Protection of MCC950 against Alzheimer's disease via inhibiting neuronal pyroptosis in SAMP8 mice

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.

Inhibition of NLRP3 inflammasome ameliorates LPS-induced neuroinflammatory injury in mice via PINK1/Parkin pathway

Parkinson's disease (PD) is characterized by the severe loss of dopaminergic neurons in the substantia nigra pars compacta, leading to motor dysfunction. The onset of PD is often accompanied by neuroinflammation and α-Synuclein aggregation, and extensive research has focused on the activation of microglial NLRP3 inflammasomes in PD, which promotes the death of dopaminergic neurons. In this study, a model of cerebral inflammatory response was constructed in wild-type and Parkin＋/－ mice through bilateral intraventricular injection of LPS. LPS-induced activation of the NLRP3 inflammasome in wild-type mice promotes the progression of PD. The use of MCC950 in wild mice injected with LPS induces activation of Parkin/PINK and improves autophagy, which in turn improves mitochondrial turnover. It also inhibits LPS-induced inflammatory responses, improves motor function, protects dopaminergic neurons, and inhibits microglia activation. Furthermore, Parkin＋/－ mice exhibited motor dysfunction, loss of dopaminergic neurons, activation of the NLRP3 inflammasome, and α-Synuclein aggregation beginning at an early age. Parkin ± mice exhibited more pronounced microglia activation, greater NLRP3 inflammasome activation, more severe autophagy dysfunction, and more pronounced motor dysfunction after LPS injection compared to wild-type mice. Notably, the use of MCC950 in Parkin ± mice did not ameliorate NLRP3 inflammasome activation, autophagy dysfunction, or α-synuclein aggregation. Thus, MCC950 can only exert its effects in the presence of Parkin/PINK1, and targeting Parkin-mediated NLRP3 inflammasome activation is expected to be a potential therapeutic strategy for Parkinson's disease.

Vitamin C inhibits NLRP3 inflammasome activation and delays the development of age-related hearing loss in male C57BL/6 mice

The efficacy of vitamin C in age-related hearing loss, i.e., presbycusis, remains debatable. On a separate note, inflammation induced by the NOD-like receptor family pyrin domain containing 3 (NLRP3) inflammasome is involved in the progression of presbycusis. In this study, we investigated the effect of vitamin C on male C57BL/6 mice's presbycusis and NLRP3 inflammasome. The results showed that vitamin C treatment improved hearing, reduced the production of inflammatory factors, inhibited NLRP3 inflammasome activation, and decreased cytosolic mitochondrial DNA (mtDNA) in the C57BL/6 mouse cochlea, inferior colliculus, and auditory cortex. According to this study, vitamin C protects auditory function in male C57BL/6 presbycusis mice through reducing mtDNA release, inhibiting the NLRP3 inflammasome activation in the auditory pathway. Our study provides a theoretical basis for applying vitamin C to treat presbycusis.

Pyroptosis-mediator GSDMD promotes Parkinson's disease pathology via microglial activation and dopaminergic neuronal death

GSDMD-mediated pyroptosis occurs in the nigrostriatal pathway in Parkinson's disease animals, yet the role of GSDMD in neuroinflammation and death of dopaminergic neurons in Parkinson's disease remains elusive. Here, our in vivo and in vitro studies demonstrated that GSDMD, as a pyroptosis executor, contributed to glial reaction and death of dopaminergic neurons across different Parkinson's disease models. The ablation of the Gsdmd attenuated Parkinson's disease damage by reducing dopaminergic neuronal death, microglial activation, and detrimental transformation. Disulfiram, an inhibitor blocking GSDMD pore formation, efficiently curtailed pyroptosis, thereby lessening the pathology of Parkinson's disease. Additionally, a modification in GSDMD was identified in the blood of Parkinson's disease patients in contrast to healthy subjects. Therefore, the detected alteration in GSDMD within the blood of Parkinson's disease patients and the protective impact of disulfiram could be promising for the diagnostic and therapeutic approaches against Parkinson's disease.

