The Role of Neuronal NLRP1 Inflammasome in Alzheimer's Disease: Bringing Neurons into the Neuroinflammation Game

NLRP3/1-mediated pyroptosis: beneficial clues for the development of novel therapies for Alzheimer's disease

The inflammasome is a multiprotein complex involved in innate immunity that mediates the inflammatory response leading to pyroptosis, which is a lytic, inflammatory form of cell death. There is accumulating evidence that nucleotide-binding domain and leucine-rich repeat pyrin domain containing 3 (NLRP3) inflammasome-mediated microglial pyroptosis and NLRP1 inflammasome-mediated neuronal pyroptosis in the brain are closely associated with the pathogenesis of Alzheimer's disease. In this review, we summarize the possible pathogenic mechanisms of Alzheimer's disease, focusing on neuroinflammation. We also describe the structures of NLRP3 and NLRP1 and the role their activation plays in Alzheimer's disease. Finally, we examine the neuroprotective activity of small-molecule inhibitors, endogenous inhibitor proteins, microRNAs, and natural bioactive molecules that target NLRP3 and NLRP1, based on the rationale that inhibiting NLRP3 and NLRP1 inflammasome-mediated pyroptosis can be an effective therapeutic strategy for Alzheimer's disease.

Neuroinflammation Targeting Pyroptosis: Molecular Mechanisms and Therapeutic Perspectives in Stroke

Pyroptosis is a recently identified type of pro-inflammatory programmed cell death (PCD) mediated by inflammasomes and nucleotide oligomerization domain-like receptors (NLs) and dependent on members of the caspase family. Pyroptosis has been widely reported to participate in the occurrence and progression of various inflammatory diseases, including stroke, a frequently lethal disease with high prevalence and many complications. To date, there have been no effectively therapeutic strategies and methods for treating stroke. Pyroptosis is thought to be closely related to the occurrence and development of stroke. Understanding inflammatory responses induced by the activation of pyroptosis would be hopeful to provide feasible approaches and strategies. Targeting on molecules in the upstream or downstream of pyroptosis pathway has shown promise in the treatment of stroke. The present review summarizes current research on the characteristics of pyroptosis, the function and pathological phenomena of pyroptosis in stroke, the molecule mechanisms related to inflammatory pathways, and the drugs and other molecules that can affect outcomes after stroke. These findings may help identify possible targets or new strategies for the diagnosis and treatment of stroke.

Inflammatory aspects of Alzheimer's disease

Alzheimer´s disease (AD) stands out as the most common chronic neurodegenerative disorder. AD is characterized by progressive cognitive decline and memory loss, with neurodegeneration as its primary pathological feature. The role of neuroinflammation in the disease course has become a focus of intense research. While microglia, the brain's resident macrophages, have been pivotal to study central immune inflammation, recent evidence underscores the contributions of other cellular entities to the neuroinflammatory process. In this article, we review the inflammatory role of microglia and astrocytes, focusing on their interactions with AD's core pathologies, amyloid beta deposition, and tau tangle formation. Additionally, we also discuss how different modes of regulated cell death in AD may impact the chronic neuroinflammatory environment. This review aims to highlight the evolving landscape of neuroinflammatory research in AD and underscores the importance of considering multiple cellular contributors when developing new therapeutic strategies.

Berberine chloride loaded nano-PEGylated liposomes attenuates imidacloprid-induced neurotoxicity by inhibiting NLRP3/Caspase-1/GSDMD-mediated pyroptosis

Concerns have been expressed about imidacloprid (IMI), one of the most often used pesticides, and its potential neurotoxicity to non-target organisms. Chronic neuroinflammation is central to the pathology of several neurodegenerative disorders. Hence, exploring the molecular mechanism by which IMI would trigger neuroinflammation is particularly important. This study examined the neurotoxic effects of oral administration of IMI (45 mg/kg/day for 30 days) and the potential neuroprotective effect of berberine (Ber) chloride loaded nano-PEGylated liposomes (Ber-Lip) (10 mg/kg, intravenously every other day for 30 days) using laboratory rat. The histopathological changes, anti-oxidant and oxidative stress markers (GSH, SOD, and MDA), proinflammatory cytokines (IL1β and TNF-α), microglia phenotype markers (CD86 and iNOS for M1; CD163 for M2), the canonical pyroptotic pathway markers (NLRP3, caspase-1, GSDMD, and IL-18) and Alzheimer's disease markers (Neprilysin and beta amyloid [Aβ] deposits) were assessed. Oral administration of IMI resulted in apparent cerebellar histopathological alterations, oxidative stress, predominance of M1 microglia phenotype, significantly upregulated NLRP3, caspase-1, GSDMD, IL-18 and Aβ deposits and significantly decreased Neprilysin expression. Berberine reduced the IMI-induced aberrations in the measured parameters and improved the IMI-induced histopathological and ultrastructure alterations brought on by IMI. This study highlights the IMI neurotoxic effect and its potential contribution to the development of Alzheimer's disease and displayed the neuroprotective effect of Ber-Lip.

The role of AMPKα subunit in Alzheimer's disease: In-depth analysis and future prospects

The AMP-activated protein kinase α (AMPKα) subunit is the catalytic subunit in the AMPK complex, playing a crucial role in AMPK activation. It has two isoforms: AMPKα1 and AMPKα2. Emerging evidence suggests that the AMPKα subunit exhibits subtype-specific effects in Alzheimer's disease (AD). This review discusses the role of the AMPKα subunit in the pathogenesis of AD, including its impact on β-amyloid (Aβ) pathology, Tau pathology, metabolic disorders, inflammation, mitochondrial dysfunction, inflammasome and pyroptosis. Additionally, it reviews the distinct roles of its isoforms, AMPKα1 and AMPKα2, in AD, which may provide more precise targets for future drug development in AD.

Thioredoxin-1 Protects Neurons Through Inhibiting NLRP1-Mediated Neuronal Pyroptosis in Models of Alzheimer's Disease

Alzheimer's disease (AD) is the most common neurodegenerative disease all over the world. In the last decade, accumulating proofs have evidenced that neuroinflammation is intimately implicated in the pathogenesis of AD and activation of NOD-like receptor family pyrin domain-containing 1 (NLRP1) inflammasome can induce neuronal pyroptosis and in turn lead to neuronal loss in AD. Thioredoxin-1 (Trx-1), a multifunctional molecule with anti-inflammation in human tissues, displays crucial neuroprotective roles in AD. Our previous research preliminarily found that Trx-1 inhibition enhanced the expression of NLRP1, caspase-1, and gasdermin D (GSDMD) in Aβ25-35-treated PC12 cells. However, it is largely unknown if Trx-1 can inhibit NLRP1-mediated neuronal pyroptosis in AD neurons. In this study, it was verified that the protein levels of NLRP1, caspase-1, and GSDMD were significantly increased in Aβ25-35-treated mouse HT22 and primary hippocampal neurons. Suppression of Trx-1 with PX-12, a selective inhibitor of Trx-1, or Trx-1 knockdown further activated NLRP1-mediated neuronal pyroptosis. On the contrary, lentivirus infection-mediated Trx-1 overexpression in differentiated PC12 cells dramatically reversed expression of NLRP1, caspase-1, and GSDMD. Furthermore, Trx-1 overexpression mediated by adeno-associated virus in the hippocampal tissues of APP/PS1 mice likewise attenuated the activation of NLRP1-mediated neuronal pyroptosis, as well as reduced the hippocampal deposition of Aβ and ameliorated the cognitive function of APP/PS1 mice. In conclusion, this article predicates a novel molecular mechanism by which Trx-1 exploits neuroprotection through attenuating NLRP1-mediated neuronal pyroptosis in AD models, suggesting that Trx-1 may be a promising therapeutic target for AD.

Mitochondrial Quality Control Processes at the Crossroads of Cell Death and Survival: Mechanisms and Signaling Pathways

Biological aging results from an accumulation of damage in the face of reduced resilience. One major driver of aging is cell senescence, a state in which cells remain viable but lose their proliferative capacity, undergo metabolic alterations, and become resistant to apoptosis. This is accompanied by complex cellular changes that enable the development of a senescence-associated secretory phenotype (SASP). Mitochondria, organelles involved in energy provision and activities essential for regulating cell survival and death, are negatively impacted by aging. The age-associated decline in mitochondrial function is also accompanied by the development of chronic low-grade sterile inflammation. The latter shares some features and mediators with the SASP. Indeed, the unloading of damage-associated molecular patterns (DAMPs) at the extracellular level can trigger sterile inflammatory responses and mitochondria can contribute to the generation of DAMPs with pro-inflammatory properties. The extrusion of mitochondrial DNA (mtDNA) via mitochondrial outer membrane permeabilization under an apoptotic stress triggers senescence programs. Additional pathways can contribute to sterile inflammation. For instance, pyroptosis is a caspase-dependent inducer of systemic inflammation, which is also elicited by mtDNA release and contributes to aging. Herein, we overview the molecular mechanisms that may link mitochondrial dyshomeostasis, pyroptosis, sterile inflammation, and senescence and discuss how these contribute to aging and could be exploited as molecular targets for alleviating the cell damage burden and achieving healthy longevity.

