Amyloid Precursor Protein Protein Research Articles

Euonymus hamiltonianus Extract Improves Amnesia in APPswe/Tau Transgenic and Scopolamine-Induced Dementia Models.

Dementia is a syndrome exhibiting progressive impairments on cognition and behavior beyond the normal course of aging, and Alzheimer's disease (AD) is one of the neurodegenerative diseases known to cause dementia. We investigated the effect of KGC07EH, the 30% ethanol extract of Euonymus hamiltonianus, against amyloid-β (Aβ) production and cognitive dysfunction in dementia models. KGC07EH was treated on Hela cells expressing the Swedish mutant form of amyloid precursor protein (APP), and the AD triple transgenic (3× TG) mice were given KGC07EH orally during 11-14 months of age (100 and 300mg/kg/day). SH-SY5Y cell line was used to test KGC07EH on scopolamine-induced elevation of acetylcholinesterase (AChE) activity. ICR mice were intraperitoneally injected with scopolamine, and KGC07EH was administered orally (50, 100, and 200mg/kg/day) for 4 weeks. KGC07EH treatment decreased Aβ, sAPPβ-sw, and sAPPβ-wt levels and APP protein expressions while sAPPα was increased in Swedish mutant-transfected HeLa cells. KGC07EH treatment also significantly reduced the accumulation of Aβ plaques and tau tangles in the brain of 3× TG mice as well as improving the cognitive function. In SH-SY5Y cells cultured with scopolamine, KGC07EH dose-dependently attenuated the increase of AChE activity. KGC07EH also improved scopolamine-induced learning and memory impairment in scopolamine-injected mice, and in their cerebral cortex and hippocampus, the expression levels of p-ERK, p-CREB, p-Akt, and BDNF were attenuated. KGC07EH inhibits APP processing and Aβ production both in vitro and in vivo, while enhancing acetylcholine signaling and cognitive dysfunction which are the major symptoms of dementia.

The amyloid precursor protein intracellular domain induces sleep disruptions and its nuclear localization fluctuates in circadian pacemaker neurons in Drosophila and mice

The most prominent symptom of Alzheimer's disease (AD) is cognitive decline; however, sleep and other circadian disruptions are also common in AD patients. Sleep disruptions have been connected with memory problems and therefore the changes in sleep patterns observed in AD patients may also actively contribute to cognitive decline. However, the underlying molecular mechanisms that connect sleep disruptions and AD are unclear. A characteristic feature of AD is the formation of plaques consisting of Amyloid-β (Aβ) peptides generated by cleavage of the Amyloid Precursor Protein (APP). Besides Aβ, APP cleavage generates several other fragments, including the APP intracellular domain (AICD) that has been linked to transcriptional regulation and neuronal homeostasis. Here we show that overexpression of the AICD reduces the early evening expression of two core clock genes and disrupts the sleep pattern in flies. Analyzing the subcellular localization of the AICD in pacemaker neurons, we found that the AICD levels in the nucleus are low during daytime but increase at night. While this pattern of nuclear AICD persisted with age, the nighttime levels were higher in aged flies. Increasing the cleavage of the fly APP protein also disrupted AICD nuclear localization. Lastly, we show that the day/nighttime nuclear pattern of the AICD is also detectable in neurons in the suprachiasmatic nucleus of mice and that it also changes with age. Together, these data suggest that AD-associated changes in APP processing and the subsequent changes in AICD levels may cause sleep disruptions in AD.

In vivo safety and efficacy of a CRISPR‐based gene therapy for Alzheimer’s disease

AbstractBackgroundOur lab has developed a gene‐editing strategy to target the extreme C‐terminus (C‐term) of APP (amyloid precursor protein) – a gene with a central and indisputable role in AD. In physiologic states, the APP protein is cleaved by α‐secretases to generate neuroprotective sAPPα; but in AD (both sporadic and familial), the alternative β‐cleavage pathway is active, generating pathologic fragments (including Aβ). Specifically, our approach attenuates pathologic β‐cleavage products by disrupting a pentapeptide “YENPTY” domain at the APP C‐term, and this retains the edited APP (APP‐ΔC) at the cell‐surface, augmenting neuroprotective and neuroregenerative α‐cleavage.MethodIn order to assess the safety and efficacy of our approach in vivo, we used two different CRISPR‐editing approaches. First, we generated germline edits in Wt and APP knockin (APPNL‐G‐F) mice by injecting embryos with APP C‐term targeting CRISPRs. We then selected founders to produce stable strains of WT and APP‐KI in which the APP C‐term was genomically deleted (referred to as WtΔC and KI‐ΔC mice respectively). In another set of experiments, we packaged APP C‐term CRISPRs into AAV vectors and systemically injected AAVs into APP‐KI mice.ResultWtΔC showed no cognitive deficits or histological abnormalities compared to Wt controls. KI‐ΔC showed a dramatic reduction of amyloid beta plaques and associated neuroinflammatory markers and similar results were observed in AAV‐treated KI mice. Moreover, both germline and somatic APP C‐term editing produced an increase in neuroprotective sAPPα.ConclusionIn total, these data demonstrate that our approach is safe and efficacious in vivo and validate the feasibility of our APP C‐terminus editing approach as a therapeutic for AD.

