Ischemic Postconditioning Confers No Benefit to Left Ventricular Systolic Function: A Meta-Analysis of Cardiac Magnetic Resonance Imaging Results

Ischemic postconditioning (IPoC) is a technique suggested to reduce reperfusion injury in patients suffering acute ST-elevation myocardial infarction (STEMI), although its use is highly controversial. This meta-analysis aimed to evaluate the effect of IPoC with percutaneous coronary intervention in patients with acute STEMI, as measured by follow-up left ventricular ejection fraction (LVEF) on cardiac magnetic resonance imaging. The investigators searched PubMed, Embase, and Web of Science for all randomized controlled trials published during the last 2 decades. After the removal of duplicates, 2,021 articles from online databases had been identified using relevant search criteria. The included randomized controlled trials had studied patients with acute STEMI and Thrombolysis in Myocardial Infarction flow 0 to 1 at presentation and had measured follow-up LVEF using cardiac magnetic resonance imaging. Overall, 11 studies (n = 1,339 patients) qualified for inclusion. In each study, the control group did not differ significantly from the experimental group. The pooled data from included studies were analyzed using standardized mean difference between IPoC and control groups, and the 95% confidence interval for LVEF; the results were visualized using a forest plot. Bivariate regression analyses and 1-way analyses of LVEF coefficient ratios were done to isolate for various clinical and procedural parameters. An analysis of pooled data of the IPoC (n = 674) and control (n = 665) groups showed that IPoC did not significantly impact follow-up LVEF (using standardized mean difference 0.10, 95% confidence interval 0.00 to 0.21). Further analysis showed that IPoC did not improve follow-up LVEF when isolating for relevant clinical and procedural parameters. In conclusion, the use of IPoC as an adjunctive therapy to percutaneous coronary intervention seemingly provides no benefit to left ventricular systolic function, as quantified with cardiac magnetic resonance imaging, in patients with acute STEMI with Thrombolysis in Myocardial Infarction flow 0 to 1.

Ischemic postconditioning protects against acute kidney injury after limb ischemia reperfusion by regulating HMGB1 release and autophagy

Ischemic postconditioning (I-PostC) has a protective effect against acute kidney injury (AKI) induced by limb ischemia-reperfusion (LIR); however, the exact mechanism remains to be elucidated. Our study aims to investigate the potential involvement of high-mobility group box 1 protein (HMGB1) and autophagy in renoprotection generated by I-PostC. A rat model of LIR-induced AKI was established and rats were randomly assigned to five groups: (i) sham-operated control, (ii) I/R, (iii) I/R + I-PostC, (iv) I/R + I-PostC + rapamycin (autophagy activator), and (v) I/R + I-PostC + 3-methyladenine (autophagy inhibitor). Morphological changes in the kidneys were assessed by histology, and ultrastructural changes in renal tubular epithelial cells and glomerular podocytes were observed by transmission electron microscopy. The levels of kidney function parameters, serum inflammatory factors, and autophagy markers were detected. The results showed that the levels of HMGB1, Beclin1, LC3-II/LC3-I, and inflammatory cytokines (TNF-α and IL-6) were significantly higher in the I/R group compared to the sham control in serum and in renal tissues. I-PostC significantly reduced the levels of HMGB1, Beclin1, LC3-II/LC3-I, and inflammatory cytokines in renal tissues and improved renal function. Renal histopathology and ultrastructural observations indicated that I-PostC alleviated renal tissue injury. In addition, rapamycin (autophagy activator) treatment increased the levels of inflammatory cytokine expression levels and decreased renal function, reversed the protective effect of I-PostC against LIR-induced AKI. In conclusion, I-PostC could play a protective role against AKI by regulating the release of HMGB1 and inhibiting autophagy activation.

Safety and Tolerability of Direct Ischemic Postconditioning Following Thrombectomy for Acute Ischemic Stroke

BACKGROUND

Experimental studies have demonstrated the neuroprotection of ischemic postconditioning (IPostC) in acute ischemic stroke by attenuating ischemia-reperfusion injury. This study aimed to investigate the safety and tolerability of direct IPostC in both a dog model and patients with acute ischemic stroke treated with thrombectomy.

METHODS

The study involved 2 parts. First, IPostC was induced by repeated balloon inflation and deflation in dogs, where a low-pressure balloon was navigated to the anterior spinal artery, and 4 cycles of 5-minute ischemia followed by 5-minute reperfusion were performed. Vascular injuries were assessed using angiography and vascular tissue specimens. Then, a 3+3 dose-escalation trial was conducted in patients with acute ischemic stroke following successful thrombectomy recanalization. Patients received direct IPostC with ischemia and reperfusion durations in progressive increments of 0, 1, 2, 3, 4, and 5 minutes ×4 cycles. Major adverse responses were defined as vessel perforation, rupture, dissection, reocclusion, severe vasospasm, thrombotic events, and rupture of the balloon.

RESULTS

IPostC was investigated in 4 dogs. No vessel perforation or rupture, dissection, or vasospasm was observed under the angiography. Only 1 vessel experienced mild injury between the intima and the internal elastic membrane detected on a histopathologic slide. Then, 18 patients were recruited. The duration of IPostC was progressively escalated with no major response happened. No patient experienced agitation, discomfort, or other tolerability issues. Five patients (27.8%) experienced any intracranial hemorrhage after thrombectomy, and 1 (5.6%) was symptomatic. At 3-month follow-up, no patient died, and 9 patients (50%) achieved functional independence.

CONCLUSIONS

Direct IPostC inducing by 4 cycles of 5-minute ischemia followed by 5-minute reperfusion is safe, feasible, and tolerable in patients with acute ischemic stroke treated with thrombectomy. Further investigations are needed to determine the safety and preliminary efficacy of direct IPostC.

REGISTRATION

URL: https://www.

CLINICALTRIALS

gov; Unique identifier: NCT05153655.

Remote Ischemic Conditioning: Challenges and Opportunities

Remote ischemic conditioning (RIC) has been investigated as a promising, safe, and well-tolerated nonpharmacological therapy for cardio-cerebrovascular disease over the past 3 decades; variable results have been found when it is used in cerebrovascular versus cardiovascular disease. For patients with cardiovascular disease, milestone studies suggest that the roles of RIC may be limited. Recently, however, 2 large trials investigating RIC in patients with cerebrovascular disease found promising results, which may reignite the field's research prospects after its setbacks in the cardiovascular field. This perspectives article highlights several important clinical trials of RIC in the cardio-cerebrovascular disease and describes the many challenges of RIC in clinical translation. Finally, based on the available evidence, several promising research directions such as chronic RIC, early initiation in target population, improvement of compliance, better understanding of dosing, and identification of specific biomarkers are proposed and should be investigated before RIC can become applied into clinical practice for patient benefit.

Hexafluoroisopropanol decreases liver ischemia-reperfusion injury by downregulation of high mobility group box-1 protein

Liver ischemia-reperfusion (IR) injury is associated with poor outcome after liver transplantation and liver resections. Hexafluoroisopropanol (HFIP) is a tri-fluorinated metabolites of volatile anesthetics and has modulatory effects on inflammation that have been observed mainly in cell culture experiments. In this survey, we investigated the effects of HFIP in a rat model of normothermic hepatic ischemia-reperfusion injury. Twenty-four male Wistar rats were randomized into three groups: (1) control in which animals were submitted to 30 min of partial liver ischemia with resection of non-ischemic liver lobes immediate after reperfusion, (2) pre-ischemia (PI) group in which animals received intravenous HFIP (67 mg/kg) 5 min before liver ischemia, and (3) pre-reperfusion (PR) group in which animals received intravenous HFIP (67 mg/kg) 5 min before reperfusion. Four hours after reperfusion, all animals were euthanized for sample collection. Aspartate and alanine transaminases, glucose, and high mobility group box-1 (HMGB-1) protein concentrations showed a significant decreased, and malondialdehyde was increased in the PR group compared with control and PI groups. Interleukin 6 (IL-6) was increased in the PI group compared with control and PR groups. IL-10 and -12 were increased in the PR and PI groups, respectively, when compared with the control group. Glucose decreased in the PR when compared with the control group. Post-conditioning with HFIP led to a decrease in hepatocellular injury and was associated with a downregulation of HMGB-1. The HFIP resulted in a better control of inflammatory response to ischemia-reperfusion even without causing a reduction in oxidative stress.

Remote ischemic postconditioning has a detrimental effect and remote ischemic preconditioning seems to have no effect on small intestinal anastomotic strength

BACKGROUND

The effect of remote pre- and postconditioning on anastomotic healing has been sparsely studied. The aim of our study was to investigate whether remote ischemic conditioning (RIC) applied before and after the creation of a small bowel anastomosis had an effect on anastomotic healing on postoperative day five evaluated by a tensile strength test and histological analysis.

MATERIALS AND METHODS

Twenty-two female piglets were randomized into two groups. The intervention group (n = 12) received RIC on the forelimbs consisting of 15 min of ischemia followed by 30 min of reperfusion before the first end-to-end ileal anastomosis was created. The RIC procedure was repeated and the second and more distal anastomosis was performed. The control group (n = 10) had two similar anastomoses with similar time intervals but without RIC. On postoperative day five, the anastomoses were subjected to macroscopic evaluation, tensile strength test and histological examination.

