Ghrelin attenuates secondary brain injury following intracerebral hemorrhage by inhibiting NLRP3 inflammasome activation and promoting Nrf2/ARE signaling pathway in mice

Ghrelin, a brain-gut peptide, has been proven to exert neuroprotection in different kinds of neurological diseases; however, its role and the potential molecular mechanisms in secondary brain injury (SBI) after intracerebral hemorrhage (ICH) are still unknown. In this study, we investigate whether treatment with ghrelin may attenuate SBI in a murine ICH model, and if so, whether the neuroprotective effects are due to the inhibition of nucleotide-binding oligomerization domain-like receptor pyrin domain-containing 3 (NLRP3) inflammasome activation and promotion of nuclear factor-E2-related factor 2 (Nrf2)/antioxidative response element (ARE) signaling pathway. Stereotactically intrastriatal infusion of autologous blood was performed to mimic ICH. Ghrelin was given intraperitoneally immediately following ICH and again 1 h later. Results showed that ghrelin attenuated neurobehavioral deficits, brain edema, hematoma volume, and perihematomal cell death post-ICH. Ghrelin inhibited the NLRP3 inflammasome activation and subsequently suppressed the neuroinflammatory response as evidenced by reduced microglia activation, neutrophil infiltration, and pro-inflammatory mediators release after ICH. Additionally, ghrelin alleviated ICH-induced oxidative stress according to the chemiluminescence of luminol and lucigenin, malondialdehyde (MDA) content, and total superoxide dismutase (SOD) activity assays. These changes were accompanied by upregulation of Nrf2 expression, Nrf2 nuclear accumulation, and enhanced Nrf2 DNA binding activity, as well as by increased expressions of Nrf2 downstream target antioxidative genes, including NAD(P)H quinine oxidoreductase-1 (NQO1), glutathione cysteine ligase regulatory subunit (GCLC), and glutathione cysteine ligase modulatory subunit (GCLM). Together, our data suggested that ghrelin protected against ICH-induced SBI by inhibiting NLRP3 inflammasome activation and promoting Nrf2/ARE signaling pathway.     

NLRP3 inflammasome and glia maturation factor coordinately regulate neuroinflammation and neuronal loss in MPTP mouse model of Parkinson’s disease

Neuroinflammation plays an active role in the pathogenesis of several neurodegenerative diseases, including Parkinson’s disease (PD). Earlier studies from this laboratory showed that glia maturation factor (GMF), a proinflammatory mediator; is up-regulated in the brain in neurodegenerative diseases and that deficiency of GMF showed decreased production of IL-1β and improved behavioral abnormalities in mouse model of PD. However, the mechanisms linking GMF and dopaminergic neuronal death have not been completely explored. In the present study, we have investigated the expression of NLRP3 inflammasome and caspase-1 in the substantia nigra (SN) of human PD and non-PD brains by immunohistochemistry. Wild-type (WT) and GMF^−/− (GMF knock-out) mice were treated with 1-methyl-4-phenyl-1,2,3,6-tetrahydro pyridine (MPTP) and the brains were isolated for neurochemical and morphological examinations. NLRP3 and caspase-1 positive cells were found significantly increased in PD when compared to non-PD control brains. Moreover, GMF co-localized with α-Synuclein within reactive astrocytes in the midbrain of PD. Mice treated with MPTP exhibit glial activation-induced inflammation, and nigrostriatal dopaminergic neurodegeneration. Interestingly, increased expression of the inflammasome components in astrocytes and microglia observed in the SN of MPTP-treated WT mice were significantly reduced in GMF^−/− mice. Additionally, we show that NLRP3 activation in microglia leads to translocation of GMF and NLRP3 to the mitochondria. We conclude that downregulation of GMF may have beneficial effects in prevention of PD by modulating the cytotoxic functions of microglia and astrocytes through reduced activation of the NLRP3 inflammasome; a major contributor of neuroinflammation in the CNS.     

NLRP3 Inflammasome Activation by Viroporins of Animal Viruses

Viroporins are a group of low-molecular-weight proteins containing about 50–120 amino acid residues, which are encoded by animal viruses. Viroporins are involved in several stages of the viral life cycle, including viral gene replication and assembly, as well as viral particle entry and release. Viroporins also play an important role in the regulation of antiviral innate immune responses, especially in inflammasome formation and activation, to ensure the completion of the viral life cycle. By reviewing the research progress made in recent years on the regulation of the NLRP3 inflammasome by viroporins of animal viruses, we aim to understand the importance of viroporins in viral infection and to provide a reference for further research and development of novel antiviral drugs.     

