Division of Gastroenterology, Department of Medicine, Inflammatory Bowel Disease Center, Mount Sinai School of Medicine, New York, NY, USA.
Lab Invest. 2010 Sep;90(9):1295-305. doi: 10.1038/labinvest.2010.100. Epub 2010 May 24.
Epiregulin (EPI) and amphiregulin (AR) are epidermal growth factor receptor (EGFR) ligands implicated in mucosal repair and tumorigenesis. We have shown that Toll-like receptor 4 (TLR4) induces intestinal epithelial cell (IEC) proliferation by activating EGFR through AR expression. We examined whether TLR4 differentially regulates expression of EGFR ligands in response to mucosal injury. The human IEC line SW480 was examined expression of EGFR ligands, EGFR phosphorylation, and proliferation in response to lipopolysaccharide (LPS). Small-interfering RNA (siRNA) was used to block TLR4. Neutralizing antibodies to EGFR ligands were used to examine inhibition of LPS-dependent EGFR activation. Acute colitis and recovery were examined in the mice given 2.5% dextran sodium sulfate (DSS). Colonic secretion of EPI and AR was analyzed by enzyme-linked immunosorbent assay. LPS selectively induces EPI and AR but not other EGFR ligands. LPS induced early EPI mRNA expression between 30 min and 24 h. The neutralizing antibodies to EPI and AR prevented activation of EGFR by LPS. LPS induces IEC proliferation (200%, P=0.01) in 24 h but blocking EPI and AR significantly decreased proliferation. In vivo, mucosal EPI and AR expression are significantly decreased in TLR4(-/-) mice (P=0.02) compared to wild-type mice during acute colitis. EPI and AR exhibit different kinetics in response to mucosal damage: EPI expression is upregulated acutely at day 7 of DSS, but falls during recovery at day 14. By contrast, a sustained upregulation of AR expression is seen during mucosal injury and repair. We show that TLR4 regulates EPI and AR expression and that both these EGFR ligands are necessary for optimal proliferation of IEC. The diverse kinetics of EPI and AR expression suggest that they function in distinct roles with respect to acute injury vs repair. Our results highlight the role of bacterial sensing for IEC homeostasis and may lead to targeted therapy for mucosal healing and prevention of tumorigenesis.
表皮生长因子受体 (EGFR) 配体表皮调节素 (EPI) 和 Amphiregulin (AR) 参与黏膜修复和肿瘤发生。我们已经表明，Toll 样受体 4 (TLR4) 通过 AR 表达激活 EGFR 诱导肠上皮细胞 (IEC) 增殖。我们检查 TLR4 是否通过调节 EGFR 配体的表达来响应黏膜损伤。检查人 IEC 系 SW480 对脂多糖 (LPS) 的反应中 EGFR 配体的表达、EGFR 磷酸化和增殖。使用小干扰 RNA (siRNA) 阻断 TLR4。使用 EGFR 配体的中和抗体检查 LPS 依赖性 EGFR 激活的抑制作用。在给予 2.5%葡聚糖硫酸钠 (DSS) 的小鼠中检查急性结肠炎和恢复情况。通过酶联免疫吸附试验分析结肠分泌的 EPI 和 AR。LPS 选择性诱导 EPI 和 AR，但不诱导其他 EGFR 配体。LPS 在 30 分钟至 24 小时之间诱导早期 EPI mRNA 表达。EPI 和 AR 的中和抗体可阻止 LPS 激活 EGFR。LPS 在 24 小时内诱导 IEC 增殖 (200%，P=0.01)，但阻断 EPI 和 AR 可显著降低增殖。在体内，与野生型小鼠相比，TLR4(-/-) 小鼠在急性结肠炎期间黏膜 EPI 和 AR 的表达明显降低 (P=0.02)。EPI 和 AR 在响应黏膜损伤时表现出不同的动力学：在 DSS 的第 7 天，EPI 的表达急剧上调，但在第 14 天的恢复期间下降。相比之下，在黏膜损伤和修复期间，AR 的表达持续上调。我们表明 TLR4 调节 EPI 和 AR 的表达，并且这两种 EGFR 配体对于 IEC 的最佳增殖都是必需的。EPI 和 AR 的表达的不同动力学表明它们在急性损伤与修复方面具有不同的作用。我们的结果强调了细菌感应对 IEC 动态平衡的作用，并可能导致针对黏膜愈合和预防肿瘤发生的靶向治疗。
