Department of Biochemistry and Genetics, School of Medicine, Zhejiang University, Hangzhou 310058, China.
Environ Toxicol. 2011 Oct;26(5):443-52. doi: 10.1002/tox.20570. Epub 2010 Mar 1.
Microcystin produced by cyanobacteria in diverse water systems is a potent hepatotoxin that has been documented to induce hepatocyte apoptosis and liver injury. There are more than eighty reported microcystins. The present work aimed at investigating the apoptotic effect of MC-RR (a common member of microcystin family), and its related mechanism. MC-RR was administered orally to ICR mice for 7 days with different dosages. Apoptotic cell death in liver was detected by TUNEL assay, and the expression levels of Bcl-2, Bax and p53, GRP 78 and CHOP which have been reported to be related to apoptosis and ER stress were determined via western-blot. The activity of PP2A was measured using the serine-threonine phosphatase assay system and PP2A A subunit expression at both transcription and protein levels was measured by RT-PCR and western blot, respectively. A significant difference was observed on the number of TUNEL positive liver cells between the control and MC-RR-treated groups. The expression levels of Bcl-2, Bax, p53, and GRP 78 in MC-RR-treated groups were altered significantly compared to the control, but no obvious alteration was found in CHOP expression. The PP2A activity and A subunit expression did not manifest any obvious change at both transcription and protein levels. The results indicated that oral exposure to MC-RR can cause apoptosis as well as moderate ER stress in mice liver. The mitochondrial pathway via Bcl-2 family members may contribute to the apoptosis. However, PP2A may not be involved in the regulation of apoptotic process under the current conditions.
微囊藻毒素由不同水系中的蓝藻产生，是一种有效的肝毒素，已被证实可诱导肝实质细胞凋亡和肝损伤。目前已报道了 80 多种微囊藻毒素。本研究旨在研究 MC-RR（微囊藻毒素家族的常见成员）的凋亡作用及其相关机制。MC-RR 以不同剂量经口给予 ICR 小鼠 7 天。通过 TUNEL 检测法检测肝内凋亡细胞死亡，通过 Western-blot 检测已报道与凋亡和 ER 应激相关的 Bcl-2、Bax 和 p53、GRP78 和 CHOP 的表达水平。使用丝氨酸-苏氨酸磷酸酶测定系统测定 PP2A 的活性，并通过 RT-PCR 和 Western blot 分别测定转录和蛋白质水平的 PP2A A 亚基表达。与对照组相比，MC-RR 处理组的 TUNEL 阳性肝细胞数量有显著差异。与对照组相比，MC-RR 处理组的 Bcl-2、Bax、p53 和 GRP78 表达水平明显改变，但 CHOP 表达无明显改变。PP2A 活性和 A 亚基的转录和蛋白质水平均未发生明显变化。结果表明，经口暴露于 MC-RR 可导致小鼠肝脏凋亡和中度内质网应激。Bcl-2 家族成员的线粒体途径可能参与了凋亡过程。然而，在目前的条件下，PP2A 可能不参与凋亡过程的调节。
