Methods: Rat ROS 17/2.8 osteoblast-like cells were cultured with Ang II (0, 10-8 M, 10-7 M or 10-6 M) in the presence or absence of the AT1 receptor blocker losartan (5 µM) or the AT2 receptor blocker PD123319 (5 µM). Expression of the AT1 and AT2 receptors, MMPs, TIMPs, PAs, and PAI-1 was examined at the mRNA and protein levels by real-time PCR and Western blotting, respectively.
Results: Both the AT1 and AT2 receptors were expressed in ROS 17/2.8 cells. While cell proliferation was slightly increased by treatment with Ang II, alkaline phosphatase activity decreased. The expression of MMP-13 (collagenase) and MMP-3 (stromelysin) increased significantly as a result of treatment with 10-6 M Ang II, whereas the expression of MMP-2, MMP-14, urokinase-type PA, tissue-type PA, TIMPs-1, -2, -3, and PAI-1 was unaffected by Ang II. Expression of MMP-1 and TIMP-4 was not detected. Losartan blocked Ang II-induced expression of MMP-3 and MMP-13, whereas PD123319 did not completely block.
Conclusions: These results suggest that Ang II stimulates the resorption process that occurs during the turnover of osteoid by increasing the production of collagenase and stromelysin in osteoblasts via the AT1 receptor. Furthermore, they suggest that Ang II does not influence the plasminogen/plasmin pathway in osteoblasts.