Determination of molecular chaperone levels in cerebrospinal fluids of Alzheimer’s patients

AbstractBackgroundMolecular chaperones are a component of the protein homeostasis network and regulate the biogenesis, folding, and trafficking of proteins, protecting the proteome against misfolding, aggregation, and proteotoxicity [1]. Therefore, they serve as the first line of defense against toxicity caused by misfolded proteins such as Aβ and tau [2]. Amyloid precursor protein (APP) interacts with chaperones from the moments of microtubule‐associated protein tau (MAPT) production. These properties keep the molecular chaperones in close contact with many proteins within the cell, including proteins associated with Alzheimer’s disease (AD), such as APP and tau [3]. According to the data we obtained using the web‐based FpClass protein‐protein association (PPI) prediction program, which investigates protein‐protein interactions, we determined that the AD‐related proteins MAPT and APP strongly interact with the chaperone proteins HSP90AA1, CHIP (STUB1) and HSPA4. In light of this information, we thought these chaperone proteins could interact with Aβ and tau and exit the CSF together, and these chaperones could be used as a biomarker.MethodFollowing this purpose, we determined the levels of HSP90AA1, STUB1, and HSPA4 chaperone proteins in CSF samples of AD, MCI, and FTD patients and individuals diagnosed with SCI using the ELISA method. Depending on the distribution of ApoE, any changes in CSF chaperone levels and co‐localization of these chaperones with MAPT and Aβ1‐42 were demonstrated by double‐immunofluorescence labeling in neuron‐differentiated human SH‐SY5Y cells. Within the scope of the study, these parameters included to be biomarkers that were investigated.ResultCSF HSP90AA1 protein levels were increased in sporadic AD and FTD patients compared to controls, CSF HSPA4 protein levels were increased in sporadic AD patients compared to family history of AD patients, and CSF STUB1 protein levels were decreased in AD, MCI, and FTD patients compared to controls.ConclusionConsidering the findings of our study, the presence of these chaperone proteins in CSF suggests that they may have an important place in the neuropathological processes of neurodegenerative diseases such as Alzheimer’s disease.The present work was supported by the Research Fund of Istanbul University‐Cerrahpasa. Project No. 33638

Mitochondrial Localized Amyloid Precursor Protein Alters Mitochondrial Function and Mitophagy

AbstractBackgroundMitochondrial dysfunction and Aβ accumulation are hallmarks of Alzheimer’s disease (AD). Decades of research describe a relationship between mitochondrial function and Aβ production. Amyloid precursor protein (APP), from which Aβ is generated, is found in mitochondria. APP and Aβ alter mitochondrial function, while mitochondrial function alters Aβ production from APP. How these interactions contribute to AD pathology and progression are unknown. Here we interrogated the association of full‐length APP with mitochondria, mitochondrial function, and AD pathological hallmarks.MethodND (n = 5, without DS) and DS with dementia (DSD, n = 5) postmortem brain tissue was obtained from the University of California Irvine. A human iPSC line underwent Crispr/Cas9 genome editing to mutate three amino acids in APP and generate a 3M APP model, with reduced mitochondrial APP localization. We also leveraged a human iPSC line with triplication of the APP gene. iPSC models were differentiated into neurons using StemCell Technologies reagents and protocols. We examined mitochondrial function using a Seahorse XF analyzer. We measured full‐length APP protein levels in whole cell extracts and mitochondrial fractions via Western Blotting. We measured Aβ levels with ELISA kits from ThermoFisher. Mitophagy and mitochondrial mass/biogenesis was measured using MitoTimer and EGFP‐Cox8 adenoviral constructs.ResultiPSC derived neurons showed alterations to Aβ production. 3M APP models had reduced Aβ production while APP triplication models had increased production. 3M APP models had reduced mitochondrial APP levels and APP triplication models had increased mitochondrial APP levels. 3M APP models had reduced mitophagy, increased mitochondrial biogenesis, and increased mitochondrial mass. APP triplication models had increased mitophagy and reduced mitochondrial mass. Mitochondrial respiratory function was reduced in both 3M APP and APP triplication models. DSD postmortem brain tissue had reduced mitochondrial function in females. Full‐length APP levels were significantly higher in mitochondrial fractions in DSD brain tissue. Full‐length APP levels in mitochondrial fractions correlated with mitochondrial function. Higher mitochondrial APP (full‐length) levels associated with lower mitochondrial function.ConclusionWe describe a relationship between mitochondrial APP accumulation, mitochondrial function, and Aβ. These data support a centralized role for mitochondrial function in APP physiology and APP may play a role in modulating mitophagy.

