Cycles Of Ischemic Preconditioning Research Articles

Remote ischaemic preconditioning increase tolerance to experimentally induced cold pain

ABSTRACT Ischaemic preconditioning (IPC) applied locally and remotely has been shown to reduce pain which may underpin its ergogenic effect on exercise performance, however, it is unclear how many IPC cycles are needed to induce hypoalgesia. Therefore the purpose of this study was to examine the number of cycles of IPC on experimental pain perception. Sixteen healthy participants underwent four, randomised, experimental sessions where they either underwent a sham protocol (1 × 5 min at 20 mmHg), and 1, 2 or 3 cycles × 5 min of remote IPC at 105% of limb occlusion pressure. Ten minutes post-intervention, participants underwent a cold-pressor test where pain threshold, pain tolerance and pain intensity were examined and compared between conditions with a one-way repeated measure analysis of variance. Pain threshold was not different between conditions (P = 0.065); but pain tolerance was increased by ∼30% in the 1 × 5 condition, 2 × 5 condition, and 3 × 5 condition compared to the sham condition. No differences in pain tolerance were seen between the different numbers of cycles (all P > 0.05). There was also no difference in the perception of pain 30 s into the cold pressor test (P = 0.279). Remote IPC appears to significantly improve tolerance to pain which may have significant implications for endurance performance and exercise rehabilitation, but this warrants further investigation.

Modulation of Inula racemosa Hook Extract on Cardioprotection by Ischemic Preconditioning in Hyperlipidaemic Rats.

Hyperlipidemia (HL) is a major cause of ischemic heart diseases. The size-limiting effect of ischemic preconditioning (IPC), a cardioprotective phenomenon, is reduced in HL, possibly because of the opening of the mitochondrial permeability transition pore (MPTP). The objective of this study is to see what effect pretreatment with Inula racemosa Hook root extract (IrA) had on IPC-mediated cardioprotection on HL Wistar rat hearts. An isolated rat heart was mounted on the Langendorff heart array, and then ischemia reperfusion (I/R) and IPC cycles were performed. Atractyloside (Atr) is an MPTP opener. The animals were divided into ten groups, each consisting of six rats (n = 6), to investigate the modulation of I. racemosa Hook extract on cardioprotection by IPC in HL hearts Sham control, I/R Control, IPC control, I/R + HL, I/R + IrA + HL, IPC + HL, IPC + NS + HL, IPC + IrA+ HL, IPC + Atr + oxidative stress, mitochondrial function, integrity, and hemodynamic parameters are evaluated for each group. The present experimental data show that pretreatment with IrA reduced the LDH, CK-MB, size of myocardial infarction, content of cardiac collagen, and ventricular fibrillation in all groups of HL rat hearts. This pretreatment also reduced the oxidative stress and mitochondrial dysfunction. Inhibition of MPTP opening by Atr diminished the effect of IrA on IPC-mediated cardioprotection in HL rats. The study findings indicate that pretreatment with IrA e restores IPC-mediated cardioprotection in HL rats by inhibiting the MPTP opening.

An inquest into regulatory mechanism of caveolin by ischemic preconditioning against orchidectomy-challenged rat heart.

