Purpose

Cigarette smoke increases the risk for age-related macular degeneration (AMD) e.g. through oxidative stress and mitochondrial damage in human retinal pigment epithelial (RPE) cells. Vascular endothelial growth factor (VEGF) promotes choroidal neovascularization in wet AMD, for which anti-VEGF injections are used as therapy. Since VEGF is important for the RPE cell functionality and integrity, too low VEGF levels increase the risk for RPE cell degeneration. Pigment epithelium-derived factor (PEDF) improves mitochondrial activity and reduces neovascularization. The aim of the present study was to examine the effects of the cigarette smoke component hydroquinone on the VEGF and PEDF levels in RPE cells.

Methods

IL-1α-primed ARPE-19 cells were exposed to hydroquinone (10 μM, 50 μM, 200 μM; 18 h, 1 h or 15 min). Enzyme-linked immunosorbent assay (ELISA) was used to detect the levels of intracellular VEGF as well as secreted VEGF and PEDF. The 2′,7′-dichlorofluorescin diacetate (DCFDA) probe was used to detect ROS production. Lactate dehydrogenase (LDH) and intracellular ATP were measured using commercial kits, and total protein concentrations using a protocol based on the Bradford method.

Results

Hydroquinone reduced the levels of both intra- and extracellular VEGF. In addition, the release of PEDF as well as the ratio between VEGF and PEDF were reduced at all used concentrations. ROS production increased at 50 μM hydroquinone, and the cell membrane was compromised at 200 μM hydroquinone after 15 min exposure. ATP levels were reduced from the 50 μM hydroquinone concentration upwards and total protein levels at all concentrations, already without cytotoxicity.

Conclusions

According to our present data, hydroquinone favors anti-angiogenic conditions but predisposes to the RPE cell degeneration, impaired mitochondrial function, and reduced protein synthesis in human RPE cells.