RESULTS

Mean tensile strength when the first transmural rupture appeared (MATS-2) was significantly lower in the first anastomosis in the intervention group compared to the control group (11.4 N vs 14.7 N, p < .05). Similar result was found by the maximal strength (MATS-3) as defined by a drop in the load curve (12.3 N vs 15.9 N, p < .05). Histologically, a significantly higher necrosis score was found in the anastomosis in the intervention group (1.4 vs 0.8, p < .05). No other significant differences were found.

CONCLUSIONS

In conclusion, post-anastomotic remote ischemic conditioning had a detrimental effect and pre-anastomotic conditioning seems to have no effect on small intestinal anastomotic strength.

Effects of ischemic postconditioning and long non-coding RNAs in ischemic stroke

Stroke is a main cause of disability and death among adults in China, and acute ischemic stroke accounts for 80% of cases. The key to ischemic stroke treatment is to recanalize the blocked blood vessels. However, more than 90% of patients cannot receive effective treatment within an appropriate time, and delayed recanalization of blood vessels causes reperfusion injury. Recent research has revealed that ischemic postconditioning has a neuroprotective effect on the brain, but the mechanism has not been fully clarified. Long non-coding RNAs (lncRNAs) have previously been associated with ischemic reperfusion injury in ischemic stroke. LncRNAs regulate important cellular and molecular events through a variety of mechanisms, but a comprehensive analysis of potential lncRNAs involved in the brain protection produced by ischemic postconditioning has not been conducted. In this review, we summarize the common mechanisms of cerebral injury in ischemic stroke and the effect of ischemic postconditioning, and we describe the potential mechanisms of some lncRNAs associated with ischemic stroke.

Melatonin-Induced Postconditioning Suppresses NMDA Receptor through Opening of the Mitochondrial Permeability Transition Pore via Melatonin Receptor in Mouse Neurons

Mitochondrial membrane potential regulation through the mitochondrial permeability transition pore (mPTP) is reportedly involved in the ischemic postconditioning (PostC) phenomenon. Melatonin is an endogenous hormone that regulates circadian rhythms. Its neuroprotective effects via mitochondrial melatonin receptors (MTs) have recently attracted attention. However, details of the neuroprotective mechanisms associated with PostC have not been clarified. Using hippocampal CA1 pyramidal cells from C57BL mice, we studied the involvement of MTs and the mPTP in melatonin-induced PostC mechanisms similar to those of ischemic PostC. We measured changes in spontaneous excitatory postsynaptic currents (sEPSCs), intracellular calcium concentration, mitochondrial membrane potential, and N-methyl-D-aspartate receptor (NMDAR) currents after ischemic challenge, using the whole-cell patch-clamp technique. Melatonin significantly suppressed increases in sEPSCs and intracellular calcium concentrations. The NMDAR currents were significantly suppressed by melatonin and the MT agonist, ramelteon. However, this suppressive effect was abolished by the mPTP inhibitor, cyclosporine A, and the MT antagonist, luzindole. Furthermore, both melatonin and ramelteon potentiated depolarization of mitochondrial membrane potentials, and luzindole suppressed depolarization of mitochondrial membrane potentials. This study suggests that melatonin-induced PostC via MTs suppressed the NMDAR that was induced by partial depolarization of mitochondrial membrane potential by opening the mPTP, reducing excessive release of glutamate and inducing neuroprotection against ischemia-reperfusion injury.

Ischemic postconditioning protects nonculprit coronary arteries against ischemia-reperfusion injury via downregulating miR-92a, miR-328 and miR-494

BACKGROUND

Nonculprit lesions are closely related to the prognosis of patients with ST-segment elevation myocardial infarction (STEMI). Our previous research found that ischemic postconditioning (IP) could inhibit the progression of nonculprit lesions. However, the mechanism by which IP regulates the occurrence and development of nonculprit lesions remains unclear.

METHODS

Firstly, a rabbit ischemia-reperfusion (IR) model was constructed. Next, the morphological characteristics of the coronary arterial tissues and myocardial tissues of the rabbits were observed using hematoxylin-eosin (H&E) staining. Then, western blot was performed to detect the expressions of AT1, Cx43, β-tubulin, Bax, Bcl-2 and cleaved caspase 3. Finally, to further confirm the effect of IP on nonculprit coronary arterial tissues, an in vitro model of oxygen and glucose deprivation/reperfusion (OGD/R) was established.

RESULTS

IR notably induced the cells apoptosis in nonculprit coronary arterial tissues and in myocardial tissues, while IR-induced cell apoptosis was significantly inhibited by IP. In addition, IP protected nonculprit coronary arterial tissues against IR via downregulating miR-92a, miR-328 and miR-494 and mRNA AT1, Cx43 and β-tubulin. Consistently, OGD/R-induced injury of Human umbilical vein endothelial cells (HUVECs) was reversed by IP.

CONCLUSIONS

In this study, IP could protect nonculprit coronary arteries against IR injury via downregulating miR-92a, miR-328 and miR-494. Our findings may provide new directions for the treatment of nonculprit lesions.

Neuroprotective effects of long noncoding RNAs involved in ischemic postconditioning after ischemic stroke

During acute reperfusion, the expression profiles of long noncoding RNAs in adult rats with focal cerebral ischemia undergo broad changes. However, whether long noncoding RNAs are involved in neuroprotective effects following focal ischemic stroke in rats remains unclear. In this study, RNA isolation and library preparation was performed for long noncoding RNA sequencing, followed by determining the coding potential of identified long noncoding RNAs and target gene prediction. Differential expression analysis, long noncoding RNA functional enrichment analysis, and co-expression network analysis were performed comparing ischemic rats with and without ischemic postconditioning rats. Rats were subjected to ischemic postconditioning via the brief and repeated occlusion of the middle cerebral artery or femoral artery. Quantitative real-time reverse transcription-polymerase chain reaction was used to detect the expression levels of differentially expressed long noncoding RNAs after ischemic postconditioning in a rat model of ischemic stroke. The results showed that ischemic postconditioning greatly affected the expression profile of long noncoding RNAs and mRNAs in the brains of rats that underwent ischemic stroke. The predicted target genes of some of the identified long noncoding RNAs (cis targets) were related to the cellular response to ischemia and stress, cytokine signal transduction, inflammation, and apoptosis signal transduction pathways. In addition, 15 significantly differentially expressed long noncoding RNAs were identified in the brains of rats subjected to ischemic postconditioning. Nine candidate long noncoding RNAs that may be related to ischemic postconditioning were identified by a long noncoding RNA expression profile and long noncoding RNA-mRNA co-expression network analysis. Expression levels were verified by quantitative real-time reverse transcription-polymerase chain reaction. These results suggested that the identified long noncoding RNAs may be involved in the neuroprotective effects associated with ischemic postconditioning following ischemic stroke. The experimental animal procedures were approved by the Animal Experiment Ethics Committee of Kunming Medical University (approval No. KMMU2018018) in January 2018.

Remote Limb Ischemic Postconditioning Protects Against Ischemic Stroke by Promoting Regulatory T Cells Thriving

Background Remote limb ischemic postconditioning (RLIPoC) has been demonstrated to protect against ischemic stroke. However, the underlying mechanisms of RLIPoC mediating cross-organ protection remain to be fully elucidated. Methods and Results Ischemic stroke was induced by middle cerebral artery occlusion for 60 minutes. RLIPoC was performed with 3 cycles of 10-minute ischemia followed by 10-minute reperfusion of the bilateral femoral arteries immediately after middle cerebral artery reperfusion. The percentage of regulatory T cells (Tregs) in the spleen, blood, and brain was detected using flow cytometry, and the number of Tregs in the ischemic hemisphere was counted using transgenic mice with an enhanced green fluorescent protein-tagged Foxp3. Furthermore, the metabolic status was monitored dynamically using a multispectral optical imaging system. The Tregs were conditionally depleted in the depletion of Treg transgenic mice after the injection of the diphtheria toxin. The inflammatory response and neuronal apoptosis were investigated using immunofluorescent staining. Infarct volume and neurological deficits were evaluated using magnetic resonance imaging and the modified neurological severity score, respectively. The results showed that RLIPoC substantially reduced infarct volume, improved neurological function, and significantly increased Tregs in the spleen, blood, and ischemic hemisphere after middle cerebral artery occlusion. RLIPoC was followed by subsequent alteration in metabolites, such as flavin adenine dinucleotide and nicotinamide adenine dinucleotide hydrate, both in RLIPoC-conducted local tissues and circulating blood. Furthermore, nicotinamide adenine dinucleotide hydrate can mimic RLIPoC in increasing Tregs. Conversely, the depletion of Tregs using depletion of Treg mice compromised the neuroprotective effects conferred by RLIPoC. Conclusions RLIPoC protects against ischemic brain injury, at least in part by activating and maintaining the Tregs through the nicotinamide adenine dinucleotide/nicotinamide adenine dinucleotide hydrate pathway.