Microglial lipid droplet accumulation in tauopathy brain is regulated by neuronal AMPK

The accumulation of lipid droplets (LDs) in aging and Alzheimer's disease brains is considered a pathological phenomenon with unresolved cellular and molecular mechanisms. Utilizing stimulated Raman scattering (SRS) microscopy, we observed significant in situ LD accumulation in microglia of tauopathy mouse brains. SRS imaging, combined with deuterium oxide (D2O) labeling, revealed heightened lipogenesis and impaired lipid turnover within LDs in tauopathy fly brains and human neurons derived from induced pluripotent stem cells (iPSCs). Transfer of unsaturated lipids from tauopathy iPSC neurons to microglia induced LD accumulation, oxidative stress, inflammation, and impaired phagocytosis. Neuronal AMP-activated protein kinase (AMPK) inhibits lipogenesis and promotes lipophagy in neurons, thereby reducing lipid flux to microglia. AMPK depletion in prodromal tauopathy mice increased LD accumulation, exacerbated pro-inflammatory microgliosis, and promoted neuropathology. Our findings provide direct evidence of native, aberrant LD accumulation in tauopathy brains and underscore the critical role of AMPK in regulating brain lipid homeostasis.

NLRP3 Inflammasome Inhibitors for Antiepileptogenic Drug Discovery and Development

Epilepsy is one of the most prevalent and serious brain disorders and affects over 70 million people globally. Antiseizure medications (ASMs) relieve symptoms and prevent the occurrence of future seizures in epileptic patients but have a limited effect on epileptogenesis. Addressing the multifaceted nature of epileptogenesis and its association with the Nod-like receptor family pyrin domain containing 3 (NLRP3) inflammasome-mediated neuroinflammation requires a comprehensive understanding of the underlying mechanisms of these medications for the development of targeted therapeutic strategies beyond conventional antiseizure treatments. Several types of NLRP3 inhibitors have been developed and their effect has been validated both in in vitro and in vivo models of epileptogenesis. In this review, we discuss the advances in understanding the regulatory mechanisms of NLRP3 activation as well as progress made, and challenges faced in the development of NLRP3 inhibitors for the treatment of epilepsy.

Neurotoxic β-amyloid oligomers cause mitochondrial dysfunction-the trigger for PANoptosis in neurons

As the global population ages, the incidence of elderly patients with dementia, represented by Alzheimer's disease (AD), will continue to increase. Previous studies have suggested that β-amyloid protein (Aβ) deposition is a key factor leading to AD. However, the clinical efficacy of treating AD with anti-Aβ protein antibodies is not satisfactory, suggesting that Aβ amyloidosis may be a pathological change rather than a key factor leading to AD. Identification of the causes of AD and development of corresponding prevention and treatment strategies is an important goal of current research. Following the discovery of soluble oligomeric forms of Aβ (AβO) in 1998, scientists began to focus on the neurotoxicity of AβOs. As an endogenous neurotoxin, the active growth of AβOs can lead to neuronal death, which is believed to occur before plaque formation, suggesting that AβOs are the key factors leading to AD. PANoptosis, a newly proposed concept of cell death that includes known modes of pyroptosis, apoptosis, and necroptosis, is a form of cell death regulated by the PANoptosome complex. Neuronal survival depends on proper mitochondrial function. Under conditions of AβO interference, mitochondrial dysfunction occurs, releasing lethal contents as potential upstream effectors of the PANoptosome. Considering the critical role of neurons in cognitive function and the development of AD as well as the regulatory role of mitochondrial function in neuronal survival, investigation of the potential mechanisms leading to neuronal PANoptosis is crucial. This review describes the disruption of neuronal mitochondrial function by AβOs and elucidates how AβOs may activate neuronal PANoptosis by causing mitochondrial dysfunction during the development of AD, providing guidance for the development of targeted neuronal treatment strategies.

The Neglected Sibling: NLRP2 Inflammasome in the Nervous System

While classical NOD-like receptor pyrin domain containing protein 1 (NLRP1) and NLRP3 inflammasomal proteins have been extensively investigated, the contribution of NLRP2 is still ill-defined in the nervous system. Given the putative significance of NLRP2 in orchestrating neuroinflammation, further inquiry is needed to gain a better understanding of its connectome, hence its specific targeting may hold a promising therapeutic implication. Therefore, bioinformatical approach for extracting information, specifically in the context of neuropathologies, is also undoubtedly preferred. To the best of our knowledge, there is no review study selectively targeting only NLRP2. Increasing, but still fragmentary evidence should encourage researchers to thoroughly investigate this inflammasome in various animal- and human models. Taken together, herein we aimed to review the current literature focusing on the role of NLRP2 inflammasome in the nervous system and more importantly, we provide an algorithm-based protein network of human NLRP2 for elucidating potentially valuable molecular partnerships that can be the beginning of a new discourse and future therapeutic considerations.

Epigenetic Mechanism of SETD1B-mediated Histone Methylation in Cognitive Impairment Induced by Sevoflurane Anesthesia in Neonatal Mice

Sevoflurane (Sev) anesthesia is associated with cognitive deficits and neurotoxicity. This study explores the epigenetic mechanism of SET domain containing 1B (SETD1B) in Sev-induced cognitive impairment in neonatal mice. Neonatal mice (C57BL/6, n = 72) were exposed to 3% Sev for 2 h per day at P6, 7, and 8, and the control neonatal mice were only separated from the mother for 2 h. The mice were divided into groups of 12 individuals, with an equal number of male and female mice in each group. Mice were intraperitoneally injected with adenovirus-packaged SETD1B overexpression vector. Behavioral tests (Morris water maze, open field test, T-maze, novel object recognition, etc.) were performed at P30. Mouse hippocampal neuronal cells were cultured in vitro. SETD1B, C-X-C motif chemokine receptor 4 (CXCR4), NLR family pyrin domain containing 1 (NLRP1), Cleaved Caspase1, and GSDMD-N expressions in hippocampal tissues or cells were determined by quantitative real-time polymerase chain reaction and Western blot. SETD1B and histone H3 lysine 4 methylation (H3K4me1, H3K4me2, and H3K4me3) enrichment on the CXCR4 promoter was analyzed by ChIP. Sev insulted cognitive impairment and diminished SETD1B expression in mouse hippocampal tissues. SETD1B overexpression mitigated cognitive impairment, enhanced H3K4me3 levels in hippocampal tissues, and restrained hippocampal neuronal pyroptosis. SETD1B increased CXCR4 expression by elevating the H3K4me3 level on the CXCR4 promoter, thereby curbing NLRP1/Caspase1-mediated hippocampal neuronal pyroptosis. To conclude, SETD1B enhances CXCR4 expression by elevating the H3K4me3 level on the CXCR4 promoter, thereby suppressing NLRP1/Caspase1-triggered hippocampal neuronal pyroptosis and alleviating Sev-induced cognitive impairment in neonatal mice.

The paradoxical role of zinc on microglia

Zinc is an essential trace element for humans, and its homeostasis is essential for the health of the central nervous system. Microglia, the resident immune cells in the central nervous system, play the roles of sustaining, nourishing, and immune surveillance. Microglia are sensitive to microenvironment changes and are easily activated to M1 phenotype to enhance disease progression or the M2 phenotype to improve peripheral nerves injury repair. Zinc is requisite for microglial activation, However, the cytotoxicity outcome of zinc against microglia, the activated microglia phenotype, and activated microglia function are ambiguous. Herein, we have reviewed the neurological function of zinc and microglia, particularly the ambiguous role of zinc on microglia. We also pay attention to the role of zinc homeostasis on microglial function within the central nervous system disease. Finally, we observe the relationship between zinc and microglia, attempting to design new therapeutic measures against major nervous system disorders.

Targeting inflammasome complexes as a novel therapeutic strategy for mood disorders

INTRODUCTION

Inflammasome complexes, especially NLRP3, have gained great attention as a potential therapeutic target in mood disorders. NLRP3 triggers a caspase 1-dependent release of the inflammatory cytokines IL-1β and IL-18, and seems to interact with purinergic and kynurenine pathways, all of which are implicated in mood disorders development and progression.

AREAS COVERED

Emerging evidence supports NLRP3 inflammasome as a promising pharmacological target for mood disorders. We discussed the available evidence from animal models and human studies and provided a reflection on drawbacks and perspectives for this novel target.

EXPERT OPINION

Several studies have supported the involvement of NLRP3 inflammasome in MDD. However, most of the evidence comes from animal models. The role of NLRP3 inflammasome in BD as well as its anti-manic properties is not very clear and requires further exploration. There is evidence of anti-manic effects of P2×R7 antagonists associated with reduction in the brain levels of IL-1β and TNF-α in a murine model of mania. The involvement of other NLRP3 inflammasome expressing cells besides microglia, like astrocytes, and of other inflammasome complexes in mood disorders also deserves further investigation. Preclinical and clinical characterization of NLRP3 and other inflammasomes in mood disorders is needed before considering translational approaches, including clinical trials.

