School of Public Health, Fudan University, 130 Dong'An Road, P.O. Box 288, Shanghai, 200032, China.
Key Laboratory of Public Health Safety, Ministry of Education, 130 Dong'An Road, Shanghai, 200032, China.
Arch Toxicol. 2019 Apr;93(4):965-986. doi: 10.1007/s00204-019-02415-8. Epub 2019 Feb 22.
Cadmium (Cd), an occupational and environmental pollutant, induces nephrotoxicity by primarily damaging renal proximal tubular cells. In this study, we hypothesized that pyroptosis, a caspase-1-dependent inflammatory programmed cell death mechanism, mediates Cd-induced nephrotoxicity. Human proximal tubular epithelial HK-2 cells were treated with 0-10 µM CdCl for 48 h. We found that Cd dose-dependently caused cytotoxicity, which correlated with activation of the NLRP3 inflammasome, increases in the expression and secretion of pro-inflammatory cytokines and upregulation of pyroptosis-related genes in HK-2 cells or/and in kidneys of Cd-treated mice. These effects were significantly abrogated by inhibiting caspase-1 activity with inhibitor YVAD or silencing NLRP3 with siRNA in vitro, suggesting that Cd induces caspase-1- and NLRP3-inflammasome-dependent pyroptosis. Moreover, Cd treatment also activated three branches (ATF6, PERK and IRE-1α) of endoplasmic reticulum stress. Selective inhibition of the IRE-1α/XBP-1s branch by a pharmacological inhibitor STF-083010 or by genetic silencing of XBP-1 significantly attenuated Cd-induced NLRP3 inflammasome activation and pyroptosis. Mechanistically, Cd suppressed deacetylase Sirtuin-1 (SIRT-1) protein expression and activity leading to decrease in physical binding with XBP-1s protein, and thus the accumulation of acetylated XBP-1s levels. Activation of SIRT1 using a pharmacological agonist resveratrol or genetic SIRT1 overexpression significantly abolished Cd-induced activation of the IRE-1α/XBP-1s pathway and the NRLP3 inflammasome as well as pyroptosis, which were counteracted by co-overexpression of both SIRT1 and XBP-1s. Collectively, our findings indicate that SIRT1 activity protects against Cd-induced pyroptosis through deacetylating XBP-1s, and thus inhibiting the IRE-1α/XBP-1s pathway in HK-2 cells. These results provide a novel mechanism for Cd-induced nephrotoxicity.
镉（Cd）作为一种职业和环境污染物，主要通过损伤肾近端小管细胞导致肾毒性。在这项研究中，我们假设细胞焦亡，一种依赖半胱氨酸天冬氨酸蛋白酶-1（caspase-1）的炎症程序性细胞死亡机制，介导了 Cd 诱导的肾毒性。用 0-10μM 的 CdCl2 处理人近端肾小管上皮细胞 HK-2 细胞 48 小时。我们发现 Cd 呈剂量依赖性地引起细胞毒性，这与 NLRP3 炎性体的激活、促炎细胞因子的表达和分泌增加以及 HK-2 细胞或/和 Cd 处理小鼠肾脏中细胞焦亡相关基因的上调相关。在体外，用抑制剂 YVAD 抑制 caspase-1 活性或用 siRNA 沉默 NLRP3，这些作用明显被阻断，表明 Cd 诱导 caspase-1 和 NLRP3 炎性体依赖性细胞焦亡。此外，Cd 处理还激活了内质网应激的三个分支（ATF6、PERK 和 IRE-1α）。用药理学抑制剂 STF-083010 或用 XBP-1 的基因沉默选择性抑制 IRE-1α/XBP-1s 分支，显著减轻了 Cd 诱导的 NLRP3 炎性体激活和细胞焦亡。在机制上，Cd 抑制去乙酰化酶 Sirtuin-1（SIRT-1）蛋白表达和活性，导致与 XBP-1s 蛋白的物理结合减少，从而导致乙酰化 XBP-1s 水平的积累。用药理学激动剂白藜芦醇激活 SIRT1 或基因过表达 SIRT1 可显著消除 Cd 诱导的 IRE-1α/XBP-1s 途径和 NLRP3 炎性体的激活以及细胞焦亡，而过表达 SIRT1 和 XBP-1s 可消除这种作用。总之，我们的研究结果表明，SIRT1 活性通过去乙酰化 XBP-1s 来保护 HK-2 细胞免受 Cd 诱导的细胞焦亡，从而抑制 IRE-1α/XBP-1s 途径。这些结果为 Cd 诱导的肾毒性提供了一种新的机制。
