Cheryl D. Johnson

Glutamine-Enriched Total Parenteral Nutrition Maintains Intestinal Interleukin-4 and Mucosal Immunoglobulin A Levels

BACKGROUND Total parenteral nutrition (TPN) prevents progressive malnutrition but fails to maintain intestinal gut-associated lymphoid tissue (GALT) or established respiratory antiviral or antibacterial mucosal immunity. Our previous work demonstrated that decreases in intestinal immunoglobulin A (IgA) were associated with decreases in Th2-type IgA-stimulating cytokines, interleukin (IL)-4 and IL-10. Because glutamine supplementation of TPN partially preserves respiratory defenses and normalizes GALT, we investigated the ability of parenteral glutamine to normalize respiratory and intestinal IgA levels and measured Th2 cytokines in intestinal homogenates. METHODS Animals were cannulated and randomly assigned to receive chow (n = 17), TPN (n = 18), or an isonitrogenous, isocaloric TPN solution formulated by removing the appropriate amount of amino acids and replacing them with 2% glutamine (n = 18) for 5 days. Respiratory tract and intestinal washings were obtained for IgA and the intestine homogenized and analyzed for IL-4 and IL-10. RESULTS TPN decreased intestinal and respiratory IgA in association with decreases in intestinal IL-4 and IL-10 compared with chow-fed animals. Glutamine significantly improved respiratory and intestinal IgA levels, significantly improved IL-4 compared with TPN animals, and maintained IL-10 levels midway between chow-fed and TPN animals. CONCLUSIONS Glutamine-enriched TPN preserved both extraintestinal and intestinal IgA levels and had a normalizing effect on Th2-type IgA-stimulating cytokines.

Enteral Nutrition Prevents Remote Organ Injury and Death After a Gut Ischemic Insult

ObjectiveTo determine whether parenteral feeding (IV-TPN) influences the local and systemic response to an intestinal insult. Summary Background DataParenteral feeding increases ICAM-1 expression and attracts neutrophils (PMNs) to the intestine compared with enterally fed animals. Because the gut is a priming bed for PMNs, the authors hypothesized that IV-TPN may affect organ injury after gut ischemia—reperfusion (I/R). MethodsMice were randomized to chow, IV-TPN, intragastric TPN, or complex enteral diet for 5 days’ feeding. In experiment 1, 162 mice underwent 15 or 30 minutes of gut I/R, and death was recorded at 72 hours. In experiment 2, 43 mice underwent 15 minutes of gut ischemia and permeability was measured by 125I-labeled albumin at 3 hours after reperfusion. Lung PMN accumulation was measured by myeloperoxidase assay. In experiment 3, albumin leak was tested in the complex enteral diet group (n = 5) and the intragastric TPN group (n = 5) after 30 minutes of gut ischemia and 1 hour of reperfusion. ResultsIn experiment 1, enteral feeding significantly reduced the death rate compared with IV-TPN after 15 minutes of I/R. After 30 minutes of gut ischemia, the IV-TPN and intragastric TPN groups showed a higher death rate than the chow and enteral diet groups. In experiment 2, IV-TPN significantly increased pulmonary and hepatic 125I albumin leak compared with enteral feeding without increasing pulmonary myeloperoxidase levels. In experiment 3, there were no differences in 125I albumin leak between the complex enteral diet and intragastric TPN groups. ConclusionEnteral feeding reduced the death rate and organ permeability after 15 minutes of ischemia. However, prolonged ischemia (30 minutes) eliminated any benefits of intragastric TPN on survival.

Impairment of Mucosal Immunity by Total Parenteral Nutrition: Requirement for IgA in Murine Nasotracheal Anti-Influenza Immunity

