MCI-186减轻Aβ1-40诱导PC12细胞tau蛋白磷酸化的研究

目的 探讨依达拉奉(MCI-186)对β样淀粉蛋白(Aβ1-40)引起的PC12细胞tau蛋白磷酸化的保护作用及其机制.方法 采用 Western 印迹等检测Ser396,Ser199/202,Tau-5及GSK-3β,GSK-3βSer9磷酸化水平,观察MCI-186对Aβ25-35致PC12细胞的损伤保护作用.结果 模型组 tau蛋白在Ser396、Ser199/202位点的磷酸化水平及总tau蛋白水平在Aβ1-40作用3 h后开始升高,同时GSK-3β的表达增多,磷酸化GSK-3βSer9的表达减少,MCI-186保护组tau蛋白在Ser396,Ser199/202位点的磷酸化水平和总tau蛋白水平均明显低于Aβ模型组(P＜0.05),GSK-3β的表达减少,磷酸化GSK-3βSer9的表达增多(P＜0.05).结论 在Aβ1-40诱导PC12细胞损伤过程中,出现了tau蛋白的过度磷酸化,可以使Ser396,Ser199/202位点及Tau-5蛋白升高.激活GSK-3β是产生tau蛋白过度磷酸化的主要途径.MCI-186可通过抑制GSK-3β的活性,从而减轻Aβ1-40诱导的tau蛋白过度磷酸化,而达到保护神经细胞的目的 .     

IGF-1对Aβ25-35致PC12细胞损伤的保护作用及其机制的探讨

目的探讨胰岛素样生长因子1(IGF-1)对β样淀粉蛋白(Aβ25-35)引起的PC12细胞凋亡及tau蛋白磷酸化的保护作用及其机制。方法采用MTT,TUNEL等检测磷酸化Akt、Akt水平及Tau蛋白磷酸化水平,观察IGF-1对Aβ25-35致PC12细胞的损伤保护作用。结果MTT分析法表明IGF-1保护组的细胞活性显著高于Aβ损伤组(P<0.01),TUNEL法检测结果显示IGF-1保护组凋亡指数低于Aβ损伤组(P<0.01),IGF-1保护组能使被Aβ下调的磷酸化Akt水平恢复至与对照组相近的水平,总Akt水平基本维持不变。IGF-1保护组tau蛋白在Ser396,Ser202位点的磷酸化水平和总tau蛋白水平均明显低于Aβ损伤组。结论IGF-1能降低Aβ的细胞毒性,抑制Aβ25-35诱导的PC12细胞的凋亡和tau蛋白磷酸化,这一作用机制是通过PI3K/Akt信号传导途径来实现的。     

氯化锂通过激活Wnt信号通路促进内皮祖细胞的增殖能力

目的探讨糖原合酶激酶3β(GSK-3β)抑制剂氯化锂对内皮祖细胞增殖的作用机制。方法密度梯度离心法分离大鼠骨髓源性内皮祖细胞,体外培养7天后分别给予不同浓度氯化锂(5、10、20、40 mmol/L)以抑制内皮祖细胞的GSK-3β活性。分别采用镜下计数法及四氮唑溴盐比色法测定内皮祖细胞增殖能力,荧光激活细胞分离仪分析各组内皮祖细胞的细胞周期变化。采用蛋白印迹法测定Wnt信号通路中磷酸化GSK-3β、β-连环蛋白及细胞周期蛋白D1的蛋白表达。结果氯化锂在一定浓度范围内可剂量依赖性地增加内皮祖细胞数量。与对照组比较,不同浓度氯化锂组(5、10、20 mmol/L)内皮祖细胞数量显著增加(P0.05,n=5)。四氮唑溴盐比色法检测氯化锂各浓度组内皮祖细胞在490 nm处吸光度值与对照组比较差异有显著性(P0.05,n=5)。荧光激活细胞分离仪分析显示氯化锂组细胞周期S期较对照组显著增加(P0.05,n=3)。蛋白印迹法测定表明,与对照组比较氯化锂可显著增加磷酸化GSK-3β、β-连环蛋白及细胞周期蛋白D1的蛋白表达(P0.05,n=3)。结论 GSK-3β抑制剂氯化锂可通过激活Wnt信号通路显著促进内皮祖细胞的增殖能力。     

