Oral arginine improves blood pressure in renal transplant and hemodialysis patients.

BACKGROUND: Hypertension in kidney transplant (KT) patients may result from attenuated whole-body nitric oxide (NO) content and abnormal NO-mediated vasodilation. Increasing NO bioavailability with L-arginine (ARG) could theoretically restore the NO-mediated vasodilatory response and lower blood pressure. METHODS: In a prospective pilot study, 6 normotensive volunteers and 10 KT patients received oral supplements of ARG (9.0 g/d) for 9 days, then 18.0 g/d for 9 more days. Six hemodialysis (HD) and 4 peritoneal dialysis patients received the same dose for 14 days. Five KT patients received 30 mL/d of canola oil (CanO) in addition to ARG. Systolic (SBP) and diastolic (DBP) blood pressure, creatinine clearance (CCr), and serum creatinine (Cr) were measured at baseline, day 9, and day 18. In a subsequent study, 20 hypertensive KT patients with stable but abnormal renal function were randomized in a crossover study to start ARG-only or ARG+CanO supplements for two 2-month periods with an intervening month of no supplementation. SBP, DBP, CCr, and Cr were measured monthly for 7 months. RESULTS: In the pilot study, ARG reduced the SBP in HD patients from 171.5 +/- 7.5 mmHg (baseline) to 142.8 +/- 8.3 mmHg (p = .028). In the crossover study, SBP was reduced from baseline (155.9 +/- 5.0 mmHg), after the first 2 months (143.2 +/- 3.2 mmHg; p = .03) and subsequent 2 months (143.3 +/- 2.5 mmHg; p = .014) of supplementation. DBP was also reduced after supplementation in both studies. CanO had no effect on blood pressure. Renal function did not change. CONCLUSIONS: Oral preparations of ARG (+/-CanO) were well tolerated for up to 60 consecutive days and had favorable effects on SBP and DBP in hypertensive KT and HD patients.

Nutritional immunomodulation leads to enhanced allograft survival in combination with cyclosporine A and rapamycin, but not FK506.

BACKGROUND: Recently, specific immunonutrients were found to increase experimental allograft survival when combined with cyclosporine A (CsA). This study compared the effect on rat cardiac allograft survival when nutritional immunomodulation was used with CsA, rapamycin (Rapa), or tacrolimus (FK506). METHODS: Intra-abdominal ACI to Lewis cardiac allografts were performed and assessed daily by palpation. Study groups included untreated controls and those receiving CsA, Rapa, or FK506. Rats were fed ad libitum with Impact diet (fortified with fish oil, arginine, and RNA) or standard rat food. Further study groups were transplanted that received a donor-specific transfusion in addition to immunosuppression and diet. RESULTS: Allograft survival was extended by combining Impact with CsA (45.3+/-19 days) and Rapa (165.3+/-52 days), but not FK506 (12.4+/-3.2 days). Mean graft survival in the Rapa/Impact group met criteria for functional tolerance. The addition of a donor-specific transfusion did not lead to graft survival advantages over similar groups not receiving a donor-specific transfusion. CONCLUSIONS: The use of immunonutrients improves transplant outcome in animals treated with short courses of CsA and Rapa, but not FK506. These findings highlight the potential differences in the effects of nutritional immunomodulation with different immunosuppressive drugs in the treatment of transplant patients.

The effect of nutritional immunomodulation on cardiac allograft survival in rats receiving mycophenolate mofetil, cyclosporine A, and donor-specific transfusion.

BACKGROUND: Immunosuppressive drugs continue to pose significant risks such as infection, toxicity, or neoplasia when used in long-term therapy. The investigation of newer and safer combined treatment strategies that decrease the need for these drugs is becoming increasingly important. Immunonutrients are known to have significant modulating effects on the immune system. Feeding with Impact, a commercially available diet enriched with arginine, omega-3 fatty acids, and RNA, recently has been shown to extend rat cardiac allograft survival when combined with a donor-specific transfusion (DST) and cyclosporine A (CsA). Because mycophenolate mofetil (MMF) is now commonly used in the clinical setting, the current study was designed to examine the effect on rat cardiac allograft survival when MMF was added to this immunosuppressive regimen. METHODS: Intra-abdominal ACI to Lewis heterotopic cardiac allografts were performed. Study groups included untreated controls and recipients receiving varying combinations of a DST (1 mL) on the day prior to engraftment, MMF 45 mg/kg/day from the day of transplant through postoperative day six, and CsA 10 mg/kg on the day prior to operation and 2.5 mg/kg from the day of transplant through postoperative day 6. Animals were fed ad libitum with Impact diet or standard lab chow. Graft survival was determined by cessation of a palpable heartbeat. RESULTS: Treatment with MMF led to a prolonged allograft survival over historical untreated controls. The combination of MMF with a donor-specific transfusion, Impact, or CsA was associated with an increase in graft survival over MMF alone. The addition of Impact to the combination of MMF and CsA resulted in further improvement. The most pronounced graft survival advantage was seen when Impact was combined with a DST and both of the immunosuppressive agents. One quarter of the animals in this group had a palpable donor heart beat at greater than 150 days, indicating functional tolerance in those animals. CONCLUSIONS: The administration of Impact diet to treatment groups in this study was associated with graft survival advantages when compared to most of the other study groups receiving a similar drug regimen and standard chow. These findings support the importance of nutritional influences on allograft survival, and highlight the potential of diet therapy when used with short courses of clinically relevant immunosuppressive drugs.

