Revisiting the critical roles of reactive astrocytes in neurodegeneration.

Astrocytes, an integral component of the central nervous system (CNS), contribute to the maintenance of physiological homeostasis through their roles in synaptic function, K+ buffering, blood-brain barrier (BBB) maintenance, and neuronal metabolism. Reactive astrocytes refer to astrocytes undergoing morphological, molecular and functional remodelling in response to pathological stimuli. The activation and differentiation of astrocytes are implicated in the pathogenesis of multiple neurodegenerative diseases. However, there are still controversies regarding their subset identification, function and nomenclature in neurodegeneration. In this review, we revisit the multidimensional roles of reactive astrocytes in Alzheimer's disease (AD), Parkinson's disease (PD), Huntington's disease (HD), multiple sclerosis (MS) and amyotrophic lateral sclerosis (ALS). Furthermore, we propose a precise linkage between astrocyte subsets and their functions based on single-cell sequencing analyses.

Friend or foe: role of pathological tau in neuronal death.

Neuronal death is one of the most common pathological hallmarks of diverse neurological diseases, which manifest varying degrees of cognitive or motor dysfunction. Neuronal death can be classified into multiple forms with complicated and unique regulatory signaling pathways. Tau is a key microtubule-associated protein that is predominantly expressed in neurons to stabilize microtubules under physiological conditions. In contrast, pathological tau always detaches from microtubules and is implicated in a series of neurological disorders that are characterized by irreversible neuronal death, such as necrosis, apoptosis, necroptosis, pyroptosis, ferroptosis, autophagy-dependent neuronal death and phagocytosis by microglia. However, recent studies have also revealed that pathological tau can facilitate neuron escape from acute apoptosis, delay necroptosis through its action on granulovacuolar degeneration bodies (GVBs), and facilitate iron export from neurons to block ferroptosis. In this review, we briefly describe the current understanding of how pathological tau exerts dual effects on neuronal death by acting as a double-edged sword in different neurological diseases. We propose that elucidating the mechanism by which pathological tau affects neuronal death is critical for exploring novel and precise therapeutic strategies for neurological disorders.

In vivo imaging of astrocytes in the whole brain with engineered AAVs and diffusion-weighted magnetic resonance imaging.

Astrocytes constitute a major part of the central nervous system and the delineation of their activity patterns is conducive to a better understanding of brain network dynamics. This study aimed to develop a magnetic resonance imaging (MRI)-based method in order to monitor the brain-wide or region-specific astrocytes in live animals. Adeno-associated virus (AAVs) vectors carrying the human glial fibrillary acidic protein (GFAP) promoter driving the EGFP-AQP1 (Aquaporin-1, an MRI reporter) fusion gene were employed. The following steps were included: constructing recombinant AAV vectors for astrocyte-specific expression, detecting MRI reporters in cell culture, brain regions, or whole brain following cell transduction, stereotactic injection, or tail vein injection. The astrocytes were detected by both fluorescent imaging and Diffusion-weighted MRI. The novel AAV mutation (Site-directed mutagenesis of surface-exposed tyrosine (Y) residues on the AAV5 capsid) significantly increased fluorescence intensity (p < 0.01) compared with the AAV5 wild type. Transduction of the rAAV2/5 carrying AQP1 induced the titer-dependent changes in MRI contrast in cell cultures (p < 0.05) and caudate-putamen (CPu) in the brain (p < 0.05). Furthermore, the MRI revealed a good brain-wide alignment between AQP1 levels and ADC signals, which increased over time in most of the transduced brain regions. In addition, the rAAV2/PHP.eB serotype efficiently introduced AOP1 expression in the whole brain via tail vein injection. This study provides an MRI-based approach to detect dynamic changes in astrocytes in live animals. The novel in vivo tool could help us to understand the complexity of neuronal and glial networks in different pathophysiological conditions.

Social isolation reinforces aging-related behavioral inflexibility by promoting neuronal necroptosis in basolateral amygdala.