Aβ寡聚体预处理的BV2细胞对PC12细胞损伤的影响及其机制

目的 研究Aβ寡聚体预处理的BV2细胞对PC12细胞损伤的影响及机制,为阿尔茨海默病(AD)的抗炎治疗提供体外实验依据.方法 分别用不同浓度Aβ1-42寡聚体(0、10 μmol/L)作用于PC12细胞作为对照组(Aβ+PC12);用相应浓度的Aβ1-42寡聚体预处理BV2细胞24 h后与PC12细胞共育作为实验组1(Aβ+BV2+PC12);不同浓度IL-1β处理PC12细胞24 h作为实验组2(IL-1β+PC12);预先用IL-1ra(50 ng/ml)孵育PC12细胞1 h后,进行实验组1的细胞培养作为实验组3[(Aβ+ BV2)+(PC12+IL-1ra)].用ELISA法检测细胞培养上清液中IL-1β水平/浓度,用Western印迹法检测tau(pS396)、tau蛋白表达情况.结果 Aβ寡聚体预处理的BV2细胞培养液中可检测出IL-1β,Aβ寡聚体浓度的增加与IL-1β含量增加呈现一定的量效关系.PC12细胞与Aβ寡聚体预处理24 h的BV2细胞共育后(实验组1),可见PC12细胞tau(pS396)蛋白表达较对照组进一步增多(P＜0.05),此作用可被IL-1ra部分抑制(P＜0.05).结论 BV2细胞可加重Aβ寡聚体对PC12细胞损伤过程;Aβ寡聚体可诱导BV2细胞产生IL-1β,IL-1β通过tau异常磷酸化通路参与的胶质炎症反应可能是PC12细胞损伤的机制之一.     

胰岛素样生长因子-1对Aβ_(25～35)诱导的SH-SY5Y细胞损伤的保护作用及机制

目的观察胰岛素样生长因子(IGF)-1对Aβ_(25～35)诱导的人神经母细胞瘤SH-SY5Y细胞损伤的保护作用,并初步探讨其可能机制。方法将SH-SY5Y细胞随机分为对照(Control)组,Aβ_(25～35)处理(Aβ_(25～35))组,IGF-1治疗(Aβ_(25～35)+IGF-1)组,Wortmannin抑制剂(Aβ_(25～35)+IGF-1+Wort)组,单纯渥曼青霉素(Wortmannin)组。CCK-8法检测细胞活力,检测乳酸脱氧酶(LDH)漏出率,判断细胞损伤程度,荧光探针DCFH-DA法检测细胞内活性氧(ROS)含量的变化,试剂盒测定丙二醛(MAD)含量及超氧化物气化酶(SOD)和谷胱甘肽过氧化物酶(GSH-Px)活性,流式细胞仪分析法测定细胞凋亡率,Western印迹法检测相关蛋白表达。结果与Aβ_(25～35)组相比,Aβ_(25～35)+IGF-1组细胞活力明显升高,LDH漏出率明显下降(P0.05)。IGF-1可明显减少Aβ_(25～35)诱导SH-SY5Y细胞ROS及MDA生成,增加SOD及GSH-Px酶活性(P0.05)。与Aβ_(25～35)组相比,IGF-1治疗还能增加蛋白激酶B(Akt)及叉头框蛋白(Fox)O3a磷酸化水平,降低Puma蛋白表达水平及细胞凋亡率(P0.05)。而加入磷脂酰肌醇-3激酶(PI3K)特异性抑制剂Wortmannin预处理,可阻断上述IGF-1的保护作用(P0.05)。结论 IGF-1对Aβ_(25～35)诱导的SH-SY5Y细胞损伤的保护作用可能与激活PI3K/Akt信号通路有关。     

