Remote Ischemic Postconditioning Research Articles

A feasible strategy for focal cerebral ischemia-reperfusion injury: remote ischemic postconditioning.

It is difficult to control the degree of ischemic postconditioning in the brain and other ischemia-sensitive organs. Remote ischemic postconditioning could protect some ischemia-sensitive organs through measures on terminal organs. In this study, a focal cerebral ischemia-reperfusion injury model was established using three cycles of remote ischemic postconditioning, each cycle consisted of 10-minute occlusion of the femoral artery and 10-minute opening. The results showed that, remote ischemic postconditioning significantly decreased the percentage of the infarct area and attenuated brain edema. In addition, inflammatory nuclear factor-κB expression was significantly lower, while anti-apoptotic Bcl-2 expression was significantly elevated in the cerebral cortex on the ischemic side. Our findings indicate that remote ischemic postconditioning attenuates focal cerebral ischemia/reperfusion injury, and that the neuroprotective mechanism is mediated by an anti-apoptotic effect and reduction of the inflammatory response.

Ischemic preconditioning produces more powerful anti-inflammatory and cardioprotective effects than limb remote ischemic postconditioning in rats with myocardial ischemia-reperfusion injury

Background Both ischemic preconditioning (IPC) and limb remote ischemic postconditioning (LRIPOC) have been shown to possess significantly different cardioprotective effects against the myocardial ischemia reperfusion injury (IRI), but no study has compared the anti-inflammatory effects of IPC and LRIPOC during myocardial IRI process. We hypothesized that IPC and LRIPOC would produce different anti-inflammatory effects in an in vivo rat model with myocardial IRI. Methods Eighty rats were randomly allocated into four equal groups: sham group, IRI group, IPC group and LRIPOC group. In 10 rats randomly selected from each group, serum levels of TNF-α, HMGB1, ICAM1, IL-1, IL-6 and IL-10 were assessed, and infarct size was determined. In another 10 rats of each group, myocardial levels of TNF-α, HMGB1, ICAM1, IL-1, IL-6 and IL-10 in both ischemic and non-ischemic regions were measured. Results The infarct size was significantly lower in IPC and LRIPOC groups than in IRI group. The serum and myocardial levels of pro-inflammatory cytokines including TNF-α, HMGB1, ICAM1, IL-1 and IL-6 during reperfusion were significantly reduced in IPC and LRIPOC groups compared to IRI group. As compared to the IPC group, infarct size, serum level of TNF-α at 60 minutes of reperfusion, serum levels of HMGB1 and ICAM1 at 120 minutes of reperfusion, myocardial levels of TNF-α, ICAM1, IL-1 and IL-6 in the ischemic region, myocardial levels of ICAM1, IL-1 and IL-6 in the non-ischemic region were significantly increased in the LRIPOC group. Conclusions In the rats with myocardial IRI, IPC produces more powerful inhibitory effects on local myocardial and systemic inflammatory responses than LRIPOC. This may be partly attributed to more potent cardioprotection produced by IPC.

Remote Ischemic Post-Conditioning of the Lower Limb During Primary Percutaneous Coronary Intervention Safely Reduces Enzymatic Infarct Size in Anterior Myocardial Infarction: A Randomized Controlled Trial

This study sought to evaluate whether remote ischemic post-conditioning (RIPC) could reduce enzymatic infarct size in patients with anterior ST-segment elevation myocardial infarction undergoing primary percutaneous coronary intervention (pPCI). Myocardial reperfusion injury may attenuate the benefit of pPCI. In animal models, RIPC mitigates myocardial reperfusion injury. One hundred patients with anterior ST-segment elevation myocardial infarction and occluded left anterior descending artery were randomized to pPCI + RIPC (n = 50) or conventional pPCI (n = 50). RIPC consisted of 3 cycles of 5 min/5 min ischemia/reperfusion by cuff inflation/deflation of the lower limb. The primary endpoint was infarct size assessed by the area under the curve of creatinine kinase-myocardial band release (CK-MB). Secondary endpoints included the following: infarct size assessed by cardiac magnetic resonance delayed enhancement volume; T2-weighted edema volume; ST-segment resolution >50%; TIMI (Thrombolysis In Myocardial Infarction) frame count; and myocardial blush grading. Four patients (2 RIPC, 2 controls) were excluded due to missing samples of CK-MB. A total of 96 patients were analyzed; median area under the curve CK-MB was 8,814 (interquartile range [IQR]: 5,567 to 11,325) arbitrary units in the RIPC group and 10,065 (IQR: 7,465 to 14,004) arbitrary units in control subjects (relative reduction: 20%, 95% confidence interval: 0.2% to 28.7%; p = 0.043). Seventy-seven patients underwent a cardiac magnetic resonance scan 3 to 5 days after randomization, and 66 patients repeated a second scan after 4 months. T2-weighted edema volume was 37 ± 16 cc in RIPC patients and 47 ± 22 cc in control subjects (p = 0.049). ST-segment resolution >50% was 66% in RIPC and 37% in control subjects (p = 0.015). We observed no significant differences in TIMI frame count, myocardial blush grading, and delayed enhancement volume. In patients with anterior ST-segment elevation myocardial infarction, RIPC at the time of pPCI reduced enzymatic infarct size and was also associated with an improvement of T2-weighted edema volume and ST-segment resolution >50%. (Remote Postconditioning in Patients With Acute Myocardial Infarction Treated by Primary Percutaneous Coronary Intervention [PCI] [RemPostCon]; NCT00865722).

