Development of new dinuclear Fe(III) coordination compounds with in vitro nanomolar antitrypanosomal activity

Understanding the mechanism of action of protease inhibitors in controlling the growth of the Candida Genus: potential candidates for development of new antifungal molecules

There is a growing imperative for research into alternative compounds for the treatment of the fungal infections. Thus, many studies have focused on the analysis of antifungal proteins and peptides from different plant sources. Among these molecules are protease inhibitors (PIs). Previously, PIs present in the peptide-rich fractions called PEF1, PEF2 and PEF3 were identified from Capsicum chinense seeds, which have strong activity against phytopathogenic fungi. The aim of this study was to evaluate the mechanism of action and antimicrobial activity of PIs from PEF2 and PEF3 on the growth of yeasts of the genus Candida. In this work, analyses of their antimicrobial activity and cell viability were carried out. Subsequently, the mechanism of action by which the PIs cause the death of the yeasts was evaluated. Cytotoxicity was assessed in vitro by erythrocytes lysis and in vivo in Galleria mellonella larvae. PEF2 and PEF3 caused 100% of the growth inhibition of C. tropicalis and C. buinensis. For C. albicans inhibition was approximately 60% for both fractions. The PEF2 and PEF3 caused a reduction in mitochondrial functionality of 54% and 46% for C. albicans, 26% and 30% for C. tropicalis, and 71% and 68% for C. buinensis, respectively. These fractions induced morphological alterations, led to membrane permeabilization, elevated ROS levels, and resulted in necrotic cell death in C. tropicalis, whilst demonstrating low toxicity toward host cells. From the results obtained here, we intend to contribute to the understanding of the action of PIs in the control of fungal diseases of medical importance.

Synergistic action of synthetic peptides and amphotericin B causes disruption of the plasma membrane and cell wall in Candida albicans

The objective of this work was to evaluate the combination of synthetic peptides based on the γ-core motif of defensin PvD1 with amphotericin B (AmB) at different concentrations against Candida albicans. We applied the checkerboard assay using different concentrations of the commercial drug AmB and the synthetic peptides γ31-45PvD1++ and γ33-41PvD1++ against C. albicans, aiming to find combinations with synergistic interactions. Between these two interactions involving γ31-45PvD1++ and AmB, an additive effect was observed. One such interaction occurred at concentrations of 0.009 µM of peptide γ31-45PvD1++ and 13.23 µM of AmB and another condition of 0.019 µM of peptide γ31-45PvD1++ and 6.61 µM of AmB. The other two concentrations of the interaction showed a synergistic effect in the combination of synthetic peptide γ31-45PvD1++ and AmB, where the concentrations were 1.40 µM peptide γ31-45PvD1++ and 0.004 µM AmB and 0.70 µM γ31-45PvD1++ peptide and 0.002 µM AmB. We proceeded with analysis of the mechanism of action involving synergistic effects. This examination unveiled a range of impactful outcomes, including the impairment of mitochondrial functionality, compromise of cell wall integrity, DNA degradation, and a consequential decline in cell viability. We also observed that both synergistic combinations were capable of causing damage to the plasma membrane and cell wall, causing leakage of intracellular components. This discovery demonstrates for the first time that the synergistic combinations found between the synthetic peptide γ31-45PvD1++ and AmB have an antifungal effect against C. albicans, acting on the integrity of the plasma membrane and cell wall.

In vitro anti-Leishmania activity of new isomeric cobalt(II)complexes and in silico insights: Mitochondria impairment and apoptosis-like cell death of the parasite

The synthesis, physico-chemical characterization and in vitro antiproliferative activity against the promastigote form of Leishmania amazonensis of two new cobalt(II) coordination compounds (i.e. [Co(HL1)Cl₂]0.4,2H₂O (1) and [Co(HL2)(Cl)(CH₃OH)](ClO₄).2H₂O (2)) are reported, where HL1 = 4-{3-[bis(pyridin-2-ylmethyl)amino]-2-hydroxypropoxy}-2H-chromen-2-one and HL2 = 7-{3-[bis(pyridin-2-ylmethyl)amino]-2-hydroxypropoxy}-2H-chromen-2-one. X-ray diffraction studies were performed for complex (2) and the structure of complex (1) was built through Density Functional Theory (DFT) calculations. Complex (1) presented no cytotoxicity to LLC-MK2, but complex (2) was toxic. IC₅₀ against promastigotes of L. amazonensis for complex (1) were 4.90 (24 h), 3.50 (48 h) and 3. 80 μmol L^-1 (72 h), and for complex (2) were 2.09, 4.20 and 2.80 μmol L^-1, respectively. Due to the high toxicity presented by complex (2) against LLC-MK2 host cells, mechanistic studies, to shed light on the probable mode of leishmanicidal activity, were carried out only for the non-cytotoxic complex. Complex (1) was able to elevate mitochondrial membrane potential of the parasites after treatment. Transmission electron microscopy revealed typical apoptotic condensation of chromatin, altered kinetoplast and mitochondria structures, suggesting that apoptosis-like cell death of the protozoa is probably mediated by an apoptotic mechanism associated with mitochondrial dysfunction (intrinsic pathway). Molecular docking studies with complex (1) upon protein tyrosine phosphatase (LmPRL-1) suggests a plausible positive complex anchoring mainly by hydrophobic and hydrogen bond forces close to the enzyme's catalytic site. These promising results for complex 1 will prompt future investigations against amastigote form of L. amazonensis.