Aging is characterized with a progressive decline in many cognitive functions, including behavioral flexibility, an important ability to respond appropriately to changing environmental contingencies. However, the underlying mechanisms of impaired behavioral flexibility in aging are not clear. In this study, we reported that necroptosis-induced reduction of neuronal activity in the basolateral amygdala (BLA) plays an important role in behavioral inflexibility in 5-month-old mice of the senescence-accelerated mice prone-8 (SAMP8) line, a well-established model with age-related phenotypes. Application of Nec-1s, a specific inhibitor of necroptosis, reversed the impairment of behavioral flexibility in SAMP8 mice. We further observed that the loss of glycogen synthase kinase 3α (GSK-3α) was strongly correlated with necroptosis in the BLA of aged mice and the amygdala of aged cynomolgus monkeys (Macaca fascicularis). Moreover, genetic deletion or knockdown of GSK-3α led to the activation of necroptosis and impaired behavioral flexibility in wild-type mice, while the restoration of GSK-3α expression in the BLA arrested necroptosis and behavioral inflexibility in aged mice. We further observed that GSK-3α loss resulted in the activation of mTORC1 signaling to promote RIPK3-dependent necroptosis. Importantly, we discovered that social isolation, a prevalent phenomenon in aged people, facilitated necroptosis and behavioral inflexibility in 4-month-old SAMP8 mice. Overall, our study not only revealed the molecular mechanisms of the dysfunction of behavioral flexibility in aged people but also identified a critical lifestyle risk factor and a possible intervention strategy.

NEXMIF/KIDLIA Knock-out Mouse Demonstrates Autism-Like Behaviors, Memory Deficits, and Impairments in Synapse Formation and Function.

Autism spectrum disorder (ASD) is a heterogeneous neurodevelopmental disability that demonstrates impaired social interactions, communication deficits, and restrictive and repetitive behaviors. ASD has a strong genetic basis and many ASD-associated genes have been discovered thus far. Our previous work has shown that loss of expression of the X-linked gene NEXMIF/KIDLIA is implicated in patients with autistic features and intellectual disability (ID). To further determine the causal role of the gene in the disorder, and to understand the cellular and molecular mechanisms underlying the pathology, we have generated a NEXMIF knock-out (KO) mouse. We find that male NEXMIF KO mice demonstrate reduced sociability and communication, elevated repetitive grooming behavior, and deficits in learning and memory. Loss of NEXMIF/KIDLIA expression results in a significant decrease in synapse density and synaptic protein expression. Consistently, male KO animals show aberrant synaptic function as measured by excitatory miniatures and postsynaptic currents in the hippocampus. These findings indicate that NEXMIF KO mice recapitulate the phenotypes of the human disorder. The NEXMIF KO mouse model will be a valuable tool for studying the complex mechanisms involved in ASD and for the development of novel therapeutics for this disorder.SIGNIFICANCE STATEMENT Autism spectrum disorder (ASD) is a heterogeneous neurodevelopmental disorder characterized by behavioral phenotypes. Based on our previous work, which indicated the loss of NEXMIF/KIDLIA was associated with ASD, we generated NEXMIF knock-out (KO) mice. The NEXMIF KO mice demonstrate autism-like behaviors including deficits in social interaction, increased repetitive self-grooming, and impairments in communication and in learning and memory. The KO neurons show reduced synapse density and a suppression in synaptic transmission, indicating a role for NEXMIF in regulating synapse development and function. The NEXMIF KO mouse faithfully recapitulates the human disorder, and thus serves as an animal model for future investigation of the NEXMIF-dependent neurodevelopmental disorders.

Identification of the downstream molecules of agrin/Dok-7 signaling in muscle.

