Using global gene expression patterns to characterize Annexin V positive and negative human monocytes in culture

Abstract

Objective. To investigate the early apoptosis that may be detected by Annexin V binding to phosphatidylserine and propidium iodide (PI) exclusion in human monocytes. When studying monocytes in culture, less than 40 % of these cells survive after 7 days. Material and methods. In the first 4 h, 24 % of monocytes in culture develop into Annexin V⁺/PI⁻ cells. Human monocytes were investigated at 0 h and sorted into Annexin V⁺ and Annexin V⁻ by FACS after 4 h. Gene expression was examined by microarray analyses. Results. At 4 h, Annexin V⁺ monocytes versus Annexin V⁻ cells showed 1220 differentially expressed genes. Ingenuity Pathway Analysis disclosed 153 genes related to cell death. Among these were caspase activators, caspase 6, Apaf 2 and FAS, as well as the autophagy gene ATG5. In addition, examination of the most up‐regulated or down‐regulated genes among the 1220 revealed genes involved in other biological processes, as well as genes not yet annotated. These included the non‐annotated genes LOC28480 (fold change: 82) and 225767‐at (fold change: 68) and the transcription factor SOX 4 (fold change: 24). Conclusions. We suggest that apoptosis in cultured monocytes, as evidenced by Annexin V⁺, operates through genes well known in apoptosis, but that the process also involves additional genes not commonly associated with apoptosis.

• Apoptosis
• microarray
• monocytes/macrophages
• sorting flow cytometry