Activation of the peripheral sympathetic nervous system increased the expression of cyclooxygenase-2 (COX-2) mRNA in mouse calvaria

Abstract

Pharmacological stimulation of adrenoceptor was demonstrated to increase the synthesis of prostaglandin (PG)-E 2, well known to modulate bone metabolism by regulating development and function of osteoclasts and osteoblasts, in cultured osteoblastic cells. Recently, intracerebroventricular (i.c.v.) injection of lipopolysaccharide (LPS), which caused the inflammatory stimuli in the brain, was demonstrated to increase the outflow of the peripheral sympathetic nervous system. In this study, to clarify the physiological role of sympathetic nerves to bone metabolism in vivo, we examined the effect of LPS (i.c.v.) on the expression of cyclooxygenase-2 (COX-2) mRNA in mouse calvaria, using reverse transcription-polymerase chain reaction analysis. The expression of COX-2 mRNA was increased by LPS (i.c.v.) in mouse calvaria. The treatment with the neurotoxin 6-hydroxydopamine or β-blocker inhibited the central LPS-induced COX-2 mRNA in mouse calvaria. In addition, the treatment of calvaria with isoprenaline, β-agonist, or noradrenaline increased PGE 2 synthesis in the organ culture system. These findings show that central LPS-induced COX-2 mRNA was mediated by the activation of postganglionic sympathetic nerve fibers and β-adrenoceptor in mouse calvaria and suggest that in vivo activation of the sympathetic nervous system modulates bone metabolism.