Lower level of testosterone in men is related to major risks of cardiovascular diseases. This risk may increase due to the opening of mitochondrial permeability transition pore (mPTP). The mPTP is also regulated by ischemic preconditioning (IPC) and a membrane protein known as caveolin. The cardioprotective effect of IPC is the most effective methodologies used in testosterone deficiency. Daidzein (DDZ) a caveolin inhibitor shows cardioprotective action. The experiment has been designed to evaluate the pretreated DDZ effect in IPC-mediated cardioprotective action in orchidectomy (OCZ)-challenged rat heart. The experiment was designed on male Wistar rats with/without OCZ. The level of testosterone is decreased by OCZ which reduces general body growth. Isolated heart from normal and OCZ rat was tied up on Langendorff's perfused apparatus and followed by ischemic reperfusion (IR) and IPC cycle. To investigate the cardioprotective effect of DDZ in heart with testosterone deficiency, a total of nine groups, each consisting of six rats (n = 6) were as follows: Sham, IR, IPC, IPC + OCZ, IPC + DDZ, IPC + OCZ + DDZ, IPC + sodium nitrite, IPC + OCZ + sodium nitrite, IPC + OCZ + DDZ + sodium nitrite. Hemodynamic parameters, cellular injury (infarct size, LDH, CKMB and cardiac troponin-T), oxidative stress, mitochondrial function, integrity and immunoblot analysis were assessed for each group. The experimental data showed that DDZ potentiated IPC-mediated increase in the heart rate, left ventricular diastolic pressure, coronary flow; + dp/dtmax, and -dp/dtmax. The pretreated DDZ decreases the action of LDH and CKMB, myocyte size, cardiac collagen content, infarct size and ventricular fibrillation and attenuation in oxidative stress and mitochondrial dysfunction in OCZ-challenged rat heart in all sets of experiments. Sodium nitrite, a producer of nitric oxide (NO), enhanced potentiating effects of DDZ on IPC-mediated cardioprotection in OCZ-challenged rats. These observations show that the downregulation of caveolin through impaired opening of mPTP during reperfusion and caveolin might be a potential adjuvant to IPC against cardiac injury in OCZ-challenged rats.

Reciprocalcation of caveolin and HSP-72 on IPC interceded cardio-protection in the orchidectomized rats

Diminished testosterone levels conjoined to cardiovascular risk factor mainly myocardial infarction which broadens the risk of cardiovascular mortality referring to age. Ischemic preconditioning (IPC) is one of the interventions to shield such injury. The present study implicated the possible involvement of caveolin and heat shock protein 72 (HSP-72) during stress in orchidectomy (OCD) challenged rats. OCD was performed in male rats and kept for 6 weeks to observe the reduction in the level of testosterone. Isolated perfused heart of normal and OCD group was subjected to ischemic insult as per IPC cycle. Myocardial infarct size, haemodynamic, enzymatic and oxidative stress parameter were assessed for each heart. Diadzein (DDZ) a caveolin inhibitor was administered before the isolation of heart and it significantly decreases myocardial infarct size, release of lactate dehydrogenase, creatinine kinase and oxidative stress marker. DDZ also potentiated the effect IPC-mediated increase in the heart rate and coronary flow. The effect of caveolin inhibitor was remarkably reduced by quercetin administered before 1 h. of the administration DDZ. The findings of this study revealed that protection of myocardium induced by caveolin inhibitor pretreatment has not been lost in OCD rat heart.

Effluent from ischemic preconditioned hearts confers cardioprotection independent of the number of preconditioning cycles.

Coronary effluent collected from ischemic preconditioning (IPC) treated hearts induces myocardial protection in non-ischemic-preconditioned hearts. So far, little is known about the number of IPC cycles required for the release of cardioprotective factors into the coronary effluent to successfully induce cardioprotection. This study investigated the cardioprotective potency of effluent obtained after various IPC cycles in the rat heart. Experiments were performed on isolated hearts of male Wistar rats, mounted onto a Langendorff system and perfused with Krebs-Henseleit buffer. In a first part, effluent was taken before (Con) and after each IPC cycle (Eff 1, Eff 2, Eff 3). IPC was induced by 3 cycles of 5 min of global myocardial ischemia followed by 5 minutes of reperfusion. In a second part, hearts of male Wistar rats were randomized to four groups (each group n = 4–5) and underwent 33 min of global ischemia followed by 60 min of reperfusion. The previously obtained coronary effluent was administered for 10 minutes before ischemia as a preconditioning stimulus. Infarct size was determined at the end of reperfusion by triphenyltetrazoliumchloride (TTC) staining. Infarct size with control effluent was 54±12%. Effluent obtained after IPC confers a strong infarct size reduction independent of the number of IPC cycles (Eff 1: 27±5%; Eff 2: 35±7%; Eff 3: 35±8%, each P<0.05 vs. Con). Effluent extracted after one cycle IPC is comparably protective as after two or three cycles IPC.

Protective effects of dexmedetomidine and remote ischemic preconditioning on renal ischemia reperfusion injury in rats.

