Strong cathode electroluminescence biosensor based on CeO2 functionalized PCN-222@Ag NPs for sensitive detection of p-Tau-181 protein.

Electrochemiluminescence (ECL) biosensors provide a convenient and high sensitivity method for early disease diagnosis. However, creating luminophore arrays relying on powerful ECL signals remains a daunting task. Porphyrin-centered metal organic frameworks (MOFs) exhibit remarkable potential in ECL sensing applications. In this paper, based on a simple one-pot synthesis method, PCN-222@Ag NPs doped with CeO2 was synthesized to enhance the ECL performance. Due to the strong catalytic ability of CeO2, the ECL signal strength of the new material PCN-222@CeO2@Ag NPs is much higher than that of the PCN-222@Ag NPs and PCN-222. The luminous properties of PCN-222@CeO2@Ag NPs become more intense and stable due to the excellent electronic conductivity of Ag NPs. Based on the fact that CuS@PDA composite can quench the ECL signal of PCN-222@CeO2@Ag NPs, we constructed a novel sandwich ECL immune sensor for the detection of phosphorylated Tau 181 (p-Tau-181) protein. The ECL sensor has a great linear relationship with p-Tau-181 protein concentration, ranging from 1 pg/mL to 100 ng/mL. The detection limit is as low as 0.147 pg/mL. This work provides new ideas for developing sensitive ECL sensors for the p-Tau-181 protein, the marker of Alzheimer's disease.

Geographic differences in psychological symptoms, sleep quality, and quality of life in patients with inflammatory bowel disease: A multicenter study in China.

OBJECTIVE: We aimed to explore the geographic differences in psychological symptoms, sleep quality, and quality of life (QoL) among adult patients with inflammatory bowel disease (IBD). METHODS: A unified questionnaire was developed to collect data on psychological status and QoL of IBD patients from 42 hospitals across 22 provinces, municipalities, and autonomous regions in China's mainland from September 2021 to May 2022. RESULTS: A total of 2478 patients with IBD were surveyed. The proportions of patients with anxiety (28.5% vs 23.1%), depression (32.3% vs 27.8%), and poor QoL (44.8% vs 32.2%) were significantly higher in patients from the northern region compared to the southern region (all P < 0.05). In the western region, the proportions of patients with anxiety (31.9% vs 23.0%), depression (37.7% vs 26.7%), sleep disturbances (64.5% vs 58.5%), and poor QoL (44.9% vs 34.8%) were significantly higher than in the eastern and central regions (all P < 0.01). Patients from inland regions had significantly higher rates of anxiety (27.1% vs 23.3%), depression (32.5% vs 26.0%), sleep disturbance (62.0% vs 57.7%), and poor QoL (43.5% vs 29.9%) compared to those from coastal regions (all P < 0.05). In economically underdeveloped areas, the proportions of patients with depression (33.1% vs 28.5%) and poor QoL (52.0% vs 32.4%) were significantly higher than in economically (relatively) developed areas (both P < 0.05). CONCLUSION: There are significant geographic differences in psychological symptoms, sleep quality, and QoL among Chinese patients with IBD, which might provide valuable insights for global IBD research and clinical practice.

ORAOV 1 Detection Made with Metal Organic Frameworks Based on Ti3C2Tx MXene.

