Type I NKT‐cell‐mediated TNF‐α is a positive regulator of NLRP3 inflammasome priming

The NLRP3 inflammasome plays a crucial role in the innate immune response to pathogens and exogenous or endogenous danger signals. Its activity must be precisely and tightly regulated to generate tailored immune responses. However, the immune cell subsets and cytokines controlling NLRP3 inflammasome activity are still poorly understood. Here, we have shown a link between NKT‐cell‐mediated TNF‐α and NLRP3 inflammasome activity. The NLRP3 inflammasome in APCs was critical to potentiate NKT‐cell‐mediated immune responses, since C57BL/6 NLRP3 inflammasome‐deficient mice exhibited reduced responsiveness to α‐galactosylceramide. Importantly, NKT cells were found to act as regulators of NLRP3 inflammasome signaling, as NKT‐cell‐derived TNF‐α was required for optimal IL‐1β and IL‐18 production by myeloid cells in response to α‐galactosylceramide, by acting on the NLRP3 inflammasome priming step. Thus, NKT cells play a role in the positive regulation of NLRP3 inflammasome priming by mediating the production of TNF‐α, thus demonstrating another means by which NKT cells control early inflammation.     

IL-27在小鼠结肠炎中的作用及对NLRP3炎性小体的影响

目的:观察白细胞介素27(IL-27)对葡聚糖硫酸钠(DSS)诱导的结肠炎小鼠结肠组织学及NOD样受体蛋白3(NLRP3)炎性小体的影响。方法:将48只雄性C57BL/6小鼠随机分为正常对照组(自由进食饮水)、DSS模型组(饮用3%DSS溶液)、低剂量IL-27组和高剂量IL-27组(在饮用DSS溶液的基础上分别腹腔注射500ng和1μg IL-27)。12 d后行疾病活动指数(DAI)及组织损伤指数(HI)评分评估炎症程度,取结肠组织行免疫组化、Western blot及qPCR检测,取血清行ELISA检测IL-1β和IL-18水平。结果:与对照组相比,模型组的DAI评分和HI评分提示小鼠的结肠炎症明显增强(P0.05),NLRP3和IL-1β的mRNA表达水平增高,NLRP3和cleaved caspase-1的蛋白水平增高,血清中IL-1β和IL-18的含量增加;与模型组相比,高剂量IL-27组的DAI评分和HI评分提示小鼠的结肠炎症明显减轻(P0.05),NLRP3和IL-1β的mRNA表达水平下降,NLRP3和cleaved caspase-1的蛋白水平降低,血清中IL-1β中和IL-18的含量也减少;与模型组比较,低剂量IL-27组除了血清中IL-1β和IL-18含量减少外,上述各项指标的差异无统计学显著性。结论:IL-27可减轻DSS结肠炎模型小鼠的炎症程度并且可抑制NLRP3炎性小体的表达和激活。     

Impaired NLRP3 inflammasome activity during fetal development regulates IL‐1β production in human monocytes

Interleukin‐1β (IL‐1β) production is impaired in cord blood monocytes. However, the mechanism underlying this developmental attenuation remains unclear. Here, we analyzed the extent of variability within the Toll‐like receptor (TLR)/NLRP3 inflammasome pathways in human neonates. We show that immature low CD14 expressing/CD16^pos monocytes predominate before 33 weeks of gestation, and that these cells lack production of the pro‐IL‐1β precursor protein upon LPS stimulation. In contrast, high levels of pro‐IL‐1β are produced within high CD14 expressing monocytes, although these cells are unable to secrete mature IL‐1β. The lack of secreted IL‐1β in these monocytes parallels a reduction of NLRP3 induction following TLR stimulation resulting in a lack of caspase‐1 activity before 29 weeks of gestation, whereas expression of the apoptosis‐associated speck‐like protein containing a CARD and function of the P2×7 receptor are preserved. Our analyses also reveal a strong inhibitory effect of placental infection on LPS/ATP‐induced caspase‐1 activity in cord blood monocytes. Lastly, secretion of IL‐1β in preterm neonates is restored to adult levels during the neonatal period, indicating rapid maturation of these responses after birth. Collectively, our data highlight important developmental mechanisms regulating IL‐1β responses early in gestation, in part due to a downregulation of TLR‐mediated NLRP3 expression. Such mechanisms may serve to limit potentially damaging inflammatory responses in a developing fetus.     

