促红细胞生成素对大鼠脑缺血再灌注的保护作用及对VEGF及ICAM-1表达的影响

目的观察促红细胞生成素(EPO)对大鼠脑缺血再灌注后梗死面积及血管内皮生长因子(VEGF)及细胞间黏附分子(ICAM)-1表达的影响。方法雄性Wistar大鼠32只,随机分为正常对照组(A组)、假手术组(B组)、缺血再灌注模型组(C组)、EPO干预组(D组)。C组、D组采用线栓法阻断大鼠一侧大脑中动脉制作大鼠局灶性缺血再灌注模型。EPD预处理组于缺血开始前2 h予腹腔注射EPD3 000 U/kg;缺血再灌注模型组和假手术组在手术前2 h予腹腔注射等量生理盐水。再灌注24 h后进行脑组织石蜡包埋切片,行HE染色、Nissl染色以及VEGF和ICAM-1免疫组化染色,光镜观察组织学变化,计算缺血侧大脑皮层VEGF及ICAM-1的表达情况。另选健康成年雄性SD大鼠32只,按上述方法造模及分组,在缺血再灌注24 h后行10%红四氮氯唑(TTC)染色,测脑梗死的面积。结果 C组梗死体积占全脑体积的百分比与D组明显增大(P<0.01),B组未见脑梗死灶。光镜下A、B组仅见少数VEGF、ICAM-1阳性细胞,C、D组VEGF、ICAM-1阳性细胞数均高于A、B组(P<0.01),D组VEGF阳性细胞数高于C组(P<0.01),D组ICAM-1阳性细胞数低于C组。结论 EPD预处理可抑制缺血损伤,减小脑梗死体积,其机制可能是通过上调VEGF表达、下调ICAM-1而实现的。     

纳洛酮对脑局灶性缺血-再灌注大鼠血红素加氧酶-1表达的影响

目的探讨大鼠局灶性脑缺血再灌注后血红素加氧酶1(HO1)蛋白在缺血灶周围区的表达和纳洛酮干预后的影响。方法SD大鼠45只,随机分为三组:即假手术组、缺血再灌注组及纳洛酮组,每组15只。采用线栓法制作大鼠大脑中动脉闭塞(MCAO)局灶性脑缺血再灌注模型,在插入栓线及抽出线栓成功再灌注后,分别给予纳洛酮组大鼠腹腔注射纳洛酮3mg/kg(总量6mg/kg),假手术组及缺血再灌注组腹腔注射等量等渗盐水。以免疫组化法检测HO1的表达,原位末端脱氧核苷酸转移酶标记(TUNEL)法观察脑细胞凋亡细胞数。结果每个高倍视野下,缺血再灌注组HO1阳性细胞数与假手术组相比明显增多,平均为(51.6±10.8)个对(9.8±2.8)个,P<0.05;纳洛酮组与缺血再灌注组比较,缺血灶周围区HO1阳性细胞数平均为(63.5±10.0)个对(51.6±10.8)个,P<0.05。纳洛酮组TUNEL阳性细胞数显著低于缺血再灌注组[(20.5±3.5)个对(29.8±4.0)个],但高于假手术组[平均为(4.2±2.0)个],组间比较,差异有显著性(P<0.05)。结论纳洛酮可减少MCAO局灶性脑缺血再灌注导致的神经细胞凋亡,其机制可能与纳洛酮增加HO1的表达有关。     

康脑液2号对局灶性脑缺血再灌注大鼠的治疗作用及其机制

目的 观察康脑液2号对局灶性脑缺血再灌注(I/R)大鼠的治疗作用.方法 150只雄性SD大鼠随机分为假手术组、模型组,康脑液2号高、中、低剂量组.线栓法制备大鼠右侧大脑中动脉闭塞(MCAO)模型.大鼠缺血2 h,于再灌注24 h后观察神经功能,再灌注1、3、7,14,21 d,HE染色观察病理变化,免疫组织化学法观察各组大鼠血管内皮生长因子(VEGF)、血管生成素-1(Ang-1)表达,再灌注21 d免疫组织化学法标记CD105检测血管密度.结果 与模型组相比,康脑液2号治疗组神经功能及病理改变明显改善.各种促血管生成因子明显多于模型组(P<0.05或P<0.01),脑组织血管显著增多(P<0.05或P<0.01).结论 康脑液2号能治疗脑I/R大鼠,可能促进脑I/R大鼠缺血周围区域血管新生.     