DNA methylation of imprint control regions associated with Alzheimer's disease in non-Hispanic Blacks and non-Hispanic Whites

Alzheimer's disease (AD) prevalence is twice as high in non-Hispanic Blacks (NHBs) as in non-Hispanic Whites (NHWs). The objective of this study was to determine whether aberrant methylation at imprint control regions (ICRs) is associated with AD. Differentially methylated regions (DMRs) were bioinformatically identified from whole-genome bisulfite sequenced DNA derived from brain tissue of 9 AD (5 NHBs and 4 NHWs) and 8 controls (4 NHBs and 4 NHWs). We identified DMRs located within 120 regions defined as candidate ICRs in the human imprintome ( https://genome.ucsc.edu/s/imprintome/hg38.AD.Brain_track ). Eighty-one ICRs were differentially methylated in NHB-AD, and 27 ICRs were differentially methylated in NHW-AD, with two regions common to both populations that are proximal to the inflammasome gene, NLRP1, and a known imprinted gene, MEST/MESTIT1. These findings indicate that early developmental alterations in DNA methylation of regions regulating genomic imprinting may contribute to AD risk and that this epigenetic risk differs between NHBs and NHWs.

Role of pyroptosis in the pathogenesis of various neurological diseases

Pyroptosis, an inflammatory programmed cell death process, has recently garnered significant attention due to its pivotal role in various neurological diseases. This review delves into the intricate molecular signaling pathways governing pyroptosis, encompassing both caspase-1 dependent and caspase-1 independent routes, while emphasizing the critical role played by the inflammasome machinery in initiating cell death. Notably, we explore the Nucleotide-binding domain leucine-rich repeat (NLR) containing protein family, the Absent in melanoma 2-like receptor family, and the Pyrin receptor family as essential activators of pyroptosis. Additionally, we comprehensively examine the Gasdermin family, renowned for their role as executioner proteins in pyroptosis. Central to our review is the interplay between pyroptosis and various central nervous system (CNS) cell types, including astrocytes, microglia, neurons, and the blood-brain barrier (BBB). Pyroptosis emerges as a significant factor in the pathophysiology of each cell type, highlighting its far-reaching impact on neurological diseases. This review also thoroughly addresses the involvement of pyroptosis in specific neurological conditions, such as HIV infection, drug abuse-mediated pathologies, Alzheimer's disease, and Parkinson's disease. These discussions illuminate the intricate connections between pyroptosis, chronic inflammation, and cell death in the development of these disorders. We also conducted a comparative analysis, contrasting pyroptosis with other cell death mechanisms, thereby shedding light on their unique aspects. This approach helps clarify the distinct contributions of pyroptosis to neuroinflammatory processes. In conclusion, this review offers a comprehensive exploration of the role of pyroptosis in various neurological diseases, emphasizing its multifaceted molecular mechanisms within various CNS cell types. By elucidating the link between pyroptosis and chronic inflammation in the context of neurodegenerative disorders and infections, it provides valuable insights into potential therapeutic targets for mitigating these conditions.

Non-Invasive Vagal Nerve Stimulation Pre-Treatment Reduces Neurological Dysfunction After Closed Head Injury in Mice

Non-invasive vagus nerve stimulation (nVNS) has recently been suggested as a potential therapy for traumatic brain injury (TBI). We previously demonstrated that nVNS inhibits cortical spreading depolarization, the electrophysiological event underlying migraine aura, and is relevant to TBI. Our past work also suggests a role for interleukin-1 beta (IL-1β) in cognitive deficits after closed head injury (CHI) in mice. We show that nVNS pre-treatment suppresses CHI-associated spatial learning and memory impairment and prevents IL-1β activation in injured neurons, but not endothelial cells. In contrast, nVNS administered 10 min after CHI was ineffective. These data suggest that nVNS prophylaxis might ameliorate neuronal dysfunction associated with CHI in populations at high risk for concussive TBI.

"Other Than NLRP3" Inflammasomes: Multiple Roles in Brain Disease

Human neuroinflammatory and neurodegenerative diseases, whose prevalence keeps rising, are still unsolved pathobiological/therapeutical problems. Among others, recent etiology hypotheses stressed as their main driver a chronic neuroinflammation, which is mediated by innate immunity-related protein oligomers: the inflammasomes. A panoply of exogenous and/or endogenous harmful agents activates inflammasomes' assembly, signaling, and IL-1β/IL-18 production and neural cells' pyroptotic death. The underlying concept is that inflammasomes' chronic activation advances neurodegeneration while their short-lasting operation restores tissue homeostasis. Hence, from a therapeutic standpoint, it is crucial to understand inflammasomes' regulatory mechanisms. About this, a deluge of recent studies focused on the NLRP3 inflammasome with suggestions that its pharmacologic block would hinder neurodegeneration. Yet hitherto no evidence proves this view. Moreover, known inflammasomes are numerous, and the mechanisms regulating their expression and function may vary with the involved animal species and strains, as well as organs and cells, and the harmful factors triggered as a result. Therefore, while presently leaving out some little-studied inflammasomes, this review focuses on the "other than NLRP3" inflammasomes that participate in neuroinflammation's complex mechanisms: NLRP1, NLRP2, NLRC4, and AIM2. Although human-specific data about them are relatively scant, we stress that only a holistic view including several human brain inflammasomes and other potential pathogenetic drivers will lead to successful therapies for neuroinflammatory and neurodegenerative diseases.

Global Research Trends and Hotspots for Ferroptosis, Necroptosis, and Pyroptosis in Alzheimer's Disease from the Past to 2023: A Combined Bibliometric Review

Background

Alzheimer's disease (AD) is a genetically intricate neurodegenerative disorder. Studies on "Ferroptosis in AD", "Pyroptosis in AD", and "Necroptosis in AD" are becoming more prevalent and there is increasing evidence that they are closely related to AD. However, there has not yet been a thorough bibliometrics-based investigation on this subject.

Objective

This study uses a bibliometric approach to visualize and analyze the literature within the field of three distinct types of cell death in AD and explores the current research hotspots and prospective research directions.

Methods

We collected relevant articles from the Web of Science and used CiteSpace, VOS viewer, and Pajek to perform a visual analysis.

Results

A total of 123, 95, and 84 articles were published in "Ferroptosis in AD", "Pyroptosis in AD", and "Necroptosis in AD", respectively. Based on keywords analysis, we can observe that "oxidative stress" and "lipid peroxidation", "cell death" and "activation", and "Nlrp3 inflammasome" and "activation" were the three most prominent words in the field of "Ferroptosis in AD", "Pyroptosis in AD", and "Necroptosis in AD", respectively. Focusing on the breakout words in the keyword analysis, we reviewed the mechanisms of ferroptosis, pyroptosis, and necroptosis in AD. By mapping the time zones of the keywords, we speculated on the evolutionary trends of ferroptosis, pyrotosis, and necroptosis in AD.

Conclusions

Our findings can help researchers grasp the research status of three types of cell death in AD and determine new directions for future research as soon as possible.

Diagnostic Model for Alzheimer's Disease Based on PANoptosis-Related Genes

BACKGROUND

The pathophysiology of Alzheimer's disease (AD) involves the interplay of three different processes: pyroptosis, apoptosis, and necroptosis.

OBJECTIVE

To explore role of PANoptosis, a novel pro-inflammatory programmed cell death pathway, in AD patients.

METHODS

We performed a consensus clustering analysis to identify distinct transcriptional profiles in the samples using the R package "ConsensusClusterPlus". The PANoptosis key genes were obtained by crossing the WGCNA brown module and differentially expressed PANoptosis genes. We accomplished regression analyses using the LASSO-Cox method, combined with pathological status and gene expression data. At the same time, we also constructed PANscore system. The expression of PANoptosis hub genes were validated by qRT-PCR in AD transgenic mice.

RESULTS

Our study utilized tissue expression profile data from AD patients to construct three distinct PANoptosis patterns, each with unique molecular and clinical characteristics. We have created a risk scoring system called PANscore, which can analyze patterns specific for each AD patient. Additionally, we observed significantly lower levels of follicular helper T (Tfh) cells in the high PANscore and AD patients. Further analysis revealed a significant negative correlation of Tfh with GSDMD and MLKL.

CONCLUSIONS

These findings provide a roadmap for personalized patient stratification, enabling clinicians to develop personalized treatment plans for AD patients and advance the field of precision medicine.

Adeno-associated virus (AAV) 9-mediated gene delivery of Nurr1 and Foxa2 ameliorates symptoms and pathologies of Alzheimer disease model mice by suppressing neuro-inflammation and glial pathology

There is a compelling need to develop disease-modifying therapies for Alzheimer's disease (AD), the most common neuro-degenerative disorder. Together with recent progress in vector development for efficiently targeting the central nervous system, gene therapy has been suggested as a potential therapeutic modality to overcome the limited delivery of conventional types of drugs to and within the damaged brain. In addition, given increasing evidence of the strong link between glia and AD pathophysiology, therapeutic targets have been moving toward those addressing glial cell pathology. Nurr1 and Foxa2 are transcription/epigenetic regulators that have been reported to cooperatively regulate inflammatory and neurotrophic response in glial cells. In this study, we tested the therapeutic potential of Nurr1 and Foxa2 gene delivery to treat AD symptoms and pathologies. A series of functional, histologic, and transcriptome analyses revealed that the combined expression of Nurr1 and Foxa2 substantially ameliorated AD-associated amyloid β and Tau proteinopathy, cell senescence, synaptic loss, and neuro-inflammation in multiple in vitro and in vivo AD models. Intra-cranial delivery of Nurr1 and Foxa2 genes using adeno-associated virus (AAV) serotype 9 improved the memory and cognitive function of AD model mice. The therapeutic benefits of gene delivery were attained mainly by correcting pathologic glial function. These findings collectively indicate that AAV9-mediated Nurr1 and Foxa2 gene transfer could be an effective disease-modifying therapy for AD.

