Neuroprotective effects of Lycium barbarum polysaccharides on retinal ischemic injury

Abstract

Purpose: Retinopathy is a common complication of diabetes. As the disease progresses, regional failure of the microvascular circulation will lead to retinal ischemia. Therefore, retinal ischemic injury is common in patients with diabetes. In the present study, we aimed to evaluate the effects of Lycium barbarum polysaccharides (LBP), a well known traditional Chinese medicine, on retinal ischemic injury in a mouse in vivo ischemia model. Methods: Mice were orally treated with either vehicle or LBP (1 mg/kg or 10 mg/kg) 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 collected, fixed, and paraffin-embedded for subsequent histological analysis. The morphology of retinal cells and the thickness of various retinal layers were determined from hematoxylin and eosin stained sections. The number of apoptotic cells was also determined by TUNEL assay. Results: Severe neuronal cell death was found in the ganglion cell and inner nuclear layers of retinae from the vehicle-treated group. On the other hand, the number of viable cells was significantly increased in the retinae of LBP-treated groups when compared with those of the vehicle-treated group. This finding of less neuronal cell death in the LBP-treated groups was further confirmed by TUNEL assay where much fewer apoptotic cells were identified. In addition, by measuring the thickness of the ganglion cell layer, inner plexiform layer and inner nuclear layer, we found that ischemia-induced retinal swelling was reduced in both LBP-treated groups (P<0.05 in 10 mg/kg group). Conclusions: Taken together, these data indicate that treatment with LBP for 1 week could protect the mouse from retinal ischemic injury via reducing neuronal cell death and retinal swelling. Our present study hence suggests that LBP may be used as a preventive medicine for diabetic retinopathy.