Antimalarial Activities of Dermaseptin S4 Derivatives

Abstract

The hemolytic antimicrobial peptide dermaseptin S4 was recently shown to exert antimalarial activity. In this study, we attempted to understand the underlying mechanism(s) and identify derivatives with improved antimalarial activity. A number of dermaseptin S4 derivatives inhibited parasite growth with a 50% inhibitory concentration (IC 50 ) in the micromolar range. Among these, the substituted S4 analog K 4 K 20 -S4 was the most potent (IC 50 ‫؍‬ 0.2 M), while its shorter version, K 4 -S4(1-13)a, retained a considerable potency (IC 50 ‫؍‬ 6 M). Both K 4 K 20 -S4 and K 4 -S4(1-13)a inhibited growth of the parasites more at the trophozoite stage than at the ring stage. Significant growth inhibition was observed after as little as 1 min of exposure to peptides and proceeded with nearly linear kinetics. The peptides selectively lysed infected red blood cells (RBC) while having a weaker effect on noninfected RBC. Thus, K 4 K 20 -S4 lysed trophozoites at concentrations similar to those that inhibited their proliferation, but trophozoites were >30-fold more susceptible than normal RBC to the lytic effect of K 4 K 20 -S4, the most hemolytic dermaseptin. The same trend was observed with K 4 -S4(1-13)a. The D isomers of K 4 K 20 -S4 or K 4 -S4(1-13)a were as active as the L counterparts, indicating that antimalarial activity of these peptides, like their membrane-lytic activity, is not mediated by specific interactions with a chiral center. Moreover, dissipation of transmembrane potential experiments with infected cells indicated that the peptides induce damage in the parasite's plasma membrane. Fluorescence confocal microscopy analysis of treated infected cells also indicated that the peptide is able to find its way through the complex series of membranes and interact directly with the intracellular parasite. Overall, the data showed that dermaseptins exert antimalarial activity by lysis of infected cells. Dermaseptin derivatives are also able to disrupt the parasite plasma membrane without harming that of the host RBC.

Direct Interaction of Dermaseptin S4 Aminoheptanoyl Derivative with Intraerythrocytic Malaria Parasite Leading to Increased Specific Antiparasitic Activity in Culture

“…It is more lytic to host cells harboring mature parasite stages, indicating dependence on changes induced by parasite in the host cell membrane. Because the latter evolves with parasite maturation, throphozoites are expected to be more sensitive than rings, as was found (5). In contrast, the selectivity of the NC7-P seems to depend on the differential ⌬⌿ of host and parasite membrane.…”

“…Antimicrobial peptides have recently emerged as interesting tools for exploring new antimalarial targets (2)(3)(4)(5)(6). These ubiquitous peptides vary considerably in structure, size, amino acid sequence, and spectrum of action (7)(8)(9)(10)(11), but the most potent peptides always have a pronounced amphipathic and distinctly basic character (12)(13)(14)(15)(16).…”

Translocation of Analogues of the Antimicrobial Peptides Magainin and Buforin across Human Cell Membranes

“…The information on cell penetration available is limited to dermaseptins (13)(14)(15), PR-39 (16), and protegrin 1 (17), although many investigators examined hemolytic activity (9,18) and cytotoxicity (19 -22). In contrast, short Arg-rich cationic peptides have recently been shown to enter mammalian cells by an energy (ATP)-independent, non-endocytotic pathway and have been utilized as vectors for delivering membrane-impermeable drugs, oligonucleotides, and proteins into cells (23).…”

Beyond Lysozyme: Antimicrobial Peptides Against Malaria

“…Ghosh and colleagues compared hemolytic dermaseptin S4 (amino acidic sequence in Table 7.4) with nonhemolytic dermaseptin S3 for their physical properties (aggregation in solution and dissociation in membranes, binding to and interaction with RBCs) and for the effect on P. falciparum growth in vitro (Ghosh et al 1997). Several derivatives were prepared starting from dermaseptin S4, with many showing a selective activity on the membrane of infected RBCs compared to the activity on the membranes of normal RBCs (Krugliak et al 2000). The effects of dermaseptin S4 and its derivatives on malaria parasites were further investigated with respect to stage specificity Efron et al 2002).…”

“…An example is given by dermaseptin S4, which is hemolytic and disrupts uninfected RBCs too. Development of more selective substitutes was necessary to decrease toxicity (Krugliak et al 2000). …”