study was to examine the effect of IPost on myocardial IR injury in hyperthyroid male rats. Hyperthyroidism was induced with administration of thyroxine in drinking water (12 mg/L) over a period of 21 days. After thoracotomy, the hearts of control and hyperthyroid rats were perfused in the Langendorff apparatus and subjected to 30 minutes global ischemia, followed by 120 minutes reperfusion; IPost, intermittent early reperfusion, was induced instantly following ischemia. In control rats, IPost significantly improved the left ventricular developed pressure (LVDP) and ±dp/dt during reperfusion (p<0.05); however it had no effect in hyperthyroid rats. In addition, hyperthyroidism significantly increased basal NO_x (nitrate+nitrite) content in serum (125.5±5.4 µmol/L vs. 102.8±3.7 µmol/L; p< 0.05) and heart (34.9±4.1 µmol/L vs. 19.9±1.94 µmol/L; p<0.05). In hyperthyroid groups, heart NO_x concentration significantly increased after IR and IPost, whereas in the control groups, heart NO_x were significantly higher after IR and lower after IPost (p< 0.05). IPost reduced infarct size (p<0.05) only in control groups. In hyperthyroid group subjected to IPost, aminoguanidine, an inducible nitric oxide (NO) inhibitor, significantly reduced both the infarct size and heart NO_x concentrations. In conclusion, unlike normal rats, IPost cycles following reperfusion does not provide cardioprotection against IR injury in hyperthyroid rats; an effect that may be due to NO overproduction because it is restored by iNOS inhibition.

Luteolin inhibits ROS-activated MAPK pathway in myocardial ischemia/reperfusion injury

AIMS

Luteolin is a falconoid compound that has an antioxidant effect, but its contribution to ROS-activated MAPK pathways in ischemia/reperfusion injury is seldom reported. Here, we have confirmed that it exhibits an antioxidant effect in myocardial ischemia/reperfusion injury (MIRI) by inhibiting ROS-activated MAPK pathways.

MAIN METHODS

We exposed rat hearts into the left anterior descending coronary artery (LAD) ligation for 30min followed by 1h of reperfusion. Observations were carried out using electrocardiography; detection of hemodynamic parameters; and testing levels of lactate dehydrogenase (LDH), creatine kinase (CK), total superoxide dismutase (T-SOD), and malondialdehyde (MDA). Mitogen-activated protein kinase (MAPK) pathway was measured by western blot and transmission electron microscopy was applied to observe the myocardial ultrastructure. Rat H9c2 cell in 95% N2 and 5% CO2 stimulated the MIRI. Oxidation system mRNA levels were measured by real-time PCR; mitochondrial membrane potential and apoptosis were measured by confocal microscopy and flow cytometry; western blot analysis was used to assay caspase-3, -8, and -9 and MAPK pathway protein expression; the MAPK pathway was inhibited using SB203580 (p38 MAPK inhibitor) and SP600125 (c-Jun NH2-terminal kinase inhibitor) before H9c2 cells were exposed to hypoxia/reoxygenation injury to show the modulation of the changes in ROS generation, cell viability and apoptosis.

KEY FINDINGS

In vivo, luteolin can ameliorate the impaired mitochondrial morphology, regulating the MAPK pathway to protect MIRI. In vitro, luteolin can affect the oxidation system, mitochondrial membrane potential and MAPK pathway to anti-apoptosis.

SIGNIFICANCE

These results reveal a ROS-MAPK mediated mechanism and mitochondrial pathway through which luteolin can protect myocardial ischemia/reperfusion injury.

