Remote ischaemic conditioning: defining critical criteria for success-report from the 11th Hatter Cardiovascular Workshop

Cardioprotection strategies for anthracycline cardiotoxicity

Thanks to the fantastic progress in cancer therapy options, there is a growing population of cancer survivors. This success has resulted in a need to focus much effort into improving the quality of life of this population. Cancer and cardiovascular disease share many common risk factors and have an interplay between them, with one condition mechanistically affecting the other and vice versa. Furthermore, widely prescribed cancer therapies have known toxic effects in the cardiovascular system. Anthracyclines are the paradigm of efficacious cancer therapy widely prescribed with a strong cardiotoxic potential. While some cancer therapies cardiovascular toxicities are transient, others are irreversible. There is a growing need to develop cardioprotective therapies that, when used in conjunction with cancer therapies, can prevent cardiovascular toxicity and thus improve long-term quality of life in survivors. The field has three main challenges: (i) identification of the ultimate mechanisms leading to cardiotoxicity to (ii) identify specific therapeutic targets, and (iii) more sensible diagnostic tools to early identify these conditions. In this review we will focus on the cardioprotective strategies tested and under investigation. We will focus this article into anthracycline cardiotoxicity since it is still the agent most widely prescribed, the one with higher toxic effects on the heart, and the most widely studied.

Vago-splenic signal transduction of cardioprotection in humans

BACKGROUND AND AIMS

The spleen serves as an important relay organ that releases cardioprotective factor(s) upon vagal activation during remote ischaemic conditioning (RIC) in rats and pigs. The translation of these findings to humans was attempted.

METHODS

Remote ischaemic conditioning or electrical auricular tragus stimulation (ATS) were performed in 10 healthy young volunteers, 10 volunteers with splenectomy, and 20 matched controls. Venous blood samples were taken before and after RIC/ATS or placebo, and a plasma dialysate was infused into isolated perfused rat hearts subjected to global ischaemia/reperfusion.

RESULTS

Neither left nor right RIC or ATS altered heart rate and heart rate variability in the study cohorts. With the plasma dialysate prepared before RIC or ATS, respectively, infarct size (% ventricular mass) in the recipient rat heart was 36 ± 6% (left RIC), 34 ± 3% (right RIC) or 31 ± 5% (left ATS), 35 ± 5% (right ATS), and decreased with the plasma dialysate from healthy volunteers after RIC or ATS to 20 ± 4% (left RIC), 23 ± 6% (right RIC) or to 19 ± 4% (left ATS), 26 ± 9% (right ATS); infarct size was still reduced with plasma dialysate 4 days after ATS and 9 days after RIC. In a subgroup of six healthy volunteers, such infarct size reduction was abrogated by intravenous atropine. Infarct size reduction by RIC or ATS was also abrogated in 10 volunteers with splenectomy, but not in their 20 matched controls.

CONCLUSIONS

In humans, vagal innervation and the spleen as a relay organ are decisive for the cardioprotective signal transduction of RIC and ATS.

Remote ischemic preconditioning prevents sarcolemmal-associated proteolysis by MMP-2 inhibition

The death of myocytes occurs through different pathways, but the rupture of the plasma membrane is the key point in the transition from reversible to irreversible injury. In the myocytes, three major groups of structural proteins that link the extracellular and intracellular milieus and confer structural stability to the cell membrane: the dystrophin-associated protein complex, the vinculin-integrin link, and the spectrin-based submembranous cytoskeleton. The objective was to determine if remote ischemic preconditioning (rIPC) preserves membrane-associated cytoskeletal proteins (dystrophin and β-dystroglycan) through the inhibition of metalloproteinase type 2 (MMP-2) activity. A second objective was to describe some of the intracellular signals of the rIPC, that modify mitochondrial function at the early reperfusion. Isolated rat hearts were subjected to 30 min of global ischemia and 120 min of reperfusion (I/R). rIPC was performed by 3 cycles of ischemia/reperfusion in the lower limb (rIPC). rIPC significantly decreased the infarct size, induced Akt/GSK-3 β phosphorylation and inhibition of the MPTP opening. rIPC improved mitochondrial function, increasing membrane potential, ATP production and respiratory control. I/R increased ONOO- production, which activates MMP-2. This enzyme degrades β-dystroglycan and dystrophin and collaborates to sarcolemmal disruption. rIPC attenuates the breakdown of β-dystroglycan and dystrophin through the inhibition of MMP-2 activity. Furthermore, we confirm that rIPC activates different intracellular pathway that involves the an Akt/Gsk3β and MPTP pore with preservation of mitochondrial function.

ALDH2 polymorphism and myocardial infarction: From alcohol metabolism to redox regulation

Acute myocardial infarction (AMI) remains a leading cause of death worldwide. Increased formation of reactive oxygen species (ROS) during the early reperfusion phase is thought to trigger lipid peroxidation and disrupt redox homeostasis, leading to myocardial injury. Whilst the mitochondrial enzyme aldehyde dehydrogenase 2 (ALDH2) is chiefly recognised for its central role in ethanol metabolism, substantial experimental evidence suggests an additional cardioprotective role for ALDH2 independent of alcohol intake, which mitigates myocardial injury by detoxifying breakdown products of lipid peroxidation including the reactive aldehydes, malondialdehyde (MDA) and 4-hydroxynonenal (4-HNE). Epidemiological evidence suggests that an ALDH2 mutant variant with reduced activity that is highly prevalent in the East Asian population increases AMI risk. Additional studies have uncovered a strong association between coronary heart disease and this ALDH2 mutant variant. It appears this enzyme polymorphism (in particular, in ALDH2*2/2 carriers) has the potential to have wide-ranging effects on thiol reactivity, redox tone and therefore numerous redox-related signaling processes, resilience of the heart to cope with lifestyle-related and environmental stressors, and the ability of the whole body to achieve redox balance. In this review, we summarize the journey of ALDH2 from a mitochondrial reductase linked to alcohol metabolism, via pre-clinical studies aimed at stimulating ALDH2 activity to reduce myocardial injury to clinical evidence for its protective role in the heart.

