Epidermal growth factor reduces hepatic sequelae in experimental necrotizing enterocolitis

Extracellular Nicotinamide Phosphoribosyltransferase Is a Therapeutic Target in Experimental Necrotizing Enterocolitis

Necrotizing enterocolitis (NEC) is the most common gastrointestinal emergency of prematurity. Postulated mechanisms leading to inflammatory necrosis of the ileum and colon include activation of the pathogen recognition receptor Toll-like receptor 4 (TLR4) and decreased levels of transforming growth factor beta (TGFβ). Extracellular nicotinamide phosphoribosyltransferase (eNAMPT), a novel damage-associated molecular pattern (DAMP), is a TLR4 ligand and plays a role in a number of inflammatory disease processes. To test the hypothesis that eNAMPT is involved in NEC, an eNAMPT-neutralizing monoclonal antibody, ALT-100, was used in a well-established animal model of NEC. Preterm Sprague-Dawley pups delivered prematurely from timed-pregnant dams were exposed to hypoxia/hypothermia and randomized to control-foster mother dam-fed rats, injected IP with saline (vehicle) 48 h after delivery; control + mAB-foster dam-fed rats, injected IP with 10 µg of ALT-100 at 48 h post-delivery; NEC-orally gavaged, formula-fed rats injected with saline; and NEC + mAb-formula-fed rats, injected IP with 10 µg of ALT-100 at 48 h. The distal ileum was processed 96 h after C-section delivery for histological, biochemical, molecular, and RNA sequencing studies. Saline-treated NEC pups exhibited markedly increased fecal blood and histologic ileal damage compared to controls (q < 0.0001), and findings significantly reduced in ALT-100 mAb-treated NEC pups (q < 0.01). Real-time PCR in ileal tissues revealed increased NAMPT in NEC pups compared to pups that received the ALT-100 mAb (p < 0.01). Elevated serum levels of tumor necrosis factor alpha (TNFα), interleukin 6 (IL-6), interleukin-8 (IL-8), and NAMPT were observed in NEC pups compared to NEC + mAb pups (p < 0.01). Finally, RNA-Seq confirmed dysregulated TGFβ and TLR4 signaling pathways in NEC pups that were attenuated by ALT-100 mAb treatment. These data strongly support the involvement of eNAMPT in NEC pathobiology and eNAMPT neutralization as a strategy to address the unmet need for NEC therapeutics.

Hepatoblastoma with neonatal necrotizing enterocolitis: Two case reports

We report two children with hepatoblastoma (HB) with a history of neonatal necrotizing enterocolitis (NEC). Case 1 was diagnosed with HB at 5 months of age. Liver enlargement was found during the NEC operation at 3 months of age and then was clinically diagnosed by imaging. After six chemotherapy courses, a partial hepatectomy was performed. Three months after ceasing the chemotherapy, a chest computed tomography scan suggested that distant metastasis of the tumor should be considered, and the lesion was removed. However, 9 months after the operation, alpha-fetoprotein concentrations were increased, and abdominal imaging showed a recurrence of the tumor in situ, resulting in a hepatectomy. Case 2 was diagnosed with NEC shortly after birth and underwent an intestinal resection and anastomosis 1 month later. He was diagnosed with HB at 3 years of age. Hepatectomy was performed after five courses of chemotherapy. Chemotherapy was stopped after 10 courses, and alpha-fetoprotein concentrations were normal. At present, both children have survived and are in a healthy condition. Physicians should be aware of the possibility of HB and a history of NEC in children. Premature birth and low birth weight are common factors leading to the pathogenesis of HB and NEC. The association between these two diseases requires further study.

Necrotizing Enterocolitis: Clinical Features, Histopathological Characteristics, and Genetic Associations

Necrotizing enterocolitis (NEC) is an inflammatory bowel necrosis seen in premature infants. Although the etiopathogenesis of NEC is unclear, genetic factors may alter a patient's susceptibility, clinical course, and outcomes. This review draws from existing studies focused on individual genes and others based on microarray-based high-throughput discovery techniques. We have included evidence from our own studies and from an extensive literature search in the databases PubMed, EMBASE, and Scopus. To avoid bias in the identification of studies, keywords were short-listed a priori from anecdotal experience and PubMed's Medical Subject Heading (MeSH) thesaurus.

