Cardiopulmonary bypass associated acute kidney injury: better understanding and better prevention

Cardiopulmonary bypass (CPB) is a common technique in cardiac surgery but is associated with acute kidney injury (AKI), which carries considerable morbidity and mortality. In this review, we explore the range and definition of CPB-associated AKI and discuss the possible impact of different disease recognition methods on research outcomes. Furthermore, we introduce the specialized equipment and procedural intricacies associated with CPB surgeries. Based on recent research, we discuss the potential pathogenesis of AKI that may result from CPB, including compromised perfusion and oxygenation, inflammatory activation, oxidative stress, coagulopathy, hemolysis, and endothelial damage. Finally, we explore current interventions aimed at preventing and attenuating renal impairment related to CPB, and presenting these measures from three perspectives: (1) avoiding CPB to eliminate the fundamental impact on renal function; (2) optimizing CPB by adjusting equipment parameters, optimizing surgical procedures, or using improved materials to mitigate kidney damage; (3) employing pharmacological or interventional measures targeting pathogenic factors.

Assessment of remote ischemic conditioning delivery with optical sensor in acute ischemic stroke: Randomised clinical trial protocol

BACKGROUND

Remote ischemic conditioning (RIC) is delivered by a blood pressure cuff over the limb, raising pressure 50 mmHg above the systolic blood pressure, to a maximum of 200 mmHg. The cuff is inflated for five minutes and then deflated for five minutes in a sequential ischemia-reperfusion cycle 4-5 times per session. Elevated pressure in the limb may be associated with discomfort and consequently reduced compliance. Continuous assessment of relative blood concentration and oxygenation with a tissue reflectance spectroscopy (a type of optical sensor device) placed over the forearm during the RIC sessions of the arm will allow us to observe the effect of inflation and deflation of the pressure cuff. We hypothesize, in patients with acute ischemic stroke (AIS) and small vessel disease, RIC delivered together with a tissue reflectance sensor will be feasible.

METHODS

The study is a prospective, single-center, randomized control trial testing the feasibility of the device. Patients with AIS within 7 days from symptoms onset; who also have small vessel disease will be randomized 2:1 to intervention or sham control arms. All patients randomized to the intervention arm will receive 5 cycles of ischemia/reperfusion in the non-paralyzed upper limb with a tissue reflectance sensor and patients in the sham control arm will receive pressure by keeping the cuff pressure at 30 mmHg for 5 minutes. A total of 51 patients will be randomized, 17 in the sham control arm and 34 in the intervention arm. The primary outcome measure will be the feasibility of RIC delivered for 7 days or at the time of discharge. The secondary device-related outcome measures are fidelity of RIC delivery and the completion rate of intervention. The secondary clinical outcome includes a modified Rankin scale, recurrent stroke and cognitive assessment at 90 days.

DISCUSSION

RIC delivery together with a tissue reflectance sensor will allow insight into the blood concentration and blood oxygenation changes in the skin. This will allow individualized delivery of the RIC and improve compliance.

CLINICAL TRIAL REGISTRATION

ClinicalTrials.gov Identifier: NCT05408130, June 7, 2022.

Effects of Multimodal Bundle with Remote Ischemic Preconditioning and Intrathecal Analgesia on Early Recovery of Estimated Glomerular Filtration Rate after Robot-Assisted Laparoscopic Partial Nephrectomy for Renal Cell Carcinoma

Simple Summary

This study suggested that robot-assisted laparoscopic partial nephrectomy (RALPN) may have benefits with regard to the preservation of renal function and few complications postoperatively in patients with renal cell carcinoma (RCC). However, a reduction in the estimated glomerular filtration rate may be unavoidable. Our results suggested that the preservation of renal function may be enhanced by combining robot-assisted nephron-sparing surgery with an intraoperative bundle strategy consisting of remote ischemic preconditioning (RIPC) and an intrathecal morphine block (ITMB), to protect against ischemia–reperfusion injury and the pain-related stress induced by renal artery clamping and surgical insults. It is important to adjust modifiable variables related to the progression of renal impairment in a timely and appropriate manner for the recovery of renal function after RALPN. Together with surgical and pharmacological methods to minimize irreversible injury, RIPC and ITMB combined bundle therapy may relieve ischemia–reperfusion- and pain-induced stress and serve as a safe and efficient method for improving renal outcomes of RALPN in patients with RCC.

Abstract

We investigated the effects of multimodal combined bundle therapy, consisting of remote ischemic preconditioning (RIPC) and intrathecal morphine block (ITMB), on the early recovery of kidney function after robot-assisted laparoscopic partial nephrectomy (RALPN) in patients with renal cell carcinoma (RCC). In addition, we compared the surgical and analgesic outcomes between patients with and without bundle treatment. This prospective randomized double-blind controlled trial was performed in a cohort of 80 patients with RCC, who were divided into two groups: a bundle group (n = 40) and non-bundle group (n = 40). The primary outcome was postoperative kidney function, defined as the lowest estimated glomerular filtration rate (eGFR) on postoperative day (POD) 2. Surgical complications, pain, and length of hospital stay were assessed as secondary outcomes. The eGFR immediately after surgery was significantly lower in the bundle group compared to the preoperative baseline, but serial levels on PODs 1 and 2 and at three and six months after surgery were comparable to the preoperative baseline. The eGFR level immediately after surgery was lower in the non-bundle than bundle group, and serial levels on PODs 1 and 2 and at three months after surgery remained below the baseline. The eGFR level immediately after surgery was higher in the bundle group than in the non-bundle group. The eGFR changes immediately after surgery, and on POD 1, were smaller in the bundle than in the non-bundle group. The non-bundle group had longer hospital stays and more severe pain than the bundle group, but there were no severe surgical complications in either group. The combined RIPC and ITMB bundle may relieve ischemia–reperfusion- and pain-induced stress, as a safe and efficient means of improving renal outcomes following RALPN in patients with RCC.

Hypoxic preconditioning in renal ischaemia-reperfusion injury: a review in pre-clinical models

Ischaemia-reperfusion injury (IRI) is a major cause of acute kidney injury (AKI) and chronic kidney disease, which consists of cellular damage and renal dysfunction. AKI is a major complication that is of particular concern after cardiac surgery and to a lesser degree following organ transplantation in the immediate post-transplantation period, leading to delayed graft function. Because effective therapies are still unavailable, several recent studies have explored the potential benefit of hypoxic preconditioning (HPC) on IRI. HPC refers to the acquisition of increased organ tolerance to subsequent ischaemic or severe hypoxic injury, and experimental evidences suggest a potential benefit of HPC. There are three experimental forms of HPC, and, for better clarity, we named them as follows: physical HPC, HPC via treated-cell administration and stabilised hypoxia-inducible factor (HIF)-1α HPC, or mimicked HPC. The purpose of this review is to present the latest developments in the literature on HPC in the context of renal IRI in pre-clinical models. The data we compiled suggest that preconditional activation of hypoxia pathways protects against renal IRI, suggesting that HPC could be used in the treatment of renal IRI in transplantation.

Remote ischaemic conditioning for stroke: unanswered questions and future directions

Remote ischaemic conditioning (RIC) refers to a process whereby periods of intermittent ischaemia, typically via the cyclical application of a blood pressure cuff to a limb at above systolic pressure, confers systemic protection against ischaemia in spatially distinct vascular territories. The mechanisms underlying this have not been characterised fully but have been shown to involve neural, hormonal and systemic inflammatory signalling cascades. Preclinical and early clinical studies have been promising and suggest beneficial effects of RIC in acute ischaemic stroke, symptomatic intracranial stenosis and vascular cognitive impairment. Through systematic searches of several clinical trials databases we identified 48 active clinical trials of RIC in ischaemic stroke, intracerebral haemorrhage and subarachnoid haemorrhage. We summarise the different RIC protocols and outcome measures studied in ongoing clinical trials and highlight which studies are most likely to elucidate the underlying biological mechanisms of RIC and characterise its efficacy in the near future. We discuss the uncertainties of RIC including the optimal frequency and duration of therapy, target patient groups, cost-effectiveness, the confounding impact of medications and the absence of a clinically meaningful biomarker of the conditioning response. With several large clinical trials of RIC expected to report their outcomes within the next 2 years, this review aims to highlight the most important studies and unanswered questions that will need to be addressed before this potentially widely accessible and low-cost intervention can be used in clinical practice.

Which remote ischemic preconditioning protocol is favorable in renal ischemia-reperfusion injury in the rat?

BACKGROUND

The optimal timing of remote ischemic preconditioning (RIPC) in renal ischemia-reperfusion (I/R) injury is still unclear. We aimed to compare early- and delayed-effect RIPC with hematological, microcirculatory and histomorphological parameters.

METHODS

In anesthetized male CrI:WI Control rats (n = 7) laparotomy and femoral artery cannulation were performed. In I/R group (n = 7) additionally a 45-minute unilateral renal ischemia with 120-minute reperfusion was induced. The right hind-limb was strangulated for 3×10 minutes (10-minute intermittent reperfusion) 1 hour (RIPC-1 group, n = 7) or 24 hour (RIPC-24 group, n = 6) prior to the I/R. Hemodynamic, hematological parameters and organs' surface microcirculation were measured.

RESULTS

Control and I/R group had the highest heart rate (p < 0.05 vs base), while the lowest mean arterial pressure (p < 0.05 vs RIPC-1) were found in the RIPC-24 group. The highest microcirculation values were measured in the I/R group (liver: p < 0.05 vs Control). The leukocyte count increased in I/R group (base: p < 0.05 vs Control), also this group's histological score was the highest (p < 0.05 vs Control). The RIPC-24 group had a significantly lower score than the RIPC-1 (p = 0.0025 vs RIPC-1).

