Transient limb ischemia induces remote ischemic preconditioning in vivo

Remote ischemic post‑conditioning alleviates ischemia/reperfusion‑induced intestinal injury via the ERK signaling pathway‑mediated RAGE/HMGB axis

Intestinal ischemia reperfusion (I/R) injury is a tissue and organ injury that frequently occurs during surgery and significantly contributes to the pathological processes of severe infection, injury, shock, cardiopulmonary insufficiency and other diseases. However, the mechanism of intestinal I/R injury remains to be elucidated. A mouse model of intestinal I/R injury was successfully established and the model mice were treated with remote ischemic post‑conditioning (RIPOC) and/or an ERK inhibitor (CC‑90003), respectively. Histopathological changes of the intestinal mucosa were determined by hematoxylin and eosin staining. In addition, the levels of high‑mobility group box 1 (HMGB1) and receptor for advanced glycation end products (RAGE) expression were confirmed by reverse transcription‑quantitative polymerase chain reaction, western blotting and immunohistochemistry assays. The levels of antioxidants, oxidative stress markers (8‑OHdG) and interleukin 1 family members were evaluated by ELISA assays and the levels of NF‑κB pathway proteins were analyzed by western blotting. The data demonstrated that RIPOC could attenuate the histopathological features of intestinal mucosa in the intestinal I/R‑injury mouse models via the ERK pathway. It was also revealed that HMGB1 and RAGE expression in the mouse models could be markedly reduced by RIPOC (P<0.05) and that these reductions were associated with inhibition of the ERK pathway. Furthermore, it was demonstrated that RIPOC produced significant antioxidant and anti‑inflammatory effects following an intestinal I/R injury and that these effects were mediated via the ERK pathway (P<0.05). In addition, RIPOC was demonstrated to suppress the NF‑κB (p65)/NLR family pyrin domain containing 3 (NLRP3) inflammatory pathways in the intestinal I/R injury mouse models via the ERK pathway. The findings of the present study demonstrated that RIPOC helped to protect mice with an intestinal I/R injury by downregulating the ERK pathway.

The Effects of Ischemia During Rest Intervals on Bar Velocity in the Bench Press Exercise With Different External Loads

The main aim of the present study was to evaluate the acute effects of ischemia used during rest periods on bar velocity changes during the bench press exercise at progressive loads, from 20 to 90% of 1RM. Ten healthy resistance trained men volunteered for the study (age = 26.3 ± 4.7 years; body mass = 89.8 ± 6.3 kg; bench press 1RM = 142.5 ± 16.9 kg; training experience = 7.8 ± 2.7 years). During the experimental sessions the subjects performed the bench press exercise under two different conditions, in a randomized and counterbalanced order: (a) ischemia condition, with ischemia applied before the first set and during every rest periods between sets, and (b) control condition where no ischemia was applied. During each experimental session eight sets of the bench press exercise were performed, against loads starting from 20 to 90% 1RM, increased progressively by 10% in each subsequent set. A 3-min rest interval between sets was used. For ischemia condition the cuffs was applied 3 min before the first set and during every rest period between sets. Ischemia was released during exercise. The cuff pressure was set to ∼80% of full arterial occlusion pressure. The two-way repeated measures ANOVA showed a statistically significant interaction effect for peak bar velocity (p = 0.04) and for mean bar velocity (p = 0.01). There was also a statistically significant main effect of condition for peak bar velocity (p < 0.01) but not for mean bar velocity (p = 0.25). The post hoc analysis for interaction showed significantly higher peak bar velocity for the ischemia condition compared to control at a load of 20% 1RM (p = 0.007) and at a load of 50% 1RM (p = 0.006). The results of the present study indicate that ischemia used before each set even for a brief duration of <3 min, has positive effects on peak bar velocity at light loads, but it is insufficient to induce such effect on higher loads.

Effect of Remote Ischemic Conditioning on Bleeding Complications in Surgery: A Systematic Review and Meta-Analysis

Remote ischemic conditioning (RIC) is administered with an inflatable tourniquet by inducing brief, alternating cycles of limb ischemia and reperfusion. RIC possibly impacts the hemostatic system, and the intervention has been tested as protective therapy against ischemia-reperfusion injury and thrombotic complications in cardiac surgery and other surgical procedures. In the present systematic review, we aimed to investigate the effect of RIC on intraoperative and postoperative bleeding complications in meta-analyses of randomized controlled trials including adult patients undergoing surgery. A systematic search was performed on November 7, 2020 in PubMed, Embase, and the Cochrane Central Register of Controlled Trials. Randomized controlled trials comparing RIC versus no RIC in adult patients undergoing surgery that reported bleeding outcomes in English publications were included. Effect estimates with 95% confidence intervals were calculated using the random-effects model for intraoperative and postoperative bleeding outcomes. Thirty-two randomized controlled trials with 3,804 patients were eligible for inclusion. RIC did not affect intraoperative bleeding volume (nine trials; 392 RIC patients, 399 controls) with the effect estimate -0.95 [-9.90; 7.99] mL (p = 0.83). RIC significantly reduced postoperative drainage volume (seven trials; 367 RIC patients, 365 controls) with mean difference -83.6 [-134.9; -32.4] mL (p = 0.001). The risk of re-operation for bleeding was reduced in the RIC group (16 trials; 838 RIC patients, 839 controls), albeit not significantly, with the relative risk 0.65 [0.39; 1.09] (p = 0.10). In conclusion, RIC reduced postoperative bleeding measured by postoperative drainage volume in this meta-analysis of adult patients undergoing surgery.

Remote ischaemic conditioning in ST elevation myocardial infarction: a registry-based randomised trial

OBJECTIVES

Remote ischaemic conditioning (RIC) has been tested as a possible strategy for mitigating reperfusion injury in ST elevation myocardial infarction (STEMI) with primary percutaneous coronary intervention (PPCI). However, surrogate outcomes have shown inconsistent effects with lack of clinical correlation.

METHODS

We performed a registry-based randomised study of patients with STEMI allocated to RIC (4 cycles of blood pressure cuff inflation to 200 mm Hg for 5 min of ischaemia followed by 5 min of reperfusion) or standard of care (SOC) during PPCI. We examined the associations of RIC on core laboratory measurements of myocardial perfusion, infarct size (IS), left ventricular (LV) performance and clinical outcomes.

RESULTS

A total of 252 patients were enrolled. The median age was 61 (IQR: 55-70) years and 72.8% were male. Sum ST segment deviation resolution ≥50% was similar between RIC and SOC (65.2% vs 55.7%, p=0.269). In those with 3-day cardiovascular MRI (n=88), no difference in median (25th, 75th percentiles) IS (14.9% (4.5%, 23.1%) vs 16.1% (3.3%, 22.0%), p=0.980), LV dimensions (LV end-diastolic volume index: 78.7 (71.1, 91.2) mL/m² vs 79.9 (71.2, 88.8) mL/m², p=0.630; LV end-systolic volume index: 48.8 (35.7, 51.4) mL/m² vs 37.9 (31.8, 47.5) mL/m², p=0.551) or ejection fraction (50.0% (41.0%-55.0%) vs 50.0% (43.0%-56.0%), p=0.554) was demonstrated. Similar results were observed with 90-day cardiovascular MRI. At 1 year, the clinical composite of death, congestive heart failure, cardiogenic shock and recurrent myocardial infarction was similar in RIC and SOC (21.7% vs 13.3%, p=0.110).

CONCLUSIONS

In a contemporary registry-based randomised study of patients with STEMI undergoing PPCI, adjunctive therapy with RIC did not improve myocardial perfusion, reduce IS or alter LV performance. Consequently, there was no difference in clinical outcomes within 1 year.

TRIAL REGISTRATION NUMBER

NCT03930589.

The Effects of Ischemic Preconditioning Supplementation on Endothelial Function: A Systematic Review and Meta-Analysis

Objective

Ischemic preconditioning (IPC) has gradually been promoted in clinical practice to lower the risk of cardiovascular surgery and postoperative complications. We investigated the role of IPC on vascular endothelial function and the relationship between IPC, flow-mediated dilation (FMD), and brachial artery diameter (BAD).

Methods

Systematic searches were conducted in PubMed, Medline, Cochrane Library, Embase, and Scopus databases from their inception to March 20, 2020. This research included randomized controlled trials (RCTs) with adults, and the values of FMD and BAD were considered as the primary outcomes. Ten studies comprising 292 participants were included in the meta-analysis.

Results

Regarding FMD, we observed beneficial effects of IPC on endothelial function (standardized mean difference (SMD): 1.82; 95% confidence interval (CI): 0.64, 3.01; p < 0.001; I ² = 89.9%). However, the available evidence did not indicate that IPC affected BAD (SMD: 0.08; 95% CI: -0.03, 0.18; p > 0.05; I ² = 76.5%).

Conclusions

Our meta-analysis indicated a significant effect of IPC on the endothelial function of the blood vessels, affecting FMD but not BAD.

