Interleukin-1 mediates pathological effects of microglia on tau phosphorylation and on synaptophysin synthesis in cortical neurons through a p38-MAPK pathway

Alternatively spliced mini-exon B in PTPδ regulates excitatory synapses through cell-type-specific trans-synaptic PTPδ-IL1RAP interaction

PTPδ, encoded by PTPRD, is implicated in various neurological, psychiatric, and neurodevelopmental disorders, but the underlying mechanisms remain unclear. PTPδ trans-synaptically interacts with multiple postsynaptic adhesion molecules, which involves its extracellular alternatively spliced mini-exons, meA and meB. While PTPδ-meA functions have been studied in vivo, PTPδ-meB has not been studied. Here, we report that, unlike homozygous PTPδ-meA-mutant mice, homozygous PTPδ-meB-mutant (Ptprd-meB-/-) mice show markedly reduced early postnatal survival. Heterozygous Ptprd-meB+/- male mice show behavioral abnormalities and decreased excitatory synaptic density and transmission in dentate gyrus granule cells (DG-GCs). Proteomic analyses identify decreased postsynaptic density levels of IL1RAP, a known trans-synaptic partner of meB-containing PTPδ. Accordingly, IL1RAP-mutant mice show decreased excitatory synaptic transmission in DG-GCs. Ptprd-meB+/- DG interneurons with minimal IL1RAP expression show increased excitatory synaptic density and transmission. Therefore, PTPδ-meB is important for survival, synaptic, and behavioral phenotypes and regulates excitatory synapses in cell-type-specific and IL1RAP-dependent manners.

Cellular and molecular mechanisms of pathological tau phosphorylation in traumatic brain injury: implications for chronic traumatic encephalopathy

Tau protein plays a critical role in the physiological functioning of the central nervous system by providing structural integrity to the cytoskeletal architecture of neurons and glia through microtubule assembly and stabilization. Under certain pathological conditions, tau is aberrantly phosphorylated and aggregates into neurotoxic fibrillary tangles. The aggregation and cell-to-cell propagation of pathological tau leads to the progressive deterioration of the nervous system. The clinical entity of traumatic brain injury (TBI) ranges from mild to severe and can promote tau aggregation by inducing cellular mechanisms and signalling pathways that increase tau phosphorylation and aggregation. Chronic traumatic encephalopathy (CTE), which is a consequence of repetitive TBI, is a unique tauopathy characterized by pathological tau aggregates located at the depths of the sulci and surrounding blood vessels. The mechanisms leading to increased tau phosphorylation and aggregation in CTE remain to be fully defined but are likely the result of the primary and secondary injury sequelae associated with TBI. The primary injury includes physical and mechanical damage resulting from the head impact and accompanying forces that cause blood-brain barrier disruption and axonal shearing, which primes the central nervous system to be more vulnerable to the subsequent secondary injury mechanisms. A complex interplay of neuroinflammation, oxidative stress, excitotoxicity, and mitochondrial dysfunction activate kinase and cell death pathways, increasing tau phosphorylation, aggregation and neurodegeneration. In this review, we explore the most recent insights into the mechanisms of tau phosphorylation associated with TBI and propose how multiple cellular pathways converge on tau phosphorylation, which may contribute to CTE progression.

Association of neurodegeneration, cognitive impairment, and short stature in Down syndrome; Could proinflammatory cytokines be the common factor?

Down syndrome (DS), caused by an extra copy of chromosome 21, is the most prevalent chromosomal disorder. It leads to various complications including, cardiac and endocrine dysfunctions, impairment of the immune system, growth retardation, and certain neurological conditions. Stunted growth in this population might be linked to an increased risk of a variety of co-occurring conditions, particularly neurological disorders. Studies indicate that the levels of neurodegeneration and neuroinflammation markers are higher in shorter children with DS. The disruption of insulin-like growth factor 1 (IGF1) signalling pathway due to the overexpression of proinflammatory cytokine genes could help establish a connection between short stature and neurodegeneration in DS. These cytokines disrupt the production of IGF1 in the liver, thereby inhibiting IGF1 from promoting bone and brain growth. Additionally, elevated cytokines levels impair the production of sex hormones by affecting the gonadal axis, further exacerbating the aforementioned conditions. The group of GnRH neurons responsible for cognitive functions is also impaired in DS, and treatment with GnRH agonists has demonstrated improvements in cognition. Although GnRH agonists can delay the fusion of growth plates by inhibiting pulsatile GnRH secretion, they may also lead to cognitive impairments. Hypothyroidism, the most prevalent endocrine complication of DS, can also contribute to both cognitive impairment and short stature. In conclusion, the increase of proinflammatory cytokines, through various mechanisms, can play a significant role in the development of both cognitive impairments and short stature in DS.

P-glycoprotein and Alzheimer's Disease: Threats and Opportunities

Alzheimer's disease (AD) is a progressive neurodegenerative disorder that affects more than 50 million people worldwide. One of the hallmark features of AD is the accumulation of amyloid β-peptide (Aβ) protein in the brain. P-glycoprotein (P-gp) is a membrane-bound protein expressed in various tissues, including the cerebrovascular endothelium. It plays a crucial role in the efflux of toxic substances, including Aβ, from the brain. Aberrations in P-gp levels or activity have been implicated in the pathogenesis of AD by promoting the accumulation of Aβ in the brain. Therefore, modulating the P-gp function represents a promising therapeutic strategy for treating AD. P-gp has multiple substrate binding sites, creating the potential for substrates to fall into complementation groups based on these sites; two substrates in the same complementation group may compete with one other, but two substrates in different groups may exhibit cooperativity. Thus, a given P-gp substrate may interfere with Aβ efflux whereas another may promote clearance. These threats and opportunities, as well as other aspects of P-gp relevance to AD, are discussed here.

Pyroptosis; igniting neuropsychiatric disorders from mild depression to aging-related neurodegeneration

Neuropsychiatric disorders significantly impact global health and socioeconomic well-being, highlighting the urgent need for effective treatments. Chronic inflammation, often driven by the innate immune system, is a key feature of many neuropsychiatric conditions. NOD-like receptors (NLRs), which are intracellular sensors, detect danger signals and trigger inflammation. Among these, NLR protein (NLRP) inflammasomes play a crucial role by releasing pro-inflammatory cytokines and inducing a particular cell death process known as pyroptosis. Pyroptosis is defined as a proinflammatory form of programmed cell death executed by cysteine-aspartic proteases, also known as caspases. Currently, the role of pyroptotic flux has emerged as a critical factor in innate immunity and the pathogenesis of multiple diseases. Emerging evidence suggests that the induction of pyroptosis, primarily due to NLRP inflammasome activation, is involved in the pathophysiology of various neuropsychiatric disorders, including depression, stress-related issues, schizophrenia, autism spectrum disorders, and neurodegenerative diseases. Within this framework, the current review explores the complex relationship between pyroptosis and neuropsychiatric diseases, aiming to identify potential therapeutic targets for these challenging conditions.

Unraveling the genetic underpinnings of mitochondrial traits and associated circulating inflammatory proteins in Alzheimer's disease: Mitochondrial HtrA2-T cell CD5 negative axis

BackgroundPrevious studies with limited sample sizes have indicated a link between mitochondrial traits, inflammatory proteins, and Alzheimer's disease. The exact causality and their mediation relationships remain unclear.ObjectiveOur study aimed to delve into the genetic underpinnings of mitochondrial function and circulating inflammatory proteins in the pathogenesis of Alzheimer's disease.MethodsWe leveraged aggregated data from the largest genome-wide association study, including 69 mitochondrial traits, 91 circulating inflammatory proteins, and Alzheimer's disease. Bidirectional mendelian randomization (MR) analyses were performed to investigate their primary causal relationships. Thereafter a two-step MR mediation analysis was utilized to clarify the modulating effects of inflammatory proteins on mitochondria and Alzheimer's disease.ResultsOur study identified mitochondrial phenylalanine-tRNA ligase and 4-hydroxy-2-oxoglutarate aldolase as risk factors for Alzheimer's disease, and serine protease HtrA2 and carbonic anhydrase 5A as protective factors against Alzheimer's disease. Four inflammatory proteins (T-cell surface glycoprotein CD5, C-X-C motif chemokine 11, TGF-α, and TNF-related apoptosis-inducing ligand) played protective roles against Alzheimer's disease. Axin-1 and IL-6 increased the risk of Alzheimer's disease. Furthermore, T-cell surface glycoprotein CD5 was found to be a significant mediator between mitochondrial serine protease HTRA2 and Alzheimer's disease with the two-step MR method, accounting for 10.83% of the total effect.ConclusionsOur study emphasized mitochondrial HtrA2-T cell CD5 as a negative axis in Alzheimer's disease, offering novel perspectives on its etiology, pathogenesis, and treatment.

