Prothrombin conversion and thrombin decay in patients with cirrhosis-role of prothrombin and antithrombin deficiencies

BACKGROUND

Thrombin generation (TG) in the presence of thrombomodulin (TG-TM) in the plasma of patients with cirrhosis (PWC) is tilted toward a hypercoagulable phenotype. Low protein C and elevated factor VIII levels play a role, but other determinants, such as the prothrombin/antithrombin pair, must also be studied.

OBJECTIVES

The objectives were (i) to quantitatively assess the subprocesses (prothrombin conversion and thrombin decay) and (ii) to understand the underlying mechanism by studying TG dynamics after prothrombin and antithrombin plasma level correction in PWC.

METHODS

We studied TG-TM in plasma samples of 36 healthy controls (HCs) and 41 PWC with prothrombin and antithrombin levels of <70% and after their correction. We initiated coagulation with an intermediate picomolar concentration of tissue factor. We determined the overall thrombin potential, prothrombin conversion, and thrombin decay.

RESULTS

TG-TM was increased in PWC compared with HC due to impaired thrombin inhibition. Indeed, thrombin decay capacity (min-1) decreased from 0.37 (0.35-0.40) in HC to 0.33 (0.30-0.37) in the Child-Turcotte-Pugh A (CTP-A; P = .09), 0.27 (0.26-0.30) in the CTP-B (P < .001), and 0.20 (0.19-0.20) in the CTP-C (P < .001) group. Concomitant correction of prothrombin and antithrombin increased endogenous thrombin potential with prothrombin conversion surpassing thrombin decay. By contrast, when we corrected only antithrombin, TG-TM was normalized and even consistent with a hypocoagulable phenotype in the CTP-C group.

CONCLUSION

Our results highlight that in PWC, hypercoagulability (evidenced in the presence of TM) is due to impaired thrombin decay, whereas low prothrombin levels do not translate into decreased prothrombin conversion, likely due to altered TM-activated protein C negative feedback.

A simple method to resolve rate constants when the binding mechanism obeys induced fit or conformational selection

Many interactions involving a ligand and its molecular target are studied by rapid kinetics using a stopped-flow apparatus. Information obtained from these studies is often limited to a single, saturable relaxation that is insufficient to resolve all independent rate constants even for a two-step mechanism of binding obeying induced fit (IF) or conformational selection (CS). We introduce a simple method of general applicability where this limitation is overcome. The method accurately reproduces the rate constants for ligand binding to the serine protease thrombin determined independently from the analysis of multiple relaxations. Application to the inactive zymogen precursor of thrombin, prethrombin-2, resolves all rate constants for a binding mechanism of IF or CS from a single, saturable relaxation. Comparison with thrombin shows that the prethrombin-2 to thrombin conversion enhances ligand binding to the active site not by improving accessibility through the value of kon but by reducing the rate of dissociation koff. The conclusion holds regardless of whether binding is interpreted in terms of IF or CS and has general relevance for the mechanism of zymogen activation of serine proteases. The method also provides a simple test of the validity of IF and CS and indicates when more complex mechanisms of binding should be considered.

Effect of prothrombin Belgrade mutation, causing antithrombin resistance, on fibrin clot properties

INTRODUCTION

Prothrombin Belgrade mutation is the result of the c.1787G>A substitution in the prothrombin gene. It is located in the antithrombin and sodium binding site and leads to impaired inactivation of thrombin by antithrombin, resulting in antithrombin resistance and thrombotic disorders. However, it negatively affects sodium binding and may have hypocoagulant effects. Considering that prothrombin Belgrade mutation mechanism is still not fully elucidated and that sodium binding is important for thrombin affinity towards fibrinogen, our aim was to determine whether this mutation affects fibrin clot formation and lysis.

METHODS

Using HEK293T cell line, recombinant wild type and mutated prothrombin were generated by transient transfection. Samples that correspond to plasma of a non-carrier, heterozygous and homozygous carriers were reconstituted using prothrombin deficient plasma and recombinant proteins. Reconstituted samples were used in OHP assay (Overall Hemostasis Potential) to determine kinetic profiles of coagulation and fibrinolysis. Clot turbidity assay was performed to observe kinetics of clot formation and lysis more closely. Fibrin clots formed in reconstituted plasma samples were analyzed by confocal microscopy to determine density of fibrin network. Fibrin clots were additionally observed using electron microscopy to determine thickness of individual fibrin fibers.

RESULTS

No significant difference found in OHP, OCP, OFP, and fibrin network density between wild type, heterozygous, and homozygous carrier reconstituted plasma samples. There were significant differences between samples for slope and slope time parameters in kinetic profiles and fibrin fiber thickness.

CONCLUSIONS

Results indicate that prothrombin Belgrade mutation has no significant impact on fibrinolysis, however it may affect kinetics of clot formation and its architecture.

A nonneutralizing antibody as cause of prothrombin deficiency in a patient with follicular lymphoma

Acquired inhibitors of blood coagulation are rare but of clinical importance. Prothrombin is a vitamin K-dependent protein, and acquired antibodies toward prothrombin are often associated with the presence of lupus anticoagulant. We describe a previously healthy 70-year-old man presenting with both hemorrhage and thrombosis as well as a prolonged prothrombin time. At arrival at the hospital, he was diagnosed with deep venous thrombosis, and an enlarged lymph node in the left groin was noted (revealed as follicular lymphoma grade 1 by biopsy). Prothrombin activity and antibody titer were followed for 5 months with 15 sampling time points to monitor the treatment outcome of the patient. Diagnostic work-up identified prothrombin deficiency as cause of bleeding. A nonneutralizing calcium-dependent antiprothrombin antibody was found, suspected to increase the clearance of prothrombin, which has previously only occasionally been reported. Lupus anticoagulant was ruled out and thrombosis was judged to be caused by a combination of malignant disease and stagnant venous flow following enlarged lymph nodes in the groin. This report illustrates how investigation of prolonged global coagulation tests, triggered the diagnosis of a rare but critical condition, immune-mediated prothrombin deficiency. The diagnosis is challenging and involves proper differential diagnosis.

To Test or Not to Test: Routine Thrombophilia Diagnostic Screening of Women with Reproductive Failures

BACKGROUND

Recurrent reproductive failure is a global health issue affecting a significant number of women. Thrombophilias have been implicated as a possible cause. Inherited thrombophilias include a single nucleotide variant on factor V Leiden and prothrombin.

OBJECTIVE

The aim of this study was to evaluate the association between the following single nucleotide variants: factor V Leiden (c.1601G>A), the prothrombin gene (c.*97G>A) and the reproductive failure in the Polish population.

METHODS

The study was conducted in a group of 545 patients with recurrent pregnancy loss, RPL (≥2 miscarriages), and in a group of 641 patients with infertility. The distribution of genotypes for the selected variants were determined by RFLP-PCR and by the real-time PCR method.

RESULTS

A variant of the F5 gene was found in 5.14% of patients with RPL and in 6.08% of infertile women. A variant of the F2 gene was identified in 0.73% of patients with RPL and in 2.03% of women with infertility. The frequency in the study groups did not differ from that in the general population. No association between the studied variants of the F5 gene or the F2 gene and the predisposition to reproductive wastage was found.

CONCLUSIONS

Recommendations for routine thrombophilia testing in women with recurrent miscarriages should be revisited. The decision regarding testing should be made individually depending on additional factors indicating an increased risk of venous thromboembolism.

Multivariate Analysis of Protein-Nanoparticle Binding Data Reveals a Selective Effect of Nanoparticle Material on the Formation of Soft Corona

When nanoparticles are introduced into the bloodstream, plasma proteins accumulate at their surface, forming a protein corona. This corona affects the properties of intravenously administered nanomedicines. The firmly bound layer of plasma proteins in direct contact with the nanomaterial is called the "hard corona". There is also a "soft corona" of loosely associated proteins. While the hard corona has been extensively studied, the soft corona is less understood due to its inaccessibility to analytical techniques. Our study used dynamic light scattering to determine the dissociation constant and thickness of the protein corona formed in solutions of silica or gold nanoparticles mixed with serum albumin, transferrin or prothrombin. Multivariate analysis showed that the nanoparticle material had a greater impact on binding properties than the protein type. Serum albumin had a distinct binding pattern compared to the other proteins tested. This pilot study provides a blueprint for future investigations into the complexity of the soft protein corona, which is key to developing nanomedicines.

Close link between antiphosphatidylserine/prothrombin antibodies, lupus anticoagulant, and activated protein C resistance in tetra antiphospholipid antibody-positive subjects

BACKGROUND

Most of the carriers/patients triple-positive for antiphospholipid antibodies (lupus anticoagulant [LAC], immunoglobulin G [IgG]/immunoglobulin M [IgM] anticardiolipin, and anti-β2-glycoprotein I antibodies) are tetra-positive, being positive for antiphosphatidylserine/prothrombin (aPS/PT) antibodies. The relationship between aPS/PT titer, LAC potency, and resistance to activated protein C (aPC-R) has not been investigated.

OBJECTIVES

The aim of this study was to clarify the mutual interdependence of these parameters in tetra-positive subjects.

