MMP/TIMP expression in spontaneously hypertensive heart failure rats: the effect of ACE- and MMP-inhibition

OBJECTIVE: Determine the effect of a matrix metalloproteinase inhibitor (MMPi) and angiotensin converting enzyme inhibitor (ACEi) on collagen, MMP, tissue inhibitors of MMPs (TIMPs) expression in the spontaneously hypertensive heart failure (SHHF) rat. METHODS: Six groups were tested: normotensive 9- and 13-month-old Wistar-Furth (WF) rats, 9-month-old SHHFs (compensatory hypertrophy), 13-month-old SHHFs with HF, and 13-month-old SHHFs orally administered with either an MMPi (PD166793, 5 mgkg(-1)day(-1)) or ACEi (quinapril, 10 mgkg(-1)day(-1)) for 4 months. Collagen volume fraction was assessed histomorphometrically. Left ventricular (LV) mRNA [MMP-1,-2,-3,-7,-9,-11,-13,-14; TIMP-1,-2,-3,-4; and collagen alpha1(I) and alpha1(III)] and protein (MMP-2 and MMP-9 zymographic activity; Western blot analysis of MMP-13, and TIMP-1,-2,-4) levels could be quantified. RESULTS: Collagen mRNA levels were elevated in SHHFs compared to age-matched controls, but collagen volume fraction was elevated only in 13-month-old SHHFs (approximately 2x). Only MMP-2 mRNA levels increased significantly with HF. However, MMP-2 and MMP-9 zymographic activity, and MMP-13 protein levels increased. TIMP-1 and TIMP-2 mRNA and protein levels increased, and TIMP-4 protein levels decreased in SHHFs vs. controls. Both drug treatments reduced LV dilation; preserved systolic function; and normalized MMP/TIMP expression. Both drug treatments also reduced collagen volume fraction, but only quinapril reduced collagen mRNA levels and LV hypertrophy. CONCLUSIONS: The divergent effect of MMPi and ACEi on collagen mRNA levels and hypertrophy indicate that drug efficacy is mediated by different pathways in the SHHF rat.     

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.     

Downregulation of vascular matrix metalloproteinase inducer and activator proteins in hypertensive patients

BACKGROUND: Peripheral vasculature undergoes extensive vascular remodeling in the hypertensive state. Regulation of extracellular matrix turnover by the matrix metalloproteinase (MMP) system is an important step in the vascular remodeling process. However, the expression pattern of the vascular MMP system in human hypertension remained unknown. METHODS AND RESULTS: Internal mammary artery specimens were obtained from normotensive (n = 13) and hypertensive (n = 19) patients undergoing coronary artery bypass grafting surgery. Zymographic analysis indicated a threefold decrease in total gelatinolytic activity of MMP-2 and MMP-9 in hypertension. MMP-1 activity was also decreased by fourfold without a significant change in protein levels. Tissue levels of extracellular matrix inducer protein (EMMPRIN), MMP activator protein (MT1-MMP), MMP-1, MMP-2, and MMP-9, as well as tissue inhibitors of MMPs (TIMP-1 and TIMP-2) were assessed by immunoblotting and yielded a significant decrease in MMP-9, EMMPRIN, and MT1-MMP levels in hypertension. In addition, measurement of plasma markers of collagen synthesis (procollagen type I amino-terminal propeptide [PINP]) and collagen degradation (carboxy-terminal telopeptide of collagen type I [ICTP]) indicated no difference in PINP levels but suppressed degradation of collagen in hypertension. Evaluation of profibrotic growth factors demonstrated higher levels of fibroblast growth factor (FGF)-2 in tissue preparations from hypertensive patients but no difference in transforming growth factor-beta1 levels. CONCLUSIONS: These findings demonstrate that not only MMP-1 and MMP-9, but MMP inducer and activator proteins are also downregulated in the hypertensive state. Augmented FGF-2 levels may contribute to parallel decreases in MMP activity and MMP induction system resulting in enhanced collagen deposition in hypertension.     

