NaィイD1+ィエD1/CaィイD12+ィエD1 exchanger (NCX) catalyzes the electrogenic exchange of 3 NaィイD1+ィエD1 for 1 CaィイD12+ィエD1 across the plasma membrane in many mammalian cells. We have previously reported that the NaィイD1+ィエD1/CaィイD12+ィエD1 exchange activity had an important role for CSF-1-induced osteoclast differentiation. In the present study, we sought to confirm the role of NCX1, one of the isoforms of NCX and imports CaィイD12+ィエD1 into the cells from extracellular in the reverse mode, in osteoclast differentiation.
Osteoclast formation was studied in mouse bone marrow cells cultured for 6-day in the presence of sRANKLigand and CSF-1, Treatment with KB-R7943, a new NCX1 inhibitor, not only blocked the reverse mode of NCX1 activity but also the osteoclast differentiation and bone resorption induced by CSF-1. It also dose-dependently inhibited NaィイD1+ィエD1-dependent ィイD145ィエD1Ca uptake In mature osteoclasts. However, Ouabain, a NaィイD1+ィエD1KィイD1+ィエD1ATPase inhibitor stimulated osteoclast formation.
In addition, NCX1 antisense oligodeoxynucleotide (ODN) reduced the number of tartrate-resistant acid phosphatase-positive multinucleated cells and decreased the amount of NCX1, while non-sense or mismatched ODN did not.
In conclusion, the activation of NCX1 is essential for CSF-1-induced osteoclast differentiation.