In this work, a two-dimensional (2D) MOF sheet with electrochemiluminescence (ECL) activity is prepared with Ti3C2Tx MXene as the metal precursor and the meso-tetra(4-carboxyl-phenyl) porphyrin (H2TCPP) as the organic ligand. The atomically thin 2D Ti3C2Tx MXene is utilized as the metal precursor and soft template to produce the MOF with a 2D nanosheet morphology (Ti3C2Tx-PMOF). Ti3C2Tx MXene is a kind of strong electron acceptor, which can deprotonate H2TCPP due to the high electronegativity and low work function of its terminal atoms. The deprotonated H2TCPP continues to bind with Ti atoms to form the 2D MOF sheet. The ECL activity is inherited from H2TCPP and stabilized by introducing Ag NPs. Then, we construct an ECL biosensor based on the Ag NPs/Ti3C2Tx-PMOF to detect the oral cancer overexpressed 1 (ORAOV 1). A bipedal three-dimensional DNA walker strategy is adopted to further improve the biosensor sensitivity. As expected, the biosensor exhibits sterling sensitivity and selectivity. The ECL biosensor responds linearly to ORAOV 1 concentrations in the range of 10 fM-1 nM, and the detection limit is as low as 3.3 fM (S/N = 3). It means that Ag NPs/Ti3C2Tx-PMOF is a potential material to design and construct the high-performance ECL biosensors.

An electrochemiluminescence biosensor for p53 antibody based on Zn-MOF/GO nanocomposite and Ag+-DNA amplification.

An ultrasensitive electrochemiluminescence biosensor was established based on the Zn-MOF/GO nanocomposite. Ag(I)-embedded DNA complexes were used as a signal amplification reagent. In this work, 5,10,15,20-tetrakis(4-carboxyphenyl)porphyrin (TCPP) and Zn2+ were integrated into a porphyrin paddlewheel framework (Zn-MOF) by a hydrothermal method. The synthesized Zn-MOF material has electrochemiluminescence property, and the luminescence intensity is improved after being composited with graphene oxide (GO). Based on the composite material, we constructed an ultrasensitive ECL biosensor for the p53 antibody detection. The composite material acted as an admirable substrate and then loaded plenty of p53 antigens to recognize the target (p53 antibody) accurately. Because of the bridging effect of streptavidin and biotin-conjugated goat anti-rabbit IgG (bio-ab2), the rich-C DNA with positive correlation with the target was modified on the electrode and then captured the co-reactant accelerator Ag+ to amplify the signal. Therefore, the ECL biosensor response increases with increasing p53 antibody concentration. In the range 0.1 fg/mL-0.01 ng/mL, the response signal of the biosensor has a good linear relationship with the p53 antibody concentration. The detection limit is 0.03 fg/mL (S/N = 3). Impressively, the biosensor not only featured high sensitivity, good stability, and excellent specificity for the detection of p53 antibody, but also provides a new way for early detection of cancer. Graphical abstract Schematic representation of the electrochemiluminescence sensor based on a Zn-MOF/GO nanocomposite, which can be applied to the determination of p53 antibody.

A silver nanoparticle-assisted signal amplification electrochemiluminescence biosensor for highly sensitive detection of mucin 1.

A novel electrochemiluminescence (ECL) biosensor was developed in this study, which was based on the Ag-NP modified tetrahedral DNA nanostructure. First, a stable and rigid three-dimensional tetrahedral DNA nanostructure (TDN) was modified on a gold electrode, which was used as a capture element. The TDN improves the accuracy and sensitivity of this biosensor. In addition, silver nanoparticles (Ag NPs) with excellent electrical conductivity were introduced on the edges of TDNs to enhance the ECL intensity of the metal-organic framework (MOF) nanomaterial. Apart from imparting conductivity, the Ag NPs can also act as co-reactant accelerators to enhance the ECL intensity. A Eu3+ doped Zr-MOF material (Eu@MOF) was proposed and used as an ECL material for the first time. Terminal phosphate-modified MUC1 aptamer DNA bonded with the exposed Zr nodes on the surface of MOFs through Zr-O-P bonds to construct the DNA-Eu@MOF signal element. Based on the Ag NP-modified TDN capture element and the DNA-Eu@MOF signal element, a hypersensitive biosensor was established. Under the optimal conditions, this biosensor exhibited a wide detection range from 1.135 fg mL-1 to 0.1135 ng mL-1 and a low detection limit of 0.37 fg mL-1 (S/N = 3) toward the target MUC1. The biosensor also showed excellent stability and high selectivity for MUC1 detection.

