Identification of specifically activated angiogenic molecules in HMGB-1-induced angiogenesis

High-mobility group box-1 (HMGB-1), a nonhistone chromosomal protein, is expressed in almost all types of cells with nucleus, and dysregulation of its expression correlates with pathological conditions such as inflammatory diseases, ischemia and cancers. Some of these conditions accompany abnormal angiogenesis induced by HMGB-1 mediated activation of downstream signaling pathways. So far, the underlying mechanism by which HMGB-1 induces angiogenesis remains largely unknown. In this study, we performed time-dependent gene expression microarray in endothelial cells (ECs) after HMGB-1 or VEGF treatment. By pathway analysis using each gene set up-regulated by HMGB-1 or VEGF, we found that most of HMGB-1 induced angiogenic pathways were also commonly activated by VEGF, while activation time and gene sets belonging to the pathways were different. In addition, HMGB-1 up-regulated some VEGFR signaling related conventional angiogenic factors including EGR1 and importantly, novel angiogenic factors such as ABL2, CEACAM1, KIT and VIPR1 which have been reported to independently promote angiogenesis in physiological and pathological conditions. Our gene expression profiling suggests that HMGB-1 is capable of independently inducing angiogenesis through activation of HMGB-1 specific angiogenic factors and also functions as an accelerator for VEGF mediated conventional angiogenesis according to physiological and pathological condition. Primary human umbilical vein endothelial cells (HUVECs) were treated with recombinant HMGB-1 at 1 µg/mL and recombinant VEGF at 50 ng/mL for 20 minutes, 45 minutes, 2 hours, 6 hours, or 12 hours.