Brefeldin A inhibits osteoclastic bone resorption through induction of apoptosis.
Brefeldin A (BFA), a fungal metabolite with a macrocyclic lactone structure, has been developed for the treatment of cancer, and its major biological activity is the inhibition of intracellular protein transport from the endoplasmic reticulum to the cis-Golgi apparatus. In this study, we investigated the effect of BFA on osteoclastic pit formation in vitro. BFA reduced pit formation in a concentration-dependent manner, and the IC50 values on the pit number and the pit volume were 11.3 +/- 2.2 and 13.3 +/- 2.0 nM, respectively. In parallel with the inhibitory effect on pit formation, BFA also reduced the cell viability of osteoclasts-enriched bone cells with an IC50 value of 13.9 +/- 2.2 nM. These results suggest that the inhibition of bone resorption by BFA is caused by the induction of osteoclast cell death. BFA at a concentration of 100 nM induced DNA fragmentation in purified osteoclasts, assessed by the terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling and DNA ladder formation, demonstrating that BFA induces cell death of osteoclasts in an apoptotic manner. In addition, the accumulation of p53 proteins to the nuclei was observed in the osteoclasts treated with 100 nM BFA. These results, taken together, suggest that BFA inhibits osteoclastic bone resorption by inducing apoptosis in osteoclasts through a p53-dependent mechanism.
Niwa
S
S
Takarazuka Research Institute, Novartis Pharma K. K, Japan.
Ishibashi
O
O
Inui
T
T
D000818:Animals; D017209:Apoptosis / Q000187:drug effects*; D001862:Bone Resorption / Q000517:prevention & control*; D020126:Brefeldin A / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D010010:Osteoclasts / Q000187:drug effects*; D011817:Rabbits; D016159:Tumor Suppressor Protein p53 / Q000378:metabolism
D016159:Tumor Suppressor Protein p53; D020126:Brefeldin A