Antimicrobial peptides produced by multi-cellular organisms protect against pathogenic microorganisms, whereas such peptides produced by bacteria provide an ecological advantage over competitors. Certain antimicrobial peptides of metazoan origin also kill a variety of tumour cells. Plantaricin A (PlnA) is a peptide with membrane-permeabilizing strain-specific antimicrobial activity produced by Lactobacillus plantarum C11. Recently, we have reported that PlnA also permeabilizes cancerous rat pituitary cells (GH4 cells), whereas normal rat anterior pituitary cells are resistant (Sand et al. 2007). To investigate if the preferential effect on cancerous cells is a general feature of PlnA, we have studied effects of the peptide on normal and cancerous lymphocytes and neurons. The sensitivity to PlnA of normal human T- and B- cells, Jurkat cells (from human T-cell leukaemia), and Reh cells (from human B-cell leukaemia) was studied by using flow cytometric techniques to detect morphological changes. The membrane-permeabilizing effect of PlnA on normal cortical neurons in primary cultures from embryonic rats, PC12 cells (postganglionic, sympathetic neuron-related cells derived from a rat adrenal chromaffin tumour), and murine Neuro- 2A cells (derived from the C1300 spinal cord tumor) were studied by Ca²⁺- imaging using a combination of fluo-4 and fura-red as fluorochromes. All the tested cell types were affected by 10–100 mM PlnA, whereas concentrations below 10 mM had no detectable effect. We conclude that PlnA permeabilizes normal neurons and lymphocytes, and various cancerous counterparts, at about the same concentration.

Reference:

Sand, S.L., Haug, T.M, Nissen-Meyer, J. & Sand, O. 2007. J Membrane Biol 216, 61–71.