Effects of supplemental dietary arginine on the exogenous advanced glycosylation end product-induced interleukin-23/interleukin-17 immune response in rats.

OBJECTIVES: Arginine (Arg) is known to possess numerous useful physiological properties and immunomodulatory effects. Th17 cells are a unique T-helper cell lineage. Regulation of Th17 cells plays a significant role in the pathogenesis of inflammatory disorders. This study investigated the effect of Arg on the exogenous advanced glycosylation end product (AGE)-induced Th17-mediated immune response. METHODS: Rats were randomly divided into three groups. The control BSA (CB) group was fed a common diet and given a tail vein injection of non-glycated bovine serum albumin (BSA). The control AGE (CA) group was fed the common diet and injected with 2 mg AGE-BSA. Arg-AGE (AA) group was fed the Arg-supplemented diet and injected with 2 mg AGE-BSA. The experimental diets were identical in energy and nutrient distributions except for the amino acid content. Arg provided 2% of the total energy. Tail vein injections and diets were given daily. After 10 d, all rats were sacrificed, and blood samples were collected for further analysis. RESULTS: The AA group had the highest inducible nitric oxide (NO) synthase expression and plasma NO levels. The percentage of Foxp3 T-regulatory cells in the AA group was lower than those of the CA and CB groups. Transforming growth factor-ß1, interleukin (IL)-6, and IL-17A gene expression was higher in the AGE-administered groups. The AA group had higher TGF-ß1 and IL-17A expression than did the CA group. CONCLUSION: These results suggest that in a condition of exogenous AGE administration, supplemental dietary Arg resulted in a more pronounced IL-23/IL-17 immune response, possibly by increasing NO secretion.

Tetrandrine attenuates dendritic cell-mediated alloimmune responses and prolongs graft survival in mice.

Tetrandrine, a bisbenzylisoquinoline alkaloid, has significant immunosuppressive effects; however, the effects of tetrandrine on dendritic cells (DCs) and the associated immune reactions are unclear. In this study, we investigated the effects of tetrandrine on DCs and the effects of the tetrandrine-treated DCs on alloimmune reactions in vitro and graft survival in vivo. Tetrandrine significantly downregulated the expression of CD80 and CD86 of DCs and increased their secretion of IL-10 (p = 0.0001). Mixed leukocyte reaction showed that tetrandrine inhibited dendritic-cell allo-stimulatory activity, which was reversed by the anti-IL-10 treatment. An in vivo study demonstrated that tetrandrine-treated DCs prolonged the survival time of skin grafts in mice compared to control (p = 0.005) and decreased cellular infiltration of the graft in the histopathological study. The data suggest that tetrandrine-treated DCs cause immunosuppression and protect skin grafts from rejection. The tetrandrine-induced immunosuppression seems to be partially due to increased IL-10 secretion.

Effects of omega-3 fatty acids on leukocyte Th1/Th2 cytokine and integrin expression in rats with gut-derived sepsis.

OBJECTIVES: This study examined the effect of fish oil (FO)-enriched diets before and/or omega-3 fatty acid-containing total parenteral nutrition (TPN) after sepsis on the distribution of the T-lymphocyte subpopulation, intracellular cytokine, and intestinal immunity in rats with gut-derived sepsis. METHODS: Rats were assigned to a control or one of four experimental groups. The control group and groups 1 and 2 were fed a semipurified diet, and groups 3 and 4 received FO instead of 20% soybean oil. After feeding the diets for 10 d, sepsis was induced by cecal ligation and puncture (CLP) in the experimental groups, whereas a sham operation was performed in the control group. TPN was maintained for 3 d after the CLP or sham operation. The control group and groups 1 and 3 were infused with conventional TPN, whereas the TPN solution used for groups 2 and 4 were supplemented with FO. All rats were sacrificed 3 d after the operation to examine their immune responses. RESULTS: Plasma and intestinal immunoglobin A levels were higher in the FO-supplemented groups than in the control group and group 1. Lymphocyte interferon-gamma expression in groups 3 and 4 was significantly lower, whereas interleukin-4 expression was higher than those of the control group and groups 1 and 2. The splenocyte CD4 percentage in groups 3 and 4 and the CD4/CD8 ratio in group 4 were significantly higher than those in group 1. CONCLUSION: These findings suggest that FO administration before and/or after CLP are not immunosuppressive. FO-enriched diets before or before and after CLP resulted in a T-helper type 2 response and enhanced immunoglobulin A secretion. In addition, the splenocyte CD4 levels and CD4/CD8 ratio were maintained in rats with gut-derived sepsis.

