Louise Domeneghini Chiaradia-Delatorre's research while affiliated with Federal University of Santa Catarina and other places

Identification of allosteric inhibitors of PTPs has attracted great interest as a new strategy to overcome the challenge of discover potent and selective molecules for therapeutic intervention. YopH is a virulence factor of the genus Yersinia, validated as an antimicrobial target. The finding of a second substrate binding site in YopH has revealed a putative allosteric site that could be further exploited. Novel chalcone compounds that inhibit PTPs activity were designed and synthesized. Compound 3j was the most potent inhibitor, interestingly, with different mechanisms of inhibition for the panel of enzymes evaluated. Further, our results showed that compound 3j is an irreversible non-competitive inhibitor of YopH that binds to a site different than the catalytic site, but close to the well-known second binding site of YopH.

Currently available chemotherapeutic drugs against hematological malignancies have several adverse effects and are associated with high mortality rates. Thus, in this study we evaluated the cytotoxic effect of 26 new sulfonamide derivatives on acute leukemia and multiple myeloma cells in order to try to discover a new selective and safe compound that might be used as a prototype for new chemotherapeutic agents. The most cytotoxic compound, DFS16, reduced the cell viability of K562, Jurkat and MM.1S cells in a concentration- and time- dependent manner and it was significantly less cytotoxic to non-tumor cells. On acute leukemia cells, sulfonamide DFS16 activated intrinsic and extrinsic apoptosis with Bax/Bcl-2 inversion, increased FasR expression and ΔΨm loss. In K562, DFS16 induced apoptosis by caspase-3 activation, while in Jurkat, it induced AIF release and caspase-3 independent apoptosis. In multiple myeloma, DFS16 induced cell cycle arrest at the G2/M phase and apoptosis with ΔΨm loss. Altogether, the results suggest that the new sulfonamide derivative DFS16 induces apoptotic-like cell death in acute leukemia and multiple myeloma cells. DFS16 is a promising new molecule that could be used as a prototype for the development of chemotherapeutics against hematological malignancies.

Aim: Investigate the apoptotic mechanisms of two new aldehyde biphenyl chalcones on leukemia cells. Materials & methods: From a series of 71 new chalcones, we selected the two most cytotoxic. Results: JA3 and JA7 were cytotoxic not only against hematological malignancies but also against solid tumor and cancer stem cells, yet with no toxicity to normal cells. Moreover, they induced immunogenic apoptotic-like cell death independently of promyelocytic leukemia protein, with extensive mitochondrial damages downstream of endoplasmic reticulum stress. Preventing endoplasmic reticulum stress and the upregulation of proapoptotic machinery inhibited JA3- and JA7-induced cell death. Likewise, blocking receptor Fas protected cells from killing. They increased the antileukemic effect of cytarabine and vincristine and killed leukemic cells collected from patients with different acute leukemia subtypes. Conclusion: JA3 and JA7 represent new promising prototypes for the development of new chemotherapeutics.

Mycobacterium tuberculosis (Mtb) protein tyrosine phosphatases A and B (PtpA and PtpB) have been recognized as potential molecular targets for the development of new therapeutic strategies against tuberculosis (TB). In this context, we have recently reported that the naturally occurring Diels-Alder-type adduct Kuwanol E is an inhibitor of PtpB (Ki = 1.6 ± 0.1 μM). Here, we describe additional Diels-Alder-type adducts isolated from Morus nigra roots bark that inhibit PtpB at sub-micromolar concentrations. The two most potent compounds, namely Kuwanon G and Kuwanon H, showed Ki values of 0.39 ± 0.27 and 0.20 ± 0.01 μM, respectively, and interacted with the active site of the enzyme as suggested by kinetics and mass spectrometry studies. Molecular docking coupled with intrinsic fluorescence analysis and isothermal titration calorimetry (ITC) further characterized the interaction of these promising PtpB inhibitors. Notably, in an Mtb survival assay inside macrophages, Kuwanon G showed inhibition of Mtb growth by 61.3%. All these results point to the common Diels-Alder-type adduct scaffold, and highlight its relevance for the development of PtpB inhibitors as candidate therapeutics for TB.

Chalcones are natural compounds described in the literature by its several properties including cytotoxic activity against several tumor types. Considering that the search for new chemotherapeutic agents is still necessary, the aim of this study was to investigate the cytotoxic mechanisms involved in cell death induced by a synthetic chalcone (A23) on different tumor cells. Chalcone A23 reduced the cell viability of twelve tumor cell lines in a concentration and time dependent manner and it was more cytotoxic against acute leukemia cells. Interestingly, the compound was non cytotoxic to normal cells and non-hemolytic to normal red blood cells. Chalcone A23 decreased the expression of cell proliferation marker KI-67 and blocked the G2/M phase in both K562 and Jurkat cell lines. Cells treated with A23 showed morphological features suggestive of apoptosis, the “latter pattern” in agarose gel, the externalization of phosphatidylserine and caspase-3 and PARP cleavage. Chalcone A23 significantly reduced the mitochondrial membrane potential, decreased the expression of anti-apoptotic proteins Bcl-2 and survivin and increased the expression of pro-apoptotic protein Bax, confirming the involvement of the intrinsic pathway. The increased mitochondrial permeability resulted in the release of AIF, cytochrome c and endonuclease G from the mitochondria to the cytosol. In addition, chalcone A23 increased the expression of FasR and induced Bid cleavage, showing the involvement of the extrinsic pathway. Finally, chalcone A23 seems to have a synergic effect with the chemotherapy drugs cytarabine and vincristine. These results suggest that A23 is an interesting compound with strong and selective anti-tumor activity.

