Membrane Aging as the Real Culprit of Alzheimer's Disease: Modification of a Hypothesis

Identification and immunological characterization of genes associated with ferroptosis in Alzheimer's disease and experimental demonstration

The incidence of Alzheimer's disease (AD) is rising globally, yet its treatment and prediction of this condition remain challenging due to the complex pathophysiological mechanisms associated with it. Consequently, the objective of the present study was to analyze and characterize the molecular mechanisms underlying ferroptosis‑related genes (FEGs) in the pathogenesis of AD, as well as to construct a prognostic model. The findings will provide new insights for the future diagnosis and treatment of AD. First, the AD dataset GSE33000 from the Gene Expression Omnibus database and the FEGs from FerrDB were obtained. Next, unsupervised cluster analysis was used to obtain the FEGs that were most relevant to AD. Subsequently, enrichment analyses were performed on the FEGs to explore biological functions. Subsequently, the role of these genes in the immune microenvironment was elucidated through CIBERSORT. Then, the optimal machine learning was selected by comparing the performance of different machine learning models. To validate the prediction efficiency, the models were validated using nomograms, calibration curves, decision curve analysis and external datasets. Furthermore, the expression of FEGs between different groups was verified using reverse transcription quantitative PCR and western blot analysis. In AD, alterations in the expression of FEGs affect the aggregation and infiltration of certain immune cells. This indicated that the occurrence of AD is strongly associated with immune infiltration. Finally, the most appropriate machine learning models were selected, and AD diagnostic models and nomograms were built. The present study provided novel insights that enhance understanding with regard to the molecular mechanism of action of FEGs in AD. Moreover, the present study provided biomarkers that may facilitate the diagnosis of AD.

Lysosome-targeting benzothiazole-based fluorescent probe for imaging viscosity and hypochlorite levels in living cells and zebrafish

Viscosity and hypochlorite (OCl^-) play an important role in biological activities and may cause negative effects at abnormal levels. In this study, a novel lysosome-target fluorescent probe BDHA was obtained based on a benzothiazole derivative. Probe BDHA showed linear ranges of detection for viscosity from 1.62 cP to 851.6 cP with a fluorescent turn-on response. It can also be used as a sensor for OCl^- with a turn-off response and showed a good linear range from 0 to 390 μM, with the detection limit calculated to be 2.8 μM. Moreover, BDHA can also be used to image viscosity and OCl^- levels in HeLa cells and zebrafish, owing to its excellent optical properties.

A Bioinformatics Perspective on the Dysregulation of Ferroptosis and Ferroptosis-related Immune Cell Infiltration in Alzheimer's Disease

Alzheimer's disease (AD) is the most prevalent dementia worldwide, but its pathophysiology and molecular events remain unknown. Herein, we first analyzed the differential expression pattern of patients' AD hippocampus through gene expression array data from the GEO database. Notch2nl, TGFB1I1, and LTF were up-regulated in AD patients, while ARPC1A, CHGB, and MPV17 down-regulated. Second, dysregulation of ferroptosis related genes was demonstrated from our data: PCBP2 and FTL significantly up-significant in AD hippocampus, while VDAC2, LPCAT3, GSS, ACSL4, and ACSL6 significantly down-regulated. The protein-protein interactions (PPI) network revealed that FTL was involved in iron metabolism and utilization, while ACSL4 and ACSL6 were involved in a polyunsaturated fatty acids metabolism network. Gene correlation analysis on differential expressed genes (DEGs) indicated that ferroptosis regulates a series of biological processes and pathways related to AD pathogenesis. Third, ferroptosis-related DEGs regulated the immune cell infiltration pattern in the AD hippocampus, characterized by decreased memory B cells, increased memory resting CD4⁺ T cells, memory activated CD4⁺ T cells, and resting NK cells. The altered expression of ferroptosis-related DEGs affected the infiltration of specific immune cell types. The model constructed by the seven ferroptosis-related differential genes may accurately predict the outcome of AD occurrence. Finally, qPCR validation on these ferroptosis-related DEGs in APPswe/PSEN1dE9 mice confirmed the dysregulated expression of Pcbp2, FTL, GSS, and ACSL4 in the AD hippocampus and forebrain. In conclusion, our results supported the conception that the AD brain revealed dysregulated ferroptosis and immune cell infiltration.

