Early Preconditioning Research Articles

Autocrine Bradykinin Release Promotes Ischemic Preconditioning-Induced Cytoprotection in Bovine Aortic Endothelial Cells.

The aims of this study were to assess whether ischemic preconditioning (PC) induces bradykinin (Bk) synthesis in bovine aortic endothelial cells (bAECs) and, if so, to explore the molecular mechanisms by which this peptide provides cytoprotection against hypoxia. PC was induced by exposing bAECs to three cycles of 15 min of hypoxia followed by 15 min of reoxygenation. Bk synthesis peaked in correspondence to the early and late phases of PC (10−12 M and 10−11 M, respectively) and was abolished by a selective tissue kallikrein inhibitor, aprotinin. Stimulation with exogenous Bk at concentrations of 10−12 M and 10−11 M reduced the cell death induced by 12 h of hypoxia by 50%. Pretreatment with HOE−140, a Bk receptor 2 (BKR2) inhibitor, in bAECs exposed to 12 h of hypoxia, abrogated the cytoprotective effect of early and late PC, whereas des-Arg-HOE-140, a Bk receptor 1 (BKR1) inhibitor, affected only the late PC. In addition, we found that PC evoked endocytosis and the recycling of BKR2 during both the early and late phases, and that inhibition of these pathways affected PC-mediated cytoprotection. Finally, we evaluated the activation of PKA and Akt in the presence or absence of BKR2 inhibitor. HOE-140 abrogated PKA and Akt activation during both early and late PC. Consistently, BKR2 inhibition abolished cross-talk between PKA and Akt in PC. In bAECs, Bk-synthesis evoked by PC mediates the protection against both apoptotic and necrotic hypoxia-induced cell death in an autocrine manner, by both BKR2- and BKR1-dependent mechanisms.

P291Non-invasive in vivo human model of the involvement of human epidermal mitochondria in the early post-ischaemic preconditioning

P291Non-invasive in vivo human model of the involvement of human epidermal mitochondria in the early post-ischaemic preconditioning

АКТИВНЫЕ ФОРМЫ КИСЛОРОДА КАК ТРИГГЕРЫ ИНФАРКТ-ЛИМИТИРУЮЩЕГО ЭФФЕКТА РАННЕГО ГИПОКСИЧЕСКОГО ПРЕКОНДИЦИОНИРОВАНИЯ МИОКАРДА КРЫСЫ

It is believed that reactive oxygen species (ROS) are involved in the performance of this adaptive hepatoprotective effect phenomenon. However, the role of ROS in the signaling mechanism of the early hypoxic preconditioning (early HP) and the contribution of individual types of oxygen radicals in the infarct-limiting effect of early HP remains uncertain to the end. Objective was to investigate the role of various types of reactive oxygen species in the signaling mechanism of the infarct-limiting effect of early hypoxic preconditioning. We investigated the role of reactive oxygen species in the signaling mechanism of early HP in vivo. Adaptation of animals was conducted with 6 transient hypoxia-reoxygenation sessions before prolonged ischemia (45 min) and reperfusion (120 min). Low molecular weight antioxidants were administered 15 minutes prior to the HP. We found out that pretreatment with the nonselective antioxidant indirect action of N-(2-mercaptopropionyl)-glycine and "trap" of hydroxyl radicals 1,3-dimethylthiourea completely eliminated the infarct-limiting effect of adaptation. Administration of antioxidants tempol and trolox, as well as the use of N-(2-mercaptopropionyl)-glycine after HP had no effect on the protective effect of adaptation. Consequently, reactive oxygen species, including hydroxyl radical, operate as the trigger function in the signaling mechanism of early HP.

