Differences in the characteristics and pulmonary toxicity of nano- and micron-sized respirable coal dust

Abstract

Background The characteristics of coal dust (CD) particles affect the inhalation of CD, which causes coal worker’s pneumoconiosis (CWP). CD nanoparticles (CD-NPs, < 500 nm) and micron particles (CD-MPs, < 5 μm) are components of the respirable CD. However, the differences in physicochemical properties and pulmonary toxicity between CD-NPs and CD-MPs remain unclear. Methods CD was analyzed by scanning electron microscopy, Malvern nanoparticle size potentiometer, energy dispersive spectroscopy, infrared spectroscopy, and electron paramagnetic resonance spectroscopy. CCK-8 assay, ELISA, transmission electron microscope, JC-1 staining, reactive oxygen species activity probe, calcium ion fluorescent probe, AO/EB staining, flow cytometry, and western blot were used to determine the differences between CD-NPs and CD-MPs on acute pulmonary toxicity. CCK-8, scratch healing and Transwell assay, hematoxylin–eosin and Masson staining, immunohistochemistry, immunofluorescence, and western blot were applied to examine the effects of CD-NPs and CD-MPs on pneumoconiosis. Results Analysis of the size distribution of CD revealed that the samples had been size segregated. The carbon content of CD-NPs was greater than that of CD-MPs, and the oxygen, aluminum, and silicon contents were less. In in vitro experiments with A549 and BEAS-2B cells, CD-NPs, compared with CD-MPs, had more inflammatory vacuoles, release of pro-inflammatory cytokines (IL-6, IL-1β, TNFα) and profibrotic cytokines (CXCL2, TGFβ1), mitochondrial damage (reactive oxygen species and Ca2+ levels and decreased mitochondrial membrane potential), and cell death (apoptosis, pyroptosis, and necrosis). CD-NPs-induced fibrosis model cells had stronger proliferation, migration, and invasion than did CD-MPs. In in vivo experiments, lung coefficient, alveolar inflammation score, and lung tissue fibrosis score (mean: 1.1%, 1.33, 1.33) of CD-NPs were higher than those of CD-MPs (mean: 1.3%, 2.67, 2.67). CD-NPs accelerated the progression of pulmonary fibrosis by upregulating the expression of pro-fibrotic proteins and promoting epithelial–mesenchymal transition. The regulatory molecules involved were E-cadherin, N-cadherin, COL-1, COL-3, ZO-1, ZEB1, Slug, α-SMA, TGFβ1, and Vimentin. Conclusions Stimulation with CD-NPs resulted in more pronounced acute and chronic lung toxicity than did stimulation with CD-MPs. These effects included acute inflammatory response, mitochondrial damage, pyroptosis, and necrosis, and more pulmonary fibrosis induced by epithelial–mesenchymal transition.

Coal dust nanoparticles induced pulmonary fibrosis by promoting inflammation and epithelial-mesenchymal transition via the NF-κB/NLRP3 pathway driven by IGF1/ROS-mediated AKT/GSK3β signals

“…When poorly soluble particles remain in the lungs, they can cause oxidative stress, leading to inflammation, fibrosis, or cancer [59,60]. Thus, CD-NPs are more pulmonary toxic than CD-MPs, which was also confirmed in our previous research [11]. However, the mechanism by which CD-NPs induce PF remains unclear.…”

“…S2). Data from a nonreplicated parallel assay of the above results have been published in the Journal of Respiratory Research [11].…”

“…Based on previous methods and standard parameters, we established in vivo and in vitro mouse and cellular models with pre-fibrotic state [11,50]. As illustrated in Fig.…”

“…Sources and cultures of human normal bronchial epithelial BEAS-2B cells and alveolar type II epithelial A549 cells have been described in detail in our previous research [11]. IGF1R was silenced in 40 passages of AECs induced by CD-NPs (IGF1R-siRNA) with use of knockout lentiviruses according to the manufacturer's instructions (Sangon Biotechnology Co., Ltd., Shanghai, China).…”

“…Extensive literature suggests that nanoparticles are highly pathogenic due to their unique physicochemical properties [8][9][10]. Our previous work [11] revealed that CD nanoparticles (CD-NPs) more seriously induce pulmonary fibrosis (PF) than do CD micron particles (CD-MPs), but the mechanism needs further exploration.…”