Peripheral administration of the soluble TNF inhibitor XPro1595 modifies brain immune cell profiles, decreases beta-amyloid plaque load, and rescues impaired long-term potentiation in 5xFAD mice

C-reactive protein-mediated dementia

Loss of memory is the main feature of dementia, accompanied by personality changes. Alzheimer's disease (AD) is the most prevalent type of dementia globally and a major contributor to disability and mortality in older individuals. Most notably, the neurological damage caused by AD is irreversible, but the current market still lacks effective medications for the treatment of dementia. Numerous research studies have indicated that the inflammatory response is significantly involved in the development of cognitive impairment, and elevated C-reactive protein (CRP) levels in healthy people increases the likelihood of future AD. CRP is a nonspecific indicator of inflammation. In clinical practice, CRP has long been proven to be one of the risk factors and powerful predictors of neurodegenerative diseases. Given the accessibility and cost-effectiveness of CRP testing, it is reasonable to anticipate its utilisation for early screening and monitoring the progression of AD in the future. This review therefore focuses on the specific relationship between CRP and various types of dementia and explores how CRP contributes to cognitive impairment.

Unraveling the Immune Puzzle: Role of Immunomodulation in Alzheimer's Disease

Alzheimer's disease (AD) is a complex neurodegenerative disorder with growing evidence highlighting the dual role of immunomodulation in its pathogenesis and potential therapeutic strategies. Disturbance in the immune system increases the inflammatory cytokines that cause tau hyperphosphorylation and neuroinflammation. Also, immune checkpoint inhibition further increases the amyloid-beta deposition. Therefore, this review examines the intricate interplay between the immune system and AD, focusing on how immunomodulatory mechanisms influence key pathological hallmarks, including amyloid-beta aggregation, tau hyperphosphorylation, neuroinflammation, and cholinergic dysfunction. We analyse critical signaling pathways involved in immune regulation, such as Toll-like receptor (TLR), Janus kinase/signal transducer and activator of transcription (JAK/STAT), phosphoinositide 3-kinase/Akt (PI3K/Akt), Wnt/β-catenin, tumor necrosis factor (TNF), and triggering receptor expressed on myeloid cells (TREM), along with immune checkpoints like programmed cell death protein 1 (PD-1). Preclinical studies of immunomodulatory agents, including salidroside, festidinol, astragalin, sulforaphane, BM-MSC, simvastatin, Ab-T1, hTREM2, and XENP345, demonstrate promising effects. Additionally, clinical investigations of drugs such as simufilam, AL002, TB006, VGL101, DNL919, XPro1595, astragalus, and IBC-Ab002 underscore the therapeutic potential of targeting immune pathways in AD. This review emphasizes how neuroinflammation, microglial activation, and peripheral immune responses contribute to disease progression. By exploring immunomodulatory mechanisms, the article sheds light on potential therapeutic targets that could help mitigate AD pathology which may pave the way for novel interventions preventing neurodegeneration in AD.

MHCII reduction is insufficient to protect mice from alpha-synuclein-induced degeneration and the Parkinson's HLA locus exhibits epigenetic regulation

Major histocompatibility complex class II (MHCII) molecules are antigen presentation proteins and increased in post-mortem Parkinson's disease (PD) brain. Attempts to decrease MHCII expression have led to neuroprotection in PD mouse models. Our group reported that a single nucleotide polymorphism (SNP) at rs3129882 in the MHCII gene Human Leukocyte Antigen (HLA) DRA is associated with increased MHCII transcripts and surface protein and increased risk for late-onset idiopathic PD. We therefore hypothesized that decreased MHCII may mitigate dopaminergic degeneration. During an ongoing α-synuclein lesion, mice with MHCII reduction in systemic and brain innate immune cells (LysMCre + I-Abfl/fl or CRE+) displayed brain T cell repertoire shifts and greater preservation of the dopaminergic phenotype in nigrostriatal terminals. Next, we investigated a human cohort to characterize the immunophenotype of subjects with and without the high-risk GG genotype at the rs3129882 SNP. We confirmed that the high-risk GG genotype is associated with peripheral changes in MHCII inducibility, frequency of CD4 + T cells, and differentially accessible chromatin regions within the MHCII locus. Although our mouse studies indicate that myeloid MHCII reduction coinciding with an intact adaptive immune system is insufficient to fully protect dopamine neurons from α-synuclein-induced degeneration, our data are consistent with the overwhelming evidence implicating antigen presentation in PD pathophysiology.

Role of metabolic dysfunction and inflammation along the liver-brain axis in animal models with obesity-induced neurodegeneration

The interaction between metabolic dysfunction and inflammation is central to the development of neurodegenerative diseases such as Alzheimer's disease and Parkinson's disease. Obesity-related conditions like type 2 diabetes and non-alcoholic fatty liver disease exacerbate this relationship. Peripheral lipid accumulation, particularly in the liver, initiates a cascade of inflammatory processes that extend to the brain, influencing critical metabolic regulatory regions. Ceramide and palmitate, key lipid components, along with lipid transporters lipocalin-2 and apolipoprotein E, contribute to neuroinflammation by disrupting blood-brain barrier integrity and promoting gliosis. Peripheral insulin resistance further exacerbates brain insulin resistance and neuroinflammation. Preclinical interventions targeting peripheral lipid metabolism and insulin signaling pathways have shown promise in reducing neuroinflammation in animal models. However, translating these findings to clinical practice requires further investigation into human subjects. In conclusion, metabolic dysfunction, peripheral inflammation, and insulin resistance are integral to neuroinflammation and neurodegeneration. Understanding these complex mechanisms holds potential for identifying novel therapeutic targets and improving outcomes for neurodegenerative diseases.

Lack of neuroprotection after systemic administration of the soluble TNF inhibitor XPro1595 in an rAAV6-α-Syn + PFFs-induced rat model for Parkinson's disease

Parkinson's disease (PD) is characterized by dopaminergic neurodegeneration, α-Synuclein (α-Syn) pathology, and inflammation. Microglia in the substantia nigra pars compacta (SNpc) upregulate major histocompatibility complex class II (MHCII), and variants in genes encoding MHCII affect PD risk. Additionally, elevated TNF levels and α-Syn-reactive T cells in circulation suggest a strong link between innate and adaptive immune responses in PD. We have previously reported that reduced levels of the class II transactivator, the master regulator of MHCII expression, increases susceptibility to α-Syn-induced PD-like pathology in rats and are associated with higher serum levels of soluble TNF (sTNF). Here, we demonstrate that inhibiting sTNF with a dominant-negative TNF variant, XPro1595, known to be neuroprotective in endotoxin- and toxin-induced neurodegeneration models, fails to protect against robust α-Syn-induced PD-like pathology in rats. We used a model combining rAAV-mediated α-Syn overexpression in SNpc with striatal injection of α-Syn preformed fibrils two weeks later. Systemic XPro1595 treatment was initiated one-week post-rAAV-α-Syn. We observed up to 70 % loss of striatal dopaminergic fibers without treatment, and no protective effects on dopaminergic neurodegeneration after XPro1595 administration. Pathological α-Syn levels as well as microglial and astrocytic activation were not reduced in SNpc or striatum following XPro1595 treatment. An increase in IL-6 and IL-1β levels in CSF was observed in rats treated with XPro1595, possibly explaining a lack of protective effects following treatment. Our results highlight the need to determine the importance of timing of treatment initiation, which is crucial for future applications of sTNF therapies in PD patients.

Nrf2/Bach1 signaling axis: A promising multifaceted therapeutic strategy for Alzheimer's disease

Alzheimer's disease (AD) is the most prevalent form of dementia, which continues to elude effective treatment despite decades of research and numerous clinical trials. While existing therapeutic strategies have primarily targeted neuropathological hallmarks such as amyloid plaques and tau tangles, they have failed to halt disease progression, leaving patients with limited options. This persistent failure reveals a critical gap in our understanding of AD and calls for a fresh perspective - one that goes beyond the traditional targets and dives deeper into the fundamental cellular processes that drive neurodegeneration. Recent advances in molecular biology underscore the significance of nuclear factor E2-related factor 2 (Nrf2), often termed the "guardian of redox homeostasis," in the pathophysiology of AD. Nrf2 orchestrates cellular responses to oxidative stress and neuroinflammation - two interlinked pathological features of AD. In the brains of AD patients, Nrf2 activity is diminished, weakening the brain's ability to counteract oxidative damage. Additionally, the BTB and CNC homology 1 (Bach1) protein, a transcriptional repressor of Nrf2, has emerged as a potential therapeutic target. Here, we review the current landscape of clinical trials in AD and identify the limitations of the conventional approaches. We then explore the prospects of a novel approach that combines Nrf2 activation with Bach1 inhibition to achieve a multipronged defense against oxidative stress, neuroinflammation, and other molecular culprits driving AD. This innovative strategy holds promise for synergistically modulating multiple neuroprotective pathways to advance AD treatment.

