The Effect Of Carvedilol On Heat Shock Protein 60 Expression And Plaque Stability In Rabbit Arthrosclerosis Model

Objective:heat shock proteins(HSPs),previously called as stress proteins,are produced by tissues in response to stress stimuli,which functional protect cell from unfavorable conditions.Data from different researches have recently provided evidences that HSPs may be involved in the initiation of AS.But few focus on the AS complication and possible role in the plaque stability.The major condition of plaque instability participates in the occurrence of clinical symptomatic cardiovascular events.Carvedilol is a 3-generation nonselective adrenoceptor blocker with powerful antioxidant properties,which have enormous potentiality in AS treatment.At present, there are still no study published reveal carvedilol's influence on HSP60 and plaque stability.This study aims to provide evidences of relationship between HSP60,AS progression and carvedilol,to demonstrate whether local vessel wall HSP60 expression and releasing has impact on plaque type besides vulnerability,whether carvedilol antioxidant activity has a amelioration on both aspects.Methods:New Zealand rabbits feed hyper cholesterol diet for 4 weeks followed by iliac artery balloon denudation to create AS animal model.All animals are divided randomly into hyperlipidemia group and carvedilol group,giving fat-rich diet and carvedilol for another 6 weeks.There is also a group geed normal diet with sham operation served as control group.After sacrificed by overdose of anesthesia,iliac arteries are harvested for further histological analysis.HSP60 and matrix metalloprotease-2(MMP-2)are staining by immunohistochemical assay.Enzyme linked immunosorbent assaies(ELISA)are used to detect serum HSP60,IL-18,IL-6, ox-LDL levels.SOD,MDA and LDH are measured to demonstrate lipid peroxidation and systemic antioxidant capability.Data between groups and within groups was compared and correlations are calculated to reveal relationships between variables.Results:1.after hypercholesterol diet and angioplasty,typical AS lesions are exhibited in rabbit iliac arteries.There are excentric stenosises in vessel lumina. Histological analysis reveal mass foam cells accumulation beneath intima, inter-elastic membrane elongation,disruption,accompany with large necrotic core. The lesions in carvedilol group are less typical intimal thickness and few foam cells. The vascular area and lesion area in carvedilol group has a significant decrease than hyperlipemia group(76299.00±29053.36μm~2 vs 181265.3±51605.97μm~2,P=0.012; 56277.9±31518.72μm~2 vs 145364.1±44414.71μm~2,P=0.013).Vulnerable plaques in carvedilol group have a degrading tendency but no statistic meanings.2.The HSP60 and MMP-2 expression in hyperlipemia group is stronger positive with a heterogeneity distribution,especial in the shoulder region of lesions.In carvedilol group,the expressions levels decrease and less distribute.HSP60 positive expression area in carvedilol group is significant less than hyperlipemia group (11493.67±2970.02μm~2 vs 18530.23±2187.44μm~3,P=0.00;13419.64±4700.10μm~2 vs 18530.23±2187.44μm~2,P=0.028).MMP-2 expression also has a similar result (6604.13±1887.48μm~2 vs 8141.57±1770.57.44μm~2,P=0.00;7401.00±1815.42μm~2 vs 8141.57±1770.57μm~2,P=0.007).The expression levels of HSP60 and MMP-2 has a positive correlation(r=0.709,P=0.001).3.The serum levels of sHSP60,ox-LDL,MDA,IL-6 in hyperlipemia group have a significant elevated than control group.After carvedilol application,all levels in high dosage group decease significantly(106.30±28.45ng/ml vs 140.58±25.56ng/ ml,P=0.045;111.23±25.18pg/ml vs 132.73±29.11pg/ml,P=0.016;28.23±4.31nmol /ml vs 12.77±2.74nmol/ml,P=0.000,17.08±3.02μg/ml vs 20.93±1.87μg/ml,P=0.024). IL-18 levels between groups and within group have no obvious changing tendency. The sHSP60 level has positive correlation with serum ox-LDL,MDA,IL-6, especially a stronger connection with ox-LDL.Conclusions:1.Feeding hyper cholesterol diet for 4 weeks followed by iliac artery balloon denudation can create rabbit AS animal model successfully.The histological characters have favorable comparability with human AS lesions.2.There are HSP60 and MMP-2 expression in rabbit AS plaque lesions with a heterogeneity distribution.The positive correlation between HSP60 and MMP-2 may indicate that HSP60 has a inducing-up effect on MMP-2 expression.3.sHSP60 existed in rabbit peripheral circulation can be induced by hyperlipemia. After fat-diet feeding,IL-6 expression level along with sHSP60 level is upgraded. This means proinflammatory activity of sHSP60 may has a mutual effect on IL-6,and can be the potential mechanism involved in atherogenesis and plaque stability development.But proinflammatory activity of sHSP60 on IL-18 can not be observed.4.Carvedilol has a significant effective down-regulation on HSP60,MMP-2 expression in rabbit AS plaque lesions through its enormous antioxidant properties cleaning free redial,inhibiting lipid peroxidation and HSP60 production,improving plaque stability.