Drug-drug interaction between NSAIDS and low-dose aspirin: a focus on cardiovascular and GI toxicity

INTRODUCTION

The aging of the population in the US and other countries means that a large number of people will likely take NSAIDs for the relief of pain and low-dose aspirin (LD-ASA) for cardioprotection. However, the cardioprotective value of LD-ASA can be compromised in patients who take NSAIDs concomitantly, because some NSAIDs competitively bind to critical amino-acid residues on cyclooxygenase (COX) enzymes and interfere with the mechanism of antiplatelet activity of LD-ASA.

AREAS COVERED

A review of the literature was conducted to provide an overview of current issues surrounding the concomitant use of NSAIDs and LD-ASA, to explore potential mechanisms for this drug-drug interaction and to consider current and future treatment options that may mitigate the risk associated with their concomitant use.

EXPERT OPINION

NSAIDs offer effective pain relief for the most common forms of pain, such as low back pain, musculoskeletal pain associated with arthritis, postsurgical pain, headache, acute pain syndromes, menstrual pain and dental pain. The development of NSAID formulations that offer effective pain control with fewer or less serious adverse effects due to interference with ASA would be a valuable medical advance. Several promising treatment options and regimens may be available in the future.

Cyclovirobuxinum D suppresses lipopolysaccharide-induced inflammatory responses in murine macrophages in vitro by blocking JAK-STAT signaling pathway

AIM

Cyclovirobuxinum D (CVB-D), an alkaloid isolated from the Chinese medicinal plant Buxus microphylla, has been found to be effective to treat cardiac insufficiency, arrhythmias and coronary heart disease. In the present study, we investigated the effects of CVB-D on the inflammatory responses in lipopolysaccharide (LPS)-stimulated murine macrophages in vitro and the underlying mechanisms.

METHODS

Murine macrophage cell line RAW264.7 cells were incubated in the presence of LPS (0.1 μg/mL) for 24 h. The cell viability was measured using MTT assay. The release of NO and cytokines were detected using the Griess test and ELISA, respectively. The mRNA and protein levels were determined using RT-PCR and Western blot, respectively. Reporter gene assays were used to analyze the transcriptional activity of NF-κB.

RESULTS

Treatment of RAW264.7 cells with CVB-D (25-300 μmol/L) did not affect the cell viability. Pretreatment with CVB-D (50, 100 and 200 μmol/L) concentration-dependently decreased NO release and iNOS expression in LPS-treated RAW264.7 cells (its IC50 value in inhibition of NO production was 144 μmol/L). CVB-D also concentration-dependently inhibited the secretion and mRNA expression of IL-1β and IL-6 in LPS-treated RAW264.7 cells. Furthermore, CVB-D remarkably inhibited the phosphorylation of STAT1 and STAT3, as well as JAK2 in LPS-treated RAW264.7 cells, but did not affect the activation of NF-κB and MAPKs pathways. Pretreatment with the JAK2 specific inhibitor AG490 (30 μmol/L) produced similar effects on NO release and iNOS expression in LPS-treated RAW264.7 cells.

CONCLUSION

CVB-D exerts anti-inflammatory effects in LPS-stimulated murine macrophages in vitro at least in part by blocking the JAK-STAT signaling pathway. The anti-inflammatory actions of CVB-D may contribute to its cardioprotection.

MicroRNAs associated with ischemia-reperfusion injury and cardioprotection by ischemic pre- and postconditioning: protectomiRs

We aimed to characterize early changes in microRNA expression in acute cardioprotection by ischemic pre- and postconditioning in rat hearts. Hearts isolated from male Wistar rats were subjected to 1) time-matched nonischemic perfusion, 2) ischemia-reperfusion (30 min of coronary occlusion and 120 min of reperfusion), 3) preconditioning (3 × 5 min of coronary occlusion) followed by ischemia-reperfusion, or 4) ischemia-reperfusion with postconditioning (6 × 10 s of global ischemia-reperfusion at the onset of reperfusion). Infarct size was significantly reduced by both interventions. Of 350 different microRNAs assessed by microarray analysis, 147-160 microRNAs showed detectable expression levels. Compared with microRNA alterations induced by ischemia-reperfusion versus time-matched nonischemic controls, five microRNAs were significantly affected by both pre- and postconditioning (microRNA-125b*, microRNA-139-3p, microRNA-320, microRNA-532-3p, and microRNA-188), four microRNAs were significantly affected by preconditioning (microRNA-487b, microRNA-139-5p, microRNA-192, and microRNA-212), and nine microRNAs were significantly affected by postconditioning (microRNA-1, microRNA let-7i, microRNA let-7e, microRNA let-7b, microRNA-181a, microRNA-208, microRNA-328, microRNA-335, and microRNA-503). Expression of randomly selected microRNAs was validated by quantitative real-time PCR. By a systematic comparison of the direction of microRNA expression changes in all groups, we identified microRNAs, specific mimics, or antagomiRs that may have pre- and postconditioning-like cardioprotective effects (protectomiRs). Transfection of selected protectomiRs (mimics of microRNA-139-5p, microRNA-125b*, microRNA let-7b, and inhibitor of microRNA-487b) into cardiac myocytes subjected to simulated ischemia-reperfusion showed a significant cytoprotective effect. This is the first demonstration that the ischemia-reperfusion-induced microRNA expression profile is significantly influenced by both pre- and postconditioning, which shows the involvement of microRNAs in cardioprotective signaling. Moreover, by analysis of microRNA expression patterns in cardioprotection by pre- and postconditioning, specific protectomiRs can be revealed as potential therapeutic tools for the treatment of ischemia-reperfusion injury.

Deletion of the aquaporin-4 gene alters expression and phosphorylation of protective kinases in the mouse heart

AIM

Aquaporins are channel-forming proteins highly permeable to water and some small molecular solutes. We have previously shown that aquaporin-4 knockout mice have increased tolerance to ischemia. However, the mechanism of cardioprotection was unclear. The aim of the current study was to investigate the effects of aquaporin-4 deletion on baseline expression and phosphorylation of some cardioprotective protein kinases.

METHODS

Proteins were extracted from hearts of aquaporin-4 knockout mice and littermate wild-type controls and analyzed with Western blot. Samples were taken from young (≤ 6 months of age), and old (≥ 1 year) mice.

RESULTS

Western blots showed three different isoforms of aquaporin-4 in wild types, likely representing M1, M23, and Mz. Total AMP-dependent kinase expression was decreased in aquaporin-4 knockout hearts by 18 ± 13% (p = 0.02), while the expression of Akt kinase, extracellular signal regulated kinase 1/2, protein kinase C-epsilon, mitogen-associated kinase P38 and C-Jun N-terminal kinase was unchanged. The phosphorylation of Akt kinase was reduced in hearts from knockout mice by 41 ± 16% (p = 0.01). No other alterations in phosphorylation were found. These effects were only detected in young mice.

CONCLUSION

Deletion of the aquaporin-4 gene decreased AMP-dependent kinase expression and Akt kinase phosphorylation in the heart. These changes may influence energy metabolism and endogenous cardioprotection.

All-trans retinoic acid stimulates gene expression of the cardioprotective natriuretic peptide system and prevents fibrosis and apoptosis in cardiomyocytes of obese ob/ob mice

In hypertensive rodents, retinoic acid (RA) prevents adverse cardiac remodelling and improves myocardial infarction outcome, but its role in obesity-related changes of cardiac tissue are unclear. We hypothesized that all-trans RA (ATRA) treatment will improve the cardioprotective oxytocin-natriuretic peptides (OT-NP) system, preventing apoptosis and collagen accumulation in hearts of ob/ob mice, a mouse model of obesity and insulin resistance. Female 9-week-old B6.V-Lep/J ob/ob mice (n = 16) were divided into 2 groups: 1 group (n = 8) treated with 100 μg of ATRA dissolved in 100 μL of corn oil (vehicle) delivered daily (∼2 μg·g body weight(-1)·day(-1)) by stomach intubation for 16 days, and 1 group (n = 8) that received the vehicle alone. A group of nonobese littermate mice (n = 9) served as controls. Ob/ob mice exhibited obesity, hyperglycaemia, and downregulation of the cardiac OT-NP system, including the mRNA for the transcription factor GATA4, OT receptor and brain NP, and the protein expression for endothelial nitric oxide synthase. Hearts from ob/ob mice also demonstrated increased apoptosis and collagen accumulation. ATRA treatment induced weight loss and decreased adipocytes diameter in the visceral fat, thus reducing visceral obesity, which is associated with a high risk for cardiovascular disease. RA treatment was associated with a reduction in hyperglycemia and a normalization of the OT-NP system's expression in the hearts of ob/ob mice. Furthermore, ATRA treatment prevented apoptosis and collagen accumulation in hearts of ob/ob mice. The present study indicates that ATRA treatment was effective in restoring the cardioprotective OT-NP system and in preventing abnormal cardiac remodelling in the ob/ob mice.

