Department of Internal Medicine, Jeju National University School of Medicine.
Biol Pharm Bull. 2013;36(10):1570-6. doi: 10.1248/bpb.b13-00292. Epub 2013 Aug 3.
We investigated whether α-lipoic acid (LA) could prevent 2-deoxy-D-ribose (dRib)-induced oxidative damage and suppression of insulin expression in pancreatic β-cells. Stimulation with 50 mM dRib elevated cytotoxicity, apoptosis and intracellular reactive oxygen species (ROS) levels in HIT-T15 cells, but pretreatment with LA significantly reversed the dRib-induced changes. LA directly scavenged hydroxyl radicals generated by a Fenton reaction. Intracellular reduced glutathione (GSH) and oxidized glutathione (GSSG) were depleted by stimulation with dRib but levels were restored by addition of LA to HIT-T15 cells. However, the GSH/GSSG ratio was unchanged by LA treatment. In rat islets, stimulation with 10 mM dRib for 6 h suppressed expression of insulin and pancreatic and duodenal homeobox 1 mRNA and decreased insulin content, but these were dose-dependently reversed when LA was added. Treatment with l-buthionine-sulfoximine, an inhibitor of intracellular glutathione biosynthesis, completely abolished the protective effects of LA on dRib-mediated glutathione depletion and cytotoxicity in HIT-T15 cells. In summary, LA reversed the dRib-induced oxidative damage and suppression of insulin expression in β-cells. Enhanced intracellular total glutathione production, rather than the scavenging of ROS, is possibly the mechanism for the protective effect of LA.
我们研究了是否α-硫辛酸（LA）可以防止 2-脱氧-D-核糖（dRib）诱导的胰腺β细胞氧化损伤和胰岛素表达抑制。50mM dRib 刺激可提高 HIT-T15 细胞的细胞毒性、细胞凋亡和细胞内活性氧（ROS）水平，但 LA 的预处理可显著逆转 dRib 诱导的变化。LA 可直接清除 Fenton 反应产生的羟自由基。dRib 刺激可耗尽细胞内还原型谷胱甘肽（GSH）和氧化型谷胱甘肽（GSSG），但加入 LA 可使 HIT-T15 细胞内的 GSH 和 GSSG 水平恢复正常。然而，LA 处理对 GSH/GSSG 比值没有影响。在大鼠胰岛中，10mM dRib 刺激 6 小时可抑制胰岛素和胰腺十二指肠同源盒 1 mRNA 的表达，并降低胰岛素含量，但当加入 LA 时，这些作用呈剂量依赖性逆转。用 l-丁硫氨酸亚砜胺（一种抑制细胞内谷胱甘肽生物合成的抑制剂）处理可完全消除 LA 对 HIT-T15 细胞中 dRib 介导的谷胱甘肽耗竭和细胞毒性的保护作用。总之，LA 逆转了 dRib 诱导的β细胞氧化损伤和胰岛素表达抑制。增强细胞内总谷胱甘肽的产生，而不是 ROS 的清除，可能是 LA 保护作用的机制。
