The involvement of NLRP3 inflammasome in CUMS-induced AD-like pathological changes and related cognitive decline in mice

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.

TXNIP Regulates NLRP3 Inflammasome-Induced Pyroptosis Related to Aging via cAMP/PKA and PI3K/Akt Signaling Pathways

Aging is an inevitable natural process with time-dependent dysfunction and the occurrence of various diseases, which impose heavy burdens on individuals, families, and society. It has been reported that NLRP3 inflammasome-induced pyroptosis contributes significantly to age-related diseases and aging, while TXNIP is suggested to be involved in regulating pyroptosis mediated by NLRP3. However, the mechanism between TXNIP and NLRP3 inflammasome is still unclear. In this study, we used HT-22 cells to explore the effect of TXNIP on pyroptosis and its potential association with the aging. Also, we delved into the underlying mechanisms. Our findings revealed that TXNIP significantly augmented pyroptosis in HT-22 cells, primarily by enhancing the activation of the NLRP3 inflammasome and promoting the release of proinflammatory cytokines. Remarkably, as TXNIP levels increased, we observed a corresponding rise in the number of p16-positive cells, which is indicative of aging. Furthermore, we conducted experiments to modulate the improvement of TXNIP on NLRP3 inflammasome-induced pyroptosis, that is, the PI3K activator 740 Y-P and the PKA activator DC2797 inhibited the effect, while the PI3K inhibitor LY294002 and the PKA inhibitor H89 enhanced the effect. In conclusion, our study demonstrated that TXNIP regulates NLRP3 inflammasome-induced pyroptosis in HT-22 cells related to aging via the PI3K/Akt and cAMP/PKA pathways.

VGLUT2 may improve cognitive function in depressed rats by protecting prefrontal cortex neurons

Objective

Depression may be accompanied by cognitive impairment, but its pathogenesis remains unclear. This study aims to investigate the protective effects of fluoxetine on behavioral performance and prefrontal cortex neuronal damage in rats with depression-associated cognitive impairment, based on the observation of VGLUT2 protein expression.

Methods

Forty-five SPF-grade male SD rats were randomly divided into three groups (n = 15): normal control group (CON), depression group (DD), and fluoxetine group (DD + F). The CON group was reared normally, while the DD and DD + F groups underwent chronic unpredictable mild stress (CUMS) combined with social isolation to induce a depression-related cognitive dysfunction model. After modeling, the DD + F group was treated with fluoxetine (10 mg/kg, ig) for 14 days. Behavioral tests were performed to assess changes in mood, cognition, learning, and social abilities. Histopathological observations were made to examine pathological changes, neuronal apoptosis, ultrastructure, and dendritic spine density in the prefrontal cortex. The concentration, relative expression level, and mRNA expression of VGLUT2 protein were also measured. Finally, a correlation analysis was performed between the relative expression level and mRNA expression of VGLUT2 protein and the pathological changes in neurons.

Results

Compared to the CON group, the DD group exhibited decreased body weight, anhedonia, increased behavioral despair, reduced locomotor activity and spontaneous exploratory behavior, impaired spatial learning and memory, and decreased social interaction and social cognitive ability. Pathological damage was observed in the prefrontal cortex, with neuronal apoptosis, ultrastructural damage, and reduced neuroplasticity. The concentration, relative expression, and mRNA expression levels of VGLUT2 protein were decreased. Following fluoxetine intervention, the above behavioral phenotypes improved; pathological damage showed varying degrees of recovery; and the concentration, relative expression, and mRNA expression levels of VGLUT2 protein increased. Finally, there was a significant correlation between VGLUT2 protein expression and pathological changes in the prefrontal cortex.

Conclusion

After 28 days of CUMS combined with isolation rearing, rats exhibited impairments in mood, cognition, learning, and social abilities, with neuronal damage and decreased VGLUT2 protein levels in the prefrontal cortex. Following fluoxetine intervention, VGLUT2 protein expression increased, neuronal repair in the prefrontal cortex occurred, depressive-like behavior improved, and cognitive learning and social abilities were restored.

