Avaliação das características fenotípicas e funcionais de monócitos humanos durante a infecção por Leishmania e submetidos a tratamento com drogas leishmanicidas convencionais e alternativas

• Ano de defesa: 2012
• Autor(a) principal: Erica Leandro Marciano Vieira
• Tipo de documento: Tese
• Tipo de acesso: Acesso aberto
• Idioma: por
• Instituição de defesa: Universidade Federal de Minas Gerais; UFMG
• Palavras-chave em Português: Bioquímica e Imunologia; Bioquímica; Imunomodulação; Leishmaniose Tratamento
• Link de acesso: http://hdl.handle.net/1843/BUBD-9XJGKP

Leishmaniasis is an endemic disease caused by infection with protozoa of the genus Leishmania, affecting millions of people worldwide. Monocytes/macrophages play an important role in host defense against infections by being able to phagocytose and generate toxic molecules such as nitric oxide (NO) in combating parasite. The Toll-like receptors (TLR) have an essential role in the immune response against infections, but little is known about their role in human infection with Leishmania braziliensis. The search for new chemotherapeutic approaches is a need for control and treatment of leishmaniasis. In this context, molecules and immunomodulatory natural compounds with an adjuvant potential to conventional therapy are emerging as an important strategy for new studies. Natural products known as herbal extracts are popularly used as medicine since ancient times. Among these, we have obtained naftoquininas of the family Biognoniaceae, abundant in many species and with some species native in Brazil. These plant extracts have been studied in various diseases, with proven antimicrobial activity, in addition to anti-inflammatory action and antineoplastic. Another compound studied for its various actions on the immune system was N-acetylcysteine (NAC), a copound capable of incrasing greatly intracelular glutathione. Its action has been assessed in cystic fibrosis, atherosclerosis, HIV infection and in different types of cancers. Previous studies demonstrated that oral treatment with NAC reduced skin lesion and parasitism in a murine model for cutaneous leishmaniasis, caused by L. major infection. In this work, we investigated costimulatory molecules, TLR9 and cytokine expression by CD14+ monocytes from peripheral blood mononuclear cells (PBMC), in patients with cutaneous leishmaniasis caused by Leishmania braziliensis infection. We also investigated possible therapeutic candidates for leishmaniasis treatment, such as a naphthoquinone called DT.15 and NAC using monocytes from PBMC of healthy donors, and infected in vitro with L. (Viannia) braziliensis, Leishmania infantum and Leishmania major. We analyzed the leishmanicidal activity of these compounds, characterizing the expression of activation markers and cytokine production. The results concerning the PBMC of patients infected by L. braziliensis and residents in the endemic area of Corte de Pedra, demonstrated a reduction in the frequency of CD80 and CD86, and increased frequency of CD16, compared to non-infected individuals (NI) in different culture conditions. Additionally, correlation analysis indicated that CD80 and CD40 molecules were positively correlated with each other and the production of IL-12, however, negatively with CD86 expression. While evaluating these individuals, we found a high production of TNF and a low expression of IL-12 compared to NI individuals. TLR9 expression, were high in patients submitted to soluble Leishmania antigen (SLA) cultures, and when compared to individuals NI in the presence of the stimulus. Interestingly, the expression of TLR9 by monocytes correlates positively with the lesion size in the patients. These findings suggest that there was a negative regulation in the expression of costimulatory molecules CD80 and CD86, and a relationship exists between these markers. However, increased expression of TLR9, CD16 and TNF on infected monocytes, suggest an immunomodulatory compensatory mechanism. In the second part of this thesis, it was noted that the drugs DT.15 and NAC showed leishmanicidal activity on different strains of Leishmania, mainly in the direct treatment of these parasites. The results showed that the drugs reduced parasites numbers, increased the rate of death and inhibited parasite proliferation when compared to control media. The results of the test drugs (DT.15 and NAC) were similar to standard treatment with amphotericin B and Glucantime ®. In monocytes from healthy individuals infected in vitro by different strains of Leishmania, the results showed no significant differences as seen in the cultures of parasite isolates. How ever, there were important changes, such as low cytotoxicity of test compounds in human cells, changes in activation markers, especially CD11b, CD80 and CD86. In addition, different strains of Leishmania showed a distinct profile of cytokines and activation marker expression, as well as the treatments with conventional drugs in this in vitro model of infection. In conclusion, the results of this study demonstrated that monocytes play an important role in the course and development of human leishmaniasis, both in the characterization of infected individuals in endemic areas, as well as in vitro models of infection. Furthermore, the compounds evaluated (DT.15 and NAC) showed therapeutic potential on the Leishmania isolated cultures, as well as using in vitro infected cells. However, further studies are needed to determine the mechanisms behind these potential therapeutic candidates.