How brain 'cleaners' fail: Mechanisms and therapeutic value of microglial phagocytosis in Alzheimer's disease.

Microglia are the resident phagocytes of the brain, where they primarily function in the clearance of dead cells and the removal of un- or misfolded proteins. The impaired activity of receptors or proteins involved in phagocytosis can result in enhanced inflammation and neurodegeneration. RNA-seq and genome-wide association studies have linked multiple phagocytosis-related genes to neurodegenerative diseases, while the knockout of such genes has been demonstrated to exert protective effects against neurodegeneration in animal models. The failure of microglial phagocytosis influences AD-linked pathologies, including amyloid ß accumulation, tau propagation, neuroinflammation, and infection. However, a precise understanding of microglia-mediated phagocytosis in Alzheimer's disease (AD) is still lacking. In this review, we summarize current knowledge of the molecular mechanisms involved in microglial phagocytosis in AD across a wide range of pre-clinical, post-mortem, ex vivo, and clinical studies and review the current limitations regarding the detection of microglia phagocytosis in AD. Finally, we discuss the rationale of targeting microglial phagocytosis as a therapeutic strategy for preventing AD or slowing its progression.

The MYB family and their response to abiotic stress in ginger (Zingiber officinale Roscoe).

BACKGROUND: Zingiber officinale Roscoe, colloquially known as ginger, is a crop of significant medicinal and culinary value that frequently encounters adversity stemming from inhospitable environmental conditions. The MYB transcription factors have garnered recognition for their pivotal role in orchestrating a multitude of plant biological pathways. Nevertheless, the enumeration and characterization of the MYBs within Z. officinale Roscoe remains unknown. This study embarks on a genome-wide scrutiny of the MYB gene lineage in ginger, with the aim of cataloging all ZoMYB genes implicated in the biosynthesis of gingerols and curcuminoids, and elucidating their potential regulatory mechanisms in counteracting abiotic stress, thereby influencing ginger growth and development. RESULTS: In this study, we identified an MYB gene family comprising 231 members in ginger genome. This ensemble comprises 74 singular-repeat MYBs (1R-MYB), 156 double-repeat MYBs (R2R3-MYB), and a solitary triple-repeat MYB (R1R2R3-MYB). Moreover, a comprehensive analysis encompassing the sequence features, conserved protein motifs, phylogenetic relationships, chromosome location, and gene duplication events of the ZoMYBs was conducted. We classified ZoMYBs into 37 groups, congruent with the number of conserved domains and gene structure analysis. Additionally, the expression profiles of ZoMYBs during development and under various stresses, including ABA, cold, drought, heat, and salt, were investigated in ginger utilizing both RNA-seq data and qRT-PCR analysis. CONCLUSION: This work provides a comprehensive understanding of the MYB family in ginger and lays the foundation for the future investigation of the potential functions of ZoMYB genes in ginger growth, development and abiotic stress tolerance of ginger.

SIRT1 in the BNST modulates chronic stress-induced anxiety of male mice via FKBP5 and corticotropin-releasing factor signaling.

Although clinical reports have highlighted association of the deacetylase sirtuin 1 (SIRT1) gene with anxiety, its exact role in the pathogenesis of anxiety disorders remains unclear. The present study was designed to explore whether and how SIRT1 in the mouse bed nucleus of the stria terminalis (BNST), a key limbic hub region, regulates anxiety. In a chronic stress model to induce anxiety in male mice, we used site- and cell-type-specific in vivo and in vitro manipulations, protein analysis, electrophysiological and behavioral analysis, in vivo MiniScope calcium imaging and mass spectroscopy, to characterize possible mechanism underlying a novel anxiolytic role for SIRT1 in the BNST. Specifically, decreased SIRT1 in parallel with increased corticotropin-releasing factor (CRF) expression was found in the BNST of anxiety model mice, whereas pharmacological activation or local overexpression of SIRT1 in the BNST reversed chronic stress-induced anxiety-like behaviors, downregulated CRF upregulation, and normalized CRF neuronal hyperactivity. Mechanistically, SIRT1 enhanced glucocorticoid receptor (GR)-mediated CRF transcriptional repression through directly interacting with and deacetylating the GR co-chaperone FKBP5 to induce its dissociation from the GR, ultimately downregulating CRF. Together, this study unravels an important cellular and molecular mechanism highlighting an anxiolytic role for SIRT1 in the mouse BNST, which may open up new therapeutic avenues for treating stress-related anxiety disorders.