MCC950 as a promising candidate for blocking NLRP3 inflammasome activation: A review of preclinical research and future directions

The NOD-like receptor thermal protein domain associated protein 3 (NLRP3) inflammasome is a key component of the innate immune system that triggers inflammation and pyroptosis and contributes to the development of several diseases. Therefore, blocking the activation of the NLRP3 inflammasome has therapeutic potential for the treatment of these diseases. MCC950, a selective small molecule inhibitor, has emerged as a promising candidate for blocking NLRP3 inflammasome activation. Ongoing research is focused on elucidating the specific targets of MCC950 as well as assessfing its metabolism and safety profile. This review discusses the diseases that have been studied in relation to MCC950, with a focus on stroke, Alzheimer's disease, liver injury, atherosclerosis, diabetes mellitus, and sepsis, using bibliometric analysis. It then summarizes the potential pharmacological targets of MCC950 and discusses its toxicity. Furthermore, it traces the progression from preclinical to clinical research for the treatment of these diseases. Overall, this review provides a solid foundation for the clinical therapeutic potential of MCC950 and offers insights for future research and therapeutic approaches.

Du-moxibustion ameliorates depression-like behavior and neuroinflammation in chronic unpredictable mild stress-induced mice

BACKGROUND

Neuroinflammation is involved in the advancement of depression. Du-moxibustion can treat depression. Here, we explored whether Du-moxibustion could alleviate neuroglia-associated neuro-inflammatory process in chronic unpredictable mild stress (CUMS) mice.

METHODS

C57BL/6J mice were distributed into five groups. Except for the CON group, other four groups underwent CUMS for four consecutive weeks, and Du-moxibustion was given simultaneously after modeling. Behavioral tests were then carried out. Additionally, Western blot was conducted to measure the relative expression levels of high-mobility group box 1 (HMGB1), toll-like receptor 4 (TLR4), myeloid differentiation factor 88 (MyD88), and nuclear factor-kappa B (NF-κB). Immunofluorescence was employed to evaluate the positive cells of ionized calcium binding adapter molecule 1 (Iba-1) and glial fibrillary acidic protein (GFAP). Furthermore, interleukin-1 beta (IL-1β) and tumor necrosis factor-alpha (TNF-α) were analyzed using an ELISA assay.

RESULTS

We found that CUMS induced depression-like behaviors, such as reduced sucrose preference ratio, decreased locomotor and exploratory activity, decreased the time in open arms and prolonged immobility. Furthermore, versus the CON group, the expression of HMGB1, TLR4, MyD88, NF-κB, positive cells of Iba-1, IL-1β and TNF-α were increased but positive cells of GFAP were decreased in CUMS group. However, the detrimental effects were ameliorated by treatment with CUMS+FLU and CUMS+DM.

LIMITATIONS

A shortage of this study is that only CUMS model of depression were used, while other depression model were not included.

CONCLUSIONS

Du-moxibustion alleviates depression-like behaviors in CUMS mice mainly by reducing neuroinflammation, which offers novel insights into the potential treatment of depression.

Chronic kidney disease leads to microglial potassium efflux and inflammasome activation in the brain

Cognitive impairment is common in extracerebral diseases such as chronic kidney disease (CKD). Kidney transplantation reverses cognitive impairment, indicating that cognitive impairment driven by CKD is therapeutically amendable. However, we lack mechanistic insights allowing development of targeted therapies. Using a combination of mouse models (including mice with neuron-specific IL-1R1 deficiency), single cell analyses (single-nuclei RNA-sequencing and single-cell thallium autometallography), human samples and in vitro experiments we demonstrate that microglia activation impairs neuronal potassium homeostasis and cognition in CKD. CKD disrupts the barrier of brain endothelial cells in vitro and the blood-brain barrier in vivo, establishing that the uremic state modifies vascular permeability in the brain. Exposure to uremic conditions impairs calcium homeostasis in microglia, enhances microglial potassium efflux via the calcium-dependent channel KCa3.1, and induces p38-MAPK associated IL-1β maturation in microglia. Restoring potassium homeostasis in microglia using a KCa3.1-specific inhibitor (TRAM34) improves CKD-triggered cognitive impairment. Likewise, inhibition of the IL-1β receptor 1 (IL-1R1) using anakinra or genetically abolishing neuronal IL-1R1 expression in neurons prevent CKD-mediated reduced neuronal potassium turnover and CKD-induced impaired cognition. Accordingly, in CKD mice, impaired cognition can be ameliorated by either preventing microglia activation or inhibiting IL-1R-signaling in neurons. Thus, our data suggest that potassium efflux from microglia triggers their activation, which promotes microglia IL-1β release and IL-1R1-mediated neuronal dysfunction in CKD. Hence, our study provides new mechanistic insight into cognitive impairment in association with CKD and identifies possible new therapeutic approaches.