Novel peptidomimetic compounds attenuate hypoxic-ischemic brain injury in neonatal rats

Hypoxic-ischemic (HI) brain injury is a common neurological problem in neonates. The postsynaptic density protein-95 (PSD-95) is an excitatory synaptic scaffolding protein that regulates synaptic function, and represents a potential therapeutic target to attenuate HI brain injury. Syn3 and d-Syn3 are novel high affinity cyclic peptides that bind the PDZ3 domain of PSD-95. We investigated the neuroprotective efficacy of Syn3 and d-Syn3 after exposure to HI in neonatal rodents. Postnatal (P) day-7 rats were treated with Syn3 and d-Syn3 at zero, 24, and 48-h after carotid artery ligation and 90-min of 8 % oxygen. Hemispheric volume atrophy and Iba-1 positive microglia were quantified by cresyl violet and immunohistochemical staining. Treatment with Syn3 and d-Syn3 reduced tissue volume loss by 47.0 % and 41.0 % in the male plus female, and by 42.1 % and 65.0 % in the male groups, respectively. Syn3 reduced tissue loss by 52.3 % in females. D-Syn3 reduced Iba-1 positive microglia/DAPI ratios in the pooled group, males, and females. Syn3 effects were observed in the pooled group and females. Changes in Iba-1 positive microglia/DAPI cellular ratios correlated directly with reduced hemispheric volume loss, suggesting that Syn3 and d-Syn3 provide neuroprotection in part by their effects on Iba-1 positive microglia. The pathogenic cis phosphorylated Thr231 in Tau (cis P-tau) is a marker of neuronal injury. Cis P-tau was induced in cortical cells of the placebo-treated pooled group, males and females after HI, and reduced by treatment with d-Syn3. Therefore, treatment with these peptidomimetic agents exert neuroprotective effects after exposure of neonatal subjects to HI related brain injury.

Cathepsin B Modulates Alzheimer's Disease Pathology Through SAPK/JNK Signals Following Administration of Porphyromonas gingivalis-Derived Outer Membrane Vesicles

AIM

Porphyromonas gingivalis , a consensus periodontal pathogen, is thought to be involved in Alzheimer's disease (AD) progression, and P. gingivalis -derived outer membrane vesicles (PgOMVs) are a key toxic factor in inducing AD pathology. This study aimed to clarify the regulatory mechanism underlying the PgOMV-induced AD-like phenotype.

MATERIALS AND METHODS

We intraperitoneally injected PgOMVs into the periphery of wild-type and CatB knockout mice for 4 or 8 weeks to assess the effect of CatB on PgOMV-induced AD pathology. Mice were evaluated for cognitive change, tau phosphorylation, microglial activation, neuroinflammation and synapse loss. Microglial and primary neuron culture were prepared to verify the in vivo results.

RESULTS

CatB deficiency significantly alleviated PgOMV-induced cognitive dysfunction, microglia-mediated neuroinflammation, tau hyperphosphorylation and synapse loss. Subsequent transcriptomic analysis, immunofluorescence and immunoblotting suggested that CatB modulates microglia-mediated neuroinflammation through stress-activated protein kinases (SAPK)/Jun amino-terminal kinases (JNK) signals after administration of PgOMVs, which in turn regulates neuronal tau phosphorylation and synapse loss in a SAPK/JNK-dependent manner.

CONCLUSION

Our study unveils a previously unknown role of CatB in regulating PgOMV-induced AD pathology.

Evaluation of the Anti-Amyloid and Anti-Inflammatory Properties of a Novel Vanadium(IV)-Curcumin Complex in Lipopolysaccharides-Stimulated Primary Rat Neuron-Microglia Mixed Cultures

Lipopolysaccharides (LPS) are bacterial mediators of neuroinflammation that have been detected in close association with pathological protein aggregations of Alzheimer's disease. LPS induce the release of cytokines by microglia and mediate the upregulation of inducible nitric oxide synthase (iNOS)-a mechanism also associated with amyloidosis. Curcumin is a recognized natural medicine but has extremely low bioavailability. V-Cur, a novel hemocompatible Vanadium(IV)-curcumin complex with higher solubility and bioactivity than curcumin, is studied here. Co-cultures consisting of rat primary neurons and microglia were treated with LPS and/or curcumin or V-Cur. V-Cur disrupted LPS-induced overexpression of amyloid precursor protein (APP) and the in vitro aggregation of human insulin (HI), more effectively than curcumin. Cell stimulation with LPS also increased full-length, inactive, and total iNOS levels, and the inflammation markers IL-1β and TNF-α. Both curcumin and V-Cur alleviated these effects, with V-Cur reducing iNOS levels more than curcumin. Complementary insights into possible bioactivity mechanisms of both curcumin and V-Cur were provided by In silico molecular docking calculations on Aβ1-42, APP, Aβ fibrils, HI, and iNOS. This study renders curcumin-based compounds a promising anti-inflammatory intervention that may be proven a strong tool in the effort to mitigate neurodegenerative disease pathology and neuroinflammatory conditions.

A review on synthetic inhibitors of dual-specific tyrosine phosphorylation-regulated kinase 1A (DYRK1A) for the treatment of Alzheimer's disease (AD)

Alzheimer's disease (AD) is a complex disorder that is influenced by a number of variables, such as age, gender, environmental factors, disease, lifestyle, infections, and many more. The main characteristic of AD is the formation of amyloid plaque and neurofibrillary tangles (NFT), which are caused by various reasons such as inflammation, impairment of neurotransmitters, hyperphosphorylation of tau protein, generation of toxic amyloid beta (Aβ) 40/42, oxidative stress, etc. Protein kinases located in chromosome 21, namely dual-specific tyrosine phosphorylation-regulated kinase 1A (DYRK1A), play an essential role in the pathogenesis of AD. DYRK1A stimulates the Aβ peptide aggregation and phosphorylation of tau protein to generate the NFT formation that causes neurodegeneration. Thus, DYRK1A is associated with AD, and inhibition of DYRK1A has the potential to treat AD. In this review, we discussed the pathophysiology of AD, various factors responsible for AD, and the role of DYRK1A in AD. We have also discussed the latest therapeutic potential of DYRK1A inhibitors for neurogenerative disease, along with their structure-activity relationship (SAR) studies. This article provides valuable information for guiding the future discovery of novel and target-specific DYRK1A inhibitors over other kinases and their structural optimization to treat AD.

Cellular and pathological functions of tau

Tau protein is involved in various cellular processes, including having a canonical role in binding and stabilization of microtubules in neurons. Tauopathies are neurodegenerative diseases marked by the abnormal accumulation of tau protein aggregates in neurons, as seen, for example, in conditions such as frontotemporal dementia and Alzheimer disease. Mutations in tau coding regions or that disrupt tau mRNA splicing, tau post-translational modifications and cellular stress factors (such as oxidative stress and inflammation) increase the tendency of tau to aggregate and interfere with its clearance. Pathological tau is strongly implicated in the progression of neurodegenerative diseases, and the propagation of tau aggregates is associated with disease severity. Recent technological advancements, including cryo-electron microscopy and disease models derived from human induced pluripotent stem cells, have increased our understanding of tau-related pathology in neurodegenerative conditions. Substantial progress has been made in deciphering tau aggregate structures and the molecular mechanisms that underlie protein aggregation and toxicity. In this Review, we discuss recent insights into the diverse cellular functions of tau and the pathology of tau inclusions and explore the potential for therapeutic interventions.

Complement 3a induces the synapse loss via C3aR in mitochondria-dependent NLRP3 activating mechanisms during the development and progression of Alzheimer's disease

As a central molecule in complement system (CS), complement (C) 3 is upregulated in the patients and animal models of Alzheimer's disease (AD). C3 will metabolize to iC3b and C3a. iC3b is responsible for clearing β-amyloid protein (Aβ). In this scenario, C3 exerts neuroprotective effects against the disease via iC3b. However, C3a will inhibit microglia to clear the Aβ, leading to the deposition of Aβ and impair the functions of synapses. To their effects on AD, activation of C3a and C3a receptor (C3aR) will impair the mitochondria, leading to the release of reactive oxygen species (ROS), which activates the NOD-like receptor thermal protein domain associated protein 3 (NLRP3) inflammasomes. The overloading of NLRP3 inflammasomes activate microglia, leading to the formation of inflammatory environment. The inflammatory environment will facilitate the deposition of Aβ and abnormal synapse pruning, which results in the progression of AD. Therefore, the current review will decipher the mechanisms of C3a inducing the synapse loss via C3aR in mitochondria-dependent NLRP3 activating mechanisms, which facilitates the understanding the AD.