The aim of this study was to evaluate the effects of remote ischemic preconditioning (RIPC) and dexmedetomidine as pharmacological conditioning in a rat renal ischemia/reperfusion (IR) injury model. Total of 28 male Wistar Albino rats weighing 250 to 300 g were divided into 4 equal groups. Group I (Sham; n=7): Laparotomy and renal pedicle dissection were performed, and the rats were observed under anesthesia without any intervention. Group II (IR; n=7): Following laparotomy and 45 minutes of left renal pedicle occlusion, 4 hours of reperfusion was performed. Group III (IR+D; n=7): Following laparotomy and ischemia, dexmedetomidine was administrated intraperitoneally (100 µg/kg) at fifth minute of reperfusion. Group IV (RIPC+IR; n=7): Under anesthesia, 3 cycles of ischemic preconditioning were applied to the left hind leg, and after 5 minutes, renal IR was performed. All rats were sacrificed after the left kidney was processed for conventional histomorphology. Total histomorphological renal injury score was significantly lower in the Sham group compared with the other groups (p<0.01). Total renal injury score of IR group was significantly higher than IR+D and RIPC+IR groups (p<0.01). There was no significant difference in the total renal injury score between the dexmedetomidine and RIPC groups (p=0.89). In the present study, it was demonstrated histomorphologically that both dexmedetomidine and RIPC decreased renal IR injury significantly. In addition, no significant difference was found between dexmedetomidine and RIPC groups.

Effect of pioglitazone on the abrogated cardioprotective effect of ischemic preconditioning in hyperlipidemic rat heart.

Objectives:The signaling pathways upstream of glycogen synthase kinase-3β (GSK-3β) get reduced during ischemic preconditioning (IPC) in hyperlipidemic rat heart. Pioglitazone, an insulin sensitizer, exerts cardioprotection through GSK-3β. The objective of the study is to investigate the role of pioglitazone on the attenuated cardioprotective effect of IPC in hyperlipidemic rat heart.Materials and Methods:The rats were administered high-fat diet for 8 weeks to induce experimental hyperlipidemia (HL). After mounting on a Langendorff apparatus, isolated perfused hearts were given four cycles of IPC; each consists of 5 min of both ischemia and reperfusion followed by 30 min of ischemia and 120 min of reperfusion. Insulin (50 mU/ml) was perfused alone and in combination with pioglitazone (2 μM), while in other groups, this combination was repeated with wortmannin (100 nM), a selective PI3K inhibitor and rapamycin (1 nM), a selective mammalian target of rapamycin (mTOR) inhibitor, separately, and in combination. Myocardial injury was assessed by measuring infarct size and the levels of creatinine kinase-myocardial band (CK-MB) and lactate dehydrogenase (LDH) in the coronary effluent.Results:IPC significantly decreased the infarct size and levels of LDH and CK-MB in normal but not in HL rat heart. Perfusion of insulin along with pioglitazone significantly reduced the infarct size and release of CK-MB and LDH in IPC-treated HL rat hearts. Perfusion of wortmannin or rapamycin alone significantly and in combination almost completely abolished the pioglitazone-induced restored cardioprotection (P < 0.05).Conclusion:Cardioprotective effect of IPC gets lost in hyperlipidemic rat heart. The results suggest that perfusion of pioglitazone restored the cardioprotective effect of IPC in hyperlipidemic rat heart, an effect that may be via PI3K and mTOR.

Determinants of the Efficacy of Cardiac Ischemic Preconditioning: A Systematic Review and Meta-Analysis of Animal Studies.

BackgroundIschemic preconditioning (IPC) of the heart is a protective strategy in which a brief ischemic stimulus immediately before a lethal ischemic episode potently limits infarct size. Although very promising in animal models of myocardial infarction, IPC has not yet been successfully translated to benefit for patients.ObjectiveTo appraise all preclinical evidence on IPC for myocardial infarction and identify factors hampering translation.Methods and resultsUsing systematic review and meta-analysis, we identified 503 animal studies reporting infarct size data from 785 comparisons between IPC-treated and control animals. Overall, IPC reduced myocardial infarction by 24.6% [95%CI 23.5, 25.6]. Subgroup analysis showed that IPC efficacy was reduced in comorbid animals and non-rodents. Efficacy was highest in studies using 2–3 IPC cycles applied <45 minutes before myocardial infarction. Local and remote IPC were equally effective. Reporting of study quality indicators was low: randomization, blinding and a sample size calculation were reported in 49%, 11% and 2% of publications, respectively.ConclusionsTranslation of IPC to the clinical setting may be hampered by the observed differences between the animals used in preclinical IPC studies and the patient population, regarding comorbidity, sex and age. Furthermore, the IPC protocols currently used in clinical trials could be optimized in terms of timing and the number of ischemic cycles applied. In order to inform future clinical trials successfully, future preclinical studies on IPC should aim to maximize both internal and external validity, since poor methodological quality may limit the value of the preclinical evidence.

