Attenuated RANKL-induced cytotoxicity by Portulaca oleracea ethanol extract enhances RANKL-mediated osteoclastogenesis

BACKGROUND: Portulaca oleracea (PO) has been widely used as traditional medicine because of its pharmacological activities. However, the effects of PO on osteoclasts that modulate bone homeostasis are still elusive. METHODS: In this study, we examined the effects of PO ethanol extract (POEE) on receptor activator of nuclear factor-κB ligand (RANKL)-mediated Ca(2+) mobilization, nuclear factor of activated T-cell c1 (NFATc1) amplification, tartrate-resistant acid phosphatase-positive (TRAP+) multinucleated cell (MNC) formation, and cytotoxicity. RESULTS: Our results demonstrated that POEE suppressed RANKL-induced Ca(2+) oscillations by inhibition of Ca(2+) release from internal Ca(2+) stores, resulting in reduction of NFATc1 amplification. Notably, POEE attenuated RANKL-mediated cytotoxicity and cleavage of polyadenosine 5′-diphosphate-ribose polymerase (PARP), resulted in enhanced formation of TRAP+ MNCs. CONCLUSIONS: These results present in vitro effects of POEE on RANKL-mediated osteoclastogenesis and suggest the possible use of PO in treating bone disorders, such as osteopetrosis.