Acute methadone treatment reduces myocardial infarct size via the delta-opioid receptor in rats during reperfusion

Inhibition of the protective effects of preconditioning in ischemia-reperfusion injury by chronic methadone: the role of pAkt and pSTAT3

Cardiac ischemic preconditioning (Pre) reduces cardiac ischemia-reperfusion injury (IRI) by stimulating opioid receptors. Chronic use of opioids can alter the signaling pathways. We investigated the effects of chronic methadone use on IRI and Pre. The experiments were performed on isolated hearts of male Wistar rats in four groups: IRI, Methadone + IRI (M-IRI), Pre + IRI (Pre-IRI), Methadone + Pre + IRI (M-Pre-IRI). The infarct size (IS) in the Pre-IRI group was smaller than the IRI group (26.8% vs. 47.8%, P < 0.05). In the M-IRI and M-Pre-IRI groups, the infarct size was similar to the IRI group. Akt (Ak strain transforming) phosphorylation in the Pre-IRI, M-IRI, and M-Pre-IRI groups was significantly higher than in the IRI group (0.56 ± 0.15, 0.63 ± 0.20, and 0.93 ± 0.18 vs 0.28 ± 0.17 respectively). STAT3 (signal transducer and activator of transcription 3) phosphorylation in the Pre-IRI and M-Pre-IRI groups (1.38 ± 0.14 and 1.46 ± 0.33) was significantly higher than the IRI and M-IRI groups (0.99 ± 0.1 and 0.98 ± 0.2). Thus, chronic use of methadone not only has no protective effect against IRI but also destroys the protective effects of ischemic preconditioning. This may be due to the hyperactivation of Akt and changes in signaling pathways.

Myocardial Ischemia-Reperfusion Injury: Unraveling Pathophysiology, Clinical Manifestations, and Emerging Prevention Strategies

Myocardial ischemia-reperfusion injury (MIRI) remains a challenge in the context of reperfusion procedures for myocardial infarction (MI). While early revascularization stands as the gold standard for mitigating myocardial injury, recent insights have illuminated the paradoxical role of reperfusion, giving rise to the phenomenon known as ischemia-reperfusion injury. This comprehensive review delves into the intricate pathophysiological pathways involved in MIRI, placing a particular focus on the pivotal role of endothelium. Beyond elucidating the molecular intricacies, we explore the diverse clinical manifestations associated with MIRI, underscoring its potential to contribute substantially to the final infarct size, up to 50%. We further navigate through current preventive approaches and highlight promising emerging strategies designed to counteract the devastating effects of the phenomenon. By synthesizing current knowledge and offering a perspective on evolving preventive interventions, this review serves as a valuable resource for clinicians and researchers engaged in the dynamic field of MIRI.

δ-Opioid Receptor as a Molecular Target for Increasing Cardiac Resistance to Reperfusion in Drug Development

An analysis of published data and the results of our own studies reveal that the activation of a peripheral δ₂-opioid receptor (δ₂-OR) increases the cardiac tolerance to reperfusion. It has been found that this δ₂-OR is localized in cardiomyocytes. Endogenous opioids are not involved in the regulation of cardiac resistance to reperfusion. The infarct-limiting effect of the δ₂-OR agonist deltorphin II depends on the activation of several protein kinases, including PKCδ, ERK1/2, PI3K, and PKG. Hypothetical end-effectors of the cardioprotective effect of deltorphin II are the sarcolemmal K_ATP channels and the MPT pore.

Long-acting opioids and cardiovascular diseases: Help or hindrance!

Opioids are widely being used for chronic pain management, cough and diarrhea suppressants, anesthetic agents, and opioid de-addiction therapy. Opioid receptors, present in the central nervous system and peripheral tissues, are documented to regulate several cardiac functions through different signaling pathways. Long-acting opioids (LAO) have been successfully evaluated for their beneficial effects in various cardiovascular diseases viz. myocardial infarction, ischemic reperfusion injuries, atherosclerosis etc. However, on the other hand, several research studies pointed towards the harmful effects of LAOs which are mainly associated with QTc prolongation, torsade de pointes, ventricular arrhythmias, and cardiac arrest. This review shall familiarize readers with the benefits as well as the harmful effects of long-acting opioids in cardiovascular diseases. We have also provided an overview of cardiac opioid receptors, endogenous cardiac opioid peptides, and regulation of cardiovascular functions by central and cardiac opioid receptors.

Outcomes of Patients with Opioid-Related Diagnoses in Acute Coronary Syndrome: a National Inpatient Sample-Based Analysis

BACKGROUND

Acute coronary syndrome (ACS) and opioid use are both major causes of morbidity and mortality globally. Although epidemiological studies point to increased risk of ACS in opioid users, in-hospital management and outcomes are unknown for this population when presenting with ACS. We sought to determine whether there are differences for in-hospital outcomes and management of ACS for those with and without opioid-related diagnoses (ORD).

METHODS AND RESULTS

From the National Inpatient Sample database, we extracted patients hospitalized between 2012 and 2016 for ACS. The primary independent variable was ORD by International Classification of Diseases, 9th and 10th Revision, codes. The primary outcome was in-hospital mortality; secondary outcomes were cardiac arrest, receipt of angiogram, and percutaneous coronary intervention (PCI). Statistical comparisons were performed using χ2 test and Student's t test. Multivariable logistic regression was performed to determine the independent association between ORD and outcomes of interest. Among the estimated 5.8 million admissions for ACS, the proportion of patients with ORD increased over the study period (p for trend < 0.01). Compared to patients without ORD presenting with ACS, patients with ORD were younger with fewer cardiovascular risk factors. Yet, in-hospital mortality was higher in patients with ORD presenting with ACS (AOR 1.36, 95% CI 1.26-1.48). Patients with ORD were more likely to experience in-hospital cardiac arrest (AOR 1.42, 95% CI 1.23-1.63) and less likely to undergo angiogram (AOR 0.42, 95% CI 0.38-0.45) or PCI (AOR 0.30, 95% CI 0.28-0.32).

