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

ABSTRACT

Alzheimer's disease is the most prevalent neurodegenerative disease affecting older adults. Primary features of Alzheimer's disease include extracellular aggregation of amyloid-β plaques and the accumulation of neurofibrillary tangles, formed by tau protein, in the cells. While there are amyloid-β-targeting 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-β in 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.

Targeting vulnerable microcircuits in the ventral hippocampus of male transgenic mice to rescue Alzheimer-like social memory loss

BACKGROUND

Episodic memory loss is a prominent clinical manifestation of Alzheimer's disease (AD), which is closely related to tau pathology and hippocampal impairment. Due to the heterogeneity of brain neurons, the specific roles of different brain neurons in terms of their sensitivity to tau accumulation and their contribution to AD-like social memory loss remain unclear. Therefore, further investigation is necessary.

METHODS

We investigated the effects of AD-like tau pathology by Tandem mass tag proteomic and phosphoproteomic analysis, social behavioural tests, hippocampal electrophysiology, immunofluorescence staining and in vivo optical fibre recording of GCaMP6f and iGABASnFR. Additionally, we utilized optogenetics and administered ursolic acid (UA) via oral gavage to examine the effects of these agents on social memory in mice.

RESULTS

The results of proteomic and phosphoproteomic analyses revealed the characteristics of ventral hippocampal CA1 (vCA1) under both physiological conditions and AD-like tau pathology. As tau progressively accumulated, vCA1, especially its excitatory and parvalbumin (PV) neurons, were fully filled with mislocated and phosphorylated tau (p-Tau). This finding was not observed for dorsal hippocampal CA1 (dCA1). The overexpression of human tau (hTau) in excitatory and PV neurons mimicked AD-like tau accumulation, significantly inhibited neuronal excitability and suppressed distinct discrimination-associated firings of these neurons within vCA1. Photoactivating excitatory and PV neurons in vCA1 at specific rhythms and time windows efficiently ameliorated tau-impaired social memory. Notably, 1 month of UA administration efficiently decreased tau accumulation via autophagy in a transcription factor EB (TFEB)-dependent manner and restored the vCA1 microcircuit to ameliorate tau-impaired social memory.

CONCLUSION

This study elucidated distinct protein and phosphoprotein networks between dCA1 and vCA1 and highlighted the susceptibility of the vCA1 microcircuit to AD-like tau accumulation. Notably, our novel findings regarding the efficacy of UA in reducing tau load and targeting the vCA1 microcircuit may provide a promising strategy for treating AD in the future.

Acetylated tau exacerbates apoptosis by disturbing mitochondrial dynamics in HEK293 cells

An increase in tau acetylation at K274 and K281 and abnormal mitochondrial dynamics have been observed in the brains of Alzheimer's disease (AD) patients. Here, we constructed three types of tau plasmids, TauKQ (acetylated tau mutant, by mutating its K274/K281 into glutamine to mimic disease-associated lysine acetylation), TauKR (non-acetylated tau mutant, by mutating its K274/K281 into arginine), and TauWT (wild-type human full-length tau). By transfecting these tau plasmids in HEK293 cells, we found that TauWT and TauKR induced mitochondrial fusion by increasing the level of mitochondrial fusion proteins. Conversely, TauKQ induced mitochondrial fission by reducing mitochondrial fusion proteins, exacerbating mitochondrial dysfunction and apoptosis. BGP-15 ameliorated TauKQ-induced mitochondrial dysfunction and apoptosis by improving mitochondrial dynamics. Our findings suggest that acetylation of K274/281 represents an important post-translational modification site regulating mitochondrial dynamics, and that BGP-15 holds potential as a therapeutic agent for mitochondria-associated diseases such as AD.

Acetylated tau exacerbates learning and memory impairment by disturbing with mitochondrial homeostasis

Increased tau acetylation at K274 and K281 has been observed in the brains of Alzheimer's disease (AD) patients and animal models, and mitochondrial dysfunction are noticeable and early features of AD. However, the effect of acetylated tau on mitochondria has been unclear until now. Here, we constructed three type of tau forms, acetylated tau mutant by mutating its K274/K281 into Glutamine (TauKQ) to mimic disease-associated lysine acetylation, the non-acetylation tau mutant by mutating its K274/K281 into Arginine (TauKR) and the wild-type human full-length tau (TauWT). By overexpression of these tau forms in vivo and in vitro, we found that, TauKQ induced more severe cognitive deficits with neuronal loss, dendritic plasticity damage and mitochondrial dysfunctions than TauWT. Unlike TauWT induced mitochondria fusion, TauKQ not only induced mitochondria fission by decreasing mitofusion proteins, but also inhibited mitochondrial biogenesis via reduction of PGC-1a/Nrf1/Tfam levels. TauKR had no significant difference in the cognitive and mitochondrial abnormalities compared with TauWT. Treatment with BGP-15 rescued impaired learning and memory by attenuation of mitochondrial dysfunction, neuronal loss and dendritic complexity damage, which caused by TauKQ. Our data suggested that, acetylation at K274/281 was an important post translational modification site for tau neurotoxicity, and BGP-15 is a potential therapeutic drug for AD.

DI-3-n-butylphthalide mitigates stress-induced cognitive deficits in mice through inhibition of NLRP3-Mediated neuroinflammation

Our previous study has demonstrated that chronic stress could cause cognitive deficits and tau pathology. However, the underlying mechanism and whether/how DI-3-n-Butylphthalide (NBP) ameliorates these effects are still unclear. Here, Wild-type mice were subjected to chronic unpredictable and mild stress (CUMS) for 8 weeks. Following the initial 4 weeks, the stressed animals were separated into susceptible (depressive) and unsusceptible (resilient) groups based on behavioral tests. Then, NBP (30 mg/kg i.g) was administered for 4 weeks. Morris water maze (MWM), Western-blot, Golgi staining, immunofluorescence staining and ELISA were used to examine behavioral, biochemical, and pathological changes. The results showed that both depressive and resilient mice displayed spatial memory deficits and an accumulation of tau in the hippocampus. Activated microglia and NLRP3 inflammasome were found after 8-week chronic stress. We also found a decreased level of postsynaptic density (PSD) related proteins (PSD93 and PSD95) and decreased the number of dendritic spines in the hippocampus. Interestingly, almost all the pathological changes in depressive and resilient mice previously mentioned could be reversed by NBP treatment. To further investigate the role of NLRP3 inflammasome in chronic stress-induced cognitive deficits, NLRP3 KO mice were also exposed to chronic stress. And these changes induced by chronic stress could not be found in NLRP3 KO mice. These results show an important role for the NLRP3/caspase-1/IL-1β axis in chronic stress-induced cognitive deficits and NBP meliorates cognitive impairments and selectively attenuates phosphorylated tau accumulation in stressed mice through regulation of NLRP3 inflammatory signaling pathway.

