ABSTRACT
BACKGROUND: The purpose of this study was to assess the effect of arginine supplementation on arginase activity, tumor necrosis factor-α (TNF-α) and interleukin-10 (IL-10) synthesis in cultured splenic macrophages from a murine model of intestinal obstruction (IO). The effects of nitric oxide synthase (iNOS) inhibition were also studied using iNOS knockout animals. MATERIAL AND METHODS: Male C57BL6/J wild-type (WT) and iNOS knockout (iNOS-/-) mice were randomized into 6 groups: Sham and Sham-/- (standard chow), IO and IO-/- (standard chow + IO), and Arg and Arg-/- (standard chow supplemented with arginine + IO). After 7 days of treatment with standard or supplemented chow, IO was induced. Arginase activity as well as TNF-α and IL-10 levels were analyzed in splenic macrophage cultures. RESULTS: Arginine supplementation and the absence of iNOS increased arginase activity in splenic macrophages (Arg, IO-/-, and Arg-/- groups vs the Sham group; P < .05). Arginine was also related to a decrease in TNF-α levels (Arg vs IO group, P < .05) and maintenance of IL-10 levels (Arg vs other groups, P > .05). The inhibition of iNOS did not result in effects on the concentration of cytokines (Sham-/-, IO-/-, and Arg-/- vs other, P < .05). CONCLUSIONS: Arginine supplementation and iNOS inhibition led to increased arginase activity. Arginine availability decreased plasma TNF-α levels, which may be directly related to nitric oxide derived from arginine.
Subject(s)
Arginase/metabolism , Arginine/pharmacology , Intestinal Obstruction/drug therapy , Macrophages/drug effects , Spleen/drug effects , Tumor Necrosis Factor-alpha/metabolism , Animals , Dietary Supplements , Interleukin-10/metabolism , Macrophages/metabolism , Male , Mice , Mice, Inbred C57BL , Nitric Oxide/metabolism , Nitric Oxide Synthase Type II/antagonists & inhibitors , Nitric Oxide Synthase Type II/metabolism , Spleen/cytology , Tumor Necrosis Factor-alpha/antagonists & inhibitorsABSTRACT
BACKGROUND: Arginine has been shown to have several immunological and trophic properties in stressful diseases. Its metabolites, nitric oxide (NO) and polyamines, are related to arginine's effects. Thus, the aim of this study was to determine the effects of the NO donor L-arginine and the role of inducible NO synthase (iNOS) on intestinal permeability and bacterial translocation in a model of intestinal obstruction (IO) induced by a simple knot in the terminal ileum. MATERIAL AND METHODS: Male C57BL6/J wild-type (WT) and iNOS knockout (iNOS-/-) mice were randomized into 6 groups: Sham and Sham-/- (standard chow), IO and IO-/- (standard chow +IO), and Arg and Arg-/- (standard chow supplemented with arginine + IO). After 7 days of treatment with standard or supplemented chows, IO was induced and intestinal permeability and bacterial translocation were evaluated. The small intestine and its contents were harvested for histopathological and morphometric analysis and the determination of polyamine concentration. RESULTS: Pretreatment with arginine maintained intestinal permeability (P > .05; Arg and Arg-/- groups vs Sham and Sham-/- groups), increased polyamine concentration in intestinal content (P < .05; Arg vs IO group), and decreased bacterial translocation in WT animals (Arg group vs IO and IO-/- groups). Absence of iNOS also presented a protective effect on permeability but not on bacterial translocation. CONCLUSION: Arginine supplementation and synthesis of NO by iNOS are important factors in decreasing bacterial translocation. However, when intestinal permeability was considered, NO had a detrimental role.
