Bone-marrow derived monocyte-macrophages (BMMs) differentiate into osteoclasts by M-CSF along subsequent RANKL stimulation possibly in collaboration with many other unknown cytokines released by pre- or mature osteoblasts. The differentiation process requires receptor activator of nuclear factor kappa-B ligand (RANKL)/RANK signaling and reactive oxygen species (ROS) such as superoxide anion (O2•−). Gp91phox, a plasma membrane subunit of NADPH oxidase (Nox), is constitutively expressed in BMMs and plays a major role in superoxide anion production. In this study, we found that mice deficient in gp91phox (gp91phox−/−) showed defects in osteoclast differentiation. Femurs of these mice produced osteoclasts at about 70% of the levels seen in femurs from wild-type mice, and accordingly exhibited excessive bone density. This abnormal bone growth in the femurs of gp91phox−/− mice resulted from impaired osteoclast differentiation. In addition, gp91phox−/− mice were defective for RANKL-induced expression of nuclear factor of activated T cells c1 (NFATc1). However, H2O2 treatment compensated for gp91phox deficiency in BMMs, almost completely rescuing osteoclast differentiation. Treating wild-type BMMs with antioxidants and superoxide inhibitors resulted in a differentiation defect resembling the phenotype of gp91phox−/− BMMs. Therefore, our results demonstrate that gp91phox-derived superoxide is important for promoting efficient osteoclast differentiation by inducing NFATc1 as a downstream signaling mediator of RANK.

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AtSFT12, an Arabidopsis Qc-SNARE protein, is localized to Golgi organelles and is involved in salt and osmotic stress responses via accumulation of Na (+) in vacuoles. To reduce the detrimental effects of environmental stresses, plants have evolved many defense mechanisms. Here, we identified an Arabidopsis Qc-SNARE gene, AtSFT12, involved in salt and osmotic stress responses using an activation-tagging method. Both activation-tagged plants and overexpressing transgenic plants (OXs) of the AtSFT12 gene were tolerant to high concentrations of NaCl, LiCl, and mannitol, whereas loss-of-function mutants were sensitive to NaCl, LiCl, and mannitol. AtSFT12 transcription increased under NaCl, ABA, cold, and mannitol stresses but not MV treatment. GFP-fusion AtSFT12 protein was juxtaposed with Golgi marker, implying that its function is associated with Golgi-mediated transport. Quantitative measurement of Na(+) using induced coupled plasma atomic emission spectroscopy revealed that AtSFT12 OXs accumulated significantly more Na(+) than WT plants. In addition, Na(+)-dependent fluorescence analysis of Sodium Green showed comparatively higher Na(+) accumulation in vacuoles of AtSFT12 OX cells than in those of WT plant cells after salt treatments. Taken together, our findings suggest that AtSTF12, a Golgi Qc-SNARE protein, plays an important role in salt and osmotic stress responses and functions in the salt stress response via sequestration of Na(+) in vacuoles.

Postmenopausal osteoporosis is a common disorder resulting from increased osteoclastic activity. To determine the effect of Panax ginseng on postmenopausal osteoporosis, ovariectomized (OVX) mice were treated with 500 mg/kg/day P. ginseng extract (Pg) alone or in combination with hot water extract of Brassica oleracea (Bo) daily for 10 weeks, and the effect of the treatments on OVX-induced bone loss was examined. Bone weight, bone mineral density (BMD), osteoclast (OC) formation, OC marker expression, and biochemical parameters in blood were determined. OVX significantly increased body weight and decreased bone weight compared with those in the Sham group (p < 0.01). Pg or Bo alone did not affect OVX-induced bone loss, but a combination of Pg and Bo (Pg:Bo) recovered bone weight. The bones of OVX mice showed lower BMD than that of Sham mice, and the Pg:Bo = 3:1 restored the decreased BMD. Single treatment with Pg or Bo did not alter OC formation; however, the Pg:Bo = 3:1 inhibited OC formation. In addition, Pg and Bo lowered the OVX-induced elevation in blood glucose level. Thus, we suggest that Pg in combination with proper materials, such as Bo, might be a potential candidate treatment with minimal side effects protect against postmenopausal osteoporosis.