F. Enrique Gomez

Effects of sterculic acid on stearoyl-CoA desaturase in differentiating 3T3-L1 adipocytes

The effects of sterculic acid on cell size, adiposity, and fatty acid composition of differentiating 3T3-L1 adipocytes are correlated with stearoyl-CoA desaturase (SCD) expression (mRNA and protein levels) and enzyme activity. Fluorescence-activated cell scanning (FACS) analysis showed that adipocytes differentiated with methylisobutylxanthine, dexamethasone, and insulin (MDI) plus 100 microM sterculic acid comprised a population of predominantly large cells with reduced adiposity compared to MDI-treated cells. Although both groups had similar amounts of total fat, their fatty acid profiles were strikingly different: MDI-treated cells had high levels of the unsaturated palmitoleic (Delta(9)-16:1) and oleic (Delta(9)-18:1) acids, whereas the cells cultured with MDI plus sterculic acid accumulated palmitic (16:0) and stearic (18:0) acids together with a marked reduction in Delta(9)-16:1. Although the cells treated with MDI plus sterculic acid had similar levels of scd1 and scd2 mRNAs and antibody-detectable SCD protein as the MDI-treated cells, the SCD enzyme activity was inhibited more than 90%. The accumulation of 16:0 and 18:0, together with normal levels of fatty acid synthase (FAS) and aP2 mRNAs, shows that de novo synthesis and elongation of fatty acids, as well as cell differentiation, were not affected by sterculic acid. Because of the increase in cell size in the sterculic acid-treated cells, the insulin-stimulated 2-deoxyglucose (2-DOG) uptake was determined. Compared to MDI-treated cells, the 2-DOG uptake in the cells treated with sterculic acid was not affected. These results indicate that sterculic acid directly inhibits SCD activity, possibly by a turnover-dependent reaction, without affecting the processes required for adipocyte differentiation, scd gene expression or SCD protein translation.

Parenteral Nutrition Impairs Gut-Associated Lymphoid Tissue and Mucosal Immunity by Reducing Lymphotoxin β Receptor Expression

Objective:To determine the effects of parenteral nutrition (PN) on LTβR in gut-associated lymphoid tissue (GALT), particularly the intestine and Peyers patches (PP). Summary Background Data:Lack of enteral stimulation with PN impairs mucosal immunity and reduces IgA levels through depression of GALT cytokines (IL-4 and IL-10) and GALT specific adhesion molecules. We have shown that each is critical to intact mucosal immunity through effects on lymphocyte homing, IgA production, and resistance to antibacterial and antiviral immunity. IgA is the principal specific immunologic mucosal defense. LTβR stimulation controls production of IL-4, the adhesion molecule MAdCAM-1, and other key components of GALT, all of which are important in increasing IgA levels and maintaining mucosal defenses. Methods:Experiment 1: LTβR expression in intestine and PP was analyzed by Western blot after 5 days of chow, a complex enteral diet (CED), or PN. Diets were isocaloric and isonitrogenous except for chow. Experiment 2: After completing pilot experiments to determine the appropriate dose of the LTβR agonistic antibody, mice received chow, PN + 5 &mgr;g of anti-LTβR mAb (2 times/d, i.v.) or PN + isotype control antibody. PP lymphocytes and intestinal IgA levels were measured after 2 days. Results:Lack of enteral stimulation with PN significantly decreased LTβR expression in intestine and PP compared with chow and CED. LTβR stimulation with an agonistic anti-LTβR mAb significantly increased PP lymphocyte counts and intestinal IgA in PN fed-mice. Conclusions:LTβR expression is critical for GALT control mechanisms and intact mucosal immunity. PN reduces LTβR expression, PP lymphocytes, and intestinal IgA production. Exogenous LTβR stimulation reverses PN-induced depression of gut mucosal immunity.

Intestinal polymeric immunoglobulin receptor is affected by type and route of nutrition.