CONCLUSION

Despite evidence of increased risk of mortality and cardiac arrest, patients with ORD admitted for ACS are less likely to receive ACS management.

Impact of timing of morphine treatment on infarct size in experimental animal model of acute myocardial ischemia and reperfusion

Morphine is generally used in clinical treatment for the patients who have not been effectively alleviated for chest pain after the treatment with nitrites or who contraindicate nitrite drugs. However, it was reported that the treatment with morphine in acute myocardial infarction or acute coronary artery syndromes induced increase in myocardial injury even increase of the mortality of the patients. After comparing the reported laboratory studies showing the cardioprotective effects and the clinical observations presenting the harmful consequences, we query whether the timing of the morphine treatment makes the difference in the prognosis of the ischemic/infarct myocardium. We found that intravenous injections of morphine (0.3 mg/kg) at 15 min before the acute myocardial ischemia, at 5 min and 20 min or 60 min after ligation of the coronary artery in separate groups of rats scheduled for acute myocardial ischemia, for 30 min or 90 min followed by reperfusion for 120 min, induced different results, reduction in the size of infarction, no effect and increases of the infarct sizes, respectively. The opioid μ- and kappa-receptors mediated the detrimental effect of morphine on the myocardial injury. The findings of this study suggest that administration of morphine may cause different consequences when used at different time in the pathology of acute myocardial ischemia and reperfusion. The underlying mechanisms in the pathology of acute myocardial ischemia warrant further study.

MicroRNA-489 Promotes the Apoptosis of Cardiac Muscle Cells in Myocardial Ischemia-Reperfusion Based on Smart Healthcare

With the development of information technology, the concept of smart healthcare has gradually come to the fore. Smart healthcare uses a new generation of information technologies, such as the Internet of Things (loT), big data, cloud computing, and artificial intelligence, to transform the traditional medical system in an all-around way, making healthcare more efficient, more convenient, and more personalized. miRNAs can regulate the proliferation, differentiation, and apoptosis of human cells. Relevant studies have also shown that miRNAs may play a key role in the occurrence and development of myocardial ischemia-reperfusion injury (MIRI). This study aims to explore the effects of miR-489 in MIRI. In this study, miR-489 expression in a myocardial ischemia-reperfusion animal model and H9C2 cells induced by H/R was detected by qRT-PCR. The release of lactate dehydrogenase (LDH) and the activity of creatine kinase (CK) was detected after miR-489 knockdown in H9C2 cells induced by H/R. The apoptosis of H9C2 cells and animal models were determined by ELISA. The relationship between miR-489 and SPIN1 was verified by a double fluorescence reporter enzyme assay. The expression of the PI3K/AKT pathway-related proteins was detected by Western blot. Experimental results showed that miR-489 was highly expressed in cardiac muscle cells of the animal model and in H9C2 cells induced by H/R of the myocardial infarction group, which was positively associated with the apoptosis of cardiac muscle cells with ischemia-reperfusion. miR-489 knockdown can reduce the apoptosis of cardiac muscle cells caused by ischemia-reperfusion. In downstream targeting studies, it was found that miR-489 promotes the apoptosis of cardiac muscle cells after ischemia-reperfusion by targeting the inhibition of the SPIN1-mediated PI3K/AKT pathway. In conclusion, high expression of miR-489 is associated with increased apoptosis of cardiac muscle cells after ischemia-reperfusion, which can promote the apoptosis after ischemia-reperfusion by targeting the inhibition of the SPIN1-mediated PI3K/AKT pathway. Therefore, miR-489 can be one of the potential therapeutic targets for reducing the apoptosis of cardiac muscle cells after ischemia-reperfusion.

New targets of morphine postconditioning protection of the myocardium in ischemia/reperfusion injury: Involvement of HSP90/Akt and C5a/NF-κB

Background

Activation of the complement component 5a (C5a) and nuclear factor κB (NF-κB) signaling is an important feature of myocardial ischemia/reperfusion (I/R) injury and recent studies show that morphine postconditioning (MP) attenuates the myocardial injury. However, the mediating cardioprotective mechanisms remain unclear. The present study explores the role and interaction of heat shock protein 90 (HSP90), Akt, C5a, and NF-κB in MP-induced cardioprotection.

Methods

Male Sprague Dawley rats (n = 160) were randomized into eight groups (n = 20 per group). Rats in the sham group underwent thoracotomy, passing the ligature through the heart but without tying it (150 min), and the other seven groups were subjected to 30 min of anterior descending coronary artery occlusion followed by 2 h of reperfusion and the following treatments: I/R (30 min of ischemia and followed by 2 h of reperfusion); ischemic postconditioning (IPostC, 30 s of ischemia altered with 30 s of reperfusion, repeated for three cycles, and followed by reperfusion for 2 h); MP (0.3 mg/kg morphine administration 10 min before reperfusion); MP combined with the HSP90 inhibitor geldanamycin (GA, 1 mg/kg); MP combined with the Akt inhibitor GSK-690693 (GSK, 20 mg/kg); and MP combined with the C5a inhibitor PMX205 (PMX, 1 mg/kg/day, administration via drinking water for 28 days) and MP combined with the NF-κB inhibitor EVP4593 (QNZ, 1 mg/kg). All inhibitors were administered 10 min before morphine and followed by 2 h reperfusion.

Results

MP significantly reduced the I/R-induced infarct size, the apoptosis, and the release of cardiac troponin I, lactate dehydrogenase (LDH), and creatine kinase-MB. These beneficial effects were accompanied by increased expression of HSP90 and p-Akt, and decreased expression of C5a, NF-κB, tumor necrosis factor α, interleukin-1β, and intercellular cell adhesion molecule 1. However, HSP90 inhibitor GA or Akt inhibitor GSK increased the expression of C5a and NF-κB and prevented MP-induced cardioprotection. Furthermore, GA inhibited the MP-induced upregulation of p-Akt, while GSK did not affect HSP90, indicating that p-Akt acts downstream of HSP90 in MP-induced cardioprotection. In addition, C5a inhibitor PMX enhanced the MP-induced downregulation of NF-κB, while NF-κB inhibitor QNZ had no effect on C5a, indicating that the C5a/NF-κB signaling pathway is involved in MP-induced cardioprotection.

