The protein C anticoagulant system: inherited defects as basis for venous thrombosis

Loss of function in protein Z (PROZ) is associated with increased risk of ischemic stroke in the UK Biobank

BACKGROUND

The vitamin K-dependent coagulation factor protein Z (PZ), encoded by the PROZ gene, is canonically considered to have anticoagulant effects through negative regulation of factor Xa. Paradoxically, higher circulating PZ concentrations have repeatedly been associated with an elevated risk of acute ischemic stroke.

OBJECTIVES

We performed a large-scale genetic association study to examine the relationship between germline genetic variants in PROZ and the risk of ischemic stroke.

METHODS

Using whole-exome sequencing and clinical data for 416 711 participants in the UK Biobank (UKB), we identified individuals with rare (minor allele frequency ≤0.1%) putatively function-altering variants in PROZ. Using Firth's logistic regression and controlling for known stroke risk factors, we evaluated the association between variant carrier status and noncardioembolic ischemic stroke (NCEIS). Additionally, we evaluated differences in the plasma levels of 1472 proteins between PROZ variant carriers and noncarriers in a subset of 48 893 UKB participants.

RESULTS

After accounting for missing data, qualifying variants in PROZ were identified in 414 UKB participants (99.0% heterozygous). Variant carriers had a significantly increased risk of NCEIS (odds ratio, 2.34; 95% CI, 1.15-4.13; P = .02) but not of venous thromboembolism, myocardial infarction, or peripheral artery disease. Plasma proteomics analysis revealed that PROZ variant carriers had significantly elevated levels of 2 proteins related to the response to cerebral ischemia, peroxiredoxins 1 and 6 (PRDX1: fold change, 1.83; P = 1.3 × 10-5; PRDX6: fold change, 1.78; P = 9.6 × 10-10).

CONCLUSION

Lifelong exposure to decreased PZ levels confers a significantly increased risk of NCEIS, consistent with the role of PZ as an anticoagulant factor.

Mutation Ter462GlnextTer17 introduces a tail to C-terminus of protein C and causes venous thrombosis

Protein C (PC), a vitamin K-dependent serine protease zymogen in plasma, can be activated by thrombin-thrombomodulin(TM) complex, resulting in the formation of activated protein C (APC). APC functions to downregulate thrombin generation by inactivating active coagulation factors V(FVa) and VIII(FVIIIa). Deficiency in PC increases the risk of venous thromboembolism (VTE). We have identified two unrelated VTE patients with the same heterozygous mutation (c.1384 T > C, p.Ter462GlnextTer17) in PROC. To comprehend the role of this mutation in VTE development, we expressed recombinant PC-Ter462GlnextTer17 in mammalian cells and evaluated its characteristics using established coagulation assay systems. Functional studies revealed a significant impairment in the activation of the mutant by thrombin or thrombin-TM complex. Furthermore, APC-Ter462GlnextTer17 demonstrated diminished hydrolytic activity towards the chromogenic substrate S2366. APTT and FVa degradation assays showed that both the anticoagulant activity of the mutant protein was markedly impaired, regardless of whether protein S was present or absent. These results were further supported by a thrombin generation assay conducted using purified and plasma-based systems. In conclusion, the Ter462GlnextTer17 mutation introduces a novel tail at the C-terminus of PC, leading to impaired activity in both PC zymogen activation and APC's anticoagulant function. This impairment contributes to thrombosis in individuals carrying this heterozygous mutation and represents a genetic risk factor for VTE.

