Protective effects of limb remote ischemic per-conditioning on the heart injury induced by renal ischemic-reperfusion through the interaction of the apelin with the RAS/iNOS pathway.

Introduction: Remote ischemic conditioning upregulates endogenous protective pathways in response to ischemia-reperfusion injury. This study tested the hypothesis that limb remote ischemic per- conditioning (RIPerC) exerts cardioprotective effects via the renin-angiotensin system (RAS)/inducible nitric oxide synthase (iNOS)/apelin pathway. Methods: Renal ischemia-reperfusion injury (I/R) was induced by bilateral occlusion of the renal pedicles for 60 minutes, followed by 24 hours of reperfusion; sham-operated rats served as controls. RIPerC was induced by four cycles (5 minutes) of limb ischemia-reperfusion along with bilateral renal ischemia. The functional disturbance was evaluated by renal (BUN and creatinine) and cardiac (troponin I and lactate dehydrogenase) injury biomarkers. Results: Renal I/R injury increased renal and cardiac injury biomarkers that were reduced in the RIPerC group. Histopathological findings of the kidney and heart were also suggestive of amelioration injury-induced changes in the RIPerC group. Assessment of cardiac electrophysiology revealed that RIPerC ameliorated the decline in P wave duration without significantly affecting other cardiac electrophysiological changes. Further, renal I/R injury increased the plasma (322.40±34.01 IU/L), renal (8.27±1.10 mIU/mg of Protein), and cardiac (68.28±10.28 mIU/mg of protein) angiotensin-converting enzyme (ACE) activities in association with elevations in the plasma and urine nitrite (25.47±2.01 & 16.62±3.05 µmol/L) and nitrate (15.47±1.33 & 5.01±0.96 µmol/L) levels; these changes were reversed by RIPerC. Further, renal ischemia-reperfusion injury significantly (P=0.047) decreased the renal (but not cardiac) apelin mRNA expression, while renal and cardiac ACE2 (P<0.05) and iNOS (P=0.043) mRNA expressions were significantly increased compared to the sham group; these effects were largely reversed by RIPerC. Conclusion: Our results indicated that RIPerC protects the heart against renal ischemia- reperfusion injury, likely via interaction of the apelin with the RAS/iNOS pathway.

Exosome is involved in liver graft protection after remote ischemia reperfusion conditioning.

BACKGROUND: Remote ischemic perconditioning (RIPerC) has been demonstrated to protect grafts from hepatic ischemia-reperfusion injury (IRI). This study investigated the role of exosomes in RIPerC of liver grafts in rats. METHODS: Twenty-five rats (including 10 donors) were randomly divided into five groups (n = 5 each group): five rats were used as sham-operated controls (Sham), ten rats were for orthotopic liver transplantation (OLT, 5 donors and 5 recipients) and ten rats were for OLT + RIPerC (5 donors and 5 recipients). Liver architecture and function were evaluated. RESULTS: Compared to the OLT group, the OLT + RIPerC group exhibited significantly improved liver graft histopathology and liver function (P < 0.05). Furthermore, the number of exosomes and the level of P-Akt were increased in the OLT + RIPerC group. CONCLUSIONS: RIPerC effectively improves graft architecture and function, and this protective effect may be related to the increased number of exosomes. The upregulation of P-Akt may be involved in underlying mechanisms.

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

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

Excess ischemic tachyarrhythmias trigger protection against myocardial infarction in hypertensive rats.

