Cardioprotection by remote ischemic conditioning and its signal transduction

Activation of the nonneuronal cholinergic cardiac system by hypoxic preconditioning protects isolated adult cardiomyocytes from hypoxia/reoxygenation injury

Activation of the vagus nerve mediates cardioprotection and attenuates myocardial ischemia/reperfusion (I/R) injury. In response to vagal activation, acetylcholine (ACh) is released from the intracardiac nervous system (ICNS) and activates intracellular cardioprotective signaling cascades. Recently, however, a nonneuronal cholinergic cardiac system (NNCCS) in cardiomyocytes has been described as an additional source of ACh. To investigate whether the NNCCS mediates cardioprotection in the absence of vagal and ICNS activation, we used a reductionist approach of isolated adult rat ventricular cardiomyocytes without neuronal cells, using hypoxic preconditioning (HPC) as a protective stimulus. Adult rat ventricular cardiomyocytes were isolated, the absence of neuronal cells was confirmed, and HPC was induced by 10/20 min hypoxia/reoxygenation (H/R) before subjection to 30/5 min H/R to simulate I/R injury. Cardiomyocyte viability was assessed by trypan blue staining at baseline and after HPC+H/R or H/R. Intra- and extracellular ACh was quantified using liquid chromatography-coupled mass spectrometry at baseline, after HPC, after hypoxia, and after reoxygenation, respectively. In a subset of experiments, muscarinic and nicotinic ACh receptor (m- and nAChR) antagonists were added during HPC or during H/R. Cardiomyocyte viability at baseline (69 ± 4%) was reduced by H/R (10 ± 3%). With HPC, cardiomyocyte viability was preserved after H/R (25 ± 6%). Intra- and extracellular ACh increased during hypoxia; HPC further increased both intra- and extracellular ACh (from 0.9 ± 0.7 to 1.5 ± 1.0 nmol/mg; from 0.7 ± 0.6 to 1.1 ± 0.7 nmol/mg, respectively). The addition of mAChR and nAChR antagonists during HPC had no impact on HPC's protection; however, protection was abrogated when antagonists were added during H/R (cardiomyocyte viability after H/R: 23 ± 5%; 13 ± 4%). In conclusion, activation of the NNCCS is involved in cardiomyocyte protection; HPC increases intra- and extracellular ACh during H/R, and m- and nAChRs are causally involved in HPC's cardiomyocyte protection during H/R. The interplay between upstream ICNS activation and NNCCS activation in myocardial cholinergic metabolism and cardioprotection needs to be investigated in future studies.NEW & NOTEWORTHY The intracardiac nervous system is considered to be involved in ischemic conditioning's cardioprotection through the release of acetylcholine (ACh). However, we demonstrate that hypoxic preconditioning (HPC) protects from hypoxia/reoxygenation injury and increases intra- and extracellular ACh during hypoxia in isolated adult ventricular rat cardiomyocytes. HPC's protection involves cardiomyocyte muscarinic and nicotinic ACh receptor activation. Thus, besides the intracardiac nervous system, a nonneuronal cholinergic cardiac system may also be causally involved in cardiomyocyte protection by ischemic conditioning.

Expanding landscape of coronary microvascular disease in co-morbid conditions: Metabolic disease and beyond

Coronary microvascular disease (CMD) and impaired coronary blood flow control are defects that occur early in the pathogenesis of heart failure in cardiometabolic conditions, prior to the onset of atherosclerosis. In fact, recent studies have shown that CMD is an independent predictor of cardiac morbidity and mortality in patients with obesity and metabolic disease. CMD is comprised of functional, structural, and mechanical impairments that synergize and ultimately reduce coronary blood flow in metabolic disease and in other co-morbid conditions, including transplant, autoimmune disorders, chemotherapy-induced cardiotoxicity, and remote injury-induced CMD. This review summarizes the contemporary state-of-the-field related to CMD in metabolic and these other co-morbid conditions based on mechanistic data derived mostly from preclinical small- and large-animal models in light of available clinical evidence and given the limitations of studying these mechanisms in humans. In addition, we also discuss gaps in current understanding, emerging areas of interest, and opportunities for future investigations in this field.

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.

Mitochondrial Kinase Signaling for Cardioprotection

Myocardial ischemia/reperfusion injury is reduced by cardioprotective adaptations such as local or remote ischemic conditioning. The cardioprotective stimuli activate signaling cascades, which converge on mitochondria and maintain the function of the organelles, which is critical for cell survival. The signaling cascades include not only extracellular molecules that activate sarcolemmal receptor-dependent or -independent protein kinases that signal at the plasma membrane or in the cytosol, but also involve kinases, which are located to or within mitochondria, phosphorylate mitochondrial target proteins, and thereby modify, e.g., respiration, the generation of reactive oxygen species, calcium handling, mitochondrial dynamics, mitophagy, or apoptosis. In the present review, we give a personal and opinionated overview of selected protein kinases, localized to/within myocardial mitochondria, and summarize the available data on their role in myocardial ischemia/reperfusion injury and protection from it. We highlight the regulation of mitochondrial function by these mitochondrial protein kinases.

Lysophosphatidic acid contributes to myocardial ischemia/reperfusion injury by activating TRPV1 in spinal cord

Lysophosphatidic acid (LPA) is a bioactive phospholipid that plays a crucial role in cardiovascular diseases. Here, we question whether LPA contributes to myocardial ischemia/reperfusion (I/R) injury by acting on transient receptor potential vanilloid 1 (TRPV1) in spinal cord. By ligating the left coronary artery to establish an in vivo I/R mouse model, we observed a 1.57-fold increase in LPA level in the cerebrospinal fluid (CSF). The I/R-elevated CSF LPA levels were reduced by HA130, an LPA synthesis inhibitor, compared to vehicle treatment (4.74 ± 0.34 vs. 6.46 ± 0.94 μg/mL, p = 0.0014). Myocardial infarct size was reduced by HA130 treatment compared to the vehicle group (26 ± 8% vs. 46 ± 8%, p = 0.0001). To block the interaction of LPA with TRPV1 at the K710 site, we generated a K710N knock-in mouse model. The TRPV1K710N mice were resistant to LPA-induced myocardial injury, showing a smaller infarct size relative to TRPV1WT mice (28 ± 4% vs. 60 ± 7%, p < 0.0001). Additionally, a sequence-specific TRPV1 peptide targeting the K710 region produced similar protective effects against LPA-induced myocardial injury. Blocking the K710 region through K710N mutation or TRPV1 peptide resulted in reduced neuropeptides release and decreased activity of cardiac sensory neurons, leading to a decrease in cardiac norepinephrine concentration and the restoration of intramyocardial pro-survival signaling, namely protein kinase B/extracellular regulated kinase/glycogen synthase kinase-3β pathway. These findings suggest that the elevation of CSF LPA is strongly associated with myocardial I/R injury. Moreover, inhibiting the interaction of LPA with TRPV1 by blocking the K710 region uncovers a novel strategy for preventing myocardial ischemic injury.

Is There a Mitochondrial Protection via Remote Ischemic Conditioning in Settings of Anticancer Therapy Cardiotoxicity?

PURPOSE OF REVIEW

To provide an overview of (a) protective effects on mitochondria induced by remote ischemic conditioning (RIC) and (b) mitochondrial damage caused by anticancer therapy. We then discuss the available results of studies on mitochondrial protection via RIC in anticancer therapy-induced cardiotoxicity.

RECENT FINDINGS

In three experimental studies in healthy mice and pigs, there was a RIC-mediated protection against anthracycline-induced cardiotoxicity and there was some evidence of improved mitochondrial function with RIC. The RIC-mediated protection was not confirmed in the two available studies in cancer patients. In adult cancer patients, RIC was associated with an adverse outcome. There are no data on mitochondrial function in cancer patients. Studies in tumor-bearing animals are needed to determine whether RIC does not interfere with the anticancer properties of the drugs and whether RIC actually improves mitochondrial function, ultimately resulting in improved cardiac function.

