Myocardial ischemic conditioning: Physiological aspects and clinical applications in cardiac surgery

Ischemic preconditioning modulates the DNA methylation process of the rat heart to provide tolerance to withstand ischemia reperfusion injury and its associated mitochondrial dysfunction

DNA methylation plays a crucial role in the pathogenesis of myocardial ischemia reperfusion injury(I/R) and the I/R injury can be combated effectively by ischemia preconditioning (IPC), but the role is DNA methylation in this process is unknown. In this study, we uncovered the role of ischemic preconditioning (IPC)- mediated cardioprotection of rat myocardium by using a Langendorff rat heart model with 30 min of ischemia followed by 60 min of reperfusion. Heart conditioned with short cycles of ischemia and reperfusion (IPC procedure) prior to I/R protocol significantly reduced the I/R-induced global DNA hypermethylation level by 32% and the DNMT activity by 33% while rendering cardioprotection. Blocking the PI3K pathway via wortmannin not only negates the cardio-protection by IPC, but also increases the methylation of DNA by 75%. Besides, the correlation analysis showed a negative relationship between PI3K gene expression and the global DNA methylation level (r = - 0.8690, p = 0.0419) in IPC-treated rat hearts. Moreover, the global level DNA hypomethylation induced by IPC exhibited a regulatory effect on the genes involved in I/R pathology mediators like apoptosis (Caspase3), mitochondrial function (PGC 1α, TFAM, ND1) and oxidative stress (CuZnSOD, SOD2), and their corresponding function. The present study results provide novel evidence for the involvement of DNA methylation in the IPC procedure, and suggest DNA methylation as one of the potential therapeutic targets regulated by ischemic preconditioning in rat hearts subjected to ischemia reperfusion.

Supplementary Information

The online version contains supplementary material available at 10.1007/s13205-024-03965-0.

The role of PI3K/AKT signaling pathway in myocardial ischemia-reperfusion injury

Myocardial ischemia has a high incidence and mortality rate, and reperfusion is currently the standard intervention. However, reperfusion may lead to further myocardial damage, known as myocardial ischemia/reperfusion injury (MIRI). There are currently no effective clinical treatments for MIRI. The PI3K/Akt signaling pathway is involved in cardiovascular health and disease and plays an important role in reducing myocardial infarct size and restoring cardiac function after MIRI. Activation of the PI3K/Akt pathway provides myocardial protection through synergistic upregulation of antioxidant, anti-inflammatory, and autophagy activities and inhibition of mitochondrial dysfunction and cardiomyocyte apoptosis. Many studies have shown that PI3K/Akt has a significant protective effect against MIRI. Here, we reviewed the molecular regulation of PI3K/Akt in MIRI and summarized the molecular mechanism by which PI3K/Akt affects MIRI, the effects of ischemic preconditioning and ischemic postconditioning, and the role of related drugs or activators targeting PI3K/Akt in MIRI, providing novel insights for the formulation of myocardial protection strategies. This review provides evidence of the role of PI3K/Akt activation in MIRI and supports its use as a therapeutic target.

Di-5-ANEQ(F)PTEA Offers Better Performance than Di-4-ANEQ(F)PTEA for In-Situ Cardiac Optical Mapping. ANNUAL INTERNATIONAL CONFERENCE OF THE IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. ANNUAL INTERNATIONAL CONFERENCE 2023;2023:1-4. [PMID: 38082915 DOI: 10.1109/embc40787.2023.10340445] [Citation(s) in RCA: 0] [Impact Index Per Article: 0]

Cardiac optical mapping has traditionally been performed in ex-vivo, motion-arrested hearts. Recently, in-situ cardiac optical mapping has been made possible by both motion correction techniques and long-wavelength voltage sensitive dyes (VSDs). However, VSDs have been observed to wash out quickly from blood-perfused in-situ hearts. In this study, we evaluate the performance of a newly developed VSD, di-5-ANEQ(F)PTEA, relative to an earlier VSD, di-4-ANEQ(F)PTEA. We find that di-5-ANEQ(F)PTEA persists over 3 times longer, produces improved signal-to-noise ratio, and does not prolong loading unacceptably.Clinical Relevance-Optical mapping has provided many insights into cardiac arrhythmias, but has traditionally been limited to ex-vivo preparations. The present findings extend the utility of optical mapping in the more realistic in-vivo setting and may eventually enable its use in patients.

