Endoplasmic reticulum stress regulates autophagy and tumor necrosis factor-α secretion of RAW264.7 cells induced by silica

Abstract

Objective: To investigate the role of endoplasmic reticulum stress (ERS) in the autophagy of RAW264.7 cells induced by SiO(2) and its effect on the secretion of tumor necrosis factor-α. Methods: RAW264.7 cells stimulated by 200 μg/ml SiO(2) were used as an vitro cell model, and different treatment times of SiO(2) were used as variables. They were divided into 0 h treatment group (blank control group) , 6 h, 12 h, 24 h, and 48 h treatment group. The formation of autophagospores was detected by acridine orange and mondane-sulfonate (MDC) staining. Application of real-time quantitative PCR (Real-time PCR) to detect autophagy related molecular Beclin1 mRNA expression and protein immunoblot (Western Blotting) detecting autophagy related proteins LC3Ⅰ, LC3Ⅱ and expression of Beclin1. Real-time PCR and Western blotting were used to detect the expression of ERS specific marker BiP. Secretion of RAW 264.7 cell transforming growth factor-β1 (TGF-β1) and tumor necrosis factor-α (TNF-α) was detected by enzyme-linked immunosorbent assay (ELISA) . ERS inhibitors 4-PBA intervention experiment, including blank control group, SiO(2), 1 μmol/L 4-PBA+SiO(2), 10 μmol/L 4-PBA+SiO(2), 20 μmol/L 4-PBA+SiO(2) treatment group, Western blotting testing LC3Ⅰ, LC3Ⅱ and expression of Beclin1 changes. Results: Compared with the control group, SiO(2)-induced fluorescence intensity in RAW264.7 cells was significantly increased, with statistically significant differences (P<0.05) . Compared with control group, with SiO(2) processing time prolonged, LC3Ⅰ, LC3Ⅱ Beclin1 mRNA and protein expression and protein expression increased, 6 h, 24 h, the height of the differences were statistically significant (P<0.05) ; Compared with the control group, the mRNA and protein expression level of BiP reached the peak for 6 h, and the expression level in 6 h, 12 h and 24 h groups increased significantly, and the difference was statistically significant (P<0.05) . Compared with the SiO(2) stimulation group, the LC3Ⅱand Beclin 1 protein levels of RAW264.7 cells were gradually down-regulated by increasing the dose of 4-PBA. With the increase of 4-PBA concentration, the down-regulated levels were more significant, and the difference was statistically significant (P<0.05) . Compared with the SiO(2) stimulation group, the TNF-α secretion level of RAW264.7 cells significantly decreased of 1, 10, 20 μmol/L 4-PBA+SiO(2) treatment group, and the difference was statistically significant (P<0.05) . Conclusion: ERS induced by SiO(2) is involved in the secretion of autophagy and TNF-α in RAW264.7 cells.