Institute of Vascular Medicine and Li Ka Shing Institute of Health Sciences, School of Biomedical Sciences, Chinese University of Hong Kong, Hong Kong, China.
Circ Res. 2012 Jul 20;111(3):e55-66. doi: 10.1161/CIRCRESAHA.112.271361. Epub 2012 Jun 7.
The expression of osteocalcin is augmented in human atherosclerotic lesions. How osteocalcin triggers vascular pathogenesis and remodeling is unclear.
To investigate whether osteocalcin promotes transformation of adventitial fibroblast to myofibroblasts and the molecular mechanism involved.
Immunohistochemistry indicated that osteocalcin was expressed in the neointima of renal arteries from diabetic patients. Western blotting and wound-healing assay showed that osteocalcin induced fibroblast transformation and migration, which were attenuated by blockers of the renin-angiotensin system and protein kinase Cδ (PKCδ), toll-like receptor 4 (TLR4) neutralizing antibody, and antagonist and inhibitors of free radical production and cyclooxygenase-2. Small interfering RNA silencing of TLR4 and PKCδ abolished fibroblast transformation. Angiotensin II level in the conditioned medium from the osteocalcin-treated fibroblasts was found elevated using enzyme immunoassay. Culturing of fibroblasts in conditioned medium collected from differentiated osteoblasts promoted fibroblast transformation. The expression of fibronectin, TLR4, and cyclooxygenase-2 is augmented in human mesenteric arteries after 5-day in vitro exposure to osteocalcin.
Osteocalcin transforms adventitial fibroblasts to myofibroblasts through stimulating angiotensin II release and subsequent activation of PKCδ/TLR4/reactive oxygen species/cyclooxygenase-2 signaling cascade. This study reveals that the skeletal hormone osteocalcin cross-talks with vascular system and contributes to vascular remodeling.
骨钙素在人类动脉粥样硬化病变中的表达增加。骨钙素如何引发血管发病机制和重塑尚不清楚。
研究骨钙素是否促进血管外膜成纤维细胞向肌成纤维细胞的转化及其相关的分子机制。
免疫组织化学染色表明，糖尿病患者肾动脉的新生内膜中存在骨钙素的表达。Western blot 和划痕实验表明，骨钙素诱导成纤维细胞的转化和迁移，这些作用可被肾素-血管紧张素系统和蛋白激酶 Cδ（PKCδ）抑制剂、Toll 样受体 4（TLR4）中和抗体以及自由基产生和环氧化酶-2 的拮抗剂和抑制剂所减弱。TLR4 和 PKCδ 的小干扰 RNA 沉默可消除成纤维细胞的转化。酶联免疫吸附试验发现，骨钙素处理的成纤维细胞条件培养基中的血管紧张素 II 水平升高。在骨钙素诱导分化的成骨细胞条件培养基中培养成纤维细胞可促进成纤维细胞的转化。在体外暴露于骨钙素 5 天后，人肠系膜动脉中的纤维连接蛋白、TLR4 和环氧化酶-2 的表达增加。
骨钙素通过刺激血管紧张素 II 的释放，随后激活 PKCδ/TLR4/活性氧/环氧化酶-2 信号级联，将血管外膜成纤维细胞转化为肌成纤维细胞。本研究揭示了骨骼激素骨钙素与血管系统相互作用，促进了血管重塑。
