摘要
为研究生姜提取物(ginger extract,GE)对高温胁迫的影响及机制,建立秀丽隐杆线虫急性热应激(37 ℃)模型,测定了生姜对热应激下野生型线虫的寿命及运动状态、基因缺失株系的热应激寿命以及不同热应激程度下野生型线虫中与热休克反应相关基因的mRNA表达量。结果显示,相比于对照组(CK),30、60、120 μg/mL的GE处理组分别显著延长野生型线虫热应激寿命16.96%、18.73%、14.44%,显著改善热应激过程中(1 h、2 h、3 h)线虫的运动状态。GE介导的野生型线虫热应激寿命的延长依赖调控热休克反应(heat shock response,HSR)的转录因子hsf-1。GE的干预显著上调常温(20 ℃)下野生型线虫HSR相关基因hsf-1、hsp-90和hsp-16.2的mRNA表达水平以及HSP-16.2的蛋白表达水平。此外,在不同程度热应激(短暂热应激、持续热应激)状态下,GE对野生型线虫体内参与HSR相关基因的mRNA表达水平都具有调节作用。相比于常温(20 ℃),短暂热应激使野生型线虫hsf-1、hsp-16.2、hsp-70和hsp-90显著上调,而GE处理后显著下调;相比于常温(20 ℃),持续热应激使线虫HSR相关基因下调,而GE处理后hsp-16.2显著上调,并且hsf-1和hsp-90具有上调趋势,表明膳食补充GE在一定程度上可以使参与HSR相关基因的mRNA表达恢复至常态水平。以上结果表明,生姜提取物可通过调节HSR缓解秀丽隐杆线虫热胁迫。
持续的高温环境会打破机体的热平衡,破坏机体氧化还原稳态和蛋白质稳态,进一步导致肺、心、肾等器官损伤,甚至引发热相关疾病,如热痉挛、热射病
生姜(Zingiber officinale Roscoe),作为我国传统药食两用资源,具有解表散寒、温中止呕等功效。研究表明,生姜中主要的活性成分是一类具有辛辣味的非挥发性物质,具有3-甲氧基-4酚羟基苯基结构,统称为姜辣素类化合物。姜辣素类化合物赋予了生姜丰富的生物活性功能,能够调节机体代谢紊乱如降血
秀丽隐杆线虫(Caenorhabditis elegans)因其具有生命周期短、与人类基因有着40%的同源性以及3 000多株突变株系等优势,广泛用于药物开发以及食品成分的生物活性及分子机制的研
因此,本研究采用秀丽隐杆线虫模型,从生姜提取物调节HSR的角度探究其对机体应答热应激的作用机制,旨在进一步为生姜提取物缓解热胁迫提供一定的理论依据。
生姜(乙醇)提取物(ginger extract,GE)购自西安赛邦生物科技有限公司,生产批号为XASBSJ200825,生产日期为2020年8月25日。
一水合柠檬酸、一水合柠檬酸钾、EDTA、七水合硫酸亚铁、四水合氯化锰、七水合硫酸锌、五水合硫酸铜、十二水合磷酸氢二钠、氯化钠、磷酸二氢钾、磷酸氢二钾、无水氯化钙、七水合硫酸镁、氢氧化钠、次氯酸钠、无水乙醇、胆固醇、98%福林酚、葡萄糖、苯酚、浓硫酸、碳酸钠、亚硝酸钠、三氯化铝,国药集团化学试剂有限公司;没食子酸、香兰素、芦丁、考马斯亮蓝、牛血清白蛋白,上海源叶生物科技有限公司;二甲亚砜(dimethyl sulfoxide,DMSO),上海鼎国生物科技有限公司;总RNA提取试剂盒,北京艾德莱生物科技有限公司; cDNA反转录试剂盒、qPCR试剂盒SYBR® Premix Ex Taq™,日本TaKaRa Bio株式会社;正反引物,北京擎科生物科技有限公司。
野生型线虫株系N2和CL2070[(dvls70)hsp16.2::GFP]购自美国明尼苏达大学秀丽隐杆线虫遗传学中心(Caenorhabditis Genetics Center,CGC)。大肠埃希氏菌OP50(E. coli OP50)和PS3551[hsf-1(sy441)Ⅰ] 由西南医科大学罗怀荣教授惠赠。
1)姜辣素含量测定。参照孔繁东
2)总酚含量测定。采用福林-酚
3)总黄酮含量测定。采用亚硝酸钠-三氯化铝
4)总糖含量测定。采用苯酚-硫酸
5)总蛋白含量测定。采用考马斯亮蓝
试验所用线虫的传代和同步化过程以及缓冲液和培养基的配制,参考WormBook (http://www.wormbook.org/)。
