MMP Induction and Inhibition in Myocardial Infarction

Short-term survival following a myocardial infarction (MI) has greatly improved, due in part to therapeutic interventions that restore blood flow and limit infarct size. The increased incidence of infarct-stimulated left ventricular (LV) remodeling that advances to congestive heart failure (CHF), however, is a significant long-term complication and a leading cause of mortality. Changes to ECM structure and function are primary components of LV remodeling and are precipitated by the early increase in infarct area collagen levels that replace necrotic myocytes and form a scar. ECM turnover is coordinated through the synthesis and degradation of ECM and non-ECM components, particularly the matrix metalloproteinases (MMP), a family of proteolytic enzymes that cleave ECM. MMPs have multiple roles in remodeling events that lead to LV dilation. The inhibition or targeted deletion of specific MMPs attenuates LV remodeling events post-MI. MMP inhibitors have been used in animal models to delineate LV remodeling mechanisms and to evaluate the pharmacologic potential of targeting the ECM to modify LV remodeling post-MI. This review summarizes the current knowledge and limitations of MMP inhibition in the post-MI myocardium.     

Differences in inflammation, MMP activation and collagen damage account for gender difference in murine cardiac rupture following myocardial infarction

Cardiac rupture remains a fatal complication of acute myocardial infarction (MI) with its mechanism partially understood. We hypothesized that damage to the collagen matrix of infarcted myocardium is the central mechanism of rupture and therefore responsible for the difference in the incidence of rupture between genders. We examined left ventricular (LV) remodeling during the acute phase post-MI in 129sv mice. Following induction of MI, we monitored rupture events and assessed the extent of LV remodeling by echocardiography. Muscle tensile strength, content of insoluble and soluble collagen, expression and activity of matrix metalloproteinases (MMPs) and density of inflammatory cells were determined in the infarcted and non-infarcted myocardium. We then tested the effects of MMP inhibition on rupture. Compared to female mice, males with MI displayed greater extent of LV remodeling, reduced muscle tensile strength, loss of insoluble collagen, local inflammatory response and MMP-9 activation, changes associated with a 3 times higher incidence of rupture than in females. MMP-9 expression by circulating blood mononuclear cells was also increased in male mice with acute MI. Treatment of male mice with an MMP inhibitor reduced MMP activity and halved rupture incidence. Our findings demonstrate that the differences in the severity of inflammation, MMP activation and damage to collagen matrix account for gender difference in cardiac rupture. Our study illustrates the breakdown of fibril collagen as a central mechanism of cardiac rupture.     

Effect of ramipril and furosemide treatment on interstitial remodeling in post-infarction heart failure rat hearts

Extracellular matrix (ECM) remodeling and increased matrix metalloproteinase (MMP) expression and activity have been observed to be relevant in the development of heart failure (HF). We examined the effects of ramipril alone or with furosemide on ECM in a heart failure model. HF was induced by occlusion of the left coronary artery in spontaneously hypertensive rats (SHR). Rats were assigned to placebo (n=9), ramipril 1 mg/kg/day (n=11), furosemide 2 x 2 mg/kg/day (n=7) or both (1 mg/kg/day + 2 x 2 mg/kg/day n=8). LV-function, collagen content, MMP/TIMP (tissue inhibitor of matrix metalloproteinases) protein- and mRNA-expression were examined in non-infarcted LV tissue. MMP-2/TIMP-4 ratio was increased in HF. Ramipril reduced MMP-2 expression (active form), collagen type I mRNA expression and content and increased TIMP-4 levels associated with decreased left ventricular end diastolic pressure (LVEDP), mortality rate and increased LV pressure (LVP). Combination therapy with furosemide is less efficient with regard to collagen content and MMP-2 (active form) reduction but did not worsen beneficial effects of ramipril on LV function and mortality rate. Furosemide alone had no effect on MMP-2 (active form) expression, collagen content, LV function and mortality rate. Prevention of LV dilatation by ramipril was associated with decreased gelatinolytic activity and increased MMP-inhibition in heart failure SHR. Furthermore, ramipril reduced fibrosis by enhanced interstitial collagenase expression. Furosemide did not show the beneficial effects of ramipril on ECM remodeling but did not worsen LV function. Positive effects of furosemide treatment alone on LV remodeling and function were not observed.     

