Targeting vulnerable microcircuits in the ventral hippocampus of male transgenic mice to rescue Alzheimer-like social memory loss.

BACKGROUND: Episodic memory loss is a prominent clinical manifestation of Alzheimer's disease (AD), which is closely related to tau pathology and hippocampal impairment. Due to the heterogeneity of brain neurons, the specific roles of different brain neurons in terms of their sensitivity to tau accumulation and their contribution to AD-like social memory loss remain unclear. Therefore, further investigation is necessary. METHODS: We investigated the effects of AD-like tau pathology by Tandem mass tag proteomic and phosphoproteomic analysis, social behavioural tests, hippocampal electrophysiology, immunofluorescence staining and in vivo optical fibre recording of GCaMP6f and iGABASnFR. Additionally, we utilized optogenetics and administered ursolic acid (UA) via oral gavage to examine the effects of these agents on social memory in mice. RESULTS: The results of proteomic and phosphoproteomic analyses revealed the characteristics of ventral hippocampal CA1 (vCA1) under both physiological conditions and AD-like tau pathology. As tau progressively accumulated, vCA1, especially its excitatory and parvalbumin (PV) neurons, were fully filled with mislocated and phosphorylated tau (p-Tau). This finding was not observed for dorsal hippocampal CA1 (dCA1). The overexpression of human tau (hTau) in excitatory and PV neurons mimicked AD-like tau accumulation, significantly inhibited neuronal excitability and suppressed distinct discrimination-associated firings of these neurons within vCA1. Photoactivating excitatory and PV neurons in vCA1 at specific rhythms and time windows efficiently ameliorated tau-impaired social memory. Notably, 1 month of UA administration efficiently decreased tau accumulation via autophagy in a transcription factor EB (TFEB)-dependent manner and restored the vCA1 microcircuit to ameliorate tau-impaired social memory. CONCLUSION: This study elucidated distinct protein and phosphoprotein networks between dCA1 and vCA1 and highlighted the susceptibility of the vCA1 microcircuit to AD-like tau accumulation. Notably, our novel findings regarding the efficacy of UA in reducing tau load and targeting the vCA1 microcircuit may provide a promising strategy for treating AD in the future.

P301S-hTau acetylates KEAP1 to trigger synaptic toxicity via inhibiting NRF2/ARE pathway: A novel mechanism underlying hTau-induced synaptic toxicities.

BACKGROUND: Human Tau (hTau) accumulation and synapse loss are two pathological hallmarks of tauopathies. However, whether and how hTau exerts toxic effects on synapses remain elusive. METHODS: Mutated hTau (P301S) was overexpressed in the N2a cell line, primary hippocampal neurons and hippocampal CA3. Western blotting and quantitative polymerase chain reaction were applied to examine the protein and mRNA levels of synaptic proteins. The protein interaction was tested by co-immunoprecipitation and proximity ligation assays. Memory and emotion status were evaluated by a series of behavioural tests. The transcriptional activity of nuclear factor-erythroid 2-related factor 2 (NRF2) was detected by dual luciferase reporter assay. Electrophoresis mobility shift assay and chromosome immunoprecipitation were conducted to examine the combination of NRF2 to specific anti-oxidative response element (ARE) sequences. Neuronal morphology was analysed after Golgi staining. RESULTS: Overexpressing P301S decreased the protein levels of post-synaptic density protein 93 (PSD93), PSD95 and synapsin 1 (SYN1). Simultaneously, NRF2 was decreased, whereas Kelch-like ECH-associated protein 1 (KEAP1) was elevated. Further, we found that NRF2 could bind to the specific AREs of DLG2, DLG4 and SYN1 genes, which encode PSD93, PSD95 and SYN1, respectively, to promote their expression. Overexpressing NRF2 ameliorated P301S-reduced synaptic proteins and synapse. By means of acetylation at K312, P301S increased the protein level of KEAP1 via inhibiting KEAP1 degradation from ubiquitin-proteasome pathway, thereby decreasing NRF2 and reducing synapse. Blocking the P301S-KEAP1 interaction at K312 rescued the P301S-suppressed expression of synaptic proteins and memory deficits with anxiety efficiently. CONCLUSIONS: P301S-hTau could acetylate KEAP1 to trigger synaptic toxicity via inhibiting the NRF2/ARE pathway. These findings provide a novel and potential target for the therapeutic intervention of tauopathies.

Predisposition to Alzheimer's and Age-Related Brain Pathologies by PM2.5 Exposure: Perspective on the Roles of Oxidative Stress and TRPM2 Channel.

