Maternal milk reduces severity of necrotizing enterocolitis and increases intestinal IL-10 in a neonatal rat model

Apical sodium-dependent bile acid transporter upregulation is associated with necrotizing enterocolitis

Necrotizing enterocolitis (NEC) is the most common gastrointestinal emergency of premature infants. Previously, we showed that luminal bile acids (BAs) are increased and correlated with disease development and that the apical sodium-dependent BA transporter (ASBT), which transports BAs from the ileal lumen into enterocytes, is upregulated in rats with NEC. We hypothesized that intraenterocyte, rather than luminal, BAs are associated with NEC and that upregulation of ASBT may be a mechanism by which this occurs. Neonatal rats with or without the ASBT inhibitor SC-435, mice in which ASBT was knocked out, and mice that overproduce BAs were subjected to the NEC protocol. Disease development, ASBT, and the farnesoid X receptor protein, along with luminal and intraenterocyte BA levels, were assessed. In addition, ileal sections from premature infants with and without NEC were examined for ASBT via immunohistology and real-time PCR. When BAs were not transported into enterocytes (rats given SC-435 and ASBT knockout mice), severity and incidence of NEC were reduced. In contrast, in mice that overproduce BAs, ASBT was elevated, intraenterocyte BAs were increased, and disease development was increased. ASBT staining was more intense on the apical membrane of ileal enterocytes from premature infants with NEC than premature infants with non-NEC diagnoses. In addition, ASBT mRNA levels were significantly higher in infants with NEC. These data show that accumulation of intraenterocyte BAs contributes to disease development, elevated ASBT increases disease severity in experimental models of NEC, and ASBT is elevated in human NEC. These data confirm that BAs and upregulation of ASBT play a crucial role in NEC pathogenesis and suggest that inhibition of ASBT could be utilized as a therapeutic modality against this disease.

Doppler sonographic findings in an experimental rabbit model of necrotizing enterocolitis

OBJECTIVE

The purpose of this study was to examine the clinical applicability of Doppler sonography by evaluating Doppler sonographic findings in an experimental rabbit model of necrotizing enterocolitis (NEC).

METHODS

Necrotizing enterocolitis was experimentally induced using a combination of endotoxin, hypoxia, and cold stress in 23 rabbits. Doppler sonography was performed to obtain the Doppler spectrum of the superior mesenteric artery. From the flow profile, the peak systolic velocity (PSV) and resistive index (RI) were calculated at 5 time sessions: initial and 1 to 2, 3 to 4, 5 to 6, and 20 to 24 hours. Animals were divided into 2 groups based on pathologic NEC scores (NEC-positive [NEC+] group versus NEC-negative [NEC-] group). Differences between the groups with regard to RI and PSV values were evaluated for each time session.

RESULTS

Comparison of RI and PSV values between the NEC+ and NEC- groups revealed a significant increase in the PSV in the NEC+ group during the 1- to 2-hour session (P = .0199). Comparison of RI and PSV differences revealed a significant increase in RI and PSV differences in the NEC+ group during the 1- to 2-hour session (P = .0095 and .0013, respectively). In the other time sessions, there was no difference between the groups.

CONCLUSIONS

The NEC+ group showed a significant increase in the PSV and RI during the 1- to 2-hour period.

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.

Energy expenditure for breastfeeding and bottle-feeding preterm infants

OBJECTIVE

We hypothesized that resting energy expenditure (REE) would be higher after breastfeeding than after bottle-feeding.

METHODS

Nineteen preterm infants (gestational age: 32 weeks) in stable condition who were nourished entirely with their mothers' breast milk were assigned randomly to feeding either by bottle or at the breast. Each infant served as his or her own control subject. REE was measured for 20 minutes after feeding. Breast milk quantity was evaluated with prefeeding and postfeeding weighing. REE values for bottle-feeding and breastfeeding were compared with paired t tests.

RESULTS

Contrary to our null hypothesis, the group's mean REE values after bottle-feeding and breastfeeding were very similar (284.7 +/- 26.8 kJ/kg per day [68.3 +/- 6.4 kcal/kg per day] vs 282.6 +/- 28.5 kJ/kg per day [67.5 +/- 6.8 kcal/kg per day]; not significant). The duration of feeding was significantly longer for breastfeeding than for bottle-feeding (20.1 +/- 7.9 vs 7.8 +/- 2.9 minutes; P < .0001).

CONCLUSION

There was no significant difference in REE when infants were breastfed versus bottle-fed. Longer feeding times at the breast did not increase REE. We speculate that it is safe to recommend feeding at the breast for infants born at >32 weeks when they can tolerate oral feeding.

Changes in intestinal Toll-like receptors and cytokines precede histological injury in a rat model of necrotizing enterocolitis

It is unclear whether the broad inflammatory response shown in neonatal necrotizing enterocolitis (NEC) is the cause or the effect of tissue injury. Toll-like receptors (TLRs) on intestinal dendritic, mononuclear, and epithelial cells recognize bacterial ligands and damaged tissues, thus activating the inflammatory response. The present study aimed to determine whether active TLR signaling would precede histological injury in NEC. Newborn rat pups were divided into four groups: dam fed, dam fed-hypoxic, formula fed, and formula fed-hypoxic (NEC). The ileal tissues were evaluated for NEC scores at 24, 48, 72, and 120 h. Quantitative real-time reverse transcription-polymerase chain reaction and immunohistochemistry were used to measure and localize intestinal TLRs. Cytokines were assessed by a multispot cytokine array. Among the four groups, ileal injury was seen only after 72 h of formula feeding and hypoxia. We found selective induction of mRNA levels in NEC compared with dam-fed controls for TLR2 > TLR4 > TLR1 = TLR3, TLR7, and TLR9 > TLR6 (P < 0.01); TLR5 was downregulated (P < 0.01). All TLR changes started at 48 h, before any histological evidence of NEC. Both Th1-type cytokines (IFN-gamma, IL-1beta, TNF-alpha, and KC/GRO) and Th2-type cytokines (IL-4, IL-5 and IL-13) were significantly increased in NEC but also in nondamaged formula-fed rat ileum. In conclusion, the intestinal expression of TLRs and cytokines precedes histological injury in the experimental NEC.

