title: GATA-3 transduces survival signals in osteoblasts through upregulation of bcl-x(L) gene expression.
abstract: GATA-3, a transcription factor, participates in regulating cell development, proliferation, and death. This study was aimed at evaluating the roles of GATA-3 in protecting osteoblasts against oxidative stress-induced apoptotic insults and their possible mechanisms. Pretreatment with nitric oxide (NO) for 24 hours protected osteoblasts, prepared from neonatal rat calvaria, against oxidative stress-induced apoptotic insults. Such protection involved enhancement of Bcl-X(L) messenger mRNA and protein syntheses and the translocation of this antiapoptotic protein from the cytoplasm to mitochondria. GATA-3 was detected in rat osteoblasts, and GATA-3-specific DNA-binding elements exist in the promoter region of the bcl-x(L) gene. NO preconditioning attenuated oxidative stress-caused suppression of GATA-3 mRNA and protein synthesis and the translocation of this transcription factor from the cytoplasm to nuclei. Application of GATA-3 small interfering siRNA into osteoblasts decreased the levels of this transcription factor and simultaneously inhibited Bcl-X(L) mRNA synthesis. Pretreatment with NO lowered the oxidative stress-caused alteration in the binding of GATA-3 to its specific DNA motifs. Oxidative stress-inhibited Runx2 mRNA expression, but NO preconditioning decreased such inhibition. NO pretreatment time-dependently enhanced the association of GATA-3 with Runx2. Knocking down the translation of GATA-3 using RNA interference significantly decreased the protection of NO preconditioning against oxidative stress-induced alterations of cell morphologies, DNA fragmentation, and cell apoptosis. In comparison, overexpression of GATA-3 could promote NO preconditioning-involved Bcl-X(L) expression and cell survival. Therefore, this study shows that GATA-3 plays critical roles in mediating survival signals in osteoblasts, possibly through upregulating bcl-x(L) gene expression.
authors.affiliation: Graduate Institute of Medical Sciences, College of Medicine, Taipei Medical University, Taipei, Taiwan. rmchen@tmu.edu.tw
authors.forename: Ruei-Ming
authors.initials: RM
authors.lastname: Chen
authors.forename: Yi-Ling
authors.initials: YL
authors.lastname: Lin
authors.forename: Chih-Wei
authors.initials: CW
authors.lastname: Chou
mesh_terms: D000818:Animals; D001483:Base Sequence; D015153:Blotting, Western; D002478:Cells, Cultured; D017931:DNA Primers; D024202:Electrophoretic Mobility Shift Assay; D050990:GATA3 Transcription Factor / Q000235:genetics / Q000502:physiology*; D055785:Gene Knockdown Techniques; D047468:Immunoprecipitation; D018613:Microscopy, Confocal; D010006:Osteoblasts / Q000378:metabolism*; D018384:Oxidative Stress; D016133:Polymerase Chain Reaction; D034741:RNA, Small Interfering; D051381:Rats; D017208:Rats, Wistar; D015398:Signal Transduction; D015854:Up-Regulation; D051020:bcl-X Protein / Q000235:genetics*
chemical_list: D017931:DNA Primers; D050990:GATA3 Transcription Factor; D034741:RNA, Small Interfering; D051020:bcl-X Protein