基质金属蛋白酶及抑制物与慢性阻塞性肺疾病发病机制的关系

基质金属蛋白酶（matrix metalloproteinases．MMP）是一类高度保守的依赖于锌离子的蛋白水解酶家族,能降解肺组织细胞外基质中的多种蛋白成份．导致细胞外基质合成与降解失衡．组织金属蛋白酶抑制剂（tissue inhibitor of metalloproteinases．TIMP）能特异性抑制其活性．本文对MMP和TIMP在慢性阻塞性肺疾病发生发展中发挥的重要作用作一综述。     

What role do extracellular matrix changes contribute to the cardiovascular disease burden of diabetes mellitus?

Matrix metalloproteinases (MMP) and their inhibitors (TIMP) are central factors in the control of extracellular matrix turnover. They are important in normal physiology and also during a range of pathological states. In this review, we have systematically identified clinical articles relevant to cardiovascular disease in diabetes from the last 10 years. Our aim was to outline the structure, function and regulation of metalloproteinases and their key roles in cardiomyopathy and vasculopathy in diabetes. We also explore the effects of drug intervention on both human subjects with diabetes and experimental animal models. The modulation of MMP and TIMP activity using drugs that affect the expression and function of these proteins may provide us with new ways to treat this serious and disabling disease, and we explore potential mechanisms and treatments.     

TIMPs and cardiac remodeling: ‘Embracing the MMP-independent-side of the family’

Unraveling the biological role of tissue inhibitors of metalloproteinases (TIMPs) during cardiac remodeling and the progression of heart failure has proven to be an enormous challenge. Remodeling of the cardiac extracellular matrix (ECM), regulated by matrix metalloproteinases (MMPs) and their endogenous inhibitors, TIMPs, is a well-established paradigm in cardiac health and disease. Originally, TIMPs were thought to function exclusively as endogenous inhibitors of MMP activity, thereby fine-tuning MMP-mediated ECM degradation and numerous related processes. However, during the last two decades, the concept of MMP-independent TIMP-mediated receptor signaling and regulation of cell fate has emerged. Although our current knowledge is still limited, in this review, we highlight some of the novel data, illustrating the MMP-independent biological properties of the four TIMP family members. Moreover, we discuss how these cell-specific insights may contribute to the process of cardiac remodeling, disease and failure. Finally, we identify where additional research is needed that will codetermine the possible future of TIMPs as therapeutic targets.     

Mechanisms of fibrinolysis in chronic liver injury (with special emphasis on MMPs and TIMPs)

Regeneration from liver fibrosis is characterized by four essential events: 1. eradication of pathological agents, 2. apoptosis of activated hepatic stellate cells, 3. remodeling of extracellular matrix, and 4. regeneration of parenchyma and liver function. The temporal and spatial regulation of matrix metalloproteinase (MMP) activity and expression of their specific inhibitors, the tissue inhibitors of metalloproteinases (TIMPs), play a pivotal role in matrix remodeling during hepatic fibrogenesis and recovery. According to current knowledge, the main topics and mechanisms in regeneration from hepatic fibrosis with special emphasis on MMPs and TIMPs are presented. MMP and TIMP expression patterns during hepatic fibrogenesis and fibrolysis, specific characteristics like regulation, expression of cell types, gene expression (RNA/protein), and the underlying disease are summarized. Studies presenting a time course for MMP and TIMP expression during recovery from hepatic fibrosis were taken into consideration to point out a synchronizing behavior in the expression pattern.     

Release of matrix metalloproteinases following alcohol septal ablation in hypertrophic obstructive cardiomyopathy

