摘要目的 观察大鼠心肌损伤后心肌组织环磷酸腺苷(cAMP)信号转导系统相关基因表达的变化及与心室重构、心功能变化的关系.方法雄性Wistar大鼠28只,体质量220～250 g.将大鼠按体质量随机分为急性心肌损伤组(AMD,n=10)、慢性心肌损伤组(CMD,n=9)和对照组(n=9).AMD和CMD组大鼠开胸,结扎左前降支,建立急性心肌损伤动物模型;对照组开胸后不做结扎.在术后24 h,处死AMD和对照组大鼠,CMD组大鼠8周后处死,大鼠处死前进行心脏超声和血流动力学检查.TUNEL法检测行心肌细胞凋亡,放射免疫法测量心肌组织中环磷酸腺苷(cAMP)水平,实时定量(RT)-PCR法测定受损心肌周围组织中诱导性cAMP早期阻遏物(ICER)mRNA、cAMP反应元件结合蛋白(CREB)mRNA、磷酸二酯酶3A(PDE3A)mRNA和bcl-2mRNA表达.结果心脏超声和血流动力学显示,AMD、CMD、对照组左心室舒张末内径(LVEDD)、舒张末压(LVEDP),左心室内压最大上升速率(+dp/dtmax)、下降速率(-dp/dtmax),左心室收缩压(LVSP)、射血分数(EF)、短轴缩短率(FS)组间比较差异有统计学意义(F值分别为285.9、196.8、83.2、80.4、54.9、196.6、95.2,P均＜0.01).其中AMD和CMD组,LVEDD[(7.03±0.28)、(8.20±0.27)mm]和LVEDP[(11.19±2.89)、(19.76±3.34)mmHg]明显高于对照组[(5.05±030)mm、(-5.62±3.01)mmHg,P均＜0.01];左室内压+dp/dtmax [(2964±449)、(2214±434)mmHg/s]和-dp/dtmax[(-2617±441)、(-1891±424)mmHg/s]、左室LVSP[(94.19±4.03)、(85.85±6.39)mmHg]、EF[(41.6±5.9)%、(35.9±4.1)%]和FS[(36.9±4.6)%、(23.1±4.9)%]均显著低于对照组[(4759±406)mmHg/s、(-4327±388)mmHg/s、(116.29±8.25)mmHg、(80.9±5.6)%、(53.1±4.3)%,P均＜0.01];与AMD组相比,CMD组上述改变更显著(P＜0.05或＜0.01).心肌凋亡指数、cAMP、ICER、CREB、PDE3A、bcl-2 mRNA表达,组问比较差异有统计学意义(F值分别为172.5、141.0、540.8、246.8、165.1、563.9,P均＜0.01).其中AMD和CMD组心肌凋亡指数[(32.8±4.2)%、(18.4±3.9)‰]和cAMP[(9.95±0.30)、(5.60±0.25)nmol/kg]明显高于对照组[(3.9±1.7)‰、(2.48±0.29)nmol/kg,P均＜0.01],CMD组低于AMD组(P＜0.01);ICER、CREB mRNA表达,AMD(1.434±0.093、5.70±0.50)和CMD组(0.942±0.076、2.64±0.51)明显高于对照组(0.154±0.063、1.08±0.35,P均＜0.01),AMD组高于CMD组(P＜0.01);PDE3A mRNA表达,AMD和CMD组(48.98±8.14、16.68±8.46)明显低于对照组(105.94±12.61,P均＜0.01),CMD组低于AMD组(P均＜0.01);bcl-2 mRNA表达AMD组(4.55±0.27)高于对照组(2.18±0.30,P＜0.01),CMD组(0.35±0.15)明显减少(P均＜0.01).结论慢性心肌损伤较急性心肌损伤心室重构更明显,cAMP信号转导系统过度激活后形成ICER和cAMP的自循环,致使ICER mRN升高,PDE3A mRN减少,可能是心肌损伤后心室重构和心力衰竭发生发展的原因之一.

