Molecular mechanisms of action of bisphosphonates and strontium ranelate

Bisphosphonates are chemical analogs of isoprene lipids, which competitively decrease the activity of farnesyl diphosphate synthase in osteoclasts and thus retard prenylation. The non-prenylated small GTPases cannot attach to the membrane of osteoclasts, which decreases their resorptive function and accelerates apoptosis. Strontium ranelate activates the Wnt signal pathway (with participation of calcium-sensitive receptor), increases the replication activity (by changing the function of RANKL/RANK/OPG system) thus suppressing the apoptosis of osteoblasts, and retards the resorptive function by accelerating the apoptosis of osteoclasts.