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This Article Full Text Full Text (PDF) All Versions of this Article: 296/1/E139    most recent 90677.2008v1 Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Kanazawa, I. Articles by Sugimoto, T. Search for Related Content PubMed PubMed Citation Articles by Kanazawa, I. Articles by Sugimoto, T.

Activation of AMP kinase and inhibition of Rho kinase induce the mineralization of osteoblastic MC3T3-E1 cells through endothelial NOS and BMP-2 expression

Department of Internal Medicine 1, Shimane University Faculty of Medicine, Enya-cho, Japan

Submitted 6 August 2008 ; accepted in final form 6 November 2008

AMP-activated protein kinase (AMPK) and Rho kinase (ROK) are known to modulate the mevalonate pathway. Activation of AMPK suppresses 3-hydroxy-3-methylglutaryl (HMG)-coenzyme A (CoA) reductase. ROK acts downstream of HMG-CoA reductase, and its inhibition exerts antiatherosclerosis effects. However, whether or not these enzymes are involved in bone metabolism is unclear. The present study was undertaken to investigate the effects of an AMPK activator, 5-aminoimidazole-4-carboxamide1-β-D-ribonucleoside (AICAR), and a ROK inhibitor, fasudil hydrochrolide, on the mineralization of osteoblastic MC3T3-E1 cells. Real-time PCR and mineralization stainings revealed that both AICAR and fasudil significantly stimulated endothelial nitric oxide synthase (eNOS), bone morphogenetic protein-2 (BMP-2), and osteocalcin mRNA expression as well as mineralization in the cells. Supplementation of either mevalonate or geranyl-geranyl pyrophosphate, the downstream molecules of HMG-CoA reductase, or coincubation with either a nitric oxide synthase inhibitor, N^G-nitro-L-arginine methyl ester, or a BMP-2 antagonist, noggin, significantly reversed these AICAR-induced reactions. Western blot analysis showed that AICAR activated protein kinase B and extracellular signal-regulated kinase (ERK). ERK inhibitor significantly reversed the AICAR-induced increase in eNOS and BMP-2 mRNA expression. Measurement of ROK activities by enzyme-linked immunosorbent assay revealed that both AICAR and fasudil significantly suppressed the phosphorylation of the myosin-binding subunit of myosin phosphate, a ROK substrate. These findings suggest that the AMPK activator and the ROK inhibitor are able to stimulate the mineralization of osteoblasts through modulating the mevalonate pathway. These agents could be candidate drugs that promote bone formation for the treatment of osteoporosis.

adenosine 5'-monophosphate protein kinase; Rho kinase; bone morphogenetic protein-2; endothelial nitric oxide synthase; osteoblast