Coumarin-chalcone hybrid LM-021 and indole derivative NC009-1 targeting inflammation and oxidative stress to protect BE(2)-M17 cells against α-synuclein toxicity

Parkinson's disease (PD) is featured mainly by the loss of dopaminergic neurons and the presence of α-synuclein-containing aggregates in the substantia nigra of brain. The α-synuclein fibrils and aggregates lead to increased oxidative stress and neural toxicity in PD. Chronic inflammation mediated by microglia is one of the hallmarks of PD pathophysiology. In this report, we showed that coumarin-chalcone hybrid LM-021 and indole derivative NC009-1 reduced the expression of major histocompatibility complex-II, NLR family pyrin domain containing (NLRP) 3, caspase-1, inducible nitric oxide synthase, interleukin (IL)-1β, IL-6, and tumor necrosis factor (TNF)-α in α-synuclein-activated mouse BV-2 microglia. Release of pro-inflammatory mediators including nitric oxide, IL-1β, IL-6 and TNF-α was also mitigated. In BE(2)-M17 cells expressing A53T α-synuclein aggregates, LM-021 and NC009-1 reduced α-synuclein aggregation, neuroinflammation, oxidative stress and apoptosis, and promoted neurite outgrowth. These protective effects were mediated by downregulating NLRP1, IL-1β and IL-6, and their downstream pathways including nuclear factor (NF)-κB inhibitor alpha (IκBα)/NF-κB P65 subunit (P65), c-Jun N-terminal kinase (JNK)/proto-oncogene c-Jun (JUN), mitogen-activated protein kinase 14 (P38)/signal transducer and activator of transcription (STAT) 1, and Janus kinase 2 (JAK2)/STAT3. The study results indicate LM-021 and NC009-1 as potential new drug candidates for PD.

Activation of the NLRP1 Inflammasome and Its Role in Transmissible Gastroenteritis Coronavirus Infection

The inflammasome pathway is a critical early response mechanism of the host that detects pathogens, initiates the production of inflammatory cytokines, and recruits effector cells to the infection site. Nonetheless, the mechanism of inflammasome activation in coronavirus infection and its biological functions in host defense remain unclear. Transmissible gastroenteritis virus (TGEV), a member of the genus Alphacoronavirus, is a significant pathogen that mainly infects piglets and causes intestinal inflammation and inflammatory cell infiltration. Here, we investigated the mechanism of inflammasome activation in intestinal epithelial cells (IECs) infected with TGEV. We observed a substantial increase in interleukin 1β (IL-1β) and IL-18 levels in both IECs and TGEV-infected porcine intestinal tissues. Furthermore, TGEV infection resulted in increased activation of caspase-1 and the NLRP1 (NOD-like receptor [NLR]-containing pyrin domain [PYD]) inflammasome. Our findings revealed that TGEV infection impeded the interaction between porcine NLRP1 (pNLRP1) and porcine dipeptidyl peptidases 9 (pDPP9), yet it did not reduce the expression of pDPP9. Importantly, the ZU5 domain, not the function-to-find domain (FIIND) reported in human NLRP1, was identified as the minimal domain of pNLRP1 for pDPP9 binding. In addition, the robust type I IFN expression induced by TGEV infection also upregulated pNLRP1 expression and pNLRP1 itself acts as an interferon-stimulated gene to counteract TGEV infection. Our data demonstrate that pNLRP1 has antiviral capabilities against coronavirus infection, which highlights its potential as a novel therapeutic target for coronavirus antiviral therapy. IMPORTANCE Coronavirus primarily targets the epithelial cells of the respiratory and gastrointestinal tracts, leading to damage in both humans and animals. NLRP1 is a direct sensor for RNA virus infection which is highly expressed in epithelial barrier tissues. However, until recently, the precise molecular mechanisms underlying its activation in coronavirus infection and subsequent downstream events remained unclear. In this study, we demonstrate that the alphacoronavirus TGEV induces the production of IL-1β and IL-18 and upregulates the expression of pNLRP1. Furthermore, we found that pNLRP1 can serve as an interferon-stimulated gene (ISG) to inhibit the infection of enterovirus TGEV. Our research highlights the crucial role of NLRP1 as a regulator of innate immunity in TGEV infection and shows that it may serve as a potential therapeutic target for the treatment of coronavirus infection.

Bat ASC2 suppresses inflammasomes and ameliorates inflammatory diseases

Bats are special in their ability to live long and host many emerging viruses. Our previous studies showed that bats have altered inflammasomes, which are central players in aging and infection. However, the role of inflammasome signaling in combating inflammatory diseases remains poorly understood. Here, we report bat ASC2 as a potent negative regulator of inflammasomes. Bat ASC2 is highly expressed at both the mRNA and protein levels and is highly potent in inhibiting human and mouse inflammasomes. Transgenic expression of bat ASC2 in mice reduced the severity of peritonitis induced by gout crystals and ASC particles. Bat ASC2 also dampened inflammation induced by multiple viruses and reduced mortality of influenza A virus infection. Importantly, it also suppressed SARS-CoV-2-immune-complex-induced inflammasome activation. Four key residues were identified for the gain of function of bat ASC2. Our results demonstrate that bat ASC2 is an important negative regulator of inflammasomes with therapeutic potential in inflammatory diseases.

Targeting pyroptosis as a preventive and therapeutic approach for stroke

Stroke has caused tremendous social stress worldwide, yet despite decades of research and development of new stroke drugs, most have failed and rt-PA (Recombinant tissue plasminogen activator) is still the accepted treatment for ischemic stroke. the complexity of the stroke mechanism has led to unsatisfactory efficacy of most drugs in clinical trials, indicating that there are still many gaps in our understanding of stroke. Pyroptosis is a programmed cell death (PCD) with inflammatory properties and are thought to be closely associated with stroke. Pyroptosis is regulated by the GSDMD of the gasdermin family, which when cleaved by Caspase-1/Caspase-11 into N-GSDMD with pore-forming activity can bind to the plasma membrane to form small 10-20 nm pores, which would allow the release of inflammatory factors IL-18 and IL-1β before cell rupture, greatly exacerbating the inflammatory response. The pyroptosis occurs mainly in the border zone of cerebral infarction, and glial cells, neuronal cells and brain microvascular endothelial cells (BMECs) all undergo pyroptosis after stroke, which largely exacerbates the breakdown of the blood-brain barrier (BBB) and thus aggravates brain injury. Therefore, pyroptosis may be a good direction for the treatment of stroke. In this review, we focus on the latest mechanisms of action of pyroptosis and the process by which pyroptosis regulates stroke development. We also suggest potential therapeutic stroke drugs that target the pyroptosis pathway, providing additional therapeutic strategies for the clinical management of stroke. The role of pyroptosis after stroke. After stroke, microglia first rush to the damaged area and polarize into M1 and M2 types. Under the influence of various stimuli, microglia undergo pyroptosis, release pro-inflammatory factors, and are converted to the M1 type; astrocytes and neuronal cells also undergo pyroptosis under the stimulation of various pro-inflammatory factors, leading to astrocyte death due to increased osmotic pressure in the membrane, resulting in water absorption and swelling until rupture. BMECs, the main structural component of the BBB, also undergo pyroptosis when stimulated by pro-inflammatory factors released from microglia and astrocytes, leading to the destruction of the structural integrity of the BBB, ultimately causing more severe brain damage. In addition, GSDMD in neutrophils mainly mediate the release of NETs rather than pyroptosis, which also aggravates brain injury. IL-10=interleukin-10; TGF-β = transforming growth factor-β; IL-18=interleukin-18; IL-1β = interleukin-1β; TNF-α = tumor necrosis factor-α; iNOS=induced nitrogen monoxide synthase; MMPs=Matrix metalloproteinases; GSDMD = gasdermin D; BMECs=brain microvascular endothelial cells; BBB = blood-brain barrier.

Inhibition of NLRP1 inflammasome improves autophagy dysfunction and Aβ disposition in APP/PS1 mice

Increasing evidence has shown that the NOD-like receptor protein 1 (NLRP1) inflammasome is associated with Aβ generation and deposition, which contributes to neuronal damage and neuronal-inflammation in Alzheimer's disease (AD). However, the specific mechanism of NLRP1 inflammasome in the pathogenesis of AD is still unclear. It has been reported that autophagy dysfunction can aggravate the pathological symptoms of AD and plays an important role in regulating Aβ generation and clearance. We hypothesized that NLRP1 inflammasome activation may induce autophagy dysfunction contributing to the progression of AD. In the present study, we observed the relationship between Aβ generation and NLRP1 inflammasome activation, as well as AMPK/mTOR mediated-autophagy dysfunction in WT 9-month-old (M) mice, APP/PS1 6 M and APP/PS1 9 M mice. Additionally, we further studied the effect of NLRP1 knockdown on cognitive function, Aβ generation, neuroinflammation and AMPK/mTOR mediated autophagy in APP/PS1 9 M mice. Our results indicated that NLRP1 inflammasome activation and AMPK/mTOR mediated-autophagy dysfunction are closely implicated in Aβ generation and deposition in APP/PS1 9 M mice, but not in APP/PS1 6 M mice. Meanwhile, we found that knockdown of NLRP1 significantly improved learning and memory impairments, decreased the expressions of NLRP1, ASC, caspase-1, p-NF-κB, IL-1β, APP, CTF-β, BACE1 and Aβ_1-42, and decreased the level of p-AMPK, Beclin 1 and LC3 II, and increased the level of p-mTOR and P62 in APP/PS1 9 M mice. Our study suggested that inhibition of NLRP1 inflammasome activation improves AMPK/mTOR mediated-autophagy dysfunction, resulting in the decrease of Aβ generation, and NLRP1 and autophagy might be important targets to delay the progression of AD.

