Effects of human urotensin II on ischemia/reperfusion injury in isolated perfused rat hearts

AIM: To investigate the effects of human urotensin II (hUII) on ischemia/reperfusion (I/R) injury in isolated rat hearts. METHODS: In the ischemia/reperfusion (I/R) model of isolated perfused rat hearts, the effects of hUII pretreatment on cardiac function was monitored with cardiac function software of MFL Lab200. ATP, total calcium, and malondialdehyde (MDA) content in myocardium were detected. The coronary perfusion flow (CPF) and lactate dehydrogenase (LDH) activity in coronary effluent were measured during reperfusion. RESULTS: In the hUII pretreated group, the release of LDH from myocardium was lower [(78.3±18.1)U/L] than I/R group [(109.3±23.9) U/L, P< 0.05], with decreased contents of MDA and calcium in myocardium (decreased by 24% and 27%, respectively, P< 0.05) and an increased myocardial ATP content [(3.8±0.4)μmol/g dw vs (2.2±0.4)μmol/g dw, P< 0.05)]. At the same time, hUII pretreatment increased CPF [(5.4±0.7) mL/min vs (3.8±0.8) mL/min in I/R group, P< 0.05], reduced left ventricular end-diastolic pressure (LVEDP) by 20% ( P< 0.05) with increased±d p /d t max [(217±38) kPa/s and (119±18) kPa/s vs (173±29) kPa/s and (82±25) kPa/s in I/R groups, respectively, P< 0.05]. hUII pretreatment also increased natrite/natrate (NO₂^-/NO₃^-) content in coronary effluent [(52.2±12.0)μmol/L vs (32.1±10.2)μmol/L in I/R group, P< 0.05)]. CONCLUSION: hUII pretreatment attenuated I/R injury in isolated perfused rat hearts. The protective mechanism might be associated with NO-mediated coronary vasodilation.     

Nitric oxide opens the second window of protection in ischemic preconditioning via induction of heat shock protein 72

AIM:To examine the inhibition of nitric oxide (NO) synthesis during ischemic preconditioning (IP) on the induction of heat shock protein 72 (HSP72) and infarct size-limiting effect of the second window of protection. METHODS:Rabbits were subjected to 4 cycles of 5 min of coronary artery occlusion separated by 10 min reperfusion, or received a sham operation. During this procedure, N^G-nitro-L-arginine methyl ester (L-NAME, an inhibitor of NO synthase) was injected intravenously 5 min before IP followed by its continuous infusion. Twenty-four hours later, the hearts were rapidly excised for assaying HSP72 expression or were subjected to 30 min coronary artery occlusion followed by 120 min reperfusion and then measured infarct size (IS). RESULTS:Twenty-four hours later, immunoblotting revealed an increase in HSP72 protein levels in the IP group, and this was blocked by L-NAME. IS of the IP rabbits was reduced as compared with the control (29.8%±3.7% vs 50.8%±4.3%, P＜0.01). IS in the IP rabbits was elevtated as a result of L-NAME treatment (46.0%±5.1%). Administration of L-arginine reversed the effects of L-NAME on the induction of HSP72 and IS (33.5%±4.0%). The intravenous administration of S-nitroso-N-acetylpenicillamine (SNAP, a NO donor) increased the induction of HSP72 and reduced IS (31.3%±5.7%, P＜0.01vs control) 24 h later. CONCLUSION:These findings suggest that NO may be involved in the induction of HSP72 and the opening of the second window of protection of IP.     

