| Stroke is the most common disease that cause death and disability all overthe world. The incidence rate of stroke is about200per100,000in the worldwide.The incidence rate of stroke in China depends on the areas. It is about136~486per100,000. Stroke is the top2cause of death and top1cause of disability inChina currently.The guideline for stroke therapy is restoring the cerebral blood flow(reperfusion) as soon as possible by thrombolysis, protecting the survival braintissue in the ischemic penumbra and preventing cerebral secondary injury.Tissue-type plasminogen activator (tPA) is the only FDA-approved treatment forstroke. However, clinical use of tPA was constrained to roughly3%of eligiblepatients because of a narrow3h time window for safe administration. If the timeof thrombolysis exceeds three hours, the risk rate of hemorrhagic transformationand fatal cerebral edema caused by cerebral ischemia/reperfusion (I/R) injury willbe increased. The first line neuroprotective agent remains glucocorticoid, but theside effect of glucocorticoid limits its clinical application including increasingrisk of infection and peptic ulcer. Astragalus membranaceus was routinely used in traditional Chinesemedicine for patients who suffered stroke or chronic debilitating disease.Sometimes, it was even used for normal people who want to further improve theirvital function. It is demonstrated that astragalus membranaceus has the potentialof inhibiting the oxidative stress, antiedema and anti-apoptosis.Astragaloside IV is a purified small molecular saponin from astragalusmembranaceus. It is one of the major components of astragalus membranaceus.Pharmacological studies have demonstrated that astragaloside IV can exert theeffect of decreasing oxidative stress and infarction volume. Moreover,astragaloside IV can regulate the expressions of iNOS, NGF and TrkA mRNA inrats to protect brain tissue from secondary injury.In the present study, we found that astragaloside IV can protect blood brainbarrier from cerebral ischemia/reperfusion injury and inhibit the inflammationpost ischemia/reperfusion injury. It is an important evidence for astragaloside IVto be a neuroprotective agent post thrombolysis.Part one: Astragaloside IV attenuates cerebral ischemia–reperfusion-induced increase in permeability of the blood-brain barrier in rats[Objectives] We investigate the effect of astragaloside IV on the permeability ofthe blood-brain barrier after cerebral ischemia/reperfusion. Additionally, weassess the blood brain barriers associated proteins to study the mechanism.[Methods]48rats (250~300g，8week-old) were selected and assigned to fourgroups which are sham group, vehicle group, astragaloside IV (10mg/kg),astragaloside IV (20mg/kg). The rat model was induced by intraluminalocclusion of middle cerebral artery, then withdrew the line. We evaluated theblood brain barrier integrity by Evens blue experiment and transmissionelectronic microscope study. We also assess the tight junctional proteinsincluding occluding and ZO-1by immunohistochemistry. [Results] The permeability of blood-brain barrier in rats received astragalosideIV administration (10,20mg/kg) was significantly attenuated compared tovehicle group after ischemia/reperfusion assessed by Evans blue leakage(P<0.05). Under the electron microscope, lanthanum, a tracer of blood vesselpermeability, was limited within the blood vessel in sham group, rather than inperivascular tissues as shown in vehicle group. In astragaloside IV groups,lanthanum stain was mainly limited within the cerebral capillary, demonstratingthe protective effect of astragaloside IV on the integrity of blood-brain barrierpost I/R. Moreover, expression of occludin and zonae occludens-1(ZO-1) wasdecreased in vehicle group. Astragaloside IV administration can reverse thedown-regulation of occluding and ZO-1after cerebral I/R injury.[Conclusions] Regulation of tight junctional proteins in the endothelial cells maybe an important molecular mechanism which astragaloside IV-mediated inattribution to blood-brain barrier protection in the ischemia/reperfusion rats.Part two: Astragaloside IV protects against focal cerebral ischemia/reperfusion injury correlating to suppression of neutrophils adhesion-relatedmolecules[Objectives] We studied the potential of astragaloside IV to protect rats againstcerebral inflammation injury elicited by focal cerebral ischemia and reperfusionand assess the correlation with the neutrophils adhesion-related molecules.[Methods]96(250~300g,8week-old rats) were selected and assigned to shamgroup, vehicle group, astragaloside IV (10mg/kg), astragaloside IV (20mg/kg).The rat model was induced by intraluminal occlusion of the middle cerebralartery, then withdrew the line. Animals received astragaloside IV administrationwhen reperfusion was started to. Neurobehavioral evaluation and infarctassessment were assessed. Tumor necrosis factor-α (TNF-α), interleukin-1β (IL-1β) in the serum and brain tissue and Myeloperoxidase (MPO) in the brain tissuewere measured by enzyme-linked immunosorbent assay (ELISA). The rate of CD11b/CD18-positive neutrophils in the serum was analyzed by flow cytometry.Intercellular adhesion molecule-1(ICAM-1) and nuclear factor κB (NF-κB) wereassayed by Western blot and immunohistochemistry.[Results] Astragaloside IV can improved neurological outcome and reducedcerebral infarct volume at24hours after reperfusion. The protective effect wasachieved through reducing the concentration of MPO in brain tissue, blockingneutrophils accumulation in the brain parenchyma. Additionally, astragaloside IVexerted the function by decreasing the percentage of CD11b/CD18-positiveneutrophils in the serum and down-regulating the expression of intercellularadhesion molecule-1(ICAM-1) on the endothelial cells by inhibiting theproduction of TNF-α and IL-1β and suppressing the level of nuclear factor-κB(NF-κB).[Conclusions] Inflammation plays a key role in the clinical course of cerebralinjury induced by ischemia/reperfusion (I/R). We demonstrated an anti-inflammatory mechanism evoked by astragaloside IV by interfering with neutro-phils-endothelial cell interactions, which exerts neuroprotection against I/R injury. |
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