转染人血管内皮生长因子165基因的骨髓间充质干细胞移植改善兔心肌梗死后心功能

目的探讨将骨髓间充质干细胞移植和血管内皮生长因子基因治疗相结合治疗兔心肌梗死的疗效及其机制。方法将48只新西兰大白兔随机分为心肌梗死组、骨髓间充质干细胞移植组、血管内皮生长因子组和骨髓间充质干细胞 血管内皮生长因子组。建立兔心肌梗死模型,在心肌梗死后2周取107个骨髓间充质干细胞移植至梗死区。移植后4周测定心功能,梗死区骨髓间充质干细胞进行鉴定及计数,进行Ⅷ因子免疫组织化学染色。结果血流动力学比较发现,骨髓间充质干细胞 血管内皮生长因子组各项参数明显优于骨髓间充质干细胞组;心肌梗死区BrdU阳性细胞数骨髓间充质干细胞 血管内皮生长因子组明显多于骨髓间充质干细胞组(61.24±8.51个/视野比44.21±7.68个/视野,P<0.01);梗死区血管的数量骨髓间充质干细胞 血管内皮生长因子组(48.75±7.96个/视野)明显多于骨髓间充质干细胞组(33.08±6.12个/视野,P<0.01)、血管内皮生长因子组(29.98±8.04个/视野,P<0.01)和心肌梗死组(18.32±3.88个/视野,P<0.01)。结论转染血管内皮生长因子基因的骨髓间充质干细胞移植可改善兔心肌梗死后的心功能,其疗效明显优于单纯骨髓间充质干细胞移植及血管内皮生长因子基因治疗,可能是通过增加骨髓间充质干细胞的存活及改善梗死区的血供而起作用的。     

阿司匹林预处理对大鼠脑缺血再灌注损伤的保护作用

目的观察阿司匹林(ASA)预处理对大鼠局灶性脑缺血再灌注损伤(CIRI)中凋亡诱导因子(AIF)表达的影响,探讨其通过抗凋亡机制发挥脑保护的作用。方法健康雄性SD大鼠,随机分为假手术组、模型加溶媒组、ASA50mg/kg预处理组。以线栓法制作大鼠大脑中动脉缺血再灌注模型,于缺血2h再灌注24h后进行神经功能评分,并断头取脑分别测定脑梗死体积、凋亡细胞数及AIF的表达。结果脑梗死体积ASA预处理组为(0.20±0.48)%,与模型加溶媒组(0.35±0.34)%相比明显减小(P<0.05),神经功能缺损评分为(1.98±0.34)分获不同程度改善(P<0.05),脑组织AIF的表达及凋亡细胞数减少(P<0.01)。结论ASA对大鼠脑缺血再灌注损伤有一定保护作用,通过抑制脑组织中AIF的表达,进而减少细胞凋亡。     

促血小板生成素对大鼠脑缺血再灌注脑组织的保护作用

目的探讨促血小板生成素对大鼠局灶性脑缺血再灌注损伤后的保护作用及机制。方法采用线栓法阻断大鼠大脑中动脉血流制成局灶性脑缺血再灌注损伤模型。将60只雄性SD大鼠随机分成促血小板生成素(TPO)组、缺血再灌注组、假手术组和正常组。于缺血开始时TPO组给予TPO 5μg/kg腹腔注射;缺血再灌注组给予等剂量生理盐水。分别于再灌注6、12、24、48 h后断头取脑、切片,进行HE染色、Bcl-2免疫组化染色和细胞凋亡检测。结果缺血再灌注后,TPO组和缺血再灌注组大鼠缺血侧皮层可检测到凋亡细胞,且TPO组凋亡细胞数明显少于缺血再灌注组,差异有统计学意义(P0.05),而假手术组及正常组未检测到凋亡细胞;TPO组和缺血再灌注组缺血侧皮层Bcl-2阳性细胞数均高于假手术组及正常组,与缺血再灌注组相比,TPO组Bcl-2蛋白表达显著增高,差异有统计学意义(P0.05)。结论 TPO可抑制缺血再灌注损伤后缺血侧皮层的细胞凋亡,其机制可能是通过上调Bcl-2基因表达而实现。     