Increased level of C-reactive protein (CRP) is a risk factor for cardiovascular diseases, including myocardial infarction and hypertension. Here, we analyzed the effects of CRP overexpression on cardiac susceptibility to ischemia/reperfusion (I/R) injury in adult spontaneously hypertensive rats (SHR) expressing human CRP transgene (SHR-CRP). Using an in vivo model of coronary artery occlusion, we found that transgenic expression of CRP predisposed SHR-CRP to repeated and prolonged ventricular tachyarrhythmias. Excessive ischemic arrhythmias in SHR-CRP led to a significant reduction in infarct size (IS) compared with SHR. The proarrhythmic phenotype in SHR-CRP was associated with altered heart and plasma eicosanoids, myocardial composition of fatty acids (FAs) in phospholipids, and autonomic nervous system imbalance before ischemia. To explain unexpected IS-limiting effect in SHR-CRP, we performed metabolomic analysis of plasma before and after ischemia. We also determined cardiac ischemic tolerance in hearts subjected to remote ischemic perconditioning (RIPer) and in hearts ex vivo. Acute ischemia in SHR-CRP markedly increased plasma levels of multiple potent cardioprotective molecules that could reduce IS at reperfusion. RIPer provided IS-limiting effect in SHR that was comparable with myocardial infarction observed in naïve SHR-CRP. In hearts ex vivo, IS did not differ between the strains, suggesting that extra-cardiac factors play a crucial role in protection. Our study shows that transgenic expression of human CRP predisposes SHR-CRP to excess ischemic ventricular tachyarrhythmias associated with a drop of pump function that triggers myocardial salvage against lethal I/R injury likely mediated by protective substances released to blood from hypoxic organs and tissue at reperfusion.

REMOTE Ischemic Perconditioning Among Acute Ischemic Stroke Patients in Catalonia: REMOTE-CAT PROJECT.

Rationale: Remote ischemic perconditioning during cerebral ischemia (RIPerC) refers to the application of brief episodes of transient limb ischemia commonly to a limb, it represents a new safe, simple and low-cost paradigm in neuroprotection. Aim and/or Hypothesis: To evaluate the effects of RIPerC on acute ischemic stroke (AIS) patients, applied in the ambulance, to improve functional outcomes compared with standard of care. Sample Size Estimates: A sample size of 286 patients in each arm achieves 80% power to detect treatment differences of 14% in the outcome, using a two-sided binomial test at significance level of 0.05, assuming that 40% of the control patients will experience good outcome and an initial misdiagnosis rate of 29%. Methods and Design: We aim to conduct a multicentre study of pre-hospital RIPerC application in AIS patients. A total of 572 adult patients diagnosed of suspected clinical stroke within 8 h of symptom onset and clinical deficit >0 according to prehospital rapid arterial occlusion evaluation (RACE) scale score will be randomized, in blocks of size 4, to RIPerC or sham. Patients will be stratified by RACE score scale. RIPerC will be started in the ambulance before hospital admission and continued in the hospital if necessary. It will consist of five cycles of electronic tourniquet inflation and deflation (5 min each). The cuff pressure for RIPerC will be 200 mmHg during inflation. Sham will only simulate vibration of the device. Study Outcome(s): The primary outcome will be the difference in the proportion of patients with good outcomes as defined by a mRS score of 2 or less at 90 days. Secondary outcomes to be monitored will include early neurological improvement rate, treatment related serious adverse event rates, size of the infarct volume, symptomatic intracranial hemorrhage, metabolomic and lipidomic response to RIPerC and Neuropsychological evaluation at 90 days. Discussion: Neuroprotective therapies could not only increase the benefits of available reperfusion therapies among AIS patients but also provide an option for patients who are not candidates for these treatments. REMOTE-CAT will investigate the clinical benefit of RIC as a new neuroprotective strategy in AIS. Clinical Trial Registration: www.ClinicalTrials.gov, identifier: NCT03375762.

Induced neuroprotection by remote ischemic perconditioning as a new paradigm in ischemic stroke at the acute phase, a systematic review.

