STAT3 ameliorates truncated tau-induced cognitive deficits

Proteolytic cleavage of tau by asparagine endopeptidase(AEP)creates tau-N368 fragments,which may drive the pathophysiology associated with synaptic dysfunction and memory deterioration in the brain of Alzheimer’s disease patients.Nonetheless,the molecular mechanisms of truncated tau-induced cognitive deficits remain unclear.Evidence suggests that signal transduction and activator of transcription-3(STAT3)is associated with modulating synaptic plasticity,cell apoptosis,and cognitive function.Using luciferase reporter assays,electrophoretic mobility shift assays,western blotting,and immunofluorescence,we found that human tau-N368 accumulation inhibited STAT3 activity by suppressing STAT3 translocation into the nucleus.Overexpression of STAT3 improved tau-N368-induced synaptic deficits and reduced neuronal loss,thereby improving the cognitive deficits in tau-N368 mice.Moreover,in tau-N368 mice,activation of STAT3 increased N-methyl-D-aspartic acid receptor levels,decreased Bcl-2 levels,reversed synaptic damage and neuronal loss,and thereby alleviated cognitive deficits caused by tau-N368.Taken together,STAT3 plays a critical role in truncated tau-related neuropathological changes.This indicates a new mechanism behind the effect of tau-N368 on synapses and memory deficits.STAT3 can be used as a new molecular target to treat tau-N368-induced protein pathology.

Lamotrigine protects against cognitive deficits,synapse and nerve cell damage,and hallmark neuropathologies in a mouse model of Alzheimer’s disease

Lamotrigine(LTG)is a widely used drug for the treatment of epilepsy.Emerging clinical evidence suggests that LTG may improve cognitive function in patients with Alzheimer’s disease.However,the underlying molecular mechanisms remain unclear.In this study,amyloid precursor protein/presenilin 1(APP/PS1)double transgenic mice were used as a model of Alzheimer’s disease.Five-month-old APP/PS1 mice were intragastrically administered 30 mg/kg LTG or vehicle once per day for 3 successive months.The cognitive functions of animals were assessed using Morris water maze.Hyperphosphorylated tau and markers of synapse and glial cells were detected by western blot assay.The cell damage in the brain was investigated using hematoxylin and eosin staining.The levels of amyloid-βand the concentrations of interleukin-1β,interleukin-6 and tumor necrosis factor-αin the brain were measured using enzyme-linked immunosorbent assay.Differentially expressed genes in the brain after LTG treatment were analyzed by high-throughput RNA sequencing and real-time polymerase chain reaction.We found that LTG substantially improved spatial cognitive deficits of APP/PS1 mice;alleviated damage to synapses and nerve cells in the brain;and reduced amyloid-βlevels,tau protein hyperphosphorylation,and inflammatory responses.High-throughput RNA sequencing revealed that the beneficial effects of LTG on Alzheimer’s disease-related neuropathologies may have been mediated by the regulation of Ptgds,Cd74,Map3k1,Fosb,and Spp1 expression in the brain.These findings revealed potential molecular mechanisms by which LTG treatment improved Alzheimer’s disease.Furthermore,these data indicate that LTG may be a promising therapeutic drug for Alzheimer’s disease.

Transplantation of bone marrow mesenchymal stem cells improves cognitive deficits and alleviates neuropathology in animal models of Alzheimer’s disease: a meta-analytic review on potential mechanisms

Background Alzheimer’s disease is a neurodegenerative disorder.Therapeutically,a transplantation of bone marrow mesenchymal stem cells(BMMSCs)can play a beneficial role in animal models of Alzheimer’s disease.However,the relevant mechanism remains to be fully elucidated.Main body Subsequent to the transplantation of BMMSCs,memory loss and cognitive impairment were significantly improved in animal models with Alzheimer’s disease(AD).Potential mechanisms involved neurogenesis,apoptosis,angiogenesis,inflammation,immunomodulation,etc.The above mechanisms might play different roles at certain stages.It was revealed that the transplantation of BMMSCs could alter some gene levels.Moreover,the differential expression of representative genes was responsible for neuropathological phenotypes in Alzheimer’s disease,which could be used to construct gene-specific patterns.Conclusions Multiple signal pathways involve therapeutic mechanisms by which the transplantation of BMMSCs improves cognitive and behavioral deficits in AD models.Gene expression profile can be utilized to establish statistical regression model for the evaluation of therapeutic effect.The transplantation of autologous BMMSCs maybe a prospective therapy for patients with Alzheimer’s disease.

