title: Massive elimination of multinucleated osteoclasts by eupatilin is due to dual inhibition of transcription and cytoskeletal rearrangement.
abstract: Osteoporosis is an aging-associated disease requiring better therapeutic modality. Eupatilin is a major flavonoid fromArtemisiaplants such asArtemisia princepsandArtemisia argyiwhich has been reported to possess various beneficial biological effects including anti-inflammation, anti-tumor, anti-cancer, anti-allergy, and anti-oxidation activity. Complete blockade of RANK-dependent osteoclastogenesis was accomplished upon stimulation prior to the receptor activator of nuclear factor κB (RANK)-ligand (RANKL) treatment or post-stimulation of bone marrow macrophages (BMCs) in the presence of RANKL with eupatilin. This blockade was accompanied by inhibition of rapid phosphorylation of Akt, GSK3β, ERK and IκB as well as downregulation of c-Fos and NFATc1 at protein, suggesting that transcriptional suppression is a key mechanism for anti-osteoclastogenesis. Transient reporter assays or gain of function assays confirmed that eupatilin was a potent transcriptional inhibitor in osteoclasts (OC). Surprisingly, when mature osteoclasts were cultured on bone scaffolds in the presence of eupatilin, bone resorption activity was also completely blocked by dismantling the actin rings, suggesting that another major acting site of eupatilin is cytoskeletal rearrangement. The eupatilin-treated mature osteoclasts revealed a shrunken cytoplasm and accumulation of multi-nuclei, eventually becoming fibroblast-like cells. No apoptosis occurred. Inhibition of phosphorylation of cofilin by eupatilin suggests that actin may play an important role in the morphological change of multinucleated cells (MNCs). Human OC similarly responded to eupatilin. However, eupatilin has no effects on osteoblast differentiation and shows cytotoxicity on osteoblast in the concentration of 50 μM. When eupatilin was administered to LPS-induced osteoporotic mice after manifestation of osteoporosis, it prevented bone loss. Ovariectomized (OVX) mice remarkably exhibited bone protection effects. Taken together, eupatilin is an effective versatile therapeutic intervention for osteoporosis via; 1) transcriptional suppression of c-Fos and NFATc1 of differentiating OC and 2) inhibition of actin rearrangement of pathogenic MNCs.
authors.affiliation: Imaging Science-based Lung and Bone Diseases Research Center, Wonkwang University, Iksan, Jeonbuk 570-749, Republic of Korea.
authors.forename: Ju-Young
authors.initials: JY
authors.lastname: Kim
authors.affiliation: Imaging Science-based Lung and Bone Diseases Research Center, Wonkwang University, Iksan, Jeonbuk 570-749, Republic of Korea; Division of Rheumatology, Department of Internal Medicine, Wonkwang University, Iksan, Jeonbuk 570-749, Republic of Korea; Institute for Skeletal Disease, Wonkwang University, Iksan, Jeonbuk 570-749, Republic of Korea.
authors.forename: Myeung Su
authors.initials: MS
authors.lastname: Lee
authors.affiliation: Department of Anatomy, School of Medicine, Wonkwang University, Iksan, Jeonbuk 570-749, Republic of Korea.
authors.forename: Jong Min
authors.initials: JM
authors.lastname: Baek
authors.affiliation: Department of Neurosurgery, Wonkwang University, Iksan, Jeonbuk 570-749, Republic of Korea.
authors.forename: Jongtae
authors.initials: J
authors.lastname: Park
authors.affiliation: Biomedical Research Center, University of Ulsan College of Medicine, Ulsan University Hospital, 877 Bangeojinsunwhando-ro, Dong-Ku, Ulsan 682-714, Republic of Korea; OsteoNeuroGen 40 MiKeum-ro, Bundang, Kyunggi 461-871, Republic of Korea.
authors.forename: Byung-Soo
authors.initials: BS
authors.lastname: Youn
authors.affiliation: Imaging Science-based Lung and Bone Diseases Research Center, Wonkwang University, Iksan, Jeonbuk 570-749, Republic of Korea; Division of Rheumatology, Department of Internal Medicine, Wonkwang University, Iksan, Jeonbuk 570-749, Republic of Korea; Institute for Skeletal Disease, Wonkwang University, Iksan, Jeonbuk 570-749, Republic of Korea; Department of Anatomy, School of Medicine, Wonkwang University, Iksan, Jeonbuk 570-749, Republic of Korea.
authors.forename: Jaemin
authors.initials: J
authors.lastname: Oh
keywords: ALP, alkaline phosphatase; Actin depolymerization;; BMCs, bone marrow cells; BMMs, bone marrow macrophages; Cytoskeletal rearrangement; FBS, fetal bovine serum; H&E, hematoxylin and eosin; HDACis, Histone deacetylase inhibitors; LPS, lipopolysaccharide; M-CSF, macrophage colony-stimulating factor; MNCs, multinucleated cells; NFATc1, nuclear factor of activated T cells c1; OB, osteoblasts; OC, osteoclasts; OVX, ovariectomized; Osteoclastogenesis;; PGE2, prostaglandin E2; RANK, the receptor activator of nuclear factor κB; RANKL, RANK ligand; SD, standard deviation; SE, standard error; SOST, sclerostin; TBST, tris-buffered saline contacting 0.1% Tween-20; TRAP, tartrate-resistant acid phosphate; Transcriptional repression;; XTT, sodium3’-[1-(phenyl-aminocarbonyl)-3,4-tetrazolium]-bis(4-methoxy-6-nitro); α-MEM, α-minimum essential medium; μCT, micro-computed tomography