HBB contributes to individualized aconitine-induced cardiotoxicity in mice via interfering with ABHD5/AMPK/HDAC4 axis.

The root of Aconitum carmichaelii Debx. (Fuzi) is an herbal medicine used in China that exerts significant efficacy in rescuing patients from severe diseases. A key toxic compound in Fuzi, aconitine (AC), could trigger unpredictable cardiotoxicities with high-individualization, thus hinders safe application of Fuzi. In this study we investigated the individual differences of AC-induced cardiotoxicities, the biomarkers and underlying mechanisms. Diversity Outbred (DO) mice were used as a genetically heterogeneous model for mimicking individualization clinically. The mice were orally administered AC (0.3, 0.6, 0.9 mg· kg-1 ·d-1) for 7 d. We found that AC-triggered cardiotoxicities in DO mice shared similar characteristics to those observed in clinic patients. Most importantly, significant individual differences were found in DO mice (variation coefficients: 34.08%-53.17%). RNA-sequencing in AC-tolerant and AC-sensitive mice revealed that hemoglobin subunit beta (HBB), a toxic-responsive protein in blood with 89% homology to human, was specifically enriched in AC-sensitive mice. Moreover, we found that HBB overexpression could significantly exacerbate AC-induced cardiotoxicity while HBB knockdown markedly attenuated cell death of cardiomyocytes. We revealed that AC could trigger hemolysis, and specifically bind to HBB in cell-free hemoglobin (cf-Hb), which could excessively promote NO scavenge and decrease cardioprotective S-nitrosylation. Meanwhile, AC bound to HBB enhanced the binding of HBB to ABHD5 and AMPK, which correspondingly decreased HDAC-NT generation and led to cardiomyocytes death. This study not only demonstrates HBB achievement a novel target of AC in blood, but provides the first clue for HBB as a novel biomarker in determining the individual differences of Fuzi-triggered cardiotoxicity.

Discovery of Novel Diphenyl Acrylonitrile Derivatives That Promote Adult Rats' Hippocampal Neurogenesis.

We previously discovered WS-6 as a new antidepressant in correlation to its function of stimulating neurogenesis. Herein, several different scaffolds (stilbene, 1,3-diphenyl 1-propene, 1,3-diphenyl 2-propene, 1,2-diphenyl acrylo-1-nitrile, 1,2-diphenyl acrylo-2-nitrile, 1,3-diphenyl trimethylamine), further varied through substitutions of twelve amide substituents plus the addition of a methylene unit and an inverted amide, were examined to elucidate the SARs for promoting adult rat neurogenesis. Most of the compounds could stimulate proliferation of progenitors, but just a few chemicals possessing a specific structural profile, exemplified by diphenyl acrylonitrile 29b, 32a, and 32b, showed better activity than the clinical drug NSI-189 in promoting newborn cells differentiation into mature neurons. The most potent diphenyl acrylonitrile 32b had an excellent brain AUC to plasma AUC ratio (B/P = 1.6), suggesting its potential for further development as a new lead.

Zinc finger protein 335 mediates lipopolysaccharide-induced neurodegeneration and memory loss as a transcriptional factor in microglia.

Zinc finger protein 335 (Zfp335) is a transcription factor that regulates mammalian neurogenesis and neuronal differentiation. It is a causative factor for severe microcephaly, small somatic size, and neonatal death. Here, we evaluated the effects of Zfp335 in the adult mouse brain after lipopolysaccharide (LPS) challenge. We used wild-type (WT) and Zfp335 knock-down (Zfp335+/- ) mice with LPS administered in the intracerebral ventricle in vivo and cultured microglia treated with LPS in vitro. The impact of Zfp335 was evaluated by RT-PCR, RNA-sequencing, western blotting, immunocytochemistry, ELISA, and the memory behavior tests. Knockdown of Zfp335 expression ameliorated microglia activation significantly, including reduced mRNA and protein expression of Iba1, reduced numbers of microglia, reduced cell diameter, and increased branch length, in the brains of 2-month-old mice after LPS treatment. Zfp335 was expressed in microglia and neurons, but increased in microglia, not neurons, in the brain of mice after LPS administration. LPS-induced microglia-mediated neurodegeneration was dependent upon microglial Zfp335 controlled by nuclear factor-kappa B. Microglial Zfp335 affected neuronal activity through transcriptional regulation of lymphocyte antigen-6M (Ly6M). Our data suggest that Zfp335 is a key transcription factor that exacerbates microglia-mediated neurodegeneration through upregulation of Ly6M expression. Inhibition of microglial Zfp335 may be a new strategy for preventing brain disease induced by microglia activation.

