P-selectin and blood coagulation: it's not only about inflammation any more

The Role of P-Selectin in COVID-19 Coagulopathy: An Updated Review

In severe COVID-19, which is characterized by blood clots and neutrophil-platelet aggregates in the circulating blood and different tissues, an increased incidence of cardiovascular complications and venous thrombotic events has been reported. The inflammatory storm that characterizes severe infections may act as a driver capable of profoundly disrupting the complex interplay between platelets, endothelium, and leukocytes, thus contributing to the definition of COVID-19-associated coagulopathy. In this frame, P-selectin represents a key molecule expressed on endothelial cells and on activated platelets, and contributes to endothelial activation, leucocyte recruitment, rolling, and tissue migration. Briefly, we describe the current state of knowledge about P-selectin involvement in COVID-19 pathogenesis, its possible use as a severity marker and as a target for host-directed therapeutic intervention.

A new way to treat proximal deep venous thrombosis using E-selectin inhibition

OBJECTIVE

There is an inter-relationship between thrombosis and inflammation. Previously, we have shown the importance of P-selectin in thrombogenesis and thrombus resolution in many preclinical animal models. The role of E-selectin has been explored in rodent models and in a small pilot study of clinical calf vein deep venous thrombosis. The purpose of this study was to determine the role of E-selectin in thrombosis in a primate model of proximal iliac vein thrombosis, a model close to the human condition.

METHODS

Iliac vein thrombosis was induced with a well-characterized primate model. Through a transplant incision, the hypogastric vein and iliac vein branches were ligated. Thrombus was induced by balloon occlusion of the proximal and distal iliac vein for 6 hours. The balloons were then deflated, and the primates recovered. Starting on postocclusion day 2, animals were treated with the E-selectin inhibitor GMI-1271, 25 mg/kg subcutaneously, once daily until day 21 (n = 4). Nontreated control animals received no treatment (n = 5). All animals were evaluated by magnetic resonance venography (MRV); evaluation of vessel area by ultrasound, protein analysis, hematology (complete blood count), and coagulation tests (bleeding time, prothrombin time, activated partial thromboplastin time, fibrinogen, and thromboelastography) were performed at baseline, day 2, day 7, day 14, and day 21 with euthanasia. In addition, platelet function and CD44 expression on leukocytes were determined.

RESULTS

E-selectin inhibition by GMI-1271 significantly increased vein recanalization by MRV vs control animals on day 14 (P < .05) and day 21 (P < .0001). GMI-1271 significantly decreased vein wall inflammation by MRV with gadolinium vein wall enhancement vs control also on day 14 (P < .0001) and day 21 (P < .0001). The thromboelastographic measure of clot strength (maximum amplitude) showed significant decreases in animals treated with GMI-1271 vs controls at day 2 (P < .05) and day 7 (P < .05). Animals treated with GMI-1271 had significant vessel area increase by day 21 vs controls (P < .05) by ultrasound. Vein wall intimal thickening (P < .001) and intimal fibrosis (P < .05) scores were significantly decreased in GMI-1271-treated animals vs controls. Importantly, no significant differences in hematology or coagulation test results were noted between all groups, suggesting that E-selectin inhibition carries no bleeding potential. GMI-1271 did not affect platelet function or aggregation or CD44 expression on leukocytes. In addition, no episodes of bleeding were noted in either group.

CONCLUSIONS

This study suggests that E-selectin modulates venous thrombus progression and that its inhibition will increase thrombus recanalization and decrease vein wall inflammation, without affecting coagulation. The use of an E-selectin inhibitor such as GMI-1271 could potentially change how we treat deep venous thrombosis.

