Protective effects of resveratrol in ischemia-reperfusion injury of skeletal muscle: A clinically relevant animal model for lower extremity ischemia

Ischemia and reperfusion injury of the skeletal muscle is a common and serious condition observed in patients admitting to peripheral vascular surgery, interventional radiology and cardiology departments. Resveratrol (RVT) being a strong natural antioxidant is found in deal of red wine and Mediterranean diet. In the present study, male Spraque-Dawley rats were randomized into two groups of equal size. The first group was the control group, and these rats were administered with tap water with a gastric tube for fourteen consecutive days once daily. According to the same protocol, the rats in the second group were treated with tap water containing 20 mg/kg RVT. All the rats in the two groups were subjected to acute hind limb ischemia through clamping of the abdominal aorta for 120 min. Following this procedure, 60 minutes of reperfusion was applied by reestablishing blood flow in both iliac arteries. Ischemic damage in the skeletal muscle tissue was assessed by measuring myoglobin, lactate dehydrogenase, creatinine phosphokinase, aspartate transaminase enzymes in venous blood samples obtained at the end of the reperfusion period. Oxidative stress caused by reperfusion was determined by measuring MDA, carbonyl and protein sulphydryl levels in quadriceps muscle tissue retrieved at the end of the experiment. In Group II rats, all the measured ischemic enzymes and the markers of oxidative stress reflected robust anti-ischemic properties obtained by RVT administration. The data from both groups revealed statistically significant protection against acute skeletal muscle ischemia and reperfusion injury in Group II rats, compared to Group I. As a major dietary flavonoid RVT can protect the skeletal muscle tissue against global ischemia and reperfusion injury because of its strong antioxidant and cytoprotective properties.     

Endothelium function in ischemia-reperfusion (a literature review)

Endothelium was shown to be one of the most hypoxia-tolerant mammalian cell types and to be injured in ischemia to a lesser extent than other cells. Alteration in the endothelial function during hypoxia and ischemia protects the organs against ischemic injury. Postischemic reperfusion contributes to endothelial dysfunction and initiates the reperfusion injury. Some data show ischemia/reperfusion to cause a systemic alteration of endothelial function in remote organs.     

Prevention and repair of cerebral ischemia-reperfusion injury by Chinese herbal medicine, Shengmai San, in rats

The protective activity of Shengmai San, a traditional Chinese herbal medicine, was studied in cerebral ischemia-reperfusion injury in rats. Shengmai San consists of three herbal components, Panax Ginseng, Ophiopogon Japonicus and Schisandra Chinensis and is routinely being used for treating coronary heart disease.

When Shengmai San was injected directly into rat duodenum 2 h before cerebral ischemia by bilateral carotid artery occlusion, thiobarbituric acid reactive substance (TBARS) formation during reperfusion following ischemia was almost completely suppressed in the brain. The loss of glutathione perioxidase activity after the ischemia-reperfusion was also effectively prevented by the Shengmai San pre-administration whereas the activity was considerably decreased in the damaged brain.

It was found that Shengmai San also effectively suppressed the TBARS formation even when it was administered after 45 min reperfusion following ischemia, indicating that Shengmai San improves the oxidative damage already established in the brain. Likewise, the decrease of glutathione peroxidase activity was minimized in the damaged brain by the post-administration of Shengmai San.

On the other hand, none of the Shengmai San components were active in protecting the ischemia-reperfusion brain damage when they were independently administered.

These experiments suggest the potential of Shengmai San in both preventive and therapeutic usages for cerebral ischemia-reperfusion injury.     

The effect of antioxidant supplementation on bacterial translocation after intestinal ischemia and reperfusion

The intestine is highly sensitive to ischemia/reperfusion (I/R) injury. Intestinal I/R may cause local tissue injury and disruption of the intestinal mucosal barrier, allowing the passage of viable bacteria and endotoxins from the gastrointestinal lumen to distant organs. This phenomenon, known as bacterial translocation (BT), may lead to systemic disorders with high morbidity and mortality. Oxidative stress mediators such as reactive oxygen species, polymorphonuclear neutrophils and nitric oxide are believed to contribute to the intestinal I/R injury. Many antioxidants have shown protective effects against I/R injury of various organs. The present article provides an overview of studies investigating the effect of antioxidant supplementation on BT after intestinal I/R.     