The development of the neuromuscular junction depends on signaling processes that involve protein phosphorylation. Motor neuron releases agrin to activate muscle protein Dok-7, a key tyrosine kinase essential for the formation of a mature and functional neuromuscular junction. However, the signaling cascade downstream of Dok-7 remains poorly understood. In this study, we combined the clustered regularly interspaced short palindromic repeats/Cas9 technique and quantitative phosphoproteomics analysis to study the tyrosine phosphorylation events triggered by agrin/Dok-7. We found tyrosine phosphorylation level of 36 proteins increased specifically by agrin stimulation. In Dok-7 mutant myotubes, however, 13 of the 36 proteins failed to be enhanced by agrin stimulation, suggesting that these 13 proteins are Dok-7-dependent tyrosine-phosphorylated proteins, could work as downstream molecules of agrin/Dok-7 signaling. We validated one of the proteins, Anxa3, by in vitro and in vivo assays. Knocking down of Anxa3 in the cultured myotubes inhibited agrin-induced AChR clustering, whereas reduction of Anxa3 in mouse muscles induced abnormal postsynaptic development. Collectively, our phosphoproteomics analysis provides novel insights into the complicated signaling network downstream of agrin/Dok-7.

Correcting abnormalities in miR-124/PTPN1 signaling rescues tau pathology in Alzheimer's disease.

MicroRNAs have been implicated in diverse physiological and pathological processes. We previously reported that aberrant microRNA-124 (miR-124)/non-receptor-type protein phosphatase 1 (PTPN1) signaling plays an important role in the synaptic disorders associated with Alzheimer's disease (AD). In this study, we further investigated the potential role of miR-124/PTPN1 in the tau pathology of AD. We first treated the mice with intra-hippocampal stereotactic injections. Then, we used quantitative real-time reverse transcription PCR (qRT-PCR) to detect the expression of microRNAs. Western blotting was used to measure the level of PTPN1, the level of tau protein, the phosphorylation of tau at AD-related sites, and alterations in the activity of glycogen synthase kinase 3ß (GSK-3ß) and protein phosphatase 2 (PP2A). Immunohistochemistry was also used to detect changes in tau phosphorylation levels at AD-related sites and somadendritic aggregation. Soluble and insoluble tau protein was separated by 70% formic acid (FA) extraction to examine tau solubility. Finally, behavioral experiments (including the Morris water maze, fear conditioning, and elevated plus maze) were performed to examine learning and memory ability and emotion-related behavior. We found that artificially replicating the abnormalities in miR-124/PTPN1 signaling induced AD-like tau pathology in the hippocampus of wild-type mice, including hyperphosphorylation at multiple sites, insolubility and somadendritic aggregation, as well as learning/memory deficits. We also found that disruption of miR-124/PTPN1 signaling was caused by the loss of RE1-silencing transcription factor protein, which can be initiated by Aß insults or oxidative stress, as observed in the brains of P301S mice. Correcting the deregulation of miR-124/PTPN1 signaling rescued the tau pathology and learning/memory impairments in the P301S mice. We also found that miR-124/PTPN1 abnormalities induced activation of glycogen synthase kinase 3 (GSK-3) and inactivation of protein phosphatase 2A (PP2A) by promoting tyrosine phosphorylation, implicating an imbalance in tau kinase/phosphatase. Thus, targeting the miR-124/PTPN1 signaling pathway is a promising therapeutic strategy for AD.

miR-214-3p Targets ß-Catenin to Regulate Depressive-like Behaviors Induced by Chronic Social Defeat Stress in Mice.

ß-Catenin has been implicated in major depressive disorder (MDD), which is associated with synaptic plasticity and dendritic arborization. MicroRNAs (miRNA) are small noncoding RNAs containing about 22 nucleotides and involved in a variety of physiological and pathophysiological process, but their roles in MDD remain largely unknown. Here, we investigated the expression and function of miRNAs in the mouse model of chronic social defeat stress (CSDS). The regulation of ß-catenin by selected miRNA was validated by silico prediction, target gene luciferase reporter assay, and transfection experiment in neurons. We demonstrated that the levels of miR-214-3p, which targets ß-catenin transcripts were significantly increased in the medial prefrontal cortex (mPFC) of CSDS mice. Antagomir-214-3p, a neutralizing inhibitor of miR-214-3p, increased the levels of ß-catenin and reversed the depressive-like behavior in CSDS mice. Meanwhile, antagomir-214-3p increased the amplitude of miniature excitatory postsynaptic current (mEPSC) and the number of dendritic spines in mPFC of CSDS mice, which may be related to the elevated expression of cldn1. Furthermore, intranasal administered antagomir-214-3p also significantly increased the level of ß-catenin and reversed the depressive-like behaviors in CSDS mice. These results may represent a new therapeutic target for MDD.

