RO4929097, a Selective.-Secretase Inhibitor, Inhibits Subretinal Fibrosis Via Suppressing Notch and ERK1/2 Signaling in Laser-Induced Mouse Model

PURPOSE. This study aimed to explore whether RO4929097 (RO), a specific gamma-secretase inhibitor, could inhibit the subretinal fibrosis in laser-induced mouse model and the relevant molecular mechanisms. METHODS. Male C57BL/6J mice were used to produce choroidal neovascularization (CNV) and subretinal fibrosis by laser photocoagulation, and RO was administered intravitreally 1 day after laser induction. The sizes of CNV and subretinal fibrosis were measured and quantified in both 2D and 3D constructions. The ARPE-19 cell line and primary human RPE (phRPE) cells were treated with TGF beta 1, in combination with or without RO, to examine Notch related molecules, epithelial mesenchymal transition (EMT), cell viability, migration, and contractile function, as well as the crosstalk between Notch and other EMT relevant signaling pathways. RESULTS. Intravitreal injection of RO reduced the sizes of both CNV and subretinal fibrosis in laser-induced young and old mice at day 7 and day 14 after laser induction. Moreover, EMT and Notch activation in RPE-choroid complexes from laser-induced mice were significantly attenuated by RO. In vitro, TGF beta 1 activated Notch signaling and induced EMT in ARPE-19 cells, accompanied by enhanced EMT-related function, which were inhibited by RO. The inhibition of RO on EMT was further confirmed in TGF beta 1-treated phRPE cells. Blockage of Notch signaling by RO could inhibit ERK1/2 signaling; whereas ERK1/2 inhibition had no effect on Notch. The action of RO was independent of Smad2/3 or p38, and co-inhibition of Notch and Smad2/3 showed synergistic effect on EMT inhibition. CONCLUSIONS. RO exerts its antifibrotic effect by directly inhibiting Notch signaling and indirectly suppressing ERK1/2 signaling. Targeting Notch signaling might provide a therapeutic strategy in prevention and treatment of subretinal fibrosis in neovascular age-related macular degeneration (nAMD).