scholarly journals A190 ATP-INDUCED INFLAMMASOME ACTIVATION GENERATES MITOCHONDRIAL ROS PRODUCTION IN MACROPHAGES

2021 ◽  
Vol 4 (Supplement_1) ◽  
pp. 206-207
Author(s):  
M Bording-Jorgensen ◽  
H Armstrong ◽  
E Wine

Abstract Background The etiology of Inflammatory Bowel Diseases is unknown; however, a dysfunctional immune response has been well characterized. The role of the NLRP3 inflammasome in IBD is controversial with both beneficial and detrimental results. This pathway is required for the secretion of the proinflammatory cytokine IL-1β. Extracellular ATP is a well characterized inflammasome activator, which we have previously shown can increase the ability of J774A.1 macrophages to clear the mouse pathogen Citrobacter rodentium in an in vitro environment through the generation of reactive oxygen species (ROS). Aims Our objectives were to determine: 1) if extracellular ATP was inducing mitochondrial stress, causing the production of ROS, leading to microbial death; and 2) what effects these activated macropahges have on naïve macrophages. Methods Murine macrophage J774A.1 cells were infected with C. rodentium; extracellular ATP was added as an inflammasome activator and YVAD as an inhibitor. Lysotracker red and MitoSOX were used to determine cellular location of bacteria and quantify mitochondrial ROS, respectively. Secreted cytokines were measured using ELISA and a proteome profiler, ROS was measured using DCFDA, Gasdermin D and Caspase 11 activities were determined by Western Blot. Supernatants taken from infected macrophages were filtered and then added to naïve macrophages during infection with C. rodentium. Results Activation of mitochondrial ROS by ATP was found to be independent of infection. Secreted cytokines sICAM-1, MIP-1α, and MCP-2 were all increased by ATP but not inhibited by YVAD. Cleavage of Gasdermin D was increased with the addition of ATP but not inhibited by YVAD whereas Caspase 11 was unchanged between treatments. Supernatants from ATP-induced macrophages were able to induce IL-1β secretion in naïve macrophages and increase bacterial killing. Conclusions Mitochondrial ROS production in response to extracellular ATP may be involved in the decrease of bacterial survival. ATP induces the secretion of cytokines, chemokines, and other factors that affect newly infected macrophages. Gasdermin D cleavage, independent of caspase 11, suggests that a noncannonical pathway is activated; this may explain the lack of pyroptotic cells in our study. In addition, we have shown that these macrophages are able to illicit the same behavior in naive macrophages, suggesting that a corrected dysfunctional pathway in macrophages can have beneficial effects downstream. Understanding how the NLRP3 inflammasome is activated and what the downstream pathways are may lead to potential therapies for inflammatory conditions, including IBD. Funding Agencies CCC, CIHR

2021 ◽  
Author(s):  
Sahabuddin Ahmed ◽  
Samir Ranjan Panda ◽  
Mohit Kwatra ◽  
Bidya Dhar Sahu ◽  
VGM Naidu

Abstract Several activators of NLRP3 inflammasome have been described; however, the central mechanisms of NLRP3 inflammasome activation in brain microglia, especially at the activating step through free radical generation, still require further clarification. Hence the present study aimed to investigate the role of free radicals in activating NLRP3 inflammasome driven neurodegeneration and elucidated the neuroprotective role of perillyl alcohol (PA) in vitro and in vivo models of Parkinson’s disease. Initial priming of microglial cells with lipopolysaccharide (LPS) following treatment with hydrogen peroxide (H2O2) induces NF-κB translocation to nucleus with robust generation of free radicals that act as Signal 2 in augmenting NLRP3 inflammasome assembly and its downstream targets. PA treatment suppresses nuclear translocation of NF-κB and maintains cellular redox homeostasis in microglia that limits NLRP3 inflammasome activation along with processing active caspase-1, IL-1β and IL-18. To further correlates the in vitro study with in vivo MPTP model, treatment with PA also inhibits the nuclear translocation of NF-κB and downregulates the NLRP3 inflammasome activation. PA administration upregulates various antioxidant enzymes levels and restored the level of dopamine and other neurotransmitters in the striatum of the mice brain with improved behavioural activities. Additionally, treatment with Mito-TEMPO (a mitochondrial ROS inhibitor) was also seen to inhibit NLRP3 inflammasome and rescue dopaminergic neuron loss in the mice brain. Therefore, we conclude that NLRP3 inflammasome activation requires a signal from damaged mitochondria for its activation. Further pharmacological scavenging of free radicals restricts microglia activation and simultaneously supports neuronal survival via targeting NLRP3 inflammasome pathway in Parkinson’s disease.


