Disease-modifying benefit of Fyn blockade persists after washout in mouse Alzheimer's model

SRC family kinase inhibition rescues molecular and behavioral phenotypes, but not protein interaction network dynamics, in a mouse model of Fragile X syndrome

Glutamatergic synapses encode information from extracellular inputs using dynamic protein interaction networks (PINs) that undergo widespread reorganization following synaptic activity, allowing cells to distinguish between signaling inputs and generate coordinated cellular responses. Here, we investigate how Fragile X Messenger Ribonucleoprotein (FMRP) deficiency disrupts signal transduction through a glutamatergic synapse PIN downstream of NMDA receptor or metabotropic glutamate receptor (mGluR) stimulation. In cultured cortical neurons or acute cortical slices from P7, P17 and P60 FMR1-/y mice, the unstimulated protein interaction network state resembled that of wildtype littermates stimulated with mGluR agonists, demonstrating resting state pre-activation of mGluR signaling networks. In contrast, interactions downstream of NMDAR stimulation were similar to WT. We identified the Src family kinase (SFK) Fyn as a network hub, because many interactions involving Fyn were pre-activated in FMR1-/y animals. We tested whether targeting SFKs in FMR1-/y mice could modify disease phenotypes, and found that Saracatinib (SCB), an SFK inhibitor, normalized elevated basal protein synthesis, novel object recognition memory and social behavior in FMR1-/y mice. However, SCB treatment did not normalize the PIN to a wild-type-like state in vitro or in vivo, but rather induced extensive changes to protein complexes containing Shank3, NMDARs and Fyn. We conclude that targeting abnormal nodes of a PIN can identify potential disease-modifying drugs, but behavioral rescue does not correlate with PIN normalization.

Dual Drug Repurposing: The Example of Saracatinib

Saracatinib (AZD0530) is a dual Src/Abl inhibitor initially developed by AstraZeneca for cancer treatment; however, data from 2006 to 2024 reveal that this drug has been tested not only for cancer treatment, but also for the treatment of other diseases. Despite the promising pre-clinical results and the tolerability shown in phase I trials, where a maximum tolerated dose of 175 mg was defined, phase II clinical data demonstrated a low therapeutic action against several cancers and an elevated rate of adverse effects. Recently, pre-clinical research aimed at reducing the toxic effects and enhancing the therapeutic performance of saracatinib using nanoparticles and different pharmacological combinations has shown promising results. Concomitantly, saracatinib was repurposed to treat Alzheimer's disease, targeting Fyn. It showed great clinical results and required a lower daily dose than that defined for cancer treatment, 125 mg and 175 mg, respectively. In addition to Alzheimer's disease, this Src inhibitor has also been studied in relation to other health conditions such as pulmonary and liver fibrosis and even for analgesic and anti-allergic functions. Although saracatinib is still not approved by the Food and Drug Administration (FDA), the large number of alternative uses for saracatinib and the elevated number of pre-clinical and clinical trials performed suggest the huge potential of this drug for the treatment of different kinds of diseases.

Saracatinib inhibits necroptosis and ameliorates psoriatic inflammation by targeting MLKL

Necroptosis is a kind of programmed cell death that causes the release of damage-associated molecular patterns and inflammatory disease including skin inflammation. Activation of receptor-interacting serine/threonine kinase 1 (RIPK1), RIPK3, and mixed lineage kinase domain-like protein (MLKL) is the hallmark of tumour necrosis factor α (TNF)-induced necroptosis. Here, we screened a small-molecule compound library and found that saracatinib inhibited TNF-induced necroptosis. By targeting MLKL, Saracatinib interfered with the phosphorylation, translocation, and oligomerization of MLKL induced by TNF. Consistently, mutation of the saracatinib-binding site of MLKL reduced the inhibitory effect of saracatinib on TNF-induced necroptosis. In an imiquimod (IMQ)-induced psoriasis mouse model, saracatinib effectively blocked MLKL phosphorylation and inflammatory responses in vivo. Taken together, these findings indicate that saracatinib inhibits necroptosis by targeting MLKL, providing a potential therapeutic approach for skin inflammation-related diseases such as psoriasis.

In vivo imaging of synaptic density in neurodegenerative disorders with positron emission tomography: A systematic review

Positron emission tomography (PET) with radiotracers that bind to synaptic vesicle glycoprotein 2 A (SV2A) enables quantification of synaptic density in the living human brain. Assessing the regional distribution and severity of synaptic density loss will contribute to our understanding of the pathological processes that precede atrophy in neurodegeneration. In this systematic review, we provide a discussion of in vivo SV2A PET imaging research for quantitative assessment of synaptic density in various dementia conditions: amnestic Mild Cognitive Impairment and Alzheimer's disease, Frontotemporal dementia, Progressive supranuclear palsy and Corticobasal degeneration, Parkinson's disease and Dementia with Lewy bodies, Huntington's disease, and Spinocerebellar Ataxia. We discuss the main findings concerning group differences and clinical-cognitive correlations, and explore relations between SV2A PET and other markers of pathology. Additionally, we touch upon synaptic density in healthy ageing and outcomes of radiotracer validation studies. Studies were identified on PubMed and Embase between 2018 and 2023; last searched on the 3rd of July 2023. A total of 36 studies were included, comprising 5 on normal ageing, 21 clinical studies, and 10 validation studies. Extracted study characteristics were participant details, methodological aspects, and critical findings. In summary, the small but growing literature on in vivo SV2A PET has revealed different spatial patterns of synaptic density loss among various neurodegenerative disorders that correlate with cognitive functioning, supporting the potential role of SV2A PET imaging for differential diagnosis. SV2A PET imaging shows tremendous capability to provide novel insights into the aetiology of neurodegenerative disorders and great promise as a biomarker for synaptic density reduction. Novel directions for future synaptic density research are proposed, including (a) longitudinal imaging in larger patient cohorts of preclinical dementias, (b) multi-modal mapping of synaptic density loss onto other pathological processes, and (c) monitoring therapeutic responses and assessing drug efficacy in clinical trials.

Cancer drugs with high repositioning potential for Alzheimer's disease

INTRODUCTION

Despite the recent full FDA approval of lecanemab, there is currently no disease modifying therapy (DMT) that can efficiently slow down the progression of Alzheimer's disease (AD) in the general population. This statement emphasizes the need to identify novel DMTs in the shortest time possible to prevent a global epidemic of AD cases as the world population experiences an increase in lifespan.

AREAS COVERED

Here, we review several classes of anti-cancer drugs that have been or are being investigated in Phase II/III clinical trials for AD, including immunomodulatory drugs, RXR agonists, sex hormone therapies, tyrosine kinase inhibitors, and monoclonal antibodies.