Neuroprotective effects of cortexin and ischemic preconditioning

The purpose was to assess neuroprotective effects of cortexin and ischemic preconditioning in rats with occlusion of both carotid arteries. Methods. The Wistar rats were divided into two groups according to their resistance to hypoxia. All rats were raised in barocamera on altitude 11 000 m with speed 50 m/sec and exposition up to agonal breath. Rats resistant to hypoxia more than 10 min were qualified as high resistant (HR), less than 5 min as low resistant (LR) to hypoxia. Ischemic preconditioning was reproduced by the 3-times temporary occlusions of common carotid arteries (5 min each) with 15-min reperfusion interval between occlusions. The chronic ischemia was modeled by means of ligation (permanent occlusion) of both carotid arteries in 1 h (early preconditioning) or 24 h (delayed preconditioning) after preconditioning procedure. Cortexin 1 mg/kg was administered intraperitoneally 7 days after occlusion of carotid arteries. Neurological status was assessed using McGrow’s stroke-index. Results. In postischemic period, the functional and metabolic changes in the brain of HR and LR rats were more significant in conditions of delayed preconditioning. In group of early preconditioning, a number of survival rats on 7th day was more than in delayed preconditioning group. Cortexin administration (1 mg/kg, 7 days) increased quantity of survival rats, especially in delayed preconditioning group. The maximal effect of cortexin was observed in delayed preconditioning group. Also cortexin decreased malonic dialdehyde level and increased superoxide dismutase activity of the brain tissue in all groups of rats. Conclusion. The course administration of polypeptide drug cortexin reduces neurological deficit signs, recovers structure of individual behavior of rats with different resistance to hypoxia and performs antioxidant action in chronic ischemic damage of the brain on the background of early and delayed preconditioning.

Exercise preconditioning of myocardial infarct size in dogs is triggered by calcium.

We showed that exercise induces early and late myocardial preconditioning in dogs and that these effects are mediated through nicotinamide adenine dinucleotide phosphate reduced form (NADPH) oxidase activation. As the intracoronary administration of calcium induces preconditioning and exercise enhances the calcium inflow to the cell, we studied if this effect of exercise triggers exercise preconditioning independently of its hemodynamic effects. We analyzed in 81 dogs the effect of blocking sarcolemmal L-type Ca channels with a low dose of verapamil on early and late preconditioning by exercise, and in other 50 dogs, we studied the effect of verapamil on NADPH oxidase activation in early exercise preconditioning. Exercise reduced myocardial infarct size by 76% and 52% (early and late windows respectively; P < 0.001 both), and these effects were abolished by a single low dose of verapamil given before exercise. This dose of verapamil did not modify the effect of exercise on metabolic and hemodynamic parameters. In addition, verapamil blocked the activation of NADPH oxidase during early preconditioning. The protective effect of exercise preconditioning on myocardial infarct size is triggered, at least in part, by calcium inflow increase to the cell during exercise and, during the early window, is mediated by NADPH oxidase activation.

Innovative Pharmacological/Therapeutic Approaches against Hepatic Ischemia/Reperfusion Injury.

