H3K4 Trimethylation Mediate Hyperhomocysteinemia Induced Neurodegeneration via Suppressing Histone Acetylation by ANP32A.

Homocysteine (Hcy) is an independent and serious risk factor for dementia, including Alzheimer's disease (AD), but the precise mechanisms are still poorly understood. In the current study, we observed that the permissive histone mark trimethyl histone H3 lysine 4 (H3K4me3) and its methyltransferase KMT2B were significantly elevated in hyperhomocysteinemia (HHcy) rats, with impairment of synaptic plasticity and cognitive function. Further research found that histone methylation inhibited synapse-associated protein expression, by suppressing histone acetylation. Inhibiting H3K4me3 by downregulating KMT2B could effectively restore Hcy-inhibited H3K14ace in N2a cells. Moreover, chromatin immunoprecipitation revealed that Hcy-induced H3K4me3 resulted in ANP32A mRNA and protein overexpression in the hippocampus, which was regulated by increased transcription Factor c-fos and inhibited histone acetylation and synapse-associated protein expression, and downregulating ANP32A could reverse these changes in Hcy-treated N2a cells. Additionally, the knockdown of KMT2B restored histone acetylation and synapse-associated proteins in Hcy-treated primary hippocampal neurons. These data have revealed a novel crosstalk mechanism between KMT2B-H3K4me3-ANP32A-H3K14ace, shedding light on its role in Hcy-related neurogenerative disorders.

Pathological features and molecular signatures of early olfactory dysfunction in 3xTg-AD model mice.

BACKGROUND: Olfactory dysfunction is known to be an early manifestation of Alzheimer's disease (AD). However, the underlying mechanism, particularly the specific molecular events that occur during the early stages of olfactory disorders, remains unclear. METHODS: In this study, we utilized transcriptomic sequencing, bioinformatics analysis, and biochemical detection to investigate the specific pathological and molecular characteristics of the olfactory bulb (OB) in 4-month-old male triple transgenic 3xTg-AD mice (PS1M146V/APPSwe/TauP301L). RESULTS: Initially, during the early stages of olfactory impairment, no significant learning and memory deficits were observed. Correspondingly, we observed significant accumulation of amyloid-beta (Aß) and Tau pathology specifically in the OB, but not in the hippocampus. In addition, significant axonal morphological defects were detected in the olfactory bulb, cortex, and hippocampal brain regions of 3xTg-AD mice. Transcriptomic analysis revealed a significant increase in the expression of neuroinflammation-related genes, accompanied by a significant decrease in neuronal activity-related genes in the OB. Moreover, immunofluorescence and immunoblotting demonstrated an activation of glial cell biomarkers Iba1 and GFAP, along with a reduction in the expression levels of neuronal activity-related molecules Nr4a2 and FosB, as well as olfaction-related marker OMP. CONCLUSION: In sum, the early accumulation of Aß and Tau pathology induces neuroinflammation, which subsequently leads to a decrease in neuronal activity within the OB, causing axonal transport deficits that contribute to olfactory disorders. Nr4a2 and FosB appear to be promising targets for intervention aimed at improving early olfactory impairment in AD.

Aerobic exercise attenuates autophagy-lysosomal flux deficits by ADRB2/ß2-adrenergic receptor-mediated V-ATPase assembly factor VMA21 signaling in APP-PSEN1/PS1 mice.

Growing evidence suggests that macroautophagy/autophagy-lysosomal pathway deficits contribute to the accumulation of amyloid-ß (Aß) in Alzheimer disease (AD). Aerobic exercise (AE) has long been investigated as an approach to delay and treat AD, although the exact role and mechanism are not well known. Here, we revealed that AE could reverse autophagy-lysosomal deficits via activation of ADRB2/ß2-adrenergic receptor, leading to significant attenuation of amyloid-ß pathology in APP-PSEN1/PS1 mice. Molecular mechanism research found that AE could reverse autophagy deficits by upregulating the AMP-activated protein kinase (AMPK)-MTOR (mechanistic target of rapamycin kinase) signaling pathway. Moreover, AE could reverse V-ATPase function by upregulating VMA21 levels. Inhibition of ADRB2 by propranolol (antagonist, 30 µM) blocked AE-attenuated Aß pathology and cognitive deficits by inhibiting autophagy-lysosomal flux. AE may mitigate AD via many pathways, while ADRB2-VMA21-V-ATPase could improve cognition by enhancing the clearance of Aß through the autophagy-lysosomal pathway, which also revealed a novel theoretical basis for AE attenuating pathological progression and cognitive deficits in AD.