局部亚低温对大鼠脑缺血-再灌注后的神经保护作用

目的探讨脑局部亚低温对脑缺血-再灌注大鼠模型的神经保护作用及其机制。方法健康雄性SD大鼠96只,随机将大鼠分为亚低温组和正常温度组,每组48只。每组中12只用于脑梗死体积的测定;36只用于DNA单链损伤的测定。每组再分为假手术组,缺血3h再灌注0.5、2、8、24、72h亚组,每个亚组6只大鼠。采用线栓法制作大鼠脑缺血-再灌注模型。使用冰帽控制基底核区温度在32～34℃,同时使用电热毯维持肛温在36.5～37.5℃。应用2,3,5-氯化三苯基四氮唑(TTC)染色测定脑梗死体积;观察再灌注72h两组大鼠存活率;行DNA多聚酶Ⅰ介导的生物素偶联腺嘌呤脱氧核苷酸的缺口平移标记(PANT)染色,检测DNA单链损伤。结果①生理学指标:亚低温组及正常温度组血糖、血压及血气差异无统计学意义。②72h生存率:亚低温组再灌注72h大鼠的生存率为92%,正常温度组为58%(χ2=6.75,P=0.027)。③梗死体积:亚低温组总的脑梗死体积,脑皮质、基底核区梗死体积分别为(61±28)、(20±17)、(42±14)mm3;正常温度组为(240±55)、(163±41)、(77±17)mm3,两组比较,总的脑梗死体积(P<0.05),皮质、基底核区脑梗死体积,差异均有统计学意义(P<0.01)。④DNA氧化损伤:PANT染色阳性细胞数于再灌注0.5h开始出现,亚低温组和正常体温组分别为(20±7)、(44±4)个/高倍视野(P<0.05);24h达高峰,亚低温组和正常体温组分别为(44±9)、(133±12)个/高倍视野(P<0.01)。亚低温可以减轻所有时间点的PANT染色阳性细胞数。结论局部亚低温可降低大鼠缺血-再灌注脑损伤,其机制可能与减轻缺血后DNA氧化损伤有关。     

异丙肾上腺素预处理对大鼠胰腺移植后缺血再灌注损伤的抑制作用

目的:探讨减轻大鼠胰腺移植后缺血再灌注损伤的保护作用机制.方法:IPC后动态检测大鼠胰腺组织热休克蛋白表达.建立大鼠胰腺移植缺血再灌注模型,选择表达热休克蛋白高峰时段供体大鼠胰腺移植作为实验组,未预处理供体大鼠胰腺移植作为对照组.移植后6 h,采集静脉血及移植胰腺.热休克蛋白70(HSP70)分别用Western blot法及免疫组织化学法检测.免疫组织化学法测定肿瘤坏死因子-α(TNF-α)表达.流式细胞仪检测胰腺细胞凋亡率.碘淀粉比色法检测血淀粉酶水平.结果:IPC后供体大鼠胰腺中HSP70的表达在24 h达到高峰,与其他各时段比较具有显著差异(0.92±0.25 vs 0.24±0.04,0.34±0.06,0.58±0.07,0.62±0.11,0.25±0.09,均P<0.05),IPC后6 h,12 h,24 h,36 h大鼠胰腺中HSP70的表达与未预处理组相应时段比较差异也显著(0.34±0.06 vs 0.28±0.07,0.58±0.07 vs 0.25±0.04.0.92±0.25 vs 0.27±0.05,0.62±0.11vs 0.25±0.06,均P<0.05),48 h恢复到原来水平.而未预处理组各时段间比较差异无统计学意义(P>0.05).HSP70主要表达于胰腺腺泡细胞及血管壁.对照组胰腺组织中TNF-α、细胞凋亡率、中性粒细胞、血淀粉酶的水平明显升高,与假手术组相比差异显著(均P<0.01).实验组降低了胰腺组织中TNF-α、细胞凋亡率、白细胞数、血淀粉酶的水平,与对照组比较差异具有统计学意义(11 929±1220vs46 111±3127,26.7%±4.5%vs 37.4%±4.7%,3 308±531 vs 6668±1506,1057 IU/L±148IU/L vs 1 408 IU/L±195IU/L,均P<0.05).结论:IPC减轻了大鼠胰腺移植后缺血再灌注损伤,IPC保护作用与HSP70的诱导生成有关.     