BACKGROUND: Remote ischemic conditioning during cerebral ischemia (remote ischemic perconditioning, RIPerC) refers to the application of several cycles of brief ischemia and reperfusion (I/R) commonly to a limb, and it represents a new paradigm in neuroprotection with multiple mechanisms of action in ischemic stroke (IS) patients during acute phase. Some clinical trials just finished, and a few others are still ongoing; gather the current knowledge and pull it down to influence the present and future studies was the goal of this paper. METHODS: A systematic review of published research papers and/or registered clinical trials since 2000 was performed. RESULTS: Nineteen studies were identified and only four studies were completed. All of them have demonstrated that RIPerC is safe, feasible and well tolerated in IS patients. However, a high heterogeneity of clinical trial characteristics was observed: five (26.3%) randomized clinical trials (RCTs) included only thrombolytic-treated patients, three (15.8%) RCTs only thrombectomy-treated patients, and five (26.3%) RCTs required radiological confirmation of IS. Temporal inclusion criteria vary from 4 h to 48 h. Most of the clinical trials used 4 cycles of RIPerC in the upper non-affected limb. Interestingly, only three (16.7%) RCTs applied RIPerC during the transportation in the ambulance. Neuroimaging outputs were the main endpoints when endovascular therapy was applied; functional outcome is also the main endpoint in large-medium size studies. CONCLUSIONS: This review summarizes the completed and ongoing clinical trials on RIPerC in IS patients, where RIPerC has been used alone or in combination with recanalization therapies. Ongoing clinical trials will provide new information on the best RIPerC intervention strategy and potentially improve the functional outcome of IS patients; definition of new RIPerC strategies would ideally aim at enhancing tissue preservation, promoting neurological recovery, and stratify patients to improve treatment feasibility.

An increase in AMPK/e-NOS signaling and attenuation of MMP-9 may contribute to remote ischemic perconditioning associated neuroprotection in rat model of focal ischemia.

Remote ischemic perconditioning (RIPerC) results in collateral enhancement and a reduction in middle cerebral artery occlusion (MCAO) induced ischemia. RIPerC likely activates multiple metabolic protective mechanisms, including effects on matrix metalloproteinases (MMPs) and protein kinases. Here we explore if RIPerC improves neuroprotection and collateral flow by modifying the activities of MMP-9 and AMPK/e-NOS. Age matched adult male Sprague Dawley rats were subjected to MCAO followed one hour later by RIPerC (3 cycles of 15 min ischemia). Animals were euthanized 24 h post-MCAO. Haematoxylin and Eosin (H&E) staining 24 h post-MCAO revealed a significant (p < 0.02) reduction in the infarction volume in RIPerC treated animals (24.9 ± 5.4%) relative to MCAO controls (42.5 ± 4.2, %). TUNEL staining showed a 42.6% reduction in the apoptotic cells with RIPerC treatment (p < 0.01). Immunoblotting in congruence with RT-PCR and Zymography showed that RIPerC significantly reduced MMP-9 expression and activity in RIPerC + MCAO group compared to MCAO group (218.3 ± 19.1% vs. 148.9 ± 12.05% (p < 0.01). Immunoblotting revealed that RIPerC was associated with a significant 2.5-fold increase in activation of p-AMPK compared to the MCAO group (p < 0.01) which was also associated with a significant increase in the e-NOS activity (p < 0.01). RIPerC resulted in reduction of infarction volume, decreased apoptotic cell death and attenuated MMP-9 activity. This together with the increased activity of p-AMPK and increase in p-eNOS may, in part explain the neuroprotection and sustained increase in blood flow observed with RIPerC following acute stroke.

Remote Ischemic Conditioning in Acute Myocardial Infarction and Shock States.

Remote ischemic conditioning is the phenomenon whereby brief, nonlethal episodes of ischemia in one organ (such as a limb) protect a remote organ from ischemic necrosis induced by a longer duration of severe ischemia followed by reperfusion. This phenomenon has been reproduced by dozens of experimental laboratories and was shown to reduce the size of myocardial infarction in many but not all clinical studies. In one recent large clinical trial, remote ischemic conditioning induced by repetitive blood pressure cuff inflations on the arm did not reduce infarct size or improve clinical outcomes. This negative result may have been related in part to the overall success of early reperfusion and current adjunctive therapies, such as antiplatelet therapy, antiremodeling therapies, and low-risk patients, that may make it difficult to show any advantage of newer adjunctive therapies on top of existing therapies. One relevant area in which current outcomes are not as positive as in the treatment of heart attack is the treatment of shock, where mortality rates remain high. Recent experimental studies show that remote ischemic conditioning may improve survival and organ function in shock states, especially hemorrhagic shock and septic shock. In this study, we review the preclinical studies that have explored the potential benefit of this therapy for shock states and describe an ongoing clinical study.