Comparison of haploidentical-allogeneic hematopoietic stem cell transplantation and intensive immunosuppressive therapy for patients with severe aplastic anemia with an absolute neutrophil count of zero: a retrospective study.

A retrospective analysis was conducted based on the clinical data from 60 patients older than 16 years from January 2016 to January 2021. All the patients were newly diagnosed with severe aplastic anemia (SAA) with an absolute neutrophil count (ANC) of zero. We compared the hematological response and survival of haploidentical-allogeneic hematopoietic stem cell transplantation (HID-HSCT) (n = 25) and intensive immunosuppressive therapy (IST) (n = 35) treatments. At six months, the overall response rate and complete response were significantly higher in the HID-HSCT group than those in the IST group (84.0% vs. 40.0%, P = 0.001; 80.0% vs. 17.1%, P = 0.001). With a median follow-up of 18.5 months (4.3~30.8 months), patients in the HID-HSCT group had longer overall survival and event-free survival (80.0% vs. 47.9%, P = 0.0419; 79.2% vs. 33.5%, P = 0.0048). These data suggested that HID-HSCT might be an effective alternative treatment option for adult patients with SAA with an ANC of zero, which requires further validation in an additional prospective study.

Central GLP-1 Resistance Induced by Severe Traumatic Brain Injury Was Associated with Persistent Hyperglycemia in Humans.

INTRODUCTION: Whether central glucagon-like peptide 1 (GLP-1)/GLP-1 receptor system mediated peripheral glucose homeostasis in patients with traumatic brain injury (TBI) is not clear. We aim to determine if plasma GLP-1 level could distinguish the non-survivors from the survivors during the first 14 days after TBI that could prognose 6 months mortality. METHODS: Metabolic, inflammatory, and hematologic profiles were examined in 73 patients with TBI in neurological intensive care unit. Factors that discriminate non-survivors from survivors were determined by two-way ANOVA. Biomarkers associated with mortality were determined by binary logistic regression and Cox proportional hazard regression. RESULTS: The non-survivors had higher infectious SOFA scores (p < 0.001), lower first 3 days' body temperature (p = 0.017), greater chance of cerebral hernia (p = 0.048), and decompressive craniectomy (p = 0.001) than the survivors. Higher 14-day plasma GLP-1 (p < 0.0001), glucose (p = 0.002), and IL-6 (p = 0.005) levels, in contrast with lower insulin level at days 4-7 (p = 0.020) were found in non-survivors than in survivors. Except the survivors who had an increased 14-day platelet number (p < 0.001), the two groups did not differ in hematological profile and intestinal barrier function. Although GLP-1 correlated closely with IL-6 in both the groups, it correlated with neither insulin nor glucose in each group. GLP-1 on days 8-10 and IL-6 on days 1-3 were positively, while insulin on days 4-7 was negatively associated with mortality. CONCLUSION: Persistent higher GLP-1 level in non-survivors over the survivors may present more severe central resistance to endogenous GLP-1 in non-survivors, which may be associated with progressive hyperglycemia with increased mortality in TBI.

Metal Cation-Doped ns-Cucurbit[10]uril: Adsorption of Para-Phenylenediamine.

The separation of phenylenediamine (PDA) isomers is crucial in the field of chemical manufacturing. Herein, we presented a strategy for the separation of PDA isomers (para-phenylenediamine, p-PDA; meta-phenylenediamine, m-PDA; ortho-phenylenediamine, o-PDA) using four supramolecular framework materials of ns-cucurbit[10]uril (ns-Q[10]), (1) ns-Q[10](Cd), (2) ns-Q[10](Mn), (3) ns-Q[10](Cu), (4) ns-Q[10](Pb). Our findings indicated that these supramolecular framework materials of ns-Q[10] showed remarkable selectivity for para-phenylenediamine (p-PDA) in p-PDA, m-PDA, and o-PDA mixtures, respectively. The variations in selectivity observed in these four single-crystal structures arose from variations in the thermodynamic stabilities and binding modes of the host-guest complexes. Importantly, the supramolecular framework based on ns-Q[10] exhibited selective accommodation of p-PDA over its isomers. This study highlighted the practical application of ns-Q[10] in effectively separating PDA isomers and demonstrated the potential utility of ns-Q[10] in isolating other organic molecules.