TLR2 and the NLRP3 inflammasome mediate IL-1β production in Prevotella nigrescens-infected dendritic cells

Prevotella nigrescens is an oral pathogen that is frequently observed in the subgingival plaque of periodontitis patients. Interleukin-1β (IL-1β) is known to be involved in the immunopathology of periodontal diseases and has been implicated in the destruction of bone. In this study, we investigated the mechanism of IL-1β production by P. nigrescens in murine bone marrow-derived dendritic cells (BMDCs). Our results showed that a host receptor, Toll-like receptor 2 (TLR2), but not TLR4 is required for pro-IL-1β induction and nucleotide-binding oligomerization domain like receptor pyrin domain containing 3 (NLRP3) priming in BMDCs in response to P. nigrescens and activation of the NLRP3 inflammasome is necessary for processing of pro-IL-1β into mature IL-1β. In addition, an inhibitor assay revealed that production of reactive oxygen species, P2X₇R activity, and release of cathepsin B are involved in IL-1β production in BMDCs in response to P. nigrescens.     

Listeria monocytogenes is sensed by the NLRP3 and AIM2 inflammasome

The inflammasome pathway functions to regulate caspase‐1 activation in response to a broad range of stimuli. Caspase‐1 activation is required for the maturation of the pivotal pro‐inflammatory cytokines of the pro‐IL‐1β family. In addition, caspase‐1 activation leads to a certain type of cell death known as pyroptosis. Activation of the inflammasome has been shown to play a critical role in the recognition and containment of various microbial pathogens, including the intracellularly replicating Listeria monocytogenes; however, the inflammasome pathways activated during L. monocytogenes infection are only poorly defined. Here, we demonstrate that L. monocytogenes activates both the NLRP3 and the AIM2 inflammasome, with a predominant involvement of the AIM2 inflammasome. In addition, L. monocytogenes‐triggered cell death was diminished in the absence of both AIM2 and NLRP3, and is concomitant with increased intracellular replication of L. monocytogenes. Altogether, these data establish a role for DNA sensing through the AIM2 inflammasome in the detection of intracellularly replicating bacteria.     

Nrf2和HO-1在实验性自身免疫性脑脊髓炎大鼠脊髓中的动态表达及依达拉奉保护机制的研究

目的:探讨依达拉奉对实验性自身免疫性脑脊髓炎(Experimental autoimmuneen cephalomyelitis,EAE)大鼠的影响及作用机制。方法:应用豚鼠脊髓匀浆抗原(GPSCH)免疫Wistar大鼠建立EAE模型,随机分为对照组、EAE组、依达拉奉小剂量组、依达拉奉大剂量组及地塞米松组(DXM),比较各组不同时间点的发病率并进行神经功能评分,脊髓组织切片进行HE染色、三色染色观察病理变化,免疫组化染色观察Nrf2及血红素加氧酶(HO-1)表达。结果:依达拉奉大剂量组(8.33%)和DXM组(0%)的发病率均低于EAE组(58.3%)(P0.05);在发病高峰期时,依达拉奉大剂量组(0.32±1.10)、DXM组(0)各大鼠神经功能评分明显低于EAE组(2.06±2.01)及依达拉奉小剂量组(1.21±1.51)(P0.05);依达拉奉大剂量组(1.25±1.67)、DXM组(0)大鼠16天时脊髓组织内炎症细胞浸润形成的血管袖套数目明显低于EAE组(8.17±3.49)及依达拉奉小剂量组(7.67±4.37)(P0.05);依达拉奉大剂量组的轴突及髓鞘损伤程度较EAE组和依达拉奉小剂量组轻;与正常组比较,EAE组、依达拉奉小剂量组、依达拉奉大剂量组及DXM组大鼠的脊髓组织中Nrf2及HO-1表达均上调,依达拉奉大剂量组的表达数目最高,且与其他组比较差异具有统计学意义(P0.05)。结论:依达拉奉可以降低EAE大鼠的发病率,减轻发病时神经功能损伤的程度以及脊髓内炎性细胞浸润的程度,其神经保护作用可能是通过上调Nrf2及HO-1的表达,发挥抗氧化应激作用来实现的。     

