Exosomal HSP90 induced by remote ischemic preconditioning alleviates myocardial ischemia/reperfusion injury by inhibiting complement activation and inflammation.

BACKGROUND/AIMS: The activation of the complement system and subsequent inflammatory responses are important features of myocardial ischemia/reperfusion (I/R) injury. Exosomes are nanoscale extracellular vesicles that play a significant role in remote ischemic preconditioning (RIPC) cardioprotection. The present study aimed to test whether RIPC-induced plasma exosomes (RIPC-Exo) exert protective effects on myocardial I/R injury by inhibiting complement activation and inflammation and whether exosomal heat shock protein 90 (HSP90) mediates these effects. METHODS: Rat hearts underwent 30 min of coronary ligation followed by 2 h of reperfusion. Plasma exosomes were isolated from RIPC rats and injected into the infarcted myocardium immediately after ligation. Sixty rats were randomly divided into Sham, I/R, I/R + RIPC-Exo (50 µg/µl), and RIPC-Exo + GA (geldanamycin, 1 mg/kg, administration 30 min before ligation) groups. Cardiomyocyte apoptosis, the release of myocardial markers (LDH, cTnI and CK-MB), infarct size, the expression of HSP90, complement component (C)3, C5a, c-Jun N-terminal kinase (JNK), interleukin (IL)-1ß, tumor necrosis factor (TNF)-alpha and intercellular adhesion molecule -1 (ICAM-1) were assessed. RESULTS: RIPC-Exo treatment significantly reduced I/R-induced cardiomyocyte apoptosis, the release of myocardial markers (LDH, cTnI and CK-MB) and infarct size. These beneficial effects were accompanied by decreased C3 and C5a expression, decreased inflammatory factor levels (IL-1ß, TNF-α, and ICAM-1), decreased JNK and Bax, and increased Bcl-2 expression. Meanwhile, the expression of HSP90 in the exosomes from rat plasma increased significantly after RIPC. However, treatment with HSP90 inhibitor GA significantly reversed the cardioprotection of RIPC-Exo, as well as activated complement component, JNK signalling and inflammation, indicating that HSP90 in exosomes isolated from the RIPC was important in mediating the cardioprotective effects during I/R. CONCLUSION: Exosomal HSP90 induced by RIPC played a significant role in cardioprotection against I/R injury, and its function was in part linked to the inhibition of the complement system, JNK signalling and local and systemic inflammation, ultimately alleviating I/R-induced myocardial injury and apoptosis by the upregulation of Bcl-2 expression and the downregulation of proapoptotic Bax.

Retraction Note: Resveratrol rescues hyperglycemia-induced endothelial dysfunction via activation of Akt.

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

Novel Functional Role of Heat Shock Protein 90 in Mitochondrial Connexin 43-Mediated Hypoxic Postconditioning.

BACKGROUND/AIMS: Previous studies have shown that heat shock protein 90 (HSP90)-mediated mitochondrial import of connexin 43 (Cx43) is critical in preconditioning cardioprotection. The present study was designed to test whether postconditioning has the same effect as preconditioning in promoting Cx43 translocation to mitochondria and whether mitochondrial HSP90 modulates this effect. METHODS: Cellular models of hypoxic postconditioning (HPC) from rat heart-derived H9c2 cells and neonatal rat cardiomyocytes were employed. The effects of HPC on cardiomyocytes apoptosis were examined by flow cytometry and Hoechst 33342 fluorescent staining. Reactive oxidative species (ROS) production was assessed with the peroxide-sensitive fluorescent probe 2',7'-dichlorofluorescin in diacetate (DCFH-DA). The anti- and pro-apoptotic markers Bcl-2 and Bax, HSP90 and Cx43 protein levels were studied by Western blot analysis in total cell homogenate and sarcolemmal and mitochondrial fractions. The effects on HPC of the HSP90 inhibitor geldanamycin (GA), ROS scavengers superoxide dismutase (SOD) and catalase (CAT), and small interfering RNA (siRNA) targeting Cx43 and HSP90 were also investigated. RESULTS: HPC significantly reduced hypoxia/reoxygenation (H/R)-induced cardiomyocyte apoptosis. These beneficial effects were accompanied by an increase in Bcl-2 levels and a decrease in Bax levels in both sarcolemmal and mitochondrial fractions. HPC with siRNA targeting Cx43 or the ROS scavengers SOD plus CAT significantly prevented ROS generation and HPC cardioprotection, but HPC with either SOD or CAT did not. These data strongly supported the involvement of Cx43 in HPC cardioprotection, likely via modulation of the ROS balance which plays a central role in HPC protection. Furthermore, HPC increased total and mitochondrial levels of HSP90 and the mitochondria-to-sarcolemma ratio of Cx43; blocking the function of HSP90 with the HSP90 inhibitor geldanamycin (GA) or siRNA targeting HSP90 prevented the protection of HPC and the HPC-induced association of Cx43, indicating that mitochondrial HSP90 was important for mitochondrial translocation of Cx43 during HPC. CONCLUSION: Mitochondrial HSP90 played a central role in HPC cardioprotection, and its activity was linked to the mitochondrial targeting of Cx43, the activation of which triggered ROS signaling and the subsequent reduction of redox stress. Consequently, its target gene, Bcl-2, was upregulated, and proapoptotic Bax was inhibited in the sarcolemma and mitochondria, ultimately attenuating H/R-induced cardiomyocyte apoptosis. These data reveal a novel mechanism of HPC protection.