Interindividual variability in cold-pressor pain sensitivity is not explained by peripheral vascular responding and generalizes to a C-nociceptor-specific pain phenotype

ABSTRACT

Pain sensitivity of healthy subjects in the cold-pressor (CP) test was proposed to be dichotomously distributed and to represent a pain sensitivity trait. Still, it has not been systematically explored which factors influence this pain sensitivity readout. The aim of this study was to distinguish potential contributions of local tissue-related factors such as perfusion and thermoregulation or gain settings in nociceptive systems. Cold-pressor-sensitive and CP-insensitive students screened from a medical student laboratory course were recruited for a CP retest with additional cardiovascular and bilateral local vascular monitoring. In addition, comprehensive quantitative sensory testing according to Deutscher Forschungsverbund Neuropathischer Schmerz standards and a sustained pinch test were performed. Cold pressor was reproducible across sessions (Cohen kappa 0.61 ± 0.14, P < 0.005). At 30 seconds in ice water, CP-sensitive subjects exhibited not only more pain (78.6 ± 26.3 vs 29.5 ± 17.5, P < 0.0001) but also significantly stronger increases in mean arterial blood pressure (12.6 ± 9.3 vs 5.6 ± 8.1 mm Hg, P < 0.05) and heart rate (15.0 ± 8.2 vs 7.1 ± 6.2 bpm, P < 0.005), and lower baroreflex sensitivity, but not local or vasoconstrictor reflex-mediated microcirculatory responses. Cold-pressor-sensitive subjects exhibited significantly lower pain thresholds also for cold, heat, and blunt pressure, and enhanced pain summation, but no significant differences in Aδ-nociceptor-mediated punctate mechanical pain. In conclusion, differences in nociceptive signal processing drove systemic cardiovascular responses. Baroreceptor activation suppressed pain and cardiovascular responses more efficiently in CP-insensitive subjects. Cold-pressor sensitivity generalized to a pain trait of C-fiber-mediated nociceptive channels, which was independent of local thermal and vascular changes in the ice-water-exposed hand. Thus, the C-fiber pain trait reflects gain setting of the nociceptive system.

Remote ischemic preconditioning reduces mitochondrial apoptosis mediated by calpain 1 activation in myocardial ischemia-reperfusion injury through calcium channel subunit Cacna2d3

Remote Ischemic Preconditioning (RIPC) can reduce myocardial ischemia-reperfusion injury, but its mechanism is not clear. In order to explore the mechanism of RIPC in myocardial protection, we collected myocardial specimens during cardiac surgery in children with tetralogy of Fallot for sequencing. Our study found RIPC reduces the expression of the calcium channel subunit cacna2d3, thereby impacting the function of calcium channels. As a result, calcium overload during ischemia-reperfusion is reduced, and the activation of calpain 1 is inhibited. This ultimately leads to a decrease in calpain 1 cleavage of Bax, consequently inhibiting increased mitochondrial permeability-mediated apoptosis. Notably, in both murine and human models of myocardial ischemia-reperfusion injury, RIPC inhibiting the expression of the calcium channel subunit cacna2d3 and the activation of calpain 1, improving cardiac function and histological outcomes. Overall, our findings put forth a proposed mechanism that elucidates how RIPC reduces myocardial ischemia-reperfusion injury, ultimately providing a solid theoretical foundation for the widespread clinic application of RIPC.

Reperfusion Injury: How Can We Reduce It by Pre-, Per-, and Postconditioning

While early coronary reperfusion via primary percutaneous coronary intervention (pPCI) is established as the most efficacious therapy for minimizing infarct size (IS) in acute ST-elevation myocardial infarction (STEMI), the restoration of blood flow also introduces myocardial ischemia-reperfusion injury (IRI), leading to cardiomyocyte death. Among diverse methods, ischemic conditioning (IC), achieved through repetitive cycles of ischemia and reperfusion, has emerged as the most promising method to mitigate IRI. IC can be performed by applying the protective stimulus directly to the affected myocardium or indirectly to non-affected tissue, which is known as remote ischemic conditioning (RIC). In clinical practice, RIC is often applied by serial inflations and deflations of a blood pressure cuff on a limb. Despite encouraging preclinical studies, as well as clinical studies demonstrating reductions in enzymatic IS and myocardial injury on imaging, the observed impact on clinical outcome has been disappointing so far. Nevertheless, previous studies indicate a potential benefit of IC in high-risk STEMI patients. Additional research is needed to evaluate the impact of IC in such high-risk cohorts. The objective of this review is to summarize the pathophysiological background and preclinical and clinical data of IRI reduction by IC.

Targeting mitochondrial shape: at the heart of cardioprotection

There remains an unmet need to identify novel therapeutic strategies capable of protecting the myocardium against the detrimental effects of acute ischemia-reperfusion injury (IRI), to reduce myocardial infarct (MI) size and prevent the onset of heart failure (HF) following acute myocardial infarction (AMI). In this regard, perturbations in mitochondrial morphology with an imbalance in mitochondrial fusion and fission can disrupt mitochondrial metabolism, calcium homeostasis, and reactive oxygen species production, factors which are all known to be critical determinants of cardiomyocyte death following acute myocardial IRI. As such, therapeutic approaches directed at preserving the morphology and functionality of mitochondria may provide an important strategy for cardioprotection. In this article, we provide an overview of the alterations in mitochondrial morphology which occur in response to acute myocardial IRI, and highlight the emerging therapeutic strategies for targeting mitochondrial shape to preserve mitochondrial function which have the future therapeutic potential to improve health outcomes in patients presenting with AMI.

Heart graft preservation technics and limits: an update and perspectives

Heart transplantation, the gold standard treatment for end-stage heart failure, is limited by heart graft shortage, justifying expansion of the donor pool. Currently, static cold storage (SCS) of hearts from donations after brainstem death remains the standard practice, but it is usually limited to 240 min. Prolonged cold ischemia and ischemia-reperfusion injury (IRI) have been recognized as major causes of post-transplant graft failure. Continuous ex situ perfusion is a new approach for donor organ management to expand the donor pool and/or increase the utilization rate. Continuous ex situ machine perfusion (MP) can satisfy the metabolic needs of the myocardium, minimizing irreversible ischemic cell damage and cell death. Several hypothermic or normothermic MP methods have been developed and studied, particularly in the preclinical setting, but whether MP is superior to SCS remains controversial. Other approaches seem to be interesting for extending the pool of heart graft donors, such as blocking the paths of apoptosis and necrosis, extracellular vesicle therapy, or donor heart-specific gene therapy. In this systematic review, we summarize the mechanisms involved in IRI during heart transplantation and existing targeting therapies. We also critically evaluate all available data on continuous ex situ perfusion devices for adult donor hearts, highlighting its therapeutic potential and current limitations and shortcomings.

Outcomes of hypothalamic oxytocin neuron-driven cardioprotection after acute myocardial infarction

Altered autonomic balance is a hallmark of numerous cardiovascular diseases, including myocardial infarction (MI). Although device-based vagal stimulation is cardioprotective during chronic disease, a non-invasive approach to selectively stimulate the cardiac parasympathetic system immediately after an infarction does not exist and is desperately needed. Cardiac vagal neurons (CVNs) in the brainstem receive powerful excitation from a population of neurons in the paraventricular nucleus (PVN) of the hypothalamus that co-release oxytocin (OXT) and glutamate to excite CVNs. We tested if chemogenetic activation of PVN-OXT neurons following MI would be cardioprotective. The PVN of neonatal rats was transfected with vectors to selectively express DREADDs within OXT neurons. At 6 weeks of age, an MI was induced and DREADDs were activated with clozapine-N-oxide. Seven days following MI, patch-clamp electrophysiology confirmed the augmented excitatory neurotransmission from PVN-OXT neurons to downstream nuclei critical for parasympathetic activity with treatment (43.7 ± 10 vs 86.9 ± 9 pA; MI vs. treatment), resulting in stark improvements in survival (85% vs. 95%; MI vs. treatment), inflammation, fibrosis assessed by trichrome blue staining, mitochondrial function assessed by Seahorse assays, and reduced incidence of arrhythmias (50% vs. 10% cumulative incidence of ventricular fibrillation; MI vs. treatment). Myocardial transcriptomic analysis provided molecular insight into potential cardioprotective mechanisms, which revealed the preservation of beneficial signaling pathways, including muscarinic receptor activation, in treated animals. These comprehensive results demonstrate that the PVN-OXT network could be a promising therapeutic target to quickly activate beneficial parasympathetic-mediated cellular pathways within the heart during the early stages of infarction.

Platelet-Mediated Transfer of Cardioprotection by Remote Ischemic Conditioning and Its Abrogation by Aspirin But Not by Ticagrelor

PURPOSE

The role of platelets during myocardial ischemia/reperfusion (I/R) is ambivalent. They contribute to injury but also to cardioprotection. Repeated blood flow restriction and reperfusion in a tissue/organ remote from the heart (remote ischemic conditioning, RIC) reduce myocardial I/R injury and attenuate platelet activation. Whether or not platelets mediate RIC's cardioprotective signal is currently unclear.

