PHOSPHODIESTERASE-4 INHIBITORS AND DB-CAMP INHIBIT TNF-ALPHA RELEASE FROM HUMAN MONONUCLEAR-CELLS - EFFECTS OF CAMP AND CGMP-DEPENDENT PROTEIN-KINASE INHIBITORS

WE investigated the effects of specific inhibitors of cAMP-dependent p rotein kinase (PKA) and cGMP-dependent protein kinase (PKG) on the inh ibitory activity of phosphodiesterase (PDE) type 4 inhibitors and of t he cell permeable analogue of cAMP, db-cAMP on LPS-induced TNF-alpha r elease from human mononuclear cells. Incubation from 30 min of mononuc lear cells with db-cAMP (10(-5) to 10(-3) M), rolipram (10(-9) M to 10 (-5) M) or Ro 20-1724 (10(-9) M to 10(-5) M) significantly inhibited L PS-induced TNF-alpha release. When mononuclear cells were preincubated for 30 min with the selective PKA inhibitor, H89 (10(-4) M), but not with the selective PKG inhibitor, Rp-8-pCPT-cGMPs (10(-4) M), a signif icant reduction of the inhibitory effect of db-cAMP was noted. Thirty min incubation of mononuclear cells with Rp-8-pCPT-cGMPs induced a sig nificant reduction of the inhibitory activities of both rolipram and R o 20-1724 (10(-9) to 10(-5) M) on LPS-induced TNF-alpha release, where as H89 elicited a moderate, but significant inhibition. The present da ta indicate that db-cAMP inhibits TNF-alpha release from human mononuc lear cells through a PKA-dependent mechanism. In contrast, PDE 4 inhib itors elicit their in vitro anti-inflammatory activities via a PKG-dep endent rather than PKA-dependent activation.