PDE4s-cAMP信号通路对神经病理性痛的调控作用

Neuropathic pain (NP) is a high incidence of chronic pain. Inflammation in the spinal dorsal horn is considered the major cause of NP, and it is regulated by cyclic adenosine monophosphate (cAMP), but the mechanism is not yet clearly understood. cAMP is hydrolyzed by phosphodiesterase type 4 (PDE4) specifically. Our basic study found that PDE4 inhibitor could significantly alleviate NP which induced by partial sciatic nerve ligation, it showed that PDE4 may participate in NP by cAMP mediated signaling cascade. PDE4 family includes four subtypes, PDE4B is reported to be a high expressed subtype in spinal dorsal horn. Furthermore, PDE4B1 isoform plays a major role in the hydrolysis of cAMP. Thus, whether PDE4B, especially PDE4B1, may regulate cAMP level and its downstream. These pathways may be involved in NP. This study hypothesized that the PDE4s-cAMP signaling pathway regulates NP. Pharmacological method, Knock-down and Overexpression mice, and behavior will be used to elucidate the role and mechanism of PDE4 subtype and variant on the NP systematically. The above results may support to design new drug, which targets PDE4, to ameliorate NP.

神经病理性痛（NP）为人群中高发的慢性疼痛，脊髓背角内炎症反应被认为是NP发生的主要诱因，而环磷酸腺苷（cAMP）参与此调控反应，但其详细机制尚未明确。4-型磷酸二酯酶（PDE4）是特异性催化水解cAMP的酶，我们前期研究发现PDE4抑制剂可明显缓解坐骨神经部分结扎引起的NP，说明PDE4可能通过调控cAMP参与NP。PDE4有四种亚型，有研究报道PDE4B在脊髓背角内明显高表达，且其剪切变异体PDE4B1对cAMP水解起主要作用。因此是否PDE4B，尤其PDE4B1调控cAMP及其下游通路参与NP发生呢？本课题提出，PDE4s-cAMP信号通路调控NP的假说。并拟通过行为学、神经化学和分子生物学等多种技术，运用药理学、基因敲减和过表达等多手段，系统阐明PDE4亚型及有关变异体对NP的调节作用及其信号机制。以期为以PDE4为靶点研发治疗NP的药物奠定基础。

脊髓神经元-胶质细胞在调控慢性疼痛中起到重要作用。4-型磷酸二酯酶（PDE4）是水解体内重要第二信使环磷酸腺苷(cAMP)的特异性水解酶。近年研究报道抑制PDE4可缓解慢性疼痛，然而其详细机制仍不明确。Connexin43（cx43）是一种缝隙连接蛋白，脊髓Cx43已被证明参与痛觉传导。当脊髓星形胶质细胞的cx43表达恢复到正常水平时，可缓解神经损伤引起的疼痛。本项目，我们锁定了脊髓cAMP-Cx43信号通路，探讨PDE4抑制剂缓解疼痛反应的机制。单次或重复、腹腔内或脊髓鞘内给rolipram和roflumilast均可显著降低PSNL小鼠的机械性痛觉超敏。反复鞘内注射PDE4抑制剂，可阻断PSNL诱导的神经元-胶质细胞的激活，cAMP和Cx43的下调及促炎性细胞因子TNF-α和IL-1β的上调。并且，PDE4抑制剂的抗伤害作用被蛋白激酶A (PKA)抑制剂H89或Cx43拮抗剂carbenoxolone所减弱。PSNL诱导PDE4B和PDE4D的上调，尤其是PDE4B亚型的上调被PDE4抑制剂阻断了。这些结果提示，PDE4抑制剂通过调控cAMP-PKA-cytokine信号通路，增加Cx43的表达从而缓解疼痛反应。我们的研究结果将为以PDE4为靶标研发治疗神经病理性疼痛的药物奠定基础。