Liver damage, proliferation, and progenitor cell markers in experimental necrotizing enterocolitis

BACKGROUND

Necrotizing enterocolitis (NEC) is a disease known to cause injury to multiple organs including the liver. Liver regeneration is essential for the recovery after NEC-induced liver injury. Our aim was to investigate hepatic proliferation and progenitor cell marker expression in experimental NEC.

METHODS

Following ethical approval (#32238), NEC was induced in mice by hypoxia, gavage feeding of hyperosmolar formula, and lipopolysaccharide. Breastfed pups were used as control. We analyzed serum ALT level, liver inflammatory cytokines, liver proliferation markers, and progenitor cell marker expression. Comparison was made between NEC and controls.

RESULTS

Serum ALT level was higher in NEC (p<0.05). The mRNA expression of inflammatory cytokines in the liver was also higher in NEC (IL6: p<0.05, TNF-α: p<0.01). Conversely, mRNA expression of proliferation markers in the liver was lower in NEC (Ki67; p<0.01, PCNA: p<0.01). LGR5 expression was also significantly decreased in NEC as demonstrated by mRNA (p<0.05) and protein (p<0.01) levels.

CONCLUSIONS

Inflammatory injury was present in the liver during experimental NEC. Proliferation and LGR5 expression were impaired in the NEC liver. Modulation of progenitor cell expressing LGR5 may result in stimulation of liver regeneration in NEC-induced liver injury and improved clinical outcome.

LEVEL OF EVIDENCE

Level IV.

Pathogenesis of NEC: Role of the innate and adaptive immune response

Necrotizing enterocolitis (NEC) is a devastating disease in premature infants with high case fatality and significant morbidity among survivors. Immaturity of intestinal host defenses predisposes the premature infant gut to injury. An abnormal bacterial colonization pattern with a deficiency of commensal bacteria may lead to a further breakdown of these host defense mechanisms, predisposing the infant to NEC. Here, we review the role of the innate and adaptive immune system in the pathophysiology of NEC.

Cytokines and growth factors in the developing intestine and during necrotizing enterocolitis

Cytokines and growth factors play diverse roles in the uninflamed fetal/neonatal intestinal mucosa and in the development of inflammatory bowel injury during necrotizing enterocolitis (NEC). During gestational development and the early neonatal period, the fetal/premature intestine is exposed to high levels of many "inflammatory" cytokines and growth factors, first via swallowed amniotic fluid in utero and then, after birth, in colostrum and mother's milk. This article reviews the dual, seemingly counter-intuitive roles of cytokines, where these agents play a "trophic" role and promote maturation of the uninflamed mucosa, but can also cause inflammation and promote intestinal injury during NEC.

Intraluminal intestinal microdialysis detects markers of hypoxia and cell damage in experimental necrotizing enterocolitis

BACKGROUND/PURPOSE

Necrotizing enterocolitis (NEC) represents one of the gravest complications in premature infants and carries significant morbidity and mortality. There is a great need for improved diagnostic methods to reduce the severity and incidence of NEC. The aim of the study was to investigate if intraluminal microdialysis can detect intestinal ischemia in newborn rats with induced experimental NEC.

METHODS

The studies were performed on 1-day-old Sprague-Dawley rat pups. Experimental NEC was induced using hypoxia/reoxygenation treatment. Microdialysis catheters were rectally inserted and placed in the rectosigmoid part of the colon. Microdialysate levels of glucose, lactate, pyruvate, and glycerol were measured. Intestinal specimens were collected at the end of the experiments for microscopic evaluation.

RESULTS

Intraluminal microdialysis revealed signs of intestinal hypoxia and cellular damage, with a marked increase of lactate and glycerol. Microscopic evaluation confirmed intestinal damage in the NEC group.

CONCLUSION

Intraluminal microdialysis can detect intestinal hypoxic stress and mucosal cell membrane decay in a rat model of NEC. Intestinal intraluminal microdialysis is easily accessible through the rectum and may be a useful noninvasive complement to other methods in the assessment of NEC.