Prolonged oxygen deprivation corresponding to the ischemic period is observed during liver resection, transplantation, and trauma and subsequent oxygen restoration always leads to reperfusion injury. In particular, the ischemic period represents an inevitable event during conventional organ preservation before transplantation and the magnitude and severity of reperfusion injury depend on the time of liver preservation. Faced with the increasing shortage of donor organs for transplantation, there is renewed interest in marginal livers, such as those obtained from donation after circulatory death or fatty livers, which are particularly susceptible to ischemia/reperfusion (I/R) injury. The decreased tolerance towards I/R observed in fatty livers has not been fully elucidated yet, and underlying mechanisms appear different in lean and steatotic livers. The paper of A. Matsuda et al. proposed the use of activated protein C (APC), an anticoagulant, found to induce an initial attenuation of tissue damage by inhibiting inflammatory cell infiltration and sinusoidal endothelial injury in normal liver. Of interest, in steatotic mice livers, APC did not affect initial liver damage but attenuated late damage, suggesting the existence of an additional pathway to the anti-inflammatory cytoprotective effect of APC which may occur via activation of adenosine monophosphate-activated protein kinase (AMPK) phosphorylation. A further attempt to reduce the fatty liver susceptibility was reported by E. Pantazi et al. that used a peroxisome proliferator-activated receptor α (PPARα) agonist WY-14643. PPARα is a nuclear receptor highly expressed in liver and it functions as a lipid sensor. Treatment with WY-14643 reduced liver injury in fatty rat livers, enhanced the deacetylase enzyme sirtuin 1 (SIRT1), recently found to be a target for preventing I/R, and prevented endoplasmic reticulum stress. M. Bejaoui et al. investigated the use of polyethylene glycols (PEGs) that, besides their usefulness as oncotic agents in preservation solution, have been shown to protect against cold injury and ischemic damage. The intravenous PEG 35 administration by a unique dose protected steatotic rat liver grafts against the deleterious effects of cold storage and the subsequent reperfusion. The rationale for the intravenous administration of PEG 35 was to induce a pharmacological preconditioning effect; its protective mechanisms are related to preservation of mitochondria and the induction of protective cell signaling pathways (eNOS, Akt, and AMPK). An additional model of liver preconditioning by pharmacological induction of adenosine A2a receptor (A2aR) was reported by E. Alchera et al. The analysis of the molecular changes induced by A2aR stimulation revealed multiple mechanisms of liver cell protection that can be both immediate (early preconditioning) and delayed (late preconditioning). Note that the A2aR activation also protects against lipotoxicity by preventing lipoapoptosis in primary rat hepatocytes. Among the hepatic mechanisms involved in the development of I/R, mitochondrial dysfunction represents a crucial cellular event contributing to I/R injury. As reported by K. Go et al., the elimination of abnormal and dysfunction mitochondria by mitophagy appears to increase both the quality of the mitochondria and cell survival. Although the mechanisms underlying the onset and propagation of mitophagy remain elusive, this event represents an early adaptive response to facilitate cell survival during I/R. Articles published in this issue not only help to identify new pharmacological approaches for improving liver function during ischemia/reperfusion damage but also stimulate the identification of molecular mediators of hepatic injury. Mariapia Vairetti Hartmut Jaeschke Diethard Monbaliu Jae-Sung Kim Andrea Ferrigno

Comparative analysis of early and delayed cardioprotective and antiarrhythmic efficacy of hypoxic preconditioning.

Hypoxic preconditioning produces an infarct-limiting effect both in the early and delayed periods. The increase in heart resistance to ischemia-repefusion was more pronounced after early preconditioning. Hypoxic preconditioning did not change heart resistance to the arrhythmogenic effect of coronary occlusion and reperfusion.

Volatile anesthetic-induced preconditioning

The myocardium has an innate ability to protect itself from ischemic events. This protection occurs when the myocardium is exposed to a brief ischemic period prior to a more extreme ischemic event. This is termed ischemic preconditioning. Ischemic preconditioning induces a series of molecular pathways that protect the cardiac myocyte; first, for a period of 1-6 hours (early preconditioning) and, also, for a second period from 24-72 hours (delayed phase). The early preconditioning is mediated by the release of adenosine which induces a protective signal that is related to the mitochondrial KATP channel activation and activation of the δ-opioid and bradykinin receptors. The delayed phase is related to the induction of inducible nitric oxide synthase, superoxide dismutase and heat-shock proteins. Indirect evidence indicates that O2-derived free radicals are involved in the delayed phase, as noted in the early preconditioning phase. Applying ischemic preconditioning to clinical practice can be dangerous and difficult to implement in a controlled fashion. However, recent studies have shown that the use of volatile anesthetics, such as sevoflurane, isoflurane and desflurane, can mimic the early phase of ischemic preconditioning through a multi-pathway signaling of mitochondrial KATP channels. This important finding can easily be applied to clinical practice for patients undergoing surgery. It can also be significantly important for patients undergoing off-pump cardiac bypass surgery or cardiac bypass surgery where there is no cross-clamp or cardioplegia used where the probability of myocardial ischemia is greatly increased. This report will, therefore, discuss the mechanism, safety and efficacy of volatile anesthetics as inducers of cardiac preconditioning.