Rationale and Design of the IMPROVE Trial: A Multicenter, Randomized, Controlled, Open-label, Blinded-endpoint Trial Assessing the Efficacy of Remote Ischemic Conditioning in Patients Undergoing Off-Pump Coronary Artery Bypass Grafting

INTRODUCTION

Despite the appearance of off-pump coronary artery bypass grafting (CABG), ischemia-reperfusion injury (IRI) in the perioperative period still arouses concerns of clinicians. Remote ischemic conditioning (RIC) is the process of repeated ischemia and reperfusion in the peripheral vessels, which is proven to reduce IRI in vital organs. However, the effect of RIC in patients undergoing off-pump CABG is still unclear.

METHODS

This IMPROVE trial is a national, multicenter, randomized, controlled, open-label, blinded-endpoint clinical trial designed to assess whether RIC intervention can improve short-term prognosis of patients undergoing off-pump CABG. It plans to enroll 648 patients who will be randomly assigned into a RIC group or control group. Patients in the RIC group will receive four cycles of 5 min of pressurization (about 200 mmHg) and 5 min of rest in the 3 days before and 7 days after the surgery.

PLANNED OUTCOMES

The primary outcome is the occurrence of major adverse cardiovascular and cerebrovascular events (MACCE) within the 3-month follow-up. MACCE is defined as all-cause death, myocardial infarction, stroke, and coronary revascularization surgery.

CLINICAL TRIAL REGISTRATION

NCT06141525 (ClinicalTrials.gov).

Reperfusion Injury in Patients With Acute Myocardial Infarction: JACC Scientific Statement

Despite impressive improvements in the care of patients with ST-segment elevation myocardial infarction, mortality remains high. Reperfusion is necessary for myocardial salvage, but the abrupt return of flow sets off a cascade of injurious processes that can lead to further necrosis. This has been termed myocardial ischemia-reperfusion injury and is the subject of this review. The pathologic and molecular bases for myocardial ischemia-reperfusion injury are increasingly understood and include injury from reactive oxygen species, inflammation, calcium overload, endothelial dysfunction, and impaired microvascular flow. A variety of pharmacologic strategies have been developed that have worked well in preclinical models and some have shown promise in the clinical setting. In addition, there are newer mechanical approaches including mechanical unloading of the heart prior to reperfusion that are in current clinical trials.

Effect of Remote Ischaemic Conditioning on the Inflammatory Cytokine Cascade of COVID-19 (RIC in COVID-19): a Randomized Controlled Trial

PURPOSE

Patients hospitalized with COVID-19 may develop a hyperinflammatory, dysregulated cytokine "storm" that rapidly progresses to acute respiratory distress syndrome, multiple organ dysfunction, and even death. Remote ischaemic conditioning (RIC) has elicited anti-inflammatory and cytoprotective benefits by reducing cytokines following sepsis in animal studies. Therefore, we investigated whether RIC would mitigate the inflammatory cytokine cascade induced by COVID-19.

METHODS

We conducted a prospective, multicentre, randomized, sham-controlled, single-blind trial in Brazil and South Africa. Non-critically ill adult patients with COVID-19 pneumonia were randomly allocated (1:1) to receive either RIC (intermittent ischaemia/reperfusion applied through four 5-min cycles of inflation (20 mmHg above systolic blood pressure) and deflation of an automated blood-pressure cuff) or sham for approximately 15 days. Serum was collected following RIC/sham administration and analyzed for inflammatory cytokines using flow cytometry. The endpoint was the change in serum cytokine concentrations. Participants were followed for 30 days.

RESULTS

Eighty randomized participants (40 RIC and 40 sham) completed the trial. Baseline characteristics according to trial intervention were overall balanced. Despite downward trajectories of all cytokines across hospitalization, we observed no substantial changes in cytokine concentrations after successive days of RIC. Time to clinical improvement was similar in both groups (HR 1.66; 95% CI, 0.938-2.948, p 0.08). Overall RIC did not demonstrate a significant impact on the composite outcome of all-cause death or clinical deterioration (HR 1.19; 95% CI, 0.616-2.295, p = 0.61).

CONCLUSION

RIC did not reduce the hypercytokinaemia induced by COVID-19 or prevent clinical deterioration to critical care.

TRIAL REGISTRATION

ClinicalTrials.gov Identifier: NCT04699227.

Research hotspots and frontiers of preconditioning in cerebral ischemia: A bibliometric analysis

Background

Preconditioning is a promising strategy against ischemic brain injury, and numerous studies in vitro and in vivo have demonstrated its neuroprotective effects. However, at present there is no bibliometric analysis of preconditioning in cerebral ischemia. Therefore, a comprehensive overview of the current status, hot spots, and emerging trends in this research field is necessary.

