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Arginine supplementation improves histone and acute-phase protein synthesis during gram-negative sepsis in the rat.

Mechanisms of nutrient alteration of hepatic protein synthesis during sepsis are unclear. In vitro, arginine downregulates endotoxin-stimulated hepatocyte protein synthesis but in vivo effects are unknown. This study evaluated the effects of supplemental arginine or glycine on fibrinogen (acute-phase protein), histone, albumin, and liver protein synthesis after Gram-negative sepsis in the rat. Adult rats (225 g, n=36) were randomized to receive isonitrogenous isocaloric total parenteral nutrition supplemented with 264 mg of N per kilogram per day as either arginine or glycine. On day 5, each group was further randomized to control or sepsis. Sepsis was induced by injection of 8 x 10(7) Escherichia coli per 100 g body weight, and then a continuous infusion of [1-14C] leucine was started. The rats were sacrificed 4 hours later. The fractional protein synthesis rates (percent per day) of histone, fibrinogen, albumin, and liver were determined. Supplemental arginine led to significantly increased histone (p < 0.05, analysis of variance) and fibrinogen (p < 0.01, analysis of variance) synthesis in the septic rats compared with all other groups. Histone and albumin synthesis were also significantly increased (p < 0.05) in the arginine-supplemented control group compared with the glycine-supplemented control group. Arginine supplementation during sepsis significantly increased (p < 0.05) albumin and liver protein synthesis compared with controls. Histones which are involved in DNA synthesis and are rich in arginine may play a role in the host response to stress and sepsis. These in vivo results appear to contradict hepatocyte-Kupffer cell coculture studies perhaps because of the hormonal and cytokine responses to nutrient substrate and acute septicemia.

Dietary Manipulation of Methotrexate-Induced Enterocolitis

Administration of chemotherapy is limited by host toxicity, which is often manifested by severe enterocolitis. This study evaluated the effects of a liquid, elemental, chemically defined diet (ED) supplemented with 2% glutamine (Glu-ED) compared with a polypeptide diet (PPD) on the morbidity and mortality after methotrexate (MTX) administration. Fischer 344 rats (n = 80) were fed either a regular rat chow diet (RD), a 2% glycine supplemented elemental diet (Gly-ED), a 2% glutamine-supplemented elemental diet (GLU-ED), and a glycine-supplemented polypeptide diet(Gly-PPD) for 7 days prior to administration of MTX (20 mg/kg, ip). After 72 hours, eight rats per group were killed; portal vein and vena cava blood, mesenteric lymph nodes (MLN), liver, small intestine, and cecum were sampled for bacterial culture. Remaining animals were followed to calculate survival. One hundred percent of the Gly-PPD and 25% of the Glu-ED animals survived compared with 0% of the Gly-ED animals. Our data showed that ED resulted in an increased quantity of intestinal Gram-negative bacteria and diminished intestinal mucosal height and mucosal DNA/protein content. The polypeptide diet prevented intestinal mucosal atrophy, avoided MTX-induced enterocolitis and significantly improved animal survival compared with an elemental diet with or without glutamine supplementation.

Protein-calorie malnutrition impairs host defense against Candida albicans.

Protein-calorie malnutrition (PCM) impairs immune responsiveness predisposing to Candida albicans sepsis, but mechanisms are unclear. This study examined the effect of PCM on enteric-derived C. albicans intestinal translocation and the ability of in vivo interferon-gamma (IFN-gamma) to upregulate macrophage (MO) candidacidal mechanisms in PCM mice. Control (24% casein) and low protein (2.5%) diets were given for 4 weeks. Mice (n = 160) were fed C. albicans in their drinking water for 3 days and C. albicans translocation (mean colony-forming units (CFU)/g tissue +/- SEM) to the GI tract, liver, spleen, and kidney was assessed at 1 and 5 days following endotoxin challenge of 1, 5, and 10 mg/kg body wt. In a separate study (n = 100 mice), IFN-gamma (1000-10,000 U/day ip) vs saline was given for 3 days prior to harvesting peritoneal macrophages for assay of superoxide anion (O2-), percentage macrophage phagocytosis of C. albicans, and percentage killing of C. albicans. On Day 1, fungal translocation to the intestinal wall and systemic organs in the PCM group was significantly higher. On Day 5, mean CFU were significantly higher in the PCM group, indicating impaired organ clearance. Mean O2-, phagocytosis, and killing were significantly impaired in the PCM group (P less than 0.05), but IFN-gamma improved all functions. PCM significantly depressed host responses to C. albicans. IFN-gamma treatment enhanced candidacidal mechanisms, suggesting a therapeutic role in the malnourished host predisposed to C. albicans sepsis.