Induction and Assessment of Ischemia-reperfusion Injury in Langendorff-perfused Rat Hearts

The biochemical events surrounding ischemia reperfusion injury in the acute setting are of great importance to furthering novel treatment options for myocardial infarction and cardiac complications of thoracic surgery. The ability of certain drugs to precondition the myocardium against ischemia reperfusion injury has led to multiple clinical trials, with little success. The isolated heart model allows acute observation of the functional effects of ischemia reperfusion injury in real time, including the effects of various pharmacological interventions administered at any time-point before or within the ischemia-reperfusion injury window. Since brief periods of ischemia can precondition the heart against ischemic injury, in situ aortic cannulation is performed to allow for functional assessment of non-preconditioned myocardium. A saline filled balloon is placed into the left ventricle to allow for real-time measurement of pressure generation. Ischemic injury is simulated by the cessation of perfusion buffer flow, followed by reperfusion. The duration of both ischemia and reperfusion can be modulated to examine biochemical events at any given time-point. Although the Langendorff isolated heart model does not allow for the consideration of systemic events affecting ischemia and reperfusion, it is an excellent model for the examination of acute functional and biochemical events within the window of ischemia reperfusion injury as well as the effect of pharmacological intervention on cardiac pre- and postconditioning. The goal of this protocol is to demonstrate how to perform in situ aortic cannulation and heart excision followed by ischemia/reperfusion injury in the Langendorff model.     

Nitric oxide mediated oxidative stress injury in rat skeletal muscle subjected to ischemia/reperfusion as evaluated by chemiluminescence.

The involvement of nitric oxide (*NO) in oxidative stress in the rat gastrocnemius muscle subjected to ischemia/reperfusion injury was investigated using a specific and sensitive chemiluminescence (CL) method for measurement of both membrane lipid peroxide and total tissue antioxidant capacity (TRAP). In addition, inhibitors of nitric oxide synthase enzymes were used. The CL time-course curve increased dramatically after 1, 2, and 4 h of reperfusion, reaching values about 12 times higher than those of both control and ischemic rats. Initial velocity (V0) increased from 13.6 cpm mg protein(-1) min(-1) in the ischemic group, to 7341-8524 cpm mg protein(-1) min(-1) following reperfusion. The administration of L-NAME prior to reperfusion significantly reduced (p<0.007) the time-course of the CL curve, decreasing the V(0) value by 51% and preventing antioxidant consumption for 1h following reperfusion. No significant change in CL time-course curve and TRAP values were observed with aminoguanidine treatment. On contrary, after 4h following reperfusion, pre treatment with aminoguanidine led to a significant decrease (p < 0.0001) in the time-course of the CL curve, where V0 decreased by 75% and TRAP returned to control levels. No significant change in CL time-course curve and TRAP values were observed with L-NAME treatment. When RT-PCR was carried out with an iNOS-specific primer, a single band was detected in RNA extracted from muscle tissue of only the 4 h ischemia/4 h reperfusion group. No bands were found in either the control, 4 h ischemia or 4 h ischemia/1 h reperfusion groups. Based on these results, we conclude that *NO plays an important role in oxidative stress injury, possibly via -ONOO, in skeletal muscle subjected to ischemia/reperfusion. Our results also show that cNOS isoenzymes are preferentially involved in *NO generation at the beginning of reperfusion and that iNOS isoenzyme plays an important role in reperfusion injury producing *NO later in the process.     

The Effect of Vitamin E-Deficiency in Isolated Rat Heart on the Cellular Defence System Against Free Radicals During Normal Reperfusion After Hypoxic, Ischemic and Ca2+-Free Perfusion

We investigated whether vitamin E plays a role in the protection against potential free radical formation and related biochemical changes in hypoxic, ischemic and Ca²⁺-depleted rat heart upon normal reperfusion.

In the heart of normally fed rats a decrease in the activity of superoxide dismutase and the capacity of the glutathione system, factors of the cellular protective mechanisms against free radicals, occurred upon exposure to the above mentioned treatments. This decrease was not further enhanced if vitamin E-deficient rat hearts were treated. Vitamin E-deficiency, however, led to detectable peroxidation of lipids if Ca²⁺-depleted or hypoxic hearts were reperfused. Lipid peroxidation was measured as the formation of thiobarbituric acid reactive material, which is readily formed during this process. Reflow after ischemia did not induce lipid peroxidation either in normal or in vitamin E-deficient rat heart.