Resveratrol rescues hyperglycemia-induced endothelial dysfunction via activation of Akt.

Resveratrol (RSV), a phytoalexin, has shown to prevent endothelial dysfunction and reduce diabetic vascular complications and the risk of cardiovascular diseases. The aim of this study was to investigate the signaling mechanisms underlying the protecting effects of RSV against endothelial dysfunction during hyperglycemia in vitro and in vivo. Human umbilical vein endothelial cells (HUVECs) were treated with RSV, and then exposed to high glucose (HG, 30 mmol/L). Akt-Ser473 phosphorylation, eNOS-Ser1177 phosphorylation, and PTEN protein levels in the cells were detected using Western blot. For in vivo studies, WT and Akt-/- mice were fed a normal diet containing RSV (400 mg·kg-1·d-1) for 2 weeks, then followed by injection of STZ to induce hyperglycemia (300 mg/dL). Endothelial function was evaluated using aortic rings by assessing ACh-induced vasorelaxation. RSV (5-20 µmol/L) dose-dependently increased Akt-Ser473 phosphorylation, accompanied by increased eNOS-Ser1177 phosphorylation in HUVECs; these effects were more prominent under HG stimulation. Transfection with Akt siRNA abolished RSV-enhanced eNOS phosphorylation and NO release. Furthermore, RSV (5-20 µmol/L) dose-dependently decreased the levels of PTEN, which was significantly increased under HG stimulation, and PTEN overexpression abolished RSV-stimulated Akt phosphorylation in HG-treated HUVECs. Moreover, RSV dramatically increased 26S proteasome activity, which induced degradation of PTEN. In in vivo studies, pretreatment with RSV significantly increased Akt and eNOS phosphorylation in aortic tissues and ACh-induced vasorelaxation, and improved diabetes-induced endothelial dysfunction in wild-type mice but not in Akt-/- mice. RSV attenuates endothelial function during hyperglycemia via activating proteasome-dependent degradation of PTEN, which increases Akt phosphorylation, and consequentially upregulation of eNOS-derived NO production.

Comparison of Empiric Isolation and Conventional Isolation of Superior Vena Cava in Addition to Pulmonary Vein Isolation on the Outcome of Paroxysmal Atrial Fibrillation Ablation.

Radiofrequency catheter ablation (RFCA) in the treatment of AF is currently based on pulmonary vein isolation (PVI). Some studies have investigated the efficacy of empiric SVC isolation (SVCI) in addition to conventional PVI in order to improve success rates and reduce recurrence rates. However, the results of the studies have given conflicting data.We performed a meta-analysis to evaluate the efficacy and safety of the empiric SVCI compared with conventional SVCI for paroxysmal atrial fibrillation (PAF) ablation.We searched MEDLINE, EMBASE, the Web of Science, and the Cochrane Database from the period January 1986 to August 2016 and identified qualified studies. The primary clinical outcome was the recurrence rate of atrial tachyarrhythmias, and the secondary clinical outcomes were procedure time, fluoroscopy time, and complications.We identified 3 randomized controlled trials (RCTs) and one nonrandomized, observational study (nROS) involving 245 patients with empiric SVCI and 269 patients with conventional SVCI. The empiric SVCI group had a lower recurrence rate of atrial tachyarrhythmia after a single procedure compared with the conventional SVCI group (16.7% versus 29.4%, OR: 0.48, 95%CI: 0.31 to 0.74, P = 0.0009). There was no significant difference in fluoroscopic time (P = 0.22), procedure time (P = 0.32), or clinical complications (P = 0.33) between the two groups.Empiric SVCI is more effective than conventional SVCI in terms of the long-term outcomes of PAF patients after a single PVI procedure, with the same fluoroscopic time, procedure time, and clinical complications.

Novel functional role of heat shock protein 90 in protein kinase C-mediated ischemic postconditioning.

