Magnesium maintains endothelial integrity, up-regulates proteolysis of ultra-large von Willebrand factor, and reduces platelet aggregation under flow conditions

Mg ⁺⁺ regulates endothelial functions and has anti-inflammatory effects. Its effects on thrombosis have been demonstrated, but the mechanism remains poorly understood. We investigated the roles of MgSO₄ in regulating the release and cleavage of the prothrombotic ultra-large (UL) von Willebrand factor (VWF) and VWF-mediated platelet adhesion and aggregation. Washed platelets were perfused over cultured endothelial cells from human umbilical cord veins under a shear stress of 2.5 dyn/cm². Release and cleavage of ULVWF by ADAMTS-13 was measured in the absence or presence of physiological or therapeutic levels of MgSO₄. Whole blood or plasma-free reconstituted blood was perfused over immobilized collagen to measure the effect of MgSO₄ on platelet adhesion and aggregation. Also studied were the effects of MgSO4 on ristocetin-induced platelet aggregation and VWF-collagen interaction. Maintenance of endothelial integrity required physiological levels of MgSO₄, but exogenous MgSO ₄ showed no additional benefits. Exogenous MgSO₄ significantly enhanced the cleavage of the newly released ULVWF strings by ADAMTS-13 and markedly reduced platelet aggregation on immobilized collagen under flow conditions. This effect is likely to be mediated through VWF as Mg⁺⁺ partially inhibited ristocetin-induced platelet aggregation and VWF binding to collagen. MgSO₄ is critical for maintaining endothelial integrity and regulates ULVWF proteolysis and aggregation under flow conditions. These results provide a new insight into additional mechanisms involved with magnesium therapy.