METHODS AND RESULTS

Venous blood from healthy volunteers (without or with pretreatment of 500/1000 mg aspirin or 180 mg ticagrelor orally, 2-3 h before the study, n = 18 each) was collected before and after RIC (3 × 5 min blood pressure cuff inflation at 200 mmHg on the left upper arm/5 min deflation). Washed platelets were isolated. Platelet-poor plasma was used to prepare plasma-dialysates. Platelets (25 × 103/µL) or plasma-dialysates (1:10) prepared before and after RIC from untreated versus aspirin- or ticagrelor-pretreated volunteers, respectively, were infused into isolated buffer-perfused rat hearts. Hearts were subjected to global 30 min/120 min I/R. Infarct size was stained. Infarct size was less with infusion of platelets/plasma-dialysate after RIC (18 ± 7%/23 ± 9% of ventricular mass) than with platelets/plasma-dialysate before RIC (34 ± 7%/33 ± 8%). Aspirin pretreatment abrogated the transfer of RIC's cardioprotection by platelets (after/before RIC, 34 ± 7%/33 ± 7%) but only attenuated that by plasma-dialysate (after/before RIC, 26 ± 8%/32 ± 5%). Ticagrelor pretreatment induced an in vivo formation of cardioprotective factor(s) per se (platelets/plasma-dialysate before RIC, 26 ± 7%/26 ± 7%) but did not impact on RIC's cardioprotection by platelets/plasma-dialysate (20 ± 7%/21 ± 5%).

CONCLUSION

Platelets serve as carriers for RIC's cardioprotective signal through an aspirin-sensitive and thus cyclooxygenase-dependent mechanism. The P2Y12 inhibitor ticagrelor per se induces a humoral cardioprotective signal.

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].

Perspective: mitochondrial STAT3 in cardioprotection

Activation of signal transducer and activator of transcription 3 (STAT3) has been identified as a key cardioprotective signal not only in animal studies but also in humans-in animals, STAT3 is causally involved in cardioprotection. In response to late ischemic conditioning, canonical function of STAT3 activation upregulates the expression of cardioprotective and anti-apoptotic proteins. In its non-canonical function, STAT3 is activated during ischemic conditioning and is part of the cardioprotective cytosolic survival activating factor enhancement pathway. Activated STAT3 is imported and localized to the mitochondria. Mitochondrial STAT3 stimulates the activity of mitochondrial electron transport chain complex I, reduces mitochondrial reactive oxygen species production and mitochondrial permeability transition pore opening. Finally, two novel aspects of STAT activation in cardioprotection are discussed: a genetic variance of the STAT encoding region as a potential primordial confounding variable for cardioprotection, and the cardioprotective potential of sodium-glucose cotransporter 2 inhibitors through STAT3 activation.

Effects of remote ischemic conditioning on conditioned pain modulation and cardiac autonomic modulation in women with knee osteoarthritis: placebo-controlled randomized clinical trial protocol

BACKGROUND

It is estimated that over 240 million people worldwide have osteoarthritis, which is a major contributor to chronic pain and central changes in pain processing, including endogenous pain modulation. The autonomic nervous system plays a crucial role in the pain regulatory process. One of the main mechanisms of remote ischemic conditioning is neuronal signaling from the preconditioned extremity to the heart. This study aims to analyze the acute effect of remote ischemic conditioning on local pain, conditioned pain modulation, and cardiac autonomic control in women with knee osteoarthritis and to see if there is a correlation between them.

METHODS

Women more than 50 years with knee osteoarthritis diagnosed according to the American College of Rheumatology criteria in the postmenopausal period will be considered eligible. The study will have blind randomization, be placebo-controlled, and be balanced in a 1:1 ratio. The total of 44 participants will be divided into two groups (22 participants per group): (i) remote ischemic conditioning and (ii) placebo remote ischemic conditioning. Protocol consisting of four cycles of total ischemia, followed immediately by four cycles of 5 min of vascular reperfusion, totaling 40 min. The primary outcomes in the protocol are conditioned pain modulation, which has the pressure pain threshold (kgf/cm2) as its primary outcome measure, and cardiac autonomic modulation, which has the indices found in heart rate variability as its primary outcome measure. Comparisons will be performed using generalized linear mixed models fitted to the data. For correlation, the Pearson or Spearman test will be used depending on the normality of the data. All analyses will assume a significance level of p < 0.05.

DISCUSSION

It is believed that the results of this study will present a new perspective on the interaction between the pain processing system and the cardiovascular system; they will provide the professional and the patient with a greater guarantee of cardiovascular safety in the use of the intervention; it will provide knowledge about acute responses and this will allow future chronic intervention strategies that aim to be used in the clinical environment, inserted in the multimodal approach, for the treatment of osteoarthritis of the knee.

TRIAL REGISTRATION

ClinicalTrials.gov NCT05059652. Registered on 30 August 2021. Last update on 28 March 2023.

Myocardial ischemia-reperfusion injury and the influence of inflammation

Acute myocardial infarction is caused by a sudden coronary artery occlusion and leads to ischemia in the corresponding myocardial territory which generally results in myocardial necrosis. Without restoration of coronary perfusion, myocardial scar formation will cause adverse remodelling of the myocardium and heart failure. Successful introduction of percutaneous coronary intervention and surgical coronary artery bypass grafting made it possible to achieve early revascularisation/reperfusion, hence limiting the ischemic zone of myocardium. However, reperfusion by itself paradoxically triggers an exacerbated and accelerated injury in the myocardium, called ischemia-reperfusion (I/R) injury. This mechanism is partially driven by inflammation through multiple interacting pathways. In this review we summarize the current insights in mechanisms of I/R injury and the influence of altered inflammation. Multiple pharmacological and interventional therapeutic strategies (ischemic conditioning) have proven to be beneficial during I/R in preclinical models but were notoriously unsuccessful upon clinical translation. In this review we focus on common mechanisms of I/R injury, altered inflammation and potential therapeutic strategies. We hypothesize that a dual approach may be of value because I/R injury patients are predestined with multiple comorbidities and systemic low-grade inflammation, which requires targeted intervention before other strategies can be fully effective.

Regulation of the JAK/STAT signaling pathway: The promising targets for cardiovascular disease

Individuals have known that Janus kinase (JAK) signal transducer and activator of transcription (STAT) signaling pathway was involved in the growth of the cell, cell differentiation courses advancement, immune cellular survival, as well as hematopoietic system advancement. Researches in the animal models have already uncovered a JAK/STAT regulatory function in myocardial ischemia-reperfusion injury (MIRI), acute myocardial infarction (MI), hypertension, myocarditis, heart failure, angiogenesis and fibrosis. Evidences originating in these studies indicate a therapeutic JAK/STAT function in cardiovascular diseases (CVDs). In this retrospection, various JAK/STAT functions in the normal and ill hearts were described. Moreover, the latest figures about JAK/STAT were summarized under the background of CVDs. Finally, we discussed the clinical transformation prospects and technical limitations of JAK/STAT as the potential therapeutic targets for CVDs. This collection of evidences has essential meanings for the clinical application of JAK/STAT as medicinal agents for CVDs. In this retrospection, various JAK/STAT functions in the normal and ill hearts were described. Moreover, the latest figures about JAK/STAT were summarized under the background of CVDs. Finally, we discussed the clinical transformation prospects and toxicity of JAK/STAT inhibitors as potential therapeutic targets for CVDs. This collection of evidences has essential meanings for the clinical application of JAK/STAT as medicinal agents for CVDs.

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.

Effect of remote ischemic conditioning on the immune-inflammatory profile in patients with traumatic hemorrhagic shock in a randomized controlled trial

Resuscitation induced ischemia/reperfusion predisposes trauma patients to systemic inflammation and organ dysfunction. We investigated the effect of remote ischemic conditioning (RIC), a treatment shown to prevent ischemia/reperfusion injury in experimental models of hemorrhagic shock/resuscitation, on the systemic immune-inflammatory profile in trauma patients in a randomized trial. We conducted a prospective, single-centre, double-blind, randomized, controlled trial involving trauma patients sustaining blunt or penetrating trauma in hemorrhagic shock admitted to a Level 1 trauma centre. Patients were randomized to receive RIC (four cycles of 5-min pressure cuff inflation at 250 mmHg and deflation on the thigh) or a Sham intervention. The primary outcomes were neutrophil oxidative burst activity, cellular adhesion molecule expression, and plasma levels of myeloperoxidase, cytokines and chemokines in peripheral blood samples, drawn at admission (pre-intervention), 1 h, 3 h, and 24 h post-admission. Secondary outcomes included ventilator, ICU and hospital free days, incidence of nosocomial infections, 24 h and 28 day mortality. 50 eligible patients were randomized; of which 21 in the Sham group and 18 in the RIC group were included in the full analysis. No treatment effect was observed between Sham and RIC groups for neutrophil oxidative burst activity, adhesion molecule expression, and plasma levels of myeloperoxidase and cytokines. RIC prevented significant increases in Th2 chemokines TARC/CCL17 (P < 0.01) and MDC/CCL22 (P < 0.05) at 24 h post-intervention in comparison to the Sham group. Secondary clinical outcomes were not different between groups. No adverse events in relation to the RIC intervention were observed. Administration of RIC was safe and did not adversely affect clinical outcomes. While trauma itself modified several immunoregulatory markers, RIC failed to alter expression of the majority of markers. However, RIC may influence Th2 chemokine expression in the post resuscitation period. Further investigation into the immunomodulatory effects of RIC in traumatic injuries and their impact on clinical outcomes is warranted.ClinicalTrials.gov number: NCT02071290.

