Oral arginine reduces gut mucosal injury caused by lipopolysaccharide endotoxemia in rat

Intestinal barrier disruption with Plasmodium falciparum infection in pregnancy and risk of preterm birth: a cohort study

BACKGROUND

Malaria in early pregnancy is a risk factor for preterm birth and is associated with sustained inflammation and dysregulated angiogenesis across gestation. This study investigated whether malaria is associated with increased gut leak and whether this contributes to systemic inflammation, altered angiogenesis, and preterm birth.

METHODS

We quantified plasma concentrations of gut leak markers, soluble CD14 (sCD14) and lipopolysaccharide binding protein (LBP) from 1339 HIV-negative pregnant Malawians at <24 weeks gestational age. We assessed the relationship of sCD14 and LBP concentrations with markers of inflammation, angiogenesis, and L-arginine bioavailability and compared them between participants with and without malaria, and with and without preterm birth.

FINDINGS

Plasma concentrations of sCD14 and LBP were significantly higher in participants with malaria and were associated with parasite burden (p <0.0001, both analyses and analytes). The odds ratio for preterm birth associated with one log sCD14 was 2.67 (1.33 to 5.35, p = 0.006) and 1.63 (1.07-2.47, p = 0.023) for LBP. Both gut leak analytes were positively associated with increases in proinflammatory cytokines CRP, sTNFR2, IL18-BP, CHI3L1 and Angptl3 (p <0.05, all analytes) and sCD14 was significantly associated with angiogenic proteins Angpt-2, sENG and the sFLT:PlGF ratio (p <0.05, all analytes). sCD14 was negatively associated with L-arginine bioavailability (p <0.001).

INTERPRETATION

Malaria in early pregnancy is associated with intestinal barrier dysfunction, which is linked to an increased risk of preterm birth.

FUNDING

Open Philanthropy, Canadian Institutes of Health Research, Canada Research Chair program, European and Developing Countries Clinical Trials Partnership, Bill & Melinda Gates Foundation.

Water- and feed-based arginine impacts on gut integrity in weanling pigs

Two hundred and forty newly weaned pigs (PIC, Hendersonville, TN) were used to determine if supplementing additional arginine (Arg) either in the water or in the feed, and the combinations thereof, improved intestinal integrity and growth performance in nursery pigs. Each of the 80 pens contained three pigs (21 ± 2 d of age) which were randomly allotted to treatments in 4 × 3 factorial arrangement consisting of four water treatments (0%, 4%, 8%, and 12% Arg stock delivered through a 1:128 medication delivery system) in combination with three dietary Arg treatments (1.35%, 1.55%, and 1.75% standardized ileal digestible Arg; SID). Pigs and feeders were weighed at the d0, d6 (water and diet change), d20 (diet change), and d41 for the calculation of average daily gain (ADG), average daily feed intake (ADFI), and feed efficiency (G:F). Eighty pigs, 1 pig/pen, were euthanized at d6 for ileum evaluation of villus height and crypt depth. The remaining pigs were taken off the Arg-water treatment and fed phase-2 diets formulated to contain 1.35%, 1.55%, and 1.75% SID Arg. All pigs received a common diet from d20 to d41. Data were analyzed by pen as repeated measures (SAS 9.4). No interaction between water- and dietary-Arg was detected on nursery pig growth performance. There was a significant quadratic effect of SID Arg in the feed on pig final body weight (BW), ADG, ADFI, and G:F (P ≤ 0.037), where feeding 1.55% dietary Arg tended to improve growth performance compared to the 1.35% level for the 41 d of the trial (P ≤ 0.088). The use of the stock 8% Arg in the water resulted in a reduction in crypt depth (0:132.5, 4:140.7, 8:117.3, 12:132.0; P ≤ 0.01) and an improvement in intestinal permeability. The 4% oral Arg significantly reduced villous height:crypt depth ratio (0:2.50, 4:2.09, 8:2.56, 12:2.43; P ≤ 0.02). In conclusion, the feeding of 1.55% Arg resulted in an improvement in nursery pig ADG, ADFI, G:F, and final BW but did not alter intestinal villi morphology; however, the use of Arg in the water resulted in an improvement in intestinal villi, but no phenotypical change in piglet growth in the nursery.

l-Arginine Ameliorates Lipopolysaccharide-Induced Intestinal Inflammation through Inhibiting the TLR4/NF-κB and MAPK Pathways and Stimulating β-Defensin Expression in Vivo and in Vitro

Nutritional regulation of endogenous antimicrobial peptide (AMP) expression is considered a promising nonantibiotic approach to suppressing intestinal infection of pathogen. The current study investigated the effects of l-arginine on LPS-induced intestinal inflammation and barrier dysfunction in vivo and in vitro. The results revealed that l-arginine attenuated LPS-induced inflammatory response, inhibited the downregulation of tight junction proteins (TJP) (p < 0.05) by LPS, and maintained intestinal integrity. In porcine intestinal epithelial cells (IPEC-J2), l-arginine obviously suppressed (p < 0.05) the levels of IL-6 (220.63 ± 2.82), IL-8 (333.95 ± 3.75), IL-1β (693.08 ± 2.38), and TNF-α (258.04 ± 4.14) induced by LPS. Furthermore, l-arginine diminished the LPS-induced expression of Toll-like receptor 4 (TLR4) and inhibited activation of TLR4-mediated nuclear factor kappa B (NF-κB) and mitogen-activated protein kinase (MAPK) signaling pathways. Importantly, we proposed a new mechanism that l-arginine had the ability to stimulate the expression of porcine epithelial β-defensins through activating the mammalian target of the rapamycin (mTOR) pathway, which exerts anti-inflammatory influence. Moreover, pBD-1 gene overexpression decreased (p < 0.05) the TNF-α level stimulated by LPS in IPEC-J2 cells (4.22 ± 1.64). The present study indicated that l-arginine enhanced disease resistance through inhibiting the TLR4/NF-κB and MAPK pathways and partially, possibly through increasing the intestinal β-defensin expression.

