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8 CCFC STUDENT PRIZE. EXPRESSION OF NERVE GROWTH FACTOR (NGF) IN THE MUCOSA OF THE CONTROL AND INFLAMED RAT COLON RDP Stanzel, SR Lourenssen, MG Blennerhassett BACKGROUND: The enteric nervous system (ENS), a complex neuronal network, influences all aspects of intestinal function. Inflammation causes structural damage to the ENS ranging from axonal degeneration to neuronal death. We have recently identified extensive axonal growth following colitis that restored innervation of target tissues. The factors regulating this are unknown, but may involve neurotrophins such as NGF.
GIDRU, Department of Biology, Queen’s University, Kingston, Ontario
HYPOTHESIS: NGF is a candidate neurotrophin due to its involvement in axonal regeneration and proliferation elsewhere. We hypothesized that proinflammatory mediators may stimulate its production from intestinal epithelial cells and/or immune cells in the inflamed mucosa.
METHODS AND RESULTS: NGF expression in the rat intestinal mucosa was characterized using the TNBS model of colitis. Semiquantitative PCR analysis of the mucosa showed that NGF transcription was upregulated 10-fold within 6 h postinduction of colitis and remained elevated at two days post-TNBS. While ELISA and western blot analysis identified a very low basal level of NGF in the control mucosa, this rose markedly with inflammation: the mature 13 kDa NGF was up-regulated 36-fold over control within 6 hr and thereafter, corresponding to the profile of mRNA shown by PCR. A bioassay using the NGF-responsive PC12 cell line confirmed the activity of mucosa-derived NGF, with this activity reduced by prior incubation with a NGF-specific antibody. Immunocytochemistry showed elevated NGF expression that was limited to the epithelial layer of the inflamed mucosa. Preliminary PCR data from laser capture microdissection (LCM) experiments indicate that a rapid increase of NGF mRNA by epithelial cells of the inflamed mucosa is responsible for the observed upregulation of NGF in the inflamed intestine.
CONCLUSION: Inflammation causes the rapid elevation of NGF in the intestinal mucosa due to increased expression in the epithelial layer. This may contribute to the axonal proliferation seen in colitis, and could be important in the restoration of homeostasis after an inflammatory episode.
Supported by the Crohn’s and Colitis Foundation of Canada