OBJECTIVES: This study examined plasma levels of certain matrix metalloproteinase (MMP) and tissue inhibitor of matrix metalloproteinase (TIMP) species before and after alcohol-induced myocardial infarction (MI) in patients with hypertrophic obstructive cardiomyopathy (HOCM). BACKGROUND: Matrix metalloproteinases contribute to tissue remodeling, and endogenous control of MMP activity is achieved by the concordant release and binding of TIMPs. Animal models of MI have demonstrated a role for MMP activation in myocardial remodeling. However, the temporal relationship of MMP and TIMP release following a controlled myocardial injury in humans remains unknown. METHODS: Plasma levels for the gelatinases MMP-2 and MMP-9, and for the collagenases MMP-8 and MMP-13, as well as TIMP-1 profiles were examined (by enzyme-linked immunosorbent assay) at baseline and serially up to 60 h following alcohol injection into the septal perforator artery in order to induce an MI in 51 patients with HOCM (age 55 +/- 2 years). RESULTS: Plasma creatine kinase (MB isoform), indicating myocardial injury, increased 2,150% 18 h post-MI (p < 0.05). Plasma MMP-9 increased by over 400% and MMP-8 by over 100% from baseline values by 12 h post-MI (p < 0.05 vs. baseline). A similar temporal profile was not observed for MMP-2 and MMP-13. In addition, a concomitant increase in plasma TIMP-1 levels did not occur post-MI. As a result, MMP/TIMP stoichiometry (MMP-9/TIMP-1 ratio) increased significantly post-MI, suggestive of reduced TIMP-1 mediated MMP-9 inhibition, which would potentially enhance extracellular myocardial remodeling. CONCLUSIONS: These unique results demonstrated that induction of a controlled myocardial injury in humans, specifically through alcohol-induced MI, caused species- and time-dependent perturbations of MMP/TIMP stoichiometry that would facilitate myocardial remodeling in the early post-MI setting.     

Matrix Metalloproteinases: Pathways of Induction by Bioactive Molecules

Regulation of the extracellular matrix (ECM) is an important therapeutic target that can potentially attenuate the adverse ventricular remodeling seen in the progression of heart failure. Matrix metalloproteinases (MMPs) degrade numerous ECM proteins. Importantly, the activation of MMPs and their endogenous inhibitors (TIMPs) are associated with ventricular remodeling. Bioactive-molecules (vasoactive peptides) become activated in proportion to the magnitude of heart failure and have been demonstrated to affect directly collagen degradation as well as collagen synthesis in the myocardium. Pro-fibrotic factors such as norepinephrine, angiotensin II, and endothelin-1 stimulate fibrosis by modulating collagen synthesis and MMP/TIMP activity. Antagonism of these bioactive-molecules has produced improved hemodynamic performance concomitant with modulation of MMP/TIMP activity and in association with reverse remodeling. The natriuretic peptides and nitric oxide, both of which function via the second messenger cGMP, demonstrate anti-fibrotic actions by inhibiting collagen synthesis and by stimulating MMP activity. Furthermore, bioactive-molecules along with certain cytokines are reported to amplify MMP activity, suggesting that different signaling systems work together to modulate ECM turnover. Taken together, the evidence supports an important functional role for bioactive-molecules in the regulation of ECM turnover and suggests that pharmacological intervention at the level of such bioactive molecules may provide potential therapeutic strategies for attenuation of the adverse ventricular remodeling associated with the progression of heart failure.     

Novel approaches to retard ventricular remodeling in heart failure

While the etiologies of congestive heart failure (CHF) are diverse, a common event in the progression of this disease process is LV remodeling, increased wall stress, and subsequent pump dysfunction. Therapeutic approaches for CHF have been focused upon reducing LV afterload through vasodilator therapy, or by blocking/interrupting the effects of neurohormonal stimuli. However, another therapeutic approach would be to directly intervene in the LV remodeling process with CHF. An important determinant in the maintenance of myocyte shape, alignment and transduction of myocyte shortening into an overall ejection is the structural support provided by the fibrillar collagen matrix. As in most tissue remodeling processes, LV myocardial remodeling with CHF is accompanied by changes in the structure and composition of the collagen matrix. Matrix metalloproteinases (MMPs) are an endogenous family of zinc-dependent enzymes which have been identified to be responsible for matrix remodeling and alterations in MMP expression and activity have been identified in clinical and animal models of CHF. Moreover, alterations in the tissue inhibitors of MMPs (TIMPs) have also been identified to occur in the end-stage CHF myocardium. Thus, it is very likely that increased MMP activity and reduced inhibitory control of the TIMPs contribute to the LV remodeling process with CHF. A number of bioactive peptides and cytokines influence MMP and TIMP expression and activity. In addition, pharmacologically active MMP inhibitors have been synthesized and are currently under study. Accordingly, the control of MMP and TIMP expression and activity within the failing myocardium represents a new and potentially significant therapeutic target for CHF.     

