Diabetic retinopathy (DR) is a common complication of diabetes mellitus (DM) and it is the main cause of loss of vision. In previous years, interest in the biological activities of marine organisms has intensified. The effect of fucoidan from the seaweed Fucus vesiculosus on the molecular mechanisms of numerous diseases has been studied, while to date, its effect on DR was yet to be investigated. Therefore, the aim of the present study was to evaluate the role of fucoidan in DR. The human

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... l pigment epithelial cell line ARPE-19 was exposed to high D-glucose in the presence or absence of fucoidan. Cell viability was monitored using MTT and lactate dehydrogenase assays. The intracellular reactive oxygen species (ROS) generation was measured using fluorescence spectrophotometry. Cell apoptosis was measured by flow cytometry using Annexin V-fluorescein isothiocyanate staining. Ca 2+ influx was measured with a calcium imaging system and the activation of the extracellular signal-regulated kinase (ERK) protein was evaluated using western blot analysis. The non-toxic fucoidan protected ARPE-19 cells from high glucose-induced cell death and normalized high glucose-induced generation of ROS. Fucoidan also inhibited high glucose-induced cell apoptosis, as well as the Ca 2+ influx and ERK1/2 phosphorylation in ARPE-19 cells. Taken together, these findings indicated that fucoidan protects ARPE-19 cells against high glucose-induced oxidative damage via normalization of ROS generation through the Ca 2+ -dependent ERK signaling pathway.