Safety and improvement in exercise tolerance with interval training vs moderate-intensity continuous training in heart disease patient of very high cardiovascular risk

Objetivo:

Evaluar la seguridad y el efecto del entrenamiento por intervalos de moderada y alta intensidad (EIMI, EIAI) y compararlo con el entrenamiento de intensidad moderada continua (EIMC) en pacientes de riesgo cardiovascular (RCV) muy alto.

Método:

Estudio cuasi experimental de 81 pacientes que ingresaron al programas de rehabilitación cardíaca y prevención secundaria (PRHCPS); en la estratificación de riesgo, todos los pacientes presentaron ≥ 2 factores de RCV alto. Entrenamiento concurrente: aeróbico supervisado: 2 semanas de entrenamiento de base de EIMC; luego el grupo EIMC con la misma prescripción, EIMI a 3 intervalos de 3’ al 70 a 80% de FCR con pausas activas de 3’ al 60 a 70% de FCR; EIAI, 3 intervalos de 3’ a 80 a 90% de FCR con pausas activas de 3’ al 70 a 80% de FCR, entrenamiento de fuerza con tres sesiones semanales de ejercicios isotónicos y una de calistenia e intervención multidisciplinaria.

Resultados:

81 pacientes asignados en tres grupos: 61 a EIMC, 13 a EIMI y 7 a EIAI, sin diferencias significativas en las variables epidemiológicas. Hubo ganancias porcentuales en MET-carga de 45%, 60% y 86% (p = 0.17) y carga-vatios de 51, 44 y 48 en EIMC, EIMI, EIAI, respectivamente (p = 0.54). A pesar de no existir diferencias estocásticamente significativas intergrupales, sí se registró una ganancia mayor en MET-carga en el grupo de EIAI. No se observó desenlace adverso en ningún tipo de entrenamiento.

Conclusiones:

En cardiópatas de riesgo cardiovascular muy alto, el entrenamiento interválico EIMI/EIAI supervisado es seguro, con tendencia a mayor ganancia en tolerancia al esfuerzo (MET-carga) con el EIAI en comparación con el EIMC.

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

Objective:

Protective effects of ischemic postconditioning (PostC) decrease/disappear with age and chronic heart diseases. Similarly, low serum melatonin levels have been reported in the same risk groups. The aims of this study were to investigate the effects of melatonin on the protection of PostC in ischemia–reperfusion (I/R)-induced infarct size and roles of uncoupling protein (UCP) 3, irisin, and nuclear factor kappa B (NFkB) levels.

Methods:

Rats were pinealectomized (Px) or sham operated (non-Px) 2 months before the I/R studies. The left main coronary artery was occluded for 30 min followed by 120 min reperfusion. PostC was induced with three cycles of R/I (10 s each) after ischemia.

Results:

The infarct size was found to be significantly higher in Px rats (54.68±1.5%) than in the control group (35.1±2.5%). PostC and melatonin administrations to non-Px rats significantly reduced the infarct size. On the other hand, PostC did not create a significant effect in Px rats, but protection was provided when PostC was co-administrated with melatonin. While significant decreases were detected in the UCP3 levels, irisin and NFkB levels increased with I/R and Px. Treatment with PostC and melatonin in non-Px groups and their co-administration in Px groups were found to return all the genes close to normal levels.

Conclusion:

The physiological and pharmacological concentrations of melatonin may play a role in the protection of PostC. In cases when physiological melatonin is reduced, such as aging and heart diseases, this protection may decrease, and this effect may be restored by melatonin replacement. PostC and melatonin may regulate energy metabolism and inflammatory mediators and protect mitochondria by affecting the UCP3, irisin, and NFkB levels.

Heat shock protein 90 inhibition and multi-target approach to maximize cardioprotection in ischaemic injury

Despite several advances in medicine, ischaemic heart disease remains a major cause of morbidity and mortality. The unravelling of molecular mechanisms underlying disease pathophysiology has revealed targets for pharmacological interventions. However, transfer of these pharmcological possibilities to clinical use has been disappointing. Considering the complexity of ischaemic disease at the cellular and molecular levels, an equally multifaceted treatment approach may be envisioned. The pharmacological principle of 'one target, one key' may fall short in such contexts, and optimal treatment may involve one or many agents directed against complementary targets. Here, we introduce a 'multi-target approach to cardioprotection' and propose heat shock protein 90 (HSP90) as a target of interest. We report on a member of a distinct class of HSP90 inhibitor possessing pleiotropic activity, which we found to exhibit potent infarct-sparing effects.

