Autoantibody against prothrombin aberrantly alters the proenzyme to facilitate formation of a complex with its physiological inhibitor antithrombin III without thrombin conversion

Therapeutic mechanism of Toujie Quwen granules in COVID-19 based on network pharmacology

Background

Chinese medicine Toujie Quwen granule (TJQW) has proven to be effective in the treatment of mild coronavirus disease 2019 (COVID-19) cases by relieving symptoms, slowing the progression of the disease, and boosting the recovery of patients. But the bioactive compounds and potential mechanisms of TJQW for COVID-19 prevention and treatment are unclear. This study aimed to explore the potential therapeutic mechanism of TJQW in coronavirus disease 2019 (COVID-19) based on an integrated network pharmacology approach.

Methods

TCMSP were used to search and screen the active ingredients in TJQW. The Swiss TargetPrediction was used to predict the potential targets of active ingredients. Genes co-expressed with ACE2 were considered potential therapeutic targets on COVID-19. Venn diagram was created to show correlative targets of TJQW against COVID-19. Cytoscape was used to construct a “drug-active ingredient-potential target” network, STRING were used to construct protein-protein interaction network, and cytoHubba performed network topology analysis. Enrichment of biological functions and signaling pathways of core targets was performed by using the clusterProfiler package in R software and ClueGO with CluePedia plugins in Cytoscape.

Results

A total of 156 active ingredients were obtained through oral bioavailability and drug-likeness screenings. Two hundred twenty-seven potential targets of TJQW were related to COVID-19. The top ten core targets are EGFR, CASP3, STAT3, ESR1, FPR2, F2, BCL2L1, BDKRB2, MPO, and ACE. Based on that, we obtained 19 key active ingredients: umbelliprenin, quercetin, kaempferol, luteolin, praeruptorin E, stigmasterol, and oroxylin A. And the enrichment analysis obtained multiple related gene ontology functions and signaling pathways. Lastly, we constructed a key network of “drug-component-target-biological process-signaling pathway”. Our findings suggested that TJQW treatment for COVID-19 was associated with elevation of immunity and suppression of inflammatory stress, including regulation of inflammatory response, viral process, neutrophil mediated immunity, PI3K-Akt signaling pathway, MAPK signaling pathway, Jak-STAT signaling pathway, Complement and coagulation cascades, and HIF-1 signaling pathway.

Conclusions

Our study uncovered the pharmacological mechanism underlying TJQW treatment for COVID-19. These results should benefit efforts for people around the world to gain more knowledge about Chinese medicine TJQW in the treatment of this vicious epidemic COVID-19, and help to address this pressing problem currently facing the world.

Antibodies against thrombin in dengue patients contain both anti-thrombotic and pro-fibrinolytic activities

Dengue virus (DENV) infection may result in severe life-threatening Dengue haemorrhagic fever (DHF). The mechanisms causing haemorrhage in those with DHF are unclear. In this study, we demonstrated that antibodies against human thrombin were increased in the sera of Dengue patients but not in that of patients infected with other viruses. To further characterise the properties of these antibodies, affinity-purified anti-thrombin antibodies (ATAs) were collected from Dengue patient sera by thrombin and protein A/L affinity columns. Most of the ATAs belonged to the IgG class and recognized DENV nonstructural protein 1 (NS1). In addition, we found that dengue patient ATAs also cross-reacted with human plasminogen (Plg). Functional studies in vitro indicated that Dengue patient ATAs could inhibit thrombin activity and enhance Plg activation. Taken together, these results suggest that DENV NS1-induced thrombin and Plg cross-reactive antibodies may contribute to the development of haemorrhage in patients with DHF by interfering with coagulation and fibrinolysis.

Antiphospholipid antibodies: paradigm in transition

OBJECTIVES

This is a critical review of anti-phospholipid antibodies (aPL). Most prior reviews focus on the aPL syndrome (APS), a thrombotic condition often marked by neurological disturbance. We bring to attention recent evidence that aPL may be equally relevant to non-thrombotic autoimmune conditions, notably, multiple sclerosis and ITP.

ORGANIZATION

After a brief history, the recent proliferation of aPL target antigens is reviewed. The implication is that many more exist. Theories of aPL in thrombosis are then reviewed, concluding that all have merit but that aPL may have more diverse pathological consequences than now recognized. Next, conflicting results are explained by methodological differences. The lupus anticoagulant (LA) is then discussed. LA is the best predictor of thrombosis, but why this is true is not settled. Finally, aPL in non-thrombotic disorders is reviewed.

CONCLUSION

The current paradigm of aPL holds that they are important in thrombosis, but they may have much wider clinical significance, possibly of special interest in neurology.

The conformational switch from the factor X zymogen to protease state mediates exosite expression and prothrombinase assembly

Zymogens of the chymotrypsin-like serine protease family are converted to the protease state following insertion of a newly formed, highly conserved N terminus. This transition is accompanied by active site formation and ordering of several surface loops in the catalytic domain. Here we show that disruption of this transition in factor X through mutagenesis (FXa(I16L) and FXa(V17A)) not only alters active site function, but also significantly impairs Na(+) and factor Va binding. Active site binding was improved in the presence of high NaCl or with saturating amounts of factor Va membranes, suggesting that allosteric linkage exists between these sites. In line with this, irreversible stabilization of FXa(I16L) with Glu-Gly-Arg-chloromethyl ketone fully rescued FVa binding. Furthermore, the K(m) for prothrombin conversion with the factor Xa variants assembled into prothrombinase was unaltered, whereas the k(cat) was modestly reduced (3- to 4-fold). These findings show that intramolecular activation of factor X following the zymogen to protease transition not only drives catalytic site activation but also contributes to the formation of the Na(+) and factor Va binding sites. This structural plasticity of the catalytic domain plays a key role in the regulation of exosite expression and prothrombinase assembly.

Acquired hemophilia

Acquired hemophilia is a serious coagulopathy usually affecting the elderly, persons with autoimmune disorders and, infrequently, women in the immediate postpartum period. It is due to autoantibodies directed against specific domains of the factor VIII molecule, leading to inhibition of factor VIII binding to von Willebrand factor, to activated factor IX or to negatively charged phospholipids. This results in bleeding into the skin, muscles, gastrointestinal and genitourinary tracts, and other sites. Mixing patient plasma with normal plasma prolongs the activated partial thromboplastin time of the normal plasma and the Bethesda assay provides a quantitative estimate of the strength of the inhibitor. The selection of therapeutic concentrates for the management of acute bleeding is related to the titer of the inhibitor; if less than 5 Bethesda Units, human factor VIII may be effective, but higher titer inhibitors usually respond only to porcine factor VIII, recombinant factor VIIa or activated prothrombin complex concentrates. Corticosteroid treatment leads to disappearance of the autoantibody in 50% of patients; cyclophosphamide and cyclosporine are effective in many who do not respond to steroids. Occasionally, high dose intravenous immunoglobulin or immunosorbent columns transiently decrease inhibitor titers and enable control of bleeding. Other autoantibodies have been described against factors V, VII, XI and, rarely, factor XIII and prothrombin. New approaches in the management of autoimmune disease and, especially, methods to establish tolerance are in development.