Dietary glutamine supplementation reduces cellular adhesion molecule expression and tissue myeloperoxidase activity in mice with gut-derived sepsis.

OBJECTIVES: This study investigated the effects of glutamine (Gln) on plasma intracellular adhesion molecule-1 levels and leukocyte integrin (CD11a/CD18 and CD11b/CD18) expressions in gut-derived sepsis. Myeloperoxidase (MPO) activities in organs were also analyzed to identify the extent of tissue injury resulting from neutrophil infiltration. METHODS: Mice were randomly assigned to a normal group (NC), a control group, or a Gln group. The NC group was fed standard chow diet; the control group was fed a common semipurified diet; and the Gln group received a diet in which part of the casein was replaced by Gln, which provided 25% of total amino acid nitrogen. After 3 wk, sepsis was induced by cecal ligation and puncture (CLP) in the control and Gln groups. Mice in the experimental groups were killed at 0, 6, 12, and 24 h after CLP. Mice in the NC group were killed when CLP was performed. Blood and organ samples were collected for further analysis. RESULTS: Plasma intracellular adhesion molecule-1 levels were significantly lower in the Gln group than in the control group at 6, 12, and 24 h after CLP. Expressions of lymphocyte CD11a/CD18 were significantly higher, whereas polymorphonuclear lymphocyte expressions of CD11b/CD18 were lower in the Gln group than in the corresponding control group at 6 and 12 h after CLP. In comparisons of MPO activities in various organs, the Gln group had lower MPO activities at 6 and 12 h in the lung, at 6, 12, and 24 h in the liver, at 12 and 24 h in the kidneys, and at 12 h in the intestine than those in the control group. CONCLUSIONS: Results of this study demonstrate that a Gln-supplemented enteral diet increased lymphocyte CD11a/CD18 expressions, whereas neutrophil CD11b/CD18 expressions, circulating intracellular adhesion molecule-1 levels, and MPO activities in various organs decreased with gut-derived sepsis. These findings suggest that, under septic conditions, Gln administration may enhance lymphocyte function, attenuate interactions between polymorphonuclear lymphocytes and endothelium, and thus may decrease neutrophil infiltration into tissues.

Parenteral N-3 fatty acids modulate inflammatory and immune response in rats undergoing total gastrectomy.

This study investigated the effect of n-3 fatty acid (FA)-containing parenteral nutrition on the circulatory lymphocyte subpopulation, intracellular cytokine and leukocyte adhesion molecule expression, and phagocytic activity in rats undergoing total gastrectomy. Normal rats with internal jugular catheters were assigned to normal control (NC) and two experimental groups and received total parenteral nutrition (TPN). At the same time, a total gastrectomy was performed in the experimental groups, whereas the NC group underwent a sham operation. The TPN solutions were isonitrogenous and identical in nutrient compositions except for differences in fat emulsion contents. The NC and one of the experimental groups received a soybean oil emulsion (SO), and the other experimental group received 50% soybean oil and 50% fish oil emulsion (FO). Half of the rats in each respective group were sacrificed 1 or 3 days after surgery or the sham operation to examine their immune response. The results showed that the FO group had a higher CD4 proportion and CD4/CD8 ratio than those of the SO and NC groups postoperatively. The phagocytic activity of peritoneal macrophages was higher in the FO group than in the NC group, but no difference was found between the SO and NC groups 3 days after surgery. The intracellular interferon (IFN)-gamma distribution in the FO group was higher than that of the SO group on postoperative days. Leukocyte adhesion molecule expressions and peritoneal monocyte chemotactic protein-1 levels were lower in the FO group than in the SO group on postoperative day 3. These results suggest that parenterally infused FO did not result in immunosuppression. In addition, FO administration promotes lymphocyte Th1 cytokine production, enhances peritoneal macrophage phagocytic activity, and reduces leukocyte adhesion molecule expression in rats with total gastrectomy.