Influence of Tau on Neurotoxicity and Cerebral Vasculature Impairment Associated with Alzheimer's Disease

Alzheimer's disease is a fatal chronic neurodegenerative condition marked by a gradual decline in cognitive abilities and impaired vascular function within the central nervous system. This affliction initiates its insidious progression with the accumulation of two aberrant protein entities including Aβ plaques and neurofibrillary tangles. These chronic elements target distinct brain regions, steadily erasing the functionality of the hippocampus and triggering the erosion of memory and neuronal integrity. Several assumptions are anticipated for AD as genetic alterations, the occurrence of Aβ plaques, altered processing of amyloid precursor protein, mitochondrial damage, and discrepancy of neurotropic factors. In addition to Aβ oligomers, the deposition of tau hyper-phosphorylates also plays an indispensable part in AD etiology. The brain comprises a complex network of capillaries that is crucial for maintaining proper function. Tau is expressed in cerebral blood vessels, where it helps to regulate blood flow and sustain the blood-brain barrier's integrity. In AD, tau pathology can disrupt cerebral blood supply and deteriorate the BBB, leading to neuronal neurodegeneration. Neuroinflammation, deficits in the microvasculature and endothelial functions, and Aβ deposition are characteristically detected in the initial phases of AD. These variations trigger neuronal malfunction and cognitive impairment. Intracellular tau accumulation in microglia and astrocytes triggers deleterious effects on the integrity of endothelium and cerebral blood supply resulting in further advancement of the ailment and cerebral instability. In this review, we will discuss the impact of tau on neurovascular impairment, mitochondrial dysfunction, oxidative stress, and the role of hyperphosphorylated tau in neuron excitotoxicity and inflammation.

Neuro-inflammatory Responses in Alzheimer’s v/s Parkinson’s Diseases

Neurodegenerative diseases are a heterogeneous group of disorders and are the leading cause of morbidity and disability. These are described by the progressive degeneration of the neurons and impaired function of the central nervous system. Prevailing neurodegenerative diseases in the world include Alzheimer's disease and Parkinson's disease and reports predict that on average, the prevalence of both diseases will double in a span of the next twenty years. Pieces of evidence showed that the immune system is profoundly involved in brain development, maintenance, and repair as well as in damage, therefore, may provide a wide scope to focus on the neuroinflammation-based therapeutic approaches. In this chapter, the various neuroinflammatory responses will be discussed during the onset and progression of both Alzheimer’s and Parkinson’s disease pathologies. We will be focusing on both central and peripheral inflammatory responses and their consideration for disease diagnosis and therapeutics.

The Therapeutic Potential of Dalbergia pinnata (Lour.) Prain Essential Oil in Alzheimer's Disease: EEG Signal Analysis In Vivo, SH-SY5Y Cell Model In Vitro, and Network Pharmacology

Alzheimer's disease (AD) is a neurodegenerative disorder that is projected by the WHO to affect over 100 million people by 2050. Clinically, AD patients undergoing long-term antipsychotic treatment often experience severe anxiety or depression in later stages. Furthermore, early-stage AD manifests with weakened α waves in the brain, progressing to diminished α and β waves in late-stage disease, reflecting changes in emotional states and disease progression. In this study, EEG signal analysis revealed that inhalation of Dalbergia pinnata (Lour.) Prain essential oil (DPEO) enhanced δ, θ, α and β wave powers in the frontal and parietal lobes, with a rising trend in the β/α ratio in the temporal lobe. These findings suggest an alleviation of anxiety and an enhancement of cognitive functions. Treatment of the AD SH-SY5Y (human neuroblastoma cells) cell model with DPEO resulted in decreased intracellular levels of Aβ, GSK-3β, P-Tau, IL-1β, TNF-α, IL-6, COX-2, OFR, and HFR, alongside reduced AchE and BchE activities and increased SOD activity. Network pharmacology analysis indicated a potential pharmacological mechanism involving the JAK-STAT pathway. Our study provides evidence supporting DPEO's role in modulating anxiety and slowing AD pathological progression.

Inflammasomes at the crossroads of traumatic brain injury and post-traumatic epilepsy

Post-traumatic epilepsy (PTE) is one of the most debilitating consequences of traumatic brain injury (TBI) and is one of the most drug-resistant forms of epilepsy. Novel therapeutic treatment options are an urgent unmet clinical need. The current focus in healthcare has been shifting to disease prevention, rather than treatment, though, not much progress has been made due to a limited understanding of the disease pathogenesis. Neuroinflammation has been implicated in the pathophysiology of traumatic brain injury and may impact neurological sequelae following TBI including functional behavior and post-traumatic epilepsy development. Inflammasome signaling is one of the major components of the neuroinflammatory response, which is increasingly being explored for its contribution to the epileptogenic mechanisms and a novel therapeutic target against epilepsy. This review discusses the role of inflammasomes as a possible connecting link between TBI and PTE with a particular focus on clinical and preclinical evidence of therapeutic inflammasome targeting and its downstream effector molecules for their contribution to epileptogenesis. Finally, we also discuss emerging evidence indicating the potential of evaluating inflammasome proteins in biofluids and the brain by non-invasive neuroimaging, as potential biomarkers for predicting PTE development.

Metabolic Endotoxemia: From the Gut to Neurodegeneration

Metabolic endotoxemia is a severe health problem for residents in developed countries who follow a Western diet, disrupting intestinal microbiota and the whole organism's homeostasis. Although the effect of endotoxin on the human immune system is well known, its long-term impact on the human body, lasting many months or even years, is unknown. This is due to the difficulty of conducting in vitro and in vivo studies on the prolonged effect of endotoxin on the central nervous system. In this article, based on the available literature, we traced the path of endotoxin from the intestines to the blood through the intestinal epithelium and factors promoting the development of metabolic endotoxemia. The presence of endotoxin in the bloodstream and the inflammation it induces may contribute to lowering the blood-brain barrier, potentially allowing its penetration into the central nervous system; although, the theory is still controversial. Microglia, guarding the central nervous system, are the first line of defense and respond to endotoxin with activation, which may contribute to the development of neurodegenerative diseases. We traced the pro-inflammatory role of endotoxin in neurodegenerative diseases and its impact on the epigenetic regulation of microglial phenotypes.

Plasma VEGFA and PGF impact longitudinal tau and cognition in preclinical Alzheimer's disease

Vascular dysfunction is increasingly recognized as an important contributor to the pathogenesis of Alzheimer's disease. Alterations in vascular endothelial growth factor (VEGF) pathways have been implicated as potential mechanisms. However, the specific impact of VEGF proteins in preclinical Alzheimer's disease and their relationships with other Alzheimer's disease and vascular pathologies during this critical early period remain to be elucidated. We included 317 older adults from the Harvard Aging Brain Study, a cohort of individuals who were cognitively unimpaired at baseline and followed longitudinally for up to 12 years. Baseline VEGF family protein levels (VEGFA, VEGFC, VEGFD, PGF and FLT1) were measured in fasting plasma using high-sensitivity immunoassays. Using linear mixed effects models, we examined the interactive effects of baseline plasma VEGF proteins and amyloid PET burden (Pittsburgh Compound-B) on longitudinal cognition (Preclinical Alzheimer Cognitive Composite-5). We further investigated if effects on cognition were mediated by early neocortical tau accumulation (flortaucipir PET burden in the inferior temporal cortex) or hippocampal atrophy. Lastly, we examined the impact of adjusting for baseline cardiovascular risk score or white matter hyperintensity volume. Baseline plasma VEGFA and PGF each showed a significant interaction with amyloid burden on prospective cognitive decline. Specifically, low VEGFA and high PGF were associated with greater cognitive decline in individuals with elevated amyloid, i.e. those on the Alzheimer's disease continuum. Concordantly, low VEGFA and high PGF were associated with accelerated longitudinal tau accumulation in those with elevated amyloid. Moderated mediation analyses confirmed that accelerated tau accumulation fully mediated the effects of low VEGFA and partially mediated (31%) the effects of high PGF on faster amyloid-related cognitive decline. The effects of VEGFA and PGF on tau and cognition remained significant after adjusting for cardiovascular risk score or white matter hyperintensity volume. There were concordant but non-significant associations with longitudinal hippocampal atrophy. Together, our findings implicate low VEGFA and high PGF in accelerating early neocortical tau pathology and cognitive decline in preclinical Alzheimer's disease. Additionally, our results underscore the potential of these minimally-invasive plasma biomarkers to inform the risk of Alzheimer's disease progression in the preclinical population. Importantly, VEGFA and PGF appear to capture distinct effects from vascular risks and cerebrovascular injury. This highlights their potential as new therapeutic targets, in combination with anti-amyloid and traditional vascular risk reduction therapies, to slow the trajectory of preclinical Alzheimer's disease and delay or prevent the onset of cognitive decline.

miRNAs in cerebrospinal fluid associated with Alzheimer's disease: A systematic review and pathway analysis using a data mining and machine learning approach

Alzheimer's disease (AD) is the most common type and accounts for 60%-70% of the reported cases of dementia. MicroRNAs (miRNAs) are small non-coding RNAs that play a crucial role in gene expression regulation. Although the diagnosis of AD is primarily clinical, several miRNAs have been associated with AD and considered as potential markers for diagnosis and progression of AD. We sought to match AD-related miRNAs in cerebrospinal fluid (CSF) found in the GeoDataSets, evaluated by machine learning, with miRNAs listed in a systematic review, and a pathway analysis. Using machine learning approaches, we identified most differentially expressed miRNAs in Gene Expression Omnibus (GEO), which were validated by the systematic review, using the acronym PECO-Population (P): Patients with AD, Exposure (E): expression of miRNAs, Comparison (C): Healthy individuals, and Objective (O): miRNAs differentially expressed in CSF. Additionally, pathway enrichment analysis was performed to identify the main pathways involving at least four miRNAs selected. Four miRNAs were identified for differentiating between patients with and without AD in machine learning combined to systematic review, and followed the pathways analysis: miRNA-30a-3p, miRNA-193a-5p, miRNA-143-3p, miRNA-145-5p. The pathways epidermal growth factor, MAPK, TGF-beta and ATM-dependent DNA damage response, were regulated by these miRNAs, but only the MAPK pathway presented higher relevance after a randomic pathway analysis. These findings have the potential to assist in the development of diagnostic tests for AD using miRNAs as biomarkers, as well as provide understanding of the relationship between different pathophysiological mechanisms of AD.

