Jeppsson Sabrina, Srinivasan Shanthi, Chandrasekharan Bindu
Division of Digestive Diseases, Department of Medicine, Emory University, Atlanta, Georgia.
Veterans Affairs Medical Center, Decatur, Atlanta, Georgia; and.
Am J Physiol Gastrointest Liver Physiol. 2017 Feb 1;312(2):G103-G111. doi: 10.1152/ajpgi.00410.2015. Epub 2016 Nov 17.
We have demonstrated that neuropeptide Y (NPY), abundantly produced by enteric neurons, is an important regulator of intestinal inflammation. However, the role of NPY in the progression of chronic inflammation to tumorigenesis is unknown. We investigated whether NPY could modulate epithelial cell proliferation and apoptosis, and thus regulate tumorigenesis. Repeated cycles of dextran sodium sulfate (DSS) were used to model inflammation-induced tumorigenesis in wild-type (WT) and NPY knockout (NPY) mice. Intestinal epithelial cell lines (T84) were used to assess the effects of NPY (0.1 µM) on epithelial proliferation and apoptosis in vitro. DSS-WT mice exhibited enhanced intestinal inflammation, polyp size, and polyp number (7.5 ± 0.8) compared with DSS-NPY mice (4 ± 0.5, P < 0.01). Accordingly, DSS-WT mice also showed increased colonic epithelial proliferation (PCNA, Ki67) and reduced apoptosis (TUNEL) compared with DSS-NPY mice. The apoptosis regulating microRNA, miR-375, was significantly downregulated in the colon of DSS-WT (2-fold, P < 0.01) compared with DSS-NPY-mice. In vitro studies indicated that NPY promotes cell proliferation (increase in PCNA and β-catenin, P < 0.05) via phosphatidyl-inositol-3-kinase (PI3-K)-β-catenin signaling, suppressed miR-375 expression, and reduced apoptosis (increase in phospho-Bad). NPY-treated cells also displayed increased c-Myc and cyclin D1, and reduction in p21 (P < 0.05). Addition of miR-375 inhibitor to cells already treated with NPY did not further enhance the effects induced by NPY alone. Our findings demonstrate a novel regulation of inflammation-induced tumorigenesis by NPY-epithelial cross talk as mediated by activation of PI3-K signaling and downregulation of miR-375.
NEW & NOTEWORTHY: Our work exemplifies a novel role of neuropeptide Y (NPY) in regulating inflammation-induced tumorigenesis via two modalities: first by enhanced proliferation (PI3-K/pAkt), and second by downregulation of microRNA-375 (miR-375)-dependent apoptosis in intestinal epithelial cells. Our data establish the existence of a microRNA-mediated cross talk between enteric neurons producing NPY and intestinal epithelial cells, and the potential of neuropeptide-regulated miRNAs as potential therapeutic molecules for the management of inflammation-associated tumors in the gut.
我们已经证明，由肠道神经元大量产生的神经肽Y（NPY）是肠道炎症的重要调节因子。然而，NPY在慢性炎症进展为肿瘤发生过程中的作用尚不清楚。我们研究了NPY是否可以调节上皮细胞增殖和凋亡，从而调节肿瘤发生。使用葡聚糖硫酸钠（DSS）的重复循环来模拟野生型（WT）和NPY基因敲除（NPY）小鼠的炎症诱导肿瘤发生。使用肠道上皮细胞系（T84）评估NPY（0.1μM）对体外上皮细胞增殖和凋亡的影响。与DSS-NPY小鼠（4±0.5，P<0.01）相比，DSS-WT小鼠表现出更强的肠道炎症、息肉大小和息肉数量（7.5±0.8）。因此，与DSS-NPY小鼠相比，DSS-WT小鼠还表现出结肠上皮细胞增殖增加（PCNA、Ki67）和凋亡减少（TUNEL）。与DSS-NPY小鼠相比，DSS-WT小鼠结肠中凋亡调节性微小RNA miR-375显著下调（2倍，P<0.01）。体外研究表明，NPY通过磷脂酰肌醇-3-激酶（PI3-K）-β-连环蛋白信号通路促进细胞增殖（PCNA和β-连环蛋白增加，P<0.05），抑制miR-375表达，并减少凋亡（磷酸化Bad增加）。NPY处理的细胞还表现出c-Myc和细胞周期蛋白D1增加，以及p21减少（P<0.05）。向已经用NPY处理的细胞中添加miR-375抑制剂并没有进一步增强单独由NPY诱导的作用。我们的研究结果证明了NPY与上皮细胞通过PI3-K信号通路激活和miR-375下调介导的相互作用对炎症诱导肿瘤发生的新调节作用。
我们的工作例证了神经肽Y（NPY）在通过两种方式调节炎症诱导肿瘤发生中的新作用：首先是通过增强增殖（PI3-K/pAkt），其次是通过下调肠道上皮细胞中微小RNA-375（miR-375）依赖性凋亡。我们的数据证实了产生NPY的肠道神经元与肠道上皮细胞之间存在微小RNA介导的相互作用，以及神经肽调节的微小RNA作为肠道炎症相关肿瘤治疗潜在分子的潜力。