EXPERT OPINION

Given the overall course of brain pathologies during the progression of AD, we express a great enthusiasm for the repositioning of anti-cancer drugs as possible AD DMTs. We anticipate an increasing number of combinatorial therapy strategies to tackle AD symptoms and their underlying pathologies. However, we strongly encourage improvements in clinical trial study designs to better assess target engagement and possible efficacy over sufficient periods of drug exposure.

Recent Updates on the Development of Therapeutics for the Targeted Treatment of Alzheimer's Disease

Alzheimer's disease (AD) is a complicated, multifaceted, irreversible, and incurable neurotoxic old age illness. Although NMDA (N-methyl D-aspartate)-receptor antagonists, cholinesterase repressors, and their pairings have been approved for the treatment, they are useful for short symptomatic relief. Researchers throughout the globe have been constantly working to uncover the therapy of Alzheimer's disease as new candidates must be determined, and newer treatment medicines must be developed. The aim of this review is to address recent advances in medication research along with new Alzheimer's disease therapy for diverse targets. Information was gathered utilizing a variety of internet resources as well as websites, such as ALZFORUM (alzforum.org) and clinicaltrials.gov. In contrast to other domains, the proposed medicines target amyloids (secretases, A42 generation, neuroinflammation, amyloid precipitation, and immunization), tau proteins (tau phosphorylation/aggregation and immunotherapy), and amyloid deposition. Despite tremendous advancement in our understanding of the underlying pathophysiology of Alzheimer's disease, the FDA (Food and Drug Administration) only approved aducanumab for diagnosis and treatment in 2003. Hence, novel treatment tactics are needed to find and develop therapeutic medicines to combat Alzheimer's disease.

Heat shock protein amplification improves cerebellar myelination in the Npc1nih mouse model

BACKGROUND

Niemann-Pick disease type C (NPC) is a rare prematurely fatal lysosomal lipid storage disease with limited therapeutic options. The prominent neuropathological hallmarks include hypomyelination and cerebellar atrophy. We previously demonstrated the efficacy of recombinant human heat shock protein 70 (rhHSP70) in preclinical models of the disease. It reduced glycosphingolipid levels in the central nervous system (CNS), improving cerebellar myelination and improved behavioural phenotypes in Npc1^nih (Npc1^-/-) mice. Furthermore, treatment with arimoclomol, a well-characterised HSP amplifier, attenuated lysosomal storage in NPC patient fibroblasts and improved neurological symptoms in Npc1^-/- mice. Taken together, these findings prompted the investigation of the effects of HSP amplification on CNS myelination.

METHODS

We administered bimoclomol daily or rhHSP70 6 times per week to Npc1^-/- (BALB/cNctr-Npc1^m1N/J, also named Npc1^nih) mice by intraperitoneal injection from P7 through P34 to investigate the impact on CNS myelination. The Src-kinase inhibitor saracatinib was administered with/without bimoclomol twice daily to explore the contribution of Fyn kinase to bimoclomol's effects.

FINDINGS

Treatment with either bimoclomol or rhHSP70 improved myelination and increased the numbers of mature oligodendrocytes (OLs) as well as the ratio of active-to-inactive forms of phosphorylated Fyn kinase in the cerebellum of Npc1^-/- mice. Additionally, treatment with bimoclomol preserved cerebellar weight, an effect that was abrogated when co-administered with saracatinib, an inhibitor of Fyn kinase. Bimoclomol-treated mice also exhibited increased numbers of immature OLs within the cortex.

INTERPRETATION

These data increase our understanding of the mechanisms by which HSP70 regulates myelination and provide further support for the clinical development of HSP-amplifying therapies in the treatment of NPC.

FUNDING

Funding for this study was provided by Orphazyme A/S (Copenhagen, Denmark) and a Pathfinder Award from The Wellcome Trust.

Gut dysbiosis following organophosphate, diisopropylfluorophosphate (DFP), intoxication and saracatinib oral administration

Organophosphate nerve agents (OPNAs) act as irreversible inhibitors of acetylcholinesterase and can lead to cholinergic crisis including salivation, lacrimation, urination, defecation, gastrointestinal distress, respiratory distress, and seizures. Although the OPNAs have been studied in the past few decades, little is known about the impact on the gut microbiome which has become of increasing interest across fields. In this study, we challenged animals with the OPNA, diisopropylfluorophosphate (DFP, 4mg/kg, s.c.) followed immediately by 2mg/kg atropine sulfate (i.m.) and 25mg/kg 2-pralidoxime (i.m.) and 30 minutes later by 3mg/kg midazolam (i.m.). One hour after midazolam, animals were treated with a dosing regimen of saracatinib (SAR, 20mg/kg, oral), a src family kinase inhibitor, to mitigate DFP-induced neurotoxicity. We collected fecal samples 48 hours, 7 days, and 5 weeks post DFP intoxication. 16S rRNA genes (V4) were amplified to identify the bacterial composition. At 48 hours, a significant increase in the abundance of Proteobacteria and decrease in the abundance of Firmicutes were observed in DFP treated animals. At 7 days there was a significant reduction in Firmicutes and Actinobacteria, but a significant increase in Bacteroidetes in the DFP groups compared to controls. The taxonomic changes at 5 weeks were negligible. There was no impact of SAR administration on microbial composition. There was a significant DFP-induced reduction in alpha diversity at 48 hours but not at 7 days and 5 weeks. There appeared to be an impact of DFP on beta diversity at 48 hours and 7 days but not at 5 weeks. In conclusion, acute doses of DFP lead to short-term gut dysbiosis and SAR had no effect. Understanding the role of gut dysbiosis in long-term toxicity may reveal therapeutic targets.

The synapse as a treatment avenue for Alzheimer's Disease

Alzheimer's disease (AD) is a neurodegenerative disorder with devastating symptoms, including memory impairments and cognitive deficits. Hallmarks of AD pathology are amyloid-beta (Aβ) deposition forming neuritic plaques and neurofibrillary tangles (NFTs). For many years, AD drug development has mainly focused on directly targeting the Aβ aggregation or the formation of tau tangles, but this disease has no cure so far. Other common characteristics of AD are synaptic abnormalities and dysfunctions such as synaptic damage, synaptic loss, and structural changes in the synapse. Those anomalies happen in the early stages of the disease before behavioural symptoms have occurred. Therefore, better understanding the mechanisms underlying the synaptic dysfunction found in AD and targeting the synapse, especially using early treatment windows, can lead to finding novel and more effective treatments that could improve the lives of AD patients. Researchers have recently started developing different disease-modifying treatments targeting the synapse to rescue and prevent synaptic dysfunction in AD. The main objectives of these new strategies are to halt synaptic loss, strengthen synaptic connections, and improve synaptic density, potentially leading to the rescue or prevention of cognitive impairments. This article aims to address the mechanisms of synaptic degeneration in AD and discuss current strategies that focus on the synapse for AD therapy. Alzheimer's disease (AD) is a neurodegenerative disorder that significantly impairs memory and causes cognitive and behavioural deficits. Scientists worldwide have tried to find a treatment that can reverse or rescue AD symptoms, but there is no cure so far. One prominent characteristic of AD is the brain atrophy caused by significant synaptic loss and overall neuronal damage, which starts at the early stages of the disease before other AD hallmarks such as neuritic plaques and NFTs. The present review addresses the underlying mechanisms behind synaptic loss and dysfunction in AD and discusses potential strategies that target the synapse.

