Clark Jessica A, Lane Robert H, Maclennan Nicole K, Holubec Hana, Dvorakova Katerina, Halpern Melissa D, Williams Catherine S, Payne Claire M, Dvorak Bohuslav
Dept. of Pediatrics, Univ. of Arizona, 1501 N. Campbell Ave, P.O. Box 245073, Tucson, AZ 85724-5073, USA.
Am J Physiol Gastrointest Liver Physiol. 2005 Apr;288(4):G755-62. doi: 10.1152/ajpgi.00172.2004. Epub 2004 Nov 4.
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.
坏死性小肠结肠炎（NEC）是一种严重的早产儿肠道疾病。尽管终末期NEC在组织病理学上的特征是广泛坏死，但在疾病充分发展之前，细胞凋亡可能是上皮细胞最初丧失的原因。我们之前已经表明，表皮生长因子（EGF）可降低大鼠模型中NEC的发病率。尽管已证明EGF可保护肠道肠上皮细胞免于凋亡，但EGF介导的预防NEC的机制尚不清楚。本研究的目的是调查在NEC发展过程中，EGF治疗是否会引起回肠中凋亡标志物表达的变化。使用成熟的新生大鼠NEC模型，将大鼠分为以下三个实验组：母鼠喂养组（DF）、奶粉喂养组（NEC）或喂养添加500 ng/ml EGF的奶粉组（NEC+EGF）。评估回肠形态、基因和蛋白质表达以及凋亡调节因子的组织学定位的变化。与DF对照组相比，NEC组中抗凋亡的Bcl-２ mRNA水平显著降低，促凋亡的Bax mRNA水平显著升高。在奶粉中添加EGF可显著增加抗凋亡的Bcl-２ mRNA，而促凋亡的Bax则显著降低。与NEC组相比，NEC+EGF组动物中mRNA和蛋白质的Bax与Bcl-２ 比率显著降低。在EGF治疗的大鼠中，caspase-3阳性上皮细胞的数量显著减少。这些数据表明，损伤部位促凋亡蛋白和抗凋亡蛋白之间平衡的改变可能是EGF维持肠道完整性并保护肠道上皮免受NEC损伤的一种机制。
