Celafolin A-1 Ameliorates Subretinal Fibrosis via Inhibition of Crystallin Alpha B in a Laser-Induced Choroidal Neovascularization Mouse Model

Age-related macular degeneration (AMD) is a leading cause of blindness in people over 65 years old. Anti-vascular endothelial growth factor (VEGF) therapy is the first-line treatment for neovascular AMD (nAMD); however, fibrosis remains an unmet medical need due to the lack of effective medications. This study evaluated eight natural products from <i>Celastrus orbiculatus</i>, which has been reported to have anti-inflammatory effects, for their effects on the fibrotic pathological process as well as choroidal neovascularization (CNV). We investigated the half-maximal inhibitory concentration (IC₅₀) values of these compounds on VEGF and alphasmooth muscle actin (α-SMA, a fibrosis marker) expression-induced by human acute monocytic cell (THP-1) conditioned media in retinal pigment epithelium cells (ARPE-19). Four compounds reduced both VEGF and α-SMA at 10 μM, with three-Celafolin A-1, COFH5645, and COFH543435-showing the highest potency. Intravitreal injections of the compound in a mouse model of CNV induced by laser photocoagulation confirmed its efficacy. Celafolin A-1 significantly reduced α-SMA and VEGF expression and decreased hyper-reflective lesions and CNV areas. Binding affinity measurements using biolayer interferometry identified an interaction between Celafolin A-1 and crystallin alpha B (Cryab), a protein involved in stress responses and fibrosis. Celafolin A-1 reduced the expression levels of Cryab as well as its phosphorylated form at Ser45, indicating that its mechanism involves the regulation of Cryab phosphorylation. Taken together, Celafolin A-1 exhibits dual inhibitory effects on VEGF and fibrosis, suggesting it as a candidate for the treatment of nAMD.