Tumor necrosis factor alpha (TNFα) is a multifunctional inflammatory cytokine that regulates various cellular and bio-logical processes. Increased levels of TNFα have been im-plicated in a number of human diseases including diabetes and arthritis. Sympathetic nervous system stimulation via the beta2-adrenergic receptor (β2AR) in osteoblasts suppresses osteogenic activity. We previously reported that TNFα up- regulates β2AR expression in murine osteoblastic cells and that this modulation is associated with TNFα inhibition of osteoblast differentiation. In our present study, we explored whether TNFα induces β2AR expression in human osteo-blasts and then identified the downstream signaling path-way. Our results indicated that β2AR expression was increa-sed in Saos-2 and C2C12 cells by TNFα treatment, and that this increase was blocked by the inhibition of NF-κB acti-vation. Chromatin immunoprecipitation and luciferase reporter assay results indicated that NF-κB directly binds to its cog-nate elements on the β2AR promoter and thereby stimulates β2AR expression. These findings suggest that the activation of TNFα signaling in osteoblastic cells leads to an upregu-lation of β2AR and also that TNFα induces β2AR exp-ression in an NF-κB-dependent manner.

• Kyunghwa Baek(Department of Pharmacology, College of Dentistry, Research Institute of Oral Biology, Gangneung-Wonju National University)
• Jiho Kang(Department of Molecular Genetics, School of Dentistry and Dental Research Institute, Seoul National University)
• Hyo Rin Hwang(Department of Molecular Genetics, School of Dentistry and Dental Research Institute, Seoul National University)
• Jeong-Hwa Baek(Department of Molecular Genetics, School of Dentistry and Dental Research Institute, Seoul National University) Correspondence