The multifaceted effects of fluoxetine treatment on cognitive functions

Fluoxetine, the prototypical selective serotonin reuptake inhibitor (SSRI), is widely used to treat major depressive disorder (MDD) and a variety of other central nervous system conditions, primarily due to its established clinical safety profile. Although its efficacy in treating depression is well-recognized, the impact of fluoxetine on cognitive functions remains inconsistent and elusive. In this review, we first examine the well-substantiated biological mechanisms underlying fluoxetine's antidepressant effects, which include serotonin reuptake inhibition and activation of TrkB receptors-key to brain-derived neurotrophic factor (BDNF) signaling. Subsequently, we delve into the cognitive side effects observed in both preclinical and clinical studies, affecting domains such as memory, attention, and executive functions. While certain studies indicate cognitive improvements in patients with underlying disorders, there is also evidence of negative effects, influenced by variables like gender, duration of treatment, age, disease pathology, and the specifics of cognitive testing. Significantly, the negative cognitive outcomes reported in preclinical research often involve healthy, non-diseased animals. This review underscores the necessity for heightened caution in fluoxetine prescription and further investigation into its potentially detrimental cognitive effects, even when used prophylactically.

Role of NLRP3 inflammasome in central nervous system diseases

The central nervous system (CNS) is the most delicate system in human body, with the most complex structure and function. It is vulnerable to trauma, infection, neurodegeneration and autoimmune diseases, and activates the immune system. An appropriate inflammatory response contributes to defence against invading microbes, whereas an excessive inflammatory response can aggravate tissue damage. The NLRP3 inflammasome was the first one studied in the brain. Once primed and activated, it completes the assembly of inflammasome (sensor NLRP3, adaptor ASC, and effector caspase-1), leading to caspase-1 activation and increased release of downstream inflammatory cytokines, as well as to pyroptosis. Cumulative studies have confirmed that NLRP3 plays an important role in regulating innate immunity and autoimmune diseases, and its inhibitors have shown good efficacy in animal models of various inflammatory diseases. In this review, we will briefly discuss the biological characteristics of NLRP3 inflammasome, summarize the recent advances and clinical impact of the NLRP3 inflammasome in infectious, inflammatory, immune, degenerative, genetic, and vascular diseases of CNS, and discuss the potential and challenges of NLRP3 as a therapeutic target for CNS diseases.

Transcutaneous vagus nerve stimulation modulates depression-like phenotype induced by high-fat diet via P2X7R/NLRP3/IL-1β in the prefrontal cortex

BACKGROUND

Depression is a common psychiatric disorder in diabetic patients. Depressive mood associated with obesity/metabolic disorders is related to the inflammatory response caused by long-term consumption of high-fat diets, but its molecular mechanism is unclear. In this study, we investigated whether the antidepressant effect of transcutaneous auricular vagus nerve stimulation (taVNS) in high-fat diet rats works through the P2X7R/NLRP3/IL-1β pathway.

METHODS

We first used 16S rRNA gene sequencing analysis and LC-MS metabolomics assays in Zucker diabetic fatty (ZDF) rats with long-term high-fat diet (Purina #5008) induced significant depression-like behaviors. Next, the forced swimming test (FST) and open field test (OFT) were measured to evaluate the antidepressive effect of taVNS. Immunofluorescence and western blotting (WB) were used to measure the microglia state and the expression of P2X7R, NLRP3, and IL-1β in PFC.

RESULTS

Purina#5008 diet induced significant depression-like behaviors in ZDF rats and was closely related to purine and inflammatory metabolites. Consecutive taVNS increased plasma insulin concentration, reduced glycated hemoglobin and glucagon content in ZDF rats, significantly improved the depressive-like phenotype in ZDF rats through reducing the microglia activity, and increased the expression of P2X7R, NLRP3, and IL-1β in the prefrontal cortex (PFC).

CONCLUSION

The P2X7R/NLRP3/IL-1β signaling pathway may play an important role in the antidepressant-like behavior of taVNS, which provides a promising mechanism for taVNS clinical treatment of diabetes combined with depression.

New Insights on NLRP3 Inflammasome: Mechanisms of Activation, Inhibition, and Epigenetic Regulation

