Aconine inhibits RANKL-induced osteoclast differentiation in RAW264.7 cells by suppressing NF-κB and NFATc1 activation and DC-STAMP expression.

AIM: Aconiti Lateralis Radix Preparata is a traditional Chinese medicine used to treat chronic arthritis and is highly effective against rheumatoid arthritis. However, the effects of aconine, a derivative of aconitum alkaloids, on osteoclasts, which can absorb bone, remain unknown. Here, we investigated the effects of aconine on osteoclast differentiation and bone resorption in vitro. METHODS: The viability of mouse leukemic monocyte/macrophage cell line RAW264.7 was measured using CCK-8 assays. Osteoclast differentiation was induced by incubation of RAW264.7 cells in the presence of RANKL, and assessed with TRAP staining assay. Bone resorption was examined with bone resorption pits assay. The expression of relevant genes and proteins was analyzed using RT-PCR and Western blots. The activation of NF-κB and nuclear factor of activated T-cells (NFAT) was examined using stable NF-κB and NFATc1 luciferase reporter gene systems, RT-PCR and Western blot analysis. RESULTS: Aconine (0.125, 0.25 µmol/L) did not affect the viability of RAW264.7 cells, but dose-dependently inhibited RANKL-induced osteoclast formation and bone resorptive activity. Furthermore, aconine dose-dependently inhibited the RANKL-induced activation of NF-κB and NFATc1 in RAW264.7 cells, and subsequently reduced the expression of osteoclast-specific genes (c-Src, ß3-Integrin, cathepsin K and MMP-9) and the expression of dendritic cell-specific transmembrane protein (DC-STAMP), which played an important role in cell-cell fusion. CONCLUSION: These findings suggest that aconine inhibits RANKL-induced osteoclast differentiation in RAW264.7 cells by suppressing the activation of NF-κB and NFATc1 and the expression of the cell-cell fusion molecule DC-STAMP.

Sinomenine induces apoptosis in RAW 264.7 cell-derived osteoclasts in vitro via caspase-3 activation.

AIM: Sinomenine (SIN) is an alkaloid found in the roots and stems of Sinomenium acutum, which has been used to treat rheumatic arthritis in China and Japan. In this study we investigated the effects of SIN on osteoclast survival in vitro and the mechanisms of the actions. METHODS: Mature osteoclasts were differentiated from murine monocyte/macrophage cell line RAW264.7 through incubation in the presence of receptor activator of NF-κB ligand (RANKL, 100 ng/mL) for 4 d. The cell viability was detected using the CCK-8 method. The survival and actin ring construction of the osteoclasts were scored using TRACP staining and phalloidin-FITC staining, respectively. The apoptosis of the osteoclasts was detected by DNA fragmentation and Hoechst 33258 staining, and the cell necrosis was indicated by LDH activity. The activation of caspase-3 in osteoclasts was measured using Western blotting and the caspase-3 activity colorimetric method. RESULTS: SIN (0.25-2 mmol/L) inhibited the viability of mature osteoclasts in dose-dependent and time-dependent manners, but did not affect that of RAW264.7 cells. Consistently, SIN dose-dependently suppressed the survival of mature osteoclasts. The formation of actin ring, a marker associated with actively resorbing osteoclasts, was also impaired by the alkaloid. SIN (0.5 mmol/L) induced the apoptosis of mature osteoclasts, which was significantly attenuated in the presence of the caspase-3 inhibitor Ac-DEVD-CHO. SIN increased the cleavage of caspase-3 in mature osteoclasts in dose-dependent and time-dependent manners. Furthermore, SIN dose-dependently enhanced caspase-3 activity, which was blocked in the presence of Ac-DEVD-CHO. CONCLUSION: Sinomenine inhibits osteoclast survival in vitro through caspase-3-mediated apoptosis, thus it is a potential agent for treating excessive bone resorption diseases.

Sinomenine down-regulates TLR4/TRAF6 expression and attenuates lipopolysaccharide-induced osteoclastogenesis and osteolysis.