BACKGROUND: Previous studies have shown that heat shock protein 90 (HSP90) plays a vital role in ischemic preconditioning. The present study was designed to explore whether HSP90 might be responsible for cardioprotection in ischemic postconditioning (PostC). MATERIALS AND METHODS: Rat hearts underwent 30 min of regional ischemia and 2 h of reperfusion in situ, and PostC was effected with three cycles of 30-s reperfusion and 30-s coronary artery occlusion at the end of ischemia. Ninety rats were randomized into five groups: sham; ischemia-reperfusion (I/R); PostC; 1 mg/kg HSP90 inhibitor geldanamycin (GA) plus PostC (PostC + GA1); and 5 mg/kg GA plus PostC (PostC + GA5). The GA was administered 10 min before reperfusion. RESULTS: Compared with the I/R group, the PostC group exhibited lower infarct size (46.7 ± 3.0% versus 27.4 ± 4.0%, respectively), release of lactate dehydrogenase and creatine kinase-MB (2252.6 ± 350.8 versus 1713.7 ± 202.4 IU/L, 2804.3 ± 315.7 versus 1846.2 ± 238.0 IU/L, respectively), cardiomyocyte apoptosis (48.4 ± 5.6% versus 27.6 ± 3.8%, respectively), and mitochondrial damage. These beneficial effects were accompanied by an increase in mitochondrial Bcl-2 levels and a decrease in Bax levels. In addition, mitochondrial protein kinase Cepsilon (PKCepsilon) was relatively low in the I/R group but significantly higher in the PostC group, whereas cytosolic PKCepsilon was relatively high in the I/R group but significantly lower in the PostC group, suggesting the translocation of PKCepsilon from cytosol to mitochondria during PostC. However, blocking HSP90 function with GA inhibited the protection of PostC and PKCepsilon mitochondrial translocation. CONCLUSIONS: HSP90 is critical in PostC-induced cardioprotection, and its activity might be linked to mitochondrial targeting of PKCepsilon, the activation of which results in upregulation of its target gene, Bcl-2, and the inhibition of proapoptotic Bax in mitochondria.

[A systematic review and meta-analysis on efficacy and safety of cardiac resynchronization therapy alone or in combination with implantable cardioversion defibrillation in patients with mild to severe heart failure].

OBJECTIVE: To evaluate the efficacy and safety of cardiac resynchronization therapy (CRT) alone or in combination with implantable cardioversion defibrillation (ICD) in patients with mild to severe heart failure. METHOD: Electronic searches of MEDLINE, EMBASE, CENTREN and affiliated clinical trial registration data center, US Food and Drug Administration reports, CBMdisc, VIP, and CNKI databases from establishment to Dec 2010, using the search terms "CRT, heart failure", "biventricular pacer, heart failure", "biventricular pacing, heart failure", and "biventricular pacemaker, heart failure", were performed to identify randomized controlled trials (RCTs). Meta-analysis was performed by using RevMan 5.0 software after the strict evaluation of the methodological quality of the included RCTs. RESULTS: A total of 23 trials including 8521 patients were included. In patients with New York Heart Association (NYHA) class I/II, CRT improved left ventricular ejection fraction (LVEF) [weighted mean difference (WMD) = 0.05, 95% CI 0.01 - 0.08], reduced heart failure hospitalizations [risk ratio (RR) = 0.70, 95%CI 0.61 - 0.81] and all-cause mortality (RR = 0.78, 95%CI 0.65 - 0.93) with increasing complications (RR = 1.74, 95%CI 1.42 - 2.13). In patients with NYHA class III/IV, CRT improved LVEF (WMD = 0.03, 95%CI 0.01 - 0.05), reduced both heart failure hospitalizations (RR = 0.64, 95%CI 0.55 - 0.73) and all-cause mortality (RR = 0.80, 95%CI 0.70 - 0.91) without increasing complications (RR = 1.01, 95%CI 0.91 - 1.12). Compared with ICD alone, CRT in combination with ICD significantly improved LVEF (WMD = 0.03, 95%CI 0.00 - 0.06), reduced heart failure hospitalizations (RR = 0.73, 95%CI 0.64 - 0.82) and all-cause mortality (RR = 0.82, 95%CI 0.72 - 0.95) without increasing complications (RR = 1.36, 95%CI 0.91 - 2.03) in patients with NYHA class I-IV symptoms. CONCLUSIONS: CRT offered additional benefits on top of standard medication for heart failure patients with ventricular dyssynchrony in terms of improving LV function, and reducing heart failure hospitalization and all-cause mortality, regardless of NYHA class. CRT offers also additional benefit in heart failure patients implanted with ICD. However, CRT is associated with more adverse events in patients with NYHA class I/II.

Microvesicles with mitochondrial content are increased in patients with sepsis and associated with inflammatory responses.

BACKGROUND: Endothelial activation plays an important role in sepsis-mediated inflammation, but the triggering factors have not been fully elucidated. Microvesicles carrying mitochondrial content (mitoMVs) have been implicated in several diseases and shown to induce endothelial activation. AIM: To explore whether mitoMVs constitute a subset of MVs isolated from plasma of patients with sepsis and contribute to endothelial activation. METHODS: MVs were isolated from human plasma and characterized by confocal microscopy and flow cytometry. Proinflammatory cytokines, including interleukin (IL)-6, IL-8 and tumour necrosis factor (TNF)-α, and soluble vascular cell adhesion molecule (sVCAM)-1 were detected by ELISA. Human umbilical vein endothelial cells (HUVECs) were stimulated with the circulating MVs to evaluate their effect on endothelial activation. RESULTS: MitoMVs were observed in plasma from patients with sepsis. Compared with those in healthy controls, expression of MVs, mitoMVs, proinflammatory cytokines and sVCAM-1 was increased. The number of mitoMVs was positively associated with TNF-α and sVCAM-1. In vitro, compared with MVs isolated from the plasma of healthy controls, MVs isolated from the plasma of patients with sepsis induced expression of OAS2, RSAD2, and CXCL10 in HUVECs. MitoMVs were taken up by HUVECs, and sonication of MVs significantly reduced the uptake of mitoMVs by HUVECs and expression of the above three type I IFN-dependent genes. CONCLUSION: MitoMVs are increased in the plasma of patients with sepsis, which induces elevated expression of type I IFN-dependent genes. This suggests that circulating mitoMVs activate the type I IFN signalling pathway in endothelial cells and lead to endothelial activation.

