Figure 5.

PDE1 – 5 activities in human OA chondrocytes. Upregulation of PDE4 by IL-1β and cyclic AMP agonists. (A) Chondrocytes were recovered from alginate beads and PDE activities were assessed in lysates at 0.5 μM cyclic AMP or cyclic GMP substrate concentrations. Results from six chondrocyte cultures derived from different donors are shown as the means±s.e.m. (B) Chondrocytes were preincubated with vehicle or 1 mM IBMX and 100 nM PGE₂ and stimulated with 200 pg ml⁻¹ IL-1β over 12 h. Chondrocytes were recovered from alginate beads and PDE activities were measured in lysates at 0.5 μM cyclic AMP or cyclic GMP substrate concentration. PDE4 was calculated as the fraction of total cAMP-PDE activity that was inhibited by 1 μM Piclamilast. Total cAMP-PDE and PDE4 were both increased by IL-1β and IL-1β and IBMX and PGE₂. Statistical significance: ^*P<0.05; ^***P<0.001 versus control activities. Changes in total cAMP-PDE and PDE4 activities with IBMX and PGE₂ added to IL-1β compared to IL-1β alone were not significant. Results are shown as the means of six experiments±s.e.m.