Phosphorylated tau as a toxic agent in synaptic mitochondria: implications in aging and Alzheimer’s disease

During normal aging,there is a decline in all physiological functions in the organism.One of the most affected organs is the brain,where neurons lose their proper synaptic function leading to cognitive impairment.Aging is one of the main risk factors for the development of neurodegenerative diseases,such as Alzheimer’s disease.One of the main responsible factors for synaptic dysfunction in aging and neurodegenerative diseases is the accumulation of abnormal proteins forming aggregates.The most studied brain aggregates are the senile plaques,formed by Aβpeptide;however,the aggregates formed by phosphorylated tau protein have gained relevance in the last years by their toxicity.It is reported that neurons undergo severe mitochondrial dysfunction with age,with a decrease in adenosine 5′-triphosphate production,loss of the mitochondrial membrane potential,redox imbalance,impaired mitophagy,and loss of calcium buffer capacity.Interestingly,abnormal tau protein interacts with several mitochondrial proteins,suggesting that it could induce mitochondrial dysfunction.Nevertheless,whether tau-mediated mitochondrial dysfunction occurs indirectly or directly is still unknown.A recent study of our laboratory shows that phosphorylated tau at Ser396/404(known as PHF-1),an epitope commonly related to pathology,accumulates inside mitochondria during normal aging.This accumulation occurs preferentially in synaptic mitochondria,which suggests that it may contribute to the synaptic failure and cognitive impairment seen in aged individuals.Here,we review the main tau modifications promoting mitochondrial dysfunction,and the possible mechanism involved.Also,we discuss the evidence that supports the possibility that phosphorylated tau accumulation in synaptic mitochondria promotes synaptic and cognitive impairment in aging.Finally,we show evidence and argue about the presence of phosphorylated tau PHF-1 inside mitochondria in Alzheimer’s disease,which could be considered as an early event in the neurodegenerative process.Thus,phosphorylated tau PHF-1 inside the mitochondria could be considered such a potential therapeutic target to prevent or attenuate age-related cognitive impairment.

Tau protein,phosphorylated tau protein,and beta-amyloid 42 levels in patients with neurodegenerative diseases complicated by cognitive deficits A non-randomized,concurrent,case-control investigation

BACKGROUND： The differential diagnosis of many neurodegenerative disorders depends primarily on clinical symptoms together with imaging methods. Recently, increased importance has been placed on the use of biomarkers for diagnosing various neurodegenerative disorders. OBJECTIVE： To assess the feasibility of tau-protein, phosphorylated tau-protein, beta-amyloid 42 （Aβ42）, and 14-3-3 protein as biomarkers for diagnosing several neurodegenerative diseases complicated by cognitive deficits. DESIGN, TIME AND SETTING： A non-randomized, concurrent, case-control investigation was performed in three medical centers in the Czech Republic （Department of Neurology at the University Hospital in Hradec Kralove, Department of Neurology at the 2rd Medical Faculty, and the University Hospital Motol） between October 2000 and November 2006. PARTICIPANTS： Eighteen patients with probable AIzheimer＇s disease, 4 patients with Creutzfeldt-Jakob disease, 10 patients with frontotemporal dementia, 9 patients with clinically isolated syndrome suggestive of multiple sclerosis, and 7 patients with multiple sclerosis, as well as 38 race-, nationality-, and age-matched cognitively intact controls, were included in the study. Diagnoses were established based on the following criteria： the criteria for Alzheimer＇s disease proposed by the National Institute of Neurological and Communicative Disorders and Stroke/Alzheimer＇s Disease and Related Disorders Association, WHO criteria for Creutzfeldt-Jakob disease, Neary criteria for frontotemporal dementia, and McDonald＇s criteria for multiple sclerosis. All included patients were confirmed to suffer from various degrees of dementia. METHODS： Enzyme-linked immunosorbent assay was used to measure concentrations of tau-protein, phosphorylated tau-protein, and Aβ42 in cerebrospinal fluid （CSF） samples collected by standard lumbar puncture from each patient. Moreover, 14-3-3 protein was assessed by Western blot in CSF of Creutzfeldt-Jakob disease patients. Cognitive status was assessed using the Mini Mental Scale Examination （MMSE） in all subjects. MAIN OUTCOME MEASURES： Establishment of biomarkers with greatest specificity and sensitivity for the investigated disorders according to Receiver Operating Characteristic curves, which were based on values from patients and controls; correlation between concentrations of given biomarkers and demographic parameters, diagnosis, duration of disease, and level of cognitive deficit. RESULTS： Increased concentrations of total tau protein and phosphorylated tau protein, and decreased levels of Aβ42, in CSF of Alzheimer＇s disease patients reached the required sensitivity/specificity ratio of 80% or greater. A marked elevation in CSF concentrations of total tau protein showed even greater sensitivity than 14-3-3 protein in Creutzfeldt-Jakob disease. There was no association between selected biomarkers and frontotemporal dementia or multiple sclerosis. Phosphorylated tau-protein was the only biomarker that noticeably correlated with MMSE scores for Alzheimer＇s disease.CONCLUSION： Levels of total tau protein, phosphorylated tau protein, and A!342 in the CSF could differentiate patients with Alzheimer＇s disease and Creutzfeldt-Jakob disease from healthy controls and patients with other neurodegenerative disorders. The diversity of absolute values demonstrates the necessity to establish a specific standard for each laboratory.