Accumulating epidemiological evidence supports that chronic exposure to ambient fine particular matters of <2.5 µm (PM2.5) predisposes both children and adults to Alzheimer's disease (AD) and age-related brain damage leading to dementia. There is also experimental evidence to show that PM2.5 exposure results in early onset of AD-related pathologies in transgenic AD mice and development of AD-related and age-related brain pathologies in healthy rodents. Studies have also documented that PM2.5 exposure causes AD-linked molecular and cellular alterations, such as mitochondrial dysfunction, synaptic deficits, impaired neurite growth, neuronal cell death, glial cell activation, neuroinflammation, and neurovascular dysfunction, in addition to elevated levels of amyloid ß (Aß) and tau phosphorylation. Oxidative stress and the oxidative stress-sensitive TRPM2 channel play important roles in mediating multiple molecular and cellular alterations that underpin AD-related cognitive dysfunction. Documented evidence suggests critical engagement of oxidative stress and TRPM2 channel activation in various PM2.5-induced cellular effects. Here we discuss recent studies that favor causative relationships of PM2.5 exposure to increased AD prevalence and AD- and age-related pathologies, and raise the perspective on the roles of oxidative stress and the TRPM2 channel in mediating PM2.5-induced predisposition to AD and age-related brain damage.

[Effect of NaHS on ATP-induced P2X receptor expression in rat microglia].

OBJECTIVE: To observed the effect of sodium hydrosulphide (NaHS), a donor of H2S on the cell viability,the membrane permeability and the expression of P2X7 receptor induced by adenosine triphosphate(ATP) in rat microglia. METHODS: Rat microglia in logarithmic growth phase was randomly divided into 4 groups. In control group, the cells were cultured without ATP treatment. In ATP group, the cells were treatment with ATP after cultured for 24 hours. In NaHS+ATP group, the cells were incubated with NaHS for 30 min before ATP, and NaHS always existed in the reaction system. In KN-62+ATP group, the cells were pretreated with KN-62 for 30 min, the others were as the same as NaHS+ATP group. The cell viability was detected by MTT. Fluorescent dyes YO-PRO-1 was used to observe the membrane permeability. The expression of P2X7 receptor was examined by immunofluorescence staining. RESULTS: ① Compared with control group, the cell viability dropped after treatment with ATP (1、3、5、10 mmol/L) for 3 hours. When pre-incubation with NaHS(200 µmol/L), the cell viability was apparently higher than that of ATP alone group(P<0.01), while 400 µmol/L had no further beneficial.②The YO-PRO-1 fluorescence intensity was obviously elevated by ATP in rat microglia, but this effect was counteracted by NaHS pretreatment (P<0.01). ③ The expression of P2X7 receptor protein was significantly increased after ATP(3 mmol/L) for 3 h. While the expression upregulation of P2X7 receptor protein induced by ATP was significantly counteracted by pretreating with NaHS(200 µmol/L) (P<0.01). CONCLUSIONS: NaHS could reduce the expression of P2X7 receptor, decrease membrane permeability, and increase the cell viability in rat microglia injured by ATP. So the cytoprotection of hydrogen sulfide may be related to the expression and function of P2X7 receptor.

[Construction of eukaryotic expressing vector of human P2X7 and establishment of stable transfectant cell line].

OBJECTIVE: To construct eukaryotic expression vector of human P2X7gene and transfect HEK293 cells so as to establish stable HEK293 cell line. METHODS: P2X7 gene was amplified by polymerase chain reaction from the human brain P2X7 cDNA and inserted into a vector pEGFP-N1 to construct a recombinant plasmidcalled pEGFP-N1/P2X7. The correct recombinant plasmid was transfected into HEK293 cells by X-fect transfection reagent. The cell line stably expressing EGFP tagged-P2X7 gene were established by screening with G418 and fluorescence microscope. The expression levels and localization of human P2X7 in HEK293 cells was identified by flow cytometry, Western blot and laser scanning confocal microscope. RESULTS: The recombinant plasmid pEGFP-N1/P2X7 was constructed correctly and the stable HEK293 cell line expressing EGFP tagged-P2X7 fusion protein was established. Both Western blot and flow cytometry revealed the higher expression of humanP2X7 in the stably transfected HEK293 cells. Under the laser scanning confocal microscope the EGFP tagged-P2X7 fusion protein was located on the membrane of HEK293 cells. CONCLUSIONS: The eukaryotic expressing vector of pEGFP-N1/P2X7 is successfully constructed and the HEK293 cell line stably expressing P2X7-EGFP fusion protein is established which have provided solid experimental foundation for further studies on the structure and function of P2X7 ionic channel.

[Construction of acid-sensitive potassium channel-3 eukaryotic expression plasmid and its express in SH-SY5Y cells].

