Biology subjects

Barbosa da Silva, E.

Publications and source records attributed to Barbosa da Silva, E..

4 recordsLinked to original sources

bioRxiv2025

Chalcogen derivatives for the treatment of African trypanosomiasis: biological evaluation of thio and seleno- semicarbazones and their azole derivatives

Human African Trypanosomiasis (HAT) is caused by Trypanosoma brucei. Drug therapy remains challenging due to drug resistance and/or toxicity. New drugs are needed. Using thiosemicarbazones as a starting point, we employed a S to Se isosteric replacement strategy to design 44 analogs which were evaluated against T. brucei in vitro. Compounds were divided into eleven groups of four derivatives corresponding to thio-, selenosemicarbazones, and their cyclic counterparts, thio- and selenazoles. We selected three groups which contained a total of six derivatives that inhibited parasite growth by >70%. Then, we investigated the mechanism of action of these compounds, performing quantitative assays to measure their inhibition of the T. brucei cathepsin L-like protease (TbrCATL) and DPPH antioxidant activities. The lead compound (SeO3) showed antioxidant capacity and the best activity against T. brucei (EC50 = 0.47 {micro}M). Nevertheless, its toxicity should be improved. We also predicted the interactions of these compounds with TbrCATL utilizing molecular dynamics. We demonstrate that the Se derivatives are more active than their S analogues, and that the selenazole ring decreases Se-associated toxicity. Also, thio- and selenosemicarbazones are more potent against TbrCATL than the cyclic derivatives. We conclude that TbrCATL inhibition should be combined with antioxidant activity to obtain active compounds against T. brucei.

microbiology↗

bioRxiv2024

Aspartic proteases are abundant and active in acidified wound fluid

Wound healing necessitates a balance between synthesis and breakdown of extracellular matrix components, which is tightly regulated by proteases and their inhibitors. Studies have shown that treatment of poorly healing wounds with acid results in improved healing. In this study, we systematically evaluated changes in proteolytic activity of murine wound fluid upon acidification. A library of 228 synthetic peptides served as reporters of protease activity at pH 7.4, pH 5.0 and pH 3.5. The peptide digestion patterns differed at each pH, revealing that proteases active at pH 7.4 are inactivated at pH 3.5. Notably, aspartic acid proteases emerged as the dominant active enzymes at pH 3.5 and their activity was inhibited by pepstatin. Using a fluorogenic substrate, we quantified aspartic protease activity across varying pH levels and demonstrated optimal activity between pH 3.0 and 3.8. This activity was detectable as early as one day post-injury and persisted over the following ten days. Importantly, human wound fluid exhibited the same activity profile, validating the mouse model as a relevant system for studying acid-mediated wound healing processes.

biochemistry↗

bioRxiv2022

Structure-based identification of naphthoquinones and derivatives as novel inhibitors of main protease Mpro and papain-like protease PLpro of SARS-CoV-2

The worldwide COVID-19 pandemic caused by the coronavirus SARS-CoV-2 urgently demands novel direct antiviral treatments. The main protease (Mpro) and papain-like protease (PLpro) are attractive drug targets among coronaviruses due to their essential role in processing the polyproteins translated from the viral RNA. In the present work, we virtually screened 688 naphthoquinoidal compounds and derivatives against Mpro of SARS-CoV-2. Twenty-four derivatives were selected and evaluated in biochemical assays against Mpro using a novel fluorogenic substrate. In parallel, these compounds were also assayed with SARS-CoV-2 PLpro. Four compounds inhibited Mpro with half-maximal inhibitory concentration (IC50) values between 0.41 {micro}M and 66 {micro}M. In addition, eight compounds inhibited PLpro with IC50 ranging from 1.7 {micro}M to 46 {micro}M. Molecular dynamics simulations suggest stable binding modes for Mpro inhibitors with frequent interactions with residues in the S1 and S2 pockets of the active site. For two PLpro inhibitors, interactions occur in the S3 and S4 pockets. In summary, our structure-based computational and biochemical approach identified novel naphthoquinonal scaffolds that can be further explored as SARS-CoV-2 antivirals.

biochemistry↗

bioRxiv2021

Identification of Leucinostatins from Ophiocordyceps sp. as Antiparasitic Agents Against Trypanosoma cruzi

Safe and effective treatments for Chagas disease, a potentially fatal parasitic infection associated with cardiac and gastrointestinal pathology and caused by the kinetoplastid parasite Trypanosoma cruzi, have yet to be developed. Benznidazole and nifurtimox, which are currently the only available drugs against T. cruzi, are associated with severe adverse effects and questionable efficacy in the late stage of the disease. Natural products have proven to be a rich source of new chemotypes for other infectious agents. We utilized a microscopy-based high-throughput phenotypic screen to identify inhibitors of T. cruzi from a library of natural product samples obtained from fungi procured through a Citizen Science Soil Collection Program (https://whatsinyourbackyard.org/), and the Great Lakes (USA) benthic environment. We identified five leucinostatins (A, B, F, NPDG C and NPDG D) as potent inhibitors of the intracellular amastigote form of T. cruzi. Leucinostatin B also showed in vivo efficacy in a mouse model of Chagas disease. Given prior reports that leucinostatins A and B have antiparasitic activity against the related kinetoplastid T. brucei, our findings suggest a potential cross-trypanocidal compound class and provide a platform for further chemical derivatization of a potent chemical scaffold against T. cruzi.

microbiology↗