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.     

A murine model of thoracic aortic aneurysms

BACKGROUND: The mechanisms of thoracic aortic aneurysm (TAA) formation are poorly understood, mainly due to the lack of a useful and reproducible model. Accordingly, the goal of this study was to test the hypothesis that abluminal calcium chloride (CaCl(2)) application could create TAAs in the mouse. MATERIALS AND METHODS: Adult 129/SvE mice (n = 8) were anesthetized and their thoracic aortas exposed via left thoracotomy. CaCl(2) (0.5M) was applied to the distal descending thoracic aorta for 15 min followed by chest closure. At 4 weeks, the perfusion-fixed aorta was harvested from the root to the renal arteries. Diameter measurements were made using confocal microscopy, and wall thickness was measured from hematoxylin and eosin-stained sections. RESULTS: The control (n = 15) distal descending thoracic aortic diameter was 0.60 +/- 0.04 mm and increased by 25% (0.76 +/- 0.06 mm, P < 0.05) following CaCl(2) treatment. Control aortic wall thickness was 48 +/- 9 mum and decreased by 47% in corresponding CaCl(2)-exposed segments (25 +/- 8 mum, P < 0.05). The diameter and wall thickness of the ascending aorta (used as an internal control) were not significantly different between groups. Picrosirius red staining of the TAA showed adventitial collagen breakdown and disruption of lamellar organization. CONCLUSIONS: We conclude that abluminal application of CaCl(2) to the thoracic aorta reliably produces dilation, wall-thinning, and disruption of mural architecture, the hallmark signs of aneurysm formation. To our knowledge, these findings describe for the first time the generation of a reproducible model of isolated TAA formation in a murine system.     

Effect of Nebivolol and Atenolol on Brachial Artery Flow-Mediated Vasodilation in Patients with Coronary Artery Disease

Summary Endothelial dysfunction is considered to be the first step in atherogenesis as well as a predictor of adverse cardiovascular events in patients with coronary artery disease (CAD), while endothelial function improvement is associated with improved clinical outcome. Nebivolol is a beta₁-adrenoreceptor antagonist with an independent beneficial action on endothelial function, increasing nitric oxide bioavailability. The aim of the present study was to examine the effects of nebivolol on endothelial function in the brachial artery in patients with CAD compared with another selective beta₁ adrenergic receptor antagonist, atenolol. Thirty-five patients with stable CAD were randomized to receive either 5 mg nebivolol (n = 17) or 50 mg atenolol (n = 18) daily for 4 weeks. Each patient underwent measurement of endothelial function by means of flow-mediated dilatation (FMD) of the brachial artery before and after 4 weeks of treatment. All vasoactive drugs and cardiovascular risk factors were comparable in the two groups. No significant differences were observed between the two groups at baseline in FMD. In the atenolol group FMD remained unchanged at the end of the 4-week treatment, but in patients treated with nebivolol FMD showed a significant increase by the end of the treatment period (3.9 ± 2.7% vs. 5.6 ± 2.9%, p = 0.047) leading to a significantly higher value compared to patients treated with atenolol (5.6 ± 2.9% vs. 3.4 ± 3.2%, p = 0.041). Beta₁ blockade by nebivolol but not atenolol improves endothelial dysfunction in patients with CAD, an effect that might further reduce the risk for cardiovascular events in patients with CAD.