Synthesis and antimicrobial activity of dermaseptin S1 analogues

In vitro Antileishmanial Activity and In silico Molecular Modeling Studies of Novel Analogs of Dermaseptins S4 and B2

BACKGROUND

Leishmaniasis is responsible for approximately 65,000 annual deaths. Various Leishmania species are the predominant cause of visceral, cutaneous, or mucocutaneous leishmaniasis, affecting millions worldwide. The lack of a vaccine, emergence of resistance, and undesirable side effects caused by antileishmanial medications have prompted researchers to look for novel therapeutic approaches to treat this disease. Antimicrobial peptides (AMPs) offer an alternative for promoting the discovery of new drugs.

METHODS

In this study, we detail the synthesis process and investigate the antileishmanial activity against Leishmania (Viannia) braziliensis for peptides belonging to the dermaseptin (DS) family and their synthetic analogs. The MTT assay was performed to investigate the cytotoxicity of these peptides on the murine macrophage cell line RAW 264.7. Subsequently, we performed molecular modeling analysis to explore the structure-function correlation of the derivatives interacting with the parasitic membrane.

RESULTS

All examined derivatives displayed concentration-dependent antileishmanial effect at low concentrations. Their effectiveness varied according to the peptide's proprieties. Notably, peptides with higher levels of charge demonstrated the most pronounced activities. Cytotoxicity assays showed that all the tested peptides were not cytotoxic compared to the tested conventional drug. The structure-function relationships demonstrated that the charged N-terminus could be responsible for the antileishmanial effect observed on promastigotes.

CONCLUSION

Collectively, these results propose that dermaseptins (DS) might offer potential as promising candidates for the development of effective antileishmanial therapies.

Regulation of oxidative stress enzymes in Candida auris by Dermaseptin: potential implications for antifungal drug discovery

The emergence of Candida auris poses a significant global health threat due to its high mortality rates and multidrug resistance. The development of new antifungal drugs is essential to effectively combat this pathogen. Antimicrobial peptides, such as Dermaseptin, have demonstrated potent anti-Candida activity. This study aimed to investigate the antifungal activity of Dermaseptin against C. auris isolates and its ability to induce oxidative stress and apoptosis. The results revealed the robust anti-Candida activity of Dermaseptin, with a minimum inhibitory concentration (MIC) of 15.62 μg mL-1 and a minimum fungicidal concentration (MFC) of 31.25 μg mL-1. Spectrophotometric analysis demonstrated that Dermaseptin induced significant oxidative stress, as evidenced by the notable differences in the activity of primary antioxidant enzymes and lipid peroxidation (LPO) levels between the treated and untreated control groups. Moreover, Dermaseptin influenced the gene expression of antioxidant enzymes, as confirmed by reverse transcription quantitative polymerase chain reaction (RT-qPCR). Additionally, Dermaseptin induced apoptosis in C. auris in a dose-dependent manner. This study highlights the potential of Dermaseptin to inhibit and potentially eradicate C. auris by increasing oxidative stress levels. The low MICs and fungicidal properties of Dermaseptin against C. auris isolates suggest its potential as a candidate for the development of a novel antifungal agent.

Targeting Leishmania Promastigotes and Amastigotes Forms through Amino Acids and Peptides: A Promising Therapeutic Strategy

Millions of people worldwide are affected by leishmaniasis, caused by the Leishmania parasite. Effective treatment is challenging due to the biological complexity of the parasite, drug toxicity, and increasing resistance to conventional drugs. To combat this disease, the development of specific strategies to target and selectively eliminate the parasite is crucial. This Review highlights the importance of amino acids in the developmental stages of Leishmania as a factor determining whether the infection progresses or is suppressed. It also explores the use of peptides as alternatives in parasite control and the development of novel targeted treatments. While these strategies show promise for more effective and targeted treatment, further studies to address the remaining challenges are imperative.

