Hemolysis of erythrocytes and fluorescence polarization changes elicited by peptide toxins, aliphatic alcohols, related glycols and benzylidene derivatives

Abstract

Hemolysis rates of human erythrocytes induced by C 2 and C 8–C 14 straight chain 1-alkanols, 1,2-alkanediols and the corresponding benzylidene derivatives (benzaldehyde acetals) have been studied and compared with hemolysis rates obtained by three peptide toxins. The peak of activity occurs at C 12 for the alkanols and glycols and at C 10 for the benzylidene derivatives. The most active compound is 1-dodecanol, followed by 1,2-dodecanediol and the C 10 benzylidene acetal, which show 50% hemolysis at 15, 99 and 151 μM, respectively, at 37°C. A few lysolecithins and longer chain cis-unsaturated alcohols were studied for comparison purposes, and were found to be more active than 1-dodecanol. The most active were the 16:0 lysolecithin and cis-9-tetradecene-1-ol, which gave 50% hemolysis at concentrations of 2.8 and 5.6 μM respectively. The hemolytic activities of 1-dodecanol, 1,2-dodecanediol and the C 10 benzylidene acetal were compared to activities of Pyrularia thionin and melittin with cow, horse, sheep, pig and human erythrocytes. Whereas the peptide toxins showed clear specificity for human erythrocytes, no selectivity was shown by any of the other compounds tested. Addition of the thionin or Naja naja kaouthia cardiotoxin to erythrocyte ghosts caused a slight but reproducible increase in the order of the phospholipid bilayer, as measured with the fluorescent probe NBD-PC. Cardiotoxin gave a greater response than did the P thionin, and extensively iodinated P thionin gave a smaller change than did P thionin. Similar results were obtained with melittin, but this peptide gave a markedly greater response than all other peptides. Addition of dodecanol or the C 10 benzylidene acetal caused a marked increase in membrane fluidity. All of these data indicate that the organic compounds interact directly with and are incorporated nonspecifically into the membrane lipid bilayer, but the peptide toxins interact specifically with some component on the surface of the membrane, either a protein or specific phospholipid domain, followed by insertion into the membrane and decreasing phospholipid movement.