Ultrasensitive assays for detection of plasma tau and phosphorylated tau 181 in Alzheimer's disease:a systematic review and meta-analysis

A lack of convenient and reliable biomarkers for diagnosis and prognosis is a common challenge for neurodegenerative diseases such as Alzheimer's disease(AD).Recent advancement in ultrasensitive protein assays has allowed the quantification of tau and phosphorylated tau proteins in peripheral plasma.Here we identified 66 eligible studies reporting quantification of plasma tau and phosphorylated tau 181(ptau181)using four ultrasensitive methods.Meta-analysis of these studies confirmed that the AD patients had significantly higher plasma tau and ptau181 levels compared with controls,and that the plasma tau and ptau181 could predict AD with high-accuracy area under curve of the Receiver Operating Characteristic Therefore,plasma tau and plasma ptau181 can be considered as biomarkers for AD diagnosis.

cPKCγ Deficiency Exacerbates Autophagy Impairment and Hyperphosphorylated Tau Buildup through the AMPK/mTOR Pathway in Mice with Type 1 Diabetes Mellitus

Type 1 diabetes mellitus(T1DM)-induced cognitive dysfunction is common,but its underlying mechanisms are still poorly understood.In this study,we found that knockout of conventional protein kinase C(cPKC)γsignificantly increased the phosphorylation of Tau at Ser214 and neurofibrillary tangles,but did not affect the activities of GSK-3βand PP2A in the hippocampal neurons of T1DM mice.cPKCγdeficiency significantly decreased the level of autophagy in the hippocampal neurons of T1DM mice.Activation of autophagy greatly alleviated the cognitive impairment induced by cPKCγdeficiency in T1DM mice.Moreover,cPKCγdeficiency reduced the AMPK phosphorylation levels and increased the phosphorylation levels of mTOR in vivo and in vitro.The high glucose-induced Tau phosphorylation at Ser214 was further increased by the autophagy inhibitor and was significantly decreased by an mTOR inhibitor.In conclusion,these results indicated that cPKCγpromotes autophagy through the AMPK/mTOR signaling pathway,thus reducing the level of phosphorylated Tau at Ser214 and neurofibrillary tangles.

Specific serum antibody binding to phosphorylated and non-phosphorylated tau in non-cognitively impaired,mildly cognitively impaired,and Alzheimer’s disease subjects:an exploratory study