Reducing Cardiac Injury during ST-Elevation Myocardial Infarction: A Reasoned Approach to a Multitarget Therapeutic Strategy

The significant reduction in ‘ischemic time’ through capillary diffusion of primary percutaneous intervention (pPCI) has rendered myocardial-ischemia reperfusion injury (MIRI) prevention a major issue in order to improve the prognosis of ST elevation myocardial infarction (STEMI) patients. In fact, while the ischemic damage increases with the severity and the duration of blood flow reduction, reperfusion injury reaches its maximum with a moderate amount of ischemic injury. MIRI leads to the development of post-STEMI left ventricular remodeling (post-STEMI LVR), thereby increasing the risk of arrhythmias and heart failure. Single pharmacological and mechanical interventions have shown some benefits, but have not satisfactorily reduced mortality. Therefore, a multitarget therapeutic strategy is needed, but no univocal indications have come from the clinical trials performed so far. On the basis of the results of the consistent clinical studies analyzed in this review, we try to design a randomized clinical trial aimed at evaluating the effects of a reasoned multitarget therapeutic strategy on the prevention of post-STEMI LVR. In fact, we believe that the correct timing of pharmacological and mechanical intervention application, according to their specific ability to interfere with survival pathways, may significantly reduce the incidence of post-STEMI LVR and thus improve patient prognosis.

Regular transient limb ischemia protects endothelial function against hypercholesterolemic damage in rabbits

Regular transient limb ischemia (RTLI) can prevent atherosclerosis in hypercholesterolemic rabbits. As endothelial dysfunction is the initial factor leading to atherosclerosis, we investigated the effect of RTLI on endothelial function in hypercholesterolemic rabbits. We randomly allocated 15 New Zealand white rabbits to three groups, five animals per group: the hypercholesterolemic group (Group H), the sham RTLI group (Group S), and the RTLI group (Group L). All rabbits received hypercholesterolemic fodder daily. No intervention was performed on the rabbits in Group H. Rabbits in Group S were kept in hutches, with a deflated cuff applied to their left hind limb for 60 min every day. For rabbits in Group L, RTLI (six cycles of 5-min ischemia and 5-min reperfusion of the left hind limb) was applied once daily for 12 weeks. At the end of week 12, a segment of the abdominal aorta was isolated from each rabbit for in vitro measurement of the endothelium-dependent vasodilation (EDV) response to different concentrations of acetylcholine and the endothelium-independent vasodilation (EIV) response to sodium nitroprusside. The EDV response was significantly higher in Group L than in Groups S and H (p < 0.05), with no significant difference between Groups S and H (p > 0.05). There was no difference in the EIV response among the three groups. RTLI could improve the EDV response, protecting endothelial function against hypercholesterolemic damage.

Ischemic Preconditioning: Modulating Pain Sensitivity and Exercise Performance

Purpose The purpose of this study was to examine whether an individual’s IPC-mediated change in cold pain sensitivity is associated with the same individual’s IPC-mediated change in exercise performance.

Methods Thirteen individuals (8 males; 5 females, 27 ± 7 years, 55 ± 5 ml.kgs^–1.min^–1) underwent two separate cold-water immersion tests: with preceding IPC treatment and without. In addition, each participant undertook two separate 5-km cycling time trials: with preceding IPC treatment and without. Pearson correlation coefficients were used to assess the relationship between an individual’s change in cold-water pain sensitivity following IPC with their change in 5-km time trial performance following IPC.

Results During the cold-water immersion test, pain intensity increased over time (p < 0.001) but did not change with IPC (p = 0.96). However, IPC significantly reduced the total time spent under pain (−9 ± 7 s; p = 0.001) during the cold-water immersion test. No relationship was found between an individual’s change in time under pain (r = −0.2, p = 0.6) or pain intensity (r = −0.3, p = 0.3) following IPC and their change in performance following IPC.

Conclusion These findings suggest that IPC can modulate sensitivity to a painful stimulus, but this altered sensitivity does not explain the ergogenic efficacy of IPC on 5-km cycling performance.

Myocardial remote ischemic preconditioning: from cell biology to clinical application

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

Remote ischemic preconditioning improves tissue oxygenation in a porcine model of controlled hemorrhage without fluid resuscitation

Remote ischemic preconditioning (RIPC) involves deliberate, brief interruptions of blood flow to increase the tolerance of distant critical organs to ischemia. This study tests the effects of limb RIPC in a porcine model of controlled hemorrhage without replacement therapy simulating an extreme field situation of delayed evacuation to definitive care. Twenty-eight pigs (47 ± 6 kg) were assigned to: (1) control, no procedure (n = 7); (2) HS = hemorrhagic shock (n = 13); and (3) RIPC + HS = remote ischemic preconditioning followed by hemorrhage (n = 8). The animals were observed for 7 h after bleeding without fluid replacement. Survival rate between animals of the RIPC + HS group and those of the HS group were similar (HS, 6 of 13[46%]-vs-RIPC + HS, 4 of 8[50%], p = 0.86 by Chi-square). Animals of the RIPC + HS group had faster recovery of mean arterial pressure and developed higher heart rates without complications. They also had less decrease in pH and bicarbonate, and the increase in lactate began later. Global oxygen delivery was higher, and tissue oxygen extraction ratio lower, in RIPC + HS animals. These improvements after RIPC in hemodynamic and metabolic status provide essential substrates for improved cellular response after hemorrhage and reduction of the likelihood of potentially catastrophic consequences of the accompanying ischemia.

Perioperative Clinical Trials in AKI

To characterize current evidence and current foci of perioperative clinical trials, we systematically reviewed Medline and identified perioperative trials involving 100 or more adult patients undergoing surgery and reporting renal end points that were published in high-impact journals since 2004. We categorized the 101 trials identified based on the nature of the intervention and summarized major trial findings from the five categories most applicable to perioperative management of patients. Trials that targeted ischemia suggested that increasing perioperative renal oxygen delivery with inotropes or blood transfusion does not reliably mitigate acute kidney injury (AKI), although goal-directed therapy with hemodynamic monitors appeared beneficial in some trials. Trials that have targeted inflammation or oxidative stress, including studies of nonsteroidal anti-inflammatory drugs, steroids, N-acetylcysteine, and sodium bicarbonate, have not shown renal benefits, and high-dose perioperative statin treatment increased AKI in some patient groups in two large trials. Balanced crystalloid intravenous fluids appear safer than saline, and crystalloids appear safer than colloids. Liberal compared with restrictive fluid administration reduced AKI in a recent large trial in open abdominal surgery. Remote ischemic preconditioning, although effective in several smaller trials, failed to reduce AKI in two larger trials. The translation of promising preclinical therapies to patients undergoing surgery remains poor, and most interventions that reduced perioperative AKI compared novel surgical management techniques or existing processes of care rather than novel pharmacologic interventions.

Fibrinolysis and Remote Ischemic Conditioning: Mechanisms and Treatment Perspectives in Stroke

Stroke is a leading cause of death and disability. Intravenous thrombolysis and mechanical thrombectomy have greatly improved outcomes in acute ischemic stroke (AIS). However, only a minority of patients receive reperfusion therapies, highlighting the need for novel neuroprotective therapies. Remote ischemic conditioning (RIC), consisting of brief, intermittent extremity occlusion and reperfusion induced with an inflatable cuff, is a potential neuroprotective therapy in acute stroke. The objective of this narrative review is to describe the effect of RIC on endogenous fibrinolysis and, from this perspective, investigate the potential of RIC in the prevention and treatment of stroke. A systematic literature search was performed in PubMed, and human studies in English were included. Seven studies had investigated the effect of RIC on fibrinolysis in humans. Long-term daily administration of RIC increased endogenous fibrinolysis, whereas a single RIC treatment did not acutely influence endogenous fibrinolysis. Fifteen studies had investigated the effect of RIC as a neuroprotective therapy in the prevention and treatment of stroke. Long-term RIC administration proved effective in reducing new cerebral vascular lesions in patients with established cerebrovascular disease. In patients with acute stroke, RIC was safe and feasible, though its clinical efficacy as a neuroprotectant is yet unproven. In conclusion, a single RIC treatment does not affect fibrinolysis in the acute phase, whereas long-term RIC administration may increase endogenous fibrinolysis. Increased endogenous fibrinolysis is unlikely to be the mediator of the acute neuroprotective effect of RIC in stroke patients, whereas it may partly explain the reduced stroke recurrence associated with long-term RIC treatment.

Influence of strain, age, origin, and anesthesia on the cardioprotective efficacy by local and remote ischemic conditioning in an ex vivo rat model

Background

Local ischemic preconditioning (IPC) and remote ischemic conditioning (RIC) induced by brief periods of ischemia and reperfusion protect against ischemia‐reperfusion injury.

