OBJECTIVETo study and compare the effect of neutrophil elastase inhibitors (GW311616A and sivelestat) on the proliferation and apoptosis of U937 cells.

METHODSInhibitory effects of GW311616A and sivelestat on the proliferation of U937 cells were assayed by MTT assay. The morphologic changes of U937 cells were detected by transmission electron microscope, and apoptosis was observed by AnnexinV-FITC/PI staining. The changes of cell cycle and apoptosis were detected by flow cytometry. The expression of NE in U937 cells was observed by indirect immunofluorescence, the variations of content and activity of NE in U937 cells were measured through ELISA assay and colorimetric method.

RESULTSMTT showed that both NE inhibitors could inhibit the proliferation of U937 cells in a dose dependent manner. The IC50 of GW311616A and sivelestat were 150 and 214 μmol/L respectively. The inhibition effect of GW311616A was significantly higher than of sivelestat (P<0.01). Typical apoptosis morphological changes of U937 cells was observed through electron microscope. AnnexinV-FITC/PI staining showed that U937 cells could be induced to undergo apoptosis by the two inhibitors, the apoptosis ratio of 150μmol/L GW311616A group (13.60%) was significantly higher than that of 150μmol/L sivelestat group (3.69%)(P<0.01). The result of flow cytometry indicated that the apoptosis ratio of 150 μmol/L GW311616A group was 14.61%, U937 cell cycle was mainly blocked in G2/M phase; meanwhile 150 μmol/L sivelestat group as 4.25% with cell cycle in S phase. The fluorescence intensity of GW311616A group obviously decreased than of sivelestat group. And the two inhibitors could reduce the content and activity of NE in U937 cells, but the effect of GW311616A was significantly higher than of sivelestat (P<0.01).

CONCLUSIONGW311616A and sivelestat could inhibit the proliferation and cause apoptosis of U937 cells. Furthermore, GW311616A was more effective and harmful to cells than sivelestat.