Dermaseptin B2 bioactive gene's potential for anticancer and anti-proliferative effect is linked to the regulation of the BAX/BBC3/AKT pathway

Dermaseptin B2 (DrsB2) is an antimicrobial peptide with anticancer and angiostatic properties. We aimed to assess the in vitro inhibitory effect of pDNA/DrsB2 on the growth of breast cancer cells and its impact on the expression of genes involved in the BAX/BBC3/AKT pathway. The nucleic acid sequence of DrsB2 was artificially synthesized and inserted into the pcDNA3.1( +) Mammalian Expression Plasmid. PCR testing and enzyme digesting procedures evaluated the accuracy of cloning. The vectors were introduced into cells using LipofectamineTM2000 transfection reagent. The breast cancer cells were assessed by flow cytometry, MTT assessment, soft agar colony method, and wound healing investigation. The gene's transcription was evaluated using real-time PCR with a significance level of P < 0.05. The recombinant plasmid harboring the pDNA/DrsB2 vector was effectively produced, and the gene sequence showed absolute homogeneity (100% similarity) with the DrsB2 gene. The transfection effectiveness of MCF-7 and MCF-10A cells was 79% and 68%, respectively. The findings are measured using the growth inhibition 50% (GI50) metric, which indicates the concentration of pDNA/DrsB2 that stops 50% of cell growth. The proportions of early apoptosis, late apoptosis, necrosis, and viable MCF-7 cells in the pDNA/DrsB2 group were 40.50%, 2.31%, 1.69%, and 55.50%, respectively. The results showed a 100% increase in gene expression in programmed cell death following treatment with pDNA/DrsB2 (**P < 0.01). To summarize, the results described in this work offer new possibilities for treating cancer by targeting malignancies via pDNA/DrsB2 and activating the BAX/BBC3/AKT signaling pathways.

Compounds with potentialities as novel chemotherapeutic agents in leishmaniasis at preclinical level

Leishmaniasis are neglected infectious diseases caused by kinetoplastid protozoan parasites from the genus Leishmania. These sicknesses are present mainly in tropical regions and almost 1 million new cases are reported each year. The absence of vaccines, as well as the high cost, toxicity or resistance to the current drugs determines the necessity of new treatments against these pathologies. In this review, several compounds with potentialities as new antileishmanial drugs are presented. The discussion is restricted to the preclinical level and molecules are organized according to their chemical nature, source and molecular targets. In this manner, we present antimicrobial peptides, flavonoids, withanolides, 8-aminoquinolines, compounds from Leish-Box, pyrazolopyrimidines, and inhibitors of tubulin polymerization/depolymerization, topoisomerase IB, proteases, pteridine reductase, N-myristoyltransferase, as well as enzymes involved in polyamine metabolism, response against oxidative stress, signaling pathways, and sterol biosynthesis. This work is a contribution to the general knowledge of these compounds as antileishmanial agents.

Inhibition of SARS-CoV-2 3CL protease by the anti-viral chimeric protein RetroMAD1

COVID-19 results from SARS-CoV-2, which mutates frequently, challenging current treatments. Therefore, it is critical to develop new therapeutic drugs against this disease. This study explores the interaction between SARS-CoV-2 3CLpro and RetroMAD1, a well-characterized coronavirus protein and potential drug target, using in-silico methods. The analysis through the HDOCK server showed stable complex formation with a binding energy of -12.3, the lowest among reference drugs. The RetroMAD1-3CLpro complex underwent a 100 ns molecular dynamics simulation (MDS) in an explicit solvation system, generating various trajectories, including RMSD, RMSF, hydrogen bonding, radius of gyration, and ligand binding energy. MDS results confirmed intact interactions within the RetroMAD1-3CLpro complex during simulations. In vitro experiments validated RetroMAD1's ability to inhibit 3CLpro enzyme activity and prevent SARS-CoV-2 infection in human bronchial cells. RetroMAD1 exhibited antiviral efficacy comparable to Remdesivir without cytotoxicity at effective concentrations. These results suggest RetroMAD1 as a potential drug candidate against SARS-CoV-2, warranting further in vivo and clinical studies to assess its efficiency.

