人参皂苷对蛋白磷酸酶抑制剂冈田酸拟阿尔采末病细胞模型的影响

目的探讨人参皂苷(ginsenoside,GS)对蛋白磷酸酶抑制剂冈田酸(OA)诱导拟Alzheimer病(AD)细胞模型神经细胞tau蛋白的磷酸化、微管、细胞凋亡和凋亡调节因子的影响。方法GS与人神经母细胞瘤细胞系SK-N-SH细胞预孵育24h,弃去培养基,然后用OA10nmol·L-1与SK-N-SH细胞共孵育6h;用倒置显微镜观察细胞形态的变化,激光共聚焦显微镜观察微管变化,Western blot方法观察磷酸化tau蛋白、凋亡因子Bcl-2、Bax和Caspase-3的表达,用TUNEL法观察凋亡细胞的变化。结果正常SK-N-SH神经细胞铺展良好,OA模型组细胞突起断裂,GS显示了细胞保护作用。通过激光共聚焦显微镜观察,正常SK-N-SH细胞微管粗壮、连续,而OA模型组微管断裂、消失;GS能够减少OA引起的微管破坏作用。OA模型组tau蛋白Ser-199/202和Ser-404位点磷酸化水平较正常对照组明显增高,非磷酸化水平较正常对照组明显下降;GS 50mg·L-1和100mg·L-1组使神经细胞tau蛋白Ser-199/202和Ser-404位点磷酸化水平较OA模型组明显下降,GS 50mg·L-1和100mg·L-1组的tau蛋白Ser202非磷酸化水平较模型组则明显升高;正常对照组未见凋亡细胞;OA模型组凋亡细胞明显增多,Bax和Caspase-3表达水平较正常对照组明显增高,Bcl-2水平明显下降;GS能够明显抑制OA诱导的细胞凋亡,减少Bax和Caspase-3表达。结论人参皂苷对蛋白磷酸酶抑制剂OA所致的神经细胞病理变化有明显的保护作用,可能是通过抑制tau蛋白过度磷酸化,防止细胞凋亡来发挥作用的,提示该药在防治AD方面可能具有良好的应用前景。     

Silica nanoparticles induced intrinsic apoptosis in neuroblastoma SH-SY5Y cells via CytC/Apaf-1 pathway

The present study was to investigate effects of Silica nanoparticles (SiNPs) on nervous system and explore potential mechanisms in human neuroblastoma cells (SH-SY5Y). Cytotoxicity was detected by cell viability and Lactate dehydrogenase (LDH) release. Flow cytometry analysis was applied to assess mitochondrial membrane potential (MMP) loss, intracellular Ca²⁺ and apoptosis. To clarify the mechanism of SiNPs-induced apoptosis, intrinsic apoptosis-related proteins were detected. Our results showed that SiNPs caused cytotoxicity, cell membrane damage and Ca²⁺ increase in a dose-dependent manner in SH-SY5Y cells. Both the mitochondrial membrane potential (MMP) loss and potential mitochondria damage resulted in Cyt C release to the cytoplasm. The elevated Cyt C and Apaf1 further triggered intrinsic apoptosis via executive molecular caspase-9 and caspase-3. The present study confirmed that SiNPs induced intrinsic apoptosis in neuroblastoma SH-SY5Y cells via CytC/Apaf-1 pathway and provided a better understanding of the potential toxicity induced by SiNPs on human neurocyte.     

