Glucagon-like peptide 2 induces vasoactive intestinal polypeptide expression in enteric neurons via phophatidylinositol 3-kinase-γ signaling.
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.
Gastrointestinal Research Group, Snyder Institute for Chronic Diseases.
Elaine
E
de Heuvel
Laurie
L
Wallace
Keith A
KA
Sharkey
David L
DL
Sigalet
D000818:Animals; D002454:Cell Differentiation / Q000187:drug effects / Q000235:genetics; D002478:Cells, Cultured; D051959:ELAV Proteins / Q000378:metabolism; D017615:Enteric Nervous System / Q000187:drug effects / Q000378:metabolism*; D066246:ErbB Receptors / Q000378:metabolism; D005904:Glial Fibrillary Acidic Protein / Q000378:metabolism; D053767:Glucagon-Like Peptide 2 / Q000494:pharmacology*; D007150:Immunohistochemistry; D051379:Mice; D020880:Neuregulins / Q000378:metabolism; D009457:Neuroglia / Q000187:drug effects / Q000378:metabolism; D009474:Neurons / Q000187:drug effects / Q000378:metabolism*; D018739:Oncogene Proteins v-erbB / Q000096:biosynthesis / Q000235:genetics; D058539:Phosphatidylinositol 3-Kinase / Q000378:metabolism* / Q000502:physiology; D051381:Rats; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology; D058570:TOR Serine-Threonine Kinases / Q000378:metabolism; D014660:Vasoactive Intestinal Peptide / Q000096:biosynthesis*
D051959:ELAV Proteins; D005904:Glial Fibrillary Acidic Protein; D053767:Glucagon-Like Peptide 2; D020880:Neuregulins; D018739:Oncogene Proteins v-erbB; D014660:Vasoactive Intestinal Peptide; D058539:Phosphatidylinositol 3-Kinase; D066246:ErbB Receptors; D058570:TOR Serine-Threonine Kinases