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.

Localization and characterization of proenkephalin-A as a potential biomarker for kidney disease in murine and human kidneys

INTRODUCTION

Exact measurement of renal function is essential for the treatment of patients. Elevated serum-creatinine levels, while established, are influenced by other parameters and show a significant time-lag. This drives the search for novel biomarkers of renal function and injury. Beside Lipocalin-2 and kidney-injury-molecule-1 (KIM-1), the endogenous opioid precursor proenkephalin-A (Penk) has recently emerged as a promising marker for renal function. But the cellular origin and regulation of Penk outside the brain has not yet been investigated in depth.

MATERIALS AND METHODS

This study characterizes the cellular origin of Penk expression with high-resolution in situ hybridization in two models of renal fibrosis in mice and human tissue.

RESULTS

Interstitial cells are the main expression site for renal Penk. This classifies Penk as biomarker for interstitial damage as opposed to tubular damage markers like Lipocalin-2 and KIM-1. Furthermore, our data indicate that renal Penk expression is not regulated by classical profibrotic pathways.

DISCUSSION

This study characterizes changing Penk expression in the kidneys. The similarity of Penk expression across species gives rise to further investigations into the function of Penk in healthy and injured kidneys.

CONCLUSION

Penk is a promising biomarker for interstitial renal damage that warrants further studies to utilize its predictive potential.Clinical significanceKnowledge of real-time renal function is essential for proper treatment of critically ill patients and in early diagnosis of acute kidney injury (AKI). Proenkephalin-A has been measured in a number of patient cohorts as a highly accurate and predictive biomarker of renal damage.The present study identifies Penk as a biomarker for interstitial damage in contrast to the tubular biomarkers such as Lipocalin-2 or KIM-1.Our data show that Penk is regulated independently of classical profibrotic or proinflammatory pathways, indicating it might be more robust against extra-renal influences.Data presented in this study provide fundamental information about cell type-specific localization and regulation of the potential new biomarker Penk across species as foundation for further research.

TRPA1 as Target in Myocardial Infarction

Transient receptor potential cation channel subfamily A member 1 (TRPA1), an ion channel primarily expressed on sensory neurons, can be activated by substances occurring during myocardial infarction. Aims were to investigate whether activation, inhibition, or absence of TRPA1 affects infarcts and to explore underlying mechanisms. In the context of myocardial infarction, rats received a TRPA1 agonist, an antagonist, or vehicle at different time points, and infarct size was assessed. Wild type and TRPA1 knockout mice were also compared in this regard. In vitro, sensory neurons were co-cultured with cardiomyocytes and subjected to a model of ischemia-reperfusion. Although there was a difference between TRPA1 activation or inhibition in vivo, no experimental group was different to control animals in infarct size, which also applies to animals lacking TRPA1. In vitro, survival probability of cardiomyocytes challenged by ischemia-reperfusion increased from 32.8% in absence to 45.1% in presence of sensory neurons, which depends, at least partly, on TRPA1. This study raises doubts about whether TRPA1 is a promising target to reduce myocardial damage within a 24 h period. The results are incompatible with relevant enlargements of infarcts by TRPA1 activation or inhibition, which argues against adverse effects when TRPA1 is targeted for other indications.

Remote ischaemic preconditioning versus no remote ischaemic preconditioning for vascular and endovascular surgical procedures

BACKGROUND

Despite advances in perioperative care, elective major vascular surgical procedures still carry a significant risk of morbidity and mortality. Remote ischaemic preconditioning (RIPC) is the temporary blocking of blood flow to vascular beds remote from those targeted by surgery. It has the potential to provide local tissue protection from further prolonged periods of ischaemia. However, the efficacy and safety of RIPC in people undergoing major vascular surgery remain unknown. This is an update of a review published in 2011.  OBJECTIVES: To assess the benefits and harms of RIPC versus no RIPC in people undergoing elective major vascular and endovascular surgery.

SEARCH METHODS

The Cochrane Vascular Information Specialist searched the Cochrane Vascular Specialised Register, CENTRAL, MEDLINE, Embase, and CINAHL databases and the World Health Organization International Clinical Trials Registry Platform and ClinicalTrials.gov to 1 April 2022.

SELECTION CRITERIA

We included all randomised controlled trials that evaluated the role of RIPC in reducing perioperative mortality and morbidities in people undergoing elective major vascular or endovascular surgery.

DATA COLLECTION AND ANALYSIS

We collected data on the characteristics of the trial, methodological quality, and the remote ischaemic preconditioning stimulus used. Our primary outcome was perioperative mortality, and secondary outcomes included myocardial infarction, renal impairment, stroke, hospital stay, limb loss, and operating time or total anaesthetic time. We analysed the data using random-effects models. For each outcome, we calculated the risk ratio (RR) or mean difference (MD) with a 95% confidence interval (CI) based on an intention-to-treat analysis. In addition, we used GRADE to assess the certainty of the evidence for each outcome.

MAIN RESULTS

We included 14 trials which randomised a total of 1295 participants (age range: 64.5 to 76 years; 84% male; study periods ranged from 2003 to 2019). In general, the included studies were at low to unclear risk of bias for most risk of bias domains. The certainty of evidence of main outcomes was moderate due to imprecision of results, moderate heterogeneity, or possible publication bias. We found that RIPC made no clear difference in perioperative mortality compared with no RIPC (RR 1.41, 95% CI 0.59 to 3.40; I2 = 0%; 10 studies, 965 participants; moderate-certainty evidence). Similarly, we found no clear difference between the two groups for myocardial infarction (RR 0.82, 95% CI 0.49 to 1.40; I2 = 7%; 11 studies, 1001 participants; moderate-certainty evidence), renal impairment (RR 1.07, 95% CI 0.62 to 1.86; I2 = 40%; 12 studies, 1054 participants; moderate-certainty evidence), stroke (RR 0.33, 95% CI 0.04 to 3.15; I2 = 0%; 4 studies, 392 participants; moderate-certainty evidence), limb loss (RR 0.74, 95% CI 0.05 to 10.61; I2 = 32%; 3 studies, 322 participants; low-certainty evidence), hospital stay (MD -0.94 day, 95% CI -1.95 to 0.07; I2 = 17%; 7 studies, 569 participants; moderate-certainty evidence), and operating time or total anaesthetic time (MD 5.76 minutes, 95% CI -3.25 to 14.76; I2 = 44%; 10 studies, 803 participants; moderate-certainty evidence).  AUTHORS' CONCLUSIONS: Overall, compared with no RIPC, RIPC probably leads to little or no difference in perioperative mortality, myocardial infarction, renal impairment, stroke, hospital stay, and operating time, and may lead to little or no difference in limb loss in people undergoing elective major vascular and endovascular surgery. Adequately powered and designed randomised studies are needed, focusing in particular on the clinical endpoints and patient-centred outcomes.

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.

Interaction of Cardiovascular Nonmodifiable Risk Factors, Comorbidities and Comedications With Ischemia/Reperfusion Injury and Cardioprotection by Pharmacological Treatments and Ischemic Conditioning

Preconditioning, postconditioning, and remote conditioning of the myocardium enhance the ability of the heart to withstand a prolonged ischemia/reperfusion insult and the potential to provide novel therapeutic paradigms for cardioprotection. While many signaling pathways leading to endogenous cardioprotection have been elucidated in experimental studies over the past 30 years, no cardioprotective drug is on the market yet for that indication. One likely major reason for this failure to translate cardioprotection into patient benefit is the lack of rigorous and systematic preclinical evaluation of promising cardioprotective therapies prior to their clinical evaluation, since ischemic heart disease in humans is a complex disorder caused by or associated with cardiovascular risk factors and comorbidities. These risk factors and comorbidities induce fundamental alterations in cellular signaling cascades that affect the development of ischemia/reperfusion injury and responses to cardioprotective interventions. Moreover, some of the medications used to treat these comorbidities may impact on cardioprotection by again modifying cellular signaling pathways. The aim of this article is to review the recent evidence that cardiovascular risk factors as well as comorbidities and their medications may modify the response to cardioprotective interventions. We emphasize the critical need for taking into account the presence of cardiovascular risk factors as well as comorbidities and their concomitant medications when designing preclinical studies for the identification and validation of cardioprotective drug targets and clinical studies. This will hopefully maximize the success rate of developing rational approaches to effective cardioprotective therapies for the majority of patients with multiple comorbidities. SIGNIFICANCE STATEMENT: Ischemic heart disease is a major cause of mortality; however, there are still no cardioprotective drugs on the market. Most studies on cardioprotection have been undertaken in animal models of ischemia/reperfusion in the absence of comorbidities; however, ischemic heart disease develops with other systemic disorders (e.g., hypertension, hyperlipidemia, diabetes, atherosclerosis). Here we focus on the preclinical and clinical evidence showing how these comorbidities and their routine medications affect ischemia/reperfusion injury and interfere with cardioprotective strategies.

