| Objective: Cerebral ischemia is the first leading cause of death and themost frequent cause of permanent disability in adults. The pathologicalmechanism for ischemic injury was a perplexing cascade reaction, includinginflammation, oxidative stress and perturbation of calcium homeostasis,cytotoxic effect and reactive oxygen species/reactive nitrogen species(ROS/RNS). It is generally believed that excessive immunological reaction ofand oxidative stress are two important pathophysiologic mechanisms whichreside in necrosis and ischemic region, then result in brain injury. Duringreperfusion the generation of reactive oxygen species (ROS) is greatlyelevated which could overwhelming the antioxidant capacity of the ischemicbrain. ROS itself can oxidize low density lipoproteins (LDL), and thenox-LDL binds to lectin-like oxidized low-density lipoprotein receptor-1(LOX-1) resulting in the production of ROS in turn, and activation of proteinkinase C and mitogen-activated protein kinase (MAPK), as well as thesubsequent upregulation of MCP-1, AP-1and NF-κB, leading to the relateddisease.Therefore, how to alleviate the inflammation injury and oxidativestress is the crucial way to protect brain from cerebral ischemia injury. Aboveall, LOX-l may present as a therapeutic targets at acute phase of ischemicstroke, but there is no systematic exposition of the role of LOX-1in ischemiccerebrovascular disease, and thus needs further experimental studies toprovide evidence for clinical treatment. LOX-1is a type II membrane proteinwhich belongs to the C-type lectin family and is identified as a receptor foroxidatively modified LDL. The expression of LOX-1is regulated by freeradicals, cytokines, sheer stress, angiotensin II, and ox-LDL itself. LOX-1expression is upregulated during myocardial and renal ischemia-reperfusion, which implied a pathophysiological role for LOX-1in ischemia-reperfusioninjury. Recent study showed LOX-1was up-regulated in the cortices ofspontaneously hypertensive rats.Pterostilbene (Pte), a dimethyl ether analogue of resveratrol, has drawnmuch attention recently due to its potential health benefits as an antioxidant,anticancer, antidiabetic agent. Although the structure of Pte and resveratrol issimilar, the dimethylether structure of Pte enhances its lipophilicity and thusincreases its membrane permeability, which leads to improvedpharmacokinetic profiles over resveratrol. In recent study, it has beendemonstrated that Pte can inhibit apoptosis by downregulating LOX-1througha pathway involving oxidative stress. However, little is known about therelationship between Pte and LOX-1in cerebral ischemic reperfusion.Methods: This study was consisted with two sections: Experiment1wasused to detect pterostilbene’s neuroprotective effect in focal cerebral ischemia.Experiment2was conducted to evaluate pterostilbene’s effect on theexpression of LOX-l、p-ERK1/2and NF-κB.Experiment1, seventy-two male CD-1(ICR) mice were divided randomlyand equally into six groups (12mice in each group): Sham operated group(Sham); tMCAO group (tMCAO); Vehicle group (Vehicle); Low dose group(Pte-L); Medium dose group (Pte-M) and High dose group (Pte-H). Vehicleand tMCAO groups were subjected to transient focal cerebral ischemia byright MCAO occlusion. Neurological deficit was evaluated on a six point scaleat24h after MCAO; brain water content was measured; infarct size wasanalyzed with2,3,5-triphenyltetrazolium chloride (TTC).Experiment2,108mice were randomly and equally divided into sixgroups:(18mice in each group): Sham operated group (Sham); tMCAO group(tMCAO); Vehicle group (Vehicle); Low dose group (Pte-L); Medium dosegroup (Pte-M) and High dose group (Pte-H). Pte solution (5mg/kg,10mg/kgor25mg/kg) was administrated through intraperitoneal injection. Westernblotting was used to analyse the expression of LOX-l、p-ERK1/2and NF-κB. Meanwhile the indexes were also detected by qR-T PCR. Results:1Mann–Whitney U test analysis was conducted to detect the scores ofneurologic deficit on a6-point scale at24h after tMCAO. Mice in tMCAOgroup, Vehicle group, Pte-L group, Pte-M group, Pte-H group performed a leftpalsy. Compared with Vehicle group, the scores in Pte-M group and Pte-Hgroup were lowered (Pte-M vs. Vehicle:2.96±0.14vs.3.38±0.13, P <0.05; Pte-H vs. Vehicle:2.67±0.13vs.3.38±0.13, P <0.05）. Althoughdeficit scores in the Pte-L group were reduced, there were no significantdifferences in neurological deficit scores between the low dose group andVehicle group （Pte-L vs. Vehicle:3.21±0.10vs.3.38±0.13, P>0.05）.2In Sham operated group, ipsilateral brain water content was77.02±0.31. InVehicle group, the water content increased to82.33±0.87at24h afterocclusion. In Pte-L group, Pte-M group and Pte-H group, the brain watercontent of ipsilateral hemispheres was reduced significantly compared withthe Vehicle group (Pte-L vs. Vehicle:79.67%±0.46%vs.82.33%±0.53%, P<0.05; Pte-M vs. Vehicle:79.00%±0.57%vs.82.33%±0.53%, P <0.05;Pte-H vs. Vehicle:78.85%±0.49%vs.82.33%±0.53%, P <0.05). Howeverno statistical difference was observed between these two groups.(n=6ineach group)3Extensive lesion was developed in both striatum and lateral cortex intMCAO and Vehicle group. The Pte-M group and Pte-H significantly reducedthe infarct volume after tMCAO (Pte-M vs. Vehicle:46.28%±3.04%vs.50.99%±5.97%, P <0.05; Pte-H vs. Vehicle:34.75%±3.14%vs.50.99%±5.97%, P <0.05). However, there was no significant difference in infarctvolume between Vehicle group and Pte-L group (Pte-L vs. Vehicle:46.28%±3.04%vs.50.99%±5.97%, P＞0.05).4Pte’s role in the expression of LOX-l、p-ERK1/2and NF-κB: We analyzedthe expression of LOX-l、p-ERK1/2and nuclear NF-κB at protein level aftertreating with Pte in ischemia brain by Western blot. It showed Pte-M and thePte-H treatment downregulated the expression of LOX-1, p-ERK1/2and NF-κB after tMCAO both at protein level and mRNA level (P <0.05). However, there was no significant difference between Vehicle group and Pte-L group (P>0.05).5Immunohistochemical staining of LOX-1, p-ERK1/2and NF-κB in thecerebral cortex at24h after tMCAO (×400magnification). Compared withtMCAO group, the expression of LOX-1, p-ERK1/2and NF-κB weresignificantly reduced in Pte-M and Pte-H group.Conclusions: Above all, our findings showed that systemicadministration of pterostilbene has ability of reducing neurological deficits,brain edema and infarct volumes in cerebral ischemia; the down-regulation ofLOX-l、p-ERK1/2and NF-κB demonstrated the potential neuroprotection ofpterostilbene. Thus, a corollary of this study is that pte may represent apotentially beneficial therapeutic avenue for focal cerebral ischemic stroketreatment. |
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