Intermittent cycles of remote ischemic preconditioning augment diabetic foot ulcer healing.

The morbidity and mortality caused by diabetic foot ulcer (DFU) are still significant. Conservative treatment of DFU is often ineffective. Treatment modalities using stem cells directly into the DFU or systematically have been introduced recently. Ischemic preconditioning (IPC) has been proved to be a cheap, simple, and safe method which can augment stem cells number in the peripheral blood circulation. This study's purpose was to test whether IPC can improve DFU healing. Forty diabetic patients were enrolled and divided into study and control groups. All patients received their regular treatment. The study group patients received in addition brief, transient cycles of IPC while the control group patients received a sham procedure only. The procedure was repeated every 2 weeks to complete a follow-up period of 6 weeks. The ulcers were photographed to measure wound area, and the degree of granulation tissue was assessed. No serious adverse events were noted. Twenty-two patients from the study group and 12 from the control group completed the entire follow-up. The ratio of patients who reached complete healing of their ulcer was 9/22 (41%) in the study group compared with 0/12 (0%) in the control group, p = 0.01. Furthermore, the mean remaining ulcer area at the end of the follow-up was significantly smaller in the study group, 25 ± 6% of the initial area vs. 61 ± 10% in the control group, p = 0.007. The degree of granulation increased after one cycle of treatment in 8/24 (33%) study patients compared to 3/16 (19%) in the control group, p = 0.47. Remote, repeated IPC significantly improves the healing of DFU. This simple, safe, inexpensive treatment method should be considered to be routinely applied to diabetic patients with DFU in addition to other regular treatment modalities.

Efectos de la dexmedetomidina en conjunto con el precondicionamiento isquémico remoto en la lesión de isquemia-reperfusión renal en ratones

Background and objectivesThe aim of this study was to evaluate the effects of remote ischemic preconditioning by brief ischemia of unilateral hind limb when combined with dexmedetomidine on renal ischemia-reperfusion injury by histopathology and active caspase-3 immunoreactivity in rats. Methods28 Wistar albino male rats were divided into 4 groups. Group I (Sham, n=7): laparotomy and renal pedicle dissection were performed at 65th minute of anesthesia and the rats were observed under anesthesia for 130min. Group II (ischemia-reperfusion, n=7): at 65th minute of anesthesia bilateral renal pedicles were clamped. After 60min ischemia 24h of reperfusion was performed. Group III (ischemia-reperfusion+dexmedetomidine, n=7): at the fifth minute of reperfusion (100μg/kg intra-peritoneal) dexmedetomidine was administered with ischemia-reperfusion group; reperfusion lasted 24h. Group IV (ischemia-reperfusion+remote ischemic preconditioning+dexmedetomidine, n=7): after laparotomy, three cycles of ischemic preconditioning (10min ischemia and 10min reperfusion) were applied to the left hind limb and after 5min with group iii. ResultsHistopathological injury scores and active caspase-3 immunoreactivity were significantly lower in the Sham group compared to the other groups. Histopathological injury scores in groups iii and iv were significantly lower than group ii (P=.03 and P=.05). Active caspase-3 immunoreactivity was significantly lower in the group iv than group ii (P=.01) and there was no significant difference between group ii and group iii (P=.06). ConclusionsPharmacologic conditioning with dexmedetomidine and remote ischemic preconditioning when combined with dexmedetomidine significantly decreases renal ischemia-reperfusion injury histomorphologically. Combined use of two methods prevents apoptosis via active caspase-3.

