Angiopoietin2 is associated with coagulation activation and tissue factor expression in extracellular vesicles in COVID-19.

Coagulation activation in immunothrombosis involves various pathways distinct from classical hemostasis, offering potential therapeutic targets to control inflammation-induced hypercoagulability while potentially sparing hemostasis. The Angiopoietin/Tie2 pathway, previously linked to embryonic angiogenesis and sepsis-related endothelial barrier regulation, was recently associated with coagulation activation in sepsis and COVID-19. This study explores the connection between key mediators of the Angiopoietin/Tie2 pathway and coagulation activation. The study included COVID-19 patients with hypoxia and healthy controls. Blood samples were processed to obtain platelet-free plasma, and frozen until analysis. Extracellular vesicles (EVs) in plasma were characterized and quantified using flow cytometry, and their tissue factor (TF) procoagulant activity was measured using a kinetic chromogenic method. Several markers of hemostasis were assessed. Levels of ANGPT1, ANGPT2, and soluble Tie2 correlated with markers of coagulation and platelet activation. EVs from platelets and endothelial cells were increased in COVID-19 patients, and a significant increase in TF+ EVs derived from endothelial cells was observed. In addition, ANGPT2 levels were associated with TF expression and activity in EVs. In conclusion, we provide further evidence for the involvement of the Angiopoietin/Tie2 pathway in the coagulopathy of COVID-19 mediated in part by release of EVs as a potential source of TF activity.

Association of heme-oxygenase 1, hemopexin, and heme levels with markers of disease severity in COVID-19.

Heme-oxygenase 1 (HO-1) is an enzyme with well-known anti-inflammatory and antioxidant properties, whose levels have been previously associated with disease severity in the context of sterile and infectious diseases. Moreover, the heme/HO-1 pathway has been associated with prothrombotic changes in other diseases. Accordingly, the potential of modulating HO-1 levels for the treatment of COVID-19 was extensively speculated during the COVID-19 pandemic, but very few actual data were generated. The aim of our study was to explore the association of HO-1, heme, and hemopexin (HPX) levels with COVID-19 severity and with markers of inflammation and coagulation activation. The study was conducted in 30 consecutive patients with COVID-19 admitted due to hypoxemia, and 30 healthy volunteers matched by sex, age, and geographic region. HO-1 and HPX levels were measured by enzyme immunoassay (ELISA) and heme levels were measured by a colorimetric method. A comprehensive panel of coagulation and fibrinolysis activation was also used. Patients with COVID-19 presented increased levels of HO-1 when compared to controls (5741 ± 2696 vs 1953 ± 612 pg/mL, respectively, P < 0.0001), as well as a trend toward increased levels of HPX (3.724 ± 0.880 vs 3.254 ± 1.022 mg/mL, respectively; P = 0.06). In addition, HO-1 and HPX levels reduced from admission to day + 4. HO-1 levels were associated with duration of intensive care unit stay and with several markers of coagulation activation. In conclusion, modulation of HO-1 could be associated with the prothrombotic state observed in COVID-19, and HO-1 could also represent a relevant biomarker for COVID-19. New independent studies are warranted to explore and expand these findings.

Contact and intrinsic coagulation pathways are activated and associated with adverse clinical outcomes in COVID-19.

Coagulation activation is a prominent feature of severe acute respiratory syndrome coronavirus 2 (COVID-19) infection. Activation of the contact system and intrinsic pathway has increasingly been implicated in the prothrombotic state observed in both sterile and infectious inflammatory conditions. We therefore sought to assess activation of the contact system and intrinsic pathway in individuals with COVID-19 infection. Baseline plasma levels of protease:serpin complexes indicative of activation of the contact and intrinsic pathways were measured in samples from inpatients with COVID-19 and healthy individuals. Cleaved kininogen, a surrogate for bradykinin release, was measured by enzyme-linked immunosorbent assay, and extrinsic pathway activation was assessed by microvesicle tissue factor-mediated factor Xa (FXa; MVTF) generation. Samples were collected within 24 hours of COVID-19 diagnosis. Thirty patients with COVID-19 and 30 age- and sex-matched controls were enrolled. Contact system and intrinsic pathway activation in COVID-19 was demonstrated by increased plasma levels of FXIIa:C1 esterase inhibitor (C1), kallikrein:C1, FXIa:C1, FXIa:α1-antitrypsin, and FIXa:antithrombin (AT). MVTF levels were also increased in patients with COVID-19. Because FIXa:AT levels were associated with both contact/intrinsic pathway complexes and MVTF, activation of FIX likely occurs through both contact/intrinsic and extrinsic pathways. Among the protease:serpin complexes measured, FIXa:AT complexes were uniquely associated with clinical indices of disease severity, specifically total length of hospitalization, length of intensive care unit stay, and extent of lung computed tomography changes. We conclude that the contact/intrinsic pathway may contribute to the pathogenesis of the prothrombotic state in COVID-19. Larger prospective studies are required to confirm whether FIXa:AT complexes are a clinically useful biomarker of adverse clinical outcomes.

Antifungal Proteins from Plant Latex.

Latex, a milky fluid found in several plants, is widely used for many purposes, and its proteins have been investigated by researchers. Many studies have shown that latex produced by some plant species is a natural source of biologically active compounds, and many of the hydrolytic enzymes are related to health benefits. Research on the characterization and industrial and pharmaceutical utility of latex has progressed in recent years. Latex proteins are associated with plants' defense mechanisms, against attacks by fungi. In this respect, there are several biotechnological applications of antifungal proteins. Some findings reveal that antifungal proteins inhibit fungi by interrupting the synthesis of fungal cell walls or rupturing the membrane. Moreover, both phytopathogenic and clinical fungal strains are susceptible to latex proteins. The present review describes some important features of proteins isolated from plant latex which presented in vitro antifungal activities: protein classification, function, molecular weight, isoelectric point, as well as the fungal species that are inhibited by them. We also discuss their mechanisms of action.