Acute liver failure as initial presentation in a Chinese patient with Budd-Chiari syndrome due to protein C deficiency: A case report and literature review

Acute liver failure is an uncommon presentation in the clinic. Common causes for acute liver failure include viral hepatitis and drug-related hepatotoxicity. However, acute liver failure due to Budd-Chiari syndrome is rare. This case highlights the importance of necessary constrast-enhanced imaging studies to rule out vascular etiologies of acute liver failure, in addition to common causes like viral or drug-induced hepatic failure. We present a case of a male Chinese patient who presented with nausea, vomiting, fatigue, and fever after eating a large amount of fatty food. Six days after hospitalization, the patient developed acute liver failure and hepatic encephalopathy. Contrast-enhanced computerized tomography and ultrasound examinations revealed thromboses in the hepatic veins and inferior vena cava. Further testing also showed decreased protein C activity. Therefore, a diagnosis of Budd-Chiari syndrome secondary to protein C deficiency was made. He received supportive care and a transjugular intrahepatic portal shunt. Hepatic function, coagulation panel results, and clinical presentations gradually returned to normal. Budd-Chiari syndrome from protein C deficiency could be a rare but valid cause of acute liver failure in Chinese patients.

Successful ECMO treatment in patients with cerebral hemorrhage and PROC gene mutation associated with VTE: a case report

In this report, we report a case of a middle-aged male, admitted to the ICU with cerebral hemorrhage resulting from a severe high-altitude fall. The patient encountered significant challenges in oxygenation index correction, attributed to extensive embolism in both the primary and branch pulmonary arteries. Consequently, the patient underwent an immediate initiation of veno-arterial extracorporeal membrane oxygenation (VA-ECMO) therapy, persisting for 20 days. During this treatment period, a mutation in the protein C (PROC) gene was identified. The medical team meticulously navigated the delicate balance between anticoagulation and bleeding risks. Eventually, the patient was successfully weaned off VA-ECMO and subsequently discharged. This report aims to delve into the etiology and therapeutic approaches of this uncommon case, with the intention of offering insightful reference for managing similar clinical scenarios in the future.

Acute Portal Vein Thrombosis as an Initial Presentation of Protein C Deficiency: A Case Report

Protein C (PC) is an essential vitamin K-dependent protein that regulates thrombosis and hemostasis in the body. A mutation in the PROC gene on chromosome 2q14.3 results in PC deficiency. The clinical presentation of PC deficiency can vary, ranging from a single vein thrombosis to disseminated intravascular coagulation, purpura fulminans, or even life-threatening complications such as sepsis. Here, we present a case of a 37-year-old female who was found to have acute portal vein thrombosis as an initial presentation of PC deficiency. She presented to the hospital with acute onset of abdominal pain associated with nausea, blood-streaked emesis, and bloody bowel movement.

The Tissue Factor Pathway in Cancer: Overview and Role of Heparan Sulfate Proteoglycans

Historically, the only focus on tissue factor (TF) in clinical pathophysiology has been on its function as the initiation of the extrinsic coagulation cascade. This obsolete vessel-wall TF dogma is now being challenged by the findings that TF circulates throughout the body as a soluble form, a cell-associated protein, and a binding microparticle. Furthermore, it has been observed that TF is expressed by various cell types, including T-lymphocytes and platelets, and that certain pathological situations, such as chronic and acute inflammatory states, and cancer, may increase its expression and activity. Transmembrane G protein-coupled protease-activated receptors can be proteolytically cleaved by the TF:FVIIa complex that develops when TF binds to Factor VII (PARs). The TF:FVIIa complex can activate integrins, receptor tyrosine kinases (RTKs), and PARs in addition to PARs. Cancer cells use these signaling pathways to promote cell division, angiogenesis, metastasis, and the maintenance of cancer stem-like cells. Proteoglycans play a crucial role in the biochemical and mechanical properties of the cellular extracellular matrix, where they control cellular behavior via interacting with transmembrane receptors. For TFPI.fXa complexes, heparan sulfate proteoglycans (HSPGs) may serve as the primary receptor for uptake and degradation. The regulation of TF expression, TF signaling mechanisms, their pathogenic effects, and their therapeutic targeting in cancer are all covered in detail here.