Dietary omega-3 and omega-9 fatty acids uniquely enhance allograft survival in cyclosporine-treated and donor-specific transfusion-treated rats.

BACKGROUND: Both laboratory and clinical studies have shown that dietary lipids may affect immunologic responses. This study was conducted to compare different classes of long-chain unsaturated fatty acids for their effect on allograft survival in animals receiving a donor-specific transfusion and a short course of low-dose cyclosporine (CsA). METHODS: Heterotopic ACI strain cardiac allografts were transplanted to Lewis strain rat recipients given diets with different lipid composition. In experiment 1, animals received CsA for 14 days and different diets were enriched with lipids with high concentrations of omega-3, omega-6, or omega-9 fatty acids. In experiment 2, animals received CsA for only 8 days and different diets were enriched with corn oil (omega-6), canola oil (omega-3 and omega-9), fish oil (omega-3) or a mixture of sunflower oil and fish oil (omega-3 and omega-9). RESULTS: In experiment 1, animals receiving the diet with 30% sunflower oil had the best allograft survival (200+/-42 days vs. 53+/-8 days for regular chow plus donor-specific transfusion and CsA, P<0.05). In experiment 2, diets containing canola oil (a mixture of omega-3 and omega-9 fatty acids) were associated with the best survival (P=0.0011 vs. regular chow). CONCLUSION: Dietary omega-3 and omega-9 fatty acids both enhanced cardiac allograft survival in a stringent rat strain combination. Canola oil is a convenient oil for administering both alpha-linoleic acid (omega-3) and oleic acid (omega-9) in a palatable form for human consumption. Further investigation of the potential usefulness of lipids in transplant therapy is warranted.

Effects of the angiotensin converting enzyme inhibitor enalapril on bacterial translocation after thermal injury and bacterial challenge.

Burn injury and sepsis produce acute gastrointestinal derangements that may predispose patients to bacterial translocation. We studied the effects of enalapril, an angiotensin converting enzyme inhibitor (ACEI), on gastrointestinal anatomic alterations, bacterial translocation, and related mortality during gut-derived sepsis in burned mice that had received a prior bacterial challenge. BALB/c mice (n = 111) were treated with enalapril 10 or 1 mg/kg body weight or sterile saline as control twice daily for 3 days. They were then gavaged with 10(a)111 in radiolabeled or unlabeled Escherichia coli and given a 20% total body surface area (TBSA) burn injury. Animals gavaged with unlabeled bacteria were observed for survival (n = 60). Survival was significantly higher in the group receiving enalapril 10 mg/Kg compared with control (75% vs. 10%). Mice treated with enalapril maintained small intestine weight, measured 4 h postburn, and ileal mucosal height was preserved, whereas burned untreated animals lost intestinal weight and mucosal height. Bacterial translocation was decreased in mice treated with enalapril, but killing was unaffected. This study suggests that treatment with enalapril positively affects the outcome in gut-derived sepsis by ameliorating gastrointestinal structural and functional damage and decreasing bacterial translocation.

High doses of dietary arginine during repletion impair weight gain and increase infectious mortality in protein-malnourished mice.

There is considerable evidence for the beneficial effects of dietary arginine, a conditionally-essential amino acid that enhances anabolism and T-cell function. However, the safety and efficacy of higher doses of arginine supplementation following infection have not been investigated completely. These issues were explored therefore, in a murine model of malnutrition and infection. Severe protein malnutrition was induced by feeding mice for 6 weeks on an isoenergetic diet containing only 10 g protein/kg. Mice were then allowed to consume diets with normal amounts of protein (200 g/kg) with 50 g/kg provided as amino acid mixtures of glycine and arginine in which the arginine content ranged from 0 to 50 g/kg. During the repletion period a significant weight gain was noted in the groups fed on diets with either 10 or 20 g arginine/kg, but not in the group fed on the diet with 50 g arginine/kg, compared with the diet with 0 g arginine/kg. Mortality rates after infection with Salmonella typhimurium were not decreased by the addition of 10 or 20 g arginine/kg to the diet, and were in fact worsened by supplementation with 50 g arginine/kg. The results of the present study showed that not only are the beneficial effects of arginine supplementation after infection lost when high doses are administered, but also that these high doses become toxic. Mice fed on higher doses showed significant impairment of weight gain and an increase in mortality rates.

