C5a-Induced Autophagy Dysfunction Promotes Choroidal Neovascularization Through the ROS-Inflammatory Pathway

Age-related macular degeneration (AMD) is the leading cause of blindness in aging populations. C5a is the primary component of drusen and exerts a pivotal role in AMD, facilitating its progression. In the present research, we explored how C5a exacerbates AMD pathogenesis and its interplay with autophagic pathways, mitochondrial reactive oxygen species (ROS), and proinflammatory cytokines.

Human retinal pigment epithelial (ARPE-19) cells were exposed to recombinant C5a. Autophagy was modulated using rapamycin or 3-MA, and ROS dynamics were perturbed with DPI or rotenone. Autophagy markers (LC3-II, Beclin-1, p62/SQTSM1) were analyzed via Western blot. Mitochondrial ROS levels were quantified using MitoSOX Red, while cytokine secretion (VEGF, MCP-1, IL-6, and IL-8) was measured by ELISA. C57BL/6 mice were utilized to model choroidal neovascularization (CNV), a prevalent subtype of AMD, which was induced by laser photocoagulation.

C5a stimulation significantly increased LC3-II, Beclin-1, and p62/SQTSM1. The cytokine secretion (VEGF, MCP-1, IL-6, and IL-8), ROS, and the areas in laser-induced CNV were significantly enlarged after C5a treatment. Autophagy activator significantly downregulated the cytokine secretion (VEGF, MCP-1, IL-6, and IL-8), ROS, and the areas in laser-induced CNV. ROS inhibitors can markedly diminish IL-6, IL-8, MCP-1, and VEGF, as well as the progression of CNV.

Our results suggest that C5a induced the dysfunction of autophagy and increased the mitochondrial ROS, as well as the mitochondrial ROS-driven cytokine release that fuels CNV formation.