Medical ozone therapy reduces oxidative stress and intestinal damage in an experimental model of necrotizing enterocolitis in neonatal rats

PURPOSE

Necrotizing enterocolitis (NEC) remains a major cause of morbidity and death in neonates. Evidence suggests that an imbalance between activated proinflammatory response with inadequate antiinflammatory protection results in NEC. Ozone has been proposed as an antioxidant enzyme activator, immunomodulator, and cellular metabolic activator. Therefore, this study was designed to investigate whether medical ozone therapy is effective on neonatal rat model of NEC.

MATERIALS AND METHODS

Thirty-eight newborn Sprague-Dawley pups were randomly divided into 3 groups of NEC, NEC + ozone, and control (left to breast feed). Necrotizing enterocolitis was induced by enteral formula feeding and exposure to 100% carbon dioxide inhalation for 10 minutes after +4 degrees C cold exposures for 5 minutes and 97% oxygen for 5 minutes 2 times daily. The NEC + ozone group received 0.7 mg/kg per day ozone/oxygen mixture intraperitoneally for a total of 3 days after first day of NEC procedure. The pups were killed at fourth day, and their intestinal tissues were harvested for biochemical and histopathologic analysis. Blood sample from pups were also obtained.

RESULTS

The mortality rate and the weight loss were significantly higher in NEC group than control and treatment groups. Oxidative stress markers (malondialdehyde and protein carbonyl content) significantly increased and antioxidant enzyme activities (superoxide dismutase and glutathione peroxidase) were significantly decreased in NEC group. All these biochemical changes were ameliorated in NEC + ozone group. Nitrate plus nitrite levels and serum tumor necrosis factor alpha were elevated in NEC group and reduced in treatment group. In addition, histopathologic injury score of NEC group was significantly higher than NEC + ozone group.

CONCLUSION

Ozone treatment significantly reduced the severity of NEC by modulating antioxidative defense and antiinflammatory protection in our experimental animal model.

Prevention of necrotising enterocolitis: Year 2004 and beyond

The incidence of necrotising enterocolitis (NEC) has not changed significantly despite the dramatic advances in perinatal-neonatal care. The absolute number of survivors of NEC is expected to rise, as prevention of prematurity, the single most important risk factor for the illness, continues to be difficult. Prevention of NEC has thus become an area of research priority. Given the role of inflammatory mediators in its pathogenesis newer immune modulators are being studied as potential agents for prevention/treatment of NEC. Caution, however, is warranted because the failure of sepsis trials in adults has clearly indicated that the concept of down-regulating the inflammatory response is deceptively simple. Clinical trials of any such promising preventative agent(s) need to be designed carefully and must include long-term neurodevelopmental outcomes as almost an entire population of high-risk preterm neonates will be exposed to their adverse effects. As new frontiers continue to be explored, the proven benefits of simple and safe interventions like antenatal glucocorticoid therapy and the preferential use of breast milk for feeding high-risk neonates must not be forgotten. Given that a single effective agent is unlikely in the near future, utilizing a package of "potentially better practices" seems to be the most appropriate strategy to prevent and minimize NEC.

The effects of formula feeding on physiological and immunological parameters in the gut of neonatal rats

A unique model of formula feeding in the neonatal rat was utilized to investigate the effects of an enterally delivered artificial milk formula on clinically relevant immunological and biological characteristics in the gut, compared to naturally reared pups. Hooded Wistar rat pups were randomly allocated to two treatment groups: formula-fed (FF) or naturally suckled (NS). A flexible silastic intra-gastric cannula was surgically implanted into the FF pups, through which an artificial rat milk supplement was continuously delivered from day 4 to day 10 of life. Rat pups were sacrificed at 10 days of age. Body weight, small intestinal weight, mucosal CD8(+) cell numbers, and ileal lactase activity in FF animals were significantly decreased compared to their NS counterparts (P < 0.05). Numbers of eosinophils, mucosal mast cells, CD4(+) T-cells, ileal villus height and gastric emptying times were significantly increased in FF pups (P < 0.05). We have developed a new rat model of artificial feeding which possesses important immunological and biological similarities to the premature human infant.

Hyperbaric oxygen therapy reduces the severity of necrotizing enterocolitis in a neonatal rat model

INTRODUCTION

Hyperbaric oxygen (HBO) therapy is known to increase oxygen concentration in tissues leading to induction of an adaptive increase in antioxidants, stimulation of angiogenesis, improvement of white blood cell action, and regulation of inflammatory process. Therefore, we tested the potential beneficial effect of HBO in neonatal rat model of necrotizing enterocolitis (NEC).

MATERIALS AND METHODS

Thirty newborn Sprague-Dawley rats, provided by the Experimental Research Council, Gulhane Military Medical Academy, Ankara,Turkey, were randomly divided into 3 groups as follows: NEC, NEC + HBO, and control. Necrotizing enterocolitis was induced by enteral formula feeding and exposure to hypoxia after cold stress at 4 degrees C and oxygen. The NEC + HBO group received HBO at 2.8 atmosphere absolute (ATA) for 90 minutes daily for 3 days. The pups were killed on the fourth day, and their intestinal tissues were harvested for biochemical and histopathologic analysis. Blood samples were also obtained from the pups.