热休克预处理对大鼠肠缺血-再灌注损伤的保护效应

目的:探讨全身热休克预处理对肠缺血-再灌注(ischemia/reperfusion,IR)损伤的保护作用.方法:将40只SD♂大鼠随机分为4组:正常体温 假手术对照组(CTRL,n=10),正常体温 肠IR组(IR,n=10),41.5℃-42℃热休克 假手术组(42C,n=10),41.5℃-42℃热休克 肠IR组(42IR,n=10).Western blot检测肠黏膜HSP72蛋白表达,原位末端缺口标记法(TUNEL)检测肠黏膜上皮细胞凋亡,比色法检测肠黏膜caspase-3活性,Annexin-V/PI法流式细胞仪检测外周血白细胞凋亡比例.结果:42C、42IR组HSP72蛋白表达水平比CTRL、IR组显著增高(1.59±0.32、2.71±0.64 vs 0.41±0.1、0_30±0.04.P<0.01).42IR组caspase-3活性.白细胞凋亡比例比IR组相比有显著性差异(1.16±0.31 vs 2.32±0.54;39.65%vs 16.94%;P<0.01),且42IR组肠黏膜上皮细胞凋亡指数比IR组明显减少.42IR组与42C、CTRL组之间,caspase-3活性,肠黏膜上皮细胞凋亡指数,白细胞凋亡比例均无明显差异.结论:全身热休克预处理对肠缺血-再灌注损伤有保护作用,其机制可能与增加热休克诱导HSP72的表达和抑制外周血白细胞激活有关.     

疏血通对局灶性脑缺血大鼠神经保护和p53表达的影响

目的 探讨疏血通对大鼠脑缺血再灌注后可能的神经保护作用机制.方法 制备脑缺血再灌注模型,用疏血通进行干预,观察脑组织细胞的形态学改变,p53蛋白表达,细胞原位凋亡情况,脑梗死体积的变化.结果 大鼠脑缺血2 h再灌注24 h,治疗组的脑梗死体积较缺血组明显缩小(P<0.01).治疗组大鼠的神经功能缺损评分,在6 h时间点与缺血组比较无统计学意义,其余时间点均明显低于缺血组(P<0.05或P<0.01).缺血组和治疗组缺血再灌注6 h均可见凋亡细胞,表达高峰分别为48 h、72 h,治疗组的表达高峰时间延迟,且数量明显减少(P<0.05).p53蛋白在缺血再灌注后6 h出现表达,缺血组的表达高峰为48 h,治疗组的表达高峰为72 h,治疗组各时间点p53阳性细胞教较缺血组明显减少(P<0.05或P<0.01).结论 疏血通可减轻大鼠脑缺血再灌注损伤,缩小梗死体积,抑制p53蛋白的表达,改善神经功能.     

