A novel radioligand for the ATP-gated ion channel P2X7: [³H] JNJ-54232334

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• 作者：Brian Lord^a ; ^{blord@its.jnj.com" class="auth_mail" title="E-mail the corresponding author} ; Michael K. Ameriks^a ; Qi Wang^a ; Lawrence Fourgeaud^a ; Maarten Vliegen^b ; Willy Verluyten^b ; Pieter Haspeslagh^b ; Nicholas I. Carruthers^a ; Timothy W. Lovenberg^a ; Pascal Bonaventure^a ; Michael A. Letavic^a ; Anindya Bhattacharya^a
• 关键词：P2X7 ; Radioligand binding ; Depression ; Autoradiography ; Receptor occupancy ; JNJ-54232334 ; JNJ-54140515
• 刊名：European Journal of Pharmacology
• 出版年：2015
• 出版时间：15 October 2015
• 年：2015
• 卷：765
• 期：Complete
• 页码：551-559
• 全文大小：6169 K

文摘

The ATP-gated ion channel P2X7 has emerged as a potential central nervous system (CNS) drug target based on the hypotheses that pro-inflammatory cytokines such as IL-1β that are released by microglia, may contribute to the etiology of various disorders of the CNS including depression. In this study, we identified two closely related P2X7 antagonists, JNJ-54232334 and JNJ-54140515, and then tritium labeled the former to produce a new radioligand for P2X7. JNJ-54232334 is a high affinity ligand for the rat P2X7 with a pK_i of 9.3±0.1. In rat cortical membranes, [³H] JNJ-54232334 reached saturable binding with equilibrium dissociation (K_d) constant of 4.9±1.3 nM. The compound displayed monophasic association and dissociation kinetics with fast on and off rates. In rat brain sections, specific binding of [³H] JNJ-54232334 was markedly improved compared to the previously described P2X7 radioligand, [³H] A-804598. In P2X7 knockout mouse brain sections, [³H] A-804598 bound to non-P2X7 binding sites in contrast to [³H] JNJ-54232334. In rat or wild type mouse brain sections [³H] JNJ-54232334 bound in a more homogenous and region independent manner. The ubiquitous expression of P2X7 receptors was confirmed with immunohistochemistry in rat brain sections. The partial displacement of [³H] A-804598 binding resulted in the underestimation of the level of ex vivo P2X7 occupancy for JNJ-54140515. Higher levels of P2X7 ex vivo occupancy were measured using [³H] JNJ-54232334 due to less non-specific binding. In summary, we describe [³H] JNJ-54232334 as a novel P2X7 radioligand, with improved properties over [³H] A-804598.