Role of opioid-induced S1P/S1PR1 axis activation in neuroinflammatory reponses

阿片类药物用于慢性疼痛受到抗伤害性耐受，阿片类药物诱导的痛觉过敏（OIH）， 1 -3触发机制仍然难以捉摸。我们发表的作品4，5和 初步数据首次表明，中枢神经系统中鞘脂代谢失调， 中枢神经系统（CNS）导致1-磷酸鞘氨醇（S1 P）的过度产生和神经系统的激活。 基于星形胶质细胞的S1 P受体亚型1（S1 PR 1）信号传导通路在这些过程中起着关键作用。口服 施用CNS渗透剂S1 PR 1竞争性和功能性拮抗剂，包括FTY 720（Gilenya®），6 阻断吗啡和羟考酮诱导的两种性别啮齿动物的镇痛耐受和OIH， 以及吗啡诱导的依赖和奖励。FTY 720已获得FDA批准6，因此， 预期结果的临床转化是非常可行的。我们还发现，持续的阿片类药物， 在脊髓星形胶质细胞缺乏S1 PR 1的条件性S1 PR 1敲除小鼠中， S1 PR 1靶向剂的有益作用在条件性S1 PR 1敲低中减弱至少90 雄性和雌性小鼠，与同窝小鼠相比，脊髓星形胶质细胞中缺少一个S1 pr 1等位基因 对照这些结果揭示了基于星形胶质细胞的S1 PR 1信号传导的重要性，并表明， 星形胶质细胞是抗S1 PR 1活性的细胞靶标。CNS中S1 P水平的升高与 增加的1）星形胶质细胞反应性，2）Nod样受体家族的表达，含有pyrin结构域的3 （NLRP 3）炎性小体（在IL 1 β形成和信号传导中至关重要）7和3）炎性/巨噬细胞的形成。 神经兴奋性细胞因子阻断S1 PR 1抑制了这些过程。相反，IL 10（一种重要的抗- 炎性和神经保护性细胞因子）显著增加。鞘内注射中和抗- IL 10抗体阻断S1 PR 1拮抗剂的作用，表明它们的有益作用是由IL-10抑制剂驱动的。 内源性IL 10通路。 一个多学科的计划建立在我们强有力的初步数据，以测试我们的假设： 由NLRP 3诱导的CNS神经炎症驱动的SphK 1/S1 P/S1 PR 1信号通路是神经细胞凋亡的基础。 吗啡诱导的抗伤害性耐受/OIH和奖赏的发展。针对S1 PR 1提供了 治疗干预的新方法。三个目标将测试我们的假设：1）建立S1 PR 1作为一个 持续阿片类药物干预的分子靶点，2）检查阿片类药物诱导的鞘脂变化 代谢和SphK 1/S1 P/S1 PR 1信号传导和3）确定参与的分子和生化途径 S1 PR 1激活的下游。 影响：我们的成果将 揭示了以前未被认识到的基于星形胶质细胞的SphK 1/S1 P/S1 PR 1的作用， 信号通路的持续阿片类药物的使用，并将提供基础的临床评价S1 PR 1- 作为阿片类药物的辅助靶向治疗剂。

Opioid use for chronic pain is limited by antinociceptive tolerance, opioid-induced hyperalgesia (OIH), physical dependence and addiction.1-3 The triggering mechanisms remain elusive. Our published work4,5 and preliminary data suggest for the first time that dysregulation of sphingolipid metabolism in the central nervous system (CNS) leading to exaggerated production of sphingosine 1-phosphate (S1P) and activation of an astrocyte-based S1P receptor subtype 1 (S1PR1) signaling pathway is central to these processes. Oral administration of CNS penetrant S1PR1 competitive and functional antagonists, including FTY720 (Gilenya®),6 blocked morphine and oxycodone-induced antinociceptive tolerance and OIH in rodents of both genders, as well as morphine-induced dependence and reward. FTY720 is already FDA-approved6 and therefore, rapid clinical translation of the expected finding is very feasible. We also discovered that sustained opioid-unwanted actions do not develop in conditional S1PR1-knockout mice lacking S1PR1 in spinal astrocytes and that the beneficial effects of S1PR1-targeted agents are attenuated by at least 90% in conditional S1PR1-knockdown mice of both genders, which lack one S1pr1 allele in spinal astrocytes when compared to their littermate controls. These results unravel the importance of astrocyte-based S1PR1 signaling and suggest that astrocytes are a cellular target for anti-S1PR1 activity. Increased levels of S1P in CNS were associated with increased 1) astrocyte reactivity, 2) expression of the Nod-like receptor family, pyrin domain containing 3 (NLRP3) inflammasome (critical in IL1β formation and signaling)7 and 3) formation of inflammatory/ neuroexcitatory cytokines. Blocking S1PR1 inhibited these processes. In contrast, IL10 (an important anti- inflammatory and neuroprotective cytokine) increased significantly. Intrathecal delivery of a neutralizing anti- IL10 antibody blocked the effects of S1PR1 antagonists suggesting that their beneficial effects are driven by an endogenous IL10 pathway. A multidisciplinary plan builds on our strong preliminary data to test our hypothesis: An astrocyte-based SphK1/S1P/S1PR1 signaling pathway driven by NLRP3-induced neuroinflammation in the CNS underlies the development of morphine-induced antinociceptive tolerance/OIH and reward. Targeting S1PR1 provides a novel approach for therapeutic intervention. Three aims will test our hypothesis: 1) Establish S1PR1 as a molecular target for sustained opioid intervention, 2) Examine opioid-induced alterations of sphingolipid metabolism and SphK1/S1P/S1PR1 signaling and 3) Determine molecular and biochemical pathways engaged downstream of S1PR1 activation. Impact: Our results will unravel a previously unrecognized role for an astrocyte based SphK1/S1P/S1PR1- signaling pathway in sustained opioid use and will provide the foundation for clinical evaluation of S1PR1- targeted therapeutics as adjunct to opioids.