The redox state of the alarmin HMGB1 is a pivotal factor in neuroinflammatory and microglial priming: A role for the NLRP3 inflammasome.
The redox state of the alarmin HMGB1 is a pivotal factor in neuroinflammatory and microglial priming: A role for the NLRP3 inflammasome.
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DOI：
10.1016/j.bbi.2015.10.009
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发表时间：
2016-07
期刊：
影响因子：
--
通讯作者：
Maier SF
中科院分区：
文献类型：
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作者：
Frank MG;Weber MD;Fonken LK;Hershman SA;Watkins LR;Maier SF
Alarmin高迁移率族蛋白-1（HMGB 1）被认为是介导神经炎症过程的关键因子。最近的研究结果表明，HMGB 1的氧化还原状态是HMGB 1的关键分子特征，使得还原形式（fr-HMGB 1）是趋化性的，而二硫化物形式（ds-HMGB 1）是促炎性的。本研究检查了这些分子形式的神经炎症作用以及这些形式引发神经炎症和小胶质细胞对免疫挑战的反应的能力。为了检查这些分子形式在体内的神经炎性作用，向动物小脑延髓池（ICM）内施用单剂量的fr-HMGB 1（10 μg）、ds-HMGB 1（10 μg）或媒介物，并在海马中注射后2和24小时测量基础促炎作用。初步实验结果表明，ds-HMGB 1在注射后2 h（NF-κBIα mRNA、NLRP 3 mRNA和IL-1β蛋白）和24 h（NF-κBIα mRNA、TNFα mRNA和NLRP 3蛋白）增加海马促炎介质。fr-HMGB 1对这些介质没有影响。ds-HMGB 1的这些神经炎症作用表明ds-HMGB 1可能具有引发后续免疫挑战的神经炎症反应的功能。为了评估这些分子形式的神经炎症引发效应，向动物ICM给予单剂量的fr-HMGB 1（10 µg）、ds-HMGB 1（10 µg）或溶剂，注射后24小时，用LPS（10 µg/kg IP）或溶剂攻击动物。免疫激发后2 h测定神经炎症介质和疾病反应（注射后3、8和24 h）。结果发现，ds-HMGB 1可增强LPS诱导的神经炎症反应（NF-κBIα mRNA、TNFα mRNA、IL-1β mRNA、IL-6 mRNA、NLRP 3 mRNA和IL-1β蛋白）和疾病反应（减少社会探索）。fr-HMGB 1不能增强对LPS的神经炎症反应。为了检查这些分子形式的HMGB 1是否在分离的小胶质细胞中直接诱导神经炎性作用，分离全脑小胶质细胞并用fr-HMGB 1（0、1、10、100或1000 ng/ml）或ds-HMGB 1（0、1、10、100或1000 ng/ml）处理4小时，并测量促炎介质。为了评估这些分子形式对小胶质细胞引发的影响，将全脑小胶质细胞预先暴露于这些形式的HMGB 1（0、1、10、100或1000 ng/ml），随后用LPS（10 ng/ml）攻击。结果发现，ds-HMGB 1可增加小胶质细胞NF-κBIα mRNA和NLRP 3 mRNA的表达，增强小胶质细胞对LPS的促炎反应（TNFα mRNA、IL-1β mRNA和IL-1β蛋白）。fr-HMGB 1不能增强小胶质细胞对LPS的促炎反应。与先前的报道一致，本研究结果表明，HMGB 1的二硫键形式不仅增强了体内对随后免疫攻击的神经炎症反应，而且增强了对该攻击的疾病反应。此外，本研究结果首次证明，ds-HMGB 1直接增强小胶质细胞对免疫攻击的促炎反应，这一发现与ds-HMGB 1在体内的作用相似。此外，在体内和体外，ds-HMGB 1诱导NLRP 3和NF-κBIα的表达，提示NLRP 3炎性小体可能在ds-HMGB 1的启动效应中发挥作用。综上所述，本研究结果表明，HMGB 1的氧化还原状态是HMGB 1的引发特性的关键决定因素，使得HMGB 1的二硫键形式在CNS中诱导引发的免疫表型，这可能导致在暴露于随后的促炎刺激后加剧的神经炎症反应。
The alarmin high mobility group box-1 (HMGB1) has been implicated as a key factor mediating neuroinflammatory processes. Recent findings suggest that the redox state of HMGB1 is a critical molecular feature of HMGB1 such that the reduced form (fr-HMGB1) is chemotactic, while the disulfide form (ds-HMGB1) is pro-inflammatory. The present study examined the neuroinflammatory effects of these molecular forms as well as the ability of these forms to prime the neuroinflammatory and microglial response to an immune challenge. To examine the neuroinflammatory effects of these molecular forms in vivo, animals were administered intra-cisterna magna (ICM) a single dose of fr-HMGB1 (10 µg), ds-HMGB1 (10 µg) or vehicle and basal pro-inflammatory effects were measured 2 and 24h post-injection in hippocampus. Results of this initial experiment demonstrated