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.     

Microecology, intestinal epithelial barrier and necrotizing enterocolitis

Soon after birth, the neonatal intestine is confronted with a massive antigenic challenge of microbial colonization. Microbial signals are required for maturation of several physiological, anatomical, and biochemical functions of intestinal epithelial barrier (IEB) after birth. Commensal bacteria regulate intestinal innate and adaptive immunity and provide stimuli for ongoing repair and restitution of IEB. Colonization by pathogenic bacteria and/or dysmature response to microbial stimuli can result in flagrant inflammatory response as seen in necrotizing enterocolitis (NEC). Characterized by inflammation and hemorrhagic–ischemic necrosis, NEC is a devastating complication of prematurity. Although there is evidence that both prematurity and presence of bacteria, are proven contributing factors to the pathogenesis of NEC, the molecular mechanisms involved in IEB dysfunction associated with NEC have begun to emerge only recently. The metagenomic advances in the field of intestinal microecology are providing insight into the factors that are required for establishment of commensal bacteria that appear to provide protection against intestinal inflammation and NEC. Perturbations in achieving colonization by commensal bacteria such as premature birth or hospitalization in intensive care nursery can result in dysfunction of IEB and NEC. In this article, microbial modulation of functions of IEB and its relationship with barrier dysfunction and NEC are described.     

谷氨酰胺和表皮生长因子对新生鼠坏死性小肠结肠炎的影响

目的探讨谷氨酰胺(Gln)和表皮生长因子(EGF)对新生鼠坏死性小肠结肠炎(NEC)肠黏膜修复的影响。方法新生1日龄Wistar大鼠40只随机分为4组,A组(正常对照组),B组(NEC模型组),C组(NEC Gln),D组(NEC EGF Gln)。建立NEC模型,4 d后分别取近回盲段2~3 cm肠道组织固定、包埋、切片。HE染色光镜下作病理学检查,应用免疫组织化学技术检测肠黏膜增殖细胞核抗原(PCNA)的表达,TUNEL法检测肠黏膜细胞凋亡。结果B组HE染色切片见肠黏膜损伤,病理评分的中位积分为3分;C、D组损伤程度较轻,病理评分的中位积分为1分。B组PCNA阳性细胞数低于A组(P<0.01);C、D组PCNA阳性细胞数高于B组(P<0.01);且D组PCNA阳性细胞数高于C组(P<0.05)。B组肠黏膜细胞凋亡数高于A组(P<0.01);C、D组肠黏膜细胞凋亡数低于B组(P<0.01);且D组肠黏膜细胞凋亡数低于C组(P<0.05)。结论NEC新生鼠肠黏膜受损,增殖减慢,细胞凋亡数增加;补充Gln和EGF可促进NEC新生鼠肠黏膜隐窝细胞的增殖,减少肠黏膜细胞的凋亡,加快肠黏膜修复。     

Heparin-binding EGF-like growth factor (HB-EGF) and necrotizing enterocolitis

Necrotizing enterocolitis (NEC) is a common and devastating gastrointestinal disease that occurs predominantly in premature infants. Despite various advances in management, the mortality of this disease remains high. During the last decade, studies from our laboratory have shown that heparin-binding epidermal growth factor-like growth factor (HB-EGF), a member of the epidermal growth factor (EGF) family, can protect intestinal epithelial cells (IEC) from various forms of injury in vitro. Furthermore, we have used both an intestinal I/R injury model in adult rats, and a neonatal rat pup model of NEC, to show that HB-EGF can protect the intestines from injury. On administration of HB-EGF in the neonatal rat model, the incidence of NEC is reduced from 65% to 27.3% (P < 0.05), and the histological injury score is decreased from 2 to 1.1 (P < 0.05). In addition, the survival rate is increased from 25% to 63.6% and the survival time extended from 59 hours to 73 hours (P < 0.05). In addition, using human specimens from newborns undergoing bowel resection for NEC, we found that the expression of endogenous HB-EGF mRNA in normal areas of the intestine at the resection margins was higher than that of the intestine afflicted with acute NEC. Endogenous HB-EGF may be involved in epithelial cell repair, proliferation, and regeneration during recovery from injury. Exogenous administration of HB-EGF potentiates recovery from intestinal injury in vitro and in vivo. Taken together, these results support a potential therapeutic role for HB-EGF in the treatment of NEC in the future.     

