Structure-based discovery of small molecules that disaggregate Alzheimer's disease tissue derived tau fibrils in vitro.

Alzheimer's disease (AD) is the consequence of neuronal death and brain atrophy associated with the aggregation of protein tau into fibrils. Thus disaggregation of tau fibrils could be a therapeutic approach to AD. The small molecule EGCG, abundant in green tea, has long been known to disaggregate tau and other amyloid fibrils, but EGCG has poor drug-like properties, failing to fully penetrate the brain. Here we have cryogenically trapped an intermediate of brain-extracted tau fibrils on the kinetic pathway to EGCG-induced disaggregation and have determined its cryoEM structure. The structure reveals that EGCG molecules stack in polar clefts between the paired helical protofilaments that pathologically define AD. Treating the EGCG binding position as a pharmacophore, we computationally screened thousands of drug-like compounds for compatibility for the pharmacophore, discovering several that experimentally disaggregate brain-derived tau fibrils in vitro. This work suggests the potential of structure-based, small-molecule drug discovery for amyloid diseases.

Post-Ischemic Brain Neurodegeneration in the Form of Alzheimer's Disease Proteinopathy: Possible Therapeutic Role of Curcumin.

For thousands of years, mankind has been using plant extracts or plants themselves as medicinal herbs. Currently, there is a great deal of public interest in naturally occurring medicinal substances that are virtually non-toxic, readily available, and have an impact on well-being and health. It has been noted that dietary curcumin is one of the regulators that may positively influence changes in the brain after ischemia. Curcumin is a natural polyphenolic compound with pleiotropic biological properties. The observed death of pyramidal neurons in the CA1 region of the hippocampus and its atrophy are considered to be typical changes for post-ischemic brain neurodegeneration and for Alzheimer's disease. Additionally, it has been shown that one of the potential mechanisms of severe neuronal death is the accumulation of neurotoxic amyloid and dysfunctional tau protein after cerebral ischemia. Post-ischemic studies of human and animal brains have shown the presence of amyloid plaques and neurofibrillary tangles. The significant therapeutic feature of curcumin is that it can affect the aging-related cellular proteins, i.e., amyloid and tau protein, preventing their aggregation and insolubility after ischemia. Curcumin also decreases the neurotoxicity of amyloid and tau protein by affecting their structure. Studies in animal models of cerebral ischemia have shown that curcumin reduces infarct volume, brain edema, blood-brain barrier permeability, apoptosis, neuroinflammation, glutamate neurotoxicity, inhibits autophagy and oxidative stress, and improves neurological and behavioral deficits. The available data suggest that curcumin may be a new therapeutic substance in both regenerative medicine and the treatment of neurodegenerative disorders such as post-ischemic neurodegeneration.

Identification and analysis of a selective DYRK1A inhibitor.

The dysregulation of DYRK1A is implicated in many diseases such as cancer, diabetes, and neurodegenerative diseases. Alzheimer's disease is one of the most common neurodegenerative disease and has elevated interest in DYRK1A research. Overexpression of DYRK1A has been linked to the formation of tau aggregates. Currently, an effective therapeutic treatment that targets DYRK1A is lacking. A specific small-molecule inhibitor would further our understanding of the physiological role of DYRK1A in neurodegenerative diseases and could be presented as a possible therapeutic option. In this study, we identified pharmacological interactions within the DYRK1A active site and performed a structure-based virtual screening approach to identify a selective small-molecule inhibitor. Several compounds were selected in silico for enzymatic and cellular assays, yielding a novel inhibitor. A structure-activity relationship analysis was performed to identify areas of interactions for the compounds selected in this study. When tested in vitro, reduction of DYRK1A dependent phosphorylation of tau was observed for active compounds. The active compounds also improved tau turbidity, suggesting that these compounds could alleviate aberrant tau aggregation. Testing the active compound against a panel of kinases across the kinome revealed greater selectivity towards DYRK1A. Our study demonstrates a serviceable protocol that identified a novel and selective DYRK1A inhibitor with potential for further study in tau-related pathologies.

Testosterone attenuates sevoflurane-induced tau phosphorylation and cognitive impairment in neonatal male mice.

