Modulation of AβPP and GSK3β by Endoplasmic Reticulum Stress and Involvement in Alzheimer's Disease

Integrative single-cell RNA sequencing and mendelian randomization analysis reveal the potential role of synaptic vesicle cycling-related genes in Alzheimer's disease

BACKGROUND

Alzheimer's disease (AD) involves alterations in synaptic vesicle cycling (SVC), which significantly affect neuronal communication and function. Therefore, a thorough investigation into the potential roles of SVC-related genes (SVCRGs) in AD can enhance the identification of critical biomarkers that may influence disease progression and treatment responses.

METHODS

The datasets used in this study were sourced exclusively from public databases. By integrating differential expression analysis with Mendelian randomization (MR), we identified SVCRGs as biomarkers for AD. Functional characterization of these biomarkers was performed, followed by integration into a nomogram. Further investigation of immune infiltration in AD patients and healthy individuals was carried out. Ultimately, the potential cellular mechanisms of AD were explored through single-cell RNA sequencing (scRNA-seq) analysis.

RESULTS

ATP6V1D, ATP6V1G2, CLTB, and NSF were identified as biomarkers, exhibiting a positive correlation with each other and a downregulated expression in AD. These markers were pinpointed as protective factors for AD [odds ratio (OR) < 1, P < 0.05], with potential to reduce the risk of the disease. Integrated into a nomogram, they demonstrated satisfactory diagnostic performance and clinical utility, surpassing the use of single gene. They were collectively enriched in pathways related to "interferon gamma response", "inflammatory response", and "TNFα signaling via NFκB". Additionally, an increase in infiltration of 17 immune cell types in AD was noted, particularly cells associated with neuroinflammation such as activated CD8 T cells and various dendritic cells (DCs), suggesting an inflammatory milieu in AD while also displaying a negative correlation with the biomarkers. The cell types were further annotated, revealing specific expressions of biomarkers and uncovering the heterogeneity of excitatory neurons. A significant reduction in the overall number of excitatory neurons under AD conditions was observed, alongside consistent expression of biomarkers during the developmental stages of excitatory neurons.

CONCLUSION

By using MR, we firstly identified four SVCRGs as protective factors for AD, functioning through pathways associated with mitochondrial dysfunction, chronic inflammation, immune dysregulation, and neuronal damage. These genes had the potential to modulate immune cell infiltration activated in AD patients and exhibited cell-type-specific expression profiles within AD-related cellular contexts. Their findings provide novel insights and valuable references for future research on AD pathogenesis and therapeutic strategies.

Methylsulfinyl Hexyl Isothiocyanate (6-MSITC) from Wasabi Is a Promising Candidate for the Treatment of Cancer, Alzheimer's Disease, and Obesity

Methylsulfinyl hexyl isothiocyanate (6-MSITC) isolated from Eutrema japonicum is a promising candidate for the treatment of breast cancer, colorectal and stomach cancer, metabolic syndrome, heart diseases, diabetes, and obesity due to its anti-inflammatory and antioxidant properties. Also, its neuroprotective properties, improving cognitive function and protecting dopaminergic neurons, make it an excellent candidate for treating neurodegenerative diseases like dementia, Alzheimer's, and Parkinson's disease. 6-MSITC acts on many signaling pathways, such as PPAR, AMPK, PI3K/AKT/mTOR, Nrf2/Keap1-ARE, ERK1/2-ELK1/CHOP/DR5, and MAPK. However, despite the very promising results of in vitro and in vivo animal studies and a few human studies, the molecule has not yet been thoroughly tested in the human population. Nonetheless, wasabi should be classified as a "superfood" for the primary and secondary prevention of human diseases. This article reviews the current state-of-the-art research on 6-MSITC and its potential clinical uses, discussing in detail the signaling pathways activated by the molecule and their interactions.