Lipids in Pathophysiology and Development of the Membrane Lipid Therapy: New Bioactive Lipids

Membranes are mainly composed of a lipid bilayer and proteins, constituting a checkpoint for the entry and passage of signals and other molecules. Their composition can be modulated by diet, pathophysiological processes, and nutritional/pharmaceutical interventions. In addition to their use as an energy source, lipids have important structural and functional roles, e.g., fatty acyl moieties in phospholipids have distinct impacts on human health depending on their saturation, carbon length, and isometry. These and other membrane lipids have quite specific effects on the lipid bilayer structure, which regulates the interaction with signaling proteins. Alterations to lipids have been associated with important diseases, and, consequently, normalization of these alterations or regulatory interventions that control membrane lipid composition have therapeutic potential. This approach, termed membrane lipid therapy or membrane lipid replacement, has emerged as a novel technology platform for nutraceutical interventions and drug discovery. Several clinical trials and therapeutic products have validated this technology based on the understanding of membrane structure and function. The present review analyzes the molecular basis of this innovative approach, describing how membrane lipid composition and structure affects protein-lipid interactions, cell signaling, disease, and therapy (e.g., fatigue and cardiovascular, neurodegenerative, tumor, infectious diseases).

PADI4 mediates autophagy and participates in the role of ganoderic acid A monomers in delaying the senescence of Alzheimer's cells through the Akt/mTOR pathway

The effects of PADI4 and GAA on the senescence of Alzheimer's cells were explored in the present work. HT22 cells were treated with Aβ25-35 to establish an Alzheimer's model and were then treated with different concentrations of GAA and transfected with a siPADI4 lentiviral vector. GAA could reverse the effects of Aβ25-35 on inhibiting cell viability and promoting apoptosis and senescence. siPADI4 reduced Aβ25-35-induced cell viability and upregulated Aβ25-35-induced cell apoptosis and senescence, as well as partially reversed the effect of GAA on cells, and these results were confirmed by detecting the expressions of senescence- and apoptosis-related proteins. In addition, siPADI4 was found to promote the phosphorylation of Akt and mTOR, which was partially reversed by GAA. In conclusion, PADI4 mediates autophagy and participates in the role of GAA monomers in delaying the senescence of Alzheimer's cells through the Akt/mTOR pathway.

Naphthalimide-4-(4-nitrophenyl)thiosemicarbazide: A Fluorescent Probe for Simultaneous Monitoring of Viscosity and Nitric Oxide in Living Cells

Intracellular viscosity is a physicochemical factor that determines the outcomes of various biological processes, while nitric oxide (NO) is an essential signaling molecule that controls many cellular processes, including oxidative stress. Anticipating that both may be interrelated with a variety of pathologies, their simultaneous measurement would be highly valuable for the investigation of the pathological condition of cells. However, the development of a sensor for such simultaneous detection has not been attempted yet. Herein, we present the synthesis of naphthalimide-4-(4-nitrophenyl)thiosemicarbazide, probe 1, and its application to living cells under conditions of lipopolysaccharide or nystatin treatment, adopted as oxidative stress and altered intracellular viscosity models, respectively. The probe showed increased fluorescence in response to elevation of viscosity and NO levels at 470 and 550 nm, respectively, in the solution studies. When the probe was used for a confocal microscopic study of HeLa cells under stressed conditions, simultaneous monitoring of viscosity and NO level elevations was possible through fluorescence imaging using band-pass filters of 420-475 and 505-600 nm, respectively, upon excitation at a wavelength of 405 nm. Interestingly, both the cellular viscosity and NO levels increased together under lipopolysaccharide or nystatin treatment. Therefore, we suggest that probe 1 is a fluorescent chemical probe that enables the monitoring of alterations in intracellular viscosity and NO levels in living cells, which would be valuable in studies of various cellular damage models.

Clinical efficacy of sertraline in the treatment of depression caused by Alzheimer disease: A protocol of systematic review

BACKGROUND

This study will appraise the clinical efficacy of sertraline in the treatment of depression caused by Alzheimer disease (AD).