BACKGROUND: Sevoflurane anaesthesia induces phosphorylation of the microtubule-associated protein tau and cognitive impairment in neonatal, but not adult, mice. The underlying mechanisms remain largely to be determined. Sex hormones can be neuroprotective, but little is known about the influence of testosterone on age-dependent anaesthesia effects. METHODS: Six- and 60-day-old male mice received anaesthesia with sevoflurane 3% for 2 h daily for 3 days. Morris water maze, immunoassay, immunoblotting, co-immunoprecipitation, nanobeam technology, and electrophysiology were used to assess cognition; testosterone concentrations; tau phosphorylation; glycogen synthase kinase-3ß (GSK3ß) activation; binding or interaction between tau and GSK3ß; and neuronal activation in mice, cells, and neurones. RESULTS: Compared with 60-day-old male mice, 6-day-old male mice had lower testosterone concentrations (3.03 [0.29] vs 0.44 [0.12] ng ml-1; P<0.01), higher sevoflurane-induced tau phosphorylation in brain (133 [20]% vs 100 [6]% in 6-day-old mice, P<0.01; 103 [8]% vs 100 [13]% in 60-day-old mice, P=0.77), and sevoflurane-induced cognitive impairment. Testosterone treatment increased brain testosterone concentrations (1.76 [0.10] vs 0.39 [0.05] ng ml-1; P<0.01) and attenuated the sevoflurane-induced tau phosphorylation and cognitive impairment in neonatal male mice. Testosterone inhibited the interaction between tau and GSK3ß, and attenuated sevoflurane-induced inhibition of excitatory postsynaptic currents in hippocampal neurones. CONCLUSIONS: Lower brain testosterone concentrations in neonatal compared with adult male mice contributed to age-dependent tau phosphorylation and cognitive impairment after sevoflurane anaesthesia. Testosterone might attenuate the sevoflurane-induced tau phosphorylation and cognitive impairment by inhibiting the interaction between tau and GSK3ß.

Low molecular weight chondroitin sulfate ameliorates pathological changes in 5XFAD mice by improving various functions in the brain.

Our previous study found that low molecular weight chondroitin sulfate (LMWCS) had neuroprotective effects against the toxicity of amyloid-ß (Aß) peptides both in vitro and in vivo, and we speculated that the effects might be related with its anti-oxidative activities. In this study, the anti-Alzheimer's disease (AD) activity of LMWCS was further studied in 5XFAD transgenic mice. After 4-month gavage, the levels of Aß1-42 level, amyloid precursor protein (APP) and presenilin 1 (PS1) were significantly decreased in the brains of 5XFAD mice, indicating the alteration of APP metabolism by LMWCS. Besides, LMWCS inhibited the secretions of pro-inflammatory cytokines, including interleukin-1ß (IL-1ß), tumor necrosis factor-α (TNF-α) and IL-6. Furthermore, the suppression of neuroinflammation by LMWCS was supported by the decreased expressions of glial fibrillary acidic protein (GFAP) and toll-like receptor 2 (TLR2) in the brains. LMWCS also reduced the production of reactive oxygen species (ROS) and the level of phospho-tau (Ser404) in the brains. Nevertheless, the changes in the behavior tests were moderate. In conclusion, LMWCS administration ameliorated APP metabolism, neuroinflammation, ROS production and tau protein abnormality in the brains of 5XFAD mice, displaying the potential to improve the pathological changes of AD mouse brain. LMWCS could be considered as a promising anti-AD drug candidate, nonetheless, the therapy regimen need to be optimized to improve its pharmacotherapy efficacy.

Neuroprotective Studies of Evodiamine in an Okadaic Acid-Induced Neurotoxicity.

