没食子酸衍生物对 Terminalia chebula Retz. 的下调表达可调节群体感应基因的表达，从而减轻铜绿假单胞菌 PAO1 的毒力。
Ellagic acid derivatives from Terminalia chebula Retz. downregulate the expression of quorum sensing genes to attenuate Pseudomonas aeruginosa PAO1 virulence.
机构信息
Department of Microbiology, Panjab University, Chandigarh, India.
出版信息
PLoS One. 2013;8(1):e53441. doi: 10.1371/journal.pone.0053441. Epub 2013 Jan 8.
BACKGROUND
Burgeoning antibiotic resistance in Pseudomonas aeruginosa has necessitated the development of anti pathogenic agents that can quench acylhomoserine lactone (AHL) mediated QS with least risk of resistance. This study explores the anti quorum sensing potential of T. chebula Retz. and identification of probable compounds(s) showing anti QS activity and the mechanism of attenuation of P. aeruginosa PAO1 virulence factors.
METHODS AND RESULTS
Methanol extract of T. chebula Retz. fruit showed anti QS activity using Agrobacterium tumefaciens A136. Bioactive fraction (F7), obtained by fractionation of methanol extract using Sephadex LH20, showed significant reduction (p<0.001) in QS regulated production of extracellular virulence factors in P. aeruginosa PAO1. Biofilm formation and alginate were significantly (p<0.05) reduced with enhanced (20%) susceptibility to tobramycin. Real Time PCR of F7 treated P. aeruginosa showed down regulation of autoinducer synthase (lasI and rhlI) and their cognate receptor (lasR and rhlR) genes by 89, 90, 90 and 93%, respectively. Electrospray Ionization Mass Spectrometry also showed 90 and 64% reduction in the production of 3-oxo-C(12)HSL and C(4)HSL after treatment. Decrease in AHLs as one of the mechanisms of quorum quenching by F7 was supported by the reversal of inhibited swarming motility in F7-treated P. aeruginosa PAO1 on addition of C(4)HSL. F7 also showed antagonistic activity against 3-oxo-C(12)HSL-dependent QS in E. coli bioreporter. C. elegans fed on F7-treated P. aeruginosa showed enhanced survival with LT50 increasing from 24 to 72 h. LC-ESI-MS of F7 revealed the presence of ellagic acid derivatives responsible for anti QS activity in T. chebula extract.
CONCLUSIONS
This is the first report on anti QS activity of T. chebula fruit linked to EADs which down regulate the expression of lasIR and rhlIR genes with concomitant decrease in AHLs in P. aeruginosa PAO1 causing attenuation of its virulence factors and enhanced sensitivity of its biofilm towards tobramycin.
背景
铜绿假单胞菌中抗生素耐药性的迅速增加，需要开发能够淬灭酰基高丝氨酸内酯（AHL）介导的群体感应的治疗剂，而这些治疗剂的耐药风险最小。本研究探讨了诃子 T. chebula Retz 的抗群体感应潜力，并鉴定了可能具有抗群体感应活性的化合物（s），以及衰减铜绿假单胞菌 PAO1 毒力因子的机制。
方法和结果
用根癌农杆菌 A136 测定，T. chebula Retz 果实的甲醇提取物显示出抗群体感应活性。用 Sephadex LH20 对甲醇提取物进行分级得到的生物活性级分（F7），显著降低了铜绿假单胞菌 PAO1 中 QS 调控的胞外毒力因子的产生（p<0.001）。生物膜形成和藻酸盐的形成明显减少（p<0.05），对妥布霉素的敏感性增强（20%）。F7 处理的铜绿假单胞菌的实时 PCR 显示，自动诱导物合成酶（lasI 和 rhlI）及其同源受体（lasR 和 rhlR）基因分别下调 89%、90%、90%和 93%。电喷雾电离质谱也显示，处理后 3-氧代-C（12）HSL 和 C（4）HSL 的产量分别减少了 90%和 64%。F7 通过淬灭群体感应减少 AHLs，这一机制得到了 F7 处理的铜绿假单胞菌 PAO1 在添加 C（4）HSL 后抑制的群集运动逆转的支持。F7 还显示出对大肠杆菌生物报告物中 3-氧代-C（12）HSL 依赖性群体感应的拮抗活性。用 F7 处理的铜绿假单胞菌喂养秀丽隐杆线虫，可使 LT50 从 24 小时延长至 72 小时，从而提高了存活率。F7 的 LC-ESI-MS 显示，诃子提取物中的鞣花酸衍生物具有抗群体感应活性。
结论
这是首次报道诃子果实具有抗群体感应活性，与 EADs 相关，EADs 下调铜绿假单胞菌 PAO1 中 lasIR 和 rhlIR 基因的表达，同时降低 AHLs，从而减弱其毒力因子的作用，并增强其生物膜对妥布霉素的敏感性。
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