Ischemic Postconditioning Research Articles

Ischemic postconditioning improves the outcome of organs from donors after cardiac death in a pig liver transplantation model and provides synergistic protection with hypothermic machine perfusion.

This study investigated whether ischemic postconditioning (IPO) improved the outcome of organs from donors after cardiac death and had a synergistic effect with hypothermic machine perfusion (HMP) in a pig liver transplantation model. A donor after cardiac death (DCD) model was developed in 48 healthy Bama miniature pigs randomly divided into four groups: simple cold storage group (SCS group), IPO group, HMP group, HMP-IPO group. The levels of serum alanine aminotransferase (ALT), total bilirubin, histopathological findings, apoptotic activity of hepatocytes, international normalized ratio (INR), tumor necrosis factor-α (TNF-α), and Malondialdehyde (MDA) were compared. All recipients in the SCS group died within 6h after transplantation. The livers of the recipients in the IPO had 50% survival on day 5. HMP allowed 83.3% survival and HMP-IPO allowed 100% survival. After reperfusion, the recipients in the IPO and HMP-IPO group had lower ALT and total bilirubin levels, less Suzuki score, less apoptosis, and less injury to hepatocytes and biliary ducts and attenuated inflammatory response and oxidative load. IPO improved the outcome of organs from donors after cardiac death and had a synergistic effect with HMP in the pig liver transplantation model.

Cardioprotective effects of co-administration of thymoquinone and ischemic postconditioning in diabetic rats.

Objective(s): Ischemia/reperfusion (I/R) is a leading cause of myocardial infarction (MI) injury, contributing to excess injury to cardiac tissues involved in inflammation, apoptosis, and oxidative stress. The present study was conducted to examine the effects of combined thymoquinone (TQ) with ischemic postconditioning (IPostC) therapy on apoptosis and inflammation due to I/R injury in diabetic rat hearts. Materials and Methods:A single dose injection of streptozotocin (STZ; 60 mg/kg) was administered to thirty-two Wistar male rats to induce diabetes. Hearts were fixed on a Langendorff setting and exposed to a 30 min regional ischemia subsequently to 60 min reperfusion. IPostC was induced at the onset of reperfusion by 3 cycles of 30 sec R/I. ELISA, Western blotting assay, and TUNEL staining were applied to assess the cardioprotective effect of IPostC and TQ against I/R injury in diabetic and non-diabetic rats.Results:Administration of TQ alone in non-diabetic isolated hearts significantly diminished CK-MB, TNF-α, IL-1β, and apoptosis and enhanced p-GSK-3β and Bcl-2 (P<0.05). Following administration of TQ, the cardioprotective effects of IPostC by elevating p-GSK-3β and Bcl-2 and alleviating apoptosis and inflammation were reestablished compared with non-IPostC diabetic hearts. Conclusion:These results provide substantial evidence that co-administration of TQ plus IPostC can exert cardioprotective effects on diabetic myocardium during I/R damage by attenuating the inflammatory response and apoptosis.

Ischemic postconditioning ameliorates acute kidney injury induced by limb ischemia/reperfusion via transforming TLR4 and NF-\u03baB signaling in rats

BackgroundThe present study investigated the influence of ischemic postconditioning (I-postC) on the adjustment of renal injury after limb ischemia-reperfusion (I/R) injury, to elucidate the mechanisms of the Toll-like receptor 4 (TLR 4)/NF-κB signaling pathway using histopathological and immunohistochemical methods.MethodsMale Sprague-Dawley rats were randomly assigned to five groups (numbered from 1 to 5): the sham group (Group 1, only the anesthesia procedure was conducted without limb I/R), the I/R group (Group 2, 4 h of reperfusion was conducted following 4 h limb ischemia under anesthesia), the I/R + I-postC group (Group 3, 4 h of ischemia and 4 h of reperfusion was conducted; before perfusion, 5 min of limb ischemia and 5 min of reperfusion were performed in the rats and repeated 3 times), the I/R + TAK group (Group 4, rats were injected with TLR4 antagonist TAK through the caudal vein before limb ischemia and reperfusion under anesthesia), the TAK group (Group 5, rats were injected with TAK, and the anesthesia procedure was conducted without limb I/R). Histological changes in the kidney in different groups were observed, and the extent of tubular injury was assessed. Changes in biochemical indexes and the expression of inflammatory factors, TLR4, and NF-κB were also evaluated.ResultsCompared with rats in the I/R group, the secretion of inflammatory factors and the expression levels of TLR4 and NF-κB were decreased in rats in the I/R + I-postC group. Histological analysis revealed renal injury, including inflammatory cell infiltration, dilatation of the tubuli lumen, congestion in glomerular capillaries, degeneration of tubuli epithelial cells, and necrosis was ameliorated by I-postC. Immunohistochemical studies showed that I/R-induced elevation in TLR4 and NF-κB expression was reduced by I-postC treatment. Moreover, the expression levels of TLR4, NF-κB, and inflammatory factors in rats in the I/R + TAK group were also decreased, and the renal pathological lesion was alleviated, which was similar to that in rats in the I/R + I-postC group.ConclusionsThe present findings suggest that I-postC can reduce tissue injury and kidney inflammation induced by limb I/R injury, possibly via inhibition of the TLR4 and NF-κB pathways.