Chronic inhibition of phosphodiesterase 5 with tadalafil attenuates mitochondrial dysfunction in type 2 diabetic hearts: potential role of NO/SIRT1/PGC-1α signaling

Enhanced nitric oxide (NO) production is known to activate silent information regulator 1 (SIRT1), which is a histone deacetylase that regulates PGC-1α, a regulator of mitochondrial biogenesis and coactivator of transcription factors impacting energy homeostasis. Since phosphodiesterase-5 inhibitors potentiate NO signaling, we hypothesized that chronic treatment with phosphodiesterase-5 inhibitor tadalafil would activate SIRT1-PGC-1α signaling and protect against metabolic stress-induced mitochondrial dysfunction in diabetic hearts. Diabetic db/db mice (n = 32/group; 40 wk old) were randomized to receive DMSO (10%, 0.2 ml ip) or tadalafil (1 mg/kg ip in 10% DMSO) for 8 wk. Wild-type C57BL mice served as nondiabetic controls. The hearts were excised and homogenized to study SIRT1 activity and downstream protein targets. Mitochondrial function was determined by measuring oxidative phosphorylation (OXPHOS), and reactive oxygen species generation was studied in isolated mitochondria. Tadalafil-treated diabetic mice demonstrated significantly improved left ventricular function, which is associated with increased cardiac SIRT1 activity. Tadalafil also enhanced plasma NO oxidation levels, myocardial SIRT1, PGC-1α expression, and phosphorylation of eNOS, Akt, and AMPK in the diabetic hearts. OXPHOS with the complex I substrate glutamate was decreased by 50% in diabetic hearts compared with the nondiabetic controls. Tadalafil protected OXPHOS with an improved glutamate state 3 respiration rates. The increased reactive oxygen species production from complex I was significantly decreased by tadalafil treatment. In conclusion, chronic treatment with tadalafil activates NO-induced SIRT1-PGC-1α signaling and attenuates mitochondrial dysfunction in type 2 diabetic hearts.

ATP-binding cassette transporter Abcg2 lineage contributes to the cardiac vasculature after oxidative stress

Due to their specialized location, stem and progenitor cells are often exposed to oxidative stress. Although ATP-binding cassette transporter subfamily G member 2 (Abcg2)-expressing cells have been implicated in cardiac protective mechanisms involving oxidative stress, there remains a lack of understanding regarding the behavior of cardiac Abcg2-expressing cells when exposed to ROS. The aim of the present study was to characterize the response of the cardiac Abcg2 lineage to oxidative stress. In vitro analysis demonstrated that the antioxidant program regulated by Abcg2 is dependent on a functional transporter. Delivery of paraquat dichloride (PQ), a systemic oxidative stress-inducing agent, to mice confirmed that Abcg2 provides a survival benefit. When exposed to PQ, reporter mice showed an increase in the Abcg2 lineage. Transcriptional and immunohistochemical analysis of Abcg2 lineage-positive cells revealed an enhanced vascular commitment after stress. Finally, preconditioning with PQ demonstrated a reduction in scar size and an increase in angiogenesis after permanent left coronary artery ligation. In conclusion, the data suggest that Abcg2 plays a cytoprotective role in response to in vivo oxidative stress. The contribution of the Abcg2 lineage to the vasculature in the heart is increased after PQ delivery.

Incretin-based therapies: can we achieve glycemic control and cardioprotection?

Glucagon-like (GLP-1) is a peptide hormone secreted from the small intestine in response to nutrient ingestion. GLP-1 stimulates insulin secretion in a glucose-dependent manner, inhibits glucagon secretion and gastric emptying, and reduces appetite. Because of the short circulating half-life of the native GLP-1, novel GLP-1 receptor (GLP-1R) agonists and analogs and dipeptidyl peptidase 4 (DPP-4) inhibitors have been developed to facilitate clinical use. Emerging evidence indicates that GLP-1-based therapies are safe and may provide cardiovascular (CV) benefits beyond glycemic control. Preclinical and clinical studies are providing increasing evidence that GLP-1 therapies may positively affect CV function and metabolism by salutary effects on CV risk factors as well as via direct cardioprotective actions. However, the mechanisms whereby the various classes of incretin-based therapies exert CV effects may be mechanistically distinct and may not necessarily lead to similar CV outcomes. In this review, we will discuss the potential mechanisms and current understanding of CV benefits of native GLP-1, GLP-1R agonists and analogs, and of DPP-4 inhibitor therapies as a means to compare their putative CV benefits.

The TRPM4 channel inhibitor 9-phenanthrol

The phenanthrene-derivative 9-phenanthrol is a recently identified inhibitor of the transient receptor potential melastatin (TRPM) 4 channel, a Ca(2+) -activated non-selective cation channel whose mechanism of action remains to be determined. Subsequent studies performed on other ion channels confirm the specificity of the drug for TRPM4. In addition, 9-phenanthrol modulates a variety of physiological processes through TRPM4 current inhibition and thus exerts beneficial effects in several pathological conditions. 9-Phenanthrol modulates smooth muscle contraction in bladder and cerebral arteries, affects spontaneous activity in neurons and in the heart, and reduces lipopolysaccharide-induced cell death. Among promising potential applications, 9-phenanthrol exerts cardioprotective effects against ischaemia-reperfusion injuries and reduces ischaemic stroke injuries. In addition to reviewing the biophysical effects of 9-phenanthrol, here we present information about its appropriate use in physiological studies and possible clinical applications.

Delayed remote ischemic preconditioning produces an additive cardioprotection to sevoflurane postconditioning through an enhanced heme oxygenase 1 level partly via nuclear factor erythroid 2-related factor 2 nuclear translocation

Although both sevoflurane postconditioning (SPoC) and delayed remote ischemic preconditioning (DRIPC) have been proved effective in various animal and human studies, the combined effect of these 2 strategies remains unclear. Therefore, this study was designed to investigate this effect and elucidate the related signal mechanisms in a Langendorff perfused rat heart model. After 30-minute balanced perfusion, isolated hearts were subjected to 30-minute ischemia followed by 60-minute reperfusion except 90-minute perfusion for control. A synergic cardioprotective effect of SPoC (3% v/v) and DRIPC (4 cycles 5-minute occlusion/5-minute reflow at the unilateral hindlimb once per day for 3 days before heart isolation) was observed with facilitated cardiac functional recovery and decreased cardiac enzyme release. The infarct size-limiting effect was more pronounced in the combined group (6.76% ± 2.18%) than in the SPoC group (16.50% ± 4.55%, P < .001) or in the DRIPC group (10.22% ± 2.57%, P = .047). Subsequent analysis revealed that an enhanced heme oxygenase 1 (HO-1) expression, but not protein kinase B/AKt or extracellular signal-regulated kinase 1 and 2 activation, was involved in the synergic cardioprotective effect, which was further confirmed in the messenger RNA level of HO-1. Such trend was also observed in the nuclear factor erythroid 2-related factor 2 (Nrf2) nuclear translocation, an upstream regulation of HO-1. In addition, correlation analysis showed a significantly positive relationship between HO-1 expression and Nrf2 translocation (r = 0.729, P < .001). Hence, we conclude that DRIPC may produce an additive cardioprotection to SPoC through an enhanced HO-1 expression partly via Nrf2 translocation.

Chronic total artery occlusions in noninfarct-related coronary arteries

It has been rarely encountered some patients in clinical practice with coronary artery chronic total occlusion (CTO) on angiography but no any clinical history or electrocardiographic, echocardiographic, or left ventriculographic evidence of previous myocardial infarction. These noninfarct-related artery CTO (non-IRA CTO) lesions may be used as a clinical role model of endogenous cardioprotective mechanisms in addition to continuing the process of atherosclerosis. The objective of this study was to characterize the clinical characteristics of patients with non-IRA CTO patients and compared them to those with infarct-related CTO (IRA-CTO). We reviewed our invasive cardiology database searching for the CTO of any major coronary arteries, and assessed whether or not they have the clinical history or electrocardiographic, echocardiographic, and left ventriculographic evidence of previous myocardial infarction. Interestingly, we detected that all these patients with non-IRA CTO had diabetes mellitus, and the clinical and demographic features of these non-IRA CTO patients were compared with age- and sex-matched diabetic IRA-CTO patients with regard to conventional coronary risk factors and the angiographic collateral grading system. There were total 99 CTO patients (49 patients with non-IRA CTO and 50 patients with IRA-CTO).All patients with non-IRA CTO had better collateral circulation (96 vs. 40% p < 0.001) compared with those having IRA-CTO. The only significant difference between the groups was the status of current smoking (4 vs. 88%; p < 0.001). The present study showed that the non-IRA CTOs were associated with diabetes mellitus and better collateral development compared with IRA-CTO. In diabetic patients, the concomitant smoking use may be harmful by preventing endogenous cardioprotective mechanisms.

Antioxidant effect of isoflavones: A randomized, double-blind, placebo controlled study in oophorectomized women

Background:

One of the postulated mechanism for cardioprotective potential of isoflavones is their ability to exert antioxidant action. However, various reports give conflicting results in this area.

Aim:

The present study was conducted with an objective to probe into the cardioprotective mechanism of isoflavones by evaluating their antioxidant potential in oophorectomized women.

Materials and Methods:

This was a randomized, double-blind, parallel, placebo controlled study. A total of 43 women were randomized to receive 75 mg/day isoflavones tablet or placebo for 12 weeks. Red blood cell antioxidant parameters including lipid peroxidation, superoxide dismutase (SOD), catalase and glutathione peroxidase (GSH-Px) were determined at baseline and at the end of the study.

Results:

After 12 weeks of administration of isoflavones, there was no statistically significant difference in lipid peroxidation (P value for isoflavones: 0.37; for placebo: 0.37), catalase (P value for isoflavones: 0.35; for placebo: 0.84), SOD (P value for isoflavones: 0.41; for placebo: 0.28) and GSH-Px (P value for isoflavones: 0.92; for placebo: 0.29). There was no statistically significant difference in the proportion of patients experiencing adverse events in the two groups (P -1.00).

Conclusion:

The study strengthens the concept that the cardioprotective mechanism of isoflavones might be due to some other reason apart from the antioxidant pathway.

