Guangdong Medical University, Zhanjiang, Guangdong, China.
Department of Pain Medicine and Shenzhen Municipal Key Laboratory for Pain Medicine, The 6th Affiliated Hospital of Shenzhen University Medical School, Shenzhen, Guangdong, China.
Br J Pharmacol. 2023 Jul;180(13):1730-1747. doi: 10.1111/bph.16042. Epub 2023 Feb 16.
BACKGROUND AND PURPOSE: Chemotherapy-induced neuropathic pain (CINP) currently has limited effective treatment. Although the roles of oxytocin (OXT) and the oxytocin receptor (OXTR) in central analgesia have been well documented, the expression and function of OXTR in the peripheral nervous system remain unclear. Here, we evaluated the peripheral antinociceptive profiles of OXTR in CINP. EXPERIMENTAL APPROACH: Paclitaxel (PTX) was used to establish CINP. Quantitative real-time polymerase chain reaction (qRT-PCR), in situ hybridization, and immunohistochemistry were used to observe OXTR expression in dorsal root ganglia (DRG). The antinociceptive effects of OXT were assessed by hot-plate and von Frey tests. Whole-cell patch clamp was performed to record sodium currents, excitability of DRG neurons, and excitatory synapse transmission. KEY RESULTS: Expression of OXTR in DRG neurons was enhanced significantly after PTX treatment. Activation of OXTR exhibited antinociceptive effects, by decreasing the hyperexcitability of DRG neurons in PTX-treated mice. Additionally, OXTR activation up-regulated the phosphorylation of protein kinase C (pPKC) and, in turn, impaired voltage-gated sodium currents, particularly the voltage-gated sodium channel 1.7 (Na 1.7) current, that plays an indispensable role in PTX-induced neuropathic pain. OXT suppressed excitatory transmission in the spinal dorsal horn as well as excitatory inputs from primary afferents in PTX-treated mice. CONCLUSION AND IMPLICATIONS: The OXTR in small-sized DRG neurons is up-regulated in CINP and its activation relieved CINP by inhibiting the neural excitability by impairment of Na 1.7 currents via pPKC. Our results suggest that OXTR on peripheral sensory neurons is a potential therapeutic target to relieve CINP.
背景与目的:化疗诱导性神经病理性疼痛(CINP)目前的有效治疗方法有限。尽管催产素(OXT)及其受体(OXTR)在中枢镇痛中的作用已得到充分证实,但 OXTR 在周围神经系统中的表达和功能仍不清楚。在这里,我们评估了 OXTR 在 CINP 中的外周镇痛作用。
实验方法:紫杉醇(PTX)用于建立 CINP。采用定量实时聚合酶链反应(qRT-PCR)、原位杂交和免疫组织化学观察背根神经节(DRG)中 OXTR 的表达。通过热板和von Frey 试验评估 OXT 的镇痛作用。全细胞膜片钳记录钠电流、DRG 神经元兴奋性和兴奋性突触传递。
主要结果:PTX 处理后,DRG 神经元中 OXTR 的表达显著增强。激活 OXTR 表现出镇痛作用,通过降低 PTX 处理小鼠 DRG 神经元的过度兴奋。此外,OXTR 激活上调蛋白激酶 C(pPKC)的磷酸化,进而损害电压门控钠电流,特别是在 PTX 诱导的神经病理性疼痛中发挥不可或缺作用的钠通道 1.7(Na 1.7)电流。OXT 抑制了 PTX 处理小鼠脊髓背角中的兴奋性传递以及初级传入中的兴奋性输入。
结论和意义:CINP 中小型 DRG 神经元中的 OXTR 上调,其通过损害 pPKC 介导的 Na 1.7 电流来抑制神经元兴奋性,从而缓解 CINP。我们的结果表明,外周感觉神经元上的 OXTR 是缓解 CINP 的潜在治疗靶点。