abstractsObjective To investigate the relationship between alteration of gene in cyclic adenosine monophosphate(cAMP) signal transduction system in rats after myocardial damage and changes of cardiac function and ventricular remodeling. Methods Twenty eight male Wistar rats weighing 220 g to 250 g were randomly divided into three groups: acute myocardial damage group(AMD, n = 10), chronic myocardial damage group (CMD,n = 9 ) and sham-operation group (control, n = 9). Animal model of acute myocardial damage was established by ligation of rats left coronary artery in the AMD and the CMD groups. Rats in control group were treated similarly, except that the coronary suture was not tied. Hemodynamics and echocardiography were measured before rats were sacrificed 24 hours after operation in control and AMD groups but those in CMD groups were sacrificed 8 weeks later. Cadiocyte apoptosis were estimated by TUNEL method, cAMP levels in heart were tested by radioimmunity and the mRNA expressions for inducible cAMP early repressor (ICER), cAMP response element binding protein (CREB), phosphodiesterase 3A (PDE3A) and bcl-2 were assayed by real-time quantitative reverse transcriptase polymerase chain reaction (RT-PCR). Results The difference of left ventricular end diastolic diameter (LVEDD), left ventricular end diastolic pressure(LVEDP), maximal rising and falling rate of ventricular pressure,left ventricular systolic pressure (LVSP), eject fraction (EF) and fraction shortening (FS) were statistically significant among the three groups(F = 285.9, 196.8, 83.2, 80.4, 54.9, 196.6, 95.2, all P ＜ 0.01). LVEDD[(7.03 ±0.28), (8.20 ± 0.27)mm] and LVEDP[(11.19 ± 2.89), (19.76 ± 3.34)mmHg] in AMD and CMD groups were significantly increased, compared with those in control group[ (5.05 ± 0.30)mm, (- 5.62 ± 3.01 )mmHg, all P ＜0.01 ]. While maximal rising rate[ (2964 ± 449), (2214 ± 434)mmHg/s] and falling rate[(- 2617 ± 441),(- 1891± 424)mmHg/s] of left ventricular pressure, LVSP[ (94.19 ± 4.03), (85.85 ± 6.39)mmHg], EF[ (41.6 ±5.9)%, (35.9 ± 4.1 )%] and FS[ (36.9 ± 4.6)%, (23.1 ± 4.9)%] of left ventricular in the two groups were lower than those in control[(4759 ± 406)mmHg/s, (- 4327 ± 388)mmHg/s, (116.29 ± 8.25)mmHg, (80.9 ± 5.6)%,(53.1 ± 4.3)%, all P ＜ 0.01 ]. These changes in CMD group were more significant than those in AMD groups(P ＜0.05 or P ＜ 0.01 ). The difference of apoptotic index, cAMP and expression of ICER, CREB, PDE3A mRNA and bcl-2 mRNA were statistically significant among the three groups(F= 172.5, 141.0, 540.8, 246.8, 165.1, 563.9,all P＜ 0.01 ). Apoptotic index[ (32.8 ± 4.2)‰, (18.4 ± 3.9)‰] and cAMP in heart[ (9.95 ± 0.30), (5.60 ± 0.25)nmol/kg] in AMD and CMD groups were increased compared to control group[ (3.9 ± 1.7)‰, (2.48 ± 0.29)nmol/kg,all P ＜ 0.01 ], and those in CMD group were lower than in AMD group(all P ＜ 0.01 ). Expression of ICER mRNA (1.434 ± 0.093, 0.942 ± 0.076) and CREB mRNA(5.70 ± 0.50, 2.64 ± 0.51) in AMD and CMD groups were higher, and expression of PDE3A mRNA(48.98 ± 8.14, 16.68 ± 8.46) were lower than those in control group (0.154 ± 0.063, 1.08 ± 0.35, 105.94 ± 12.61, all P ＜ 0.01 ). The three genes in CMD group were fewer than those in AMD group(all P ＜ 0.01 ). bcl-2 mRNA was up regulated in AMD group(4.55 ± 0.27) and was down regulated in CMD group(0.35 ± 0.15) compared to control(2.18 ± 0.30, all P＜ 0.01). Conclusions There is PDE3A-ICER positive-feedback loop leading to myocyte apoptosis and heart failure after myocardial damage. The downregulation of PDE3A mRNA observed in chronic myocardial damage may play a causative role in the progression of ventricular remodeling and heart failure, in part, by inducing ICER mRNA and promoting cardiac myocyte dysfunction.