Notch信号途径对缺氧/复氧乳鼠心肌细胞的保护作用

目的:观察缺氧/复氧(H/R)后Notch信号途径相关分子的变化及阻断Notch信号途径对在H/R条件下乳鼠心肌细胞凋亡的影响。方法:将乳鼠心肌细胞分为常氧组和H/R组,每组再分为3组,即对照组、二甲基亚砜(DMSO)组及抑制Notch信号途径的γ分泌酶抑制剂(GSI)组。分别用实时PCR和Western blot检测Notch信号途径相关分子mRNA及其蛋白表达的水平。用原位缺口末端标记法(TUNEL)染色观察心肌细胞凋亡。用荧光探针DCFH-DA检测心肌细胞内活性氧簇(ROS)水平的变化。结果:H/R后,Notch信号途径相关分子的mRNA及其蛋白的水平、ROS水平及心肌细胞的凋亡与DMSO组相比均显著增加(P0.01)。加入GSI后,对Notch信号途径上游的配基及受体的水平没有显著的影响,但对其下游的转录因子Hes1却可以显著抑制其表达,此时ROS的水平和心肌细胞凋亡进一步增加。结论:Notch信号途径在H/R后反应性上调可能对心肌细胞具有保护作用,该作用可能与抑制ROS的水平有关。     

缺氧后处理对缺氧复氧心肌线粒体活性氧及细胞凋亡的影响

目的 观察缺氧后处理对缺氧复氧心肌线粒体活性氧及细胞膜和线粒体Bcl-2和Bax蛋白表达的影响,探讨其调控心肌细胞凋亡的机制.方法 构建大鼠乳鼠心肌细胞缺氧复氧损伤模型,将细胞分为对照组、缺氧/复氧纽(缺氧3h后复氧6h)、缺氧后处理组(缺氧3h后行复氧5min、缺氧5 min,反复3次,再复氧6 h).应用荧光酶标仪测定线粒体活性氧量,流式细胞仪检测心肌细胞凋亡,Western blot检测细胞膜和线粒体Bcl-2和Bax蛋白的表达.结果 缺氧/复氧组和缺氧后处理组心肌细胞线粒体活性氧量较对照组显著升高(P＜0.01).缺氧后处理组心肌细胞线粒体平均荧光强度为30.74±1.88a.u./μg,显著低于缺氧/复氧组(63.17±2.75a.u./μg,P＜0.01),仍高于对照组(14.41±2.15a.u./μg).缺氧/复氧组和缺氧后处理组心肌细胞凋亡率较对照组显著升高(45.86％±3.29％和26.99％±3.35％比5.72％±1.63％,P＜0.01),缺氧后处理组低于缺氧/复氧组(P＜0.01).细胞膜和线粒体Bcl-2蛋白在缺氧后处理组显著上调,在缺氧/复氧组显著下调;Bax蛋白在缺氧后处理组显著下调,在缺氧/复氧组显著上调.结论 缺氧后处理抑制线粒体活性氧爆发,减轻缺氧/复氧诱导的心肌细胞凋亡,其抗凋亡机制可能与线粒体和细胞膜Bcl-2蛋白表达上调及Bax蛋白表达下调有关.     

缺氧与缺氧/复氧诱导心肌细胞凋亡的比较及意义

目的 :研究单纯缺氧与缺氧复氧对体外培养的新生大鼠心肌细胞凋亡的影响 ,探讨凋亡在心肌细胞缺氧 /复氧损伤中的作用。方法 :取体外培养的新生大鼠心肌细胞 ,分两组 ,均置于 95 0 ml/ L N2 ,5 0 ml/ L CO2 孵箱中培养16 ,32 ,4 8h,其中一组缺氧后再恢复正常条件培养 6 h,分别造成缺氧和缺氧 /复氧损伤的细胞模型 ,TUNEL 染色观察凋亡细胞形态学变化 ,流式细胞仪检测心肌细胞凋亡率。结果 :心肌细胞经历缺氧和缺氧 /复氧损伤后 ,TU NEL 染色可见凋亡阳性细胞 ;应用流式细胞仪定量检测 ,心肌细胞缺氧培养 16 ,32 ,4 8h后 ,其凋亡率分别为 :（2 .9± 0 .5 ） % ,（6 .2± 0 .8） %和 （2 6 .6± 3.0 ） % ;心肌细胞在缺氧 16 ,32和 4 8h后复氧 6 h,其凋亡率分别为 :（5 .5± 0 .7） % ,（11.0± 1.1） %和 （14 .2± 1.6 ） %。结论 :心肌细胞凋亡率随着缺氧时间的延长而增高 ;缺氧 /复氧较单纯缺氧可进一步加重心肌细胞的损伤     

