Effects And Mechanisms Of Spironolactone On Myocardial Extracellular Matrix In Myocardial Injury

Myocardia consist of cardiomyocytes and extracellular matrix. Cardiomyocytes perform their function through extracellular matrix. They interdepend on each other, and make up an organic entity. Ectracellular matrix plays an important role in the process of myocardial injury and restruction. Over past decade, with advances of knowledge of extracelluar matrix on construction, function, physiology and pathophysiology, it has been found that the imbalance of ectracellualr matrix after myocardial injury could result in myocardial fibrosis and ventricular remodeling, and eventually lead to heart failure and arrhythmia. Therefore, it has been, so far, a hot point in the medical research. Myocardial extracellular matrix mainly consist of collagen and glycoprotein with a kind of precise ordered network-like structure, through which myocardial extracellular matrix plays a key role in cardiac diastole and systole. There are 5 types of collagen. The typeⅠcollagen is a mature collagen, which mainly polymerises to coarse fiber characterized by great tensile strength and small extension. It can prevent heart ventricles intension. The typeⅢcollagen is a embryonic collagen, which mainly polymerises to fine fibers featured by great extension and small tensile strength. The fine fibers are associated with ventricle compliance. Theoretically, we can improve myocardial relaxation and hemodynamics by adjusting the ratio of collagenⅠ/Ⅲ. Matrix metalloproteinases (MMPs) are a group of proteinases in myocardial extracellular matrix. Activated MMPs degrade extracellular matrix protein. In physiological condition, its function is to keep myocardial collagen fibrous reticulum's stabilization. After myocardial injury, over-activated MMPs break stabilization of myocardial collagen fibrous reticulum. Myocardial cells slide and elongate, which further leads to deformation in cardiac organization structure, decline in solidity, reduction in capillary vessel density, eccentric hypertrophy, dilatation of cardiac chambers, thinning in ventricles wall, and cardiac dysfunction. Tissue inhibitors of metalloproteinases (TIMP) are endogenous MMPs inhibitors, which play an importance role in ventricular remodeling.Aldosterone (Ald) is a crucial mineralocorticoid in vivo. Conventional teaching dictates that aldosterone spares sodium, excretes potassium and magnesuim, and adjusts electrolyte balance. However, over past decade, its effects on myocardia have attracted much more attention. It has been well recognized that renin-angiotensin-alosterone system (RAAS) is active in most patients with heart failure. Among patients with sever heart failure, the plasma renine, angiotensin and aldosterone concentration are high.Vivo and vitro studies showed that aldosterone could stimulate myocardial fibroblast, resulting in increase of collagen synthesis, collagen deposition, and fibrosis, and eventually progresses to heart failure. Studies showed that Angiotensin converting enzyme inhibitor (ACEI), angiotensin II blockers (ARB),β-blockers could partially inhibit RAAS, and improve myocardial function in heart failure. Despite the efforts on RAAS inhibition, there is still a phenomenon called aldosterone escape occurs. Aldosterone receptor blocker spironolactone has analogous chemical structure with aldosterone. After binding with the aldosterone receptor, it could block the effects that aldosterone has. Theoretically, it can inhibit collagen deposition, improve myocardial extracellular matrix reconstruction, and facilitate myocardial injury restoration. Large-scale clinical trials, such as EPHESUS and RALES, have confirmed that aldosterone receptor blockers could delay the progress of ventricle remodeling and heart failure. As a result, aldosterone receptor blockers could significantly decrease the mortality in patients with congestive heart failure. Currently, there was no clinical research reported the effects of spironolactone in acute myocardial infarction and hypertension patients with diastolic dysfunction. The mechanisms of spironolactone to improve myocardial ECM remodeling and cardiac function remain unclear.In the section of animal study, we established two kinds of rat model of heart failure. The first one was established by coronary artery ligation, and the other one was by spurt repeated cryoinjury. Through the rat model of heart failure established by coronary ligation, we observed the effects of spironolactone and losartan on hemodynamics and collagen remodeling after myocardial infarction. Through the rat