Pharmacological study on bone metabolism by nervous activity

脊椎动物骨骼具有丰富的肾上腺素能和肽能神经末梢，这些神经末梢在骨重塑中起着重要作用。最近的研究表明，交感神经活动的增加通过增加骨吸收和减少骨形成导致骨质流失。骨吸收的增加是基于破骨细胞形成和破骨细胞活性的刺激。我们还证明，人类成骨细胞和破骨细胞都配备有肾上腺素能受体（Ars）和神经肽受体，它们组成性地表达可扩散的轴突引导分子，这些分子被称为神经纤维生长的化学引诱剂和/或化学驱剂。这些发现表明，交感神经和外周感觉神经元轴突向成骨细胞和破骨细胞的延伸是局部骨代谢的动态神经调节所必需的。然而，尽管有几项研究表明神经-骨细胞之间存在功能性相互作用，但目前尚不清楚成骨细胞和破骨细胞的激活是作为神经元激活的直接反应发生，还是需要一个中间细胞。因此，我们通过使用由小鼠成骨细胞、MC3T3-El和神经喷射器小鼠颈上神经节组成的体外共培养模型来检测神经-成骨细胞的直接交流。用荧光蛋白Fluo-3装载后，用共聚焦激光扫描显微镜检查神经突成骨细胞单位。蝎子毒液（SV）的加入引起神经突激活（即Ca^<2+>动员），并在一段滞后期后引起成骨细胞Ca^<2+>动员。在没有神经突的情况下，SV对MC3T3-El细胞没有直接影响。α1-AR拮抗剂（吡唑嗪）浓度依赖性的添加阻止了SV神经激活导致的成骨细胞激活。因此，我们最近的研究结果表明，通过Ca^<2+>动员判断，MC3T3-E1激活可能是与特定激活的神经纤维接触的直接结果。在体外获得的证据表明，神经-成骨细胞串扰可以在没有中间转导细胞的情况下发生，而去甲肾上腺素是这种交流的重要介质。最近的几项体内和体外研究表明，分别通过表达α和β-Ars的成骨细胞和破骨细胞对骨形成和吸收具有拟交感神经作用。少

The vertebrate skeleton is richly innervated with adrenergic and peptidergic nerve terminals, and these play important roles in bone remodelling. Recently showed that increased sympathetic nervous activity causes bone loss via an increase in bone resorption and a decrease in bone formation. Increased bone resorption is based on the stimulation of both osteoclast formation and osteoclast activity. And we also demonstrated that human osteoblastic as well as osteoclastic cells are equipped with adrenergic receptors (Ars) and neuropeptide receptors and that they constitutively express diffusible axon guidance molecules known to function as a chemoattractant and/or chemorepellent for growing nerve fibers. These findings suggest that the extension of axons of sympathetic and peripheral sensory neurons to osteoblastic and osteoclastic cells is required for the dynamic neural regulation of local bone metabolism. However, while several studies have shown a functional nerve-bone cell interplay, … More whether both osteoblastic and osteoclastic cells activation occurs as a direct response to neuronal activation or requires an intermediary cell is unclear. Therefore, we examined direct nerve-osteoblastic cell communication by using an in vitro co-culture model comprising mouse osteoblastic cells, MC3T3-El, and neurite-spouting mouse superior cervical ganglia. Following loading with the calcium fluorophore Fluo-3, neurite-osteoblastic cell units were examined by confocal laser scanning microscopy. The addition of scorpion venom (SV) elicited neurite activation (i.e., Ca^<2+> mobilization) and, after a lag period, osteoblastic Ca^<2+> mobilization. The SV had no direct effect on the MC3T3-El cells in the absence of neurites. The addition of an α1-AR antagonist, prazosin concentration-dependently prevented the osteoblastic activation that resulted as a consequence of the neural activation by SV. Thus, our recent findings demonstrate that MC3T3-E1 activation, as judge by Ca^<2+> mobilization, can be a direct consequence of contact with a specific activated nerve fiber. This evidence obtained in vitro demonstrates that nerve-osteoblastic cell cross-talk can occur in the absence of an intermediary transducing cell and that noradrenaline is an important mediator of this communication. Several recent in vivo and in vitro studies have demonstrated a sympathomimetic action on bone formation and resorption via osteoblastic and osteoclastic cells, respectively, expressing α-and β-Ars. Less