Late Phase Of Preconditioning Research Articles

Effects of preconditioned plasma collected during the late phase of remote ischaemic preconditioning on ventricular arrhythmias caused by myocardial ischaemia reperfusion in rats.

ObjectiveThe administration of preconditioned plasma collected during the late phase of preconditioning has been shown to reduce myocardial infarct size. This study aimed to investigate if preconditioned plasma could attenuate ventricular arrhythmias in a rat model in vivo.MethodsEighty rats were randomized to eight groups (10 rats/group). Two groups provided preconditioned or non-preconditioned plasma 48 h after transient limb ischaemia or the control protocol. Six groups of ischaemia-reperfusion (IR) rats received normal saline, non-preconditioned plasma, or preconditioned plasma, respectively, 1 h (groups A1, A2, A3) or 24 h (groups B1, B2, B3) before undergoing myocardial IR. Electrocardiograms were monitored using a BIOPAC system, and the incidence and duration of ventricular tachycardia (VT) and ventricular fibrillation (VF) were analysed.ResultsNo significant differences existed in the incidence and duration of VT or VF among groups A1–A3 or in the incidence and duration of VT among groups B1–B3. However, there was a significantly lower incidence and shorter duration of VF in group B3 rats than in group B1 rats.ConclusionPreconditioned plasma collected during the late phase of preconditioning can reduce the incidence and duration of VF compared with normal saline, suggesting its anti-arrhythmic potential.

Influence of the new tiazoloindole derivative on organism resistance to hypoxia in the early and late periodsof preconditioning

The aim of this investigation was to study an ability of tiazoloindole derivative encoded VM-606 to influence the lifespan of mice in experimental acute hypoxia with hypercapnia and hypobaric hypoxia in early and late phase of preconditioning. It was found that the use of VM-606 in dose of 50 mg/kg leads to significant increase in the duration of animal life in case of subsequent acute hypoxia in early phase of preconditioning, but doesn’t produce effect in the late phase of preconditioning.

Influence of the new tiazoloindole derivative on the organism resistance to hypoxia in the early and late periods of preconditioning

The aim of this investigation was to study an ability of tiazoloindole derivative encoded VM-606 to influence the lifespan of mice in experimental acute hypoxia with hypercapnia and hypobaric hypoxia in early and late phase of preconditioning. It was found that the use of VM- 606 in dose of 50 mg/kg leads to significant increase in the duration of animal life in case of subsequent acute hypoxia in early phase of preconditioning, but doesn’t produce effect in the late phase of preconditioning.

The role of hypoxia-inducible factor-1 and vascular endothelial growth factor in late-phase preconditioning with xenon, isoflurane and levosimendan in rat cardiomyocytes

The protective effects of late-phase preconditioning can be triggered by several stimuli. Unfortunately, the transfer from bench to bedside still represents a challenge, as concomitant medication or diseases influence the complex signalling pathways involved. In an established model of primary neonatal rat cardiomyocytes, we analysed the cardioprotective effects of three different stimulating pharmaceuticals of clinical relevance. The effect of additional β-blocker treatment was studied as these were previously shown to negatively influence preconditioning. Twenty-four hours prior to hypoxia, cells pre-treated with or without metoprolol (0.55 µg/ml) were preconditioned with isoflurane, levosimendan or xenon. The influences of these stimuli on hypoxia-inducible factor-1α (HIF-1α), vascular endothelial growth factor (VEGF) as well as inducible and endothelial nitric synthase (iNOS/eNOS) and cyclooxygenase-2 (COX-2) were analysed by polymerase chain reaction and western blotting. The preconditioning was proved by trypan blue cell counts following 5 h of hypoxia and confirmed by fluorescence staining. Five hours of hypoxia reduced cell survival in unpreconditioned control cells to 44 ± 4%. Surviving cell count was significantly higher in cells preconditioned either by 2 × 15 min isoflurane (70 ± 16%; P = 0.005) or by xenon (59 ± 8%; P = 0.049). Xenon-preconditioned cells showed a significantly elevated content of VEGF (0.025 ± 0.010 IDV [integrated density values when compared with GAPDH] vs 0.003 ± 0.006 IDV in controls; P = 0.0003). The protein expression of HIF-1α was increased both by levosimendan (0.563 ± 0.175 IDV vs 0.142 ± 0.042 IDV in controls; P = 0.0289) and by xenon (0.868 ± 0.222 IDV; P < 0.0001) pretreatment. A significant elevation of mRNA expression of iNOS was measureable following preconditioning by xenon but not by the other chosen stimuli. eNOS mRNA expression was found to be suppressed by β-blocker treatment for all stimuli. In our model, independently of the chosen stimulus, β-blocker treatment had no significant effect on cell survival. We found that the stimulation of late-phase preconditioning involves several distinct pathways that are variably addressed by the different stimuli. In contrast to isoflurane treatment, xenon-induced preconditioning does not lead to an increase in COX-2 gene transcription but to a significant increase in HIF-1α and subsequently VEGF.

