Neuroprotective effects of Lycium barbarum polysaccharides on ischemic stroke injury

Abstract

Objective: The polysaccharides in Lycium barbarum, a well known traditional Chinese medicine, have been demonstrated to possess multiple biological effects including anti-aging, anti-tumor, cytoprotective, and neuromodulation. In the present study, we aimed to evaluate the effects of Lycium barbarum polysaccharides (LBP) on brain ischemic injury in a mouse Middle Cerebral Artery Occlusion (MCAO) model. Methods: Mice were orally treated with either vehicle (PBS) or LBP (1 mg/kg or 10 mg/kg) for 1 week before induction of brain ischemia by MCAO. After 2 hours of ischemia followed by 22 hours of reperfusion, animals were evaluated for neurological deficits. Immediately after scoring of the neurological deficits, brains were isolated, cut into 6 coronal slices of 2 mm thickness and stained with 2% 2,3,5-triphenyltetrazolium chloride (TTC) to detect lesion areas. The posterior surface of each brain slice was subsequently photographed and analyzed using a digital image analysis system. Infarct area, volume, and hemispheric brain swelling were calculated using an indirect method in which the effects of edema and brain swelling have been normalized. Results: Neurological deficits were scored as follows: 0, no observable neurological deficits (normal); 1, failure to extend opposite forepaw (mild); 2, circling to the contralateral side (moderate); and 3, loss of walking and righting reflex (severe). Our results showed that mice treated with either 1 mg/kg LBP or 10 mg/kg LBP (n=7 for each group) had less neurological deficits than the vehicle-treated mice (n=8) (vehicle=2.0±0.3, 1 mg/kg LBP=1.4±0.2, 10 mg/kg LBP=1.1±0.1; P<0.05 (by Mann-Whitney test) for vehicle vs. 10 mg/kg LBP). Moreover, the infarct area of brain slice number 4 was significantly reduced in the LBP-treated mice when compared with the vehicle-treated mice (vehicle=35.4±4.2%, 1 mg/kg LBP=17.5±5.8%, 10 mg/kg LBP=17.6±4.9%). Consistent with the infarct area data, the overall infarct volumes were decreased in the LBP-treated groups (vehicle=25.8±3.1%, 1 mg/kg LBP=21.5±2.5%, 10 mg/kg LBP=16.6±2.7%). In addition, less hemispheric brain swelling was also found in mice with the LBP treatment (vehicle=11.1±0.9%, 1 mg/kg LBP=9.7±1.1%, 10 mg/kg LBP=7.9±0.6%). Conclusions: Taken together, these data indicate that treatment with LBP for 1 week could protect the mouse from brain ischemic injury. Our present study suggests that LBP may be used as a preventive medicine for stroke.