Background:Tau vaccination and administration of anti-tau antibodies can prevent pathology and cognitive impairment in transgenic mouse models of tauopathy,suggesting that therapies which increase anti-tau antibodies might slow the development and/or progression of Alzheimer’s disease(AD).The extent to which individuals with no cognitive impairment(NCI)possess serum anti-tau antibodies,and whether their concentrations of these antibodies differ from anti-tau antibody levels in persons with mild cognitive impairment(MCI)or AD,are unclear.Previous studies measuring these antibodies did not account for antibody polyvalent binding,which can be extensive,nor that antibody binding to phosphorylated tau peptides could be due to binding to non-phosphorylated epitopes on those peptides.Methods:An ELISA controlling for these factors was used to measure the specific binding of serum IgG and IgM to phosphorylated(“pTau;”phosphorylated at Serine-199 and Serine-202)and non-phosphorylated(“non-pTau”)tau 196-207 in subjects with NCI,MCI,or AD(n=10/group).Between-group differences in these antibody levels were evaluated for statistical significance,and correlations were examined in pooled data from all subjects between these antibody levels and subject age,global cognitive functioning,and NFT counts.Results:Specific IgG binding to pTau and non-pTau was detected in all subjects except for one NCI control.Specific IgM binding was detected to pTau in all subjects except for two AD patients,and to non-pTau in all subjects.Mean pTau IgG was increased in MCI subjects by 53% and 70% vs.AD and NCI subjects respectively(both p<0.05),while no significant differences were found between groups for non-pTau IgG(p=0.052),pTau IgM,or non-pTau IgM.Non-pTau IgG was negatively associated with global cognition(Spearman rho=−0.50).Conclusions:Specific binding of serum IgG and IgM to phosphorylated and non-phosphorylated tau may be present in older persons regardless of their cognitive status.Serum IgG to phosphorylated tau may be increased in individuals with MCI,but this unexpected finding requires confirmation.The approach used in this study to measure specific serum antibodies to phosphorylated tau should be useful for measuring antibodies to other post-translationally-modified proteins that are of relevance to neurodegenerative disorders.

Do tau-synaptic long-term depression interactions in the hippocampus play a pivotal role in the progression of Alzheimer’s disease?

Cognitive decline in Alzheimer’s disease correlates with the extent of tau pathology,in particular tau hyperphosphorylation that initially appears in the transentorhinal and related regions of the brain including the hippocampus.Recent evidence indicates that tau hyperphosphorylation caused by either amyloid-βor long-term depression,a form of synaptic weakening involved in learning and memory,share similar mechanisms.Studies from our group and others demonstrate that long-term depression-inducing low-frequency stimulation triggers tau phosphorylation at different residues in the hippocampus under different experimental conditions including aging.Conversely,certain forms of long-term depression at hippocampal glutamatergic synapses require endogenous tau,in particular,phosphorylation at residue Ser396.Elucidating the exact mechanisms of interaction between tau and long-term depression may help our understanding of the physiological and pathological functions of tau/tau(hyper)phosphorylation.We first summarize experimental evidence regarding tau-long-term depression interactions,followed by a discussion of possible mechanisms by which this interplay may influence the pathogenesis of Alzheimer’s disease.Finally,we conclude with some thoughts and perspectives on future research about these interactions.

Changes in microtubule-associated protein tau during peripheral nerve injury and regeneration

Tau, a primary component of microtubule-associated protein, promotes microtubule assembly and/or disassembly and maintains the stability of the microtubule structure. Although the importance of tau in neurodegenerative diseases has been well demonstrated, wheth- er tau is involved in peripheral nerve regeneration remains unknown. In the current study, we obtained sciatic nerve tissue from adult rats 0, 1, 4, 7, and 14 days after sciatic nerve crush and examined tau mRNA and protein expression levels and the location of tau in the sciatic nerve following peripheral nerve injury. The results from our quantitative reverse transcription polymerase chain reaction analysis showed that compared with the uninjured control sciatic nerve, mRNA expression levels for both tau and tau tubulin kinase 1, a serine/ threonine kinase that regulates tau phosphorylation, were decreased following peripheral nerve injury. Our western blot assay results suggested that the protein expression levels of tau and phosphorylated tau initially decreased 1 day post nerve injury but then gradually increased. The results of our immunohistochemical labeling showed that the location of tau protein was not altered by nerve injury. Thus, these results showed that the expression of tau was changed following sciatic nerve crush, suggesting that tau may be involved in periph- eral nerve repair and regeneration.