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.     

Cardiac remodeling after long term norepinephrine treatment in rats.

OBJECTIVE: In this study we have tested the hypothesis that degradation of collagen by matrix metalloproteinase 2 (MMP-2) precedes the deposition of extracellular matrix (ECM) after long term norepinephrine (NE) treatment. METHODS: Female Sprague-Dawley rats received continuous i.v. infusion of NE (0.1 mg/kg.h) for 1, 2, 3, 4 and 14 days. Heart function and weight as well as expression of cardiac colligin and of collagen I and III were examined. Furthermore, we have assessed the degradation pathway of collagen by measuring the mRNA and activity of myocardial MMP-2 and tissue inhibitor of metalloproteinase 2 (TIMP-2) as well as the protein level of TIMP-2. RESULTS: NE induced hypertrophy predominantly of the left ventricle (LV) in a time-dependent manner. It increased the mRNAs of colligin, collagen I and III, and of MMP-2 and TIMP-2 as well as MMP-2 activity in two phases: In the initial phase, at 3 and 4 days, the mRNA of colligin and of collagen I and III was elevated predominantly in the LV, MMP-2 and TIMP-2 mRNA, as well as TIMP-2 protein and MMP-activity were increased in both ventricles. The second phase, after 14 days, was characterized by a less pronounced increase in colligin, collagen I and III and in MMP-2 activity which occurred exclusively in the LV. Finally, long-term treatment with NE induced a 37% increase in interstitial fibrosis which was shown to occur exclusively in the LV after 14 days. CONCLUSION: NE treatment induced fibrosis exclusively in the LV which was associated with hypertrophy predominantly of the LV. The elevated MMP-2 activity seems to be necessary for the ECM to adapt to the enlargement of myocytes and to reduce overproduction of collagen.     

Plasma matrix metalloproteinase and inhibitor profiles in patients with heart failure

BACKGROUND: Changes in myocardial matrix metalloproteinases (MMPs) and the inhibitors of MMPs (TIMPs) have been demonstrated in congestive heart failure (CHF). The first objective of this study was to measure plasma profiles of MMPs and TIMPs in CHF patients (n = 24; 62 +/- 3 years; left ventricular ejection fraction [LVEF] = 24 +/- 2%) and age-matched nonfailing patients (n = 48; 63 +/- 2 years; LVEF >/= 55%). Cytokines such as tumor necrosis factor (TNF)-alpha can induce MMP expression in vitro. The second objective of this study was to determine the relationship between soluble TNF-alpha receptors (TNFR1; TNFR2) and MMP plasma profiles. METHODS AND RESULTS: Plasma levels of MMP-2, MMP-9, MMP-8, TIMP-1, TIMP-2, TNF-alpha, TNFR1, and TNFR2 were measured by enzyme-linked immunosorbent assay kits. Plasma MMP-9 levels were increased in CHF patients (25 +/- 6 versus 72 +/- 15 ng/mL, P <.05). Interestingly, plasma levels of MMP-8 were decreased in CHF patients (16 +/- 2 versus 9 +/- 2 ng/mL, P <.05). The MMP-9/TIMP-1 ratio was increased by 3-fold, whereas the MMP-9/TIMP-2 ratio was increased by 16-fold in CHF patients (both P <.05). With a 48-week follow-up in CHF patients, an absolute reduction in plasma TNFR1 from baseline was accompanied by reduced MMP-9 levels (-30 +/- 16 ng/mL; P =.058), whereas stable or increased plasma TNFR1 resulted in persistently elevated MMP-9 levels. CONCLUSIONS: The unique findings of this study were 2-fold. First, a discordant change in plasma MMP and TIMP levels occurred in CHF patients. Second, changes in cytokine activity were related to changes in plasma MMP levels. These changes in MMP/TIMP levels likely reflect the progression and/or acceleration of the LV remodeling process in CHF. Thus serial measurements of plasma MMP/TIMP levels may hold diagnostic/prognostic significance in CHF patients.     