Role of cAMP signaling in cardioprotective mechanism of ischemic postconditioning

AIM: To assess the role of the cAMP signaling in cardioprotection by brief intermittent ischemia at the time of onset of reperfusion (i.e. postconditioning). METHODS: The model of rat myocardial ischemia/reperfusion (I/R) was used. The left ventricular functions were assessed by measuring the left ventricular developed pressure (LVDP) and the coronary flow (CF). The injury of myocardium was further confirmed by detecting the releases of lactate dehydrogenase(LDH) and creatine kinase(CK) in coronary effluent. The mRNA expression of caspase-3, bcl-2 and bax in myocardium was determined by real-time PCR. RESULTS: I/R treatment led to the decrease in LVDP and CF, and the increase in the releases of CK and LDH in coronary artery effluent. The mRNA expression of caspase-3 and bax/bcl-2 ratio was up-regulated simultaneously. Postconditioning treatment relieved the injury induced by I/R, which was enhanced by the specific phosphodiesterase 4(PDE4) inhibitor rolipram. On the other hand, the specific adenylyl cyclase inhibitor SQ22536 attenuated those protective effects of postconditioning. CONCLUSION: The cAMP signaling participates in the protective effect of postconditioning on heart from I/R injury, and the effect may be associated with the regulation of apoptosis.     

Hypoxic preconditioning alleviates oxygen-glucose deprivation in PC12 cells:the involvement of autophagy

AIM: To examined the effects of hypoxic preconditioning(HPC) on oxygen-glucose deprivation(OGD)-induced PC12 cells, and to investigate its possible mechanisms of autophagy.METHODS: Cultured PC12 cells were randomly divided into control group, HPC group, 3-methyladenine(3-MA) group, HPC+OGD group, 3-MA+HPC+OGD group and OGD group. CCK-8 assay was used to detect the cell viability. The caspase-3 activity was also tested. TUNEL staining and flow cytometry were used to detect the cell apoptosis. The protein levels of apoptosis-related protein caspase-3 and autophagy-marked protein LC3-2 and beclin-1 were determined by Western blot.RESULTS: Compared with control group, the viability of PC12 cells was significantly reduced, and the activity of caspase-3 was significantly increased in OGD group. Compared with 3-MA+ HPC+OGD group and OGD group, the viability of PC12 cells was significantly increased, and the activity of caspase-3 was significantly reduced in HPC+OGD group(P<0.05). The PC12 cell injury was apparent after OGD with a great increase in the apoptotic rate(P<0.05). Compared with OGD group, the apoptotic rate significantly decreased in HPC+OGD group(P<0.05). Compared with control group, the protein level of cleaved caspase-3 was significantly increased in OGD group(P<0.05). Compared with OGD group, the protein level of cleaved caspase-3 was significantly decreased, and the levels of LC3-2 and beclin-1 were significantly increased in HPC+OGD group(P<0.05).CONCLUSION: OGD decreases cell survival and induces apoptosis.Activation of cell autophagy may be the mechanism by which hypoxic preconditioning protects the PC12 cells from OGD induced injury.     

COX-2抑制剂预处理对大鼠脑缺血再灌注损伤的保护作用

观察选择性环氧合酶-2（COX2）抑制剂帕瑞昔布钠（parecoxib）预处理对大鼠局灶性脑缺血（focalcerebralischemic,FCI）脑保护作用。参照线栓法制备大鼠局灶性大脑中动脉缺血（MCAO）模型,将60只大鼠随机分为假手术组（A组）、局灶性大脑中动脉缺血/再灌注模型组（B组）、帕瑞昔布钠小剂量组（C组）和帕瑞昔布钠大剂量组（D组）。分别采用神经功能缺失评分、TTC染色法、免疫组化和原位杂交检测观察帕瑞昔布钠的脑保护作用,探讨帕瑞昔布钠在脑保护作用中的重要地位。结果,与模型组相比帕瑞昔布钠不同剂量治疗组神经功能缺失明显减轻（P〈0．05）,梗死体积明显缩小（P〈0．05）,凋亡细胞明显减少,帕瑞昔布钠1．6Pag／kg及帕瑞昔布钠3．2mg／kg组COX-2mRNA阳性细胞数与模型组比较显著减少（P〈0．001,P〈0．05）;结果表明,帕瑞昔布钠预处理可减轻脑缺血再灌注损伤,具有一定的脑保护作用。     

