Neuroprotective Effect Of Isosteviol Sodium On Focal Cerebral Ischemia In Rats

Background & Objective: Isosteviol is a molecule derived from Steviaside which has been used as sweetener worldwide. In this study, sodium salt of isosteviol (STVNA) was given i.v. in rats hours after the transient or permanent middle cerebral artery occlusion (tMCAO or pMCAO) to investigate its therapeutic neuroprotective effects. Methods: In male Sprague-Dawley rats 2 hours tMCAO with reperfusion or pMCAO was induced and ischemia were confirmed by a laser doppler flowmetry simultaneously. In dosage study, animals were divided into 6 groups: sham, vehicle, or treatment with STVNA at dosage of 1, 5, 10mg•kg-1 or Edaravone 1 hour before the onset of reperfusion. In therapeutic time window study, animals were divided into 5 groups: sham, vehicle, STVNA (10mg•kg-1) at 0, 2 or 4 hours after reperfusion. In pMCAO study, animals were divided into 5 groups: sham, vehicle or STVNA (10mg•kg-1) at 1, 2 or 4 hours after ischemia. Rats were assessed for neurobehavioral deficits after 24 hours and sacrificed for infarct volume quantitation and histology evaluation. Proteomic analysis of the penumbra area in some rats used a Snaps G2x MS-TOF system. Results: In dosage study, the infarct volume of STVNA 10mg•kg-1 group was significantly less compared either with the vehicle group (22±2% vs 41±5%, p< 0.01) or with the Edaravone group (22±2% vs 30±3%, p< 0.05 ). The therapeutic window study shows that STVNA treated at 4h after reperfusion still has significant effects than vehicle group (32±4% vs 41±5%, p<0.05). In pMCAO study, the infarct volume of STVNA at 4h still decreased comparing the vehicle group(29±5% vs 50±6%, p< 0.05).In all STVNA treated groups the neurobehavioral deficits were significantly improved, and there are more restored NeuN-labeled neurons and alleviated TUNEL positive cells in penumbra in comparing with the vehicle group. Proteomic analysis indicates that proteins involved in various inflammations associated signal pathways were dramatically increased by tMCAO, and then were greatly reduced after treated with STVNA. Conclusions: STVNA exhibited remarkable neuroprotective effects when administered 4 hours after pMCAO or 4 hours after reperfusion of tMCAO. Since STVNA has low systemic toxicity, it may be a better alternative for the treatment of stroke.