Repurposing Tirazone as an effective quorum-sensing inhibitor against Pseudomonas aeruginosa virulence and biofilm formation

Antibiotic resistance has emerged as a critical global public health challenge. Quorum sensing (QS), a density-dependent regulatory mechanism, plays a pivotal role in Bacterial pathogenesis by coordinating virulence factor expression, making it a critical target for antivirulence therapy. Leveraging a drug repositioning strategy, this study investigated the antivirulence potential of drugs in the database of DrugBank on the common opportunistic pathogen Pseudomonas aeruginosa by virtual screening. Molecular docking analysis predicted that the antitumor drug, Tirazone, could bind to the core QS regulatory proteins, LasR, RhlR, and PqsR of P. aeruginosa with abundant active sites, whereas the binding free energies were higher than those of the native QS signals. In vitro experiments demonstrated that Tirazone significantly suppressed virulence factor secretion, cell motilities, and biofilm formation in the model P. aeruginosa strain PAO1, and downregulated the expression of a series of QS-related genes with low effective concentration (≤ 8 μM). A competitive binding model of QS signal molecules further elucidated that Tirazone interfered with QS signaling by competitively inhibiting the function of LasR, RhlR, and PqsR. Additionally, Tirazone treatment significantly protected Caenorhabditis elegans and mouse models from P. aeruginosa Infection, and reduced the Bacterial loads and pathological lesions in mouse lungs. Moreover, Tirazone demonstrated synergistic effects with polymyxin B, levofloxacin, and amikacin, significantly enhancing their bactericidal efficacy in treating P. aeruginosa. This study reveals the molecular mechanism underlying Tirazone's multi-target intervention in the QS system, and provides an experimental foundation for developing combination therapies based on antivirulence strategies.