Luteolin increases susceptibility to macrolides by inhibiting MsrA efflux pump in Trueperella pyogenes

Area of Science:

• Veterinary Microbiology
• Pharmacology
• Natural Product Chemistry

Background:

• Trueperella pyogenes is an opportunistic pathogen causing diseases in domestic animals.
• Antimicrobial resistance, particularly due to efflux pumps like MsrA, limits treatment options for T. pyogenes infections.
• Natural compounds are being explored as adjunct therapies to overcome antimicrobial resistance.

Purpose of the Study:

• To evaluate the inhibitory effect of luteolin on the MsrA efflux pump in T. pyogenes.
• To investigate the mechanism by which luteolin affects MsrA activity and gene/protein expression.
• To explore luteolin's potential as a therapeutic agent against antimicrobial-resistant T. pyogenes.

Main Methods:

• Antimicrobial susceptibility testing of T. pyogenes isolates with and without luteolin treatment.
• Quantitative analysis of msrA gene transcription and MsrA protein expression levels.
• Affinity testing to determine luteolin-MsrA binding kinetics and interaction type (e.g., hydrogen bonding).

Main Results:

• Luteolin treatment increased macrolide susceptibility in msrA-positive T. pyogenes isolates, but not in msrA-negative ones.
• Significant reduction in msrA gene transcription (55.0-97.7%) and MsrA protein expression (36.5-71.5%) observed after luteolin exposure.
• Luteolin demonstrated affinity for MsrA (KD = 6.462 × 10⁻⁵ M), primarily through hydrogen bonding, potentially inhibiting its ATPase activity.

Conclusions:

• Luteolin effectively inhibits the MsrA efflux pump in T. pyogenes, thereby restoring macrolide susceptibility.
• The mechanism involves downregulating msrA gene transcription and MsrA protein expression, and potentially inhibiting ATPase activity.
• Luteolin shows promise as an adjuvant therapy to combat infections caused by multidrug-resistant T. pyogenes.