Intracellular amyloid beta expression leads to dysregulation of the mitogen-activated protein kinase and bone morphogenetic protein-2 signaling axis

Gastrodin ameliorates synaptic impairment, mitochondrial dysfunction and oxidative stress in N2a/APP cells

Alzheimer's disease is characterized by abnormal β-amyloid and tau accumulation, mitochondrial dysfunction, oxidative stress, and synaptic dysfunction. Here, we aimed to assess the mechanisms and signalling pathways in the neuroprotective effect of gastrodin, a phenolic glycoside, on murine neuroblastoma N2a cells expressing human Swedish mutant APP (N2a/APP). We found that gastrodin increased the levels of presynaptic-SNAP, synaptophysin, and postsynaptic-PSD95 and reduced phospho-tau Ser396, APP and Aβ1-42 levels in N2a/APP cells. Gastrodin treatment reduced reactive oxygen species generation, lipid peroxidation, mitochondrial fragmentation and DNA oxidation; restored mitochondrial membrane potential and intracellular ATP production. Upregulated phospho-GSK-3β and reduced phospho-ERK and phospho-JNK were involved in the protective effect of gastrodin. In conclusion, we demonstrated the neuroprotective effect of gastrodin in the N2a/APP cell line by ameliorating the impairment on synaptic and mitochondrial function, reducing tau phosphorylation, Aβ1-42 levels as well as reactive oxygen species generation. These results provide new mechanistic insights into the potential effect of gastrodin in the treatment of Alzheimer's disease.

Targeting CDH17 with Chimeric Antigen Receptor-Redirected T Cells in Small Cell Lung Cancer

BACKGROUND

Chimeric antigen receptor T cell (CAR-T) therapy stands as a precise and targeted approach in the treatment of malignancies. In this study, we investigated the feasibility of targeting Cadherin 17 (CDH17) with CDH17 CAR-T cells as a therapeutic modality for small cell lung cancer (SCLC).

METHODS

CDH17 expression levels were assessed in human SCLC tumor tissues and cell lines using qPCR and Western blot. Subsequently, we established CDH17 CAR-T cells and assessed their cytotoxicity by co-culturing them with various SCLC cell lines at different effector-to-target (E:T) ratios, complemented by ELISA assays. To ascertain the specificity of CDH17 CAR-T cells, we conducted experiments on SCLC cells with and without CDH17 expression (shRNAs). Furthermore, we employed an SCLC xenograft model to evaluate the in vivo efficacy of CDH17 CAR-T cells.

RESULTS

Our results revealed a significant upregulation of CDH17 in both SCLC tissues and cell lines. CDH17 CAR-T cells exhibited robust cytotoxic activity against SCLC cells in vitro, while demonstrating no cytotoxicity towards CDH17-deficient SCLC cells and HEK293 cells that lack CDH17 expression. Importantly, the production of IFN-γ and TNF-α by CDH17 CAR-T cells correlated with their cytotoxic potency. Additionally, treatment with CDH17 CAR-T cells significantly decelerated the growth rate of SCLC-derived xenograft tumors in vivo. Remarkably, no significant difference in body weight was observed between the control group and the group treated with CDH17 CAR-T cells.

CONCLUSIONS

The preclinical data open further venues for the clinical use of CDH17 CAR-T cells as an immunotherapeutic strategy for SCLC treatment.

Comparative phytochemical studies on the roots of Polygala azizsancarii and P. peshmenii and neuroprotective activities of the two xanthones