The suckling rat as a model for immunonutrition studies in early life

Diet plays a crucial role in maintaining optimal immune function. Research demonstrates the immunomodulatory properties and mechanisms of particular nutrients; however, these aspects are studied less in early life, when diet may exert an important role in the immune development of the neonate. Besides the limited data from epidemiological and human interventional trials in early life, animal models hold the key to increase the current knowledge about this interaction in this particular period. This paper reports the potential of the suckling rat as a model for immunonutrition studies in early life. In particular, it describes the main changes in the systemic and mucosal immune system development during rat suckling and allows some of these elements to be established as target biomarkers for studying the influence of particular nutrients. Different approaches to evaluate these immune effects, including the manipulation of the maternal diet during gestation and/or lactation or feeding the nutrient directly to the pups, are also described in detail. In summary, this paper provides investigators with useful tools for better designing experimental approaches focused on nutrition in early life for programming and immune development by using the suckling rat as a model.

Direct peritoneal resuscitation augments ileal blood flow in necrotizing enterocolitis via a novel mechanism

PURPOSE

Endothelin-1, prostaglandins (PGs), and nitric oxide (NO) have been implicated in the intestinal microvascular dysfunction of necrotizing enterocolitis (NEC). We hypothesized that direct peritoneal resuscitation (DPR) dilates the intestinal microvasculature and improves blood flow independent of these mechanisms.

METHODS

Rat pups were assigned by litter to experimental NEC or CONTROL groups. Laser Doppler flowmetry evaluation of intestinal microvascular blood flow was studied at baseline, with mediator blockade (endothelin-A receptor, endothelin-B receptor, PG synthesis, or NO synthase) and with DPR. Repeated-measures analysis of variance test was applied with Tukey-Kramer honestly significant difference test (P < .05).

RESULTS

At baseline, NEC animals demonstrated significantly decreased ileal blood flow as compared with CONTROLs (P < .05). Endothelin-A receptor and PG inhibition increased flow in the intestinal microvasculature, but this was significantly augmented by the addition of DPR (P < .05). Blockade of NO synthase decreased intestinal blood flow, which was overcome with addition of DPR (P < .05).

CONCLUSION

Ileal blood flow was significantly reduced in NEC animals as compared with CONTROLs. The addition of DPR to the peritoneum increased ileal blood flow significantly in all groups in spite of blockade of these known vasoactive mechanisms. Direct peritoneal resuscitation may be a novel strategy to improve intestinal blood flow in NEC.

Epidermal growth factor and necrotizing enterocolitis

PURPOSE OF REVIEW

This review will summarize the clinical and experimental studies evaluating the role of epidermal growth factor (EGF) in prophylaxis and treatment of necrotizing enterocolitis (NEC).

RECENT FINDINGS

Clinical studies have suggested the importance of EGF in protection of the intestine against NEC, as well as its safety for infants suffering from NEC. The recent experimental studies identified the molecular mechanisms EGF uses for intestinal protection, which involves regulation of intestinal epithelial homeostasis and barrier function. Further studies are necessary to identify the optimal dose, timing, and route of administration of EGF to NEC patients. No clinical studies are currently underway.

SUMMARY

NEC is a devastating problem for preterm neonates, but the exact disease pathogenesis remains unclear. Growing clinical evidence supports the use of EGF as a predictive marker of NEC and its use for prevention and treatment of NEC. In addition, experimental data indicate potential mechanisms of EGF prevention against NEC. These include reduction of inflammation, improvement of barrier function, and regulation of epithelial apoptosis and autophagy.

Milk epidermal growth factor and gut protection

Maternal milk is a complex fluid, with multifunctional roles within the developing gastrointestinal tract. Epidermal growth factor (EGF) and heparin-binding EGF-like growth factor (HB-EGF) are members of the family of EGF-related peptides. Biological actions of these growth factors are mediated via interaction with the EGF-receptor (EGF-R). In the early postnatal period, breast milk is the major source of EGF for the developing intestinal mucosa. HB-EGF is also detected in breast milk, but in concentrations 2 to 3 times lower than EGF. With normal physiological conditions, the intestinal epithelium undergoes a continuing process of cell proliferation, differentiation, and maturation. EGF plays an important role in these processes. In pathophysiologic situations, EGF contributes to epithelial protection from injury and post-injury mucosal repair. Necrotizing enterocolitis (NEC) is a devastating disease affecting infants born prematurely. The pathogenesis of NEC is not known, and there is no effective treatment for this disease. In an experimental NEC model, oral administration of a physiological dose of EGF significantly reduces the incidence and severity of NEC. HB-EGF provides similar protection against NEC, but only when pharmacological doses are used. Further studies are necessary before EGF can be introduced as an efficient therapeutic approach of intestinal injury.

