Xie Hui, Tang Si-yuan, Cui Rong-rong, Huang Jiao, Ren Xiao-hong, Yuan Ling-qing, Lu Ying, Yang Min, Zhou Hou-de, Wu Xian-ping, Luo Xiang-hang, Liao Er-yuan
Institute of Endocrinology and Metabolism, The Second Xiangya Hospital of Central South University, 139# Middle Renmin Road, Changsha, Hunan, 410011, PR China.
Regul Pept. 2006 May 15;134(2-3):118-25. doi: 10.1016/j.regpep.2006.02.004. Epub 2006 Mar 6.
Apelin is a recently discovered peptide that is the endogenous ligand for the orphan G-protein-coupled receptor APJ. Adipocytes can express and secrete apelin. The aim of this study was to characterize apelin and APJ expression in human osteoblasts and to investigate the effects of apelin on osteoblasts.
Apelin and APJ were expressed in human osteoblasts. Apelin stimulated proliferation of human osteoblasts, but had no effect on alkaline phosphatase (ALP) activity, osteocalcin and type I collagen production in human osteoblasts. Suppression of APJ with small-interfering RNA (siRNA) abolished the apelin-induced cell proliferation. Apelin induced activation of Akt (Phosphatidylinositol-3 kinase downstream effector), but not MAPKs, such as c-jun N-terminal Kinase (JNK), p38 and ERK1/2 in human osteoblasts. This effect was blocked by suppression of APJ with siRNA. Furthermore, LY294002 (PI3 kinase inhibitor) blocked the activation of Akt by apelin and abolished the apelin-induced cell proliferation.
Human osteoblasts express apelin and APJ and apelin enhances human osteoblast proliferation, but has no effect on osteoblast differentiation, and APJ/PI3 kinase/Akt pathway is involved in the proliferation response. These findings suggest that apelin may function as a mitogenic agent for osteoblasts.
Apelin是最近发现的一种肽，是孤儿G蛋白偶联受体APJ的内源性配体。脂肪细胞能够表达并分泌Apelin。本研究旨在描述人成骨细胞中Apelin和APJ的表达情况，并研究Apelin对成骨细胞的影响。
人成骨细胞中表达Apelin和APJ。Apelin可刺激人成骨细胞增殖，但对人成骨细胞的碱性磷酸酶（ALP）活性、骨钙素及I型胶原蛋白的产生没有影响。用小干扰RNA（siRNA）抑制APJ可消除Apelin诱导的细胞增殖。Apelin可诱导人成骨细胞中Akt（磷脂酰肌醇-3激酶下游效应器）的激活，但不影响丝裂原活化蛋白激酶（MAPKs），如c-jun氨基末端激酶（JNK）、p38和细胞外调节蛋白激酶1/2（ERK1/2）的激活。用siRNA抑制APJ可阻断这种效应。此外，LY294002（PI3激酶抑制剂）可阻断Apelin对Akt的激活，并消除Apelin诱导的细胞增殖。
人成骨细胞表达Apelin和APJ，Apelin可增强人成骨细胞增殖，但对成骨细胞分化没有影响，且APJ/PI3激酶/Akt信号通路参与了增殖反应。这些发现表明，Apelin可能作为成骨细胞的促有丝分裂剂发挥作用。