Mitochondrial Quality Control in Cardiac-Conditioning Strategies against Ischemia-Reperfusion Injury

Mitochondria are the central target of ischemic preconditioning and postconditioning cardioprotective strategies, which consist of either the application of brief intermittent ischemia/reperfusion (I/R) cycles or the administration of pharmacological agents. Such strategies reduce cardiac I/R injury by activating protective signaling pathways that prevent the exacerbated production of reactive oxygen/nitrogen species, inhibit opening of mitochondrial permeability transition pore and reduce apoptosis, maintaining normal mitochondrial function. Cardioprotection also involves the activation of mitochondrial quality control (MQC) processes, which replace defective mitochondria or eliminate mitochondrial debris, preserving the structure and function of the network of these organelles, and consequently ensuring homeostasis and survival of cardiomyocytes. Such processes include mitochondrial biogenesis, fission, fusion, mitophagy and mitochondrial-controlled cell death. This review updates recent advances in MQC mechanisms that are activated in the protection conferred by different cardiac conditioning interventions. Furthermore, the role of extracellular vesicles in mitochondrial protection and turnover of these organelles will be discussed. It is concluded that modulation of MQC mechanisms and recognition of mitochondrial targets could provide a potential and selective therapeutic approach for I/R-induced mitochondrial dysfunction.

Serum of limb remote ischemic postconditioning inhibits fMLP-triggered activation and reactive oxygen species releasing of rat neutrophils

Objectives

The study explores the protective role of the peripheral serum of limb remote ischemic postconditioning (LRIP) in reducing the reactive oxygen species (ROS) levels and neutrophil activation, which are responsible for the deleterious reperfusion injury.

Methods

LRIP was induced in Sprague–Dawley rats by three cycles of 5 min occlusion /5 min reperfusion on the left hind limb. The blood samples were collected before LRIP or 0 and 1 h after LRIP (named Serum_Sham, Serum_LRIP0, Serum_LRIP1, respectively). The effects of LRIP serum on ROS level and neutrophils activation were determined. The expression of MyD88-TRAF6-MAPKs and PI3K/AKT pathways in neutrophils were examined.

Results

When compared with Serum_Sham, Serum_LRIP0 and Serum_LRIP1 significantly reduced the ROS released from neutrophils activated by fMLP. Meanwhile, the mRNA expression levels of NADPH oxidase subunit p22^phox and multiple ROS-producing related key proteins, such as NADPH oxidase subunit p47^phox ser 304, ser 345. MyD88, p-ERK, p-JNK and p-P38 expression of neutrophils were downregulated by Serum_LRIP0 and Serum_LRIP1. Serum_LRIP1 also downregulated p47^phox mRNA expression and tumor necrosis factor receptor-associated factor 6 (TRAF6) protein expression.

Conclusion

LRIP serum protects against ROS level and neutrophils activation involving the MyD88-TRAF6-MAPKs. This finding provides new insight into the understanding of LRIP mechanisms.

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

AIM

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.

METHODS

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.

RESULTS

All recipients in the SCS group died within 6 h 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.

CONCLUSIONS

IPO improved the outcome of organs from donors after cardiac death and had a synergistic effect with HMP in the pig liver transplantation model.

Effects of Shenfu injection on myocardial adenosine receptors in rats with myocardial ischemia-reperfusion postconditioning

OBJECTIVE

Shenfu injection (SFI) has been reported to have a protection against myocardial ischemia-reperfusion (MI/R) injury. However, the changes of adenosine receptors in MI/R postconditioning when pretreated with SFI are unclear.

METHODS

Forty-five rats were randomly divided into sham group (sham), MI/R postconditioning group (MI/R-post), low-dose SFI group (1 mL/kg), middle-dose SFI group (2.5 mL/kg), and high-dose SFI group (5 mL/kg). In SFI groups, SFI was intravenously injected before reperfusion, and rats were treated with ischemic postconditioning after ischemia for 30 min. After 24 h of reperfusion, the levels of Ca²⁺ and cAMP in blood platelets were analyzed. Myocardial infarct volume and myocardial pathology were observed. The levels of adenosine receptor subtypes A₁, A_2b, and A₃ in myocardium were analyzed using immunohistochemistry and Western blot. The oxidative stress-related indicators were also observed.

RESULTS

Compared with the MI/R-post group, SFI ameliorated the MI/R injury by decreasing the myocardial infarct area, oxidative stress, and concentration of Ca²⁺ and cAMP (p < 0.01). Pretreatment with SFI enhanced the expression of adenosine receptors A₁ and A_2b in a dose manner compared with the MI/R-post group. In contrast, the levels of adenosine receptor A₃ were increased after MI/R postconditioning compared with the sham group, and its expression continued to increase with the increase of SFI. Furthermore, the oxidative stress reduced with the concentrations of SFI.

CONCLUSION

These results demonstrated that pretreatment with SFI might regulate the expression of adenosine receptors to improve the MI/R postconditioning.

Systematic Study of Immune Cell Diversity in ischemic postconditioning Using High-Dimensional Single-Cell Analysis with Mass Cytometry

Ischemic postconditioning (IPostC) is a concept of ischemic stroke treatment, in which several cycles of brief reocclusion after reperfusion are repeated. It is essential to have an accurate understanding of the immune response in IPostC. By using high parametric single-cell mass cytometry, immune cell subsets and characterize their unique functions from ischemic brain and peripheral blood were identified after IPostC. This study enabled us to better understand the immune cell phenotypical and functional characteristics in ischemic brain and peripheral blood at the single-cell and protein levels. Since some cell surface markers can serve as functional markers, reflecting the degree of inflammation, the cell surface marker intensity among different groups was analyzed. The results showed that downregulation of 4E-BP1 and p38 of Microglia and MoDM in the ischemic brain was involved in IPostC-induced protection. In the peripheral blood, downregulation of P38 of CD4 T cell and Treg has also participated in IPostC-induced protection.

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.

Role of HSP90 in suppressing TLR4-mediated inflammation in ischemic postconditioning

BACKGROUND

Myocardial inflammation mediated by toll-like receptor 4 (TLR4) plays an active role in myocardial ischemia/reperfusion (I/R) injury. Studies show that heat shock protein 90 (HSP90) is involved in ischemic postconditioning (IPostC) cardioprotection. This study investigates the roles of TLR4 and HSP90 in IPostC.

METHODS

Rats were subjected to 30 min ischemia, then 2 h reperfusion. IPostC was applied by three cycles of 30 s reperfusion, then 30 s reocclusion at reperfusion onset. Sixty rats were randomly divided into four groups: sham, I/R, IPostC, and geldanamycin (GA, HSP90 inhibitor, 1 mg/kg) plus IPostC (IPostC + GA).

RESULTS

IPostC significantly reduced I/R-induced infarct size (40.2±2.1% versus 28.4±2.4%; P < 0.05); the release of cardiac Troponin T, creatine kinase-MB, and lactate dehydrogenase (191.5±3.1 versus 140.6±3.3 pg/ml, 3394.6±132.7 versus 2880.7±125.5 pg/ml, 2686.2±98.6 versus 1848.8±90.1 pg/ml, respectively; P < 0.05); and cardiomyocyte apoptosis (40.3±2.2% versus 27.0±1.6%; P < 0.05). Further, local and circulating IL-1β, IL-6, TNF-α, and ICAM-1 levels decreased; TLR4 expression and nuclear factor-KB (NF-κB) signaling decreased; and cardiac HSP90 expression increased. Blocking HSP90 function with GA inhibited IPostC protection and anti-inflammation, suggesting that IPostC has a HSP90-dependent anti-inflammatory effect.

CONCLUSION

HSP90 may play a role in IPostC-mediated cardioprotection by inhibiting TLR4 activation, local and systemic inflammation, and NF-kB signaling.

Ischemia-Reperfusion Intervention: From Enhancements in Exercise Performance to Accelerated Performance Recovery-A Systematic Review and Meta-Analysis

It has been demonstrated that brief cycles of ischemia followed by reperfusion (IR) applied before exercise can improve performance and, IR intervention, applied immediately after exercise (post-exercise ischemic conditioning—PEIC) exerts a potential ergogenic effect to accelerate recovery. Thus, the purpose of this systematic review with meta-analysis was to identify the effects of PEIC on exercise performance, recovery and the responses of associated physiological parameters, such as creatine kinase, perceived recovery and muscle soreness, over 24 h after its application. From 3281 studies, six involving 106 subjects fulfilled the inclusion criteria. Compared to sham (cuff administration with low pressure) and control interventions (no cuff administration), PEIC led to faster performance recovery (p = 0.004; ES = −0.49) and lower increase in creatine kinase (p < 0.001; effect size (ES) = −0.74) and muscle soreness (p < 0.001; ES = −0.88) over 24 h. The effectiveness of this intervention is more pronounced in subjects with low/moderate fitness level and at least a total time of 10 min of ischemia (e.g., two cycles of 5 min) is necessary to promote positive effects.

