sinomenine and Osteolysis

Sinomenine (SIN) is an anti-inflammatory and antiarthritic alkaloid derived from Sinomenium acutum, and the product Zhengqing Fengtongning produced from SIN has been marketed in China for treating rheumatoid arthritis (RA). Interestingly, we recently found that SIN could significantly ameliorate bone destruction induced by breast cancer cells in mice. Micro-CT examination showed that bone loss of the trabecular bones in tumor-bearing mice was markedly decreased by i.p. treatment of SIN at 150 mg/kg body weight. A mechanistic study demonstrated that SIN could suppress osteoclast formation and bone absorption induced by both MDA-MB-231 cells and MDA-MB-231 cell-conditioned medium (MDA-MB-231 CM) in preosteoclastic RAW264.7 cells. The MDA-MB-231 CM-induced osteoclast-related genes TRAP and OSCAR were obviously downregulated by SIN. In addition, mRNA expression of c-Fos and NFATc1 and nuclear translocation of c-Fos and NFATc1 protein were inhibited by SIN during MDA-MB-231 CM-induced osteoclastogenesis, while NF-κB signaling was not impacted by SIN. More interestingly, SIN was demonstrated to decrease hIL-8 mRNA expression in cultured MDA-MB-231 cells and to inhibit hIL-8 protein expression in MDA-MB-231 cells cocultured with preosteoclastic RAW264.7 cells while simultaneously downregulating CXCR1, the ligand of IL-8 related to bone destruction, during MDA-MB-231 CM-induced osteoclastogenesis. Previously, IL-8/CXCR1 was reported to be associated with the pathogenesis and progression of RA, and SIN was observed to markedly ameliorate bone erosion of RA patients. Our current findings may extend the utilization of SIN to preventing osteoclastogenesis and bone destruction in breast cancer patients and may enable IL-8/CXCR1 to serve as new targets for both anticancer and antiarthritic drug discovery.

Topics: Animals; Cell Line, Tumor; Female; Humans; Interleukin-8; Mammary Neoplasms, Experimental; Mice; Mice, Inbred BALB C; Morphinans; NFATC Transcription Factors; Osteoclasts; Osteogenesis; Osteolysis; Proto-Oncogene Proteins c-fos; RAW 264.7 Cells; Receptors, Interleukin-8A; Signal Transduction

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.

Topics: Animals; Calcium; Cell Survival; Lipopolysaccharides; MAP Kinase Signaling System; Mice; Morphinans; NF-kappa B; NFATC Transcription Factors; Osteoclasts; Osteogenesis; Osteolysis; RAW 264.7 Cells; TNF Receptor-Associated Factor 6; Toll-Like Receptor 4; Transcription Factor AP-1; Tumor Necrosis Factor-alpha