Department of Internal Medicine, Institute of Clinical Sciences, Lund University, Sweden.
J Neuroinflammation. 2010 Feb 26;7:14. doi: 10.1186/1742-2094-7-14.
Cerebral ischemia from middle cerebral artery wall (MCA) occlusion results in increased expression of cerebrovascular endothelin and angiotensin receptors and activation of the mitogen-activated protein kinase (MAPK) pathway, as well as reduced local cerebral blood flow and increased levels of pro-inflammatory mediators in the infarct region. In this study, we hypothesised that inhibition of the cerebrovascular inflammatory reaction with a specific MEK1/2 inhibitor (U0126) to block transcription or a combined receptor blockade would reduce infarct size and improve neurological score.
Rats were subjected to a 2-hours middle cerebral artery occlusion (MCAO) followed by reperfusion for 48 hours. Two groups of treated animals were studied; (i) one group received intraperitoneal administration of a specific MEK1/2 inhibitor (U0126) starting at 0, 6, or 12 hours after the occlusion, and (ii) a second group received two specific receptor antagonists (a combination of the angiotensin AT1 receptor inhibitor Candesartan and the endothelin ETA receptor antagonist ZD1611), given immediately after occlusion. The middle cerebral arteries, microvessels and brain tissue were harvested; and the expressions of tumor necrosis factor-alpha (TNF-alpha), interleukin-1ss (IL-1ss), interleukin-6 (IL-6), inducible nitric oxide synthase (iNOS) and phosphorylated ERK1/2, p38 and JNK were analysed using immunohistochemistry.
We observed an infarct volume of 25 +/- 2% of total brain volume, and reduced neurological function 2 days after MCAO followed by 48 hours of recirculation. Immunohistochemistry revealed enhanced expression of TNF-alpha, IL-1ss, IL-6 and iNOS, as well as elevated levels of phosphorylated ERK1/2 in smooth muscle cells of ischemic MCA and in associated intracerebral microvessels. U0126, given intraperitoneal at zero or 6 hours after the ischemic event, but not at 12 hours, reduced the infarct volume (11.7 +/- 2% and 15 +/- 3%, respectively), normalized pERK1/2, and prevented elevation of the expressions of TNF-alpha IL-1ss, IL-6 and iNOS. Combined inhibition of angiotensin AT1 and endothelin ETA receptors decreased the volume of brain damaged (12.3 +/- 3; P < 0.05) but only slightly reduced MCAO-induced enhanced expression of iNOS and cytokines
The present study shows elevated microvascular expression of TNF-alpha, IL-1ss, IL-6 and iNOS following focal ischemia, and shows that this expression is transcriptionally regulated via the MEK/ERK pathway.
大脑中动脉壁（MCA）闭塞引起的脑缺血导致脑血管内皮素和血管紧张素受体表达增加，并激活丝裂原激活蛋白激酶（MAPK）通路，同时梗死区局部脑血流减少，促炎介质水平升高。在这项研究中，我们假设通过使用特定的 MEK1/2 抑制剂（U0126）阻断转录或联合受体阻断来抑制脑血管炎症反应，将减少梗死面积并改善神经功能评分。
大鼠进行 2 小时大脑中动脉闭塞（MCAO），然后再灌注 48 小时。研究了两组治疗动物；（i）一组动物在闭塞后 0、6 或 12 小时开始腹腔内给予特定的 MEK1/2 抑制剂（U0126），（ii）第二组动物立即给予两种特定的受体拮抗剂（血管紧张素 AT1 受体抑制剂坎地沙坦和内皮素 ETA 受体拮抗剂 ZD1611 的组合）。收获大脑中动脉、微血管和脑组织；并使用免疫组织化学分析肿瘤坏死因子-α（TNF-α）、白细胞介素-1β（IL-1β）、白细胞介素-6（IL-6）、诱导型一氧化氮合酶（iNOS）和磷酸化 ERK1/2、p38 和 JNK 的表达。
我们观察到 MCAO 后 25% +/- 2%的总脑体积梗死，并且在再灌注 48 小时后神经功能降低。免疫组织化学显示缺血性 MCA 平滑肌细胞和相关颅内微血管中 TNF-α、IL-1β、IL-6 和 iNOS 的表达增强，以及磷酸化 ERK1/2 水平升高。U0126 在缺血事件后 0 或 6 小时腹腔内给药，但在 12 小时后给药，可减少梗死体积（分别为 11.7 +/- 2%和 15 +/- 3%），使 pERK1/2 正常化，并防止 TNF-α、IL-1β、IL-6 和 iNOS 表达升高。联合抑制血管紧张素 AT1 和内皮素 ETA 受体减少了脑损伤的体积（12.3 +/- 3；P < 0.05），但仅轻度降低了 MCAO 诱导的 iNOS 和细胞因子的增强表达。
本研究表明局灶性缺血后微血管 TNF-α、IL-1β、IL-6 和 iNOS 的表达升高，并表明这种表达通过 MEK/ERK 通路转录调节。
