摘要
为进一步明晰黄芩苷(BCN)对脂多糖(LPS)诱导的小鼠炎症损伤的缓解作用机制,采用体内体外试验结合,体外试验采用LPS建立RAW264.7细胞炎症模型,测定细胞吞噬能力、一氧化氮释放、炎症细胞因子及TGF⁃β/SMAD2通路相关mRNA表达;体内试验采用不同浓度的黄芩苷对BALB/c小鼠连续7 d灌胃后腹腔注射LPS建立炎症模型,测定小鼠脾脏指数、T细胞亚群及免疫平衡,RT-qPCR法测定脾脏炎症细胞因子和TGF⁃β/SMAD2通路相关基因的mRNA表达。结果显示:黄芩苷在0~25 μg/mL范围内对RAW264.7增殖无抑制作用,LPS质量浓度为1 mg/mL时,细胞存活率为54.55%。不同质量浓度黄芩苷均可增强RAW264.7细胞的吞噬能力(P<0.05),降低NO释放(P<0.05);LPS刺激后炎症细胞因子mRNA表达上升(P<0.05),TGF⁃β和SMAD2表达下降,黄芩苷干预后上述mRNA表达得到逆转。此外,LPS处理后小鼠脾脏指数显著上升(P<0.05),不同剂量的黄芩苷组均改善这一情况(P<0.05)。黄芩苷能够改善LPS刺激的CD
关键词
在畜禽养殖产业中,由于饲养管理不当、畜禽养殖条件差引起的细菌入侵是炎症性疾病产生的重要因
黄芩苷(baicalin,BCN)是从黄芩中提取的一种黄酮类有效活性成分。研究表明,黄芩苷具有抗炎、抑菌和免疫增强效
TGF⁃β/SMAD2信号通路调节许多细胞反应,包括细胞分化、增殖和凋
RAW264.7小鼠巨噬细胞(武汉普诺赛生命科技有限公司),RPMI-1640培养基,胎牛血清,0.25% EDTA胰酶(Gibco,赛默飞世尔科技(中国)有限公司),黄芩苷(纯度≥98%,上海源叶生物有限公司),DMSO(纯度>99.5%,北京索莱宝科技有限公司),LPS(纯度≥98%,北京索莱宝科技有限公司),一氧化氮含量检测试剂盒(S0021S,碧云天生物技术有限公司),总RNA提取试剂盒(R1200,北京索莱宝科技有限公司),cDNA逆转录酶(RK20428,武汉爱博泰克生物有限公司),Genious 2X SYBR Green Fast qPCR Mix(RK21204,武汉爱博泰克生物有限公司),FoxP3/Transcription Factor Staining Buffer Kit、CD3e、CD4、CD8a抗体(美国BD生物公司)。
细胞培养箱(MCO-15AC,日本三洋电机有限公司),多功能酶标仪(SpectraMax iD3,美谷分子仪器有限公司),RT-qPCR仪(CXT96,伯乐生命医学(上海)产品有限公司),BD FACSAria™ Fusion 细胞分选仪(美国BD生物公司)。
1)RAW264.7细胞活力的测定。将RAW264.7细胞培养于RPMI-1640完全培养基(89% RPMI-1640+10%胎牛血清+1%青霉素-链霉素)中,接种96孔板,待细胞贴壁弃上清,使用DMSO溶解黄芩
2)RAW264.7细胞吞噬能力的测定。参考易首利
3)RAW264.7细胞NO释放的测定。将RAW264.7细胞接种6孔板,设置分组并培养24 h后取上清,3 000 r/min离心10 min,按照试剂盒制造商提供的说明书检测NO含量。
4)细胞炎症因子及TGF⁃β/SMAD2信号通路相关mRNA表达水平的测定。消化收集细胞,使用RNA提取试剂盒进行总RNA提取,随后使用Abconal提供的试剂说明书进行逆转录。
基因 Gene | 引物序列 Primer sequences | 基因编号Gene ID |
---|---|---|
