Lin Shuying, Rhodes Philip G, Lei Manping, Zhang Feng, Cai Zhengwei
Department of Pediatrics, Division of Newborn Medicine, University of Mississippi Medical Center, Jackson, MS 39216, USA.
Brain Res. 2004 May 8;1007(1-2):132-41. doi: 10.1016/j.brainres.2004.01.074.
White matter of the neonatal brain is highly sensitive to hypoxic-ischemic insult. The susceptibility of premature oligodendrocytes (OLs) to free radicals (FRs) produced during hypoxia-ischemia (HI) has been proposed as one of the mechanisms involved. To test this hypothesis, and to further investigate if the FR scavenger alpha-phenyl-N-tert-butyl-nitrone (PBN) attenuates hypoxic-ischemic white matter damage (WMD), postnatal day 4 (P4) SD rats were subjected to bilateral common carotid artery ligation (BCAL), followed by 8% oxygen exposure for 20 min. Pathological changes were evaluated on P6 and P9, 2 and 5 days after the HI insult. HI caused severe WMD including rarefaction, necrosis and cavity formation in the corpus callosum, external and internal capsule areas. OL injury was evidenced by degeneration of O4 positive OLs on P6. Disrupted myelination was verified by decreased immunostaining of myelin basic protein (MBP) on P9. Axonal injury was demonstrated by increased amyloid precursor protein (APP) immunostaining on both P6 and P9. Two lipid peroxidation end products, malondialdehyde (MDA) and 4-hydroxynonenal (4-HNE), showed a one-fold elevation within 1-24 h following HI. 4-HNE immunostaining was found to specifically localize in the white matter area. Furthermore, pyknotic O4+ OLs were double-labeled with 4-HNE. These findings suggest that FRs are involved in the pathogenesis of neonatal WMD. PBN (100 mg/kg, i.p.) treatment alleviated the pathological changes of WMD following HI. It improved the survival of O4 positive OLs, attenuated hypomyelination and reduced axonal damage. PBN treatment also decreased the brain concentration of MDA/4-HNE and positive 4-HNE staining in the white matter area. These findings indicate that in the current WMD model, PBN protects both OLs and axons, the two main components in the white matter, from neonatal HI insult. FR scavenging appears to be the primary mechanism underlying its neuroprotective effect.
新生大脑的白质对缺氧缺血性损伤高度敏感。有人提出，缺氧缺血（HI）期间产生的自由基（FRs）对早产少突胶质细胞（OLs）的易感性是其中涉及的机制之一。为了验证这一假设，并进一步研究FR清除剂α-苯基-N-叔丁基硝酮（PBN）是否能减轻缺氧缺血性白质损伤（WMD），对出生后第4天（P4）的SD大鼠进行双侧颈总动脉结扎（BCAL），然后暴露于8%氧气中20分钟。在HI损伤后2天（P6）和5天（P9）评估病理变化。HI导致严重的WMD，包括胼胝体、外囊和内囊区域的稀疏、坏死和空洞形成。P6时O4阳性OLs的变性证明了OL损伤。P9时髓鞘碱性蛋白（MBP）免疫染色减少证实了髓鞘形成中断。P6和P9时淀粉样前体蛋白（APP）免疫染色增加证明了轴突损伤。两种脂质过氧化终产物，丙二醛（MDA）和4-羟基壬烯醛（4-HNE），在HI后1-24小时内升高了一倍。发现4-HNE免疫染色特异性定位于白质区域。此外，固缩的O4+OLs与4-HNE呈双重标记。这些发现表明FRs参与了新生儿WMD的发病机制。PBN（100mg/kg，腹腔注射）治疗减轻了HI后WMD的病理变化。它提高了O4阳性OLs的存活率，减轻了髓鞘形成不足并减少了轴突损伤。PBN治疗还降低了大脑中MDA/4-HNE的浓度以及白质区域4-HNE阳性染色。这些发现表明，在当前的WMD模型中，PBN保护白质中的两个主要成分OLs和轴突免受新生儿HI损伤。FR清除似乎是其神经保护作用的主要机制。