内皮素-1对缺氧/复氧所致心肌细胞凋亡的影响

目的探讨在缺氧/复氧过程中不同时期给予内皮素-1（ET-1）对缺氧/复氧所致心肌损伤与凋亡的影响。方法乳鼠心肌细胞缺氧/复氧模型,流式细胞仪检测心肌细胞凋亡,Hoechst 33258染色计算凋亡率,试剂盒检测乳酸脱氢酶（LDH）的活性。结果ET-1预处理组（EP）细胞生存率较缺氧复氧组（HR）提高,凋亡率下降,LDH活性下降;ET-1缺氧即刻处理组（EH）细胞生存率较HR组降低,凋亡率升高,LDH释放量增加;ET-1复氧处理组（ER）的细胞生存率、凋亡率及LDH活性与HR组均无统计学差异。结论ET-1预处理有心肌细胞保护作用,ET-1缺氧时有促进心肌细胞损伤和凋亡的作用。     

石蒜碱上调Notch1信号通路并减轻心肌细胞缺氧/复氧诱导的损伤

目的 研究石蒜碱对H9c2心肌细胞缺氧/复氧（H/R）损伤的保护作用及机制。方法 将H9c2心肌细胞随机分为4组：对照组、H/R组、H/R+石蒜碱低剂量组、H/R+石蒜碱高剂量组;使用CCK-8分析H9c2心肌细胞活力;用试剂盒测定乳酸脱氢酶（LDH）释放量,丙二醛（MDA）和活性氧簇（ROS）的含量,超氧化物歧化酶（SOD）和谷胱甘肽过氧化物酶（GSH-Px）活性;用流式细胞仪检测细胞凋亡率;Western blot检测Notch1蛋白水平;用Realtime聚合酶链反应检测HES-1、HES-5和Hey-1 mRNA水平。结果 与对照组比较,H/R组H9c2心肌细胞的活力减弱（P<0.05）,SOD和GSH-Px的活性减弱（P<0.05）,细胞凋亡率,LDH释放量,MDA和ROS含量,Notch1蛋白水平,HES-1、HES-5和Hey-1 mRNA水平均增加（P<0.05）;与H/R组相比,石蒜碱低、高剂量组H9c2心肌细胞的活力增强（P<0.05）,SOD和GSH-Px的活性增强（P<0.05）,细胞凋亡率,LDH释放量,MDA和ROS含量均降低（...     

胡椒碱对缺氧复氧心肌细胞的保护作用及机制研究

目的探讨胡椒碱(piperine,PIP)对缺氧复氧(hypoxia/reoxygenation,H/R)心肌细胞的保护作用及对磷脂酰肌醇3-激酶(phosphoinositide 3-kinase,PI3K)/蛋白激酶B(protein kinase B,AKT)通路影响。方法分离培养原代心肌细胞,随机分为3组(n=3):对照组、H/R组、H/R+PIP处理组。4 h缺氧联合6 h复氧构建H/R损伤模型,在机制探讨中给予PI3K/AKT抑制剂(LY294002)干预。以心肌细胞存活率与心肌损伤酶浓度评估细胞损伤程度;促炎症标志物(IL-6/TNF-α)检测评估炎症反应;超氧化物歧化酶(SOD)/丙二醛(MDA)浓度检测氧化应激反应;流式细胞术评估细胞凋亡;Western blotting检测相关蛋白表达。结果 (1)与H/R组相比,H/R+PIP处理组心肌细胞活性增加而乳酸脱氢酶和肌酸激酶同工酶浓度降低,差异有统计学意义(均P0.05)。(2)与H/R组相比,H/R+PIP处理组能够显著抑制H/R诱导的心肌细胞凋亡、炎症与活性氧反应,表现为凋亡率、促炎症介质、丙二醛浓度降低而超氧化物歧化酶酶活性升高,差异有统计学意义(均P0.05)。(3)在机制探讨中我们观察到,PIP能够上调PI3K/AKT磷酸化水平,而抑制PI3K/AKT通路后PIP的心肌细胞保护功能被逆转(均P0.05)。结论 PIP主要通过PI3K/AKT依赖性途径改善心肌细胞H/R损伤。     