Glutamine-supplemented total parenteral nutrition attenuates plasma interleukin-6 in surgical patients with lower disease severity.

AIM: Previous reports have shown that decrease in plasma glutamine (Gln) level following major surgery may contribute to the state of immunosuppression. Gln supplementation improves the depletion of body Gln pool, and may have indirect effect on reducing proinflammatory mediator release. This study evaluated whether the effect of Gln dipeptide-enriched total parenteral nutrition (TPN) on postoperative cytokine alteration depended on the disease severity of surgical patients. METHODS: Forty-eight patients with major abdominal surgery were allocated to two groups to receive isonitrogenous (0.228 g nitrogen/kg per d) and isocaloric (30 kcal/kg per d) TPN for 6 d. Control group (Conv) using conventional TPN solution received 1.5 g amino acids/kg per day, whereas the test group received 0.972 g amino acids/kg per day and 0.417 g L-alanyl-L-glutamine (Ala-Gln)/kg per day. Blood samples were collected on d 1 and d 6 postoperatively for plasma interleukin (IL)-2, IL-6, IL-8, and interferon (IFN)-gamma analysis. RESULTS: Plasma IL-2 and IFN-gamma were not detectable. IL-6 concentrations were significantly lower on the 6(th) postoperative day in the Ala-Gln group than those in the Conv group in patients with APACHE II <=6, whereas no difference was noted in patients with APACHE II >6. There was no difference in IL-8 levels between the two groups. No difference in cumulative nitrogen balance was observed on d 2-5 after the operation between the two groups (Ala-Gln -3.2+/-1.6 g vs Conv -6.5+/-2.7 g). A significant inverse correlation was noted between plasma IL-6 levels and cumulative nitrogen balance postoperatively in the Ala-Gln group, whereas no such correlation was observed in the Conv group. CONCLUSION: TPN supplemented with Gln dipeptide had no effect on plasma IL-8 levels after surgery. However, Gln supplementation had a beneficial effect on decreasing systemic IL-6 production after surgery in patients with low admission illness severity, and lower plasma IL-6 may improve nitrogen balance in patients with abdominal surgery when Gln was administered.

Dietary glutamine supplementation modulates Th1/Th2 cytokine and interleukin-6 expressions in septic mice.

Glutamine (Gln) has been demonstrated to have benefit in the modulation of systemic immunity in sepsis. However, the effects of Gln on local immunity and intra-lymphocyte cytokine expression have not been investigated in mice with gut-derived sepsis. This study evaluated the influence of a Gln-enriched diet on interleukin (IL)-6 expression in organs and Th1/Th2 type cytokine production within lymphocytes in septic mice. Male ICR mice were assigned to control and Gln groups. The control group was fed a semi-purified diet, while in the Gln group, Gln replaced part of the casein. After feeding the respective diets for 3 weeks, sepsis was induced by cecal ligation and puncture (CLP). Mice were sacrificed at 0, 6, 12 and 24h after CLP and their organs were harvested for further analysis. Results showed that IL-6 levels in the liver were decreased, whereas levels were increased in the lungs, kidneys and intestines with the progression of sepsis in both groups. Also, intra-lymphocyte interferon (IFN)-gamma expression decreased and IL-4 expression increased during sepsis. Compared to the control group, the Gln group had higher levels of IL-6 in the liver and lower levels in other organs at various time points. Lymphocyte IFN-gamma expression in the Gln group was higher, and IL-4 levels were lower than those of the control group after CLP. These results suggest that Gln supplementation decreased IL-6 production in non-hepatic organs, while reducing intra-lymphocyte IL-4 and enhancing IFN-gamma expressions. This change may reverse the Th2 type response to a more-balanced Th1/Th2 response during sepsis.

