Pepstatin A, an aspartic proteinase inhibitor, suppresses RANKL-induced osteoclast differentiation.
Pepstatin A is well known to be an inhibitor of aspartic proteinases such as pepsin, cathepsins D and E. Except for its role as a proteinase inhibitor, however, the pharmacological action of pepstatin A upon cells remain unclear. In this study, we found that pepstatin A suppressed receptor activator of NF-kappaB ligand (RANKL)-induced osteoclast differentiation. Pepstatin A suppressed the formation of multinuclear osteoclasts dose-dependently. This inhibition of the formation only affected osteoclast cells, i.e., not osteoblast-like cells. Furthermore, pepstatin A also suppressed differentiation from pre-osteoclast cells to mononuclear osteoclast cells dose-dependently. This inhibition seems to be independent of the activities of proteinases such as cathepsin D, because the formation of osteoclasts was not suppressed with the concentration that inhibited the activity of cathepsin D. Cell signaling analysis indicated that the phosphorylation of ERK was inhibited in pepstatin A-treated cells, while the phosphorylation of IkappaB and Akt showed almost no change. Furthermore, pepstatin A decreased the expression of nuclear factor of activated T cells c1 (NFATc1). These results suggest that pepstatin A suppresses the differentiation of osteoclasts through the blockade of ERK signaling and the inhibition of NFATc1 expression.
Yoshida
Hajime
H
Division of Oral and Maxillofacial Surgery, Department of Development and Reconstructive Medicine, Graduate School of Biomedical Sciences, Nagasaki University, Nagasaki 852-8588.
Okamoto
Kuniaki
K
Iwamoto
Tsutomu
T
Sakai
Eiko
E
Kanaoka
Kazuhiro
K
Hu
Jin-Ping
JP
Shibata
Mitsue
M
Hotokezaka
Hitoshi
H
Nishishita
Kazuhisa
K
Mizuno
Akio
A
Kato
Yuzo
Y
D000818:Animals; D000831:Animals, Newborn; D016282:Aspartic Acid Endopeptidases / Q000037:antagonists & inhibitors*; D002454:Cell Differentiation / Q000187:drug effects*; D008297:Male; D051379:Mice; D010010:Osteoclasts / Q000166:cytology / Q000187:drug effects*; D010436:Pepstatins / Q000494:pharmacology*; D011480:Protease Inhibitors / Q000494:pharmacology*; D053245:RANK Ligand / Q000502:physiology
D010436:Pepstatins; D011480:Protease Inhibitors; D053245:RANK Ligand; D016282:Aspartic Acid Endopeptidases; C031375:pepstatin