Glucagon-like peptide 2 (GLP-2) is an important intestinal
growth factor with anti-inflammatory activity. We hypothesized that GLP-2 decreases mucosal
inflammation and the associated increased epithelial proliferation by downregulation of Th1
cytokines attributable to reprogramming of lamina propria immune regulatory cells via an
interleukin-10 (IL-10)-independent pathway. The effects of GLP-2 treatment were studied using the IL-10-deficient (IL-10(-/-)) mouse model of
colitis. Wild-type and IL-10(-/-) mice received saline or GLP-2 (50 microg/kg sc) treatment for 5 days. GLP-2 treatment resulted in significant amelioration of animal
weight loss and reduced intestinal
inflammation as assessed by histopathology and
myeloperoxidase levels compared with saline-treated animals. In
colitis animals, GLP-2 treatment also reduced crypt cell proliferation and crypt cell apoptosis. Proinflammatory (IL-1beta, TNF-alpha, IFN-gamma,)
cytokine protein levels were significantly reduced after GLP-2 treatment, whereas
IL-4 was significantly increased and
IL-6 production was unchanged. Fluorescence-activated cell sorting analysis of lamina propria cells demonstrated a decrease in the CD4(+) T cell population following GLP-2 treatment in colitic mice and an increase in CD11b(+)/F4/80(+) macrophages but no change in CD25(+)FoxP3 T cells or CD11c(+) dendritic cells. In
colitis animals, intracellular
cytokine analysis demonstrated that GLP-2 decreased lamina propria macrophage
TNF-alpha production but increased
IGF-1 production, whereas
transforming growth factor-beta was unchanged. GLP-2-mediated reduction of crypt cell proliferation was associated with an increase in intestinal epithelial cell suppressor of
cytokine signaling (SOCS)-3 expression and reduced STAT-3 signaling. This study shows that the anti-inflammatory effects of GLP-2 are
IL-10 independent and that GLP-2 alters the mucosal response of inflamed intestinal epithelial cells and macrophages. In addition, the suggested mechanism of the reduction in
inflammation-induced proliferation is attributable to GLP-2 activation of the SOCS-3 pathway, which antagonizes the IL-6-mediated increase in STAT-3 signaling.