Antecedents of Bell stage III necrotizing enterocolitis

OBJECTIVE

New biopharmaceuticals hold promise for preventing or treating necrotizing enterocolitis. However, it is unclear whether any such biopharmaceutical that requires enteral administration could be administered using an 'early-treatment' paradigm. This study was undertaken to assess this issue based on data from every case of Bell stage III NEC cared for during the past 7 years at Intermountain Healthcare.

STUDY DESIGN

Patients with Bell stage III NEC were identified from electronic medical record repositories and the diagnosis was validated using operative reports. Electronic and paper records of each patient were then used to identify potential clinical and laboratory antecedents occurring within the 48 h period preceding the diagnosis of NEC.

RESULT

One hundred eighteen patients had Stage III NEC. The earliest recognized antecedents were nonspecific for NEC (apnea/bradycardia, skin mottling and irritability). These were recorded at 2.8+/-2.1, 4.5+/-3.1 and 5.4+/-3.7 (mean+/-s.d.) hours, respectively, before NEC was diagnosed. The most commonly identified gastrointestinal antecedents were blood in the stools, increased abdominal girth and elevated pre-feeding gastric residuals or emesis. These were identified 2.0+/-1.9, 2.8+/-3.1 and 4.9+/-4.0 h before NEC was recognized. Thirty-eight percent had a blood transfusion (18+/-12 h) preceding the NEC. Tachycardia, tachypnea, hypotension and diarrhea were rarely identified as antecedents and no consistent laboratory antecedents were discovered.

CONCLUSION

We judge that an 'early treatment of NEC' paradigm testing any pharmacological agent that must be administered enterally is not feasible. The first recognized antecedents of Bell stage III NEC are nonspecific for gastrointestinal pathology and insufficient time exists for dosing between the first gastrointestinal signs and placement of the gastric decompression tube.

Heat susceptibility of interleukin-10 and other cytokines in donor human milk

OBJECTIVE

Holder pasteurization renders donor human milk safe for consumption. Because human milk reduces the risk of necrotizing enterocolitis in preterm infants, we tested whether Holder pasteurization affects certain factors in human milk that protect the intestines: epidermal growth factor (EGF), transforming growth factor (TGF)-beta1, erythropoietin (EPO), and interleukin (IL)-10. Donor human milk from a milk bank was examined.

METHODS

The aqueous phase of 17 samples of donor term human milk (mean duration of lactation, 8 +/- 3.5 months) was examined before and after Holder pasteurization. In the case of IL-10, lesser degrees of pasteurization were also evaluated. The agents were quantified using enzyme immunoassays. The function of IL-10 was also tested.

RESULTS

Concentrations of EGF and IL-10 were markedly lower than previously reported values in human milk from earlier phases of lactation. Holder pasteurization significantly reduced the concentrations of EPO and IL-10, whereas lesser degrees of heating increased the detection of IL-10. The immunosuppression of T-cell proliferation by human milk, thought to be attributed to IL-10 alone, persisted after Holder pasteurization.

CONCLUSIONS

Holder pasteurization greatly decreased concentrations of EPO and IL-10 in human milk. These decreases may impact the ability of human milk to protect against necrotizing enterocolitis. Evidence of possible binding of IL-10 to other proteins in human milk was also found. Experiments to test whether Holder pasteurization affects the function of IL-10 in human milk produced evidence for an agent in human milk other than IL-10 that inhibits T-cell proliferation and resists Holder pasteurization.