miR-181c-5p suppresses neuronal pyroptosis via NLRP1 in Alzheimer's disease

Alzheimer's disease (AD) is neurodegenerative disease common in the elderly, whose pathological mechanism is the deposition of amyloid-β (Aβ) plaques and neurofibrillary tangles in the brain. Pyroptosis is a programmed cell death mediated by Gasdermin protein. After the activation of inflammasomes, the cleaved caspase⁃ 1/4/5/11 activates GSDMD, which promotes the release of inflammatory substances and eventually causes cell swelling and death. Pyroptosis caused by inflammasomes plays a role in AD. However, the specific regulatory mechanism of pyroptosis in AD still needs more experimental studies. To further study the effects of NLRP1-induced pyroptosis on AD, miR-181c-5p, which could targeted bind to NLRP1, was knocked down or overexpression in HT22 cells to detect cell apoptosis with Tunel assay, the expression of inflammasome-related proteins with Western blot and the content of inflammatory factors with ELISA. miR-181c-5p was overexpressed in AD model mice to detect the learning and cognitive ability with morris water maze testing and the expression of inflammasoma-related proteins with Western blot. The results showed that miR-181c-5p mimic attenuated Aβ1-42-induced neuronal pyroptosis in HT22 cells, while up-regulation of NLRP1 aggravated neuronal pyroptosis in HT22 cells. In mice, miR-181c-5p agomir attenuated neuronal pyroptosis in both hippocampal and cortical tissues, and miR-181c-5p antagomir improved neuronal pyroptosis and cognitive impairment through NLRP1. Therefore, the study suggests that miR-181c-5p can alleviated AD process by targeted downregulation of NLRP1, which is expected to be a target site for AD treatment.

NLRP3 Inflammasome’s Activation in Acute and Chronic Brain Diseases—An Update on Pathogenetic Mechanisms and Therapeutic Perspectives with Respect to Other Inflammasomes

Increasingly prevalent acute and chronic human brain diseases are scourges for the elderly. Besides the lack of therapies, these ailments share a neuroinflammation that is triggered/sustained by different innate immunity-related protein oligomers called inflammasomes. Relevant neuroinflammation players such as microglia/monocytes typically exhibit a strong NLRP3 inflammasome activation. Hence the idea that NLRP3 suppression might solve neurodegenerative ailments. Here we review the recent Literature about this topic. First, we update conditions and mechanisms, including RNAs, extracellular vesicles/exosomes, endogenous compounds, and ethnic/pharmacological agents/extracts regulating NLRP3 function. Second, we pinpoint NLRP3-activating mechanisms and known NLRP3 inhibition effects in acute (ischemia, stroke, hemorrhage), chronic (Alzheimer’s disease, Parkinson’s disease, Huntington’s disease, MS, ALS), and virus-induced (Zika, SARS-CoV-2, and others) human brain diseases. The available data show that (i) disease-specific divergent mechanisms activate the (mainly animal) brains NLRP3; (ii) no evidence proves that NLRP3 inhibition modifies human brain diseases (yet ad hoc trials are ongoing); and (iii) no findings exclude that concurrently activated other-than-NLRP3 inflammasomes might functionally replace the inhibited NLRP3. Finally, we highlight that among the causes of the persistent lack of therapies are the species difference problem in disease models and a preference for symptomatic over etiologic therapeutic approaches. Therefore, we posit that human neural cell-based disease models could drive etiological, pathogenetic, and therapeutic advances, including NLRP3’s and other inflammasomes’ regulation, while minimizing failure risks in candidate drug trials.

Pyroptosis and degenerative diseases of the elderly

Pyroptosis is a recently described mechanism of programmed cell death mediated by proteins of the gasdermin family. Widely recognized signaling cascades include the classical, non-classical, caspase-3-dependent gasdermin E and caspase-8-dependent gasdermin D pathways. Additional pyroptotic pathways have been subsequently reported. With the rising prevalence of advanced age, the role of pyroptosis in the degenerative diseases of the elderly has attracted increased research attention. This article reviews the primary mechanisms of pyroptosis and summarizes progress in the research of degenerative diseases of the elderly such as presbycusis, age-related macular degeneration, Alzheimer's disease, intervertebral disc degeneration, and osteoarthritis.

Mechanism of pyroptosis in neurodegenerative diseases and its therapeutic potential by traditional Chinese medicine

Neurodegenerative diseases (NDs) are disorders characterized by degenerative degeneration of neurons and loss of their function. NDs have a complicated pathophysiology, of which neuroinflammation and neuronal death are significant factors. The inflammatory process known as pyroptosis ("fiery death") is caused by a family of pore-forming proteins called Gasdermins (GSDMs), which appears downstream from the activation of the inflammasome. Clear evidence of enhanced pyroptosis-related proteins activity in common NDs has coincided with abnormal aggregation of pathological proteins (such as Aβ, tau, α-synuclein et al.), making pyroptosis an attractive direction for the recent study of NDs. The purpose of this review is to provide an overview of the molecular mechanisms driving pyroptosis, the mechanistic links between pyroptosis and NDs, and emerging therapeutic strategies in Traditional Chinese Medicine (TCM) to inhibit pyroptosis for the treatment of NDs.

The Role of Endophilin A1 in Lipopolysaccharide-Induced Parkinson's Disease Model Mice

BACKGROUND

Endophilin A1 (EPA1) is encoded by the SH3GL2 gene, and SH3GL2 was designated as a Parkinson's disease (PD) risk locus by genome-wide association analysis, suggesting that EPA1 may be involved in the occurrence and development of PD.

OBJECTIVE

To investigate the role of EPA1 in lipopolysaccharide (LPS)-induced PD model mice.

METHODS

The mice PD model was prepared by injecting LPS into the substantia nigra (SN), and the changes in the behavioral data of mice in each group were observed. The damage of dopaminergic neurons, activation of microglia, and reactive oxygen species (ROS) generation were detected by immunofluorescence method; calcium ion concentration was detected by calcium content detection kit; EPA1 and inflammation and its related indicators were detected by western blot method. EPA1 knockdown was performed by an adeno-associated virus vector containing EPA1-shRNA-eGFP infusion.

RESULTS

LPS-induced PD model mice developed behavioral dysfunction, SN dopaminergic nerve damage, significantly increased calcium ion, calpain 1, and ROS production, activated NLRP1 inflammasome and promoted pro-inflammatory cell release, and SN EPA1 knockdown improves behavioral disorders, alleviates dopaminergic neuron damage, reduces calcium, calpain 1, ROS generation, and blocks NLRP1 inflammasome-driven inflammatory responses.

CONCLUSION

The expression of EPA1 in the SN of LPS-induced PD model mice was increased, and it played a role in promoting the occurrence and development of PD. EPA1 knockdown inhibited the NLRP1 inflammasome activation, decreased the release of inflammatory factors and ROS generation, and alleviated dopaminergic neuron damage. This indicated that EPA1 may participating in the occurrence and development of PD.

Canonical Inflammasomes

The innate immune response represents the first line of host defense, and it is able to detect pathogen- and damage-associated molecular patterns (PAMPs and DAMPs, respectively) through a variety of pattern recognition receptors (PRRs). Among these PRRs, certain cytosolic receptors of the NLRs family (specifically NLRP1, NLRP3, NLRC4, and NAIP) or those containing at least a pyrin domain (PYD) such as pyrin and AIM2, activate the multimeric complex known as inflammasome, and its effector enzyme caspase-1. The caspase-1 induces the proteolytic maturation of the pro-inflammatory cytokines IL-1ß and IL-18, as well as the pore-forming protein gasdermin D (GSDMD). GSDMD is responsible for the release of the two cytokines and the induction of lytic and inflammatory cell death known as pyroptosis. Each inflammasome receptor detects specific stimuli, either directly or indirectly, thereby enhancing the cell's ability to sense infections or homeostatic disturbances. In this chapter, we present the activation mechanism of the so-called "canonical" inflammasomes.

Inhibition of neutrophil extracellular trap formation attenuates NLRP1-dependent neuronal pyroptosis via STING/IRE1α pathway after traumatic brain injury in mice

Introduction

Increased neutrophil extracellular trap (NET) formation has been reported to be associated with cerebrovascular dysfunction and neurological deficits in traumatic brain injury (TBI). However, the biological function and underlying mechanisms of NETs in TBI-induced neuronal cell death are not yet fully understood.

Methods

First, brain tissue and peripheral blood samples of TBI patients were collected, and NETs infiltration in TBI patients was detected by immunofluorescence staining and Western blot. Then, a controlled cortical impact device was used to model brain trauma in mice, and Anti-Ly6G, DNase, and CL-amidine were given to reduce the formation of neutrophilic or NETs in TBI mice to evaluate neuronal death and neurological function. Finally, the pathway changes of neuronal pyroptosis induced by NETs after TBI were investigated by administration of peptidylarginine deiminase 4 (a key enzyme of NET formation) adenovirus and inositol-requiring enzyme-1 alpha (IRE1α) inhibitors in TBI mice.