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.

Potential physiological responses contributing to the ergogenic effects of acute ischemic preconditioning during exercise: A narrative review

Ischemic preconditioning (IPC) has been reported to augment exercise performance, but there is considerable heterogeneity in the magnitude and frequency of performance improvements. Despite a burgeoning interest in IPC as an ergogenic aid, much is still unknown about the physiological mechanisms that mediate the observed performance enhancing effects. This narrative review collates those physiological responses to IPC reported in the IPC literature and discusses how these responses may contribute to the ergogenic effects of IPC. Specifically, this review discusses documented central and peripheral cardiovascular responses, as well as selected metabolic, neurological, and perceptual effects of IPC that have been reported in the literature.

Myocardial Protection and Current Cancer Therapy: Two Opposite Targets with Inevitable Cost

Myocardial protection against ischemia/reperfusion injury (IRI) is mediated by various ligands, activating different cellular signaling cascades. These include classical cytosolic mediators such as cyclic-GMP (c-GMP), various kinases such as Phosphatydilinositol-3- (PI3K), Protein Kinase B (Akt), Mitogen-Activated-Protein- (MAPK) and AMP-activated (AMPK) kinases, transcription factors such as signal transducer and activator of transcription 3 (STAT3) and bioactive molecules such as vascular endothelial growth factor (VEGF). Most of the aforementioned signaling molecules constitute targets of anticancer therapy; as they are also involved in carcinogenesis, most of the current anti-neoplastic drugs lead to concomitant weakening or even complete abrogation of myocardial cell tolerance to ischemic or oxidative stress. Furthermore, many anti-neoplastic drugs may directly induce cardiotoxicity via their pharmacological effects, or indirectly via their cardiovascular side effects. The combination of direct drug cardiotoxicity, indirect cardiovascular side effects and neutralization of the cardioprotective defense mechanisms of the heart by prolonged cancer treatment may induce long-term ventricular dysfunction, or even clinically manifested heart failure. We present a narrative review of three therapeutic interventions, namely VEGF, proteasome and Immune Checkpoint inhibitors, having opposing effects on the same intracellular signal cascades thereby affecting the heart. Moreover, we herein comment on the current guidelines for managing cardiotoxicity in the clinical setting and on the role of cardiovascular confounders in cardiotoxicity.

Spinal cord astrocytes regulate myocardial ischemia-reperfusion injury

Astrocytes play a key role in the response to injury and noxious stimuli, but its role in myocardial ischemia-reperfusion (I/R) injury remains largely unknown. Here we determined whether manipulation of spinal astrocyte activity affected myocardial I/R injury and the underlying mechanisms. By ligating the left coronary artery to establish an in vivo I/R rat model, we observed a 1.7-fold rise in glial fibrillary acidic protein (GFAP) protein level in spinal cord following myocardial I/R injury. Inhibition of spinal astrocytes by intrathecal injection of fluoro-citrate, an astrocyte inhibitor, decreased GFAP immunostaining and reduced infarct size by 29% relative to the I/R group. Using a Designer Receptor Exclusively Activated by Designer Drugs (DREADD) chemogenetic approach, we bi-directionally manipulated astrocyte activity employing GFAP promoter-driven Gq- or Gi-coupled signaling. The Gq-DREADD-mediated activation of spinal astrocytes caused transient receptor potential vanilloid 1 (TRPV1) activation and neuropeptide release leading to a 1.3-fold increase in infarct size, 1.2-fold rise in serum norepinephrine level and higher arrhythmia score relative to I/R group. In contrast, Gi-DREADD-mediated inhibition of spinal astrocytes suppressed TRPV1-mediated nociceptive signaling, resulting in 35% reduction of infarct size and 51% reduction of arrhythmia score from I/R group, as well as lowering serum norepinephrine level from 3158 ± 108 to 2047 ± 95 pg/mL. Further, intrathecal administration of TRPV1 or neuropeptide antagonists reduced infarct size and serum norepinephrine level. These findings demonstrate a functional role of spinal astrocytes in myocardial I/R injury and provide a novel potential therapeutic approach targeting spinal cord astrocytes for the prevention of cardiac injury.

Cerebral protection by remote ischemic post-conditioning in patients with ischemic stroke: A systematic review and meta-analysis of randomized controlled trials

Background

There is evidence that remote limb ischemic postconditioning (RIPostC) can reduce ischemia-reperfusion injury (IRI) and improve the prognosis of patients with ischemic stroke. However, so far, only few relevant clinical studies have been conducted. Therefore, we carried out a meta-analysis of eligible randomized controlled trials to compare the RIPostC group with a control group (no intervention or sham surgery) in patients with ischemic stroke.

Methods

Four English-language publication databases, PubMed, Cochrane, Embase, and Web of Science, were systematically searched up to March 2022. The data were analyzed using Review Manager fixed-effects and random-effects models.

Results

A total of 12 studies were included, and 11 of those were analyzed quantitatively. Compared to controls, The RIPostC group showed significantly reduced NIHHS scores in patients with ischemic stroke, (MD: −1.09, 95% confidence interval [CI]: −1.60, −0.57, P < 0.0001) and improved patients' Montreal Cognitive Assessment (MoCA) scores, (MD: 1.89, 95% CI: 0.78, 3.00, P = 0.0009), Our results showed that RIPostC is safe, (RR = 0.81, 95%CI: 0.61, 1.08, P = 0.15).

Conclusion

Our meta-analysis showed that RIPostC is safe and effective and has a positive cerebral protective effect in patients with ischemic stroke, which is safe and effective, and future large-sample, multicenter trials are needed to validate the cerebral protective effect of RIPostC.

Adaptive mechanisms in no flow vs. low flow ischemia in equine jejunum epithelium: Different paths to the same destination

Intestinal ischemia reperfusion injury (IRI) is a frequent complication of equine colic. Several mechanisms may be involved in adaptation of the intestinal epithelium to IRI and might infer therapeutic potential, including hypoxia-inducible factor (HIF) 1α, AMP-activated protein kinase (AMPK), nuclear factor-erythroid 2-related factor 2 (NRF2), and induction of autophagy. However, the mechanisms supporting adaptation and thus cellular survival are not completely understood yet. We investigated the activation of specific adaptation mechanisms in both no and low flow ischemia and reperfusion simulated in equine jejunum epithelium in vivo. We found an activation of HIF1α in no and low flow ischemia as indicated by increased levels of HIF1α target genes and phosphorylation of AMPKα tended to increase during ischemia. Furthermore, the protein expression of the autophagy marker LC3B in combination with decreased expression of nuclear-encoded mitochondrial genes indicates an increased rate of mitophagy in equine intestinal IRI, possibly preventing damage by mitochondria-derived reactive oxygen species (ROS). Interestingly, ROS levels were increased only shortly after the onset of low flow ischemia, which may be explained by an increased antioxidative defense, although NFR2 was not activated in this setup. In conclusion, we could demonstrate that a variety of adaptation mechanisms manipulating different aspects of cellular homeostasis are activated in IRI irrespective of the ischemia model, and that mitophagy might be an important factor for epithelial survival following small intestinal ischemia in horses that should be investigated further.