Hereditary protein C deficiency with portal vein thrombosis in a Chinese male: A case report

Hereditary protein C deficiency (PCD) is caused by mutation in the PC gene (PROC). The homozygous mutation form of PCD is rare. Furthermore, in Asia, cases of noncirrhotic patients with portal vein thrombosis (PVT) secondary to PCD have been rarely reported. The present study reported the case of a patient with PVT due to hereditary PCD. Of note, the mutation of PROCc.152G>A was observed in the patient of the present study. According to the current literature, there has been no previous report regarding the mutation of this gene in China. The patient suffered abdominal pain for 20 days, which was accompanied by vomiting for 2 days. Multiple ulcers and diverticula in the sigmoid colon, as well as erosive small ulcers throughout the colon, were discovered during a colonoscopy. Abdominal angiography indicated thrombosis of the portal vein and its branches. Furthermore, laboratory parameters indicated a hypercoagulable state with normal PC antigen values but decreased PC activity. The discovery of blood coagulation-related genes suggested that homozygous mutation in PC resulted in an amino acid missense mutation. Anticoagulants were prescribed after a diagnosis of type II hereditary PCD with PVT was made. After 15 days, the blood coagulation function of the patient was restored to normal and the symptoms were substantially alleviated. Hence, the present study expanded the mutation spectrum of PROC in China and reaffirmed the value of anticoagulant therapy in PCD.

Characterization of thrombophilia-related plasmas evaluated by anticoagulants-mediated thrombin and plasmin generation assays

Disturbances in the balance between coagulation, anticoagulation and fibrinolysis may lead to thrombosis or haemorrhage. Simultaneous assessments of thrombin and plasmin facilitate overall understandings of pathological haemostasis, especially for thrombophilia. Here, we characterized coagulation-fibrinolysis potentials in plasmas with thrombophilia using anticoagulants-mediated thrombin-plasmin generation assay (T/P-GA). T/P-GA was initiated by adding tissue factor, tissue-type plasminogen activator and anticoagulants [recombinant-thrombomodulin (rTM), activated protein (P)C (APC) and antithrombin (AT)], followed by simultaneous thrombin generation and plasma generation monitoring. Patients' plasmas with PC-deficiency (PC-def), PS-deficiency (PS-def), AT-deficiency (AT-def), factor VLeiden (FVL) and antiphospholipid syndrome (APS) were evaluated. A ratio of peak-thrombin (or peak-plasmin) with and without anticoagulants was calculated as anticoagulants (+)/anticoagulants (-). First, TG, in rTM-mediated, PC-def, PS-def and FVL showed higher peak-thrombin ratios than the controls, whereas AT-def and APS exhibited no differences from the controls. In APC-mediated, PC-def, PS-def and AT-def showed low peak-thrombin ratios, similar to the controls, but immune-depleted PS-def (<1%) showed the higher ratio than the controls. FVL and APS showed higher peak-thrombin ratios than the controls. In AT-mediated, peak-thrombin ratios in PS-def, PC-def and APS were lower than in controls, but those in AT-def and FVL was not significantly different from the controls. Second, PG, in rTM-mediated, all thrombophilia plasmas showed low peak-plasmin ratios (∼0.5), but no significant difference was observed, relative to the controls. In APC and AT-mediated, peak-plasmin ratios in thrombophilia-related plasmas were similar to the controls (∼1.0). Anticoagulants-mediated T/P-GA may classify thrombin generation characteristics in thrombophilia-related plasmas upon adding anticoagulants.

A Case of Type 2 Protein S Deficiency Presenting as Cerebral Venous Thrombosis (CVT) in an 18-Year-Old Female

Here, we report a case of cerebral venous thrombosis in an 18-year-old female. On evaluation, she was found to have type 2 protein S deficiency, which is the rarest form of protein S deficiency and is also known as a qualitative defect. Protein S is primarily synthesized by hepatocytes and undergoes vitamin K-dependent gamma-carboxylation. Mature protein S circulates in two states: free and bound to the complement component C4b-binding protein (C4b-BP). The free form of protein S acts as a cofactor for activated protein C. This case is unique as here, there is a qualitative effect that is responsible for the manifestations.