BACKGROUND Secretory immunoglobulin A (SIgA) prevents adherence of pathogens at mucosal surfaces to prevent invasive infection. Polymeric immunoglobulin receptor (pIgR) is located on the basolateral surface of epithelial cells and binds dimeric immunoglobulin A (IgA) produced by plasma cells in the lamina propria. This IgA-pIgR complex is transported apically, where IgA is exocytosed as SIgA to the mucosal surface. Our prior work shows that mice fed intragastric (IG, an elemental diet model) and IV parenteral nutrition (PN) solution have reduced intestinal T and B cells, SIgA, and interleukin-4 (IL-4) compared with mice fed chow or a complex enteral diet (CED). Prior work also demonstrates a reduction in IgA transport to mucosal surfaces in IV PN-fed mice. Because IL-4 up-regulates pIgR production, this work studies the effects of these diets on intestinal pIgR. METHODS Male Institute of Cancer Research (ICR) mice were randomized to chow (n = 11) with IV catheter, CED (n = 10) or IG PN (n = 11) via gastrostomy and IV PN (n = 12) for 5 days. CED and PN were isocaloric and isonitrogenous. Small intestine was harvested for pIgR and IL-4 assays after mucosal washing for IgA. IgA and IL-4 levels were analyzed by enzyme-linked immunosorbent assay and pIgR by Western blot. RESULTS Small intestinal pIgR expression, IgA levels, and IL-4 levels decreased significantly in IV PN and IG PN groups. CONCLUSIONS Lack of enteral stimulation affects multiple mechanisms responsible for decreased intestinal SIgA levels, including reduced T and B cells in the lamina propria, reduced Th-2 IgA-stimulating cytokines, and impaired expression of the IgA transport protein, pIgR.

Parenteral nutrition induces organ specific alterations in polymeric immunoglobulin receptor levels

BACKGROUND Secretory immunoglobulin A (IgA) prevents pathogen adherence at mucosal surfaces to prevent infection. Polymeric immunoglobulin receptor (pIgR), located on the basolateral surface of mucosal cells, binds dimeric IgA produced by B cells with the cooperation of T cells in the lamina propria. This IgA-pIgR complex is transported apically, where it is exocytosed as secretory IgA to the mucosal surface. Our prior work shows that parenteral nutrition (PN) impairs both airway and small intestine mucosal immunity by reducing T and B cells and IgA levels. This work examines intestinal and respiratory tissue-specific pIgR responses to PN. METHODS Cannulated male Institute of Cancer Research mice were randomized to Chow (n = 10) or PN (n = 10). After 5 days, animals were sacrificed and lavages obtained from the small intestine, lung (BAL = bronchoalveolar lavage), and nasal airways (NAL). Small intestine, lung, and nasal passage tissues were also collected. Lavage and tissue homogenate IgA levels were quantified by enzyme-linked immunosorbent assay and pIgR by Western blot. RESULTS PN group SIL and NAL IgA levels dropped significantly compared with Chow. PN significantly reduced pIgR levels in the SI while no pIgR change was noted in nasal passages and lung pIgR actually increased with PN. Tissue homogenate IgA levels did not change with PN in the SI while levels in the nasal passage and lung decreased. CONCLUSIONS PN impairs airway mucosal immunity by reduction in IgA available for transport rather than via a reduction in pIgR levels. In the small intestine, diminished pIgR is implicated in the deterioration of antibody-mediated mucosal immunity.

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.