Differential Cellular Interactome in Schizophrenia and Bipolar Disorder-Discriminatory Biomarker Role

Schizophrenia (SCH) and bipolar disorder (BD) are two of the most important psychiatric pathologies due to their high population incidence and disabling power, but they also present, mainly in their debut, high clinical similarities that make their discrimination difficult. In this work, the differential oxidative stress, present in both disorders, is shown as a concatenator of the systemic alterations-both plasma and erythrocyte, and even at the level of peripheral blood mononuclear cells (PBMC)-in which, for the first time, the different affectations that both disorders cause at the level of the cellular interactome were observed. A marked erythrocyte antioxidant imbalance only present in SCH generalizes to oxidative damage at the plasma level and shows a clear impact on cellular involvement. From the alteration of protein synthesis to the induction of death by apoptosis, including proteasomal damage, mitochondrial imbalance, and autophagic alteration, all the data show a greater cellular affectation in SCH than in BD, which could be linked to increased oxidative stress. Thus, patients with SCH in our study show increased endoplasmic reticulum (ER)stress that induces increased proteasomal activity and a multifactorial response to misfolded proteins (UPR), which, together with altered mitochondrial activity, generating free radicals and leading to insufficient energy production, is associated with defective autophagy and ultimately leads the cell to a high apoptotic predisposition. In BD, however, oxidative damage is much milder and without significant activation of survival mechanisms or inhibition of apoptosis. These clear differences identified at the molecular and cellular level between the two disorders, resulting from progressive afflictions in which oxidative stress can be both a cause and a consequence, significantly improve the understanding of both disorders to date and are essential for the development of targeted and preventive treatments.

The Protective Effect of Mangiferin on Formaldehyde-Induced HT22 Cell Damage and Cognitive Impairment

Formaldehyde (FA) has been found to induce major Alzheimer's disease (AD)-like features including cognitive impairment, Aβ deposition, and Tau hyperphosphorylation, suggesting that it may play a significant role in the initiation and progression of AD. Therefore, elucidating the mechanism underlying FA-induced neurotoxicity is crucial for exploring more comprehensive approaches to delay or prevent the development of AD. Mangiferin (MGF) is a natural C-glucosyl-xanthone with promising neuroprotective effects, and is considered to have potential in the treatment of AD. The present study was designed to characterize the effects and mechanisms by which MGF protects against FA-induced neurotoxicity. The results in murine hippocampal cells (HT22) revealed that co-treatment with MGF significantly decreased FA-induced cytotoxicity and inhibited Tau hyperphosphorylation in a dose-dependent manner. It was further found that these protective effects were achieved by attenuating FA-induced endoplasmic reticulum stress (ERS), as indicated by the inhibition of the ERS markers, GRP78 and CHOP, and downstream Tau-associated kinases (GSK-3β and CaMKII) expression. In addition, MGF markedly inhibited FA-induced oxidative damage, including Ca2+ overload, ROS generation, and mitochondrial dysfunction, all of which are associated with ERS. Further studies showed that the intragastric administration of 40 mg/kg/day MGF for 6 weeks significantly improved spatial learning ability and long-term memory in C57/BL6 mice with FA-induced cognitive impairment by reducing Tau hyperphosphorylation and the expression of GRP78, GSK-3β, and CaMKII in the brains. Taken together, these findings provide the first evidence that MGF exerts a significant neuroprotective effect against FA-induced damage and ameliorates mice cognitive impairment, the possible underlying mechanisms of which are expected to provide a novel basis for the treatment of AD and diseases caused by FA pollution.

Roles of traditional chinese medicine regulating neuroendocrinology on AD treatment

The incidence of sporadic Alzheimer's disease (AD) is increasing in recent years. Studies have shown that in addition to some genetic abnormalities, the majority of AD patients has a history of long-term exposure to risk factors. Neuroendocrine related risk factors have been proved to be strongly associated with AD. Long-term hormone disorder can have a direct detrimental effect on the brain by producing an AD-like pathology and result in cognitive decline by impairing neuronal metabolism, plasticity and survival. Traditional Chinese Medicine(TCM) may regulate the complex process of endocrine disorders, and improve metabolic abnormalities, as well as the resulting neuroinflammation and oxidative damage through a variety of pathways. TCM has unique therapeutic advantages in treating early intervention of AD-related neuroendocrine disorders and preventing cognitive decline. This paper reviewed the relationship between neuroendocrine and AD as well as the related TCM treatment and its mechanism. The advantages of TCM intervention on endocrine disorders and some pending problems was also discussed, and new insights for TCM treatment of dementia in the future was provided.

