Age is a critical risk factor for many neurologic conditions, including progressive multiple sclerosis. Yet the mechanisms underlying the relationship are unknown. Using lysolecithin-induced demyelinating injury to the mouse spinal cord, we characterized the acute lesion and investigated the mechanisms of increased myelin and axon damage with age. We report exacerbated myelin and axon loss in middle-aged (8–10 months of age) compared with young (6 weeks of age) female C57BL/6 mice by 1–3 d of lesion evolution in the white matter. Transcriptomic analysis linked elevated injury to increased expression of Cybb, the gene encoding the catalytic subunit of NADPH oxidase gp91phox. Immunohistochemistry in male and female Cx₃cr1^CreER/+:Rosa26^tdTom/+ mice for gp91phox revealed that the upregulation in middle-aged animals occurred primarily in microglia and not infiltrated monocyte-derived macrophages. Activated NADPH oxidase generates reactive oxygen species and elevated oxidative damage was corroborated by higher malondialdehyde immunoreactivity in lesions from middle-aged compared with young mice. From a previously conducted screen for generic drugs with antioxidant properties, we selected the antihypertensive CNS-penetrant medication indapamide for investigation. We report that indapamide reduced superoxide derived from microglia cultures and that treatment of middle-aged mice with indapamide was associated with a decrease in age-exacerbated lipid peroxidation, demyelination and axon loss. In summary, age-exacerbated acute injury following lysolecithin administration is mediated in part by microglia NADPH oxidase activation, and this is alleviated by the CNS-penetrant antioxidant, indapamide.

SIGNIFICANCE STATEMENT Age is associated with an increased risk for the development of several neurologic conditions including progressive multiple sclerosis, which is represented by substantial microglia activation. We demonstrate that in the lysolecithin demyelination model in young and middle-aged mice, the latter group developed greater acute axonal and myelin loss attributed to elevated oxidative stress through NADPH oxidase in lineage-traced microglia. We thus used a CNS-penetrant generic medication used in hypertension, indapamide, as we found it to have antioxidant properties in a previous drug screen. Following lysolecithin demyelination in middle-aged mice, indapamide treatment was associated with decreased oxidative stress and axon/myelin loss. We propose indapamide as a potential adjunctive therapy in aging-associated neurodegenerative conditions such as Alzheimer's disease and progressive multiple sclerosis.

年龄是许多神经系统疾病（包括进行性多发性硬化症）的关键危险因素。然而，这种关系的潜在机制尚不清楚。使用溶血卵磷脂诱导的小鼠脊髓脱髓鞘损伤，我们表征了急性损伤并研究了随着年龄的增长髓鞘和轴突损伤的机制。我们报道，与C6BL / 6小鼠相比，年轻（6周龄）中龄（8-10个月）中的髓鞘和轴突丧失加剧了白质病灶发展1–3 d。转录组学分析表明，损伤加剧与Cybb的表达增加有关，该基因编码NADPH氧化酶gp91phox的催化亚基。免疫组织化学在雄性和雌性CX ₃ CR1 ^{CreER / +} ：ROSA26^{tdTom / +}gp91phox的小鼠发现，中年动物的上调主要发生在小胶质细胞中，而未渗入单核细胞衍生的巨噬细胞。活化的NADPH氧化酶产生活性氧，与年轻小鼠相比，中年病患的丙二醛免疫反应性更高，证实了氧化损伤的增加。从先前进行的具有抗氧化特性的通用药物筛选中，我们选择了抗高血压的中枢神经系统渗透性药物吲达帕胺进行研究。我们报道，吲达帕胺减少了源自小胶质细胞培养物的超氧化物，与吲达帕胺的中年小鼠的治疗与年龄加剧的脂质过氧化，脱髓鞘和轴突丢失的减少有关。综上所述，

重要性声明年龄与多种神经系统疾病（包括进行性多发性硬化症）发展的风险增加相关，这由大量的小胶质细胞活化表示。我们证明，在年轻和中年小鼠的溶血卵磷脂脱髓鞘模型中，后一组发展出更大的急性轴突和髓磷脂损失，这归因于沿袭谱系小胶质细胞中通过NADPH氧化酶的氧化应激升高。因此，我们在高血压中使用了CNS渗透性通用药物indapamide，因为我们在先前的药物筛选中发现它具有抗氧化特性。溶血卵磷脂使中年小鼠脱髓鞘后，吲达帕胺治疗与氧化应激降低和轴突/髓磷脂损失有关。