Saptarshi Shruti R, Feltis Bryce N, Wright Paul Fa, Lopata Andreas L
Molecular Immunology Group, College of Public Health, Medical and Veterinary Sciences, Centre for Biodiscovery and Molecular Development of Therapeutics, James Cook University, Building 21, Molecular Sciences, James Cook Drive, Douglas Campus, Townsville, QLD, 4811, Australia.
School of Medical Sciences, RMIT University, Melbourne, VIC, Australia.
J Nanobiotechnology. 2015 Feb 3;13:6. doi: 10.1186/s12951-015-0067-7.
This study evaluates the time-dependent pro-inflammatory response of the model human lung epithelial cells (A549) to industrially relevant zinc oxide nanoparticles (ZnO NPs). In terms of toxicity, ZnO-NPs are categorised into the group of high toxicity nanomaterials. However information on pro-inflammatory potential of these NPs at sub-toxic concentrations is limited. Understanding how cellular defense mechanisms function in the presence of sub-cytotoxic concentrations of these NPs is vital. Moreover, there is an urgent need for additional in vivo studies addressing pulmonary toxicity due to accidental inhalation of ZnO NPs.
Exposure to sub-cytotoxic ZnO NP concentrations (20 μg/mL) induced significant up-regulation of mRNA for the pro-inflammatory cytokine IL-8 and redox stress marker heme oxygenase-1, along with increased release of IL-8. The highest pro-inflammatory response was recorded after 4 to 6 hr exposure to ZnO NPs over a 24 hr period. Pre-treatment of A549 cells with the sulfhydryl antioxidant N-acetyl cysteine (at 5 mM) resulted in significant reduction of the up-regulation of inflammatory markers, confirming the role of reactive oxygen species in the observed immunomodulatory effects, independent of cytotoxicity. Furthermore, we report for the first time that, intranasal instillation of a single dose (5 mg/kg) of pristine or surfactant-dispersed ZnO NPs can cause pulmonary inflammation, already after 24 hr in a murine model. This was confirmed by up-regulation of eotaxin mRNA in the lung tissue and release of pro-inflammatory cytokines in the sera of mice exposed to ZnO NPs.
Our study highlights that even at sub-cytotoxic doses ZnO NPs can stimulate a strong inflammatory and antioxidant response in A549 cells. ZnO NP mediated cytotoxicity may be the outcome of failure of cellular redox machinery to contain excessive ROS formation. Moreover exposure to a single but relatively high dose of ZnO NPs via intranasal instillation may provoke acute pulmonary inflammatory reactions in vivo.
本研究评估了模型人肺上皮细胞（A549）对工业相关氧化锌纳米颗粒（ZnO NPs）的时间依赖性促炎反应。在毒性方面，ZnO-NPs被归类为高毒性纳米材料组。然而，关于这些纳米颗粒在亚毒性浓度下的促炎潜力的信息有限。了解细胞防御机制在这些纳米颗粒的亚细胞毒性浓度存在时如何发挥作用至关重要。此外，迫切需要进行更多的体内研究，以解决因意外吸入ZnO NPs而导致的肺部毒性问题。
暴露于亚细胞毒性的ZnO NP浓度（20μg/mL）会导致促炎细胞因子IL-8和氧化还原应激标志物血红素加氧酶-1的mRNA显著上调，同时IL-8的释放增加。在24小时内暴露于ZnO NPs 4至6小时后，记录到最高的促炎反应。用巯基抗氧化剂N-乙酰半胱氨酸（5 mM）预处理A549细胞，导致炎症标志物上调显著降低，证实了活性氧在观察到的免疫调节作用中的作用，与细胞毒性无关。此外，我们首次报告，在小鼠模型中，鼻内滴注单剂量（5 mg/kg）的原始或表面活性剂分散的ZnO NPs在24小时后即可引起肺部炎症。这通过暴露于ZnO NPs的小鼠肺组织中嗜酸性粒细胞趋化因子mRNA的上调和血清中促炎细胞因子的释放得到证实。
我们的研究强调，即使在亚细胞毒性剂量下，ZnO NPs也能在A549细胞中刺激强烈的炎症和抗氧化反应。ZnO NP介导的细胞毒性可能是细胞氧化还原机制无法抑制过量ROS形成的结果。此外，通过鼻内滴注暴露于单一但相对高剂量的ZnO NPs可能会在体内引发急性肺部炎症反应。
