Department of Cell Biology, Physiology and Immunology, Unit of Medical Histology, Faculty of Medicine and Institute of Neuroscience, UniversitatAutonoma, Barcelona, Bellaterra 08193, Barcelona, Spain.
Exp Gerontol. 2011 Sep;46(9):723-30. doi: 10.1016/j.exger.2011.05.003. Epub 2011 May 13.
Brain aging is associated to several morphological and functional alterations that influence the evolution and outcome of CNS damage. Acute brain injury such as an excitotoxic insult induces initial tissue damage followed by associated inflammation and oxidative stress, partly attributed to neutrophil recruitment and the expression of oxidative enzymes such as myeloperoxidase (MPO), among others. However, to date, very few studies have focused on how age can influence neutrophil infiltration after acute brain damage. Therefore, to evaluate the age-dependent pattern of neutrophil cell infiltration following an excitotoxic injury, intrastriatal injection of N-methyl-d-aspartate was performed in young and aged male Wistar rats. Animals were sacrificed at different times between 12h post-lesion (hpl) to 14 days post-lesion (dpl). Cryostat sections were processed for myeloperoxidase (MPO) immunohistochemistry, and double labeling for either neuronal cells (NeuN), astrocytes (GFAP), perivascular macrophages (ED-2), or microglia/macrophages (tomato lectin histochemistry). Our observations showed that MPO + cells were observed in the injured striatum from 12 hpl (when maximum values were found) until 7 dpl, when cell density was strongly diminished. However, at all survival times analyzed, the overall density of MPO + cells was lower in the aged versus the adult injured striatum. MPO + cells were mainly identified as neutrophils (especially at 12 hpl and 1 dpl), but it should be noted that MPO + neurons and microglia/macrophages were also found. MPO + neurons were most commonly observed at 12 hpl and reduced in the aged. MPO + microglia/macrophages were the main population expressing MPO from 3 dpl, when density was also reduced in aged subjects. These results point to neutrophil infiltration as another important factor contributing to the different responses of the adult and aged brain to damage, highlighting the need of using aged animals for the study of acute age-related brain insults.
大脑老化与多种形态和功能改变有关，这些改变会影响中枢神经系统损伤的演变和结果。急性脑损伤，如兴奋性损伤，会导致最初的组织损伤，随后伴随炎症和氧化应激，部分归因于中性粒细胞的募集和氧化酶如髓过氧化物酶（MPO）的表达等。然而，迄今为止，很少有研究关注年龄如何影响急性脑损伤后中性粒细胞的浸润。因此，为了评估兴奋性损伤后中性粒细胞浸润的年龄依赖性模式，我们在年轻和老年雄性 Wistar 大鼠的纹状体中注射 N-甲基-D-天冬氨酸。动物在损伤后 12 小时（hpl）至 14 天（dpl）的不同时间点处死。对髓过氧化物酶（MPO）免疫组织化学和神经元细胞（NeuN）、星形胶质细胞（GFAP）、血管周巨噬细胞（ED-2）或小胶质细胞/巨噬细胞（番茄凝集素组织化学）的双重标记的冷冻切片进行处理。我们的观察结果表明，从 12 hpl 开始（此时达到最大值），MPO +细胞在损伤纹状体中被观察到，直到 7 dpl，此时细胞密度显著降低。然而，在所有分析的存活时间中，与成年损伤纹状体相比，老年损伤纹状体中的 MPO +细胞总体密度较低。MPO +细胞主要被鉴定为中性粒细胞（尤其是在 12 hpl 和 1 dpl 时），但应注意，也发现了 MPO +神经元和小胶质细胞/巨噬细胞。MPO +神经元最常见于 12 hpl，并在老年中减少。从 3 dpl 开始，MPO +小胶质细胞/巨噬细胞是表达 MPO 的主要群体，老年动物的密度也降低。这些结果表明中性粒细胞浸润是导致成年和老年大脑对损伤反应不同的另一个重要因素，强调了使用老年动物研究与年龄相关的急性脑损伤的必要性。