SERP1 reduces inchoate acute hepatic injury through regulation of endoplasmic reticulum stress via the GSK3β/β‑catenin/TCF/LEF signaling pathway

The liver is a crucial digestive organ of humans and in charge of detoxification. Acute hepatic injury is an aggressive type of hepatic disease and its harmful effect cannot be ignored. The present study examined the role and mechanism of stress-associated endoplasmic reticulum protein 1 (SERP1) in acute hepatic injury. Mice were injected intraperitoneally with D-galactosamine/lipopolysaccharide (LPS) and rat hepatocytes were induced by LPS to establish an acute hepatic injury model. Tissue lesions were observed by H&E staining, and biomarkers of hepatic injury in the serum were examined. Western blotting, immunohistochemistry and reverse transcription-quantitative PCR were performed to assess SERP1 expression in tissues and hepatocytes. A SERP1 overexpression plasmid was constructed to evaluate the role of SERP1 in inflammation, apoptosis, endoplasmic reticulum stress (ERS) and the GSK3β/β-catenin/T-cell factor (TCF)/lymphoid enhancing factor (LEF) signaling pathway. In addition, a GSK3β overexpression plasmid was constructed to investigate the role of GSK3β/β-catenin signal activation. Additionally, the present study investigated whether SERP1 regulated the endoplasmic reticulum via this pathway. In the present study, reliable animal and cellular hepatic injury models were established and verified. SERP1 overexpression reduced the expression of inflammatory factors, apoptosis-related proteins and ERS-related proteins, as well as the expression of proteins related to GSK3β/β-catenin/TCF/LEF signaling pathways. A GSK3β overexpression plasmid was constructed and it was revealed that GSK3β overexpression could reverse the effects of SERP1 overexpression in aforementioned aspects. This suggested that the activation of the GSK3β/β-catenin/TCF/LEF signaling pathway may be required for the regulation of SERP1. In conclusion, SERP1 regulated ERS via the GSK3β/β-catenin/TCF/LEF signaling pathway, thereby reducing inchoate acute hepatic injury.

Protective Effects and Mechanisms of Dendrobium nobile Lindl. Alkaloids on PC12 Cell Damage Induced by Aβ 25-35

BACKGROUND

Aβ deposition abnormally in the mitochondria can damage the mitochondrial respiratory chain and activate the mitochondrial-mediated apoptosis pathway, resulting in AD-like symptoms.

OBJECTIVE

To observe the protective effects of Dendrobium nobile Lindl. alkaloids (DNLA) on Aβ 25-35-induced oxidative stress and apoptosis in PC12 cells explore its possible protective mechanisms.

METHODS

PC12 cells were treated with DNLA with different concentrations (0.035 mg/L, 0.3 mg/L, and 3.5 mg/L) for 6 h, followed by administration with Aβ 25-35 (10 μM) for 24 h. MTT assay and flow cytometer observe the effect of DNLA on Aβ 25-35-induced cytotoxicity and apoptosis of PC12 cell. Based on the mitochondrial apoptosis pathway to study the antiapoptotic effect of DNLA on this model and its relationship with oxidative stress, flow cytometer detected the level of reactive oxygen species (ROS), and ELISA kits were used to detect superoxide dismutase activity (SOD) and glutathione (GSH) content in cells. The JC-1 fluorescent staining observed the effect of DNLA on the mitochondrial membrane potential (MMP) with inverted immunofluorescence microscopy. Western blot was used to detect the levels of mitochondrial apoptosis pathway-related protein and its major downstream proteins Bax, Bcl-2, cleaved-caspase-9, and cleaved-caspase-3.

RESULTS

DNLA can significantly improve the viability and apoptosis rate of PC12 cell damage induced by Aβ 25-35. It also can restore the reduced intracellular ROS content and MMP, while SOD activity and GSH content increase significantly. The expression of apoptosis-related protein Bax, cleaved-caspase-9, and cleaved-caspase-3 decreased when the Bcl-2 protein expression was significantly increased.