Melatonin in Synaptic Impairments of Alzheimer's Disease.

Alzheimer's disease (AD) underlies dementia for millions of people worldwide with no effective treatment. The dementia of AD is thought stem from the impairments of the synapses because of their critical roles in cognition. Melatonin is a neurohormone mainly released by the pineal gland in a circadian manner and it regulates brain functions in various manners. It is reported that both the melatonin deficit and synaptic impairments are present in the very early stage of AD and strongly contribute to the progress of AD. In the mammalian brains, the effects of melatonin are mainly relayed by two of its receptors, melatonin receptor type 1a (MT1) and 1b (MT2). To have a clear idea on the roles of melatonin in synaptic impairments of AD, this review discussed the actions of melatonin and its receptors in the stabilization of synapses, modulation of long-term potentiation, as well as their contributions in the transmissions of glutamatergic, GABAergic and dopaminergic synapses, which are the three main types of synapses relevant to the synaptic strength. The synaptic protective roles of melatonin in AD treatment were also summarized. Regarding its protective roles against amyloid-ß neurotoxicity, tau hyperphosphorylation, oxygenation, inflammation as well as synaptic dysfunctions, melatonin may be an ideal therapeutic agent against AD at early stage.

Highly sensitive electrochemical biosensor for streptavidin detection based on CdSe quantum dots.

An electrochemical biosensor was developed based on a steric hindrance hybridization assay to allow the highly sensitive detection of streptavidin. In the steric hindrance hybridization assay, the signaling strand DNA (sig-DNA) was labeled at the 3' end with CdSe quantum dots (QDs) and at the 5' end with biotin, and capturing strand DNA (the complementary strand of sig-DNA) was labeled at the 5' end with thiol. The steric hindrance effect generated by streptavidin which was bound with the signaling DNA strand. The streptavidin limited the ability of the sig-DNA to hybridize with the cap-DNA, which were linked on the surface of a gold electrode. Therefore, the concentration of streptavidin was detected indirectly based on the concentration of CdSe QDs on the electrode surface. The concentration of CdSe QDs on the electrode surface was detected by differential pulse anodic stripping voltammetry. Under optimal conditions, the streptavidin detection range using the as-prepared biosensor was 1.96pg/mL to 1.96µg/mL and the detection limit was 0.65pg/mL. The experimental results showed that the electrochemical biosensor could detect streptavidin rapidly and accurately.

Tau-Induced Ca2+/Calmodulin-Dependent Protein Kinase-IV Activation Aggravates Nuclear Tau Hyperphosphorylation.

Hyperphosphorylated tau is the major protein component of neurofibrillary tangles in the brains of patients with Alzheimer's disease (AD). However, the mechanism underlying tau hyperphosphorylation is not fully understood. Here, we demonstrated that exogenously expressed wild-type human tau40 was detectable in the phosphorylated form at multiple AD-associated sites in cytoplasmic and nuclear fractions from HEK293 cells. Among these sites, tau phosphorylated at Thr205 and Ser214 was almost exclusively found in the nuclear fraction at the conditions used in the present study. With the intracellular tau accumulation, the Ca2+ concentration was significantly increased in both cytoplasmic and nuclear fractions. Further studies using site-specific mutagenesis and pharmacological treatment demonstrated that phosphorylation of tau at Thr205 increased nuclear Ca2+ concentration with a simultaneous increase in the phosphorylation of Ca2+/calmodulin-dependent protein kinase IV (CaMKIV) at Ser196. On the other hand, phosphorylation of tau at Ser214 did not significantly change the nuclear Ca2+/CaMKIV signaling. Finally, expressing calmodulin-binding protein-4 that disrupts formation of the Ca2+/calmodulin complex abolished the okadaic acid-induced tau hyperphosphorylation in the nuclear fraction. We conclude that the intracellular accumulation of phosphorylated tau, as detected in the brains of AD patients, can trigger nuclear Ca2+/CaMKIV signaling, which in turn aggravates tau hyperphosphorylation. Our findings provide new insights for tauopathies: hyperphosphorylation of intracellular tau and an increased Ca2+ concentration may induce a self-perpetuating harmful loop to promote neurodegeneration.

