Enteral nutrition and keratinocyte growth factor regulate expression of glutathione-related enzyme messenger RNAs in rat intestine

Renalase is localized to the small intestine crypt and expressed upon the activation of NF-κB p65 in mice model of fasting-induced oxidative stress

AIMS

Renalase expression is regulated by Nuclear Factor (NF)-κB and hypoxia inducible factor (HIF)-1α, and antioxidative stress function in renal cells were reported. However, dynamics of renalase and localizes in intestine were remain unknown. We evaluated the effects of oxidative stress on renalase expression and localization using model of fasting induced oxidative stress and Caco-2 cell, and examined the its physiological effects.

MAIN METHODS

24 male mice were divided into three groups: Control (Con), 72 h fasting (Fast), and 24 h refeeding after fasting (Refeed). Jejunum and ileum were collected respectively. The structure of jejunum and ileum were observed by hematoxylin and eosin (HE) stain. The expression levels of carbonylated protein, renalase, NF-κB p65 and HIF-1α were measured by immunoblotting. Localization of renalase was observed by immunofluorescent. in vitro assay was performed using Caco-2 cell. Renalase was overexpressed using adenovirus. After that, Caco-2 cell was treated with 2 mM H₂O₂ for 30 min or 24 h.

KEY FINDINGS

Renalase was increased in Fast and it was localized in crypt. HIF-1α did not increase, but NF-κB p65 increased in Fast. Renalase overexpression protects the Caco-2 cells against H₂O₂ induced oxidative stress.

SIGNIFICANCE

Renalase was localized in crypt and increased in Fast. This increase suggested protect response to oxidative stress because undifferenced cells were localized in crypt and need to be protected. Actually, renalase protected Caco-2 cells against H₂O₂ induced oxidative stress. Small intestinal renalase expression was regulated by NF-κB p65 and was considered to be a defense mechanism against oxidative stress.

Protective effects of oral glutathione on fasting-induced intestinal atrophy through oxidative stress

AIM

To determine whether oral glutathione (GSH) administration can alleviate the effects of fasting-induced intestinal atrophy in the small intestinal mucosa.

METHODS

Rats were divided into eight groups. One group was fed ad libitum, another was fed ad libitum and received oral GSH, and six groups were administrated saline (SA) or GSH orally during fasting. Mucosal height, apoptosis, and cell proliferation in the jejunum were histologically evaluated. iNOS protein expression (by immunohistochemistry), nitrite levels (by high performance liquid chromatography, as a measure of NO production), 8-hydroxydeoxyguanosine formation (by ELISA, indicating ROS levels), glutathione/oxidized glutathione (GSH/GSSG) ratio (by enzymatic colorimetric detection), and γ-glutamyl transpeptidase (Ggt1) mRNA levels in the jejunum (by semi-quantitative RT-PCR) were also estimated.

RESULTS

Oral GSH administration was demonstrated to drastically reduce fasting-induced intestinal atrophy in the jejunum. In particular, jejunal mucosal height was enhanced in GSH-treated animals compared to SA-treated animals [527.2 ± 6.9 for 50 mg/kg GSH, 567.6 ± 5.4 for 500 mg/kg GSH vs 483.1 ± 4.9 (μm), P < 0.01 at 72 h]. This effect was consistent with decreasing changes in GSH-treated animals compared to SA-treated animals for iNOS protein staining [0.337 ± 0.016 for 50 mg/kg GSH, 0.317 ± 0.017 for 500 mg/kg GSH vs 0.430 ± 0.023 (area of staining part/area of tissue), P < 0.01 at 72 h] and NO [2.99 ± 0.29 for 50 mg/kg GSH, 2.88 ± 0.19 for 500 mg/kg GSH vs 5.34 ± 0.35 (nmol/g tissue), P < 0.01 at 72 h] and ROS [3.92 ± 0.46 for 50 mg/kg GSH, 4.58 ± 0.29 for 500 mg/kg GSH vs 6.42 ± 0.52 (8-OHdG pg/μg DNA), P < 0.01, P < 0.05 at 72 h, respectively] levels as apoptosis mediators in the jejunum. Furthermore, oral GSH administration attenuated cell proliferation decreases in the fasting jejunum [182.5 ± 1.9 for 500 mg/kg GSH vs 155.8 ± 3.4 (5-BrdU positive cells/10 crypts), P < 0.01 at 72 h]. Notably, both GSH concentration and Ggt1 mRNA expression in the jejunum were also attenuated in rats following oral administration of GSH during fasting as compared with fasting alone [0.45 ± 0.12 vs 0.97 ± 0.06 (nmol/mg tissue), P < 0.01; 1.01 ± 0.11 vs 2.79 ± 0.39 (Ggt1 mRNA/Gapdh mRNA), P < 0.01 for 500 mg/kg GSH at 48 h, respectively].

