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Vascular dysfunction in cardiovascular diseases includes vasomotor response impairments, endothelial cells (ECs) activation, and smooth muscle cells (SMCs) proliferation and migration to the intima. This results in intimal hyperplasia and vessel failure. We previously reported that activation of the P2Y11 receptor (P2Y11R) in human dendritic cells, cardiofibroblasts and cardiomyocytes was protective against hypoxia/reoxygenation (HR) lesions. In this study, we investigated the role of P2Y11R signaling in vascular dysfunction. P2Y11R activity was modulated using its pharmacological agonist NF546 and antagonist NF340. Rat aortic rings were exposed to angiotensin II (AngII) and evaluated for their vasomotor response. The P2Y11R agonist NF546 reduced AngII-induced vascular dysfunction by promoting EC-dependent vasorelaxation, through an increased nitric oxide (NO) bioavailability and reduced AngII-induced H 2 O 2 release; these effects were prevented by the use of the P2Y11R antagonist NF340. Human vascular SMCs and ECs were subjected to AngII or H/R simulation in vitro. P2Y11R agonist modulated vasoactive factors in human ECs, that is, endothelial nitric oxide synthase (eNOS) and endothelin-1, reduced SMC proliferation and prevented the switch towards a synthetic phenotype. H/R and AngII increased ECs secretome-induced SMC proliferation, an effect prevented by P2Y11R activation. Thus, our data suggest that P2Y11R activation may protect blood vessels from HR-/AngII-induced injury and reduce vascular dysfunctions. These results open the way for new vasculoprotective interventions.

Sterile inflammation is a key determinant of myocardial reperfusion injuries. It participates in infarct size determination in acute myocardial infarction and graft rejection following heart transplantation. We previously showed that P2Y11 exerted an immunosuppressive role in human dendritic cells, modulated cardiofibroblasts' response to ischemia/reperfusion in vitro and delayed graft rejection in an allogeneic heterotopic heart transplantation model. We sought to investigate a possible role of P2Y11 in the cellular response of cardiomyocytes to ischemia/reperfusion. We subjected human AC16 cardiomyocytes to 5 h hypoxia/1 h reoxygenation (H/R). P2Y11R (P2Y11 receptor) selective agonist NF546 and/or antagonist NF340 were added at the onset of reoxygenation. Cellular damages were assessed by LDH release, MTT assay and intracellular ATP level; intracellular signaling pathways were explored. The role of P2Y11R in mitochondria-derived ROS production and mitochondrial respiration was investigated. In vitro H/R injuries were significantly reduced by P2Y11R stimulation at reoxygenation. This protection was suppressed with P2Y11R antagonism. P2Y11R stimulation following H 2 O 2 -induced oxidative stress reduced mitochondria-derived ROS production and damages through PKCε signaling pathway activation. Our results suggest a novel protective role of P2Y11 in cardiomyocytes against reperfusion injuries. Pharmacological post-conditioning targeting P2Y11R could therefore contribute to improve myocardial ischemia/reperfusion outcomes in acute myocardial infarction and cardiac transplantation.

Introduction: Ischemia/reperfusion (I/R) injury, such as myocardial infarction, stroke, and peripheral vascular disease, has been recognized as the most frequent causes of devastating disorders and death currently. Protective effect of various preconditioning stimuli, including hyperbaric oxygen (HBO), has been proposed in the management of I/R., Methods: In this study, we searched and reviewed up-to-date published papers to explore the pathophysiology of I/R injury and to understand the mechanisms underlying the protective effect of HBO as conditioning strategy., Results: Animal study and clinic observation support the notion that HBO therapy and conditioning provide beneficial effect against the deleterious effects of postischemic reperfusion. Several explanations have been proposed. The first likely mechanism may be that HBO counteracts hypoxia and reduces I/R injury by improving oxygen delivery to an area with diminished blood flow. Secondly, by reducing hypoxia-ischemia, HBO reduces all the pathological events as a consequence of hypoxia, including tissue edema, increased affective area permeability, postischemia derangement of tissue metabolism, and inflammation. Thirdly, HBO may directly affect cell apoptosis, signal transduction, and gene expression in those that are sensitive to oxygen or hypoxia. HBO provides a reservoir of oxygen at cellular level not only carried by blood, but also by diffusion from the interstitial tissue where it reaches high concentration that may last for several hours, improves endothelial function and rheology, and decreases local inflammation and edema., Conclusion: Evidence suggests the benefits of HBO when used as a preconditioning stimulus in the setting of I/R injury. Translating the beneficial effects of HBO into current practice requires, as for the "conditioning strategies", a thorough consideration of risk factors, comorbidities, and comedications that could interfere with HBO-related protection.