Circulation ◽  
2014 ◽  
Vol 130 (suppl_2) ◽  
Author(s):  
Zufeng Ding ◽  
Sadip Pant ◽  
Abhishek Deshmukh ◽  
Jawahar L Mehta

Objective: This study tested the hypothesis that mitochondrial DNA damage could trigger NLRP3 inflammasome activation during inflammation, and LOX-1 may play a critical role in this process. Methods and Results: We performed studies in cultured human THP1 macrophages exposed to ox-LDL or LPS,which are often used as inflammation stimuli in vitro . We examined and confirmed the increase in LOX-1 expression when cells were treated with ox-LDL or LPS. Parallel groups of cells were treated with LOX-1 Ab to bind LOX-1. In accordance with our previous studies in endothelial cells and smooth muscle cells, LOX-1 Ab markedly reduced ox-LDL- as well as LPS-stimulated LOX-1 expression. To assess mitochondrial ROS generation, MitoSOX™ Red mitochondrial superoxide indicator was used. Both fluorescence staining and flow cytometry analysis showed that LPS induced (more than ox-LDL) mitochondrial ROS generation. Pretreatment with LOX-1 Ab significantly attenuated mitochondrial ROS generation in response to ox-LDL or LPS. Then we observed mtDNA damage in THP1 cells exposed to ox-LDL or LPS. Importantly, pretreatment with LOX-1 Ab protected mtDNA from damage in response to both stimuli. This was also confirmed by q-PCR (mtDNA/nDNA ratio) analysis. Further, ox-LDL or LPS induced the expression of phos-NF-kB p65, caspase-1 p10 and p20, and cleaved proteins IL-1β and IL-18. Of note, NLRP3 inflammasome was activated in response to ox-LDL or LPS in a similar manner. Pretreatment of cells with LOX-1 Ab treatment blocked or significantly attenuated these inflammatory responses. Conclusions: These observations based on in vitro observations indicate that LOX-1 via ROS generation plays a key role in mtDNA damage which then leads to NLRP3 inflammasome activation during inflammation.


Inflammasome ◽  
2016 ◽  
Vol 2 (1) ◽  
Author(s):  
Xuesong Sang ◽  
Hongbin Wang ◽  
Yihui Chen ◽  
Qiuhong Guo ◽  
Ailing Lu ◽  
...  

AbstractInflammasomes are intracellular protein complexes that mediate maturation and secretion of the pro-inflammatory cytokines IL-1β and IL-18. Inflammasomes have been connected with various diseases, therefore the regulation of inflammasome activation is important for the development of novel therapies for many inflammatory syndromes. Vitamin C is an essential nutrient and has regulatory effects on immune cells. Here we report that vitamin C has an inhibitory effect on the activation of the NLRP3 inflammasome in vitro and in vivo. Mechanistically, this inhibition is through scavenging mitochondrial ROS but not through NF-κB inhibition. Moreover, specificity tests show that the AIM2 inflammasome and the NLRC4 inflammasome can also be inhibited by vitamin C. Our results have thus identified a new inflammasome regulator and provide therapeutic potential for inflammasome-associated diseases.


2018 ◽  
Author(s):  
Francesca La Rosa ◽  
Marina Saresella ◽  
Ivana Marventano ◽  
Federica Piancone ◽  
Enrico Ripamonti ◽  
...  

AbstractAlzheimer’s disease (AD) is associated with amyloid-beta (Aβ) deposition and neuroinflammation, possibly driven by activation of the NLRP3 inflammasome. Nucleoside reverse transcriptase inhibitors (NRTI) hamper the assembly of the NLRP3 inflammasome; we analyzed whether stavudine (D4T), a prototypical NRTI, modulates Aβ-mediated inflammasome activation; because neuroinflammation impairs Aβ clearance by phagocytes, phagocytosis and autophagy were examined as well. THP-1-derived macrophages were stimulated in vitro with Aβ42 alone or after LPS priming with/without D4T. NLRP3 and TREM2 expression was analyzed by RT-PCR, phagocytosis and ASC-Speck by AmnisFlowSight, NLRP3-produced cytokines by ELISA, authophagy by P-ELISA evaluation of P-ERK and P-AKT. Results showed that IL1β, IL18 and caspase-1 were increased whereas Aβ-phagocytosis and TREM2 were reduced in LPS+Aβ42-stimulated cells. D4T reduced NLRP3 assembly as well as IL18 and caspase-1 production, but not IL1β, phagocytosis, and TREM2. P-AKT expression was augmented and P-ERK was reduced by D4T, suggesting a stimulatory effect on autophagy. D4T reduces NLRP3 inflammasome-associated inflammation, possibly restoring autophagy, in an in vitro model of AD; it will be interesting to verify its possibly beneficial effects in the clinical scenario.


