From Division of Molecular Medicine, Department of Medicine, and Department of Biochemistry and Molecular Biology, University of Oklahoma Health Sciences Center, Oklahoma City, OK.
Circ Res. 2014 Jan 31;114(3):480-92. doi: 10.1161/CIRCRESAHA.114.302113. Epub 2013 Nov 26.
The kynurenine (Kyn) pathway is the major route for tryptophan (Trp) metabolism in mammals. The Trp-Kyn pathway is reported to regulate several fundamental biological processes, including cell death.
The aim of this study was to elucidate the contributions and molecular mechanism of Trp-Kyn pathway to endothelial cell death.
Endogenous reactive oxygen species, endothelial cell apoptosis, and endothelium-dependent and endothelium-independent vasorelaxation were measured in aortas of wild-type mice or mice deficient for nicotinamide adenine dinucleotide phosphate [NAD(P)H] oxidase subunits (p47(phox) or gp91(phox)) or indoleamine-pyrrole 2,3-dioxygenase 1 with or without angiotensin (Ang) II infusion. As expected, AngII increased plasma levels of Kyn- and 3-hydroxykynurenine-modified proteins in endothelial cells in vivo. Consistent with this, AngII markedly increased the expression of indoleamine-pyrrole 2,3-dioxygenase in parallel with increased expression of interferon-γ. Furthermore, in wild-type mice, AngII significantly increased oxidative stress, endothelial cell apoptosis, and endothelial dysfunction. These effects of AngII infusion were significantly suppressed in mice deficient for p47(phox), gp91(phox), or indoleamine-pyrrole 2,3-dioxygenase 1, suggesting that AngII-induced enhancement of Kynurenines via NAD(P)H oxidase-derived oxidants causes endothelial cell apoptosis and dysfunction in vivo. Furthermore, interferon-γ neutralization eliminates AngII-increased superoxide products and endothelial apoptosis by inhibiting AngII-induced Kynurenines generation, suggesting that AngII-activated Kyn pathway is interferon-γ-dependent. Mechanistically, we found that AngII-enhanced 3-hydroxykynurenine promoted the generation of NAD(P)H oxidase-mediated superoxide anions by increasing the translocation and membrane assembly of NAD(P)H oxidase subunits in endothelial cells, resulting in accelerated apoptosis and consequent endothelial dysfunction.
Kyn pathway activation accelerates apoptosis and dysfunction of the endothelium by upregulating NAD(P)H-derived superoxide.
犬尿氨酸（Kyn）途径是哺乳动物中色氨酸（Trp）代谢的主要途径。据报道，Trp-Kyn 途径可调节包括细胞死亡在内的多种基本生物过程。
本研究旨在阐明 Trp-Kyn 途径对内皮细胞死亡的贡献和分子机制。
在野生型小鼠或缺乏烟酰胺腺嘌呤二核苷酸磷酸（NAD(P)H）氧化酶亚基（p47(phox)或 gp91(phox)）或色氨酸-吡咯 2,3-双加氧酶 1 的小鼠的主动脉中测量内源性活性氧、内皮细胞凋亡以及内皮依赖性和非内皮依赖性血管舒张。正如预期的那样，AngII 增加了体内内皮细胞中犬尿氨酸和 3-羟基犬尿氨酸修饰蛋白的血浆水平。与此一致，AngII 显著增加了色氨酸-吡咯 2,3-双加氧酶的表达，同时增加了干扰素-γ的表达。此外，在野生型小鼠中，AngII 显著增加了氧化应激、内皮细胞凋亡和内皮功能障碍。在缺乏 p47(phox)、gp91(phox)或色氨酸-吡咯 2,3-双加氧酶 1 的小鼠中，AngII 输注的这些作用明显受到抑制，表明 AngII 通过 NAD(P)H 氧化酶衍生的氧化剂诱导的犬尿氨酸增强导致体内内皮细胞凋亡和功能障碍。此外，干扰素-γ中和消除了 AngII 增加的超氧化物产物和内皮细胞凋亡，通过抑制 AngII 诱导的犬尿氨酸生成，表明 AngII 激活的犬尿氨酸途径是干扰素-γ依赖性的。从机制上讲，我们发现 AngII 增强的 3-羟基犬尿氨酸通过增加内皮细胞中 NAD(P)H 氧化酶亚基的易位和膜组装来促进 NAD(P)H 氧化酶介导的超氧阴离子的产生，导致加速凋亡和随后的内皮功能障碍。
犬尿氨酸途径的激活通过上调 NAD(P)H 衍生的超氧化物加速内皮细胞的凋亡和功能障碍。
