Signal transduction system in osteoclasts through tetrahydrobiopterin-mediated production of NO and cGMP.

点击翻译按钮获取中文摘要

Nitric oxide (NO) inhibits osteoclast activity, but the signal transduction mechanism is not understood. cGMP and cGMP-dependent protein kinase signling pathway mediate several physiologic effects of NO possiblly including bone resorption. NO synthase (NOS) was recently shown to require tetrahydrobiopter in (BH4) as an natural cofactor in its activity. Thus it is of great interest to know the regulation mechanism of bone resorption by BH4 content in the osteoclast through activation of NOS and the resulted formations of NO and cGMP.However, nothing is known about the ability of BH4 synthesis in osteoclasts. Therefore, we studied the occurence of BH4-synthesyzing enzymes and BH4 content in the osteoclaset, cDNA of sepiapterin reductase, an enzyme involved in the last step of the biosynthetic pathway of BH4, was amplified by RT-PCR method and expressed by E.coli. The protein which shows the enzyme activity has been obtained and purified to homogeneity. And the polyclonal antibody was prepared against the protein. These are usefull for detecting the level and localization of BH4-synthesis in the osteoclasts. We could isolated cell mass containing more than 95% osteoclasts from bonemarrows of rabbit thigh bones with great difficulty as the enough amount to assay BH4 or NO content in the cell. And contents of BH4 and NO detected per 10^5cells were quite significant. Thus we have found that the osteoclast has the ability for BH4 synthesis and we could established a kit for analysis the relation between the formation of BH4, NO,and cGMP,and osteoclasis.