Nanoligomers targeting NF-κB and NLRP3 reduce neuroinflammation and improve cognitive function with aging and tauopathy

Neuroinflammation contributes to impaired cognitive function in brain aging and neurodegenerative disorders like Alzheimer's disease, which is characterized by the aggregation of pathological tau. One major driver of both age- and tau-associated neuroinflammation is the NF-κB and NLRP3 signaling axis. However, current treatments targeting NF-κB or NLRP3 may have adverse/systemic effects, and most have not been clinically translatable. In this study, we tested the efficacy of a novel, nucleic acid therapeutic (Nanoligomer) cocktail specifically targeting both NF-κB and NLRP3 in the brain for reducing neuroinflammation and improving cognitive function in old (aged 19 months) wildtype mice, and in rTg4510 tau pathology mice (aged 2 months). We found that 4 weeks of NF-κB/NLRP3-targeting Nanoligomer treatment strongly reduced neuro-inflammatory cytokine profiles in the brain and improved cognitive-behavioral function in both old and rTg4510 mice. These effects of NF-κB/NLRP3-targeting Nanoligomers were also associated with reduced glial cell activation and pathology, favorable changes in transcriptome signatures of glia-associated inflammation (reduced) and neuronal health (increased), and positive systemic effects. Collectively, our results provide a basis for future translational studies targeting both NF-κB and NLRP3 in the brain, perhaps using Nanoligomers, to inhibit neuroinflammation and improve cognitive function with aging and neurodegeneration.

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.

Neuroinflammation of Microglial Regulation in Alzheimer's Disease: Therapeutic Approaches

Alzheimer's disease (AD) is a complex degenerative disease of the central nervous system that is clinically characterized by a progressive decline in memory and cognitive function. The pathogenesis of AD is intricate and not yet fully understood. Neuroinflammation, particularly microglial activation-mediated neuroinflammation, is believed to play a crucial role in increasing the risk, triggering the onset, and hastening the progression of AD. Modulating microglial activation and regulating microglial energy metabolic disorder are seen as promising strategies to intervene in AD. The application of anti-inflammatory drugs and the targeting of microglia for the prevention and treatment of AD has emerged as a new area of research interest. This article provides a comprehensive review of the role of neuroinflammation of microglial regulation in the development of AD, exploring the connection between microglial energy metabolic disorder, neuroinflammation, and AD development. Additionally, the advancements in anti-inflammatory and microglia-regulating therapies for AD are discussed.

MCC950 alleviates seizure severity and angiogenesis by inhibiting NLRP3/ IL-1β signaling pathway-mediated pyroptosis in mouse model of epilepsy

Epilepsy is one of the most common serious chronic brain disorders, affecting up to 70 million people worldwide. Vascular disruption, including blood-brain barrier impairment and pathological angiogenesis, exacerbates its occurrence. However, its underlying mechanisms remain elusive. MCC950 is a specific small-molecule inhibitor that selectively blocks NLRP3 inflammatory vesicle activation across the blood-brain barrier, limits downstream IL-1β maturation and release, and exerts therapeutic effects across multiple diseases. In the present study, an epilepsy model was established by intraperitoneal administration of Kainic acid to adult male C57BL/6J wild-type mice. The results revealed that the epilepsy susceptibility of MCC950-treated mice was decreased, and neural damage following seizure episodes was reduced. In addition, immunofluorescence staining, RT-qPCR, and Western blot demonstrated that MCC950 inhibited the expression of the NLRP3 inflammasome and its related proteins in microglia, whereas microangiogenesis was found to be increased in the cerebral cortex and hippocampus of epileptic mice, and these effects could be reversed by MCC950. Furthermore, neurobehavioral impairment was observed in the epileptic mouse model, and MCC950 similarly alleviated the aforementioned pathological process. To the best of our knowledge, this is the first study to establish that pathological microangiogenesis is associated with NLRP3/IL-1β signaling pathway activation in a Kainic acid-induced epilepsy mouse model and that MCC950 administration attenuates the above-mentioned pathological changes and exerts neuroprotective effects. Therefore, MCC950 is a promising therapeutic agent for the treatment of epilepsy.

