Abstract

Purpose

To compare the binding and agonistic activity of Acthar^® Gel and synthetic melanocortin receptor (MCR) agonists and examine how the activity of select agonists affects the in vivo production of corticosterone.

Materials and Methods

In vitro binding was determined using concentration-dependent displacement of the ligand [¹²⁵I]Nle⁴, D-Phe⁷-α-melanocyte-stimulating hormone (α-MSH) on cells expressing MC1R, MC3R, MC4R, or MC5R. Functional activity was determined using a time-resolved fluorescence cyclic adenosine monophosphate (cAMP) assay in cells expressing MC1R, MC2R, MC3R, MC4R, or MC5R. In vivo corticosterone analyses were performed by measuring plasma corticosterone levels in Sprague Dawley rats.

Results

Acthar Gel and synthetic MCR agonists exhibited the highest binding at MC1R, lowest binding at MC5R, and moderate binding at MC3R and MC4R. Acthar Gel stimulated the production of cAMP in all 5 MCR-expressing cell lines, with MC2R displaying the lowest level of full agonist activity, 3-, 6.6-, and 10-fold lower than MC1R, MC3R, and MC4R, respectively. Acthar Gel was a partial agonist at MC5R. The synthetic MCR agonists induced full activity at all 5 MCRs, with the exception of α-MSH having no activity at MC2R. Acthar Gel treatment had less of an impact on in vivo production of corticosterone compared with synthetic ACTH_1-24 depot.

Conclusions

Acthar Gel bound to and activated each MCR tested in this study, with partial agonist activity at MC5R and the lowest level of full agonist activity at MC2R, which distinguished it from synthetic MCR agonists. The minimal activity of Acthar Gel at MC2R corresponded to lower endogenous corticosteroid production.

中文翻译：

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与其他黑皮质素受体激动剂相比，Acthar Gel 具有独特的结合和信号传导活性

摘要

目的

比较 Acthar ^® Gel 和合成黑皮质素受体 (MCR) 激动剂的结合和激动活性，并检查选定激动剂的活性如何影响体内皮质酮的产生。

材料和方法

^{在表达 MC1R、MC3R、MC4R 或 MC5R 的细胞上，使用配体 [ 125} I]Nle ⁴、D-Phe ⁷ -α-黑素细胞刺激素 (α-MSH) 的浓度依赖性置换来确定体外结合。在表达 MC1R、MC2R、MC3R、MC4R 或 MC5R 的细胞中，使用时间分辨荧光环磷酸腺苷 (cAMP) 测定确定功能活性。通过测量 Sprague Dawley 大鼠的血浆皮质酮水平进行体内皮质酮分析。

结果

Acthar Gel 和合成的 MCR 激动剂在 MC1R 上表现出最高的结合，在 MC5R 上表现出最低的结合，在 MC3R 和 MC4R 上表现出适度的结合。Acthar Gel 刺激了所有 5 种 MCR 表达细胞系中 cAMP 的产生，其中 MC2R 显示出最低水平的完全激动剂活性，分别比 MC1R、MC3R 和 MC4R 低 3 倍、6.6 倍和 10 倍。Acthar Gel 是 MC5R 的部分激动剂。合成的 MCR 激动剂在所有 5 个 MCR 上均诱导完全活性，但在 MC2R 上没有活性的 α-MSH 除外。与合成 ACTH _1-24库相比，Acthar Gel 治疗对体内皮质酮产生的影响较小。

结论

Acthar Gel 与本研究中测试的每个 MCR 结合并激活，在 MC5R 具有部分激动剂活性，在 MC2R 具有最低水平的完全激动剂活性，这将其与合成的 MCR 激动剂区分开来。Acthar Gel 在 MC2R 的最小活性对应于较低的内源性皮质类固醇产生。