Rat Model Of Necrotizing Enterocolitis Research Articles

Recombinant Human Trefoil Factor 3 Ameliorates Bowel Injury: Its Anti-Inflammatory Effect on Experimental Necrotizing Enterocolitis

Aim. Recombinant human trefoil factor 3 (intestinal trefoil factor) has been suggested to be partially protective against necrotizing enterocolitis (NEC), but the mechanisms of this protection have not been defined. We investigated whether the protective effects of rhTFF3 are the result of an anti-inflammatory response. Methods. The rats were killed on day 4, the distal ileum was harvested for morphological studies and immunohistochemistry for NF-κB (p65), and the amounts of IL-1β, IL-6, and IL-10 in the intestinal tissue were measured using commercial ELISA assay kits. Results. In the neonatal NEC, IL-1β, IL-6, and IL-10 were significantly higher than in normal group. In normal group, IL-1β and IL-6 were significantly decreased, and the amount of IL-10 was markedly increased compared with NEC group. In the NEC model, immunohistochemical staining for NF-κB (p65) was demonstrated to be of a strong brown color and was distributed in the intestinal epithelium. Treatment with rhTFF3 significantly decreased the immunoreactivity of NF-κB (p65) in the NEC model. Conclusions. Intestinal inflammation was ameliorated after rhTFF3 was injected. rhTFF3 may protect against the intestinal injury of the neonatal rat NEC model by suppression of the inflammatory response.

L-FABP and I-FABP expression in newborn rats changes inversely in the model of necrotizing enterocolitis.

To determine the expression of hepatic L-FABP and intestinal I-FABP in an experimental model of necrotizing enterocolitis (NEC) in neonatal rats. Newborn Sprague-Dawley rats were divided into four groups: Control (C1) - exclusive breastfeeding at the first and sixth procedures (C6), NEC1 - fed formula milk and submitted to hypoxia and hypothermia at the first and sixth procedures (NEC6). The newborn pups were fed twice a day for three days, for a total of six procedures. Samples were collected for morphometric evaluation (body weight, liver weight, liver weight/body weight ratio, intestinal weight and intestinal/body weight ratio) and for immunohistochemical and Western blotting analysis. The values obtained were analyzed statistically, with the level of significance set at p<0.05. Morphometric measurements showed reduction of body and liver weights in the NEC group (p<0.05). Both immunohistochemistry and western blotting revealed that L-FABP expression in the liver was decreased and I-FABP expression in the ileum was increased in the NEC group (p<0.05). L-FABP and I-FABP expression changed inversely in the rat NEC model. These findings can contribute to a better diagnosis of NEC in human newborns.

FoxP3+ Regulatory T Cells Attenuate Experimental Necrotizing Enterocolitis

Necrotizing enterocolitis (NEC) results from severe intestinal inflammation in premature infants. FoxP3+ regulatory T cells (Tregs) are central to gut homeostasis. While Treg proportions are significantly reduced in the ileums of premature infants with NEC, it is unknown whether they play a critical function in preventing NEC. This study investigated Treg development in newborn rat pups and their role in experimental NEC induction. Utilizing an established rat model of experimental NEC, the ontogeny of T cells and Tregs in newborn pups was characterized by flow cytometry. To investigate the functions of Tregs, newborn pups were given Tregs harvested from adult rats prior to NEC induction to assess clinical improvement and mechanisms of immune regulation. The results revealed that there were few Treg numbers in the terminal ileums of newborn rats and 8-fold reduction after NEC. Adoptive transfer of Tregs significantly improved weight loss, survival from 53% to 88%, and NEC incidence from 87% to 35%. The Tregs modulated the immune response as manifested in reduced CD80 expression on antigen presenting cells and decreased T cell activation within the mesenteric lymph nodes. These findings suggest that while Tregs are present in the intestines, their numbers might be insufficient to dampen the excessive inflammatory state in NEC. Adoptive transfer of Tregs attenuates the severity of NEC by limiting the immune response. Strategies to enhance Tregs have a therapeutic potential in controlling the development of NEC.

