Praeruptorin A inhibits in vitro migration of preosteoclasts and in vivo bone erosion, possibly due to its potential to target calmodulin.

Excessive activity and/or increased number of osteoclasts lead to bone resorption-related disorders. Here, we investigated the potential of praeruptorin A to inhibit migration/fusion of preosteoclasts in vitro and bone erosion in vivo. Praeruptorin A inhibited the RANKL-induced migration/fusion of preosteoclasts accompanied by the nuclear translocation of NFATc1, a master regulator of osteoclast differentiation. Antimigration/fusion activity of praeruptorin A was also confirmed by evaluating the mRNA expression of fusion-mediating molecules. In silico binding studies and several biochemical assays further revealed the potential of praeruptorin A to bind with Ca(2+)/calmodulin and inhibit its downstream signaling pathways, including the Ca(2+)/calmodulin-CaMKIV-CREB and Ca(2+)/calmodulin-calcineurin signaling axis responsible for controlling NFATc1. In vivo application of praeruptorin A significantly reduced lipopolysaccharide-induced bone erosion, indicating its possible use to treat bone resorption-related disorders. In conclusion, praeruptorin A has the potential to inhibit migration/fusion of preosteoclasts in vitro and bone erosion in vivo by targeting calmodulin and inhibiting the Ca(2+)/calmodulin-CaMKIV-CREB-NFATc1 and/or Ca(2+)/calmodulin-calcineurin-NFATc1 signaling axis.