NLRP3 Inflammasome Assembly in Neutrophils Is Supported by PAD4 and Promotes NETosis Under Sterile Conditions

Neutrophil extracellular trap formation (NETosis) and the NLR family pyrin domain containing 3 (NLRP3) inflammasome assembly are associated with a similar spectrum of human disorders. While NETosis is known to be regulated by peptidylarginine deiminase 4 (PAD4), the role of the NLRP3 inflammasome in NETosis was not addressed. Here, we establish that under sterile conditions the cannonical NLRP3 inflammasome participates in NETosis. We show apoptosis-associated speck-like protein containing a CARD (ASC) speck assembly and caspase-1 cleavage in stimulated mouse neutrophils without LPS priming. PAD4 was needed for optimal NLRP3 inflammasome assembly by regulating NLRP3 and ASC protein levels post-transcriptionally. Genetic ablation of NLRP3 signaling resulted in impaired NET formation, because NLRP3 supported both nuclear envelope and plasma membrane rupture. Pharmacological inhibition of NLRP3 in either mouse or human neutrophils also diminished NETosis. Finally, NLRP3 deficiency resulted in a lower density of NETs in thrombi produced by a stenosis-induced mouse model of deep vein thrombosis. Altogether, our results indicate a PAD4-dependent formation of the NLRP3 inflammasome in neutrophils and implicate NLRP3 in NETosis under noninfectious conditions in vitro and in vivo.

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Soluble α-synuclein–antibody complexes activate the NLRP3 inflammasome in hiPSC-derived microglia

Proceedings of the National Academy of Sciences ◽

10.1073/pnas.2025847118 ◽

2021 ◽

Vol 118 (15) ◽

pp. e2025847118

Author(s):

Dorit Trudler ◽

Kristopher L. Nazor ◽

Yvonne S. Eisele ◽

Titas Grabauskas ◽

Nima Dolatabadi ◽

...

Keyword(s):

Nlrp3 Inflammasome ◽

Amyloid Β ◽

Induced Pluripotent Stem Cell ◽

Amyloid Β Peptide ◽

Human Microglia ◽

Pyrin Domain ◽

Toll Like Receptor 2 ◽

Induced Pluripotent

Parkinson’s disease is characterized by accumulation of α-synuclein (αSyn). Release of oligomeric/fibrillar αSyn from damaged neurons may potentiate neuronal death in part via microglial activation. Heretofore, it remained unknown if oligomeric/fibrillar αSyn could activate the nucleotide-binding oligomerization domain (NOD)-like receptor (NLR) family pyrin domain-containing 3 (NLRP3) inflammasome in human microglia and whether anti-αSyn antibodies could prevent this effect. Here, we show that αSyn activates the NLRP3 inflammasome in human induced pluripotent stem cell (hiPSC)-derived microglia (hiMG) via dual stimulation involving Toll-like receptor 2 (TLR2) engagement and mitochondrial damage. In vitro, hiMG can be activated by mutant (A53T) αSyn secreted from hiPSC-derived A9-dopaminergic neurons. Surprisingly, αSyn–antibody complexes enhanced rather than suppressed inflammasome-mediated interleukin-1β (IL-1β) secretion, indicating these complexes are neuroinflammatory in a human context. A further increase in inflammation was observed with addition of oligomerized amyloid-β peptide (Aβ) and its cognate antibody. In vivo, engraftment of hiMG with αSyn in humanized mouse brain resulted in caspase-1 activation and neurotoxicity, which was exacerbated by αSyn antibody. These findings may have important implications for antibody therapies aimed at depleting misfolded/aggregated proteins from the human brain, as they may paradoxically trigger inflammation in human microglia.

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Potentiation of NETs release is novel characteristic of TREM-1 activation and the pharmacological inhibition of TREM-1 could prevent from the deleterious consequences of NETs release in sepsis

Cellular and Molecular Immunology ◽

10.1038/s41423-020-00591-7 ◽

2021 ◽

Author(s):

Amir Boufenzer ◽

Kevin Carrasco ◽

Lucie Jolly ◽

Benjamin Brustolin ◽

Elisa Di-Pillo ◽

...