Six known sucrose mono-, di- and triesters and five xanthone derivatives were isolated from the roots of Polygala peshmenii Eren, Parolly, Raus & Kürschner which is a narrow species endemic to Türkiye. Among the xanthones, 1,7-dihydroxy-2,3-methylenedioxy-5,6-dimethoxy-xanthone is an undescribed compound isolated for the first time from a natural source. The studies on the roots of P. azizsancarii Dönmez have resulted in the isolation of four known compounds including sucrose mono-, di- and triesters. The structures of the sucrose esters and xanthones isolated from P. azizsancarii and P. peshmenii were established by spectroscopic methods, including 1D-NMR (¹H NMR, ¹³C NMR, DEPT-135), 2D-NMR (COSY, NOESY, HSQC, HMBC). Neuroprotective activities of two xanthones, 1,3,6-trihydroxy-2,5,7-trimethoxyxanthone and 3-O-β-D-glucopyranosyloxy-1,6-dihydroxy-2,5,7-trimethoxyxanthone isolated from the roots of P. azizsancarii were evaluated in vitro using in a cellular model of Alzheimer's disease. SKNAS human neuroblastoma cells were used in the study and treated with different consecrations of Aβ₂₅₋₃₅ oligomer for up to 48 h. Cell viability was evaluated using MTT assay. The distribution of β-amyloid, α-synuclein, tau, JAK2, STAT3, caspase 3 and BMP-2 were investigated using indirect immunoperoxidase staining. Our results suggested that both xanthones control tau aggregation with no effect on β-amyloid plaque formation. In addition, for neuronal pathophysiology in AD cell model, decreased distributions of JAK/STAT3 and BMP2 signaling pathways were demonstrated, therefore they play a role in the protective effect on neurons in neurodegenerative disease. A significant decrease in caspase 3 immunoreactivity was detected after the administration of both compounds in AD cells. Therefore, both compounds control neuronal pathophysiology and rescue cell death in AD disease.

Network pharmacology reveals that Berberine may function against Alzheimer's disease via the AKT signaling pathway

Objective

To investigate the mechanism underlying the effects of berberine (BBR) in the treatment of Alzheimer's disease (AD).

Methods

3 × Tg AD mice were treated with BBR for 3 months, then the open field test (OFT), the novel object recognition test (NOR) and the Morris water maze (MWM) test were performed to assess behavioral performance. Hematoxylin-eosin (HE) staining, Nissl staining were used to examine histopathological changes. The pharmacological and molecular properties of BBR were obtained from the TCMSP database. BBR-associated AD targets were identified using the PharmMapper (PM), the comparative toxicogenomics database (CTD), DisGeNet and the human gene database (GeneCards). Core networks and BBR targets for the treatment of AD were identified using PPI network and functional enrichment analyses. AutoDock software was used to model the interaction between BBR and potential targets. Finally, RT-qPCR, western blotting were used to validate the expression of core targets.

Results

Behavioral experiments, HE staining and Nissl staining have shown that BBR can improve memory task performance and neuronal damage in the hippocampus of AD mice. 117 BBR-associated targets for the treatment of AD were identified, and 43 genes were used for downstream functional enrichment analysis in combination with the results of protein-protein interaction (PPI) network analysis. 2,230 biological processes (BP) terms, 67 cell components (CC) terms, 243 molecular function (MF) terms and 118 KEGG terms were identified. ALB, EGFR, CASP3 and five targets in the PI3K-AKT signaling pathway including AKT1, HSP90AA1, SRC, HRAS, IGF1 were selected by PPI network analysis, validated by molecular docking analysis and RT-q PCR as core targets for further analysis. Akt1 mRNA expression levels were significantly decreased in AD mice and significantly increased after BBR treatment (p < 0.05). Besides, AKT and ERK phosphorylation decreased in the model group, and BBR significantly increased their phosphorylation levels.

Conclusion

AKT1, HSP90AA1, SRC, HRAS, IGF1 and ALB, EGFR, CASP3 were core targets of BBR in the treatment of AD. BBR may exert a neuroprotective effect by modulating the ERK and AKT signaling pathways.

