Halogenated Dihydropyrrol-2-One Molecules Inhibit Pyocyanin Biosynthesis by Blocking the Pseudomonas Quinolone...

Area of Science:

• Microbiology
• Medicinal Chemistry
• Bacterial Pathogenesis

Background:

• Quorum-sensing (QS) systems regulate critical virulence factors and biofilm formation in *Pseudomonas aeruginosa*, a significant opportunistic pathogen.
• Targeting QS pathways offers a promising strategy to control *P. aeruginosa* infections by attenuating its pathogenicity.
• Dihydropyrrol-2-ones (DHPs) are heterocyclic compounds with potential antimicrobial applications.

Purpose of the Study:

• To evaluate the efficacy of halogenated (Br, Cl, F) and non-halogenated dihydropyrrol-2-ones (DHPs) in inhibiting *Pseudomonas aeruginosa* quorum-sensing (QS) receptor proteins.
• To assess the impact of these DHPs on QS-controlled virulence factors, specifically pyocyanin production and biofilm formation.
• To compare the inhibitory effects of halogenated DHPs against their non-halogenated counterpart.

Main Methods:

• Synthesis and characterization of halogenated (Br, Cl, F) and non-halogenated DHPs.
• In vitro assays to measure the concentration-dependent inhibition of LasR and PqsR QS receptor proteins by DHPs.
• Quantification of pyocyanin production in various *P. aeruginosa* strains (PAO1, MH602, ATCC 25619, clinical isolates) treated with DHPs.
• Assessment of biofilm formation inhibition in *P. aeruginosa* exposed to DHPs.

Main Results:

• All tested DHPs demonstrated concentration-dependent inhibition of LasR and PqsR receptor proteins.
• Compound 4a (brominated DHP) exhibited the most potent inhibition of the PqsR receptor, showing a two-fold decrease even at the lowest concentration.
• DHP treatment significantly reduced pyocyanin production across all tested *P. aeruginosa* strains, with strain ATCC 25619 showing the greatest reduction and clinical isolate DFU-53 the least.
• Halogenated DHPs reduced biofilm formation by 31-34%. The non-halogenated DHP showed complete LasR inhibition and moderate inhibition of PqsR, pyocyanin, and biofilm formation, but was less effective than halogenated variants.

Conclusions:

• Halogenated dihydropyrrol-2-ones are effective inhibitors of *Pseudomonas aeruginosa* quorum-sensing systems.
• The brominated DHP (4a) shows particular promise for targeting the PqsR receptor, a key component of the QS network.
• These findings suggest that DHPs, especially halogenated derivatives, represent a viable therapeutic strategy for combating *P. aeruginosa* infections by disrupting virulence mechanisms.