Antifungal peptides at membrane interaction

Department of Biomedical and Pharmaceutical Sciences, University of Salerno, Via Ponte Don Melillo 8, 84024 Fisciano (SA), Italy.
European Journal of Medicinal Chemistry (Impact Factor: 3.45). 03/2012; 51:154-62. DOI: 10.1016/j.ejmech.2012.02.037
Source: PubMed


Many drugs are available for the treatment of systemic or superficial mycoses, but only a limited number of them are effective antifungal drugs, devoid of toxic and undesirable side effects. Furthermore, resistance development and fungistatic rather than fungicidal activities represent limitations of current antifungal therapy. Therefore an urgent need for a new generation of antifungal agents remains. We recently synthesised a set of linear and cyclic peptides characterized by sequences typical of membrane-active antimicrobial peptides (AMP). AMT2, cyclo-AMT2, AMT3 and cyclo-AMT3 (Scheme 1) were tested against different yeast species and exhibited general antifungal activity, with a specificity against Cryptococcus neoformans. To evaluate the role of the membrane cell in the mechanism of antifungal activity, we investigated the conformational behaviour of AMT2, cyclo-AMT2, AMT3 and cyclo-AMT3 in different bio-membrane mimicking systems using a combined approach based on spectroscopy and microscopy techniques. Our data highlight the behaviour of the peptides to interact with the bilayer surface, excluding their ability to destabilize or permeabilize the fungal cell wall. Microbial membrane, indeed, may be an important platform for specific interactions of peptides with specific targets involved in the cell wall synthesis.

Download full-text


Available from: Manuela Grimaldi
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Nature has provided inspiration for Drug Discovery studies and amphibian secretions have been used as a promising source of effective peptides which could be explored as novel drug prototypes for neglected parasitic diseases as Leishmaniasis and Chagas disease. In this study, we isolated four antimicrobial peptides (AMPs) from Phyllomedusa nordestina secretion, and studied their effectiveness against Leishmania (L.) infantum and T. cruzi. The antiparasitic fractions were characterized by mass spectrometry and Edman degradation, leading to the identification of dermaseptin 1 and 4 and phylloseptin 7 and 8. Trypanosoma cruzi trypomastigotes were susceptible to peptides, showing IC50 values in the range concentration of 0.25 to 0.68 μM. Leishmania (L.) infantum showed susceptibility to phylloseptin 7, presenting an IC50 value of 10 μM. Except for phylloseptin 7 which moderate showed cytotoxicity (IC50= 34 μM), the peptides induced no cellular damage to mammalian cells. The lack of mitochondrial oxidative activity of parasites detected by the MTT assay, suggested that peptides were leishmanicidal and trypanocidal. By using the fluorescent probe SYTOX(®) Green, dermaseptin 1 and 4 and phylloseptin 7 and 8 showed time-dependent plasma membrane permeabilization of T. cruzi; phylloseptin 7 also showed a similar effect in Leishmania parasites. The present study demonstrates for the first time that AMPs target the plasma membrane of Leishmania and T. cruzi, leading to cellular death. Considering the potential of amphibian peptides against protozoan parasites and the reduced mammalian toxicity, they may contribute as scaffolds for drug design studies.
    Full-text · Article · Oct 2013 · Experimental Parasitology
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Among the tropical parasitic diseases, those caused by protozoans are considered a challenge to public health, being represented by leishmaniasis and Chagas disease. In view of the low effectiveness and toxicity of the current therapy, animal venoms such as amphibian secretions have been used as a promising source of new drug prototypes. The present work aimed to achieve bioguided fractionation of metabolites present in a cutaneous secretion of the caecilian Siphonops annulatus (Amphibia: Gymnophiona: Siphonopidae) with antileishmanial and antitrypanosomal activity. Through liquid-liquid partition and chromatographic techniques, the secretion was fractionated using bioguided assays. The 50% inhibitory concentration (IC50) of the main fraction (SaFr1) was studied against Leishmania (L.) infantum promastigotes and intracellular amastigotes, trypomastigotes of Trypanosoma cruzi and mammalian cells; viability was detected by the colorimetric MTT assay. By using a spectrofluorimetric assay with the probe SYTOX® Green and transmission electron microscopy (TEM), we also investigated the potential damage caused by SaFr1 in the plasma membrane and mitochondria of Leishmania. The bioguided assay enabled isolation of a highly purified fraction (SaFr1) with an IC50 of 0.065 μg/mL against promastigotes and 2.75 μg/mL against trypomastigotes. Due to its high toxicity to peritoneal macrophages, SaFr1 showed no selectivity towards the intracellular forms of Leishmania. Ultrastructural studies with Leishmania demonstrated severe mitochondrial damage and the formation of large cytoplasmic vacuoles, leading to the parasite's death within a few hours. Nevertheless, it caused no alteration in the plasma membrane permeability as detected by the fluorescent probe and TEM. The present study demonstrated for the first time the antiparasitic activity of the skin secretion of the caecilian S. annulatus against Leishmania and T. cruzi, confirming that skin secretions of these amphibians, similarly to those of anurans and salamanders, are also potential tools for the development of new drug candidates against neglected diseases.
    Full-text · Article · Nov 2014 · Journal of Venomous Animals and Toxins including Tropical Diseases