Butyrate acts as a G-protein-coupled receptor ligand that prevents high glucose-induced amyloidogenesis in N2a cells through the protein kinase B/glycogen synthase kinase-3β pathway.

Butyrate acts as a G-protein-coupled receptor ligand that prevents high glucose-induced amyloidogenesis in N2a cells through the protein kinase B/glycogen synthase kinase-3β pathway.

O-GlcNAcylation regulates extracellular signal-regulated kinase (ERK) activation in Alzheimer's disease.

Aberrant activation of Extracellular Signal-Regulated Kinase (ERK) signaling is associated with Alzheimer's disease (AD) pathogenesis. For example, enhanced ERK signal activation mediated by Apolipoprotein E4 (APOE4), which is a critical genetic risk factor for AD, increases the transcription of amyloid precursor protein (APP). We hypothesize that O-linked N-acetylglucosamine (O-GlcNAc) regulates the phosphorylation and activation of ERK. O-GlcNAc is a single sugar post-translational modification that dynamically cycles on and off proteins in response to nutrient changes by the action of the enzymes O-GlcNAc transferase (OGT) and O-GlcNAcase (OGA), respectively. However, O-GlcNAc quickly returns to a baseline level after stimulus removal (called O-GlcNAc homeostasis). We did a serum reactivation time-course followed by western blot in SH-SY5Y neuroblastoma cells after long-term O-GlcNAcase (OGA) inhibition by Thiamet-G (TMG) treatment, O-GlcNAc transferase (OGT) knock-down (KD) and OGA KD. Brain tissues of C57BL6/J mice and 5XFAD Alzheimer's disease mice intra-peritoneally injected with TMG for 1 month and C57BL6/J mice intra-peritoneally injected with TMG for 6 months were also used for western blot. We found that ERK1/2 phosphorylation at Thr 202/Tyr204 and Thr183/Tyr185 (p-ERK) are amplified and hence ERK1/2 are activated after long-term OGA inhibition in SH-SY5Y cells. In addition to pharmacological treatment, genetic disruption of O-GlcNAc by OGT KD and OGA KD also increased p-ERK in SH-SY5Y cells suggesting O-GlcNAc homeostasis controls ERK signaling. To determine how O-GlcNAc regulates p-ERK, we probed the expression of phosphorylated mitogen-activated protein kinase-kinase (p-MEK) which phosphorylates and activates ERK and Dual specificity phosphatase-4 (DUSP4) which dephosphorylates and inactivates ERK in SH-SY5Y cells. p-MEK increases in TMG treated and OGT KD cells whereas total DUSP4 decreases in OGT KD and OGA KD cells with serum reactivation time course. Next, we probed the role of OGA inhibition in regulating ERK activation using mice brain-tissue samples. Interestingly, 6-month intra-peritoneal TMG injection in C57BL/6J mice showed an increase in amplitude of p-ERK and APP protein levels, indicating long-term OGA inhibition potentially contributes to AD progression. Furthermore, 1-month TMG injection was sufficient to increase the amplitude of p-ERK in 5XFAD AD mice brains suggesting AD phenotype contributes to the acceleration of ERK activation mediated by OGA inhibition. Together, these results indicate that disruptions to O-GlcNAc homeostasis amplify ERK signal activation in AD.