Electroacupuncture with Bushen Jiannao improves cognitive deficits in senescence-accelerated mouse prone 8 mice by inhibiting neuroinflammation

OBJECTIVE:To investigate effect of electroacupuncture(EA)with Bushen Jiannao on learning and memory ability in senescence-accelerated mouse prone 8(SAMP8)mice and the related mechanisms.METHODS:8-month-old senescence-accelerated-resistant(SAMR1)and SAMP8 mice were treated with EA at Baihui(GV 20),Shenshu(BL 23),and Taixi(KI 3)acupoint once a week for 8 weeks.The Morris water maze,enzyme linked immunosorbent assay,immunohistochemistry,and Western blot were used to assess Alzheimer’s disease(AD)-associated cognitive and neuroinflammatory phenotypes.RESULTS:Our data showed that EA treatment decreased activation of microglia and astrocytes,decreased levels of inflammatory factors including tumor necrosis factor-α(TNF-α),interleukin(IL)-6,and IL-17,and improved spatial memory deficits in SAMP8 mice.EA therapy with Bushen Jiannao exhibited anti-inflammatory properties and improved cognitive function.CONCLUSION:The present study indicates that EA treatment based on the interaction between kidney and brain can improve learning and memory ability by inhibiting activation of astrocytes and microglia and decreasing expression of pro-inflammatory cytokines,TNF-αand IL-17.EA treatment based on the interaction between kidney and brain may be an effective treatment for AD.

Activation of medial septum cholinergic neurons restores cognitive function in temporal lobe epilepsy

Cognitive impairment is the most common complication in patients with temporal lobe epilepsy with hippocampal scle rosis.There is no effective treatment for cognitive impairment.Medial septum cholinergic neurons have been reported to be a potential target for controlling epileptic seizures in tempo ral lobe epile psy.However,their role in the cognitive impairment of temporal lobe epilepsy remains unclear.In this study,we found that patients with temporal lobe epile psy with hippocampal sclerosis had a low memory quotient and severe impairment in verbal memory,but had no impairment in nonverbal memory.The cognitive impairment was slightly correlated with reduced medial septum volume and medial septum-hippocampus tra cts measured by diffusion tensor imaging.In a mouse model of chronic temporal lobe epilepsy induced by kainic acid,the number of medial septum choline rgic neurons was reduced and acetylcholine release was reduced in the hippocampus.Furthermore,selective apoptosis of medial septum cholinergic neurons mimicked the cognitive deficits in epileptic mice,and activation of medial septum cholinergic neurons enhanced hippocampal acetylcholine release and restored cognitive function in both kainic acid-and kindling-induced epile psy models.These res ults suggest that activation of medial septum cholinergic neurons reduces cognitive deficits in temporal lobe epilepsy by increasing acetylcholine release via projections to the hippocampus.

