Characterization of cerebral microvasculature in transgenic mice with endothelium targeted over-expression of GTP-cyclohydrolase I.
Characterization of cerebral microvasculature in transgenic mice with endothelium targeted over-expression of GTP-cyclohydrolase I.
复制标题
内皮靶向过度表达 GTP-环水解酶 I 的转基因小鼠脑微血管的表征。
DOI：
10.1016/j.brainres.2015.08.034
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发表时间：
2015
期刊：
影响因子：
2.9
通讯作者：
Katusic,ZvonimirS
中科院分区：
文献类型：
--
作者：
Santhanam,AnanthaVijayR;d'Uscio,LiviusV;Katusic,ZvonimirS
四氢生物蝶呤(BH4)是血管内皮细胞一氧化氮合酶(NOS)产生一氧化氮(NO)的关键决定因素，其生物合成受GTP-环水解酶I(GTPCH I)活性的调节。本研究旨在探讨内皮靶向过表达GTPCH I(eGCH-TG)对小鼠脑血管功能的影响。内皮靶向性GTPCH I的过度表达与脑微血管中BH4及其氧化产物7，8-二氢生物蝶呤(7，8-BH2)的水平显著增加有关。重要的是，在eGCH-TG小鼠中，BH4与7，8-BH2的比率显著增加，这表明BH4可用于eNOS激活。然而，在野生型和eGCH-TG小鼠的脑微血管中，内皮一氧化氮合酶的表达、硝酸盐/亚硝酸盐水平-指示NO产生-保持不变。此外，BH4生物合成的增加既不影响超氧阴离子的产生，也不影响抗氧化蛋白的表达。此外，内皮特异性GTPCH I的过度表达不会改变细胞内cGMP的水平，这反映了脑微血管中的NO信号。这些结果表明，尽管BH4的生物利用度显著增加，但eGCH-TG小鼠脑微血管内皮细胞NO的生成没有变化。我们得出结论：在生理条件下，脑微血管中BH4的水平是激活内皮型一氧化氮合酶和NO/cGMP信号的最佳水平。
Tetrahydrobiopterin (BH4) is a critical determinant of nitric oxide (NO) production by nitric oxide synthase (NOS) in the vascular endothelium and its biosynthesis is regulated by the enzymatic activity of GTP-cyclohydrolase I (GTPCH I). The present study was designed to determine the effects of endothelium-targeted overexpression of GTPCH I (eGCH-Tg) on murine cerebral vascular function. Endothelium targeted over-expression of GTPCH I was associated with a significant increase in levels of BH4, as well as its oxidized product, 7,8-dihydrobiopterin (7,8-BH2) in cerebral microvessels. Importantly, ratio of BH4to 7,8-BH2, indicative of BH4available for eNOS activation, was significantly increased in eGCH-Tg mice. However, expression of endothelial NOS, levels of nitrate/nitrite – indicative of NO production – remained unchanged between cerebral microvessels of wild-type and eGCH-Tg mice. Furthermore, increased BH4biosynthesis neither affected production of superoxide anion nor expression of antioxidant proteins. Moreover, endothelium-specific GTPCH I overexpression did not alter intracellular levels of cGMP, reflective of NO signaling in cerebral microvessels. The obtained results suggest that, despite a significant increase in BH4bioavailability, generation of endothelial NO in cerebral microvessels remained unchanged in eGCH-Tg mice. We conclude that under physiological conditions the levels of BH4in the cerebral microvessels are optimal for activation of endothelial NOS and NO/cGMP signaling.