Elemental diet alters macrophage function in mice.

Administration of a chemically defined liquid elemental diet (ED) induces spontaneous bacterial translocation to mesenteric lymph nodes (MLN) in animal models. The influence of this process on host immunity is unclear. This study evaluated the effects of ED on peritoneal macrophage (PM phi) antimicrobial functions. Conventional C57/BL6 mice and endotoxin-resistant C3H/HeJ mice (n = 60) were randomized to be pair-fed either an ED or regular chow diet (RD) for 14 days. Blood, spleen, liver, and MLN were cultured for bacteria. PM phi were harvested for: percentage Candida albicans (CA) phagocytosis, percentage killing of CA, PM phi superoxide anion (O2-) production, and TNF-dependent macrophage cytotoxicity. Enteral feeding of ED in conventional C57/BL6 mice caused significant bacterial translocation to MLN but not other organs. Significant impairment of CA killing by PM phi occurred in the ED group and was associated with reduced O2- production. Tumor necrosis factor (TNF)-dependent cytotoxicity of PM phi was also decreased. In endotoxin-resistant C3H/HeJ mice, bacterial translocation was not observed and PM phi antifungal functions remained similar in both RD and ED groups. Thus, enteral feeding of an elemental diet downregulates host oxidative and antimicrobial mechanisms and TNF-dependent cytotoxicity in conventional mice which may be secondary to elemental diet-induced bacterial translocation.

Anti-neoplastic effects of interleukin-4

Interleukin-4 (IL-4) is a cytokine, with potential anti-neoplastic effects. This study examined the effects of IL-4 on host anti-tumor responses in a murine model. C57/B16 mice (n = 40) were randomized to receive Lewis lung carcinoma (10(6) cells: right flank; sc) or saline, and sacrificed 10 days postinoculation for assessment of peritoneal macrophage (PMO) anti-tumor mechanisms [superoxide anion generation (O2-), tumor necrosis factor (TNF), and TNF-independent (P815) cytotoxicity], splenocyte mixed lymphocyte response (MLR) (Balb/c stimulator), and cytotoxic lymphocyte generation (CTL against P815). Cells were cultured +/- IL-4 (100 U/ml). In a second study, 20 mice received Lewis lung implants (sc) and were randomized on Day 21 to receive daily IL-4 (1000 U/mouse; ip) or saline. Tumor volumes and median survival were assessed. Tumor necrosis factor-independent cytotoxicity (O2-, MLR and CTL) was impaired in the tumor-bearing (TB) study group. Interleukin-4 administered to cultured cells from TB mice enhanced O2-, as well as MLR and CTL (P less than 0.01), and decreased TNF release but did not alter PM phi TNF-independent anti-tumor responses (P815). In vivo administration of IL-4 significantly decreased tumor growth (P less than 0.05) after 10 days of treatment and significantly prolonged median host survival (P less than 0.05). These findings indicate the therapeutic potential of IL-4 in the TB host which may function through downregulation of TNF production while potentiating certain T cell-dependent and independent anti-tumor immune mechanisms.

Comparison of acute and chronic protein-energy malnutrition on host antitumor immune mechanisms

Protein-calorie malnutrition (PCM) is prevalent in cancer patients. However, the effect of PCM on anti-tumor immunity is unclear and critically important in an era of improving results with adoptive immunotherapy. This study examined the effect of short- and long-term PCM on tumor-specific and natural immune effector mechanisms in a murine neuroblastoma (C1300 NRB) model. A/J mice received an isocaloric 2.5% or 24% casein diet for 3 or 8 weeks before inoculation with tumor. Three weeks later lymphocytes from tumor-bearing mice were harvested for determination of cytotoxic T lymphocyte (CTL) generation and natural killer (NK) cell cytotoxicity. Both 3 and 8 weeks of PCM significantly reduced mean total body weight by 25% (p less than 0.001) and 41% (p less than 0.001), respectively, compared with regularly nourished mice. Short-term PCM did not inhibit CTL or NK cytotoxicity, whereas long-term PCM significantly diminished CTL generation (p less than 0.001) but preserved NK cytotoxic function. These results indicate that CTL development against autologous tumor, in contrast to basal NK function, is dependent on host nutritional status. Mean tumor growth, determined by tumor-weight to carcass-weight ratio, was unchanged for both short- and long-term protein-energy deprived groups compared with results in regularly nourished mice. These findings suggest that NK function is the predominant effector mechanism inhibiting C1300 NRB growth and that NK tumoricidal capacity is preserved during PCM.