2020 ◽  
Author(s):  
Zhixia Dong ◽  
Qian Zhuang ◽  
Xin Ye ◽  
Min Ning ◽  
Shan Wu ◽  
...  

Abstract Background Adiponectin, an adipose-derived adipokine, possesses a hepatoprotective role in various liver disorders. Inflammasome activation has been recognized to play a major role during the progression of non-alcoholic fatty liver diseases (NAFLD). However, the effect of adiponectin on NLRP3 inflammasome activation in liver and the exact mechanism remains largely unclear. Here, we assessed the effect of adiponectin on NLRP3 inflammasome activation and its potential molecular mechanisms through both in vivo and in vitro experiments. Methods Male adiponectin-knockout (adiponectin-KO) mice and C57BL/6 (wild-type) mice were fed a high-fat-diet (HFD) for 12 weeks as an in vivo model of non-alcoholic steatohepatitis (NASH). Serum biochemical markers, liver histology and inflammasome-related gene and protein expression were determined. In addition, the hepatocytes isolated from SD rats were exposed to palmitic acid(PA) in the absence or presence of adiponectin and/or AMPK inhibitor. The activation of NLRP3 inflammasome was assessed by mRNA and protein expression. Furthermore, ROS production and related signaling pathways were also evaluated. Results In the in vivo experiments, we found that adiponectin deficiency mice fed with HFD presented excessive hepatic steatosis with increased NLRP3 inflammasome activation compared to wild-type mice. Moreover, the expression levels of NLRP3 inflammasome activation pathway molecules (NFκB and ROS) were upregulated, while the phosphorylation levels of AMPK, JNK and Erk1/2 were downregulated in adiponectin-knockout mice compared with wild-type mice. In the in vitro study, PA significantly promoted NLRP3 inflammasome activation in hepatocytes. Additionally, PA increased lipid droplet deposition, NF-kB signaling and ROS production, while adiponectin could abolish PA-mediated NLRP3 inflammasome activation and decrease ROS production, which was reversed by AMPK inhibitor (compound C). The results indicated that the inhibitory effect of adiponectin on PA-mediated NLRP3 inflammasome activation was regulated by AMPK-JNK/ErK1/2-NFκB/ROS signaling pathway. Conclusion Adiponectin inhibited PA-mediated NLRP3 inflammasome activation in hepatocytes. Adiponectin analogs or AMPK agonists could serve as a potential novel agent for preventing or delaying the progression of NASH and NAFLD.


2018 ◽  
Vol 2018 ◽  
pp. 1-15 ◽  
Author(s):  
Shuang Li ◽  
Hao Wu ◽  
Dong Han ◽  
Sai Ma ◽  
Wensi Fan ◽  
...  

Sepsis, a systemic inflammatory response to infection, is the leading cause of death in the intensive care unit (ICU). Previous studies indicated that mesenchymal stromal cells (MSCs) might have therapeutic potential against sepsis. The current study was designed to investigate the effects of MSCs on sepsis and the underlying mechanisms focusing on inflammasome activation in macrophages. The results demonstrated that the bone marrow-derived mesenchymal stem cells (BMSCs) significantly increased the survival rate and organ function in cecal ligation and puncture (CLP) mice compared with the control-grouped mice. BMSCs significantly restricted NLRP3 inflammasome activation, suppressed the generation of mitochondrial ROS, and decreased caspase-1 and IL-1β activation when cocultured with bone marrow-derived macrophages (BMDMs), the effects of which could be abolished by Mito-TEMPO. Furthermore, the expression levels of caspase-1, IL-1β, and IL-18 in BMDMs were elevated after treatment with mitophagy inhibitor 3-MA. Thus, BMSCs exert beneficial effects on inhibiting NLRP3 inflammasome activation in macrophages primarily via both enhancing mitophagy and decreasing mitochondrial ROS. These findings suggest that restricting inflammasome activation in macrophages by increasing mitophagy and decreasing mitochondrial ROS might be a crucial mechanism for MSCs to combat sepsis.


