Yu-Chen Hou

Glutamine administration ameliorates sepsis-induced kidney injury by downregulating the high-mobility group box protein-1-mediated pathway in mice

Acute kidney injury (AKI) is a severe complication of sepsis. High-mobility group box (HMGB)-1 was implicated as a late mediator of lethal systemic inflammation in sepsis. Since glutamine (GLN) was shown to have anti-inflammatory and antioxidant properties, we hypothesized that GLN administration may downregulate an HMGB-1-mediated pathway and thus ameliorate sepsis-induced AKI. Mice were randomly assigned to a normal group (NC), a septic saline group (SS), or a septic GLN group (SG). Sepsis was induced by cecal ligation and puncture (CLP). The SS group was injected with saline, and the SG group was given 0.75 g GLN/kg body wt once via a tail vein 1 h after CLP. Mice were killed 2, 6, and 24 h after CLP, and blood and kidneys of the animals were harvested for further analysis. The results showed that sepsis resulted in higher mRNA and/or protein expressions of kidney HMGB-1, toll-like receptor (TLR) 4, myeloid differentiation primary-response protein (MyD) 88, and receptor of advanced glycation end products (RAGE) compared with normal mice. Septic mice with GLN administration exhibited decreased HMGB-1, TLR4, RAGE, and phosphorylated NF-κB p65 protein expressions and reduced nitrotyrosine levels in kidney tissues. The histological findings showed that damage to the kidneys was less severe, and survival improved in the SG group. These results indicated that a single dose of GLN administered after the initiation of sepsis plays a prophylactic role in downregulating the expressions of HMGB-1-related mediators and decreasing oxidative stress in the kidneys, which may consequently have ameliorated AKI induced by sepsis.

Pretreatment with alanyl-glutamine suppresses T-helper-cell-associated cytokine expression and reduces inflammatory responses in mice with acute DSS-induced colitis

T-helper (Th) cells play a major role in initiating and shaping the pathologic response in inflammatory bowel disease (IBD). Glutamine (GLN) is a nutrient with immune-modulating effects. This study investigated the effect of GLN on cytokine expressions and inflammatory responses of three subsets of Th cells in dextran sulfate sodium (DSS)-induced IBD. There were one normal control (NC) and two DSS groups. Mice in the DSS groups drank distilled water containing 3% DSS for 5 days, whereas the NC group received distilled water. Mice in the G-DSS group were given intraperitoneal injection of 0.5 g GLN/kg/d for 3 days before receiving DSS water. The other DSS group (C-DSS) received an identical amount of amino acid solution without GLN. After induction of IBD, the mice were allowed to recover for 3 days and then were sacrificed. Blood and colon samples were collected for further analysis. The C-DSS group had higher percentages of blood interleukin (IL)-17A, IL-17F, IL-22, IL-4 and interferon-γ than the NC group. The G-DSS group had lower Th1/Th17/Th2 cytokine expressions, which showed no differences from the NC group. Plasma haptoglobin, colon immunoglobin G and chemokine levels and myeloperoxidase activities were higher in the DSS groups than the NC group. These parameters were significantly lower in the G-DSS than the C-DSS group. These results suggest that pretreatment with GLN suppressed Th-associated cytokine expressions and may consequently reduce inflammatory mediator production and leukocyte infiltration into tissues, thus ameliorating the severity of acute DSS-induced colitis.

Dietary fish oil enhances adhesion molecule and interleukin-6 expression in mice with polymicrobial sepsis

This study investigated the effects of fish oil (FO) diet on plasma intercellular adhesion molecule 1 (ICAM-1) levels and leucocyte integrin expression in polymicrobial sepsis. Mice were randomly assigned to a control group and an FO group. The control group was fed a medium-fat diet containing soyabean oil, whereas in the FO group, 70 % of the soyabean oil was replaced by FO for 3 weeks. After that, sepsis was induced by caecal ligation and puncture (CLP) in the experimental groups and mice were killed at 0, 6, 12 and 24 h, respectively, after CLP. Results showed that compared with the control group, plasma ICAM-1 levels were higher in the FO group 6 h after CLP. Intra-lymphocyte interferon-gamma expression in the FO group was lower, whereas IL-4 expression was higher than in the control group 12 and 24 h after CLP. The expression of leucocyte integrin was significantly higher in the FO group 12 and 24 h after CLP. The FO group had higher IL-6 levels at 12 h in the lungs, at 6 and 12 h in the kidneys, and at 6, 12 and 24 h in the intestines after CLP. The survival rate did not differ between the two groups after CLP. The present findings suggest that pretreatment with an FO diet enhances adhesion molecule and inflammatory cytokine expressions during sepsis, which might aggravate the inflammatory reaction and increase neutrophil infiltration into tissues. In addition, FO diet promotes the Th2-type response and suppresses cellular immune response in polymicrobial sepsis.

