Esculentin-2CHa: A host-defense peptide with differential cytotoxicity against bacteria, erythrocytes and tumor cells

The host-defense peptide, esculentin-2CHa (GFSSIFRGVA(10)KFASKGLGK D(20)LAKLGVDLVA(30) CKISKQC) shows potent (MIC <= 6 mu M) growth inhibitory activity against clinical isolates of multidrug-resistant strains of Staphylococcus aureus, Acinetobacter baumannii, and Stenotrophomonas maltophilia and differential cytotoxic activity against human erythrocytes (LC50 = 150 mu M) and human non-small cell lung adenocarcinoma A549 cells (LC50 = 10 mu M). Esculentin-2CHa significantly (P < 0.01) stimulates the release of the anti-inflammatory cytokine IL-10 by mouse lymphoid cells and elevates its production after stimulation with concanavalin A and significantly (P < 0.05) stimulates TNF-alpha production by peritoneal macrophages. Effects on IL-6 and IL-1 beta production were not significant. Removal of the hydrophobic N-terminal hexapeptide (GFSSIF) from esculentin-2CHa results in abolition of growth inhibitory activity against S. aureus and cytotoxic activity against erythrocytes and A549 cells as well as a marked (>= 16-fold) reduction in potency against A. baumannii and S. maltophilia. The primary structure of esculentin-2 has been poorly conserved between frog species but evolutionary pressure has acted to maintain the hydrophobic character of this N-terminal hexapeptide sequence. Removal of the cyclic C-terminal domain (CKISKQC) and replacement of the Cys(31) and Cys(37) residues by serine resulted in appreciable decreases in cytotoxicity against all microorganisms and against mammalian cells. The more cationic [D20K, D27K] analog showed a modest increase in potency against all microorganisms (up to 4-fold) but a marked increase in cytotoxicity against erythrocytes (LC50 = 11 mu M) and A549 cells (LC50 = 3 mu M). (C) 2012 Elsevier Inc. All rights reserved.