小檗碱抗新生隐球菌活性和作用机制

Antifungal activity and mechanism of berberine against Cryptococcus neoformans

摘要:

【目的】研究小檗碱对新生隐球菌的抗菌活性及其作用机制。【方法】采用微量肉汤稀释法测定小檗碱对新生隐球菌标准菌株和临床分离菌株的最小抑菌浓度，通过棋盘法测定小檗碱与氟康唑、两性霉素B的协同作用，测定小檗碱对隐球菌重要毒力因子的表达，以及对巨噬细胞和隐球菌互作的影响，采用隐球菌感染大蜡螟模型测定小檗碱的体内杀菌活性。【结果】小檗碱是一种杀真菌化合物，在测试的菌株中，最小抑菌浓度(minimum inhibitory concentration, MIC)范围为8−16 µg/mL。亚致死剂量小檗碱能够抑制隐球菌荚膜大小、产黑色素能力和有性生殖能力，并能增强巨噬细胞的杀菌能力。锌指转录因子Nrg1介导了上述重要的过程。在隐球菌感染动物模型中，小檗碱能够延长感染大蜡螟的存活时间。【结论】小檗碱在体内外具有优异的抗隐球菌活性，有望作为抗隐球菌药物开发的起始化合物。

Abstract:

[Objective] To investigate the antifungal activity and mechanism of berberine against Cryptococcus neoformans. [Methods] The minimum inhibitory concentration (MIC) of berberine against the standard strain and clinical isolates of C. neoformans was determined by micro-broth dilution method. The synergistic effect of berberine with the marketed antifungal drugs (fluconazole and amphotericin B) was determined by checkerboard method. Further, we determined the effects of berberine on the expression of key virulence factors of Cryptococcus and on the macrophage-Cryptococcus interaction. The in vivo fungicidal activity of berberine was examined with the Galleria mellonella model of Cryptococcus infection. [Results] Berberine was a fungicidal compound with a MIC range of 8−16 µg/mL against the tested strains. Berberine at the sublethal concentration inhibited capsule size, melanin-producing ability, and sexual reproduction and enhanced the fungicidal ability of macrophages. The zinc-finger transcription factor Nrg1 mediated these important processes. The experiment with the G. mellonella model of cryptococcal infection showed that berberine prolonged the survival time of infected G. mellonella. [Conclusion] Berberine exhibits excellent anti-cryptococcal activity in vitro and in vivo and is expected to be a promising starting compound for the development of anti-cryptococcal agents.