Hyperactivation Of NLRP3 Inflammasome Research Articles

Card9 protects sepsis by regulating Ripk2-mediated activation of NLRP3 inflammasome in macrophages

Sepsis is characterized by systemic inflammation, it’s caused by primary infection of pathogenic microorganisms or secondary infection of damaged tissue. In this study, we focus on sepsis-induced intestine barrier functional disturbalice, presenting as increased permeability of intestinal epithelium. We observed that the phenotype of LPS-induced sepsis was exacerbated in Card9−/− mice, especially displaying more serious intestinal inflammation and gut barrier dysfunction. Next, we found the hyperactivation of NLRP3 inflammasome in the intestinal macrophages of Card9−/−-sepsis mice. Moreover, Card9 over-expression decreased NLRP3 inflammasome activation in macrophages. Furthermore, we found that Card9 inhibited NLRP3 inflammasome activation by recruiting Ripk2. The competitive binding between Ripk2 with Caspase-1, instead of ASC with Caspase-1, inhibited the NLRP3 inflammasome activation. Over-expression of Ripk2 alleviated septic intestinal injury caused by Card9 deficiency. Taken together, we suggested Card9 acts as a negative regulation factor of NLRP3 inflammasome activation, which protects against intestinal damage during sepsis. Therefore, maintaining Card9-Ripk2 signaling homeostasis may provide a novel therapy of septic intestinal damage.

CCDC50 suppresses NLRP3 inflammasome activity by mediating autophagic degradation of NLRP3.

The NLRP3-directed inflammasome complex is crucial for the host to resist microbial infection and monitor cellular damage. However, the hyperactivation of NLRP3 inflammasome is implicated in pathogenesis of inflammatory diseases, including inflammatory bowel disease (IBD). Autophagy and autophagy-related genes are closely linked to NLRP3-mediated inflammation in these inflammatory disorders. Here, we report that CCDC50, a novel autophagy cargo receptor, negatively regulates NLRP3 inflammasome assembly and suppresses the cleavage of pro-caspase-1 and interleukin 1β (IL-1β) release by delivering NLRP3 for autophagic degradation. Transcriptome analysis showed that knockdown of CCDC50 results in upregulation of signaling pathways associated with autoinflammatory diseases. CCDC50 deficiency leads to enhanced proinflammatory cytokine response triggered by a wide range of endogenous and exogenous NLRP3 stimuli. Ccdc50-deficient mice are more susceptible to dextran sulfate (DSS)-induced colitis and exhibit more severe gut inflammation with elevated NLRP3 inflammasome activity. These results illustrate the physiological significance of CCDC50 in the pathogenicity of inflammatory diseases, suggesting protective roles of CCDC50 in keeping gut inflammation under control.

NLRP3 Inflammasome Pharmacological Inhibitors in Glycyrrhiza for NLRP3-Driven Diseases Treatment: Extinguishing the Fire of Inflammation.

Inflammation is the tissues’ defense response after the body is stimulated by microbial infection or damage signals, and it is initiated when pattern recognition receptors recognize pathogen-related molecular patterns and danger-related molecular patterns. The hyperactivation of NLRP3 inflammasome, the main driving force of immune outbreaks, is involved in a wide range of inflammatory diseases. Meanwhile, growing evidence has indicated that the development of NLRP3-targeted therapies offers great potential and promise for the treatment of related diseases. The search for and development of efficacious anti-inflammatory prodrugs from natural sources of plants and traditional Chinese medicines (TCMs) have received extensive attention. Glycyrrhiza, an important minister in the kingdom of TCMs, has high activity and a wide range of therapeutic effects. Studies have shown that a variety of active components found in Glycyrrhiza, such as licochalcone A, echinatin, isoliquiritigenin, and glycyrrhizin, produce a wide range of anti-inflammatory effects by discouraging NLRP3 inflammasome activation. Here, we summarize the role and mechanism of the active ingredients in Glycyrrhiza that target the NLRP3 inflammasome and treat related inflammatory diseases. We describe a favorable approach for the development of natural, safe, and efficient drugs that exploit these naturally occurring active ingredients to treat NLRP3-driven diseases.

P38 MAPK Activity Is Required to Prevent Hyperactivation of NLRP3 Inflammasome.