山茱萸多糖对阿尔茨海默病模型大鼠海马区糖原合酶激酶-3β和磷酸化-tau蛋白的影响

目的观察山茱萸多糖(CFPs)对阿尔茨海默病(AD)大鼠海马区糖原合酶激酶(GSK)-3β和磷酸化tau(p-tau)蛋白的影响,探讨CFPs对AD大鼠神经元的保护机制。方法将Wistar大鼠100只随机分为青年组、假手术组、模型组、多奈哌齐组、CFPs组。采用D-半乳糖联合Aβ1~40制备AD模型,采用免疫组化(SABC)法检测海马CA1区GSK-3β和p-tau蛋白表达量,Western印迹法检测海马GSK-3β和p-tau蛋白表达量。结果与模型组比较,CFPs和多奈哌齐可显著降低AD大鼠海马区GSK-3β和p-tau蛋白表达量(P<0.05),CFPs组和多奈哌齐组GSK-3β和ptau蛋白表达量无显著差异(P>0.05)。结论 CFPs通过抑制大鼠海马区GSK-3β蛋白表达从而降低tau蛋白过度磷酸化,实现其对AD大鼠神经元的保护作用。     

山茱萸多糖对阿尔茨海默病模型大鼠GSK-3β和磷酸化GSK-3β的影响

目的 研究山茱萸多糖对阿尔茨海默病(AD)大鼠GSK-3β和磷酸化GSK-3β的影响,探讨其对AD大鼠的保护作用机制.方法 清洁级Wistar大鼠120只,随机分为青年组、假手术组、模型组、多奈哌嗪对照组、山茱萸多糖水提液组、山茱萸水煎剂组,每组20只.采用海马注射Aβ-淀粉样蛋白1-40(Aβ1-40)制作AD大鼠模型,免疫组化(SABC)法和免疫蛋白印迹法检测GSK-3β蛋白和GSK-3β(Ser9)蛋白的表达水平.结果 与青年组、假手术组比较,模型组大鼠海马组织GSK-3β蛋白表达增加(P＜0.05),GSK-3β(Ser9)蛋白表达降低(P＜0.05);与模型组比较,多奈哌嗪对照组,山茱萸多糖水提液组,山茱萸水煎剂组大鼠的GSK-3β蛋白表达显著减少(P＜0.05),GSK-3β(Ser9)蛋白表达增加(P＜0.05).结论 山茱萸多糖通过抑制GSK-3β蛋白过度激活,促进GSK-3β(Ser9)蛋白表达途径防治AD的发生发展.     

β淀粉样蛋白25-35诱导的大鼠嗜铬细胞瘤细胞凋亡过程中核因子кB激活的调控

目的 探讨β淀粉样蛋白(amyloid-β,Aβ)25-35诱导的大鼠嗜铬细胞瘤细胞(PC12)凋亡过程中核因子кB(nuclear factor кB,NF-кB)的活化与蛋白激酶B(Akt)和糖原合成酶激酶3β(glycogen synthase kinase 3β,GSK-3β)之间的关系.方法 用Aβ(25-35)诱导PC12细胞凋亡,并分析在此过程中Akt、GSK-3β以及NF-кB的活性变化.在Aβ(25-35)诱导PC12细胞凋亡过程中,分别阻断Akt通路和GSK-3β通路,测定细胞活性以及Akt、GSK-3β、NF-кB的关系.结果 Aβ(25-35)诱导细胞凋亡过程中,细胞凋亡率与Aβ(25-35)的用量呈现剂量依赖关系,用0、5、10、20、40μmol/L Aβ(25-35)处理PC12细胞48 h后,细胞的凋亡率分别为(3.01±0.03)%、(3.08±0.03)%、(25.32±0.76)%、(42.88±0.60)%、(60.85±2.39)%.与对照组比较,Aβ(25-35)诱导细胞凋亡过程中NF-кB被激活,而Akt、GSK-3β的活性则均受到抑制.用渥曼青霉素(wortmannin)抑制Akt的活性可引起NF-кB活性的下降.GSK-3β活性上升.用GSK-3β的特异性抑制剂氯化锂(LiC1)抑制其活性,则NF-кB活性同样下降.而对Akt的活性无显著影响.结论 Akt和GSK-3β都是NF-кB的上游调节因子,他们共同调控Aβ(25-35)诱导的PC12细胞凋亡过程中NF-кB的活化.这些结果有助于更好地理解阿尔茨海默病的发病机制,并对其防治提供新的思路.     

