Rabbit antibodies against human GFR-1, IL-17R, nuclear factor kappa B (NF-B) p65, and antibody-specific blocking peptides were purchased from Santa Cruz Biotechnology (Santa Cruz, CA,http://www.scbt.com). or hyperosmotic media. IL-17 activated NF-B by p65 phosphorylation at serine 536 and nuclear translocation. GDNF or NF-B-I blocked IL-17-induced NF-B p65 activation and production of inflammatory mediators. Furthermore, GDNF suppressed the production of Th17-inducing cytokines through inhibiting NF-B activation. These findings demonstrate that limbal progenitor cell-produced neurotrophic factor GDNF suppresses IL-17-mediated inflammation via NF-B signaling pathway. This may represent a unique immunoprotective property of limbal stem cells against inflammatory challenges on the ocular surface. Cinnamaldehyde Keywords:Glial cell-derived neurotrophic factor, Adult stem cell, Immunoprotection, Th17, Corneal epithelium == Introduction == The concept that the corneal epithelium is maintained by stem cells residing in the limbal region of the eye was originally proposed by Davanger and Evensen [1]. Since then, substantial evidence supporting the limbal location of corneal epithelial stem cells has emerged, although a Rabbit Polyclonal to ADCK3 definitive marker identifying the limbal stem cells remains elusive. The major evidence includes the following: limbal epithelial basal cells retain tritiated thymidine for long periods thus indicating that they are slow cycling [2]; limbal basal cells have a greater proliferative capacity in vitro than central and paracentral corneal epithelial cells [3]; wounding or surgical removal of the limbus results in delayed healing with noncorneal epithelium [4]. Evidence of limbal stem cell deficiency is often seen in patients with severe or chronic ocular surface inflammation. The ability of these cells to resist damaging effects of inflammation is essential for their survival. Glial cell line-derived neurotrophic factor (GDNF) is a potent neurotrophic Cinnamaldehyde factor (NTF) that enhances the survival of cells in the peripheral and central nervous system, such as dopaminergic neurons, motor neurons, and auditory neurons. GDNF binds to its high-affinity membrane-bound GDNF family receptor (GFR) -1 and initiates a signaling cascade [5]. Although NTFs are defined as molecules that maintain neuronal cells, they possess a range of functions outside the nervous system [6,7]. For example, GDNF was identified as an essential growth factor supporting self-renewal of spermatogonial stem cells. GDNF receptor GFR-1 is strongly expressed by a subset of spermatogonia, including the stem cells for spermatogenesis [8,9]. Interestingly, we have found that GDNF and GFR-1 are components of the human corneal epithelial precursor cell phenotype [10] and that GDNF gene delivery enhances survival of human corneal epithelial cells [11]. Interleukin (IL)-17-producing T lymphocytes have been recently shown to comprise a lineage of T-helper cells known as T-helper-17 (Th17) cells, which are distinct from Th1 and Th2 cells. The Th17 pathway has been shown to be involved in the pathogenesis of many autoimmune and inflammatory diseases, particularly those occurring in mucosal tissues such as the ocular surface [1215]. The initiation of Th17 cell differentiation from naive CD4+T-cells requires transforming growth factor (TGF)- and IL-6; and the survival, expansion, and efficient production of IL-17 by these Th17 cells require additional cytokines including IL-23, IL-21, and IL-1 [1618]. IL-17 initiates proinflammatory effects by binding to the IL-17 receptor (IL-17R), which is expressed by a variety of cell types including epithelial, endothelial, and fibroblastic stromal cells [19,20]. We have observed that mucosal epithelium are enriched for Th17-inducing cytokines, Th17 inflammation developed on ocular surface, and the inducing cytokines produced by ocular surface epithelium promote Th17 differentiation of nave CD4+ T-cells [2123]. Cinnamaldehyde In this study, we show that GDNF Cinnamaldehyde and its receptor GFR-1 are exclusively localized to the basal layer of limbal epithelium where stem cells reside, whereas IL-17R are not expressed by this cell layer. We further investigated the potential role of GDNF in suppressing IL-17-mediated inflammation in corneal epithelial stem cells. Our findings indicate that the immunoprotective property of adult stem cells by Cinnamaldehyde producing a novel neurotrophic factor GDNF, which may have therapeutic implication for treating Th17-mediated ocular surface diseases. == Materials and Methods == == Material and Reagents == Cell culture dishes, plates, centrifuge tubes, and other plastic ware were purchased from Becton Dickinson (Lincoln.