Fexinidazole interferes with the growth and structural organization of Trypanosoma cruzi

Fexinidazole (FEX) is a heterocyclic compound and constitutes the first 100% oral treatment drug for African trypanosomiasis. Its effectiveness against Trypanosoma brucei encouraged the investigation of its antiparasitic potential against T. cruzi, the aetiological agent of Chagas disease. Although previous studies addressed the antitrypanosomal effects of FEX, none used electron microscopy to identify the main target structures of T. brucei or T. cruzi. In this work, we used microscopy techniques to analyze the ultrastructural alterations caused by FEX in different developmental stages of T. cruzi. In addition to inhibiting T. cruzi proliferation, with IC₅₀ of 1 µM for intracellular amastigotes, FEX promoted massive disorganization of reservosomes, the detachment of the plasma membrane, unpacking of nuclear heterochromatin, mitochondrial swelling, Golgi disruption and alterations in the kinetoplast-mitochondrion complex. Together, these observations point to FEX as a potential drug leader for further developing of chemotherapy against Chagas disease.

Monomethylsulochrin isolated from biomass extract of Aspergillus sp. against Leishmania amazonensis: In vitro biological evaluation and molecular docking

Leishmaniasis represents a serious world health problem, with 1 billion people being exposed to infection and a broad spectrum of clinical manifestations with a potentially fatal outcome. Based on the limitations observed in the treatment of leishmaniasis, such as high cost, significant adverse effects, and the potential for drug resistance, the aim of the present study was to evaluate the leishmanicidal activity of the compounds pseurotin A and monomethylsulochrin isolated from the biomass extract of Aspergillus sp. The chromatographic profiles of the extract were determined by high-performance liquid chromatography coupled with a diode-array UV-Vis detector (HPLC-DAD-UV), and the molecular identification of the pseurotin A and monomethylsulochrin were carried out by electrospray ionization mass spectrometry in tandem (LC-ESI-MS-MS) and nuclear magnetic resonance (NMR). Antileishmanial activity was assayed against promastigote and intracellular amastigote of Leishmania amazonensis. As a control, cytotoxicity assays were performed in non-infected BALB/c peritoneal macrophages. Ultrastructural alterations in parasites were evaluated by transmission electron microscopy. Changes in mitochondrial membrane potential were determined by flow cytometry. Only monomethylsulochrin inhibited the promastigote growth (IC₅₀ 18.04 ± 1.11 µM), with cytotoxicity to peritoneal macrophages (CC₅₀ 5.09 91.63 ± 1.28 µM). Activity against intracellular amastigote forms (IC₅₀ 5.09 ± 1.06 µM) revealed an increase in antileishmanial activity when compared with promastigotes. In addition to a statistically significant reduction in the evaluated infection parameters, monomethylsulochrin altered the ultrastructure of the promastigote forms with atypical vacuoles, electron-dense corpuscles in the cytoplasm, changes at the mitochondria outer membrane and abnormal disposition around the kinetoplast. It was showed that monomethylsulochrin leads to a decrease in the mitochondrial membrane potential (25.9%, p = 0.0286). Molecular modeling studies revealed that monomethylsulochrin can act as inhibitor of sterol 14-alpha-demethylase (CYP51), a therapeutic target for human trypanosomiasis and leishmaniasis. Assessed for its drug likeness, monomethylsulochrin follows the Lipinski Rule of five and Ghose, Veber, Egan, and Muegge criteria. Furthermore, monomethylsulochrin can be used as a reference in the development of novel and therapeutically useful antileishmanial agents.