CONCLUSION

Renal I/R caused significant functional and morphological, also in the RIPC groups. According to the histological examination the delayed-effect RIPC method was more effective.

The Role of Heme Oxygenase-1 in Remote Ischemic and Anesthetic Organ Conditioning

The cytoprotective effects of the heme oxygenase (HO) pathway are widely acknowledged. These effects are mainly mediated by degradation of free, pro-oxidant heme and the generation of carbon monoxide (CO) and biliverdin. The underlying mechanisms of protection include anti-oxidant, anti-apoptotic, anti-inflammatory and vasodilatory properties. Upregulation of the inducible isoform HO-1 under stress conditions plays a crucial role in preventing or reducing cell damage. Therefore, modulation of the HO-1 system might provide an efficient strategy for organ protection. Pharmacological agents investigated in the context of organ conditioning include clinically used anesthetics and sedatives. A review from Hoetzel and Schmidt from 2010 nicely summarized the effects of anesthetics on HO-1 expression and their role in disease models. They concluded that HO-1 upregulation by anesthetics might prevent or at least reduce organ injury due to harmful stimuli. Due to its clinical safety, anesthetic conditioning might represent an attractive pharmacological tool for HO-1 modulation in patients. Remote ischemic conditioning (RIC), first described in 1993, represents a similar secure option to induce organ protection, especially in its non-invasive form. The efficacy of RIC has been intensively studied herein, including on patients. Studies on the role of RIC in influencing HO-1 expression to induce organ protection are emerging. In the first part of this review, recently published pre-clinical and clinical studies investigating the effects of anesthetics on HO-1 expression patterns, the underlying signaling pathways mediating modulation and its causative role in organ protection are summarized. The second part of this review sums up the effects of RIC.

Remote ischemic preconditioning attenuates intestinal mucosal damage: insight from a rat model of ischemia-reperfusion injury

Background

Remote ischemic preconditioning (RIPC) is a phenomenon, whereby repeated, non-lethal episodes of ischemia to an organ or limb exert protection against ischemia–reperfusion (I/R) injury in distant organs. Despite intensive research, there is still an apparent lack of knowledge concerning the RIPC-mediated mechanisms, especially in the intestine. Aim of this study was to evaluate possible protective effects RIPC on intestinal I/R injury.

Methods

Thirty rats were randomly assigned to four groups: I/R; I/R + RIPC; Sham; Sham + RIPC. Animals were anesthetized and the superior mesenteric artery was clamped for 30 min, followed by 60 min of reperfusion. RIPC-treated rats received 3 × 5 min of bilateral hindlimb I/R prior to surgery, sham groups obtained laparotomy without clamping. After I/R injury serum/tissue was analyzed for: Mucosal damage, Caspase-3/7 activity, expression of cell stress proteins, hydrogen peroxide (H₂O₂) and malondialdehyde (MDA) production, Hypoxia-inducible factor-1α (HIF-1α) protein expression and matrix metalloproteinase (MMP) activity.

Results

Intestinal I/R resulted in increased mucosal injury (P < 0.001) and elevated Caspase-3/7 activity (P < 0.001). RIPC significantly reduced the histological signs of intestinal I/R injury (P < 0.01), but did not affect Caspase-3/7 activity. Proteome profiling suggested a RIPC-mediated regulation of several cell stress proteins after I/R injury: Cytochrome C (+ 157%); Cited-2 (− 39%), ADAMTS1 (+ 74%). Serum concentrations of H₂O₂ and MDA remained unchanged after RIPC, while the reduced intestinal injury was associated with increased HIF-1α levels. Measurements of MMP activities in serum and intestinal tissue revealed an attenuated gelatinase activity at 130 kDa within the serum samples (P < 0.001) after RIPC, while the activity of MMPs within the intestinal tissue was not affected by I/R injury or RIPC.

Conclusions

RIPC ameliorates intestinal I/R injury in rats. The underlying mechanisms may involve HIF-1α protein expression and a decreased serum activity of a 130 kDa factor with gelatinase activity.

Electronic supplementary material

The online version of this article (10.1186/s12967-019-1885-4) contains supplementary material, which is available to authorized users.

The role of adenosine in up-regulation of p38 MAPK and ERK during limb ischemic preconditioning-induced brain ischemic tolerance

Our previous studies have demonstrated that limb ischemic preconditioning (LIP) induced brain ischemic tolerance and up-regulated the expression of p38 MAPK and ERK in the hippocampal CA1 region in rats. The present study was undertaken to investigate the role of adenosine in brain protection and up-regulation of p38 MAPK and ERK induced by LIP. It was found that adenosine A1 receptor antagonist DPCPX dose-dependently inhibited the protective effect of LIP. The up-regulation of p38 MAPK and ERK induced by LIP could be blocked by DPCPX. Furthermore, we observed the effect of adenosine on the brain ischemia. The results showed that pre-administration of adenosine could partly mimic the neuroprotective effect on the brain, up-regulate the expression of p38 MAPK and ERK. Based on the above results, it can be concluded that adenosine participated in brain protection and up-regulation of the expression of p38 MAPK and ERK during the induction of brain ischemic tolerance after LIP.

Remote ischemic conditioning as a cytoprotective strategy in vasculopathies during hyperhomocysteinemia: An emerging research perspective

Higher levels of nonprotein amino acid homocysteine (Hcy), that is, hyperhomocysteinemia (HHcy) (~5% of general population) has been associated with severe vasculopathies in different organs; however, precise molecular mechanism(s) as to how HHcy plays havoc with body's vascular networks are largely unknown. Interventional modalities have not proven beneficial to counter multifactorial HHcy's effects on the vascular system. An ancient Indian form of exercise called 'yoga' causes transient ischemia as a result of various body postures however the cellular mechanisms are not clear. We discuss a novel perspective wherein we argue that application of remote ischemic conditioning (RIC) could, in fact, deliver anticipated results to patients who are suffering from chronic vascular dysfunction due to HHcy. RIC is the mechanistic phenomenon whereby brief episodes of ischemia-reperfusion events are applied to distant tissues/organs; that could potentially offer a powerful tool in mitigating chronic lethal ischemia in target organs during HHcy condition via simultaneous reduction of inflammation, oxidative and endoplasmic reticulum stress, extracellular matrix remodeling, fibrosis, and angiogenesis. We opine that during ischemic conditioning our organs cross talk by releasing cellular messengers in the form of exosomes containing messenger RNAs, circular RNAs, anti-pyroptotic factors, protective cytokines like musclin, transcription factors, small molecules, anti-inflammatory, antiapoptotic factors, antioxidants, and vasoactive gases. All these could help mobilize the bone marrow-derived stem cells (having tissue healing properties) to target organs. In that context, we argue that RIC could certainly play a savior's role in an unfortunate ischemic or adverse event in people who have higher levels of the circulating Hcy in their systems.

Comparison of Direct and Remote Ischaemic Preconditioning of Renal Ischaemia Reperfusion Injury in Rats

Objective

One of the methods that can be used to prevent ischaemia reperfusion (IR) injury is ischaemic preconditioning. The aim of this study was to evaluate and compare the effects of remote and direct ischaemic preconditioning (RIPC and DIPC) histopathologically in the rat renal IR injury model.

Methods

After obtaining an approval from the Dokuz Eylül University School of Medicine Ethics Committee, 28 Wistar Albino male rats were divided into four groups. In Group I (Sham, n=7), laparotomy and left renal pedicle dissection were performed, but nothing else was done. In Group II (IR, n=7), after 45 minutes of left renal pedicle occlusion, reperfusion lasting 4 hours was performed. In Group III (DIPC+IR, n=7), after four cycles of ischaemic preconditioning applied to the left kidney, renal IR was performed. In Group IV (RIPC+IR, n=7), after three cycles of ischaemic preconditioning applied to the left hind leg, renal IR was performed. All rats were sacrificed, and the left kidney was processed for conventional histopathology.

Results

The histopathological injury score of the kidney was significantly lower in the sham group compared with the other groups (p<0.01). The injury scores of the DIPC+IR and RIPC+IR groups were significantly lower than in the IR group (p<0.05). In the RIPC+IR group, the injury score for erythrocyte extravasation was found to be significantly lower than in the DIPC+IR group (p<0.05).

Conclusion

In the present study, it was demonstrated that both DIPC and RIPC decreased renal IR injury, but RIPC was found to be more effective than DIPC. This protective effect requiresfurther detailed experimental and clinical studies.

The effect of remote ischemic preconditioning on serum creatinine in patients undergoing partial nephrectomy: a study protocol for a randomized controlled trial

Background

Acute kidney injury (AKI) may develop during partial nephrectomy due to ischemic reperfusion injury induced by renal artery clamping or surgical insult. The effect of remote ischemic preconditioning (RIPC) on reducing the renal injury after partial nephrectomy has not been evaluated in terms of urinary biomarkers.

Methods/design

We will conduct a randomized controlled trial enrolling the patients who will undergo partial nephrectomy. In the study group, RIPC which consisted of four 5-min cycles of limb ischemia and reperfusion will be conducted after induction of anesthesia. Postoperative serum creatinine values, the incidence of AKI, and urinary biomarkers, including urinary creatinine, microalbumin, β-2 microglobulin, and N-acetyl-beta-D-glucosaminidase, will be compared between groups during the postoperative 2 weeks. Regional oxygen saturation on the skin of the contralateral kidney will be measured to evaluate the association between intraoperative regional oxygen saturation values and renal injury of the operating side.