A Diet Containing Rutin Ameliorates Brain Intracellular Redox Homeostasis in a Mouse Model of Alzheimer’s Disease

Quercetin has been studied extensively for its anti-Alzheimer's disease (AD) and anti-aging effects. Our previous studies have found that quercetin and in its glycoside form, rutin, can modulate the proteasome function in neuroblastoma cells. We aimed to explore the effects of quercetin and rutin on intracellular redox homeostasis of the brain (reduced glutathione/oxidized glutathione, GSH/GSSG), its correlation with β-site APP cleaving enzyme 1 (BACE1) activity, and amyloid precursor protein (APP) expression in transgenic TgAPP mice (bearing human Swedish mutation APP transgene, APPswe). On the basis that BACE1 protein and APP processing are regulated by the ubiquitin-proteasome pathway and that supplementation with GSH protects neurons from proteasome inhibition, we investigated whether a diet containing quercetin or rutin (30 mg/kg/day, 4 weeks) diminishes several early signs of AD. Genotyping analyses of animals were carried out by PCR. In order to determine intracellular redox homeostasis, spectrofluorometric methods were adopted to quantify GSH and GSSG levels using o-phthalaldehyde and the GSH/GSSG ratio was ascertained. Levels of TBARS were determined as a marker of lipid peroxidation. Enzyme activities of SOD, CAT, GR, and GPx were determined in the cortex and hippocampus. ΒACE1 activity was measured by a secretase-specific substrate conjugated to two reporter molecules (EDANS and DABCYL). Gene expression of the main antioxidant enzymes: APP, BACE1, a Disintegrin and metalloproteinase domain-containing protein 10 (ADAM10), caspase-3, caspase-6, and inflammatory cytokines were determined by RT-PCR. First, overexpression of APPswe in TgAPP mice decreased GSH/GSSG ratio, increased malonaldehyde (MDA) levels, and, overall, decreased the main antioxidant enzyme activities in comparison to wild-type (WT) mice. Treatment of TgAPP mice with quercetin or rutin increased GSH/GSSG, diminished MDA levels, and favored the enzyme antioxidant capacity, particularly with rutin. Secondly, both APP expression and BACE1 activity were diminished with quercetin or rutin in TgAPP mice. Regarding ADAM10, it tended to increase in TgAPP mice with rutin treatment. As for caspase-3 expression, TgAPP displayed an increase which was the opposite with rutin. Finally, the increase in expression of the inflammatory markers IL-1β and IFN-γ in TgAPP mice was lowered by both quercetin and rutin. Collectively, these findings suggest that, of the two flavonoids, rutin may be included in a day-to-day diet as a form of adjuvant therapy in AD.

The Amyloid Precursor Protein Modulates the Position and Length of the Axon Initial Segment.

The amyloid precursor protein (APP) is linked to the genetics and pathogenesis of Alzheimer's disease (AD). It is the parent protein of the β-amyloid (Aβ) peptide, the main constituent of the amyloid plaques found in an AD brain. The pathways from APP to Aβ are intensively studied, yet the normal functions of APP itself have generated less interest. We report here that glutamate stimulation of neuronal activity leads to a rapid increase in App gene expression. In mouse and human neurons, elevated APP protein changes the structure of the axon initial segment (AIS) where action potentials are initiated. The AIS is shortened in length and shifts away from the cell body. The GCaMP8f Ca2+ reporter confirms the predicted decrease in neuronal activity. NMDA antagonists or knockdown of App block the glutamate effects. The actions of APP on the AIS are cell-autonomous; exogenous Aβ, either fibrillar or oligomeric, has no effect. In culture, APPSwe (a familial AD mutation) induces larger AIS changes than wild type APP. Ankyrin G and βIV-spectrin, scaffolding proteins of the AIS, both physically associate with APP, more so in AD brains. Finally, in humans with sporadic AD or in the R1.40 AD mouse model, both females and males, neurons have elevated levels of APP protein that invade the AIS. In vivo as in vitro, this increased APP is associated with a significant shortening of the AIS. The findings outline a new role for the APP and encourage a reconsideration of its relationship to AD.SIGNIFICANCE STATEMENT While the amyloid precursor protein (APP) has long been associated with Alzheimer's disease (AD), the normal functions of the full-length Type I membrane protein have been largely unexplored. We report here that the levels of APP protein increase with neuronal activity. In vivo and in vitro, modest amounts of excess APP alter the properties of the axon initial segment. The β-amyloid peptide derived from APP is without effect. Consistent with the observed changes in the axon initial segment which would be expected to decrease action potential firing, we show that APP expression depresses neuronal activity. In mouse AD models and human sporadic AD, APP physically associates with the scaffolding proteins of the axon initial segment, suggesting a relationship with AD dementia.