Photoelectrochemical immunoassay for human interleukin 6 based on the use of perovskite-type LaFeO3 nanoparticles on fluorine-doped tin oxide glass.

A film of perovskite-type LaFeO3 nanoparticles (NPs) was deposited on fluorine-doped tin oxide (FTO) conducting glass via dipping-lifting and calcination. Scanning electron microscopy shows that the NPs are evenly distributed on the surface of the glass. The modified glass was further coated with antibody against human interleukin 6 (IL-6) to result in a photoelectrochemical immunosensor for IL-6. The well-established photoelectrochemical immunoassay has a linear current response in the range of 0.1 pg·mL-1 to 0.1 µg·mL-1 and a detection limit as low as 33 fg·mL-1. Graphical abstract Schematic of a novel photoelectochemical immunoassay for the measurement of IL-6 based on perovskite-type LaFeO3 nanoparticles. The immunoassay had a higher sensitivity and may also be applied to other bioanalysis and environment monitoring.

A case of myeloproliferative neoplasm with a normal complete blood cell count: A novel problem of the JAK2 era.

The present study reported a case of a myeloproliferative neoplasm (MPN) in a patient with a normal complete blood cell count. Bone marrow biopsy showed bone marrow hyperplasia, an elevated megakaryocyte count, megakaryocytic dysplasia and pleomorphic changes, multiple megakaryocyte clusters and focal reticulin fiber hyperplasia. Furthermore, genetic analysis revealed that the patient was positive for the JAK2-V617F mutation, and negative for the JAK2 exon 12 and 13 mutations and the BCR-ABL (p210) fusion gene. The patient's condition was basically stable and at the time of writing, the patient remained in a stable condition with no specific symptoms of disease. The present study also analyzed the diagnostic and clinical features of MPNs, and a literature review was performed. MPN with a normal complete blood cell count is a rare disease, and attention should be focused on this entity in the clinic.

Disturbed Th17/Treg Balance in Patients with Non-small Cell Lung Cancer.

The fine balance of T help-17 (Th17)/regulatory T(Treg) cells is crucial for maintenance of immune homeostasis. However, there is little information concerning the role played in non-small cell lung cancer (NSCLC) by Th17/Treg cells. The objective of this study was to investigate the variation of Th17 and Treg cells in the peripheral blood of patients with NSCLC. Blood samples were collected from 19 patients with NSCLC and 19 healthy donors. Samples were processed to detect CD4(+)IL-17(+) Th17 cells and CD4(+)CD25(+)Foxp3(+) Treg cells by flow cytometry, and related gene expressions were assessed by real-time quantitative polymerase chain reaction. The concentrations of interleukin (IL)-1ß, IL-6, IL-10, IL-17, IL-23, and transforming growth factor-beta (TGF-ß1) were also measured by enzyme-linked immunosorbent assay analysis (ELISA). The frequency of circulating Th17 cells and Treg cells was increased in samples derived from patients with NSCLC, accompanied by the upregulation of Foxp3 and RORγt. However, a negative correlation between Treg cells and Th17 cells was found in patients with NSCLC. Additionally, the Th17/Treg ratio and the related cytokines were also significantly higher in patients with NSCLC than in healthy controls. Furthermore, the frequency of Th17 cells was positively correlated with IL-1ß, IL-6, and IL-23 in patients with NSCLC, and the frequency of Treg cells was positively correlated with TGF-ß1 and IL-10. More importantly, the Th17/Treg ratio was positively correlated with the CEA concentrations in patients with NSCLC. Our data indicated that Th17 and Treg subset are involved in the immunopathology of NSCLC. Distinct cytokine environment might play a key role in the differentiation of the Th17 and Treg cells in NSCLC. Reconstituting an adequate balance between Th17 and Treg may be beneficial in the treatment of NSCLC.