[Characteristics of the white matter involvement sites on MRI in patients with multiple gliomas]

The retrospective study included 122 cases of multiple glioma and 183 cases of single glioma. Of these, there were 74 males and 48 female with multiple gliomas, aged 18 to 83 (53±13) years, and 104 males and 79 females with single gliomas, aged 10 to 84 (51±14) years. A standard spatial-based lesion analysis method was used for constructing a spatially distributed frequency heatmap of multiple gliomas, to observe the characteristics of their white matter invasion sites. The spatial distribution was more frequent in the subventricular zone, corpus callosum and cingulate gyrus in the multiple glioma group compared to the single glioma group (P<0.001).The white matter areas of multiple gliomas were more extensively involved, with more frequent involvement of the conjoined fibers (corpus callosum, P<0.05) and contact fibers (cingulate, dome, 0.05<P<0.10) areas.The spatial distribution of the brain and the white matter invasion of multiple gliomas have certain site specificity.

Human tau accumulation promotes glycogen synthase kinase-3β acetylation and thus upregulates the kinase: A vicious cycle in Alzheimer neurodegeneration

BACKGROUND

Glycogen synthase kinase-3β (GSK-3β) is one of the most effective kinases in promoting tau hyperphosphorylation and accumulation in Alzheimer's disease (AD). However, it is not clear how GSK-3β activity is regulated during AD progression.

METHODS

We firstly used mass spectrometry to identify the acetylation site of GSK-3β, and then established the cell and animal models of GSK-3β acetylation. Next, we conducted molecular, cell biological and behavioral tests. Finally, we designed a peptide to test whether blocking tau-mediated GSK-3β acetylation could be beneficial to AD.

FINDINGS

We found that GSK-3β protein levels increased in the brains of AD patients and the transgenic mice. Overexpressing tau increased GSK-3β protein level with increased acetylation and decreased ubiquitination-related proteolysis. Tau could directly acetylate GSK-3β at K15 both in vitro and in vivo. K15-acetylation inhibited ubiquitination-associated proteolysis of GSK-3β and changed its activity-dependent phosphorylation, leading to over-activation of the kinase. GSK-3β activation by K15-acetylation in turn exacerbated the AD-like pathologies. Importantly, competitively inhibiting GSK-3β K15-acetylation by a novel-designed peptide remarkably improved cognitive impairment and the AD-like pathologies in 3xTg-AD mice.

INTERPRETATION

Tau can directly acetylate GSK-3β at K15 which reveals a vicious cycle between tau hyperphosphorylation and GSK-3β activation.

FUNDING

This study was supported in parts by grants from Science and Technology Committee of China (2016YFC1305800), Hubei Province (2018ACA142), Natural Science Foundation of China (91949205, 82001134, 31730035, 81721005), Guangdong Provincial Key S&T Program (018B030336001).

Melatonin ameliorates cognitive deficits through improving mitophagy in a mouse model of Alzheimer's disease

While melatonin is known to have protective effects in mitochondria-related diseases, aging, and neurodegenerative disorders, there is poor understanding of the effects of melatonin treatment on mitophagy in Alzheimer's disease (AD). We used proteomic analysis to investigate the effects and underlying molecular mechanisms of oral melatonin treatment on mitophagy in the hippocampus of 4-month-old wild-type mice versus age-matched 5 × FAD mice, an animal model of AD. 5 × FAD mice showed disordered mitophagy and mitochondrial dysfunction as revealed by increased mtDNA, mitochondrial marker proteins and MDA production, decreased electron transport chain proteins and ATP levels, and co-localization of Lamp1 and Tomm20. Melatonin treatment reversed the abnormal expression of proteins in the signaling pathway of lysosomes, pathologic phagocytosis of microglia, and mitochondrial energy metabolism. Moreover, melatonin restored mitophagy by improving mitophagosome-lysosome fusion via Mcoln1, and thus, ameliorated mitochondrial functions, attenuated Aβ pathology, and improved cognition. Concurrent treatment with chloroquine and melatonin blocked the positive behavioral and biochemical effects of administration with melatonin alone. Taken in concert, these results suggest that melatonin reduces AD-related deficits in mitophagy such that the drug should be considered as a therapeutic candidate for the treatment of AD.

R13 preserves motor performance in SOD1G93A mice by improving mitochondrial function

Amyotrophic lateral sclerosis (ALS) is a progressive neurodegenerative disease characterized by death of motor neurons in the brain and spinal cord. However, so far, there is no effective treatment for ALS.

Methods: In this study, R13, a prodrug of 7,8-dihydroxyflavone, selectively activating tyrosine kinase receptor B (TrkB) signaling pathway, was administered prophylactically to 40-day old SOD1^G93A mice for 90 days. The motor performance was investigated by rotarod test, climbing-pole test, grip strength test and hanging endurance test. Afterwards, the spinal cord and medulla oblongata of 130-day old mice were harvested, and the proteomics revealed the effect of R13 on mouse protein expression profile. Astrocytes and microglial proliferation were assessed by immunohistochemical analysis. The number of motor neurons in the spinal cord is determined by Nissl staining. The effect of R13 on gastrocnemius morphology was assessed by HE staining. The effect of R13 on the survival rate was accomplished with worms stably expressing G93A SOD1.

Results: Behavioral tests showed that R13 significantly attenuated abnormal motor performance of SOD1^G93A mice. R13 reduced the advance of spinal motor neuron pathology and gastrocnemius muscle atrophy. The proliferation of microglia and astrocytes was reduced by R13 treatment. Mitochondriomics analysis revealed that R13 modified the mitochondrial protein expression profiles in the medulla oblongata and spinal cord of SOD1^G93A mice, particularly promoting the expression of proteins related to oxidative phosphorylation (OXPHOS). Further study found that R13 activated AMPK/PGC-1α/Nrf1/Tfam, promoted mitochondrial biogenesis and ameliorated mitochondrial dysfunction. Lastly, R13 prolonged the survival rate of worms stably expressing G93A SOD1.

Conclusions: These findings suggest oral R13 treatment slowed the advance of motor system disease in a reliable animal model of ALS, supporting that R13 might be useful for treating ALS.

