No ischemic preconditioning in heterozygous connexin43-deficient mice

Protein kinase Cepsilon (PKCepsilon) plays a central role in ischemic preconditioning (IP) in mice and rabbits, and activated PKCepsilon colocalizes with and phosphorylates connexin43 (Cx43) in rats and humans. Whether or not Cx43 contributes to the mechanism(s) of IP in vivo is yet unknown. Therefore, wild-type (n = 8) and heterozygous Cx43-deficient mice (n = 8) were subjected to 30 min occlusion and 120 min reperfusion of the left anterior descending coronary artery. IP was induced by one cycle of 5 min occlusion and 10 min reperfusion (n = 8/8 mice) before the sustained occlusion. Infarct size was reduced by IP in wild-type mice [11.3 +/- 3.4% vs. 23.7 +/- 7.2% of the left ventricle (LV), P < 0.05] but not in Cx43-deficient mice (26.0 +/- 6.0% vs. 25.1 +/- 3.8% of LV). Also, three cycles of 5 min occlusion and 10 min reperfusion (n = 5) did not induce protection in Cx43-deficient mice (27.6 +/- 5.5 % of LV). Thus Cx43 contributes to the protection of IP in mice in vivo.     

Minimal protection of the liver by ischemic preconditioning in pigs

Ischemic preconditioning (IP) protects the rat liver. In pigs, in which hepatic tolerance to ischemia is similar to that in humans, information on IP is lacking. Therefore, in enflurane-anesthetized pigs, hepatic vessels were occluded for 120 min (protocol 1) or 200 min (protocol 2) without (control) and with IP (3 times 10 min ischemia-reperfusion each). In protocol 1, cumulative bile flow (CBF) during reperfusion was greater in IP (47.3 +/- 5.2 ml/8 h) than in control (17.1 +/- 7.8 ml/8 h, P < 0.05). ATP content tended to recover toward normal during reperfusion in IP, whereas it remained at ischemic levels in control. Serum enzyme concentrations increased similarly during reperfusion, and <1% hepatocytes were necrotic or stained terminal deosynucleotidyl transferase-mediated dUTP nick-end labeling-positive in control and IP groups. In protocol 2, no differences in CBF, ATP, or serum enzyme concentrations during reperfusion were measured between control and IP groups, except for a somewhat reduced lactate dehydrogenase in IP. The number of necrotic or terminal deosynucleotidyl transferase-mediated dUTP nick-end labeling-positive hepatocytes tended to be greater in the IP than the control group. Thus IP provides some functional protection against reversible ischemia but no protection during prolonged ischemia in pigs.     

Protective effect of liver ischemic preconditioning on rat hepatocytes

Ischemic preconditioning (IPC) protects liver graft function following ischemia in liver transplantation and liver resection. The aim of this study was to assess the advantages and any potential disadvantages of liver IPC prior to isolation for rat hepatocytes during isolation and cryopreservation. After isolating and thawing the cryopreserved hepatocytes after 14 and 28 d,cell viability,efficiency,and lactate dehydrogenase (LDH) levels in preserve solution were examined for every group. Groups treated with...     

无创性肢体缺血预适应对小鼠抗应激能力的影响

目的:探讨无创性肢体缺血预适应在提高小鼠抗应激能力方面的作用。方法:小鼠分为正常组、对照组、预适应组和药物组,进行常压耐缺氧、耐疲劳负重游泳、耐高、低温实验,分别记录各种应激状态下小鼠的耐受时间,测定常压缺氧耐受后小鼠血清中SOD的活性和负重游泳后血清中乳酸的含量。结果:预适应组能显著提高小鼠常压耐缺氧时间,且SOD活性较对照组有显著的提高,但提高的程度均低于普萘洛尔组。预适应组平均游泳时间显著延长,且程度与咖啡因组相当。预适应能明显延长高温下小鼠的存活时间,且延长程度与氯丙嗪没有显著性差异。与正常组比较,预适应组能显著延长小鼠的耐低温时间。结论:无创性肢体缺血预适应能提高小鼠耐缺氧、抗疲劳、耐高温和耐低温的能力。     

