Suda M, Tanaka K, Natsui K, Usui T, Tanaka I, Fukushima M, Shigeno C, Konishi J, Narumiya S, Ichikawa A, Nakao N
Department of Medicine, Kyoto University Graduate School of Medicine, Japan.
Endocrinology. 1996 May;137(5):1698-705. doi: 10.1210/endo.137.5.8612504.
PGE2 is one of the key molecules in the osteoblast. It is the major prostanoid in the bone, and its production is under the control of both systemic and local factors. PGE2 has been reported to have multiple actions in the osteoblast, such as growth promotion and cell differentiation. To better understand the action of PGE2 in the osteoblast, we determined the PGE receptor subtypes in MC3T3-E1, an osteoblastic cell line derived from the normal mouse calvaria. Northern blot analysis revealed that EP1 and EP4 subtypes are expressed in MC3T3-E1. In contrast, EP3 subtype was not detected by either Northern blot analysis or RT-PCR. The contribution of each subtype was evaluated by studying the effects of subtype-specific analogs on osteoblastic function at confluency and 5 days after confluency. An EP1 agonist, 17-phenyl-omega-trinor PGE2, increased DNA synthesis and decreased alkaline phosphatase activity. 11-Deoxy-PGE1, and EP2 and EP4 agonist, decreased DNA synthesis and increased alkaline phosphatase activity at both stages. Butaprost, an EP2-selective agonist, showed effects similar to those of 11-deoxy-PGE1 only at confluency. Another and more differentiated osteoblastic marker, osteocalcin production, was detectable and was stimulated by 11-deoxy-PGE1 only 5 days after confluency. The exposure of these cells to EP1 agonist changed the cell shape to a more fibroblastic appearance. These results indicate that EP1, EP4, and probably EP2 are present in MC3T3-E1 cells; EP1 promotes cell growth, and EP2 and EP4 mediate differentiation of the osteoblast. Furthermore, the decreased response to EP2-specific agonist 5 days after confluency suggests that the expression of PGE receptor subtype is dependent on the stage of osteoblastic differentiation. This is the first report to determine PGE receptor subtypes in the bone.
前列腺素E2（PGE2）是成骨细胞中的关键分子之一。它是骨骼中主要的前列腺素，其产生受全身和局部因素的控制。据报道，PGE2在成骨细胞中具有多种作用，如促进生长和细胞分化。为了更好地了解PGE2在成骨细胞中的作用，我们确定了MC3T3-E1细胞中PGE受体亚型，MC3T3-E1是一种源自正常小鼠颅骨的成骨细胞系。Northern印迹分析显示，EP1和EP4亚型在MC3T3-E1中表达。相比之下，通过Northern印迹分析或逆转录聚合酶链反应（RT-PCR）均未检测到EP3亚型。通过研究亚型特异性类似物在汇合时和汇合后5天对成骨细胞功能的影响，评估了每种亚型的作用。EP1激动剂17-苯基-ω-三降PGE2增加了DNA合成并降低了碱性磷酸酶活性。11-脱氧-PGE1以及EP2和EP4激动剂在两个阶段均降低了DNA合成并增加了碱性磷酸酶活性。EP2选择性激动剂布他前列素仅在汇合时显示出与11-脱氧-PGE1相似的作用。另一种更具分化性的成骨细胞标志物骨钙素的产生在汇合后5天可检测到，并且仅在汇合后5天受到11-脱氧-PGE1的刺激。这些细胞暴露于EP1激动剂后，细胞形态变为更具成纤维细胞样外观。这些结果表明，MC3T3-E1细胞中存在EP1、EP4，可能还有EP2；EP1促进细胞生长，EP2和EP4介导成骨细胞的分化。此外，汇合后5天对EP2特异性激动剂的反应降低表明PGE受体亚型的表达取决于成骨细胞分化的阶段。这是首次在骨骼中确定PGE受体亚型的报告。
