Cardiomyocyte death induced by myocardial ischemia and reperfusion: measurement with recombinant human annexin-V in a mouse model

UBIAD1 effectively alleviated myocardial ischemia reperfusion injury by activating SIRT1/PGC1α

BACKGROUND AND OBJECTIVES

Myocardial ischemia-reperfusion injury (MIRI) threatens global health and lowers people's sense of happiness. Till now, the mechanism of MIRI has not been well-understood. Therefore, this study was designed to explore the role of UBIAD1 in MIRI as well as its detailed reaction mechanism.

METHODS

The mRNA and protein expressions of UBIAD1 before or after transfection were measured using RT-qPCR and western blot. Western blot was also adopted to measure the expressions of signaling pathway-, mitochondrial damage- and apoptosis-related proteins. Moreover, mitochondrial membrane potential and ATP level were verified by JC-1 immunofluorescence and ATP kits, respectively. With the application of CCK-8, LDH and CK-MB assays, the cell viability, LDH and CK-MB levels were evaluated, respectively. In addition, the cell apoptosis was detected using TUNEL. Finally, the expressions of ROS, SOD, MDA and CAT were measured using DCFH-DA, SOD, MDA and CAT assays, respectively.

RESULTS

In the present study, we found that UBIAD1 was downregulated in hypoxia-reoxygenation (H/R) -induced H9C2 cells and its upregulation could activate SIRT1/PGC1α signaling pathway. It was also found that UBIAD1 regulated mitochondrial membrane potential and ATP level via activating SIRT1/PGC1α signaling pathway. In addition, the injury of H/R-induced H9C2 cells could be relieved by UBIAD1 through the activation of SIRT1/PGC1α signaling pathway. Moreover, UBIAD1 exhibited inhibitory effects on apoptosis and oxidative stress of H/R-induced H9C2 cells through activating SIRT1/PGC1α signaling pathway.

CONCLUSION

To sum up, UBIAD1 could alleviate apoptosis, oxidative stress and H9C2 cell injury by activating SIRT1/PGC1α, which laid experimental foundation for the clinical treatment of MIRI.

Blocking RIPK2 Function Alleviates Myocardial Ischemia/Reperfusion Injury by Regulating the AKT and NF-κB Pathways

OBJECTIVE

Inflammation and oxidation brought on by myocardial ischemia-reperfusion (MI/R) injury lead to cardiomyocyte apoptosis and necrosis. The receptor interacting serine/threonine kinase 2 (RIPK2) plays significant roles in oxidative stress and excessive inflammation. The purpose of this research is to examine the roles of RIPK2 in MI/R injury.

METHODS

The in vivo animal model was constructed by acute coronary I/R, and the in vitro cell model was established by oxygen and glucose deprivation/reperfusion (OGD/R)-stimulated cardiomyocyte injury. RIPK2 expression was examined using qRT-PCR and Western blot. CCK-8 was proposed as a method for detecting cell proliferation. ELISA was utilized to measure inflammatory cytokines (TNF-α, IL-6, and IL-1β) and myocardial injury indicators (CK-MB, Mb, cTnI, and LDH). The levels of MDA and ROS were determined by the kit and fluorescent probe. H&E was conducted to assess MI/R injury after silencing of RIPK2.

RESULTS

In MI/R rats and OGD/R-treated H9C2 cardiomyocytes, RIPK2 was overexpressed at both the mRNA and protein levels. RIPK2 inhibition promoted cell proliferation while inhibiting apoptosis, as evidenced by decreased TUNEL-positive cells and cleaved caspase-3. RIPK2 inhibition reduced MDA and ROS levels, as well as the contents of inflammatory factors. RIPK2 silencing reduced CK-MB, Mb, cTnI, and LDH levels in rat serum and alleviated MI/R injury. Furthermore, RIPK2 inhibition increased p-AKT while decreasing NF-B p-p65 expression.

CONCLUSION

Silencing of RIPK2 reduced apoptosis, proinflammatory factors, and oxidative stress in MI/R by activating AKT and suppressing NF-κB signals, suggesting a potential therapeutic strategy for MI/R injury.

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

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

Detection of apoptosis by [18F]ML-10 after cardiac ischemia-reperfusion injury in mice

OBJECTIVE

Myocardial infarction leads to ischemic heart disease and cell death, which is still a major obstacle in western society. In vivo imaging of apoptosis, a defined cascade of cell death, could identify myocardial tissue at risk.

METHODS

Using 2-(5-[¹⁸F]fluoropentyl)-2-methyl-malonic acid ([¹⁸F]ML-10) in autoradiography and positron emission tomography (PET) visualized apoptosis in a mouse model of transient ligation of the left anterior descending (LAD) artery. 2-deoxy-2-[18F]fluoro-D-glucose ([¹⁸F]FDG) PET imaging indicated the defect area. Terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) histology stain indicated cardiac apoptosis.

RESULTS

[¹⁸F]ML-10 uptake was evident in the ischemic area after transient LAD ligation in ex vivo autoradiography and in vivo PET imaging. Detection of [¹⁸F]ML-10 is in line with the defect visualized by [¹⁸F]FDG and the histological approach of TUNEL staining.

CONCLUSION

The tracer [¹⁸F]ML-10 is suitable for detecting apoptosis after transient LAD ligation in mice.

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

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

Activation of the sigma-1 receptor exerts cardioprotection in a rodent model of chronic heart failure by stimulation of angiogenesis

Background

Angiogenesis plays a critical role on post-infarction heart failure (PIHF), the presence of which facilitates additional blood supply to maintain the survival of residual cardiomyocytes. The sigma-1 receptor (S1R) has been substantiated to stimulate angiogenesis, with the effect on a model of PIHF remaining unknown.

Aims

This study aims to investigate the effects of S1R on PIHF and the underlying mechanisms involved.

Methods

Rats were implemented left anterior descending artery ligation followed by rearing for 6 weeks to induce a phenotype of heart failure. Daily intraperitoneal injection of S1R agonist or antagonist for 5 weeks was applied from 2nd week after surgery. The effects exerted by S1R were detected by echocardiography, hemodynamic testing, western blot, Sirius red dyeing, ELISA, immunohistochemistry and fluorescence. We also cultured HUVECs to verify the mechanisms in vitro.

Results

Stimulation of S1R significantly ameliorated the cardiac function resulted from PIHF, in addition to the observation of reduced fibrosis in the peri-infarct region and the apoptosis of residual cardiomyocytes, which were associated with augmentation of microvascular density in peri-infarct region through activation of the JAK2/STAT3 pathway. We also indicated that suppression of JAK2/STAT3 pathway by specific inhibitor in vitro reversed the pro-angiogenic effects of S1R on HUVECs, which further confirmed that angiogenesis, responsible for PIHF amelioration, by S1R stimulation was in a JAK2/STAT3 pathway-dependent manner.

