Heparan sulfate (HS), MS-222, 1-phenyl-2-thiourea, o-dianisidine and Fluorescein isothiocyanate-dextran and BSA was from Millipore-Sigma (St. Unfractionated heparin was generously provided by Qilu Pharmaceutical (Jinan, China). HCII, Texas Red and low melting agarose were obtained from Thermo Fisher Scientific (Rockford, USA). AT, Xa, thrombin and chromogenic substrates for anticoagulation experiment were purchased from Adhoc International Technologies (Beijing, China). The AlexaFluor (AF) 488-labeled goat anti-mouse IgG and AF 647-labeled rabbit anti-His-tag were purchased from Cell Signaling Technology (Danvers, USA). AT and HCII with His-tag were obtained from Sino Biologicals (Beijing, China). These proteins are expressed from human 293 cells (HEK293) with the tag at C-terminus. The SARS-CoV-2 S trimer with His-tag, and S1 subunit with mouse IgG2a Fc-tag (mFc-tag) were obtained from ACRO Biosystems (Beijing, China). The effects of S protein on thrombin activity and thrombus formation were investigated by in vitro anticoagulation experiments and in vivo experiments using the zebrafish embryo model. To investigate whether SARS-CoV-2 can interfere directly with the anticoagulation process by binding to HS/heparin, we established competitive binding experiments on heparin/HS polysaccharide microarrays for the first time. A question is therefore raised on whether SARS-CoV-2 can interfere with the anticoagulation process by competing with HS in the vascular endothelium. Recent reports have shown that SARS-CoV-2 spike (S) protein can bind heparin and heparan sulfate (HS) with high affinity, ,. Heparin can allosterically activate AT/HCII and increase their inhibitory ability by 1000–10,000 folds,. In this overall complex process, HS/heparin play an important role as allosteric activators to increase the activities of AT and HCII, which exist in blood with usually low activity in a repressed reactivity state. Along with the clotting process, a series of serine protease inhibitors ( e.g., AT and HCII) can inactivate thrombin to prevent excessive clotting. Thrombin, also called factor IIa, is the main effector protease of the coagulation cascade, which converts circulating fibrinogen to fibrin monomer before its polymerization to form fibrin, the fibrous matrix with platelets of blood clots. thrombin, and coagulation factor Xa) and anticoagulation factors, such as antithrombin (AT) and heparin cofactor II (HCII), ,,. Under normal physiological conditions, hemostasis is exquisitely initiated, controlled, and terminated by a series of processes involving the action of different serine proteases ( e.g. Consistent with heparin, one of the important function of heparin sulfate on the endothelium of blood vessels is to regulate blood coagulation. ![]() The endothelium covered with heparan sulfate (HS), a polydisperse glycosaminoglycan. Vascular endothelial damage is part of the pathogenesis of organ injury in severe COVID-19. However, it remains unclear whether SARS-CoV-2 is directly involved in the coagulation process. ![]() Furthermore, severe hypoxemia may result in reducing blood flow and vasoconstriction in COVID-19. SARS-CoV-2 infection could induce a cytokine storm with the activation of leukocytes, endothelium and platelets, which would promote the upregulation of tissue factor, coagulation activation, thrombin generation, and fibrin formation. ![]() Severe infection and inflammation invariably lead to hemostatic abnormalities. However, the pathogenesis of coagulopathy in COVID-19 has not been fully elucidated. Apart from inflammation, increasing clinical data have emerged to indicate that thrombotic complications are an important feature in critically ill patients with COVID-19, ,. The new coronavirus pneumonia (COVID-19) caused by SARS-CoV-2 virus infection has become a major threat to human health.
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |