氧化应激和植物凝集素样氧化型低密度脂蛋白受体1在氧化低密度脂蛋白上调内皮细胞自噬水平中的作用

摘要

目的 探讨氧化应激和植物凝集素样氧化型低密度脂蛋白受体1(LOX-1)在氧化低密度脂蛋白(ox-LDL)上调人脐静脉内皮细胞(HUVEC)自噬水平中的作用.方法 用LOX-1 mAb及抗氧化剂维生素C(vitC)、vitE预处理ox-LDL作用的HUVEC;酶联免疫技术观察培养上清中丙二醛(MDA)、超氧化物歧化物(SOD)含量;免疫印迹技术检测自噬标记物LC3-Ⅱ/LC3-Ⅰ、beclin1及溶酶体膜蛋白2a(Lamp2a)蛋白含量.结果 ox-LDL作用在0.5 h和6 h能显著减少细胞培养上清中TSOD活力[0.5 h(32.73±1.09比40.16±1.28)U/ml;6 h(29.32±1.56比40.16±1.28)U/ml,均P＜0.01];增加其MDA含量[0.5 h(1.11±0.04比0.57±0.05)nmol/ml,P＜0.01;6 h(0.69±0.03比0.57±0.05)nmol/ml,P＜0.05],与上调自噬水平的高峰时间点相吻合,该作用能部分性被抗氧化剂vitC、vitE拮抗.ox-LDL诱导的LC3-Ⅱ/LC3-Ⅰ表达上调能被viC、vitE(0.5 h,vitC:3.11±0.02比4.31±0.50;vitE:3.46±0.19比4.31±0.50,均P＜0.05;6 h,vitC:1.44±0.05比2.31±0.16,P＜0.05)而非LOX-1 mAb抑制;LOX-1mAb能抑制ox-LDL诱导的Lamp2a表达上调(0.5 h,0.75±0.02比1.12±0.02,P＜0.01;6 h,0.88±0.02比1.06±0.04,P＜0.05),而vitC和ritE仅能抑制Lamp2a 6 h的表达上调(vitC,0.73±0.01比1.06±0.04,P＜0.01;vitE,0.84±0.02比1.06±0.04,P＜0.05).结论 100μg/ml ox-LDL上调HUVEC的自噬水平作用不依赖LOX-1受体途径,而是与氧化应激有关.自噬溶酶体形成的增加可能与LOX-1受体介导的ox-LDL入胞有关,氧化应激仪参与了晚期人胞后ox-LDL对自噬溶酶体形成增加的调节.%Objective Our previous studies found that 100 μg/ml oxidized low-density lipoprotein (ox-LDL) could up-regulate the autophagic level in human umbilical vein endothelial cells (HUVEC). The present study was conducted to observe the roles of oxidative stress and lectin-like oxidized low density lipoprotein-1 ( LOX-1 ) in the ox-LDL-induced up-regulation of autophagy. Methods Prior to the ox-LDL exposure, LOX-1mAb, vitamin C and vitamin E were used to study the roles of LOX-1 and oxidative stress in the activation of autophagy. The contents of total-superoxide dismutase (T-SOD) and MDA (malondialdehyde) in the culture medium were detected with enzyme linked immunosorbent assay. Western blot was employed to detect the levels of autophagic marker microtubule-associated protein light chain 3 ( MAP1-LC3 ) - Ⅱ/LC3- Ⅰ , beclinl and lysosome associated membrane protein 2a (lamp2a). Results After the ox-LDL exposure, the down-regulated level of T-SOD [0. 5 h (32. 73 ± 1.09 vs 40. 16 ± 1.28) U/ml,P ＜0. 01; 6 h ( 29. 32 ± 1.56 vs 40. 16 ± 1.28 ) U/ml, P ＜ 0. 01]and the up-regulated level of MDA [0.5 h(1.11 ±0.04 vs 0.57 ±0.05) nmol/ml, P＜0. 01; 6 h (0.69 ±0.03 vs 0.57 ±0.05) nmol/ml,P ＜0. 05]in culture medium were also significant at 0. 5 h and 6 h. The ox-LDL-induced increased ratio of LC3- Ⅱ/LC3- Ⅰ was reversed by the pretreatments of vitamin C and vitamin E (0. 5 h, vitC:3. 11 ±0. 02 vs 4.31 ±0.50, P＜0. 05; vitE: 3.46 ±0. 19 vs 4.31 ±0.50, P ＜0.05;6 h,vitC: 1.44 ±0.05 vs 2.31 ±0. 16,P ＜0. 05 ), but not LOX-1mAb. LOX-1 mAb decreased the ox-LDL-induced elevated level of lamp2a protein while vitamin C and vitamin E only inhibited the elevation of lamp2a at the timepoint of 6 h, but not 0. 5 h. Conclusion Oxidative stress, rather than LOX-1, plays an important role in the ox-LDL-induced upregulation of autophagy in HUVEC. The formation of autolysosomes is associated with the LOX-1-mediated endocytosis of ox-LDL. Oxidative stress only plays a minor role in the formation of autolysosomes induced by the engulfed ox-LDL.