Sec-O-Glucosylhamaudol Inhibits RANKL-Induced Osteoclastogenesis by Repressing 5-LO and AKT/GSK3β Signaling

Abstract

Sec-O-glucosylhamaudol (SOG), an active flavonoid compound derived from the root of Saposhnikovia divaricata (Turcz. ex Ledeb.) Schischk., exhibits analgesic, anti-inflammatory, and high 5-lipoxygenase (5-LO) inhibitory effects. However, its effect on osteoclastogenesis was unclear. We demonstrated that SOG markedly attenuated RANKL-induced osteoclast formation, F-actin ring formation, and mineral resorption by reducing the induction of key transcription factors NFATc1, c-Fos, and their target genes such as TRAP, CTSK, and DC-STAMP during osteoclastogenesis. Western blotting showed that SOG significantly inhibited the phosphorylation of AKT and GSK3β at the middle–late stage of osteoclastogenesis without altering calcineurin catalytic subunit protein phosphatase-2β-Aα expression. Moreover, GSK3β inhibitor SB415286 partially reversed SOG-induced inhibition of osteoclastogenesis, suggesting that SOG inhibits RANKL-induced osteoclastogenesis by activating GSK3β, at least in part. 5-LO gene silencing by small interfering RNA in mouse bone marrow macrophages markedly reduced RANKL-induced osteoclastogenesis by inhibiting NFATc1. However, it did not affect the phosphorylation of AKT or GSK3β, indicating that SOG exerts its inhibitory effects on osteoclastogenesis by suppressing both the independent 5-LO pathway and AKT-mediated GSK3β inactivation. In support of this, SOG significantly improved bone destruction in a lipopolysaccharide-induced mouse model of bone loss. Taken together, these results suggest a potential therapeutic effect for SOG on osteoclast-related bone lysis disease.

Glycogen Synthase Kinase-3 Beta (GSK3β) as a Potential Drug Target in Regulating Osteoclastogenesis: An Updated Review on Current Evidence

“…The p-AKT/AKT and p-GSK3β/GSK3β ratio were found to be increased during osteoclastogenesis. Incubation of M-CSF-and RANKL-stimulated BMMs with natural products (sec-O-glucosylhamaudol and purple tea water extract) resulted in the reduction of AKT and GSK3β phosphorylation, causing the inhibition of mature osteoclast formation [28,35]. A similar trend in the phosphorylation status of AKT and GSK3β was noted in LPS-treated BMMs [29].…”

“…In in vivo studies, the group receiving LPS displayed a higher number of TRAP-positive osteoclasts and expression of osteoclastogenic markers [including RANKL, NFATc1, Fos proto-oncogene (c-Fos), MMP-9, CTSK, and TRAF6], as well as a higher level of inflammatory markers [interleukin-1 beta (IL-1β) and interleukin-6 (IL-6)]. The signalling molecules involved were activation of TRAF6 expression, phosphorylation of nuclear factor-kappa B (NF-κB), and degradation of IκBα (a NF-κB inhibitory protein) [28,29]. RANKL, as an important regulator of osteoclast formation and activation in the RANK/RANKL/OPG pathway, can be used to establish an osteoporotic animal model.…”