Conclusion

HSP90 is critical for MP-mediated cardioprotection possibly by promoting the phosphorylation of Akt and inhibiting the activation of C5a and NF-κB signaling and the subsequent myocardial inflammation, ultimately attenuating the infarct size and cardiomyocyte apoptosis.

Smoking, alcohol and opioids effect on coronary microcirculation: an update overview

Smoking, heavy alcohol drinking and drug abuse are detrimental lifestyle factors leading to loss of million years of healthy life annually. One of the major health complications caused by these substances is the development of cardiovascular diseases (CVD), which accounts for a significant proportion of substance-induced death. Smoking and excessive alcohol consumption are related to the higher risk of acute myocardial infarction. Similarly, opioid addiction, as one of the most commonly used substances worldwide, is associated with cardiac events such as ischemia and myocardial infarction (MI). As supported by many studies, coronary artery disease (CAD) is considered as a major cause for substance-induced cardiac events. Nonetheless, over the last three decades, a growing body of evidence indicates that a significant proportion of substance-induced cardiac ischemia or MI cases, do not manifest any signs of CAD. In the absence of CAD, the coronary microvascular dysfunction is believed to be the main underlying reason for CVD. To date, comprehensive literature reviews have been published on the clinicopathology of CAD caused by smoking and opioids, as well as macrovascular pathological features of the alcoholic cardiomyopathy. However, to the best of our knowledge there is no review article about the impact of these substances on the coronary microvascular network. Therefore, the present review will focus on the current understanding of the pathophysiological alterations in the coronary microcirculation triggered by smoking, alcohol and opioids.

IcyHot analgesic topical cream limits cardiac injury in rodents

Little is known whether topical analgesic creams, whose natural products enter the blood stream after application, affect myocardial infarct size. Here we tested whether topical analgesic creams can trigger remote cardioprotection and the mechanism involved. Male Sprague Dawley rats were used for an in vivo rodent model consisting of 30 minutes left anterior descending coronary artery ischemia and 2 hours of reperfusion followed by infarct size assessment. The topical analgesic IcyHot, applied to the abdomen prior to ischemia, reduced myocardial infarct size versus control (41 ± 3* vs 62 ± 1, n= 6/group, *P < 0.001). In contrast, the topical analgesic creams Preparation H, Aspercreme Heat, or Tiger Balm did not alter infarct size. IcyHot, unlike Preparation H, increased circulating methyl salicylate levels during reperfusion (3.0 ± 0.6 vs 0.4 ± 0.2 mg/dL, n = 6, *P < 0.001, measured at the internal jugular vein). Methyl salicylate (10 μM) applied to isolated adult cardiac myocytes during reoxygenation reduced cell death when compared to vehicle (21% ± 2%* vs 30% ± 2% of trypan blue positive cells, n = 9/group, *P < 0.01). Further, treatment with the TRP ankyrin 1 (TRPA1) inhibitors TCS-5861528 (1 μM) or AP-18 (1 μM) blocked the methyl salicylate-induced protective effect in isolated adult cardiomyocytes. In intact rodents, either of the TRPA1 inhibitors (1 mg/kg, intravenous) given prior to IcyHot topical application blocked IcyHot-induced infarct size reduction. IcyHot also reduced infarct size when applied 24 hours prior to myocardial ischemia or during myocardial ischemia versus control. Together, these findings support IcyHot analgesic cream can trigger remote cardioprotection through releasing methyl salicylate into the bloodstream with cardioprotection occurring by a TRPA1-dependent mechanism.

Naltrexone-Associated Non-ST-Elevated Myocardial Infarction

Medications for opioid use disorder (MOUD) and opioid agonist therapy (OAT) are the mainstays of treatment in opioid use disorder. Significant caution is encouraged upon initiation to reduce the precipitation of opioid withdrawal. Cardiac events in the setting of opioid withdrawal are rare and incompletely understood.

A 46-year-old woman with a history of opioid-use disorder, hypertension, hyperlipidemia, diabetes, tobacco-use disorder, and rheumatoid arthritis presented with nausea, vomiting, and lightheadedness after taking naltrexone following buprenorphine. She was found to be hypertensive and tachycardic in the emergency department, with a troponin of 0.38 ng/mL (reference: 0.00-0.30 ng/mL) and an electrocardiogram (ECG) without ST or T-wave changes. She was admitted for a non-ST-elevation myocardial infarction (NSTEMI) and hypertensive emergency in the setting of opioid withdrawal. Her blood pressure was controlled, and she received full-dose aspirin and high intensity atorvastatin. Afterwards she was started on a modified OAT regimen of buprenorphine 8 mg daily. Her cardiac enzymes down-trended and her condition became stable after which she was discharged home.

Cardiac events are an uncommon yet lethal occurrence in opioid withdrawal. The likely etiology of NSTEMI in our patient was demand ischemia induced by opioid withdrawal, augmented by her various other cardiac risk factors. Practitioners should be aware of these possible adverse events, especially in those with preexisting cardiac disease. Meticulous efforts should be made to instruct patients as to the proper dosing schedule when initiating opioid therapy, and when initiating MOUD/OAT in order to prevent poor outcomes.

Targeted pharmacotherapy for ischemia reperfusion injury in acute myocardial infarction

INTRODUCTION

Achieving reperfusion immediately after acute myocardial infarction improves outcomes; despite this, patients remain at a high risk for mortality and morbidity at least for the first year after the event. Ischemia-reperfusion injury (IRI) has a complex pathophysiology and plays an important role in myocardial tissue injury, repair, and remodeling.

AREAS COVERED

In this review, the authors discuss the various mechanisms and their pharmacological agents currently available for reducing myocardial ischemia-reperfusion injury (IRI). They review important original investigations and trials in various clinical databases for treatments targeting IRI.