Intestinal microcirculation and necrotizing enterocolitis: The vascular endothelial growth factor system

Necrotizing enterocolitis (NEC), a leading cause of morbidity and mortality in preterm neonates, is a devastating disease characterized by intestinal tissue inflammation and necrosis. NEC pathogenesis is multifactorial but remains unclear. Translocation of bacteria and/or bacterial products across a weak intestinal barrier in the setting of impaired mucosal immunity leads to an exaggerated inflammatory response and secondary mucosal epithelial injury. In addition to prematurity, other risk factors for NEC include congenital heart disease, maternal pre-eclampsia with placental vascular insufficiency, severe anemia and blood transfusion – all conditions that predispose the intestine to ischemia. We recently found that maldevelopment of the intestinal microvasculature plays an important role in NEC pathogenesis. Here we review the evidence supporting a role for defective development of the intestinal mucosal microvasculature and perturbations of intestinal blood flow in NEC, emphasizing the importance of vascular endothelial growth factor (VEGF) and the VEGF receptor-2 signaling pathway.     

Enteral glutamine supplementation and dexamethasone attenuate the local intestinal damage in rats with experimental necrotizing enterocolitis

The pathogenesis of necrotizing enterocolitis (NEC) presumptively is due to an inappropriate intestinal epithelial immunologic response of immature gut to luminal stimuli. Glutamine is essential for intestinal crypt cell proliferation and enhances the cellular response to growth factors. We aimed to test the hypothesis that the supplementation of enteral feedings with glutamine may stimulate an immature intestine and decrease the intestinal inflammatory change in NEC. Immediately after birth, the neonatal rats were weighed and randomized into one of four treatment groups. Group 1 consisted of rats whom were breast-fed. Group 2 (NEC group) consisted of neonates whom were fed with a special rodent formula. Rats in groups 3 and 4 were fed in a similar fashion to those in group 2, and glutamine 0.3 mg/kg per day and dexamethasone 0.5 mg/kg per day were added to their formula, respectively. The neonatal rats were weighed and killed on day 4: the last 4 cm of terminal ileum was harvested for morphological studies and detection of nitrite and nitrate levels in tissue. The animals in the NEC group showed various degrees of inflammatory changes similar to clinical NEC. The inflammatory changes of the intestine appeared to be attenuated in both glutamine- and steroid-treated animals compared to those in the NEC group. Only steroid treatment decreased the tissue levels of these nitrogen oxides that were increased in rats in the NEC group. We herein provide evidence that maturational agents such as glutamine and dexametasone can attenuate the local intestinal inflammatory damage in experimental NEC. These findings support the hypothesis that the gut immaturity in premature infants represents a risk factor for NEC.     

Neonatal inflammatory intestinal diseases: necrotising enterocolitis and allergic colitis

The occurrence in the neonatal period and into early infancy of two inflammatory conditions, necrotising enterocolitis (NEC), and allergic colitis, that do not occur in later life highlight the peculiar vulnerability of the gastrointestinal tract in the newborn period to otherwise innocuous insults. The pathogenesis of the relatively benign allergic colitis as a mucosal inflammatory process driven by dietary antigens is relatively well characterised, and its treatment with dietary manipulation is well established. For NEC, hypoxic/ischaemic insult, mucosal immaturity, and its interaction with the intestinal microflora are understood to be the main factors in pathogenesis. Thus far, the most productive interventions have been in preventative approaches, in particular feeding strategies, to reduce the incidence of the condition whilst establishing adequate growth and progression onto enteral feeding. For established NEC, supportive medical therapy or surgical intervention remains the mainstay or treatment, although novel therapies, such as platelet-activating factor (PAF) inhibitors and epidermal growth factor (EGF), have shown some promise in animal models of the condition.     

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 相似文献   

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.     