CONCLUSION

Oral GSH administration during fasting enhances jejunal regenerative potential to minimize intestinal mucosal atrophy by diminishing fasting-mediated ROS generation and enterocyte apoptosis and enhancing cell proliferation.

Preoperative vitamin C supplementation improves colorectal anastomotic healing and biochemical parameters in malnourished rats

PURPOSES

The objective of this study was to evaluate the effect of supplementation with vitamin C on intestinal anastomosis healing in malnourished rats.

METHODS

Male Wistar rats were divided into three groups: (1) sham, well-nourished rats that received vehicle; (2) FR+Veh, rats that were subjected to food restriction and received vehicle; and (3) FR+VC, rats that were subjected to food restriction and received vitamin C. Four days before surgery, the animals received vitamin C (100 mg/kg/day) via gavage and underwent colon resection with anastomosis in a single plane. The survival rate of rats was monitored until day 7 after surgery. Regarding anastomosis tissues, we examined intra-abdominal adhesion index, hydroxyproline content, collagen density, inflammatory parameters, and oxidative damage to proteins and lipids.

RESULTS

Malnutrition decreases body weight and increases mortality; the survival rate was 90 % in group 1, 60 % in group 2, and 80 % in group 3. Vitamin C was able to increase hydroxyproline concentration and density of collagen and decrease the intra-abdominal adhesion index, as well as the infiltration of neutrophils and oxidative damage to proteins in malnourished rats compared to group treated with vehicle.

CONCLUSIONS

Preoperative vitamin C supplementation can improve the intestinal anastomosis healing, biochemical alterations, and prolong survival in rats subjected to food restriction.

Effect of dietary lysine on growth, intestinal enzymes activities and antioxidant status of sub-adult grass carp (Ctenopharyngodon idella)

The dietary lysine requirement of sub-adult grass carp (460 ± 1.5 g) was assessed by feeding diets supplemented with grade levels of lysine (6.6, 8.5, 10.8, 12.9, 15.0 and 16.7 g kg(-1) diet) for 56 days. The test diets (28% CP) contained fish meal, casein and gelatin as sources of intact protein, supplemented with crystalline amino acids. Weight gain (WG), feed intake and feed efficiency were significantly improved with increasing levels of lysine up to 12.9 g kg(-1) diet and thereafter declined (P < 0.05). Quadratic regression analysis of WG at 95% maximum response indicated lysine requirement was 10.9 g kg(-1) diet. Activities of trypsin, chymotrypsin, lipase, Na(+), K(+)-ATPase and alkaline phosphatase in intestine, creatine kinase activity in proximal and mid-intestine responded similar to WG (P < 0.05). In addition, lipid and protein oxidation decreased with increasing levels of lysine up to certain values and increased thereafter (P < 0.05); the anti-hydroxyl radical capacity, dismutase, catalase, glutathione peroxidase, glutathione reductase, glutathione-S-transferase (GST) activities and glutathione content were increased with increasing dietary lysine levels up to certain values in the detected tissues, except for hepatopancreatic GST. Requirement estimated on the basis of malondialdehyde content in intestine and hepatopancreas was 10.6 and 9.53 g lysine kg(-1) diet, respectively.