ZBP1 mediates the progression of Alzheimer's disease via pyroptosis by regulating IRF3

Alzheimer's disease (AD) is one of the leading causes of death throughout the world. Z-DNA binding protein 1 (ZBP1), a DNA-related gene, is associated with inflammation, and its expression is altered in AD brain. We aimed to elucidate the exact role of ZBP1 in AD development and its potential regulatory mechanism. First, we constructed both in vivo and in vitro models of AD and investigated the ZBP1 expression profile. A loss-of-function assay was performed by transfecting lentivirus carrying ZBP1 short hairpin RNA (shRNA). By evaluating cell death, oxidative stress, inflammation response and pyroptosis, the function of ZBP1 was validated. Finally, the correlation between ZBP1 and interferon regulatory factor 3 (IRF3) was verified. We also performed rescue experiments to validate the crucial role of IRF3 in ZBP1-mediated AD progression. According to our results, ZBP1 was upregulated in AD rat tissue and AD neurons. Silencing ZBP1 dramatically decreased cell injury, oxidative stress and inflammation in AD neurons and improved the cognitive function of AD rats. Additionally, IRF3 expression and phosphorylation were significantly elevated during AD development and positively correlated with ZBP1. Taken together, silencing ZBP1 suppressed cell injury and pyroptosis of AD neurons and improved cognitive function of AD rats via inhibiting IRF3. These findings might provide a novel insight for AD target diagnosis and therapy.

Fermented soybean foods (natto) ameliorate age-related cognitive decline by hippocampal TAAR1-mediated activation of the CaMKII/CREB/BDNF signaling pathway in senescence-accelerated mouse prone 8 (SAMP8)

Natto is a traditional fermented soybean-based food that has been an integral part of Japanese cuisine for several centuries. Although there have been extensive studies on the cognitive benefits of soybeans, only limited studies have examined the effects of natto on cognitive function. This study investigated the potential cognitive benefits of natto in senescence-accelerated mouse-prone 8 (SAMP8) mice. After 12 weeks of oral administering natto fermented for 18 h, the spatial learning and memory performance were improved compared with those in SAMP8 control mice. Furthermore, activation of the brain-derived neurotrophic factor (BDNF)/tropomyosin receptor kinase B (TrkB)/cAMP response element-binding protein (CREB) signaling and N-methyl-D-aspartate receptor (NMDAR)-calcium/calmodulin-dependent protein kinase II (CaMKII) cascade was observed in the hippocampus of SAMP8 mice that were fed natto. Additionally, natto administration upregulated trace amine-associated receptor 1 (TAAR1) as a modulator of NMDAR. These findings suggest that natto ameliorates cognitive decline by activating the TAAR1-mediated CaMKII/CREB/BDNF signaling pathway in the hippocampus of SAMP8 mice.

NLRP3 inflammasome in cognitive impairment and pharmacological properties of its inhibitors

Cognitive impairment is a multifactorial and multi-step pathological process that places a heavy burden on patients and the society. Neuroinflammation is one of the main factors leading to cognitive impairment. The inflammasomes are multi-protein complexes that respond to various microorganisms and endogenous danger signals, helping to initiate innate protective responses in inflammatory diseases. NLRP3 inflammasomes produce proinflammatory cytokines (interleukin IL-1β and IL-18) by activating caspase-1. In this review, we comprehensively describe the structure and functions of the NLRP3 inflammasome. We also explore the intrinsic relationship between the NLRP3 inflammasome and cognitive impairment, which involves immune cell activation, cell apoptosis, oxidative stress, mitochondrial autophagy, and neuroinflammation. Finally, we describe NLRP3 inflammasome antagonists as targeted therapies to improve cognitive impairment.

Targeting NLRP3 inflammasome for neurodegenerative disorders

Neuroinflammation is a key pathological feature in neurological diseases, including Alzheimer's disease (AD). The nucleotide-binding domain leucine-rich repeat-containing proteins (NLRs) belong to the pattern recognition receptors (PRRs) family that sense stress signals, which play an important role in inflammation. As a member of NLRs, the NACHT, LRR and PYD domains-containing protein 3 (NLRP3) is predominantly expressed in microglia, the principal innate immune cells in the central nervous system (CNS). Microglia release proinflammatory cytokines to cause pyroptosis through activating NLRP3 inflammasome. The active NLRP3 inflammasome is involved in a variety of neurodegenerative diseases (NDs). Recent studies also indicate the key role of neuronal NLRP3 in the pathogenesis of neurological disorders. In this article, we reviewed the mechanisms of NLRP3 expression and activation and discussed the role of active NLRP3 inflammasome in the pathogenesis of NDs, particularly focusing on AD. The studies suggest that targeting NLRP3 inflammasome could be a novel approach for the disease modification.