Targeting the HDAC2/HNF-4A/miR-101b/AMPK Pathway Rescues Tauopathy and Dendritic Abnormalities in Alzheimer's Disease.

Histone deacetylase 2 (HDAC2) plays a major role in the epigenetic regulation of gene expression. Previous studies have shown that HDAC2 expression is strongly increased in Alzheimer's disease (AD), a major neurodegenerative disorder and the most common form of dementia. Moreover, previous studies have linked HDAC2 to Aß overproduction in AD; however, its involvement in tau pathology and other memory-related functions remains unclear. Here, we show that increased HDAC2 levels strongly correlate with phosphorylated tau in a mouse model of AD. HDAC2 overexpression induced AD-like tau hyperphosphorylation and aggregation, which were accompanied by a loss of dendritic complexity and spine density. The ectopic expression of HDAC2 resulted in the deacetylation of the hepatocyte nuclear factor 4α (HNF-4A) transcription factor, which disrupted its binding to the miR-101b promoter. The suppression of miR-101b caused an upregulation of its target, AMP-activated protein kinase (AMPK). The introduction of miR-101b mimics or small interfering RNAs (siRNAs) against AMPK blocked HDAC2-induced tauopathy and dendritic impairments in vitro. Correspondingly, miR-101b mimics or AMPK siRNAs rescued tau pathology, dendritic abnormalities, and memory deficits in AD mice. Taken together, the current findings implicate the HDAC2/miR-101/AMPK pathway as a critical mediator of AD pathogenesis. These studies also highlight the importance of epigenetics in AD and provide novel therapeutic targets.

Selective Degeneration of Entorhinal-CA1 Synapses in Alzheimer's Disease via Activation of DAPK1.

Excitatory pyramidal neurons in the entorhinal cortical layer II region (ECIIPN) form functional excitatory synapses with CA1 parvalbumin inhibitory neurons (CA1PV) and undergo selective degeneration in the early stages of Alzheimer's disease (AD). Here, we show that death-associated protein kinase 1 (DAPK1) is selectively activated in ECIIPN of AD mice. Inhibition of DAPK1 by deleting a catalytic domain or a death domain of DAPK1 rescues the ECIIPN-CA1PV synaptic loss and improves spatial learning and memory in AD mice. This study demonstrates that activation of DAPK1 in ECIIPN contributes to a memory loss in AD and hence warrants a promising target for the treatment of AD. SIGNIFICANCE STATEMENT: Our recent study reported that excitatory pyramidal neurons in the entorhinal cortical layer II region (ECIIPN) target to CA1 parvalbumin-type inhibitory neurons (CA1PV) at a direct pathway and are one of the most vulnerable brain cells that are selectively degenerated in the early stage of Alzheimer's disease (AD). Our present study shows that death-associated protein kinase 1 (DAPK1) is selectively activated in ECIIPN of AD mice. Inhibition of DAPK1 by deleting a catalytic domain or a death domain of DAPK1 rescues the ECIIPN-CA1PV synaptic loss and improves spatial learning and memory in the early stage of AD. These data not only demonstrate a crucial molecular event for synaptic degeneration but also provide a therapeutic target for the treatment of AD.

A Novel Mechanism of Spine Damages in Stroke via DAPK1 and Tau.

Synaptic spine loss is one of the major preceding consequences of stroke damages, but its underlying molecular mechanisms remain unknown. Here, we report that a direct interaction of DAPK1 with Tau causes spine loss and subsequently neuronal death in a mouse model with stroke. We found that DAPK1 phosphorylates Tau protein at Ser262 (pS(262)) in cortical neurons of stroke mice. Either genetic deletion of DAPK1 kinase domain (KD) in mice (DAPK1-KD(-/-)) or blocking DAPK1-Tau interaction by systematic application of a membrane permeable peptide protects spine damages and improves neurological functions against stroke insults. Thus, disruption of DAPK1-Tau interaction is a promising strategy in clinical management of stroke.