EXPERT OPINION

Encouraging results observed in many preclinical studies failed to show similar success in attenuating myocardial IRI in large-scale clinical trials. Identification of critical risk factors for IRI and targeting them individually rather than one size fits all approach should be the major focus of future research. Various newer therapies like tocilizumab, anakinra, colchicine, revacept, and therapies targeting the reperfusion injury salvage kinase pathway, survivor activating factor enhancement, mitochondrial pathways, and angiopoietin-like peptide 4 hold promise for the future.

Bidirectional Regulation of Opioid and Chemokine Function

The opioid family of GPCRs consists of the classical opioid receptors, designated μ-, κ-, and δ-opioid receptors, and the orphanin-FQ receptor, and these proteins are expressed on both neuronal and hematopoietic cells. A number of laboratories have reported that an important degree of cross-talk can occur between the opioid receptors and the chemokine and chemokine receptor families. As a part of this, the opioid receptors are known to regulate the expression of certain chemokines and chemokine receptors, including those that possess strong pro-inflammatory activity. At the level of receptor function, it is clear that certain members of the chemokine family can mediate cross-desensitization of the opioid receptors. Conversely, the opioid receptors are all able to induce heterologous desensitization of some of the chemokine receptors. Consequently, activation of one or more of the opioid receptors can selectively cross-desensitize chemokine receptors and regulate chemokine function. These cross-talk processes have significant implications for the inflammatory response, since the regulation of both the recruitment of inflammatory cells, as well as the sensation of pain, can be controlled in this way.

Genetic polymorphisms in the opioid receptor delta 1 (OPRD1) gene are associated with methadone dose in methadone maintenance treatment for heroin dependence

Delta opioid receptor (DOR) is well known to be involved in heroin dependence. This study tested the hypothesis that single nucleotide polymorphisms (SNPs) in the opioid receptor delta 1 (OPRD1) gene coding region are associated with treatment responses in a methadone maintenance therapy (MMT) cohort in Taiwan. Three hundred forty-four MMT patients were recruited. Diastolic/systolic blood pressure, heart rate, methadone dosage, and plasma concentrations of methadone were recorded. Twenty-five SNPs located within the OPRD1 genetic region were selected and genotyped from the genomic DNA of all 344 participants. After pairwise tagger analyses, tagger SNP rs204047 showed a significant association with methadone dosage (P = 0.0019), and tagger SNPs rs204047 and rs797397 were significantly associated with plasma R, S-methadone concentrations (P < 0.0006) in patients tested negative in the urine morphine test, which indicated patients with a better response to MMT. The major genotype carriers showed a higher methadone dosage and higher plasma concentrations of R, S-methadone than the minor genotype carriers. The results indicated that OPRD1 genetic variants were associated with methadone dosage and methadone plasma concentration in MMT patients with a negative morphine test result.

Novel Roles of Non-Coding RNAs in Opioid Signaling and Cardioprotection

Cardiovascular disease (CVD) is a significant cause of morbidity and mortality across the world. A large proportion of CVD deaths are secondary to coronary artery disease (CAD) and myocardial infarction (MI). Even though prevention is the best strategy to reduce risk factors associated with MI, the use of cardioprotective interventions aimed at improving patient outcomes is of great interest. Opioid conditioning has been shown to be effective in reducing myocardial ischemia-reperfusion injury (IRI) and cardiomyocyte death. However, the molecular mechanisms behind these effects are under investigation and could provide the basis for the development of novel therapeutic approaches in the treatment of CVD. Non-coding RNAs (ncRNAs), which are functional RNA molecules that do not translate into proteins, are critical modulators of cardiac gene expression during heart development and disease. Moreover, ncRNAs such as microRNAs (miRNAs) and long non-coding RNAs (lncRNAs) are known to be induced by opioid receptor activation and regulate opioid signaling pathways. Recent advances in experimental and computational tools have accelerated the discovery and functional characterization of ncRNAs. In this study, we review the current understanding of the role of ncRNAs in opioid signaling and opioid-induced cardioprotection.

Transient receptor potential vanilloid 1 inhibitors block laparotomy- and opioid-induced infarct size reduction in rats

BACKGROUND AND PURPOSE

In light of the opioid epidemic, physicians are increasingly prescribing non-opioid analgesics to surgical patients. Transient receptor potential vanilloid 1 (TRPV1) inhibitors are potentially alternative pain therapeutics for surgery. Here, we examined in rodents whether the cardioprotection conferred by two common procedures during surgery, a laparotomy or morphine delivery, is mediated by the TRPV1 channel. We further tested whether an experimental analgesic peptide (known as P5) targeted against the TRPV1 C-terminus region interferes with laparotomy- or morphine-induced cardioprotection.

EXPERIMENTAL APPROACH

Male Sprague-Dawley rats were subjected to 30 min coronary occlusion followed by 120 min reperfusion. Before ischaemia, a laparotomy with or without capsaicin application (0.1% cream, a TRPV1 activator) was performed. Additional rats were given morphine (0.3 mg·kg^-1 ) with or without capsaicin. In addition, capsazepine (3 mg·kg^-1 , a classical TRPV1 inhibitor), or P5 (3 mg·kg^-1 , a peptide analgesic and TRPV1 inhibitor), was given either alone or prior to a laparotomy or morphine administration. Myocardial infarct size was determined.

KEY RESULTS

A laparotomy, in addition to combining a laparotomy with capsaicin cream, reduced infarct size versus control. Morphine, in addition to combining morphine administration with capsaicin cream, also reduced infarct size versus control. When TRPV1 inhibitors capsazepine or P5 were given, either TRPV1 inhibitor abolished the infarct size reduction mediated by a laparotomy or morphine.

CONCLUSIONS AND IMPLICATIONS

Inhibiting the TRPV1 channel blocks laparotomy- or morphine-induced cardioprotection. Impaired organ protection may be a potential pitfall of using TRPV1 inhibitors for pain control.