Neurovascular protection by ischaemic tolerance: role of nitric oxide

Nitric oxide (NO) has emerged as a key mediator in the mechanisms of ischaemic tolerance induced by a wide variety of preconditioning stimuli. NO is involved in the brain protection that develops either early (minutes-hours) or late (days-weeks) after the preconditioning stimulus. However, the sources of NO and the mechanisms underlying the protective effects differ substantially. While in early preconditioning NO is produced by the endothelial and neuronal isoform of NO synthase, in delayed preconditioning NO is synthesized by the inducible or 'immunological' isoform of NO synthase. Furthermore, in early preconditioning, NO acts through the canonical cGMP pathway, possibly through protein kinase G and opening of mitochondrial K(ATP) channels. In late preconditioning, the protection is mediated by peroxynitrite formed by the reaction of NO with superoxide derived from the enzyme NADPH oxidase. The mechanisms by which peroxynitrite exerts its protective effect may include improvement of post-ischaemic cerebrovascular function, leading to enhancement of blood flow to the ischaemic territory, and expression of prosurvival genes resulting in cytoprotection. The evidence suggests that NO can engage highly effective and multifunctional prosurvival pathways, which could be exploited for the prevention and treatment of cerebrovascular pathologies.

Molecular mechanisms underlying neurovascular protection in stroke

Molecular mechanisms underlying neurovascular protection in stroke

Remote Ischemic Preconditioning

Circulatory arrest and stroke are among the leading causes of death and disability worldwide, and they are difficult to treat. Only a limited number of therapeutic approaches have reached the bedside (eg, hypothermia and recombinant tissue plasminogen activator)1 and, unfortunately, relatively few patients are eligible. Virtually all experimental compounds tested so far have failed at some stage of translational development. Preconditioning is an attractive strategy that makes the brain and other visceral organs relatively resistant to tissue injury. It develops when a noxious stimulus, below the damage threshold, leads to reduced tissue injury on subsequent challenge with a stimulus given above injury threshold. It is an appealing strategy to identify novel endogenous protective mechanisms and, as demonstrated by Jensen, Loukogeorgakis, and their colleagues in this issue of Circulation ,2 it may prove useful to prevent brain damage in the clinical context when there is a high probability of cerebral ischemia (eg, before high-risk surgery or in patients with subarachnoid hemorrhage). Article see p 714 Various types of preconditioning stimuli have been used experimentally to protect brain, heart, retina, liver, kidney, and other organs.3 Some use ischemic preconditioning, in which the blood supply to a target organ is temporarily interrupted before introducing a longer infarct-generating insult that would ordinarily produce infarction; other studies use hypoxic preconditioning, in which animals are exposed to oxygen levels around 8% to 9% for a few hours. But ischemia and hypoxia are just 2 examples in a larger list of strategies that induce tolerance to brain injury: hypoglycemia, hypoxia, kainate-induced seizures, and exposure to volatile anesthetics, to name a few.4 Preconditioning can protect the brain either rapidly after stimulation (known as early, first window, or classical preconditioning) or after a 24-hour delay to induce protein synthesis-dependent protection lasting up to 96 hours …

Late Cardiac Preconditioning by Exercise in Dogs Is Mediated by Mitochondrial Potassium Channels

We previously showed that exercise induces myocardial preconditioning in dogs and that early preconditioning is mediated through mitochondrial adenosine triphosphate-sensitive potassium channels. We decided to study if late preconditioning by exercise is also mediated through these channels. Forty-eight dogs, surgically instrumented and trained to run daily, were randomly assigned to 4 groups: (1) Nonpreconditioned dogs: under anesthesia, the coronary artery was occluded during 1 hour and then reperfused during 4.5 hours. (2) Late preconditioned dogs: similar to group 1, but the dogs run on the treadmill for 5 periods of 5 minutes each, 24 hours before the coronary occlusion. (3) Late preconditioned dogs plus 5-hydroxydecanoate (5HD): similar to group 2, but 5HD was administered before the coronary occlusion. (4) Nonpreconditioned dogs plus 5HD: similar to group 1, but 5HD was administered before the coronary occlusion. Infarct size (percent of the risk region) decreased by effect of exercise by 56% (P < 0.05), and this effect was abolished with 5HD. 5HD by itself did not modify infarct size. Exercise did not induce myocardial ischemia, and the hemodynamics during ischemia-reperfusion period did not differ among groups. These effects were independent of changes in collateral flow to the ischemic region. We concluded that late cardiac preconditioning by exercise is mediated through mitochondrial adenosine triphosphate-sensitive potassium channels.