Palifermin for the protection and regeneration of epithelial tissues following injury: new findings in basic research and pre-clinical models

Keratinocyte growth factor (KGF) is a paracrine-acting epithelial mitogen produced by cells of mesenchymal origin, that plays an important role in protecting and repairing epithelial tissues. Pre-clinical data initially demonstrated that a recombinant truncated KGF (palifermin) could reduce gastrointestinal injury and mortality resulting from a variety of toxic exposures. Furthermore, the use of palifermin in patients with hematological malignancies reduced the incidence and duration of severe oral mucositis experienced after intensive chemoradiotherapy. Based upon these findings, as well as the observation that KGF receptors are expressed in many, if not all, epithelial tissues, pre-clinical studies have been conducted to determine the efficacy of palifermin in protecting different epithelial tissues from toxic injury in an attempt to model various clinical situations in which it might prove to be of benefit in limiting tissue damage. In this article, we review these studies to provide the pre-clinical background for clinical trials that are described in the accompanying article and the rationale for additional clinical applications of palifermin.

Fasting-induced intestinal damage is mediated by oxidative and inflammatory responses

Background

Green tea has been shown to repair fasting-induced mucosal damage in rat intestine. The aim of this study was to elucidate the underlying mechanism.

Methods

Five groups of rats were used. Group 1 had free access to chow diet and water, and those in group 2 were fasted for 3 days. Animals in group 3 were fasted for 3 days, then were allowed drinking water for a further 7 days. Groups 4 and 5 were fasted for 3 days, then given drinking water containing green tea or vitamin E respectively for 7 days. Blood was collected for estimation of total plasma antioxidants, and jejunal samples were used for immunohistochemical analysis of superoxide dismutase (SOD), catalase and glutathione peroxidase (GPx), and for estimation of myeloperoxidase (MPO) activity.

Results

Use of green tea was associated with a significant increase in total plasma antioxidants (P &lt; 0·001), and mucosal SOD (P &lt; 0·001), catalase (P = 0·006) and GPx (P = 0·017), but a significant decrease in MPO activity (P &lt; 0·001). Vitamin E produced similar changes, but the effects were smaller.

Conclusion

Green tea reverses the fasting-induced damage to the intestinal mucosa by its antioxidant and anti-inflammatory effect.

Morphological, kinetic, membrane biochemical and genetic aspects of intestinal enteroplasticity

The process of intestinal adaptation (“enteroplasticity”) is complex and multifaceted. Although a number of trophic nutrients and non-nutritive factors have been identified in animal studies, successful, reproducible clinical trials in humans are awaited. Understanding mechanisms underlying this adaptive process may direct research toward strategies that maximize intestinal function and impart a true clinical benefit to patients with short bowel syndrome, or to persons in whom nutrient absorption needs to be maximized. In this review, we consider the morphological, kinetic and membrane biochemical aspects of enteroplasticity, focus on the importance of nutritional factors, provide an overview of the many hormones that may alter the adaptive process, and consider some of the possible molecular profiles. While most of the data is derived from rodent studies, wherever possible, the results of human studies of intestinal enteroplasticity are provided.

Decline in intestinal mucosal IL-10 expression and decreased intestinal barrier function in a mouse model of total parenteral nutrition