实验性高血压大鼠局灶性脑缺血再灌注后肾上腺髓质素及其mRNA的表达

目的探讨肾上腺髓质素与脑缺血再灌注损伤及高血压的关系。方法应用改良Kellen的方法制备实验性高血压大鼠,采用栓线法制成大鼠大脑中动脉闭塞模型,阻断血流2 h后进行再灌注。免疫组织化学法检测高血压大鼠与非高血压大鼠局灶性脑缺血再灌注后肾上腺髓质素阳性细胞百分率并进行比较,逆转录聚合酶链反应检测大鼠局灶性脑缺血再灌注后脑组织肾上腺髓质素mRNA表达的情况。结果正常大鼠脑内有肾上腺髓质素mRNA表达,假手术后肾上腺髓质素mRNA表达略有增加,但与正常对照组相比差异无显著性(P>0.05);大鼠脑缺血再灌注后肾上腺髓质素mRNA过表达,与正常对照组及假手术组相比差异有显著性(均P<0.05);大鼠脑缺血再灌注后,缺血侧及缺血对侧肾上腺髓质素mRNA均有高表达,但以缺血侧最显著(P<0.05)。正常对照组和假手术组大鼠大脑组织中均有肾上腺髓质素阳性细胞表达,肾上腺髓质素阳性细胞百分率分别为2.87%±0.78%和2.47%±0.59%(P>0.05)。缺血再灌注非高血压组肾上腺髓质素阳性细胞高表达,以缺血侧为明显,阳性细胞百分率为59.42%±3.71%,缺血对侧亦明显,阳性细胞百分率为36.87%±5.28%,两者相比差异有显著性(P<0.05),与假手术组及正常对照组相比差异也有显著性(P<0.05)。比较高血压组与非高血压组肾上腺髓质素阳性细胞百分率发现,高血压组肾上腺髓质素阳性细胞百分率(缺血侧为78.60%±4.82%,缺血对侧为57.52%±5.22%)明显高于非高血压组(P<0.05)。结论脑缺血再灌注后肾上腺髓质素及其mRNA高表达。高血压组肾上腺髓质素的高表达更显著。肾上腺髓质素与脑缺血再灌注损伤相关,与高血压血管内皮损伤有关。     

海风藤提取物对脑缺血再灌注模型大鼠神经细胞凋亡和线粒体膜电位变化的干预作用

目的观察脑缺血再灌注2h后大鼠神经细胞凋亡和线粒体膜电位的变化及海风藤提取物的干预作用。方法应用线栓法建立大鼠大脑中动脉阻塞再灌注模型,流式细胞术分别观察假手术组、模型组、二甲基亚砜组和海风藤组缺血灶周神经细胞凋亡和线粒体膜电位的变化。结果与模型组神经细胞凋亡率(72.7%±6.5%)和线粒体膜电位(0.117±0.011)比较,海风藤组神经细胞凋亡率(47.0%±3.8%)明显下降(P<0.01),线粒体膜电位(0.182±0.023)明显升高(P<0.01);而假手术组神经细胞凋亡率(5.8%±1.8%)和线粒体膜电位(0.331±0.016)与模型组比较差异均有显著性(P<0.01)。结论海风藤可以减轻脑缺血再灌注后早期神经细胞凋亡,并对线粒体膜电位有稳定作用,可以保护缺血脑组织。     

Reduction in myocardial apoptosis associated with overexpression of heat shock protein 70

It is reported that ischemia-reperfusion induces apoptotic cell death in myocardium. It is also demonstrated that heat shock protein 70 (HSP70) enhances myocardial tolerance. Therefore, it is hypothesized that HSP70 may play a role in the attenuation of myocardial apoptosis. To elucidate this goal, HSP70-overexpressing and control-transfected rat hearts were prepared using gene transfection by intra-coronary infusion of the hemagglutinating virus of Japan-liposome. In vivo experiment Hearts fo both groups were subjected to global ischemia, followed by reperfusion in situ. Shorter recovery time to spontaneous beating (HSP70-transfected vs control-transfected; 46.7±4.6 vs 67.5±7.0 s, p = 0.033) and lower serum CPK levels (415±27 vs 533±36 IU, p = 0.027) were observed in the HSP70-transfected group. The HSP70-transfected group also showed a lower percentage of cardiac myocytes positively stained by nick end labeling after ischemia-reperfusion (17.5±4.9 vs 40.0±5.1%, p = 0.010). In vitro experiment Cardiac myocytes isolated from the hearts of both groups (prepared separately from the in vivo eperiment) were subjected to hypoxia-reoxygenation. Flow cytometry was used to identify the cells that showed sub-G₁ DNA content as apoptotic cells. Apoptotic cels as a percentage of viable cells increased more in the control-transfected group after hypoxia-reoxygenation (13.0±0.77 vs 21.9±1.18%, p < 0.0001). In conclusion, we demonstrated that apoptosis after ischemia-reperfusion was decreased in the HSP70-overexpressing heart in vivo and in vitro, leading to the suggestions that HSP70 could be associated with the reduction in myocardial apoptosis. Received: 24 January 2000 Returned for revision: 23 February 2000 Revision received: 18 May 2000 Accepted: 22 May 2000     