Since changes in Ca²⁺ -homeostasis are thought to be primarily responsible for the Ca²⁺-reperfusion injury, a role for Ca²⁺-ions in lipid peroxidative processes, either directly or indirectly, seems indicated. Furthermore the results imply that even a sharp and extensive decrease of reduced glutathione, as seen upon Ca²⁺ -repletion after a period of Ca²⁺ -depletion, does not necessarily induce peroxidation of lipids in heart tissue. Obviously, vitamin E is very important in the protection of cardiac membranes. Replenishment of the water-soluble protective factors in the heart seems, however, more important during above mentioned treatments, especially since repair of the vitamin E-free radical is dependent on water-soluble factors.     

The effects of carbenoxolone, a semisynthetic derivative of glycyrrhizinic acid, on peripheral and central ischemia-reperfusion injuries in the skeletal muscle and hippocampus of rats

As carbenoxolone, a semisynthetic derivative of glycyrrhizinic acid, has a free radical scavenging property, thus the effects of carbenoxolone during ischemia-reperfusion was evaluated on an animal model of ischemia-reperfusion injury in the rat hind limb and hippocampus. Peripheral and central ischemia were induced by free-flap surgery in skeletal muscle and four-vessel-occulation (4VO) of rat, respectively. Carbenoxolone (50-200 mg/kg) and normal saline (10 ml/ kg) were administered intraperitoneally. In peripherlal ischemia, during preischemia, ischemia and reperfusion conditions the electromyographic (EMG) potentials in the muscles were recorded. The malondialdehyde (MDA) was measured by the thiobarbituric acid (TBA) test after reperfusion in peripheral and central ischemia. In peripheral ischemia, the average peak-to-peak amplitude during ischemic-reperfusion was found to be significantly larger in carbenoxolone group (100-200mg/kg) in comparison to control group. The MDA levels were recovered significantly upon carbenoxolone (100-200 mg/kg) therapy in the skeletal muscle and hippocampus of ischemic rats. These results suggest that carbenoxolone can salvage the skeletal muscle and hippocampus from acute ischemia-reperfusion injury.     

不同强度及时间窗骨骼肌缺血后处理对兔心肌的保护作用

目的:通过比较不同强度及时间窗骨骼肌缺血后处理对兔缺血/再灌注心肌的保护效能,试图寻找最佳强度和时间窗的骨骼肌缺血后处理方案。方法:健康新西兰大白兔42只(雄性)随机分为7组(n=6):①假手术组(Sham)、②缺血对照组(CON)、③标准骨骼肌后处理组(SP)、④延迟6min骨骼肌后处理组(6M-DSP)、⑤延迟1 min骨骼肌后处理组(1M-DSP)、⑥骨骼肌后处理加强组(SSP)、⑦骨骼肌后处理减弱组(WSP)。以开胸结扎冠状动脉左室支固定部位方法制作缺血/再灌注模型,以游离并夹闭双侧腹股沟髂外动脉固定位置方法造成骨骼肌缺血,再灌注末以TTC法确定心肌梗死范围,并分别于心肌缺血前、后及再灌注1 h、2 h,以生化法测定血清肌酸激酶(CK)及乳酸脱氢酶(LDH)水平。结果:和CON组相比,1M-DSP组心肌梗死重量比及面积比分别下降了42.32%及42.68%、SP组分别下降了49.97%及43.78%、SSP组分别下降了48.36%及48.86%,(P均<0.05),但三组之间相比,心梗范围未见明显差异;而6M-DSP、WSP组与CON组相比未见心肌保护作用;肌酸激酶(CK)的水平和梗死范围变化趋势一致。结论:兔在心肌缺血/再灌注之前完成骨骼肌5 min缺血/1 min再灌注1次循环的缺血后处理,可以起到明显的心肌保护作用。     

The balance between the production of tumor necrosis factor-alpha and interleukin-10 determines tissue injury and lethality during intestinal ischemia and reperfusion