Transient Receptor Potential Ankyrin 1 Activation within the Cardiac Myocyte Limits Ischemia-reperfusion Injury in Rodents

BACKGROUND

Recent evidence suggests that cross talk exists between cellular pathways important for pain signaling and ischemia-reperfusion injury. Here, the authors address whether the transient receptor potential ankyrin 1 (TRPA1) channel, important in pain signaling, is present in cardiac myocytes and regulates cardiac ischemia-reperfusion injury.

METHODS

For biochemical analysis of TRPA1, techniques including quantitative polymerase chain reaction, Western blot, and immunofluorescence were used. To determine how TRPA1 mediates cellular injury, the authors used an in vivo model of rat cardiac ischemia-reperfusion injury and adult rat-isolated cardiac myocytes subjected to hypoxia-reoxygenation.

RESULTS

The authors' biochemical analysis indicates that TRPA1 is within the cardiac myocytes. Further, using a rat in vivo model of cardiac injury, the TRPA1 activators ASP 7663 and optovin reduce myocardial injury (45 ± 5%* and 44 ± 8%,* respectively, vs. control, 66 ± 6% infarct size/area at risk; n = 6 per group; mean ± SD; *P < 0.001). TRPA1 inhibition also blocked the infarct size-sparing effects of morphine. In isolated cardiac myocytes, the TRPA1 activators ASP 7663 and optovin reduce cardiac myocyte cell death when given during reoxygenation (20 ± 3%* and 22 ± 4%* vs. 36 ± 3%; percentage of dead cells per field, n = 6 per group; mean ± SD; *P < 0.05). For a rat in vivo model of cardiac injury, the infarct size-sparing effect of TRPA1 activators also occurs during reperfusion.

CONCLUSIONS

The authors' data suggest that TRPA1 is present within the cardiac myocytes and is important in regulating myocardial reperfusion injury. The presence of TRPA1 within the cardiac myocytes may potentially explain why certain pain relievers that can block TRPA1 activation, such as cyclooxygenase-2 inhibitors or some nonsteroidal antiinflammatory drugs, could be associated with cardiovascular risk.

Acute Myocardial Infarction following Naltrexone Consumption; a Case Report

Cardiovascular effects of opioid withdrawal have long been studied. It was reported that patients with underlying ischemic heart disease and atherosclerotic vessels may be complicated by a sudden physical and emotional stress due to withdrawal syndrome. But some other believes sudden increase in catecholamine level as a sympathetic overflow might effect on heart with and without underlying ischemia. In the current study, a patient on methadone maintenance therapy (MMT) who experienced myocardial infarction (MI) after taking naltrexone was described.

Transient Receptor Potential Vanilloid 1 Regulates Mitochondrial Membrane Potential and Myocardial Reperfusion Injury

Background

The transient receptor potential vanilloid 1 (TRPV1) mediates cellular responses to pain, heat, or noxious stimuli by calcium influx; however, the cellular localization and function of TRPV1 in the cardiomyocyte is largely unknown. We studied whether myocardial injury is regulated by TRPV1 and whether we could mitigate reperfusion injury by limiting the calcineurin interaction with TRPV1.

Methods and Results

In primary cardiomyocytes, confocal and electron microscopy demonstrates that TRPV1 is localized to the mitochondria. Capsaicin, the specific TRPV1 agonist, dose‐dependently reduced mitochondrial membrane potential and was blocked by the TRPV1 antagonist capsazepine or the calcineurin inhibitor cyclosporine. Using in silico analysis, we discovered an interaction site for TRPV1 with calcineurin. We synthesized a peptide, V1‐cal, to inhibit the interaction between TRPV1 and calcineurin. In an in vivo rat myocardial infarction model, V1‐cal given just prior to reperfusion substantially mitigated myocardial infarct size compared with vehicle, capsaicin, or cyclosporine (24±3% versus 61±2%, 45±1%, and 49±2%, respectively; n=6 per group; P<0.01 versus all groups). Infarct size reduction by V1‐cal was also not seen in TRPV1 knockout rats.

Conclusions

TRPV1 is localized at the mitochondria in cardiomyocytes and regulates mitochondrial membrane potential through an interaction with calcineurin. We developed a novel therapeutic, V1‐cal, that substantially reduces reperfusion injury by inhibiting the interaction of calcineurin with TRPV1. These data suggest that TRPV1 is an end‐effector of cardioprotection and that modulating the TRPV1 protein interaction with calcineurin limits reperfusion injury.

Prospects for Creation of Cardioprotective and Antiarrhythmic Drugs Based on Opioid Receptor Agonists

It has now been demonstrated that the μ, δ1 , δ2 , and κ1 opioid receptor (OR) agonists represent the most promising group of opioids for the creation of drugs enhancing cardiac tolerance to the detrimental effects of ischemia/reperfusion (I/R). Opioids are able to prevent necrosis and apoptosis of cardiomyocytes during I/R and improve cardiac contractility in the reperfusion period. The OR agonists exert an infarct-reducing effect with prophylactic administration and prevent reperfusion-induced cardiomyocyte death when ischemic injury of heart has already occurred; that is, opioids can mimic preconditioning and postconditioning phenomena. Furthermore, opioids are also effective in preventing ischemia-induced arrhythmias.

Treatment of Myocardial Ischemia/Reperfusion Injury by Ischemic and Pharmacological Postconditioning

Timely reperfusion is the only way to salvage ischemic myocardium from impending infarction. However, reperfusion also adds a further component to myocardial injury such that the ultimate infarct size is the result of both ischemia- and reperfusion-induced injury. Modification of reperfusion can attenuate reperfusion injury and thus reduce infarct size. Ischemic postconditioning is a maneuver of repeated brief interruption of reperfusion by short-lasting coronary occlusions which results in reduced infarct size. Cardioprotection by ischemic postconditioning is mediated through delayed reversal of acidosis and the activation of a complex signal transduction cascade, including triggers such as adenosine, bradykinin, and opioids, mediators such as protein kinases and, notably, mitochondrial function as effector. Inhibition of the mitochondrial permeability transition pore appears to be a final signaling step of ischemic postconditioning. Several drugs which recruit in part such signaling steps of ischemic postconditioning can induce cardioprotection, even when the drug is only administered at reperfusion, that is, there is also pharmacological postconditioning. Ischemic and pharmacological postconditioning have been translated to patients with acute myocardial infarction in proof-of-concept studies, but further mechanistic insight is needed to optimize the conditions and algorithms of cardioprotection by postconditioning.

