Department of Physiology, University of Kentucky, Lexington, Kentucky, USA.
Department of Spinal Cord and Brain Injury Research Center, University of Kentucky, Lexington, Kentucky, USA.
J Neurotrauma. 2022 Aug;39(15-16):1075-1089. doi: 10.1089/neu.2022.0010. Epub 2022 Jul 13.
Advanced age at the time of spinal cord injury (SCI) exacerbates damage from reactive oxygen species (ROS). Mechanisms underlying this age-dependent response are not well understood and may arise from decreased antioxidant defense. We investigated how spinal cord levels of the antioxidant glutathione (GSH), and its regulation, change with age and SCI. GSH is used by GSH peroxidase to sequester ROS and is recycled by GSH reductase. Male and female, 4- and 14-month-old (MO) mice received a 60 kDyn contusion SCI, and the levels of GSH and its regulatory enzymes were evaluated at one and three days post-injury (dpi). The mice with SCI were treated with N-acetylcysteine-amide (NACA; 150 mg/kg), a cysteine supplement that increases GSH, to determine effects on functional and histological outcomes. GSH was decreased with older age in sham mice, and an SCI-dependent depletion was observed in 4-MO mice by three dpi. Neither age nor injury affected the abundance of proteins regulating GSH synthesis or recycling. GSH peroxidase activity, however, increased after SCI only in 4-MO mice. In contrast, GSH peroxidase activity was increased in 14-MO sham mice, indicating that spinal cords of older mice have an elevated oxidative state. Indeed, 14-MO sham mice had more oxidized protein (3-nitrotyrosine [3-NT]) within their spinal cords compared with 4-MO sham mice. Only 4-MO mice had significant injury-induced increases in 3-NT at three dpi. NACA treatment restored GSH and improved the redox environment in injured 4- and 14-MO mice at one dpi; however, three days of NACA delivery did not improve motor, sensory, or anatomical deficits at 28 dpi in 4-MO mice and trended toward toxicity in all outcomes in 14-MO mice. Our observation suggests that GSH levels at acute stages of SCI play a minimal role in age-dependent outcomes reported after SCI in mice. Collective results implicate elements of injury occurring after three dpi, such as inflammation, as key regulators of age-dependent effects.
脊髓损伤 (SCI) 时的高龄会加剧活性氧 (ROS) 造成的损伤。这种年龄依赖性反应的机制尚不清楚，可能源于抗氧化防御能力的下降。我们研究了脊髓中抗氧化剂谷胱甘肽 (GSH) 的水平及其调节如何随年龄和 SCI 而变化。GSH 被 GSH 过氧化物酶用于隔离 ROS，并被 GSH 还原酶回收。雄性和雌性，4 月龄和 14 月龄 (MO) 小鼠接受 60 kDyn 挫伤性 SCI，在损伤后 1 天和 3 天 (dpi) 评估 GSH 及其调节酶的水平。对 SCI 小鼠进行 N-乙酰半胱氨酸酰胺 (NACA；150 mg/kg) 治疗，这是一种增加 GSH 的半胱氨酸补充剂，以确定对功能和组织学结果的影响。在假手术小鼠中，随着年龄的增长，GSH 减少，在 4-MO 小鼠中，在 3 dpi 时观察到 SCI 依赖性消耗。年龄或损伤均不影响调节 GSH 合成或回收的蛋白质的丰度。然而，只有在 4-MO 小鼠中，SCI 后 GSH 过氧化物酶活性才增加。相比之下，14-MO 假手术小鼠的 GSH 过氧化物酶活性增加，表明老年小鼠的脊髓处于氧化状态升高。实际上，与 4-MO 假手术小鼠相比，14-MO 假手术小鼠的脊髓内有更多的氧化蛋白 (3-硝基酪氨酸 [3-NT])。只有 4-MO 小鼠在 3 dpi 时才有明显的损伤诱导的 3-NT 增加。NACA 治疗在 1 dpi 时恢复了 GSH 并改善了受伤的 4-MO 和 14-MO 小鼠的氧化还原环境；然而，3 天的 NACA 给药并没有改善 4-MO 小鼠在 28 dpi 时的运动、感觉或解剖学缺陷，并且在所有结果中都有向 14-MO 小鼠毒性的趋势。我们的观察表明，在 SCI 后的急性阶段，GSH 水平在 SCI 后在小鼠中报告的年龄依赖性结果中作用不大。综合结果表明，损伤后 3 天发生的炎症等因素是年龄依赖性影响的关键调节因素。