Protein S gene mutation c.946C > T (p.R316C) contributed to ischemic stroke in a man with von Willebrand disease type 3 caused by two novel VWF gene mutations, c.2328delT (p.A778Lfs* 23) and c.6521G > T (p.C2174F)

The risk factors for a family with VWD presenting with an ischemic stroke (IS) were explored. FVIII activity (FVIII:C), VWF antigen (VWF:Ag), and protein S activity were measured. Next generation sequencing (NGS) was performed targeting F8, F9, VWF, PROC, and PROS1. Sanger sequencing validation was performed on family members. The proband and his sister both had low FVIII:C (1 IU/dL) and VWF:Ag (3 IU/dL) levels, confirming the diagnosis of type 3 VWD. His father had nearly normal levels of FVIII:C (58 IU/dL) and VWF:Ag (57 IU/dL). His daughter had type 1 VWD with decreased FVIII:C (46 IU/dL) and VWF:Ag (19 IU/dL). NGS identified a heterozygous VWF c.2328delT (p.A778Lfs*23) frame shift mutation only in the proband and his sister. Another VWF missense mutation, c.6521G > T (p.C2174F), was found heterozygous in all members studied. A PROS1 mutation, c.946C > T (p.R316C), previously reported to relate to ischemic stroke, was found heterozygous in the patient, his father, and his daughter. Only the proband and daughter have a slightly decreased plasma protein S level. This may be the first case with type 3 VWD with severe VWF/FVIII deficiency presented with ischemic stroke contributed to by a protein S defect.

Dyslipidaemia-Genotype Interactions with Nutrient Intake and Cerebro-Cardiovascular Disease

A comprehensive understanding of gene-diet interactions is necessary to establish proper dietary guidelines to prevent and manage cardio-cerebrovascular disease (CCD). We investigated the role of genetic variants associated with dyslipidaemia (DL) and their interactions with macro-nutrients for cardiovascular disease using a large-scale genome-wide association study of Korean adults. A total of 58,701 participants from a Korean genome and epidemiology study were included. Their dietary intake was assessed using a food frequency questionnaire. Dyslipidaemia was defined as total cholesterol (TCHL) ≥ 240 mg/dL, high-density lipoprotein (HDL) < 40 mg/dL, low-density lipoprotein (LDL) ≥ 160 mg/dL, triglycerides (TG) ≥ 200 mg/dL, or dyslipidaemia history. Their nutrient intake was classified as follows: protein intake: high ≥ 30%, 30% > moderate ≥ 20%, and 20% > low in daily total energy intake (TEI); carbohydrate intake: high ≥ 60%, 60% > moderate ≥ 50%, and 50% > low; fat intake: high ≥ 40%, 40% > moderate ≥ 30%, and 30% > low. Odds ratios and 95% confidence intervals were calculated after adjusting for age; sex; body mass index (BMI); exercise status; smoking status; alcohol intake; principal component 1 (PC1); principal component 2 (PC2); and intake of carbohydrates, fats, and proteins. This analysis included 20,596 patients with dyslipidaemia and 1027 CCD patients. We found that rs2070895 related to LIPC was associated with HDL-cholesterol. Patients with the minor allele (A) in rs2070895 had a lower risk of CCD than those carrying the reference allele (G) (odds ratio [OR] = 0.8956, p-value = 1.78 × 10−2). Furthermore, individuals consuming protein below 20% TEI with the LIPC reference allele had a higher risk of CCD than those with the minor allele (interaction p-value 6.12 × 10−3). Our findings suggest that the interactions of specific polymorphisms associated with dyslipidaemia and nutrients intake can influence CCD.

Atypical presentation of pulmonary embolism and deep vein thrombosis due to protein S deficiency in a young female with chest pain

Venous thromboembolism has many risk factors including protein S deficiency, which poses a significant diagnostic challenge as it presents with atypical complaints. A treatable yet potentially fatal condition, acute pulmonary embolism, is currently third most common cause of cardiovascular death. Clinicians should include pulmonary embolism as differential diagnosis in young adults with atypical symptoms with 2 D ECHO findings of the dilated right atrium, right ventricle, and elevated pulmonary artery pressure, and diagnosis is confirmed by computed tomography pulmonary angiography (CTPA). Anticoagulants including NOACs should be initiated promptly to improve the outcome for patients.