Protective effects of colchicine in an experimental model of necrotizing enterocolitis in neonatal rats

BackgroundThe pathophysiology of necrotizing enterocolitis (NEC) includes the massive production of endogenous cytokines with exaggerated activation of inflammatory pathways. Colchicine has been used as an anti-inflammatory agent. The aim of this study was to investigate the possible beneficial effects of colchicine in a neonatal rat model of NEC. Materials and methodsWe randomly divided rat pups into three groups: a control group, a saline-treated NEC group, and a colchicine-treated NEC group. We induced NEC by hyperosmolar enteral formula feeding and exposure to hypoxia/reoxygenation after cold stress. Intestinal samples were harvested for biochemical and histopathologic analyses. ResultsThe grade of intestinal injury of pups in the saline-treated NEC group was significantly higher than in the control and colchicine-treated groups (P < 0.001 and 0.003, respectively). The median level of intestinal malondialdehyde was significantly higher in the saline-treated NEC group compared with the control group (P = 0.006) or the colchicine-treated NEC group (P = 0.015). We observed significantly higher activity levels of intestinal superoxide dismutase and glutathione peroxidase in the colchicine-treated NEC group compared with the saline-treated NEC group (P = 0.033 and 0.030, respectively). The tissue levels of tumor necrosis factor-α and interleukin-1β were significantly higher in the saline-treated NEC group compared with the colchicine-treated NEC group (P < 0.001 and 0.003, respectively). ConclusionsWe observed that in this model of NEC, colchicine had favorable effects on intestinal histologic and biochemical changes.

Protective Function of FoxP3+ Regulatory T Cells in Experimental Necrotizing Enterocolitis

Necrotizing enterocolitis (NEC) results from severe intestinal inflammation in premature infants. FoxP3+ regulatory T cells (Tregs) are central to gut homeostasis. While Tregs are significantly reduced in the ileum of premature infants with NEC, it is unknown whether they play a critical function in preventing NEC. This study investigates whether Treg development is delayed in newborn rat pups and whether Tregs play a protective role in experimental NEC induction. Utilizing a rat model of experimental NEC, the ontogeny of T cells and Tregs in newborn pups was characterized by flow cytometry. To investigate the functions of Tregs, newborn pups were given Tregs harvested from adult rats prior to NEC induction to assess clinical improvement and mechanisms of immune regulation. There were few Tregs in the mesenteric lymph nodes (MLN) and ileums of newborn rats, which were further reduced after NEC. Adoptive transfer of Tregs significantly improved weight loss, survival from 53% to over 85%, and intestinal damage based on preservation of cellular composition and reduction of NEC score from maximum of 3 to 1 in severity. The Tregs suppressed the upregulation of costimulatory molecule CD80 on dendritic cells (DCs) and regulated the trafficking of effector cells in the MLN. There is a developmental delay in Tregs which contributes to the excessive inflammatory state in NEC. Adoptive transfer of Tregs attenuates the induction of NEC by regulating DCs and modulating effector cell trafficking. Treg immunotherapy has an enormous therapeutic potential in the prevention and treatment of NEC.

CDP-choline reduces severity of intestinal injury in a neonatal rat model of necrotizing enterocolitis

BackgroundCytidine 5′-diphosphocholine (CDP-choline) is an endogenous intermediate in the biosynthesis of phosphatidylcholine, a contributor to the mucosal defense of the intestine. The aim of this study was to evaluate the possible cytoprotective effect of CDP-choline treatment on intestinal cell damage, membrane phospholipid content, inflammation, and apoptosis in a neonatal rat model of necrotizing enterocolitis (NEC). MethodsWe divided a total of 30 newborn pups into three groups: control, NEC, and NEC + CDP-choline. We induced NEC by enteral formula feeding, exposure to hypoxia-hyperoxia, and cold stress. We administered CDP-choline intraperitoneally at 300 mg/kg/d for 3 d starting from the first day of life. We evaluated apoptosis macroscopically and histopathologically in combination with proinflammatory cytokines in the gut samples. Moreover, we determined membrane phospholipid levels as well as activities of xanthine oxidase, superoxide dismutase, glutathione peroxidase, and myeloperoxidase enzymes and the malondialdehyde content of intestinal tissue. ResultsMean clinical sickness score, macroscopic gut assessment score, and intestinal injury score were significantly improved, whereas mean apoptosis score and caspase-3 levels were significantly reduced in pups in the NEC + CDP-choline group compared with the NEC group. Tissue proinflammatory cytokine (interleukin-1β, interleukin-6, and tumor necrosis factor-α) levels as well as tissue malondialdehyde content and myeloperoxidase activities were reduced, whereas glutathione peroxidase and superoxide dismutase activities were preserved in the NEC + CDP-choline group. In addition, NEC damage reduced intestinal tissue membrane phospholipids, whereas CDP-choline significantly enhanced total phospholipid and phosphatidylcholine levels. Long-term follow-up in additional experiments revealed increased body weight, decreased clinical sickness scores, and enhanced survival in CDP-choline–receiving versus saline-receiving pups with NEC lesions. ConclusionsOur study reports, for the first time, beneficial effects of CDP-choline treatment on intestinal injury in a neonatal rat model of NEC. Our data suggest that CDP-choline may be used as an effective therapeutic agent to prevent NEC.