Materials and methods

Studies on preconditioning in cerebral ischemia from January 1999-December 2022 were retrieved from the Web of Science Core Collection (WOSCC) database. CiteSpace was used for data mining and visual analysis.

Results

A total of 1738 papers on preconditioning in cerebral ischemia were included in the study. The annual publications showed an upwards and then downwards trend but currently remain high in terms of annual publications. The US was the leading country, followed by China, the most active country in recent years. Capital Medical University published the largest number of articles. Perez-Pinzon, Miguel A contributed the most publications, while KITAGAWA K was the most cited author. The focus of the study covered three areas: (1) relevant diseases and experimental models, (2) types of preconditioning and stimuli, and (3) mechanisms of ischemic tolerance. Remote ischemic preconditioning, preconditioning of mesenchymal stem cells (MSCs), and inflammation are the frontiers of research in this field.

Conclusion

Our study provides a visual and scientific overview of research on preconditioning in cerebral ischemia, providing valuable information and new directions for researchers.

The role of cardiac pericytes in health and disease: therapeutic targets for myocardial infarction

Millions of cardiomyocytes die immediately after myocardial infarction, regardless of whether the culprit coronary artery undergoes prompt revascularization. Residual ischaemia in the peri-infarct border zone causes further cardiomyocyte damage, resulting in a progressive decline in contractile function. To date, no treatment has succeeded in increasing the vascularization of the infarcted heart. In the past decade, new approaches that can target the heart's highly plastic perivascular niche have been proposed. The perivascular environment is populated by mesenchymal progenitor cells, fibroblasts, myofibroblasts and pericytes, which can together mount a healing response to the ischaemic damage. In the infarcted heart, pericytes have crucial roles in angiogenesis, scar formation and stabilization, and control of the inflammatory response. Persistent ischaemia and accrual of age-related risk factors can lead to pericyte depletion and dysfunction. In this Review, we describe the phenotypic changes that characterize the response of cardiac pericytes to ischaemia and the potential of pericyte-based therapy for restoring the perivascular niche after myocardial infarction. Pericyte-related therapies that can salvage the area at risk of an ischaemic injury include exogenously administered pericytes, pericyte-derived exosomes, pericyte-engineered biomaterials, and pharmacological approaches that can stimulate the differentiation of constitutively resident pericytes towards an arteriogenic phenotype. Promising preclinical results from in vitro and in vivo studies indicate that pericytes have crucial roles in the treatment of coronary artery disease and the prevention of post-ischaemic heart failure.

A Novel Postconditioning Approach Attenuates Myocardial Ischaemia-Reperfusion Injury in Rats

Background

Ischaemia-reperfusion injury (IRI) is the damage that occurs when blood flow is restored to a tissue or organ after a period of ischaemia. Postconditioning is a therapeutic strategy aimed at reducing the tissue damage caused by IRI. Postconditioning in rodents is a useful tool to investigate the potential mechanisms of postconditioning. Currently, there is no convenient approach for postconditioning rodents.

Methods

Rats were subjected to a balloon postconditioning procedure. A balloon was used to control the flow in the vessel. This allowed for easy and precise manipulation of perfusion. Evans blue and triphenyltetrazolium chloride (TTC) double staining were used to determine the infarct size. Apoptosis in the myocardium was visualised and quantified by terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL). Western blotting was performed to assess the expression of key apoptotic proteins, i.e., B-cell lymphoma 2 (Bcl-2), Bcl-2 Associated X (Bax), and cleaved caspase-3.

Results

The balloon control approach to postconditioning provided accurate control of coronary blood flow and simplified the postconditioning manipulation. Infarct size reduction was observed in IRI rats after post-conditioning. There was a decrease in cardiac apoptosis in IRI rats after conditioning, as detected by TUNEL staining. IRI rats showed increased Bcl-2 levels and decreased Bax and cleaved caspase-3 levels in the myocardium.

Conclusions

Postconditioning was successfully applied in rats using this novel approach. Postconditioning with this approach reduced infarct size and apoptosis in the area at risk.

Remote ischemic conditioning reduces adverse events in patients with acute ischemic stroke complicating acute myocardial infarction: a randomized controlled trial

BACKGROUND

Acute ischemic stroke (AIS) complicating an acute myocardial infarction (AMI) is not uncommon, but can severely worsen the clinical prognosis. This study aimed to investigate whether remote ischemic conditioning (RIC) could provide clinical benefits to patients with AIS complicating AMI.

METHODS

Subjects with AIS complicating AMI were recruited in this double-blind, randomized, controlled trial; assigned to the RIC and sham groups; and respectively underwent twice daily RIC and sham RIC for 2 weeks. All subjects received standard medical therapy. The primary endpoint was the rate of major adverse cardiac and cerebrovascular events (MACCEs) within 3 months after enrollment. MACCEs comprise of death from all causes, unstable anginas, AMI, acute ischemic strokes, and transient ischemic attacks.

RESULTS

Eighty subjects were randomly assigned; 37 patients in the RIC group and 40 patients in the sham-RIC group completed the 3-month follow-up and were included in the final analysis. Both RIC and sham RIC procedures were well tolerated. At 3-month follow-up, 11 subjects (29.7%) in the RIC group experienced MACCEs compared to 21 (52.5%) in the sham group (hazard ratio [HR], 0.396; 95% confidence interval, 0.187-0.838; adjusted p < 0.05). Six subjects (16.2%) in the RIC group had died at the 3-month follow up, significantly lower than the 15 (37.5%) deaths in the sham group (adjusted HR 0.333; 95% CI 0.126-0.881; p = 0.027). Seventeen subjects (45.9%) in the RIC group and 6 subjects (15.0%) in the sham group achieved functional independence (mRS score ≤ 2) at 3-month follow-up (adjusted OR 12.75; 95% CI 2.104-77.21; p = 0.006).