Dilator method and needle method for atrial transseptal puncture: a retrospective study from a cohort of 4443 patients.

AIMS: To compare the safety and efficacy of a new dilator method vs the traditional needle method for transseptal puncture (TSP) in a large cohort study. METHODS AND RESULTS: From February 1995 to December 2010, 4443 consecutive patients undergoing TSP done either by a needle method or by a new dilator method were reviewed retrospectively. Data as procedure-related time and complications were evaluated. For the standard needle method, TSP was performed by extending out the needle. In comparison, for the new dilator technique, TSP was performed without an outer sheath and with the needle kept within the dilator; the blunt tip of the dilator was used to help locating the position of the fossa ovalis on purpose. Transseptal puncture was performed by the new dilator method in 2151 patients (48.4%) and by the traditional needle method in 2292 patients (51.6%). The average TSP time needed by the dilator method was longer than that needed by the needle method (5.6 ± 3.9 vs. 3.8 ± 2.9 min, P< 0.05). Additional left atrial angiography was required in seven (0.33%) patients for the dilator and in 39 patients (1.70%) for the needle method (P< 0.05). The total rate of severe complications and obvious TSP-related complications was significantly lower in patients who underwent the dilator method than in those who underwent the needle method (0.33 vs. 1.18%, and 0.20 vs. 1.00%, respectively, P < 0.05). CONCLUSION: Our data suggest that the new dilator technique is much safer than that of the standard needle method. It needs relatively longer procedure time but results in significantly fewer episodes of severe complications. Particularly, the blunt tip of the dilator can be used to help locate the fossa ovalis. Therefore, the new dilator technique might be a better choice for relatively less-experienced operators.

[The effect of mitochondrial oxidative stress and the expression of Bcl-2 and Bax proteins on cardiomyocyte apoptosis during hypoxia postconditioning].

OBJECTIVE: To investigate mitochondrial oxidative stress on cardiomyocyte apoptosis and the expression of Bcl-2 and Bax proteins in cardiac sarcolemma and mitochondria after application of hypoxia postconditioning and free radical scavengers. METHODS: Primary cultured neonatal rat cardiomyocytes were exposed to 3 h hypoxia (H) followed by (1) 6 h of reoxygenation (R) (H/R), (2) 3 intermittent cycles of 5 min H and R before 6 h of R (PC), (3) application of superoxide dismutase (SOD) before PC (SOD+PC), (4) application of catalase (CAT) before PC (CAT+PC), and (5) application of SOD plus CAT before PC (SOD+CAT+PC). Cardiac sarcolemma and mitochondria were isolated by differential centrifugation. Mitochondrial reactive oxygen species (ROS) was detected with fluorescent probes (DCFH-DA) and cardiomyocyte apoptosis was detected with flow cytometry. The expressions of Bcl-2 and Bax proteins in cardiac sarcolemma and mitochondria were measured by Western blot. RESULTS: Mitochondrial ROS reduced significantly in PC, SOD+PC, CAT+PC and especially in SOD+CAT+PC groups (all P<0.01). The number of apoptotic cardiomyocytes reduced significantly in PC, SOD+PC and CAT+PC (all P<0.01) but not in SOD+CAT+PC groups. Bcl-2 levels increased while Bax levels decreased in cardiac sarcolemma and mitochondria in PC, SOD+PC and CAT+PC groups (all P<0.01), Bcl-2 levels decreased and Bax levels increased in H/R and PC+SOD+CAT groups (all P<0.01). CONCLUSIONS: PC attenuated H/R induced ROS and cardiomyocyte apoptosis, which might be mediated by upregulating the expression of Bcl-2 and downregulating the Bax in mitochondria and sarcolemma; SOD or CAT alone did not but SOD plus CAT attenuate the anti-apoptotic effect of hypoxia postconditioning; mitochondrial ROS thus plays an important role in PC's cardioprotection.

Hypertrophic Obstructive Cardiomyopathy with SAM Phenomenon: A Case Report and Literature Review.