STAT3 ameliorates cognitive deficits via regulation of NMDAR expression in an Alzheimer's disease animal model

Background: Abnormal tau accumulation in the brain has a positively correlation with neurodegeneration and memory deterioration, but the mechanism underlying tau-associated synaptic and cognitive impairments remains unclear. Our previous work has found that human full length tau (hTau) accumulation activated signal transducer and activator of transcription-1 (STAT1) to suppress N-methyl-D-aspartate receptors (NMDARs) expression, followed by memory deficits. STAT3 also belongs to STAT protein family and is reported to involve in regulation of synaptic plasticity and cognition. Here, we investigated the role of STAT3 in the cognitive deficits induced by hTau accumulation. Methods: In vitro studies HEK293 cells were used. EMSA, Luciferase reporter assay, and Immunoprecipitation were applied to detect STAT3 activity. In vivo studies, AAV virus were injected into the hippocampal CA3 region of C57 mice. Western blotting, quantitative real-time polymerase chain reaction, and immunofluorescence were applied to examine the level of synaptic proteins. Electrophysiological analysis, behavioral testing and Golgi impregnation were used to determine synaptic plasticity and memory ability recovery after overexpressing STAT3 or non-acetylated STAT1. Results: Our results showed that hTau accumulation acetylated STAT1 to retain STAT3 in the cytoplasm by increasing the binding of STAT1 with STAT3, and thus inactivated STAT3. Overexpressing STAT3 or non-acetylated STAT1 ameliorated hTau-induced synaptic loss and memory deficits by increasing the expression of NMDARs. Conclusions: Taken together, our study indicates that hTau accumulation impaired synaptic plasticity through STAT3 inactivation induced suppression of NMDARs expression, revealing a novel mechanism for hTau-associated synapse and memory deficits.

δ-Secretase-cleaved Tau stimulates Aβ production via upregulating STAT1-BACE1 signaling in Alzheimer's disease

δ-Secretase, an age-dependent asparagine protease, cleaves both amyloid precursor protein (APP) and Tau and is required for amyloid plaque and neurofibrillary tangle pathologies in Alzheimer's disease (AD). However, whether δ-secretase activation is sufficient to trigger AD pathogenesis remains unknown. Here we show that the fragments of δ-secretase-cleavage, APP (586-695) and Tau(1-368), additively drive AD pathogenesis and cognitive dysfunctions. Tau(1-368) strongly augments BACE1 expression and Aβ generation in the presence of APP. The Tau(1-368) fragment is more robust than full-length Tau in binding active STAT1, a BACE1 transcription factor, and promotes its nuclear translocation, upregulating BACE1 and Aβ production. Notably, Aβ-activated SGK1 or JAK2 kinase phosphorylates STAT1 and induces its association with Tau(1-368). Inhibition of these kinases diminishes stimulatory effect of Tau(1-368). Knockout of STAT1 abolishes AD pathologies induced by δ-secretase-generated APP and Tau fragments. Thus, we show that Tau may not only be a downstream effector of Aβ in the amyloid hypothesis, but also act as a driving force for Aβ, when cleaved by δ-secretase.

Repeated Restraint Stress Led to Cognitive Dysfunction by NMDA Receptor-Mediated Hippocampal CA3 Dendritic Spine Impairments in Juvenile Sprague-Dawley Rats

Although numerous studies have indicated that chronic stress causes cognitive dysfunction with the impairment of synaptic structures and functions, the relationship between cognitive deficits induced by repeated restraint stress and the level of NMDA receptors in the subregion of the hippocampus has been relatively unknown until now. In this study, 3-week-old male Sprague-Dawley rats were exposed to repeated restraint stress for seven consecutive days, their cognitive functions were evaluated through behavioral tests, and then they were sacrificed for electrophysiological, morphological, and biochemical assays. Chronic repeated restraint stress led to cognitive and electrophysiological impairments, with a reduced density of dendritic spines. We also found that the protein level of NMDA receptors only increased in the hippocampal CA3 region. Nevertheless, repeated restraint stress-induced cognitive and synaptic dysfunction were effectively reversed by Ro25-6981, an inhibitor of the GluN2B receptor. These findings suggest that repeated restraint stress-induced synaptic and cognitive deficits are probably mediated through NMDA receptors.

Tau acetylates and stabilizes β-catenin thereby promoting cell survival

Overexpressing Tau counteracts apoptosis and increases dephosphorylated β-catenin levels, but the underlying mechanisms are elusive. Here, we show that Tau can directly and robustly acetylate β-catenin at K49 in a concentration-, time-, and pH-dependent manner. β-catenin K49 acetylation inhibits its phosphorylation and its ubiquitination-associated proteolysis, thus increasing β-catenin protein levels. K49 acetylation further promotes nuclear translocation and the transcriptional activity of β-catenin, and increases the expression of survival-promoting genes (bcl2 and survivin), counteracting apoptosis. Mutation of Tau's acetyltransferase domain or co-expressing non-acetylatable β-catenin-K49R prevents increased β-catenin signaling and abolishes the anti-apoptotic function of Tau. Our data reveal that Tau preserves β-catenin by acetylating K49, and upregulated β-catenin/survival signaling in turn mediates the anti-apoptotic effect of Tau.

MAPT/Tau accumulation represses autophagy flux by disrupting IST1-regulated ESCRT-III complex formation: a vicious cycle in Alzheimer neurodegeneration