CONCLUSIONS

Among patients with acute ischemic stroke complicating acute myocardial infarction, treatment with remote ischemic conditioning decreased the major adverse cardiac and cerebrovascular events and improved functional outcomes at 90 days.

TRIAL REGISTRATION

URL: www.

CLINICALTRIALS

gov . Unique identifier: NCT03868007. Registered 8 March 2019.

The Infarct-Limiting Effect of Remote Ischemic Conditioning in Rats Is Not Affected by Aspirin

PURPOSE

Remote ischemic conditioning (RIC) has been shown to be a powerful cardioprotective therapy in animal models. However, a protective effect in patients presenting with acute myocardial infarction has failed to be confirmed. A recent pre-clinical study reported that aspirin which is routinely given to patients undergoing reperfusion therapy blocked the infarct-limiting effect of ischemic postconditioning. The present study was designed to test whether aspirin could also be blocking the infarct-limiting effect of RIC.

METHODS

This was investigated in vivo using male Sprague Dawley rats (n = 5 to 6 per group) subjected to either 30 min of regional myocardial ischemia, followed by 120-min reperfusion, or additionally to a RIC protocol initiated after 20-min myocardial ischemia. The RIC protocol included four cycles of 5-min hind limb ischemia interspersed with 5-min reperfusion. Intravenous aspirin (30 mg/kg) or vehicle (saline) was administered after 15-min myocardial ischemia.

RESULTS

RIC significantly reduced infarct size (IS) normalized to the area at risk, by 47%. Aspirin administration did not affect IS nor did it attenuate the infarct-limiting effect of RIC.

CONCLUSION

Aspirin administration in the setting of myocardial infarction is not likely to interfere with the cardioprotective effect of RIC.

Health position paper and redox perspectives on reactive oxygen species as signals and targets of cardioprotection

The present review summarizes the beneficial and detrimental roles of reactive oxygen species in myocardial ischemia/reperfusion injury and cardioprotection. In the first part, the continued need for cardioprotection beyond that by rapid reperfusion of acute myocardial infarction is emphasized. Then, pathomechanisms of myocardial ischemia/reperfusion to the myocardium and the coronary circulation and the different modes of cell death in myocardial infarction are characterized. Different mechanical and pharmacological interventions to protect the ischemic/reperfused myocardium in elective percutaneous coronary interventions and coronary artery bypass grafting, in acute myocardial infarction and in cardiotoxicity from cancer therapy are detailed. The second part keeps the focus on ROS providing a comprehensive overview of molecular and cellular mechanisms involved in ischemia/reperfusion injury. Starting from mitochondria as the main sources and targets of ROS in ischemic/reperfused myocardium, a complex network of cellular and extracellular processes is discussed, including relationships with Ca2+ homeostasis, thiol group redox balance, hydrogen sulfide modulation, cross-talk with NAPDH oxidases, exosomes, cytokines and growth factors. While mechanistic insights are needed to improve our current therapeutic approaches, advancements in knowledge of ROS-mediated processes indicate that detrimental facets of oxidative stress are opposed by ROS requirement for physiological and protective reactions. This inevitable contrast is likely to underlie unsuccessful clinical trials and limits the development of novel cardioprotective interventions simply based upon ROS removal.

Chronic remote ischemic conditioning treatment in patients with chronic stable angina (EARLY-MYO-CSA): a randomized, controlled proof-of-concept trial

BACKGROUND

Chronic remote ischemic conditioning (CRIC) has been shown to improve myocardial ischemia in experimental animal studies; however, its effectiveness in patients with chronic stable angina (CSA) has not been investigated. We conducted a proof-of-concept study to investigate the efficacy and safety of a six-month CRIC treatment in patients with CSA.

METHODS

The EARLY-MYO-CSA trial was a prospective, randomized, controlled trial evaluating the CRIC treatment in patients with CSA with persistent angina pectoris despite receiving ≥ 3-month guideline-recommended optimal medical therapy. The CRIC and control groups received CRIC (at 200 mmHg) or sham CRIC (at 60 mmHg) intervention for 6 months, respectively. The primary endpoint was the 6-month change of myocardial flow reserve (MFR) on single-photon emission computed tomography. The secondary endpoints were changes in rest and stress myocardial blood flow (MBF), angina severity according to the Canadian Cardiovascular Society (CCS) classification, the Seattle Angina Questionnaire (SAQ), and a 6-min walk test (6-MWT).

RESULTS

Among 220 randomized CSA patients, 208 (105 in the CRIC group, and 103 in the control group) completed the treatment and endpoint assessments. The mean change in MFR was significantly greater in the CRIC group than in the control group (0.27 ± 0.38 vs. - 0.04 ± 0.25; P < 0.001). MFR increased from 1.33 ± 0.48 at baseline to 1.61 ± 0.53 (P < 0.001) in the CRIC group; however, a similar increase was not seen in the control group (1.35 ± 0.45 at baseline and 1.31 ± 0.44 at follow-up, P = 0.757). CRIC treatment, when compared with controls, demonstrated improvements in angina symptoms assessed by CCS classification (60.0% vs. 14.6%, P < 0.001), all SAQ dimensions scores (P < 0.001), and 6-MWT distances (440 [400-523] vs. 420 [330-475] m, P = 0.016). The incidence of major adverse cardiovascular events was similar between the groups.

