Nitrosative stress induces osteoblast apoptosis through downregulating MAPK-mediated NFkappaB/AP-1 activation and subsequent Bcl-X(L) expression.
During inflammation, a large amount of reactive oxygen species is produced and causes insults to osteoblasts. This study was aimed to evaluate the molecular mechanisms of sodium nitroprusside (SNP)-induced insults to rat osteoblasts. Exposure of osteoblasts, prepared from neonatal rat calvaria to SNP increased the levels of cellular nitric oxide and intracellular reactive oxygen species, and simultaneously induced apoptotic insults in concentration- or time-dependent manners. Exposure of rat osteoblasts to SNP time-dependently decreased antiapoptotic Bcl-X(L) messenger RNA and protein syntheses. Treatment of rat osteoblasts with SNP decreased the translocation of transcription factors nuclear factor-kappaB (NFkappaB) and activator protein (AP)-1 from the cytoplasm to nuclei. Sequentially, phosphorylations of the mitogen-activated protein kinases (MAPKs) of ERK1/2, JNK1/2, and p38 MAPK decreased following SNP administration. Application of ERK1 and JNK1 small interference (si)RNAs into rat osteoblasts decreased the translation of these MAPKs and synergistically enlarged SNP-caused alterations in Bcl-X(L) mRNA expression and cell apoptosis. Therefore, this study shows that the SNP-induced nitrosative stress decreased Bcl-X(L) expression, and then induced apoptotic insults to rat osteoblasts through downregulating phosphorylation of MAPKs and subsequent activation of NFkappaB and AP-1.
Department of Anesthesiology, Taipei Medical University, Taipei, Taiwan.
Ta-Liang
TL
Chen
Gong-Jhe
GJ
Wu
Chun-Sen
CS
Hsu
Tsorng-Harn
TH
Fong
Ruei-Ming
RM
Chen
D000818:Animals; D017209:Apoptosis; D015536:Down-Regulation; D048052:Mitogen-Activated Protein Kinase 3 / Q000378:metabolism; D048055:Mitogen-Activated Protein Kinase 8 / Q000378:metabolism; D048056:Mitogen-Activated Protein Kinase 9 / Q000378:metabolism; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism*; D016328:NF-kappa B / Q000378:metabolism*; D009569:Nitric Oxide / Q000378:metabolism; D020030:Nitric Oxide Donors / Q000494:pharmacology; D009599:Nitroprusside / Q000494:pharmacology; D015538:Nitrosation; D010006:Osteoblasts / Q000187:drug effects / Q000378:metabolism*; D018384:Oxidative Stress / Q000187:drug effects; D010766:Phosphorylation; D034741:RNA, Small Interfering / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D017382:Reactive Oxygen Species / Q000378:metabolism; D018808:Transcription Factor AP-1 / Q000378:metabolism*; D051020:bcl-X Protein / Q000235:genetics / Q000378:metabolism*; D048051:p38 Mitogen-Activated Protein Kinases / Q000378:metabolism
D016328:NF-kappa B; D020030:Nitric Oxide Donors; D034741:RNA, Small Interfering; D017382:Reactive Oxygen Species; D018808:Transcription Factor AP-1; D051020:bcl-X Protein; D009599:Nitroprusside; D009569:Nitric Oxide; D048056:Mitogen-Activated Protein Kinase 9; D048052:Mitogen-Activated Protein Kinase 3; D048055:Mitogen-Activated Protein Kinase 8; D020928:Mitogen-Activated Protein Kinases; D048051:p38 Mitogen-Activated Protein Kinases