2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Ao Chen ◽  
Zhangwei Chen ◽  
You Zhou ◽  
Yuan Wu ◽  
Yan Xia ◽  
...  

AbstractCoronary microembolization (CME), a common reason for periprocedural myocardial infarction (PMI), bears very important prognostic implications. However, the molecular mechanisms related to CME remain largely elusive. Statins have been shown to prevent PMI, but the underlying mechanism has not been identified. Here, we examine whether the NLRP3 inflammasome contributes to CME-induced cardiac injury and investigate the effects of statin therapy on CME. In vivo study, mice with CME were treated with 40 mg/kg/d rosuvastatin (RVS) orally or a selective NLRP3 inflammasome inhibitor MCC950 intraperitoneally (20 mg/kg/d). Mice treated with MCC950 and RVS showed improved cardiac contractile function and morphological changes, diminished fibrosis and microinfarct size, and reduced serum lactate dehydrogenase (LDH) level. Mechanistically, RVS decreased the expression of NLRP3, caspase-1, interleukin-1β, and Gasdermin D N-terminal domains. Proteomics analysis revealed that RVS restored the energy metabolism and oxidative phosphorylation in CME. Furthermore, reduced reactive oxygen species (ROS) level and alleviated mitochondrial damage were observed in RVS-treated mice. In vitro study, RVS inhibited the activation of NLRP3 inflammasome induced by tumor necrosis factor α plus hypoxia in H9c2 cells. Meanwhile, the pyroptosis was also suppressed by RVS, indicated by the increased cell viability, decreased LDH and propidium iodide uptake in H9c2 cells. RVS also reduced the level of mitochondrial ROS generation in vitro. Our results indicate the NLRP3 inflammasome-dependent cardiac pyroptosis plays an important role in CME-induced cardiac injury and its inhibitor exerts cardioprotective effect following CME. We also uncover the anti-pyroptosis role of RVS in CME, which is associated with regulating mitochondrial ROS.


2017 ◽  
Vol 37 (suppl_1) ◽  
Author(s):  
Sai Ma ◽  
Jiangwei Chen ◽  
Zhenli Luo ◽  
Yabin Wang ◽  
Feng Cao

Introduction: NLRP3 inflammasome mediated inflammatory factors secretion is critically involved in atherosclerosis (AS). Melatonin has anti-inflammatory properties. However, it is unknown whether melatonin is beneficial in AS. Hypothesis: Melatonin plays a beneficial role in AS by decreasing NLRP3 inflammasome activation in macrophages. Methods: AS model was induced with high fat diet in apoE -/- mice. Plaque stability was examined with historical staining. In vitro study was performed in ox-LDL treated RAW264.7 cells. NLRP3 inflammasome activation, inflammatory factors secretion, mitochondrial ROS generation, autophagy, mitophagy indexes and potential signaling pathways were investigated. Results: Historical staining results showed that melatonin treatment markedly alleviated AS plaque progression. Despite of unchanged protein expression, Sirt 3 activity was elevated in plaque tissue in melatonin treated mice. Melatonin attenuated NLRP3 inflammasome activation and inflammatory factors secretion in ox-LDL treated macrophages, while this protective effect was abolished by Sirt3-siRNA. Mitochondrial ROS (mitoROS), which was an inducer for NLRP3 inflammasome, was reduced by melatonin through the elimination of damaged mitochondria (mitophagy). Similar with Sirt3-siRNA, autophagy inhibitor 3-MA also abolished the effects of melatonin on mitoROS clearance, indicating the crucial role of autophagy and mitophagy in melatonin caused NLRP3 inactivation. Furthermore, melatonin protected against AS via Sirt3/FoxO3/Parkin signaling pathway. Conclusions: Melatonin prevented atherosclerotic progression. Melatonin reduced mitochondrial ROS through the activation of autophagy and mitophagy, thereby attenuating NLRP3 inflammasome activation in macrophages. Moreover, the protective effect of melatonin was mediated by Sirt3/FoxO3/Parkin signaling pathway. Our study provides insight into a new therapeutic target for AS.


