School of Pharmaceutical Sciences, Center of Laboratory Animals, Sun Yat-sen University, Guangzhou 510006, PR China.
Food Chem Toxicol. 2012 Mar;50(3-4):1149-58. doi: 10.1016/j.fct.2011.12.018. Epub 2011 Dec 21.
Aloe-emodin (AE; 1,8-dihydroxy-3-hydroxymethyl-9,10-anthracenedione) is one of the primary active compounds in total rhubarb anthraquinones (TRAs), which induce nephrotoxicity in rats. However, it is still not known whether AE has a similar effect on human kidney cells. In this study, 3-(4,5,-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assays showed that AE decreases the viability of HK-2 cells (a human proximal tubular epithelial cell line) in a dose- and time-dependent manner. AE induced G2/M arrest of cell cycle in HK-2 cells, which was detected with propidium iodide (PI) staining. This apoptosis was further investigated by Hoechst staining, transmission electron microscopy (TEM), DNA fragmentation, and Annexin V/PI staining. Apoptosis of the cells was associated with caspase 3 activation, which was detected by Western blot analysis and a caspase activity assay. In addition, changes in the endoplasmic reticulum (ER) ultrastructure as observed by TEM showed the effects of AE on ER. Treatment with AE also resulted in an increase in eukaryotic initiation factor-2α (eIF-2α) phosphorylation, X-box binding protein 1 (XBP1) mRNA splicing, c-Jun N-terminal kinase (JNK) phosphorylation, glucose-regulated protein (GRP) 78 and CAAT/enhancer-binding protein-homologous protein (CHOP) accumulation. These results suggest that AE induces ER stress in HK-2 cells, which is involved in AE-induced apoptosis. In conclusion, AE induces apoptosis in HK-2 cells, and the ER stress is involved in AE-induced apoptosis in vitro. The implications of the toxic effects of AE for clinical use are unclear and these findings should be taken into account in the risk assessment for human exposure.
大黄素（AE；1,8-二羟基-3-羟甲基-9,10-蒽二酮）是总大黄蒽醌（TRAs）中的主要活性化合物之一，可在大鼠中引起肾毒性。然而，目前尚不清楚 AE 是否对人肾细胞有类似的影响。在这项研究中，3-（4,5,-二甲基噻唑-2-基）-2,5-二苯基四氮唑溴盐（MTT）测定表明，AE 以剂量和时间依赖的方式降低 HK-2 细胞（人近端肾小管上皮细胞系）的活力。AE 诱导 HK-2 细胞的细胞周期 G2/M 期阻滞，通过碘化丙啶（PI）染色检测到。通过 Hoechst 染色、透射电子显微镜（TEM）、DNA 片段化和 Annexin V/PI 染色进一步研究了这种细胞凋亡。细胞凋亡与 caspase 3 激活有关，通过 Western blot 分析和 caspase 活性测定检测到。此外，TEM 观察到的内质网（ER）超微结构的变化表明 AE 对 ER 的影响。用 AE 处理也导致真核起始因子-2α（eIF-2α）磷酸化、X 盒结合蛋白 1（XBP1）mRNA 剪接、c-Jun N 末端激酶（JNK）磷酸化、葡萄糖调节蛋白（GRP）78 和 CAAT/增强子结合蛋白同源蛋白（CHOP）积累增加。这些结果表明，AE 诱导 HK-2 细胞内质网应激，这涉及 AE 诱导的细胞凋亡。总之，AE 诱导 HK-2 细胞凋亡，内质网应激参与 AE 诱导的细胞凋亡。AE 的毒性作用对临床应用的影响尚不清楚，在进行人类暴露风险评估时应考虑这些发现。
