Signal transduction of epidermal growth factor on the production of nitric oxide in rat intestinal epithelial cells

表皮生长因子（EGF）是小肠移植后肠道适应的营养因子之一。最近的研究表明，一氧化氮（NO）对SBT后的细菌易位（BT）有细胞保护作用。我们假设EGF刺激SBT后移植物中诱导型一氧化氮合酶（iNOS）基因的表达，随后NO的产生增加，导致bt的减少。在存在和不存在磷脂酰肌醇3-激酶（PI3K）和EGF受体激酶抑制剂（LY294002和tyrphostin A25）的情况下，EGF或/和白细胞介素-1β (IL-1β)处理肠上皮细胞（IEC-6）。分析NO和iNOS的诱导作用及其信号分子包括NF-κB抑制蛋白（i -κB）、核因子-κB （NF-κB）和Akt。IL-1β刺激了i -κB的降解和NF-κB的活化，但对iNOS的诱导没有影响。EGF不影响NF-κB活化和iNos诱导，但通过PI3K/Akt刺激1型白介素-1受体（IL-1R1）上调。同时加入EGF和IL-1b协同刺激iNOS的诱导，导致NO的产生增加。我们的研究结果表明，EGF和IL-1β分别通过PI3K/Akt上调IL-1R1和通过i -κb激酶激活NF-κb，刺激IEC-6细胞诱导iNOS的两个必要信号。同时添加EGF和IL-1β可以促进NO的产生，这可能有助于EGF对肠道损伤的细胞保护作用。

Epidermal growth factor (EGF) is one of trophic factors for intestinal adaptation after small bowel transplantation (SBT). Recent report indicates that nitric oxide (NO) has cytoprotective effect on bacterial translocation (BT) after SBT. We hypothesized that EGF stimulates the expression of inducible nitric oxide synthase (iNOS) gene in the graft after SBT, followed by increased production of NO, resulting in the decrease of BT.Intestinal epithelial cells (IEC-6) were treated with EGF or/and interleukin-1β (IL-1β) in the presence and absence of phosphatidylinositol 3-kinase (PI3K) and EGF receptor kinase inhibitors (LY294002 and tyrphostin A25). The induction of NO production and iNOS, and its signal molecules including the inhibitory protein of NF-κB (IκB), nuclear factor-κB (NF-κB) and Akt were analyzed.IL-1β stimulated the degradation of IκB and the activation of NF-κB, but had no effect on iNOS induction. EGF, which had no effect on the NF-κB activation and iNos induction, stimulated the up-regulation of type 1 interleukin-1 receptor (IL-1R1) through PI3K/Akt. Simultaneous addition of EGF and IL-1b stimulated synergistically the induction of iNOS, leading to the increased production of NO.Our results indicate that EGF and IL-1β stimulate two essential signals for iNOS induction in IEC-6 cells, the up-regulation of IL-1R1 through PI3K/Akt and the activation of NF-κb through IκB kinase, respectively. Simultaneous addition of EGF and IL-1β can enhance the production of NO, which may contribute to the cytoprotective effect of EGF against intestinal injury.