Extracellular Vesicles Mediate Anti-Oxidative Response-In Vitro Study in the Ocular Drainage System

The importance of extracellular vesicles (EVs) as signaling mediators has been emphasized for several pathways with only limited data regarding their role as protective messages during oxidative stress (OS). The ocular drainage system is unique by being continuously exposed to OS and having a one-way flow of the aqueous humor carrying EVs taking role in glaucoma disease. Here, we aimed to examine the ability of EVs derived from the non-pigmented ciliary epithelium (NPCE)-the aqueous humor producing cells exposed to OS-to deliver protecting messages to the trabecular meshwork (TM)-the aqueous humor draining cells-a process with significance to the pathophysiology of glaucoma disease. EVs extracted from media of NPCE cells exposed to non-lethal OS and their unstressed control were incubated with TM cells. The effects of EVs derived from oxidative stressed cells on the activation of the nuclear factor erythroid 2-related factor 2-Kelch-like ECH-associated protein 1 (Nrf2-Keap1), a major OS pathway, and of the Wnt pathway, known for its role in primary open-angle glaucoma, were evaluated. EVs derived from oxidized NPCE cells significantly protected TM cells from direct OS. The TM cells uptake of EVs from oxidized NPCE and their cytosolic Nrf2 levels were significantly higher at 8 h post-exposure. EVs derived from oxidized NPCE cells significantly attenuated Wnt protein expression in TM cells and activated major antioxidant genes as measured by qRT-PCR. TM cells exposed to EVs derived from oxidized NPCE cells exhibited significantly lower OS and higher super oxide dismutase and catalase activity. Finally, we were able to show that carbonylated proteins and products of oxidized protein are presented in significantly higher levels in EVs derived from oxidized NPCE cells, supporting their suggested role in the signaling process. We hypothesize that these findings may have implications beyond understanding the pathophysiology of glaucoma disease and that transmitting signals that activate the antioxidant system in target cells represent a broad response common to many tissues communication.