Keyword(s):

Vascular Reactivity ◽

Myeloid Cell ◽

Neutrophil Extracellular Trap ◽

Toll Like Receptor 4 ◽

Genetic Ablation ◽

Experimental Septic Shock ◽

Net Release

AbstractDuring sepsis, neutrophil activation induces endothelial cell (EC) dysfunction partly through neutrophil extracellular trap (NET) release. The triggering receptor expressed on myeloid cell-1 (TREM-1) is an orphan immune receptor that amplifies the inflammatory response mediated by Toll-like receptor-4 (TLR4) engagement. Although the key role of TLR4 signaling in NETosis is known, the role of TREM-1 in this process has not yet been investigated. Here, we report that TREM-1 potentiates NET release by human and murine neutrophils and is a component of the NET structure. In contrast, pharmacologic inhibition or genetic ablation of TREM-1 decreased NETosis in vitro and during experimental septic shock in vivo. Moreover, isolated NETs were able to activate ECs and impair vascular reactivity, and these deleterious effects were dampened by TREM-1 inhibition. TREM-1 may, therefore, constitute a new therapeutic target to prevent NETosis and associated endothelial dysfunction.

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TIFA as a crucial mediator for NLRP3 inflammasome

Proceedings of the National Academy of Sciences ◽

10.1073/pnas.1618773114 ◽

2016 ◽

Vol 113 (52) ◽

pp. 15078-15083 ◽

Cited By ~ 25

Author(s):

Ting-Yang Lin ◽

Tong-You Wade Wei ◽

Shuai Li ◽

Shen-Chih Wang ◽

Ming He ◽

...

Keyword(s):

Nlrp3 Inflammasome ◽

Vascular Endothelial Cells ◽

Regulatory Element ◽

Innate Immune ◽

Interacting Protein ◽

Pyrin Domain ◽

Element Binding Protein ◽

Nucleotide Oligomerization

Toll-like receptor-mediated NF-κB activation is a major innate immune reaction of vascular endothelial cells (ECs) in response to prooxidative and proinflammatory stimuli. We identified that TNF-α receptor-associated factor-interacting protein with a forkhead-associated domain (TIFA) is a regulator of priming (signal 1) and activating (signal 2) signals of nucleotide oligomerization domain-like receptor family pyrin domain-containing protein 3 (NLRP3) inflammasome in ECs. Oxidative and inflammatory stresses such as atheroprone flow and hyperlipidemia induce and activate TIFA in vitro and in vivo. For the priming of signal 1, sterol regulatory element-binding protein 2 transactivates TIFA, which in turn induces NF-κB activation and augments the transcription of NLRP3 inflammasome components. For the activation of signal 2, Akt is involved in TIFA Thr9 phosphorylation, which is essential for TIFA–TIFA homophilic oligomerization. Thr9 phosphorylation-dependent TIFA oligomerization facilitates the higher-order assembly of NLRP3 inflammasome, as indicated by the interaction between TIFA and caspase-1 in the activated ECs. Our results suggest that TIFA is a crucial mediator in the endothelial innate immune response by potentiating and amplifying NLRP3 inflammasome via augmenting signals 1 and 2.

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Heparin: a potent inhibitor of hepcidin expression in vitro and in vivo

Blood ◽

10.1182/blood-2010-06-289082 ◽

2011 ◽

Vol 117 (3) ◽

pp. 997-1004 ◽

Cited By ~ 91

Author(s):

Maura Poli ◽

Domenico Girelli ◽

Natascia Campostrini ◽

Federica Maccarinelli ◽

Dario Finazzi ◽

...

Keyword(s):

Bone Morphogenetic Proteins ◽

Serum Iron ◽

Iron Homeostasis ◽

Iron Concentration ◽

Deficiency Anemia ◽

Hepcidin Expression ◽

Vein Thrombosis ◽

Protein Levels

Abstract Hepcidin is a major regulator of iron homeostasis, and its expression in liver is regulated by iron, inflammation, and erythropoietic activity with mechanisms that involve bone morphogenetic proteins (BMPs) binding their receptors and coreceptors. Here we show that exogenous heparin strongly inhibited hepcidin expression in hepatic HepG2 cells at pharmacologic concentrations, with a mechanism that probably involves bone morphogenetic protein 6 sequestering and the blocking of SMAD signaling. Treatment of mice with pharmacologic doses of heparin inhibited liver hepcidin mRNA expression and SMAD phosphorylation, reduced spleen iron concentration, and increased serum iron. Moreover, we observed a strong reduction of serum hepcidin in 5 patients treated with heparin to prevent deep vein thrombosis, which was accompanied by an increase of serum iron and a reduction of C-reactive protein levels. The data show an unrecognized role for heparin in regulating iron homeostasis and indicate novel approaches to the treatment of iron-restricted iron deficiency anemia.