Role of Notoginsenoside Rg1 in Improving Spatial Cognitive Ability and Lowering Phosphorylation Level of Tau Protein in AD Model Rats

[Objectives] To study the effects and mechanism of notoginsenoside Rg1 on the spatial learning and memory and phosphorylated tau protein in the AD( Alzheimer's Disease) model rat. [Methods]The AD model rat was replicated by injection of Aβ_(25-35) in the left lateral ventricles of SD rats. The low dose( 25 mg/kg),middle dose( 50 mg/kg) and high dose( 100 mg/kg) notoginsenoside Rg1 was used for intragastric administration,respectively,two times every day. After 4 weeks,the Morris water maze test was done to detect the learning and memory capacity,and the immunoblotting,immunohistochemical methods were used to detect the changes in the phosphorylation level and distribution of tau protein in hippocampus of the rats. [Results] After the intracerebroventricular injection of Aβ_(25-35),the learning and memory capacity of the model rats was significantly lower than the learning and memory capacity of the normal control rats. The immunoblotting test results showed that the phosphorylation level of tau protein threonine 231 site( Thr231) in hippocampus was significantly increased,and the nonphosphorylation level was significantly decreased. The morphological testing results showed that the phosphorylation level of tau protein Thr231 of AD model rats was increased markedly in region of DG,CA1 and CA3 of the hippocampus. The intervention of the middle dose notoginsenoside Rg1 could significantly improve the learning and memory capacity of the model rats in Morris water maze. The notoginsenoside Rg1 in three different doses could all reduce the phosphorylation level of tau protein Thr231 in the hippocampal DG,CA1,CA3 regions,and there were no significant differences among the three doses. [Conclusions]The notoginsenoside Rg1 could improve Aβ_(25-35)-induced spatial learning and memory impairment of the AD model rats,and decreased the phosphorylation level of tau protein in hippocampus.

Development of an Ultrasensitive ELISA-Bienzyme Colorimetric Substrate Recycle Assay for Measurement of Tau

On the basis of convemional enzyme-linked immunosorbent assay （ELISA） and bienzyme suhstrate recycle, ELISA-bienzyme colorimetric substrate recycle was developed in the present study. The sensitivity of this method increased 15 times than that of ELISA for the measurement of Tau and increased 55 times for p-Tau. The linear detective rang of this method expanded 3 times higher than that of conventional EI.ISA for Tau and had the san;e as EI.ISA for p-Tau.So, EI.ISA-bienzyme colorimetric substrate recycle could be used to detect abnormally phosphorylated tau in cerehrospinal fluid.

Protective Effect of Hydroxy safflor Yellow A against Chronic Mild Stress-induced Memory Impairments by Suppressing Tau Phosphorylation in Mice

Chronic stress plays a critical role in the etiology of sporadic Alzheimer's disease(AD).However,there are currently no effective drugs that can target chronic stress to prevent AD.In this study,we explored the neuroprotective effect of hydroxysafflor yellow A(HSYA)against chronic mild stress(CMS)-induced memory impairments in mice and the underlying mechanism.The Morris water maze test showed that HSYA significantly reduced CMS-induced learning and memory impairments in mice.HSYA increased the expression of brain-derived neurotrophic factor(BDNF)and activated downstream tropomyosin-related kinase B(TrkB)and phosphatidylinositol 3-kinase(PI3K)/protein kinase B(Akt)/mammalian target of rapamycin(mTOR)signaling.HSYA decreased the expression of regulator of calcineurin 1-1L(RCAN1-1L)that could promote the activity of glycogen synthase kinase-3β(GSK-3β).HSYA also attenuated tau phosphorylation by inhibiting the activity of GSK-3βand cyclin-dependent kinase-5(Cdk5).Our data indicated that HSYA has protective effects against CMS-induced BDNF downregulation,tau phosphorylation and memory impairments.HSYA may be a promising therapeutic candidate for AD by targeting chronic stress.

Cornel Iridoid Glycoside Suppresses Hyperactivity Phenotype in rTg4510 Mice through Reducing Tau Pathology and Improving Synaptic Dysfunction

rTg4510 mice are transgenic mice expressing P301L mutant tau and have been developed as an animal model of tauopathies including Alzheimer’s disease(AD).Besides cognitive impairments,rTg4510 mice also show abnormal hyperactivity behavior.Cornel iridoid glycoside(CIG)is an active ingredient extracted from Cornus officinalis,a traditional Chinese herb.The purpose of the present study was to investigate the effects of CIG on the emotional disorders such as hyperactivity,and related mechanisms.The emotional hyperactivity was detected by locomotor activity test and Y maze test.Immunofluorescent and immunohistochemical analyses were conducted to measure neuron loss and phosphorylated tau.Western blotting was used to detect the expression of related proteins.The results showed that intragastric administration of CIG for 3 months decreased the hyperactivity phenotype,prevented neuronal loss,reduced tau hyperphosphorylation and aggregation in the amygdala of rTg4510 mice.Meanwhile,CIG alleviated the synaptic dysfunction by increasing the expression of N-methyl-D-aspartate receptors(NMDARs)subunits GluN1 and GluN2A andαamino-3-hydroxy-5-methyl-4-isoxazole propionic acid receptor(AMPAR)subunits GluA1 and GluA2,and increased the level of phosphorylated Ca2+/calmodulin dependent protein kinase IIα(p-CaMK IIα)in the brain of rTg4510 mice.In conclusion,CIG may have potential to treat the emotional disorders in tauopathies such as AD through reducing tau pathology and improving synaptic dysfunction.

