Analysis of Nanomaterial Toxicity by Western Blot

HDAC6-Mediated NLRP3 Inflammasome Activation Is Involved in Nickel Nanoparticle-Induced Pulmonary Inflammation and Fibrosis

Nickel nanoparticles (Nano-Ni) are increasingly utilized in industrial and biomedical applications, drawing growing attention to their potential adverse health effects. Our previous studies have demonstrated that Nano-Ni exposure induces severe, widespread, and persistent pulmonary inflammation and fibrosis. However, the underlying mechanisms are still unclear. The NLRP3 inflammasome is a vital component of the innate immune system and inflammatory signaling. In this study, we investigated whether Nano-Ni exposure activated the NLRP3 inflammasome and also examined its role in Nano-Ni-induced pulmonary inflammation and fibrosis. Our findings demonstrated that intratracheal instillation of wild-type mice (C57BL/6J) with 50 μg Nano-Ni per mouse resulted in NLRP3 inflammasome activation, IL-1β production, and extensive pulmonary inflammation and fibrosis. In contrast, Nano-Ni exposure induced only mild pulmonary inflammation and fibrosis in Nlrp3-/- mice (lacking functional NLRP3 inflammasome) or Il-1r1-/- mice (unresponsive to IL-1), highlighting the critical role of NLRP3 inflammasome activation in Nano-Ni-induced pulmonary damage. Further investigations using mouse alveolar macrophages (MH-S) revealed that Nano-Ni acts as a secondary activation signal for the NLRP3 inflammasome, triggering its activation in LPS-primed but not unprimed cells. Moreover, siRNA-mediated knockdown experiments demonstrated that this activation depended on Nano-Ni-induced upregulation of HDAC6. These findings suggest that Nano-Ni activates the NLRP3 inflammasome via HDAC6 as a second activation signal, leading to IL-1β production and subsequent pulmonary inflammation and fibrosis.

MMP-3 activation is involved in copper oxide nanoparticle-induced epithelial-mesenchymal transition in human lung epithelial cells

Copper oxide nanoparticles (Nano-CuO) are widely used in medical and industrial fields and our daily necessities. However, the biosafety assessment of Nano-CuO is far behind their rapid development. Here, we investigated the adverse effects of Nano-CuO on normal human bronchial epithelial BEAS-2B cells, especially determined whether Nano-CuO exposure would cause dysregulation of MMP-3, an important mediator in pulmonary fibrosis, and its potential role in epithelial-mesenchymal transition (EMT). Our results showed that exposure to Nano-CuO, but not Nano-TiO₂, caused increased ROS generation, MAPKs activation, and MMP-3 upregulation. Nano-CuO-induced ROS generation was not observed in mitochondrial DNA-depleted BEAS-2B ρ⁰ cells, indicating that mitochondria may be the main source of Nano-CuO-induced ROS generation. Pretreatment of the cells with ROS scavengers or inhibitors or depleting mitochondrial DNA significantly attenuated Nano-CuO-induced MAPKs activation and MMP-3 upregulation, and pretreatment of cells with MAPKs inhibitors abolished Nano-CuO-induced MMP-3 upregulation, suggesting Nano-CuO-induced MMP-3 upregulation is through Nano-CuO-induced ROS generation and MAPKs activation. In addition, exposure of the cells to Nano-CuO for 48 h resulted in decreased E-cadherin expression and increased expression of vimentin, α-SMA, and fibronectin, which was ameliorated by MMP-3 siRNA transfection, suggesting an important role of MMP-3 in Nano-CuO-induced EMT. Taken together, our study demonstrated that Nano-CuO exposure caused mitochondrial ROS generation, MAPKs activation, and MMP-3 upregulation. Nano-CuO exposure also caused cells to undergo EMT, which was through Nano-CuO-induced dysregulation of ROS/MAPKs/MMP-3 pathway. Our findings will provide further understanding of the potential mechanisms involved in metal nanoparticle-induced various toxic effects including EMT and pulmonary fibrosis.

The role of miR-21 in nickel nanoparticle-induced MMP-2 and MMP-9 production in mouse primary monocytes: In vitro and in vivo studies

Exposure to metal nanoparticles causes both pulmonary and systemic effects. Nanoparticles can enter the circulation and act directly or indirectly on blood cells, such as monocytes. Monocytes/macrophages are among the first cells to home to inflammatory sites and play a key role in the immune response. Here we investigated the effects of nickel nanoparticles (Nano-Ni), partially [O]-passivated Nano-Ni (Nano-Ni-P), and carbon-coated Nano-Ni (Nano-Ni-C) on MMP-2 and MMP-9 production in mouse primary monocytes both in vitro and in vivo and explored the potential mechanisms involved. The dose- and time-response studies showed that exposure of primary monocytes from wild-type (WT) mice to 30 μg/mL of Nano-Ni for 24 h caused significant MMP-2 and MMP-9 production; therefore, these dose and time point were chosen for the following in vitro studies. Nano-Ni and Nano-Ni-P caused miR-21 upregulation, as well as MMP-2, MMP-9, TIMP-1 and TIMP-2 upregulation in monocytes from WT, but not miR-21 knock-out (KO), mice, indicating the important role of miR-21 in Nano-Ni-induced MMPs and TIMPs upregulation. However, Nano-Ni-C did not cause these effects, suggesting surface modification of Nano-Ni, such as carbon coating, alleviates Nano-Ni-induced miR-21 and MMPs upregulation. These results were further confirmed by in vivo studies by intratracheal instillation of nickel nanoparticles into WT and miR-21 KO mice. Finally, our results demonstrated that exposure of primary monocytes from WT mice to Nano-Ni and Nano-Ni-P caused downregulation of RECK, a direct miR-21 target, suggesting the involvement of miR-21/RECK pathway in Nano-Ni-induced MMP-2 and MMP-9 production.

miR-21 mediates nickel nanoparticle-induced pulmonary injury and fibrosis

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.