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Melatonin Reduces NLRP3 Inflammasome Activation by Increasing α7 nAChR-Mediated Autophagic Flux

Antioxidants ◽

10.3390/antiox9121299 ◽

2020 ◽

Vol 9 (12) ◽

pp. 1299

Author(s):

Víctor Farré-Alins ◽

Paloma Narros-Fernández ◽

Alejandra Palomino-Antolín ◽

Céline Decouty-Pérez ◽

Ana Belen Lopez-Rodriguez ◽

...

Keyword(s):

Nlrp3 Inflammasome ◽

System Response ◽

Autophagic Flux ◽

Inflammasome Activation ◽

In Vivo Models ◽

Knock Out ◽

Protein Levels ◽

Α7 Nachr

Microglia controls the immune system response in the brain. Specifically, the activation and dysregulation of the NLRP3 inflammasome is responsible for the initiation of the inflammatory process through IL-1β and IL-18 release. In this work, we have focused on studying the effect of melatonin on the regulation of the NLRP3 inflammasome through α7 nicotinic receptor (nAChR) and its relationship with autophagy. For this purpose, we have used pharmacological and genetic approaches in lipopolysaccharide (LPS)-induced inflammation models in both in vitro and in vivo models. In the BV2 cell line, LPS inhibited autophagy, which increased NLRP3 protein levels. However, melatonin promoted an increase in the autophagic flux. Treatment of glial cultures from wild-type (WT) mice with LPS followed by extracellular adenosine triphosphate (ATP) produced the release of IL-1β, which was reversed by melatonin pretreatment. In cultures from α7 nAChR knock-out (KO) mice, melatonin did not reduce IL-1β release. Furthermore, melatonin decreased the expression of inflammasome components and reactive oxygen species (ROS) induced by LPS; co-incubation of melatonin with α-bungarotoxin (α-bgt) or luzindole abolished the anti-inflammatory and antioxidant effects. In vivo, melatonin reverted LPS-induced cognitive decline, reduced NLRP3 levels and promoted autophagic flux in the hippocampi of WT mice, whereas in α7 nAChR KO mice melatonin effect was not observed. These results suggest that melatonin may modulate the complex interplay between α7 nAChR and autophagy signaling.

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Hyperoside inhibits lipopolysaccharide-induced mastitis in mice by inactivating the NLRP3 inflammasome

Archives of Medical Science ◽

10.5114/aoms/143781 ◽

2022 ◽

Author(s):

Xingxiao Gao ◽

Ying Han ◽

Xianrong Yan ◽

Ming Yan ◽

Xiao Lin

Keyword(s):

Signaling Pathway ◽

Nlrp3 Inflammasome ◽

Mammary Epithelial Cells ◽

Bovine Mastitis ◽

Animal Husbandry ◽

Inflammatory Factor ◽

Protein Levels ◽

Pyrin Domain ◽

The Impact

IntroductionThe impact of bovine mastitis on animal husbandry is great huge. It is anincurable an incurable disease mainly characterized by milk and pathological changes in milk and the mammary gland, which causescause reduced yield and quality of milk, but. Unfortunately, the use of antibiotics to combat mastitis affects the production of milk, so it is urgent to find additional therapeutic molecules for mastitis treatment.Material and methodsIn this study, we analyzed the protection provided by hyperoside (HYP) in a model of mastitis in vivo and explored its functional mechanism in mouse mammary epithelial cells (mMECs) by overexpression of NOD-, LRR- and pyrin domain-containing 3 (NLRP3).ResultsOur results showed that HYP at 12.5, 25 and 50 mg/kg prevented the inflammatory response induced in lipopolysaccharide (LPS)-stimulated micemouse mammary glands as well as inflammatory cytokine production, including tumor necrosis factor (TNF)-α, interleukin (IL)-6, IL-1β and IL-8. The protection provided by HYP was also correlated with the reduction of NLRP3 signaling pathway protein levels in vivo. However, overexpression of NLRP3 reversed the effects of HYP on the NLRP3 inflammasome, cell viability and inflammatory factor levels in LPS-stimulated mMECs.ConclusionsIn summary, this study showed that HYP inhibited LPS-stimulated symptoms of breast inflammation by regulating expression of inflammatory cytokines and inhibiting the NLRP3 signaling pathway.

