脂联素通过激活PP2A减轻H_2O_2诱导的SH-SY5Y细胞损伤及tau蛋白过度磷酸化

目的:观察脂联素(adiponectin)对H2O2诱导的人神经母细胞瘤SH-SY5Y细胞活力及tau蛋白磷酸化的影响并探讨其作用机制。方法:采用MTT法并观察细胞形态,检测脂联素对H2O2诱导的SH-SY5Y细胞活力损伤的影响;应用Western blotting观察脂联素对tau蛋白磷酸化及蛋白磷酸酶2A(protein phosphatase 2A,PP2A)和糖原合酶激酶3β(glycogen synthase kinase-3β,GSK-3β)活性的影响。结果:脂联素减轻了H2O2诱导的SH-SY5Y细胞损伤(P0.01)。脂联素上调了H2O2诱导的SH-SY5Y细胞的PP2A活性,明显减轻此时tau的异常过度磷酸化(P0.01)。PP2A抑制剂冈田酸阻断了脂联素的保护作用(P0.01)。脂联素同时使H2O2诱导的SH-SY5Y细胞的GSK-3β磷酸化水平上升(P0.01)。结论:脂联素减轻H2O2诱导的SH-SY5Y细胞损伤及tau蛋白异常过度磷酸化,其机制可能与激活PP2A并抑制GSK-3β信号途径有关。     

人参皂苷Rg1通过调节GSK-3β/PP2A活性减轻皮层神经元Tau蛋白过度磷酸化

目的 探讨人参皂苷Rg1是否通过调节GSK-3β/PP2A活性而减轻凝聚态Aβ25～35诱导的胎鼠皮层神经元Tau蛋白过度磷酸化.方法 选用孕期(18±2)d的SD大鼠,分离纯化胎鼠皮层神经元.实验分为阴性对照组、模型组、LiCl处理组、Rg1预处理组.阴性对照组不加任何处理因素;模型组用20μmol/L Aβ25～35作用于皮层神经元12h;LiCl处理组用10mmol/L LiCl和20μmol/L Aβ25～35共同作用于皮层神经元12h;Rg1预处理组分别用5、10、20、40、80μmol/L Rg1预处理皮层神经元24h,再加入20μmol/L Aβ25～35作用12h.通过免疫印迹法和免疫细胞化学染色法检测皮层神经元Tau蛋白磷酸化水平、总Tau蛋白水平和糖原合成酶3β(GSK-3β)表达水平,通过非放射性免疫法检测皮层神经元蛋白磷酸酯酶2A(PP2A)活性.结果 模型组Tau蛋白在Ser396、Ser199/202和Thr231位点的磷酸化水平、总Tau蛋白水平和GSK-3β的蛋白表达水平均增加,但PP2A的活性不受影响;LiCl处理组和Rg1预处理组,Tau蛋白在Ser396、Ser199/202和Thr231位点的磷酸化水平、总Tau蛋白水平和GSK-3β的蛋白表达水平均降低(P＜0.05).在Rg1预处理组中,以20μmol/L Rg1预处理后Tau蛋白磷酸化水平、总Tau蛋白水平和GSK-3β的表达水平下降最为明显,而且PP2A的活性明显增强(P＜0.01).结论 人参皂苷Rg1可通过上调PP2A活性和下调GSK-3β活性从而减轻凝聚态Aβ25～35所诱导的皮层神经元Tau蛋白过度磷酸化.     

雌激素减轻H2O2诱导PCI2细胞凋亡

目的 观察雌激素对H2O2诱导细胞凋亡的作用,探讨雌激素保护作用机制.方法 在PCI2细胞建立H2O2诱导细胞凋亡的实验模型.用MTT法检测细胞存活率,比色法测定乳酸脱氢酶(LDH)活性,Hoechst染色检测细胞凋亡,碘化丙啶(PI)染色流式细胞术检测细胞凋亡率,比色法测定caspase-3活性.结果 H2O2明显降低PCI2细胞的存活率,使LDH释放增加,促进细胞凋亡,并能明显地升高caspase-3的活性.雌激素能显著地减轻上述变化.结论 雌激素对抗H2O2诱导的细胞凋亡,抑制caspase-3的激活是其细胞保护机制之一.     