Methods

We studied the sensitivity to IR‐injury and the influence of strain, age, supplier, and anesthesia upon the efficacy of IPC and RIC in 7‐ and 16‐weeks‐old Sprague‐Dawley and Wistar rats from three different suppliers. The influence of sedation with a hypnorm and midazolam mixture (rodent mixture) and pentobarbiturate was compared.

Results

IPC attenuated infarct size in both 7‐weeks‐old Sprague–Dawley (48.4 ± 17.7% vs. 20.3 ± 6.9, p < 0.001) and 7‐weeks‐old Wistar (55.6 ± 10.9% vs. 26.8 ± 5.0%, p < 0.001) rats. Infarct size was larger in 16‐weeks‐old Sprague–Dawley rats, however, IPC still lowered infarct size (78.8 ± 9.2% vs. 58.3 ± 12.3%, p < 0.01). RIC reduced infarct sizes in 7‐weeks‐old Sprague–Dawley (75.3 ± 11.8% vs. 58.6 ± 8.9%, p < 0.05), but not in 7‐weeks‐old Wistar rats (31.7 ± 17.6% and 24.0 ± 12.6%, p = 0.2). In 16‐weeks‐old Sprague–Dawley rats, RIC did not induce protection (76.4 ± 5.5% and 73.2 ± 14.7%, p = 0.6). However, RIC induced protection in 16‐weeks‐old Wistar rats (45.2 ± 8.5% vs. 14.7 ± 10.8%, p < 0.001). RIC did not reduce infarct size in 7‐weeks‐old Sprague–Dawley rats from Charles River (62.0 ± 13.5% and 69.4 ± 10.4% p = 0.3) or 16‐weeks‐old Wistar rats from Janvier (50.7 ± 11.3 and 49.2 ± 16.2, p = 0.8). There was no difference between sedation with rodent mixture or pentobarbiturate.

Conclusion

The cardioprotective effect of IPC is consistent across rat strains independent of age, strain, and supplier. RIC seems to be less reproducible, but still yields protection across different rat strains. However, age, animal supplier, and anesthetics may modulate the sensitivity of IR‐injury and the response to RIC.

Endothelium-dependent remote signaling in ischemia and reperfusion: Alterations in the cardiometabolic continuum

Intact endothelial function plays a fundamental role for the maintenance of cardiovascular (CV) health. The endothelium is also involved in remote signaling pathway-mediated protection against ischemia/reperfusion (I/R) injury. However, the transfer of these protective signals into clinical practice has been hampered by the complex metabolic alterations frequently observed in the cardiometabolic continuum, which affect redox balance and inflammatory pathways. Despite recent advances in determining the distinct roles of hyperglycemia, insulin resistance (InR), hyperinsulinemia, and ultimately diabetes mellitus (DM), which define the cardiometabolic continuum, our understanding of how these conditions modulate endothelial signaling remains challenging. It is widely accepted that endothelial cells (ECs) undergo functional changes within the cardiometabolic continuum. Beyond vascular tone and platelet-endothelium interaction, endothelial dysfunction may have profound negative effects on outcome during I/R. In this review, we summarize the current knowledge of the influence of hyperglycemia, InR, hyperinsulinemia, and DM on endothelial function and redox balance, their influence on remote protective signaling pathways, and their impact on potential therapeutic strategies to optimize protective heterocellular signaling.

Hypoxic preconditioning attenuates ischemia-reperfusion injury in young healthy adults

Ischemia-reperfusion injury induced by restoration of blood flow following occlusion impairs flow-mediated dilation, a marker of endothelium-dependent vasodilation. In young healthy adults, exposure to intermittent hypoxia, consisting of alternating short bouts of breathing hypoxic and normoxic air, before an ischemia-reperfusion injury significantly attenuated the reduction in flow-mediated dilation. Thus, hypoxic preconditioning represents a potential strategy to mitigate the effect of ischemia-reperfusion injury associated with ischemic events.

The effect of remote ischaemic conditioning on blood pressure response: A systematic review and meta-analysis

BACKGROUND

Previous work has evaluated the effect of remote ischaemic conditioning (RIC) in a number of clinical conditions (e.g. cardiac surgery and acute kidney injury), but only one analysis has examined blood pressure (BP) changes. While individual studies have reported the effects of acute bouts and repeated RIC exposure on resting BP, efficacy is equivocal. We conducted a systematic review and meta-analysis to evaluate the effects of acute and repeat RIC on BP.

METHODS

A systematic search was performed using PubMed, Web of Science, EMBASE, and Cochrane Library of Controlled Trials up until October 31, 2020. Additionally, manual searches of reference lists were performed. Studies that compared BP responses after exposing participants to either an acute bout or repeated cycles of RIC with a minimum one-week intervention period were considered.

RESULTS

Eighteen studies were included in this systematic review, ten examined acute effects while eight investigated repeat effects of RIC. Mean differences (MD) for outcome measures from acute RIC studies were: systolic BP 0.18 mmHg (95%CI -0.95, 1.31; p = 0.76), diastolic BP -0.43 mmHg (95%CI -2.36, 1.50; p = 0.66), MAP -1.73 mmHg (95%CI -3.11, -0.34; p = 0.01) and HR -1.15 bpm (95%CI -2.92, 0.62; p = 0.20). Only MAP was significantly reduced. Repeat RIC exposure showed non-significant change in systolic BP -3.23 mmHg (95%CI -6.57, 0.11; p = 0.06) and HR -0.16 bpm (95%CI -7.08, 6.77; p = 0.96) while diastolic BP -2.94 mmHg (95%CI -4.08, -1.79; p < 0.00001) and MAP -3.21 mmHg (95%CI -4.82, -1.61; p < 0.0001) were significantly reduced.

CONCLUSIONS

Our data suggests repeated, but not acute, RIC produced clinically meaningful reductions in diastolic BP and MAP.

Nitrite and myocardial ischaemia reperfusion injury. Where are we now?

Cardiovascular disease remains the leading cause of death worldwide despite major advances in technology and treatment, with coronary heart disease (CHD) being a key contributor. Following an acute myocardial infarction (AMI), it is imperative that blood flow is rapidly restored to the ischaemic myocardium. However, this restoration is associated with an increased risk of additional complications and further cardiomyocyte death, termed myocardial ischaemia reperfusion injury (IRI). Endogenously produced nitric oxide (NO) plays an important role in protecting the myocardium from IRI. It is well established that NO mediates many of its downstream functions through the 'canonical' NO-sGC-cGMP pathway, which is vital for cardiovascular homeostasis; however, this pathway can become impaired in the face of inadequate delivery of necessary substrates, in particular L-arginine, oxygen and reducing equivalents. Recently, it has been shown that during conditions of ischaemia an alternative pathway for NO generation exists, which has become known as the 'nitrate-nitrite-NO pathway'. This pathway has been reported to improve endothelial dysfunction, protect against myocardial IRI and attenuate infarct size in various experimental models. Furthermore, emerging evidence suggests that nitrite itself provides multi-faceted protection, in an NO-independent fashion, against a myriad of pathophysiologies attributed to IRI. In this review, we explore the existing pre-clinical and clinical evidence for the role of nitrate and nitrite in cardioprotection and discuss the lessons learnt from the clinical trials for nitrite as a perconditioning agent. We also discuss the potential future for nitrite as a pre-conditioning intervention in man.

Remote ischemic conditioning for acute respiratory distress syndrome in COVID-19

Acute respiratory distress syndrome and subsequent respiratory failure remains the leading cause of death (>80%) in patients severely impacted by COVID-19. The lack of clinically effective therapies for COVID-19 calls for the consideration of novel adjunct therapeutic approaches. Though novel antiviral treatments and vaccination hold promise in control and prevention of early disease, it is noteworthy that in severe cases of COVID-19, addressing "run-away" inflammatory cascades are likely more relevant for improvement of clinical outcomes. Viral loads may decrease in severe, end-stage coronavirus cases, but a systemically damaging cytokine storm persists and mediates multiple organ injury. Remote ischemic conditioning (RIC) of the limbs has shown potential in recent years to protect the lungs and other organs against pathological conditions similar to that observed in COVID-19. We review the efficacy of RIC in protecting the lungs against acute injury and current points of consideration. The beneficial effects of RIC on lung injury along with other related cardiovascular complications are discussed, as are the limitations presented by sex and aging. This adjunct therapy is highly feasible, noninvasive, and proven to be safe in clinical conditions. If proven effective in clinical trials for acute respiratory distress syndrome and COVID-19, application in the clinical setting could be immediately implemented to improve outcomes.

Perioperative Cardioprotection: Clinical Implications

Perioperative cardioprotection aims to minimize the consequences of myocardial ischemia-reperfusion injury. In isolated tissue and animal experiments, several treatments have been identified providing cardioprotection. Some of these strategies have been confirmed in clinical proof-of-concept studies. However, the final translation of cardioprotective strategies to really improve clinical outcome has been disappointing: large randomized controlled clinical trials mostly revealed inconclusive, neutral, or negative results. This review provides an overview of the currently available evidence regarding clinical implications of perioperative cardioprotective therapies from an anesthesiological perspective, highlighting nonpharmacological as well as pharmacological strategies. We discuss reasons why translation of promising experimental results into clinical practice and outcome improvement is hampered by potential confounders and suggest future perspectives to overcome these limitations.

