Regulation of cyclooxygenase-2 expression in human osteoblastic cells by N-acetylcysteine

Cyclooxygenase (COX) plays a pivotal role in the inflammatory process of in flammatory arthropathies, Inflammatory cytokines induce COX-2 expression in osteoblasts of inflamed joints, followed by osteoclast activation. The inh ibition of COX-2 expression could help prevent prostaglandin E-2 secretion, followed by osteoclast activation for bone destruction and resorption. We examined whether the antioxidant N-acetylcysteine (NAC) inhibited COX-2 exp ression induced in the human osteoblastic cell line MG63 by interleukin-1 b eta (IL-1 beta). According to Western blot and reverse transcription-polyme rase chain reaction (RT-PCR) test results, NAC inhibited IL-1 beta -induced COX-2 expression in protein and messenger RNA. We also demonstrated immuno histochemically that NAC inhibited NF kappaB nuclear translocation. These r esults suggested that NAC inhibited both COX-2 expression and NF kappaB nuc lear translocation in MG63, which in turn indicated that NAC could inhibit the inflammatory process involved in bone resorption by regulating COX-2 ex pression at the level of transcription.