Hye-Seon Choi

Recombinant glucocorticoid induced tumor necrosis factor receptor (rGITR) induces NOS in murine macrophage.

Glucocorticoid induced tumor necrosis factor receptor (GITR) is a new member of the tumor necrosis factor–nerve growth factor receptor superfamily of which the function has not been well studied. The extracellular domain of GITR was produced in Escherichia coli and purified as a single band of predicted M r of 18.0 kDa. GITR and GITR ligand were expressed constitutively on the surface of Raw 264.7 macrophage cell line and murine peritoneal macrophages. An extracellular domain of GITR can activate murine macrophages to express inducible nitric oxide synthase and to generate nitric oxide in a dose‐ and time‐dependent manner.

Soluble glucocorticoid‐induced tumor necrosis factor receptor (sGITR) increased MMP‐9 activity in murine macrophage

Glucocorticoid induced tumor necrosis factor receptor (GITR), a new TNFR family, increased production of matrix matalloproteinase (MMP‐9) in murine macrophages. Murine macrophages produced a band of gelatinolytic activity at 100 kDa when stimulated for 18 h with soluble GITR. MMP‐9 was identified by gelatin zymography and Western blot. Previous results demonstrated that murine macrophages express GITR and GITR ligand constitutively. Induction of MMP‐9 was synergistic with co‐treatment of INF‐γ. MMPs could play a critical role in progression and promotion of tissue injury after inflammation stimulated by GITR/ligand system. J. Cell. Biochem. 88: 1048–1056, 2003.

Saturated fatty acids enhance osteoclast survival.

Hyperlipidemia and marrow fat are associated with lowering bone density in vivo, suggesting that lipid contributes to bone loss. Using bone marrow-derived macrophages, we investigated the effect of saturated fatty acids (SFA) on osteoclastogenesis. The level of free fatty acids and adiposity in bone marrow was significantly elevated in obese mice. SFA increased osteoclast (OC) survival by preventing apoptosis. SFA caused the production of MIP-1alpha and led to activation of nuclear factor (NF)-kappaB in the OC. The absence of Toll-like receptor 4 (TLR4) or myeloid differentiation factor 88 (MyD88) abolished the survival effect of SFA on OC.

Osteoclastogenesis by Bone Marrow-Derived Macrophages Is Enhanced in Obese Mice

Obesity induces a low-grade systemic chronic inflammatory condition for which macrophages are responsible. We hypothesized that obesity affects osteoclastogenesis by acting on bone marrow-derived macrophages (BMM). Male mice were fed a high-fat diet (45% of energy) or a standard diet (10% of energy) for 13 wk. We found that the density of the femurs of obese mice was significantly lower than that of the femurs of lean mice. Osteoclastogenesis was enhanced in the BMM from obese mice. Lower levels of interleukin (IL)-10 were generated by the BMM from obese mice than by those from lean mice upon stimulation of receptor activator of nuclear factor-kappaB ligand. Neutralization of IL-10 in the BMM from obese mice was not as effective in increasing osteoclast (OC) formation as that in those from lean mice. Exogenous IL-10 inhibited OC formation more strongly in the BMM from obese mice than those from lean mice. The elevated level of OC formation in the BMM from obese mice may thus be due to in part to the lower level of IL-10, a negative regulator of osteoclastogenesis. Our results suggest that obesity is associated with bone loss via enhanced osteoclastogenesis due to reduced IL-10 production by the BMM from obese mice.

Gold Nanoparticles Inhibited the Receptor Activator of Nuclear Factor-κB Ligand (RANKL)-Induced Osteoclast Formation by Acting as an Antioxidant

Gold nanoparticles inhibited osteoclast (OC) formation induced by the receptor activator of nuclear factor-κB ligand (RANKL) in bone marrow-derived macrophages (BMMs). This was accompanied by a decreased level of tartrate-resistant alkaline phosphatase (TRAP) and less activation of nuclear factor (NF)-κB. The nanoparticles also reduced the production of reactive oxygen species (ROS) in response to RANKL and upregulated RANKL-induced glutathione peroxidase-1 (Gpx-1), suggesting a role as an antioxidant in the BMM. The inhibitory effects on OC formation might have been due to elevated defense against oxidative stress.