CONCLUSIONS

CSA patients benefit from 6-month CRIC treatment with improvements in MFR, angina symptoms, and exercise performance. This treatment is well-tolerated and can be recommended for symptom relief in this clinical population.

TRIAL REGISTRATION

[chictr.org.cn], identifier [ChiCTR2000038649].

Chronic Remote Ischemic Conditioning on Mild Hypertension in the Absence of Antihypertensive Medication: A Multicenter, Randomized, Double-Blind, Proof-of-Concept Clinical Trial

BACKGROUND

Exploratory studies have shown that remote ischemic conditioning (RIC) has the potential to lower blood pressure (BP). We investigated whether chronic RIC reduces BP for hypertension.

METHODS

This is a multicenter, randomized, double-blind, parallel-controlled trial. Patients with an office BP of 130/80 to 160/100 mm Hg and a 24-hour average BP ≥125/75 mm Hg not on antihypertensive medications were recruited. After a 1-week compliance screening phase, they were randomly assigned in a 1:1 ratio to receive RIC or sham RIC twice daily for 4 weeks. The primary efficacy outcome was the change in 24-hour average systolic BP from baseline to 4 weeks. Safety events were assessed over the study period.

RESULTS

Ninety-five participants were randomly allocated to the RIC (n=49) and sham RIC (n=46) groups. In the intention-to-treat analysis, the reduction in 24-hour average systolic BP was greater in the RIC group than the sham RIC group (-4.6±9.5 versus -0.9±6.8 mm Hg; baseline-adjusted between-group mean difference: -3.6 mm Hg [95% CI, -6.9 to -0.3 mm Hg]; adjusted P=0.035). The per-protocol analysis showed that 24-hour average systolic BP reduced -5.9±8.6 mm Hg in the RIC group and -0.7±6.7 mm Hg in the sham RIC group (baseline-adjusted between-group mean difference: -5.2 mm Hg [95% CI, -8.5 to -1.9 mm Hg]; adjusted P=0.002). No major adverse events were reported in both groups.

CONCLUSIONS

RIC is safe in patients with mild hypertension and may lower BP in the absence of antihypertensive medications. However, the effects of RIC on clinical outcomes in these patients require further investigation.

REGISTRATION

URL: https://www.

CLINICALTRIALS

gov; Unique identifier: NCT04915313.

The RISK pathway leading to mitochondria and cardioprotection: how everything started

Ischaemic heart disease, which often manifests clinically as myocardial infarction (MI), remains a major cause of mortality worldwide. Despite the development of effective pre-clinical cardioprotective therapies, clinical translation has been disappointing. Nevertheless, the 'reperfusion injury salvage kinase' (RISK) pathway appears to be a promising target for cardioprotection. This pathway is crucial for the induction of cardioprotection by numerous pharmacological and non-pharmacological interventions, such as ischaemic conditioning. An important component of the cardioprotective effects of the RISK pathway involves the prevention of mitochondrial permeability transition pore (MPTP) opening and subsequent cardiac cell death. Here, we will review the historical perspective of the RISK pathway and focus on its interaction with mitochondria in the setting of cardioprotection.

Transcriptome analysis reveals ADAMTS15 is a potential inflammation-related gene in remote ischemic postconditioning

Background

Remote ischemic postconditioning (RIPostC) induced by brief episodes of the limb ischemia is a potential therapeutic strategy for myocardial ischemia/reperfusion injury, achieved by reducing cardiomyocyte death, inflammation and so on. The actual mechanisms underlying cardioprotection conferred by RIPostC remain unclear. Exploring gene expression profiles in myocardium at transcriptional level is helpful to deepen the understanding on the cardioprotective mechanisms of RIPostC. This study aims to investigate the effect of RIPostC on gene expressions in rat myocardium using transcriptome sequencing.

Methods

Rat myocardium samples from the RIPostC group, the control group (myocardial ischemia/reperfusion group) and the sham group were performed transcriptome analysis using RNA sequencing. The levels of cardiac IL-1β, IL-6, IL-10 and TNFα were analyzed by Elisa. The expression levels of candidate genes were verified by qRT-PCR technique. Infarct size was measured by Evans blue and TTC staining. Apoptosis was assessed by TUNEL assays and caspase-3 levels were detected using western blotting.

Results

RIPostC can markedly decrease infarct size and reduce the levels of cardiac IL-1β, IL-6 and increase the level of cardiac IL-10. This transcriptome analysis showed that 2 genes were up-regulated (Prodh1 and ADAMTS15) and 5 genes (Caspase-6, Claudin-5, Sccpdh, Robo4 and AABR07011951.1) were down-regulated in the RIPostC group. Go annotation analysis showed that Go terms mainly included cellular process, metabolic process, cell part, organelle, catalytic activity and binding. The KEGG annotation analysis of DEGs found only one pathway, amino acid metabolism, was up-regulated. The relative mRNA expression levels of ADAMTS15, Caspase-6, Claudin-5 and Prodh1 were verified by qRT-PCR, which were consistent with the RNA-seq results. In addition, the relative expression of ADAMTS15 was negatively correlated with the level of cardiac IL-1β (r = -0.748, P = 0.005) and positively correlated with the level of cardiac IL-10 (r = 0.698, P = 0.012). A negative correlation statistical trend was found between the relative expression of ADAMTS15 and the level of cardiac IL-6 (r = -0.545, P = 0.067).

