Proinflammatory S100A9 stimulates TLR4/NF-κB signaling pathways causing enhanced phagocytic capacity of microglial cells

α -Lipoic acid alleviates Parkinson's disease by suppressing S100A9-mediated pyroptosis

Parkinson's disease (PD) is a neurodegenerative disease, and inflammation is a key factor in the progression of PD. S100A9 mediates pyroptosis and implicates in various diseases including PD. Pyroptosis, an emerging form of programmed cell death, usually causes cell rupture and death via an inflammatory response. α-Lipoic acid (α-ALA), a cellular coenzyme, participates in anti-inflammatory and antioxidant processes. Although its role in PD has been confirmed, but the exact mechanism of its anti-inflammatory effect remains unclear. In our research, we examined the potential mechanisms of pyroptosis mediated by S100A9 in PD and the neuroprotective effects of α-ALA. We used 6-hydroxydopamine (6-OHDA) to induce SH-SY5Y cells in vitro and in C57BL/6 mice in vivo. The cell viability of SH-SY5Y cells confirmed the neuroprotective effect of α-ALA. Proteomics analysis indicated that S100A9 was involved in 6-OHDA-mediated neuronal injury, while α-ALA could inhibit. We found that α-ALA ameliorated PD symptoms induced by 6-OHDA and decreased the levels of NLRP3 inflammasome, Gasdermin D, and IL-1β, which are major hallmarks of pyroptosis. Furthermore, our research demonstrated that α-ALA mitigated cell injury by suppressing NLRP3-dependent pyroptosis mediated by S100A9. In brief, pyroptosis is pivotal in PD, while α-ALA protects dopaminergic neurons by suppressing pyroptosis mediated through the NLRP3 inflammasome, directly reducing S100A9, and subsequently inhibiting the NLRP3/Gasdermin D signaling pathways. Our results collectively suggest that suppressing S100A9-mediated pyroptosis and administering α-ALA may represent a novel approach in treating of PD.

A 3D human iPSC-derived multi-cell type neurosphere system to model cellular responses to chronic amyloidosis

BACKGROUND

Alzheimer's disease (AD) is characterized by progressive amyloid beta (Aβ) deposition in the brain, with eventual widespread neurodegeneration. While the cell-specific molecular signature of end-stage AD is reasonably well characterized through autopsy material, less is known about the molecular pathways in the human brain involved in the earliest exposure to Aβ. Human model systems that not only replicate the pathological features of AD but also the transcriptional landscape in neurons, astrocytes and microglia are crucial for understanding disease mechanisms and for identifying novel therapeutic targets.

METHODS

In this study, we used a human 3D iPSC-derived neurosphere model to explore how resident neurons, microglia and astrocytes and their interplay are modified by chronic amyloidosis induced over 3-5 weeks by supplementing media with synthetic Aβ1 - 42 oligomers. Neurospheres under chronic Aβ exposure were grown with or without microglia to investigate the functional roles of microglia. Neuronal activity and oxidative stress were monitored using genetically encoded indicators, including GCaMP6f and roGFP1, respectively. Single nuclei RNA sequencing (snRNA-seq) was performed to profile Aβ and microglia driven transcriptional changes in neurons and astrocytes, providing a comprehensive analysis of cellular responses.

RESULTS

Microglia efficiently phagocytosed Aβ inside neurospheres and significantly reduced neurotoxicity, mitigating amyloidosis-induced oxidative stress and neurodegeneration following different exposure times to Aβ. The neuroprotective effects conferred by the presence of microglia was associated with unique gene expression profiles in astrocytes and neurons, including several known AD-associated genes such as APOE. These findings reveal how microglia can directly alter the molecular landscape of AD.

CONCLUSIONS

Our human 3D neurosphere culture system with chronic Aβ exposure reveals how microglia may be essential for the cellular and transcriptional responses in AD pathogenesis. Microglia are not only neuroprotective in neurospheres but also act as key drivers of Aβ-dependent APOE expression suggesting critical roles for microglia in regulating APOE in the AD brain. This novel, well characterized, functional in vitro platform offers unique opportunities to study the roles and responses of microglia to Aβ modelling key aspects of human AD. This tool will help identify new therapeutic targets, accelerating the transition from discovery to clinical applications.