Background: Infarct size (IS) is a major determinant of patient outcome after acute ST-segment elevation myocardial infarction (STEMI). Interventions aimed at reducing reperfusion injury, such as cardiac ischaemic postconditioning (IPost), may reduce IS and improve clinical outcomes. IPost has been shown to be feasible in patients with STEMI treated by primary percutaneous coronary intervention (PPCI)., Aims: To provide an updated summary of the efficacy of IPost, assessed by analysing accurate surrogate markers of IS., Methods: We performed a meta-analysis of randomized controlled trials that evaluated the efficacy of IPost in STEMI patients undergoing PPCI. The main outcome was area under the curve of serum creatine kinase release (CK-AUC). Secondary outcomes were other surrogate biomarkers of IS, complete ST-segment resolution, direct measurement of IS by single-photon emission computed tomography and estimation of IS by cardiac magnetic resonance (CMR-IS)., Results: Eleven studies were retrieved, including 1313 STEMI patients undergoing PPCI with or without IPost. Compared with controls, we observed a significant reduction in CK-AUC (standard mean difference [SMD] -2.84 IU/L, 95% CI -5.43 to -0.25 IU/L; P=0.03). Other surrogate markers, such as CMR-IS (SMD -0.36, 95% CI -0.88 to 0.15; P=0.16), showed a non-significant IS reduction in the IPost group., Conclusions: This meta-analysis, dealing with accurate surrogate markers of IS, suggests that IPost reduces IS. However, results should be interpreted cautiously because of limited sample sizes and significant heterogeneity. Whether this translates into improvements in cardiac function and patient prognosis still needs to be demonstrated in larger prospective randomized controlled studies that are powered sufficiently., (Copyright © 2014 Elsevier Masson SAS. All rights reserved.)

Background: We have previous evidence that in anesthetized dogs the inorganic sodium nitrite protects against the severe ventricular arrhythmias, resulting from coronary artery occlusion and reperfusion, when administered 24 h before. The present study aimed to examine, whether in this effect changes in mitochondrial morphology and function would play a role. Methods: Thirty dogs were infused intravenously either with saline (n = 15) or sodium nitrite (0.2 µmol/kg/min; n = 15) for 20min, and 24 h later, 10 dogs from each group were subjected to a 25min period of occlusion and then reperfusion of the left anterior descending coronary artery. The severity of ischaemia and ventricular arrhythmias were examined in situ. Left ventricular tissue samples were collected either before the occlusion (5 saline and 5 nitrite treated dogs) or, in dogs subjected to occlusion, 2min after reperfusion. Changes in mitochondrial morphology, in complex I and complex II-dependent oxidative phosphorylation (OXPHOS), in ATP, superoxide, and peroxynitrite productions were determined. Results: The administration of sodium nitrite 24 h before ischemia/reperfusion significantly attenuated the severity of ischaemia, and markedly reduced the number and incidence of ventricular arrhythmias. Nitrite also attenuated the ischaemia and reperfusion (I/R)-induced structural alterations, such as reductions in mitochondrial area, perimeter, and Feret diameter, as well as the increase in mitochondrial roundness. The administration of nitrite, however, enhanced the I/R-induced reduction in the mitochondrial respiratory parameters; compared to the controls, 24 h after the infusion of nitrite, there were further significant decreases, e.g., in the complex I-dependent OXPHOS (by -20 vs. -53%), respiratory control ratio (by -14 vs. -61%) and in the P/E control coupling ratio (by 2 vs. -36%). Nitrite also significantly reduced the I/R-induced generation of superoxide, without substantially influencing the ATP production. Conclusions: The results suggest that sodium nitrite may have an effect on the mitochondria; it preserves the mitochondrial structure and modifies the mitochondrial function, when administered 24 h prior to I/R. We propose that nitrite affects primary the phosphorylation system (indicated by the decreased P/E ratio), and the reduction in superoxide production would result from the subsequent suppression of the ROS producing complexes; an effect which may certainly contribute to the antiarrhythmic effect of nitrite. [ABSTRACT FROM AUTHOR]