Results

We detected that both peripheral circulating biomarkers of NETs and local NETs infiltration in the brain tissue were significantly increased and had positive correlations with worse intracranial pressure (ICP) and neurological dysfunction in TBI patients. Furthermore, the depletion of neutrophils effectively reduced the formation of NET in mice subjected to TBI. we found that degradation of NETs or inhibition of NET formation significantly inhibited nucleotide-binding oligomerization domain (NOD)-like receptor pyrin domain containing 1 (NLRP1) inflammasome-mediated neuronal pyroptosis after TBI, whereas these inhibitory effects were abolished by cyclic GMP-AMP (cGAMP), an activator of stimulating Interferon genes (STING). Moreover, overexpression of PAD4 in the cortex by adenoviruses could aggravate NLRP1-mediated neuronal pyroptosis and neurological deficits after TBI, whereas these pro-pyroptotic effects were rescued in mice also receiving STING antagonists. Finally, IRE1α activation was significantly upregulated after TBI, and NET formation or STING activation was found to promote this process. Notably, IRE1α inhibitor administration significantly abrogated NETs-induced NLRP1 inflammasome-mediated neuronal pyroptosis in TBI mice.

Discussion

Our findings indicated that NETs could contribute to TBI-induced neurological deficits and neuronal death by promoting NLRP1-mediated neuronal pyroptosis. Suppression of the STING/ IRE1α signaling pathway can ameliorate NETs-induced neuronal pyroptotic death after TBI.

Identification of inflammasome signaling proteins in neurons and microglia in early and intermediate stages of Alzheimer's disease

Alzheimer's disease (AD) is a progressive neurodegenerative disease that destroys memory and cognitive function. Inflammasome activation has been suggested to play a critical role in the neuroinflammatory response in AD progression, but the cell-type expression of inflammasome proteins in the brain has not been fully characterized. In this study, we used samples from the hippocampus formation, the subiculum, and the entorhinal cortex brain from 17 donors with low-level AD pathology and 17 intermediate AD donors to assess the expression of inflammasome proteins. We performed analysis of hippocampal thickness, β-amyloid plaques, and hyperphosphorylated tau to ascertain the cellular pathological changes that occur between low and intermediate AD pathology. Next, we determined changes in the cells that express the inflammasome sensor proteins NOD-like receptor proteins (NLRP) 1 and 3, and caspase-1. In addition, we stained section with IC100, a humanized monoclonal antibody directed against the inflammasome adaptor protein apoptosis-associated speck-like protein containing a caspase recruitment domain (ASC), and a commercially available anti-ASC antibody. Our results indicate that hippocampal cortical thickness did not significantly change between low and intermediate AD pathology, but there was an increase in pTau and β-amyloid clusters in intermediate AD cases. NLRP3 was identified mainly in microglial populations, whereas NLRP1 was seen in neuronal cytoplasmic regions. There was a significant increase of ASC in neurons labeled by IC100, whereas microglia in the hippocampus and subiculum were labeled with the commercial anti-ASC antibody. Caspase-1 was present in the parenchyma in the CA regions where amyloid and pTau were identified. Together, our results indicate increased inflammasome protein expression in the early pathological stages of AD, that IC100 identifies neurons in early stages of AD and that ASC expression correlates with Aβ and pTau in postmortem AD brains.

Identifying an Optimal Neuroinflammation Treatment Using a Nanoligomer Discovery Engine

Acute activation of innate immune response in the brain, or neuroinflammation, protects this vital organ from a range of external pathogens and promotes healing after traumatic brain injury. However, chronic neuroinflammation leading to the activation of immune cells like microglia and astrocytes causes damage to the nervous tissue, and it is causally linked to a range of neurodegenerative diseases such as Alzheimer's diseases (AD), Multiple Sclerosis (MS), Parkinson's disease (PD), and many others. While neuroinflammation is a key target for a range of neuropathological diseases, there is a lack of effective countermeasures to tackle it, and existing experimental therapies require fairly invasive intracerebral and intrathecal delivery due to difficulty associated with the therapeutic crossover between the blood-brain barrier, making such treatments impractical to treat neuroinflammation long-term. Here, we present the development of an optimal neurotherapeutic using our Nanoligomer Discovery Engine, by screening downregulation of several proinflammatory cytokines (e.g., Interleukin-1β or IL-1β, tumor necrosis factor-alpha or TNF-α, TNF receptor 1 or TNFR1, Interleukin 6 or IL-6), inflammasomes (e.g., NLRP1), key transcription factors (e.g., nuclear factor kappa-B or NF-κβ) and their combinations, as upstream regulators and canonical pathway targets, to identify and validate the best-in-class treatment. Using our high-throughput drug discovery, target validation, and lead molecule identification via a bioinformatics and artificial intelligence-based ranking method to design sequence-specific peptide molecules to up- or downregulate gene expression of the targeted gene at will, we used our discovery engine to perturb and identify most effective upstream regulators and canonical pathways for therapeutic intervention to reverse neuroinflammation. The lead neurotherapeutic was a combination of Nanoligomers targeted to NF-κβ (SB.201.17D.8_NF-κβ1) and TNFR1 (SB.201.18D.6_TNFR1), which were identified using in vitro cell-based screening in donor-derived human astrocytes and further validated in vivo using a mouse model of lipopolysaccharide (LPS)-induced neuroinflammation. The combination treatment SB_NI_111 was delivered without any special formulation using a simple intraperitoneal injection of low dose (5 mg/kg) and was found to significantly suppress the expression of LPS-induced neuroinflammation in mouse hippocampus. These results point to the broader applicability of this approach towards the development of therapies for chronic neuroinflammation-linked neurodegenerative diseases, sleep countermeasures, and others, and the potential for further investigation of the lead neurotherapeutic molecule as reversible gene therapy.

JQ1 attenuates neuroinflammation by inhibiting the inflammasome-dependent canonical pyroptosis pathway in SAE

Sepsis-associated encephalopathy (SAE) manifests clinically in hyperneuroinflammation. Pyroptosis, which can induce an inflammatory cascade response, has been considered to be a causative factor of SAE. Evidence has shown that the bromo- and extraterminal (BET) proteins (including BRD2, BRD3, BRD4 and BRDT) inhibitor JQ1 can inhibit inflammation and suppress pyroptosis in various diseases. Therefore, we examined the effect of JQ1 on inflammasome-induced pyroptosis in the hippocampus in a mouse model of sepsis induced by lipopolysaccharide (LPS) injection. The results showed that JQ1 treatment alleviated sepsis-related symptoms, protected the blood-brain barrier (BBB), as indicated by upregulated expression of the tight junction proteins occludin and ZO-1, and remarkably rescued neuronal damage in SAE mice. Mechanistically, we demonstrated that JQ1 intervention inhibited the expression of BRD proteins and decreased the expression of inflammasomes by blocking phospho-nuclear factor kappa B (p-NF-κB) signalling, attenuating the canonical pyroptosis (mediated by cleaved-Caspase1/11) pathway and the release of proinflammatory factors in the hippocampus of septic mice. Interestingly, we also found that JQ1 selectively suppressed the activation of hippocampal microglia in SAE mice. Thus, JQ1 protected the hippocampal BBB and neuronal damage through the attenuation of neuroinflammation by inhibiting the inflammasome-dependent canonical pyroptosis pathway induced by LPS injection in mice, and JQ1 may be a promising target for the prevention of SAE.

Pyroptosis as a candidate therapeutic target for Alzheimer’s disease

Pyroptosis is a form of cell death mediated by inflammasomes and gasdermins, and the relevance of pyroptosis to neurodegenerative diseases is currently receiving increasing attention. Alzheimer’s disease (AD) is a chronic progressive neurodegenerative disease that is closely associated with neuroinflammation. Its main pathological features include β-amyloid (Aβ) deposition, Tau protein hyperphosphorylation and neuronal loss. Aβ, tau-induced microglia pyroptosis and polarization leading to neuroinflammation play an important role in the pathogenesis of AD. Studying the pathogenesis and treatment of AD based on cellular pyroptosis has become a new direction in AD research. In this paper, we review the research progress of pyroptosis and will focus on the pathogenic roles of pyroptosis in AD and the role of targeted inhibition of inflammasome-dependent pyroptosis in AD treatment. These results deepen our understanding of the pathogenesis of AD and provide ideas for the development of new drugs based on the regulation of pyroptosis in AD patients.

Mechanisms of NLRP3 activation and pathology during neurodegeneration

Inflammasomes are multiprotein complexes that are mainly present in resident and infiltrating immune cells in the central nervous system. Inflammasomes function as intracellular sensors of immunometabolic stress, infection and changes in the local microenvironment. Inflammasome assembly in response to these 'danger signals', triggers recruitment and cluster-dependent activation of caspase-1 and the subsequent proteolytic activation of inflammatory cytokines such as interleukin-1β and interleukin-18. This is typically followed by a form of inflammatory cell death through pyroptosis. Since the discovery of inflammasomes in 2002, they have come to be recognized as central regulators of acute and chronic inflammation, a hallmark of progressive neurological diseases. Indeed, over the last decade, extensive inflammasome activation has been found at the sites of neuropathology in all progressive neurodegenerative diseases. Disease-specific misfolded protein aggregates which accumulate in neurodegenerative diseases, such as alpha synuclein or beta amyloid, have been found to be important triggers of NLRP3 inflammasome activation in the central nervous system. Together, these discoveries have transformed our understanding of how chronic inflammation is triggered and sustained in the central nervous system, and how it can contribute to neuronal death and disease progression in age-related neurodegenerative diseases. Therapeutic strategies around inhibition of NLRP3 activation in the central nervous system are already being evaluated to determine their effectiveness to slow progressive neurodegeneration. This review summarizes current understanding of inflammasomes in the most prevalent neurodegenerative diseases and discusses current knowledge gaps and inflammasome inhibition as a therapeutic strategy.

