Protective Effects Of Ischemic Postconditioning Research Articles

Role of Quercetin in attenuated cardio-protective effects of ischemic post-conditioning in STZ induced hyperglycemic rat heart

The cardio protective effects of Ischemic Post-Conditioning (IPOC) are abrogated in Hyperglycemic condition. The present study has been designed to investigate the effects of Quercetin in abrogated cardio-protective effect of IPOC against I/R injury in hyperglycemic rat heart.

Ischemic Postconditioning-Mediated DJ-1 Activation Mitigate Intestinal Mucosa Injury Induced by Myocardial Ischemia Reperfusion in Rats Through Keap1/Nrf2 Pathway.

Intestinal mucosal barrier dysfunction induced by myocardial ischemia reperfusion (IR) injury often leads to adverse cardiovascular outcomes after myocardial infarction. Early detection and prevention of remote intestinal injury following myocardial IR may help to estimate and improve prognosis after acute myocardial infarction (AMI). This study investigated the protective effect of myocardial ischemic postconditioning (IPo) on intestinal barrier injury induced by myocardial IR and the underlying cellular signaling mechanisms with a focus on the DJ-1. Adult SD rats were subjected to unilateral myocardial IR with or without ischemic postconditioning. After 30 min of ischemia and 120 min of reperfusion, heart tissue, intestine, and blood were collected for subsequent examination. The outcome measures were (i) intestinal histopathology, (ii) intestinal barrier function and inflammatory responses, (iii) apoptosis and oxidative stress, and (iv) cellular signaling changes. IPo significantly attenuated intestinal injury induced by myocardial IR. Furthermore, IPo significantly increased DJ-1, nuclear Nrf2, NQO1, and HO-1 expression in the intestine and inhibited IR-induced apoptosis and oxidative stress. The protective effect of IPo was abolished by the knockdown of DJ-1. Conversely, the overexpression of DJ-1 provided a protective effect similar to that of IPo. Our data indicate that IPo protects the intestine against myocardial IR, which is likely mediated by the upregulation of DJ-1/Nrf2 pathway.

Ischemic Postconditioning Attenuates Bilateral Renal Ischemia-induced Cognitive Impairments.

Introduction:Acute Kidney Injury (AKI) is a frequent complication of kidney failure with high mortality, leading to brain dysfunction. This study aimed to investigate the possible protective effect of Ischemic Postconditioning (IPo) against brain dysfunction induced by Bilateral Renal Ischemia (BRI).Methods:Male Wistar rats underwent BRI, sham, or IPo surgery 24h and 1w after reperfusion. The rats’ explorative behaviors and motor function were evaluated by an open field, rotarod, and wire grip tests. The cognitive function was assessed by passive avoidance learning and Morris water maze tests. Western blotting was performed to evaluate hippocampal Brain-Derived Neurotrophic Factor (BDNF) expression.Results:The impairment of balance function induced by BRI was not reversed; however, passive avoidance learning impairment was reversed by postconditioning 24h after reperfusion. IPo increased muscle strength compared to the BRI group; however, explorative behaviors and balance function had no difference 1w after reperfusion. BRI significantly decreased the BDNF protein expression in the hippocampus, and postconditioning increased 24h after reperfusion.Conclusion:The obtained results demonstrated the deleterious effect of BRI on cognitive and balance function 24h after reperfusion. IPo indicated a curative effect against cognitive dysfunction probably by enhancing BDNF protein expression in the hippocampus.HighlightsIPo improved passive avoidance learning impairment induced by BRI.IPo increased muscle strength compared to the BRI group.BRI significantly decreased the BDNF protein expression in the hippocampus.IPo increased BDNF protein expression 24h after reperfusion.Plain Language SummaryAcute kidney injury may be associated with numerous complications in different regions of brain, as it may alter the permeability of the blood-brain barrier, accumulate the toxins, decreased blood flow to the brain, increased risk of encephalopathy, higher mental dysfunctions like delirium, stroke, memory and thinking problems (dementia) in people with kidney failure. It has been demonstrated that the most common causes of mortality in acute kidney injury is brain dysfunction. Therefore, discovering new treatments can decrease the brain injuries and help the patients with kidney dysfunction to have a higher quality of life. Ischemic postconditioning, which refers to a series of brief ischemia and reperfusion cycles applied immediately at the site of the ischemic organ after reperfusion, results in reduced injuries induced by ischemia. The purpose of the current study was designed to investigate whether ischemic postconditioning exerts neuroprotective effects against brain dysfunctions induced by renal ischemia in rats. Results of this study demonstrated that acute kidney injury triggers distant organ dysfunction and leads to cognitive and balance dysfunction 24h after induction of renal ischemia and ischemic postconditioning protects the brain as a remote organ against cognitive dysfunction from the injury induced by renal ischemia.