Macroautophagy/autophagy deficit induces intracellular MAPT/tau accumulation, the hallmark pathology in Alzheimer disease (AD) and other tauopathies; however, the reverse role of MAPT accumulation in autophagy and neurodegeneration is not clear. Here, we found that overexpression of human wild-type full-length MAPT, which models MAPT pathologies as seen in sporadic AD patients, induced autophagy deficits via repression of autophagosome-lysosome fusion leading to significantly increased LC3 (microtubule-associated protein 1 light chain 3)-II and SQSTM1/p62 (sequestosome 1) protein levels with autophagosome accumulation. At the molecular level, intracellular MAPT aggregation inhibited expression of IST1 (IST1 factor associated with ESCRT-III), a positive modulator for the formation of ESCRT (the Endosomal Sorting Complex Required for Transport) complex that is required for autophagosome-lysosome fusion. Upregulating IST1 in human MAPT transgenic mice attenuated autophagy deficit with reduced MAPT aggregation and ameliorated synaptic plasticity and cognitive functions, while downregulating IST1 per se induced autophagy deficit with impaired synapse and cognitive function in naïve mice. IST1 can facilitate association of CHMP2B (charged multivesicular body protein 2B) and CHMP4B/SNF7-2 to form ESCRT-III complex, while lack of IST1 impeded the complex formation. Finally, we demonstrate that MAPT accumulation suppresses IST1 transcription with the mechanisms involving the ANP32A-regulated mask of histone acetylation. Our findings suggest that the AD-like MAPT accumulation can repress autophagosome-lysosome fusion by deregulating ANP32A-INHAT-IST1-ESCRT-III pathway, which also reveals a vicious cycle of MAPT accumulation and autophagy deficit in the chronic course of AD neurodegeneration.Abbreviations: AAV: adeno-associated virus; Aβ: β-amyloid; aCSF: artificial cerebrospinal fluid; AD: Alzheimer disease; ANP32A: acidic nuclear phosphoprotein 32 family member A; ATG: autophagy related; AVs: autophagic vacuoles; CEBPB: CCAAT enhancer binding protein beta; CHMP: charged multivesicular body protein; DMEM: Dulbecco's modified eagle's medium; EBSS: Earle's balanced salt solution; EGFR: epidermal growth factor receptor; ESCRT: endosomal sorting complex required for transport; fEPSPs: field excitatory postsynaptic potentials; GAPDH: glyceraldehyde-3-phosphate dehydrogenase; GSK3B: glycogen synthase kinase 3 beta; HAT: histone acetyl transferase; HDAC: histone deacetylase; INHAT: inhibitor of histone acetyl transferase; IST1: IST1 factor associated with ESCRT-III; LAMP2: lysosomal associated membrane protein 2; LTP: long-term potentiation; MAP1LC3: microtubule associated protein 1 light chain 3; MAPT/tau: microtubule associated protein tau; MVB: multivesicular bodies; MWM: Morris water maze; PBS: phosphate-buffered saline solution; RAB7: member RAS oncogene family; SNAREs: soluble N-ethylmaleimide-sensitive factor attachment protein receptors; SQSTM1/p62: sequestosome 1.

Tau accumulation triggers STAT1-dependent memory deficits by suppressing NMDA receptor expression

Intracellular tau accumulation forming neurofibrillary tangles is hallmark pathology of Alzheimer's disease (AD), but how tau accumulation induces synapse impairment is elusive. By overexpressing human full-length wild-type tau (termed hTau) to mimic tau abnormality as seen in the brain of sporadic AD patients, we find that hTau accumulation activates JAK2 to phosphorylate STAT1 (signal transducer and activator of transcription 1) at Tyr701 leading to STAT1 dimerization, nuclear translocation, and its activation. STAT1 activation suppresses expression of N-methyl-D-aspartate receptors (NMDARs) through direct binding to the specific GAS element of GluN1, GluN2A, and GluN2B promoters, while knockdown of STAT1 by AAV-Cre in STAT1^flox/flox mice or expressing dominant negative Y701F-STAT1 efficiently rescues hTau-induced suppression of NMDAR expression with amelioration of synaptic functions and memory performance. These findings indicate that hTau accumulation impairs synaptic plasticity through JAK2/STAT1-induced suppression of NMDAR expression, revealing a novel mechanism for hTau-associated synapse and memory deficits.

[A mini-incision on the anterior hip for pediatric femur neck fractures of type Delbet Ⅱ]

Objective: To investigate the early clinical outcomes of hip anterior short incision and open reduction and internal fixation for the treatment of children with Delbet Ⅱ femoral neck fracture. Methods: A retrospective analysis of 12 children with DelbetⅡ femoral neck fractures was performed with the anterior short incision approach at Department of Pediatric Orthopaedic, Children's Hospital, Nanjing Medical University from January 2014 to August 2016. There were 7 males and 5 females including 8 cases at left side and 4 cases at right side,aged (11.5±0.8) years (range: 8-14 years).Patients underwent surgery in (12.0±0.9) hours (range: 6-20 hours) after the injury. Displaced fractures were treated by open reduction if closed reduction failed.The surgical incision was performed with the anterior inferior iliac spine centered on, extending along the groin crease, and the length was 3 to 4 cm. The interval between the sartorius and the tensor fascia latae was applied, and the direct and indirect head of rectus femoris were resected to visualize the hip joint capsule. T-shaped incision was made in the capsule. After the reduction was obtained, two or three compression canulated screws were used to fix the fracture site. The healing time, complications and corresponding record outcome by X-ray and clinical examination were recorded. At the latest follow-up,the results were analyzed using the Ratliff criteria and clinical outcomes were assessed by pain, restrictive hip movement, normal activity or the avoidance of games, and the femoral neck in the radiograph. Results: Twelve patients had been followed-up for (30.0±4.1)months(range: 24-36 months). X-ray showed the fractures' healing time was (8.0±0.4) weeks(range: 7-9 weeks). Ten of the 12 fractures healed after one operation and were associated with no evidence of osteonecrosis of the femoral head. One case occurred premature physeal closure. There were no cases with fracture relocation, coaxvara, delayed union and nonunion or any significant postoperative complications. There was no infection, flexible internal fixation or ruptures. According to Ratliff grade, 9 cases of 12 patients were fine and 3 cases was acceptable. Conclusions: Satisfactory short-term effects can be achieved by a mini-incision on the anterior hip for Delbet Ⅱ pediatric femur neck fractures. The anterior incision has the advantage of less trauma, smaller incision scar, better fracture reduction and fixation, and less wound complications.

Monosodium glutamate exposure during the neonatal period leads to cognitive deficits in adult Sprague-Dawley rats

Epidemiological surveys show that 70-80% of patients with Alzheimer's disease (AD) have type 2 diabetes mellitus (T2DM) or show an abnormality of blood glucose levels. Therefore, an increasing number of evidence has suggested that diabetic hyperglycemia is tightly linked with the pathogenesis and progression of AD. In the present study, we replicated T2DM animal model via subcutaneous injection of newborn Sprague-Dawley (SD) rats with monosodium glutamate (MSG) during the neonatal period to investigate the effects and underlying mechanisms of hyperglycemia on cognitive ability. We found that neonatal MSG exposure induced hyperglycemia as well as Alzheimer-like learning and memory deficits with decreased dendritic spine density and hippocampal synaptic-related protein expression and increased phosphorylated tau levels in ∼3-month-old SD rats. Our results suggested that hyperglycemia probably causes cognitive impairment and Alzheimer-like neuropathological changes, which provide the experimental data connecting T2DM and AD.