Mitochondrial DNA and Inflammation in Alzheimer's Disease

Mitochondrial dysfunction and neuroinflammation are implicated in the pathogenesis of most neurodegenerative diseases, such as Alzheimer's disease (AD). In fact, although a growing number of studies show crosstalk between these two processes, there remain numerous gaps in our knowledge of the mechanisms involved, which requires further clarification. On the one hand, mitochondrial dysfunction may lead to the release of mitochondrial damage-associated molecular patterns (mtDAMPs) which are recognized by microglial immune receptors and contribute to neuroinflammation progression. On the other hand, inflammatory molecules released by glial cells can influence and regulate mitochondrial function. A deeper understanding of these mechanisms may help identify biomarkers and molecular targets useful for the treatment of neurodegenerative diseases. This review of works published in recent years is focused on the description of the mitochondrial contribution to neuroinflammation and neurodegeneration, with particular attention to mitochondrial DNA (mtDNA) and AD.

Role of gasdermin family proteins in cancers (Review)

The gasdermin (GSDM) family comprises six proteins, including GSDMA‑GSDME and Pejvakin. Most of these proteins have a crucial role in inducing pyroptosis; in particular, GSDMD and GSDME are the most extensively studied proteins as the executioners of the pyroptosis process. Pyroptosis is a highly pro‑inflammatory form of programmed cell death and is closely associated with the incidence, development and prognosis of multiple cancer types. The present review focused on the current knowledge of the molecular mechanism of GSDM‑mediated pyroptosis, its intricate role in cancer and the potential therapeutic value of its anti‑tumor effects.

Discovery of a selective NLRP3-targeting compound with therapeutic activity in MSU-induced peritonitis and DSS-induced acute intestinal inflammation

The aberrant activation of the nucleotide-binding oligomerization domain-like receptor family pyrin domain containing 3 (NLRP3) inflammasome is known to contribute to the pathogenesis of various human inflammation-related diseases. However, to date, no small-molecule NLRP3 inhibitor has been used in clinical settings. In this study, we have identified SB-222200 as a novel direct NLRP3 inhibitor through the use of drug affinity responsive target stability assay, cellular thermal shift assay, and surface plasmon resonance analysis. SB-222200 effectively inhibits the activation of the NLRP3 inflammasome in macrophages, while having no impact on the activation of NLRC4 or AIM2 inflammasome. Furthermore, SB-222200 directly binds to the NLRP3 protein, inhibiting NLRP3 inflammasome assembly by blocking the NEK7 - NLRP3 interaction and NLRP3 oligomerization. Importantly, treatment with SB-222200 demonstrates alleviation of NLRP3-dependent inflammatory diseases in mouse models, such as monosodium urate crystal-induced peritonitis and dextran sulfate sodium-induced acute intestinal inflammation. Therefore, SB-222200 holds promise as a lead compound for the development of NLRP3 inhibitors to combat NLRP3-driven disease and serves as a versatile tool for pharmacologically investigating NLRP3 biology.

The role of pyroptosis in cognitive impairment

Cognitive impairment is a major global disease, manifests as a decline in cognitive functioning and endangers the health of the population worldwide. The incidence of cognitive impairment has increased rapidly with an increasingly aging population. Although the mechanisms of cognitive impairment have partly been elucidated with the development of molecular biological technology, treatment methods are very limited. As a unique form of programmed cell death, pyroptosis is highly pro-inflammatory and is closely associated with the incidence and progression of cognitive impairment. In this review, we discuss the molecular mechanisms of pyroptosis briefly and the research progress on the relationship between pyroptosis and cognitive impairment and its potential therapeutic values, to provide a reference for research in the field of cognitive impairment.

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.

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.

Interlacing the relevance of caspase activation in the onset and progression of Alzheimer's disease

Caspases, a family of cysteine proteases is a renowned regulator of apoptosis. Members of this family are responsible for the proteolytic dismantling of numerous cellular structures. Apart from apoptosis, caspases remarkably contribute to a diverse range of molecular processes. Being the imperative members of several cellular cascades their abnormal activation/deactivation has severe implications and also leads to various diseased conditions. Similar aberrant activation of caspases is one of the several causes of neuropathologies associated with Alzheimer's disease (AD), a form of dementia severely affecting neuropsychiatric and cognitive functions. Emerging studies are providing deeper insights into the mechanisms of caspase action in the progression of AD. Current article is an attempt to review these studies and present the action mechanisms of different mammalian caspases in the advancement of AD associated neuropathologies.