Immune modulation to treat Alzheimer's disease

Immune mechanisms play a fundamental role in Alzheimer's disease (AD) pathogenesis, suggesting that approaches which target immune cells and immunologically relevant molecules can offer therapeutic opportunities beyond the recently approved amyloid beta monoclonal therapies. In this review, we provide an overview of immunomodulatory therapeutics in development, including their preclinical evidence and clinical trial results. Along with detailing immune processes involved in AD pathogenesis and highlighting how these mechanisms can be therapeutically targeted to modify disease progression, we summarize knowledge gained from previous trials of immune-based interventions, and provide a series of recommendations for the development of future immunomodulatory therapeutics to treat AD.

MHCII reduction is insufficient to protect mice from alpha-synuclein-induced degeneration and the Parkinson's HLA locus exhibits epigenetic regulation

Major histocompatibility complex class II (MHCII) molecules are antigen presentation proteins and increased in post-mortem Parkinson's disease (PD) brain. Attempts to decrease MHCII expression have led to neuroprotection in PD mouse models. Our group reported that a SNP at rs3129882 in the MHCII gene Human leukocyte Antigen (HLA) DRA is associated with increased MHCII transcripts and surface protein and increased risk for late-onset idiopathic PD. We therefore hypothesized that decreased MHCII may mitigate dopaminergic degeneration. During an ongoing α-synuclein lesion, mice with MHCII reduction in systemic and brain innate immune cells (LysMCre+I-Abfl/fl or CRE+) displayed brain T cell repertoire shifts and greater preservation of the dopaminergic phenotype in nigrostriatal terminals. Next, we investigated a human cohort to characterize the immunophenotype of subjects with and without the high-risk GG genotype at the rs3129882 SNP. We confirmed that the high-risk GG genotype is associated with peripheral changes in MHCII inducibility, frequency of CD4+ T cells, and differentially accessible chromatin regions within the MHCII locus. Although our mouse studies indicate that myeloid MHCII reduction coinciding with an intact adaptive immune system is insufficient to fully protect dopamine neurons from α-synuclein-induced degeneration, our data are consistent with the overwhelming evidence implicating antigen presentation in PD pathophysiology.

Peripherally administered TNF inhibitor is not protective against α-synuclein-induced dopaminergic neuronal death in rats

The underlying cause of neuronal loss in Parkinson's disease (PD) remains unknown, but evidence implicates neuroinflammation in PD pathobiology. The pro-inflammatory cytokine soluble tumor necrosis factor (TNF) seems to play an important role and thus has been proposed as a therapeutic target for modulation of the neuroinflammatory processes in PD. In this regard, dominant-negative TNF (DN-TNF) agents are promising antagonists that selectively inhibit soluble TNF signaling, while preserving the beneficial effects of transmembrane TNF. Previous studies have tested the protective potential of DN-TNF-based therapy in toxin-based PD models. Here we test for the first time the protective potential of a DN-TNF therapeutic against α-synuclein-driven neurodegeneration in the viral vector-based PD female rat model. To do so, we administered the DN-TNF agent XPro1595 subcutaneously for a period of 12 weeks. In contrast to previous studies using different PD models, neuroprotection was not achieved by systemic XPro1595 treatment. α-Synuclein-induced loss of nigrostriatal neurons, accumulation of pathological inclusions and microgliosis was detected in both XPro1595- and saline-treated animals. XPro1595 treatment increased the percentage of the hypertrophic/ameboid Iba1+ cells in SN and reduced the striatal MHCII+ expression in the α-synuclein-overexpressing animals. However, the treatment did not prevent the MHCII upregulation seen in the SN of the model, nor the increase of CD68+ phagocytic cells. Therefore, despite an apparently immunomodulatory effect, this did not suffice to protect against viral vector-derived α-synuclein-induced neurotoxicity. Further studies are warranted to better elucidate the therapeutic potential of soluble TNF inhibitors in PD.

Akkermansia muciniphila and its metabolite propionic acid maintains neuronal mitochondrial division and autophagy homeostasis during Alzheimer's disease pathologic process via GPR41 and GPR43

BACKGROUND

Alzheimer's disease (AD) is a prevalent neurodegenerative disease (ND). In recent years, multiple clinical and animal studies have shown that mitochondrial dysfunction may be involved in the pathogenesis of AD. In addition, short-chain fatty acids (SCFA) produced by intestinal microbiota metabolism have been considered to be important factors affecting central nervous system (CNS) homeostasis. Among the main mediators of host-microbe interactions, volatile fatty acids play a crucial role. Nevertheless, the influence and pathways of microorganisms and their metabolites on Alzheimer's disease (AD) remain uncertain.

RESULTS

In this study, we present distinctions in blood and fecal SCFA levels and microbiota composition between healthy individuals and those diagnosed with AD. We found that AD patients showed a decrease in the abundance of Akkermansia muciniphila and a decrease in propionic acid both in fecal and in blood. In order to further reveal the effects and the mechanisms of propionic acid on AD prevention, we systematically explored the effects of propionic acid administration on AD model mice and cultured hippocampal neuronal cells. Results showed that oral propionate supplementation ameliorated cognitive impairment in AD mice. Propionate downregulated mitochondrial fission protein (DRP1) via G-protein coupled receptor 41 (GPR41) and enhanced PINK1/PARKIN-mediated mitophagy via G-protein coupled receptor 43 (GPR43) in AD pathophysiology which contribute to maintaining mitochondrial homeostasis both in vivo and in vitro. Administered A. muciniphila to AD mice before disease onset showed improved cognition, mitochondrial division and mitophagy in AD mice.

CONCLUSIONS

Taken together, our results demonstrate that A. muciniphila and its metabolite propionate protect against AD-like pathological events in AD mouse models by targeting mitochondrial homeostasis, making them promising therapeutic candidates for the prevention and treatment of AD. Video Abstract.

Disease-modifying therapies for Alzheimer's disease: Clinical trial progress and opportunity

The U.S. Food and Drug Administration (FDA) recently approved lecanemab and donanemab for the treatment of early symptomatic Alzheimer's disease (AD) after their phase III trials reached endpoints. These two anti-amyloid β monoclonal antibodies represent the latest promise of disease-modifying therapy (DMT) for AD, which undoubtedly reignites new hope for DMTs to combat the staggering financial and human costs of AD. However, in addition to these two successful antibodies, there have been enormous efforts to develop DMTs in various aspects to meet the therapeutic requirement of AD. In this review, we delineate the core principles and methodologies of diverse DMTs, covering the advances in clinical trials of drug candidates that either have been discontinued, completed, or are ongoing, as well as brain stimulation and lifestyle interventions. In addition, by overseeing the fate of various candidate molecules, we hope to provide references and ideas for prospective approaches and promising applications of DTMs for AD, particularly in terms of universality and clinical application economics, to optimize efficacy and maximize AD patient benefits in the future.

Investigation of Novel Aronia Bioactive Fraction-Alginic Acid Nanocomplex on the Enhanced Modulation of Neuroinflammation and Inhibition of Aβ Aggregation

BACKGROUND/OBJECTIVES

Aronia extract or its active compounds, especially anthocyanin, have shown potential for Alzheimer's disease (AD)-related pathologies, including neuroinflammation, fibrillogenesis of amyloid beta (Aβ), and cognitive impairment. However, there was still concern about their structural instability in vivo and in vitro. To solve the instability of anthocyanins, we combined aronia bioactive factions (ABFs) and alginic acid via electrostatic molecular interactions and created an ABF-alginic acid nanocomplex (AANCP). We evaluated whether it is more stable and effective in cognitive disorder mice and neuroinflammation cell models.

METHODS

The physicochemical properties of the AANCP, such as nanoparticle size, structural stability, and release rate, were characterized. The AANCP was administered to scopolamine-injected Balb/c mice, and to BV2 microglia treated with lipopolysaccharide (LPS) and amyloid beta (Aβ). Inflammation responses were measured via qPCR and ELISA in vitro, and cognitive functions were measured via behavior tests in vivo.

RESULTS

The AANCP readily formed nanoparticles, 209.6 nm in size, with a negatively charged zeta potential. The AANCP exhibited better stability in four plasma samples (human, dog, rat, and mouse) and was slowly released in different pH conditions (pH 2.0, 7.4, and 8.0) compared with non-complexedABF. In vitro studies on microglial cells treated with AANCPs revealed a suppression of inflammatory cytokines (tumor necrosis factor-alpha and interleukin-6) induced by LPS. The AANCP increased microglial Aβ phagocytosis through the activation of triggering receptor expressed on myeloid cell 2 (TREM2)-related microglial polarization. The AANCP inhibited aggregation of Aβ in vitro and alleviated cognitive impairment in a scopolamine-induced in vivo dementia mouse model.

CONCLUSIONS

Our data indicate that AANCPs are more stable than ABFs and effective for cognitive disorders and neuroinflammation via modulation of M2 microglial polarization.

