畜牧兽医学报  2022, Vol. 53 Issue (2): 618-627. DOI: 10.11843/j.issn.0366-6964.2022.02.028    PDF    
基于16S rDNA测序分析腹腔注射苦参碱的昆明小鼠肠道菌群结构
曹志刚1, 王弘2, 张华1, 孙盼盼3, 李宏全1, 孙耀贵1, 杨惠珍1, 王建中1, 尹伟1, 范阔海3, 孙娜1     
1. 山西农业大学动物医学学院, 太谷 030801;
2. 山西农业大学体育部, 太谷 030801;
3. 山西农业大学实验动物管理中心, 太谷 030801
摘要:旨在通过16S rDNA测序技术分析腹腔注射苦参碱的昆明小鼠肠道菌群的结构。本研究将20只昆明小鼠随机分为2组,分别是苦参碱组(MT组)和阴性对照组(NC组),连续腹腔给药5 d,每天给药2次,收集各组粪便和各肠段组织,进行β多样性、Lefse及Metastats分析,qPCR检测差异菌种在各肠段的mRNA表达量,通过KEGG分析肠道菌群变化导致的代谢途径差异。稀释曲线结果显示,所测样本数据足以反映样品中物种多样性;β多样性分析结果显示,苦参碱可以调节肠道菌群的结构,Lefse及Metastats分析结果均显示,苦参碱显著增加了拟杆菌门(Bacteroidetes)、拟杆菌目(Bacteroidales)、Muribaculaceae、益生菌嗜酸乳杆菌(Lactobacillus acidophilus)的丰度,而显著减少了厚壁菌门(Firmicutes)、瘤胃菌科(Ruminococcaceae)和脱硫弧菌属(Desulfovibrio)的丰度。与Lefse及Metastats分析结果一致,qPCR结果显示苦参碱组小鼠粪便中嗜酸乳杆菌含量增加。同时,苦参碱可以增强嗜酸乳杆菌在各肠段的定植。通过KEGG分析发现,NC与MT组之间在聚糖的生物合成与代谢、运输与分解代谢等代谢途径存在显著差异。本研究结果表明,腹腔注射苦参碱可以显著改变昆明小鼠肠道菌群的结构,增加有益菌嗜酸乳杆菌在肠道中的定植,并造成了聚糖生物合成与代谢、运输与分解代谢等代谢途径的差异,为进一步揭示苦参碱发挥药效作用的机理奠定了基础。
关键词苦参碱    昆明小鼠    肠道菌群    16S rDNA测序    嗜酸乳杆菌    
Influence of Matrine on Intestinal Flora of Kunming Mice through Intraperitoneal Injection Based on 16S rDNA Sequencing
CAO Zhigang1, WANG Hong2, ZHANG Hua1, SUN Panpan3, LI Hongquan1, SUN Yaogui1, YANG Huizhen1, WANG Jianzhong1, YIN Wei1, FAN Kuohai3, SUN Na1     
1. College of Veterinary Medicine, Shanxi Agricultural University, Taigu 030801, China;
2. Department of Physical Education, Shanxi Agricultural University, Taigu 030801, China;
3. Laboratory Animal Center, Shanxi Agricultural University, Taigu 030801, China
Abstract: The study aimed to analyse the structure of the intestinal flora of Kunming mice injected with matrine by 16S rDNA sequencing. Twenty Kunming mice were randomly divided into 2 groups named as matrine group (MT group) and negative control group (NC group). The intraperitoneal administration was administered twice a day for 5 days, the feces and intestinal tissues of each group were collected for β diversity, Lefse and Metastats analysis. qPCR was used to detect the mRNA expression of different strains in each intestinal segment, and KEGG was used to analyze the differences in metabolic pathways caused by the changes in intestinal flora. The rarefaction curve results showed that the measured sample data was sufficient to reflect the species diversity in the samples. The results of β diversity analysis showed that matrine regulated the structure of the intestinal flora. Lefse and Metastats analysis results showed that matrine significantly increased the abundance of Bacteroidetes, Bacteroidales, Muribaculaceae and probiotic Lactobacillus acidophilus, and significantly reduced the abundance of Firmicutes, Ruminococcaceae and Desulfovibrio. The qPCR results showed that the expression of Lactobacillus acidophilus in the feces of mice in the matrine group was increased, which was consistent with the results of Lefse and Metastats analysis. It was also found that matrine enhanced the colonization of Lactobacillus acidophilus in various segments of the intestine. KEGG analysis found that there were significant differences in metabolic pathways such as glycan biosynthesis and metabolism, transport and catabolism between NC and MT groups. The study results showed that matrine significantly changed the structure of the intestinal flora in mice, increase the colonization of probiotic Lactobacillus acidophilus in the intestine and caused the differences in metabolic pathways such as glycan biosynthesis and metabolism, transport and catabolism. These results have accumulated data for further study of the mechanism of matrine exerting its pharmacological effects.
Key words: matrine    Kunming mice    intestinal flora    16S rDNA sequencing    Lactobacillus acidophilus    