Red Room-Temperature Phosphorescence Supramolecular Assemblies Based on Cucurbit[7]uril: Reversible Temperature Stimulation Response and Cell-Specific Silver Ion Imaging.

Solid-state materials with efficient room-temperature phosphorescence (RTP) emission have been widely used in materials science, and organic RTP-emitting systems with heavy-metal doping in aqueous solutions have attracted much attention in recent years. A novel supramolecular interaction was induced by host-guest assembly using cucurbit[7]uril (Q[7]) as the host and brominated naphthalimide phosphor as the guest. This interaction was further enhanced through synergistic chelation stimulated by analytical silver ion complexation. This approach facilitated the system's structural rigidity, intersystem crossing, and oxygen shielding. We achieved deep red phosphorescence emission in aqueous solution and ambient conditions along with quantitative determination of silver ions. The new complex exhibited good reversible thermoresponsive behavior and was successfully applied for the first time to target phosphorescence imaging of silver ions in the mitochondria of A549 cancer cells. These results are beneficial for constructing novel RTP systems with stimulus-responsive luminescence in aqueous solution, contributing to future research in bioimaging, detection, optical sensors, and thermometry materials.

Prognostic Significance of Plasma Insulin Level for Deep Venous Thrombosis in Patients with Severe Traumatic Brain Injury in Critical Care.

BACKGROUND: Whether insulin resistance underlies deep venous thrombosis (DVT) development in patients with severe traumatic brain injury (TBI) is unclear. In this study, the association between plasma insulin levels and DVT was analyzed in patients with severe TBI. METHODS: A prospective observational study of 73 patients measured insulin, glucose, glucagon-like peptide 1 (GLP-1), inflammatory factors, and hematological profiles within four preset times during the first 14 days after TBI. Ultrasonic surveillance of DVT was tracked. Two-way analysis of variance was used to determine the factors that discriminated between patients with and without DVT or with and without insulin therapy. Partial correlations of insulin level with all the variables were conducted separately in patients with DVT or patients without DVT. Factors associated with DVT were analyzed by multivariable logistic regression. Neurological outcomes 6 months after TBI were assessed. RESULTS: Among patients with a mean (± standard deviation) age of 53 (± 16 years), DVT developed in 20 patients (27%) on median 10.4 days (range 4-22), with higher Acute Physiology and Chronic Health Evaluation II scores but similar Sequential Organ Failure Assessment scores and TBI severity. Patients with DVT were more likely to receive insulin therapy than patients without DVT (60% vs. 28%; P = 0.012); hence, they had higher 14-day insulin levels. However, insulin levels were comparable between patients with DVT and patients without DVT in the subgroups of patients with insulin therapy (n = 27) and patients without insulin therapy (n = 46). The platelet profile significantly discriminated between patients with and without DVT. Surprisingly, none of the coagulation profiles, blood cell counts, or inflammatory mediators differed between the two groups. Patients with insulin therapy had significantly higher insulin (P = 0.006), glucose (P < 0.001), and GLP-1 (P = 0.01) levels and were more likely to develop DVT (60% vs. 15%; P < 0.001) along with concomitant platelet depletion. Insulin levels correlated with glucose, GLP-1 levels, and platelet count exclusively in patients without DVT. Conversely, in patients with DVT, insulin correlated negatively with GLP-1 levels (P = 0.016). Age (P = 0.01) and elevated insulin levels at days 4-7 (P = 0.04) were independently associated with DVT. Patients with insulin therapy also showed worse Glasgow Outcome Scale scores (P = 0.001). CONCLUSIONS: Elevated insulin levels in the first 14 days after TBI may indicate insulin resistance, which is associated with platelet hyperactivity, and thus increasing the risk of DVT.

A method for ultrafast tissue clearing that preserves fluorescence for multimodal and longitudinal brain imaging.

