Ação de desferoxamina e deferasirox em eritrócitos de portadores de anemias dependentes de transfusão, com sobrecarga oxidativa, in vitro

Abstract

Resumo: Os eritrócitos sao celulas altamente especializadas, continuamente expostas ao estresse oxidativo, devido a exposicao a alta tensao de oxigenio e ao ion ferro, ambos capazes de iniciar a geracao de radicais livres. Pacientes portadores de algumas doencas como talassemias e anemia falciforme, entre outras, podem apresentar sobrecarga de ferro transfusional e consequente aumento nos parametros de estresse oxidativo. O presente trabalho teve como objetivo avaliar a acao dos quelantes de ferro desferoxamina (DFO) e deferasirox (DFX) no metabolismo oxidativo de eritrocitos normais e de pacientes em tratamento com esses medicamentos. Foram obtidas amostras de 10 individuos considerados normais, 14 pacientes com ƒÀ-talassemia maior em tratamento com DFO e 5 pacientes em tratamento com DFX, sendo 4 com ƒÀ-talassemia maior e 1 com anemia falciforme. Foram avaliadas, ainda, amostras de 2 pacientes com ƒÀ-talassemia intermedia e 10 pacientes com anemia falciforme, sem tratamento quelante. Os eritrocitos dos pacientes foram incubados com os agentes oxidantes tBHP e AAPH e os eritrocitos dos individuos normais foram incubados com solucoes dos quelantes em estudo e, posteriormente, com os mesmos oxidantes. Foram realizadas determinacoes de concentracoes de metemoglobina, glutationa reduzida, substancias reativas ao acido tiobarbiturico, atividade da enzima glicose 6-fosfato desidrogenase e porcentagens de hemolise. A partir dos resultados obtidos demonstrou-se que os valores basais dos individuos normais e dos pacientes foram semelhantes. A incubacao com os oxidantes alterou significativamente os parametros de estresse oxidativo em todos os grupos, sendo significativamente diferentes nos pacientes com anemias, comparados com os normais. Foram observados aumentos nas concentracoes de metemoglobina, formacao de substancias reativas ao acido tiobarbiturico e porcentagens de hemolise, bem como diminuicao nas concentracoes de glutationa reduzida e atividades enzimaticas da glicose 6-fosfato desidrogenase. Foi observada uma protecao parcial dos quelantes de ferro estudados, DFO e DFX, contra a oxidacao, evidenciada principalmente pela determinacao das substancias reativas ao acido tiobarbiturico e porcentagens de hemolise. Esses resultados confirmam a maior susceptibilidade aos processos oxidativos dos eritrocitos de pacientes portadores de sobrecarga de ferro transfusional, quando comparados aos eritrocitos de individuos normais.

Abstract: Red blood cells are highly specialized, being continuously exposed to oxidative stress, due to the presence of high-tension oxygen and iron ion, both able to start generating free radicals. Patients with certain diseases such as sickle cell anemia and thalassaemia, among others, can have transfusional iron overload and consequent increase in oxidative stress parameters. The present study aimed to evaluate the action of iron chelating agents as deferoxamine (DFO) and deferasirox (DFX) in the erythrocyte oxidative metabolism in normal individuals and patients in treatment with these medications. Samples were obtained of 10 individuals considered normal, in 14 â-thalassaemic major patients under DFO treatment plus 5 patients under DFX treatment, being 4 with â-thalassaemia major and 1 with sickle cell anemia. It were still evaluated, 2 samples of patients with â-thalassaemia intermedia and 10 patients with sickle-cell disease, without chelation treatment. Red cells of patients were incubated with oxidizing agents tBHP and AAPH. Red cells of normal individuals were incubated with solutions of chelating agents under study and, later, with the same oxidants. It were carried out determinations of methemoglobin concentration, reduced glutathione, thiobarbituric acid reactive substances, activity of the enzyme glucose 6-phosphate dehydrogenase and percentages of hemolysis. There results obtained showed that the basal values of normal individuals and patients were similar. Incubation with oxidants significantly changed the parameters of oxidative stress in all groups, being significantly higher in anemic patients than in normal individuals. There were observed increased concentrations of methemoglobin, formation of thiobarbituric acid reactive substances and percentages of hemolysis as well as decrease in concentrations of reduced glutathione and enzymatic activity of glucose 6-phosphate dehydrogenase. There was observed partial protection against oxidation iron chelating agents, evidenced mainly on thiobarbituric acid reactive substances parameters and percentages of hemolysis. The results obtained confirmed the higher susceptibility of the erythrocyte from patients with transfusional iron overload to oxidation processes, compared thus with erythrocytes from normal individuals.