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.

The Role of Platelets in Ischemic Conditioning

Ischemic heart disease (IHD) is one of the leading causes of death and disability worldwide. Platelets, as the main regulators of hemostasis, are major players in acute myocardial ischemia/reperfusion injury (IRI). Additionally, platelets are modified by endogenous cardioprotective strategies such as ischemic preconditioning, postconditioning, and remote ischemic conditioning. In this article, we provide an overview of the functionional role of platelets in acute myocardial IRI, and highlight their potential as targets for cardioprotection to improve health outcomes in patients with IHD.

Noninvasive approach to mend the broken heart: Is "remote conditioning" a promising strategy for application in humans?

Currently, there are no satisfactory interventions to protect the heart against the detrimental effects of ischemia-reperfusion injury. Although ischemic preconditioning (PC) is the most powerful form of intrinsic cardioprotection, its application in humans is limited to planned interventions, due to its short duration and technical requirements. However, many organs/tissues are capable of producing "remote" PC (RPC) when subjected to brief bouts of ischemia-reperfusion. RPC was first described in the heart where brief ischemia in one territory led to protection in other area. Later on, RPC started to be used in patients with acute myocardial infarction, albeit with ambiguous results. It is hypothesized that the connection between the signal triggered in remote organ and protection induced in the heart can be mediated by humoral and neural pathways, as well as via systemic response to short sublethal ischemia. However, although RPC has a potentially important clinical role, our understanding of the mechanistic pathways linking the local stimulus to the remote organ remains incomplete. Nevertheless, RPC appears as a cost-effective and easily performed intervention. Elucidation of protective mechanisms activated in the remote organ may have therapeutic and diagnostic implications in the management of myocardial ischemia and lead to development of pharmacological RPC mimetics.

Remote preconditioning as a novel "conditioning" approach to repair the broken heart: potential mechanisms and clinical applications

Remote ischemic preconditioning (RIPC) is a novel strategy of protection against ischemia-reperfusion (IR) injury in the heart (and/or other organs) by brief episodes of non-lethal IR in a distant organ/tissue. Importantly, RIPC can be induced noninvasively by limitation of blood flow in the extremity implying the applicability of this method in clinical situations. RIPC (and its delayed phase) is a form of relatively short-term adaptation to ischemia, similar to ischemic PC, and likely they both share triggering mechanisms, whereas mediators and end-effectors may differ. It is hypothesized that communication between the signals triggered in the remote organs and protection in the target organ may be mediated through substances released from the preconditioned organ and transported via the circulation (humoral pathways), by neural pathways and/or via systemic anti-inflammatory and antiapoptotic response to short ischemic bouts. Identification of molecules involved in RIPC cascades may have therapeutic and diagnostic implications in the management of myocardial ischemia. Elucidation of the mechanisms of endogenous cardioprotection triggered in the remote organ could lead to the development of diverse pharmacological RIPC mimetics. In the present article, the authors provide a short overview of RIPC-induced protection, proposed underlying mechanisms and factors modulating RIPC as a promising cardioprotective strategy.

A pilot study of perioperative esmolol for myocardial protection during on-pump cardiac surgery

The protective effects of preprocedural esmolol on myocardial injury and hemodynamics have not, to date, been investigated in patients who were scheduled for cardiac surgeries under a cardiopulmonary bypass (CPB). A pilot randomized controlled trial was performed at The First Affiliated Hospital of Dalian Medical University (Dalian, China). Patients scheduled for elective open-heart surgeries under CBP were included, and were randomized to esmolol and control groups. For patients in the esmolol groups, intravenous esmolol (70 µg/kg/min) was administered at the time of incision until CPB was performed. For patients assigned to the control group, equal volumes of 0.9% saline were administered. Markers of myocardial injury and hemodynamic parameters were observed until 12 h post surgery. A total of 24 patients were included in the present study. No significant differences in hemodynamic parameters, including the central venous pressure and heart rate, were detected between patients in the two groups during the perioperative period or within the first 12 h post-surgery (P>0.05), except for the mean arterial pressure, which was higher in the esmolol group compared with the control group at 5 and 12 h post-surgery (P<0.05). However, the serum level of cardiac troponin I was higher in patients of the control group compared with those of the esmolol group during the preoperative period (P<0.05). Although creatinine kinase was significantly different at T2 between the two groups, its MB isoenzyme was not significantly different between the groups (P>0.05). In addition, administration of esmolol was not associated with an increased risk for severe complications and adverse events in these patients. In conclusion, preoperative esmolol may be an effective and safe measure of myocardial protection for patients who undergo elective cardiac surgeries under CBP.