Effects of dietary supplementation with l-arginine on the intestinal barrier function in finishing pigs with heat stress

Previous studies showed heat stress reduces body weight gain and feed intake associated with damaged intestinal barrier function, and l-arginine (L-Arg) enhanced intestinal barrier function in young animals under stress. The aim of this study was to evaluate effects of L-Arg on serum hormones, intestinal morphology, nutrients absorption and epithelial barrier functions in finishing pigs with heat stress. Forty-eight finishing pigs (Landrace) were balanced for sex and then randomly assigned to six groups: TN group, thermal neutral (22°C, ~80% humidity) with a basal diet; HS group, heat stress (cyclical 35°C for 12 hr and 22°C for 12 hr, ~80% humidity) with a basal diet; PF group, thermal neutral (22°C, ~80% humidity) and pair-fed with the HS; the TNA, HSA and PFA groups were the basal diet of TN group, HS group and PF group supplemented with 1% L-Arg. Results showed that HS decreased (p < .05) the thyroxine concentrations and increased (p < .05) the insulin concentrations in serum compared with the TN group, but 1% L-Arg had no significant effects on them. Both HS and PF significantly increased (p < .05) the mRNA expression of cationic amino acid transporters (CAT1 and CAT2) and decreased the mRNA expression of solute carrier family 5 member 10 (SGLT1) in the jejunum compared with the TN group. Compared with the TN group, HS reduced the expression of tight junction (TJ) protein zonula occluden-1 (ZO-1) and occludin, but PF only decreased ZO-1 expression in the jejunum. Results exhibited that dietary supplementation with 1% L-Arg improved the intestinal villous height, the ratio of villous height to crypt depth, and the expression of occludin and porcine beta-defensin 2 (pBD2) in the jejunum of intermittent heat-treated finishing pigs. In conclusion, dietary supplementation with 1% L-Arg could partly attenuate the intermittent heat-induced damages of intestinal morphology and epithelial barrier functions in finishing pigs.

Lipopolysaccharide-Induced Increase in Intestinal Permeability Is Mediated by TAK-1 Activation of IKK and MLCK/MYLK Gene

Lipopolysaccharides (LPSs) are a major component of Gram-negative bacterial cell wall and play an important role in promoting intestinal inflammatory responses. Recent studies have shown that physiologically relevant concentrations of LPS (0 to 2000 pg/mL) cause an increase in intestinal epithelial tight junction (TJ) permeability without causing cell death. However, the intracellular pathways and the mechanisms that mediate LPS-induced increase in intestinal TJ permeability remain unclear. The aim was to delineate the intracellular pathways that mediate the LPS-induced increase in intestinal permeability using in vitro and in vivo intestinal epithelial models. LPS-induced increase in intestinal epithelial TJ permeability was preceded by an activation of transforming growth factor-β-activating kinase-1 (TAK-1) and canonical NF-κB (p50/p65) pathways. The siRNA silencing of TAK-1 inhibited the activation of NF-κB p50/p65. The siRNA silencing of TAK-1 and p65/p50 subunit inhibited the LPS-induced increase in intestinal TJ permeability and the increase in myosin light chain kinase (MLCK) expression, confirming the regulatory role of TAK-1 and NF-κB p65/p50 in up-regulating MLCK expression and the subsequent increase in TJ permeability. The data also showed that toll-like receptor (TLR)-4/myeloid differentiation primary response (MyD)88 pathway was crucial upstream regulator of TAK-1 and NF-κB p50/p65 activation. In conclusion, activation of TAK-1 by the TLR-4/MyD88 signal transduction pathway and MLCK by NF-κB p65/p50 regulates the LPS-induced increase in intestinal epithelial TJ permeability.

Intervention of Dietary Dipeptide Gamma-l-Glutamyl-l-Valine (γ-EV) Ameliorates Inflammatory Response in a Mouse Model of LPS-Induced Sepsis

Sepsis, the systemic inflammatory response syndrome (SIRS) with infection is one of the leading causes of death in critically ill patients in the developed world due to the lack of effective antisepsis treatments. This study examined the efficacy of dietary dipeptide gamma-l-glutamyl-l-valine (γ-EV), which was characterized previously as an anti-inflammatory peptide, in an LPS-induced mouse model of sepsis. BALB/c mice were administered γ-EV via oral gavage followed by an intraperitoneal injection of LPS to induce sepsis. The γ-EV exhibited antisepsis activity by reducing the expression of pro-inflammatory cytokines TNF-α, IL-6, and IL-1β in plasma and small intestine. γ-EV also reduced the phosphorylation of the signaling proteins JNK and IκBα. We concluded that γ-EV could possess an antisepsis effect against bacterial infection in intestine. This study proposes a signaling mechanism whereby the calcium-sensing receptor (CaSR) allosterically activated by γ-EV stimulates the interaction of β-arrestin2 with the TIR(TLR/IL-1R) signaling proteins TRAF6, TAB1, and IκBα to suppress inflammatory signaling.

Alterations in Intestinal Permeability: The Role of the "Leaky Gut" in Health and Disease

All species, including horses, suffer from alterations that increase intestinal permeability. These alterations, also known as "leaky gut," may lead to severe disease as the normal intestinal barrier becomes compromised and can no longer protect against harmful luminal contents including microbial toxins and pathogens. Leaky gut results from a variety of conditions including physical stressors, decreased blood flow to the intestine, inflammatory disease, and pathogenic infections, among others. Several testing methods exist to diagnose these alterations in both a clinical and research setting. To date, most research has focused on regulation of the host immune response due to the wide variety of factors that can potentially influence the intestinal barrier. This article serves to review the normal intestinal barrier, measurement of barrier permeability, pathogenesis and main causes of altered permeability, and highlight potential alternative therapies of leaky gut in horses while relating what has been studied in other species. Conditions resulting in barrier dysfunction and leaky gut can be a major cause of decreased performance and also death in horses. A better understanding of the intestinal barrier in disease and ways to optimize the function of this barrier is vital to the long-term health and maintenance of these animals.

Hepato- and gastro- protective activity of purified oat 1-3, 1-4-β-d-glucans of different molecular weight

Protective and antioxidant properties of highly purified oat β-glucans of high and low molecular weight in liver and stomach were evaluated. The novelty in approach was to determine whether dietary β-glucans affect the parameters of oxidative stress directly in the stomach and indirectly in the liver, especially in inflammation states. Physicochemical properties e.g. viscoelastic was found as strictly dependent from molecular weight of oat β-glucans hence its metabolic activity could also show dependence. Three groups of rats were fed control diet and diet supplemented with low and high molecular weights oat β-glucans. Animals were divided into controls and individuals with experimentally induced intestinal inflammation. Most active in increasing of total antioxidant status was low molecular weight β-glucan. High molecular weight β-glucan supplementation inhibits lipid oxidation the most in LPS treated animals. The results obtained from experiment encourage for dietary intervention with oat β-glucans for stomach and liver protection during existing enteritis.

