Photoreceptor and vision protective effects of astragaloside IV in mice model with light-evoked retinal damage

Cone cell-enriched macular degeneration is a major cause of functional vision deterioration. Astragaloside IV (Asg IV), an active triterpenoid saponin component with properties of anti-oxidative and anti-apoptotic damage, which benefit retinal tissue and capillaries. But, the nutraceutical therapeutic effects on functional vision have not been fully evaluated. In this study, mice were administrated to high-intensity light exposure after either receiving a vehicle or Asg IV (0.05, 0.5, and 50 mg/kg, BID). During this time, their spatial-visual performance, visual acuity (VA), and visual contrast sensitivity function (VCSF) were measured using the behavioral opto-motor reflex method. Morphological changes in the retina were determined by histological examination. High energy light-evoked visual damage was confirmed by the loss in structural tissue integrity in the retina accompanied by a decline in both VA and VCSF, whereas the retina tissue exhibited loss of cone cell density and severe cone-specific opsin misplacement. In contrast, prophylactic oral Asg IV (0.5, and 50 mg/kg, BID)-treated exerted protective and improvement effects against light-evoked deterioration of functional vision. Asg IV treatment significantly improved the thresholds of VA and VCSF. In particular, Asg IV (50 mg/kg, BID) modu-lated and increased the survival of the photoreceptors, especially the cone cells, which targeted and enhanced the high spatial frequency-characterized VCSF. In contrast, the cellular protective effect of Asg IV (50 mg/kg, BID) on photoreceptors was significantly reversed by synchronous injection of a glucocorticoid receptor (GR) antagonist (mifepristone). This study demonstrated the major neuroretina-protective effect and functional vision-improving effect of Asg IV in vivo.