Brain-immune interactions: implication for cognitive impairments in Alzheimer's disease and autoimmune disorders

Progressive memory loss and cognitive dysfunction, encompassing deficits in learning, memory, problem solving, spatial reasoning, and verbal expression, are characteristics of Alzheimer's disease and related dementia. A wealth of studies has described multiple roles of the immune system in the development or exacerbation of dementia. Individuals with autoimmune disorders can also develop cognitive dysfunction, a phenomenon termed "autoimmune dementia." Together, these findings underscore the pivotal role of the neuroimmune axis in both Alzheimer's disease and related dementia and autoimmune dementia. The dynamic interplay between adaptive and innate immunity, both in and outside the brain, significantly affects the etiology and progression of these conditions. Multidisciplinary research shows that cognitive dysfunction arises from a bidirectional relationship between the nervous and immune systems, though the specific mechanisms that drive cognitive impairments are not fully understood. Intriguingly, this reciprocal regulation occurs at multiple levels, where neuronal signals can modulate immune responses, and immune system-related processes can influence neuronal viability and function. In this review, we consider the implications of autoimmune responses in various autoimmune disorders and Alzheimer's disease and explore their effects on brain function. We also discuss the diverse cellular and molecular crosstalk between the brain and the immune system, as they may shed light on potential triggers of peripheral inflammation, their effect on the integrity of the blood-brain barrier, and brain function. Additionally, we assess challenges and possibilities associated with developing immune-based therapies for the treatment of cognitive decline.

Unveiling the role of astrogliosis in Alzheimer's disease Pathology: Insights into mechanisms and therapeutic approaches

Alzheimer's disease (AD) is one of the most debilitating age-related disorders that affect people globally. It impacts social and cognitive behavior of the individual and is characterized by phosphorylated tau and Aβ accumulation. Astrocytesmaintain a quiescent, anti-inflammatory state on anatomical level, expressing few cytokines and exhibit phagocytic activity to remove misfolded proteins. But in AD, in response to specific stimuli, astrocytes overstimulate their phagocytic character with overexpressing cytokine gene modules. Upon interaction with generated Aβ and neurofibrillary tangle, astrocytes that are continuously activated release a large number of inflammatory cytokines. This cytokine storm leads to neuroinflammation which is also one of the recognizable features of AD. Astrogliosis eventually promotes cholinergic dysfunction, calcium imbalance, oxidative stress and excitotoxicity. Furthermore, C5aR1, Lcn2/, BDNF/TrkB and PPARα/TFEB signaling dysregulation has a major impact on the disease progression. This review clarifies numerous ways that lead to astrogliosis, which is stimulated by a variety of processes that exacerbate AD pathology and make it a suitable target for AD treatment. Drugs under clinical and preclinical investigations that target several pathways managing astrogliosis and are efficacious in ameliorating the pathology of the disease are also included in this study. D-ALA2GIP, TRAM-34, Genistein, L-serine, MW150 and XPro1595 are examples of few drugs targeting astrogliosis. Therefore, this study may aid in the development of a potent therapeutic agent for ameliorating astrogliosis mediated AD progression.

Alzheimer's Disease, Obesity, and Type 2 Diabetes: Focus on Common Neuroglial Dysfunctions (Critical Review and New Data on Human Brain and Models)

BACKGROUND/OBJECTIVES

Obesity, type 2 diabetes (T2D), and Alzheimer's disease (AD) are pathologies that affect millions of people worldwide. They have no effective therapy and are difficult to prevent and control when they develop. It has been known for many years that these diseases have many pathogenic aspects in common. We highlight in this review that neuroglial cells (astroglia, oligodendroglia, and microglia) play a vital role in the origin, clinical-pathological development, and course of brain neurodegeneration. Moreover, we include the new results of a T2D-AD mouse model (APP+PS1 mice on a high-calorie diet) that we are investigating.

METHODS

Critical bibliographic revision and biochemical neuropathological study of neuroglia in a T2D-AD model.

RESULTS

T2D and AD are not only "connected" by producing complex pathologies in the same individual (obesity, T2D, and AD), but they also have many common pathogenic mechanisms. These include insulin resistance, hyperinsulinemia, hyperglycemia, oxidative stress, mitochondrial dysfunction, and inflammation (both peripheral and central-or neuroinflammation). Cognitive impairment and AD are the maximum exponents of brain neurodegeneration in these pathological processes. both due to the dysfunctions induced by metabolic changes in peripheral tissues and inadequate neurotoxic responses to changes in the brain. In this review, we first analyze the common pathogenic mechanisms of obesity, T2D, and AD (and/or cerebral vascular dementia) that induce transcendental changes and responses in neuroglia. The relationships between T2D and AD discussed mainly focus on neuroglial responses. Next, we present neuroglial changes within their neuropathological context in diverse scenarios: (a) aging involution and neurodegenerative disorders, (b) human obesity and diabetes and obesity/diabetes models, (c) human AD and in AD models, and (d) human AD-T2D and AD-T2D models. An important part of the data presented comes from our own studies on humans and experimental models over the past few years. In the T2D-AD section, we included the results of a T2D-AD mouse model (APP+PS1 mice on a high-calorie diet) that we investigated, which showed that neuroglial dysfunctions (astrocytosis and microgliosis) manifest before the appearance of amyloid neuropathology, and that the amyloid pathology is greater than that presented by mice fed a normal, non-high-caloric diet A broad review is finally included on pharmacological, cellular, genic, and non-pharmacological (especially diet and lifestyle) neuroglial-related treatments, as well as clinical trials in a comparative way between T2D and AD. These neuroglial treatments need to be included in the multimodal/integral treatments of T2D and AD to achieve greater therapeutic efficacy in many millions of patients.

CONCLUSIONS

Neuroglial alterations (especially in astroglia and microglia, cornerstones of neuroinflammation) are markedly defining brain neurodegeneration in T2D and A, although there are some not significant differences between each of the studied pathologies. Neuroglial therapies are a very important and p. promising tool that are being developed to prevent and/or treat brain dysfunction in T2D-AD. The need for further research in two very different directions is evident: (a) characterization of the phenotypic changes of astrocytes and microglial cells in each region of the brain and in each phase of development of each isolated and associated pathology (single-cell studies are mandatory) to better understand the pathologies and define new therapeutic targets; (b) studying new therapeutic avenues to normalize the function of neuroglial cells (preventing neurotoxic responses and/or reversing them) in these pathologies, as well as the phenotypic characteristics in each moment of the course and place of the neurodegenerative process.

The impact of neuroinflammation on neuronal integrity

Neuroinflammation, characterized by a complex interplay among innate and adaptive immune responses within the central nervous system (CNS), is crucial in responding to infections, injuries, and disease pathologies. However, the dysregulation of the neuroinflammatory response could significantly affect neurons in terms of function and structure, leading to profound health implications. Although tremendous progress has been made in understanding the relationship between neuroinflammatory processes and alterations in neuronal integrity, the specific implications concerning both structure and function have not been extensively covered, with the exception of perspectives on glial activation and neurodegeneration. Thus, this review aims to provide a comprehensive overview of the multifaceted interactions among neurons and key inflammatory players, exploring mechanisms through which inflammation influences neuronal functionality and structural integrity in the CNS. Further, it will discuss how these inflammatory mechanisms lead to impairment in neuronal functions and architecture and highlight the consequences caused by dysregulated neuronal functions, such as cognitive dysfunction and mood disorders. By integrating insights from recent research findings, this review will enhance our understanding of the neuroinflammatory landscape and set the stage for future interventions that could transform current approaches to preserve neuronal integrity and function in CNS-related inflammatory conditions.

Thinking outside the brain: Gut microbiome influence on innate immunity within neurodegenerative disease

The complex network of factors that contribute to neurodegeneration have hampered the discovery of effective preventative measures. While much work has focused on brain-first therapeutics, it is becoming evident that physiological changes outside of the brain are the best target for early interventions. Specifically, myeloid cells, including peripheral macrophages and microglia, are a sensitive population of cells whose activity can directly impact neuronal health. Myeloid cell activity includes cytokine production, migration, debris clearance, and phagocytosis. Environmental measures that can modulate these activities range from toxin exposure to diet. However, one of the most influential mediators of myeloid fitness is the gut microenvironment. Here, we review the current data about the role of myeloid cells in gastrointestinal disorders, Parkinson's disease, dementia, and multiple sclerosis. We then delve into the gut microbiota modulating therapies available and clinical evidence for their use in neurodegeneration. Modulating lifestyle and environmental mediators of inflammation are one of the most promising interventions for neurodegeneration and a systematic and concerted effort to examine these factors in healthy aging is the next frontier.