Antioxidant effects of N-acetylcysteine in a neonatal rat model of necrotizing enterocolitis

Background/PurposeHypoxia and ischemia appear to play an important role in the pathogenesis of necrotizing enterocolitis (NEC), which may be related to oxygen-derived free radical formation. This study was designed to evaluate the role of oxidative stress and potentially beneficial effects of N-acetylcysteine (NAC) in a neonatal rat model of NEC. MethodsThirty Wistar albino rat pups were randomly divided into 3 groups: group 1, control; group 2, NEC and saline; and group 3, NEC and NAC treatment. Necrotizing enterocolitis was induced by hyperosmolar enteral formula feeding and exposure to hypoxia after cold stress at 4°C and oxygen. The pups were killed on the fourth day, and their intestinal tissues were harvested for biochemical and histopathologic analysis. ResultsMucosal injury scores and intestinal malondialdehyde levels in group 2 were found to be significantly higher than that in other groups (P ≤ .05). Intestinal superoxide dismutase activities in group 3 were significantly higher than that in group 2 (P = .018). Intestinal tissue tumor necrosis factor α levels were significantly reduced with NAC treatment in group 3 compared with group 2 (P < .003). ConclusionsIt is likely that oxidative stress and inflammatory mediators contribute to the pathogenesis of NEC and that NAC has a protective effect on intestinal injury through its antiinflammatory and antioxidant properties.

Heat Shock Pretreatment Reduces Intestinal Injury in a Neonatal Rat Model of Early Necrotizing Enterocolitis

Background: Increased pro-inflammatory cytokines are suggested in the pathogenesis of necrotizing enterocolitis (NEC). The transcription factor, nuclear factor-ĸB (NF-ĸB), is a central regulator of inflammatory and immune responses, and recent rodent NEC models have shown that NF-ĸB may have a critical role in the disease processes that underlie NEC. Heat shock proteins have important functions in response to stress-related events in a variety of systems, including digestive organs. Objectives: We investigated whether heat shock pretreatment protects intestinal epithelial damage in the early NEC rat model. Methods: We generated human NEC-like lesions in neonatal rat ileum by administering oral endotoxin (10 mg/kg), intermittent 8% hypoxia, and hypertonic formula. Heat shock was administered by raising the chamber temperature to 42°C for 20 min, 3 h prior to endotoxin ingestion. Results: Heat shock pretreatment increased the expression of HSP70 in the ileal tissue and attenuated histological severity of early experimental NEC. NF-ĸB was activated in the ileal tissue of the NEC group and this activation was attenuated by heat shock pretreatment, which was determined by electrophoretic mobility shift assay and Western blot analysis of p50 in subcellular fractionated samples. Conclusions: Heat shock pretreatment reduced the incidence and severity of early experimental NEC in rats. A possible mechanism underlying this protective effect includes inhibition of NF-ĸB activation through increased HSP70 expression.

Pomegranate seed oil reduces intestinal damage in a rat model of necrotizing enterocolitis

Pomegranate seed oil (PSO), which is the major source of conjugated linolenic acids such as punicic acid (PuA), exhibits strong anti-inflammatory properties. Necrotizing enterocolitis (NEC) is a devastating disease associated with severe and excessive intestinal inflammation. The aim of this study was to evaluate the effects of orally administered PSO on the development of NEC, intestinal epithelial proliferation, and cytokine regulation in a rat model of NEC. Premature rats were divided into three groups: dam fed (DF), formula-fed rats (FF), or rats fed with formula supplemented with 1.5% of PSO (FF + PSO). All groups were exposed to asphyxia/cold stress to induce NEC. Intestinal injury, epithelial cell proliferation, cytokine production, and trefoil factor 3 (Tff3) production were evaluated in the terminal ileum. Oral administration of PSO (FF+PSO) decreased the incidence of NEC from 61 to 26%. Feeding formula with PSO improved enterocyte proliferation in the site of injury. Increased levels of proinflammatory IL-6, IL-8, IL-12, IL-23, and TNF-α in the ileum of FF rats were normalized in PSO-treated animals. Tff3 production in the FF rats was reduced compared with DF but not further affected by the PSO. In conclusion, administration of PSO protects against NEC in the neonatal rat model. This protective effect is associated with an improvement of intestinal epithelial homeostasis and a strong anti-inflammatory effect of PSO on the developing intestinal mucosa.