Binding of Pro-Inflammatory Proteins S100A8 or S100A9 to Amyloid-β Peptide Suppresses Its Fibrillation

Human serum albumin (HSA) is a natural depot of amyloid-β peptide (Aβ), a key player in Alzheimer's disease (AD). HSA and pro-inflammatory Ca2+-binding proteins S100A8 and S100A9 are involved in Aβ metabolism and its deposition in the brain, serving as probable triggers and therapeutic targets in AD, but their interplay with regard to Aβ binding/fibrillation is unclear. To this end, here we explore the in vitro binding of Ca2+-bound S100A8 or S100A9 to monomeric Aβ and the influence of the S100 proteins on Aβ fibrillation. The equilibrium dissociation constants of the complexes of dimeric S100A8/S100A9 with Aβ40/42 estimated by biolayer interferometry are 1-5 µM. S100A8 and S100A9 interfere with HSA binding to Aβ. Thioflavin T assay and electron microscopy data show that micromolar S100A8/S100A9 inhibit Aβ40 fibrillation, and the inhibitory effect of S100A8 exceeds that for HSA. The competition for Aβ between HSA and S100A8/S100A9 may contribute to the Aβ-HSA imbalance in the pro-inflammatory conditions in AD.

S100A9 protein activates microglia and stimulates phagocytosis, resulting in synaptic and neuronal loss

S100 calcium-binding protein A9 (S100A9, also known as calgranulin B) is expressed and secreted by myeloid cells under inflammatory conditions, and S100A9 can amplify inflammation. There is a large increase in S100A9 expression in the brains of patients with neurodegenerative diseases, such as Alzheimer's disease, and S100A9 has been suggested to contribute to neurodegeneration, but the mechanisms are unclear. Here we investigated the effects of extracellular recombinant S100A9 protein on microglia, neurons and synapses in primary rat brain neuronal-glial cell cultures. Incubation of cell cultures with 250-500 nM S100A9 caused neuronal loss without signs of apoptosis or necrosis, but accompanied by exposure of the "eat-me" signal - phosphatidylserine on neurons. S100A9 caused activation of microglial inflammation as evidenced by an increase in the microglial number, morphological changes, release of pro-inflammatory cytokines, and increased phagocytic activity. At lower concentrations, 10-100 nM S100A9 induced synaptic loss in the cultures. Depletion of microglia from the cultures prevented S100A9-induced neuronal and synaptic loss, indicating that neuronal and synaptic loss was mediated by microglia. These results suggest that extracellular S100A9 may contribute to neurodegeneration by activating microglial inflammation and phagocytosis, resulting in loss of synapses and neurons. This further suggests the possibility that neurodegeneration may be reduced by targeting S100A9 or microglia.

Inflammatory role of S100A8/A9 in the central nervous system non-neoplastic diseases

S100A8 (MRP8) and S100A9 (MRP14) are critical mediators of the inflammatory response; they are usually present as heterodimers because of the instability of homodimers. Studies have demonstrated that S100A8/A9 expression is significantly upregulated in several central nervous system (CNS) diseases. S100A8/A9 is actively released by neutrophils and monocytes; it plays a key role in regulating the inflammatory response by stimulating leukocyte recruitment and inducing cytokine secretion during inflammation. Additionally, S100A8/A9 can be used as a diagnostic biomarker for several CNS diseases and as a predictor of therapeutic response to inflammation-related diseases. In this work, we reviewed our current understanding of S100A8/A9 overexpression in inflammation and its importance in the development and progression of CNS inflammatory diseases, such as Alzheimer's disease (AD), Parkinson's disease (PD), multiple sclerosis (MS), and stroke, and the functional roles and therapeutic applications of S100A8/A9 in these diseases. Finally, we discussed the current barriers and future research directions of S100A8/A9 in CNS diseases.

Pro-inflammatory protein S100A9 targeted by a natural molecule to prevent neurodegeneration onset

Accumulation of the pro-inflammatory protein S100A9 has been implicated in neuroinflammatory cascades in neurodegenerative diseases (NDs) such as Alzheimer's disease (AD) and Parkinson's disease (PD). S100A9 co-aggregates with other proteins such as α-synuclein in PD and Aβ in AD, contributing to amyloid plaque formation and neurotoxicity. The amyloidogenic nature of this protein and its role in chronic neuroinflammation suggest that it may play a key role in the pathophysiology of these diseases. Research into molecules targeting S100A9 could be a potential therapeutic strategy to prevent its amyloidogenic self-assembly and to attenuate the neuroinflammatory response in affected brain tissue. This work suggests that bioactive natural molecules, such as those found in the Mediterranean diet, may have the potential to alleviate neuroinflammation associated with the accumulation of proteins such as S100A9 in neurodegenerative diseases. A major component of extra virgin olive oil (EVOO), hydroxytyrosol (HT), with its ability to interact with and modulate S100A9 amyloid self-assembly and expression, offers a compelling approach for the development of novel and effective interventions for the prevention and treatment of ND. The findings highlight the importance of exploring natural compounds, such as HT, as potential therapeutic options for these complex and challenging neurological conditions.

