Albany College of Pharmacy and Health Sciences, Albany, NY, USA.
Wadsworth Center, Albany, NY, USA.
Cell Physiol Biochem. 2023 Jan 25;57(1):1-14. doi: 10.33594/000000601.
BACKGROUND/AIMS: The ribosome-inactivating proteins include the biothreat agent, ricin toxin (RT). When inhaled, RT causes near complete destruction of the lung epithelium coincident with a proinflammatory response that includes TNF family cytokines, which are death-inducing ligands. We previously demonstrated that the combination of RT and TNF-related apoptosis inducing ligand (TRAIL) induces caspase-dependent apoptosis, while RT and TNF-α or RT and Fas ligand (FasL) induces cathepsin-dependent cell death in lung epithelial cells. We hypothesize that airway macrophages constitute a major source of cytokines that drive lung epithelial cell death.
Here, we show that RT-induced apoptosis of the monocytic cell line, U937, leads to the bystander killing of the lung epithelial cell line, A549. U937 cells were treated with ricin. Following this, A549 cells were treated with supernatants from U937 cells and death was measured by WST-1 viability assay.
Upon RT-induced U937 cell death, released RT and FasL contributed to A549 cell death. U937 cells also released nuclear protein HMGB1. The release of RT, FasL, and HMGB1 triggered A549 cell necroptosis, rather than cathepsin-dependent killing observed previously with RT and FasL. Reactive oxygen species (ROS) were produced in A549 cells due to HMGB1 ligation of the receptor for advanced glycation end products (RAGE).
These findings demonstrate the potential for bystander necroptosis of lung epithelial cells during RT toxicosis which may perpetuate or increase the proinflammatory response.
背景/目的：核糖体失活蛋白包括生物威胁剂蓖麻毒素（RT）。吸入 RT 会导致肺上皮细胞几乎完全破坏，同时伴有促炎反应，包括 TNF 家族细胞因子，它们是诱导细胞死亡的配体。我们之前的研究表明，RT 与 TNF 相关凋亡诱导配体（TRAIL）的联合使用会诱导细胞凋亡，而 RT 与 TNF-α或 RT 与 Fas 配体（FasL）的联合使用会诱导肺上皮细胞的组织蛋白酶依赖性细胞死亡。我们假设气道巨噬细胞是驱动肺上皮细胞死亡的细胞因子的主要来源。
在这里，我们表明 RT 诱导单核细胞系 U937 的凋亡会导致肺上皮细胞系 A549 的旁观者杀伤。用蓖麻毒素处理 U937 细胞。在此之后，用 U937 细胞的上清液处理 A549 细胞，并通过 WST-1 活力测定法测量细胞死亡。
在 RT 诱导的 U937 细胞死亡后，释放的 RT 和 FasL 导致 A549 细胞死亡。U937 细胞还释放了核蛋白 HMGB1。RT、FasL 和 HMGB1 的释放触发了 A549 细胞的坏死性凋亡，而不是之前观察到的 RT 和 FasL 诱导的组织蛋白酶依赖性杀伤。由于 HMGB1 与晚期糖基化终产物受体（RAGE）的结合，A549 细胞中产生了活性氧（ROS）。
这些发现表明，在 RT 中毒期间，肺上皮细胞可能会发生旁观者坏死性凋亡，这可能会延续或增加促炎反应。
