Cardiothoracic Pharmacology, NHLI, Imperial College, Dovehouse Street, London, UK.
Biochem Biophys Res Commun. 2011 May 20;408(4):511-5. doi: 10.1016/j.bbrc.2011.04.024. Epub 2011 Apr 13.
Toll like receptor (TLR)4 is a pattern recognition receptor expressed in endothelial and other cells, responsible for the sensing of endotoxin and host derived ligands. Our group has shown previously that the absence of TLR4 is associated with reduced endothelial dependent vasodilator responses and left heart hypertrophy in animal models. However, the mechanism behind reduced endothelial cell function in TLR4(-/-) mice is not known. We have used en face confocal imaging of mesenteric arteries from mice deficient in the TLR4 receptor stained with dihydroethidium (DHE) to measure superoxide production. Using the isometric wire myograph, mesenteric artery vasodilator responses to acetylcholine and MnCl(2) (a superoxide dismutase mimetic) were measured. Mesenteric arteries from TLR4(-/-) mice had a reduced endothelial dependent relaxant response and increased superoxide levels when stimulated with acetylcholine. Increased levels of superoxide, as detected by DHE staining, were seen in vessels from TLR4(-/-) mice, which were reduced to control levels in the presence of MnCl(2). Our observations suggest that loss of TLR4 increases superoxide generation which reduces the biological activity of endothelial derived nitric oxide and thereby explains the endothelial dysfunction and associated cardiovascular phenotype in TLR4(-/-) mice. These data implicate a novel cardio-protective role for TLR4 in vascular homeostasis.
Toll 样受体 (TLR)4 是一种在血管内皮细胞和其他细胞中表达的模式识别受体，负责识别内毒素和宿主来源的配体。我们的研究小组之前已经表明，TLR4 缺失与动物模型中内皮依赖性血管舒张反应减弱和左心肥大有关。然而，TLR4(-/-) 小鼠内皮细胞功能减弱的机制尚不清楚。我们使用缺乏 TLR4 受体的小鼠肠系膜动脉的正面共聚焦成像，并用二氢乙锭 (DHE) 染色来测量超氧化物的产生。使用等长金属丝肌动描记器，测量肠系膜动脉对乙酰胆碱和 MnCl2（一种超氧化物歧化酶模拟物）的血管舒张反应。当用乙酰胆碱刺激时，TLR4(-/-) 小鼠的肠系膜动脉内皮依赖性舒张反应减弱，超氧化物水平升高。在 TLR4(-/-) 小鼠的血管中可以检测到 DHE 染色的超氧化物水平升高，在存在 MnCl2 的情况下，超氧化物水平降低至对照水平。我们的观察表明，TLR4 的缺失会增加超氧化物的产生，从而降低内皮源性一氧化氮的生物学活性，从而解释了 TLR4(-/-) 小鼠中的内皮功能障碍和相关心血管表型。这些数据表明 TLR4 在血管稳态中具有新的心脏保护作用。
