The NLRP3 inflammasome contributes to host protection during Sporothrix schenckii infection

Sporotrichosis is a mycosis caused by fungi from the Sporothrix schenckii species complex, whose prototypical member is Sporothrix schenckii sensu stricto. Pattern recognition receptors (PRRs) recognize and respond to pathogen‐associated molecular patterns (PAMPs) and shape the following adaptive immune response. A family of PRRs most frequently associated with fungal recognition is the nucleotide‐binding oligomerization domain‐like receptor (NLR). After PAMP recognition, NLR family pyrin domain‐containing 3 (NLRP3) binds to apoptosis‐associated speck‐like protein containing a caspase recruitment domain (ASC) and caspase‐1 to form the NLRP3 inflammasome. When activated, this complex promotes the maturation of the pro‐inflammatory cytokines interleukin‐1β (IL‐1β) and IL‐18 and cell death through pyroptosis. In this study, we aimed to evaluate the importance of the NLRP3 inflammasome in the outcome of S. schenckii infection using the following three different knockout (KO) mice: NLRP3^−/−, ASC^−/− and caspase‐1^−/−. All KO mice were more susceptible to infection than the wild‐type, suggesting that NLRP3‐triggered responses contribute to host protection during S. schenckii infection. Furthermore, the NLRP3 inflammasome appeared to be critical for the ex vivo release of IL‐1β, IL‐18 and IL‐17 but not interferon‐γ. Additionally, a role for the inflammasome in shaping the adaptive immune response was suggested by the lower frequencies of type 17 helper T (Th17) cells and Th1/Th17 but not Th1 cells in S. schenckii‐infected KO mice. Overall, our results indicate that the NLRP3 inflammasome links the innate recognition of S. schenckii to the adaptive immune response, so contributing to protection against this infection.     

Function of Nod-like receptors in microbial recognition and host defense

Summary:  Nucleotide oligomerization domain (NOD)-like receptors (NLRs) are a specialized group of intracellular proteins that play a critical role in the regulation of the host innate immune response. NLRs act as scaffolding proteins that assemble signaling platforms that trigger nuclear factor-κB and mitogen-activated protein kinase signaling pathways and control the activation of inflammatory caspases. Importantly, mutations in several members of the NLR family have been linked to a variety of inflammatory diseases consistent with these molecules playing an important role in host–pathogen interactions and the inflammatory response. In this review, we focus on the role of Nod1 and Nod2 in host defense and in particular discuss recent finding regarding the role of Nlrc4, Nlpr1, and Nlrp3 inflammasomes in caspase-1 activation and subsequent release of proinflammatory cytokines such as interleukin-1β.     

千金藤素通过抑制TLR4-NLRP3炎症小体及炎症因子治疗痛风性关节炎

[目的] 评价千金藤素的体内外抗炎效果，探讨其治疗痛风性关节炎的作用机制。[方法]采用噻唑蓝(3-(4，5-Dimethylthiazol-2-yl)-2，5-diphenyltet -razolium bromide，MTT)比色法检测千金藤素对RAW264.7巨噬细胞的活性抑制作用。采用酶联免疫吸附试验(enzyme linked immunosorbent assay，ELISA)检测千金藤素对肿瘤坏死因子-α(tumor necrosis factor-α，TNF-α)、白细胞介素-1β(interleukin-1β，IL-1β)和 IL-6分泌的影响。以免疫印迹法分别检测千金藤素对Toll样受体4(Toll-like receptor 4，TLR4)、髓样分化因子88(myeloid differentiation factor 88，MYD88)、NOD样受体蛋白3(NOD-like receptor protein 3，NLRP3)/凋亡相关微粒蛋白(apoptosis-associated speck-like protein containing a CARD，ASC)/半胱天冬酶-1(caspase-1)炎症小体的蛋白表达的影响。采用尿酸钠诱导SD大鼠关节炎模型，通过炎症指数以及TNF-α、IL-1β和IL-6炎症因子及TLR4-NLRP3相关蛋白的表达，评价千金藤素的体内抗炎作用。[结果] 千金藤素抑制RAW264.7细胞活力的半数抑制浓度(half maximal inhibitory concentration，IC50)为(62.51±5.36) μmol·L-1，弱于秋水仙碱(26.89±5.14) μmol·L-1。在RAW264.7细胞中，1～10 μmol·L-1千金藤素显著抑制尿酸钠晶体诱导的炎症因子TNF-α、IL-1β和IL-6的分泌与mRNA表达，也抑制了尿酸钠晶体诱导的TLR4、MYD88及NLRP3炎性小体的蛋白表达。在关节炎大鼠模型中，1～10 mg·kg-1千金藤素能够剂量依赖性地减轻关节肿胀，并抑制TNF-α、IL-1β和IL-6分泌及TLR4-NLRP3炎症小体的蛋白表达。[结论] 千金藤素可通过抑制炎症因子TNF-α、IL-1β和IL-6的表达，以及抑制尿酸钠介导的TLR4-NLRP3炎症小体的表达，发挥抗关节炎作用。     