山茱萸环烯醚萜苷对蛋白磷酸酶抑制剂冈田酸拟阿尔采末病细胞模型的作用

目的探讨中药山茱萸环烯醚萜苷(COIG)对蛋白磷酸酶2A和1(PP2A和PP1)抑制剂冈田酸(okadaicacid,OA)拟阿尔采末病细胞模型tau蛋白过度磷酸化水平和细胞微管的影响。方法COIG与人神经母细胞瘤细胞系SKNSH细胞预孵育24h,再用OA10nmol·L-1与SKNSH细胞共孵育6h,在显微镜下观测细胞形态变化,用Westernblot方法观察磷酸化和非磷酸化tau蛋白表达,用间接免疫荧光法观察神经细胞微管的变化。结果正常SKNSH细胞铺展良好,OA模型组细胞变圆,突起断裂;OA模型组tau蛋白ser199/202和ser404位点磷酸化水平较正常对照组明显增高,非磷酸化水平下降;OA模型组细胞微管平均面积较正常对照组明显减少。COIG(100和200mg·L-1)给药组细胞形态基本恢复正常,tau蛋白ser199/202和ser404位点磷酸化水平较OA模型组明显下降、非磷酸化水平升高,细胞微管平均面积比模型组明显增大。结论山茱萸环烯醚萜苷能够抑制神经细胞tau蛋白过度磷酸化,保护细胞微管结构,因此可能具有治疗AD的应用前景。     

Chlorzoxazone exhibits neuroprotection against Alzheimer’s disease by attenuating neuroinflammation and neurodegeneration in vitro and in vivo

Alzheimer’s disease (AD), a complex and an age-related brain disease, is induced by the accumulation of amyloid beta (Aβ) and neuroinflammation. Chlorzoxazone (CZ) is a classical FDA-approved drug, and shows anti-inflammatory effects. However, up until now, its regulatory role in AD has not been investigated. Therefore, in this study we attempted to explore if CZ could be an effective therapeutic strategy for AD treatment. At first, the in vitro study was performed to mimic AD using Aβ. We found that Aβ caused p65 nuclear translocation in both primary microglial cells and astrocytes, which were, however, restrained by CZ treatments. Meanwhile, CZ incubation markedly decreased the expression of pro-inflammatory cytokines including tumor necrosis factor α (TNF-α), interleukin-1β (IL-1β). Aβ deposition was also markedly reduced in glial cells treated with CZ. Importantly, we found that glial activation and its-related pro-inflammation induced by Aβ led to obvious neurodegeneration and neuroinflammation, which were effectively attenuated by CZ pre-treatment in the isolated primary cortical neurons. Then, the in vivo study was performed using APP/PS1 mice with AD. Behavior tests showed that CZ administration effectively improved cognitive deficits in AD mice. Neuron death in hippocampus of AD mice was also inhibited by CZ. Aβ accumulation in brain was markedly decreased in CZ-treated AD mice. We finally found that hippocampal glial activation in AD mice was obviously blocked by CZ supplementation, along with remarkable decreases in TNF-α, IL-1β and p65 nuclear translocation. Together, these findings above demonstrated that CZ could inhibit glial activation and inflammatory response, contributing to the suppression of neurodegeneration and neuroinflammation. Therefore, CZ may be an effective therapeutic strategy for AD treatment.     

Glycogen synthase kinase-3β2 has lower phosphorylation activity to tau than glycogen synthase kinase-3β1

Glycogen synthase kinase-3β (GSK-3β) is a serine/threonine kinase that phosphorylate protein substrates involved in Alzheimer's disease (AD), such as microtubule-associated protein tau and amyloid precursor protein (APP). GSK-3β consists of two splice variants; the major short form (GSK-3β1) distributes in many organs and the minor long form (GSK-3β2), whose structural difference is the insert of only 13 amino acid residues to the C-terminal side of the catalytic site of GSK-3β1, is present in central nervous system. However, the physiological significances of the two variants are unclear. Here we examined whether the phosphorylation activities of two variants to tau and APP are different in cells. We found that GSK-3β2 has lower phosphorylation activity to tau at AD-relevant epitope (Ser396) than GSK-3β1 in cells, whereas the two variants exhibit equivalent levels of phosphorylation activities to APP. Recombinant GSK-3β2 has also lower phosphorylation activity to tau than GSK-3β1 in vitro, although the phosphorylation activities of the two variants to a synthetic peptide substrate pGS-2 are comparable. Furthermore, the deletion of the C-terminal tail (CT) of GSK-3β2 resulted in considerable reduction of tau phosphorylation activity as compared with GSK-3β1, suggesting that the lower phosphorylation activity of GSK-3β2 to tau is attributed to weak interaction with tau through its unique higher-order structure of CT constructed by the 13 amino acids insertion. Such information may provide a clue for understanding of the physiological significance of the two splice variants of GSK-3β and a new insight into the regulation of tau phosphorylation in central nervous system.     