Gastrointestinal ulcers, role of aspirin, and clinical outcomes: pathobiology, diagnosis, and treatment

Peptic ulcer disease is a major cause of morbidity and mortality in the US with more than six million diagnoses annually. Ulcers are reported as the most common cause of hospitalization for upper gastrointestinal (GI) bleeding and are often a clinical concern due to the widespread use of aspirin and nonsteroidal anti-inflammatory drugs, both of which have been shown to induce ulcer formation. The finding that Helicobacter pylori infection (independent of aspirin use) is associated with the development of ulcers led to a more thorough understanding of the causes and pathogenesis of ulcers and an improvement in therapeutic options. However, many patients infected with H. pylori are asymptomatic and remain undiagnosed. Complicating matters is a current lack of understanding of the association between aspirin use and asymptomatic ulcer formation. Low-dose aspirin prescriptions have increased, particularly for cardioprotection. Unfortunately, the GI side effects associated with aspirin therapy continue to be a major complication in both symptomatic and asymptomatic patients. These safety concerns should be important considerations in the decision to use aspirin and warrant further education. The medical community needs to continue to improve awareness of aspirin-induced GI bleeding to better equip physicians and improve care for patients requiring aspirin therapy.

Detrimental effects of acute hyperglycaemia on the rat heart

AIM

Hyperglycaemia is an important risk factor for acute myocardial infarction. It can lead to increased induction of non-oxidative glucose pathways (NOGPs) - polyol and hexosamine biosynthetic pathways, advanced glycation end products and protein kinase C - that may contribute to cardiovascular diseases onset. However, the precise underlying mechanisms remain poorly understood. Here we hypothesized that acute hyperglycaemia increases myocardial oxidative stress and NOGP activation resulting in cardiac dysfunction during ischaemia-reperfusion and that inhibition of, and/or shunting flux away from NOGPs [by benfotiamine (BFT) treatment], leads to cardioprotection.

METHODS

We employed several experimental systems: (i) Isolated rat hearts were perfused ex vivo with Krebs-Henseleit buffer containing 33 mm glucose vs. controls (11 mm glucose) ± global ischaemia and reperfusion ± BFT (first 20 min of reperfusion); (ii) Infarct size determination as per the ischaemic protocol, but with regional ischaemia and reperfusion ± BFT treatment; in separate experiments, NOGP inhibitors were also employed for (i) and (ii); and (iii) In vivo coronary ligations performed on streptozotocin-treated rats ± BFT treatment (early reperfusion).

RESULTS

Acute hyperglycaemia generated myocardial oxidative stress, NOGP activation and apoptosis, but caused no impairment of cardiac function during pre-ischaemia, thereby priming hearts for later damage. Following ischaemia-reperfusion (under hyperglycaemic conditions), such effects were exacerbated together with cardiac contractile dysfunction. Moreover, inhibition of respective NOGPs and shunting away by BFT treatment (in part) improved cardiac function during ischaemia-reperfusion.

CONCLUSION

Coordinate NOGP activation in response to acute hyperglycaemia results in contractile dysfunction during ischaemia-reperfusion, allowing for the development of novel cardioprotective agents.

Rapid endovascular catheter core cooling combined with cold saline as an adjunct to percutaneous coronary intervention for the treatment of acute myocardial infarction. The CHILL-MI trial: a randomized controlled study of the use of central venous catheter core cooling combined with cold saline as an adjunct to percutaneous coronary intervention for the treatment of acute myocardial infarction

OBJECTIVES

The aim of this study was to confirm the cardioprotective effects of hypothermia using a combination of cold saline and endovascular cooling.

BACKGROUND

Hypothermia has been reported to reduce infarct size (IS) in patients with ST-segment elevation myocardial infarctions.

METHODS

In a multicenter study, 120 patients with ST-segment elevation myocardial infarctions (<6 h) scheduled to undergo percutaneous coronary intervention were randomized to hypothermia induced by the rapid infusion of 600 to 2,000 ml cold saline and endovascular cooling or standard of care. Hypothermia was initiated before percutaneous coronary intervention and continued for 1 h after reperfusion. The primary end point was IS as a percent of myocardium at risk (MaR), assessed by cardiac magnetic resonance imaging at 4 ± 2 days.

RESULTS

Mean times from symptom onset to randomization were 129 ± 56 min in patients receiving hypothermia and 132 ± 64 min in controls. Patients randomized to hypothermia achieved a core body temperature of 34.7°C before reperfusion, with a 9-min longer door-to-balloon time. Median IS/MaR was not significantly reduced (hypothermia: 40.5% [interquartile range: 29.3% to 57.8%; control: 46.6% [interquartile range: 37.8% to 63.4%]; relative reduction 13%; p = 0.15). The incidence of heart failure was lower with hypothermia at 45 ± 15 days (3% vs. 14%, p < 0.05), with no mortality. Exploratory analysis of early anterior infarctions (0 to 4 h) found a reduction in IS/MaR of 33% (p < 0.05) and an absolute reduction of IS/left ventricular volume of 6.2% (p = 0.15).

CONCLUSIONS

Hypothermia induced by cold saline and endovascular cooling was feasible and safe, and it rapidly reduced core temperature with minor reperfusion delay. The primary end point of IS/MaR was not significantly reduced. Lower incidence of heart failure and a possible effect in patients with early anterior ST-segment elevation myocardial infarctions need confirmation. (Efficacy of Endovascular Catheter Cooling Combined With Cold Saline for the Treatment of Acute Myocardial Infarction [CHILL-MI]; NCT01379261).

Doxorubicin-induced carbonylation and degradation of cardiac myosin binding protein C promote cardiotoxicity

Dose-dependent oxidative stress by the anthracycline doxorubicin (Dox) and other chemotherapeutic agents causes irreversible cardiac damage, restricting their clinical effectiveness. We hypothesized that the resultant protein oxidation could be monitored and correlated with physiological functional impairment. We focused on protein carbonylation as an indicator of severe oxidative damage because it is irreversible and results in proteasomal degradation. We identified and investigated a specific high-molecular weight cardiac protein that showed a significant increase in carbonylation under Dox-induced cardiotoxic conditions in a spontaneously hypertensive rat model. We confirmed carbonylation and degradation of this protein under oxidative stress and prevention of such effect in the presence of the iron chelator dexrazoxane. Using MS, the Dox-induced carbonylated protein was identified as the 140-kDa cardiac myosin binding protein C (MyBPC). We confirmed the carbonylation and degradation of MyBPC using HL-1 cardiomyocytes and a purified recombinant untagged cardiac MyBPC under metal-catalyzed oxidative stress conditions. The carbonylation and degradation of MyBPC were time- and drug concentration-dependent. We demonstrated that carbonylated MyBPC undergoes proteasome-mediated degradation under Dox-induced oxidative stress. Cosedimentation, immunoprecipitation, and actin binding assays were used to study the functional consequences of carbonylated MyBPC. Carbonylation of MyBPC showed significant functional impairment associated with its actin binding properties. The dissociation constant of carbonylated recombinant MyBPC for actin was 7.35 ± 1.9 μM compared with 2.7 ± 0.6 μM for native MyBPC. Overall, our findings indicate that MyBPC carbonylation serves as a critical determinant of cardiotoxicity and could serve as a mechanistic indicator for Dox-induced cardiotoxicity.

The protective effects of puerarin in cardiomyocytes from anoxia/reoxygenation injury are mediated by PKCε

Puerarin is an isoflavone isolated from traditional Chinese medicine Ge-gen (Radix Puerariae). Clinical studies have confirmed the cardioprotective effects of puerarin; however, the mechanisms underlying these effects are still unclear. On the basis of previous findings, we hypothesized that puerarin protects cardiomyocytes from ischemia-reperfusion injury via the protein kinase C epsilon (PKCε) (a critical cardioprotective protein) signalling pathway. Neonatal rat primary cardiomyocytes were preconditioned with puerarin or puerarin plus εV1-2, a selective PKCε inhibitor, prior to anoxia/reoxygenation (A/R) treatment. Western blot analysis showed that expression and activity of PKCε protein in puerarin preconditioned group were both increased compared with the control or A/R group. Subsequent assays showed that preconditioning with puerarin could increase the viability of neonatal rat primary cardiomyocytes treated with A/R, decreased the generation of reactive oxygen species (ROS), loss of mitochondrial membrane potential, cell necrosis and apoptosis induced by A/R injury. However, the protective effects of puerarin completely disappeared in the group pretreated with puerarin plus εV1-2. Thus, for the first time, we revealed the protective effects of puerarin in cardiomocytes from anoxia/reoxygenation injury are mediated by PKCε.

Agonist of inward rectifier K+ channels enhances the protection of ischemic postconditioning in isolated rat hearts

BACKGROUND

Selective inhibition of inward rectifier K⁺ channels could abolish the protection mediated by ischemic preconditioning, but the roles of these channels in ischemic postconditioning have not been well characterized. Our study aims to evaluate the effect of inward rectifier K⁺ channels on the protection induced by ischemic postconditioning.

METHODS

Langendorff-perfused rat hearts (n=8 per group) were split into four groups: postconditioning hearts (IPO group); ischemic postconditioning with BaCl₂ hearts (PB group); ischemic postconditioning with zacopride hearts (PZ group); and without ischemic postconditioning (CON group). After suffering 30 minutes of global ischemia, groups IPO, PB and PZ went through 10 seconds of ischemic postconditioning with three different perfusates: respectively, Krebs-Henseleit buffer (IPO group); 20 μmol/L BaCl₂ (antagonist of the channel, PB group); 1 μmol/L zacopride (agonist of the channel, PZ group).

RESULTS

At the end of reperfusion, the myocardial performance was better preserved in the PZ group than the other three groups. The PB group showed no significant differences from the CON group.

CONCLUSIONS

Our study has shown that the I_K1 channel agonist zacopride is associated with the enhancement of ischemic postconditioning.

Role of Notch signaling in the mammalian heart

Notch signaling is an evolutionarily ancient, highly conserved pathway important for deciding cell fate, cellular development, differentiation, proliferation, apoptosis, adhesion, and epithelial-to-mesenchymal transition. Notch signaling is also critical in mammalian cardiogenesis, as mutations in this signaling pathway are linked to human congenital heart disease. Furthermore, Notch signaling can repair myocardial injury by promoting myocardial regeneration, protecting ischemic myocardium, inducing angiogenesis, and negatively regulating cardiac fibroblast-myofibroblast transformation. This review provides an update on the known roles of Notch signaling in the mammalian heart. The goal is to assist in developing strategies to influence Notch signaling and optimize myocardial injury repair.