RESULTS

The mortality rate was highest in the NEC group (3 pups in the NEC group vs 1 pup in the NEC + HBO group). Malondialdehyde and protein carbonyl content were significantly increased, whereas superoxide dismutase and glutathione peroxidase were significantly decreased in the NEC group. All these changes were similar to control levels in the NEC group by HBO treatment. Nitrate plus nitrite (NO(x)) levels and serum tumor necrosis factor alpha were increased in the NEC group and histopathologic injury score and apoptosis index in the NEC group were significantly higher than in the NEC + HBO group.

CONCLUSION

Hyperbaric oxygen significantly reduced the severity of NEC in our study.

The relationship between feeding and necrotizing enterocolitis in very low birth weight infants

Necrotizing enterocolitis (NEC) is the most common gastrointestinal emergency in the NICU, with often devastating consequences. The etiology of NEC is probably multifactorial, with preterm infants at the highest risk. The relationship between feeding and NEC was identified in the 1970s, leading to delayed feeding becoming standard treatment in NICUs. More recent research suggests that early feedings not only are safe, but reduce other morbidities associated with prematurity. Standardized feeding guidelines seem to confer some benefits in decreasing NEC, despite a wide variability in feeding practices within the published guidelines. A standardized approach to the management of feeding problems may be the key. This article briefly reviews the pathogenesis of NEC and examines studies of various feeding practices for their relationship to the development of NEC. It also highlights the potential benefits of breast milk in NEC prevention.

Oropharyngeal administration of colostrum to extremely low birth weight infants: theoretical perspectives

Studies in adults have shown that the oropharyngeal route can be used to effectively and safely administer interferon-alpha, an immune cell-derived cytokine, to patients who are unable to tolerate its parenteral administration. The mechanism for this appears to be the stimulatory effects of the cytokine, on the oropharyngeal-associated lymphoid tissue system. Own mother's colostrum (OMC) is rich in cytokines and other immune agents that provide bacteriostatic, bacteriocidal, antiviral, anti-inflammatory and immunomodulatory protection against infection. OMC may be especially protective for the extremely low birth weight (ELBW) infant in the first days of life; however clinical instability typically precludes enteral feedings during this period. Oropharyngeal administration is a potential alternative method of providing OMC. Oropharyngeal administration of OMC may have immunomodulatory effects on the recipient infant, and would be especially beneficial to the ELBW infant who would otherwise remain nil per os during the first days of life.

The development of animal models for the study of necrotizing enterocolitis

Necrotizing enterocolitis (NEC) is the leading cause of death and long-term disability from gastrointestinal disease in preterm infants, and is characterized by acute and chronic intestinal inflammation that may lead to systemic sepsis and multi-system organ failure. NEC typically develops in the preterm infant after the administration of tube feeds, although it may occasionally be seen in full-term babies. Despite extensive clinical experience in the management of patients with NEC, the underlying cellular and molecular mechanisms leading to its development remain incompletely understood. Several animal models have therefore been developed in a variety of species in order to study the pathogenesis of NEC and to develop more effective treatment strategies. This review seeks to examine the pros and cons of animal models that have been developed in the study of NEC over the past 30 years. It will highlight the various strengths and weaknesses of experimental approaches that have been used, and discuss potential directions for the development of such models for the future.

Uso de fatores de crescimento epidérmico e estimulador de colônias de granulócitos na prevenção e tratamento da enterocolite necrosante no recém-nascido

OBJETIVO: Revisar os conhecimentos existentes em relação ao uso de fatores de crescimento epidérmico e estimulador de colônias de granulócitos na prevenção e/ou no tratamento da enterocolite necrosante (ECN) durante o período neonatal. FONTES DE DADOS: Revisão da literatura, nas bases de dados Medline, Lilacs, SciELO e PubMed, utilizando os unitermos "recém-nascidos", "enterocolite" e "fatores de crescimento", no período de 2003 a 2007. Nesta busca, 49 artigos foram encontrados, sendo 17 pertinentes ao tema. Também foram utilizados outros artigos, independente do ano de publicação, relacionados a aspectos definidores da ECN no recém-nascido. SÍNTESE DOS DADOS: A ECN continua sendo responsável por uma elevada morbimortalidade neonatal. Os mecanismos fisiopatológicos vêm sendo elucidados e, a partir deles, são discutidas novas terapias, como o uso de fatores de crescimento, destacando-se o fator de crescimento epidérmico e o fator estimulador de colônias de granulócitos. CONCLUSÕES: O uso de fatores de crescimento no tratamento e prevenção da ECN neonatal parece promissor. É necessário maior número de ensaios clínicos para comprovar sua eficácia e segurança. Enquanto isso, a melhor prática médica continua sendo a prevenção da doença.

Does abnormal bile acid metabolism contribute to NEC?

Bile acids (BAs) facilitate emulsification, absorption, and transport of fats and sterols in the intestine and liver and are essential for normal digestion. However, accumulation of BAs in the intestine can result in damage to the intestinal epithelium. Using the neonatal rat model of necrotizing enterocolitis (NEC), we have recently shown that BAs accumulate in both the ileal lumen and enterocytes of neonatal rats with NEC and the increased BA levels are positively correlated with disease severity. Importantly, when BAs are not allowed to accumulate, neonatal rat pups develop significantly less disease. In addition, BA transporters are altered during disease development. These data indicate that BAs play an important role in the development of experimental NEC, and suggest that the inability of neonatal rats to adequately regulate BA transporters may be a mechanism by which ileal damage occurs.