Effects of hyperglycemia on ionic homeostasis in hippocampal microenvironment and secondary neuronal injury after focal ischemia in cerebral cortex of tree shrews

AIM：To observe the effects of hyperglycemia on the ionic homeostasis in hippocampal microenvironment after thrombotic cortical ischemia in tree shrews, and to explore the action and mechanisms of hyperglycemia in secondary neuronal injury after ischemia. METHODS：High blood glucose in tree shrews was induced by intraperitoneal injection of streptozocin. Focal thrombotic cortical ischemia was induced by photochemical method in tree shrews. At 4, 24 and 72 h after ischemia, the changes of pH, K+, Na+, Ca2+ and Cl- in the ipsilateral ischemic hippocampal microenvironment were tested by a single-pumped push-pull microdialysis system and an ion analyzer. The histopathological changes and hippocampal neuronal density were also examined. RESULTS：After cortical ischemia in tree shrews, the pH and the concentrations of Na+, Ca2+ and Cl- in the hippocampal microenvironment decreased, while the concentration of K+ increased. These differences were the most significant at 4 h, the second at 24 h and insignificant at 72 h. Combination of hyperglycemia and cerebral ischemia worsened the turbulence of ionic homeostasis. Compared with the normoglycemic ischemic animals, the changes of pH, K+ and Ca2+ concentrations at 4 h as well as pH and Na+ at 24 h in the hyperglycemic ischemic animals were more significant (P<0.05). The results of histopathological examination showed that there was ischemic neuronal damage in the exposed cerebral cortex and the ipsilateral hippocampal CA1 region at 4 h after photochemical reaction, and the damage was the most severe at 24 h, subsequently accompanied with glial proliferation at 72 h. The hyperglycemic ischemic animals suffered from greater neuronal injury in the cortex and hippocampus than the normoglycemic ischemic animals, especially at 24 h (P<0.01) and 72 h (P<0.05). CONCLUSION: The disturbance of acid-base equilibrium and ionic homeostasis in hippocampal microenvironment, following the spreading of the microenvironment in ischemic core, may be an important reason for secondary neuronal injury in the hippocampus after thrombotic cortical ischemia in tree shrews. Hyperglycemia aggravates the turbulence of ischemic ionic microenvironment.     

干旱预处理对抗旱性不同的2个草地早熟禾品种耐热性能的影响

为探讨干旱预处理诱导草地早熟禾耐热性效应和生理机制及不同品种对干旱预处理的差异响应,对抗旱性不同的2个草地早熟禾品种,“Midnight”(抗)和“Brilliant”(敏感)分别进行充足浇水(对照)和两轮干旱预处理,然后置入35℃/30℃(昼/夜)高温中胁迫25 d。在胁迫的0,5,10,15,20,25 d分别测定草坪外观质量及相应生理反应的动态变化。在胁迫期间,预处理“Brilliant”的草坪质量(TQ)显著(P<0.05)高于未经预处理材料;在胁迫5 d后,经预处理的“Brilliant”渗透势(OP)不断下降,而对照材料基本维持不变,在10和15 d时,预处理Brilliant的相对含水量(RWC)显著(P<0.05)高于对照;在胁迫的10～20 d,经预处理“Brilliant”的超氧化物歧化酶(SOD)和过氧化氢酶(CAT)活性显著(P<0.05)高于未经预处理材料,而电解质渗透率(EL)值则相反;15 d时,经预处理的棕榈酸(16∶0)和硬脂酸(18∶0)含量显著(P<0.05)低于未经预处理材料,而亚麻酸(18∶3)含量正好相反,与之相对应,预处理“Brilliant”的双键系数(DBI)显著(P<0.05)高于对照。“Midnight”两处理的各测定指标变化趋势相近,无明显差异。结果表明,干旱预处理未能进一步提高抗旱性品种“Midnight”的耐热性,而有效提高了干旱敏感品种“Brilliant”的耐热性。“Brilliant”耐热性的获得与干旱预处理诱导其渗透调节能力的提高,激活抗氧化酶(SOD、CAT)活性从而保护膜脂中不饱和脂肪酸(18∶3)免受活性氧伤害而急剧下降密切相关,从而有效阻止叶片失水,稳定膜结构,延缓植株衰老。     