Effect of eNOS on Ischemic Postconditioning-Induced Autophagy against Ischemia/Reperfusion Injury in Mice.

Autophagy is involved in the development of numerous illnesses, including ischemia/reperfusion (I/R). Endothelial nitric oxide synthase (eNOS) participates in the protective effects of ischemic postconditioning (IPostC). However, it remains unclear whether eNOS-mediated autophagy serves as a critical role in IPostC in the hearts of mice, in protecting against I/R injury. In the present study, the hearts of mice with left anterior descending coronary artery ligation were studied as I/R models. H9c2 cells underwent exposure to hypoxia/reoxygenation (H/R) and were examined as in vitro model. IPostC reduced mice myocardial infarct size and improved the structure of the heart. IPostC increased the formation of autophagosomes and increased the phosphorylation of eNOS and adenosine monophosphate-activated protein kinase (AMPK). Autophagy and eNOS inhibition suppressed the cardioprotective effects of IPostC. AMPK or eNOS inhibition abolished the improvement effect of IPostC on autophagy. AMPK inhibition decreased eNOS phosphorylation in the heart. Additionally, H9c2 cells suffering hypoxia were used as in vitro model. Autophagy or eNOS inhibition abolished the protective effects of hypoxic postconditioning (HPostC) against H/R injury. AMPK and eNOS inhibition/knockout decreased autophagic activity in the HPostC group. These results indicated that IPostC protects the heart against I/R injury, partially via promoting AMPK/eNOS-mediated autophagy.

Ischemic postconditioning reduced myocardial ischemia-reperfusion injury: The roles of melatonin and uncoupling protein 3.

Objective:Protective effects of ischemic postconditioning (PostC) decrease/disappear with age and chronic heart diseases. Similarly, low serum melatonin levels have been reported in the same risk groups. The aims of this study were to investigate the effects of melatonin on the protection of PostC in ischemia–reperfusion (I/R)-induced infarct size and roles of uncoupling protein (UCP) 3, irisin, and nuclear factor kappa B (NFkB) levels.Methods:Rats were pinealectomized (Px) or sham operated (non-Px) 2 months before the I/R studies. The left main coronary artery was occluded for 30 min followed by 120 min reperfusion. PostC was induced with three cycles of R/I (10 s each) after ischemia.Results:The infarct size was found to be significantly higher in Px rats (54.68±1.5%) than in the control group (35.1±2.5%). PostC and melatonin administrations to non-Px rats significantly reduced the infarct size. On the other hand, PostC did not create a significant effect in Px rats, but protection was provided when PostC was co-administrated with melatonin. While significant decreases were detected in the UCP3 levels, irisin and NFkB levels increased with I/R and Px. Treatment with PostC and melatonin in non-Px groups and their co-administration in Px groups were found to return all the genes close to normal levels.Conclusion:The physiological and pharmacological concentrations of melatonin may play a role in the protection of PostC. In cases when physiological melatonin is reduced, such as aging and heart diseases, this protection may decrease, and this effect may be restored by melatonin replacement. PostC and melatonin may regulate energy metabolism and inflammatory mediators and protect mitochondria by affecting the UCP3, irisin, and NFkB levels.

Troxerutin Preconditioning and Ischemic Postconditioning Modulate Inflammatory Response after Myocardial Ischemia/Reperfusion Injury in Rat Model.