Temporal changes in insulin-like growth factors I and II and in insulin-like growth factor binding proteins 1, 2, and 3 in human milk

AIM

To evaluate the postpartum time course of changes in insulin-like growth factors (IGFs) and their binding proteins (IGFBPs).

METHODS

Breast milk IGF-I and IGF-II and IGFBP-1, IGFBP-2, and IGFBP-3 levels were determined in 23 women with babies born at term, from day 4 until up to 9 months after birth.

RESULTS

The IGFBP-3 levels were highest from day 4 to day 6 and then decreased by days 10-12. In contrast, IGF-I and IGF-II and IGFBP-1 and IGFBP-2 showed little change over the first 2 weeks after birth. Subsequently, all the IGF components showed a moderate decline over approximately the first 1-3 months and then stable levels up to 9 months after birth.

CONCLUSION

Although the possibility cannot be excluded that these changes in levels of IGFs and their binding proteins in human milk represent passive loss from the mammary gland, we speculate that higher early levels of the human milk IGF system contribute to maturation of the infant gut.

Prevention and treatment of necrotising enterocolitis in preterm neonates

Prevention and treatment of NEC has become an area of priority for research due to the increasing number of preterm survivors at risk, and the significant mortality and morbidity related to the illness. Probiotic supplementation appears to be a promising option for primary prevention of NEC but further large trials are necessary for documenting their safety in terms of sepsis as well as long-term neurodevelopmental outcomes and immune function. As new frontiers including immunomodulating agents like pentoxifylline continue to be explored, the impact of well-established simple strategies like antenatal glucocorticoid therapy, and early and preferential use of breast milk must not be forgotten. Clinical research on manifestations of ileus of prematurity, and feeding in the presence of common risk factors such as IUGR is needed. Safety of minimal enteral feeds in terms of NEC and benefits of standardised feeding regimens need to be confirmed. Association of common clinical practices such as red cell transfusions, H2 receptor blockade, and thickening of feeds with NEC warrants attention. An approach utilising a package of potentially better practices seems to be the most appropriate strategy for the prevention and treatment of NEC.

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.

Maternal milk contains antimicrobial factors that protect young rabbits from enteropathogenic Escherichia coli infection

Enteropathogenic Escherichia coli (EPEC) colibacillosis represents a major cause of lethal diarrhea in young children in developing countries. EPEC strains also infect numerous mammal species and represent a major economical problem in rabbit industry. Protection against this pathogen is a challenging goal both in humans and in other mammal species. Despite a good knowledge of the pathogenicity mechanisms of EPEC, the intrinsic and environmental factors that control the expression of EPEC virulence in mammals remain unknown. For instance, the exacerbated sensitivity of young mammals to EPEC infection is still unexplained. Our goal was to investigate if age or other factors, like milk consumption, could be determinants that trigger the disease. We used rabbits as an animal model to study the role of milk in the sensitivity to an EPEC infection. Weaned and suckling rabbits were orally inoculated with EPEC strain E22 (O103:H2:K-) at 28 days of age, and the evolution of the disease was investigated in the two groups. In addition, in order to better characterize the interactions between milk and EPEC, we determined in vitro bacterial growth and the abilities of EPEC cells to adhere to epithelial cells in the presence of milk. Our results demonstrate a protective role of milk in vivo in association with in vitro antibacterial activity. These effects are independent of the presence of specific anti-EPEC antibodies.

Seasonal changes in the intestinal immune system of hibernating ground squirrels

Hibernation is associated with a prolonged fast (5-8 mo) which has the potential to affect intestinal immunity. We examined several aspects of the intestinal immune system in summer (non-hibernating) and hibernating ground squirrels. Peyer's patches were largely unaffected by hibernation, but numbers of intraepithelial lymphocytes (IEL) and lamina propria leukocytes (LPL) were greater in hibernators compared with summer. Hibernator IEL were less mature as demonstrated by low numbers of cells expressing activation-associated markers and co-receptors. Compared with summer, the percentage of B cells was higher and percentage of T cells was lower in the hibernator LPL. Hibernation was associated with greater mucosal levels of IFN-gamma, TNF-alpha, IL-10 and IL-4, but IL-6 and TGF-beta were unchanged. Mucosal IgA levels were greater in entrance and torpid hibernators compared with summer. The results suggest that modifications of the intestinal immune system during hibernation may help preserve gut integrity throughout the winter fast.

Heparin-binding epidermal growth factor-like growth factor promotes enterocyte migration and proliferation in neonatal rats with necrotizing enterocolitis

PURPOSE

We have shown that heparin-binding epidermal growth factor-like growth factor (HB-EGF) decreases experimental necrotizing enterocolitis (NEC). Intestinal epithelial cell (IEC) migration (restitution) and proliferation are key elements in recovery from intestinal injury. Here, we investigated whether the beneficial effects of HB-EGF are mediated, in part, by its ability to affect these processes.

METHODS

Necrotizing enterocolitis was induced in newborn rats by exposure to stress (hypoxia, hypothermia, hypertonic feedings, and lipopolysaccharide), with pups receiving different doses of HB-EGF (0, 25, 50, 100, 200, 400, 600, and 800 microg/kg). To investigate the effect of HB-EGF on enterocyte proliferation and migration, bromodeoxyuridine was administered intraperitoneally 18 hours before sacrifice, with intestine subjected to bromodeoxy-uridine immunohistochemistry.

