Lycium barbarum polysaccharides protects retina from ischemia/reperfusion injury

Abstract

PURPOSE: Retinal ischemia/reperfusion (I/R) injury leads to irreversible damage to retinal neurons and structures. It is common in various ocular complications, such as glaucoma, diabetic retinopathy and retinal vessel occlusion. In the present study, we aimed to evaluate the effects of Lycium barbarum polysaccharides (LBP), a traditional Chinese medicine, in a mouse model of retinal I/R injury. METHODS: Adult C57/BL6N mice were orally treated with either vehicle (PBS) or LBP (1 mg/kg or 10 mg/kg once daily) for 1 week before induction of retinal ischemia by the intraluminal suture method. After 2 hours of retinal ischemia followed by 22 hours of reperfusion, retinae were immediately harvested, fixed, and paraffin-embedded for subsequent histological and immunohistochemical analyses. Morphological changes, cell counting and retinal thickness were assessed on hematoxylin and eosin-stained retinal sections. Apoptosis was determined using TUNEL assay and number of apoptotic cells was counted. Blood vessel leakage indicated by IgG extravasations was quantified. Glial fibrillary acidic protein (GFAP) immunohistochemistry was performed. RESULTS: Significantly fewer viable cells were found in the ganglion cell layer (GCL) of vehicle-treated retinae after retinal I/R injury. However, LBP treatment yielded more viable cells and fewer dead cells in GCL. This finding of less neuronal cell death in LBP-treated groups was further confirmed by TUNEL assay where significantly fewer apoptotic cells were identified. In addition, the significant retinal swelling induced by retinal I/R injury in the vehicle-treated group was not observed in LBP-treated groups. Moreover, intense GFAP immunoreactivity and IgG extravasations were observed in vehicle-treated group but not in LBP treated groups. CONCLUSIONS: Our data indicate that pre-treatment with LBP could protect the retina from retinal I/R damage via reducing neuronal cell death, apoptosis, retinal swelling, GFAP activation and blood vessel leakage. These suggest that LBP may be used as a preventive medicine for retinal ischemia.