Fluoxetine administration during adolescence attenuates cognitive and synaptic deficits in adult 3×TgAD mice

Fluoxetine (FLX) has broad neurobiological functions and neuroprotective effects; however, the preventive effects of FLX on cognitive impairments in Alzheimer's disease (AD) have not been reported. Here, we studied whether adolescent administration of fluoxetine can prevent memory deficits in AD transgenic mice that harbour PS1_m146v, APP_swe and TauP_301L mutations (3 × TgAD). FLX was applied through peritoneal injection to the mice at postnatal day 35 (p35) for 15 consecutive days, and the effects of FLX were observed at 6-month. We found that adolescent administration of FLX improved learning and memory abilities in 6-month-old 3 × TgAD mice. FLX exposure also increased the sizes of the hippocampal CA1, dentate gyrus (DG) and extensive cortex regions, with increased numbers of neurons and higher dendritic spine density. Meanwhile, the synaptic plasticity of neurons in the hippocampus was remodelled, and the expression levels of synaptic-related proteins were increased along with activation of the cyclic AMP response element-binding (CREB) protein/brain-derived neurotrophic factor (BDNF) signalling pathway. Finally, we found that FLX effectively prevented the increase of beta-amyloid (Aβ) levels. These data suggest that adolescent administration of the antidepressant drug FLX can efficiently preserve cognitive functions and improve pathologies in 3×Tg AD mice.

Effects of fluoride on proliferation and mineralization in periodontal ligament cells in vitro

Fluoride, which is often added to toothpaste or mouthwash in order to protect teeth from decay, may be a novel therapeutic approach for acceleration of periodontal regeneration. Therefore, we investigated the effects of fluoride on proliferation and mineralization in human periodontal ligament cells in vitro. The periodontal ligament cells were stimulated with various concentrations of NaF added into osteogenic inductive medium. Immunohistochemistry of cell identification, cell proliferation, alkaline phosphatase (ALP) activity assay, Alizarin red S staining and quantitative real-time-polymerase chain reaction (RT-PCR) were performed. Moderate concentrations of NaF (50-500 μmol/L) had pro-proliferation effects, while 500 μmol/L had the best effects. ALP activity and calcium content were significantly enhanced by 10 μmol/L NaF with osteogenic inductive medium. Quantitative RT-PCR data varied in genes as a result of different NaF concentrations and treatment periods. We conclude that moderate concentrations of NaF can stimulate proliferation and mineralization in periodontal ligament cells. These in vitro findings may provide a novel therapeutic approach for acceleration of periodontal regeneration by addition of suitable concentrations of NaF into the medication for periodontitis treatment, i.e., into periodontal packs and tissue patches.

Role of microtubule-associated protein tau phosphorylation in Alzheimer's disease

As a major microtubule-associated protein, tau plays an important role in promoting microtubule assembly and stabilizing microtubules. In Alzheimer's disease (AD) and other tauopathies, the abnormally hyperphosphorylated tau proteins are aggregated into paired helical filaments and accumulated in the neurons with the form of neurofibrillary tangles. An imbalanced regulation in protein kinases and protein phosphatases is the direct cause of tau hyperphosphorylation. Among various kinases and phosphatases, glycogen synthase kinase-3β (GSK-3β) and protein phosphatase 2A (PP2A) are the most implicated. Accumulation of the hyperphosphorylated tau induces synaptic toxicity and cognitive impairments. Here, we review the upstream factors or pathways that can regulate GSK-3β or PP2A activity mainly based on our recent findings. We will also discuss the mechanisms that may underlie tau-induced synaptic toxicity.

Downregulating ANP32A rescues synapse and memory loss via chromatin remodeling in Alzheimer model

Background

The impairment of histone acetylation is causally linked to the cognitive decline in Alzheimer’s disease (AD). In addition to histone acetyltransferases (HATs) and histone deacetylases (HDACs), inhibitor of acetyltransferases (INHAT) can also regulate histone acetylation. As a key component of INHAT, level of ANP32A is selectively upregulated in the brain of AD patients. Here we investigated whether downregulating ANP32A can rescue AD-like synapse and memory deficits.

Methods

RFP-labeled lentiviral ANP32A-shRNA was infused stereotaxically into the hippocampal CA3 region of the human tau transgenic mice (termed htau). The spatial learning and memory were assessed by Morris water maze (MWM). The synaptic function was measured by electrophysiological recording and the spine density was detected by Golgi staining. RT-PCR and Western blotting were used to detect the mRNA and protein levels.

Results

Elevation of ANP32 in htau transgenic mice was correlated with learning deficits, while the hippocampal infusion of lenti-siANP32A to downregulate ANP32A in 12 m-old htau mice could rescue memory loss. Further studies demonstrated that downregulating ANP32A restored synapse morphology and the function. In the brain of htau mice, the acetylated histone decreased while knockdown ANP32A unmasked histone for a robust acetylation with reduced INHAT complex formation. Downregulating of ANP32A also attenuated AD-like tau hyperphosphorylation. Finally, several AD-associated risk factors, including tau accumulation, β-amyloid and H₂O₂ exposure, increased ANP32A by activating CCAAT/enhancer binding protein-β (C/EBPβ).

Conclusion

We conclude that downregulating ANP32A rescues synaptic plasticity and memory ability by reducing INHAT formation and unmasking histone for hyperacetylation. Our findings reveal novel mechanisms for AD memory loss and potential molecular markers for protection.

Electronic supplementary material

The online version of this article (doi:10.1186/s13024-017-0178-8) contains supplementary material, which is available to authorized users.

Knockdown of pp32 Increases Histone Acetylation and Ameliorates Cognitive Deficits

Aging is a cause of cognitive decline in the elderly and the major risk factor for Alzheimer's disease, however, aging people are not all destined to develop into cognitive deficits, the molecular mechanisms underlying this difference in cognition of aging people are obscure. Epigenetic modifications, particularly histone acetylation in the nervous system, play a critical role in regulation of gene expression for learning and memory. An inhibitor of acetyltransferases (INHAT) is reported to suppress histone acetylation via a histone-masking mechanism, and pp32 is a key component of INHAT complex. In the present study, we divided ~18 m-old aged mice into the cognitive-normal and the cognitive-impaired group by Morris water maze, and found that pp32 level was significantly increased in the hippocampus of cognitive-impaired aged mice. The mRNA and protein levels of synaptic-associated proteins decreased with reduced dendrite complexity and histone acetylation. Knockdown of pp32 rescued cognitive decline in cognitive-impaired aged mice with restoration of synaptic-associated proteins, the increase of spine density and elevation of histone acetylation. Our study reveals a novel mechanism underlying the aging-associated cognitive disturbance, indicating that suppression of pp32 might represent a promising therapeutic approach for learning and memory impairments.

