Seno Tadashi, Inoue Nobutaka, Matsui Kiyoko, Ejiri Junya, Hirata Ken-Ichi, Kawashima Seinosuke, Yokoyama Mitsuhiro
Division of Cardiovascular and Respiratory Medicine, Department of Internal Medicine, Kobe University Graduate School of Medicine, Kobe, Japan.
J Vasc Res. 2004 Jul-Aug;41(4):345-51. doi: 10.1159/000080525. Epub 2004 Aug 15.
Since oxidative stress plays an important role in dysregulation of the microcirculation as well as the pathogenesis of atherosclerosis, therapeutic intervention with antioxidants has been speculated to prevent cardiovascular diseases. Ascorbic acid (AA) has been reported to improve endothelial function; however, its intracellular metabolic pathway has not been fully determined. Sodium-dependent vitamin C transporter (SVCT) types 1 and 2 were recently cloned. In the present study, we investigated whether SVCT-2 is functionally expressed in vascular endothelial cells and, if so, what factors modulate its activity. The uptake of AA into human umbilical vein endothelial cells (HUVECs) was examined by incubation with radiolabeled AA (14C-AA). AA was transported into HUVECs in a dose- and time-dependent manner. Replacement of sodium chloride with choline chloride in the medium suppressed the uptake of AA. RT-PCR revealed that HUVECs expressed SVCT-2 mRNA, but not SVCT-1. Transfection of HUVECs with the antisense oligonucleotide of SVCT-2 significantly suppressed the uptake of AA. Furthermore, tumor necrosis factor-alpha and interleukin-1beta inhibited the transport activity of AA. Thus, SVCT-2 is functionally expressed in human endothelial cells, and its activity is negatively regulated by inflammatory cytokines. Our findings might provide a new insight into understanding the treatment of cardiovascular diseases with AA.
由于氧化应激在微循环失调以及动脉粥样硬化发病机制中起重要作用，因此推测用抗氧化剂进行治疗干预可预防心血管疾病。据报道，抗坏血酸（AA）可改善内皮功能；然而，其细胞内代谢途径尚未完全明确。钠依赖性维生素C转运体（SVCT）1型和2型最近已被克隆。在本研究中，我们调查了SVCT - 2是否在血管内皮细胞中功能性表达，如果是，哪些因素调节其活性。通过与放射性标记的AA（14C - AA）孵育来检测AA进入人脐静脉内皮细胞（HUVECs）的摄取情况。AA以剂量和时间依赖性方式转运进入HUVECs。用氯化胆碱替代培养基中的氯化钠可抑制AA的摄取。逆转录聚合酶链反应（RT - PCR）显示，HUVECs表达SVCT - 2 mRNA，但不表达SVCT - 1。用SVCT - 2的反义寡核苷酸转染HUVECs可显著抑制AA的摄取。此外，肿瘤坏死因子 - α和白细胞介素 - 1β抑制AA的转运活性。因此，SVCT - 2在人内皮细胞中功能性表达，其活性受到炎性细胞因子的负调控。我们的研究结果可能为理解用AA治疗心血管疾病提供新的见解。
