Cui Xiu-Fang, Zhou Wei-Mei, Yang Yan, Zhou Jun, Li Xue-Liang, Lin Lin, Zhang Hong-Jie
Xiu-Fang Cui, Wei-Mei Zhou, Yan Yang, Jun Zhou, Xue-Liang Li, Lin Lin, Hong-Jie Zhang, Department of Gastroenterology, First Affiliated Hospital of Nanjing Medical University, Nanjing 210029, Jiangsu Province, China.
World J Gastroenterol. 2014 Oct 7;20(37):13521-9. doi: 10.3748/wjg.v20.i37.13521.
To investigate the role of epidermal growth factor (EGF) in visceral hypersensitivity and its effect on the serotonin transporter (SERT).
A rat model for visceral hypersensitivity was established by intra-colonic infusion of 0.5% acetic acid in 10-d-old Sprague-Dawley rats. The visceral sensitivity was assessed by observing the abdominal withdrawal reflex and recording electromyographic activity of the external oblique muscle in response to colorectal distension. An enzyme-linked immunosorbent assay was used to measure the EGF levels in plasma and colonic tissues. SERT mRNA expression was detected by real-time PCR while protein level was determined by Western blot. The correlation between EGF and SERT levels in colon tissues was analyzed by Pearson's correlation analysis. SERT function was examined by tritiated serotonin (5-HT) uptake experiments. Rat intestinal epithelial cells (IEC-6) were used to examine the EGF regulatory effect on SERT expression and function via the EGF receptor (EGFR).
EGF levels were significantly lower in the rats with visceral hypersensitivity as measured in plasma (2.639 ± 0.107 ng/mL vs 4.066 ± 0.573 ng/mL, P < 0.01) and in colonic tissue (3.244 ± 0.135 ng/100 mg vs 3.582 ± 0.197 ng/100 mg colon tissue, P < 0.01) compared with controls. Moreover, the EGF levels were positively correlated with SERT levels (r = 0.820, P < 0.01). EGF displayed dose- and time-dependent increased SERT gene expressions in IEC-6 cells. An EGFR kinase inhibitor inhibited the effect of EGF on SERT gene upregulation. SERT activity was enhanced following treatment with EGF (592.908 ± 31.515 fmol/min per milligram vs 316.789 ± 85.652 fmol/min per milligram protein, P < 0.05) and blocked by the EGFR kinase inhibitor in IEC-6 cells (590.274 ± 25.954 fmol/min per milligram vs 367.834 ± 120.307 fmol/min per milligram protein, P < 0.05).
A decrease in EGF levels may contribute to the formation of visceral hypersensitivity through downregulation of SERT-mediated 5-HT uptake into enterocytes.
探讨表皮生长因子（EGF）在内脏高敏感性中的作用及其对5-羟色胺转运体（SERT）的影响。
通过向10日龄的Sprague-Dawley大鼠结肠内注入0.5%醋酸建立内脏高敏感性大鼠模型。通过观察腹部退缩反射并记录腹外斜肌对结肠扩张的肌电活动来评估内脏敏感性。采用酶联免疫吸附测定法测量血浆和结肠组织中的EGF水平。通过实时PCR检测SERT mRNA表达，同时用蛋白质印迹法测定蛋白质水平。采用Pearson相关分析分析结肠组织中EGF与SERT水平之间的相关性。通过氚标记的5-羟色胺（5-HT）摄取实验检测SERT功能。使用大鼠肠上皮细胞（IEC-6）通过表皮生长因子受体（EGFR）研究EGF对SERT表达和功能的调节作用。
与对照组相比，在内脏高敏感性大鼠中，血浆（2.639±0.107 ng/mL对4.066±0.573 ng/mL，P<0.01）和结肠组织（3.244±0.135 ng/100 mg对3.582±0.197 ng/100 mg结肠组织，P<0.01）中测量的EGF水平显著降低。此外，EGF水平与SERT水平呈正相关（r = 0.820，P<0.01）。EGF在IEC-6细胞中显示出剂量和时间依赖性增加SERT基因表达。一种EGFR激酶抑制剂抑制了EGF对SERT基因上调的作用。用EGF处理后SERT活性增强（592.908±31.515 fmol/min每毫克对316.789±85.652 fmol/min每毫克蛋白质，P<0.05），并在IEC-6细胞中被EGFR激酶抑制剂阻断（590.274±25.954 fmol/min每毫克对367.834±120.307 fmol/min每毫克蛋白质，P<0.05）。
EGF水平降低可能通过下调SERT介导的5-HT摄取进入肠细胞而导致内脏高敏感性的形成。