Electroacupuncture pre-treatment alleviates sepsis-induced cardiac inflammation and dysfunction by inhibiting the calpain-2/STAT3 pathway

Electroacupuncture (EA) has both anti-inflammatory and cardio-protective effects. Activation of calpain pathway is involved in several myocardiopathy. In sepsis, the role of calpain-2-regulated STAT3 in cardio-protective mechanism of electroacupuncture remains unclear. In this study, we aimed to elucidate the mechanism by which electroacupuncture reduces cardiac inflammation and apoptosis and improves cardiac function during sepsis. Electroacupuncture pretreatment for 7 days was applied in septic cardiomyopathy model induced by lipopolysaccharide (LPS). lipopolysaccharide-induced sepsis was associated with a dramatically systemic inflammation and cardiac dysfunction, which was alleviated by electroacupuncture pre-treatment. Lipopolysaccharide resulted in increases of pro-inflammatory factors (TNF-α,IL1βand IL-6) and apoptosis (TUNEL staining and BAX/Bcl2) via activation of calpain-2/STAT3 pathway.Electroacupuncture pre-treatment inhibited LPS-induced activation of cardiac calpain-2/STAT3 signalling and ameliorated inflammatory and apoptosis. Additionally, inhibition of calpain-2 expression using the corresponding siRNA decreased the Phosphorylation of STAT3,pro-inflammatory factors and apoptosis in lipopolysaccharide- treated cardiomyocytes, confirming that calpain-2 activated p-STAT3 participate in septic cardiomyopathy. Furthermore, suppression of STAT3 by stattic enhanced anti-inflammatory and anti-apoptosis effects of electroacupuncture. These findings reveal mechanisms of electroacupuncture preconditioning protection against cardiac inflammation and apoptosis in sepsis mouse via calpain-2/STAT3 pathway and may provide novel targets for clinical treatments of the sepsis-induced cardiac dysfunction.

Neuroprotective effect of remote ischemic preconditioning in patients undergoing cardiac surgery: A randomized controlled trial

Background

The neuroprotective effect of remote ischemic preconditioning (RIPC) in patients undergoing elective cardiopulmonary bypass (CPB)-assisted coronary artery bypass graft (CABG) or valvular cardiac surgery remains unclear.

Methods

A randomized, double-blind, placebo-controlled superior clinical trial was conducted in patients undergoing elective on-pump coronary artery bypass surgery or valve surgery. Before anesthesia induction, patients were randomly assigned to RIPC (three 5-min cycles of inflation and deflation of blood pressure cuff on the upper limb) or the control group. The primary endpoint was the changes in S-100 calcium-binding protein β (S100-β) levels at 6 h postoperatively. Secondary endpoints included changes in Neuron-specific enolase (NSE), Mini-mental State Examination (MMSE), and Montreal Cognitive Assessment (MoCA) levels.

Results

A total of 120 patients [mean age, 48.7 years; 36 women (34.3%)] were randomized at three cardiac surgery centers in China. One hundred and five patients were included in the modified intent-to-treat analysis (52 in the RIPC group and 53 in the control group). The primary result demonstrated that at 6 h after surgery, S100-β levels were lower in the RIPC group than in the control group (50.75; 95% confidence interval, 67.08 to 64.40 pg/ml vs. 70.48; 95% CI, 56.84 to 84.10 pg/ml, P = 0.036). Compared to the control group, the concentrations of S100-β at 24 h and 72 h and the concentration of NSE at 6 h, 24 h, and 72 h postoperatively were significantly lower in the RIPC group. However, neither the MMSE nor the MoCA revealed significant between-group differences in postoperative cognitive performance at 7 days, 3 months, and 6 months after surgery.

Conclusion

In patients undergoing CPB-assisted cardiac surgery, RIPC attenuated brain damage as indicated with the decreased release of brain damage biomarker S100-β and NSE.

Clinical trial registration

[ClinicalTrials.gov], identifier [NCT01231789].

Preclinical multi-target strategies for myocardial ischemia-reperfusion injury

Despite promising breakthroughs in diagnosing and treating acute coronary syndromes, cardiovascular disease’s high global mortality rate remains indisputable. Nearly half of these patients died of ischemic heart disease. Primary percutaneous coronary intervention (PCI) and coronary artery bypass grafting can rapidly restore interrupted blood flow and become the most effective method for salvaging viable myocardium. However, restoring blood flow could increase the risk of other complications and myocardial cell death attributed to myocardial ischemia-reperfusion injury (IRI). How to reduce the damage of blood reperfusion to ischemic myocardium has become an urgent problem to be solved. In preclinical experiments, many treatments have substantial cardioprotective effects against myocardial IRI. However, the transition from these cardioprotective therapies to clinically beneficial therapies for patients with acute myocardial infarction remains elusive. The reasons for the failure of the clinical translation may be multi-faceted, and three points are summarized here: (1) Our understanding of the complex pathophysiological mechanisms of myocardial IRI is far from enough, and the classification of specific therapeutic targets is not rigorous, and not clear enough; (2) Most of the clinical patients have comorbidities, and single cardioprotective strategies including ischemia regulation strategies cannot exert their due cardioprotective effects under conditions of hyperglycemia, hypertension, hyperlipidemia, and aging; (3) Most preclinical experimental results are based on adult, healthy animal models. However, most clinical patients had comorbidities and received multiple drug treatments before reperfusion therapy. In 2019, COST Action proposed a multi-target drug combination initiative for prospective myocardial IRI; the optimal cardioprotective strategy may be a combination of additive or synergistic multi-target therapy, which we support. By establishing more reasonable preclinical models, screening multi-target drug combinations more in line with clinical practice will benefit the translation of clinical treatment strategies.

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

The Hatter Cardiovascular Institute biennial workshop, originally scheduled for April 2020 but postponed for 2 years due to the Covid pandemic, was organised to debate and discuss the future of Remote Ischaemic Conditioning (RIC). This evolved from the large multicentre CONDI-2-ERIC-PPCI outcome study which demonstrated no additional benefit when using RIC in the setting of ST-elevation myocardial infarction (STEMI). The workshop discussed how conditioning has led to a significant and fundamental understanding of the mechanisms preventing cell death following ischaemia and reperfusion, and the key target cyto-protective pathways recruited by protective interventions, such as RIC. However, the obvious need to translate this protection to the clinical setting has not materialised largely due to the disconnect between preclinical and clinical studies. Discussion points included how to adapt preclinical animal studies to mirror the patient presenting with an acute myocardial infarction, as well as how to refine patient selection in clinical studies to account for co-morbidities and ongoing therapy. These latter scenarios can modify cytoprotective signalling and need to be taken into account to allow for a more robust outcome when powered appropriately. The workshop also discussed the potential for RIC in other disease settings including ischaemic stroke, cardio-oncology and COVID-19. The workshop, therefore, put forward specific classifications which could help identify so-called responders vs. non-responders in both the preclinical and clinical settings.

Triiodothyronine improves contractile recovery of human atrial trabeculae after hypoxia/reoxygenation

BACKGROUND

In patients undergoing interventional or surgical coronary revascularization, subclinical hypothyroidism is common and associated with worse outcome, including the need for postoperative inotropic support. In isolated rat hearts with global ischemia/reperfusion, exogenous triiodothyronine (T3) reduces infarct size. Aim of this study was, to investigate whether or not exogenous T3 protects human myocardium from ischemia/reperfusion injury.

METHODS

Right atrial trabeculae from patients undergoing routine coronary artery bypass grafting were isolated and transferred to Tyrode's buffer. Electrically initiated (1 Hz) contractile stress (mN/mm²) was recorded for 10 min at baseline (95% O₂/ 5% CO₂, glucose). Sixty min hypoxia were induced by changing buffer gas and increasing stimulation rate (95% N₂/ 5% CO₂, choline chloride, 3 Hz) before return to reoxygenation for 30 min. T3 (500 μg/l) vs. NaOH (solvent control) was administered A) throughout (n = 11 vs. n = 9) or B) only 15 min before and during reoxygenation (n = 12 vs. n = 13). Western blot analyses of established cardioprotective signaling proteins were performed.

RESULTS

At baseline, contractile stress was comparable. T3 improved the cumulative recovery of contractile stress during reoxygenation from 41 ± 16 with NaOH to 55 ± 11% of baseline with T3, when given continuously in A or from 52 ± 13 with NaOH to 63 ± 11% of baseline with T3 when given just before and during reoxygenation in B. The ratio of mitochondrial complex I matrix arm to membrane NADH:ubiquinone oxidoreductase subunits (NDUF)V2 to NDUFA9 was reduced, reflecting increased complex I activity.

CONCLUSION

T3 increases contractile recovery of human right atrial trabeculae from hypoxia/reoxygenation.

Remote ischaemic preconditioning - translating cardiovascular benefits to humans

Remote ischaemic preconditioning (RIPC), induced by intermittent periods of limb ischaemia and reperfusion, confers cardiac and vascular protection from subsequent ischaemia–reperfusion (IR) injury. Early animal studies reliably demonstrate that RIPC attenuated infarct size and preserved cardiac tissue. However, translating these adaptations to clinical practice in humans has been challenging. Large clinical studies have found inconsistent results with respect to RIPC eliciting IR injury protection or improving clinical outcomes. Follow‐up studies have implicated several factors that potentially affect the efficacy of RIPC in humans such as age, fitness, frequency, disease state and interactions with medications. Thus, realizing the clinical potential for RIPC may require a human experimental model where confounding factors are more effectively controlled and underlying mechanisms can be further elucidated. In this review, we highlight recent experimental findings in the peripheral circulation that have added valuable insight on the mechanisms and clinical benefit of RIPC in humans. Central to this discussion is the critical role of timing (i.e. immediate vs. delayed effects following a single bout of RIPC) and the frequency of RIPC. Limited evidence in humans has demonstrated that repeated bouts of RIPC over several days uniquely improves vascular function beyond that observed with a single bout alone. Since changes in resistance vessel and microvascular function often precede symptoms and diagnosis of cardiovascular disease, repeated bouts of RIPC may be promising as a preclinical intervention to prevent or delay cardiovascular disease progression.

