Background: 

Inflammation and endothelium-derived superoxides are important pathomechanisms in atherothrombotic diseases. We could previously show that the tyrosine phosphatase SHP-1 acts as a negative regulator in endothelial superoxide production. We investigated the influence of SHP-1 on platelet-endothelium-interaction and arterial thrombosis in endothelial inflammation in vivo.

Methods: 

In human endothelial cells (HUVEC) superoxide production was investigated by cytochrom-c-reduction and expression of p-selectin by flow-cytometry. In vivo, firm adhesion, rolling of platelets and arterial thrombosis upon FeCl₃ superfusion were analyzed by intravital microscopy in the dorsal skinfold chamber mouse model. SHP-1 was specifically inhibited by knock-down via antisense-oligonucleotides or the pharmacological inhibitor Sodium Stibogluconate respectively. An inflammatory situation was induced by TNFa.

Results: 

SHP-1 inhibition in HUVEC led to increased superoxide production as well as to upregulation of p-selectin on the surface membrane. These effects were further enhanced when cells were additionally stimulated with TNFa. In vivo inhibition of SHP-1 did not significantly enhance platelet-endothelium-interaction under physiological conditions, whereas in acute systemic inflammation (TNFa) SHP-1 inhibition led to an augmented fraction of rolling platelets. Thrombotic vessel occlusion time was significantly reduced by SHP-1 inhibition, pre-treatment with TNFa further increased this effect.

Conclusions: 

SHP-1 acts especially in TNFa-induced endothelial activation as a negative regulator of superoxide production, which can lead to an upregulation of adhesion molecules that are relevant for platelet-endothelium-interaction. Indeed, in systemic inflammation SHP-1 impairs the rolling of platelets on the vessel wall and thus mediates antithrombotic effects in vivo.