Inhibitory effect of ischemic postconditioning on autophagy induced by focal cerebral ischemia reperfusion in rats

AIM: To investigate the effect of ischemic postconditioning (IPC) on autophagy induced by focal cerebral ischemia reperfusion (I/R) in rats. METHODS: Healthy male SD rats were assigned randomly into sham-operation (sham) group, I/R group and IPC group with 10 rats in each group. The rats in sham group were only exposed the right common, internal and external carotid artery surgically. The rats in I/R group were subjected to right middle cerebral artery occlusion (MCAO) by the modified Longa suture method for 2 h followed by 24 h of reperfusion. The rats in IPC group were subjected to MCAO for 2 h followed by reperfusion of the ipsilateral common carotid artery occlusion for 10 s for 5 episodes, and then reperfusion for 24 h. Autophagy was obeserved by transmission electron microscopy (TEM). The protein levels of mammalian target of rapamycin (mTOR), p-mTOR and microtubule associated protein light chain 3 (LC3)-II in brain tissue of the rats were determined by Western blot. Pathological changes of brain tissue were observed by HE staining. RESULTS: The protein levels of mTOR and p-mTOR in IPC group were significantly higher than those in I/R group (P<0.05). The expression of LC3-II in IPC group was significantly lower than that in I/R group (P<0.01). The cerebral infarction area and brain water content in IPC group were significantly lower than those in I/R group (P<0.01). HE staining showed that neurons degeneration and necrosis in IPC group were significantly alleviated compared with I/R group. TEM observation showed that IPC revealed fewer autophagosomes, with much less severe cell damage than that in I/R group. CONCLUSION: IPC reduces brain ischemia reperfusion damage by decreasing autophagy of brain cells, which might be related to the activation of mTOR.     

低氧预适应对魁蚶在低氧胁迫下生理生化指标的影响

本研究以未进行低氧预适应的魁蚶(Scapharca broughtonii)为对照组(C组),分析了2次低氧预适应(H2组)和4次低氧预适应(H4组)的魁蚶在溶解氧(DO)约为2.0 mg/L低氧胁迫48 h内的摄食、呼吸代谢和酶活力的变化规律。结果显示,3组魁蚶的摄食率(IR)在胁迫初期急剧下降,后期均随时间的延长逐渐恢复,至48 h时,H组恢复程度显著高于C组(P＜0.05＝;C组、H2组和H4组魁蚶的耗氧率(OR)随时间变化呈逐渐升高的趋势,48 h比0 h分别提高了1.15、1.08、0.73倍;3组排氨率(NR)表现出不同的变化趋势,至48 h时,C组、H2组和H4组分别为0 h的1.67、1.30、0.97倍;C组的氧氮比(O/N)相对平稳,H组的变化范围相对较大。3组的细胞色素C氧化酶(COX)随着低氧胁迫时间的延长呈逐渐降低的趋势,乳酸脱氢酶(LDH)活力和还原型谷胱甘肽酶(GSH)含量整体呈上升趋势,与对照组相比,预低氧组的酶活力在低氧胁迫期间变化相对平稳,应激反应小。研究表明,魁蚶经低氧预适应后再次受到低氧胁迫时,IR升高,OR降低,酶活性相对稳定,低氧预适应能提高魁蚶的耐低氧能力。本研究丰富了魁蚶低氧耐受相关研究的基础数据,为进一步探讨魁蚶低氧耐受机制和创制耐低氧新种质提供了参考资料。