Does remote ischaemic preconditioning with postconditioning improve clinical outcomes of patients undergoing cardiac surgery? Remote Ischaemic Preconditioning with Postconditioning Outcome Trial

The aim of this study was to evaluate whether remote ischaemic preconditioning (RIPC) combined with remote ischaemic postconditioning (RIPostC) improves the clinical outcomes of patients undergoing cardiac surgery. From June 2009 to November 2010, 1280 patients who underwent elective cardiac surgery were randomized into the RIPC with RIPostC group or the control group in the morning of the surgery. In the RIPC with RIPostC group, four cycles of 5-min ischaemia and 5-min reperfusion were administered twice to the upper limb-before cardiopulmonary bypass (CPB) or coronary anastomoses for RIPC and after CPB or coronary anastomoses for RIPostC. The primary endpoint was the composite of major adverse outcomes, including death, myocardial infarction, arrhythmia, stroke, coma, renal failure or dysfunction, respiratory failure, cardiogenic shock, gastrointestinal complication, and multiorgan failure. Remote ischaemic preconditioning with RIPostC did not reduce the composite outcome compared with the control group (38.0 vs. 38.1%, respectively; P = 0.998) and there was no difference in each major adverse outcome. The intensive care unit and hospital stays were not different between the two groups. However, in the off-pump coronary artery bypass surgery subgroup, multivariate logistic regression analysis revealed that RIPC with RIPostC was related to increased composite outcome (odds ratio: 1.54; 95% confidence interval: 1.02-2.30; P = 0.038). Remote ischaemic preconditioning with RIPostC by transient upper limb ischaemia did not improve clinical outcome in patients who underwent cardiac surgery.

Remote ischaemic postconditioning: does it protect against ischaemic damage in percutaneous coronary revascularisation? Randomised placebo-controlled clinical trial

ObjectiveDetermine whether remote ischaemic postconditioning (RIP) protects against percutaneous coronary intervention-related myocardial infarction (PCI-MI).DesignSingle-centre, randomised, blinded to the researchers, clinical trial. ClinicalTrials.gov (NCT 01113008).SettingTertiary hospital centre.Patients232 patients underwent elective PCI...

Remote Ischemic Postconditioning Promotes the Survival of Retinal Ganglion Cells after Optic Nerve Injury

Ischemic conditioning, the application of a mild ischemic stimulus to an ischemia-sensitive structure like the heart or brain either before (preconditioning) or after (postconditioning) its exposure to a lethal ischemic insult, is known to switch on endogenous protective mechanisms. However, most studies of its neuroprotective effect in the central nervous system (CNS) have focused on ischemic damage or related conditions like hypoxia, while its potential in treating other neural diseases remains uncertain. In particular, the recent discovery of remote ischemic postconditioning whereby mild ischemia applied to a region remote from the target after the main ischemic insult also confers protection offers an attractive paradigm to study its potential in other types of neural injury. Retinal ganglion cells damaged by optic nerve transection undergo extensive cell death. However, application of a series of mild ischemic/reperfusion cycles to the hind limb (limb remote ischemic postconditioning) at 10 min or 6 h after optic nerve cut was found to promote ganglion cell survival at 7 days post-injury, with the 10 min postconditioning still exerting protection at 14 days post-injury. Concomitant with the increased ganglion cell survival, 51 % more ganglion cells expressed the small heat shock protein HSP27, when remote ischemic postconditioning was performed at 10 min post-injury, as compared to the sham conditioning group. Our results highlight the potential of using remote ischemic postconditioning as a noninvasive neuroprotective strategy in different CNS disorders like spinal cord and traumatic brain injury.

