Zhang David X, Yi Fu-Xian, Zou Ai-Ping, Li Pin-Lan
Department of Pharmacology and Toxicology, Medical College of Wisconsin, 8701 Watertown Plank Road, Milwaukee, WI 53226, USA.
Am J Physiol Heart Circ Physiol. 2002 Nov;283(5):H1785-94. doi: 10.1152/ajpheart.00318.2002.
The present study tested the hypothesis that ceramide, a sphingomylinase metabolite, serves as an second messenger for tumor necrosis factor-alpha (TNF-alpha) to stimulate superoxide production, thereby decreasing endothelium-dependent vasorelaxation in coronary arteries. In isolated bovine small coronary arteries, TNF-alpha (1 ng/ml) markedly attenuated vasodilator responses to bradykinin and A-23187. In the presence of N(G)-nitro-L-arginine methyl ester, TNF-alpha produced no further inhibition on the vasorelaxation induced by these vasodilators. With the use of 4,5-diaminofluorescein diacetate fluorescence imaging analysis, bradykinin was found to increase nitric oxide (NO) concentrations in the endothelium of isolated bovine small coronary arteries, which was inhibited by TNF-alpha. Pretreatment of the arteries with desipramine (10 microM), an inhibitor of acidic sphingomyelinase, tiron (1 mM), a superoxide scavenger, and polyethylene glycol-superoxide dismutase (100 U/ml) largely restored the inhibitory effect of TNF-alpha on bradykinin- and A-23187-induced vasorelaxation. In addition, TNF-alpha activated acidic sphingomyelinase and increased ceramide levels in coronary endothelial cells. We conclude that TNF-alpha inhibits NO-mediated endothelium-dependent vasorelaxation in small coronary arteries via sphingomyelinase activation and consequent superoxide production in endothelial cells.
神经酰胺（一种鞘磷脂酶代谢产物）作为肿瘤坏死因子-α（TNF-α）的第二信使，刺激超氧化物生成，从而降低冠状动脉中内皮依赖性血管舒张。在离体牛小冠状动脉中，TNF-α（1 ng/ml）显著减弱了对缓激肽和A-23187的血管舒张反应。在存在N(G)-硝基-L-精氨酸甲酯的情况下，TNF-α对这些血管舒张剂诱导的血管舒张没有进一步抑制作用。使用4,5-二氨基荧光素二乙酸荧光成像分析发现，缓激肽可增加离体牛小冠状动脉内皮中的一氧化氮（NO）浓度，而这被TNF-α抑制。用去甲丙咪嗪（10 microM，一种酸性鞘磷脂酶抑制剂）、替诺（1 mM，一种超氧化物清除剂）和聚乙二醇超氧化物歧化酶（100 U/ml）预处理动脉，可很大程度上恢复TNF-α对缓激肽和A-23187诱导的血管舒张的抑制作用。此外，TNF-α激活了酸性鞘磷脂酶并增加了冠状动脉内皮细胞中的神经酰胺水平。我们得出结论，TNF-α通过激活鞘磷脂酶并随后在内皮细胞中产生超氧化物，抑制小冠状动脉中NO介导的内皮依赖性血管舒张。
