ENOS signaling is essential in GLP‐2‐mediated stimulation of blood flow, but not cell proliferation in the mouse gut

Abstract

Through a G protein‐coupled receptor, glucagon‐like peptide‐2 (GLP‐2) stimulates intestinal crypt cell proliferation and mucosal blood flow. GLP‐2 receptor is localized to enteric neurons, endocrine cells, and myofibroblasts, but not enterocytes. However, it is largely unknown how GLP‐2 receptor‐activated mitogenic, cytoprotective, and vasoactive signals are conveyed to the intestinal epithelium. Nitric oxide can function as a cellular signal to regulate cell growth and blood flow. Thus, our objective was to determine whether nitric oxide is a key mediator in the GLP‐2 receptor‐activated enteric signaling network. Endothelial nitric oxide synthase knockout (eNOS KO) and wild‐type (eNOS WT) mice (n=40) were subcutaneously injected with GLP‐2 or saline for 14 d, and with BrdU 2 h prior to euthanization. Mucosal cell proliferation, apoptosis, and blood flow were determined by BrdU‐positive cells, active caspase‐3 abundance, and hemoglobin (Hb) content, respectively. There was no difference between eNOS KO and WT mice in gut growth (indicated by mucosal weight, protein mass, villous height and crypt depth), cell proliferation, apoptosis, or blood flow. GLP‐2 increased gut growth by stimulating crypt cell proliferation in both KO and WT mice. GLP‐2 appeared to decrease apoptosis in the WT mice, but increase it in the KO mice. Importantly, GLP‐2 increased gut blood flow in the WT mice, but not in the KO mice. We conclude that GLP‐2‐induced vasoactive action is mediated by the eNOS signaling, but GLP‐2‐stimulated tropic action is independent of it. (Supported by USDA CRIS 6250‐51000‐043 and NIDDK K01DK75489)