Inhibition of Tnf–A Reduces Laser–Induced Choroidal Neovascularization

Abstract

Purpose: : To investigate the role of the TNF–α in the development of laser–induced choroidal neovascularization (CNV) in a mouse model.

Methods: : Laser photocoagulation was used to induce CNV in wild–type C57BL/6J mice by making four separate choroidal burns in each eye. The level of protein expression of TNF–α was semiquantitatively evaluated by Western blot analysis of the choroidal and RPE layer from C57/BL6 mice with or without laser treatment. Animals were treated 3 days before or 3 days after laser injury with recombinant TNF receptor P75 (etanercept, 5ug/h), chimeric monoclonal antibody (infliximab, 5ug/h), and purified rat anti–mouse/rat TNF monoclonal antibody (TNF–mAb, 50ng/h) respectively for 7 days by intraperitonealy implanted osmotic pumps. Histopathology and flat–mount preparations were performed immediately after fluorescein angiography at day 7, 10 or 14 after laser

Results: : Western blotting demonstrated that TNF–α was highly expressed in choroidal endothelial cells and RPE cells 1 week after laser injury compared to control mice without laser. Etanercept and infliximab administrated 3 days before laser–damage significantly reduced CNV size and pathological fluorescein leakage in comparison to the control group when evaluated, one and two weeks after laser injury. The inhibitory effect of the monoclonal TNF–α antibody on CNV formation was evident at two weeks after photocoagulation but not at one week. Only etanercept administered 3 days after laser injury still reduced significantly the development of CNV lesions. Histopathology confirmed that CNV lesions in treated mice had smaller diameter and thinner center compared to the control animals.Anti–TNF–a treatment reduces the size and leakage of laser–induced CNV. Theses results suggest the involvement of TNF–a in the development of laser–induced CNV and its potential use as a therapeutic agent in the matter of age related macular degeneration.

Keywords: age-related macular degeneration • choroid: neovascularization