Efeitos de dexmedetomidina em conjunto com o pré‐condicionamento isquêmico remoto em lesão de isquemia‐reperfusão renal em ratos

Background and objectivesThe aim of this study was to evaluate the effects of remote ischemic preconditioning by brief ischemia of unilateral hind limb when combined with dexmedetomidine on renal ischemia–reperfusion injury by histopathology and active caspase‐3 immunoreactivity in rats. Methods28 Wistar albino male rats were divided into 4 groups. Group I (Sham, n=7): Laparotomy and renal pedicle dissection were performed at 65th minute of anesthesia and the rats were observed under anesthesia for 130min. Group II (ischemia–reperfusion, n=7): At 65th minute of anesthesia bilateral renal pedicles were clamped. After 60min ischemia 24h of reperfusion was performed. Group III (ischemia–reperfusion+dexmedetomidine, n=7): At the fifth minute of reperfusion (100μg/kg intra‐peritoneal) dexmedetomidine was administered with ischemia–reperfusion group. Reperfusion lasted 24h. Group IV (ischemia–reperfusion+remote ischemic preconditioning+dexmedetomidine, n=7): After laparotomy, three cycles of ischemic preconditioning (10min ischemia and 10min reperfusion) were applied to the left hind limb and after 5min with group III. ResultsHistopathological injury scores and active caspase‐3 immunoreactivity were significantly lower in the Sham group compared to the other groups. Histopathological injury scores in groups III and IV were significantly lower than group II (p=0.03 and p=0.05). Active caspase‐3 immunoreactivity was significantly lower in the group IV than group II (p=0.01) and there was no significant difference between group II and group III (p=0.06). ConclusionsPharmacologic conditioning with dexmedetomidine and remote ischemic preconditioning when combined with dexmedetomidine significantly decreases renal ischemia–reperfusion injury histomorphologically. Combined use of two methods prevents apoptosis via active caspase‐3.

Effect of One-Cycle Remote Ischemic Preconditioning to Reduce Myocardial Injury During Percutaneous Coronary Intervention

Up to 1/3 of percutaneous coronary interventions (PCIs) are complicated by troponin release. Remote ischemic preconditioning (IPC) confers effective cardioprotection; however, a 30-minute remote IPC protocol may be difficult to implement during ad hoc PCI. This study was performed to assess the ability of a brief remote IPC protocol to attenuate cardiac troponin I (cTnI) release after ad hoc PCI. Ninety-four patients undergoing ad hoc PCI for stable coronary artery disease, with undetectable preprocedural cTnI, were recruited and randomized to receive remote IPC (induced by one 5-minute inflation of a blood pressure cuff to 200 mm Hg around the upper arm) or control after the decision for PCI was made. The primary outcome was the difference between cTnI levels 24 hours after PCI and cTnI levels before coronary angiography (ΔcTnI). ΔcTnI in the remote IPC group was significantly lower compared with the control group (0.04 ng/ml [interquartile range 0.01 to 0.14] vs 0.19 ng/ml [interquartile range 0.18 to 0.59], p <0.001). The incidence of PCI-related myocardial infarction (MI) was greater in the control group (42.6% vs 19.1%, p = 0.014). In multivariate analysis, remote IPC was independently associated with ΔcTnI and PCI-related MI. In conclusion, our results suggest that even 1 cycle of remote IPC immediately before ad hoc PCI attenuates periprocedural cTnI release and reduces the incidence of type 4a MI.

Effects of dexmedetomidine in conjunction with remote ischemic preconditioning on renal ischemia–reperfusion injury in rats