Protective effects of ischemic postconditioning in myocardial ischemia/reperfusion (I/R) injury have been ever demonstrated, but the exact mechanisms remain unclear. Because of their multiplex activities, using natural pharmaceuticals seems to be clinically interesting. The aim of present study was to investigate the effects of troxerutin preconditioning and ischemic postconditioning on inflammatory responses after myocardial I/R injury in a rat model. Twenty-four Wistar rats were divided into four groups as the control, troxerutin receiving (TXR), postconditioning receiving (PostC), and combined therapy (TXR + PostC). Rats' isolated hearts underwent 30-min LAD regional ischemia followed by 45-min reperfusion. Troxerutin was orally administered for a month before I/R. Ischemic PostC was applied by alternative three cycles of 30-s R/I at the onset of reperfusion. The coronary effluent and ischemic left ventricular samples were used to determine the activities of creatine kinase (CK), intercellular adhesion molecule-1 (ICAM-1), interlukin-1beta (IL-1β), tumor-necrosis factor (TNF-α), and also histopathological studies. Pretreatment of rats with troxerutin significantly reduced myocardial inflammatory cytokines TNF-α and IL-1β levels and ICAM-1 activity after I/R insult compared to those of control I/R hearts (P < 0.05). Application of PostC showed similar impacts on those parameters. In fact, anti-inflammatory mechanisms of both treatments were associated with their protective effects against myocardial damages causing from I/R injury. Pretreatment with troxerutin as well as postconditioning can induce cardioprotection through prevention of the cell-cell interaction and release of inflammatory mediators, minimizing I/R pathological changes in myocardial cells. These two treatments may share same mechanisms in their actions since they showed no significant additive effects.

Ischemic Postconditioning-Regulated miR-499 Protects the Rat Heart Against Ischemia/Reperfusion Injury by Inhibiting Apoptosis through PDCD4

Background: Here, we determined miR-499 involvement in the protective effect of ischemic postconditioning (IPC) against myocardial ischemia/reperfusion (I/R) injury and identified the underlying mechanisms. Methods: To investigate the cardioprotective effect of IPC-induced miR-499, rats were divided into the following five groups: sham, I/R, IPC, IPC + scramble, and IPC + antagomiR-499. Hemodynamic indexes were measured by carotid-artery intubation to assess left ventricular function . Ischemia and infarction areas of rat hearts were determined by Evans blue and triphenyltetrazolium chloride staining, and cardiomyocyte apoptosis was detected by terminal deoxynucleotidyl transferase dUTP nick-end-labeling assay. Results: IPC attenuated I/R-induced infarct size of the left ventricle (45.28 ± 5.40% vs. 23.56 ± 6.20%, P < 0.05), myocardial apoptosis, and decreased creatine kinase (1867.31 ± 242.41% vs. 990.21 ± 172.39%, P < 0.05), lactate dehydrogenase (2257.50 ± 305.11% vs. 1289.11 ± 347.28%, P < 0.05), and malondialdehyde levels (7.18 ± 1.63% vs. 4.85 ± 1.52%, P < 0.05). Additionally, left ventricular systolic pressure, +dp/dtmax, and -dp/dtmax were elevated, and left ventricular end diastolic pressure was significantly reduced in the IPC group. Furthermore, IPC-mediated cardiac protection against I/R injury was inhibited in vivo and in vitro by knockdown of cardiac miR-499, suggesting that miR-499 may participate in the protective function of IPC against I/R injury through targeting programmed cell death 4 (PDCD4). Conclusion: Our data revealed that IPC-regulated miR-499 plays an important role in IPC-mediated cardiac protection against I/R injury by targeting PDCD4.

GW26-e3821 Hypercholesterolemia abrogates the protective effect of ischemic postconditioning by induction of apoptosis and impairment of activation of reperfusion injury salvage kinase pathway

GW26-e3821 Hypercholesterolemia abrogates the protective effect of ischemic postconditioning by induction of apoptosis and impairment of activation of reperfusion injury salvage kinase pathway

Ischemic Postconditioning and Nitric Oxide Administration Failed to Confer Protective Effects in a Porcine Model of Extracorporeal Cardiopulmonary Resuscitation.