Cryptotanshinone ameliorates cladribine-induced cognitive impairment in rats

Objective:To evaluate the neuroprotective effect of cryptotanshinone against cladribine-induced cognitive impairment in rats.Methods:Rats were administered with cladribine(1 mg/kg,p.o.)and cryptotanshinone(10 and 20 mg/kg,i.p.)for four weeks.Behavioral tests such as Morris water maze and elevated plus maze were conducted to check memory impairment caused by cladribine.On day 29,all rats were sacrificed,and the brains were separated for estimation of neuroinflammatory factors,biochemical parameters,neurotransmitters,Aβ(1-42),blood-brain barrier permeability,nuclear factor erythroid 2-related factor 2(Nrf2),and brain-derived neurotrophic factor(BDNF).Results:Treatment with cryptotanshinone dose-dependently enhanced spatial memory,improved the levels of neurotransmitter and antioxidant enzymes,and suppressed proinflammatory cytokine release.Cryptotanshinone also decreased Aβ(1-42)accumulation and increased the levels of Nrf2 and BDNF in the hippocampus.Additionally,the histopathological results showed that cryptotanshinone reduced cladribine-induced neuronal death in the hippocampus.Conclusions:Cryptotanshinone exhibits a promising neuroprotective effect against cladribine-induced cognitive impairment in preclinical studies,and may be a potential phytochemical for the treatment and management of cognitive impairment.

Targeting tau in Alzheimer's disease:from mechanisms to clinical therapy

Alzheimer’s disease is the most prevalent neurodegenerative disease affecting older adults.Primary features of Alzheimer’s disease include extra cellular aggregation of amyloid-βplaques and the accumulation of neurofibrillary tangles,fo rmed by tau protein,in the cells.While there are amyloid-β-ta rgeting therapies for the treatment of Alzheimer’s disease,these therapies are costly and exhibit potential negative side effects.Mounting evidence suggests significant involvement of tau protein in Alzheimer’s disease-related neurodegeneration.As an important microtubule-associated protein,tau plays an important role in maintaining the stability of neuronal microtubules and promoting axonal growth.In fact,clinical studies have shown that abnormal phosphorylation of tau protein occurs before accumulation of amyloid-βin the brain.Various therapeutic strategies targeting tau protein have begun to emerge,and are considered possible methods to prevent and treat Alzheimer’s disease.Specifically,abnormalities in post-translational modifications of the tau protein,including aberrant phosphorylation,ubiquitination,small ubiquitin-like modifier(SUMO)ylation,acetylation,and truncation,contribute to its microtubule dissociation,misfolding,and subcellular missorting.This causes mitochondrial damage,synaptic impairments,gliosis,and neuroinflammation,eventually leading to neurodegeneration and cognitive deficits.This review summarizes the recent findings on the underlying mechanisms of tau protein in the onset and progression of Alzheimer’s disease and discusses tau-targeted treatment of Alzheimer’s disease.

Understanding the spectrum of non-motor symptoms in multiple sclerosis:insights from animal models

Multiple sclerosis is a chronic autoimmune disease of the central nervous system and is generally considered to be a non-traumatic,physically debilitating neurological disorder.In addition to experiencing motor disability,patients with multiple sclerosis also experience a variety of nonmotor symptoms,including cognitive deficits,anxiety,depression,sensory impairments,and pain.However,the pathogenesis and treatment of such non-motor symptoms in multiple scle rosis are still under research.Preclinical studies for multiple sclerosis benefit from the use of disease-appropriate animal models,including experimental autoimmune encephalomyelitis.Prior to understanding the pathophysiology and developing treatments for non-motor symptoms,it is critical to chara cterize the animal model in terms of its ability to replicate certain non-motor features of multiple sclerosis.As such,no single animal model can mimic the entire spectrum of symptoms.This review focuses on the non-motor symptoms that have been investigated in animal models of multiple sclerosis as well as possible underlying mechanisms.Further,we highlighted gaps in the literature to explain the nonmotor aspects of multiple sclerosis in expe rimental animal models,which will serve as the basis for future studies.

French Validation of the Screen for Cognitive Impairment in Psychiatry (SCIP-F)

Background: Measuring cognition in clinical practice is clearly essential to the appropriate characterisation of patients’ clinical status and to the development of a personalised care plan. The Screen for Cognitive Impairment in Psychiatry (SCIP) has been developed in order to provide a brief and accessible tool allowing the evaluation of cognitive function in psychiatric conditions. Objective: We present a validation of a French version of the SCIP. Method: Translation from English into French is carried out using the accepted back-translation method. Seventy-two healthy volunteers are characterised by demographic questionnaires and a neuropsychological battery. The French version of the SCIP is then administered on two separate occasions separated by at least a one-week interval. Results: High internal consistencies as well as strong correlations with comparable neuropsychological tests are obtained. A normalised Cronbach’s α = 0.66 is obtained. Conclusions: The French version of the SCIP (SCIP-F) yields results comparable to the English version. The SCIP represents an essential tool for the preliminary evaluation of cognition. Its characteristics, brevity and the lack of need for a technological platform, allow for its integration into clinical practice. Further testing of SCIP-F in various psychiatric conditions will yield valuable information on its potential in clinical settings.