Interleukin 6 protects H2O2-induced cardiomyocytes injury through upregulation of prohibitin via STAT3 phosphorylation

Hydrogen peroxide (H(2)O(2)) is a potent reactive oxygen species that causes cardiomyocytes injury. As an important cytokine, interleukin 6 (IL-6) has cardioprotective effects as it plays an essential role in the late phase of preconditioning. Our work is to investigate if IL-6 preconditioning has protective effects on neonatal rat ventricular cardiomyocytes in response to H(2)O(2) and its underlying mechanism. Gel-based comparative proteomic approach along with small interfering RNA (siRNA) and Western blot analysis was used to analyse mechanisms of IL-6 preconditioning on H(2)O(2)-induced neonatal rat ventricular cardiomyocytes injury. IL-6 preconditioning protected cardiomyocytes against H(2)O(2)-induced cell death. Proteomic analysis showed that IL-6 pretreatment further increased the expression of prohibitin and improved the viability of cardiomyocytes exposed to H(2)O(2). Knocking down of prohibitin with siRNA abrogated this protection by increasing apoptosis rate. Tyrosine kinase inhibitor AG490 decreased signal transducers and activators of transcription 3 (STAT3) phosphorylation and down-regulated prohibitin expression in cardiomyocytes pretreated with IL-6 and exposed to H(2)O(2), which further dampened the protective effects of IL-6 preconditioning. Our results provide direct evidence that prohibitin is a protective factor of IL-6 preconditioning in H(2)O(2)-induced neonatal rat ventricular cardiomyocytes death. The upregulation of prohibitin by IL-6 is, at least, partially regulated through STAT3 phosphorylation.

Effects of metoprolol on hypoxia- and isoflurane-induced late-phase preconditioning

Objectives: Cardioprotection during surgical procedure has in vitro been achieved by preconditioning (pc). Yet so far translation into clinical therapy has failed. We investigated the effect of metoprolol on the late phase of pc which is mediated via gene transcription.

Hydrogen sulfide triggers late-phase preconditioning in postischemic small intestine by an NO- and p38 MAPK-dependent mechanism

Hydrogen sulfide (H(2)S) is one of three endogenous gases, along with carbon monoxide (CO) and nitric oxide (NO), that exert a variety of important vascular actions in vivo. Although it has been demonstrated that CO or NO can trigger the development of a preconditioned phenotype in postischemic tissues, it is unclear whether H(2)S may also induce protection in organs subsequently exposed to ischemia-reperfusion (I/R). In light of these observations, we postulated that preconditioning with the exogenous H(2)S donor sodium hydrosulfide (NaHS-PC) would inhibit leukocyte rolling (LR) and adhesion (LA) induced by I/R. We used intravital microscopic techniques to demonstrate that NaHS-PC 24 h, but not 1 h, before I/R causes postcapillary venules to shift to an anti-inflammatory phenotype in wild-type (WT) mice such that these vessels fail to support LR and LA during reperfusion. The protective effect of NaHS-PC on LR was largely abolished by coincident pharmacological inhibition of NO synthase (NOS) in WT animals and was absent in endothelial NOS-deficient (eNOS(-/-)) mice. A similar pattern of response was noted in WT mice treated concomitantly with NaHS plus p38 mitogen-activated protein kinase (MAPK) inhibitors (SB 203580 or SK-86002). Whereas the reduction in LA induced by antecedent NaHS was attenuated by pharmacological inhibition of NOS or p38 MAPK in WT mice, the antiadhesive effect of NaHS was still evident in eNOS(-/-) mice. Thus NaHS-PC prevents LR and LA by triggering the activation of an eNOS- and p38 MAPK-dependent mechanism. However, the role of eNOS in the antiadhesive effect of NaHS-PC was less prominent than its effect to reduce LR.

