Dynamic compression counteracts IL-1β induced iNOS and COX-2 activity by human chondrocytes cultured in agarose constructs

Abstract

^.NO and PGE₂ are inflammatory mediators derived from the inducible iNOS and COX enzymes and are potentially important pharmacological targets in OA. Both mechanical loading and IL-1β will influence the release of ^.NO and PGE₂. Accordingly, the current study examines the effect of dynamic compression on ^.NO and PGE₂ release by human chondrocytes cultured in agarose constructs in the presence and absence of selective iNOS and COX-2 inhibitors. The current data demonstrate that IL-1β induced nitrite and PGE₂ release and inhibited [³H]-thymidine and ³⁵SO₄ incorporation. Inhibitor experiments indicate that 1400W and NS-398 either partially reversed or abolished IL-1β induced nitrite and PGE₂ release. IL-1β induced inhibition of cell proliferation and proteoglycan synthesis was partially reversed with 1400W but was not influenced by NS-398. For the dynamic loading experiments, 1400W and NS-398 either reduced or abolished the compression-induced inhibition of ^.NO and PGE₂ release in the presence of IL-1β. The IL-1β induced inhibition of cell proliferation was not influenced by 1400W or NS-398 whereas strain-induced stimulation of proteoglycan synthesis in the presence of IL-1β was enhanced by 1400W. The data obtained using human chondrocytes demonstrate that IL-1β induced ^.NO and PGE₂ release via an iNOS-driven-COX-2 inter-dependent pathway. This response could be reversed by dynamic compression. These data indicate interactions exist between the NOS and COX pathways, a finding which will provide new insights in the development of pharmacological or biophysical treatments for cartilage disorders such as OA.