Discussion

We expect that our trial may demonstrate the effect of RIPC on mitigating the immediate postoperative renal injury and improving patient outcomes after partial nephrectomy. Moreover, our patients will undergo ^99mTc-DTPA radionuclide scintigraphy to calculate glomerular filtration rate 6 and 12 months after surgery. This data should show the long-term effect of RIPC.

Trial registration

ClinicalTrials.gov, ID: NCT03273751. Registered on 6 September 2017.

Electronic supplementary material

The online version of this article (10.1186/s13063-018-2820-3) contains supplementary material, which is available to authorized users.

An Overview on Renoprotective Effects of Thymoquinone

Background

Kidneys as vital organs remove waste material from blood. Additionally, they may also have a role in the electrolyte balance, regulation of blood pressure, and red blood cell genesis. Kidney diseases may be caused by several factors such as ischemia/reperfusion injury, diabetes, and nephrotoxic agents. Oxidative stress and inflammation are involved in the pathogenesis and progression of kidney diseases. Traditionally, natural antioxidants are used for treatment of renal failure in various countries.

Summary

People usually select natural antioxidants since they have an opinion that herbal medicine has not any important side effects. Nigella sativa is a flavoring herb that is widely used as a condiment and as a remedy for many disorders. Thymoquinone (TQ), the most important component of black seeds, mainly oil, is considered as an active agent responsible for a lot of the seed's useful effects. This review describes the protective roles and related mechanisms of TQ against renal disorders. The search terms, including TQ, antioxidant, renal ischemia-reperfusion, diabetic nephropathy, and nephrotoxic agent were searched in scientific databases. TQ showed anti-inflammatory and antioxidant properties in animal and in vitro models of several renal diseases caused by inflammation and oxidative stress.

Key Messages

Experimental studies have shown beneficial effects of TQ against renal diseases; however, well-designed clinical trials in humans are required to confirm these effects.

Adrenomedullin serves a role in the humoral pathway of delayed remote ischemic preconditioning via a hypoxia-inducible factor-1α-associated mechanism

Remote ischemic preconditioning (RIPC) is a minimally invasive method that provides protection by reducing injury to the heart, kidneys, brain and other tissues or organs. RIPC may improve the outcome in patients undergoing surgery. Although the role of RIPC has been studied, the results remain controversial. It is difficult to confirm whether RIPC has a kidney protective effect and the understanding of the preconditioning signal pathway involved remains unclear. In the present study, the effect of RIPC in urology was evaluated. The protection against renal damage was assessed by investigating the potential mediator, hypoxia-inducible factor-1α (HIF-1α), and the functional adrenomedullin (ADM) pathway. Male Sprague-Dawley (SD) rats were used in the present study. The animal model of kidney damage induced by ischemia reperfusion (IR) was used to investigate the protective effect of the acute and delayed phase RIPC. Furthermore, the protective effects of RIPC mediated by a HIF-1α-ADM pathway were assessed. The indexes of renal function and oxidative damage indicators were measured by Cr, BUN, mALB, β2-MG, MPO, MDA and SOD assays, and the expression of HIF-1α and ADM were detected by western blot analysis, immunohistochemistry and ELISA assays. Tubular score, determined using hematoxylin and eosin staining, was used to evaluate renal tissue damage. Applying RIPC prevented IR-induced renal dysfunction and oxidative damage by decreasing Cr, BUN, mALB, β2-MG, MPO, MDA levels and increasing SOD activity. Findings showed that delayed RIPC had an improved effect compared with acute treatment. Delayed RIPC also upregulated the expression of HIF-1α and ADM, indicating that the protective effect of the delayed RIPC may be associated with a HIF-1α-ADM-mediated mechanism. The effect of the delayed RIPC to reduce IR-induced renal damage and increase ADM expression was enhanced by HIF-1α agonists DMOG and BAY 85–3934, whereas the effect was whittled by HIF-1α antagonists YC-1 and 2-MeOE2. Furthermore, receiving ADM also offered protection to the kidney in comparison with the IR+Vehicle group. These findings suggest that RIPC prevents IR-mediated renal damage by HIF-1α via an ADM humoral pathway. In the present study, RIPC provided an effective renal protection. ADM could also offer protection regulated by HIF-1α in renal tissue. However, the mechanism of ADM as a protective factor in RIPC requires further research.

Remote ischaemic conditioning reduces infarct size in animal in vivo models of ischaemia-reperfusion injury: a systematic review and meta-analysis

Aims

The potential of remote ischaemic conditioning (RIC) to ameliorate myocardial ischaemia-reperfusion injury (IRI) remains controversial. We aimed to analyse the pre-clinical evidence base to ascertain the overall effect and variability of RIC in animal in vivo models of myocardial IRI. Furthermore, we aimed to investigate the impact of different study protocols on the protective utility of RIC in animal models and identify gaps in our understanding of this promising therapeutic strategy.

Methods and results

Our primary outcome measure was the difference in mean infarct size between RIC and control groups in in vivo models of myocardial IRI. A systematic review returned 31 reports, from which we made 22 controlled comparisons of remote ischaemic preconditioning (RIPreC) and 21 of remote ischaemic perconditioning and postconditioning (RIPerC/RIPostC) in a pooled random-effects meta-analysis. In total, our analysis includes data from 280 control animals and 373 animals subject to RIC. Overall, RIPreC reduced infarct size as a percentage of area at risk by 22.8% (95% CI 18.8–26.9%), when compared with untreated controls (P < 0.001). Similarly, RIPerC/RIPostC reduced infarct size by 22.2% (95% CI 17.1–25.3%; P < 0.001). Interestingly, we observed significant heterogeneity in effect size (T2 = 92.9% and I2 = 99.4%; P < 0.001) that could not be explained by any of the experimental variables analysed by meta-regression. However, few reports have systematically characterized RIC protocols, and few of the included in vivo studies satisfactorily met study quality requirements, particularly with respect to blinding and randomization.

Conclusions

RIC significantly reduces infarct size in in vivo models of myocardial IRI. Heterogeneity between studies could not be explained by the experimental variables tested, but studies are limited in number and lack consistency in quality and study design. There is therefore a clear need for more well-performed in vivo studies with particular emphasis on detailed characterization of RIC protocols and investigating the potential impact of gender. Finally, more studies investigating the potential benefit of RIC in larger species are required before translation to humans.

One session of remote ischemic preconditioning does not improve vascular function in acute normobaric and chronic hypobaric hypoxia

NEW FINDINGS

What is the central question of this study? It is suggested that remote ischemic preconditioning (RIPC) might offer protection against ischaemia-reperfusion injuries, but the utility of RIPC in high-altitude settings remains unclear. What is the main finding and its importance? We found that RIPC offers no vascular protection relative to pulmonary artery pressure or peripheral endothelial function during acute, normobaric hypoxia and at high altitude in young, healthy adults. However, peripheral chemosensitivity was heightened 24 h after RIPC at high altitude. Application of repeated short-duration bouts of ischaemia to the limbs, termed remote ischemic preconditioning (RIPC), is a novel technique that might have protective effects on vascular function during hypoxic exposures. In separate parallel-design studies, at sea level (SL; n = 16) and after 8-12 days at high altitude (HA; n = 12; White Mountain, 3800 m), participants underwent either a sham protocol or one session of four bouts of 5 min of dual-thigh-cuff occlusion with 5 min recovery. Brachial artery flow-mediated dilatation (FMD; ultrasound), pulmonary artery systolic pressure (PASP; echocardiography) and internal carotid artery (ICA) flow (ultrasound) were measured at SL in normoxia and isocapnic hypoxia (end-tidal PO2 maintained at 50 mmHg) and during normal breathing at HA. The hypoxic ventilatory response (HVR) was measured at each location. All measures at SL and HA were obtained at baseline (BL) and at 1, 24 and 48 h post-RIPC or sham. At SL, RIPC produced no changes in FMD, PASP, ICA flow, end-tidal gases or HVR in normoxia or hypoxia. At HA, although HVR increased 24 h post-RIPC compared with BL [2.05 ± 1.4 versus 3.21 ± 1.2 l min^-1  (% arterial O₂ saturation)^-1 , P < 0.01], there were no significant differences in FMD, PASP, ICA flow and resting end-tidal gases. Accordingly, a single session of RIPC is insufficient to evoke changes in peripheral, pulmonary and cerebral vascular function in healthy adults. Although chemosensitivity might increase after RIPC at HA, this did not confer any vascular changes. The utility of a single RIPC session seems unremarkable during acute and chronic hypoxia.

Remote Ischemic Conditioning and Renal Protection

Over the course of the last 2 decades, the concept of remote ischemic conditioning (RIC) has attracted considerable research interest, because RIC, in most of its embodiments offers an inexpensive way of protecting tissues against ischemic damage inflicted by a number of medical conditions or procedures. Acute kidney injury (AKI) is a common side effect in the context of various medical procedures, and RIC has been suggested as a means of reducing its incidence. Outcomes regarding kidney function have been reported in numerous studies that evaluated the effects of RIC in a variety of settings (eg, cardiac surgery, interventions requiring intravenous administration of contrast media). Although several individual studies have implied a beneficial effect of RIC in preserving kidney function, 3 recently published randomized controlled trials evaluating more than 1000 patients each (Effect of Remote Ischemic Preconditioning in the Cardiac Surgery, Remote Ischaemic Preconditioning for Heart Surgery, and ERICCA) were negative. However, AKI or any other index of renal function was not a stand-alone primary end point in any of these trials. On the other hand, a range of meta-analyses (each including thousands of participants) have reported mixed results, with the most recent among them showing benefit from RIC, pinpointing at the same time a number of shortcomings in published studies, adversely affecting the quality of available data. The present review provides a critical appraisal of the current state of this field of research. It is the opinion of the authors of this review that there is a clear need for a common clinical trial framework for ischemic conditioning studies. If the current babel of definitions, procedures, outcomes, and goals persists, it is most likely that soon ischemic conditioning will be "yesterday's news" with no definitive conclusions having been reached in terms of its real clinical utility.