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

Remote ischemic postconditioning (RPostC) is a noninvasive intervention that has demonstrated cardioprotection and neuroprotection in animal studies. Our goal was to investigate the cardio-cerebral protective effects of RPostC on children undergoing open-heart surgery for repair of congenital heart defects (CHD). Children undergoing open-heart repair of CHD were randomly assigned to a RPostC or control group. RPostC was induced by three 5-min cycles of lower limb ischemia and reperfusion using a blood pressure cuff (200mmHg) at the onset of aortic unclamping. Serum cardiac troponin I (cTnI), creatine kinase-MB (CK-MB), neuron-specific enolase (NSE), S100β, cytokines, and clinical outcomes were assessed. There were 35 children in the control group and 34 in the RPostC group. The mean age (3.64±1.95years vs. 3.45±3.02years, P=0.80), weight (15.11±6.91kg vs. 13.40±6.33kg, P=0.37), surgical time (144.82±38.51min vs. 129.92±30.76min, P=0.15), and bypass time (78.01±27.22min vs. 72.52±26.05min, P=0.49) were not different. Compared with the control group, the postoperative levels of cTnI (P=0.037) and CK-MB (P=0.046) were significantly reduced in the RPostC group. Furthermore, the MAP was higher (P=0.008), and ICU stay (36.87±3.30h vs. 60.57±7.35h, P=0.006) and postoperative hospital stay (8.56±1.50days vs. 10.06±2.41days, P=0.048) were shorter in the RPostC group than in the control group. However, the postoperative CVP and the concentrations of NSE, S100β, CRP, TNF-α, IL-1β, IL-6, and IL-10 were not significantly different. RPostC significantly alleviates cardiac injury in children undergoing open-heart repair of CHD and may also reduce cerebral injury.

Endoplasmic Reticulum Stress Pathway Involvement in Local and Remote Myocardial Ischemic Conditioning

Remote ischemic perconditioning (RIPer) and local ischemic postconditioning (IPost) are promising methods to decrease ischemia-reperfusion injury. We tested whether these two methods were effective in reducing infarct size through activation of endoplasmic reticulum (ER) stress response, a potential survival pathway. Rats exposed to myocardial ischemia-reperfusion were allocated to one of six groups: control, no intervention at myocardial reperfusion; IPost, three cycles of 10-s coronary artery occlusion followed by 10-s reperfusion applied at the onset of myocardial reperfusion; RIPer, 10-min limb ischemia followed by 10-min reperfusion initiated during coronary artery occlusion; control + 4-PBA, injection of ER stress inhibitor 4-phenylbutyrate (4-PBA) 1 h before coronary occlusion; IPost + 4-PBA; and RIPer + 4-PBA. Infarct size was significantly reduced in IPost and RIPer groups (33.32% ± 3.65% and 21.86% ± 3.98%, respectively) compared with the control group (54.86% ± 6.01%, P < 0.05). Western blot analysis of GRP78 (glucose-regulated protein) level and cleaved activating transcription factor 6, two ER stress markers, demonstrated an enhancement of ER stress response in IPost group but not in RIPer group at 15-min reperfusion. Furthermore, 4-PBA abolished cardioprotection induced by IPost (infarct size 53.75 ± 3.49 vs. 33.32 ± 3.65%, P < 0.05) but not by RIPer (28.80 ± 10.45% vs. 21.86 ± 3.98%, not statistically significant). GRP78 and cleaved activating transcription factor 6 levels were no longer increased in IPost group after 4-PBA. These findings point to a role for ER stress response in cardioprotection against reperfusion injury in IPost but not RIPer, suggesting differences in cardioprotective mechanisms between local and remote conditioning.

Comparison of the effects of ischemic preconditioning and limb remote ischemic postconditioning on inflammatory response during myocardial ischemia/reperfusion injury in rats in vivo