Changes in hepatic cell junctions structure during experimental necrotizing enterocolitis: effect of EGF treatment

Necrotizing enterocolitis (NEC) is a devastating disease of premature babies. Previously, we have shown that EGF reduces NEC and that overproduction of hepatic TNF-alpha is associated with intestinal damage. Leakage of TNF-alpha may be a consequence of epithelial hepatic cellular junction dysfunction. The aim of this study was to investigate changes in the composition of hepatic tight junctions (TJs) and adherens junctions (AJs). Using an established rat model of NEC, animals were divided into the following groups: dam fed (DF), formula fed (NEC), or fed with formula supplemented with EGF (EGF). Serum EGF and histologic localization of major TJ and AJ proteins were evaluated. Distribution patterns of hepatic TJ and AJ proteins were significantly altered in the NEC group compared with those in DF or EGF groups. Cytoplasmic accumulation of occludin, claudin-2, and ZO-1 with reduction of claudin-3 signal was detected in the liver of NEC rats. Localization of beta-catenin was associated with the hepatocyte membrane in EGF and DF groups, but diffused in the NEC group. These data show that hepatic cellular junctions are significantly altered during NEC pathogenesis. EGF-mediated reduction of experimental NEC is associated with protection of hepatic integrity and structure.

CD4+ lymphocytes control gut epithelial apoptosis and mediate survival in sepsis

Lymphocytes help determine whether gut epithelial cells proliferate or differentiate but are not known to affect whether they live or die. Here, we report that lymphocytes play a controlling role in mediating gut epithelial apoptosis in sepsis but not under basal conditions. Gut epithelial apoptosis is similar in unmanipulated Rag-1(-/-) and wild-type (WT) mice. However, Rag-1(-/-) animals have a 5-fold augmentation in gut epithelial apoptosis following cecal ligation and puncture (CLP) compared to septic WT mice. Reconstitution of lymphocytes in Rag-1(-/-) mice via adoptive transfer decreases intestinal apoptosis to levels seen in WT animals. Subset analysis indicates that CD4(+) but not CD8(+), gammadelta, or B cells are responsible for the antiapoptotic effect of lymphocytes on the gut epithelium. Gut-specific overexpression of Bcl-2 in transgenic mice decreases mortality following CLP. This survival benefit is lymphocyte dependent since gut-specific overexpression of Bcl-2 fails to alter survival when the transgene is overexpressed in Rag-1(-/-) mice. Further, adoptively transferring lymphocytes to Rag-1(-/-) mice that simultaneously overexpress gut-specific Bcl-2 results in improved mortality following sepsis. Thus, sepsis unmasks CD4(+) lymphocyte control of gut apoptosis that is not present under homeostatic conditions, which acts as a key determinant of both cellular survival and host mortality.

Comparison of epidermal growth factor and heparin-binding epidermal growth factor-like growth factor for prevention of experimental necrotizing enterocolitis

BACKGROUND

Necrotizing enterocolitis (NEC) is a devastating gastrointestinal disease of prematurely born infants. Epidermal growth factor (EGF) and heparin-binding EGF-like growth factor (HB-EGF) have protective effects against intestinal injury. The aim of this study was to compare the effect of oral administration of HB-EGF, EGF, or both on the incidence of NEC in a neonatal rat model.

MATERIALS AND METHODS

Premature rats were fed by hand and exposed to asphyxia and cold stress to develop NEC. Four diets were used: formula (NEC), formula supplemented with 500 ng/mL HB-EGF (HB), 500 ng/mL EGF (EGF), or a combination of both (E+HB). Ileal injury, endogenous HB-EGF production, expression of EGF receptors, goblet cell density, and expression of apoptotic proteins were evaluated.

RESULTS

Oral administration of either EGF or HB-EGF significantly reduced the incidence of NEC; however, EGF provided better protection in physiologically relevant doses. Simultaneous administration of both growth factors did not result in any synergistic protective effect against NEC. There were no significant differences between treatment groups in ileal gene expression of EGF receptors or HB-EGF. However, the balance of apoptotic proteins in the ileum was shifted in favor of cell survival in EGF-treated rats. This mechanism may be responsible for the higher efficiency of EGF protection against NEC.

CONCLUSIONS

These data suggest that a physiological dosage of EGF or a pharmacological dosage of HB-EGF could be used for prevention of NEC.