Cardioprotective efficiency of pharmacological postconditioning using lactic acid in ischemia-reperfusion of the myocardium in rats with transitional hypercholesterolemia

Cardiovascular disease is the leading cause of death all over the world: for no other reason as many people die every year as from the cardiovascular disease. Taking into account the high medical and social significance of the problem of treating patients with coronary heart disease and acute myocardial infarction, the search for new effective methods of preventing or weakening ischemic myocardial damage and revealing the mechanisms of their implementation is an urgent task of modern experimental and clinical medicine. The aim of the study was to experimentally test the cardioprotective efficiency of pharmacological postconditioning with lactic acid in myocardial ischemia-reperfusion in rats with transient hypercholesterolemia.In the course of the study, it was found that remote ischemic postconditioning (RIPostC) during myocardial ischemia-reperfusion leads to an increase in the level of lactate in the blood and has an infarction-limiting effect in rats. It was revealed that lactate, after injection into the bloodstream of animals at a dose of 10 mg/kg 25 minutes after the start of reperfusion, like RIPostC, leads to a decrease in the necrosis area in the left ventricular of the myocardium. Pharmacological postconditioning with lactate is ineffective in the limiting necrosis area in the myocardium of the left ventricle of rats with transient hypercholesterolemia. The presence of such a risk factor for cardiovascular diseases as hypercholesterolemia can serve as a criterion for excluding the use of pharmacological postconditioning with lactate as a way to reduce ischemic and reperfusion damage to the myocardium in patients with acute myocardial infarction.

The effect of ischaemic postconditioning on mucosal integrity and function in equine jejunal ischaemia.

Ischaemic postconditioning (IPoC) has been shown to ameliorate ischaemia reperfusion injury in different species and tissues. To assess the feasibility of IPoC in equine small intestinal ischaemia and to assess its effect on histomorphology, electrophysiology and paracellular permeability. Randomised in vivo experiment. Experimental jejunal ischaemia was induced for 90min in horses under general anaesthesia. In the control group (C; n=7), the jejunum was reperfused without further intervention. In the postconditioning group (IPoC; n=7), reocclusion was implemented following release of ischaemia by clamping the mesenteric vessels in three cycles of 30seconds. This was followed by 120minutes of reperfusion in both groups. Intestinal microperfusion and oxygenation was measured during IPoC using spectrophotometry and Doppler flowmetry. Histomorphology and histomorphometry of the intestinal mucosa were assessed. Furthermore, electrophysiological variables and unidirectional flux rates of 3 H-mannitol were determined in Ussing chambers. Western blot analysis was performed to determine the tight junction protein levels of claudin-1, claudin-2 and occludin in the intestinal mucosa. Comparisons between the groups and time points were performed using a two-way repeated measures analysis of variance (ANOVA) or non-parametric statistical tests for the ordinal and not normally distributed data (significance P<.05). IPoC significantly reduced intestinal microperfusion during all clamping cycles yet affected oxygen saturation only during the first cycle. After reperfusion, Group IPoC showed significantly less mucosal villus denudation (mean difference 21.5%, P=.02) and decreased mucosal-to-serosal flux rates (mean difference 15.2nM/cm2 /h, P=.007) compared to Group C. There were no significant differences between the groups for the other tested variables. Small sample size, long-term effects were not investigated. Following IPoC, the intestinal mucosa demonstrated significantly less villus denudation and paracellular permeability compared to the untreated control group, possibly indicating a protective effect of IPoC on ischaemia reperfusion injury.