Interactions between Cytokines and the Pathogenesis of Prion Diseases: Insights and Implications

Transmissible Spongiform Encephalopathies (TSEs), including prion diseases such as Bovine Spongiform Encephalopathy (Mad Cow Disease) and variant Creutzfeldt-Jakob Disease, pose unique challenges to the scientific and medical communities due to their infectious nature, neurodegenerative effects, and the absence of a cure. Central to the progression of TSEs is the conversion of the normal cellular prion protein (PrPC) into its infectious scrapie form (PrPSc), leading to neurodegeneration through a complex interplay involving the immune system. This review elucidates the current understanding of the immune response in prion diseases, emphasizing the dual role of the immune system in both propagating and mitigating the disease through mechanisms such as glial activation, cytokine release, and blood-brain barrier dynamics. We highlight the differential cytokine profiles associated with various prion strains and stages of disease, pointing towards the potential for cytokines as biomarkers and therapeutic targets. Immunomodulatory strategies are discussed as promising avenues for mitigating neuroinflammation and delaying disease progression. This comprehensive examination of the immune response in TSEs not only advances our understanding of these enigmatic diseases but also sheds light on broader neuroinflammatory processes, offering hope for future therapeutic interventions.

The neurotransmitter puzzle of Alzheimer's: Dissecting mechanisms and exploring therapeutic horizons

Alzheimer's Disease (AD) represents a complex interplay of neurological pathways and molecular mechanisms, with significant impacts on patients' lives. This review synthesizes the latest developments in AD research, focusing on both the scientific advancements and their clinical implications. We examine the role of microglia in AD, highlighting their contribution to the disease's inflammatory aspects. The cholinergic hypothesis, a cornerstone of AD research, is re-evaluated, including the role of Alpha-7 Nicotinic Acetylcholine Receptors in disease progression. This review places particular emphasis on the neurotransmission systems, exploring the therapeutic potential of GABAergic neurotransmitters and the role of NMDA inhibitors in the context of glutamatergic neurotransmission. By analyzing the interactions and implications of neurotransmitter pathways in AD, we aim to shed light on emerging therapeutic strategies. In addition to molecular insights, the review addresses the clinical and personal aspects of AD, underscoring the need for patient-centered approaches in treatment and care. The final section looks at the future directions of AD research and treatment, discussing the integration of scientific innovation with patient care. This review aims to provide a comprehensive update on AD, merging scientific insights with practical considerations, suitable for both specialists and those new to the field.

The role of neuroinflammation in neurodegenerative diseases: current understanding and future therapeutic targets

Neuroinflammation refers to a highly complicated reaction of the central nervous system (CNS) to certain stimuli such as trauma, infection, and neurodegenerative diseases. This is a cellular immune response whereby glial cells are activated, inflammatory mediators are liberated and reactive oxygen and nitrogen species are synthesized. Neuroinflammation is a key process that helps protect the brain from pathogens, but inappropriate, or protracted inflammation yields pathological states such as Parkinson's disease, Alzheimer's, Multiple Sclerosis, and other neurodegenerative disorders that showcase various pathways of neurodegeneration distributed in various parts of the CNS. This review reveals the major neuroinflammatory signaling pathways associated with neurodegeneration. Additionally, it explores promising therapeutic avenues, such as stem cell therapy, genetic intervention, and nanoparticles, aiming to regulate neuroinflammation and potentially impede or decelerate the advancement of these conditions. A comprehensive understanding of the intricate connection between neuroinflammation and these diseases is pivotal for the development of future treatment strategies that can alleviate the burden imposed by these devastating disorders.

The endotoxin hypothesis of Alzheimer's disease

Lipopolysaccharide (LPS) constitutes much of the surface of Gram-negative bacteria, and if LPS enters the human body or brain can induce inflammation and act as an endotoxin. We outline the hypothesis here that LPS may contribute to the pathophysiology of Alzheimer's disease (AD) via peripheral infections or gut dysfunction elevating LPS levels in blood and brain, which promotes: amyloid pathology, tau pathology and microglial activation, contributing to the neurodegeneration of AD. The evidence supporting this hypothesis includes: i) blood and brain levels of LPS are elevated in AD patients, ii) AD risk factors increase LPS levels or response, iii) LPS induces Aβ expression, aggregation, inflammation and neurotoxicity, iv) LPS induces TAU phosphorylation, aggregation and spreading, v) LPS induces microglial priming, activation and neurotoxicity, and vi) blood LPS induces loss of synapses, neurons and memory in AD mouse models, and cognitive dysfunction in humans. However, to test the hypothesis, it is necessary to test whether reducing blood LPS reduces AD risk or progression. If the LPS endotoxin hypothesis is correct, then treatments might include: reducing infections, changing gut microbiome, reducing leaky gut, decreasing blood LPS, or blocking LPS response.

Porphyromonas gingivalis and the pathogenesis of Alzheimer's disease

The cause of Alzheimer's disease (AD), and the pathophysiological mechanisms involved, remain major unanswered questions in medical science. Oral bacteria, especially those species associated with chronic periodontitis and particularly Porphyromonas gingivalis, are being linked causally to AD pathophysiology in a subpopulation of susceptible individuals. P. gingivalis produces large amounts of proteolytic enzymes, haem and iron capture proteins, adhesins and internalins that are secreted and attached to the cell surface and concentrated onto outer membrane vesicles (OMVs). These enzymes and adhesive proteins have been shown to cause host tissue damage and stimulate inflammatory responses. The ecological and pathophysiological roles of P. gingivalis OMVs, their ability to disperse widely throughout the host and deliver functional proteins lead to the proposal that they may be the link between a P. gingivalis focal infection in the subgingivae during periodontitis and neurodegeneration in AD. P. gingivalis OMVs can cross the blood brain barrier and may accelerate AD-specific neuropathology by increasing neuroinflammation, plaque/tangle formation and dysregulation of iron homeostasis, thereby inducing ferroptosis leading to neuronal death and neurodegeneration.

Factor H's Control of Complement Activation Emerges as a Significant and Promising Therapeutic Target for Alzheimer's Disease Treatment

The complement is a component of the innate immune system designed to fight infections and tissue- or age-related damages. Complement activation creates an inflammatory microenvironment, which enhances cell death. Excessive complement inflammatory activity has been linked to alterations in the structure and functions of the blood-brain barrier, contributing to a poor prognosis for Alzheimer's disease (AD). In the AD preclinical phase, individuals are often clinically asymptomatic despite evidence of AD neuropathology coupled with heightened inflammation. Considering the involvement of the complement system in the risk of developing AD, we hypothesize that inhibiting complement activation could reduce this inflammatory period observed even before clinical signs, thereby slowing down the onset/progression of AD. To validate our hypothesis, we injected complement inhibitor factor H into the brain of APP/PS1 AD mice at early or late stages of this pathology. Our results showed that the injection of factor H had effects on both the onset and progression of AD by reducing proinflammatory IL6, TNF-α, IL1β, MAC and amyloid beta levels. This reduction was associated with an increase in VGLUT1 and Psd95 synaptic transmission in the hippocampal region, leading to an improvement in cognitive functions. This study invites a reconsideration of factor H's therapeutic potential for AD treatment.

Amelioration of Tau and ApoE4-linked glial lipid accumulation and neurodegeneration with an LXR agonist

Apolipoprotein E (APOE) is a strong genetic risk factor for late-onset Alzheimer's disease (LOAD). APOE4 increases and APOE2 decreases risk relative to APOE3. In the P301S mouse model of tauopathy, ApoE4 increases tau pathology and neurodegeneration when compared with ApoE3 or the absence of ApoE. However, the role of ApoE isoforms and lipid metabolism in contributing to tau-mediated degeneration is unknown. We demonstrate that in P301S tau mice, ApoE4 strongly promotes glial lipid accumulation and perturbations in cholesterol metabolism and lysosomal function. Increasing lipid efflux in glia via an LXR agonist or Abca1 overexpression strongly attenuates tau pathology and neurodegeneration in P301S/ApoE4 mice. We also demonstrate reductions in reactive astrocytes and microglia, as well as changes in cholesterol biosynthesis and metabolism in glia of tauopathy mice in response to LXR activation. These data suggest that promoting efflux of glial lipids may serve as a therapeutic approach to ameliorate tau and ApoE4-linked neurodegeneration.

