Browsing by Issue Date, starting with "2017-03-10"
Now showing 1 - 3 of 3
Results Per Page
Sort Options
- Desenvolvimento de heterociclos pirimidínicos derivados de ácidos barbitúricos, como potenciais inibidores da xantina oxidasePublication . Figueiredo, Joana Patrícia Rodrigues; Silvestre, Samuel Martins; Almeida, Paulo Jorge da SilvaO desenvolvimento da biologia molecular e da química computacional entre outras áreas levou ao isolamento e caraterização de diversos alvos biológicos, sendo a xantina oxidase um destes casos. Esta enzima chamou a atenção dos químicos medicinais, uma vez que o aumento da sua atividade conduz a estados patológicos graves. A xantina oxidase é uma importante e versátil molibdoflavoproteina, envolvida no metabolismo de purinas, que catalisa a transformação da hipoxantina em xantina e da xantina em ácido úrico, com concomitante produção de espécies reativas de oxigénio. Além disso, níveis elevados de ácido úrico podem levar à gota, uma doença geralmente controlada utilizando o fármaco alopurinol, que é considerado o inibidor protótipo desta enzima. No entanto, a utilização deste fármaco na clínica está associada a efeitos adversos relevantes, o que levou ao desenvolvimento de novos inibidores. Os barbituratos constituíram, ao longo dos anos uma estrutura base importante para o desenvolvimento de novos fármacos, sendo as modificações no anel pirimidínico, em especial, alterações em C-5, as mais relevantes na descoberta de novas moléculas bioativas. Com este trabalho de dissertação, e com o objetivo de se obterem análogos ao alopurinol, pretendia-se a síntese de novos barbituratos ciclizados em C-5-C-6 do anel pirimidínico. Não se confirmando a ciclização pretendida, optou-se por realizar modificações ao anel pirimídico em C-5, obtendo-se derivados de hidrazinilpirimidinas, descritos com diversas atividades biológicas. Após a caraterização estrutural dos compostos sintetizados foram testadas as suas atividades biológicas, avaliando-se as suas capacidades de inibição da atividade da enzima xantina oxidase, e o seu potenciai anti-oxidante, anti-bacteriano e anti-proliferativo, numa linha celular do cancro da mama e numa linha celular normal. Adicionalmente, foram realizados estudos complementares in silico, nomeadamente estudos de docking molecular e de previsão de propriedades farmacocinéticas. Dos resultados obtidos, destaca-se o potencial de inibição da atividade da enzima xantina oxidase de duas hidrazinilpirimidinas, tal como a capacidade de outros destes compostos como anti-oxidantes e anti-bacterianos, sendo estes últimos resultados bastantes promissores.
- Utilização de um modelo de transfusão de eritrócitos in vitro para monitorizar a divisão e expressão de CD28 em linfócitos T ativadosPublication . Padrão, Carolina Alves; Arosa, Fernando AguilarIntroduction: Blood transfusions are associated with transfusion related inflammatory and immunomodulatory effects. Although residual leukocytes present in the transfused red blood cell units have been implicated in these effects, clinical trials of leukoreduction have shown conflicting results. Our previous in vitro studies with human T cells have demonstrated that red blood cells (RBC), either autologous or heterologous, have cell growth and survival bioactivities that allow activated T cells to enter consecutive cycles of cell division. However, these studies did not characterize expression of CD28, an important receptor for naïve T cells that is lost by most CD8+ T cells during aging and chronic inflammation. Objective: The purpose of this study was to use our in vitro model of blood transfusion to analyze the extent of proliferation and the expression of CD28 on CD4+ and CD8+ T cells. Methods: Peripheral blood mononuclear cells were isolated from blood samples of regular blood donors and iron overloaded phlebotomized patients after centrifugation over Lymphoprep, labeled with carboxyfluorescein diacetate succinimidyl ester, a fluorescent dye that allows monitoring of cell division, and cultured for 6 days with the polyclonal T cell mitogen phytohaemagglutinin (PHA) in the absence or presence of red blood cells at a 50:1 RBC to PBMC ratio. Afterwards, cells were harvested, labeled with fluorochrome-conjugated antibodies against CD4, CD8 and CD28, acquired in a flow cytometer, and proliferation and expression of CD28 determined. Results: T cells proliferated more vigorously when RBC were present in the culture. Dividing CD8+ T cells showed a higher loss of CD28 than CD4+ T cells, namely in cultures with red blood cells. As a result, the percentage of CD8+CD28- T cells increased at the end of the culture period. Finally, a tendency to downregulate CD28 expression with each cell division is seen in cultures with PHA+RBC. In cultures with PHA alone a tendency to increase the values of CD28 is observed in CD4+. Conclusions & Discussion: This preliminary study suggests that red blood cells induce a population of CD8+CD28- T cells by promoting CD28 downregulation. Taking into consideration that CD8+CD28- T cells contain both immunosuppressive and inflammatory lymphocytes, these results may be relevant in the context of human pathologies where blood transfusions are needed.
- Synthesis of 5-methylene(thio)ureas (thio)barbiturates as potential xanthine oxidase inhibitorsPublication . Cavalheiro, Eunice Cerdeira Soares; Silvestre, Samuel Martins; Moreira, VâniaBarbituric acids have an important role on the development of new drugs due to their various biological effects. Nowadays, these derivatives can be used as sedatives, hypnotics, anticonvulsants and anesthetics. Moreover, they possess antibacterial, antioxidant and anticancer activities. Most of these pharmacological properties are generally due to different side groups attached on C5 of the pyrimidine ring. By means of their general chemical and physical properties, barbituric acid and its thio-analogue are great precursors for the synthesis of several heterocyclic bioactive compounds. Some studies indicate that barbiturate derivatives can also inhibit xanthine oxidase (XO). This enzyme plays an important role in purines metabolism by transforming hypoxanthine to xanthine and then to uric acid. As the overproduction of uric acid is linked to gout disease, it is of high interest to inhibit XO. In this context, during the attempts to synthetize pyrimido [4,5-d]pyrimidine-5,7-diones and 7-thione analogues using (thio)barbituric acid and their 1,3-diphenyl and dimethyl analogues, new 5-methylene(thio)urea (thio)barbiturate compounds were prepared by one-pot reaction with ureas or thioureas and trialkyl ortho-formates in acetic acid. 5-(2-Nitro)benzilidene derivatives were synthesised as well. All these precursors were structurally characterized by Infrared (IR) spectroscopy, 1H, 13C NMR, HMBC and HSQC and MS-analysis. Antioxidant evaluation though the 2,2-diphenyl-1-picrylhydrazyl (DPPH) method was performed in all synthesised compounds, however no promising antioxidant activity was revealed. These derivatives were also tested as XO inhibitors, revealing insignificant inhibitory activity towards this enzyme, excepting 1,3-dimethyl-5-[(2-nitrophenyl)methylidene]-1,3-diazinane-2,4,6-trione which revealed 60% of inhibitory activity at 30µM. In addition, a cell proliferation assay in breast cancer cell line (MCF-7) through the colorimetric 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) method showed that these derivatives do not have relevant cytotoxic effects.Additionally, it was performed molecular docking studies in order to predict the binding energies and possible interactions with XO enzyme verifying that 5-methylenethiourea thiobarbiturates presented the lowest binding energy among the other synthesised compounds.