Neglected Zoonotic Diseases: Advances in the Development of Cell-Penetrating and Antimicrobial Peptides against Leishmaniosis and Chagas Disease

In 2020, the WHO established the road map for neglected tropical diseases 2021-2030, which aims to control and eradicate 20 diseases, including leishmaniosis and Chagas disease. In addition, since 2015, the WHO has been developing a Global Action Plan on Antimicrobial Resistance. In this context, the achievement of innovative strategies as an alternative to replace conventional therapies is a first-order socio-sanitary priority, especially regarding endemic zoonoses in poor regions, such as those caused by Trypanosoma cruzi and Leishmania spp. infections. In this scenario, it is worth highlighting a group of natural peptide molecules (AMPs and CPPs) that are promising strategies for improving therapeutic efficacy against these neglected zoonoses, as they avoid the development of toxicity and resistance of conventional treatments. This review presents the novelties of these peptide molecules and their ability to cross a whole system of cell membranes as well as stimulate host immune defenses or even serve as vectors of molecules. The efforts of the biotechnological sector will make it possible to overcome the limitations of antimicrobial peptides through encapsulation and functionalization methods to obtain approval for these treatments to be used in clinical programs for the eradication of leishmaniosis and Chagas disease.

Amphibian Skin and Skin Secretion: An Exotic Source of Bioactive Peptides and Its Application

Amphibians have been consumed as an alternative protein source all around the world due to their delicacy. The skin of edible amphibians, particularly frogs and giant salamanders, always goes to waste without further utilization. However, these wastes can be utilized to extract protein and bioactive peptides (BPs). Various BPs have been extracted and reported for numerous biological activities such as antioxidant, antimicrobial, anticancer, antidiabetic, etc. The main BPs identified were brevinins, bombesins, dermaseptins, esculentins, magainin, temporins, tigerinins, and salamandrins. This review provides a comprehensive discussion on various BPs isolated and identified from different amphibian skins or skin secretion and their biological activities. The general nutritional composition and production statues of amphibians were described. Additionally, multiple constraints against the utilization of amphibian skin and secretions are reported. Finally, the prospective applications of BPs in food and biomedical industries are presented such as multifunctional food additives and/or supplements as well as drug delivery agents.

Antimicrobial Peptides with Anti-Candida Activity

Mycoses are accountable for millions of infections yearly worldwide. Invasive candidiasis is the most usual, presenting a high morbidity and mortality. Candida albicans remains the prevalent etiologic agent, but the incidence of other species such as Candida parapsilosis, Candida glabrata and Candida auris keeps increasing. These pathogens frequently show a reduced susceptibility to commonly used antifungal drugs, including polyenes, triazoles and echinocandins, and the incidence of emerging multi-drug-resistant strains of these species continues to increase. Therefore, the need to search for new molecules that target these pathogenic species in a different manner is now more urgent than ever. Nature is an almost endless source of interesting new molecules that could meet this need. Among these molecules, antimicrobial peptides, present in different sources in nature, possess some advantages over conventional antifungal agents, even with their own drawbacks, and are considered as a promising pharmacological option against a wide range of microbial infections. In this review, we describe 20 antimicrobial peptides from different origins that possess an activity against Candida.

Progress Report: Antimicrobial Drug Discovery in the Resistance Era

Antibiotic resistance continues to be a most serious threat to public health. This situation demands that the scientific community increase their efforts for the discovery of alternative strategies to circumvent the problems associated with conventional small molecule therapeutics. The Global Antimicrobial Resistance and Use Surveillance System (GLASS) Report (published in June 2021) discloses the rapidly increasing number of bacterial infections that are mainly caused by antimicrobial-resistant bacteria. These concerns have initiated various government agencies and other organizations to educate the public regarding the appropriate use of antibiotics. This review discusses a brief highlight on the timeline of antimicrobial drug discovery with a special emphasis on the historical development of antimicrobial resistance. In addition, new antimicrobial targets and approaches, recent developments in drug screening, design, and delivery were covered. This review also discusses the emergence and roles of various antibiotic adjuvants and combination therapies while shedding light on current challenges and future perspectives. Overall, the emergence of resistant microbial strains has challenged drug discovery but their efforts to develop alternative technologies such as nanomaterials seem to be promising for the future.