The Contributions of the Endolysosomal Compartment and Autophagy to APOEɛ4 Allele-Mediated Increase in Alzheimer's Disease Risk

Apolipoprotein E4 (APOE4), although yet-to-be fully understood, increases the risk and lowers the age of onset of Alzheimer's disease (AD), which is the major cause of dementia among elderly individuals. The endosome-lysosome and autophagy pathways, which are necessary for homeostasis in both neurons and glia, are dysregulated even in early AD. Nonetheless, the contributory roles of these pathways to developing AD-related pathologies in APOE4 individuals and models are unclear. Therefore, this review summarizes the dysregulations in the endosome-lysosome and autophagy pathways in APOE4 individuals and non-human models, and how these anomalies contribute to developing AD-relevant pathologies. The available literature suggests that APOE4 causes endosomal enlargement, increases endosomal acidification, impairs endosomal recycling, and downregulates exosome production. APOE4 impairs autophagy initiation and inhibits basal autophagy and autophagy flux. APOE4 promotes lysosome formation and trafficking and causes ApoE to accumulate in lysosomes. APOE4-mediated changes in the endosome, autophagosome and lysosome could promote AD-related features including Aβ accumulation, tau hyperphosphorylation, glial dysfunction, lipid dyshomeostasis, and synaptic defects. ApoE4 protein could mediate APOE4-mediated endosome-lysosome-autophagy changes. ApoE4 impairs vesicle recycling and endosome trafficking, impairs the synthesis of autophagy genes, resists being dissociated from its receptors and degradation, and forms a stable folding intermediate that could disrupt lysosome structure. Drugs such as molecular correctors that target ApoE4 molecular structure and enhance autophagy may ameliorate the endosome-lysosome-autophagy-mediated increase in AD risk in APOE4 individuals.

Cellular and Molecular Mechanisms of Neuronal Degeneration in Early-Stage Diabetic Retinopathy

BACKGROUND

Studies on the early retinal changes in Diabetic Retinopathy (DR) have demonstrated that neurodegeneration precedes vascular abnormalities like microaneurysms or intraretinal hemorrhages. Therefore, there is a growing field of study to analyze the cellular and molecular pathways involved to allow for the development of novel therapeutics to prevent the onset or delay the progression of DR. Molecular Mechanisms: Oxidative stress and mitochondrial dysfunction contribute to neurodegeneration through pathways involving polyol, hexosamine, advanced glycation end products, and protein kinase C. Potential interventions targeting these pathways include aldose reductase inhibitors and protein kinase C inhibitors. Neurotrophic factor imbalances, notably brain-derived neurotrophic factor and nerve growth factor, also play a role in early neurodegeneration, and supplementation of these neurotrophic factors show promise in mitigating neurodegeneration. Cellular Mechanisms: Major cellular mechanisms of neurodegeneration include caspase-mediated apoptosis, glial cell reactivity, and glutamate excitotoxicity. Therefore, inhibitors of these pathways are potential therapeutic avenues. Vascular Component: The nitric oxide pathway, critical for neurovascular coupling, is disrupted in DR due to increased reactive oxygen species. Vascular Endothelial Growth Factor (VEGF), a long-known angiogenic factor, has demonstrated both damaging and neuroprotective effects, prompting a careful consideration of long-term anti-VEGF therapy.

CONCLUSION

Current DR treatments primarily address vascular symptoms but fall short of preventing or halting the disease. Insights into the mechanisms of retinal neurodegeneration in the setting of diabetes mellitus not only enhance our understanding of DR but also pave the way for future therapeutic interventions aimed at preventing disease progression and preserving vision.

Activation of p38 MAPK hinders the reactivation of visual cortical plasticity in adult amblyopic mice

OBJECTIVE

To investigate the impact of p38 mitogen-activated protein kinase (MAPK) signaling on reactivating visual cortical plasticity in adult amblyopic mice.

MATERIALS AND METHODS

Reverse suture (RS), environment enrichment (EE), and combined with left intracerebroventricular injection of p38 MAPK inhibitor (SB203580, SB) or p38 MAPK agonist (dehydrocorydaline hydrochloride, DHC) were utilized to treat adult amblyopic mice with monocular deprivation (MD). The visual water task, visual cliff test, and Flash visual-evoked potential were used to measure the visual function. Then, Golgi staining and transmission electron microscopy were used to assess the reactivation of structural plasticity in adult amblyopic mice. Western blot and immunohistochemistry detected the expression of ATF2, PSD-95, p38 MAPK, and phospho-p38 MAPK in the left visual cortex.

RESULTS

No statistically significant difference was observed in the visual function in each pre-intervention group. Compared to pre-intervention, the visual acuity of deprived eyes was improved significantly, the impairment of visual depth perception was alleviated, and the P wave amplitude and C/I ratio were increased in the EE + RS, the EE + RS + SB, and the EE + RS + DMSO groups, but no significant difference was detected in the EE + RS + DHC group. Compared to EE + RS + DHC group, the density of dendritic spines was significantly higher, the synaptic density of the left visual cortex increased significantly, the length of the active synaptic zone increased, and the thickness of post-synaptic density (PSD) thickened in the left visual cortex of EE + RS, EE + RS + SB, and EE + RS + DMSO groups. And that, the protein expression of p-p38 MAPK increased while that of PSD-95 and ATF2 decreased significantly in the left visual cortex of the EE + RS + DHC group mice.

CONCLUSION

RS and EE intervention improved the visual function and synaptic plasticity of the visual cortex in adult amblyopic mice. However, activating p38 MAPK hinders the recovery of visual function by upregulating the phosphorylation of p38 MAPK and decreasing the ATF2 protein expression.

Adipose tissue-derived mesenchymal stem cells ameliorate cognitive impairment in Alzheimer's disease rat model: Emerging role of SIRT1

Alzheimer's disease (AD) is a complex form of neurodegenerative dementia. Growing body of evidence supports the cardinal role of sirtuin1 (SIRT1) in neurodegeneration and AD development. Recently, adipose tissue-derived mesenchymal stem cells (Ad-MSCs) have made their mark for a wide array of regenerative medicine applications, including neurodegenerative disorders. Therefore, the present study aimed to investigate the therapeutic potential of Ad-MSCs in AD rat model, and to explore the possible implication of SIRT1. Ad-MSCs were isolated from rat epididymal fat pads and properly characterized. Aluminum chloride was used to induce AD in rats, and afterward, a group of AD-induced rats received a single dose of Ad-MSCs (2 × 106 cell, I.V per rat). One month after Ad-MSCs transplantation, behavioral tests were done, brain tissues were collected, then histopathological and biochemical assessments were performed. Amyloid beta and SIRT1 levels were determined by enzyme-linked immunosorbent assay. Whereas expression levels of neprilysin, BCL2 associated X protein, B-cell lymphoma-2, interleukin-1β, interleukin-6, and nerve growth factor in hippocampus and frontal cortex brain tissues were assessed using reverse transcriptase quantitative polymerase chain reaction. Our data demonstrated that transplantation of Ad-MSCs alleviated cognitive impairment in AD rats. Additionally, they exhibited anti-amyloidogenic, antiapoptotic, anti-inflammatory, as well as neurogenic effects. Furthermore, Ad-MSCs were found to possibly mediate their therapeutic effects, at least partially, via modulating both central and systemic SIRT1 levels. Hence, the current study portrays Ad-MSCs as an effective therapeutic approach for AD management and opens the door for future investigations to further elucidate the role of SIRT1 and its interrelated molecular mediators in AD.

The Role of Glucose Concentration and Resveratrol in Modulating Neuroinflammatory Cytokines: Insights from an In Vitro Blood-Brain Barrier Model

BACKGROUND The prevalence of type 2 diabetes mellitus is rising, presumably because of a coexisting pandemic of obesity. Since diabetic neuropathy and neuroinflammation are frequent and significant complications of both prolonged hyperglycemia and iatrogenic hypoglycemia, the effect of glucose concentration and resveratrol (RSV) supplementation on cytokine profile was assessed in an in vitro model of the blood-brain barrier (BBB). MATERIAL AND METHODS The in vitro model of BBB was formed of endothelial cells and astrocytes, which represented the microvascular and brain compartments (MC and BC, respectively). The BC concentrations of selected cytokines - IL-10, IL-12, IL-17A, TNF-alpha, IFN-γ, GM-CSF in response to different glucose concentrations in the MC were studied. The influence of LPS in the BC and RSV in the MC on the cytokine profile in the BC was examined. RESULTS Low glucose concentration (40 mg/dL) in the MC resulted in increased concentration of all the cytokines in the BC except TNF-alpha, compared to normoglycemia-imitating conditions (90 mg/dL) (P<0.05). High glucose concentration (450 mg/dL) in the MC elevated the concentration of all the cytokines in the BC (P<0.05). RSV decreased the level of all cytokines in the BC after 24 h following its administration for all glucose concentrations in the MC (P<0.02). The greatest decline was observed in normoglycemic conditions (P<0.05). CONCLUSIONS Both hypo- and hyperglycemia-simulating conditions impair the cytokine profile in BC, while RSV can normalize it, despite relatively poor penetration through the BBB. RSV exhibits anti-neuroinflammatory effects, especially in the group with normoglycemia-simulating conditions.

