Protein anticoagulants targeting factor VIIa-tissue factor complex: a comprehensive review

Immunothrombosis and the molecular control of tissue factor by pyroptosis: prospects for new anticoagulants

The interplay between innate immunity and coagulation after infection or injury, termed immunothrombosis, is the primary cause of disseminated intravascular coagulation (DIC), a condition that occurs in sepsis. Thrombosis associated with DIC is the leading cause of death worldwide. Interest in immunothrombosis has grown because of COVID-19, the respiratory disease caused by SARS-CoV-2, which has been termed a syndrome of dysregulated immunothrombosis. As the relatively new field of immunothrombosis expands at a rapid pace, the focus of academic and pharmacological research has shifted from generating treatments targeted at the traditional 'waterfall' model of coagulation to therapies better directed towards immune components that drive coagulopathies. Immunothrombosis can be initiated in macrophages by cleavage of the non-canonical inflammasome which contains caspase-11. This leads to release of tissue factor (TF), a membrane glycoprotein receptor that forms a high-affinity complex with coagulation factor VII/VIIa to proteolytically activate factors IX to IXa and X to Xa, generating thrombin and leading to fibrin formation and platelet activation. The mechanism involves the post-translational activation of TF, termed decryption, and release of decrypted TF via caspase-11-mediated pyroptosis. During aberrant immunothrombosis, decryption of TF leads to thromboinflammation, sepsis, and DIC. Therefore, developing therapies to target pyroptosis have emerged as an attractive concept to counteract dysregulated immunothrombosis. In this review, we detail the three mechanisms of TF control: concurrent induction of TF, caspase-11, and NLRP3 (signal 1); TF decryption, which increases its procoagulant activity (signal 2); and accelerated release of TF into the intravascular space via pyroptosis (signal 3). In this way, decryption of TF is analogous to the two signals of NLRP3 inflammasome activation, whereby induction of pro-IL-1β and NLRP3 (signal 1) is followed by activation of NLRP3 (signal 2). We describe in detail TF decryption, which involves pathogen-induced alterations in the composition of the plasma membrane and modification of key cysteines on TF, particularly at the location of the critical, allosterically regulated disulfide bond of TF in its 219-residue extracellular domain. In addition, we speculate towards the importance of identifying new therapeutics to block immunothrombotic triggering of TF, which can involve inhibition of pyroptosis to limit TF release, or the direct targeting of TF decryption using cysteine-modifying therapeutics.

Prothrombotic SERPINC1 Gene Polymorphism may Affect Heparin Sensitivity Among Different Ethnicities of Chinese Patients Receiving Heart Surgery

The purpose of this study was to investigate a possible correlation between single-nucleotide polymorphisms (SNPs) of the antithrombin (gene, SERPINC1, and perioperative sensitivity to heparin in patients receiving heart surgery. The SERPINC1 genotype and allele frequency, coagulation parameters 24 hours before and after surgery, and clinical findings were compared among 3 ethnic groups, Han, Uighur, and Kazakh, patientswho received heart surgery. In Han patients, longer coagulation time as well as higher heparin and protamine dosage was observed. SERPINC1 gene sequencing identified 2 mutations in exon 5, g.981A>G (rs5877) and g.1011A>G (rs5878). The minor allele frequency of allele (A>G) for rs5877 and rs5878 was higher in the Han patients and was significantly different among the ethnic groups ( P = .004 and P = .006, respectively). The increased SERPINC1 SNP frequency among Han patients receiving heart surgery might contribute to the differences in their perioperative sensitivity to heparin.