Reduction of infarct size by the therapeutic protein TAT-Ndi1 in vivo

Lethal myocardial ischemia-reperfusion (I/R) injury has been attributed in part to mitochondrial respiratory dysfunction (including damage to complex I) and the resultant excessive production of reactive oxygen species. Recent evidence has shown that reduced nicotinamide adenine dinucleotide-quinone internal oxidoreductase (Ndi1; the single-subunit protein that in yeast serves the analogous function as complex I), transduced by addition of the TAT-conjugated protein to culture media and perfusion buffer, can preserve mitochondrial function and attenuate I/R injury in neonatal rat cardiomyocytes and Langendorff-perfused rat hearts. However, this novel metabolic strategy to salvage ischemic-reperfused myocardium has not been tested in vivo. In this study, TAT-conjugated Ndi1 and placebo-control protein were synthesized using a cell-free system. Mitochondrial uptake and functionality of TAT-Ndi1 were demonstrated in mitochondrial preparations from rat hearts after intraperitoneal administration of the protein. Rats were randomized to receive either TAT-Ndi1 or placebo protein, and 2 hours later all animals underwent 45-minute coronary artery occlusion followed by 2 hours of reperfusion. Infarct size was delineated by tetrazolium staining and normalized to the volume of at-risk myocardium, with all analysis conducted in a blinded manner. Risk region was comparable in the 2 cohorts. Preischemic administration of TAT-Ndi1 was profoundly cardioprotective. These results demonstrate that it is possible to target therapeutic proteins to the mitochondrial matrix and that yeast Ndi1 can substitute for complex I to ameliorate I/R injury in the heart. Moreover, these data suggest that cell-permeable delivery of mitochondrial proteins may provide a novel molecular strategy to treat mitochondrial dysfunction in patients.

Iloprost reduces myocardial edema in a rat model of myocardial ischemia reperfusion

OBJECTIVE

Myocardial ischemia severely reduces myocyte longevity and function. Extensive interstitial edema and cell damage occur as a result of myocardial reperfusion injury. Current therapies are directed at prevention of ischemia-induced damage to cardiac tissue. Iloprost is a novel pharmaceutical agent for the treatment of ischemia.

METHODS

Twenty rats were segregated into four experimental groups. The procedure control group consisted of four rats undergoing a sham operation. The remaining 16 rats were divided into two equal groups. The first group (control group) received a continuous intravenous infusion of physiological serum immediately prior to the procedure. Iloprost was administered by a continuous intravenous infusion into the right jugular vein at an infusion rate of 100 ng/kg/min for 30 minutes prior to reperfusion in the experimental group (study group). Following the infusion treatments, ligation of the left coronary artery was conducted for 30 minutes to induce myocardial ischemia. The rats were euthanized 24 hours after reperfusion and cardiac tissue was harvested from all specimens for analysis.

RESULTS

Histological examination revealed three myocardial tissue specimens with grade II damage and five myocardial tissue specimens with grade III reperfusion injury in the control group. However, the study group consisted of two grade III myocardial tissue specimens, five grade II myocardial tissue specimens and one grade I myocardial tissue specimen. Moreover, a statistically significant reduction in myocardial edema was observed in the study group (p=0.022).

CONCLUSION

Our results support the hypothesis that iloprost enhances protection against cardiac ischemia reperfusion injury. This protective effect may be associated with vasodilation, antioxidant or anti-edema mechanisms.

Resveratrol and its metabolites modulate cytokine-mediated induction of eotaxin-1 in human pulmonary artery endothelial cells

Coronary heart disease (CHD) is a leading cause of death in many developed countries. Evidence has long implicated endothelial injury and inflammation as apical events in the pathogenesis of atherosclerosis, the primary cause of CHD. Numerous risk factors contribute to a damaged, inflamed endothelium. Conversely, cardioprotective agents targeting the dysfunctional endothelium have also been identified, notably from dietary sources. We have used cultured human pulmonary artery endothelial cells (HPAECs) to test the diet-mediated cardioprotective hypothesis. In this review, we summarize our recent findings on control of transcription and expression of inflammation biomarker eotaxin-1 in HPAECs exposed to single or combined proinflammatory cytokines interleukin-13 (IL-13) and tumor necrosis factor-α (TNF-α), and attenuation of the observed eotaxin-1 responses by prior or simultaneous treatment with resveratrol and its metabolites. Control of eotaxin-1 gene regulation may be considered an in vitro model to evaluate agents linking cardioprotection with endothelial cell damage and inflammation.

Hypoxia-inducible factor 1 is required for remote ischemic preconditioning of the heart

Both preclinical and clinical studies suggest that brief cycles of ischemia and reperfusion in the arm or leg may protect the heart against injury following prolonged coronary artery occlusion and reperfusion, a phenomenon known as remote ischemic preconditioning. Recent studies in mice indicate that increased plasma interleukin-10 (IL-10) levels play an important role in remote ischemic preconditioning induced by clamping the femoral artery for 5 min followed by 5 min of reperfusion for a total of three cycles. In this study, we demonstrate that remote ischemic preconditioning increases plasma IL-10 levels and decreases myocardial infarct size in wild-type mice but not in littermates that are heterozygous for a knockout allele at the locus encoding hypoxia-inducible factor (HIF) 1α. Injection of a recombinant adenovirus encoding a constitutively active form of HIF-1α into mouse hind limb muscle was sufficient to increase plasma IL-10 levels and decrease myocardial infarct size. Exposure of C2C12 mouse myocytes to cyclic hypoxia and reoxygenation rapidly increased levels of IL-10 mRNA, which was blocked by administration of the HIF-1 inhibitor acriflavine or by expression of short hairpin RNA targeting HIF-1α or HIF-1β. Chromatin immunoprecipitation assays demonstrated that binding of HIF-1 to the Il10 gene was induced when myocytes were subjected to cyclic hypoxia and reoxygenation. Taken together, these data indicate that HIF-1 activates Il10 gene transcription and is required for remote ischemic preconditioning.

The genetic basis for survivorship in coronary artery disease

Survivorship is a trait characterized by endurance and virility in the face of hardship. It is largely considered a psychosocial attribute developed during fatal conditions, rather than a biological trait for robustness in the context of complex, age-dependent diseases like coronary artery disease (CAD). The purpose of this paper is to present the novel phenotype, survivorship in CAD as an observed survival advantage concurrent with clinically significant CAD. We present a model for characterizing survivorship in CAD and its relationships with overlapping time- and clinically-related phenotypes. We offer an optimal measurement interval for investigating survivorship in CAD. We hypothesize genetic contributions to this construct and review the literature for evidence of genetic contribution to overlapping phenotypes in support of our hypothesis. We also present preliminary evidence of genetic effects on survival in people with clinically significant CAD from a primary case-control study of symptomatic coronary disease. Identifying gene variants that confer improved survival in the context of clinically appreciable CAD may improve our understanding of cardioprotective mechanisms acting at the gene level and potentially impact patients clinically in the future. Further, characterizing other survival-variant genetic effects may improve signal-to-noise ratio in detecting gene associations for CAD.

Postnatal shifts in ischemic tolerance and cell survival signaling in murine myocardium

The immature heart is known to be resistant to ischemia-reperfusion (I/R) injury; however, key proteins engaged in phospho-dependent signaling pathways crucial to cell survival are not yet defined. Our goal was to determine the postnatal changes in myocardial tolerance to I/R, including baseline expression of key proteins governing I/R tolerance and their phosphorylation during I/R. Hearts from male C57Bl/6 mice (neonates, 2, 4, 8, and 12 wk of age, n = 6/group) were assayed for survival signaling/effectors [Akt, p38MAPK, glycogen synthase kinase-3β (GSK-3β), heat shock protein 27 (HSP27), connexin-43, hypoxia-inducible factor-1α (HIF-1α), and caveolin-3] and regulators of apoptosis (Bax and Bcl-2) and autophagy (LC3B, Parkin, and Beclin1). The effect of I/R on ventricular function was measured in isolated perfused hearts from immature (4 wk) and adult (12 wk) mice. The neonatal myocardium exhibits a large pool of inactive Akt; high phospho-activation of p38MAPK, HSP27 and connexin-43; phospho-inhibition of GSK-3β; and high expression of caveolin-3, HIF-1α, LC3B, Beclin1, Bax, and Bcl-2. Immature hearts sustained less dysfunction and infarction following I/R than adults. Emergence of I/R intolerance in adult vs. immature hearts was associated with complex proteomic changes: decreased expression of Akt, Bax, and Bcl-2; increased GSK-3β, connexin-43, HIF-1α, LC3B, and Bax:Bcl-2; enhanced postischemic HIF-1α, caveolin-3, Bax, and Bcl-2; and greater postischemic GSK-3β and HSP27 phosphorylation. Neonatal myocardial stress resistance reflects high expression of prosurvival and autophagy proteins and apoptotic regulators. Notably, there is high phosphorylation of GSK-3β, p38MAPK, and HSP27 and low phosphorylation of Akt (high Akt "reserve"). Subsequent maturation-related reductions in I/R tolerance are associated with reductions in Akt, Bcl-2, LC3B, and Beclin1, despite increased expression and reduced phospho-inhibition of GSK-3β.