Long-term Helicobacter pylori Infection Does Not Induce Tauopathy and Memory Impairment in SD Rats

Helicobacter pylori（H.pylori） infection is a recognized risk factor of dementia, while its role and mechanism in Alzheimer disease（AD） remained unclarified. Our previous study has identified that injection of soluble H.pylori filtrate could induce AD-like pathologic changes and cognitive impairment in SD rats. In the present study, we further explored the effect of long-term stomach colonization of H.pylori bacteria on the brains of SD rats. The results showed that H.pylori bacteria gavage induced an efficient colonization of H.pylori in the stomach after four weeks. However, there was no significant change of tau phosphorylation at Thr205（pT205）, Thr231（pT231）, Ser396（pS396） and Ser404（pS404） sites in the hippocampus and cerebral cortex. The H.pylori-infected rats also showed no cognitive impairment. These observations may result from inefficient release of bacterial pathogenic factors or the overall lack of host inflammatory responses. We conclude that SD rat with long-term H.pylori colonization in the stomach is not a suitable animal model for exploring the effects of H.pylori infection on brain function in human beings; administration of bacterial filtrates may better reveal the systemic pathologic changes induced by bacterial infection in animals which show a negative host response to bacterial colonization.

The neuroprotective effects of oxygen therapy in Alzheimer’s disease:a narrative review

Alzheimer’s disease(AD)is a degenerative neurological disease that primarily affects the elderly.Drug therapy is the main strategy for AD treatment,but current treatments suffer from poor efficacy and a number of side effects.Non-drug therapy is attracting more attention and may be a better strategy for treatment of AD.Hypoxia is one of the important factors that contribute to the pathogenesis of AD.Multiple cellular processes synergistically promote hypoxia,including aging,hypertension,diabetes,hypoxia/obstructive sleep apnea,obesity,and traumatic brain injury.Increasing evidence has shown that hypoxia may affect multiple pathological aspects of AD,such as amyloid-beta metabolism,tau phosphorylation,autophagy,neuroinflammation,oxidative stress,endoplasmic reticulum stress,and mitochondrial and synaptic dysfunction.Treatments targeting hypoxia may delay or mitigate the progression of AD.Numerous studies have shown that oxygen therapy could improve the risk factors and clinical symptoms of AD.Increasing evidence also suggests that oxygen therapy may improve many pathological aspects of AD including amyloid-beta metabolism,tau phosphorylation,neuroinflammation,neuronal apoptosis,oxidative stress,neurotrophic factors,mitochondrial function,cerebral blood volume,and protein synthesis.In this review,we summarized the effects of oxygen therapy on AD pathogenesis and the mechanisms underlying these alterations.We expect that this review can benefit future clinical applications and therapy strategies on oxygen therapy for AD.

Lactoferrin modification of berberine nanoliposomes enhances the neuroprotective effects in a mouse model of Alzheimer’s disease

Previous studies have shown that berberine has neuroprotective effects against Alzheimer’s disease,including antagonizing tau phosphorylation,and inhibiting acetylcholinesterase activity and neural cell apoptosis.However,its low bioavailability and adverse reactions with conventional administration limit its clinical application.In this study,we prepared berberine nanoliposomes using liposomes characterized by low toxicity,high entrapment efficiency,and biodegradability,and modified them with lactoferrin.Lactoferrin-modified berberine nanoliposomes had uniform particle size and high entrapment efficiency.We used the lactoferrin-modified berberine nanoliposomes to treat a mouse model of Alzheimer’s disease established by injection of amyloid-beta 1-42 into the lateral ventricle.Lactoferrin-modified berberine nanoliposomes inhibited acetylcholinesterase activity and apoptosis in the hippocampus,reduced tau over-phosphorylation in the cerebral cortex,and improved mouse behavior.These findings suggest that modification with lactoferrin can enhance the neuroprotective effects of berberine nanoliposomes in Alzheimer’s disease.

