Abstract

We and other groups have demonstrated that exposure to nickel nanoparticles (Nano-Ni) results in severe and persistent lung inflammation and fibrosis, but the underlying mechanisms remain unclear. Here, we propose that miR-21 may play an important role in Nano-Ni-induced lung inflammation, injury, and fibrosis. Our dose- and time-response studies demonstrated that exposure of C57BL/6J (WT) mice to Nano-Ni resulted in upregulation of miR-21, proinflammatory cytokines, and profibrotic mediators. Histologically, exposure to Nano-Ni caused severe pulmonary inflammation and fibrosis. Based on the dose- and time-response studies, we chose a dose of 50 µg of Nano-Ni per mouse to compare the effects of Nano-Ni on WT with those on miR-21 KO mouse lungs. At day 3 post-exposure, Nano-Ni caused severe acute lung inflammation and injury that were reflected by increased neutrophil count, CXCL1/KC level, LDH activity, total protein concentration, MMP-2/9 protein levels and activities, and proinflammatory cytokines in the BALF or lung tissues from WT mice, which were confirmed histologically. Although Nano-Ni had similar effects on miR-21 KO mice, the above-mentioned levels were significantly lower than those in WT mice. Histologically, lungs from WT mice exposed to Nano-Ni had infiltration of a large number of polymorphonuclear (PMN) cells and macrophages in the alveolar space and interstitial tissues. However, exposure of miR-21 KO mice to Nano-Ni only caused mild acute lung inflammation and injury. At day 42 post-exposure, Nano-Ni caused extensive pulmonary fibrosis and chronic inflammation in the WT mouse lungs. However, exposure of miR-21 KO mice to Nano-Ni only caused mild lung fibrosis and chronic lung inflammation. Our results also showed that exposure to Nano-Ni caused upregulation of TGF-β1, phospho-Smad2, COL1A1, and COL3A1 in both WT and miR-21 KO mouse lungs. However, levels were significantly lower in miR-21 KO mice than in WT mice, except TGF-β1, which was similar in both kinds of mice. Decreased expression of Smad7 was observed in WT mouse lungs, but not in miR-21 KO mice. Our results demonstrated that knocking out miR-21 ameliorated Nano-Ni-induced pulmonary inflammation, injury, and fibrosis, suggesting the important role of miR-21 in Nano-Ni-induced pulmonary toxicity.

摘要

我们和其他研究小组已经证明，接触镍纳米颗粒（Nano-Ni）会导致严重且持续的肺部炎症和纤维化，但其潜在机制仍不清楚。在这里，我们提出miR-21可能在纳米镍诱导的肺部炎症、损伤和纤维化中发挥重要作用。我们的剂量和时间反应研究表明，C57BL/6J (WT) 小鼠暴露于 Nano-Ni 会导致 miR-21、促炎细胞因子和促纤维化介质上调。从组织学角度来看，接触纳米镍会导致严重的肺部炎症和纤维化。基于剂量和时间反应研究，我们选择每只小鼠 50 µg Nano-Ni 的剂量来比较 Nano-Ni 对 WT 和 miR-21 KO 小鼠肺部的影响。暴露后第 3 天，纳米镍引起严重的急性肺部炎症和损伤，表现为中性粒细胞计数、CXCL1/KC 水平、LDH 活性、总蛋白浓度、MMP-2/9 蛋白水平和活性以及促炎细胞因子增加在 BALF 或 WT 小鼠的肺组织中，经组织学证实。尽管Nano-Ni对miR-21 KO小鼠也有类似的作用，但上述水平明显低于WT小鼠。组织学上，暴露于纳米镍的WT小鼠的肺的肺泡腔和间质组织中有大量多形核（PMN）细胞和巨噬细胞浸润。然而，将 miR-21 KO 小鼠暴露于 Nano-Ni 仅引起轻度急性肺部炎症和损伤。暴露后第 42 天，纳米镍引起 WT 小鼠肺部广泛的肺纤维化和慢性炎症。然而，将 miR-21 KO 小鼠暴露于 Nano-Ni 仅引起轻度肺纤维化和慢性肺部炎症。我们的结果还表明，暴露于 Nano-Ni 会导致 WT 和 miR-21 KO 小鼠肺中 TGF-β1、磷酸化 Smad2、COL1A1 和 COL3A1 上调。然而，除 TGF-β1 外，miR-21 KO 小鼠的水平显着低于 WT 小鼠，两种小鼠的 TGF-β1 水平相似。在 WT 小鼠肺部观察到 Smad7 表达降低，但在 miR-21 KO 小鼠中未观察到。我们的结果表明，敲除 miR-21 可改善纳米镍诱导的肺部炎症、损伤和纤维化，表明 miR-21 在纳米镍诱导的肺毒性中发挥重要作用。