Loss of intestinal epithelial barrier function (EBF) is a major problem associated with total parenteral nutrition (TPN) administration. We have previously identified intestinal intraepithelial lymphocyte (IEL)-derived interferon-gamma (IFN-gamma) as a contributing factor to this barrier loss. The objective was to determine whether other IEL-derived cytokines may also contribute to intestinal epithelial barrier breakdown. C57BL6J male mice received TPN or enteral nutrition (control) for 7 days. IEL-derived interleukin-10 (IL-10) was then measured. A significant decline in IEL-derived IL-10 expression was seen with TPN administration, a cytokine that has been shown in vitro to maintain tight junction integrity. We hypothesized that this change in IEL-derived IL-10 expression could contribute to TPN-associated barrier loss. An additional group of mice was given exogenous recombinant IL-10. Ussing chamber experiments showed that EBF markedly declined in the TPN group. TPN resulted in a significant decrease of IEL-derived IL-10 expression. The expression of several tight junction molecules also decreased with TPN administration. Exogenous IL-10 administration in TPN mice significantly attenuated the TPN-associated decline in zonula occludens (ZO)-1, E-cadherin, and occludin expression, as well as a loss of intestinal barrier function. TPN administration led to a marked decline in IEL-derived IL-10 expression. This decline was coincident with a loss of intestinal EBF. As the decline was partially attenuated with the administration of exogenous IL-10, our findings suggest that loss of IL-10 may be a contributing mechanism to TPN-associated epithelial barrier loss.

Chronically administered retinoic acid has trophic effects in the rat small intestine and promotes adaptation in a resection model of short bowel syndrome

Following the loss of functional small bowel surface area, the intestine undergoes a compensatory adaptive response. The observation that adaptation is inhibited in vitamin A-deficient rats following submassive intestinal resection suggested that vitamin A is required for this response and raised the possibility that exogenous vitamin A could augment adaptation. Therefore, to directly assess whether chronically administered retinoic acid could stimulate gut adaptation in a model of short bowel syndrome and to address the mechanisms of any such effects, Sprague-Dawley rats were implanted with controlled release retinoic acid or control pellets and then subjected to mid-small bowel or sham resections. At 2 wk postoperation, changes in gut morphology, crypt cell proliferation and apoptosis, enterocyte migration, the extracellular matrix, and gene expression were assessed. Retinoic acid had significant trophic effects in resected and sham-resected rats. Retinoic acid markedly inhibited apoptosis and stimulated crypt cell proliferation and enterocyte migration postresection. Data presented indicate that these proadaptive effects of retinoic acid may be mediated via changes in the extracellular matrix (e.g., by increasing collagen IV synthesis, decreasing E-cadherin expression, and reducing integrin beta(3) levels), via affects on Hedgehog signaling (e.g., by reducing expression of the Hedgehog receptors Ptch and Ptch2 and the Gli1 transcription factor), by increasing expression of Reg1 and Pap1, and by modulation of retinoid and peroxisome proliferator-activated receptor signaling pathways. These studies are the first to demonstrate that retinoic acid can significantly enhance intestinal adaptation and suggest it may be beneficial in patients with short bowel syndrome.

Palifermin (recombinant keratinocyte growth factor-1): a pleiotropic growth factor with multiple biological activities in preventing chemotherapy- and radiotherapy-induced mucositis

Oral and intestinal mucositis are among the most significant dose-limiting toxic effects of intensive cancer treatment and are associated with adverse clinical and economic outcomes. Palifermin (Kepivancetrade mark), an N-truncated recombinant human keratinocyte growth factor-1, is the first agent to be approved for prevention of oral mucositis. Keratinocyte growth factor, a potent epithelial mitogen, appears to play a major role in the healing process. Palifermin has multiple biological activities that appear to protect the mucosal epithelium and promote its early regeneration after irradiation- and chemotherapy-induced injury. These include inhibition of epithelial cell apoptosis and DNA damage, up-regulation of detoxifying enzymes and down-regulation of pro-inflammatory cytokines, as well as enhanced migration, proliferation and differentiation of epithelial cells. Palifermin reduces the incidence, severity and duration of oral mucositis in patients with haematological malignancies undergoing myelotoxic conditioning therapy and haematopoietic stem-cell transplantation. Clinical sequelae, including febrile neutropenia and resource use (opioid analgesia and parenteral feeding), are concomitantly reduced. Other potential applications being explored include use in the solid tumour setting, reduction of intestinal mucositis and reduction of GVHD in allogenic transplantation. Thus, the development of palifermin and other potential new agents for preventing chemotherapy- and radiotherapy-induced mucositis represents an important breakthrough in oncological supportive care.