Secretory IgA (SIgA) is the primary mucosal Ig and has been shown to mediate nasotracheal (NT) mucosal immunity in normal immune BALB/c mice. This finding has been challenged by a report of NT immunity without IgA in knockout mice, suggesting that IgA may not be necessary for the protection of mucosal surfaces. Although other protective mechanisms may become active in the congenital absence of SIgA, these mechanisms are not the primary means of protection in normal mice. In this paper we show that feeding chemically defined total parenteral nutrition (TPN) to genetically normal, immune ICR mice by the i.v. route results in loss of nasal anti-influenza immunity and a significant drop in influenza-specific SIgA in the upper respiratory tract compared with chow-fed mice (p < 0.005), while the serum influenza-specific IgG titer is unaffected. Loss of upper respiratory tract mucosal immunity is not related to serum Ab, because 10 of 13 TPN-fed mice shed virus into their nasal secretions despite adequate serum anti-influenza IgG titers. The number of IgG Ab-secreting cells in the nasal passages and spleens of TPN-fed mice was unaffected, while both the number and the percentage of splenic IgA-secreting cells were decreased relative to those in chow-fed animals. The loss of immunity is due to the route of nutrition, not the composition of the diet, because TPN solution fed orally via gastrostomy instead of i.v. maintains NT anti-influenza mucosal immunity. We hypothesize that delivery of nutrition via the gut triggers the release of gastrointestinal neuropeptides necessary for maintenance of the mucosal immune system.

Total parenteral nutrition supplementation with glutamine improves survival after gut ischemia/reperfusion.

BACKGROUND Total parenteral nutrition (TPN) alters gut cytokines and mucosal immunity and increases intercellular adhesion molecule-1 (ICAM-1) expression, gut neutrophil levels, and mortality after gut ischemia. Supplementation of TPN with glutamine partially supports mucosal immunity by preserving respiratory and intestinal IgA levels, maintaining the proper IgA-stimulating cytokine milieu within the intestine, and reducing intestinal ICAM-1 expression and neutrophil accumulation. This work investigates whether glutamine supplementation of TPN affects mortality in mice after gut ischemic insult. METHODS Thirty-eight mice were randomized to receive chow, TPN, or 2% glutamine-supplemented TPN (GLN-TPN) for 5 days. After feeding their respective diets, gut ischemia/reperfusion (I/R) was induced with superior mesenteric artery occlusion for 30 minutes followed by resuscitation with 1 mL saline. Survival was recorded until 72 hours after reperfusion. RESULTS Survival time was significantly reduced in the TPN-fed mice compared with both chow-fed and GLN-TPN-fed mice (p < .05). Survival at 72 hours after reperfusion was also significantly lower in the TPN-fed mice than in the chow-fed and GLN-TPN-fed mice (p < .05) CONCLUSIONS Glutamine supplementation of TPN significantly improves survival after gut I/R, suggesting modulation of the inflammatory response or improved gut tolerance to low-flow states.

Enteral Feeding Preserves Mucosal Immunity Despite In Vivo MAdCAM-1 Blockade of Lymphocyte Homing

ObjectiveTo determine the influence of route of nutrition on gut mucosal addressin cellular adhesion molecule-1 (MAdCAM-1) expression and the effect of MAdCAM-1 blockade on gut-associated lymphoid tissue (GALT) lymphocyte populations and established respiratory antibacterial immunity. Summary Background DataLymphocytes, sensitized to antigens in Peyer’s patches, migrate via mesenteric lymph nodes and home to intestinal lamina propria. MAdCAM-1 located on endothelial cells regulates this trafficking. Experimentally, parenteral nutrition (PN) decreases GALT cell mass and mucosal immunity when compared with enteral feeding. MethodsIn experiment 1, MAdCAM-1 expression was quantified in 32 mice after 4 days of feeding chow, a complex diet, intragastric (IG)-PN, or PN. In experiment 2, MAdCAM-1 was measured in 102 mice 0, 4, 8, 12, 24, 48, or 72 hours after starting PN and at 0, 4, 8, 12, 24, or 48 hours after reinstituting chow following 5 days of PN. In experiment 3, 56 mice received chow, PN, chow + MECA-367 (anti-MAdCAM-1 mAb), or chow + Isotype control Ab (IsoAb) for 5 days, followed by Peyer’s patches, lamina propria, and intraepithelial lymphocyte yield with respiratory and intestinal IgA levels. In experiment 4, 10 days after Pseudomonas immunization, mice received chow + MECA-367 or chow + IsoAb for 4 days followed by 1.2 × 108Pseudomonas intratracheally. ResultsDiet and route affect MAdCAM-1 expression (chow > complex diet > IG-PN > PN). Decreased MAdCAM-1 expression occurred within hours of starting PN in Peyer’s patches, but not mesenteric lymph nodes or the intestine, and recovered quickly with enteral refeeding. MAdCAM-1 blockade reduced all GALT populations. Blockade had little effect on IgA levels and partially impaired the late response of established respiratory immunity. ConclusionsEnteral feeding affects MAdCAM-1 expression. Complete MAdCAM-1 blockade reduces GALT lymphocytes to PN levels, but the chow feeding stimulus preserves IgA and early antibacterial resistance, implying the existence of non-MAdCAM-1 mechanisms to preserve mucosal immunity.