Later phase cardioprotection of ischemic post-conditioning against ischemia/reperfusion injury depends on iNOS and PI3K-Akt pathway

BACKGROUND

The cardioprotection of ischemic post-conditioning (IPO) has been well demonstrated after a short period of reperfusion. However, little is known about the long-term effects of IPO. This study aimed to investigate the long term cardioprotection of IPO in a rat myocardial ischemia/reperfusion model and to explore the potential mechanism.

METHODS AND RESULTS

Rats were either sham-operated (Sham group) or underwent 30-min left anterior descending coronary artery ischemia followed by immediate reperfusion (I/R group) or post-conditioning with 5 cycles of 10-s ischemia and 10-s reperfusion (IPO group). At 24 h after reperfusion, infarct size reduced from 34.7±1.1% in I/R group to 24.9±1.3% in IPO group (P<0.05) and the iNOS expression in IPO group was 4.7-fold higher than in I/R group. iNOS inhibitor 1400 W (1 mg/kg, 5 min before postconditioning or reperfusion) prevented the increase in iNOS expression and abolished IPO-induced protection (34.4±1.0%, P>0.05 vs. I/R group). When rats were treated with PI3K inhibitor LY294002 5 min before reperfusion (0.3 mg/kg), p-Akt expression at R 3 h and iNOS expression at R 24 h were significantly inhibited. Moreover, the delayed infarct-sparing effect of IPO was absent in the presence of LY294002.

CONCLUSION

IPO has prolonged cardioprotective effects and iNOS as an important downstream effector of PI3K-Akt pathway contributes to the delayed phase cardioprotection of IPO.

Diazoxide protects L6 skeletal myoblasts from H2O2-induced apoptosis via the phosphatidylinositol-3 kinase/Akt pathway

OBJECTIVES AND DESIGN

Transplanted cell survival might greatly improve the therapeutic efficacy of cell therapy. Diazoxide (DZ), a highly selective mitochondrial ATP-sensitive potassium channel opener, is known to suppress cell apoptosis and protect cells in oxidative stressed ischemic environment. We explored the mechanisms involved in DZ pre-treatment-induced anti-apoptotic effect on L6 skeletal myoblast (SKM).

MATERIALS AND METHODS

L6 SKMs were divided into control group, H2O2 group, DZ + H2O2 group and DZ + LY + H2O2 group. Treatments of 400 μmol/L H2O2 for 24 h alone, or after 200 μmol/L DZ pre-treatment for 30 min, or after DZ and 50 μmol/L LY294002 co-administration for 30 min were performed. The cell apoptosis rates were assessed by flow cytometric analysis. The changes of mitochondrial membrane potential were determined by JC-1 mitochondrial staining. The activation of phosphatidylinositol-3 kinase (PI3K)/Akt, caspase-9 and caspase-3 was detected by western blot.

RESULTS

Compared with the H2O2 group, DZ pre-treatment protected cells from H2O2-induced damage, increased Akt phosphorylation, prevented mitochondrial membrane depolarization as well as the activation of caspase-9 and caspase-3 and decreased the cell apoptosis rate. However, the DZ-induced cytoprotective and anti-apoptosis effects were partly inhibited by co-administration of a PI3K inhibitor, LY294002.

CONCLUSIONS

These data suggest that DZ pre-treatment contributes to protection of L6 SKMs against apoptosis at least partly by activating the PI3K/Akt pathway and subsequently inhibiting the mitochondrial-mediated caspase-dependent apoptotic signalling pathway.