Innate immunity gene expression changes in critically ill patients with sepsis and disease-related malnutrition

The aim of this study was an attempt to determine whether the expression of genes involved in innate antibacterial response (TL R2, NOD 1, TRAF6, HMGB 1 and Hsp70) in peripheral blood leukocytes in critically ill patients, may undergo significant changes depending on the severity of the infection and the degree of malnutrition. The study was performed in a group of 128 patients with infections treated in the intensive care and surgical ward. In 103/80.5% of patients, infections had a severe course (sepsis, severe sepsis, septic shock, mechanical ventilation of the lungs). Clinical monitoring included diagnosis of severe infection (according to the criteria of the ACC P/SCC M), assessment of severity of the patient condition and risk of death (APACHE II and SAPS II), nutritional assessment (NRS 2002 and SGA scales) and the observation of the early results of treatment. Gene expression at the mRNA level was analyzed by real-time PCR. The results of the present study indicate that in critically ill patients treated in the IC U there are significant disturbances in the expression of genes associated with innate antimicrobial immunity, which may have a significant impact on the clinical outcome. The expression of these genes varies depending on the severity of the patient condition, severity of infection and nutritional status. Expression disorders of genes belonging to innate antimicrobial immunity should be diagnosed as early as possible, monitored during the treatment and taken into account during early therapeutic treatment (including early nutrition to support the functions of immune cells).

Lipopolysaccharide Regulation of Intestinal Tight Junction Permeability Is Mediated by TLR4 Signal Transduction Pathway Activation of FAK and MyD88

Gut-derived bacterial LPS plays an essential role in inducing intestinal and systemic inflammatory responses and have been implicated as a pathogenic factor in necrotizing enterocolitis and inflammatory bowel disease. The defective intestinal tight junction barrier was shown to be an important factor contributing to the development of intestinal inflammation. LPS, at physiological concentrations, causes an increase in intestinal tight junction permeability (TJP) via a TLR4-dependent process; however, the intracellular mechanisms that mediate LPS regulation of intestinal TJP remain unclear. The aim of this study was to investigate the adaptor proteins and the signaling interactions that mediate LPS modulation of intestinal tight junction barrier using in vitro and in vivo model systems. LPS caused a TLR4-dependent activation of membrane-associated adaptor protein focal adhesion kinase (FAK) in Caco-2 monolayers. LPS caused an activation of both MyD88-dependent and -independent pathways. Small interfering RNA silencing of MyD88 prevented an LPS-induced increase in TJP. LPS caused MyD88-dependent activation of IL-1R-associated kinase 4. TLR4, FAK, and MyD88 were colocalized. Small interfering silencing of TLR4 inhibited TLR4-associated FAK activation, and FAK knockdown prevented MyD88 activation. In vivo studies also confirmed that the LPS-induced increase in mouse intestinal permeability was associated with FAK and MyD88 activation; knockdown of intestinal epithelial FAK prevented an LPS-induced increase in intestinal permeability. Additionally, high-dose LPS-induced intestinal inflammation was dependent on the TLR4/FAK/MyD88 signal transduction axis. To our knowledge, our data show for the first time that the LPS-induced increases in intestinal TJP and intestinal inflammation were regulated by TLR4-dependent activation of the FAK/MyD88/IL-1R-associated kinase 4 signaling pathway.

L-arginine and aminoguanidine reduce colonic damage of acetic acid-induced colitis in rats: potential modulation of nuclear factor-κB/p65

The transcription factor, nuclear factor-κB (NF-κB) is a key inducer of inducible nitric oxide synthase (iNOS) gene expression. The aim of the present study was to investigate the potential protective effect of l-arginine (Arg; nitric oxide precursor) and aminoguanidine (inducible nitric oxide synthase inhibitor) against acetic acid (AA)-induced colitis in rats, and the potential role of NF-κB. Colitis was induced by intrarectal inoculation of rats with 4% acetic acid for three consecutive days. The effect of Arg and aminoguanidine on nitric oxide levels was assessed by Greiss assay and protein expression of NF-κB/p65, and inducible nitric oxide synthase was also investigated by immunohistochemistry. Slides were examined using ImageJ, and results reported as the percent area positive for each marker. Intrarectal AA caused a significant increase in bodyweight loss and colon weights. Arg at 100 mg/day for 7 days before induction of colitis diminished the changes in both bodyweight loss and colon weights. Furthermore, Arg attenuated the colonic tissues macroscopic and microscopic damage induced by acetic acid. In addition, i.p. AG 100 mg/kg given during and after induction of colitis recovered the colonic ulcerative lesion induced by AA. Arg can protect against colonic inflammation; an effect that probably be attributed to its nitric oxide-donating property, resulting in modulatory effects on the expression of NF-κB/p65 in the colon tissues. The results suggested that Arg might reduce the inflammation associated with colitis as confirmed by histopathological investigations. Arg might inhibit AA-induced colitis through the NF-κB/nitric oxide pathway.

Increased hepatic blood flow during enteral immune-enhancing diet gavage requires intact enterohepatic bile cycling

OBJECTIVES

Total hepatic blood flow (HBF) via the hepatic artery and portal vein is highly dependent on gastrointestinal perfusion. During postprandial hyperemia, intestinal blood flow depends on nutrient composition, gastrointestinal location, and time. Immune-enhancing diets (IEDs) containing n-3 polyunsaturated fatty acids (PUFAs) selectively augment blood flow in the ileum at 60-120 min via a bile-dependent mechanism. My colleagues and I hypothesized that liver blood flow would be similarly affected by IEDs containing n-3 PUFAs.

METHODS

Mean arterial blood pressure, heart rate, and effective HBF (galactose clearance) were measured in anesthetized male Sprague-Dawley rats after gastric gavage of either a control diet (CD, Boost, Novartis) or an IED (Impact, Nestle Nutrition), with or without bile-duct ligation (BDL), and with or without supplemental bile (bovine, dried, unfractionated). Significance was assessed by 2-way ANOVA for repeated measures with the Tukey-Kramer honestly significant difference test.