Conclusion

S1R stimulation improved PIHF-induced cardiac dysfunction and ventricular remodeling through promoting angiogenesis by activating the JAK2/STAT3 pathway.

Supplementary Information

The online version contains supplementary material available at 10.1186/s10020-022-00517-1.

Cardiac fibroblast heat shock protein 47 aggravates cardiac fibrosis post myocardial ischemia–reperfusion injury by encouraging ubiquitin specific peptidase 10 dependent Smad4 deubiquitination

Despite complications were significantly reduced due to the popularity of percutaneous coronary intervention (PCI) in clinical trials, reperfusion injury and chronic cardiac remodeling significantly contribute to poor prognosis and rehabilitation in AMI patients. We revealed the effects of HSP47 on myocardial ischemia–reperfusion injury (IRI) and shed light on the underlying molecular mechanism. We generated adult mice with lentivirus-mediated or miRNA (mi1/133TS)-aided cardiac fibroblast-selective HSP47 overexpression. Myocardial IRI was induced by 45-min occlusion of the left anterior descending (LAD) artery followed by 24 h reperfusion in mice, while ischemia-mediated cardiac remodeling was induced by four weeks of reperfusion. Also, the role of HSP47 in fibrogenesis was evaluated in cardiac fibroblasts following hypoxia–reoxygenation (HR). Extensive HSP47 was observed in murine infarcted hearts, human ischemic hearts, and cardiac fibroblasts and accelerated oxidative stress and apoptosis after myocardial IRI. Cardiac fibroblast-selective HSP47 overexpression exacerbated cardiac dysfunction caused by chronic myocardial IRI and presented deteriorative fibrosis and cell proliferation. HSP47 upregulation in cardiac fibroblasts promoted TGFβ1–Smad4 pathway activation and Smad4 deubiquitination by recruiting ubiquitin-specific peptidase 10 (USP10) in fibroblasts. However, cardiac fibroblast specific USP10 deficiency abolished HSP47-mediated fibrogenesis in hearts. Moreover, blockage of HSP47 with Col003 disturbed fibrogenesis in fibroblasts following HR. Altogether, cardiac fibroblast HSP47 aggravates fibrosis post-myocardial IRI by enhancing USP10-dependent Smad4 deubiquitination, which provided a potential strategy for myocardial IRI and cardiac remodeling.

The protective role of prolyl oligopeptidase (POP) inhibition in acute lung injury induced by intestinal ischemia-reperfusion

Intestinal ischemia-reperfusion (II/R) develops when the blood flow to the intestines decreases, followed by the reestablishment of the blood supply to the ischemic tissue, resulting in intestinal mucosal barrier dysfunction, with consequent severe local and systemic inflammation. Acute lung injury (ALI) represents the most serious complication after II/R. KYP-2047 is a selective inhibitor of prolyl oligopeptidase (POP), a serine protease involved in the release of pro-angiogenic and inflammatory molecules. The aim of the present study is to assess the effects of POP-inhibition mediated by KYP-2047 treatment in the pathophysiology of ALI following II/R. An in vivo model of II/R was performed and mice were subjected to KYP-2047 treatment (intraperitoneal, 1, 2.5 and 5 mg/kg). Histological analysis, Masson’s trichrome staining, immunohistochemical, immunofluorescence, biochemical and western blots analysis were performed on ileum and lung samples. KYP-2047 treatment ameliorated histological alteration in ileum and lung, reduced collagen amount and lowered inflammatory protein levels. Moreover, TGF-β1, eNOS, VEGF and CD34 positive staining has been modulated; also, a reduction in apoptosis expression was confirmed. This research revealed the strong anti-inflammatory potential of KYP-2047 associated to its modulatory role on angiogenesis and apoptosis, suggesting POP as a novel therapeutic target for ALI after II/R.

WTAP promotes myocardial ischemia/reperfusion injury by increasing endoplasmic reticulum stress via regulating m6A modification of ATF4 mRNA

Myocardial infarction (MI) is one of the leading causes of death. Wilms' tumor 1-associating protein (WTAP), one of the components of the m⁶A methyltransferase complex, has been shown to affect gene expression via regulating mRNA modification. Although WTAP has been implicated in various diseases, its role in MI is unclear. In this study, we found that hypoxia/reoxygenation (H/R) time-dependently increased WTAP expression, which in turn promoted endoplasmic reticulum (ER) stress and apoptosis, in human cardiomyocytes (AC16). H/R effects on ER stress and apoptosis were all blocked by silencing of WTAP, promoted by WTAP overexpression, and ameliorated by administration of ER stress inhibitor, 4-PBA. We then investigated the underlying molecular mechanism and found that WTAP affected m⁶A methylation of ATF4 mRNA to regulate its expression, and that the inhibitory effects of WTAP on ER stress and apoptosis were ATF4 dependent. Finally, WTAP’s effects on myocardial I/R injury were confirmed in vivo. WTAP promoted myocardial I/R injury through promoting ER stress and cell apoptosis by regulating m⁶A modification of ATF4 mRNA. These findings highlight the importance of WTAP in I/R injury and provide new insights into therapeutic strategies for MI.

The Protective of Baicalin on Myocardial Ischemia-Reperfusion Injury

BACKGROUND

The aim of this study was to explore the inhibitory effect of baicalin on myocardial apoptosis induced by Ischemia-Reperfusion (I/R).

METHODS

Sprague Dawley rats' heart and myocardial cells I/R model were established in vivo and vitro, then 100 mg/kg and 10 μmol/l baicalin were administrated, respectively. The experiment was randomly divided into 4 groups (n=10): Control; I/R; IR+DMEM; and I/R+baicalin groups. Postoperation, the Left Ventricular (LV) End-Diastolic Pressure (LVEDP), the maximum velocity of LV contraction (dP/dtmax) and the maximum velocity of LV diastole (dP/dtmin) were recorded by the transthoracic echocardiography; the myocardial apoptosis percentage was analyzed by Annexin VFITC/ PI and TUNEL staining, and the apoptosis gene and protein were detected by RT-PCR and western blot. Furthermore, the protein expression of the calcium-sensing receptor (CaSR) and ERK1/2 phosphorylation were observed by western blot and Fura-2-acetoxymethyl ester. Moreover, primary rats' cardiomyocytes were cultured and ERK1/2 specific inhibitor PD98059 was added to the culture medium. The cell survival rate, vitality and apoptosis were detected by MTT, lactate dehydrogenase (LDH) and TUNEL staining assay Kit, respectively.