Integrated transcriptomics reveals the brain and blood biomarkers in Alzheimer's disease.

BACKGROUND: The systematic molecular associations between the peripheral blood cells and brain in Alzheimer's disease (AD) remains unclear, which hinders our understanding of AD pathological mechanisms and the exploration of new diagnostic biomarkers. METHODS: Here, we performed an integrated analysis of the brain and peripheral blood cells transcriptomics to establish peripheral biomarkers of AD. By employing multiple statistical analyses plus machine learning, we identified and validated multiple regulated central and peripheral network in patients with AD. RESULTS: By bioinformatics analysis, a total of 243 genes were differentially expressed in the central and peripheral systems, mainly enriched in three modules: immune response, glucose metabolism and lysosome. In addition, lysosome related gene ATP6V1E1 and immune response related genes (IL2RG, OSM, EVI2B TNFRSF1A, CXCR4, STAT5A) were significantly correlated with Aß or Tau pathology. Finally, receiver operating characteristic (ROC) analysis revealed that ATP6V1E1 showed high-diagnostic potential for AD. CONCLUSION: Taken together, our data identified the main pathological pathways in AD progression, particularly the systemic dysregulation of the immune response, and provided peripheral biomarkers for AD diagnosis.

Danggui Buxue decoction ameliorates mitochondrial biogenesis and cognitive deficits through upregulating histone H4 lysine 12 acetylation in APP/PS1 mice.

ETHNOPHARMACOLOGICAL RELEVANCE: Danggui Buxue decoction (DBD) is a classic herbal decoction consisting of Astragali Radix (AR) and Angelica Sinensis Radix (ASR) with a 5:1 wt ratio, which can supplement 'blood' and 'qi' (vital energy) for the treatment of clinical diseases. According to Traditional Chinese Medicine (TCM) theory, dementia is induced by Blood deficiency and Qi weakness, which causes a decline in cognition. However, the underlying mechanisms of DBD improving cognition deficits in neurodegenerative disease are no clear. AIM OF THE STUDY: This study aims at revealing the underlying mechanisms of DBD plays a protective role in the cognitive deficits and pathology process of Alzheimer's disease (AD). MATERIALS AND METHODS: The APP/PS1 (Mo/HuAPP695swe/PS1-dE9) double transgenic mice were adopted as an experimental model of AD. Qualitative and quantitative analysis of 3 compounds in DBT was analyzed by HPLC. Morris water maze test, Golgi staining and electrophysiology assays were used to evaluate the effects of DBD on cognitive function and synaptic plasticity in APP/PS1 mice. Western blot, immunofluorescence and Thioflavin S staining were used for the pathological evaluation of AD. Monitoring the level of ATP, mitochondrial membrane potential, SOD and MDA to evaluate the mitochondrial function, and with the usage of qPCR and CHIP for the changes of histone post-translational modification. RESULTS: In the current study, we found that DBD could effectively attenuate memory impairments and enhance long-term potentiation (LTP) with concurrent increased expression of memory-associated proteins. DBD markedly decreased Aß accumulation in APP/PS1 mice by decreasing the phosphorylation of APP at the Thr668 level but not APP, PS1 or BACE1. Further studies demonstrated that DBD restored mitochondrial biogenesis deficits and mitochondrial dysfunction. Finally, the restored mitochondrial biogenesis and cognitive deficits are under HADC2-mediated histone H4 lysine 12 (H4K12) acetylation at the peroxisome proliferator-activated receptor-gamma coactivator 1α (PGC-1α) and N-methyl-D-aspartate receptor type 2B (GluN2B) promoters. CONCLUSIONS: These findings reveal that DBD could ameliorate mitochondrial biogenesis and cognitive deficits by improving H4K12 acetylation. DBD might be a promising complementary drug candidate for AD treatment.

Activation of ß2-adrenergic Receptor Ameliorates Amyloid-ß-induced Mitophagy Defects and Tau Pathology in Mice.