Collagen degradation in a murine myocarditis model: relevance of matrix metalloproteinase in association with inflammatory induction

OBJECTIVE: Myocardial collagen degradation is regulated by matrix metalloproteinases (MMPs) and tissue inhibitors of matrix metalloproteinase (TIMPs). The possible relevance of MMPs in association with the inflammatory induction was investigated in a murine coxsackievirus B3 myocarditis model. METHODS: Hearts from viral infected and sham-infected BALB/c mice were analyzed by semi-quantitative RT-PCR, picrosirius red staining, Western blot analysis, and immunohistochemistry. RESULTS: In viral infected mice, both mRNA and protein abundance for collagen type I remained unaltered. In addition, picrosirius red staining showed the unchanged total collagen content. However, degraded soluble fraction of collagen type I protein was increased. Moreover, the mRNA abundance for MMP-3 and MMP-9 was upregulated, whereas the mRNAs for TIMP-1 and TIMP-4 were downregulated, respectively. The upregulation of MMP-3/MMP-9 and downregulation of TIMP-4 were confirmed at the protein level, and were associated with significantly increased mRNA levels of interleukin 1beta, tumor necrosis factor-alpha, transforming growth factor-beta1 and interleukin-4. CONCLUSION: The increment of MMPs in the absence of counterbalance by TIMPs may lead to a functional defect of the myocardial collagen network by posttranslational mechanisms. This may contribute significantly to the development of left ventricular dysfunction in murine viral myocarditis. The inflammatory response with induction of cytokines may mediate the dysregulation of the myocardial MMP/TIMP systems.     

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.     

Extracellular matrix remodelling in human aortic valve disease: the role of matrix metalloproteinases and their tissue inhibitors.

AIMS: Aortic valve diseases are characterized by pathological remodelling of valvular tissue but the cellular and molecular effectors involved in these processes are not well known. The role of matrix metalloproteinase (MMP)-2, MMP-9, MMP-3, MMP-7, and tissue inhibitor of matrix metalloproteinase (TIMP)-1 and TIMP-2 are investigated here. METHODS AND RESULTS: Histological analysis of pathological valves [aortic stenosis (AS) (n=49), aortic regurgitation (AR) (n=23)] and control valves (n=8) was performed. The main tissue abnormalities (calcification, inflammatory cells, and capillaries) observed in AS were less severe or absent in AR. However, both groups of pathological valves displayed similar histological signs of extracellular matrix (ECM) remodelling. Biochemical analysis of MMPs and TIMPs (gelatin and casein zymography and ELISA) was performed on valve extracts. MMP-2 activity was not significantly different in control and pathological valves. Increases in MMP-9 and MMP-3 in AS demonstrated an inflammatory state. Finally, there was a four- to seven-fold increase of TIMP-1 in pathological valves. TIMP-1, TIMP-2, and MMP-2 were synthesized by the valvular interstitial cells in primary culture. CONCLUSION: This study demonstrates the involvement of the MMP/TIMP system in ECM remodelling of both AS and AR. These findings provide evidence of inflammatory injury more severe in AS than in AR and involvement of mesenchymal cell response.     