OBJECTIVE: To construct the acid-sensitive potassium hannel-3(TASK3) eukaryotic expression plasmid and to establish a stable SH-SY5Y cell line expressing enhanced green fluorescent protein (EGFP)-tagged TASK3. METHODS: TASK3 coding region was subcloned into pEGFP-N1 plasmid to construct a recombinant vector alled pEGFP-TASK3. The correct recombinant expressing plasmid was transfected with X-feet transfection reagent to SH-SY5Y cells. The cell line stably expressiing EGFP tagged-TASK3 gene was established by screening with antibiotic G418 and fluorescence microscope. The expression and localization of the EGFP tagged-TASK3 fusion protein was detected by Western blot and confocal microscope. Exposure of the SH-SY5Y cell line expressing stably TASK3-eGFP fusion proteins was exposed to different pH media (7.0, 6.7, 6.4, 6.1) for 24 h, the cell viability was assessed with cell counting Kit-8 (CCK-8). RESULTS: All the results of identification by PCR, digestion with restriction endonuclease and sequencing indicated that the recombinant eukaryotic expression plasmid pEGFP-TASK3 was constructed correctly. The stable SH-SY5Y cell line expressing EGFP tagged-TASK3 fusion protein was successfully established. Exposure of the wild type SH-SY5Y cells and the stable SH-SY5Y-GFP tag-TASK3 cell line to different pH media (7.0, 6.7, 6.4, 6.1) for 24 h, the cell viability of two group cells significantly reduced with pH declining, and the difference was statistically significant (P < 0.05). Compared with wild type SH-SY5Y cells, the cell viability of stable SH-SYSY-GFP tag-TASK3 cell line increased significantly with the same pH media, and the difference was statistically significant (P < 0.05). CONCLUSION: The eukaryotic expression vector pEGFP-TASK3 is successfully constructed and the cell line stably expressing TASK3-eGFP fusion is established which is important for their fundamental research and potential applications.

[Neuroprotective effect of progesterone on focal cerebral ischemia/reperfusion injury in rats and its mechanism].

OBJECTIVE: To observe the neurological protective effects of progesterone (PROG) on focal cerebral ischemia/reperfusion injury in rats and to explore its possible mechanism. METHODS: One handred and twenty male SD rats were divided into three groups randomly: sham-operated group, middle cerebral artery occlusion ( MCAO ) group and PROG + MCAO group( n = 40). The right temporary MCAO model was established by the line-embolism method. The PROG + MCAO group rats were according to 8 mg/kg intraperitoneal injection PROG, after that 30 min, the rats were suffered ischemia/reperfusion. After rats were suffered ischemia for 2 h and reperfusion 0, 24, 48, 72 h stress, the nervous functional defect degree were evaluated by longe scoring, and the expression of two-pore domain K channel 3 (TASK3) mRNA in brain tissue were detected by the real-time PCR. RESULTS: PROG (8 mg/kg) could significantly reduced the nervous functional defect degree in rats after ischemia/reperfusion 24, 48, 72 h (P < 0.05). The results of real-time PCR showed that the TASK3 mRNA expression in the brain tissue at all time points significantly decreased in MCAO group compared with sham-operated group (P < 0.05). However, compared with MCAO group, the expression of TASK3 mRNA in brain tissue at all time points dramatically increased in PROG + MCAO group (P < 0.05). CONCLUSION: PROG can improve the nervous functional defect degree after focal cerebral ischemia/reperfusion injury in rats, and the mechanism might be associated with up-regulating the expression of TASK3 mRNA in brain tissue.

Hydrogen sulfide intervention in focal cerebral ischemia/reperfusion injury in rats.

The present study aimed to explore the mechanism underlying the protective effects of hydrogen sulfide against neuronal damage caused by cerebral ischemia/reperfusion. We established the middle cerebral artery occlusion model in rats via the suture method. Ten minutes after middle cerebral artery occlusion, the animals were intraperitoneally injected with hydrogen sulfide donor compound sodium hydrosulfide. Immunofluorescence revealed that the immunoreactivity of P2X7 in the cerebral cortex and hippocampal CA1 region in rats with cerebral ischemia/reperfusion injury decreased with hydrogen sulfide treatment. Furthermore, treatment of these rats with hydrogen sulfide significantly lowered mortality, the Longa neurological deficit scores, and infarct volume. These results indicate that hydrogen sulfide may be protective in rats with local cerebral ischemia/reperfusion injury by down-regulating the expression of P2X7 receptors.

[Effects of taurine on the ultrastructure and P2X7 receptor expression in brain following traumatic brain injury in rats].

OBJECTIVE: To explore the effects of taurine on the ultrastructure and P2X7 receptor protein expression in brain following traumatic brain injury (TBI) in rats. METHODS: Forty male SD rats, were divided randomly into four groups that were sham-operated group, TBI group, TBI plus low-dose taurine group and TBI plus high-dose taurine group. The TBI model was established by Marmarou's method, the expression of P2X7 receptor protein in parietal cortex and hippocampus was detected by the immunohistochemical method, the ultrastructure of parietal cortex were observed by transmission electron microscope. RESULTS: Compared with sham-operated group, the positive expression cells of P2X7 receptor protein in parietal cortex and hippocampus of TBI group were significantly increased (P < 0.01). Compared with TBI group, the positive expression cells of P2X7 receptor protein in parietal cortex and hippocampus of TBI plus low-dose taurine group and TBI plus high-dose taurine group were significantly decreased (P <0.01 or P <0.05). Compared with TBI plus low-dose taurine group, the positive expression cells of P2X7 receptor protein in parietal cortex and hippocampus of TBI plus high-dose taurine group were significantly decreased (P < 0.05 or P < 0.01). The pathological damage of parietal cortex in the TBI plus high-dose taurine group was obviously lightened. CONCLUSION: Taurine exerts the neuroprotective effect on TBI in rats, the protective mechanism might be associated with down-regulating the expression of P2X7 receptor protein in parietal cortex and hippocampus.