Remote Ischemic Perconditioning Modulates Apelin Expression After Renal Ischemia-Reperfusion Injury.

BACKGROUND: Renal ischemia/reperfusion injury (IRI) can result in impaired ability of urine concentration and increased sodium fractional excretion. Apelin, a (neuro) vasoactive peptide, enhances diuresis by increasing the renal microcirculation and by counteracting the antidiuretic effect of arginine vasopressin on the tubules. However, changes in renal apelin expression in renal IRI rat model have not been elucidated. Remote ischemic perconditioning (RIPerC) improves renal sodium and water handling after IRI. Here, we investigated whether RIPerC prevents dysregulation of renal sodium and water handling in response to IRI by apelin signaling pathway in rats. MATERIALS AND METHODS: Renal IRI was induced by 45-min clamping of renal arteries followed by 24 h reperfusion. RIPerC was created by applying four cycles of 2-min ischemia of the left femoral artery followed by 3-min reperfusion at the start of renal ischemia. Rats were randomly divided into sham, ischemia/reperfusion, and RIPerC + ischemia/reperfusion groups. Urine and blood were sampled after reperfusion period. The kidney was harvested for mRNA isolation and histopathological study. RESULTS: IRI resulted in decreased clearance of creatinine, increased sodium fractional excretion, and reduced urine osmolality compared with sham animals. This occurred with an increase in mRNA expression levels of apelin and histological damages in both cortical and medullary regions of kidney tissues. RIPerC treatment ameliorated all these changes. CONCLUSIONS: This study showed that RIPerC has protective effects against dysregulation of renal sodium and water handling after renal IRI, which might be related with inhibition of apelin signaling pathway.

Scintigraphic evaluation of remote pre-conditioning protection against unilateral renal ischemia/reperfusion injury in rats: a longitudinal study.

PURPOSE: To determine the role of remote perconditioning (RPeC) on renal function and histology in an animal model of unilateral renal ischemia and reperfusion (IR) injury. METHODS: Rats were subjected to 60 min unilateral renal ischemia. RPeC protocol was the application of four cycles of 5 min IR of left femoral artery during renal ischemia. Assessments of histological changes and renal function were made 24 h, 1 week, or 3 weeks later. 99mTc-DMSA scan was performed using a small-animals SPECT system. RESULTS: 24-h reperfusion decreased the 99mTc-DMSA uptake in the left kidney compared to the intact kidney of control animals. RPeC group has higher uptake compared to the IR group. After 1 week and 3 weeks, uptakes were gradually increased in both groups and no differences were observed. Severe morphological changes in the ischemic kidneys of both groups were observed after 24 h which attenuated after 1 week and 3 weeks. Moreover, no differences in creatinine and BUN levels between IR-treated and intact animals were observed. CONCLUSION: These data suggest that RPeC exerts a partially transient improvement in the renal function in the first day after reperfusion. However, long-term follow-up study showed no beneficial effects of RPeC. Moreover, noninvasive 99mTc-DMSA scan revealed a suitable tool in the follow-up evaluation of recovery process in the unilateral renal IR injury models.

Physiological and pharmacological effects of melatonin on remote ischemic perconditioning after myocardial ischemia-reperfusion injury in rats: Role of Cybb, Fas, NfκB, Irisin signaling pathway.

