Department of Anatomy and Cell Biology, College of Veterinary Medicine and BK21 Program for Veterinary Science, Seoul National University, Seoul, 151-742, South Korea.
Cell Mol Neurobiol. 2010 May;30(4):531-41. doi: 10.1007/s10571-009-9477-0. Epub 2009 Nov 12.
In this study, we observed the effects of lipopolysaccharide (LPS) on neurodegeneration and immune response in the hippocampus. LPS is a gram-negative bacterial cell surface proteoglycan and known as a bacterial endotoxin. For this, we investigated the optimal concentration of LPS influencing the ICR mouse hippocampus to measure the LPS receptor, e.g., toll-like receptor 4 (TLR4), expression in mouse hippocampal homogenates. TLR4 expression was significantly and prominently increased in the hippocampal homogenates of the LPS (1 mg/kg)-treated group. Next, we examined pro-inflammatory response in the hippocampus using cyclooxygenase-2 (COX-2, a marker for inflammatory response) immunohistochemistry after LPS treatment. COX-2 immunoreactivity was significantly increased in the endothelium of blood vessels in the hippocampus 6 h after LPS treatment, judging from double immunofluorescence study with platelet-derived endothelial cell adhesion molecule-1 (PECAM-1, a marker for endothelial cells): it decreased 12 h and disappeared 24 h after LPS treatment. In addition, the ionized calcium-binding adapter molecule 1 (Iba-1)-immunoreactive ((+)) microglia were morphologically activated in the mouse hippocampus after LPS treatment. At 24 h after LPS treatment, Iba-1(+) microglia of activated forms were abundant in the hippocampus. However, NeuN (a neuron-specific soluble nuclear antigen)(+) neurons were not significantly changed in the hippocampus after LPS treatment. Fluoro-jade B (a marker for neuronal degeneration)(+) cells were not detected in the hippocampus at any time after LPS treatment. In addition, there were no significant differences in permeability of blood-brain barriers at any time points after LPS treatment. In brief, our results indicate that intraperitoneal administration of 1 mg/kg LPS effectively induces LPS receptor (TLR4) expression in the hippocampus, and the treatment increases corticosterone levels, inflammation in the blood vessels, and microglial activation in the hippocampus without any neuronal damage.
在这项研究中，我们观察了脂多糖（LPS）对海马体神经退行性变和免疫反应的影响。LPS 是革兰氏阴性细菌表面糖蛋白，是一种细菌内毒素。为此，我们研究了影响 ICR 小鼠海马体的 LPS 最佳浓度，以测量小鼠海马匀浆中的 LPS 受体，例如 Toll 样受体 4（TLR4）的表达。TLR4 表达在 LPS（1mg/kg）处理组的海马匀浆中显著且明显增加。接下来，我们在 LPS 处理后使用环氧化酶-2（COX-2，炎症反应的标志物）免疫组织化学检查海马体中的促炎反应。COX-2 免疫反应性在 LPS 处理后 6 小时在海马体血管内皮中显着增加，从血小板衍生的内皮细胞粘附分子-1（PECAM-1，内皮细胞的标志物）的双重免疫荧光研究判断：它在 LPS 处理后 12 小时和 24 小时减少。此外，离子钙结合接头分子 1（Iba-1）-免疫反应性（+）小胶质细胞在 LPS 处理后在小鼠海马体中形态激活。在 LPS 处理后 24 小时，Iba-1（+）激活形式的小胶质细胞在海马体中丰富。然而，在 LPS 处理后，海马体中的神经元特异性可溶性核抗原（NeuN）（+）神经元没有明显变化。在 LPS 处理后的任何时间点都没有在海马体中检测到氟-爪哇 B（神经元变性的标志物）（+）细胞。此外，在 LPS 处理后的任何时间点，血脑屏障的通透性都没有显着差异。总之，我们的结果表明，腹腔内注射 1mg/kg LPS 可有效诱导海马体中的 LPS 受体（TLR4）表达，并且该治疗可增加皮质酮水平、血管内炎症和海马体中的小胶质细胞激活，而不会引起任何神经元损伤。