METHODS

Twenty-three carriers and 30 patients with antiphospholipid syndrome, none of whom were being treated with anticoagulants, and 30 age- and sex-matched controls were studied. Detection of aPS/PT, LAC, and aPC-R in each individual was performed with established methods in our laboratory. Carriers and patients were positive for IgG or IgM aPS/PT or for both isotypes without significant difference. Since both IgG and IgM aPS/PT have anticoagulant activity, we used the sum of their titers (total aPS/PT) for the correlation studies.

RESULTS

Total aPS/PT in all individuals studied exceeded that in controls. There was no difference in total aPS/PT titers (P = .72), LAC potency (P = .56), and aPC-R (P = .82) between antiphospholipid antibody-carriers and patients with antiphospholipid syndrome. There was a significant correlation between total aPS/PT and LAC potency (r = 0.78; P < .0001) and between total aPS/PT titers and aPC-R (r = 0.80; P < .0001). LAC potency also was correlated significantly with aPC-R (r = 0.72; P < .0001).

CONCLUSION

This study shows that there is interdependence between aPS/PT, LAC potency, and aPC-R.

Anti-β2-glycoprotein I and anti-phosphatidylserine/prothrombin antibodies interfere with cleavage of factor V(a) by activated protein C

BACKGROUND

The acquired thrombotic risk factor known as lupus anticoagulant (LA) interferes with laboratory clotting assays and can be caused by autoantibodies against β2-glycoprotein I (β2GPI) and prothrombin. LA is associated with activated protein C (APC) resistance, which might contribute to thrombotic risk in patients with antiphospholipid syndrome. How antibodies against β2GPI and prothrombin cause APC resistance is currently unclear.

OBJECTIVES

To investigate how anti-β2GPI and antiphosphatidylserine/prothrombin (PS/PT) antibodies induce APC resistance.

METHODS

The effects of anti-β2GPI and anti-PS/PT antibodies on APC resistance were studied in plasma (of patients with antiphospholipid syndrome) and with purified coagulation factors and antibodies.

RESULTS

APC resistance was observed in LA-positive patients with anti-β2GPI or anti-PS/PT antibodies and in normal plasma spiked with monoclonal anti-β2GPI or anti-PS/PT antibodies with LA activity. Analysis of factor (F)V cleavage patterns after APC incubation indicated that anti-β2GPI antibodies attenuated APC-mediated FV cleavage at R506 and R306. APC-mediated cleavage at R506 is required for FV cofactor activity during inactivation of FVIIIa. Assays with purified coagulation factors confirmed that anti-β2GPI antibodies interfered with the cofactor function of FV during FVIIIa inactivation but not with FVa inactivation. Anti-PS/PT antibodies attenuated APC-mediated FVa and FVIIIa inactivation. Analysis of FV(a) cleavage patterns after APC incubation indicated that anti-PS/PT antibodies interfere with APC-mediated cleavage of FV at positions R506 and R306.

CONCLUSION

Anti-β2GPI antibodies with LA activity contribute to a procoagulant state by causing APC resistance via interference with the cofactor function of FV during FVIIIa inactivation. LA-causing anti-PS/PT antibodies interfere with the anticoagulant function of APC by preventing FV(a) cleavage.

Coagulation Biomarkers and Clinical Outcomes in Elderly Patients With Nonvalvular Atrial Fibrillation: ANAFIE Subcohort Study

Background

Little is known about the relationship between coagulation biomarkers and clinical outcomes in patients with atrial fibrillation (AF) treated with anticoagulants, especially direct oral anticoagulants (DOACs) and warfarin.

Objectives

This subcohort study evaluated the association between coagulation biomarkers and clinical outcomes in elderly Japanese patients with nonvalvular AF using the ANAFIE (All Nippon AF In the Elderly) Registry.

Methods

Patients with a definitive diagnosis of nonvalvular AF and aged ≥75 years at enrollment were included. At enrollment, biomarker levels for D-dimer, thrombin-antithrombin complex (TAT), prothrombin fragment 1+2 (F1+2), and soluble fibrin monomer complex (SFMC), along with data on anticoagulant use, were recorded.

Results

Of the 3,194 patients, 95.1% were using oral anticoagulants (OACs) (71.7% DOACs, 23.4% warfarin). D-dimer, TAT, and F1+2 levels, as well as the proportion of patients with a positive SFMC, were lower among those receiving OACs compared with those not receiving OACs. In the DOAC group, higher levels of D-dimer (≥1.0 μg/mL) and TAT (>3 ng/mL) were significantly associated with increased incidences of cardiovascular (CV) events (stroke, myocardial infarction, cardiac intervention, heart failure, and CV death), all-cause death, and CV death. In the warfarin group, higher levels of D-dimer were significantly associated with increased rates of all-cause death, higher levels of TAT with increased major bleeding, and positive SFMC with increased major bleeding and CV events.

Conclusions

Higher levels of coagulation biomarkers were associated with a higher risk of worse clinical outcomes, and the relationships between the coagulation biomarkers and outcomes differed between the DOAC and warfarin groups. (Prospective Observational Study in Late-Stage Elderly Patients with Non-Valvular Atrial Fibrillation All Nippon AF In Elderly Registry-ANAFIE Registry; UMIN000024006).

Anti-Phosphatidylserine, Anti-Prothrombin, and Anti-Annexin V Autoantibodies in Antiphospholipid Syndrome: A Real-Life Study

The antiphospholipid antibodies (aPL) increase the risk of developing thrombotic events and may coexist with a variety of autoimmune diseases. They can be detected chronically or temporarily in patients with infectious diseases, during drug therapy, or in cases of cancer. A thrombotic event with aPL detection is known as antiphospholipid syndrome (APS) and the diagnostic criteria include the presence of lupus anticoagulant (LA), anticardiolipin (aCL) and β2-glycoprotein-1(aβ2GPI) antibodies. Other autoantigens recognized in APS are phosphatidylserine (aPS), prothrombin (aPT) and Annexin-5 (aA5). This real life study aimed to explore the connections between laboratory criteria and the prevalence of "non-criteria aPL" in APS. This study followed 300 patients with thrombosis and employed two phospholipid sensitivity assays for LA detection, chemiluminescence assays for aCL and aβ2GPI and enzyme-linked immunoassays for aPS, aPT and aA5. A significant association was found between aPS and aCL (r = 0.76) as well as aβ2GPI (r = 0.77), while the association with LA was less significant (r = 0.33). The results of the aPT and aA5 test did not correlate with criteria-antiphospholipid antibodies (r < 0.30). Since the risk of thrombotic complications increases with the intensity and the number of positive autoantibodies, measuring aPT and aA5 autoantibodies may be useful, particularly in aCL/aβ2GPI-negative patients or in cases of isolated LA positivity.

Added value of antiphosphatidylserine/prothrombin antibodies in the workup of obstetric antiphospholipid syndrome: communication from the ISTH SSC Subcommittee on Lupus Anticoagulant/Antiphospholipid Antibodies

BACKGROUND

The added value of antiphosphatidylserine/prothrombin antibodies (aPS/PT) in the diagnostic workup of antiphospholipid syndrome (APS) is unclear. Currently, diagnosis of thrombotic APS (TAPS) and obstetric APS (OAPS) requires persistent presence of lupus anticoagulant (LAC), anticardiolipin (aCL) immunoglobulin (Ig) G/IgM, or anti-β2-glycoprotein I (aβ2GPI) IgG/IgM antibodies.

OBJECTIVES

To evaluate the role of aPS/PT IgG and IgM in OAPS.

METHODS

aPS/PT IgG/IgM, aCL IgG/IgM, aβ2GPI IgG/IgM, and LAC were determined in 653 patients (OAPS, TAPS, and controls). In-house aPS/PT cut-off values were calculated, titers and prevalence were compared between OAPS, TAPS, and controls and type of pregnancy morbidity. Sensitivity, specificity, likelihood ratios, and odds ratios (OR) with 95% CI were calculated.

RESULTS

In OAPS, aPS/PT IgG and IgM showed an OR of 4.32 (95% CI, 2.54-7.36) and 3.37 (95% CI, 1.93-5.89), respectively, but the association was not independent of LAC. Prevalence and titers of aPS/PT IgG and IgM were lower in OAPS than in patients with TAPS. aPS/PT were more prevalent and showed higher titers in patients with late pregnancy loss than in patients with early pregnancy loss with a positivity of 86.4% and 39.3%, respectively. Higher aPS/PT titers did not increase the likelihood of having OAPS.

CONCLUSION

The added value of aPS/PT testing in the current diagnostic workup of OAPS seems limited compared with LAC, aCL, and aβ2GPI. aPS/PT might be useful in specific subsets of patients with OAPS. However, future multicentric studies are needed to elucidate the risk of less frequent and most severe obstetrical manifestations.

Monitoring prothrombin activation in plasma through loss of Förster resonance energy transfer

BACKGROUND

Current assays that monitor thrombin generation in plasma rely on fluorogenic substrates to follow the kinetics of zymogen activation, which may be complicated by substrate cleavage from other proteases. In addition, these assays depend on activation following cleavage at the prothrombin R320 site and fail to report the cleavage at the alternative R271 site, leading to the shedding of the auxiliary Gla and kringle domains of prothrombin.

OBJECTIVES

To develop a plasma assay that directly monitors prothrombin activation independent of fluorogenic substrate hydrolysis.