model of heart failure by spurt repeated cryoinjury, we observed the effects of spironolactone on MMP-2, TIMP-1, and myocardial angiogenesis, through which we tried to probe the mechanisms of spironolactone in improving myocardial ECM metabolism and cardiac function recovery.In the clinical study section, we investigated the effects of spironolactone on left ventricular remodeling in patients with acute myocardial infarction. We measured brain natriuretic peptide (BNP) and amino-terminal pro-peptide of type III procollagen (PⅢNP). We also investigated the clinical efficacy of spironolactone on the diastolic heart failure in the elderly hypertensive patients through assessment of the changes in biochemistry surrogate and echocardiographical parameters.This paper comprises four sections, which detailed as follows:1. Effects of spironolactone on hemodynamics and myocardial collagen remodeling after myocardial infarction in ratsObjective: To observe the effects of spironolactone and losartan on hemodynamics and collagen remodeling after myocardial infarction.Methods: we conducted the study at Hebei academy of medical science. The rat model of heart failure was made by left coronary artery ligation. The rats which remained alive after 24 hours operation were randomized into sham operation group (n=18), placebo group (n=18), spironolactone group(n=18, 20mg·kg-1·d-1), losartan group (n=19, 20mg·kg-1·d-1), and combination therapy group, i.e. losartan +spironolactone (n=17) respectively. Mean blood pressure (MBP), left ventricular end-diastolic pressure (LVEDP), interstitial collagen content and the ratio of typeⅠa ndⅢcollagen in non-infarction zone were measured at the end of week 2 and week 6.Results: As compared with sham operation group, there was significant increase in LVEDP, collagen content, and the ratio of typeⅠa ndⅢcollagen (P<0.05) in the placebo group either at the end of week 2 or week 6. Whereas there was a significant reduction in MBP, LVEDP and the ratio of typeⅠa ndⅢcollagen in both losartan group and the combination therapy group when compared with placebo group at the end of week 2.At the end of week 6, LVEDP, collagen contents, the ratios of typeⅠa ndⅢcollagen was significantly decreased in rats given spironolactone, losartan or the combination therapy. However, MBP, LVEDP, collagen contents, the ratio of typeⅠa ndⅢcollagen were significantly reduced in the rats receiving combination therapy as compared with rats given spironolactone group or lasartan alone.Conclusion: Our data showed that both spironolactone and losartan could significantly improve the cardiac hemodynamics and the left ventricular collagen remodeling after myocardial infarction in rats. However, the efficacy of combination therapy was superior to spironolactone or losartan alone.2. Effects of spironolactone on myocardial angiogenesis and Matrix metalloproteinases in rats with myocardial injuryObjective: To observe the effects of aldosterone receptors blocker spironolactone (20mg.d-1.kg-1) on MMP-2, TIMP-1, and myocardial angiogenesis in rats with myocardial injury.Methods: Myocardial injury models of Wister rats was established by spurt repeated ventricule cryoinjury. Twenty-four hours later, the rats remained alive were randomized into sham operation group (n=24), myocardial injury group (n=30), and spironolactone group(n=30). MMP-2 and TIMP-1 protein levels in non-infarcted zone and the ratio of left ventricular weight and body weight (LVW/BW) were measured by immunohistochemistry at the end of week 2 and week 14. The capillary density also determined at the same time.Result: (1) MMP-2 level, MMP-2/TIMP-1 ratio, and collagen protein content in myocardial injury group were significantly higher than those in sham operation group. However, TIMP-1 level and capillary density was significantly lower in placebo group than those in sham operation at the end of week 2 and week 14 (P<0.05). (2) TIMP-1 level and capillary density in spironolactone group was significantly higher in rats given spironolactone than those in myocardial injury group either at the end of week 2 or week 14. However, MMP-2 level, MMP-2/TIMP-1 ratio was significantly reduced in the rats receiving spironolactone at the end of week 2 and week 14, as compared with those given placebos. (P<0.05) (3) As compared with myocardial injury group, collagen protein content and LVW/BW in spironolactone group was significantly lower at the end of week 14. (P<0.05)Conclusion: Spironolactone could significant improve the collateral circulation and collagen remodeling in non-infarcted zone through mediating production of MMP-2 and