Microglia in neurodegenerative diseases: mechanism and potential therapeutic targets

Microglia activation is observed in various neurodegenerative diseases. Recent advances in single-cell technologies have revealed that these reactive microglia were with high spatial and temporal heterogeneity. Some identified microglia in specific states correlate with pathological hallmarks and are associated with specific functions. Microglia both exert protective function by phagocytosing and clearing pathological protein aggregates and play detrimental roles due to excessive uptake of protein aggregates, which would lead to microglial phagocytic ability impairment, neuroinflammation, and eventually neurodegeneration. In addition, peripheral immune cells infiltration shapes microglia into a pro-inflammatory phenotype and accelerates disease progression. Microglia also act as a mobile vehicle to propagate protein aggregates. Extracellular vesicles released from microglia and autophagy impairment in microglia all contribute to pathological progression and neurodegeneration. Thus, enhancing microglial phagocytosis, reducing microglial-mediated neuroinflammation, inhibiting microglial exosome synthesis and secretion, and promoting microglial conversion into a protective phenotype are considered to be promising strategies for the therapy of neurodegenerative diseases. Here we comprehensively review the biology of microglia and the roles of microglia in neurodegenerative diseases, including Alzheimer's disease, Parkinson's disease, multiple system atrophy, amyotrophic lateral sclerosis, frontotemporal dementia, progressive supranuclear palsy, corticobasal degeneration, dementia with Lewy bodies and Huntington's disease. We also summarize the possible microglia-targeted interventions and treatments against neurodegenerative diseases with preclinical and clinical evidence in cell experiments, animal studies, and clinical trials.

The core inflammatory factors in patients with major depressive disorder: a network analysis

Introduction

The symptoms of major depressive disorder (MDD) vary widely. Psycho-neuro-inflammation has shown that MDD's inflammatory factors can accelerate or slow disease progression. This network analysis study examined the complex interactions between depressed symptoms and inflammatory factors in MDD prevention and treatment.

Measures

We gathered participants' inflammatory factor levels, used the Hamilton Depression Scale (HAMD-17), and network analysis was used to analyzed the data. Network analysis revealed the core inflammatory (nodes) and their interactions (edges). Stability and accuracy tests assessed these centrality measures' network robustness. Cluster analysis was used to group persons with similar dimension depressive symptoms and examine their networks.

Results

Interleukin-1β (IL-1β) is the core inflammatory factor in the overall sample, and IL-1β-interleukin-4 (IL-4) is the strongest correlation. Network precision and stability passed. Network analysis showed significant differences between Cluster 1 (with more severe anxiety/somatization and sleep disruption) and Cluster 3 (with more severe retardation and cognitive disorders), as well as between Cluster 2 (with more severe anxiety/somatization, sleep disruption and body weight) and Cluster 3. IL-1β is the core inflammatory factor in Cluster 1 and Cluster 2, while tumor necrosis factor alpha (TNF-α) in Cluster 3.

Conclusion

IL-1β is the central inflammatory factor in the network, and there is heterogeneity in the core inflammatory factor of MDD with specific depressive dimension symptoms as the main manifestation. In conclusion, inflammatory factors and their links should be prioritized in future theoretical models of MDD and may provide new research targets for MDD intervention and treatment.

NRSF regulates age-dependently cognitive ability and its conditional knockout in APP/PS1 mice moderately alters AD-like pathology

NRSF/REST (neuron-restrictive silencer element, also known as repressor element 1-silencing transcription factor), plays a key role in neuronal homeostasis as a transcriptional repressor of neuronal genes. NRSF/REST relates to cognitive preservation and longevity of humans, but its specific functions in age-dependent and Alzheimer's disease (AD)-related memory deficits remain unclear. Here, we show that conditional NRSF/REST knockout either in the dorsal telencephalon or specially in neurons induced an age-dependently diminished retrieval performance in spatial or fear conditioning memory tasks and altered hippocampal synaptic transmission and activity-dependent synaptic plasticity. The NRSF/REST deficient mice were also characterized by an increase of activated glial cells, complement C3 protein and the transcription factor C/EBPβ in the cortex and hippocampus. Reduction of NRSF/REST by conditional depletion upregulated the activation of astrocytes in APP/PS1 mice, and increased the C3-positive glial cells, but did not alter the Aβ loads and memory retrieval performances of 6- and 12-month-old APP/PS1 mice. Simultaneously, overexpression of NRSF/REST improved cognitive abilities of aged wild type, but not in AD mice. These findings demonstrated that NRSF/REST is essential for the preservation of memory performance and activity-dependent synaptic plasticity during aging and takes potential roles in the onset of age-related memory impairments. However, while altering the glial activation, NRSF/REST deficiency does not interfere with the Aβ deposits and the electrophysiological and cognitive AD-like pathologies.

Tau and neuroinflammation in Alzheimer's disease: interplay mechanisms and clinical translation

Alzheimer's Disease (AD) contributes to most cases of dementia. Its prominent neuropathological features are the extracellular neuritic plaques and intercellular neurofibrillary tangles composed of aggregated β-amyloid (Aβ) and hyperphosphorylated tau protein, respectively. In the past few decades, disease-modifying therapy targeting Aβ has been the focus of AD drug development. Even though it is encouraging that two of these drugs have recently received accelerated US Food and Drug Administration approval for AD treatment, their efficacy or long-term safety is controversial. Tau has received increasing attention as a potential therapeutic target, since evidence indicates that tau pathology is more associated with cognitive dysfunction. Moreover, inflammation, especially neuroinflammation, accompanies AD pathological processes and is also linked to cognitive deficits. Accumulating evidence indicates that inflammation has a complex and tight interplay with tau pathology. Here, we review recent evidence on the interaction between tau pathology, focusing on tau post-translational modification and dissemination, and neuroinflammatory responses, including glial cell activation and inflammatory signaling pathways. Then, we summarize the latest clinical trials targeting tau and neuroinflammation. Sustained and increased inflammatory responses in glial cells and neurons are pivotal cellular drivers and regulators of the exacerbation of tau pathology, which further contributes to its worsening by aggravating inflammatory responses. Unraveling the precise mechanisms underlying the relationship between tau pathology and neuroinflammation will provide new insights into the discovery and clinical translation of therapeutic targets for AD and other tau-related diseases (tauopathies). Targeting multiple pathologies and precision therapy strategies will be the crucial direction for developing drugs for AD and other tauopathies.

Alzheimer's Disease Treatment: The Search for a Breakthrough

As the search for modalities to cure Alzheimer's disease (AD) has made slow progress, research has now turned to innovative pathways involving neural and peripheral inflammation and neuro-regeneration. Widely used AD treatments provide only symptomatic relief without changing the disease course. The recently FDA-approved anti-amyloid drugs, aducanumab and lecanemab, have demonstrated unclear real-world efficacy with a substantial side effect profile. Interest is growing in targeting the early stages of AD before irreversible pathologic changes so that cognitive function and neuronal viability can be preserved. Neuroinflammation is a fundamental feature of AD that involves complex relationships among cerebral immune cells and pro-inflammatory cytokines, which could be altered pharmacologically by AD therapy. Here, we provide an overview of the manipulations attempted in pre-clinical experiments. These include inhibition of microglial receptors, attenuation of inflammation and enhancement of toxin-clearing autophagy. In addition, modulation of the microbiome-brain-gut axis, dietary changes, and increased mental and physical exercise are under evaluation as ways to optimize brain health. As the scientific and medical communities work together, new solutions may be on the horizon to slow or halt AD progression.

Interleukin 1β triggers synaptic and memory deficits in Herpes simplex virus type-1-infected mice by downregulating the expression of synaptic plasticity-related genes via the epigenetic MeCP2/HDAC4 complex

Extensive research provides evidence that neuroinflammation underlies numerous brain disorders. However, the molecular mechanisms by which inflammatory mediators determine synaptic and cognitive dysfunction occurring in neurodegenerative diseases (e.g., Alzheimer's disease) are far from being fully understood. Here we investigated the role of interleukin 1β (IL-1β), and the molecular cascade downstream the activation of its receptor, to the synaptic dysfunction occurring in the mouse model of multiple Herpes simplex virus type-1 (HSV-1) reactivations within the brain. These mice are characterized by neuroinflammation and memory deficits associated with a progressive accumulation of neurodegenerative hallmarks (e.g., amyloid-β protein and tau hyperphosphorylation). Here we show that mice undergone two HSV-1 reactivations in the brain exhibited increased levels of IL-1β along with significant alterations of: (1) cognitive performances; (2) hippocampal long-term potentiation; (3) expression synaptic-related genes and pre- and post-synaptic proteins; (4) dendritic spine density and morphology. These effects correlated with activation of the epigenetic repressor MeCP2 that, in association with HDAC4, affected the expression of synaptic plasticity-related genes. Specifically, in response to HSV-1 infection, HDAC4 accumulated in the nucleus and promoted MeCP2 SUMOylation that is a post-translational modification critically affecting the repressive activity of MeCP2. The blockade of IL-1 receptors by the specific antagonist Anakinra prevented the MeCP2 increase and the consequent downregulation of gene expression along with rescuing structural and functional indices of neurodegeneration. Collectively, our findings provide novel mechanistic evidence on the role played by HSV-1-activated IL-1β signaling pathways in synaptic deficits leading to cognitive impairment.