β⁃actin |
F:GGACTTCGAGCAGGAGATGG R:AGGAAGGAGGGCTGGAAGAG | 11461 |
iNOS |
F:CAAGCACATTTGGGAATGGAGA R:CAGAACTGAGGGTACATGCTGGAG | 18126 |
IL⁃1 |
F:TGACGGACCCCAAAAGAT R:GTGATACTGCCTGCCTGAAG | 111343 |
IL⁃6 |
F:AGCCAGAGTCCTTCAGAGAG R:GCCACTCCTTCTGTGACTCC | 16193 |
IL⁃10 |
F:ACCCGTGGCTTCTAGTGCTGA R:GAAGGCAGTCCGCAGCTCTA | 16153 |
TGF⁃β |
F:GCCACTGCCCATCGTCTACT R:CACTTGCAGGAGCGCACAAT | 21083 |
SMAD2 |
F:ATGTCGTCCATCTTGCCATTC R:AACCGTCCTGTTTTCTTTAGCTT | 17126 |
IL⁃17 |
F:GCTCCAGAAGGCCCTCAGAC R:CGGCACTGAGCTTCCCAGAT | 16171 |
IL⁃22 |
F:CAGCCATGATCAGCCTCCCA R:TAGAGCTGGCTCCCTGGACA | 50929 |
1)实验动物分组与试验设计。雄性BALB/c小鼠55只,体质量为(20±2) g,6~8周龄,购自三峡大学动物实验中心,实验动物许可证号:SCXK(鄂)2022-0012,动物实验伦理经长江大学医学部审核批准(YJ202346)。在长江大学动物科学技术学院提供的标准动物房中饲养,环境条件为湿度(55±5)%、温度(23±2) ℃,明暗周期为12 h//12 h,试验开始前适应性饲喂1周。使用10%DMSO溶液配制1 g/mL黄芩苷母液,并使用生理盐水稀释DMSO终含量为1%。
将55只小鼠随机分为5
2)T细胞分化的测定。剪切新鲜脾脏,置于孔径200 μm的滤网研磨,RPMI-1640冲洗收集滤液,4 ℃、2 000 r/min离心5 min,弃上清。加入500 μL红细胞裂解液静置2 min后离心5 min,弃上清,1 mL RPMI-1640完全培养基混匀重悬。使用孔径48 μm灭菌尼龙膜过滤,即得T细胞原液。取少量T细胞悬液使用RPMI-1640基础培养基稀释至1×1
3)调节性T细胞Treg细胞的测定。取T细胞原液,加入CD4抗体和CD25抗体表面染色30 min;加入100 μL PBS重悬,并立即加入转录因子固定破核剂500 μL,避光孵育50 min;收集细胞,加入10 μL Foxp3-APC 抗体再次孵育50 min,随后加入300 μL PBS重悬细胞,混匀后上机检测。
4)辅助性T细胞Th17的测定。取T细胞原液,每管加入刺激阻断剂100 μL,细胞培养箱中刺激培养6 h,加入100 μL PBS重悬细胞,随后加入10 μL CD4抗体,避光孵育30 min,孵育结束弃上清;加入1 mL固定破膜剂重悬细胞,孵育1 h弃上清,使用1×Perm/Wash重悬细胞。最后用IL-17A-APC(Th17)抗体进行胞内染色,定容至300 μL混匀后上机。
5)相关mRNA的表达水平检测。利用总RNA提取试剂盒从小鼠脾脏中提取总RNA,使用逆转录试剂盒合成cDNA,储存在-20 ℃备用。RT-qPCR检测IL⁃1、TNF⁃α、IL⁃17、IL⁃22、TGF⁃β及SMAD2的mRNA表达水平,引物见
黄芩苷和LPS对RAW264.7细胞增殖的影响如