IGF-I receptor signaling pathway is involved in the neuroprotective effect of genistein in the neuroblastoma SK-N-SH cells

Genistein, an isoflavone naturally found in soy products, displays estrogenic properties. Our previous study clearly demonstrated that genistein can activate the insulin-like growth factor-I receptor (IGF-IR) signaling pathway in human breast cancer MCF-7 cells. The present study aims to test the hypothesis that the IGF-I receptor signaling pathway is involved in the neuroprotective effects of genistein in neuroblastoma SK-N-SH cells. Our results revealed that pretreatment with genistein resulted in an enhancement in the survival of human neuroblastoma SK-N-SH cells against 6-hydroxydopamine (6-OHDA)-induced neurotoxicity. 6-OHDA arrested the cells at G(0)G(1) phase and prevented S phase entry. Genistein pretreatment could reverse the cytostatic effect of 6-OHDA on cell cycle. The decreased mitochondrial membrane potential induced by 6-OHDA could be also reversed by genistein pretreatment. These effects could be completely blocked by co-treatment with JB-1, which is the specific antagonist of the IGF-I receptor. Furthermore, genistein pretreatment restored the 6-OHDA-induced up-regulation of Bax and down-regulation of Bcl-2 mRNA and protein expression. Genistein treatment alone could significantly increase the phosphorylation level of MEK and induce ERE luciferase activity. Co-treatment with IGF-I could enhance the effect of genistein on cell proliferation and MEK phosphorylation. This study provides the first evidence that genistein has neuroprotective effects against 6-OHDA-induced neurotoxicity in SK-N-SH cells and activation of the IGF-I receptor signaling pathway might be involved in actions of genistein.     

Perfluorooctane sulfonate (PFOS) impairs the proliferation of C17.2 neural stem cells via the downregulation of GSK‐3β/β‐catenin signaling

The neurotoxic effects of perfluorooctane sulfonate (PFOS) have attracted significant research attention in recent years. In the present study, we investigated the impact of PFOS exposure on the physiology of neural stem cells (NSCs) in vitro. We showed that PFOS exposure markedly attenuated the proliferation of C17.2 neural stem cells in both dose‐ and time‐dependent manners. Additionally, we found that PFOS decreased Ser9 phosphorylation of glycogen synthase kinase‐3β (pSer9‐GSK‐3β), leading to the activation of GSK‐3β and resultant downregulation of cellular β‐catenin. Furthermore, blockage of GSK‐3β with lithium chloride significantly attenuated both the PFOS‐induced downregulation of GSK‐3β/β‐catenin and the proliferative impairment of C17.2 cells. Notably, the expression of various downstream targets was altered accordingly, such as c‐myc, cyclin D1 and survivin. In conclusion, the present study demonstrated that PFOS decreased the proliferation of C17.2 cells via the negative modulation of the GSK‐3β/β‐catenin pathway. We present the potential mechanisms underlying the PFOS‐induced toxic effects on NSCs to provide novel insights into the neurotoxic mechanism of PFOS. Copyright © 2016 John Wiley & Sons, Ltd.     

Resveratrol alleviates amyloid β-induced neuronal apoptosis,inflammation, and oxidative and endoplasmic reticulum stress by circ_0050263/miR-361-3p/PDE4A axis during Alzheimer's disease

