Role of stromal interaction molecule 2 in chronic itch

摘要 慢性瘙痒是一种使人虚弱的疾病，是临床上的一个挑战。越来越多的证据表明 脊髓中的神经元和星形胶质细胞信号通路在慢性瘙痒中起关键作用。虽然 有几个分子已被确定为关键的瘙痒介体/调节器，其分子机制 慢性瘙痒仍未完全被了解。我们的研究一直集中在商店经营的钙的作用上 疼痛和瘙痒的经络(SOC)。我们已经展示了主要的SOC家族成员STIM1和STIM2 (内质网钙感受器)在背角神经元和星形胶质细胞中表达，但其功能 脊髓中的意义仍然难以捉摸。我们最近产生了囊泡状谷氨酸转运体2(VGlu2， 兴奋性神经元标记)条件性STIM1和STIM2基因敲除(KO)小鼠。我们的试点数据显示， Vher2+神经元中STIM1基因的缺失可减弱痛觉，但不影响瘙痒原引起的抓挠。在……里面 相反，消融Vher2+神经元中的STIM2(v-STIM2KO)可显著减轻瘙痒原引起的划痕， 但对伤害性感受没有影响。这些令人兴奋的试点工作表明，STIM1和STIM2在 又痛又痒。我们的初步数据还表明，鞘内注射而不是皮内注射对Stims的抑制作用有所减少。 组胺(His)和氯喹(CQ)诱导的瘙痒行为。此外，抑制或删除兴奋性 神经元STIM2减轻FITC和DNFB诱导的慢性瘙痒，提示神经元STIM2起一定作用 急性和慢性瘙痒都有。重要的是，STIM2在后角的表达增加 二苯基环丙烯(DCP)和1-氟-2，4-二硝基苯(DNFB)诱导小鼠慢性瘙痒模型。 GRPR在瘙痒传播中起着关键作用。我们的试验数据显示，Vlos2或Lbx1中STIM2的缺失 (在脊髓和后脑神经元中特异表达)表达神经元显著减弱GRP诱导的 钙离子反应和瘙痒行为。已知信号转导和转录激活因子3(STAT3)和 其下游的Lipocalin-2(Lcn2)是慢性瘙痒的关键调节因子。我们发现TLR4的激活 通过STAT3信号通路上调STIM2的表达。基于这些发现，我们假设脊髓STIM2 通过神经元和星形胶质细胞信号通路的组合，在慢性瘙痒中发挥关键作用。在AIM 1，我们将确定消融或敲除脊髓STIM2是否能缓解慢性瘙痒。在目标2中，我们将 检测STIM2在慢性瘙痒条件下的表达和功能。在目标3中，我们将调查 脊髓STIM2参与慢性瘙痒的机制。拟议的工作将建立一个新的角色 STIM2在瘙痒感觉中的作用，并将为GRPR在瘙痒传递中的机制提供新的见解。 这项研究的成功完成不仅将确定STIM2是慢性瘙痒的关键调节因子，而且 破译慢性瘙痒的细胞和分子机制。

Abstract Chronic itch is a debilitating condition and represents a clinical challenge. Increase evidence has demonstrated that neuronal and astrocytic signaling pathways in the spinal cord play a crucial role in chronic itch. Although several molecules have been identified as key itch mediators/modulators, molecular mechanisms underlying chronic itch remain incompletely understood. Our research has been focused on role of store-operated calcium channels (SOCs) in pain and itch. We have shown that the primary SOC family members STIM1 and STIM2 (endoplasmic reticulum Ca2+ sensors) are expressed in dorsal horn neurons and astrocytes, but their functional significance in the spinal cord is still elusive. We recently generated vesicular glutamate transporters 2 (Vglut2, an excitatory neuron marker) conditional STIM1 and STIM2 knockout (KO) mice. Our pilot data showed that deletion of STIM1 in Vglut2+ neurons attenuated nociception, but did not affect pruritogen-induced scratches. In contrast, ablation of STIM2 in Vglut2+ neurons (v-STIM2 KO) markedly attenuated pruritogen-induced scratches, but had no effect on nociception. These exciting pilot work suggests that STIM1 and STIM2 play distinct roles in pain and itch. Our pilot data also show that inhibition of STIMs by intrathecal, not intradermal injection, decreased histamine (His)- and chloroquine (CQ)-induced itch behavior. Moreover, inhibition or deletion of excitatory neuronal STIM2 attenuated FITC- and DNFB-induced chronic itch, suggesting that neuronal STIM2 play a role in both acute and chronic itch. Importantly, STIM2 expression was increased in the dorsal horn from diphenylcyclopropenone (DCP)- and 1-fluoro-2, 4-dinitrobenzene (DNFB)-induced mouse models of chronic itch. GRPR plays a critical role in itch transmission. Our pilot data showed that deletion of STIM2 in Vglut2 or Lbx1 (specifically expressed in spinal and hindbrain neurons)-expressing neurons drastically attenuated GRP-induced Ca2+ responses and itch behavior. It is known that signal transducer and activator of transcription 3 (STAT3) and its downstream lipocalin-2 (LCN2) are key modulators of chronic itch. We found that activation of TLR4 upregulated STIM2 expression via STAT3 signaling. Based on these findings, we hypothesize that spinal STIM2 plays a crucial role in chronic itch through a combination of neuronal and astrocytic signaling pathways. In Aim 1, we will determine whether ablation or knockdown of spinal STIM2 attenuates chronic itch. In Aim 2, we will examine the expression and function of STIM2 under chronic itch conditions. In Aim 3, we will investigate the mechanisms underlying spinal STIM2 involvement in chronic itch. The proposed work will establish a novel role of STIM2 in itch sensation and will provide new insights into the mechanisms of GRPR in itch transmission. Successful completion of this research will not only identify STIM2 as a key modulator in chronic itch, but also decipher the cellular and molecular mechanisms underlying chronic itch.