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| Author(s): |
Mônica Sakai
Total Authors: 1
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| Document type: | Master's Dissertation |
| Press: | São Paulo. |
| Institution: | Universidade de São Paulo (USP). Faculdade de Medicina Veterinária e Zootecnia (FMVZ/SBD) |
| Defense date: | 2004-12-07 |
| Examining board members: |
João Palermo Neto;
Roger Chammas;
Maria Lucia Zaidan Dagli
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| Advisor: | João Palermo Neto |
| Abstract | |
Benzodiazepines (BDZ) are drugs widely used due to their anxiolytic and sedative properties, acting on specific sites coupled to GABAA complex in the Central Nervous System (CNS). Besides these central receptors, BDZ have affinity for peripheral-type receptors (PBR), which have been found in immune cells, such as lymphocytes and macrophages, in tumor cells and in the adrenal glands. The present study evaluated the effects of diazepam, a commonly used BDZ, on tumor growth and immunity of mice bearing Ehrlich Ascitic Tumor (EAT). Specifically, this study evaluated the following parameters of the immune system: macrophage activity, populations of B, helper and cytotoxic T lymphocytes, and Natural Killer (NK) cells cytotoxicity. Furthermore, the evaluation of PBR expression in EAT cells and possible in vitro effects of diazepam or Ro5-4864 on EAT cell cycle were performed. Results showed the following diazepam effects in vivo (3.0 mg/kg per day): (1) increased tumor growth without changes in cell cycle, after 7 days; (2) decreased the number of leucocytes in the peritoneal cavity, the production of NO and the spreading index, but did not modify the production of hydrogen peroxide and the phagocytosis index, after 2 days; (3) did not modify the relative spleen weight and the population of lymphocytes after 2 or 7 days, (4) increased NK cytotoxicity after 3 days; (5) reduced the percentage of EAT cells expressing PBR after 7 days. Experiments performed in vitro showed that diazepam or Ro5-4864 increased the proliferation of EAT cells. Diazepam treatment in vivo using lower doses (0.3 mg/kg and 1mg/kg) did not modify tumor growth. Therefore, diazepam in the dose of 3.0 mg/kg increased the growth of EAT and reduced innate immunity, probably through the decrease in the activity of peritoneal macrophages. A role of B and helper or cytotoxic T lymphocytes in our experiments seems unlikely since the population of these cells types remained unchanged. On the other hand, it was not possible to determine the relevance of NK cells cytotoxicity on tumor development. The expression of PBR in EAT cells and the increase of their proliferation induced by in vitro treatment with diazepam or Ro5-4684 were observed. The results of these two last experiments suggest that the increase on tumor growth following diazepam treatment in vivo can be attributed, at least in part, to a direct action of this drug on EAT cells (AU) | |