Supporting data for Matrix metalloproteinase 7 deficiency acts as a protective effect against vascular dysfunction during atherosclerosis

Atherosclerosis is a chronic inflammatory condition characterized by plaque buildup in the arterial lumen and is the underlying cause of cardiovascular disorders such as coronary artery disease (CAD) and stroke (Hurtutise, Jessica et al 2006). The pathogenesis of atherosclerosis involves the buildup of lipids, foam cells and necrotic debris in the intimal layer of the artery. The atherosclerotic plaque at the shoulder region is prone to rupture and when this occurs, blood clots are formed leading to myocardial infarction and death in patients (Lindstedt et al. 1999).There is a correlation between the induction of matrix metalloproteinase-7 (MMP-7), which is one of the zinc ion (Zn2+)-dependent endopeptidases capable of degrading or remodeling the extracellular matrix (ECM), and the occurrence and development of cardiovascular diseases, especially atherosclerosis (Tuomainen et al. 2014). An increased activity of MMP-7 appears to play an important role in the development of coronary artery disease (Alp et al. 2017), During the formation of atherosclerotic plaque, vascular smooth muscle cells secrete ECM proteins to form a fibrous cap , which helps to maintain plaque stability (Williams et al. 2010). Apoptosis of vascular smooth muscle cells leads to plaque instability in mice with atherosclerosis (von der Thüsen et al. 2002). MMP-7 promotes the cleavage of N-cadherin and the apoptosis of smooth muscle cells, thereby weakening the stability of the fibrous cap and increasing the risk of plaque rupture (Koutsouki et al. 2005; Williams et al. 2010). Additionally, MMP-7, while not being expressed in normal arteries (Halpert et al. 1996), is present in vascular cells and inflammatory macrophages in the atherosclerotic plaque (Burke 2004).Polymorphisms in the promoter region of the MMP-7 gene that contribute to its expression has been identified: the presence of MMP-7-181A/G allele in hypercholesterolemic patients appeared to be associated with a reduced coronary arterial luminal diameter (Jormsjö et al. 2001). People with MMP-7-181A/G (rs11568818) allele had higher plasma MMP-7 levels and a higher risk of developing atherosclerotic plaques in the femoral artery (Panayiotou et al. 2013; Lee et al. 2007). There was a strong association between high plasma MMP-7 levels and the risk of coronary artery events (Goncalves et al. 2015). Moreover, MMP-7 polymorphisms or increased plasma levels of MMP-7 are related to the reduction of reactive hyperemia index and lower microvascular response (Boumiza et al. 2017). Taken together, these findings suggest that an elevated MMP-7 level may contribute to vascular dysfunction in cardiovascular disease.Based on these findings, it is hypothesized that up-regulation of MMP-7 expression may lead to endothelial dysfunction. In the present studies, we found that upregulation of MMP-7 in ApoE-deficient mice fed with high-fat diet is associated with the occurrence of endothelium-dependent contractions to acetylcholine, without affecting any endothelium-independent vascular responses in the aorta. Therefore, the protection by MMP-7-deficiency against vascular dysfunction in ApoE-deficient mice may be related to a direct action of MMP-7 on endothelial function. MMP-7 promotes the occurrence of endothelium-dependent contractions in ApoE-deficient mice fed with high-fat diet likely through enhancing the activity of cytosolic phospholipase A2 and upregulating cyclooxygenase-2 to increase endothelial production of prostanoids; this effect can be inhibited by MMP inhibitors.MMP-7-deficiency prevents the activation of NF-κB, a major transcription factor involved in inflammatory responses, and PI3K/AKT as well as MAPK/ERK in ApoE-deficient mice fed with high fat diet.These findings demonstrated that MMP-7 deficiency prevents the development of endothelial dysfunction and vascular inflammation during hyperlipidaemia, thereby inhibiting atherogenesis.

动脉粥样硬化是一种以动脉腔内斑块形成为特征的慢性炎症性疾病，是冠状动脉疾病（CAD）和卒中等心血管疾病的基础病因（Hurtutise, Jessica 等人，2006年）。动脉粥样硬化的发病机制涉及脂质、泡沫细胞和坏死碎屑在动脉内膜层的积累。位于肩部区域的动脉粥样硬化斑块易于破裂，一旦发生破裂，便会导致血栓形成，进而引发心肌梗死和患者死亡（Lindstedt 等人，1999年）。基质金属蛋白酶-7（MMP-7）的诱导与心血管疾病，尤其是动脉粥样硬化的发生和发展之间存在相关性，MMP-7是一种依赖锌离子（Zn2+）的端肽酶，能够降解或重塑细胞外基质（ECM）（Tuomainen 等人，2014年）。MMP-7活性的增加似乎在冠状动脉疾病的发展中起着重要作用（Alp 等人，2017年）。在动脉粥样硬化斑块的形成过程中，血管平滑肌细胞分泌ECM蛋白形成纤维帽，有助于维持斑块稳定性（Williams 等人，2010年）。血管平滑肌细胞的凋亡导致动脉粥样硬化小鼠的斑块不稳定（von der Thüsen 等人，2002年）。MMP-7促进N-钙粘蛋白的裂解和平滑肌细胞的凋亡，从而削弱纤维帽的稳定性，增加斑块破裂的风险（Koutsouki 等人，2005年；Williams 等人，2010年）。此外，MMP-7虽不在正常动脉中表达（Halpert 等人，1996年），但在动脉粥样硬化斑块中的血管细胞和炎症巨噬细胞中存在（Burke，2004年）。已发现MMP-7基因启动子区域的突变，这些突变有助于其表达：MMP-7-181A/G等位基因在高胆固醇血症患者中的存在似乎与冠状动脉腔直径的减小相关（Jormsjö 等人，2001年）。携带MMP-7-181A/G（rs11568818）等位基因的人具有更高的血浆MMP-7水平和更高的股动脉动脉粥样硬化斑块形成的风险（Panayiotou 等人，2013年；Lee 等人，2007年）。高血浆MMP-7水平与冠状动脉事件的风险之间存在强烈关联（Goncalves 等人，2015年）。此外，MMP-7的多态性或血浆MMP-7水平的升高与反应性充血指数的降低和微血管反应的减弱相关（Boumiza 等人，2017年）。综合这些发现，表明MMP-7水平的升高可能有助于心血管疾病中的血管功能障碍。基于这些发现，假设MMP-7表达的上调可能导致内皮功能障碍。在本研究中，我们发现，在高脂饮食喂养的ApoE缺陷小鼠中，MMP-7的上调与乙酰胆碱引起内皮依赖性收缩的发生相关，而不影响主动脉中内皮独立性血管反应。因此，MMP-7缺陷对ApoE缺陷小鼠血管功能障碍的保护作用可能与MMP-7对内皮功能的直接作用有关。MMP-7通过增强细胞溶胶磷脂酶A2的活性和上调环氧合酶-2以增加内皮细胞前列腺素的生产，从而促进ApoE缺陷小鼠在高脂饮食喂养中内皮依赖性收缩的发生；这种作用可以通过MMP抑制剂抑制。MMP-7缺陷防止了在高脂饮食喂养的ApoE缺陷小鼠中NF-κB（炎症反应的主要转录因子）、PI3K/AKT以及MAPK/ERK的激活。这些发现表明，MMP-7缺陷可以防止高脂血症期间内皮功能障碍和血管炎症的发展，从而抑制动脉粥样硬化。