School of Medicine and Life Sciences, Nanjing University of Chinese Medicine, Nanjing 210023, Jiangsu, China.
Research Center of Endocrine and Metabolic Diseases, Affiliated Hospital of Integrated Traditional Chinese and Western Medicine, Nanjing University of Chinese Medicine, Jiangsu Province Academy of Traditional Chinese Medicine, Nanjing 210023, Jiangsu, China.
Food Chem Toxicol. 2018 Feb;112:290-298. doi: 10.1016/j.fct.2018.01.004. Epub 2018 Jan 4.
Microcystin (MC)-LR is a cyclic heptapeptide that acts as a potent reproductive system toxin. However, the underlying pathways of MCLR-induced reproductive system toxicity have not been well elucidated. The blood-testis barrier is mainly constituted by tight junctions (TJs) between adjacent Sertoli cells in the seminiferous epithelium near the basement membrane. The present study was designed to investigate changes in TJs and the underlying pathway in MC-LR-induced TJs toxicity in Sertoli cell. In our study, the transepithelial electrical resistance (TER) value was decreased in a dose dependent manner due to the markers of TJs occludin, claudin and zonula occludens-1 (ZO-1) expression decline. MC-LR is shown to induce cytotoxicity by inhibiting protein phosphatase 2A (PP2A) activity. Our results also showed that the PP2A activity presented a dose-dependent decline. Moreover, MC-LR stimulated protein expression of snail by Akt/GSK-3β activation. The activated Akt/GSK-3β and snail signaling pathway largely accounted for MC-LRinduced TJs toxicity, which could be partially reversed by snail siRNA interference or AKT chemical inhibitor in TM4 cells. These findings indicated that MC-LR inhibit the protein expression of TJs, and the activation of Akt/Snail signaling pathways due to PP2A inhibition is proposed to participate in this process.
微囊藻毒素-LR（MC-LR）是一种环状七肽，具有很强的生殖系统毒性。然而，MC-LR 诱导生殖系统毒性的潜在途径尚未得到很好的阐明。血睾屏障主要由基底膜附近生精上皮中相邻支持细胞之间的紧密连接（TJ）构成。本研究旨在探讨 MC-LR 诱导的支持细胞 TJ 毒性中 TJ 及其潜在途径的变化。在我们的研究中，由于 TJ 标志物紧密连接蛋白（occludin）、闭合蛋白（claudin）和封闭蛋白-1（ZO-1）表达下降，跨上皮电阻（TER）值呈剂量依赖性下降。MC-LR 通过抑制蛋白磷酸酶 2A（PP2A）活性显示出细胞毒性。我们的结果还表明，PP2A 活性呈剂量依赖性下降。此外，MC-LR 通过 Akt/GSK-3β 激活刺激 snail 蛋白表达。激活的 Akt/GSK-3β 和 snail 信号通路在很大程度上解释了 MC-LR 诱导的 TJ 毒性，这可以通过 TM4 细胞中的 snail siRNA 干扰或 Akt 化学抑制剂部分逆转。这些发现表明，MC-LR 抑制 TJ 的蛋白表达，由于 PP2A 抑制，Akt/Snail 信号通路的激活可能参与了这一过程。
