Resistance-Nodulation-Division (RND) family pumps are responsible for producing multidrug resistance in Escherichia coli; however, there has been little study of targeted inhibitors of RNDs. In the present study, we investigated the inhibition of RND pumps by artesunate (AS) in E. coli, and further investigated the mechanism with respect to MarA, a regulator of RNDs. Although AS had no direct antibacterial effect, it showed a synergistic effect in combination with β-lactams against E. coli ATCC35218 in vitro and in vivo, suggesting it possesses antibacterial enhancement activity. Notably, AS, alone or in combination with β-lactams, downregulated the mRNA expression levels of marA, soxS, and rob, known as the marA-soxS-rob regulon, which then decreased the expression levels of RNDs, thereby increased ampicillin accumulation within ATCC35218. Using gene-deletion strains, we found that the antibacterial sensitization effect of AS persisted in wildtype bacteria, but was completely lost in the strain lacking marA, and decreased in the strain lacking soxS or rob, suggesting marA plays a crucial role in the sensitization of AS. Critically, we showed that AS inhibited the binding of MarA to the promoter of marA itself, not acrB, resulting in decreased mRNA expression of both acrB and marA. Mechanistically, we found AS directly bound to the central cavity of MarA through the R59 and K62 residues, and thus altered the charge distribution of MarA to interrupt the recognition between MarA and its promoter. We concluded that AS interrupts the self-transcriptional activation of MarA, thereby inhibits MarA-dependent mRNA expression of marA, acrAB, and tolC, and also certain other RNDs and regulatory genes related to MarA. Therefore, AS is a novel inhibitor of RND pumps that acts on the regulator MarA.

耐药-结节-分区（RND）系列泵负责在大肠杆菌中产生多药耐药性；然而，关于RNDs的靶向抑制剂的研究很少。在本研究中，我们研究了青蒿琥酯（AS）对E对RND泵的抑制作用。大肠杆菌，并进一步研究了有关RND调节剂MarA的机制。尽管AS没有直接的抗菌作用，但它与β-内酰胺类药物在体外和体内对大肠杆菌ATCC35218的协同作用均显示出协同作用，表明它具有抗菌增强作用。值得注意的是，AS单独或与β-内酰胺类药物联合使用，均会下调mRNA的表达水平。marA，soxS和rob（称为marA-soxS-rob调节剂），然后降低RND的表达水平，从而增加氨苄青霉素在ATCC35218中的积累。使用基因缺失菌株，我们发现AS的抗菌增敏作用在野生型细菌中仍然存在，但在缺少marA的菌株中完全消失，而在缺少soxS或rob的菌株中下降，这表明marA在对Ax的敏化中起关键作用如。至关重要的是，我们表明AS抑制了MarA与marA本身而不是acrB的启动子的结合，导致acrB和marA的mRNA表达下降。从机理上讲，我们发现AS通过R59和K62残基直接结合到MarA的中央腔，从而改变了MarA的电荷分布，从而中断了MarA及其启动子之间的识别。我们的结论是，中断马拉的自转录激活，从而抑制马拉依赖性表达和marA，acrAB的，和TOLC，以及某些其他RNDs及相关马拉调控基因。因此，AS是作用于调节器MarA的RND泵的新型抑制剂。