Glutamine modulates lipopolysaccharide-induced activation of NF-κB via the Akt/mTOR pathway in lung epithelial cells

Lung epithelial cells are important barriers in the respiratory system that provoke inflammatory responses through nuclear factor (NF)-κB activation to prevent pathogens from invading the body. Lipopolysaccharide (LPS) is a common pathogen-associated stimulus that activates IκB kinase (IKK) to regulate NF-κB-mediated inflammation through modulating nuclear translocation and phosphorylation of NF-κB. Previously, it was shown that Akt and the mammalian target of rapamycin (mTOR) are involved in the phosphorylation of IKK to activate NF-κB. Herein, we demonstrate that glutamine (GLN) modulated LPS-induced activation of NF-κB through the Akt/mTOR/IKK pathway in BEAS-2B cells. BEAS-2B cells in submerged culture were placed in medium containing different concentrations of GLN (0, 0.5, 1, and 2.5 mM) with 1 μg/ml LPS. Results showed that GLN deprivation induced phosphorylation of Akt/mTOR/IKK signaling, increased levels of NF-κB nuclear translocation and phosphorylated NF-κB, and upregulated NF-κB-dependent transcriptional activity, which was suppressed by GLN administration. Expressions of NF-κB-targeted genes were also reduced by supplemental GLN. GLN administration improved cell viability, whereas 0.5 mM GLN had a greater extent of inhibition on the Akt/mTOR/IKK/NF-κB signaling cascade. The inhibitory effects of GLN on NF-κB activation were also observed in cells cultured under air-liquid interface condition. These results indicate that GLN deprivation increased LPS-induced NF-κB activation and transcriptional activity, which was reversed by GLN administration. The findings provide potential mechanisms of GLNs modulation of LPS-induced NF-κB activation in lung epithelial cells and imply that maintaining a physiological concentration of GLN is essential in preventing LPS-induced lung inflammation.

Dietary fish oil reduces systemic inflammation and ameliorates sepsis-induced liver injury by up-regulating the peroxisome proliferator-activated receptor gamma-mediated pathway in septic mice.

This study investigated the effect of dietary fish oil on systemic inflammation and hepatic injury in mice with polymicrobial sepsis. Male ICR mice were assigned to a control group (C, n=30) and a fish oil group (FO, n=30). Mice in the C group were fed a semi-purified diet with 10% soybean oil, and those in the FO group were fed a fish oil diet (2.5% fish oil+7.5% soybean oil; w/w). Three weeks later, sepsis was induced by cecal ligation and puncture (CLP), and mice were sacrificed at 0, 6 and 24 h after CLP, respectively. Results showed that compared with C group, the FO group had lower plasma levels of tumor necrosis factor (TNF)-α, interleukin (IL)-6, IL-10, and nitrite at 6 and 24 h after CLP. Also, peritoneal lavage fluid concentrations of TNF-α and prostaglandin (PG) E2 were significantly lower at 24 h in the FO than in the C group. The FO group had lower myeloperoxidase activities at 6 h after CLP in various organs. Plasma aminotransferase and alanine aminotransferase activities revealed significantly decreased in the FO group. The DNA-binding activity of peroxisome proliferators-activated receptor gamma (PPARγ) and mRNA expression of I kappaB alpha (IκBα) were up-regulated while nuclear factor (NF)-κB p65 DNA-binding activity, inducible nitric oxide synthase protein expression and the concentration of nitrotyrosine were significantly decreased in the FO group in liver after CLP. These results indicate that dietary fish oil administration may attenuate systemic inflammation and up-regulate hepatic PPARγ DNA-binding activity, which may consequently have ameliorated liver injury in these septic mice.