Objective To compare the effects of ischemic preconditioning with limb remote ischemic postconditioning on inflammatory response during myocardial ischemia/reperfusion injury (I/RI) in rat in vivo.Methods Eighty male Sprague-Dawley rats weighing 250 g-350 g were randomly allocated into four groups (n=20 in each group):sham group (S group); ischemia reperfusion group (I/R group); ischemic preconditioning group (IPC group) and limb remote ischemic postconditioning group (LRIPOC group).In the groups other than the sham group,the myocardial ischemia reperfusion model was preparated by ligation of left anterior descending coronary artery for 30 min followed by 120 min reperfusion.During the process of ischemia and reperfusion,HR and MAP were recorded and the rate pressure product (RPP) at every measuring point was calculated as the index of myocardial oxygen consumption.In ten rats randomly selected from each group,the blood samples were collected from jugular vein at 30,60 min and 120 min after reperfusion.Then,serum concentrations of cardiac troponin I (cTnI),creatine kinase-MB (CK-MB),tumor necrosis factor αt (TNF-α),high mobility group box-1 protein (HMGB-1),intercellular adhesion molecule 1 (ICAM-1),interleukin1 (IL-1),IL-6 and IL-10 were all assessed.At the end of experiment,the infarct volumes were assessed by evans blue and triphenyltetrazolium chloride (TTC) staining.In another ten rats randomly selected from each group,the myocardial contents of TNF-α,HMGB-1,ICAM-1,IL-1,IL-6 and IL-10 in ischemic and non-ischemic regions were all measured after the rats were euthanized.Results The infarct volume was (72±9)％ in I/R group,(36±13)％ in IPC group,and (57±9)％ in LRIPOC group,respectively.And the serum concentration of cTnI was (0.99 ± 0.14) μg/L in I/R group,(0.37 ±0.08) μg/L in IPC group,and (0.54±0.07) μg/L in LRIPOC group,separately.In addition,the serum concentration of CK-MB was (110±13) μg/L in I/R group,(38±8) μ g/L in IPC group,and (45±6) μg/L in LRIPOC group,respectively.Compared to the I/R group,the infarct volume,serum concentrations of cTnI and CK-MB in both IPC and LRIPOC groups,the serum concentrations of TNF-α at 30,60 min and 120 min after reperfusion,serum concentrations of HMGB-1 at 60 min and 120 min,serum concentrations of ICAM-1,IL-1 and IL-6,myocardial concentrations of TNF-α,HMGB-1,ICAM-1,IL-1 and IL-6 in ischemic region,myocardial concentrations of TNF-α,ICAM-1,IL-1 and IL-6 in non-ischemic region in the IPC group,the serum concentrations of TNF-α at 30,60 min and 120 min after reperfusion,serum concentrations of HMGB-1,ICAM-1,IL-1 and IL-6 at 120 min after reperfusion,myocardial concentrations of TNF-α,HMGB-1,ICAM-1,IL-1 and IL-6 in both ischemic and non-ischemic regions in the LRIPOC group all significantly decreased(P＜0.05).As compared to the IPC group,the infarct volume,serum concentrations of cTnI and CK-MB,serum concentration of TNF-α at 60 min after reperfusion,serum concentrations of HMGB-1 and ICAM-1 at 120 min after reperfusion,myocardial concentrations of TNF-α,ICAM-1,IL-1 and IL-6 in ischemic region,myocardial concentrations of ICAM-1,IL-1 and IL-6 in non-ischemic region significantly increased in the LRIPOC group (P＜0.05).Conclusions The inflammation inhibiting effect of IPC is stronger than that of LRIPOC during myocardial I/RI,which may be one of reasons why the IPC can provide a more powerful protection against myocardial I/RI than the LRIPOC. Key words: Myocardial ischemia/reperfusion injury; Inflammatory response; Ischemic preconditioning; Limb remote ischemic postconditioning

Renoprotective Effect of Remote Ischemic Post-Conditioning by Intermittent Balloon Inflations in Patients Undergoing Percutaneous Coronary Intervention

The aim of the present study was to assess the efficacy of remote ischemic post-conditioning (RIPC) by repeated intermittent balloon inflations in preventing acute kidney injury (AKI) in patients with a non-ST-segment elevation myocardial infarction undergoing percutaneous coronary intervention (PCI). AKI complicating PCI is associated with increased morbidity and mortality. Remote ischemic preconditioning, using cycles of upper limb ischemia-reperfusion as a conditioning stimulus, has been recently shown to prevent AKI in patients undergoing elective coronary angiography. Eligible patients were randomized to receive RIPC by cycles of inflation and deflation of the stent balloon during PCI or a sham procedure (control patients). The primary endpoint was AKI, defined as an increase of ≥ 0.5 mg/dl or ≥ 25% in serum creatinine within 96 h from PCI. The 30-day rate of death or re-hospitalization for any cause was one of the secondary endpoints. A total of 225 patients were included (median age, 68 years; 36% female). The AKI rate in the RIPC group was 12.4% versus 29.5% in the control group (p = 0.002; odds ratio: 0.34; 95% confidence interval: 0.16 to 0.71). The number needed to treat to avoid 1 case of AKI was 6 (95% confidence interval: 3.6 to 15.2). The 30-day rate of death or re-hospitalization for any cause was 22.3% in the control group versus 12.4% in RIPC patients (p = 0.05). RIPC by serial balloon inflations and deflations during PCI was found to confer protection against AKI in patients with a non-ST-segment elevation myocardial infarction undergoing PCI. The reduction in the rate of AKI translated into a clear trend (of borderline significance) toward better 30-day clinical outcome.

