Abstract
Neuronal cell death, glial cell activation, retinal swelling and oxidative injury are complications in retinal ischemia/reperfusion (I/R) injuries. Lycium barbarum polysaccharides (LBP), extracts from the wolfberries, are good for “eye health” according to Chinese medicine. The aim of our present study is to explore the use of LBP in retinal I/R injury. Retinal I/R injury was induced by surgical occlusion of the internal carotid artery. Prior to induction of ischemia, mice were treated orally with either vehicle (PBS) or LBP (1 mg/kg) once a day for 1 week. Paraffin-embedded retinal sections were prepared. Viable cells were counted; apoptosis was assessed using TUNEL assay. Expression levels of glial fibrillary acidic protein (GFAP), aquaporin-4 (AQP4), poly(ADP-ribose) (PAR) and nitrotyrosine (NT) were investigated by immunohistochemistry. The integrity of blood-retinal barrier (BRB) was examined by IgG extravasations. Apoptosis and decreased viable cell count were found in the ganglion cell layer (GCL) and the inner nuclear layer (INL) of the vehicle-treated I/R retina. Additionally, increased retinal thickness, GFAP activation, AQP4 up-regulation, IgG extravasations and PAR expression levels were observed in the vehicle-treated I/R retina. Many of these changes were diminished or abolished in the LBP-treated I/R retina. Pre-treatment with LBP for 1 week effectively protected the retina from neuronal death, apoptosis, glial cell activation, aquaporin water channel up-regulation, disruption of BRB and oxidative stress. The present study suggests that LBP may have a neuroprotective role to play in ocular diseases for which I/R is a feature.
Highlights
Many ocular diseases such as acute glaucoma and amaurosis fugax may be associated with ischemia/reperfusion (I/R)
It has been shown that Muller cells and AQP4 are involved in retinal swelling which is associated with neuronal death [1,2]
Lycium barbarum has a high content of polysaccharides which is approximately 40% by dry mass; studies have been focused to the liquid fraction of the berries, the Lycium barbarum polysaccharides (LBP) [7]
Summary
Many ocular diseases such as acute glaucoma and amaurosis fugax may be associated with ischemia/reperfusion (I/R). It has been shown that Muller cells and AQP4 are involved in retinal swelling which is associated with neuronal death [1,2]. Previous studies have shown that LBP can modulate the immune function [9,10], act against the effects of aging and oxidation [11,12], protect against liver damage [13], lower blood glucose level [14], and reduce the side effects of chemotherapy and radiotherapy [15,16]. LBP has been shown to protect retinal ganglion cells (RGCs) in an animal model of chronic ocular hypertension [17]. The protective effects of LBP in minimizing neuronal death, glial cell activation, BRB disruption and oxidative stress after I/R injury have not been investigated. Our present study aimed to determine whether LBP could limit the damages from retinal I/R injury in mice
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