Activated Protein C Strengthens Cardiac Tolerance to Ischemic Insults in Aging

BACKGROUND

APC (activated protein C) is a plasma serine protease with anticoagulant and anti-inflammatory activities. EPCR (Endothelial protein C receptor) is associated with APC's activity and mediates its downstream signaling events. APC exerts cardioprotective effects during ischemia and reperfusion (I/R). This study aims to characterize the role of the APC-EPCR axis in ischemic insults in aging.

METHODS

Young (3-4 months) and aged (24-26 months) wild-type C57BL/6J mice, as well as EPCR point mutation (EPCR^R84A/R84A) knockin C57BL/6J mice incapable of interaction with APC and its wild type of littermate C57BL/6J mice, were subjected to I/R. Wild-type APC, signaling-selective APC-2Cys, or anticoagulant-selective APC-E170A were administrated before reperfusion.

RESULTS

The results demonstrated that cardiac I/R reduces APC activity, and the APC activity was impaired in the aged versus young hearts possibly attributable to the declined EPCR level with aging. Serum EPCR measurement showed that I/R triggered the shedding of membrane EPCR into circulation, while administration of APC attenuated the I/R-induced EPCR shedding in both young and aged hearts. Subsequent echocardiography showed that APC and APC-2Cys but not APC-E170A ameliorated cardiac dysfunction during I/R in both young and aged mice. Importantly, APC elevated the resistance of the aged heart to ischemic insults through stabilizing EPCR. However, all these cardioprotective effects of APC were blunted in the EPCR^R84A/R84A mice versus its wild-type littermates. The ex vivo working heart and metabolomics results demonstrated that AMPK (AMP-activated protein kinase) mediates acute adaptive response while AKT (protein kinase B) is involved in chronic metabolic programming in the hearts with APC treatment.

CONCLUSIONS

I/R stress causes shedding of the membrane EPCR in the heart, and administration of APC prevents I/R-induced cardiac EPCR shedding that is critical for limiting cardiac damage in aging.

Genetic Variants in the Protein S ( PROS1 ) Gene and Protein S Deficiency in a Danish Population

Protein S (PS) deficiency is a risk factor for venous thromboembolism (VTE) and can be caused by variants of the gene encoding PS ( PROS1 ). This study aimed to evaluate the clinical value of molecular analysis of the PROS1 gene in PS-deficient participants. We performed Sanger sequencing of the coding region of the PROS1 gene and multiplex ligation-dependent probe amplification to exclude large structural rearrangements. Free PS was measured by a particle-enhanced immunoassay, while PS activity was assessed by a clotting method.

A total of 87 PS-deficient participants and family members were included. In 22 index participants, we identified 13 PROS1 coding variants. Five variants were novel. In 21 index participants, no coding sequence variants or structural rearrangements were identified. The free PS level was lower in index participants carrying a PROS1 variant compared with index participants with no variant (0.51 [0.32–0.61] vs. 0.62 [0.57–0.73] × 10 ³ IU/L; p  < 0.05). The p.(Thr78Met) variant was associated with only slightly decreased free PS levels (0.59 [0.53–0.66] × 10 ³ IU/L) compared with the p.(Glu390Lys) variant (0.27 [0.24–0.37] × 10 ³ IU/L, p  < 0.01). The frequency of VTE in participants with a coding PROS1 variant was 43 and 17% in the group with normal PROS1 gene ( p  = 0.05).

In conclusion, we report 13 PROS1 coding variants including five novel variants. PS levels differ by PROS1 variant and the frequency of VTE was higher when a coding PROS1 variant was present. Hence, molecular analysis of the PROS1 gene may add clinical value in the diagnostic work-up of PS deficiency.