葡萄膜炎并发白内障患者晶状体前囊膜中NLRP3炎症小体相关蛋白的表达和前囊膜超微结构改变

目的　探究葡萄膜炎并发白内障患者晶状体前囊膜中NLRP3炎症小体相关蛋白的表达和前囊膜超微结构改变。方法　随机选取2018年8月至2019年6月在我院诊治的葡萄膜炎并发白内障患者17例(22眼)作为试验组；老年性白内障患者10例(18眼)作为对照组。均于白内障超声乳化手术中环形撕囊获取前囊膜。采用免疫组织化学法检测两组患者晶状体前囊膜NLRP3炎症小体的三个组成结构NLRP3、Caspase-1和接头蛋白ASC的蛋白表达，并对前囊膜进行电镜观察。结果　两组患者晶状体前囊膜中均有NLRP3炎症小体相关蛋白的表达；试验组晶状体前囊膜中NLRP3、Caspase-1及接头蛋白ASC（光密度值分别为0.383±0.067、0.313±0.058、0.335±0.035）表达水平均明显高于对照组（光密度值分别为0.330±0.085、0.271±0.039、0.268±0.036）（均为P<0.05）。试验组患者前囊膜的晶状体上皮细胞可见明显的细胞核固缩，染色质浓缩边集，细胞核膜皱褶、轻度增宽，线粒体形态基本正常、部分线粒体嵴突消失，细胞质中可见典型的凋亡小体。对照组有轻度凋亡改变。结论　NLRP3炎症小体可能参与了葡萄膜炎并发白内障的发病过程，细胞凋亡是葡萄膜炎并发白内障的重要病理改变。     

Metformin inhibition of mitochondrial ATP and DNA synthesis abrogates NLRP3 inflammasome activation and pulmonary inflammation

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NLRP3 inflammasome: a new therapeutic target for high-risk reproductive disorders?

The NOD-like receptor protein 3 (NLRP3) inflammasome is a key regulator of the host''s immune response, and many immune and metabolic disorders are linked to its activation. This review aimed to investigate and clarify the relationship between this inflammasome and high-risk reproductive disorders. Papers cited here were retrieved from PubMed up to August 2020 using the keywords “NLRP3” or “NALP3”, “caspase-1”, “endometriosis”, “gestational diabetes”, “interleukin (IL)-18”, “IL-1β”, “pre-eclampsia (PE)”, “preterm birth”, “polycystic ovarian syndrome (PCOS)”, “recurrent spontaneous abortion (RSA)”, and combinations of these terms. The results show that NLRP3 inflammasome is associated with various high-risk reproductive disorders and many inflammatory factors are secreted during its activation, such as IL-1β induced during the development of endometriosis. PCOS is also associated with activation of the NLRP3 inflammasome, especially in overweight patients. It also participates in the pathogenesis of RSA and is activated in fetal membranes before preterm birth. The placentas of pregnant women with PE show higher expression of the NLRP3 inflammasome, and gestational diabetes mellitus occurs simultaneously with its activation. Current evidence suggest that the NLRP3 inflammasome plays an important role in female reproductive disorders. New treatment and management methods targeting it might help reduce the incidence of such disorders and improve neonatal outcomes.     

钙离子信号介导Nod样受体蛋白炎性小体激活的研究进展

Nod样受体蛋白（Nod-like receptor protein 3, NLRP3）炎性小体可识别多种病原体及细胞损伤,诱导分泌白细胞介素1β（interleukin-1β, IL-1β）、IL-18,调节炎症反应,是固有免疫系统的重要组成部分。近年研究表明,钙离子（Ca²⁺）信号参与多种NLRP3激动剂诱导的NLRP3炎性小体激活过程,并与相关疾病的发生密切相关。本文综述了有关钙离子与NLRP3炎性小体的相关研究,重点关注钙离子信号在NLRP3炎性小体激活和调节中的潜在作用,为治疗NLRP3炎性小体驱动的炎症性疾病提供新思路。     