RESULTS

The incidence and severity of experimental NEC decreased, and the survival rate increased, with increasing doses of HB-EGF. Results were confirmed using scanning electron microscopy. Migration of IEC in breast-fed pups was 7.07 microm/h, decreased significantly to 2.29 microm/h in stressed pups, and was significantly improved at 5.95 microm/h in pups subjected to stress but treated with HB-EGF (P < .05). Quantification of IEC proliferation revealed 208 (+) cells per high-power field (HPF) in breast-fed pups, which decreased significantly to 99 (+) cells per HPF in stressed pups and increased to 190 (+) cells per HPF in stressed pups treated with HB-EGF (P < .05).

CONCLUSIONS

These results demonstrate that HB-EGF protects newborn rats from experimental NEC in a dose-dependent fashion. The ability of HB-EGF to protect the intestines from NEC is due, in part, to the ability of HB-EGF to preserve enterocyte migration and proliferation.

Intestinal barrier failure during experimental necrotizing enterocolitis: protective effect of EGF treatment

Necrotizing enterocolitis (NEC) is the most common intestinal disease of premature infants. Although increased mucosal permeability and altered epithelial structure have been associated with many intestinal disorders, the role of intestinal barrier function in NEC pathogenesis is currently unknown. We investigated the structural and functional changes of the intestinal barrier in a rat model of NEC. In addition, the effect of EGF treatment on intestinal barrier function was evaluated. Premature rats were divided into three groups: dam fed (DF), formula fed (NEC), or fed with formula supplemented with 500 ng/ml EGF (NEC + EGF); all groups were exposed to asphyxia/cold stress to develop NEC. Intestinal permeability, goblet cell density, mucin production, and composition of tight junction (TJ) proteins were evaluated in the terminal ileum, the site of NEC injury, and compared with the proximal jejunum, which was unaffected by NEC. Animals with NEC had significantly increased intestinal paracellular permeability compared with DF pups. Ileal goblet cell morphology, mucin production, and TJ composition were altered in animals with NEC. EGF treatment significantly decreased intestinal paracellular permeability, increased goblet cell density and mucin production, and normalized expression of two major TJ proteins, occludin and claudin-3, in the ileum. In conclusion, experimental NEC is associated with disruption of the intestinal barrier. EGF treatment maintains intestinal integrity at the site of injury by accelerating goblet cell maturation and mucin production and normalizing expression of TJ proteins, leading to improved intestinal barrier function.

Intestinal immune defences and the inflammatory response in necrotising enterocolitis

Necrotising enterocolitis is a devastating neonatal gastrointestinal emergency predominantly affecting low birth weight, premature infants and is accompanied by significant mortality and morbid sequelae. The pathophysiology remains obscure and the management of infants with necrotising enterocolitis has not changed since the recognition of this disease. Necrotising enterocolitis is most likely the clinical culmination of multiple different risk factors interacting with each other to produce bowel injury through a final, common inflammatory pathway. Here, we review intestinal immunity and the specific inflammatory mediators involved in this disease process.

Reduction of experimental necrotizing enterocolitis with anti-TNF-alpha

Necrotizing enterocolitis (NEC) is the most common gastrointestinal disease of premature infants. However, despite significant morbidity and mortality, the etiology and pathogenesis of NEC are poorly understood. Evidence suggests that ileal proinflammatory mediators such as IL-18 contribute to the pathology associated with this disease. In addition, we have previously shown that upregulation of TNF-alpha in the liver is correlated with ileal disease severity in a neonatal rat model of NEC. With the use of a neonatal rat model of NEC, we evaluated the incidence and severity of ileal damage along with the production of both hepatic and ileal proinflammatory cytokines in animals injected with (anti-TNF-alpha; n = 23) or without (NEC; n = 25) a monoclonal anti-TNF-alpha antibody. In addition, we assessed changes in apoptosis and ileal permeability in the NEC and anti-TNF-alpha groups. Ileal damage was significantly decreased, and the incidence of NEC was reduced from 80% to 17% in animals receiving anti-TNF-alpha. Hepatic TNF-alpha and hepatic and ileal IL-18 were significantly decreased in pups given anti-TNF-alpha compared with those sham injected. In addition, ileal luminal levels of both TNF-alpha and IL-18 were significantly decreased in the anti-TNF-alpha-injected group. Ileal paracellular permeability and the proapoptotic markers Bax and cleaved caspase-3 were significantly decreased in the anti-TNF-alpha group. These data show that hepatic TNF-alpha is an important component for the development of NEC in the neonatal rat model and suggest that anti-TNF-alpha could be used as a potential therapy for human NEC.

Bile acids induce ileal damage during experimental necrotizing enterocolitis

BACKGROUND & AIMS

Necrotizing enterocolitis (NEC) is the most common gastrointestinal emergency of premature infants. While the effect of bile acids (BAs) on intestinal mucosal injury is known, we investigated the contribution of BAs during the development of NEC in neonatal rats.

METHODS

Premature rats were fed with cow's milk-based formula and subjected to asphyxia and cold stress to develop NEC. Jejunal and ileal luminal BAs, portal blood BAs, and messenger RNA and protein for the apical sodium-dependent bile acid transporter, the ileal bile acid binding protein, and the heteromeric organic solute transporter (Ostalpha/Ostbeta)were evaluated.

RESULTS

Ileal luminal BAs levels were increased significantly during disease development and the removal of ileal BAs significantly decreased the incidence and severity of disease. Furthermore, when NEC was reduced via treatment with epidermal growth factor (EGF), BA levels were reduced significantly. Jejunal luminal BA levels were similar between animals with NEC and controls, but portal/ileal luminal BA ratios were decreased significantly in animals with NEC. The apical sodium-dependent bile acid transporter was up-regulated at the site of injury in animals with NEC and decreased after EGF treatment; however, the ileal bile acid binding protein was up-regulated only in the NEC and EGF group. Ostalpha/Ostbeta expression was low in all groups, and only slightly increased in the NEC group.

