Smad protein mediated transforming growth factor beta1 induction of apoptosis in the MDPC-23 odontoblast-like cell line.
OBJECTIVE
The function of apoptosis and its regulation in odontoblasts remain unclear. In this study, we characterize the possible role of transforming growth factor (TGF)-beta 1 in the induction of apoptosis and the molecular mechanisms that mediate TGF-beta1-induced apoptosis in odontoblasts.


METHODS
Annexin V/propidium iodide staining, cell Death Detection ELISA and DNA ladder were used to examine the effect of TGF-beta1 on apoptosis in a mouse odontoblast-like cell line, MDPC-23. Stable cell clones expressing Smad2 or Smad3 dominant negative mutants, or wild-type Smad7 were constructed to investigate the role of Smad proteins in the mediation of apoptosis by TGF-beta1 in MDPC-23 cells. The TGF-beta1-induced transcriptional activity in stable cell clones expressing Smad proteins was analyzed by a transient transfected TGF-beta-responsive reporter gene, p3TP-Lux.


RESULTS
TGF-beta1 can induce apoptotic cell death in MDPC-23 cells in a dose-dependent manner. Transfection of dominant negative mutant forms of Smad2 or Smad3 blocked TGF-beta1-induced apoptosis; moreover, the Smad3 mutant was more efficient than the Smad2 mutant. Transfection of Smad7, an inhibitory Smad, also significantly inhibited TGF-beta1-induced apoptosis of these cells. Over-expression of Smad3 dominant negative mutant or Smad7 significantly inhibited TGF-beta1-induced transcriptional activity.


CONCLUSIONS
These results suggest that Smad proteins are involved in TGF-beta1-induced apoptosis of odontoblast cells.
He
Wen-Xi
WX
Department of Conservative Dentistry, Qin Du Stomatological Hospital, School of Dentistry, The Fourth Military Medical University, Xi'an 710032, PR China. hwenxi@yahoo.com.cn
Niu
Zhong-Ying
ZY
Zhao
Shou-Liang
SL
Smith
Anthony J
AJ
D000818:Animals; D017304:Annexin A5 / Q000032:analysis; D017209:Apoptosis; D015415:Biomarkers / Q000032:analysis; D002460:Cell Line; D053938:DNA Fragmentation; D004305:Dose-Response Relationship, Drug; D015536:Down-Regulation; D004797:Enzyme-Linked Immunosorbent Assay / Q000379:methods; D051379:Mice; D009804:Odontoblasts / Q000378:metabolism*; D051785:Smad Proteins / Q000378:metabolism*; D051899:Smad2 Protein / Q000378:metabolism; D051900:Smad3 Protein / Q000378:metabolism; D051906:Smad7 Protein / Q000378:metabolism; D013194:Staining and Labeling; D015533:Transcriptional Activation; D016212:Transforming Growth Factor beta / Q000494:pharmacology*
D017304:Annexin A5; D015415:Biomarkers; D051785:Smad Proteins; D051899:Smad2 Protein; D051900:Smad3 Protein; D051906:Smad7 Protein; D016212:Transforming Growth Factor beta