Cardioprotective Role of Caveolae in Ischemia-Reperfusion Injury

Caveolae are flask-like invaginations of the plasma membrane enriched in cholesterol, sphingolipids, the marker protein caveolin and the coat protein cavin. In cardiomyocytes, multiple signaling molecules are concentrated and organized within the caveolae to mediate signaling transduction. Recent studies suggest that caveolae and caveolae-associated signaling molecules play an important role in protecting the myocardium against ischemia-reperfusion injury. For example, cardiac-specific overexpression of caveolin-3 has been shown to lead to protection that mimics ischemic preconditioning, while the knockout of caveolin-3 abolished ischemic preconditioning. In this review, we discuss the molecular mechanisms and signaling pathways that are involved in caveolae-mediated cardioprotection, and examine the potential for caveolae as a therapeutic target for pharmaceutical intervention to treat cardiovascular disease.

Kir6.2 limits Ca(2+) overload and mitochondrial oscillations of ventricular myocytes in response to metabolic stress

ATP-sensitive K(+) (KATP) channels are abundant membrane proteins in cardiac myocytes that are directly gated by intracellular ATP and form a signaling complex with metabolic enzymes, such as creatine kinase. KATP channels are known to be essential for adaption to cardiac stress, such as ischemia; however, how all the molecular components of the stress response interact is not fully understood. We examined the effects of decreasing the KATP current density on Ca(2+) and mitochondrial homeostasis and ischemic preconditioning. Acute knockdown of the pore-forming subunit, Kir6.2, was achieved using adenoviral delivery of short hairpin RNA targeted to Kir6.2. The acute nature of the knockdown of Kir6.2 accurately shows the effects of Kir6.2 depletion without any compensatory effects that may arise in transgenic studies. We also investigated the effect of reducing the KATP current while maintaining KATP channel protein in the sarcolemmal membrane using a nonconducting Kir6.2 construct. Only 50% KATP current remained after Kir6.2 knockdown, yet there were profound effects on myocyte responses to metabolic stress. Kir6.2 was essential for cardiac myocyte Ca(2+) homeostasis under both baseline conditions before any metabolic stress and after metabolic stress. Expression of nonconducting Kir6.2 also resulted in increased Ca(2+) overload, showing the importance of K(+) conductance in the protective response. Both ischemic preconditioning and protection during ischemia were lost when Kir6.2 was knocked down. KATP current density was also important for the mitochondrial membrane potential at rest and prevented mitochondrial membrane potential oscillations during oxidative stress. KATP channel density is important for adaption to metabolic stress.

The neuroimmune guidance cue netrin-1: a new therapeutic target in cardiovascular disease

Netrins are a family of proteins involved in cell migration and axon guidance during embryogenesis. The different functions and mechanisms of action of this family of proteins have been better characterized with the study of the netrin-1. They are chemotropic and act as a bifunctional regulator of neuron migration. Apart from its role in the central nervous system, researchers have proven that netrin-1 plays a role in the development and formation of non-neural tissue, thus netrin-1 is involved in regulation of cancers, cardiovascular diseases, kidney diseases and other diseases. Concerning the cardio-vascular realm, netrin-1 promotes angiogenesis and accelerates atherosclerosis, protects the heart against ischemia-reperfusion injury and reduces the infarct size. These findings make the neuroimmune guidance cue netrin-1 an important therapeutic target. This work seeks to review the subject based on studies that have been conducted over the past decade to identify the perspectives and extent of the research on this protein in the field of cardiology.

Mitochondrial reactive oxygen species: which ROS signals cardioprotection?

Mitochondria are the major effectors of cardioprotection by procedures that open the mitochondrial ATP-sensitive potassium channel (mitoKATP), including ischemic and pharmacological preconditioning. MitoKATP opening leads to increased reactive oxygen species (ROS), which then activate a mitoKATP-associated PKCε, which phosphorylates mitoKATP and leaves it in a persistent open state (Costa AD, Garlid KD. Am J Physiol Heart Circ Physiol 295, H874-H882, 2008). The ROS responsible for this effect is not known. The present study focuses on superoxide (O2(·-)), hydrogen peroxide (H2O2), and hydroxyl radical (HO(·)), each of which has been proposed as the signaling ROS. Feedback activation of mitoKATP provides an ideal setting for studying endogenous ROS signaling. Respiring rat heart mitochondria were preincubated with ATP and diazoxide, together with an agent being tested for interference with this process, either by scavenging ROS or by blocking ROS transformations. The mitochondria were then assayed to determine whether or not the persistent phosphorylated open state was achieved. Dimethylsulfoxide (DMSO), dimethylformamide (DMF), deferoxamine, Trolox, and bromoenol lactone each interfered with formation of the ROS-dependent open state. Catalase did not interfere with this step. We also found that DMF blocked cardioprotection by both ischemic preconditioning and diazoxide. The lack of a catalase effect and the inhibitory effects of agents acting downstream of HO(·) excludes H2O2 as the endogenous signaling ROS. Taken together, the results support the conclusion that the ROS message is carried by a downstream product of HO(·) and that it is probably a product of phospholipid oxidation.

Cardioprotective effect of remote ischemic postconditioning on children undergoing cardiac surgery: a randomized controlled trial

BACKGROUND

Remote ischemic postconditioning (RPostC) is a noninvasive intervention that has demonstrated cardioprotection and neuroprotection in animal studies.

OBJECTIVE

Our goal was to investigate the cardio-cerebral protective effects of RPostC on children undergoing open-heart surgery for repair of congenital heart defects (CHD).

METHODS

Children undergoing open-heart repair of CHD were randomly assigned to a RPostC or control group. RPostC was induced by three 5-min cycles of lower limb ischemia and reperfusion using a blood pressure cuff (200 mmHg) at the onset of aortic unclamping. Serum cardiac troponin I (cTnI), creatine kinase-MB (CK-MB), neuron-specific enolase (NSE), S100β, cytokines, and clinical outcomes were assessed.

RESULTS

There were 35 children in the control group and 34 in the RPostC group. The mean age (3.64 ± 1.95 years vs. 3.45 ± 3.02 years, P = 0.80), weight (15.11 ± 6.91 kg vs. 13.40 ± 6.33 kg, P = 0.37), surgical time (144.82 ± 38.51 min vs. 129.92 ± 30.76 min, P = 0.15), and bypass time (78.01 ± 27.22 min vs. 72.52 ± 26.05 min, P = 0.49) were not different. Compared with the control group, the postoperative levels of cTnI (P = 0.037) and CK-MB (P = 0.046) were significantly reduced in the RPostC group. Furthermore, the MAP was higher (P = 0.008), and ICU stay (36.87 ± 3.30 h vs. 60.57 ± 7.35 h, P = 0.006) and postoperative hospital stay (8.56 ± 1.50 days vs. 10.06 ± 2.41 days, P = 0.048) were shorter in the RPostC group than in the control group. However, the postoperative CVP and the concentrations of NSE, S100β, CRP, TNF-α, IL-1β, IL-6, and IL-10 were not significantly different.

CONCLUSION

RPostC significantly alleviates cardiac injury in children undergoing open-heart repair of CHD and may also reduce cerebral injury.

HIF-1α in heart: protective mechanisms

Hypoxia-inducible factor-1α (HIF-1α) is a transcription factor that directs many of the cellular responses to hypoxia. In these studies, we have used a mouse model containing a cardiac-specific, oxygen-stabilized, doxycycline (Dox)-off regulated HIF-1α transgene to probe the role of HIF-1α in cardioprotection. Hearts used in these studies were derived from wild-type (WT), noninduced (Non-I), and 2 day (2D) and 6 day (6D) Dox-deprived mice. Whereas HIF-1α protein is undetectable in WT mice, it is present in heart tissue of "noninduced" transgenic mice, presumably because of leakiness of the promoter construct. In mice denied Dox for 2 or 6 days, HIF-1α is overexpressed to a much greater extent than Non-I or WT animals, as expected. WT and HIF-1α-expressing hearts (Non-I, 2D and 6D induced) were subjected to 30 min of ischemia, and functional recovery was measured upon reperfusion. Recovery of preischemic left ventricular developed pressure was 14% for WT, 67% for Non-I hearts, 64% for 2D-induced, and 62% for 6D-induced hearts. 6D-induced HIF hearts have increased preischemic glycogen reserves, higher glycogen synthase protein levels, and significantly higher lactic acid release during ischemia. 6D-induced HIF hearts were also better able to maintain ATP levels during ischemia compared with WT and Non-I hearts. Interestingly, Non-I hearts showed no significant increase in glycogen reserves, glycolytic flux, or greater ATP preservation during ischemia and yet were protected to a similar extent as the 6D-induced hearts. Finally, the mitochondrial membrane potential of isolated adult myocytes was monitored during anoxia or treatments with cyanide and 2-deoxyglucose. HIF-1α expression was shown to protect mitochondrial polarization during both stress treatments. Taken together these data indicate that, while HIF-1α expression in heart does induce increases in compensatory glycolytic capacity, these changes are not necessarily required for cardioprotection, at least in this model of ischemic stress.

Emulsified isoflurane postconditioning produces cardioprotection against myocardial ischemia-reperfusion injury in rats

Emulsified isoflurane (EIso) preconditioning can induce cardioprotection. We investigated whether EIso application after ischemia protects hearts against reperfusion injury and whether it is mediated by the inhibition of apoptosis. Rats were subjected to 30-min coronary occlusion followed by 180-min reperfusion. At the onset of reperfusion, rats were intravenously administered saline (sham, control group), 30 % intralipid (IL group) or 2 ml kg(-1) EIso (EIso group) for 30 min. After reperfusion, infarct sizes, myocardial apoptosis and expression of Bcl-2, Bax and caspase-3 proteins were determined. Hemodynamic parameters were not different among groups. Compared with control and intralipid group, EIso limited infarct size, inhibited apoptosis, increased the expression of Bcl-2, decreased the expression of Bax, cleaved caspase-3, and enhanced Bcl-2/Bax ratio. EIso protects hearts against reperfusion injury when administered at the onset of reperfusion, which may be mediated by the inhibition of apoptosis via modulation of the expression of pro- and anti-apoptotic proteins.