CONCLUSIONS

These data strongly suggest that BAs play a role in the development of ileal damage in experimental NEC and that alterations in BA transport in the neonatal ileum may contribute to disease development.

Strategies for prevention of feed intolerance in preterm neonates: a systematic review

Postnatal growth restriction and failure to thrive have been recently identified as a major issue in preterm, especially extremely-low-birth-weight neonates. An increased length of time to reach full enteral feedings is also significantly associated with a poorer mental outcome in preterm neonates at 24 months corrected age. Optimization of enteral nutrition without increasing the risk of necrotizing enterocolitis (NEC) has thus become a priority in preterm neonates. A range of feeding strategies currently exists for preventing/minimizing feed intolerance in preterm neonates reflecting the dilemma surrounding the definition and significance of signs of feed intolerance due to ileus of prematurity and the fear of NEC. The results of a systematic review of current strategies for preventing/minimizing feed intolerance in preterm neonates are discussed. The need for clinical research in the area of signs of feed intolerance is emphasized to develop a scientific basis to feeding strategies. Only large pragmatic trials based on such strategies will reveal whether the benefits (improved growth and long term neurodevelopmental outcomes) of aggressive enteral nutrition can outweigh the risks of a potentially devastating illness like NEC, and of prolonged parenteral nutrition in preterm neonates.

Epidermal growth factor reduces hepatic sequelae in experimental necrotizing enterocolitis

BACKGROUND AND AIM

Neonatal necrotizing enterocolitis (NEC) is the most common gastrointestinal disease of premature infants. We recently demonstrated that the gut/liver axis plays an important role in the pathophysiology of NEC through the release of inflammatory mediators into the intestinal lumen. We have also shown that supplementation of formula with epidermal growth factor (EGF) dramatically decreases ileal pathology associated with experimental NEC. In this study, we examined the effects of EGF on the liver portion of the gut/liver axis in the neonatal rat model of NEC.

METHODS

Newborn rats were divided into three experimental groups, NEC, hand-fed with growth-factor free formula; NEC + EGF, hand-fed with formula supplemented with 500 ng/ml rat EGF; or DF, dam fed. All animals were exposed to asphyxia and cold stress twice daily for 4 days to develop NEC.

RESULTS

EGF receptor expression was significantly (p <or= 0.01) decreased in the NEC+EGF group compared to the NEC group. EGF supplementation significantly decreased Kupffer cell numbers (p <or= 0.01) as well as hepatic tumor necrosis factor (TNF)-alpha and interleukin-18 production (p <or= 0.05). Further, TNF-alpha in the intestinal luminal contents of the NEC+EGF group were normalized to levels observed in DF controls compared to the NEC group (p <or= 0.05). Activated nuclear factor-kappaB was also substantially decreased in the NEC+EGF group versus the NEC group.

CONCLUSION

The results of this study indicate that EGF normalizes cytokine overproduction in the liver of neonatal rats with NEC, which contributes to diminished intestinal damage during the development of experimental NEC. These data suggest that supplementation of formula with EGF can have beneficial effects on the gut/liver axis during NEC pathogenesis.

Protective effect of tumor necrosis factor alpha antibody on experimental necrotizing enterocolitis in the rat

BACKGROUND

Necrotizing enterocolitis (NEC) is a common and devastating disorder of premature infants. Elevated proinflammatory cytokines, especially tumor necrosis factor alpha (TNF-alpha), have been implicated in the pathogenesis of NEC. The aim of this study was to evaluate the effects of TNF-alpha on the inflammatory response in NEC by immunoneutralizing TNF-alpha with a selective antibody.

METHODS

Neonatal Sprague-Dawley rats were divided in 3 groups: group 1 (n = 20), a NEC-like enterocolitis was induced by formula feeding, asphyxia, and cold exposure; group 2 (n = 9), animals were treated like in group 1 and additionally received TNF-alpha antibody intraperitoneally; and group 3 (n = 17), animals were dam-fed (controls). Animals were killed in case of imminent death or after 96 hours. Specimens from small bowel were processed for blinded histologic (H&E) and immunhistologic (myeloperoxidase [MPO]) analysis.

RESULTS

In group 1, animals developed severe NEC (mean NEC score, 3.28 +/- 0.32; mean MPO, 65.85 +/- 9.46). In group 2, animals developed mild NEC (mean NEC score, 1.72 +/- 0.41; mean MPO, 34.33 +/- 9.69; P < .05). In group 3, no NEC was induced (mean NEC score, 0.0 +/- 0; mean MPO, 6 +/- 1.32; P < .05).

CONCLUSION

Tumor necrosis factor alpha antibody may have an attenuating effect on experimental NEC in rats.

Intestinal innate immunity: how does it relate to the pathogenesis of necrotizing enterocolitis

The pathogenesis of necrotizing enterocolitis (NEC) is poorly understood, but appears to be multifactorial and highly associated with immaturity of the gastrointestinal tract, colonization of the intestinal microbiota, and immature innate immune system. The goal of this review is to provide an overview of some of these risk factors and how they might lead to the genesis of NEC. A better understanding of these factors should help us prevent and treat this devastating disease.

