title: Quercetin accelerates TNF-alpha-induced apoptosis of MC3T3-E1 osteoblastic cells through caspase-dependent and JNK-mediated pathways.
abstract: The bioflavonoid, quercetin, is believed to inhibit bone loss by regulating many systemic and local factors including hormones and cytokines. However, our previous findings revealed that quercetin did not inhibit but facilitate the tumor necrosis factor (TNF)-alpha-mediated apoptosis of MC3T3-E1 osteoblastic cells. Therefore, this study was carried out to examine the cellular mechanisms for how quercetin accelerates TNF-alpha-mediated apoptosis, and to determine whether the accelerating effect of quercetin is a general effect in osteoblastic cells. Quercetin promoted the TNF-alpha-induced apoptosis of MC3T3-E1 cells through both the mitochondrial-mediated and caspase-dependent mechanisms. Quercetin also augmented the TNF-alpha-mediated apoptosis by activating c-Jun N-terminal kinase (JNK) with the attendant activation of activator protein-1, where the nuclear translocation of c-Jun protein appeared to be a critical event responsible for the accelerating action of quercetin. However, TNF-alpha-mediated apoptosis and its acceleration by quercetin were not observed in primary osteoblasts. These results strongly suggest that quercetin accelerates TNF-alpha-mediated apoptosis of osteoblasts through caspase-dependent and JNK-mediated pathways, and that the cellular responses of osteoblasts to TNF-alpha and/or quercetin might differ according to their origins.
authors.affiliation: Laboratory of Cell Biology in Department of Orthodontics and Institute of Oral Biosciences, Chonbuk National University, Jeonju 561-756, Republic of Korea.
authors.forename: Young-Ok
authors.initials: YO
authors.lastname: Son
authors.forename: Sung-Ho
authors.initials: SH
authors.lastname: Kook
authors.forename: Ki-Choon
authors.initials: KC
authors.lastname: Choi
authors.forename: Yong-Suk
authors.initials: YS
authors.lastname: Jang
authors.forename: Yong-Sung
authors.initials: YS
authors.lastname: Choi
authors.forename: Young-Mi
authors.initials: YM
authors.lastname: Jeon
authors.forename: Jong-Ghee
authors.initials: JG
authors.lastname: Kim
authors.forename: Hyeon-Shik
authors.initials: HS
authors.lastname: Hwang
authors.forename: Jeong-Chae
authors.initials: JC
authors.lastname: Lee
mesh_terms: D016475:3T3 Cells; D000818:Animals; D000975:Antioxidants / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects*; D020169:Caspases / Q000187:drug effects / Q000378:metabolism; D048031:JNK Mitogen-Activated Protein Kinases / Q000187:drug effects / Q000378:metabolism; D051379:Mice; D008928:Mitochondria / Q000187:drug effects / Q000378:metabolism; D010006:Osteoblasts / Q000187:drug effects / Q000378:metabolism; D011794:Quercetin / Q000494:pharmacology*; D018808:Transcription Factor AP-1 / Q000187:drug effects / Q000378:metabolism; D014409:Tumor Necrosis Factor-alpha / Q000187:drug effects* / Q000378:metabolism
chemical_list: D000975:Antioxidants; D018808:Transcription Factor AP-1; D014409:Tumor Necrosis Factor-alpha; D011794:Quercetin; D048031:JNK Mitogen-Activated Protein Kinases; D020169:Caspases