We have previously reported the cytotoxic effects of chalcone A1, derived from 1-naphthaldehyde, in leukemia cell lines. On the basis of these findings, the main aim of this study was to elucidate some of the molecular mechanisms involved in apoptosis induced by chalcone A1 toward K562 and Jurkat cells. In both cell lines, chalcone A1 decreased the mitochondrial membrane potential, increased the expression of Bax proapoptotic protein, and decreased the expression of Bcl-2 antiapoptotic protein (resulting in the inversion of the Bcl-2/Bax ratio), which indicates the involvement of the intrinsic pathway. In addition, chalcone A1 increased the expression of FasR in Jurkat cells, which also indicates the involvement of the extrinsic pathway in this cell line. The results also showed an increased expression of effector caspase-3 and cleaved PARP-1 and a decreased expression of IAP protein survivin, which are consistent with apoptotic cell death. The decreased expression of Ki67 suggests that the mechanism involved in cell death induced by chalcone A1 also involves a decrease in cell proliferation. In ex-vivo experiments, chalcone A1 reduced the cell viability of blast cells collected from eight patients with different types of acute leukemia, confirming the cytotoxicity results found in vitro. The results obtained so far are very promising and further studies need to be carried out so that chalcone A1 can be used as a prototype for the development of new antileukemia agents.

Glioblastoma multiforme is the main and most frequent tumor in adults' central nervous system. With a survival average of 5% two years after diagnosis, this type of cancer is a main health problem. Substances like the chalcones have been tested in order to develop new treatments. Here, we studied the effects of three synthetic chalcones (A23, C31 and J11) on A172 and surgery obtained-glioma cells. All chalcones showed a decrease in cell viability, mainly C31. An increase in apoptosis levels with no further increase of necrosis was observed. This augmentation may be linked to the high oxidative effect found, caused by the increased presence of reactive oxygen species and nitric oxide production. Cell cycle distribution showed an arrest at G0/G1 and S phases, suggesting that C31 interferes in cell cycle control. Our results shall aid in directing future research with this substance and its antitumor effect.

Tuberculosis (TB) is an infectious disease caused by Mycobacterium tuberculosis (Mtb), which primarily affects the respiratory tract. Combinations of drugs are used for therapeutic synergism and to prevent the emergence of drug resistant strains, but even first- or second-choice drugs present some disadvantages, such as significant side effects and the need for long duration of treatments. Thus, new strategies for TB control and treatment are highly demanded. In this context, protein tyrosine phosphatases (PtpA and PtpB) are secreted by Mtb within the host macrophage and they have been shown to contribute to Mtb pathogenicity. The understanding of the role of these PTPs has led to interesting anti-TB drugs discovery. Here, we review the current knowledge on these two proteins as targets for novel anti-TB therapies, with particular emphasis on their mechanism of action and current advancements in developing small molecule inhibitors from natural sources.

Alternaria brown spot (ABS), caused by the fungus Alternaria alternata pathotype tangerine, is one of the main phytosanitary problems for mandarin growers. About 15 applications per year of harmful fungicides are required for controlling ABS disease in citrus orchards. As chalcones seem to be less toxic to humans and environment than the commercial fungicides in use, this study initially aimed at synthesizing 137 chalcones through aldolic condensations between benzaldehydes and acetophenones. The resulting chalcones were screened for activity against A. alternata through a fungal growth assay that was carried out in 96-cell polypropylene plates, using the same concentration to all studied substances. The four active chalcones underwent conidia germination and mycelial growth, which confirmed the antifungal activity of the compounds. These chalcones were then poured onto Murcott tangor fruit that had been inoculated with conidia of the fungus. All four chalcones reduced the ABS progress to values significantly smaller (P≤0.05) than that observed for the control. Statistical calculations showed that the best results were afforded by two compounds, bearing a 2,4,5-trimethoxyphenyl group at position 3 of prop-2-enal and a 3-nitro-or 3-hydroxyphenyl group at position 1 of the aldehyde. Such compounds reduced the incidence of the disease in Murcott tangor fruit to values that did not differ statistically from those obtained with a commercial fungicide. © 2016, Universidade Federal de Uberlandia. All rights reserved.