Combined preconditioning and postconditioning provides synergistic protection against liver ischemic reperfusion injury

Hepatic Ischemia and Reperfusion Injury (IRI) is a major cause of liver damage during liver surgery and transplantation. Ischemic preconditioning and postconditioning are strategies that can reduce IRI. In this study, different combined types of pre- and postconditioning procedures were tested in a murine warm hepatic IRI model to evaluate their protective effects. Proanthocyanidins derived from grape seed was used before ischemia process as pharmacological preconditioning to combine with technical preconditioning and postconditioning. Three pathways related to IRI, including reactive oxygen species (ROS) generation, pro-inflammatory cytokines release and hypoxia responses were examined in hepatic IRI model. Individual and combined pre- and postconditioning protocols significantly reduce liver injury by decreasing the liver ROS and cytokine levels, as well as enhancing the hypoxia tolerance response. Our data also suggested that in addition to individual preconditioning or postconditioning, the combination of these two treatments could reduce liver ischemia/reperfusion injury more effectively by increasing the activity of ROS scavengers and antioxidants. The utilization of grape seed proanthocyanidins (GSP) could improve the oxidation resistance in combined pre- and postconditioning groups. The combined protocol also further increased the liver HIF-1 alpha protein level, but had no effect on pro-inflammatory cytokines release compared to solo treatment.     

SAPKs regulation of ischemic preconditioning

The role of stress-activated protein kinases (SAPKs), c-Jun NH(2)-terminal kinase (JNK) and p38 mitogen-activated protein (MAP) kinase, in preconditioning (PC) was examined with the use of isolated rat hearts subjected to four cyclic episodes of 5-min ischemia and 10-min reperfusion followed by 30-min ischemia and 2-h reperfusion (I/R). A group of hearts was preperfused with 100 microM curcumin, a c-Jun and JNK1 inhibitor, or 5 microM SB 203580, a p38 MAP kinase inhibitor. Another group of hearts was preperfused with 20 microM anisomycin, a stimulator for both JNK and p38 MAP kinases. I/R increased the protein levels of JNK1, c-Jun, and p38 MAP kinase. PC also enhanced the induction of these kinases, but subsequent I/R-mediated increase was blocked by PC. Curcumin blocked I/R- and PC-mediated increase in JNK1 and c-Jun protein levels, whereas it had no effects on p38 MAP kinase. SB 203580, on the other hand, was equally effective in reducing the p38 MAP kinase activation but exerted no effects on JNK1 and c-Jun induction. I/R-mediated increased myocardial infarction was reduced by any of the following compounds: anisomycin, curcumin, and SB 203580. The cardioprotective effects of PC were abolished by either curcumin or SB 203580. The results demonstrate that PC is mediated by a signal-transduction pathway involving both JNK1 and p38 MAP kinase. Activation of SAPKs, although transient, is obligatory for PC.     

肾上腺素受体腺苷酸环化酶系统在大鼠心肌缺血预适应中的变化

目的 :研究心肌缺血预适应时 β 肾上腺素受体腺苷酸环化酶系统各部分变化及意义。 方法 :选择SD大鼠 ,随机分成假手术组 (CON组 ) ,预适应组 (IP组 ) ,缺血 /再灌注组 (I/R组 )。以手术套管法造成左冠状动脉主干缺血及再灌注 ,损伤后取心脏用TTC法测梗塞面积 ,取血清测心肌酶改变 ,放射配基结合法测 β 肾上腺素受体 (β AR)密度及亲和力变化 ,生化法测AC活性变化 ,放免测cAMP水平。结果 :IP组较I/R组心梗面积明显缩小 (P <0 .0 1 ) ,心肌酶CK、CK MB、LDH明显降低 (P <0 .0 1 )。IP组受体密度较I/R组显著增加 (P <0 .0 1 ) ,两组受体解离常数无明显差异。IP组较I/R组AC活性增高 (P <0 .0 5) ,cAMP含量增加 (P <0 .0 1 )。结论 :缺血预适应对心脏具有保护作用 ,可缩小梗塞面积 ,减少心肌酶漏出 ,并使 β AR密度增高 ,cAMP产量增加 ,β 肾上腺素腺苷酸环化酶系统可能参与预适应心肌保护作用     