Hsp90 chaperone inhibitor 17-AAG attenuates Aß-induced synaptic toxicity and memory impairment.

The excessive accumulation of soluble amyloid peptides (Aß) plays a crucial role in the pathogenesis of Alzheimer's disease (AD), particularly in synaptic dysfunction. The role of the two major chaperone proteins, Hsp70 and Hsp90, in clearing misfolded protein aggregates has been established. Despite their abundant presence in synapses, the role of these chaperones in synapses remains elusive. Here, we report that Hsp90 inhibition by 17-AAG elicited not only a heat shock-like response but also upregulated presynaptic and postsynaptic proteins, such as synapsin I, synaptophysin, and PSD95 in neurons. 17-AAG treatment enhanced high-frequency stimulation-evoked LTP and protected neurons from synaptic damage induced by soluble Aß. In AD transgenic mice, the daily administration of 17-AAG over 7 d resulted in a marked increase in PSD95 expression in hippocampi. 17-AAG treatments in wild-type C57BL/6 mice challenged by soluble Aß significantly improved contextual fear memory. Further, we demonstrate that 17-AAG activated synaptic protein expression via transcriptional mechanisms through the heat shock transcription factor HSF1. Together, our findings identify a novel function of Hsp90 inhibition in regulating synaptic plasticity, in addition to the known neuroprotective effects of the chaperones against Aß and tau toxicity, thus further supporting the potential of Hsp90 inhibitors in treating neurodegenerative diseases.

DAPK1-p53 interaction converges necrotic and apoptotic pathways of ischemic neuronal death.

Necrosis and apoptosis are two distinct types of mechanisms that mediate ischemic injury. But a signaling point of convergence between them has yet to be identified. Here, we show that activated death-associated protein kinase 1 (DAPK1), phosphorylates p53 at serine-23 (pS(23)) via a direct binding of DAPK1 death domain (DAPK1DD) to the DNA binding motif of p53 (p53DM). We uncover that the pS(23) acts as a functional version of p53 and mediates necrotic and apoptotic neuronal death; in the nucleus, pS(23) induces the expression of proapoptotic genes, such as Bax, whereas in the mitochondrial matrix, pS(23) triggers necrosis via interaction with cyclophilin D (CypD) in cultured cortical neurons from mice. Deletion of DAPK1DD (DAPK1(DDΔ)) or application of Tat-p53DM that interrupts DAPK1-p53 interaction blocks these dual pathways of pS(23) actions in mouse cortical neurons. Thus, the DAPK1-p53 interaction is a signaling point of convergence of necrotic and apoptotic pathways and is a desirable target for the treatment of ischemic insults.

Acid-sensing ion channels promote the inflammation and migration of cultured rat microglia.

Microglia, the major immune cells in central nervous system, act as the surveillance and scavenger of immune defense and inflammatory response. Previous studies suggest that there might be close relationship between acid-sensing ion channels (ASICs) and inflammation, however, the exact role of ASICs in microglia during inflammation remains elusive. In the present study, we identified the existence of ASICs in the primary cultured rat microglia and explored their functions. By using reverse transcriptase polymerase chain reaction (RT-PCR), quantitative real-time PCR (qPCR), western blotting, and immunofluorescence experiments, we demonstrated that ASIC1, ASIC2a, and ASIC3 were existed in cultured and in situ rat microglia. After lipopolysaccharide (LPS) stimulation, the expressions of microglial ASIC1 and ASIC2a were upregulated. Meanwhile, ASIC-like currents and acid-induced elevation of intracellular calcium were increased, which could be inhibited by the nonspecific ASICs antagonist amiloride and specific homomeric ASIC1a blocker PcTx1. In addition, both inhibitors reduced the expression of inflammatory cytokines, including inducible nitric oxide synthase and cyclooxygenase 2 stimulated by LPS. Furthermore, we also observed significant increase in the expression of ASIC1 and ASIC2a in scrape-stimulated microglial migration. Amiloride and PcTx1 prevented the migration by inhibiting ERK phosphorylation. Taken together, these results suggest that ASICs participate in neuroinflammatory response, which will provide a novel therapeutic strategy for controlling the inflammation-relevant neuronal diseases.