Prescription Opioid Use and Risk of Coronary Heart Disease, Stroke, and Cardiovascular Death Among Adults from a Prospective Cohort (REGARDS Study)

OBJECTIVE

Despite unknown risks, prescription opioid use (POU) for nonmalignant chronic pain has grown in the US over the last decade. The objective of this study was to examine associations between POU and coronary heart disease (CHD), stroke, and cardiovascular disease (CVD) death in a large cohort.

DESIGN, SETTING, SUBJECTS

POU was assessed in the prospective cohort study of 29,025 participants of the REasons for Geographic and Racial Differences in Stroke study, enrolled between 2003 and 2007 from the continental United States and followed through December 31, 2010. CHD, stroke, and CVD death were expert adjudicated outcome measures.

METHODS

Cox proportional hazards models adjusted for CVD risk factors were used.

RESULTS

Over a median (SD) of 5.2 (1.8) years of follow-up, 1,362 CHD events, 749 strokes, and 1,120 CVD death occurred (105, 55, and 104, respectively, in the 1,851 opioid users). POU was not associated with CHD (adjusted hazard ratio [aHR]) 1.03 [95% CI 0.83-1.26] or stroke (aHR 1.04 [95% CI 0.78-1.38]), but was associated with CVD death (aHR 1.24 [95% CI 1.00-1.53]) in the overall sample. In the sex-stratified analyses, POU was associated with increased risk of CHD (aHR 1.38 [95% CI 1.05-1.82]) and CVD death (aHR 1.66 [95% CI 1.27-2.17]) among females but not males (aHR 0.70 [95% CI 0.50-0.97] for CHD and 0.78 [95% CI 0.54-1.11] for CVD death).

CONCLUSION

Female but not male POU were at higher risk of CHD and CVD death. POU was not associated with stroke in overall or sex-stratified analyses.

Combined morphine and limb remote ischemic perconditioning provides an enhanced protection against myocardial ischemia/reperfusion injury by antiapoptosis

BACKGROUND

Both morphine and limb remote ischemic perconditioning (RIPer) can protect against myocardial ischemia/reperfusion injury (IRI). This experiment was designed to assess whether combined morphine and limb RIPer could provide and enhanced protection against myocardial IRI in an in vivo rat model.

METHODS

One hundred male Sprague-Dawley rats were randomly allocated to six groups: sham, ischemia/reperfusion (IR), ischemic preconditioning, RIPer, morphine (M), and combined morphine and remote ischemic perconditioning (M + RIPer). Ventricular arrhythmias that occurred during ischemia and early reperfusion were scored, and serum creatine kinase isoenzyme and cardiac troponin I levels were assayed. The infarct size was determined by Evans blue and triphenyl tetrazolium chloride staining. The apoptosis in the myocardial ischemic core, ischemic border, and nonischemic areas was assessed through real-time polymerase chain reaction for Bax and Bcl-2 and with the transferase-mediated deoxyuridine triphosphate-biotin nick end labeling assay.

RESULTS

The infarct size, serum cardiac troponin I level, incidence, and score of the arrhythmias during the initial reperfusion were significantly reduced in the M + RIPer group compared with the IR group but did not differ significantly between the ischemic preconditioning and M + RIPer groups. Transferase-mediated deoxyuridine triphosphate-biotin nick end labeling-positive cells were significantly decreased, and the Bcl-2/Bax ratio was significantly increased in the M + RIPer group compared with the IR group.

CONCLUSIONS

This experiment demonstrates that combined morphine and limb RIPer provides an enhanced protection against myocardial IRI by the Bcl-2-linked apoptotic signaling pathway.

The Wide and Unpredictable Scope of Synthetic Cannabinoids Toxicity

Drug use and abuse continue to be a large public health concern worldwide. Over the past decade, novel or atypical drugs have emerged and become increasingly popular. In the recent past, compounds similar to tetrahydrocannabinoid (THC), the active ingredient of marijuana, have been synthetically produced and offered commercially as legal substances. Since the initial communications of their abuse in 2008, few case reports have been published illustrating the misuse of these substances with signs and symptoms of intoxication. Even though synthetic cannabinoids have been restricted, they are still readily available across USA and their use has been dramatically increasing, with a concomitant increment in reports to poison control centers and emergency department (ED) visits. We describe a case of acute hypoxemic/hypercapnic respiratory failure as a consequence of acute congestive heart failure (CHF) developed from myocardial stunning resulting from a non-ST-segment elevation myocardial infarction (MI) following the consumption of synthetic cannabinoids.

Morphine Reduces Myocardial Infarct Size via Heat Shock Protein 90 in Rodents

Opioids reduce injury from myocardial ischemia-reperfusion in humans. In experimental models, this mechanism involves GSK3β inhibition. HSP90 regulates mitochondrial protein import, with GSK3β inhibition increasing HSP90 mitochondrial content. Therefore, we determined whether morphine-induced cardioprotection is mediated by HSP90 and if the protective effect is downstream of GSK3β inhibition. Male Sprague-Dawley rats, aged 8–10 weeks, were subjected to an in vivo myocardial ischemia-reperfusion injury protocol involving 30 minutes of ischemia followed by 2 hours of reperfusion. Hemodynamics were continually monitored and myocardial infarct size determined. Rats received morphine (0.3 mg/kg), the GSK3β inhibitor, SB216763 (0.6 mg/kg), or saline, 10 minutes prior to ischemia. Some rats received selective HSP90 inhibitors, radicicol (0.3 mg/kg), or deoxyspergualin (DSG, 0.6 mg/kg) alone or 5 minutes prior to morphine or SB216763. Morphine reduced myocardial infarct size when compared to control (42 ± 2% versus 60 ± 1%). This protection was abolished by prior treatment of radicicol or DSG (59 ± 1%, 56 ± 2%). GSK3β inhibition also reduced myocardial infarct size (41 ± 2%) with HSP90 inhibition by radicicol or DSG partially inhibiting SB216763-induced infarct size reduction (54 ± 3%, 47 ± 1%, resp.). These data suggest that opioid-induced cardioprotection is mediated by HSP90. Part of this protection afforded by HSP90 is downstream of GSK3β, potentially via the HSP-TOM mitochondrial import pathway.