Defective mitophagy and mitochondrial dysfunction have been linked to aging and Alzheimer's disease (AD). ß2-Adrenergic receptor (ADRB2) is critical for mitochondrial and cognitive function. However, researchers have not clearly determined whether ADRB2 activation ameliorates defective mitophagy and cognitive deficits in individuals with AD. Here, we observed that the activation of ADRB2 by clenbuterol (Clen, ADRB2 agonist, 2 mg/kg/day) ameliorated amyloid-ß-induced (Aß1-42 bilateral intracerebral infusion, 2 µl, 5 µg/µl) memory deficits. Activation of ADRB2 also attenuated Aß-induced mitochondrial dysfunction, as revealed by increased ATP levels, mitochondrial membrane potential (MMP/Δψm) and complex I activity. Further studies revealed that ADRB2 activation restored mitophagy deficits, as revealed by the increased light chain 3 (LC3)-II/LC3-I ratio, Atg5 levels, and Atg7 levels and decreased p62 levels, along with the upregulation of PTEN-induced putative kinase 1 (PINK1), Parkin and NAD+ levels. Activation of ADRB2 rescued Aß-induced oxidative stress and neuronal death. ADRB2 activation also attenuated Aß-induced tau hyperphosphorylation by regulating glycogen synthase kinase-3ß expression in the hippocampus. Finally, we established that Clen improved mitophagy and attenuated mitochondrial dysfunction, and tau pathology in mice by activating the ADRB2/Akt/PINK1 signaling pathway. Conversely, the inhibition of ADRB2 by propranolol (ßAR antagonist, 10 µM) blocked the Clen-mediated improvements in pathological changes in N2a cells. The results from the present study indicate that ADRB2 activation may be a therapeutic strategy for AD.

Inhibition of Histone Acetylation by ANP32A Induces Memory Deficits.

There is accumulating evidence that decreased histone acetylation is involved in normal aging and neurodegenerative diseases. Recently, we found that ANP32A, a key component of INHAT (inhibitor of acetyltransferases) that suppresses histone acetylation, increased in aged and cognitively impaired C57 mice and expressing wild-type human full length tau (htau) transgenic mice. Downregulating ANP32A restored cognitive function and synaptic plasticity through upregulation of the expressions of synaptic-related proteins via increasing histone acetylation. However, there is no direct evidence that ANP32A can induce neurodegeneration and memory deficits. In the present study, we overexpressed ANP32A in the hippocampal CA3 region of C57 mice and found that ANP32A overexpression induced cognitive abilities and synaptic plasticity deficits, with decreased synaptic-related protein expression and histone acetylation. Combined with our recent studies, our findings reveal that upregulated ANP32A induced-suppressing histone acetylation may underlie the cognitive decline in neurodegenerative disease, and suppression of ANP32A may represent a promising therapeutic approach for neurodegenerative diseases including Alzheimer's disease.

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.

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, ß-amyloid and H2O2 exposure, increased ANP32A by activating CCAAT/enhancer binding protein-ß (C/EBPß). 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.

Activation of ß2-adrenergic receptor promotes dendrite ramification and spine generation in APP/PS1 mice.

Alzheimer's disease (AD) is the most common neurodegenerative disorder, and currently there is no effective cure for this devastating disease. Decreases in the levels of ß2-adrenoceptor (ß2-AR) and norepinephrine have been reported in several regions of AD brains. The activation of ß2AR can prevent the amyloid ß (Aß)-mediated inhibition of LTP (Long-term potentiation), but the mechanism is not fully understood. Here, we used APP/PS1 mice to study whether the activation of ß2AR could remodel synaptic and/or dendritic plasticity. We found that the activation of ß2AR by Clenbuterol (Clen) ameliorated memory deficits and promoted dendrite ramification and spine generation in hippocampal CA1 neurons, which was accompanied by the upregulation of postsynaptic density protein 95 (PSD95), synapsin 1 and synaptophysin. Conversely, the inhibition of ß2AR by a siRNA blocked the Clen-induced increase in dendrite ramification and dendritic spines in primary hippocampal neurons. Furthermore, the activation of ß2AR decreased cerebral amyloid plaques through the up-regulation of α-secretase activity and by decreasing the phosphorylation of APP at Thr668. Based on the roles of ß2AR in dendrite ramification and spine generation, memory deficits and AD pathogenesis, compounds designed to activate ß2AR might shed light on the cure of AD.

Beta 2-adrenergic receptor activation enhances neurogenesis in Alzheimer's disease mice.

Impaired hippocampal neurogenesis is one of the early pathological features of Alzheimer's disease. Enhancing adult hippocampal neurogenesis has been pursued as a potential therapeutic strategy for Alzheimer's disease. Recent studies have demonstrated that environmental novelty activates ß2-adrenergic signaling and prevents the memory impairment induced by amyloid-ß oligomers. Here, we hypothesized that ß2-adrenoceptor activation would enhance neurogenesis and ameliorate memory deficits in Alzheimer's disease. To test this hypothesis, we investigated the effects and mechanisms of action of ß2-adrenoceptor activation on neurogenesis and memory in amyloid precursor protein/presenilin 1 (APP/PS1) mice using the agonist clenbuterol (intraperitoneal injection, 2 mg/kg). We found that ß2-adrenoceptor activation enhanced hippocampal neurogenesis, ameliorated memory deficits, and increased dendritic branching and the density of dendritic spines. These effects were associated with the upregulation of postsynaptic density 95, synapsin 1 and synaptophysin in APP/PS1 mice. Furthermore, ß2-adrenoceptor activation decreased cerebral amyloid plaques by decreasing APP phosphorylation at Thr668. These findings suggest that ß2-adrenoceptor activation enhances neurogenesis and ameliorates memory deficits in APP/PS1 mice.