Liver ischemia/reperfusion induces an increase of microvascular leukocyte flux,but not heterogeneity of leukocyte trafficking

Abstract: Leukocytic response plays a major role in the manifestation of hepatic ischemia/reperfusion (I/R) injury. To clarify whether post-ischemic hepatic leukocyte accumulation is based on increased leukocyte flux to the hepatic tissue due to systemic inflammation or chemoattractant activities or whether it represents solely a local tissue response without changing overall leukocyte flux and trafficking characteristics through the microvasculature, we studied acinar and sinusoidal leukocyte flux and distribution in rat livers in vivo both under normal (sham, n=8) and post-ischemic (60′ ischemia/75′ reperfusion) conditions (I/R, n=8), using fluorescence epi-illumination microscopy (rhodamine-6G). Hepatic ischemia/reperfusion significantly (p<0.05) increased acinar leukocyte flux (58.4±20.9 cells/min vs 36.4±12.8 cells/min in sham controls); however, it did not exhibit increased heterogeneity of acinar leukocyte distribution, as indicated by the unchanged coefficient of variance (CV) of 0.36±0.16 (sham controls: 0.31 ±0.14). In parallel, analysis of individual sinusoidal leukocyte flux demonstrated significantly (p<0.05) higher values (8.9±3.7 cells/min) after ischemia/reperfusion when compared with sham controls (5.7±1.9 cells/min), which, however, was not associated with increased heterogeneity of sinusoidal leukocyte trafficking (CV: 0.85±0.15 vs 0.85±0.16 in sham controls) and manifestation of preferential pathways. Analysis of blood cell count did not demonstrate an overall increase of total blood leukoycte count; however, an increased (p<0.01) fraction of polymorphonuclear leukocytes (65.2±11.2%) and stab cells (9.5±7.9%) during post-ischemic reperfusion when compared with sham controls (8.8±3.5% and 0.2±0.4%) was demonstrated. Thus, the increase of hepatic leukocyte flux after ischemia/reperfusion may be the result of both the manifestation of a systemic inflammatory response and the increase of local chemoattractant activities, such as the production and release of the cytokine-induced neutrophil chemoattractant of the IL-8 family.     

肢体缺血预处理诱导大鼠缺血再灌注海马HSP70表达

目的探讨肢体缺血预处理(limb ischemic preconditioning,LIP)对大鼠缺血再灌注海马HSP70表达的影响。方法将66只凝闭椎动脉大鼠随机分为假手术组、脑缺血组和LIP+脑缺血组,后两组根据脑缺血后再灌流时间不同进一步分为1、62、4、72和120 h组。采用免疫组织化学方法检测海马HSP 70的变化。结果假手术组海马各区未见明显的HSP70表达。脑缺血组海马CA1区未见明显着色,但在CA3区及齿状回颗粒细胞中可见HSP70着色,以再灌注后24 h最明显。在LIP+脑缺血组,海马CA1区于再灌注1 h未见明显的HSP70表达;再灌注6 h HSP70表达明显增强,与假手术组和脑缺血6 h组比较,阳性细胞数明显增加(P<0.01);再灌注24 h HSP70表达达高峰;再灌注72 h HSP70表达有所下降;至再灌注120 h HSP70表达明显下降。结论损伤性脑缺血前给予LIP,可明显增加CA1区HSP70的阳性表达,诱导CA1区锥体细胞耐受缺血损伤。     

