Figure. The chemotactic effect of NAP3 on THP-1 cells.
Neutrophil-activating protein 3 (NAP3) also known as chemokine (C-X-C motif) ligand 1 (CXCL1) is a small cytokine belonging to the CXC chemokine family. NAP3 is expressed by macrophages, neutrophils and epithelial cells,and has neutrophil chemoattractant activity. Thus, chemotaxis assay used 24-well microchemotaxis system was undertaken to detect the chemotactic effect of NAP3 on the human monocytic cell line THP-1. Briefly, THP-1 cells were seeded into the upper chambers (100uL cell suspension, 106 cells/mL in RPMI 1640 with FBS free) and SLC (31.25ng/mL, 62.5ng/mL ,125ng/mL and 250ng/mL diluted separately in serum free RPMI 1640) was added in lower chamber with a polycarbonate filter (8µm pore size) used to separate the two compartments. After incubation at 37℃ with 5% CO2 for 1h, the filter was removed, then cells in low chamber were observed by inverted microscope at low magnification (×100) and the number of migrated cells were counted at high magnification (×400) randomly (five fields for each filter). Result shows NAP3 is able to induce migration of THP-1 cells. The migrated THP-1 cells in low chamber at low magnification (×100) were shown in Figure 1. Five fields of each chamber were randomly chosen, and the migrated cells were counted at high magnification (×400). Statistical results were shown in Figure 2. The optimum chemotaxis of NAP3 occurs at 31.25-250ng/mL.
(A) THP-1 cells were seeded into the upper chambers and serum free RPMI 1640 with 62.5ng/mL NAP3 was added in lower chamber, then cells in lower chamber were observed at low magnification (×100) after incubation for 1h;
(B) THP-1 cells were seeded into the upper chambers and serum free RPMI 1640 without NAP3 was added in lower chamber, then cells in lower chamber were observed at low magnification (×100) after incubation for 1h.

Figure.The chemotactic effect of NAP3 on THP-1 cells.