Resveratrol (Res) has been identified to reduce neurodegeneration. Circular RNAs (circRNAs) are stable noncoding RNAs that are considered to be ideal biomarkers for molecular targeting treatment. Here, this study focused on investigating the function and relationship of circ_0050263 and Res in Alzheimer's Disease (AD). Human neuroblastoma cell line SK-N-SH was exposed to amyloid-β (Aβ) to induce AD cell model in vitro. Cell viability, apoptosis, and inflammatory reaction were evaluated by CCK-8 assay, flow cytometery, and ELISA analysis. The oxidative stress and endoplasmic reticulum stress (ERS) were determined by detecting related markers. Levels of genes and proteins were detected by qRT-PCR and Western blot. Dual-luciferase reporter assay was adopted to verify the binding between miR-361-3p and circ_0050263 or PDE4A (Phosphodiesterase 4A). Subsequently, we found that Res treatment alleviated Aβ-induced apoptosis, inflammatory response, oxidative stress, and ERS in SK-N-SH cells. Circ_0050263 is a stable circRNA, which was increased by Aβ, but decreased by Res in SK-N-SH cells. Circ_0050263 overexpression reversed Res-induced neuroprotective effects. Mechanistically, circ_0050263 acted as a sponge for miR-361-3p, which targeted PDE4A. Circ_0050263 silencing abated Aβ-induced neuronal injury, which were counteracted by following PDE4A overexpression. Moreover, PDE4A upregulation could attenuate Res-mediated neuroprotective effects. In all, Res alleviated Aβ-induced neuronal apoptosis, inflammation, oxidative stress, and ERS via circ_0050263/miR-361-3p/PDE4A axis, providing new insights for AD therapy.     

智脑胶囊调控PI3K/AKT/GSK-3β信号通路诱导阿尔茨海默病模型细胞增殖的研究

目的:探讨智脑胶囊(Zhinao Capsule,ZNC)对阿尔茨海默病(Alzheimer's disease,AD)体外细胞模型增殖的影响及其作用机制。方法:采用全反式维甲酸(all trans retinoic acid,ATRA)+冈田酸(okadaic acid,OA)刺激人神经母细胞瘤细胞(human neuroblastoma cell,SK-N-SH)建立AD体外模型,CCK8法筛选ZNC含药血清最佳作用浓度和时间;流式细胞术、RT-qPCR和Western blot法检测最佳浓度ZNC含药血清作用最佳时间后,对SK-N-SH细胞周期、凋亡及PI3K、AKT、GSK-3β mRNA、总蛋白和磷酸化蛋白表达的影响。结果:ATRA＋OA刺激后,SK-N-SH细胞活力降低,细胞凋亡增加,p-PI3K、p-AKT和p-GSK-3β蛋白表达显著降低,GSK-3β mRNA和总蛋白表达明显升高;给予ZNC干预后,不仅可明显促进SK-N-SH细胞增殖,抑制其凋亡,还可显著升高p-PI3K、p-AKT和p-GSK-3β蛋白表达,降低GSK-3β mRNA和总蛋白表达。结论:智脑胶囊可促进AD模型细胞增殖,其机制可能与调控PI3K/AKT/GSK-3β信号通路有关。     

Curcumin mediates presenilin-1 activity to reduce β-amyloid production in a model of Alzheimer's Disease

Curcumin has been reported to inhibit the generation of Aβ, but the underlying mechanisms by which this occurs remain unknown. Aβ is thought to play an important role in the pathogenesis of Alzheimer's disease (AD). The amyloid hypothesis argues that aggregates of Aβ trigger a complex pathological cascade that leads to neurodegeneration. Aβ is generated by the processing of APP (amyloid precursor protein) by β- and γ-secretases. Presenilin 1 (PS1) is central to γ-secretase activity and is a substrate for GSK-3β, both of which are implicated in the pathogenesis of AD. The present study aimed to investigate the effects of curcumin on the generation of Aβ in cultured neuroblastoma cells and on the in vitro expression of PS1 and GSK-3β. To stimulate Aβ production, a plasmid expressing APP was transfected into human SH-SY5Y neuroblastoma cells. The transfected cells were then treated with curcumin at 0-20 μM for 24 h or with 5 μM curcumin for 0-48 h, and the extracellular levels of Aβ(40/42) were determined by ELISA. The levels of PS1 and GSK-3β mRNA were measured by RT-PCR, and the expression of the PS1 and GSK-3β proteins (including the phosphorylated form of GSK-3β, p-GSK-3β-Ser9) were evaluated by western blotting. Curcumin treatment was found to markedly reduce the production of Aβ(40/42). Treatment with curcumin also decreased both PS1 and GSK-3β mRNA and protein levels in a dose- and time-dependent manner. Furthermore, curcumin increased the inhibitory phosphorylation of GSK-3β protein at Ser9. Therefore, we propose that curcumin decreases Aβ production by inhibiting GSK-3β-mediated PS1 activation.     