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.

The hypoxia sensitive metal transcription factor MTF-1 activates NCX1 brain promoter and participates in remote postconditioning neuroprotection in stroke

Remote limb ischemic postconditioning (RLIP) is an experimental strategy in which short femoral artery ischemia reduces brain damage induced by a previous harmful ischemic insult. Ionic homeostasis maintenance in the CNS seems to play a relevant role in mediating RLIP neuroprotection and among the effectors, the sodium-calcium exchanger 1 (NCX1) may give an important contribution, being expressed in all CNS cells involved in brain ischemic pathophysiology. The aim of this work was to investigate whether the metal responsive transcription factor 1 (MTF-1), an important hypoxia sensitive transcription factor, may (i) interact and regulate NCX1, and (ii) play a role in the neuroprotective effect mediated by RLIP through NCX1 activation. Here we demonstrated that in brain ischemia induced by transient middle cerebral occlusion (tMCAO), MTF-1 is triggered by a subsequent temporary femoral artery occlusion (FAO) and represents a mediator of endogenous neuroprotection. More importantly, we showed that MTF-1 translocates to the nucleus where it binds the metal responsive element (MRE) located at −23/−17 bp of Ncx1 brain promoter thus activating its transcription and inducing an upregulation of NCX1 that has been demonstrated to be neuroprotective. Furthermore, RLIP restored MTF-1 and NCX1 protein levels in the ischemic rat brain cortex and the silencing of MTF-1 prevented the increase of NCX1 observed in RLIP protected rats, thus demonstrating a direct regulation of NCX1 by MTF-1 in the ischemic cortex of rat exposed to tMCAO followed by FAO. Moreover, silencing of MTF-1 significantly reduced the neuroprotective effect elicited by RLIP as demonstrated by the enlargement of brain infarct volume observed in rats subjected to RLIP and treated with MTF-1 silencing. Overall, MTF-dependent activation of NCX1 and their upregulation elicited by RLIP, besides unraveling a new molecular pathway of neuroprotection during brain ischemia, might represent an additional mechanism to intervene in stroke pathophysiology.

Effect of remote ischemic post conditioning on incidence of contrast induce acute kidney injury in STEMI patients undergoing primary percutaneous coronary intervention

Abstract Funding Acknowledgements Type of funding sources: None. Background Primary percutaneous coronary intervention (PPCI) is a treatment of choice in ST elevation myocardial infarction patients (STEMI). However, this approach could increase the risk of contrast induce acute kidney injury (CI-AKI) due to iodinated contrast exposure to the patient. Remote ischemic post conditioning (RIPostC) is a non-invasive and simple method that not only has cardioprotective but also renoprotective effect that could prevent the incidence of CI-AKI. Purpose The aim of this study was to investigate the effect of RIPostC to CI-AKI incident in STEMI patients undergoing PPCI. Methods This study uses pre and post-test only with control group design with experimental research designs. Data was taken at the Instalasi Pelayanan Jantung Terpadu (IPJT) RSUP Dr. M. Djamil Padang from June 2019 until March 2020, there were 66 patients with ST-segment elevation myocardial infarction (STEMI) being performed RIPostC procedure. with intermittent ischaemia and reperfusion applied to the arm through five cycles of 5-min inflation and 5-min deflation of an automated cuff device after crossing wire. Creatinine and eGFR were measured pre and 48 hours post PPCI. CI-AKI diagnosis based on increase of creatinine level &amp;gt;0,5 mg/dL or 25% from baseline value on 48 hours after PPCI. Bivariate analysis was performed to determine the effect RIPostC to incidence of CI-AKI using the Chi-square test. Result A total of 66 patients who underwent the PPCI procedure were divided into two groups RIPostC (n = 33) and without RIPostC (n = 33). The baseline characteristic in both of group was similar. The RIPostC group had a lower CI-AKI incident if we compare with the non RIPostC (15,2% vs 42,4%, p &amp;lt; 0,05). Conclusion RIPostC effectively reduced incidence of CI-AKI in STEMI patient who underwent the PPCI with statistically significant result. Effect of RIPostC in CI-AKI post PPCIPPCICI-AKI (+)(f/%)CI-AKI (-)(f/%)Total(f/%)OR (95% CI)p valueRIPostC (+)5 (15,2)28 (84,8)33 (100)0,024 (0,07-0,76)0,03*bRIPostC (-)14 (42,4)19 (57,6)33 (100)Total19 (28,8)47 (71,2)66 (100)* significant p if &amp;lt; 0,05b, chi square testAbstract Figure. Effect of RIPostC in CI-AKI post PPCI