RESULTS

Compared with baseline levels, a CD increased HBF (peak at 40 min , *P < 0.05) whereas an IED increased HBF in two distinct peaks at 40 min (*P < 0.05) and 120 min (*P < 0.05), but BDL prevented both the early (CD and IED, †P < 0.05) and late peaks (IED, †P < 0.05). Bile supplementation in the CD + BDL or IED + BDL groups restored neither the CD peak nor the early or late IED peaks.

CONCLUSIONS

HBF during absorptive intestinal hyperemia is modulated by a mechanism that requires an intact enterohepatic circulation. The early peaks at 40 min (CD or IED) were prevented by BDL, even though fat absorption in the proximal gut occurs by bile-independent direct absorption. Bile supplementation with the diet (CD + BDL or IED + BDL) was insufficient to restore HBF hyperemia, which implies that a relationship exists between intestinal and hepatic blood flow that is not solely dependent on bile-mediated intestinal fat absorption and bile recirculation.

The immune modifying effects of amino acids on gut-associated lymphoid tissue

The intestine and the gut-associated lymphoid tissue (GALT) are essential components of whole body immune defense, protecting the body from foreign antigens and pathogens, while allowing tolerance to commensal bacteria and dietary antigens. The requirement for protein to support the immune system is well established. Less is known regarding the immune modifying properties of individual amino acids, particularly on the GALT. Both oral and parenteral feeding studies have established convincing evidence that not only the total protein intake, but the availability of specific dietary amino acids (in particular glutamine, glutamate, and arginine, and perhaps methionine, cysteine and threonine) are essential to optimizing the immune functions of the intestine and the proximal resident immune cells. These amino acids each have unique properties that include, maintaining the integrity, growth and function of the intestine, as well as normalizing inflammatory cytokine secretion and improving T-lymphocyte numbers, specific T cell functions, and the secretion of IgA by lamina propria cells. Our understanding of this area has come from studies that have supplemented single amino acids to a mixed protein diet and measuring the effect on specific immune parameters. Future studies should be designed using amino acid mixtures that target a number of specific functions of GALT in order to optimize immune function in domestic animals and humans during critical periods of development and various disease states.

Malaria-associated L-arginine deficiency induces mast cell-associated disruption to intestinal barrier defenses against nontyphoidal Salmonella bacteremia

Coinfection with malaria and nontyphoidal Salmonella serotypes (NTS) can cause life-threatening bacteremia in humans. Coinfection with malaria is a recognized risk factor for invasive NTS, suggesting that malaria impairs intestinal barrier function. Here, we investigated mechanisms and strategies for prevention of coinfection pathology in a mouse model. Our findings reveal that malarial-parasite-infected mice, like humans, develop L-arginine deficiency, which is associated with intestinal mastocytosis, elevated levels of histamine, and enhanced intestinal permeability. Prevention or reversal of L-arginine deficiency blunts mastocytosis in ileal villi as well as bacterial translocation, measured as numbers of mesenteric lymph node CFU of noninvasive Escherichia coli Nissle and Salmonella enterica serotype Typhimurium, the latter of which is naturally invasive in mice. Dietary supplementation of malarial-parasite-infected mice with L-arginine or L-citrulline reduced levels of ileal transcripts encoding interleukin-4 (IL-4), a key mediator of intestinal mastocytosis and macromolecular permeability. Supplementation with L-citrulline also enhanced epithelial adherens and tight junctions in the ilea of coinfected mice. These data suggest that increasing L-arginine bioavailability via oral supplementation can ameliorate malaria-induced intestinal pathology, providing a basis for testing nutritional interventions to reduce malaria-associated mortality in humans.

Fish oil increases blood flow in the ileum during chronic feeding in rats

Benefits of enteral feeding with immune-enhancing diets (IEDs) depend on route, timing, and composition. We hypothesized that chronic enteral feeding with certain individual immunonutrients would enhance gastrointestinal blood flow. Male rats were fed a standard enteral diet supplemented with immunonutrients for 5 days before study. Groups were (1) standard rat chow, (2) liquid control diet (CD) alone (CD), (3) CD + fish oil, (4) CD + L-arginine, and (5) CD + RNA fragments. Whole organ blood flow distribution was measured by colorimetric microsphere technique in antrum, small intestine (in thirds), colon, liver, spleen, pancreas, and kidneys. Chronic feeding for 5 days with CD + fish oil increased blood flow in the distal third of the small intestine compared with CD alone, whereas feeding with CD + L-arginine decreased blood flow in the small intestine (all segments) compared with CD alone. Acute gavage of CD + L-arginine or CD + fish oil increased blood flow in the proximal and middle third of the small intestine compared with CD alone. Control diet + RNA increased blood flow in the proximal small intestine compared with CD alone. These findings support prior acute feeding studies with CD, CD + individual immunonutrients, or IED. Our current data suggest that blood flow benefits associated with fish oil persist during chronic feeding in rats. Enhanced gastrointestinal perfusion might partially explain the benefits of early enteral feeding with IEDs not seen with regular enteral diets and parenteral immunonutrient delivery.

Effect of l-arginine on intestinal mucosal immune barrier function in weaned pigs after Escherichia coli LPS challenge

The effects of l-arginine (Arg) supplementation on intestinal mucosal immune barrier function in weaned pigs after Escherichia coli LPS challenge were evaluated. Twenty-four weaned pigs were allotted to four treatments including: (i) non-challenged control; (ii) LPS-challenged control; (iii) LPS + 0.5% Arg; and (iv) LPS + 1.0% Arg. On d 16, pigs in the LPS, LPS + 0.5% Arg and LPS + 1.0% Arg groups were challenged by injection with 100 µg/kg of body mass LPS, whereas the control group were given sterile saline. At 48 h post-challenge, all pigs were sacrificed for evaluation of small intestinal morphology and mucosal immune barrier function. In the jejunum and ileum, LPS caused villous atrophy and intestinal morphology disruption, whereas 0.5% or 1.0% Arg supplementation mitigated villus atrophy and intestinal morphology impairment caused by LPS challenge. Arg (0.5%) supplementation increased the numbers of IgA-secreting cells, CD8+ and CD4+ T cells in the ileum ( P < 0.05). Arg supplementation prevented the elevation of mast cell numbers induced by LPS challenge ( P < 0.05). Dietary supplementation of Arg caused a decreased lymphocyte apoptosis of Peyer’s patches in pigs challenged by LPS ( P < 0.05). These results indicated that Arg supplementation protects and enhances intestinal mucosal immune barrier function and maintains intestinal integrity in weaned pigs after E. coli LPS challenge.