Neuroprotective effects of exogenous brain-derived neurotrophic factor on amyloid-beta 1-40-induced retinal degeneration

Amyloid-beta (Aβ)-related alterations, similar to those found in the brains of patients with Alzheimer's disease, have been observed in the retina of patients with glaucoma. Decreased levels of brain-derived neurotrophic factor (BDNF) are believed to be associated with the neurotoxic effects of Aβ peptide. To investigate the mechanism underlying the neuroprotective effects of BDNF on Aβ1-40-induced retinal injury in Sprague-Dawley rats, we treated rats by intravitreal administration of phosphate-buffered saline (control), Aβ1-40 (5 nM), or Aβ1-40 (5 nM) combined with BDNF (1 µg/mL). We found that intravitreal administration of Aβ1-40 induced retinal ganglion cell apoptosis. Fluoro-Gold staining showed a significantly lower number of retinal ganglion cells in the Aβ1-40 group than in the control and BDNF groups. In the Aβ1-40 group, low number of RGCs was associated with increased caspase-3 expression and reduced TrkB and ERK1/2 expression. BDNF abolished Aβ1-40-induced increase in the expression of caspase-3 at the gene and protein levels in the retina and upregulated TrkB and ERK1/2 expression. These findings suggest that treatment with BDNF prevents RGC apoptosis induced by Aβ1-40 by activating the BDNF-TrkB signaling pathway in rats.

Novel therapeutic mechanism of action of metformin and its nanoformulation in Alzheimer's disease and role of AKT/ERK/GSK pathway

INTRODUCTION

Brain Insulin-resistance plays a critical role in pathogenesis of Alzheimer's disease (AD). Current study explored the therapeutic mechanism of metformin (insulin sensitizer) and its solid-lipid nanoformulation (SLN) in rat-model of AD. In our study, SLN was prepared using microemulsion method. AD was induced with ICV-Aβ whereas the control-group (sham) received ICV-NS. Treatment arms included, disease-control (no treatment), Metformin (50 mg/kg, 100 mg/kg and 150 mg/kg), SLN-metformin 50 mg/kg and memantine 1.8 mg/kg (positive-control). Animals were tested for cognitive performance (EPM, MWM) after 21 days of therapy and sacrificed. Aβ (1-42), hyperphosphorylated tau, pAKTser473, GSK-3β, p-ERK (ELISA), metformin level(HPLC), neuronal injury score(H&E), Bcl2 and Bax(IHC) was evaluated in isolated brain. In our study, metformin-SLN were of spherical shape (size<200 nm) with 94.08% entrapment efficiency. Metformin was detectable in brain. Compared to sham, the disease-control group showed significantly higher (p ≤ 0.05) memory impairment(MWM and EPM), hyperphosphorylated tau, Aβ(1-42), neuronal-injury, Bax and lower Bcl-2 expression. Treatment with metformin and nanoformulation significantly reverse these parameters. AKT-ERK-GSK3β-Hyperphosphorylated tau pathway was found to be involved in the protective efficacy of metformin. To conclude, both metformin and its SLN were found to be effective as therapeutic agents in AD which act through the AKT-ERK-GSK3β-Hyperphosphorylated tau pathway. We need population based studies to confirm the same.

Implicative role of epidermal growth factor receptor and its associated signaling partners in the pathogenesis of Alzheimer's disease

Epidermal growth factor receptor (EGFR) plays a pivotal role in early brain development, although its expression pattern declines in accordance with the maturation of the active nervous system. However, recurrence of EGFR expression in brain cells takes place during neural functioning decline and brain atrophy in order to maintain the homeostatic neuronal pool. As a consequence, neurotoxic lesions such as amyloid beta fragment (Aβ_1-42) formed during the alternative splicing of amyloid precursor protein in Alzheimer's disease (AD) elevate the expression of EGFR. This inappropriate peptide deposition on EGFR results in the sustained phosphorylation of the downstream signaling axis, leading to extensive Aβ_1-42 production and tau phosphorylation as subsequent pathogenesis. Recent reports convey that the pathophysiology of AD is correlated with EGFR and its associated membrane receptor complex molecules. One such family of molecules is the annexin superfamily, which has synergistic relationships with EGFR and is known for membrane-bound signaling that contributes to a variety of inflammatory responses. Besides, Galectin-3, tissue-type activated plasminogen activator, and many more, which lineate the secretion of pro-inflammatory cytokines (TNF-α, IL-1β, IL-6, and IL-18) result in severe neuronal loss. Altogether, we emphasized the perspectives of cellular senescence up-regulated by EGFR and its associated membrane receptor molecules in the pathogenesis of AD as a target for a therapeutical alternative to intervene in AD.

