Faculty of Health and Life Sciences, Centre for Research in Biosciences, University of the West of England, Coldharbour Lane, Frenchay, Bristol, UK.
Int J Biochem Cell Biol. 2013 Dec;45(12):2715-23. doi: 10.1016/j.biocel.2013.09.009. Epub 2013 Oct 3.
Adrenomedullin (AM) is a novel vasodilatory peptide, which acts primarily through the calcitonin receptor-like receptor (CLR) in combination with either receptor-activity-modifying-protein (RAMP) 2 or 3 (forming receptors, AM1 and AM2 respectively). AM is also highly expressed in the brain and it has shown neuropeptide characteristics. Furthermore, AM plays an important role during inflammation. Interestingly, AM secretion and AM receptor expression had also proven to be glucocorticoid (GC)-dependent in a variety of cell types, suggesting an intriguing relationship between the two compounds that needed to be further characterized. Protein studies have never been carried out in endothelial cells and neither have astrocytes been thoroughly investigated. Hence we studied the effect of GC treatments on AM secretion and AM-sensitivity in ECV304 an endothelial-like cell line and C6 rat astrocytes, focusing on receptor protein expression. We demonstrated that GCs could directly up-regulate RAMP2 expression intracellularly in endothelial cells. On the contrary, GCs were essential to maintain RAMP basal levels in astrocytes, where they could alter AM secretion within 24h. Although RAMP2 has shown to be similarly up-regulated also by AM exposure, no change in AM receptor expression was noted in C6 cells. In conclusion, our study indicates that GCs are able to regulate AM-sensitivity and AM secretion differently in endothelial-like cells and astrocytes. In particular, GCs altered RAMP2 in ECV304 cells, while affecting AM secretion in astrocytes, an interaction which could have interesting therapeutic implications for the blood-brain barrier regulation during both physiological and inflammatory conditions.
肾上腺髓质素 (AM) 是一种新型的血管舒张肽，主要通过降钙素受体样受体 (CLR) 与受体活性修饰蛋白 (RAMP) 2 或 3 结合而发挥作用（分别形成 AM1 和 AM2 受体）。AM 在大脑中也高度表达，并表现出神经肽的特征。此外，AM 在炎症过程中发挥重要作用。有趣的是，AM 的分泌和 AM 受体表达已被证明在多种细胞类型中依赖于糖皮质激素 (GC)，这表明这两种化合物之间存在着需要进一步研究的有趣关系。蛋白质研究从未在血管内皮细胞中进行过，也没有对星形胶质细胞进行过彻底的研究。因此，我们研究了 GC 处理对内皮样细胞系 ECV304 和大鼠星形胶质细胞 C6 中 AM 分泌和 AM 敏感性的影响，重点研究了受体蛋白表达。我们证明 GC 可以在血管内皮细胞内直接上调细胞内的 RAMP2 表达。相反，GC 对于维持星形胶质细胞中 RAMP 的基础水平是必不可少的，它们可以在 24 小时内改变 AM 的分泌。尽管 RAMP2 也被证明可以通过 AM 暴露而被类似地上调，但在 C6 细胞中没有注意到 AM 受体表达的变化。总之，我们的研究表明，GC 可以在血管内皮样细胞和星形胶质细胞中以不同的方式调节 AM 敏感性和 AM 分泌。特别是，GC 在 ECV304 细胞中改变了 RAMP2，而在星形胶质细胞中影响 AM 分泌，这种相互作用可能对生理和炎症条件下血脑屏障的调节具有有趣的治疗意义。
