The Influence of Neuroactive Steroid Lipophilicity on GABAA Receptor Modulation: Evidence for a Low-Affinity Interaction
The Influence of Neuroactive Steroid Lipophilicity on GABAA Receptor Modulation: Evidence for a Low-Affinity Interaction
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DOI：
10.1152/jn.00346.2009
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发表时间：
2009-08-01
影响因子：
2.5
通讯作者：
Mennerick, Steven
中科院分区：
文献类型：
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作者：
Chisari, Mariangela;Eisenman, Lawrence N.;Mennerick, Steven
Chisari M，Eisenman LN，Krishnan K，Bandyopadhyaya AK，Wang C，Taylor A，Benz A，Covey DF，Zorumski CF，Mennerick S.神经活性类固醇亲脂性对GABA（A）受体调节的影响：低亲和力相互作用的证据。J Neurophysiol 102：1254-1264，2009.首次发表于2009年6月24日; doi：10.1152/jn.00346.2009。作用于γ-氨基丁酸A型受体（GABA（A）Rs）的麻醉类固醇可直接从浆细胞膜进入跨膜结构域结合位点。因此，脂质相中的有效浓度和类固醇满足药效团活性要求的能力都将有助于观察到的稳态效价。此外，受体效应的发生和抵消可能受到脂质分配的速率限制。在这里，我们表明，几种GABA活性类固醇，包括天然存在的神经甾体，不同的亲脂性不同的动力学和GABA（A）Rs的效力。疏水性排序预测GABA（A）R增强的相对效力和预测电流抵消动力学。类固醇之间的动力学偏移差异在很大程度上消除了γ-环糊精，未结合的类固醇的清道夫，这表明类似物之间的亲和力差异是相形见绌的非特异性积累的贡献。低亲脂性阿法沙龙的7-硝基苯-2-氧杂-1，3-二唑（NBD）标记的荧光类似物（C17-NBD-阿法沙龙）表现出比高亲脂性（3 α，5 α）-3-羟基异戊烯-20-酮（C17-NBD-3 α 5 α A）的荧光类似物更快的非特异性蓄积和去分配。这些差异被GABA（A）R功能增强的差异所掩盖。C17-NBD-3 α 5 α A的对映异构体不满足类固醇增效的药效团要求，其表现出与C17-NBD 3 α 5 α A相同的荧光动力学和分布，但对GABA A Rs无活性。简单的模拟支持了我们的主要发现，这表明神经类固醇结合亲和力低。因此，两者都是特定的（例如，满足药效团要求）和非特异性（例如，脂溶性）性质有助于麻醉类固醇作用的效力和持久性。
Chisari M, Eisenman LN, Krishnan K, Bandyopadhyaya AK, Wang C, Taylor A, Benz A, Covey DF, Zorumski CF, Mennerick S. The influence of neuroactive steroid lipophilicity on GABA(A) receptor modulation: evidence for a low-affinity interaction. J Neurophysiol 102: 1254-1264, 2009. First published June 24, 2009; doi:10.1152/jn.00346.2009. Anesthetic steroids with actions at gamma-aminobutyric acid type A receptors (GABA(A)Rs) may access transmembrane domain binding site(s) directly from the plasma cell membrane. Accordingly, the effective concentration in lipid phase and the ability of the steroid to meet pharmacophore requirements for activity will both contribute to observed steady-state potency. Furthermore, onset and offset of receptor effects may be rate limited by lipid partitioning. Here we show that several GABA-active steroids, including naturally occurring neurosteroids, of different lipophilicity differ in kinetics and potency at GABA(A)Rs. The hydrophobicity ranking predicted relative potency of GABA(A)R potentiation and predicted current offset kinetics. Kinetic offset differences among steroids were largely eliminated by gamma-cyclodextrin, a scavenger of unbound steroid, suggesting that affinity differences among the analogues are dwarfed by the contributions of nonspecific accumulation. A 7-nitrobenz-2-oxa-1,3-diazole (NBD)-tagged fluorescent analogue of the low-lipophilicity alphaxalone (C17-NBD-alphaxalone) exhibited faster nonspecific accumulation and departitioning than those of a fluorescent analogue of the high-lipophilicity (3 alpha,5 alpha)-3-hydroxypregnan-20-one (C17-NBD-3 alpha 5 alpha A). These differences were paralleled by differences in potentiation of GABA(A)R function. The enantiomer of C17-NBD-3 alpha 5 alpha A, which does not satisfy pharmacophore requirements for steroid potentiation, exhibited identical fluorescence kinetics and distribution to C17-NBD3 alpha 5 alpha A, but was inactive at GABA A Rs. Simple simulations supported our major findings, which suggest that neurosteroid binding affinity is low. Therefore both specific (e.g., fulfilling pharmacophore requirements) and nonspecific (e.g., lipid solubility) properties contribute to the potency and longevity of anesthetic steroid action.