Adrenergic stimulation of osteoclastogenesis mediated by expression of osteoclast differentiation factor in MC3T3-E1 osteoblast-like cells

Abstract

It is well known that adrenergic agonists efficiently activate β-adrenoceptors on osteoblastic cells and can stimulate bone resorption in intact mouse calvaria. Recently, an osteoclastogenic factor of osteoblastic origin was found to be a novel tumor necrosis factor ligand family member and was termed osteoclast differentiation factor (ODF). Using a reverse transcription–polymerase chain reaction approach, we investigated the effect of epinephrine on mRNA levels of ODF and its decoy receptor, osteoclastogenesis inhibitory factor (OCIF), in MC3T3-E1 cells. Treatment with epinephrine (1 μM) rapidly increased ODF and OCIF mRNA levels, which peaked after 0.5 hr of treatment. Epinephrine (1 μM) also increased interleukin (IL)-6, IL-11, and cyclooxygenase (COX)-II mRNA levels, as well as increased prostaglandin E 2 (PGE 2) accumulation in the culture medium. Treatment of the cells with IL-11 (10 ng/mL) or PGE 2 (1 μM) increased ODF and OCIF mRNA levels as observed with epinephrine. However, increases in ODF and OCIF mRNA levels by epinephrine were more rapid than those by IL-11, and were not influenced by NS-398 (100 μM; an inhibitor of COX-II), suggesting a direct effect of epinephrine on ODF and OCIF mRNA expressions as well as an indirect effect mediated by IL-11 and PGE 2 production. Epinephrine-induced increases in ODF and OCIF mRNA levels were inhibited by pretreatment with timolol (1 μM; β-antagonist) and phentolamine (1 μM; α-antagonist), respectively. Furthermore, the formation of tartrate-resistant acid phosphatase-positive multinucleated cells from mouse bone marrow cells was stimulated by isoproterenol (0.1 to 10 μM) or epinephrine (0.1 to 10 μM). The action of isoproterenol, a β-agonist, was clearly stronger than that of epinephrine, suggesting the importance of the physiological balance between ODF and OCIF productions for osteoclastogenesis. These findings suggest that β-adrenergic stimulation induces not only IL-6, IL-11, and PGE 2 but also ODF expression in osteoblastic cells, leading to a stimulation of osteoclastogenesis.