Novel Selective and Low-Toxic Inhibitor of LmCPB2.8ΔCTE (CPB) One Important Cysteine Protease for Leishmania Virulence

Design, Synthesis, and In Vitro and In Silico Evaluation of 1,3,4-Oxadiazoles as Anti-Trypanosoma cruzi and Anti-Leishmania mexicana Agents

A series of novel 4-acetyl-1,3,4-oxadiazole derivatives was designed and synthesized for their biological evaluation in vitro against Trypanosoma cruzi (T. cruzi) and Leishmania mexicana (L. mexicana). Additionally, all compounds were evaluated by molecular docking on the cruzain of T. cruzi (TcCz) and the cysteine protease B (CPB) of L. mexicana (LmCPB) to know their potential mechanism of binding. Compound OX-12 had better trypanocidal activity against NINOA (IC50=10.5 μM) and A1 (IC50=21.7 μM) T. cruzi strains that reference drug benznidazole (IC50=30.3 μM and 39.8 μM, respectively). Compound OX-2 had the best biological activity against L. mexicana in M379 (IC50=11.9 μM) and FCQEPS (IC50=34.0 μM) strains that the reference drug glucantime (IC50>120 μM). All the compounds showed important interactions with residues on the active site of TcCz (Gly66, Trp26, Leu67, and Ala138) and LmCPB (Gly67, Asn62, Leu68, and Ala140). Finally, the molecular dynamics simulations of the compound OX-12 shown moderate stability from 40-115 ns with an RMSD value of 6.5 Å. Meanwhile, compound OX-2 showed a minor stability in complex with CPB from 25-200 ns of simulation (RMSD<9 Å). These results encourage to develop more potent and efficient trypanocidal and leishmanicidal agents using the 1,3,4-oxadiazole scaffold.

Peptide Dimerization as a Strategy for the Development of Antileishmanial Compounds

Leishmaniasis is recognized as a serious public health problem in Brazil and around the world. The limited availability of drugs for treatment, added to the diversity of side effects and the emergence of resistant strains, shows the importance of research focused on the development of new molecules, thus contributing to treatments. Therefore, this work aimed to identify leishmanicidal compounds using a peptide dimerization strategy, as well as to understand their mechanisms of action. Herein, it was demonstrated that the dimerization of the peptide TSHa, (TSHa)2K, presented higher potency and selectivity than its monomeric form when evaluated against Leishmania mexicana and Leishmania amazonensis. Furthermore, these compounds are capable of inhibiting the parasite cysteine protease, an important target explored for the development of antileishmanial compounds, as well as to selectively interact with the parasite membranes, as demonstrated by flow cytometry, permeabilization, and fluorescence microscopy experiments. Based on this, the identified molecules are candidates for use in in vivo studies with animal models to combat leishmaniasis.

Evidence of Guanidines Potential against Leishmania (Viannia) braziliensis: Exploring In Vitro Effectiveness, Toxicities and of Innate Immunity Response Effects

Leishmaniasis is a complex group of infectious and parasitic diseases that afflict many thousands of individuals across five continents. Leishmaniasis treatment remains a challenge because it relies on drugsknown for their high toxicity and limited efficacy, making itimperative to identify new molecules that offer greater effectiveness and safety. This study sought to explore the impact of seven synthetic guanidine derivatives (LQOF-G1, LQOF-G2, LQOF-G6, LQOF-G7, LQOF-G32, LQOF-G35 and LQOF-G36) onthe parasite Leishmania (Viannia) braziliensis and in vitro macrophage infection by this parasite, as well as cytotoxic approaches in vitro models of mammalian host cells and tissues. The synthesized compounds showed purity ≥ 99.65% and effectively inhibited parasite growth. LQOF-G1 proved the most potent, yielding the best half-maximal inhibitory concentration (IC50) values against promastigotes (4.62 μmol/L), axenic amastigotes (4.27 μmol/L), and intracellular amastigotes (3.65 μmol/L). Notably, the antileishmanial activity of LQOF-G1, LQOF-G2, and LQOF-G6 was related to immunomodulatory effects, evidenced by alterations in TNF-α, IL-12, IL-10, nitric oxide (NO), and reactive oxygen species (ROS) levels in the supernatant of culture macrophages infected with L. (V.) braziliensis and coincubated with these compounds. LQOF-G2 and LQOF-G36 compounds exhibited vasodilator and spasmolytic effects at higher concentrations (≥100 μmol/L). Generally, LQOF-G1, LQOF-G2, and LQOF-G32 compounds were found to be nontoxic to assessed organs and cells. No toxic effects were observed in human cell lines, such as HEK-293, CaCo-2 and A549, at concentrations ≥ 500 μmol/L. Collectively, data have shown unequivocal evidence of the effectiveness of these compounds against L. (V.) braziliensis parasite, one of the causative agents of Tegumentary Leishmaniasis and Mucocutaneous Leishmaniasis in America.

