ANGPT1 adenovirus

Disordered coagulation contributes to death in sepsis and lacks effective treatments. Existing markers of disseminated intravascular coagulation (DIC) reflect its sequelae rather than its cause, delaying diagnosis and treatment. Here, researchers show that disruption of the endothelial Tie2 axis is a precursor event in sepsis DIC. Proteomics of patients with sepsis DIC revealed a network involving inflammation and coagulation, with the Tie2 antagonist angiopoietin-2 (Angpt-2) occupying a central node. Angpt-2 correlated well with traditional DIC markers, including platelet counts, but more accurately predicted mortality in 2 large independent cohorts. In endotoxemic mice, reduced Tie2 signaling preceded overt signs of DIC. In vivo imaging of microvascular injury at this early stage revealed excessive fibrin accumulation, a pattern closely mimicked by Tie2 deficiency even in the absence of inflammation. Conversely, Tie2 activation normalized prothrombotic responses by suppressing endothelial tissue factor and phosphatidylserine exposure. Crucially, Tie2 activation had no adverse effects on bleeding. These results mechanistically implicate Tie2 signaling as a central regulator of microvascular thrombosis in septic DIC and suggest that circulating markers of the Tie2 axis could facilitate early diagnosis.

Tie2 activation normalizes thrombotic responses to sepsis without increasing bleeding risk. Here, researchers injected endotoxemic mice with adenovirus expressing human Angpt-1 (AdAngpt-1) by gene transfer. The amount of fibrin deposition at the site of vascular injury in mice exposed to LPS normalized to the levels of mice treated with control virus (Figure 1A, D, and E), and the amount of platelet aggregation tended to be reduced (Figure 1A-C). This could not be attributed to baseline differences in coagulation parameters or the potential for thrombosis in mice injected with adenoviral vectors. AdAngpt-1 treatment restored normal bleeding time and reduced the number of rebleedings in endotoxemic mice (Figure 1F and G), without directly affecting total platelet counts. Consistent with in vitro observations, delivery of AdAngpt-1 reduced spontaneous in situ fibrin aggregation triggered by LPS (Figure 1H and I). AdAngpt-1 also reduced LPS-induced thrombin generation compared with control vehicle-treated endotoxemic mice, as indicated by measuring the fold change in TAT complex levels (Figure 1J). Furthermore, Angpt-1 significantly reduced Angpt-2 expression (Figure 1L and M), whose elevated levels are associated with DIC in a human sepsis cohort by maintaining Tie2 activation (Figure 1M). These results suggest that Angpt-1 normalizes thrombosis in vivo during systemic inflammation without increasing bleeding risk.

Figure 1. Tie2 activation normalizes the septic thrombotic response to injury without increasing bleeding risk. (Higgins S J, et al., 2018)