Dietary L-arginine supplementation reduces Methotrexate-induced intestinal mucosal injury in rat

Background

Arginine (ARG) and nitric oxide maintain the mucosal integrity of the intestine in various intestinal disorders. In the present study, we evaluated the effects of oral ARG supplementation on intestinal structural changes, enterocyte proliferation and apoptosis following methotrexate (MTX)-induced intestinal damage in a rat.

Methods

Male rats were divided into four experimental groups: Control rats, CONTR-ARG rats, were treated with oral ARG given in drinking water 72 hours before and 72 hours following vehicle injection, MTX rats were treated with a single dose of methotrexate, and MTX-ARG rats were treated with oral ARG following injection of MTX. Intestinal mucosal damage, mucosal structural changes, enterocyte proliferation and enterocyte apoptosis were determined 72 hours following MTX injection. RT-PCR was used to determine bax and bcl-2 mRNA expression.

Results

MTX-ARG rats demonstrated greater jejunal and ileal bowel weight, greater ileal mucosal weight, greater ileal mucosal DNA and protein levels, greater villus height in jejunum and ileum and crypt depth in ileum, compared to MTX animals. A significant decrease in enterocyte apoptosis in the ileum of MTX-ARG rats (vs MTX) was accompanied by decreased bax mRNA and protein expression and increased bcl-2 protein levels.

Conclusions

Treatment with oral ARG prevents mucosal injury and improves intestinal recovery following MTX- injury in the rat.

Preventive oral supplementation with glutamine and arginine has beneficial effects on the intestinal mucosa and inflammatory cytokines in endotoxemic rats

The objective of this study was to evaluate the effect of oral supplementation with a combination of arginine and glutamine on the intestinal mucosa and inflammatory cytokines of lipopolysaccharide (LPS)-induced adult rats. Fifty Sprague-Dawley rats (average weight of 185 ± 15 g) were randomly divided into five groups: control group A (CA) and control group B (CB), both orally supplemented with 0.9% saline; group Arg, supplemented with 300 mg/kg day(-1) arginine; group Gln, supplemented with 300 mg/kg day(-1) glutamine; group AG, supplemented with 150 mg/kg day(-1) arginine and 150 mg/kg day(-1) glutamine. The experiment lasted for 2 weeks. Food intake and body weight were measured during the experiment. At 10.00 h of day 15, animals were injected with 4 mg/kg LPS (group CB, Arg, Gln, and AG) or sterile saline (group CA) after supplementation. Then at 14.00 h, all animals were killed and blood and tissue collected. The results showed that compared with group CB, arginine concentration tended to be increased (P > 0.05) in group Arg and AG, while there was no significant difference in glutamine concentration among the groups challenged with LPS. Oral supplementation with arginine or/and glutamine mitigated morphology impairment (lower villus height, P < 0.05) in the jejunum and ileum induced by LPS challenge. LPS administration resulted in a significant increase in TNF-α, IL-1β, IL-6 and IL-10 mRNA abundance. Arginine only significantly decreased TNF-α mRNA abundance in the ileum, while glutamine significantly decreased both TNF-α and IL-10 mRNA in the ileum. A combination of arginine and glutamine significantly decreased TNF-α and IL-1β mRNA abundance in both the jejunum and ileum, while they also significantly decreased anti-inflammatory IL-10 in the ileum. These results revealed that an oral supply of combined arginine and glutamine had more favorable effects on the intestinal mucosa and inflammatory cytokines than a supply of arginine or glutamine alone.

Berberine protects against lipopolysaccharide-induced intestinal injury in mice via alpha 2 adrenoceptor-independent mechanisms

AIM

To investigate the mechanisms responsible for the protective action of berberine (Ber) against gut damage in endotoxemic mice.

METHODS

Male BALB/c mice were administered intragastrically with distilled water (0.1 mL/10 g), Ber (50 mg/kg) alone, yohimbine (2 mg/kg) alone, or Ber (50 mg/kg) in combination with yohimbine (2 mg/kg) for 3 d. On the third day, lipopolysaccharide (LPS, 18 mg/kg) or normal saline was intraperitoneally injected one hour after the intragastric administration. Following the treatment, intestinal injury in the ileum was histopathologically accessed; enterocyte apoptosis was examined using TUNEL method; Toll-like receptor 4 (TLR4) mRNA expression was measured using RT-PCR assay; inhibitor protein-κBα (I-κBα) phosphorylation and myeloperoxidase content were examined using Western blloting. The macrophage inflammatory protein-2 (MIP-2) production was measured using ELISA assay.

RESULTS

Mice challenged with LPS caused extensive ileum injury, including a significantly increased injury score, decreased intestinal villus height, reduced gut mucosal weight and increased intestinal permeability. Furthermore, LPS significantly induced enterocyte apoptosis, increased TLR4 mRNA expression, I-κBα phosphorylation, MIP-2 production and myeloperoxidase content in the ileum. Pretreatment with Ber significantly alleviated all the alterations in the ileum in the endotoxemic mice. Pretreatment with the α2-adrenoceptor antagonist yohimbine did not block the protective action of Ber against LPS-induced intestinal injury. In addition, treatment with yohimbine alone did not prevent LPS-induced intestinal injury.

CONCLUSION

Pretreatment with Ber provides significant protection against LPS-induced intestinal injury in mice, via reducing enterocyte apoptosis, inhibiting the TLR4-nuclear factor κB-MIP-2 pathway and decreasing neutrophil infiltration that are independent of α2-adrenoceptors.

Berberine attenuates lipopolysaccharide-induced impairments of intestinal glutamine transport and glutaminase activity in rat

Berberine was reported to protect against the intestinal injury and improve the survival rate in sepsis, and glutamine deficiency was considered to be correlated with mortality in sepsis. We found that berberine pretreatment ameliorated lipopolysaccharide-induced direct intestinal injury and mucosal hypoplasia and attenuated impairments of intestinal glutamine transport and glutaminase activity, B(0)AT1 mRNA and protein expressions, and glutaminase protein expression. These findings showed the first time that berberine pretreatment could improve intestinal recovery and attenuate the impairment of glutamine transport and glutaminase activity in rat sepsis. This might be one of the mechanisms for the beneficial effect of berberine on sepsis.

Effects of early enteral nutrition supplemented with arginine on intestinal mucosal immunity in severely burned mice

BACKGROUND

To investigate the effects of early enteral nutrition (EN) supplemented with Arginine (Arg) on intestinal mucosal immunity in severely burned mice.