Parenteral Feeding Depletes Pulmonary Lymphocyte Populations

BACKGROUND The effect of parenteral nutrition (PN) on lymphocyte mass in the lung is unknown, but reduced mucosal lymphocytes are hypothesized to play a role in the reduced immunoglobulin A-mediated immunity in both gut and lung. The ability to transfer and track cells between mice may allow study of diet-induced mucosal immune function. The objectives of this study are to characterize lung T-cell populations following parenteral feeding and to study distribution patterns of transferred donor lung T cells in recipient mice. METHODS In experiment 1, cannulated male Balb/c mice are randomized to receive chow or PN for 5 days. Lung lymphocytes are obtained via collagenase digestion, and flow cytometric analysis is used to identify total T (CD3+) and B (CD45/B220+) cells. In experiment 2, isolated lung T cells from chow-fed male Balb/c mice are pooled and labeled in vitro with a fluorescent dye (carboxyfluorescein diacetate succinimidyl ester [CFSE]), and 1.1 x 10(8) CFSE+ cells (3.1 x 10(6) T cells) are transferred to chow-fed Balb/c recipients. Cells recovered from recipient lungs and intestinal lamina propria (LP) are analyzed by flow cytometry to determine CFSE/CD3+ T cells at 1, 2, and 7 days. In experiment 3, cells are transferred to PN-fed recipients. RESULTS In experiment 1, PN significantly decreases lung T- and B-cell populations compared with chow feeding. In experiment 2, CFSE+ T-cell retention is highest on day 1 in lung and LP, and decreases on day 2. Cells are gone by day 7; 98.1% of retained donor lung T cells migrate to recipient lungs and 1.9% to the intestine on day 1. Similar results are seen in experiment 3 after transfer of cells to PN-fed recipients. CONCLUSIONS PN reduces pulmonary lymphocyte populations consistent with impaired respiratory immunity. Transferred lung T cells preferentially localize to recipient lungs rather than intestine with maximal accumulation at 24 hours. Limited cross-talk of transferred lung T cells to the intestine indicates that mucosal lymphocyte traffic might be programmed to localize to specific effector sites.

Injury stimulates an innate respiratory immunoglobulin a immune response in humans.

BACKGROUND Secretory immunoglobulin A (SIgA) is the specific immune antibacterial defense. Since pneumonia frequently complicates the course of trauma patients, we studied early airway immune responses after injury. METHODS Twelve severely injured, intubated (expected for >/=5 d) patients had tracheal and bilateral lung lavage (BAL) within 30 hours of injury (n = 12). Epithelial lining fluid (ELF) volume and SIgA were measured by urea dilution and enzyme-linked immunosorbent assay (ELISA), respectively. Control BAL specimens were obtained from eight healthy elective surgical patients. Anatomically based comparisons were made between groups with Welchs unpaired t test. To verify human data, 30 male mice received no injury (time 0, n = 7) or injury with abdominal and neck incisions and were killed for airway IgA at 4 (n = 7), 8 (n = 8), and 24 (n = 8) hours. Analysis of variance (ANOVA) and Fishers protected least significant difference testing was used to analyze animal data. RESULTS Initial trauma patient SIgA concentration (SIgA/mL ELF) increased compared with control in the lungs bilaterally (p < 0.05 both right and left). ELF volume was significantly higher in the right lung (p = 0.02) and just missed statistical significance (p = 0.07) on the left. Mouse IgA increased 8 hours after stress (p < 0.05 versus 0, 4, and 24 hours) and returned to normal by 24 hours. CONCLUSION A previously unrecognized innate human airway mucosal immune response with increased airway SIgA and ELF occurs after severe injury and is reproducible experimentally. This accessible, quantifiable human response allows study of clinical strategies to reduce infections via mucosal immune therapies.

Parenteral Nutrition Inhibits Tumor Necrosis Factor-α-Mediated IgA Response to Injury