Effect of remote ischemic post conditioning on kidney function in STEMI patients undergoing primary percutaneous coronary intervention

Abstract Funding Acknowledgements Type of funding sources: None. Background Primary percutaneous coronary intervention (PPCI) is a treatment of choice in ST elevation myocardial infarction patients (STEMI). However, this approach could affect the kidney function due to iodinated contrast exposure to the patient. Remote ischemic post conditioning (RIPostC) is a non-invasive and simple method that not only has cardioprotective but also renoprotective effect for kidney function. Purpose The aim of this study was to investigate the effect of RIPostC to kidney function in STEMI patients undergoing PPCI. Methods This study uses pre and post-test only with control group design with experimental research designs. Data was taken at an Indonesian Heart Center from June 2019 until March 2020, there were 66 patients with ST-segment elevation myocardial infarction (STEMI) being performed RIPostC procedure with intermittent ischaemia and reperfusion applied to the arm through five cycles of 5-min inflation and 5-min deflation of an automated cuff device after crossing wire. Creatinine and eGFR were measured pre and 48 hours post PPCI. Kidney function were determined by eGFR post PPCI, ΔeGFR (pre and 48 hours post PPCI), creatinine post PPCI and Δcreatinine (pre and 48 hours post PPCI). Bivariate analysis was performed to determine the effect RIPostC to kidney function using the Chi-square test. Result A total of 66 patients who underwent the PPCI procedure were divided into two groups RIPostC (n = 33) and without RIPostC (n = 33). The baseline characteristic in both of group was similar. We found that there were no differences of eGFR (70,46 ± 23,06 vs 65,88 ± 23,36, p = 0,424), ΔeGFR (0 [-34,68 - 37,32] vs 0 [-121,53 - 29,70], p value= 0,406), creatinine (1,00 [0,70 - 4,60] vs 1,20 [0,60-4,10], p value= 0,633) and Δcreatinine (0 [-1,20-1,10] vs 0 [-0,50-0,90], p value= 0,390) RIPostC group had a lower CI-AKI incident if we compare with the non RIPostC (15,2% vs 42,4%, p &amp;lt; 0,05). Conclusion Remote ischaemic conditioning does not significantly improve kidney function (eGFR, ΔeGFR, creatinine and Δcreatinine) in patients with STEMI undergoing PPCI The differences of kidney functionVariableRIPostCControlp valueeGFR post PPCI (ml/min/1,73 m2), mean70,46 ± 23,0665,88 ± 23,360,424aΔeGFR(ml/min/1,73 m2), median0 [-34,68 - 37,32]0 [-121,53 - 29,70]0,406bCreatinine post PPCI (mg/dL), median1,00 [0,70 - 4,60]1,20 [0,60-4,10]0,633bΔcreatinine (mg/dL), median0 [-1,20-1,10]0 [-0,50-0,90]0,390ba = Independent sample T testb = mann whitney testAbstract Figure. ΔeGFR and Δcreatinine pre and post PPCI

Postconditioning attenuates myocardial ischemia-reperfusion injury by inhibiting complement activation and upregulation of miR-499.