Ischemic postconditioning attenuates acute kidney injury following intestinal ischemia-reperfusion through Nrf2-regulated autophagy, anti-oxidation, and anti-inflammation in mice

Intestinal ischemia-reperfusion (IIR) often occurs during and following major cardiovascular or gut surgery and causes significant organ including kidney injuries. This study was to investigate the protective effect of intestinal ischemic postconditioning (IPo) on IIR-induced acute kidney injury (AKI) and the underling cellular signaling mechanisms with focus on the Nrf2/HO-1. Adult C57BL/6J mice were subjected to IIR with or without IPo. IIR was established by clamping the superior mesenteric artery (SMA) for 45 minutes followed by 120 minutes reperfusion. Outcome measures were: (i) Intestinal and renal histopathology; (ii) Renal function; (iii) Cellular signaling changes; (iv) Oxidative stress and inflammatory responses. IPo significantly attenuated IIR-induced kidney injury. Furthermore, IPo significantly increased both nuclear Nrf2 and HO-1 expression in the kidney, upregulated autophagic flux, inhibited IIR-induced inflammation and reduced oxidative stress. The protective effect of IPo was abolished by the administration of Nrf2 inhibitor (Brusatol) or Nrf2 siRNA. Conversely, a Nrf2 activator t-BHQ has a similar protective effect to that of IPo. Our data indicate that IPo protects the kidney injury induced by IIR, which was likely mediated through the Nrf2/HO-1 cellular signaling activation.

Ischemic postconditioning for stroke treatment: current experimental advances and future directions

Ischemic postconditioning (IPostC) protects against brain injury induced by stroke and is a potential strategy for ischemic stroke treatment. Understanding its underlying mechanisms and potential hurdles is essential for clinical translation. In this review article, we will summarize the current advances in IPostC for stroke treatment and the underlying protective mechanisms. Strong evidence suggests that IPostC reduces brain infarct size, attenuates blood-brain barrier (BBB) damage and brain edema, and improves neurological outcomes. IPostC also promotes neurogenesis and angiogenesis at the recovery phase of ischemic stroke. The protective mechanisms involve its effects on anti-oxidative stress, anti-inflammation, and anti-apoptosis. In addition, it regulates neurotransmitter receptors, ion channels, heat shock proteins (HSP) 40/70, as well as growth factors such as BDNF and VEGF. Furthermore, IPostC modulates several cell signaling pathways, including the PI3K/Akt, MAPK, NF-κB, and the Gluk2/PSD95/MLK3/MKK7/JNK3 pathways. We also discuss the potential hurdles for IPostC's clinical translation, including insufficient IPostC algorithm studies, such as therapeutic time windows and ischemia-reperfusion periods and cycles, as well as its long-term protection. In addition, future studies should address confounding factors such as age, sex, and pre-existing conditions such as hypertension and hyperglycemia before stroke onset. At last, the combination of IPostC with other treatments, such as tissue plasminogen activator (t-PA), merits further exploration.

The inhibition of apoptosis through myocardial postconditioning by affecting Fas/FasIg signaling through miR139-3p and miR181a-1

BACKGROUND AND AIM OF THE STUDY

Ischemic postconditioning (PostC) is considered to be one of the strongest mechanisms limiting the extent of myocardial infarction, and reducing ischemia-reperfusion (I/R) injury. I/R-induced myocardial injury results in apoptosis, autophagy, and necrosis. The aim of the present study was to investigate the roles of the necrotic gene cytochrome b-245 beta chain (Cybb); Cybb-related microRNA miR139-3p; the autophagy gene Beclin-1 (Becn1); proapoptotic genes Fas, Faslg and growth arrest and DNA-damage-inducible 45 alpha (Gadd45a); and apoptosis-related microRNA miR181a-1 levels on I/R injury, as well as, the potential protective effects of PostC through this gene and microRNAs.

METHODS

The left main coronary artery was subjected to ischemia for 30 minutes, followed by reperfusion for 120 minutes. PostC involved three cycles of I/R, each lasting 10 seconds. Gene and microRNA levels were analyzed using a quantitative reverse transcription-polymerase chain reaction.

RESULTS

Although an increase was observed in the expression levels of the Cybb, Fas, Faslg and Gadd45a genes, the miR139-3p, miR181a-1, and Becn1 expression levels were found to decrease with I/R injury. PostC was determined to restore the expression of all the genes to the normal levels.

CONCLUSIONS

The abovementioned genes can be used as important prognostic markers in the diagnosis of reperfusion injury and in the evaluation of treatment efficacy. It was further noted that increased expression of CYBB, which is one of the target genes for miR139-3p, and a decreased expression of miR181a-1 may cause apoptosis by affecting Fas and Faslg signaling. PostC can inhibit apoptosis by increasing miR139-3p and miR181a-1 levels.

Ischemic Postconditioning Recovers Cortex Ascorbic Acid during Ischemia/Reperfusion Monitored with an Online Electrochemical System

As a promising therapeutic treatment, ischemic postconditioning has recently received considerable attention. Although the neuroprotection effect of postconditioning has been observed, a reliable approach that can evaluate the neuroprotective efficiency of postconditioning treatment during the acute period after ischemia remains to be developed. This study investigates the dynamics of cortex ascorbic acid during the acute period of cerebral ischemia before and after ischemic postconditioning with an online electrochemical system (OECS). The cerebral ischemia/reperfusion injury and the neuronal functional outcome are evaluated with triphenyltetrazolium chloride staining, immunohistochemistry, and electrophysiological recording techniques. Electrochemical recording results show that cortex ascorbic acid sharply increases 10 min after middle cerebral artery occlusion and then reaches a plateau. After direct reperfusion following ischemia (i.e., without ischemic postconditioning), the cortex ascorbic acid further increases and then starts to decrease slowly at a time point of about 40 min after reperfusion. In striking contrast, the cortex ascorbic acid drops and recovers to its basal level after ischemic postconditioning followed by reperfusion. With the recovery of cortex ascorbic acid, ischemic postconditioning concomitantly promotes the recovery of neural function and reduces the oxidative damage. These results demonstrate that our OECS for monitoring cortex ascorbic acid can be used as a platform for evaluating the neuroprotective efficiency of ischemic postconditioning in the acute phase of cerebral ischemia, which is of great importance for screening proper postconditioning parameters for preventing ischemic damages.

Effects of Combined Remote Ischemic Pre-and Post-Conditioning on Neurologic Complications in Moyamoya Disease Patients Undergoing Superficial Temporal Artery-Middle Cerebral Artery Anastomosis

Superficial temporal artery-middle cerebral artery (STA-MCA) anastomosis is the most commonly used treatment for Moyamoya disease. During the perioperative period, however, these patients are vulnerable to ischemic injury or hyperperfusion syndrome. This study investigated the ability of combined remote ischemic pre-conditioning (RIPC) and remote ischemic post-conditioning (RIPostC) to reduce the occurrence of major neurologic complications in Moyamoya patients undergoing STA-MCA anastomosis. The 108 patients were randomly assigned to a RIPC with RIPostC group (n = 54) or a control group (n = 54). Patients in the RIPC with RIPostC group were treated with four cycles of 5-min ischemia and 5-min reperfusion before craniotomy and after STA-MCA anastomosis (RIPostC). The incidence of postoperative neurologic complications and the duration of hospital stay were determined. The overall incidence of neurologic complication was significantly higher in the control group than in the RIPC with RIPostC group (13 vs. 3, p = 0.013). The duration of hospital stay was significantly longer in the control group than in the RIPC with RIPostC group (17.8 (11.3) vs. 13.8 (5.9) days, p = 0.023). Combined remote ischemic pre- and post-conditioning can be effective in reducing neurologic complications and the duration of hospitalization in Moyamoya patients undergoing STA-MCA anastomosis.

Effect of Ischemic Preconditioning and Postconditioning on Exosome-Rich Fraction microRNA Levels, in Relation with Electrophysiological Parameters and Ventricular Arrhythmia in Experimental Closed-Chest Reperfused Myocardial Infarction

We investigated the antiarrhythmic effects of ischemic preconditioning (IPC) and postconditioning (PostC) by intracardiac electrocardiogram (ECG) and measured circulating microRNAs (miRs) that are related to cardiac conduction. Domestic pigs underwent 90-min. percutaneous occlusion of the mid left anterior coronary artery, followed by reperfusion. The animals were divided into three groups: acute myocardial infarction (AMI, n = 7), ischemic preconditioning-acute myocardial infarction (IPC-AMI) (n = 9), or AMI-PostC (n = 5). IPC was induced by three 5-min. episodes of repetitive ischemia/reperfusion cycles (rI/R) before AMI. PostC was induced by six 30-s rI/R immediately after induction of reperfusion 90 min after occlusion. Before the angiographic procedure, a NOGA endocardial mapping catheter was placed again the distal anterior ventricular endocardium to record the intracardiac electrogram (R-amplitude, ST-Elevation, ST-area under the curve (AUC), QRS width, and corrected QT time (QTc)) during the entire procedure. An arrhythmia score was calculated. Cardiac MRI was performed after one-month. IPC led to significantly lower ST-elevation, heart rate, and arrhythmia score during ischemia. PostC induced a rapid recovery of R-amplitude, decrease in QTc, and lower arrhythmia score during reperfusion. Slightly higher levels of miR-26 and miR-133 were observed in AMI compared to groups IPC-AMI and AMI-PostC. Significantly lower levels of miR-1, miR-208, and miR-328 were measured in the AMI-PostC group as compared to animals in group AMI and IPC-AMI. The arrhythmia score was not significantly associated with miRNA plasma levels. Cardiac MRI showed significantly smaller infarct size in the IPC-AMI group when compared to the AMI and AMI-PostC groups. Thus, IPC led to better left ventricular ejection fraction at one-month and it exerted antiarrhythmic effects during ischemia, whereas PostC exhibited antiarrhythmic properties after reperfusion, with significant downregulaton of ischemia-related miRNAs.

