Department of Cell and Molecular Physiology, UNC Neuroscience Center, University of North Carolina, CB #7545, Chapel Hill, North Carolina 27599, USA.
Mol Pain. 2010 Apr 14;6:20. doi: 10.1186/1744-8069-6-20.
Ecto-5'-nucleotidase (NT5E, also known as CD73) hydrolyzes extracellular adenosine 5'-monophosphate (AMP) to adenosine in nociceptive circuits. Since adenosine has antinociceptive effects in rodents and humans, we hypothesized that NT5E, an enzyme that generates adenosine, might also have antinociceptive effects in vivo.
To test this hypothesis, we purified a soluble version of mouse NT5E (mNT5E) using the baculovirus expression system. Recombinant mNT5E hydrolyzed AMP in biochemical assays and was inhibited by alpha,beta-methylene-adenosine 5'-diphosphate (alpha,beta-me-ADP; IC50 = 0.43 microM), a selective inhibitor of NT5E. mNT5E exhibited a dose-dependent thermal antinociceptive effect that lasted for two days when injected intrathecally in wild-type mice. In addition, mNT5E had thermal antihyperalgesic and mechanical antiallodynic effects that lasted for two days in the complete Freund's adjuvant (CFA) model of inflammatory pain and the spared nerve injury (SNI) model of neuropathic pain. In contrast, mNT5E had no antinociceptive effects when injected intrathecally into adenosine A1 receptor (A1R, Adora1) knockout mice.
Our data indicate that the long lasting antinociceptive effects of mNT5E are due to hydrolysis of AMP followed by activation of A1R. Moreover, our data suggest recombinant NT5E could be used to treat chronic pain and to study many other physiological processes that are regulated by NT5E.
外核苷酸酶 5′-（NT5E，也称为 CD73）在伤害感受回路中水解细胞外腺苷 5′-单磷酸（AMP）为腺苷。由于腺苷在啮齿动物和人类中具有抗伤害感受作用，我们假设生成腺苷的酶 NT5E 也可能在体内具有抗伤害感受作用。
为了验证这一假设，我们使用杆状病毒表达系统纯化了一种可溶性的小鼠 NT5E（mNT5E）。重组 mNT5E 在生化测定中水解 AMP，并被 α，β-亚甲基-腺苷 5′-二磷酸（α，β-me-ADP；IC50=0.43μM）抑制，这是一种选择性的 NT5E 抑制剂。mNT5E 表现出剂量依赖性的热镇痛作用，当鞘内注射到野生型小鼠中时，这种作用可持续两天。此外，mNT5E 在完全弗氏佐剂（CFA）诱导的炎症痛模型和 spared nerve injury（SNI）诱导的神经病理性痛模型中具有热抗超敏和机械抗痛觉过敏作用，可持续两天。相比之下，当鞘内注射到腺苷 A1 受体（A1R，Adora1）敲除小鼠中时，mNT5E 没有镇痛作用。
我们的数据表明，mNT5E 的长期镇痛作用是由于 AMP 的水解，随后激活 A1R。此外，我们的数据表明，重组 NT5E 可用于治疗慢性疼痛，并研究许多其他受 NT5E 调节的生理过程。