Involvement of CCR-2 chemokine receptor activation in ischemic preconditioning and postconditioning of brain in mice

The present study has been designed to investigate the potential role of CCR-2 chemokine receptor in ischemic preconditioning as well as postconditioning induced reversal of ischemia-reperfusion injury in mouse brain. Bilateral carotid artery occlusion of 17min followed by reperfusion for 24h was employed in present study to produce ischemia and reperfusion induced cerebral injury in mice. Cerebral infarct size was measured using triphenyltetrazolium chloride staining. Memory was evaluated using elevated plus-maze test and Morris water maze test. Rota rod test was employed to assess motor incoordination. Bilateral carotid artery occlusion followed by reperfusion produced cerebral infarction and impaired memory and motor co-ordination. Three preceding episodes of bilateral carotid artery occlusion for 1min and reperfusion of 1min were employed to elicit ischemic preconditioning of brain, while three episodes of bilateral carotid artery occlusion for 10s and reperfusion of 10s immediately after the completion of were employed to elicit ischemic postconditioning of brain. Both prior ischemic preconditioning as well as ischemic postconditioning immediately after global cerebral ischemia prevented markedly ischemia-reperfusion-induced cerebral injury as measured in terms of infarct size, loss of memory and motor coordination. RS 102895, a selective CCR-2 chemokine receptor antagonist, attenuated the neuroprotective effect of both the ischemic preconditioning as well as postconditioning. It is concluded that the neuroprotective effect of both ischemic preconditioning as well as ischemic postconditioning may involve the activation of CCR-2 chemokine receptors.     

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。     

Protective effects of sodium nitrite preconditioning against alcohol-induced acute liver injury in mice

The purpose of the present study was to investigate the effect of sodium nitrite (SN) on alcohol-induced acute liver injury in mice. Forty male C57bL/6 mice were randomly divided into 4 groups. Acute alcohol-induced liver injury group were injected intraperitoneal (ip) with alcohol (4.5 g/kg); SN preconditioning group were pretreated with SN (16 mg/kg, ip) for 12 h, and received alcohol (4.5 g/kg, ip) injection; Control and SN groups were treated with saline and SN, respectively. After the treatments, liver index (liver/body weight ratio) was determined. Colorimetric technique was performed to measure the serum alanine transaminase (ALT), aspartate transaminase (AST), liver superoxide dismutase (SOD), glutathione peroxidase (GSH-Px), catalase (CAT) activities, as well as malondialdehyde (MDA) content. The pathological index of liver tissue was assayed by HE and TUNEL fluorometric staining. Using Western blot and immunohistochemistry staining, the expression of hypoxia-inducible factor-1α (HIF-1α) protein was detected. The results showed that, compared with acute alcohol-induced liver injury group, pretreatment with low doses of SN decreased liver index and serum levels of ALT and AST, weakened acute alcohol-induced hepatocyte necrosis, improved pathological changes in liver tissue, increased live tissue SOD, GSH-Px and CAT activities, reduced MDA content and apoptosis index of hepatocytes, and up-regulated HIF-1α protein level in liver tissue. These results suggest that the pretreatment of SN can protect hepatocytes against alcohol-induced acute injury, and the protective mechanism involves inhibition of oxidative stress and up-regulation of HIF-1α protein level.     