2021 ◽  
Vol 12 ◽  
Author(s):  
Rongfang Que ◽  
Jialing Zheng ◽  
Zihan Chang ◽  
Wenjie Zhang ◽  
Hualing Li ◽  
...  

BackgroundNeuroinflammation and mitochondrial impairment play important roles in the neuropathogenesis of Parkinson’s disease (PD). The activation of NLRP3 inflammasome and the accumulation of α-synuclein (α-Syn) are strictly correlated to neuroinflammation. Therefore, the regulation of NLRP3 inflammasome activation and α-Syn aggregation might have therapeutic potential. It has been indicated that Dl-3-n-butylphthalide (NBP) produces neuroprotection against some neurological diseases such as ischemic stroke. We here intended to explore whether NBP suppressed NLRP3 inflammasome activation and reduced α-Syn aggregation, thus protecting dopaminergic neurons against neuroinflammation.MethodsIn our study, we established a MPTP-induced mouse model and 6-OHDA-induced SH-SY5Y cell model to examine the neuroprotective actions of NBP. We then performed behavioral tests to examine motor dysfunction in MPTP-exposed mice after NBP treatment. Western blotting, immunofluorescence staining, flow cytometry and RT-qPCR were conducted to investigate the expression of NLRP3 inflammasomes, neuroinflammatory cytokines, PARP1, p-α-Syn, and markers of microgliosis and astrogliosis.ResultsThe results showed that NBP exerts a neuroprotective effect on experimental PD models. In vivo, NBP ameliorated behavioral impairments and reduced dopaminergic neuron loss in MPTP-induced mice. In vitro, treatment of SH-SY5Y cells with 6-OHDA (100uM,24 h) significantly decreased cell viability, increased intracellular ROS production, and induced apoptosis, while pretreatment with 5uM NBP could alleviated 6-OHDA-induced cytotoxicity, ROS production and cell apoptosis to some extent. Importantly, both in vivo and in vitro, NBP suppressed the activation of the NLRP3 inflammasome and the aggregation of α-Syn, thus inhibited neuroinflammation ameliorated mitochondrial impairments.ConclusionsIn summary, NBP rescued dopaminergic neurons by reducing NLRP3 inflammasome activation and ameliorating mitochondrial impairments and increases in p-α-Syn levels. This current study may provide novel neuroprotective mechanisms of NBP as a potential therapeutic agent.


Author(s):  
Ting Zhang ◽  
Mao-Tao He ◽  
Xiao-Peng Zhang ◽  
Li Jing ◽  
Jian-Zhong Zhang

AbstractMitochondrial uncoupling protein 2 (UCP2) deficiency exacerbates brain damage following cerebral ischemia/reperfusion (I/R). The Nod-like receptor protein-3 (NLRP3) inflammasome also plays a vital role in cerebral I/R damage. However, the effect of UCP2 on NLRP3 inflammasome-mediated hyperglycemia and I/R damage is not clear. In the present study, UCP2-knockout (UCP2−/−) and wild-type (WT) mice were used to establish a model of middle cerebral artery occlusion (MCAO) and reperfusion under normo- and hyperglycemic conditions. HT22 cells were established as a model of oxygen–glucose deprivation and reoxygenation (OGD/R) with high glucose to mimic hyperglycemia and I/R in vitro. HT22 cells were treated with/without different concentrations of the UCP2-specific inhibitor genipin for different periods of time. The results showed that UCP2 deficiency significantly increased histopathological changes and apoptosis after cerebral I/R damage in hyperglycemic mice. Moreover, UCP2 deficiency enhanced NLRP3 inflammasome activation in neurons when cerebral I/R damage was exacerbated by hyperglycemia. Furthermore, UCP2 deficiency enhanced NLRP3 inflammasome activation and reactive oxygen species (ROS) production in HT22 cells under OGD/R and high-glucose conditions. UCP2 deficiency aggravated hyperglycemia-induced exacerbation of cerebral I/R damage. UCP2 deficiency also enhanced NLRP3 inflammasome activation and ROS production in neurons in vitro and in vivo. These findings suggest that UCP2 deficiency enhances NLRP3 inflammasome activation following hyperglycemia-induced exacerbation of cerebral I/R damage in vitro and in vivo. UCP2 may be a potential therapeutic target for hyperglycemia-induced exacerbation of cerebral I/R damage.


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