PB0880 - The Brain-Derived Neurotrophic Factor (BDNF) sex-dependently affects platelet function in rats

Background: The Brain-derived neurotrophic factor (BDNF) induces platelet aggregation/secretion and enhances clot lysis in vitro. It is essential to study the physiological effect of BDNF in animal models of hemostasis.

Aims: We investigated the role of BDNF in platelet reactivity and hemostasis in female and male rats.

Methods: Platelet expression of BDNF, proBDNF, and their receptors, TrkB and p75NTR, was assessed using flow cytometry, immunoblotting and confocal microscopy. P-selectin was assessed using flow cytometry before and after PAR4-AP or BDNF activation. Platelet aggregation was assessed using light transmission aggregometry with washed platelets in response to classical agonists or BDNF. Plasma, serum and BDNF/proBDNF release upon platelet activation were quantified by ELISA. Viscoelastic properties of clots were studied using ROTEM. The tail transection bleeding model was performed following IV administration of BDNF-neutralizing antibody.

Results: Sixty-six Sprague-Dawley rats (50% females, mean age 12.6±1.4 weeks, weighing 347±103g) were included. BDNF, proBDNF, TrkB and p75NTR were expressed on the platelet surface and in their intracellular compartment. proBDNF concentrations were 8-fold higher than BDNF in plasma (p < 0.0001) and 3-fold in serum (p < 0.0001) due to the release of BDNF from platelet stores during clotting. Addition of exogenous BDNF induced biphasic platelet aggregation with no difference between sexes (p>0.99). At low concentrations, BDNF primed platelets, acting synergistically with collagen and PAR4-AP only in females. P-selectin expression was enhanced upon PAR4-AP and BDNF platelet activation, more significantly in females than in males (p=0.007 and p=0.01, respectively). Blood clot firmness was significantly reduced in presence of BDNF only in females (p=0.01). BDNF neutralization had no effect on tail bleeding in both sexes.

Conclusion(s): We show for the first time that BDNF might be an interesting novel modulator of hemostasis in rats with more pronounced effects in females.