Inhibiting the NLRP3 Inflammasome with MCC950 Alleviates Neurological Impairment in the Brain of EAE Mice

FUBP3 mediates the amyloid-β-induced neuronal NLRP3 expression

JOURNAL/nrgr/04.03/01300535-202507000-00028/figure1/v/2024-09-09T124005Z/r/image-tiff Alzheimer's disease is characterized by deposition of amyloid-β, which forms extracellular neuritic plaques, and accumulation of hyperphosphorylated tau, which aggregates to form intraneuronal neurofibrillary tangles, in the brain. The NLRP3 inflammasome may play a role in the transition from amyloid-β deposition to tau phosphorylation and aggregation. Because NLRP3 is primarily found in brain microglia, and tau is predominantly located in neurons, it has been suggested that NLRP3 expressed by microglia indirectly triggers tau phosphorylation by upregulating the expression of pro-inflammatory cytokines. Here, we found that neurons also express NLRP3 in vitro and in vivo, and that neuronal NLRP3 regulates tau phosphorylation. Using biochemical methods, we mapped the minimal NLRP3 promoter and identified FUBP3 as a transcription factor regulating NLRP3 expression in neurons. In primary neurons and the neuroblastoma cell line Neuro2A, FUBP3 is required for endogenous NLRP3 expression and tau phosphorylation only when amyloid-β is present. In the brains of aged wild-type mice and a mouse model of Alzheimer's disease, FUBP3 expression was markedly increased in cortical neurons. Transcriptome analysis suggested that FUBP3 plays a role in neuron-mediated immune responses. We also found that FUBP3 trimmed the 5' end of DNA fragments that it bound, implying that FUBP3 functions in stress-induced responses. These findings suggest that neuronal NLRP3 may be more directly involved in the amyloid-β-to-phospho-tau transition than microglial NLRP3, and that amyloid-β fundamentally alters the regulatory mechanism of NLRP3 expression in neurons. Given that FUBP3 was only expressed at low levels in young wild-type mice and was strongly upregulated in the brains of aged mice and Alzheimer's disease mice, FUBP3 could be a safe therapeutic target for preventing Alzheimer's disease progression.

An expanded polyglutamine in ATAXIN1 results in a loss-of-function that exacerbates severity of Multiple Sclerosis in an EAE mouse model

BACKGROUND AND OBJECTIVES

Ataxin-1 (ATXN1) is a protein in which expansion of its polyglutamine tract causes the neurodegenerative disorder spinocerebellar ataxia type 1 (SCA1) via a gain-of-function. Wild type ATXN1 was recently shown to have a protective role in regulating severity of experimental autoimmune encephalomyelitis (EAE), a well-established mouse model for Multiple sclerosis (MS). This study further investigates the role of ATXN1 with an expanded polyglutamine tract in the context of MS using an EAE mouse model.

METHODS

Hemizygous Atxn1 (Atxn12Q/-) mice or f-ATXN1146Q/2Q, heterozygous mice that have one copy of the endogenous mouse gene replaced with a polyQ expanded pathogenic human ATXN1 gene, were injected with myelin oligodendrocytes glycoprotein (MOG35 - 55) peptide to induce EAE. Immunohistochemical and biochemical approaches were used to analyze the degree of demyelination, cell loss, axonal degeneration as well as detecting the activated immune cells and inflammatory cytokines upon EAE induction in Atxn12Q/- and f-ATXN1146Q/2Q mice.

RESULTS

Our findings reveal that a loss-of-function of wild type Atxn1 in Atxn12Q/- and f-ATXN1146Q/2Q mice significantly exacerbates the EAE symptoms, leading to increased demyelination, oligodendrocytes loss, heightened axon degeneration, and greater clinical disability in affected mice. Importantly, the data reveals that neurotoxic astrocytes are activated at acute stage of disease (PID-14) and at the chronic stage of disease (PID-30) neurotoxic astrocytes no longer show signs of activation. The data also demonstrated enhanced infiltration of immune cells into the lesions of mutant mice.

DISCUSSION

These results indicate that ATXN1 plays a protective role in modulating immune responses and maintaining neural integrity during MS. Importantly, expansion of the polyQ tract in ATXN1 results in a loss-of-function in ATXN1's ability to dampen the immune response. Understanding the functional role of ATXN1 in MS pathogenesis may open new avenues for therapeutic strategies aimed at mitigating disease progression.

