Pathogenic roles of CXCL10 signaling through CXCR3 and TLR4 in macrophages and T cells: relevance for arthritis

Abbreviations ACK: Ammonium–chloride–potassium; BMM: Bone marrow-derived macrophage; CAIA: Collagen antibody-induced arthritis; CIA: Collagen-induced arthritis; CsA: Cyclosporin A; CTX: C-terminal telopeptide; CXCL10: C-X-C motif chemokine 10; CXCR3: Chemokine receptor 3; DAPI: 4′,6-Diamidino-2- phenylindole; EDTA: Ethylenediaminetetraacetic acid; ELISA: Enzyme-linked immunosorbent assay; FITC: Fluorescein isothiocyanate; H&E: Hematoxylin and eosin; IFN-γ: Interferon gamma; IL: Interleukin; LPS: Lipopolysaccharide; NFATc1: Nuclear factor of activated T cells, cytoplasmic 1; PBS: Phosphatebuffered saline; RA: Rheumatoid arthritis; RANKL: Receptor activator of nuclear factor kappa-B; TLR4: Toll-like receptor 4; TNFα: Tumor necrosis factor alpha; TRAP: Tartrate-resistant acid phosphatase; WT: Wild-typeAbstract Background Rheumatoid arthritis (RA) is a chronic autoimmune disease characterized by uncontrolled joint inflammation and destruction of bone and cartilage. We previously reported that C-X-C motif chemokine 10 (CXCL10; also called IP-10) has important roles in joint inflammation and bone destruction in arthritis. However, the specific mechanisms by which CXCL10 regulates the recruitment of inflammatory cells and the production of osteoclastogenic cytokines in RA progression are not fully understood. Methods Bone marrow-derived macrophages and CD4+ T cells were isolated from wild-type (WT), Cxcl10 –/–, and Cxcr3 –/– mice. CXCL10-induced migration was performed using a Boyden chamber, and CXCL10-stimulated production of osteoclastogenic cytokines was measured by quantitative real-time PCR and ELISA. Collagen antibody-induced arthritis (CAIA) was induced by administration of collagen type II antibodies and lipopolysaccharide to the mice. Clinical scores were analyzed and hind paws were collected for high-resolution micro-CT, and histomorphometry. Serum was used to assess bone turnover and levels of osteoclastogenic cytokines. Results CXCL10 increased the migration of inflammatory cells through C-X-C chemokine receptor 3 (CXCR3)-mediated, but not toll-like receptor 4 (TLR4)-mediated, ERK activation. Interestingly, both receptors CXCR3 and TLR4 were simultaneously required for CXCL10-stimulated production of osteoclastogenic cytokines in CD4+ T cells. Furthermore, calcineurin-dependent NFATc1 activation was essential for CXCL10-induced RANKL expression. In vivo, F4/80+ macrophages and CD4+ T cells robustly infiltrated into synovium of WT mice with CAIA but were significantly reduced in both Cxcl10 –/– and Cxcr3 –/– mice. Serum concentrations of osteoclastogenic cytokines and bone destruction were also reduced in the knockout mice, leading to attenuated progression of arthritis. Conclusion These findings highlight the importance of CXCL10 signaling in the pathogenesis of RA and provide previously unidentified details of the mechanisms by which CXCL10 promotes the development of arthritis.This study was supported by the Basic Science Research Program through the National Research Foundation of Korea funded by the Ministry of Science, ICT & Future Planning (NRF-2014R1A2A2A01002531)

Tanshinone IIA inhibits osteoclast differentiation through down-regulation of c-Fos and NFATc1.

Bone is a dynamic tissue that is regulated by the activity of bone-resorbing osteoclasts and boneforming osteoblasts. Excessive osteoclast forma - tion causes diseases such as osteoporosis and rheumatoid arthritis. Natural substances may be useful as therapeutic drugs to prevent many diseases in humans because they avoid the many side effects of treatment with chemical compounds. Here we show that tanshinone IIA isolated from Salvia miltiorrhiza Bunge inhibits the receptor activator of NF-κB ligand (RANKL)-mediated osteoclast differen - tiation of osteoclast precursors. Tanshinone IIA suppressed the expression levels of c-Fos and NFATc1 induced by RANKL. However, retrovirusmediated overexpression of c-Fos induced the expression of NFATc1 despite the presence of tans - hinone IIA and reversed the inhibitory effect of tanshinone IIA on osteoclast differentiation. Also, the introduction of osteoclast precursors with the NFATc1 retrovirus led to osteoclast differentiation in the presence of tanshinone IIA. Our results suggest that tanshinone IIA may have a role as a therapeutic drug in the treatment of bone disease such as osteoporosis