Copyright of Canadian Journal of Physiology & Pharmacology is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Canadian Journal of Physiology & Pharmacology is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Myocardial ischemic/reperfusion (I/R) injury remains a major public health burden and cardioprotection defined as the totality of both non-pharmacological and pharmacological interventions aimed at preventing the reperfusion injury, still represents a stringent necessity. There is accumulating evidence that volatile anaesthetics induce myocardial preconditioning when given prior to ischemia and they also protect the heart at the very onset of reperfusion, an effect referred to as anaesthetic postconditioning. The aims of the present study were: (i) to develop and validate an experimental model of regional myocardial I/R injury in rat hearts in situ and (ii) to investigate in this model the protective effects of cardioprotection elicited by anesthetic pre- and postconditioning with Isoflurane and Sevoflurane. METHODS: Anaesthetized rats (n = 6-8/group) subjected to 30 min ischemia by coronary artery ligation and 2 h reperfusion were randomly assigned to one of the following groups: 1) Control group (Ctrl, no other intervention); 2) Ischemic preconditioning (I-PreC, preconditioning by three episodes of 5 min ischemia interspersed with three episodes of 10 min reperfusion); 3) Isoflurane preconditioning (Iso-PreC, preconditioning by three episodes of 5 min isoflurane 2.1% interspersed with three 10 min washout episodes); 4) Isoflurane postconditioning (Iso-PostC, 5 min postconditioning with isoflurane 2.1% started 3 min prior to and administered for 2 min within reperfusion); 5) Sevoflurane preconditioning (Sevo-PreC, preconditioning by two episodes of 5 min sevoflurane 2.5% interspersed with two 10 min washout episodes) and 6) Sevoflurane postconditioning (Sevo-PostC, 5 mitt postconditioning with sevoflurane 2.5% started 3 min prior to and administered for 2 min within reperfusion). RESULTS: Myocardial injury expressed as the percent of infarct to risk area ratio (I/R%) was significantly reduced in I-PreC (14.3 ± 6.8%) and Iso-PreC (17 ± 5.1%) and Sevo-PreC (19.5±8.5%) when compared to the Ctrl group (46.4±6.5%, mean ± SD; P<0.01), but no protection was found with the postconditioning protocols. CONCLUSIONS: We have validated an experimental model of regional ischemia that can be used in studies of in vivo cardioprotection. In this model anesthetic preconditioning but not postconditioning was associated with infarct size reduction. [ABSTRACT FROM AUTHOR]

Abstract: The aim of the present study was to determine whether specific inhibition of mitochondrial permeability transition (MPT) by NIM811 at the time of reperfusion following acute myocardial infarction may protect the heart. MPT pore opening appears to be a pivotal event in cell death following acute myocardial infarction. Recently, MPT pore opening has been involved in ischemic preconditioning. In protocol 1, NZW rabbits underwent either no intervention (sham) or 10 min of ischemia followed by 5 min of reperfusion, preceded (preconditioned, PC) or not (control, C) by 5 min of ischemia and 5 min of reperfusion. Additional rabbits were treated by cyclosporin A (CsA) or its non-immunosuppressive and more specific derivative (NIM811) (10 mg kg–1, IV bolus), either 10 min before ischemia or 1 min before reperfusion. Hearts were excised and mitochondria isolated for further assessment of Ca2+-induced MPT. In protocol 2, animals were randomly assigned into similar experimental groups and underwent 30 min of ischemia and 4 h of reperfusion. Infarct size was assessed by TTC staining, and apoptosis by TUNEL assay. The Ca2+ overload required to induce MPT pore opening was significantly higher in NIM811, CsA and PC groups than in controls. Both necrotic and apoptotic cardiomyocyte death were significantly reduced by NIM811, CsA and PC. In both protocols, administration of NIM811 at reperfusion provided full protection. These data indicate that specific inhibition of MPT pore opening at reperfusion following acute myocardial infarction provides a powerful antinecrotic and antiapoptotic protection. [Copyright &y& Elsevier]

