Effect of Remote Ischemic Preconditioning on Perioperative Cardiac Events in Patients Undergoing Elective Percutaneous Coronary Intervention: A Meta-Analysis of 16 Randomized Trials

Morphine Prevents Ischemia/Reperfusion-Induced Myocardial Mitochondrial Damage by Activating δ-opioid Receptor/EGFR/ROS Pathway

OBJECTIVE

The purpose of this study was to determine whether the epidermal growth factor receptor (EGFR), which is a classical receptor tyrosine kinase, is involved in the protective effect of morphine against ischemia/reperfusion (I/R)-induced myocardial mitochondrial damage.

METHODS

Isolated rats hearts were subjected to global ischemia followed by reperfusion. Cardiac H9c2 cells were exposed to a simulated ischemia solution followed by Tyrode's solution to induce hypoxia/reoxygenation (H/R) injury. Triphenyltetrazolium chloride (TTC) was used to measure infarct size. The mitochondrial morphological and functional changes were determined using transmission election microscopy (TEM), mitochondrial stress assay, and mitochondrial swelling, respectively. Mitochondrial fluorescence indicator JC-1, DCFH-DA, and Mitosox Red were used to determine mitochondrial membrane potential (△Ψm), intracellular reactive oxygen species (ROS) and mitochondrial superoxide. A TUNUL assay kit was used to detect the level of apoptosis. Western blotting analysis was used to measure the expression of proteins.

RESULTS

Treatment of isolated rat hearts with morphine prevented I/R-induced myocardial mitochondrial injury, which was inhibited by the selective EGFR inhibitor AG1478, suggesting that EGFR is involved in the mitochondrial protective effect of morphine under I/R conditions. In support of this hypothesis, the selective EGFR agonist epidermal growth factor (EGF) reduced mitochondrial morphological and functional damage similarly to morphine. Further study demonstrated that morphine may alleviate I/R-induced cardiac damage by inhibiting autophagy but not apoptosis. Morphine increased protein kinase B (Akt), extracellular regulated protein kinases (ERK) and signal transducer and activator of transcription-3 (STAT-3) phosphorylation, which was inhibited by AG1478, and EGF had similar effects, indicating that morphine may activate Akt, ERK, and STAT-3 via EGFR. Morphine and EGF increased intracellular reactive oxygen species (ROS) generation. This effect of morphine was inhibited by AG1478, indicating that morphine promotes intracellular ROS generation by activating EGFR. However, morphine did not increase ROS generation when cells were transfected with siRNA against EGFR. In addition, EGFR activity was markedly increased by morphine, but the effect of morphine was reversed by naltrindole. These results suggest that morphine may activate EGFR via δ-opioid receptor activation.

CONCLUSIONS

Morphine may prevent I/R-induced myocardial mitochondrial damage by activating EGFR through δ-opioid receptors, in turn increasing RISK and SAFE pathway activity via intracellular ROS. Moreover, morphine may reduce myocardial injury by regulating autophagy but not apoptosis.

Myocardial remote ischemic preconditioning: from cell biology to clinical application

Remote ischemic preconditioning (rIPC) is a cardioprotective phenomenon where brief periods of ischemia followed by reperfusion of one organ/tissue can confer subsequent protection against ischemia/reperfusion injury in other organs, such as the heart. It involves activation of humoral, neural or systemic communication pathways inducing different intracellular signals in the heart. The main purpose of this review is to summarize the possible mechanisms involved in the rIPC cardioprotection, and to describe recent clinical trials to establish the efficacy of these strategies in cardioprotection from lethal ischemia/reperfusion injury. In this sense, certain factors weaken the subcellular mechanisms of rIPC in patients, such as age, comorbidities, medication, and anesthetic protocol, which could explain the heterogeneity of results in some clinical trials. For these reasons, further studies, carefully designed, are necessary to develop a clearer understanding of the pathways and mechanism of early and late rIPC. An understanding of the pathways is important for translation to patients.

Perioperative Renoprotection: General Mechanisms and Treatment Approaches

In the perioperative setting, acute kidney injury (AKI) is a frequent complication, and AKI itself is associated with adverse outcomes such as higher risk of chronic kidney disease and mortality. Various risk factors are associated with perioperative AKI, and identifying them is crucial to early interventions addressing modifiable risk and increasing monitoring for nonmodifiable risk. Different mechanisms are involved in the development of postoperative AKI, frequently picturing a multifactorial etiology. For these reasons, no single renoprotective strategy will be effective for all surgical patients, and efforts have been attempted to prevent kidney injury in different ways. Some renoprotective strategies and treatments have proven to be useful, some are no longer recommended because they are ineffective or even harmful, and some strategies are still under investigation to identify the best timing, setting, and patients for whom they could be beneficial. With this review, we aim to provide an overview of recent findings from studies examining epidemiology, risk factors, and mechanisms of perioperative AKI, as well as different renoprotective strategies and treatments presented in the literature.