苦参碱(matrine,MT)具有抗炎[1-2]、抗氧化[3-4]、抗肿瘤[5-6]、镇痛[7]等药理作用,其治疗新冠肺炎的临床疗效已经得到了证实[8],且初步揭示了苦参碱通过TNF信号通路调控病毒复制、细胞凋亡以及炎症反应以发挥其抗病毒作用[9]。实验室前期研究发现,苦参碱具有抗脑心肌炎病毒(encephalomyocarditis virus,EMCV)[10]、猪圆环病毒(porcine circovirus type 2,PCV2)[11]、猪繁殖与呼吸综合征病毒(porcine reproductive and respiratory syndrome virus,PRRSV)[12]的作用。并对PRRSV/PCV2共感染诱发的间质性肺炎有缓解作用[13]

大量研究表明,肠道菌群与多种疾病密切相关,深刻影响着糖尿病[14-15]、肠道疾病[16]、炎症[17-18]和神经系统[19]等疾病的治疗与临床研究。研究结果表明,PCV2、PRRSV感染可以引起肠道菌群的改变[20-21]。Iddir等[22]研究发现,肠道菌群与新冠病毒诱发的炎症高度相关。李兰娟院士的“四抗二平衡”救治模式也证明了从肠道菌群治疗新冠肺炎的有效性[23]。PCV2、PRRSV及新冠病毒感染均可以导致肺部病变及腹泻等症状,中医脏腑理论有“肺与大肠相表里”、“肺病治肠”等说法,2018年,Mjösberg和Rao[24]提出了肠-肺轴理论,提示肠道菌群可能是苦参碱发挥药理作用的靶标。

因此本研究基于16S rDNA高通量测序技术,分析腹腔注射苦参碱的昆明小鼠肠道菌群的结构,为后续苦参碱的抗病毒、抗炎、缓解肺损伤等药理作用的研究及苦参碱的进一步开发利用奠定基础。

1 材料与方法 1.1 试验动物

清洁级昆明小鼠,雌性,体重18~22 g,购自北京维通利华实验动物技术有限公司,许可证号SCXK(京)2016-0006。动物试验遵循山西农业大学动物伦理委员会规定,试验动物饲养于山西农业大学实验动物管理中心(饲养环境温度:20~25 ℃,饲养环境相对湿度:40%~70%),许可证号SYXK(晋)2020-0003。

1.2 药物和试剂

苦参碱购买于南京泽朗生物科技有限公司,其纯度为98.7%;2×SYBR Green qPCR Master Mix(Low ROX,Biotool,美国)。

1.3 试验设计

将20只昆明小鼠随机分为2组,每组10只,分别是阴性对照组(NC组)和苦参碱组(MT组),适应性饲养1周后,按照0.02 mL·g-1剂量,腹腔注射40 mg·kg-1的苦参碱,连续给药5 d,每日2次。NC组等剂量腹腔注射生理盐水。给药第6天,收集各组粪便及各肠段组织,粪便样品进行16S rDNA肠道菌群结构谱测序分析。提取各肠段组织总RNA,利用qPCR技术测定差异菌种的表达量。

1.4 小鼠粪便及肠道组织的收集

给药第6天,对小鼠腹部按摩,促使其排便,迅速将粪便收集至无菌管中,液氮速冻后-80 ℃保存,干冰运输;按照山西农业大学动物伦理委员会规定,解剖小鼠,分别将各肠段组织收集至对应的冻存管,液氮速冻后-80 ℃保存。