CONCLUSION

These findings suggest that it can significantly inhibit the apoptosis of PC12 cell damage induced by Aβ 25-35. The mechanism may reduce the level of cellular oxidative stress and thus inhibit the mitochondrial-mediated apoptosis pathway.

Berberine Reduces Aβ42 Deposition and Tau Hyperphosphorylation via Ameliorating Endoplasmic Reticulum Stress

Alzheimer’s disease (AD) is tightly related to endoplasmic reticulum stress (ER stress), which aggravates two dominant pathological manifestations of AD: senile plaques and neurofibrillary tangles. Berberine is widely applied in the clinical treatment of many diseases and is reported to have anti-AD effects. In the present study, berberine was shown to ameliorate ER stress and cognitive impairment in APP/PS1 mice. We found ER stress plays a role as a central hub for signal transduction, which was evidenced by the hyperactivation of glycogen synthase kinase 3β (GSK3β) to phosphorylate tau and the activation of PRKR-like endoplasmic reticulum kinase (PERK) subsequently to phosphorylate eukaryotic translation initiation factor-2 α (eIF2α). Also, eIF2α has regulated the expression of beta-site APP cleaving enzyme-1 (BACE1), which cleaves APP into pro-oligomerized amyloid beta 42 (Aβ₄₂), the main component of senile plaques, proven by using siRNA targeting at eIF2α. Mechanically, berberine can reduce GSK3β activity, contributing to the downregulation of tau phosphorylation. Berberine also suppressed Aβ₄₂ production via inhibiting the PERK/eIF2α/BACE1 signaling pathway. Taken together, these findings indicated that berberine had the potential to ameliorate two major pathological manifestations of AD mainly by suppressing ER stress. Our work provided knowledge on the pharmacological intervention of AD and the possible targets for future drug development.

Rutaecarpine Ameliorated High Sucrose-Induced Alzheimer's Disease Like Pathological and Cognitive Impairments in Mice

High sucrose can induce tau hyperphosphorylation and cognitive dysfunction/memory impairment as observed in Alzheimer's disease (AD). Rutaecarpine, a specific (transient receptor potential vanilloid 1 [TRPV1]) agonist, is neuroprotective against high sucrose diet-induced impairment, but detailed mechanisms are still elusive. In this study, we investigated whether rutaecarpine mitigates high sucrose diet-induced pathological alterations and cognitive in AD-like mice. Mice were administered fodder containing 0.01% rutaecarpine and 20% sucrose solution. Our results showed that rutaecarpine significantly attenuated high sucrose diet-induced spatial memory impairment and enhanced synaptic plasticity; rutaecarpine prevented high sucrose diet-induced tau hyperphosphorylation by decreasing glycogen synthase kinase-3β (GSK-3β) activity; activation of GSK-3β reversed the protective effect of rutaecarpine on learning and memory deficits, synaptic plasticity, and tau hyperphosphorylation induced by high-glucose diet significantly, suggesting that GSK-3β activation is required for high glucose-induced tau hyperphosphorylation. These results demonstrated that rutaecarpine can mitigate high sucrose diet-induced hyperphosphorylation of AD-associated tau protein and cognitive impairment by inhibiting GSK-3β, which supported that dietary rutaecarpine might have a promising use for therapeutic intervention of AD.

Gelsemine, a natural alkaloid extracted from Gelsemium elegans Benth. alleviates neuroinflammation and cognitive impairments in Aβ oligomer-treated mice

INTRODUCTION

Gelsemine is a natural alkaloid extracted from Gelsemium elegans Benth., a traditional Chinese medicinal herb. Gelsemine has been shown to penetrate the brain, and could produce neurological activities, such as anxiolytic and neuralgia-alleviating effects, suggesting that this natural compound might be used for treating nervous system diseases.