Sinomenine (SIN) is an anti-inflammatory and anti-arthritic alkaloid derived from Sinomenioum acutum. Effects of SIN on lipopolysaccharide (LPS)-induced osteolysis have not been reported. Here, we found that SIN reduced LPS-induced erosion of skull bones in C57BL/6 mice significantly. LPS can induce bone-absorbing osteoclast formation independent of RANKL in pre-osteoclastic RAW264.7 cells in vitro. Here, SIN suppressed LPS-induced osteoclast formation and osteoclast survival in RAW264.7 cells. Expression of osteoclastic-specific marker genes was also inhibited by SIN during osteoclast differentiation and osteoclast survival stimulated with LPS. SIN showed much stronger inhibitory effects on expression of Fra-1 and MMP-9 mRNA in osteoclast differentiation rather than osteoclast survival. SIN dramatically inhibited LPS-induced TNF-α production in vitro and in vivo. Further signaling studies revealed that SIN suppressed the activation and relative gene expression of three notable nuclear factors (NF-κB, AP-1, NFAT), reduced intracellular levels of Ca(2+), and down-regulated phosphorylation of MAPK p38 (but not JNK) in LPS-induced osteoclastogenesis. Focusing on upstream signals after LPS stimulation, SIN decreased expression of TLR4 and TRAF6 during osteoclast differentiation, and reduced expression of TLR4 (but not TRAF6) in osteoclast survival. These data suggest that SIN might be a potential agent for the treatment of osteolysis caused by Gram-negative bacteria infection or inflammation due to its inhibition of osteoclastogenesis through reduction of TLR4/TRAF6 expression and downstream signal transduction.

A novel synthetic dibenzocyclooctadiene lignan analog XLYF-104-6 attenuates lipopolysaccharide-induced inflammatory response in RAW264.7 macrophage cells and protects BALB/c mice from sepsis.

The wide range of inflammation mechanisms under control by NF-κB makes this pathway as an attractive target for new anti-inflammatory drugs. Herein, we showed that a new dibenzocyclooctadiene lignan analog XLYF-104-6, with a chemical name of 1,2,3,10,11-pentamethoxydibenzocycloocta-6,7-[c] pyrrole-1,3-dione, inhibited lipopolysaccharide (LPS)-induced NF-κB activation in RAW264.7 cells through preventing IκBα degradation and p65 nuclear translocation. The inhibitory activity of this compound on NF-κB activation contributes to the reduction of LPS-induced TNF-α and IL-6 productions. Notably, XLYF-104-6 suppressed LPS-induced iNOS expression and NO production in a NF-κB independent manner, since IKK inhibitor BAY 11-7082 has failed to exert similar inhibitory effect on iNOS expression and NO production. In addition, XLFY-104-6 also exerted anti-inflammatory action in endotoxemic mice by decreasing plasma LPS-induced TNF-α and IL-1ß levels as well as increasing plasma LPS-induced IL-10 concentrations. These findings suggest XLYF-104-6 could act as a leading compound for developing a potential anti-inflammatory drug.

Sinomenine suppresses osteoclast formation and Mycobacterium tuberculosis H37Ra-induced bone loss by modulating RANKL signaling pathways.

Receptor activator of NF-κB ligand (RANKL) is essential for osteoclastogenesis. Targeting RANKL signaling pathways has been an encouraging strategy for treating lytic bone diseases such as osteoporosis and rheumatoid arthritis (RA). Sinomenine (SIN), derived from Chinese medicinal plant Sinomenioumacutum, is an active compound to treat RA, but its effect on osteoclasts has been hitherto unknown. In the present study, SIN was found to ameliorate M. tuberculosis H37Ra (Mt)-induced bone loss in rats with a decreased serum level of TRACP5b and RANKL, and an increased level of osteoprotegerin (OPG). In vitro study also showed that SIN could inhibit RANKL-induced osteoclast formation and bone resorption. The osteoclastic specific marker genes induced by RANKL including c-Src, MMP-9, TRACP were inhibited by SIN in a dose dependent manner. Signal transduction studies showed that SIN could obviously reduce the expression of RANK adaptor molecule TRAF6 and down-regulate RANKL-induced NF-κB activation. It decreased the RANKL-induced p38, JNK posphorylation but not ERK1/2 posphorylation. SIN could also reduce RANKL-mediated calcium influx which is associated with TRAF6/c-Src complex. Finally, SIN suppressed RANKL induced AP-1 and NFAT transcription, as well as the gene expression of NFATc1 and AP-1 components (Fra-1, Fra-2, c-Fos). The protein expression of c-Fos and TRAF6 were also inhibited by SIN after RANKL stimulation. Taken together, SIN could attenuate osteoclast formation and Mt-induced bone loss by mediating RANKL signaling pathways.