Effects of glutamine supplementation on splenocyte cytokine mRNA expression in rats with septic peritonitis.

AIM: To investigate the effects of glutamine (GLN)-enriched diets before and GLN-containing total parenteral nutrition (TPN) after sepsis or both on the secretion of cytokines and their mRNA expression levels in splenocytes of rats with septic peritonitis. METHODS: Rats were assigned to a control group and 4 experimental groups. The control group and experimental groups 1 and 2 were fed a semipurified diet, while experimental groups 3 and 4 had part of the casein replaced by GLN which provided 25% of the total nitrogen. After rats were fed with these diets for 10 d, sepsis was induced by cecal ligation and puncture (CLP), whereas the control group underwent a sham operation, at the same time, an internal jugular vein was cannulated. All rats were maintained on TPN for 3 d. The control group and experimental groups 1 and 3 were infused with conventional TPN, while the TPN in experimental groups 2 and 4 was supplemented with GLN, providing 25% of the total nitrogen in the TPN solution. All rats were kiued 3 d after sham operation or CLP to examine their splenocyte subpopulation distribution and cytokine expression levels. RESULTS: Most cytokines could not be detected in plasma except for IL-10. No difference in plasma IL-10 was observed among the 5 groups. The IL-2, IL-4, IL-10, and TNF-alpha mRNA expression levels in splenocytes were significantly higher in experimental groups 2 and 4 than in the control group and group 1. The mRNA expression of IFN-gamma was significantly higher in the GLN-supplemented groups than in the control group and experimental group 1. The proportion of CD45Ra+ was increased, while those of CD3+ and CD4+ were decreased in experimental group 1 after CLP was performed. There were no differences in spleen CD3+ lymphocyte distributions between the control and GLN-supplemented groups. CONCLUSION: GLN supplementation can maintain T-lymphocyte populations in the spleen and significantly enhance the mRNA expression levels of Th1 and Th2 cytokines and TNF-alpha in the spleen of rats with septic peritonitis.

Glutamine supplementation enhances mucosal immunity in rats with Gut-Derived sepsis.

OBJECTIVE: Supplemental glutamine (Gln) has been demonstrated to improve the immunologic response and reduce mortality in rodents with sepsis. However, the effects of Gln on gut-associated lymphoid tissue function after infection and sepsis are not clear. We investigated the effects of Gln-supplemented diets before sepsis, Gln-enriched total parenteral nutrition (TPN) after sepsis, or both on the intestinal immunity in rats with gut-derived sepsis. METHODS: Male Wistar rats were assigned to control and four experimental groups. The control and experimental groups 1 and 2 were fed a semi-purified diet; in experimental groups 3 and 4, part of the casein in the diets was replaced with Gln. After feeding rats the respective diets for 10 d, sepsis was induced by cecal ligation and puncture (CLP) in the experimental groups, whereas the control group underwent a sham operation; at the same time, the internal jugular vein of all rats was cannulated. All rats were maintained on TPN for 3 d. The control group and groups 1 and 3 were infused with conventional TPN, and groups 2 and 4 were given a TPN solution supplemented with Gln, which provided 25% of total amino acid nitrogen. All rats were killed 3 d after the sham operation or CLP. Intestinal immunoglobin A levels, total lymphocyte yields, and lymphocyte subpopulations in Peyer's patches were analyzed. RESULTS: Total Peyer's patch lymphocyte numbers were significantly higher in the Gln-supplemented groups than in the control group. Distributions of CD3+ and CD4+ in group 1 were significantly lower than those in the control group, whereas no differences were observed among the control and Gln-supplemented groups. Plasma immunoglobulin A levels were higher in the Gln-supplemented groups than the control group and group 1. Intestinal immunoglobulin A levels were significantly higher in groups 2 and 4 than in the control group and group 1. CONCLUSIONS: Preventive use of a Gln-supplemented enteral diet before CLP or intravenous Gln supplementation after CLP have similar effects in promoting proliferation of total lymphocyte in gut-associated lymphoid tissue, enhancing IgA secretion, and maintaining T-lymphocyte populations in Peyer's patches. Gln administered before and after CLP did not seem to have a synergistic effect on enhancing mucosal immunity in rats with gut-derived sepsis.

