Arginine-supplemented diet decreases expression of inflammatory cytokines and improves survival in burned rats

Background: We examined whether the expression of inflammatory cytokines in organs was influenced by the enteral diet supplemented with arginine in burned rats. Methods: Male Wistar rats weighing about 200 g underwent catheter jejunostomy and received scald burns covering 30% of the whole-body surface area. Animals were divided into two groups: a control group (no supplemental arginine, n = 12) and an arginine group (supplemental arginine: 7.7 g/L, n = 10), which continuously received total enteral nutrition for 7 days (250 kcal/kg/d, 1.72 gN/kg/d). The following were measured after the experiment: (1) messenger RNA (mRNA) expression of tumor necrosis factor-alpha (TNF-alpha), interferon-gamma (IFN-gamma), interleukin-1beta (IL-1 beta), and IL-6 in the spleen, thymus, lung, and liver by a semiquantitative reverse transcription-polymerase chain reaction method, (2) inflammatory cytokines in the plasma and supernatant of cultured splenic lymphocytes by enzyme-linked immunosorbant assay, (3) nitric oxide (NO) product, NO2-/NO3-, in the plasma and supernatant of cultured splenic lymphocytes by the Griess method, and (4) survival rate by the Kaplan-Meier method. Results: The mRNA expression of TNF-alpha was significantly decreased in the spleen and lung (p < .01, p < .05), IFN-gamma in the lung (p < .05), IL-1 beta in the spleen (p < .05), and IL-6 in the thymus and liver (p < .05, p < .05) in the arginine group when compared with the control group. The production of TNF-alpha by splenic lymphocytes was suppressed in the arginine group in both concanavalin A (Con A)-treated and -untreated cultures (p < .01, p < .05). The production of IFN-gamma by splenic lymphocytes treated with Con A was suppressed in the arginine group (p < .05). The NO product in the supernatant without Con A was increased in the arginine group (p < .05). The mortality rate of the arginine group (0%) was lower than that in the control group (33.3%) on day 7 after the burn injury (p < .05). Conclusions: The data suggest that dietary arginine supplementation decreases the mRNA expression of inflammatory cytokines in organs and improves the survival rate after thermal injury.