PARTICIPATION OF OXIDATIVE STRESS IN THE PROCESS OF OSTEOCLAST DIFFERENTIATION

In the present paper, the involvement of active oxygen species in bone resorption has been studied. In order to compare the production of ac tive oxygen by mouse marrow culture cells, fluorescence due to peroxid es reacted with 2,7-dichlorofluorescin was measured. After marrow cell s were cultured with 1,25-(OH)2D, for 8 days, there were tartrate resi stant acid phosphatase positive multinucleated cells (TRACP(+)MNCs), T RACP positive mononucleated cells, macrophage-like cells and marrow de rived stromal cells. Among these cells, TRACP(+) cells could produce a lmost the equivalent amount of peroxides as could the macrophage-like cells. In order to examine the role of active oxygen in bone metabolis m, the amount of oxidative stress was altered during the culture perio d in the same marrow culture system. Catalase, a catabolic enzyme of h ydrogen peroxide (H2O2), significantly suppressed the formation of TRA CP(+)MNCs in a dose dependent manner. This suppression was limited in the early stage of the culture period and was reduced by the addition of exogenous H2O2 to culture. Moreover, when superoxide dismutase, a c onverting enzyme from superoxide anion to H2O2, was added in this syst em, the formation of TRACP(+)MNCs was significantly increased. These r esults strongly suggest that active oxygen species, especially H2O2, m ay be involved in the regulation of osteoclast formation.