定志益聪颗粒对血管性痴呆大鼠认知功能的改善作用及其机制

目的 观察定志益聪颗粒(DZYC)对血管性痴呆(VD)大鼠糖原合成酶激酶(GSK)-3β、细胞周期素依赖性蛋白激酶(CDK)5及β淀粉样肽(Aβ)_1～42、磷酸化tau蛋白(P-tauS202、P-tauS396、P-tauT231)的影响,探讨DZYC对VD的可能作用机制。方法 SPF级雄性SD大鼠,通过双侧颈总动脉永久性闭塞法制作VD模型,随机分为正常组、假手术组、模型组、多奈哌齐组、DZYC组,每组10只。多奈哌齐组以2.6×10^-4 g/kg、DZYC组以5 g/kg予相应药液,正常组、假手术组、模型组予等量生理盐水。造模后56 d开始灌胃给药,每日1次,连续30 d。Morris水迷宫(MWM)行为学测试后取材。免疫组织化学法(IHC)检测大鼠海马CA1区GSK-3β、CDK5的阳性表达;Western印迹检测海马组织GSK-3β、CDK5、Aβ_1～42及P-tauS202、P-tauS396、P-tauT231的表达量。结果 与正常组、假手术组比较,模型组大鼠的空间学习、记忆能力明显下降(P<0.05)...     

调心方对大鼠杏仁核注射Aβ25-35致P35和tau蛋白磷酸化的调节作用

目的　观察大鼠单侧杏仁核注射 β淀粉样蛋白 (Aβ)多肽片段Aβ2 5 3 5后 ,其学习记忆能力改变、脑内tau蛋白磷酸化和P35蛋白的表达变化 ,并用此动物模型观察调心方的作用。　方法　Morris水迷宫检测学习记忆能力 ,免疫组化法检测大鼠脑内P35和磷酸化tau蛋白。　结果　Morris水迷宫测试显示 ,Aβ注射组大鼠平均潜伏期 (2 0 4± 36 5 )s比手术对照组 (8 8± 12 1)s明显延长 ,Aβ加用调心方组 (9 8± 10 3)s较Aβ注射组显著缩短 (P <0 0 5 )。免疫组化和积分光密度分析显示Aβ注射后脑内P35和磷酸化tau增加 ,但术后 2 1dP35蛋白水平开始下降 ,而磷酸化tau蛋白继续增高 ;调心方治疗组P35和磷酸化tau蛋白均较Aβ注射组有不同程度的降低。　 结论　Aβ的毒性作用可导致脑内神经元tau蛋白磷酸化增加 ,其部分原因可能与P35蛋白表达增加有关 ;而调心方具有抑制Aβ诱导的这些反应。     

Melatonin arrests peroxynitrite-induced tau hyperphosphorylation and the overactivation of protein kinases in rat brain

The purpose of this study was to examine the in vivo effect of melatonin (MEL) on peroxynitrite-induced tau hyperphosphorylation and the involvement of glycogen synthase kinase-3beta (GSK-3beta) and mitogen-activated protein kinase (MAPK) families. Melatonin was injected into the right cerebroventricle of the rats 1 hr before the bilateral hippocampal injection of 3-morpholino-sydnonimine chloride (SIN-1), the recognized donor of peroxynitrite. Thereafter, the phosphorylation level of tau and the activity of the kinases were analyzed. The injection of SIN-1 induced hyperphosphorylation of tau at pS396 epitope with a concomitant activation of GSK-3beta and selective MAPK isoforms including p38alpha, p38beta, and p38delta but not p38gamma. The effect of peroxynitrite was confirmed using uric acid, a recognized scavenger of peroxynitrite. Preinjection of MEL significantly arrested the peroxynitrite-induced hyperphosphorylation of tau and the activation of GSK-3beta and MAPKs. Melatonin also ameliorated peroxynitrite-induced oxidative stress. We conclude that MEL can efficiently arrest peroxynitrite-induced tau hyperphosphorylation, and the underlying mechanism may involve scavenging the reactive species and suppressing the activated GSK-3beta and p38 MAPK family.     