The age-associated loss of ischemic preconditioning in the kidney is accompanied by mitochondrial dysfunction, increased protein acetylation and decreased autophagy

In young rats, ischemic preconditioning (IPC), which consists of 4 cycles of ischemia and reperfusion alleviated kidney injury caused by 40-min ischemia. However,old rats lost their ability to protect the ischemic kidney by IPC. A similar aged phenotype was demonstrated in 6-month-old OXYS rats having signs of premature aging. In the kidney of old and OXYS rats, the levels of acetylated nuclear proteins were higher than in young rats, however, unlike in young rats, acetylation levels in old and OXYS rats were further increased after IPC. In contrast to Wistar rats, age-matched OXYS demonstrated no increase in lysosome abundance and LC3 content in the kidney after ischemia/reperfusion. The kidney LC3 levels were also lower in OXYS, even under basal conditions, and mitochondrial PINK1 and ubiquitin levels were higher, suggesting impaired mitophagy. The kidney mitochondria from old rats contained a population with diminished membrane potential and this fraction was expanded by IPC. Apparently, oxidative changes with aging result in the appearance of malfunctioning renal mitochondria due to a low efficiency of autophagy. Elevated protein acetylation might be a hallmark of aging which is associated with a decreased autophagy, accumulation of dysfunctional mitochondria, and loss of protection against ischemia by IPC.

Effects of Remote Ischemic Preconditioning on Heme Oxygenase-1 Expression and Cutaneous Wound Repair

Skin wounds may lead to scar formation and impaired functionality. Remote ischemic preconditioning (RIPC) can induce the anti-inflammatory enzyme heme oxygenase-1 (HO-1) and protect against tissue injury. We aim to improve cutaneous wound repair by RIPC treatment via induction of HO-1. RIPC was applied to HO-1-luc transgenic mice and HO-1 promoter activity and mRNA expression in skin and several other organs were determined in real-time. In parallel, RIPC was applied directly or 24h prior to excisional wounding in mice to investigate the early and late protective effects of RIPC on cutaneous wound repair, respectively. HO-1 promoter activity was significantly induced on the dorsal side and locally in the kidneys following RIPC treatment. Next, we investigated the origin of this RIPC-induced HO-1 promoter activity and demonstrated increased mRNA in the ligated muscle, heart and kidneys, but not in the skin. RIPC did not change HO-1 mRNA and protein levels in the wound 7 days after cutaneous injury. Both early and late RIPC did not accelerate wound closure nor affect collagen deposition. RIPC induces HO-1 expression in several organs, but not the skin, and did not improve excisional wound repair, suggesting that the skin is insensitive to RIPC-mediated protection.

Repeated remote ischemic preconditioning and isoflurane anesthesia in an experimental model of renal ischemia-reperfusion injury

Background

In animal studies, remote ischemic preconditioning (RIPC) and anesthetic preconditioning are successful in reducing renal ischemia reperfusion injury (IRI), however the protective effect of RIPC may be improved by repeating the RIPC stimulus.

Methods

Sprague-Dawley rats underwent unilateral nephrectomy followed by 30 min of renal pedicle clamping. Animals were allocated into six groups: sham, control (IRI), RepISO (daily isoflurane anesthesia), RIPC (single dose isoflurane anesthesia and single dose RIPC), RepISO + RIPC (7-day isoflurane anesthesia and single dose RIPC) and RepISO + RepRIPC (7-day isoflurane anesthesia with 7-day RIPC). RIPC was applied by 3×5 min of cuff inflation on both thighs. Serum creatinine and urea levels were measured and histology was obtained at day two.

Results

RepISO diminished renal IRI, as reflected by a significant reduction in serum creatinine levels as compared to the control group, 170 ± 74 resp. 107 ± 29 μmol/L. The other preconditioning protocols showed similar reduction in serum creatinine levels as compared to the control group. No significant differences were observed between the different preconditioning protocols. For urea levels, only RepISO + RIPC resulted in significantly lower levels as compared to the control group, 14 ± 4 resp. 22 ± 7 mmol/L (p = 0.010). In the preconditioning groups only RepISO showed less histological damage as compared to controls 1.73 ± 1.19 resp. 2.91 ± 1.22 (p = 0.032).

Conclusions

In this study no additional protective effect of repeated ischemic preconditioning was observed as compared to single dose RIPC. Repeated administration of isoflurane provided stronger protection against renal IRI as compared to single dose isoflurane.

MicroRNA-29a/b/c targets iNOS and is involved in protective remote ischemic preconditioning in an ischemia-reperfusion rat model of non-alcoholic fatty liver disease

Remote ischemic preconditioning (RIPC) protects against the injury that is incurred by ischemia and reperfusion (IR); however, the role of RIPC in liver IR injury in non-alcoholic fatty liver disease (NAFLD) remains unclear. In this study, a NAFLD rat model was utilized in a series of different surgical procedures and molecular experiments. Rats of the IR group and the RIPC+IR group exhibited more severe injury than NAFLD control rats (in which the liver was prodded following a median-incision laparotomy). The liver condition, measured by serum alanine transaminase and aspartate transaminase levels, of the RIPC+IR group was better than that of the IR group. In addition, alanine transaminase and aspartate transaminase levels were lower in the RIPC+IR group compared with the IR group (P<0.001). Flow cytometry revealed that the cell apoptosis ratio was significantly lower in the RIPC+IR group than in the IR group (P<0.001). Reverse transcription-polymerase chain reaction (RT-qPCR) was used to assess miR-29a/b/c levels, revealing that they were significantly reduced in the RIPC and RIPC+IR groups, but did not vary in the IR group compared with the control group. RT-qPCR also revealed that iNOS mRNA levels were not significantly different among any of the NAFLD groups; however, western blot analysis indicated that iNOS protein levels were increased in the RIPC group and the RIPC+IR group compared with the control and IR groups. A luciferase reporter assay demonstrated that transfection with miR-29a/b/c mimics significantly decreased the luciferase activities of plasmids containing the wild-type iNOS 3'-untranslated region (UTR) (relative fluorescence intensity: 0.47±0.06 for miR-29a, 0.36±0.07 for miR-29b, 0.41±0.04 for miR-29c; P<0.001), whereas the activities of plasmids containing the mutant iNOS 3'-UTR sequence were not markedly affected [relative fluorescence intensity: 0.99±0.08 for miR-29a (P=0.1349), 0.99±0.09 for miR-29b (P=0.1607), 0.97±0.07 for miR-29c (P=0.1824)]. This suggested that miR-29a/b/c downregulates iNOS by directly targeting its 3'-UTR. In summary, the results suggest that RIPC has a protective effect in NAFLD liver IR injury, which may be due to reduced miR-29a/b/c levels in the skeletal muscle, leading to increased iNOS and, therefore, nitric oxide.

Remote Preconditioning on Rat Hepatic Ischemia-Reperfusion Injury Downregulated Bax and Cleaved Caspase-3 Expression

OBJECTIVE

Hepatic ischemia-reperfusion injury (IRI) is considered a major cause of hepatic damage in liver surgery. The aim of this study was to investigate the effect of the remote ischemic perconditioning method on hepatic IRI in a rat model.

METHODS

Seventeen rats underwent hepatic IRI for 30 minutes followed by reperfusion, and were divided into 3 groups: group I, only hepatic IRI (n = 5); group II, hepatic IRI with remote perconditioning (n = 7); and group III, hepatic IRI with remote postconditioning (n = 5).

RESULTS

For Bax/β-actin, mean values of the 3 groups (±standard deviation) were 1.29 ± 0.26 (group I), 0.89 ± 0.15 (group II), and 1.02 ± 0.23 (group III). The level of Bax/β-actin in group II was significantly lower than in group I (P < .01). The cleaved Caspase-3/β-actin ratio for groups I, II, and III was 0.93 ± 0.22, 0.46 ± 0.16, and 0.63 ± 0.22, respectively. The level of cleaved Caspase-3/β-actin in groups II and III were significantly lower than in group I (P < .01 and P < .05, respectively). The Bcl-2/β-actin ratio for groups I, II, and III was 1.01 ± 0.09, 1.19 ± 0.39, and 1.20 ± 0.12, respectively. However, there were no significant difference between groups II and III and group I.

CONCLUSIONS

The remote perconditioning on rat hepatic IRI downregulated the Bax and cleaved Caspase-3 expression.