BACKGROUND: Tissue-clearing techniques have recently been developed to make tissues transparent for three-dimensional (3D) imaging at different scales, including single-cell resolution. However, current tissue-clearing workflows have several disadvantages, including complex protocols, time-consuming application, and fluorescence quenching. Additionally, they can be used mainly for clearing larger-volume samples, preventing wide and easy applicability in conventional experimental approaches. In this study, we aimed to develop a versatile, fast, and convenient method for clearing thin and semi-thick samples, which can be used for three-dimensional imaging of experimental or even clinical samples. RESULTS: We developed an alkaline solution (AKS) containing a combination of 2,2'-thiodiethanol (TDE), DMSO, D-sorbitol, and Tris for tissue clearing, as the alkaline environment is suitable for maintaining the fluorescence of most commonly used fluorescence protein GFP and its variants, and tested its clearing effect on samples from mice and human brains. We assessed the clearing speed, the preservation of fluorescence protein and dyes, and the imaging depth and quality. The results showed that AKS treatment rapidly cleared 300-µm-thick brain slices and 1-mm-thick slices from different organs within 5 min and 1 h, respectively. Moreover, AKS was compatible with a variety of fluorescence proteins and dyes. Most importantly, AKS enhanced the fluorescence of YFP, in contrast to the majority of existing tissue-clearing methods which reduce the fluorescence intensity of fluorescent proteins. Using AKS, we performed long-time high-resolution imaging of weak fluorescent protein-labelled tissues, long-distance fibre tracking, larger-scale 3D imaging and cell counting of the entire brain area, neural circuit tracing, 3D neuromorphic reconstruction, and 3D histopathology imaging. CONCLUSIONS: AKS can be used for simple and rapid clearing of samples from mice and human brains and is widely compatible with a variety of fluorescent dyes. Therefore, AKS has great potential to be used as a broad tissue-clearing reagent for biological optical imaging, especially for time-sensitive experiments.

Appropriate Macronutrients or Mineral Elements Are Beneficial to Improve Depression and Reduce the Risk of Depression.

Depression is a common mental disorder that seriously affects the quality of life and leads to an increasing global suicide rate. Macro, micro, and trace elements are the main components that maintain normal physiological functions of the brain. Depression is manifested in abnormal brain functions, which are considered to be tightly related to the imbalance of elements. Elements associated with depression include glucose, fatty acids, amino acids, and mineral elements such as lithium, zinc, magnesium, copper, iron, and selenium. To explore the relationship between these elements and depression, the main literature in the last decade was mainly searched and summarized on PubMed, Google Scholar, Scopus, Web of Science, and other electronic databases with the keywords "depression, sugar, fat, protein, lithium, zinc, magnesium, copper, iron, and selenium". These elements aggravate or alleviate depression by regulating a series of physiological processes, including the transmission of neural signals, inflammation, oxidative stress, neurogenesis, and synaptic plasticity, which thus affect the expression or activity of physiological components such as neurotransmitters, neurotrophic factors, receptors, cytokines, and ion-binding proteins in the body. For example, excessive fat intake can lead to depression, with possible mechanisms including inflammation, increased oxidative stress, reduced synaptic plasticity, and decreased expression of 5-Hydroxytryptamine (5-HT), Brain Derived Neurotrophic Factor (BDNF), Postsynaptic density protein 95(PSD-95), etc. Supplementing mineral elements, such as selenium, zinc, magnesium, or lithium as a psychotropic medication is mostly used as an auxiliary method to improve depression with other antidepressants. In general, appropriate nutritional elements are essential to treat depression and prevent the risk of depression.

The Role of Oxytocin in Early-Life-Stress-Related Neuropsychiatric Disorders.

Early-life stress during critical periods of brain development can have long-term effects on physical and mental health. Oxytocin is a critical social regulator and anti-inflammatory hormone that modulates stress-related functions and social behaviors and alleviates diseases. Oxytocin-related neural systems show high plasticity in early postpartum and adolescent periods. Early-life stress can influence the oxytocin system long term by altering the expression and signaling of oxytocin receptors. Deficits in social behavior, emotional control, and stress responses may result, thus increasing the risk of anxiety, depression, and other stress-related neuropsychiatric diseases. Oxytocin is regarded as an important target for the treatment of stress-related neuropsychiatric disorders. Here, we describe the history of oxytocin and its role in neural circuits and related behaviors. We then review abnormalities in the oxytocin system in early-life stress and the functions of oxytocin in treating stress-related neuropsychiatric disorders.