Effects of glutamine supplementation on innate immune response in rats with gut-derived sepsis.

The present study examined the effect of glutamine (Gln)-enriched diets before sepsis or Gln-containing total parenteral nutrition (TPN) after sepsis, or both, on the phagocytic activity and blood lymphocyte subpopulation in rats with gut-derived sepsis. Rats were assigned to a control group or one of four experimental groups. The control group and groups 1 and 2 were fed a semipurified diet; groups 3 and 4 had part of casein replaced by Gln. After feeding the diets for 10 d, sepsis was induced by caecal ligation and puncture (CLP); TPN was maintained for 3 d after CLP. The control group and groups 1 and 3 were infused with conventional TPN and groups 2 and 4 were supplemented with Gln in the TPN solution. All rats were killed 3 d after CLP or sham operation to examine their immune responses. The results showed that compared with the control group, the phagocytic activities of peritoneal macrophages were enhanced in groups 3 and 4, but not in groups 1 and 2. The proportion of CD3+ cells in group 1 was significantly lower (P<0.05) than that of the control group, whereas no differences were observed among the control and Gln-supplemented groups. The CD4+ cell proportion was significantly lower (P<0.05) in group 1 compared with the control group and groups 3 and 4. These findings suggest that Gln-enriched diets before CLP significantly enhanced peritoneal macrophage phagocytic activity, preserved CD4+ cells and maintained blood total T lymphocytes in gut-derived sepsis. However, parenteral Gln administration after caecal ligation and puncture had no favourable effects on modulating immune response in septic rats.

Effects of dietary glutamine on antioxidant enzyme activity and immune response in burned mice.

OBJECTIVES: We investigated the effect of dietary glutamine (Gln) on specific antibody production and antioxidant enzyme activities in burned mice vaccinated with detoxified Pseudomonas exotoxin A linked with the outer membrane proteins I and F (PEIF). We also evaluated the survival rate of vaccinated and non-vaccinated burned mice infected with Pseudomonas aeruginosa. METHODS: There were three consecutive experiments. In experiment 1, 30 BALB/c mice were assigned to one of two groups. The control group was fed casein as the protein source; the Gln group received 4% Gln (w/w) to replace part of the casein. Mice were immunized twice with PEIF, and the production of specific antibodies against PEIF was measured every week. Eight weeks after immunization, all mice received a 30% body surface area burn injury. Mice were killed 24 h after the burn. The antioxidant enzyme activities and lipid peroxides in the tissues and specific antibody production were analyzed. In experiment 2, 12 mice were assigned to a control or a Gln group and fed with one the experimental diets for 4 wk. Then burn injury was induced, and mice were killed 24 h later. In vitro, splenocytes were cultured, and interleukin (IL)-4 and IL-10 were measured after mitogen stimulation. In experiment 3, survival rates of vaccinated and non-vaccinated burned mice complicated with P. aeruginosa infection were evaluated. The survival rate was observed for 8 d after the burn. RESULTS: Antioxidant enzyme activities and lipid peroxides in tissues tended to be lower in the Gln group than in the control group after the burn. Specific antibody production against P. aeruginosa increased significantly in the Gln group at 4 and 7 wk after immunization and at 24 h after the burn. IL-4 concentrations in mitogen-stimulated splenocytes were significantly higher in the Gln group than in the control group. Survival rates of non-vaccinated burned mice in the Gln group were significantly higher than those in the control group, whereas there was no difference in the survival of vaccinated burned mice after bacterial infection. CONCLUSIONS: These results suggested that vaccinated mice receiving a Gln-enriched diet may have enhanced humoral immunity and attenuated oxidative stress induced by burn injury. Also, Gln supplementation improved the survival of burned mice complicated with P. aeruginosa infection.

