Parenteral nutrition inhibits tumor necrosis factor-alpha-mediated IgA response to injury

The effect of enteral stimulation on the immune response of the intestinal mucosa and its application in nutritional support

The intestine plays a fundamental role as a regulator of the mucosal immune response, mostly through the production and secretion of secretory Immunoglobulin A (sIgA) by the gut-associated lymphoid tissue (GALT). Enteral stimulation, a balance between the commensal microbiota and pathogenic microorganisms, in addition to an adequate nutritional status is required for the optimal immune function of the intestine. Fasting subjects or those supported only with parenteral nutrition, show a progressive anatomical and physiological deterioration of the GALT, triggering a series of alterations resulting in a decrease in the intestinal immune response, modification in the type of microbiota, and changes that lead to or aggravate malnutrition. Patients with malnutrition present an increase in the rate of nosocomial infections, hospital length of stay, and mortality. An adequate nutritional assessment at hospital admission and avoiding long periods of fasting are paramount to prevent these unfavorable outcomes. Herein, we present a mini-state of the art review on the role and importance of enteral stimulation by GALT-mediated immune response.

Innate Mucosal Immune System Response of BALB/c vs C57BL/6 Mice to Injury in the Setting of Enteral and Parenteral Feeding

BACKGROUND

Outbred mice exhibit increased airway and intestinal immunoglobulin A (IgA) following injury when fed normal chow, consistent with humans. Parenteral nutrition (PN) eliminates IgA increases at both sites. Inbred mice are needed for detailed immunological studies; however, specific strains have not been evaluated for this purpose. BALB/c and C57BL/6 are common inbred mouse strains but demonstrate divergent immune responses to analogous stress. This study addressed which inbred mouse strain best replicates the outbred mouse and human immune response to injury.

METHODS

Intravenously cannulated mice received chow or PN for 5 days and then underwent sacrifice at 0 or 8 hours following controlled surgical injury (BALB/c: n = 16-21/group; C57BL/6: n = 12-15/group). Bronchoalveolar lavage (BAL) was analyzed by enzyme-linked immunosorbent assay for IgA, tumor necrosis factor-α (TNF-α), interleukin (IL)-1β, and IL-6, while small intestinal wash fluid (SIWF) was analyzed for IgA.

RESULTS

No significant increase in BAL IgA occurred following injury in chow- or PN-fed BALB/c mice (chow: P = .1; PN: P = .7) despite significant increases in BAL TNF-α and SIWF IgA (chow: 264 ± 28 vs 548 ± 37, P < .0001; PN: 150 ± 12 vs 301 ± 17, P < .0001). Injury significantly increased mucosal IgA in chow-fed C57BL/6 mice (BAL: 149 ± 33 vs 342 ± 87, P = .01; SIWF: 236 ± 28 vs 335 ± 32, P = .006) and BAL cytokines. After injury, PN-fed C57BL/6 mice exhibited no difference in BAL IgA (P = .9), BAL cytokines, or SIWF IgA (P = .1).

CONCLUSIONS

C57BL/6 mice exhibit similar airway responses to injury as outbred mice and humans, providing an appropriate model for studying mucosal responses to injury. The BALB/c mucosal immune system responds differently to injury and does not replicate the human injury response.

Nutrition and gut immunity

The human intestine contains huge amounts of nonpathologic bacteria surviving in an environment that is beneficial to both the host and the bacterial populations. When short pauses in oral intake occur with minimal alterations in the mucosa-microbial interface, critical illness, with its attendant acidosis, prolonged gastrointestinal tract starvation, exogenous antibiotics, and breakdown in mucosal defenses, renders the host vulnerable to bacterial challenge and also threatens the survival of the bacteria. This review examines the altered innate and adaptive immunologic host defenses that occur as a result of altered oral or enteral intake and/or injury.