Cdk5-p25 as a key element linking amyloid and tau pathologies in Alzheimer's disease: Mechanisms and possible therapeutic interventions

Despite the fact that the small atypical serine/threonine cyclin-dependent kinase 5 (Cdk5) is expressed in a number of tissues, its activity is restricted to the central nervous system due to the neuron-only localization of its activators p35 and p39. Although its importance for the proper development and function of the brain and its role as a switch between neuronal survival and death are unmistakable and unquestionable, Cdk5 is nevertheless increasingly emerging, as supported by a large number of publications on the subject, as a therapeutic target of choice in the fight against Alzheimer's disease. Thus, its aberrant over activation via the calpain-dependent conversion of p35 into p25 is observed during the pathogenesis of the disease where it leads to the hyperphosphorylation of the β-amyloid precursor protein and tau. The present review highlights the pivotal roles of the hyperactive Cdk5-p25 complex activity in contributing to the development of Alzheimer's disease pathogenesis, with a particular emphasis on the linking function between Aβ and tau that this kinase fulfils and on the fact that Cdk5-p25 is part of a deleterious feed forward loop giving rise to a molecular machinery runaway leading to AD pathogenesis. Additionally, we discuss the advances and challenges related to the possible strategies aimed at specifically inhibiting Cdk5-p25 activity and which could lead to promising anti-AD therapeutics.

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.

Targeting NLRP3-Mediated Neuroinflammation in Alzheimer’s Disease Treatment

Alzheimer’s disease (AD) is the most common cause of dementia in the general population and, to date, constitutes a major therapeutic challenge. In the pathogenesis of AD, aggregates of amyloid β (Aβ) and neurofibrillary tangles (NFTs) containing Tau-microtubule-associated protein (tau) are known to trigger a neuroinflammatory response with subsequent formation of an inflammasome. In particular, the NOD-like receptor pyrin domain-containing 3 (NLRP3) inflammasome is thought to play a crucial role in AD-related pathology. While the mechanisms for NLRP3 activation are not fully understood, it has been demonstrated that, after detection of protein aggregates, NLRP3 induces pro-inflammatory cytokines, such as interleukin 18 (IL-18) or interleukin 1β (IL-1β), that further potentiate AD progression. Specific inhibitors of NLRP3 that exhibit various mechanisms to attenuate the activity of NLRP3 have been tested in in vivo studies and have yielded promising results, as shown by the reduced level of tau and Aβ aggregates and diminished cognitive impairment. Herein, we would like to summarize the current state of knowledge on NLRP3 inflammasome priming, activation, and its actual role in AD pathogenesis, and to characterize the NLRP3 inhibitors that have been studied most and their impact on AD-related pathology.

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.

Therapeutic potential of MCC950, a specific inhibitor of NLRP3 inflammasome

NOD-like receptor protein 3 (NLRP3), an important intracellular pattern recognition receptor, is a component of the NLRP3 inflammasome along with apoptosis-associated speck-like protein containing a caspase-recruitment domain (ASC) and pro-caspase-1. Previous studies have shown that dysregulation of NLRP3 inflammasome may be associated with several human diseases, and therefore blocking NLRP3 inflammasome activation may represent a therapeutic strategy for various diseases. MCC950 is a specific small-molecule inhibitor that selectively blocks activation of the NLRP3 inflammasome. In recent years, research on MCC950 has expanded; its targets are gradually being elucidated, and its metabolism and toxicity have been a focus of study. Preclinical research of MCC950 has yielded promising findings, and MCC950 has shown good efficacy in the treatment of autoimmune diseases, cardiovascular diseases, metabolic diseases and other diseases. Furthermore, clinical trials of MCC950 and other inhibitors of NLRP3 inflammasome have also been conducted. In this review, we discuss the drug targets, metabolism, toxicity and preclinical and clinical research advances of MCC950. We further discuss the clinical therapeutic potential of MCC950 to provide insights for the further study and application of MCC950.