Transcriptional Alterations by Ischaemic Postconditioning in a Pig Infarction Model: Impact on Microvascular Protection

Although the application of cardioprotective ischaemia/reperfusion (I/R) stimuli after myocardial infarction (MI) is a promising concept for salvaging the myocardium, translation to a clinical scenario has not fulfilled expectations. We have previously shown that in pigs, ischaemic postconditioning (IPostC) reduces myocardial oedema and microvascular obstruction (MVO), without influencing myocardial infarct size. In the present study, we analyzed the mechanisms underlying the IPostC-induced microvascular protection by transcriptomic analysis, followed by pathway analysis. Closed-chest reperfused MI was induced by 90 min percutaneous balloon occlusion of the left anterior descending coronary artery, followed by balloon deflation in anaesthetised pigs. Animals were randomised to IPostC (n = 8), MI (non-conditioned, n = 8), or Control (sham-operated, n = 4) groups. After three hours or three days follow-up, myocardial tissue samples were harvested and subjected to RNA-seq analysis. Although the transcriptome analysis revealed similar expression between IPostC and MI in transcripts involved in cardioprotective pathways, we identified gene expression changes responding to IPostC at the three days follow-up. Focal adhesion signaling, downregulated genes participating in cardiomyopathy and activation of blood cells may have critical consequences for microvascular protection. Specific analyses of the gene subsets enriched in the endothelium of the infarcted area, revealed strong deregulation of transcriptional functional clusters, DNA processing, replication and repair, cell proliferation, and focal adhesion, suggesting sustentative function in the endothelial cell layer protection and integrity. The spatial and time-dependent transcriptome analysis of porcine myocardium supports a protective effect of IPostC on coronary microvasculature post-MI.

Gene Expression Profiling in Ischemic Postconditioning to Alleviate Mouse Liver Ischemia/Reperfusion Injury

Ischemic postconditioning (IPO) attenuates hepatic ischemia/reperfusion (I/R) injury. However, little is known about the underlying biological pathophysiology, which could be, at least in part, informed by exploring the transcriptomic changes using next-generation RNA sequencing (RNA-Seq). In this study, 18 mice (C57BL/6) were involved and randomly assigned to three groups: normal (n=6), I/R (n=6, subjected to 70% hepatic I/R), and IR+IPO (n=6, applying IPO to mice with I/R injury). We randomly selected 3 mice per group and extracted their liver tissues for next-generation RNA-Seq. We performed a bioinformatics analysis for two comparisons: normal vs. I/R and I/R vs. IR+IPO. From the analysis, 2416 differentially expressed genes (DEGs) were identified (p < 0.05 and fold change ≥ 1.5). Gene ontology (GO) analysis revealed that these genes were mainly related to cellular metabolic processes, nucleic acids and protein binding processes. The enriched Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways for the DEGs were the mitogen-activated protein kinase (MAPK), IL-17 signalling pathway, regulating pluripotency of stem cells, and insulin resistance pathway. Validation of 12 selected DEGs by qRT-PCR showed that Cyr61, Atf3, Nr4a1, Gdf15, Osgin1, Egr1, Epha2, Dusp1, Dusp6, Gadd45a and Gadd45b were significantly amplified. Finally, a protein-protein interaction (PPI) network constructed to determine interactions of these 11 DEGs. In summary, by exploring gene expression profiling in regard to hepatic I/R and IPO using next-generation RNA-Seq, we suggested a few progression-related genes and pathways, providing some clues for future experimental research.

A Brief Ischemic Postconditioning Protects Against Amyloid-β Peptide Neurotoxicity by Downregulating MLK3-MKK3/6-P38MAPK Signal in Rat Hippocampus

BACKGROUND

Oligomeric amyloid-β peptide (Aβ) is associated with dysfunctional neuronal networks and neuronal loss in the development of Alzheimer's disease (AD). Ischemic postconditioning protects against post-ischemic excitotoxicity, oxidative stress, and inflammatory process that have also been implicated in the pathogenesis of AD. Evaluating the roles of ischemic postconditioning in oligomeric Aβ-induced neurotoxicity and underlying signal events may provide potential strategy for medical therapy in AD.

OBJECTIVES

The aim of the present study was to explore whether and how a brief ischemic postconditioning protects against Aβ neurotoxicity in rat hippocampus.

METHODS

Oligomeric Aβ25-35 (20 nmol/rat) or Aβ1-42 (5 nmol/rat) was infused by intracerebroventricular injection in adult male Sprague-Dawley rats. Ischemic postconditioning, a brief episode of global brain ischemia (3 min), was conducted at 1, 3, or 7 days after Aβ treatment, respectively.

RESULTS

A brief ischemic postconditioning reduced neuronal loss and inhibited the activation of MLK3, MKK3/6, and P38MAPKs in rat hippocampal CA1 and CA3 subfields after Aβ oligomer infusion. An N-methyl-D-aspartate (NMDA) receptor antagonist amantadine, but not non-NMDA receptor antagonist CNQX, reversed the MLK3-MKK3/6-P38MAPK signal events and beneficial effect of ischemic postconditioning on neuronal survival. Such reversion was also realized by NVP-AAM077, a GluN2A-subunit-selective NMDA receptor antagonist. Moreover, posttreatment with low doses of NMDA (5 nmol-40 nmol/rat) suppressed the Aβ-induced P38MAPK signaling and imitated the neuroprotection of ischemic postconditioning against Aβ neurotoxicity.

CONCLUSIONS

Ischemic postconditioning provides neuroprotection against Aβ neurotoxicity by moderate upregulation of NMDA receptor signaling, especially GluN2A-containing NMDA receptor pathway, and thereafter downregulation of MLK3-MKK3/6-P38MAPK signal events.

Neuroprotective effect of ischemic postconditioning on sciatic nerve transection

Ischemic preconditioning or postconditioning has been shown to have neuroprotective effect on cerebral ischemia, but it has not been studied in peripheral nerve injury. In this study, a rat model of sciatic nerve transection was established, and subjected to three cycles of ischemia for 10 minutes + reperfusion for 10 minutes, once a day. After ischemic postconditioning, serum insulin-like growth factor 1 expression increased; sciatic nerve Schwann cell myelination increased; sensory function and motor function were restored. These findings indicate that ischemic postconditioning can effectively protect injured sciatic nerve. The protective effect is possibly associated with upregulation of insulin-like growth factor 1.

Adverse Effects on β-Adrenergic Receptor Coupling: Ischemic Postconditioning Failed to Preserve Long-Term Cardiac Function

BACKGROUND

Ischemic preconditioning (IPC) and ischemic postconditioning (IPoC) are currently among the most efficient strategies protecting the heart against ischemia/reperfusion injury. However, the effect of IPC and IPoC on functional recovery following ischemia/reperfusion is less clear, particularly with regard to the specific receptor-mediated signaling of the postischemic heart. The current article examines the effect of IPC or IPoC on the regulation and coupling of β-adrenergic receptors and their effects on postischemic left ventricular function.

METHODS AND RESULTS

The β-adrenergic signal transduction was analyzed in 3-month-old Wistar rats for each of the intervention strategies (Sham, ischemia/reperfusion, IPC, IPoC) immediately and 7 days after myocardial infarction. Directly after the infarction a cardioprotective potential was demonstrated for both IPC and IPoC: the infarct size was reduced, apoptosis and production of reactive oxygen species were lowered, and the myocardial tissue was preserved. Seven days after myocardial ischemia, only IPC hearts showed significant functional improvement. Along with a deterioration in fractional shortening, IPoC hearts no longer responded adequately to β-adrenergic stimulation. The stabilization of β-adrenergic receptor kinase-2 via increased phosphorylation of Mdm2 (an E3-ubiquitin ligase) was responsible for desensitization of β-adrenergic receptors and identified as a characteristic specific to IPoC hearts.

CONCLUSIONS

Immediately after myocardial infarction, rapid and transient activation of β-adrenergic receptor kinase-2 may be an appropriate means to protect the injured heart from excessive stress. In the long term, however, induction and stabilization of β-adrenergic receptor kinase-2, with the resultant loss of positive inotropic function, leads to the functional picture of heart failure.

cGMP-Elevating Compounds and Ischemic Conditioning Provide Cardioprotection Against Ischemia and Reperfusion Injury via Cardiomyocyte-Specific BK Channels

BACKGROUND

The nitric oxide-sensitive guanylyl cyclase/cGMP-dependent protein kinase type I signaling pathway can afford protection against the ischemia/reperfusion injury that occurs during myocardial infarction. Reportedly, voltage and Ca²⁺-activated K⁺ channels of the BK type are stimulated by cGMP/cGMP-dependent protein kinase type I, and recent ex vivo studies implicated that increased BK activity favors the survival of the myocardium at ischemia/reperfusion. It remains unclear, however, whether the molecular events downstream of cGMP involve BK channels present in cardiomyocytes or in other cardiac cell types.