Evolution of matrix metalloprotease and tissue inhibitor expression during heart failure progression in the infarcted rat

OBJECTIVE: Characterize the timecourse of matrix metalloproteinase (MMP-1, -2, -3, -7, -9, -11, -12, -13, and -14) and endogenous tissue inhibitors of MMPs (TIMP-1, -2, -3, and -4) upregulation during left ventricular (LV) remodeling following myocardial infarction (MI) in rats. METHODS: The descending left coronary artery of male rats (Rattus norvegicus) was ligated to produce a MI. LV function and dilation were assessed from 1 day to 16 weeks post-MI. Protein and mRNA extraction was done on LV samples containing scar and myocardium together. Gelatinase activity was measured by zymography. Westerns were run on the MMPs known to cleave fibrillar collagen in the rat (MMP-8, -13, and -14) as well as TIMP-1, -2, and -4. RESULTS: Average infarct size was 38.6+/-1.1%, and produced LV dysfunction and progressive LV dilation. Thoracic ascites, a marker of congestive heart failure (HF), was not present until 12 weeks post-MI. Upregulation of MMP-2, -8, -9, -13, and -14 and TIMP-1 and TIMP-2 was detected at different timepoints during HF progression. Increased MMP protein levels occurred sometimes without a corresponding elevation in mRNA levels, and increased TIMP mRNA levels without increased protein levels. MMP-13 active form was elevated during the first 2 weeks post-MI while TIMP-1 and TIMP-2 protein levels were not significantly elevated until 2 weeks post-MI. MMP-8 and MMP-14 protein levels increased later during heart failure progression. CONCLUSION: MMP/TIMP upregulation evolves over time following infarction in the rat LV. Some MMPs were significantly elevated during the first week post-MI (MMP-13, -2, and -9) and another was not until 16 weeks post-MI (MMP-14). The dissociation between LV MMP/TIMP mRNA and protein levels shows that post-translation processing occurs in the rat heart.     

基质金属蛋白酶/基质金属蛋白酶组织抑制剂与心房颤动

基质金属蛋白酶是一个细胞外基质降解酶家族,基质金属蛋白酶组织抑制剂是其内源性抑制物.二者平衡在细胞外基质合成及降解过程中起重要作用,与心房颤动过程中心房结构重塑,即心房纤维化及心房扩大相关.目前研究显示基质金属蛋白酶/基质金属蛋白酶组织抑制剂失衡与心房颤动的发生、发展及复发相关,抑制基质金属蛋白酶可改善心房重塑并阻止心房颤动进展.恢复基质金属蛋白酶/基质金属蛋白酶组织抑制剂平衡可能成为治疗心房颤动的新型治疗途径.     

Simultaneous up-regulation of matrix metalloproteinases 1, 2, 3, 7, 8, 9 and tissue inhibitors of metalloproteinases 1, 4 in serum of patients with chronic obstructive pulmonary disease

Background and objective: Matrix metalloproteinases (MMP) and tissue inhibitors of metalloproteinases (TIMP) have been implicated in chronic obstructive pulmonary disease (COPD) pathogenesis. However, the majority of studies have focused on single MMP, and there is limited information on parallel expression of MMP and their antagonists TIMP. We, therefore, investigated the serum profile of MMP 1–3, 7–9, 12 and 13, and TIMP 1–4 in COPD patients. Methods: Serum MMP 1–3, 7–9, 12 and 13, and TIMP 1–4 were measured in 74 COPD patients and 20 control subjects by multiple microsphere technology. Results: MMP 1–3 and MMP 7–9 were elevated in COPD patients compared with control subjects (P= 0.001–0.043). The increased concentrations of MMP 1, 8 and 9 paralleled GOLD stage (P= 0.002–0.007). TIMP 1 and 4 concentrations were elevated in COPD (P < 0.001). MMP 1, 8 and 9, and TIMP 1 and 4 serum levels in COPD non‐smokers were higher than in control non‐smokers (P= 0.002–0.025). MMP 12 and 13 levels were undetectable in our serum samples. Conclusions: This study provides further evidence for increased MMP 1, 7–9, and TIMP 1 serum levels in COPD, and demonstrates for the first time serum elevation of MMP 2 and 3, and TIMP 4. The finding that circulating TIMP 4 levels are increased in COPD and the observed relationship between serum levels of MMP 1, 8 and 9, and GOLD stage requires verification in an expanded patient cohort.     