RESULTS

In this study, we have found, for the first time, that gelsemine at low concentrations (5-10 μg/kg) significantly alleviated cognitive impairments induced by β-amyloid (Aβ) oligomer, a main neurotoxin of Alzheimer's disease (AD). In addition, gelsemine substantially prevented Aβ oligomer-induced over-activation of microglia and astrocytes, indicating that gelsemine might reduce AD-related gliosis. Consistently, gelsemine inhibited the over-expression of pro-inflammatory cytokines, including interleukin-1β (IL-1β), interleukin-6 (IL-6), and tumor necrosis factor-α (TNF-α), in the brain of mice. Moreover, gelsemine largely increased the expression of pSer9-glycogen synthase kinase-3β (GSK3β), and decreased the hyper-phosphorylation of tau protein as evidenced by Western blotting analysis. Furthermore, gelsemine prevented Aβ oligomer-induced reduction of PSD-95, a representative post-synaptic protein.

CONCLUSION

All these results directly demonstrated the anti-Aβ oligomer neuroprotective properties of gelsemine, opening a novel perspective for the development of gelsemine-based therapeutics against Aβ-associated neurodegeneration disorders, including AD in particular.

Protein-protein interactions underlying the behavioral and psychological symptoms of dementia (BPSD) and Alzheimer's disease

Alzheimer’s Disease (AD) is a devastating neurodegenerative disorder currently affecting 45 million people worldwide, ranking as the 6^th highest cause of death. Throughout the development and progression of AD, over 90% of patients display behavioral and psychological symptoms of dementia (BPSD), with some of these symptoms occurring before memory deficits and therefore serving as potential early predictors of AD-related cognitive decline. However, the biochemical links between AD and BPSD are not known. In this study, we explored the molecular interactions between AD and BPSD using protein-protein interaction (PPI) networks built from OMIM (Online Mendelian Inheritance in Man) genes that were related to AD and two distinct BPSD domains, the Affective Domain and the Hyperactivity, Impulsivity, Disinhibition, and Aggression (HIDA) Domain. Our results yielded 8 unique proteins for the Affective Domain (RHOA, GRB2, PIK3R1, HSPA4, HSP90AA1, GSK3beta, PRKCZ, and FYN), 5 unique proteins for the HIDA Domain (LRP1, EGFR, YWHAB, SUMO1, and EGR1), and 6 shared proteins between both BPSD domains (APP, UBC, ELAV1, YWHAZ, YWHAE, and SRC) and AD. These proteins might suggest specific targets and pathways that are involved in the pathogenesis of these BPSD domains in AD.

Tanshinone IIA ameliorates cognitive deficits by inhibiting endoplasmic reticulum stress-induced apoptosis in APP/PS1 transgenic mice

Our previous data indicated that tanshinone IIA (tan IIA) improves learning and memory in a mouse model of Alzheimer's disease (AD) induced by streptozotocin via restoring cholinergic function, attenuating oxidative stress and blocking p38 MAPK signal pathway activation. This study aims to estimate whether tan IIA inhibits endoplasmic reticulum (ER) stress-induced apoptosis to prevent cognitive decline in APP/PS1 transgenic mice. Tan IIA (10 mg/kg and 30 mg/kg) was intraperitoneally administered to the six-month-old APP/PS1 mice for 30 consecutive days. β-amyloid (Aβ) plaques were measured by immunohistochemisty and Thioflavin S staining, apoptotic cells were observed by TUNEL, ER stress markers and apoptosis signaling proteins were investigated by western blotting and RT-PCR. Our results showed that tan IIA significantly ameliorates cognitive deficits and improves spatial learning ability of APP/PS1 mice in the nest-building test, novel object recognition test and Morris water maze test. Furthermore, tan IIA significantly reduced the deposition of Aβ plaques and neuronal apoptosis, and markedly prevented abnormal expression of glucose regulated protein 78 (GRP78), initiation factor 2α (eIF2α), inositol-requiring enzyme 1α (IRE1α), activating transcription factor 6 (ATF6), as well as suppressed the activation of C/EBP homologous protein (CHOP) and c-Jun N-terminal kinase (JNK) pathways in the parietal cortex and hippocampus. Moreover, tan IIA induced an up-regulation of the Bcl-2/Bax ratio and down-regulation of caspase-3 protein activity. Taken together, the above findings indicated that tan IIA improves learning and memory through attenuating Aβ plaques deposition and inhibiting ER stress-induced apoptosis. These results suggested that tan IIA might become a promising therapeutic candidate drug against AD.

