Effect of Escherichia coli infection on cell apoptosis of human macrophage cell line U937

Objective: To study the relationship between Escherichia coli ( E. coli ) infection and cell apoptosis of human macrophage cell line U937. Methods: The U937 apoptosis induced by E. coli infection was detected with Annexin V FITC/PI assay, Hoechst 33258 fluorochrome staining, and Giemsa staining. Results: Giemsa staining showed that few apoptotic U937 cells were found 10 and 20 minutes after E. coli infection (U937: E.coli =1∶20), and U937 cells underwent typical apoptotic changes including karyopyknosis, condensation, swelling, and apoptotic bodies 30, 60 and 90 minutes later. Annexin V FITC/PI assay showed that the percentage of apoptotic U937 cells increased with the progression of the E. coli infection. Hoechst 33258 fluorochrome staining and Annexin VFITC/PI assay showed that the percentage of apoptotic U937 cells increased with the concentrations of E.coli . Conclusion: E. coli could induce U937 apoptosis in a dose-and time-dependent manner.