Activation and Regulation of the Pattern Recognition Receptors in Obesity-Induced Adipose Tissue Inflammation and Insulin Resistance

Obesity-associated chronic tissue inflammation is a key contributing factor to type 2 diabetes mellitus, and a number of studies have clearly demonstrated that the immune system and metabolism are highly integrated. Recent advances in deciphering the various immune cells and signaling networks that link the immune and metabolic systems have contributed to our understanding of the pathogenesis of obesity-associated inflammation. Other recent studies have suggested that pattern recognition receptors in the innate immune system recognize various kinds of endogenous and exogenous ligands, and have a crucial role in initiating or promoting obesity-associated chronic inflammation. Importantly, these mediators act on insulin target cells or on insulin-producing cells impairing insulin sensitivity and its secretion. Here, we discuss how various pattern recognition receptors in the immune system underlie the etiology of obesity-associated inflammation and insulin resistance, with a particular focus on the TLR (Toll-like receptor) family protein Radioprotective 105 (RP105)/myeloid differentiation protein-1 (MD-1).     

Role of AIM2 inflammasome in inflammatory diseases,cancer and infection

AIM2 is a cytosolic innate immune receptor which recognizes double‐stranded DNA (dsDNA) released during cellular perturbation and pathogenic assault. AIM2 recognition of dsDNA leads to the assembly of a large multiprotein oligomeric complex termed the inflammasome. This inflammasome assembly leads to the secretion of bioactive interleukin‐1β (IL‐1β) and IL‐18 and induction of an inflammatory form of cell death called pyroptosis. Sensing of dsDNA by AIM2 in the cytosol is crucial to mediate protection against the invading pathogens including bacteria, virus, fungi and parasites. AIM2 also responds to dsDNA released from damaged host cells, resulting in the secretion of the effector cytokines thereby driving the progression of sterile inflammatory diseases such as skin disease, neuronal disease, chronic kidney disease, cardiovascular disease and diabetes. Additionally, the protection mediated by AIM2 in the development of colorectal cancer depends on its ability to regulate epithelial cell proliferation and gut microbiota in maintaining intestinal homeostasis independently of the effector cytokines. In this review, we will highlight the recent progress on the role of the AIM2 inflammasome as a guardian of cellular integrity in modulating chronic inflammatory diseases, cancer and infection.     

