何翰阳, 颜学勤, 温赛娴, 干李梦, 王琳琳, 王会丽,唐海杰, 潘锐, 付咏梅, 董军△
p62/NF-κB通路调控HIV-1 gp120 V3环所致小鼠神经炎症的机制研究*
何翰阳1, 颜学勤1, 温赛娴1, 干李梦1, 王琳琳1, 王会丽1,唐海杰1, 潘锐2, 付咏梅1, 董军1△
(1暨南大学基础医学与公共卫生学院病理生理学系,国家中医药管理局病理生理科研实验室,粤港澳中枢神经再生研究院,广东 广州 510632;2暨南大学附属第一医院骨科,广东 广州 510632)
探讨自噬关键蛋白p62在HIV-1 gp120 V3环所致小鼠神经炎症中的作用及相关信号分子机制。野生型C57BL6小鼠随机分成4组:空白组、假手术组(人工脑脊液组)、模型组(gp120 V3环组)及gp120 V3环+NF-κB活化阻滞剂BAY 11-7082组,每组12只。用Morris水迷宫检测小鼠学习记忆能力;免疫荧光染色检测海马和皮层Iba-1表达水平;ELISA法检测海马和皮层炎症因子的表达水平;Western blot检测海马和皮层相关蛋白表达水平。(1)Morris水迷宫结果显示,与空白组相比,模型组小鼠逃避潜伏期显著延长(<0.01),平台区域停留时间及穿越平台次数显著减少(<0.05);与模型组相比,gp120 V3环+BAY 11-7082组小鼠逃避潜伏期显著缩短(<0.01),平台区域停留时间及穿越平台次数显著增加(<0.05)。(2)免疫荧光染色结果显示,与空白组相比,模型组海马和皮层Iba-1荧光强度显著增强(0.05);与模型组相比,gp120 V3环+BAY 11-7082组海马和皮层Iba-1荧光强度显著降低(0.05)。(3)ELISA结果显示,与空白组相比,模型组IL-1β、TNF-α和IL-6水平均显著上调(<0.05);与模型组相比,gp120 V3环+BAY 11-7082组IL-1β、TNF-α和IL-6水平显著下调(<0.05)。(4)Western blot结果显示,与空白组相比,模型组p62蛋白表达水平显著上调(<0.01),p-p65/p65及p-IκB/IκB比值均显著升高(<0.01);与模型组相比,gp120 V3环+BAY 11-7082组p62蛋白显著下调(<0.05),p-p65/p65及p-IκB/IκB比值均显著下降(分别<0.01和<0.05)。HIV-1 gp120 V3环所致小鼠学习记忆功能障碍的机制可能与通过激活p62/NF-κB信号通路引起神经炎症有关,p62-NF-κB正反馈环的抑制可能会减轻神经炎症。
HIV相关神经认知障碍;HIV-1 gp120 V3环;p62/NF-κB信号通路;神经炎症
人类免疫缺陷病毒(human immunodeficiency virus, HIV)相关神经认知障碍(HIV-associated neurocognitive disorder, HAND)是HIV感染中枢神经系统(central nervous system, CNS)的直接表现[1],其特征是获得性认知功能缺损、记忆力、注意力、处理信息的速度及精细运动功能发生障碍[2]。据统计,HAND的发病率为30%~60%,且会随着患者年龄的增长而升高[3]。到目前为止,HAND仍然是HIV感染出现的严重并发症之一,且没有有效的防治方法。因此,阐明HAND的发病机制尤为迫切。
HIV进入CNS后,感染刺激小胶质细胞,使其释放具有神经毒性的炎症因子[4],引发神经炎症,损坏神经元。研究表明,HIV包膜上的gp120蛋白是参与HAND发病机制的关键蛋白[5],而其上的V3环是主要活性结构域。p62蛋白不仅是一种自噬的关键蛋白,还是一种多功能信号中枢。且值得注意的是,p62蛋白水平的降低可以减轻神经炎症[6]。核因子κB(nuclear factor kappa B, NF-κB)是细胞凋亡、死亡和炎症等过程的关键因子。已有研究表明,NF-κB信号通路的激活会促进神经炎症的发生发展[7],但p62与NF-κB信号通路在HAND中的作用尚未阐明。因此,本研究拟通过侧脑室注射HIV-1 gp120 V3环,观察小鼠发生神经认知功能障碍及其分子机制,并使用NF-κB活化阻滞剂,观察HIV-1 gp120 V3环致小鼠神经炎症反应中p62蛋白和NF-κB通路相关信号蛋白的表达情况,为HAND的防治提供实验依据。