2型糖尿病及阿尔茨海默病大鼠糖原合成酶-3β和tau蛋白磷酸化的研究

目的 研究2型糖尿病(T2DM)并发阿尔茨海默病(AD)的可能机制. 方法 选取同龄Wistar大鼠,随机分为正常对照组、T2DM组、AD组及T2DM+AD组.采用血糖仪监测大鼠血糖,水迷宫实验观测大鼠行为学改变,免疫组化染色检测大鼠糖原合成激酶-3β(GSK-3β)及tau蛋白磷酸化水平. 结果 各模型组大鼠均较正常对照组学习记忆力减退,T2DM组与AD组及T2DM+AD组之间差异有统计学意义(F=28.65 P<0.001).T2DM+AD组GSK-3β表达水平(4319.02±653.24)显著高于T2DM组(540.43±558.49)、正常对照组(315.56±91.64)及AD组(304.39±175.83)(H=19.335,P<0.001).AD组(2799.61±1070.02)及T2DM+AD组(8583.814±2236.11)tau蛋白磷酸化表达水平显著高于正常对照组(252.024±58.37)及T2DM组(287.75±192.53)(H=32.950,P<0.001). 结论 T2DM大鼠GSK-3β活性的上调可能是引起大鼠tau蛋白磷酸化的一个重要原因.     

谷胱甘肽过氧化物酶1高表达对β淀粉样蛋白介导PC12细胞损伤的保护作用

目的探讨β淀粉样蛋白(Aβ)所致阿尔茨海默病发病的分子机制,以及谷胱甘肽过氧化物酶1(GPX1)高表达时对其所致细胞损伤的保护作用。方法将PC12细胞转染合人GPX1基因的plncx质粒及空载体plncx质粒,对PCl2、GPXl-PCl2、plncx-PCl2 3组细胞,分别给予Aβ_(25-35)和亚硒酸钠+Aβ_(25-35)2种干预方式,MTT法检测细胞的存活情况,免疫细胞化学法观察磷酸化环磷酸腺苷反应元件结合蛋白(pCREB)的表达情况。结果 PCl2组与plncx-PCl2组细胞存活率比较,差异无统计学意义(P>0.05);GPXl-PC12组较plncx-PCl2组细胞存活率明显增高(P<0.01);Aβ_(25-35)干预后,plncx-PC12组和GPX1-PC12组pCREB蛋白阳性率明显下降,plncx-PC12组较GPX1-PCl2组下降更明显(P<0.05)。亚硒酸钠+Aβ_(25-35)干预后,plncx-PC12组和GPX1-PC12组pCREB蛋白阳性率明显上升,GPX1-PC12组较plncx-PC12组增高更明显(P<0.01)。结论 GPX1基因高表达对Aβ_(25-35)所介导的PCl2细胞损伤有明显保护作用;Aβ_(25-35)可下调pCREB在PCl2细胞中表达,而GPXl与pCREB共同参与保护PCl2细胞,减少Aβ_(25-35)所引起的细胞损伤。     

Phosphorylation of tau antagonizes apoptosis by stabilizing beta-catenin, a mechanism involved in Alzheimer's neurodegeneration

