IGF-1-Mediated Survival from Induced Death of Human Primary Cultured Retinal Pigment Epithelial Cells Is Mediated by an Akt-Dependent Signaling Pathway

Degeneration of the human retinal pigmented epithelium (hRPE) is involved in several eye disorders such as age-related macular degeneration (AMD). In this study, we investigated the protective effect of IGF-1 on human primary cultured RPE cells and its underlying mechanism. IGF-1 dose- and time-dependently promoted the survival of RPE cells from serum deprivation. Western blot showed that IGF-1 stimulated the activation of the PI3K/Akt and MAPK pathways in hRPE. Inhibition of the PI3K/Akt pathway by the PI3K-specific inhibitor, LY294002 or inhibition of Akt by Akt-specific inhibitors Akt inhibitor VIII or SN-38, or downregulation Akt with siRNA specific for Akt blocked the effect of IGF-1 on hRPE. In contrast, blockade of the MAPK pathway with a specific inhibitor PD98059 had no effect. Interestingly, vitreous IGF-1 injection reversed the inhibitory effect of light exposure (a dry AMD model) on both a wave and b wave. Immunocytochemistry showed that vitreous IGF-1 injections promoted the survival of RPE cells in rat retina and the expression of RPE65 in RPE cells from light injury. These results indicate that IGF-1 is able to protect hRPE cell from different insults in vivo and in vitro. Further detailed studies may lead the way to a therapeutic intervention for retinal diseases in which cell death is an underlying contributory mechanism.