A major goal in the treatment of acute ischemia of a vascular territory is to restore blood flow to normal values, i.e. to "reperfuse" the ischemic vascular bed. However, reperfusion of ischemic tissues is associated with local and systemic leukocyte activation and trafficking, endothelial barrier dysfunction in postcapillary venules, enhanced production of inflammatory mediators and great lethality. This phenomenon has been referred to as "reperfusion injury" and several studies demonstrated that injury is dependent on neutrophil recruitment. Furthermore, ischemia and reperfusion injury is associated with the coordinated activation of a series of cytokines and adhesion molecules. Among the mediators of the inflammatory cascade released, TNF-alpha appears to play an essential role for the reperfusion-associated injury. On the other hand, the release of IL-10 modulates pro-inflammatory cytokine production and reperfusion-associated tissue injury. IL-1beta, PAF and bradykinin are mediators involved in ischemia and reperfusion injury by regulating the balance between TNF-alpha and IL-10 production. Strategies that enhance IL-10 and/or prevent TNF-alpha concentration may be useful as therapeutic adjuvants in the treatment of the tissue injury that follows ischemia and reperfusion.     

Effects of natural antioxidant Ginkgo biloba extract (EGB 761) on myocardial ischemia-reperfusion injury

Recently, it was reported that Ginkgo biloba extract (EGb 761), which is known to have antioxidant properties, also has antiarrhythmic effects on cardiac reperfusion-induced arrhythmias. In the present study, effects of EGb 761 on cardiac ischemia-reperfusion injury were investigated from the point of view of recovery of mechanical function as well as the endogenous antioxidant status of ascorbate. Isolated rat hearts were perfused using the Langendorff technique, and 40 min of global ischemia were followed by 20 min of reperfusion. EGb 761 improved cardiac mechanical recovery and suppressed the leakage of lactate dehydrogenase (LDH) during reperfusion. Furthermore, EGb 761 diminished the decrease of myocardial ascorbate content after 40 min of ischemia and 20 min of reperfusion. Interestingly, EGb 761 also suppressed the increase of dehydroascorbate. These results indicate that EGb 761 protects against cardiac ischemia-reperfusion injury and suggest that the protective effects of EGb 761 depend on its antioxidant properties.     

Dose-dependent protection of cardiac function by propofol during ischemia and early reperfusion in rats: effects on 15-F2t-isoprostane formation

We examined the effects of propofol (2,6-diisopropylphenol) on functional recovery and 15-F2t-isoprostane generation during ischemia-reperfusion in Langendorff-perfused rat hearts. Before the induction of 40 min of global ischemia, hearts were perfused (10 min) with propofol at 5 (lo-P) or 12 microg/mL (hi-P) in saline or with saline only (control). During ischemia, saline, lo-P, or hi-P was perfused through the aorta at 60 microL/min. During the first 15 min of reperfusion, propofol (5 or 12 microg/mL) was continued, followed by perfusion with 5 microg/mL propofol for 75 min in both propofol-treated groups. After 90 min of reperfusion (Rep-90), heart tissues were harvested for assessment of antioxidant status. In hi-P, we observed increased latency to and greater reduction of ischemic contracture relative to the lo-P or control groups. 15-F2t-Isoprostane concentrations increased during ischemia and were significantly lower in hi-P and lo-P than in control (P < 0.01). At Rep-90, myocardial functional recovery was greater in both propofol-treated groups relative to control, and it correlated positively with tissue antioxidant capacity preservation. Tissue antioxidant capacity was better preserved in hi-P than in lo-P treatment (P < 0.05). We conclude that oxidant injury occurs during ischemia and reperfusion, and propofol provides dose-dependent protection primarily by enhancing tissue antioxidant capacity and reducing lipid peroxidation.     