Oral glutamine decreases bacterial translocation and improves survival in experimental gut-origin sepsis.

BACKGROUND: Glutamine has been shown to be an important dietary component for the maintenance of gut metabolism. The purpose of this study was to assess the potential benefit of glutamine-enriched diets on experimental gut-derived sepsis. METHODS: BALB/c mice were fed either 2% glutamine-supplemented or 1% glycine-supplemented (near-isonitrogenous control) AIN-76A diets. Control mice received either nonsupplemented AIN-76A or regular Purina Rodent Laboratory Mouse Chow 5001 diets. After 10 days of feeding, the mice were transfused with allogeneic blood (from C3H/HeJ mice), and the feeding protocols were continued for an additional 5 days. The mice then underwent gavage with 10(10) Escherichia coli labeled with either indium-111 oxine or [14C]glucose followed immediately by a 20% burn injury. Some mice were observed 10 days postburn for survival rates. Others were killed 4 hours after burn, and the mesenteric lymph nodes, liver, and spleen were harvested to determine radionuclide and bacterial colony counts. The percentages of viable translocated E coli were also calculated. RESULTS: Mice fed glutamine-enriched diets had a lower degree of translocation (as measured by both radionuclide and bacterial counts) to the tissues than did the other groups and had an improvement in the ability to kill translocated E coli (as measured by the percentage of viable bacteria). Survival was significantly higher in the group fed 2% glutamine (81%) compared with the groups fed 1% glycine (36%), AIN-76A (35%), and Purina Rodent Laboratory Mouse Chow 5001 (36%) diets (p < .004). CONCLUSIONS: Glutamine-supplemented enteral diets may exert important benefits in preventing gut-origin sepsis after trauma.

Immunomodulation by an inhibitor of S-adenosyl-L-homocysteine hydrolase: inhibition of in vitro and in vivo allogeneic responses.

The response of murine T cells to MHC class II determinants on allogeneic cells induces helper T cell activation and the development of cytotoxic T cells. We have recently established that an S-adenosyl-L-homocysteine hydrolase inhibitor, (Z)-5'-fluoro-4',5'-didehydro-5'-deoxyadenosine (MDL 28,842), is a potent immunosuppressive agent which selectively inhibits T cell activation. In this report we characterize the effect of MDL 28,842 on in vitro and in vivo models of transplant rejection. In vitro, MDL 28,842 inhibited the generation of cytotoxic T cells in the murine mixed lymphocyte reaction with an IC50 of less than 0.1 microM. MDL 28,842 (1.0 microM) totally inhibited the generation of cytotoxic T cells when added up to 3 days after the initiation of culture with no apparent cell toxicity. In vivo, MDL 28,842 given by gavage at 5.0, 2.5, or 1.0 mg/kg/day inhibited the increase in popliteal lymph node weight induced by injection of allogeneic spleen cells into the footpad. MDL 28,842 was also evaluated in a model of graft rejection. Skin allografts on animals given MDL 28,842 at 5 mg/kg/day (ip) for the first 6 days following transplantation survived for 12.2 days, compared to 8.7 days for control animals. Cyclosporin A (CSA) given at 5.0 mg/kg/day did not prolong graft survival. The combination of MDL 28,842 and CSA was not any more effective than MDL 28,842 alone. Based on these findings, we suggest that MDL 28,842 is useful in the prevention of allograft rejection.

Dietary fat and infection in burned animals.

Dietary lipids can influence the immune response, chiefly through modulation of eicosanoid synthesis. Previous studies showed that diets high in linoleic or oleic acid significantly improved survival rates, compared with diets high in either saturated fats or omega-3 fatty acids, when fed to mice for 2 to 3 weeks before burn injury. These experiments suggest that neutrophil function in rats is not altered by diets high in either fish or safflower oil before burn injury. Serum opsonization is marginally improved by safflower oil diets for 2 weeks before burn injury but not for 6 weeks before burn injury.

The effect of dietary fatty acids on response to Pseudomonas infection in burned mice.