[Effects of salidroside on proliferation of bone marrow mesenchymal stem cells].

This study was aimed to investigate the effect of salidroside on proliferation of bone marrow mesenchymal stem cells (MSC) and their secretion of stem cell factor (SCF). MSC were isolated and amplified in vitro via density gradient centrifugation and adherence screening method. MCS were identified by flow cytometry and osteogenic/adipogenic induction. The effects of salidroside on cell proliferation, cell cycle and the SCF secretion of MSC were detected by flow cytometry. The results showed that the salidroside could induce the proliferation of MSC, peaked at the concentration of 1.5 mg/ml and in a time-dependent manner (in 24 h, 48 h and 72 h). Salidroside at 1.5 mg/ml could more effectively increase the percentage of cells in S and G1/M phase. Co-cultured with salidroside at the concentration of 1.5 mg/ml for 48 h, the SCF and the expression levels of SCF mRNA in co-culture supernatant were both significantly increased (P < 0.01). It is concluded that salidroside in a range of certain concentration can obviously promote the proliferation of MSC and increase the expression and secretion of SCF.

Multiscale evaluation of pore curvature effects on protein structure in nanopores.

Protein structure in nanopores is an important determinant in porous substrate utilization in biotechnology and materials science. To date, accurate residue details of pore curvature induced protein binding and unfolding were still unknown. Here, a multiscale ensemble of chromatography, NMR hydrogen and deuterium (H/D) exchange, confocal scanning and molecular docking simulations was combined to obtain the protein adsorption information induced by pore size and curvature. Lysozyme and polystyrene microspheres within pores in the 14-120 nm range were utilized as models. With pore size increasing, the bound lysozyme presented a tendency of significantly decreased retention, less unfolding and fewer interacted sites. However, such a significant dependence between pore curvature and protein size only existed in a limited micro-pore range comparable to protein sizes. The mechanism behind the above events could be attributed to the diverse protein interaction area determined by pore curvature and size change, by models calculating the binding of lysozyme onto surfaces. Another surface of opposite curvature for nanoparticles was also calculated and compared, the rules were similar but with opposite direction and such a critical size also existed. These studies of proteins on curved interfaces may ultimately help to guide the design of novel porous materials and assist in the discrimination of the target protein from molecular banks.

Golgin-84-associated Golgi fragmentation triggers tau hyperphosphorylation by activation of cyclin-dependent kinase-5 and extracellular signal-regulated kinase.

Tau hyperphosphorylation is a critical event in Alzheimer's disease, in which the neuronal Golgi fragmentation occurs earlier than tau hyperphosphorylation. However, the intrinsic link between Golgi impairment and tau pathology is missing. By electron microscopy and western blotting, we observed in the present study that the neuronal Golgi fragmentation was increased age-dependently with a correlated tau hyperphosphorylation in the brains of C57BL/6 mice aged from 4 to 16 months. Simultaneously, golgin-84 and Golgi reassembly stacking protein 65, 2 important Golgi matrix proteins, were decreased in the brains of elder mice. Further studies in HEK293/tau cells showed that Golgi-disturbing agents, brefeldin A and nocodazole induced tau hyperphosphorylation. Knockdown of golgin-84, not Golgi reassembly stacking protein 65, by small interfering RNA was sufficient to induce tau hyperphosphorylation, while over-expressing golgin-84 arrested the brefeldin A-induced Golgi fragmentation and tau hyperphosphorylation. Finally, we demonstrated that cyclin-dependent kinase-5 and extracellular signal-regulated kinase were activated after golgin-84 knockdown, and simultaneous inhibition of these kinases abolished the golgin-84 deficit-induced tau hyperphosphorylation. These data suggest Golgi fragmentation could be an upstream event triggering tau hyperphosphorylation through golgin-84 deficit-induced activation of cyclin-dependent kinase-5 and extracellular signal-regulated kinase.

