Department of Neonatology, Charité University Medical Center, Berlin, Germany.
PLoS One. 2012;7(11):e49023. doi: 10.1371/journal.pone.0049023. Epub 2012 Nov 14.
Intrauterine infection and inflammation are major reasons for preterm birth. The switch from placenta-mediated to lung-mediated oxygen supply during birth is associated with a sudden rise of tissue oxygen tension that amounts to relative hyperoxia in preterm infants. Both infection/inflammation and hyperoxia have been shown to be involved in brain injury of preterm infants. Hypothesizing that they might be additive or synergistic, we investigated the influence of a systemic lipopolysaccharide (LPS) application on hyperoxia-induced white matter damage (WMD) in newborn rats. Three-day-old Wistar rat pups received 0.25 mg/kg LPS i.p. and were subjected to 80% oxygen on P6 for 24 h. The extent of WMD was assessed by immunohistochemistry, western blots, and diffusion tensor (DT) magnetic resonance imaging (MRI). In addition, the effects of LPS and hyperoxia were studied in an in vitro co-culture system of primary rat oligodendrocytes and microglia cells. Both noxious stimuli, hyperoxia, and LPS caused hypomyelination as revealed by western blot, immunohistochemistry, and altered WM microstructure on DT-MRI. Even so, cellular changes resulting in hypomyelination seem to be different. While hyperoxia induces cell death, LPS induces oligodendrocyte maturity arrest without cell death as revealed by TUNEL-staining and immunohistological maturation analysis. In the two-hit scenario cell death is reduced compared with hyperoxia treated animals, nevertheless white matter alterations persist. Concordantly with these in vivo findings we demonstrate that LPS pre-incubation reduced premyelinating-oligodendrocyte susceptibility towards hyperoxia in vitro. This protective effect might be caused by upregulation of interleukin-10 and superoxide dismutase expression after LPS stimulation. Reduced expression of transcription factors controlling oligodendrocyte development and maturation further indicates oligodendrocyte maturity arrest. The knowledge about mechanisms that triggered hypomyelination contributes to a better understanding of WMD in premature born infants.
宫内感染和炎症是早产的主要原因。出生时从胎盘介导的供氧向肺介导的供氧的转变与组织氧张力的突然升高有关，早产儿的相对高氧血症。感染/炎症和高氧血症都与早产儿的脑损伤有关。假设它们可能是相加的或协同的，我们研究了全身脂多糖（LPS）应用对新生大鼠高氧诱导的白质损伤（WMD）的影响。3 天大的 Wistar 大鼠幼崽腹腔内注射 0.25mg/kg LPS，并在 P6 时接受 80%氧气 24 小时。通过免疫组织化学、western blot 和扩散张量（DT）磁共振成像（MRI）评估 WMD 的程度。此外，还在原代大鼠少突胶质细胞和小胶质细胞的体外共培养系统中研究了 LPS 和高氧的作用。两种有害刺激，高氧和 LPS，通过 western blot、免疫组织化学和 DT-MRI 上 WM 微观结构的改变导致少突胶质细胞脱髓鞘。即便如此，导致少突胶质细胞脱髓鞘的细胞变化似乎不同。高氧诱导细胞死亡，而 LPS 诱导少突胶质细胞成熟停滞而不发生细胞死亡，如 TUNEL 染色和免疫组织化学成熟分析所示。在双打击情况下，与高氧处理动物相比，细胞死亡减少，但白质改变仍然存在。与这些体内发现一致，我们证明 LPS 预孵育降低了体外前髓鞘形成少突胶质细胞对高氧的敏感性。这种保护作用可能是由 LPS 刺激后白细胞介素 10 和超氧化物歧化酶表达的上调引起的。转录因子表达减少，这些转录因子控制少突胶质细胞的发育和成熟，进一步表明少突胶质细胞成熟停滞。对引发少突胶质细胞脱髓鞘的机制的了解有助于更好地理解早产儿的 WMD。