1.1实验动物SPF级雌性野生型C57/BL6小鼠48只,8~10周龄,体重18~22 g,购自广州言诚公司,动物合格证编号为SCXK(京)2019-0010,编号:110324211104727252。小鼠在SPF环境下饲养,温度(22±2) ℃,湿度(55±5)%,光照12 h/黑暗12 h交替,自由饮水和摄食。实验动物分为4组:空白(blank)组、假手术(sham)组、模型(gp120 V3环)组和模型+阻滞剂(gp120 V3环+NF-κB活化阻滞剂BAY 11-7082)组,每组12只。实验程序通过暨南大学实验动物伦理委员会严格审查。
1.2主要试剂及仪器HIV-1 gp120 V3环粉末购自上海楚肽生物科技有限公司;NF-κB活化阻滞剂BAY 11-7082购自Selleck;小鼠白细胞介素1β(interleukin-1β, IL-1β)、肿瘤坏死因子α(tumor necrosis factor-α, TNF-α)及IL-6检测试剂盒均购自武汉云克隆科技股份有限公司。脑立体定位仪购自深圳市瑞沃德生命科技有限公司。
2.1小鼠分组及侧脑室注射
2.1.1小鼠分组空白组:不作任何处理;模型组:小鼠侧脑室注射5 μL的HIV-1 gp120 V3环溶液[1 mg HIV-1 gp120 V3环溶于1 mL人工脑脊液(artifical cerebrospinal fluid, ACSF)中,配成1 g/L的母液,吸取50 μL母液加入至2.45 mL ACSF中,配成100 ng/5 μL的注射液],每天1次,共3次;假手术组:小鼠侧脑室注射5 μL ACSF,每天1次,共3次;模型+阻滞剂组:小鼠在侧脑室注射5 μL HIV-1 gp120 V3环溶液前30 min腹腔注射1 mg/kg的BAY 11-7082(按0.2 mL/20 g注射,需把0.3 mg粉末溶于150 μL DMSO中,配成2 g/L母液,吸取150 μL母液加至2 850 μL ACSF中,配制成0.1 g/L的注射液),每天1次,共10次。实验模型和方法剂量参考相关文献[8-10]。
2.1.2小鼠侧脑室注射手术前,腹腔注射三溴乙醇麻醉小鼠(1.5 mL/kg),然后将其固定在脑立体定位仪上。小鼠头皮处消毒后切开,暴露前囟点,在前囟点向后0.2~0.5 mm中线左侧或右侧1.0 mm处钻孔,用微量注射器在颅骨以下2.5~3.0 mm处以0.5 μL/min进行侧脑室注射给药,注射完后留针10 min缓慢拔出,消毒缝合。
2.2Morris水迷宫实验本实验历时7 d。平台隐藏于水下,水温保持在21~22 ℃,水池划分为四个象限。为了排除个体差异对实验结果的影响,我们首先训练小鼠使它们学会游泳,并且能够学习记忆水池中周边的环境。根据每天每只小鼠的逃避潜伏期,评判小鼠的学习记忆能力,我们训练6 d,取最后两天小鼠在四个象限的平均值,作为小鼠的最终逃避潜伏期。第1~6天的定位航行实验检测小鼠学习能力:随机选择一象限将小鼠面向池壁放入水中,记录小鼠寻找并爬上平台所需时间(逃避潜伏期),并让小鼠在平台上休息30 s。如果小鼠在60 s内未找到平台,需将其引至平台,且同让休息30 s,这时潜伏期记录为60 s。第7天的空间探索实验检测小鼠记忆能力:撤去平台,在平台所在象限的对角象限的同一入水点,将小鼠面向池壁放入水中,在60 s内记录小鼠在平台区域的逗留时间和穿越平台的次数。
2.3免疫荧光法检测小鼠海马和皮层小胶质细胞活化情况4%多聚甲醛固定小鼠脑组织,石蜡包埋、切片。脱蜡、抗原修复,PBS漂洗3遍。室温封闭1 h,PBS漂洗3遍。滴加Ⅰ抗,4 ℃过夜。PBS漂洗3遍。滴加Ⅱ抗1.5 h,PBS漂洗3遍,每次10 min,滴加DAPI染液10 min。PBS漂洗3遍,滴加抗荧光淬灭剂,封片。在荧光显微镜下观察小胶质细胞活化情况。将所得荧光图片使用ImageJ软件进行分析。
2.4ELISA法检测小鼠海马和皮层组织炎症因子水平 冰上操作,取待测组织于遇冷的EP管内,加入1×PBS和钢珠匀浆,超声处理匀浆液至澄清,4 ℃离心5 min,弃沉淀,吸取上清液为待测样品。在酶标板上加入标准品、待测样本各100 μL,37 ℃温育1 h。弃去液体,甩干,加入检测溶液A工作液100 μL,37 ℃温育1 h。弃去液体,加入洗涤液,浸泡1~2 min,轻拍移除液体。加入检测溶液B工作液,37 ℃温育30 min,弃去液体,甩干,洗板5遍。加入TMB底物溶液,37 ℃避光显色20 min。加入终止液,在酶标仪450 nm波长测量各孔的吸光度()。
2.5Western blot实验取待测组织于预冷的EP管内,匀浆后4 ℃离心,吸取上清液。用BCA方法检测蛋白浓度,加入5×上样缓冲液调整统一蛋白浓度,煮沸变性。使用10%的SDS-PAGE分离蛋白,用湿转法将蛋白转移至PVDF膜上,TBST洗膜3遍。5%脱脂奶粉于室温封闭1 h,Ⅰ抗4 ℃孵育12~16 h,TBST洗膜3遍,Ⅱ抗室温孵育1 h,TBST洗膜3遍,将显影液均匀滴在膜上,化学发光,应用ImageJ软件分析发光图片的灰度值。