The effect of the NLRP1 inflammasome on methamphetamine-induced cognitive impairment in rats

Methamphetamine (METH) use disorder has been shown to be in high comorbidity with cognitive deficits. METH-induced cognitive deficits are accompanied by neurotoxicity which could result from neuroinflammation. The potential role of NLRP1 inflammasome (NLRP1) and the downstream signalling pathway in METH-induced cognitive impairment was explored in the current study. Cognitive functions and the changes of NLRP1/Caspase-1/GSDMD signalling pathway were firstly determined in rats receiving daily injections of METH. Subsequently, the effects of aspirin-triggered-lipoxin A4 (ATL), a potent anti-inflammatory mediator, and NLRP1 siRNA was investigated were investigated in both METH-treated rats and HT22 cells. METH induces significant cognitive deficits in rats, using the NOR test. METH-induced cognitive impairment was in line with increased activities of NLRP1, cleaved-Caspase-11, IL-1β and TNF-α and the presence of GSDMD-mediated pyroptosis in the hippocampus of rats. NLRP1 inhibition by ATL significantly attenuated METH-induced cognitive impairment, in conjunction with the decreased activities of NLRP1 and cleaved-Caspase-1, IL-1β and TNF-α. ATL and NLRP1 siRNA also prevented the presence of apoptosis in the hippocampus of METH-treated rats and the cell death in METH-treated HT22 cells. These results reveal a novel role of NLRP1 and the downstream signaling pathways in the complex actions of METH-induced cognitive deficits.

NLRP1 Inflammasome Activation in the Hippocampal Formation in Alzheimer's Disease: Correlation with Neuropathological Changes and Unbiasedly Estimated Neuronal Loss

Neuroinflammation is one of the core pathological features of Alzheimer's disease (AD) as both amyloid β (Aβ) and tau monomers and oligomers can trigger the long-term pro-inflammatory phenotype of microglial cells with consequent overactivation of the inflammasomes. To investigate the NLRP1 inflammasome activation in AD, we analyzed the expression of NLRP1, ASC, cleaved gasdermin (cGSDMD), and active caspase-6 (CASP-6) proteins in each hippocampal subdivision (hilar part of CA3, CA2/3, CA1, subiculum) of postmortem tissue of 9 cognitively healthy controls (HC) and 11 AD patients whose disease duration varied from 3 to 7 years after the clinical diagnosis. The total number of neurons, along with the total number of neurofibrillary tangles (NFTs), were estimated in Nissl- and adjacent modified Bielschowsky-stained sections, respectively, using the optical disector method. The same 9 HC and 11 AD cases were additionally semiquantitatively analyzed for expression of IBA1, HLA-DR, and CD68 microglial markers. Our results show that the expression of NLRP1, ASC, and CASP-6 is present in a significantly greater number of hippocampal formation neurons in AD brains compared to controls, suggesting that the NLRP1 inflammasome is more active in the AD brain. None of the investigated inflammasome and microglial markers were found to correlate with the age of the subjects or the duration of AD. However, besides positive correlations with microglial IBA1 expression in the subiculum and with microglial CD68 expression in the CA1 field and subiculum in the AD group, the overall NLRP1 expression in the hippocampal formation was positively correlated with the number of NFTs, thus providing a causal link between neuroinflammation and neurofibrillary degeneration. The accumulation of AT8-immunoreactive phosphorylated tau proteins that we observed at nuclear pores of large pyramidal neurons of the Ammon's horn further supports their role in the extent of neuronal dysfunction and degeneration in AD. This is important because unlike fibrillar amyloid-β deposits that are not related to dementia severity, total NFTs and neuron numbers in the hippocampal formation, especially in the CA1 field, are the best correlates of cognitive deterioration in both human brain aging and AD. Our findings also support the notion that the CA2 field vulnerability is strongly linked to specific susceptibilities to different tauopathies, including primary age-related tauopathy. Altogether, these findings contrast with reports of nonsignificant microglial activation in aged nonhuman primates and indicate that susceptibility to inflammasome activation may render the human brain comparatively more vulnerable to neurodegenerative changes and AD. In conclusion, our results confirm a key role of NLRP1 inflammasome in AD pathogenesis and suggest NLRP1 as a potential diagnostic marker and therapeutic target to slow or prevent AD progression.

Aging Promotes Chronic Stress-Induced Depressive-Like Behavior by Activating NLRP1 Inflammasome-Driven Inflammatory Signaling in Mice

NLRP1 inflammasome has been reported to participate in many neurological disorders. Our previous study has demonstrated that NLRP1 inflammasome is implicated in chronic stress-induced depressive-like behaviors in mice. Age has been reported to be related to depression. Here we examine whether NLRP1 inflammasome is involved in the effect of age on depressive disorder. Two chronic stress stimuli, chronic social defeat stress (CSDS) and repeat social defeat stress (RSDS), were used to establish a depression model in mice of different ages. We found that aged mice exhibited worse depressive-like behaviors and locomotor activity compared to young mice. Interestingly, the expression of hippocampal NLRP1 inflammasome complexes and the levels of the inflammatory cytokines were increased in an age-dependent manner. Also, chronic stress-induced increase in the expression of the hippocampal chemokine C-X-C motif ligand 1 (CXCL1), and its cognate receptor, CXC-motif receptor 2 (CXCR2), was more remarkable in aged mice than that in young mice. Moreover, aged mice exhibited lower hippocampal BDNF levels compared to young mice. Hippocampal Nlrp1a knockdown reduced the levels of pro-inflammatory cytokines and the expression of CXCL1/CXCR2, restored BDNF levels, and alleviated chronic stress-induced depressive-like behaviors in aged mice. Our results suggest that NLRP1 inflammasome-CXCL1/CXCR2-BDNF signaling contributes to the effect of age on chronic stress-induced depressive-like behavior in mice.

Stress level of glucocorticoid exacerbates neuronal damage and Aβ production through activating NLRP1 inflammasome in primary cultured hippocampal neurons of APP-PS1 mice

Glucocorticoid (GC), secreted by adrenal cortex, plays important roles in regulating many physiological functions, while chronic stress level of GC exposure has many adverse effects on the structure and function of hippocampal neurons, and is closely implicated to the deterioration of Alzheimer's disease (AD). Oxidative stress and neuroinflammation play an important role in the occurrence and development of AD. However, it is still unclear whether chronic GC exposure promotes beta-amyloid (Aβ) accumulation and neuronal injury by increasing oxidative stress and neuroinflammation. In this study, we investigated the effects of chronic GC exposure on NOX2-NLRP1 inflammasome activation and the protective effects of NLRP1-siRNA against GC-induced neuronal injury in primary hippocampal neurons of APP/PS1 mice. The results showed that chronic dexamethasone (DEX, 1 µM) exposure 72 h had no significant effect on the primary hippocampal neurons of WT mice, but significantly increased Aβ_1-42 accumulation (2.17 ± 0.19 fold in APP group and 3.06 ± 0.49 fold in APP + DEX group over WT group) and neuronal injury in primary hippocampal neurons of APP/PS1 mice. Meanwhile, chronic DEX exposure significantly increased the levels of reactive oxygen species (ROS) production and IL-1β, and significantly up-regulated the expressions of NOX2- and NLRP1-related proteins and mRNAs in primary hippocampal neurons of APP/PS1 mice but not in WT mice. Moreover, inhibition of NLRP1 by NLRP1-siRNA treatment also significantly alleviated neuronal injury and Aβ_1-42 accumulation (1.96 ± 0.11 fold in APP + DEX group and 0.25 ± 0.01 fold in APP + NLRP1-siRNA + DEX group over APP group), and down-regulated the expressions of APP, BACE1, NCSTN and p-TAU/TAU in chronic DEX-induced hippocampal neurons of APP/PS1 mice. The results suggest that chronic GC exposure can accelerate neuronal damage and Aβ production by activating oxidative stress and NLRP1 inflammasome in primary hippocampal neurons of APP/PS1 mice, resulting in deterioration of AD.And inhibition of NLRP1 inflammasome may be an important strategy in improving chronic GC-induced neuronal injury.

Research Progress of Pyroptosis in Alzheimer's Disease

Alzheimer's disease (AD) is a disease characterized by insidious and progressive neurodegeneration, with clinical syndromes of memory and visuospatial skills damage. The pathogenic mechanism of AD is complex in which neural inflammation and neuron death play important roles. Pyroptosis, an inflammatory programmed cell death, has been reported to be involved in neuron death. Pyroptosis is executed by the protein family of gasdermins which punch pores on plasma membrane when activated by the upstream signals including the activation of NLRP3 and caspases, and subsequently triggers the inflammatory cascades featured by the release of interleukin (IL) -1β and IL-18. Herein, we summarized the current research on the roles of neuron pyroptosis in AD, aiming to provide a comprehensive view of the molecular mechanisms underlying AD pathogenesis and potential therapeutic targets for AD.

