title: Interleukin-1beta regulates angiopoietin-1 expression in human endothelial cells.
abstract: Angiopoietin (Ang)-1 is an important regulator of endothelial cell (EC) survival and stabilization. Ang-1 exerts its biological effects by binding to the EC-specific tyrosine kinase receptor Tie-2, and initiates intracellular signaling in ECs. However, regulatory mechanisms for endothelial Ang-1 expression have not been completely elucidated. In this study, we investigated the effects of angiogenic cytokines and growth factors on Ang-1 expression in human umbilical vein ECs (HUVECs). Northern blot analysis was performed after HUVECs were exposed to interleukin-1beta (IL-1beta), tumor necrosis factor-alpha, platelet-derived growth factor-BB, insulin-like growth factor-1, or vascular endothelial growth factor (VEGF). Both IL-1beta and tumor necrosis factor-alpha caused marked down-regulation of Ang-1 mRNA levels at 4 h with a further decrease observed at 24 h. Using signaling inhibitors, we identified the P38 pathway as the pathway that mediates IL-1beta down-regulation of Ang-1. Furthermore, treatment of cells with IL-1beta indirectly (via down-regulation of Ang-1) led to a decrease in Tie-2 autophosphorylation levels in HUVECs. We previously demonstrated that IL-1beta regulates VEGF expression in tumor cells. This observation was confirmed in ECs in the present study. Because pericytes play a role in regulating EC function, we also determined whether IL-1beta would also down-regulate Ang-1 in human vascular smooth muscle cells. Similar to our findings in HUVECs, we found that IL-1beta decreased Ang-1 expression in human vascular smooth muscle cells. Direct effects of IL-1beta on angiogenesis were investigated by use of an in vivo Gelfoam angiogenesis assay in which IL-1beta produced a significant increase in vessel counts (P = 0.0189). These results suggest that IL-1beta indirectly regulates angiogenesis by modulating the expression of Ang-1. IL-1beta may trigger a proangiogenic response by decreasing Ang-1 levels in ECs and pericytes and up-regulating VEGF in ECs and tumor cells.
authors.affiliation: Department of Cancer Biology, The University of Texas M. D. Anderson Cancer Center, Houston, Texas 77030-4009, USA.
authors.forename: Fan
authors.initials: F
authors.lastname: Fan
authors.forename: Oliver
authors.initials: O
authors.lastname: Stoeltzing
authors.forename: Wenbiao
authors.initials: W
authors.lastname: Liu
authors.forename: Marya F
authors.initials: MF
authors.lastname: McCarty
authors.forename: Young D
authors.initials: YD
authors.lastname: Jung
authors.forename: Niels
authors.initials: N
authors.lastname: Reinmuth
authors.forename: Lee M
authors.initials: LM
authors.lastname: Ellis
mesh_terms: D042683:Angiopoietin-1 / Q000096:biosynthesis* / Q000235:genetics; D000818:Animals; D002478:Cells, Cultured; D004730:Endothelium, Vascular / Q000187:drug effects* / Q000378:metabolism* / Q000502:physiology; D005786:Gene Expression Regulation / Q000187:drug effects / Q000502:physiology; D006801:Humans; D007375:Interleukin-1 / Q000494:pharmacology* / Q000502:physiology; D008297:Male; D051379:Mice; D008807:Mice, Inbred BALB C; D018919:Neovascularization, Physiologic / Q000187:drug effects / Q000502:physiology; D010766:Phosphorylation / Q000187:drug effects; D012333:RNA, Messenger / Q000096:biosynthesis / Q000235:genetics; D042787:Receptor, TIE-2 / Q000378:metabolism; D042461:Vascular Endothelial Growth Factor A / Q000096:biosynthesis / Q000235:genetics
chemical_list: C467630:ANGPT1 protein, human; D042683:Angiopoietin-1; D007375:Interleukin-1; D012333:RNA, Messenger; D042461:Vascular Endothelial Growth Factor A; D042787:Receptor, TIE-2