METHODS

Cleavage at the R271 site of prothrombin is monitored through loss of Förster resonance energy transfer in plasma coagulated along the extrinsic or intrinsic pathway.

RESULTS

The availability of factor (F)V in plasma strongly influences the rate of prothrombin activation. The rate of thrombin formation is equally perturbed in FV or prothrombin-depleted plasma, implicating that the thrombin-catalyzed feedback reactions that amplify the coagulation response play an important role in generating sufficient amounts of FVa required for the assembly of prothrombinase. Congenital deficiencies in FVIII and FIX significantly slow down cleavage at R271 in plasma coagulated along the extrinsic and intrinsic pathways. Prothrombin activation in FXI-deficient plasma is only perturbed when coagulation is triggered along the intrinsic pathway.

CONCLUSION

The Förster resonance energy transfer assay enables direct monitoring of prothrombin activation through cleavage at R271 without the need for fluorogenic substrates. The assay is sensitive enough to assess how deficiencies in coagulation factors affect thrombin formation.

Blood coagulation factors and platelet response to drug-induced hepatitis and hepatosis in rats

BACKGROUND

Knowing the variability of blood coagulation responses to liver damage of different origins can provide a key to curing liver tissues or to mitigating treatment side effects. The aim of the present work was to compare the changes in the main components of hemostasis under experimental drug-induced hepatosis and hepatitis in rats.

METHODS

We modeled diclofenac-induced hepatitis and tetracycline-induced hepatosis. Hemostasis response was gauged by measuring fibrinogen, factor X, protein C (PC), and prothrombin in plasma. The decarboxylated form of prothrombin was detected by measuring prothrombin index and ecamulin index. Platelet reactivity was studied using aggregometry.

RESULTS

Both hepatitis and hepatosis decreased the synthesis of fibrinogen, factor X, and prothrombin. However, protein carboxylation was not disrupted in hepatosis but was much impaired in hepatitis. PC decreased in both models as a consequence of its consumption possibly during inflammatory response. Platelet aggregation rate was lower in hepatosis but higher in hepatitis.

CONCLUSIONS

Our findings imply the need for a thorough monitoring of the hemostasis system in liver diseases to avoid possible thrombotic complications. Its state indicates the disorder's rate and character.

Early-phase prothrombin time-international normalized ratio in acute liver injury indicates the timing of therapeutic intervention and predicts prognostic improvement

AIM

We investigated whether an early-phase prothrombin time-international normalized ratio (PT-INR) is an interventional prognostic indicator for patients with acute liver injury, including acute liver failure.

METHODS

This was a multicenter retrospective observational study. We included 595 patients with alanine aminotransferase levels ≥300 U/L due to acute liver injury who were admitted to Kagoshima University Hospital or other collaborative investigation organizations between January 1, 2010, and December 31, 2015. Patients with alanine aminotransferase levels ≥300 U/L and no previous liver disease were defined as having an acute liver injury. Acute liver failure was defined by PT-INR ≥1.5 with or without hepatic encephalopathy in acute liver injury patients. Data were obtained retrospectively from case reports and analyzed.

RESULTS

The PT-INR on day 1 was the most accurate independent prognosis predictor in patients with acute liver injury and acute liver failure. On day 1, the transplant-free survival rates were significantly lower in patients with PT-INR ≥1.3. The transplant-free survival rates were also significantly higher in patients with acute liver injury and acute liver failure, in whom the PT-INR had recovered from ≥1.3 on day 1 to <1.3 by day 8.

CONCLUSION

Early-phase changes in the PT-INR can predict the prognosis of patients with acute liver injury and acute liver failure. Furthermore, PT-INR ≥1.3 could be an interventional marker, whereas PT-INR <1.3 after 1 week could reflect prognostic improvement.

Comparative sequence analysis of vitamin K-dependent coagulation factors

BACKGROUND

Prothrombin, protein C, and factors VII, IX, and X are vitamin K (VK)-dependent coagulation proteins that play an important role in the initiation, amplification, and subsequent attenuation of the coagulation response. Blood coagulation evolved in the common vertebrate ancestor as a specialization of the complement system and immune response, which in turn bear close evolutionary ties with developmental enzyme cascades. There is currently no comprehensive analysis of the evolutionary changes experienced by these coagulation proteins during the radiation of vertebrates and little is known about conservation of residues that are important for zymogen activation and catalysis.

OBJECTIVES

To characterize the conservation level of functionally important residues among VK-dependent coagulation proteins from different vertebrate lineages.

METHODS

The conservation level of residues important for zymogen activation and catalysis was analyzed in >1600 primary sequences of VK-dependent proteins.

RESULTS

Functionally important residues are most conserved in prothrombin and least conserved in protein C. Some of the most profound functional modifications in protein C occurred in the ancestor of bony fish when the basic residue in the activation site was replaced by an aromatic residue. Furthermore, during the radiation of placental mammals from marsupials, protein C acquired a cysteine-rich insert that introduced an additional disulfide in the EGF1 domain and evolved a proprotein convertase cleavage site in the activation peptide linker that also became significantly elongated.

CONCLUSIONS

Sequence variabilities at functionally important residues may lead to interspecies differences in the zymogen activation and catalytic properties of orthologous VK-dependent proteins.

Cryo-EM structures of coagulation factors

A State of the Art lecture titled "Cryo-EM structures of coagulation factors" was presented at the ISTH Congress in 2022. Cryogenic electron microscopy (cryo-EM) is a revolutionary technique capable of solving the structure of high molecular weight proteins and their complexes, unlike nuclear magnetic resonance (NMR), and under conditions not biased by crystal contacts, unlike X-ray crystallography. These features are particularly relevant to the analysis of coagulation factors that are too big for NMR and often recalcitrant to X-ray investigation. Using cryo-EM, we have solved the structures of coagulation factors V and Va, prothrombinase on nanodiscs, and the prothrombin-prothrombinase complex. These structures have advanced basic knowledge in the field of thrombosis and hemostasis, especially on the function of factor V and the molecular mechanism for prothrombin activation, and set the stage for exciting new lines of investigation. Finally, we summarize relevant new data on this topic presented during the 2022 ISTH Congress.

Added value of antiphosphatidylserine/prothrombin antibodies in the workup of thrombotic antiphospholipid syndrome: Communication from the ISTH SSC Subcommittee on Lupus Anticoagulant/Antiphospholipid Antibodies

BACKGROUND

Diagnosis of antiphospholipid syndrome (APS) requires persistent presence of lupus anticoagulant (LAC), anticardiolipin (aCL) IgG/IgM, or anti-β2 glycoprotein I (aβ2GPI) IgG/IgM antibodies. Other antiphospholipid antibodies (aPL) such as antiphosphatidylserine/prothrombin antibodies (aPS/PT) are promising in assessment of thrombotic APS (TAPS).

AIM

To evaluate the added value of aPS/PT IgG and IgM in TAPS.

MATERIAL AND METHODS

aPS/PT IgG/IgM, aCL IgG/IgM, aβ2GPI IgG/IgM, and LAC were determined in 757 patients (TAPS and controls). aPS/PT cut-off values were calculated, and aPS/PT titers and positivity were compared between TAPS and controls, type of thrombosis, and antibody profiles. Likelihood ratios (LR), odds ratios (OR), and aPL score were determined.

RESULTS

aPS/PT IgG and IgM were associated with TAPS and triple positivity. In-house calculated cut-offs were higher for IgM (43 units), compared to manufacturer's cut-off (30 units). Thresholds of 90 (IgG) and 200 (IgM) units were determined as high-titer cut-off. Higher aPS/PT titers were observed in triple positive patients and showed higher LR and OR for TAPS. aPS/PT was independently associated with TAPS when adjusted for aCL/aβ2GPI, but not when adjusted for LAC. In isolated LAC positive patients, aPS/PT was positive in 27.1% TAPS patients and in 77.3% patients with autoimmune disease. Diagnostic value of aPL score did not differ with and without including aPS/PT.

CONCLUSION

aPS/PT positivity, especially with high antibody titer, is associated with TAPS diagnosis. Analysis on top of current laboratory criteria is not essential in TAPS diagnosis, but aPS/PT could be useful in patients with thrombosis and a double positive aPL profile (aCL+/aβ2GPI+).

