Astrocytic Inducible Nitric Oxide Synthase Upregulation Contributes to Chronic Below-Level Neuropathic Pain Following Spinal Cord Injury in Male Rats

IF 3.5 2区医学 Q1 ANESTHESIOLOGY

European Journal of Pain Pub Date : 2025-05-24 DOI:10.1002/ejp.70047

Youngkyung Kim, Hyunggoo Kang, Young Wook Yoon

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引用次数: 0

Abstract

Background

Spinal cord injury (SCI) leads to persistent inflammation, contributing to chronic neuropathic pain. However, current treatments show limited efficacy. Three types of nitric oxide synthase (NOS) play different roles in inflammation and neuronal hyperexcitation. Therefore, this study aimed to determine the predominant NOS subtype involved in neuropathic pain after spinal contusion.

Methods

We investigated the effects of intrathecal NOS inhibitors on mechanical sensitivity following a moderate spinal contusion injury in male Sprague-Dawley rats. These NOS inhibitors were N(G)-nitro-L-arginine methyl ester hydrochloride (L-NAME; non-selective NOS inhibitor), 1400W (iNOS inhibitor), Nω-propyl-L-arginine hydrochloride (NPLA; nNOS inhibitor) and N5-(1-iminoethyl)-L-ornithine (L-NIO; eNOS inhibitor). Additionally, we analysed protein expression and cellular localisation of spinal NOS subtypes in rats that underwent SCI or sham procedures.

Results

Treatment with L-NAME significantly reduced paw withdrawal threshold in a dose-dependent manner, although motor deficits appeared at the highest dose (30 μM), while 1400W effectively alleviated mechanical hypersensitivity without motor side effects. NPLA showed limited efficacy, and L-NIO had no effect. Protein expression of iNOS increased two-fold in the L4-5 spinal segment of SCI rats compared with sham controls. After SCI, iNOS-immunoreactivity colocalized with GFAP in the superficial laminae of the L4-5 spinal segment. Treatment with 1400W reduced the hyper-reactivity of both iNOS and GFAP.

Conclusions

These findings indicate that iNOS plays a significant role in below-level neuropathic pain following thoracic spinal cord contusion in rats. Specific blockade of iNOS activity may have potential as a therapeutic intervention for spinal-contusion-induced neuropathic pain with reduced risk of side effects.

Significance Statement

iNOS inhibition effectively alleviated pain without motor side effects, unlike non-selective NOS, nNOS and eNOS inhibitors. The colocalization of iNOS with astrocytes in the spinal cord suggests a key mechanism in pain maintenance. These findings highlight the potential of targeting iNOS as a therapeutic strategy for SCI-induced neuropathic pain with reduced risks of side effects.

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星形细胞诱导型一氧化氮合酶上调与雄性大鼠脊髓损伤后慢性低水平神经性疼痛有关

脊髓损伤（SCI）可导致持续性炎症，导致慢性神经性疼痛。然而，目前的治疗方法疗效有限。三种类型的一氧化氮合酶（NOS）在炎症和神经元亢奋中起着不同的作用。因此，本研究旨在确定NOS主要亚型参与脊髓挫伤后神经性疼痛。方法研究鞘内NOS抑制剂对雄性Sprague-Dawley大鼠中度脊髓挫伤后机械敏感性的影响。这些NOS抑制剂有N(G)-硝基- l -精氨酸甲酯盐酸盐(L-NAME；非选择性NOS抑制剂),1400W （iNOS抑制剂），n ω-丙基- l-精氨酸盐酸盐(NPLA；N5-（1-亚氨基乙基）- l -鸟氨酸(L-NIO；以挪士抑制剂)。此外，我们分析了脊髓损伤或假手术大鼠脊髓NOS亚型的蛋白表达和细胞定位。结果在最高剂量（30 μM）时出现运动缺陷，但L-NAME治疗显著降低了足部戒断阈值，且呈剂量依赖性，而1400W可有效缓解机械超敏反应，且无运动副作用。NPLA疗效有限，L-NIO无效果。与假对照组相比，脊髓损伤大鼠L4-5脊髓节段iNOS蛋白表达增加2倍。脊髓损伤后，inos免疫反应性与GFAP共定位于L4-5脊柱节段浅层。1400W治疗降低了iNOS和GFAP的高反应性。结论iNOS在大鼠胸段脊髓挫伤后低水平神经性疼痛中起重要作用。特异性阻断iNOS活性可能有潜力作为治疗性干预脊髓挫伤引起的神经性疼痛，降低副作用的风险。与非选择性NOS、nNOS和eNOS抑制剂不同，iNOS抑制可有效缓解疼痛，无运动副作用。iNOS与星形胶质细胞在脊髓中的共定位提示了疼痛维持的关键机制。这些发现强调了靶向iNOS作为一种治疗sci诱导神经性疼痛的策略的潜力，并且降低了副作用的风险。

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来源期刊

European Journal of Pain 医学-临床神经学

CiteScore

7.50

自引率

5.60%

发文量

163

审稿时长

4-8 weeks

期刊介绍： European Journal of Pain (EJP) publishes clinical and basic science research papers relevant to all aspects of pain and its management, including specialties such as anaesthesia, dentistry, neurology and neurosurgery, orthopaedics, palliative care, pharmacology, physiology, psychiatry, psychology and rehabilitation; socio-economic aspects of pain are also covered. Regular sections in the journal are as follows: • Editorials and Commentaries • Position Papers and Guidelines • Reviews • Original Articles • Letters • Bookshelf The journal particularly welcomes clinical trials, which are published on an occasional basis. Research articles are published under the following subject headings: • Neurobiology • Neurology • Experimental Pharmacology • Clinical Pharmacology • Psychology • Behavioural Therapy • Epidemiology • Cancer Pain • Acute Pain • Clinical Trials.