RESULTS

Our present study showed that baicalin significantly improved LV hemodynamic parameters and myocardial apoptosis in myocardial I/R injury rats. Furthermore, we found that baicalin could down-regulate the protein expression of CaSR, but up-regulate the protein expression of ERK1/2. Furthermore, when the cells were pretreated with ERK1/2 inhibitor PD98059, the cells survival rate significantly decreased, but LDH activity and apoptosis significantly increased. The results indicated that the effect of baicalin on myocardial I/R injury could be inhibited by ERK1/2 inhibitor.

CONCLUSION

In conclusion, our data suggests that baicalin attenuates I/R-induced myocardial injury maybe through the suppression of the CaSR/ERK1/2 signaling pathway.

RETRACTED: Human bone mesenchymal stem cells-derived exosomes overexpressing microRNA-26a-5p alleviate osteoarthritis via down-regulation of PTGS2

This article has been retracted: please see Elsevier Policy on Article Withdrawal (http://www.elsevier.com/locate/withdrawalpolicy). This article has been retracted at the request of the Editor-in-Chief. Concern was raised about the reliability of the Western blot results in Figures 2E, 3D and F, 4B, E+G, 5D+I, and 6D+F, which appear to have a similar phenotype as contained in many other publications, detailed here: https://pubpeer.com/publications/73C0A79F5EDF9ECC9818CE2D9B2A09; and here: https://docs.google.com/spreadsheets/d/1r0MyIYpagBc58BRF9c3luWNlCX8VUvUuPyYYXzxWvgY/edit#gid=262337249. The provenance of the flow cytometry data in Figure 5A was also questioned, as it appeared to have histograms that were hand drawn. The journal requested the corresponding author comment on these concerns and provide the raw data. The authors did not respond to this request and therefore the Editor-in-Chief decided to retract the article.

The bifunctional SDF-1-AnxA5 fusion protein protects cardiac function after myocardial infarction

Stromal cell‐derived factor‐1 (SDF‐1) is a well‐characterized cytokine that protects heart from ischaemic injury. However, the beneficial effects of native SDF‐1, in terms of promoting myocardial repair, are limited by its low concentration in the ischaemic myocardium. Annexin V (AnxA5) can precisely detect dead cells in vivo. As massive cardiomyocytes die after MI, we hypothesize that AnxA5 can be used as an anchor to carry SDF‐1 to the ischaemic myocardium. In this study, we constructed a fusion protein consisting of SDF‐1 and AnxA5 domains. The receptor competition assay revealed that SDF‐1‐AnxA5 had high binding affinity to SDF‐1 receptor CXCR4. The treatment of SDF‐1‐AnxA5 could significantly promote phosphorylation of AKT and ERK and induce chemotactic response, angiogenesis and cell survival in vitro. The binding membrane assay and immunofluorescence revealed that AnxA5 domain had the ability to specifically recognize and bind to cells injured by hypoxia. Furthermore, SDF‐1‐AnxA5 administered via peripheral vein could accumulate at the infarcted myocardium in vivo. The treatment with SDF‐1‐AnxA5 attenuated cell apoptosis, enhanced angiogenesis, reduced infarcted size and improved cardiac function after mouse myocardial infarction. Our results suggest that the bifunctional SDF‐1‐AnxA5 can specifically bind to dead cells. The systemic administration of bifunctional SDF‐1‐AnxA5 effectively provides cardioprotection after myocardial infarction.

Cardioprotective mechanism of FTY720 in ischemia reperfusion injury

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

Cardiac fibrosis: potential therapeutic targets

Cardiovascular disease is a leading cause of mortality in the world and is exacerbated by the presence of cardiac fibrosis, defined by the accumulation of noncontractile extracellular matrix proteins. Cardiac fibrosis is directly linked to cardiac dysfunction and increased risk of arrhythmia. Despite its prevalence, there is a lack of efficacious therapies for inhibiting or reversing cardiac fibrosis, largely due to the complexity of the cell types and signaling pathways involved. Ongoing research has aimed to understand the mechanisms of cardiac fibrosis and develop new therapies for treating scar formation. Major approaches include preventing the formation of scar tissue and replacing fibrous tissue with functional cardiomyocytes. While targeting the renin-angiotensin-aldosterone system is currently used as the standard line of therapy for heart failure, there has been increased interest in inhibiting the transforming growth factor-β signaling pathway due its established role in cardiac fibrosis. Significant advances in cell transplantation therapy and biomaterials engineering have also demonstrated potential in regenerating the myocardium. Novel techniques, such as cellular direct reprogramming, and molecular targets, such as noncoding RNAs and epigenetic modifiers, are uncovering novel therapeutic options targeting fibrosis. This review provides an overview of current approaches and discuss future directions for treating cardiac fibrosis.

Human Tissue-Engineered Model of Myocardial Ischemia-Reperfusion Injury

IMPACT STATEMENT

Reducing ischemia-reperfusion injury would significantly improve patient survival. Current preclinical models are inadequate because they rely on animals, which do not emulate human physiology and the clinical setting. We developed a human tissue platform that allowed us to assess the human cardiac response, and demonstrated the platform's utility by measuring injury during ischemia-reperfusion and the effects of cardioprotective strategies. The model provides a foundation for future studies on how patient-specific backgrounds may affect response to therapeutic strategies. These steps will be necessary to help translate therapies into the clinical setting.

6-Gingerol Activates PI3K/Akt and Inhibits Apoptosis to Attenuate Myocardial Ischemia/Reperfusion Injury

6-Gingerol (6-G) is known to alleviate myocardial ischemia/reperfusion injury. However, the underlying molecular mechanisms of 6-G myocardial protection are not known. In this study, the protective effect of 6-G on ischemia/reperfusion (I/R) damage and whether such a mechanism was related to apoptosis inhibition and activation of phosphoinositide 3-kinases (PI3K)/serine/threonine kinase (Akt) signaling pathway were investigated. Rats were subjected to I/R in the presence or absence of 6-G and the changes of cardiac function, infarct size and histopathological changes, and the levels of cardiac troponin T, creatine kinase-MB, and myocardial apoptosis were examined. The expression of caspase-3, PI3K, p-Akt, and Akt was also determined. We found that 6-G (6 mg/kg) pretreatment significantly improved heart function and ameliorated infarct size and histopathological changes and cardiac troponin T and creatine kinase-MB levels induced by I/R. Moreover, pretreatment with 6-G significantly inhibited myocardial apoptosis and caspase-3 activation induced by I/R. 6-G also upregulated expression of PI3K, p-Akt, and Akt in myocardial tissues. Taken together, these findings suggest that 6-G inhibits apoptosis and activates PI3K/Akt signaling in response to myocardial I/R injury as a possible mechanism to attenuate I/R-induced injury in heart. These results might be important for developing novel strategies for preventing myocardial I/R injury.

