Abstract
Osteoporosis is a metabolic bone disease that is characterized by decreased bone density and strength due to excessive loss of bone protein and mineral content, which can be induced by increased osteoclast activity. Developing agents targeting osteoclast activation is considered to be the most effective method to reverse bone destruction and alleviate the pain caused by osteoporosis. MTT assay was conducted to detect the cell viability after artesunate treatment of RAW264.7 cells. TRACP staining and pit formation assays were performed to examine the TRACP-positive cells and pit-forming activity of osteoclasts. qRT-PCR and Western blot analysis were performed to assess the mRNA and protein expression levels of the osteoclastogenesis-related genes NFATc1, TRAP, and cathepsin k. The protein levels of RANK, p-Akt, p-p38, and p-ERK were examined by Western blotting. Luciferase reporter assay was conducted to determine whether miR-503 targeted RANK directly. Artesunate inhibited TRACP-positive cells and the pit-forming activity of osteoclasts. However, artesunate increased the expression of miR-503. Artesunate suppressed osteoclastogenesis-related gene expression and RANKL-induced activation of MAPKs and the AKT pathway. In addition, miR-503 inhibited RANK expression by directly targeting RANK during osteoclast differentiation. Artesunate inhibited osteoclastogenesis and osteoclast functions in vitro by regulating the miR-503/RANK axis and suppressing the MAPK and AKT pathways, which resulted in decreased expression of osteoclastogenesis-related markers.
Highlights
The bone remodelling process is characterized by a highly dynamic balance between bone absorption by osteoclasts (OC) and bone matrix synthesis by osteoblasts (OB)
We demonstrated that artesunate inhibited RANKL-induced osteoclastogenesis and osteoclast functions by regulating the miR-503/RANK axis and inhibiting the AKT and MAPK signaling pathways
To investigate the influence of artesunate on osteoclastogenesis, RAW264.7 cells were incubated with RANKL at 2 μM, 4 μM or 8 μM concentrations of artesunate
Summary
The bone remodelling process is characterized by a highly dynamic balance between bone absorption by osteoclasts (OC) and bone matrix synthesis by osteoblasts (OB). During RANKL-induced osteoclastogenesis, the binding of RANKL to its receptor RANK (receptor activator of nuclear NF-κB) results in the recruitment and activation of adaptor TRAF6 and triggers the activation of MAP kinases (ERK, JNK and p38) and transcription factors such as NF-κB, AP-1, and NFAT [8,9]. The activation of these transcription factors can regulate osteoclast differentiation by promoting the expression of osteoclast-associated genes
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