Dysregulated APP expression and α-secretase processing of APP is involved in manganese-induced cognitive impairment

Circular RNA circRest regulates manganese induced cell apoptosis by targeting the mmu-miR-6914-5p/Ephb3 axis

Overexposure to manganese (Mn) can lead to neurotoxicity, the underlying mechanisms remain incompletely understood. Circular RNAs (circRNAs) have emerged as important regulators in various biological processes. It is plausible that circRNAs may be involved in the biological mechanisms underlying Mn caused neurotoxicity. Here, circRest was downregulated in Mn-exposed mouse neuroblastoma cells (N2a cells) by RNA sequencing and quantitative real-time PCR. When circRest was overexpressed, it led to an increase in cell viability and a decrease in apoptosis following Mn exposure. Conversely, silencing circRest resulted in opposite effects in N2a cells. Further investigation revealed that circRest acts as a mmu-miR-6914-5p sponge, and mmu-miR-6914-5p could bind and inhibit Ephb3, thereby promoting apoptosis in N2a cells. This was confirmed through RNA antisense purification and dual luciferase reporter assays. Additionally, the circRest/mmu-miR-6914-5p/Ephb3 axis may influence memory and learning in mice following Mn exposure. In conclusion, our study uncovers a novel mechanism by which circRest may attenuate Mn caused neurotoxicity via the mmu-miR-6914-5p/Ephb3 axis.

Ferroptosis at the crossroads of manganese-induced neurotoxicity: A retrospective study

Manganese is an essential trace element, but overexposure can cause neurotoxicity and subsequent neurodegenerative diseases. Ferroptosis is a form of cell death characterized by lipid peroxidation and iron overload inside cells, which is closely related to manganese neurotoxicity. Manganese can induce ferroptosis through multiple pathways: causing oxidative stress and increased cellular reactive oxygen species (ROS), resulting in lipid peroxidation; depleting glutathione (GSH) and weakening the antioxidant capacity of cells; disrupting iron metabolism and increasing iron-dependent lipid peroxidation; damaging mitochondrial function and disrupting the electron transport chain, leading to increased ROS production. Oxidative stress, iron metabolism disorders, lipid peroxidation, GSH depletion, and mitochondrial dysfunction, typical features of ferroptosis, have been observed in animal and cell models after manganese exposure. In summary, manganese can participate in the pathogenesis of neurodegenerative diseases by inducing events related to ferroptosis. This provides new insights into studying the mechanism of manganese neurotoxicity and developing therapeutic drugs.

A systematic review for the development of Alzheimer's disease in in vitro models: a focus on different inducing agents

Alzheimer's disease (AD) is the most common progressive neurodegenerative disease and is associated with dementia. Presently, various chemical and environmental agents are used to induce in-vitro models of Alzheimer disease to investigate the efficacy of different therapeutic drugs. We screened literature from databases such as PubMed, ScienceDirect, and Google scholar, emphasizing the diverse targeting mechanisms of neuro degeneration explored in in-vitro models. The results revealed studies in which different types of chemicals and environmental agents were used for in-vitro development of Alzheimer-targeting mechanisms of neurodegeneration. Studies using chemically induced in-vitro AD models included in this systematic review will contribute to a deeper understanding of AD. However, none of these models can reproduce all the characteristics of disease progression seen in the majority of Alzheimer's disease subtypes. Additional modifications would be required to replicate the complex conditions of human AD in an exact manner. In-vitro models of Alzheimer's disease developed using chemicals and environmental agents are instrumental in providing insights into the disease's pathophysiology; therefore, chemical-induced in-vitro AD models will continue to play vital role in future AD research. This systematic screening revealed the pivotal role of chemical-induced in-vitro AD models in advancing our understanding of AD pathophysiology and is therefore important to understand the potential of these chemicals in AD pathogenesis.

Long-term cadmium exposure impairs cognitive function by activating lnc-Gm10532/m6A/FIS1 axis-mediated mitochondrial fission and dysfunction

Cadmium (Cd), a ubiquitous environmental contaminant, is deemed a possible aetiological cause of cognitive disorders in humans. Nevertheless, the exact mechanism by which chronic exposure to Cd causes neurotoxicity is not fully understood. In this study, mouse neuroblastoma cells (Neuro-2a cells) and primary hippocampal neurons were exposed to low-dose (1, 2, and 4 μM for Neuro-2a cells or 0.5, 1, and 1.5 μM for hippocampal neurons) cadmium chloride (CdCl₂) for 72 h (h), and male mice (C57BL/6J, 8 weeks) were orally administered CdCl₂ (0.6 mg/L, approximately equal to 2.58 μg/kg·bw/d) for 6 months to investigate the effects and mechanism of chronic Cd-induced neurotoxicity. Here, chronic exposure to Cd impaired mitochondrial function by promoting excess reactive oxygen species (ROS) production, altering mitochondrial membrane potential (Δψm) and reducing adenosine triphosphate (ATP) content, contributing to neuronal cell death. Specifically, microarray analysis revealed that the long noncoding RNA Gm10532 (lnc-Gm10532) was most highly expressed in Neuro-2a cells exposed to 4 μM CdCl₂ for 72 h compared with controls, and inhibition of lnc-Gm10532 significantly antagonized CdCl₂-induced mitochondrial dysfunction and neurotoxicity. Mechanistically, lnc-Gm10532 increased Fission 1 (FIS1) expression and mitochondrial fission by recruiting the m6A writer methyltransferase-like 14 (METTL14) and enhancing m6A modification of Fis1 mRNA. Moreover, lnc-Gm10532 was also required for chronic Cd-induced mitochondrial dysfunction and memory deficits in a rodent model. Therefore, data of this study reveal a new epigenetic mechanism of chronic Cd neurotoxicity.