Cdk5 and aberrant cell cycle activation at the core of neurodegeneration

Neurodegenerative diseases are caused by the progressive loss of specific neurons.The exact mechanisms of action of these diseases are unknown,and many studies have focused on pathways related to abnormal accumulation and processing of proteins,mitochondrial dysfunction,and oxidative stress leading to apoptotic death.However,a growing body of evidence indicates that aberrant cell cycle re-entry plays a major role in the pathogenesis of neurodegeneration.The activation of the cell cycle in mature neurons could be promoted by several signaling mechanisms,including c-Jun N-terminal kinases,p38 mitogen-activated protein kinases,and mitogen-activated protein kinase/extracellular signal-regulated kinase cascades;post-translational modifications such as Tau-phosphorylation;and DNA damage response.In all these events,implicated Cdk5,a proline-directed serine/threonine protein kinase,seems to be responsible for several cellular processes in neurons including axon growth,neurotransmission,synaptic plasticity,neuronal migration,and maintenance of neuronal survival.However,under pathological conditions,Cdk5 dysregulation may lead to cell cycle re-entry in post-mitotic neurons.Thus,Cdk5 hyperactivation,by its physiologic activator p25,hyper-phosphorylates downstream substrates related to neurodegenerative diseases.This review summarizes factors such as oxidative stress,DNA damage response,signaling pathway disturbance,and Ubiquitin proteasome malfunction contributing to cell cycle re-entry in post-mitotic neurons.It also describes how all these factors are linked to a greater or lesser extent with Cdk5.Thus,it offers a global vision of the function of cell cycle-related proteins in mature neurons with a focus on Cdk5 and how this protein contributes to the development of Alzheimer’s disease,Parkinson’s disease,amyotrophic lateral sclerosis,and Huntington’s disease by cell cycle activation.

Cellular and molecular mechanisms underlying the action of ginsenoside Rg1 against Alzheimer’s disease

Ginsenoside Rgl inhibits oxidation, aging and ce this study, we pretreated rat brain tissue sections I apoptosis, and improves cognitive function. In with ginsenoside Rgl, and established brain slice models of Alzheimer＇s disease induced by okadaic acid. The results revealed that ginsenoside Rgl pretreatment suppressed the increase in phosphorylated Tau protein expression induced by incubation with okadaic acid, and reduced brain-derived neurotrophic factor expression. These results suggest that ginsenoside Rgl upregulates brain-derived neurotrophic factor expression and inhibits Tau protein phosphorylation in brain slices from a rat model of Alzheimer＇s disease.

Ligustrazine Attenuates Hyperhomocysteinemia-induced Alzheimer-like Pathologies in Rats

Ligustrazine,an alkaloid extracted from the traditional Chinese herbal medicine Ligusticum Chuanxiong Hort,has been clinically applied to treat the cerebrovascular diseases.Hyperhomocystcincmia(Hhcy)is an independent risk factor for Alzheimer's disease(AD).Memory deficits can be caused by Hhcy via pathologies of Aβ-like tau and amyloid-β(Aβ)in the hippocampus.Here,we investigated whether homocysteine(Hey)can induce Aβ-like pathologies and the effects of ligustrazine on these pathologies.The Hey rat model was constructed by 14-day Hey injection via vena caudalis,and rats were treated with daily intragastric administration of ligustrazine at the same time.We found that the pathologies of tau and Aβ were induced by Hey in the hippocampus,while the Hcy-induced tau hyperphosphorylation and Aβ accumulation could be markedly attenuated by simultaneous ligustrazine treatment.Our data demonstrate that ligustrazine may be used as a promising neuroprotective agent to treat the Hcy-induced Aβ-like pathologies.

