Song Xiang-Bin, Liu Gang, Liu Fei, Yan Zhen-Gui, Wang Zhen-Yong, Liu Zong-Ping, Wang Lin
College of Animal Science and Veterinary Medicine, Shandong Agricultural University, Tai'an, China.
College of Veterinary Medicine, Yangzhou University, Yangzhou, China.
Cell Death Dis. 2017 Jun 8;8(6):e2863. doi: 10.1038/cddis.2017.262.
Lead (Pb) is a known nephrotoxicant that causes damage to proximal tubular cells. Autophagy has an important protective role in various renal injuries, but the role of autophagy in Pb-elicited nephrotoxicity remains largely unknown. In this study, Pb promoted the accumulation of autophagosomes in primary rat proximal tubular (rPT) cells, and subsequent findings revealed that this autophagosome accumulation was caused by the inhibition of autophagic flux. Moreover, Pb exposure did not affect the autophagosome-lysosome fusion in rPT cells. Next, we found that Pb caused lysosomal alkalinization, may be through suppression of two V-ATPase subunits. Simultaneously, Pb inhibited lysosomal degradation capacity by affecting the maturation of cathepsin B (CTSB) and cathepsin D (CTSD). Furthermore, translocation of CTSB and CTSD from lysosome to cytoplasm was observed in this study, suggesting that lysosomal membrane permeabilization (LMP) occurred in Pb-exposed rPT cells. Meanwhile, Pb-induced caspase-3 activation and apoptosis were significantly but not completely inhibited by CTSB inhibitor (CA 074) and CTSD inhibitor (pepstatin A), respectively, demonstrating that LMP-induced lysosomal enzyme release was involved in Pb-induced apoptosis in rPT cells. In conclusion, Pb-mediated autophagy blockade in rPT cells is attributed to the impairment of lysosomal function. Both inhibition of autophagic flux and LMP-mediated apoptosis contribute to Pb-induced nephrotoxicity in rPT cells.
铅（Pb）是一种已知的肾毒性物质，可导致近端肾小管细胞损伤。自噬在各种肾损伤中具有重要的保护作用，但自噬在铅诱导的肾毒性中的作用仍 largely 未知。在本研究中，铅促进了原代大鼠近端肾小管（rPT）细胞中自噬体的积累，随后的研究结果表明，这种自噬体积累是由自噬流的抑制引起的。此外，铅暴露并未影响 rPT 细胞中自噬体与溶酶体的融合。接下来，我们发现铅导致溶酶体碱化，可能是通过抑制两个 V-ATP 酶亚基。同时，铅通过影响组织蛋白酶 B（CTSB）和组织蛋白酶 D（CTSD）的成熟来抑制溶酶体降解能力。此外，在本研究中观察到 CTSB 和 CTSD 从溶酶体向细胞质的转位，表明在铅暴露的 rPT 细胞中发生了溶酶体膜通透性增加（LMP）。同时，CTSB 抑制剂（CA 074）和 CTSD 抑制剂（胃蛋白酶抑制剂 A）分别显著但未完全抑制铅诱导的半胱天冬酶-3 激活和细胞凋亡，表明 LMP 诱导的溶酶体酶释放参与了铅诱导的 rPT 细胞凋亡。总之，铅介导的 rPT 细胞自噬阻断归因于溶酶体功能的损害。自噬流的抑制和 LMP 介导的凋亡均导致铅诱导的 rPT 细胞肾毒性。