Effects of glycomacropeptide on damage to intestinal tissue and apoptosis of intestinal epithelial cells in neonatal rats with necrotizing enterocolitis

To establish an appropriate neonatal rat model of necrotizing enterocolitis (NEC) and to investigate the protective effects of glycomacropeptide (GMP) on the gut from injury in neonatal rats with NEC. A total of 36 neonatal SD rats were randomly divided into 3 groups: NEC model group (Group M), NEC + GMP group (Group G) and normal control group (Group N), each group had 12 rats. All the neonatal rats were fed with breast milk in the first 3 days after birth. During the second 3 days after birth, the rats of Group N were still maternal breast-fed, but the rats of Group M and Group G were separated from their mothers and lived in incubator and began to be formula fed, and were subjected to cold exposure shortly after hypoxic-reoxygenation treatment. After being fed in such means for 6 days, all the neonatal rats were placed into the incubator and fasted for 24 hours. Then all the rats were sacrificed by cervical dislocation. Intestinal tissue located at the boundary of ileum and cecum was obtained for: (1) histological examination after HE staining, (2) TUNEL detection, (3) electron microscopic observation; and the tissue homogenate was obtained for checking TNF-α and IL-1β levels by ELISA and platelet activating factor (PAF) mRNA expression by quantitative fluorescence (QF)-PCR. (1) The pathological scores of the 3 groups were 2.17 ± 0.83 (Group M), 0.92 ± 0.79 (Group G) and 0.17 ± 0.39 (Group N) separately. There was significant difference between Group M and Group G (H = 8.819, P = 0.003). (2) TNF-α levels of 3 groups were (41.94 ± 13.51) pg/ml (Group M), (31.69 ± 11.68) pg/ml (Group G) and (17.42 ± 7.18) pg/ml (Group N) separately, and TNF-α level in Group G was significantly lower than that of Group M (F = 3.959, P = 0.030). (3) IL-1β levels of 3 groups were (150.33 ± 36.41) pg/ml (Group M), (118.36 ± 33.00) pg/ml (Group G) and (28.44 ± 15.04) pg/ml (Group N) separately, and IL-1β level in Group G was lower than that of Group M (F = 5.080, P = 0.013). (4) Expression levels of intestinal PAF mRNA (2(-ΔΔCt) value): 3.01 ± 0.96 (Group M), 1.56 ± 0.29 (Group G), 1.01 ± 0.13 (Group N), the level of Group G was significantly lower than that of Group M (F = 25.251, P = 0.000). (5)Electron microscopy: Group N showed that its cell volume was mostly occupied by the nucleus, the structure was clear, nuclear membrane existed, suggesting the normal phase of cell; Group M showed that apoptotic body existed, suggesting that the advanced stage phase of apoptosis; Group G showed that condensed chromatin marginated around the nuclear envelope, nuclear pores expanded, suggesting the early phase of apoptosis. (6) The apoptosis rate of intestinal epithelial cells by TUNEL detection: 38.79 ± 9.79 (Group M), 29.54 ± 7.30 (Group G), 6.37 ± 1.96 (Group N); the apoptosis rate of intestinal epithelial cells of Group G was significantly lower than that of Group M (F = 6.888, P = 0.003). GMP has protective effects on guts of neonatal rats with NEC, which may probably work by reducing TNF-α, IL-1β and PAF expression, inhibiting the apoptosis of intestinal epithelial cells and reducing intestinal tissue injury.

