MAGAININ-INDUCED CYTOTOXICITY IN EUKARYOTIC CELLS - KINETICS, DOSE-RESPONSE AND CHANNEL CHARACTERISTICS

Magainin 1 and magainin 2 are broad-spectrum antimicrobial and antifun gal peptides initially purified from Xenopus laevis skin glands. The m echanism of cytotoxicity of the naturally occurring magainin 2 and a p otent all-D amino acid analogue, MSI-238, was examined for eukaryotic cells using flow cytometric analysis with propidium iodide (PI). Expos ure to MSI-238 resulted in cell death within seconds to minutes, depen ding on the concentration of the peptide. Several cell types were exam ined including a mouse fibroblast cell line Balb/3T3 and a Rous sarcom a virus Balb/3T3-transformed cell line, SRD/3T3, primary chick embryo fibroblasts and cells derived from a human ovarian carcinoma, OVCA-3. The K-0.5 values determined from 5 min exposures ranged from 24 to 80 mu g/ml for MSI-238 and similar to 600 mu g/ml for magainin 2. Molecul ar properties of MSI-238 induced channels were studied in excised memb rane patch recordings from Balb/3T3 and SRD/3T3 cells. At low concentr ations of 0.1 mu g/ml, occasional, brief, multiple-level current fluct uations were seen suggesting channels with multiple, rapidly changing conductance levels. At 5 or 10 mu g/ml of MSI-238, the current fluctua tions were larger in magnitude and occurred more frequently producing a general disruption of the membrane similar to the effects of melitti n on membranes.