采用SPSS 22.0进行统计学分析。实验数据以均数±标准误(mean±SEM)表示。组间均数比较采用单因素方差分析(one-way ANOVA)及LSD-检验。以<0.05为差异有统计学意义。
在第1~6天定位航行实验中观察到:与空白组相比,在第5天和第6天,模型组小鼠逃避潜伏期显著延长(<0.01);与模型组相比,在第5天和第6天,模型+阻滞剂组小鼠逃避潜伏期显著缩短(<0.01),见图1。在第7天空间探索实验中观察到:与空白组相比,模型组小鼠穿越平台次数和在平台区域停留时间显著减少(<0.05);与模型组相比,模型+阻滞剂组小鼠穿越平台次数和在平台区域停留时间显著增多(<0.05),见图2。
Figure 1. The effect of NF-κB activation blocker on learning and memory impairment induced by HIV-1 gp120 V3 loop in mice was tested by positioning navigation experiment of Morris water maze. Mean±SEM. n=12. **P<0.01 vs blank group;##P<0.01 vs gp120 V3 loop group.
Figure 2. The effect of NF-κB activation blocker on learning and memory impairment induced by HIV-1 gp120 V3 loop in mice was tested by spatial probe test of Morris water maze. A: time in the target platform; B: number of crossing platform. Mean±SEM. n=12. *P<0.05 vs blank group;#P<0.05 vs gp120 V3 loop group.
与空白组相比,模型组小鼠海马和皮层区小胶质细胞活化增强,表现为细胞胞体增大,突起增粗,Iba-1荧光强度显著增强(<0.05或<0.01);与模型组相比,模型+阻滞剂小鼠海马和皮层区小胶质细胞胞体体积缩小,突起变细,Iba-1荧光强度显著降低(<0.05),见图3、4。
Figure 3. Observation of microglia activation and detection of Iba-1 (green) protein fluorescence intensity in the hippocampus. The scale bar=250 µm. Mean±SEM. n=6. *P<0.05 vs blank group;#P<0.05 vs gp120 V3 loop group.
Figure 4. Observation of microglia activation and detection of Iba-1 protein fluorescence intensity in the cortex. The scale bar=100 µm. Mean±SEM. n=6. **P<0.01 vs blank group;#P<0.05 vs gp120V3 loop group.
与空白组相比,模型组小鼠海马和皮层炎症因子TNF-α、IL-6和IL-1β水平显著升高(<0.05或<0.01);与模型组相比,模型+阻滞剂组小鼠海马和皮层炎症因子TNF-α、IL-6和IL-1β水平显著下降(<0.05,<0.01),见图5。
Figure 5. The effect of HIV-1 gp120 V3 loop on the expression levels of inflammatory factors in the hippocampus and cortex after NF-κB activation blocker treatment was detected by ELISA. A: the relative expression of IL-1β; B: the relative expression of TNF-α; C: the relative expression of IL-6. Mean±SEM. n=6. *P<0.05,**P<0.01 vs blank group;#P<0.05,##P<0.01 vs gp120 V3 loop group.
