Enterocin AS-48 as Evidence for the Use of Bacteriocins as New Leishmanicidal Agents

Abstract

We report the feasibility of enterocin AS-48, a circular cationic peptide produced by Enterococcus faecalis, as a new leishmanicidal agent. AS-48 is lethal to Leishmania promastigotes as well as to axenic and intracellular amastigotes at low micromolar concentrations, with scarce cytotoxicity to macrophages. AS-48 induced a fast bioenergetic collapse of L. donovani promastigotes but only a partial permeation of their plasma membrane with limited entrance of vital dyes, even at concentrations beyond its full lethality. Fluoresceinated AS-48 was visualized inside parasites by confocal microscopy and seen to cause mitochondrial depolarization and reactive oxygen species production. Altogether, AS-48 appeared to have a mixed leishmanicidal mechanism that includes both plasma membrane permeabilization and additional intracellular targets, with mitochondrial dysfunctionality being of special relevance. This complex leishmanicidal mechanism of AS-48 persisted even for the killing of intracellular amastigotes, as evidenced by transmission electron microscopy. We demonstrated the potentiality of AS-48 as a new and safe leishmanicidal agent, expanding the growing repertoire of eukaryotic targets for bacteriocins, and our results provide a proof of mechanism for the search of new leishmanicidal bacteriocins, whose diversity constitutes an almost endless source for new structures at moderate production cost and whose safe use on food preservation is well established.

Synergy between Circular Bacteriocin AS-48 and Ethambutol against Mycobacterium tuberculosis

“…The determination of viable bacteria after treatment with EMB and AS-48 resulted in a reduction of CFU counts between 90 and 99.9% in comparison with totals in untreated controls. The efficacy of AS-48 for killing intracellular pathogens was previously proven by Abengózar et al (14) when they showed the anti-leishmanial activity of AS-48 in Raw 264.7 infected macrophages. Despite the fact that the infection mechanism is different between Leishmania and mycobacteria, these experiments show that AS-48 is active against pathogens residing intracellularly in macrophages.…”

Circular and Leaderless Bacteriocins: Biosynthesis, Mode of Action, Applications, and Prospects

“…A few select bacteriocins showed some potential as antiviral agents, as plant growth promoters, and as anti-cancer agents ( Drider et al, 2016 ). Recently, it was reported that enterocin AS-48 showed promising bioactivity against the protozoan parasites of the genera Leishmania ( Abengózar et al, 2017 ) and Trypanosoma ( Martínez-García et al, 2018 ).…”

Draft Genome Sequence of Enterococcus faecalis DD14, a Bacteriocinogenic Lactic Acid Bacterium with Anti- Clostridium Activity

“…Recently, E. faecalis DD14 was isolated from meconium ( 5 ) and characterized for its Clostridium perfringens leaderless two-peptide bacteriocin designated enterocin DD14 ( 6 ). Enterocins are safe bacteriocins ( 7 ) with possible applications as food additives and antibiotic-complementary and leishmanicidal agents ( 8 – 11 ).…”