The complement system plays a vital role in myocardial ischemia/reperfusion (I/R) injury. microRNA (miR)-499 is involved in the cardioprotection of ischemic postconditioning (IPostC). The present study aimed to study the role of the complement system and miR-499 in IPostC. Rat hearts were subjected to coronary ligation for 30 min, followed by reperfusion for 2 h. IPostC was introduced at the onset of reperfusion with three cycles of reperfusion for 30 sec and coronary artery occlusion for 30 sec. To study the role of miR-499 in IPostC, adeno-associated virus (AAV) vectors of miR-499-5p (AAV-miR-499-5p) and miR-499-5p-sponge (AAV-miR-499-5p-sponge) were transfected via tail vein injection, followed by IPostC protocols. Cardiac injury as well as the status of local and systemic complement activation and inflammation were assessed. IPostC significantly attenuated I/R-induced rat cardiomyocyte apoptosis and the myocardial infarct size. These beneficial effects were accompanied by decreased local and circulating complement component (C)3a and C5a levels, decreased inflammatory marker expression, decreased NF-κB signaling and increased cardiac miR-499 expression. AAV-miR-499-5p prevented local and systemic complement activation and inflammation as well as enhanced the cardioprotection of IPostC, whereas AAV-miR-499-5p-sponge produced the opposite effects. In summary, IPostC protected the rat myocardium against I/R injury, by inhibiting local and systemic complement activation; inflammation; NF-κB signaling; and upregulation of miR-499. As such, miR-499 may have a critical role in IPostC-mediated cardioprotection against I/R injury.

Ischaemic postconditioning reduces apoptosis in experimental jejunal ischaemia in horses

BackgroundIschaemic postconditioning (IPoC) refers to brief periods of reocclusion of blood supply following an ischaemic event. This has been shown to ameliorate ischaemia reperfusion injury in different tissues, and it may represent a feasible therapeutic strategy for ischaemia reperfusion injury following strangulating small intestinal lesions in horses. The objective of this study was to assess the degree cell death, inflammation, oxidative stress, and heat shock response in an equine experimental jejunal ischaemia model with and without IPoC.MethodsIn this randomized, controlled, experimental in vivo study, 14 horses were evenly assigned to a control group and a group subjected to IPoC. Under general anaesthesia, segmental ischaemia with arterial and venous occlusion was induced in 1.5 m jejunum. Following ischaemia, the mesenteric vessels were repeatedly re-occluded in group IPoC only. Full thickness intestinal samples and blood samples were taken at the end of the pre-ischaemia period, after ischaemia, and after 120 min of reperfusion. Immunohistochemical staining or enzymatic assays were performed to determine the selected variables.ResultsThe mucosal cleaved-caspase-3 and TUNEL cell counts were significantly increased after reperfusion in the control group only. The cleaved-caspase-3 cell count was significantly lower in group IPoC after reperfusion compared to the control group. After reperfusion, the tissue myeloperoxidase activity and the calprotectin positive cell counts in the mucosa were increased in both groups, and only group IPoC showed a significant increase in the serosa. Tissue malondialdehyde and superoxide dismutase as well as blood lactate levels showed significant progression during ischaemia or reperfusion. The nuclear immunoreactivity of Heat shock protein-70 increased significantly during reperfusion. None of these variables differed between the groups. The neuronal cell counts in the myenteric plexus ganglia were not affected by the ischaemia model.ConclusionsA reduced apoptotic cell count was found in the group subjected to IPoC. None of the other tested variables were significantly affected by IPoC. Therefore, the clinical relevance and possible protective mechanism of IPoC in equine intestinal ischaemia remains unclear. Further research on the mechanism of action and its effect in clinical cases of strangulating colic is needed.

Abstract P781: Ischemic Postconditioning Protects Against Hemorrhagic Transformation Induced by Hyperglycemia in Ischemic Stroke

Background: Hyperglycemia occurs in over 40% of ischemic stroke patients, which induces hemorrhagic transformation (HT) and worsens stroke outcomes. The management of hyperglycemia with insulin did not show favorable outcomes. Thus, strategies for managing hyperglycemia-exacerbated stroke injury are urgently needed. We previously demonstrated that ischemic postconditioning (IPostC) (repeated transient interruption of cerebral blood flow during reperfusion) can reduce brain infarct size and improve neurological outcomes. In this study, we hypothesized that IPostC can reduce HT in ischemic stroke with acute hyperglycemia. Method: Male mice were subjected to middle cerebral artery occlusion (MCAO) for 1 hour, followed by reperfusion to mimic ischemic stroke. Glucose was injected before MCAO to induce hyperglycemia. IPostC was initiated upon reperfusion with 3 cycles of 30-second reperfusion followed by 10 seconds of MCA occlusion. Brain infarct was visualized by TTC staining and quantitated using Image J. Hemorrhagic transformation was evaluated by hemorrhagic scores. Result: Acute hyperglycemia significantly increased the brain infarct size (by 25%, p&lt;0.01), brain edema (p&lt;0.001) and hemorrhagic transformation (HT) (average HT scores: 0.75 in MCAO group vs 15.6 in MCAO plus hyperglycemia group, p&lt;0.001), Mice with hyperglycemia also exhibited more severe neurological deficit and higher mortality rate at 24 hours after MCAO. 2) IPostC treatment significantly reduced brain infarct size (p&lt;0.01), brain edema (p&lt;0.05) and attenuated HT (p&lt;0.001). Neurological deficit and mortality rate was reduced with IPostC treatment. Conclusion: Our findings suggest that IPostC can counteract the effects of acute hyperglycemia and reduce brain injury, edema and HT after stroke. Grant/Other Support: NIH Grant R01NS064136C