辛伐他汀对缺氧/复氧诱导的心肌细胞凋亡的拮抗作用及其作用机制

目的: 探讨辛伐他汀对缺氧/复氧诱导的心肌细胞损伤的拮抗作用及潜在机制。方法: 分离培养 Sprague-Dawley(SD)大鼠(乳鼠)心肌细胞,随机分为对照组、缺氧2h/复氧4h(H/R4h)组、不同浓度(0.1、1.0及10 μmol/L)的辛伐他汀干预组及Toll样受体4(TLR4)中和性抗体MTS510组(浓度为10 μg/L)。H/R4h组给予缺氧2 h后，随即复氧4 h。细胞处理后，进行PI-AnnexinV染色用流式细胞仪检测心肌细胞的凋亡率，用ELISA法检测心肌乳酸脱氢酶(LDH)的活性；用免疫印迹法测TLR4蛋白的含量。结果:与H/R4h组相比,辛伐他汀干预组可显著降低心肌细胞的凋亡率(16.0% vs. 28.6%,P<0.01)及LDH 的活性(P<0.01)，并呈剂量依赖性。中浓度的辛伐他汀组开始出现拮抗作用，峰值出现在高浓度辛伐他汀组, 加入MTS510阻断剂可降低心肌细胞的凋亡率及LDH的活性(P<0.01)。结论:辛伐他汀对H/R造成的心肌细胞损伤具有拮抗作用,并呈剂量依赖性,其作用机制可能与TLR4信号通路有关。     

西洛他唑对乳鼠心肌细胞缺氧/复氧损伤的保护作用

目的:研究西洛他唑(Cilostazol,CIL)对乳鼠心肌细胞缺氧/复氧(hypoxia/reoxygenation,H/R)损伤的影响及机制。方法:①分离培养SD乳鼠心肌细胞,建立H/R模型。心肌细胞随机分4组:对照组;H/R组,缺氧2 h,复氧4 h;H/R CIL组,缺氧前1 h予以CIL(10μmol.L-1)随即缺氧2 h,复氧4 h;H/R CIL Wort mannin(H/R CIL W)组,CIL处理前30 min予磷脂酰肌醇-3激酶(phosphatidylinositol-3 kinase PI3K)特异性抑制剂——渥曼青霉素(Wort mannin 0.1μmol.L-1);②检测各组培养液中乳酸脱氢酶、肌酸激酶同工酶含量,流式细胞术检测心肌细胞凋亡率,Western blot检测丝氨酸/苏氨酸蛋白激酶(Akt)及磷酸化丝氨酸/Akt(p-Akt)的表达。结果:CIL明显抑制H/R损伤导致的心肌细胞凋亡,并使p-Akt/Akt比值明显增加;Wort mannin可使p-Akt/Akt比值明显减少,抑制CIL的抗凋亡作用。结论:H/R损伤可导致心肌细胞凋亡,CIL可能通过PI3K-Akt途径发挥抗凋亡作用。     

莱菔硫烷对H9C2心肌细胞缺氧/复氧损伤的保护作用

目的:探讨莱菔硫烷(sulforaphane,SFN)对H9C2心肌细胞缺氧/复氧损伤的保护作用。方法:H9C2心肌细胞随机分为3组:正常对照组、缺氧/复氧组(H/R组)和SFN预处理组(10μmol/L SFN预处理细胞12 h后,进行缺氧/复氧处理)。采用倒置显微镜观察各组细胞形态及凋亡程度,CCK8法检测各组H9C2心肌细胞存活率,Western blot法检测血红素氧化酶1(HO-1)、醌氧化还原酶1(NQO1)、Bcl-2和Bax蛋白的表达水平。结果:与正常对照组相比,H/R组和SFN预处理组心肌细胞存活率均降低(P均0.01),HO-1、NQO1、Bcl-2和Bax蛋白表达水平及Bcl-2/Bax均升高(P均0.01)。与H/R组相比,SFN预处理组的细胞生长状态较好,细胞存活率明显提高[(76.00±0.52)%对(55.73±0.43)%,P0.01],HO-1(3.24±0.01对1.86±0.01,P0.01)、NQO1(1.67±0.01对0.95±0.01,P0.01)和Bcl-2(0.70±0.00对0.48±0.01,P0.01)蛋白表达水平及Bcl-2/Bax(1.22±0.01对0.56±0.00,P0.01)均明显升高,Bax蛋白表达水平明显降低(0.57±0.00对0.85±0.01,P0.01)。结论:SFN对H9C2心肌细胞缺氧/复氧损伤有保护作用,可能与促进HO-1、NQO1、Bcl-2蛋白表达,抑制Bax蛋白表达有关。     

