De-methylation Inducer, 5’–zacytidine Regulates Dedifferentiation and Cyclooxygenase (COX–2) Expression through the p38 Kinase Pathway in Rabbit Articular Chondrocytes

Abstract

DNA methylation during gene transcription is auniversal and important process. 5’–Azacytidine is known as a DNA methylation inhibitor that regulates various cancer cellular responses, including apoptosis, migration and inflammation. However, the effect of changes in DNA methylation on dedifferentiation and inflammation of articular chondrocytes are not well-understood. In the present study, the effects of 5’–Azacytidine on dedifferentiation and inflammation in rabbit articular chondrocytes. 5’–Azacytidine decreased expression of type 2 collagen, SOX–9 and DNMT1, as indicated by the western blot analysis, immunofluorescence staining, and sulfated proteoglycan was determined by Alcian blue staining. Also, 5’–azacytidine induces the expression of COX–2, as determined by western blot analysis. Additionally, treatment of 5’– azacytidine stimulated activation of p38 kinase. The inhibition of p38 kinase with SB203580 rescued the 5’–azacytidineinduced loss of type 2 collagen expression and decreased 5’–azacytidine-induced COX–2 expression according to western blot analysis and immunofluorescence results. These results indicated that 5’–azacytidine induces dedifferentiation and COX–2 expression by de-methylation via p38 kinase in rabbit articular chondrocytes.