A public-private collaboration model for clinical innovation

Launched in May 2012 as part of the New Therapeutic Uses program, NCATS' NIH-Industry Partnerships initiative fostered collaboration between pharmaceutical companies and the biomedical research community to advance therapeutic development. Over the 10-year life of the initiative, the industry partners included: AstraZeneca; AbbVie (formerly Abbott); Bristol-Myers Squibb; Eli Lilly and Company; GlaxoSmithKline; Janssen Pharmaceutical Research & Development, L.L.C.; Pfizer; Sanofi; and Mereo (out licensed assets). The initiative provided researchers at academic medical centers with a rare opportunity to propose clinical trials to test ideas for new therapeutic uses for a selection of clinic-ready and often previously proprietary experimental pharmaceutical assets that were provided by industry partners. Here we describe the process by which collaborations between pharmaceutical companies with viable experimental assets and academic researchers with ideas for new uses of those assets were established; and how NCATS/NIH funding supported not only phase 1 and 2 clinical trials as well as any non-clinical studies needed before testing in a new patient population, it also provided an opportunity for testing innovative outcome measures for proof of concept trials. While the program did not demonstrate improved success rates for phase 2 clinical trials, this collaboration model leverages the strengths of each party and with a focus toward evaluating innovative outcome measure, could be used to reduce patient burden and trial costs, and improve patient engagement.

Saracatinib, a Src Tyrosine Kinase Inhibitor, as a Disease Modifier in the Rat DFP Model: Sex Differences, Neurobehavior, Gliosis, Neurodegeneration, and Nitro-Oxidative Stress

Diisopropylfluorophosphate (DFP), an organophosphate nerve agent (OPNA), exposure causes status epilepticus (SE) and epileptogenesis. In this study, we tested the protective effects of saracatinib (AZD0530), a Src kinase inhibitor, in mixed-sex or male-only Sprague Dawley rats exposed to 4-5 mg/kg DFP followed by 2 mg/kg atropine and 25 mg/kg 2-pralidoxime. Midazolam (3 mg/kg) was given to the mixed-sex cohort (1 h post-DFP) and male-only cohort (~30 min post-DFP). Saracatinib (20 mg/kg, oral, daily for 7 days) or vehicle was given two hours later and euthanized eight days or ten weeks post-DFP. Brain immunohistochemistry (IHC) showed increased microgliosis, astrogliosis, and neurodegeneration in DFP-treated animals. In the 10-week post-DFP male-only group, there were no significant differences between groups in the novel object recognition, Morris water maze, rotarod, or forced swim test. Brain IHC revealed significant mitigation by saracatinib in contrast to vehicle-treated DFP animals in microgliosis, astrogliosis, neurodegeneration, and nitro-oxidative stressors, such as inducible nitric oxide synthase, GP91phox, and 3-Nitrotyrosine. These findings suggest the protective effects of saracatinib on brain pathology seem to depend on the initial SE severity. Further studies on dose optimization, including extended treatment regimen depending on the SE severity, are required to determine its disease-modifying potential in OPNA models.

Revisiting the grammar of Tau aggregation and pathology formation: how new insights from brain pathology are shaping how we study and target Tauopathies

Converging evidence continues to point towards Tau aggregation and pathology formation as central events in the pathogenesis of Alzheimer's disease and other Tauopathies. Despite significant advances in understanding the morphological and structural properties of Tau fibrils, many fundamental questions remain about what causes Tau to aggregate in the first place. The exact roles of cofactors, Tau post-translational modifications, and Tau interactome in regulating Tau aggregation, pathology formation, and toxicity remain unknown. Recent studies have put the spotlight on the wide gap between the complexity of Tau structures, aggregation, and pathology formation in the brain and the simplicity of experimental approaches used for modeling these processes in research laboratories. Embracing and deconstructing this complexity is an essential first step to understanding the role of Tau in health and disease. To help deconstruct this complexity and understand its implication for the development of effective Tau targeting diagnostics and therapies, we firstly review how our understanding of Tau aggregation and pathology formation has evolved over the past few decades. Secondly, we present an analysis of new findings and insights from recent studies illustrating the biochemical, structural, and functional heterogeneity of Tau aggregates. Thirdly, we discuss the importance of adopting new experimental approaches that embrace the complexity of Tau aggregation and pathology as an important first step towards developing mechanism- and structure-based therapies that account for the pathological and clinical heterogeneity of Alzheimer's disease and Tauopathies. We believe that this is essential to develop effective diagnostics and therapies to treat these devastating diseases.

Prions and Neurodegenerative Diseases: A Focus on Alzheimer's Disease

Specific protein misfolding and aggregation are mechanisms underlying various neurodegenerative diseases such as prion disease and Alzheimer's disease (AD). The misfolded proteins are involved in prions, amyloid-β (Aβ), tau, and α-synuclein disorders; they share common structural, biological, and biochemical characteristics, as well as similar mechanisms of aggregation and self-propagation. Pathological features of AD include the appearance of plaques consisting of deposition of protein Aβ and neurofibrillary tangles formed by the hyperphosphorylated tau protein. Although it is not clear how protein aggregation leads to AD, we are learning that the cellular prion protein (PrPC) plays an important role in the pathogenesis of AD. Herein, we first examined the pathogenesis of prion and AD with a focus on the contribution of PrPC to the development of AD. We analyzed the mechanisms that lead to the formation of a high affinity bond between Aβ oligomers (AβOs) and PrPC. Also, we studied the role of PrPC as an AβO receptor that initiates an AβO-induced signal cascade involving mGluR5, Fyn, Pyk2, and eEF2K linking Aβ and tau pathologies, resulting in the death of neurons in the central nervous system. Finally, we have described how the PrPC-AβOs interaction can be used as a new potential therapeutic target for the treatment of PrPC-dependent AD.