Effects of ω-3 fatty acids on inflammatory mediators and splenocyte cytokine mRNA expressions in rats with polymicrobial sepsis

OBJECTIVES Many studies have shown that omega-3 fatty acids (FAs) have immunomodulatory effects. However, the influence of omega-3 FAs on septic conditions is not certain. This study examined the effect of fish oil (FO)-enriched diets before and/or omega-3 FA-containing total parenteral nutrition (TPN) after sepsis on the distribution of T-lymphocyte subpopulations and splenocyte cytokine mRNA expressions in rats with polymicrobial sepsis. METHODS Rats were assigned to a control group and four experimental groups. The control group and groups 1 and 2 were fed a semipurified diet, and groups 3 and 4 had 20% soybean oil replaced by FO. After feeding the diets for 10 d, sepsis was induced by cecal ligation and puncture (CLP) in the experimental groups, whereas sham operation was performed on the control group. TPN was maintained for 3 d after CLP or sham operation. The control group and groups 1 and 3 were infused with conventional TPN, whereas the TPN solution of groups 2 and 4 was supplemented with FO. All rats were sacrificed 3 d after the operation to examine their immune responses. RESULTS Messenger RNA expressions of interleukin-2 and tumor necrosis factor-alpha in splenocytes were higher in groups 3 and 4 than in the control group and group 1. Interleukin-10 mRNA expression in group 3 was higher than in the control group and group 2. Blood CD4 percentage and CD4/CD8 ratio in group 1 were significantly lower, whereas no differences were observed in FO-supplemented groups compared with the control group. CONCLUSION FO administration before and/or after CLP maintained blood T-lymphocyte subpopulations and modulated T-helper type 1 and 2 cytokine mRNA expressions in rats with polymicrobial sepsis.

Effects of dietary glutamine supplementation on lung injury induced by lipopolysaccharide administration

Acute lung injury (ALI) is a critical syndrome associated with respiratory dysfunction, and neutrophils are considered to be central to the pathogenesis of ALI. This study investigated the effects of glutamine (Gln) on neutrophil recruitment in a model of lipopolysaccharide (LPS)-induced ALI. C57BL/6 mice were fed a standard diet either with casein as the nitrogen source or with 25% of total nitrogen replaced by Gln. After 10 days, intratracheal instillation of LPS was used to induce ALI. Mice were killed at 0, 6, 12, and 24 h after LPS administration (n = 10/group). Bronchoalveolar lavage fluid and lung tissues were collected for further analysis. The results showed that, compared with the control group, lipid peroxide levels in the lungs were higher at 12 and 24 h after LPS administration in the Gln group. CXC chemokines as well as tumor necrosis factor-alpha were significantly elevated and reached peaks at 6 h in the Gln group, which was earlier than in the control group. Histopathological findings showed that the thickening of alveolar septal space was extensive in the Gln group 24 h and 2 wk after LPS. Also, greater amounts of collagen had accumulated in lung tissue in the Gln group. This study indicates that dietary Gln administration resulted in higher inflammatory cytokine production, with more neutrophils recruited at the early stage of ALI. These results were consistent with the histopathological findings that Gln supplementation causes more severe interstitial inflammation and fibrosis in a model of ALI induced by LPS.

Effects of arginine-containing total parenteral nutrition on N balance and phagocytic activity in rats undergoing a partial gastrectomy

The present study investigated the effect of arginine (Arg)-containing parenteral nutrition on phagocytic activity to elucidate the possible roles of Arg in the secretion of anabolic hormones and N balance in rats undergoing gastrectomy. Rats were divided into two experimental groups and received total parenteral nutrition (TPN). The TPN solutions were isonitrogenous and identical in nutrient compositions except for differences in amino acid content. One group received conventional TPN, the other group replaced 2 % of the total energy as Arg. After receiving TPN for 3 d, one-third of the rats in each experimental group were killed as the baseline group. The remaining rats underwent a partial gastrectomy and were killed 1 or 3 d after surgery. The results showed that there were no differences in N balance, plasma growth hormone and insulin-like growth factor-1 levels between the two groups before or after surgery. The phagocytic activity of peritoneal macrophages was higher in the Arg group than in the control group 1 d after surgery. There were no differences in the phagocytic activities of blood polymorphonuclear neutrophils between the two groups at various time points. TNF-alpha levels in peritoneal lavage fluid were lower in the Arg group than in the control group on post-operative day 3. These results suggest that parenterally infused Arg enhances phagocytic activity and reduces the production of inflammatory mediators at the site of injury. However, Arg supplementation did not influence the secretion of anabolic hormones nor N balance in rats with a partial gastrectomy.

