Zahid M Shamim Hasan, Awasthi Sharda Prasad, Asakura Masahiro, Chatterjee Shruti, Hinenoya Atsushi, Faruque Shah M, Yamasaki Shinji
Graduate School of Life and Environmental Sciences, Osaka Prefecture University, Osaka, Japan.
Centre for Food and Water Borne Diseases, International Centre for Diarrhoeal Disease Research, Bangladesh, Dhaka, Bangladesh.
PLoS One. 2015 Sep 11;10(9):e0137529. doi: 10.1371/journal.pone.0137529. eCollection 2015.
Use of natural compounds as antivirulence drugs could be an alternative therapeutic approach to modify the outcome of bacterial infections, particularly in view of growing resistance to available antimicrobials. Here, we show that sub-bactericidal concentration of anethole, a component of sweet fennel seed, could suppress virulence potential in O1 El Tor biotype strains of toxigenic Vibrio cholerae, the causative agent of the ongoing 7th cholera pandemic. The expression of cholera toxin (CT) and toxin coregulated pilus (TCP), the major virulence factors of V. cholerae, is controlled through a regulatory cascade involving activation of ToxT with synergistic coupling interaction of ToxR/ToxS with TcpP/TcpH. We present evidence that anethole inhibits in vitro expression of CT and TCP in a toxT-dependent but toxR/toxS-independent manner and through repression of tcpP/tcpH, by using bead-ELISA, western blotting and quantitative real-time RT-PCR assays. The cyclic AMP (cAMP)-cAMP receptor protein (CRP) is a well-studied global signaling system in bacterial pathogens, and this complex is known to suppress expression of tcpP/tcpH in V. cholerae. We find that anethole influences the virulence regulatory cascade by over-expressing cyaA and crp genes. Moreover, suppression of toxigenic V. cholerae-mediated fluid accumulation in ligated ileum of rabbit by anethole demonstrates its potentiality as an antivirulence drug candidate against the diseases caused by toxigenic V. cholerae. Taken altogether, these results revealing a mechanism of virulence inhibition in V. cholerae by the natural compound anethole, may have relevance in designing antivirulence compounds, particularly against multiple antibiotic resistant bacterial pathogens.
使用天然化合物作为抗毒力药物可能是一种改变细菌感染结局的替代治疗方法,特别是考虑到对现有抗菌药物的耐药性不断增加。在这里,我们表明,小茴香籽成分茴香脑的亚杀菌浓度可以抑制产毒霍乱弧菌O1 El Tor生物型菌株的毒力潜力,霍乱弧菌是正在进行的第七次霍乱大流行的病原体。霍乱弧菌的主要毒力因子霍乱毒素(CT)和毒素协同调节菌毛(TCP)的表达通过一个调控级联来控制,该调控级联涉及ToxT的激活以及ToxR/ToxS与TcpP/TcpH的协同偶联相互作用。我们提供的证据表明,茴香脑以一种依赖于toxT但不依赖于toxR/toxS的方式,通过抑制tcpP/tcpH,来抑制CT和TCP的体外表达,这是通过珠子ELISA、蛋白质印迹和定量实时RT-PCR分析得出的。环磷酸腺苷(cAMP)-cAMP受体蛋白(CRP)是细菌病原体中一个经过充分研究的全局信号系统,已知该复合物可抑制霍乱弧菌中tcpP/tcpH的表达。我们发现茴香脑通过过表达cyaA和crp基因来影响毒力调控级联。此外,茴香脑抑制产毒霍乱弧菌介导的兔结扎回肠液体蓄积,证明了其作为抗产毒霍乱弧菌引起疾病的抗毒力药物候选物的潜力。综上所述,这些结果揭示了天然化合物茴香脑对霍乱弧菌毒力抑制的机制,可能与设计抗毒力化合物有关,特别是针对多重耐药细菌病原体。