Differential Impact of Severity and Duration of Status Epilepticus, Medical Countermeasures, and a Disease-Modifier, Saracatinib, on Brain Regions in the Rat Diisopropylfluorophosphate Model

Acute organophosphate (OP) toxicity poses a significant threat to both military and civilian personnel as it can lead to a variety of cholinergic symptoms including the development of status epilepticus (SE). Depending on its severity, SE can lead to a spectrum of neurological changes including neuroinflammation and neurodegeneration. In this study, we determined the impact of SE severity and duration on disease promoting parameters such as gliosis and neurodegeneration and the efficacy of a disease modifier, saracatinib (AZD0530), a Src/Fyn tyrosine kinase inhibitor. Animals were exposed to 4 mg/kg diisopropylfluorophosphate (DFP, s.c.) followed by medical countermeasures. We had five experimental groups: controls (no DFP), animals with no continuous convulsive seizures (CS), animals with ∼20-min continuous CS, 31-60-min continuous CS, and > 60-min continuous CS. These groups were then assessed for astrogliosis, microgliosis, and neurodegeneration 8 days after DFP exposure. The 31-60-min and > 60-min groups, but not ∼20-min group, had significantly upregulated gliosis and neurodegeneration in the hippocampus compared to controls. In the piriform cortex and amygdala, however, all three continuous CS groups had significant upregulation in both gliosis and neurodegeneration. In a separate cohort of animals that had ∼20 and > 60-min of continuous CS, we administered saracatinib for 7 days beginning three hours after DFP. There was bodyweight loss and mortality irrespective of the initial SE severity and duration. However, in survived animals, saracatinib prevented spontaneous recurrent seizures (SRS) during the first week in both severity groups. In the ∼20-min CS group, compared to the vehicle, saracatinib significantly reduced neurodegeneration in the piriform cortex and amygdala. There were no significant differences in the measured parameters between the naïve control and saracatinib on its own (without DFP) groups. Overall, this study demonstrates the differential effects of the initial SE severity and duration on the localization of gliosis and neurodegeneration. We have also demonstrated the disease-modifying potential of saracatinib. However, its’ dosing regimen should be optimized based on initial severity and duration of CS during SE to maximize therapeutic effects and minimize toxicity in the DFP model as well as in other OP models such as soman.

Fyn Kinase Activity and Its Role in Neurodegenerative Disease Pathology: a Potential Universal Target?

Fyn is a non-receptor tyrosine kinase belonging to the Src family of kinases (SFKs) which has been implicated in several integral functions throughout the central nervous system (CNS), including myelination and synaptic transmission. More recently, Fyn dysfunction has been associated with pathological processes observed in neurodegenerative diseases, such as multiple sclerosis (MS), Alzheimer's disease (AD) and Parkinson's disease (PD). Neurodegenerative diseases are amongst the leading cause of death and disability worldwide and, due to the ageing population, prevalence is predicted to rise in the coming years. Symptoms across neurodegenerative diseases are both debilitating and degenerative in nature and, concerningly, there are currently no disease-modifying therapies to prevent their progression. As such, it is important to identify potential new therapeutic targets. This review will outline the role of Fyn in normal/homeostatic processes, as well as degenerative/pathological mechanisms associated with neurodegenerative diseases, such as demyelination, pathological protein aggregation, neuroinflammation and cognitive dysfunction.

Mechanisms of disease-modifying effect of saracatinib (AZD0530), a Src/Fyn tyrosine kinase inhibitor, in the rat kainate model of temporal lobe epilepsy

We have recently demonstrated the role of the Fyn-PKCδ signaling pathway in status epilepticus (SE)-induced neuroinflammation and epileptogenesis in experimental models of temporal lobe epilepsy (TLE). In this study, we show a significant disease-modifying effect and the mechanisms of a Fyn/Src tyrosine kinase inhibitor, saracatinib (SAR, also known as AZD0530), in the rat kainate (KA) model of TLE. SAR treatment for a week, starting the first dose (25 mg/kg, oral) 4 h after the onset of SE, significantly reduced spontaneously recurring seizures and epileptiform spikes during the four months of continuous video-EEG monitoring. Immunohistochemistry of brain sections and Western blot analyses of hippocampal lysates at 8-day (8d) and 4-month post-SE revealed a significant reduction of SE-induced astrogliosis, microgliosis, neurodegeneration, phosphorylated Fyn/Src-419 and PKCδ-tyr311, in SAR-treated group when compared with the vehicle control. We also found the suppression of nitroxidative stress markers such as iNOS, 3-NT, 4-HNE, and gp91phox in the hippocampus, and nitrite and ROS levels in the serum of the SAR-treated group at 8d post-SE. The qRT-PCR (hippocampus) and ELISA (serum) revealed a significant reduction of key proinflammatory cytokines TNFα and IL-1β mRNA in the hippocampus and their protein levels in serum, in addition to IL-6 and IL-12, in the SAR-treated group at 8d in contrast to the vehicle-treated group. These findings suggest that SAR targets some of the key biomarkers of epileptogenesis and modulates neuroinflammatory and nitroxidative pathways that mediate the development of epilepsy. Therefore, SAR can be developed as a potential disease-modifying agent to prevent the development and progression of TLE.

Stachydrine Inhibits PC12 Cell Apoptosis Induced by Aβ25-35 in an in vitro Cell Model of Neurocognitive Disorders

Background:

Abnormal deposition of amyloid beta (Aβ) is considered the primary cause of neurocognitive disorders (NCDs). Inhibiting cytotoxicity is an important aspect of the treatment of NCDs. Stachydrine (STA) has been widely used for gynecological and cardiovascular disorders. However, whether STA has protective functions in PC12 cells treated with Aβ25-35 remains unclear.

Introduction:

Traditional Chinese Medicine, stachydrine (STA), is a water-soluble alkaloid of Leonurus heterophyllus, which can inhibit cell apoptosis, suppress tumor growth, maintain homeostasis of myocardial cells, and alleviate endothelial dysfunction. This study will investigate the effect of STA on inhibiting PC12 cell apoptosis induced by Aβ25-35 in an in vitro cell model of neurocognitive disorders.

Methods:

The differentially expressed genes (DEGs) in cells treated with STA were analyzed according to the Gene Expression Omnibus (GSE) 85871 data, and the STITCH database was used to identify the target genes of STA. PC12 cells were treated with Aβ25-35 and/or STA, 3-(4,5- dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay was performed and lactate dehydrogenase (LDH) activity was determined. The cell cycle distribution was detected by flow cytometry, and quantitative reverse transcription-polymerase chain reaction (qRT-PCR) or Western blotting were used to detect the expression of genes or proteins.

Results:

GSE85871 data showed 37 upregulated and 48 downregulated genes among the DEGs affected by STA. The results from the STITCH database showed that RPS8 and EED were target genes of STA. GSE1297 analysis showed the 13 most significantly upregulated genes. STA might affect the occurrence of NCDs through the interaction of TP53 with EED and RPS8. Finally, Aβ25-35 promoted apoptosis and LDH release of PC-12 cells, arrested the cell cycle in the G2/M phase, and inhibited the expression of the RPS8, EED, Bcl-2 and P53 genes. STA could reverse the effect of Aβ25-35.

Conclusion:

STA may play an important role in inhibiting apoptosis induced by Aβ25-35 by targeting the RPS8 and EED genes in the NCDs model in vitro.