外源性硫化氢对肝细胞NLRP3炎症小体的影响

目的:研究外源性硫化氢(H_2S)对人肝细胞NLRP3炎症小体的影响。方法:采用不同浓度的脂多糖(LPS)诱导人肝细胞L02和SMMC-7721建立炎症模型,Western blot检测细胞中NLRP3炎症小体的表达并结合细胞毒性实验(MTT法)确定合适的LPS浓度。细胞分为4组:对照组用普通培养基培养18.5 h;LPS组用普通培养基培养0.5 h后,再用100μg/L LPS刺激18 h;LPS+H_2S组和H_2S组用200μmol/L硫氢化钠(Na HS)刺激0.5 h后,再分别用100μg/L LPS和普通培养基培养18 h。各组处理后分别收集细胞,Western blot检测细胞中NLRP3和caspase-1的蛋白表达量。结果:与对照组相比,LPS组细胞内NLRP3和caspase-1的表达增加(P0.05),H_2S组细胞内的NLRP3和caspase-1表达无明显变化;与LPS组相比,LPS+H_2S组细胞内的NLRP3和caspase-1表达减少(P0.05)。结论:外源性H_2S可抑制人肝细胞中NLRP3炎症小体的表达。     

New evidence of connections between increased O‐GlcNAcylation and inflammasome in the oral mucosa of patients with oral lichen planus

Oral lichen planus (OLP) is considered a chronic inflammatory immune‐mediated disease of the oral mucosa. Immunopathogenesis of OLP is thought to be associated with cell‐mediated immune dysregulation. O‐GlcNAcylation is a form of reversible glycosylation. It has been demonstrated that O‐GlcNAcylation promoted nuclear factor kappa B (NF‐κB) signalling. Activation of NF‐кB can induce expression of nucleotide‐binding domain‐like receptor family pyrin domain containing 3 (NLRP3) inflammasome, which is a large intracellular multi‐protein complex involving an immune response. Dysregulated expression of the NLRP3 inflammasome was reported to be associated with autoinflammatory diseases. No integrative studies between O‐GlcNAcylation and NLRP3 inflammasome in OLP patients have been reported. The present study aimed to determine the immunohistochemical expression of O‐GlcNAcylation, NF‐κB signalling molecules and NLRP3 inflammasome in oral mucosae of OLP patients. Oral tissue samples were collected from 30 OLP patients and 30 healthy individuals. Immunohistochemical staining and analyses of immunostaining scores were performed to evaluate expression of O‐GlcNAcylation, NF‐κB signalling molecules and NLRP3 inflammasome. According to observations in this study, significantly higher levels of O‐GlcNAcylation, NF‐κB signalling molecules and NLRP3 inflammasome were demonstrated in OLP patients compared with control subjects (P < 0·001). Positive correlations among O‐GlcNAcylation, NF‐κB signalling molecules and NLRP3 inflammasome were also observed in OLP samples (P < 0·01). In conclusion, the present study provides supportive evidence that increased O‐GlcNAcylation is associated with increased expression of NLRP3 inflammasome via the NF‐κB signalling pathway. These findings provide a new perspective on immunopathogenesis of OLP in relation to autoinflammation.     

Negative regulation of Nod‐like receptor protein 3 inflammasome activation by T cell Ig mucin‐3 protects against peritonitis

The Nod‐like receptor protein 3 (NLRP3) inflammasome plays roles in host defence against invading pathogens and in the development of autoimmune damage. Strict regulation of these responses is important to avoid detrimental effects. Here, we demonstrate that T cell Ig mucin‐3 (Tim‐3), an immune checkpoint inhibitor, inhibits NLRP3 inflammasome activation by damping basal and lipopolysaccharide‐induced nuclear factor‐κB‐mediated up‐regulation of NLRP3 and interleukin‐1β during the priming step and basal and ATP/lipopolysaccharide‐induced ATP production, K⁺ efflux, and reactive oxygen species production during the activation step. Residues Y256/Y263 in the C‐terminal region of Tim‐3 are required for these inhibitory effects on the NLRP3 inflammasome. In mice with alum‐induced peritonitis, blockade of Tim‐3 exacerbates peritonitis by overcoming the inhibitory effect of Tim‐3 on NLRP3 inflammasome activation, while transgenic expression of Tim‐3 attenuates inflammation by inhibiting NLRP3 inflammasome activation. Our results show that Tim‐3 is a critical negative regulator of NLRP3 inflammasome and provides a potential target for intervention of diseases with uncontrolled inflammasome activation.