Iodine and doxorubicin, a good combination for mammary cancer treatment: antineoplastic adjuvancy, chemoresistance inhibition, and cardioprotection

BACKGROUND

Although mammary cancer (MC) is the most common malignant neoplasia in women, the mortality for this cancer has decreased principally because of early detection and the use of neoadjuvant chemotherapy. Of several preparations that cause MC regression, doxorubicin (DOX) is the most active, first-line monotherapeutic. Nevertheless, its use is limited due to the rapid development of chemoresistance and to the cardiotoxicity caused by free radicals. In previous studies we have shown that supplementation with molecular iodine (I2) has a powerful antineoplastic effect in methylnitrosourea (MNU)-induced experimental models of MC. These studies also showed a consistent antioxidant effect of I2 in normal and tumoral tissues.

METHODS

Here, we analyzed the effect of I2 in combination with DOX treatment in female Sprague Dawley rats with MNU-induced MC. In the first experiment (short) animals were treated with the therapeutic DOX dose (16 mg/kg) or with lower doses (8 and 4 mg/Kg), in each case with and without 0.05% I2 in drinking water. Iodine treatment began on day 0, a single dose of DOX was injected (ip) on day 2, and the analysis was carried out on day 7. In the second experiment (long) animals with and without iodine supplement were treated with one or two injections of 4 mg/kg DOX (on days 0 and 14) and were analyzed on day 56.

RESULTS

At all DOX doses, the short I2 treatment induced adjuvant antineoplastic effects (decreased tumor size and proliferating cell nuclear antigen level) with significant protection against body weight loss and cardiotoxicity (creatine kinase MB, cardiac lipoperoxidation, and heart damage). With long-term I2, mammary tumor tissue became more sensitive to DOX, since a single injection of the lowest dose of DOX (4 mg/Kg) was enough to stop tumor progression and a second DOX4 injection on day 14 caused a significant and rapid decrease in tumor size, decreased the expression of chemoresistance markers (Bcl2 and survivin), and increased the expression of the apoptotic protein Bax and peroxisome proliferator-activated receptor type gamma.

CONCLUSIONS

The DOX-I2 combination exerts antineoplastic, chemosensitivity, and cardioprotective effects and could be a promising strategy against breast cancer progression.

Doxorubicin-induced markers of myocardial autophagic signaling in sedentary and exercise trained animals

Doxorubicin (DOX) is an effective antitumor agent used in cancer treatment. However, its clinical use is limited due to cardiotoxicity. Indeed, the side effects of DOX are irreversible and include the development of cardiomyopathy and ultimately congestive heart failure. Although many studies have investigated the events leading to DOX-induced cardiotoxicity, the mechanisms responsible for DOX-induced cardiotoxicity remain unknown. In general, evidence suggests that DOX-induced cardiotoxicity is associated with an increased generation of reactive oxygen species and oxidative damage, leading to the activation of cellular proteolytic systems. In this regard, the autophagy/lysosomal proteolytic system is a constitutively active catabolic process that is responsible for the degradation of both organelles and cytosolic proteins. We tested the hypothesis that systemic DOX administration results in altered cardiac gene and protein expression of mediators of the autophagy/lysosomal system. Our results support this hypothesis, as DOX treatment increased both the mRNA and protein levels of numerous key autophagy genes. Because exercise training has been shown to be cardioprotective against DOX-induced damage, we also determined whether exercise training before DOX administration alters the expression of important components of the autophagy/lysosomal system in cardiac muscle. Our findings show that exercise training inhibits DOX-induced cardiac increases in autophagy signaling. Collectively, our results reveal that DOX administration promotes activation of the autophagy/lysosomal system pathway in the heart, and that endurance exercise training can be a cardioprotective intervention against myocardial DOX-induced toxicity.

Remote ischemic preconditioning improves outcome at 6 years after elective percutaneous coronary intervention: the CRISP stent trial long-term follow-up

BACKGROUND

Postprocedural myocardial infarction (type 4a) has been shown to be an adverse prognostic indicator after elective percutaneous coronary intervention (PCI). The Cardiac Remote Ischemic Preconditioning in Coronary Stenting (CRISP Stent) study demonstrated that remote ischemic preconditioning reduced procedural symptoms, ECG ST-segment deviation, and cardiac troponin I release after elective PCI and reduced the major adverse cardiac and cerebral event (MACCE) rate at 6 months. We were interested to confirm if this early benefit in MACCE rate in the remote ischemic preconditioning group was sustained long-term.

METHODS AND RESULTS

Patients were telephoned by researchers blinded to the randomization details. MACCE, defined as all-cause mortality, nonfatal myocardial infarction, transient ischemic attack or stroke, and heart failure requiring hospital admission, were adjudicated by case note and national database review. One hundred ninety-two (89.3%) of the 225 patients with elective PCI randomized in the original study were available for long-term follow-up (mean time to event or last follow-up: 1579.7±603.6 days). There were a total of 59 (30.7%) MACCEs. Patients with an MACCE had a higher mean cardiac troponin I after PCI (±SD): 2.07±6.99 versus 0.91±2.07 ng/mL (P=0.05). The MACCE rate at 6 years remained lower in the remote ischemic preconditioning group (hazard ratio, 0.58; 95% confidence interval, 0.35-0.97; P=0.039; absolute risk reduction=0.13 and number needed to treat=8 to prevent the MACCE at 6 years).

CONCLUSIONS

Remote ischemic preconditioning reduces the incidence of postprocedural cardiac troponin I after elective PCI and confers an MACCE-free survival benefit at both short- and long-term follow-up.

CLINICAL TRIAL REGISTRATION

URL: http://www.ukcrn.org.uk. Unique identifier: UKCRN 4074.

Apolipoprotein A-1 mimetic D-4F enhances isoflurane-induced eNOS signaling and cardioprotection during acute hyperglycemia

Acute hyperglycemia (AHG) decreases the availability of nitric oxide (NO) and impairs anesthetic preconditioning (APC)-elicited protection against myocardial infarction. We investigated whether D-4F, an apolipoprotein A-1 mimetic, rescues the myocardium by promoting APC-induced endothelial NO signaling during AHG. Myocardial infarct size was measured in mice in the absence or presence of APC [isoflurane (1.4%)] with or without AHG [dextrose (2 g/kg ip)] and D-4F (0.12 or 0.6 mg/kg ip). NO production, superoxide generation, protein compartmentalization, and posttranslational endothelial NO synthase (eNOS) modifications were assessed in human coronary artery endothelial cells cultured in 5.5 or 20 mM glucose with or without isoflurane (0.5 mM) in the presence or absence of D-4F (0.5 μg/ml). Myocardial infarct size was significantly decreased by APC (36 ± 3% of risk area) compared with control (54 ± 3%) in the absence, but not presence, of AHG (49 ± 4%). D-4F restored the cardioprotective effect of APC during AHG (36 ± 3% and 30 ± 3%, 0.12 and 0.6 mg/kg, respectively), although D-4F alone had no effect on infarct size (53 ± 3%). Isoflurane promoted caveolin-1 and eNOS compartmentalization within endothelial cell caveolae and eNOS dimerization, concomitant with increased NO production (411 ± 28 vs. 68 ± 10 pmol/mg protein in control). These actions were attenuated by AHG (NO production: 264 ± 18 pmol/mg protein). D-4F reduced superoxide generation and enhanced caveolin-1 and eNOS caveolar compartmentalization and posttranslational eNOS modifications, thus restoring NO production during isoflurane and AHG (418 ± 36 pmol/mg protein). In conclusion, D-4F restored the cardioprotective effect of APC during AHG, possibly by decreasing superoxide generation, which promoted isoflurane-induced eNOS signaling and NO biosynthesis.

The cardioprotective effects of urocortin are mediated via activation of the Src tyrosine kinase-STAT3 pathway

Src tyrosine kinase family was recently identified as a novel upstream modulator of MAP kinase subfamily, p42/p44, whose activation is required for urocortin (Ucn)-mediated cardioprotection. Src kinase was also shown to reduce apoptosis in different cancer cell lines, enhancing phosphorylation and DNA binding affinity of signal transducer and activator of transcription (STAT)3. In order to evaluate the effects of Ucn on the activation status of different STAT family members, HL-1 cardiac cells were incubated with Ucn (10 nM) for increasing periods of time. STAT3 was rapidly phosphorylated at Tyr705, while neither phosphorylation at Ser727 nor induction of total STAT3 was observed. Pretreatment with PP2, a selective inhibitor of Src tyrosine kinase, reduced the pSTAT^−T705 phosphorylation and transcriptional activity induced by Ucn in a dose-dependent manner. Overexpression of STAT3 in HL-1 cardiac myocytes pretreated with Ucn reduced the magnitude of cell death as compared with Ucn treatment alone, while transfection of HL-1 cells with a STAT3 mutant functionally inactive, acting as a dominant negative (DN-STAT3), enhanced the extent of cell death in a dose-dependent manner. In line with this finding, in HL-1 cardiac myocytes overexpressing STAT3 treated with Ucn, addition of the Src kinase inhibitor PP2 reversed the cytoprotective effects of Ucn, proving that the cytoprotective effects of Ucn are also mediated via the Src-pSTAT^−T705 phosphorylation pathway. By immunocytochemistry, Ucn induced nuclear translocation of pST3-T705, which was inhibited by pretreatment with PP2. Together, these data strongly suggest that Ucn can mediate cardioprotection by activating the Src-pSTAT-T705 phosphorylation pathway.