Diverse signaling mechanisms and heterogeneity of astrocyte reactivity in Alzheimer's disease

Alzheimer's disease (AD) affects various brain cell types, including astrocytes, which are the most abundant cell types in the central nervous system (CNS). Astrocytes not only provide homeostatic support to neurons but also actively regulate synaptic signaling and functions and become reactive in response to CNS insults through diverse signaling pathways including the JAK/STAT, NF-κB, and GPCR-elicited pathways. The advent of new technology for transcriptomic profiling at the single-cell level has led to increasing recognition of the highly versatile nature of reactive astrocytes and the context-dependent specificity of astrocyte reactivity. In AD, reactive astrocytes have long been observed in senile plaques and have recently been suggested to play a role in AD pathogenesis and progression. However, the precise contributions of reactive astrocytes to AD remain elusive, and targeting this complex cell population for AD treatment poses significant challenges. In this review, we summarize the current understanding of astrocyte reactivity and its role in AD, with a particular focus on the signaling pathways that promote astrocyte reactivity and the heterogeneity of reactive astrocytes. Furthermore, we explore potential implications for the development of therapeutics for AD. Our objective is to shed light on the complex involvement of astrocytes in AD and offer insights into potential therapeutic targets and strategies for treating and managing this devastating neurodegenerative disorder.

Inflammaging and Brain Aging

Progress made by the medical community in increasing lifespans comes with the costs of increasing the incidence and prevalence of age-related diseases, neurodegenerative ones included. Aging is associated with a series of morphological changes at the tissue and cellular levels in the brain, as well as impairments in signaling pathways and gene transcription, which lead to synaptic dysfunction and cognitive decline. Although we are not able to pinpoint the exact differences between healthy aging and neurodegeneration, research increasingly highlights the involvement of neuroinflammation and chronic systemic inflammation (inflammaging) in the development of age-associated impairments via a series of pathogenic cascades, triggered by dysfunctions of the circadian clock, gut dysbiosis, immunosenescence, or impaired cholinergic signaling. In addition, gender differences in the susceptibility and course of neurodegeneration that appear to be mediated by glial cells emphasize the need for future research in this area and an individualized therapeutic approach. Although rejuvenation research is still in its very early infancy, accumulated knowledge on the various signaling pathways involved in promoting cellular senescence opens the perspective of interfering with these pathways and preventing or delaying senescence.

Diet-induced metabolic and immune impairments are sex-specifically modulated by soluble TNF signaling in the 5xFAD mouse model of Alzheimer's disease

Emerging evidence indicates that high-fat, high carbohydrate diet (HFHC) impacts central pathological features of Alzheimer's disease (AD) across both human incidences and animal models. However, the mechanisms underlying this association are poorly understood. Here, we identify compartment-specific metabolic and inflammatory dysregulations that are induced by HFHC diet in the 5xFAD mouse model of AD pathology. We observe that both male and female 5xFAD mice display exacerbated adiposity, cholesterolemia, and dysregulated insulin signaling. Independent of biological sex, HFHC diet also resulted in altered inflammatory cytokine profiles across the gastrointestinal, circulating, and central nervous systems (CNS) compartments demonstrating region-specific impacts of metabolic inflammation. Interestingly, inhibiting the inflammatory cytokine, soluble tumor necrosis factor (TNF) with the brain-permeant soluble TNF inhibitor XPro1595 was able to restore aspects of HFHC-induced metabolic inflammation, but only in male mice. Targeted transcriptomics of CNS regions revealed that inhibition of soluble TNF was sufficient to alter expression of hippocampal and cortical genes associated with beneficial immune and metabolic responses. Collectively, these results suggest that HFHC diet impairs metabolic and inflammatory pathways in an AD-relevant genotype and that soluble TNF has sex-dependent roles in modulating these pathways across anatomical compartments. Modulation of energy homeostasis and inflammation may provide new therapeutic avenues for AD.

Diet-induced metabolic and immune impairments are sex-specifically modulated by soluble TNF signaling in the 5xFAD mouse model of Alzheimer's disease

Emerging evidence indicates that high-fat, high carbohydrate diet (HFHC) impacts central pathological features of Alzheimer's disease (AD) across both human incidences and animal models. However, the mechanisms underlying this association are poorly understood. Here, we identify compartment-specific metabolic and inflammatory dysregulations that are induced by HFHC diet in the 5xFAD mouse model of AD pathology. We observe that both male and female 5xFAD mice display exacerbated adiposity, cholesterolemia, and dysregulated insulin signaling. Independent of biological sex, HFHC diet also resulted in altered inflammatory cytokine profiles across the gastrointestinal, circulating, and central nervous systems (CNS) compartments demonstrating region-specific impacts of metabolic inflammation. In male mice, we note that HFHC triggered increases in amyloid beta, an observation not seen in female mice. Interestingly, inhibiting the inflammatory cytokine, soluble tumor necrosis factor (TNF) with the brain-permeant soluble TNF inhibitor XPro1595 was able to restore aspects of HFHC-induced metabolic inflammation, but only in male mice. Targeted transcriptomics of CNS regions revealed that inhibition of soluble TNF was sufficient to alter expression of hippocampal and cortical genes associated with beneficial immune and metabolic responses. Collectively, these results suggest that HFHC diet impairs metabolic and inflammatory pathways in an AD-relevant genotype and that soluble TNF has sex-dependent roles in modulating these pathways across anatomical compartments. Modulation of energy homeostasis and inflammation may provide new therapeutic avenues for AD.

A case for seeking sex-specific treatments in Alzheimer's disease

There is no satisfactory explanation for the sex-related differences in the incidence of many diseases and this is also true of Alzheimer's disease (AD), where females have a higher lifetime risk of developing the disease and make up about two thirds of the AD patient population. The importance of understanding the cause(s) that account for this disproportionate distribution cannot be overestimated, and is likely to be a significant factor in the search for therapeutic strategies that will combat the disease and, furthermore, potentially point to a sex-targeted approach to treatment. This review considers the literature in the context of what is known about the impact of sex on processes targeted by drugs that are in clinical trial for AD, and existing knowledge on differing responses of males and females to these drugs. Current knowledge strongly supports the view that trials should make assessing sex-related difference in responses a priority with a focus on exploring the sex-stratified treatments.

Modeling the neuroimmune system in Alzheimer's and Parkinson's diseases

Parkinson's disease (PD) and Alzheimer's disease (AD) are neurodegenerative disorders caused by the interaction of genetic, environmental, and familial factors. These diseases have distinct pathologies and symptoms that are linked to specific cell populations in the brain. Notably, the immune system has been implicated in both diseases, with a particular focus on the dysfunction of microglia, the brain's resident immune cells, contributing to neuronal loss and exacerbating symptoms. Researchers use models of the neuroimmune system to gain a deeper understanding of the physiological and biological aspects of these neurodegenerative diseases and how they progress. Several in vitro and in vivo models, including 2D cultures and animal models, have been utilized. Recently, advancements have been made in optimizing these existing models and developing 3D models and organ-on-a-chip systems, holding tremendous promise in accurately mimicking the intricate intracellular environment. As a result, these models represent a crucial breakthrough in the transformation of current treatments for PD and AD by offering potential for conducting long-term disease-based modeling for therapeutic testing, reducing reliance on animal models, and significantly improving cell viability compared to conventional 2D models. The application of 3D and organ-on-a-chip models in neurodegenerative disease research marks a prosperous step forward, providing a more realistic representation of the complex interactions within the neuroimmune system. Ultimately, these refined models of the neuroimmune system aim to aid in the quest to combat and mitigate the impact of debilitating neuroimmune diseases on patients and their families.

Cranial venous-outflow obstruction promotes neuroinflammation via ADAM17/solTNF-α/NF-κB pathway following experimental TBI

Traumatic brain injury (TBI) is a global public health problem. As an important cause of secondary injury, cerebrovascular reaction can cause secondary bleeding, venous sinus thrombosis, and malignant brain swelling. Recent clinical studies have confirmed that intracranial venous return disorder is closely related to the prognosis of patients, yet the specific molecular mechanism involved in this process is still unclear. This study used an acute subdural hematoma (ASDH) model with cranial venous outflow obstruction (CVO) to explore how CVO aggravates the pathological process after TBI, especially for inflammation and tissue damage. The results suggest that intracranial venous return disorder exacerbates neurological deficits and brain edema in rats with ASDH by aggravating the destruction of endothelial cell tight junctions (TJs) proteins and promoting the expression of inflammatory factors, the activation of microglia and expression of recombinant A disintegrin and metalloprotease 17 (ADAM17) as well as the secretion of solTNF-α, a soluble form of tumor necrosis factor-alpha (TNFα), which in turn increase IκB-α ((inhibitor of the transcription factor nuclear factor-κB) and NF-κB p65. Our study revealed a molecular basis of how CVO aggravates inflammation and tissue damage.

Implicative role of Cytokines in Neuroinflammation mediated AD and associated signaling pathways: Current Progress in molecular signaling and therapeutics

Alzheimer's Disease (AD) is one of the most devastating age-related disorder causing significant social and economic burden worldwide. It affects the cognitive and social behavior of individuals and characterized by accumulation of Aβ, phosphorylated tau and cytokines formation. The synthesis and release of cytokines are regulated by specific groups of immune and non-immune cells in response to microglia or astrocyte activation through multiple pathways. Physiologically, microglia assert an anti-inflammatory, quiescent state with minimal cytokine expression and little phagocytic activity in motion to carry out their housekeeping role to eliminate pathogens, aggregated Aβ and tau protein. However, they develop a phagocytic nature and overexpress cytokine gene modules in response to certain stimuli in AD. Microglia and astrocytes upon chronic activation release an enormous amount of inflammatory cytokines due to interaction with formed Aβ and neurofibrillary tangle. Gut microbiota dysbiosis also stimulates the release of inflammatory cytokines contributing to AD pathogenesis. In addition, the dysregulation of few signaling pathways significantly influences the development of disease, and the pace of advancement also rises with age. This review sheds light on multiple pathways results into neuroinflammation triggered by activated cytokines worsening AD pathology and making it an appropriate target for AD treatment. This review also included drugs targeting different neuroinflammation pathways under clinical and preclinical studies that are found to be effective in attenuating the disease pathology.