白细胞介素-10对急性心肌梗死后细胞外基质重构影响的实验研究

目的 观察白细胞介素-10(IL-10)对大鼠急性心肌梗死后心肌基质金属蛋白酶(MMP)-2、9,金属蛋白酶组织抑制因子(TIMP)-1表达及胶原代谢的作用,探讨其对急性心肌梗死后心肌基质重构的影响.方法 18只大鼠随机分为假手术组、MI/AAV2转染组作为对照和MI/AAV2-IL-10转染组,每组6只.结扎大鼠左冠状动脉前降支建立急性心肌梗死动物模型,同时应用基因重组2型腺相关病毒(AAV-2)携带IL-10基因转染心肌组织.RT-PCR和ELISA观察心肌IL-10 mRNA和蛋白的表达.逆转录聚合酶链反应、免疫印迹法、明胶酶谱、免疫组化检测转染后心肌组织表达MMP-2、9,TIMP-1,Ⅰ、Ⅲ型胶原水平的变化.结果 心肌梗死5 d后,MI/AAV2-IL-10组检测到IL-10 mRNA和蛋白的表达;MI/AAV2组较假手术组心肌MMP-2、9,Ⅰ、Ⅲ型胶原表达明显升高;而MI/AAV2-IL-10组较MI/AAV2组梗死心肌各部位MMP-2、9表达减少,TIMP-1表达升高,其中,梗死边缘区的MMP-2表达降低14.6%(P＜0.01),MMP-9降低24.7%(P＜0.01),TIMP-1升高73.1%(P＜0.01),Ⅰ、Ⅲ型胶原表达分别下降了47.6%(P＜0.01)、23.6%(P＜0.05),Ⅰ/Ⅲ型胶原比值下降.结论 IL-10通过对MMP/TIMP的作用,改善大鼠急性心肌梗死后心肌胶原沉积和组织重构.     

Effects of high glucose and thiamine on the balance between matrix metalloproteinases and their tissue inhibitors in vascular cells

Pericyte survival in diabetic retinopathy depends also on interactions with extracellular matrix (ECM) proteins, which are degraded by matrix metalloproteinases (MMP). Elevated glucose influences ECM turnover, through expression of MMP and their tissue inhibitors, TIMP. We reported on reduced pericyte adhesion to high glucose-conditioned ECM and correction by thiamine. We aimed at verifying the effects of thiamine and benfotiamine on MMP-2, MMP-9 and TIMP expression and activity in human vascular cells with high glucose. In HRP, MMP-2 activity, though not expression, increased with high glucose and decreased with thiamine and benfotiamine; TIMP-1 expression increased with high glucose plus thiamine and benfotiamine; MMP-9 was not expressed. In EC, MMP-9 and MMP-2 expression and activity increased with high glucose, but thiamine and benfotiamine had no effects; TIMP-1 expression was unchanged. Neither glucose nor thiamine modified TIMP-2 and TIMP-3 expression. TIMP-1 concentrations did not change in either HRP or EC. High glucose imbalances MMP/TIMP regulation, leading to increased ECM turnover. Thiamine and benfotiamine correct the increase in MMP-2 activity due to high glucose in HRP, while increasing TIMP-1.     

Combination of tumor necrosis factor-alpha ablation and matrix metalloproteinase inhibition prevents heart failure after pressure overload in tissue inhibitor of metalloproteinase-3 knock-out mice

Cytokine and extracellular matrix (ECM) homeostasis are distinct systems that are each dysregulated in heart failure. Here we show that tissue inhibitor of metalloproteinase (TIMP)-3 is a critical regulator of both systems in a mouse model of left ventricular (LV) dilation and dysfunction. Timp-3(-/-) mice develop precipitous LV dilation and dysfunction reminiscent of dilated cardiomyopathy (DCM), culminating in early onset of heart failure by 6 weeks, compared with wild-type aortic-banding (AB). Timp-3 deficiency resulted in increased TNFalpha converting enzyme (TACE) activity within 6 hours after AB leading to enhanced tumor necrosis factor-alpha (TNFalpha) processing. In addition, TNFalpha production increased in timp-3(-/-)-AB myocardium. A significant elevation in gelatinase and collagenase activities was observed 1 week after AB, with localized ECM degradation in timp-3(-/-)-AB myocardium. Timp-3(-/-)/tnfalpha(-/-) mice were generated and subjected to AB for comparative analyses with timp-3(-/-)-AB mice. This revealed the critical role of TNFalpha in the early phase of LV remodeling, de novo expression of Matrix metalloproteinases (MMP)-8 in the absence of TNFalpha, and highlighted the importance of interstitial collagenases (MMP-2, MMP-13, and MT1-MMP) for cardiac ECM degradation. Ablation of TNFalpha, or limiting MMP activity with a synthetic MMP inhibitor (PD166793), each partially attenuated LV dilation and cardiac dysfunction in timp-3(-/-)-AB mice. Notably, combining TNFalpha ablation with MMP inhibition completely rescued heart disease in timp-3(-/-)-AB mice. This study provides a basis for anti-TNFalpha and MMP inhibitor combination therapy in heart disease.     