Background: Hypertrophic cardiomyopathy (HCM) is defined by the presence of left ventricular hypertrophy (LVH) in the absence of other potentially causative cardiac, systemic, syndromic, or metabolic diseases [1]. It is the most common genetic abnormality of the myocardium, with an anaesthetized prevalence ranging from 1:500 to as high as 1:200 [2-4]. It is the primary cause of sudden cardiac death (SCD) among teenagers and athletes. Patient: A 56-year-old man presented with chest tightness and palpitations which had been occurring post-activity for the previous 6 months. The patient was advised to be admitted. He underwent echocardiography, cardiac magnetic resonance (CMR), coronary angiography (CAG) examination, and left ventriculography. He was diagnosed with hypertrophic obstructive cardiomyopathy (HOCM) with systolic anterior motion (SAM) phenomenon. Results: Echocardiography results showed that the interventricular septal thickness was 14-16 mm and that there were 2 degrees of SAM of the mitral valve. This resulted in severe stenosis of the left ventricular outflow tract (LVOT) and moderate to severe mitral insufficiency. Left ventriculography confirmed mitral regurgitation (MR) associated with HOCM with SAM phenomenon. Under the protection of a permanent pacemaker, the patient was treated with alcohol septal ablation (ASA). After discharge, the symptoms of chest tightness and palpitation did not recur. Conclusion: Beneficial effects were observed when patients with HOCM and SAM were treated with ASA under the condition of a permanent pacemaker.

HSP90-Mediates Liraglutide Preconditioning-Induced Cardioprotection by Inhibiting C5a and NF-κB.

OBJECTIVE: We previously showed that HSP90 is involved in postconditioning cardioprotection by inhibiting complement C5a. Here, we investigated whether HSP90-mediated C5a/NF-κB inhibition is responsible for the cardioprotection conferred by liraglutide. METHODS: Rat hearts underwent a 30 min occlusion of the anterior descending coronary artery, after which reperfusion was performed for 2 h. A total of 100 rats were randomly assigned to the following groups: ischemia/reperfusion (I/R), sham, liraglutide preconditioning (LP, liraglutide, 0.18 mg/kg, intravenously, 12 h before ischemia), HSP90 inhibitor geldanamycin (GA, 1 mg/kg, intraperitoneally, 30 min before ischemia) plus LP, and C5a receptor antagonist PMX53 (1 mg/kg, intravenously, 30 min before ischemia) plus LP. Cardiac injury, C5a/NF-κB activation, and inflammation were investigated. RESULTS: LP significantly attenuated I/R-induced cardiomyocyte apoptosis, infarct size, and secretion of creatine kinase-MB, lactate dehydrogenase and cardiac troponin I. These effects were complemented by decreased C5a levels, nuclear factor (NF)-κB signaling, inflammatory cytokine expression, and increased HSP90 levels. GA, an HSP90 inhibitor, promotes C5a activation, NF-κB signaling, and inflammation and suppresses cardioprotection by LP. By contrast, PMX53, a C5a inhibitor, suppressed C5a activation, NF-κB signaling, and inflammation, and enhanced cardioprotection by LP. CONCLUSION: HSP90 markedly contributes to LP cardioprotection by inhibiting inflammatory responsesand C5a/NF-κB signaling , ultimately attenuating I/R-induced cardiomyocyte apoptosis by suppressing the proapoptotic factor Bax, and inducing the anti-apoptotic factor Bcl2.

[A meta-analysis on efficacy of anti-platelet agents and anticoagulants for preventing stroke in patients with nonvalvular atrial fibrillation].

OBJECTIVE: To evaluate the efficacy and security of anti-platelet and anticoagulant therapy on prevention of ischemic stroke in patients with nonvalvular atrial fibrillation (NAF). METHODS: We searched PubMed, EMbase, CENTREN and its affiliated clinical trial registration data center, CBMdisc, VIP, and CNKI databases from establishment to Dec 2009 to identify randomized controlled trials (RCTs) covering the use of anti-platelet agents and anticoagulants for patients with NAF. Meta-analysis was performed by using RevMan 5.0 software after the strict evaluation of the methodological quality of the included RCTs. RESULTS: Fourteen RCTs involving 15 880 patients were include. Compared with placebo or no use of anti-platelet drugs, antiplatelet therapy didn't reduce ischemic stroke (RR = 0.83, 95%CI 0.68 to 1.00, P = 0.05), systemic emboli (RR = 0.71, 95%CI 0.34 to 1.51, P = 0.38) and all-cause mortality (RR = 0.88, 95%CI 0.73 to 1.07, P = 0.21) while significantly increased the major bleeding (RR = 2.88, 95%CI 1.21 to 6.86, P = 0.02) in patients with NAF, intracranial hemorrhage was not affected by antiplatelet therapy in patients with atrial fibrillation (RR = 3.25, 95%CI 0.84 to 12.62, P = 0.09). Compared with anti-platelet therapy, anticoagulant therapy significantly reduced the incidence of ischemic stroke (RR = 1.84, 95%CI 1.48 to 2.28, P < 0.01) and systemic emboli (RR = 1.94, 95%CI 1.24 to 3.03, P = 0.004) but significantly increased the incidence of intracranial hemorrhage (RR = 0.49, 95%CI 0.31 to 0.78, P = 0.003), did not affect all-cause mortality (RR = 1.06, 95%CI 0.90 to 1.23, P = 0.50) and the incidence of major bleeding (RR = 0.95, 95%CI 0.76 to 1.19, P = 0.66) in NAF patients. CONCLUSIONS: Compared with the placebo and no use of anti-platelet drugs, anti-platelet therapy didn't reduce ischemic stroke and systemic emboli but increased the risk of major bleeding in NAF patients. Compared with anti-platelet therapy, anticoagulant therapy significantly reduced the ischemic stroke and systemic emboli without increasing the risk of major bleeding, but significantly increased the incidence of intracranial hemorrhage in NAF patients. Since the study included RCTs with limited and less uniform outcome endpoints, the conclusions should be verified with RCTs with more uniform endpoints and longer follow-up time.