Spatial training promotes short-term survival and neuron-like differentiation of newborn cells in Aß1-42-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 ß-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.

Erythropoietin attenuates Alzheimer-like memory impairments and pathological changes induced by amyloid ß42 in mice.

Amyloid beta (Aß) is a key molecule in the neurodegenerative progression of Alzheimer׳s disease (AD). It is critical to develop a treatment that can arrest the Aß-induced pathologic progression of AD. Erythropoietin (EPO) has various protective effects in the nervous system. However, the effect of EPO on Aß-induced Alzheimer-like cognitive deficits and pathological changes remains unclear. In the present study, we observed that the treatment of mice with EPO (1000 IU/kg) attenuated Aß42-induced cognitive deficits and tau hyperphosphorylation at multiple AD-related sites through the regulation of glycogen synthase kinase-3ß (GSK-3ß). We also observed that EPO attenuated the Aß42-induced mitochondrial dysfunction and apoptosis in brain. These results indicate a potential role for EPO in AD therapy.

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.

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.

Humanin attenuates Alzheimer-like cognitive deficits and pathological changes induced by amyloid ß-peptide in rats.

Amyloid ß-peptide (Aß) has been implicated as a key molecule in the neurodegenerative cascades of Alzheimer's disease (AD). Humanin (HN) is a secretory peptide that inhibits the neurotoxicity of Aß. However, the mechanism(s) by which HN exerts its neuroprotection against Aß-induced AD-like pathological changes and memory deficits are yet to be completely defined. In the present study, we provided evidence that treatment of rats with HN increases the number of dendritic branches and the density of dendritic spines, and upregulates pre- and post-synaptic protein levels; these effects lead to enhanced long-term potentiation and amelioration of the memory deficits induced by Aß(1-42). HN also attenuated Aß(1-42)-induced tau hyperphosphorylation, apparently by inhibiting the phosphorylation of Tyr307 on the inhibitory protein phosphatase-2A (PP2A) catalytic subunit and thereby activating PP2A. HN also inhibited apoptosis and reduced the oxidative stress induced by Aß(1-42). These findings provide novel mechanisms of action for the ability of HN to protect against Aß(1-42)-induced AD-like pathological changes and memory deficits.

Expression of Tau40 induces activation of cultured rat microglial cells.

Accumulation of microtubule-associated protein tau has been observed in the brain of aging and tauopathies. Tau was observed in microglia, but its role is not illustrated. By immunofluorescence staining and the fractal dimension value assay in the present study, we observed that microglia were activated in the brains of rats and mice during aging, simultaneously, the immunoreactivities of total tau and the phosphorylated tau were significantly enhanced in the activated microglia. Furtherly by transient transfection of tau40 (human 2N/4R tau) into the cultured rat microglia, we demonstrated that expression of tau40 increased the level of Iba1, indicating activation of microglia. Moreover, expression of tau40 significantly enhanced the membranous localization of the phosphorylated tau at Ser396 in microglia possibly by a mechanism involving protein phosphatase 2A, extracellular signal-regulated kinase and glycogen synthase kinase-3ß. It was also found that expression of tau40 promoted microglial migration and phagocytosis, but not proliferation. And we observed increased secretion of several cytokines, including interleukin (IL)-1ß, IL-6, IL-10, tumor necrosis factor-α and nitric oxide after the expression of tau40. These data suggest a novel role of human 2N/4R tau in microglial activation.

Phosphorylation of tau by death-associated protein kinase 1 antagonizes the kinase-induced cell apoptosis.