PERK通路在吗啡保护心肌H9c2细胞过程中的作用

目的:探讨吗啡(morphine)是否通过PERK通路降低内质网应激,阻止线粒体膜通透性转换孔(mPTP)开放,从而保护氧化应激损伤的心肌细胞。方法:体外培养大鼠心肌H9c2细胞,用H2O2建立氧化应激模型,随机分为对照组、H2O2组、H2O2+morphine组、H2O2+morphine+PERK通路抑制剂GSK2656157组、morphine组和GSK2656157组。免疫组化法检测吗啡对氧化应激引起葡萄糖调节蛋白(GRP)78和GRP94表达的影响;Western blot法检测PERK信号通路相关蛋白的水平;利用共聚焦显微镜观察吗啡对氧化应激所致mPTP开放及内质网的影响;乳酸脱氢酶(LDH)和MTT试剂盒分别检测细胞毒性和细胞活力。结果:与对照组相比,H2O2组GRP78和GRP94蛋白为强阳性表达,棕黄色颗粒明显增加,吗啡明显抑制此过程。与对照组相比,不同浓度GSK2656157使PERK的磷酸化明显减少,其中2μmol/L的作用效果最为显著(P<0.05)。氧化应激使GRP78、GRP94、p-PERK和CHOP的蛋白水平明显增加,使糖原合成酶激酶3β(GSK-3β)磷酸化明显减少;线粒体TMRE和内质网ER-Tracker Red红色荧光强度均明显减少;细胞毒性明显增强,细胞活力明显减弱。吗啡明显抑制H2O2引起的改变,而GSK2656157可进一步加强吗啡的作用(P<0.05)。结论:吗啡通过抑制PERK通路降低内质网应激,使GSK-3β失活,进而阻止mPTP开放,保护受氧化应激损伤的心肌H9c2细胞。     

雌激素减轻H2O2诱导PC12细胞凋亡

目的观察雌激素对H2O2诱导细胞凋亡的作用,探讨雌激素保护作用机制。方法在PC12细胞建立H2O2诱导细胞凋亡的实验模型。用MTT法检测细胞存活率,比色法测定乳酸脱氢酶(LDH)活性,Hoechst染色检测细胞凋亡,碘化丙啶(PI)染色流式细胞术检测细胞凋亡率,比色法测定caspase-3活性。结果H2O2明显降低PC12细胞的存活率,使LDH释放增加,促进细胞凋亡,并能明显地升高caspase-3的活性。雌激素能显著地减轻上述变化。结论雌激素对抗H2O2诱导的细胞凋亡,抑制caspase-3的激活是其细胞保护机制之一。     

糖元合酶激酶-3过度激活对神经细丝磷酸化的影响

目的：在细胞水平研究糖元合酶激酶((3SK-3)过度激活对神经细丝磷酸化的影响。方法：采用磷酯酰肌醇三磷酸激酶(P13K)的特异性抑制剂渥曼青霉素(wortmannin,WT)处理野生型小鼠成神经瘤细胞株(N2a／wt),免疫印迹技术及酶活性测定检测GSK-3活性,免疫荧光技术检测神经细丝(NF)的磷酸化状态。进一步采用(3SK-3特异性的抑制剂LiCl处理上述细胞,检测上述相同指标。结果：WT处理N2a细胞1h后,GSK3酶活性显著增加,并使抗体SMI31显色增强,SMI32显色减弱,提示NF被过度磷酸化。而采用WT和LiCl联合处理N2a／wt细胞,GSK-3活性显著降低,与此同时,NF的磷酸化程度明显减少。结论：GSK-3过度激活可引起细胞骨架蛋白NF的异常过度磷酸化,而过度磷酸化的NF可能参与了AD的病理过程。     