An expanded polyglutamine in ATAXIN1 results in a loss-of-function that exacerbates severity of Multiple Sclerosis in an EAE mouse model

Background and Objectives

Ataxin-1 (ATXN1) is a protein in which expansion of its polyglutamine tract causes the neurodegenerative disorder spinocerebellar ataxia type 1 (SCA1) via a gain-of-function. Wild type ATXN1 was recently shown to have a protective role in regulating severity of experimental autoimmune encephalomyelitis (EAE), a well-established mouse model for Multiple sclerosis (MS). This study further investigates the role of ATXN1 with an expanded polyglutamine tract in the context of MS using an EAE mouse model.

Methods

Hemizygous Atxn1 (Atxn1 2Q/-) mice or f-ATXN1 146Q/2Q , heterozygous mice that have one copy of the endogenous mouse gene replaced with a polyQ expanded pathogenic human ATXN1 gene, were injected with myelin oligodendrocytes glycoprotein (MOG35 - 55) peptide to induce EAE. Immunohistochemical and biochemical approaches were used to analyze the degree of demyelination, cell loss, axonal degeneration as well as detecting the activated immune cells and inflammatory cytokines upon EAE induction in Atxn1 2Q/- and f-ATXN1 146Q/2Q mice.

Results

Our findings reveal that a loss-of-function of wild type Atxn1 in Atxn1 2Q/- and f-ATXN1 146Q/2Q mice significantly exacerbates the EAE symptoms, leading to increased demyelination, oligodendrocytes loss, heightened axon degeneration, and greater clinical disability in affected mice. Importantly, the data reveals that neurotoxic astrocytes are activated at acute stage of disease (PID-14) and at the chronic stage of disease (PID-30) neurotoxic astrocytes no longer show signs of activation. The data also demonstrated enhanced infiltration of immune cells into the lesions of mutant mice.

Discussion

These results indicate that ATXN1 plays a protective role in modulating immune responses and maintaining neural integrity during MS. Importantly, expansion of the polyQ tract in ATXN1 results in a loss-of-function in ATXN1's ability to dampen the immune response. Understanding the functional role of ATXN1 in MS pathogenesis may open new avenues for therapeutic strategies aimed at mitigating disease progression.

The role of NLRP3 inflammasome in multiple sclerosis: pathogenesis and pharmacological application

Multiple sclerosis (MS) is widely acknowledged as a chronic inflammatory autoimmune disorder characterized by central nervous system (CNS) demyelination and neurodegeneration. The hyperactivation of immune and inflammatory responses is recognized as a pivotal factor contributing to the pathogenesis and progression of MS. Among various immune and inflammatory reactions, researchers have increasingly focused on the inflammasome, a complex of proteins. The initiation and activation of the inflammasome are intricately involved in the onset of MS. Notably, the NLRP3 inflammasome, the most extensively studied member of the inflammasome complex, is closely linked with MS. This review will delve into the roles of the NLRP3 inflammasome in the pathogenesis and progression of MS. Additionally, therapeutic strategies targeting the NLRP3 inflammasome for the treatment of MS, including natural compounds, autophagy regulators, and other small molecular compounds, will be detailed in this review.

Akkermansia muciniphila Modulates Central Nervous System Autoimmune Response and Cognitive Impairment by Inhibiting Hippocampal NLRP3-Mediated Neuroinflammation

BACKGROUND

Numerous studies have demonstrated the significant role of Akkermansia muciniphila (A. muciniphila) in enhancing host immune responses and metabolic functions. However, its increased presence in multiple sclerosis (MS) patients has led to a focus on the relationships between A. muciniphila and diseases, with the underlying mechanisms remaining unknown.

METHOD

Solochrome cyanin, hematoxylin-eosin staining (H&E) and immunofluorescence staining were used to assess demyelination and inflammation. Gut microbiota changes were examined by 16S rRNA sequencing. Intracellular cytokine levels were assessed by flow cytometry. Cognitive impairment was evaluated using four behavioral tests. Intestinal barrier function and pyrin domain-containing protein 3 (NLRP3)-mediated neuroinflammation were evaluated by immunoblotting.

RESULTS

We found that treatment with an appropriate dose of A. muciniphila (5.0 × 107 CFU/mL) reduced neuropathology and disease severity in experimental autoimmune encephalomyelitis (EAE) mice. In addition, A. muciniphila supplementation increased the diversity and abundance of intestinal microbiota while decreasing the Firmicutes/Bacteroidetes ratio. Moreover, it improved intestinal barrier function and attenuated Th17 responses in the gut, central nervous system (CNS), and lymphoid tissues, without affecting Treg response in the lymphoid tissue. Furthermore, A. muciniphila administration partly regulated cognitive impairment and hippocampal NLRP3-mediated neuroinflammation.