NNOS and p-ERK involvement in the neuroprotection exerted by remote postconditioning in rats subjected to transient middle cerebral artery occlusion

It has recently been hypothesized that a sub-lethal ischemic insult induced in one organ is able to protect from a harmful ischemia occurring in a different organ. The objective of this study is to identify new putative mechanisms of neuroprotection elicited by remote ischemic femoral postconditioning. A 50% reduction in the infarct volume was observed when 100min of middle cerebral artery occlusion was followed, 10min later, by the remote postconditioning stimulus represented by 20min of femoral artery occlusion. The use of in vivo silencing strategy allowed to demonstrate that NO production through nNOS mediates part of the neuroprotection. Indeed, whereas CNS nNOS expression was up-regulated by remote postconditioning, the pharmacological inhibition of nNOS or its silencing-mediated knocking-down partially prevented this neuroprotective effect. This nNOS overexpression seemed to be p-ERK dependent. In fact, p-ERK expression increased in brain cortex after remote postconditioning, and its pharmacological inhibition prevented both nNOS overexpression and remote postconditioning-mediated neuroprotection. Interestingly, neuroprotection induced by remote postconditioning was partially prevented when ganglion transmission was pharmacologically interrupted by hexamethonium, thus showing that neural factors are involved in this phenomenon.Collectively, the present study demonstrates that p-ERK and nNOS take part to the complex cascade of events triggered by ischemic remote postconditioning.

Abstract 95: Remote Postconditioning Protects Ischemic Brain by nNOS and p-ERK Activation

Objective: It has recently been hypothesized that a sub-lethal ischemic insult induced in one organ is able to protect from a harmful ischemia occurring in a different and anatomically distant organ. Objective of this study is to characterize remote ischemic femoral postconditioning as a new method to induce post-ischemic brain neuroprotection Methods and Results: Remote ischemic postconditioning was induced in adult rats by 100 minutes of middle cerebral artery occlusion (tMCAO) followed by several cycles of femoral artery occlusion-reperfusion. One hundred minutes of tMCAO followed, 10 minutes later, by 20 minutes of femoral artery occlusion effectively reduced cerebral infarct volume by 50%.Importantly, this protection was still present 7 days after remote postconditioning. Furthermore, the use of in vivo silencing strategy allowed to demonstrate that NO production through nNOS mediates part of the neuroprotection induced by remote ischemic postconditioning. Indeed, whereas CNS nNOS expression was up-regulated by remote postconditioning, the pharmacological inhibition of nNOS or its silencing-mediated knocking-down partially reverted this neuroprotective effect. This nNOS overexpression and activity seemed to be p-ERK dependent. In fact, p-ERK expression increased in brain cortex after remote postconditioning, and its pharmacological inhibition prevented both nNOS overexpression and remote postconditioning-mediated neuroprotection. Interestingly, neuroprotection induced by remote postconditioning was partially reverted when ganglion transmission was pharmacologically interrupted by hexamethonium, thus showing that neural factors are involved in this phenomenon. Interpretation: Collectively, the results of the present study demonstrate that remote postconditioning induces a marked neuroprotection through p-ERK/nNOS, neuronally-mediated activation, and may represent a new clinically feasible therapeutic approach to treat ischemic stroke.

Effects of edaravone postconditioning and remote ischemic postconditioning on myocardial ischemia/reperfusion injury in rats

Objective To evaluate the effects of edaravone postconditioning and remote ischemic postconditioning on myocardial ischemia/reperfusion (I/R) injury in rats.Methods Forty male Sprague-Dawley rats,aged 8 weeks,weighing 250-300 g,were randomly divided into 5 groups (n =8 each):sham operation group (group S); group I/R; edaravone postconditioning group (group E); remote ischemic postconditioning group (group P); edaravone postconditioning and remote ischemic postconditioning group (group EP).Myocardial I/R was induced by occlusion of anterior desending branch of left coronary artery for 30 min followed by 180 min reperfusion.Edaravone 3 mg/kg was injected intravenously at 1 min before reperfusion in groups E and EP.The animals underwent 10 min ischemia of bilateral hind limbs starting from 20 min of myocardial ischemia in groups P and EP.Left ventricular systolic pressure (LVSP),left ventricular end-diastolic pressure (LVEDP) and ± dp/dtmax were measured and recorded during reperfusion.Results Compared with group S,LVSP and ± dp/dtmax were significantly decreased and LVEDP was increased in the other groups (P ＜ 0.05).LVSP and ± dp/dtmax were significantly higher and LVEDP was lower during reperfusion in groups E,P and EP than in group I/R,and in group EP than in groups E and P (P ＜ 0.05).Conclusion Edaravone postconditioning and remote ischemic postconditioning can alleviate myocardial I/R injury and offers better efficacy than either alone. Key words: Free radical scavengers; Myocardial reperfusion injury; Ischemic postconditioning