Water extract of Uncaria sinensis suppresses RANKL-induced bone loss by attenuating osteoclast differentiation and bone resorption

Background: The hooks and stems of Uncaria sinensis have been used to mitigate cardiovascular and central nervous system disorders in Asia traditional medicine. Regulation of osteoclast differentiation and activity is a major target for preventing and treating pathological bone diseases. Methods: Tartrate-resistant acid phosphatase (TRAP) activity and the number of TRAP-stained multinucleated cells were used to examine receptor activator of nuclear factor-κB ligand (RANKL)-induced osteoclast differentiation. The activation of RANKL-induced signaling pathways and the expression of transcription factors were investigated by western blot analysis and quantitative real-time polymerase chain reaction. The bone resorption activity of osteoclast was studied using a plate coated with hydroxyl-apatite. Trabecular bone destruction was investigated using a RANKL-induced trabecular bone loss mouse model. Results: We found that water extract of the hooks and stems of U. sinensis (WEUS) inhibits RANKL-induced differentiation of murine bone marrow macrophages and RAW264.7 cells into osteoclasts. WEUS inhibited the activation of NF-κB and the expression of nuclear factor of activated T-cells, cytoplasmic 1. In addition, WEUS suppressed the bone resorbing activity of mature osteoclasts without affecting their survival. Furthermore, oral administration of WEUS suppressed RANKL-induced bone loss with a significant amelioration of trabecular bone micro-structures. WEUS also reduced RANKL-induced increase in serum TRAP5b activity and C-terminal cross-linked telopeptide of type I collagen levels. Conclusion: The present study demonstrates that WEUS has a pharmacological activity that inhibits osteoclast-mediated bone destruction by suppressing osteoclast differentiation and function. These results suggest that U. sinensis could be a promising herbal candidate for preventing and treating bone diseases such as osteoporosis. Keywords: Uncaria sinensis, Osteoclasts, Receptor activator for nuclear factor-κB ligand, Nuclear factor of activated T-cells, Cytoplasmic

Magnolol Inhibits Osteoclast Differentiation via Suppression of RANKL Expression

Magnolol, a compound from the traditional Korean herb Magnolia sp., has been exhaustively investigated as a therapeutic agent against several diseases including systemic and local inflammation. We examined the effects of magnolol on osteoclastic differentiation associated with inflammation. Magnolol markedly reduced interleukin (IL)-1-induced osteoclast formation in co-cultures of murine osteoblasts and bone marrow cells, whereas it had no effect on receptor activator of nuclear factor-κB ligand (RANKL)-induced osteoclast formation in bone marrow macrophage cultures. In osteoblasts, magnolol markedly inhibited both the up-regulation of RANKL expression and the production of prostaglandin E2 (PGE2) in response to IL-1 treatment. Addition of exogenous PGE2 reversed the inhibitory effects of magnolol on IL-1-induced RANKL expression in osteoblasts and osteoclast formation in co-cultures. Magnolol inhibited IL-1-induced PGE2 production, at least in part by suppressing cyclooxygenase-2 (COX-2) expression. Taken together, these results demonstrate that magnolol inhibits IL-1-induced RANKL expression in osteoblasts through suppression of COX-2 expression and PGE2 production, resulting in inhibition of osteoclast differentiation in co-cultures

The Natural Product 6-Gingerol Inhibits Inflammation-Associated Osteoclast Differentiation via Reduction of Prostaglandin E2 Levels

The natural product 6-gingerol, a major bioactive component of the rhizome of ginger (Zingiber officinale), is known to have several beneficial effects on health, including anti-inflammatory activity. The present study aimed to investigate the effects of 6-gingerol on osteoclast differentiation associated with inflammation. 6-Gingerol inhibited osteoclast differentiation in co-cultures of osteoblasts and osteoclast precursor cells in response to the pro-inflammatory cytokine, interleukin (IL)-1. However, it did not affect osteoclast precursor differentiation into osteoclasts induced by the receptor activator of nuclear factor-κB ligand (RANKL), a key cytokine causing osteoclast differentiation. 6-Gingerol inhibited IL-1-induced RANKL expression in osteoblasts, and the addition of RANKL to the co-cultures overcame 6-gingerol-mediated inhibition of osteoclast differentiation. It also suppressed IL-1-induced prostaglandin E2 (PGE2) production in osteoblasts, and the addition of exogenous PGE2 reversed 6-gingerol-mediated inhibition of IL-induced RANKL expression in osteoblasts and osteoclast differentiation in the co-cultures. We found that 6-gingerol reduced PGE2 levels by suppressing enzymatic activities of cyclooxygenase and PGE synthase, which cooperatively catalyze the conversion of arachidonic acid to PGE2. Our findings demonstrate that 6-gingerol inhibits IL-1-induced osteoclast differentiation via suppression of RANKL expression in osteoblasts though reduction of PGE2 levels, suggesting its potential use in treating inflammatory bone destruction associated with excessive PGE2 production