Conclusions

ADAMTS15 may be a potential inflammation-related gene in regulation of cardioprotection conferred by remote ischemic postconditioning and a possible therapeutic target for myocardial ischemia reperfusion injury in the future.

Elamipretide mitigates ischemia-reperfusion injury in a swine model of hemorrhagic shock

ischemia-reperfusion injury (IRI) after hemorrhage is potentiated by aortic occlusion or resuscitative endovascular balloon occlusion of the aorta (REBOA). Given the central role of mitochondrial injury in shock, we hypothesized that Elamipretide, a peptide that protects mitochondria, would mitigate IRI after hemorrhagic shock and REBOA. Twelve pigs were subjected to hemorrhagic shock and 45 min of REBOA. After 25 min of REBOA, animals received either saline or Elamipretide. Animals were transfused with autologous blood during balloon deflation, and pigs were resuscitated with isotonic crystalloids and norepinephrine for 4.25 h. Elamipretide-treated animals required less crystalloids than the controls (62.5 [50-90] and 25 [5-30] mL/kg, respectively), but similar amounts of norepinephrine (24.7 [8.6-39.3] and 9.7 [2.1-12.5] mcg/kg, respectively). Treatment animals had a significant reduction in serum creatinine (control: 2.7 [2.6-2.8]; Elamipretide: 2.4 [2.4-2.5] mg/dL; p = 0.04), troponin (control: 3.20 [2.14-5.47] ng/mL, Elamipretide: 0.22 [0.1-1.91] ng/mL; p = 0.03), and interleukin-6 concentrations at the end of the study. There were no differences in final plasma lactate concentration. Elamipretide reduced fluid requirements and protected the kidney and heart after profound IRI. Further understanding the subcellular consequences of REBOA and mitochondrial rescue will open new therapeutic avenues for patients suffering from IRI after hemorrhage.

Effects of different remote ischemia perconditioning methods on cerebral infarct volume and neurological impairment in rats

Remote ischemic perconditioning (RIPerC) is a novel neuroprotective method against cerebral infarction that has shown efficacy in animal studies but has not been consistently neuroprotective in clinical trials. We focused on the temporal regulation of ischemia-reperfusion by RIPerC to establish an optimal method for RIPerC. Rats were assigned to four groups: 10 min ischemia, 5 min reperfusion; 10 min ischemia, 10 min reperfusion; 5 min ischemia, 10 min reperfusion; and no RIPerC. RIPerC interventions were performed during ischemic stroke, which was induced by a 60-min left middle cerebral artery occlusion. Infarct volume, sensorimotor function, neurological deficits, and cellular expressions of brain-derived neurotrophic factor (BDNF), B-cell lymphoma 2 (Bcl-2), Bcl-2-associated X protein (Bax), and caspase 3 were evaluated 48 h after the induction of ischemia. Terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick-end labeling (TUNEL) was also performed. RIPerC of 10 min ischemia/10 min reperfusion, and 5 min ischemia/10 min reperfusion decreased infarct volume, improved sensorimotor function, decreased Bax, caspase 3, and TUNEL-positive cells, and increased BDNF and Bcl-2 expressions. Our findings suggest RIPerC with a reperfusion time of approximately 10 min exerts its neuroprotective effects via an anti-apoptotic mechanism. This study provides important preliminary data to establish more effective RIPerC interventions.

Anti-angiogenic effect of exo-LncRNA TUG1 in myocardial infarction and modulation by remote ischemic conditioning

The successful use of exosomes in therapy after myocardial infarction depends on an improved understanding of their role in cardiac signaling and regulation. Here, we report that exosomes circulating after myocardial infarction (MI) carry LncRNA TUG1 which downregulates angiogenesis by disablement of the HIF-1α/VEGF-α axis and that this effect can be counterbalanced by remote ischemic conditioning (RIC). Rats with MI induced through left coronary artery ligation without (MI model) and with reperfusion (ischemia/reperfusion I/R model) were randomized to RIC, or MI (I/R) or sham-operated (SO) control. Data from one cohort study and one randomized-controlled trial of humans with MI were also utilized, the former involving patients who had not received percutaneous coronary intervention (PCI) and the latter patients with PCI. Exosome concentrations did not differ between intervention groups (RIC vs. control) in rats (MI and I/R model) as well as humans (with and without PCI). However, MI and I/R exosomes attenuated HIF-1α, VEGF-α, and endothelial function. LncRNA TUG1 was increased in MI and I/R exosomes, but decreased in SO and RIC exosomes. HIF-1α expression was downregulated with MI and I/R exosomes but increased with RIC exosomes. Exosome inhibition suppressed HIF-1α upregulation through RIC exosomes. VEGF-α was identified as HIF-1α-regulated target gene. Knockdown of HIF-1α decreased VEGF-α, endothelial cell capability, and tube formation. Overexpression of HIF-1α exerted opposite effects. Transfection and co-transfection of 293 T cells with exosome-inhibitor GW4869 and HIF-1α inhibitor si-HIF-1α confirmed the exosomal-LncRNA TUG1/HIF-1α/VEGF-α pathway. LncRNA TUG1 is a potential therapeutic target after MI with or without reperfusion through PCI.

