Evidence to suggest that the phosphodiesterase 4 isoenzyme is present and involved in the proliferation of umbilical cord blood mononuclear cells

Background The type 4 phosphodiesterase (PDE) isoenzyme is the main isoenzy me of PDE involved in the control of adult mononuclear cell proliferation. Objective To establish whether PDE isoenzymes are present in umbilical cord blood mononuclear cells by the use of selective PDE inhibitors, and to ide ntify which PDE isoenzymes are involved in controlling the proliferation of cord blood mononuclear cells. Methods Cord blood was obtained from normal deliveries and mononuclear cell s isolated as described previously [1] with some modifications. Mononuclear cells were then stimulated to proliferate with phytohaemagglutinin (PHA) ( 2 mu g/mL) in the presence of selective PDE inhibitors. Proliferation was m easured by [H-3]-thymidine incorporation. Results The type 4 PDE inhibitors (CDP840, rolipram and RO 20-1724), and th e mixed PDE3/4 inhibitor, zardaverine, produced a concentration-related inh ibition of PHA-stimulated cord blood mononuclear cell proliferation (P < 0. 05, anova). The non-selective PDE inhibitor, theophylline, also produced a concentration-related inhibition of proliferation (P < 0.05, anova). In con trast, the PDE1 inhibitor, vinpocetine, the PDE3 inhibitor, siguazodan, and the PDE5 inhibitor, zaprinast, were unable to inhibit cord blood mononucle ar cell proliferation. Conclusion PDE4 is present in umbilical cord mononuclear cells and is invol ved in the control of cord blood mononuclear cell proliferation.