Remote ischemic postconditioning enhances cell retention in the myocardium after intravenous administration of bone marrow mesenchymal stromal cells

Efficacy of intravenous administration of mesenchymal stromal cells (MSCs) for myocardial infarction (MI) is limited by low cell retention in the damaged myocardium. Previous studies indicated that remote ischemic conditioning could protect against ischemia–reperfusion-induced injury by release of various cytokines including stromal cell derived factor-1 alpha (SDF-1α). However, whether remote ischemic postconditioning (RIPostC) can also enhance the retention of infused cells in the myocardium by activating MSC homing is unclear. In this study, RIPostC was induced with 4cycles of 5min occlusion and reperfusion of the abdominal aorta in female Sprague–Dawley (SD) rats which underwent ligation of the coronary artery 1week previously. Cytokine levels in serum and myocardium were evaluated by enzyme-linked immunosorbent assay (ELISA) at 1, 6, 24 and 48h after RIPostC. Then, a total of 4×106 male MSCs were infused intravenously at 24h after RIPostC. The number of survived cells in the myocardium was evaluated by real-time polymerase chain reaction analysis for Y chromosome and the heart function was evaluated by echocardiography at 1month after cell infusion. Furthermore, 10μg/kg rabbit anti-rat CXCR4 polyclonal antibody was injected intraperitoneally to prove the role of SDF-1α for RIPostC. RIPostC induced an increase in SDF-1α in serum at 1h and enhanced SDF-1α transcription and protein synthesis in the myocardium at 24h after the procedure. 1month after cell transplantation, RIPostC significantly increased MSC myocardial retention by 79.1±12.3% and thereby contributed to enhanced cardiac function in comparison with cell transplantation without RIPostC. Furthermore, blockade with a CXCR4-specific antibody after RIPostC markedly attenuated the enhancement of therapeutic efficacy. We conclude that RIPostC activated SDF-1α expression and enhanced retention of the infused MSCs in the injured myocardium. Priming of the heart with RIPostC might be a novel adjunctive approach for intravenous cell delivery.

AKT/GSK3β‐Dependent Autophagy Contributes to the Neuroprotection of Limb Remote Ischemic Postconditioning in the Transient Cerebral Ischemic Rat Model

Limb remote ischemic postconditioning (RIPostC) has been recognized as an applicable strategy in protecting against cerebral ischemic injury. However, the time window for application of limb RIPostC and the mechanisms behind RIPostC are still unclear. In this study, we investigated the protective efficacy and the role of autophagy in limb RIPostC using a transient middle cerebral artery occlusion rat model. Limb RIPostC applied in the early phase of reperfusion reduced infarct size and improved neurological function. Autophagy levels in penumbral tissues were elevated in neurons of limb RIPostC rats, with an increase in the phosphorylation of AKT and glycogen synthase kinase 3β (GSK3β). Blocking the AKT/GSK3β pathway via the AKT inhibitor LY294002 prior to limb RIPostC suppressed the RIPostC-induced autophagy and resulted in the activation of caspase-3 in RIPostC rats, suggesting a critical role for AKT/GSK3β-dependent autophagy in reducing cell death after cerebral ischemia. These results aid optimization of the time window for RIPostC use and offer novel insight into, and a better understanding of, the protective mechanism of autophagy in limb RIPostC.

Local and Remote Ischemic Postconditioning Are Synergistic in Reducing Renal Damage, an Animal Study

Local and Remote Ischemic Postconditioning Are Synergistic in Reducing Renal Damage, an Animal Study

Roles of reactive oxygen species in the reduction of myocardial ischemia-reperfusion injury by fentanyl postconditioning and remote limb ischemic postconditioning in rats