Matrix metalloproteinase-9 and tissue inhibitor of metalloproteinase-1 in hypertension and their relationship to cardiovascular risk and treatment: a substudy of the Anglo-Scandinavian Cardiac Outcomes Trial (ASCOT)

BACKGROUND: Hypertension results in structural changes to the cardiac and vascular extracellular matrix (ECM). Matrix metalloproteinases (MMP) and their inhibitors (TIMP) may play a central role in the modulation of this matrix. We hypothesized that both MMP-9 and TIMP-1 would be abnormal in hypertension, reflecting alterations in ECM turnover, and that their circulating levels should be linked to cardiovascular (CHD) and stroke (CVA) risk scores using the Framingham equation. Second, we hypothesized that treatment would result in changes in ECM indices. METHODS: Plasma MMP-9 and TIMP-1 were measured before and after treatment (median 3 years) from 96 patients with uncontrolled hypertension participating in the Anglo-Scandinavian Cardiac Outcomes Trial (ASCOT). Pretreatment values were compared to circulating MMP-9 and TIMP-1 levels in 45 age- and sex-matched healthy controls. RESULTS: Circulating pretreatment MMP-9 and TIMP-1 levels were significantly higher in patients with hypertension than in the normotensive controls (P =.0041 and P =.0166, respectively). Plasma MMP-9 levels decreased, and TIMP-1 levels increased after treatment (P =.035 and P =.005, respectively). Levels of MMP-9 correlated with CHD risk (r = 0.317, P =.007) and HDL cholesterol (r = -0.237, P =.022), but not CVA risk. There were no significant correlations between TIMP-1 and CVA or CHD scores. CONCLUSIONS: Increased circulating MMP-9 and TIMP-1 at baseline in patients with hypertension could reflect an increased deposition and retention of type I collagen at the expense of other components of ECM within the cardiac and vascular ECM. After cardiovascular risk management, MMP-9 levels decreased and TIMP-1 levels increased. Elevated levels of MMP-9 also appeared to be associated with higher Framingham cardiovascular risk scores. Our observations suggest a possible role for these surrogate markers of tissue ECM composition and the prognosis of cardiovascular events in hypertension.     

Effects of early and late chronic pressure overload on extracellular matrix remodeling

The left ventricle (LV) remodels with age and in response to pressure overload. While aging and pressure overload are superimposed in the clinical context, the structural and functional consequences of the individual processes are not well-understood. Accordingly, the objective of this study was to compare the effects of both early and late chronic hypertension on extracellular matrix (ECM) remodeling. The following groups of Dahl rats were studied: 1) young salt-resistant (control, n=6); 2) young salt-sensitive (early phase of chronic hypertension, n=6); 3) middle-aged salt-resistant (aging, n=5); and 4) middle-aged salt-sensitive (late phase of chronic hypertension, n=6). We measured LV mass (LVM) and body weight (BW) and immunoblotted a panel of matrix metalloproteinases (MMPs), tissue inhibitors of metalloproteinases (TIMPs), and ECM proteins. Total collagen increased, several MMPs decreased, and TIMP-1 increased in the early phase of hypertension, consistent with fibrosis. Active MMP-8 decreased from 8,010+/-81 U in young salt-resistant to 5,260+/-313 U in young salt-sensitive (p<0.05) rats. During the late phase, chronic hypertension decreased total collagen levels and increased MMP-8 and MMP-14 (all p<0.05). Based on good-fit modeling analysis, MMP-14 (45 kDa) correlated positively with changes in LVM/BW during the early phase. In conclusion, this is the first study to evaluate MMP levels during both early and late chronic phases of hypertension. Our results highlight that ECM remodeling in response to pressure overload is a dynamic process involving excessive ECM accumulation and degradation.     

