Dynamic compression influences interleukin-1β-induced nitric oxide and prostaglandin E2 release by articular chondrocytes via alterations in iNOS and COX-2 expression
Issue title: Selected papers of the 5th International Symposium on Mechanobiology of Cartilage and Chondrocyte, Athens, May 2007
Affiliations: School of Engineering and Materials Science, Queen Mary, University of London, London, E1 4NS, UK | Queens Medical Research Institute, Edinburgh University, Edinburgh, UK
Note: [] Address for correspondence: Prof. David Lee, School of Engineering and Materials Science, Queen Mary, University of London, Mile End Road, London, E1 4NS, UK. Tel.: +44 207 882 5433; Fax: +44 208 983 1007; E-mail: [email protected].
Abstract: Interleukin-1β (IL-1β) induces the release of nitric oxide (·NO) and prostaglandin E2 (PGE2) by chondrocytes and this effect can be reversed with the application of dynamic compression. Previous studies have indicated that integrins may play a role. In addition, IL-1β upregulates the expression of iNOS and COX-2 mRNA via upstream activation of p38 MAPK. The current study examines the involvement of these pathways in mediating ·NO and PGE2 release in IL-1β stimulated bovine chondrocytes subjected to dynamic compression. Bovine chondrocytes were seeded in agarose constructs and cultured with 0 or 10 ng·ml−1 IL-1β with or without the application of 15% dynamic compressive strain at 1 Hz. Selected inhibitors were used to interrogate the role of α5β1 integrin signalling and p38 MAPK activation in mediating the release of ·NO and PGE2 in response to both IL-1β and dynamic compression. The relative expression levels of iNOS and COX-2 were assessed using real-time quantitative PCR. Nitrite, a stable end product of ·NO, was measured using the Griess assay and PGE2 release was measured using an enzyme immunoassay. IL-1β enhanced ·NO and PGE2 release and this effect was reversed by the application of dynamic compression. Co-incubation with an integrin binding peptide (GRGDSP) abolished the compression-induced effect. Real-time quantitative PCR analysis revealed that IL-1β enhanced iNOS and COX-2 mRNA levels, with the maximum expression at 6 or 12 hours. Dynamic compression reduced this effect via a p38 MAPK sensitive pathway. These results suggest that dynamic compression acts to abrogate of ·NO and PGE2 release by directly influencing the expression levels of iNOS and COX-2.
