title: 6-Mercaptopurine, an activator of Nur77, enhances transcriptional activity of HIF-1alpha resulting in new vessel formation.
abstract: Hypoxia-inducible factor-1alpha (HIF-1alpha) plays a central role in oxygen homeostasis. Previously, we reported that the orphan nuclear receptor Nur77 functions in stabilizing HIF-1alpha. Here, we demonstrate that 6-mercaptopurine (6-MP), an activator of the NR4A family members, enhances transcriptional activity of HIF-1. 6-MP enhanced the protein-level of HIF-1alpha as well as vascular endothelial growth factor (VEGF) in a dose- and time-dependent manner. The induction of HIF-1alpha was abolished by the transfection of either a dominant-negative Nur77 mutant or si-Nur77, indicating a critical role of Nur77 in the 6-MP action. The HIF-1alpha protein level remained up to 60 min in the presence of 6-MP when de novo protein synthesis was blocked by cycloheximide, suggesting that 6-MP induces stabilization of the HIF-1alpha protein. The fact that 6-MP decreased the association of HIF-1alpha with von Hippel-Lindau protein and the acetylation of HIF-1alpha, may explain how 6-MP induced stability of HIF-1alpha. Further, 6-MP induced the transactivation function of HIF-1alpha by recruiting co-activator cyclic-AMP-response-element-binding protein. Finally, 6-MP enhanced the expression of HIF-1alpha and VEGF, and the formation of capillary tubes in human umbilical vascular endothelial cells. Together, our results provide a new insight for 6-MP action in the stabilization of HIF-1alpha and imply a potential application of 6-MP in hypoxia-associated human vascular diseases.
authors.affiliation: College of Pharmacy, Seoul National University, Seoul, Korea.
authors.forename: Y-G
authors.initials: YG
authors.lastname: Yoo
authors.forename: T-Y
authors.initials: TY
authors.lastname: Na
authors.forename: W-K
authors.initials: WK
authors.lastname: Yang
authors.forename: H-J
authors.initials: HJ
authors.lastname: Kim
authors.forename: I-K
authors.initials: IK
authors.lastname: Lee
authors.forename: G
authors.initials: G
authors.lastname: Kong
authors.forename: J-H
authors.initials: JH
authors.lastname: Chung
authors.forename: M-O
authors.initials: MO
authors.lastname: Lee
mesh_terms: D045744:Cell Line, Tumor; D004268:DNA-Binding Proteins / Q000187:drug effects* / Q000378:metabolism; D006801:Humans; D051795:Hypoxia-Inducible Factor 1, alpha Subunit / Q000187:drug effects* / Q000378:metabolism; D007166:Immunosuppressive Agents / Q000494:pharmacology*; D015122:Mercaptopurine / Q000494:pharmacology*; D018919:Neovascularization, Physiologic / Q000187:drug effects*; D057105:Nuclear Receptor Subfamily 4, Group A, Member 1; D018160:Receptors, Cytoplasmic and Nuclear / Q000187:drug effects* / Q000378:metabolism; D011987:Receptors, Steroid / Q000187:drug effects* / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014157:Transcription Factors / Q000187:drug effects* / Q000378:metabolism; D014158:Transcription, Genetic; D014162:Transfection; D042461:Vascular Endothelial Growth Factor A / Q000187:drug effects / Q000378:metabolism
chemical_list: D004268:DNA-Binding Proteins; C497442:HIF1A protein, human; D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D007166:Immunosuppressive Agents; C539821:NR4A1 protein, human; D057105:Nuclear Receptor Subfamily 4, Group A, Member 1; D018160:Receptors, Cytoplasmic and Nuclear; D011987:Receptors, Steroid; D014157:Transcription Factors; D042461:Vascular Endothelial Growth Factor A; D015122:Mercaptopurine