The effects of high glucose and atorvastatin on endothelial cell matrix production.

BACKGROUND: Statins are known to enhance atherosclerotic plaque stability through influences on extracellular matrix homeostasis. Net matrix production reflects the relative balance of matrix production and degradation through enzymes such as matrix metalloproteinases (MMPs) and their inhibitors, tissue inhibitor of MMP (TIMPs). The effects of statins on endothelial cell production of these parameters following co-exposure with a proatherogenic stimulus such as high glucose are not known. METHODS: Human endothelial cells were exposed for 72 h to 5 mm (control) or 25 mm (high) glucose +/- atorvastatin (1 micromol/l). Extracellular matrix homeostasis was assessed by measuring matrix metalloproteinase (MMP)-2 secretion, tissue inhibitor of MMP (TIMP)-1 and -2 secretion and net collagen IV production. Results were expressed as percentage +/- SEM of control values. RESULTS: Exposure to high glucose increased cellular collagen IV expression to 190.1 +/- 11.7% (P < 0.0001) of control levels. No change in MMP-2 secretion (111.6 +/- 5.2%; P > 0.05) was observed but both TIMP-1 and TIMP-2 expression were increased to 136.3 +/- 6.4% and 144.0 +/- 27.5%, respectively (both P < 0.05). The presence of atorvastatin in high glucose conditions reduced collagen IV expression to 136.1 +/- 20.6%. This was paralleled by increased secretion of MMP-2 to 145.8 +/- 7.8% (P < 0.01), increased TIMP-2 expression to 208.0 +/- 21.3% (P < 0.005 compared with high glucose) but no change in TIMP-1 expression (155.1 +/- 14.6%) compared with high glucose alone. The presence of atorvastatin in control conditions did not affect levels of collagen IV expression (114.5 +/- 13.2%). CONCLUSIONS: Endothelial cell exposure to high glucose was associated with a MMP/TIMP profile that increased extracellular matrix production which was attenuated by concurrent exposure to atorvastatin. Consequently, a mechanism by which the atherosclerotic plaque regression that is observed in patients taking these drugs has been demonstrated.     

Cardiac mast cell- and chymase-mediated matrix metalloproteinase activity and left ventricular remodeling in mitral regurgitation in the dog

The present study tested the hypothesis that cardiac mast cells and chymase are associated with matrix metalloproteinase (MMP) activation and extracellular matrix (ECM) degradation in the evolution of left ventricular (LV) chamber remodeling secondary to experimental mitral regurgitation (MR) in dogs. LV mast cell density, chymase activity, and angiotensin II (ANG II) levels were significantly increased 2 and 4 weeks post-MR, while an increase in angiotensin-converting enzyme (ACE) activity was not seen prior to the chronic 24 week stage. As early as 2 and 4 weeks, there was a significant decrease in interstitial myocardial collagen content that was associated with an increase in LV end-diastolic diameter (LVEDD) but a normal LVEDD/wall thickness ratio. While mast cell density decreased to normal at 24 weeks, both chymase and MMP-2 activity remained increased throughout the entire 24-week period post-MR. By 24 weeks a transition to an adverse pattern of LV remodeling characterized by a 2-fold increase in the LVEDD/wall thickness ratio had occurred. Thus, this study supports the hypothesis that mast cells and chymase are important modulators of MMP activity and ECM degradation, contributing to adverse LV remodeling in chronic volume overload secondary to MR.