Remote Ischemic Postconditioning vs. Physical Exercise After Stroke: an Alternative Rehabilitation Strategy?

There remain debates on neuroprotection and rehabilitation techniques for acute ischemic stroke patients. Therapeutic physical exercise following stroke has shown promise but is challenging to apply clinically. Ischemic conditioning, which has several clinical advantages, is a potential neuroprotective method for stroke rehabilitation that is less understood. In the present study, the rehabilitative properties and mechanisms of physical exercise and remote ischemic postconditioning (RIPostC) after stroke were compared and determined. A total of 248 adult male Sprague-Dawley rats were divided into five groups: (1) sham, (2) stroke, (3) stroke with intense treadmill exercise, (4) stroke with mild treadmill exercise, and (5) stroke with RIPostC. Focal ischemia was evaluated by infarct volume and neurological deficit. Long-term functional outcomes were represented through neurobehavioral function tests: adhesive removal, beam balance, forelimb placing, grid walk, rota-rod, and Morris water maze. To further understand the mechanisms underlying neurorehabilitation and verify the presence thereof, we measured mRNA and protein levels of neuroplasticity factors, synaptic proteins, angiogenesis factors, and regulation molecules, including HIF-1α, BDNF, TrkB, and CREB. The key role of HIF-1α was elucidated by using the inhibitor, YC-1. Both exercise intensities and RIPostC significantly decreased infarct volumes and neurological deficits and outperformed the stroke group in the neurobehavioral function tests. All treatment groups showed significant increases in mRNA and protein expression levels of the target molecules for neurogenesis, synaptogenesis, and angiogenesis, with intermittent further increases in the RIPostC group. HIF-1α inhibition nullified most beneficial effects and indicative molecule expressions, including HIF-1α, BDNF, TrkB, and CREB, in both procedures. RIPostC is equally, or superiorly, effective in inducing neuroprotection and rehabilitation compared to exercise in ischemic rats. HIF-1α likely plays an important role in the efficacy of neuroplasticity conditioning, possibly through HIF-1α/BDNF/TrkB/CREB regulation.

Mitochondrial dysfunction in fatal ventricular arrhythmias.

Ventricular fibrillation (VF) and sudden cardiac arrest (SCA) remain some of the most important public health concerns worldwide. For the past 50years, the recommendation in the Advanced Cardiac Life Support (ACLS) guidelines has been that defibrillation is the only option for shockable cardiac arrest. There is growing evidence to demonstrate that mitochondria play a vital role in the outcome of postresuscitation cardiac function. Although targeting mitochondria to improve resuscitation outcome following cardiac arrest has been proposed for many years, understanding concerning the changes in mitochondria during cardiac arrest, especially in the case of VF, is still limited. In addition, despite new research initiatives and improved medical technology, the overall survival rates of patients with SCA still remain the same. Understanding cardiac mitochondrial alterations during fatal arrhythmias may help to enable the formulation of strategies to improve the outcomes of resuscitation. The attenuation of cardiac mitochondrial dysfunction during VF through pharmacological intervention as well as ischaemic postconditioning could also be a promising target for intervention and inform a new paradigm of treatments. In this review, the existing evidence available from in vitro, ex vivo and in vivo studies regarding the roles of mitochondrial dysfunction during VF is comprehensively summarized and discussed. In addition, the effects of interventions targeting cardiac mitochondria during fatal ventricular arrhythmias are presented. Since there are no clinical reports from studies targeting mitochondria to improve resuscitation outcome available, this review will provide important information to encourage further investigations in a clinical setting.