Decreased development of necrotizing enterocolitis in IL-18-deficient mice

Necrotizing enterocolitis (NEC) is a devastating gastrointestinal disease predominantly of prematurely born infants, characterized in its severest from by extensive hemorrhagic inflammatory necrosis of the distal ileum and proximal colon. Proinflammatory cytokines have been implicated in the development of NEC, and we have previously shown that IL-18 is significantly elevated in the well-established neonatal rat model of NEC. To determine whether IL-18 contributes to intestinal pathology in NEC, we subjected IL-18 knockout mice to the protocol used to develop experimental NEC in newborn rats. Newborn B6.129P2-Il18(tm1Aki)/J (NEC IL-18(-/-)) and wild-type (NEC WT) mice were hand fed every 3 h with cow's milk-based formula and exposed to asphyxia and cold stress twice daily. After 72 h, animals were killed and distal ileum and liver were removed. Disease development was determined via histological changes in the ileum as scored by a blinded evaluator. The number of TNF-alpha-, IL-12-, and IL-1beta-positive cells and macrophages were determined in both ileum and liver via immunohistology. IkappaB-alpha and IkappaB-beta were determined from protein extracts from both ileum and liver using Western blot analysis. The incidence and severity of NEC was significantly reduced in NEC IL-18(-/-) mice compared with NEC WT. Furthermore, mean ileal macrophages and hepatic IL-1beta were significantly reduced in IL-18(-/-) mice subjected to the NEC protocol. There were no statistically significant changes in Kupffer cells, hepatic TNF-alpha, ileal IL-1beta, or IL-12. IkappaB-alpha and IkappaB-beta were significantly increased in NEC IL-18(-/-) mice ileum and liver, respectively. These results confirm that IL-18 plays a crucial role in experimental NEC pathogenesis.

High-dose erythropoietin inhibits apoptosis and stimulates proliferation in neonatal rat intestine

BACKGROUND

Erythropoietin (Epo) receptors are widely expressed in the small bowel of neonatal rats and evidence suggests Epo has important trophic effects in developing bowel.

OBJECTIVE

To compliment in vitro data, we directly examine in vivo the hypotheses that systemic Epo treatment can promote cell division and enterocyte migration, and arrest apoptosis in the ileum of neonatal rats.

DESIGN

Epo (5000 U/kg s.c.) or vehicle treatments were given to one week old Sprague-Dawley rats (n = 86) along with timed injections of the thymidine analog 5-bromo-2-deoxyuridine (BrdU, 50mg/kg s.c.) to label DNA synthesis and track newly proliferating cells. To characterize the time course of effects, animals were killed at scheduled times from 30 min to 24 h after treatment. BrdU-containing cells were immunostained and counted in intestinal crypts, villi, and muscle wall of ileum. Effects of Epo on apoptosis were analyzed by TUNEL staining. Calibrated measurements were made to determine the density or relative proportion of BrdU- and TUNEL-positive cells.

RESULTS

Systemic high-dose Epo promoted cell division in intestinal smooth muscle and enterocytes, stimulated migration of intestinal epithelial cells, and arrested apoptosis of enterocytes at the villous tips.

CONCLUSION

These data provide in vivo evidence that Epo functions trophically in developing intestine tissues.

The role of the intestinal barrier in the pathogenesis of necrotizing enterocolitis

Necrotizing enterocolitis (NEC) is the leading cause of death from gastrointestinal disease in neonates and is increasing in frequency because of recent advances in neonatal care. NEC develops in a stressed preterm infant in the setting of intestinal barrier disruption, systemic inflammation, and leads to, multisystem organ failure. The intestinal barrier lies at the interface between microbes within the intestinal lumen and the immune system of the host, and has both immunological and mechanical components. These components serve to protect the host from invading pathogens and, at the same time, provide a surface area for nutrient absorption. Factors that lead to impairments in the function of the intestinal barrier may predispose the host to the invasion of gut-derived microbes and to the development of systemic inflammatory disease. This process, termed "bacterial translocation," may be compounded during instances in which the mechanisms that regulate the repair of the intestinal barrier are disrupted. Bacterial translocation is of particular concern to the newborn patient, in which immaturity of the mechanical barrier and incomplete development of the host immune system combine to render the host at particular risk for the development of intestinal inflammation. This review will serve to provide an overview of recent evidence regarding the components of the intestinal barrier, and the mechanisms by which disruptions in barrier function may contribute to the pathogenesis of NEC.