Navegando por Palavras-chave "Violaceína"
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- ItemSomente MetadadadosInteração de violaceína com modelos de membranas(Universidade Federal de São Paulo, 2017-03-28) Souza, Karine Damaceno de [UNIFESP]; Caseli, Luciano [UNIFESP]; Universidade Federal de São Paulo (UNIFESP)Violacein is a violet pigment produced by the gram-negative bacterium Chromobacterium violaceum, which exhibits a multiplicity of biological effects, from which we can highlight bactericidal, antitumoral, antihagasic, antileishmanial and antiviral actions. However, its efficacy is still not fully proven, and the mechanisms of action and interaction of the drug with cells and biomembranes at the molecular level are not yet fully understood. In this work, Langmuir lipid films were used as cell membrane models to study at a molecular level the interactions and effects caused by violacein. First, it was observed that violacein, which is poorly soluble in water, presents superficial activity induced by the presence of a monomolecular lipid film, demonstrating that the drug has a favorable interaction with membrane models. The lipids used were dipalmitoyl phosphatidylcholine (DPPC), dipalmitoyl phosphatidylserine (DPPS), and cholesterol, which were dissolved in chloroform and dispersed at the air-water interface. For mixed drug-lipid monolayers, violacein was incorporated into the lipid monolayers by inserting aliquots of the compound after lipid scattering. The adsorption of the drug was evaluated by measurements of surface pressure, infrared reflection-absorption spectroscopy with polarization modulation (PM-IRRAS) and Brewster angle microscopy (BAM). The monolayers were then compressed to obtain surface-area pressure isotherms. After adsorbing to the monolayers, violacein expands them by shifting the surface-area pressure-isotherms of the lipids to higher molecular areas. The films of DPPC and violacein reached pressure values around 50mN/m and mean molecular area of 70 to 55 Å2/mol. DPPS and violacein films reached a pressure of around 55 mN/m and a mean molecular area around 55 to 60 Å2/mol. Cholesterol films reached pressure values around 50mN/m and a molecular area of 45 Å2/mol. These isotherms suggest that violacein is incorporated into the DPPC, DPPS and cholesterol monolayers between the lipid chains. PM-IRRAS spectra show that the bands attributed to vibrational transitions of chemical groups present in the lipids are altered in terms of position and relative intensity, demonstrating the violacein-lipid affinity. Images obtained by BAM showed alteration in the interfacial morphology of the lipid films after incorporation of the drug. In general, the action of violacein on monolayers is governed primarily by non-electrostatic intermolecular interactions. Violacein was added inside unilamellar vesicles (LUVs), showing that it can not easily break the lipid bilayer by moving into the extra aqueous medium.
- ItemAcesso aberto (Open Access)Investigação da atividade antitumoral e anti-angiogênica da violaceína em co-culturas de células leucêmicas e células endoteliais(Universidade Federal de São Paulo (UNIFESP), 2018-10-25) Palladino, Marcelly Valle [UNIFESP]; Justo, Giselle Zenker [UNIFESP]; Regatieri, Juliana Luporini Dreyfuss [UNIFESP]; http://lattes.cnpq.br/2390066977030420; http://lattes.cnpq.br/9147445236159161; http://lattes.cnpq.br/0828096610832474; Universidade Federal de São Paulo (UNIFESP)Introduction: The bone marrow microenvironment is a milieu complex of various types of stromal and hematopoietic cells involved in the selfrenewal and differentiation of stem cells and hematopoietic progenitors (HSPC). Several soluble and membranebound factors produced by endothelial cells (EC) and perivascular stroma are crucial signals to maintain quiescence and facilitate the return to homeostasis after myeloablative chemotherapy. In addition, several studies have shown a relationship between HSPCs and ECs, pointing to hemangioblastic activity in HSPCs, both in the generation of cells and blood vessels. Considering the relationships between HSPCs and CSs in the bone marrow, it is possible to implicate CDEs in the establishment and progression of malignant HSPCs such as acute and chronic myeloid leukemias. In fact, in leukemias, studies have shown that angiogenesis also contributes to its pathogenesis, with an increase in bone marrow