Heparin-binding EGF-like growth factor protects intestinal stem cells from injury in a rat model of necrotizing enterocolitis

Necrotizing enterocolitis (NEC) is an often catastrophic disease that typically affects premature newborns. Although the exact etiology of NEC is uncertain, the disease is associated with formula feeding, bacterial colonization of the gut, hypoxia and hypoperfusion. In light of the pathogenesis of NEC, the integrity and function of the intestinal mucosa has a major defensive role against the initiation of NEC. Various forms of intestinal injury, including NEC, injure the intestinal epithelial cell (IEC) lineages, including the intestinal stem cells (ISCs), thereby disrupting the normal homeostasis needed to maintain gut barrier function. In the current study, we examined the effects of heparin-binding EGF-like growth factor (HB-EGF) administration on enterocytes, goblet cells, neuroendocrine cells and ISCs in a newborn rat model of experimental NEC. We also examined the cytoprotective effects of HB-EGF on ISCs in in vitro cell cultures and in ex vivo crypt-villous organoid cultures. We found that HB-EGF protects all IEC lineages, including ISCs, from injury. We further found that HB-EGF protects isolated ISCs from hypoxic injury in vitro, and promotes ISC activation and survival, and the expansion of crypt transit-amplifying cells, in ex vivo crypt-villous organoid cultures. The protective effects of HB-EGF were dependent on EGF receptor activation, and were mediated via the MEK1/2 and PI3K signaling pathways. These results show that the intestinal cytoprotective effects of HB-EGF are mediated, at least in part, through its ability to protect ISCs from injury.

Intestinal Alkaline Phosphatase Prevents the Systemic Inflammatory Response Associated With Necrotizing Enterocolitis

Introduction: Necrotizing enterocolitis (NEC) is the most common surgical emergency in neonates with an incidence of 0.5-2.4 cases per 1000 live births. the mortality rate is between 10-50% and has not improved significantly in the past two decades. Neonates affected by NEC develop a septic injury that is associated with an increased risk of chronic lung disease and neurological impairment due to intraventricular bleeding. Intestinal alkaline phosphatase (IAP) is an endogenous protein that has been shown to inactivate the endotoxin lipopolysaccharide (LPS), and has recently been used successfully as an adjunct to treat sepsis in adult patients. Our hypothesis is that systemic, exogenous IAP will mitigate the inflammatory response as measured by serum levels of pro-inflammatory cytokines in a rat model of NEC. Methods: Newborn Sprague Dawley rats were divided into groups. Control pups were breast-fed. in the remaining pups, NEC was induced by feeding formula containing LPS and exposure to intermittent hypoxia. NEC pups were also given intra-peritoneal injections of 4 or 40 glyceine units (U) of IAP or placebo twice daily. Rats were sacrificed on days 1-3. Intestine was harvested to grade intestinal injury and serum was collected for cytokine analysis using a bioplex assay as well as measurement of alkaline phosphatase (AP) activity. Results: Systemic IAP administration had no effect on increasing intestinal AP activity or preventing NEC as measured by histology. However, systemic IAP administration significantly increased serum AP activity in a dose and time dependent fashion. the serum AP activity for the 40 U IAP treated groups on days of life 1-3 were 0.285, 0.344, and 0.496 U/mL respectively, while the controls and NEC groups had serum activities ranging from 0.007-0.0489 U/mL on days 1-3 (p<0.05 for all). We also found that the pro-inflammatory cytokines (measured in pg/mL) TNF-a, IL-6, and IL-1b were significantly increased in NEC rats as compared to controls on days 2 and 3 (TNF-a: 1390 vs. 25 on DOL 2 and 2896 vs. 1332 on DOL 3; IL-1b: 3295 vs. 66 DOL 2 and 7010 vs. 2394 on DOL3; IL-6: 1718 vs. 21 on DOL2; (p<0.05 for all). Importantly, we found that treatment with 40 U of systemic IAP not only increased serum AP activity, but also decreased these pro-inflammatory cytokines back to near-control levels. (TNF-a: 26 on DOL 2 and 1018 on DOL3; IL-1b 183 on DOL 2 and 1339 on DOL 3; IL-6: 381 on DOL 3; (p<0.05 for all). Figure 1 shows serum TNF-a levels in control, NEC, and 40 U IAP treated pups. Conclusions: Systemic IAP administration appears effective in preventing the systemic inflammatory response associated with NEC, and may prove to be a valuable adjunctive treatment for NEC.

