NLRP3 Knockout Cell Line (BV2)

Heart failure (HF) affects over 64 million individuals worldwide and is strongly associated with cognitive impairment (CI), yet the underlying mechanisms remain poorly understood. Here, we identify solute carrier family 22 member 3 (SLC22A3) might be a candidate gene for HF-induced CI through Mendelian randomization and bioinformatics analysis. To investigate its functional role in vivo, we established a mouse model of HF after myocardial infarction (MI). Cognitive performance was evaluated using the Morris water maze. Expression of SLC22A3, blood-brain barrier (BBB) integrity, and neuroinflammatory signalling were examined via immunofluorescence and Western blotting. The involvement of the HA/H1R/NLRP3 signalling pathway was further evaluated using cardiac-specific SLC22A3 overexpression mice, hippocampal-specific H1R knockdown mice, NLRP3 knockout mice, and BV2 cell assays. Consistent with the findings in HF patients, cardiac SLC22A3 expression was dramatically downregulated in HF mice, accompanied by an increase in peripheral histamine (HA) levels, while HA levels in the mouse brain were also significantly raised. Using cardiac-specific SLC22A3 overexpression in HF mice, we demonstrated that restoring SLC22A3 reduced HA accumulation and improved cognitive performance. Mechanistically, HA breached the compromised BBB in HF mice, activating hippocampal microglia H1 receptor (H1R) and the NLRP3 inflammasome. In BV2 cells, HA stimulation elevated NLRP3 expression in a dose-dependent manner, an effect blocked by H1R antagonist. Knockdown of H1R or NLRP3 in the hippocampus attenuated neuroinflammation and rescued HF-induced CI. Our findings unveil a novel cardio-neuroinflammatory axis driven by SLC22A3 deficiency, highlighting HA/H1R/NLRP3 pathway as a therapeutic target for HF-induced CI.

BACKGROUND:Parkinson's disease (PD) is characterized by dopaminergic neuron loss, neuroinflammation, and motor dysfunction. PD is a multifactorial disease, with neuroinflammation driven by NLRP3 inflammasome activation representing an important component of its pathological progression. Therefore, we aimed to evaluate the therapeutic potential of rebamipide (Mucosta®), a clinically approved anti-inflammatory agent, in PD by targeting the NLRP3 inflammasome. Specifically, we examined the effects of rebamipide on neuroinflammation, dopaminergic neuron preservation, and motor deficits using BV2 microglia cells and a 1-methyl-4-phenyl-1, 2, 3, 6-tetrahydropyridine (MPTP)-induced mouse model. MAIN BODY:Rebamipide alleviated microglial activation and downstream neuroinflammation by suppressing the NLRP3-NEK7 interaction, resulting in dopaminergic neuron protection in the MPTP-induced PD model. Rebamipide downregulated IL-1β levels in BV2 microglia cells treated with α-synuclein and MPP. Molecular docking analysis revealed a high binding affinity between rebamipide and the NLRP3-NEK7 interaction interface. Surface plasmon resonance analysis confirmed the direct binding of rebamipide to NLRP3, with notable kinetic affinity, supporting its role as a novel NLRP3 inflammasome inhibitor. Rebamipide significantly downregulated IL-1β levels, microglial activation, and dopaminergic neuron loss in the MPTP mouse model by disrupting inflammasome activation. Rebamipide preserved dopamine levels in the striatum and improved motor deficits, including bradykinesia and motor coordination. The neuroprotective effects of rebamipide were neutralized in NLRP3 knockout mice, confirming the dependency of its action on NLRP3. CONCLUSION:Considering its established clinical use, this study supports repurposing rebamipide for treating PD and other NLRP3 inflammasome-driven neuroinflammatory diseases.

BACKGROUND:Neuroinflammation induced by lead exposure (Pb) is a major cause of neurotoxicity of Pb in the central nervous system (CNS). The NLR family, domain of pyrin containing 3 (NLRP3) involves in various neurological diseases, while the question of whether NLRP3 plays a role in lead-induced neuroinflammation has not yet been reported. METHODS:Developmental and knockout (KO) NLRP3 mice were used to establish two in vivo models, and BV2 cells were used to establish an in vitro model. Behavioral and electrophysiologic tests were used to assess the neurotoxicity of Pb, and immunofluorescence staining was used to assess neuroinflammation. Real-time PCR and western blot were performed to examine the mRNA and protein levels of inflammatory cytokines and NLRP3 inflammasomes. siRNA technology was used to block NLRP3 expression. RESULTS:Pb exposure led to neural injure and microglial activation in the hippocampus region, while minocycline intervention attenuated Pb-induced neurotoxicity by inhibiting neuroinflammation. Pb increased the expression of NLRP3 and promoted cleavage of caspase-1 in mRNA and protein levels, and minocycline partially reversed the effects of Pb on NLRP3 inflammasomes. Blocking of NLRP3 by KO mice or siRNA attenuated neural alterations induced by Pb, weakened microglial activation in vivo and in vitro as well, without affecting the accumulation of Pb. Pb increased autophagic protein levels and phosphorylation of NF-κB, while suppressing autophagy or NF-κB inhibited Pb's effects on NLRP3. CONCLUSIONS:NLRP3 is involved in the regulation of Pb-induced neurotoxicity. These findings expand mechanism research of Pb neurotoxicity and may help establish new prevention strategies for Pb neurotoxicity.