METHODS

Gene-targeted mice with a cardiomyocyte- or smooth muscle cell-specific deletion of the BK (CMBK or SMBK knockouts) were subjected to the open-chest model of myocardial infarction. Infarct sizes of the conditional mutants were compared with litter-matched controls, global BK knockout, and wild-type mice. Cardiac damage was assessed after mechanical conditioning or pharmacological stimulation of the cGMP pathway and by using direct modulators of BK. Long-term outcome was studied with respect to heart functions and cardiac fibrosis in a chronic myocardial infarction model.

RESULTS

Global BK knockouts and CMBK knockouts, in contrast with SMBK knockouts, exhibited significantly larger infarct sizes compared with their respective controls. Ablation of CMBK resulted in higher serum levels of cardiac troponin I and elevated amounts of reactive oxygen species, lower phosphorylated extracellular receptor kinase and phosphorylated AKT levels and an increase in myocardial apoptosis. Moreover, CMBK was required to allow beneficial effects of both nitric oxide-sensitive guanylyl cyclase activation and inhibition of the cGMP-degrading phosphodiesterase-5, ischemic preconditioning, and postconditioning regimens. To this end, after 4 weeks of reperfusion, fibrotic tissue increased and myocardial strain echocardiography was significantly compromised in CMBK-deficient mice.

CONCLUSIONS

Lack of CMBK channels renders the heart more susceptible to ischemia/reperfusion injury, whereas the pathological events elicited by ischemia/reperfusion do not involve BK in vascular smooth muscle cells. BK seems to permit the protective effects triggered by cinaciguat, riociguat, and different phosphodiesterase-5 inhibitors and beneficial actions of ischemic preconditioning and ischemic postconditioning by a mechanism stemming primarily from cardiomyocytes. This study establishes mitochondrial CMBK channels as a promising target for limiting acute cardiac damage and adverse long-term events that occur after myocardial infarction.

Effect of Ischemic Postconditioning on Myocardial Function and Infarct Size Following Reperfusion Injury in Diabetic Rats Pretreated With Vildagliptin

BACKGROUND

Cardioprotective actions of ischemic postconditioning (IPostC) against ischemia/reperfusion (I/R) injury are abolished in diabetic hearts. This study has investigated the combined effects of IPostC and vildagliptin (Vilda) on myocardial function and infarct size (IS) against I/R injury in diabetic myocardium.

METHODS

Diabetes was induced by a high-fat diet/low dose of streptozotocin (35 mg/kg; intraperitoneally) in Wistar rats (200-250 g) and lasted for 12 weeks. Vilda (6 mg/kg/d) was orally administered for 5 weeks in diabetic groups after seventh week of diabetes. At the end of the 12-week period, the hearts of rats were removed and subjected to 35-minute regional ischemia (through left anterior descending ligation) followed by 60-minute reperfusion, on Langendorff apparatus. Ischemic postconditioning was induced by 6 repetitive cycles of 10-second ischemia and 10-second reperfusion, immediately at the onset of the reperfusion. Myocardial hemodynamic was measured throughout the experiment. The IS was assessed by triphenyltetrazolium chloride staining method. The myocardial contents of troponin-I (cTnI), interleukin-6 (IL-6), and 8-isoprostane were measured in the homogenate from ischemic zone of left ventricles by enzyme-linked immunosorbent assay kit.

RESULTS

Pretreatment of the diabetic rats with Vilda significantly recovered the diabetes-induced reduction in left ventricular developed pressures and contractility at the baseline ( P < .05 to P < .01). After I/R injury, IPostC could not significantly improve the myocardial function, cTnI content, and IS of the diabetic hearts. However, in Vilda-treated hearts, concomitant application of IPostC significantly recovered the heart functions, returned cTnI content as well as myocardial IL-6 and 8-isoprostane levels back to the control values ( P < .01 to P < .001), and reduced IS more effectively (by 45%) in comparison to the diabetic group ( P < .001).

CONCLUSION

Besides its glycemic and lipid profile controlling effects, Vilda has a protective effect on heart function and tends to restore cardioprotective effects of IPostC on diabetic hearts.

Acute atorvastatin treatment restores the cardioprotective effects of ischemic postconditioning in hyperlipidemic rats

Background

Ischemic Postconditioning (IPC) reduces ischemia/reperfusion (I/R) injury under normal conditions. HMG-CoA reductase inhibitors (statins), which inhibit the synthesis of mevalonate, can interfere with the cardioprotective effect of IPC. However, the beneficial role of IPC in hyperlipidemic patients, post-acute administration of statins remains unknown. This study was to determine if acute administration of atorvastatin affect the infarct size-limiting effect of IPC in hyperlipidemic rats.

Results

Compared to control group, infarct size decreased more significantly in atorvastatin+IPC and atorvastatin+IPC+wortmannin groups than IPC or atorvastatin+IPC+PD98059 groups. Phosphorylation of PI3K/Akt was attenuated in atorvastatin + IPC+ wortmannin group, phosphorylation of P42 MAPK/ERK was increased in atorvastatin+IPC and atorvastatin+IPC+wortmannin groups.

Materials and Methods

Ninety four-weeks old male SD rats fed with cholesterol enriched diet for six weeks were randomized into nine groups (n = 10/group) - sham group, control group, IPC group, atorvastatin group, wortmannin group, PD98059 group, atorvastatin+IPC group, atorvastatin+IPC+wortmannin group and atorvastatin+IPC+PD98059 group. Atorvastatin was administered orally 12 hours before myocardial reperfusion.

Conclusions

Post-translational activation of P42 MAPK/ERK, rather than PI3K/Akt, participates in the net protective effect of IPC and atorvastatin in hyperlipidemia.

Effect of Ischemia Duration and Protective Interventions on the Temporal Dynamics of Tissue Composition After Myocardial Infarction

Supplemental Digital Content is available in the text.

Rationale:

The impact of cardioprotective strategies and ischemia duration on postischemia/reperfusion (I/R) myocardial tissue composition (edema, myocardium at risk, infarct size, salvage, intramyocardial hemorrhage, and microvascular obstruction) is not well understood.

Objective:

To study the effect of ischemia duration and protective interventions on the temporal dynamics of myocardial tissue composition in a translational animal model of I/R by the use of state-of-the-art imaging technology.

Methods and Results:

Four 5-pig groups underwent different I/R protocols: 40-minute I/R (prolonged ischemia, controls), 20-minute I/R (short-duration ischemia), prolonged ischemia preceded by preconditioning, or prolonged ischemia followed by postconditioning. Serial cardiac magnetic resonance (CMR)-based tissue characterization was done in all pigs at baseline and at 120 minutes, day 1, day 4, and day 7 after I/R. Reference myocardium at risk was assessed by multidetector computed tomography during the index coronary occlusion. After the final CMR, hearts were excised and processed for water content quantification and histology. Five additional healthy pigs were euthanized after baseline CMR as reference. Edema formation followed a bimodal pattern in all 40-minute I/R pigs, regardless of cardioprotective strategy and the degree of intramyocardial hemorrhage or microvascular obstruction. The hyperacute edematous wave was ameliorated only in pigs showing cardioprotection (ie, those undergoing short-duration ischemia or preconditioning). In all groups, CMR-measured edema was barely detectable at 24 hours postreperfusion. The deferred healing-related edematous wave was blunted or absent in pigs undergoing preconditioning or short-duration ischemia, respectively. CMR-measured infarct size declined progressively after reperfusion in all groups. CMR-measured myocardial salvage, and the extent of intramyocardial hemorrhage and microvascular obstruction varied dramatically according to CMR timing, ischemia duration, and cardioprotective strategy.

Conclusions:

Cardioprotective therapies, duration of index ischemia, and the interplay between these greatly influence temporal dynamics and extent of tissue composition changes after I/R. Consequently, imaging techniques and protocols for assessing edema, myocardium at risk, infarct size, salvage, intramyocardial hemorrhage, and microvascular obstruction should be standardized accordingly.

Is there a role for ischaemic conditioning in cardiac surgery?