艾芬地尔对大鼠脑缺血再灌注后Survivin表达的影响

目的探讨大脑中动脉缺血再灌注后缺血侧海马区Survivin的表达规律及艾芬地尔对大鼠脑缺血再灌注后不同时相Survivin表达的影响。方法 72只Wistar大鼠随机分为假手术组、模型组和艾芬地尔干预组,采用线拴法制作局灶性大鼠脑缺血再灌注模型,假手术组于术后,模型组和艾芬地尔干预组于脑缺血2 h分别再灌注3 h、24 h、72 h及7天后处死取材,免疫荧光法测量不同时相缺血侧海马神经元Survivin的表达。结果假手术组Survivin呈现少基础量表达,模型组和艾芬地尔干预组Survivin表达规律基本一致,即在再灌注3 h时表达即有升高,至72 h达到高峰,7天表达有所下降,与假手术组比较差异显著(P0.05);艾芬地尔干预组荧光强度值明显高于对应模型组(P0.05)。结论大脑中动脉缺血再灌注后Survivin的表达升高,72 h达高峰;艾芬地尔对大脑中动脉缺血再灌注损伤具有保护作用。     

Chronic Erythropoietin Treatment Limits Infarct-size in the Myocardium in Vitro

Summary It has been well established that erythropoietin (EPO) can limit myocardial ischemia/reperfusion injury in a variety of acute settings. However, despite EPO being used chronically to treat anemia the infarct limiting effects of long term treatment (chronic) have never been fully investigated. In this study we examined the effects of a 3 week treatment of EPO (5,000 IU/Kg) in male Sprague Dawley rats in limiting myocardial infarction after 35 min ischemia and 2 h reperfusion in an in vitro isolated heart perfusion model. Treating the animals ‘once a week’ failed to limit infarct size significantly compared to a saline control (54.1% ± 3.5 v 52.3% ± 4.4), whereas a ‘3 times a week’ regime succeeded in significantly reducing infarct size (36.2% ± 3.2 v 52.3% ± 4.4, p < 0.05). To demonstrate that the effect was not due to improved oxygen supply caused by a raised hematocrit level, we also administered EPO 24 h prior to ischemia/reperfusion. This treatment again reduced infarct size compared to a saline control (39.9% ± 4.4 v 58.4% ± 5.0, p < 0.05). To examine the mechanism of protection we used the PI3K inhibitor wortmannin and the nitric oxide synthase inhibitor L-NAME to try to abrogate EPO mediated protection. Where wortmannin failed to block the effects of EPO (31.7% ± 6.0 v 36.2% ± 3.2), L-NAME did abrogate protection (51.6% ± 5.6 v 36.2% ± 3.2, p < 0.05). We demonstrate that chronic EPO treatment limits infarct size and that it does so in a nitric oxide dependent manner.     

丹星通络汤对脑缺血再灌注大鼠神经生长因子表达的影响

目的 观察丹星通络汤( DXTLD)治疗脑缺血再灌注大鼠后脑组织神经生长因子(NGF)的变化,探讨其对脑缺血再灌注损伤的保护机制. 方法 SD大鼠40只随机分为5组(n=8):假手术组、缺血再灌注组(模型组)、尼莫地平组、DXTLD预处理小剂量组、DXTLD预处理大剂量组.线栓法建立大鼠大脑中动脉缺血再灌注模型.应用免疫组织化学染色、灰度分析等方法检测缺血2h再灌注24 h后脑组织海马区NGF的表达. 结果 各治疗组缺血侧海马区的NGF表达显著增加,与模型组比较差异有统计学意义(P＜0.05或P＜0.01).结论 DXTLD通过上调脑缺血再灌注损伤后脑组织内NGF的表达,起到保护脑的作用.     