Brevibacillin 2V, a Novel Antimicrobial Lipopeptide With an Exceptionally Low Hemolytic Activity

Bacterial non-ribosomally produced peptides (NRPs) form a rich source of antibiotics, including more than 20 of these antibiotics that are used in the clinic, such as penicillin G, colistin, vancomycin, and chloramphenicol. Here we report the identification, purification, and characterization of a novel NRP, i.e., brevibacillin 2V (lipo-tridecapeptide), from Brevibacillus laterosporus DSM 25. Brevibacillin 2V has a strong antimicrobial activity against Gram-positive bacterial pathogens (minimum inhibitory concentration = 2 mg/L), including difficult-to-treat antibiotic-resistant Enterococcus faecium, Enterococcus faecalis, and Staphylococcus aureus. Notably, brevibacillin 2V has a much lower hemolytic activity (HC₅₀ > 128 mg/L) and cytotoxicity (CC₅₀ = 45.49 ± 0.24 mg/L) to eukaryotic cells than previously reported NRPs of the lipo-tridecapeptide family, including other brevibacillins, which makes it a promising candidate for antibiotic development. In addition, our results demonstrate that brevibacillins display a synergistic action with established antibiotics against Gram-negative bacterial pathogens. Probably due to the presence of non-canonical amino acids and D-amino acids, brevibacillin 2V showed good stability in human plasma. Thus, we identified and characterized a novel and promising antimicrobial candidate (brevibacillin 2V) with low hemolytic activity and cytotoxicity, which can be used either on its own or as a template for further total synthesis and modification.

Peptides to Tackle Leishmaniasis: Current Status and Future Directions

Peptide-based drugs are an attractive class of therapeutic agents, recently recognized by the pharmaceutical industry. These molecules are currently being used in the development of innovative therapies for diverse health conditions, including tropical diseases such as leishmaniasis. Despite its socioeconomic influence on public health, leishmaniasis remains long-neglected and categorized as a poverty-related disease, with limited treatment options. Peptides with antileishmanial effects encountered to date are a structurally heterogeneous group, which can be found in different natural sources—amphibians, reptiles, insects, bacteria, marine organisms, mammals, plants, and others—or inspired by natural toxins or proteins. This review details the biochemical and structural characteristics of over one hundred peptides and their potential use as molecular frameworks for the design of antileishmanial drug leads. Additionally, we detail the main chemical modifications or substitutions of amino acid residues carried out in the peptide sequence, and their implications in the development of antileishmanial candidates for clinical trials. Our bibliographic research highlights that the action of leishmanicidal peptides has been evaluated mainly using in vitro assays, with a special emphasis on the promastigote stage. In light of these findings, and considering the advances in the successful application of peptides in leishmaniasis chemotherapy, possible approaches and future directions are discussed here.

Neglected tropical diseases and infectious illnesses: potential targeted peptides employed as hits compounds in drug design

Neglected Tropical Diseases (NTDs) and infectious illnesses, such as malaria, tuberculosis and Zika fever, represent a major public health concern in many countries and regions worldwide, especially in developing ones. They cause thousands of deaths per year, and certainly compromise the life of affected patients. The drugs available for therapy are toxic, have considerable adverse effects, and are obsolete, especially with respect to resistance. In this context, targeted peptides are considered promising in the design of new drugs, since they have specific action and reduced toxicity. Indeed, there is a rising interest in these targeted compounds within the pharmaceutical industry, proving their importance to the Pharmaceutical Sciences field. Many have been approved by the Food and Drug Administration (FDA) to be used as medicines, plus there are more than 300 peptides currently in clinical trials. The main purpose of this review is to show the most promising potential targeted peptides acting as hits molecules in NTDs and other infectious illnesses. We hope to contribute to the discovery of medicines in this relatively neglected area, which will be extremely useful in improving the health of many suffering people.