It has been found that remote organ/limb temporary ischemia, known as remote ischemic conditioning, can provide protection against the formation of lethal ischemic outcome. Current evidence suggests that aging and age-releated comorbidities impair the cardioprotective effects of conditionings. In conjuction with aging, decrease in melatonin synthesis from pineal gland can have role in the pathogenesis of aging and age-related cardiovascular diseases. In this study, we investigated the effects of remote ischemic perconditioning (RIPerC) and physiological and pharmacological concentrations of melatonin on the infarct size, Fas gene, cytochrome b-245 beta chain (Cybb) gene, nuclear factor-kappa B (NfκB), and irisin using an in vivo model of myocardial ischemia/reperfusion (I/R) injury. Sprague-Dawley rats that were divided into two groups first as non-pinealectomized (Non-Px) and pinealectomized (Px), and then (a) Control; (b) I/R (30-minute ischemia, 120-minute reperfusion caused by left coronary artery ligation); (c) I/R + RIPerC (when myocardial ischemia initiated, three cycles of 5-minute occlusion followed by 5-minute reperfusion); (d) I/R + Mel; (e) Px; (f) Px + I/R; (g) Px + I/R + RIPerC; (h) Px + I/R + RIPerC + Mel groups. The infarct size was determined by TTC staining and analyzed by the ImageJ program. Molecular parameters were evaluated by qRT-PCR and Western blot. Results showed that increased infarct size in Non-Px groups decreased with RIPerC and melatonin. However, increased infarct size in Px groups was decreased minimally with RIPerC and significantly decreased with RIPerC + Melatonin. Fold change in Fas gene was associated with the infarct size. RIPerC and melatonin reduced expressions of Cybb, NfκB, and irisin genes. The physiological release and pharmacological concentration of melatonin may improve protective effect of RIPerC against I/R-induced infarct size by modulating Cybb, Fas, NfκB, Irisin signaling pathways.

Remote ischemic perconditioning attenuates adverse cardiac remodeling and preserves left ventricular function in a rat model of reperfused myocardial infarction.

AIMS: Remote ischemic conditioning (RIC) is considered a potential clinical approach to reduce myocardial infarct size and ameliorate adverse post-infarct left ventricular (LV) remodeling, however the mechanisms are unknown. The aim was to clarify the impact of RIC on Neuregulin-1 (NRG-1)/ErbBs expression, inflammation and LV hemodynamic function. METHODS AND RESULTS: Male Sprague-Dawley rats were subjected to 30 min occlusion of the left coronary artery (LCA) followed by 2 weeks of reperfusion and separated into three groups: (1) sham operated (without LCA occlusion); (2) Myocardial ischemia/reperfusion (MIR) and (3) remote ischemic perconditioning group (MIR + RIPerc). Cardiac structural and functional changes were evaluated by echocardiography and on the isolated working heart system. The level of H3K4me3 at the NRG-1 promoter, and both plasma and LV tissue levels of NRG-1 were assessed. The expression of pro-inflammatory cytokines, ECM components and ErbB receptors were assessed by RT-qPCR. MIR resulted in a significant decrease in LV function and enlargement of LV chamber. This was accompanied with a decrease in the level of H3K4me3 at the NRG-1 promoter. Consequently NRG-1 protein levels were reduced in the infarcted myocardium. Subsequently, an upregulated influx of CD68+ macrophages, high expression of MMP-2 and -9 as well as an increase of IL-1ß, TLR-4, TNF-α, TNC expression were observed. In contrast, RIPerc significantly decreased inflammation and improved LV function in association with the enhancement of NRG-1 levels and ErbB3 expression. CONCLUSIONS: These findings may reveal a novel anti-remodeling and anti-inflammatory effect of RIPerc, involving activation of NRG-1/ErbB3 signaling.

Remote ischemic per-conditioning protects against renal ischemia-reperfusion injury via suppressing gene expression of TLR4 and TNF-α in rat model.

The pathogenesis of renal ischemia-reperfusion injury (IRI) involves both inflammatory processes and oxidative stress in the kidney. This study determined whether remote ischemic per-conditioning (RIPerC) is mediated by toll-like receptor 4 (TLR4) signaling pathway in rats. Renal IR injury was induced by occluding renal arteries for 45 min followed by 24 h of reperfusion. RIPerC included 4 cycles of 2 min of ischemia of the left femoral artery followed by 3 min of reperfusion performed at the start of renal ischemia. Rats were divided into sham, IR, and RIPerC groups. At the end of the reperfusion period, urine, blood and tissue samples were gathered. IR created kidney dysfunction, as ascertained by a significant decrease in creatinine clearance and a significant increase in sodium fractional excretion. These changes occurred in concert with a decrease in the activities of glutathione peroxidase, catalase, and superoxide dismutase with an increment in malondialdehyde levels, mRNA expression levels of TLR4 and tumor necrosis factor α (TNF-α), and histological damage in renal tissues. RIPerC treatment diminished all these changes. This study demonstrates that RIPerC has protective effects on the kidney after renal IR, which might be related to the inhibition of the TLR4 signaling pathway and augmentation of antioxidant systems.

