Amiloride inhibits osteoclastogenesis by suppressing nuclear factor-κB and mitogen-activated protein kinase activity in receptor activator of nuclear factor-κB-induced RAW264.7 cells.

Amiloride is widely used in clinical practice as a diuretic and is known to interact with the epithelial sodium channel and acid‑sensing ion channel proteins, as well as Na+/H+ antiporters and Na+/Ca2+ exchangers. The aim of the present study was to examine the effects of amiloride on receptor activator of nuclear factor‑κB ligand (RANKL)‑induced osteoclastogenesis and to elucidate the underlying mechanisms in the RAW264.7 murine macrophage cell line. The number of tartrate‑resistant acid phosphatase (TRAP)‑positive multinucleated cells were counted and the bone resorption area was estimated. In addition the expression levels of nuclear factor of activated T cells, cytoplasmic 1 (NFATc1) mRNA and osteoclast‑specific genes, including TRAP, matrix metalloproteinase 9, cathepsin K and osteoclast‑associated receptor, were examined using reverse transcription‑quantitative polymerase chain reaction. The nuclear factor‑κB (NF‑κB) and mitogen‑activated protein kinase (MAPK) signaling pathways were also investigated using western blotting. The results showed that amiloride significantly reduced the number of TRAP‑positive multinucleated cells as well as the bone resorption area. Amiloride also downregulated the expression of NFATc1 mRNA and inhibited the expression of osteoclast‑specific genes. A possible underlying mechanism may be that amiloride suppresses the degradation of the inhibitor of NF‑κB and blocks the activation of c‑Jun N‑terminal kinase, extracellular signal‑regulated kinase and p38, thus implicating the NF‑κB and MAPK pathway is this process. In conclusion, the current data suggest that amiloride is a strong inhibitor of osteoclast differentiation, indicating a novel indication for amiloride in the treatment of bone‑loss‑related diseases.