Lactadherin: An unappreciated haemostasis regulator and potential therapeutic agent

Lactadherin is a small (53-66kDa) multifunctional glycoprotein belonging to the secreted extracellular matrix protein family. It has a multi-domain structure and is involved in many biological and physiological processes, including phagocytosis, angiogenesis, atherosclerosis, tissue remodeling, and haemostasis regulation. Lactadherin binds phosphatidylserine (PS)-enriched cell surfaces in a receptor-independent manner. Interaction between lactadherin and PS is crucial for regulation of blood coagulation processes. This review summarizes recent knowledge on the possible role of lactadherin in haemostasis control, emphasizing the great significance of the interaction between lactadherin and PS expressed on activated platelets and extracellular vesicles. The possible role of lactadherin as a therapeutic target and biomarker is also discussed.

Tissue factor pathway inhibitor and P-selectin as markers of sepsis-induced non-overt disseminated intravascular coagulopathy

Inflammation and coagulation occur concomitantly in sepsis. Thrombin activates platelet that leads to P-selectin translocation, which upregulate tissue factor (TF) generation. Tissue factor pathway inhibitor (TFPI) is an anticoagulant that modulates coagulation induced by TF. The term non-overt disseminated intravascular coagulation (DIC) refers to a state of affairs prevalent before the occurrence of overt DIC. It was suggested that an initiation of treatment in non-overt DIC has better outcome than overt DIC. This study investigated the role of TFPI level, P-selectin, and thrombin activation markers in non-overt and overt DIC induced by sepsis and its relationship to outcome and organ dysfunction as measured by the Sequential Organ Failure Assessment (SOFA) score. It included 176 patients with sepsis. They were admitted to the pediatric intensive care unit (ICU).They included 144 cases of non-overt DIC and 32 cases of overt DIC. There was a significant difference in hemostatic markers, platelet count, partial thromboplastin time (PTT), P-selectin, thrombin activation markers, TFPI, and DIC score between overt and non-overt DIC in both groups. It was noticed that P-selectin was positively correlated with DIC score, fibrinogen consumption, fibrinolysis (D-dimer), thrombin activation markers, and TFPI. Tissue factor pathway inhibitor was significantly correlated with fibrinolysis, DIC score, and prothrombin fragment 1+2. Sequential Organ Failure Assessment score was correlated with DIC score and other hemostatic markers in patients with overt DIC. To improve the outcome of patients with DIC, there is a need to establish more diagnostic criteria for non-overt-DIC. Plasma levels of TFPI and P-selectin may be helpful in this respect.

Enhanced peripheral thrombogenicity after lung inflammation is mediated by platelet-leukocyte activation: role of P-selectin

BACKGROUND

Inhaled ultrafine particles trigger peripheral thrombotic complications.

METHODS

We have analyzed the systemic prothrombotic risk following lung inflammation induced by pulmonary carbon nanotubes (CNTs).

RESULTS

Intratracheal instillation in Swiss mice of 200 and 400 microg of multiwall ground CNTs triggered substantial lung neutrophil, but not macrophage influx, 24 h later. The detection of circulating platelet-leukocyte conjugates exclusively 6 h after CNT instillation pointed to early but transient activation of circulating platelets. At 24 h, elevated plasma procoagulant microvesicular tissue factor activity was found in CNT-exposed but not in saline-exposed mice. However, at 24 h, both the tail and jugular vein bleeding times were prolonged in CNT-exposed but not in saline-exposed mice, arguing against strong CNT-induced platelet activation at this point. Nevertheless, at 24 h, enhanced peripheral thrombogenicity was detected in CNT-exposed but not in saline-exposed mice, via quantitative photochemically induced carotid artery thrombosis measurements. P-selectin neutralization abrogated platelet-leukocyte conjugate formation and microvesicular tissue factor generation, and abolished the CNT-induced thrombogenicity amplification. In contrast, the weak vascular injury-triggered thrombus formation in saline-treated mice was not affected by P-selectin neutralization at 24 h.

CONCLUSIONS

The mild CNT-induced lung inflammation translates via rapid but mild and transient activation of platelets into P-selectin-mediated systemic inflammation. Leukocyte activation leads to tissue factor release, in turn eliciting inflammation-induced procoagulant activity and an associated prothrombotic risk.