Inhibiting 5-hydroxytryptamine receptor 3 alleviates pathological changes of a mouse model of Alzheimer's disease

Extracellular amyloid beta(Aβ) plaques are main pathological feature of Alzheimer’s disease.However,the specific type of neuro ns that produce Aβ peptides in the initial stage of Alzheimer’s disease are unknown.In this study,we found that 5-hydroxytryptamin receptor 3A subunit(HTR3A) was highly expressed in the brain tissue of transgenic amyloid precursor protein and presenilin-1 mice(an Alzheimer’s disease model) and patients with Alzheimer’s disease.To investigate whether HTR3A-positive interneurons are associated with the production of Aβ plaques,we performed double immunostaining and found that HTR3A-positive interneurons were clustered around Aβ plaques in the mouse model.Some amyloid precursor protein-positive or β-site amyloid precursor protein cleaving enzyme-1-positive neurites near Aβ plaques were co-localized with HTR3A interneurons.These results suggest that HTR3A-positive interneurons may partially contribute to the generation of Aβ peptides.We treated 5.0-5.5-month-old model mice with tro pisetron,a HTR3 antagonist,for 8 consecutive weeks.We found that the cognitive deficit of mice was partially reversed,Aβ plaques and neuroinflammation we re remarkably reduced,the expression of HTR3 was remarkably decreased and the calcineurin/nuclear factor of activated T-cell 4 signaling pathway was inhibited in treated model mice.These findings suggest that HTR3A interneurons partly contribute to generation of Aβ peptide at the initial stage of Alzheimer’s disease and inhibiting HTR3 partly reve rses the pathological changes of Alzheimer’s disease.

Mitochondrial transplantation ameliorates hippocampal damage following status epilepticus

Background:Hippocampal damage caused by status epilepticus(SE)can bring about cognitive decline and emotional disorders,which are common clinical comorbidities in patients with epilepsy.It is therefore imperative to develop a novel therapeutic strat-egy for protecting hippocampal damage after SE.Mitochondrial dysfunction is one of contributing factors in epilepsy.Given the therapeutic benefits of mitochondrial replenishment by exogenous mitochondria,we hypothesized that transplantation of mitochondria would be capable of ameliorating hippocampal damage following SE.Methods:Pilocarpine was used to induced SE in mice.SE-generated cognitive de-cline and emotional disorders were determined using novel object recognition,the tail suspension test,and the open field test.SE-induced hippocampal pathology was assessed by quantifying loss of neurons and activation of microglia and astrocytes.The metabolites underlying mitochondrial transplantation were determined using metabonomics.Results:The results showed that peripheral administration of isolated mitochon-dria could improve cognitive deficits and depressive and anxiety-like behaviors.Exogenous mitochondria blunted the production of reactive oxygen species,pro-liferation of microglia and astrocytes,and loss of neurons in the hippocampus.The metabonomic profiles showed that mitochondrial transplantation altered multiple metabolic pathways such as sphingolipid signaling pathway and carbon metabolism.Among potential affected metabolites,mitochondrial transplantation decreased levels of sphingolipid(d18:1/18:0)and methylmalonic acid,and elevated levels of D-fructose-1,6-bisphosphate.Conclusion:To the best of our knowledge,these findings provide the first direct ex-perimental evidence that artificial mitochondrial transplantation is capable of amelio-rating hippocampal damage following SE.These new findings support mitochondrial transplantation as a promising therapeutic strategy for epilepsy-associated psychiat-ric and cognitive disorders.