[Hand, foot and mouth disease in Hubei province, 2009-2015: an epidemiological and etiological study]

Objective: To clarify the age patterns and types of differences so as to provide reference on prevention and interventions of hand, foot and mouth disease (HFMD) cases, in Hubei province. Methods: We collected the HFMD case information of Hubei province from the Chinese National Notifiable Infectious Disease Reporting System in 2009-2015 while the information on pathogens from the laboratory monitoring system of Center for Disease Control and Prevention at all levels in Hubei province. All the data were stratified by age, disease severity, laboratory confirmation status, and serotypes of enterovirus. Results: There were 495 783 reported HFMD cases from 2009 to 2015, in Hubei province, of which 1 045 were severe with 99 fatal. The annual notification rate was 1 231.0/10(6). HFMD cases were concentrated mainly in 0.5-5 year olds, with highest severity and mortality seen in 6-11 month-olds. The predominated pathogen in mild laboratory-confirmed cases each year, in order during 2009-2015 as: EV71, Cox A16, Cox A16, Cox A16, EV71, Cox A16 and other EV. HFMD showed semiannual peaks in April-June, November-December, and with more cases in the even years than in the odd years. Conclusions: Children aged 0.5 to 5 years with 6 to 11 month-olds in particular, were the focused groups of attention in Hubei province. Our findings provided evidence for the improvement on monitoring program. Targeted intervention approaches should be strengthened to reduce the mortality and morbidity of HFMD in the province.

[Robotic mitral valve repair: perioperative and seven-year follow-up results]

OBJECTIVE

To summarize surgical experience during the conduction of robotic mitral valve repair and evaluate the long-term follow-up results.

METHODS

From January 2007 to September 2014, 110 consecutive patients underwent robotic mitral valve repair under da Vinci Surgical System (Intuitive Surgical, USA) in Chinese PLA General Hospital were enrolled. The age of the patients was 14 to 65(45±12) years old. The male to female ratio was 2.3∶1. Among them, 95.5%(105/110) of the cases was diagnosed as mitral regurgitation and 4.5%(5/110) of them was diagnosed as mitral stenosis, and most of them (63.3%) needed triangular or quadrangular resection. Nitinol U-clips (58.1%), running suture (31.2%) and Cor-Knot™ suture device (10.8%) were used to secure the annuloplasty ring. The operative data were collected and patients were regularly followed up echocardiographically as long as 7 years.

RESULTS

All the surgeries were finished by the same surgeon. One case required conversion to sternotomy. The mean cardiopulmonary bypass (CPB) and cross-clamp time was 70 to 152 (121.0±34.3) and 47 to 122 (82.6±25.3) minutes respectively. After surgery, one death (0.91%) and two cases of stroke (1.82%) occurred. Three cases of early prosthetic failure (2.73%) were noticed. All patients were successfully followed up for a median of 50 (range, 1 month to 7 years) months and 94.5%(104/110) of them had no re-operation.

CONCLUSION

Robotic mitral valve repair is a safe and effective surgical method with excellent long-term outcomes.

Tau accumulation impairs mitophagy via increasing mitochondrial membrane potential and reducing mitochondrial Parkin

Intracellular accumulation of wild type tau is a hallmark of sporadic Alzheimer's disease (AD). However, the molecular mechanisms underlying tau toxicity is not fully understood. Here, we detected mitophagy deficits evidenced by the increased levels of mitophagy markers, including COX IV, TOMM20, and the ratio of mtDNA to genomic DNA indexed as mt-Atp6/Rpl13, in the AD brains and in the human wild type full-length tau (htau) transgenic mice. More interestingly, the mitophagy deficit was only shown in the AD patients who had an increased total tau level. Further studies demonstrated that overexpression of htau induced mitophagy deficits in HEK293 cells, the primary hippocampal neurons and in the brains of C57 mice. Upon overexpression of htau, the mitochondrial membrane potential was increased and the levels of PTEN-induced kinase 1 (PINK1) and Parkin decreased in the mitochondrial fraction, while upregulation of Parkin attenuated the htau-induced mitophagy deficits. Finally, we detected a dose-dependent allocation of tau proteins into the mitochondrial outer membrane fraction along with its cytoplasmic accumulation. These data suggest that intracellular accumulation of htau induces mitophagy deficits by direct inserting into the mitochondrial membrane and thus increasing the membrane potential, which impairs the mitochondrial residence of PINK1/Parkin. Our findings reveal a novel mechanism underlying the htau-induced neuronal toxicities in AD and other tauopathies.

Correcting miR92a-vGAT-Mediated GABAergic Dysfunctions Rescues Human Tau-Induced Anxiety in Mice

Patients with Alzheimer's disease (AD) commonly show anxiety behaviors, but the molecular mechanisms are not clear and no efficient intervention exists. Here, we found that overexpression of human wild-type, full-length tau (termed htau) in hippocampus significantly decreased the extracellular γ-aminobutyric acid (GABA) level with inhibition of γ oscillation and the evoked inhibitory postsynaptic potential (eIPSP). With tau accumulation, the mice show age-dependent anxiety behaviors. Among the factors responsible for GABA synthesis, release, uptake, and transport, we found that accumulation of htau selectively suppressed expression of the intracellular vesicular GABA transporter (vGAT). Tau accumulation increased miR92a, which targeted vGAT mRNA 3' UTR and inhibited vGAT translation. Importantly, we found that upregulating GABA tones by intraperitoneal injection of midazolam (a GABA agonist), ChR2-mediated photostimulating and overexpressing vGAT, or blocking miR92a by using specific antagomir or inhibitor efficiently rescued the htau-induced GABAergic dysfunctions with attenuation of anxiety. Finally, we also demonstrated that vGAT level decreased while the miR92a increased in the AD brains. These findings demonstrate that the AD-like tau accumulation induces anxiety through disrupting miR92a-vGAT-GABA signaling, which reveals molecular mechanisms underlying the anxiety behavior in AD patients and potentially leads to the development of new therapeutics for tauopathies.