Enhancement of Radiation Sensitivity by Cathepsin L Suppression in Colon Carcinoma Cells

Cancer is one of the main causes of death globally. Radiotherapy/Radiation therapy (RT) is one of the most common and effective cancer treatments. RT utilizes high-energy radiation to damage the DNA of cancer cells, leading to their death or impairing their proliferation. However, radiation resistance remains a significant challenge in cancer treatment, limiting its efficacy. Emerging evidence suggests that cathepsin L (cath L) contributes to radiation resistance through multiple mechanisms. In this study, we investigated the role of cath L, a member of the cysteine cathepsins (caths) in radiation sensitivity, and the potential reduction in radiation resistance by using the specific cath L inhibitor (Z-FY(tBu)DMK) or by knocking out cath L with CRISPR/Cas9 in colon carcinoma cells (caco-2). Cells were treated with different doses of radiation (2, 4, 6, 8, and 10), dose rate 3 Gy/min. In addition, the study conducted protein expression analysis by western blot and immunofluorescence assay, cytotoxicity MTT, and apoptosis assays. The results demonstrated that cath L was upregulated in response to radiation treatment, compared to non-irradiated cells. In addition, inhibiting or knocking out cath L led to increased radiosensitivity in contrast to the negative control group. This may indicate a reduced ability of cancer cells to recover from radiation-induced DNA damage, resulting in enhanced cell death. These findings highlight the possibility of targeting cath L as a therapeutic strategy to enhance the effectiveness of RT. Further studies are needed to elucidate the underlying molecular mechanisms and to assess the translational implications of cath L knockout in clinical settings. Ultimately, these findings may contribute to the development of novel treatment approaches for improving outcomes of RT in cancer patients.

The Significance of Cathepsin B in Mediating Radiation Resistance in Colon Carcinoma Cell Line (Caco-2)

Cathepsins (Caths) are lysosomal proteases that participate in various physiological and pathological processes. Accumulating evidence suggests that caths play a multifaceted role in cancer progression and radiotherapy resistance responses. Their proteolytic activity influences the tumor's response to radiation by affecting oxygenation, nutrient availability, and immune cell infiltration within the tumor microenvironment. Cathepsin-mediated DNA repair mechanisms can promote radioresistance in cancer cells, limiting the efficacy of radiotherapy. Additionally, caths have been associated with the activation of prosurvival signaling pathways, such as PI3K/Akt and NF-κB, which can confer resistance to radiation-induced cell death. However, the effectiveness of radiotherapy can be limited by intrinsic or acquired resistance mechanisms in cancer cells. In this study, the regulation and expression of cathepsin B (cath B) in the colon carcinoma cell line (caco-2) before and after exposure to radiation were investigated. Cells were exposed to escalating ionizing radiation doses (2 Gy, 4 Gy, 6 Gy, 8 Gy, and 10 Gy). Analysis of protein expression, in vitro labeling using activity-based probes DCG04, and cath B pull-down revealed a radiation-induced up-regulation of cathepsin B in a dose-independent manner. Proteolytic inhibition of cathepsin B by cathepsin B specific inhibitor CA074 has increased the cytotoxic effect and cell death due to ionizing irradiation treatment in caco-2 cells. Similar results were also obtained after cathepsin B knockout by CRISPR CAS9. Furthermore, upon exposure to radiation treatment, the inhibition of cath B led to a significant upregulation in the expression of the proapoptotic protein BAX, while it induced a significant reduction in the expression of the antiapoptotic protein BCL-2. These results showed that cathepsin B could contribute to ionizing radiation resistance, and the abolishment of cathepsin B, either by inhibition of its proteolytic activity or expression, has increased the caco-2 cells susceptibility to ionizing irradiation.

Development of New Leishmanicidal Compounds via Bioconjugation of Antimicrobial Peptides and Antileishmanial Guanidines

Leishmaniasis refers to a collection of diseases caused by protozoa from the Leishmania genus. These diseases, along with other parasitic afflictions, pose a significant public health issue, particularly given the escalating number of at-risk patients. This group includes immunocompromised individuals and those residing in impoverished conditions. The treatment of leishmaniasis is crucial, particularly in light of the mortality rate associated with nontreatment, which stands at 20-30,000 deaths per year globally. However, the therapeutic options currently available are limited, often ineffective, and potentially toxic. Consequently, the pursuit of new therapeutic alternatives is warranted. This study aims to design, synthesize, and evaluate the leishmanicidal activity of antimicrobial peptides functionalized with guanidine compounds and identify those with enhanced potency and selectivity against the parasite. Accordingly, three bioconjugates were obtained by using the solid-phase peptide synthesis protocol. Each proved to be more potent against intracellular amastigotes than their respective peptide or guanidine compounds alone and demonstrated higher selectivity to the parasites than to the host cells. Thus, the conjugation strategy employed with these compounds effectively contributes to the development of new molecules with leishmanicidal activity.