Protein C Pathway, Inflammation, and Pump Thrombosis in Patients With Left Ventricular Assist Devices

Use of left ventricular assist devices (LVADs) for management of advanced heart failure is becoming increasingly common; however, device associated thrombosis remains an important cause of mortality in this patient population. We hypothesize that inflammation in LVAD implanted patients dysregulates the protein C pathway, creating a hypercoagulable state leading to thrombosis. Plasma samples from 22 patients implanted with the Thoratec HeartMate II LVAD were analyzed by commercial ELISAs. Retrospective sample selection included those collected 1-3 months prior to and within 1 month after a thrombotic or bleeding event. Unrelated to warfarin dosing, total protein S and free protein S (p = 0.033) levels were 20% lower in patients with LVAD-thrombosis than in patients with LVAD-bleeding. Levels of protein C, soluble endothelial cell protein C receptor, and soluble thrombomodulin were similar in both groups before and after the event. Compared to normal, C-reactive protein levels were 25-fold elevated in LVAD-thrombosis patients but only 9-fold elevated in LVAD-bleeding patients. This study suggests that protein S, influenced by the inflammatory state, is a gatekeeper for the function of protein C in patients with LVAD-associated thrombosis.

Pathogenic variants of PROC gene caused type II activity deficiency in a Chinese family: A case report

RATIONALE

Hereditary Protein C (PC) deficiency is a rare genetic disorder caused by PROC gene mutation. In this article, we report a case of PC deficiency in a Chinese family due to a novel PROC gene mutation.

STUDY SUBJECT

The proband presented with recurrent cerebral infarction over the course of the previous 3 years. He was admitted to the hospital due to signs of mental retardation.

DIAGNOSES

Physical examination, laboratory tests, and magnetic resonance imaging demonstrated that the proband had a manifestation of PC deficiency that included acute cerebral infarction. DNA sequencing analysis revealed a missense variant, c.1015G > A (p.V339 M from valine to methionine) in exon 9 of the PROC gene. In addition, Sanger sequencing confirmed that the proband's son was heterozygous for the same variant. Therefore, the PROC gene mutation was transmitted in an autosomal dominant inheritance manner.

INTERVENTIONS

The patient was treated with a daily dosage of Warfarin (3.5 mg) and was scheduled to undergo regular blood coagulation tests.

OUTCOMES

At the 3-month follow-up appointment, the patient showed improvements in his overall health condition.

LESSONS

We identified a novel missense mutation in the PROC gene in a Chinese family which caused a decrease in the PC antigen level and recurrent cerebral infarction.

Role of Gly197 in the structure and function of protein C

We previously demonstrated that heterozygous Gly197 to Arg mutation in PROC is associated with venous thrombosis due to the mutation abrogating both zymogenic and enzymatic activities of protein C and activated protein C (APC). In this study, we investigated the role of Gly197 on the structure and function of protein C by replacing it with Ala, Lys and Glu in separate constructs. Characterization of protein C mutants indicated their activation by thrombin is improved ~5-20-fold with the order of PC-G197K > PC-G197E > PC-G197A > PC-WT. Interestingly, the cofactor function of thrombomodulin (TM) in promoting the activation of zymogens by thrombin followed the reverse order of PC-WT > PC-G197A > PC-G197E > PC-G197K. The thrombin-generation inhibitory profiles of zymogens in a tissue factor-mediated thrombin generation assay using protein C-deficient plasma with or without supplementation with TM followed the same order of zymogen activation in the purified system. Evaluation of anticoagulant activities of APC derivatives by prothrombinase and aPTT assays revealed a normal activity for APC-G197A but dramatically impaired activity for the other two mutants. In the endothelial cell permeability assay, APC-G197A exhibited normal antiinflammatory activity, but the other two mutants were nearly inactive. These results suggest that Gly197 plays a key role in TM cofactor-dependent protein C activation by thrombin. It facilitates the recognition of protein C by thrombin in the presence of TM but impedes it in the absence of the cofactor. In APC, a small residue at this position is required for the proper folding/reactivity of the active-site pocket of the protease, a hypothesis supported by structural modeling.