Recent Advances in the Study of Na+/K+-ATPase in Neurodegenerative Diseases

Na⁺/K⁺-ATPase (NKA), a large transmembrane protein, is expressed in the plasma membrane of most eukaryotic cells. It maintains resting membrane potential, cell volume and secondary transcellular transport of other ions and neurotransmitters. NKA consumes about half of the ATP molecules in the brain, which makes NKA highly sensitive to energy deficiency. Neurodegenerative diseases (NDDs) are a group of diseases characterized by chronic, progressive and irreversible neuronal loss in specific brain areas. The pathogenesis of NDDs is sophisticated, involving protein misfolding and aggregation, mitochondrial dysfunction and oxidative stress. The protective effect of NKA against NDDs has been emerging gradually in the past few decades. Hence, understanding the role of NKA in NDDs is critical for elucidating the underlying pathophysiology of NDDs and identifying new therapeutic targets. The present review focuses on the recent progress involving different aspects of NKA in cellular homeostasis to present in-depth understanding of this unique protein. Moreover, the essential roles of NKA in NDDs are discussed to provide a platform and bright future for the improvement of clinical research in NDDs.

Amyloid Cascade Hypothesis for the Treatment of Alzheimer's Disease: Progress and Challenges

The amyloid cascade hypothesis has always been a research focus in the therapeutic field of Alzheimer's disease (AD) since it was put forward. Numerous researchers attempted to find drugs for AD treatment based on this hypothesis. To promote the research of anti-AD drugs development, the current hypothesis and pathogenesis were reviewed with expounding of β-amyloid generation from its precursor protein and related transformations. Meanwhile, the present drug development strategies aimed at each stage in this hypothesis were also summarized. Several strategies especially immunotherapy showed the optimistic results in clinical trials, but only a small percentage of them eventually succeeded. In this review, we also tried to point out some common problems of drug development in preclinical and clinical studies which might be settled through multidisciplinary cooperation as well as the understanding that reinforces the amyloid cascade hypothesis.

Role of p53 methylation in manganese-induced cyclooxygenase-2 expression in BV2 microglial cells

Manganese (Mn) is an essential cofactor for many enzymes and plays an important role in normal growth and development. However, excess exposure to manganese (Mn) may be an important environmental factor leading to neurodegeneration. The overexpression of microglial cyclooxygenase-2 (COX-2) plays a key role in neuroinflammation in neurodegenerative diseases. The existing data suggest that Mn can induce neuroinflammation by up-regulating COX-2 expression. However, the mechanisms involved in Mn-induced microglial COX-2 up-regulation remain to be determined. The aim of this study was to investigate the role of p53 in Mn-induced COX-2 expression in microglial cells. The results showed that Mn exposure induced the up-regulation of COX-2 and inhibited the expression of p53 in BV2 microglial cells. The addition of p53 activator and the over-expression of p53 blocked the expression of COX-2 and prostaglandin E2 (PGE2), a COX-2 downstream effector, induced by Mn. Further, Mn increased the methylation of p53 DNA in microglia, while the addition of demethylation reagent 5-Aza-dC enhanced the expression of p53 but decreased the expression of COX-2. These results suggested that Mn may inhibit p53 expression through induction of DNA methylation, which can further induce the expression of COX-2 in microglial cells.

Chitosan-Poly(Acrylic Acid) Nanoparticles Loaded with R848 and MnCl2 Inhibit Melanoma via Regulating Macrophage Polarization and Dendritic Cell Maturation

Purpose

Since immune cells in the tumor microenvironment (TME) can affect the development and progression of tumors, strategies modulating immune cells are considered to have an important therapeutic effect. As a TLR7/8 agonist, R848 effectively activates the innate immune cells to exert an anti-tumor effect. Mn²⁺ has been reported to strongly promote the maturation of antigen-presenting cells (APCs), thereby enhancing the cytotoxicity of CD8⁺ T cells. Thus, we tried to investigate whether chitosan-poly(acrylic acid) nanoparticles (CS-PAA NPs) loaded with R848 and MnCl₂ (R-M@CS-PAA NPs) could exert an anti-tumor effect by regulating the function of immune cells.

Methods

R-M@CS-PAA NPs were prepared, and their basic characteristics, anti-tumor effect, and potential mechanisms were explored both in vitro and in vivo.

Results

R-M@CS-PAA NPs easily released MnCl₂ and R848 at low pH. In B16F10 mouse melanoma model, R-M@CS-PAA NPs exerted the most significant anti-melanoma effect compared with the control group and CS-PAA NPs loaded with R848 or MnCl₂ alone. FITC-labeled R-M@CS-PAA NPs were displayed to be accumulated at the tumor site. R-M@CS-PAA NPs significantly increased the infiltration of M1 macrophages and CD8⁺ T cells but reduced the number of suppressive immune cells in the TME. Moreover, in vitro experiments showed that R-M@CS-PAA NPs polarized macrophages into the M1 phenotype to inhibit the proliferation of B16F10 cells. R-M@CS-PAA NPs also enhanced the killing function of CD8⁺ T cells to B16F10 cells. Of note, R-M@CS-PAA NPs not only promoted the maturation of APCs such as dendritic cells and macrophages by STING and NF-кB pathways, but also enhanced the ability of dendritic cells to present ovalbumin to OT-I CD8⁺ T cells to enhance the cytotoxicity of OT-I CD8⁺ T cells to ovalbumin-expressing B16F10 cells.

Conclusion

These data indicate that the administration of R-M@CS-PAA NPs is an effective therapeutic strategy against melanoma.