Effects of remote ischemic preconditioning on platelet activation and reactivity in patients undergoing cardiac surgery using cardiopulmonary bypass: a randomized controlled trial

During cardiopulmonary bypass (CPB), platelet activation and dysfunction are associated with adverse outcomes. Remote ischemic preconditioning (RIPC) has been shown to attenuate platelet activation. We evaluated the effects of RIPC on platelet activation during CPB in patients undergoing cardiac surgery. Among 58 randomized patients, 26 in the RIPC group and 28 in the sham-RIPC group were analyzed. RIPC consisted of 4 cycles of 5-min ischemia induced by inflation of pneumatic cuff pressure to 200 mmHg, followed by 5-min reperfusion comprising deflation of the cuff on the upper arm. Platelet activation was assessed using flow cytometry analysis of platelet activation markers. The primary endpoint was the AUC of CD62P expression during the first 3 h after initiation of CPB. Secondary outcomes were the AUC of PAC-1 expression and monocyte-platelet aggregates (MPA) during 3 h of CPB. The AUCs of CD62P expression during 3 h after initiation of CPB were 219.4 ± 43.9 and 211.0 ± 41.2 MFI in the RIPC and sham-RIPC groups, respectively (mean difference, 8.42; 95% CI, -14.8 and 31.7 MFI; p =.471). The AUCs of PAC-1 expression and MPA did not differ between groups. RIPC did not alter platelet activation and reactivity during CPB in patients undergoing cardiac surgery.

Two weeks of remote ischemic conditioning improves brachial artery flow mediated dilation in chronic stroke survivors

Many stroke survivors have reduced cardiorespiratory fitness as a result of their stroke. Ischemic conditioning (IC) is a noninvasive, cost-effective, easy-to-administer intervention that can be performed at home and has been shown to improve both motor function in stroke survivors and vascular endothelial function in healthy individuals. In this study, we examined the effects of 2 wk of remote IC (RIC) on brachial artery flow mediated dilation (FMD) in chronic stroke survivors. We hypothesized that FMD would be improved following RIC compared with a sham RIC control group. This was a prospective, randomized, double-blinded, controlled study. Twenty-four chronic stroke survivors (>6 mo after stroke) were enrolled and randomized to receive either RIC or sham RIC on their affected thigh every other day for 2 wk. For the RIC group, a blood pressure cuff was inflated to 225 mmHg for 5 min, followed by 5 min of recovery, and repeated a total of five times per session. For the sham RIC group, the inflation pressure was 10 mmHg. Brachial artery FMD was assessed on the nonaffected arm at study enrollment and following the 2-wk intervention period. Nine men and fourteen women completed all study procedures. Brachial artery FMD increased from 5.4 ± 4.8 to 7.8 ± 4.4% (P = 0.030; n = 12) in the RIC group, while no significant change was observed in the sham RIC group (3.5 ± 3.9% pretreatment versus 2.4 ± 3.1% posttreatment; P = 0.281, n = 11). Two weeks of RIC increases brachial artery FMD in chronic stroke survivors.NEW & NOTEWORTHY In this study, we report that 2 wk of remote ischemic conditioning (RIC) improves brachial artery flow-mediated dilation in chronic stroke survivors. Because poor cardiovascular health puts stroke survivors at a heightened risk for recurrent stroke and other cardiovascular events, an intervention that is simple, cost-effective, and easy to perform like RIC holds promise as a means to improve cardiovascular health in this at-risk population.

Co-morbidities and co-medications as confounders of cardioprotection-Does it matter in the clinical setting?

The translation of cardioprotection from robust experimental evidence to beneficial clinical outcome for patients suffering acute myocardial infarction or undergoing cardiovascular surgery has been largely disappointing. The present review attempts to critically analyse the evidence for confounders of cardioprotection in patients with acute myocardial infarction and in patients undergoing cardiovascular surgery. One reason that has been proposed to be responsible for such lack of translation is the confounding of cardioprotection by co-morbidities and co-medications. Whereas there is solid experimental evidence for such confounding of cardioprotection by single co-morbidities and co-medications, the clinical evidence from retrospective analyses of the limited number of clinical data is less robust. The best evidence for interference of co-medications is that for platelet inhibitors to recruit cardioprotection per se and thus limit the potential for further protection from myocardial infarction and for propofol anaesthesia to negate the protection from remote ischaemic conditioning in cardiovascular surgery. LINKED ARTICLES: This article is part of a themed issue on Risk factors, comorbidities, and comedications in cardioprotection. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v177.23/issuetoc.

Randomised sham-controlled double-blind trial evaluating remote ischaemic preconditioning in solid organ transplantation: a study protocol for the RIPTRANS trial

INTRODUCTION

Remote ischaemic preconditioning (RIPC) using a non-invasive pneumatic tourniquet is a potential method for reducing ischaemia-reperfusion injury. RIPC has been extensively studied in animal models and cardiac surgery, but scarcely in solid organ transplantation. RIPC could be an inexpensive and simple method to improve function of transplanted organs. Accordingly, we aim to study whether RIPC performed in brain-dead organ donors improves function and longevity of transplanted organs.

METHODS AND ANALYSES

RIPTRANS is a multicentre, sham-controlled, parallel group, randomised superiority trial comparing RIPC intervention versus sham-intervention in brain-dead organ donors scheduled to donate at least one kidney. Recipients of the organs (kidney, liver, pancreas, heart, lungs) from a randomised donor will be included provided that they give written informed consent. The RIPC intervention is performed by inflating a thigh tourniquet to 300 mm Hg 4 times for 5 min. The intervention is done two times: first right after the declaration of brain death and second immediately before transferring the donor to the operating theatre. The sham group receives the tourniquet, but it is not inflated. The primary endpoint is delayed graft function (DGF) in kidney allografts. Secondary endpoints include short-term functional outcomes of transplanted organs, rejections and graft survival in various time points up to 20 years. We aim to show that RIPC reduces the incidence of DGF from 25% to 15%. According to this, the sample size is set to 500 kidney transplant recipients.

ETHICS AND DISSEMINATION

This study has been approved by Helsinki University Hospital Ethics Committee and Helsinki University Hospital's Institutional Review Board. The study protocol was be presented at the European Society of Organ Transplantation congress in Copenhagen 14-15 September 2019. The study results will be submitted to an international peer-reviewed scientific journal for publication.

TRIAL REGISTRATION NUMBER

NCT03855722.

Reduced effect of ischemic preconditioning against endothelial ischemia-reperfusion injury with cardiovascular risk factors in humans

The extent that clustered CVD risk factors interfere with ischemic preconditioning (IPC) to protect against microvascular endothelial dysfunction with ischemia-reperfusion (I/R) injury in humans is unclear. We hypothesized that adults with a clustered burden of ≥3 CVD risk factors would demonstrate a reduced capacity of IPC to protect endothelial function with I/R injury. Twenty-two (age: 45 ± 14 year) adults [12 healthy controls; 10 raised risk (10-year FRS risk score ~3%)] were studied using a 2 × 2 randomized cross-over design. Pulse arterial tonometry was used to assess microvascular endothelium-dependent vasodilation during reactive hyperemia in response to endothelial I/R injury (20 min brachial artery occlusion/45 min reperfusion) that was preceded by remote IPC (3 × 5 min ischemia/reperfusion) or mock IPC. In both groups, microvascular reactive hyperemia was reduced ~20% (both P < 0.01) after endothelial I/R injury without remote IPC. However, in control subjects remote IPC prevented endothelial I/R injury (from baseline reactive hyperemic ratio: 2.1 ± 0.4 AU to post I/R injury: 2.5 ± 0.5 AU; P = 0.09). In contrast, the reactive hyperemia ratio in raised risk subjects was significantly reduced from 2.2 ± 0.6 AU to 1.9 ± 0.5 AU (P = 0.0087) despite attempts to induce protection by remote IPC, with the magnitude of reduction similar to their mock IPC trial. The magnitude of remote IPC-mediated endothelial protection against I/R injury was inversely related to the number of risk factors. CVD risk factors diminish the effect of IPC to protect the microvasculature from I/R injury in humans. Translating IPC to clinical practice for vasculoprotection will continue to be challenging in patients with increased CVD risk.

