Laboratory for Neurogenetics and Developmental Genetics, Croatian Institute for Brain Research, School of Medicine, University of Zagreb, Salata 12, Zagreb HR-10000, Croatia.
J Neuroinflammation. 2012 Aug 8;9:191. doi: 10.1186/1742-2094-9-191.
Using a live imaging approach, we have previously shown that microglia activation after stroke is characterized by marked and long-term induction of the Toll-like receptor (TLR) 2 biophotonic signals. However, the role of TLR2 (and potentially other TLRs) beyond the acute innate immune response and as early neuroprotection against ischemic injury is not well understood.
TLR2-/- mice were subjected to transient middle cerebral artery occlusion followed by different reperfusion times. Analyses assessing microglial activation profile/innate immune response were performed using in situ hybridization, immunohistochemistry analysis, flow cytometry and inflammatory cytokine array. The effects of the TLR2 deficiency on the evolution of ischemic brain injury were analyzed using a cresyl violet staining of brain sections with appropriate lesion size estimation.
Here we report that TLR2 deficiency markedly affects post-stroke immune response resulting in delayed exacerbation of the ischemic injury. The temporal analysis of the microglia/macrophage activation profiles in TLR2-/- mice and age-matched controls revealed reduced microglia/macrophage activation after stroke, reduced capacity of resident microglia to proliferate as well as decreased levels of monocyte chemotactic protein-1 (MCP-1) and consequently lower levels of CD45(high)/CD11b(+) expressing cells as shown by flow cytometry analysis. Importantly, although acute ischemic lesions (24 to 72 h) were smaller in TLR2-/- mice, the observed alterations in innate immune response were more pronounced at later time points (at day 7) after initial stroke, which finally resulted in delayed exacerbation of ischemic lesion leading to larger chronic infarctions as compared with wild-type mice. Moreover, our results revealed that TLR2 deficiency is associated with significant decrease in the levels of neurotrophic/anti-apoptotic factor Insulin-like growth factor-1 (IGF-1), expressed by microglia in the areas both in and around ischemic lesion.
Our results clearly suggest that optimal and timely microglial activation/innate immune response is needed to limit neuronal damage after stroke.
我们之前通过活体成像的方法发现，中风后小胶质细胞的激活表现为 Toll 样受体（TLR）2 生物光子信号的显著且长期诱导。然而，TLR2（和潜在的其他 TLR）在急性先天免疫反应之外以及作为对缺血性损伤的早期神经保护作用的作用尚未得到很好的理解。
TLR2-/- 小鼠接受短暂性大脑中动脉闭塞，然后进行不同的再灌注时间。使用原位杂交、免疫组织化学分析、流式细胞术和炎症细胞因子阵列评估分析评估小胶质细胞激活谱/先天免疫反应。通过对大脑切片进行亚甲蓝染色并适当估计病变大小，分析 TLR2 缺失对缺血性脑损伤演变的影响。
我们报告称，TLR2 缺失会显著影响中风后的免疫反应，导致缺血性损伤的延迟恶化。TLR2-/- 小鼠和年龄匹配的对照组中风后小胶质细胞/巨噬细胞激活谱的时间分析显示，中风后小胶质细胞/巨噬细胞激活减少，驻留小胶质细胞增殖能力降低，单核细胞趋化蛋白-1（MCP-1）水平降低，因此通过流式细胞术分析，CD45(high)/CD11b(+) 表达细胞的水平降低。重要的是，尽管 TLR2-/- 小鼠的急性缺血性病变（24 至 72 小时）较小，但在初始中风后更晚的时间点（第 7 天）观察到的先天免疫反应的改变更为明显，这最终导致缺血性病变的延迟恶化，导致与野生型小鼠相比更大的慢性梗死。此外，我们的结果表明，TLR2 缺失与中风后缺血性病变内和周围区域小胶质细胞表达的神经营养/抗凋亡因子胰岛素样生长因子-1（IGF-1）水平显著降低有关。
我们的结果清楚地表明，中风后需要适当和及时的小胶质细胞激活/先天免疫反应来限制神经元损伤。