Intestinal mucosal adaptation

Intestinal failure is a condition characterized by malnutrition and/or dehydration as a result of the inadequate digestion and absorption of nutrients. The most common cause of intestinal failure is short bowel syndrome, which occurs when the functional gut mass is reduced below the level necessary for adequate nutrient and water absorption. This condition may be congenital, or may be acquired as a result of a massive resection of the small bowel. Following resection, the intestine is capable of adaptation in response to enteral nutrients as well as other trophic stimuli. Identifying factors that may enhance the process of intestinal adaptation is an exciting area of research with important potential clinical applications.

Epithelium-specific glutathione peroxidase, Gpx2, is involved in the prevention of intestinal inflammation in selenium-deficient mice

Mice deficient in 2 intracellular selenium (Se)-dependent glutathione peroxidases (Gpx1 and Gpx2), by genetically disrupting both alleles of the Gpx1 and Gpx2 genes (Gpx1(-/-)Gpx2(-/-)), develop ileocolitis around weaning. However, decreased Gpx activity in Se-depleted wild-type animals does not produce pathology in the gastrointestinal tract. Because a small percentage of Se-sufficient Gpx1(+/-)Gpx2(-/-) mice have mild ileocolitis, we hypothesized that Se-deficient Gpx1(+/-)Gpx2(-/-) mice will develop severe ileocolitis similarly to the Gpx1(-/-)Gpx2(-/-) mice, and even a trace amount of Gpx2 can protect intestinal mucosa against inflammation. To test our hypothesis, we fed mice at various stages of development with either Gpx1(+/)(-)Gpx2(-/-) or Gpx1(-/-)Gpx2(+/)(-) genotypes an Se-deficient diet for 4-5 wk and assessed the symptoms and pathology. Gpx1(+/)(-)Gpx2(-/-) mice that were deprived of Se in utero or at weaning (18-22 d of age), but not as young adults (31-51 d of age), manifested significantly worse pathology than their Se-sufficient counterparts. Both Gpx1 and Gpx2 activities and mRNA levels were significantly depressed in the ileum of Se-deprived mice. In mice deprived in utero, the pathology included acute inflammation with neutrophil and monocyte infiltration particularly in the colon and was externally manifested by perianal alopecia and ulceration. On the other hand, Gpx1(-/-)Gpx2(+/)(-) mice were unaffected by Se deprivation, regardless of the age of onset. The results show that a trace amount of Gpx2 is protective against ileocolitis, and Se-deficient young Gpx1(+/-)Gpx2(-/-) mice will develop pathology and symptoms similar to Se-adequate Gpx1(-/-)Gpx2(-/-) mice.

Keratinocyte growth factor/fibroblast growth factor 7, a homeostatic factor with therapeutic potential for epithelial protection and repair

Keratinocyte growth factor (KGF) is a paracrine-acting, epithelial mitogen produced by cells of mesenchymal origin. It is a member of the fibroblast growth factor (FGF) family, and acts exclusively through a subset of FGF receptor isoforms (FGFR2b) expressed predominantly by epithelial cells. The upregulation of KGF after epithelial injury suggested it had an important role in tissue repair. This hypothesis was reinforced by evidence that intestinal damage was worse and healing impaired in KGF null mice. Preclinical data from several animal models demonstrated that recombinant human KGF could enhance the regenerative capacity of epithelial tissues and protect them from a variety of toxic exposures. These beneficial effects are attributed to multiple mechanisms that collectively act to strengthen the integrity of the epithelial barrier, and include the stimulation of cell proliferation, migration, differentiation, survival, DNA repair, and induction of enzymes involved in the detoxification of reactive oxygen species. KGF is currently being evaluated in clinical trials to test its ability to ameliorate severe oral mucositis (OM) that results from cancer chemoradiotherapy. In a phase 3 trial involving patients who were treated with myeloablative chemoradiotherapy before autologous peripheral blood progenitor cell transplantation for hematologic malignancies, KGF significantly reduced both the incidence and duration of severe OM. Similar investigations are underway in patients being treated for solid tumors. On the basis of its success in ameliorating chemoradiotherapy-induced OM in humans and tissue damage in a variety of animal models, additional clinical applications of KGF are worthy of investigation.