Non-perfectly Amphipathic α-Helical Structure Containing the XXYXX Sequence Improves the Biological Activity of Bovine αs2-Casein Antimicrobial Peptides

Non-amphiphilic WIQPKTKVIPYVRYL (WI-6) derived from bovine α_s2-casein f (193-207) was modified by a defined mutation method to obtain five engineered peptides with mirror symmetry structures. The five engineered peptide sequences were WF-1 (WFQVKTRVRTKVQFW), FW-2 (FWRRYKKVKKYRRWF), FW-3 (FWQVIKKVKKIVQWF), FK-4 (FKQFYRRVRRYFQKF), and FR-5 (FRQWYRRVRRYWQRF). However, FW-2, FW-3, FK-4, and FR-5 had obvious XXYXX sequences. Among these, FW-3 was demonstrated to have the highest antibacterial activity, which indicates that the non-perfectly amphipathic α-helical structure containing the XXYXX sequence has a better bactericidal effect. Therefore, peptide FW-3 could be widely used as a substitute for antibiotics in food, medicine, and other fields. These findings provide a potential method for designing novel antimicrobial peptides.

Antimicrobial Peptides-based Nanostructured Delivery Systems: An Approach for Leishmaniasis Treatment

BACKGROUND

Leishmaniasis is a major health problem mainly in tropical and subtropical areas worldwide, although in the last decades it has been treated with the use of conventional drugs such as amphotericin, the emergence of multidrug-resistant strains has raised a warning signal to the public health systems thus a new call for the creation of new leishmanicidal drugs is needed.

METHODS

The goal of this review was to explore the potential use of antimicrobial peptides-based nanostructured delivery systems as an approach for leishmaniasis treatment.

RESULTS

Within these new potential drugs, human host defense peptides (HDP) can be included given their remarkable antimicrobial activity and their outstanding immunomodulatory functions for the therapy of leishmaniasis.

CONCLUSION

Though several approaches have been done using these peptides, new ways for delivering HDPs need to be analyzed, such is the case for nanotechnology.

The Physical Matrix of the Plasma Membrane as a Target: The Charm of Drugs with Low Specificity

Antimicrobial peptides (AMPs) are ubiquitous through living organisms from different kingdoms. Their role is either defense against invading pathogens, or to strive for survival against microorganisms sharing the same ecological niche. Many AMPs are active against a broad variety of target microorganisms. This, together with their low induction of resistance, heralded the use of AMPs as a new generation of antibiotics. However, studies addressing the feasibility of AMP implementation on leishmaniasis are scarce. This review describes the different approaches to leishmaniasis carried out with AMPs regardless their biological origin. The chapter encompasses studies of AMPs both in vitro and in animal models of Leishmania infection. The mechanisms of action of AMPs both on Leishmania and on the macrophage are described, as well as the underlying molecular determinants of AMPs driving their effectiveness on Leishmania. Finally, the prospects for the feasible implementation of a pharmacological strategy for leishmaniasis based on peptide-based therapies are outlined.

Antiparasitic peptides

: The most important parasitic diseases, malaria, leishmaniasis, trypanosomiasis, and schistosomiasis, are a great burden to mankind, threatening the life of millions of people worldwide and mostly affecting the poorest. Because drug resistance is increasing and vaccines are rarely available, novel chemotherapeutic compounds are necessary in order to treat these devastating diseases. Insects serve as vectors of many human parasitic diseases and have been shown to express a huge variety of antimicrobial peptides (AMPs). Therefore, research activity on insect-derived AMPs has been increasing in the last 40 years. This chapter summarizes the current state of research on the possible role of AMPs as potential chemotherapeutic compounds against human parasitic diseases. As a representative antimicrobial peptide with antiparasitic activity, the structure of insect defensin A is shown [PDB accession code: 1ICA]. The molecule is surrounded by schematic representations of the human pathogenic parasites Plasmodium, Leishmania and Trypanosoma.

