Integrin-associated protein (CD47) is a putative mediator for soluble fibrinogen interaction with human red blood cells membrane

Abstract

Fibrinogen is a multifunctional plasma protein that plays a crucial role in several biological processes. Elevated fibrinogen induces erythrocyte hyperaggregation, suggesting an interaction between this protein and red blood cells (RBCs). Several studies support the concept that fibrinogen interacts with RBC membrane and this binding, due to specific and non-specific mechanisms, may be a trigger to RBC hyperaggregation in inflammation. The main goals of our work were to prove that human RBCs are able to specifically bind soluble fibrinogen, and identify membrane molecular targets that could be involved in this process. RBCs were first isolated from blood of healthy individuals and then separated in different age fractions by discontinuous Percoll gradients. After isolation RBC samples were incubated with human soluble fibrinogen and/or with a blocking antibody against CD47 followed by fluorescence confocal microscopy, flow cytometry acquisitions and zeta potential measurements. Our data show that soluble fibrinogen interacts with the human RBC membrane in an age-dependent manner, with younger RBCs interacting more with soluble fibrinogen than the older cells. Importantly, this interaction is abrogated in the presence of a specific antibody against CD47. Our results support a specific and age-dependent interaction of soluble fibrinogen with human RBC membrane; additionally we present CD47 as a putative mediator in this process. This interaction may contribute to RBC hyperaggregation in inflammation.

Factor XIIIa-dependent retention of red blood cells in clots is mediated by fibrin α-chain crosslinking

“…Although previous studies demonstrated specific interactions between fibrin and RBCs, [28][29][30] and implicate CD47 45 and a b3-like molecule 46 on the RBC surface, we were unable to detect any FXIIIa substrates on the RBC surface. We were also unable to detect differences in retention of young vs old RBCs in clots (data not shown), indicating age-dependent changes in RBC protein expression or morphology 47 do not influence their presence in clots.…”

Fibrinogen effects on erythrocyte nitric oxide mobilization in presence of acetylcholine

“…It is important to highlight that recently we described that CD47 is a putative binding site for fibrinogen at erythrocyte membrane (de Oliveira et al, 2012). Erythrocyte membrane CD47 at the complex Table 1 Mean values of erythrocyte elongation index (EEI) expressed in percentage obtained at shear stress values varied from 0.3 and 60.0 Pa.…”

Fibrinogen Effects of Erythrocyte Nitric Oxide Metabolism in Presence of Timolol

“…So, cAMP synthesis, are affected by the presence of AChE-timolol less active form and by Fib-CD47 receptor complex because both type of complexes are associated to Gi protein and consequently adenylyl cyclase inhibition [4,9,10]. Our results evidenced the effect of Fib in ED is synergic with timolol plus or not with MDL because maintaining cAMP synthesis inhibited.…”

“…Fibrinogen binding to erythrocyte CD47 receptor protein belonging to Rh complex that stablish contact with 4.2 cytoskeletal protein which interact with band 3 protein [4,15]. Mimicking, in vitro hyperfibrinogenemia increased values of nitric oxide (NO) efflux from RBCs dependent on band 3 protein phosphorylation degree and lower cyclic adenosine monophosphate (cAMP) concentration was evidenced [6,7].…”