Remote Conditioning by Rhythmic Compression of Limbs Ameliorated Myocardial Infarction by Downregulation of Inflammation via A2 Adenosine Receptors

Background

Remote ischemic conditioning (RIC) is a cardioprotective phenomenon, yet transient ischemia is not a requisite trigger for remote cardioprotection. In fact, RIC is a stimulus compound containing interruption of the blood vessel and tissue compression. In this study, we evaluate the effects of remote tissue compression on infarct size after myocardial infarction and explore its preliminary mechanisms.

Methods and Results

We used a murine model of myocardial infarction to assess ischemia injury and identified remote conditioning by rhythmic compression on forelimb as a novel cardioprotective intervention. We show that the cardioprotective signal transduction of remote conditioning from the trigger limb to the heart involves the release of adenosine. Our results demonstrate that A2a and A2b receptors are indispensable parts for cardioprotection of remote conditioning, which is linked to its anti-inflammatory properties by the subsequent activation of cAMP/PKA/NF-κB axis.

Conclusion

Our results establish a new connection between remote tissue compression and cardiovascular diseases, which enhances our cognition about the role of tissue compression on RIC cardioprotection.

A TRICk to Improve the Effectiveness of RIC: Role of Limb Temperature in Enhancing the Effectiveness of Remote Ischemic Conditioning

Simple Summary

Remote ischemic conditioning is a simple cardioprotective practice consisting in brief intermittent ischemia applied to a limb. Remote ischemic conditioning has been repeatedly validated in animal models. However, translation from animal experiments to clinics for remote ischemic conditioning has been disappointing. We have demonstrated that keeping the animal’s limb warm while performing intermittent ischemia reduces infarct size more effectively than cold intermittent ischemia; thus, we propose that a more accurate temperature control of the limb undergoing remote ischemic conditioning can increase the efficacy of this cardioprotective maneuver. A simple thermal blanket around the ischemic limb while performing remote ischemic conditioning could be an easy approach to test in humans, as it is simple and safe.

Abstract

Background: Treatment of myocardial ischemia/reperfusion (IR) injury is still an unmet clinical need. A large variability of remote ischemic conditioning (RIC) protection has been reported; however, no studies have considered the temperature of the ischemic limb. We analyzed the effects of temperature on RIC protection. Methods: Left hind-limbs of anesthetized male mice were immersed in warm (40 °C, warm-RIC) or cold (20 °C, cold-RIC) water and subjected to a RIC protocol (4 × 5 min limb ischemia/reperfusion). In the control groups (warm-CTR or cold-CTR), the limbs underwent thermic conditions only. Isolated hearts underwent 30 min ischemia and 60 min reperfusion. A PI3K-inhibitor, LY294002 (5 µM), was infused in warm-RIC hearts before the IR protocol (warm-RIC LY). Infarct size was evaluated by nitro blue tetrazolium staining and expressed as the percent of risk area. Results: While cold-RIC did not reduce the infarct size compared to cold-CTR (51 ± 1.62% vs. 54 ± 1.07% of risk area, p = NS), warm-RIC (44 ± 1.13%) significantly reduced the infarct size with respect to either cold-RIC (p < 0.001) or warm-CTR (58 ± 1.41%, p < 0.0001). LY294002 infusion revealed the PI3K/Akt involvement in the warm-RIC protection. Infarct size reduction was abrogated by LY294002 pretreatment (warm-RIC: 44 ± 1.13% vs. warm-CTR 58 ± 1.41% p < 0.0001; vs. warm-RIC LY 54 ± 1.69% p = 0.0002). Conclusion: our study shows a remarkable difference between warm-RIC and cold-RIC in terms of infarct size reduction, supporting a pivotal role for limb temperature in RIC-induced cardioprotection.

Remote cyclic compression ameliorates myocardial infarction injury in rats via AMPK-dependent pathway

BACKGROUND

Remote ischemic conditioning (RIC) displays a cardioprotective role in acute myocardial infarction (AMI). Since interruption of blood vessel is not an essential trigger of remote cardioprotection, tissue compression may play a prominent part in the effect. The purpose of this study was to confirm the protective effect of tissue compression on AMI and the underlying mechanisms.

METHODS AND RESULTS

Rat model of AMI was induced by ligation of the left anterior descending coronary artery. Remote cyclic compression (RCC) on forelimb was applied to AMI rats for 3 days after the operation. RCC postconditioning displayed cardioprotective effects against AMI injury by limiting infarct size, alleviating cardiac dysfunction, and suppressing cardiomyocyte apoptosis. In addition, RCC postconditioning induced myocardial autophagy as evidenced by increased LC3-II and Beclin-1 and reduced mTOR levels. Furthermore, RCC treatment upregulated AMPK phosphorylation in the context of AMI hearts. AMPK inhibitor Compound C administration markedly abrogated RCC-mediated cardioprotective effect, as evidenced by decreased infarct size and cardiac function.

CONCLUSION

Our results indicated that RCC postconditioning could attenuate AMI injury through inhibiting apoptosis and promoting autophagy via AMPK signaling pathway. The research provided a novel perspective for studying the cardioprotection of RIC and possible therapeutic strategy for managing AMI injury.

Sympathetic nerve innervation and metabolism in ischemic myocardium in response to remote ischemic perconditioning

Sympathetic nerve denervation after myocardial infarction (MI) predicts risk of sudden cardiac death. Therefore, therapeutic approaches limit infarct size, improving adverse remodeling and restores sympathetic innervation have a great clinical potential. Remote ischemic perconditioning (RIPerc) could markedly attenuate MI-reperfusion (MIR) injury. In this study, we aimed to assess its effects on cardiac sympathetic innervation and metabolism. Transient myocardial ischemia is induced by ligature of the left anterior descending coronary artery (LAD) in male Sprague-Dawley rats, and in vivo cardiac 2-[¹⁸F]FDG and [¹¹C]mHED PET scans were performed at 14-15 days after ischemia. RIPerc was induced by three cycles of 5-min-long unilateral hind limb ischemia and intermittent 5 min of reperfusion during LAD occlusion period. The PET quantitative parameters were quantified in parametric polar maps. This standardized format facilitates the regional radioactive quantification in deficit regions to remote areas. The ex vivo radionuclide distribution was additionally identified using autoradiography. Myocardial neuron density (tyrosine hydroxylase positive staining) and chondroitin sulfate proteoglycans (CSPG, inhibiting neuron regeneration) expression were assessed by immunohistochemistry. There was no significant difference in the mean hypometabolism 2-[¹⁸F]FDG uptake ratio (44.6 ± 4.8% vs. 45.4 ± 4.4%) between MIR rats and MIR + RIPerc rats (P > 0.05). However, the mean [¹¹C]mHED nervous activity of denervated myocardium was significantly elevated in MIR + RIPerc rats compared to the MIR rats (35.9 ± 7.1% vs. 28.9 ± 2.3%, P < 0.05), coupled with reduced denervated myocardium area (19.5 ± 5.3% vs. 27.8 ± 6.6%, P < 0.05), which were associated with preserved left-ventricular systolic function, a less reduction in neuron density, and a significant reduction in CSPG and CD68 expression in the myocardium. RIPerc presented a positive effect on cardiac sympathetic-nerve innervation following ischemia, but showed no significant effect on myocardial metabolism.

