ABSTRACT
Objective@#To investigate the effect of PM2.5 exposure on nasal inflammatory cytokines and nasal mucosal pathology in a rat model of allergic rhinitis (AR).@*Methods@#Twenty-four healthy female SD rats were randomly divided into 3 groups by random number table method, with 8 rats in each group: normal control group (NC group), ovalbumin (OVA) induced AR model (AR group), and AR model group inhaled to PM2.5 at 200 μg/m3, 3 h/d, for 30 d (ARE group). Nasal symptoms including sneezing, nasal rubs and nasal secretion were recorded. Levels of OVA specific IgE in serum, interleukin 6 (IL-6) and tumor necrosis factor-ɑ (TNF-ɑ) in nasal irrigating solution were measured by enzyme-linked immunosorbent assay (ELISA). The histopathological changes of nasal mucosa were observed by HE staining. SPSS 17.0 software was used to analyze the data.@*Results@#The number of sneezing, nasal rubs and the amount of nasal secretion in the ARE group were significantly higher than that in the AR group and the NC group (number of sneezing (15.38±1.68) times/15 min vs (11.63±1.13) times/15 min vs (1.75±0.71) times/15 min, number of nasal rubs (27.75±2.12) times/15 min vs (21.25±2.96) times/15 min vs (5.25±1.04) times/15 min, amount of nasal secretion (18.90±2.07) mg vs (13.83±1.81) mg vs (3.78±0.41) mg, F values was 236.089, 224.139, 183.971, respectively, all P<0.001). Statistically significant differences in OVA specific IgE, IL-6 and TNF-ɑ levels were observed in ARE group exceeded AR group and NC group (OVA specific IgE (25.42±2.51) ng/ml vs (18.07±1.07) ng/ml vs (1.47±0.26) ng/ml, IL-6 (123.30±18.86) pg/ml vs (63.49±11.29) pg/ml vs (16.87±3.29) pg/ml, TNF-ɑ (162.50±38.15) pg/ml vs (72.96±11.28) pg/ml vs (27.52±4.15) pg/ml, F values was 481.604, 138.277, 63.938, respectively, all P<0.001). HE staining showed that the nasal epithelial cells of NC group were intact and neatly arranged. Nasal mucosa epithelial cells were arranged in disorder in AR group, with tissue structure swelling. Partial shedding of nasal epithelial cells, mucosal basement membrane thickening, submucosal tissue interstitial edema, vasodilation and gland hyperplasia were found in ARE group.@*Conclusion@#An increase inflammatory factors level such as IL-6 and TNF-ɑ aggravates pathological damage of nasal mucosa in a rat model of AR by exposure to PM2.5.
ABSTRACT
Objective@#To explore the role of autophagy in PM2.5-induced inflammation in human nasal epithelial cells and related mechanism.@*Methods@#Human nasal epithelial cells were exposed to different concentration of PM2.5 for different times, and the expression levels of microtubule-associated protein-1 light chain-3 Ⅱ (LC3 Ⅱ) and Beclin1 proteins were measured by Western blot. The typical autophagosome and autolysosome were observed by using transmission electron microscopy (TEM). To observe autophagic flux, mRFP-GFP-LC3 plasmid was transfected to nasal epithelial cells and the punctate staining of mRFP-GFP-LC3 were determined by confocal laser scanning microscope. The expression of inflammatory cytokines interleukin 6 (IL-6) and tumor necrosis factor-α (TNF-α) in cell culture supernatant were assessed by enzyme-linked immunosorbent assay (ELISA). To assess the role of autophagy in PM2.5-mediated inflammation, autophagy related gene Atg5 and Beclin-1 were silenced by siRNA knockdown, and inflammatory cytokines were analyzed.GraphPad Prism 6.0 was used for statistical analysis.@*Results@#PM2.5 exposure increased the expression of LC3 Ⅱ and Beclin-1 proteins in a dose- (in PM2.5 group with concentration of 0, 15, 30, 60, 120 μg/ml, the expression of LC3 Ⅱ was 0.021±0.001(±s), 0.037±0.002, 0.058±0.005, 0.075±0.006, 0.085±0.004, respectively, F=126.8, P<0.05; the expression of Beclin-1 was 0.002±0.000, 0.003±0.000, 0.005±0.000, 0.007±0.001, 0.008±0.001, respectively, F=137.3, P<0.05) and time-dependent manner (in PM2.5 group with exposure time of 0, 3, 6, 12, 24 h, the expression of LC3Ⅱ was 0.160±0.007, 0.222±0.003, 0.251±0.015, 0.483±0.029, 0.585±0.035, respectively, F=215.3, P<0.05; the expression of Beclin-1 was 0.059±0.002, 0.080±0.002, 0.087±0.002, 0.183±0.007, 0.228±0.005, respectively, F=137.3, P<0.05) in human nasal epithelial cells. TEM analysis showed typical autophagosome and autolysosome in cells after PM2.5 exposure for 24 h. PM2.5 significantly increased the number of yellow and red dots representing autophagosomes and autolysosomes respectively, indicating autophagic flux was elevated. Moreover, PM2.5 enhanced the secretion of inflammatory cytokines such as IL-6 and TNF-α, which was dramatically prevented by Atg5-siRNA and Beclin-1-siRNA.@*Conclusion@#Autophagy plays an important role in PM2.5-caused inflammation response in nasal epithelial cells, which can induce release of inflammatory factors such as IL-6 and TNF-α and advance the inflammatory reaction.