The protective effects of ischemic postconditioning (IPC) and nitric oxide (NO) administration have been demonstrated in several ischemic scenarios. However, current evidence regarding the effect of IPC and NO in extracorporeal cardiopulmonary resuscitation remains lacking. Fifteen female swine (body weight 45 kg) underwent veno-arterial extracorporeal membrane oxygenation (ECMO) implantation; cardiac arrest-ventricular fibrillation was induced by rapid ventricular pacing. After 20 min of cardiac arrest, blood flow was restored by increasing the ECMO flow rate to 4.5 L/min. The animals (five per group) were then randomly assigned to receive IPC (three cycles of 3 min ischemia and reperfusion), NO (80 ppm via oxygenator), or mild hypothermia (HT; 33.0°C). Cerebral oximetry and aortic blood pressure were monitored continuously. After 90 min of reperfusion, blood samples were drawn for the measurement of troponin I, myoglobin, creatine-phosphokinase, alanine aminotransferase, neuron-specific enolase, cystatin C, and reactive oxygen metabolite (ROM) levels. Significantly higher blood pressure and cerebral oxygen saturation values were observed in the HT group compared with the IPC and NO groups (P < 0.05). The levels of troponin I, myoglobin, creatine phosphokinase, and alanine aminotransferase were significantly lower in the HT group (P < 0.05); levels of neuron-specific enolase, cystatin C, and ROM were not significantly different. IPC and NO were comparable in all monitored parameters. The results of the present study indicate that IPC and NO administration are not superior interventions to HT for the maintenance of blood pressure, cerebral oxygenation, organ protection, and suppression of oxidative stress following extracorporeal cardiopulmonary resuscitation.

The Protective Effects of Myocardial Ischemic Postconditioning on Cardiac Surgry: A Systematic Review and Meta-Analysis of Rats and Clinical Trials

Background: Ischemic postconditioning (IPC) is a potent protective strategy implemented in animal myocardial ischemic-reperfusion (IR) models, while it has not yet been translated universally into clinical practice. We performed a unique systematic review and meta-analysis of animal and clinical studies respectively, to assess the protective effects of myocardial IPC and provide a new perspective for clinical practice.Methods: PubMed and Web of Science were searched for relevant researches. Trials met our inclusion criteria were selected and reviewed, and the meta-analyses were performed via Review Manager.Results: 44 trials were included in the meta-analysis. In animal studies, IPC demonstrated a decrease in size of myocardial infarction (standardized mean difference [SMD] -3.21, 95% confidence interval [CI] -3.89 to -2.52, P<0.00001), however, subgroup analysis showed that the protective effects of IPC disappeared in diabetic rats and hyperlipidemia rats (SMD -0.10, 95% CI -1.32 to 1.12, P=0.05; SMD -2.02, 95% CI -4.29 to 0.26, P=0.08, respectively). IPC reduced apoptosis index significantly (SMD -2.56, 95% CI -3.56 to -1.55, P<0.00001), while subgroup analysis indicted that IPC had no effect on decrease in level of myocardium apoptosis in hyperlipidemia rats (SMD -0.31, 95% CI -1.13 to 0.50, P=0.46). In clinical trials, no differences were noted in mortality between IPC and IR patients (SMD 0.44, 95% CI 0.07 to 2.85, P=0.41). IPC decreased the level of cardiac troponin I (cTnI) (SMD -1.74, 95% CI -2.71 to -0.78, P=0.0004), reduced the inotrope score (SMD -2.31, 95% CI -2.85 to -1.76, P<0.00001), shortened the time of ventilation and intensive care unit (ICU) stay (SMD -0.57, 95% CI -0.87 to -0.26, P=0.0002; SMD -0.57, 95% CI -0.84 to -0.30, P<0.0001, respectively).Conclusions: Myocardial IPC provided efficient protective effects for healthy rats rather than diabetic or hyperlipidemia rats. In clinical trials, IPC appeared to be beneficial to cardiac function and cardiac surgery prognosis, but had no effect on postoperative cardiac death. Citation: Bin Zhou, Zhong-Yuan Xia, Ming Guo. The protective effects of myocardial ischemic postconditioning on cardiac surgry: a systematic review and meta-analysis of rats and clinical trials. J Anesth Perioper Med 2015; 2: 256-67. doi: 10.24015/JAPM.2015.0035This is an open-access article, published by Evidence Based Communications (EBC). This work is licensed under the Creative Commons Attribution 4.0 International License, which permits unrestricted use, distribution, and reproduction in any medium or format for any lawful purpose. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/.