Guanidino groups greatly enhance the action of antimicrobial peptidomimetics against bacterial cytoplasmic membranes

Antimicrobial peptides or their synthetic mimics are a promising class of potential new antibiotics. Herein we assess the effect of the type of cationic side chain (i.e., guanidino vs. amino groups) on the membrane perturbing mechanism of antimicrobial α-peptide-β-peptoid chimeras. Langmuir monolayers composed of 1,2-dipalmitoyl-sn-glycero-3-phosphatidylglycerol (DPPG) were used to model cytoplasmic membranes of both Gram-positive and Gram-negative bacteria, while lipopolysaccharide Kdo2-lipid A monolayers were mimicking the outer membrane of Gram-negative species. We report the results of the measurements using an array of techniques, including high-resolution synchrotron surface X-ray scattering, epifluorescence microscopy, and in vitro antimicrobial activity to study the molecular mechanisms of peptidomimetic interaction with bacterial membranes. We found guanidino group-containing chimeras to exhibit greater disruptive activity on DPPG monolayers than the amino group-containing analogues. However, this effect was not observed for lipopolysaccharide monolayers where the difference was negligible. Furthermore, the addition of the nitrobenzoxadiazole fluorophore did not reduce the insertion activity of these antimicrobials into both model membrane systems examined, which may be useful for future cellular localization studies.

Antimicrobial peptides isolated from Phyllomedusa nordestina (Amphibia) alter the permeability of plasma membrane of Leishmania and Trypanosoma cruzi

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 Trypanosoma cruzi. The antiparasitic fractions were characterized by mass spectrometry and Edman degradation, leading to the identification of dermaseptins 1 and 4 and phylloseptins 7 and 8. T. cruzi trypomastigotes were susceptible to peptides, showing IC50 values in the range concentration of 0.25-0.68 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, dermaseptins 1 and 4 and phylloseptins 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.

Antibacterial and leishmanicidal activities of temporin-SHd, a 17-residue long membrane-damaging peptide

Temporins are a family of short antimicrobial peptides (8-17 residues) that mostly show potent activity against Gram-positive bacteria. Herein, we demonstrate that temporin-SHd, a 17-residue peptide with a net charge of +2 (FLPAALAGIGGILGKLF(amide)), expressed a broad spectrum of antimicrobial activity. This peptide displayed potent antibacterial activities against Gram-negative and Gram-positive bacteria, including multi-drug resistant Staphylococcus aureus strains, as well as antiparasitic activity against promastigote and the intracellular stage (amastigote) of Leishmania infantum, at concentration not toxic for the macrophages. Temporin-SHd that is structured in a non-amphipathic α-helix in anionic membrane-mimetic environments, strongly and selectively perturbs anionic bilayer membranes by interacting with the polar head groups and acyl region of the phospholipids, with formation of regions of two coexisting phases: one phase rich in peptide and the other lipid-rich. The disruption of lipid packing within the bilayer may lead to the formation of transient pores and membrane permeation/disruption once a threshold peptide accumulation is reached. To our knowledge, Temporin-SHd represents the first known 17-residue long temporin expressing such broad spectrum of antimicrobial activity including members of the trypanosomatidae family. Additionally, since only a few shorter members (13 residues) of the temporin family are known to display antileishmanial activity (temporins-TA, -TB and -SHa), SHd is an interesting tool to analyze the antiparasitic mechanism of action of temporins.

Overview on the recent study of antimicrobial peptides: origins, functions, relative mechanisms and application

Antimicrobial peptides (AMPs), which are produced by several species including insects, other animals, micro-organisms and synthesis, are a critical component of the natural defense system. With the growing problem of pathogenic organisms resistant to conventional antibiotics, especially with the emergence of NDM-1, there is increased interest in the pharmacological application of AMPs. They can protect against a broad array of infectious agents, such as bacteria, fungi, parasite, virus and cancer cells. AMPs have a very good future in the application in pharmaceuticals industry and food additive. This review focuses on the AMPs from different origins in these recent years, and discusses their various functions and relative mechanisms of action. It will provide some detailed files for clinical research of pharmaceuticals industry and food additive in application.

