Abstract
In end‐stage renal disease (ESRD) endothelium may represent a key target for the action of circulating elements, such as modified erythrocytes (RBC) and/or plasmatic factors, that may facilitate inflammation and the vasculopathy associated with uremia. We have previously demonstrated that phosphatidylserine (PS) exposure on the surface of RBC from ESRD patients increases RBC‐human umbilical vein endothelial cell (HUVEC) interactions and causes decreased nitric oxide (NO) production. We postulated that, besides the pro‐inflammatory effects due to decreased NO bio‐availability, enhanced ESRD‐RBC‐HUVEC interactions might directly stimulate pro‐inflammatory pathways leading to increased vascular adhesion molecule expression. ESRD‐RBC‐endothelial cell interactions induced a time‐dependent up‐regulation of VCAM‐1 and ICAM‐1 (measured by Western blot (WB) and real‐time PCR), associated with mitogen‐activated protein kinase (MAPK) activation and impairment of the Akt/endothelial nitric oxide synthase (eNOS) signaling cascade, measured by WB. In reconstitution experiments, normal RBC incubated with uremic plasma showed increased PS exposure and significantly increased VCAM‐1 and ICAM‐1 mRNA levels when incubated on HUVEC. Interestingly, ESRD‐RBC induced increased expression of adhesion molecules was prevented by Annexin‐V (AnV, able to mask PS on RBC surface), anti‐integrin‐αvβ3, anti‐thrombospondin‐1 (TSP‐1), and PD98059 (a selective inhibitor of MAPK phosphorylation). Moreover, AnV reversed the ESRD‐RBC effects on MAPK and Akt/eNOS signaling pathways. Our data demonstrate that, possibly via a direct interaction with the endothelial thrombospondin‐(αvβ3) integrin complex, ESRD‐RBC‐HUVEC adhesion induces a vascular inflammatory phenotype. Thus, intervention targeting ESRD‐RBC increased adhesion to endothelium and/or MAPK and Akt/eNOS pathways may have the potential to prevent vascular lesions under uremic conditions. J. Cell. Physiol. 213:699–709. © 2007 Wiley‐Liss, Inc.