Forsythia suspensa Protects against Bone Loss in Ovariectomized Mice

In traditional oriental medicine, the fruit of Forsythia suspensa has been used as a nutritional supplement to alleviate inflammation and treat gastrointestinal diseases. However, there is no information available on its beneficial effects on bone. We investigated the beneficial effects of F. suspensa water extract (WFS) on osteoclast differentiation and bone loss. The microarchitecture of trabecular bone was analyzed by micro-computed tomography. Osteoclast differentiation was evaluated based on tartrate-resistant alkaline phosphatase activity, and bone resorption activity was examined on a bone-like mineral surface. The mechanism of action of WFS was assessed by evaluating the expression and activation of signaling molecules. Phytochemical constituents were identified and quantitated by ultrahigh-performance liquid chromatography–tandem mass spectrometry. WFS reduced ovariectomy-induced trabecular bone loss and inhibited receptor activator of nuclear factor-κB ligand (RANKL)-induced osteoclast formation and resorption activity. WFS suppressed RANKL-induced expression of nuclear factor of activated T cells cytoplasmic 1, a crucial transcription factor for osteoclast differentiation by decreasing c-Fos protein levels and suppressing the activation of p38 and c-Jun-N-terminal kinase. We also identified 12 phytochemicals in WFS including lignans, phenylethanoids, and flavonoids. Collectively, these results suggest that WFS inhibits osteoclast differentiation and can potentially be used to treat postmenopausal osteoporosis

Anti-Osteoporotic Effects of Commiphora Myrrha and Its Poly-Saccharide via Osteoclastogenesis Inhibition

In traditional oriental medicines, Commiphora myrrha and its resinous exudate (i.e., myrrh) are used as herbal remedies to treat various inflammatory and metabolic disorders. Until now, C. myrrha-derived herbal products are considered useful source for bioactive compounds to manage numerous human diseases. This study investigated the effects of water extract of C. myrrha resin (WCM) and its polysaccharide (WCM-PE) on modulatory effects of osteoclast differentiation and/or ovariectomized-induced bone loss. Oral administration of WCM (200 and 500 mg/kg/day for four weeks) notably decreased trabecular bone loss and lipid accumulation in the bone marrow cavity. WCM and WCM-PE dose-dependently inhibited receptor activator of nuclear factor-κB ligand (RANKL)-induced osteoclastogenesis and suppressed RANKL-mediated overexpression of c-Fos and nuclear factor of activated T cells, cytoplasmic 1, thereby downregulating osteoclast-specific gene (Atp6v0d2, DC-STAMP and cathepsin K) expression. Thus, our results suggest that WCM and WCM-PE are promising nutraceutical candidates for the management of osteoporosis in postmenopausal women

Poria Cocos Ameliorates Bone Loss in Ovariectomized Mice and Inhibits Osteoclastogenesis In Vitro

Estrogen deprivation in postmenopausal women causes disruption of bone homeostasis, resulting in bone loss and osteoporosis. Conventional therapies can exert adverse effects. The sclerotum of Poria cocos has been used in traditional medicine and as a nutritional supplement and to treat various diseases. However, the effects of P. cocos on the bone remain largely undetermined. In this study, we examined the effects of P. cocos hydroethanolic extract (PC) on osteoclast differentiation and estrogen-deprivation-induced bone loss in an ovariectomized mouse model of postmenopausal osteoporosis. PC-mediated inhibition of receptor activator of nuclear factor-κB ligand (RANKL)-induced osteoclast formation and resorption activity suppressed RANKL-induced expression of nuclear factor of activated T cells cytoplasmic 1 (NFATc1), which is a crucial transcription factor for osteoclast differentiation. In ovariectomized mice, PC markedly alleviated trabecular bone loss and reduced the accumulation of lipid droplets in the bone marrow. We additionally identified ten triterpenoid constituents of PC using UPLC-MS/MS analysis. Our results indicate that PC negatively regulated osteoclast differentiation and function, and can potentially be used to manage postmenopausal osteoporosis