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??Necrotizing enterocolitis??NEC?? is considered to be the most common gastrointestinal emergency among neonates. Although the pathogenesis of NEC is incompletely understood??there are several established risk factors??including prematurity??altered intestinal blood flow/oxygen delivery??formula feeding and bacterial infection. Recently??a large number of studies showed that intestinal flora imbalance had been implicated as key risk factor in the pathogenesis of NEC. After birth??the neonatal gut must acquire a healthy complement of commensal bacteria??which leads to deficient or abnormal microbial colonization of the gut??may protect the immature gut from inflammation and injury. Providing a healthy complement of commensal bacteria can maintain the intestinal microflora balance??shift the balance of intestinal microbiota from a pathegenic to protective complement of bacteria??protect the gut from inflammation and subsequent injury??and prevent NEC. We review the relationship between intestinal microbiota and NEC in preterm infants??the mechanism of probiotics in preventing NEC??and the efficacy and safety of probiotics in preterm infants.     

Neonatal necrotizing enterocolitis, a disease of the immature intestinal mucosal barrier

Necrotizing enterocolitis (NEC) is an enigmatic process in that one single etiologic factor has been sought and not found. Epidemiologic studies suggest that immaturity of the host plays a very important role. This article reviews the intestinal host defense system and its immature nature early in life in animal models and humans and suggests that it is this immaturity, along with other factors, which allows for the proliferation and invasion of antigens and organism, and the subsequent development of NEC. Data are presented which support the efficacy of pharmacologic maturation of the intestinal barrier with growth factors, either prenatally or postnatally, to decrease the incidence of NEC or, potentially, to provide a more benign course for the disease.     

新生儿坏死性小肠结肠炎的研究进展

坏死性小肠结肠炎(necrotizing enterocolitis,NEC)是早产儿常见的危重症之一,不仅病死率高,部分存活儿有肠狭窄、肠梗阻、营养不良、肠外营养相关胆汁淤积症等并发症,甚至发生短肠综合征、肠道功能衰竭及神经功能障碍等严重结局.NEC的病因复杂,发病机制尚未完全清楚,早期诊断较困难.近年来,早产、喂养不当、Toll样受体异常表达、异常细菌定植、缺氧缺血及血流动力学改变等,被认为是NEC发生的高危因素,母乳喂养及益生菌对降低早产儿NEC的发生有一定的作用.     

新生儿坏死性小肠结肠炎研究进展

坏死性小肠结肠炎（NEC）是由多种因素导致的新生儿,尤其是早产儿的灾难性疾病。严重的NEC病死率高,幸存者多面临短期及长期不良预后。与NEC有关的危险因素包括早产、非母乳喂养、消化道内微生物异常、缺血再灌注损伤等。高分辨腹腔超声检查有助于NEC的早期诊断。通过营养干预保护肠黏膜、干扰肠道损伤信号、改变肠道微生态环境及早期微量喂养有助于预防NEC。该病进展迅速,目前尚无有效措施,以支持治疗为主,严重者需外科治疗,雷公藤红素、脂多糖结合蛋白、粪便移植可能有助于治疗NEC,但仍有待于进一步研究。     

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.     

Intestinal mitochondrial apoptotic signaling is activated during oxidative stress

Purpose  

Reactive oxygen species (ROS) are thought to contribute to the pathogenesis of necrotizing enterocolitis (NEC). Mitochondria as a major source of intracellular ROS and apoptotic signaling during oxidative stress in NEC have not been investigated. We sought to determine: (1) the effects of oxidative stress on intestinal mitochondrial apoptotic signaling, and (2) the role of growth factors in this process.     

新生儿感染与新生儿坏死性小肠结肠炎

新生儿坏死性小肠结肠炎(necrotizing enterocolitis,NEC)是新生儿时期比较常见的消化系统危重症,严重者甚至可能危及新生儿生命.NEC的发生机制具有复杂性和不确定性,新生儿期的感染是其中重要的环节.早产儿肠道屏障结构和功能未成熟,肠道固有免疫存在缺陷以及异常的肠道细菌定植均会导致早产儿NEC的高发生率.目前明确有效的特异性治疗措施是有限的,对已经发现的风险因素采取有效的预防措施对于减少NEC发生是有益的.     