METHODS

Forty-four mice were randomly assigned into four groups: a sham injury+EN group (n=10), a sham injury+EN+Arg group (n=10), a burn+EN group (n=12), and a burn+EN+Arg group (n=12) and the mice in two experimental groups received a 20% total body surface area (TBSA), full-thickness scald burn on the back. Then, the burned mice were given a 175 kcal/kg body wt/day of conventional enteral nutrition or an isonitrogenous and isocaloric enteral nutrition supplemented with Arg by gastric gavage for 7 days. There was isonitrogenous and isocaloric intake in two experimental groups. The mice in two control groups received the same procedures as above, except for burn injury. On day 7 after injury, all mice among four groups were euthanized and the entire intestine was harvested. Intestinal immunoglobulin A (IgA) levels, total lymphocyte yield, and lymphocyte subpopulations in Peyer's patches were analyzed. Levels of IFN-gamma, IL-2, IL-4 and IL-10 in gut homogenates were also measured by ELISA.

RESULTS

Total lymphocyte yield, numbers of lymphocyte subpopulations, and intestinal IgA levels in the EN+ARG group were higher than those in the EN group (p<0.05). Levels of gut tissue cytokines were significantly altered with enteral Arg supplementation: levels of IL-4 and IL-10 were increased, and levels of IFN-gamma and IL-2 declined, when compared with the EN-fed mice (p<0.05).

CONCLUSIONS

The results of this study suggested that enteral nutrition supplemented with Arg has changed the cytokine concentrations in intestinal homogenates from a pro- to an anti-inflammatory profile, increased sIgA levels and changed lymphocytes in severely burned mice.

lipopolysaccharide induces atrial arrhythmogenesis via down-regulation of L-type Ca2+ channel genes in rats

Septic shock has been reported as an independent risk factor for atrial fibrillation (AF), however, the mechanism remains unknown. We investigated whether lipopolysaccharide (LPS) could alter cardiac ion channel gene expression, thereby leading to atrial arrhythmogenesis. LPS (2.5 mg/kg) was injected intraperitoneally into 10 week old Sprague-Dawley rats (n = 5). Hemodynamic data were obtained and the atrial appendages were removed after LPS injection (0, 3, 6, 12, and 24 hours) for an RNase protection assay for alpha1C, beta2, alpha1G, and SCN5A. An electrophysiological study in isolated perfused hearts was performed before and 12 hours after the LPS injection. Heart rate and body temperature were significantly increased (P < 0.05) and mean blood pressure was slightly decreased (P < 0.1) at 12 hours after LPS injection. The mRNA levels of the L-type calcium channel gene (beta2 and alpha1C) were significantly decreased at 6 and 12 hours after LPS injection. Atrial ERP became significantly shortened and the number of repetitive atrial responses induced by an extrastimulus were significantly increased after LPS injection. LPS induced the down-regulation of L-type calcium channel gene expression and ERP shortening, which might be a mechanism underlying sepsis-induced AF.

Nitric oxide levels in the intestines of mice submitted to ischemia and reperfusion: L-arginine effects

OBJECTIVE

Usually an experimental necrotizing enterocolitis experimental model, we Investigated nitric oxide levels in intestinal tissues of newborn mice with or without l-arginine therapy during sessions of ischemia and reoxygenation.

METHODS

Twenty-six newborn mice from the Wistar EPM-1 lineage, weighing from 4.5 to 6.2 g, were randomly assigned to three groups: G-I/R, hypoxia and reoxygenation; G-Arg, l-arginine treatment I/R; and G-CTL, controls. G-I/R and G-Arg mice underwent twice a day during their first 3 days of life exposure to gas chambers with 100% CO(2) for 5 minutes at 22 degrees C before reoxygenation with 100% O(2) for another 5 minutes. After 12 hours, all animals were sedated, laparotomized, and had samples of ileum and colon taken and- either formalin fixed histopathologic examinations or frozen to -80 degrees C for estimation of tissue nitric oxide levels. Intestinal injuries were classified according to the criteria of Chiu et al.

RESULTS

The G-I/R and G-Arg groups showed injuries characteristic of necrotizing enterocolitis (NEC) with an improved structural preservation rate in G-Arg. The concentration of nitric oxide in the Ileum was much higher with G-Arg (16.5 +/- 4.9; P = 0.0019) G-I/R (7.3 +/- 2.0). This effect was not observed in the colon: G-I/R = 10.7 +/- 4.6 versus G-Arg = 15.5 +/- 8.7 (P = .2480).

CONCLUSION

Supply of L-arginine increased tissue levels of nitricoxide and reduced morphologic intestinal injury among mice undergoing I/R.

Amino acids and gut function

The intestine is not only critical for the absorption of nutrients, but also interacts with a complex external milieu. Most foreign antigens enter the body through the digestive tract. Dietary amino acids are major fuels for the small intestinal mucosa, as well as important substrates for syntheses of intestinal proteins, nitric oxide, polyamines, and other products with enormous biological importance. Recent studies support potential therapeutic roles for specific amino acids (including glutamine, glutamate, arginine, glycine, lysine, threonine, and sulfur-containing amino acids) in gut-related diseases. Results of these new lines of work indicate trophic and cytoprotective effects of amino acids on gut integrity, growth, and health in animals and humans.

Oral insulin up-regulates Toll-like receptor 4 expression and enhances intestinal recovery following lipopolysaccharide-induced gut injury in a rat

In the present study, we evaluated the protective effect of oral insulin (OI) on intestinal mucosa following lipopolysaccharide-induced intestinal damage in a rat. Male Sprague-Dawley rats were divided into three experimental groups: Sham rats, LPS-rats that were treated with lipopolysaccharide (LPS), and LPS-INS rats that were treated with OI given in drinking water 72 h before and following injection of LPS. Intestinal structural changes, enterocyte proliferation, enterocyte apoptosis, and mucosal expression of Toll-like receptor 4 (TLR4) were determined 24 h after the last LPS injection. LPS-INS animals showed a significantly greater bowel and mucosal weight in jejunum and ileum, mucosal DNA and protein in jejunum and ileum, villus height in ileum, crypt depth in jejunum and ileum, cell proliferation rates in jejunum, and significantly lower apoptotic index in ileum compared to LPS- animals. LPS rats demonstrated 50% increase in TLR4 expression in jejunum compared to sham animals. Treatment with OI resulted in a three-fold increase in TLR4 expression in jejunum, compared to LPS animals. In conclusion, OI improves intestinal recovery after LPS endotoxemia in a rat.