Microglial hyperactivation of the NOD-, LRR-, and pyrin domain-containing 3 (NLRP3) inflammasome contributes to the pathogenesis of Parkinson's disease (PD). Recently, neuronally expressed NLRP3 was demonstrated to be a Parkin polyubiquitination substrate and a driver of neurodegeneration in PD. However, the role of Parkin in NLRP3 inflammasome activation in microglia remains unclear. Thus, we aimed to investigate whether Parkin regulates NLRP3 in microglia. We investigated the role of Parkin in NLRP3 inflammasome activation through the overexpression of Parkin in BV2 microglial cells and knockout of Parkin in primary microglia after lipopolysaccharide (LPS) treatment. Immunoprecipitation experiments were conducted to quantify the ubiquitination levels of NLRP3 under various conditions and to assess the interaction between Parkin and NLRP3. In vivo experiments were conducted by administering intraperitoneal injections of LPS in wild-type and Parkin knockout mice. The Rotarod test, pole test, and open field test were performed to evaluate motor functions. Immunofluorescence was performed for pathological detection of key proteins. Overexpression of Parkin mediated NLRP3 degradation via K48-linked polyubiquitination in microglia. The loss of Parkin activity in LPS-induced mice resulted in excessive microglial NLRP3 inflammasome assembly, facilitating motor impairment, and dopaminergic neuron loss in the substantia nigra. Accelerating Parkin-induced NLRP3 degradation by administration of a heat shock protein (HSP90) inhibitor reduced the inflammatory response. Parkin regulates microglial NLRP3 inflammasome activation through polyubiquitination and alleviates neurodegeneration in PD. These results suggest that targeting Parkin-mediated microglial NLRP3 inflammasome activity could be a potential therapeutic strategy for PD.

Obstructive sleep apnea (OSA) associated neurocognitive impairment is mainly caused by chronic intermittent hypoxia (CIH)-triggered neuroinflammation and oxidative stress. Previous study has demonstrated that mitochondrial reactive oxygen species (mtROS) was pivotal for hypoxia-related tissue injury. As a cytosolic multiprotein complex that participates in various inflammatory and neurodegenerative diseases, NLRP3 inflammasome could be activated by mtROS and thereby affected by the mitochondria-selective autophagy. However, the role of NLRP3 and possible mitophagy mechanism in CIH-elicited neuroinflammation remain to be elucidated. Compared with wild-type mice, NLRP3 deficiency protected them from CIH-induced neuronal damage, as indicated by the restoration of fear-conditioning test results and amelioration of neuron apoptosis. In addition, NLRP3 knockout mice displayed the mitigated microglia activation that elicited by CIH, concomitantly with elimination of damaged mitochondria and reduction of oxidative stress levels (malondialdehyde and superoxide dismutase). Elevated LC3 and beclin1 expressions were remarkably observed in CIH group. experiments, intermittent hypoxia (IH) significantly facilitated mitophagy induction and NLRP3 inflammasome activation in microglial (BV2) cells. Moreover, IH enhanced the accumulation of damaged mitochondria, increased mitochondrial depolarization and augmented mtROS release. Consistently, NLRP3 deletion elicited a protective phenotype against IH through enhancement of Parkin-mediated mitophagy. Furthermore, Parkin deletion or pretreated with 3MA (autophagy inhibitor) exacerbated these detrimental actions of IH, which was accompanied with NLRP3 inflammasome activation. These results revealed NLRP3 deficiency acted as a protective promotor through enhancing Parkin-depended mitophagy in CIH-induced neuroinflammation. Thus, NLRP3 gene knockout or pharmacological blockage could be as a potential therapeutic strategy for OSA-associated neurocognitive impairment.

BACKGROUND:Ischaemia-evoked neuroinflammation is a critical pathogenic event following ischaemic stroke. Gasdermin D (GSDMD)-associated pyroptosis represents a type of inflammation-associated programmed cell death, which can exacerbate neuroinflammatory responses and brain damage. Stimulator of interferon genes (STING) was recently described as a vital innate immune adaptor protein associated with neuroinflammation. Nevertheless, the regulatory effects of STING on microglial pyroptosis post-stroke have not been well elaborated. METHODS:STING-knockout and wild-type (WT) mice were subjected to middle cerebral artery occlusion (MCAO). STING small interfering RNA (siRNA) was transfected into BV2 cells before oxygen-glucose deprivation/reoxygenation (OGD/R). STING-overexpressing adeno-associated virus (AAV) and NOD-like receptor family pyrin domain containing 3 (NLRP3) siRNA were administered by stereotaxic injection. 2,3,5-Triphenyl tetrazolium chloride (TTC) staining, TdT-mediated dUTP nick end labeling (TUNEL) staining, Fluoro-Jade C (FJC) staining, neurobehavioural tests, immunohistochemistry, cytokine antibody array assay, transmission electron microscopy, immunoblot, Enzyme-linked immunosorbent assay (ELISA) and quantitative real-time polymerase chain reaction (qRT-PCR) were carried out. Co-immunoprecipitation assays were used to investigate the interplay between STING and NLRP3. RESULTS:STING expression was increased after MCAO and mainly detected on microglia. STING deletion alleviated brain infarction, neuronal damage and neurobehavioural impairment in mice subjected to MCAO. STING knockout suppressed microglial activation and the secretion of inflammatory chemokines, accompanied by mitigation of microglial pyroptosis. Specific upregulation of microglial STING by AAV-F4/80-STING aggravated brain injury and microglial pyroptosis. Mechanistically, co-immunoprecipitation showed that STING bound to NLRP3 in microglia. Supplementation of NLRP3 siRNA reversed AAV-F4/80-STING-induced deterioration of microglial pyroptosis. CONCLUSIONS:The current findings indicate that STING modulates NLRP3-mediated microglial pyroptosis following MCAO. STING may serve as a therapeutic target in neuroinflammation induced by cerebral ischaemic/reperfusion (I/R) injury.

Cognitive impairment is often found at the acute stages and sequelae of coronavirus disease 2019 (COVID-19), and the underlying mechanisms remain unclear. The S1 protein from severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) might be a cause of cognitive impairment associated with COVID-19. The nucleotide-binding domain, leucine-rich-containing family, pyrin domain-containing-3 (NLRP3) inflammasome and neuroinflammation play important roles in Alzheimer's disease (AD) with cognitive impairment. However, their roles remain unknown in COVID-19 with cognitive impairment. We stimulated BV2 cells with S1 protein in vitro and injected the hippocampi of wild-type (WT) mice, NLRP3 knockout (KO), and microglia NLRP3 KO mice in vivo with S1 protein to induce cognitive impairment. We assessed exploratory behavior as associative memory using novel object recognition and Morris water maze tests. Neuroinflammation was analyzed using immunofluorescence and western blotting to detect inflammatory markers. Co-localized NLRP3 and S1 proteins were investigated using confocal microscopy. We found that S1 protein injection led to cognitive impairment, neuronal loss, and neuroinflammation by activating NLRP3 inflammation, and this was reduced by global NLRP3 KO and microglia NLRP3 KO. Furthermore, TAK 242, a specific inhibitor of Toll-like receptor-4, resulted in a significant reduction in NLRP3 and pro-IL-1β in BV2 cells with S1 protein stimulation. These results reveal a distinct mechanism through which the SARS-CoV-2 spike S1 protein promotes NLRP3 inflammasome activation and induces excessive inflammatory responses.

Golgi stress has been observed in various neurodegenerative diseases, such as Alzheimer's disease and Parkinson's disease. Whether Golgi stress participates in hyperglycemia-induced neuroinflammation, and how it is regulated remain unclear. First, we found that high glucose (HG) could induce dispersed Golgi apparatus (GA) in BV2 cells, which can be reversed by knockout of NLRP3. Next, we discovered that HG could promote the interaction of NLRP3 and VPS35 and then enhances the interaction of VPS35 and Golph3; knockout of NLRP3 suppressed the expression of VPS35 and Golph3; knockout of VPS35 reduced the expression of Golph3 but not NLRP3, indicating that HG induced the activation of NLRP3/VPS35/Golph3 pathway in BV2 cells. Further, we elucidated the signaling pathway that Golph3 mediated GA stress in HG condition. We used GST-pulldown and Co-IP experiments methods to show that HG promoted the interaction of Golph3 and Vimentin, knockout of Golph3 alleviated the expression of Vimentin. Knockout out of Golph3 and Vimentin both ameliorated HG induced dispersed Golgi apparatus. Collectively, our study demonstrated that HG regulates GA stress through NLRP3/VPS35/Golph3/Vimentin pathway. At last, we found that a combination of small molecular inhibitors targeting NLRP3 and Golph3 selected by molecular docking could alleviate HG-induced neuroinflammation and Therefore, the molecular inhibitors targeting NLRP3 and Golph3 have great potential for use in the development of anti-diabetes neuroinflammatory therapies.