A substantial body of evidence indicates that pharmacological activation of mitochondrial ATP-sensitive potassium channels (mKATP) in the heart is protective in conditions associated with ischemia/reperfusion injury. Several mechanisms have been postulated to be responsible for cardioprotection, including the modulation of mitochondrial respiratory function. The aim of the present study was to characterize the dose-dependent effects of novel synthetic benzopyran analogues, derived from a BMS-191095, a selective mKATP opener, on mitochondrial respiration and reactive oxygen species (ROS) production in isolated rat heart mitochondria. Mitochondrial respiratory function was assessed by high-resolution respirometry, and H2O2 production was measured by the Amplex Red fluorescence assay. Four compounds, namely KL-1487, KL-1492, KL-1495, and KL-1507, applied in increasing concentrations (50, 75, 100, and 150 μmol/L, respectively) were investigated. When added in the last two concentrations, all compounds significantly increased State 2 and 4 respiratory rates, an effect that was not abolished by 5-hydroxydecanoate (5-HD, 100 μmol/L), the classic mKATP inhibitor. The highest concentration also elicited an important decrease of the oxidative phosphorylation in a K+ independent manner. Both concentrations of 100 and 150 μmol/L for KL-1487, KL-1492, and KL-1495, and the concentration of 150 μmol/L for KL-1507, respectively, mitigated the mitochondrial H2O2 release. In isolated rat heart mitochondria, the novel benzopyran analogues act as protonophoric uncouplers of oxidative phosphorylation and decrease the generation of reactive oxygen species in a dose-dependent manner. [ABSTRACT FROM AUTHOR]

It is widely accepted that mitochondria contribute to their own damage in the settings of experimental ischemia/reperfusion injury. The aim of the present work was to investigate the degree of mitochondrial dysfunction elicited by an in vivo rat heart model of regional ischemia/reperfusion injury. Mitochondria were isolated from ischemic and non-ischemic zones rat hearts subjected to 30 min of regional ischemia by coronary ligation and 15 min of reperfusion. Oxygen consumption was assessed by polarographic oxymetry in a Clark-type electrode in the presence of complex I substrates (glutamate/malate) and complex II (succinate). State 3 respiration rate and the respiratory control ratio for glutamate/malate were significantly decreased in mitochondria isolated from the ischemic area, suggesting an early alteration of complex I supported respiration (p < 0.01 vs. non-ischemic area). In another set of experiments mitochondrial calcium retention capacity was evaluated by luminescence spectroscopy using the calcium-sensitive probe Calcium Green 5N and mitochondrial swelling was monitored as the decrease in light scattering at 520 nm. In the presence of complex IIdependent substrate, less calcium was required to zone induce permeability transition, suggesting the pre-existence of calcium overload in mitochondria isolated from ischemic zone vs. non-ischemic zone. Mitochondria isolated from the ischemic (vs. non-ischemic) zone presented an increased rate of swelling in the case of complex I supported respiration. These results are suggestive for an early damage to the phosphorylation apparatus at complex I in mitochondria isolated at reperfusion after regional ischemia in the in vivo rat hearts. [ABSTRACT FROM AUTHOR]

Mitochondria have emerged as key players in cardioprotection against ischemia/reperfusion (I/R) injury. Diazoxide (Dx) has been shown to reduce infarct size in several experimental models through the opening of mitochondrial ATP-dependent potassium channels (mKATP) and also to exert a substrate-dependent effect on mitochondrial respiration. The aim of the present study performed in mitochondria isolated from rat hearts subjected to 30 min global ischemia and 60 min of reperfusion was to investigate the effects of Dx (100 ?M) given at reperfusion on respiratory function. Oxygen consumption was assessed by polarographic oxymetry in a Clark-type electrode. State 3 respiration rate (oxygen uptake during ADP phosphorylation, expressed in natoms oxygen/min/mg mitochondrial protein) and the respiratory control ratio (RCR, the ratio of state 3 and state 2 oxygen uptake rates) were assessed in the presence of complex I substrates (glutamate/malate). Our data showed that RCR was significantly reduced in the non-treated group vs. the group treated with Dx (RCR = 3.45 vs. 4.5; p < 0.05). In a second set of experiments performed in mitochondria isolated from hearts treated with Dx at reperfusion, mitochondrial calcium retention capacity (CRC) was further evaluated by luminescence spectroscopy using the calcium-sensitive probe Calcium Green 5N in the presence of different substrates. The amount of calcium required by ischemic mitochondria to undergo permeability transition was higher, albeit not statistically significant in the presence of CI substrates (glutamate/malate) as compared to CII substrate (succinate). [ABSTRACT FROM AUTHOR]