Alanyl-glutamine resolves lipopolysaccharide-induced lung injury in mice by modulating the polarization of regulatory T cells and T helper 17 cells☆

Regulatory T cells (Tregs) and T helper (Th) 17 cells are two subsets of Th cells with opposing actions which participate in the process of resolving acute lung injury (ALI). Glutamine (Gln) is a nutrient commonly used in nutrition regimens due to its immunomodulatory effects. This study investigated whether alanyl-glutamine (Ala-Gln) administration modulated polarization of Th subsets in a model of lipopolysaccharide (LPS)-induced ALI during the resolution period. Intratracheal instillation of LPS in male C57BL/6J mice was used to induce ALI. On day 1 after LPS instillation, mice in the Gln group were given an intragastric gavage of 0.75 g Ala-Gln/kg daily, whereas the control (Con) group received identical amounts of sterilized distilled water. At 4, 7 and 10 days after a single dose of LPS, mice were killed by cardiac puncture. Bronchoalveolar lavage (BAL) fluid and lung tissues were collected for further analysis. Compared to the Con group, weight loss was less in the Gln group. Percentages of Tregs and interleukin-2 levels in BAL fluid increased, whereas Th17 cells were suppressed in the Gln group. Neutrophil clearance was promoted in the Gln group. Expressions of proinflammatory-related and fibrosis-related genes in lung tissues decreased in the Gln group. Histopathological findings also showed that interstitial inflammation was less severe in the Gln group. These results suggest that Ala-Gln administration after the onset of ALI can help resolve lung inflammation and injury by modulating the polarization of Tregs and Th17 cells.

Dietary arginine enhances adhesion molecule and T helper 2 cytokine expression in mice with gut-derived sepsis

ABSTRACT This study investigated the effects of arginine (Arg) on cellular adhesion molecules and intracellular Th1/Th2 cytokine expressions in mice with polymicrobial sepsis. Myeloperoxidase activity in organs was also analyzed to identify the extent of tissue injury resulting from neutrophil infiltration. Mice were randomly assigned to a normal group (NC), a control group, or an Arg group. The NC group was fed a standard chow diet. The control group was fed a common semipurified diet, and in the Arg group, part of the casein was replaced by Arg, which provided 2% of the total calories. After 3 weeks, sepsis was induced by cecal ligation and puncture (CLP) in the control and Arg groups. Mice in the experimental groups were sacrificed at 0, 6, 12, and 24 h after CLP, whereas mice in the NC group were sacrificed when the CLP was performed. Blood and organ samples were immediately collected for further analysis. Results showed that compared with the control group, plasma intracellular adhesion molecule-1 levels were significantly higher in the Arg group 12 and 24 h after CLP. Lymphocyte interferon-&ggr; expression in the Arg groups was significantly lower, whereas interleukin (IL)-4 expression was higher than the control group at various time points after CLP. The expression of lymphocyte CD11a/CD18 was significantly higher in the Arg group 6, 12, and 24 h after CLP than those of the corresponding control group and the NC group. PMN expressions of CD11b/CD18 in the Arg groups were higher than those in the control group at 12 and 24 h after CLP. The Arg group had higher IL-6 levels at 6 and 12 h in the kidney and intestine and 12 h in the lung after CLP. Higher myeloperoxidase activities were observed in the Arg groups at 24 h after CLP than those in the control group in various organs. These findings suggest that pretreatment with an Arg-supplemented diet enhances adhesion molecule and inflammatory cytokine expression during sepsis, which may aggravate the inflammatory reaction and increase neutrophil infiltration into tissues. In addition, Arg supplementation reduced intracellular interferon-&ggr; and enhanced IL-4 expression. This change may promote the Th2-type response and suppress the cellular immune response in gut-derived sepsis.