图1 黄芩苷(A)和LPS(B)对RAW264.7细胞增殖的影响
Fig. 1 Effect of baicalin (A) and LPS (B) on the proliferation of RAW264.7 cell
不同小写字母代表差异显著(P<0.05)。下同。Different letters represent significant differences (P < 0.05). The same as below.
细胞吞噬试验结果如

图2 黄芩苷处理的LPS刺激RAW264.7细胞的吞噬能力(A)和NO释放(B)
Fig. 2 Phagocytosis (A) and NO content (B) of LPS-stimulated RAW264.7 cells by baicalin treatment
组别1:对照组;2:1 mg/mL LPS;3:3.125 μg/mL 黄芩苷;4:6.25 μg/mL 黄芩苷;5:12.5 μg/mL 黄芩苷;6:25 μg/mL 黄芩苷。图3同。Group 1: The control group; 2: 1 mg/mL LPS; 3: 3.125 μg/mL baicalin; 4: 6.25 μg/mL baicalin; 5: 12.5 μg/mL baicalin; 6: 25 μg/mL baicalin. The same as in Fig.3.
RAW264.7细胞相关基因的mRNA表达水平见

图3 黄芩苷处理的LPS刺激RAW264.7细胞相关基因mRNA表达水平
Fig. 3 Relative mRNA expression levels in RAW264.7 cells after LPS stimulation and baicalin treatment
A: iNOS; B: IL⁃1; C:IL⁃6; D:IL⁃10; E:TGF⁃β; F:SMAD2.
小鼠脾脏指数见

图4 饲喂不同水平黄芩苷和LPS刺激的小鼠脾脏指数
Fig. 4 Spleen index of mice after different levels of baicalin feeding and LPS stimulation
组别1:对照组;2:1 mg /mL LPS;3:50 mg/kg 黄芩苷;4:100 mg/kg 黄芩苷;5:200 mg/kg 黄芩苷。下同。Group 1:The control group; 2:1 mg/mL LPS;3:50 mg/kg baicalin;4:100 mg/kg baicalin; 5:200 mg/kg baicalin. The same as below.
小鼠脾脏T细胞分化结果如

图5 饲喂不同水平黄芩苷和LPS刺激的小鼠T细胞分化结果
Fig. 5 Results of T Cell differentiation after different levels of baicalin feeding and LPS stimulation
A:流式细胞术分区;B:CD3细胞比例;C:CD4细胞比例;D:CD8细胞比例;E:CD4/CD8。A:Flow cytometry zonation; B:CD3 cell proportion; C:CD4 cell proportion; D:CD8 cells proportion; E:CD4/CD8.
如

图6 饲喂不同水平黄芩苷和LPS刺激的免疫平衡流式细胞图
Fig. 6 Immuno-equilibrium flow cytometry after different levels of baicalin feeding and LPS stimulation
A:Th17的表达情况;B:Treg的表达情况;C:Th17/Treg;D:Th17流式分区;E:Treg流式分区。A:Th17 expression; B:Treg expression; C:Th17/Treg; D:Th17 flow partition; E:Treg flow partition.
如

图7 饲喂不同水平黄芩苷和LPS刺激的脾脏相关炎症细胞因子mRNA表达水平
Fig.7 mRNA expression of cytokines associated with spleen after different levels of baicalin feeding and LPS stimulation
A:IL⁃1;B:TNF⁃α;C:IL⁃17;D:IL⁃22;E:TGF⁃β;F:SMAD2.
黄芩苷是中药黄芩中最主要的活性成分之一,调查发现,在众多黄酮类化合物中,黄芩苷含量最高可占生药材的20.7
炎症反应是机体稳态系统应对外界和内部刺激时的必要生理过程,在正常情况下,轻微的炎症反应能够刺激机体快速清除病原体,改善免疫失衡从而维持自身健
RAW264.7等巨噬细胞在遭受外界刺激时能够促进NO的释放,而这一机制是由iNOS激活引起
研究表明,TGF⁃β/SMAD信号通路在细胞早期发育、免疫监督、组织修复及稳态平衡的过程中发挥重要作用,Lan
T细胞亚群紊乱可能与局部炎症和免疫反应激活有
Th17细胞能够促进组织的炎症反应,而Treg细胞则抑制自身免疫。IL⁃17是许多自身免疫性疾病发病机制的核心,同样存在有效的宿主耐受与调节机制来控制自身反应性Th17细胞与IL⁃17诱导的炎症反
综上所述,LPS可刺激RAW264.7细胞和小鼠产生炎症反应,促进炎症因子释放导致免疫失衡,黄芩苷干预后能够缓解LPS诱导的小鼠炎症反应,该机制可能是通过降低相关炎症因子mRNA表达、提高免疫能力、恢复Th17/Treg平衡及激活TGF⁃β/SMAD信号通路实现的。
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