Nrf2在EGCG诱导结肠肿瘤组织UGT1A及其同工酶表达中的作用

目的 探讨核因子E2p45相关因子2（Nrf2）在表没食子儿茶素没食子酸酯（EGCG）对结肠原位种植肿瘤中诱导尿苷二磷酸葡萄糖醛酸转移酶(UGT)及其同工酶表达中的作用机制。方法 运用RNAi技术建立Nrf2基因低表达的结肠癌细胞系HT-29,常规培养至对数生长期,在BALB/cA nude小鼠中建立皮下肿瘤模型,用皮下肿瘤构建裸鼠结肠原位肿瘤模型。分别用低、中、高剂量EGCG作用4周,实验结束后,剥离结肠原位肿瘤组织,用免疫组化检测其中Nrf2蛋白表达和RT-PCR法检测Nrf2、UGT1A、UGT1A8和UGT1A10基因的mRNA表达水平。结果 与对照组比较,不同剂量EGCG组的动物体重、对肿瘤生长的抑制率和Nrf2的蛋白水平均无显著性差异,Nrf2、UGT1A、UGT1A8 和 UGT1A10的mRNA水平无显著性差异。结论 Nrf2在EGCG诱导裸鼠结肠原位种植肿瘤UGT1A及其同工酶的表达中发挥着重要作用。     

硒对自身免疫性甲状腺炎大鼠Nrf2表达和甲状腺细胞凋亡的影响

目的探讨硒对自身免疫性甲状腺炎(autoimmune thyroiditis,AT)大鼠Nrf2表达的影响及凋亡机制。方法通过甲状腺球蛋白免疫诱导AT大鼠模型,同时给予亚硒酸钠灌胃治疗。TUNEL染色检测甲状腺细胞凋亡情况,免疫荧光染色检测甲状腺Nrf2的表达,Western blot检测Nrf2、Bcl-2、Bax蛋白表达,同时检测各组大鼠自身抗体TGAb、TMAb水平及组织匀浆中SOD活性、MDA含量。结果 AT大鼠经过硒处理后Nrf2、Bcl-2表达及SOD活性明显增加,而Bax表达、MDA含量、TGAb、TMAb水平明显降低(均为P<0.05)。结论通过补硒可显著激活AT大鼠甲状腺Nrf2的表达,降低氧化应激水平,抑制甲状腺细胞凋亡,提示Nrf2可能通过对抗氧化应激损伤进而保护AT大鼠受损的甲状腺细胞。     

The CDK domain of p21 is a suppressor of IL‐1β‐mediated inflammation in activated macrophages

Significant morbidity and mortality can be attributed to inflammatory diseases; therefore, a greater understanding of the mechanisms involved in the progression of inflammation is crucial. Here, we demonstrate that p21^(WAF1/CIP1), an established suppressor of cell cycle progression, is a inhibitor of IL‐1β synthesis in macrophages. Mice deficient in p21 (p21^?/?) display increased susceptibility to endotoxic shock, which is associated with increased serum levels of IL‐1β. Administration of IL‐1 receptor antagonist reduces LPS‐induced lethality in p21^?/? mice. Analysis of isolated macrophages, which are one of the central producers of IL‐1β, reveals that deficiency for p21 led to more IL‐1β mRNA and pro‐protein synthesis following TLR ligation. The increase in IL‐1β pro‐protein is associated with elevated secretion of active IL‐1β by p21^?/? macrophages. siRNA‐mediated knockdown of p21 in human macrophages results in increased IL‐1β secretion as well. A peptide mapping strategy shows that the cyclin‐dependent‐kinase (CDK)‐binding domain of p21 is sufficient to reduce the secretion of IL‐1β by p21^?/? macrophages. These data suggest a novel role for p21 and specifically for the CDK‐binding domain of p21^(WAF1/CIP1) in inhibiting inflammation.     

