Vacuolar-ATPase inhibitors are antimicrobial agents active against intracellular mycobacteria

Area of Science:

• Microbiology
• Immunology
• Drug Discovery

Background:

• Mycobacterium tuberculosis evades host defenses by inhibiting phagosome acidification via PtpA binding to v-ATPase.
• This inhibition disrupts crucial cellular events, aiding bacterial survival within host cells.

Purpose of the Study:

• To investigate the antimicrobial effects of three v-ATPase inhibitors (Bafilomycin A1, Bafilomycin D, Cladoniamide B) against Mycobacterium tuberculosis, M. abscessus, and M. bovis BCG.
• To explore the mechanisms underlying v-ATPase inhibitor activity and their interaction with bacterial virulence factors.

Main Methods:

• Testing v-ATPase inhibitors against intracellular mycobacteria in THP-1 macrophages and murine infection models.
• Assessing bacterial growth in axenic culture and macrophage lysates.
• Investigating Bafilomycin A1's effects on host cell apoptosis and its interaction with Mtb PtpA using knockout mutants and in vitro thermal shift assays.

Main Results:

• Potent inhibition of intracellular mycobacterial growth with MIC50 in the nanomolar range.
• Compounds exhibited bacteriostatic effects on Mtb in macrophages but not in axenic cultures.
• Bafilomycin A1 amplified Mtb-induced cytotoxicity and its interaction with PtpA was confirmed.

Conclusions:

• v-ATPase inhibitors demonstrate significant potential for treating intracellular mycobacterial infections.
• The findings challenge traditional views on phagosome acidification's role in pathogenesis.
• Suggests novel host-directed therapeutic strategies targeting the v-ATPase-PtpA interaction.