Department of Physiology and Pathophysiology, School of Basic Medical Sciences, Peking University Health Science Center, Key Laboratory of Molecular Cardiovascular Science, Ministry of Education, Beijing Key Laboratory of Cardiovascular Receptors Research, Beijing 100191, China.
Institute of Systems Biomedicine, Department of Pathology, School of Basic Medical Sciences, Peking University Health Science Center, Beijing 100191, China.
J Mol Cell Cardiol. 2018 Mar;116:135-144. doi: 10.1016/j.yjmcc.2018.02.006. Epub 2018 Feb 10.
Cardiac fibrosis is characterized by excessive deposition of extracellular matrix (ECM) proteins in the myocardium and results in decreased ventricular compliance and diastolic dysfunction. Cartilage intermediate layer protein-1 (CILP-1), a novel identified cardiac matricellular protein, is upregulated in most conditions associated with cardiac remodeling, however, whether CILP-1 is involved in pressure overload-induced fibrotic response is unknown. Here, we investigated whether CILP-1 was critically involved in the fibrotic remodeling induced by pressure overload. Western blot analysis and immunofluorescence staining showed that CILP-1 was predominantly detected in cardiac myocytes and to a less extent in the interstitium. In isolated adult mouse ventricular myocytes and nonmyocytes, CILP-1 was found to be mainly synthesized by myocytes. CILP-1 expression in left ventricles was upregulated in C57BL/6 mice undergoing transverse aortic constriction (TAC). Myocardial CILP-1 knockdown aggravated whereas CILP-1 overexpression attenuated TAC-induced ventricular remodeling and dysfunction, as measured by echocardiography test, morphological examination, and gene expressions of fibrotic molecules. Incubation of cardiac fibroblasts with the conditioned medium containing full-length, N-terminal, or C-terminal CILP-1 inhibited transforming growth factor (TGF)-β1-induced Smad3 phosphorylation and the subsequent profibrotic events. We first demonstrated that C-terminal CILP-1 increased Akt phosphorylation, promoted the interaction between Akt and Smad3, and suppressed Smad3 phosphorylation. Blockade of PI3K-Akt pathway attenuated the inhibitory effect of C-CILP-1 on TGF-β1-induced Smad3 activation. We conclude that CILP-1 is a novel ECM protein possessing anti-fibrotic ability in pressure overload-induced fibrotic remodeling. This anti-fibrotic effect of CILP-1 attributes to interfering TGF-β1 signaling through its N- and C- terminal fragments.
心肌纤维化的特征是心肌细胞外基质（ECM）蛋白过度沉积，导致心室顺应性降低和舒张功能障碍。软骨中间层蛋白-1（CILP-1）是一种新发现的心脏基质细胞蛋白，在与心脏重构相关的大多数情况下均上调，然而，CILP-1 是否参与压力超负荷诱导的纤维化反应尚不清楚。在这里，我们研究了 CILP-1 是否在压力超负荷诱导的纤维化重塑中起关键作用。Western blot 分析和免疫荧光染色显示，CILP-1 主要在心肌细胞中检测到，在间质中检测到的程度较低。在分离的成年小鼠心室肌细胞和非肌细胞中，发现 CILP-1 主要由心肌细胞合成。在接受横主动脉缩窄（TAC）的 C57BL/6 小鼠的左心室中，CILP-1 的表达上调。心肌 CILP-1 敲低加重了 TAC 诱导的心室重构和功能障碍，而 CILP-1 过表达则减轻了 TAC 诱导的心室重构和功能障碍，这可以通过超声心动图测试、形态学检查和纤维化分子的基因表达来衡量。用含有全长、N 端或 C 端 CILP-1 的条件培养基孵育心脏成纤维细胞，抑制转化生长因子（TGF）-β1 诱导的 Smad3 磷酸化及随后的促纤维化事件。我们首次证明 C 端 CILP-1 增加了 Akt 磷酸化，促进了 Akt 和 Smad3 之间的相互作用，并抑制了 Smad3 磷酸化。PI3K-Akt 通路的阻断减弱了 C-CILP-1 对 TGF-β1 诱导的 Smad3 激活的抑制作用。我们得出结论，CILP-1 是一种新的 ECM 蛋白，在压力超负荷诱导的纤维化重塑中具有抗纤维化能力。CILP-1 的这种抗纤维化作用归因于通过其 N 端和 C 端片段干扰 TGF-β1 信号。
