Monocytes reduce the inflammatory response induced by necrotic lung cells and DOTAP liposomes via PGE2 production. (A-C) Intracellular cytokine staining for TNF-α produced by neutrophils (CD45+CD11b+Ly6G+) stimulated with necrotic lung cells or mtDNA and cultured with control medium or monocytes. Numbers represent the percentage of cells in each gate. (D) TNF-α produced by neutrophils stimulated with necrotic lung cells and treated with increasing concentrations of purified PGE2 (n=3). (E) TNF-α produced by neutrophils stimulated with mtDNA and treated with increasing concentrations of purified PGE2 (n=3). (F) TNF-α produced by neutrophils (CD45+CD11b+Ly6G+) in the lungs of mice injected with DOTAP liposomes and treated with increasing concentrations of diMePGE2 (n=3). (G) TNF-α produced by neutrophils stimulated by necrotic lung cells and cultured with monocytes or indomethacin (indo; 10 μM) (n=3). (H) Monocytes from bone marrow were stimulated with mtDNA for 20 h in the presence of indomethacin or vehicle and were injected into DOTAP liposome-treated mice. TNF-α production by neutrophils (CD45+CD11b+Ly6G+) in the lungs was analysed by flow cytometry (n=3). (I)
WT and IL-10-/- monocytes were isolated from C57BL/6 and IL-10-/-mouse bone marrow. EIA test for PGE2 in the supernatants from WT monocytes, IL-10-/- monocytes and control medium (n=3). (J) TNF-α expression in inflammatory neutrophils (CD45+CD11b+Ly6G+) stimulated with mtDNA for 4 h and cultured with WT monocytes, IL-10-/- monocytes and IL-10-/- monocytes treated with indomethacin (10 μM), as determined by flow cytometry (n=3). (K-L) After being stimulated with mtDNA for 20 h, WT monocytes, IL-10-/- monocytes and IL-10-/- monocytes treated with indomethacin (10 μM) were injected into C57BL/6 mice after DOTAP liposome administration. Mice were sacrificed 48 h after the injection; the number of monocytes (CD45+CD11b+Ly6C+) in the lung and the TNF-α produced by neutrophils were determined by flow cytometry (n=3). Data represent three independent experiments, and the results are expressed as the mean ± S.E.M. Statistical comparisons were performed using Student's t-test or Dunnet's t-test (*P<0.05; **P<0.01; ***P<0.005)