Remote Ischemic Preconditioning Fails to Benefit Pediatric Patients Undergoing Congenital Cardiac Surgery: A Meta-Analysis of Randomized Controlled Trials

Remote ischemic preconditioning (RIPC) has been proven to reduce the ischemia-reperfusion injury. However, its effect on children receiving congenital cardiac surgery (CCS) was inconsistent. We therefore performed the current meta-analysis of randomized controlled trials (RCTs) to comprehensively evaluate the effect of RIPC in pediatric patients undergoing CCS.PubMed, Embase, and Cochrane library were searched to identify RCTs assessing the effect of RIPC in pediatric patients undergoing CCS. The outcomes included the duration of mechanical ventilation (MV), intensive care unit (ICU) length of stay, postoperative cardiac troponin (cTnI) level, hospital length of stay (HLOS), postoperative inotropic score, and mortality. Subgroup and sensitivity analysis were also performed as predesigned. The meta-analysis was performed with random-effects model despite of heterogeneity. Sensitivity and subgroup analysis were predesigned to identify the robustness of the pooled estimate.Nine RCTs with 697 pediatric patients were included in the meta-analysis. Overall, RIPC failed to alter clinical outcomes of duration of MV (standard mean difference [SMD] -0.03, 95% confidence interval [CI] -0.23-0.17), ICU length of stay (SMD -0.22, 95% CI -0.47-0.04), or HLOS (SMD -0.14, 95% CI -0.55-0.26). Additionally, RIPC could not reduce postoperative cTnI (at 4-6 hours: SMD -0.25, 95% CI -0.73-0.23; P = 0.311; at 20-24 hours: SMD 0.09, 95% CI -0.51-0.68; P = 0.778) or postoperative inotropic score (at 4-6 hours: SMD -0.19, 95% CI -0.51-0.14; P = 0.264; at 24 hours: SMD -0.15, 95% CI -0.49-0.18; P = 0.365).RIPC may have no beneficial effects in children undergoing CCS. However, this finding should be interpreted with caution because of heterogeneity and large-scale RCTs are still needed.

Profiling of cell stress protein expression in cardiac tissue of cardiosurgical patients undergoing remote ischemic preconditioning: implications for thioredoxin in cardioprotection

Background

Transient episodes of ischemia in a remote organ (remote ischemic preconditioning, RIPC) can attenuate myocardial ischemia/reperfusion injury but the underlying mechanisms of RIPC in the target organ are still poorly understood. Recent animal studies suggested that the small redox protein thioredoxin may be a potential candidate for preconditioning-induced organprotection. Here we employed a human proteome profiler array to investigate the RIPC regulated expression of cell stress proteins and particularly of thioredoxin in heart tissue of cardiosurgical patients with cardiopulmonary bypass (CPB).

Methods

RIPC was induced by four 5 minute cycles of transient upper limb ischemia/reperfusion using a blood pressure cuff. Right atrial tissue was obtained from patients receiving RIPC (N = 19) and control patients (N = 19) before and after CPB. Cell stress proteome profiler arrays as well as Westernblotting and ELISA experiments for thioredoxin (Thio-1) were performed employing the respective tissue samples.

Results

Protein arrays revealed an up-regulation of 26.9% (7/26; CA IX, Cyt C, HSP-60, HSP-70, pJNK, SOD2, Thio-1) of cell stress associated proteins in RIPC tissue obtained before CPB, while 3.8% (1/26; SIRT2) of the proteins were down-regulated. Array results for thioredoxin were verified by semi-quantitative Westernblotting studies which showed a significant up-regulation of thioredoxin protein levels in cardiac tissue samples of RIPC patients taken before CPB (RIPC: 5.36 ± 0.85 a.u.; control: 3.23 ± 0.39 a.u.; P < 0.05). Quantification of thioredoxin levels in tissue of RIPC and control patients by ELISA experiments further confirmed the Westernblotting results (RIPC: 0.30 ± 0.02 ng/mg protein; control: 0.24 ± 0.02 ng/mg protein; P < 0.05).

Conclusion

We provide evidence for thioredoxin as a RIPC-induced factor in heart tissue of cardiosurgical patients and identified several cell stress associated proteins that are regulated by RIPC and may play a role in RIPC-mediated cardioprotection.

Electronic supplementary material

The online version of this article (doi:10.1186/s12967-015-0403-6) contains supplementary material, which is available to authorized users.