Low-dose exposure of silica nanoparticles induces cardiac dysfunction via neutrophil-mediated inflammation and cardiac contraction in zebrafish embryos

The toxicity mechanism of nanoparticles on vertebrate cardiovascular system is still unclear, especially on the low-level exposure. This study was to explore the toxic effect and mechanisms of low-dose exposure of silica nanoparticles (SiNPs) on cardiac function in zebrafish embryos via the intravenous microinjection. The dosage of SiNPs was based on the no observed adverse effect level (NOAEL) of malformation assessment in zebrafish embryos. The mainly cardiac toxicity phenotypes induced by SiNPs were pericardial edema and bradycardia but had no effect on atrioventricular block. Using o-Dianisidine for erythrocyte staining, the cardiac output of zebrafish embryos was decreased in a dose-dependent manner. Microarray analysis and bioinformatics analysis were performed to screen the differential expression genes and possible pathway involved in cardiac function. SiNPs induced whole-embryo oxidative stress and neutrophil-mediated cardiac inflammation in Tg(mpo:GFP) zebrafish. Inflammatory cells were observed in atrium of SiNPs-treated zebrafish heart by histopathological examination. In addition, the expression of TNNT2 protein, a cardiac contraction marker in heart tissue had been down-regulated compared to control group using immunohistochemistry. Confirmed by qRT-PCR and western blot assays, results showed that SiNPs inhibited the calcium signaling pathway and cardiac muscle contraction via the down-regulated of related genes, such as ATPase-related genes (atp2a1l, atp1b2b, atp1a3b), calcium channel-related genes (cacna1ab, cacna1da) and the regulatory gene tnnc1a for cardiac troponin C. Moreover, the protein level of TNNT2 was decreased in a dose-dependent manner. For the first time, our results demonstrated that SiNPs induced cardiac dysfunction via the neutrophil-mediated cardiac inflammation and cardiac contraction in zebrafish embryos.     

氟丙胺磷对人成神经细胞瘤SK-N-SH细胞分化的毒性机制

目的研究诱发迟发性神经病的氟丙胺磷对人成神经细胞瘤SK-N-SH细胞分化的影响及其作用机理。方法MTT法测定细胞增殖,全反式维A酸诱导细胞分化,显微测量有机磷酸酯对细胞分化的影响,比色法测定NTE活力和Western印迹分析总的和磷酸化的神经纤丝重链蛋白以及肌动蛋白的表达。结果50μmol·L-1对氧磷和氟丙胺磷对细胞增殖没有影响;此浓度下对氧磷不抑制细胞的分化,而氟丙胺磷抑制细胞分化;氟丙胺磷抑制神经病靶标酯酶,而对氧磷对其不抑制;氟丙胺磷抑制总的和磷酸化的神经纤维丝重链蛋白的表达,而对氧磷对两种状态的神经纤维丝重链蛋白没有明显的作用。对氧磷和氟丙胺磷对肌动蛋白的表达都无影响。结论氟丙胺磷对人成神经细胞瘤细胞分化的抑制是通过对总的和磷酸化的神经纤维丝重链蛋白表达的抑制实现的,并伴随着神经病靶标酯酶的抑制。     

Testosterone replacement therapy promotes angiogenesis after acute myocardial infarction by enhancing expression of cytokines HIF-1a, SDF-1a and VEGF