[Effect of salidroside on apoptosis of bone marrow mesenchymal stem cells induced by ara-C].

The purpose of this study was to investigate the effect of salidroside on human bone marrow mesenchymal stem cell (hBMMSC) apoptosis induced by cytarabine C (Ara-C) and its mechanism, hBMMSC were cultured in vitro and isolated by Fircoll density gradient centrifugation; cell surface antigens were measured by flow cytometry; the osteogenic and adipogenic differentiation of MSC was tested and evaluated by specific staining methods. The proliferation and apoptosis of cells exposed to Ara- C were detected by MTT and flow cytometry respectively. The experiments were divided into 4 groups: control group, Ara-C group, salidroside group and Ara-C+salidroside group. The mRNA expression of BCL-2 and BAX was assayed by RT-PCR. The results showed that the adherent cells displayed spindle and fibroblast cell-like shape; the hBMMSC expressed CD44, CD71 and HLA-ABC, not expressed CD34, CD45 and HLA-DR; the hBMMSC successfully differentiated into osteogenic and adipogenic lineages, which showed mineralization with von Kossa staining. Furthermore, liquid vacuoles were detected by oil red O staining; Ara- C exhibited a less inhibitory effect on the proliferation of hBMMSC treated with salidroside. The apoptosis of hBMMSC treated with salidroside were significantly higher as compared with control group (P < 0.05); RT-PCR results demonstrated that the BCL-2 expression was significantly down regulated but BAX mRNA expressions was up-regulated in Ara- C group as compared with those in the control group. Salidroside significantly inhibited the apoptosis of MSC and reversed the mRNA expression of BCL-2 and BAX. It is concluded that salidroside can inhibit the apoptosis of hBMMSC induced by Ara-C, its mechanism may be related with the regulation of BCL-2/BAX expression.

[Effect of XPA expression on the chemotherapy sensitivity of A549/DDP cells].

AIM: To investigate the influence on platinum-based chemotherapy sensitivity by silencing xeroderma pigmentosum group A (XPA) gene expression in non-small cell lung cancer (NSCLC) drug resistance cell lines (A549/DDP). METHODS: We detected the expression of XPA in lung normal and tumor tissues by immunohistochemistry, quantitative real-time PCR (qPCR) and Western blotting. We silenced XPA expression in A549/DDP cells by XPA-shRNA transfection, and detected the expression of XPA by qPCR and Western blotting. The cell sensitivity to cisplatin and the apoptosis of A549/DDP cells transfected with XPA-shRNA were determined by MTT assay. RESULTS: The expression of XPA was higher in NSCLC tissues than that in normal lung tissues. Silencing XPA gene increased the apoptosis and sensitivity of A549/DDP cells to cisplatin. CONCLUSION: Silencing XPA gene can partly reverse the cisplatin resistance in human cisplatin-resistant NSCLC cell line A549/DDP.

[Expression of MADD in lung adenocarcinoma tissues and its effects on proliferation and apoptosis of lung adenocarcinoma A549 cells].