1型和2型黏蛋白在新生儿坏死性小肠结肠炎患儿肠组织中的表达变化

目的观察新生儿坏死性小肠结肠炎（NEC）患儿肠黏膜屏障中1型和2型黏蛋白（MUC1和MUC2）的表达变化。方法病例对照研究。NEC组为重庆医科大学附属儿童医院病理科NEC患儿手术肠组织病理切片中随机选取10份，并查阅住院病历收集一般临床资料；对照组为重庆医科大学附属儿童医院病理科先天性肠闭锁病理切片，以选取的NEC患儿的胎龄、发病日龄行1∶1匹配，利用HE染色对NEC组肠组织结构变化进行研究，以免疫组织化学方法对肠组织样本中MUC1及MUC2的表达变化进行分析。结果NEC组及对照组肠组织在结构上有明显差异，NEC组患儿肠组织结构的完整性破坏甚至消失，表现为大量绒毛脱落、坏死，黏膜下层及肌层水肿，毛细血管扩张充血，样本肠壁层炎性细胞浸润，肠组织杯状细胞及隐窝减少；NEC患儿肠组织MUC1及MUC2表达均明显低于对照组（以累计光密度值统计，MUC1中位数：NEC组780 455.5 vs 对照组19 175 070.4，P=0.004；MUC2中位数：NEC组3 039 120 vs 对照组45 750 707.5，P=0.001）。结论NEC患儿肠黏膜屏障中MUC1及MUC2表达显著降低，可能参与了NEC的发病过程。     

Bugs and the barrier: A review of the gut microbiome and intestinal barrier in necrotizing enterocolitis

Necrotizing enterocolitis (NEC) is a devastating gastrointestinal disease that affects premature neonates. It frequently results in significant morbidity and mortality for those affected. Years of research into the pathophysiology of NEC have revealed it to be a variable and multifactorial disease. However, there are risk factors associated with NEC including low birth weight, prematurity, intestinal immaturity, alterations in microbial colonization, and history of rapid or formula based enteral feeds (Fig. 1).1, 2, 3 An accepted generalization of the pathogenesis of NEC includes a hyperresponsive immune reaction to insults such as ischemia, starting formula feeds, or alterations in the microbiome with pathologic bacterial colonization and translocation. This reaction causes a hyperinflammatory response disrupting the normal intestinal barrier, allowing abnormal bacterial translocation and ultimately sepsis.^1,2,4 This review will focus specifically on the interactions with the microbiome and intestinal barrier function in NEC.     

血小板活化因子在新生儿坏死性小肠结肠炎发病中的作用

坏死性小肠结肠炎是新生儿,尤其是早产儿或极低出生体重儿最常见的胃肠道急症,至今仍是早产儿发病和死亡最常见的原因.大量流行病学、动物实验模型及临床研究发现NEC是与早产、配方奶喂养、肠缺血缺氧、细菌异常增殖等多种因素相互作用的结果,但其确切的发病机制尚不完全清楚.目前有研究者通过模拟上述因素建立NEC动物模型,发现模型鼠中NEC组回肠中血小板活化因子水平较对照组明显升高,予以PAF拮抗剂预处理后NEC的发病率显著降低,表明PAF在NEC发病中有关键作用.PAF通过与其受体特异性结合后,可激活多条信号传导通路,导致多种炎症介质合成与释放增加;肠道黏膜屏障受损,大量毒素吸收,进一步增加内源性PAF合成;通过依赖线粒体途径凋亡肠上皮细胞;激活核因子NF-κB通路放大级联炎症反应;诱导活性氧产生,引起细胞凋亡导致肠管坏死.     

The science and necessity of using animal models in the study of necrotizing enterocolitis

Necrotizing enterocolitis (NEC) remains one of the highest causes of mortality and of acute and long-term morbidity in premature infants. Multiple factors are involved in the pathophysiology of NEC including the immaturity of the immune system and the complex changing composition of the intestinal microbiome. This is compounded by the fact that the premature infant should ideally still be a developing fetus and has an immature intestinal tract. Because these complexities are beyond the scope of studies in single-cell cultures, animal models are absolutely essential to understand the mechanisms involved in the pathophysiology of NEC and the effects of inflammation on the immature intestinal tract. To this end, investigators have utilized many different species (e.g., rats, mice, rabbits, quails, piglets, and non-human primates) and conditions to develop models of NEC. Each animal has distinct advantages and drawbacks related to its preterm viability, body size, genetic variability, and cost. The choice of animal model is strongly influenced by the scientific question being addressed. While no model perfectly mimics human NEC, each has greatly improved our understanding of disease. Examples of recent discoveries in NEC pathogenesis and prevention underscore the importance of continued animal research in NEC.