Arctigenin Prevents Retinal Edema in a Murine Retinal Vein Occlusion Model

Macular edema causes vision loss in patients with retinal vein occlusion (RVO) and diabetic macular edema (DME). The intravitreal injection of anti-vascular endothelial growth factor (VEGF) agents is used for treatment; however, this therapy is invasive, and recurrence occurs in some cases. The establishment of a non-invasive treatment would help to solve these problems. Here, we focused on arctigenin, a lignan polyphenol found in burdock sprout, and has effects on inflammatory and microcirculatory when taken orally. We hypothesized that oral intake of arctigenin could be effective against retinal edema in RVO and DME. In this study, the degree of retinal edema by measuring the total retinal thickness using optical coherence tomography (OCT) and the thickness of the inner nuclear layer (INL) by hematoxylin-eosin (H&E) staining were investigated. Oral administration of arctigenin ameliorated retinal edema in an RVO murine model by inhibiting the decrease in occludin and vascular endothelial (VE)-cadherin. Moreover, in retinas with edema, arctigenin suppressed the induction of VEGF, tumor necrosis factor α (TNFα), and matrix metallopeptidase 9 (MMP9). Next, the effects of arctigenin on barrier function were assessed in human retinal microvascular endothelial cells (HRMECs) by measuring the trans-endothelial electrical resistance (TEER) and conducting fluorescein isothiocyanate (FITC)-dextran permeability assays. Arctigenin showed a protective effect against VEGF-induced barrier dysfunction. In addition, arctigenin inhibited the TNFα-mediated activation of the nuclear factor-kappaB (NF-κB)/p38 mitogen-activated protein kinase (MAPK) pathway. These results suggested that oral administration of arctigenin has beneficial effects on retinal edema by inhibiting vascular hyperpermeability in endothelial cells.