Dendrobium Nobile Lindl. Alkaloid Suppresses NLRP3-Mediated Pyroptosis to Alleviate LPS-Induced Neurotoxicity

Alzheimer’s disease (AD) is a neurodegenerative disorder recognized as a global public health priority. Although available treatments temporarily relieve the symptoms, they could not prevent the progression of cognitive decline. Natural compounds have been rich sources for drug discovery. Dendrobium nobile Lindl. alkaloid (DNLA) is the main active compound in Dendrobium nobile Lindl, a traditional Chinese herbal medicine. Recent studies indicated that DNLA produced neuroprotection. However, the mechanisms underlying DNLA-generated neuroprotection remain unknown. To investigate neuroprotection and the underlying mechanisms of DNLA, mouse hippocampus injection of lipopolysaccharide (LPS)-induced neuronal damage was performed. DNLA protected hippocampus neurons and working memory disorder against LPS-induced neurotoxicity. In addition, DNLA suppressed cell undergoing membrane lysis and cell swelling and inhibited the essential mediator of pyroptosis GSDMD-N expressions. Furthermore, DNLA-mediated neuroprotection was dependent on the inhibition of NLRP3 inflammasome activation, as evidenced by the fact that DNLA reduced pro-inflammatory factor (IL-18 and IL-1β) production and inhibited the expression of related proteins. DNLA-exerted neuroprotection against LPS-induced neuronal damage, and cognitive impairment was not observed in NLRP3 knockout mice. Together, this study suggested that DNLA attenuated NLRP3-mediated pyroptosis to generate neuroprotection against LPS-induced neuronal damage and cognitive impairment.

NLRP3 and pyroptosis blockers for treating inflammatory diseases

The nucleotide-binding oligomerization domain, leucine-rich repeat and pyrin domain-containing protein 3 (NLRP3) inflammasome has emerged as a key mediator of pathological inflammation in many diseases and is an exciting drug target. Here, we review the molecular basis of NLRP3 inhibition by drug-like small molecules under development as novel therapeutics. We also summarize recent strategies to block pyroptosis as a novel approach to suppress chronic inflammation. Major recent developments in this area include the elucidation of mechanisms of action (MoAs) by which small molecules block NLRP3 inflammasome assembly and gasdermin D (GSDMD)-induced pyroptosis. We also discuss the status of clinical trials using agents that block specific components of the NLRP3 pathway, including their potential clinical applications for the treatment of many diseases.

The Role of NLRP3 Inflammasome in Alzheimer’s Disease and Potential Therapeutic Targets

Alzheimer’s disease (AD) is a common age-related neurodegenerative disease characterized by progressive cognitive dysfunction and behavioral impairment. The typical pathological characteristics of AD are extracellular senile plaques composed of amyloid ß (Aβ) protein, intracellular neurofibrillary tangles formed by the hyperphosphorylation of the microtubule-associated protein tau, and neuron loss. In the past hundred years, although human beings have invested a lot of manpower, material and financial resources, there is no widely recognized drug for the effective prevention and clinical cure of AD in the world so far. Therefore, evaluating and exploring new drug targets for AD treatment is an important topic. At present, researchers have not stopped exploring the pathogenesis of AD, and the views on the pathogenic factors of AD are constantly changing. Multiple evidence have confirmed that chronic neuroinflammation plays a crucial role in the pathogenesis of AD. In the field of neuroinflammation, the nucleotide-binding oligomerization domain-like receptor pyrin domain-containing 3 (NLRP3) inflammasome is a key molecular link in the AD neuroinflammatory pathway. Under the stimulation of Aβ oligomers and tau aggregates, it can lead to the assembly and activation of NLRP3 inflammasome in microglia and astrocytes in the brain, thereby causing caspase-1 activation and the secretion of IL-1β and IL-18, which ultimately triggers the pathophysiological changes and cognitive decline of AD. In this review, we summarize current literatures on the activation of NLRP3 inflammasome and activation-related regulation mechanisms, and discuss its possible roles in the pathogenesis of AD. Moreover, focusing on the NLRP3 inflammasome and combining with the upstream and downstream signaling pathway-related molecules of NLRP3 inflammasome as targets, we review the pharmacologically related targets and various methods to alleviate neuroinflammation by regulating the activation of NLRP3 inflammasome, which provides new ideas for the treatment of AD.