Alzheimer's Disease: Novel Targets and Investigational Drugs for Disease Modification

Novel agents addressing non-amyloid, non-tau targets in Alzheimer's Disease (AD) comprise 70% of the AD drug development pipeline of agents currently in clinical trials. Most of the target processes identified in the Common Alzheimer's Disease Research Ontology (CADRO) are represented by novel agents in trials. Inflammation and synaptic plasticity/neuroprotection are the CADRO categories with the largest number of novel candidate therapies. Within these categories, there are few overlapping targets among the test agents. Additional categories being evaluated include apolipoprotein E [Formula: see text] 4 (APOE4) effects, lipids and lipoprotein receptors, neurogenesis, oxidative stress, bioenergetics and metabolism, vascular factors, cell death, growth factors and hormones, circadian rhythm, and epigenetic regulators. We highlight current drugs being tested within these categories and their mechanisms. Trials will be informative regarding which targets can be modulated to produce a slowing of clinical decline. Possible therapeutic combinations of agents may be suggested by trial outcomes. Biomarkers are evolving in concert with new targets and novel agents, and biomarker outcomes offer a means of supporting disease modification by the putative treatment. Identification of novel targets and development of corresponding therapeutics offer an important means of advancing new treatments for AD.

Novel small molecules inhibit proteotoxicity and inflammation: Mechanistic and therapeutic implications for Alzheimer's Disease, healthspan and lifespan- Aging as a consequence of glycolysis

Inflammation drives many age-related, especially neurological, diseases, and likely mediates age-related proteotoxicity. For example, dementia due to Alzheimer's Disease (AD), cerebral vascular disease, many other neurodegenerative conditions is increasingly among the most devastating burdens on the American (and world) health system and threatens to bankrupt the American health system as the population ages unless effective treatments are developed. Dementia due to either AD or cerebral vascular disease, and plausibly many other neurodegenerative and even psychiatric conditions, is driven by increased age-related inflammation, which in turn appears to mediate Abeta and related proteotoxic processes. The functional significance of inflammation during aging is also supported by the fact that Humira, which is simply an antibody to the pro-inflammatory cytokine TNF-a, is the best-selling drug in the world by revenue. These observations led us to develop parallel high-throughput screens to discover small molecules which inhibit age-related Abeta proteotoxicity in a C. elegans model of AD AND LPS-induced microglial TNF-a. In the initial screen of 2560 compounds (Microsource Spectrum library) to delay Abeta proteotoxicity, the most protective compounds were, in order, phenylbutyrate, methicillin, and quetiapine, which belong to drug classes (HDAC inhibitors, beta lactam antibiotics, and tricyclic antipsychotics, respectably) already robustly implicated as promising to protect in neurodegenerative diseases, especially AD. RNAi and chemical screens indicated that the protective effects of HDAC inhibitors to reduce Abeta proteotoxicity are mediated by inhibition of HDAC2, also implicated in human AD, dependent on the HAT Creb binding protein (Cbp), which is also required for the protective effects of both dietary restriction and the daf-2 mutation (inactivation of IGF-1 signaling) during aging. In addition to methicillin, several other beta lactam antibiotics also delayed Abeta proteotoxicity and reduced microglial TNF-a. In addition to quetiapine, several other tricyclic antipsychotic drugs also delayed age-related Abeta proteotoxicity and increased microglial TNF-a, leading to the synthesis of a novel congener, GM310, which delays Abeta as well as Huntingtin proteotoxicity, inhibits LPS-induced mouse and human microglial and monocyte TNF-a, is highly concentrated in brain after oral delivery with no apparent toxicity, increases lifespan, and produces molecular responses highly similar to those produced by dietary restriction, including induction of Cbp inhibition of inhibitors of Cbp, and genes promoting a shift away from glycolysis and toward metabolism of alternate (e.g., lipid) substrates. GM310, as well as FDA-approved tricyclic congeners, prevented functional impairments and associated increase in TNF-a in a mouse model of stroke. Robust reduction of glycolysis by GM310 was functionally corroborated by flux analysis, and the glycolytic inhibitor 2-DG inhibited microglial TNF-a and other markers of inflammation, delayed Abeta proteotoxicity, and increased lifespan. These results support the value of phenotypic screens to discover drugs to treat age-related, especially neurological and even psychiatric diseases, including AD and stroke, and to clarify novel mechanisms driving neurodegeneration (e.g., increased microglial glycolysis drives neuroinflammation and subsequent neurotoxicity) suggesting novel treatments (selective inhibitors of microglial glycolysis).

Infiltrating CD8+ T cells exacerbate Alzheimer's disease pathology in a 3D human neuroimmune axis model

Brain infiltration of peripheral immune cells and their interactions with brain-resident cells may contribute to Alzheimer's disease (AD) pathology. To examine these interactions, in the present study we developed a three-dimensional human neuroimmune axis model comprising stem cell-derived neurons, astrocytes and microglia, together with peripheral immune cells. We observed an increase in the number of T cells (but not B cells) and monocytes selectively infiltrating into AD relative to control cultures. Infiltration of CD8+ T cells into AD cultures led to increased microglial activation, neuroinflammation and neurodegeneration. Using single-cell RNA-sequencing, we identified that infiltration of T cells into AD cultures led to induction of interferon-γ and neuroinflammatory pathways in glial cells. We found key roles for the C-X-C motif chemokine ligand 10 (CXCL10) and its receptor, CXCR3, in regulating T cell infiltration and neuronal damage in AD cultures. This human neuroimmune axis model is a useful tool to study the effects of peripheral immune cells in brain disease.

Selective Inhibition of Soluble Tumor Necrosis Factor Alters the Neuroinflammatory Response following Moderate Spinal Cord Injury in Mice

Clinical and animal model studies have implicated inflammation and glial and peripheral immune cell responses in the pathophysiology of spinal cord injury (SCI). A key player in the inflammatory response after SCI is the pleiotropic cytokine tumor necrosis factor (TNF), which exists both in both a transmembrane (tmTNF) and a soluble (solTNF) form. In the present study, we extend our previous findings of a therapeutic effect of topically blocking solTNF signaling after SCI for three consecutive days on lesion size and functional outcome to study the effect on spatio-temporal changes in the inflammatory response after SCI in mice treated with the selective solTNF inhibitor XPro1595 and compared to saline-treated mice. We found that despite comparable TNF and TNF receptor levels between XPro1595- and saline-treated mice, XPro1595 transiently decreased pro-inflammatory interleukin (IL)-1β and IL-6 levels and increased pro-regenerative IL-10 levels in the acute phase after SCI. This was complemented by a decrease in the number of infiltrated leukocytes (macrophages and neutrophils) in the lesioned area of the spinal cord and an increase in the number of microglia in the peri-lesion area 14 days after SCI, followed by a decrease in microglial activation in the peri-lesion area 21 days after SCI. This translated into increased myelin preservation and improved functional outcomes in XPro1595-treated mice 35 days after SCI. Collectively, our data suggest that selective targeting of solTNF time-dependently modulates the neuroinflammatory response by favoring a pro-regenerative environment in the lesioned spinal cord, leading to improved functional outcomes.

The role of peripheral inflammatory insults in Alzheimer's disease: a review and research roadmap

Peripheral inflammation, defined as inflammation that occurs outside the central nervous system, is an age-related phenomenon that has been identified as a risk factor for Alzheimer's disease. While the role of chronic peripheral inflammation has been well characterized in the context of dementia and other age-related conditions, less is known about the neurologic contribution of acute inflammatory insults that take place outside the central nervous system. Herein, we define acute inflammatory insults as an immune challenge in the form of pathogen exposure (e.g., viral infection) or tissue damage (e.g., surgery) that causes a large, yet time-limited, inflammatory response. We provide an overview of the clinical and translational research that has examined the connection between acute inflammatory insults and Alzheimer's disease, focusing on three categories of peripheral inflammatory insults that have received considerable attention in recent years: acute infection, critical illness, and surgery. Additionally, we review immune and neurobiological mechanisms which facilitate the neural response to acute inflammation and discuss the potential role of the blood-brain barrier and other components of the neuro-immune axis in Alzheimer's disease. After highlighting the knowledge gaps in this area of research, we propose a roadmap to address methodological challenges, suboptimal study design, and paucity of transdisciplinary research efforts that have thus far limited our understanding of how pathogen- and damage-mediated inflammatory insults may contribute to Alzheimer's disease. Finally, we discuss how therapeutic approaches designed to promote the resolution of inflammation may be used following acute inflammatory insults to preserve brain health and limit progression of neurodegenerative pathology.