Concentration-dependent wrestling between detrimental and protective effects of H2O2 during myocardial ischemia/reperfusion

Reactive oxygen species (ROS) and endoplasmic reticulum (ER) stress are paradoxically implicated in myocardial ischemia/reperfusion (I/R) injury and cardioprotection. However, the precise interpretation for the dual roles of ROS and its relationship with the ER stress during I/R remain elusive. Here we investigated the concentration-dependent effects of hydrogen peroxide (H2O2) preconditioning (PC) and postconditioning (PoC) on the ER stress and prosurvival reperfusion injury salvage kinase (RISK) activation using an ex vivo rat myocardial I/R model. The effects of H2O2 PC and PoC showed three phases. At a low level (1 μM), H2O2 exacerbated I/R-induced left ventricular (LV) contractile dysfunction and ER stress, as indicated by enhanced phosphorylation of protein kinase-like ER kinase and expressions of glucose-regulated protein 78, X-box-binding protein 1 splicing variant, TNF receptor-associated factor 2, activating transcription factor-6 cleaved 50 kDa fragment, and caspase-12 cleavage, but the I/R-induced RISK activation including protein kinase B (PKB/Akt) and protein kinase Cɛ (PKCɛ) remained unchanged. Consistently, the postischemic LV performance in 1 μM H2O2 PC and PoC groups was improved by inhibiting ER stress with 4-phenyl butyric acid but not affected by the ER stress inducer, tunicamycin. At a moderate level (10-100 μM), H2O2 significantly improved postischemic LV performance and enhanced RISK activation, but it did no further alter the ER stress. The cardioprotection but not ER stress was abrogated with Akt or PKCɛ inhibitor wortmannin or ɛV1-2. At a high level (1 mM), H2O2 markedly aggravated the reperfusion injury and the oxidative stress but did not further enhance the RISK activation. In addition, 1 or 20 μM of H2O2 PC did not alter cardioprotective effects of ischemic PC in postischemic contractile performance and protein oxidation. Our data suggest that the differential effects of H2O2 are derived from a concentration-dependent wrestling between its detrimental stress and protective signaling.

Preconditioning by isoflurane elicits mitochondrial protective mechanisms independent of sarcolemmal KATP channel in mouse cardiomyocytes

Cardiac mitochondria and the sarcolemmal (sarc)KATP channels contribute to cardioprotective signaling of anesthetic-induced preconditioning. Changes in mitochondrial bioenergetics influence the sarcolemmal ATP-sensitive K (sarcKATP) channel function, but whether this channel has impacts on mitochondria is uncertain. We used the mouse model with deleted pore-forming Kir6.2 subunit of sarcKATP channel (Kir6.2 KO) to investigate whether the functional sarcKATP channels are necessary for isoflurane activation of mitochondrial protective mechanisms. Ventricular cardiomyocytes were isolated from C57Bl6 wild-type (WT) and Kir6.2 KO mouse hearts. Flavoprotein autofluorescence, mitochondrial reactive oxygen species production, and mitochondrial membrane potential were monitored by laser-scanning confocal microscopy in intact cardiomyocytes. Cell survival was assessed using H2O2-induced stress. Isoflurane (0.5 mM) increased flavoprotein fluorescence to 180% ± 14% and 190% ± 15% and reactive oxygen species production to 118% ± 2% and 124% ± 6% of baseline in WT and Kir6.2 KO myocytes, respectively. Tetramethylrhodamine ethyl ester fluorescence decreased to 84% ± 6% in WT and to 86% ± 4% in Kir6.2 KO myocytes. This effect was abolished by 5HD. Pretreatment with isoflurane decreased the stress-induced cell death from 31% ± 1% to 21% ± 1% in WT and from 44% ± 2% to 35% ± 2% in Kir6.2 KO myocytes. In conclusion, Kir6.2 deletion increases the sensitivity of intact cardiomyocytes to oxidative stress, but does not alter the isoflurane-elicited protective mitochondrial mechanisms, suggesting independent roles for cardiac mitochondria and sarcKATP channels in anesthetic-induced preconditioning by isoflurane.

Do we know enough about the immune pathogenesis of acute coronary syndromes to improve clinical practice?