Route of Nutrition Influences Generation of Antibody-Forming Cells and Initial Defense to an Active Viral Infection in the Upper Respiratory Tract

ObjectiveTo assess whether lack of enteral feeding significantly impairs generation of specific immune responses to an acute viral infection. Summary Background DataParenteral feeding provides adequate nutrients to meet metabolic needs, but lack of enteral stimulation creates a defect in mucosal immunity characterized by loss of IgA-mediated defenses in the respiratory tract. MethodsThe enzyme-linked Immunospot (ELISPOT) assay was used to determine accumulation of immunologic cells in the nasal passages after diet manipulation. Viral shedding and nasal IgA levels were measured in additional groups of mice. ResultsAfter determining the time course of antibody-forming cells (AFCs) via ELISPOT to an active infection with the A/PR8 influenza virus, a significant reduction was found in total AFCs, IgA-producing AFCs, and IgG-producing AFCs over the course of a 13-day experiment with significant depression in viral-specific respiratory IgA levels. Eight days following an active infection, seven of nine total parenteral nutrition-fed animals continued to have viral shedding in the nasal passages compared to one of nine chow-fed mice and one of six animals fed a complex enteral diet. ConclusionsLack of enteral stimulation significantly impairs the generation of IgA-mediated mucosal immunity.

Modulation of organ ICAM-1 expression during IV-TPN with glutamine and bombesin.

The gut primes neutrophils (PMNs) during injury, which can then induce distant organ damage after a second insult. ICAM-1 is an important adhesion molecule in PMN attachment to the vascular endothelium. Parenteral nutrition (TPN) decreases gut levels of interleukin (IL)-4 and IL-10, two cytokines that are normal inhibitors of ICAM-1 expression. TPN also increases gut ICAM-1 expression and PMN accumulation. Since glutamine (GLN) and bombesin (BBS) prevent TPN-associated impairment of mucosal immunity, we hypothesized that GLN and BBS would modulate organ ICAM-1 expression in association with normalization of IL-4 and IL-10 levels. Forty-four mice were fed chow, TPN, or GLN-TPN (isonitrogenous 2% GLN-enriched TPN). After 5 days of diets, ICAM-1 expression was quantified in organs using the dual radiolabeled monoclonal antibody technique. In the next experiment, 29 mice were fed chow, TPN, or BBS-TPN (BBS 15 microg/kg TID) for 5 days to measure organ ICAM-1 expression. Total IL-4 and IL-10 levels were measured with ELISA from intestinal homogenates of another set of 52 mice fed chow, TPN, GLN-TPN, or BBS-TPN. TPN significantly increased ICAM-1 expression in the lung, kidney, and intestine compared with chow mice. GLN-TPN decreased intestinal, but not lung, ICAM-1 expression, while BBS-TPN reduced pulmonary, but not gut, ICAM-1 levels. GLN- and BBS-TPN returned gut IL-4 levels to normal, but failed to increase IL-10 levels. GLN and BBS had different effects on organ ICAM-1 expression induced by lack of enteral nutrition. Mechanisms other than recovery of IL-4 alone may be responsible for gut ICAM-1 expression.

Increased ICAM-1 and beta2 integrin expression in parenterally fed mice after a gut ischemic insult.