Hyperphosphorylated tau is the major protein subunit of neurofibrillary tangles in Alzheimer's disease (AD) and related tauopathies. It is not understood, however, why the neurofibrillary tangle-containing neurons seen in the AD brains do not die of apoptosis but rather degeneration even though they are constantly awash in a proapoptotic environment. Here, we show that cells overexpressing tau exhibit marked resistance to apoptosis induced by various apoptotic stimuli, which also causes correlated tau hyperphosphorylation and glycogen synthase kinase 3 (GSK-3) activation. GSK-3 overexpression did not potentiate apoptotic stimulus-induced cell apoptosis in the presence of high levels of tau. The resistance of neuronal cells bearing hyperphosphorylated tau to apoptosis was also evident by the inverse staining pattern of PHF-1-positive tau and activated caspase-3 or fragmented nuclei in cells and the brains of rats or tau-transgenic mice. Tau hyperphosphorylation was accompanied by decreases in beta-catenin phosphorylation and increases in nuclear translocation of beta-catenin. Reduced levels of beta-catenin antagonized the antiapoptotic effect of tau, whereas overexpressing beta-catenin conferred resistance to apoptosis. These results reveal an antiapoptotic function of tau hyperphosphorylation, which likely inhibits competitively phosphorylation of beta-catenin by GSK-3beta and hence facilitates the function of beta-catenin. Our findings suggest that tau phosphorylation may lead the neurons to escape from an acute apoptotic death, implying the essence of neurodegeneration seen in the AD brains and related tauopathies.     

Safflower yellow ameliorates cognition deficits and reduces tau phosphorylation in APP/PS1 transgenic mice

Alzheimer’s disease (AD), the most common cause of dementia worldwide, is mainly characterized by the aggregated β-amyloid (Aβ) and hyperphosphorylated tau. Safflower yellow (SY) is a novel water extract of natural safflower and has been suggested to ameliorate memory deficits in several animal models of dementia. In this study, we aimed to investigate the effect and mechanism of SY on deficits of learning and memory and hyperphosphorylation of tau in APP/PS1 double transgenic mice. APP/PS1 mice were administered with SY (10, 30, 100 mg/kg) by oral gavage for three months at the age of six months. The ability of learning and memory was investigated using the step-down test and Morris water maze test, and protein level in the brain was evaluated using western blot. Here, we found that SY treatment can improve spatial learning and memory ability, and reduce tau hyperphosphorylation at Ser199, Thr205, Ser396, Ser404 sites in APP/PS1 mice. In addition, the activity the of cyclin-dependent kinase 5 (CDK-5) and glycogen synthase kinase 3β (GSK-3β), major kinases involved in tau phosphorylation, was siginificantly decreased in APP/PS1 mice by SY treatment. These results support SY can serve as a promising multitarget neuronal therapeutic agent for the treatment of AD.     

吡格列酮改善胰岛素抵抗大鼠脑组织Tau蛋白磷酸化水平

目的探讨胰岛素增敏剂吡格列酮(PIO)对胰岛素抵抗(IR)模型大鼠皮质Tau蛋白磷酸化水平的影响及可能的机制。方法选择Wistar大鼠46只,随机选20只分为对照组和PIO组,每组10只;另26只通过果糖喂养建立IR大鼠模型后,分为IR组和IR+PIO组,每组13只,采用免疫印迹法检测皮质Tau蛋白磷酸化、磷酸化磷脂酰肌醇3激酶(PI3K)、磷酸化蛋白激酶B(PKB)、糖原合成激酶-3β(GSK-3β)及GSK-3β位点中Ser9的磷酸化水平。结果与对照组比较,IR组大鼠皮质Tau蛋白磷酸化水平明显增高;磷酸化PI3K、磷酸化PKB和磷酸化GSK-3β蛋白表达明显降低(P<0.05,P<0.01);而PIO能显著抑制Tau蛋白磷酸化水平,上调磷酸化PI3K、磷酸化PKB和磷酸化GSK-3β的水平(P<0.05,P<0.01);各组GSK-3β差异无统计学意义(P>0.05)。结论 IR通过抑制PI3K-丝/苏氨酸蛋白激酶通路激活,促进GSK-3β活性上调,可能是引起大鼠海马Tau蛋白过度磷酸化的重要原因;PIO可能通过降低GSK-3β活性进而抑制Tau蛋白的过度磷酸化。     

tau kinases in the rat heat shock model: possible implications for Alzheimer disease