Hepatorenal protection during renal ischemia by quercetin and remote ischemic perconditioning.

BACKGROUND: Pathogenesis of renal ischemia/reperfusion injury (IRI) involves oxidative stress response in the kidney and remote organs. Both quercetin and remote ischemic perconditioning (RIPerC) can protect partially against IRI. This study determined whether combined quercetin and RIPerC could provide an augmented hepatorenal protection against renal IRI. MATERIALS AND METHODS: I/R was induced by clamping renal arteries for 45 min followed by 24-h reperfusion. RIPerC consisted of four cycles of 2 min of left femoral artery ischemia followed by 3 min of reperfusion administered at the beginning of renal ischemia. Rats were divided into five groups: sham, I/R, RIPerC, quercetin (Q + I/R), and combined quercetin and RIPerC (Q + RIPerC). At the end of reperfusion period, blood, urine, and tissue samples were collected. RESULTS: I/R caused kidney dysfunction, as proved by significant decrease in creatinine clearance, and a significant increase in liver functional indicators as evidenced by increased plasma alanine aminotransferase and aspartate aminotransferase activity. This was accompanied by a decrease of glutathione peroxidase and catalase activities with an increase of malondialdehyde levels and histological damages in renal and hepatic tissues. Treatment with RIPerC and quercetin reduced all these changes. However, the measure of improvements was enhanced by combined quercetin and RIPerC treatment. CONCLUSIONS: This study demonstrated protective effects of quercetin and RIPerC strategy on the both kidney and liver after renal I/R. The results suggest that combined quercetin and RIPerC provides an enhanced protection against renal IRI by reduction of lipid peroxidation and augmentation of antioxidant systems.

The role of nitric oxide in the protective action of remote ischemic per-conditioning against ischemia/reperfusion-induced acute renal failure in rat.

OBJECTIVES: We investigated the role of nitric oxide (NO) in the protective effects of remote ischemic per-conditioning (rIPerC) on renal ischemia/reperfusion (I/R) injury in male rats. MATERIALS AND METHODS: I/R treatment consisted of 45 min bilateral renal artery ischemia and 24 hr reperfusion interval. rIPerC was performed using four cycles of 2 min occlusions of the left femoral artery and 3 min reperfusion at the beginning of renal ischemia. The animals were given normal saline (vehicle), NG-nitro-L-arginine methyl ester (L-NAME) or L-arginine. Following the reperfusion period, renal functional- and oxidative stress- parameters, as well as histopathological changes were assessed. RESULTS: In comparison with the sham group, I/R resulted in renal dysfunction, as indicated by significantly lower creatinine clearance and higher fractional excretion of sodium. This went along with decreased glutathione peroxidase (GPX) and catalase (CAT) activity in the I/R group, increased malondialdehyde (MDA) contents and histological damages. In comparison with the I/R group, the rIPerC group displayed improved renal function, increased activity of GPX and CAT enzymes, and decreased MDA level. However, these effects were abrogated by L-NAME injection and augmented by L-arginine treatment. CONCLUSION: According to the results, the functional and structural consequences of rIPerC against I/R-induced kidney dysfunction, which is associated with reduction of lipid peroxidation and intensification of anti-oxidant systems, is partially dependent on NO production.

Humoral transfer and intramyocardial signal transduction of protection by remote ischemic perconditioning in pigs, rats, and mice.