与空白组相比,模型组小鼠海马和皮层p62蛋白表达显著上调(<0.01),NF-κB通路激活,表现为磷酸化IκB蛋白与IκB蛋白比值显著上调(<0.01),磷酸化p65蛋白与p65蛋白比值显著上调(<0.01);与模型组相比,模型+阻滞剂组小鼠海马和皮层p62蛋白水平显著下调(<0.05),NF-κB通路的激活得到缓解,表现为磷酸化IκB蛋白与IκB蛋白比值显著下调(<0.05),磷酸化p65蛋白与p65蛋白比值显著下调(<0.01),见图6。
Figure 6. Western blot was used to detect the expression levels of p62 protein and NF-κB signaling pathway-related proteins. Mean±SEM. n=6. **P<0.01 vs blank group;#P<0.05,##P<0.01 vs gp120 V3 loop group.
HAND呈现典型的神经退行性疾病的特征,且从确诊HAND到死亡的平均时间仅为4.7个月。因此,阐明HAND的发病机制尤为迫切。
已有研究显示,HIV-1gp120是致神经元凋亡的关键蛋白,而其中的V3环是HIV-1 gp120发挥毒性的最主要的结构域[11]。本课题组前期研究结果显示,侧脑室注射HIV-1 gp120 V3环可致大鼠神经元凋亡及空间学习记忆障碍,但其具体机制尚未阐明[12]。因此,本研究拟根据课题组的前期研究工作和相关参考文献[8-9],观察侧脑室注射HIV-1 gp120 V3环致小鼠神经炎症及学习记忆功能障碍,并在此基础上探究HAND发病的分子机制。
小胶质细胞激活、分泌IL-1β和TNF-α等炎症细胞因子,作用于神经元,使神经元受损是HAND发生发展的主要病理生理过程;而自噬参与小胶质细胞的激活。有研究报道,LPS处理小胶质细胞24 h后,其自噬相关蛋白Beclin 1表达升高,表明在炎症反应下,小胶质细胞中自噬调控的分子和通路被激活[13]。我们课题组前期研究结果显示,加入自噬阻断剂3-甲基腺嘌呤后,HIV-1 gp120致BV2小胶质细胞炎症因子MCP-1和IL-1的表达水平下降,提示一定程度阻断自噬可减轻炎症反应[14]。另外,在LPS诱导的大鼠神经炎症中也检测到自噬关键蛋白p62大量上调[15]。Li等[16]观察到,冬凌草素可以通过下调p62蛋白的表达,减轻LPS介导的星形胶质细胞引起的神经炎症。Yao等[17]也报道了miR-124可通过抑制p62的表达,减轻帕金森病中神经炎症的发展。以上研究结果显示,自噬关键蛋白p62的上调在神经炎症中起着一定的促进作用。但是到目前为止,p62蛋白与HAND的关系仍未见报道,而本研究中我们观察到,侧脑室注射HIV-1 gp120V3环的小鼠海马和皮层中p62蛋白显著上调。
p62不仅是一种自噬关键蛋白,还是一种多功能信号中枢。它可以参与mTORC1、炎症和凋亡过程中NF-κB的激活。研究表明,NF-κB的活化促进神经炎症,Cui等[18]报道了中草药loganin通过调节TLR4/TRAF6/NF-κB轴减轻BV-2小胶质细胞发生Aβ1-42诱导的炎症反应。另外,已有研究报道,p62可以选择性地与肿瘤坏死因子受体相关因子6(TNF receptor-associated factor 6, TRAF6)相互作用,使NF-κB活化,形成p62-TRAF6复合体,导致NF-κB的激活[19]。值得注意的是,p62蛋白的上调激活NF-κB信号通路,NF-κB的活化也可以促进基因的转录,从而形成一个正反馈环,进一步促进了NF-κB通路的激活和炎症细胞因子的释放[20-21]。Zhong等[22]报道,在LPS刺激的巨噬细胞中检测到呈NF-κB活化依赖性的p62基因转录的激活。但目前p62与NF-κB激活在HAND中的具体机制仍未见报道。因此,本研究以此为切入点,探讨p62-NF-κB调控HIV-1 gp120 V3环所致小鼠神经炎症的具体机制。
在本研究中我们观察到,HIV-1 gp120 V3环致神经认知障碍小鼠的海马和皮层内p62蛋白表达显著上调,且NF-κB信号通路也显著激活。因此,我们推测HIV-1 gp120 V3环可能通过上调p62蛋白使NF-κB激活,而活化的NF-κB会进一步促进基因的转录,从而形成一个正反馈环,引发神经炎症损伤神经元,导致小鼠学习记忆障碍。随后我们使用了NF-κB活化阻滞剂进行验证,观察到与模型组相比,HIV-1 gp120 V3环+NF-κB活化阻滞剂组的小鼠学习记忆能力显著改善,小胶质细胞活化减轻和炎症因子水平显著下降。并且观察到,NF-κB信号通路的激活显著下调,从而导致p62蛋白表达水平也显著下调。以上结果显示,NF-κB活化阻滞剂的使用可能阻断了p62-NF-κB正反馈环,从而导致p62显著下降,减轻神经炎症,缓解HIV-1 gp120 V3环导致的小鼠学习记忆功能障碍。
综上所述,HIV-1 gp120 V3环所致小鼠学习记忆功能障碍可能与通过激活p62/NF-κB信号通路引起神经炎症有关;p62-NF-κB正反馈环的抑制可能会减轻神经炎症。本研究为HAND的防治提供了实验依据。
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Mechanism of p62/NF-κB pathway regulating HIV-1 gp120 V3 loop-induced neuroinflammation in mice
HE Han-yang1, YAN Xue-qin1, WEN Sai-xian1, GAN Li-meng1, WANG Lin-lin1, WANG Hui-li1, TANG Hai-jie1, PAN Rui2, FU Yong-mei1, DONG Jun1△
