Department of Animal Medicine, College of Agriculture and Forestry, Linyi University, No.1, Gong'ye Road, Linyi, Shandong 276000, PR China; College of Veterinary Medicine, China Agricultural University, No.2 Yuanmingyuan West Road, Haidian District, Beijing 100193, PR China.
Department of Animal Science, College of Agriculture, Liaocheng University, No. 1, Hu'nan Road, Liaocheng, Shandong 252000, PR China.
Phytomedicine. 2018 Sep 15;48:21-31. doi: 10.1016/j.phymed.2018.04.063. Epub 2018 May 9.
The worsening problems of antibiotic resistance prompt the need for alternative strategies. Baicalin, which is isolated from Scutellaria baicalensisi, has been demonstrated to exhibit anti-inflammatory, anti-virulence and antimicrobial effects. Salmonella typhimurium is an important foodborne pathogenic bacteriaum that causes gastrointestinal disease in humans and many animals.
The aim of this study was to investigate the effects of baicalin on S. typhimurium infection in mice and its possible mechanism in vitro.
To evaluate the effect of baicalin in vivo, mice were orally administered of baicalin, and then were infected by an intragastric administration of S. typhimurium. The minimal inhibitory concentrations (MICs) and minimum bactericidal concentrations (MBCs) of baicalin, baicalein, and oroxylin A against S. typhimurium were detected under the guides of the Clinical and Laboratory Standards Institute. In vitro, Caco-2 cells were infected with S. typhimurium in the presence or absence of baicalin, baicalein, and oroxylin A at sub-MICs.
In the in vivo experiment, the body weight loss, the serum levels of TNFα, IL-6, and lactic dehydrogenase (LDH), the pathological changes of the caecum and the caecum bacterial burdens were examined. The MICs and MBCs of baicalin, baicalein, and oroxylin A against S. typhimurium were detected by two-fold serial dilutions. In vitro, Caco-2 cells were infected with S. typhimurium, and the invasion capacity, TNFα, nitrate, and LDH were analysed. The transcription levels of Salmonella pathogenicity island 1 virulence associated genes (sopB, sopE, sopE2) of S. typhimurium in the presence of baicalin, baicalein, and oroxylin A were detected by qRT-PCR.
Our results showed that baicalin significantly decreased the body weight loss, the serum levels of TNFα, IL-6, and LDH, and the caecum bacterial burdens of mice challenged with S. typhimurium. Histological examination showed that baicalin decreased the lesion in the caecum of S. typhimurium-infected mice. MICs and MBCs of baicalin, and oroxylin A. against S. typhimurium were > 128 µg/ml. MICs and MBCs of baicalein against S. typhimurium were 64 µg/ml, and > 128 µg/ml, respectively. Pretreatment of Caco-2 cells or S. typhimurium with baicalin, baicalein, and oroxylin A significantly inhibited the invasion of Caco-2 cells by S. typhimurium in a dose-dependent manner. Sub-MICs of baicalin, baicalein, and oroxylin A also significantly decreased the levels of TNFα, nitrate, and LDH from S. typhimurium-infected Caco-2 cells. Moreover, the transcription levels of sopB, sopE, and sopE2 were significantly suppressed by baicalin, baicalein, and oroxylin A.
These results demonstrated that baicalin is a promising agent for the prevention of S. typhimurium infection via the modulation of both bacterial virulence and host response.
抗生素耐药性问题日益严重，需要寻找替代策略。黄芩苷是从黄芩中分离得到的，已被证明具有抗炎、抗毒力和抗菌作用。鼠伤寒沙门氏菌是一种重要的食源性致病菌，可引起人类和许多动物的胃肠道疾病。
本研究旨在探讨黄芩苷对小鼠鼠伤寒沙门氏菌感染的影响及其在体外的可能机制。
为了评估黄芩苷的体内作用，小鼠经口给予黄芩苷，然后经胃内给予鼠伤寒沙门氏菌感染。在临床和实验室标准协会的指导下，检测黄芩苷、黄芩素和白杨素对鼠伤寒沙门氏菌的最小抑菌浓度（MICs）和最小杀菌浓度（MBCs）。在体外，Caco-2 细胞在亚 MIC 浓度下用黄芩苷、黄芩素和白杨素感染鼠伤寒沙门氏菌。
在体内实验中，检测体重减轻、血清 TNFα、IL-6 和乳酸脱氢酶（LDH）水平、盲肠病理变化和盲肠细菌负荷。通过两倍系列稀释法检测黄芩苷、黄芩素和白杨素对鼠伤寒沙门氏菌的 MIC 和 MBC。体外，用鼠伤寒沙门氏菌感染 Caco-2 细胞，分析侵袭能力、TNFα、硝酸盐和 LDH。用 qRT-PCR 检测黄芩苷、黄芩素和白杨素对鼠伤寒沙门氏菌毒力相关基因（sopB、sopE、sopE2）转录水平的影响。
结果表明，黄芩苷显著降低了鼠伤寒沙门氏菌感染小鼠的体重减轻、血清 TNFα、IL-6 和 LDH 水平以及盲肠细菌负荷。组织学检查显示，黄芩苷减轻了鼠伤寒沙门氏菌感染小鼠盲肠的损伤。黄芩苷和白杨素对鼠伤寒沙门氏菌的 MIC 和 MBC 均大于 128 µg/ml。黄芩素对鼠伤寒沙门氏菌的 MIC 和 MBC 分别为 64 µg/ml 和大于 128 µg/ml。黄芩苷、黄芩素和白杨素预处理 Caco-2 细胞或鼠伤寒沙门氏菌，可剂量依赖性抑制鼠伤寒沙门氏菌对 Caco-2 细胞的侵袭。黄芩苷、黄芩素和白杨素的亚 MICs 也显著降低了鼠伤寒沙门氏菌感染 Caco-2 细胞后的 TNFα、硝酸盐和 LDH 水平。此外，黄芩苷、黄芩素和白杨素显著抑制 sopB、sopE 和 sopE2 的转录水平。
这些结果表明，黄芩苷通过调节细菌毒力和宿主反应，是一种有前途的预防鼠伤寒沙门氏菌感染的药物。