Effects of fish oil in parenteral nutrition.

OBJECTIVE: Fish oil is a rich source of omega-3 fatty acids (FAs), especially eicosapentaenoic acid and docosahexaenoic acid. The existing data suggest that eicosapentaenoic acid and docosahexaenoic acid are the active agents in fish oil. A number of clinical trials have shown that dietary fish oil supplementation has antiatherogenic properties and immunomodulation effects. Fish oils are not used widely in parenteral nutrition because fish oil emulsions have not been commercially available until very recently. Studies concerning the use of fish oil in parenteral route are rare. METHODS: We reviewed the effect of parenteral fish oil infusion on lipid metabolism and immune response in normal and disease conditions. RESULTS: Studies showed that the main effects of parenteral infusion of fish oil are: 1) incorporation of omega-3 FAs into cellular membranes of many cell populations that consequently influence the disease process of some disease conditions, 2) an effect on eicosanoid metabolism leading to a decrease in platelet aggregation and thrombosis, 3) amelioration of the severity of diet-induced hepatic steatosis, 4) less accumulation of lipid peroxidation products in liver tissue, and 5) immunomodulation effects and therapeutic benefits in animal disease models or various disease conditions of humans. Most of these studies suggested that parenteral infusion of omega-3 FAs have clinical beneficial effects comparable to those of dietary administration. However, different effects of omega-3 and omega-6 FAs in some situations has been reported. For example, plasma triacylglycerol levels were not lowered after fish oil infusion in normal or diabetic rats when compared with those of safflower oil or soybean oil infusion. The reason for the difference remain unclear. CONCLUSION: The metabolic and immunologic effects of parenteral use of omega-3 FAs requires further evaluation, especially in some disease conditions.

Effects of arginine-enriched total parenteral nutrition on inflammatory-related mediator and T-cell population in septic rats.

OBJECTIVES: Previous reports have shown that oral arginine (Arg) has immune-enhancing properties in injury. However, the effects of parenterally infused Arg on sepsis are not well understood. We used a septic rat model to study Arg infusion in inflammatory-related cytokines and blood T lymphocyte population in vivo. METHODS: Rats with internal jugular catheters were assigned to one of two groups. Both groups received isonitrogenous total parenteral nutrition (TPN) supplemented with 270 mg of nitrogen per kilogram per day as Arg or glycine (Gly). TPN provided 270 kcal/kg of body weight, and the kilocalorie:nitrogen ratio was 143:1. TPN was maintained for 5 d plus 2, 4, or 6 h or 6 d, according to the scheduled deaths of the rats. On day 5, sepsis was induced by cecal ligation and puncture (CLP). After CLP for 2, 4, 6, and 24 h, rats were killed. RESULTS: The results showed that interleukin-1beta and tumor necrosis factor-alpha concentrations in peritoneal lavage fluid at 6 h and interleukin-6 levels at 24 h after CLP in the Gly group were significantly higher than those in the Arg group. The T-lymphocyte population in blood showed that CD8(+) suppressor T-cell number was significantly higher in the Gly group than in the Arg group at 6 h after CLP. The blood CD4(+):CD8(+) ratio was significantly higher in the Arg group than in the Gly group at 24 h after CLP. A negative nitrogen balance was observed in the Arg and Gly groups after CLP; there was no significant difference in nitrogen balance between the septic groups. No difference in survival rate at 24 h after CLP was observed between the groups. CONCLUSIONS: The results showed that, compared with the Gly group, TPN preinfused with Arg reduces the production of inflammatory mediators at the site of injury and that cellular immunity is enhanced at 24 h after CLP. Parenterally administered Arg had no beneficial effect in preventing nitrogen loss and improving survival in septic rats. Whether Gly has specific effects that reduce the effects of Arg require further investigation.