The intracellular accumulation of hyperphosphorylated tau plays a crucial role in neurodegeneration of Alzheimer's disease (AD), but the mechanism is not fully understood. From the observation that tau hyperphosphorylation renders cells more resistant to chemically-induced cell apoptosis, we have proposed that tau-involved apoptotic abortion may be the trigger of neurodegeneration. Here, we further studied whether this phenomenon is also applicable for the cell death induced by constitutively expressed factors, such as death-associated protein kinase 1 (DAPK1). We found that DAPK1 was upregulated and accumulated in the brain of human tau transgenic mice. Overexpression of DAPK1 in HEK293 and N2a cells decreased cell viability with activation of caspase-3, whereas simultaneous expression of tau antagonized DAPK1-induced apoptotic cell death. Expression of DAPK1 induced tau hyperphosphorylation at Thr231, Ser262, and Ser396 with no effects on protein phosphatase 2A, glycogen synthase kinase-3ß, protein kinase A, calcium/calmodulin dependent protein kinase II, cell division cycle 2, or cyclin dependent protein kinase 5. The phosphorylation level of microtubule affinity-regulating kinase 2 (MARK2) was increased by expression of DAPK1, but simultaneous downregulation of MARK2 did not affect the DAPK1-induced tau hyperphosphorylation. DAPK1 was co-immunoprecipitated with tau proteins both in vivo and in vitro, and expression of the kinase domain-truncated DAPK1 did not induce tau hyperphosphorylation. These data suggest that tau hyperphosphorylation at Thr231, Ser262, and Ser396 by DAPK1 renders the cells more resistant to the kinase-induced apoptotic cell death, providing new insights into the tau-involved apoptotic abortion in the course of chronic neurodegeneration.

Silencing PP2A inhibitor by lenti-shRNA interference ameliorates neuropathologies and memory deficits in tg2576 mice.

Deficits of protein phosphatase-2A (PP2A) play a crucial role in tau hyperphosphorylation, amyloid overproduction, and synaptic suppression of Alzheimer's disease (AD), in which PP2A is inactivated by the endogenously increased inhibitory protein, namely inhibitor-2 of PP2A (I2(PP2A)). Therefore, in vivo silencing I2(PP2A) may rescue PP2A and mitigate AD neurodegeneration. By infusion of lentivirus-shRNA targeting I2(PP2A) (LV-siI2(PP2A)) into hippocampus and frontal cortex of 11-month-old tg2576 mice, we demonstrated that expression of LV-siI2(PP2A) decreased remarkably the elevated I2(PP2A) in both mRNA and protein levels. Simultaneously, the PP2A activity was restored with the mechanisms involving reduction of the inhibitory binding of I2(PP2A) to PP2A catalytic subunit (PP2AC), repression of the inhibitory Leu309-demethylation and elevation of PP2AC. Silencing I2(PP2A) induced a long-lasting attenuation of amyloidogenesis in tg2576 mice with inhibition of amyloid precursor protein hyperphosphorylation and ß-secretase activity, whereas simultaneous inhibition of PP2A abolished the antiamyloidogenic effects of I2(PP2A) silencing. Finally, silencing I2(PP2A) could improve learning and memory of tg2576 mice with preservation of several memory-associated components. Our data reveal that targeting I2(PP2A) can efficiently rescue Aß toxicities and improve the memory deficits in tg2576 mice, suggesting that I2(PP2A) could be a promising target for potential AD therapies.

Betaine attenuates Alzheimer-like pathological changes and memory deficits induced by homocysteine.

Hyperhomocysteinemia (Hhcy) may induce memory deficits with ß-amyloid (Aß) accumulation and tau hyperphosphorylation. Simultaneous supplement of folate and vitamin B12 partially restored the plasma homocysteine level and attenuated tau hyperphosphorylation, Aß accumulation and memory impairments induced by Hhcy. However, folate and vitamin B12 treatment have no effects on Hhcy which has the methylenetetrahydrofolate reductase genotype mutation. In this study, we investigated the effects of simultaneous supplement of betaine on Alzheimer-like pathological changes and memory deficits in hyperhomocysteinemic rats after a 2-week induction by vena caudalis injection of homocysteine (Hcy). We found that supplementation of betaine could ameliorate the Hcy-induced memory deficits, enhance long-term potentiation (LTP) and increase dendritic branches numbers and the density of the dendritic spines, with up-regulation of NR1, NR2A, synaptotagmin, synaptophysin, and phosphorylated synapsin I protein levels. Supplementation of betaine also attenuated the Hcy-induced tau hyperphosphorylation at multiple AD-related sites through activation protein phosphatase-2A (PP2A) with decreased inhibitory demethylated PP2A(C) at Leu309 and phosphorylated PP2A(C) at Tyr307. In addition, supplementation of betaine also decreased Aß production with decreased presenilin-1 protein levels. Our data suggest that betaine could be a promising candidate for arresting Hcy-induced AD-like pathological changes and memory deficits.