The US9-Derived Protein gPTB9TM Modulates APP Processing Without Targeting Secretase Activities

Alteration of neuronal protein processing is often associated with neurological disorders and is highly dependent on cellular protein trafficking. A prime example is the amyloidogenic processing of amyloid precursor protein (APP) in intracellular vesicles, which plays a key role in age-related cognitive impairment. Most approaches to correct this altered processing aim to limit enzymatic activities that lead to toxic products, such as protein cleavage by β-secretase and the resulting amyloid β production. A viable alternative is to direct APP to cellular compartments where non-amyloidogenic mechanisms are favored. To this end, we exploited the molecular properties of the herpes simplex virus 1 (HSV-1) transport protein US9 to guide APP interaction with preferred endogenous targets. Specifically, we generated a US9 chimeric construct that facilitates APP processing through the non-amyloidogenic pathway and tested it in primary cortical neurons. In addition to reducing amyloid β production, our approach controls other APP-dependent biochemical steps that lead to neuronal deficits, including phosphorylation of APP and tau proteins. Notably, it also promotes the release of neuroprotective soluble αAPP. In contrast to other neuroprotective strategies, these US9-driven effects rely on the activity of endogenous neuronal proteins, which lends itself well to the study of fundamental mechanisms of APP processing/trafficking. Overall, this work introduces a new method to limit APP misprocessing and its cellular consequences without directly targeting secretase activity, offering a novel tool to reduce cognitive decline in pathologies such as Alzheimer’s disease and HIV-associated neurocognitive disorders.

Verbenalin Reduces Amyloid-Beta Peptide Generation in Cellular and Animal Models of Alzheimer's Disease.

Verbenalin, among the major constituents of Verbena officinalis, has been reported to exhibit sleep-promoting and antioxidant activities. This study demonstrates the effects of verbenalin on amyloid-beta (Aβ) peptide generation in Swedish mutant amyloid precursor protein (APP)-overexpressing Neuro2a cells (SweAPP/N2a) and in Alzheimer's disease (AD) animal models. We further performed molecular biological analyses of these in vitro and in vivo models of AD. The effects of verbenalin were assessed based on the expression of factors related to Aβ peptide production using Western blotting, enzyme-linked immunosorbent assay, and immunohistochemistry (IHC). The intracellular expression and release of APP protein were both decreased by verbenalin treatment in SweAPP/N2a cells. Thus, the production of Aβ peptides was decreased. Compared to those in AD transgenic (Tg) mice, IHC revealed that verbenalin-treated animals showed decreased Aβ and tau expression levels in the hippocampus. In addition, verbenalin restored the expression of brain-derived neurotrophic factor (BDNF) in the hippocampus of AD animal models. These findings suggest that verbenalin may decrease Aβ formation both in vitro and in vivo. Verbenalin may also help improve the pathological hallmarks of AD.

Vav2 is a novel APP-interacting protein that regulates APP protein level

Amyloid precursor protein (APP) is a transmembrane protein that plays critical role in the pathogenesis of Alzheimer's disease (AD). It is also involved in many types of cancers. Increasing evidence has shown that the tyrosine phosphorylation site Y682 in the intracellular tail of APP is crucial for APP function. Here, we report that Vav2, a guanine nucleotide exchange factor (GEF) for Rho family GTPase, is a novel interaction partner of APP. We found that Vav2-SH2 domain was able to bind directly to the Y682-phosphorylated intracellular tail of APP through isothermal titration calorimetry and NMR titrating experiments. The crystal structure of Vav2-SH2 in complex with an APP-derived phosphopeptide was determined to understand the structural basis of this recognition specificity. The interaction of APP and Vav2 in a full-length manner was further confirmed in cells by GST pull-down, co-immunoprecipitation and immunofluorescence staining experiments. In addition, we found overexpression of Vav2 could inhibit APP degradation and markedly increase the protein levels of APP and its cleavage productions in 20E2 cells, and this function of Vav2 required a functional SH2 domain.

Aβ/Amyloid Precursor Protein-Induced Hyperexcitability and Dysregulation of Homeostatic Synaptic Plasticity in Neuron Models of Alzheimer's Disease.

Alzheimer’s disease (AD) is increasingly seen as a disease of synapses and diverse evidence has implicated the amyloid-β peptide (Aβ) in synapse damage. The molecular and cellular mechanism(s) by which Aβ and/or its precursor protein, the amyloid precursor protein (APP) can affect synapses remains unclear. Interestingly, early hyperexcitability has been described in human AD and mouse models of AD, which precedes later hypoactivity. Here we show that neurons in culture with either elevated levels of Aβ or with human APP mutated to prevent Aβ generation can both induce hyperactivity as detected by elevated calcium transient frequency and amplitude. Since homeostatic synaptic plasticity (HSP) mechanisms normally maintain a setpoint of activity, we examined whether HSP was altered in AD transgenic neurons. Using methods known to induce HSP, we demonstrate that APP protein levels are regulated by chronic modulation of activity and that AD transgenic neurons have an impaired adaptation of calcium transients to global changes in activity. Further, AD transgenic compared to WT neurons failed to adjust the length of their axon initial segments (AIS), an adaptation known to alter excitability. Thus, we show that both APP and Aβ influence neuronal activity and that mechanisms of HSP are disrupted in primary neuron models of AD.