Hypercholesterolemia abrogates the protective effect of ischemic postconditioning by induction of apoptosis and impairment of activation of reperfusion injury salvage kinase pathway

Ischemic postcontioning (IPoC) is an effective method to prevent myocardial ischemia reperfusion injury (MIRI), but its cardioprotection is usually blocked in the presence of hypercholesterolemia (HC) and the potential mechanism is still unknown. In this study, we investigated the roles of reperfusion injury salvage kinase (RISK) and apoptosis-related pathways in the attenuation of cardioprotection of IPoC in the presence of HC. The results showed that IPoC significantly decreased the infarct size and apoptosis, improved the recovery of ischemic myocardium, but these beneficial effects were reversed by high cholesterol diet-induced HC. Moreover, we also found that HC inhibited the phosphorylation of Akt and ERK1/2 which usually activated by IPoC in normal heart, induced excessive apoptosis by down-regulating Bcl-2 and up-regulating Bax, cytochrome c, caspase 9 and caspase 3 when compared with that in normal heart. Taken together, our results demonstrated that the cardioprotection of IPoC was abolished by HC, which was associated with inactivation of RISK signal pathway and dysregulation of downstream apoptosis-related pathway.

Toll-like Receptor 4 Is Involved in Renoprotective Effect of Ischemic Postconditioning After Renal Ischemia/Reperfusion Injury in Rats

To investigate whether the protective effects of ischemic postconditioning (IPoC) are associated with the modulation of toll-like receptor 4 (TLR4) expression. We subjected Wistar rats to 45minutes of ischemia followed by reperfusion at 24 hours. Before reperfusion, rats were treated with 6 cycles of 10 seconds of reperfusion followed by 10 seconds of ischemia. Blood samples were collected for the detection of blood urea nitrogen and creatinine levels. Histologic examinations were evaluated, and immunohistochemistry was also performed for localization of TLR4. The expression of TNF-α, IL-1β, IL-6, MCP-1, and TLR4 were studied by real-time polymerase chain reaction or Western blot. The results indicated that blood urea nitrogen and creatinine levels increased significantly in the ischemia/reperfusion (I/R) group. Rats treated with IPoC showed obviously less renal damage. Immunohistochemistry showed that TLR4 was ameliorated by IPoC. Real-time polymerase chain reaction showed that IPoC could significantly inhibit the increased messenger ribonucleic acid level of TNF-α, IL-1β, IL-6, MCP-1, and TLR4 induced by I/R. Western blot indicated that the expression of TLR4 was upregulated in I/R group, but IPoC could inhibit this increase. These findings indicated that IPoC could reduce the expression of TLR4 after renal I/R injury, and the modulation of TLR4 may play a role in the renoprotective effect of IPoC.

Ischemic postconditioning prevents renal ischemia reperfusion injury through the induction of heat shock proteins in rats.

Ischemic postconditioning (IPo) attenuates ischemia-reperfusion injuries (IRI) in various organs, of both animals and humans. This study tested the hypothesis that IPo attenuates renal IRI through the upregulation of heat shock protein (HSP)70, HSP27 and heme oxygenase-1 (HO-1, also known as HSP 32) expression. Adult Sprague Dawley rats were subjected to bilateral renal ischemia for 45 min followed by reperfusion for up to 48 h. One group of rats received IPo prior to restoring full perfusion. Another group was administered 100 mg/kg HSP inhibitor quercetin, injected intraperitoneally 1 h prior to ischemia. Control rats received sham operations. Renal IR resulted in severe morphological and pathological changes, with increased serum creatinine and blood urea nitrogen concentrations. IR resulted in increased inflammation by inducing plasma tumor necrosis factor-α and renal nuclear factor kappa-light-chain-enhancer of activated B cells expression. IR also increased lipid peroxidation, as indicated by elevated malondialdehyde content, reduced superoxide dismutase activity and increased renal apoptosis. Renal HSP70, HSP27 and HO-1 mRNA and protein levels were increased by IR and further elevated by IPo. IPo attenuated these changes observed in pathology, lipid peroxidation, apoptosis and inflammation. Quercetin treatment abolished all the protective effects of IPo. In conclusion, this study showed that IPo can attenuate lipid peroxidation, apoptosis and inflammation as well as renal IRI by upregulating the expression of HSP70, HSP27 and HO-1.