Mechanistic Role of mPTP in Ischemia-Reperfusion Injury

Acute myocardial infarction (MI) is a major cause of death and disability worldwide. The treatment of choice for reducing ischemic injury and limiting infarct size (IS) in patients with ST-segment elevation MI (STEMI) is timely and effective myocardial reperfusion via primary percutaneous coronary intervention (PCI). However, myocardial reperfusion itself may induce further cardiomyocyte death, a phenomenon known as reperfusion injury (RI). The opening of a large pore in the mitochondrial membrane, namely, the mitochondrial permeability transition pore (mPTP), is widely recognized as the final step of RI and is responsible for mitochondrial and cardiomyocyte death. Although myocardial reperfusion interventions continue to improve, there remain no effective therapies for preventing RI due to incomplete knowledge regarding RI components and mechanisms and to premature translations of findings from animals to humans. In the last year, increasing amounts of data describing mPTP components, structure, regulation and function have surfaced. These data may be crucial for gaining a better understanding of RI genesis and for planning future trials evaluating new cardioprotective strategies. In this chapter, we review the role of the mPTP in RI pathophysiology and report on recent studies investigating its structure and components. Finally, we provide a brief overview of principal cardioprotective strategies and their pitfalls.

Remote ischemic preconditioning attenuates EGR-1 expression following myocardial ischemia reperfusion injury through activation of the JAK-STAT pathway

BACKGROUND/OBJECTIVES

Remote ischemic preconditioning (RIPC) protects the myocardium from ischemia/reperfusion (I/R) injury however the molecular pathways involved in cardioprotection are yet to be fully delineated. Transcription factor Early growth response-1 (Egr-1) is a key upstream activator in a variety of cardiovascular diseases. In this study, we elucidated the role of RIPC in modulating the regulation of Egr-1.

METHODS

This study subjected rats to transient blockade of the left anterior descending (LAD) coronary artery with or without prior RIPC of the hind-limb muscle and thereafter excised the heart 24h following surgical intervention. In vitro, rat cardiac myoblast H9c2 cells were exposed to ischemic preconditioning by subjecting them to 3cycles of alternating nitrogen-flushed hypoxia and normoxia. These preconditioned media were added to recipient H9c2 cells which were then subjected to 30min of hypoxia followed by 30min of normoxia to simulate myocardial I/R injury. Thereafter, the effects of RIPC on cell viability, apoptosis and inflammatory markers were assessed.

RESULTS

We showed reduced infarct size and suppressed Egr-1 in the heart of rats when RIPC was administered to the hind leg. In vitro, we showed that RIPC improved cell viability, reduced apoptosis and attenuated Egr-1 in recipient cells.

CONCLUSIONS

Selective inhibition of intracellular signaling pathways confirmed that RIPC increased production of intracellular nitric oxide (NO) and reactive oxygen species (ROS) via activation of the JAK-STAT pathway which then inactivated I/R-induced ERK 1/2 signaling pathways, ultimately leading to the suppression of Egr-1.

Heart-resident CCR2+ macrophages promote neutrophil extravasation through TLR9/MyD88/CXCL5 signaling

It is well established that maladaptive innate immune responses to sterile tissue injury represent a fundamental mechanism of disease pathogenesis. In the context of cardiac ischemia reperfusion injury, neutrophils enter inflamed heart tissue, where they play an important role in potentiating tissue damage and contributing to contractile dysfunction. The precise mechanisms that govern how neutrophils are recruited to and enter the injured heart are incompletely understood. Using a model of cardiac transplant-mediated ischemia reperfusion injury and intravital 2-photon imaging of beating mouse hearts, we determined that tissue-resident CCR2⁺ monocyte-derived macrophages are essential mediators of neutrophil recruitment into ischemic myocardial tissue. Our studies revealed that neutrophil extravasation is mediated by a TLR9/MyD88/CXCL5 pathway. Intravital 2-photon imaging demonstrated that CXCL2 and CXCL5 play critical and nonredundant roles in guiding neutrophil adhesion and crawling, respectively. Together, these findings uncover a specific role for a tissue-resident monocyte-derived macrophage subset in sterile tissue inflammation and support the evolving concept that macrophage ontogeny is an important determinant of function. Furthermore, our results provide the framework for targeting of cell-specific signaling pathways in myocardial ischemia reperfusion injury.

Lidocaine Enhances Contractile Function of Ischemic Myocardial Regions in Mouse Model of Sustained Myocardial Ischemia

RATIONALE

Perioperative myocardial ischemia is common in high-risk patients. The use of interventional revascularisation or even thrombolysis is limited in this patient subset due to exceedingly high bleeding risks. Blockade of voltage-gated sodium channels (VGSC) with lidocaine had been suggested to reduce infarct size and cardiomyocyte cell death in ischemia/reperfusion models. However, the impact of lidocaine on cardiac function during sustained ischemia still remains unclear.

METHODS

Sustained myocardial ischemia was induced by ligation of the left anterior descending artery in 12-16 weeks old male BALB/c mice. Subcutaneous lidocaine (30 mg/kg) was used to block VGSC. Cardiac function was quantified at baseline and at 72h by conventional and speckle-tracking based echocardiography to allow high-sensitivity in vivo phenotyping. Infarct size and cardiomyocyte cell death were assessed post mortem histologically and indirectly using troponin measurements.

RESULTS

Ischemia strongly impaired both, global systolic and diastolic function, which were partially rescued in lidocaine treated in mice. No differences regarding infarct size and cardiomyocyte cell death were observed. Mechanistically, and as shown with speckle-tracking analysis, lidocaine specifically improves residual contractility in the ischemic but not in the remote, non-ischemic myocardium.

CONCLUSION

VGSC blockade with lidocaine rescues function of ischemic myocardium as a potential bridging to revascularisation in the setting of perioperative myocardial ischemia.

The Fifth Domain of Beta 2 Glycoprotein I Protects from Natural IgM Mediated Cardiac Ischaemia Reperfusion Injury

Reperfusion after a period of ischemia results in reperfusion injury (IRI) which involves activation of the inflammatory cascade. In cardiac IRI, IgM natural antibodies (NAb) play a prominent role through binding to altered neoepitopes expressed on damaged cells. Beta 2 Glycoprotein I (β2GPI) is a plasma protein that binds to neoepitopes on damaged cells including anionic phospholipids through its highly conserved Domain V. Domain I of β2GPI binds circulating IgM NAbs and may provide a link between the innate immune system, IgM NAb binding and cardiac IRI. This study was undertaken to investigate the role of Β2GPI and its Domain V in cardiac IRI using wild-type (WT), Rag-1 ^-/- and β2GPI deficient mice. Compared with control, treatment with Domain V prior to cardiac IRI prevented binding of endogenous β2GPI to post-ischemic myocardium and resulted in smaller myocardial infarction size in both WT and β2GPI deficient mice. Domain V treatment in WT mice also resulted in less neutrophil infiltration, less apoptosis and improved ejection fraction at 24 h. Rag-1 -/- antibody deficient mice reconstituted with IgM NAbs confirmed that Domain V prevented IgM NAb induced cardiac IRI. Domain V remained equally effective when delivered at the time of reperfusion which has therapeutic clinical relevance.Based upon this study Domain V may function as a universal inhibitor of IgM NAb binding in the setting of cardiac IRI, which offers promise as a new therapeutic strategy in the treatment of cardiac IRI.