CONCLUSION

Our results suggest that A. muciniphila holds promise as a probiotic for treating NLRP3-associated inflammatory disorders and cognitive impairment, including MS.

The NLRP3 inflammasome: A central player in multiple sclerosis

Multiple sclerosis (MS) is a neurological autoimmune condition associated with many symptoms including spasticity, pain, limb numbness and weakness. It is characterised by inflammatory demyelination and axonal degeneration of the brain and spinal cord. A range of disease-modifying therapies (DMTs) are available to suppress inflammatory disease activity in MS, however, there is a pressing need for new therapeutic avenues as DMTs have a limited ability to suppress confirmed disability progression. A body of literature indicates that innate immune inflammation is linked to MS progression. The nucleotide-binding oligomerization domain (NOD)-like receptor pyrin domain containing protein 3 (NLRP3) inflammasome has a well-established function in innate immunity which is closely associated with the pathogenesis of neuroinflammatory conditions. Evidence suggests that the inflammasome may be a therapeutic target in disorders such as MS and at present, inhibitors of the NLRP3 inflammasome are in pre-clinical development. Therefore, this review systematically highlights the pathogenic role of inflammasomes in MS, presenting an overview of research evidence linking inflammasome-related polymorphisms to MS susceptibility, and gathering evidence investigating NLRP3 biomarkers in MS. The role of the NLRP3 inflammasome in murine models of MS is furthermore discussed. Finally, a significant component of this review focuses on evidence that NLRP3 signalling components are novel drug targets in MS. Overall this review defines the role of the inflammasome in MS pathogenesis and identifies inflammasome inhibitor targets that warrant full investigation in MS and related disorders.

NLRP3 inflammasome and gut microbiota-brain axis: a new perspective on white matter injury after intracerebral hemorrhage

ABSTRACT

Intracerebral hemorrhage is the most dangerous subtype of stroke, characterized by high mortality and morbidity rates, and frequently leads to significant secondary white matter injury. In recent decades, studies have revealed that gut microbiota can communicate bidirectionally with the brain through the gut microbiota-brain axis. This axis indicates that gut microbiota is closely related to the development and prognosis of intracerebral hemorrhage and its associated secondary white matter injury. The NACHT, LRR, and pyrin domain-containing protein 3 (NLRP3) inflammasome plays a crucial role in this context. This review summarizes the dysbiosis of gut microbiota following intracerebral hemorrhage and explores the mechanisms by which this imbalance may promote the activation of the NLRP3 inflammasome. These mechanisms include metabolic pathways (involving short-chain fatty acids, lipopolysaccharides, lactic acid, bile acids, trimethylamine-N-oxide, and tryptophan), neural pathways (such as the vagus nerve and sympathetic nerve), and immune pathways (involving microglia and T cells). We then discuss the relationship between the activated NLRP3 inflammasome and secondary white matter injury after intracerebral hemorrhage. The activation of the NLRP3 inflammasome can exacerbate secondary white matter injury by disrupting the blood-brain barrier, inducing neuroinflammation, and interfering with nerve regeneration. Finally, we outline potential treatment strategies for intracerebral hemorrhage and its secondary white matter injury. Our review highlights the critical role of the gut microbiota-brain axis and the NLRP3 inflammasome in white matter injury following intracerebral hemorrhage, paving the way for exploring potential therapeutic approaches.

Co-administration of Naringin and NLRP3 Inhibitor Improves Myelin Repair and Mitigates Oxidative Stress in Cuprizone-Induced Demyelination Model

BACKGROUND

Naringin and MCC950 as an inflammasome inhibitor have exhibited numerous pharmacological activities, including antioxidant and anti-inflammatory effects. The present study has examined the combined impacts of naringin and MCC950 on the levels of oxidative stress, demyelination, and inflammation in the cuprizone (CPZ)-induced demyelination model.

METHODS

In order to induce demyelination, CPZ (0.2% w/w) was added to the normal diet of mice for 42 days. Subsequently, the male C57BL/6 mice received naringin (oral administration), MCC950 (intraperitoneal injection), or their combination for 14 days. Working memory was tested by the Y maze. FluoroMyelin staining, MOG, and GFAP immunostaining assessed the demyelination extent, myelin intensity, and astrocyte activation, respectively. Oxidant/antioxidant biomarkers were measured using colorimetric techniques. The expression levels of MBP, PDGFRα, Olig2, Nrf2, HO-1, NQO-1, GSK3β, IL1α, and IL18 were assessed by reverse transcription-quantitative polymerase chain reaction (RT-qPCR).