Background and objectivesThe aim of this study was to evaluate the effects of remote ischemic preconditioning by brief ischemia of unilateral hind limb when combined with dexmedetomidine on renal ischemia–reperfusion injury by histopathology and active caspase-3 immunoreactivity in rats. Methods28 Wistar albino male rats were divided into 4 groups. Group I (Sham, n=7): Laparotomy and renal pedicle dissection were performed at 65th minute of anesthesia and the rats were observed under anesthesia for 130min. Group II (ischemia–reperfusion, n=7): At 65th minute of anesthesia bilateral renal pedicles were clamped. After 60min ischemia 24h of reperfusion was performed. Group III (ischemia–reperfusion+dexmedetomidine, n=7): At the fifth minute of reperfusion (100μg/kg intra-peritoneal) dexmedetomidine was administered with ischemia–reperfusion group. Reperfusion lasted 24h. Group IV (ischemia–reperfusion+remote ischemic preconditioning+dexmedetomidine, n=7): After laparotomy, three cycles of ischemic preconditioning (10min ischemia and 10min reperfusion) were applied to the left hind limb and after 5min with group III. ResultsHistopathological injury scores and active caspase-3 immunoreactivity were significantly lower in the Sham group compared to the other groups. Histopathological injury scores in groups III and IV were significantly lower than group II (p=0.03 and p=0.05). Active caspase-3 immunoreactivity was significantly lower in the group IV than group II (p=0.01) and there was no significant difference between group II and group III (p=0.06). ConclusionsPharmacologic conditioning with dexmedetomidine and remote ischemic preconditioning when combined with dexmedetomidine significantly decreases renal ischemia–reperfusion injury histomorphologically. Combined use of two methods prevents apoptosis via active caspase-3.

Improved cardioprotection using a novel stepwise ischemic preconditioning protocol in rabbit heart

BackgroundThe current commonly used cardiac ischemic preconditioning (IPC) protocol, involving three 5-min cycles of ischemia–reperfusion (I/R), may not be clinically beneficial because of its acutely deleterious effects on hemodynamics. This study attempted to assess the effects of a novel stepwise IPC scheme on cardiac function, infarct size, and arrhythmogenesis in a rabbit model of prolonged I/R. MethodsAnesthetized open-chest rabbits were subjected to 60-min occlusion of a proximal branch of the left coronary artery followed by 180-min reperfusion. Animals were divided into five groups (n = 6 each): (1) control group (no IPC); (2) 2-min IPC group (three cycles of 2-min IPC); (3) 5-min IPC group (three cycles of 5-min IPC); (4) 10-min IPC group (three cycles of 10-min IPC); and (5) stepwise IPC group (2-, 5-, and 10-min I/R). ResultsCompared with control group, 2-, 5-, and 10-min IPC decreased arrhythmia score by 16%, 67%, and 33%, respectively. Remarkably, stepwise IPC resulted in a 78% reduction of arrhythmias. Stepwise IPC also produced the least ventricular infarct size when compared with 2-, 5-, and 10-min IPC groups (16.4% versus 39.3%, 28.1%, and 38.5%, P < 0.05). ConclusionsThese results suggest that stepwise IPC has better cardioprotective effects against prolonged I/R injury and may serve as an acceptable approach to clinical revascularization procedures on the heart, including catheter-based and surgical approaches.

Remote ischemic preconditioning is feasible in ad hoc percutaneous coronary interventions

Purpose: Percutaneous coronary intervention (PCI)-induced troponin cTnI release is associated with a worst prognosis. Recently, 3 cycles of 5-minute ischemia followed by 5-minute reperfusion of the upper extremities were shown to reduce troponin release in elective PCI. However, this ischemic preconditioning (IPC) protocol requires 30 minutes and is of limited use in the context of ad hoc PCI. Since experimental evidence suggests that IPC is a graded than an all-or-nothing phenomenon, and even a short, single IPC cycle may have protective effects in the myocardium, we hypothesized that patients undergoing ad hoc PCI would have reduced peri-procedural troponin release if subjected to a single, remote IPC cycle, between diagnostic catheterization and coronary intervention. Methods: Subjects were randomized to receive remote IPC (induced by one single 5-minute inflation of a blood pressure cuff to 200 mm Hg around the upper arm, followed by 1 minute of reperfusion) or control (an uninflated cuff around the arm) in the catheter laboratory. The primary outcome was the difference between post-procedural cTnI (at 24 hours after PCI) and pre-procedural cTnI. Results: Ninety-three patients were included in the study (46 control group, 47 remote IPC group). Peri-procedural troponin release was significantly higher in the control group compared to the remote IPC group (0.49±0.42 vs. 0.10±0.19, p<0.001). No significant difference in ECG ST-segment deviation or ischemic discomfort was observed. Conclusion: One cycle of remote IPC attenuates procedure-related cTnI release, thus IPC may be feasible without introducing any delays in the catheter laboratory.

