p38/NF-kB-dependent expression of COX-2 during differentiation and inflammatory response of chondrocytes.
Studying cartilage differentiation, we observed the emergence of inflammation-related proteins suggesting that a common pathway was activated in cartilage differentiation and inflammation. In the present paper, we investigated the expression pathway of the inflammation-related enzyme Cyclooxygenase-2 (COX-2) during differentiation and inflammatory response of the chondrocytic cell line MC615. Cells were cultured either as (i) proliferating prechondrogenic cells expressing type I collagen or (ii) differentiated hyperconfluent cells expressing Sox9 and type II collagen. The p38 and the NF-kB pathways were investigated in standard conditions and after inflammatory agents treatment. NF-kB was constitutively activated in differentiated cells. The activation level of NF-kB in differentiated cells was comparable to the level in proliferating cells treated with the inflammatory agent LPS. In both cases, p65 was bound to the NF-kB consensus sequence of COX-2 promoter. p38, constitutively activated in differentiated cells, was activated in proliferating cells by treatment with LPS or IL-1alpha. In stimulated proliferating cells the two pathways are connected since addition of the p38-specific inhibitor SB203580 inhibited p38 activation, significantly reduced NF-kB activation and repressed COX-2 synthesis indicating that p38 is upstream NF-kB activation and COX-2 synthesis. In differentiated cells, the treatment with the inflammatory agent neither enhance NF-kB activation, nor synthesis of COX-2 while the addition of SB203580 neither repressed activation of p38, nor COX-2 synthesis, suggesting a constitutive activation of a p38/NF-kB/COX2 pathway. Our data indicate that in chondrocytes, COX-2 is expressed via p38 activation/NF-kB recruitment during both differentiation and inflammatory response.
Ulivi
Valentina
V
Istituto Nazionale per la Ricerca sul Cancro, Genova, Italy.
Giannoni
Paolo
P
Gentili
Chiara
C
Cancedda
Ranieri
R
Descalzi
Fiorella
F
D000818:Animals; D001706:Biopsy; D002454:Cell Differentiation; D002460:Cell Line; D019902:Chondrocytes / Q000378:metabolism / Q000473:pathology*; D051546:Cyclooxygenase 2 / Q000235:genetics*; D005786:Gene Expression Regulation / Q000502:physiology*; D006801:Humans; D007249:Inflammation / Q000378:metabolism*; D051379:Mice; D016328:NF-kappa B / Q000378:metabolism*; D015398:Signal Transduction; D048051:p38 Mitogen-Activated Protein Kinases / Q000378:metabolism*
D016328:NF-kappa B; D051546:Cyclooxygenase 2; D048051:p38 Mitogen-Activated Protein Kinases