TIMP-1 in rats with myocardial injury.3. Effect of spironolactone on left ventricles remodeling in patients with acute myocardial infarctionObjective: To determine the effects of spironolactone on left ventricular remodeling (LVRM) in patients with acute myocardial infarction.Methods: In this multicenter, randomized, standard-therapy controlled study, 88 AMI patients were randomized into spironolactone group (n=46) in which they received spironolactone 4 mg/d in conjunction with conventional therapy, and control group (n=42) in which they received conventional therapy. During the 6-month follow up, we assessed the serum PⅢNP, BNP and echocardiography to evaluate myocardial fibrosis, LV function and volume.Results: Altogether, we enrolled 88 AMI patients from 4 hospitals in Shijiazhuang. There were 43 patients with anterior MI and 45 with inferior MI. In anterior MI group, 23 patients received spironolactone and 20 accepted the conventional therapy. In inferior MI group, 23 received spironolactone and 22 accepted the conventional therapy. Regarding anterior MI①Out data showed that serum PⅢNP and BNP levels were significantly lower in the spironolactone group than those in control group [PⅢNP (260.2±59.9) vs. (328.0±70.3) ng/L at month 3, P =0.001, (197.1±46.3) vs. (266.7±52.4) ng/L at month 6, P <0.001] , [BNP (347.4±84.0) vs. (430.1±62.9) ng/L at month 3, P <0.001, (243.7±79.7) vs. (334.6±62.8) ng/L at month 6, P <0.001];②There was a significant reduction in LVEDD and LVESD in patients given spironolactone compared with those in control group after 6 months intervention [(51.0±5.5) vs. (55.6±4.5)mm, P = 0.005, (35.7±4.6) vs. (39.1±5.6) mm, P =0.046]. However, with respect to inferior MI, our data showed:①There were no significant differences in PⅢNP and BNP value between the two groups after 6 months treatment in patients with inferior MI ;②There were also no significant differences in the LVEDD, LVESD, LVEF after 6 months treatment in patients with inferior MI.Conclusion:①In patients with anterior MI, spironolactone combined with the conventional therapy could significantly inhibit myocardial fibrosis, left ventricular dilation and prevent LVRM;②out data also showed that there was no significant difference in LVRM prevention between two groups in patients with inferior MI.4. Effects of spironolactone on the diastolic heart failure in the elderly patients with essential hypertensionObjective: To investigate the clinical efficacy of spironolactone on the diastolic heart failure in the elderly patients with essential hypertension.Methods: Seventy eight elderly hypertensive patients with diastolic heart failure were randomized into spironolactone group in which they received spironolactone plus conventional therapy, and control group in which they received conventional therapy alone. The concentration of PⅢNP and BNP were measured before at baseline and after six months of treatment. Doppler ultrasound recordings and 6-minute walk test were obtained from all patients to determine several parameters related to the left ventricular diastolic function.Results: The walking distance in six minutes in spironolactone group significantly increased from 318±41m at baseline to 559±62 m at the end of 6months treatment. As compared with control group, there was a significant increase in six-min walking distance in sprinolactone group (559±62 m versus 442±57 m, P<0.05). All echocardiography parameters of the left ventricular diastolic function were significantly better than those in the control group (P<0.01) after six months treatment.Conclusion: Spironolactone could significantly increase walking distance in six minutes and improve the heart diastolic function in elderly hypertensive patients with diastolic heart failure. In summary, our study results indicated that:1. Both spironolactone and losartan or their combination use could coordinate and improve the cardiac hemodynamics and the left ventricular collagen remodeling after myocardial infarction in rats.2. Spironolactone could improve the development of collateral circulation and collagen remodeling in non-infarcted zone through mediating production of MMP-2 and TIMP-1 in rats with myocardial injury.3. In patients with anterior MI, spironolactone combined with the conventional therapy could further inhibit myocardial fibrosis and left ventricular dilation and prevent LVRM; however, there was no significant difference in prevention of LVRM between two groups.4. The spironolactone could significantly increase the walking distance in 6 minutes and improve the ventricular diastolic function in elderly hypertensive patients.