Ischemic preconditioning attenuates lipid peroxidation and apoptosis in the cecal ligation and puncture model of sepsis

Sepsis and septic shock are are among the major causes of mortality in intensive care units. The lung and kidney are the organs most affected by sepsis. Evidence exists that lipid peroxidation and apoptosis may be responsible for the high mortality due to sepsis. Ischemic preconditioning (IP) is a method for the protection of tissues and organs against ischemia/reperfusion injury by reducing reactive oxygen species levels, lipid peroxidation and apoptosis. In the present study, the effects of IP were investigated in cecal ligation and puncture (CLP)-induced sepsis in rats. The three groups of animals used in the present controlled study were the sham-operated group (sham, n=7), which only underwent a laparotomy; the sepsis group (sepsis, n=7), which underwent cecal ligation and perforation; and the IP + sepsis group (IP+sepsis, n=7), which underwent CLP immediately prior to the application of three cycles of IP to the hind limb. The study was terminated at 6 h after the induction of CLP. Blood, kidney and lung tissue samples were collected for the determination of serum creatinine, blood urea nitrogen (BUN), neutrophil gelatinase-associated lipocalin (NGAL) and lung tissue malondialdehyde (MDA) levels, as well as histological examination. The serum creatinine, plasma NGAL and lung tissue MDA levels in the sepsis group were significantly increased compared with those in the sham and the IP+sepsis groups (P<0.05). Alveolar macrophage counts, histological kidney and lung injury scores, kidney (caspase 3) and lung tissue immuonreactivity (M30) scores in the sepsis group were also significantly increased compared with those in the sham and IP+sepsis groups (P<0.05). The alveolar macrophage count in the IP+sepsis group was increased compared with that in the sham group (P<0.05). In conclusion, IP inhibits lipid peroxidation and attenuates histological injury and apoptosis in the lung and kidney during sepsis.

Use of Near Infrared Spectroscopy to Asses Remote Ischemic Preconditioning in Skeletal Muscle

Remote ischemic preconditioning (IPC) is a procedure during which brief periods of ischemia protect distant organ from ischemia-reperfusion injury. Appling IPC on an upper arm, this phenomenon has been demonstrated in several studies. Skeletal muscle tissue oxygenation at rest (StO2) and StO2 deoxygenation rate during vascular occlusion can be measured using near infrared spectroscopy (NIRS). We aimed to investigate the effects of remote upper arm IPC on StO2 and flow-mediated dilatation (FMD) in healthy male volunteers. In a randomized controlled crossover trial, resting StO2, StO2 deoxygenation rate, and FMD were measured on testing arm at baseline and after 60 minutes. After basal measurements IPC protocol on a contralateral arm was performed. StO2 deoxygenation rate was significantly lower after remote, the IPC cycles in comparison to deoxygenation rate at baseline (9.7±2.6 versus 7.5±2.5%, P=0.002). Comparison of deoxygenation rates showed a significant difference between the IPC and the control protocol (F=5.512, P=0.003). No differences were observed in FMD before and after remote IPC and in the control protocol. In healthy young adults, remote IPC reduces StO2 deoxygenation rate but has no significant impact on FMD. NIRS technique offers a novel approach to asses skeletal muscle adaptation in response to remote ischemic stimuli.