New targets of morphine postconditioning protection of the myocardium in ischemia/reperfusion injury: Involvement of HSP90/Akt and C5a/NF-κB.

BACKGROUND: Activation of the complement component 5a (C5a) and nuclear factor κB (NF-κB) signaling is an important feature of myocardial ischemia/reperfusion (I/R) injury and recent studies show that morphine postconditioning (MP) attenuates the myocardial injury. However, the mediating cardioprotective mechanisms remain unclear. The present study explores the role and interaction of heat shock protein 90 (HSP90), Akt, C5a, and NF-κB in MP-induced cardioprotection. METHODS: Male Sprague Dawley rats (n = 160) were randomized into eight groups (n = 20 per group). Rats in the sham group underwent thoracotomy, passing the ligature through the heart but without tying it (150 min), and the other seven groups were subjected to 30 min of anterior descending coronary artery occlusion followed by 2 h of reperfusion and the following treatments: I/R (30 min of ischemia and followed by 2 h of reperfusion); ischemic postconditioning (IPostC, 30 s of ischemia altered with 30 s of reperfusion, repeated for three cycles, and followed by reperfusion for 2 h); MP (0.3 mg/kg morphine administration 10 min before reperfusion); MP combined with the HSP90 inhibitor geldanamycin (GA, 1 mg/kg); MP combined with the Akt inhibitor GSK-690693 (GSK, 20 mg/kg); and MP combined with the C5a inhibitor PMX205 (PMX, 1 mg/kg/day, administration via drinking water for 28 days) and MP combined with the NF-κB inhibitor EVP4593 (QNZ, 1 mg/kg). All inhibitors were administered 10 min before morphine and followed by 2 h reperfusion. RESULTS: MP significantly reduced the I/R-induced infarct size, the apoptosis, and the release of cardiac troponin I, lactate dehydrogenase (LDH), and creatine kinase-MB. These beneficial effects were accompanied by increased expression of HSP90 and p-Akt, and decreased expression of C5a, NF-κB, tumor necrosis factor α, interleukin-1ß, and intercellular cell adhesion molecule 1. However, HSP90 inhibitor GA or Akt inhibitor GSK increased the expression of C5a and NF-κB and prevented MP-induced cardioprotection. Furthermore, GA inhibited the MP-induced upregulation of p-Akt, while GSK did not affect HSP90, indicating that p-Akt acts downstream of HSP90 in MP-induced cardioprotection. In addition, C5a inhibitor PMX enhanced the MP-induced downregulation of NF-κB, while NF-κB inhibitor QNZ had no effect on C5a, indicating that the C5a/NF-κB signaling pathway is involved in MP-induced cardioprotection. CONCLUSION: HSP90 is critical for MP-mediated cardioprotection possibly by promoting the phosphorylation of Akt and inhibiting the activation of C5a and NF-κB signaling and the subsequent myocardial inflammation, ultimately attenuating the infarct size and cardiomyocyte apoptosis.

Postconditioning attenuates myocardial ischemia-reperfusion injury by inhibiting complement activation and upregulation of miR-499.

The complement system plays a vital role in myocardial ischemia/reperfusion (I/R) injury. microRNA (miR)-499 is involved in the cardioprotection of ischemic postconditioning (IPostC). The present study aimed to study the role of the complement system and miR-499 in IPostC. Rat hearts were subjected to coronary ligation for 30 min, followed by reperfusion for 2 h. IPostC was introduced at the onset of reperfusion with three cycles of reperfusion for 30 sec and coronary artery occlusion for 30 sec. To study the role of miR-499 in IPostC, adeno-associated virus (AAV) vectors of miR-499-5p (AAV-miR-499-5p) and miR-499-5p-sponge (AAV-miR-499-5p-sponge) were transfected via tail vein injection, followed by IPostC protocols. Cardiac injury as well as the status of local and systemic complement activation and inflammation were assessed. IPostC significantly attenuated I/R-induced rat cardiomyocyte apoptosis and the myocardial infarct size. These beneficial effects were accompanied by decreased local and circulating complement component (C)3a and C5a levels, decreased inflammatory marker expression, decreased NF-κB signaling and increased cardiac miR-499 expression. AAV-miR-499-5p prevented local and systemic complement activation and inflammation as well as enhanced the cardioprotection of IPostC, whereas AAV-miR-499-5p-sponge produced the opposite effects. In summary, IPostC protected the rat myocardium against I/R injury, by inhibiting local and systemic complement activation; inflammation; NF-κB signaling; and upregulation of miR-499. As such, miR-499 may have a critical role in IPostC-mediated cardioprotection against I/R injury.