Acylphloroglucinols as kinase inhibitors from Sargassum nigrifoloides

Three new acylphloroglucinols (1-3) and four known biosynthetically related analogs (4-7) were isolated from the ethanol extract of a brown alga Sargassum nigrifoloides. Structures for 1-7 were characterized via detailed spectroscopic analyses especially 2D NMR data. Screening of these compounds in Alzheimer's diseases-related bioassays revealed moderate inhibitory activities against two therapeutically important kinases, CDK5 and GSK3β. A preliminary structure-activity relationship was also discussed.

Astragaloside IV ameliorates endoplasmic reticulum stress‑induced apoptosis of Aβ25‑35‑treated PC12 cells by inhibiting the p38 MAPK signaling pathway

Endoplasmic reticulum stress (ERS) serves a vital role in the pathological development of Alzheimer's disease (AD). ERS can promote programmed cell death (apoptosis) during AD; however, the specific molecular mechanisms that lead to ERS remain unclear. It is very important that a drug for the treatment of AD is identified. Our previous studies indicated that astragaloside IV (AST IV) has anti-inflammatory effects and helps cells resist oxidative stress. In the present study, western blotting and reverse transcription semi-quantitative polymerase chain reaction were used to detect protein and mRNA expression levels, flow cytometry was used to measure intracellular reactive oxygen species (ROS) levels, and superoxide dismutase (SOD) and malondialdehyde (MDA) activity was detected using commercially available kits. The results demonstrated that SOD activity was decreased, and MDA content, ROS levels, and the expression levels of p38 mitogen-activated protein kinase (MAPK) and ERS-associated proteins, including binding immunoglobulin protein/glucose-regulated protein and growth arrest- and DNA damage -inducible gene 153/C/EBP homologous protein, were increased in amyloid β (Aβ)_25-35-treated PC12 cells. Furthermore, to investigate the role of p38 MAPK and the effects of AST IV in an in vitro model of AD, SB203580, a p38 MAPK signaling pathway inhibitor, and AST IV were administered to Aβ_25-35-treated PC12 cells. The results revealed that AST IV protected the cells against AD. This effect may be caused by decreases in ROS levels, which may inhibit the p38 MAPK signaling pathway and thereby suppress ERS in Aβ_25-35-treated PC12 cells.

Protective Effects of 6-(Methylsulfinyl)hexyl Isothiocyanate on Aβ1-42-Induced Cognitive Deficit, Oxidative Stress, Inflammation, and Apoptosis in Mice

Alzheimer's disease (AD) is the most common form of dementia among older people. Although soluble amyloid species are recognized triggers of the disease, no therapeutic approach is able to stop it. 6-(Methylsulfinyl)hexyl isothiocyanate (6-MSITC) is a major bioactive compound in Wasabia japonica, which is a typical Japanese pungent spice. Recently, in vivo and in vitro studies demonstrated that 6-MSITC has several biological properties. The aim of the present study was to investigate the neuroprotective activity of 6-MSITC in a murine AD model, induced by intracerebroventricular injection of β-amyloid oligomers (Aβ1-42O). The treatment with 6-MSITC started 1 h after the surgery for the next 10 days. Behavioral analysis showed that 6-MSITC ameliorated Aβ1-42O-induced memory impairments. The decrease of glutathione levels and increase of reactive oxygen species in hippocampal tissues following Aβ1-42O injection were reduced by 6-MSITC. Moreover, activation of caspases, increase of inflammatory factors, and phosphorylation of ERK and GSK3 were inhibited by 6-MSITC. These results highlighted an interesting neuroprotective activity of 6-MSITC, which was able to restore a physiological oxidative status, interfere positively with Nrf2-pathway, decrease apoptosis and neuroinflammation and contribute to behavioral recovery. Taken together, these findings demonstrated that 6-MSITC could be a promising complement for AD therapy.