Microglia regulation of synaptic plasticity and learning and memory

Microglia are the resident macrophages of the central nervous system.Microglia possess varied morphologies and functions.Under normal physiological conditions,microglia mainly exist in a resting state and constantly monitor their microenvironment and survey neuronal and synaptic activity.Through the C1 q,C3 and CR3"Eat Me"and CD47 and SIRPα"Don't Eat Me"complement pathways,as well as other pathways such as CX3 CR1 signaling,resting microglia regulate synaptic pruning,a process crucial for the promotion of synapse formation and the regulation of neuronal activity and synaptic plasticity.By mediating synaptic pruning,resting microglia play an important role in the regulation of experience-dependent plasticity in the barrel cortex and visual cortex after whisker removal or monocular deprivation,and also in the regulation of learning and memory,including the modulation of memory strength,forgetfulness,and memory quality.As a response to brain injury,infection or neuroinflammation,microglia become activated and increase in number.Activated microglia change to an amoeboid shape,migrate to sites of inflammation and secrete proteins such as cytokines,chemokines and reactive oxygen species.These molecules released by microglia can lead to synaptic plasticity and learning and memory deficits associated with aging,Alzheimer's disease,traumatic brain injury,HIV-associated neurocognitive disorder,and other neurological or mental disorders such as autism,depression and post-traumatic stress disorder.With a focus mainly on recently published literature,here we reviewed the studies investigating the role of resting microglia in synaptic plasticity and learning and memory,as well as how activated microglia modulate disease-related plasticity and learning and memory deficits.By summarizing the function of microglia in these processes,we aim to provide an overview of microglia regulation of synaptic plasticity and learning and memory,and to discuss the possibility of microglia manipulation as a therapeutic to ameliorate cognitive deficits associated with aging,Alzheimer's disease,traumatic brain injury,HIV-associated neurocognitive disorder,and mental disorders.

Hippocampal neurogenesis and pro-neurogenic therapies for Alzheimer's disease

Adult hippocampal neurogenesis(AHN)facilitates hippocampal circuits plasticity and regulates hippocampus-dependent cognition and emotion.However,AHN malfunction has been widely reported in both human and animal models of Alzheimer's disease(AD),the most common form of dementia in the elderly.Proneurogenic therapies including rescuing innate AHN,cell engraftment and glianeuron reprogramming hold great potential for compensating the neuronal loss and rewiring the degenerated neuronal network in AD,but there are still great challenges to be overcome.This review covers recent advances in unraveling the involvement of AHN in AD and highlights the prospect of emerging proneurogenic remedies.

Stem cell therapy for Alzheimer’s disease:An overview of experimental models and reality

Alzheimer's disease(AD)is a neurodegenerative disorder.The pathology of AD is characterized by extracellular amyloid beta(Aβ)plaques,neurofibrillary tangles com-posed of hyperphosphorylated tau,neuronal death,synapse loss,and brain atrophy.Many therapies have been tested to improve or at least effectively modify the course of AD.Meaningful data indicate that the transplantation of stem cells can alleviate neuropathology and significantly ameliorate cognitive deficits in animal models with Alzheimer's disease.Transplanted stem cells have shown their inherent advantages in improving cognitive impairment and memory dysfunction,although certain weak-nesses or limitations need to be overcome.This review recapitulates rodent models for AD,the therapeutic efficacy of stem cells,influencing factors,and the underlying mechanisms behind these changes.Stem cell therapy provides perspective and chal-lenges for its clinical application in the future.

Reserpine Improves Working Memory

Despite exhaustive search, no drug is in sight for AD. Earlier, we reported that reserpine, an antihypertensive and antipsychotic drug, ameliorates Amyloid beta (Aβ-AD causing peptide) toxicity and confers several positive enhancements in the C. elegans model system. Here, we evaluate whether reserpine can provide protection against working memory and against AD in the mouse model. Reserpine (0.08 mg) was administered orally on alternate days to the non-Tg and accelerated Aβ deposition (at 2 months of age)and cognitive deficit (4 months of age) developing 5XFAD AD Tg mouse model expressing mutant human APP (3 familial mutations) and human Presenilin1(2 familial mutations) in the neurons, and follow their working memory for 2 months using the spontaneous Y-maze alteration behavioral paradigm. Reserpine enhanced working memory in non-Tg mice and improved the cognitive deficit in the 5XFAD AD Tg mice. Hence, reserpine can be considered for a detailed evaluation in the 3X Tg AD mouse model and a pilot study in AD patients.

