Placental and pineal gland regulation of bone mass accrual: genetics evidence and molecular bases

项目摘要--项目#3 这个项目的目标是描述成年期和成年期对骨骼重塑的影响。 色氨酸羟化酶1(TPH1)的肠外部位表达的衰老 控制两种细胞外信号的合成：5-羟色胺和褪黑素。而不是高大的骨头 我们观察到肠道细胞中由TPH1特异性失活引起的质量/骨形成表型增加 TPH1-/-小鼠表现出轻微的骨形成增加，而破骨细胞的轻微增加弥补了这一点 数。这表明TPH1在肠道外的表达调节分子的产生， 能抵消肠源性5-羟色胺对骨量增加的影响。尽管TPH1是 它优先在肠道细胞中表达，在松果体中的表达是褪黑素生物合成所必需的。 因此，TPH1的全局失活会导致5-羟色胺和褪黑素的缺失。这让我们找到了 假设褪黑素是骨量增加的积极调节因素，从而对抗肠道的负面影响。 衍生的5-羟色胺对骨形成的影响。与这一假设一致的是，褪黑素治疗初发 成骨细胞增加D-型细胞周期蛋白的表达，而D-型细胞周期蛋白的表达则受肠道细胞周期蛋白的下调。 衍生5-羟色胺。进一步的分析表明，褪黑素可以抵消交感神经信号对 CREB、ATF4及其各自的靶基因在这些细胞中的表达。这些初步研究表明， 褪黑素可通过拮抗两种肠源性激素对骨量的增加起积极作用 5-羟色胺和成骨细胞中的交感信号，这是我们的项目建议评估的一个论点。一个 我们进行的第二个观察是，TPH1-/-母亲所生的TPH1+/-小鼠的死亡率显著降低。 3个月龄时的骨量高于野生型母亲所生的TPH1+/-小鼠。这些数据表明 母体5-羟色胺和/或褪黑素可能是成年后代峰值骨量的决定因素。 5-羟色胺不会穿过胎盘，但TPH1在胎盘组织中的表达会导致其在胎儿血液中释放。 同样，母体的褪黑素也会进入胎儿的血液循环。因此，我们建议评估是否 母体产生的褪黑素和/或5-羟色胺是获得适当骨量所必需的，并且 后代体内的动态平衡。我们的具体目标是： 1)通过遗传学手段评估松果体产生的褪黑素在骨生物学中的作用。 2)确定体内成骨细胞中介导褪黑素功能的受体(S)和信号通路(S)。 3)明确母体TPH1表达对骨骼影响的细胞和分子基础 后代的大量应计利润。

Project Summary – Project #3 The goal of this project is to characterize the influence on bone remodeling during adulthood and aging of extra-intestinal sites of expression of Tryptophan hydroxylase 1 (Tph1), the enzyme controlling the synthesis of two extracellular cues: serotonin and melatonin. Instead of the high bone mass/increased bone formation phenotype caused by Tph1 specific inactivation in gut cells we have observed that Tph1-/- mice show a mild increase in bone formation compensated by a mild increase in osteoclast number. This suggests that Tph1 expression outside the gut regulates the production of molecules that can counteract the effect on bone mass accrual caused by gut-derived serotonin. Although Tph1 is preferentially expressed in gut cells, its expression in the pineal gland is required for melatonin biosynthesis. Thus, a global inactivation of Tph1 causes an absence of both serotonin and melatonin. This led us to hypothesize that melatonin is a positive regulator of bone mass accrual that opposes the negative effect of gut- derived serotonin on bone formation. Consistent with this hypothesis, melatonin treatment of primary osteoblasts increases the expression of D-type cyclins, whose expression is instead down-regulated by gut- derived serotonin. Further analyses showed that melatonin could offset the effect of sympathetic signaling on CREB, ATF4 and their respective target genes in these cells. These preliminary studies suggest that melatonin could positively act on bone mass accrual by antagonizing the effect of both gut-derived serotonin and sympathetic signaling in osteoblasts, a contention that our project proposes to assess. A second observation we made was that Tph1+/- mice born from Tph1-/- mothers have a significantly lower bone mass at 3 months of age than Tph1+/- mice born from wild-type mothers. These data suggest that maternal serotonin and/or melatonin could be determinants of peak bone mass in the adult offspring. Serotonin does not cross the placenta but Tph1 expression in this tissue causes its release in fetal blood. Likewise, maternal melatonin reaches the fetal circulation. We therefore propose to evaluate whether maternally-produced melatonin and/or serotonin are required for proper bone mass acquisition and homeostasis in the offspring. Our specific aims are: 1) To assess through genetic means the role of melatonin produced by the pineal gland on bone biology. 2) To identify the receptor(s) and signaling pathway(s) mediating melatonin function(s) in osteoblasts in vivo. 3) To define the cellular and molecular bases of the influence exerted by maternal Tph1 expression on bone mass accrual in the offspring.