Partial volume correction analysis for 11C-UCB-J PET studies of Alzheimer's disease

Purpose:

¹¹C-UCB-J PET imaging, targeting synaptic vesicle glycoprotein 2A (SV2A), has been shown to be a useful indicator of synaptic density in Alzheimer’s disease (AD). For SV2A imaging, a decrease in apparent tracer uptake is often due to the combination of gray-matter (GM) atrophy and SV2A decrease in the remaining tissue. Our aim is to reveal the true SV2A change by performing partial volume correction (PVC).

Methods:

We performed two PVC algorithms, Müller-Gärtner (MG) and ‘iterative Yang’ (IY), on 17 AD participants and 11 cognitive normal (CN) participants using the brain-dedicated HRRT scanner. Distribution volume V_T, the rate constant K₁, binding potential BP_ND (centrum semiovale as reference region), and tissue volume were compared.

Results:

In most regions, both PVC algorithms reduced the between-group differences. Alternatively, in hippocampus, IY increased the significance of between-group differences while MG reduced it (V_T, BP_ND and K₁ group differences: uncorrected: 20%, 27%, 17%; MG: 18%, 22%, 14%; IY: 22%, 28%, 17%). The group difference in hippocampal volume (10%) was substantially smaller than any PET measures. MG increased GM binding values to a greater extent than IY due to differences in algorithm assumptions.

Conclusion:

¹¹C-UCB-J binding is significantly reduced in AD hippocampus, but PVC is important to adjust for significant volume reduction. After correction, PET measures are substantially more sensitive to group differences than volumetric MRI measures. Assumptions of each PVC algorithm are important and should be carefully examined and validated. For ¹¹C-UCB-J, the less stringent assumptions of IY support its use as a PVC algorithm over MG.

Microglia Dysfunction Caused by the Loss of Rhoa Disrupts Neuronal Physiology and Leads to Neurodegeneration

Nervous tissue homeostasis requires the regulation of microglia activity. Using conditional gene targeting in mice, we demonstrate that genetic ablation of the small GTPase Rhoa in adult microglia is sufficient to trigger spontaneous microglia activation, producing a neurological phenotype (including synapse and neuron loss, impairment of long-term potentiation [LTP], formation of β-amyloid plaques, and memory deficits). Mechanistically, loss of Rhoa in microglia triggers Src activation and Src-mediated tumor necrosis factor (TNF) production, leading to excitotoxic glutamate secretion. Inhibiting Src in microglia Rhoa-deficient mice attenuates microglia dysregulation and the ensuing neurological phenotype. We also find that the Rhoa/Src signaling pathway is disrupted in microglia of the APP/PS1 mouse model of Alzheimer disease and that low doses of Aβ oligomers trigger microglia neurotoxic polarization through the disruption of Rhoa-to-Src signaling. Overall, our results indicate that disturbing Rho GTPase signaling in microglia can directly cause neurodegeneration.

Tyrosine phosphorylation regulates hnRNPA2 granule protein partitioning and reduces neurodegeneration

mRNA transport in neurons requires formation of transport granules containing many protein components, and subsequent alterations in phosphorylation status can release transcripts for translation. Further, mutations in a structurally disordered domain of the transport granule protein hnRNPA2 increase its aggregation and cause hereditary proteinopathy of neurons, myocytes, and bone. We examine in vitro hnRNPA2 granule component phase separation, partitioning specificity, assembly/disassembly, and the link to neurodegeneration. Transport granule components hnRNPF and ch-TOG interact weakly with hnRNPA2 yet partition specifically into liquid phase droplets with the low complexity domain (LC) of hnRNPA2, but not FUS LC. In vitro hnRNPA2 tyrosine phosphorylation reduces hnRNPA2 phase separation, prevents partitioning of hnRNPF and ch-TOG into hnRNPA2 LC droplets, and decreases aggregation of hnRNPA2 disease variants. The expression of chimeric hnRNPA2 D290V in Caenorhabditis elegans results in stress-induced glutamatergic neurodegeneration; this neurodegeneration is rescued by loss of tdp-1, suggesting gain-of-function toxicity. The expression of Fyn, a tyrosine kinase that phosphorylates hnRNPA2, reduces neurodegeneration associated with chimeric hnRNPA2 D290V. These data suggest a model where phosphorylation alters LC interaction specificity, aggregation, and toxicity.

Recent advances on drug development and emerging therapeutic agents for Alzheimer's disease

Alzheimer's disease (AD) is a neurodegenerative old age disease that is complex, multifactorial, unalterable, and progressive in nature. The currently approved therapy includes cholinesterase inhibitors, NMDA-receptor antagonists and their combination therapy provides only temporary symptomatic relief. Sincere efforts have been made by the researchers globally to identify new targets, discover, and develop novel therapeutic agents for the treatment of AD. This brief review article is intended to cover the recent advances in drug development and emerging therapeutic agents for AD acting at different targets. The article is compiled using various scientific online databases and by referring to clinicaltrials.gov and ALZFORUM (alzforum.org) websites. The upcoming therapies act on one or more targets including amyloids (secretases, Aβ₄₂ production, amyloid deposition, and immunotherapy), tau proteins (tau phosphorylation/aggregation and immunotherapy) and neuroinflammation in addition to other miscellaneous targets. Despite the tremendous improvement in our understanding of the underlying pathophysiology of AD, only aducanumab was approved by FDA for the treatment of AD in 18 years i.e., since 2003. Hence, it is concluded that novel therapeutic strategies are required to discover and develop therapeutic agents to fight against the century old AD.

Saracatinib Fails to Reduce Alcohol-Seeking and Consumption in Mice and Human Participants

