Ascorbic Acid on Platelet Activation. New Functions for an Old Drug.

SCHATTNER, MIRTA; IVANI, PAOLA C.; SUAREZ, SEBASTIAN; MARTI, MARCELO A.; POZNER, ROBERTO G.

Berlin

Congreso; XXVI ISTH Congress; 2017

ISTH

Background: Early studies have shown that ascorbic acid (Asc), inhibits platelet (Plt) by reducing the levels of ROS. However, recent studies revealed that excessive vitamin C consumption may aggravate cardiovascular diseases in susceptible populations.Aims: We evaluated Plt responses at normal or low concentration of arachidonic acid (AA) and PAR1-AP.Methods: Plt aggregation was quantified by LTA, fibrinogen binding and p-selectin externalization were evaluated by FACS. The level of HNO, an interesting reactive nitrogen specie, produced by Plt was determined by the classical spectral changes in a manganese(III) prophyrin and by a new HNO-selective electrode (based on a cobalt(II) porphyrin).Results: Plt aggregation induced by AA 0.9mM or PAR1-AP 6μM were significantly inhibited when Asc 10mM was added to the aggregometer cuvette (49±10 or 24±9% of inhibition for AA or PAR1-AP, respectively). This effect was dependent on GPIIbIIIa activation, revealed by a similar inhibition of fibrinogen binding obtained in the presence of Asc. Moreover, p-selectin externalization was also abrogated by Asc. All the inhibitory effects on the Plt activation responses tested were dependent on the concentration of Asc.Surprisingly, when Plt were stimulated with non-aggregating concentrations of the agonists, the presence of Asc resulted in an aggregatory response (60±5 or 45±6% of aggregation for AA 0.2mM or PAR1-AP 3μM, respectively, p< 0.05). HNO was produced concomitantly with the aggregation induced by AA 0.9mM or PAR1-AP 6µM (290±20 or 216±36nM, respectively). Interestingly, the HNO production was significantly higher in the presence of Asc (963±146 or 980±126nM). However, HNO was not detected when Plt were stimulated by non-aggregating concentrations of agonists,All these responses were dependent on the concentration of Asc.Conclusions: Altogether, these results present Asc as a dual modulator for Plt aggregation and present evidence of HNO production in primary cell as a new endogenous negative regulator for Plt function.