Role of Intracellular Amyloid β as Pathway Modulator, Biomarker, and Therapy Target

The β- and γ-secretase-driven cleavage of the amyloid precursor protein (APP) gives rise to the amyloid β peptide, which is believed to be the main driver of neurodegeneration in Alzheimer’s disease (AD). As it is prominently detectable in extracellular plaques in post-mortem AD brain samples, research in recent decades focused on the pathological role of extracellular amyloid β aggregation, widely neglecting the potential meaning of very early generation of amyloid β inside the cell. In the last few years, the importance of intracellular amyloid β (iAβ) as a strong player in neurodegeneration has been indicated by a rising number of studies. In this review, iAβ is highlighted as a crucial APP cleavage fragment, able to manipulate intracellular pathways and foster neurodegeneration. We demonstrate its relevance as a pathological marker and shed light on initial studies aiming to modulate iAβ through pharmacological treatment, which has been shown to have beneficial effects on cognitive properties in animal models. Finally, we display the relevance of viral infections on iAβ generation and point out future directions urgently needed to manifest the potential relevance of iAβ in Alzheimer’s disease.

Does polysaccharide glycogen behave as a promoter of amyloid fibril formation at physiologically relevant concentrations?

We investigated the influence of glycogen (GG), phytoglycogen (PG), mannan (MAN) and cinnamoyl-modified GG (GG-CIN) on amyloid fibril formation. We used hen egg-white lysozyme (HEWL) as a model system and amyloid beta peptide (1-42) (Aβ1-42) as an Alzheimer's disease-relevant system. For brief detection of fibrils was used thioflavin T (ThT) fluorescence assay and the results were confirmed by transmission electron microscopy (TEM). We also deal with the interaction of polysaccharides and HEWL with isothermal titration calorimetry (ITC) and dynamic light scattering (DLS). We found that all polysaccharides accelerated the formation of amyloid fibrils from both HEWL and Aβ1-42. At high but physiologically relevant concentrations of GG, amyloid fibril formation was extremely accelerated for HEWL. Therefore, on the basis of the herein presented in vitro data, we hypothesize, that dietary d-glucose intake may influence amyloid fibril formation not only by influencing regulatory pathways, but also by direct glycogen-amyloid precursor protein molecular interaction, as glycogen levels in tissues are highly dependent on d-glucose intake.

Amyloidosis increase is not attenuated by long-term calorie restriction or related to neuron density in the prefrontal cortex of extremely aged rhesus macaques

As human lifespan increases and the population ages, diseases of aging such as Alzheimer's disease (AD) are a major cause for concern. Although calorie restriction (CR) as an intervention has been shown to increase healthspan in many species, few studies have examined the effects of CR on brain aging in primates. Using postmortem tissue from a cohort of extremely aged rhesus monkeys (22-44 years old, average age 31.8 years) from a longitudinal CR study, we measured immunohistochemically labeled amyloid beta plaques in Brodmann areas 32 and 46 of the prefrontal cortex, areas that play key roles in cognitive processing, are sensitive to aging and, in humans, are also susceptible to AD pathogenesis. We also evaluated these areas for cortical neuron loss, which has not been observed in younger cohorts of aged monkeys. We found a significant increase in plaque density with age, but this was unaffected by diet. Moreover, there was no change in neuron density with age or treatment. These data suggest that even in the oldest-old rhesus macaques, amyloid beta plaques do not lead to overt neuron loss. Hence, the rhesus macaque serves as a pragmatic animal model for normative human aging but is not a complete model of the neurodegeneration of AD. This model of aging may instead prove most useful for determining how even the oldest monkeys are protected from AD, and this information may therefore yield valuable information for clinical AD treatments.