Antitumor and angiostatic activities of the antimicrobial peptide dermaseptin B2

Recently, we have found that the skin secretions of the Amazonian tree frog Phyllomedusa bicolor contains molecules with antitumor and angiostatic activities and identified one of them as the antimicrobial peptide dermaseptin (Drs) B2. In the present study we further explored the in vitro and in vivo antitumor activity of this molecule and investigated its mechanism of action. We showed that Drs B2 inhibits the proliferation and colony formation of various human tumor cell types, and the proliferation and capillary formation of endothelial cells in vitro. Furthermore, Drs B2 inhibited tumor growth of the human prostate adenocarcinoma cell line PC3 in a xenograft model in vivo. Research on the mechanism of action of Drs B2 on tumor PC3 cells demonstrated a rapid increasing amount of cytosolic lactate dehydrogenase, no activation of caspase-3, and no changes in mitochondrial membrane potential. Confocal microscopy analysis revealed that Drs B2 can interact with the tumor cell surface, aggregate and penetrate the cells. These data together indicate that Drs B2 does not act by apoptosis but possibly by necrosis. In conclusion, Drs B2 could be considered as an interesting and promising pharmacological and therapeutic leader molecule for the treatment of cancer.

Current developments in the therapy of protozoan infections

Protozoan parasites cause serious human and zoonotic infections, including life-threatening diseases such as malaria, African and American trypanosomiasis, and leishmaniasis. These diseases are no more common in the developed world, but together they still threaten about 40% of the world population (WHO estimates). Mortality and morbidity are high in developing countries, and the lack of vaccines makes chemotherapy the only suitable option. However, available antiparasitic drugs are hampered by more or less marked toxic side effects and by the emergence of drug resistance. As the main prevalence of parasitic diseases occurs in the poorest areas of the world, the interest of the pharmaceutical companies in the development of new drugs has been traditionally scarce. The establishment of public-private partnerships focused on tropical diseases is changing this situation, allowing the exploitation of the technological advances that took place during the past decade related to genomics, proteomics, and in silico drug discovery approaches. These techniques allowed the identification of new molecular targets that in some cases are shared by different parasites. In this review we outline the recent developments in the fields of protease and topoisomerase inhibitors, antimicrobial and cell-penetrating peptides, and RNA interference. We also report on the rapidly developing field of new vectors (micro and nano particles, mesoporous materials) that in some cases can cross host or parasite natural barriers and, by selectively delivering new or already in use drugs to the target site, minimize dosage and side effects.

Peptide-based Antifungal Therapies against Emerging Infections

Acquired drug resistance to mycotic infections is rapidly emerging as a major medical problem. Opportunistic fungal infections create therapeutic challenges, particularly in high risk immunocompromised patients with AIDS, cancer, and those undergoing transplantation. Higher mortality and/or morbidity rates due to invasive mycosis have been increasing over the last 20 years, and in light of growing resistance to commonly used antibiotics, novel antifungal drugs and approaches are required. Currently there is considerable interest in antifungal peptides that are ubiquitous in plant and animal kingdoms. These small cationic peptides may have specific targets or may be multifunctional in their mechanism of action. On the basis of recent advances in protein engineering and solid phase syntheses, the utility and potential of selected peptides as efficient antifungal drugs with acceptable toxicity profiles are being realized. This review will discuss recent advances in peptide therapy for opportunistic fungal infections.

Interactions of antimicrobial peptides with Leishmania and trypanosomes and their functional role in host parasitism

Antimicrobial peptides (AMPs) are multifunctional components of the innate systems of both insect and mammalian hosts of the pathogenic trypanosomatids Leishmania and Trypanosoma species. Structurally diverse AMPs from a wide range of organisms have in vitro activity against these parasites acting mainly to disrupt surface-membranes. In some cases AMPs also localize intracellularly to affect calcium levels, mitochondrial function and induce autophagy, necrosis and apoptosis. In this review we discuss the work done in the area of AMP interactions with trypanosomatid protozoa, propose potential targets of AMP activity at the cellular level and discuss how AMPs might influence parasite growth and differentiation in their hosts to determine the outcome of natural infection.