Spatial training promotes short-term survival and neuron-like differentiation of newborn cells in Aβ1-42-injected rats

Neurogenesis plays a role in hippocampus-dependent learning and impaired neurogenesis may correlate with cognitive deficits in Alzheimer's disease. Spatial training influences the production and fate of newborn cells in hippocampus of normal animals, whereas the effects on neurogenesis in Alzheimer-like animal are not reported until now. Here, for the first time, we investigated the effect of Morris water maze training on proliferation, survival, apoptosis, migration, and differentiation of newborn cells in β-amyloid-treated Alzheimer-like rats. We found that spatial training could preserve a short-term survival of newborn cells generated before training, during the early phase, and the late phase of training. However, the training had no effect on the long-term survival of mature newborn cells generated at previously mentioned 3 different phases. We also demonstrated that spatial training promoted newborn cell differentiation preferentially to the neuron direction. These findings suggest a time-independent neurogenesis induced by spatial training, which may be indicative for the cognitive stimulation in Alzheimer's disease therapy.

Human wild-type full-length tau accumulation disrupts mitochondrial dynamics and the functions via increasing mitofusins

Intracellular accumulation of tau protein is hallmark of sporadic Alzheimer’s disease (AD), however, the cellular mechanism whereby tau accumulation causes neurodegeneration is poorly understood. Here we report that overexpression of human wild-type full-length tau (termed htau) disrupted mitochondrial dynamics by enhancing fusion and induced their perinuclear accumulation in HEK293 cells and rat primary hippocampal neurons. The htau accumulation at later stage inhibited mitochondrial functions shown by the decreased ATP level, the ratio of ATP/ADP and complex I activity. Simultaneously, the cell viability was decreased with retraction of the cellular/neuronal processes. Further studies demonstrated that htau accumulation increased fusion proteins, including OPA1 and mitofusins (Mfn1, Mfn2) and reduced the ubiquitination of Mfn2. Downregulation of the mitofusins by shRNA to ~45% or ~52% of the control levels attenuated the htau-enhanced mitochondrial fusion and restored the functions, while downregulation of OPA1 to ~50% of the control level did not show rescue effects. Finally, abnormal mitochondrial accumulation and dysfunction were also observed in the brains of htau transgenic mice. Taken together, our data demonstrate that htau accumulation decreases cell viability and causes degeneration via enhancing mitofusin-associated mitochondrial fusion, which provides new insights into the molecular mechanisms underlying tauopathies.

Biomarkers for Early Diagnostic of Mild Cognitive Impairment in Type-2 Diabetes Patients: A Multicentre, Retrospective, Nested Case-Control Study

Background

Both type 2 diabetes mellitus (T2DM) and Alzheimer's disease (AD) are common age-associated disorders and T2DM patients show an increased risk to suffer from AD, however, there is currently no marker to identify who in T2DM populations will develop AD. Since glycogen synthase kinase-3β (GSK-3β) activity, ApoE genotypes and olfactory function are involved in both T2DM and AD pathogenesis, we investigate whether alterations of these factors can identify cognitive impairment in T2DM patients.

Methods

The cognitive ability was evaluated using Minimum Mental State Examination (MMSE) and Clinical Dementia Rating (CDR), and the mild cognitive impairment (MCI) was diagnosed by Petersen's criteria. GSK-3β activity in platelet, ApoE genotypes in leucocytes and the olfactory function were detected by Western/dot blotting, the amplification refractory mutation system (ARMS) PCR and the Connecticut Chemosensory Clinical Research Center (CCCRC) test, respectively. The odds ratio (OR) and 95% confidence intervals (95% CI) of the biomarkers for MCI diagnosis were calculated by logistic regression. The diagnostic capability of the biomarkers was evaluated by receiver operating characteristics (ROC) analyses.

Findings

We recruited 694 T2DM patients from Jan. 2012 to May. 2015 in 5 hospitals (Wuhan), and 646 of them met the inclusion criteria and were included in this study. 345 patients in 2 hospitals were assigned to the training set, and 301 patients in another 3 hospitals assigned to the validation set. Patients in each set were randomly divided into two groups: T2DM without MCI (termed T2DM-nMCI) or with MCI (termed T2DM-MCI). There were no significant differences for sex, T2DM years, hypertension, hyperlipidemia, coronary disease, complications, insulin treatment, HbA1c, ApoE ε2, ApoE ε3, tGSK3β and pS9GSK3β between the two groups. Compared with the T2DM-nMCI group, T2DM-MCI group showed lower MMSE score with older age, ApoE ε4 allele, higher olfactory score and higher rGSK-3β (ratio of total GSK-3β to Ser9-phosphorylated GSK-3β) in the training set and the validation set. The OR values of age, ApoE ε4 gene, olfactory score and rGSK-3β were 1.09, 2.09, 1.51, 10.08 in the training set, and 1.06, 2.67, 1.47, 7.19 in the validation set, respectively. The diagnostic accuracy of age, ApoE ε4 gene, olfactory score and rGSK-3β were 0.76, 0.72, 0.66, 0.79 in the training set, and 0.70, 0.68, 0.73, 0.79 in the validation set, respectively. These four combined biomarkers had the area under the curve (AUC) of 82% and 86%, diagnostic accuracy of 83% and 81% in the training set and the validation set, respectively.

Interpretation

Aging, activation of peripheral circulating GSK-3β, expression of ApoE ε4 and increase of olfactory score are diagnostic for the mild cognitive impairment in T2DM patients, and combination of these biomarkers can improve the diagnostic accuracy.

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ApoE ε4 gene, platelet GSK-3β activation, olfactory dysfunction and aging are non-invasive, affordable and accessible biomarkers for diagnosing mild cognitive impairment in type 2 diabetes mellitus patients, and the combination of these non-invasive, affordable and accessible biomarkers can improve the accuracy of the diagnosis.

Epidemiological studies show that type 2 diabetes mellitus is an independent risk factor of Alzheimer disease, and a large proportion of diabetic patients will develop Alzheimer disease, but no early diagnostic tool to identify them. We find that ApoE ε4 gene, platelet GSK-3β activation, olfactory dysfunction and aging are early markers for dementia in type 2 diabetes patients, and combination of these non-invasive markers can improve the diagnostic accuracy. These findings shed light on the early identification in type 2 diabetes population who will develop Alzheimer disease and thus enable early intervention to this currently incurable neurodegenerative disorder.

Protective efficacy of a genetic subunit bacterin against edema disease of swine in mice

The exotoxin SLT-IIeB from the Escherichia coli Ee strain was expressed in E. coli, and the recombinant protein was purified, mixed with the Ee strain, then emulsified with oil-emulsion adjuvants to obtain a mixed subunit bacterin. Groups of Kunming mice were immunized at weeks 0 and 2, and challenged intraperitoneally with the Ee strain at week 4. Antibodies were detected by ELISA and an agglutination test. After the second immunization, the antibody level increased and the rate of immune protection against the Ee strain was 70 and 91.7% in the subunit bacterin and bacterin groups, respectively. Therefore, the mixed subunit bacterin provided good protection against the homologous Ee strain, which provides a basis for further research, into high-efficacy vaccines against porcine edema disease.