[Collagen spatial distribution in rapid atrial pacing dogs with or without superior vena cava and aortic root fat pad].

OBJECTIVE: To observe the collagen spatial distribution, collagen volume fraction (CVF) and Cx40, Cx43mRNA expressions in rapid atrial pacing dogs post vagal denervation by removing fat pad located between the medial superior vena cava and aortic root (SVC-Ao fat pad). METHODS: Twenty-four dogs were randomly divided into unpaced sham operation group (S group, n = 8), Keeping SVC-Ao fat pad group (K group, n = 8) and Removing SVC-Ao fat pad group (R group, SVC-Ao fat pad was removed by surgical excision before pacing, n = 8). K and R groups were paced for six weeks. Six weeks later, all dogs were sacrificed, left atrium (LA), right atrium (RA), left atrial appendage (LAA), right atrial appendage (RAA) and atrial septum (AS) were collected and stained with HE or Masson Trichrome or frozen in liquid nitrogen for quantifying the expression of Cx40, Cx43 mRNA by Real-time quantitative Reverse Transcription Polymerase Chain Reaction (RT-PCR). RESULTS: Spatial distribution of collagen fibers as well as CVF between S and R group were similar (all P > 0.05). CVF was significantly higher in K group compared to R group, especially at LAA and AS locations (all P < 0.05). Cx40mRNA expression in K group was significantly decreased in LA, RA, and significantly increased in LAA, RAA and AS compared those in S group (all P < 0.05), significantly lower in LA and RA while significantly higher in LAA and RAA compared to R group (all P < 0.05). Cx43mRNA expression in K group was significantly reduced in LA, RA, LAA and RAA while significantly increased in AS compared to S group (all P < 0.05), significantly higher in LA, RA, RAA and AS while significantly lower in LAA compared to R group. CONCLUSION: Pacing induced collagen remodeling and modulation on Cx40mRNA and Cx43 mRNA expressions could be partially attenuated by removing SVC-Ao fat pad suggesting vagal denervation plays a key role in the initiation and preservation of atrial fibrillation.

[Mitochondrial connexin43 and postconditioning protection in rabbits underwent myocardial ischemia/reperfusion injury].

OBJECTIVE: To investigate the roles of mitochondrial connexin43 (Cx43) and mitochondrial ATP sensitive potassium channe1 (mitoK(ATP)+) in the postconditioning protection for rabbits underwent myocardial ischemia/reperfusion injury. METHODS: In anesthetized open-chest rabbits, the left anterior descending artery (LAD) was occluded for 30 min and reperfused for 4 h and randomly divided into four groups (n = 16 each): sham operation group (Sham), ischemic reperfusion group (IR), ischemic postconditioning group (PC) and PC plus 5-HD, a specific mitoK(ATP)+ inhibitor (PC + 5-HD). Rabbits were sacrificed post 4 h reperfusion. Heart rate and the mean arterial pressure were recorded and plasma CK-MB and cTnI activity were measured at baseline, at the end of ischemia, and after 2 h and 4 h of reperfusion, respectively. Myocardial infarct size was determined and mitochondria structure was observed under electron microscope at the end of the experiment. Mitochondria were isolated and the protein content of the mitochondrial Cx43 was determined by Western blot. RESULTS: Plasma CK-MB, cTnI activity and myocardial infarct size were significantly reduced in PC [(19.1 +/- 3.9)%] group compared to IR [(35.7 +/- 5.8)%] and PC + 5HD [(34.2 +/- 3.9)%] groups (all P < 0.01). Degree of mitochondria damage was significantly reduced in PC group compared to IR and PC + 5HD groups (all P < 0.01). The mitochondria Cx43 content was significantly decreased in IR group and PC + 5-HD group compared to sham group (all P < 0.05) and restored in PC group. CONCLUSION: Ischemic postconditioning protected the heart from I/R injury by improving mitochondrial ultrastructure and by attenuating I/R induced decrease of mitochondria Cx43 expression. The protective effects of postconditioning was partly mediated by activating mitoK(ATP)+ pathway.

Role of HSP90 in suppressing TLR4-mediated inflammation in ischemic postconditioning.