Remote ischemic perconditioning (RPER) during ongoing myocardial ischemia reduces infarct size. The signal transduction of RPER's cardioprotection is still largely unknown. Anesthetized pigs were therefore subjected to RPER by 4 × 5 min/5 min of hindlimb ischemia-reperfusion during 60 min of coronary occlusion before 3 h of reperfusion. Pigs without RPER served as placebo (PLA). The phosphorylation of Akt and ERK [reperfusion injury salvage kinase (RISK) pathway] and STAT3 [survivor activating factor enhancement (SAFE) pathway] in the area at risk was determined by Western blot analysis. Wortmannin/U0126 or AG490 was used for pharmacological RISK or SAFE blockade, respectively. Pig plasma/plasma dialysate sampled after RPER or PLA, respectively, was transferred to isolated rat and mouse hearts subjected to 30 min/120 min of global ischemia-reperfusion. Mitochondria were isolated from rat hearts at early reperfusion. Isolated mouse cardiomyocytes were subjected to 1 h of hypoxia/5 min of reoxygenation without and with prior plasma dialysate incubation. RPER reduced infarct size in pigs to 21 ± 15% versus 44 ± 9% in PLA (percentage of the area at risk, mean ± SD, P < 0.05) and increased STAT3 phosphorylation at early reperfusion. AG490 but not RISK blockade abolished the protection. RPER plasma/plasma dialysate reduced infarct size in rat (22 ± 3% of ventricular mass vs. 40 ± 11% with PLA plasma, P < 0.05) and mouse (29 ± 4% vs. 63 ± 8% with PLA plasma dialysate, P < 0.05) hearts and improved mitochondrial function (e.g., increased respiration, ATP formation, and calcium retention capacity and decreased reactive oxygen species formation). RPER dialysate also improved the viability of mouse cardiomyocytes after hypoxia/reoxygenation. RISK or SAFE blockade each abrogated these beneficial effects. NEW & NOTEWORTHY Remote ischemic perconditioning salvages the myocardium in patients with acute infarction. We identified a signal transduction with humoral transfer and STAT3 activation in pigs and an involvement of reperfusion injury salvage kinases and STAT3 in rat and mouse hearts, along with better cardiomyocyte viability and mitochondrial function.

Limb remote ischemia per-conditioning protects the heart against ischemia-reperfusion injury through the opioid system in rats.

Remote ischemia per-conditioning (RPerC) has been demonstrated to have cardiac protection, but the underlying mechanism remains unclear. This study aimed to investigate the mechanism underlying cardiac protection of RPerC. Adult male Sprague-Dawley rats were used in this study. Cardiac ischemia/reperfusion (I/R) was induced by 30 min of occlusion and 3 h of reperfusion of the left anterior descending coronary artery. RPerC were performed by 5 min of occlusion of the right femoral artery followed by 5 min of reperfusion for three times during cardiac ischemia. The hemodynamics, left ventricular function, arrhythmia, and infarct area were measured. Protein expression levels of endothelial nitric oxide synthase (eNOS), inducible NOS (iNOS), protein kinase C-ε (PKCε), and PKCδ in the myocardium were assayed. During I/R, systolic artery pressure and left ventricular function were decreased, infarct area was increased, and arrhythmia score was increased (P < 0.05). However, changes of the above parameters were significantly attenuated in RPerC-treated rats compared with control rats (P < 0.05). The cardiac protective effects of RPerC were prevented by naloxone or glibenclamide. Also, RPerC increased the protein expression levels of eNOS, iNOS, PKCε, and PKCδ in the myocardium compared with control rats. These effects were blocked by naloxone, an opioid receptor antagonist, and glibenclamide, an ATP-sensitive K+ channel blocker (KATP). In summary, this study suggests that RPerC protects the heart against I/R injury through activation of opioid receptors and the NO-PKC-KATP channel signaling pathways.

Mitofusin-2 mediated mitochondrial Ca2+ uptake 1/2 induced liver injury in rat remote ischemic perconditioning liver transplantation and alpha mouse liver-12 hypoxia cell line models.