Matrix metalloproteinase abundance in human myocardial fibroblasts: effects of sustained pharmacologic matrix metalloproteinase inhibition

BACKGROUND: A cause-effect relationship has been established between matrix metalloproteinases (MMPs) and left ventricular (LV) myocardial remodeling through the use of pharmacologic MMP inhibitors. However, the direct effects of MMP inhibition on MMPs and endogenous tissue inhibitors of metalloproteinases (TIMPs) in LV human myocardial fibroblasts (LVHMFs) remain unknown. This study measured MMP-2, MMP-9, MMP-13, MT1-MMP, and TIMP-1 release in LVHMFs. METHODS AND RESULTS: LVHMF cultures were established from six individual patients (passages 2-5) and incubated with and without the broad-spectrum MMP inhibitor PD166793 (100 microM) for 12-36 h. While PD166793 did not influence MMP-2 release, MMP-9 levels based on substrate zymography increased at 36 h by over 30% (P < 0.05). TIMP-1 levels increased in a time-dependent manner with no effect from PD166793 incubation. However, the MMP-9/TIMP-1 ratio was increased by over 20% from time-matched values following 12-36 h of exposure to PD166793 (P < 0.05). Similar results obtained after incubation of LVHMF cultures with the broad-spectrum MMP inhibitor Batimastat (BB-94) suggest that these observations are due to a general class effect of broad-spectrum MMP inhibitors. CONCLUSIONS: This study is the first to demonstrate that a selective induction and release of an MMP species occurs with sustained exposure to pharmacologic MMP inhibition in LVHMFs. These observations may have particular importance with respect to controlling this proteolytic system in the context of LV myocardial remodeling.     

Extracellular matrix turnover and signaling during cardiac remodeling following MI: Causes and consequences

The concept that extracellular matrix (ECM) turnover occurs during cardiac remodeling is a well-accepted paradigm. To date, a multitude of studies document that remodeling is accompanied by increases in the synthesis and deposition of ECM components as well as increases in extracellular proteases, especially matrix metalloproteinases (MMPs), which break down ECM components. Further, soluble ECM fragments generated from enzymatic action serve to stimulate cell behavior and have been proposed as candidate plasma biomarkers of cardiac remodeling. This review briefly summarizes our current knowledge base on cardiac ECM turnover following myocardial infarction (MI), but more importantly extends discussion by defining avenues that remain to be explored to drive the ECM remodeling field forward. Specifically, this review will discuss cause and effect roles for the ECM changes observed following MI and the potential role of the ECM changes that may serve as trigger points to regulate remodeling. While the pattern of remodeling following MI is qualititatively similar but quantitively different from various types of injury, the basic theme in remodeling is repeated. Therefore, while we use the MI model as the prototype injury model, the themes discussed here are also relevant to cardiac remodeling due to other types of injury.     