BACKGROUND:The role of ferroptosis in ischemic stroke has been hotly debated recently, but the mechanism is not clearly clarified. It has been reported that the NLRP3 inflammasome is essential for the progression of ischemic stroke. Whether the ferroptosis after ischemic stroke mediated by the activation of NLRP3 inflammasome is still not reported. In this study, we investigated the effect of NLRP3 deficiency on ferroptosis following cerebral ischemia-reperfusion injury (CIRI) in vivo and in vitro. MATERIALS:In vivo, we used C57BL/6J mice and NLRP3 mice to establish a model of middle cerebral artery occlusion (MCAO). After 3 days of reperfusion, we assessed neurological function and then performed TTC staining to measure the infarct volume. Besides, we measured the expression of NLRP3 inflammasome-related proteins and the ferroptosis-inhibiting protein glutathione peroxidase 4 (GPX4) by western blotting (WB) and immunofluorescence (IF). Moreover, we evaluated the levels of ferroptosis-related factors (Fe, MDA and GSH) in the infarct area by using appropriate kits. Furthermore, we used WB to measure the expression of Kelch-like epichlorohydrin-associated protein 1 (Keap1) and nuclear factor erythroid 2-related factor 2 (Nrf2), which participate in the progression of ischemic stroke. In vitro, we knocked down NLRP3 with small interfering RNAs (siRNAs) and established an oxygen glucose deprivation/Reperfusion (OGD/R) model in BV2 cells to simulate ischemic conditions. Next, we assessed the viability of BV2 cells by the Cell Counting Kit (CCK)-8 cytotoxicity assay. Moreover, we used WB to measure the expression of NLRP3, IL-1β, GPX4, Keap1 and Nrf2 proteins which are involved in CIRI. RESULTS:Three days after MCAO, the NLRP3 mice exhibited smaller cerebral infarct volumes and lower neurological deficit scores. The expression of NLRP3 inflammasome-associated proteins (IL-18 and IL-1β) and Keap1/Nrf2 signaling pathway moleculars (Keap1 and Nrf2) in mice brain tissue and BV2 cells were inhibited by NLRP3 knockout/knockdown, while the expression of GPX4, one of the ferroptosis-related factors was increased. Furthermore, the contents of Fe and MDA in the brain tissues of NLRP3 mice were decreased, while the content of GSH were increased significantly. CONCLUSION:Inhibition of the NLRP3 inflammasome alleviates CIRI by inhibiting ferroptosis and inflammation, possibly through a mechanism of the Keap1-Nrf2 pathway.

TREM2 expressed on microglia plays an important role in modulating inflammation in neurodegenerative diseases. It remains unknown whether TREM2 modulates hyperglycemia-induced microglial inflammation. We investigated the molecular function of TREM2 in high glucose-induced microglial inflammation using western blotting, qPCR, ELISA, pulldown, and co-IP methods. Our data showed that in high glucose-induced BV2 cells, TREM2 was increased, and the proinflammatory cytokine IL-1β was increased. TREM2 knockout (KO) attenuated the proinflammatory cytokine IL-1β; conversely, TREM2 overexpression (OE) exacerbated IL-1β expression. Furthermore, we found that high glucose promoted the interaction of TREM2 with NLRP3. TREM2 KO abolished the interaction of TREM2 with NLRP3, while TREM2 OE enhanced the interaction. Moreover, TREM2 KO reduced high glucose-induced NLRP3 inflammasome activation, and TREM2 OE augmented high glucose-induced NLRP3 inflammasome activation, indicating that high glucose enhances the expression of TREM2, which activates the NLRP3 inflammasome. To further clarify whether the NLRP3 signaling pathway mediates the TREM2-regulated inflammatory response, we blocked the NLRP3 inflammasome by knocking out NLRP3 and treating cells with a caspase1 inhibitor, which decreased the levels of the IL-1β proinflammatory cytokine but did not affect the high glucose-induced expression of TREM2. TREM2 modulates high glucose-induced microglial inflammation via the NLRP3 signaling pathway.