EPAC inhibition of SUR1 receptor increases glutamate release and seizure vulnerability.

EPAC (Exchange Proteins Activated by cAMP) regulates glutamate transmitter release in the central neurons, but a role underlying this regulation has yet to be identified. Here we show that EPAC binds directly to the intracellular loop of an ATP-sensitive potassium (KATP) channel type-1 sulfonylurea receptor (SUR1) receptor consisting of amino acids 859-881 (SUR1(859-881)). Ablation of EPAC or expression of SUR1(859-881), which intercepts EPAC-SUR1 binding, increases the open probability of KATP channels consisting of the Kir6.1 subunit and SUR1. Opening of KATP channels inhibits glutamate release and reduces seizure vulnerability in adult mice. Therefore, EPAC interaction with SUR1 controls seizure susceptibility and possibly acts via regulation of glutamate release.

The mechanisms of mitochondrial abnormalities that contribute to sleep disorders and related neurodegenerative diseases.

Sleep is a highly intricate biological phenomenon, and its disorders play a pivotal role in numerous diseases. However, the specific regulatory mechanisms remain elusive. In recent years, the role of mitochondria in sleep disorders has gained considerable attention. Sleep deprivation not only impairs mitochondrial morphology but also decreases the number of mitochondria and triggers mitochondrial dysfunction. Furthermore, mitochondrial dysfunction has been implicated in the onset and progression of various sleep disorder-related neurological diseases, especially neurodegenerative conditions. Therefore, a greater understanding of the impact of sleep disorders on mitochondrial dysfunction may reveal new therapeutic targets for neurodegenerative diseases. In this review, we comprehensively summarize the recent key findings on the mechanisms underlying mitochondrial dysfunction caused by sleep disorders and their role in initiating or exacerbating common neurodegenerative diseases. In addition, we provide fresh insights into the diagnosis and treatment of sleep disorder-related diseases.

Sexually dimorphic phenotypes and the role of androgen receptors in UBE3A-dependent autism spectrum disorder.

Autism spectrum disorders (ASDs) are characterized by social, communication, and behavioral challenges. UBE3A is one of the most common ASD genes. ASDs display a remarkable sex difference with a 4:1 male to female prevalence ratio; however, the underlying mechanism remains largely unknown. Using the UBE3A-overexpressing mouse model for ASD, we studied sex differences at behavioral, genetic, and molecular levels. We found that male mice with extra copies of Ube3A exhibited greater impairments in social interaction, repetitive self-grooming behavior, memory, and pain sensitivity, whereas female mice with UBE3A overexpression displayed greater olfactory defects. Social communication was impaired in both sexes, with males making more calls and females preferring complex syllables. At the molecular level, androgen receptor (AR) levels were reduced in both sexes due to enhanced degradation mediated by UBE3A. However, AR reduction significantly dysregulated AR target genes only in male, not female, UBE3A-overexpressing mice. Importantly, restoring AR levels in the brain effectively normalized the expression of AR target genes, and rescued the deficits in social preference, grooming behavior, and memory in male UBE3A-overexpressing mice, without affecting females. These findings suggest that AR and its signaling cascade play an essential role in mediating the sexually dimorphic changes in UBE3A-dependent ASD.

Friend or foe: Lactate in neurodegenerative diseases.

Lactate, a byproduct of glycolysis, was considered as a metabolic waste until identified by studies on the Warburg effect. Increasing evidence elucidates that lactate functions as energy fuel, signaling molecule, and donor for protein lactylation. Altered lactate utilization is a common metabolic feature of the onset and progression of neurodegenerative diseases, such as Alzheimer's disease, multiple sclerosis, amyotrophic lateral sclerosis, Parkinson's disease and Huntington's disease. This review offers an overview of lactate metabolism from the perspective of production, transportation and clearance, and the role of lactate in neurodegenerative progression, as well as a summary of protein lactylation and the signaling function of lactate in neurodegenerative diseases. Besides, this review delves into the dual roles of changed lactate metabolism during neurodegeneration and explores prospective therapeutic methods targeting lactate. We propose that elucidating the correlation between lactate and neurodegeneration is pivotal for exploring innovative therapeutic interventions for neurodegenerative diseases.