Objective To investigate the role of reactive oxygen species (ROS) in the reduction of myocardial ischemia-reperfusion (I/R) injury by fentanyl postconditioning and remote limb ischemic postconditioning in rats.Methods Sixty-three male Sprague-Dawley rats,aged 8 weeks,weighing 250-350 g,were equally and randomly allocated into 7 groups:sham operation group (group S),group I/R,fentanyl postconditioning group (group F),remote limb ischemic postconditioning group (group R),ROS scavenger N-(2-Mercaptopropionyl) glycine (MPG) group (group M),MPG + fentanyl postconditioning group (group MF),and MPG + remote limb ischemic postconditioning group (group MR).Myocardial I/R was induced by occlusion of anterior descending branch of left coronary artery for 30 min followed by 180 min of reperfusion.In group S the anterior descending branch was only exposed but not ligated.MPG 5 mg/kg was infused intravenously from 5 min before ischemia to 15 min of reperfusion in groups M,MF and MR,while the equal volume of normal saline was given in the other four groups.In groups F and MF,fentanyl 30 μg/kg was injected intravenously at 15 min of myocardial ischemia.In groups R and MR,the animals underwent 10 min ischemia of bilateral hind limbs starting from 15 min of myocardial ischemia.Arterial blood samples were taken at 180 min of reperfusion to determine the serum cardiac troponin I (cTnI) concentration.The rats were then sacrificed.The infarct size was measured by TTC.Results Compared with group S,the serum cTnI concentration and infarct size were significantly increased in the other six groups (P ＜0.05).Compared with group I/R,no significant change was found in the serum cTnI concentration and infarct size in M group,and the serum cTnI concentration and infarct size were significantly decreased in F and R groups (P ＜ 0.05).There was no significant difference in the serum cTnI concentration and infarct size between MF group and F group (P ＞ 0.05).The serum cTnI concentration was significantly higher and the infarct size was larger in group MR than in group R (P ＜ 0.05).Conclusion ROS is involved in the reduction of myocardial I/R injury by remote limb ischemic postconditioning in rats,but not in the myocardial protection provided by fentanyl postconditioning. Key words: Reactive oxygen species; Fentanyl ; Lower extremity ; Myocardial reperfusion injury; Ischemic postconditioning

Phosphoinositide-3 kinase/protein kinase B pathway participates in the neuroprotection of remote ischemic postconditioning by up-regulating endothelial nitric oxide synthase

Objective To investigate the roles of endothelial nitric oxide synthase (eNOS) and phosphoinositide-3 kinase/protein kinase B (PI3K/Akt) pathway in the neuroprotection of remote ischemic postconditioning (RIPoC) on global cerebral ischemia/reperfusion (I/R) injury in rats. Methods One hundred male adult SD rats weighing 200 g-250 g were randomly divided into 5 groups (n=20 each):group sham,group I/R,group I/R+RIPoC,group L-NAME+I/R+RIPoC,group LY+I/R+RIPoC.Global cerebral I/R was induced by four-vessel occlusion.Group I/R+RIPoC,group L-NAME+I/R+RIPoC and group LY+I/R+RIPoC received 3 cycles of 15 min ischemia in bilateral femoral arteries at the beginning of cerebral reperfusion followed by 15 min repeffusion.The group L-NAME+I/R+RIPoC:4-VO with coinjection of N (ω)-nitro-L-arginine methyl ester (L-NAME),5 mg/kg,in normal saline.intraperitoneslly,10 min before 4-VO,then followed by RIPoC and 48 h and 7 d of reperfusion.The group LY+I/R+RIPoC:I/R+RIPoC with injection of LY294002(a highly selective inhibitor of PI3K,LY,10 μL,10 mol/L,in 3％ DMSO,intracerebroventricularly.10 min before 4-VO),then followedby RIPoC and 48 h and 7 d of reperfusion.The rats were sacrificed at 48 h of cerebral rep effusion,and brains were removed for determination of neuronal apoptosis [by terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling (TUNEL) method] in hippocampal CA1 region and p-eNOS,eNOS,p-Akt and Akt expression (by Western blot)in hippocampal CA1 region.Morris water maze task was used to test the learning and memory function at 4 d of cerebral reperfusion,and the rats were sacrificed at 7 d of cerebral reperfusion,and brains were removed for determination of neuronal density in hippocampal CA1 region.Results Compared with group sham,the number of apoptotic neurons in CA1 region [(0.8±0.8),(84.7±6.8), (52.8±7.8), (74.3±9.0), (79.5±7.3)/mm] increased (P＜0.01),learning and memory function decreased (P＜0.01) and neuronal density in CA1 region [ (193±7),(10±7),(91±11),(38±7),(26±7)/mm]decreased(P＜0.01) in group I/R,I/R+RIPoC,L-NAME+I/R+RIPoC and LY+I/R+RIPoC.RIPoC significantly attenuated these cerebral I/R-induced changes in apoptotic neurons (P＜0.01),learning and memory function (P＜0.01) and neuronal density (P＜0.01).Pre-administration of N (ω)-nitro-1-arginine methyl ester (L-NAME,a nonselective NOS inhibitor) significantly abolished the neuroprotective effect of RIPoC,and significantly attenuated the RIPoC induced up-regulation of p-eNOS (0.48±0.03,0.23±0.04) and eNOS (0.91±0.07,0.64±0.06) in CA1 region (P＜0.01).Moreover,pre-administration of LY not only significantly reversed the RIPoC induced neuroprotective effect and up-regulation of p-Akt (0.74±0.06,0.44±0.04) in CA1 region,but also obviously inhibited the RIPoC induced up-regulation of both p-eNOS (0.48±0.03,0.24±0.04) and eNOS (0.91±0.07,0.63±0.06) in CA1 region(P＜0.01). Conclusions RIPoC protects the brain against global cerebral I/R injury and that this neuroprotection is mediated by up-regulation and activation of eNOS through the PI3K/Akt pathway. Key words: Reperfusion injury; Brain; Remote ischemic postconditioning; Nitric oxide synthase; Phosphatidylinositol-3 kinase/protein kinase B