vascularization, associated with elevated levels of angiogenic factors. Thus, therapeutic strategies that aim to inhibit the angiogenic process may aid in the treatment of leukemia. OBJECTIVE: The objective of this study was to investigate the antiangiogenic effect of violacein on rabbit aortic endothelial cell (RAEC) and leukemic cells from the K562 and Lucena1 (K562 with MDR1 phenotype) lines. Results: It was observed that violacein, at concentrations lower than its IC 50, is able to inhibit capillary tube formation, proliferation, migration and invasion of ECs, with IC50 of RAEC cells (5.0 μM) higher than IC 50 Of the leukemic cells (3.5 μM). When RAEC cells were cocultured with leukemia cells in direct contact, in the presence of inserts or with the conditioned medium of the leukemic cells, an increase in proliferation, capillary formation, migration and invasion of RAEC cells was observed. In addition, the increase in these parameters was higher in cocultures with the Lucena1 lineage. In contrast, pretreatment of leukemic cells with violacein significantly reduced these effects, with inhibition of the VEGFR2 / PI3K / AKT and VEGFR2 / Src / MAPK pathways in the studied strains (ECs and leukemias). Taken together, the results show the importance of soluble factors in the modulation of the events associated with the angiogenic process and demonstrate the antiangiogenic potential of violacein with action in important ways of regulating angiogenesis and cell proliferation.
- ItemSomente MetadadadosModulação do eixo PLCγ1, Ca2+/CAMKII e PKC em células de leucemia mieloide crônica tratadas com violaceína(Universidade Federal de São Paulo (UNIFESP), 2020-07-30) Miura, Natalia Tamagusko [UNIFESP]; Justo, Giselle Zenker [UNIFESP]; Universidade Federal de São PauloViolacein is an indole derivative isolated from Chromobacterium violaceum with potential antitumor activity and specific mechanisms of action in vitro and in vivo. This compound was evaluated in vitro in cultures of chronic myeloid leukemia (CML), which is a myeloproliferative disease associated with a genetic translocation that leads to the formation of the BCR-ABL oncoprotein. BCR-ABL is capable of inducing multiple signal transduction pathways responsible for the leukemogenic process. Moreover, BCR-ABL acts with additional mechanisms, dependent or independent of BCR-ABL, to induce resistance, leading to an unfavorable prognosis in the treatment of the disease and the search for alternative drug therapies. One of the factors that lead to the phenotype of multiple drug resistance (MDR) is related to the increase in the expression of efflux pumps, among them, the P glycoproteins (Pgp), which is one of the most studied mechanisms of chemoresistance in CML. Hence, we compared the phosphoproteomic profile of K562 cells and their variant that overexpresses the Pgp and, therefore, presents the MDR phenotype, the Lucena 1 cell line, using a microarray approach of peptides that allows to analyze the activity of different cell kinases. Data analysis showed that the exposure of K562 cells to violacein significantly modulated 13 kinases, whereas the activity of 6 kinases in Lucena 1 cells showed significant changes after treatment. The results showed a reduction in the activity of Axl and c-Met in K562 cells, while p38MAPK and JNK stimulation were observed in Lucena 1 cells. Of particular importance, the quinoma analysis indicated significant modulation in protein kinase C (PKC) activity after treatment of cells of both strains with violacein. In this sense, a reduction in phosphorylation of PKCα(Ser657) by immunoblotting was also observed. On the other hand, the pretreatment of cells with the specific classic PKC inhibitor, chelerythrine, inhibited about 80% of cell death induced by violacein, corroborating the increase in intracellular Ca2+ concentration. In addition, a significant increase in CAMKII(Thr286) activity was observed, suggesting that stimulation of the Ca2+/CAMKII axis and PKCs is important for cell death induced by violacein. In addition, the results also demonstrated the inhibition of PLCγ1(Tyr783), suggesting that this effect is also involved in inducing cell death. Together, the results indicate an important role for Ca2+ signaling and PLCγ1 inhibition in violacein-induced CML cell death. They also open perspectives for investigating new targets of action of this naturally derived compound.