The First Hospital and Institute of Infection and Immunity, Jilin University, Changchun, China.
Key Laboratory of Zoonosis, Ministry of Education, College of Veterinary Medicine, Jilin University, Changchun, China.
J Cell Mol Med. 2017 Oct;21(10):2586-2598. doi: 10.1111/jcmm.13179. Epub 2017 Apr 12.
Streptococcus pneumoniae (pneumococcus), the causative agent of several human diseases, possesses numerous virulence factors associated with pneumococcal infection and pathogenesis. Pneumolysin (PLY), an important virulence factor, is a member of the cholesterol-dependent cytolysin family and has cytolytic activity. Sortase A (SrtA), another crucial pneumococcal virulence determinate, contributes greatly to the anchoring of many virulence-associated surface proteins to the cell wall. In this study, epigallocatechin gallate (EGCG), a natural compound with little known antipneumococcal activity, was shown to directly inhibit PLY-mediated haemolysis and cytolysis by blocking the oligomerization of PLY and simultaneously reduce the peptidase activity of SrtA. The biofilm formation, production of neuraminidase A (NanA, the pneumococcal surface protein anchored by SrtA), and bacterial adhesion to human epithelial cells (Hep2) were inhibited effectively when S. pneumoniae D39 was cocultured with EGCG. The results from molecular dynamics simulations and mutational analysis confirmed the interaction of EGCG with PLY and SrtA, and EGCG binds to Glu277, Tyr358, and Arg359 in PLY and Thr169, Lys171, and Phe239 in SrtA. In vivo studies further demonstrated that EGCG protected mice against S. pneumoniae pneumonia. Our results imply that EGCG is an effective inhibitor of both PLY and SrtA and that an antivirulence strategy that directly targets PLY and SrtA using EGCG is a promising therapeutic option for S. pneumoniae pneumonia.
肺炎链球菌（肺炎球菌）是多种人类疾病的病原体，拥有许多与肺炎球菌感染和发病机制相关的毒力因子。肺炎球菌溶血素（PLY）是一种重要的毒力因子，属于胆固醇依赖性细胞溶解素家族，具有细胞溶解活性。另一种重要的肺炎球菌毒力决定因素——天冬氨酸转肽酶 A（SrtA），极大地促进了许多与毒力相关的表面蛋白与细胞壁的锚定。在这项研究中，表没食子儿茶素没食子酸酯（EGCG）是一种具有未知抗肺炎球菌活性的天然化合物，被证明可以通过阻断 PLY 的寡聚化来直接抑制 PLY 介导的溶血和细胞溶解，同时降低 SrtA 的肽酶活性。当肺炎链球菌 D39 与 EGCG 共培养时，生物膜形成、神经氨酸酶 A（NanA，由 SrtA 锚定的肺炎球菌表面蛋白）的产生以及细菌对人上皮细胞（Hep2）的黏附均被有效抑制。分子动力学模拟和突变分析的结果证实了 EGCG 与 PLY 和 SrtA 的相互作用，EGCG 结合到 PLY 中的 Glu277、Tyr358 和 Arg359 以及 SrtA 中的 Thr169、Lys171 和 Phe239。体内研究进一步证明 EGCG 可保护小鼠免受肺炎球菌肺炎的侵害。我们的结果表明，EGCG 是 PLY 和 SrtA 的有效抑制剂，使用 EGCG 直接针对 PLY 和 SrtA 的抗病毒策略是治疗肺炎球菌肺炎的一种有前途的选择。