Rationally engineered Troponin C modulates in vivo cardiac function and performance in health and disease

Treatment for heart disease, the leading cause of death in the world, has progressed little for several decades. Here we develop a protein engineering approach to directly tune in vivo cardiac contractility by tailoring the ability of the heart to respond to the Ca(2+) signal. Promisingly, our smartly formulated Ca(2+)-sensitizing TnC (L48Q) enhances heart function without any adverse effects that are commonly observed with positive inotropes. In a myocardial infarction (MI) model of heart failure, expression of TnC L48Q before the MI preserves cardiac function and performance. Moreover, expression of TnC L48Q after the MI therapeutically enhances cardiac function and performance, without compromising survival. We demonstrate engineering TnC can specifically and precisely modulate cardiac contractility that when combined with gene therapy can be employed as a therapeutic strategy for heart disease.

Assessing viability of extracorporeal preserved muscle transplants using external field stimulation: a novel tool to improve methods prolonging bridge-to-transplantation time

Preventing ischemia-related cell damage is a priority when preserving tissue for transplantation. Perfusion protocols have been established for a variety of applications and proven to be superior to procedures used in clinical routine. Extracorporeal perfusion of muscle tissue though cumbersome is highly desirable since it is highly susceptible to ischemia-related damage. To show the efficacy of different perfusion protocols external field stimulation can be used to immediately visualize improvement or deterioration of the tissue during active and running perfusion protocols. This method has been used to show the superiority of extracorporeal perfusion using porcine rectus abdominis muscles perfused with heparinized saline solution. Perfused muscles showed statistically significant higher ability to exert force compared to nonperfused ones. These findings can be confirmed using Annexin V as marker for cell damage, perfusion of muscle tissue limits damage significantly compared to nonperfused tissue. The combination of extracorporeal perfusion and external field stimulation may improve organ conservation research.

NAD(+)-dependent SIRT1 deactivation has a key role on ischemia-reperfusion-induced apoptosis

Ischemia-reperfusion (IR) leads to severe organ injury and dysfunction. Sirtuins (SIRTs) are a family of histone deacetylases (HDACs) that require nicotinamide adenine dinucleotide (NAD(+)) for the deacetylation reaction. SIRTs play a major role in counteracting cellular stress and apoptosis. This study aimed to investigate the mechanisms of heart protection against apoptosis by SIRTs and the molecular pathways involved in SIRTs regulation and function in a rat model of IR injury. Hearts of male Wistar-Kyoto rats were subjected to 30-min ischemia followed by reperfusion up to 6h. IR increased cardiomyocyte apoptosis; the cleavage of caspase 3, induced a transient upregulation of SIRT1 and downregulation of SIRT6 expression, but decreased SIRT1 activity and reduced NAD(+) content. IR also increased forkhead box protein O1 (FoxO1) expression and FoxO1 binding to SIRT1 promoter region. Resveratrol restored SIRT1 activity and NAD(+) level by an AMPK-dependent mechanism, reduced cardiomyocyte apoptosis, and attenuated caspase 3 cleavage via heat shock factor-1 deacetylation and heat shock protein (HSP) expression upregulation. Our data show new potential molecular mechanisms of up and downstream regulation of SIRT1 in IR. The interplay among FoxO1, SIRT1, NAD(+), AMPK, HSP, and SIRT6 depicts a complex molecular network that protects the heart from apoptosis during IR and may be susceptible to therapeutic interventions.

Direct coupling of annexin A5 to VSOP yields small, protein-covered nanoprobes for MR imaging of apoptosis

Annexin A5 (Anx) has been extensively used for imaging apoptosis by single-photon emission computed tomography, positron emission tomography, optical imaging and MRI. Recently we introduced ultrasmall Anx-VSOP (very small iron oxide particles)--the smallest high-relaxivity probe for MRI of apoptosis. Here we present a simplified method for the direct coupling of Anx to VSOP, which resulted in nanoparticles that are nearly completely covered with human Anx. These superparamagnetic nanoparticles are only 14.4 ± 2.3 nm in diameter and have higher T2* relaxivity. Compared with existing probes, the small size and the Anx shielding provide prerequisites for good biocompatibility and bioavailability in target tissues. In vitro characterization showed specific binding of Anx-VSOP to apoptotic cells, which led to a signal loss in T2*-weighted MR measurements, while control probe M1324-VSOP produced no such change. Exploratory MRI was done in vivo in a cardiac model of ischemia-reperfusion damage illustrating the potential of the probe for future studies.

miRNA signature of unfolded protein response in H9c2 rat cardiomyoblasts

Background

Glucose and oxygen deprivation during ischemia is known to affect the homeostasis of the endoplasmic reticulum (ER) in ways predicted to activate the unfolded protein response (UPR). Activation of UPR signalling due to ER stress is associated with the development of myocardial infarction (MI). MicroRNAs (miRNAs) are key regulators of cardiovascular development and deregulation of miRNA expression is involved in the onset of many cardiovascular diseases. However, little is known about the mechanisms regulating the miRNA expression in the cardiovascular system during disease development and progression. Here we performed genome-wide miRNA expression profiling in rat cardiomyoblasts to identify the miRNAs deregulated during UPR, a crucial component of ischemia.

Results

We found that expression of 86 microRNAs changed significantly during conditions of UPR in H9c2 cardiomyoblasts. We found that miRNAs with known function in cardiomyoblasts biology (miR-206, miR-24, miR-125b, miR-133b) were significantly deregulated during the conditions of UPR in H9c2 cells. The expression of miR-7a was upregulated by UPR and simulated in vitro ischemia in cardiomyoblasts. Further, ectopic expression of miR-7a provides resistance against UPR-mediated apoptosis in cardiomyoblasts. The ample overlap of miRNA expression signature between our analysis and different models of cardiac dysfunction further confirms the role of UPR in cardiovascular diseases.

Conclusions

This study demonstrates the role of UPR in deregulating the expression of miRNAs in MI. Our results provide novel insights about the molecular mechanisms of deregulated miRNA expression during the heart disease pathogenesis.