Lack of enteral feeding increases P- and E-selectin and ICAM-1 expression on endothelial cells in organs, such as the small intestine and lung, and increases neutrophils in the intestine. These changes are associated with increased mortality after gut ischemia. We hypothesize that nutritional regimen affects endothelial ICAM-1 levels and leukocyte &bgr;2 integrins after gut ischemia. Mice received chow, intravenous (IV) TPN, or intragastric (IG) TPN. In experiment 1, after 5 days of diet, 28 mice underwent 15 min of superior mesenteric artery (SMA) occlusion (I/R) for quantification of ICAM-1 expression in organs 3 h later. In experiment 2, after the same nutrient pretreatments of 38 mice, peripheral blood was obtained with or without gut I/R to measure CD11a and CD11b expression on myeloid cells. CD18 immunofluorescence staining was studied in the lung. Expression of ICAM-1 in the liver, kidney, and small intestine was significantly higher after IV-TPN than chow. IG-TPN reduced liver and kidney ICAM-1 levels midway between the chow and IV-TPN groups, but not intestinal expression. Expression of CD11b on the myeloid cell population in each group was similar before I/R, but CD11b levels increased after IV-TPN on circulating cells after I/R compared with all uninjured animals or injured chow or IG-TPN mice. Only IV-TPN mice had lung CD18-positive leukocytes after I/R. After I/R, lack of enteral feeding increases organ expression of ICAM-1, CD11b levels on myeloid cells, and lung of CD18 positive leukocytes. Through these changes, lack of enteral feeding may increase organ damage after gut ischemia.

Glutamine improves impaired cellular exudation and polymorphonuclear neutrophil phagocytosis induced by total parenteral nutrition after glycogen-induced murine peritonitis.

Clinical and laboratory evidence shows that enteral feeding significantly reduces pneumonia and intra-abdominal abscess formation after celiotomy for severe trauma. Supplementation of total parenteral nutrition (TPN) with glutamine (GLN) supports impaired immunity induced by TPN in several animal and human studies. This work investigates the peritoneal cellular response and polymorphonuclear neutrophil (PMN) bactericidal function after mouse chemical peritonitis after TPN with and without GLN. Thirty-three mice received chow, TPN, or 2% GLN-supplemented TPN (GLN-TPN) for 5 days. All mice then received 2 mL of a 1% glycogen solution intraperitoneally to induce cell exudation, and peritoneal exudative cells (PECs) were recovered 4 h later. Total and differential PEC numbers, as well as PMN phagocytosis, reactive oxygen intermediate production (ROI), CD11b (integrin &agr;M chain) expression, and CD16/32 (Fc&ggr; II/III receptor) expression were measured. PMN, macrophage, and lymphocyte cell numbers were significantly lower with TPN than with chow or GLN-TPN groups, with no differences between chow and GLN-TPN. TPN significantly lowered peritoneal PMN phagocytosis compared with chow (P < 0.05) and approached significance with GLN-TPN (P = 0.06). There were no significant differences in ROI production or CD11b and CD16/32 expression on peritoneal PMN. GLN supplementation improved the reduction in cell exudation and PMN phagocytosis induced by TPN after chemical peritonitis.

Mucosal immunity preservation with bombesin or glutamine is not dependent on mucosal addressin cell adhesion molecule-1 expression.

BACKGROUND Mucosal addressin cell adhesion molecule-1 (MAdCAM-1) is an adhesion molecule that directs naive T and B cells into Peyers patches for sensitization and distribution to intestinal and extraintestinal sites. With no enteral stimulation, its expression drops rapidly in association with reduced Peyers patch cell populations and increases rapidly with reinstitution of enteral feeding. Because both glutamine (GLN) and bombesin (BBS) preserve mucosal immunity, this study examined whether they preserve MAdCAM-1 expression. METHODS In 2 separate experiments, animals were randomized to IV cannulation with chow, total parenteral nutrition (TPN), and (experiment 1) 15 microg/kg BBS 3 times per day or (experiment 2) an isocaloric, isonitrogenous 2% GLN-supplemented solution. After 5 days of feeding, MAdCAM-1 expression in Peyers patches, spleen, and intestine was measured using a dual radiolabeled monoclonal antibody technique. RESULTS MAdCAM-1 expression was not significantly improved from TPN levels either with BBS or GLN supplementation. Levels of MAdCAM-1 expression remained unchanged in non-Peyers patch sites. CONCLUSIONS Although MAdCAM-1 is considered the gateway molecule for cell entry into mucosal immunity, this does not seem to be the mechanism for mucosal immunity preservation in nonenterally fed mice receiving bombesin or glutamine.