Fibrinogen signalling in erythrocyte nitric oxide mobilization in presence of PI3-K and adenylyl cyclase inhibitors

Soluble form of fibrinogen (Fib) and the peptide 4N1K are ligands of erythrocyte membrane CD47. Fibrinogen reinforces the ability of erythrocyte to scavenger nitric oxide (NO). Hiperfibrinogenemia increased NO efflux from erythrocyte in dependence of band 3 phosphorylation which is abolished by the presence of 4N1K. Herein we study in vitro the effect of high fibrinogen levels, on the NO efflux from erythrocytes and on its mobilization under influence of phosphoinositide-3 kinase (PI3-K) and adenylyl cyclase (AC) inhibitors in presence of 4N1K. Erythrocyte NO efflux, peroxynitrite, nitrite, nitrate and S-nitrosoglutathione (GSNO) were determined in blood samples in presence of 4N1K, wortmannin (WORT, PI3-K inhibitor) and MDL (AC inhibitor) under high fibrinogen concentrations. 4N1K with WORT and high fibrinogen levels induce, in relation to Fib plus WORT samples no variations on the erythrocyte NO efflux, decreased peroxynitrite, increased of nitrite, nitrate and GSNO concentrations. When 4N1K is present with MDL and high fibrinogen levels show, in relation to fibrinogen plus MDL samples increased erythrocyte NO efflux and nitrite, nitrate and GSNO concentrations. In conclusion, under high Fib levels and 4N1K the erythrocytes show: preservation of NO and impaired peroxynitrite in presence of PI3K inhibition; increased efflux of NO at lower levels of cAMP resulting from adenylyl cyclase inhibition.This study was supported by grants from the FCT— Fundação para a Ciência e a Tecnologia (project reference PTDC/SAU-OSM/73449/2006).