Role of iNOS and peroxynitrite–matrix metalloproteinase-2 signaling in myocardial late preconditioning in rats

We have previously shown that the inhibition of myocardial nitric oxide (NO) and peroxynitrite-matrix metalloproteinase (MMP) signaling by early preconditioning (PC) is involved in its cardioprotective effect. Therefore, in the present study, we investigated the role of NO and peroxynitrite-MMP signaling in the development of late PC. PC was performed by five consecutive cycles of 4-min coronary occlusion and 4-min reperfusion in anesthetized rats in vivo. Twenty-four hours later, hearts were subjected to a 30-min coronary occlusion followed by 180-min reperfusion to measure infarct size. In separate experiments, heart tissue was sampled to measure biochemical parameters before and 3, 6, 12, or 24 h after the PC protocol, respectively. Late PC decreased infarct size, increased cardiac inducible NO synthase (iNOS) activity and gene expression, and decreased SOD activity at 24 h significantly compared with sham-operated controls. Late PC increased cardiac superoxide levels significantly at 24 h; however, it did not change cardiac NO levels. Cardiac peroxynitrite levels were significantly decreased. Downstream cellular targets of peroxynitrite, MMP-2 and MMP-9 activities were decreased in the late PC group at 24 h compared with the sham-operated group. To verify if PC-induced inhibition of MMPs had a causative role in the reduction of infarct size, in separate experiments, we measured infarct size after the pharmacological inhibition of MMPs by ilomastat and found a significant reduction of infarct size compared with the vehicle-treated group. In conclusion, this is the first demonstration that the inhibition of cardiac peroxynitrite-MMP signaling contributes to cardioprotection by late PC and that pharmacological inhibition of MMPs is able to reduce infarct size in vivo. Furthermore, increased expression of iNOS may play a role in the development of late PC; however, increased iNOS activity does not lead to increased NO production in late PC.

Early preconditioning protection against stunning in conscious sheep. Role of KATP channels

The aim of this study was to assess early preconditioning protection against stunning in conscious sheep and analyze the role of ATP-dependent potassium (KATP) channels in the protective mechanism. Chronically instrumented animals were submitted to a 12 min reversible ischemia and 2 h reperfusion. Early preconditioning, consisting of six 5 min occlusion-5 min reperfusion periods, followed by 45 min normoperfusion before the prolonged ischemia protected against stunning (P < 0.01). In these experimental conditions, current agents used to analyze sarcolemmal (sKATP) and mitochondrial (mKATP) KATP channels could not clearly establish their participation in the protective mechanism. At doses that inhibit sKATP channels they were unable to block preconditioning protection against stunning (glibenclamide) or conversely, blocked preconditioning at doses that do not inhibit these channels (HMR1098). Moreover, both mKATP channel agonists (diazoxide) and antagonists (5HD) protected against stunning, a response that could be due to their effect via an alternative mitochondrial pathway.

Cross-Talk Between PKA and Akt Protects Endothelial Cells From Apoptosis in the Late Ischemic Preconditioning

The aim of this study was to explore the molecular mechanisms involved in late preconditioning-induced cell protection in endothelial cells. Preconditioning (PC) was induced by exposing bovine aortic endothelial cells (BAECs) to 3 cycles of 15 minutes of hypoxia followed by 15 minutes of reoxygenation. A 12-hour period of hypoxia induced cell death in 60% of BAECs (48+/-5% apoptosis, 12+/-4% necrosis). Early and late PC decreased hypoxia-induced apoptotic (25+/-5% and 28+/-4%, respectively) and necrotic (6+/-3%, and 8+/-2%, respectively) cell death. Consistently, hypoxia-induced caspase-3 cleavage was reduced by PC. Pretreatment with H89 (protein kinase A [PKA] inhibitor), LY294002 (phosphatidyl-inositol-3-kinase [PI3K] inhibitor), and N-acetyl-cysteine (antioxidant) abrogated late PC-induced cell protection, whereas inhibition of protein kinase C by Go6983, and of nitric oxide synthesis by L-NAME,1400W and bovine eNOS siRNA did not. In addition, in early and late PC, PKA physically interacted with the phosphorylated form of Akt, suggesting that PKA is required for Akt phosphorylation. Expression of PKA and Akt dominant negative mutants inhibited ischemic late PC-induced protection, indicating that these kinases play a key role in late PC-mediated cell protection. Late ischemic PC protects BAECs against hypoxia through PKA- and PI3K-dependent activation of Akt.