Mechanisms underpinning protection against eccentric exercise-induced muscle damage by ischemic preconditioning

Eccentric exercise training is effective for increasing muscle mass and strength, and improving insulin sensitivity and blood lipid profiles. However, potential muscle damage symptoms such as prolonged loss of muscle function and delayed onset of muscle soreness may restrict the use of eccentric exercise, especially in clinical populations. Therefore, strategies to reduce eccentric exercise-induced muscle damage (EIMD) are necessary, and an extensive number of scientific studies have tried to identify potential intervention modalities to perform eccentric exercises without adverse effects. The present paper is based on a narrative review of current literature, and provides a novel hypothesis by which an ischemic preconditioning (IPC) of the extremities may reduce EIMD. IPC consists of an intermittent application of short-time non-lethal ischemia to an extremity (e.g. using a tourniquet) followed by reperfusion and was discovered in clinical settings in an attempt to minimize inflammatory responses induced by ischemia and ischemia-reperfusion-injury (I/R-Injury) during surgery. The present hypothesis is based on morphological and biochemical similarities in the pathophysiology of skeletal muscle damage during clinical surgery and EIMD. Even though the primary origin of stress differs between I/R-Injury and EIMD, subsequent cellular alterations characterized by an intracellular accumulation of Ca²⁺, an increased production of reactive oxygen species or increased apoptotic signaling are essential elements for both. Moreover, the incipient immune response appears to be similar in I/R-Injury and EIMD, which is indicated by an infiltration of leukocytes into the damaged soft-tissue. Thus far, IPC is considered as a potential intervention strategy in the area of cardiovascular or orthopedic surgery and provides significant impact on soft-tissue protection and downregulation of undesired excessive inflammation induced by I/R-Injury. Based on the known major impact of IPC on skeletal muscle physiology and immunology, the present paper aims to illustrate the potential protective effects of IPC on EIMD by discussing possible underlying mechanisms.

Renal Protection Using Remote Ischemic Peri-Conditioning During Inter-Facility Helicopter Transport of Patients With ST-Segment Elevation Myocardial Infarction: A Retrospective Study

OBJECTIVE

To assess the impact of remote ischemic peri-conditioning (RIPC) during inter-facility air medical transport of ST-segment elevation myocardial infarction (STEMI) patients on the incidence of acute kidney injury (AKI) following primary percutaneous coronary intervention (pPCI).

BACKGROUND

STEMI patients who receive pPCI have an increased risk of AKI for which there is no well-defined prophylactic therapy in the setting of emergent pPCI.

METHODS

Using the ACTION Registry-GWTG, we evaluated the impact of RIPC applied during inter-facility helicopter transport of STEMI patients from non-PCI capable hospitals to 2 PCI-hospitals in the United States between March, 2013 and September, 2015 on the incidence of AKI following pPCI. AKI was defined as ≥0.3 mg/dL increase in creatinine within 48-72 hours after pPCI.

RESULTS

Patients who received RIPC (n = 127), compared to those who did not (n = 92), were less likely to have AKI (11 of 127 patients [8.7%] vs. 17 of 92 patients [18.5%]; adjusted odds ratio = 0.32, 95% CI 0.12-0.85, P = 0.023) and all-cause in-hospital mortality (2 of 127 patients [1.6%] vs. 7 of 92 patients [7.6%]; adjusted odds ratio = 0.14, 95% CI 0.02-0.86, P = 0.034) after adjusting for socio-demographic and clinical characteristics. There was no difference in hospital length of stay (3 days [interquartile range, 2-4] vs. 3 days [interquartile range, 2-5], P = 0.357) between the 2 groups.

CONCLUSION

RIPC applied during inter-facility helicopter transport of STEMI patients for pPCI is associated with lower incidence of AKI and in-hospital mortality. The use of RIPC for renal protection in STEMI patients warrants further in depth investigation.

Investigating the involvement of TRPV1 ion channels in remote hind limb preconditioning-induced cardioprotection in rats

Remote ischemic preconditioning (RIPC) treatment strategy is a breakthrough in the field of cardiovascular pharmacology as it has the potential to attenuate myocardial ischemia-reperfusion injury. However, the underlying intracellular pathways have not been widely explored. The present study intends to explore the possible role of TRPV₁ channels in mediating remote hind limb preconditioning-induced cardioprotection. Remote hind limb preconditioning stimulus (4 cycles in succession) was delivered by tying the blood pressure cuff at the inguinal level of the rat. The Langendorff system was used to perfuse the isolated heart and afterward was subjected to 30 min of global ischemia and 120 min of reperfusion. Sustained ischemia and, thereafter, reperfusion led to cardiac injury that was assessed in terms of infarct size, lactate dehydrogenase (LDH) release, creatine kinase (CK) release, left ventricular end diastolic pressure (LVEDP), left ventricular developed pressure (LVDP), +dp/dt_max, -dp/dt_min, heart rate, rate pressure product, and coronary flow rate. The pharmacological modulators employed included capsaicin as TRPV₁ agonist and capsazepine as TRPV₁ antagonist. Remote hind limb preconditioning stimulus and capsaicin preconditioning (5 and 10 mg/kg) led to significant reduction in infarct size, LVEDP, LDH release, CK release, and significant improvement in LVDP, +dp/dt_max, -dp/dt_min, heart rate, rate pressure product, and coronary flow rate. However, remote hind limb preconditioning-induced cardioprotective effects were considerably abolished in the presence of capsazepine (2.5 and 5 mg/kg). This indicates that remote hind limb preconditioning stimulus possibly activates TRPV₁ channels to produce cardioprotective effects.

Adenosine Receptor Activation in the "Trigger" Limb of Remote Pre-Conditioning Mediates Human Endothelial Conditioning and Release of Circulating Cardioprotective Factor(s)

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Pre-conditioning has emerged as a potentially powerful means of reducing ischemia-reperfusion injury.

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Several animal models have implicated adenosine in pre-conditioning pathways, but its role in human physiology is unknown.

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In human volunteers, the authors demonstrate that adenosine receptor activation in “trigger” tissue is an important step in initiating a pre-conditioning signal, but adenosine receptor blockade in “target” tissue does not block the protection afforded by pre-conditioning.

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The authors also demonstrate that pre-conditioning elaborates a transferrable cardioprotective factor(s) into the serum. This elaboration is prevented by adenosine receptor blockade but can be mirrored by the infusion of exogenous adenosine.

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An improved understanding of the physiological effectors of pre-conditioning may allow for better targeted clinical studies of pre-conditioning and pre-conditioning mimetics in the future.

Remote ischemic pre-conditioning (rIPC) has emerged as a potential mechanism to reduce ischemia-reperfusion injury. Clinical data, however, have been mixed, and its physiological basis remains unclear, although it appears to involve release of circulating factor(s) and/or neural pathways. Here, the authors demonstrate that adenosine receptor activation is an important step in initiating human pre-conditioning; that pre-conditioning liberates circulating cardioprotective factor(s); and that exogenous adenosine infusion is able to recapitulate release of this factor. However, blockade of adenosine receptors in ischemic tissue does not block the protection afforded by pre-conditioning. These data have important implications for defining the physiology of human pre-conditioning and its translation to future clinical trials.

Remote Ischemic Preconditioning and Protection of the Kidney--A Novel Therapeutic Option

OBJECTIVE

Acute kidney injury is a common complication in critically ill patients and is associated with increased morbidity and mortality. Sepsis, major surgery, and nephrotoxic drugs are the most common causes of acute kidney injury. There is currently no effective strategy available to prevent or treat acute kidney injury. Therefore, novel treatment regimens are required to decrease acute kidney injury prevalence and to improve clinical outcomes. Remote ischemic preconditioning, triggered by brief episodes of ischemia and reperfusion applied in distant tissues or organs before the injury of the target organ, attempts to invoke adaptive responses that protect against acute kidney injury. We sought to evaluate the clinical evidence for remote ischemic preconditioning as a potential strategy to protect the kidney and to review the underlying mechanisms in light of recent studies.

DATA SOURCES

We searched PubMed for studies reporting the effect of remote ischemic preconditioning on kidney function in surgical patients (search terms: "remote ischemic preconditioning," "kidney function," and "surgery"). We also reviewed bibliographies of relevant articles to identify additional citations.

STUDY SELECTION

Published studies, consisting of randomized controlled trials, are reviewed.

DATA EXTRACTION

The authors used consensus to summarize the evidence behind the use of remote ischemic preconditioning.

DATA SYNTHESIS

In addition, the authors suggest patient populations and clinical scenarios in which remote ischemic preconditioning might be best applied.

CONCLUSIONS

Several experimental and clinical studies have shown tissue-protective effects of remote ischemic preconditioning in various target organs, including the kidneys. Remote ischemic preconditioning may offer a novel, noninvasive, and inexpensive treatment strategy for decreasing acute kidney injury prevalence in high-risk patients. Although many new studies have further advanced our knowledge in this area, the appropriate intensity of remote ischemic preconditioning, its mechanisms of action, and the role of biomarkers for patient selection and monitoring are still unknown.

Remote ischemic postconditioning protects against renal ischemia/reperfusion injury by activation of T-LAK-cell-originated protein kinase (TOPK)/PTEN/Akt signaling pathway mediated anti-oxidation and anti-inflammation

BACKGROUND

Recent clinical and animal studies suggested that remote limb ischemic postconditioning (RIPostC) can invoke potent cardioprotection or neuroprotection. However, the effect and mechanism of RIPostC against renal ischemia/reperfusion injury (IRI) are poorly understood. T-LAK-cell-originated protein kinase (TOPK) is crucial for the proliferation and migration of tumor cells. However, the function of TOPK and the molecular mechanism underlying renal protection remain unknown. Therefore, this study aimed to evaluate the role of TOPK in renoprotection induced by RIPostC.

MATERIALS AND METHODS

The renal IRI model was induced by left renal pedicle clamping for 45min followed by 24h reperfusion and right nephrectomy. All mice were intraperitoneally injected with vehicle, TOPK inhibitor HI-TOPK-032 or Akt inhibitor LY294002. After 24h reperfusion, renal histology, function, and inflammatory cytokines and oxidative stress were assessed. The proteins were measured by Western blotting.

