Age-related macular degeneration (AMD), especially neovascular AMD with choroidal neovascularization (CNV), is the leading cause of blindness in the elderly. Although matrix metalloproteinases (MMPs) are involved in pathological ocular angiogenesis, including CNV, the cellular origin of MMPs in AMD remains unknown. The present study investigated the role of microglial MMPs in CNV. MMP activities were analyzed by gelatin zymography in aqueous humor samples from patients with CNV and laser-induced CNV mice. Active MMP-9 was increased in the aqueous humor samples from neovascular AMD patients compared with control subjects. In the retinal pigment epithelium (RPE)/choroid from CNV mice, active MMP-9 increased, beginning 1 h post-CNV induction, and remained upregulated until Day 7. In RPE/choroid from CNV mice, active MMP-9 was suppressed by minocycline, a known microglial inhibitor, at 6 h and 1-day post-CNV induction. Flow cytometry revealed that the proportion of activated microglia increased very early, beginning at 1 h post-CNV induction, and was maintained until Day 7. Similarly, immunohistochemistry revealed increased microglial activation and MMP-9 expression on CNV lesions at 6 h and 1-day post-CNV induction. SB-3CT, an MMP inhibitor, decreased vascular leakage and lesion size in laser-induced CNV mice. These findings indicated nearly immediate recruitment of activated microglia and very early MMP-9 activation in the RPE/choroid. The present study newly identified a potential role for early microglial MMP-9 expression in CNV, and furthermore that modulating microglial MMP expression is a novel putative therapeutic for CNV.

Purpose To assess the therapeutic effects of fursultiamine on choroidal neovascularization (CNV) through its modulation of inflammation and metabolic reprogramming in the retinal pigment epithelium (RPE). Methods The anti-angiogenic effects of fursultiamine were assessed by measuring vascular leakage and CNV lesion size in the laser-induced CNV mouse model. Inflammatory responses were evaluated by quantitative polymerase chain reaction, western blot, and ELISA in both CNV eye tissues and in vitro cell cultures using ARPE-19 cells or primary human RPE (hRPE) cells under lipopolysaccharide (LPS) treatment or hypoxia. Mitochondrial respiration was assessed by measuring oxygen consumption in ARPE-19 cells treated with LPS with or without fursultiamine, and lactate production was measured in ARPE-19 cells subjected to hypoxia with or without fursultiamine. Results In laser-induced CNV, fursultiamine significantly decreased vascular leakage and lesion size, as well as the numbers of both choroidal and retinal inflammatory cytokines, including IL-1β, IL-6, IL-8, and TNF-α. In LPS-treated ARPE-19 cells, fursultiamine decreased proinflammatory cytokine secretion and nuclear factor kappa B phosphorylation. Furthermore, fursultiamine suppressed LPS-induced upregulation of IL-6, IL-8, and monocyte chemoattractant protein-1 in a dose-dependent and time-dependent manner in primary hRPE cells. Interestingly, fursultiamine significantly enhanced mitochondrial respiration in the LPS-treated ARPE-19 cells. Additionally, fursultiamine attenuated hypoxia-induced aberrations, including lactate production and inhibitory phosphorylation of pyruvate dehydrogenase. Furthermore, fursultiamine attenuated hypoxia-induced VEGF secretion and mitochondrial fission in primary hRPE cells that were replicated in ARPE-19 cells. Conclusions Our findings show that fursultiamine is a viable putative therapeutic for neovascular age-related macular degeneration by modulating the inflammatory response and metabolic reprogramming by enhancing mitochondrial respiration in the RPE.