Role of epidermal growth factor in the pathogenesis of neonatal necrotizing enterocolitis

Neonatal necrotizing enterocolitis (NEC) is an increasingly frequent condition encountered in premature infants for which the etiology is not well understood. Epidermal growth factor (EGF) is abundant in many fluids bathing the fetal and neonatal gastrointestinal tract, including amniotic fluid, saliva, and breast milk. EGF is acknowledged to be important for normal intestinal development as well as repair following injury to the gastrointestinal mucosa. There appears to be mounting evidence to support a possible link between deficient EGF production and the development of NEC. The relevant evidence for the role of EGF in intestinal development and mucosal repair, as well as its potential involvement in the genesis of NEC will be reviewed.

Mechanisms of nitric oxide-mediated intestinal barrier failure in necrotizing enterocolitis

Necrotizing enterocolitis (NEC) is the leading intestinal emergency in premature infants. The underlying etiology of NEC remains elusive, but hypoxic conditions and early enteral feeding are consistently implicated as the main risk factors in the pathogenesis of NEC. We postulate that nitric oxide (NO) plays a key role as a molecular signaling "hub" in the generation of gut barrier failure in NEC. Clinical studies suggest that inflammatory cytokines and excessive NO production may contribute to the pathogenesis of NEC. One of the major challenges in defining the critical signaling pathways that lead to the development of NEC is the lack of specific biochemical markers that consistently delineate the early stages of NEC. Intestinal pathology and molecular markers derived from late-stage NEC represent end-stage findings and thus provide little insight into the early events that led to intestinal inflammation. Such markers may not represent viable therapeutic targets for the treatment or prevention of NEC. Therefore, novel strategies are needed to identify the patients at risk for NEC and define the clinically relevant molecules that characterize the early stages of NEC. This review will examine the mechanisms of NO-mediated gut barrier failure and propose novel genetic-based approaches for elucidating the critical molecular pathways in NEC.

A pilot study of the use of epidermal growth factor in pediatric short bowel syndrome

BACKGROUND

This study examined the effects of enterally administered epidermal growth factor (EGF) on nutrient absorption and tolerance of enteral feeds in pediatric patients with short bowel syndrome (SBS).

METHODS

Patients identified with severe SBS (<25% bowel length predicted for age) were prospectively enrolled in treatment using human recombinant EGF (1-53); 100 microg/kg per day given mixed with enteral feeds and patients were treated for 6 weeks. End points followed were patient weight, tolerance of enteral feeds, nutrient absorption, and intestinal permeability as determined using carbohydrate probes and hematologic values for liver function parameters.

RESULTS

Five patients were treated with EGF; all showed a significant improvement in carbohydrate absorption (3-0 methylglucose): absorption 24.7% +/- 9.7% pretreatment vs 34.1% +/- 13.8% posttreatment and improved tolerance of enteral feeds (enteral energy as % of total energy, 25% +/- 28% pretreatment vs 36% +/- 24% posttreatment; mean +/- SD; P < .05 by Wilcoxon's signed rank test). Epidermal growth factor treatment was not associated with significant changes in intestinal permeability, the rate of weight gain, or liver function tests. During the treatment phase, no patients developed episodes of sepsis; however, within 2 weeks of discontinuation of EGF treatment, 3 patients developed septic episodes. No adverse effects of EGF administration were noted.

CONCLUSIONS

These results suggest that enteral treatment with EGF in pediatric SBS improves nutrient absorption, increases tolerance with enteral feeds, and may improve the infection rate. Further studies exploring treatment strategies including the timing and duration of EGF administration are indicated.

Epidermal growth factor reduces intestinal apoptosis in an experimental model of necrotizing enterocolitis

Necrotizing enterocolitis (NEC) is a devastating intestinal disease of premature infants. Although end-stage NEC is characterized histopathologically as extensive necrosis, apoptosis may account for the initial loss of epithelium before full development of disease. We have previously shown that epidermal growth factor (EGF) reduces the incidence of NEC in a rat model. Although EGF has been shown to protect intestinal enterocytes from apoptosis, the mechanism of EGF-mediated protection against NEC is not known. The aim of this study was to investigate if EGF treatment elicits changes in expression of apoptotic markers in the ileum during the development of NEC. With the use of a well-established neonatal rat model of NEC, rats were divided into the following three experimental groups: dam fed (DF), milk formula fed (NEC), or fed with formula supplemented with 500 ng/ml EGF (NEC+EGF). Changes in ileal morphology, gene and protein expression, and histological localization of apoptotic regulators were evaluated. Anti-apoptotic Bcl-2 mRNA levels were markedly reduced and pro-apoptotic Bax mRNA levels were markedly elevated in the NEC group compared with DF controls. Supplementation of EGF into formula significantly increased anti-apoptotic Bcl-2 mRNA, whereas pro-apoptotic Bax was significantly decreased. The Bax-to-Bcl-2 ratio for mRNA and protein was markedly decreased in NEC+EGF animals compared with the NEC group. The presence of caspase-3-positive epithelial cells was markedly reduced in EGF-treated rats. These data suggest that alteration of the balance between pro-and anti-apoptotic proteins in the site of injury is a possible mechanism by which EGF maintains intestinal integrity and protects intestinal epithelium against NEC injury.

Fetal and neonatal inflammatory response and adverse outcome

This article will define the concept of fetal/neonatal inflammatory response, and examine the complex interaction between inflammation and neurotoxicity. There appear to be important interactions between infection/inflammation and hypoxia-ischaemia leading to cytokine release and subsequent brain injury. This article will also define adverse outcome and summarize the complexities inherent to neurodevelopmental assessment. Finally, this article will investigate the currently available evidence suggesting a link between inflammatory response and adverse neurodevelopmental outcome, and focus on those variables that need further study: timing and nature of the infectious/inflammatory process; established and new anti-insult strategies; morbidity in organs other than the brain; genetic influences; and environmental factors.