Duration of Anticoagulation Therapy in Patients with Genetic Inherited Thrombophilia

Background: Genetic factors play an important role in deep vein thrombosis (DVT). The duration of anticoagulation therapy in patients with verified genetic inheritance and previous events of DVT is still questionable. Case reports: We present three cases of siblings (two brothers and one sister) with verified Venous thromboembolism (VTE) and genetic inheritance. The first case is a 33 y.o. male who was admitted with bilateral massive pulmonary thromboembolism and DVT of the right femoral vein. He had an episode of DVT 4 years ago. Fibrinolytic therapy was introduced immediately. Afterwards, unfractionated heparin was introduced, and then switched to enoxaparin and acenocoumarol. Because of inappropriate INR, it was switched then to rivaroxaban. The imaging methods showed significant improvement, and the patient was discharged from the hospital with rivaroxaban at 2x15 mg/day for another 2 weeks and was instructed to continue 20 mg/day until his next control. In the meantime, the second case, a 36 y.o. male, brother to the first patient, came with vein thrombosis of vena saphena magna of the left leg. Treatment with Acenocoumarol was started and continued for 2 years until complete resolution of the thrombi, and then it was changed to Aspirin. The third case is the sister of the first 2 cases, a 38 y.o female with symptoms and findings almost similar to those in the second case. She was treated with Acenocoumarol for 6 months. Doppler ultrasound showed complete resolution of the thrombosis and anticoagulation therapy was stopped. Genetic investigations for mutation showed presence of homozygous gene mutation for Prothrombin (PTB G20210A) in the first patient, his brother (the second case) was compound heterozygote for PTB and for MTHFR C677T, and his sister (third case) was heterozygous only for the PTB mutation. According to the clinical (recurrent unprovoked DVT with thromboembolic complications) and genetic testing (homozygous gene mutation for PTB) in the first patient, we decided to continue the secondary thromboprophylaxis with rivaroxaban 10 mg/day indefinitely. Conclusion: Testing for genetically inherited thrombophilia should be included in the risk assessment for recurrence, and performed in all patients under 50 y.o. who have a first, non-provoked episode of thrombosis, in order to determine the duration of anticoagulation therapy.

Large-scale screening for factor V Leiden (G1691A), prothrombin (G20210A), and MTHFR (C677T) mutations in Greek population

Background and aims

To provide a fair estimate of the prevalence of factor V Leiden (FVL) (G1691A), prothrombin (G20210A), and MTHFR (C677T) mutations in the Greek population.

Methods

We genotyped a representative sample of 974 apparently healthy Greek adults by the method of real‐time PCR and we calculated the allele frequencies of factor V Leiden (FVL) (G1691A), prothrombin (G20210A), and MTHFR (C677T) mutations. In addition, we determined the frequency of co‐occurrence of FVL (1691A) and prothrombin (20210A), FVL (1691A) and MTHFR (677T), prothrombin (20210A) and MTHFR (677T) mutations.

Results

Τhe career frequencies of FVL (1691A), prothrombin (20210A), and MTHFR (677T) alleles were 7.5%, 4.5%, and 49.3% while the allele frequencies were 4%, 2.25%, and 39.5%, respectively. The coexistence of the allele frequencies combinations of two, FVL (1691A) and Prothrombin (20210A), FVL (1691A) and MTHFR (677T), prothrombin (20210A) and MTHFR (677T) was found in 1 (0.9%), 29 (3.5%), and 22 (3%) samples, respectively. Triple heterozygous carriers were not found.

Conclusion

Allele frequencies of the two (FVL and MTHFR) mutations are higher compared with published data. The large sample size of our study enhances the validity of our results and suggests a biological affinity of Greek population with Southern Italian populations.

Coagulation parameters in lung cancer patients: A systematic review and meta-analysis

Background

Hypercoagulability in lung cancer patients is associated with a high incidence of mortality and morbidity in the world. Therefore, this meta‐analysis aimed to explore the correlation of the basic coagulation abnormalities in lung cancer patients compared with the control.

Method

PubMed, Scopus, and other sources were employed to identify eligible studies. The outcome variable was expressed using mean ± standard deviation (SD). Heterogeneity among studies and publication bias were evaluated. The quality of included studies was also assessed based on Newcastle–Ottawa Scale checklist.

Result

Finally, through a total of eight studies, prolonged prothrombin time (PT; standard mean difference [SMD]: 1.29; 95% CI: 0.47–2.11), plasma D‐dimer value (SMD 3.10; 95% CI 2.08–4.12), fibrinogen (SMD 2.18; 95% CI:1.30–3.06), and platelet (PLT) count (SMD 1.00; 95% CI 0.84–1.16) were significantly higher in lung cancer patients when compared with the control group. The single‐arm meta‐analysis also showed that compared with control, lung cancer patients had high pooled PT 13.7 (95% CI:12.2–15.58) versus 11.79 (95% CI = 10.56–13.02), high D‐dimer 275.99 (95% CI:172.9–11735.9) versus 0.2 (95% CI:0.20–0.37), high plasma fibrinogen 5.50 (95% CI:4.21–6.79) versus 2.5 (95% CI:2.04–2.91), and high PLT count 342.3 (95% CI:236.1–448.5) versus 206.6 (95% CI:176.4–236.7).

Conclusion

In conclusion, almost all the coagulation abnormalities were closely associated with lung cancer, and hence coagulation indexes provide an urgent clue for early diagnosis and timely management.

Multicenter study on recent portal venous system thrombosis associated with cytomegalovirus disease

BACKGROUND & AIMS

Recent non-malignant non-cirrhotic portal venous system thrombosis (PVT) is a rare condition. Among risk factors for PVT, cytomegalovirus (CMV) disease is usually listed based on a small number of reported cases. The aim of this study was to determine the characteristics and outcomes of PVT associated with CMV disease.

METHODS

We conducted a French multicenter retrospective study comparing patients with recent PVT and CMV disease ("CMV positive"; n = 23) to patients with recent PVT for whom CMV testing was negative ("CMV negative"; n = 53) or unavailable ("CMV unknown"; n = 297).

RESULTS

Compared to patients from the "CMV negative" and "CMV unknown" groups, patients from the "CMV positive" group were younger, more frequently had fever, and had higher heart rate, lymphocyte count and serum ALT levels (p ≤0.01 for all). The prevalence of immunosuppression did not differ between the 3 groups (4%, 4% and 6%, respectively). Extension of PVT was similar between the 3 groups. Thirteen out of 23 "CMV positive" patients had another risk factor for thrombosis. Besides CMV disease, the number of risk factors for thrombosis was similar between the 3 groups. Heterozygosity for the prothrombin G20210A gene variant was more frequent in "CMV positive" patients (22%) than in the "CMV negative" (4%, p = 0.01) and "CMV unknown" (8%, p = 0.03) groups. Recanalization rate was not influenced by CMV status.

CONCLUSIONS

In patients with recent PVT, features of mononucleosis syndrome should raise suspicion of CMV disease. CMV disease does not influence thrombosis extension nor recanalization. More than half of "CMV positive" patients have another risk factor for thrombosis, with a particular link to the prothrombin G20210A gene variant.

LAY SUMMARY

Patients with cytomegalovirus (CMV)-associated portal venous system thrombosis have similar thrombosis extension and evolution as patients without CMV disease. However, patients with CMV-associated portal venous system thrombosis more frequently have the prothrombin G20210A gene variant, suggesting that these entities act synergistically to promote thrombosis.

Mapping of the fibrinogen-binding site on the staphylocoagulase C-terminal repeat region

Fibrin (Fbn) deposits are a hallmark of staphylocoagulase (SC)-positive endocarditis. Binding of the N terminus of Staphylococcus aureus SC to host prothrombin triggers formation of an active SC·prothrombin∗ complex that cleaves host fibrinogen to Fbn. In addition, the C-terminal domain of the prototypical SC contains one pseudorepeat (PR) and seven repeats (R1 → R7) that bind fibrinogen/Fbn fragment D (frag D) by a mechanism that is unclear. Here, we define affinities and stoichiometries of frag D binding to C-terminal SC constructs, using fluorescence equilibrium binding, NMR titration, alanine scanning, and native PAGE. We found that constructs containing the PR and single repeats bound frag D with K_D ∼50 to 130 nM and a 1:1 stoichiometry, indicating a conserved binding site bridging the PR and each repeat. NMR titration of PR-R7 with frag D revealed that residues 22 to 49, bridging PR and R7, constituted the minimal peptide (MP) for binding, corroborated by alanine scanning, and binding of labeled MP to frag D. MP alignment with the PR-R and inter-repeat junctions identified critical conserved residues. Full-length PR-(R1 → R7) bound frag D with K_D ∼20 nM and a stoichiometry of 1:5, whereas constructs containing the PR and various three repeats competed with PR-(R1 → R7) for frag D binding, with a 1:3 stoichiometry. These findings are consistent with binding at PR-R and R-R junctions with modest inter-repeat sequence variability. CD of PR-R7 and PR-(R1 → R7) suggested a disordered flexible structure, allowing binding of multiple fibrin(ogen) molecules. Taken together, these results provide insights into pathogen localization on host fibrin networks.

Expanding the family of extracellular chaperones: Identification of human plasma proteins with chaperone activity

Proteostasis, the balance of protein synthesis, folding and degradation, is essential to maintain cellular function and viability, and the many known intracellular chaperones are recognized as playing key roles in sustaining life. In contrast, the identity of constitutively secreted extracellular chaperones (ECs) and their physiological roles in extracellular proteostasis is less completely understood. We designed and implemented a novel strategy, based on the well-known propensity of chaperones to bind to regions of hydrophobicity exposed on misfolding proteins, to discover new ECs present in human blood. We used a destabilized protein that misfolds at 37°C as "bait" to bind to potential ECs in human serum and captured the complexes formed on magnetic beads. Proteins eluted from the beads were identified by mass spectrometry and a group of seven abundant serum proteins was selected for in vitro analysis of chaperone activity. Five of these proteins were shown to specifically inhibit protein aggregation. Vitronectin and plasminogen activator-3 inhibited both the in vitro aggregation of the Alzheimer's β peptide (Aβ1-42 ) to form fibrillar amyloid, and the aggregation of citrate synthase (CS) to form unstructured (amorphous) aggregates. In contrast, prothrombin, C1r, and C1s inhibited the aggregation of Aβ1-42 but did not inhibit CS aggregation. This study thus identified five novel and abundant putative ECs which may play important roles in the maintenance of extracellular proteostasis, and which apparently have differing abilities to inhibit the amorphous and amyloid-forming protein aggregation pathways.