Alpha- and Gamma-Tocopherol Modulates the Amyloidogenic Pathway of Amyloid Precursor Protein in an in vitro Model of Alzheimer's Disease: A Transcriptional Study.

The amyloid precursor protein (APP) processing pathway was altered in Alzheimer’s disease (AD) and contributed to abnormal amyloid-beta (Aβ) production, which forms insoluble interneuron protein aggregates known as amyloid plaques in the brain. Targeting the APP processing pathway is still fundamental for AD modifying therapy. Extensive research has evaluated the protective effects of vitamin E as an antioxidant and as a signaling molecule. The present study aimed to investigate the modulatory effects of different tocopherol isomers on the expression of genes involved in regulating the APP processing pathway in vitro. The screening for the effective tocopherol isomers in reducing APP expression and Aβ-42 was carried out in SH-SY5Y stably overexpressed APP Swedish. Subsequently, quantitative one-step real-time PCR was performed to determine the modulatory effects of selected tocopherol isomers on the expression of genes in SH-SY5Y stably overexpressed three different types of APP (wild-type, APP Swedish, and APP Swedish/Indiana). Our results showed that all tocopherol isomers, especially at higher concentrations (80–100 μM), significantly increased (p < 0.05) the cell viability in all cells group, but only α-tocopherol (ATF) and γ-tocopherol (GTF) significantly decreased (p < 0.05) the APP mRNA level without statistically significant APP protein level, accompanied with a reduced significance (p < 0.05) on the level of Aβ-42 in SH-SY5Y APP Swedish. On the other hand, β- and δ-tocopherol (BTF and DTF) showed no effects on the level of APP expression and Aβ-42. Subsequent results demonstrated that ATF and GTF significantly decreased (p < 0.05) the expression of gene beta-site APP cleaving enzyme (BACE1), APH1B, and Nicastrin (NCSTN), but significantly increased (p < 0.05) the expression of Sirtuin 1 (SIRT1) in SH-SY5Y stably expressed the mutant APP form. These findings suggested that ATF and GTF could modulate altered pathways and may help ameliorate the burden of amyloid load in AD.

The neuroprotective effects of oxygen therapy in Alzheimer’s disease: a narrative review

Alzheimer’s disease (AD) is a degenerative neurological disease that primarily affects the elderly. Drug therapy is the main strategy for AD treatment, but current treatments suffer from poor efficacy and a number of side effects. Non-drug therapy is attracting more attention and may be a better strategy for treatment of AD. Hypoxia is one of the important factors that contribute to the pathogenesis of AD. Multiple cellular processes synergistically promote hypoxia, including aging, hypertension, diabetes, hypoxia/obstructive sleep apnea, obesity, and traumatic brain injury. Increasing evidence has shown that hypoxia may affect multiple pathological aspects of AD, such as amyloid-beta metabolism, tau phosphorylation, autophagy, neuroinflammation, oxidative stress, endoplasmic reticulum stress, and mitochondrial and synaptic dysfunction. Treatments targeting hypoxia may delay or mitigate the progression of AD. Numerous studies have shown that oxygen therapy could improve the risk factors and clinical symptoms of AD. Increasing evidence also suggests that oxygen therapy may improve many pathological aspects of AD including amyloid-beta metabolism, tau phosphorylation, neuroinflammation, neuronal apoptosis, oxidative stress, neurotrophic factors, mitochondrial function, cerebral blood volume, and protein synthesis. In this review, we summarized the effects of oxygen therapy on AD pathogenesis and the mechanisms underlying these alterations. We expect that this review can benefit future clinical applications and therapy strategies on oxygen therapy for AD.