Morbidities related to atherosclerosis, such as acute coronary syndromes (ACS) including unstable angina and myocardial infarction, remain leading causes of mortality. Unstable plaques are inflamed and infiltrated with macrophages and T lymphocytes. Activated dendritic cells interact with T cells, yielding predominantly Th1 responses involving interferon-gamma (IFN-γ) and tumour necrosis factor-alpha (TNF-α), while the role of interleukin 17 (IL-17) is questionable. The expansion of CD28nullCD4 or CD8 T cells as well as pattern recognition receptors activation (especially Toll-like receptors; TLR2 and TLR4) is characteristic for unstable plaque. Inflammation modifies platelet and fibrin clot characteristics, which are critical for ACS. Understanding of the inflammatory mechanisms of atherothrombosis, bridging inflammation, oxidative stress and immune regulation, will allow for the detection of subjects at risk, through the use of novel biomarkers and imaging techniques including intravascular ultrasound, molecular targeting, magnetic resonance imaging (MRI) and 18F-fluorodeoxyglucose (18F-FDG) positron emission tomography (PET). Moreover, understanding the specific inflammatory pathways of plaque rupture and atherothrombosis may allow for immunomodulation of ACS. Statins and anti-platelet drugs are anti-inflammatory, but importance of immune events in ACS warrants the introduction of novel, specific treatments directed either on cytokines, TLRs or inflammasomes. While the prime time for the introduction of immunologically inspired diagnostic tests and treatments for atherosclerosis have not come yet, we are closer than ever before to finally being able to benefit from this vast body of experimental and clinical evidence. This paper provides a comprehensive review of the role of the immune system and inflammation in ACS.

Exercise preconditioning provides early cardioprotection against exhaustive exercise in rats: potential involvement of protein kinase C delta translocation

The objective of this study was to investigate the early cardioprotective effect of exercise preconditioning (EP) on the exhaustive exercise-induced myocardial injury in rats and the role of protein kinase C delta isoform (PKCδ) in EP. Rats were subjected to run on the treadmill for four periods of 10 min each at 30 m/min with intervening periods of rest of 10 min as an EP protocol. The exhaustive exercise was performed 0.5 h after EP. PKC inhibitor chelerythrine (CHE) was injected before EP. Our results showed that EP markedly attenuated the exhaustive exercise-induced myocardial ischemia/hypoxia, ultrastructural damage, high serum cTnI, and NT-proBNP levels. CHE injection before EP did not abolish the protection of EP. Both exhaustive exercise and EP produced a significant increase in PKCδ and p-PKCδ(Thr507) protein levels in cardiomyocytes. However, the immunostaining of p-PKCδ(Thr507) in EP cardiomyocytes was primarily localized to intercalated disks and nuclei while the exhaustive exercise-induced high level p-PKCδ(Thr507) was mainly distributed in the cytoplasm. Moreover, the high PKCδ and p-PKCδ(Thr507) levels in exhaustive exercise were significantly down-regulated by EP. CHE did not attenuate the expressions of PKCδ and p-PKCδ(Thr507). These results indicate that an appropriate activation and translocation of PKCδ may represent a mechanism whereby EP can exert an early cardioprotection against exhaustive exercise-induced myocardial injury.

Protective effect of novel pyridoindole derivatives on ischemia/reperfusion injury of the isolated rat heart