BACKGROUND: Alzheimer's disease (AD) is the most common neurodegenerative disease, and it manifests as progressive memory loss and cognitive decline. However, there are no effective therapies for AD, which is an urgent problem to solve. Evodiamine, one of the main bioactive ingredients of Evodia rutaecarpa, has been reported to ameliorate blood-brain barrier (BBB) permeability and improve cognitive impairment in ischemia and AD mouse models. However, whether evodiamine alleviates tauopathy remains unclear. This study aimed to examine whether evodiamine ameliorates tau phosphorylation and cognitive deficits in AD models. METHODS: A protein phosphatase 2A inhibitor, okadaic acid (OA), was used to induce tau phosphorylation to mimic AD-like models in neuronal cells. Protein expression and cell apoptosis were detected using Western blotting and flow cytometry, respectively. Spatial memory/cognition was assessed using water maze, passive avoidance tests, and magnetic resonance imaging assay in OA-induced mice models, and brain slices were evaluated further by immunohistochemistry. RESULTS: The results showed that evodiamine significantly reduced the expression of phosphor-tau, and further decreased tau aggregation and neuronal cell death in response to OA treatment. This inhibition was found to be via the inhibition of glycogen synthase kinase 3ß, cyclin-dependent kinase 5, and mitogen-activated protein kinase pathways. In vivo results indicated that evodiamine treatment ameliorated learning and memory impairments in mice, whereas Western blotting and immunohistochemical analysis of the mouse brain also confirmed the neuroprotective effects of evodiamine. CONCLUSIONS: Evodiamine can decrease the neurotoxicity of tau aggregation and exhibit a neuroprotective effect. Our results demonstrate that evodiamine has a therapeutic potential for AD treatment.

Effects of Berberine on Diabetes and Cognitive Impairment in an Animal Model: The Mechanisms of Action.

Diabetes is a group of metabolic disorders with an increased risk of developing cognitive impairment and dementia. The hippocampus in the forebrain contains an abundance of insulin receptors related to cognitive function and plays an important role in the pathophysiology of neurodegenerative disorders. Berberine from traditional Chinese medicine has been used to treat diabetes and diabetic cognitive impairment, although its related mechanisms are largely unknown. In this study, a STZ diabetes rat model feeding with a high-fat diet was used to test the effects of berberine compared with metformin. Oral glucose tolerance and hyperinsulinemic-euglycemic clamp were used for glucose metabolism and insulin resistance. The Morris water maze was used to observe the compound effects on cognitive impairment. Serum and hippocampal [Formula: see text]-amyloid peptide (A[Formula: see text], Tau and phosphorylated Tau protein deposition in the hippocampi were measured. The TUNEL assay was used to detect the neuronal apoptosis, supported by histomorphological changes and transmissional electron microscopy (TEM) image. Our data showed that the diabetic rats had a significantly cognitive impairment. In addition to improving glucose metabolism and reducing insulin resistance, berberine significantly improved the cognitive function in the rat. Berberine also effectively decreased the expression of hippocampal tau protein, phosphorylated Tau, and increased insulin receptor antibodies. Moreover, berberine downregulated the abnormal phosphorylation of A[Formula: see text] and Tau protein and improved hippocampal insulin signaling. The TUNEL assay confirmed that berberine reduced hippocampal neuronal apoptosis supported by TEM. Thus, berberine significantly improved the cognitive function in diabetic rats by changing the peripheral and central insulin resistance. The reduction of neuronal injury, A[Formula: see text] deposition, abnormal phosphorylation of Tau protein, and neuronal apoptosis in the hippocampus were observed as the related mechanisms of action.

Exploring the inhibitory effects of liquiritigenin against tau fibrillation and related neurotoxicity as a model of preventive care in Alzheimer's disease.

Aggregation of tau protein into the form of insoluble amyloid fibrils is linked with Alzheimer's disease. The identification of potential small molecules that can inhibit tau protein from undergoing aggregation has received a great deal of interest, recently. In the present study, the possible inhibitory effects of liquiritigenin as a member of chiral flavanone family on tau amyloid fibrils formation and their resulting neurotoxicity were assessed by different biophysical and cellular assays. The inhibitory effect of the liquiritigenin against tau amyloid formation was investigated using thioflavin T (ThT) and 1-Anilino-8-naphthalene sulfonate (ANS) fluorescence spectroscopy, Congo red (CR) binding assays, transmission electron microscopy (TEM) analysis, and circular dichroism (CD) spectroscopy. Neurotoxicity assays were also performed against neuron-like cells (SH-SY5Y) using 3-(4,5-Dimethylthiazol)-2,5-diphenyltetrazolium bromide (MTT) reduction, reactive oxygen species (ROS), catalase (CAT) and caspase-3 activity measurements. We found that liquiritigenin served as an efficient inhibitor of tau amyloid fibrils formation through prevention of structural transition in tau structure, exposure of hydrophobic patches and their associated neurotoxicity mediated by decrease in the production of ROS and caspase-3 activity and elevation of CAT activity. These data may finally find applications in the development of promising inhibitors against amyloid fibril formation and treatment of Alzheimer's disease.

