Effect Of TNF-α And Pharmacological Interventionson On Ventricular Remodeling Of Rats Cardiac Muscle After Acute Myocardial Infarction

Objective: Evidence has demonstrated that myocardial fibrosis caused by impaired extracellular matrix (ECM) remodeling was assosiated with cardiac dysfunction. Matrix metalloproteinases (MMPs) were responsible for extracellular matrix remodeling on condition that they were activated. MMPs gene expression was affected by bioactive peptide and cytokines. It was proved in vivo experiment that tumor necrosis factor-α(TNF-α) can activate the MMPs and inhibit the expression of TIMPs in rat cardiac fibroblasts. Previous study reported that the high expression of TNF-αin myocardium was a time dependent relationship with ventriculus sinister remodeling in animal models with congestive heart failure.This study based on the experimental animal model that myocardial infarction was induced in SD rat through ligation of the left anterior descending left coronary artery, to investigate the the effects of myocardial TNF-αexpression on MMP/TIMP system and myocardial ECM remodeling and drug intervention by the inhibitor of TNF-αexpression, and provide further evidences for therapies of heart failure and the improvement of prognosis in patients with myocardial infarction. Materials and Methods: SD rats weight 250~300g (n=42) were supplied by the Experimental Animal Center of Hebei Medical University. Myocardial infarction (MI) was induced in SD rats through ligation of the left anterior descending left coronary artery. After 24h of operation, the living rats were randomized to three matched groups (n=12/group), myocardial infarction control group (MI), etanercept therapy group (ETC) and sham operation group (Sham). The rats in ETC group were injected with 20 mg etanercept injection per kg body weight through abdominal cavity twice a week for 4 weeks. The rats in MI group and Sham group were injected with 20 mg physiological saline per kg body weight through abdominal cavity at the same time. The hemodynamicparameters such as left ventricular systolic pressure(LVSP), left ventricular end-diastolic pressure(LVEDP), left intraventricular pressure maximum upstroke velocity(+dp/dtmax) and descend velocity(-dp/dtmin) were observed through catheterization at the end of the fourth week. The TNF-αmRNA level in cardiac muscle was examined by semiquantitative reverse transcription polymerase chain reaction (RT-PCR) methods and the TNF-αand MMP-2 protein level was examined by western-blot methods at the end of the first week and the fourth week. Collagen content was calculated by picrosirius red staining image analysis software. Cardiac muscle was observed by light microscope and transmission electron microscope.Statistical analysis: All measurement data are expressed as mean±SD. Data were analyzed using SPSS 11.5 software. A student's t-test was used in evaluation of the data between two comparisons. A P value less than 0.05 was considered to be statistically significant.Results:1 Effect of etanercept on hemodynamics Compared with sham-operated group rats, MI rats hemodynamics increased significantly in left ventricular weiht/body weight (2.45±0.03mg/g vs 1.91±0.07mg/g p<0.01) and left ventricular end-diastolic pressure (12.28±1.61mmHg vs.3.69±1.94mmHg p<0.01). Compared with sham-operated group rats, MI rats hemodynamics significant decreased in maximum rate of pressure rise (5378±234 mmHg/s vs. 6608±281 mmHg/s P<0.01). It suggested that heart ventricle remodeling was induced. Compared with MI group rats, LVW/BW decreased significantly (2.45±0.02mg/gvs. 2.88±0.11 mg/g P<0.01) and LVEDP increased significantly (12.28±1.61mmHg vs. 24.89±2.44mmHg p<0.01) in ETC