Administration of the isotype-matched control antibody did not have a significant effect on the amount of VEGF. Activin A Modulates Corneal Neovascularization in the Cornea Scrape Model In agreement with our previous report,27 the percentage of vascularized corneal surface increased on day 12 after the scraping to 32.16 6.79%, whereas unscraped corneas are not vascularized (therefore the percentage of vascularized corneal area is 0). specific inhibitors of p38 or p42/44 MAPK abolished the stimulatory effect of activin A on VEGF production. We conclude that activin A stimulates inflammatory corneal Rabbit polyclonal to pdk1 angiogenesis by increasing VEGF levels through a p38 and p42/44 MAPK-dependent mechanism. Corneal neovascularization is usually a disabling condition that results in loss of the immunological privilege of the cornea and ultimately in visual impairment. It is a common manifestation of inflammatory, infectious, and traumatic diseases of the cornea and the limbal stem cell barrier. Although laser treatment and surgical intervention offer potential therapeutic options, corneal neovascularization still remains a therapeutic puzzle because, in many occasions, cornea avascularity and transparency are not restored. The potential benefits of controlling Trofosfamide angiogenesis have been exhibited in experimental models for various untreatable ocular conditions that involve neovascularization.1C3 These studies have highlighted the pivotal role of vascular endothelial growth factor (VEGF) in regulating endothelial cell growth and neovascularization. VEGF refers to a family of angiogenic and vascular permeability-enhancing peptides derived from alternatively spliced mRNAs. 4 VEGF bioactivity is usually primarily mediated via two high-affinity cognate receptors, KDR/Flk-1 and Flt-1.5,6 Recently, it was suggested that VEGF plays an important role in corneal neovascularization because exogenous VEGF stimulates this process7 and a neutralizing anti-VEGF antibody inhibits it.8 We have previously reported that VEGF expression is up-regulated in scraped corneas during the course of corneal neovascularization. Understanding the molecular mechanisms regulating this forced expression will help identify potential therapeutic candidates for the treatment or even prevention of corneal neovascularization. Activins represent a distinct group of the transforming growth factor (TGF)- superfamily, that comprise one and three chains (A, B, and C).9,10 The bioactive molecule activin A consists of two monomeric A chains linked by disulfide bonds.10 The biological effects of activins are mediated via signaling through two families (type I and II) of transmembranous serine-threonine kinase receptors.11C15 After ligand binding, a heterodimeric complex is formed by a type I and Trofosfamide a type II receptor that initiates phosphorylation of the type I receptor and activation of downstream signaling cascades involving the Sma and Mad (mothers against decapentaplegic)-related protein (Smad).16 One of the most important functions of activin A Trofosfamide is the regulation of cell differentiation. Activin A controls several aspects of hematopoiesis17,18,19 and regulates cell differentiation in the ovary, placenta, prostate, and testis.10,20 During embryogenesis, it is instrumental for axis development and organogenesis in a variety of species.21 In Trofosfamide adults, activins function as hormone-like feedback regulators in the reproductive system.22 Furthermore, the presence of activin has been related to wound healing. In the eye, members of the activin family have been discovered in retinal pigment epithelium.23 Activin A and its receptors were recently described in preretinal membranes from eyes with ischemic and nonischemic vitreoretinal proliferative diseases, a result that agrees with a role of activin A in neovascularization.24 We have recently found that VEGF and activin A expression is co-ordinated in fibrovascular membranes from patients with Trofosfamide age-related macular degeneration (manuscript submitted). Because we have also shown that genes encoding for the A chain as well as several activin receptors are transcribed in the cornea,25 we investigated the role of activin A in corneal angiogenesis and the regulation of VEGF expression. Materials and Methods Cell Culture Human corneal epithelial cells (passage 2; Cascade Biologics, Portland, OR) were maintained in tissue culture media according to the manufacturers instructions. Cells were plated into six-well plastic dishes and used for experiments when they reached 80% confluence. Fresh serum-free media were placed on the cells 12 hours before experiments. The p38 kinase inhibitor SB 202190 or the MAPK inhibitor PD 098059 (Calbiochem, La Jolla, CA) or vehicle (dimethyl sulfoxide), were added to the cells at a concentration of 50 mol/L, followed 1 hour later by activin A (100.