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.

Apoptotic cell death in disease-Current understanding of the NCCD 2023

Apoptosis is a form of regulated cell death (RCD) that involves proteases of the caspase family. Pharmacological and genetic strategies that experimentally inhibit or delay apoptosis in mammalian systems have elucidated the key contribution of this process not only to (post-)embryonic development and adult tissue homeostasis, but also to the etiology of multiple human disorders. Consistent with this notion, while defects in the molecular machinery for apoptotic cell death impair organismal development and promote oncogenesis, the unwarranted activation of apoptosis promotes cell loss and tissue damage in the context of various neurological, cardiovascular, renal, hepatic, infectious, neoplastic and inflammatory conditions. Here, the Nomenclature Committee on Cell Death (NCCD) gathered to critically summarize an abundant pre-clinical literature mechanistically linking the core apoptotic apparatus to organismal homeostasis in the context of disease.

Soluble TNF mediates amyloid-independent, diet-induced alterations to immune and neuronal functions in an Alzheimer's disease mouse model

Introduction: Increasing evidence indicates that neurodegenerative diseases, including Alzheimer's disease (AD), are a product of gene-by-environment interplay. The immune system is a major contributor mediating these interactions. Signaling between peripheral immune cells and those within the microvasculature and meninges of the central nervous system (CNS), at the blood-brain barrier, and in the gut likely plays an important role in AD. The cytokine tumor necrosis factor (TNF) is elevated in AD patients, regulates brain and gut barrier permeability, and is produced by central and peripheral immune cells. Our group previously reported that soluble TNF (sTNF) modulates cytokine and chemokine cascades that regulate peripheral immune cell traffic to the brain in young 5xFAD female mice, and in separate studies that a diet high in fat and sugar (HFHS) dysregulates signaling pathways that trigger sTNF-dependent immune and metabolic responses that can result in metabolic syndrome, which is a risk factor for AD. We hypothesized that sTNF is a key mediator of peripheral immune cell contributions to gene-by-environment interactions to AD-like pathology, metabolic dysfunction, and diet-induced gut dysbiosis. Methods: Female 5xFAD mice were subjected to HFHS diet for 2 months and then given XPro1595 to inhibit sTNF for the last month or saline vehicle. We quantified immune cell profiles by multi-color flow cytometry on cells isolated from brain and blood; metabolic, immune, and inflammatory mRNA and protein marker biochemical and immunhistological analyses, gut microbiome, and electrophysiology in brain slices were also performed. Results: Here, we show that selective inhibition of sTNF signaling via the biologic XPro1595 modulates the effects of an HFHS diet in 5xFAD mice on peripheral and central immune profiles including CNS-associated CD8+ T cells, the composition of gut microbiota, and long-term potentiation deficits. Discussion: Obesogenic diet induces immune and neuronal dysfunction in 5xFAD mice and sTNF inhibition mitigates its effects. A clinical trial in subjects at risk for AD due to genetic predisposition and underlying inflammation associated with peripheral inflammatory co-morbidities will be needed to investigate the extent to which these findings translate to the clinic.

In Vitro Antiviral Effect and Potential Neuroprotection of Salvadora persica L. Stem Bark Extract against Lipopolysaccharides-Induced Neuroinflammation in Mice: LC-ESI-MS/MS Analysis of the Methanol Extract

Neuroinflammation is a serious immunomodulatory complex disorder that causes neurological and somatic ailments. The treatment of brain inflammation with new drugs derived from natural sources is a significant therapeutic goal. Utilizing LC-ESI-MS/MS analysis, the active constituents of Salvadora persica extract (SPE) were identified tentatively as exerting antioxidant and anti-inflammatory effects in natural medicine. Herein, we determined the antiviral potential of SPE against herpes simplex virus type 2 (HSV-2) using the plaque assay. HSV-2 is a neurotropic virus that can cause neurological diseases. SPE exhibited promising antiviral potential with a half-maximal cytotoxic concentration (CC50) of 185.960 ± 0.1 µg/mL and a half-maximal inhibitory concentration (IC50) of 8.946 ± 0.02 µg/mL. The in vivo study of the SPE impact against lipopolysaccharide (LPS)-induced neuroinflammation was performed using 42 mice divided into seven groups. All groups were administered LPS (0.25 mg/kg) intraperitoneally, except for the normal and SPE groups 1 and 2. Groups 5, 6, and 7 received 100, 200, and 300 mg/kg SPE. It was revealed that SPE inhibited acetylcholinesterase in the brain. It increased superoxide dismutase and catalase while decreasing malondialdehyde, which explains its antioxidative stress activity. SPE downregulated the gene expression of the inducible nitric oxide synthase, as well as the apoptotic markers (caspase-3 and c-Jun). In addition, it decreased the expression of the proinflammatory cytokines (interleukin-6 and tumor necrosis factor-alpha). Mice administered SPE (300 mg/kg) with LPS exhibited normal neurons in the cerebral cortices, hippocampus pyramidal layer, and cerebellum, as determined by the histopathological analysis. Therefore, using S. persica to prevent and treat neurodegeneration could be a promising new therapeutic strategy to be explored.

Past, Present and (Foreseeable) Future of Biological Anti-TNF Alpha Therapy

Due to the key role of tumor necrosis factor-alpha (TNF-α) in the pathogenesis of immunoinflammatory diseases, TNF-α inhibitors have been successfully developed and used in the clinical treatment of autoimmune disorders. Currently, five anti-TNF-α drugs have been approved: infliximab, adalimumab, golimumab, certolizumab pegol and etanercept. Anti-TNF-α biosimilars are also available for clinical use. Here, we will review the historical development as well as the present and potential future applications of anti-TNF-α therapies, which have led to major improvements for patients with several autoimmune diseases, such as rheumatoid arthritis (RA), ankylosing spondylitis (AS), Crohn's disease (CD), ulcerative colitis (UC), psoriasis (PS) and chronic endogenous uveitis. Other therapeutic areas are under evaluation, including viral infections, e.g., COVID-19, as well as chronic neuropsychiatric disorders and certain forms of cancer. The search for biomarkers able to predict responsiveness to anti-TNF-α drugs is also discussed.

The neuroimmune axis of Alzheimer's disease

Alzheimer's disease (AD) is a genetically complex and heterogeneous disorder with multifaceted neuropathological features, including β-amyloid plaques, neurofibrillary tangles, and neuroinflammation. Over the past decade, emerging evidence has implicated both beneficial and pathological roles for innate immune genes and immune cells, including peripheral immune cells such as T cells, which can infiltrate the brain and either ameliorate or exacerbate AD neuropathogenesis. These findings support a neuroimmune axis of AD, in which the interplay of adaptive and innate immune systems inside and outside the brain critically impacts the etiology and pathogenesis of AD. In this review, we discuss the complexities of AD neuropathology at the levels of genetics and cellular physiology, highlighting immune signaling pathways and genes associated with AD risk and interactions among both innate and adaptive immune cells in the AD brain. We emphasize the role of peripheral immune cells in AD and the mechanisms by which immune cells, such as T cells and monocytes, influence AD neuropathology, including microglial clearance of amyloid-β peptide, the key component of β-amyloid plaque cores, pro-inflammatory and cytotoxic activity of microglia, astrogliosis, and their interactions with the brain vasculature. Finally, we review the challenges and outlook for establishing immune-based therapies for treating and preventing AD.

Molecular Mechanisms of Neuroinflammation in Aging and Alzheimer's Disease Progression

Aging is the most prominent risk factor for late-onset Alzheimer's disease. Aging associates with a chronic inflammatory state both in the periphery and in the central nervous system, the evidence thereof and the mechanisms leading to chronic neuroinflammation being discussed. Nonetheless, neuroinflammation is significantly enhanced by the accumulation of amyloid beta and accelerates the progression of Alzheimer's disease through various pathways discussed in the present review. Decades of clinical trials targeting the 2 abnormal proteins in Alzheimer's disease, amyloid beta and tau, led to many failures. As such, targeting neuroinflammation via different strategies could prove a valuable therapeutic strategy, although much research is still needed to identify the appropriate time window. Active research focusing on identifying early biomarkers could help translating these novel strategies from bench to bedside.

Pathogenesis, Animal Models, and Drug Discovery of Alzheimer's Disease

Alzheimer's disease (AD), the most common cause of dementia, is a chronic neurodegenerative disease induced by multiple factors. The high incidence and the aging of the global population make it a growing global health concern with huge implications for individuals and society. The clinical manifestations are progressive cognitive dysfunction and lack of behavioral ability, which not only seriously affect the health and quality of life of the elderly, but also bring a heavy burden to the family and society. Unfortunately, almost all the drugs targeting the classical pathogenesis have not achieved satisfactory clinical effects in the past two decades. Therefore, the present review provides more novel ideas on the complex pathophysiological mechanisms of AD, including classical pathogenesis and a variety of possible pathogenesis that have been proposed in recent years. It will be helpful to find out the key target and the effect pathway of potential drugs and mechanisms for the prevention and treatment of AD. In addition, the common animal models in AD research are outlined and we examine their prospect for the future. Finally, Phase I, II, III, and IV randomized clinical trials or on the market of drugs for AD treatment were searched in online databases (Drug Bank Online 5.0, the U.S. National Library of Medicine, and Alzforum). Therefore, this review may also provide useful information in the research and development of new AD-based drugs.