New Insights into Neuroinflammation Involved in Pathogenic Mechanism of Alzheimer's Disease and Its Potential for Therapeutic Intervention

Alzheimer's disease (AD) is the most common form of dementia, affecting more than 50 million people worldwide with an estimated increase to 139 million people by 2050. The exact pathogenic mechanisms of AD remain elusive, resulting in the fact that the current therapeutics solely focus on symptomatic management instead of preventative or curative strategies. The two most widely accepted pathogenic mechanisms of AD include the amyloid and tau hypotheses. However, it is evident that these hypotheses cannot fully explain neuronal degeneration shown in AD. Substantial evidence is growing for the vital role of neuroinflammation in AD pathology. The neuroinflammatory hypothesis provides a new, exciting lead in uncovering the underlying mechanisms contributing to AD. This review aims to highlight new insights into the role of neuroinflammation in the pathogenesis of AD, mainly including the involvement of nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB), nucleotide-binding oligomerization domain, leucine-rich repeat-containing protein 3 (NLRP3)/caspase-1 axis, triggering receptor expressed on myeloid cells 2 (TREM2) and cGAS-STING as key influencers in augmenting AD development. The inflammasomes related to the pathways of NF-κB, NLRP3, TREM2, and cGAS-STING as biomarkers of the neuroinflammation associated with AD, as well as an overview of novel AD treatments based on these biomarkers as potential drug targets reported in the literature or under clinical trials, are explored.

Pyroptosis in neurodegenerative diseases: What lies beneath the tip of the iceberg?

Neurodegenerative diseases gradually receive attention with a rapidly aging global population. The hallmark of them is a progressive neuronal loss in the brain or peripheral nervous system due to complex reasons ranging from protein aggregation, immune dysregulation to abnormal cell death. The death style of nerve cell is no longer restricted to apoptosis, autophagy and necrosis as confirmed before. With the successive discoveries of the gasdermin (GSDM) protein family and key caspase molecules in the past several decades, pyroptosis emerges as a novel kind of programmed cell death. A substantial body of evidence has recognized the close connection between pyroptosis and the occurrence and development of neurodegenerative diseases. In this review, we summarize molecular mechanisms of pyroptosis, evidences for pyroptosis involvement in neurodegenerative diseases and finally we hope to provide a novel angle for clinical decision-making.

Chemical Modulation of Gasdermin-Mediated Pyroptosis and Therapeutic Potential

Pyroptosis, a lytic form of programmed cell death, both stimulates effective immune responses and causes tissue damage. Gasdermin (GSDM) proteins are a family of pore-forming executors of pyroptosis. While the most-studied member, GSDMD, exerts critical functions in inflammasome biology, emerging evidence demonstrates potential broad relevance for GSDM-mediated pyroptosis across diverse pathologies. In this review, we describe GSDM biology, outline conditions where inflammasomes and GSDM-mediated pyroptosis represent rational therapeutic targets, and delineate strategies to manipulate these central immunologic processes for the treatment of human disease.

Functional Selectivity of Coumarin Derivates Acting via GPR55 in Neuroinflammation

Anti-neuroinflammatory treatment has gained importance in the search for pharmacological treatments of different neurological and psychiatric diseases, such as depression, schizophrenia, Parkinson’s disease, and Alzheimer’s disease. Clinical studies demonstrate a reduction of the mentioned diseases’ symptoms after the administration of anti-inflammatory drugs. Novel coumarin derivates have been shown to elicit anti-neuroinflammatory effects via G-protein coupled receptor GPR55, with possibly reduced side-effects compared to the known anti-inflammatory drugs. In this study, we, therefore, evaluated the anti-inflammatory capacities of the two novel coumarin-based compounds, KIT C and KIT H, in human neuroblastoma cells and primary murine microglia. Both compounds reduced PGE₂-concentrations likely via the inhibition of COX-2 synthesis in SK-N-SH cells but only KIT C decreased PGE₂-levels in primary microglia. The examination of other pro- and anti-inflammatory parameters showed varying effects of both compounds. Therefore, the differences in the effects of KIT C and KIT H might be explained by functional selectivity as well as tissue- or cell-dependent expression and signal pathways coupled to GPR55. Understanding the role of chemical residues in functional selectivity and specific cell- and tissue-targeting might open new therapeutic options in pharmacological drug development and might improve the treatment of the mentioned diseases by intervening in an early step of their pathogenesis.

NLRP1 inflammasome involves in learning and memory impairments and neuronal damages during aging process in mice

Background

Brain aging is an important risk factor in many human diseases, such as Alzheimer’s disease (AD). The production of excess reactive oxygen species (ROS) mediated by nicotinamide adenine dinucleotide phosphate oxidase 2 (NOX2) and the maturation of inflammatory cytokines caused by activation of the NOD-like receptor protein 1 (NLRP1) inflammasome play central roles in promoting brain aging. However, it is still unclear when and how the neuroinflammation appears in the brain during aging process.

Methods

In this study, we observed the alterations of learning and memory impairments, neuronal damage, NLRP1 inflammasome activation, ROS production and NOX2 expression in the young 6-month-old (6 M) mice, presenile 16 M mice, and older 20 M and 24 M mice.

Results

The results indicated that, compared to 6 M mice, the locomotor activity, learning and memory abilities were slightly decreased in 16 M mice, and were significantly decreased in 20 M and 24 M mice, especially in the 24 M mice. The pathological results also showed that there were no significant neuronal damages in 6 M and 16 M mice, while there were obvious neuronal damages in 20 M and 24 M mice, especially in the 24 M group. Consistent with the behavioral and histological changes in the older mice, the activity of β-galactosidase (β-gal), the levels of ROS and IL-1β, and the expressions of NLRP1, ASC, caspase-1, NOX2, p47phox and p22phox were significantly increased in the cortex and hippocampus in the older 20 M and 24 M mice.

Conclusion

Our study suggested that NLRP1 inflammasome activation may be closely involved in aging-related neuronal damage and may be an important target for preventing brain aging.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12993-021-00185-x.

Association of Cholinergic Basal Forebrain Volume and Functional Connectivity with Markers of Inflammatory Response in the Alzheimer’s Disease Spectrum

Background: Inflammation has been described as a key pathogenic event In Alzheimer’s disease (AD), downstream of amyloid and tau pathology. Preclinical and clinical data suggest that the cholinergic basal forebrain may moderate inflammatory response to different pathologies. Objective: To study the association of cholinergic basal forebrain volume and functional connectivity with measures of neuroinflammation in people from the AD spectrum. Methods: We studied 261 cases from the DELCODE cohort, including people with subjective cognitive decline, mild cognitive impairment, AD dementia, first degree relatives, and healthy controls. Using Bayesian ANCOVA, we tested associations of MRI indices of cholinergic basal forebrain volume and functional connectivity with cerebrospinal fluid (CSF) levels of sTREM2 as a marker of microglia activation, and serum levels of complement C3. Using Bayesian elastic net regression, we determined associations between basal forebrain measures and a large inflammation marker panel from CSF and serum. Results: We found anecdotal to moderate evidence in favor of the absence of an effect of basal forebrain volume and functional connectivity on CSF sTREM2 and serum C3 levels both in Aβ 42/ptau-positive and negative cases. Bayesian elastic net regression identified several CSF and serum markers of inflammation that were associated with basal forebrain volume and functional connectivity. The effect sizes were moderate to small. Conclusion: Our data-driven analyses generate the hypothesis that cholinergic basal forebrain may be involved in the neuroinflammation response to Aβ 42 and phospho-tau pathology in people from the AD spectrum. This hypothesis needs to be tested in independent samples.

Anti-Inflammatory and Anti-Oxidative Effects of AM404 in IL-1β-Stimulated SK-N-SH Neuroblastoma Cells

An emerging number of studies address the involvement of neuroinflammation and oxidative stress in the pathophysiology of central nervous system (CNS) disorders such as depression, schizophrenia, anxiety, and neurodegenerative diseases. Different cytokines and molecules, such as prostaglandin (PG) E₂, are associated with neuroinflammatory processes. The active acetaminophen metabolite AM404 has been shown to prevent inflammation and neuroinflammation in primary microglia and organotypic hippocampal slice cultures. However, its effects on pathophysiological conditions in the CNS and especially on neurons are still poorly understood. In this study, we therefore evaluated the effects of AM404 and acetaminophen on the arachidonic acid cascade and oxidative stress induced by interleukin (IL)-1β in human SK-N-SH neuronal cells. We observed that AM404 and acetaminophen significantly and concentration-dependent inhibited IL-1β-induced release of PGE₂, independent of cyclooxygenases (COX)-1 and COX-2 enzymatic activity as well as COX-2 mRNA and protein levels in SK-N-SH-cells. The reduction of IL-1β-induced PGE₂-release by AM404 and acetaminophen treatment might be mediated by the 8-iso-PGF_2α pathway since IL-1β-induced synthesis of this free radical marker is dose-dependently reduced by both compounds, respectively. Therefore, understanding of the potential therapeutic properties of AM404 in neuroinflammation and oxidative stress might lead to future treatment options of different neurological disorders.