Autophagy in ischemic preconditioning and hibernating myocardium

Autophagy is a major protective mechanism and has been identified in response to hypoxia and more recently, myocardial ischemia, but it is not known whether it is involved in mediating ischemic preconditioning, the most powerful intervention known to protect myocardium against lethal ischemic injury. We examined autophagy in several models of preconditioning induced by 6 repetitive episodes of ischemia every 12 hours versus classical first or second-window preconditioning in swine. The results indicated that autophagy is an important mechanism mediating cardioprotection following repetitive episodes of coronary stenosis or coronary occlusion, but less for traditional first or second window preconditioning.     

Role of decoy molecules in neuronal ischemic preconditioning

AimsDecoy receptors bind with TNF related apoptosis inducing ligands (TRAIL) but do not contain the cytoplasmic domains necessary to transduce apoptotic signals. We hypothesized that decoy receptors may confer neuronal protection against lethal ischemia after ischemic preconditioning (IPC).Main methodMixed cortical neurons were exposed to IPC one day prior to TRAIL treatment or lethal ischemia.Key findingsIPC increased decoy receptor but reduced death receptor expression compared to lethal ischemia. IPC-induced increase in decoy receptor expression was reduced by prior treatment with CAPE, a nuclear factor-kappa B inhibitor (NFκB).SignificanceExpression of decoy molecules, dependent on NFκB, may mediate neuronal survival induced by IPC.     

Synergistic protective effect of ischemic preconditioning and allopurinol on ischemia/reperfusion injury in rat liver

This study examined the effects of ischemic preconditioning (IPC), allopurinol (Allo) or a combination of both on the extent of mitochondrial injury caused by hepatic ischemia/reperfusion (I/R). I/R increased the serum aminotransferase activity and the level of mitochondrial lipid peroxidation, whereas it decreased the mitochondrial glutathione level. Either IPC or Allo alone attenuated these changes with Allo+IPC having a synergistic effect. Allo increased the serum nitrite and nitrate level after brief ischemia. The significant peroxide production observed after 10 min of reperfusion after sustained ischemia was markedly attenuated by Allo+IPC. The mitochondria isolated after I/R were swollen, which was reduced by Allo+IPC. At the end of ischemia, the hepatic ATP level was lower and there was significant xanthine accumulation, which was attenuated by Allo+IPC. These results suggest that IPC and Allo act synergistically to protect cells against mitochondrial injury and preserve the hepatic energy metabolism during hepatic I/R.     

Ceramide in the antiapoptotic effect of ischemic preconditioning

Although the mechanism by which ischemic preconditioning (PC) inhibits myocardial apoptosis during ischemia-reperfusion is unclear, evidence indicates a role for the secondary messenger ceramide. We investigated in vivo whether PC may affect ceramide and sn-1,2-diacylglycerol (DAG) production, and attenuate apoptosis during ischemia. Rabbits underwent 30 min of ischemia, followed by 4 h of reperfusion. Before this, they received either no intervention (control group) or one episode of 5 min of ischemia, followed by 5 min of reperfusion (PC group), or an intravenous administration of the sphingomyelinase inhibitor D609. Myocardial content of ceramide and DAG was measured using the DAG kinase assay at different time points of the experiment. Apoptosis was detected and quantified by a sandwich enzyme immunoassay. Both AR and infarct size were measured using blue dye injection and triphenyltetrazolium chloride staining. Control hearts exhibited a peak of ceramide production at 5 min of the prolonged ischemia, with a mean value averaging 64 +/- 5 ng/mg tissue (P < 0.05 vs. 48 +/- 4 ng/mg at baseline). In contrast, ischemic PC and D609 prevented ceramide increase during the prolonged ischemia. Myocardial DAG content was increased only in PC hearts at 30 min of ischemia. Preconditioned and D609 groups developed less apoptosis, as well as a limited infarct size, compared with the control group. These results suggest that the antiapoptotic effect of PC may be due to a reduced ceramide production during sustained ischemia in the rabbit heart.     

