We performed a comparative study of effects of two structurally different
cationic antimicrobial peptides of
cathelicidin family, porcine protegrin 1 (PG1) and caprine
bactenecin 5 (Bac5) on selected
tumor and normal mammalian cells in vitro. Protegrins are amphiphilic beta-hairpin molecules having broad-spectrum antimicrobial activity due to their marked membranolytic properties. Bac5 belongs to the group of
proline-rich
peptides, which adopt a
polyproline type II extended helix and kill microorganisms rather by a non-lytic mechanism. We have shown that while PG1 exerts distinct and fast cytotoxic effects on most of used
tumor cells being slightly less toxic for nontransformed host cell, the
proline-rich Bac5 is much less cytotoxic for all the cells tested. The toxic effects of PG1 were partially declined in the presence of 10%
fetal calf serum. It was revealed that PG1 was able to interact with
proteins of
serpin family (as had been previously established for human
defensins by Panyutich et al., 1995). Pre-incubation of PG1 with alpha1-antitrypsin caused the decrease of the cytotoxic activity of the
peptide and, on the other hand, the
antiprotease activity of alpha1-antitrypsin was reduced after interaction of the
serpin with PG1 (not with Bac5). Confocal microscopy experiments allowed to monitor the internalization of fluorescent labeled (by
BODIPY FL)
peptides into target cells and their intracellular distribution. Bac5-BODIPY (at 5 microM) was rapidly taken into the cells. PG1-BODIPY at non-toxic concentrations was also able to enter the cells without significant damage to them. The comparative study of the kinetics of the
peptides uptake into the target cells and the influence of low temperature, energy-depletion and endocytosis inhibitors on the process of the internalization of the
peptides into the cells was carried out using flow cytometry.