Evaluation of heptelidic acid as a potential inhibitor for tau aggregation-induced Alzheimer's disease and associated neurotoxicity.

Tau is a major component of protein plaques in tauopathies, especially Alzheimer's disease (AD). The purpose of the present study is to explore the inhibitory effects of heptelidic acid as a bioactive compound from fungus T. koningii on tau fibrillization and associated neurotoxicity. The influences of various concentrations of heptelidic acid on tau fibrillization and underlying neurotoxicity were explored by assessment of the biophysical (ThT/Nile red fluorescence, CR absorbance, CD, and TEM) and cellular (MTT, LDH, and caspase-3) assays. It was shown that heptelidic acid inhibited tau fibrillization in a concentration-dependent manner. On the other hand, cellular assays indicated that the viability, LDH release, and caspase-3 activity were regulated when neurons were exposed to tau samples co-incubated with heptelidic acid. In conclusion, it may be indicated that heptelidic acid inhibited tau fibrillization which was accompanied by formation of amorphous aggregated species of tau with much less neurotoxicity than tau amyloid alone. Thus, heptelidic acid can be considered as a potential candidate in preventive care studies to inhibit the formation of tau plaques as neurotoxic species.

Alkoxy glycerol enhanced activity of Oxyresveratrol in Alzheimer's disease by rescuing Tau protein.

Alzheimer's disease perpetually demands enormous research on the development of effective treatment strategies. The present study aims to define the role of Oxyresveratrol (OXY) alone and in combination with Alkoxy glycerols (AKG) to reduce Tau protein level and improve the climbing behaviour of Drosophila fly models expressed with human-Tau protein. Oxyresveratrol, a polyphenolic stilbene, possesses a wide range of biological activities like antioxidant, anti-inflammatory, and neuroprotective effects. Nevertheless, chemical instability and low solubility of OXY in aqueous solutions reduce its bioavailability and hinder it from exerting neuroprotective activities. An inclusion complex of OXY with ß- cyclodextrin (CD) (OXY-CD complex) was employed in the study for increased dissolution rate and oral availability of OXY. Fish oils and their derivatives have a plethora of applications in in vivo biological activities. Herein, we also remark on the role of AKG in reducing Tau protein level in flies by enhancing OXY-CD activity. Dietary supplementation of OXY-CD together with AKG improved the learning and memory abilities during the climbing assay in Tau flies. The study highlights OXY-CD and AKG as neuroprotective agents and put forward a plausible approach towards the increased permeability of pharmacological agents across the blood-brain barrier (BBB) for the central nervous system elicited by AKG.

Advances in developing therapeutic strategies for Alzheimer's disease.

Alzheimer's disease (AD) is a progressive deterioration of brain function, initially characterized by cognitive deficits, with loss of recent memory and language ability, impairment of orientation, problem solving, and abstract thinking. While existing drug treatments help reduce the symptoms of AD and improve people's quality of life, they neither slow its progression nor cure it. Currently, targeted drug delivery to the central nervous system (CNS), for therapy of AD, is confined by the challenges posed by blood-brain interfaces surrounding the CNS, limiting the bioavailability of therapeutics. Among new strategies to overcome these limitations and successfully deliver drugs to the CNS, nanoparticles (NPs) are able to overcome these limitations, offering new therapeutic designations in term of driving drugs to cross the BBB and enter the brain more effectively. The current article aimed to summary and highlight advances in recent research on the development of nanotechnology-based therapeutics for their implications in therapy of AD.

Neoline Improves Memory Impairment and Reduces Amyloid-ß Level and Tau Phosphorylation Through AMPK Activation in the Mouse Alzheimer's Disease Model.