The Early Phase of Preconditioning is Abrogated by COX‐2 Inhibition, but not by a Specific Prostaglandin Receptor Antagonist

COX‐2 is an important mediator of cardiovascular protection after ischemia and reperfusion and is essential for ischemic preconditioning (PC), mediated by the synthesis of PGE2 and/or PGI2. Recently, the importance of the PGI2 in the late phase of ischemic preconditioning has been established. The present study was designed to determine the contribution of PGI2 to the early phase of ischemic preconditioning. Male New Zealand white rabbits were administered the prostaglandin receptor (IP) antagonist RO3244794 (3mg/kg), nimesulide (5mg/kg), or vehicle thirty minutes prior to PC, 30 minutes of ischemia and 4 hours of reperfusion. PC reduced myocardial infarct size as a percent of area at risk (12.0 +/− 2.2 vs. control 42.3 +/− 2.9; P &lt; 0.001) and treatment with the COX‐2 inhibitor nimesulide abolished the protective effect (41.0 +/− 2.7). Surprisingly, treatment with the IP receptor antagonist had no effect on PC (17.0 +/− 3.1; P &lt; 0.001 vs. control). The data suggest that COX‐2 does not protect the myocardium from the early phase of preconditioning through the production of PGI2. These results differ from those seen in the late phase of PC, where RO3244794 abrogated the protective effects of PC, suggesting that the upregulation of COX‐2 differentially modulates protection in the early and late phases of ischemic preconditioning.

Repeated exercise stress testing identifies early and late preconditioning

Background: The warm-up phenomenon has been considered to trigger preconditioning. We investigated whether repeated exercise treadmill tests in humans are capable of inducing adaptation to ischemia by triggering both the early and late phase of preconditioning. Methods: In 25 consecutive patients with stable coronary artery disease, four repeated treadmill tests were performed. Thirty minutes following the first test (T1) a second one was performed (T2), followed 6 h later by a third test (T3). Twenty-four hours later all patients were subjected to a fourth exercise test (T4). In every fifth patient, simultaneous echocardiographic examination was performed at the time of the exercise tests in an attempt to reveal ischemic abnormalities. Results: At baseline there was no difference between the variables. At ST segment depression >1.5 mm, the rate-pressure product (RPP) was higher in T2 and T4 (231.3±17.9 and 232.6±15.8 mm Hg s 10 2) than in T1 and T3 (210±17 and 210.2±16.7 mm Hg s 10 2), p<0.001. Additionally, time to the onset of chest pain was longer in T2 and T4 (430.8±60.5 and 438±47 s) than in T1 and T3 (345.6±69 and 345.6±58 s), p<0.001. At peak exercise, the RPP was higher in T2 and T4 (278.6±21.6 and 278.3±19.6 mm Hg s 10 2) than in T1 and T3 (255.6±23.1 and 256.6±23 mm Hg s 10 2), p<0.001. The wall motion score index was higher in T1 and T3 (1.65±0.17 and 1.53±0.16) than in T2 and T4 (1.3±0.07 and 1.37±0.1), p<0.001. Conclusion: By using repeated exercise treadmill tests both the early and late phase of protection can be obtained.

Inducible nitric oxide synthase modulates cyclooxygenase-2 activity in the heart of conscious rabbits during the late phase of ischemic preconditioning.