Inflammation contributes to the pathogenesis and morbidity of wide spectrum of human diseases. The inflammatory response must be actively controlled to prevent bystander damage to tissues. Yet, the mechanisms controlling excessive inflammatory responses are poorly understood. NLRP3 inflammasome plays an important role in innate immune response to cellular infection or stress. Its activation must be tightly regulated because uncontrolled inflammasome activation is associated with a number of human diseases. p38 MAPK signaling plays an essential role in the regulation of inflammation. The role of p38 MAPK in inflammatory response associated with the expression of proinflammatory molecules is known. However, the anti-inflammatory functions of p38 MAPK are largely unknown. In this study, we show that pharmacologic inhibition or genetic deficiency of p38 MAPK leads to hyperactivation of NLRP3 inflammasome, resulting in enhanced Caspase 1 activation and IL-1β and IL-18 production. The deficiency of p38 MAPK activity induced an increase of cytosolic Ca2+ and excessive mitochondrial Ca2+ uptake, leading to exacerbation of mitochondrial damage, which was associated with hyperactivation of NLRP3 inflammasome. In addition, mice with deficiency of p38 MAPK in granulocytes had evidence of in vivo hyperactivation of NLRP3 inflammasome and were more susceptible to LPS-induced sepsis compared with wild-type mice. Our results suggest that p38 MAPK negatively regulates NLRP3 inflammasome through control of Ca2+ mobilization. Hyperactivity of inflammasome in p38-deficient mice causes lung inflammation and increased susceptibility to septic shock.

Common pathogen-associated molecular patterns induce the hyper-activation of NLRP3 inflammasome in circulating B lymphocytes of HIV-infected individuals.

Despite the antiretroviral treatment, people with HIV (PWH) still experience systemic chronic inflammation and immune-senescence, which represent risk factors for severe comorbidities and inefficient response to pathogens and vaccines. Given the dysregulation of NLRP3 inflammasome in PWH and the recently demonstrated role played by NLRP3 in B lymphocytes, we hypothesized that NLRP3 dysregulation in B cells can contribute to chronic inflammation and humoral dysfunction in PWH. NLRP3 inflammasome activation was evaluated in B lymphocytes and correlated with antibodies production and immunization response in PWH. NLRP3 inflammasome activation was compared in B lymphocytes isolated from PWH and healthy donors, in resting and stimulated conditions. Functional polymorphic variants in NLRP3 and IL1B genes were analysed in a cohort of PWH submitted to anti-HBV vaccine to assess the effect of NLRP3 inflammasome on humoral response. The NLRP3 inflammasome activation in response to common PAMPs (LPS, ß-glucan) resulted higher in B lymphocytes of PWH than in HD. CpG-induced IgM secretion was also increased in B cells of PWH. NLRP3, but not IL1B, gain-of-function polymorphism associated to anti-HBs levels. These data reveal the dysregulation of NLRP3 inflammasome in B lymphocytes of PWH. Differently from myeloid compartment, which present an exhausted NLRP3 inflammasome, the complex appears to be hyper-activated in B cells of PWH, likely contributing to chronic inflammation and affecting humoral response.

PB1-F2 protein of highly pathogenic influenza A (H7N9) virus selectively suppresses RNA-induced NLRP3 inflammasome activation through inhibition of MAVS-NLRP3 interaction.

Infection with seasonal as well as highly pathogenic avian influenza A virus (IAV) causes significant morbidity and mortality worldwide. As a major virulence factor, PB1-F2 protein of IAV affects the severity of disease through multiple mechanisms including perturbation of host innate immune response. Macrophages are known to phagocytose extracellular PB1-F2 protein aggregate, leading to hyperactivation of NLRP3 inflammasome and excessive production of IL-1β and IL-18. On the other hand, when expressed intracellularly PB1-F2 suppresses NLRP3 inflammasome maturation. How extracellular and intracellular PB1-F2 orchestrates to drive viral pathogenesis remains unclear. In this study, we demonstrated the suppression of NLRP3 inflammasome activation and IL-1β secretion by PB1-F2 of highly pathogenic influenza A (H7N9) virus in infected human monocyte-derived macrophages. Mechanistically, H7N9 PB1-F2 selectively mitigated RNA-induced NLRP3 inflammasome activation by inhibiting the interaction between NLRP3 and MAVS. Intracellular PB1-F2 of H7N9 virus did not affect extracellular PB1-F2-induced NLRP3 inflammasome maturation. In contrast, PB1-F2 of WSN laboratory strain of human IAV effectively suppressed IL-1β processing and secretion induced by various stimuli including NLRP3, AIM2, and pro-IL-1β. This subtype-specific effect of PB1-F2 on inflammasome activation correlates with the induction of a proinflammatory cytokine storm by H7N9 but not WSN virus. Our findings on selective suppression of MAVS-dependent activation of NLRP3 inflammasome by H7N9 PB1-F2 have implications in viral pathogenesis and antiviral development.