Ticagrelor inhibits the NLRP3 inflammasome to protect against inflammatory disease independent of the P2Y12 signaling pathway

Ticagrelor is the first reversibly binding oral P2Y₁₂ receptor antagonist to inhibit platelet activation and has been approved by the Food and Drug Administration for the treatment of coronary artery disease. At present, the other pharmacological functions of ticagrelor remain poorly understood. The NOD-, LRR-, and pyrin domain-containing protein 3 (NLRP3) inflammasome plays a critical role in the innate immune system, but its excessive activation also contributes to the pathogenesis of complex diseases. In this study, we systematically examined the effects of ticagrelor on the NLRP3 inflammasome and found that ticagrelor inhibits NLRP3 inflammasome activation in macrophages independent of its classic inhibitory effect on the P2Y₁₂ signaling pathway. Further mechanistic studies demonstrate that ticagrelor attenuates the oligomerization of apoptosis-associated speck-like protein containing a CARD (ASC) by blocking chloride efflux, an effect achieved through the degradation of chloride intracellular channel proteins (CLICs) and blockade of the translocation of CLICs to the plasma membrane. Moreover, experiments on lipopolysaccharide-induced sepsis and alum-induced peritonitis in mice confirmed that ticagrelor mitigates the severity of systemic inflammation independent of P2Y₁₂ receptor antagonism. Importantly, oral administration of ticagrelor rapidly and strongly inhibited NLRP3 inflammasome activation in peripheral blood mononuclear cells from patients with acute coronary syndrome. Overall, our study reveals a novel pharmacological function of ticagrelor in addition to its classic antiplatelet properties, which suggests that ticagrelor may serve as a potential therapeutic agent for use in NLRP3-associated diseases.     

NLRP3 inflammasome induced liver graft injury through activation of telomere‐independent RAP1/KC axis

Acute‐phase inflammation plays a critical role in liver graft injury. Inflammasomes, multi‐molecular complexes in the cytoplasm, are responsible for initiating inflammation. Here, we aimed to explore the role of inflammasomes in liver graft injury and further to investigate the regulatory mechanism. In a clinical liver transplant cohort, we found that intragraft expression of nucleotide‐binding oligomerization domain‐like receptor family pyrin domain containing 3 (NLRP3 ) inflammasomes was significantly up‐regulated post‐transplantation. Importantly, overexpression of NLRP3 was strongly associated with poor liver function characterized by high levels of ALT , AST , and urea, as well as neutrophil infiltration after transplantation. The significant correlation between NLRP3 and IL ‐1β mRNA levels led us to focus on one of the associated upstream regulators, telomere‐independent repressor activator protein 1 (RAP1 ), which was further proved to be co‐localized with NLRP3 in neutrophils. In the liver of a mouse model (hepatic ischaemia/reperfusion and hepatectomy model) and isolated neutrophils from RAP1 ^?/? mice, the expression levels of NLRP3 and keratinocyte chemoattractant (KC ) were significantly down‐regulated in contrast to those in wild types. The levels of ALT and AST , as well as the neutrophil infiltration, were also decreased by RAP1 deficiency. In our clinical validation, intragraft KC expression was associated with NLRP3 and co‐localized with RAP1 in neutrophils. Furthermore, NLRP3 inflammasomes were up‐regulated by recombinant KC in the isolated neutrophils and liver of the mouse model. Our data demonstrated that NLRP3 inflammasomes, activated by the RAP1 /KC axis, played a critical role in initiating inflammation during the early stage of liver graft injury. Targeting RAP1 /KC /NLRP3 inflammasomes may offer a new therapeutic strategy against liver graft injury. Copyright © 2017 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.     