Differentiated expressed miRNAs in splenic monocyte induced by burn injury in mice.

To find potential biomarkers based on miRNA and their potential targets in splenic monocytes in burn-injured mice. Male Balb/c mice were subjected to sham or scalding injury of 15% total body surface area. Spenic CD11b+ monocytes were purified with magnetic beads. The monocytes were cultured in the presence of lipopolysaccharide. The proliferation of monocytes was detected by MTT assay, and the cytokines in the supernatant were examined by enzyme linked immunosorbent assay. The purified monocytes were also under total RNA extraction. The differential monocytic miRNAs expression between the sham and burn-injured mice was analysed by miRNA microarray. The activity of monocytes was comparable between the two groups (p > 0.05). However, monocytes from burn-injured mice secreted higher levels of tumour necrosis factor (TNF)-α and transforming growth factor-ß, but lower level of monocyte chemoattratctant protein-1. A total of 54 miRNAs were differentially expressed in monocytes from burn relative to sham-injured mice (fold >3). Further quantitative reverse transcription polymerase chain reaction confirmed that the expression of miR-146a was significantly down-regulated, while miR-3091-6p was up-regulated after burn injury. Using the combination of Miranda and TargetScan softwares, we found that mir-146a may regulate 180 potential target genes including TNF receptor related factor 6 (TRAF6), interleukin-1 receptor related kinase 1 (IRAK1) and CD28. Mir-3091-6p may regulate 39 potential targets, including SOCS7 (cytokine signal transduction inhibitor 7) and ARRB2 (arrestin, ß 2). The miRNAs expressed by monocytes after burn injury may be involved in the regulation of innate immune response in burn injury.

Exendin-4 Exacerbates Burn-Induced Mortality in Mice by Switching to Th2 Response.

INTRODUCTION: To determine if Exendin-4 could be a therapeutic agent for burn-induced hyperglycemia. MATERIALS AND METHODS: Male Balb/c mice received a bolus of Exendin-4 intraperitoneally immediately after 15% total body surface area scald injury. Tail glucose levels were recorded and T-cell functions were analyzed at 4 h and 24 h postburn (pb). Pancreatic pathology was observed consecutively. The secretions of cytokines were detected in serum, spleen, and lung. Apoptosis of splenic CD3+ T-cells was examined by terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling and flow cytometry. RESULTS: Although Exendin-4 could attenuate burn-induced hyperglycemia in mice at 4 h pb, it accelerated their survival dose dependently with progressive depletion of splenocyte number. T-cell function underwent two-phasic changes following Exendin-4 treatment. Compared to placebo mice, T-cell from Exendin-4-treated mice was manifested with increased proliferation, while decreased IL-2 secretion and lower ratio of IL-4/IFN-γ at 4 h pb. However, at 24 h pb, it showed decreased proliferation, while increased IL-2 secretion and higher ratio of IL-4/IFN-γ. Exendin-4 could elicit higher circulating IL-6 and IL-10 levels at 4 h pb, which were pronounced in the lung at 24 h pb. In the meanwhile, severe inflammation could be found in the pancreas. At 24 h pb, the numbers of terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling or caspase-3 positive cells and the apoptosis of CD3+ T-cells were significantly increased in the spleens of Exendin-4 mice relative to placebo mice. CONCLUSIONS: These data support a pathogenic role of Exendin-4 signaling during thermal injury, warning against its clinical application in acute insults.

PS1 Affects the Pathology of Alzheimer's Disease by Regulating BACE1 Distribution in the ER and BACE1 Maturation in the Golgi Apparatus.