Parenteral nutrition impairs lymphotoxin β receptor signaling via NF-κB

OBJECTIVE

To determine effects of (1) parenteral nutrition (PN), (2) exogenous Lymphotoxin β receptor (LTβR) stimulation in PN animals, and (3) exogenous LTβR blockade in chow animals on NF-κB activation pathways and products: MAdCAM-1, chemokine (C-C motif) Ligand (CCL) 19, CCL20, CCL25, interleukin (IL)-4, and IL-10.

BACKGROUND

LT stimulates LTβR in Peyer's patches (PP) to activate NF-κB via the noncanonical pathway. The p100/RelB precursor yields p52/RelB producing MAdCAM-1, cytokines, and chemokines important in cell trafficking. TNFα, IL-1β, and bacterial products stimulate the inflammatory canonical NF-κB pathway producing p65/p50 and c-Rel/p50. PN decreases LTβR, MAdCAM-1, and chemokines in PP and lowers small intestinal IgA compared with chow.

METHODS

Canonical (p50 and p65) and noncanonical (p52 and Rel B) NF-κB proteins in PP were analyzed by TransAM NF-κB kit after 5 days of chow or PN, 2 days of LTβR stimulation or 3 days of LTβR blockade. MAdCAM-1, chemokines, and cytokines in PP were measured by ELISA after LTβR stimulation or blockade.

RESULTS

PN significantly reduced all NF-κB proteins in PP compared with chow. Exogenous LTβR stimulation during PN increased p50, p52, Rel B, MAdCAM-1, IL-4, and IL-10 in PP, but not p65, CCL19, CCL20, or CCL25 compared with PN. LTβR blockade reduced noncanonical products (p52 and Rel B), MAdCAM-1, CCL19, CCL20, CCL25, IL-4, and IL-10 but had no effect on the inflammatory pathway (p50 and p65) compared with chow.

CONCLUSION

Lack of enteral stimulation during PN decreases both canonical and noncanonical NF-κB pathways in PP. LTβR stimulation during PN feeding completely restores PP noncanonical NF-κB activity, MAdCAM-1, IL-4, IL-10, and partly the canonical pathway. LTβR blockade decreases the noncanonical NF-κB activity, MAdCAM-1, chemokines, and cytokines without effect on the canonical NF-κB activity in PP.

Neutrophil elastase inhibitor restores gut ischemia reperfusion-induced impairment of gut immunity with reduced plasma interleukin-6 concentrations in mice

BACKGROUND AND PURPOSE

Gut-associated lymphoid tissue (GALT) is regarded as central mucosa-associated lymphoid tissue that influences systemic mucosal immunity. Our previous study revealed that gut ischemia and reperfusion (I/R) reduces GALT lymphocyte numbers. Because gut hypoperfusion frequently occurs in trauma, shock, and surgery patients, establishment of a therapeutic method to preserve GALT mass after gut I/R may be important for the prevention of infections. We examined the effects of sivelestat sodium hydrate, a selective inhibitor of neutrophil elastase, on GALT mass and plasma cytokine concentrations in a murine gut I/R model.

METHODS

Seventy male ICR mice were randomized to the control (n = 34) or the sivelestat (n = 36) group. After intravenous cannulation of the animals, the superior mesenteric artery was occluded for 60 min. After reperfusion, physiologic saline or sivelestat 5 mg/kg hourly was infused for 24 h. Sixteen mice in the control and 22 in the sivelestat group were alive at 24 h. Twenty-six mice (n = 13 in each group) were chosen randomly for harvest of the small intestine. Lymphocytes from Peyer patches (PP), the intraepithelial space (IE), and the lamina propria (LP) were counted; and their phenotypes (αβT-cell receptor (TCR), γδTCR, CD4, CD8, B cell) were determined by flow cytometry. Cytokine concentrations (interleukin [IL]-6, IL-1β, IL-10) in the plasma and bronchoalveolar lavage fluid were measured by enzyme-linked immunosorbent assay.

