Ação do pré-condicionamento com Arginina e do óxido nítrico via óxido nítico sintase induzida sobre translocação bacteriana permeabilidade intestinal e síntese de citocinas em modelo de obstrução intestinal

Abstract

Arginine has been shown to have several trophic properties under stressful situations such trauma, ischemia and intestinal resection. Arginine also presents an immunological effect, especially to lymphocyte proliferation. Recent experimental studies have shown that arginine reduces bacterial translocation in trauma and septic animal models whose diets were supplemented with it. Its metabolites nitric oxide (NO) and polyamines are related. Thus, the objectives of this work were evaluate the effects of arginine and nitric oxide synthase (iNOS) on intestinal permeability, bacterial translocation, arginase activity and cytokines levels in animal fed arginine supplemented diet and submitted to intestinal obstruction induced by a simple knot. The animals were randomly divided into 6 groups: the Sham and Sham-/- groups (1, 2), which included C57BL6/J WT or C57BL6/J iNOS-/- mice fed standard chow and without IO; the IO and IO-/- groups (3, 4), which included C57BL6/J WT or C57BL6/J iNOS-/- mice fed standard chow and given an IO; and the Arg and Arg-/- groups (5, 6), which included C57BL6/J WT or C57BL6/J iNOS-/- mice fed arginine-supplemented chow and given an IO The animals were fed these diets for 7 days prior to intestinal injury. After seven days, all mice received E.coli or diethylene triamine pentaacetic acid (DTPA) radiolabeled with of 99mTechnetium. Intestinal obstruction was induced by a simple knot. After 18 hours, the animals were euthanized, and the blood, mesenteric lymph nodes, liver, spleen, and lungs were removed for radioactivity detection. Samples of the small bowel and its content were taken for histological and morphometric analysis, evaluation of intestinal permeability and intestinal polyamines. Arginase activity and cytokines levels were evaluated in distinct experiments. After 18 hours of IO, spleen was harvested. Macrophages were isolated and kept in culture to proliferation. After 7 days, supernatant was collected to evaluation of TNF- α and IL-10. Macrophages were used to arginase assay. Pre-treatment with arginine maintained intestinal permeability (p>0.05; Arg and Arg-/- groups versus Sham and Sham-/- groups), increased polyamine concentration in intestinal content (p<0.05; Arg versus IO group) and decreased bacterial translocation in WT animals (Arg group versus IO group). Absence of iNOS also presented a protective effect on permeability, but not on bacterial translocation. Arginine supplementation and the absence of iNOS increased arginase activity in splenic macrophage (Arg, OI-/- and Arg-/- groups versus Sham group; p<0,05). Arginine also was related to decrease of TNF- α and maintenance of IL-10 levels (Arg groups versus others; p>0,05). Inhibition of iNOS did not affect cytokines levels (Sham-/-; OI-/- and Arg-/- groups versus others; p>0,05). These results show that arginine supplementation and the synthesis of NO by iNOS were able to decrease bacterial translocation. Therefore, NO had a deleterious effect on intestinal permeability. Immune modulator role of arginine was seen through reduction of TNF-α levels. It is possible that this propriety was linked to NO synthesis by iNOS.