Intraoperative Methadone for the Prevention of Postoperative Pain

Background:

The intensity of pain after cardiac surgery is often underestimated, and inadequate pain control may be associated with poorer quality of recovery. The aim of this investigation was to examine the effect of intraoperative methadone on postoperative analgesic requirements, pain scores, patient satisfaction, and clinical recovery.

Methods:

Patients undergoing cardiac surgery with cardiopulmonary bypass (n = 156) were randomized to receive methadone (0.3 mg/kg) or fentanyl (12 μg/kg) intraoperatively. Postoperative analgesic requirements were recorded. Patients were assessed for pain at rest and with coughing 15 min and 2, 4, 8, 12, 24, 48, and 72 h after tracheal extubation. Patients were also evaluated for level of sedation, nausea, vomiting, itching, hypoventilation, and hypoxia at these times.

Results:

Postoperative morphine requirements during the first 24 h were reduced from a median of 10 mg in the fentanyl group to 6 mg in the methadone group (median difference [99% CI], −4 [−8 to −2] mg; P &lt; 0.001). Reductions in pain scores with coughing were observed during the first 24 h after extubation; the level of pain with coughing at 12 h was reduced from a median of 6 in the fentanyl group to 4 in the methadone group (−2 [−3 to −1]; P &lt; 0.001). Improvements in patient-perceived quality of pain management were described in the methadone group. The incidence of opioid-related adverse events was not increased in patients administered methadone.

Conclusions:

Intraoperative methadone administration resulted in reduced postoperative morphine requirements, improved pain scores, and enhanced patient-perceived quality of pain management.

Intravenous morphine administration and reperfusion success in ST-elevation myocardial infarction: insights from cardiac magnetic resonance imaging

AIMS

Intravenous (IV) morphine has been shown to be independently associated with adverse clinical outcome in patients with non-STEMI. Currently, there are no data on the association of IV morphine and reperfusion success in STEMI. Thus, we thought to analyse the impact of IV morphine on ischemic injury and salvaged myocardium assessed by cardiac magnetic resonance imaging (CMR) in patients with STEMI reperfused by primary coronary intervention (PCI).

METHODS AND RESULTS

STEMI patients reperfused by primary PCI (n = 276) within 12 h after symptom onset underwent CMR 3 days after the index event [interquartile range (IQR) 2-4]. IV morphine administration was recorded in all patients. IV morphine was administered in 44.7% (n = 123) of all patients. Patients in the IV morphine group displayed larger infarct size, higher extent of MO and lower myocardial salvage index (MSI) in comparison to the non-IV morphine group (all p < 0.05). In multivariable logistic regression analysis adjusted for TIMI-flow pre-PCI, time from symptom onset to PCI, Killip class and left ventricular ejection fraction, IV morphine was identified as an independent predictor for MSI <median (odds ratio 1.71, 95% CI 1.02-2.87, p = 0.04).

CONCLUSION

In patients with STEMI, IV morphine administration prior to PCI is independently associated with suboptimal reperfusion success. These findings warrant randomised clinical trials assessing the effect of IV morphine on clinical outcome.

Extracellular signalling molecules in the ischaemic/reperfused heart - druggable and translatable for cardioprotection?

In patients with acute myocardial infarction, timely reperfusion is essential to limit infarct size. However, reperfusion also adds to myocardial injury. Brief episodes of ischaemia/reperfusion in the myocardium or on organ remote from the heart, before or shortly after sustained myocardial ischaemia effectively reduce infarct size, provided there is eventual reperfusion. Such conditioning phenomena have been established in many experimental studies and also translated to humans. The underlying signal transduction, that is the molecular identity of triggers, mediators and effectors, is not clear yet in detail, but several extracellular signalling molecules, such as adenosine, bradykinin and opioids, have been identified to contribute to cardioprotection by conditioning manoeuvres. Several trials have attempted the translation of cardioprotection by such autacoids into a clinical scenario of myocardial ischaemia and reperfusion. Adenosine and its selective agonists reduced infarct size in a few studies, but this benefit was not translated into improved clinical outcome. All studies with bradykinin or drugs which increase bradykinin's bioavailability reported reduced infarct size and some of them also improved clinical outcome. Synthetic opioid agonists did not result in a robust infarct size reduction, but this failure of translation may relate to the cardioprotective properties of the underlying anaesthesia per se or of the comparator drugs. The translation of findings in healthy, young animals with acute coronary occlusion/reperfusion to patients of older age, with a variety of co-morbidities and co-medications, suffering from different scenarios of myocardial ischaemia/reperfusion remains a challenge.

Opioid-induced cardioprotection

Ischemic heart disease and myocardial infarction continue to be leading causes of cardiovascular morbidity and mortality. Activation of opioid, adenosine, bradykinin, adrenergic and other G-protein coupled receptors has been found to be cardioprotective. κ- and/or δ-opioid receptor activation is involved in direct myocardial protection, while the role of µ-opioid receptors seems less clear. In addition, differential affinities to the three opioid-receptor subtypes by various agonists and cross-talk among different G-protein coupled receptors render conclusions regarding opioid-mediated cardioprotection challenging. The present review will focus on the protective effects of endogenously released opioid peptides as well as exogenously administered opioids such as morphine, fentanyl, remifentanil, butorphanol, and methadone against myocardial ischemia/reperfusion injury. Receptor heterodimerization and cross-talk as well as interactions with other cardioprotective techniques will be discussed. Implications for opioid-induced cardioprotection in humans and for future drug development to improve myocardial salvage will be provided.