Lactobacillus reuteristrains reduce incidence and severity of experimental necrotizing enterocolitis via modulation of TLR4 and NF-κB signaling in the intestine

Necrotizing enterocolitis (NEC) is the leading gastrointestinal cause of mortality and morbidity in the premature infant. Premature infants have a delay in intestinal colonization by commensal bacteria and colonization with potentially pathogenic organisms. Lactobacillus reuteri is a probiotic that inhibits enteric infections, modulates the immune system, and may be beneficial to prevent NEC. In previous studies, L. reuteri strains DSM 17938 and ATCC PTA 4659 differentially modulated inflammation in vitro; however, the strains had equivalent anti-inflammatory responses in LPS feeding-induced ileitis in neonatal rats in vivo. The impact of these two strains in the prevention of NEC has not been previously investigated. NEC was induced in newborn rats by orogastric formula feeding and exposure to hypoxia. L. reuteri was added to the formula to prevent NEC. NEC score, Toll-like receptor (TLR)-signaling genes, phospho-IκB activity, and cytokine levels in the intestine were examined. Both strains significantly increased survival rate and decreased the incidence and severity of NEC, with optimal effects from DSM 17938. In response to probiotic, mRNA expression of IL-6, TNF-α, TLR4, and NF-κB was significantly downregulated, while mRNA levels of anti-inflammatory cytokine IL-10 were significantly upregulated. In parallel, L. reuteri treatment led to decrease intestinal protein levels of TLR4 and cytokine levels of TNF-α and IL-1β in newborn rats with NEC. Both strains significantly inhibited not only intestinal LPS-induced phospho-IκB activity in an ex vivo study but also decreased the levels of phospho-IκB in the intestines of NEC rat model. Cow milk formula feeding produced a similar but milder proinflammatory profile in the intestine that was also ameliorated by 17938. Our studies demonstrate that each of the two L. reuteri strains has potential therapeutic value in our NEC model and in enteritis associated with cow milk feeding. These results support the concept that L. reuteri may represent a valuable treatment to prevent NEC.

Mesenchymal Stem Cell Therapy in Necrotizing Enterocolitis: A Rat Study

We evaluated the potential therapeutic use of exogenous human bone marrow-derived mesenchymal stem cells (hBM-MSCs) in an experimental rat model of necrotizing enterocolitis (NEC). Thirty-six newborn Sprague-Dawley rats were randomly divided into three groups: NEC, NEC + hBM-MSC, and a control (control and control + hBM-MSC). NEC was induced by enteral formula feeding, exposure to hypoxia-hyperoxia, and cold stress. After NEC was induced, iron-labeled hBM-MSCs were administered by intraperitoneal injection. All pups were killed on the fourth day following injection, and the terminal ileum was excised for a histopathological and immunohistochemical evaluation. The pups in the NEC + hBM-MSC group showed significant weight gains and improvements in their clinical sickness scores (p < 0.01). Bowel damage severity observed in the histopathological evaluation was significantly lower in the NEC + hBM-MSC group than that in the NEC group (p = 0.012). The number of MSCs homing to the bowel was significantly higher in the NEC + hBM-MSC group than that in the control + hBM-MSC group. In conclusion, this is the first study that has evaluated the effectiveness of hBM-MSCs in a neonatal rat NEC model. MSCs reduced histopathological damage significantly.

Poly(ADP-Ribose) Polymerase-1: A Novel Therapeutic Target in Necrotizing Enterocolitis

Necrotizing enterocolitis (NEC) is the most common gastrointestinal disease of infancy, afflicting 11% of infants born 22-28 wk GA. Both inflammation and oxidation may be involved in NEC pathogenesis through reactive nitrogen species production, protein oxidation, and DNA damage. Poly(ADP-ribose) polymerase-1 (PARP-1) is a critical enzyme activated to facilitate DNA repair using nicotinamide adenine dinucleotide (NAD+) as a substrate. However, in the presence of severe oxidative stress and DNA damage, PARP-1 overactivation may ensue, depleting cells of NAD+ and ATP, killing them by metabolic catastrophe. Here, we tested the hypothesis that NO dysregulation in intestinal epithelial cells during NEC leads to marked PARP-1 expression and that administration of a PARP-1 inhibitor (nicotinamide) attenuates intestinal injury in a newborn rat model of NEC. In this model, 56% of control pups developed NEC (any stage) versus 14% of pups receiving nicotinamide. Forty-four percent of control pups developed high-grade NEC (grades 3-4), whereas only 7% of pups receiving nicotinamide developed high-grade NEC. Nicotinamide treatment protects pups against intestinal injury incurred in the newborn rat NEC model. We speculate that PARP-1 overactivation in NEC may drive mucosal cell death in this disease and that PARP-1 may be a novel therapeutic target in NEC.