1.5 16S rDNA肠道菌群结构谱测序分析

16S rDNA肠道菌群结构谱测序分析基于Illumina HiSeq测序平台,利用双末端测序(Paired-End)的方法,构建小片段文库进行测序。通过对原始测序序列进行过滤、双端拼接,得到优化序列(Tags)。将优化序列进行聚类,划分OTU,并根据OTU的序列组成得到其物种分类;基于OTU分析结果,进一步进行α多样性分析(alpha diversity)、β多样性分析(beta diversity)和显著物种差异分析等,可以挖掘样品之间的差异。

稀释曲线是α多样性分析的其中一种,可以衡量所测样本数据量是否充足,以反映样品中的物种多样性。使用QIIME软件进行β多样性分析,通过β多样性分析可以比较不同样品在物种多样性方面存在的相似程度。ANOSIM分析是β多样性分析的一种,ANOSIM分析通过4种不同算法计算样本间β多样性的距离,其中Unweighted unifrac与Jaccard是非加权算法,Weighted unifrac与Bray-curtis是加权算法,非加权算法反映的是物种的有无,而加权算法不仅考虑物种的有无,而且考虑物种的丰度。通过Lefse(Line Discriminant Analysis (LDA) Effect Size)分析在不同组间寻找具有统计学差异的标记性质物种,本试验中设定筛选标准为|LDA score|>4。Metastats分析通过Metastats软件对组间的物种丰度数据进行t检验,KEGG分析通过PICRUSt软件完成。扩增所用引物为细菌16S rDNA (V3+V4)区域引物:338F:5′- ACTCCTACGGGAGGCAGCA-3′,806R:5′- GGACTAC-HVGGGTWTCTAAT-3′,DNA提取、PCR扩增及测序均由百迈客生物技术公司协作完成。

1.6 qPCR检测嗜酸乳杆菌在各肠段的表达量

利用SYBR Green Ⅰ实时荧光定量PCR相对定量法验证测序结果,选用β-actin作为内参基因,目的基因引物和内参基因引物序列如下:嗜酸乳杆菌F:5′-GAAAGAGCCCAAACCAAGTGATT-3′,嗜酸乳杆菌R:5′-CTTCCCAGATAATTCAA-CTATCGCTTA-3′;β-actin F:5′-AGGGAAATC-GTGCGTGACAT-3′,β-actin R:5′-GGAAAA-GAGCCTCAGGGCAT-3′。qPCR反应采用ABI 7500 Real-Time PCR系统,采用20 μL体系:F-Primer 1 μL,R-Primer 1 μL,Template≤100 ng,2×SYBR Green qPCR Master Mix with ROX 10 μL,H2O补至20 μL,按照两步法PCR扩增标准程序进行试验。然后经过95 ℃ 15 s,60 ℃ 1 min,95 ℃ 30 s及60 ℃ 15 s进行熔解曲线分析。嗜酸乳杆菌基因相对表达量的计算是根据内参基因和目的基因的CT值,采用2-△△CT法进行计算。

1.7 统计分析

16S rDNA肠道菌群结构谱测序数据基于Illumina HiSeq测序平台分析所得。所有数据以“平均值±标准差”表示,通过Graphpad Prism 5.0软件处理,采用t检验进行组间差异性分析,分析结果以P<0.05表示为差异显著,以P<0.01表示为差异极显著。

2 结果 2.1 稀释曲线衡量测序数据量

稀释曲线结果显示,MT、NC组的稀释曲线均逐渐平缓,表明肠道中的物种并不会随测序数量的增加而增加,本试验中所测的样本数量足以反映样本的菌群特征(图 1)。

图 1 稀释曲线衡量测序数据量 Fig. 1 Rarefaction curve measures the amount of sequencing data
2.2 苦参碱调节小鼠肠道菌群结构

ANOSIM分析结果显示,通过加权算法所得P值均小于0.01,通过非加权算法所得P值均大于0.05(表 1),该结果表明,苦参碱可以对肠道菌群物种丰度造成显著影响(P<0.01)。

表 1 苦参碱对小鼠肠道菌群β多样性的影响 Table 1 Effects of matrine on β diversity of intestinal flora in mice
2.3 苦参碱对小鼠肠道菌群丰度的影响