Deregulation of the Glymphatic System in Alzheimer's Disease: Genetic and Non-Genetic Factors.

Alzheimer's disease (AD) is the most prevalent form of dementia and is characterized by progressive degeneration of brain function. AD gradually affects the parts of the brain that control thoughts, language, behavior and mental function, severely impacting a person's ability to carry out daily activities and ultimately leading to death. The accumulation of extracellular amyloid-ß peptide (Aß) and the aggregation of intracellular hyperphosphorylated tau are the two key pathological hallmarks of AD. AD is a complex condition that involves both non-genetic risk factors (35%) and genetic risk factors (58-79%). The glymphatic system plays an essential role in clearing metabolic waste, transporting tissue fluid, and participating in the immune response. Both non-genetic and genetic risk factors affect the glymphatic system to varying degrees. The main purpose of this review is to summarize the underlying mechanisms involved in the deregulation of the glymphatic system during the progression of AD, especially concerning the diverse contributions of non-genetic and genetic risk factors. In the future, new targets and interventions that modulate these interrelated mechanisms will be beneficial for the prevention and treatment of AD.

Neuroprotective effect of the traditional decoction Tian-Si-Yin against Alzheimer's disease via suppression of neuroinflammation.

ETHNOPHARMACOLOGICAL RELEVANCE: Alzheimer's disease (AD) is the most prevalent neurodegenerative disease among old adults. As a traditional Chinese medicine, the herbal decoction Tian-Si-Yin consists of Morinda officinalis How. and Cuscuta chinensis Lam., which has been widely used to nourish kidney. Interestingly, Tian-Si-Yin has also been used to treat dementia, depression and other neurological conditions. However, its therapeutic potential for neurodegenerative diseases such as AD and the underlying mechanisms remain unclear. AIM OF THE STUDY: To evaluate the therapeutic effect of the herbal formula Tian-Si-Yin against AD and to explore the underlying mechanisms. MATERIALS AND METHODS: The N2a cells treated with amyloid ß (Aß) peptide or overexpressing amyloid precursor protein (APP) were used to establish cellular models of AD. The in vivo anti-AD effects were evaluated by using Caenorhabditis elegans and 3 × Tg-AD mouse models. Tian-Si-Yin was orally administered to the mice for 8 weeks at a dose of 10, 15 or 20 mg/kg/day, respectively. Its protective role on memory deficits of mice was examined using the Morris water maze and fear conditioning tests. Network pharmacology, proteomic analysis and ultra-high performance liquid chromatography-mass spectrometry/mass spectrometry (UHPLC-MS/MS) were used to explore the underlying molecular mechanisms, which were further investigated by Western blotting and immunohistochemistry. RESULTS: Tian-Si-Yin was shown to improve cell viability of Aß-treated N2a cells and APP-expressing N2a-APP cells. Tian-Si-Yin was also found to reduce ROS level and extend lifespan of transgenic AD-like C. elegans model. Oral administration of Tian-Si-Yin at medium dose was able to effectively rescue memory impairment in 3 × Tg mice. Tian-Si-Yin was further shown to suppress neuroinflammation by inhibition of glia cell activation and downregulation of inflammatory cytokines, diminishing tau phosphoralytion and Aß deposition in the mice. Using UHPLC-MS/MS and network pharmacology technologies, 17 phytochemicals from 68 components of Tian-Si-Yin were identified as potential anti-AD components. MAPK1, BRAF, TTR and Fyn were identified as anti-AD targets of Tian-Si-Yin from network pharmacology and mass spectrum. CONCLUSIONS: This study has established the protective effect of Tian-Si-Yin against AD and demonstrates that Tian-Si-Yin is capable of improving Aß level, tau pathology and synaptic disorder by regulating inflammatory response.