YXL-13 attenuates virulence in Pseudomonas aeruginosa mutants and clinical isolates by inhibiting quorum sensing regulators LasR and RhlR.

Given the critical role of quorum sensing (QS) in the pathogenicity of Pseudomonas aeruginosa, inhibiting QS is considered a promising alternative to traditional antibiotics for treating P. aeruginosa infections. The QS system of P. aeruginosa comprises two acyl-homoserine lactone (AHL) circuits, LasI/R and RhlI/R, along with a third system, the PQS system. However, due to the frequent clinical isolation of lasR mutants and the avirulent nature of rhlR mutants, targeting both the LasI/R and RhlI/R systems represent a more viable therapeutic strategy. YXL-13, an AHL analog, has been identified as a QS inhibitor, though its precise molecular target remains unclear. This study demonstrates that YXL-13 effectively inhibits the QS response in P. aeruginosa QS mutants (ΔlasR, ΔrhlR, and ΔpqsR) as well as in clinically isolated strains (PA1, PA2, and PA3), while also providing protection to C. elegans against infection. The related evidences, including qPCR analysis, QS reporter assays, isothermal titration calorimetry (ITC), molecular docking, and molecular dynamics (MD) simulations, indicate that YXL-13 targets both LasR and RhlR. In summary, YXL-13 exhibits potent inhibitory effects on the QS response of various P. aeruginosa strains.