Two episodes of remote ischemia preconditioning improve motor and sensory function of hind limbs after spinal cord ischemic injury

Objectives: To investigate the effect of one and two remote ischemia preconditioning episodes (1-RIPC or 2-RIPC, respectively) on neuro-protection after spinal cord ischemic injury (SCI) in rats. Design: Experimental animal study. Setting: College of Medicine, King Khalid University, Abha, KSA. Interventions: Male rats (n = 10/group) were divided into control, sham, SCIRI, 1-RIPC + SCIRI, and 2-RIPC + SCIRI. SCI was induced by aortic ligation for 45 min and each RIPC episode was induced by 3 cycles of 10 min ischemia/10 min perfusion. The two preconditioning procedures were separated by 24 h. Outcome measures: after 48 h of RIPC procedure, Tarlov's test, withdrawal from the painful stimulus and placing/stepping reflex (SPR) were used to evaluate the hind limbs neurological function. SC homogenates were used to measure various biochemical parameters. Results: Motor and sensory function of hind limbs were significantly improved and levels of MDA, AOPPs, PGE2, TNF-α, and IL-6, as well as the activity of SOD, was significantly decreased in SC tissue in either 1 or 2 episodes of RIPC intervention. Concomitantly, levels of total nitrate/nitrite and eNOS activity were significantly increased in both groups. Interestingly, except for activity of SOD, eNOS and levels of nitrate/nitrite, the improvements in all neurological biochemical endpoint were more profound in 2-RIPC + SCIRI compared with 1-RIPC + SCIRI. Conclusion: applying two preconditioning episodes of 3 cycles of 10 min ischemia/10 min perfusion, separated by 24 h, boost the neuro-protection effect of RIPC maneuver in rats after ischemic induced SCI in rats.

Remote Ischemic Pre-conditioning in Subarachnoid Hemorrhage: A Prospective Pilot Trial

BACKGROUND

Cerebral injury from aneurysmal subarachnoid hemorrhage (aSAH) is twofold. The initial hemorrhage causes much of the injury; secondary injury can occur from delayed cerebral ischemia (DCI). Remote ischemic preconditioning (RIPC) is a mechanism of organ protection in response to transient ischemia within a distant organ. This pilot trial sought to apply RIPC in patients with aSAH to evaluate its effect on secondary cerebral injury and resultant outcomes.

METHODS

Patients were randomized to the high-pressure occlusion group (HPO) or the low-pressure occlusion group (LPO). Lower extremity RIPC treatment was initiated within 72 h of symptom onset and every other day for 14 days or until Intensive Care Unit (ICU) discharge. In HPO, each treatment consisted of 4 five-minute cycles of manual blood pressure cuff inflation with loss of distal pulses. LPO received cuff inflation with lower pressures while preserving distal pulses. Retrospectively matched controls were also analyzed. Efficacy of treatment was measured by total days spent in vasospasm out of study enrollment days, hospital and ICU length of stay (LOS), cerebral infarction, one and six month modified Rankin score, and mortality.

RESULTS

The final analysis included 33 patients with 11 in each group. Patient demographics, aneurysm location, admission airway status, Glasgow Coma Scale (GCS), modified Rankin score, Hunt and Hess score, modified Fisher Score and aneurysm management were not significantly different between groups. Hospital and ICU LOS was shorter in LPO compared to the control (p = 0·0468 and p = 0·0409, respectively). Total vasospasm days/study enrollment days, cerebral infarction, one and six month modified Rankin score, and mortality were not significantly different between the groups.

CONCLUSIONS

This pilot trial did demonstrate feasibility and safety. The shortened LOS in the LPO may implicate a protective role of RIPC and warrants future study.

Bilateral Remote Ischaemic Conditioning in Children (BRICC) trial: protocol for a two-centre, double-blind, randomised controlled trial in young children undergoing cardiac surgery

INTRODUCTION

Myocardial protection against ischaemic-reperfusion injury is a key determinant of heart function and outcome following cardiac surgery in children. However, with current strategies, myocardial injury occurs routinely following aortic cross-clamping, as demonstrated by the ubiquitous rise in circulating troponin. Remote ischaemic preconditioning, the application of brief, non-lethal cycles of ischaemia and reperfusion to a distant organ or tissue, is a simple, low-risk and readily available technique which may improve myocardial protection. The Bilateral Remote Ischaemic Conditioning in Children (BRICC) trial will assess whether remote ischaemic preconditioning, applied to both lower limbs immediately prior to surgery, reduces myocardial injury in cyanotic and acyanotic young children.

METHODS AND ANALYSIS

The BRICC trial is a two-centre, double-blind, randomised controlled trial recruiting up to 120 young children (age 3 months to 3 years) undergoing primary repair of tetralogy of Fallot or surgical closure of an isolated ventricular septal defect. Participants will be randomised in a 1:1 ratio to either bilateral remote ischaemic preconditioning (3×5 min cycles) or sham immediately prior to surgery, with follow-up until discharge from hospital or 30 days, whichever is sooner. The primary outcome is reduction in area under the time-concentration curve for high-sensitivity (hs) troponin-T release in the first 24 hours after aortic cross-clamp release. Secondary outcome measures include peak hs-troponin-T, vasoactive inotrope score, arterial lactate and central venous oxygen saturations in the first 12 hours, and lengths of stay in the paediatric intensive care unit and the hospital.

ETHICS AND DISSEMINATION

The trial was approved by the West Midlands-Solihull National Health Service Research Ethics Committee (16/WM/0309) on 5 August 2016. Findings will be disseminated to the academic community through peer-reviewed publications and presentation at national and international meetings. Parents will be informed of the results through a newsletter in conjunction with a local charity.

TRIAL REGISTRATION NUMBER

ISRCTN12923441.

Remote ischemic conditioning counteracts the intestinal damage of necrotizing enterocolitis by improving intestinal microcirculation

Necrotizing enterocolitis (NEC) is a devastating disease of premature infants with high mortality rate, indicating the need for precision treatment. NEC is characterized by intestinal inflammation and ischemia, as well derangements in intestinal microcirculation. Remote ischemic conditioning (RIC) has emerged as a promising tool in protecting distant organs against ischemia-induced damage. However, the effectiveness of RIC against NEC is unknown. To address this gap, we aimed to determine the efficacy and mechanism of action of RIC in experimental NEC. NEC was induced in mouse pups between postnatal day (P) 5 and 9. RIC was applied through intermittent occlusion of hind limb blood flow. RIC, when administered in the early stages of disease progression, decreases intestinal injury and prolongs survival. The mechanism of action of RIC involves increasing intestinal perfusion through vasodilation mediated by nitric oxide and hydrogen sulfide. RIC is a viable and non-invasive treatment strategy for NEC.

Necrotizing enterocolitis (NEC) is one of the most lethal gastrointestinal emergencies in neonates needing precision treatment. Here the authors show that remote ischemic conditioning is a non-invasive therapeutic method that enhances blood flow in the intestine, reduces damage, and improves NEC outcome.

State of the Art: No-Reflow Phenomenon

Primary percutaneous coronary intervention is the preferred reperfusion strategy for the management of acute ST-segment elevation myocardial infarction. No reflow is characterized by the inadequate myocardial perfusion of a given segment without angiographic evidence of persistent mechanical obstruction of epicardial vessels. Both pharmacologic and device-based strategies have been tested to resolve coronary no reflow. This article provides an updated overview of the no-reflow phenomenon, discussing clinical evidence and ongoing investigations of existing and novel therapeutic strategies to counteract it.

Preconditioning in cardiac anesthesia…… where are we?

Preconditioning, a milestone concept in the cardiovascular sciences introduced 32 years back by Murry. This concept opened a new era in the field of organ protection. To start with extensive studies done on ischemic preconditioning for myocardial protection, ischemic preconditioning is an endogenous science of cellular kinetics. Several components in signal transduction cascade have been identified but still some mechanisms not yet revealed. Anesthetic preconditioning also contributed a lot for myocardial protection and concreted the concept of preconditioning. We, with an inquisitive brain meticulously persuing newer methods of cardioprotection. Remote ischemic preconditioning (RIPC) is a brilliant example of it. RIPC can be future of cardioprotection, clinical trials and studies proved the benefits but yet to conclude the superiority of RIPC over myocardial ischemic cardioprotection. This review is an attempt to reveal this extraordinary concept with its basic cellular kinetics, methods, and recent trends.

Cardioprotection for Acute MI in Light of the CONDI2/ERIC-PPCI Trial: New Targets Needed

Protection against ischaemia-reperfusion injury after revascularisation in acute myocardial infarction remains an enigma. Many targets have been identified, but after the failure of the recent Effect of Remote Ischaemic Conditioning on Clinical Outcomes in ST-elevation Myocardial Infarction Patients Undergoing Primary Percutaneous Coronary Intervention (CONDI2/ERIC-PPCI) trial to show translation to clinical benefit, there is still no pharmacological or mechanical strategy that has translated to clinical practice. This article addresses the results of the CONDI2/ERIC-PPCI trial in the context of previous studies of ischaemic conditioning, and then considers the prospects for other potential targets of cardioprotection. Finally, the authors examine the pitfalls and challenges in trial design for future investigation of cardioprotective strategies. In particular, this article highlights the need for careful endpoint and patient selection, as well as the need to pay attention to the biology of cardioprotection during the study.