散发性早发阿尔茨海默病中磷酸化tau蛋白的高负荷和特异性楔前叶萎缩:一项前瞻性队列研究

早发性阿尔茨海默病(EOAD)是阿尔茨海默病(AD)的罕见且严重的亚型,于65岁之前发病,占所有AD病例的5%~10%.以往关于EOAD的研究主要集中在家族性遗传人群,而对于占EOAD病例85%~90%的散发性EOAD(sEOAD)的研究则较为有限.在这项前瞻性队列研究中,共纳入sEOAD110例,晚发性AD(LOAD)89例,年龄匹配对照组75例.研究对象排除了家族性EOAD患者,所有纳入AD患者均符合基于ATN框架下的生物标志物证据的诊断标准.对纳入患者进行了患病危险因素分析、多维度认知功能评估、多模态分子影像学评估及脑脊液/外周血生物标记物检测.结果显示,与LOAD患者相比,sEOAD患者没有表现出特定的危险因素,但表现出更严重的执行功能损害和双侧楔前叶萎缩.在sEOAD患者中的脑脊液和血浆中磷酸化tau181(P-tau181)水平较LOAD组显著升高.本研究探讨了散发性EOAD人群的临床特征,发现了tau蛋白磷酸化在sEOAD发生和进展中的重要性,有助于全面了解AD的病因、发病年龄决定因素和疾病进展,并为潜在的治疗策略提供了重要思路.

Loss of canonical Wnt signaling is involved in the pathogenesis of Alzheimer's disease

Alzheimer＇s disease（AD） is the most common form of dementia in the older population, however, the precise cause of the disease is unknown. The neuropathology is characterized by the presence of aggregates formed by amyloid-β（Aβ） peptide and phosphorylated tau; which is accompanied by progressive impairment of memory. Diverse signaling pathways are linked to AD, and among these the Wnt signaling pathway is becoming increasingly relevant, since it plays essential roles in the adult brain. Initially, Wnt signaling activation was proposed as a neuroprotective mechanism against Aβ toxicity. Later, it was reported that it participates in tau phosphorylation and processes of learning and memory. Interestingly, in the last years we demonstrated that Wnt signaling is fundamental in amyloid precursor protein（APP） processing and that Wnt dysfunction results in Aβ production and aggregation in vitro. Recent in vivo studies reported that loss of canonical Wnt signaling exacerbates amyloid deposition in a transgenic（Tg） mouse model of AD. Finally, we showed that inhibition of Wnt signaling in a Tg mouse previously at the appearance of AD signs, resulted in memory loss, tau phosphorylation and Aβ formation and aggregation; indicating that Wnt dysfunction accelerated the onset of AD. More importantly, Wnt signaling loss promoted cognitive impairment, tau phosphorylation and Aβ1–42 production in the hippocampus of wild-type（WT） mice, contributing to the development of an Alzheimer＇s-like neurophatology. Therefore, in this review we highlight the importance of Wnt/β-catenin signaling dysfunction in the onset of AD and propose that the loss of canonical Wnt signaling is a triggering factor of AD.

Neuroprotective effect of the Chinese medicine Tiantai No.1 and its molecular mechanism in the senescence-accelerated mouse prone 8

Tiantai No.1, a Chinese medicine predominantly composed of powdered Rhizoma Gastrodiae, Radix Ginseng, and Ginkgo leaf at a ratio of 2：1：2 and dissolved in pure water, is neuroprotective in animal models of various cognitive disorders, but its molecular mechanism remains unclear. We administered Tiantai No.1 intragastrically to senescence-accelerated mouse prone 8（SAMP8） mice（a model of Alzheimer＇s disease） at doses of 50, 100 or 150 mg/kg per day for 8 weeks and evaluated their behavior in the Morris water maze and expression of Alzheimer＇s disease-related proteins in the brain. Tiantai No.1 shortened the escape latency in the water maze training trials, and increased swimming time in the target quadrant during the spatial probe test, indicating that Tiantai No.1 improved learning and memory in SAMP8 mice. Immunohistochemistry revealed that Tiantai No.1 restored the proliferation potential of Ki67-positive cells in the hippocampus. In addition, mice that had received Tiantai No.1 had fewer astrocytes, and less accumulation of amyloid-beta and phosphorylated tau. These results suggest that Tiantai No.1 is neuroprotective in the SAMP8 mouse model of Alzheimer＇s disease and acts by restoring neuronal number and proliferation potential in the hippocampus, decreasing astrocyte infiltration, and reducing the accumulation of amyloid-beta and phosphorylated tau.