Expression of 1N3R-Tau isoform inhibits cell proliferation by inducing S phase arrest in N2a cells

Tau is a microtubule-associated protein implicated in neurodegenerative tauopathies. Six tau isoforms are generated from a single gene through alternative splicing of exons 2, 3 and 10 in human brain. Differential expression of tau isoforms has been detected in different brain areas, during neurodevelopment and in neurodegenerative disorders. However, the biological significance of different tau isoforms is not clear. Here, we investigated the individual effect of six different isoforms of tau on cell proliferation and the possible mechanisms by transient expression of eGFP-labeled tau isoform plasmid in N2a cells. Our study showed the transfection efficiency was comparable between different isoforms of tau by examining GFP expression. Compared with other isoforms, we found expression of 1N3R-tau significantly inhibited cell proliferation by Cell Counting Kit-8 assay and BrdU incorporation. Flow cytometry analysis further showed expression of 1N3R-tau induced S phase arrest. Compared with the longest isoform of tau, expression of 1N3R-tau induced cyclin E translocation from the nuclei to cytoplasm, while it did not change the level of cell cycle checkpoint proteins. These data indicate that 1N3R-tau inhibits cell proliferation through inducing S phase arrest.

Spatial training preserves associative memory capacity with augmentation of dendrite ramification and spine generation in Tg2576 mice

Alzheimer's disease (AD) is the most common neurodegenerative disorder and there is currently no efficient cure for this devastating disease. Cognitive stimulation can delay memory loss during aging and in patients with mild cognitive impairment. In 3 × Tg-AD mice, training decreased the neuropathologies with transient amelioration of memory decline. However, the neurobiological mechanisms underlying the learning-improved memory capacity are poorly understood. Here, we found in Tg2576 mice spatial training in Morris water maze (MWM) remarkably improved the subsequent associative memory acquisition detected by contextual fear conditioning. We also found that spatial training enhanced long term potentiation, dendrite ramification and spine generation in hippocampal dentate gyrus (DG) and CA1 neurons at 24 h after the training. In the molecular level, the MWM training remarkably activated calcium/calmodulin-dependent protein kinase II (CaMKII) with elevation of glutamate AMPA receptor GluA1 subunit (GluA1), postsynaptic density protein 93 (PSD93) and postsynaptic density protein 95 (PSD95) in the hippocampus. Finally, the training also significantly ameliorated AD-like tau and amyloid pathologies. We conclude that spatial training in MWM preserves associative memory capacity in Tg2576 mice, and the mechanisms involve augmentation of dendrite ramification and spine generation in hippocampus.

Fluorocitrate induced the alterations of memory-related proteins and tau hyperphosphorylation in SD rats

Astrocytes provide structural, metabolic and trophic supports for neurons. However, there are no direct evidences whether astrocytes involve in the regulation of synaptic proteins expression and tau phosphorylation until now. Here, we injected 1 nmol fluorocitrate (FC), which preferentially taken up by astrocytes and results in reversible inhibition of the astrocytic tricarboxylic acid cycle, into the left lateral ventricle of the brain in the SD rats for 1h, and found that FC treatment decreased several memory-related proteins levels, such as AMPA receptor GluR1/2, postsynaptic density protein 93/95, Arc and phosphorylated cAMP response element binding proteins, while increased synaptophysin and synapsin I levels in the hippocampus. FC treatment also increased the levels of phosphorylated tau at multiple Alzheimer-related phosphorylation sites, as well as activation of glycogen synthase kinase-3β and inactivation of protein phosphatase-2A. Similar effects were also observed in the primary hippocampal neurons, which were cultured with the conditioned media from FC-treatment primary astrocytes. Our data suggest that astrocytes regulate neuronal tau phosphorylation and several synaptic proteins expression.

CaMKII-dependent dendrite ramification and spine generation promote spatial training-induced memory improvement in a rat model of sporadic Alzheimer's disease

Participation in cognitively stimulating activities can preserve memory capacities in patients with Alzheimer's disease (AD), but the mechanism is not fully understood. Here, we used a rat model with hyperhomocysteinemia, an independent risk factor of AD, to study whether spatial training could remodel the synaptic and/or dendritic plasticity and the key molecular target(s) involved. We found that spatial training in water maze remarkably improved the subsequent short-term and long-term memory performance in contextual fear conditioning and Barnes maze. The trained rats showed an enhanced dendrite ramification, spine generation and plasticity in dentate gyrus (DG) neurons, and stimulation of long-term potentiation between perforant path and DG circuit. Spatial training also increased the levels of postsynaptic GluA1, GluN2A, GluN2B, and PSD93 with selective activation of calcium/calmodulin-dependent protein kinase II (CaMKII), although inhibition of CaMKII by stereotaxic injection of KN93 into hippocampal DG, abolished the training-induced cognitive improvement, dendrite ramification, and spine generation. We conclude that spatial training can preserve the cognitive function by CaMKII-dependent remodeling of dendritic plasticity in hyperhomocysteinemia-induced sporadic AD-like rats.

Magnesium protects cognitive functions and synaptic plasticity in streptozotocin-induced sporadic Alzheimer's model

Alzheimer's disease (AD) is characterized by profound synapse loss and impairments of learning and memory. Magnesium affects many biochemical mechanisms that are vital for neuronal properties and synaptic plasticity. Recent studies have demonstrated that the serum and brain magnesium levels are decreased in AD patients; however, the exact role of magnesium in AD pathogenesis remains unclear. Here, we found that the intraperitoneal administration of magnesium sulfate increased the brain magnesium levels and protected learning and memory capacities in streptozotocin-induced sporadic AD model rats. We also found that magnesium sulfate reversed impairments in long-term potentiation (LTP), dendritic abnormalities, and the impaired recruitment of synaptic proteins. Magnesium sulfate treatment also decreased tau hyperphosphorylation by increasing the inhibitory phosphorylation of GSK-3β at serine 9, thereby increasing the activity of Akt at Ser473 and PI3K at Tyr458/199, and improving insulin sensitivity. We conclude that magnesium treatment protects cognitive function and synaptic plasticity by inhibiting GSK-3β in sporadic AD model rats, which suggests a potential role for magnesium in AD therapy.