Activation of endothelial roundabout receptor 4 (Robo4) reduces the severity of virus induced keratitis (112.2)

Abstract

Abstract Anti angiogenic molecules exert a feedback control to restrain pathological angiogenesis, which include physical binding or inhibition of angiogenic signaling in blood vessel endothelial cells. The latter is the case when Slit2 ligand dependent activation of the blood vessel endothelial cell receptor roundabout 4 (Robo4) occurs. In this study, we demonstrate that Robo4 receptors are up regulated following herpes simplex virus (HSV) infection of the eye on the majority of the new blood vessel endothelial cells that occur in the corneal stroma. However, expression levels of the ligand for Robo4 receptors, Slit2, was not significantly increased during the disease process and the knockdown of Slit2 gene expression using lentiviral shRNAs had no effect on the extent of pathological angiogenesis. In contrast, providing additional Slit2 protein by subconjunctival administration resulted in significantly reduced angiogenesis. The Slit2 binding to Robo4 was shown to block the downstream VEGF signaling molecules Arf 6 and Rac 1 and reduced the anti-apoptotic molecule Bcl-xL in blood vessel endothelial cells. Our results indicate that augmenting the host Robo4/Slit2 system could provide a useful therapeutic approach to control pathological angiogenesis associated with HSV induced stromal keratitis (SK).