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To explore the role of autophagy key protein p62 in HIV-1 gp120 V3 loop-induced neuroinflammation in mice and its molecular mechanisms.Wild-type C57BL6 mice were randomly divided into 4 groups: blank group, sham group (artifical cerebrospinal fluid group), model group (gp120 V3 loop group) and gp120 V3 loop+NF-κB activation blocker BAY 11-7082 group, with 12 mice in each group. Learning and memory ability of the mice was detected by Morris water maze. The Iba-1 expression in the hippocampus and cortex was detected by immunofluorescence. The expression levels of inflammatory factors in the hippocampus and cortex were examined by ELISA. Protein expression levels in the hippocampus and cortex were examined by Western blot.The results of Morris water maze showed that compared with blank group, the escape latency of the mice in model group was significantly prolonged (<0.01), and the residence time in the target platform and the number of crossing the platform were significantly reduced (<0.05). Compared with model group, the escape latency of gp120 V3 loop+BAY 11-7082 group was significantly shortened, and the residence time in the target platform and the number of crossing the platform were significantly increased (<0.05). Immunofluorescence results showed that compared with blank group, the fluorescence intensity of Iba-1 in the hippocampus and cortex of the mice in model group was significantly up-regulated (<0.05), while that in gp120 V3 loop+BAY 11-7082 group was significantly down-regulated compared with model group (<0.05). ELISA results showed that compared with blank group, the levels of IL-1β, TNF-α and IL-6 in model group were significantly increased (<0.05), while those in gp120 V3 loop+BAY 11-7082 group were significantly lowered compared with model group (<0.01). Western blot showed that compared with blank group, the expression of p62 protein was significantly up-regulated (<0.01), and the NF-κB signaling pathway was activated in model group, indicated by the increases in the ratios of p-IκB/IκB and p-p65/p65 (<0.01). Compared with model group, the level of p62 protein was significantly down-regulated (<0.05), and the activation of the NF-κB signaling pathway was alleviated in gp120 V3 loop+BAY 11-7082 group, which was manifested as significant decreases in the ratio of p-IκB/IκB and p-p65/p65 (<0.01).HIV-1 gp120 V3 loop-induced learning and memory dysfunction in mice may be caused by neuroinflammation through activation of p62/NF-κB signaling pathway, and inhibition of the p62-NF-κB positive feedback loop may reduce neuroinflammation.
HIV-associated neurocognitive disorders; HIV-1 gp120 V3 loop; p62/NF-κB signaling pathway; Neuroinflammation
R363; R741
A
10.3969/j.issn.1000-4718.2022.06.003
1000-4718(2022)06-0978-08
2022-02-07
2022-05-24
国家自然科学基金资助项目(No. 81974185);广东省自然科学基金资助项目(No. 2019A1515012024; No. 2022A1515010268); 高等学校学科创新引智计划项目(No. B14036)
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