β-雌二醇经ERβ-ERK1/2雌激素胞膜信号传导途径促进肺癌A549细胞迁移和侵袭

目的:研究β-雌二醇(β-estradiol)促进肺癌A549细胞迁移和侵袭的调控机制。方法:体外培养乳腺癌MCF-7细胞和肺癌A549细胞,以MCF-7细胞作为阳性对照明确雌激素受体(ER)在A549细胞中的表达情况; real-time PCR检测ERβ亚型ERβ1、ERβ2和ERβ5在A549细胞中的表达情况,免疫荧光定位ERβ在细胞内的胞膜和胞核分布情况;予β-estradiol刺激A549细胞,Western blot检测胞内ERK1/2磷酸化水平改变,Transwell小室侵袭实验和细胞实时监测培养系统检测细胞迁移和侵袭能力的变化;利用ERK1/2抑制剂PD98059预先处理,Transwell小室侵袭实验和细胞实时监测培养系统检测β-estradiol刺激后细胞迁移和侵袭能力的变化。结果:ER在A549细胞中以表达ERβ为主,且表达的ERβ以ERβ2和ERβ5为主,免疫荧光显示细胞内ERβ以胞质分布为主。β-estradiol可以引起A549细胞ERK1/2磷酸化水平的增加,并促进细胞的迁移和侵袭,抑制ERK1/2信号传导可以逆转β-estradiol促进的细胞迁移和侵袭。结论:β-estradiol经ERβ活化ERK1/2雌激素胞膜信号传导,从而促进A549细胞的侵袭和转移。ERK1/2是ERβ雌激素胞膜信号传导中与肺癌侵袭和转移相关的重要信号节点。     

PI3K/AKT通路介导H_2O_2预处理减轻PC12细胞氧化损伤

目的探讨PI3K/AKT信号通路是否参与H2O2预处理诱导的适应性细胞保护作用。方法体外培养PC12细胞,建立H2O2预处理对抗高浓度H2O2诱导细胞损伤的实验模型。应用甲氮甲唑蓝(MTT)法测定细胞的存活率,比色法测定乳酸脱氢酶(LDH)的活性,碘化丙啶(PI)染色流式细胞术检测细胞凋亡率,免疫印迹法(Westernblot)测定AKT的表达。结果 100μmol H2O2预处理PC12细胞90 min可显著地抑制300μmol H2O2引起的损伤,使细胞存活率从50.2%±4.6%升高至83.8%±3.5%,LDH活性由103%±10.2%下降至68.5%±5.3%,细胞凋亡率由65.5%±4.1%下降至37.1%±2.3%(P<0.01)。100μmol H2O2预处理诱导p-AKT的表达,PI3K抑制剂ly294002阻断了H2O2预处理引起的p-AKT表达。同时ly294002拮抗了H2O2预处理诱导的抗细胞损伤和凋亡作用。结论 H2O2预处理通过PI3K途径引起AKT的活化,PI3K/AKT通路的活化介导了H2O2预处理诱导的适应性细胞保护作用。     

酪氨酸磷酸酯酶抑制剂对tau蛋白磷酸化作用的研究

目的:探讨受体酪氨酸磷酸酯酶对大鼠海马tau蛋白磷酸化的影响。方法: 大鼠海马直接注射酪氨酸磷酸酯酶(PTP)抑制剂钒酸钠(PVN)或糖原合酶激酶(GSK-3)抑制剂氯化锂(LiCl),24h后用免疫印迹和免疫组织化学方法检测大鼠海马tau蛋白磷酸化水平。结果: PVN可以明显降低大鼠海马tau蛋白PHF-1位点磷酸化水平,且比LiCl的作用强(P<0.01),与LiCl联用使非磷酸化位点tau-1明显增强(P<0.05),总tau蛋白(R111d)含量显著降低(P<0.05)。结论: PTP抑制剂明显降低大鼠海马tau蛋白磷酸化, 其机制可能与GSK-3失活有关。     

