The Effects Of Atorvastatin On Platelet Activation And Aggregation And The Level Of Intimal Hyperplasia In Cholesterol-enriched Fed Rabbits After Carotid Balloon Injury

Objective1. To investigate the expression of platelet activation and aggregation in the earlyphase after balloon-induced carotid artery injury in cholesterol fed rabbits, aswell as the changes of intimal hyperplasia in the late phase.2. To observe the effects of atorvastatin on platelet activation and aggregation，meanwhile, to explore the inhibition effects and mechanism of intimalhyperplasia, in order to provide a new therapeutic approach for the thrombosisand vascular restenosis after carotid artery balloon injury.Methods30rabbits were randomly divided into five groups: control group （normal dietgroup, n=6）, H-cholesterol group （cholesterol-enriched diet group, n=6）, modelgroup （cholesterol-enriched diet and balloon injured group, n=6）, L-atorvastatingroup （balloon injury and treatment with5mg/（kg d） atorvastatin, n=6）,H-atorvastatin group （balloon injury and treatment with10mg/（kg d） atorvastatin,n=6）. The rabbits of model group, L-atorvastatin group and H-atorvastatin groupreceived balloon injury on the left carotid artery. Platelet aggregation rate wasmeasured by turbidimetric platelet aggregometry. Changes of the expressionlevels of P-selectin and thromboxane B2（TXB2） were detected by enzyme-linkedimmunosorbent assay （ELISA）. The protein expression of protease activatereceptors-1（PAR-1） was detected with immunohistochemical method andwestern blotting. After four weeks, all rabbits were sacrificed and the leftinjured carotid artery and right normal carotid artery were used for HE-stainedpathological study. The wall-to-lumen area ratios （W/L） were analyzed by usingthe analysis software of Image Pro Plus V6.0image. Results1. The level of serum lipids: Compared with control group, the level of TC, TG,LDL-C were significantly increased but HDL-C/TC was decreased in the othergroups （P<0.01, respectively）. The level of lipid were significantly decreased inatorvastatin treatment group in comparation with model group （P<0.05）.Furthermore, the improvement effects of10mg/（kg d） atorvastatin treatment inlipid level was much more notable compared with5mg/（kg d） atorvastatintreatment（P<0.05）.2. The level of platelet aggregation and P-selectin and TXB2:（1） Compared with control group, the serum level of P-selectin inH-cholesterol group significantly increased （P<0.05）, while there were nosignificant changes in platelet aggregation rate and TXB2level between thesetwo groups.（2） After carotid artery balloon injury, the level of P-selectin and TXB2andplatelet aggregation significantly increased and reached a peak at24hoursafter balloon injury（P<0.05）, compared with H-cholesterol group.（3） In comparation with model group,5mg/（kg d） atorvastatin treatmentsignificantly decreased the level of P-selectin and TXB2, as well as, inhibitedthe platelet aggregation（P<0.05）.（4） Compared with5mg/（kg d） atorvastatin group,10mg/（kg d） atorvastatintreatment could further downregulate the level of platelet activation andaggregation（P<0.05）.3. Morphological observation of carotid artery after the four weeks treatment：Noadnormality was found in the control group. However, different degrees ofpathological damage and the form of foam cells in carotid artery appeared inH-cholesterol group and model group. The degrees of pathological damage waslighter in atorvastatin treatment, compared with model group. In addition,compared with control group, the W/L ratios of H-cholesterol group and modelgroup was increased obviously, with a significant difference in statistics（P<0.05）. The W/L ratios of5mg/（kg d） and10mg/（kg d） atorvastatin treatment were respectively decreased by27%and49%（P<0.01） incomparation with model group.4. The protein expression of PAR-1of carotid artery after balloon injury：Compared with control group, there were no significant changes inH-cholesterol group. After carotid artery balloon injury, the protein expressionof PAR-1significantly increased （P<0.05）. In comparation with model group,atorvastatin treatment significantly decreased the protein expression of PAR-1.Meanwhile, the protein expression of PAR-1after10mg/（kg d） atorvastatintreatment could further downregulate, compared with L-cholesterolgroup（P<0.05）.Conclusions1. Cholesterol-enriched diet and carotid artery balloon injury significantlyincrease the expression of PAR-1and the level of P-selectin and TXB2andplatelet aggregation, as well as, stimulate the intimal hyperplasia in the latephase.2. Atorvastatin treatment not just could significantly inhibit the expression ofPAR-1and the level of P-selectin and TXB₂and platelet aggregation, at thesame time, could dose-dependently restrain the level of intimal hyperplasia inthe late phase after vascular injury.3. The inhibition of atorvastatin treatment on the expression of platelet activationand aggregation might be a potential mechanism of the inhibition of intimalhyperplasia in the late phase after vascular injury.