Subject(s)
Arginine/administration & dosage , Bacterial Translocation/drug effects , Escherichia coli/physiology , Intestine, Small/metabolism , Intestine, Small/microbiology , Nitric Oxide Synthase Type II/genetics , Animals , Ileum/drug effects , Ileum/metabolism , Ileum/pathology , Intestinal Obstruction/metabolism , Intestinal Obstruction/microbiology , Intestinal Obstruction/pathology , Intestine, Small/pathology , Male , Mice , Mice, Inbred C57BL , Mice, Knockout , Nitric Oxide/metabolism , Nitric Oxide Synthase Type II/metabolism , Permeability , Polyamines/metabolismABSTRACT
BACKGROUND: Citrulline has been shown to be an important marker of gut function, regulator of protein metabolism, and precursor of arginine. The authors assessed the effects of citrulline on gut barrier integrity and bacterial translocation (BT) in mice undergoing intestinal obstruction. METHODS: Mice were divided into 3 groups: sham, intestinal obstruction (IO), and citrulline (CIT). The CIT group received a diet containing 0.6% citrulline; the IO and sham groups were fed a standard chow diet. On the eighth day of treatment, all animals received a diethylenetriamine pentaacetic acid (DTPA) solution labeled with (99m)Technetium ((99m)Tc-DTPA) by gavage for the intestinal permeability study. Terminal ileum was ligated except the sham group, which only underwent laparotomy. After 4, 8, and 18 hours, blood was collected to determine radioactivity. Samples of ileum were removed 18 hours after intestinal obstruction for histological analysis. In another set of animals, BT was evaluated. Animals received 10(8) CFU/mL of (99m)Tc-Escherichia coli by gavage; 90 minutes later, they underwent ileum ligation. Intestinal fluid and serum were collected to measure sIgA and cytokines. RESULTS: The CIT group presented decreased intestinal permeability and BT when compared with the IO group (P < .05). Histopathology showed that citrulline preserved the ileum mucosa. The sIgA concentration was higher in the CIT group (P < .05). The IO group presented the highest levels of interferon-γ (P < .05). CONCLUSIONS: Pretreatment with citrulline was able to preserve barrier integrity and also modulated the immune response that might have affected BT decrease.
Subject(s)
Citrulline/pharmacology , Ileum/drug effects , Intestinal Mucosa/drug effects , Intestinal Obstruction/drug therapy , Animals , Arginine/pharmacology , Bacterial Translocation/drug effects , Escherichia coli/drug effects , Ileum/metabolism , Ileum/microbiology , Immunoglobulin A, Secretory/blood , Interferon-gamma/blood , Intestinal Mucosa/metabolism , Intestinal Mucosa/microbiology , Intestinal Obstruction/microbiology , Male , Mice , Pentetic Acid/administration & dosage , PermeabilityABSTRACT
BACKGROUND & AIMS: Arginine has been shown to have multiple beneficial metabolic and immunologic effects in stress situations. Supplementation of arginine has been shown to promote wound healing and intestinal mucosal recovery after trauma, ischemia or intestinal resection. Bacterial translocation has also been evaluated although with conflicting results and using different assessing techniques. Therefore, the aim of this study was to evaluate the effects of arginine on bacterial translocation in an intestinal obstruction model in rats using Escherichia coli labeled with 99mTechnetium. METHODS: Male Wistar rats (250-350 g) were randomized to receive conventional chow, diet supplemented with pure arginine or diet supplemented with an immunonutrition enteral formula, enriched with arginine, omega-3 fatty acid and RNA. After 7 days, the animals were anesthetized. Terminal ileum was isolated and a ligature was placed around it. E. coli labeled with 99mTechnetium (99mTc-E. coli) was inoculated into the intestinal lumen (terminal ileum). After 24 h, the animals were sacrificed. Blood, mesenteric lymph nodes (MLN), liver, spleen and lungs were removed for radioactivity determination. RESULTS: Arginine supplementation (300 mg/day, 600 mg/day or present in the enteral formula) reduced the level of bacterial translocation when compared with the control group (p<0.05). This was shown by significantly decrease uptake of 99mTc-E. coli in blood, MLN, liver, spleen and lungs of the animals in the experimental groups (p < 0.05). CONCLUSIONS: These results have shown that arginine was able to decrease bacteria translocation despite intestinal obstruction. There are several mechanisms which might explain the role of arginine and these will be the subject of future studies.
