Jiang Houli, Harrison Fiona E, Jain Kavita, Benjamin Samantha, May James M, Graves Joan P, Zeldin Darryl C, Falck John R, Hammock Bruce D, McGiff John C
Department of Pharmacology, New York Medical College, Valhalla, New York, USA.
Department of Medicine, Vanderbilt University, Nashville, Tennessee, USA.
Adv Biosci Biotechnol. 2012 Jun 1;3(3):204-218. doi: 10.4236/abb.2012.33029.
The cardiovascular effects of vitamin C (VitC) could be mediated by epoxyeicosatrienoic acids (EETs). We aimed to study the mechanism of VitC-dependent microsomal formation of - and -EETs and the regulation of EET levels in rat isolated perfused kidneys and . VitC biphasically stimulated rat kidney microsomal - and -EET formation in a ratio of 1:2, involving the participation of lipid hydroperoxides (LOOHs), Fe, and cytochrome P450 (CYP). Levels of LOOHs correlated with microsomal EET production. LOOH stimulation of CYP isoforms resulted in preferred -over -EET formation from arachidonic acid and was associated with the cleavage of LOOHs, which indicated a CYP peroxygenase activity. EETs contributed to VitC-induced vasodilator responses in rat isolated perfused kidneys. VitC (1 mg/ml) given in the drinking water for 9 days doubled rat urinary EET excretion, increased plasma levels of EETs, mostly -EETs, by 40%, and reduced plasma levels of 20-hydroxyeicosatetraenoic acid. Depletion of VitC in brain cortex and kidney tissues by more than 20- and 50-fold, respectively, in gulonolactone oxidase-knockout mice was associated with mild increases in tissue EETs. These data suggest that LOOHs are a determinant factor for EET formation in which VitC exerts a key regulatory effect. VitC-activated CYP peroxygenase activity may represent a CYP interaction with lipoxygenases and cyclooxygenases to mediate the cardiovascular effects of VitC via formation of EETs.
维生素C（VitC）的心血管效应可能由环氧二十碳三烯酸（EETs）介导。我们旨在研究VitC依赖性微粒体中α-和β-EETs形成的机制以及大鼠离体灌注肾脏中EET水平的调节。VitC以1:2的比例双相刺激大鼠肾脏微粒体中α-和β-EET的形成，这涉及脂质氢过氧化物（LOOHs）、铁和细胞色素P450（CYP）的参与。LOOHs的水平与微粒体EET的产生相关。LOOH对CYP同工型的刺激导致花生四烯酸优先形成α-EET而非β-EET，并且与LOOHs的裂解有关，这表明存在CYP过氧物酶活性。EETs促成了VitC诱导的大鼠离体灌注肾脏中的血管舒张反应。饮用含1 mg/ml VitC的水9天，大鼠尿中EET排泄量增加一倍，血浆EETs水平（主要是α-EETs）升高40%，并降低了20-羟基二十碳四烯酸的血浆水平。在古洛糖酸内酯氧化酶基因敲除小鼠中，大脑皮层和肾脏组织中的VitC分别耗竭20倍和50倍以上，与组织EETs轻度增加有关。这些数据表明，LOOHs是EET形成的决定性因素，其中VitC发挥关键调节作用。VitC激活的CYP过氧物酶活性可能代表CYP与脂氧合酶和环氧化酶的相互作用，以通过EETs的形成介导VitC的心血管效应。
