Toxicity study of antimicrobial peptides from wild bee venom and their analogs toward mammalian normal and cancer cells

Recently, we have isolated and characterized remarkable antimicrobial peptides (AMPs) from the venom reservoirs of wild bees. These peptides (melectin, lasioglossins, halictines and macropin) and their analogs display high antimicrobial activity against Gram-positive and -negative bacteria, antifungal activity and low or moderate hemolytic activity. Here we describe cytotoxicity of the above-mentioned AMPs and some of their analogs toward two normal cell lines (human umbilical vein endothelial cells, HUVEC, and rat intestinal epithelial cells, IEC) and three cancer cell lines (HeLa S3, CRC SW 480 and CCRF-CEM T). HeLa S3 cells were the most sensitive ones (concentration causing 50% cell death in the case of the most toxic analogs was 2.5-10 μM) followed by CEM cells. For the other cell lines to be killed, the concentrations had to be four to twenty times higher. These results bring promising outlooks of finding medically applicable drugs on the basis of AMPs. Experiments using fluorescently labeled lasioglossin III (Fl-VNWKKILGKIIKVVK-NH(2)) as a tracer confirmed that the peptides entered the mammalian cells in higher quantities only after they reached the toxic concentration. After entering the cells, their concentration was the highest in the vicinity of the nucleus, in the nucleolus and in granules which were situated at very similar places as mitochondria. Experiments performed using cells with tetramethylrhodamine labeled mitochondria showed that mitochondria were fragmented and lost their membrane potential in parallel with the entrance of the peptides into the cell and the disturbance of the cell membrane.