Effects of ischemic postconditioning in patients with acute myocardial infarction undergoing primary PCI: a review and meta-analysis

To evaluate the cardiac protective effects of ischemic postconditioning (IPC) in patients with acute myocardial infarction (AMI) undergoing primary percutaneous coronary intervention (PCI). Both foreign and Chinese databases including PubMed, EMbase, Cochrane library, and CNKI were searched to identify randomized controlled trials (RCTs) that reported the effects of IPC on the myocardial infarction size, myocardial blush grade (MBG), left ventricular ejection fraction (LVEF) and major adverse cardiac events (MACE). Two reviews assessed the quality of each trial and extracted data independently. The Cochrane Collaboration's RevMan 4.2.8 software was used for statistical analysis. Twelve studies were identified and the Meta-analysis included a total of 937 patients with AMI undergoing primary PCI with or without IPC. Pooled analysis of all studies demonstrated no significant reductions of peak CK and CK-MB with IPC relative to standard care. A secondary analysis of the studies didn't show improvements of left ventricular ejection fraction during hospitalization with IPC. However, the incidence of MACE within 3 month after primary PCI in IPC group was less than that in the control group (P = 0.04). No significant benefit of IPC for reduction of myocardial infarct size as determined by peak creatine kinase and CK-MB release, as well as LVEF. The incidence of MACE was improved in patients who received IPC.

Evolving possible link between PI3K and NO pathways in neuroprotective mechanism of ischemic postconditioning in mice.

The present study was conducted to pharmacologically investigate the influence of NO signaling pathway in PI3K mediated neuroprotective mechanism of ischemic postconditioning (iPoCo). Bilateral carotid artery occlusion (BCAO) of 12min followed by reperfusion for 24h was employed to produce ischemia/reperfusion-induced cerebral injury in male Swiss mice. Memory was assessed using Morris water maze test. Degree of motor incoordination was evaluated using inclined beam walk test, rotarod test, and lateral push test. Cerebral infarct size was measured using triphenyltetrazolium chloride staining. Brain acetylcholinesterase activity, thiobarbituric acid reactive species (TBARS), nitrite/nitrate and reduced glutathione (GSH) levels were also estimated. BCAO followed by reperfusion produced significant rise in cerebral infarct size, acetylcholinesterase activity, and TBARS levels along with fall in nitrite/nitrate and GSH levels. A significant impairment of memory and motor coordination was also noted. iPoCo consisting of three episodes of 10s carotid artery occlusion and reperfusion significantly attenuated infarct size, memory impairment, motor incoordination, and altered biochemicals. iPoCo-induced neuroprotective effects were significantly abolished by wortmannin (a selective PI3K inhibitor). However, administration of L-Arginine (a NO precursor) in the presence of wortmannin restored the protective effect of ischemic postconditioning. It may be concluded that neuroprotective mechanism of iPoCo involves PI3K-mediated pathway with NO signaling as an important downstream step.

Mammalian target of rapamycin cell signaling pathway contributes to the protective effects of ischemic postconditioning against stroke.

