Anti-apoptotic action of nerve growth factor in mouse osteoblastic cell line

We investigated the potential role of nerve growth factor (NGF) in osteobla st survival in vitro. We found the expression of the mRNAs encoding NGF, br ain-derived neurotrophic factor (BDNF), and trk-b, which is the receptor mo lecule of BDNF in mouse osteoblastic MC3T3-E1 cells. NGF high affinity rece ptor trk-a was expressed continuously in the cells as visualized by Western blotting. A proinflammatory cytokine mixture stimulated NGF mRNA, and NGF protein release from MC3T3-E1 cells. When the effect of the nuclear factor- KB inhibitor pyrrolidine dithiocarbamate (PDTC) and activating protein-1 in hibitor curcumin were examined, a dose-dependent inhibition of cytokine-act ivated NGF expression occurred in the presence of PDTC or curcumin. Further , a specific inhibitor of p38 mitogen activated protein kinase (MAPK), i.e. , SB203580, inhibited the induction of NGF in cytokines-treated cells in a dose-dependent manner whereas a specific inhibitor of classic MAPK, PD98D59 had no effect on the induction of NGF. Treatment of anti-NGF IgG resulted in a potent increase of DNA fragmentation at a dose-dependent manner. NGF b ut not BDNF caused a dose-dependent reduction in the extent of apoptotic DN A breakdown under treatment with cytokines. Under similar conditions, the a ddition of NGF resulted in a potent reduction in bar protein but not in Fas , or bcl-xl. These findings demonstrated that NGF in non-neuronal osteoblas tic cells may play an important role in cell survival as an anti-apoptotic factor. (C) 2000 Elsevier Science Inc. All rights reserved.