Protein kinase C and cyclic AMP modulate thrombin-induced platelet-activating factor synthesis in human endothelial cells

Regine Heller, Federico Bussolino, Dario Ghigo, Giovanni Garbarino, Henning Schröder, Gianpiero Pescarmona, Uwe Till, Amalia Bosia

Research output: Contribution to journalArticlepeer-review


Stimulation of human endothelial cells (EC) by thrombin elicits a rapid increase of intracellular free Ca2+ [(Ca2+]i), platelet-activating factor (PAF) production and 1-O-alkyl-2-lyso-sn-glycero-3-phosphocholine (lyso-PAF):acetyl-CoA acetyltransferase (EC activity. The treatment of EC with thrombin leads to a 90% decrease in the cytosolic protein kinase C (PKC) activity; this dramatic decline is accompanied by an increase of the enzymatic activity in the particulate fraction. The role of PKC in thrombin-mediated PAF synthesis has been assessed: (1) by the blockade of PKC activity with partially selective inhibitors (palmitoyl-carnitine, sphingosine and H-7); (2) by chronic exposure of EC to phorbol 12-myristate 13-acetate (PMA), which results in down-regulation of PKC. In both cases, a strong inhibition of thrombin-induced PAF production is observed, suggesting obligatory requirement of PKC activity for PAF synthesis. It is suggested that PKC regulates EC phospholipase A2 (PLA2) activity as thrombin-induced arachidonic acid (AA) release is 90% inhibited in PKC-depleted cells. Brief exposure of EC to PMA strongly inhibits thrombin-induced [Ca2+]i rise, acetyltransferase activation and PAF production, suggesting that, in addition to the positive forward action, PKC provides a negative feedback control over membrane signalling pathways involved in the thrombin effect on EC. Forskolin and iloprost, two agents that increase the level of cellular cAMP in EC, are very effective in inhibiting thrombin-evoked cytosolic Ca2+ rise, acetyltransferase activation and PAF production; this suggests that endogenously generated prostacyclin (PGI2) may modulate the synthesis of PAF in human endothelial cells.

Original languageEnglish
Pages (from-to)55-64
Number of pages10
JournalBiochimica et Biophysica Acta - Molecular Cell Research
Issue number1
Publication statusPublished - Jun 7 1991


  • Calcium ion
  • cyclic AMP
  • Endothelium
  • PAF synthesis
  • Protein kinase C
  • Thrombin

ASJC Scopus subject areas

  • Biophysics
  • Cell Biology
  • Molecular Biology


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