钙网蛋白参与缺血后处理减轻大鼠骨骼肌缺血/再灌注损伤

本实验分别在整体和细胞水平观察缺血后处理（ischemic postconditioning,I-postC）对骨骼肌缺血／再灌注（ischemia／reperfusion,I／R）损伤的影响,并探讨钙网蛋白（calreticulin,CRT）介导的信号转导机制。（1）整体实验：健康雄性Wistar大鼠48只,无创动脉夹夹闭右侧股动脉4h,松夹再灌注12h或24h建立大鼠右后肢I／R损伤模型,随机分为I／R组、缺血预处理（ischemic preconditioning,IPC）组（5min缺血／5min再灌,3个循环）和I-postC组（1min再灌／1min缺血,3个循环）（n=16）,大鼠左后肢做对照处理。再灌注结束时测定血浆乳酸脱氢酶（1actate dehydrogenase,LDH）活性、骨骼肌湿干重比值（wet／dryweightratio,W／D）;电镜观察骨骼肌超微结构变化：Westernblot检测骨骼肌CRT、钙调神经磷酸酶（calcineurin,CaN）的表达。（2）细胞培养实验：原代培养Sprague-Dawley乳鼠骨骼肌细胞,随机分为6组：正常对照组、缺氧／复氧（hypoxia／reoxygenation,H／R）组、缺氧预处理（hypoxic preconditioning,HPC）组、缺氧后处理（hypoxic postconditioning,H-postC）组、CaN抑制剂环孢素A（cyclosporine,CsA）＋H／R组和CsA＋H-postC组。台盼蓝排斥实验、流式细胞仪检测细胞损伤情况：Westernblot检测骨骼肌细胞CRT和CaN的表达。结果显示：（1）在整体动物实验中,I-postC可显著降低血浆LDH活性和组织水肿,骨骼肌超微结构损伤减轻,无细胞核凋亡现象,与IPC组相比无显著差异。I-postC再灌注12h和24hCRT表达分别较I／R12h和24h组高4．39倍和1．02倍（P〈0．05）,CaN表达分别增高1．96倍和0．63倍（尸〈0．05）。相关分析显示CRT表达与CaN表达呈正相关（r-0．865,P〈0．01）。（2）在细胞培养实验中,H-postC可减轻H／R诱导的骨骼肌细胞凋亡,增加细胞存活率,与HPC组相比无显著差异,CsA可抑制H-postC的保护作用;H-postC可上调CRT和CaN的表达,分别较H／R组增加31．8％（P〈0．05）和6．02％,加入CsA后CaN表达降低44．02％（P〈0．05vsH-postC）。上述整体实验和细胞培养实验结果提示,I-postC与IPC保护作用相似,可显著减轻I／R损伤;CRT上调介导的CaN表达增加可能参与了I-postC的保护作用,抑制CaN表达可降低I-postC的保护作用。     

Ischemic preconditioning by brief extremity ischemia before flap ischemia in a rat model

Ischemic preconditioning is a protective endogenous mechanism to reduce ischemia/reperfusion injury and is defined as a brief period of ischemia the authors term "preclamping." This is followed by tissue reperfusion and is believed to increase the ischemic tolerance. The objective of this study was to determine whether acute remote ischemic preconditioning, which has been reported to be successful for other organs, such as the heart, kidney, intestine, and liver, will also result in an enhancement of survival in flaps, and whether remote ischemic preconditioning is as effective as preclamping. Forty male Wistar rats were divided into four experimental groups. An extended epigastric adipocutaneous flap (6 x 10 cm) was raised, based on the left superficial epigastric artery and vein. In the control group, a 3-hour flap ischemia was induced. In the preclamping group, a brief ischemia of 10 minutes was induced by clamping the flap pedicle, followed by 30 minutes of reperfusion. Ischemia of the right hind limb was induced in the femoral ischemia group by clamping the femoral artery and vein for 10 minutes after flap elevation. The limb was then reperfused for 30 minutes. Thereafter, flap ischemia was induced as in the control group. A similar protocol was used in the tourniquet group. A tourniquet was used to induce hind-limb ischemia. The experiment was then performed as in the femoral ischemia group. Mean flap necrosis area was assessed for all groups on the fifth postoperative day using planimetry software. Average flap necrosis area was 68.2 +/- 18.1 percent in the control group, 11 +/- 8.38 percent in the preclamping group, 12.5 +/- 5.83 percent in the femoral ischemia group, and 24 +/- 11.75 percent in the tourniquet group. All preconditioned animals demonstrated a significantly lower area of flap necrosis than the control group (p < 0.001, one-way analysis of variance, post hoc Tukey's test). The data show that ischemic preconditioning and enhancement of flap survival can be achieved not only by preclamping of the flap pedicle but also by induction of an ischemia/reperfusion event in a body area distant from the flap before harvest. These findings indicate that remote ischemic preconditioning is a systemic phenomenon, leading to an enhancement of flap survival. The exact mechanism is not yet completely understood. The data suggest that remote ischemic preconditioning could be performed simultaneously with flap harvest in the clinical setting, resulting in an improved flap survival without prolongation of the operation. This may decrease the rate of partial flap loss or fat necrosis, especially in high-risk groups such as smokers, those with irradiated tissues, and obese patients.     