MicroRNA-140在乳腺癌细胞中对Nrf2及其下游抗氧化基因的表达调控

目的 本研究旨在揭示microRNA在乳腺癌细胞中对Nrf2表达的影响.方法 利用生物信息学方法预测miR-140与Nrf2的结合位点,然后采用双荧光报告系统检测miR-140对Nrf2 3′UTR及启动子上的8×ARE区域活性的影响;同时以实时荧光定量PCR法和Western bloting法检测过表达miR-140和加药刺激前后细胞中Nrf2及其下游基因的mRNA和蛋白的表达变化;最后,四甲基偶氮唑蓝(MTT)法检测转染miR-140后,对于不同浓度H2O2处理的细胞,观察其生长能力及对氧化应激敏感性的变化.结果 过表达miR-140能够显著抑制Nrf2 3′UTR区域的表达(P =0.007)和启动子上ARE区域的活性(P=0.01);在过表达miR-140的对照组和加药组细胞中,Nrf2及其下游基因mRNA和蛋白水平均被明显抑制(均P＜0.05);MTT实验结果显示转染miR-140细胞活力受到抑制,同时再使用不同浓度的H2 02刺激细胞后,细胞对氧化应激的敏感性增加(P＜0.01).结论 Nrf2可能作为miR-140的一个新型靶基因,miR-140能够通过抑制Nrf2,进而影响其下游一系列抗氧化基因的表达.     

NLRP3 inflammasome mediates interleukin‐1β production in immune cells in response to Acinetobacter baumannii and contributes to pulmonary inflammation in mice

Acinetobacter baumannii is a multi‐drug resistant, Gram‐negative bacteria and infection with this organism is one of the major causes of mortality in intensive care units. Inflammasomes are multiprotein oligomers that include caspase‐1, and their activation is required for maturation of interleukin‐1β (IL‐1β). Inflammasome signalling is involved in host defences against various microbial infections, but the precise mechanism by which A. baumannii activates inflammasomes and the roles of relevant signals in host defence against pulmonary A. baumannii infection are unknown. Our results showed that NLRP3, ASC and caspase‐1, but not NLRC4, are required for A. baumannii‐induced production of IL‐1β in macrophages. An inhibitor assay revealed that various pathways, including P2X7R, K⁺ efflux, reactive oxygen species production and release of cathepsins, are involved in IL‐1β production in macrophages in response to A. baumannii. Interleukin‐1β production in bronchoalveolar lavage (BAL) fluid was impaired in NLRP3‐deficient and caspase‐1/11‐deficient mice infected with A. baumannii, compared with that in wild‐type (WT) mice. However, the bacterial loads in BAL fluid and lungs were comparable between WT and NLRP3‐deficient or caspase‐1/11‐deficient mice. The severity of lung pathology was reduced in NLRP3‐ deficient, caspase‐1/11‐ deficient and IL‐1‐receptor‐deficient mice, although the recruitment of immune cells and production of inflammatory cytokines and chemokines were not altered in these mice. These findings indicate that A. baumannii leads to the activation of NLRP3 inflammasome, which mediates IL‐1β production and lung pathology.     

TLR2‐independent induction and regulation of chronic intestinal inflammation

Interactions between the intestinal microflora and host innate immune receptors play a critical role in intestinal homeostasis. Several studies have shown that TLR2 can modulate inflammatory responses in the gut. TLR2 signals enhance tight junction formation and fortify the epithelial barrier, and may play a crucial role in driving acute inflammatory responses towards intestinal bacterial pathogens. In addition, TLR2 agonists can have direct effects on both Th1 cells and Treg. To define the role of TLR2 in the induction and regulation of chronic intestinal inflammation we examined the effects of TLR2 deletion on several complementary models of inflammatory bowel disease. Our results show that TLR2 signals are not required for the induction of chronic intestinal inflammation by either innate or adaptive immune responses. We further show that TLR2^?/? mice harbor normal numbers of Foxp3⁺ Treg that are able to suppress intestinal inflammation as effectively as their WT counterparts. We also did not find any intrinsic role for TLR2 for pathogenic effector T‐cell responses in the gut. Thus, in contrast to their role in acute intestinal inflammation and repair, TLR2 signals may have a limited impact on the induction and regulation of chronic intestinal inflammation.