The shy Angeli and his elusive creature: the HNO route to vasodilation

what we now call Angeli's salt (AS) was discovered more than a century ago by the Italian chemist Angelo Angeli (Fig. 1) . He found that “salts of nitroxylaminic acid are readily resolved into the corresponding nitrites and the unsaturated residue nitroxyl” (HNO), proposing their use as suppliers of HNO (3). However, by analogy with the genial but very reclusive personality of the discoverer (17), the physiological properties of HNO didn't draw too much attention until early 1990s. In their seminal work, Fukuto and colleagues (19) reported that HNO elicits vasorelaxation in both the rabbit aorta and bovine intrapulmonary artery by a soluble guanylate cyclase (sGC)- dependent pathway. Later, it was evident that the thiol-donating agent l-cysteine can discriminate the vasodilatative profile of HNO from that of nitric oxide (NO·) or nitrosothiols: AS/HNO action can be blocked by this agent, whereas the NO· effect is potentiated (36). In combination with the suggestion that NO· is the only species able to directly activate sGC (9), these data led to the conclusion that HNO-induced vasorelaxation is due to its intracellular conversion to NO· with subsequent activation of sGC. For several years, this idea has relegated HNO to a mere precursor of the presence and biological activity of NO·, de facto negating to HNO its own right to exist.

Early Anesthetic Preconditioning in Mixed Cortical Neuronal-Glial Cell Cultures Subjected to Oxygen-Glucose Deprivation: The Role of Adenosine Triphosphate Dependent Potassium Channels and Reactive Oxygen Species in Sevoflurane-Induced Neuroprotection

The purpose of the present study, on mixed cortical neuronal-glial cell cultures subjected to transient oxygen-glucose deprivation (OGD) was: i) to compare the neuroprotection afforded by sevoflurane added either before (preconditioning) or during (direct neuroprotection) the OGD and ii) to explore the possible involvement of adenosine triphosphate-sensitive potassium (KATP) channels and intracellular reactive oxygen species (ROS) levels in the mechanism of the early preconditioning effect of sevoflurane. Mature mixed cortical neuronal-glial cell cultures were exposed to 90-min OGD in an anaerobic chamber followed by reoxygenation. Sevoflurane (0.03-3.4 mM) was randomly administered for 90 min and discontinued 60 min before OGD (early preconditioning) or during the 90-min OGD (direct neuroprotection). Cell death was quantified 24 h after the OGD by lactate dehydrogenase release into the bathing medium. Intracellular ROS generation was assessed at the end of sevoflurane preconditioning using 2',7'-dichlorofluorescin diacetate. Sevoflurane preconditioning elicited a potent threshold-dependent neuroprotective effect at concentrations higher than 0.07 mM and sevoflurane added during OGD elicited a dose dependent neuroprotective effect. Blockers of KATP channels (glibenclamide 0.3 microM and 5 hydroxydecanoic acid 50 microM), or ROS-scavengers (N-2-mercaptopropionyl glycine 100 microM and N-acetylcysteine 50 microM), although they did not affect cell viability, counteracted the neuroprotection produced by early sevoflurane preconditioning. Sevoflurane exposure during preconditioning induced a significant increase in ROS levels which was prevented by both ROS scavengers and blockers of KATP channels. Early sevoflurane preconditioning induced a threshold-dependent protection of mixed cortical neuronal-glial cell cultures against OGD by mechanisms that seem to involve opening KATP channels, thereby leading to generation of ROS.

