A role for free radicals and nitric oxide in delayed recovery in aged rats with chronic constriction nerve injury
A role for free radicals and nitric oxide in delayed recovery in aged rats with chronic constriction nerve injury
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DOI：
10.1016/s0891-5849(01)00597-4
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发表时间：
2001-08-15
影响因子：
7.4
通讯作者：
Khodr, B
中科院分区：
文献类型：
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作者：
Khalil, Z;Khodr, B
使用可逆的慢性压迫性损伤（CCI）模型的神经性疼痛，我们以前证明，热痛觉过敏的变化与周围微血管血流的变化在受影响的爪子，恢复可以评估行为和血管反应的正常化。使用相同的模型，本研究探讨了年龄相关的变化，神经损伤后的恢复和参与自由基和一氧化氮（NO）在这些变化。将4根松散的非收缩性结扎线应用于年轻和老年（3和24个月）Sprague道利大鼠右侧大腿中部区域的坐骨神经。每周（8-10周）使用46 ℃水浴监测所有大鼠的热阈值，并使用一些组分别检查对P物质（SP）和硝普钠（SNP）的内皮和平滑肌依赖性微血管反应。将这些物质灌注在受损伤神经支配的足垫上隆起的水泡底部。通过测定黄嘌呤氧化酶（XO）和脂质过氧化氢（LPO）的活性来评估坐骨神经中的自由基活性。从第五周开始，年轻大鼠显示出恢复的迹象（热痛觉过敏减少和外周微血管血流改善）。在8周内未观察到老年大鼠的恢复迹象，在第9周和第10周观察到热痛觉过敏有所减少。XO活性在年轻损伤神经中显著高于假手术组（400%），在老年损伤神经中甚至显著更高（680%）。同样，与假手术相比，陈旧性损伤神经的LPO水平增加了300%。使用抗氧化剂甲磺酸替拉扎德研究了活性氧（ROS）在老年大鼠延迟恢复中的作用。从CCI后第1天（早期治疗）或第7天（晚期治疗）开始，在大腿中部区域肌内（im）注射替拉扎德（20 mg/kg）。损伤坐骨神经中的LPO水平使用早期或晚期治疗均显著降低，然而替拉扎德分别对恢复、延长或减轻热痛觉过敏具有相反的作用。然后使用特异性神经元型一氧化氮合酶（nNOS）抑制剂3-溴-7-硝基吲唑（3Br-7 NI）（10 mg/kg）检查神经元型一氧化氮（nNO）的作用。从第5周和第6周开始，3Br-7 NI导致热痛觉过敏的显著缓解，血管反应得到改善。还使用了3Br-7 NI和替拉扎德处理的组合，但没有显示出累加效应。结果表明，ROS和nNO有助于延迟恢复损伤的神经在老年大鼠和维持热痛觉过敏和减少微血管血流量的神经支配的区域中的损伤的神经。结果还提出了这样的概念，即可能的相互作用的自由基与NO形成过氧亚硝酸盐可能是负责这种延迟恢复。具有讽刺意味的是，这项研究还揭示了自由基在组织修复中的积极作用，并提出了早期抗氧化剂干预可能对受损神经的修复产生负面影响的观点。(C)2001 Elsevier Science Inc.
Using a reversible chronic constriction injury (CCI) model of neuropathic pain, we previously demonstrated that changes in thermal hyperalgesia correlate with the changes in peripheral microvascular blood flow in the affected paw, and that recovery can be assessed by normalization of both behavioral and vascular responses. Using the same model, this study examined age-related changes in recovery after nerve injury and the involvement of free radicals and nitric oxide (NO) in these changes. Four loose, nonconstrictive ligatures were applied to the sciatic nerve in the right, mid-thigh region of young and old (3 and 24 months) Sprague Dawley rats. All rats were monitored weekly (for 8-10 weeks) for their thermal threshold using a 46 degreesC water bath and some groups were used to examine endothelial and smooth muscle-dependent microvascular responses to substance P (SP) and sodium nitroprusside (SNP), respectively. These substances were perfused over the base of blisters raised on the footpad innervated by the injured nerve. Free radical activity in the sciatic nerve was assessed by measuring the activity of xanthine oxidase (XO) and lipid hydroperoxides (LPO). Young rats showed signs of recovery (reduction in thermal hyperalgesia and improvement of peripheral microvascular blood flow) from the fifth week. No signs of recovery were observed in old rats for 8 weeks, with some reduction in thermal hyperalgesia observed by weeks 9 and 10. XO activity was significantly higher in young injured nerves compared to sham (400%) and was even significantly greater in old injured nerves (680%). Similarly, old injured nerves showed 300% increase in LPO levels compared to sham. The role of reactive oxygen species (ROS) in delayed recovery in old rats was examined using the antioxidant tirilazad mesylate. Tirilazad (20 mg/kg) was injected intramuscularly (im) in the mid-thigh region starting on day 1 post CCI, (early treatment) or day 7 (late treatment). Levels of LPO in the injured sciatic nerves were significantly reduced using either early or late treatment, however tirilazad had opposing effects on recovery, prolonging or alleviating thermal hyperalgesia, respectively. The role of neuronal nitric oxide (nNO) was then examined using the specific neuronal nitric oxide synthase (nNOS) inhibitor, 3-bromo-7-nitroindazole (3Br-7NI) (10 mg/kg). 3Br-7NI resulted in a significant alleviation of thermal hyperalgesia with improvement in the vascular responses from weeks 5 and 6 onwards. A combination of 3Br-7NI and tirilazad treatment was also used but did not show an additive effect. The results suggest that ROS and nNO contribute to delayed recovery of injured nerves in old rats and to the maintenance of thermal hyperalgesia and the reduction in microvascular blood flow in the area innervated by the injured nerve. The results also raise the notion that possible interaction of free radicals with NO to form peroxynitrite might be responsible for such delayed recovery. Ironically, this study also reveals a positive role for free radicals in tissue repair and raises the notion that early intervention with antioxidants, could exert a negative effect on repair of injured nerves. (C) 2001 Elsevier Science Inc.