Landry Natalie, Kavosh Morvarid S, Filomeno Krista L, Rattan Sunil G, Czubryt Michael P, Dixon Ian M C
Department of Physiology and Pathophysiology, Institute of Cardiovascular Sciences, Rady Faculty of Health Sciences, Max Rady College of Medicine, University of Manitoba, Winnipeg, Manitoba, Canada.
Physiol Rep. 2018 Nov;6(22):e13897. doi: 10.14814/phy2.13897.
Many etiologies of heart disease are characterized by expansion and remodeling of the cardiac extracellular matrix (ECM or matrix) which results in cardiac fibrosis. Cardiac fibrosis is mediated in cardiac fibroblasts by TGF-β /R-Smad2/3 signaling. Matrix component proteins are synthesized by activated resident cardiac fibroblasts known as myofibroblasts (MFB). These events are causal to heart failure with diastolic dysfunction and reduced cardiac filling. We have shown that exogenous Ski, a TGF-β /Smad repressor, localizes in the cellular nucleus and deactivates cardiac myofibroblasts. This deactivation is associated with reduction of myofibroblast marker protein expression in vitro, including alpha smooth muscle actin (α-SMA) and extracellular domain-A (ED-A) fibronectin. We hypothesize that Ski also acutely regulates MMP expression in cardiac MFB. While acute Ski overexpression in cardiac MFB in vitro was not associated with any change in intracellular MMP-9 protein expression versus LacZ-treated controls,exogenous Ski caused elevated MMP-9 mRNA expression and increased MMP-9 protein secretion versus controls. Zymographic analysis revealed increased MMP-9-specific gelatinase activity in myofibroblasts overexpressing Ski versus controls. Moreover, Ski expression was attended by reduced paxillin and focal adhesion kinase phosphorylation (FAK - Tyr 397) versus controls. As myofibroblasts are hypersecretory and less motile relative to fibroblasts, Ski's reduction of paxillin and FAK expression may reflect the relative deactivation of myofibroblasts. Thus, in addition to its known antifibrotic effects, Ski overexpression elevates expression and extracellular secretion/release of MMP-9 and thus may facilitate internal cytoskeletal remodeling as well as extracellular ECM components. Further, as acute TGF-β treatment of primary cardiac MFB is known to cause rapid translocation of Ski to the nucleus, our data support an autoregulatory role for Ski in mediating cardiac ECM accumulation.
许多心脏病病因的特征是心脏细胞外基质（ECM或基质）的扩张和重塑，这会导致心脏纤维化。心脏纤维化由TGF-β/R-Smad2/3信号通路介导，在心脏成纤维细胞中发挥作用。基质成分蛋白由被激活的驻留心脏成纤维细胞（即肌成纤维细胞，MFB）合成。这些事件是导致舒张功能障碍和心脏充盈减少的心力衰竭的原因。我们已经证明，外源性Ski（一种TGF-β/Smad抑制因子）定位于细胞核并使心脏肌成纤维细胞失活。这种失活与体外肌成纤维细胞标志物蛋白表达的减少有关，包括α平滑肌肌动蛋白（α-SMA）和细胞外结构域A（ED-A）纤连蛋白。我们推测Ski也能急性调节心脏MFB中MMP的表达。虽然体外在心脏MFB中急性过表达Ski与LacZ处理的对照相比，细胞内MMP-9蛋白表达没有任何变化，但与对照相比，外源性Ski导致MMP-9 mRNA表达升高和MMP-9蛋白分泌增加。酶谱分析显示，与对照相比，过表达Ski的肌成纤维细胞中MMP-9特异性明胶酶活性增加。此外，与对照相比，Ski表达伴随着桩蛋白和粘着斑激酶磷酸化（FAK - Tyr 397）的减少。由于肌成纤维细胞相对于成纤维细胞具有高分泌性和低运动性，Ski对桩蛋白和FAK表达的降低可能反映了肌成纤维细胞的相对失活。因此，除了其已知的抗纤维化作用外，Ski过表达还能提高MMP-9的表达以及细胞外分泌/释放，从而可能促进细胞内细胞骨架重塑以及细胞外ECM成分的重塑。此外，由于已知对原代心脏MFB进行急性TGF-β处理会导致Ski迅速转位至细胞核，我们的数据支持Ski在介导心脏ECM积累中具有自调节作用。
