Department of Laboratory Sciences, Yamaguchi University Graduate School of Medicine, 1-1-1 Minami-kogushi, Ube, Yamaguchi 755-8505, Japan.
Neurocrit Care. 2012 Oct;17(2):293-300. doi: 10.1007/s12028-011-9639-z.
Therapeutic hypothermia protects neurons after severe brain injury. Activated microglia produce several neurotoxic factors, such as pro-inflammatory cytokines and nitric oxide (NO), during neuron destruction. Hence, suppression of microglial release of these factors is thought to contribute partly to the neuroprotective effects of hypothermia. After brain insults, adenosine triphosphate (ATP) is released from injured cells and activates microglia. Here, we examined the acute effects of temperature on ATP-activated microglial production of inflammatory factors, and the possible involvement of p38 mitogen-activated protein kinase (p38) underlying such effects.
Microglia were cultured with ATP at 33, 37, and 39°C, or with ATP in the presence of a p38 inhibitor, SB203580, at 37°C. Cytokine and NO levels, and p38 activation were measured.
Compared to 37°C, TNF-α was reduced at 33°C and augmented at 39°C for 1.5 h. IL-6 was reduced at 33°C for 6 h. NO was reduced at 33°C, but augmented at 39°C for 6 h. p38 was reduced at 33°C for 1 min. SB203580 inhibited ATP-induced TNF-α, IL-6, and NO production.
Lowering temperature rapidly reduced p38 activation and the subsequent p38-regulated production of pro-inflammatory cytokines and NO in ATP-activated microglia, suggesting that attenuation of early phase inflammatory responses via suppression of p38 in microglia is one possible neuroprotective mechanism of therapeutic hypothermia. Temperature elevation increased TNF-α and NO production in these cells. These temperature-dependent changes imply that monitoring of TNF-α and NO in the cerebrospinal fluid during the early phase might be useful as biomarkers for responses to therapeutic hypothermia and hyperthermia.
治疗性低温可保护严重脑损伤后的神经元。在神经元破坏过程中，激活的小胶质细胞会产生几种神经毒性因子，如促炎细胞因子和一氧化氮（NO）。因此，抑制小胶质细胞释放这些因子被认为部分有助于低温的神经保护作用。脑损伤后，损伤细胞释放三磷酸腺苷（ATP）并激活小胶质细胞。在这里，我们研究了温度对 ATP 激活的小胶质细胞产生炎症因子的急性影响，以及这种影响下 p38 丝裂原活化蛋白激酶（p38）的可能参与。
将小胶质细胞在 33、37 和 39°C 下与 ATP 孵育，或在 37°C 下与 p38 抑制剂 SB203580 存在的情况下与 ATP 孵育。测量细胞因子和 NO 水平以及 p38 激活。
与 37°C 相比，33°C 时 TNF-α 减少 1.5 小时，39°C 时 TNF-α 增加。33°C 时 IL-6 减少 6 小时。33°C 时 NO 减少，但 6 小时时增加。33°C 时 p38 减少 1 分钟。SB203580 抑制 ATP 诱导的 TNF-α、IL-6 和 NO 产生。
快速降低温度可迅速降低 ATP 激活的小胶质细胞中 p38 的激活以及随后 p38 调节的促炎细胞因子和 NO 的产生，这表明通过抑制小胶质细胞中的 p38 来减轻早期炎症反应是治疗性低温的一种可能的神经保护机制。温度升高增加了这些细胞中 TNF-α 和 NO 的产生。这些温度依赖性变化表明，在早期阶段监测脑脊液中的 TNF-α 和 NO 可能有助于作为对治疗性低温和高热反应的生物标志物。