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Bidirectional Crosstalk between C5a Receptors and the NLRP3 Inflammasome in Macrophages and Monocytes

Mediators of Inflammation ◽

10.1155/2016/1340156 ◽

2016 ◽

Vol 2016 ◽

pp. 1-11 ◽

Cited By ~ 20

Author(s):

Mikel D. Haggadone ◽

Jamison J. Grailer ◽

Fatemeh Fattahi ◽

Firas S. Zetoune ◽

Peter A. Ward

Keyword(s):

Nlrp3 Inflammasome ◽

Cellular Tissue ◽

Immune Defense ◽

Inflammasome Activation ◽

Lps Challenge ◽

Pyrin Domain ◽

Inflammatory Monocytes ◽

Nlrp3 Inflammasome Activation

C5a is an inflammatory mediator generated by complement activation that positively regulates various arms of immune defense, including Toll-like receptor 4 (TLR4) signaling. The NOD-like receptor pyrin domain-containing protein 3 (NLRP3) inflammasome is activated by pathogen products and cellular/tissue damage products and is a major contributor of IL-1β. In this study, we investigate whether C5a modulates lipopolysaccharide- (LPS-) induced NLRP3 inflammasome activation in myeloid cells. Appearance of plasma IL-1βduring endotoxemia was reduced inC5aR1-/-mice when compared to wild-type mice. In vitro, C5a significantly enhanced LPS-induced production of IL-1βin bone marrow Ly6C-high inflammatory monocytes, accompanied by augmented intracellular pro-IL-1βexpression. This effect was abolished during p38 blockade by SB 203580 and in the absence of C5aR1. Conversely, C5a suppressed LPS-induced macrophage production of IL-1β, which was accompanied by attenuated levels of pro-IL-1β, NLRP3, and caspase-1 expression. C5a’s suppressive effects were negated during phosphoinositide 3-kinase (PI3K) inhibition by wortmannin but were largely preserved in the absence of C5aR1. Thus, C5a bidirectionally amplifies TLR4-mediated NLRP3 inflammasome activation in monocytes while suppressing this pathway in macrophages. However, as C5aR1 deficiency attenuates the IL-1βresponse to LPS challenge in vivo, our results suggest overall that C5a augments physiologic inflammasome responses.

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All-Trans Retinoic Acid Increases DRP1 Levels and Promotes Mitochondrial Fission

Cells ◽

10.3390/cells10051202 ◽

2021 ◽

Vol 10 (5) ◽

pp. 1202

Author(s):

Bojjibabu Chidipi ◽

Syed Islamuddin Shah ◽

Michelle Reiser ◽

Manasa Kanithi ◽

Amanda Garces ◽

...

Keyword(s):

Retinoic Acid ◽

Mitochondrial Fission ◽

Normal Function ◽

Mitochondrial Network ◽

Protein Levels ◽

Trans Retinoic Acid ◽

All Trans Retinoic Acid ◽

Area And Perimeter

In the heart, mitochondrial homeostasis is critical for sustaining normal function and optimal responses to metabolic and environmental stressors. Mitochondrial fusion and fission are thought to be necessary for maintaining a robust population of mitochondria, and disruptions in mitochondrial fission and/or fusion can lead to cellular dysfunction. The dynamin-related protein (DRP1) is an important mediator of mitochondrial fission. In this study, we investigated the direct effects of the micronutrient retinoid all-trans retinoic acid (ATRA) on the mitochondrial structure in vivo and in vitro using Western blot, confocal, and transmission electron microscopy, as well as mitochondrial network quantification using stochastic modeling. Our results showed that ATRA increases DRP1 protein levels, increases the localization of DRP1 to mitochondria in isolated mitochondrial preparations. Our results also suggested that ATRA remodels the mitochondrial ultrastructure where the mitochondrial area and perimeter were decreased and the circularity was increased. Microscopically, mitochondrial network remodeling is driven by an increased rate of fission over fusion events in ATRA, as suggested by our numerical modeling. In conclusion, ATRA results in a pharmacologically mediated increase in the DRP1 protein. It also results in the modulation of cardiac mitochondria by promoting fission events, altering the mitochondrial network, and modifying the ultrastructure of mitochondria in the heart.