Effects of repeated brief episodes of ischemia and reperfusion in isolated perfused rat hearts

Summary The effects of ischemia and reperfusion on the coronary endothelium and myocardium as well as tolerance to ischemia/reperfusion injury were assessed using isolated retrogradely perfused rat hearts. Repeated brief episodes of myocardial ischemia followed by reperfusion is known to have a protective effect against subsequent myocardial infarction. However, no studies have been performed with perfusion in the absence of blood cells to determine the effect of repeated ischemia and reperfusion on the coronary endothelium and myocardium. Using the Langendorff perfusion technique, rat hearts were subjected to a 30-, 10-, 5-, or 2-min period of low-flow perfusion by reducing the coronary flow to 3ml/min followed by reperfusion at 20ml/min for the same period of time. Control perfusion was then performed at a constant flow rate of 20 ml/min for 60min. Acetylcholine-induced coronary vasodilation was significantly (P < 0.05) lower in hearts subjected to 30min of ischemia and 30min of reperfusion when compared with the control hearts. Myocardial creatinine kinase (CK) activity was significantly reduced (P < 0.01) in hearts subjected to ischemia and reperfusion for either 30, 10, or 5min. To assess the effect of repeated episodes of ischemia and reperfusion, the following protocols were used: a control study with constant perfusion for 60min (group A), 30min of ischemia and 30min of reperfusion (group B), three 10min episodes of ischemia and reperfusion (group C), six 5-min episodes of ischemia and reperfusion (group D), and 15 2-min episodes of ischemia and reperfusion (group E). Acetylcholine-induced coronary vasodilation was significantly inhibited in group B (80% ± 12%,P < 0.05) and group C (70% ± 13%,P < 0.01), but did not change significantly in either group D (123% ± 19%) or group E (142% ± 15%), compared with the control group (group A; 127% ± 15%, mean ± SEM). Nitroglycerin-induced coronary vasodilation was not altered by ischemia/reperfusion in any group. In contrast, myocardial CK activity was significantly lower in group B (3.6 ± 0.6IU/mg protein,P < 0.01), group C (3.2 ± 0.1IU/mg protein,P < 0.01), and group D (3.3 ± 0.2IU/mg protein,P < 0.01) than in group A (47 ± 6.7 IU/mg protein). The myocardial CK activity of group E was not significantly different from that of group A, but was significantly higher than in groups B, C, and D (P < 0.01). In isolated perfused rat hearts, both the coronary endothelium and myocardium are damaged by repeated episodes of ischemia and reperfusion. However, the coronary endothelium is more resistant to such damage than is the myocardium.     

Impairment of cardioprotective PI3K-Akt signaling by post-infarct ventricular remodeling is compensated by an ERK-mediated pathway

Recently we found that post-infarct remodeling disrupts PI3KAkt signaling triggered by erythropoietin (EPO) but an unknown compensatory mechanism preserves EPO-induced protection against infarction in those hearts. In this study, we examined the possibility that ERK-mediated signaling is the compensatory mechanism affording protection in post-infarct remodeled hearts. Four weeks after coronary ligation in situ (post-MI group, post-MI) or a sham operation (sham group, Sham), hearts were isolated, perfused and subjected to 25-min global ischemia/2-h reperfusion. Infarct size was expressed as a percentage of risk area size (%I/R), from which scarred infarct by coronary ligation was excluded. EPO infusion (5 U/ml) before ischemia reduced %I/R similarly in Sham and post-MI (from 62.0 ± 5.1 to 39.4 ± 4.8 in Sham and from 58.6 ± 6.6 to 36.3 ± 3.8 in post-MI). PD98059, a MEK1/2 inhibitor, abolished this EPO-induced protection in post-MI (%I/R = 60.7 ± 4.9) but not in Sham (%I/R = 35.1 ± 5.4). EPO induced PI3Kdependent phosphorylation of Akt in Sham but not in post-MI. EPO increased phosphorylation levels of ERK1/2 both in Sham and post-MI, but this phosphorylation was diminished by a PI3K inhibitor in Sham but not in post-MI. These results suggest that PI3K-independent activation of ERK compensates the lack of signal input from the PI3K-Akt pathway to achieve EPO-induced protection in the remodeled myocardium.