贝利司他抑制骨肉瘤细胞活力的分子机制

目的:观察组蛋白脱乙酰酶抑制剂贝利司他对骨肉瘤细胞活力的影响,并初步研究其作用机制。方法:用不同浓度的贝利司他处理体外培养的骨肉瘤细胞系SAOS-2和U2OS后,采用MTT法检测细胞的活力,荧光探针和ELISA分别检测caspase-3/-7的酶活性以及DNA片段化以观察贝利司他对骨肉瘤细胞凋亡的影响,并采用Western blot检测组蛋白乙酰化水平、caspase-3、Bcl-xL和PTEN的表达,以及Akt和糖原合成酶激酶3β(GSK-3β)的磷酸化水平。用不同浓度的贝利司他和多柔比星(又称阿霉素)共同孵育U2OS和SAOS-2细胞,MTT观察其对细胞活力的影响,并计算其联合指数(CI)。结果:0.5、1、2.5和5μmol/L贝利司他处理U2OS和SAOS-2细胞48 h后,均可呈剂量依赖性方式抑制其活力,诱导DNA片段化,增强caspase-3/-7的活性,上调cleaved caspase-3水平,减少Bcl-xL的表达,促进细胞内组蛋白H3和H4乙酰化。Western blot结果显示,贝利司他处理后,U2OS和SAOS-2细胞中磷酸化Akt和GSK-3β水平显著降低(P<0.01)。MTT结果显示,贝利司他和阿霉素联合作用后,可进一步降低细胞的活力,两者之间具有协同作用(CI<1)。结论:贝利司他能协同阿霉素抑制骨肉瘤细胞活力,其机制可能与抑制Akt信号通路有关。     

Modulation of tau phosphorylation by the kinase PKR: implications in Alzheimer's disease

Double-stranded RNA dependent kinase (PKR) is a pro-apoptotic kinase that controls protein translation. Previous studies revealed that activated PKR is increased in brains with Alzheimer's disease (AD). Glycogen Synthase Kinase Aβ (GSK-3β) is responsible for tau phosphorylation and controls several cellular functions also including apoptosis. The goal of this work was to determine if PKR could concurrently trigger GSK-3β activation, tau phosphorylation and apoptosis. In AD brains, both activated kinases co-localize with phosphorylated tau in neurons. In SH-SY5Y cell cultures, tunicamycin and Aβ(1-42) activate PKR, GSK-3β and induce tau phosphorylation and all these processes are attenuated by PKR inhibitors or PKR siRNA. Our results demonstrate that neuronal PKR co-localizes with GSK-3β and tau in AD brains and is able to modulate GSK-3β activation, tau phosphorylation and apoptosis in neuroblastoma cells exposed to tunicamycin or Aβ. PKR could represent a crucial signaling point relaying stress signals to neuronal pathways leading to cellular degeneration in AD.     

Treadmill training regulates β-catenin signaling through phosphorylation of GSK-3β in lumbar vertebrae of ovariectomized rats

Postmenopausal osteoporosis is associated with high level of adipogenesis within the bone marrow at the expense of osteoblast population. The mechanical effect on β-catenin through phosphorylation of glycogen synthase kinase-3β (GSK-3β) is critical for inhibition of adipogenesis in mesenchymal stem cells in vitro. In present study, we hypothesized that treadmill training could regulate the β-catenin signaling through phosphorylation of GSK-3β in the lumbar vertebrae of ovariectomized (OVX) rats. 3-month-old female Sprague-Dawley rats were divided randomly into the following four groups: (a) Sham, (b) OVX, (c) OVX exercised (EX), and (d) OVX estrogen replacement (E(2)). At the end of the experiment, the serum levels of estradiol (E(2)) and luteinizing hormone (LH), the ultimate lumbar vertebra strength, as well as the protein expression for peroxisome proliferators-activated receptor γ (PPARγ), β-catenin, P-GSK-3β, and osterix (Osx) in lumbar vertebrae were analyzed. Moreover, the protein expression for β-catenin and P-GSK-3β were also examined in the uterus. The EX group had lower protein level of PPARγ, higher ultimate lumbar vertebral strength, and higher protein levels of β-catenin, and P-GSK-3β in lumbar vertebral bodies compared with sedentary OVX group. The effects of EX treatment on the protein levels of β-catenin and P-GSK-3β in bones were not reproducible in the uterus. Moreover, exercise treatment produced no estrogenic effect as evidenced by serum level of LH. In conclusion, this study suggested that treadmill training could activate the GSK-3β/β-catenin signaling and inhibit the production of PPARγ in lumbar vertebrae of OVX rats, which may contribute to the prevention of bone loss in OVX rats.     