Bioassays of Humoral Cardioprotective Factors Released by Remote Ischemic Conditioning in Patients Undergoing Coronary Artery Bypass Surgery

Remote ischemic conditioning (RIC) induces the release of circulating cardioprotective factors and attenuates myocardial ischemia/reperfusion injury. Evidence for such humoral cardioprotective factor(s) is derived from transfer with plasma (derivatives) from one individual undergoing RIC to another individual's heart, even across species. With transfer into an isolated perfused heart, only a single plasma (derivative) sample can be studied with infarct size as endpoint, and therefore the comparison of samples before and after RIC or between RIC and placebo is hampered by the inter-individual variation of infarct sizes in isolated perfused hearts. We therefore developed a preparation of cardiomyocytes from a single mouse heart, where aliquots of the same heart can undergo hypoxia/reoxygenation (H/R) with exposure to buffer, RIC, or placebo samples without or with pharmacological blockade. To validate this approach, we used plasma dialysates taken before and after RIC from patients undergoing coronary bypass grafting who had experienced protection by RIC (troponin release ↓ by 28% vs placebo). The cardiomyocyte bioassay had little variation after H/R with buffer (mean ± standard deviation; 7% ± 2% viable cells) and demonstrated preserved viability after RIC (15% ± 5% vs 6% ± 3% before). For comparison, infarct size in isolated mouse hearts after global ischemia and reperfusion was 22% ± 14% of left ventricular mass after versus 42% ± 14% before RIC. Stattic, an inhibitor of signal transducer and activator of transcription (STAT)3 protein, abrogated protection in the cardiomyocytes. We have thus established a cardiomyocyte bioassay to analyze RIC's protection which minimizes inter-individual variation and the use of animals.

Why is endothelial resilience key to maintain cardiac health?

Myocardial injury as induced by myocardial infarction results in tissue ischemia, which critically incepts cardiomyocyte death. Endothelial cells play a crucial role in restoring oxygen and nutrient supply to the heart. Latest advances in single-cell multi-omics, together with genetic lineage tracing, reveal a transcriptional and phenotypical adaptation to the injured microenvironment, which includes alterations in metabolic, mesenchymal, hematopoietic and pro-inflammatory signatures. The extent of transition in mesenchymal or hematopoietic cell lineages is still debated, but it is clear that several of the adaptive phenotypical changes are transient and endothelial cells revert back to a naïve cell state after resolution of injury responses. This resilience of endothelial cells to acute stress responses is important for preventing chronic dysfunction. Here, we summarize how endothelial cells adjust to injury and how this dynamic response contributes to repair and regeneration. We will highlight intrinsic and microenvironmental factors that contribute to endothelial cell resilience and may be targetable to maintain a functionally active, healthy microcirculation.

Chronic Limb Remote Ischemic Conditioning may have an Antihypertensive Effect in Patients with Hypertension

Hypertension is the leading preventable risk factor for all-cause morbidity and mortality worldwide. Despite antihypertensive medications have been available for decades, a big challenge we are facing is to increase the blood pressure (BP) control rate among the population. Therefore, it is necessary to search for new antihypertensive means to reduce the burden of disease caused by hypertension. Limb remote ischemic conditioning (LRIC) can trigger endogenous protective effects through transient and repeated ischemia on the limb to protect specific organs and tissues including the brain, heart, and kidney. The mechanisms of LRIC involve the regulation of the autonomic nervous system, releasing humoral factors, improvement of vascular endothelial function, and modulation of immune/inflammatory responses. These underlying mechanisms of LRIC may restrain the pathogenesis of hypertension through multiple pathways theoretically, leading to a potential decline in BP. Several existing studies have explored the impact of LRIC on BP, however, controversial findings were reported. To explore the potential antihypertensive effect of LRIC and the underlying mechanisms, we systematically reviewed the relevant articles to provide an insight into the novel therapy of hypertension.

Effects of Remote Ischaemic Preconditioning on the Internal Thoracic Artery Nitric Oxide Synthase Isoforms in Patients Undergoing Coronary Artery Bypass Grafting

Remote ischaemic preconditioning (RIPC) is a medical procedure that consists of repeated brief periods of transient ischaemia and reperfusion of distant organs (limbs) with the ability to provide internal organ protection from ischaemia. Even though RIPC has been successfully applied in patients with myocardial infarction during coronary revascularization (surgery/percutaneous angioplasty), the underlying molecular mechanisms are yet to be clarified. Thus, our study aimed to determine the role of nitric oxide synthase (NOS) isoforms in RIPC-induced protection (3 × 5 min of forearm ischaemia with 5 min of reperfusion) of arterial graft in patients undergoing urgent coronary artery bypass grafting (CABG). We examined RIPC effects on specific expression and immunolocalization of three NOS isoforms — endothelial (eNOS), inducible (iNOS) and neuronal (nNOS) in patients’ internal thoracic artery (ITA) used as a graft. We found that the application of RIPC protocol leads to an increased protein expression of eNOS, which was further confirmed with strong eNOS immunopositivity, especially in the endothelium and smooth muscle cells of ITA. The same analysis of two other NOS isoforms, iNOS and nNOS, showed no significant differences between patients undergoing CABG with or without RIPC. Our results demonstrate RIPC-induced upregulation of eNOS in human ITA, pointing to its significance in achieving protective phenotype on a systemic level with important implications for graft patency.

Interactions between remote ischemic conditioning and post-stroke sleep regulation

Sleep disturbances are common in patients with stroke, and sleep quality has a critical role in the onset and outcome of stroke. Poor sleep exacerbates neurological injury, impedes nerve regeneration, and elicits serious complications. Thus, exploring a therapy suitable for patients with stroke and sleep disturbances is imperative. As a multi-targeted nonpharmacological intervention, remote ischemic conditioning can reduce the ischemic size of the brain, improve the functional outcome of stroke, and increase sleep duration. Preclinical/clinical evidence showed that this method can inhibit the inflammatory response, mediate the signal transductions of adenosine, activate the efferents of the vagal nerve, and reset the circadian clocks, all of which are involved in sleep regulation. In particular, cytokines tumor necrosis factor α (TNFα) and adenosine are sleep factors, and electrical vagal nerve stimulation can improve insomnia. On the basis of the common mechanisms of remote ischemic conditioning and sleep regulation, a causal relationship was proposed between remote ischemic conditioning and post-stroke sleep quality.

Effects of remote ischemic preconditioning (RIPC) and chronic remote ischemic preconditioning (cRIPC) on levels of plasma cytokines, cell surface characteristics of monocytes and in-vitro angiogenesis: a pilot study

Remote ischemic preconditioning (RIPC) protects the heart against myocardial ischemia/reperfusion (I/R) injury and recent work also suggested chronic remote ischemic conditioning (cRIPC) for cardiovascular protection. Based on current knowledge that systemic immunomodulatory effects of RIPC and the anti-inflammatory capacity of monocytes might be involved in cardiovascular protection, the aim of our study was to evaluate whether RIPC/cRIPC blood plasma is able to induce in-vitro angiogenesis, identify responsible factors and evaluate the effects of RIPC/cRIPC on cell surface characteristics of circulating monocytes. Eleven healthy volunteers were subjected to RIPC/cRIPC using a blood pressure cuff inflated to > 200 mmHg for 3 × 5 min on the upper arm. Plasma and peripheral blood monocytes were isolated before RIPC (Control), after 1 × RIPC (RIPC) and at the end of 1 week of daily RIPC (cRIPC) treatment. Plasma concentrations of potentially pro-angiogenic humoral factors (CXCL5, Growth hormone, IGFBP3, IL-1α, IL-6, Angiopoietin 2, VEGF, PECAM-1, sTie-2, IL-8, MCSF) were measured using custom made multiplex ELISA systems. Tube formation assays for evaluation of in-vitro angiogenesis were performed with donor plasma, monocyte conditioned culture media as well as IL-1α, CXCL5 and Growth hormone. The presence of CD14, CD16, Tie-2 and CCR2 was analyzed on monocytes by flow cytometry. Employing in-vitro tube formation assays, several parameters of angiogenesis were significantly increased by cRIPC plasma (number of nodes, P < 0.05; number of master junctions, P < 0.05; number of segments, P < 0.05) but were not influenced by culture medium from RIPC/cRIPC treated monocytes. While RIPC/cRIPC treatment did not lead to significant changes of the median plasma concentrations of any of the selected potentially pro-angiogenic humoral factors, in-depth analysis of the individual subjects revealed differences in plasma levels of IL-1α, CXCL5 and Growth hormone after RIPC/cRIPC treatment in some of the volunteers. Nevertheless, the positive effects of RIPC/cRIPC plasma on in-vitro angiogenesis could not be mimicked by the addition of the respective humoral factors alone or in combination. While monocyte conditioned culture media did not affect in-vitro tube formation, flow cytometry analyses of circulating monocytes revealed a significant increase in the number of Tie-2 positive and a decrease of CCR2 positive monocytes after RIPC/cRIPC (Tie-2: cRIPC, P < 0.05; CCR2: RIPC P < 0.01). Cardiovascular protection may be mediated by RIPC and cRIPC via a regulation of plasma cytokines as well as changes in cell surface characteristics of monocytes (e.g. Tie-2). Our results suggest that a combination of humoral and cellular factors could be responsible for the RIPC/cRIPC mediated effects and that interindividual variations seem to play a considerable part in the RIPC/cRIPC associated mechanisms.