BACKGROUND: Myocardial inflammation mediated by toll-like receptor 4 (TLR4) plays an active role in myocardial ischemia/reperfusion (I/R) injury. Studies show that heat shock protein 90 (HSP90) is involved in ischemic postconditioning (IPostC) cardioprotection. This study investigates the roles of TLR4 and HSP90 in IPostC. METHODS: Rats were subjected to 30 min ischemia, then 2 h reperfusion. IPostC was applied by three cycles of 30 s reperfusion, then 30 s reocclusion at reperfusion onset. Sixty rats were randomly divided into four groups: sham, I/R, IPostC, and geldanamycin (GA, HSP90 inhibitor, 1 mg/kg) plus IPostC (IPostC + GA). RESULTS: IPostC significantly reduced I/R-induced infarct size (40.2±2.1% versus 28.4±2.4%; P < 0.05); the release of cardiac Troponin T, creatine kinase-MB, and lactate dehydrogenase (191.5±3.1 versus 140.6±3.3 pg/ml, 3394.6±132.7 versus 2880.7±125.5 pg/ml, 2686.2±98.6 versus 1848.8±90.1 pg/ml, respectively; P < 0.05); and cardiomyocyte apoptosis (40.3±2.2% versus 27.0±1.6%; P < 0.05). Further, local and circulating IL-1ß, IL-6, TNF-α, and ICAM-1 levels decreased; TLR4 expression and nuclear factor-KB (NF-κB) signaling decreased; and cardiac HSP90 expression increased. Blocking HSP90 function with GA inhibited IPostC protection and anti-inflammation, suggesting that IPostC has a HSP90-dependent anti-inflammatory effect. CONCLUSION: HSP90 may play a role in IPostC-mediated cardioprotection by inhibiting TLR4 activation, local and systemic inflammation, and NF-kB signaling.

Ischemic postconditioning attenuates the inflammatory response in ischemia/reperfusion myocardium by upregulating miR­499 and inhibiting TLR2 activation.

Toll-like receptor 2 (TLR2)-mediated myocardial inflammation serves an important role in promoting myocardial ischemic/reperfusion (I/R) injury. Previous studies have shown that miR­499 is critical for cardioprotection after ischemic postconditioning (IPostC). Therefore, the present study evaluated the protective effect of IPostC on the myocardium by inhibiting TLR2, and also assessed the involvement of microRNA (miR)­499. Rat hearts were subjected to 30 min of ischemia and 2 h of reperfusion. The IPostC was 3 cycles of 30 sec of reperfusion and 30 sec of re­occlusion prior to reperfusion. In total, 90 rats were randomly divided into six groups (n=15 per group): Sham; I/R; IPostC; miR­499 negative control adeno­associated virus (AAV) vectors + IPostC; miR­499 inhibitor AAV vectors + IPostC; and miR­499 mimic AAV vectors + IPostC. It was identified that IPostC significantly decreased the I/R­induced cardiomyocyte apoptotic index (29.4±2.03% in IPostC vs. 42.64±2.27% in I/R; P<0.05) and myocardial infarct size (48.53±2.49% in IPostC vs. 66.52±3.1% in I/R; P<0.05). Moreover, these beneficial effects were accompanied by increased miR­499 expression levels (as demonstrated by reverse transcription­quantitative PCR) in the myocardial tissue and decreased TLR2, protein kinase C (PKC), interleukin (IL)­1ß and IL­6 expression levels (as demonstrated by western blotting and ELISA) in the myocardium and serum. The results indicated that IPostC + miR­499 mimics significantly inhibited inflammation and the PKC signaling pathway and enhanced the anti­inflammatory and anti­apoptotic effects of IPostC. However, IPostC + miR­499 inhibitors had the opposite effect. Therefore, it was speculated that IPostC may have a miR­499­dependent cardioprotective effect. The present results suggested that miR­499 may be involved in IPostC­mediated ischemic cardioprotection, which may occur via local and systemic TLR2 inhibition, subsequent inhibition of the PKC signaling pathway and a decrease in inflammatory cytokine release, including IL­1ß and IL­6. Moreover, these effects will ultimately lead to a decrease in the myocardial apoptotic index and myocardial infarct size via the induction of the anti­apoptotic protein Bcl­2, and inhibition of the pro­apoptotic protein Bax in myocardium.

Involvement of HSP90 in ischemic postconditioning-induced cardioprotection by inhibition of the complement system, JNK and inflammation.

PURPOSE: To investigate whether heat shock protein 90 (HSP90) is involved in complement regulation in ischemic postconditioning (IPC). METHODS: The left coronary artery of rats underwent 30 min of occlusion, followed by 120 min of reperfusion and treatment with IPC via 3 cycles of 30s reperfusion and 30s occlusion. The rats were injected intraperitoneally with 1 mg/kg HSP90 inhibitor geldanamycin (GA) after anesthesia. Eighty rats were randomly divided into four groups: sham, ischemia-reperfusion (I/R), IPC and IPC + GA. Myocardial infarct size, apoptosis index and the expression of HSP90, C3, C5a, tumor necrosis factor (TNF)-alpha, interleukin (IL)-1ß and c-Jun N-terminal kinase (JNK) were assessed. RESULTS: Compared with the I/R injury, the IPC treatment significantly reduced infarct size, release of troponin T, creatine kinase-MB, and lactate dehydrogenase, and cardiomyocyte apoptosis. These beneficial effects were accompanied by a decrease in TNF-α, IL-1ß, C3, C5a and JNK expression levels. However, all these effects were abrogated by administration of the HSP90 inhibitor GA. CONCLUSION: HSP90 exerts a profound effect on IPC cardioprotection, and may be linked to the inhibition of the complement system and JNK, ultimately attenuating I/R-induced myocardial injury and apoptosis.