To investigate the effects of sodium butyrate on the activity of RAW264.7 cells and the osteoclast differentiation.

The RAW264.7 cells were treated by sodium butyrate at concentrations of 0, 0.25, 0.50, 1.00, 2.00, 3.00, 4.00 and 5.00 mmol/L, with 3 double pores for each concentration. The cytotoxicity of sodium butyrate on RAW264.7 cells was detected by a CCK-8 kit. The effects of sodium butyrate (0, 0.25, 0.50 and 1.00 mmol/L) on apoptosis of RAW264.7 cells were detected by Hoechst33342 staining. RAW264.7 cells were induced into osteoclasts by osteoclast differentiation factors. The experiment was carried out in 2 groups (n=3). After induced maturation, the experimental group was treated with 1.00 mmol/L sodium butyrate and the control medium was added only with the same volume of solvent. The number of osteoclasts and the area of bone resorption were observed and compared. The differentiation of RAW264.7 cells was detected by tartrate-resistant acid phosphatase (TRAP) staining. Western blotting was used to detect the effects of sodium butyrate (0, 0.25, 0.50 and 1.00 mmol/L) on NF-κB-related signaling pathway in RAW264.7 cells.

Compared with the group of 0 mmol/L sodium butyrate, the activity of cells treated with 1.00, 2.00, 3.00, 4.00 and 5.00 mmol/L sodium butyrate for 24 h was significantly decreased (P<0.05). Treatment with 1.00 mmol/L sodium butyrate for 24 h induced apoptosis. The number of osteoclasts in the control group and the experimental group were 9.33±2.08 and 4.67±1.16, respectively, showing a significant difference between the 2 groups (t=3.395, P=0.027). The percentages of bone resorption area in the control group and the experimental group were 52.43%±5.38% and 14.28%±2.72%, respectively, also showing a significant difference between the 2 groups (t=10.970, P<0.001). Western blot results showed that, compared with other concentrations of sodium butyrate, treatment with 1 mmol/L sodium butyrate on RAW264.7 cells for 24 h led to an increase in the expression levels of cytoplasmic p65, B lymphoma-2 associated X protein and cleaved-caspase 3 and the acetylation of Histone H3 but a decrease in the phosphorylation level of α/β subunit of NF-κB kinase.

With the increased concentration of sodium butyratecan, the activity of NF-κB may be suppressed and the number of apoptotic cells may increase. 1.00 mmol/L sodium butyrate can reduce osteoclast formation and bone resorption area.

Sodium Butyrate; Osteoclasts; Apoptosis; Gut microbiome; Osteoporosis