Neuritic plaques are one of the major pathological hallmarks of Alzheimer's disease. They are formed by the aggregation of extracellular amyloid-ß protein (Aß), which is derived from the sequential cleavage of amyloid-ß precursor protein (APP) by ß- and γ-secretase. BACE1 is the main ß-secretase in the pathogenic process of Alzheimer's disease, which is believed to be a rate-limiting step of Aß production. Presenilin 1 (PS1) is the active center of the γ-secretase that participates in the APP hydrolysis process. Mutations in the PS1 gene (PSEN1) are the most common cause of early onset familial Alzheimer's disease (FAD). The PSEN1 mutations can alter the activity of γ-secretase on the cleavage of APP. Previous studies have shown that PSEN1 mutations increase the expression and activity of BACE1 and that BACE1 expression and activity are elevated in the brains of PSEN1 mutant knock-in mice, compared with wild-type mice, as well as in the cerebral cortex of FAD patients carrying PSEN1 mutations, compared with sporadic AD patients and controls. Here, we used a Psen1 knockout cell line and a PS1 inhibitor to show that PS1 affects the expression of BACE1 in vitro. Furthermore, we used sucrose gradient fractionation combined with western blotting to analyze the distribution of BACE1, combined with a time-lapse technique to show that PS1 upregulates the distribution and trafficking of BACE1 in the endoplasmic reticulum, Golgi, and endosomes. More importantly, we found that the PSEN1 mutant S170F increases the distribution of BACE1 in the endoplasmic reticulum and changes the ratio of mature BACE1 in the trans-Golgi network. The effect of PSEN1 mutations on BACE1 may contribute to determining the phenotype of early onset FAD.

Role of Vitronectin and Its Receptors in Neuronal Function and Neurodegenerative Diseases.

Vitronectin (VTN), a multifunctional glycoprotein with various physiological functions, exists in plasma and the extracellular matrix. It is known to be involved in the cell attachment, spreading and migration through binding to the integrin receptor, mainly via the RGD sequence. VTN is also widely used in the maintenance and expansion of pluripotent stem cells, but its effects go beyond that. Recent evidence shows more functions of VTN in the nervous system as it participates in neural differentiation, neuronutrition and neurogenesis, as well as in regulating axon size, supporting and guiding neurite extension. Furthermore, VTN was proved to play a key role in protecting the brain as it can reduce the permeability of the blood-brain barrier by interacting with integrin receptors in vascular endothelial cells. Moreover, evidence suggests that VTN is associated with neurodegenerative diseases, such as Alzheimer's disease, but its function has not been fully understood. This review summarizes the functions of VTN and its receptors in neurons and describes the role of VTN in the blood-brain barrier and neurodegenerative diseases.

Rab21 Protein Is Degraded by Both the Ubiquitin-Proteasome Pathway and the Autophagy-Lysosome Pathway.

Rab21 is a GTPase protein that is functional in intracellular trafficking and involved in the pathologies of many diseases, such as Alzheimer's disease (AD), glioma, cancer, etc. Our previous work has reported its interaction with the catalytic subunit of gamma-secretase, PS1, and it regulates the activity of PS1 via transferring it from the early endosome to the late endosome/lysosome. However, it is still unknown how Rab21 protein itself is regulated. This work revealed that Rab21 protein, either endogenously or exogenously, can be degraded by the ubiquitin-proteasome pathway and the autophagy-lysosome pathway. It is further observed that the ubiquitinated Rab21 is increased, but the total protein is unchanged in AD model mice. We further observed that overexpression of Rab21 leads to increased expression of a series of genes involved in the autophagy-lysosome pathway. We speculated that even though the ubiquitinated Rab21 is increased due to the impaired proteasome function in the AD model, the autophagy-lysosome pathway functions in parallel to degrade Rab21 to keep its protein level in homeostasis. In conclusion, understanding the characters of Rab21 protein itself help explore its potential as a target for therapeutic strategy in diseases.

Expansion-Based Clearing of Golgi-Cox-Stained Tissue for Multi-Scale Imaging.

Obtaining fine neuron morphology and connections data is extraordinarily useful in understanding the brain's functionality. Golgi staining is a widely used method for revealing neuronal morphology. However, Golgi-Cox-stained tissue is difficult to image in three dimensions and lacks cell-type specificity, limiting its use in neuronal circuit studies. Here, we describe an expansion-based method for rapidly clearing Golgi-Cox-stained tissue. The results show that 1 mm thick Golgi-Cox-stained tissue can be cleared within 6 hours with a well preserved Golgi-Cox-stained signal. At the same time, we found for the first time that the cleared Golgi-Cox-stained samples were compatible with three-dimensional (3D) immunostaining and multi-round immunostaining. By combining the Golgi-Cox staining with tissue clearing and immunostaining, Golgi-Cox-stained tissue could be used for large-volume 3D imaging, identification of cell types of Golgi-Cox-stained cells, and reconstruction of the neural circuits at dendritic spines level. More importantly, these methods could also be applied to samples from human brains, providing a tool for analyzing the neuronal circuit of the human brain.