RESULTS

Our results indicated that the co-administration of naringin and MCC950 improved working memory and antioxidant capacity. A significant reduction was found in the extent of demyelination and inflammatory mediatorsin naringin and MCC950-treated mice. In addition, co-administration of naringin and MCC950 elevated the expression levels of pro-myelinating and antioxidant markers.

CONCLUSION

These findings indicated improvement of the working memory through co-administration of naringin and MCC950, which might be partly mediated by enhancing antioxidant capacity, promoting remyelination, and mitigating inflammation in the CPZ-induced demyelination model.

PLUNC inhibits invasion and metastasis in nasopharyngeal carcinoma by inhibiting NLRP3 inflammasome activation

Nasopharyngeal carcinoma (NPC) is a malignant tumor that occurs in the nasopharynx. Palate, lung, and nasal epithelium clone (PLUNC) has been identified as an early secreted protein that is specifically expressed in the nasopharynx. The aim of this study was to determine the role and mechanism of PLUNC in NPC. We used mRNA sequencing (seq) combined with ribosome-nascent chain complex (RNC)-seq to determine the biological role of PLUNC. The expression of epithelial-to-mesenchymal transition (EMT)-related molecules was detected by western blotting. Then, cell migration and invasion were detected by wound healing and Transwell chamber assays. NPC cells were injected into the tail vein of nude mice to explore the biological role of PLUNC in vivo. The sequencing results showed that PLUNC inhibited the progression of NPC and its expression was correlated with that of NOD-like receptors. Experiments confirmed that PLUNC inhibited the invasion and metastasis of NPC cells by promoting the ubiquitination degradation of NLRP3. PLUNC overexpression in combination with the treatment by MCC950, an inhibitor of NLRP3 inflammasome activation, was most effective in inhibiting NPC invasion and metastasis. In vivo experiments also confirmed that the combination of PLUNC overexpression and MCC950 treatment effectively inhibited the lung metastasis of NPC cells. In summary, our research suggested that PLUNC inhibited the invasion and metastasis of NPC by inhibiting NLRP3 inflammasome activation, and targeting the PLUNC-NLRP3 inflammasome axis could provide a new strategy for the diagnosis and treatment of NPC patients.

Ion transporter cascade, reactive astrogliosis and cerebrovascular diseases

Cerebrovascular diseases and their sequalae, such as ischemic stroke, chronic cerebral hypoperfusion, and vascular dementia are significant contributors to adult disability and cognitive impairment in the modern world. Astrocytes are an integral part of the neurovascular unit in the CNS and play a pivotal role in CNS homeostasis, including ionic and pH balance, neurotransmission, cerebral blood flow, and metabolism. Astrocytes respond to cerebral insults, inflammation, and diseases through unique molecular, morphological, and functional changes, collectively known as reactive astrogliosis. The function of reactive astrocytes has been a subject of debate. Initially, astrocytes were thought to primarily play a supportive role in maintaining the structure and function of the nervous system. However, recent studies suggest that reactive astrocytes may have both beneficial and detrimental effects. For example, in chronic cerebral hypoperfusion, reactive astrocytes can cause oligodendrocyte death and demyelination. In this review, we will summarize the (1) roles of ion transporter cascade in reactive astrogliosis, (2) role of reactive astrocytes in vascular dementia and related dementias, and (3) potential therapeutic approaches for dementing disorders targeting reactive astrocytes. Understanding the relationship between ion transporter cascade, reactive astrogliosis, and cerebrovascular diseases may reveal mechanisms and targets for the development of therapies for brain diseases associated with reactive astrogliosis.

Role of NLRP3 Inflammasomes in Neurodegenerative Diseases

Large-scale neuronal degeneration in the human brain is a hallmark of neurodegenerative diseases. These diseases range in location and cause, but they all have neurodegenerative characteristics in common. Neurodegenerative diseases, which have almost no efective treatment options, tend to progress irreversibly and cause large socioeconomic and healthcare costs. In recent years, due to the increase in the elderly population, neurodegenerative diseases that have a risk factor with aging are becoming increasingly common. Evidence that neurodegenerative diseases, which have an important place in public health, may be caused by neuroinflammation, has led to comprehensive investigation of neurodegenerative diseases in this regard. Inflammasomes are innate immune system-associated multiproteins that regulate caspase-1 activation and induce inflammation. The NLRP3 inflammasome is the most researched inflammasome and also located in microglia, its activation mediates the maturation and secretion of the inflammatory cytokines interleukin1beta (IL-1β) and IL-18, thus exerting its efects in the central nervous system. Within the scope of this review, experimental and human studies evaluating the role of NLRP3 inflammasome activation and the efects of its inhibition in neurodegenerative diseases frequently encountered in society have been compiled with studies from past to present.