Protective effects of caffeic acid phenethyl ester (CAPE) on intestinal damage in necrotizing enterocolitis

To determine the preventative effect of caffeic acid phenethyl ester (CAPE) in necrotizing enterocolitis (NEC) in an experimental rat model of NEC. Thirty newborn Sprague-Dawley rats were randomly divided into three groups; as NEC, NEC + CAPE and control. NEC was induced by enteral formula feeding, subjected to hypoxia-hyperoxia and cold stress. Pups in the NEC + CAPE group were treated with CAPE at a dose of 30 mg/kg daily by intraperitoneal route from the first day to the end of the study. All pups were executed on the fourth day. Proximal colon and ileum were allocated for histopathologic and biochemical evaluation, including xanthine oxidase (XO), total antioxidant status (TAS), total oxidant status (TOS), malonaldehyde (MDA) and myeloperoxidase (MPO) activities. The pups in the NEC + CAPE group had better histopathologic and apoptosis evaluations (TUNEL and caspase-9) and the severity of bowel damage was significantly lower in the NEC + CAPE group compared to the NEC group (P < 0.01). The clinical sickness scores and body weight in the NEC + CAPE group was significantly better compared to the NEC group (P < 0.05). Tissue MDA, MPO, XO levels and TOS were remarkably reduced in the NEC + CAPE group, however, TAS was significantly increased in the NEC + CAPE group (P < 0.05). Treatment with CAPE reduces the intestinal damage in NEC.

Gut Environmental Factors May Shape the Persistence of Faecalibacterium Prausnitzii in the Healthy and Diseased Large Intestine

Background: Exposure to Helicobacter hepaticus, common enterohepatic bacteria, increases the incidence of experimental colitis and promotes colonic tumorigenesis. However, the role of H. hepaticus in pathogenesis of necrotizing enterocolitis (NEC) is not known. Neonatal NEC is a devastating disease of prematurely born babies. The cause of NEC is not clear, but inappropriate bacterial colonization plays an important role in NEC pathogenesis. Autophagy protects organisms against diverse pathologies, such as bacterial infections. However, uncontrolled activation of autophagy may lead to cellular injury. Aim: To test the effect of H. hepaticus on development of intestinal injury and expression of inflammatory and autophagic regulators in the rat model of NEC. Methods: Pregnant rats and newborn pups were kept either in H. hepaticus-free or in the H. hepaticus-contaminated environment. Prematurely born rat pups were hand-fed with formula and exposed to asphyxia/cold stress to develop NEC. After 96 hours, all animals were sacrificed and ileal tissue was collected. Incidence of NEC injury, expression of inflammatory cytokines (IL-6, IL-8, IL-18 & TNF-α) and protein levels of autophagy regulators (Beclin 1, LC3II & p62) were evaluated in the ileum. Results: Results: The incidence of NEC was significantly increased to 71% (25/35) in rats exposed to H. hepaticus compared with the H. hepaticus-free group with NEC incidence of 33% (13/39; p < 0.001). The survival rates were not affected by H. hepaticus. The presence of H. hepaticus was detected in the GI tract of the H. hepaticus group. IL-8 and IL-18 gene expression was significantly altered in the H. hepaticus group, whereas IL-6 and TNF-α levels were not changed. Protein levels of Beclin 1 and LC3II were markedly increased, whereas p62 levels were significantly decreased in the ileum from the H. hepaticus group. Conclusions: Helicobacter hepaticus exacerbates intestinal injury and induces intestinal inflammation in the rat NEC model. Exposure to H. hepaticus is also associated with a strong induction of the autophagy pathway in the site of injury the terminal ileum. Inappropriate activation of intestinal autophagy by bacterial insult may facilitate massive cell death, leading to severe mucosal injury. Supported by the NIH Grant HD-39657 (to B.D.)

Ileal Immune Dysregulation in Necrotizing Enterocolitis: Role of CD40/CD40L in the Pathogenesis of Disease

CD40, a co-stimulatory molecule, plays a critical role in coordinating enteric inflammatory immune responses. In necrotizing enterocolitis (NEC), upregulation of IL-10, a CD40-modulated cytokine, has been described, but the role of the IL-10 receptor (IL-10Rβ), CD40, and its ligand CD40L in disease pathogenesis is unknown. The study herein investigates ileal expression of CD40, CD40L, and IL-10R in a rat model of NEC. NEC was induced in newborn rats using established methods of formula feeding, asphyxia, and cold stress. Expression of CD40, CD40L, IL-10Rβ, and other proinflammatory molecules, including Toll-like receptor-4 (TLR-4) and IL-18, was assessed by immunoblotting. Tissue infiltration by macrophages, monocytes, and T cells was examined by confocal immunohistochemistry. Ileum from rat pups with NEC showed increased expression of TLR-4, IL-18, and IL-10Rβ. Sections from both NEC and control pups demonstrated preservation of ileal cells expressing CD40/CD40L. The distal ileum of controls expressed both CD40 and CD40L; conversely, neither molecule was detected in ileal tissue from NEC pups. Additional studies showed that treatment with epidermal growth factor (EGF), previously shown to ameliorate the severity of NEC in an animal model, did not restore CD40 expression. Ileal cytokine dysregulation, manifested by decreased CD40/CD40L and increased IL-10Rβ expression, may be involved in the pathogenesis of NEC. Dampened CD40 signaling may be related to enhanced IL-10 expression and a suppressed T-cell response to injury. We speculate that augmenting CD40-CD40L interactions may achieve a protective effect in this NEC model.