Cyclooxygenase-2 (COX-2) is known to mediate the cardioprotective effects of the late phase of ischemic preconditioning (PC); however, the signaling pathways involved in COX-2 induction following ischemic PC are unknown. In addition, although inducible nitric oxide synthase (iNOS) has been identified as a co-mediator of late PC together with COX-2, the interaction between iNOS and COX-2 in the heart is unknown. Using conscious rabbits, we found that the induction of COX-2 expression 24 hours after ischemic PC was blocked by pretreatment with inhibitors of protein kinase C (PKC), Src protein tyrosine kinases (PTKs), and nuclear factor-kappaB (NF-kappaB) but not by inhibitors of NOS or scavengers of reactive oxygen species (ROS). The selective iNOS inhibitors SMT and 1400W, given 24 hours after PC, abrogated the increase in myocardial prostaglandin E2 (PGE2) and 6-keto-PGF1alpha, whereas the selective soluble guanylate cyclase inhibitor ODQ had no effect. COX-2 selective inhibitors (celecoxib and NS-398) did not affect iNOS activity. These results demonstrate that (i) ischemic PC upregulates cardiac COX-2 via PKC-, Src PTK-, and NF-kappaB-dependent signaling pathways, whereas generation of NO and ROS is not necessary, and (ii) the activity of newly synthesized COX-2 following PC requires iNOS-derived NO whereas iNOS activity is independent of COX-2-derived prostanoids, indicating that COX-2 is located downstream of iNOS in the protective pathway of late PC. The data also indicate that iNOS modulates COX-2 activity via cGMP-independent mechanisms. To our knowledge, this is the first demonstration that iNOS-derived NO drives prostanoid synthesis by COX-2 in the heart. NO-mediated activation of COX-2 may be a heretofore unrecognized mechanism by which NO exerts its salubrious effects in the late phase of PC.

Bradykinin B2Receptor is Involved in the Late Phase of Preconditioning in Rabbit Heart

C. Kositprapa, R. A. Ockaili and R. C. Kukreja. Bradykinin B2Receptor is Involved in the Late Phase of Preconditioning in Rabbit Heart. Journal of Molecular and Cellular Cardiology (2001) 33, 0000–0000. Activation of bradykinin B2receptor has been shown to confer short-term cardioprotection against a prolonged ischemic insult. The present study was designed to delineate the role of B2receptor in the late phase of ischemic preconditioning. Anesthetized, open chest, male rabbits were assigned to 1 of 6 groups (n=8/group). Ischemic preconditioning was elicited by four 5-min occlusion periods interspersed with 10 min of reperfusion. To test the role of B2receptors, rabbits were pretreated with specific receptor antagonist, HOE-140 (1 μ gm/kg IV bolus), 15 min prior to ischemic preconditioning. Additionally, two separate groups of animals were treated by intra-atrial infusion with either bradykinin (0.05 μ g/kg/min for 15 min) or saline. Twenty-four hours later, the animals were subjected to 30 min of ischemia and 3 h of reperfusion. Infarct size was determined by tetrazolium staining. Ischemic preconditioning reduced infarct size from 43.09±4.66 to 20.65±1.87 (% risk area, P<0.05), which was blocked by HOE-140 as indicated by increase in infarct size (36.72±4.04%, P<0.05). HOE-140 treatment had no significant effect on infarct size in the sham group. Similarly, intra-atrial infusion of bradykinin caused decrease in the infarct size from 52.36±2.17% in the saline control group to 22.83±1.71% (P<0.05). The degree of infarct limitation with bradykinin was comparable to ischemic preconditioning (20.65±1.87%v 22.83±1.71%, P>0.05). For the first time, these results provide evidence for the involvement of B2receptor in the genesis of late phase of ischemic preconditioning.

Hypoxia-inducible factor 1: control of oxygen homeostasis in health and disease.