Poloxamer 188 Protects Neurons against Ischemia/Reperfusion Injury through Preserving Integrity of Cell Membranes and Blood Brain Barrier

Poloxamer 188 (P188), a multiblock copolymer surfactant, has been shown to protect against ischemic tissue injury of cardiac muscle, testes and skeletal muscle, but the mechanisms have not been fully understood. In this study, we explored whether P188 had a protective effect against cerebral ischemia/reperfusion injury and its underlying mechanisms. The in vivo results showed that P188 significantly reduced the infarct volume, ameliorated the brain edema and neurological symptoms 24 h after ischemia/reperfusion. In the long-term outcome study, P188 markedly alleviated brain atrophy and motor impairments and increased survival rate in 3 weeks of post stroke period. Additionally, P188 protected cultured hippucampal HT22 cells against oxygen–glucose deprivation and reoxygenation (OGD/R) injury. The ability in membrane sealing was assessed with two fluorescent membrane-impermeant dyes. The results showed that P188 treatment significantly reduced the PI-positive cells following ischemia/reperfusion injury and repaired the HT22 cell membrane rupture induced by Triton X-100. In addition, P188 inhibited ischemia/reperfusion-induced activation of matrix metalloproteinase (MMP)-9 and leakage of Evans blue. Therefore, the present study concludes that P188 can protect against cerebral ischemia/reperfusion injury, and the protection involves multi-mechanisms in addition to the membrane resealing.     

Effect of catecholestrogen administration during adriamycin-induced cardiomyopathy in ovariectomized rat

The therapeutical beneficial effect of estrogen-derived metabolites or catecholestrogens is controversial. These molecules are produced during estrogen therapy based on 17-β-estradiol treatment. The metabolization of 17-β-estradiol is carried out in brain, kidney or liver, and triggers different products such as 2- and 4- hydroxyestradiol (2OH and 4OH). These products have shown antioxidant properties against oxidative stress (OS) in several experimental models. Different noxious side effects related to those metabolites have also been observed upon estrogen therapy. In this sense, catecholestrogens seem to be implicated in tumoral and mutagenic process after long treatment with estrogens substitutive therapy.

In our study, we have verified that 2OH and 4OH have antioxidant and cardioprotective effects against adriamycin (AD)-induced cardiomyopathy in ovariectomized (OVX) rats. Catecholestrogens diminished the lipid peroxides and carbonyl protein (CO) content, and different enzymes related to cell injury (creatinine kinase, lactate dehydrogenase, aspartate aminotransferase, alanine aminotransferase) in cardiac tissue from OVX-, AD-, and OVX+AD-treated rats. All these changes were correlated to a recovery on reduced glutathione (GSH), glutathione peroxidase (GPx), superoxide dismutase (SOD) and catalase (CAT) in heart tissue.

The present study showed that 2OH and 4OH reduced all the parameters related to OS, antioxidant depletion and cardiac injury in OVX rats treated or not with AD.     

Red blood cell rheological alterations in a rat model of ischemia-reperfusion injury

Red blood cell (RBC) deformability and aggregation characteristics were investigated in an experimental model of ischemia-reperfusion injury. Ischemia was produced in rat hind limb by occluding the femoral artery for 10 minutes, followed by reperfusion. Blood samples were obtained either following the ischemia or 15 minutes after reperfusion. RBC deformability measured by ektacytometry was found to be significantly impaired immediately after the end of ischemic period in the blood samples obtained from femoral vein of the ischemic limb, while there was no significant difference after 15 minutes of reperfusion. In contrast, RBC aggregability was found to be decreased only after the reperfusion period and this alteration was not only limited to the blood returning from the ischemic limb but was also observed in the samples obtained from non-ischemic, contralateral hind limb, indicating a systemic alteration. RBC electrophoresis studies suggested that the altered aggregability might be related to altered RBC surface properties including increased RBC surface charge density.     