Generation of reactive oxygen species is a major, well-known cause of heart injury induced by ischemia-reperfusion. This injury is manifested through myocardial stunning, reperfusion and lethal reperfusion injury of cardiocytes. The pyridoindole stobadine has been shown to exhibit significant antioxidant, free-radical scavenging and hypoxic-tissue-protecting properties. The present study examined the effects of stobadine and two novel derivatives, SMe1 and SMe1EC2, which exhibit improved pharmacodynamic and toxicity profiles, on the functional properties and reperfusion dysrhythmias of the isolated rat heart in ischemia-reperfusion conditions. All experiments were performed on isolated Langendorff-perfused hearts isolated from 3-month-old male Wistar rats. After 15 min of stabilization, the hearts were subjected to a 30-minute period of global no-flow ischemia, followed by a 30-minute reperfusion period. Stobadine, SMe1 and SMe1EC2 were applied at a concentration of 1 x 10(-5) 10 min before the onset of ischemia, and during reperfusion through the perfusion medium. As compared to the untreated group, addition of SMe1EC2 during reperfusion significantly increased left ventricular developed pressure, decreased pathologically elevated left ventricular end-diastolic pressure and enhanced recovery of the stunned myocardium after ischemia. Both SMe1 and stobadine failed to influence these parameters; however, all derivatives tested inhibited serious life-threatening reperfusion dysrhythmias such as ventricular tachycardia and ventricular fibrillation. Our findings suggest that SMe1EC2 promotes an improved recovery of the left ventricular function following ischemia compared to either stobadine or SMe1. However, both SMe1EC2 and SMe1 manifested a significant anti-dysrhythmic effect comparable with that of stobadine and partially reduced myocardial ischemia-reperfusion-induced injury.

Synergistic protection of Danhong injection (丹红注射液) and ischemic postconditioning on myocardial reperfusion injury in minipigs

OBJECTIVE

To explore the synergistic protection of Danhong Injection (丹红注射液, DHI) and ischemic postconditioning on myocardial reperfusion injury in minipigs.

METHODS

Acute myocardial infarction model was made by balloon occlusion in left anterior descending coronary artery (LAD) of minipigs, and then postconditioning was simulated through inflation/deflation of the angioplasty balloon. Minipigs were divided into four groups: the sham operation group (SH group), the ischemia/reperfusion group (I/R group), the ischemic postconditioning group (POC group) and DHI combined with ischemic postconditioning group (PAD group, DHI 20 mL through ear vein), six in each group. After 24-h continuous observation, myocardial infarction size was assessed by triphenyltetrazolium staining (TTC). Morphological changes of ischemic myocardium were observed by light microscopy, and cardiomyocyte ultrastructure was studied with electron microscopy. The superoxide dismutase (SOD) and malondialdehyde (MDA) activity in heart homogenates were measured by a biochemical method.

RESULTS

The myocardial infarction size was smaller in the POC group than in the I/R group (0.26 ± 0.02 vs. 0.37 ± 0.09, P<0.05), and the PAD group (0.14 ± 0.08) displayed a significantly reduced infarction size relative to the I/R group (P<0.01) and POC group (P<0.05). The damage of myocardial tissue was severe in the I/R group shown by light and electron microscopy: myocardial fibers disorder, sarcoplasmic dissolution, myofilament fracture, mitochondria swelling and even vacuolization formation and a large number of inflammatory cell infiltrations. Compared with the I/R group, reduction of reperfusion injury in the PAD group included more orderly arranged myocardial fibers, less infiltration of inflammatory cells and maintenance of mitochondrial integrity. Compared with the I/R group, the damage of myocardial tissue in the POC group was improved, but not as significant as that in the PAD group. SOD levels in the POC group and the PAD group were significantly higher than those in the I/R group (96.96 ± 13.43, 112.25 ± 22.75 vs. 76.32 ± 10.63, P<0.05), and MDA was significantly lower in the POC group and the PAD group compared to the I/R group (1.27 ± 0.19, 1.09 ± 0.21 vs. 1.47 ± 0.16, P<0.05).

CONCLUSION

DHI and ischemic postconditioning show a synergistic cardioprotection on myocardial reperfusion injury in minipigs.

[Postconditioning in acute myocardial infarction: Primary angioplasty revisited?]

Early reperfusion of ischemic myocardium is the mean to improve prognosis of acute myocardial infarction. Nevertheless, reperfusion injury due to immediate acidosis correction and subsequent Ca(2+) overload results in formation of the mitochondrial permeability transition pore. The consequence is the death of viable myocardium due to onconecrosis and apoptosis. Mechanical (Stuttering reperfusion) or pharmacological postconditioning (cyclosporine A, adenosine…) is able to prevent reperfusion injury resulting in more myocardial salvage.