| Abstrakt: |
Recent clinical studies suggest that several antihypertensive drugs, especially angiotensin-converting enzyme inhibitors, reduced bone fractures. To clarify the relationship between hypertension and osteoporosis, we focused on the role of angiotensin II (Ang II) on bone metabolism. In bone marrow-derived mononuclear cells, Ang II (1x10-6 M) significantly increased tartrate-resistant acid phosphatase (TRAP)-positive multinuclear osteoclasts. Of importance, Ang II significantly induced the expression of receptor activator of NF-κB ligand (RANKL) in osteoblasts, leading to the activation of osteoclasts, whereas these effects were completely blocked by an Ang II type 1 receptor blockade (olmesartan) and mitogen-activated protein kinase kinase inhibitors. In a rat ovariectomy model of estrogen deficiency, administration of Ang II (200 ng/kg/min) accelerated the increase in TRAP activity, accompanied by a significant decrease in bone density and an increase in urinary deoxypyridinoline. In hypertensive rats, treatment with olmesartan attenuated the ovariectomy-induced decrease in bone density and increase in TRAP activity and urinary deoxypyridinoline. Furthermore, in wild-type mice ovariectomy with five-sixths nephrectomy decreased bone volume by microcomputed tomography, whereas these change was not detect in Ang II type 1a receptor-deficient mice. Overall, Ang II accelerates osteoporosis by activating osteoclasts via RANKL induction. Blockade of Ang II might become a novel therapeutic approach to prevent osteoporosis in hypertensive patients.--Shimizu, H., Nakagami, H., Osako, M. K., Hanayama, R., Kunugiza, Y., Kizawa, T., Tomita, T., Yoshikawa, H., Ogihara, T., Morishita, R. Angiotensin II accelerates osteoporosis by activating osteoclasts. [ABSTRACT FROM AUTHOR] |
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