Protective Effects of an Extract of Young Radish (Raphanus sativus L) Cultivated with Sulfur (Sulfur-Radish Extract) and of Sulforaphane on Carbon Tetrachloride-Induced Hepatotoxicity

The protective effects of an extract of young radish (Raphanus sativus L) cultivated with sulfur (sulfur-radish extract) and of sulforaphane, an isothiocyanate, on carbon tetrachloride (CCl4)-induced liver injury were observed in mice. CCl4 produced a marked increase in the serum level of alanine aminotransferase (ALT), primed lipid peroxidation, and resulted in intense necrosis due to oxidative stress. Oral administration of the sulfur-radish extract and of sulforaphane after CCl4-induced liver injury both decreased the serum level of ALT, reduced the necrotic zones, inhibited lipid peroxidation, and induced phase 2 enzymes without affecting cytochrome P450-2E1 (CYP2E1). These results suggest that the administration of the sulfur-radish extract and of sulforaphane may partially prevent CCl4-induced hepatotoxicity, possibly by indirectly acting as an antioxidant by improving the detoxification system.

Rutin inhibits osteoclast formation by decreasing reactive oxygen species and TNF-α by inhibiting activation of NF-κB

Rutin, a glycoside of flavonol, inhibits osteoclast formation induced by receptor activator of NF-κB ligand (RANKL) in bone marrow-derived macrophages. It reduces reactive oxygen species produced by RANKL and its inhibitory effect results from reduced levels of TNF-α. Rutin also lowers NF-κB activation in response to RANKL.

Curcumin protects against ovariectomy‐induced bone loss and decreases osteoclastogenesis

Curcumin has anti‐oxidative activity. In view of the increasing evidence for a biochemical link between increased oxidative stress and reduced bone density we hypothesized that curcumin might increase bone density by elevating antioxidant activity in some target cell type. We measured bone density by Micro‐CT, enzyme expression levels by quantitative PCR or enzyme activity, and osteoclast (OC) formation by tartrate‐resistant acid phosphatase staining. The bone mineral density of the femurs of curcumin‐administered mice was significantly higher than that of vehicle‐treated mice after ovariectomy (OVX) and this was accompanied by reduced amounts of serum collagen‐type I fragments, which are markers of bone resorption. Curcumin suppressed OC formation by increasing receptor activator of nuclear factor‐κB ligand (RANKL)‐induced glutathione peroxidase‐1, and reversed the stimulatory effect of homocysteine, a known H2O2 generator, on OC formation by restoring Gpx activity. Curcumin generated an aberrant RANKL signal characterized by reduced expression of nuclear factor of activated T cells 2 (NFAT2) and attenuated activation of mitogen‐activated protein kinases (ERK, JNK, and p38). Curcumin thus inhibited OVX‐induced bone loss, at least in part by reducing osteoclastogenesis as a result of increased antioxidant activity and impaired RANKL signaling. These findings suggest that bone loss associated with estrogen deficiency could be attenuated by curcumin administration. J. Cell. Biochem. 112: 3159–3166, 2011.

Enhanced osteoclastogenesis in 4-1BB-deficient mice caused by reduced interleukin-10.

Enhanced osteoclastogenesis was observed in bone marrow—derived macrophage cells from 4‐1BB—deficient mice than in those from wildtype mice. 4‐1BB and 4‐1BB ligand interaction may play a role at a certain stage of osteoclast formation through increased level of IL‐10, a negative regulator of osteoclastogenesis.

Absence of MCP-1 leads to elevated bone mass via impaired actin ring formation.

Monocyte chemoattractant protein‐1 (MCP‐1) is associated with various inflammatory diseases involving bone loss, and is expressed along with its receptor by bone marrow‐derived macrophages (BMM), which are osteoclast (OC) precursors. To investigate the role of MCP‐1 in bone remodeling, we compared MCP‐1‐knockout (KO) mice with wild‐type (WT) mice. The absence of MCP‐1 increased bone mass and lowered serum collagen type I fragments (CTX‐1) and TRACP 5b, but had no significant effect on the N‐terminal propeptide of type I procollagen, suggesting that OCs are primarily responsible for the bone phenotype observed in the absence of MCP‐1. MCP‐1 deficiency resulted in reduced numbers and activity of OCs in vitro. It also led to a reduced level of c‐Fms and receptor activator of nuclear factor‐κB receptor and impaired actin ring formation. Activation of ERK, Akt, Rac1, and Rho upon M‐CSF stimulation was also reduced and our evidence suggests that the aberrant actin ring formation was partly due to reduced activation of these molecules. Our findings point to a role of osteoclast MCP‐1 in regulating bone remodeling. The higher bone mass in the femurs of MCP‐1‐KO mice could be, at least in part, due to decreased osteoclastogenesis and bone resorption resulting from aberrant M‐CSF signaling in OCs. J. Cell. Physiol. 227: 1619–1627, 2012.