Integrated Bioinformatics-Based Identification and Validation of Neuroinflammation-Related Hub Genes in Primary Open-Angle Glaucoma

Glaucoma is a leading cause of permanent blindness, affecting 80 million people worldwide. Recent studies have emphasized the importance of neuroinflammation in the early stages of glaucoma, involving immune and glial cells. To investigate this further, we used the GSE27276 dataset from the GEO (Gene Expression Omnibus) database and neuroinflammation genes from the GeneCards database to identify differentially expressed neuroinflammation-related genes associated with primary open-angle glaucoma (POAG). Subsequently, these genes were submitted to Gene Ontology and the Kyoto Encyclopedia of Genes and Genomes for pathway enrichment analyses. Hub genes were picked out through protein-protein interaction networks and further validated using the external datasets (GSE13534 and GSE9944) and real-time PCR analysis. The gene-miRNA regulatory network, receiver operating characteristic (ROC) curve, genome-wide association study (GWAS), and regional expression analysis were performed to further validate the involvement of hub genes in glaucoma. A total of 179 differentially expressed genes were identified, comprising 60 upregulated and 119 downregulated genes. Among them, 18 differentially expressed neuroinflammation-related genes were found to overlap between the differentially expressed genes and neuroinflammation-related genes, with six genes (SERPINA3, LCN2, MMP3, S100A9, IL1RN, and HP) identified as potential hub genes. These genes were related to the IL-17 signaling pathway and tyrosine metabolism. The gene-miRNA regulatory network showed that these hub genes were regulated by 118 miRNAs. Notably, GWAS data analysis successfully identified significant single nucleotide polymorphisms (SNPs) corresponding to these six hub genes. ROC curve analysis indicated that our genes showed significant accuracy in POAG. The expression of these genes was further confirmed in microglia, Müller cells, astrocytes, and retinal ganglion cells in the Spectacle database. Moreover, three hub genes, SERPINA3, IL1R1, and LCN2, were validated as potential diagnostic biomarkers for high-risk glaucoma patients, showing increased expression in the OGD/R-induced glaucoma model. This study suggests that the identified hub genes may influence the development of POAG by regulation of neuroinflammation, and it may offer novel insights into the management of POAG.

Novel biomarkers related to oxidative stress and immunity in chronic kidney disease

Introduction

The incidence of chronic kidney disease (CKD) has been increasing in recent years, gradually becoming a global health crisis. Due to limited treatment options, novel molecular pathways are urgently required to advance the treatment and diagnosis of CKD.

Materials and methods

The characteristics of differentially expressed genes (DEGs) in CKD patients were analyzed using Gene Expression Omnibus (GEO) database, and genes related to oxidative stress were retrieved from the Genecard database. Subsequently, a comprehensive approach was applied, including immune infiltration analysis, weighted gene co-expression network analysis (WGCNA) and protein-protein interaction (PPI) network analysis, to identify hub genes among differentially expressed immune-related oxidative stress genes (DEIOSGs). Validation of hub genes was performed using an external data set, and diagnostic potential capability was evaluated through receiver operating curve (ROC) analysis. In animal experiments, the expression of hub genes in CKD was confirmed by inducing a CKD model through a 5/6 nephrectomy procedure. Finally, the relationship between these hub genes and clinical characteristics were assessed using the Nephroseq v5 database.

Results

29 DEIOSGs were identified by comprehensive bioinformatics analysis. PPI analysis screened the hub genes NCF2, S100A9, and SELL. ROC analysis demonstrated excellent diagnostic efficacy. Further validation from other databases and animal experiments confirmed a substantial upregulation in the expression of hub genes in CKD. Additionally, clinical correlation analysis established a clear link between hub gene expression and renal function deterioration.

Conclusions

Our study confirms NCF2, S100A9, and SELL as diagnostic biomarkers associated with immune response and oxidative stress in CKD, suggesting their potential as novel targets for CKD diagnosis and treatment.