福辛普利拉预处理对心肌细胞缺氧/复氧损伤的预防作用

目的:探讨福辛普利拉对培养乳鼠心肌细胞缺氧/复氧(A/R)损伤的预防作用。方法:取SD新生大鼠(1~3 d),培养成心肌细胞,在培养的第4天随机分为5组:①正常对照组,②A/R组,③0.2 mmol/L福辛普利拉预处理组(F1组),④0.6 mmol/L福辛普利拉预处理组(F2组),⑤1.8 mmol/L福辛普利拉预处理组(F3组)。分别观察各组心肌细胞搏动频率、细胞存活率、培养液中乳酸脱氢酶(LDH)活性、心肌细胞肌浆网钙泵(SERCA)mRNA的表达水平和心肌细胞内游离[Ca2 ]浓度。结果:①细胞搏动频率:A/R组比正常对照组明显减低(P<0.01);福辛普利拉各剂量组比A/R组显著加快(P<0.01),比正常对照组稍慢(P>0.05)。②细胞存活率:A/R组比正常对照组明显降低(P<0.01);福辛普利拉各剂量组比A/R组明显增高(P<0.01),而与正常对照组相比差异无统计学意义(P>0.05)。③LDH活性:A/R组比正常对照组明显升高(P<0.01);福辛普利拉各剂量组比A/R组明显降低(P<0.01),与正常对照组相比虽有升高但差异无统计学意义(P>0.05)。④SER-CA mRNA的表达水平:A/R组比正常对照组mRNA表达下调,为正常对照组的(0.78±0.30)倍(P<0.01);福辛普利拉各剂量组比A/R组显著上调(P<0.01)。⑤心肌细胞内游离[Ca2 ]浓度:A/R组比正常对照组明显升高(P<0.01);福辛普利拉各剂量组比A/R组明显降低(P<0.01),而与正常对照组相比差异无统计学意义(P>0.05)。结论:福辛普利拉预处理后对A/R心肌细胞损伤具有预防作用,其机制可能与SERCA表达上调、减轻细胞内Ca2 超载有关。     

Protective effect of glucagon-like peptide-1analogue on cardiomyocytes injury induced by hypoxia/reoxygenation

<正>Objective To investigate the effect of glucagon-like peptide-1(GLP-1)receptor agonist liraglutide on hypoxia/reoxygenation(H/R)-induced cardiomyocytes death under high glucose condition and the potential mechanisms.Methods H9C2 cardiomyocytes were divided into4 groups:normal glucose(N,5 mmol/L),high glucose(G,20 mmol/L),high glucose in combination with lira-     

激活Notch1通路减轻高温高湿条件下H9C2心肌细胞缺氧/复氧损伤

目的明确Notch1通路在高温高湿条件下H9C2心肌细胞缺氧/复氧(Hypoxia/Reoxygenation,H/R)损伤中的作用及其潜在机制。方法常规培养H9C2心肌细胞并将其分6组即对照组;H/R组;高温高湿组;高温高湿+H/R组;高温高湿+Jagged1(Notch1激动剂)+H/R组;高温高湿+溶剂+H/R组。TUNEL法检测细胞凋亡,荧光探针JC-1检测线粒体膜电位,ATP检测试剂盒检测ATP含量,Western blot检测Notch1细胞内段(Notch1 intracellular domain,Notch1 ICD)、Hairy和分裂增强子(Hairy and enhancer of split,Hes1)、微管相关蛋白1轻链3(microtubuleassociated protein1 light chain 3,LC3)和p62的蛋白表达水平。结果与对照组相比,急性损伤H/R后,细胞凋亡增加(P0.05),线粒体膜电位降低(P0.05),ATP含量减少(P0.05),Notch1 ICD、Hes1、LC3-II/I(p62相应降低)表达升高(P0.05),而慢性损伤高温高湿后,细胞凋亡增加(P0.05),线粒体膜电位降低(P0.05),ATP含量减少(P0.05),Notch1 ICD、Hes1、LC3-II/I表达降低(p62相应升高)(P0.05);和H/R组或高温高湿组对比,高温高湿+H/R组中细胞凋亡进一步增加(P0.05),线粒体膜电位和ATP含量进一步降低(P0.05),Notch1ICD、Hes1、LC3-II/I表达进一步降低(p62进一步升高)(P0.05);和高温高湿+H/R组对比,加入Notch1激动剂Jagged1后,细胞凋亡减少(P0.05),线粒体膜电位和ATP含量增高(P0.05),Notch1 ICD、Hes1、LC3-II/I表达升高(p62相应降低)(P0.05)。结论激活Notch1通路通过促进自噬从而缓解高温高湿条件下H9C2心肌细胞缺氧/复氧损伤。     