Role of Remote Ischemic Preconditioning in Hepatic Ischemic Reperfusion Injury

The effect of remote ischemic preconditioning (RIPC) has been proposed that mediates the protective response in ischemia reperfusion injury (IRI) of various organs. In this study, we investigated the effect of RIPC in hepatic IRI, by assessing biomarker of oxidative stress and inflammatory cytokines. Moreover, we intended to demonstrate any such protective effect through nitric oxide (NO). Twenty-five rats were divided into the 5 groups: (1) Sham; (2) RIPC; (3) hepatic IRI; (4) RIPC + hepatic IRI; (5) C-PTIO, 2-(4-carboxyphenyl)-4,5dihydro-4,4,5,5-tetramethyl-1H-imidazolyl-1-oxy-3oxide, + RIPC + hepatic IRI. RIPC downregulated the level of aspartate aminotransferase (AST), alanine aminotransferase (ALT), histologic damage, and activity of Malondialdehyde (MDA). However, there was no significant reduction in the level of tumor necrosis factor-alpha (TNF-α) and nuclear factor kappa B (NF-κB). AST and ALT levels, and hepatic tissue morphology in the C-PTIO group showed a significant improvement compared to those of the RIPC + hepatic IRI group. The application of RIPC before hepatic ischemia downregulated the oxidative stress, not the inflammatory cytokines. Moreover, these protective effect of RIPC would be mediated through the activation of NO as well as anti-oxidant effect.

Ischemic Preconditioning Improves Microvascular Endothelial Function in Remote Vasculature by Enhanced Prostacyclin Production

BACKGROUND The mechanisms underlying the effect of preconditioning on remote microvasculature remains undisclosed. The primary objective was to document the remote effect of ischemic preconditioning on microvascular function in humans. The secondary objective was to test if exercise also induces remote microvascular effects. METHODS AND RESULTS A total of 12 healthy young men and women participated in 2 experimental days in a random counterbalanced order. On one day the participants underwent 4×5 minutes of forearm ischemic preconditioning, and on the other day they completed 4×5 minutes of hand-grip exercise. On both days, catheters were placed in the brachial and femoral artery and vein for infusion of acetylcholine, sodium nitroprusside, and epoprostenol. Vascular conductance was calculated from blood flow measurements with ultrasound Doppler and arterial and venous blood pressures. Ischemic preconditioning enhanced (P<0.05) the remote vasodilator response to intra-arterial acetylcholine in the leg at 5 and 90 minutes after application. The enhanced response was associated with a 6-fold increase (P<0.05) in femoral venous plasma prostacyclin levels and with a transient increase (P<0.05) in arterial plasma levels of brain-derived neurotrophic factor and vascular endothelial growth factor. In contrast, hand-grip exercise did not influence remote microvascular function. CONCLUSIONS These findings demonstrate that ischemic preconditioning of the forearm improves remote microvascular endothelial function and suggest that one of the underlying mechanisms is a humoral-mediated potentiation of prostacyclin formation.

Two weeks of remote ischaemic preconditioning alters sympathovagal balance in healthy humans

NEW FINDINGS

What is the central question of this study? Delayed cardiovascular responses occur following a single bout of remote ischaemic preconditioning (RIPC). Is heart rate variability (HRV), a surrogate marker of cardiac vagal control, able to detect a delayed effect after a single bout of RIPC? Do repeated bouts of RIPC further alter HRV? What is the main finding and its importance? Indices of HRV indicated a shift in sympathovagal balance toward greater parasympathetic activity following 2 weeks of RIPC but not after a single bout of RIPC. Thus, repeated bouts of RIPC were necessary to elicit changes in autonomic function.

ABSTRACT

Remote ischaemic preconditioning (RIPC), induced by brief periods of ischaemia followed by reperfusion, protects against ischaemia-reperfusion injury and improves microvascular function. However, the effect of RIPC on autonomic function remains unclear. We hypothesized that RIPC, administered as a single bout or repeated over a 2-week period, will increase markers of cardiac vagal control measured by heart rate variability (HRV). Thirty-two young adults performed a single bout (n = 13), repeated bouts (n = 11), or served as a time control (n = 8). RIPC sessions consisted of four repetitions of 5 min unilateral brachial artery occlusion interspersed by 5 min of reperfusion. For the single bout protocol, resting lead II electrocardiogram (ECG) was collected before and 24, 48, 72 and 168 h post-RIPC. The repeated bout protocol consisted of three 4-day periods of RIPC training, each interspersed by a 1-day break. Similar to time controls, ECG was collected before and 24 h after the last RIPC bout. HRV was analysed by power spectral density and symbolic dynamics using 350-beat ECG segments. After a single bout of RIPC, no changes in HRV were observed at any time point (P > 0.05). After 2 weeks of repeated RIPC, the percentage of zero-variation fragments (baseline = 13.1 ± 1.9%, post-RIPC = 6.9 ± 1.5%, P < 0.05) and the LF/HF ratio decreased (baseline = 1.1 ± 0.2, post-RIPC = 0.7 ± 0.1, P < 0.01), whereas the percentage of two-variation fragments increased (baseline = 42.9 ± 3.6%, post-RIPC = 52.5 ± 3.0%, P < 0.01). These data indicate that repeated RIPC is necessary to elicit changes in sympathovagal balance, specifically resulting in increased vagal and decreased sympathetic activity.

Remote ischemic preconditioning reduces myocardial ischemia-reperfusion injury through unacylated ghrelin-induced activation of the JAK/STAT pathway

Remote ischemic preconditioning (RIPC) offers cardioprotection against myocardial ischemia-reperfusion injury. The humoral factors involved in RIPC that are released from parasympathetically innervated organs have not been identified. Previous studies showed that ghrelin, a hormone released from the stomach, is associated with cardioprotection. However, it is unknown whether or not ghrelin is involved in the mechanism of RIPC. This study aimed to determine whether ghrelin serves as one of the humoral factors in RIPC. RIPC group rats were subjected to three cycles of ischemia and reperfusion for 5 min in two limbs before left anterior descending (LAD) coronary artery ligation. Unacylated ghrelin (UAG) group rats were given 0.5 mcg/kg UAG intravenously 30 min before LAD ligation. Plasma levels of UAG in all groups were measured before and after RIPC procedures and UAG administration. Additionally, JAK2/STAT3 pathway inhibitor (AG490) was injected in RIPC and UAG groups to investigate abolishment of the cardioprotection of RIPC and UAG. Plasma levels of UAG, infarct size and phosphorylation of STAT3 were compared in all groups. Infarct size was significantly reduced in RIPC and UAG groups, compared to the other groups. Plasma levels of UAG in RIPC and UAG groups were significantly increased after RIPC and UAG administration, respectively. The cardioprotective effects of RIPC and UAG were accompanied by an increase in phosphorylation of STAT3 and abolished by AG490. This study indicated that RIPC reduces myocardial ischemia and reperfusion injury through UAG-induced activation of JAK/STAT pathway. UAG may be one of the humoral factors involved in the cardioprotective effects of RIPC.

Voluntary exercise and cardiac remodeling in a myocardial infarction model

We investigated the effects of voluntary exercise after myocardial infarction (MI) on cardiac function, remodeling, and inflammation. Male C57BL/6J mice were divided into the following four groups: sedentary + sham (Sed-Sh), sedentary + MI (Sed-MI), exercise + sham (Ex-Sh), and exercise + MI (Ex-MI). MI induction was performed by ligation of the left coronary artery. Exercise consisting of voluntary wheel running started after the operation and continued for 4 weeks. The Ex-MI mice had significantly increased cardiac function compared with the Sed-MI mice. The Ex-MI mice showed significantly reduced expression levels of tumor necrosis factor-α, interleukin (IL)-1β, IL-6, and IL-10 in the infarcted area of the left ventricle compared with the Sed-MI mice. In the Ex-MI mice, the expression levels of fibrosis-related genes including collagen I and III were decreased compared to the Sed-MI mice, and the expression levels of IL-1β, IL-6, follistatin-like 1, fibroblast growth factor 21, and mitochondrial function-related genes were significantly elevated in skeletal muscle compared with the Sed mice. The plasma levels of IL-6 were also significantly elevated in the Ex-MI group compared with the Sed-MI groups. These findings suggest that voluntary exercise after MI may improve in cardiac remodeling associated with anti-inflammatory effects in the myocardium and myokine production in the skeletal muscles.