Axonal Degeneration in AD: The Contribution of Aβ and Tau

Alzheimer's disease (AD) represents the most common age-related neurodegenerative disorder, affecting around 35 million people worldwide. Despite enormous efforts dedicated to AD research over decades, there is still no cure for the disease. Misfolding and accumulation of Aβ and tau proteins in the brain constitute a defining signature of AD neuropathology, and mounting evidence has documented a link between aggregation of these proteins and neuronal dysfunction. In this context, progressive axonal degeneration has been associated with early stages of AD and linked to Aβ and tau accumulation. As the axonal degeneration mechanism has been starting to be unveiled, it constitutes a promising target for neuroprotection in AD. A comprehensive understanding of the mechanism of axonal destruction in neurodegenerative conditions is therefore critical for the development of new therapies aimed to prevent axonal loss before irreversible neuronal death occurs in AD. Here, we review current evidence of the involvement of Aβ and tau pathologies in the activation of signaling cascades that can promote axonal demise.

LOXL1 folding in exfoliation glaucoma

Exfoliation syndrome (XFS) is an age-related disease defined by the deposition of aggregated fibrous material (XFM) in the peri-cellular space. Principal morbidity occurs in the eye, where XFM accumulates on the anterior ocular tissues. GWAS have found that certain genetic variants of lysyl oxidase-like 1 (LOXL1), a matrix cross-linking enzyme that is required for elastic fiber formation confer risk for the development of XFS, but are not a single causative factor as many genetically affected individuals do not develop XFS or subsequent glaucoma (XFG). We have found that XFG cells display defects in lysosomes, microtubules, autophagy, and mitochondria resembling defects found in cells from age-related syndromes, such as the main neurodegenerative diseases. In the majority of these diseases, the determining cellular factor is a protein containing intrinsically disordered regions (IDRs) and displaying a high propensity for aggregation. We have found that in XFG patient-derived cells, LOXL1 protein is actively subjected to autophagic clearance, suggesting that LOXL1 is undergoing aggregation. In silico analysis demonstrates that LOXL1's first 369 aa constitute an IDR with the highest disorder probability peak centering around the known risk positions. Experimentally, we have found over-expression of either unmodified LOXL1 or fluorescent chimeras preserving the well-structured N-terminus cause copious intracellular aggregation and that aggregation wanes when the high IDR peaks are deleted. Overall, our work suggests that XFS/G results from the aggregation of the LOXL1 protein coupled with a reduction of cellular proteostasis capabilities in aging, resulting in a chronic build-up of LOXL1-containing protein aggregates.

Selection of Membrane RNA Aptamers to Amyloid Beta Peptide: Implications for Exosome-Based Antioxidant Strategies

The distribution of amyloid beta peptide 42 (Aβ42) between model exosomal membranes and a buffer solution was measured. The model membranes contained liquid-ordered regions or phosphatidylserine. Results demonstrated that up to ca. 20% of amyloid peptide, generated in the plasma (or intracellular) membrane as a result of proteolytic cleavage of amyloid precursor proteins by β- and γ-secretases, can stay within the membrane milieu. The selection of RNA aptamers that bind to Aβ42 incorporated into phosphatidylserine-containing liposomal membranes was performed using the selection-amplification (SELEX) method. After eight selection cycles, the pool of RNA aptamers was isolated and its binding to Aβ42-containing membranes was demonstrated using the gel filtration method. Since membranes can act as a catalytic surface for Aβ42 aggregation, these RNA aptamers may inhibit the formation of toxic amyloid aggregates that can permeabilize cellular membranes or disrupt membrane receptors. Strategies are proposed for using functional exosomes, loaded with RNA aptamers specific to membrane Aβ42, to reduce the oxidative stress in Alzheimer's disease and Down's syndrome.