Inhibition of PP2A activity may partly protect osteoblasts from apoptosis. (a) PP2A activity assay showed that okadaic acid treatment could inhibit PP2A activity under oxidative conditions. (b) MTT assay showed that osteoblastic viability may be partly rescued by inhibition of PP2A activity via okadaic acid. (c) Western blots showed that okadaic acid may recover mTOR activity, indicated by pp70S6K, and not alter PP2A components protein levels. (d) Schematic representation explaining the network of oxidative stress, AKT/mTOR, PP2A, and cell apoptosis in osteoblasts. Oxidative stress may induce dramatic apoptosis in primary osteoblasts. The apoptotic signaling activation was closely associated with activation of PP2A activity. However, inhibition of PP2A activity may partly rescue osteoblastic apoptosis under oxidative stresses.