College of Animal Science and Veterinary Medicine, Shandong Agricultural University, 61 Daizong Street, Tai'an City, Shandong Province, 271018, China; Shandong Provincial Key Laboratory of Animal Biotechnology and Disease Control and Prevention, Shandong Agricultural University, 61 Daizong Street, Tai'an City, Shandong Province, 271018, China; Shandong Provincial Engineering Technology Research Center of Animal Disease Control and Prevention, Shandong Agricultural University, 61 Daizong Street, Tai'an City, Shandong Province, 271018, China.
College of Animal Science and Veterinary Medicine, Shandong Agricultural University, 61 Daizong Street, Tai'an City, Shandong Province, 271018, China; Shandong Provincial Key Laboratory of Animal Biotechnology and Disease Control and Prevention, Shandong Agricultural University, 61 Daizong Street, Tai'an City, Shandong Province, 271018, China; Shandong Provincial Engineering Technology Research Center of Animal Disease Control and Prevention, Shandong Agricultural University, 61 Daizong Street, Tai'an City, Shandong Province, 271018, China.
Free Radic Biol Med. 2022 Aug 1;188:35-44. doi: 10.1016/j.freeradbiomed.2022.06.002. Epub 2022 Jun 5.
Mercuric chloride (HgCl) is an environmental pollutant with serious nephrotoxic effects, but the underlying mechanism of HgCl nephrotoxicity is not well understood. Ferroptosis and necroptosis are two programmed cell death (PCD) modalities that have been reported singly in heavy metal-induced kidney injury. However, the interaction between ferroptosis and necroptosis in HgCl-induced kidney injury is unclear. Here, we established a model of HgCl-exposed chicken embryo kidney (CEK) cells to dissect the progresses and mechanisms of these two PCDs. We found that ferroptosis was initially activated in CEK cells after HgCl exposure for 12 h, and necroptosis was activated subsequently at 24 h. Importantly, further study indicated that the shift from ferroptosis to necroptosis was driven by ROS, which was produced by iron-dependent Fenton reaction, and the iron chelation by DFO prevented the sequential activation of both ferroptosis and necroptosis. To investigate the source of intracellular iron, the regulation of iron homeostasis was first explored and demonstrated a tendency for intracellular iron overload in CEK cells. Interestingly, the cellular ferritin, a free iron depository, decreased in a time-dependent manner. Further studies revealed that the degradation of ferritin was attributed to the activation of selective cargo receptor nuclear receptor coactivator 4 (NCOA4)-mediated ferritinophagy, and the inhibition of ferritinophagy by CQ prevented the HgCl-induced cell death. In conclusion, our study demonstrated that HgCl released excess free iron via ferritinophagy, led to a sustained accumulation of ROS and ultimately activated ferroptosis and necroptosis sequentially. These findings provide a new understanding for the nephrotoxic mechanism of HgCl.
氯化汞（HgCl）是一种环境污染物，具有严重的肾毒性作用，但 HgCl 肾毒性的潜在机制尚不清楚。铁死亡和坏死性凋亡是两种程序性细胞死亡（PCD）方式，它们曾被单独报道过与重金属诱导的肾损伤有关。然而，HgCl 诱导的肾损伤中，铁死亡和坏死性凋亡之间的相互作用尚不清楚。在这里，我们建立了一个暴露于 HgCl 的鸡胚肾（CEK）细胞模型，以剖析这两种 PCD 的进展和机制。我们发现，HgCl 暴露 12 小时后，CEK 细胞中首先激活铁死亡，24 小时后激活坏死性凋亡。重要的是，进一步的研究表明，从铁死亡向坏死性凋亡的转变是由 ROS 驱动的，ROS 是由铁依赖性 Fenton 反应产生的，DFO 螯合铁可以防止铁死亡和坏死性凋亡的相继激活。为了研究细胞内铁的来源，我们首先探讨了铁稳态的调节，结果表明 CEK 细胞存在细胞内铁过载的趋势。有趣的是，细胞内铁蛋白（一种游离铁储存库）呈时间依赖性下降。进一步的研究表明，铁蛋白的降解归因于选择性货物受体核受体共激活因子 4（NCOA4）介导的铁蛋白自噬的激活，CQ 抑制铁蛋白自噬可防止 HgCl 诱导的细胞死亡。总之，我们的研究表明，HgCl 通过铁蛋白自噬释放过量的游离铁，导致 ROS 的持续积累，最终依次激活铁死亡和坏死性凋亡。这些发现为 HgCl 的肾毒性机制提供了新的认识。
