Polyphenol Metabolite Pyrogallol--Sulfate Decreases Microglial Activation and VEGF in Retinal Pigment Epithelium Cells and Diabetic Mouse Retina.

(Poly)phenol-derived metabolites are small molecules resulting from (poly)phenol metabolization after ingestion that can be found in circulation. In the last decade, studies on the impact of (poly)phenol properties in health and cellular metabolism accumulated evidence that (poly)phenols are beneficial against human diseases. Diabetic retinopathy (DR) is characterized by inflammation and neovascularization and targeting these is of therapeutic interest. We aimed to study the effect of pyrogallol--sulfate (Pyr-s) metabolite in the expression of proteins involved in retinal glial activation, neovascularization, and glucose transport. The expression of PEDF, VEGF, and GLUT-1 were analyzed upon pyrogallol--sulfate treatment in RPE cells under high glucose and hypoxia. To test its effect on a diabetic mouse model, Ins2 mice were subjected to a single intraocular injection of the metabolite and the expression of PEDF, VEGF, GLUT-1, Iba1, or GFAP measured in the neural retina and/or retinal pigment epithelium (RPE), two weeks after treatment. We observed a significant decrease in the expression of pro-angiogenic VEGF in RPE cells. Moreover, pyrogallol--sulfate significantly decreased the expression of microglial marker Iba1 in the diabetic retina at different stages of disease progression. These results highlight the potential pyrogallol--sulfate metabolite as a preventive approach towards DR progression, targeting molecules involved in both inflammation and neovascularization.