Activation of TNF Receptor 2 Improves Synaptic Plasticity and Enhances Amyloid-β Clearance in an Alzheimer's Disease Mouse Model with Humanized TNF Receptor 2

BACKGROUND

Tumor necrosis factor-alpha (TNF-α) is a master cytokine involved in a variety of inflammatory and neurological diseases, including Alzheimer's disease (AD). Therapies that block TNF-α proved ineffective as therapeutic for neurodegenerative diseases, which might be explained by the opposing functions of the two receptors of TNF (TNFRs): while TNFR1 stimulation mediates inflammatory and apoptotic pathways, activation of TNFR2 is related to neuroprotection. Despite the success of targeting TNFR2 in a transgenic AD mouse model, research that better mimics the human context is lacking.

OBJECTIVE

The aim of this study is to investigate whether stimulation of TNFR2 with a TNFR2 agonist is effective in activating human TNFR2 and attenuating AD neuropathology in the J20xhuTNFR2-k/i mouse model.

METHODS

Transgenic amyloid-β (Aβ)-overexpressing mice containing a human extracellular TNFR2 domain (J20xhuTNFR2-k/i) were treated with a TNFR2 agonist (NewStar2). After treatment, different behavioral tests and immunohistochemical analysis were performed to assess different parameters, such as cognitive functions, plaque deposition, synaptic plasticity, or microglial phagocytosis.

RESULTS

Treatment with NewStar2 in J20xhuTNFR2-k/i mice resulted in a drastic decrease in plaque load and beta-secretase 1 (BACE-1) compared to controls. Moreover, TNFR2 stimulation increased microglial phagocytic activity, leading to enhanced Aβ clearance. Finally, activation of TNFR2 rescued cognitive impairments and improved synaptic plasticity.

CONCLUSION

Our findings demonstrate that activation of human TNFR2 ameliorates neuropathology and improves cognitive functions in an AD mouse model. Moreover, our study confirms that the J20xhuTNFR2-k/i mouse model is suitable for testing human TNFR2-specific compounds.

The complex role of inflammation and gliotransmitters in Parkinson's disease

Our understanding of the role of innate and adaptive immune cell function in brain health and how it goes awry during aging and neurodegenerative diseases is still in its infancy. Inflammation and immunological dysfunction are common components of Parkinson's disease (PD), both in terms of motor and non-motor components of PD. In recent decades, the antiquated notion that the central nervous system (CNS) in disease states is an immune-privileged organ, has been debunked. The immune landscape in the CNS influences peripheral systems, and peripheral immunological changes can alter the CNS in health and disease. Identifying immune and inflammatory pathways that compromise neuronal health and survival is critical in designing innovative and effective strategies to limit their untoward effects on neuronal health.

Progranulin loss results in sex-dependent dysregulation of the peripheral and central immune system

Introduction

Progranulin (PGRN) is a secreted glycoprotein, the expression of which is linked to several neurodegenerative diseases. Although its specific function is still unclear, several studies have linked it with lysosomal functions and immune system regulation. Here, we have explored the role of PGRN in peripheral and central immune system homeostasis by investigating the consequences of PGRN deficiency on adaptive and innate immune cell populations.

Methods

First, we used gene co-expression network analysis of published data to test the hypothesis that Grn has a critical role in regulating the activation status of immune cell populations in both central and peripheral compartments. To investigate the extent to which PGRN-deficiency resulted in immune dysregulation, we performed deep immunophenotyping by flow cytometry of 19-24-month old male and female Grn-deficient mice (PGRN KO) and littermate Grn-sufficient controls (WT).

Results

Male PGRN KO mice exhibited a lower abundance of microglial cells with higher MHC-II expression, increased CD44 expression on monocytes in the brain, and more CNS-associated CD8+ T cells compared to WT mice. Furthermore, we observed an increase in CD44 on CD8+ T cells in the peripheral blood. Female PGRN KO mice also had fewer microglia compared to WT mice, and we also observed reduced expression of MHC-II on brain monocytes. Additionally, we found an increase in Ly-6Chigh monocyte frequency and decreased CD44 expression on CD8+ and CD4+ T cells in PGRN KO female blood. Given that Gpnmb, which encodes for the lysosomal protein Glycoprotein non-metastatic melanoma protein B, has been reported to be upregulated in PGRN KO mice, we investigated changes in GPNMB protein expression associated with PGRN deficits and found that GPNMB is modulated in myeloid cells in a sex-specific manner.

Discussion

Our data suggest that PGRN and GPNMB jointly regulate the peripheral and the central immune system in a sex-specific manner; thus, understanding their associated mechanisms could pave the way for developing new neuroprotective strategies to modulate central and peripheral inflammation to lower risk for neurodegenerative diseases and possibly delay or halt progression.

The Role of CD4+ T Cells in the Immunotherapy of Brain Disease by Secreting Different Cytokines

Upon different stimulation, naïve CD4⁺ T cells differentiate into various subsets of T helper (Th) cells, including Th1, Th2, Th17, and Tregs. They play both protective and pathogenic roles in the central nervous system (CNS) by secreting different cytokines. Failure of the homeostasis of the subgroups in the CNS can result in different brain diseases. Recently, immunotherapy has drawn more and more attention in the therapy of various brain diseases. Here, we describe the role of different CD4⁺ T cell subsets and their secreted cytokines in various brain diseases, as well as the ways in which by affecting CD4⁺ T cells in therapy of the CNS diseases. Understanding the role of CD4⁺ T cells and their secreted cytokines in the immunotherapy of brain disease will provide new targets and therapeutics for the treatment of brain disease. The role of CD4 + T cell subtypes in different diseases and their associated regulatory genes, proteins, and enzymes. CD4 + T cell subtypes play both protective (green) and pathogenic (red) roles in different brain diseases. The immune regulatory effects of CD4 + T cells and their subtypes are promoted or inhibited by different genes, proteins, and enzymes.

Inflammation and immune dysfunction in Parkinson disease

Parkinson disease (PD) is a progressive neurodegenerative disease that affects peripheral organs as well as the central nervous system and involves a fundamental role of neuroinflammation in its pathophysiology. Neurohistological and neuroimaging studies support the presence of ongoing and end-stage neuroinflammatory processes in PD. Moreover, numerous studies of peripheral blood and cerebrospinal fluid from patients with PD suggest alterations in markers of inflammation and immune cell populations that could initiate or exacerbate neuroinflammation and perpetuate the neurodegenerative process. A number of disease genes and risk factors have been identified as modulators of immune function in PD and evidence is mounting for a role of viral or bacterial exposure, pesticides and alterations in gut microbiota in disease pathogenesis. This has led to the hypothesis that complex gene-by-environment interactions combine with an ageing immune system to create the 'perfect storm' that enables the development and progression of PD. We discuss the evidence for this hypothesis and opportunities to harness the emerging immunological knowledge from patients with PD to create better preclinical models with the long-term goal of enabling earlier identification of at-risk individuals to prevent, delay and more effectively treat the disease.

The Link between Oxidative Stress, Mitochondrial Dysfunction and Neuroinflammation in the Pathophysiology of Alzheimer's Disease: Therapeutic Implications and Future Perspectives

Alzheimer's disease (AD), the most common form of dementia, has increasing incidence, increasing mortality rates, and poses a huge burden on healthcare. None of the currently approved drugs for the treatment of AD influence disease progression. Many clinical trials aiming at inhibiting amyloid plaque formation, increasing amyloid beta clearance, or inhibiting neurofibrillary tangle pathology yielded inconclusive results or failed. Meanwhile, research has identified many interlinked vicious cascades implicating oxidative stress, mitochondrial dysfunction, and chronic neuroinflammation, and has pointed to novel therapeutic targets such as improving mitochondrial bioenergetics and quality control, diminishing oxidative stress, or modulating the neuroinflammatory pathways. Many novel molecules tested in vitro or in animal models have proven efficient, but their translation into clinic needs further research regarding appropriate doses, delivery routes, and possible side effects. Cell-based therapies and extracellular vesicle-mediated delivery of messenger RNAs and microRNAs seem also promising strategies allowing to target specific signaling pathways, but need further research regarding the most appropriate harvesting and culture methods as well as control of the possible tumorigenic side effects. The rapidly developing area of nanotechnology could improve drug delivery and also be used in early diagnosis.