Role of Se-dependent glutathione peroxidases in gastrointestinal inflammation and cancer

Increase in reactive oxygen species plays an integral part in the inflammatory response, and chronic inflammation increases cancer risk. Selenium-dependent glutathione peroxidase (GPX) is well recognized for its antioxidant, and thus anti-inflammatory, activity. However, due to the multiple antioxidant families present in the gastrointestinal tract, it has been difficult to demonstrate the importance of individual antioxidant enzymes. Using genetically altered mice deficient in individual Gpx genes has provided insight into the physiological functions of these genes. Insufficient GPX activity in the mucosal epithelium can trigger acute and chronic inflammation. The presence of certain microflora, such as Helicobacter species, may affect cancer risk significantly. However, when damaged cells have progressed into a precancerous status, increased GPX activity may become procarcinogenic, presumably due to inhibition of hydroperoxide-mediated apoptosis. This review summarizes the current view of GPX in inflammation and cancer with emphasis on the GI tract.

Adaptation following intestinal resection: mechanisms and signals

The intestine has an inherent ability to adapt morphologically and functionally in response to internal and external environmental changes. The functional adaptations encompass modifications of the brush border membrane fluidity and permeability, as well as up- or down-regulation of carrier-mediated transport. Intestinal adaptation improves the nutritional status following the loss of a major portion of the small intestine, following chronic ingestion of ethanol, following sublethal doses of abdominal irradiation, in diabetes, in pregnancy and lactation, with ageing, and with fasting and malnutrition. Following intestinal resection, morphological and functional changes occur depending upon the extent of the intestine removed, the site studied, and the lipid content of the diet. Therefore, intestinal adaptation has important implications in the survival potential and welfare of the host. An understanding of the mechanisms of, and signals for, intestinal adaptation in the experimental setting forms the basis for the use of management strategies in humans with the short-bowel syndrome.

Microflora trigger colitis in mice deficient in selenium-dependent glutathione peroxidase and induce Gpx2 gene expression

Selenium-dependent glutathione peroxidase isoenzymes-1 and -2 are the major glutathione-dependent H2O2-reducing activities in the epithelium of the mid- to lower gastrointestinal tract. The two isoenzymes protect mice against ileocolitis. We have found that luminal microflora are required for colitis to develop in mice deficient in GPX-1 and GPX-2 activity (GPX-DKO). Within 7 days of association with microflora, previously asymptomatic germ-free GPX-DKO mice developed severe acute colitis while their littermates with at least one wild-type Gpx1 or Gpx2 gene remained virtually symptom-free. Microflora also affected Gpx2 gene expression. Gpx2, but not Gpx1, mRNA levels were elevated 4-5 fold in the ileum and colon in conventionally reared or microflora-associated adult mice compared with germ-free mice. Since the gastrointestinal tract microflora undergo major changes 2-3 weeks after birth, from relatively benign to a potentially stressful composition, we examined postnatal Gpx2 gene expression. The jejunal and ileal GPX-2 activity levels were low in two to three week-old mice and increased 5-7 fold during the next two weeks. GPX-2 activity levels were correlated with the mRNA levels. Colon Gpx2 mRNA levels held steady at about 50% of adult levels from 12-21 days of age but were several times higher than ileal levels. Our results suggest that ileal Gpx2 mRNA and GPX-2 activity levels are induced by luminal microflora. This response is consistent with a role for GPX as an anti-inflammatory activity.