Objective: To compare the different methods of inducing the formation of macrophage extracellular trap (MET) in vitro.
Methods: MET release was initiated by culturing RAW264.7 cells with 0.5, 1, 5, 10 μg/mL lipopolysaccharide (LPS), or 10, 25, 50, 80 μmol/L phorbolmyristate acetate (PMA), or 50, 100, 150 μg/mL silicon dioxide (SiO2). Three and 6 hours later, MET were validated by immunofluorescence staining, followed by immunofluorescence-based semi-quantitative analysis.
Results: Immunofluorescence staining showed that the network structures were mainly composed of DNA and histones. RAW264.7 cells treated with 1 μg/mL LPS for 6 hours produced the highest percent of MET [(37.04±10.02)%], which was statistically higher compared with control group [(7.90±2.71)%]. RAW264.7 cells treated with 80 μmol/L PMA for 6 hours also produced the higher percent of MET [(22.40±1.83)%] compared with control group [(10.11±1.13)%]. However, there was no significantly increased MET formation in cells treated with SiO2 compared with control group.
Conclusion: LPS and PMA can induce MET formation in vitro, while SiO2 was not efficient inducer.