Gamma-glutamyl transferase 5 overexpression in cerebrovascular endothelial cells improves brain pathology,cognition,and behavior in APP/PS1 mice

In patients with Alzheimer’s disease,gamma-glutamyl transferase 5(GGT5)expression has been observed to be downregulated in cerebrovascular endothelial cells.However,the functional role of GGT5 in the development of Alzheimer’s disease remains unclear.This study aimed to explore the effect of GGT5 on cognitive function and brain pathology in an APP/PS1 mouse model of Alzheimer’s disease,as well as the underlying mechanism.We observed a significant reduction in GGT5 expression in two in vitro models of Alzheimer’s disease(Aβ_(1-42)-treated hCMEC/D3 and bEnd.3 cells),as well as in the APP/PS1 mouse model.Additionally,injection of APP/PS1 mice with an adeno-associated virus encoding GGT5 enhanced hippocampal synaptic plasticity and mitigated cognitive deficits.Interestingly,increasing GGT5 expression in cerebrovascular endothelial cells reduced levels of both soluble and insoluble amyloid-βin the brains of APP/PS1 mice.This effect may be attributable to inhibition of the expression ofβ-site APP cleaving enzyme 1,which is mediated by nuclear factor-kappa B.Our findings demonstrate that GGT5 expression in cerebrovascular endothelial cells is inversely associated with Alzheimer’s disease pathogenesis,and that GGT5 upregulation mitigates cognitive deficits in APP/PS1 mice.These findings suggest that GGT5 expression in cerebrovascular endothelial cells is a potential therapeutic target and biomarker for Alzheimer’s disease.

Chronic Oral Administration of Magnesium-L-Threonate Prevents Oxaliplatin-Induced Memory and Emotional Deficits by Normalization of TNF-a/NF-j B Signaling in Rats

Antineoplastic drugs such as oxaliplatin(OXA)often induce memory and emotional deficits.At present,the mechanisms underlying these side-effects are not fully understood,and no effective treatment is available.Here,we show that the short-term memory deficits and anxietylike and depression-like behaviors induced by intraperitoneal injections of OXA(4 mg/kg per day for 5 consecutive days) were accompanied by synaptic dysfunction and downregulation of the NR2 B subunit of N-methyl-Daspartate receptors in the hippocampus,which is critically involved in memory and emotion.The OXA-induced behavioral and synaptic changes were prevented by chronic oral administration of magnesium-L-threonate(L-TAMS,604 mg/kg per day,from 2 days before until the end of experiments).We found that OXA injections significantly reduced the free Mg~(2+) in serum and cerebrospinal fluid(from ~0.8 mmol/L to ~ 0.6 mmol/L).The Mg~(2+) deficiency(0.6 mmol/L) upregulated tumor necrosis factor(TNF-α) and phospho-p65(p-p65),an active form of nuclear factor-kappaB(NF-κB),and downregulated the NR2 B subunit in cultured hippocampal slices.Oral L-TAMS prevented the OXA-induced upregulation of TNF-α and p-p65,as well as microglial activation in the hippocampus and the medial prefrontal cortex.Finally,similar to oral L-TAMS,intracerebroventricular injection of PDTC,an NF-κB inhibitor,also prevented the OXAinduced memory/emotional deficits and the changes in TNF-α,p-p65,and microglia.Taken together,the activation of TNF-α/NF-κB signaling resulting from reduced brain Mg~(2+) is responsible for the memory/emotional deficits induced by OXA.Chronic oral L-TAMS may be a novel approach to treating chemotherapy-induced memory/emotional deficits.