Tissue factor

The effects of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) on ischemic stroke and the possible underlying mechanisms

Purpose: As of November 28, 2020, COVID-19 has been reported in 220 countries with 61,036,793 confirmed cases and 1,433,316 confirmed deaths; countries became vigilant around the world. In addition to SARS-CoV-2 causing pneumonia, many studies have reported ischemic stroke in patients with COVID-19. This article describes the effects and possible underlying mechanisms of SARS-CoV-2 on ischemic stroke.Materials and methods: A literature search was performed using PubMed, Web of Science, and other COVID-dedicated databases and the combination of the keywords 'SARS-CoV-2', 'COVID-19' and 'ischemic stroke' up to November 28, 2020.Results: SARS-CoV-2 invades the host through angiotensin converting enzyme 2 (ACE2). ACE2 is expressed not only in the lungs, but also in the brain and vascular endothelial cells. SARS-CoV-2 infection might cause direct vascular disease or enhance the immunogenic thrombosis environment through several mechanisms. SARS-CoV-2 infection can modulate the host immune response and can cause inflammation, coagulation disorders, renin angiotensin system disorders, hypoxia, and stress disorders, which may lead to the occurrence of ischemic stroke.Conclusions: Some patients with COVID-19 can develop ischemic stroke. Ischemic stroke has a high risk of causing disability and is associated with a high mortality rate. It is hoped that when medical staff treat patients with COVID-19, they would pay attention to the occurrence of ischemic stroke to improve the prognosis of patients with COVID-19.

Tissue factor and tissue factor pathway inhibitor in chronically inflamed gallbladder mucosa

We characterised a tissue factor (TF) and tissue factor pathway inhibitor (TFPI) expression in relation to severity of inflammatory infiltration of the gallbladder mucosa in a chronic cholecystitis. We prospectively studied the gallbladder specimens obtained from 54 patients who had undergone cholecystectomy due to chronic calculous cholecystitis and 16 calculosis-free gallbladder specimens obtained from patients who underwent cholecystectomy due to the polyp/polyps as well as in cases of gallbladder injury. To assess TF and TFPI immunoreactivity by immunohistochemistry, the monoclonal anti-human TF and TFPI antibodies were used. The inflammatory infiltration of the gallbladder mucosa was reflected by the number of CD3 and CD68 positive cells. The expression of TF and TFPI differed significantly between the cholecystitis and the control group. Most capillary endothelial cells of the cholecystitis group presented weak expression for TFPI. The mean number of CD3 positive lymphocytes in the cholecystitis group was 18.6 ± 12.2, but the mean number of CD68 positive cells was 29.7 ± 13.9. In the control sections, it was 3.1 ± 1.9 and 8.8 ± 3.9, respectively (P < 0.001). The results of the current study suggest that the tissue procoagulant state found may be engaged in the etiopathogenesis of the cholecystitis.

Annexin A5 as a novel player in prevention of atherothrombosis in SLE and in the general population

During recent years it has become evident that atherosclerosis is an inflammatory disease. Furthermore, immune reactions and especially autoimmunity, were demonstrated to modulate atherosclerosis in animal experiments. An interesting example of how autoimmune reactions can influence atherosclerosis and consequences thereafter, is systemic lupus erythematosus (SLE)-associated cardiovascular disease (CVD). Antithrombotic effect exerted by Annexin A5 (ANXA5) is thought to be mediated mainly by forming a mechanical shield over phospholipids (PLs) reducing availability of PLs for coagulation reactions. However, more specific properties of ANXA5 might be of importance for its antithrombotic function. Such examples include downregulation of surface-expressed tissue factor (TF), as well as upregulation of urokinase-type plasminogen activator (uPA) by ANXA5. Also, interaction of ANXA5 with ligands involved in hemostasis, such as sulfatide and heparin, has been demonstrated. We have recently described a novel mechanism potentially contributing to atherothrombosis in SLE, with ANXA5 binding to endothelium decreased in SLE, an effect caused by antiphospholipid antibodies (aPL). It may be hypothesized that ANXA5 can be effective as a treatment to prevent plaque rupture and atherothrombosis not only in SLE, but also in the general population prone to CVD. Antiatherothrombotic potential of ANXA5 deserves further attention and careful studies as the mechanism behind the majority of clinically significant cardiovascular ischemic disease is atherothrombosis, formed on an underlying vulnerable atherosclerotic lesion. It may be hypothesized that ANXA5 can be effective as a treatment to prevent plaque rupture and atherothrombosis not only in SLE, but also in a general population prone to CVD.

The P-selectin, tissue factor, coagulation triad

The primary importance of tissue factor (TF) in blood coagulation and thrombus propagation has been recognized for many years. Nevertheless, our view about the origin of TF activity, necessary for normal hemostasis and found in pathologic conditions, needs to be revised in the light of recent observations. Pioneering work by Yale Nemerson's group showed that circulating TF on microparticles (MPs), could promote thrombus growth. The origin and characteristics of this 'blood-borne' TF are targets of intense research as well as intense debate. Surprising observations now implicate the adhesion receptor P-selectin (P-sel), known for its role in inflammation, in these MPs' generation. P-sel, translocated from granules to the cell surfaces of activated platelets and endothelial cells, was recently found to play multiple roles in hemostasis. Expressed on endothelium, it can mediate platelet rolling. Signaling by P-sel through its receptor on leukocytes, P-selectin glycoprotein ligand 1 (PSGL-1), induces the generation of TF-positive, highly procoagulant MPs. In addition, P-sel on activated platelets helps to recruit these MPs specifically to thrombi. In this review, we discuss the roles of P-sel and TF-positive MPs and highlight strategies to modulate hemostasis by modulating the P-sel, TF, coagulation triad.