AIM: To investigate the expression of MAPK-activating death domain protein (MADD) in lung adenocarcinoma tissues and its effects on proliferation and apoptosis of lung adenocarcinoma A549 cells. METHODS: Immunohistochemistry was used to detect the expression of MADD in lung normal and tumor tissues. The expression of IG20 gene in A549 cells was measured by reverse transcription polymerase chain reaction. A549 cells were transfected with pEYFP-MADD plasmids carrying MADD gene or pNL-SIN-GFP-MID lentiviral vectors used for RNA interference. MADD expression and cell proliferation and apoptosis were determined by Western blot, MTT assay, and flow cytometry. RESULTS: The expression levels of MADD were higher in lung adenocarcinoma and squamous cell carcinoma tissues than that in lung normal tissues, and lung adenocarcinoma tissues expressed more MADD than lung squamous cell carcinoma tissues. The transcript encoding MADD was expressed in A549 cells. The transfection of pEYFP-MADD plasmids could increase MADD expression and cell proliferation of A549 cells, while the A549 cells transfected with pNL-SIN-GFP-MID lentiviral vectors showed significantly decreases in the MADD level and proliferation. It is shown that MADD overexpression could inhibit A549 cell apoptosis, and knock down of MADD could promote apoptosis of them. CONCLUSION: The expression of MADD increases obviously in lung adenocarcinoma, and MADD can promote survival of lung adenocarcinoma cells by inhibiting apoptosis.

Bip enhanced the association of GSK-3ß with tau during ER stress both in vivo and in vitro.

Hyperphosphorylated tau is the major component of intracellular neurofibrillary tangles, which is positively correlated with the cognitive decline in Alzheimer's disease (AD). The upstream factors leading to tau hyperphosphorylation are still not fully understood. Endoplasmic reticulum (ER) stress has been indicated in AD pathogenesis and the increased level of binding immunoglobulin protein (Bip), an important ER associated chaperon, is increased in AD brain. Here hyperphosphorylation of tau, activation of glycogen synthase kinase-3ß (GSK-3ß), and elevation of Bip were induced by ventricular infusion of ER stressors, tunicamycin (TM) and thapsigargin (TG), in rats. GSK-3ß was found to be responsible for tau hyperphosphorylation induced by ER stressors both in vivo and in vitro. In addition, inhibited Akt, protein tyrosine phosphatase 1B, and activated Fyn were detected in vivo. Down-regulating Bip by tranfecting its siRNA plasmid significantly revised tau hyperphosphorylation in TG treated HEK293/tau cells, but the activation of GSK-3ß was still observed. By immunoprecipitation, we found that the binding levels of Bip to tau and GSK-3ß were significantly increased with the elevation of Bip in TM-treated rats. Moreover, in Bip overexpressed HEK293/tau cells, the binding levels of Bip to tau (mainly phosphorylated tau) and GSK-3ß were also significantly increased. However, ß-catenin, another important substrate of GSK-3ß, was not found bound to the increased Bip. All these data suggest an essential role of Bip in GSK-3ß dependent tau hyperphosphorylation in ER stress by promoting the binding of GSK-3ß to tau.

Synaptic released zinc promotes tau hyperphosphorylation by inhibition of protein phosphatase 2A (PP2A).

Hyperphosphorylated tau is the major component of neurofibrillary tangles in Alzheimer disease (AD), and the tangle distribution largely overlaps with zinc-containing glutamatergic neurons, suggesting that zinc released in synaptic terminals may play a role in tau phosphorylation. To explore this possibility, we treated cultured hippocampal slices or primary neurons with glutamate or Bic/4-AP to increase the synaptic activity with or without pretreatment of zinc chelators, and then detected the phosphorylation levels of tau. We found that glutamate or Bic/4-AP treatment caused tau hyperphosphorylation at multiple AD-related sites, including Ser-396, Ser-404, Thr-231, and Thr-205, while application of intracellular or extracellular zinc chelators, or blockade of zinc release by extracellular calcium omission almost abolished the synaptic activity-associated tau hyperphosphorylation. The zinc release and translocation of excitatory synapses in the hippocampus were detected, and zinc-induced tau hyperphosphorylation was also observed in cultured brain slices incubated with exogenously supplemented zinc. Tau hyperphosphorylation induced by synaptic activity was strongly associated with inactivation of protein phosphatase 2A (PP2A), and this inactivation can be reversed by pretreatment of zinc chelator. Together, these results suggest that synaptically released zinc promotes tau hyperphosphorylation through PP2A inhibition.