The innate immune response in tauopathies

Tauopathies, which include frontotemporal dementia, Alzheimer's disease, and chronic traumatic encephalopathy, are a class of neurological disorders resulting from pathogenic tau aggregates. These aggregates disrupt neuronal health and function leading to the cognitive and physical decline of tauopathy patients. Genome-wide association studies and clinical evidence have brought to light the large role of the immune system in inducing and driving tau-mediated pathology. More specifically, innate immune genes are found to harbor tauopathy risk alleles, and innate immune pathways are upregulated throughout the course of disease. Experimental evidence has expanded on these findings by describing pivotal roles for the innate immune system in the regulation of tau kinases and tau aggregates. In this review, we summarize the literature implicating innate immune pathways as drivers of tauopathy.

Early chronic suppression of microglial p38α in a model of Alzheimer's disease does not significantly alter amyloid-associated neuropathology

The p38 alpha mitogen-activated protein kinase (p38α) is linked to both innate and adaptive immune responses and is under investigation as a target for drug development in the context of Alzheimer's disease (AD) and other conditions with neuroinflammatory dysfunction. While preclinical data has shown that p38α inhibition can protect against AD-associated neuropathology, the underlying mechanisms are not fully elucidated. Inhibitors of p38α may provide benefit via modulation of microglial-associated neuroinflammatory responses that contribute to AD pathology. The present study tests this hypothesis by knocking out microglial p38α and assessing early-stage pathological changes. Conditional knockout of microglial p38α was accomplished in 5-month-old C57BL/6J wild-type and amyloidogenic AD model (APPswe/PS1dE9) mice using a tamoxifen-inducible Cre/loxP system under control of the Cx3cr1 promoter. Beginning at 7.5 months of age, animals underwent behavioral assessment on the open field, followed by a later radial arm water maze test and collection of cortical and hippocampal tissues at 11 months. Additional endpoint measures included quantification of proinflammatory cytokines, assessment of amyloid burden and plaque deposition, and characterization of microglia-plaque dynamics. Loss of microglial p38α did not alter behavioral outcomes, proinflammatory cytokine levels, or overall amyloid plaque burden. However, this manipulation did significantly increase hippocampal levels of soluble Aβ42 and reduce colocalization of Iba1 and 6E10 in a subset of microglia in close proximity to plaques. The data presented here suggest that rather than reducing inflammation per se, the net effect of microglial p38α inhibition in the context of early AD-type amyloid pathology is a subtle alteration of microglia-plaque interactions. Encouragingly from a therapeutic standpoint, these data suggest no detrimental effect of even substantial decreases in microglial p38α in this context. Additionally, these results support future investigations of microglial p38α signaling at different stages of disease, as well as its relationship to phagocytic processes in this particular cell-type.

Revisiting the intersection of microglial activation and neuroinflammation in Alzheimer's disease from the perspective of ferroptosis

Alzheimer's disease (AD) is a neurodegenerative disorder characterized by chronic neuroinflammation with amyloid beta-protein deposition and hyperphosphorylated tau protein. The typical clinical manifestation of AD is progressive memory impairment, and AD is considered a multifactorial disease with various etiologies (genetic factors, aging, lifestyle, etc.) and complicated pathophysiological processes. Previous research identified that neuroinflammation and typical microglial activation are significant mechanisms underlying AD, resulting in dysfunction of the nervous system and progression of the disease. Ferroptosis is a novel modality involved in this process. As an iron-dependent form of cell death, ferroptosis, characterized by iron accumulation, lipid peroxidation, and irreversible plasma membrane disruption, promotes AD by accelerating neuronal dysfunction and abnormal microglial activation. In this case, disturbances in brain iron homeostasis and neuronal ferroptosis aggravate neuroinflammation and lead to the abnormal activation of microglia. Abnormally activated microglia release various pro-inflammatory factors that aggravate the dysregulation of iron homeostasis and neuroinflammation, forming a vicious cycle. In this review, we first introduce ferroptosis, microglia, AD, and their relationship. Second, we discuss the nonnegligible role of ferroptosis in the abnormal microglial activation involved in the chronic neuroinflammation of AD to provide new ideas for the identification of potential therapeutic targets for AD.

The Multifaceted Role of WNT Signaling in Alzheimer's Disease Onset and Age-Related Progression

The evolutionary conserved WNT signaling pathway orchestrates numerous complex biological processes during development and is critical to the maintenance of tissue integrity and homeostasis in the adult. As it relates to the central nervous system, WNT signaling plays several roles as it relates to neurogenesis, synaptic formation, memory, and learning. Thus, dysfunction of this pathway is associated with multiple diseases and disorders, including several neurodegenerative disorders. Alzheimer's disease (AD) is characterized by several pathologies, synaptic dysfunction, and cognitive decline. In this review, we will discuss the various epidemiological, clinical, and animal studies that demonstrate a precise link between aberrant WNT signaling and AD-associated pathologies. In turn, we will discuss the manner in which WNT signaling influences multiple molecular, biochemical, and cellular pathways upstream of these end-point pathologies. Finally, we will discuss how merging tools and technologies can be used to generate next generation cellular models to dissect the relationship between WNT signaling and AD.

Recent Development in the Understanding of Molecular and Cellular Mechanisms Underlying the Etiopathogenesis of Alzheimer's Disease

Alzheimer's disease (AD) is a progressive neurodegenerative disorder that leads to dementia and patient death. AD is characterized by intracellular neurofibrillary tangles, extracellular amyloid beta (Aβ) plaque deposition, and neurodegeneration. Diverse alterations have been associated with AD progression, including genetic mutations, neuroinflammation, blood-brain barrier (BBB) impairment, mitochondrial dysfunction, oxidative stress, and metal ion imbalance.Additionally, recent studies have shown an association between altered heme metabolism and AD. Unfortunately, decades of research and drug development have not produced any effective treatments for AD. Therefore, understanding the cellular and molecular mechanisms underlying AD pathology and identifying potential therapeutic targets are crucial for AD drug development. This review discusses the most common alterations associated with AD and promising therapeutic targets for AD drug discovery. Furthermore, it highlights the role of heme in AD development and summarizes mathematical models of AD, including a stochastic mathematical model of AD and mathematical models of the effect of Aβ on AD. We also summarize the potential treatment strategies that these models can offer in clinical trials.

The Pharmacological Activity of Garlic (Allium sativum) in Parkinson's Disease: From Molecular Mechanisms to the Therapeutic Potential

Parkinson's disease (PD), one of the most common neurological diseases worldwide, is mainly characterized neuropathologically by the dopaminergic neurodegeneration in the substantia nigra pars compacta of the brainstem. Genetic and environmental factors contribute to PD pathophysiology through modulation of pleiotropic cellular mechanisms. The currently available treatment options focus only on replenishing dopamine and do not alter disease progression. Interestingly, garlic (Allium sativum), globally famed for its flavor and taste-enhancing properties, has shown protective activity in different PD models. Numerous chemical constituents of garlic, mainly the organosulfur compounds, have been shown to exhibit anti-Parkinsonian effects by targeting oxidative stress, mitochondrial impairment, and neuroinflammation-related signaling. However, despite its therapeutic potential against PD, the major bioactive components of garlic display some stability issues and some adverse effects. In the present review, we explore the therapeutic potential of garlic and its major constituents in PD, the molecular mechanisms responsible for its pharmaceutical activity, and the associated limitations that need to be overcome for its future potential use in clinical practice.

Cortical-blood vessel assembloids exhibit Alzheimer's disease phenotypes by activating glia after SARS-CoV-2 infection

A correlation between COVID-19 and Alzheimer's disease (AD) has been proposed recently. Although the number of case reports on neuroinflammation in COVID-19 patients has increased, studies of SARS-CoV-2 neurotrophic pathology using brain organoids have restricted recapitulation of those phenotypes due to insufficiency of immune cells and absence of vasculature. Cerebral pericytes and endothelial cells, the major components of blood-brain barrier, express viral entry receptors for SARS-CoV-2 and response to systemic inflammation including direct cell death. To overcome the limitations, we developed cortical-blood vessel assembloids by fusing cortical organoid with blood vessel organoid to provide vasculature to brain organoids a nd obtained the characteristics of increased expression of microglia and astrocytes in brain organoids. Furthermore, we observed AD pathologies, including β-amyloid plaques, which were affected by the inflammatory response from SARS-CoV-2 infection. These findings provide an advanced platform to investigate human neurotrophic diseases, including COVID-19, and suggest that neuroinflammation caused by viral infection facilitates AD pathology.