Helium-Induced Early Preconditioning and Postconditioning Are Abolished in Obese Zucker Rats in Vivo

Preconditioning is abolished in the prediabetic Zucker obese rat. It has been shown that prevention of mitochondrial permeability transition pore (mPTP) opening is involved in preconditioning by the noble gas helium. Here, we investigated: 1) whether helium induces pre- and postconditioning in Zucker rats and 2) whether possible regulators of the mPTP [i.e., mitochondrial respiration or the extracellular signal-regulated kinase (Erk) 1/2, Akt/glycogen synthase kinase (GSK)-3beta signaling pathway] are influenced. Anesthetized Zucker lean (ZL) and Zucker obese (ZO) rats were randomized to seven groups. Control animals were not treated (ZL-/ZO-Con). Preconditioning groups (ZL-/ZO-He-PC) inhaled 70% helium for 3 x 5 or 6 x 5 min, and postconditioning groups (ZL-/ZO-He-PostC) inhaled 70% helium for 15 min at the onset of reperfusion. Animals underwent 25 min of ischemia and 120 min of reperfusion. In additional experiments, hearts were excised after the third helium exposure for analysis of mitochondrial respiration and for Western blot analysis of Erk1/2, Akt, and GSK-3beta phosphorylation. Helium reduced infarct size from 52 +/- 3% (mean +/- S.E.) to 32 +/- 2% and 37 +/- 2% in ZL rats (ZL-HE-PC, ZL-He-PostC), respectively, but not in ZO rats [ZO-He-PC, 56 +/- 3%; ZO-He-PC (6x), 57 +/- 4%; and ZO-He-PostC, 51 +/- 3% versus ZO-Con, 54 +/- 3%]. Mitochondrial respiration analysis showed that helium causes mild uncoupling in ZL rats (2.27 +/- 0.03 versus 2.51 +/- 0.03) but not in ZO rats (2.52 +/- 0.04 versus 2.52 +/- 0.03). Helium had no effect on Erk1/2 and Akt phosphorylation. GSK-3beta phosphorylation during ischemia was reduced after helium application in ZL but not in ZO rats. Helium-induced preconditioning is abolished in obese Zucker rats in vivo, probably caused by a diminished effect of helium on mitochondrial respiration.

Abstract 1599: Hydrogen Sulfide Mediates Myocardial Preconditioning via Upregulation of Antioxidant and Anti-Apoptotic Signaling Pathways

The emergence of hydrogen sulfide (H 2 S) as a potent cardioprotective mediator necessitates the elucidation of its cytoprotective mechanisms. Therefore, we evaluated potential mechanisms of H 2 S-mediated cardioprotection using an in vivo model of preconditioning (PC). The H 2 S donor, IK1001 (100 μg/kg), or vehicle was administered to mice via an intravenous injection 24 hours prior to left coronary artery occlusion and reperfusion. Mice were subjected to 45 min of myocardial ischemia followed by reperfusion for up to 24 hr, during which time the extent of myocardial infarction was evaluated, serum troponin-I levels were measured, and the degree of oxidative stress was assessed. In separate studies, mice were treated with IK1001 and myocardial tissue was collected during both the early (30 min and 2hr) and late (24 hr) PC periods to evaluate potential cellular targets of H 2 S. IK1001 provided profound protection against ischemic injury as evidenced by significant decreases in infarct size, serum troponin-I levels, and oxidative stress. Additional studies revealed that during the early PC period H 2 S increased the nuclear localization of Nrf-2, a transcription factor that regulates the gene expression of a number of antioxidants, and increased the nuclear localization of phosphorylated STAT-3. During the late PC period, H 2 S increased the expression of the antioxidants, Trx-1 and Trx-2, increased the expression of HSP90, HSP70, Bcl-2, and Bcl-xL and also inactivated the pro-apoptogen Bad. Our results reveal that the cardioprotective effects of H 2 S are mediated in large part by a combination of antioxidant and anti-apoptotic signaling.

An update of cardioprotective effect of morphine preconditioning on ischemia-reperfuson injury

Morphine can mimic effect of ischemia preconditioning and show some beneficial cardioprotective effects on animal hearts undertaken ischemia/reperfusion injury. Morphine preconditioning confers biphasie eardioprotection: early preconditioning and delayed preconditioning. This kind of protection is mostly mediated by opioid receptor, mitochondrial KATP channel, iNOS and COX-2. Beyond the acknowledgement of its molecular mechanism of morphine preconditioning, it is also important to induce related clinical research. Key words: morphine; ischemic preconditioning, myocardial; ischemia/reperfusion injury