Efeitos da alga Chlorella vulgaris sobre a resposta hematopoética e capacidade funcional de neutrófilos em ratos submetidos ao estresse agudo físico e psicogênico e infectados com Listeria monocytogenes / Effects of the algae Chlorella vulgaris on hematopoietic response and functional activity of neutrophils in rats submitted to physical and psychogenic acute stress and infected with Listeria monocytogenes

Julia de Souza-Queiroz

Evidence suggests that a variety of stressors can activate the hypothalamic control of the neuroendocrine and autonomic responses involved in the production´s control of blood cells and their release from bone marrow to circulation. The algae Chlorella vulgaris (CV) has several imunomodulatory activities, as the stimulation of hematopoietic cells and the activation of mature leukocytes. The present study evaluated the mieloprotective effects of CV in rats exposed to physical stressors (inescapable - CI and escapable footshock - CE) and to psychogenic stressors (animals that witnessed the inescapable shock application - T), which were inoculated or not with a sublethal dose of the bacterium Lysteria monocytogenes (LM). The immunologic parameters observed were: 1) The growth and differentiation of bone marrow progenitors into granulocytes and macrophages (CFU-GM); 2) the functional activity (oxidative burst and phagocytosis) of blood neutrophils, using flow citometric methods; 3) The rate of survival of animals infected with lethal dose of LM and submitted or not to the stressors. The CI and T groups were mielossupressed. On the other hand, in the CE group, no differences in the number of CFU-GM were observed, when compared to controls. An increase in the susceptibility of the organism was observed when the animals received the inescapable shock application and the psychogenic stressor before the inoculatium of sublethal dose (7,8x108) of the 15 bacterium. However, this mielopoietic response was recovered with the pre-treatment with 200 mg/Kg/day for 5 consecutive days of CV, reestablishing the mielossupression caused by the stress and the infection. The escapable shock didn´t produce any significant difference in the hematopoetic response observed in the infection. The study of the survival rate of rats infected with the letal dose of LM showed that the pre-treatment with CV protected 50% of the animals that were only infected with LM, whereas in the group previously stressed the protection was of 20%. Here, the same response was observed in the animals submitted to the different types of stressors evaluated in this work. To assess the effect of CV treatment in the response of mature blood cells, we considered the functional activity of neutrophils of animals submitted to the stressors. We observed a reduction in phagocytosis in the CI and T groups, and an increase in the oxidative burst induced by the phagocytosis. In the CE group there was an increase in the blood neutrophil phagocytosis, while the production of oxidative burst remained equal to that of control group. The treatment with CV reestablished the changes in phagocytosis to normal values in all the groups, but it produced no changes in the respiratory burst, which was increased in the circunstances of the inescapable shock and of the psychogenic stressor, when compared to the values of control group. Considering our results, we suggest that CV has protective properties against the effects produced by the different types of stressors on the CFU-GM, the functional activity of neutrophils and on the rate of survival of animals stressed and infected with lethal dose of LM.

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