Insights into research on myocardial ischemia/reperfusion injury from 2012 to 2021: a bibliometric analysis

BACKGROUND

Numerous studies on myocardial ischemia/reperfusion (MI/R) injury have been undertaken in recent years. Hotspots and developmental trends in MI/R research are being rapidly updated. However, there has been no bibliometric analysis that systematically evaluates existing literature on MI/R injury. Our study explores developments in MI/R research over the past decade, and provides a reference for future research.

MATERIALS AND METHODS

Both experimental and clinical publications on MI/R injury from 2012 to 2021 were retrieved from the Web of Science Core Collection database. The CiteSpace and VOSviewer tools were used to perform a bibliometric analysis.

RESULTS

A total of 8419 papers were analyzed. The number of annual publications demonstrated an overall upward trend, rising from 629 publications in 2012 to 1024 publications in 2021. China, the USA, Germany, England, and Italy were the top five contributors to MI/R studies. The Fourth Military Medical University in China contributed the most publications (188, 2.23%), while the University College London in England cooperated the most with relevant research institutions. Derek J Hausenloy (University College London), Derek M Yellon (University College London), and Gerd Heusch (University of Essen Medical School) were the top three most active and influential scholars according to the H-index. Among the top 10 journals with the most publications, Basic Research in Cardiology had the highest impact factors. The top three co-cited journals were Circulation, Circulation Research, and Cardiovascular Research. According to a co-cited reference analysis, MI/R research can be divided across 10 major subfields of mitophagy, cardioprotection, inflammation, remote ischemic preconditioning, long non-coding RNA, melatonin, postconditioning, mitochondria, microvascular obstruction, and ferroptosis. After 2018, the keywords with strongest citation bursts included extracellular vesicles, long non-coding RNA, cell proliferation, microRNA, mitochondrial quality control, mitophagy, biomarker, and mitochondrial biogenesis.

CONCLUSIONS

The present study reveals the influential authors, cooperating institutions, and main research foci in the field of MI/R injury in the past decade. The latest hotspots are a more in-depth insight into the molecular mechanisms underlying MI/R injury, such as mitochondrial quality control, non-coding RNAs, cell proliferation, and extracellular vesicles.

Effect of remote ischemic preconditioning in patients undergoing laparoscopic colorectal cancer surgery: a randomized controlled trial

BACKGROUND

Remote ischemic preconditioning (RIPC) is reported to reduce ischemia-reperfusion injury (IRI) in many vital organs by inhibiting a systemic inflammatory response. Inflammation also plays an essential role in the pathophysiology of prolonged post-operative ileus (PPOI) in patients undergoing colorectal cancer (CRC) surgery. However, the role of RIPC is unclear in reducing the incidence of PPOI in patients undergoing CRC surgery.

METHODS

This was a prospective, randomized trial of RIPC vs. placebo-controlled in patients undergoing elective laparoscopic CRC surgery. Eighty patients were randomized to either a RIPC group or a control group (40 per arm), with computer-generated randomization. The aim was to determine whether RIPC improved the recovery of gut function. The primary outcomes assessed were time to gastrointestinal tolerance and incidence of PPOI.

RESULTS

Median time to stool of the RIPC group was significantly lower than that of the control group [RIPC vs. control, 4.0 (3.0, 6.0) vs. 5.0 (4.0, 7.8) days, p = 0.027]. Median time to gastrointestinal tolerance and incidence of PPOI in the RIPC group were lower than the control group; however, there were no statistical differences between the two groups [RIPC vs. control: 5.0 (3.0, 7.0) vs. 6.0 (4.0, 8.8) days, p = 0.178; 15 vs. 30%, p = 0.108].

CONCLUSION

RIPC could shorten the median time to stool in patients undergoing laparoscopic CRC surgery, but did not improve the overall recovery time of gut function or reduce the incidence of PPOI.

REGISTRATION NUMBER

ChiCTR2100043313 (http://www.chictr.org.cn).Key pointsQuestion: In patients undergoing laparoscopic CRC surgery, does RIPC improve time to the overall recovery of gut function and reduce the incidence of PPOI?Findings: In this randomized clinical trial that included 80 patients undergoing elective laparoscopic CRC surgery, no significant difference was found between the RIPC group and the control group concerning median time to gastrointestinal tolerance and incidence of PPOI.Meaning: RIPC did not improve the time for overall recovery of gut function or reduce the incidence of PPOI in patients undergoing laparoscopic CRC surgery.

Remote ischemic conditioning in Ossabaw minipigs induces the release of humoral cardioprotective triggers, but the myocardium does not respond with reduced infarct size

Ischemic preconditioning (IPC; brief cycles of coronary occlusion/reperfusion) is operative in all species tested so far and reduces infarct size through the release of trigger molecules and activation of signal transducer and activator of transcription (STAT)3 in pigs. We have recently demonstrated that IPC failed to protect Ossabaw minipigs, which had a genetic predisposition to, but not yet established a metabolic syndrome, from infarction and did not activate STAT3. We now subjected Ossabaw minipigs to remote ischemic conditioning (RIC; 4 × 5 min/5 min bilateral hindlimb ischemia-reperfusion) and analyzed the release of cardioprotective triggers into the circulation with the aim to distinguish whether IPC failed to stimulate trigger release or to activate intracellular signaling cascades upstream of STAT3. RIC or a placebo protocol, respectively, was induced in anesthetized pigs before 60 min/180 min coronary occlusion/reperfusion. Plasma, prepared from Ossabaw minipigs after RIC or placebo, was infused into isolated rat hearts subjected to 30 min/120 min global ischemia-reperfusion. In the Ossabaw minipigs, RIC did not reduce infarct size (49.5 ± 12.1 vs. 56.0 ± 11.8% of area at risk with placebo), and STAT3 was not activated. In isolated rat hearts, infusion of RIC plasma reduced infarct size (19.7 ± 6.7 vs. 33.2 ± 5.5% of ventricular mass with placebo) and activated STAT3. Pretreatment of rat hearts with the STAT3 inhibitor stattic abrogated such infarct size reduction and STAT3 activation. In conclusion, Ossabaw minipigs release cardioprotective triggers in response to RIC into the circulation, and lack of cardioprotection is attributed to myocardial nonresponsiveness.NEW & NOTEWORTHY Ischemic conditioning reduces myocardial infarct size in all species tested so far. In the present study, we used Ossabaw minipigs that had a genetic predisposition to, but not yet established a metabolic syndrome. In these pigs, remote ischemic conditioning (RIC) induced the release of cardioprotective triggers but did not reduce infarct size. Transfer of their plasma, however, reduced infarct size in isolated recipient rat hearts, along with signal transducer and activator of transcription (STAT)3 activation.

