Background: Reactive oxygen species (ROS) accumulation plays a pivotal
role in the onset of cell damage induced by hyperglycemia and represents one of
the major factors in the pathogenesis of diabetic retinopathy. In this study, we
tested the antioxidants cyanidin-3-O-glucoside (C3G) and verbascoside (Verb) in
the protection of retinal endothelium against glucose toxicity “in vitro”. Methods: Increasing amounts (5–50 M) of C3G,
Verb or the combination of both compounds were tested in Human Retinal
Endothelial Cells (HREC) grown with normal glucose (5 mM, NG) or high glucose (25
mM, HG). Results: Reduced cell viability and enhanced
ROS levels (evaluated by MTT and H2DCFDA assays, respectively) in HG-stimulated
HREC were restored by C3G and Verb in a dose-dependent manner, achieving the
maximum protection in the presence of both compounds. Moreover, co-treatment with
C3G and Verb worked better than each single molecule alone in the prevention of
the disruption of blood-retinal-barrier-like properties by HG in a confluent HREC
monolayer, as assessed by trans endothelial electrical resistance (TEER) and
Na-Fluorescein permeability assays. Accordingly, C3G and Verb together also
better counteracted the HG-induced down-regulation of the tight junction membrane
proteins Zonula Occludens-1 and VE-Cadherin evaluated by immunocytochemical and
Western blot analyses. Conclusions: In conclusion, our data indicate
that C3G and Verb could efficiently protect the retinal endothelium against high
glucose damage.