α-Mangostin attenuates Pseudomonas aeruginosa virulence by targeting PqsR and inhibiting PQS-mediated quorum sensing.

Due to the increasing global antibiotic resistance spread, novel antibacterial strategies targeting virulence factors instead of bacterial growth are clinically crucial. One promising approach involves interfering with bacterial quorum-sensing systems, which regulate virulence and enhance adaptability. To this end, exploring quorum sensing inhibitors from Chinese medicine monomers have gained attention. The key quorum-sensing systems of Pseudomonas aeruginosa (las, rhl, and pqs) control multiple virulence factors and contribute to pathogenicity. This study screened a library of Chinese medicine monomers by constructing a pqsA'-lacZ fusion reporter system and first discovered that α-mangostin can act as a novel inhibitor of the pqs system in P. aeruginosa. Subsequent experiments demonstrated that α-mangostin can effectively inhibit the pqs system and associated virulence phenotypes, including biofilm formation, motility (swarming, swimming, and twitching), and the production of virulence factors (pyocyanin, hydrogen cyanide, elastase, and lectin), without affecting bacterial growth. Moreover, both genetic complementation assays and molecular docking analyses indicated that α-mangostin inhibits the pqs system by targeting the PqsR protein. Site-directed mutagenesis, circular dichroism spectroscopy, and isothermal titration calorimetry confirmed that PqsR is the direct target of α-mangostin and that the alanine residue at position 168 of PqsR is the key bindingsite. Finally, α-mangostin effectively attenuated P. aeruginosa virulence in Chinese cabbage (Brassica pekinensis) and bacterial adhesion to and invasion of human lung epithelial A549 cells. In summary, α-mangostin effectively inhibits P. aeruginosa virulence without affecting its growth by targeting its pqs system, providing a new strategy for the prevention and treatment of P. aeruginosa infections.