Whether the mammalian target of rapamycin (mTOR) pathway is protective against brain injury from stroke or is detrimental is controversial, and whether it is involved in the protective effects of ischemic postconditioning (IPC) against stroke is unreported. Our study focuses on the protective role of mTOR against neuronal injury after stroke with and without IPC. We used both an in vitro oxygen-glucose deprivation model with a mixed neuronal culture and hypoxic postconditioning, as well as an in vivo stroke model with IPC. Rapamycin, a specific pharmacological inhibitor of mTOR, and mTOR short hairpin RNA lentiviral vectors were used to inhibit mTOR activity. A lentiviral vector expressing S6K1, a downstream molecule of mTOR, was used to confirm the protective effects of mTOR. Infarct sizes were measured and protein levels were examined by Western blot. We report that stroke resulted in reduced levels of phosphorylated proteins in the mTOR pathway, including S6K1, S6, and 4EBP1, and that IPC increased these proteins. mTOR inhibition, both by the mTOR inhibitor rapamycin and by mTOR short hairpin RNA, worsened ischemic outcomes in vitro and in vivo and abolished the protective effects of hypoxic postconditioning and IPC on neuronal death in vitro and brain injury size in vivo. Overexpression of S6K1 mediated by lentiviral vectors significantly attenuated brain infarction. mTOR plays a crucial protective role in brain damage after stroke and contributes to the protective effects of IPC.

Tim-3 cell signaling and iNOS are involved in the protective effects of ischemic postconditioning against focal ischemia in rats.

The protective effect of ischemic postconditioning (IPostC) against stroke has been well-established, and the underlying mechanisms are known to involve inhibited-inflammation and free radical production. Nevertheless, how IPostC affects protein expression of iNOS, nitrotyrosine, and COX-2 has not been characterized. In addition, the role of the galectin-9/Tim-3 cell signaling pathway--a novel inflammatory pathway--in IPostC has not been studied. We examined whether iNOS, nitrotyrosine, and COX-2, as well as galectin-9/Tim-3 are involved in the protective effects of IpostC in a rat focal ischemia model. Western blot and confocal immunofluoresent staining results indicate that IPostC significantly inhibited Tim-3 expression, and that galectin-9 expression was also inhibited. In addition, IPostC attenuated production of iNOS and nitrotyrosine, but not COX-2, suggesting that IPostC has distinct effects on these inflammatory factors. Furthermore, the inflammation inhibitor minocycline blocked Tim-3 and iNOS expression induced by stroke. Taken together, we show that the galectin-9/Tim-3 cell signaling pathway is involved in inflammation induced by stroke, and IPostC may reduce infarction by attenuating this novel pathway as well as the inflammatory factors iNOS and nitrotyrosine, but not COX-2.

Effect of minocycline postconditioning and ischemic postconditioning on myocardial ischemia-reperfusion injury in atherosclerosis rabbits

This study examined the protective effect of ischemic postconditioning (IPoC) and minocycline postconditioning (MT) on myocardial ischemia-reperfusion (I/R) injury in atherosclerosis (AS) animals and the possible mechanism. Forty male healthy rabbits were injected with bovine serum albumin following feeding on a high fat diet for 6 weeks to establish AS model. AS rabbits were randomly divided into 3 groups: (1) I/R group, the rabbits were subjected to myocardial ischemia for 35 min and then reperfusion for 12 h; (2) IPoC group, the myocardial ischemia lasted for 35 min, and then reperfusion for 20 s and ischemia for 20 s [a total of 3 cycles (R20s/I20s×3)], and then reperfusion was sustained for 12 h; (3) MT group, minocycline was intravenously injected 10 min before reperfusion. The blood lipids, malondialdehyde (MDA), superoxide dismutase (SOD), soluble cell adhesion molecule (sICAM), myeloperoxidase (MPO), and cardiac troponin T (cTnT) were biochemically determined. The myocardial infarction size (IS) and apoptosis index (AI) were measured by pathological examination. The expression of bcl-2 and caspase-3 was detected in the myocardial tissue by using reverse transcription-polymerase chain reaction (RT-PCR). The results showed that the AS models were successfully established. The myocardial IS, the plasma levels of MDA, sICAM, MPO and cTnT, and the enzymatic activity of MPO were significantly decreased, and the plasma SOD activity was significantly increased in IPoC group and MT group as compared with I/R group (P<0.05 for all). The myocardial AI and the caspase-3 mRNA expression were lower and the bcl-2 mRNA expression was higher in IPoC and MT groups than those in I/R group (all P<0.05). It is concluded that the IPoC and MT can effectively reduce the I/R injury in the AS rabbits, and the mechanisms involved anti-oxidation, anti-inflammation, up-regulation of bcl-2 expression and down-regulation of caspase-3 expression. Minocycline can be used as an effective pharmacologic postconditioning drug to protect myocardia from I/R injury.

