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Objective We investigated the role of endoplasmic reticulum stress(ERS) in silica-induced apoptosis in alveolar macrophages in vitro. Methods RAW264.7 cells were incubated with 200 μg/mL silica for different time periods. Cell viability was assayed by the MTT assay. Cell apoptosis was evaluated by DAPI staining, flow cytometry analysis, and Western blot analysis of caspase-3. Morphological changes in the endoplasmic reticulum were observed by transmission electron microscopy. The expression of ERS markers binding protein(BiP) and CCAAT-enhancer-binding protein homologous protein(CHOP) was examined by Western blotting and real-time PCR. As an inhibitor of ERS, 4-phenylbutyric acid(4-PBA) was used in the experiments. Results Silica exposure induced nuclear condensation and caspase-3 expression in RAW264.7 cells. The number of apoptotic cells increased after silica exposure in a time-dependent manner. Silica treatment induced expansion of the endoplasmic reticulum. In addition, the expression of BiP and CHOP increased in silica-stimulated cells. Furthermore, 4-PBA treatment inhibited silica-induced endoplasmic reticulum expansion and the expression of Bi P and CHOP. Moreover, 4-PBA treatment attenuated nuclear condensation, reduced apoptotic cells, and downregulated caspase-3 expression in silica-stimulated cells. Conclusion Silica-induced ERS is involved in the apoptosis of alveolar macrophages.
Methods We performed the role of endoplasmic reticulum stress (ERS) in silica-induced apoptosis in alveolar macrophages in vitro. Methods RAW264.7 cells were incubated with 200 μg / mL silica for different time periods. Cell viability was assayed by the MTT assay. Cell apoptosis was evaluated by DAPI staining, flow cytometry analysis, and Western blot analysis of caspase-3. Morphological changes in the endoplasmic reticulum were observed by transmission electron microscopy. The expression of ERS markers binding protein (BiP) and CCAAT-enhancer-binding As a inhibitor of ERS, 4-phenylbutyric acid (4-PBA) was used in the experiments. Results Silica exposure induced nuclear condensation and caspase-3 expression in The number of apoptotic cells increased after silica exposure in a time-dependent manner. In addition, the expre ssion of BiP and CHOP increased in silica-stimulated cells. Furthermore, 4-PBA treatment performed silica-induced endoplasmic reticulum expansion and the expression of Bi P and CHOP. Furthermore, 4-PBA treatment attenuated nuclear condensation, reduced apoptotic cells, and downregulated The caspase-3 expression in silica-stimulated cells. Conclusion Silica-induced ERS is involved in the apoptosis of alveolar macrophages.