Imilarly, a TUNEL assay revealed approximately 75 fewer apoptotic cells in the lungs of the ApoA1-overexpressing mice compared with the lungs of the Silica group mice (Fig. 6B). Double-labeled immunofluorescence demonstrated that the majority of apoptotic cells were alveolar epithelial cells and macrophages (Figure S2).Effect of ApoA1 on Silica-induced Increased ProDimethylenastron inflammatory Mediators in Mouse LungTo determine whether ApoA1 inhibits the increase of the proinflammatory cytokines and chemokines that accumulate from macrophages and neutrophils stimulated by silica, mRNA levels of interleukin-1?(IL-1?, tumor necrosis factor-a (TNF-a), monocyte chemotactic protein-1 (MCP-1), macrophage inflammatory protein-2 (MIP-2) and chemokine (C-X-C motif) ligand 1 (CXCL1, synonym KC) in the lungs were measured. All of the measured levels of proinflammatory mediator mRNAs in the ApoA1_D7 and D15 group were significantly decreased compared with those in the Silica group (Fig. 7).Effect of ApoA1 Overexpression on Lipid Mediator of InflammationGiven the important role of lipid mediators in the initiation, 18325633 maintenance, and resolution of inflammation, the levels of antiinflammatory LXA4 were measured in the lungs of silica-treated ApoA1_D7 and D15 mice. ApoA1 overexpression was associated with increased levels of LXA4 in the lung parenchyma and BAL fluid (Fig. 5).Effect of ApoA1 on Silica-induced Apoptosis in Mouse LungTo determine whether ApoA1 inhibited silica-induced apoptosis, we measured the levels of caspase-3 expression in the lungs. Levels of caspase-3 protein were increased in the Silica group compared with the sham-exposed controls. The levels of activeEffect of Doxycycline on Silica-induced Lung Inflammation and Fibrosis in Mouse LungDoxycycline reportedly has an anti-fibrotic effect on bleomycininduced experimental fibrosis [21]. To determine whetherFigure 5. Quantification of LXA4 levels in the lung parenchyma(A) and BAL fluid(B) of the ApoA1 transgenic mice. *p,0.05 compared with the Silica group (D30). doi:10.1371/journal.pone.0055827.gApoA1 Attenuated Silica Induced Lung FibrosisFigure 6. Quantification of silica-induced apoptosis in the lungs of the ApoA1 transgenic mice. (A) Immunoblot analysis showed that active form of caspase-3 protein expression was significantly decreased in the ApoA1_D7 and D15 groups compared with the Silica group. **p,0.01 compared with the Silica group (D30). *p,0.05 compared with the Silica group (D30). (B) Tissues stained by the TUNEL method were observed at 6100 magnification, and the number of TUNEL-positive cells in a minimum of 20 fields per lung was counted (n = 8 mice/group). **p,0.01 compared with the Silica group (D15 and D30). doi:10.1371/journal.pone.0055827.gtreatment with doxycycline contributed to the anti-fibrotic effect on ApoA1 transgenic mice, silica was administered intratracheally to the UBC-GFP transgenic mice with or without doxycyclinecontaining water. The histologic findings showed severe peribronchial nodules, inflammatory cell accumulation, and interstitial edema in both the silica-exposed doxycycline mice and those fed drinking water that did not contain doxycycline (Figure S3A). The total numbers of inflammatory cells, macrophages, neutrophils, and lymphocytes in the BAL fluid were not different between the two groups (Figure S3B). Silica induced increased amounts of lung-soluble collagen, and the granuloma fractions were not decreased by doxycycline treatment (Figure S3C, D).Discuss.