Astaxanthin protects retinal ganglion cells from acute glaucoma via the Nrf2/HO-1 pathway

The death of retinal ganglion cells (RGCs) during acute glaucoma causes progressive degeneration of the retinal nerve and irreversible blindness. Astaxanthin (AST) is a type of xanthophyll carotenoids and naturally synthesized by multiple halobios. It has been reported to protect the retina from acute glaucoma due to its anti-oxidative and anti-neuroinflammatory properties. However, the mechanism underlying this process remains unclear. We designed a mouse model with acute glaucoma and AST was administered by oral gavage. Hematoxylin and eosin staining was utilized to evaluate the condition of retina and the number of ganglion cells was counted. QRT-PCR was performed to evaluate the mRNA levels of Bax and Bcl2 while Western blot assay was used to determine the protein levels of Bax, Bcl2, Nrf2 and HO-1. AST protected the retinal integrity of mice with acute glaucoma. The apoptosis of RGCs induced by ischemia and reperfusion was repressed by AST. The protective functions of AST on the retinal and ganglion cells decreased with the knock-down of Nrf2. AST promoted the activation of Nrf2 and Ho-1 in the RGCs of the model mice. AST protected the RGCs from apoptosis during acute glaucoma and alleviated the severe retinopathy symptoms through the Nrf2/Ho-1 pathway.