1)试验所用线虫株系的传代。将所用的株系从已有大量线虫的线虫生长培养基(nematode growth medium,NGM)固体平板中切块转移到已涂布E. coli OP50的新的NGM板中,于20 ℃恒温培养箱培养。
2)试验所用线虫株系同步化。待线虫处于产卵期,用M9缓冲液(pH=7.4)冲洗到2 mL离心管中并离心(20 ℃,12 000 r/min,1 min)。离心后弃上清,再用M9缓冲液清洗并离心去上清,重复清洗3次。最后1次弃上清后,加入1 mL裂解液,手动震荡至虫体完全裂解后离心(20 ℃,12 000 r/min,1 min),离心后弃上清,用M9再清洗3次。最后1次离心结束后,弃上清,将离心管底部虫卵转移至涂有E. coli OP50的NGM板中,并放置20 ℃培养箱。根据株系及试验要求选择不同生长时期的幼虫进行试验。
将同步化至L4时期的野生型幼虫分别用0(0.1% DMSO作对照)、30、60、120、240、360和480 μg/mL GE在含有6 mg/mL灭活的E. coli OP50的S-Complete液体培养基中处理6 d。在成虫第5天,将药物处理后的线虫转移到新的含有M9 缓冲液的96孔板中,并对其进行热应激处理,温度为37 ℃。每隔2 h对其存活率进行记录,直至所有线虫死亡(当线虫对紫外线或强光照射没有反应时,则判定为死亡)。
对暴露于热应激下1、2、3 h的野生型线虫进行运动状态分析。线虫的培养和给药方式与热应激寿命试验中一致。在成虫第5天,将处理后的线虫转移到新的含有M9缓冲液的96孔板中,对其进行热应激处理并在热应激1、2、3 h后分别对其运动状态进行观察,并根据不同的运动状态分为ABC三类。具体是:A 类指线虫自发的进行余弦曲线运动;C类指线虫在受到紫外线或强光刺激下头部或尾部轻微摆动;B 类介于 A、C 之间的运动。
将同步化至 L1时期转基因株系 CL2070(HSP-16.2::GFP)线虫转移至含有6 mg/mL灭活的E. coli OP50的S-Complete液体培养基中,并分别加入终质量浓度为0(0.1% DMSO作对照)、30、60和120 μg/mL GE进行处理,于20 ℃孵育3 d。收集线虫,用 M9 缓冲液洗涤3次后置于载玻片上,用 50 mmol/L 叠氮化钠麻醉。利用倒置荧光显微镜对每个处理组的线虫(随机取30只)进行拍摄。通过 ImageJ (ImageJ Software,Bethesda,MD,USA) 计算CL2070线虫中HSP-16.2的蛋白平均荧光强度,以确定不同药物处理组其相对表达量。
将同步化至 L4时期的野生型线虫转移至含有6 mg/mL灭活的E. coli OP50的S-Complete液体培养基中,用60 μg/mL的 GE 处理,于20 ℃孵育3 d。收集线虫并用M9进行洗涤,随后进行热应激。瞬时热应激试验:将线虫在37 ℃下孵育15 min,再于20 ℃恢复30 min;持续热应激试验:将线虫在37 ℃下孵育60 min,再于20 ℃恢复30 min,随后进行研磨、RNA提
测定GE中姜辣素、总酚、总黄酮、总糖和总蛋白含量,对应标准品所得的标准曲线分别为Y=0.031X+0.0652(
采用野生型线虫N2株系评估不同浓度GE预处理下的热应激寿命,结果如

图1 GE作用下热胁迫野生型线虫的Kaplan-Meier生存曲线图(A)和运动状态变化图(B)
Fig. 1 Kaplan-Meier survival curve (A) and movement state changes (B) of wild-type worms under heat stress with treatment of GE
*P<0.05,**P<0.01表示与CK组比较差异显著或极显著。*P<0.05 and **P<0.01 indicated a significant or extremely significant difference compared to the CK group.