Hypoxia-inducible factor 1 (HIF-1) is a transcriptional activator that mediates changes in gene expression in response to changes in cellular oxygen concentrations. HIF-1 is a heterodimer consisting of an oxygen-regulated HIF-1 alpha subunit and a constitutively expressed HIF-1 beta subunit. In mice, complete HIF-1 alpha deficiency results in embryonic lethality at midgestation because of cardiac and vascular malformations. Analyses of animal and cell culture models as well as human tissue have provided evidence that HIF-1 plays important roles in the pathophysiology of preeclampsia, intrauterine growth retardation, hypoxia-mediated pulmonary hypertension, and cancer. HIF-1 promotes neovascularization in response to myocardial or retinal ischemia by activating transcription of the gene encoding vascular endothelial growth factor. HIF-1 may also mediate the protective response to cerebral ischemia known as late-phase preconditioning.

Protein kinases and kinase-modulated effectors in the late phase of ischemic preconditioning.

In the 15 years since the first publication on ischemic preconditioning (PC), our knowledge of this phenomenon has increased exponentially. While the original studies described the early phase of ischemic PC, we now know that a second or late phase of ischemic PC also exists. In particular, the late phase of PC is triggered by factors such as adenosine, opioids, radicals, and nitric oxide. These factors in turn initiate a molecular chain reaction, which includes activation of serine/threonine kinases, tyrosine kinases, and mitogen-activated protein kinases. Subsequently, this cascade of reactions modulates a plethora of cardioprotective proteins including heat shock proteins, KATP channels, nitric oxide synthase, cyclooxygenase-2, and antioxidants. However, despite this phenomenal amount of information, the construction of a unifying hypothesis describing the signaling mechanism of late PC has proved challenging. The purpose of this article, therefore, is to review the current literature and hypothesis regarding the signaling system in the late phase of ischemic PC, to tackle areas of controversy within this model, and to address potential future directions of investigation that will hopefully promote the generation of a unifying paradigm.

Role of oxidants in the signaling pathway of preconditioning.

This review focuses on the possible role of reactive oxygen species in the pathogenesis of this phenomenon. Evidence in support of a role of oxidants in preconditioning has come from the observation that administration of oxygen radical scavengers during the reperfusion period following the initial "preconditioning" ischemia could prevent the phenomenon. In addition, a brief exposure to a low, nontoxic dose of oxygen radicals may reproduce the beneficial effects of ischemic preconditioning, thus suggesting that radicals can directly trigger the preconditioning pathway. To explain the effects of oxidants in this setting, it has been suggested that reperfusion after the initial, "preconditioning" ischemic episode results in the generation of relatively low amounts of oxygen radicals, which are insufficient to determine cell necrosis, but nevertheless could modify cellular activities that have been implicated as mediators of the preconditioning phenomenon. Recent evidence suggests that low levels of oxidants may have a modulatory role on several cell functions. Possible mechanisms of oxidant-mediated protection might be protein kinase C and other kinases, ATP-dependent potassium channels, or changes in sulfhydryl group redox state, while an effect on adenosine metabolism, or the induction of myocardial stunning presumably does not contribute to oxidant-mediated preconditioning. Finally, de novo protein synthesis and gene expression, and increased antioxidant defenses might be involved in the late phase of preconditioning. In summary, available data strongly suggest that oxygen radicals might be possible mediators of preconditioning. However, further investigation is required to clearly elucidate their exact role and mechanisms of action.

Surviving ischemia: adaptive responses mediated by hypoxia-inducible factor 1

While the other Perspectives in this series provide readers with state-of-the-art overviews of responses to ischemia on an organ-by-organ basis, I focus here on a single transcription factor, hypoxia-inducible factor 1 (HIF-1), and its role in the physiologic responses to hypoxia and ischemia. Whether in the brain, heart, kidneys, lungs, or muscle, HIF-1 is essential for ischemia-induced angiogenesis, as described by Isner (this Perspective series, ref. 1), and it may also be a critical mediator of late-phase preconditioning, as described by Williams and Benjamin (this Perspective series, ref. 2). For these reasons, HIF-1 and the genes under its control may represent novel therapeutic targets for ameliorating the effects of ischemia in a variety of clinical settings.