Coagulation Status and Surgical Approach as Predictors of Postoperative Anemia in Patients Undergoing Thoracic Surgery: A Retrospective Study

Objective: Postoperative anemia is a common complication after a major surgery. Our study aims to identify factors that are associated with higher risk of developing postoperative anemia after thoracic surgery.

Methods: We conducted a retrospective study of 465 patients who underwent pulmonary surgery in 2017 in Shanghai Pulmonary Hospital, China. Of them, 191 patients underwent standard open thoracotomy (OT), and 274 patients underwent video-assisted thoracic surgery (VATS). A total of 350 patients were diagnosed with postoperative anemia, and 115 patients did not have anemia. Multiple logistic regression was used to compute odds ratios for predicting preoperative anemia.

Results: Postoperative anemia was associated with significantly lower weight (p < 0.001) and height (p = 0.022) of the patients, as well as higher prothrombin time (PT), and international normalized ratio (INR) (p = 0.012). Open thoracotomy resulted in a 1.2-fold increase in the incidence of postoperative anemia compared to VATS (p = 0.002). Multiple logistic regression analysis identified INR [OR (95% CI) 24.46 (2.05–292.27; p = 0.012] and surgical approach [OR (95% CI) 0.48 (0.31–0.74); p < 0.001] as predictors of postoperative anemia and postoperative drop in hemoglobin (Hb).

Conclusion: Postoperative coagulation status and surgical approach are statistically significant predictors of postoperative anemia in patients undergoing thoracic surgery. International normalized ratio and surgical approach are specifically associated with Hb drop immediately after the surgery.

Antiphospholipid Antibody Assays in 2021: Looking for a Predictive Value in Addition to a Diagnostic One

Antiphospholipid antibodies (aPL) are mandatory for the diagnosis but are also a risk factor for the antiphospholipid syndrome (APS) clinical manifestations. Lupus anticoagulant (LA), anticardiolipin (aCL), and anti-beta2 glycoprotein I (β₂GPI) assays are the formal laboratory classification/diagnostic criteria. Additional nonclassification assays have been suggested; among them, antiphosphatidylserine-prothrombin (aPS/PT) and antidomain 1 β₂GPI antibodies are the most promising ones although not yet formally accepted. aPL represent the example of a laboratory test that moved from dichotomous to quantitative results consistent with the idea that reporting quantitative data offers more diagnostic/prognostic information for both vascular and obstetric manifestations. Although the general rule is that the higher the aPL titer, the higher the test likelihood ratio, there is growing evidence that this is not the case for persistent low titers and obstetric events. LA displays the highest diagnostic/prognostic power, although some isolated LAs are apparently not associated with APS manifestations. Moreover, isotype characterization is also critical since IgG aPL are more diagnostic/prognostic than IgA or IgM. aPL are directed against two main autoantigens: β₂GPI and PT. However, anti-β₂GPI antibodies are more associated with the APS clinical spectrum. In addition, there is evidence that anti-β₂GPI domain 1 antibodies display a stronger diagnostic/prognostic value. This finding supports the view that antigen and even epitope characterization represents a further step for improving the assay value. The strategy to improve aPL laboratory characterization is a lesson that can be translated to other autoantibody assays in order to improve our diagnostic and prognostic power.

Anti-phosphatidyl-serine/prothrombin antibodies (aPS/PT) in isolated lupus anticoagulant (LA): is their presence linked to dual test positivity?

OBJECTIVES

Anti phosphatidylserine/prothrombin antibodies (aPS/PT) are often present in patients with antiphospholipid syndrome (APS) and might be relevant in the pathogenesis of this condition. They are major determinant of lupus anticoagulant (LA) in triple-positive antiphospholipid (aPL) profile. Whether they are present and pathogenic in patients with isolated LA [negative anticardiolipin (aCL) and anti β2-Glycoprotein I (aβ2GPI) antibodies] is a matter of debate.

METHODS

We measured aPS/PT in a large number of isolated LA with the aim to ascertain whether there is a link between the way isolated LA is assessed and the presence of these antibodies. APS/PT were measured in 86 patients with isolated LA (aCL- and abeta2GPI-). LA was assessed by two test systems, the dilute Russell Viper Venom Time (dRVVT) and the Silica Clotting Time (SCT).

RESULTS

Sixty-six (77%) individuals with isolated LA were positive for aPS/PT (IgM 44, IgG and IgM 15, IgG in 7). Diagnosis of LA was made based on positive results in both dRVVT and SCT in 40 patients (Group 1) and based on only one positive test in the remaining 46 patients (Group 2). The rate of positive aPS/PT antibodies was significantly higher in Group 1 (OR=7.2, 95% CI 1.9-27.0, p<0.002). Moreover, the titre of IgM aPS/PT was significantly increased in Group 1 as compared to Group 2 (137 U, IQR 64-179 vs. 43 U, IQR 11-120, p=0.008).

CONCLUSIONS

These data indicate an association between LA based on two positive coagulation tests and the presence of aPS/PT antibodies, especially of IgM isotype.

Intravenous Vitamin K1 for the Correction of Prolonged Prothrombin Times in Non-Bleeding Critically Ill Patients: A Prospective Observational Study

The aim of this study was to evaluate the effects of vitamin K1 on various vitamin K-dependent proteins in critically ill patients with prolonged Owren PT. We included critically ill non-bleeding adult patients without liver failure or anticoagulation treatment, with Owren PT > 1.2, who were prescribed intravenous vitamin K1. Blood was drawn at baseline and at 20-28 h after vitamin K1 administration. At both time points, we measured various vitamin K-dependent proteins and coagulation assays. ClinicalTrials.gov; Identifier: NTC3782025. In total, 52 patients were included. Intravenous vitamin K1 reduced Owren PT, Quick PT, protein induced by vitamin K absence/antagonist-II and desphospho-uncarboxylated matrix Gla protein (dp-ucMGP), but not to normal levels. Concomitantly, there were increases in thrombin generation and the activity of coagulation factors II, VII, IX and X that was only counteracted with a small increase in Protein C activity. In conclusion, the results suggest that vitamin K1 strengthens coagulation as measured by PT decrease and increases in the activity of vitamin K-dependent clotting factors and thrombin generation. The decreased dp-ucMGP, and its potential positive short- and long-term non-coagulative effects, merits further research.

Role of sequence and position of the cleavage sites in prothrombin activation

In the penultimate step of the coagulation cascade, the multidomain vitamin-K-dependent zymogen prothrombin is converted to thrombin by the prothrombinase complex composed of factor Xa, cofactor Va, and phospholipids. Activation of prothrombin requires cleavage at two residues, R271 and R320, along two possible pathways generating either the intermediate prethrombin-2 (following initial cleavage at R271) or meizothrombin (following initial cleavage at R320). The former pathway is preferred in the absence of and the latter in the presence of cofactor Va. Several mechanisms have been proposed to explain this preference, but the role of the sequence and position of the sites of cleavage has not been thoroughly investigated. In this study, we engineered constructs where the sequences ²⁶¹DEDSDRAIEGRTATSEYQT²⁷⁹ and ³¹⁰RELLESYIDGRIVEGSDAE³²⁸ were swapped between the R271 and R320 sites. We found that in the absence of cofactor Va, the wild-type sequence at the R271 site is cleaved preferentially regardless of its position at the R271 or R320 site, whereas in the presence of cofactor Va, the R320 site is cleaved preferentially regardless of its sequence. Additional single-molecule FRET measurements revealed that the environment of R271 changes significantly upon cleavage at R320 due to the conformational transition from the closed form of prothrombin to the open form of meizothrombin. Detailed kinetics of cleavage at the R271 site were monitored by a newly developed assay based on loss of FRET. These findings show how sequence and position of the cleavage sites at R271 and R320 dictate the preferred pathway of prothrombin activation.

Hereditary thrombophilia and recurrent pregnancy loss: a systematic review and meta-analysis

STUDY QUESTION

Is there an association between hereditary thrombophilia in pregnant women and risk of recurrent pregnancy loss (RPL)?

SUMMARY ANSWER

Pregnant women with hereditary thrombophilia have an increased risk of RPL, especially for pregnant women with the G1691A mutation of the factor V Leiden (FVL) gene, the G20210A mutation of the prothrombin gene (PGM), and deficiency of protein S (PS).

WHAT IS KNOWN ALREADY

Prior studies have suggested that pregnant women with hereditary thrombophilia have a higher risk of RPL, however, the results are inconsistent; furthermore, a complete overview is missing. This lack of information is an obstacle to the risk assessment of RPL in pregnant women with hereditary thrombophilia. A comprehensive meta-analysis on the relation between hereditary thrombophilia and the risk of RPL is needed.