Role of endogenous opioid peptides in the infarct size-limiting effect of adaptation to chronic continuous hypoxia

AIMS

The objective of this study was to examine the involvement of endogenous opioid peptides and opioid receptor (OR) subtypes in the cardioprotective effect of adaptation to chronic hypoxia in rats.

MAIN METHODS

Rats were exposed to continuous normobaric hypoxia (CNH; 12% oxygen) for 3 weeks. Myocardial ischemia was induced by 20-min coronary artery occlusion followed by 3-h reperfusion in anesthetized open-chest animals. Various OR antagonists were administered to rats prior to ischemia. The size of myocardial infarction and the incidence of ischemic ventricular arrhythmias were assessed. Myocardial and plasma concentrations of opioid peptides (met-enkephalin, β-endorphin, and endomorphins) were determined.

KEY FINDINGS

Adaptation to CNH significantly increased myocardial and plasma concentrations of opioids, potentiated their further elevation by ischemia/reperfusion, and reduced myocardial infarct size, but it did not affect the incidence of ischemic arrhythmias. The infarct size-limiting effect of CNH was abolished by OR antagonists naltrexone (non-selective), naloxone methiodide (non-selective peripherally acting), TIPP[ψ] (δ-OR), naltriben (δ2-OR), or CTAP (μ-OR), while BNTX (δ1-OR) and nor-binaltorphimine (κ-OR) had no effect.

SIGNIFICANCE

The results suggest that the infarct size-limiting effect afforded by adaptation to CNH is mediated by activation of peripheral δ2- and μ-ORs by elevated levels of endogenous opioid peptides.

Morphine and remifentanil-induced cardioprotection: its experimental and clinical outcomes

During the past few decades, a large number of animal studies demonstrated that commonly used opioids could provide cardioprotection against ischemia-reperfusion (I/R) injury. Opioid-induced preconditioning or postconditioning mimics ischemic preconditioning (I-Pre) or ischemic postconditioning (I-Post). Both δ- and κ-opioid receptors (OPRs) play a crucial role in opioid-induced cardioprotection (OIC). Down stream signaling effectors of OIC include ATP-sensitive potassium (K_ATP) channels, protein kinase C (PKC), tyrosine kinase, phosphatidylinositol-3-kinase (PI3-kinase), extracellular signal regulated kinase1/2 (ERK1/2), glycogen synthase kinase-3β (GSK-3β), and mitochondrial permeability transition pore (MPTP), among others. Recently, various reports also suggest that opioids could provide cardioprotection in humans. This review will discuss OIC using mostly morphine and remifentanil which are widely used during cardiac anesthesia in addition to the clinical implications of OIC.

Morphine-induced postconditioning modulates mitochondrial permeability transition pore opening via delta-1 opioid receptors activation in isolated rat hearts

BACKGROUND

It is generally accepted that morphine affords cardioprotection against ischemia/reperfusion injury. Inhibition of the mitochondrial permeability transition pore (MPTP) is considered an end target for cardioprotection. The aim of this study was to investigate the involvement of opioid receptors (OR) and MPTP in morphine-induced postconditioning (M-Post).

METHODS

Isolated rat hearts were subjected to 30 min of regional ischemia and 2 h of reperfusion. Hearts were treated with 1 µM morphine, with or without the OR antagonists or a MPTP opener at early reperfusion. Infarct size was measured with 2,3,5-triphenyltetrazolium chloride staining.

RESULTS

There were no significant differences in cardiodynamic variables except a decrease in heart rate in the M-Post group (P < 0.01 vs. control) after reperfusion. M-Post dramatically reduced infarct-risk volume ratio (9.8 ± 2.5%, P < 0.001 vs. 30.0 ± 3.7% in control). This beneficial effect on infarct volume by M-Post was comparable with ischemic postconditioning (11.9 ± 2.2%, P > 0.05). The nonspecific OR antagonist naloxone (25.7 ± 1.9%, P < 0.01), the δ-OR antagonist naltrindole (27.8 ± 4.3%, P < 0.05) and δ(1)-OR antagonist 7-benzylidenenaltrexone (24.7 ± 3.7%, P < 0.01) totally abrogated the anti-infarct effect of M-Post. In addition, the anti-infarct effect by M-Post was also totally blocked by the MPTP opener atractyloside (26.3 ± 5.2%, P < 0.05).

CONCLUSIONS

M-Post effectively reduces myocardial infarction. The anti-infarct effect by M-Post is mediated via activation of δ-OR, especially δ(1)-OR, and inhibition of the MPTP opening.

Endogenous opiates and behavior: 2009

This paper is the 32nd consecutive installment of the annual review of research concerning the endogenous opioid system. It summarizes papers published during 2009 that studied the behavioral effects of molecular, pharmacological and genetic manipulation of opioid peptides, opioid receptors, opioid agonists and opioid antagonists. The particular topics that continue to be covered include the molecular-biochemical effects and neurochemical localization studies of endogenous opioids and their receptors related to behavior (Section 2), and the roles of these opioid peptides and receptors in pain and analgesia (Section 3); stress and social status (Section 4); tolerance and dependence (Section 5); learning and memory (Section 6); eating and drinking (Section 7); alcohol and drugs of abuse (Section 8); sexual activity and hormones, pregnancy, development and endocrinology (Section 9); mental illness and mood (Section 10); seizures and neurologic disorders (Section 11); electrical-related activity and neurophysiology (Section 12); general activity and locomotion (Section 13); gastrointestinal, renal and hepatic functions (Section 14); cardiovascular responses (Section 15); respiration and thermoregulation (Section 16); and immunological responses (Section 17).