15-deoxy-Δ¹²,¹⁴-PGJ₂ promotes inflammation and apoptosis in cardiomyocytes via the DP2/MAPK/TNFα axis

Background

Prostaglandins (PGs), lipid autacoids derived from arachidonic acid, play a pivotal role during inflammation. PGD₂ synthase is abundantly expressed in heart tissue and PGD₂ has recently been found to induce cardiomyocyte apoptosis. PGD₂ is an unstable prostanoid metabolite; therefore the objective of the present study was to elucidate whether its final dehydration product, 15-deoxy-Δ^12,14-PGJ₂ (15d-PGJ₂, present at high levels in ischemic myocardium) might cause cardiomyocyte damage.

Methods and results

Using specific (ant)agonists we show that 15d-PGJ₂ induced formation of intracellular reactive oxygen species (ROS) and phosphorylation of p38 and p42/44 MAPKs via the PGD₂ receptor DP2 (but not DP1 or PPARγ) in the murine atrial cardiomyocyte HL-1 cell line. Activation of the DP2-ROS-MAPK axis by 15d-PGJ₂ enhanced transcription and translation of TNFα and induced apoptosis in HL-1 cardiomyocytes. Silencing of TNFα significantly attenuated the extrinsic (caspase-8) and intrinsic apoptotic pathways (bax and caspase-9), caspase-3 activation and downstream PARP cleavage and γH2AX activation. The apoptotic machinery was unaffected by intracellular calcium, transcription factor NF-κB and its downstream target p53. Of note, 9,10-dihydro-15d-PGJ₂ (lacking the electrophilic carbon atom in the cyclopentenone ring) did not activate cellular responses. Selected experiments performed in primary murine cardiomyocytes confirmed data obtained in HL-1 cells namely that the intrinsic and extrinsic apoptotic cascades are activated via DP2/MAPK/TNFα signaling.

Conclusions

We conclude that the reactive α,β-unsaturated carbonyl group of 15d-PGJ₂ is responsible for the pronounced upregulation of TNFα promoting cardiomyocyte apoptosis. We propose that inhibition of DP2 receptors could provide a possibility to modulate 15d-PGJ₂-induced myocardial injury.

Involvement of cardiomyocyte survival–apoptosis balance in hypertensive cardiac remodeling

The balance between cell death and cell survival is a tightly controlled process, especially in terminally differentiated cells, such as the cardiomyocyte. Accumulating data support a role for cardiomyocyte apoptosis in the development of several cardiac diseases, including the transition from hypertensive compensatory hypertrophy to heart failure. This review briefly summarizes the status of the knowledge regarding the death-survival balance of cardiomyocytes in the context of hypertensive heart disease. Several molecular and cellular aspects as well as the most relevant pathophysiological implications are presented. Moreover, diagnosis tools under development and the possibilities for pharmacological intervention are also examined.

Imaging the myocardium at risk with ⁹⁹mTc-lactadherin administered after reperfusion in a porcine model

INTRODUCTION

Phosphatidylserine is translocated from the inner to the outer leaflet of the plasma membrane in the early stages of apoptosis and necrosis and in reversibly injured cells. In rabbit hearts, ischemia followed by reperfusion results in exposure of phosphatidylserine on myocytes unaffected by apoptosis or necrosis. Lactadherin was recently introduced as a highly sensitive phosphatidylserine ligand. We hypothesized that ischemic myocardial cell damage can be identified by radio-labeled lactadherin and that the ischemic area at risk (AAR) can be visualized retrospectively after reperfusion.

METHODS

Left anterior descending coronary artery in pigs was occluded for 20 minutes, 45 minutes or 45 minutes preceded by ischemic preconditioning. In all three groups, (99m)Tc-lactadherin was injected intravenously 30 minutes after reperfusion. The AAR was demarcated by Evans blue and the infarct size by 2,3,5,-triphenyltetrazodium chloride staining.

RESULTS

The regional myocardial uptake of (99m)Tc-lactadherin closely correlated with the AAR (r=.83, P = .001). The area of (99m)Tc-lactadherin uptake was unaltered by a shorter duration of ischemia and ischemic preconditioning (P=.23) despite significantly different infarct development (P=.001).

CONCLUSION

The results suggest that (99m)Tc-lactadherin can be used as a sensitive marker for AAR imaging when injected 30 minutes after reperfusion following acute ischemia.

Baicalin protects the myocardium from reperfusion-induced damage in isolated rat hearts via the antioxidant and paracrine effect

The aim of the present study was to investigate the protective effect of baicalin (BA) against ischemia-reperfusion (I/R) injury in isolated rat hearts. Sprague-Dawley rat hearts were rapidly removed, mounted on a Langendorff apparatus and subjected to 30 min ischemia followed by 30 min reperfusion with Krebs-Henseleit (K-H) solution at 37°C to establish the isolated I/R injury model. All animals (n=50) were randomly divided into five groups (n=10 in each): I, normal control; II, I/R; III, I/R plus 20 mg/kg BA; IV, I/R plus 40 mg/kg BA; and V, I/R plus 80 mg/kg BA. The degree of heart injury caused by the I/R was assessed by evaluating left ventricular function and by detecting the levels of lactate dehydrogenase (LDH) and creatine kinase (CK) in the coronary effluent and the myocardial superoxide dismutase (SOD) and malondialdehyde (MDA) levels in the isolated rat hearts. Myocardial infarct size and vascular density were assessed using histology and immunohistochemistry. The apoptotic cardiomyocytes were determined using flow cytometry (FCM). Compared with group II, the BA groups demonstrated improved left ventricular function, reduced CK and LDH release in the coronary effluent and increased SOD and MDA activity (P<0.05). Furthermore, histology and immunohistochemistry results showed that the infarct size was reduced and vessel density was augmented in the BA groups (P<0.01) compared with group II. The FCM results indicated that apoptosis was significantly lower in the BA groups than in group II (P<0.05) and that the protective effect was dose-dependent. In conclusion, these results demonstrated that BA exerts a dose-dependent protective effect on I/R injury in isolated rat hearts, the mechanisms of which may be associated with antioxidant and anti-apoptosis properties. To the best of our knowledge, this study is the first evaluation of the efficacy of BA in isolated rat hearts using histology and immunohistochemistry, providing a foundation for the use of BA in the treatment of acute myocardial infarction.

Mitochondrial membrane permeabilization and cell death during myocardial infarction: roles of calcium and reactive oxygen species

Excess generation of reactive oxygen species (ROS) and cytosolic calcium accumulation play major roles in the initiation of programmed cell death during acute myocardial infarction. Cell death may include necrosis, apoptosis and autophagy, and combinations thereof. During ischemia, calcium handling between the sarcoplasmic reticulum and myofilament is disrupted and calcium is diverted to the mitochondria causing swelling. Reperfusion, while essential for survival, reactivates energy transduction and contractility and causes the release of ROS and additional ionic imbalance. During acute ischemia-reperfusion, the principal death pathways are programmed necrosis and apoptosis through the intrinsic pathway, initiated by the opening of the mitochondrial permeability transition pore and outer mitochondrial membrane permeabilization, respectively. Despite intense investigation, the mechanisms of action and modes of regulation of mitochondrial membrane permeabilization are incompletely understood. Extrinsic apoptosis, necroptosis and autophagy may also contribute to ischemia-reperfusion injury. In this review, the roles of dysregulated calcium and ROS and the contributions of Bcl-2 proteins, as well as mitochondrial morphology in promoting mitochondrial membrane permeability change and the ensuing cell death during myocardial infarction are discussed.

