ABSTRACT
Although enteric glial cells (EGCs) have been demonstrated to play a key role in maintaining intestinal epithelial barrier integrity, it is not known how EGCs regulate this integrity. We therefore hypothesized that glial-derived neurotrophic factor (GDNF) produced by EGCs might be involved in this regulation. Here we investigated the role of GDNF in regulating epithelial barrier function in vivo. Recombinant adenoviral vectors encoding GDNF (Ad-GDNF) were administered intracolonically in experimental colitis induced by dextran sulphate sodium (DSS). The disease activity index (DAI) and histological score were measured. Epithelial permeability was assayed using Evans blue dye. The anti-apoptotic potency of GDNF in vivo was evaluated. The expression of tumour necrosis factor-alpha (TNF-alpha), interleukin-1beta (IL-1beta), and myeloperoxidase (MPO) activity were measured by ELISA assay and/or RT-PCR. The expression of ZO-1, Akt, caspase-3, and NF-kappaB p65 was analysed by western blot assay. Our results showed that GDNF resulted in a significant reduction in enhanced permeability, inhibited MPO activity, IL-1beta and TNF-alpha expression, and increased ZO-1 and Akt expression. Moreover, GDNF strongly prevented apoptosis in vivo and significantly ameliorated experimental colitis. Our findings indicate that GDNF participates directly in restoring epithelial barrier function in vivo via reduction of increased epithelial permeability and inhibition of mucosal inflammatory response, and is efficacious in DSS-induced colitis. These findings support the notion that EGCs are able to regulate intestinal epithelial barrier integrity indirectly via their release of GDNF in vivo. GDNF is namely an important mediator of the cross-talk between EGCs and mucosal epithelial cells. GDNF may be a useful therapeutic approach to the treatment of inflammatory bowel disease.
Subject(s)
Colitis/therapy , Glial Cell Line-Derived Neurotrophic Factor/physiology , Intestinal Absorption/physiology , Adenoviridae/genetics , Animals , Apoptosis , Colitis/pathology , Colitis/physiopathology , Colon/metabolism , Disease Models, Animal , Drug Evaluation, Preclinical/methods , Female , Genetic Therapy/methods , Genetic Vectors , Glial Cell Line-Derived Neurotrophic Factor/genetics , Glial Cell Line-Derived Neurotrophic Factor/metabolism , Inflammation Mediators/metabolism , Intestinal Mucosa/metabolism , Intestinal Mucosa/physiopathology , Membrane Proteins/metabolism , Mice , Mice, Inbred BALB C , NF-kappa B/metabolism , Permeability , Peroxidase/metabolism , Phosphatidylinositol 3-Kinases/physiology , Phosphoproteins/metabolism , Signal Transduction/physiology , Zonula Occludens-1 ProteinABSTRACT
BACKGROUND: Neuropeptide Y (NPY) from enteric neurons has been shown to play an important role in immune and inflammatory responses. The purpose of the present study was to investigate the effects of NPY antisense oligodeoxynucleotides (ODNs) on an experimental model of ulcerative colitis (UC). METHODS: NPY antisense ODNs were administered in experimental colitis induced by dextran sulfate sodium (DSS). The disease activity index (DAI) and histological score were observed. The tumor necrosis factor (TNF)-alpha and NPY levels were measured by enzyme-linked immunosorbent assay. Phosphorylated Akt (p-Akt) expression was determined by immunohistochemical staining. Activated nuclear factor (NF)-kappaB was assessed by western blot analysis. Myeloperoxidase (MPO) activity was determined by using MPO assay kit. RESULTS: A significant improvement was observed in DAI and histological score in rats with NPY antisense ODNs, and the increase in NPY and TNF-alpha levels, MPO activity, and the expression p-Akt and p-NF-kappaB in rats with DSS-induced colitis was significantly reduced following the administration of NPY antisense ODNs. CONCLUSION: The administration of NPY antisense ODNs leads to an amelioration of DSS-induced colitis, suggesting that NPY plays an important role in modulating inflammation in colitis, and NPY antisense ODNs may be a useful therapeutic approach to the treatment of UC.