注: 同列中不同字母表示组间存在显著差异,P<0.05。Note:Different letters indicated significant differences between groups,P<0.05.
采用野生型线虫评估GE处理下热应激3 h期间的运动状态,如
采用hsf-1基因缺失株系PS3551进行热应激寿命试验,结果如

图2 GE作用下热胁迫hsf -1基因缺失线虫的Kaplan-Meier生存曲线图
Fig. 2 Kaplan-Meier survival curve of hsf -1 mutants under heat stress with treatment of GE
P>0.05表示与CK组比较无显著差异。P>0.05 indicated no significant difference compared with the CK group.
注: 同列中相同字母表示组间无显著差异,P>0.05。Note:The same letter indicated no significant differences between groups,P>0.05.
野生型线虫在GE处理后,其常温下(20 ℃)HSR相关基因的mRNA表达变化量如

图3 GE作用下野生型线虫hsf -1、hsp-16.2、hsp-70和hsp-90 mRNA表达量的变化(A)、HSP-16.2蛋白表达荧光图(B)及HSP-16.2蛋白表达量的变化(C)
Fig.3 Changes of hsf-1,hsp-16.2,hsp-70 and hsp-90 mRNA expression levels (A),HSP-16.2 protein expression fluorescence images (B) and HSP-16.2 protein expression changes in nematodes with treatment of GE (C)
** P<0.01,**** P<0.000 1,表示与CK组比较差异极显著。** P<0.01,**** P<0.000 1 indicated extremely significant difference compared to the CK group.
利用绿色荧光蛋白标记HSP-16.2的转基因株系CL2070,从蛋白表达水平分析GE对HSP-16.2的调节作用,结果如图
采用野生型线虫测定了GE处理后不同热应激程度HSR基因的表达变化量。

图4 GE作用下短暂热胁迫 (A) 和持续热胁迫(B) 野生型线虫hsf-1、hsp-16.2、hsp-70和hsp-90 mRNA表达量的变化
Fig.4 Changes of hsf-1,hsp-16.2,hsp-70 and hsp-90 mRNA expression in wild-type worms under transient heat stress (A) and persistent heat stress (B) with supplement of GE
**P<0.01,****P<0.000 1表示CK组与热应激模型组比较差异极显著,#### P<0.000 1表示GE处理组与热应激模型组比较差异极显著。**P<0.01,****P<0.000 1 indicated extremely significant difference between the CK group and the heat-stress group,#### P<0.000 1 indicated extremely significant difference between GE treatment group and the heat-stress group.
当机体处于高温环境时会出现非特异性应答反应,细胞内稳态、机体的生长代谢都会受到影响进而产生炎症反应,造成组织器官的损伤,甚至导致机体急性死亡。研究表明,许多植物化学成分具有增强机体耐热性的作
秀丽隐杆线虫中参与调节热应激的信号通路主要包括核激素受体途径、转化生长因子-β途径以及胰岛素信号通路,其中胰岛素信号通路研究的最为透
已有研究表明线虫机体内的应答保护机制在常态下处于基线水平,环境温度的改变将其激活以维持内稳态,稳态恢复后该调控途径恢复至基线水平。短暂的热应激可以提高机体对不良环境的抵抗,而持续的热应激使体内保护机制崩溃,从而造成机体内稳态失
本研究采用线虫模型评价了GE的耐热性,并围绕热休克反应途径探究了其对热应激的调控机制,后续仍需进一步确定GE中通过调节HSR发挥耐热性作用的主效成分,以及GE对热应激诱发机体内活性氧过量积累造成的氧化应激和热应激引发机体炎症造成组织器官损伤的影响。
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