Fever Is Associated with Reduced Mortality in Trauma and Surgical Intensive Care Unit-Acquired Infections

Background: Fever is a common response to both infectious and non-infectious physiologic insults in the critically ill, and in certain populations it appears to be protective. Fever is particularly common in trauma patients, and even more so in those with infections. The relationship between fever, trauma status, and mortality in patients with an infection is unclear. Patients and Methods: A review of a prospectively maintained institutional database over a 17-year period was performed. Surgical and trauma intensive care unit (ICU) patients with a nosocomial infection were extracted to compare in-hospital mortality among trauma and non-trauma patients with and without fever. Univariable analyses compared patient and infection characteristics between trauma and non-trauma patients. A multivariable logistic regression model was created to identify predictors of in-hospital mortality, with a focus on fever and trauma status. Results: Nine hundred forty-one trauma patients and 1,449 non-trauma patients with ICU-acquired infections were identified. Trauma patients were younger (48 vs. 59, p < 0.001), more likely to be male (73% vs. 56%, p < 0.001), more likely to require blood transfusion (74% vs. 47%, p < 0.001), had lower Acute Physiology and Chronic Health Evaluation (APACHE) II scores (18 vs. 19, p = 0.02), and had lower rates of comorbidities. Trauma patients were more likely to develop a fever (72% vs. 43%, p < 0.001) and had lower in-hospital mortality (9.6% vs. 22.6%, p < 0.001). In multivariable analysis, non-trauma patients with fever had a lower odds of mortality compared with non-trauma patients without fever (odds ratio [OR] 0.63, p = 0.004). Trauma patients with fever had the lowest odds ratio for mortality when compared to non-trauma patients without fever (OR 0.25, p < 0.001). Conclusions: In this large cohort of trauma and surgical ICU patients with ICU-acquired infections, fever was associated with a lower odds of mortality in both trauma and non-trauma patients. Further investigation is needed to determine the mechanisms behind the interplay between trauma status, fever, and mortality.

Remote Ischemic Preconditioning in Spinal Cord Protection: A Surviving Porcine Study

Surgical repair of thoracic aorta can compromise blood flow of the spinal cord. To mitigate spinal cord ischemia (SCI) additional protection methods are needed. In experimental studies remote ischemic preconditioning (RIPC) has proven to be an effective method of protecting organs from ischemia. The aim of the study was to assess efficacy of RIPC in spinal cord protection in a chronic porcine model. Sixteen piglets were assigned into the RIPC group (8) and the control group (8). RIPC was performed using blood pressure cuff in a 5-minute ischemia followed by a 5-minute reperfusion repeating cycles 4 times. The left subclavian artery and all segmental arteries above diaphragm were ligated at 5-minute intervals to accomplish SCI. The follow-up comprised a 4-hour intensive monitoring and a 7-day recovery phase. Blood samples were obtained, motor-evoked potentials and near-infrared spectroscopy (NIRS) of longitudinal back muscles were measured. Paraplegia was assessed every day postoperatively. Histopathological analysis of the spinal cord was performed after 7 days. NIRS values 4 hours after SCI were higher in the RIPC group, 45.5 (44.5-47.0), than in the control group, 41.5 (40.5-44.0) (P = 0.042). Nadir value of NIRS was 43.4 (39.3-46.0) in the RIPC group and 38.9 (38.-40.0) in the control group (P = 0.014). On the first postoperative day the RIPC group reached modified Tarlov score of 3 (2-3) vs 2 (1-2) in the control group (P = 0.024). RIPC hastens the recovery from SCI during the first postoperative day.

Ischemic postconditioning attenuates the inflammatory response in ischemia/reperfusion myocardium by upregulating miR‑499 and inhibiting TLR2 activation

Toll-like receptor 2 (TLR2)-mediated myocardial inflammation serves an important role in promoting myocardial ischemic/reperfusion (I/R) injury. Previous studies have shown that miR-499 is critical for cardioprotection after ischemic postconditioning (IPostC). Therefore, the present study evaluated the protective effect of IPostC on the myocardium by inhibiting TLR2, and also assessed the involvement of microRNA (miR)-499. Rat hearts were subjected to 30 min of ischemia and 2 h of reperfusion. The IPostC was 3 cycles of 30 sec of reperfusion and 30 sec of re-occlusion prior to reperfusion. In total, 90 rats were randomly divided into six groups (n=15 per group): Sham; I/R; IPostC; miR-499 negative control adeno-associated virus (AAV) vectors + IPostC; miR-499 inhibitor AAV vectors + IPostC; and miR-499 mimic AAV vectors + IPostC. It was identified that IPostC significantly decreased the I/R-induced cardiomyocyte apoptotic index (29.4±2.03% in IPostC vs. 42.64±2.27% in I/R; P<0.05) and myocardial infarct size (48.53±2.49% in IPostC vs. 66.52±3.1% in I/R; P<0.05). Moreover, these beneficial effects were accompanied by increased miR-499 expression levels (as demonstrated by reverse transcription-quantitative PCR) in the myocardial tissue and decreased TLR2, protein kinase C (PKC), interleukin (IL)-1β and IL-6 expression levels (as demonstrated by western blotting and ELISA) in the myocardium and serum. The results indicated that IPostC + miR-499 mimics significantly inhibited inflammation and the PKC signaling pathway and enhanced the anti-inflammatory and anti-apoptotic effects of IPostC. However, IPostC + miR-499 inhibitors had the opposite effect. Therefore, it was speculated that IPostC may have a miR-499-dependent cardioprotective effect. The present results suggested that miR-499 may be involved in IPostC-mediated ischemic cardioprotection, which may occur via local and systemic TLR2 inhibition, subsequent inhibition of the PKC signaling pathway and a decrease in inflammatory cytokine release, including IL-1β and IL-6. Moreover, these effects will ultimately lead to a decrease in the myocardial apoptotic index and myocardial infarct size via the induction of the anti-apoptotic protein Bcl-2, and inhibition of the pro-apoptotic protein Bax in myocardium.

Blood flow-restricted resistance exercise alters the surface profile, miRNA cargo and functional impact of circulating extracellular vesicles

Ischemic exercise conducted as low-load blood flow restricted resistance exercise (BFRE) can lead to muscle remodelling and promote muscle growth, possibly through activation of muscle precursor cells. Cell activation can be triggered by blood borne extracellular vesicles (EVs) as these nano-sized particles are involved in long distance signalling. In this study, EVs isolated from plasma of healthy human subjects performing a single bout of BFRE were investigated for their change in EV surface profiles and miRNA cargos as well as their impact on skeletal muscle precursor cell proliferation. We found that after BFRE, five EV surface markers and 12 miRNAs were significantly altered. Furthermore, target prediction and functional enrichment analysis of the miRNAs revealed several target genes that are associated to biological pathways involved in skeletal muscle protein turnover. Interestingly, EVs from BFRE plasma increased the proliferation of muscle precursor cells. In addition, alterations in surface markers and miRNAs indicated that the combination of exercise and ischemic conditioning during BFRE can stimulate blood cells to release EVs. These results support that BFRE promotes EV release to engage in muscle remodelling and/or growth processes.

MicroRNA Mediated Cardioprotection - Is There a Path to Clinical Translation?

In the past 20 years, there have been several approaches to achieve cardioprotection or cardiac regeneration using a vast variety of cell therapies and remote ischemic pre-conditioning (RIPC). To date, substantial proof that either cell therapy or RIPC has the potential for clinically relevant cardiac repair or regeneration of cardiac tissue is still pending. Preclinical trials indicate that the secretome of cells in situ (during RIPC) as well as of transplanted cells may exhibit cardioprotective properties in the acute setting of cardiac injury. The secretome generally consists of cell-specific cytokines and extracellular vesicles (EVs) containing microRNAs (miRNAs). It is currently hypothesized that a subset of known miRNAs play a crucial part in the facilitation of cardioprotective effects. miRNAs are small non-coding RNA molecules that inhibit post-transcriptional translation of messenger RNAs (mRNAs) and play an important role in gene translation regulation. It is also known that one miRNAs usually targets multiple mRNAs. This makes predictability of pharmacokinetics and mechanism of action very difficult and could in part explain the inferior performance of various progenitor cells in clinical studies. Identification of miRNAs involved in cardioprotection and remodeling, the composition of miRNA profiles, and the exact mechanism of action are important to the design of future cell-based but also cell-free cardioprotective therapeutics. This review will give a description of miRNA with cardioprotective properties and a current overview on known mechanism of action and potential missing links. Additionally, we will give an outlook on the potential for clinical translation of miRNAs in the setting of myocardial infarction and heart failure.

Repeated Remote Ischemic Conditioning Reduces Doxorubicin-Induced Cardiotoxicity

Objectives

This study investigated the cardioprotective effect of repeated remote ischemic preconditioning (rRIC) on doxorubicin-induced cardiotoxicity in mice.

Background

Doxorubicin is an effective chemotherapeutic agent for a wide range of tumor types but its use and dosing are limited by acute and chronic cardiotoxicity. Remote ischemic conditioning (RIC) is cardioprotective in multiple cardiovascular injury models, but the effectiveness of rRIC in doxorubicin-induced cardiotoxicity has not been fully elucidated.

Methods

rRIC was performed on mice before and after doxorubicin administration. Cardiac function was assessed by echocardiography and myocardial biology was tested by molecular approaches.