More effective treatments to reduce pathological alcohol drinking are needed. The glutamatergic system and the NMDA receptor (NMDAR), in particular, are implicated in behavioral and molecular consequences of chronic alcohol use, making the NMDAR a promising target for novel pharmacotherapeutics. Ethanol exposure upregulates Fyn, a protein tyrosine kinase that indirectly modulates NMDAR signaling by phosphorylating the NR2B subunit. The Src/Fyn kinase inhibitor saracatinib (AZD0530) reduces ethanol self-administration and enhances extinction of goal-directed ethanol-seeking in mice. However, less is known regarding how saracatinib affects habitual ethanol-seeking. Moreover, no prior studies have assessed the effects of Src/Fyn kinase inhibitors on alcohol-seeking or consumption in human participants. Here, we tested the effects of saracatinib on alcohol consumption and craving/seeking in two species, including the first trial of an Src/Fyn kinase inhibitor to reduce drinking in humans. Eighteen male C57BL/6NCrl mice underwent operant conditioning on a variable interval schedule to induce habitual responding for 10% ethanol/0.1% saccharin. Next, mice received 5 mg/kg saracatinib or vehicle 2 h or 30 min prior to contingency degradation to measure habitual responding. In the human study, 50 non-treatment seeking human participants who drank heavily and met DSM-IV criteria for alcohol abuse or dependence were randomized to receive 125 mg/day saracatinib (n = 33) or placebo (n = 17). Alcohol Drinking Paradigms (ADP) were completed in a controlled research setting: before and after 7-8 days of treatment. Each ADP involved consumption of a priming drink of alcohol (0.03 mg%) followed by ad libitum access (3 h) to 12 additional drinks (0.015 g%); the number of drinks consumed and craving (Alcohol Urge Questionnaire) were recorded. In mice, saracatinib did not affect habitual ethanol seeking or consumption at either time point. In human participants, no significant effects of saracatinib on alcohol craving or consumption were identified. These results in mice and humans suggest that Fyn kinase inhibition using saracatinib, at the doses tested here, may not reduce alcohol consumption or craving/seeking among those habitually consuming alcohol, in contrast to reports of positive effects of saracatinib in individuals that seek ethanol in a goal-directed manner. Nevertheless, future studies should confirm these negative findings using additional doses and schedules of saracatinib administration.

New Insights Into Drug Discovery Targeting Tau Protein

Microtubule-associated protein tau is characterized by the fact that it is an intrinsically disordered protein due to its lack of a stable conformation and high flexibility. Intracellular inclusions of fibrillar forms of tau with a β-sheet structure accumulate in the brain of patients with Alzheimer's disease and other tauopathies. Accordingly, detachment of tau from microtubules and transition of tau from a disordered state to an abnormally aggregated state are essential events preceding the onset of tau-related diseases. Many reports have shown that this transition is caused by post-translational modifications, including hyperphosphorylation and acetylation. The misfolded tau is self-assembled and forms a tau oligomer before the appearance of tau inclusions. Animal and pathological studies using human samples have demonstrated that tau oligomer formation contributes to neuronal loss. During the progression of tauopathies, tau seeds are released from cells and incorporated into other cells, leading to the propagation of pathological tau aggregation. Accumulating evidence suggests several potential approaches for blocking tau-mediated toxicity: (1) direct inhibition of pathological tau aggregation and (2) inhibition of tau post-translational modifications that occur prior to pathological tau aggregation, (3) inhibition of tau propagation and (4) stabilization of microtubules. In addition to traditional low-molecular-weight compounds, newer drug discovery approaches such as the development of medium-molecular-weight drugs (peptide- or oligonucleotide-based drugs) and high-molecular-weight drugs (antibody-based drugs) provide alternative pathways to preventing the formation of abnormal tau. Of particular interest are recent studies suggesting that tau droplet formation by liquid-liquid phase separation may be the initial step in aberrant tau aggregation, as well results that implicate roles for tau in dendritic and nuclear functions. Here, we review the mechanisms through which drugs can target tau and consider recent clinical trials for the treatment of tauopathies. In addition, we discuss the utility of these newer strategies and propose future directions for research on tau-targeted therapeutics.

Glucosylpolyphenols as Inhibitors of Aβ-Induced Fyn Kinase Activation and Tau Phosphorylation: Synthesis, Membrane Permeability, and Exploratory Target Assessment within the Scope of Type 2 Diabetes and Alzheimer's Disease

Despite the rapidly increasing number of patients suffering from type 2 diabetes, Alzheimer's disease, and diabetes-induced dementia, there are no disease-modifying therapies that are able to prevent or block disease progress. In this work, we investigate the potential of nature-inspired glucosylpolyphenols against relevant targets, including islet amyloid polypeptide, glucosidases, and cholinesterases. Moreover, with the premise of Fyn kinase as a paradigm-shifting target in Alzheimer's drug discovery, we explore glucosylpolyphenols as blockers of Aβ-induced Fyn kinase activation while looking into downstream effects leading to Tau hyperphosphorylation. Several compounds inhibit Aβ-induced Fyn kinase activation and decrease pTau levels at 10 μM concentration, particularly the per-O-methylated glucosylacetophloroglucinol and the 4-glucosylcatechol dibenzoate, the latter inhibiting also butyrylcholinesterase and β-glucosidase. Both compounds are nontoxic with ideal pharmacokinetic properties for further development. This work ultimately highlights the multitarget nature, fine structural tuning capacity, and valuable therapeutic significance of glucosylpolyphenols in the context of these metabolic and neurodegenerative disorders.

Pre-symptomatic Caspase-1 inhibitor delays cognitive decline in a mouse model of Alzheimer disease and aging

Early therapeutic interventions are essential to prevent Alzheimer Disease (AD). The association of several inflammation-related genetic markers with AD and the early activation of pro-inflammatory pathways in AD suggest inflammation as a plausible therapeutic target. Inflammatory Caspase-1 has a significant impact on AD-like pathophysiology and Caspase-1 inhibitor, VX-765, reverses cognitive deficits in AD mouse models. Here, a one-month pre-symptomatic treatment of Swedish/Indiana mutant amyloid precursor protein (APP^Sw/Ind) J20 and wild-type mice with VX-765 delays both APP^Sw/Ind- and age-induced episodic and spatial memory deficits. VX-765 delays inflammation without considerably affecting soluble and aggregated amyloid beta peptide (Aβ) levels. Episodic memory scores correlate negatively with microglial activation. These results suggest that Caspase-1-mediated inflammation occurs early in the disease and raise hope that VX-765, a previously Food and Drug Administration-approved drug for human CNS clinical trials, may be a useful drug to prevent the onset of cognitive deficits and brain inflammation in AD.

[Effects of stachyine on apoptosis in an Aβ25-35-induced PC12 cell model of Alzheimer's disease]

OBJECTIVE

To investigate the effects of stachydrine (STA) on apoptosis of Aβ25-35-induced PC12 cells mimicking Alzheimer's disease and explore the mechanisms.

METHODS

The differential genes of STA were analyzed based on GSE85871 data, and the target genes of STA were identified using STITCH database. PC12 cells were treated with Aβ25-35 to establish a cell model of Alzheimer's disease, and the changes in cell viability and cell cycle in response to STA treatment were assessed using MTT assay and flow cytometry, respectively. RT-PCR and Western blotting were used to detect the relevant gene or protein expressions in the treated cells.

RESULTS

GSE85871 data showed 37 up-regulated genes and 48 down-regulated genes in cells following treatment with STA. Analysis of the data from the STITCH database indicated that RPS8 and EED were the target genes of STA. Treatment of PC12 cells with Aβ25-35 significantly lowered the cell viability (P < 0.05) and the expressions of RPS8 and EED at both the mRNA and protein levels (P < 0.05), and obviously inhibited the expression of apoptosis-related proteins Bcl-2 and p53 (P < 0.05). STA treatment of the cells significantly reversed the effect of Aβ25-35 and induced cell cycle arrest in G2/M phase, causing also significantly increases in the expression levels of RPS8, EED, Bcl-2 and p53 (P < 0.05).

