He Wen-Xi, Niu Zhong-Ying, Zhao Shou-Liang, Smith Anthony J
Department of Conservative Dentistry, Qin Du Stomatological Hospital, School of Dentistry, The Fourth Military Medical University, Xi'an 710032, PR China.
Arch Oral Biol. 2005 Nov;50(11):929-36. doi: 10.1016/j.archoralbio.2005.03.004. Epub 2005 Apr 22.
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.
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.
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.
These results suggest that Smad proteins are involved in TGF-beta1-induced apoptosis of odontoblast cells.
成牙本质细胞中细胞凋亡的功能及其调控机制仍不清楚。在本研究中，我们探讨转化生长因子（TGF）-β1在诱导成牙本质细胞凋亡中的可能作用，以及介导TGF-β1诱导成牙本质细胞凋亡的分子机制。
采用膜联蛋白V/碘化丙啶染色、细胞死亡检测ELISA和DNA梯状条带分析，检测TGF-β1对小鼠成牙本质细胞样细胞系MDPC-23凋亡的影响。构建表达Smad2或Smad3显性负性突变体或野生型Smad7的稳定细胞克隆，研究Smad蛋白在TGF-β1介导的MDPC-23细胞凋亡中的作用。通过瞬时转染TGF-β反应报告基因p3TP-Lux，分析表达Smad蛋白的稳定细胞克隆中TGF-β1诱导的转录活性。
TGF-β1能以剂量依赖的方式诱导MDPC-23细胞发生凋亡性细胞死亡。转染Smad2或Smad3的显性负性突变体可阻断TGF-β1诱导的凋亡；此外，Smad3突变体比Smad2突变体更有效。转染抑制性Smad蛋白Smad7也能显著抑制TGF-β1诱导的这些细胞凋亡。Smad3显性负性突变体或Smad7的过表达显著抑制TGF-β1诱导的转录活性。
这些结果表明Smad蛋白参与了TGF-β1诱导的成牙本质细胞凋亡。