NLRP3 Inflammasome in Vascular Disease: A Recurrent Villain to Combat Pharmacologically

Despite the great advances in medicine, mortality from cardiovascular diseases keeps on growing. This tendency is not likely to change considering the pandemic proportions of obesity and diabetes. Besides, the global population is more aged as life expectancy increases, and vascular aging plays a key role in the increased risk of vascular disease. In light of recent trials, namely the CANTOS study, showing the enormous potential of anti-inflammatory therapies and in particular those targeted to IL-1β, a change in therapeutical management of cardiovascular diseases is coming about. The NLRP3 inflammasome is a multiprotein complex that assembles to engage the innate immune defense by processing the maturation of pro-inflammatory cytokines IL-1β and IL-18. Substantial evidence has positioned the NLRP3 inflammasome at the center of vascular disease progression, with a particular significance in the context of aging and the low-grade chronic inflammation associated (inflammaging). Therefore, pharmacological blockade of the NLRP3 inflammasome and its end products has arisen as an extremely promising tool to battle vascular disease. In this review, we discuss the mechanisms by which the NLRP3 inflammasome contributes to vascular disease, with particular attention to the consequences of aging, and we enumerate the therapeutic options available to combat this recurrent villain.

Electroacupuncture ameliorates postoperative cognitive dysfunction and associated neuroinflammation via NLRP3 signal inhibition in aged mice

Background

Postoperative cognitive dysfunction (POCD) is associated with worsened prognosis especially in aged population. Clinical and animal studies suggested that electroacupuncture (EA) could improve POCD. However, the underlying mechanisms especially EA’s regulatory role of inflammasomes remain unclear.

Methods

The model of POCD was established by partial hepatectomy surgery in 18‐month mice with or without postoperative EA treatment to the Baihui acupoint (GV20) for 7 days. Cognitive functions were assessed by Morris water maze test, and proinflammatory cytokines IL‐1β and IL‐6 and microglia activity were assayed by qPCR, ELISA, or immunohistochemistry. Tight junction proteins, NLRP3 inflammasome and downstream proteins, and NF‐κB pathway proteins were evaluated by western blotting.

Results

EA markedly preserved cognitive dysfunctions in POCD mice, associated with the inhibition of neuroinflammation as evidenced by reduced microglial activation and decreased IL‐1β and IL‐6 levels in brain tissue. EA also preserved hippocampal neurons and tight junction proteins ZO‐1 and claudin 5. Mechanistically, the activation of NLRP3 inflammasome and NF‐κB was inhibited by EA, while NLRP3 activation abolished EA’s treatment effects on cognitive function.

Conclusion

EA alleviates POCD‐mediated cognitive dysfunction associated with ameliorated neuroinflammation. Mechanistically, EA’s treatment effects are dependent on NLRP3 inhibition.

Inflammasomes as therapeutic targets in human diseases

Inflammasomes are protein complexes of the innate immune system that initiate inflammation in response to either exogenous pathogens or endogenous danger signals. Inflammasome multiprotein complexes are composed of three parts: a sensor protein, an adaptor, and pro-caspase-1. Activation of the inflammasome leads to the activation of caspase-1, which cleaves pro-inflammatory cytokines such as IL-1β and IL-18, leading to pyroptosis. Effectors of the inflammasome not only provide protection against infectious pathogens, but also mediate control over sterile insults. Aberrant inflammasome signaling has been implicated in the development of cardiovascular and metabolic diseases, cancer, and neurodegenerative disorders. Here, we review the role of the inflammasome as a double-edged sword in various diseases, and the outcomes can be either good or bad depending on the disease, as well as the genetic background. We highlight inflammasome memory and the two-shot activation process. We also propose the M- and N-type inflammation model, and discuss how the inflammasome pathway may be targeted for the development of novel therapy.

Pharmacological Inhibition of the Nod-Like Receptor Family Pyrin Domain Containing 3 Inflammasome with MCC950

Activation of the Nod-like receptor family pyrin domain containing 3 (NLRP3) inflammasome drives release of the proinflammatory cytokines interleukin (IL)-1β and IL-18 and induces pyroptosis (lytic cell death). These events drive chronic inflammation, and as such, NLRP3 has been implicated in a large number of human diseases. These range from autoimmune conditions, the simplest of which is NLRP3 gain-of-function mutations leading to an orphan disease, cryopyrin-associated period syndrome, to large disease burden indications, such as atherosclerosis, heart failure, stroke, neurodegeneration, asthma, ulcerative colitis, and arthritis. The potential clinical utility of NLRP3 inhibitors is substantiated by an expanding list of indications in which NLRP3 activation has been shown to play a detrimental role. Studies of pharmacological inhibition of NLRP3 in nonclinical models of disease using MCC950 in combination with human genetics, epigenetics, and analyses of the efficacy of biologic inhibitors of IL-1β, such as anakinra and canakinumab, can help to prioritize clinical trials of NLRP3-directed therapeutics. Although MCC950 shows excellent (nanomolar) potency and high target selectivity, its pharmacokinetic and toxicokinetic properties limited its therapeutic development in the clinic. Several improved, next-generation inhibitors are now in clinical trials. Hence the body of research in a plethora of conditions reviewed herein may inform analysis of the potential translational value of NLRP3 inhibition in diseases with significant unmet medical need. SIGNIFICANCE STATEMENT: The nod-like receptor family pyrin domain containing 3 (NLRP3) inflammasome is one of the most widely studied and best validated biological targets in innate immunity. Activation of NLRP3 can be inhibited with MCC950, resulting in efficacy in more than 100 nonclinical models of inflammatory diseases. As several next-generation NLRP3 inhibitors are entering proof-of-concept clinical trials in 2020, a review of the pharmacology of MCC950 is timely and significant.