BACKGROUND: Alzheimer's disease (AD) is the most general, chronic, and progressive neurodegenerative senile disorder characterized clinically by progressive cognitive deterioration and memory impairment. Neoline is effective against neuropathic pain models, but the effects of neoline against AD-like phenotypes have not been investigated. OBJECTIVE: We offer the investigation of the effects of neoline in AD. METHODS: In this study, a Tg-APPswe/PS1dE9 AD mouse model was treated orally with neoline at a concentration of 0.5 mg/kg or 0.1 mg/kg starting at 7.5 months and administered for three months, and its anti-AD effects were evaluated. RESULTS: Neoline improved memory and cognition impairments and reduced the number of amyloid-beta plaque and the amount of amyloid-ß in the brain of AD mice. Furthermore, neoline reduced the anxiety behavior in the AD mouse model. The chronic administration of neoline also induced AMPK phosphorylation and decreased tau, amyloid-ß, and BACE1 expression in the hippocampus. These findings indicate that chronic administration of neoline has therapeutic effects via AMPK activation, and BACE1 downregulation resulted in a decrease in the amyloid-ß levels in the brain of Tg-APPswe/PS1dE9 AD mice. CONCLUSION: Our results suggest that neoline is a therapeutic agent for the cure of neurodegenerative diseases like AD.

A Single-Chain Variable Fragment Antibody Inhibits Aggregation of Phosphorylated Tau and Ameliorates Tau Toxicity in vitro and in vivo.

BACKGROUND: Alzheimer's disease (AD) is a common cause of dementia among elderly people. Hyperphosphorylation and aggregation of tau correlates with the clinical progression of AD; therefore, therapies targeting the aggregation of tau may have potential applications for anti-AD drug development. Several inhibitors of tau aggregation, including small molecules and antibodies, have been found to decrease the aggregation of tau and the corresponding pathology. OBJECTIVE: To screen one kind of single-chain variable fragment (scFv) antibody which could inhibit the aggregation of tau and ameliorate its cytotoxicity. METHODS/RESULTS: Using phosphorylated tau (pTau) as an antigen, we obtained a scFv antibody via the screening of a high-capacity phage antibody library. Biochemical analysis revealed that this scFv antibody (scFv T1) had a strong ability to inhibit pTau aggregation both in dilute solutions and under conditions of macromolecular crowding. ScFv T1 could also depolymerize preformed pTau aggregates in vitro. Furthermore, scFv T1 was found to be able to inhibit the cytotoxicity of extracellular pTau aggregates and ameliorate tau-mediated toxicity when coexpressed with a hTauR406W mutant in the eye of transgenic Drosophila flies. CONCLUSION: This scFv T1 antibody may be a potential new therapeutic agent against AD. Our methods can be used to develop novel strategies against protein aggregation for the treatment of neurodegenerative diseases.

Isoorientin, a GSK-3ß inhibitor, rescues synaptic dysfunction, spatial memory deficits and attenuates pathological progression in APP/PS1 model mice.

ß-Amyloid (Aß) elevation, tau hyperphosphorylation, and neuroinflammation are major hallmarks of Alzheimer's disease (AD). Glycogen synthase kinase-3ß (GSK-3ß) is a key protein kinase implicated in the pathogenesis of AD. Blockade of GSK-3ß is an attractive therapeutic strategy for AD. Isoorientin, a 6-C-glycosylflavone, was previously shown to be a highly selective inhibitor of GSK-3ß, while exerting neuroprotective effects in neuronal models of AD. In the present study, we evaluated the in vivo effects of isoorientin on GSK-3ß, tau phosphorylation, Aß deposition, neuroinflammatory response, long-term potentiation, and spatial memory in amyloid precursor protein/presenilin 1 (APP/PS1) transgenic mice using biochemical, electrophysiological, and behavioral tests. Chronic oral administration of isoorientin to APP/PS1 mice at 8 months of age attenuated multiple AD pathogenic hallmarks in the brains, including GSK-3ß overactivation, tau hyperphosphorylation, Aß deposition, and neuroinflammation. For neuroinflammation, isoorientin treatment reduced the number of activated microglia associated with Aß-positive plaques, and in parallel reduced the levels of pro-inflammatory factors in the brains of APP/PS1 mice. Strikingly, isoorientin reversed deficits in synaptic long-term potentiation and spatial memory relevant to cognitive functions. Together, the findings suggest that isoorientin is a brain neuroprotector and may be a promising drug lead for treatment of AD and related neurodegenerative disorders.

Prophylactic effects of sporoderm-removed Ganoderma lucidum spores in a rat model of streptozotocin-induced sporadic Alzheimer's disease.