CONCLUSIONS

STA plays an important role in inhibiting the apoptosis of PC12 cells induced by Aβ25-35 possibly by regulating RPS8 and EED expression to promote the expressions of Bcl-2 and p53.

Angiotensin (1-7) through modulation of the NMDAR-nNOS-NO pathway and serotonergic metabolism exerts an anxiolytic-like effect in rats

Although recent studies have shown that angiotensin (1-7) (Ang [1-7]) exerts anti-stress and anxiolytic-like effects, the underlying mechanisms remain elusive. The ventral hippocampus (VH) is proposed to be a critical brain region for mood and stress management through the N-methyl-d-aspartate receptor (NMDAR) signaling pathway. However, the role of VH NMDAR signaling in the effects of Ang (1-7) remains unclear. In the present study, Ang (1-7) was injected into the bilateral VH of stressed rats, or in combination with a Fyn kinase inhibitor, NMDAR antagonist, neuronal nitric oxide synthase (nNOS) inhibitor, or nitric oxide (NO) scavenger. Anxiety-like behaviors were assessed using the open field test and elevated plus maze test, while alterations in NMDAR-nNOS-NO signaling and serotonergic metabolism were examined in the VH. After 21 days of chronic restraint stress, anxiety-like behaviors were evident. Levels of phosphorylated NR2B (a key NMDAR subunit), its upstream kinase Fyn, as well as activity of nNOS and monoamine oxidase (MAO) were markedly reduced. In contrast, levels of serotonin were increased. Bilateral VH infusion of Ang (1-7) recovered NMDAR-nNOS-NO signaling and MAO-mediated serotonin metabolism, as well as reducing anxiety-like behaviors in stressed rats. These effects were diminished by blockade of MasR (Ang [1-7]-specific receptor), Fyn kinase, NMDAR, nNOS, or NO production. Altogether, these findings indicate that Ang (1-7) exerts anxiolytic effects through modulation of the NMDAR-nNOS-NO pathway and serotonergic metabolism. Future translational research should focus on the relationship between Ang (1-7), glutamatergic neurotransmission, and serotonergic neurotransmission in the VH.

Fyn kinase inhibition reduces protein aggregation, increases synapse density and improves memory in transgenic and traumatic Tauopathy

Accumulation of misfolded phosphorylated Tau (Tauopathy) can be triggered by mutations or by trauma, and is associated with synapse loss, gliosis, neurodegeneration and memory deficits. Fyn kinase physically associates with Tau and regulates subcellular distribution. Here, we assessed whether pharmacological Fyn inhibition alters Tauopathy. In P301S transgenic mice, chronic Fyn inhibition prevented deficits in spatial memory and passive avoidance learning. The behavioral improvement was coupled with reduced accumulation of phospho-Tau in the hippocampus, with reductions in glial activation and with recovery of presynaptic markers. We extended this analysis to a trauma model in which very mild repetitive closed head injury was paired with chronic variable stress over 2 weeks to produce persistent memory deficits and Tau accumulation. In this model, Fyn inhibition beginning 24 h after the trauma ended rescued memory performance and reduced phospho-Tau accumulation. Thus, inhibition of Fyn kinase may have therapeutic benefit in clinical Tauopathies.

Fyn gene silencing reduces oligodendrocytes apoptosis through inhibiting ERK1/2 phosphorylation in epilepsy

This study aimed to investigate the effect of Fyn gene silencing on the apoptosis of oligodendrocytes (OLs) in epileptic model in vitro and the involved mechanism. Primary oligodendrocyte pro-genitor cells (OPCs) were separated from rats and differentiated to OLs. Immunofluorescent labeling showed positive expression of A2B5 in OPCs and Olig2 in OLs, suggesting the successful separation of OPCs and OLs. Three Fyn siRNAs (si-Fyn) and Fyn siRNA negative control (NC) were transfected into OLs. Western blot showed that among three si-Fyn groups, si-Fyn3 caused the lowest Fyn expression, so si-Fyn3 was chosen for following experiment. Cells were divided into four groups: Control, Model, NC and si-Fyn. In the Model group, cells were cultured in Mg-free extracellular fluid for 3 h. The morphology of control cells was normal. However, the migration of neurons, the aggregation of cell bodies and the "grid-like" changes of neural networks were observed in the model cells. OLs apoptosis in various groups was assessed by flow cytometry. Expression of Fyn, ERK1/2 and phosphorylated ERK1/2 (p-ERK1/2) in OLs of various groups was evaluated by western blot. Compared with the Control group, the apoptotic rates, the Fyn expression and p-ERK1/2/ERK1/2 ratio in the Model and NC groups increased significantly (p < .05). However, the apoptotic rate, the Fyn expression and p-ERK1/2/ERK1/2 ratio in the si-Fyn group were remarkably smaller than those in the Model group (p < .05). In conclusion, Fyn gene silencing reduced the apoptosis of OLs through inhibiting the phosphorylation of ERK1/2 in epileptic model.

Aβ-induced acceleration of Alzheimer-related τ-pathology spreading and its association with prion protein

Extracellular deposition of amyloid β-protein (Aβ) in amyloid plaques and intracellular accumulation of abnormally phosphorylated τ-protein (p-τ) in neurofibrillary tangles (NFTs) represent pathological hallmark lesions of Alzheimer's disease (AD). Both lesions develop in parallel in the human brain throughout the preclinical and clinical course of AD. Nevertheless, it is not yet clear whether there is a direct link between Aβ and τ pathology or whether other proteins are involved in this process. To address this question, we crossed amyloid precursor protein (APP) transgenic mice overexpressing human APP with the Swedish mutation (670/671 KM → NL) (APP23), human wild-type APP (APP51/16), or a proenkephalin signal peptide linked to human Aβ₄₂ (APP48) with τ-transgenic mice overexpressing human mutant 4-repeat τ-protein with the P301S mutation (TAU58). In 6-month-old APP23xTAU58 and APP51/16xTAU58 mice, soluble Aβ was associated with the aggravation of p-τ pathology propagation into the CA1/subiculum region, whereas 6-month-old TAU58 and APP48xTAU58 mice neither exhibited significant amounts of p-τ pathology in the CA1/subiculum region nor displayed significant levels of soluble Aβ in the forebrain. In APP23xTAU58 and APP51/16xTAU58 mice showing an acceleration of p-τ propagation, Aβ and p-τ were co-immunoprecipitated with cellular prion protein (PrP^C). A similar interaction between PrP^C, p-τ and Aβ was observed in human AD brains. This association was particularly noticed in 60% of the symptomatic AD cases in our sample, suggesting that PrP^C may play a role in the progression of AD pathology. An in vitro pull-down assay confirmed that PrP^C is capable of interacting with Aβ and p-τ. Using a proximity ligation assay, we could demonstrate proximity (less than ~ 30-40 nm distance) between PrP^C and Aβ and between PrP^C and p-τ in APP23xTAU58 mouse brain as well as in human AD brain. Proximity between PrP^C and p-τ was also seen in APP51/16xTAU58, APP48xTAU58, and TAU58 mice. Based on these findings, it is tempting to speculate that PrP^C is a critical player in the interplay between Aβ and p-τ propagation at least in a large group of AD cases. Preexisting p-τ pathology interacting with PrP^C, thereby, appears to be a prerequisite for Aβ to function as a p-τ pathology accelerator via PrP^C.