极限门静脉压力分支结扎对肝脏再生和基质金属蛋白酶及其组织抑制因子表达的影响

目的 探讨极限门静脉压力分支结扎对大鼠肝脏基质金属蛋白酶(MMP)及其组织抑制因子(TIMP)表达的影响. 方法 Sprague-Dawley雄性大鼠96只,随机分成假手术对照组和门静脉结扎实验组.观察术后0.5、1、3、5、7、14、21 d和28 d保留侧肝脏和肝脏总质量变化,光学显微镜下观察保留侧肝细胞的形态变化,用免疫组织化学方法检测保留侧肝细胞的增殖细胞核抗原(PCNA)及MMP2、MMP9和TIMP2的表达.用SPSS11.5统计软件根据不同数据资料进行t检验或Pearson相关分析进行统计学分析. 结果 (1)90%极限门静脉分支结扎后,95.8%的大鼠存活良好.结扎侧肝叶呈进行性萎缩、变小,保留侧肝叶占总肝质量的比例在1 d内增加较缓慢,而1～5 d时,保留侧肝叶所占比例则增加速度明显加快,5 d以后保留侧肝叶所占比例增加变慢,于7 d达"平台期";(2)术后PCNA阳性细胞计数与假手术对照组比较,门静脉结扎实验组术后0.5～3 d明显增多,0.5、1、3 d组PCNA阳性率分别为13.86%±4.73%、17.45%±4.38%、21.33%±5.59%对比7.33%±2.63%、9.42%±3.98%、8.13%±2.37%,P值均＜0.01,第5天达高峰(25.70%±6.80%对比6.37%±3.38%),第7天有所减少,但仍高于对照组(P值均＜0.01),以后逐渐恢复正常;(3)保留侧肝叶的MMP2、MMP9和TIMP2蛋白的表达均在术后1 d开始明显增加,至术后7 d达高峰;此后逐渐恢复至术前水平(P＞0.05),仅见少量肝细胞胞质表达;(4)大鼠肝脏MMP2的表达在术后0.5、1、5、7、14 d组与肝组织PCNA表达均呈正相关关系,MMP9的表达在术后0.5、1、7、21 d组与肝细胞PCNA指数呈正相关关系,大鼠肝脏TIMP2的表达在术后1、7、14、21 d组与肝细胞PCNA指数呈正相关关系. 结论 90%极限门静脉分支结扎术后保留侧肝叶的MMP2、MMP9和TIMP2蛋白的表达均在术后1 d开始增加,至术后7d达高峰;此后逐渐恢复至术前水平;术后PCNA指数与保留侧肝叶的MMP2、MMP9和TIMP2蛋白的表达明显相关,MMP2、MMP9和TIMP2蛋白在肝再生的过程中发挥重要作用.     

Matrix metalloproteinases: regulation and dysregulation in the failing heart

Matrix metalloproteinases (MMPs) are a family of proteolytic enzymes responsible for myocardial extracellular protein degradation. Several MMP species identified within the human myocardium may be dysregulated in congestive heart failure (CHF). For example, MMPs that are expressed at very low levels in normal myocardium, such as collagenase-3 (MMP-13) and the membrane-type-1 MMPs, are substantially upregulated in CHF. However, MMP species are not uniformly increased in patients with end-stage CHF, suggesting that a specific portfolio of MMPs are expressed in the failing myocardium. With the use of animal models of CHF, a mechanistic relationship has been demonstrated with respect to myocardial MMP expression and the left ventricular (LV) remodeling process. The tissue inhibitors of the MMPs (TIMPs) are locally synthesized proteins that bind to active MMPs and thereby regulate net proteolytic activity. However, there does not appear to be a concomitant increase in myocardial TIMPs during the LV remodeling process and progression to CHF. This disparity between MMP and TIMP levels favors a persistent MMP activation state within the myocardium and likely contributes to the LV remodeling process in the setting of developing CHF. The elucidation of upstream signaling mechanisms that contribute to the selective induction of MMP species within the myocardium as well as strategies to normalize the balance between MMPs and TIMPs may yield some therapeutic strategies by which to control myocardial extracellular remodeling and thereby slow the progression of the CHF process.     

Stem cell mechanisms during left ventricular remodeling post-myocardial infarction:Repair and regeneration

Post-myocardial infarction(MI),the left ventricle(LV)undergoes a series of events collectively referred to as remodeling.As a result,damaged myocardium is replaced with fibrotic tissue consequently leading to contractile dysfunction and ultimately heart failure.LV remodeling post-MI includes inflammatory,fibrotic,and neovascularization responses that involve regulated cell recruitment and function.Stem cells(SCs)have been transplanted post-MI for treatment of LV remodeling and shown to improve LV function by reduction in scar tissue formation in humans and animal models of MI.The promising results obtained from the application of SCs post-MI have sparked a massive effort to identify the optimal SC for regeneration of cardiomyocytes and the paradigm for clinical applications.Although SC transplantations are generally associated with new tissue formation,SCs also secrete cytokines,chemokines and growth factors that robustly regulate cell behavior in a paracrine fashion during the remodeling process.In this review,the different types of SCs used for cardiomyogenesis,markers of differentiation,paracrine factor secretion,and strategies for cell recruitment and delivery are addressed.