Lefse分析结果显示,苦参碱显著增加了拟杆菌门(Bacteroidetes)、拟杆菌纲(Bacteroidia)、拟杆菌目(Bacteroidales)、Muribaculaceae、ML635 J 40 aquatic group、嗜酸乳杆菌(Lactobacillus acidophilus)的丰度,而显著减少了厚壁菌门(Firmicutes)、梭菌纲(Clostridia)、梭菌目(Clostridiales)、瘤胃菌科(Ruminococcaceae)和脱硫弧菌属(Desulfovibrio)的丰度(图 2)。

图 2 苦参碱对小鼠肠道菌群物种的影响 Fig. 2 Effects of matrine on the species of intestinal flora in mice
2.4 Metastats分析苦参碱对小鼠肠道菌群的影响

为了进一步分析苦参碱对肠道菌群物种丰度的影响,分别从门、纲、目、科、属、种水平对各组进行Metastats分析,结果显示,苦参碱显著增加了拟杆菌门(Bacteroidetes)(P < 0.01)、拟杆菌纲(Bacteroidia)(P < 0.01)、拟杆菌目(Bacteroidales)(P < 0.01)、Muribaculaceae(P < 0.01)、Faecalibaculum(P < 0.01)、杜氏杆菌属(Dubosiella)(P < 0.01)、Muribaculum(P < 0.05)、嗜酸乳杆菌(Lactobacillus acidophilus)(P < 0.05)的丰度;苦参碱显著减少了厚壁菌门(Firmicutes)(P < 0.05)、变形菌门(Proteobacteria)(P < 0.05)、梭菌纲(Clostridia)(P < 0.05)、梭菌目(Clostridiales)(P < 0.05)、瘤胃菌科(Ruminococcaceae)(P < 0.05)、Marvinbryantia(P < 0.05)、脱硫弧菌属(Desulfovibrio)(P < 0.05)的丰度(表 2)。

表 2 NC与MT组存在显著差异的菌属 Table 2 Bacterias with significant differences between NC and MT groups
2.5 苦参碱促进嗜酸乳杆菌在各肠段的定植

qPCR结果显示(图 3),与NC组相比,MT组十二指肠、空肠、回肠、盲肠、结肠、直肠及粪便中嗜酸乳杆菌基因相对表达量均显著增加(P < 0.05),该结果与Lefse及Metastats分析结果一致,且进一步发现苦参碱可以增强嗜酸乳杆菌在各肠段的定植。

A. 十二指肠嗜酸乳杆菌相对表达量;B. 空肠嗜酸乳杆菌相对表达量;C. 回肠嗜酸乳杆菌相对表达量;D. 盲肠嗜酸乳杆菌相对表达量;E. 结肠嗜酸乳杆菌相对表达量;F. 直肠嗜酸乳杆菌相对表达量;G. 粪便嗜酸乳杆菌相对表达量。*. P<0.05;**. P<0.01;***. P<0.001 A. Relative expression of Lactobacillus acidophilus in the duodenum; B. Relative expression of Lactobacillus acidophilus in the jejunum; C. Relative expression of Lactobacillus acidophilus in the ileum; D. Relative expression of Lactobacillus acidophilus in the cecum; E. Relative expression of Lactobacillus acidophilus in the colon; F. Relative expression of Lactobacillus acidophilus in the rectum; G. Relative expression of Lactobacillus acidophilus in the feces. *. P < 0.05; **. P < 0.01; ***. P < 0.001 图 3 苦参碱对嗜酸乳杆菌基因相对表达量的影响 Fig. 3 Effect of matrine on relative expression of Lactobacillus acidophilus genes
2.6 KEGG分析苦参碱对代谢途径的影响

基于上述肠道菌群结构的改变,通过KEGG预测分析两组之间代谢途径的差异,观测两组样品之间微生物群落的功能基因在代谢途径上的差异和变化。结果显示,NC组与MT组肠道微生物测序信息均被映射到氨基酸代谢、内分泌系统及免疫疾病等39个代谢途径(图 4),通过比对分析发现MT组的聚糖生物合成与代谢、运输与分解代谢、其他氨基酸代谢水平显著高于NC组(P<0.05),MT组的异生素生物降解与代谢、脂质代谢与信号转导、碳水化合物代谢水平显著低于NC组(P<0.05)(图 5)。