RESULTS

The results showed that RIPostC significantly protected the kidneys against IRI. The protective effects were accompanied by the attenuation of renal dysfunction, tubular damage, inflammation and oxidative stress. In addition, RIPostC increased the phosphorylation of TOPK, PTEN, Akt, GSK3β and the nuclear translocation of Nrf2 and decreased the nuclear translocation of NF-κB. However, all of the above renoprotective effects of RIPostC were eliminated either by the inhibition of TOPK or Akt with HI-TOPK-032 or LY294002.

CONCLUSIONS

The current data reveal that RIPostC protects against renal IRI via activation of TOPK/PTEN/Akt signaling pathway mediated anti-oxidation and anti-inflammation.

Limb ischemic preconditioning protects against contrast-induced nephropathy via renalase

Clinical trials shows that remote ischemic preconditioning (IPC) can protect against contrast induced nephropathy (CIN) in risky patients, however, the exact mechanism is unclear. In this study, we explored whether renalase, an amine oxidase that has been previously shown to mediate reno-protection by local IPC, would also mediate the same effect elicited by remote IPC in animal model. Limb IPC was performed for 24 h followed by induction of CIN. Our results indicated that limb IPC prevented renal function decline, attenuated tubular damage and reduced oxidative stress and inflammation in the kidney. All those beneficial effects were abolished by silencing of renalase with siRNA. This suggests that similar to local IPC, renalase is also critically involved in limb IPC-elicited reno-protection. Mechanistic studies showed that limb IPC increased TNFα levels in the muscle and blood, and up-regulated renalase and phosphorylated IκBα expression in the kidney. Pretreatment with TNFα antagonist or NF-κB inhibitor, largely blocked renalase expression. Besides, TNFα preconditioning increased expression of renal renalase in vivo and in vitro, and attenuated H₂O₂ induced apoptosis in renal tubular cells. Collectively, our results suggest that limb IPC-induced reno-protection in CIN is dependent on increased renalase expression via activation of the TNFα/NF-κB pathway.

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Limb ischemic preconditioning (IPC) leads to renalase upregulation in kidney tissue.

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Renalase is critically involved in limb IPC-elicited renal protection in contrast induced nephropathy.

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Limb IPC induces renalase upregulation via activation of the tumor necrosis factor α (TNFα)/ nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) pathway.

Renalase, a kidney-secreted protein, serves as extracellular pro-survival signals and has been reported to participate in the local ischemic preconditioning (IPC) induced renal protection against ischemia-reperfusion injury. Whether renalase contributes to the beneficial effects of limb IPC on contrast induced nephropathy (CIN) remains unknown. This study revealed that limb IPC induced reno-protection in CIN was at least in part dependent on increased renalase expression, which is evidenced by our observations that knockdown of renalase abolished reno-protective effects conferred by limb IPC. The upregulation of renalase elicited by limb IPC may be mediated by activation of TNFα/NF-κB pathway.

Gadolinium and ruthenium red attenuate remote hind limb preconditioning-induced cardioprotection: possible role of TRP and especially TRPV channels

Remote ischemic preconditioning is a well reported therapeutic strategy that induces cardioprotective effects but the underlying intracellular mechanisms have not been widely explored. The current study was designed to investigate the involvement of TRP and especially TRPV channels in remote hind limb preconditioning-induced cardioprotection. Remote hind limb preconditioning stimulus (4 alternate cycles of inflation and deflation of 5 min each) was delivered using a blood pressure cuff tied on the hind limb of the anesthetized rat. Using Langendorff's system, the heart was perfused and subjected to 30-min ischemia and 120-min reperfusion. The myocardial injury was assessed by measuring infarct size, lactate dehydrogenase (LDH), creatine kinase (CK), LVDP, +dp/dtmax, -dp/dtmin, heart rate, and coronary flow rate. Gadolinium, TRP blocker, and ruthenium red, TRPV channel blocker, were employed as pharmacological tools. Remote hind limb preconditioning significantly reduced the infarct size, LDH release, CK release and improved coronary flow rate, hemodynamic parameters including LVDP, +dp/dtmax, -dp/dtmin, and heart rate. However, gadolinium (7.5 and 15 mg kg(-1)) and ruthenium red (4 and 8 mg kg(-1)) significantly attenuated the cardioprotective effects suggesting the involvement of TRP especially TRPV channels in mediating remote hind limb preconditioning-induced cardioprotection. Remote hind limb preconditioning stimulus possibly activates TRPV channels on the heart or sensory nerve fibers innervating the heart to induce cardioprotective effects. Alternatively, remote hind limb preconditioning stimulus may also activate the mechanosensitive TRP and especially TRPV channels on the sensory nerve fibers innervating the skeletal muscles to trigger cardioprotective neurogenic signaling cascade. The cardioprotective effects of remote hind limb preconditioning may be mediated via activation of mechanosensitive TRP and especially TRPV channels.

Protection of remote ischemic preconditioning against acute kidney injury: a systematic review and meta-analysis

Background

Remote ischemic preconditioning (RIPC) is a promising approach to preventing acute kidney injury (AKI), but its efficacy is controversial.

Methods

A systematic review of 30 randomized controlled trials was conducted to investigate the effects of RIPC on the incidence and outcomes of AKI. Random effects model meta-analyses and meta-regressions were used to generate summary estimates and explore sources of heterogeneity. The primary outcome was incidence of AKI and hospital mortality.

Results

The total pooled incidence of AKI in the RIPC group was 11.5 %, significantly less than the 23.3 % incidence in the control group (P = 0.009). Subgroup analyses indicated that RIPC significantly reduced the incidence of AKI in the contrast-induced AKI (CI-AKI) subgroup from 13.5 % to 6.5 % (P = 0.000), but not in the ischemia/reperfusion-induced AKI (IR-AKI) subgroup (from 29.5 % to 24.7 %, P = 0.173). Random effects meta-regression indicated that RIPC tended to strengthen its renoprotective effect (q = 3.95, df = 1, P = 0.047) in these trials with a higher percentage of diabetes mellitus. RIPC had no significant effect on the incidence of stages 1–3 AKI or renal replacement therapy, change in serum creatinine and estimated glomerular filtration rate (eGFR), hospital or 30-day mortality, or length of hospital stay. But RIPC significantly increased the minimum eGFR in the IR-AKI subgroup (P = 0.006) compared with the control group. In addition, the length of ICU stay in the RIPC group was significantly shorter than in the control group (2.6 vs 2.0 days, P = 0.003).

Conclusions

We found strong evidence to support the application of RIPC to prevent CI-AKI, but not IR-AKI.

Electronic supplementary material

The online version of this article (doi:10.1186/s13054-016-1272-y) contains supplementary material, which is available to authorized users.

No Effect of Remote Ischemic Conditioning Strategies on Recovery from Renal Ischemia-Reperfusion Injury and Protective Molecular Mediators

Ischemia-reperfusion injury (IRI) is the major cause of acute kidney injury. Remote ischemic conditioning (rIC) performed as brief intermittent sub-lethal ischemia and reperfusion episodes in a distant organ may protect the kidney against IRI. Here we investigated the renal effects of rIC applied either prior to (remote ischemic preconditioning; rIPC) or during (remote ischemic perconditioning; rIPerC) sustained ischemic kidney injury in rats. The effects were evaluated as differences in creatinine clearance (CrCl) rate, tissue tubular damage marker expression, and potential kidney recovery mediators. One week after undergoing right-sided nephrectomy, rats were randomly divided into four groups: sham (n = 7), ischemia and reperfusion (IR; n = 10), IR+rIPC (n = 10), and IR+rIPerC (n = 10). The rIC was performed as four repeated episodes of 5-minute clamping of the infrarenal aorta followed by 5-minute release either before or during 37 minutes of left renal artery clamping representing the IRI. Urine and blood were sampled prior to ischemia as well as 3 and 7 days after reperfusion. The kidney was harvested for mRNA and protein isolation. Seven days after IRI, the CrCl change from baseline values was similar in the IR (δ: 0.74 mL/min/kg [-0.45 to 1.94]), IR+rIPC (δ: 0.21 mL/min/kg [-0.75 to 1.17], p > 0.9999), and IR+rIPerC (δ: 0.41 mL/min/kg [-0.43 to 1.25], p > 0.9999) groups. Kidney function recovery was associated with a significant up-regulation of phosphorylated protein kinase B (pAkt), extracellular regulated kinase 1/2 (pERK1/2), and heat shock proteins (HSPs) pHSP27, HSP32, and HSP70, but rIC was not associated with any significant differences in tubular damage, inflammatory, or fibrosis marker expression. In our study, rIC did not protect the kidney against IRI. However, on days 3-7 after IRI, all groups recovered renal function. This was associated with pAkt and pERK1/2 up-regulation and increased HSP expression at day 7.

