Bioactive compounds with an inhibitory activity against osteoclast differentiation and mechanisms / Supatta Chawalitpong = สารออกฤทธิ์ชีวภาพที่มีฤทธิ์ต้านการเปลี่ยนสภาพของเซลล์สลายกระดูกและกลไกการออกฤทธิ์ / สุพัตรา ชวลิตพงษ์
Osteoporosis is one of the major health concerns for aging societies. The major cause of this condition is an imbalance in cellular function between bone forming cells, osteoblasts, and bone resorbing cells, osteoclasts. The progressive decrease in bone mass especially in aging individuals leads to increased susceptibility to fracture. This study aimed to screen and identify bioactive compounds from plants with activity against osteoclast differentiation and to elucidate its mode of action. Among these compounds, (3S)-1-(3,4-dihydroxyphenyl)-3-hydroxy-7-phenyl-(6E)-6-heptene (DHPH) and cyperenoic acid isolated from the rhizomes of Curcuma comosa Rox and the roots of Croton crassifolius Geiseler, respectively, showed strong an anti-osteoclastogenesis activity in receptor activator of nuclear factor-κB (RANK) ligand-induced bone marrow-derived osteoclast in vitro system. DHPH significantly inhibited RANKL-induced osteoclast differentiation by inhibiting the formation of tartrate resistance acid phosphatase (TRAP)-positive multinucleated cells (MNCs) with the half maximum inhibitory concentration (IC50) at 325±1.37 nM. The inhibitory effect of DHPH is associated with impaired activation of multiple signaling pathways downstream of RANKL/RANK, mainly mitogen-activated protein kinases (MAPKs), including ERK (p44/42) and p38, but not NF-κB pathway. Treatment with DHPH effectively suppressed two transcriptional factors, nuclear factor of activated T cells (NFATc1) and c-Fos, both of which are critical for osteoclast differentiation. DHPH treatment also decreased bone resorption on bone slices. In addition, DHPH clearly enhanced alkaline phosphatase activity (ALP) in osteoblast precursor cell line MC3T3-E1. Cyperenoic acid dramatically suppressed TRAP+MNCs with an IC50 of 36.69±1.02 mM. Both MAPK and canonical NF-κB pathway, downstream of RANKL/RANK were not affected by cyperenoic acid treatment. Interestingly, non-canonical NF-κB pathway ((p100/p52) and TRAF3), was found to be affected by cyperenoic acid. Cyperenoic acid significantly reduced the expression of NFATc1 and c-Fos. Osteoclast-related genes i.c. nfatc1, ctsk and irf8, were all affected. The inhibitory effect of cyperenoic acid is associated with a diminution of bone resorption on the dentin slices. In vivo study using senescence-accelerated mouse prone 6 (SAMP6) mice strain revealed that cyperenoic acid significantly increased both bone area and the trabecular area in SAMP6 mice. Expression of ibsp, encoding bone sialoprotein, increased while the mRNA level of inflammatory-related genes was not affected. Taken together, plant-derived compounds, both DHPH and cyperenoic acid, were effective in inhibiting osteoclast differentiation and function. Therefore, they have potential to be lead compounds for osteoporosis treatment.