Treatment with glutamine is associated with down-regulation of Toll-like receptor-4 and myeloid differentiation factor 88 expression and decrease in intestinal mucosal injury caused by lipopolysaccharide endotoxaemia in a rat

Recent evidence suggests that lipopolysaccharide (LPS) endotoxaemia in a rat causes significant mucosal injury. Our objective was to determine the effects of glutamine (Gln) on Toll-like receptor 4 (TLR-4), myeloid differentiation factor 88 (Myd88) and tumour necrosis factor (TNF)-alpha receptor-associated factor 6 (TRAF6) expression in intestinal mucosa following LPS endotoxaemia in a rat. For this purpose, male Sprague-Dawley rats were assigned randomly to one of three experimental groups of 10 rats each: (i) control rats underwent intraperitoneal (i.p.) injection of sterile saline once a day; (ii) rats were treated with LPS given i.p. once a day at a dose of 10 mg/kg for 48 h (two doses); and (iii) rats were pretreated with oral Gln given in drinking water (2%) 48 h before and following injection of LPS. Intestinal mucosal parameters, enterocyte proliferation and apoptosis were determined at death. TLR-4 and MyD88 mRNA expression was measured with reverse transcription-polymerase chain reaction (RT-PCR). TLR-4 and MyD88 protein expression were analysed by Western immunoblotting. We observed a statistically significant (P < 0.05) decrease in mucosal weight, mucosal DNA and enterocyte proliferation and a significant increase in enterocyte apoptosis in rat intestine, following LPS administration. These changes were attenuated significantly by dietary Gln. Expression of TLR-4, MyD88 and TRAF6 mRNA in the mucosal ileum was significantly higher in LPS rats versus control rats (P = 0.0006, P = 0.0015, P = 0.03, respectively) as well as TLR-4 and MyD88 protein expression. The administration of Gln reduced significantly the expression of TLR-4, MyD88 and TRAF6 (P = 0.023, P = 0.014, P = 0.035, respectively) mRNA as well as TLR-4 and MyD88 protein expression in ileum compared to LPS animals. We did not find a significant change in the expression of TLR-4, MyD88 or TRAF6 in the jejunum of different groups. We conclude that treatment with Gln was associated with down-regulation of TLR-4, MyD88 and TRAF6 expression and concomitant decrease in intestinal mucosal injury caused by LPS endotoxaemia in a rat.

Oral glutamine prevents gut mucosal injury and improves mucosal recovery following lipopolysaccharide endotoxemia in a rat

OBJECTIVE

To evaluate the effects of oral glutamine in preventing mucosal damage caused by lipopolysaccharide (LPS) endotoxemia in a rat.

METHODS

Male Sprague Dawley rats, weighing 250 to 280 g, were divided into three experimental groups: CONTR rats (Group A), LPS rats (Group B) were treated with lipopolysaccharide given I.P. at dose 10 mg/kg every 24 h (two injections), and LPS-GLN rats (Group C) were treated with oral glutamine given in drinking water (2%) 72 h before and following injection of LPS. Intestinal structural changes, enterocyte proliferation, and enterocyte apoptosis were determined 24 h after last LPS injection.

RESULTS

LPS rats demonstrated a significant decrease in bowel and mucosal weight in jejunum and ileum, mucosal DNA and protein in jejunum and ileum, and villus height and crypt depth in jejunum and ileum compared with sham animals. LPS rats also had a significantly greater Park injury score in jejunum and ileum, a lower cell proliferation index in jejunum and ileum, and higher apoptotic index in jejunum and ileum compared with control rats. LPS-GLN animals showed a significant increase in bowel weight in jejunum, mucosal weight in jejunum and ileum, mucosal DNA in jejunum and ileum, villus height in jejunum and ileum, and cell proliferation index compared with LPS animals. The Park injury score was significantly lower in LPS-GLN rats compared with LPS animals.

CONCLUSIONS

Oral glutamine supplementation prevents mucosal injury and improves intestinal recovery after LPS endotoxemia in a rat.

Synergistic Therapeutic Potential of Dexamethasone and l-arginine in Lipopolysaccharide-Induced Septic Shock

BACKGROUND

Dexamethasone (DEX) is demonstrated to have anti-inflammatory properties and known to induce hemodynamic improvement in sepsis and septic shock. L-arginine (L-arg), a semi-essential amino acid, depending on its metabolic pathway, becomes very essential in stress situations such as heatstroke, burns, sepsis, trauma, and wound healing. The aim of this study was to evaluate the synergistic therapeutic effect of DEX and L-arg in rescuing the mice from experimental septic shock induced by bacterial lipopolysaccharide (LPS). The experiments were designed to delineate the molecular mechanisms responsible for the increased therapeutic benefit of the combination therapy (CT) in LPS-induced septic shock.

METHODS

Acute endotoxemia was induced in Swiss male mice by i.p. injection of LPS (18 mg kg(-1)) at 0 h. LPS-treated mice were divided into four groups. The first group (DEX group) received DEX (2 mg kg(-1)) i.p. at +2 h of LPS. The second group (L-arg group) received L-arg i.p. at a dose of 120 mg/kg at +6 h of LPS injection. The third group (CT group) received DEX (2 mg kg(-1)) at +2 h LPS followed by L-arg at +6 h of LPS injection. The fourth group received saline in place of L-arg or DEX (LPS group). A sham group was also included, where normal mice received saline in place of LPS or L-arg or DEX. At +6 h, mice from sham group, LPS group, and DEX group were sacrificed at +24 h. Mice from sham group, DEX group, L-arg group, and CT group were sacrificed to examine various parameters associated with LPS endotoxemia.

RESULTS

The CT with DEX followed by L-arg significantly increased the survival of mice injected with a lethal dose of LPS. Monotherapy with either DEX or L-arg given at the same dose and time did not increase the survival of the mice injected with LPS. DEX administration could significantly reduce the levels of serum TNF-alpha, IL-1beta, IFN-gamma, aspartate aminotransferase (ASAT), alanine aminotransferase (ALAT), and nitrite. DEX also down-regulated the expression of liver-inducible nitric oxide synthase (iNOS), and up-regulated the levels of serum anti-inflammatory cytokines like TGF-beta1 and IL-4, hepatic and splenic arginase, in LPS-injected mice. The enhanced therapeutic effect of CT correlated with reduced pathological symptoms, decreased Th1 cytokines, increased TGF-beta1 and arginase levels compared to the mice administered with either of the monotherapies. The CT group had significantly increased expression of hepatic Hsp 70 and reduced septic shock associated histopathology, in lung and liver, compared to the mice treated with either DEX or L-arg.