Renoprotective Mechanism of Remote Ischemic Preconditioning Based on Transcriptomic Analysis in a Porcine Renal Ischemia Reperfusion Injury Model

Ischemic preconditioning (IPC) is a well-known phenomenon in which tissues are exposed to a brief period of ischemia prior to a longer ischemic event. This technique produces tissue tolerance to ischemia reperfusion injury (IRI). Currently, IPC’s mechanism of action is poorly understood. Using a porcine single kidney model, we performed remote IPC with renal IRI and evaluated the IPC mechanism of action. Following left nephrectomy, 15 female Yorkshire pigs were divided into three groups: no IPC and 90 minutes of warm ischemia (control), remote IPC immediately followed by 90 minutes of warm ischemia (rIPCe), and remote IPC with 90 minutes of warm ischemia performed 24 hours later (rIPCl). Differential gene expression analysis was performed using a porcine-specific microarray. The microarray analysis of porcine renal tissues identified 1,053 differentially expressed probes in preconditioned pigs. Among these, 179 genes had altered expression in both the rIPCe and rIPCl groups. The genes were largely related to oxidation reduction, apoptosis, and inflammatory response. In the rIPCl group, an additional 848 genes had altered expression levels. These genes were primarily related to immune response and inflammation, including those coding for cytokines and cytokine receptors and those that play roles in the complement system and coagulation cascade. In the complement system, the membrane attack complex was determined to be sublytic, because it colocalized with phosphorylated extracellular signal-regulated kinase. Furthermore, alpha 2 macroglobulin, tissue plasminogen activator, uterine plasmin trypsin inhibitor, and arginase-1 mRNA levels were elevated in the rIPCl group. These findings indicate that remote IPC produces renoprotective effects through multiple mechanisms, and these effects develop over a long timeframe rather than immediately following IPC.

Molecular Mechanisms of Renal Ischemic Conditioning Strategies

Ischemia-reperfusion injury is the leading cause of acute kidney injury in a variety of clinical settings such as renal transplantation and hypovolemic and/or septic shock. Strategies to reduce ischemia-reperfusion injury are obviously clinically relevant. Ischemic conditioning is an inherent part of the renal defense mechanism against ischemia and can be triggered by short periods of intermittent ischemia and reperfusion. Understanding the signaling transduction pathways of renal ischemic conditioning can promote further clinical translation and pharmacological advancements in this era. This review summarizes research on the molecular mechanisms underlying both local and remote ischemic pre-, per- and postconditioning of the kidney. The different types of conditioning strategies in the kidney recruit similar powerful pro-survival mechanisms. Likewise, renal ischemic conditioning mobilizes many of the same protective signaling pathways as in other organs, but differences are recognized.

Hypoxia and Complement-and-Coagulation Pathways in the Deceased Organ Donor as the Major Target for Intervention to Improve Renal Allograft Outcome

BACKGROUND

In the last few decades, strategies to improve allograft survival after kidney transplantation have been directed to recipient-dependent mechanisms of renal injury. In contrast, no such efforts have been made to optimize organ quality in the donor. Optimizing deceased donor kidney quality opens new possibilities to improve renal allograft outcome.

METHODS

A total of 554 kidney biopsies were taken from donation after brain death (DBD) and donation after cardiac death (DCD) kidneys before donation, after cold ischemia and after reperfusion. Healthy living donor kidney biopsies served as controls. Transcriptomics was performed by whole genome microarray analyses followed by functional pathway analyses.

RESULTS

Before organ retrieval and before cessation of blood circulation, metabolic pathways related to hypoxia and complement-and-coagulation cascades were the major pathways enhanced in DBD donors. Similar pathways were also enriched in DCD donors after the first warm ischemia time. Shortly after reperfusion of DCD grafts, pathways related to prolonged and worsening deprivation of oxygen were associated with delayed graft function in the recipient.

CONCLUSION

In conclusion, this large deceased donor study shows enrichment of hypoxia and complement-and-coagulation pathways already in DBD donors before cessation of blood flow, before organ retrieval. Therefore, future intervention therapies should target hypoxia and complement-and-coagulation cascades in the donor to improve renal allograft outcome in the recipient.

Ineffectiveness of remote ischemic renal preconditioning in a porcine solitary-kidney model

PURPOSE

Our study sought to demonstrate the effects of remote ischemic preconditioning (R-IPC) on renal function in a large animal (porcine) solitary-kidney model.

METHODS

Twelve pigs were assigned to two groups: Each underwent a right nephrectomy followed by a week of recovery. Group 1 (No-IPC) underwent left renal hilar clamping for 90 minutes. Group 2 underwent right and left iliac artery clamping for 10 minutes each (R-IPC), followed by left hilar clamping for 90 minutes. Serum creatinine was drawn for both groups before ischemia (preoperative), then at 6 hours, 24 hours, 3 days, and 7 days after. Kidneys were harvested at 24 hours or 7 days for histologic analysis, and the degree of acute tubular necrosis (ATN) or lymphocyte invasion was quantified.

RESULTS

Paired serum creatinine values were analyzed between time points. For Group 1, paired differences existed at 24 hours (P=0.008) but not at 3 days or 7 days. For Group 2, paired differences existed at 24 hours (P=0.006) but not at 3 days or 7 days. The mean preoperative serum creatinine level was similar between groups (P>0.05). The change in serum creatinine level was not significantly different between groups at any time point. Histologic analysis revealed rare evidence of ATN at 24 hours in Group 2, but not in Group 1. At 7 days, neither group showed ATN, and both showed 1-2+evidence of lymphocytic infiltrates.

CONCLUSION

R-IPC in a solitary-kidney porcine model does not confer renal protection from warm ischemia either as evidenced by renal function measures or on histologic analysis.

Limb ischemic preconditioning protects against contrast-induced acute kidney injury in rats via phosphorylation of GSK-3β

Contrast-induced acute kidney injury (CI-AKI) resulting from the use of intravascular iodinated contrast media for diagnostic and interventional cardiovascular procedures is associated with substantial morbidity and mortality. Despite preventative measures intended to mitigate the risk of CI-AKI, there remains a need for a novel and effective therapeutic approach. Limb ischemic preconditioning (LIPC), where short-term ischemia/reperfusion is applied to an arm prior to administration of the contrast agent, has been shown in several trials to preserve renal function in patients at high risk for CI-AKI. However, the underlying mechanism by which this procedure provides renoprotection against contrast media insults is not known. Here, we explored the molecular mechanism(s) of LIPC-induced protection of the kidneys from CI-AKI, particularly the role of phosphorylated glycogen synthase kinase-3β (GSK-3β). We used a novel CI-AKI model consisting of 5/6 nephrectomized (NE) rats at 6 weeks after the ablative surgery. LIPC- or sham-treated rats were administered iohexol (10 ml/kg, 3.5 gI) via the tail vein. The results showed that LIPC protected the kidneys against iohexol-induced injury. This protective effect was accompanied by the attenuation of renal dysfunction, tubular damage, apoptosis, mitochondrial swelling, oxidative stress, and inflammation. Furthermore, LIPC-induced renoprotection was blocked via treatment with inhibitors of PI3K (wortmannin or LY294002), but not ERK (U0126 or PD98059). LIPC also increased the protein expression levels of phospho-Akt, phospho-GSK-3β, and nuclear Nrf2, and decreased the levels of nuclear NF-κB. A specific GSK-3β inhibitor (SB216763) mimicked this effect of LIPC, by inhibiting the opening of the mitochondrial permeability transition pore and reducing the levels of oxidative stress and inflammation via activation of Nrf2 and suppression of NF-κB. The above results demonstrate that LIPC induces protection against CI-AKI, making this procedure a promising strategy for preventing CI-AKI. In particular, this renoprotective effect involves the phosphorylation of GSK-3β.

The effect of remote ischemic postconditioning on graft function in patients undergoing living donor kidney transplantation

BACKGROUND

We evaluated whether remote ischemic postconditioning (RiPoC) could improve initial graft function in living donor kidney transplantation (KT).

METHODS

Patients undergoing living donor KT were randomly assigned to either RiPoC (n=30) or control group (n=30). Immediately after reperfusion in the RiPoC group, three cycles of ischemia and reperfusion, lasting 5 min each, were performed on one upper limb. Renal function was assessed before surgery, 2 hr after surgery, and at 12-hr intervals for 96 hr postsurgery by measuring serum creatinine (sCr) and the estimated glomerular filtration rate (eGFR). Urine output and urine creatinine were assessed until postoperative day 7, and hospital stay and complication rates were compared.

RESULTS

The time for sCr to reach 50% of its preoperative level was significantly shorter in the RiPoC group than in the control group [12 (12-24) hr for RiPoC vs. 24 (21-36) hr for the control, P=0.005]. The number of patients whose sCr was reduced by 50% within 24 hr was significantly greater in the RiPoC group than in the control group [n=26 (87%) in RiPoC vs. n=18 (60%) in control, P=0.020]. However, there were no differences in sCr and eGFR thereafter, the incidence of graft dysfunction or complication rates between groups.

CONCLUSION

In this study, RiPoC appeared to hasten the recovery of graft function within 24 hr but did not affect the graft function thereafter. However, considering most recipients had immediate graft function, further studies with deceased donors or studies powered to detect a smaller difference are needed.

Protective effects of three remote ischemic conditioning procedures against renal ischemic/reperfusion injury in rat kidneys: a comparative study

BACKGROUND

Remote ischemic perconditioning (RIPerC), remote ischemic postconditioning (RIPostC), and remote ischemic perconditioning + postconditioning (RIPerC + RIPostC) protect against renal ischemia reperfusion injury (IRI). However, the most beneficial approach among these is not known.

AIMS

To compare the protective effects and study the mechanisms of three different remote ischemic conditioning in preventing IRI in the rat kidney.

METHODS

Fifty healthy adult male Sprague-Dawley rats were randomly assigned to five groups: sham, IRI, RIPerC, RIPostC, and RIPerC + RIPostC. Right nephrectomy was performed initially in all rats. IRI was induced by occluding the left renal artery for 60 min, followed by reperfusion for 24 h. RIPerC, RIPostC, and RIPerC + RIPostC were induced with 5-min ischemia/reperfusion (I/R) cycles using a tourniquet on the right hind limb.

