[Activation of osteoclasts by RAAS and strategy of target therapy on bone metabolic diseases]

Angiotensin II is a potent stimulator of vascular smooth mustle cells that increases blood pressure, and angiotensin type 1 receptors have been identified on osteoblasts; thus, the renin-angiotensin system has been suggested to be involved in bone metabolism. The authors reported that angiotensin II significantly increased TRAP-positive multinuclear osteoclasts with the up-regulation of RANKL expression through extracellular kinase of osteoblast. These effects were abolished with co-treatment of angiotensin converting enzyme (ACE) inhibitors or angiotensin type 1 receptor blockers (ARB). Recently, RANK-RANKL-OPG system is proved to be involved in vascular calcification and RAAS also might be involved in the development of the disease. Thus, target therapy for RAAS might bring additional beneficial effects on bone metabolic diseases such as osteoporosis, rheumatoid arthritis and vascular calcification other than blood pressure lowering effect.