STUDY DESIGN, SIZE, DURATION

A systematic review and meta-analysis was performed using observational studies published in English before 1 April 2020 to evaluate the relation between hereditary thrombophilia and risk of RPL.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Relevant studies were identified from PubMed, Web of Science, and EMBASE searches and complemented with perusal of bibliographies of retrieved articles. The exposure of interest was hereditary thrombophilia, including FVL mutation, PGM, deficiency of antithrombin (AT), deficiency of protein C (PC), and deficiency of PS. The overall risk estimates were pooled using random effects models. Subgroup and sensitivity analyses were carried out to explore possible sources of heterogeneity and assess the robustness of the results.

MAIN RESULTS AND THE ROLE OF CHANCE

A total of 89 studies involving 30 254 individuals were included. Results showed that women with FVL mutation (odds ratio (OR): 2.44, 95% CI: 1.96-3.03), PGM (OR: 2.08, 95% CI: 1.61-2.68), or deficiency of PS (OR: 3.45, 95% CI: 1.15-10.35) had higher risks of developing RPL. Compared with the reference group, there was no observed relation between a deficiency in AT or PC and RPL (all P > 0.05). Heterogeneity in the risk estimates of RPL was partially explained by geographic region, definitions of RPL, types of RPL, and controlled confounders. Sensitivity analyses validated the robustness of the findings.

LIMITATIONS, REASONS FOR CAUTION

Only 39 of the included studies controlled for one or more confounders, and the heterogeneity across all included studies was high. Based on the data available, we cannot determine whether this association is confounded by other potential risk factors of RPL.

WIDER IMPLICATIONS OF THE FINDINGS

This systematic review and meta-analysis show a possible association between hereditary thrombophilia and an increased risk of RPL, suggesting that testing for hereditary thrombophilia should be considered in individuals with RPL.

STUDY FUNDING/COMPETING INTEREST(S)

The study was funded by the Hunan Provincial Key Research and Development Program (Grant number: 2018SK2062) and National Natural Science Foundation Program (Grant number: 81973137). There are no conflicts of interest.

REGISTRATION NUMBER

N/A.

The Acute Effect of Diesel Exhaust Particles and Different Fractions Exposure on Blood Coagulation Function in Mice

The toxicity and widespread exposure opportunity of diesel exhaust particles (DEP) has aroused public health concerns. This study aimed to investigate the acute effect of DEP and different fractions exposure on blood coagulation function in mice. In this study, nine- week-old C57BL/6J male mice were divided into four exposure groups (with 15 mice in each group). The water-soluble (WS) and water-insoluble (WIS) fractions of DEP were isolated, and intratracheal instillation was used for DEP, WS and WIS exposure. The phosphate buffer saline (PBS) exposure group was set as the control group. After 24 h exposure, the mice were sacrificed for blood routine, coagulation function and bleeding time examinations to estimate the acute effect of DEP, WS and WIS exposure on the blood coagulation function. In our results, no statistically significant difference in weight of body, brain and lung was observed in different exposure groups. While several core indexes in blood coagulation like bleeding time (BT), fibrinogen (FIB), activated partial thromboplastin time (APTT) and prothrombin time (PT) altered or showed a lower tendency after DEP, WS and WIS exposure. For example, BT was lower In WIS exposure group (211.00 s) compared with PBS exposure group (238.50 s) (p < 0.01), and FIB was lower in WS exposure group (233.00 g/L) compared with PBS exposure group (249.50 g/L) (p < 0.05). Additionally, systemic inflammation-related indexes like white blood cell count (WBC), neutrophil count (NEUT), lymphocyte count (LYMPH) altered after DEP, WS and WIS exposure. In conclusion, DEP, WS and WIS fractions exposure could result in the hypercoagulable state of blood in mice. The noteworthy effects of WS and WIS fractions exposure on blood coagulation function deserve further investigation of the potential mechanism.

Role of Thrombin in Central Nervous System Injury and Disease

Thrombin is a Na+-activated allosteric serine protease of the chymotrypsin family involved in coagulation, inflammation, cell protection, and apoptosis. Increasingly, the role of thrombin in the brain has been explored. Low concentrations of thrombin are neuroprotective, while high concentrations exert pathological effects. However, greater attention regarding the involvement of thrombin in normal and pathological processes in the central nervous system is warranted. In this review, we explore the mechanisms of thrombin action, localization, and functions in the central nervous system and describe the involvement of thrombin in stroke and intracerebral hemorrhage, neurodegenerative diseases, epilepsy, traumatic brain injury, and primary central nervous system tumors. We aim to comprehensively characterize the role of thrombin in neurological disease and injury.

Overview of the Therapeutic Potential of Aptamers Targeting Coagulation Factors

Aptamers are single-stranded DNA or RNA sequences that bind target molecules with high specificity and affinity. Aptamers exhibit several notable advantages over protein-based therapeutics. Aptamers are non-immunogenic, easier to synthesize and modify, and can bind targets with greater affinity. Due to these benefits, aptamers are considered a promising therapeutic candidate to treat various conditions, including hematological disorders and cancer. An active area of research involves developing aptamers to target blood coagulation factors. These aptamers have the potential to treat cardiovascular diseases, blood disorders, and cancers. Although no aptamers targeting blood coagulation factors have been approved for clinical use, several aptamers have been evaluated in clinical trials and many more have demonstrated encouraging preclinical results. This review summarized our knowledge of the aptamers targeting proteins involved in coagulation, anticoagulation, fibrinolysis, their extensive applications as therapeutics and diagnostics tools, and the challenges they face for advancing to clinical use.

Anti-β2-glycoprotein I and anti-prothrombin antibodies cause lupus anticoagulant through different mechanisms of action

BACKGROUND

The presence of lupus anticoagulant (LA) is an independent risk factor for thrombosis. This laboratory phenomenon is detected as a phospholipid-dependent prolongation of the clotting time and is caused by autoantibodies against beta2-glycoprotein I (β2GPI) or prothrombin. How these autoantibodies cause LA is unclear.

OBJECTIVE

To elucidate how anti-β2GPI and anti-prothrombin antibodies cause the LA phenomenon.

METHODS

The effects of monoclonal anti-β2GPI and anti-prothrombin antibodies on coagulation were analyzed in plasma and with purified coagulation factors.

RESULTS

Detection of LA caused by anti-β2GPI or anti-prothrombin antibodies required the presence of the procofactor factor V (FV) in plasma. LA effect disappeared when FV was replaced by activated FV (FVa), both in a model system and in patient plasma, although differences between anti-β2GPI and anti-prothrombin antibodies were observed. Further exploration of the effects of the antibodies on coagulation showed that the anti-β2GPI antibody attenuated FV activation by activated faxtor X (FXa), whereas the anti-prothrombin antibody did not. Binding studies showed that β2GPI--antibody complexes directly interacted with FV with high affinity. Anti-prothrombin complexes caused the LA phenomenon through competition for phospholipid binding sites with coagulation factors as reduced FXa binding to lipospheres was observed with flow cytometry in the presence of these antibodies.

CONCLUSION

Anti-β2GPI and anti-prothrombin antibodies cause LA through different mechanisms of action: While anti-β2GPI antibodies interfere with FV activation by FXa through a direct interaction with FV, anti-prothrombin antibodies compete with FXa for phospholipid binding sites. These data provide leads for understanding the paradoxical association between thrombosis and a prolonged clotting time in the antiphospholipid syndrome.

Discovery of Screening Biomarkers for Major Depressive Disorder in Remission by Proteomic Approach

Major depressive disorder (MDD) is a common disorder involving depressive mood and decreased motivation. Due to its high heterogeneity, novel biomarkers are required to diagnose MDD. In this study, a proteomic method was used to identify a new MDD biomarker. Using sequential window acquisition of all theoretical mass spectra acquisitions and multiple reaction monitoring analysis via mass spectrometry, relative and absolute quantification of proteins in the sera was performed. The results of the relative quantitation by sequential window acquisition for all theoretical mass spectra data showed that seven proteins were significantly differently expressed between MDD patients and other patients with remission status. However, absolute quantification by multiple reaction monitoring analysis identified prothrombin as the only significantly upregulated protein in the depressive state compared to remission (p < 0.05) and was, thus, subsequently selected as an MDD biomarker. The area under the curve for prothrombin was 0.66. Additionally, increased prothrombin/thrombin induced hyper-activation of platelets via activating protease-activated receptors, a feature associated with MDD; specifically, activated platelets secrete various molecules related to MDD, including brain-derived neurotropic factors and serotonin. Therefore, prothrombin is a potential screening, prognostic, and diagnostic marker for MDD.

Insight into the hypercoagulable state of high-risk thrombotic APS patients: Contribution of aβ2GPI and aPS/PT antibodies

OBJECTIVE

Most high-risk thrombotic antiphospholipid syndrome (APS) patients test positive for anti-β2-glycoprotein I (aβ2GPI) and anti-phosphatidylserine/prothrombin (aPS/PT) antibodies. Information on the influence of these antibodies on thrombin generation and activated protein C resistance (aPCr) is still sparse and contradictory.

METHODS

Plasma of 16 patients poured into a β2GPI affinity column allowed the perfect separation of aβ2GPI and aPS/PT antibodies. aPS/PT antibodies were further purified through a prothrombin affinity column. Obtained material was spiked into normal pooled plasma (NPP) and tested in the thrombin generation assay in the absence or presence of aPC.