Coronary artery disease (CAD) is a major cause of morbidity and mortality worldwide. Coronary artery bypass graft (CABG) surgery is the revascularisation strategy of choice in patients with diabetes mellitus and complex CAD. Owing to a number of factors, including the ageing population, the increased complexity of CAD being treated, concomitant valve and aortic surgery, and multiple comorbidities, higher-risk patients are being operated on, the result of which is an increased risk of sustaining perioperative myocardial injury (PMI) and poorer clinical outcomes. As such, new treatment strategies are required to protect the heart against PMI and improve clinical outcomes following cardiac surgery. In this regard, the heart can be endogenously protected from PMI by subjecting the myocardium to one or more brief cycles of ischaemia and reperfusion, a strategy called "ischaemic conditioning". However, this requires an intervention applied directly to the heart, which may be challenging to apply in the clinical setting. In this regard, the strategy of remote ischaemic conditioning (RIC) may be more attractive, as it allows the endogenous cardioprotective strategy to be applied away from the heart to the arm or leg by simply inflating and deflating a cuff on the upper arm or thigh to induce one or more brief cycles of ischaemia and reperfusion (termed "limb RIC"). Although a number of small clinical studies have demonstrated less PMI with limb RIC following cardiac surgery, three recently published large multicentre randomised clinical trials found no beneficial effects on short-term or long-term clinical outcomes, questioning the role of limb RIC in the setting of cardiac surgery. In this article, we review ischaemic conditioning as a therapeutic strategy for endogenous cardioprotection in patients undergoing cardiac surgery and discuss the potential reasons for the failure of limb RIC to improve clinical outcomes in this setting. Crucially, limb RIC still has the therapeutic potential to protect the heart in other clinical settings, such as acute myocardial infarction, and it may also protect other organs against acute ischaemia/reperfusion injury (such as the brain, kidney, and liver).

[Effect of adiponectin postconditioning against myocardial ischemia/reperfusion injury in rats and role of ADP/PI3K/Akt pathway in adiponectin postconditioning]

OBJECTIVE

To investigate the effects of adiponectin(ADP) postconditioning against myocardial ischemia/reperfusion injury(MIRI) in rats and role of ADP/PI3K/Akt pathway in ADP postconditioning.

METHODS

SD rat was connected to ventilator by tracheal intubation under anesthesia, then left anterior descending coronary artery (LAD) was threaded between left auricle and pulmonary artery cone after exposing heart by surgery. MIRI model was induced by ligation of LAD for 30 min and the following reperfusion for 120 min. Rats were divided randomly into 5 groups (n=12):① Sham group:LAD was threaded without ligation; ② MIRI group; ③ADP group (ADP postconditioning) were subjected to intravenous injection of ADP when LAD ligation for 10 min and the ligation held for 20 min after that, then reperfusion for 120 min; ④ ADP+LY294002 group were subjected to injection of ADP and LY294002 when LAD ligation for 10 min, the other steps were the same as ADP group; ⑤ LY294002 group were subjected to injection of LY294002 when LAD ligation for 10 min, the other steps were the same as ADP group. Titers of lactate dehydrogenase(LDH) and cardiac troponin I(cTnI) in plasma were observed, expressions of PI3K, Akt, phosphorylated-Akt(p-Akt), ADP mRNA, ADPR1 mRNA and PI3k mRNA in myocardial tissue were measured.

RESULTS

Compared with sham group, the levels of LDH and cTnI in MIRI group were increased (P<0.05); Compared with MIRI group, the levels of LDH and cTnI in ADP group were decreased (P<0.05); Compared with ADP group, the levels of LDH and cTnI were increased in LY294002 applying groups(P<0.05). Compared with MIRI group, the expressions of PI3K, p-Akt, ADP mRNA, ADPR1 mRNA and PI3K mRNA were increased in ADP group (P<0.05), the above mentioned 5 parameters in LY294002 applying groups were decreased(P<0.05).

CONCLUSIONS

ADP postconditioning could reduce MIRI in rats, the protective effect might have relation to ADP/PI3k/Akt pathway.

Molecular hydrogen potentiates beneficial anti-infarct effect of hypoxic postconditioning in isolated rat hearts: a novel cardioprotective intervention

Generation of free radicals through incomplete reduction of oxygen during ischemia-reperfusion (I/R) is well described. On the other hand, molecular hydrogen (H₂) reduces oxidative stress due to its ability to react with strong oxidants and easily penetrate cells by diffusion, without disturbing metabolic redox reactions. This study was designed to explore cardioprotective potential of hypoxic postconditioning (HpostC) against I/R (30 min global I - 120 min R) in isolated rat hearts using oxygen-free Krebs-Henseleit buffer (KHB). Furthermore, the possibility to potentiate the effect of HpostC by H₂ using oxygen-free KHB saturated with H₂ (H₂ + HpostC) was tested. HPostC was induced by 4 cycles of 1-minute perfusion with oxygen-free KHB intercepted by 1-minute perfusion with normal KHB, at the onset of reperfusion. H₂ + HPostC was applied in a similar manner using H₂-enriched oxygen-free KHB. Cardioprotective effects were evaluated on the basis of infarct size (IS, in % of area at risk, AR) reduction, post-I/R recovery of heart function, and occurrence of reperfusion arrhythmias. HPostC significantly reduced IS/AR compared with non-conditioned controls. H₂ present in KHB during HPostC further decreased IS/AR compared with the effect of HPostC, attenuated severe arrhythmias, and significantly restored heart function (vs. controls). Cardioprotection by HpostC can be augmented by molecular hydrogen infusion.

Insulin and GSK3β-inhibition abrogates the infarct sparing-effect of ischemic postconditioning in ex vivo rat hearts

OBJECTIVES

Pharmacological treatment of reperfusion injury using insulin and GSK3β inhibition has been shown to be cardioprotective, however, their interaction with the endogenous cardioprotective strategy, ischemic postconditioning, is not known.

DESIGN

Langendorff perfused ex vivo rat hearts were subjected to 30 min of regional ischemia and 120 min of reperfusion. For the first 15 min of reperfusion hearts received either vehicle (Ctr), insulin (Ins) or a GSK3β inhibitor (SB415286; SB41), with or without interruption of ischemic postconditioning (IPost; 3 × 30 s of global ischemia). In addition, the combination of insulin and SB41 for 15 min was assessed.

RESULTS

Insulin, SB41 or IPost significantly reduced infarct size versus vehicle treated controls (IPost 33.5 ± 3.3%, Ins 33.5 ± 3.4%, SB41 30.5 ± 3.0% vs. Ctr 54.7 ± 6.8%, p < 0.01). Combining insulin and SB415286 did not confer additional cardioprotection compared to the treatments given alone (SB41+ Ins 26.7 ± 3.5%, ns). Conversely, combining either of the pharmacological reperfusion treatments with IPost completely abrogated the cardioprotection afforded by the treatments separately (Ins + IPost 59.5 ± 3.4% vs. Ins 33.5 ± 3.4% and SB41 + IPost 50.2 ± 6.6% vs. SB41 30.5 ± 3.0%, both p < 0.01), and was associated with blunted Akt, GSK3β and STAT3 phosphorylation.

CONCLUSION

Pharmacological reperfusion treatment with insulin and SB41 interferes with the cardioprotection afforded by ischemic postconditioning.

Involvement of Protein Kinase C-δ in the Realization of Cardioprotective Effect of Ischemic Postconditioning

Experiments on isolated perfused rat heart modeled 45-min global ischemia followed by 30-min reperfusion. Ischemic postconditioning was modeled by 3 cycles of reperfusion (30 sec) and ischemia (30 sec). Cardiomyocyte necrosis was assessed by the level of creatine phosphokinase in the perfusate. Postconditioning reduced the release of creatine phosphokinase from the heart by 30%. The cardioprotective effect of ischemic postconditioning was eliminated after inhibition of protein kinase C with cheleritrin or after blockade of δ-isoform of protein kinase C with rottlerin. These findings attest to participation of protein kinase C-δ in the realization of the cardioprotective effect of postconditioning.

Effects of liraglutide and ischemic postconditioning on myocardial salvage after I/R injury in pigs

OBJECTIVES

Acute STEMI is routinely treated by acute PCI. This treatment may itself damage the tissue (reperfusion injury). Conditioning with GLP-1 analogs has been shown to reduce reperfusion injury. Likewise, ischemic postconditioning provides cardioprotection following STEMI. We tested if combined conditioning with the GLP-1 analog liraglutide and ischemic postconditioning offered additive cardioprotective effect after reperfusion of 45 min coronary occlusion of left anterior descending artery (LAD).

DESIGN

Fifty-eight non-diabetic female Danish Landrace pigs (60 ± 10kg) were randomly assigned to four groups. Myocardial infarction (MI) was induced by occluding the LAD for 45 min. Group 1 (n = 14) was treated with i.v. liraglutide after 15 min of ischemia. Group 2 (n = 17) received liraglutide treatment concomitant with ischemic postconditioning, after 45 min of ischemia. Group 3 (n = 15) recieved ischemic postconditioning and group 4 (n = 12) was kept as controls.

RESULTS

No intergroup differences in relative infarct size were detected (overall mean 57 ± 3%; p = 0.68). Overall mortality was 34% (CI 25-41%) including 26% post-intervention, with no intergroup differences (p = 0.99). Occurrence of ventricular fibrillation (VF) was 59% (CI 25-80%) including 39% postintervention with no intergroup differences (p = 0.65).

CONCLUSIONS

In our closed-chest pig-model, we were unable to detect any cardioprotective effect of liraglutide or ischemic postconditioning either alone or combined.