Mechanism(s) Involved in Carbon Monoxide-releasing Molecule-2-mediated Cardioprotection During Ischaemia-reperfusion Injury in Isolated Rat Heart

The purpose of the present study was to determine the mechanism(s) involved in carbon monoxide-releasing molecule-2, carbon monoxide-releasing molecule-2-induced cardioprotection. We used the transition metal carbonyl compound carbon monoxide-releasing molecule-2 that can act as carbon monoxide donor in cardiac ischaemia-reperfusion injury model using isolated rat heart preparation. Langendorff's perfused rat hearts when treated with carbon monoxide-releasing molecule-2 (50 μM) for 10 min before global ischaemia exhibited significant reduction in postischaemic levels of myocardial injury markers, creatine kinase and lactate dehydrogenase in coronary effluent. Similarly, pretreatment with carbon monoxide-releasing molecule-2 showed significantly improved postischaemic recovery of heart rate, coronary flow rate, cardiodynamic parameters and reduced infarct size as compared to vehicle control hearts. Perfusion with p38 mitogen-activated protein kinase inhibitor, SB203580, a specific inhibitor of α and β isoform, before and concomitantly with carbon monoxide-releasing molecule-2 treatment abolished carbon monoxide-releasing molecule-2-induced cardioprotection. However, p38 mitogen-activated protein kinase alpha inhibitor, SCIO-469, was unable to inhibit the cardioprotective effect of carbon monoxide-releasing molecule-2. Furthermore, protective effect of carbon monoxide-releasing molecule-2 was significantly inhibited by the protein kinase C inhibitor, chelerythrine, when added before and concomitantly with carbon monoxide-releasing molecule-2. It was also observed that, perfusion with phosphatidylinositol 3-kinase inhibitor, wortmannin, before and concomitantly with carbon monoxide-releasing molecule-2 was not able to inhibit carbon monoxide-releasing molecule-2-induced cardioprotection. Interestingly, we observed that wortmannin perfusion before ischaemia and continued till reperfusion significantly inhibited carbon monoxide-releasing molecule-2-mediated cardioprotection. Our findings suggest that the carbon monoxide-releasing molecule-2 treatment may activate the p38 mitogen-activated protein kinase β and protein kinase C pathways before ischaemia and phosphatidylinositol 3-kinase pathway during reperfusion which may be responsible for the carbon monoxide-releasing molecule-2-mediated cardioprotective effect.

Involvement of adenosine and standardization of aqueous extract of garlic (Allium sativum Linn.) on cardioprotective and cardiodepressant properties in ischemic preconditioning and myocardial ischemia-reperfusion induced cardiac injury

The present study investigated the effect of garlic (Allium sativum Linn.) aqueous extracts on ischemic preconditioning and ischemia-reperfusion induced cardiac injury, as well as adenosine involvement in ischemic preconditioning and garlic extract induced cardioprotection. A model of ischemia-reperfusion injury was established using Langendorff apparatus. Aqueous extract of garlic dose was standardized (0.5%, 0.4%, 0.3%, 0.2%, 0.1%, 0.07%, 0.05%, 0.03%, 0.01%), and the 0.05% dose was found to be the most effective. Higher doses (more than 0.05%) were highly toxic, causing arrhythmia and cardiodepression, whereas the lower doses were ineffective. Garlic exaggerated the cardioprotective effect of ischemic preconditioning. The cardioprotective effect of ischemic preconditioning and garlic cardioprotection was significantly attenuated by theophylline (1,000 µmol/L) and 8-SPT (10 mg/kg, i.p.) and expressed by increased myocardial infarct size, increased LDH level, and reduced nitrite and adenosine levels. These findings suggest that adenosine is involved in the pharmacological and molecular mechanism of garlic induced cardioprotection and mediated by the modulation of nitric oxide.

Exercise training prior to myocardial infarction attenuates cardiac deterioration and cardiomyocyte dysfunction in rats

OBJECTIVES

The present study was performed to investigate 1) whether aerobic exercise training prior to myocardial infarction would prevent cardiac dysfunction and structural deterioration and 2) whether the potential cardiac benefits of aerobic exercise training would be associated with preserved morphological and contractile properties of cardiomyocytes in post-infarct remodeled myocardium.

METHODS

Male Wistar rats underwent an aerobic exercise training protocol for eight weeks. The rats were then assigned to sham surgery (SHAM), sedentary lifestyle and myocardial infarction or exercise training and myocardial infarction groups and were evaluated 15 days after the surgery. Left ventricular tissue was analyzed histologically, and the contractile function of isolated myocytes was measured. Student's t-test was used to analyze infarct size and ventricular wall thickness, and the other parameters were analyzed by the Kruskal-Wallis test followed by Dunn's test or a one-way analysis of variance followed by Tukey's test (p<0.05).

RESULTS

Myocardial infarctions in exercise-trained animals resulted in a smaller myocardial infarction extension, a thicker infarcted wall and less collagen accumulation as compared to myocardial infarctions in sedentary animals. Myocardial infarction-induced left ventricular dilation and cardiac dysfunction, as evaluated by +dP/dt and -dP/dt, were both prevented by previous aerobic exercise training. Moreover, aerobic exercise training preserved cardiac myocyte shortening, improved the maximum shortening and relengthening velocities in infarcted hearts and enhanced responsiveness to calcium.

CONCLUSION

Previous aerobic exercise training attenuated the cardiac dysfunction and structural deterioration promoted by myocardial infarction, and such benefits were associated with preserved cardiomyocyte morphological and contractile properties.

A new calpain inhibitor protects left ventricular dysfunction induced by mild ischemia-reperfusion in in situ rat hearts

We have previously indicated that a new soluble calpain inhibitor, SNJ-1945 (SNJ), attenuates cardiac dysfunction after cardioplegia arrest-reperfusion by inhibiting the proteolysis of α-fodrin in in vitro study. Nevertheless, the in vivo study design is indispensable to explore realistic therapeutic approaches for clinical use. The aim of the present in situ study was to investigate whether SNJ attenuated left ventricular (LV) dysfunction (stunning) after mild ischemic-reperfusion (mI-R) in rat hearts. SNJ (60 μmol/l, 5 ml i.p.) was injected 30 min before gradual and partial coronary occlusion at proximal left anterior descending artery. To investigate LV function, we obtained curvilinear end-systolic pressure-volume relationship by increasing afterload 60 min after reperfusion. In the mI-R group, specific LV functional indices at midrange LV volume (mLVV), end-systolic pressure (ESP(mLVV)), and pressure-volume area (PVA(mLVV): a total mechanical energy per beat, linearly related to oxygen consumption) significantly decreased, but SNJ reversed these decreases to time control level. Furthermore, SNJ prevented the α-fodrin degradation and attenuated degradation of Ca(2+) handling proteins after mI-R. Our results indicate that improvements in LV function following mI-R injury are associated with inhibition of the proteolysis of α-fodrin in in situ rat hearts. In conclusion, SNJ should be a promising tool to protect the heart from the stunning.

Exogenous NAD(+) supplementation protects H9c2 cardiac myoblasts against hypoxia/reoxygenation injury via Sirt1-p53 pathway

Nicotinamide adenine dinucleotide (NAD(+) ) not only transfers electrons in mitochondrial respiration, but also acts as an indispensable cosubstrate for Sirt1, the class III histone/nonhistone deacetylase. However, NAD(+) is depleted in myocardial ischemia/reperfusion (IR) injury. The objective of this study was to investigate the role of exogenous NAD(+) supplementation in hypoxia/reoxygenation (HR)-stressed H9c2 cardiac myoblasts. Firstly, the effects of distinct treating time points and doses of NAD(+) supplementation on the viability of HR-stressed H9c2 cells were detected. Secondly, intracellular NAD(+) levels in HR-stressed H9c2 cells at various extracellular NAD(+) concentrations were determined. Thirdly, the role of NAD(+) supplementation in HR-induced cell apoptosis and its relevance to Sirtuin 1-p53 pathway were investigated. Exogenous NAD(+) supplementation elevated intracellular NAD(+) level and reduced HR-induced cell death in both time- and concentration-dependent manners. It appeared that NAD(+) supplementation exerted the greatest protection when extracellular concentration ranged from 500 to 1000 μm and when NAD(+) was added immediately after reoxygenation began. NAD(+) replenishment restored Sirt1 activity, reduced the acetylation level of p53 (Lys373 & 382), and attenuated cell apoptosis in HR-stressed H9c2 cells, whereas inhibition of Sirt1 activity alleviated the effects of NAD(+) replenishment. These results indicated that exogenous NAD(+) supplementation attenuated HR-induced cell apoptosis, which was at least partly mediated by restoring Sirt1 activity and subsequently inhibiting p53 activity via deacetylating p53 at lysine 373 and 382.

Activation of cGMP/protein kinase G pathway in postconditioned myocardium depends on reduced oxidative stress and preserved endothelial nitric oxide synthase coupling

BACKGROUND

The cGMP/protein kinase G (PKG) pathway is involved in the cardioprotective effects of postconditioning (PoCo). Although PKG signaling in PoCo has been proposed to depend on the activation of the phosphatidylinositol 3-kinase (PI3K)/Akt cascade, recent data bring into question a causal role of reperfusion injury signaling kinase (RISK) in PoCo protection. We hypothesized that PoCo increases PKG activity by reducing oxidative stress-induced endothelial nitric oxide synthase (NOS) uncoupling at the onset of reperfusion.

METHODS AND RESULTS

Isolated rat hearts were submitted to 40 minutes of ischemia and reperfusion with and without a PoCo protocol. PoCo reduced infarct size by 48% and cGMP depletion. Blockade of cGMP synthesis (1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one) and inhibition of PKG (KT5823) or NOS (l-NAME) abolished protection, but inhibition of PI3K/Akt cascade (LY294002) did not (n=5 to 7 per group). Phosphorylation of the RISK pathway was higher in PoCo hearts. However, this difference is due to increased cell death in control hearts because in hearts reperfused with the contractile inhibitor blebbistatin, a drug effective in preventing cell death at the onset of reperfusion, RISK phosphorylation increased during reperfusion without differences between control and PoCo groups. In these hearts, PoCo reduced the production of superoxide (O2(-)) and protein nitrotyrosylation and increased nitrate/nitrite levels in parallel with a significant decrease in the oxidation of tetrahydrobiopterin (BH4) and in the monomeric form of endothelial NOS.