AIM: To investigate the protective mechanism of mitofusin-2 (Mfn2) in rat remote ischemic perconditioning (RIC) models and revalidate it in alpha mouse liver-12 (AML-12) hypoxia cell lines. METHODS: Sprague-Dawley rats were divided into three groups (n = 6 each): sham, orthotopic liver transplantation and RIC. After operation, blood samples were collected to test alanine aminotransferase and aspartate aminotransferase. The liver lobes were harvested for histopathological examination, western blotting (WB) and quantitative real-time (qRT)-PCR. AML-12 cell lines were then subjected to normal culture, anoxic incubator tank culture (hypoxia) and anoxic incubator tank culture with Mfn2 knockdown (hypoxia + Si), and data of qRT-PCR, WB, mitochondrial membrane potential (ΔΨm), apoptosis, endoplasmic reticulum Ca2+ concentrations and mitochondrial Ca2+ concentrations were collected. RESULTS: Both sham and normal culture groups showed no injury during the experiment. The RIC group showed amelioration of liver function compared with the orthotopic liver transplantation group (P < 0.05). qRT-PCR and WB confirmed that Mfn2-mitochondrial Ca2+ uptake 1/2 (MICUs) axis was changed (P < 0.005). In AML-12 cell lines, compared with the hypoxia group, the hypoxia + Si group attenuated the collapse of ΔΨm and apoptosis (P < 0.005). The endoplasmic reticulum Ca2+ decrease and mitochondrial Ca2+ overloading observed in the hypoxia group were also attenuated in the hypoxia + Si group (P < 0.005). Finally, qRT-PCR and WB confirmed the Mfn2-MICUs axis change in all the groups (P < 0.005). CONCLUSION: Mfn2 participates in liver injury in rat RIC models and AML-12 hypoxia cell lines by regulating the MICUs pathway.

Ischemic Preconditioning in the Intensive Care Unit.

OPINION STATEMENT: Preconditioning is the premise that controlled preemptive exposure to sub-lethal doses of a stressor and can condition an organism or organ to later withstand a lethal dose. This process relies on marshaling endogenous survival resources that have evolved as part of an organism's evolutionary struggle to overcome at times harsh environmental conditions. This preconditioning response occurs through activation of myriad complex mechanisms that run the gamut from alterations in gene expression to the de novo synthesis and post-translational modification of proteins, and it may occur across exposure to a wide variety of stressors (i.e., ischemia, hypoxia, hypothermia, drugs). This review will focus on preconditioning in relation to an ischemic stressor (ischemic preconditioning) and how this process may be harnessed as a protective method to ameliorate targeted acute neurologic diseases especially. There has been considerable eagerness to translate ischemic preconditioning to the bedside, and to that end there have been recent trials examining its efficacy in various clinical settings. However, some of these trials have reached diverging conclusions with a protective effect seen in studies targeting acute kidney injury solely while no benefit was seen in larger trials targeting combined endpoints including cardio-, neuro-, and renoprotection in a cohort of patients undergoing cardiac surgery. While an extensive body of pre-clinical research offers ischemic preconditioning as a robust and highly faithful protective phenomenon, its clinical utility remains unproven. This current state may be due to persisting gaps in our understanding of how best to harness its power. This review will provide an overview of the biological mechanisms proposed to underlie ischemic preconditioning, explore initial disease targets, examine the challenges we must overcome to optimally engage this system, and report findings of recent clinical trials.

Neuroprotective delivery platforms as an adjunct to mechanical thrombectomy.

Despite the success of numerous neuroprotective strategies in animal and preclinical stroke models, none have effectively translated to clinical medicine. A multitude of influences are likely responsible. Two such factors are inefficient recanalization strategies for large vessel occlusions and suboptimal delivery methods/platforms for neuroprotective agents. The recent endovascular stroke trials have established a new paradigm for large vessel stroke treatment. The associated advent of advanced mechanical revascularization devices and new stroke technologies help address each of these existing gaps. A strategy combining effective endovascular revascularization with administration of neuroprotective therapies is now practical and could have additive, if not synergistic, effects. This review outlines past and current neuroprotective strategies assessed in acute stroke trials. The discussion focuses on delivery platforms and their potential applicability to endovascular stoke treatment.