Browsing by Author "Dreyer, Leane"
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- ItemThe ability of antimicrobial peptides to migrate across the gastrointestinal epithelial and vascular endothelial barriers(Stellenbosch : Stellenbosch University, 2018-03) Dreyer, Leane; Smith, Carine; Dicks, Leon Milner Theodore; Stellenbosch University. Faculty of Science. Dept. of Microbiology.ENGLISH ABSTRACT: Antibiotic resistance has become a major threat to humankind, necessitating research and development of alternative antimicrobial compounds. Many bacteria, including lactic acid bacteria, produce small antimicrobial peptides, referred to as bacteriocins. These peptides are generally not toxic, are active at low concentrations and have a narrow spectrum of antimicrobial activity. However, they usually have low in vivo stability due to degradation by proteolytic enzymes. Drug delivery systems are thus required to transport bacteriocins to the site of infection. Probiotic bacteria are an attractive delivery system, since these bacteria normally colonise the gastrointestinal tract and produce bacteriocins. Numerous studies have been done on the probiotic Entiro™ which consists of Lactobacillus plantarum 423 and Enterococcus mundtii ST4SA. The bacteriocins produced by these strains, plantaricin 423 and bacST4SA, respectively, are active against a variety of pathogens and are potential alternatives to antibiotics. However, it is unknown whether these bacteriocins are able to migrate across the gastrointestinal epithelium and vascular endothelium in order to enter the bloodstream. The aim of this study was to evaluate the stability, cytotoxicity and permeability of plantaricin 423 and bacST4SA in vitro and evaluate the potential use of these peptides as an alternative to antibiotics. The well-known lantibiotic, Nisin A, produced by Lactococcus lactis subsp lactis, was used as control and Listeria monocytogenes EGDe as target (sensitive) organism. Migration of the lantibiotic, nisin A and class IIa bacteriocins, plantaricin 423 and bacST4SA across simulated models of the vascular endothelial and gastrointestinal epithelial barriers was studied by growing human umbilical vein endothelial cells (HUVEC)- and human colonic adenocarcinoma (Caco-2) cells on transmigration inserts and adding fluorescently labelled nisin A, plantaricin 423 and bacST4SA to the inserts. All three peptides diffused across HUVECs and Caco2 cells. Only 21% nisin A, 11% plantaricin 423 and 12% bacST4SA remained attached to Caco-2 cells and only 6% nisin A and 3% bacST4SA attached to the HUVECs, and plantaricin 423 did not attach. The viability of both cell types remained unchanged when exposed to 50 μM nisin A, 50 μM plantaricin 423 and 50 μM bacST4SA, respectively. Furthermore, little extracellular lactate dehydrogenase (LDH) activity was recorded when cells were exposed to 100 μM of each peptide, suggesting that the peptides are not cytotoxic. The three peptides retained 60% of their antimicrobial activity when 25 μM of each were exposed to 80% human plasma for 24 h. However, at higher concentrations (50 μM) 68% of the original antimicrobial activity was recorded and at 100 μM the peptides retained 79% of their activity. This is the first report of nisin A, plantaricin 423 and bacST4SA migrating across simulated gastrointestinal- and vascular barriers. In vivo studies are required to confirm these findings and determine the effect these peptides may have in the treatment of systemic infections.
- ItemMigration of bacteriocins across gastrointestinal epithelial and vascular endothelial cells, as determined using in vitro simulations(Nature Research (part of Springer Nature), 2019-08-07) Dreyer, Leane; Smith, Carine; Deane, Shelly M.; Dicks, Leon Milner Theodore, 1961-; Van Staden, Anton D.Little is known about the migration of bacteriocins across human cells. In this study, we report on migration of three bacteriocins nisin, plantaricin 423 and bacST4SA across colonic adenocarcinoma (Caco-2) cells and human umbilical vein endothelial cells (HUVECs). Bacteriocins were fluorescently labelled while still maintaining antimicrobial activity. Migration of fluorescently labelled bacteriocins across monolayers was assessed in vitro using transmigration well inserts. After 3 h, 75% of nisin, 85% of plantaricin 423 and 82% of bacST4SA migrated across the Caco-2 cell monolayer. Over the same time span, 88% nisin, 93% plantaricin 423 and 91% bacST4SA migrated across the HUVEC monolayer. The viability of both cell types remained unchanged when exposed to 50 µM of nisin, plantaricin 423 or bacST4SA. The effect of human plasma on bacteriocin activity was also assessed. Activity loss was dependent on bacteriocin type and concentration, with the class-IIa bacteriocins retaining more activity compared to nisin. This is the first report of bacteriocins migrating across simulated gastrointestinal- and vascular-barriers. This study provides some of the first evidence that bacteriocins are capable of crossing the gut-blood-barrier. However, in vivo studies need to be performed to confirm these findings and expand on the role of bacteriocin migration across cell barriers
- ItemA review : the fate of bacteriocins in the human gastro-intestinal tract : do they cross the gut–blood barrier?(Frontiers Media, 2018) Dicks, Leon Millner Theodore, 1961-; Dreyer, Leane; Smith, Carine; Van Staden, Anton D.The intestinal barrier, consisting of the vascular endothelium, epithelial cell lining, and mucus layer, covers a surface of about 400 m2. The integrity of the gut wall is sustained by transcellular proteins forming tight junctions between the epithelial cells. Protected by three layers of mucin, the gut wall forms a non-permeable barrier, keeping digestive enzymes and microorganisms within the luminal space, separate from the blood stream. Microorganisms colonizing the gut may produce bacteriocins in an attempt to outcompete pathogens. Production of bacteriocins in a harsh and complex environment such as the gastro-intestinal tract (GIT) may be below minimal inhibitory concentration (MIC) levels. At such low levels, the stability of bacteriocins may be compromised. Despite this, most bacteria in the gut have the ability to produce bacteriocins, distributed throughout the GIT. With most antimicrobial studies being performed in vitro, we know little about the migration of bacteriocins across epithelial barriers. The behavior of bacteriocins in the GIT is studied ex vivo, using models, flow cells, or membranes resembling the gut wall. Furthermore, little is known about the effect bacteriocins have on the immune system. It is generally believed that the peptides will be destroyed by macrophages once they cross the gut wall. Studies done on the survival of neurotherapeutic peptides and their crossing of the brain–blood barrier, along with other studies on small peptides intravenously injected, may provide some answers. In this review, the stability of bacteriocins in the GIT, their effect on gut epithelial cells, and their ability to cross epithelial cells are discussed. These are important questions to address in the light of recent papers advocating the use of bacteriocins as possible alternatives to, or used in combination with, antibiotics.