Since fatty acids influence prostaglandin synthesis, and since both fatty acids and prostaglandins modulate immune function, we investigated the hypothesis that manipulation of dietary fats would affect survival after infection in a murine burn model. Mice were fed for 2 to 3 weeks with diets containing different types and amounts of fat. They were then subjected to a 20% flame burn and infected with Pseudomonas aeruginosa. Survival in the group fed 40% of total calories as fish oil had significantly higher mortality than those fed safflower oil. This difference was not noted at lower fat levels. Similar groups of animals were sacrificed the day after injection. Splenic macrophage production of PGE2 was significantly lower in the fish-oil group, but production of LTB4 and TXB2 were not affected. In vitro tests of T- and B-cell function were not different amongst groups. We conclude that manipulation of dietary fats can alter outcome in this murine model of infection after thermal injury.

Immunoregulation of transfusion-induced immunosuppression with inhibitors of the arachidonic acid metabolism.

To further define the role of arachidonic acid (AA) metabolites in transfusion-induced immunosuppression (TII), the effects of pharmacological manipulation of AA metabolism were examined in a rodent model. If the prostaglandins of the E series are mediators of TII, as has been recently hypothesized, then inhibition of cyclooxygenase (indomethacin) should abrogate whereas inhibition of lipoxygenase (nordihydroguaiaretic acid [NDGA]), or thromboxane synthetase (4-63557A) could potentiate the transfusion effect. Lewis rats received donor-specific transfusions from Buffalo rats in conjunction with one of the above inhibitors. Two weeks later they received intraabdominal Buffalo heart allografts or were used for one-way mixed lymphocyte reactions. Cyclooxygenase inhibition partially abrogated TII with shortened cardiac allograft survival. Lipoxygenase inhibition augmented TII, with depression of MLR and prolongation of allograft survival. Thromboxane synthetase inhibition had no effect. These results indicate that AA metabolites play a role in TII, and that immunoregulation via pharmacological manipulation of AA metabolism is possible.

Immune function during intravenous administration of a soybean oil emulsion.

The effect of a continuous infusion of a soybean oil emulsion on immune function was evaluated in 40 malnourished patients who were randomized to receive preoperatively either a 25% glucose-5% amino acid solution (group G) or a 15% glucose-3.3% Intralipid-5% amino acid solution (group G-F). Average length of total parenteral nutrition (TPN) was 10.3 +/- 0.9 days for group G and 9.0 +/- 0.8 days for group G-F. Initial nutritional status and response to TPN were similar for both groups. Immune function was assessed before TPN and after nutritional repletion prior to surgery for each patient. The levels of immunoglobulins, C3, C4, circulating B lymphocytes and T lymphocytes, suppressor T lymphocytes, natural killer cell activity, and monocytes were normal before TPN and after nutritional therapy. However, the total number of T cells and helper T cells were low before TPN and remained so after TPN. In addition, lymphocyte function measured by the lymphocyte blastogenic response to phytohemagglutinin and pokeweed mitogen was depressed prior to TPN and was not improved by either regimen. Neutrophil chemotaxis and bactericidal activity were not affected by either nutritional regimen while neutrophil phagocytosis was enhanced before TPN and remained elevated throughout TPN with either regimen. There were no differences in infection rates during TPN. The addition of Intralipid to the TPN regimen did not alter immune function in these patients who showed depressed cell-mediated immunity before TPN compared with the standard glucose TPN regimen.

Tuftsin: a naturally occurring immunopotentiating factor. I. In vitro enhancement of murine natural cell-mediated cytotoxicity.

Tuftsin is a physiologic tetrapeptide, which has recently been shown to possess immunoadjuvant properties including the stimulation of macrophage and granulocyte phagocytosis, migration, bactericidal, and tumoricidal activities. Tuftsin has also been reported to possess in vivo immunologically mediated anti-tumor potential. To determine the potential role of tuftsin as an antineoplastic immunoadjuvant, the in vitro effects of tuftsin on murine natural cell-mediated cytotoxicity were studied. We observed that in vitro treatment of mouse splenic effector cells with synthetic tuftsin induced a pronounced enhancement of natural killer cell (NKC) cytotoxicity against the T cell lymphoma Yac-1. The magnitude of NKC enhancement was directly dependent upon the concentration of tuftsin employed, with maximum NKC stimulation observed at tuftsin concentrations of 50 to 100 microgram/ml. The tuftsin induced enhancement of NKC activity was not strain specific, since equivalent stimulation was seen in CBA/J, C56BL/10, and DBA/2 mice. Elimination of macrophages, monocytes, T cells, and immunoglobulin-bearing cells had no effect on the dose-dependent tuftsin stimulation of natural cell-mediated cytotoxicity; thus the characteristics of the effector cells activated by tuftsin were consistent with those reported for NKC. We also observed that treatment of splenic effector cells with tuftsin prolonged the cytotoxic capabilities of these cells beyond 18 hr.