Results

Doxorubicin administration induced acute cardiotoxicity, as indicated by reduced cardiac function, reduced myocyte cross-section area and increased extracellular collagen deposition, increased circulating cardiac muscle damage markers, and decreased heart weight. Doxorubicin also adversely affected other organs, including the kidney, liver, and spleen, as evaluated by circulating markers or organ weight loss. rRIC not only abrogated doxorubicin-induced cardiotoxicity (left ventricular ejection fraction, doxorubicin 47.5 ± 1.1%, doxorubicin + rRIC 51.6 ± 0.7%, p = 0.017), but also was associated with multiorgan protection. Within the myocardium, rRIC attenuated doxorubicin-induced cardiomyocyte apoptosis, reduced inflammation, and increased autophagy signaling.

Conclusions

rRIC may be a promising approach to reduce doxorubicin-induced cardiotoxicity.

MiRNA-Mediated Mechanisms of Cardiac Protection in Ischemic and Remote Ischemic Preconditioning-A Qualitative Systematic Review

BACKGROUND

Ischemic preconditioning (IPC) and remote ischemic preconditioning (RIPC) protect myocardial tissue against subsequent ischemia and reperfusion injury (IRI) and have a high potential to improve patient outcome. The mediators and mechanisms of protection through IPC and RIPC remain largely unknown, but micro-RNAs (miRNAs) are promising candidates.

METHODS

Systematic review of Medline and Embase databases for biomedical scientific literature.

RESULTS

A total of 26 relevant publications (21 full-text original articles and 5 conference abstracts) were identified, 8 describing cell culture experiments, 14 animal experiments, and 4 randomized clinical trials in humans. Most commonly reported miRNAs with differential expression between preconditioned and control groups include miR-1, miR-21, and miR-144. Experimental designs and procedures differ widely, thereby limiting the potential to compare results between studies. Two of the four RCTs did not find any differentially expressed miRNAs.

CONCLUSIONS

Results from RCTs should feed back into basic research and focused studies confirming or rejecting hypotheses generated by these RCTs are needed.

Late Phases of Cardioprotection During Remote Ischemic Preconditioning and Adenosine Preconditioning Involve Activation of Neurogenic Pathway

BACKGROUND

The role of the neurogenic pathway in early phases of cardioprotection during remote ischemic preconditioning (RIPC) and adenosine preconditioning is reported.

AIM

This study was designed to explore the involvement of the neurogenic pathway in late phases of cardioprotection during RIPC and adenosine preconditioning.

MATERIAL AND METHODS

Fifty-four Wistar rats were used and divided into 9 experimental groups. RIPC was induced by tying the blood pressure cuff around the hind limb and subjecting to 4 cycles of inflation and deflation of 5 minutes each. In early RIPC, the heart was isolated immediately after the last episode of RIPC, whereas in late RIPC, the heart was isolated 24 hours after the last cycle of RIPC. In a similar way, adenosine preconditioning was instituted in early and late phases by either isolating the heart 40 minutes or 24 hours after adenosine (4 mg/kg, intraperitoneally [i.p.]) administration. Isolated hearts were subjected to ischemia-reperfusion (I/R) injury on the Langendorff's system.

RESULTS

Both early and late phases of RIPC and adenosine preconditioning significantly abrogated I/R-induced myocardial injury in terms of decrease in the release of lactate dehydrogenase, creatine kinase, and decrease in infarct size. Pretreatment with hexamethonium, a ganglion blocker (20 mg/kg, i.p.), significantly abolished the cardioprotective effects of both early and late phases of RIPC and adenosine preconditioning.

CONCLUSION

Apart from the involvement of the neurogenic pathway in the early phases, there is a critical role of the neurogenic pathway in the late phase of cardioprotection during RIPC and adenosine preconditioning.

The timing of propofol administration affects the effectiveness of remote ischemic preconditioning induced cardioprotection in rats

The cardioprotection of remote ischemic preconditioning (RIPC) is abolished under propofol maintained anesthesia. Transient receptor potential vanilloid 1 (TRPV1) channel is present in the heart, and its activation could induce cardioprotection. Therefore, we tested whether the anesthetic propofol administration phase interfered with the RIPC-induced cardioprotection, and RIPC-induced cardioprotection via the cardiac TRPV1 channel. Male Sprague-Dawley rats were subjected to myocardial 30 minutes of ischemia followed by 2 hours of reperfusion. RIPC consisted of three cycles of 5-minute ischemia/reperfusion applied to a hindlimb. Propofol infusion at 12 mg/kg/h was commenced either at 10 minutes before the start of RIPC in the P-pre + RIPC group, or immediately after myocardial ischemia at the onset of reperfusion (P-post + RIPC) while performing RIPC. These two propofol infusion regimes were applied to another two grou bs without RIPC (P-pre and P-post groups). Infarct size (IS) was assessed by triphenyltetrazolium staining. Heart TRPV1 expression was detected by Western blot and immunofluorescence. RIPC significantly reduced myocardial IS compared with the control group (36.7 ± 3% versus 57.2 ± 4%; P < .01). When propofol was started before RIPC, the IS sparing effect of RIPC was completely abolished. However, propofol infusion starting immediately after myocardial ischemia did not affect RIPC-induced cardioprotection. TRPV1 expression significant increase after RIPC, then propofol inhibited the TRPV1 activation of RIPC if given before RIPC but not after. Our results suggest that the timing of propofol administration is critical to preserve the cardioprotection of RIPC. Propofol might cancel RIPC-induced cardioprotection via the cardiac TRPV1 receptor.

Remote Ischemic Preconditioning in Microsurgical Head and Neck Reconstruction: A Randomized Controlled Trial

Background:

The free flap failure rate is 5% in head and neck microsurgical reconstruction, and ischemia–reperfusion injury is an important mechanism behind this failure rate. Remote ischemic preconditioning (RIPC) is a recent intervention targeting ischemia–reperfusion injury. The aim of the present study was to investigate if RIPC improved clinical outcomes in microsurgical reconstruction.

Methods:

Head and neck cancer patients undergoing tumor resection and microsurgical reconstruction were included in a randomized controlled trial. Patients were randomized (1:1) to RIPC or sham intervention administered intraoperatively just before transfer of the free flap. RIPC was administered by four 5-minute periods of upper extremity occlusion and reperfusion. Clinical data were prospectively collected in the perioperative period and at follow-up on postoperative days 30 and 90. Intention-to-treat analysis was performed.

Results:

Sixty patients were randomized to RIPC (n = 30) or sham intervention (n = 30). All patients received allocated intervention. No patients were lost to follow up. At 30-day follow-up, flap failure occurred in 7% of RIPC patients (n = 2) and 3% of sham patients (n = 1) with the relative risk and 95% confidence interval 2.0 [0.2;20.9], P = 1.0. The rate of pedicle thrombosis was 10% (n = 3) in both groups with relative risk 1.0 [0.2;4.6], P = 1.0. The flap failure rate did not change at 90-day follow-up.

Conclusions:

RIPC is safe and feasible but does not affect clinical outcomes in head and neck cancer patients undergoing microsurgical reconstruction.

Remote Ischemic Preconditioning Prevents Postoperative Acute Kidney Injury After Open Total Aortic Arch Replacement: A Double-Blind, Randomized, Sham-Controlled Trial

BACKGROUND

Acute kidney injury is a common complication after open total aortic arch replacement but lacks effective preventive strategies. Remote ischemic preconditioning has controversial results of its benefit to the kidney and may perform better in high-risk patients of acute kidney injury. We investigated whether remote ischemic preconditioning would prevent postoperative acute kidney injury after open total aortic arch replacement.

METHODS

We enrolled 130 patients scheduled for open total aortic arch replacement and randomized them to receive either remote ischemic preconditioning (4 cycles of 5-minute right upper limb ischemia and 5-minute reperfusion) or sham preconditioning (4 cycles of 5-minute right upper limb pseudo ischemia and 5-minute reperfusion), both via blood pressure cuff inflation and deflation. The primary end point was the incidence of acute kidney injury within 7 days after the surgery defined by the Kidney Disease: Improving Global Outcomes criteria. Secondary end point included short-term clinical outcomes.

RESULTS

Significantly fewer patients developed postoperative acute kidney injury with remote ischemic preconditioning compared with sham (55.4% vs 73.8%; absolute risk reduction, 18.5%; 95% CI, 2.3%-34.6%; P = .028). Remote ischemic preconditioning significantly reduced acute kidney injury stage II-III (10.8% vs 35.4%; P = .001). Remote ischemic preconditioning shortened the mechanical ventilation duration (18 hours [interquartile range, 14-33] versus 25 hours [interquartile range, 17-48]; P = .01), whereas no significant differences were observed between groups in other secondary outcomes.

CONCLUSIONS

Remote ischemic preconditioning prevented acute kidney injury after open total aortic arch replacement, especially severe acute kidney injury and shortened mechanical ventilation duration. The observed renoprotective effects of remote ischemic preconditioning require further investigation in both clinical research and the underlying mechanism.