Inflammasomes are important modulators of inflammation. Dysregulation of inflammasomes can enhance vulnerability to conditions such as neurodegenerative diseases, autoinflammatory diseases, and metabolic disorders. Among various inflammasomes, Nucleotide-binding oligomerization domain leucine-rich repeat and pyrin domain-containing protein 3 (NLRP3) is the best-characterized inflammasome related to inflammatory and neurodegenerative diseases. NLRP3 is an intracellular sensor that recognizes pathogen-associated molecular patterns and damage-associated patterns resulting in the assembly and activation of NLRP3 inflammasome. The NLRP3 inflammasome includes sensor NLRP3, adaptor apoptosis-associated speck-like protein (ASC), and effector cysteine protease procaspase-1 that plays an imperative role in caspase-1 stimulation which further initiates a secondary inflammatory response. Regulation of NLRP3 inflammasome ameliorates NLRP3-mediated diseases. Much effort has been invested in studying the activation, and exploration of specific inhibitors and epigenetic mechanisms controlling NLRP3 inflammasome. This review gives an overview of the established NLRP3 inflammasome assembly, its brief molecular mechanistic activations as well as a current update on specific and non-specific NLRP3 inhibitors that could be used in NLRP3-mediated diseases. We also focused on the recently discovered epigenetic mechanisms mediated by DNA methylation, histone alterations, and microRNAs in regulating the activation and expression of NLRP3 inflammasome, which has resulted in a novel method of gaining insight into the mechanisms that modulate NLRP3 inflammasome activity and introducing potential therapeutic strategies for CNS disorders.

Bioinformatic identification and experiment validation reveal 6 hub genes, promising diagnostic and therapeutic targets for Alzheimer's disease

BACKGROUND

Alzheimer's disease (AD) is a progressive neurodegenerative disease that can cause dementia. We aim to screen out the hub genes involved in AD based on microarray datasets.

METHODS

Gene expression profiles GSE5281 and GSE28146 were retrieved from Gene Expression Omnibus database to acquire differentially expressed genes (DEGs). Gene Ontology and pathway enrichment were conducted using DAVID online tool. The STRING database and Cytoscape tools were employed to analyze protein-protein interactions and identify hub genes. The predictive value of hub genes was assessed by principal component analysis and receiver operating characteristic curves. AD mice model was constructed, and histology was then observed by hematoxylin-eosin staining. Gene expression levels were finally determined by real-time quantitative PCR.

RESULTS

We obtained 197 overlapping DEGs from GSE5281 and GSE28146 datasets. After constructing protein-protein interaction network, three highly interconnected clusters were identified and 6 hub genes (RBL1, BUB1, HDAC7, KAT5, SIRT2, and ITGB1) were selected. The hub genes could be used as basis to predict AD. Histological abnormalities of brain were observed, suggesting successful AD model was constructed. Compared with the control group, the mRNA expression levels of RBL1, BUB1, HDAC7, KAT5 and SIRT2 were significantly increased, while the mRNA expression level of ITGB1 was significantly decreased in AD groups.

CONCLUSION

RBL1, BUB1, HDAC7, KAT5, SIRT2 and ITGB1 are promising gene signatures for diagnosis and therapy of AD.

Elevated serum levels of the NLRP3 inflammasome are associated with the severity of anti-NMDAR encephalitis in children

BACKGROUND

Anti-N-methyl-D-aspartate receptor (NMDAR) encephalitis is the most common autoimmune encephalitis, mainly impacting young females and children. The involvement of the Nod-like receptor family pyrin domain-containing 3 (NLRP3) inflammasome and related cytokines in pediatric individuals with this condition remains unclear.

METHODS

We collected information from 27 children who had anti-NMDAR encephalitis and 12 individuals with non-inflammatory neurological disorders as controls. We used an enzyme-linked immunosorbent assay (ELISA) to identify NLRP3 inflammasome, interleukin (IL)-1β, and IL-18 expression in cerebrospinal fluid (CSF) and matching serum samples. The modified Rankin Scale (mRS) score was performed throughout the acute phase and at the 6-month follow-up to determine the severity of the disease. The area under the curve (AUC) of the receiver operating characteristic curve was utilized to calculate the prediction efficacy.

RESULTS

When compared to controls, individuals with anti-NMDAR encephalitis had significantly increased serum expression of the NLRP3 inflammasome (p < 0.001), IL-1β (p < 0.05), and IL-18 (p < 0.01). In the acute phase, mRS scores were correlated positively with serum levels of NLRP3 inflammasome (p = 0.008), IL-1β (p = 0.023), and IL-18 (p < 0.001). A positive connection was also found between serum levels of NLRP3 inflammasome and IL-1β (p = 0.005). Furthermore, the expression of IL-1β and IL-18 in serum correlated with the 6-month follow-up outcome. The AUC for NLRP3 inflammasome in distinguishing patients with severe neurologic impairments from those with moderate impairments was 0.808 (95 % CI: 0.645-0.972).

CONCLUSION

In our investigation, children with anti-NMDAR encephalitis have more severe first clinical presentations when their serum concentrations of the NLRP3 inflammasome and related cytokines were higher. These findings provide a potential role for the NLRP3 inflammasome pathway in the pathogenesis of NMDAR encephalitis and provide a basis for targeted therapeutic interventions.

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.