Inhibitory effect of Carthamus tinctorius L. seed extracts on bone resorption mediated by tyrosine kinase, COX-2 (cyclooxygenase) and PG (prostaglandin) E₂

Anti-bone resorption properties of the Korean herbal formulation, Honghwain (HHI; Carthamus tinctorius L. seed) was biochemically investigated. On processing bone metabolism, PGE₂ accelerated production of IL-1β in fetal mouse osteoblast and stimulated physiological activation substance, IL-1β. The novel class of Src tyrosine kinase inhibitors, Herbimycin A (HERB) and HHI reduced COX-2 mRNA levels as well as PGE₂ production induced by IL-1β, TNF-α and IL-6. HHI inhibited in vitro and in vivo bone resorption by inhibition of phosphorylation of peptide substrates. HHI dose-dependently reduced the hypercalcemia induced in mice by IL-1β and partly prevented bone loss and microarchitectural changes in young ovariectomized rats, showing that the protective effect on bone was exerted via the inhibition of bone resorption. These results indicate that the synergy between IL-β, TNF-α, IL-6 on PGE₂ production is due to an enhanced gene expression of COX-2 and that tyrosine kinase (s) are involved in the signal transduction of COX-2 in mouse calvarial osteoblasts. Thus, HHI as a possible Src family kinase inhibitor may be useful for the treatment of diseases associated with elevated bone loss.