神经调节蛋白1通过ERK1-2通路减轻心肌细胞缺氧复氧损伤

目的探究神经调节蛋白1(NRG-1)通过细胞外调节蛋白激酶1/2(ERK1/2)通路减轻心肌细胞缺氧复氧(H/R)损伤的作用。方法培养心肌H9c2细胞株,随机分为常规条件下用不含药物DMEM处理的对照组、H/R条件下用不含药物DMEM处理的H/R组、H/R条件下用含NRG-1 DMEM处理的NRG-1组、H/R条件下用含NRG-1及ERK1/2抑制剂PD98059处理的NRG-1+PD组。检测细胞增殖活力、凋亡率及细胞中的凋亡基因、炎症指标、ERK1/2。结果 H/R组细胞的OD_(490)水平明显低于对照组,细胞凋亡率、细胞中cleaved Caspase-8、cleaved Caspase-9、cleaved Caspase-3、核因子κB(NF-κB)、ERK1/2的表达水平及培养基中肿瘤坏死因子α(TNF-α)、白细胞介素1β(IL-1β)、γ干扰素(IFN-γ)的含量明显高于对照组;NRG-1组细胞的OD_(490)水平及细胞中ERK1/2的表达水平明显高于H/R组,细胞凋亡率、细胞中cleaved Caspase-8、cleaved Caspase-9、cleaved Caspase-3、NF-κB的表达水平及培养基中TNF-α、IL-1β、IFN-γ的含量明显低于H/R组;NRG-1+PD组细胞的OD_(490)水平及细胞中ERK1/2的表达水平明显低于NRG-1组,细胞凋亡率、细胞中cleaved Caspase-8、cleaved Caspase-9、cleaved Caspase-3、NF-κB的表达水平及培养基中TNF-α、IL-1β、IFN-γ的含量明显高于NRG-1组。结论 NRG-1通过激活ERK1/2通路减轻心肌细胞H/R损伤。     

胰高血糖素样肽1对H9c2心肌细胞缺氧复氧损伤的保护作用及机制研究

目的 研究胰高血糖素样肽1(GLP-1)对H9c2心肌细胞缺氧复氧(H/R)损伤的保护作用及机制.方法 培养H9c2心肌细胞,随机分为常规处理的对照组、H/R组及1、5、10mol/L GLP-1组以验证GLP-1的保护作用,随机分为 si-NC 组、si-NC+H/R 组、si-NC+H/R+10 μmol/L GL...     

Adenosine triggers preconditioning through MEK/ERK1/2 signalling pathway during hypoxia/reoxygenation in neonatal rat cardiomyocytes

Three subtypes of adenosine receptors (A(1), A(2A) and A(3) ARs) are functionally expressed in cardiomyocytes. Adenosine released during ischemia and ischemia/reperfusion plays a major role in cardioprotection. Phosphatidylinositol 3-kinase (PI-3K)/protein kinase B (PKB) and MEK/ERK1/2 pathways are involved in cell survival. Since the role of these pathways in AR-mediated preconditioning is poorly understood, we have investigated whether PI-3K/PKB and/or MEK1/ERK1/2 pathways are involved in AR-induced cardioprotection in neonatal rat cardiomyocytes. Cells were pre-treated (15 min) with adenosine (non-selective), CPA (A(1)), CGS 21680 (A(2A)) or Cl-IB-MECA (A(3)) before 4 h hypoxia (0.5% O(2)) and 18 h reoxygenation (HX4/R). HX4/R-induced increase in LDH release was significantly reduced by adenosine (70%), CPA (59%) and Cl-IB-MECA (46%). The MEK1 inhibitor PD 98059 suppressed the effects of adenosine, CPA, and Cl-IB-MECA on LDH release, whereas the PI-3K inhibitor wortmannin did not reverse this cardioprotection. Western blotting of phosphorylated ERK1/2 and PKB during HX4/R supported the involvement of ERK1/2 and not PKB in A(1) and A(3) agonist-mediated cardioprotection. In addition, adenosine, CPA and Cl-IB-MECA inhibited HX4/R-induced caspase 3 activity by 75%, 70% and 59%, respectively, and this inhibition was abolished by PD 98059. Interestingly, wortmannin inhibited by 66% the anti-apoptotic response triggered by Cl-IB-MECA but had no effect on adenosine or CPA-induced inhibition of caspase 3. CGS 21680 did not modify cell survival or caspase 3 activity. In conclusion, these data show that the preconditioning effect of adenosine requires A(1) and A(3) but not A(2A) ARs and involves an anti-apoptotic effect via MEK1/ERK1/2 pathway in neonatal rat cardiomyocytes. In addition, A(3)AR-induced preconditioning also involves a PI-3K dependent pathway.     

