Li Ming, Hansen J Bondo, Huang Luping, Keyser Brian M, Taylor James T
Department of Pharmacology SL-83, Tulane University Health Science Center, 1430 Tulane Avenue, New Orleans, LA 70112, USA.
Cardiovasc Drug Rev. 2005 Summer;23(2):173-96. doi: 10.1111/j.1527-3466.2005.tb00164.x.
NNC 55-0396 is a structural analog of mibefradil (Ro 40-5967) that inhibits both T-type and high-voltage-activated (HVA) Ca2+ channels with a higher selectivity for T-type Ca2+ channels. The inhibitory effect of mibefradil on HVA Ca2+ channels can be attributed to a hydrolyzed metabolite of the drug: the methoxy acetate side chain of mibefradil is removed by intracellular enzymes, thus it forms (1S,2S)-2-(2-(N-[(3-benzoimidazol-2-yl)propyl]-N-methylamino)ethyl)-6-fluoro-1,2,3,4-tetrahydro-1-isopropyl-2-naphtyl hydroxy dihydrochloride (dm-mibefradil), which causes potent inhibition of HVA Ca2+ currents. By replacing the methoxy acetate chain of mibefradil with cyclopropanecarboxylate, a more stable analog was developed (NNC 55-0396). The acute IC50 of NNC 55-0396 to block recombinant Cav3.1 T-type channels expressed in HEK293 cells is approximately 7 muM, whereas 100 microM NNC 55-0396 has no detectable effect on high voltage-activated currents in INS-1 cells. Block of T-type Ca2+ current was partially reduced by membrane hyperpolarization and was enhanced at high stimulus frequency. Washing NNC 55-0396 out of the recording chamber did not reverse the T-type Ca2+ current activity, suggesting that the compound dissolves in or passes through the plasma membrane to exert its effect; however, intracellular perfusion of the compound did not block T-type Ca2+ currents, arguing against a cytoplasmic route of action. We conclude that NNC 55-0396, by virtue of its modified structure, does not produce the metabolite that causes inhibition of L-type Ca2+ channel channels, thus rendering it more selective to T-type Ca2+ channels.
NNC 55 - 0396是米贝拉地尔（Ro 40 - 5967）的结构类似物，它对T型和高电压激活（HVA）钙通道均有抑制作用，且对T型钙通道具有更高的选择性。米贝拉地尔对HVA钙通道的抑制作用可归因于该药物的一种水解代谢产物：米贝拉地尔的甲氧基乙酸侧链被细胞内酶去除，从而形成（1S，2S）-2 -（2 -（N - [（3 - 苯并咪唑 - 2 - 基）丙基] - N - 甲基氨基）乙基）-6 - 氟 - 1,2,3,4 - 四氢 - 1 - 异丙基 - 2 - 萘基羟基二盐酸盐（dm - 米贝拉地尔），它会对HVA钙电流产生强效抑制。通过用环丙烷羧酸取代米贝拉地尔的甲氧基乙酸链，开发出了一种更稳定的类似物（NNC 55 - 0396）。NNC 55 - 0396阻断在HEK293细胞中表达的重组Cav3.1 T型通道的急性半数抑制浓度（IC50）约为7μM，而100μM的NNC 55 - 0396对INS - 1细胞中的高电压激活电流没有可检测到的影响。T型钙电流的阻断因膜超极化而部分减弱，并在高刺激频率下增强。将NNC 55 - 0396从记录室中冲洗出来并没有使T型钙电流活性恢复，这表明该化合物溶解于或穿过质膜以发挥其作用；然而，向细胞内灌注该化合物并没有阻断T型钙电流，这排除了其通过细胞质途径起作用的可能性。我们得出结论，NNC 55 - 0396由于其结构修饰，不会产生导致抑制L型钙通道的代谢产物，因此使其对T型钙通道具有更高的选择性。
