LaPEC EA4278, University of Avignon, F-84000 Avignon, France.
LaPEC EA4278, University of Avignon, F-84000 Avignon, France.
J Nutr Biochem. 2018 Jan;51:8-15. doi: 10.1016/j.jnutbio.2017.09.009. Epub 2017 Oct 3.
Olive oil vascular benefits have been attributed to hydroxytyrosol (HT). However, HT biological actions are still debated because it is extensively metabolized into glucuronides (GCs). The aim of this study was to test HT and GC vasculoprotective effects and the underlying mechanisms using aorta rings from 8-week-old male Wistar rats. In the absence of oxidative stress, incubation with 100 μM HT or GC for 5 min did not exert any vasorelaxing effect and did not influence the vascular function. Conversely, in condition of oxidative stress [upon incubation with 500 μM tert-butylhydroperoxide (t-BHP) for 30 min], preincubation with HT or GC improved acetylcholine-induced vasorelaxation compared with untreated samples (no t-BHP). This protective effect was lost for GC, but not for HT, when a washing step (15 min) was introduced between preincubation with HT or GC and t-BHP addition, suggesting that only HT enters the cells. In agreement, bilitranslocase inhibition with 100 μM phenylmethanesulfonyl fluoride for 20 min reduced significantly HT, but not GC, effect on the vascular function upon stress induction. Moreover, GC protective effect (improvement of endothelium-dependent relaxation in response to acetylcholine) in oxidative stress conditions was reduced by preincubation of aorta rings with 300 μM D-saccharolactone to inhibit β-glucuronidase, which can deconjugate polyphenols. Finally, only HT was detected by high-pressure liquid chromatography in aorta rings incubated with GC and t-BHP. These results suggest that, in conditions of oxidative stress, GC can be deconjugated into HT that is transported through the cell membrane by bilitranslocase to protect vascular function.
橄榄油的血管益处归因于羟基酪醇（HT）。然而，HT 的生物学作用仍存在争议，因为它广泛代谢为葡萄糖醛酸苷（GCs）。本研究旨在使用 8 周龄雄性 Wistar 大鼠的主动脉环测试 HT 和 GC 的血管保护作用及其潜在机制。在没有氧化应激的情况下，孵育 100μM HT 或 GC 5 分钟不会产生任何血管舒张作用，也不会影响血管功能。相反，在氧化应激条件下（孵育 500μM 叔丁基过氧化物（t-BHP）30 分钟），与未处理的样品（无 t-BHP）相比，用 HT 或 GC 预孵育可改善乙酰胆碱诱导的血管舒张。当在 HT 或 GC 预孵育和 t-BHP 添加之间引入洗涤步骤（15 分钟）时，这种保护作用在 GC 中丢失，但在 HT 中没有丢失，表明只有 HT 进入细胞。一致地，用 100μM 苯甲磺酰氟抑制胆红素转运蛋白 20 分钟显著减少 HT，但不减少 GC，在应激诱导时对血管功能的作用。此外，用 300μM D-海藻糖预先孵育主动脉环以抑制β-葡萄糖醛酸酶（可使多酚脱共轭），可减少 GC 在氧化应激条件下的保护作用（增加对乙酰胆碱的内皮依赖性舒张）。最后，在用 GC 和 t-BHP 孵育的主动脉环中仅通过高压液相色谱检测到 HT。这些结果表明，在氧化应激条件下，GC 可脱共轭为 HT，HT 通过胆红素转运蛋白穿过细胞膜被转运以保护血管功能。