图 4 NC与MT组代谢通路组成柱状图 Fig. 4 Histogram of the composition of NC and MT groups metabolic pathways
图 5 NC与MT组差异代谢通路柱状图 Fig. 5 Histogram of the difference between NC and MT groups metabolic pathways
3 讨论

通过β多样性、Lefse及Metastats分析,发现腹腔注射苦参碱显著增加了拟杆菌门(Bacteroidetes)、拟杆菌目(Bacteroidales)、Muribaculaceae、Faecalibaculum和嗜酸乳杆菌(Lactobacillus acidophilus)的丰度,而显著降低了厚壁菌门(Firmicutes)、瘤胃菌科(Ruminococcaceae)和脱硫弧菌属(Desulfovibrio)等的丰度,说明苦参碱对昆明小鼠肠道菌群结构有调控作用。

研究表明,拟杆菌门(Bacteroidetes)可以抑制致病菌在肠道的定植[25]及增强宿主对病毒的抵抗力[26];拟杆菌目(Bacteroidales)对于保证肠道屏障的完整性至关重要,肠道屏障的完整性是其发挥防御作用的基础[27],Muribaculaceae通过对单糖的竞争利用,可抑制同样需要单糖的肠道致病菌[28]Faecalibaculum在结直肠癌小鼠模型中具有抗肿瘤的作用[29]。Chen等[30]研究发现,益生元长链菊粉可以调整肠道菌群结构,与苦参碱类似,长链菊粉可以抑制厚壁菌门/拟杆菌门的比值,增加乳酸杆菌等有益菌,从而改善肠道屏障功能。瘤胃菌科(Ruminococcaceae)与脱硫弧菌属(Desulfovibrio)均与机体的炎症反应相关,瘤胃菌科(Ruminococcaceae)丰度降低可以抑制炎症反应[31],而脱硫弧菌属(Desulfovibrio)丰度增加是溃疡性结肠炎疾病的一个重要特征[32]。综上,苦参碱可通过改变肠道菌群的结构,增强小鼠肠道菌群抗病毒、抗炎、抑制致病菌等方面的功能。

嗜酸乳杆菌是肠道最重要的益生菌之一,研究表明,嗜酸乳杆菌可促进肠道紧密连接蛋白Occludin的表达[33],口服乳杆菌可以保护宿主动物免受流感病毒感染,增强机体抗病毒免疫反应[34-35],同时,乳杆菌可以缓解病毒感染引起的肺炎等一般临床症状[36-38]。在抗肿瘤[39-40]、抗氧化[41-42]等方面乳杆菌也有显著效果。综上,苦参碱通过增加小鼠肠道菌群中嗜酸乳杆菌的丰度,增强其在各肠段的定植能力,继而发挥抗病毒、抗肺炎、抗氧化、抗肿瘤等药理作用。

“肺与大肠相表里”最早出自《灵枢·本输》:“肺合大肠,肠者,传导之腑”。这一理论立足于中医“脏腑理论”,对新冠病毒等疾病的防控具有重要意义。本试验中,苦参碱导致了嗜酸乳杆菌(Lactobacillus acidophilus)等具有抗肺炎、抗肿瘤、抗氧化功能肠道菌群的增多,基于“肺与大肠相表里”理论,肠道菌群结构的改变会导致肺变化,因此推测,苦参碱可能通过改变肠道菌群继而发挥抗肺炎等药理作用。

通过腹腔注射给予苦参碱,苦参碱并未与肠道菌群直接接触,但其仍然可以对肠道菌群造成影响,推测苦参碱可能通过对机体代谢水平造成影响进而改变机体肠道菌群,后续将对苦参碱影响肠道菌群的机理进一步探究。综上所述,苦参碱可以改变昆明小鼠肠道菌群的结构,增强有益菌嗜酸乳杆菌在各肠段的定植,并造成代谢途径的差异,且苦参碱抗炎、抗氧化、抗肿瘤等药理作用的发挥可能与其对肠道菌群的影响有关。

4 结论

腹腔注射苦参碱可以显著改变昆明小鼠肠道菌群的结构,增加有益菌嗜酸乳杆菌(Lactobacillus acidophilus)在肠道中的定植,并造成了聚糖生物合成与代谢、运输与分解代谢等代谢途径的差异,为进一步揭示苦参碱发挥药效作用的机理奠定了基础。

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(编辑   郭云雁)