In Vivo Synaptic Density Imaging with 11C-UCB-J Detects Treatment Effects of Saracatinib in a Mouse Model of Alzheimer Disease

¹¹C-UCB-J is a new PET tracer for synaptic density imaging. Recently, we conducted ¹¹C-UCB-J PET on patients with mild cognitive impairment or early Alzheimer disease (AD) and found a 41% decrease in specific binding in the hippocampus compared with healthy subjects. We hypothesized that ¹¹C-UCB-J may have potential to be a general biomarker for evaluating AD treatment effects via monitoring of synaptic density changes. In this study, we performed longitudinal ¹¹C-UCB-J PET on AD mice to measure the treatment effects of saracatinib, which previously demonstrated synaptic changes with postmortem methods. Methods: Nine wild-type (WT) mice and 9 amyloid precursor protein and presenilin 1 double-transgenic (APPswe/PS1ΔE9 [APP/PS1]) mice underwent 3 ¹¹C-UCB-J PET measurements: at baseline, after treatment, and during drug washout. After baseline measurements, saracatinib, a Fyn kinase inhibitor currently in clinical development for AD treatment, was administered by oral gavage for 41 ± 11 d. Treatment-phase measurements were performed on the last day of treatment, and washout-phase measurements occurred more than 27 d after the end of treatment. SUVs from 30 to 60 min after injection of ¹¹C-UCB-J were calculated and normalized by the whole-brain (WB) or brain stem (BS) average values as SUV ratio (SUVR_(WB) or SUVR-1_(BS)). Results: Hippocampal SUVR_(WB) at baseline was significantly lower in APP/PS1 than WT mice (APP/PS1: 1.11 ± 0.04, WT: 1.15 ± 0.02, P = 0.033, unpaired t test). Using SUVR-1_(BS) in the hippocampus, there was also a significant difference at baseline (APP/PS1: 0.48 ± 0.13, WT: 0.65 ± 0.10, P = 0.017, unpaired t test). After treatment with saracatinib, hippocampal SUVR_(WB) in APP/PS1 mice was significantly increased (P = 0.037, paired t test). A trend-level treatment effect was seen with hippocampal SUVR-1_(BS). Saracatinib treatment effects may persist, as there were no significant differences between WT and APP/PS1 mice after drug washout. Conclusion: On the basis of the ¹¹C-UCB-J PET results, hippocampal synaptic density was lower in APP/PS1 mice than in WT mice at baseline, and this deficit was normalized by treatment with saracatinib. These results support the use of ¹¹C-UCB-J PET to identify disease-specific synaptic deficits and to monitor treatment effects in AD.

Rescue of Transgenic Alzheimer's Pathophysiology by Polymeric Cellular Prion Protein Antagonists

Cellular prion protein (PrPC) binds the scrapie conformation of PrP (PrPSc) and oligomeric β-amyloid peptide (Aβo) to mediate transmissible spongiform encephalopathy (TSE) and Alzheimer's disease (AD), respectively. We conducted cellular and biochemical screens for compounds blocking PrPC interaction with Aβo. A polymeric degradant of an antibiotic targets Aβo binding sites on PrPC with low nanomolar affinity and prevents Aβo-induced pathophysiology. We then identified a range of negatively charged polymers with specific PrPC affinity in the low to sub-nanomolar range, from both biological (melanin) and synthetic (poly [4-styrenesulfonic acid-co-maleic acid], PSCMA) origin. Association of PSCMA with PrPC prevents Aβo/PrPC-hydrogel formation, blocks Aβo binding to neurons, and abrogates PrPSc production by ScN2a cells. We show that oral PSCMA yields effective brain concentrations and rescues APPswe/PS1ΔE9 transgenic mice from AD-related synapse loss and memory deficits. Thus, an orally active PrPC-directed polymeric agent provides a potential therapeutic approach to address neurodegeneration in AD and TSE.

PTK2B/Pyk2 overexpression improves a mouse model of Alzheimer's disease

Pyk2 is a Ca²⁺-activated non-receptor tyrosine kinase enriched in forebrain neurons and involved in synaptic regulation. Human genetic studies associated PTK2B, the gene coding Pyk2, with risk for Alzheimer's disease (AD). We previously showed that Pyk2 is important for hippocampal function, plasticity, and spine structure. However, its potential role in AD is unknown. To address this question we used human brain samples and 5XFAD mice, an amyloid mouse model of AD expressing mutated human amyloid precursor protein and presenilin1. In the hippocampus of 5XFAD mice and in human AD patients' cortex and hippocampus, Pyk2 total levels were normal. However, Pyk2 Tyr-402 phosphorylation levels, reflecting its autophosphorylation-dependent activity, were reduced in 5XFAD mice at 8 months of age but not 3 months. We crossed these mice with Pyk2^-/- mice to generate 5XFAD animals devoid of Pyk2. At 8 months the phenotype of 5XFAD x Pyk2^-/- double mutant mice was not different from that of 5XFAD. In contrast, overexpression of Pyk2 in the hippocampus of 5XFAD mice, using adeno-associated virus, rescued autophosphorylated Pyk2 levels and improved synaptic markers and performance in several behavioral tasks. Both Pyk2^-/- and 5XFAD mice showed an increase of potentially neurotoxic Src cleavage product, which was rescued by Pyk2 overexpression. Manipulating Pyk2 levels had only minor effects on Aβ plaques, which were slightly decreased in hippocampus CA3 region of double mutant mice and increased following overexpression. Our results show that Pyk2 is not essential for the pathogenic effects of human amyloidogenic mutations in the 5XFAD mouse model. However, the slight decrease in plaque number observed in these mice in the absence of Pyk2 and their increase following Pyk2 overexpression suggest a contribution of this kinase in plaque formation. Importantly, a decreased function of Pyk2 was observed in 5XFAD mice, indicated by its decreased autophosphorylation and associated Src alterations. Overcoming this deficit by Pyk2 overexpression improved the behavioral and molecular phenotype of 5XFAD mice. Thus, our results in a mouse model of AD suggest that Pyk2 impairment may play a role in the symptoms of the disease.