丙戊酸对致死性烫伤大鼠心肌的保护作用及机制研究

The protective effect of valproic acid on myocardium in rats with lethal scald injury and its mechanism

目的 研究丙戊酸（VPA）对致死性烫伤大鼠心肌的保护作用及机制.方法 78只雄性SD大鼠按随机数字表法分为假烫组（n=10）、假烫＋VPA组（n=10）、烫伤组（n=29）、烫伤＋VPA组（n=29）4组.采用80℃水浴浸泡背部15s、双下肢15s、腹部8s造成55％总体表面积（TBSA）Ⅲ度烫伤大鼠模型;假烫组用37℃水浴浸泡,部位和时间与烫伤组相同.烫伤（假烫）后即刻皮下注射VPA300 mg/kg或等体积生理盐水（作为对照）.各组分别于烫伤后6h取5只大鼠腹主动脉血,测定血浆肌酸激酶同工酶（CK-MB）水平;然后处死动物取心肌组织,用蛋白质免疫印迹试验（Western Blot）检测心肌细胞中组蛋白乙酰化水平及天冬氨酸特异性半胱氨酸蛋白酶3（caspase-3）活化水平;各组余下大鼠观察12h生存情况.结果 与假烫组相比,烫伤组大鼠伤后6h血浆CK-MB水平明显升高（U/L：5 438.0±413.6比2 881.0±324.8,P＜0.05）,心肌组蛋白3第9位乙酰化的赖氨酸（Ac-H3K9）水平明显降低（灰度值：0.55±0.18比1.00±0.20,P＜0.05）,心肌caspase-3活化水平明显增高（灰度值：1.75±0.25比1.00±0.18,P＜ 0.05）;而给予VPA处理后能明显降低血浆CK-MB水平[（4018.0±388.3） U/L],明显升高心肌Ac-H3K9水平（灰度值：2.20±0.23）,明显降低心肌caspase-3活化水平（灰度值：1.33±0.20）,与烫伤组比较差异均有统计学意义（均P＜0.05）.Kaplan-Meier生存曲线分析发现,VPA能显著延长大鼠烫伤后存活时间,12h时大鼠存活率可由0升高至50％（P＜0.05）.结论 VPA能改善致死性烫伤休克大鼠心肌酶学指标并延长其存活时间,其机制可能与其对组蛋白去乙酰化酶及caspase-3的抑制作用有关.

Objective To investigate the protective effects of valproic acid （VPA） on myocardium in rats following lethal burn injury and its mechanism.Methods Seventy-eight Sprague-Dawley （SD） rats were randomly assigned to four groups：sham-scald group （n=10）,sham-scald ＋ VPA group （n=10）,scald group （n=29）,and scald ＋ VPA group （n =29）.Rats in the latter two groups were subjected to 55% total body surface area （TBSA） third-degree burns by immersing the back of the trunk for 15 seconds,both lower extremities for 15 seconds,and the abdomen for 8 seconds in 80 ℃ water.Sham-scald rats were immersed in 37 ℃ water instead.Rats were then subcutaneously injected with VPA （300 mg/kg） or normal saline as control.Blood of 5 rats in each group was with drawn from the abdominal aorta at 6 hours after injury for measurement of plasma creatine kinase-MB （CK-MB） activities; then the rats were sacrificed and heart tissues were harvested for the measurement of acetylated histone H3 and activated caspase-3 by Western Blot.The remaining rats were used for 12-hour survival analysis.Results Compared with sham-scald group,there was a significant increase in plasma CK-MB activities （U/L：5 438.0 ± 413.6 vs.2 881.0 ± 324.8,P〈0.05） and activated caspase-3 protein levels in heart tissue （gray value：1.75 ± 0.25 vs.1.00 ± 0.18,P〈 0.05） and an significant decline in the acetylation levels of histone H3 （gray value：0.55 ± 0.18 vs.1.00 ± 0.20,P〈0.05） after major bum injury.VPA treatment significantly reduced the plasma CK-MB activities [（4 018.0 ± 388.3） U/L],activated caspase-3 protein levels in heart tissue （gray value：1.33 ± 0.20）,and raised the acetylation levels of histone H3 （gray value：2.20 ± 0.23,all P〈 0.05）.Survival analysis by Kaplan-Meier curves showed that the survival was improved after VPA treatment,and the survival rate was increased from 0 to 50% at 12 hours （P〈 0.05）.Conclusions VPA can attenuate cardiac injury and improve survival in a rodent model of lethal burn injury.These protective effects may be due to its inhibitory effects on histone deacetylase and caspase-3 activation.