Noninvasive imaging of myocyte apoptosis following application of a stem cell-engineered delivery platform to acutely infarcted myocardium

The cardioprotective effects of mesenchymal stem cells (MSCs) include reducing myocyte apoptosis, and this effect can be enhanced by preconditioning and encapsulation in a fibrin scaffold. This study aimed to test the hypothesis that apoptosis imaging can detect the cardioprotective effects of a conditioned MSC patch grafted in a rat model of acute myocardial infarction.

METHODS

Cell culture experiments simulating engraftment of fibrin patches onto beating rat ventricular myocytes exposed to hypoxia showed an effect of conditioned cells to reduce apoptosis. Twenty-three nude rats underwent successful left anterior descending coronary artery occlusion and were divided into 3 groups: transforming growth factor β1-conditioned human MSC-laden patches (CP), infarct alone without patch (no patch [NP]), and patch alone (patch only [PO]). Twenty-four hours after myocardial infarction, all rats were injected with (99m)Tc-hydrazinonicotinamide ((99m)Tc-HYNIC) annexin V and (201)Tl and underwent dual-isotope SPECT/CT imaging. Six rats were sacrificed for histology and counting. The remaining rats (n = 17; 1 rat was eliminated) were injected and imaged on day 7; of those, 3 rats were sacrificed for histology and counting, and the remaining 13 rats survived to day 21, when they were sacrificed for histology. Numbers of rats imaged on day 7 in the 3 groups were 7 in the CP group, 5 in the NP, and 5 in the PO. Perfused myocardium, infarct size, and (99m)Tc-HYNIC annexin V uptake were quantified from the scans from days 1 and 7. (99m)Tc-HYNIC annexin V uptake was correlated with quantitative caspase staining, and infarct size as percentage fibrosis was quantified at day 21.

RESULTS

(99m)Tc-HYNIC annexin V uptake as percentage injected dose (×10(-4)) decreased between days 1 and 7 by 1.04 ± 0.28 in the CP group, 0.44 ± 0.17 in the NP group, and 0.34 ± 0.27 in the PO group (P = 0.003 for NP vs. CP, P = 0.005 for PO vs. CP, and P = 0.5 for NP vs. CP). The changes in defect size as percentage myocardium between days 1 and 7 were -8.83 ± 4.40 in the CP group, +1.00 ± 2.24 in the NP group, and -0.50 ± 4.20 in the PO group (P = 0.003 for NP vs. CP, P = 0.005 for PO vs. CP, and P = 0.50 for NP vs. PO). (99m)Tc-HYNIC annexin V uptake as percentage left ventricle by scanning correlated with caspase staining (r = 0.931, P = 0.002).

CONCLUSION

Transforming growth factor β1-conditioned human MSC-laden patches reduce myocyte apoptosis in the setting of acute infarction, and this effect can be detected by in vivo imaging with (99m)Tc-HYNIC annexin V.

Vitamin K-antagonists accelerate atherosclerotic calcification and induce a vulnerable plaque phenotype

BACKGROUND

Vitamin K-antagonists (VKA) are treatment of choice and standard care for patients with venous thrombosis and thromboembolic risk. In experimental animal models as well as humans, VKA have been shown to promote medial elastocalcinosis. As vascular calcification is considered an independent risk factor for plaque instability, we here investigated the effect of VKA on coronary calcification in patients and on calcification of atherosclerotic plaques in the ApoE(-/-) model of atherosclerosis.

METHODOLOGY/PRINCIPAL FINDINGS

A total of 266 patients (133 VKA users and 133 gender and Framingham Risk Score matched non-VKA users) underwent 64-slice MDCT to assess the degree of coronary artery disease (CAD). VKA-users developed significantly more calcified coronary plaques as compared to non-VKA users. ApoE(-/-) mice (10 weeks) received a Western type diet (WTD) for 12 weeks, after which mice were fed a WTD supplemented with vitamin K(1) (VK(1), 1.5 mg/g) or vitamin K(1) and warfarin (VK(1)&W; 1.5 mg/g & 3.0 mg/g) for 1 or 4 weeks, after which mice were sacrificed. Warfarin significantly increased frequency and extent of vascular calcification. Also, plaque calcification comprised microcalcification of the intimal layer. Furthermore, warfarin treatment decreased plaque expression of calcification regulatory protein carboxylated matrix Gla-protein, increased apoptosis and, surprisingly outward plaque remodeling, without affecting overall plaque burden.

CONCLUSIONS/SIGNIFICANCE

VKA use is associated with coronary artery plaque calcification in patients with suspected CAD and causes changes in plaque morphology with features of plaque vulnerability in ApoE(-/-) mice. Our findings underscore the need for alternative anticoagulants that do not interfere with the vitamin K cycle.

Synthesis of an in vivo MRI-detectable apoptosis probe

Cellular apoptosis is a prominent feature of many diseases, and this programmed cell death typically occurs before clinical manifestations of disease are evident. A means to detect apoptosis in its earliest, reversible stages would afford a pre-clinical 'window' during which preventive or therapeutic measures could be taken to protect the heart from permanent damage. We present herein a simple and robust method to conjugate human Annexin V (ANX), which avidly binds to cells in the earliest, reversible stages of apoptosis, to superparamagnetic iron oxide (SPIO) nanoparticles, which serve as an MRI-detectable contrast agent. The conjugation method begins with an oxidation of the SPIO nanoparticles, which oxidizes carboxyl groups on the polysaccharide shell of SPIO. Purified ANX protein is then added in the setting of a sodium borate solution to facilitate covalent interaction of ANX with SPIO in a reducing buffer. A final reduction step with sodium borohydride is performed to complete the reduction, and then the reaction is quenched. Unconjugated ANX is removed from the mix by microcentrifuge filtration. The size and purity of the ANX-SPIO product is verified by dynamic light scattering (DLS). This method does not require addition to, or modification of, the polysaccharide SPIO shell, as opposed to cross-linked iron oxide particle conjugation methods or biotin-labeled nanoparticles. As a result, this method represents a simple, robust approach that may be extended to conjugation of other proteins of interest.