BACKGROUND Parenteral nutrition (PN) increases the incidence of pneumonia in severely injured patients compared with enteral feeding (ENT). Injury induces an innate airway IgA response in severely injured patients; similar responses occur in mice. Tumor necrosis factor-alpha (TNF-alpha) and interleukin-1 beta (IL-1beta) stimulate the production of polymeric immunoglobulin receptor (pIgR), the protein required to transport immunoglobulin A (IgA) to mucosal surfaces. We have shown that PN alters levels of lung and nasal passage IgA and several IgA-stimulating cytokines. We hypothesized that TNF-alpha and IL-1beta blockade, as well as PN, would blunt the airway IgA response to injury. METHODS Male Institute of Cancer Research (ICR) mice were randomized to uninjured controls (n = 10) or to intra-peritoneal phosphate-buffered saline (PBS) (n = 9), antagonistic TNF-alpha antibody (100 mcg, n = 7), or antagonistic IL-1beta antibody (50 mcg, n = 8) 30 min prior to surgical stress with laparotomy and neck incisions. Mice were sacrificed at 8 h for nasal and bronchoalveolar lavage (NAL, BAL) to measure IgA by enzyme-linked immunosorbent assay. In a separate experiment, 12 mice underwent intravenous cannulation followed by chow (n = 5) or PN (n = 7) feeding for 5 days prior to the same stress and IgA measurement. RESULTS Injury significantly increased NAL and BAL IgA (225 +/- 104 ng) compared with baseline (145 +/- 38 ng; p = 0.01). Blockade of TNF-alpha eliminated the innate airway IgA response to injury (130 +/- 47 ng; p = 0.01), whereas IL-1beta blockade blunted and PN eliminated it completely. CONCLUSIONS Tumor necrosis factor-alpha is involved in the respiratory IgA immune response to injury. Both TNF-alpha blockade and PN impair this innate response, and blockade of IL-1beta impairs it to a degree. We hypothesize that these cytokines blunt this response via their known effects on the polymeric immunoglobulin receptor (pIgR), whereas the PN-induced deficit likely is multifactorial.

Decreased Enteral Stimulation Alters Mucosal Immune Chemokines

BACKGROUND Migration of lymphocytes into and through the mucosal immune system depends upon adhesion molecules to attract circulating cells and chemokines to stimulate diapedesis into tissues. Decreased enteral stimulation significantly reduces mucosal addressin cellular adhesion molecule-1 (MAdCAM-1) levels, an adhesion molecule critical for homing of T and B cells to Peyers patches (PP), which reduces PP and intestinal T and B cells. We studied the effect of type and route of nutrition on tissue specific chemokines in PP (CXCL-12, -13 and CCL-19, -20 and -21), small intestine (SI; CCL-20, -25 and -28) and lung (CXCL-12, CCL-28). METHODS Intravenously cannulated male Institute of Cancer Research (ICR) mice were randomized to chow or parenteral nutrition (PN) for 5 days. PP, SI, and lung chemokine mRNA levels were measured using real-time qRT-polymerase chain reaction, and analyzed semiquantitatively by the DeltaDeltaCt method. Protein levels were quantified using enzyme-linked immunosorbent assay (ELISA) techniques, and groups compared using Students t-test. RESULTS PP CXCL13 protein significantly decreased, whereas CCL21 protein increased significantly in the parenterally fed group. Parenteral feeding significantly decreased SI CCL20 and CCL 25 protein levels. CCL28 decreased significantly in the SI and lung of intravenously fed animals. mRNA levels changed in the opposite direction (compared with protein) for all chemokines except CCL28. CONCLUSIONS Decreased enteral stimulation significantly alters key mucosal immune chemokine protein levels at multiple sites. In general, PN (and concomitant lack of enteral stimulation) results in decreased levels of chemokines that control lymphocyte migration within the mucosal immune system.

Effects of Lymphotoxin β Receptor Blockade on Intestinal Mucosal Immunity

Background: Mucosal addressin cellular adhesion molecule-1 (MAdCAM-1) directs lymphocyte migration into gut-associated lymphoid tissue (GALT) through Peyers patches (PPs). Parenteral nutrition (PN) impairs mucosal immunity by reducing PPs MAdCAM-1 expression, T and B cells in GALT, and intestinal and respiratory immunoglobulin (Ig) A levels. We previously showed that PN reduces lymphotoxin β receptor blockade (LTβR) in PPs and intestine, and that stimulation with LTβR agonist antibodies reverses these defects. To confirm that LTβR regulates transcription of MAdCAM-1 message and more fully understand the effects of LTβR on MAdCAM-1 function within the mucosal immune system, we studied the effect of LTβR blockade with a chimeric LTβR Ig-fusion protein on MAdCAM-1 mRNA levels, PP lymphocyte mass and IgA levels in the intestinal and respiratory tracts. Methods: Mice were cannulated and killed 3 days after receiving chow + control Ig, chow + LTβR-Ig fusion protein (100 μg IV), or PN + control Ig. The PPs of h...