Hirai Takao, Tanaka Kenjiro, Togari Akifumi
Department of Pharmacology, School of Dentistry, Aichi-Gakuin University, Nagoya 464-8650, Japan.
Department of Pharmacology, School of Dentistry, Aichi-Gakuin University, Nagoya 464-8650, Japan
J Cell Sci. 2014 Sep 1;127(Pt 17):3711-9. doi: 10.1242/jcs.148148. Epub 2014 Jul 2.
The sympathetic nervous system modulates bone remodeling and mediates the expression of core clock genes in part through the β-adrenergic receptor (β-AR) in osteoblasts. In this study, we show that in MC3T3-E1 osteoblastic cells that isoproterenol (Iso), a non-selective β-AR agonist, upregulated the transcriptional factor Nfil3, and induced rhythmic mRNA expression of prostaglandin-endoperoxide synthase 2 (Ptgs2, also known as Cox2). The rhythmic effects of Iso on Ptgs2 expression were mediated by interplay between the Per2 and Bmal1 clock genes in osteoblasts. In addition, Ptgs2 was significantly decreased in bone after continuous Iso treatment. Overexpression of Nfil3 decreased Ptgs2 expression in MC3T3-E1 cells. Knockdown of Nfil3 upregulated the expression of Ptgs2 in MC3TC-E1 cells, indicating that Nfil3 negatively regulated Ptgs2 in osteoblasts. Furthermore, Iso acutely induced the expression Nfil3 and increased the binding of Nfil3 to the Ptgs2 promoter in MC3T3-E1 cells. These results suggest that Iso-mediated induction of Nfil3 in osteoblasts regulates the expression of Ptgs2 by driving the expression of circadian clock genes. These findings provide new evidence for a physiological role of circadian clockwork in bone metabolism.
交感神经系统调节骨重塑，并部分通过成骨细胞中的β-肾上腺素能受体（β-AR）介导核心生物钟基因的表达。在本研究中，我们发现，在MC3T3-E1成骨细胞中，非选择性β-AR激动剂异丙肾上腺素（Iso）上调转录因子Nfil3，并诱导前列腺素内过氧化物合酶2（Ptgs2，也称为Cox2）的节律性mRNA表达。Iso对Ptgs2表达的节律性影响是由成骨细胞中Per2和Bmal1生物钟基因之间的相互作用介导的。此外，连续Iso处理后骨中Ptgs2显著降低。Nfil3过表达降低了MC3T3-E1细胞中Ptgs2的表达。敲低Nfil3上调了MC3TC-E1细胞中Ptgs2的表达，表明Nfil3在成骨细胞中对Ptgs2起负调控作用。此外，Iso在MC3T3-E1细胞中急性诱导Nfil3的表达，并增加Nfil3与Ptgs2启动子的结合。这些结果表明，Iso介导的成骨细胞中Nfil3的诱导通过驱动生物钟基因的表达来调节Ptgs2的表达。这些发现为生物钟机制在骨代谢中的生理作用提供了新证据。