Glimepiride Treatment Facilitates Ischemic Preconditioning in the Diabetic Heart

The diabetic heart is resistant to the myocardial infarct-limiting effects of ischemic preconditioning (IPC). This may be in part due to the downregulation of the phosphatidylinositol 3'-kinase-Akt pathway, an essential component of IPC protection. We hypothesized that treating the diabetic heart with the sulfonylurea, glimepiride, which has been reported to activate Akt, may lower the threshold required to protect the diabetic heart by IPC. Goto-Kakizaki rats (a type II lean model of diabetes) received glimepiride (20 mg/kg per d, by oral gavage) or vehicle for (a) 3 months (chronic treatment) or (b) 24 hours (subacute treatment). In the third group, glimepiride (10 μmol/L) was administered only to the isolated hearts on the Langendorff apparatus (acute treatment). All hearts were subjected to 35 minutes ischemia and 120 minutes reperfusion ex vivo, at the end of which infarct size was determined by tetrazolium staining. Preconditioning treatment comprised 1 (IPC-1) or 3 (IPC-3) cycles of 5 minutes global ischemia and 10 minutes reperfusion. The diabetic heart was found to be resistant to IPC such that 3-IPC cycles, instead of the usual 1-IPC cycle, were required for cardioprotection. However, pretreatment with glimepiride lowered the threshold for IPC such that both 1 and 3 cycles of IPC elicited cardioprotection: chronic glimepiride treatment (IPC-1 31.9% ± 3.8% and IPC-3 33.5% ± 2.4% vs 43.9% ± 1.4% control, P < .05; N > 6 per group); subacute glimepiride treatment (IPC-1 31.1% ± 3.0% and IPC-3 29.3% ± 3.3% vs 42.2% ± 2.3% control, P < .05 N > 6 per group); and acute glimepiride treatment (IPC-1 28.2% ± 3.7% and IPC-3 24.6% ± 5.4% vs 41.9% ± 5.4% control, P < .05; N > 6 per group). This effect of glimepiride was independent of changes in blood glucose. We report for the first time that glimepiride treatment facilitates the cardioprotective effect elicited by IPC in the diabetic heart.

Akt‐ and PKA‐mediated endothelial nitric oxide synthase activation triggers early ischemic preconditioning in isolated rat hearts

Ischemic preconditioning (IPC) is a powerful cardioprotective phenomenon, however, the role of endothelial nitric oxide synthase (eNOS) and mechanisms of its activation are unclear in early IPC. While eNOS is an important downstream target of Akt and/or protein kinase A (PKA), questions remain regarding the role of Akt or PKA in eNOS activation and cardioprotection. Hearts were subjected to 30 min global ischemia and 120 min reperfusion (I/R) with or without IPC cycles (3 cycles of 5 min I and 5 min R). To address signaling proteins in the trigger phase and early R, myocardial tissues were collected following IPC cycles or inhibitors (PI3K inhibitor, LY294002/LY; PKA inhibitor, H89) plus IPC cycles or IPC cycles plus 30 min global I and 15 min R and Western blot analysis was performed. IPC significantly improved postischemic LVDP and reduced myocardial infarction compared to I/R group, and IPC effects were abrogated by L-NAME. I/R caused significant loss of total myocardial eNOS, and this loss was prevented by IPC. Phosphorylation of eNOS, Akt, and PKA was significantly increased following IPC. Pretreatment with LY or H89 either abolished or decreased phosphorylation of Akt or PKA, respectively. Importantly, LY or H89 abolished IPC-induced increase in eNOS activation and abrogated the cardioprotective effect of IPC. Thus, Akt- and PKA-mediated eNOS activation is critical for early IPC-induced cardioprotection.

Methyl‐β‐cyclodextrin (MβCD) treatment abolished ischemic preconditioning (IPC)‐induced cardioprotection and increase of protein S‐nitrosylation

Nitric oxide (NO) and protein S-nitrosylation (SNO) have been shown to play important cardioprotective roles in ischemic preconditioning (IPC). Caveolae, a lipid and signaling molecule enriched microdomain of the plasma membrane, have been suggested recently to play an important role in mediating IPC-induced cardioprotection. In Langendorff perfused mouse hearts, infusion of methyl-β-cyclodextrin (MβCD), a cholesterol sequestering agent to disrupt caveolae, before and during four cycles of IPC abolished cardioprotection. In perfusion control hearts, endothelial NO synthase (eNOS) was associated with its inhibitory binding partner caveolin-3. MβCD treatment disrupted caveolae structure and decreased the association of eNOS and caveolin-3. IPC caused activation of AKT/eNOS and downstream NO/SNO signaling. The caveolae-enriched fractions were isolated from mouse hearts by a non-detergent sucrose ultracentrifugation and analyzed by two dimensional DyLight fluorescence difference gel electrophoresis proteomic method for SNO detection. A significant increase of SNO was found in IPC hearts compared to perfusion control, which was blocked by MβCD treatment. Surprisingly the most abundant SNO proteins were mitochondrial proteins. In conclusion, these results suggest an important role of caveolae and caveolin-3-associated eNOS/NO/SNO signaling involved in IPC-mediated cardioprotection.