RESULTS

The IRI group showed significant serologic evidence of renal injury compared to the sham group (P < 0.05). The RIPerC, RIPostC, and RIperC + RIpostC groups displayed significantly lower levels of renal dysfunction than the IRI group (P < 0.05). Superoxide dismutase (SOD) levels were significantly lower in the IRI group than in the sham group (P = 0.003), but were significantly less depressed in the RIPerC, RIPostC, and RIperC + RIpostC groups (P < 0.05). The IRI group displayed more severe renal tubular injury than the RIPerC, RIPostC, and RIPerC + RIPostC groups (P < 0.05).

CONCLUSION

All three remote ischemic conditioning showed similar therapeutic potential for preventing renal IRI. The RIPerC + RIPostC protocol did not show an additive effect from the combination of preconditioning and postconditioning. The protective mechanism may be due to the stimulation of endogenous antioxidant activity by transient limb ischemia-reperfusion.

Effect of remote ischemic postconditioning on patients undergoing living donor liver transplantation

The aim of this study was to evaluate the protective effect of remote ischemic postconditioning (RIPostC) on graft function and acute kidney injury (AKI) after living donor liver transplantation (LT). Recipients undergoing elective living donor LT were randomly assigned to either the RIPostC group or the control group. Immediately after reperfusion, 4 cycles of ischemia and reperfusion lasting for 5 minutes each were performed on 1 upper limb in the RIPostC group. Graft function was assessed through evaluations of the serum levels of total bilirubin and liver enzymes and the prothrombin time for 28 days after surgery. The incidence of AKI, as defined by the Risk, Injury, Failure, Loss, and End-Stage Kidney Disease classification, was evaluated within 28 days of the operation. In addition, the incidences of graft dysfunction, acute cellular rejection, and major complications; the 1-, 3-, and 6-month mortality rates; the length of stay in the intensive care unit; and the length of hospital stay were also investigated. In all, 78 patients were enrolled in the analysis (n = 39 in each group). No differences in graft function or clinical outcomes were observed between the groups. The incidences of postoperative AKI were 38% (n = 15) in the RIPostC group and 72% (n = 28) in the control group (P = 0.006). Despite no improvements in postoperative graft function, RIPostC decreased the incidence of postoperative AKI after living donor LT in this study. However, no other clinical benefits with respect to the complication rate, length of hospital stay, or short-term mortality rate were observed. Thus, further studies will be needed to evaluate the clinical efficacy of RIPostC in LT fully.

Remote ischemic preconditioning to reduce contrast-induced nephropathy: study protocol for a randomized controlled trial

Background

Despite the increasing use of pre- and posthydration protocols and low-osmolar instead of high-osmolar iodine-containing contrast media, the incidence of contrast-induced nephropathy (CIN) is still significant. There is evidence that contrast media cause ischemia-reperfusion injury of the medulla. Remote ischemic preconditioning (RIPC) is a non-invasive, safe, and low-cost method to reduce ischemia-reperfusion injury.

Methods

The RIPCIN study is a multicenter, single-blinded, randomized controlled trial in which 76 patients at risk of CIN will receive standard hydration combined with RIPC or hydration with sham preconditioning. RIPC will be applied by four cycles of 5 min ischemia and 5 min reperfusion of the forearm by inflating a blood pressure cuff at 50 mmHg above the actual systolic pressure. The primary outcome measure will be the change in serum creatinine from baseline to 48 to 72 h after contrast administration.

Discussion

A recent pilot study reported that RIPC reduced the incidence of CIN after coronary angioplasty. The unusual high incidence of CIN in this study is of concern and limits its generalizability. Therefore, we propose a randomized controlled trial to study whether RIPC reduces contrast-induced kidney injury in patients at risk for CIN according to the Dutch guidelines.

Trial registration

Current Controlled Trials ISRCTN76496973

Ischaemic conditioning strategies for the nephrologist: a promise lost in translation?

Over the last quarter of a century, a huge effort has been made to develop interventions that can minimise ischaemia reperfusion injury. The most potent of these are the ischaemic conditioning strategies, which comprise ischaemic preconditioning, remote ischaemic preconditioning and ischaemic postconditioning. While much of the focus for these interventions has been on protecting the myocardium, other organs including the kidney can be similarly protected. However, translation of these beneficial effects from animal models into routine clinical practice has been less straightforward than expected. In this review, we examine the role of ischaemic conditioning strategies in reducing tissue injury from the 'bench to the bedside' and discuss the barriers to their greater translation.

Culture media from hypoxia conditioned endothelial cells protect human intestinal cells from hypoxia/reoxygenation injury

Remote ischemic preconditioning (RIPC) is a phenomenon, whereby short episodes of non-lethal ischemia to an organ or tissue exert protection against ischemia/reperfusion injury in a distant organ. However, there is still an apparent lack of knowledge concerning the RIPC-mediated mechanisms within the target organ and the released factors. Here we established a human cell culture model to investigate cellular and molecular effects of RIPC and to identify factors responsible for RIPC-mediated intestinal protection. Human umbilical vein cells (HUVEC) were exposed to repeated episodes of hypoxia (3 × 15 min) and conditioned culture media (CM) were collected after 24h. Human intestinal cells (CaCo-2) were cultured with or without CM and subjected to 90 min of hypoxia/reoxygenation injury. Reverse transcription-polymerase chain reaction, Western blotting, gelatin zymography, hydrogen peroxide measurements and lactate dehydrogenase (LDH) assays were performed. In HUVEC cultures hypoxic conditioning did not influence the profile of secreted proteins but led to an increased gelatinase activity (P<0.05) in CM. In CaCo-2 cultures 90 min of hypoxia/reoxygenation resulted in morphological signs of cell damage, increased LDH levels (P<0.001) and elevated levels of hydrogen peroxide (P<0.01). Incubation of CaCo-2 cells with CM reduced the hypoxia-induced signs of cell damage and LDH release (P<0.01) and abrogated the hypoxia-induced increase of hydrogen peroxide. These events were associated with an enhanced phosphorylation status of the prosurvival kinase Erk1/2 (P<0.05) but not Akt and STAT-5. Taken together, CM of hypoxia conditioned endothelial cells protect human intestinal cells from hypoxia/reoxygenation injury. The established culture model may help to unravel RIPC-mediated cellular events and to identify molecules released by RIPC.

Remote ischemic preconditioning and renoprotection: from myth to a novel therapeutic option?

There is currently no effective prophylactic regimen available to prevent contrast-induced AKI (CI-AKI), a frequent and life-threatening complication after cardiac catheterization. Therefore, novel treatment strategies are required to decrease CI-AKI incidence and to improve clinical outcomes in these patients. Remote ischemic preconditioning (rIPC), defined as transient brief episodes of ischemia at a remote site before a subsequent prolonged ischemia/reperfusion injury of the target organ, is an adaptational response that protects against ischemic and reperfusion insult. Indeed, several studies demonstrated the tissue-protective effects of rIPC in various target organs, including the kidneys. In this regard, rIPC may offer a novel noninvasive and virtually cost-free treatment strategy for decreasing CI-AKI incidence. This review evaluates the current experimental and clinical evidence for rIPC as a potential renoprotective strategy, and discusses the underlying mechanisms and key areas for future research.

Remote preconditioning reduces oxidative stress, downregulates cyclo-oxygenase-2 expression and attenuates ischaemia-reperfusion-induced acute kidney injury

Remote preconditioning (rPeC) is a phenomenon by which short-time intermittent ischaemia-reperfusion (I/R) of a remote organ during ischaemia protects other organs from I/R injury (IRI). The aim of the present study was to investigate the protective effect of rPeC on renal IRI in rats. Rats were subjected to right nephrectomy and randomized as into a sham group (no additional intervention), an I/R group (subjected to 45 min left renal pedicle occlusion) and an rPeC group (subjected to four cycles of 5 min I/R of the left femoral artery administered at the beginning of renal ischaemia). After 24 h, blood, urine and tissue samples were collected. Compared with the sham group, I/R resulted in renal dysfunction, as evidenced by significantly lower creatinine clearance (CCr; 0.52 ± 0.06 vs 0.11 ± 0.02 mL/min, respectively) and higher fractional excretion of sodium (FE(Na) ; 0.80 ± 0.07% vs 2.46 ± 0.20%, respectively). This was accompanied by decreased superoxide dismutase (SOD; 6.9 ± 1.7 vs 26.7 ± 2.7 U/g tissue) and catalase (CAT; 20.2 ± 8.8 vs 32.2 ± 8.7 K/g tissue) activity in the I/R group, as well as decreased levels of reduced glutathione (GSH; 21.7 ± 8.1 vs 81.2 ± 20.2 μmol/g tissue) and increased malondialdehyde levels (MDA; 1.2 to 0.1 vs 0.5 ± 0.2 μmol/100 mg), cyclo-oxygenase (COX)-2 expression and histological damage. In the rPeC group, renal histology and function were significantly improved (CCr 0.32 ± 0.02 mL/min; FE(Na) 1.33 ± 0.12%) compared with the I/R group. Furthermore, compared with the I/R group, the rPeC group exhibited increases in SOD and CAT activity (22.8 ± 3.8 U/g tissue and 21.7 ± 8.6 K/g tissue, respectively), increased GSH levels (74.0 ± 4.9) and decreased MDA levels (1.1 ± 0.3 μmol/100 mg) and COX-2 expression. In conclusion, rPeC appears to exert protective effects against renal IRI. This protection may be a consequence of reductions in lipid peroxidation, intensification of anti-oxidant systems and downregulation of COX-2 expression. A simple approach, rPeC may be a promising strategy for protection against IRI in clinical practice.