STAT-3 activation is necessary for ischemic preconditioning in hypertrophied myocardium

The JAK-STAT pathway is activated in the early and late phases of ischemic preconditioning (IPC) in normal myocardium. The role of this pathway and the efficacy of IPC in hypertrophied hearts remain largely unknown. We hypothesized that phosphorylated STAT-3 (pSTAT-3) is necessary for effective IPC in pressure-overload hypertrophy. Male Sprague-Dawley rats 8 wk after thoracic aortic constriction (TAC) or sham operation underwent echocardiography and Langendorff perfusion. Randomized hearts were subjected to 30 min of global ischemia and 120 min of reperfusion with or without IPC in the presence or absence of the JAK-2 inhibitor AG-490 (AG). Functional recovery and STAT activation were assessed. TAC rats had a 31% increase in left ventricular mass (1,347 +/- 58 vs. 1,028 +/- 43 mg, TAC vs. sham, P < 0.001), increased anterior and posterior wall thickness but no difference in ejection fraction compared with sham-operated rats. In TAC, IPC improved end-reperfusion maximum first derivative of developed pressure (+dP/dt(max); 4,648 +/- 309 vs. 2,737 +/- 343 mmHg/s, IPC vs. non-IPC, P < 0.05) and minimum -dP/dt (-dP/dt(min); -2,239 +/- 205 vs. -1,215 +/- 149 mmHg/s, IPC vs. non-IPC, P < 0.05). IPC increased nuclear pSTAT-1 and pSTAT-3 in sham-operated rats but only pSTAT-3 in TAC. AG in TAC significantly attenuated +dP/dt(max) (4,648 +/- 309 vs. 3,241 +/- 420 mmHg/s, IPC vs. IPC + AG, P < 0.05) and -dP/dt(min) (-2,239 +/- 205 vs. -1,323 +/- 85 mmHg/s, IPC vs. IPC + AG, P < 0.05) and decreased only nuclear pSTAT-3. In myocardial hypertrophy, JAK-STAT signaling is important in IPC and exhibits a pattern of STAT activation distinct from nonhypertrophied myocardium. Limiting STAT-3 activation attenuates the efficacy of IPC in hypertrophy.     

Autophagy regulates endoplasmic reticulum stress in ischemic preconditioning

Recent studies have suggested that autophagy plays a prosurvival role in ischemic preconditioning (IPC). This study was taken to assess the linkage between autophagy and endoplasmic reticulum (ER) stress during the process of IPC. The effects of IPC on ER stress and neuronal injury were determined by exposure of primary cultured murine cortical neurons to 30 min of OGD 24 h prior to a subsequent lethal OGD. The effects of IPC on ER stress and ischemic brain damage were evaluated in rats by a brief ischemic insult followed by permanent focal ischemia (PFI) 24 h later using the suture occlusion technique. The results showed that both IPC and lethal OGD increased the LC3-II expression and decreased p62 protein levels, but the extent of autophagy activation was varied. IPC treatment ameliorated OGD-induced cell damage in cultured cortical neurons, whereas 3-MA (5–20 mM) and bafilomycin A₁ (75–150 nM) suppressed the neuroprotection induced by IPC. 3-MA, at the dose blocking autophagy, significantly inhibited IPC-induced HSP70, HSP60 and GRP78 upregulation; meanwhile, it also aggregated the ER stress and increased activated caspase-12, caspase-3 and CHOP protein levels both in vitro and in vivo models. The ER stress inhibitor Sal (75 pmol) recovered IPC-induced neuroprotection in the presence of 3-MA. Rapamycin 50–200 nM in vitro and 35 pmol in vivo 24 h before the onset of lethal ischemia reduced ER stress and ischemia-induced neuronal damage. These results demonstrated that pre-activation of autophagy by ischemic preconditioning can boost endogenous defense mechanisms to upregulate molecular chaperones, and hence reduce excessive ER stress during fatal ischemia.