that ds-HMGB1 increased hippocampal pro-inflammatory mediators at 2h (NF-κBIα mRNA, NLRP3 mRNA and IL-1β protein) and 24h (NF-κBIα mRNA, TNFα mRNA, and NLRP3 protein) after injection. fr-HMGB1 had no effect on these mediators. These neuroinflammatory effects of ds-HMGB1 suggested that ds-HMGB1 may function to prime the neuroinflammatory response to a subsequent immune challenge. To assess the neuroinflammatory priming effects of these molecular forms, animals were administered ICM a single dose of fr-HMGB1 (10 µg), ds-HMGB1 (10 µg) or vehicle and 24h after injection, animals were challenged with LPS (10 µg/kg IP) or vehicle. Neuroinflammatory mediators and the sickness response (3, 8 and 24h after injection) were measured 2h after immune challenge. We found that ds-HMGB1 potentiated the neuroinflammatory (NF-κBIα mRNA, TNFα mRNA, IL-1β mRNA, IL-6 mRNA, NLRP3 mRNA and IL-1β protein) and sickness response (reduced social exploration) to LPS challenge. fr-HMGB1 failed to potentiate the neuroinflammatory response to LPS. To examine whether these molecular forms of HMGB1 directly induce neuroinflammatory effects in isolated microglia, whole brain microglia were isolated and treated with fr-HMGB1 (0, 1, 10, 100, or 1000 ng/ml) or ds-HMGB1 (0, 1, 10, 100, or 1000 ng/ml) for 4h and pro-inflammatory mediators measured. To assess the effects of these molecular forms on microglia priming, whole brain microglia were pre-exposed to these forms of HMGB1 (0, 1, 10, 100, or 1000 ng/ml) and subsequently challenged with LPS (10 ng/ml). We found that ds-HMGB1 increased expression of NF-κBIα mRNA and NLRP3 mRNA in isolated microglia, and potentiated the microglial pro-inflammatory response (TNFα mRNA, IL-1β mRNA and IL-1β protein) to LPS. fr-HMGB1 failed to potentiate the microglial pro-inflammatory response to LPS. Consistent with prior reports, the present findings demonstrate that the disulfide form of HMGB1 not only potentiates the neuroinflammatory response to a subsequent immune challenge in vivo, but also potentiates the sickness response to that challenge. Moreover, the present findings demonstrate for the first time that ds-HMGB1 directly potentiates the microglia pro-inflammatory response to an immune challenge, a finding that parallels the effects of ds-HMGB1 in vivo. In addition, ds-HMGB1 induced expression of NLRP3 and NF-κBIα in vivo and in vitro suggesting that the NLRP3 inflammasome may play role in the priming effects of ds-HMGB1. Taken together, the present results suggest that the redox state of HMGB1 is a critical determinant of the priming properties of HMGB1 such that the disulfide form of HMGB1 induces a primed immunophenotype in the CNS, which may result in an exacerbated neuroinflammatory response upon exposure to a subsequent pro-inflammatory stimulus.