CONCLUSIONS

These results demonstrate that PoCo activates the cGMP/PKG pathway via a mechanism independent of the PI3K/Akt cascade and dependent on the reduction of O2(-) production at the onset of reperfusion, resulting in attenuated oxidation of BH4 and reduced NOS uncoupling.

The pathobiology of acute coronary syndromes: clinical implications and central role of the mitochondria

Ongoing investigation has provided new insights into the pathobiology of myocardial ischemic injury. These include an improved understanding of the roles of the major modes of cell injury and death, including oncosis, apoptosis, and unregulated autophagy, as well as the central role of the mitochondria in the progression of myocardial ischemic injury, reperfusion injury, and myocardial conditioning. This understanding is providing insights for developing new pathophysiologic, pharmacologic, and cell-based therapies, alone or in combination with percutaneous coronary interventions, for better preservation of myocardium and reduction of morbidity and mortality rates from ischemic heart disease.

G-protein-coupled receptor 30 interacts with receptor activity-modifying protein 3 and confers sex-dependent cardioprotection

Receptor activity-modifying protein 3 (RAMP3) is a single-pass transmembrane protein known to interact with and affect the trafficking of several G-protein-coupled receptors (GPCRs). We sought to determine whether RAMP3 interacts with GPR30, also known as G-protein-coupled estrogen receptor 1. GPR30 is a GPCR that binds estradiol and has important roles in cardiovascular and endocrine physiology. Using bioluminescence resonance energy transfer titration studies, co-immunoprecipitation, and confocal microscopy, we show that GPR30 and RAMP3 interact. Furthermore, the presence of GPR30 leads to increased expression of RAMP3 at the plasma membrane in HEK293 cells. In vivo, there are marked sex differences in the subcellular localization of GPR30 in cardiac cells, and the hearts of Ramp3(-/-) mice also show signs of GPR30 mislocalization. To determine whether this interaction might play a role in cardiovascular disease, we treated Ramp3(+)(/)(+) and Ramp3(-/-) mice on a heart disease-prone genetic background with G-1, a specific agonist for GPR30. Importantly, this in vivo activation of GPR30 resulted in a significant reduction in cardiac hypertrophy and perivascular fibrosis that is both RAMP3 and sex dependent. Our results demonstrate that GPR30-RAMP3 interaction has functional consequences on the localization of these proteins both in vitro and in vivo and that RAMP3 is required for GPR30-mediated cardioprotection.

Metformin: Midlife maturity, maiden charm

Metformin is one of the most commonly prescribed drugs for management of Type 2 diabetes mellitus. It has been in use for almost five decades. Now, pharmacological properties of this agent are being exapted for use in a number of other indications. New facets of its personality are coming up, generating more interest of the scientific community in this "middle-aged" molecule. This article explores the role of metformin in cardioprotection and its hepatoprotective properties. Nephroprotective, protection against excess body fat and gonadoprotective actions, properties have also been discussed. Additionally, this manuscript briefly reviews the thyroid stimulating hormone (TSH)-lowering properties in diabetic and non-diabetic patients, besides reviewing its actions on different types of cancers. Some of these actions may become approved indications for use of metformin following generation of new evidence. Metformin still has many unexplored dimensions that deserve further exploration.

Activated protein C modulates cardiac metabolism and augments autophagy in the ischemic heart

BACKGROUND

Modulation of energy substrate metabolism may constitute a novel therapeutic intervention against ischemia/reperfusion (I/R) injury. AMP-activated protein kinase (AMPK) has emerged as a key regulator of favorable metabolic signaling pathways in response to myocardial ischemia. Recently, we demonstrated that activated protein C (APC) is cardioprotective against ischemia/reperfusion (I/R) injury by augmenting AMPK signaling.

OBJECTIVES

The objective of this study was to determine whether the APC modulation of substrate metabolism contributes to its cardioprotective effect against I/R injury.

METHODS

An ex vivo working mouse heart perfusion system was used to characterize the effect of wild-type APC and its signaling-proficient mutant, APC-2Cys (which has dramatically reduced anticoagulant activity), on glucose transport in the ischemic heart.

RESULTS

Both APC and APC-2Cys (0.2 μg g(-1)) augment the ischemic stress-induced translocation of the glucose transporter (GLUT4) to the myocardial cell membrane, leading to increased glucose uptake and glucose oxidation in the ischemic heart (P < 0.05 vs. vehicle). Both APC derivatives increased the autophagic flux in the heart following I/R. The activity of APC-2Cys in modulating these metabolic pathways was significantly higher than APC during I/R (P < 0.05). Intriguingly, APC-2Cys, but not wild-type APC, attenuated the I/R-initiated fatty acid oxidation by 80% (P < 0.01 vs. vehicle).

CONCLUSIONS

APC exerts a cardioprotective effect against I/R injury by preferentially enhancing the oxidation of glucose over fatty acids as energy substrates in the ischemic heart. Given its significantly higher beneficial metabolic modulatory effect, APC-2Cys may be developed as a potential therapeutic drug for treating ischemic heart disease without risk of bleeding.

Caveolin as a potential drug target for cardiovascular protection

Caveolae and caveolin are key players in a number of disease processes. Current research indicates that caveolins play a significant role in cardiovascular disease and dysfunction. The far-reaching roles of caveolins in disease and dysfunction make them particularly notable therapeutic targets. In particular, caveolin-1 (Cav-1) and caveolin-3 (Cav-3) have been identified as potential regulators of vascular dysfunction and heart disease and might even confer cardiac protection in certain settings. Such a central role in vascular health therefore makes manipulation of Cav-1/3 function or expression levels clear therapeutic targets in a variety of cardiovascular related disease states. Here, we highlight the role of Cav-1 and Cav-3 in cardiovascular health and explore the potential of Cav-1 and Cav-3 derived experimental therapeutics.

Mitochondrial K+ channels are involved in ischemic postconditioning in rat hearts

The mitochondrial calcium-activated potassium channel (mitoK(Ca)) and the mitochondrial ATP-sensitive potassium channel (mitoK(ATP)) are both involved in cardiac preconditioning. Here, we examined whether these two channels are also involved in ischemic or pharmacological postconditioning. Using Langendorff perfusion, rat hearts were made hypoxic for 45 min and then reoxygenated for 30 min. Ischemic postconditioning (IPT) was achieved through application of 3 cycles of 10 s of reperfusion and 10 s of ischemia before reoxygenation, with and without paxilline (Pax; a mitoK(Ca) blocker) or 5-hydroxydecanoate (5-HD; a mitoK(ATP) blocker). Pharmacological postconditioning was carried out for 5 min at the onset of reoxygenation using NS1619 (a mitoK(Ca) opener) or diazoxide (Dia; a mitoK(ATP) opener). Pax and 5-HD abolished IPT-induced cardioprotection from reoxygenation injury, whereas administration of NS1619 or Dia significantly improved cardiac contractile activity and reduced aspartate aminotransferase (an index of myocyte injury) release following reoxygenation. In addition, isolated rat myocytes were loaded with tetramethylrhodamine methyl ester (TMRE; fluorescent mitochondrial membrane potential indicator) and 2',7'-dichlorofluorescein [DCFH; fluorescent reactive oxygen species (ROS) indicator] or Fluo-4-acetoxymethyl ester (Fluo-4-AM; fluorescent calcium indicator). When TMRE-loaded myocytes were laser illuminated, the DCFH and Fluo-4 fluorescence increased, and TMRE fluorescence decreased. These effects were significantly inhibited by NS1619 and Dia. We therefore conclude that IPT may protect the heart through activation of mitoK(ATP) and mitoK(Ca) channels, and that opening of these channels at the onset of reoxygenation protects the heart from reoxygenation injury, most likely by reducing excess generation of ROS and the resultant Ca(2+) overload.

Reduction of ischemia/reperfusion injury with bendavia, a mitochondria-targeting cytoprotective Peptide

Background

Manifestations of reperfusion injury include myocyte death leading to infarction, contractile dysfunction, and vascular injury characterized by the “no-reflow” phenomenon. Mitochondria-produced reactive oxygen species are believed to be centrally involved in each of these aspects of reperfusion injury, although currently no therapies reduce reperfusion injury by targeting mitochondria specifically.

Methods and Results

We investigated the cardioprotective effects of a mitochondria-targeted peptide, Bendavia (Stealth Peptides), across a spectrum of experimental cardiac ischemia/reperfusion models. Postischemic administration of Bendavia reduced infarct size in an in vivo sheep model by 15% (P=0.02) and in an ex vivo guinea pig model by 38% to 42% (P<0.05). In an in vivo rabbit model, the extent of coronary no-reflow was assessed with Thioflavin S staining and was significantly smaller in the Bendavia group for any given ischemic risk area than in the control group (P=0.0085). Myocardial uptake of Bendavia was ≈25% per minute, and uptake remained consistent throughout reperfusion. Postischemic recovery of cardiac hemodynamics was not influenced by Bendavia in any of the models studied. Isolated myocytes exposed to hypoxia/reoxygenation showed improved survival when treated with Bendavia. This protection appeared to be mediated by lowered reactive oxygen species–mediated cell death during reoxygenation, associated with sustainment of mitochondrial membrane potential in Bendavia-treated myocytes.

Conclusions

Postischemic administration of Bendavia protected against reperfusion injury in several distinct models of injury. These data suggest that Bendavia is a mitochondria-targeted therapy that reduces reperfusion injury by maintaining mitochondrial energetics and suppressing cellular reactive oxygen species levels. (J Am Heart Assoc. 2012;1:e001644 doi: 10.1161/JAHA.112.001644.)