RESULTS

aPS/PT antibodies showed a marked anticoagulant effect. Affinity purified aPS/PT and aβ2GPI antibodies from five patients were compared. aPS/PT antibodies showed significantly prolonged lag time and time to peak (5.0 minutes [interquartile range (IQR)3.5-6.1] versus 2.7 minutes [IQR2.2-3.5], P = .03 and 8.7 minutes [IQR6.7-10.3] versus 5.7 minutes [IQR4.5-6.2], P = .05, respectively) and significantly lower peak and velocity index (143 nmol/L [IQR131-163] versus 171 nmol/L [IQR157-182], P = .03 and 35 nmol/L/min [IQR32-59] versus 72 nmol/L/min [IQR54-77], P = .03, respectively). When aPC was added to the system, aPCr was significantly increased compared to controls for both aβ2GPI and aPS/PT antibodies. However, it was significantly stronger using aPS/PT antibodies. Median inhibition of endogenous thrombin potential was 22% (IQR16-33) with aPS/PT compared to 52% (IQR46-56) with aβ2GPI antibodies (P = .002).

CONCLUSIONS

Aβ2GPI antibodies show a mild anticoagulant and moderate procoagulant effect in thrombin generation and moderate aPC resistance. Conversely, aPS/PT antibodies show a strong anticoagulant effect and a strong aPCr.

Efficacy and safety of sorafenib plus vitamin K treatment for hepatocellular carcinoma: A phase II, randomized study

The previous retrospective study suggested that dosing vitamin K may enhance the anticancer action of sorafenib against hepatocellular carcinoma. To confirm it, we performed a phase II, randomized, open‐label study. Patients with hepatocellular carcinoma were randomly assigned to receive sorafenib + vitamin K2 (menatetrenone, 45 mg daily, orally) or sorafenib only. Between 1 May 2012 and 1 May 2016, 68 patients were screened. Forty‐four eligible patients were assigned at a 1:1 ratio to each cohort. The objective response rate in the vitamin K‐dosed group was significantly higher than that in the sorafenib only group (27.3% vs 4.5%, respectively; p = 0.039). The median time of progression‐free survival was significantly extended in the vitamin K‐dosed group compared with the sorafenib only group (4.9 months vs 2.7 months, respectively; hazard ratio (HR), 0.44; 95% confidence interval (CI): 0.21–0.89; p = 0.018). Although there was no significant difference between the two groups in the median time of overall survival, patients in the vitamin K‐dosed group with a complete response or partial response achieved a significantly extended median time of overall survival compared with the other patients in the vitamin K‐dosed group or the patients in the sorafenib only group (26.1 months vs 9.0 months; HR, 0.34; 95% CI: 0.11–0.95; p = 0.046 or 11.5 months; HR, 0.16; 95% CI: 0.034–0.70; p = 0.006, respectively). Dosing vitamin K could augment the anticancer action of sorafenib against HCC.

Regulation of factor V and factor V-short by TFPIα: Relationship between B-domain proteolysis and binding

Coagulation factor V (FV) plays an anticoagulant role but serves as a procoagulant cofactor in the prothrombinase complex once activated to FVa. At the heart of these opposing effects is the proteolytic removal of its central B-domain, including conserved functional landmarks (basic region, BR; 963–1008 and acidic region 2, AR2; 1493–1537) that enforce the inactive FV procofactor state. Tissue factor pathway inhibitor α (TFPIα) has been associated with FV as well as FV-short, a physiologically relevant isoform with a shortened B-domain missing the BR. However, it is unclear which forms of FV are physiologic ligands for TFPIα. Here, we characterize the binding and regulation of FV and FV-short by TFPIα via its positively charged C-terminus (TFPIα-BR) and examine how bond cleavage in the B-domain influences these interactions. We show that FV-short is constitutively active and functions in prothrombinase like FVa. Unlike FVa, FV-short binds with high affinity (K_d ∼1 nM) to TFPIα-BR, which blocks procoagulant function unless FV-short is cleaved at Arg¹⁵⁴⁵, removing AR2. Importantly, we do not observe FV binding (μM detection limit) to TFPIα. However, cleavage at Arg⁷⁰⁹ and Arg¹⁰¹⁸ displaces the FV BR, exposing AR2 and allowing TFPIα to bind via its BR. We conclude that for full-length FV, the detachment of FV BR from AR2 is necessary and sufficient for TFPIα binding and regulation. Our findings pinpoint key forms of FV, including FV-short, that act as physiologic ligands for TFPIα and establish a mechanistic framework for assessing the functional connection between these proteins.

Procoagulant factor levels and risk of venous thrombosis in the elderly

Essentials Venous thrombosis (VT) risk and coagulation factor levels increase with age. We studied the association between levels of procoagulant factors and the risk of a first VT in the elderly. Higher levels of factors VIII, IX, and XI, but not prothrombin, were associated with the risk of VT. Similar risk patterns were observed for provoked and unprovoked VT and for deep vein thrombosis and pulmonary embolism separately. ABSTRACT: Background Venous thrombosis (VT) incidence increases markedly with age. Coagulation factors are also positively associated with age. Objective To study whether higher levels of coagulation factors II (prothrombin), VIII, IX, and XI are associated with risk of a first VT in the elderly. Methods Four hundred and one patients and 431 control subjects aged 70 and older were included in the Age and Thrombosis, Acquired and Genetic risk factors in the Elderly (AT-AGE) study. Blood was collected 1 year after the event in patients and in all control subjects for measurement of coagulation factors. To assess the risk of VT, odds ratios (ORs) were calculated after stratification of coagulation factors in quartiles and at the 90th percentile, adjusting for potential confounders (age, sex, body mass index, and study center). Results Mean age was 78 years (range: 70-100 years). The ORs of VT for factors in the top quartile compared with the lowest quartile were 4.5 (95% confidence interval [CI]:2.7-7.3) for factor VIII, 2.4 (95% CI:1.1-5.2) for factor IX, and 1.7 (95% CI:1.0-2.9) for factor XI. High prothrombin was not associated with an increased VT risk. There was no dose-response association between the number of high coagulation factors and VT risk. The population attributable risk (PAR) of VT was 37.6%, 23.3%, and 12.4% for factor VIII, IX, and XI, respectively. Conclusion In this study of the elderly, higher factors VIII, IX, and XI but not prothrombin, were positively associated with the risk of VT.

Host fibrinogen drives antimicrobial function in Staphylococcus aureus peritonitis through bacterial-mediated prothrombin activation

The blood-clotting protein fibrinogen has been implicated in host defense following Staphylococcus aureus infection, but precise mechanisms of host protection and pathogen clearance remain undefined. Peritonitis caused by staphylococci species is a complication for patients with cirrhosis, indwelling catheters, or undergoing peritoneal dialysis. Here, we sought to characterize possible mechanisms of fibrin(ogen)-mediated antimicrobial responses. Wild-type (WT) (Fib+) mice rapidly cleared S. aureus following intraperitoneal infection with elimination of ∼99% of an initial inoculum within 15 min. In contrast, fibrinogen-deficient (Fib-) mice failed to clear the microbe. The genotype-dependent disparity in early clearance resulted in a significant difference in host mortality whereby Fib+ mice uniformly survived whereas Fib- mice exhibited high mortality rates within 24 h. Fibrin(ogen)-mediated bacterial clearance was dependent on (pro)thrombin procoagulant function, supporting a suspected role for fibrin polymerization in this mechanism. Unexpectedly, the primary host initiator of coagulation, tissue factor, was found to be dispensable for this antimicrobial activity. Rather, the bacteria-derived prothrombin activator vWbp was identified as the source of the thrombin-generating potential underlying fibrin(ogen)-dependent bacterial clearance. Mice failed to eliminate S. aureus deficient in vWbp, but clearance of these same microbes in WT mice was restored if active thrombin was administered to the peritoneal cavity. These studies establish that the thrombin/fibrinogen axis is fundamental to host antimicrobial defense, offer a possible explanation for the clinical observation that coagulase-negative staphylococci are a highly prominent infectious agent in peritonitis, and suggest caution against anticoagulants in individuals susceptible to peritoneal infections.

The Activation of Prothrombin Seems to Play an Earlier Role than the Complement System in the Progression of Colorectal Cancer: A Mass Spectrometry Evaluation

Colorectal cancer (CRC) is the second cause of death in men and the third in women. This work deals with the study of the low molecular weight protein fraction of sera from patients who underwent surgery for CRC and who were followed for several years thereafter. MALDI-TOF MS was used to identify serum peptidome profiles of healthy controls, non-metastatic CRC patients and metastatic CRC patients. A multiple regression model was applied to signals preliminarily selected by SAM analysis to take into account the age and gender differences between the groups. We found that, while a signal m/z 2021.08, corresponding to the C3f fragment of the complement system, appears significantly increased only in serum from metastatic CRC patients, a m/z 1561.72 signal, identified as a prothrombin fragment, has a significantly increased abundance in serum from non-metastatic patients as well. The findings were also validated by a bootstrap resampling procedure. The present results provide the basis for further studies on large cohorts of patients in order to confirm C3f and prothrombin as potential serum biomarkers. Thus, new and non-invasive tests might be developed to improve the classification of colorectal cancer.