Inflammasome NLRP3 Potentially Links Obesity-Associated Low-Grade Systemic Inflammation and Insulin Resistance with Alzheimer's Disease

Alzheimer’s disease (AD) is the most common form of neurodegenerative dementia. Metabolic disorders including obesity and type 2 diabetes mellitus (T2DM) may stimulate amyloid β (Aβ) aggregate formation. AD, obesity, and T2DM share similar features such as chronic inflammation, increased oxidative stress, insulin resistance, and impaired energy metabolism. Adiposity is associated with the pro-inflammatory phenotype. Adiposity-related inflammatory factors lead to the formation of inflammasome complexes, which are responsible for the activation, maturation, and release of the pro-inflammatory cytokines including interleukin-1β (IL-1β) and interleukin-18 (IL-18). Activation of the inflammasome complex, particularly NLRP3, has a crucial role in obesity-induced inflammation, insulin resistance, and T2DM. The abnormal activation of the NLRP3 signaling pathway influences neuroinflammatory processes. NLRP3/IL-1β signaling could underlie the association between adiposity and cognitive impairment in humans. The review includes a broadened approach to the role of obesity-related diseases (obesity, low-grade chronic inflammation, type 2 diabetes, insulin resistance, and enhanced NLRP3 activity) in AD. Moreover, we also discuss the mechanisms by which the NLRP3 activation potentially links inflammation, peripheral and central insulin resistance, and metabolic changes with AD.

A selective NLRP3 inflammasome inhibitor attenuates behavioral deficits and neuroinflammation in a mouse model of Parkinson's disease

Nod-like receptor pyrin containing (NLRP)3 inflammasome-mediated neuroinflammation is involved in the pathology of Parkinson's disease (PD), but the roles of other inflammasomes in PD remain unclear. The NLRP3 inhibitor MCC950 exerts neuroprotective effects in several neurological diseases. Using a 1-methyl-4-phenyl-1,2,3,6-tetrahydro pyridine (MPTP)-induced mouse model with or without intraperitoneal MCC950 administration, we assessed whether specifically the NLRP3 inflammasome is activated in the nigrostriatal system and whether MCC950 has therapeutic potential in this PD model. Western blots were used to determine the nigrostriatal expression of inflammasome-specific proteins, including NLRP1, NLRP2, NLRP3, nod-like receptor CARD containing 4 (NLRC4), and absent in melanoma 2 (AIM2). The pole, hanging, and swimming tests were used to assess functional deficits, western blots and immunostainings were used to analyze dopaminergic neuronal degeneration, as well as activation of glial cells and the NLRP3 inflammasome. NLRP3 expression in the nigrostriatal system of MPTP-induced mice was significantly increased compared to control, whereas NLRP1, NLRP2, NLRC4, and AIM2 expression in the nigrostriatal system, as well as NLRP3 expression in the cerebral cortex and hippocampus, were similar in the two groups. Furthermore, MPTP-induced mice exhibited behavioral dysfunctions, dopaminergic neuronal degeneration, and activation of glial cells and the NLRP3 inflammasome. MCC950 treatment of MPTP-induced mice improved behavioral dysfunctions, reduced dopaminergic neuronal degeneration, and inhibited the activation of glial cells and the NLRP3 inflammasome. In conclusion, these findings indicated that NLRP3, not NLRP1, NLRP2, NLRC4, and AIM2, may be the key inflammasome that promotes MPTP-induced pathogenesis. MCC950 protects against MPTP-induced nigrostriatal damage and may be a novel promising therapeutic approach in treating MPTP-induced PD.