Gastrointestinal Research Group, Snyder Institute for Chronic Diseases.
Am J Physiol Endocrinol Metab. 2012 Oct 15;303(8):E994-1005. doi: 10.1152/ajpendo.00291.2012. Epub 2012 Aug 14.
Glucagon-like peptide 2 (GLP-2) is an enteroendocrine hormone trophic for intestinal mucosa; it has been shown to increase enteric neuronal expression of vasoactive intestinal polypeptide (VIP) in vivo. We hypothesized that GLP-2 would regulate VIP expression in enteric neurons via a phosphatidylinositol-3 kinase-γ (PI3Kγ) pathway. The mechanism of action of GLP-2 was investigated using primary cultures derived from the submucosal plexus (SMP) of the rat and mouse colon. GLP-2 (10(-8) M) stimulation for 24 h increased the proportion of enteric neurons expressing VIP (GLP-2: 40 ± 6% vs. control: 22 ± 5%). GLP-2 receptor expression was identified by immunohistochemistry on neurons (HuC/D+) and glial cells (GFAP+) but not on smooth muscle or fibroblasts in culture. Over 1-4 h, GLP-2 stimulation of SMP increased phosphorylated Akt/Akt ratios 6.1-fold, phosphorylated ERK/ERK 2.5-fold, and p70S6K 2.2-fold but did not affect intracellular cAMP. PI3Kγ gene deletion or pharmacological blockade of PI3Kγ, mammalian target of rapamycin (mTOR), and MEK/ERK pathways blocked the increase in VIP expression by GLP-2. GLP-2 increased the expression of growth factors and their receptors in SMP cells in culture [IGF-1r (3.2-fold increase), EGFr (5-fold), and ErbB-2-4r (6- to 7-fold)] and ligands [IGF-I (1.5-fold), amphiregulin (2.5-fold), epiregulin (3.2-fold), EGF (7.5-fold), heparin-bound EGF (2.0-fold), β-cellulin (50-fold increase), and neuregulins 2-4 (300-fold increase) (by qRT-PCR)]. We conclude that GLP-2 acts on enteric neurons and glial cells in culture via a PI3Kγ/Akt pathway, stimulating neuronal differentiation via mTOR and ERK pathways, and expression of receptors and ligands for the IGF-I and ErbB pathways.
胰高血糖素样肽 2（GLP-2）是一种肠内分泌激素，对肠道黏膜具有营养作用；它已被证明可在体内增加肠神经元血管活性肠肽（VIP）的表达。我们假设 GLP-2 将通过磷脂酰肌醇-3 激酶-γ（PI3Kγ）途径调节肠神经元中的 VIP 表达。通过源自大鼠和小鼠结肠黏膜下丛（SMP）的原代培养物研究 GLP-2 的作用机制。GLP-2（10（-8）M）刺激 24 小时可增加表达 VIP 的肠神经元的比例（GLP-2：40±6%vs.对照：22±5%）。免疫组织化学在神经元（HuC/D+）和神经胶质细胞（GFAP+）上鉴定了 GLP-2 受体表达，但在培养物中的平滑肌或成纤维细胞上没有表达。在 1-4 小时内，SMP 中 GLP-2 刺激使磷酸化 Akt/Akt 比值增加 6.1 倍，磷酸化 ERK/ERK 增加 2.5 倍，p70S6K 增加 2.2 倍，但不影响细胞内 cAMP。PI3Kγ 基因缺失或 PI3Kγ、哺乳动物雷帕霉素靶蛋白（mTOR）和 MEK/ERK 途径的药理学阻断阻止了 GLP-2 引起的 VIP 表达增加。GLP-2 增加了培养物中 SMP 细胞中生长因子及其受体的表达[胰岛素样生长因子 1 受体（IGF-1r，增加 3.2 倍），表皮生长因子受体（EGFr，增加 5 倍）和 ErbB-2-4r（增加 6-7 倍）]和配体[胰岛素样生长因子 I（IGF-I，增加 1.5 倍）， Amphiregulin（增加 2.5 倍），Epiregulin（增加 3.2 倍），EGF（增加 7.5 倍），肝素结合 EGF（增加 2.0 倍），β-细胞素（增加 50 倍）和神经调节蛋白 2-4（增加 300 倍）（通过 qRT-PCR）]。我们的结论是，GLP-2 通过 PI3Kγ/Akt 途径作用于培养物中的肠神经元和神经胶质细胞，通过 mTOR 和 ERK 途径刺激神经元分化，并表达 IGF-I 和 ErbB 途径的受体和配体。