MiR-129 Regulates Cell Viability in Alzheimer’s Disease Through Targeting Amyloid Precursor Protein (APP)

This study intends to explore miR-129’s effect on cell viability of Alzheimer’s disease by regulating the target gene APP. The hippocampal neurons were assigned into model group (MO group); mimetic group (SI group); inhibitor group (IN group) followed by analysis of hippocampal neuronal cell proliferation and activity, APP protein content, miR-129 expression and cell apoptosis by CCK-8 assay, Western blot method, MTT assay, qRT-PCR and flow cytometry. miR-129 expression of hippocampal neurons in IN group was lowest. Compared with IN and MO groups, SI group had significantly increased miR-129 level and reduced number of hippocampal neuron apoptosis (P &lt; 0.05). Compared with IN group, MO group had significantly reduced cell apoptosis (P &lt; 0.05). SI group had highest number of hippocampal neurons proliferation followed by IN group. SI group had highest OD value followed by MO group and IN group. The cell activity of SI group was higher than that of IN group and MO group (both P &lt; 0.05). Compared with SI group, rat neuron activity in MO group was significantly higher than IN group (P &lt; 0.05). The APP protein expression of hippocampal neuron cells in SI group was lowest followed by MO group and IN group (P &lt; 0.05). In conclusion, the low miR-129 expression can inhibit the activity of hippocampal neurons possibly through up-regulation of APP protein content.

Ketamine promotes the amyloidogenic pathway by regulating endosomal pH

Ketamine is an anesthetic and addictive drug that can cause cognitive dysfunction and neuroinflammation. Studies have shown that carboxy-terminal fragment derived from β-secretase (CTF-β) and amyloid beta (Aβ), the amyloidogenic products of amyloid precursor protein (APP), can also induce neuroinflammation and impair cognitive function. However, it remains unclear whether ketamine regulates the amyloidogenic pathway. In the endosome, APP is cleaved by beta-site amyloid precursor protein cleaving enzyme 1 (BACE1), whose activity is influenced by pH. Endosomal acidification is mainly regulated by sodium hydrogen exchanger 6 (NHE6), which leaks protons out of endosomes, and vacuolar proton translocating ATPases (V-ATPase), which pump protons into endosomes. Therefore, we hypothesized that ketamine lowers the endosomal pH by reducing the endosomal NHE6 protein level, and this hyperacidification promotes the amyloidogenic pathway. We set up C57BL/6 J mouse models using 10, 20, 40, 80, and 100 mg/kg ketamine administration and SH-SY5Y cell models using 1, 10, 100, and 1000 μM ketamine administration to investigate its effects on the amyloidogenic pathway at different doses. Western blotting results showed that 100 mg/kg ketamine treatment in vivo and 1000 μM ketamine treatment in vitro increased endosomal BACE1 and CTF-β protein levels and reduced endosomal NHE6 and APP protein levels. The endosomal accumulation of BACE1 caused by ketamine administration was also observed using confocal imaging. Moreover, flow cytometry indicated that ketamine treatment lowered the endosomal pH value of SH-SY5Y cells. Later, cells were pretreated with monensin to restore the endosomal pH. Monensin did not affect amyloidogenic-related proteins or NHE6 directly; therefore, ketamine-promoted endosomal amyloidogenic processing and BACE1 accumulation were depleted by restoring endosomal acidity through monensin pretreatment. Finally, knockdown of NHE6 promoted the amyloidogenic pathway similarly and prevented further enhancement by ketamine. These results indicated that the effects of ketamine on the amyloidogenic pathway were dependent on the reduction of NHE6 and endosomal pH.

Correlation between microRNA-320 and postoperative delirium in patients undergoing tibial fracture internal fixation surgery

BackgroundAlthough the incidence of postoperative delirium (POD) in the elderly after surgery are rising as individuals are living longer, the pathogenesis of POD remains poorly understood. It has been suggested that miRNA-320 may play a role in POD based on animal study and human study.MethodsWe first carried out an animal study, and designed and conducted a human study based on the result of animal study. The aged rats were randomly assigned to five groups: the control (C), anesthesia and surgery (AS), saline (NS), agomir-320 (AG), and antagomir-320 (AT) groups. Postoperative spatial learning and memory in rats were analyzed by the Morris water maze and the open field tests. The plasma levels of insulin-like growth factor-1 (IGF-1), amyloid precursor protein (APP) proteins, miRNA320 and IGF-1mRNA were measured by ELISA and qRT-PCR, respectively. A total of 240 Chinese Han patients over 65 years who underwent tibial fracture internal fixation were included in the PNDABLE study. POD cases and non-POD controls (1:1 matched) were selected by an anesthesiologist using Confusion Assessment Method.ResultsFor Group AS, the escape latency was significantly longer and the ratio of time spent in the target quadrant was significantly reduced, APP and miR-320 were upregulated and IGF-1mRNA was downregulated compared with Group C. For Group AG, the escape latency was significantly longer and the ratio of time spent in the target quadrant was significantly reduced, APP and miR-320 were upregulated and IGF-1mRNA was downregulated compared with Group AS. For Group AT, the escape latency was significantly reduced and the ratio of time spent in the target quadrant was significantly longer, APP and miR-320 were downregulated and IGF-1mRNAwas upregulated compared with Group AS. Compared with NPOD patients, the expressions of plasma miR-320 and APP protein were increased and the expression of plasma IGF-1 mRNA was decreased in POD patients after surgery.ConclusionsMiRNA-320 might play a role in up-regulating the levels of IGF-1mRNA and APP protein, which offered a new target for POD treatment.Trial registrationCorrelation of perioperative neurocognitive disorders with lifestyle and biomarkers. ChiCTR2000033439. Registered 1 June 2020.