CONCLUSIONS

The therapeutic combination therapy with DEX and L-arg, at the appropriate dose, time, and sequence of administration, changed the cytokine profile, in favor of reducing the inflammatory response. The significantly enhanced survival observed in the CT group was accompanied by an increased hepatic Hsp 70, hepatic arginase, splenic arginase, and decreased organ injury. This novel concept of combined therapy could form the basis of an effective therapeutic approach in the treatment of sepsis and septic shock.

The impact of arginine on bacterial translocation in an intestinal obstruction model in rats

BACKGROUND & AIMS

Arginine has been shown to have multiple beneficial metabolic and immunologic effects in stress situations. Supplementation of arginine has been shown to promote wound healing and intestinal mucosal recovery after trauma, ischemia or intestinal resection. Bacterial translocation has also been evaluated although with conflicting results and using different assessing techniques. Therefore, the aim of this study was to evaluate the effects of arginine on bacterial translocation in an intestinal obstruction model in rats using Escherichia coli labeled with 99mTechnetium.

METHODS

Male Wistar rats (250-350 g) were randomized to receive conventional chow, diet supplemented with pure arginine or diet supplemented with an immunonutrition enteral formula, enriched with arginine, omega-3 fatty acid and RNA. After 7 days, the animals were anesthetized. Terminal ileum was isolated and a ligature was placed around it. E. coli labeled with 99mTechnetium (99mTc-E. coli) was inoculated into the intestinal lumen (terminal ileum). After 24 h, the animals were sacrificed. Blood, mesenteric lymph nodes (MLN), liver, spleen and lungs were removed for radioactivity determination.

RESULTS

Arginine supplementation (300 mg/day, 600 mg/day or present in the enteral formula) reduced the level of bacterial translocation when compared with the control group (p<0.05). This was shown by significantly decrease uptake of 99mTc-E. coli in blood, MLN, liver, spleen and lungs of the animals in the experimental groups (p < 0.05).

CONCLUSIONS

These results have shown that arginine was able to decrease bacteria translocation despite intestinal obstruction. There are several mechanisms which might explain the role of arginine and these will be the subject of future studies.

The effect of N-acetylcysteine on pulmonary lipid peroxidation and tissue damage

BACKGROUND

We aimed to investigate the effect of N-acetylcysteine (NAC) on pulmonary lipid peroxidation and tissue damage in experimental obstructive jaundice (OJ) stimulated by lipopolysaccharide (LPS) in this study.

MATERIALS AND METHODS

We randomized 40 rats into five groups. Group A: Sham (n = 8); group B: OJ (n = 8); group C: OJ + lipopolysaccharide (LPS; n = 8); group D: OJ + NAC + LPS (n = 8); group E: OJ + LPS + NAC (n = 8). OJ was performed by common bile duct ligation and division in all groups except the sham group. At the fifth day, the rats were jaundiced. At the fifth day of OJ, LPS was injected 10 mg/kg intraperitoneally to the rats and at the tenth day, the rats were sacrificed in group C. In group D; at the fifth day of OJ, NAC was started 100 mg/kg subcutaneously and the same dose NAC injection repeated every day for 5 days. At the tenth day of OJ, LPS was injected 10 mg/kg intraperitoneally to the rats and then after 6 h they were sacrificed. In group E; 10 mg/kg LPS was administered intraperitoneally at fifth day of OJ and after then NAC was started 100 mg/kg subcutaneously and the same dose NAC injection repeated every day for 5 days and at the tenth day, the rats were sacrificed. Tissue samples were harvested through a midline incision, and lungs were resected and examined histopathologically and immunohistochemically for tissue damage scoring. The blood was taken by cardiac puncture and malondialdehyde (MDA), myeloperoxidase (MPO), and levels of total antioxidant status were detected with biochemical methods to evaluate lung tissue damage.

RESULTS

Increase in lung and serum MDA and MPO levels, as well as decrease in total antioxidant status, were observed in groups B and C when compared with the sham group (P = 0.0001, for each comparison). Furthermore, the lung tissue damage was observed in the same groups by histopathological examination when compared with sham group. There was significant decrease at serum and lung MPO and MDA levels after the NAC application in groups D and E, when compared with group C (P = 0.0001, for each comparison). Antioxidant status in groups D and E were increased in the presence of NAC (P = 0.0001, for each comparison). Lung histology was prevented relatively in group D when compared with groups B and C.

CONCLUSION

Results of the study indicate that NAC has protective effect on pulmonary lipid peroxidation and tissue damage before and after LPS administration.

Oral arginine improves intestinal recovery following ischemia-reperfusion injury in rat

Arginine and nitric oxide are critical to the normal physiology of the gastrointestinal tract and maintain the mucosal integrity of the intestine in various intestinal disorders. In the present study, we evaluate the effects of oral arginine (ARG) supplementation on intestinal structural changes, enterocyte proliferation, and apoptosis following intestinal ischemia-reperfusion (IR) in the rat. Male Sprague-Dawley rats were divided into three experimental groups: sham rats underwent laparotomy and superior mesenteric artery mobilization, IR rats underwent superior mesenteric artery occlusion for 30 min following by 24 h of reperfusion, and IR-ARG rats were treated with enteral arginine given in drinking water (2%) 48 h before and following IR. Intestinal structural changes, enterocyte proliferation, and enterocyte apoptosis were determined 24 h following IR. A nonparametric Kruskal-Wallis ANOVA test was used for statistical analysis with p <0.05 considered statistically significant. IR rats demonstrated a significant decrease in bowel weight in duodenum and jejunum, mucosal weight in jejunum and ileum, and villus height in jejunum and ileum compared with control animals. IR rats also had a significantly lower cell proliferation index in jejunum and ileum and a higher apoptotic index in ileum compared with control rats. IR-ARG animals demonstrated greater duodenal and jejunal bowel weight; duodenal, jejunal, and ileal mucosal weight; and jejunal and ileal cell proliferation index compared with IR animals. In conclusion, oral ARG administration improves mucosal recovery following IR injury in the rat.