Abstract 3126: Ischemic Postconditioning Facilitates Brain Recovery After Stroke by Promoting mTOR Activity

Introduction: Ischemic postconditioning represents a series of brief occlusions of blood flow before complete restoration of reperfusion after brain stroke. We have shown that ischemic postconditioning reduces infarct size in focal ischemia in rats and improves neurological deficits, but the underlying protective mechanisms are not fully understood. The mammalian target of rapamycin (mTOR) pathway plays a key role in cell growth, differentiation and survival. We studied the hypothesis that the mTOR pathway is involved in the protective effect of ischemic postconditioning and brain recovery after stroke in rats. Methods: Focal ischemia was induced by 30 min of bilateral CCA occlusion and permanent distal MCA occlusion in rats. Ischemic postconditioning was induced by 3 cycles of 30 sec reperfusion and 10 sec occlusion at the end of stroke. Rapamycin, an mTOR inhibitor, was injected into the left lateral ventricle 1 hour before stroke onset. For the behavior test, home cage and vibrissa-elicited limb use tests were used and performed until 21d after stroke. Peri-infarct tissues were collected 1 and 3 weeks after stroke for Western blotting and immunostaining. Molecular markers related with synaptic transmission and neuronal growth and plasticity, including Gap-43, synaptophysin, MAP-2 and PSD-95 proteins were detected. Protein levels of phosphorylated mTOR (p-MTOR) and 4EPB-1 in the mTOR pathway, and the upstream molecule, Akt, were also measured. Results: Ischemic postconditioning improved neurological function when measured 2 weeks after stroke (n=6, p&lt;0.05), and reduced brain injury size by 34.2% (P&lt;0.05). These protective effects were abolished by rapamycin treatment. The results of Western blotting showed that postconditioning substantially promoted the protein level of Gap-43, MAP-2 and PSD-95, but not synaptophysin. Rapamycin significantly inhibited Gap-43 levels at 1 and 3 weeks after stroke, and inhibited Map-2 level at 1 week (P&lt;0.05). Postconditioning significantly increased the protein levels of p-Akt, p-mTOR, p-4EBP-1 compared with control ischemia (p&lt;0.05) at 1 week after stroke injury. Rapamycin attenuated p-mTOR levels 1 and 3 weeks after stroke, and inhibited p-4EBP-1 level at 1 week (p&lt;0.05), but had no effects on the expression level of p-Akt and Akt. Conclusion: Ischemic postconditioning improved brain function, which is consistent with the improved expression of proteins related with synaptic function and brain plasticity. This protection appears to be achieved by the enhanced mTOR activity.

The Protective Effects of Ischemic Postconditioning against Stroke: From Rapid to Delayed and Remote Postconditioning.

The author reviews the protective effects of ischemic postconditioning, a recently emerging strategy with broad implications in the search for new treatments in stroke and myocardial ischemic injury. Ischemic postconditioning, which refers to a series of brief ischemia and reperfusion cycles applied immediately at the site of the ischemic organ after reperfusion, results in reduced infarction in both cerebral and myocardial ischemia. Conventional postconditioning induced within a few minutes after reperfusion is arbitrarily defined as rapid postconditioning. In contrast, postconditioning performed hours to days after stroke is defined as delayed postconditioning. In addition, postconditioning can be mimicked using anesthetics or other pharmacological agents as stimuli to protect against ischemia/reperfusion injury or performed in a distant organ, which is known as remote postconditioning. In this article, the author discusses the conceptual origin of classical rapid ischemic postconditioning and its evolution into a term that represents a broad range of stimuli or triggers, including delayed postconditioning, pharmacological postconditioning, and remote postconditioning. Thereafter, various in vivo and in vitro models of postconditioning and its potential protective mechanisms are discussed. Since the concept of postconditioning is so closely associated with that of preconditioning and both share some common protective mechanisms, whether a combination of preconditioning and postconditioning offers greater protection than preconditioning or postconditioning alone is also discussed.