In vitro activities of three synthetic peptides derived from epinecidin-1 and an anti-lipopolysaccharide factor against Propionibacterium acnes, Candida albicans, and Trichomonas vaginalis

The synthetic epinecidin-1(22-42) peptide was derived from positions 22-42 of Epinephelus coioides epinecidin-1. The synthetic SALF(55-76) cyclic peptide (csSALF(55-76)) and SALF(55-76) linear peptide (lsSALF(55-76)) contained sequences from positions 55 to 76 of the Penaeus monodon anti-lipopolysaccharide factor (ALF), respectively. We studied the in vitro activities of epinecidin-1(22-42), csSALF(55-76), and lsSALF(55-76) against Propionibacterium acnes, Candida albicans, and Trichomonas vaginalis. The minimum inhibitory concentrations (MICs) of epinecidin-1(22-42) for the test pathogen strains ranged 12.5-200 microg/ml, those of csSALF(55-76) ranged 100-200 microg/ml, and those of lsSALF(55-76) ranged 25-200 microg/ml. epinecidin-1(22-42) exhibited cytotoxicity towards P. acnes, C. albicans, and T. vaginalis (one strain of which was a metronidazole-resistant strain, while the other strain was not), suggesting that epinecidin-1 functions like a lytic peptide. Similar cytotoxicity was identified against T. vaginalis treated with the csSALF(55-76) and lsSALF(55-76) peptides. The antimicrobial activities of these peptides were confirmed by scanning electron microscopy (SEM), transmission electron microscopy (TEM), a viable cell count assay, and flow cytometric analysis. TEM and SEM examinations of T. vaginalis treated with these three peptides showed that severe swelling preceded cell death and breakage of the outer membrane, and the intracellular inclusion was found to have effluxed extracellularly. This phenomenon was also found with epinecidin-1(22-42) treatment of P. acnes and C. albicans. Our results suggest that the epinecidin-1(22-42), csSALF(55-76), and lsSALF(55-76) peptides may be good candidates for treating trichomoniasis, and epinecidin-1(22-42) may have potential as a drug supporting therapy for acne and candidiasis.

Mechanism of antibacterial action of dermaseptin B2: interplay between helix-hinge-helix structure and membrane curvature strain

Dermaseptin B2 (Drs B2) is a 33-residue-long cationic, alpha-helical antimicrobial peptide endowed with membrane-damaging activity against a broad spectrum of microorganisms, including bacteria, yeasts, fungi, and protozoa, but its precise mechanism of action remained ill-defined. A detailed characterization of peptide-membrane interactions of Drs B2 was undertaken in comparison with a C-terminal truncated analogue, [1-23]-Drs B2, that was virtually inactive on bacteria despite retaining the cationic charge of the full-length peptide. Both peptides were tested on living cells using membrane permeabilization assays and on large unilamellar and multilamellar phospholipid vesicles composed of binary lipid mixtures by dye leakage assay, fluorescence spectroscopy, circular dichroism, and differential scanning calorimetry and also on SDS micelles using NMR spectroscopy. The results indicate that Drs B2 induces a strong perturbation of anionic lipid bilayers, resides at the hydrocarbon core-water interface, parallel to the plane of the membrane, and interacts preferentially with the polar head groups and glycerol backbone region of the anionic phospholipids, as well as the region of the lipid acyl chain near the bilayer surface. The interfacial location of Drs B2 induces a positive curvature of the bilayer and clustering of anionic lipids, consistent with a carpet mechanism, that may lead to the formation of mixed peptide-phospholipid toroidal, transient pores and membrane permeation/disruption once a threshold peptide accumulation is reached. In constrast, the truncated [1-23]-Drs B2 analogue interacts at the head group level without penetrating and perturbing the hydrophobic core of the bilayer. NMR study in SDS micelles showed that [1-23]-Drs B2 adopts a well-defined helix encompassing residues 2-20, whereas Drs B2 was previously found to adopt helical structures interrupted around the Val(9)-Gly(10) segment. Thus the antibacterial activity of Drs B2 depends markedly on a threshold number of hydrophobic residues to be present on both extremities of the helix. In a membrane environment with a strong positive curvature strain, Drs B2 can adopt a flexible helix-hinge-helix structure that facilitates the concomitant insertion of the strongly hydrophobic N- and C-termini of the peptide into the acyl core of the membrane.