Institute of Metabolism and Endocrinology (G.-Y.L., Q.-H.L., R.-R.C., Y.L., S.-S.W., L.-Q.Y., E.-Y.L.), Second Xiang-Ya Hospital, Central S University, Changsha, Hunan, People's Republic of China; and Department of Endocrinology and Metabolism (P.-F.S.), the Second Affiliated Hospital ZheJiang University College of Medicine, Hangzhou, Zhejiang, People's Republic of China.
Endocrinology. 2014 Feb;155(2):558-67. doi: 10.1210/en.2013-1298. Epub 2013 Nov 18.
Arterial calcification is a complex and active regulated process, which results from a process of osteoblastic differentiation of vascular smooth muscle cells (VSMCs). Leptin, the product of the ob gene, mainly regulates food intake and energy expenditure and recently has been considered to be correlated with the arterial calcification. However, the mechanisms of the effects of leptin on osteoblastic differentiation of VSMCs are unknown. We used calcifying vascular smooth muscle cells (CVSMCs) as a model to investigate the relationship between leptin and the osteoblastic differentiation of CVSMCs and the signaling pathways involved. Our experiments demonstrated that leptin could increase expression of receptor activator of nuclear factor-κB ligand (RANKL) and bone morphogenetic protein 4 (BMP4), as well as alkaline phosphatase (ALP) activity, runt-related transcription factor 2 expression, calcium deposition, and the formation of mineralized nodules in CVSMCs. Suppression of RANKL with small interfering RNA abolished the leptin-induced ALP activity and BMP4 expression in CVSMCs. Leptin could activate the ERK1/2 and phosphatidylinositol 3-kinase (PI3K)/Akt signaling pathway. Furthermore, pretreatment with the ERK inhibitor PD98059 and the PI3K inhibitor LY294002 abolished leptin-induced RANKL expression and blocked the promotion of ALP activity of CVSMCs. Silencing of the leptin receptor OB-Rb with small interfering RNA abolished leptin-induced activation of ERK and Akt and the expression of RANKL and reversed the effects of leptin on ALP activity. Meanwhile, addition of Noggin (the BMP4 inhibitor) blunted the effect of leptin on ALP activity. These results show that leptin can promote osteoblastic differentiation of CVSMCs by the OB-Rb/ERK1/2/RANKL-BMP4 and OB-Rb/PI3K/Akt/RANKL-BMP4 pathways.
动脉钙化是一个复杂且受调控的过程，其源于血管平滑肌细胞（VSMCs）的成骨细胞分化过程。瘦素是 ob 基因的产物，主要调节食物摄入和能量消耗，最近被认为与动脉钙化有关。然而，瘦素对 VSMCs 成骨细胞分化的影响机制尚不清楚。我们使用钙化血管平滑肌细胞（CVSMCs）作为模型，研究了瘦素与 CVSMCs 成骨细胞分化之间的关系以及涉及的信号通路。我们的实验表明，瘦素可以增加核因子-κB 配体受体激活剂（RANKL）和骨形态发生蛋白 4（BMP4）的表达，以及碱性磷酸酶（ALP）活性、 runt 相关转录因子 2 表达、钙沉积和 CVSMCs 中矿化结节的形成。用小干扰 RNA 抑制 RANKL 可消除瘦素诱导的 CVSMCs 中 ALP 活性和 BMP4 表达。瘦素可以激活 ERK1/2 和磷脂酰肌醇 3-激酶（PI3K）/Akt 信号通路。此外，用 ERK 抑制剂 PD98059 和 PI3K 抑制剂 LY294002 预处理可消除瘦素诱导的 RANKL 表达，并阻止 CVSMCs 中 ALP 活性的促进。用小干扰 RNA 沉默瘦素受体 OB-Rb 可消除瘦素诱导的 ERK 和 Akt 激活以及 RANKL 的表达，并逆转瘦素对 ALP 活性的作用。同时，添加 Noggin（BMP4 抑制剂）可削弱瘦素对 ALP 活性的影响。这些结果表明，瘦素可以通过 OB-Rb/ERK1/2/RANKL-BMP4 和 OB-Rb/PI3K/Akt/RANKL-BMP4 通路促进 CVSMCs 的成骨细胞分化。