ETHNOPHARMACOLOGICAL RELEVANCE: Ganoderma lucidum (G. lucidum, Lingzhi), also known as "immortality mushroom" has been broadly used to improve health and longevity for thousands of years in Asia. G. lucidum and its spores have been used to promote health, based on its broad pharmacological and therapeutic activity. This species is recorded in Chinese traditional formula as a nootropic and has been suggested to improve cognitive dysfunction in Alzheimer's disease. However, little is known about the nootropic effects and molecular mechanism of action of G. lucidum spores. AIM OF THE STUDY: The present study investigated the protective effects of sporoderm-deficient Ganoderma lucidum spores (RGLS) against learning and memory impairments and its mechanism of action. MATERIALS AND METHODS: In the Morris water maze, the effects of RGLS on learning and memory impairments were evaluated in a rat model of sporadic Alzheimer's disease that was induced by an intracerebroventricular injection of streptozotocin (STZ). Changes in amyloid ß (Aß) expression, Tau expression and phosphorylation, brain-derived neurotrophic factor (BDNF), and the BDNF receptor tropomyosin-related kinase B (TrkB) in the hippocampus were evaluated by Western blot. RESULTS: Treatment with RGLS (360 and 720 mg/kg) significantly enhanced memory in the rat model of STZ-induced sporadic Alzheimer's disease and reversed the STZ-induced increases in Aß expression and Tau protein expression and phosphorylation at Ser199, Ser202, and Ser396. The STZ-induced decreases in neurotrophic factors, including BDNF, TrkB and TrkB phosphorylation at Tyr816, were reversed by treatment with RGLS. CONCLUSION: These findings indicate that RGLS prevented learning and memory impairments in the present rat model of STZ-induced sporadic Alzheimer's disease, and these effects depended on a decrease in Aß expression and Tau hyperphosphorylation and the modulation of BDNF-TrkB signaling in the hippocampus.

Partial Inhibition of Mitochondrial Complex I Reduces Tau Pathology and Improves Energy Homeostasis and Synaptic Function in 3xTg-AD Mice.

BACKGROUND: Accumulation of hyperphosphorylated tau (pTau) protein is associated with synaptic dysfunction in Alzheimer's disease (AD). We previously demonstrated that neuroprotection in familial mouse models of AD could be achieved by targeting mitochondria complex I (MCI) and activating the adaptive stress response. Efficacy of this strategy on pTau-related pathology remained unknown. OBJECTIVE: To investigate the effect of specific MCI inhibitor tricyclic pyrone compound CP2 on levels of human pTau, memory function, long term potentiation (LTP), and energy homeostasis in 18-month-old 3xTg-AD mice and explore the potential mechanisms. METHODS: CP2 was administered to male and female 3xTg-AD mice from 3.5-18 months of age. Cognitive function was assessed using the Morris water maze. Glucose metabolism was measured in periphery using a glucose tolerance test and in the brain using fluorodeoxyglucose F18 positron-emission tomography (FDG-PET). LTP was evaluated using electrophysiology in the hippocampus. The expression of key proteins associated with neuroprotective mechanisms were assessed by western blotting. RESULTS: Chronic CP2 treatment restored synaptic activity in female 3xTg-AD mice; cognitive function, levels of synaptic proteins, glucose metabolism, and energy homeostasis were improved in male and female 3xTg-AD mice. Significant reduction of human pTau in the brain was associated with increased activity of protein phosphatase of type 2A (PP2A), and reduced activity of cyclin-dependent kinase 5 (CDK5) and glycogen synthase kinase 3ß (GSK3ß). CONCLUSION: CP2 treatment protected against synaptic dysfunction and memory impairment in symptomatic 3xTg-AD mice, and reduced levels of human pTau, indicating that targeting mitochondria with small molecule specific MCI inhibitors represents a promising strategy for treating AD.

Fasudil reduces ß-amyloid levels and neuronal apoptosis in APP/PS1 transgenic mice via inhibition of the Nogo-A/NgR/RhoA signaling axis.