Remote Limb Ischemic Postconditioning Protects against Ischemic Stroke via Modulating Microglia/Macrophage Polarization in Mice.

Aim The protection against ischemia/reperfusion injury mediated by remote limb ischemic postconditioning (RIPC) shows great clinical value in ischemic stroke therapy, but the particular mechanism of RIPC remains unclear. Methods We carried out middle cerebral artery occlusion/reperfusion (MCAO/R) surgery on C57BL/6 male mice. RIPC was generated by 10-minute occlusion followed by the same period of reperfusion of the bilateral hind limb femoral artery and repeated for 3 cycles. Infarct size and neurological score were performed to assess stroke outcomes. Ly6Chi monocytes were quantified in the blood and brain by flow cytometry. Real-time PCR, ELISA, and immunofluorescence were utilized to detect phenotype of proinflammatory M1 and anti-inflammatory M2 microglia/macrophage. Nuclear factor κB (NF-κB) and peroxisome proliferator-activated receptor γ (PPARγ) levels were detected using Western blot. Results At 24 and 72 h after MCAO, RIPC drastically attenuated infarct size and ameliorated the neurological deficits of mice and facilitated transmigration of Ly6Chi monocytes to the brain postischemia reperfusion. Furthermore, RIPC contributed to increased M2 and reduced M1 microglia/macrophage through inhibiting NF-κB and promoting PPARγ activation. Conclusion Our results reveal pharmacological effect of RIPC in promoting microglia/macrophage transferring from M1 to M2 phenotype after MCAO/R in mice, which provides theoretical support for the therapeutic effect of RIPC in ischemic stroke.

The neuroprotective role of SIRT1/PGC-1α signaling in limb postconditioning in cerebral ischemia/reperfusion injury

Limb ischemic postconditioning (LPostC) is an innovative treatment for ischemia/reperfusion injury (IRI). However, its mechanisms have not yet been elucidated. Herein, we assessed the importance of SIRT1/PGC-1α signaling in LPostC neuroprotection following cerebral I/R injury in rats. In this study, we used 40 male SD rats that were separated into sham, I/R, LPostC, and LPostC + EX-527 (SIRT1 inhibitor) groups (each with 10 rats), with a middle cerebral artery occlusion (MCAO) model used to induce IRI. LPostC was induced via three cycles of bilateral femoral artery occlusion and non-occlusion. At 24 h, we examined SIRT1 and PGC-1α protein levels by western blotting in ischemic areas. The mRNA levels of SIRT1, PGC-1α, NRF-1 and CytoC1 in the ischemic area were assessed by qRT-PCR. We also quantified neurological deficit scores and evaluated cerebral infarct volume by TTC staining. TUNEL staining was used to evaluate the apoptotic rates in neurons. In addition, antioxidant SOD activity and MDA levels were measured by the Microplate Reader. Our findings indicated that LPostC increased the protein and mRNA levels of SIRT1 and PGC-1α in cerebral ischemic tissue, then up-regulated the downstream protein NRF-1, down-regulated CytoC1, and improved mitochondrial function, thereby reducing brain damage. LPostC relieved cerebral IRI via reducing the size of the cerebral infarct, neuronal apoptosis, and neurological deficits. Meanwhile LPostC increased SOD activity and reduced MDA content in brain tissue. Treatment with EX-527 reversed the protection of LPostC after IRI (all P < 0.05). This suggests that LPosC may protect against cerebral IRI at least in part via up-regulating the SIRT1/PGC-1α signaling pathway, thereby increasing the individual’s ability to resist oxidative stress.

