Proteolytic assay-based screening identifies a potent inhibitor of anthrax lethal factor

Area of Science:

• Biochemistry
• Toxicology
• Pharmacology

Background:

• Anthrax lethal factor (LF) is a critical virulence determinant in anthrax toxin, functioning as a Zn(2+)-dependent metalloprotease.
• Identifying inhibitors of LF is crucial for developing effective countermeasures against anthrax.
• Naturally derived compounds offer a promising source for novel therapeutic agents.

Purpose of the Study:

• To screen a natural chemical library for novel inhibitors of anthrax lethal factor (LF).
• To evaluate the efficacy and safety of identified LF inhibitors in cellular models.
• To elucidate the potential binding mechanism of a promising inhibitor.

Main Methods:

• Proteolytic assay-based screening of a natural chemical library to identify LF inhibitors.
• In vitro inhibition assays to determine IC(50) values of identified compounds.
• Cytotoxicity assays using the RAW 264.7 macrophage cell line.
• Cell protection assays against anthrax toxin challenge.
• Molecular docking simulations to predict compound-LF binding modes.

Main Results:

• Four compounds demonstrated inhibition of LF's in vitro proteolytic activity, with IC(50) values in the low micromolar range (11-20 μM).
• Three of the identified compounds exhibited toxicity to RAW 264.7 cells.
• Compound 200 was found to be non-toxic and effectively protected RAW 264.7 cells from lethal anthrax toxin challenge, with an IC(50) of 39.2 μM.
• Molecular docking provided insights into the potential binding interactions of compound 200 with LF.

Conclusions:

• Natural product screening can identify potent inhibitors of anthrax lethal factor.
• Compound 200 represents a non-toxic, promising candidate for further development as an anti-anthrax agent.
• Further investigation into compound 200's mechanism of action and in vivo efficacy is warranted.