Recent studies have shown that Nogo-A and the Nogo-A receptor affect ß-amyloid metabolism and the downstream Rho GTP enzyme signaling pathway, which may affect the levels of ß-amyloid and tau. Nogo-A may play a key role in the pathogenesis of Alzheimer's disease. However, the underlying molecular mechanisms of Fasudil treatment in Alzheimer's disease are not yet clear. Our results have found that Fasudil treatment for two months substantially ameliorated behavioral deficits, diminished ß-amyloid plaque and tau protein pathology, and alleviated neuronal apoptosis in APP/PS1 transgenic mice. More importantly, two well-established markers for synaptic function, growth-associated protein 43 and synaptophysin, were upregulated after Fasudil treatment. Finally, the levels of Nogo-A, Nogo-A receptor complex NgR/p75NTR/LINGO-1 and the downstream Rho/Rho kinase signaling pathway were significantly reduced. These findings suggest that Fasudil exerts its neuroprotective function in Alzheimer's disease by inhibiting the Nogo-A/NgR1/RhoA signaling pathway.

Conformation-selective tau monoclonal antibodies inhibit tau pathology in primary neurons and a mouse model of Alzheimer's disease.

BACKGROUND: The spread of tau pathology in Alzheimer's disease (AD) is mediated by cell-to-cell transmission of pathological tau seeds released from neurons that, upon internalization by recipient neurons, template the misfolding of naïve cellular tau, thereby propagating fibrillization. We hypothesize that anti-tau monoclonal antibodies (mAbs) that selectively bind to pathological tau seeds will inhibit propagation of tau aggregates and reduce the spread of tau pathology in vivo. METHODS: We inoculated mice with human AD brain-derived extracts containing tau paired helical filaments (AD-tau) and identified two novel mAbs, DMR7 and SKT82, that selectively bind to a misfolded pathological conformation of tau relative to recombinant tau monomer. To evaluate the effects of these mAbs on the spread of pathological tau in vivo, 5xFAD mice harboring significant brain Aß plaque burden were unilaterally injected with AD-tau in the hippocampus, to initiate the formation of neuritic plaque (NP) tau pathology, and were treated weekly with intraperitoneal (i.p.) injections of DMR7, SKT82, or IgG isotype control mAbs. RESULTS: DMR7 and SKT82 bind epitopes comprised of the proline-rich domain and c-terminal region of tau and binding is reduced upon disruption of the pathological conformation of AD-tau by chemical and thermal denaturation. We found that both DMR7 and SKT82 immunoprecipitate pathological tau and significantly reduce the seeding of cellular tau aggregates induced by AD-tau in primary neurons by 60.5 + 13.8% and 82.2 + 8.3%, respectively, compared to IgG control. To investigate the mechanism of mAb inhibition, we generated pH-sensitive fluorophore-labeled recombinant tau fibrils seeded by AD-tau to track internalization of tau seeds and demonstrate that the conformation-selective tau mAbs inhibit the internalization of tau seeds. DMR7 and SKT82 treatment reduced hyperphosphorylated NP tau as measured with AT8 immunohistochemistry (IHC) staining, but did not achieve statistical significance in the contralateral cortex and SKT82 significantly reduced tau pathology in the ipsilateral hippocampus by 24.2%; p = 0.044. CONCLUSIONS: These findings demonstrate that conformation-selective tau mAbs, DMR7 and SKT82, inhibit tau pathology in primary neurons by preventing the uptake of tau seeds and reduce tau pathology in vivo, providing potential novel therapeutic candidates for the treatment of AD.

Alzheimer's disease: Recent treatment strategies.

Alzheimer Disease (AD) is a neurodegenerative disease characterized by two neuropathological hallmarks: extracellular deposition of amyloid plaques and intracellular neurofibrillary tangles. Current treatment for AD (donepezil, galantamine, rivastigmine and memantine) is only symptomatic and has modest benefits. Thus, the development of drugs with the potential to change the progression of the disease has been a priority. Therapies targeting amyloid ß have been the focus for almost 30 years. However, highly promising drugs recently failed to show clinical benefits in phase III trials. Even the positive findings presented by Biogen on Aducanumab are not entirely clear and further data is necessary to confirm its validity. Therefore, researchers are turning their efforts around to tau-targeting therapies, since tau protein appears to be better correlated with the severity of cognitive decline than amyloid ß. Currently, most anti-tau agents in clinical trials are immunotherapies and they are in the early stages of clinical research. Four monoclonal antibodies anti-tau (Gosuranemab, Tilavonemab, Semorinemab and Zagotenemab) and one anti-tau vaccine (AADvac1) have reached phase II, so far. In this review, we discuss the potential disease-modifying agents tested in clinical trials and update the information of drugs that are still under clinical evaluation.