Heme Oxygenase Protects against Placental Vascular Inflammation and Abortion by the Alarmin Heme in Mice

Both infectious as non-infectious inflammation can cause placental dysfunction and pregnancy complications. During the first trimester of human gestation, when palatogenesis takes place, intrauterine hematoma and hemorrhage are common phenomena, causing the release of large amounts of heme, a well-known alarmin. We postulated that exposure of pregnant mice to heme during palatogenesis would initiate oxidative and inflammatory stress, leading to pathological pregnancy, increasing the incidence of palatal clefting and abortion. Both heme oxygenase isoforms (HO-1 and HO-2) break down heme, thereby generating anti-oxidative and -inflammatory products. HO may thus counteract these heme-induced injurious stresses. To test this hypothesis, we administered heme to pregnant CD1 outbred mice at Day E12 by intraperitoneal injection in increasing doses: 30, 75 or 150 μmol/kg body weight (30H, 75H or 150H) in the presence or absence of HO-activity inhibitor SnMP from Day E11. Exposure to heme resulted in a dose-dependent increase in abortion. At 75H half of the fetuses where resorbed, while at 150H all fetuses were aborted. HO-activity protected against heme-induced abortion since inhibition of HO-activity aggravated heme-induced detrimental effects. The fetuses surviving heme administration demonstrated normal palatal fusion. Immunostainings at Day E16 demonstrated higher numbers of ICAM-1 positive blood vessels, macrophages and HO-1 positive cells in placenta after administration of 75H or SnMP + 30H. Summarizing, heme acts as an endogenous “alarmin” during pregnancy in a dose-dependent fashion, while HO-activity protects against heme-induced placental vascular inflammation and abortion.

Remote Ischemic Preconditioning Reduces the Risk of Contrast-Induced Nephropathy in Patients with Moderate Renal Impairment Undergoing Percutaneous Coronary Angiography: A Meta-Analysis

BACKGROUND/AIMS

This meta-analysis evaluated the effects of remote ischemic preconditioning (RIPC) on the risk of contrast-induced nephropathy (CIN) in patients undergoing percutaneous coronary intervention/coronary angiography (PCI/CA).

METHODS

PubMed, Embase, and the Cochrane Central Register of Controlled Trials databases were searched for randomized controlled trials (RCTs) that assessed the effect of RIPC on CIN in patients undergoing PCI/CA. The main outcomes of interest were the incidence of CIN 48-72 h after CA, the levels of serum creatinine, cystatin C, neutrophil gelatinase-associated lipocalin, and estimated glomerular filtration rate (eGFR), mortality, and requirement of hemodialysis and rehospitalization. The analysis was conducted using the random-effect model due to the expected heterogeneity among different studies.

RESULTS

In total, 16 trials covering 2,048 patients were identified. By assessing the methodological quality of the included studies through the Coch-rane risk of bias, we found that of the 16 RCTs, 3 had a low risk of bias, 6 a high, and 7 an unclear risk. The application of RIPC decreased the incidence of CIN (relative risk, RR, 0.50, 95% confidence interval, CI, 0.39-0.65; p < 0.001). Subgroup analyses showed that RIPC decreased the incidence of CIN in patients with eGFR <60 mL/min/1.73 m2 (RR 0.53, 95% CI 0.38-0.75; p < 0.001) but not in patients with eGRF ≥60 mL/min/1.73 m2 (RR 0.82, 95% CI 0.35-1.94; p = 0.66) at baseline. Furthermore, the increase in serum creatinine was significantly lower in patients with RIPC compared to control patients (standardized mean difference -1.41, 95% CI -2.46 to -0.35; p = 0.009).

CONCLUSIONS

Based on 16 RCTs, this meta-analysis shows that RIPC can reduce the risk of CIN in patients with moderate renal impairment undergoing PCI/CA. However, this needs to be confirmed by further high-quality evidence.

A systematic review and meta-analysis of remote ischemic preconditioning for vascular surgery

BACKGROUND

Remote ischemic preconditioning (RIPC) is a method of preparing the body for a later prolonged ischemic episode to protect against subsequent detrimental effects. This study aimed to identify the effects of RIPC in vascular surgery.

METHODS

A standard Preferred Reporting Items for Systematic Reviews and Meta-Analyses search was conducted of randomized controlled trials of RIPC in patients undergoing open or endovascular aneurysm repair, carotid endarterectomy, or lower limb bypass reporting on mortality and renal or cardiac outcomes. Random-effects meta-analysis was performed using Review Manager 5.3 (The Nordic Cochrane Center, Copenhagen, Denmark).

RESULTS

A total of 13 randomized controlled trials in the meta-analysis included 548 patients in the RIPC cohort and 549 controls. There was no significant difference in mortality, renal dysfunction, myocardial infarction, myocardial injury, or length of stay between the groups, with subgroup and sensitivity analysis showing no significant difference.

CONCLUSIONS

Current evidence demonstrates no benefit of RIPC in vascular surgery. Further large multicenter trials of RIPC in major vascular surgery should be considered.