Design of PAP-1, a Selective Small Molecule Kv1.3 Blocker, for the Suppression of Effector Memory T Cells in Autoimmune Diseases
作者:Alexander Schmitz、Ananthakrishnan Sankaranarayanan、Philippe Azam、Kristina Schmidt-Lassen、Daniel Homerick、Wolfram Hänsel、Heike Wulff
DOI:10.1124/mol.105.015669
日期:2005.11
The lymphocyte K+ channel Kv1.3 constitutes an attractive pharmacological target for the selective suppression of terminally differentiated effector memory T (TEM) cells in T cell-mediated autoimmune diseases, such as multiple sclerosis and type 1 diabetes. Unfortunately, none of the existing small-molecule Kv1.3 blockers is selective, and many of them, such as correolide, 4-phenyl-4-[3-(methoxyphenyl)-3-oxo-2-azapropyl]cyclohexanone, and our own compound Psora-4 inhibit the cardiac K+ channel Kv1.5. By further exploring the structure-activity relationship around Psora-4 through a combination of traditional medicinal chemistry and whole-cell patch-clamp, we identified a series of new phenoxyalkoxypsoralens that exhibit 2- to 50-fold selectivity for Kv1.3 over Kv1.5, depending on their exact substitution pattern. The most potent and “drug-like” compound of this series, 5-(4-phenoxybutoxy)psoralen (PAP-1), blocks Kv1.3 in a use-dependent manner, with a Hill coefficient of 2 and an EC50 of 2 nM, by preferentially binding to the C-type inactivated state of the channel. PAP-1 is 23-fold selective over Kv1.5, 33- to 125-fold selective over other Kv1-family channels, and 500- to 7500-fold selective over Kv2.1, Kv3.1, Kv3.2, Kv4.2, HERG, calcium-activated K+ channels, Na+,Ca2+, and Cl- channels. PAP-1 does not exhibit cytotoxic or phototoxic effects, is negative in the Ames test, and affects cytochrome P450-dependent enzymes only at micromolar concentrations. PAP-1 potently inhibits the proliferation of human TEM cells and suppresses delayed type hypersensitivity, a TEM cell-mediated reaction, in rats. PAP-1 and several of its derivatives therefore constitute excellent new tools to further explore Kv1.3 as a target for immunosuppression and could potentially be developed into orally available immunomodulators.
淋巴细胞K+通道Kv1.3是选择性抑制T细胞介导的自身免疫性疾病(如多发性硬化症和1型糖尿病)中终末分化效应记忆T(TEM)细胞的有吸引力的药理学靶点。不幸的是,目前存在的所有小分子Kv1.3阻断剂均不具备选择性,其中许多如柯里奥利德、4-苯基-4-[3-(甲氧苯基)-3-酮-2-氮杂丙基]环己酮以及我们自己的化合物Psora-4均可抑制心脏K+通道Kv1.5。通过结合传统药物化学和全细胞膜片钳技术进一步探索Psora-4的构效关系,我们鉴定了一系列新的苯氧烷氧基补骨脂素,它们对Kv1.3的选择性比Kv1.5高2至50倍,具体取决于其取代模式。这一系列化合物中,最具有强效和“类药物”性质的化合物为5-(4-苯氧基丁氧基)补骨脂素(PAP-1),它以使用依赖性方式阻断Kv1.3,Hill系数为2,EC50为2 nM,通过优先结合通道的C型失活态。PAP-1对Kv1.5的选择性为23倍,对其他Kv1家族通道的选择性为33至125倍,对Kv2.1、Kv3.1、Kv3.2、Kv4.2、HERG、钙激活K+通道、Na+、Ca2+及Cl-通道的选择性为500至7000倍。PAP-1无细胞毒性或光毒性,Ames试验呈阴性,对细胞色素P450依赖性酶的影响仅在微摩尔浓度下显现。PAP-1能强效抑制人TEM细胞的增殖并抑制大鼠中的迟发型超敏反应(一种TEM细胞介导的反应)。因此,PAP-1及其若干衍生物构成了探索Kv1.3作为免疫抑制靶点的新工具,并有可能开发成口服可用的免疫调节剂。