Anticoagulation Therapy in a Patient With Heterozygous Factor V Leiden and Coexisting Homozygous Prothrombin Gene Mutations

Coexistent heterozygous factor V Leiden and homozygous prothrombin G20210A gene mutations is a rare and potentially life-threatening occurrence. This inherited thrombophilia often presents as non-specific venous thromboemboli and can mimic a variety of emergent medical conditions. The pathophysiology of the disease has been well documented; however, long-term treatment efficacy remains poorly understood. We report the case of a 25-year-old male presenting with acute chest pain. A comprehensive workup revealed bilateral pulmonary emboli arising in part from concomitant heterozygous factor V Leiden and homozygous prothrombin G20210A gene mutations. Immediate and continuous treatment with anticoagulants enoxaparin and apixaban significantly reduced the patient’s symptoms and D-dimer within one week. This case provides insight into an effective treatment regimen for this rare and inherited thrombophilia.

The prevalence of antiphospholipid antibodies in women with late pregnancy complications and low-risk for chromosomal abnormalities

BACKGROUND

Antiphospholipid antibodies (aPL) are known to increase the risk of obstetrical complications. However, aPL significance and prevalence in women with late-onset pregnancy complications (LO-PC) need further clarification.

OBJECTIVES

To investigate the prevalence of aPL in a cohort of women who experienced LO-PC and to compare it with a cohort of uneventful pregnancies.

METHODS

One hundred pregnant women who experienced LO-PC, had a low risk for chromosomal abnormalities, and absence of fetal abnormalities were recruited from August 2018 to August 2019. One hundred women with uneventful pregnancy were included as controls. aPL testing was performed on serum samples derived from prenatal screening test and included both criteria and "extra criteria" aPL.

RESULTS

Patients with LO-PC had significantly higher aPL prevalence when compared with controls (31/100 [31%] vs 10/100 [10%]; P < .001). More in detail, up to 26% of women with LO-PC were positive for one aPL, with an overall prevalence significantly higher than controls (26% vs 9%; P < .05). Among single aPL positivity, patients had significantly higher rate of positivity and titers of anticardiolipin IgG (10% vs 2%; mean ± standard deviation 11 ± 13 vs 4 ± 9.6 chemoluminescent unit; P < .05) and phosphatidylserine-prothrombin antibodies (aPS/PT) IgM (15% vs 6%; mean ± standard deviation 10.2 ± 21.7 vs 3.7 ± 13.7 U; P < .05). Testing for aPS/PT (IgM/IgG) alone allowed the identification of 17 patients negative for criteria aPL. aPL-positive patients had a significantly higher risk of preterm birth (34-36 + 6 weeks; 10% vs 8%; P < .012).

CONCLUSIONS

We report a high prevalence of aPL in our cohort. Testing for both criteria and "extra criteria" aPL in women with previous LO-PC could improve the diagnostic accuracy identifying women at higher risk for recurrent pregnancy complications.

Relative Protein Abundances and Biological Ageing in Whole Skeletal Elements

Establishing biological age is an integral part of forensic investigations, currently achieved through morphological methods with varying degrees of accuracy. Furthermore, biological ageing is much easier in juveniles than in adults, at which point traditional ageing methods struggle. Therefore, biomolecular approaches are considered of great interest, with several protein markers already recognized for their potential forensic significance. However, previous studies have typically relied on subsampling different parts of skeletal elements. Here, we attempt to evaluate the proteome of complete elements using a rat model. In the analysis of specimens spanning beyond adulthood (1 week to 1.5 years), we observed 729 unique proteins across 33 samples (three for each sex for each of the five (female) or six (male)), five of which represent newly identified proteins in relation to age estimation: vimentin, osteopontin, matrilin-1, apolipoprotein A-I, and prothrombin. Most of these follow the trend of decreasing abundance through age, with the exception of prothrombin that increases. We consider the combined use of these relative abundances, along with those of previously noted fetuin-A, biglycan, albumin, and chromogranin-A signatures, as being of potential value to the development of an age estimation tool worthy of further evaluation in forensic contexts.

Anti-Phospholipid Antibodies in COVID-19 Are Different From Those Detectable in the Anti-Phospholipid Syndrome

Background

Critically ill patients with coronavirus disease 2019 (COVID-19) have a profound hypercoagulable state and often develop coagulopathy which leads to organ failure and death. Because of a prolonged activated partial-thromboplastin time (aPTT), a relationship with anti-phospholipid antibodies (aPLs) has been proposed, but results are controversial. Functional assays for aPL (i.e., lupus anticoagulant) can be influenced by concomitant anticoagulation and/or high levels of C reactive protein. The presence of anti-cardiolipin (aCL), anti-beta2-glycoprotein I (anti-β2GPI), and anti-phosphatidylserine/prothrombin (aPS/PT) antibodies was not investigated systematically. Epitope specificity of anti-β2GPI antibodies was not reported.

Objective

To evaluate the prevalence and the clinical association of aPL in a large cohort of COVID-19 patients, and to characterize the epitope specificity of anti-β2GPI antibodies.

Methods

ELISA and chemiluminescence assays were used to test 122 sera of patients suffering from severe COVID-19. Of them, 16 displayed major thrombotic events.

Results

Anti-β2GPI IgG/IgA/IgM was the most frequent in 15.6/6.6/9.0% of patients, while aCL IgG/IgM was detected in 5.7/6.6% by ELISA. Comparable values were found by chemiluminescence. aPS/PT IgG/IgM were detectable in 2.5 and 9.8% by ELISA. No association between thrombosis and aPL was found. Reactivity against domain 1 and 4-5 of β2GPI was limited to 3/58 (5.2%) tested sera for each domain and did not correlate with aCL/anti-β2GPI nor with thrombosis.

Conclusions

aPL show a low prevalence in COVID-19 patients and are not associated with major thrombotic events. aPL in COVID-19 patients are mainly directed against β2GPI but display an epitope specificity different from antibodies in antiphospholipid syndrome.

MTHFR C677T, Prothrombin G20210A, and Factor V Leiden (G1691A) Polymorphism and Beta-Thalassemia Risk: A Meta-Analysis

Background Beta (β)-thalassemia major patients frequently suffer from many vascular problems. Thrombophilia is a blood disorder that comprises imbalances in the blood coagulating factor due to ecological and hereditary components. Previous evidence shows that thrombosis is the commonest risk in beta-thalassemia patients. Several studies have examined that MTHFR C677T, prothrombin G20210A (PT G20210A), and Factor V Leiden G1691A (FVL G1691A) polymorphism play a crucial role in the development of β-thalassemia major, yet the result was questionable and uncertain. Therefore, in this study, we executed the correlation between these gene polymorphisms with β-thalassemia major patients. Methods Suitable keywords were used to search related articles in PubMed, Google Scholar, and Web of Science. In this random-effects meta-analysis, we analyzed the odds ratio (OR) for the estimation of risk. Results A total of nine research articles with 645 β-thalassemia major patients and 989 healthy controls were incorporated in this meta-analysis. The pooled OR was assessed in MTHFR C677T, PT G20210A, and FVL G1691A polymorphism. This random-effects meta-analysis demonstrated that MTHFR C677T, PT G20210A, and FVL G1691A gene polymorphism did not significantly associate with β-thalassemia major. Moreover, the heterogeneity was significantly found in genotype CC vs CT+TT C677T (I²=61%) and allele C vs T (I²=71%) of MTHFR and genotype GG vs GA (I²=95%), GG vs GA+AA (I²=95%), GA vs GG+AA (I²=95%), and allele G vs A (I²=93%) of FVL G1691A. Conclusion The results of this meta-analysis show that MTHFR C677T, prothrombin G20210A, and Factor V Leiden (G1691A) gene polymorphism are not a risk factor for β-thalassemia major.

Recurrent miscarriage is not associated with a higher prevalence of inherited and acquired thrombophilia

PROBLEM

Although not being recommended in guidelines, many physicians perform routine screening for thrombophilia in RM patients suspecting a higher prevalence in these patients. The aim of this study was to analyze the prevalence of inherited and acquired thrombophilia in a large cohort of RM patients.

METHOD OF STUDY

Within a multicenter case-control study, n = 820 RM patients and n = 141 controls were included. The prevalence of inherited and acquired thrombophilia including deficiency of protein C/S and antithrombin, elevation of factor VIII activity, APC resistance including mutation in the factor V Leiden gene, mutation in the prothrombin gene and antiphospholipid antibodies were assessed. Further, we performed a meta-analysis of the prevalence of thrombophilia in RM patients including studies between 01/2000 and 01/2020.

RESULTS

An antiphospholipid syndrome (APLS) was only present in RM patients. Increased factor VIII concentration was significantly more prevalent in controls (RM vs controls: 5.8% vs 11.0%). None of the other thrombophilia did differ significantly between RM patients and controls. The meta-analysis revealed no significant difference in the occurrence of these thrombophilia between RM patients and controls.

CONCLUSION

The prevalence of inherited thrombophilia does not differ between RM patients and controls. When analyzing rare events like thrombophilia, a high number of patients are needed to obtain reliable results, which might explain contradictory findings in previous studies analyzing small cohorts of RM patients. Despite being less prevalent than previously described, we still recommend screening for APLS as it is associated with severe pregnancy complications.