Cyclic adenosine monophosphate-dependent mechanisms induce von Willebrand factor expression in the Dami megakaryoblastic cell line.

It has been proposed that cyclic adenosine monophosphate (cAMP) is involved in the differentiation of several cell types and this study analysed whether von Willebrand factor (vWf) synthesis, which is a marker of the megakaryocyte maturation of these cells, would be enhanced by agents acting on cAMP formation. Different compounds known to stimulate cAMP accumulation in cells were used: dibutyryl cAMP (db-cAMP), isobutyl-methylxanthine (IBMX) or pentoxifylline (PTX) and forskolin. Treatments with db-cAMP or IBMX (10-1,000 microM) induced a dose-dependent increase in vWf synthesis. Associations of IBMX with forskolin produced a synergistic enhancement in vWf synthesis. PTX alone did not enhance vWf synthesis but a latent effect was revealed in the presence of forskolin or db-cAMP. The increase in vWf mRNA shown by Northern blot analysis demonstrates that the protein synthesis correlates with the transcript expression after db-cAMP or IBMX treatments. vWf synthesis paralleled the accumulation of cAMP in the cells. Moreover vWf expression induced by combination of IBMX with forskolin was associated with a moderate increase in the percentage of GPIIb/IIIa positive cells and in the ploidy level related to an important inhibition of cell growth. These data provide evidence that agents acting on cAMP metabolism induce vWf synthesis in the Dami megakaryoblastic cells.