The Immune System as a Therapeutic Target for Alzheimer’s Disease

Alzheimer’s disease (AD) is a heterogeneous neurodegenerative disorder and is the most common cause of dementia. Furthermore, aging is considered the most critical risk factor for AD. However, despite the vast amount of research and resources allocated to the understanding and development of AD treatments, setbacks have been more prominent than successes. Recent studies have shown that there is an intricate connection between the immune and central nervous systems, which can be imbalanced and thereby mediate neuroinflammation and AD. Thus, this review examines this connection and how it can be altered with AD. Recent developments in active and passive immunotherapy for AD are also discussed as well as suggestions for improving these therapies moving forward.

Selective inhibition of soluble tumor necrosis factor signaling reduces abdominal aortic aneurysm progression

Background

Tumor necrosis factor (TNF) is pathologically elevated in human abdominal aortic aneurysms (AAA). Non-selective TNF inhibition-based therapeutics are approved for human use but have been linked to several side effects. Compounds that target the proinflammatory soluble form of TNF (solTNF) but preserve the immunomodulatory capabilities of the transmembrane form of TNF (tmTNF) may prevent these side effects. We hypothesize that inhibition of solTNF signaling prevents AAA expansion.

Methods

The effect of the selective solTNF inhibitor, XPro1595, and the non-selective TNF inhibitor, Etanercept (ETN) was examined in porcine pancreatic elastase (PPE) induced AAA mice, and findings with XPro1595 was confirmed in angiotensin II (ANGII) induced AAA in hyperlipidemic apolipoprotein E (Apoe) -/- mice.

Results

XPro1595 treatment significantly reduced AAA expansion in both models, and a similar trend (p = 0.06) was observed in PPE-induced AAA in ETN-treated mice. In the PPE aneurysm wall, XPro1595 improved elastin integrity scores. In aneurysms, mean TNFR1 levels reduced non-significantly (p = 0.07) by 50% after TNF inhibition, but the histological location in murine AAAs was unaffected and similar to that in human AAAs. Semi-quantification of infiltrating leucocytes, macrophages, T-cells, and neutrophils in the aneurysm wall were unaffected by TNF inhibition. XPro1595 increased systemic TNF levels, while ETN increased systemic IL-10 levels. In ANGII-induced AAA mice, XPro1595 increased systemic TNF and IL-5 levels. In early AAA development, proteomic analyses revealed that XPro1595 significantly upregulated ontology terms including "platelet aggregation" and "coagulation" related to the fibrinogen complex, from which several proteins were among the top regulated proteins. Downregulated ontology terms were associated with metabolic processes.

Conclusion

In conclusion, selective inhibition of solTNF signaling reduced aneurysm expansion in mice, supporting its potential as an attractive treatment option for AAA patients.

A TNF receptor 2 agonist ameliorates neuropathology and improves cognition in an Alzheimer's disease mouse model

Tumor necrosis factor-α (TNF-α) is a pleiotropic, proinflammatory cytokine related to different neurodegenerative diseases, including Alzheimer's disease (AD). Although the linkage between increased TNF-α levels and AD is widely recognized, TNF-α-neutralizing therapies have failed to treat AD. Previous research has associated this with the antithetic functions of the two TNF receptors, TNF receptor 1, associated with inflammation and apoptosis, and TNF receptor 2 (TNFR2), associated with neuroprotection. In our study, we investigated the effects of specifically stimulating TNFR2 with a TNFR2 agonist (NewStar2) in a transgenic Aβ-overexpressing mouse model of AD by administering NewStar2 in two different ways: centrally, via implantation of osmotic pumps, or systemically by intraperitoneal injections. We found that both centrally and systemically administered NewStar2 resulted in a drastic reduction in amyloid β deposition and β-secretase 1 expression levels. Moreover, activation of TNFR2 increased microglial and astrocytic activation and promoted the uptake and degradation of Aβ. Finally, cognitive functions were also improved after NewStar2 treatment. Our results demonstrate that activation of TNFR2 mitigates Aβ-induced cognitive deficits and neuropathology in an AD mouse model and indicates that TNFR2 stimulation might be a potential treatment for AD.

TNF-α and IL-1β Modulate Blood-Brain Barrier Permeability and Decrease Amyloid-β Peptide Efflux in a Human Blood-Brain Barrier Model

The blood-brain barrier (BBB) is a selective barrier and a functional gatekeeper for the central nervous system (CNS), essential for maintaining brain homeostasis. The BBB is composed of specialized brain endothelial cells (BECs) lining the brain capillaries. The tight junctions formed by BECs regulate paracellular transport, whereas transcellular transport is regulated by specialized transporters, pumps and receptors. Cytokine-induced neuroinflammation, such as the tumor necrosis factor-α (TNF-α) and interleukin-1β (IL-1β), appear to play a role in BBB dysfunction and contribute to the progression of Alzheimer’s disease (AD) by contributing to amyloid-β (Aβ) peptide accumulation. Here, we investigated whether TNF-α and IL-1β modulate the permeability of the BBB and alter Aβ peptide transport across BECs. We used a human BBB in vitro model based on the use of brain-like endothelial cells (BLECs) obtained from endothelial cells derived from CD34+ stem cells cocultivated with brain pericytes. We demonstrated that TNF-α and IL-1β differentially induced changes in BLECs’ permeability by inducing alterations in the organization of junctional complexes as well as in transcelluar trafficking. Further, TNF-α and IL-1β act directly on BLECs by decreasing LRP1 and BCRP protein expression as well as the specific efflux of Aβ peptide. These results provide mechanisms by which CNS inflammation might modulate BBB permeability and promote Aβ peptide accumulation. A future therapeutic intervention targeting vascular inflammation at the BBB may have the therapeutic potential to slow down the progression of AD.

Symptomatic and Disease-Modifying Therapy Pipeline for Alzheimer's Disease: Towards a Personalized Polypharmacology Patient-Centered Approach

Since 1906, when Dr. Alois Alzheimer first described in a patient "a peculiar severe disease process of the cerebral cortex", people suffering from this pathology have been waiting for a breakthrough therapy. Alzheimer's disease (AD) is an irreversible, progressive neurodegenerative brain disorder and the most common form of dementia in the elderly with a long presymptomatic phase. Worldwide, approximately 50 million people are living with dementia, with AD comprising 60-70% of cases. Pathologically, AD is characterized by the deposition of amyloid β-peptide (Aβ) in the neuropil (neuritic plaques) and blood vessels (amyloid angiopathy), and by the accumulation of hyperphosphorylated tau in neurons (neurofibrillary tangles) in the brain, with associated loss of synapses and neurons, together with glial activation, and neuroinflammation, resulting in cognitive deficits and eventually dementia. The current competitive landscape in AD consists of symptomatic treatments, of which there are currently six approved medications: three AChEIs (donepezil, rivastigmine, and galantamine), one NMDA-R antagonist (memantine), one combination therapy (memantine/donepezil), and GV-971 (sodium oligomannate, a mixture of oligosaccharides derived from algae) only approved in China. Improvements to the approved therapies, such as easier routes of administration and reduced dosing frequencies, along with the developments of new strategies and combined treatments are expected to occur within the next decade and will positively impact the way the disease is managed. Recently, Aducanumab, the first disease-modifying therapy (DMT) has been approved for AD, and several DMTs are in advanced stages of clinical development or regulatory review. Small molecules, mAbs, or multimodal strategies showing promise in animal studies have not confirmed that promise in the clinic (where small to moderate changes in clinical efficacy have been observed), and therefore, there is a significant unmet need for a better understanding of the AD pathogenesis and the exploration of alternative etiologies and therapeutic effective disease-modifying therapies strategies for AD. Therefore, a critical review of the disease-modifying therapy pipeline for Alzheimer's disease is needed.

Identification of potential therapeutic and diagnostic characteristics of Alzheimer disease by targeting the miR-132-3p/FOXO3a-PPM1F axis in APP/PS1 mice

Alzheimer disease (AD) is a neurodegenerative disorder, which is characterized by progressive impairment of memory and cognition. Early diagnosis and treatment of AD has become a leading topic of research. In this study, we explored the effects of the miR-132-3p/FOXO3a-PPM1F axis on the onset of AD for possible early diagnosis and therapy. We found that miR-132-3p levels in the hippocampus and blood were drastically decreased in APP/PS1 mice from 9 months of age, and bi-directional manipulation of miR-132-3p levels induced magnified effects on learning memory behaviors, and manifestation of AD-related pathological characteristics and inflammatory cytokines in APP/PS1 mice of relevant ages. The hippocampal PPM1F expression levels were significantly elevated in APP/PS1 mice from 3 months of age, which was correlated with miR-132-3p levels at different ages. Overexpression of PPM1F remarkably accelerated the progression of learning memory deficits and associated pathological factors in APP/PS1 mice. Further, we showed that miR-132-3p modulated the expression of PPM1F via FOXO3a in HT22 cells. Finally, using peripheral blood samples of human study participants, we found that the miR-132-3p and PPM1F expression levels in patients with AD were also altered with prominent correlations. In conclusion, miR-132-3p indirectly regulates PPM1F expression by targeting FOXO3a, which could play an extensive role in contributing to the establishment of early diagnosis, treatment, and pathogenesis of AD.