Phosphatase SHP2-mediated mitochondrial homeostasis for the resolution of inflammation

Abstract The negative regulation of inflammation is very important for the resolution of inflammatory diseases. Although many components and mediators in inflammation have been identified, how inflammation is finely regulated remains lack of evidence. Here we show that Src homology-2 domain containing protein tyrosine phosphatase-2 (SHP2) translocates to mitochondria in the early time of inflammatory stimulation. The RRWFH motif in SH2 domain is essential for the translocation of SHP2. This phosphatase localizes in the mitochondrial matrix with the help of Tom20/Tom40 in outer membrane and Tim23 in inner membrane. Then SHP2 interacts with ANT1, a central molecule controlling mitochondrial permeability transition. This mechanism prevents the collapse of mitochondrial membrane potential, mtDNA release and ROS production, and thus inhibits the hyperactivation of NLRP3 inflammasome. Ablation or inhibition of SHP2 in macrophage causes intensified NLRP3 inflammasome activation, production of IL-1β and IL-18, and increased sensitivity to peritonitis. We are also engaged in seeking the activator of SHP2. We have found that the natural products fusaruside and trichomides A can increase the phosphorylation of SHP2 and some of synthesized compounds can directly activate the phosphatase. These SHP2 activators show a significant anti-inflammatory activity in various disease models. Collectively, our data highlight that SHP2 orchestrates an intrinsic regulatory loop for the mitochondrial homeostasis to limit excessive NLRP3 inflammasome activation, suggesting a possibility to treat inflammatory diseases via maintaining mitochondrial homeostasis.

172. Vitamin D decreases gene and protein expression of NLRP3 inflammasome in placental explants cultured with hydrogen peroxide from women with preeclampsia

Introduction Pregnancies complicated by preeclampsia (PE) are associated with placental oxidative stress and related to the activation of NLRP3 inflammasome, an important complex for activation of caspase-1, interleukin-1 beta (IL-1β) and high-mobility group box-1 (HMGB1). The hyperactivation of NLRP3 inflammasome in placental tissues may be involved in the huge systemic inflammatory state in PE, which could be modulate by administration of substances with anti-inflammatory properties such as vitamin D (VD). Objectives This study aimed to evaluate vitamin D immunomodulatory effect on the NLRP3 inflammassome in placental explants from normotensive (NT) and preeclamptic women cultured with hydrogen peroxide. Methods Placental explants from 7 PE and 7 NT women in the third trimester of pregnancy were obtained from women undergoing elective cesarean section. Explants were cultured with or without H2O2 and H2O2 plus VD. NLRP3, HMGB1, caspase-1 and IL-1β gene expression were analysed by qPCR. Protein expression were determined by western blotting or ELISA. Results Endogenous gene expression of NLRP3 and HMGB1 were significantly higher in PE than in NT explants. NLRP3, caspase-1, IL-1β and HMGB1 gene expression were higher in cultures treated with H2O2 compared to control cultures, while explants treated with H2O2 plus VD led to lower gene expression in NT and PE groups. High protein expression of NLRP3, caspase-1, IL-1β and HMGB1 was detected in explants cultured with H2O2 compared to controls whereas cultures treated with H2O2 plus VD decreased these protein expression compared to H2O2 stimuli. Conclusion Vitamin D was able to decrease the gene and protein expression of NLRP3 inflammasome and HMGB1 production in placental explants cultured with H2O2 in PE and NT groups. These results suggest that vitamin D may play an immunomodulatory role in the systemic inflammatory response present in preeclampsia. Financial support FAPESP 2016/18155-9 and 2016/23452-2.

Tyrosine phosphatase SHP2 negatively regulates NLRP3 inflammasome activation via ANT1-dependent mitochondrial homeostasis

Aberrant activation of NLRP3 inflammasome has an important function in the pathogenesis of various inflammatory diseases. Although many components and mediators of inflammasome activation have been identified, how NLRP3 inflammasome is regulated to prevent excessive inflammation is unclear. Here we show NLRP3 inflammasome stimulators trigger Src homology-2 domain containing protein tyrosine phosphatase-2 (SHP2) translocation to the mitochondria, to interact with and dephosphorylate adenine nucleotide translocase 1 (ANT1), a central molecule controlling mitochondrial permeability transition. This mechanism prevents collapse of mitochondrial membrane potential and the subsequent release of mitochondrial DNA and reactive oxygen species, thus preventing hyperactivation of NLRP3 inflammasome. Ablation or inhibition of SHP2 in macrophages causes intensified NLRP3 activation, overproduction of proinflammatory cytokines IL-1β and IL-18, and increased sensitivity to peritonitis. Collectively, our data highlight that, by inhibiting ANT1 and mitochondrial dysfunction, SHP2 orchestrates an intrinsic regulatory loop to limit excessive NLRP3 inflammasome activation.

Sa1867 Spontaneous Hyperactivation of NLRP3 Inflammasome Leads to Colitis in IL-10−/− Mice and Humans

Sa1867 Spontaneous Hyperactivation of NLRP3 Inflammasome Leads to Colitis in IL-10−/− Mice and Humans