Imaging Myocardial Ischemia and Reperfusion Injury via Cy5.5-Annexin V

AIM

The aim of this article is to present the results of an imaging study of myocardial apoptosis induced by ischemia/reperfusion injury.

METHODS

Twenty nude mice were randomly divided into an experimental group (10 mice) and control group (10 mice). In the experimental group, myocardial apoptosis was induced by ligation of the left anterior descending coronary artery (LAD) for 30 min. This was followed by reperfusion for 90 min. In the control group, the heart was exposed for the same length of time as in the experimental group. Cy5.5-annexin V (25 μg) was injected into both sets of mice after the onset of reperfusion. At 90 min post-injection, the mice were imaged. The region of interest (ROI) was obtained, and the fluorescence intensity of the ROI was quantified. The animals were sacrificed, and myocardial apoptosis was assayed by TUNEL assay.

RESULTS

Fluorescence intensity in the ischemia/reperfusion hearts was significantly higher than that in the control group (P < 0.05). In the TUNEL assay, more apoptotic cells were observed in the experimental group than in the control group, correlating with imaging results.

CONCLUSION

Fluorescence imaging of Cy5.5-annexin V in a mouse model of myocardial ischemia/reperfusion can be used in vivo as a noninvasive means of detecting ischemia/reperfusion-induced apoptotic cells in the heart.

Neuroprotective properties of Loranthus parasiticus aqueous fraction against oxidative stress-induced damage in NG108-15 cells

Loranthus parasiticus, a Chinese folk medicine, has been widely used for the treatment of brain diseases, particularly in southwest China. Hence, the present neuroprotection model was designed to investigate its neuroprotective properties against H(2)O(2)-induced oxidative stress in NG108-15 cells. L. parasiticus aqueous fraction (LPAF), which was selected in the present study, had proved to be the most active fraction among the other tested extracts and fractions in our previous screening. The restoration of depleted intracellular glutathione (GSH), a major endogenous antioxidant, by LPAF was observed after H(2)O(2) insult. Pretreatment with LPAF substantially reduced the production of intracellular reactive oxygen species generated from H(2)O(2). Apoptotic features such as externalization of phosphatidylserine and disruption of mitochondrial membrane potential were significantly attenuated by LPAF. In addition, cell cycle analysis revealed a prominent decrease in the H(2)O(2)-induced sub-G(1) population by LPAF. Moreover, apoptotic morphological analysis by DAPI nuclear staining demonstrated that NG108-15 cells treated with H(2)O(2) exhibited apoptotic features, while such changes were greatly reduced in cells pretreated with LPAF. Taken together, these findings confirmed that LPAF exerts marked neuroprotective activity, which raises the possibility of potential therapeutic application of LPAF for managing oxidative stress-related neurological disorders and supports the traditional use of L. parasiticus in treating brain-related diseases.

New roles for mitochondria in cell death in the reperfused myocardium

Mitochondria play an important role in regulating the life and death of cells. They provide the cell with energy via oxidative phosphorylation but can quickly turn into death-promoting organelles in response to stress by disrupting adenosine triphosphate synthesis, releasing pro-death proteins, and producing reactive oxygen species. Due to their high-energy requirement, cardiac myocytes are abundant in mitochondria and as a result, particularly vulnerable to mitochondrial defects. Myocardial ischaemia and reperfusion are associated with mitochondrial dysfunction and cell death. Therefore, future therapies will focus on preserving mitochondrial integrity and function in hopes of minimizing the impact of ischaemia/reperfusion (I/R) injury. It is well established that myocardial I/R activates both necrosis and apoptosis, and that blocking either process reduces the levels of injury. However, recent studies have demonstrated that alterations in mitochondrial dynamics or clearance of mitochondria via autophagy also can contribute to cell death in the myocardium. In this review, we will discuss these new developments and their impact on the role of cardiac mitochondria in cell death following reperfusion in the heart.

Radiolabeled fucoidan as a p-selectin targeting agent for in vivo imaging of platelet-rich thrombus and endothelial activation

P-selectin expression is involved in the pathophysiology of biologically active arterial thrombus and endothelial activation after a transient ischemic event. Fucoidan is a polysaccharidic ligand of P-selectin, with a nanomolar affinity. In the present study, we propose a new approach of P-selectin molecular imaging based on radiolabeled fucoidan.

METHODS

Two kinds of experimental models were selected to evaluate the ability of radiolabeled fucoidan to detect P-selectin expression: platelet-rich arterial thrombi (vegetations of infective endocarditis and arterial mural thrombus) and myocardial ischemia-reperfusion. These 2 settings were chosen because they were clinically relevant, and both were associated with an important overexpression of platelet and endothelial P-selectin, respectively.

RESULTS

(99m)Tc-fucoidan SPECT was able to detect the presence of platelet-rich arterial thrombi in all animals, with a median target-to-background ratio of 5.2 in vegetations of endocarditis and 3.6 in mural aneurysmal thrombus, and to detect a persistent endothelial activation at 2 h after reperfusion. In this latter model, the magnitude of the signal was correlated with the extent of myocardium that underwent transient ischemia. The sensitivity of selectivity of the uptake and retention of (99m)Tc-fucoidan in both settings was excellent.

CONCLUSION

This study supports (99m)Tc-fucoidan as a relevant imaging agent for in vivo detection of biologic activities associated with P-selectin overexpression, such as arterial thrombus and ischemic memory. Given the reported wide availability at a low cost, and its low toxicity, fucoidan seems to overcome some of the limitations of previous P-selectin-targeted imaging agents.

Dietary flaxseed protects against lung ischemia reperfusion injury via inhibition of apoptosis and inflammation in a murine model

BACKGROUND

The hallmark of lung ischemia-reperfusion injury (IRI) is the production of reactive oxygen species (ROS), and the resultant oxidant stress has been implicated in apoptotic cell death as well as subsequent development of inflammation. Dietary flaxseed (FS) is a rich source of naturally occurring antioxidants and has been shown to reduce lung IRI in mice. However, the mechanisms underlying the protective effects of FS in IRI remain to be determined.

METHODS

We used a mouse model of IRI with 60 min of ischemia followed by 180 min of reperfusion and evaluated the anti-apoptotic and anti-inflammatory effects of 10% FS dietary supplementation.

RESULTS

Mice fed 10% FS undergoing lung IRI had significantly lower levels of caspases and decreased apoptotic activity compared with mice fed 0% FS. Lung homogenates and bronchoalveolar lavage fluid analysis demonstrated significantly reduced inflammatory infiltrate in mice fed with 10% FS diet. Additionally, 10% FS treated mice showed significantly increased expression of antioxidant enzymes and decreased markers of lung injury.

CONCLUSIONS

We conclude that dietary FS is protective against lung IRI in a clinically relevant murine model, and this protective effect may in part be mediated by the inhibition of apoptosis and inflammation.