Soluble amyloid β-protein (Aβ) oligomers are primary mediators of synaptic dysfunction associated with the progression of Alzheimer's disease. Such Aβ oligomers exist dependent on their rates of aggregation and metabolism. Use of selective somatostatin receptor-subtype agonists have been identified as a potential means to mitigate Aβ accumulation in the brain, via regulation of the enzyme neprilysin. Herein, we first evaluated the impact of the somatostatin receptor subtype-4 agonist 1-[3-[N-(5-Bromopyridin-2-yl)-N-(3,4-dichlorobenzyl)amino]propyl]-3-[3-(1H-imidazol-4-yl)propyl]thiourea (NNC 26-9100) on learning and memory in 12-month SAMP8 mice (i.c.v. injection). NNC 26-9100 (0.2 μg-dose) was shown to enhance both learning (T-maze) and memory (object recognition) compared to vehicle controls. Cortical and hippocampal tissues were evaluated subsequent to NNC 26-9100 (0.2 μg) or vehicle administration for changes in neprilysin activity, along with protein expression of amyloid-precursor protein (APP), neprilysin, and Aβ???? oligomers within respective cellular fractions (extracellular, intracellular and membrane). NNC 26-9100 increased neprilysin activity in cortical tissue, with an associated protein expression increase in the extracellular fraction and decreased in the intracellular fraction. A decrease in intracellular APP expression was found with treatment in both cortical and hippocampal tissues. NNC 26-9100 also significantly decreased expression of Aβ???? trimers within both the extracellular and intracellular cortical fractions. No expression changes were found in membrane fractions for any protein. These finding suggest the potential use of selective SSTR4 agonists to mitigate toxic oligomeric forms of Aβ???? in critical regions of the brain identified with learning and memory decline.     

Emerging amyloid beta (Ab) peptide modulators for the treatment of Alzheimer's disease (AD)

Background: According to the ‘amyloid cascade hypothesis’ of Alzheimer's disease (AD), abnormal processing of beta-amyloid precursor protein (βAPP) into toxic amyloid beta (Aβ)-peptides is central to the etiopathology of this uniquely human brain disorder. Objective: To review current AD drugs, pharmacological approaches and strategies aimed at modulating Aβ-peptide generation and/or aggregation in the treatment of AD. Methods: Data searches at various websites: Alzheimer Research Forum; individual drug company databases; Medline; Pharmaprojects database; unpublished research; inter-University research communications. Results/conclusion: Considerable research effort has focused on secretase-mediated mechanisms of βAPP processing, and the latest pharmacological strategies have used selective Aβ-peptide-lowering agents (SALA) to provide therapeutic benefit against Aβ-initiated neurodegenerative pathology. Currently, dedicated anticholinesterase, glutamatergic agonist and Aβ-peptide immunization have had little impact in the clinical treatment of AD. One unexpected benefit of statins (HMG-CoA inhibitors), besides their cholesterol lowering abilities, has been their ancillary effects in potentiating the enzymatic mechanisms that generate Aβ-peptides. The long-term benefits or complications of statin-based therapies for use in the clinical management of AD are not known.     

氯化锂抑制β-淀粉样蛋白诱导细胞Tau蛋白磷酸化

目的探讨GSK-3β抑制剂氯化锂(LiCl)在β-淀粉样蛋白25～35片断(Aβ25-35)诱导的细胞Tau蛋白磷酸化中的作用及机制。方法MTT法观察不同浓度的LiCl(1、5、10、20mmol.L-1)单独作用24h,对SH-SY5Y细胞存活率的影响;20μmol.L-1的凝聚态Aβ25-35作用于SH-SY5Y细胞不同时间点,蛋白免疫印迹法研究Tau蛋白磷酸化位点(Ser199、Ser396及Tau1)水平的变化;LiCl(20mmol.L-1)预处理细胞1h后,观察Aβ的作用有无变化及可能的作用机制。结果不同浓度的LiCl作用24h后,MTT法示细胞存活率无明显变化(P>0.05);20μmol.L-1Aβ25-35作用不同时间点后,Tau蛋白在Ser396、Ser199位点的磷酸化水平在3h逐渐增加,6h达到最高峰,12h后又逐渐下降,在这3个时间点的增加量均具有统计学意义(P<0.05),而对非磷酸化Tau1没有影响(P>0.05);LiCl预处理可抑制Aβ25-35的作用(P<0.05),并可诱导失活形式的GSK-3β在Ser9位点的磷酸化(p-GSK-3βSer9)表达增高。结论GSK-3β参与了Aβ25-35诱导细胞Tau蛋白磷酸化的作用,LiCl可通过诱导失活形式的p-GSK-3βSer9表达增高而抑制GSK-3β的活性,进而抑制Aβ诱导的细胞Tau蛋白磷酸化。该实验为研究AD的发病机制及探索有效治疗药物提供了重要的理论基础。     