Effect of Combined Remote Ischemic Preconditioning and Postconditioning on Pulmonary Function in Valvular Heart Surgery

The aim of this study was to evaluate the lung-protective effect of combined remote ischemic preconditioning (RIPCpre) and postconditioning (RIPCpost) in patients undergoing complex valvular heart surgery. In this randomized, placebo-controlled, double-blind trial, 54 patients were assigned to an RIPCpre plus RIPCpost group or a control group (1:1). Patients in the RIPCpre plus RIPCpost group received three 10-min cycles of right-side lower-limb ischemia of 250 mm Hg at both 10 min after anesthetic induction and weaning from cardiopulmonary bypass. The primary end point was to compare postoperative Pao(2)/Fio(2). Secondary end points were to compare pulmonary variables, incidence of acute lung injury, and inflammatory cytokines. In both groups, Pao(2)/Fio(2) at 24 h postoperation was significantly decreased compared with each corresponding baseline value. However, intergroup comparisons of pulmonary variables, including Pao(2)/Fio(2) and incidence of acute lung injury, revealed no significant differences. Serum levels of IL-6, IL-8, IL-10, and tumor necrosis factor-α were all significantly increased in both groups compared with each corresponding baseline value, without any significant intergroup differences. There were also no significant differences in transpulmonary gradient of IL-6, IL-10, and tumor necrosis factor-α between the groups. RIPCpre plus RIPCpost as tested in this randomized controlled trial did not provide significant pulmonary benefit following complex valvular cardiac surgery.

Remote and local ischemic postconditioning further impaired skeletal muscle mitochondrial function after ischemia-reperfusion

Muscular injuries contribute to perioperative and long-term morbidity after vascular surgery in humans. We determined whether local and remote ischemic postconditioning might similarly decrease muscle mitochondrial dysfunction through reduced oxidative stress. Eighteen male Black-6 mice were divided in three groups: (1) sham mice had no ischemia (sham), (2) ischemia-reperfusion (IR) mice underwent 2-hour tourniquet-induced ischemia on both hind limbs, followed by 2-hour reperfusion, and (3) postconditioning (PoC) mice underwent four bouts of 30-second reperfusion and 30-second ischemia at the onset of reperfusion on the right limb; thus, the right limb underwent local PoC and left limb underwent remote PoC (rPoC). Maximal oxidative capacity (V(max)) of the gastrocnemius muscle mitochondrial respiratory chain was measured. Oxidative stress was evaluated by dihydroethidium staining. Expressions of genes involved in antioxidant defense (superoxide dismutase [SOD1], SOD2, glutathione peroxidase [GPx]), apoptosis (Bax, BclII), and inflammation (interleukin-6) were determined by quantitative real-time polymerase chain reaction. Muscle inflammation was determined using immunohistochemistry. IR reduced V(max) (8.5 ± 2.2 vs 10.2 ± 1.8 μmol O(2)/min/g dry weight; P = .034), and increased dihydroethidium staining (134.8%; P = .039). IR decreased GPx expression (-47.9%; P = .048) and increased the proapoptotic marker Bax (255.5%; P = .020). Local PoC and rPoC further increased these deleterious effects. PoC decreased V(max) to 4.4 ± 1.4 μmol O(2)/min/g dry weight (sham vs PoC, -56.9% [P < .001]; IR vs PoC, -48.2% [P < .001]). rPoC similarly reduced V(max) to 5.1 ± 1.9 μmol O(2)/min/g dry weight (sham vs PoC, -50.0% [P < .001]; IR vs PoC, -40.0% [P = .001]). Dihydroethidium staining was further increased by PoC (207.2%; P = .002) and rPoC (305.4%; P < .001) compared with sham and was associated with macrophage infiltration. Local PoC increased SOD1, SOD2, and the antiapoptotic Bcl-2, and rPoC increased Bax (391.6%; P < .001) and the Bax/BclII ratio (621.7%; P < .001). Local and remote ischemic postconditioning further increased injury by enhancing mitochondrial dysfunction, oxidative stress production, and inflammation. Caution should be applied when considering ischemic postconditioning in vascular surgery.