Empagliflozin activates JAK2/STAT3 signaling and protects cardiomyocytes from hypoxia/reoxygenation injury under high glucose conditions

Journal of Thrombosis and Thrombolysis - The morbidity and mortality rates of cardiovascular disease are markedly higher in patients with diabetes than in non-diabetic patients, including patients...     

Biglycan protects cardiomyocytes against hypoxia/reoxygenation injury: Role of nitric oxide

Biglycan, a proteoglycan component of extracellular matrix, has been suspected to contribute to the development of atherosclerosis, but overexpression of biglycan in transgenic mice has been shown to induce cardioprotective genes including nitric oxide (NO) synthases in the heart. Therefore, here we hypothesized if exogenous administration of biglycan exerts cytoprotection. Primary cardiomyocytes from neonatal rats were subjected to 150 min hypoxia and 2 h reoxygenation. Mortality of cardiomyocytes was dose-dependently attenuated by pretreatment with 1-100 nM biglycan. Biglycan enhanced eNOS mRNA and protein, and significantly increased NO content of cardiomyocytes. The NO synthase inhibitor l-nitro-arginine-methyl-ester significantly attenuated the cytoprotective effect of biglycan. This is the first demonstration that biglycan leads to cytoprotection against hypoxia/reoxygenation injury, and that this phenomenon is partially mediated by an NO-dependent mechanism.     

Protective effects of the urocortin homologues stresscopin (SCP) and stresscopin-related peptide (SRP) against hypoxia/reoxygenation injury in rat neonatal cardiomyocytes

Urocortin (UCN), a member of the Corticotropin-Releasing Factor (CRF) family of peptides is a well described cardioprotective agent. UCN is able to bind to two types of G-protein coupled receptors: CRF receptor type 1 (CRFR1) and CRF receptor type 2 (CRFR2), whereas, two homologues of UCN, stresscopin (SCP) or also known as urocortin III (UCNIII) and stresscopin related peptide (SRP), or urocortin II (UCNII), bind exclusively and with high affinity to CRFR2, we hypothesised that they will exhibit more pronounced cardioprotective effects than UCN.We show for the first time that SCP is expressed in rat cardiomyocytes and that the levels of SRP and SCP are increased by hypoxic stress. All three peptides have potent cardioprotective effects in cells exposed to hypoxia/reoxygenation. When used at 10(-8) M they increased the amount of live cells by 25% when added prior to hypoxia, and by 20% when UCN and SCP were added at the onset of reoxygenation. In addition, the peptides are equally are more potent antiapoptotic factors than UCN. The antiapoptotic effects of SCP were more pronounced than SRP and UCN at a concentration of 10(-10) M. Furthermore, SCP and SRP protect cardiomyocytes better than UCN at concentrations up to and including 10(-10) M and reduced the amount of TUNEL positive cells almost by half at concentrations of 10(-12) to 10(-10) M. More importantly, we demonstrate that SCP and SRP are able to protect cardiomyocytes even if they are administered after the hypoxic insult and prior to reoxygenation. In this case SCP was more potent than UCN and SRP at 10(-12) M and both SCP and SRP exhibited higher protection at 10(-8) M compared to UCN.Cardioprotection of cardiomyocytes by 10(-8) M of peptides was abolished when treated with 50 microM LY294002 or 100 microM PD98059, but not by 10 microM SB203580 prior to the hypoxic insult. Transfection of dominant negative Akt and MEK1 also blocked protection by the peptides, whereas dominant negative MEKK6 had no effects, demonstrating that SCP and SRP, like UCN, require activation of p42/44 Mitogen activated protein kinase and Akt/Protein Kinase B in order to produce their cardioprotective effects. In addition, we showed that SCP and UCN are potent activators of the p42/44 MAPK pathway, with SRP able to induce phosphorylation of p42/44 MAPK as well, albeit not as pronounced.