RESULTS

Sivelestat treatment did not improve survival but increased PP and IE lymphocyte numbers significantly and reduced the LP CD8(+) cell percentage and plasma IL-6 concentration compared with controls. There were no significant differences between the two groups in other cell phenotypes or cytokine concentrations.

CONCLUSION

Sivelestat treatment after gut I/R may be useful for maintaining gut immunity and preventing systemic inflammatory responses.

Injury induces localized airway increases in pro-inflammatory cytokines in humans and mice

BACKGROUND

Secretory immunoglobulin A (sIgA) increases in the airways of humans and mice after injury to protect against infection. The pro-inflammatory cytokines tumor necrosis factor (TNF)-α, interleukin (IL)-1β, and IL-6 are linked molecularly to sIgA production and secretion and are required for sIgA increases in the airway after injury in a mouse model. We investigated the injury effect on airway and serum concentrations to determine the source of the cytokines involved in the airway IgA response.

METHODS

In the first experiment, TNF-α, IL-1β, and IL-6 concentrations in bronchoalveolar lavage (BAL) fluid and serum obtained from 11 ventilated trauma patients within 30 h of admission were compared with those in eight elective surgical patients. In the second experiment, male ICR mice received no injury (n = 7) or injury with sham celiotomy and neck incisions (n = 8) with sacrifice of all animals at 8 h for BAL fluid and serum cytokine measurements by enzyme-linked immunosorbent assay.

RESULTS

Injured patients had significantly higher BAL fluid and serum TNF-α, IL-1β, and IL-6 concentrations, with greater increases in the BAL fluid than in the serum. Injured mice had significantly increased BAL fluid concentrations of TNF-α, IL-1β, and IL-6 without significant changes in serum TNF-α or IL-1β. Serum IL-6 increased significantly.

CONCLUSIONS

Injury significantly increases human and mouse airway TNF-α, IL-1β, and IL-6. Increases are greater in the airway than in serum, implying a local rather than a systemic stress response to injury.

Small intestine mucosal immune system response to injury and the impact of parenteral nutrition

BACKGROUND

Both humans and mice increase airway immunoglobulin A (IgA) after injury. This protective response is associated with TNF-α, IL-1β, and IL-6 airway increases and in mice is dependent upon these cytokines as well as enteral feeding. Parenteral nutrition (PN) with decreased enteral stimulation (DES) alters gut barrier function, decreases intestinal IgA, and decreases the principal IgA transport protein pIgR. We investigated the small intestine (SI) IgA response to injury and the role of TNF-α, IL-1β, IL-6, and PN/DES.

METHODS

Expt 1: Murine kinetics of SI washing fluid (SIWF) IgA; SI, SIWF and serum TNF-α, IL-1β, and IL-6, was determined by ELISA from 0 to 8 hours after a limited surgical stress injury (laparotomy and neck incisions). Expt 2: Mice received chow or PN/DES before injury and SIWF IgA and SI pIgR levels were determined at 0 and 8 hours. Expt 3: Mice received PBS, TNF-α antibody, or IL-1β antibody 30 minutes before injury to measure effects on the SIWF IgA response. Expt 4: Mice received injury or exogenous TNF-α, IL-1β, and IL-6 to measure effects on the SIWF IgA response.

RESULTS

Expt 1: SIWF IgA levels increased significantly by 2 hours after injury without associated increases in TNF-α or IL-1β whereas IL-6 was only increased at 1 hour after injury. Expt 2: PN/DES significantly reduced baseline SIWF IgA and SI pIgR and eliminated their increase after injury seen in Chow mice. Expt 3: TNF-α and IL-1β blockade did not affect the SIWF IgA increase after injury. Expt 4: Exogenous TNF-α, IL-1β, and IL-6 increased SIWF IgA similarly to injury.

CONCLUSION

The SI mucosal immune responds to injury or exogenous TNF-α, IL-1β, and IL-6 with an increase in lumen IgA, although it does not rely on local SI increases in TNF-α or IL-1β as it does in the lung. Similar to the lung, the IgA response is eliminated with PN/DES.

