Protective effect of NAC on formaldehyde‐containing–ZOE‐based root‐canal‐sealers–induced cyclooxygenase‐2 expression and cytotoxicity in human osteoblastic cells

Abstract Cyclooxygenase‐2 (COX‐2) is an inducible enzyme believed to be responsible for prostaglandin synthesis at site of inflammation. Recently, the activation of COX‐2 expression may be one of the important pathogenesis of root‐canal‐sealers–induced periapical inflammation. However, little is known about whether chemical interaction can modulate the COX‐2 expression and cytotoxicity induced by formaldehyde‐containing–ZOE‐based root canal sealers. The aim of this study was to investigate the effects of antioxidants such as catalase, superoxide dismutase (SOD), and N‐acetyl‐L‐cysteine (NAC) on N2‐ and endomethasone‐induced COX‐2 mRNA gene and cytotoxicity in human osteoblastic cell line U2OS cells. Our data demonstrated that both formaldehyde‐containing–ZOE‐based root canal sealers were found to induce COX‐2 mRNA gene expression in U2OS cells. The addition of glutathione (GSH) precursor NAC led to decrease the induction of COX‐2 mRNA gene expression and cytotoxicity by both N2 and Endomethasone (p < 0.05). However, catalase and SOD lacked the ability to prevent cytotoxicity and COX‐2 mRNA gene expression induced by N2 and Endomethasone (p > 0.05). The data presented here demonstrated that the activation of COX‐2 mRNA gene expression may be one of the pathogenesis of formaldehyde‐containing–ZOE‐based root‐canal‐sealers–induced periapical inflammation. In addition, GSH depletion, but not the attack of oxygen free radicals, could be the mechanism for cytotoxicity and COX‐2 mRNA gene expression induced by formaldehyde‐containing–ZOE‐based root canal sealers. NAC appears as a useful agent in protecting cell damage mediated by formaldehyde‐containing–ZOE‐based root canal sealers. © 2005 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 2005