Icaritin inhibits T cell activation and prolongs skin allograft survival in mice.

Icaritin is a native compound from Epimedium Genus, a traditional Chinese herbal medicine which is effective in treating asthma, autoimmune diseases and viral infections. In the present paper, the immunosuppressive effects of icaritin were found through in vitro and in vivo studies. Icaritin could dose-dependently inhibit murine CD4(+) T cells proliferation stimulated with mitogens or specific antigen ovabumin (OVA). Icaritin at 0.25-25µM could down-regulate T cell activation marker CD25 expression and inhibit IL-2 production. It could also reduce the Th1 cytokine IFN-γ production significantly if the T cells were activated by ConA or anti-CD3; while the inhibition of IL-4 secretion was only seen on anti-CD3 activated T cells treated with low concentrations of icaritin. In vivo study showed that treatment of icaritin at 10mg/kg/day on mice could suppress the immune response with prolonged allograft skin survival. Further study demonstrated that it reduced the alloantigen-induced splenocytes proliferation and Th1/Th2 cytokines. It could also increase NF-AT luciferase activity in Jurkat-NF-AT-luc T cells. The above results suggested that icaritin might be used to treat Th1 dominated immune diseases by interfering T cells activation with mechanism different to CsA.

[Inhibitory effects of HIV-1 gp41 fusion peptide on CD3 antibody activated regulatory T cells].

AIM: To investigate whether the HIV-1 gp41 fusion peptide (FP) could affect the regulatory T cell (Treg) function activated by CD3 antibody. METHODS: Murine CD4(+);CD25(+); Treg and CD4(+);CD25(-); effector T cells (Teff) were isolated from mice spleens by the immune magnetic beads. The splenocytes were treated with mitomycin C to obtain antigen presenting cells (APCs). CCK-8 assay and CFSE loading were employed to evaluate the effects of FP on the Treg inhibitory function via measuring Teff proliferation activated by CD3 antibody. In addition, IL-10 secretion of activated Treg was detected by ELISA. The distribution of FP and TCR on Treg surface was observed by laser scanning confocal microscope. RESULTS: Through the CCK-8 assay and flow cytometry, we found that Teff cells have significant proliferation stimulated by the CD3 antibodies. When Treg and Teff were co-cultured, the proliferation of Teff was significantly inhibited by Treg. When added with 25 µg/mL FP, the proliferation of Treg+Teff group and Teff group was not significantly affected, but when 5 µg/mL FP was added, the proliferation rate of Treg+Teff group was significantly lower than that of Teff group. IL-10 secretion was low when Treg were not activated, but it significantly increased by CD3 antibodies stimulation. When the concentration of FP was 25 µg/mL, IL-10 level significantly decreased, but 5 µg/mL FP did not significantly influence IL-10 secretion. Through the laser scanning confocal microscope, we found that T cell receptors (TCR) of non-activated Treg showed uniform distribution on the cell surface, and that FP and TCR had no common distribution. When Treg were stimulated by CD3 antibodies, the activated TCR formed half crescent, and FP and the activated TCR had common distribution on cell surface. CONCLUSION: Treg inhibitory function is significantly inhibited by 25 µg/mL FP in vitro, but 5 µg/mL FP does not affect it. This may be due to the suppression of IL-10 secretion and the influence of the signaling cross-talk between APC and TCR.