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TRIM27 interacts with Iκbα to promote the growth of human renal cancer cells through regulating the NF-κB pathway

BMC Cancer ◽

10.1186/s12885-021-08562-5 ◽

2021 ◽

Vol 21 (1) ◽

Author(s):

Chengwu Xiao ◽

Wei Zhang ◽

Meimian Hua ◽

Huan Chen ◽

Bin Yang ◽

...

Keyword(s):

Cell Lines ◽

Prognostic Indicator ◽

The Cancer Genome Atlas ◽

Mrna Levels ◽

Loss Of Function ◽

Protein Levels ◽

Kaplan Meier ◽

Cancer Genome Atlas

Abstract Background The tripartite motif (TRIM) family proteins exhibit oncogenic roles in various cancers. The roles of TRIM27, a member of the TRIM super family, in renal cell carcinoma (RCC) remained unexplored. In the current study, we aimed to investigate the clinical impact and roles of TRIM27 in the development of RCC. Methods The mRNA levels of TRIM27 and Kaplan–Meier survival of RCC were analyzed from The Cancer Genome Atlas database. Real-time PCR and Western blotting were used to measure the mRNA and protein levels of TRIM27 both in vivo and in vitro. siRNA and TRIM27 were exogenously overexpressed in RCC cell lines to manipulate TRIM27 expression. Results We discovered that TRIM27 was elevated in RCC patients, and the expression of TRIM27 was closely correlated with poor prognosis. The loss of function and gain of function results illustrated that TRIM27 promotes cell proliferation and inhibits apoptosis in RCC cell lines. Furthermore, TRIM27 expression was positively associated with NF-κB expression in patients with RCC. Blocking the activity of NF-κB attenuated the TRIM27-mediated enhancement of proliferation and inhibition of apoptosis. TRIM27 directly interacted with Iκbα, an inhibitor of NF-κB, to promote its ubiquitination, and the inhibitory effects of TRIM27 on Iκbα led to NF-κB activation. Conclusions Our results suggest that TRIM27 exhibits an oncogenic role in RCC by regulating NF-κB signaling. TRIM27 serves as a specific prognostic indicator for RCC, and strategies targeting the suppression of TRIM27 function may shed light on future therapeutic approaches.

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Long noncoding RNA SNHG14 promotes hepatocellular carcinoma progression by regulating miR-876-5p/SSR2 axis

Journal of Experimental & Clinical Cancer Research ◽

10.1186/s13046-021-01838-5 ◽

2021 ◽

Vol 40 (1) ◽

Author(s):

Zhibin Liao ◽

Hongwei Zhang ◽

Chen Su ◽

Furong Liu ◽

Yachong Liu ◽

...

Keyword(s):

Noncoding Rna ◽

Animal Experiments ◽

Luciferase Reporter ◽

Western Blot Assay ◽

Downstream Target ◽

Protein Levels ◽

Elevated Expression ◽

Rna Immunoprecipitation

Abstract Background Aberrant expressions of long noncoding RNAs (lncRNAs) have been demonstrated to be related to the progress of HCC. The mechanisms that SNHG14 has participated in the development of HCC are obscure. Methods Quantitative real-time PCR (qRT-PCR) was used to measure the lncRNA, microRNA and mRNA expression level. Cell migration, invasion and proliferation ability were evaluated by transwell and CCK8 assays. The ceRNA regulatory mechanism of SNHG14 was evaluated by RNA immunoprecipitation (RIP) and dual luciferase reporter assay. Tumorigenesis mouse model was used to explore the roles of miR-876-5p in vivo. The protein levels of SSR2 were measured by western blot assay. Results In this study, we demonstrated that SNHG14 was highly expressed in HCC tissues, meanwhile, the elevated expression of SNHG14 predicted poor prognosis in patients with HCC. SNHG14 promoted proliferation and metastasis of HCC cells. We further revealed that SNHG14 functioned as a competing endogenous RNA (ceRNA) for miR-876-5p and that SSR2 was a downstream target of miR-876-5p in HCC. Transwell, CCK8 and animal experiments exhibited miR-876-5p inhibited HCC progression in vitro and in vivo. By conducting rescue experiments, we found the overexpression of SSR2 or knocking down the level of miR-876-5p could reverse the suppressive roles of SNHG14 depletion in HCC. Conclusion SNHG14 promotes HCC progress by acting as a sponge of miR-876-5p to regulate the expression of SSR2 in HCC.

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