group rats, at the same time, an increase in +dp/dtmax (5378±2344 mmHg/s vs. 4128±224 mmHg/s P<0.05) and -dp/dtmax (4317±210 mmHg/svs.3463±211 mmHg/s) in ETC group rats compared with those in MI group rats.Figure of MPA-2000 showed: Compared with sham operated group rats, left ventricular end-diastolic pressure (LVEDP) increased significantly and intraventricular pressure and differentiate intraventricular pressure decreased significantly in MI group rats.Treatment with etanercept resulted in a decrease in LVEDP and an increase in differentiate intraventricular pressure. The data suggested etanercept improved cardiac diastolic function.2.1 Effect of etanercept on TNF-αexpression in non infarction area of cardiac muscleCompared with sham operated group rats, myocardial TNF-αmRNA and protein expression were markedly deseased in the non infarction zone at the first and the fourth week after MI (0.56±0.03 vs.0.28±0.02;0.78±0.08 vs 0.31±0.02 P<0.01). Compared with MI group rats at the first week,TNF-αmRNA and protein expression increased at the fourth week in MI group rats (TNF-αmRNA level 0.78±0.08 vs 0.56±0.03 P<0.01; TNF-αprotein level 2.15±0.14 ODu* mm2 vs 1.21±0.11 ODu* mm2, P<0.01). Treatment with etanercept resulted in a significant decrease at TNF-αmRNA and protein level (TNF-αmRNA 0.39±0.03 vs 0.56±0.03, 0.54±0.04 vs 0.78±0.08, TNF-αprotein 0.91±0.09 ODu* mm2 vs 1.21±0.11 ODu* mm2, 1.65±0.12 ODu* mm2 vs 2.15±0.14 ODu* mm2 P<0.05).2.2 Effect of etanercept on MMP-2 protein in non infarction area of the myocardial tissueCompared with sham-operated group rats, MI group rats had an increase in MMP-2 protein expression at the first week and the fourth week (0.60±0.05 ODu*mm2 vs 0.27±0.02 ODu*mm2, 1.11±0.08 Du*mm2 vs 0.28±0.02 Du*mm2, P<0.01, MI1W< MI4W). Compared with the first week in MI group rats, MMP-2 protein levels increased at the fourth week(1.11±0.08 Du*mm2 vs 0.60±0.05O Du*mm2 P<0.01). Compared with MI group rats, ETC treatment resulted in a singnificant decrease at MMP-2 protein level (0.45±0.02 ODu*mm2 vs 0.60±0.05 ODu*mm2, 0.72±0.04ODu*mm2 vs 1.11±0.08ODu*mm2 P< 0.01).3 Change of infarction size at CVF and Collagen I and III ratio in noninfarction area in different group rats.Compared with sham operated group rats, MI rats had an increase in collagen volume fraction (CVF), MI group rats increased significantly in CVF at the end of the fourth week(4.51±0.37% vs 3.21±1.12% 25.67±5.68% vs 3.45±1.18% P<0.05). Treatment with ETC resulted in a decrease in CVF(21.58±4.71% vs.25.67±5.68% P<0.05). However, an increase compared with sham-operated group at the fourth week (21.58±4.71% vs 3.45±1.18% P<0.01).Compared with sham operated group, MI and ETC rats had an increase in Collagen I /III ratio( 5.15±0.75 vs 2.88±0.64 3.67±0.81 vs 2.88±0.64 P < 0.05)at the foueth weeks after operation. Compared with MI group at the fourth week, there was a significant decrease in ETC rats (3.67±0.81 vs 5.15±0.75 P < 0.05). There were no significant diffierence in infarction size in three group rats.Conclusions:1 Hemodynamics and left ventricular dysfunction were induced in non infarction area after myocardial infarction in rats, and collagenⅠ,Ⅲand MMP-2 protein levels increased.2 Myocardial TNF-αmRNA and protein expression were markedly increased after MI. TNF-αmRNA and protein expression decreased in rats with etanercept treatment.3 The increased TNF-αexpression could promote ventricular remodeling. It was probably implicated with MMP expression and activation. The results suggested an important role of TNF-αand MMP in myocardial matrix remodeling and functional regulation and support the hypothesis that both TNF-αand MMP may serve as potential therapeutic targets for heart failure.