The role of the glutathione antioxidant system in gut barrier failure in a rodent model of experimental necrotizing enterocolitis

BACKGROUND

Evidence suggests that intestinal barrier failure in necrotizing enterocolitis results in part from overproduction of nitric oxide and other toxic oxidant species that result in enterocyte death and intestinal barrier failure. We hypothesize that the glutathione detoxifying system is important in maintaining intestinal barrier integrity by protecting against nitrosative stress.

METHODS

Newborn rats were subjected to hypoxia (5% O2, tid) and fed formula by gavage (NEC), or were breast-fed without hypoxia (BF). Rats were killed and the distal ilea were harvested for RNA, protein, and morphologic studies. RNA underwent cDNA microarray analysis. To assess glutathione in protecting against nitrosative stress, IEC-6 cells were exposed to SIN-1 and/or L-buthionine-(S,R)-sulfoximine (BSO), a glutathione inhibitor. Cells were analyzed for glutathione-S-transferase activity, apoptosis and mitochondrial function.

RESULTS

BF controls developed normal intestinal architecture, whereas NEC animals sustained damage to the intestinal epithelium. Microarray analysis demonstrated that 93 genes were overexpressed in NEC compared with controls. In the array, glutathione-S-transferase pi and alpha 2, GSH-dependent detoxifying enzymes, RNA were upregulated compared with BF controls. IEC-6 cells exposed to SIN-1/BSO produced an increase in apoptosis. Poly ADP-ribosylpolymerase cleavage and apoptosis-inducing factor (AIF) nuclear localization, markers of apoptosis, were seen in IEC-6 cells exposed to SIN-1/BSO as opposed to media controls.

CONCLUSION

These data support the hypothesis that GSH antioxidant system plays a crucial role in gut barrier protection by attenuating enterocyte death.

Characteristics of breast milk and serology of women donating breast milk to a milk bank

OBJECTIVE

Breast milk is the most important nutrient to all newborn babies. If the mother's milk production is insufficient, it is important to provide donor breast milk without reduction of its immunologic and antimicrobial properties. Early use of breast milk to preterm infants has shown a reduced incidence of necrotising enterocolitis, a faster tolerance of enteral feeding, and a reduced need of parenteral nutrition. It is important to have milk from a CMV-IgG negative donor to VLBW infants considered immunocompromised.

METHODS

Between January 1st and December 31st 2001, 69 women delivered 1.973 litres (mean 28.6 litres/woman/year). 73% had college education, were primipara, and with a mean age of 30.7 years. Those who smoked, used alcohol or any medications were refused as donors. They started to deliver approximately 7 weeks after having given birth and continued for a mean of 4 months. Each milk sample was tested for bacterial growth. Every donor was screened for HIV, CMV-IgG and hepatitis B/C before donating milk and thereafter every third month.

RESULTS

62.3% was CMV-IgG positive. Samples containing staphylococcus aureus, klebsialla-, enterobacter- and serratia-species or E. coli, and all samples containing > 10(4) cfu/ml were pasteurised. Overall, only 10.5% of the samples were pasteurised.

CONCLUSION

It is possible and important to provide VLBW babies with fresh frozen unpasteurised CMV-IgG negative breast milk until their own mothers' milk production is sufficient.

Necrotizing enterocolitis: preventative strategies

Necrotizing enterocolitis (NEC) remains a major cause of morbidity and mortality in premature infants. Although the pathogenesis of NEC is unclear, prevention strategies have been developed based on clinical observations and epidemiologic and experimental data. Most current strategies have centered on feeding practices (eg, institution of feeds, advancement of feeds, composition of feeds, and standardization of feeding practices). Emerging strategies include amino acid supplementation, the use of platelet-activating factor(PAF) antagonists or PAF-acetylhydrolase administration, polyunsaturated fatty acid administration, epidermal growth factor administration, and the use of pre- and probiotics.

Epidermal growth factor and necrotizing enterocolitis

As the number of extremely low-birth-weight infants increases,necrotizing enterocolitis remains a critical eminent problem. Supplementation of enteral feeds with biologically active substances normally present in breast milk, such as epidermal growth factor, seems to be a logical and safe way to reduce the incidence of intestinal inflammation and necrotizing enterocolitis. Continuing basic research and clinical studies are essential before epidermal growth factor can be introduced as an efficient therapeutic approach in the treatment of neonatal necrotizing enterocolitis.

Treatment and prevention of necrotizing enterocolitis

Necrotizing enterocolitis (NEC) is the most common serious, acquired gastrointestinal disorder in the newborn infant. Although many variables are associated with development of NEC, only prematurity has been consistently identified in case-controlled studies. Traditionally, the diving seal reflex has been invoked as the mechanism responsible for ischaemic injury and necrosis. Intestinal ischaemia is likely to be the final common pathway in NEC; however, it is due to the release of vasoconstricting substances, such as platelet activating factor, rather than perinatal asphyxia. Bacteria and/or bacterial toxins are likely to have a key role in the pathogenesis of NEC by fostering production of inflammatory mediators. The role of feeding practices in the pathogenesis of NEC remains controversial. Treatment of infants with NEC generally includes a regimen of bowel rest, gastric decompression, systemic antibiotics and parenteral nutrition. Infants with perforation are generally operated upon; however, there has been recent interest in primary peritoneal drainage as an alternative. Prevention of NEC still remains elusive. Avoidance of preterm birth, use of antenatal steroids and breast-milk feeding are practices that offer the greatest potential benefits. Use of any other strategy should await further trials.