雌激素对内皮素诱导心肌细胞肥大反应的影响及其机制

目的： 探讨雌激素（E₂）对内皮素-1（ET-1）诱导心肌细胞肥大反应的影响及其机制。方法： 以ET-1刺激体外培养的新生大鼠心肌细胞，建立心肌肥大细胞模型；观察E₂对ET-1诱导心肌细胞肥大反应的影响，并检测心肌细胞中ERK1/2活性的变化。结果： ET-1可使心肌细胞蛋白质含量、表面积和［³H］^-亮氨酸掺入显著增加，这些作用可被E₂明显抑制。E₂预处理抑制ET-1诱导的心肌细胞ERK1/2活性的增加。雌激素受体拮抗剂他莫昔芬（Ta）可抑制E₂对ET-1诱导的心肌细胞［³H］^-亮氨酸（［³H］^-Leu）掺入和ERK1/2活性的作用。MEK1/2抑制剂PD98059预处理使ET-1诱导的心肌细胞［³H］^-Leu掺入减少，使E2对ET-1诱导的心肌细胞肥大反应的抑制作用加强。结论： E₂通过雌激素受体抑制ET-1诱导的心肌细胞肥大反应，这一过程与ERK1/2信号转导途径有关。     

Neuroprotective effects of (±)-catechin against 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-induced dopaminergic neurotoxicity in mice

The neuroprotective effects of (±)-catechin against toxicity of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) were investigated in mice. MPTP caused the death of dopaminergic neurons in the substantia nigra and decreased the level of striatal dopamine. Additionally, MPTP increased the level of phospho-c-Jun, a known substrate of c-Jun N-terminal kinase (JNK) and caused a rapid activation of GSK-3β, evidenced by the decrease in the level of phospho-Ser9 of GSK-3β. However, pretreatment with (±)-catechin was found to protect dopaminergic neurons in the substantia nigra against MPTP toxicity, and restore the depletion of striatal dopamine in mice. (±)-Catechin attenuated the phosphorylation of c-Jun and recovered the phosphorylation of GSK-3β (Ser9). These results suggested that the suppression of JNK and GSK-3β signaling cascades might contribute to the neuroprotective effect of (±)-catechin against toxicity of MPTP.     

Estrogen Alleviates Acetic Acid-Induced Gastric or Colonic Damage via Both ERα- and ERβ-Mediated and Direct Antioxidant Mechanisms in Rats

In order to demonstrate the possible protective effects of estrogen receptor (ER)-α and ERβ receptor subtypes in the pathogenesis of colonic and gastric oxidant damage, experimental ulcer and colitis were induced by acetic acid, and the animals were randomly divided as colitis, ulcer, and their corresponding non-ulcer and non-colitis control groups. Each group of rats was treated intramuscularly with the vehicle, selective ERα agonist propylpyrazole-triol (1 mg/kg), ERβ agonist diarylpropionitrile (1 mg/kg), non-selective ER agonist 17β estradiol (E2; 1 mg/kg), or E2 plus non-selective ER antagonist ICI-182780 (1 mg/kg). The results revealed that induction of ulcer or colitis resulted in systemic inflammation as assessed by increased levels of plasma TNF-α and IL-6 levels. In both tissues, the presence of oxidant damage was verified by histological analysis and elevated myleoperoxidase activity. In the colitis and ulcer groups, both ER agonists and the non-selective E2 reversed the oxidative damage in a similar manner. These findings indicate that estrogen acts via both ERα- and ERβ-mediated and direct antioxidant mechanisms, where both ER subtypes play equal and efficient roles in the anti-inflammatory action of estrogen, in limiting the migration of neutrophils to the inflamed tissue, reducing the release and activation of cytokines and thereby alleviating tissue damage.     