Bifidobacterium bifidum reduces apoptosis in the intestinal epithelium in necrotizing enterocolitis

Necrotizing enterocolitis (NEC) is a devastating intestinal disease of neonates, and clinical studies suggest the beneficial effect of probiotics in NEC prevention. Recently, we have shown that administration of Bifidobacterium bifidum protects against NEC in a rat model. Intestinal apoptosis can be suppressed by activation of cyclooxygenase-2 (COX-2) and increased production of prostaglandin E(2) (PGE(2)). The present study investigates the effect of B. bifidum on intestinal apoptosis in the rat NEC model and in an intestinal epithelial cell line (IEC-6), as a mechanism of protection against mucosal injury. Premature rats were divided into the following three groups: dam fed, hand fed with formula (NEC), or hand fed with formula supplemented with B. bifidum (NEC + B. bifidum). Intestinal Toll-like receptor-2 (TLR-2), COX-2, PGE(2), and apoptotic regulators were measured. The effect of B. bifidum was verified in IEC-6 cells using a model of cytokine-induced apoptosis. Administration of B. bifidum increased expression of TLR-2, COX-2, and PGE(2) and significantly reduced apoptosis in the intestinal epithelium of both in vivo and in vitro models. The Bax-to-Bcl-w ratio was shifted toward cell survival, and the number of cleaved caspase-3 positive cells was markedly decreased in B. bifidum-treated rats. Experiments in IEC-6 cells showed anti-apoptotic effect of B. bifidum. Inhibition of COX-2 signaling blocked the protective effect of B. bifidum treatment in both in vivo and in vitro models. In conclusion, oral administration of B. bifidum activates TLR-2 in the intestinal epithelium. B. bifidum increases expression of COX-2, which leads to higher production of PGE(2) in the ileum and protects against intestinal apoptosis associated with NEC. This study indicates the ability of B. bifidum to downregulate apoptosis in the rat NEC model and in IEC-6 cells by a COX-2-dependent matter and suggests a molecular mechanism by which this probiotic reduces mucosal injury and preserves intestinal integrity.

Epidermal growth factor reduces autophagy in intestinal epithelium and in the rat model of necrotizing enterocolitis

Necrotizing enterocolitis (NEC) is a devastating intestinal disease of premature infants. Epidermal growth factor (EGF) is one of the most promising candidates in NEC prophylaxis. Autophagy regulates cell homeostasis, but uncontrolled activation of autophagy may lead to cellular injury. The aim was to evaluate the effects of EGF on intestinal autophagy in epithelial cells and in the rat NEC model and measure autophagy in NEC patients. Intestinal epithelial cells (IEC-6) and the rat NEC model were used to study the effect of EGF on intestinal autophagy. Protein levels of Beclin 1 and LC3II were measured in the intestinal epithelium in both in vivo and in vitro models. Ultrastructural changes in intestinal epithelium were studied by electron microscopy. Expression of Beclin 1, LC3II, and p62 protein was evaluated in biopsies from NEC patients. Autophagy was induced in IEC-6 cells and inhibited by adding EGF into the culture. In the rat NEC model, EGF treatment of NEC reduced expression of Beclin 1 and LC3II in ileal epithelium. Morphologically, typical signs of autophagy were observed in the epithelium of the NEC group, but not in the EGF group. A strong signal for Beclin 1 and LC3II was detected in the intestine from patients with NEC. Autophagy is activated in the intestinal epithelium of NEC patients and in the ileum of NEC rats. Supplementation of EGF blocks intestinal autophagy in both in vivo and in vitro conditions. Results from this study indicate that EGF-mediated protection against NEC injury is associated with regulation of intestinal autophagy.