Molecular Mechanisms Underlying Neuroinflammation Elicited by Occupational Injuries and Toxicants

Occupational injuries and toxicant exposures lead to the development of neuroinflammation by activating distinct mechanistic signaling cascades that ultimately culminate in the disruption of neuronal function leading to neurological and neurodegenerative disorders. The entry of toxicants into the brain causes the subsequent activation of glial cells, a response known as 'reactive gliosis'. Reactive glial cells secrete a wide variety of signaling molecules in response to neuronal perturbations and thus play a crucial role in the progression and regulation of central nervous system (CNS) injury. In parallel, the roles of protein phosphorylation and cell signaling in eliciting neuroinflammation are evolving. However, there is limited understanding of the molecular underpinnings associated with toxicant- or occupational injury-mediated neuroinflammation, gliosis, and neurological outcomes. The activation of signaling molecules has biological significance, including the promotion or inhibition of disease mechanisms. Nevertheless, the regulatory mechanisms of synergism or antagonism among intracellular signaling pathways remain elusive. This review highlights the research focusing on the direct interaction between the immune system and the toxicant- or occupational injury-induced gliosis. Specifically, the role of occupational injuries, e.g., trips, slips, and falls resulting in traumatic brain injury, and occupational toxicants, e.g., volatile organic compounds, metals, and nanoparticles/nanomaterials in the development of neuroinflammation and neurological or neurodegenerative diseases are highlighted. Further, this review recapitulates the recent advancement related to the characterization of the molecular mechanisms comprising protein phosphorylation and cell signaling, culminating in neuroinflammation.

Microglia PTK2B/Pyk2 in the Pathogenesis of Alzheimer's Disease

Alzheimer's disease (AD) is a highly hereditary disease with complex genetic susceptibility factors. Extensive genome-wide association studies have established a distinct susceptibility link between the protein tyrosine kinase 2β (PTK2B) gene and late-onset Alzheimer's disease (LOAD), but the specific pathogenic mechanisms remain incompletely understood. PTK2B is known to be expressed in neurons, and recent research has revealed its more important significance in microglia. Elucidating the role of PTK2B high expression in microglia in AD's progression is crucial for uncovering novel pathogenic mechanisms of the disease. Our review of existing studies suggests a close relationship between PTK2B/proline-rich tyrosine kinase 2 (Pyk2) and tau pathology, and this process might be β-amyloid (Aβ) dependence. Pyk2 is hypothesized as a pivotal target linking Aβ and tau pathologies. Concurrently, Aβ-activated Pyk2 participates in the regulation of microglial activation and its proinflammatory functions. Consequently, it is reasonable to presume that Pyk2 in microglia contributes to amyloid-induced tau pathology in AD via a neuroinflammatory pathway. Furthermore, many things remain unclear, such as identifying the specific pathways that lead to the release of downstream inflammatory factors due to Pyk2 phosphorylation and whether all types of inflammatory factors can activate neuronal kinase pathways. Additionally, further in vivo experiments are essential to validate this hypothesized pathway. Considering PTK2B/Pyk2's potential role in AD pathogenesis, targeting this pathway may offer innovative and promising therapeutic approaches for AD.

Multi-Target Neuroprotection of Thiazolidinediones on Alzheimer's Disease via Neuroinflammation and Ferroptosis

Alzheimer's disease (AD) is the main cause of dementia in older age. The prevalence of AD is growing worldwide, causing a tremendous burden to societies and families. Due to the complexity of its pathogenesis, the current treatment of AD is not satisfactory, and drugs acting on a single target may not prevent AD progression. This review summarizes the multi-target pharmacological effects of thiazolidinediones (TZDs) on AD. TZDs act as peroxisome proliferator-activated receptor gamma (PPARγ) agonists and long-chain acyl-CoA synthetase family member 4 (ACSL4) inhibitors. TZDs ameliorated neuroinflammation and ferroptosis in preclinical models of AD. Here, we discussed recent findings from clinical trials of pioglitazone in the treatment of AD, ischemic stroke, and atherosclerosis. We also dissected the major limitations in the clinical application of pioglitazone and explained the potential benefit of pioglitazone in AD. We recommend the use of pioglitazone to prevent cognitive decline and lower AD risk in a specific group of patients.

Association of Anemia with Cognitive Function and Dementia Among Older Adults: The Role of Inflammation

BACKGROUND

The association of anemia with cognitive function and dementia remains unclear.

OBJECTIVE

We aimed to investigate the association of anemia with cognitive function and dementia risk and to explore the role of inflammation in these associations.

METHODS

Within the UK Biobank, 207,203 dementia-free participants aged 60+ were followed for up to 16 years. Hemoglobin (HGB) and C-creative protein (CRP) were measured from blood samples taken at baseline. Anemia was defined as HGB <13 g/dL for males and <12 g/dL for females. Inflammation was categorized as low or high according to the median CRP level (1.50 mg/L). A subset of 18,211 participants underwent cognitive assessments (including global and domain-specific cognitive). Data were analyzed using linear mixed-effects model, Cox regression, and Laplace regression.

RESULTS

Anemia was associated with faster declines in global cognition (β= -0.08, 95% confidence interval [CI]: -0.14, -0.01) and processing speed (β= -0.10, 95% CI: -0.19, -0.01). During the follow-up of 9.76 years (interquartile range 7.55 to 11.39), 6,272 developed dementia. The hazard ratio of dementia was 1.57 (95% CI: 1.38, 1.78) for people with anemia, and anemia accelerated dementia onset by 1.53 (95% CI: 1.08, 1.97) years. The risk of dementia tended to be higher in people with both anemia and high CRP (1.89, 95% CI: 1.60, 2.22). There was a statistically significant interaction between anemia and CRP on dementia risk (p-interaction = 0.032).

CONCLUSIONS

Anemia is associated with cognitive decline (specifically for processing speed) and increased risk of dementia, especially in people with high inflammation.

Associations Between TREML2 Gene Variants and Alzheimer's Disease: Biomarkers, Neuroimage, and Cognition

BACKGROUND

Recent genetic research identified a protective factor against late-onset Alzheimer's disease (AD) in Caucasians, a variant called rs3747742-C in the TREML2 gene. However, the roles of other TREML2 variants in AD have not been fully explored.

OBJECTIVE

We conducted a focused analysis of 16 TREML2 variants, examining their connection to AD by studying their correlation with cerebrospinal fluid (CSF) proteins, neuroimage, and cognition in the Alzheimer's Disease Neuroimaging Initiative database (ADNI).

METHODS

A multiple linear regression model was utilized to estimate potential associations between TREML2 genotypes and various endophenotypes in the entire ADNI sample at baseline, with age, gender, years of education, and APOE ɛ4 status included as covariates. To examine changes in clinical outcomes over time, linear mixed-effects models were employed.

RESULTS

We found that the SNP rs17328707-A was associated with higher ADNI-VS scores, smaller ventricles, and larger middle temporal volume at baseline. The SNP rs6915083-G was linked to lower CSF t-tau and p-tau levels, and higher CSF Aβ levels. The SNP rs9394766-G was associated with a smaller hippocampus and larger ventricles at baseline. In longitudinal cohorts, the rs6915083-G SNP was associated with changes in ADNI-MEM and ADNI-EF scores, as well as the rate of hippocampal and middle temporal atrophy.

CONCLUSION

Our findings reveal that TREML2 gene variants have different effects on AD. Two variants are protective, while one may be a risk factor. This enhances our understanding of AD genetics and could guide future research and personalized treatments.

Microglia as a cellular target of diclofenac therapy in Alzheimer's disease

Alzheimer's disease (AD) is an untreatable cause of dementia, and new therapeutic approaches are urgently needed. AD pathology is defined by extracellular amyloid plaques and intracellular neurofibrillary tangles. Research of the past decades has suggested that neuroinflammation plays a critical role in the pathophysiology of AD. This has led to the idea that anti-inflammatory treatments might be beneficial. Early studies investigated non-steroidal anti-inflammatory drugs (NSAIDS) such as indomethacin, celecoxib, ibuprofen, and naproxen, which had no benefit. More recently, protective effects of diclofenac and NSAIDs in the fenamate group have been reported. Diclofenac decreased the frequency of AD significantly compared to other NSAIDs in a large retrospective cohort study. Diclofenac and fenamates share similar chemical structures, and evidence from cell and mouse models suggests that they inhibit the release of pro-inflammatory mediators from microglia with leads to the reduction of AD pathology. Here, we review the potential role of diclofenac and NSAIDs in the fenamate group for targeting AD pathology with a focus on its potential effects on microglia.