Icariin attenuates β-amyloid-induced neurotoxicity by inhibition of tau protein hyperphosphorylation in PC12 cells

Alzheimer’s disease (AD) is a neurodegenerative disease characterized by the progressive loss of neurons and production of β-amyloid proteins (Aβ). Hyperphosphorylation of tau protein is proposed to be an early event for the evolution of AD, and may play an important role in Aβ-induced neurodegeneration. Icariin, a flavonoid compound from the herb Epimedium brevicornum Maxim, exerts a protective effect on learning and memory abilities in Aβ_25-35-induced AD rats. However, the molecular mechanism of icariin-induced neuroprotective effect against tau protein hyperphosphorylation, which is one of the most representative hallmarks in AD, is still unknown. In the present study, we investigated the inhibitory effect of icariin on Aβ_25-35-induced tau protein hyperphosphorylation on PC12 cells. The results showed that treatment with icariin significantly decreased Aβ_25-35-induced cytotoxity and apoptosis rate through inhibiting tau protein hyperphosphorylation at Ser396, Ser404 and Thr205 sites, respectively. Mechanism study showed that icariin could activate PI3K/Akt signaling pathway, resulting in an inhibitory effect on glycogen synthase kinase (GSK)-3β, which is an important kinase response for tau protein hyperphosphorylation in the development of AD. These observations indicate that icariin is capable of attenuating Aβ_25-35-induced tau protein hyperphosphorylation and promoting survival of neuronal cells, meanwhile also provide some insights into the potential signaling pathway that is involved. Thus, this study promises a great potential agent for Alzheimer’s disease and other tau pathology-related neuronal degenerative diseases.     

Substance P activates ADAM9 mRNA expression and induces α-secretase-mediated amyloid precursor protein cleavage

Altered levels of Substance P (SP), a neuropeptide endowed with neuroprotective and anti-apoptotic properties, were found in brain areas and spinal fluid of Alzheimer's disease (AD) patients. One of the hallmarks of AD is the abnormal extracellular deposition of neurotoxic beta amyloid (Aβ) peptides, derived from the proteolytic processing of amyloid precursor protein (APP). In the present study, we confirmed, the neurotrophic action of SP in cultured rat cerebellar granule cells (CGCs) and investigated its effects on APP metabolism. Incubation with low (5 mM) potassium induced apoptotic cell death of CGCs and amyloidogenic processing of APP, whereas treatment with SP (200 nM) reverted these effects via NK1 receptors. The non-amyloidogenic effect of SP consisted of reduction of Aβ(1-42), increase of sAPPα and enhanced α-secretase activity, without a significant change in steady-state levels of cellular APP. The intracellular mechanisms whereby SP alters APP metabolism were further investigated by measuring mRNA and/or steady-state protein levels of key enzymes involved with α-, β- and γ-secretase activity. Among them, Adam9, both at the mRNA and protein level, was the only enzyme to be significantly down-regulated following the induction of apoptosis (K5) and up-regulated after SP treatment. In addition to its neuroprotective properties, this study shows that SP is able to stimulate non-amyloidogenic APP processing, thereby reducing the possibility of generation of toxic Aβ peptides in brain.     

The miR-124 regulates the expression of BACE1/β-secretase correlated with cell death in Alzheimer's disease

The role of miR-124 on the expression of β-site APP cleaving enzyme 1 (BACE1), an important cleavager of amyloid precursor protein that plays a pivotal role in the β-amyloid production, was studied in this paper using cellular models for Alzheimer’ disease (AD) of cultured PC12 cell lines and primary cultured hippocampal neurons. The aim of the present study was to uncover novel potential miR-124 targets and shed light on its function in the cellular AD model. MiR-124 expression was steadily altered when its mimic and inhibitor were transfected in vitro. The results showed the expression of BACE1, one of the potential functional downstream targets of miR-124, was well correlated with cell death induced by Aβ neurotoxicity, and its expression level could be up- and down-regulated by suppression or over expression of miR-124 level respectively. These findings suggest that miR-124 may work as a basilic regulating factor to alleviate cell death in the process of AD by targeting BACE1, play an essential role in the control of BACE1 gene expression, and might be considered as a novel therapeutic target in treating AD.