Palacios Lucia, Rosado Helena, Micol Vicente, Rosato Adriana E, Bernal Patricia, Arroyo Raquel, Grounds Helen, Anderson James C, Stabler Richard A, Taylor Peter W
School of Pharmacy, University College London, London, United Kingdom.
Universidad Miguel Hernández, Elche, Alicante, Spain.
PLoS One. 2014 Apr 3;9(4):e93830. doi: 10.1371/journal.pone.0093830. eCollection 2014.
Galloyl catechins, in particular (-)-epicatechin gallate (ECg), have the capacity to abrogate β-lactam resistance in methicillin-resistant strains of Staphylococcus aureus (MRSA); they also prevent biofilm formation, reduce the secretion of a large proportion of the exoproteome and induce profound changes to cell morphology. Current evidence suggests that these reversible phenotypic traits result from their intercalation into the bacterial cytoplasmic membrane. We have endeavoured to potentiate the capacity of ECg to modify the MRSA phenotype by stepwise removal of hydroxyl groups from the B-ring pharmacophore and the A:C fused ring system of the naturally occurring molecule. ECg binds rapidly to the membrane, inducing up-regulation of genes responsible for protection against cell wall stress and maintenance of membrane integrity and function. Studies with artificial membranes modelled on the lipid composition of the staphylococcal bilayer indicated that ECg adopts a position deep within the lipid palisade, eliciting major alterations in the thermotropic behaviour of the bilayer. The non-galloylated homolog (-)-epicatechin enhanced ECg-mediated effects by facilitating entry of ECg molecules into the membrane. ECg analogs with unnatural B-ring hydroxylation patterns induced higher levels of gene expression and more profound changes to MRSA membrane fluidity than ECg but adopted a more superficial location within the bilayer. ECg possessed a high affinity for the positively charged staphylococcal membrane and induced changes to the biophysical properties of the bilayer that are likely to account for its capacity to disperse the cell wall biosynthetic machinery responsible for β-lactam resistance. The ability to enhance these properties by chemical modification of ECg raises the possibility that more potent analogs could be developed for clinical evaluation.
没食子酰儿茶素，特别是（-）-表儿茶素没食子酸酯（ECg），能够消除耐甲氧西林金黄色葡萄球菌（MRSA）菌株中的β-内酰胺抗性；它们还能防止生物膜形成，减少大部分细胞外蛋白质组的分泌，并诱导细胞形态发生深刻变化。目前的证据表明，这些可逆的表型特征是由于它们插入细菌细胞质膜所致。我们试图通过逐步去除天然分子B环药效团和A:C稠环系统中的羟基来增强ECg改变MRSA表型的能力。ECg迅速与膜结合，诱导负责抵御细胞壁应激和维持膜完整性及功能的基因上调。对以葡萄球菌双层脂质组分为模型的人工膜进行的研究表明，ECg在脂质栅栏内部深处占据一个位置，引发双层膜热致行为的重大改变。非没食子酰化同系物（-）-表儿茶素通过促进ECg分子进入膜内增强了ECg介导的效应。具有非天然B环羟基化模式的ECg类似物比ECg诱导更高水平的基因表达和对MRSA膜流动性更深刻的变化，但在双层膜中占据更浅的位置。ECg对带正电荷的葡萄球菌膜具有高亲和力，并诱导双层膜生物物理性质的变化，这可能解释了其分散负责β-内酰胺抗性的细胞壁生物合成机制的能力。通过对ECg进行化学修饰来增强这些特性的能力增加了开发更有效类似物用于临床评估的可能性。