We have previously shown, by using the phosphate-dependent anti-tau antibodies Tau-1 and PHF-1, that heat shock induces rapid dephosphorylation of tau followed by hyperphosphorylation in female rats. In this study, we analyzed in forebrain homogenates from female Sprague-Dawley rats the activities of extracellular signal regulated kinase 1/2 (ERK1/2), c-Jun NH(2)-terminal kinase (JNK), glycogen synthase kinase-3beta (GSK-3beta), cyclin-dependent kinase 5 (Cdk5), cAMP-dependent protein kinase A (PKA), and Ca(2+)/calmodulin-dependent protein kinase II (CaMKII) at 0 (n = 5), 3 (n = 4), 6 (n = 5), and 12 (n = 5) h after heat shock and in non-heat-shocked controls (n = 5). Immunoprecipitation kinase assays at 0 h showed suppression of the activities of all kinases except of GSK-3beta, which showed increased activity. At 3-6 h, the activities of ERK1/2, JNK, Cdk5, and GSK-3beta toward selective substrates were increased; however, only JNK, Cdk5, and GSK-3beta but not ERK1/2 were overactivated toward purified bovine tau. At 3-6 h, kinase assays specific for PKA and CaMKII showed no increased activity toward either tau or selective substrates. All of eight anti-tau antibodies tested showed dephosphorylation at 0 h and hyperphosphorylation at 3-6 h, except for 12E8, which showed hyperphosphorylation also at 0 h. Immunoblot analysis using activity-dependent antibodies against ERK1/2, JNK, and GSK-3beta confirmed the above data. Increased activation and inhibition of kinases after heat shock were statistically significant in comparison with controls. Because tau is hyperphosphorylated in Alzheimer disease these findings suggest that JNK, GSK-3beta, and Cdk5 may play a role in its pathogenesis.     

PKR plays a positive role in osteoblast differentiation by regulating GSK-3β activity through a β-catenin-independent pathway

Double-stranded RNA-dependent protein kinase (PKR) is involved in various cellular functions. We previously reported that PKR regulates osteoblast differentiation, but the specific mechanisms by which this occurs remain unclear. In this study, we investigated the role of PKR in Glycogen synthase kinase 3β (GSK-3β) regulation of osteoblast differentiation. Lithium chloride (LiCl), a GSK-3β inhibitor, increased GSK-3β phosphorylation in MC3T3-E1 and MG-63 cells. LiCl also inhibited Runx2 and expression of its regulated genes, causing inhibition of Alkaline phosphatase activity and mineralization. LiCl injection to the calvaria in mice suppressed bone formation. Further, GSK-3β phosphorylation was increased in osteoblasts, by Akt-independent mechanisms, in which PKR was constitutively inactivated. A PKR inhibitor, 2-aminopurine, also induced GSK-3β phosphorylation in MC3T3-E1 and MG-63 cells. Further, Runx2 and its regulated genes were inhibited in PKR-inactivated osteoblasts, and differentiation was suppressed through a β-catenin-independent pathway. PKR positively regulates the differentiation of osteoblasts by mediating GSK-3β activity through a β-catenin-independent pathway.     

Acetyl-L-carnitine attenuates homocysteine-induced Alzheimer-like histopathological and behavioral abnormalities

Hyperhomocystinemia could induce tau protein hyperphosphorylation, β-amyloid (Aβ) accumulation, and memory deficits as seen in Alzheimer disease (AD), the most common cause of senile dementia with no effective cure currently. To search for possible treatment for AD, we produced a hyperhomocysteinemia model by vena caudalis injection of homocystine (Hcy) for 2 weeks and studied the effects of acetyl-L-carnitine (ALC) in rats. We found that simultaneous supplement of ALC could improve the Hcy-induced memory deficits remarkably, with attenuation of tau hyperphosphorylation and Aβ accumulation. Supplement of ALC almost abolished the Hcy-induced tau hyperphosphorylation at multiple AD-related sites. Supplementation of ALC also suppressed the phosphorylation of β-amyloid precursor proteins (APP), which may underlie the reduction of Aβ. Our data suggest that ALC could be a promising candidate for arresting Hcy-induced AD-like pathological and behavioral impairments.