Methyl gallate: Selective antileishmanial activity correlates with host-cell directed effects

Area of Science:

• Parasitology
• Pharmacology
• Immunology

Background:

• Leishmaniasis is a neglected tropical disease with limited, toxic treatment options.
• Drug resistance and toxicity necessitate the development of novel antileishmanial agents.
• Phenolic compounds are being explored for their therapeutic potential.

Purpose of the Study:

• To evaluate the in vitro antileishmanial activity of methyl gallate (MG) against Leishmania (Leishmania) amazonensis.
• To investigate the mechanisms of action of MG, including its effects on macrophage activation and immune mediators.
• To compare the efficacy and safety of MG with existing leishmaniasis drugs.

Main Methods:

• In vitro assays against L. amazonensis promastigotes and amastigotes (axenic and intramacrophagic).
• Cytotoxicity assessments on J774A.1 and THP-1 derived macrophages.
• Analysis of macrophage activation markers: TNF-α, IL-12, IFN-γ, IL-10, IL-6, NO, ROS, arginase activity, phagocytosis, and lysosomal activity.
• Comparison with meglumine antimoniate and amphotericin B as reference drugs.

Main Results:

• MG demonstrated potent inhibition of L. amazonensis promastigotes (IC50 5.71 μM) and amastigotes (EC50 5.39 μM), including intracellular forms (EC50 4.24 μM).
• MG exhibited significantly higher selectivity indexes and lower cytotoxicity towards macrophages compared to reference drugs.
• Antileishmanial activity correlated with increased TNF-α, IL-12, NO, ROS, enhanced phagocytosis, and lysosomal activity, alongside decreased IL-6 and arginase activity.

Conclusions:

• Methyl gallate is a potent antileishmanial agent with a favorable safety profile.
• MG's mechanism involves modulating macrophage functions and inflammatory responses.
• MG represents a promising candidate for the development of new drugs against leishmaniasis.