A novel cell-permeable antioxidant peptide, SS31, attenuates ischemic brain injury by down-regulating CD36

Oxidative stress is implicated in the pathogenesis of ischemia/reperfusion injury. Recently, we demonstrated that activation of CD36, a class B scavenger receptor, mediates free radical production and tissue injury in cerebral ischemia (1). Oxidized low density lipoproteins (oxLDL) are among the ligands that bind to CD36 and are elevated in acute cerebral infarction. SS31 is a cell-permeable antioxidant peptide that reduces intracellular free radicals and inhibits LDL oxidation/lipid peroxidation (2). The current study was designed to investigate whether treatment with SS31 normalizes ischemia-induced redox changes and attenuates CD36-mediated tissue injury. C57BL/6 mice were subjected to transient middle cerebral artery occlusion (MCAO). Redox status and infarct volume were measured in animals treated with either saline or SS31. Oxidative stress induced by ischemia/reperfusion profoundly depleted glutathione (GSH) concentrations in the ipsilateral cortex and striatum. Treating mice with SS31 immediately after reperfusion significantly attenuated ischemia-induced GSH depletion in the cortex and reduced infarct size. By contrast, the protective effect of SS31 was absent in CD36 knock-out mice, indicating that SS31 is acting through inhibition of CD36. Treating C57BL/6 mice with SS31 reduced CD36 expression in postischemic brain and mouse peritoneal macrophages (MPM). Further in vitro studies revealed that SS31 attenuated oxLDL-induced CD36 expression and foam cell formation in MPM. These in vivo and in vitro studies indicate that the down-regulation of CD36 by novel class antioxidant peptides may be a useful strategy to treat ischemic stroke victims.     

大鼠肢体缺血预处理对肝缺血/再灌注损伤的保护作用

目的：研究肢体缺血预处理对大鼠肝缺血/再灌注损伤是否具有保护作用。方法：雄性SD大鼠32只,随机分为对照组（S组）;缺血/再灌注组（I/R组）;经典缺血预处理组（IPC组）;肢体缺血预处理组（远端缺血预处理组,RPC组）。S组仅行开腹,不作其他处理;IPC组以肝缺血5min作预处理;RPC组以双后肢缺血5min,反复3次作预处理,2个预处理组及I/R组均行肝缺血1h再灌注3h。取血用于血清谷丙转氨酶（ALT）与血清谷草转氨酶（AST）检测。切取肝组织用于测定湿干比（W/D）、中性粒细胞（PMN）计数及观察显微、超微结构的变化。结果：与I/R组比较,IPC组,RPC组ALT,AST,W/D值,及PMN计数均明显降低（P〈0.01）,肝脏的显微及超微结构损伤减轻。结论：肢体缺血预处理对大鼠肝脏I/R损伤有明显的保护作用,强度与经典缺血预处理相当,其机制可能与抑制肝脏炎症反应、减轻肝脏水肿、改善肝组织微循环有关。     

Cardioprotective effects of erythropoietin in the reperfused ischemic heart: a potential role for cardiac fibroblasts

Erythropoietin has recently been shown to have effects beyond hematopoiesis such as prevention of neuronal and cardiac apoptosis secondary to ischemia. In this study, we evaluated the in vivo protective potential of erythropoietin in the reperfused rabbit heart following ventricular ischemia. We show that "preconditioning" with erythropoietin activates cell survival pathways in myocardial tissue in vivo and adult rabbit cardiac fibroblasts in vitro. These pathways, activated by erythropoietin in both whole hearts and cardiac fibroblasts, are also activated acutely by ischemia/reperfusion injury. Moreover, in vivo studies indicate that erythropoietin treatment either prior to or during ischemia significantly enhances cardiac function and recovery, including left ventricular contractility, following myocardial ischemia/reperfusion. Our data indicate that a contributing in vivo cellular mechanism of this protection is mitigation of myocardial cell apoptosis. This results in decreased infarct size as evidenced by area at risk studies following in vivo ischemia/reperfusion injury, translating into more viable myocardium and less ventricular dysfunction. Therefore, erythropoietin treatment may offer novel protection against ischemic heart disease and may act, at least in part, by direct action on cardiac fibroblasts and myocytes to alter survival and ventricular remodeling.