Domain-specific inhibition of angiotensin-converting enzyme as a therapeutic strategy for opioid use disorders

摘要 该项目结合了Patrick Rothwell博士和Swati More博士(首席调查员)在 伏隔核类阿片信号与药物化学。作为正在进行的协作的一部分，由 NIDA(R21 DA050120)，我们发现血管紧张素转换酶(ACE)具有非典范功能。 伏隔核：降解Met-Enkephin-Arg-Phe(MERF)，从而调节内源性 阿片类药物信号。传统的血管紧张素转换酶抑制剂阻断MERF的降解，导致增强 伏隔核内的内源性阿片信号传导。这会导致谷氨酸释放的选择性减少。 在表达血管紧张素转换酶的DRD1多巴胺受体(D1MSN)的中等刺突投射神经元上 处于比其他神经元更高的水平。这种作用机制具有巨大的治疗潜力，正如我们的初步研究 数据表明，降低对D_1-MSN的兴奋驱动可减弱芬太尼的奖赏效应。 先前发表的使用重组蛋白的酶分析表明，MERF通过 血管紧张素转换酶的催化N区，尽管这还没有在脑组织中被检测到。这引发了令人兴奋的 血管紧张素转换酶催化结构域(C-结构域)和血管紧张素转换酶催化结构域(C-结构域)之间双重解离的可能性 MERF(N-域)。该项目的目标是独立评估每个ACE催化剂的贡献 在伏核中，结构域到MERF降解和内源性阿片信号转导，以便产生 用于治疗阿片类药物使用障碍的具有优化性能的新的领域特定的ACE抑制剂。我们将使用 作为实验系统的小鼠，通过组合分别操纵ACE的每个催化结构域 互补的遗传和药理操作。目标1是确定哪个催化域 血管紧张素转换酶可降解伏隔核组织中的MERF。我们将直接量化细胞外MERF的水平 用液相色谱-串联质谱仪测定兴奋性突触传递 伏隔核神经元的全细胞膜片钳记录。目标2是确定行为 区域特异性ACE抑制对芬太尼CPP和自我给药的影响。这将建立在我们的 使用非或有芬太尼暴露(CPP)的初步实验，纳入平行分析 间歇性静脉注射芬太尼自我给药。目标3是优化中央 结构域特异性ACE抑制剂的活性和类药物特性。我们将进行系统的化学研究 涉及(但不限于)前药和给药系统的迭代，目标是改善渗透性 穿过血脑屏障。这些实验应该会导致识别和早期优化 抑制大脑中ACE降解MERF的化合物。这一新的机制可以构成基础 一种可行的治疗阿片类药物使用障碍的新治疗策略。

ABSTRACT This project combines the mutual expertise of Drs. Patrick Rothwell and Swati More (Principal Investigators) in nucleus accumbens opioid signaling and medicinal chemistry. As part of an ongoing collaboration supported by NIDA (R21 DA050120), we have found that angiotensin-converting enzyme (ACE) has a non-canonical function in the nucleus accumbens: it degrades Met-enkephalin-Arg-Phe (MERF) and thereby regulates endogenous opioid signaling. Conventional ACE inhibitors block the degradation of MERF, leading to an enhancement of endogenous opioid signaling in the nucleus accumbens. This causes a selective reduction of glutamate release onto medium spiny projection neurons that express the Drd1 dopamine receptor (D1-MSNs), which express ACE at a higher level than other neurons. This mechanism of action has great therapeutic potential, as our preliminary data indicate the decrease in excitatory drive to D1-MSNs can diminish the rewarding effects of fentanyl. Previously published enzymatic assays using recombinant protein suggest that MERF is efficiently degraded by the catalytic N-domain of ACE, though this has not been examined in brain tissue. This raises the exciting possibility of a double-dissociation between catalytic domains of ACE that degrade angiotensin (C-domain) and MERF (N-domain). The goal of this project is to independently evaluate the contribution of each ACE catalytic domain to MERF degradation and endogenous opioid signaling in the nucleus accumbens, in order to generate new domain-specific ACE inhibitors with optimized properties for treatment of opioid use disorders. We will use mice as an experimental system to separately manipulate each catalytic domain of ACE, through a combination of complementary genetic and pharmacological manipulations. AIM 1 is to determine which catalytic domain of ACE degrades MERF in nucleus accumbens tissue. We will directly quantify extracellular levels of MERF using liquid chromatography-tandem mass spectrometry, and measure excitatory synaptic transmission using whole-cell patch-clamp recordings from nucleus accumbens neurons. AIM 2 is to determine the behavioral impact of domain-specific ACE inhibition on fentanyl CPP and self-administration. This will build on our preliminary experiments using non-contingent fentanyl exposure (CPP), by incorporating parallel analysis of intravenous fentanyl self-administration on an intermittent access schedule. AIM 3 is to optimize the central activity and drug-like properties of domain-specific ACE inhibitors. We will perform systematic chemical iterations involving (but not limited to) prodrug and drug delivery systems, with the goal of improving permeability across the blood-brain barrier. These experiments should result in the identification and early optimization of compounds that inhibit degradation of MERF by ACE in the brain. This novel mechanism could form the basis of a viable new therapeutic strategy for treating opioid use disorders.