Cláudia Alves

The membrane-active nature of phospholipase A₂-derived peptides makes them potential candidates for antineoplastic and antibacterial therapies. Two short 13-mer C-terminal fragments taken from snake venom Lys49-PLA₂ toxins (p-AppK and p-Acl), differing by a leucine/phenylalanine substitution, were synthesized and their bioactivity was evaluated. Their capacity to interfere with the survival of Gram-positive and Gram-negative bacteria as well as with solid and liquid tumors was assessed in vitro. Toxicity to red blood cells was investigated via in silico and in vitro techniques. The mode of action was mainly studied by molecular dynamics simulations and membrane permeabilization assays. Briefly, both peptides have dual activity, i.e., they act against both bacteria, including multidrug-resistant strains and tumor cells. All tested bacteria were susceptible to both peptides, Pseudomonas aeruginosa being the most affected. RAMOS, K562, NB4, and CEM cells were the main leukemic targets of the peptides. In general, p-Acl showed more significant activity, suggesting that phenylalanine confers advantages to the antibacterial and antitumor mechanism, particularly for osteosarcoma lines (HOS and MG63). Peptide-based treatment increased the uptake of a DNA-intercalating dye by bacteria, suggesting membrane damage. Indeed, p-AppK and p-Acl did not disrupt erythrocyte membranes, in agreement with in silico predictions. The latter revealed that the peptides deform the membrane and increase its permeability by facilitating solvent penetration. This phenomenon is expected to catalyze the permeation of solutes that otherwise could not cross the hydrophobic membrane core. In conclusion, the present study highlights the role of a single amino acid substitution present in natural sequences towards the development of dual-action agents. In other words, dissecting and fine-tuning biomembrane remodeling proteins, such as snake venom phospholipase A₂ isoforms, is again demonstrated as a valuable source of therapeutic peptides.

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.

Drug repurposing and drug combination are two strategies that have been widely used to overcome the traditional development of new anticancer drugs. Several FDA-approved drugs for other indications have been tested and have demonstrated beneficial anticancer effects. In this connection, our research group recently reported that Tacrine, used to treat Alzheimer’s Disease, inhibits the growth of breast cancer MCF-7 cells both alone and in combination with a reference drug. In this view, we have now coupled Tacrine with the model amphipathic cell-penetrating peptide (CPP) MAP, to ascertain whether coupling of the CPP might enhance the drug’s antiproliferative properties. To this end, we synthesized MAP through solid-phase peptide synthesis, coupled it with Tacrine, and made a comparative evaluation of the parent drug, peptide, and the conjugate regarding their permeability across the blood-brain barrier (BBB), ability to inhibit acetylcholinesterase (AChE) in vitro, and antiproliferative activity on cancer cells. Both MAP and its Tacrine conjugate were highly toxic to MCF-7 and SH-SY5Y cells. In turn, BBB-permeability studies were inconclusive, and conjugation to the CPP led to a considerable loss of Tacrine function as an AChE inhibitor. Nonetheless, this work reinforces the potential of repurposing Tacrine for cancer and enhances the antiproliferative activity of this drug through its conjugation to a CPP.

Ethionamide (ETH) is a commercial drug, used as a second-line resource to neutralize Mycobacterium tuberculosis infections. It is proven that its metabolization in the organism leads to the formation of the active form of the drug, but some metabolic pathways may lead to the loss of its activity. Our work proved that the presence of oxidized methionine in cells could influence ETH's degradation, leading to the appearance of an inactive metabolite that is detectable by HPLC and mass spectrometry. In addition, it was found this process increases with the degree of methionine oxidation. This study contributes to a better understanding of ethionamide's metabolism in living organisms, and can help in the design of new drugs or ethionamide boosters for the combat of multidrug resistant tuberculosis.

Parkinson’s disease (PD) is the second most common neurodegenerative disease of the elderly. Current therapies are only symptomatic, and have no disease-modifying effect. Therefore, disease progresses continuously over time, presenting with both motor and non-motor features. The precise molecular basis for PD is still elusive, but the aggregation of the protein alpha-synuclein (α-syn) is a key pathological hallmark of the disease and is, therefore, a major focus of current research. Considering the intrinsic properties of cell-penetrating peptides (CPPs) for mediating drug delivery of neurotherapeutics across the blood brain barrier (BBB), these might open novel opportunities for the development of new solutions for the treatment of brain-related aspects of PD and other neurodegenerative disorders.

Two series of novel cationic gemini surfactants based on the amino acid serine have been synthesized. These compounds contain long alkyl chains linked to the nitrogen atoms of the amino acid residues, as well as spacers interconnecting two carboxylic acid groups, through amide or ester bonds. The most efficient synthetic pathway was established; it involves the introduction of the spacers into the N,N‐dialkylated monomeric precursors by peptide condensation methods with diamines or diols, with subsequent methylation and deprotection to yield the final target surfactants. The effects of molecular structure, type of spacer linkage, and spacer length on the interfacial and cytotoxic properties of these gemini surfactants are reported and discussed; studies on gemini surfactants with amine linkages and other relevant homologous compounds (conventional bis‐quat gemini and monomeric surfactants) are also included. Overall, it is shown that cationic serine‐based gemini surfactants have enhanced interfacial properties and low cytotoxicities, offering potential use in technical and biological applications.