抵挡汤对糖尿病心肌病小鼠NLRP3炎症小体的作用及机制

目的 探讨不同剂量抵挡汤对糖尿病小鼠心肌炎性病变的影响。方法 选取60只C57BL/6J小鼠,随机分为正常组（10只）和模型组（50只）。模型组小鼠采用高脂饲料联合链脲佐菌素（STZ）腹腔注射制备糖尿病小鼠模型,模型制备成功后继续高脂饲料喂养,8周后采用超声成像平台检测小鼠心功能,出现心功能减退,则糖尿病心肌病小鼠造模成功,剔除未成模小鼠,最终成模小鼠40只,模型组小鼠按照心功能随机分为模型组、抵挡汤低、中、高（1.5,3,6 g·kg^-1）和辛伐他汀组（0.001 5 g·kg^-1）,每组8只。超声成像平台检测小鼠心功能,全自动生化仪检测小鼠空腹血糖（FBG）,甘油三酯（TG）,总胆固醇（TC）,苏木素-伊红（HE）染色观察心肌组织病理学改变,蛋白免疫印迹法（Western blot）检测心肌组织NOD样受体3（NLRP3）,硫氧还蛋白相互作用蛋白（TXNIP）,半胱氨酸的天冬氨酸蛋白水解酶-1（Caspase-1）,白细胞介素-1β（IL-1β）蛋白水平,检测心肌组织活性氧（ROS）含量。结果 与正常组比较,模型组的FBG,TC,TG的水平显著升高（P<0.01）,左室射血分数（EF）,左室短轴缩短率（FS）数值显著降低（P<0.01）,ROS表达明显升高（P<0.05）,心肌组织中NLRP3,TXNIP,Caspase-1,IL-1β表达明显升高（P<0.05）。与模型组比较,抵挡汤中、高剂量组及辛伐他汀组FBG,TC,TG水平明显降低（P<0.05）;抵挡汤各剂量组及辛伐他汀组EF,FS均有改善（P<0.05）,抵挡汤中剂量组变化更为明显（P<0.05）;HE染色结果发现,抵挡汤能够改善小鼠心肌组织病理学变化;抵挡汤各剂量组及辛伐他汀组小鼠ROS表达水平明显减少,抵挡汤中剂量组变化更为明显;抵挡汤各剂量组NLRP3,TXNIP,Caspase-1,IL-1β表达明显降低,抵挡汤中剂量降低心肌组织NLRP3,TXNIP,Caspase-1表达的效果更为明显;抵挡汤高剂量降低心肌组织IL-1β表达的效果更为明显。结论 抵挡汤可通过抑制NLRP3炎症小体的激活,改善糖尿病心肌病小鼠心肌炎性病变。     

Expression of NLRP3 inflammasome in the BSA-overloaded rats kidney

Objective To observe NLRP3 inflammasome expression and inflammatory cells infiltration in the BSA-overloaded rats kidney, and to investigate the potential mechanism of renal injury induced by proteinuria. Methods After unilateral right nephrectomy, eighteen healthy male Wistar rats were randomly divided into two groups: protein overload nephropathy model group (n=10), treated with intraperitoneal injections of bovine serum albumin (BSA); control group (n=8), treated with intraperitoneal injections of 0.9% saline for 9 weeks. Body weigh were measured every week and 24 h urine were collected in 0, 2, 5, 7, 9 week. The plasma levels of blood total protein (TP), albumin (Alb), serum creatinine (Scr) and blood urea nitrogen (BUN) were determined by automatic analyzers. Renal pathological changes were evaluated by PAS and Masson stains. Immunohistochemical staining was used to detect the expression of NLRP3, caspase-1, IL-1β, and IL-18, as well as the types of inflammatory cells. The NLRP3, caspase-1, IL-1β, and IL-18 protein and mRNA levels were also analyzed by Western blot and real-time PCR in two groups. Results It was found that there was a significant increase of proteinuria and BUN in model group compare to that in control group (all P＜0.05). However, there were no significant changes in body weight, TP, Alb and Scr between the two groups. Morphological study demonstrated that renal tubular epithelial cell injury, proteinaceous casts in tubular lumen, accompanying with the dominant macrophages and lymphocytes infiltration in interstitium in model group. The immunohistochemistry showed that there were more T (CD3+), B cells (CD20+) and macrophages (CD68+) in renal interstitium in model group than that in control group (P＜0.05). Tubulointerstitial injury score was higher than that of the control group (P＜0.05). Immunohistochemistry, Western blot and real-time PCR all showed that the expression of NLRP3, caspase-1, IL-18 and IL-1 β were significantly increased compared to those in control group (P＜0.05). Furthermore, there were significant correlations between proteinuria and IL-1β/IL-18 expression (P＜0.05). Conclusion NLRP3 inflammasome activation is involved in tubulointerstitial inflammation caused by proteinuria.