Proinflammatory cytokine surge after injury stimulates an airway immunoglobulin a increase

BACKGROUND

: Injury stimulates an innate airway IgA response in severely injured patients, which also occurs in mice. Tumor necrosis factor (TNF)-α and interleukin (IL)-1β stimulate the production of polymeric immunoglobulin receptor, the protein required to transport immunoglobulin A (IgA) to mucosal surfaces. Blockade of TNF-α and IL-1β eliminates the airway IgA response to injury. IL-6 stimulates differentiation of B cells into IgA-secreting plasma cells at mucosal sites. We investigated the local and systemic kinetics of TNF-α, IL-1β, and IL-6 after injury in mice. We also hypothesized that injection of exogenous TNF-α, IL-1β, and IL-6 would replicate the airway IgA response to injury.

METHODS

: Experiment 1: male Institute of Cancer Research mice were randomized to uninjured controls (n = 8) or to surgical stress with laparotomy and neck incisions, with killing at 1, 2, 3, 5, or 8 hours after injury (n = 8/group). Bronchoalveolar lavage (BAL) and serum levels of TNF-α, IL-1β, and IL-6 were analyzed by enzyme-linked immunosorbent assay. Experiment 2: male Institute of Cancer Research mice were randomized to uninjured controls (n = 6), injury (surgical stress that was similar to experiment 1 except the peritoneum was left intact, n = 6), or cytokine injection with intraperitoneal injection of recombinant TNF-α, IL-1β, and IL-6. Animals were killed at 2 hours after injury, and nasal airway lavage and BAL IgA were analyzed by enzyme-linked immunosorbent assay.

RESULTS

: Experiment 1: BAL TNF-α, IL-1β, and IL-6 levels increased in bimodal pattern after injury at 3 hours and 8 hours versus controls (p < 0.05). Serum IL-6 did not increase at 3 hours, but did show a significant increase by 5 hours versus control (p < 0.05). Serum levels of TNF-α and IL-1β did not change. Experiment 2: both Injury and combination TNF-α, IL-1β, and IL-6 cytokine injection significantly increased IgA levels in airway lavage (BAL + nasal airway lavage) compared with control (p < 0.01 for both).

CONCLUSIONS

: Airway levels of TNF-α, IL-1β, and IL-6 increase in a bimodal pattern after injury with peaks at 3 hours and 8 hours, which do not correspond to serum changes. The peak at 8 hours is consistent with the known increase in airway IgA after injury. Intraperitoneal injection of a combination exogenous TNF-α, IL-1β, and IL-6 replicates the airway IgA increase after injury. This effect is not seen with individual cytokine injections.

Parenteral nutrition maintains pulmonary IgA antibody transport capacity, but not active transport, following injury

BACKGROUND

Parenteral nutrition (PN) increases post-trauma pneumonia versus enteral feeding. PN impairs murine immunoglobulin A (IgA) airway defenses and abrogates a normal IgA increase following injury. This work investigates the effect of type/route of nutrition on lung IgA and its transport protein, polymeric immunoglobulin receptor (pIgR), after injury.

METHODS

Catheterized mice were randomized to Chow or PN for 5 days and sacrificed without injury (Chow: n = 12; PN n = 11), or 8 hours after laparotomy + neck incisions (Chow-injury: n = 11, PN-injury: n = 13). Bronchoalveolar lavage (BAL) and lung IgA levels were analyzed by enzyme-linked immunosorbent assay (ELISA) and lung pIgR by Western blot.

RESULTS

BAL IgA levels increased in Chow-injury versus PN-injury (P <.01) with no differences in pIgR. PN-injury tissue IgA levels decreased versus Chow (P <.01), Chow-injury (P <.01), and PN (P <.05).

CONCLUSIONS

PN impairs the airway IgA response to injury but not due to impaired IgA transport capacity/pIgR level.