17β-Estradiol regulates insulin-degrading enzyme expression via an ERβ/PI3-K pathway in hippocampus: Relevance to Alzheimer's prevention

Insulin-degrading enzyme (IDE), an enzyme that primarily degrades insulin, has recently been demonstrated to play a significant role in the catabolism of amyloid β (Aβ) protein in the brain. Reduced IDE expression and/or activity have been associated with the etiology and development of Alzheimer's disease (AD). Using three model systems, the present investigation provides the first documentation indicating that estrogen robustly regulates the expression of IDE in normal, menopausal and early-stage AD brains. In vitro analyses in primary cultures of rat hippocampal neurons revealed that 17β-estradiol (17β-E2) increased IDE in both mRNA and protein levels in a time-dependent manner. Further pharmacological analyses indicated that 17β-E2-induced IDE expression was dependent upon estrogen receptor (ER) β and required activation of phosphatidylinositol 3-kinase (PI3-K). In vivo analyses in adult female rats revealed a brain region-specific responsive profile. Ovariectomy (OVX) induced a significant decline in IDE expression in the hippocampus, which was prevented by 17β-E2. Neither OVX nor 17β-E2 affected IDE expression in the cerebellum. In vivo analyses in triple transgenic AD (3xTg-AD) female mice revealed an inverse correlation between the age-related increase in Aβ load and the decrease in IDE expression in the hippocampal formation. Treatment with 17β-E2 attenuated Aβ accumulation/plaque formation and elevated hippocampal IDE expression in 12-month-old 3xTg-AD OVX mice. Collectively, these findings indicate that 17β-E2 regulates IDE expression in a brain region-specific manner and such a regulatory role in the hippocampus, mediated by an ERβ/PI3-K pathway, could serve as a direct mechanism underlying estrogen-mediated preventative effect against AD when initiated at the onset of menopause.     

Roles of estrogen receptors alpha and beta in sexually dimorphic neuroprotection against glutamate toxicity

Although most agree that 17β-estradiol is neuroprotective via a variety of mechanisms, less is known about the role that biological sex plays in receptor-mediated estradiol neuroprotection. To address this issue we isolated primary cortical neurons from rat pups sorted by sex and assessed the ability of estradiol to protect the neurons from death induced by glutamate. Five-minute pretreatment with 10–50 nM 17β-estradiol protected female but not male neurons from glutamate toxicity 24 h later. Both estrogen receptor alpha (ERα) and estrogen receptor beta (ERβ) are expressed in these cultures. Experiments using an ERα selective agonist or antagonist indicate that this receptor is important for neuroprotection in female cortical neurons. The ERβ selective agonist conveys a small degree of neuroprotection to both male and female cortical neurons. Interestingly, we found that 17α estradiol and the novel membrane estrogen receptor (mER) agonist STX, but not bovine serum albumin conjugated estradiol or the GPR30 agonist G1 were neuroprotective in both male and female neurons. Taken together these data highlight a role for ERα in sexually dimorphic neuroprotection.     

在体转染GSK-3β引起tau蛋白在PHF-1位点的过度磷酸化

目的：探讨在体转染GSK-3β对tau蛋白在PHF-1位点磷酸化的影响。 方法： 21只大鼠随机分为GSK-3β转染组、空载体组和空白对照组3组：0.1 μg/3 μL GSK-3β-HA质粒和空载体分别注射入大鼠大脑，对照组大鼠不作处理，应用免疫印迹和免疫组织化学检测GSK-3β的表达，并应用磷酸化位点特异性抗体PHF-1检测tau蛋白的磷酸化水平。 结果： 转染48 h后，GSK-3β-HA表达在转染组；并且在转染区域的神经元内异常过度磷酸化tau蛋白（在PHF-1表位）聚积；异常过度磷酸化的tau蛋白与GSK-3β共定位。 结论： 在体转染GSK-3β引起导致神经退行性疾病发生机制相关的tau蛋白异常过度磷酸化，这进一步证明了GSK-3β是tau蛋白异常过度磷酸化的一个关键激酶，并且可作为一个防治与tau相关的神经退行性疾病的靶点。