Immunomodulatory efficacy of nisin—a bacterial lantibiotic peptide

Abstract

Nisin is a peptide bacteriocin, grouped under the category of lantibiotics. It is naturally produced by Lactococcus lactis to eliminate other competing gram-positive bacteria from its vicinity. Moreover under certain conditions it is reported to be effective against a broad range of gram-negative bacteria as well. Thus, it has been widely used as a safe food preservative especially in the dairy industry. Because of its wide-scale consumption, its effect on eukaryotic cells should be of great concern. Here we examine the immunomodulatory efficacy of nisin in vitro. MTT-based cytotoxicity assay demonstrated nisin's cytotoxicity on human T-cell lymphoma Jurkat cells, Molt-4 cells and freshly cultured human lymphocytes at over 200 µM concentration (IC(50) 225 µM). The cell death mechanism induced by nisin in all these lymphocyte types was independent of oligonucleosomal DNA fragmentation, as analyzed by agarose gel electrophoresis and comet assay. Additionally, scanning electron microscope and fluorescence microscopy demonstrated the ability of nisin to activate human PMNs in vitro. Nisin-activated neutrophils extruded intact nuclear chromatin to form NETs, well known for neutralization of virulence factors and extermination of bacterial pathogens. Nisin's presence also elevated neutrophil intracellular superoxide levels, normally produced by activated NADPH oxidase and prerequisite to NET formation. These nisin-induced responses in cellular representatives of two separate branches of human immune system-adaptive and innate-although leading to cell death, did not include DNA fragmentation. From these findings, we propose that nisin might trigger similar AICD mechanisms in lymphocytes and neutrophils, different from conventional apoptosis which involves DNA fragmentation.

Toxicity of bovicin HC5 against mammalian cell lines and the role of cholesterol in bacteriocin activity

“…Vaucher et al (2010) investigated the cytotoxicity of the antimicrobial peptides P40 and nisin, by MTT assays using Vero cells, and the IC 50 was 0.3 and 0.35 mg ml 21 for the purified peptide P40 and commercial nisin, respectively. The IC 50 determined for nisin against the human intestinal epithelial cell lines HT29 and Caco-2 was 89.9 and 115 mM, respectively (Maher & McClean, 2006), while the IC 50 determined for the same bacteriocin against Jurkat and Moult-4 cells was 225 mM (Begde et al, 2011). Those values are much higher than the IC 50 determined for nisin against the cell lines used in the present study.…”

“…Maher & McClean (2006) reported a relative haemolysis of 12.14 %±10.10 (compared with 0.1 % Triton X-100) when 230 mM nisin was assayed. In another study, 750 mM nisin caused approximately 10 % relative haemolysis against human red blood cells (Begde et al, 2011).…”

Antimicrobial nisin acts against saliva derived multi-species biofilms without cytotoxicity to human oral cells

“…Cationic antimicrobial peptides are unique in that they are hypothesized to play an important role in the immune system or to exert different effects on eukaryotic cells (Hancock and Diamond, 2000). Although bacterially secreted, nisin is known to trigger immune responses in host eukaryotic cells (Hancock and Diamond, 2000; Begde et al, 2011). As an immunogenic agent, nisin was reported to elevate the T-cell population (CD4 and CD8) while reducing the B-cell population (Pablo et al, 1999).…”

Immunomodulatory effects of anti-microbial peptides

“…Nisin is a lantibiotic produced by Lactococcus lactis and is primarily used as a food preservative. Originally considered only as an antibiotic, new data document that nisin activates human polymorphonuclear neutrophils in vitro and additionally elevates neutrophil intracellular superoxide levels [47]. Nisin induces responses in both adaptive and innate immunities leading to cell death.…”