Non-responsiveness to cardioprotection by ischaemic preconditioning in Ossabaw minipigs with genetic predisposition to, but without the phenotype of the metabolic syndrome

The translation of successful preclinical and clinical proof-of-concept studies on cardioprotection to the benefit of patients with reperfused acute myocardial infarction has been difficult so far. This difficulty has been attributed to confounders which patients with myocardial infarction typically have but experimental animals usually not have. The metabolic syndrome is a typical confounder. We hypothesised that there may also be a genuine non-responsiveness to cardioprotection and used Ossabaw minipigs which have the genetic predisposition to develop a diet-induced metabolic syndrome, but before they had developed the diseased phenotype. Using a prospective study design, a reperfused acute myocardial infarction was induced in 62 lean Ossabaw minipigs by 60 min coronary occlusion and 180 min reperfusion. Ischaemic preconditioning by 3 cycles of 5 min coronary occlusion and 10 min reperfusion was used as cardioprotective intervention. Ossabaw minipigs were stratified for their single nucleotide polymorphism as homozygous for valine (V/V) or isoleucine (I/I)) in the γ-subunit of adenosine monophosphate-activated protein kinase. Endpoints were infarct size and area of no-reflow. Infarct size (V/V: 54 ± 8, I/I: 54 ± 13% of area at risk, respectively) was not reduced by ischaemic preconditioning (V/V: 55 ± 11, I/I: 46 ± 11%) nor was the area of no-reflow (V/V: 57 ± 18, I/I: 49 ± 21 vs. V/V: 57 ± 21, I/I: 47 ± 21% of infarct size). Bioinformatic comparison of the Ossabaw genome to that of Sus scrofa and Göttingen minipigs identified differences in clusters of genes encoding mitochondrial and inflammatory proteins, including the janus kinase (JAK)-signal transducer and activator of transcription (STAT) pathway. The phosphorylation of STAT3 at early reperfusion was not increased by ischaemic preconditioning, different from the established STAT3 activation by cardioprotective interventions in other pig strains. Ossabaw pigs have not only the genetic predisposition to develop a metabolic syndrome but also are not amenable to cardioprotection by ischaemic preconditioning.

The protective effect of remote ischemic conditioning is lost in patients with hypercholesterolemia

Remote ischemic conditioning (RIC), brief repetitive cycles of ischemia and reperfusion in remote tissues, is known to induce robust protection against myocardial ischemia-reperfusion (I/R) injury in preclinical studies. However, translation of the beneficial effects to the clinical setting has been challenging. A possibility is that comorbidities, including hypercholesterolemia, interfere with the protective mechanisms of RIC. The aim of this study was to test if hypercholesterolemia attenuates the efficacy of RIC in patients with hypercholesterolemia. Patients with familial hypercholesterolemia (FH) with high (≥5.5 mmol/L) low-density lipoprotein cholesterol (LDL-C), FH with low (≤2.5 mmol/L) and healthy control subjects (n = 12 in each group) were included. Flow-mediated vasodilatation (FMD) of the brachial artery was evaluated, before and after a 20-min period of forearm ischemia and 20 min reperfusion (I/R) as a measure of endothelial function. Study subjects were randomized to a RIC protocol consisting of four cycles of 5 min of leg ischemia or sham using a crossover design. Forearm I/R induced significant reduction in FMD in all three groups during the sham procedure. RIC protected from endothelial dysfunction induced by forearm ischemia-reperfusion in healthy controls [FMD baseline 2.8 ± 2.3 vs. FMD after I/R + RIC 4.5 ± 4.0%; means (SD)] and in patients with FH with low LDL-C (4.5 ± 3.5 vs. 4.4 ± 4.2%). By contrast, RIC fails to protect against I/R-induced endothelial dysfunction in patients with FH and high LDL-C (3.9 ± 3.0 vs. 1.1 ± 1.5%; P < 0.01). These findings provide the first evidence in humans that the protective effect of RIC is lost in patients with elevated cholesterol.NEW & NOTEWORTHY We investigated the impact of hypercholesterolemia on the protective effect of RIC on ischemia-reperfusion injury in a well-characterized patient population with isolated hypercholesterolemia. The results show that the protective effect of RIC is absent in patients with hypercholesterolemia but is apparent in patients with hypercholesterolemic following treatment with lipid-lowering drugs. The results are of importance for the understanding of how comorbidities affect the therapeutic potential of RIC.