Members of the vertebrate contactin and amyloid precursor protein families interact through a conserved interface

Contactins (CNTNs) are neural cell adhesion molecules that encode axon-target specificity during the patterning of the vertebrate visual and olfactory systems. Because CNTNs are tethered to the plasma membrane by a glycosylphosphatidylinositol anchor, they lack an intracellular region to communicate across the membrane. Instead, they form coreceptor complexes with distinct transmembrane proteins to transmit signals inside the cell. In particular, a complex of CNTN4 and amyloid precursor protein (APP) is known to guide the assembly of specific circuits in the visual system. Here, using in situ hybridization in zebrafish embryos, we show that CNTN4, CNTN5, and the APP homologs, amyloid beta precursor like protein 1 and amyloid beta precursor like protein 2, are expressed in olfactory pits, suggesting that these receptors may also function together in the organization of olfactory tissues. Furthermore, we use biochemical and structural approaches to characterize interactions between members of these two receptor families. In particular, APP and amyloid beta precursor like protein 1 interact with CNTN3–5, whereas amyloid beta precursor like protein 2 only binds to CNTN4 and CNTN5. Finally, structural analyses of five CNTN–amyloid pairs indicate that these proteins interact through a conserved interface involving the second fibronectin type III repeat of CNTNs and the copper-binding domain of amyloid proteins. Overall, this work sets the stage for analyzing CNTN–amyloid-mediated connectivity in vertebrate sensory circuits.

Posiphen Reduces the Levels of Huntingtin Protein through Translation Suppression.

Posiphen tartrate (Posiphen) is an orally available small molecule that targets a conserved regulatory element in the mRNAs of amyloid precursor protein (APP) and α-synuclein (αSYN) and inhibits their translation. APP and αSYN can cause neurodegeneration when their aggregates induce neurotoxicity. Therefore, Posiphen is a promising drug candidate for neurodegenerative diseases, including Alzheimer’s disease and Parkinson’s disease. Posiphen’s safety has been demonstrated in three independent phase I clinical trials. Moreover, in a proof of concept study, Posiphen lowered neurotoxic proteins and inflammatory markers in cerebrospinal fluid of mild cognitive impaired patients. Herein we investigated whether Posiphen reduced the expression of other proteins, as assessed by stable isotope labeling with amino acids in cell culture (SILAC) followed by mass spectrometry (MS)-based proteomics. Neuroblastoma SH-SY5Y cells, an in vitro model of neuronal function, were used for the SILAC protein profiling response. Proteins whose expression was altered by Posiphen treatment were characterized for biological functions, pathways and networks analysis. The most significantly affected pathway was the Huntington’s disease signaling pathway, which, along with huntingtin (HTT) protein, was down-regulated by Posiphen in the SH-SY5Y cells. The downregulation of HTT protein by Posiphen was confirmed by quantitative Western blotting and immunofluorescence. Unchanged mRNA levels of HTT and a comparable decay rate of HTT proteins after Posiphen treatment supported the coclusion that Posiphen reduced HTT via downregulation of the translation of HTT mRNA. Meanwhile, the downregulation of APP and αSYN proteins by Posiphen was also confirmed. The mRNAs encoding HTT, APP and αSYN contain an atypical iron response element (IRE) in their 5′-untranslated regions (5′-UTRs) that bind iron regulatory protein 1 (IRP1), and Posiphen specifically bound this complex. Conversely, Posiphen did not bind the IRP1/IRE complex of mRNAs with canonical IREs, and the translation of these mRNAs was not affected by Posiphen. Taken together, Posiphen shows high affinity binding to the IRE/IRP1 complex of mRNAs with an atypical IRE stem loop, inducing their translation suppression, including the mRNAs of neurotoxic proteins APP, αSYN and HTT.