Acute administration of the olive constituent, oleuropein, combined with ischemic postconditioning increases myocardial protection by modulating oxidative defense

Oleuropein, one of the main polyphenolic constituents of olive, is cardioprotective against ischemia reperfusion injury (IRI). We aimed to assess the cardioprotection afforded by acute administration of oleuropein and to evaluate the underlying mechanism. Importantly, since antioxidant therapies have yielded inconclusive results in attenuating IRI-induced damage on top of conditioning strategies, we investigated whether oleuropein could enhance or imbed the cardioprotective manifestation of ischemic postconditioning (PostC). Oleuropein, given during ischemia as a single intravenous bolus dose reduced the infarct size compared to the control group both in rabbits and mice subjected to myocardial IRI. None of the inhibitors of the cardioprotective pathways, l-NAME, wortmannin and AG490, influence its infarct size limiting effects. Combined oleuropein and PostC cause further limitation of infarct size in comparison with PostC alone in both animal models. Oleuropein did not inhibit the calcium induced mitochondrial permeability transition pore opening in isolated mitochondria and did not increase cGMP production. To provide further insights to the different cardioprotective mechanism of oleuropein, we sought to characterize its anti-inflammatory potential in vivo. Oleuropein, PostC and their combination reduce inflammatory monocytes infiltration into the heart and the circulating monocyte cell population. Oleuropein's mechanism of action involves a direct protective effect on cardiomyocytes since it significantly increased their viability following simulated IRI as compared to non-treated cells. Οleuropein confers additive cardioprotection on top of PostC, via increasing the expression of the transcription factor Nrf-2 and its downstream targets in vivo. In conclusion, acute oleuropein administration during ischemia in combination with PostC provides robust and synergistic cardioprotection in experimental models of IRI by inducing antioxidant defense genes through Nrf-2 axis and independently of the classic cardioprotective signaling pathways (RISK, cGMP/PKG, SAFE).

Remote Ischemic Postconditioning Inhibited Mitophagy to Achieve Neuroprotective Effects in the Rat Model of Cardiac Arrest.

Remote ischemic postconditioning (RI-postC) is an effective measure to improve nerve function after cardiac arrest. However, the brain protective mechanism of RI-postC has not been fully elucidated, and whether it is related to mitophagy is unclear. In this study, we used the rat model of cardiac arrest to study the effect of RI-postC on mitophagy and explore its possible signaling pathways. Rats were randomly divided into Sham group, CA/CPR group, Mdivi-1 group and RI-postC group. The animal model of cardiac arrest was established by asphyxia. RI-postC was performed by clamping and loosening the left femoral artery. Mdivi-1 was treated with a single intravenous injection. Levels of TOMM20, TIM23, Mfn1, PINK1 and parkin were detected by western blots. Mitochondrial membrane potential was measured by flow cytometry. Real-time PCR was used to detect relative mitochondrial DNA levels. The apoptosis of hippocampal neurons was detected by flow and TUNEL. In addition, Histopathological tests were performed. The results showed that RI-postC was similar to the mitophagy inhibitor Mdivi-1, which could inhibit the decrease of mitophagy-related protein level, improve mitochondrial membrane potential and up-regulate the ratio of mt-Atp6/Rpl13 after cardiopulmonary resuscitation (CPR). Furthermore, RI-postC could also reduce the rate of hippocampal nerve apoptosis and the damage of hippocampal neurons after CPR. Moreover, RI-postC and Mdivi-1 could reduce the protein levels of PINK1 and parkin in mitochondria after CPR, while increasing PINK1 levels in the cytoplasm. These findings suggested that RI-postC could inhibit the overactivation mitophagy through the PINK1/parkin signaling pathway, thus providing neuroprotective effects.

Connection of reactive oxygen species as an essential actor for the mechanism of phenomena; ischemic preconditioning and postconditioning: Come to age or ripening?

Ischemic preconditioning (IPC), in 1986, and then ischemic postconditioning (IPoC), in 2003, were determined and lots of studies on the many organs were performed about the preventive effects of these strong endogenous mechanisms on the relevant tissues against ischemia-reperfusion and their protective impressions have been emphasized by many authorities up to date. Reactive oxygen molecules are immensely active molecules, originating from molecular oxygen, playing a principal role in intracellular signalization, aging, and various pathologic conditions. Reactive oxygen species (ROS) such as superoxide anion and hydrogen peroxide are known in the pathogenesis of ischemia-reperfusion (I/R) injury. In the pathogenesis of cellular and tissue injury in I/R, the significant output of ROS in the initial phase of reperfusion, particularly between the 1st and 7th min, has been propounded as being an essential and crucial main factor for the phenomena. Even though a great deal of mechanisms has been asserted for IPC and IPoC, the distinct shielder mechanism(s) was/were not clearly proved yet. However, occupying a significant place of ROS among these forecasted mechanisms has been advocated up to date.

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.