METHODS

Comprehensive searches in PUBMED, EMBASE, Cochrane Library, Scopus, AMED, CNKI, and WANGFANG will be performed from inception to the present without language restriction. In addition, other sources will also be searched to avoid losing more potential studies. We will only consider randomized controlled trials that examined the efficacy of sertraline for depression in patients with AD. Two team members will independently undertake literature selection, data collection, and risk of bias assessment. We will use Cochrane Risk of Bias Tool to assess the risk of bias for each eligible trial, and will utilize RevMan 5.3 software to carry out data analysis.

RESULTS

This study will recapitulate high-quality evidence to assess the efficacy of sertraline for the treatment of depression following AD.

CONCLUSION

The findings of this study will help to determine whether or not sertraline is effective for the treatment of depression after AD. OSF REGISTRATION:: osf.io/f29v6.

Screening for a suitable cell membrane anchoring tag for Pseudomonas aeruginosa and applying it in cell membrane real-time tracking to investigate membrane aging

Membrane proteins that have been widely used in drug delivery and cell labeling can localize onto the cell membrane by interacting with lipid bilayers. A membrane-binding tag fused with a fluorescent protein can enable tracking of the cell outline. However, numerous known membrane proteins have species preferences, and thus, a suitable membrane-binding tag for Pseudomonas aeruginosa has not been reported. In this study, we examined the membrane-binding effects of a series of endogenous and exogenous proteins (peptides) in P. aeruginosa; the proteins included LacY, WspA, tsr and its truncated mutant (tsrMut), exotoxin A signal peptide (ESP), and TAT. Among them, tsrMut exhibited a faster and steadier membrane positioning ability than others, and it also did not interfere with bacteria growth. In addition, tsrMut could be further applied for identifying and tracking cell membrane aging areas in real-time. By linking it with a tandem fluorescent timer (EGFP-Tdimer2), the aging areas of the cell membrane could easily be displayed and observed under the microscope. These findings suggest that tsrMut is a highly favorable binding tag for P. aeruginosa and integrating the tag with an aging timer may be a promising approach for studying bacterial membrane senescence at the single-cell level.

TDP-43-Mediated Toxicity in HEK293T Cells: A Fast and Reproducible Protocol To Be Employed in the Search of New Therapeutic Options against Amyotrophic Lateral Sclerosis

Cytoplasmic TDP-43 aggregates are a hallmark of amyotrophic lateral sclerosis (ALS). Today, only two drugs are available for ALS treatment, and their modest effect prompts researchers to search for new therapeutic options. TDP-43 represents one of the most promising targets for therapeutic intervention, but reliable and reproducible in vitro protocols for TDP-43-mediated toxicity are lacking. Here, we used HEK293T cells transfected with increasing concentrations of TDP-43-expressing plasmid to evaluate different parameters of toxicity and alterations in cellular metabolism. Overexpression of TDP-43 induced aggregates occurrence followed by the detection of 25- and 35-kDa forms of TDP-43. TDP-43 overexpression decreased cell viability and increased cells arrested at G2/M phase and nuclear fragmentation. Analysis of the energetic metabolism showed a tendency to decrease oxidative phosphorylation and increase glycolysis, but no statistical differences were observed. Metabolomics revealed alterations in different metabolites (mainly sphingolipids and glycerophospholipids) in cells overexpressing TDP-43. Our data reveal the main role of TDP-43 aggregation in cellular death and highlight novel insight into the mechanism of cellular toxicity induced by TDP-43. Here, we provide a simple, sensitive, and reliable protocol in a human-derived cell line to be used in high-throughput screenings of potential therapeutic molecules for ALS treatment.

The role of mitochondrial defects and oxidative stress in Alzheimer's disease

Alzheimer's disease (AD) is a complex, progressive, and irreversible neurodegenerative disorder. Recent reports suggest that it affects more than 36 million people worldwide and accounts 60-80% of all cases of dementia. It is characterised by aberrations of multiple interactive systems and pathways, which ultimately lead to memory loss and cognitive dysfunction. The exact mechanisms and initial triggering factors that underpin the known pathological defects in AD remain to be fully elucidated. In addition, an effective treatment strategy to reduce the progression of AD is yet to be achieved. In the light of above-mentioned facts, our article deals with the exploration of the mitochondrial defect and oxidative stress leading to this devastating disease. In this communication, we have highlighted specific mitochondrial and antioxidant-directed approach to ameliorate and manage AD. Nonetheless, new approaches should also be investigated that could tackle various molecular events involved in AD pathogenicity.