Ischemic postconditioning protects against ischemic brain injury by up-regulation of acid-sensing ion channel 2a

Ischemic postconditioning renders brain tissue tolerant to brain ischemia, thereby alleviating ischemic brain injury. However, the exact mechanism of action is still unclear. In this study, a rat model of global brain ischemia was subjected to ischemic postconditioning treatment using the vessel occlusion method. After 2 hours of ischemia, the bilateral common carotid arteries were blocked immediately for 10 seconds and then perfused for 10 seconds. This procedure was repeated six times. Ischemic postconditioning was found to mitigate hippocampal CA1 neuronal damage in rats with brain ischemia, and up-regulate acid-sensing ion channel 2a expression at the mRNA and protein level. These findings suggest that ischemic postconditioning up-regulates acid-sensing ion channel 2a expression in the rat hippocampus after global brain ischemia, which promotes neuronal tolerance to ischemic brain injury.

Effects of Postconditioning on Neurogenesis and Angiogenesis During the Recovery Phase After Focal Cerebral Ischemia

BACKGROUND AND PURPOSE

Postconditioning may be a clinically feasible way to protect the brain after a stroke. However, its effects during the recovery phase post stroke remain to be fully elucidated. Here, we examine the hypothesis that ischemic postconditioning amplifies neurogenesis and angiogenesis during stroke recovery.

METHODS

Male Sprague-Dawley rats were subjected to 100-minute transient middle cerebral artery occlusion (MCAO) or postconditioning (100-minute middle cerebral artery occlusion plus 10-minute reperfusion plus 10-minute reocclusion). After 2 weeks, infarct volumes, behavioral outcomes, and immunohistochemical markers of neurogenesis and angiogenesis were quantified.

RESULTS

Postconditioning significantly reduced infarction and improved neurological outcomes. Concomitantly, brains subjected to postconditioning showed an increase in doublecortin/BrdU and collagen-IV/Ki67-positive cells.

CONCLUSIONS

These results suggest that therapeutic effects of postconditioning may involve the promotion of neurogenesis and angiogenic remodeling during the recovery phase after focal cerebral ischemia.

Ischemic postconditioning provides protection against ischemia-reperfusion injury in intestines of rats

In the present study, we investigated the protective role of ischemic postconditioning (IPOST) against intestine ischemia-reperfusion (I/R) injury in rats. Male Sprague-Dawley rats were divided into sham-operation group (S), I/R group (I/R), ischemic preconditioning group (IPC), ischemic postconditioning group (IPOST). After reperfusion, small intestines were resected for histopathologic evaluations. To evaluate DNA fragmentation, resolving agarose gel electrophoresis was performed. To measure cellular apoptotic rates in intestine tissues, we performed TUNEL staining. To examine lipid peroxidation, production of superoxide radicals and tissue neutrophil infiltration, we tested the content of malondialdehyde and activities of superoxidase dismutase and myeloperoxidase in intestine tissues, respectively. Under light microscope, intestinal mucosal impairment in IPOST and IPC groups was found milder than that in I/R group (P < 0.05). The number of apoptosis cells in I/R group was significantly higher than that in IPOST and IPC groups (P < 0.05). The content of malondialdehyde and activity of myeloperoxidase were significantly reduced in IPOST group and IPC group compared with I/R group, but the activity of superoxidase dismutase in IPOST group and IPC group was enhanced compared with I/R group (P < 0.05). These results suggest that IPOST results in protection against intestine I/R injury, which may be related to reduced production of reactive oxygen species, enhanced activities of antioxidant systems and inhibited apoptosis of intestinal mucosal cells.

Ischemic postconditioning attenuates inflammation in rats following renal ischemia and reperfusion injury

Ischemic postconditioning (IPoC) involves a series of brief rapid intermittent ischemic episodes applied at the onset of reperfusion in the previously ischemic tissue or organ. Previous studies have demonstrated that IPoC attenuates tissue damage induced by ischemia and reperfusion (I/R) injury. The aim of the present study was to investigate whether IPoC has a beneficial effect on inflammation in a rat model of renal I/R injury. Wistar rats were subjected to 45 min of ischemia followed by 24, 72 or 120 h of reperfusion (I/R group). In the IPoC group, rats subjected to I/R were treated with six cycles of 10 sec reperfusion followed by a 10-sec ischemic episode. Blood samples were collected for the determination of blood urea nitrogen (BUN) and creatinine (Cr) levels. Furthermore, histological examination and immunohistochemical staining for the localization of nuclear factor-κB (NF-κB) were performed. In addition, quantitative polymerase chain reaction (qPCR) analysis was used to determine the expression levels of intercellular adhesion molecule-1 (ICAM-1), interleukin-6 (IL-6) and tumor necrosis factor-α (TNF-α), while western blot analysis was used to detect the protein expression levels of NF-κB. The results indicated that the BUN and Cr levels increased significantly in the I/R group, while the IPoC rats showed evidently reduced renal damage. Immunohistochemical analysis revealed that the expression levels of NF-κB were decreased by IPoC. In addition, the qPCR results revealed that IPoC significantly inhibited the increased mRNA expression levels of ICAM-1, IL-6 and TNF-α, induced by I/R injury. Western blot analysis indicated that the expression levels of NF-κB were upregulated in the I/R group, while IPoC was shown to inhibit the expression. In conclusion, IPoC was demonstrated to exhibit potent anti-inflammatory properties against renal I/R injury.

Molecular basis of cardioprotection: signal transduction in ischemic pre-, post-, and remote conditioning

Reperfusion is mandatory to salvage ischemic myocardium from infarction, but reperfusion per se contributes to injury and ultimate infarct size. Therefore, cardioprotection beyond that by timely reperfusion is needed to reduce infarct size and improve the prognosis of patients with acute myocardial infarction. The conditioning phenomena provide such cardioprotection, insofar as brief episodes of coronary occlusion/reperfusion preceding (ischemic preconditioning) or following (ischemic postconditioning) sustained myocardial ischemia with reperfusion reduce infarct size. Even ischemia/reperfusion in organs remote from the heart provides cardioprotection (remote ischemic conditioning). The present review characterizes the signal transduction underlying the conditioning phenomena, including their physical and chemical triggers, intracellular signal transduction, and effector mechanisms, notably in the mitochondria. Cardioprotective signal transduction appears as a highly concerted spatiotemporal program. Although the translation of ischemic postconditioning and remote ischemic conditioning protocols to patients with acute myocardial infarction has been fairly successful, the pharmacological recruitment of cardioprotective signaling has been largely disappointing to date.

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.

Ischemic postconditioning enhances glycogen synthase kinase-3β expression and alleviates cerebral ischemia/reperfusion injury

The present study established global brain ischemia using the four-vessel occlusion method. Following three rounds of reperfusion for 30 seconds, and occlusion for 10 seconds, followed by reperfusion for 48 hours, infarct area, the number of TUNEL-positive cells and Bcl-2 expression were significantly reduced. However, glycogen synthase kinase-3β activity, cortical Bax and caspase-3 expression significantly increased, similar to results following ischemic postconditioning. Our results indicated that ischemic postconditioning may enhance glycogen synthase kinase-3β activity, a downstream molecule of the phosphatase and tensin homolog deleted on chromosome 10/phosphatidylinositol 3-kinase/protein kinase B signaling pathway, which reduces caspase-3 expression to protect the brain against ischemic injury.

Cellular postconditioning: allogeneic cardiosphere-derived cells reduce infarct size and attenuate microvascular obstruction when administered after reperfusion in pigs with acute myocardial infarction

BACKGROUND

Intracoronary delivery of cardiosphere-derived cells (CDCs) has been demonstrated to be safe and effective in porcine and human chronic myocardial infarction. However, intracoronary delivery of CDCs after reperfusion in acute myocardial infarction has never been assessed in a clinically-relevant large animal model. We tested CDCs as adjunctive therapy to reperfusion in a porcine model of myocardial infarction.

METHODS AND RESULTS

First, escalating doses (5, 7.5, and 10 million cells) of allogeneic CDCs were administered intracoronary 30 minutes after reperfusion. Forty-eight hours later, left ventriculography was performed and animals euthanized to measure area at risk, infarct size (IS), and microvascular obstruction. Second, identical end points were measured in a pivotal study of minipigs (n=14) that received 8.5 to 9 million allogeneic CDCs, placebo solution, or sham. Multiple indicators of cardioprotection were observed with 7.5 and 10 million allogeneic CDCs, but not 5 million CDCs, relative to control. In the pivotal study, IS, microvascular obstruction, cardiomyocyte apoptosis, and adverse left ventricular remodeling were all smaller in the CDC group than in sham or placebo groups. In addition, serum troponin I level at 24 hours was lower after CDC infusion than that in the placebo or sham groups, consistent with the histologically-demonstrated reduction in IS.

CONCLUSIONS

Intracoronary delivery of allogeneic CDCs is safe, feasible, and effective in cardioprotection, reducing IS, preventing microvascular obstruction, and attenuating adverse acute remodeling. This novel cardioprotective effect, which we call cellular postconditioning, differs from previous strategies to reduce IS in that it works even when initiated with significant delay after reflow.