Esophagectomy for Esophageal Cancer in a Patient with Protein C Deficiency: A Case Report

A 63-year-old man with protein C deficiency underwent thoracoscopic esophagectomy and digestive reconstruction using a gastric tube for thoracic esophageal cancer. On postoperative day 3, the gastric tube was removed because of anastomotic leakage and gastric tube necrosis. Digestive reconstruction using a free jejunal graft was attempted 140 days after the first surgery. However, thrombus formation in the artery and vein of the jejunal graft resulted in a failed reconstruction. Ten days after this surgery, digestive reconstruction using the colon was performed with intraoperative heparin administered for anticoagulation control. The surgery was successful, with no thrombus formation afterward. When performing digestive reconstruction in patients with conditions predisposing to thrombus formation, perioperative management should be completed with careful attention toward preventing thrombus formation. In particular, appropriate anticoagulation control, such as the administration of intraoperative heparin, is recommended in patients with protein C deficiency because necrosis of the reconstructed organ is likely.

Gly197Arg mutation in protein C causes recurrent thrombosis in a heterozygous carrier

BACKGROUND

Activated protein C (APC) downregulates thrombin generation by inactivating procoagulant cofactors Va and VIIIa by limited proteolysis. We identified two protein C-deficient patients both of whom carry a heterozygous Gly197 to Arg (G197R) mutation in PROC and experience venous thrombosis.

OBJECTIVE

The objective of this study was to determine the molecular basis of the clotting defect in patients carrying the G197R mutation.

METHODS

We expressed protein C-G197R in mammalian cells and characterized its properties in established coagulation and anti-inflammatory assay systems.

RESULTS

The activation of protein C-G197R by thrombin was improved ~10-fold; however, its activation by thrombin was not promoted by thrombomodulin (TM). In a tissue factor-mediated thrombin generation assay, the addition of soluble TM to protein C-deficient plasma, supplemented with protein C-G197R, did not have a significant inhibitory effect on thrombin generation parameters. APC-G197R did not exhibit a significant anticoagulant activity in either purified or plasma-based assay systems. APC-G197R was essentially inactive because it showed no activity in an aPTT assay. Anti-inflammatory activity of APC-G197R was also dramatically impaired as determined by an endothelial cell permeability assay. Structural modeling predicted that the side-chain of Arg cannot be accommodated at this site of APC without a major distortion of the local structure that appears to propagate and adversely affect the reactivity/folding of the catalytic pocket.

CONCLUSION

The G197R mutation in patients appears to be functionally equivalent to a heterozygous protein C knockout with half of the protein having no significant activity and thus causing thrombosis.

Childhood Nephrotic Syndrome Complicated by Catastrophic Multiple Arterial Thrombosis Requiring Bilateral Above-Knee Amputation

Background: Thromboembolic events are rare but critical complications in childhood nephrotic syndrome. The veins are more commonly affected, while arterial thrombosis is extremely rare but often life-threatening. Herein, we describe the clinical course of a 10-years-old girl with catastrophic multiple arterial thrombosis at the primary onset of nephrotic syndrome who underwent bilateral above-knee amputation. Case diagnosis/treatment: A previous healthy 10-years-old girl contracted the influenza B virus. Five days later, she suddenly developed severe ischemia in both legs. Physical examination showed eyelid and leg edema, and laboratory tests revealed hypoalbuminemia and acute kidney injury. After undergoing contrast-enhanced computed tomography, the patient was diagnosed with multiple arterial thrombosis (including the bilateral iliac arteries) due to nephrotic syndrome. Despite the performance of surgical thrombectomies, fasciotomy, and systematic heparinization, she required bilateral above-knee amputation. The patient achieved spontaneous remission of nephrotic syndrome, and her renal function fully recovered. There were no findings suggestive of secondary nephrotic syndrome and antiphospholipid syndrome. Her protein C and protein S concentrations were slightly decreased at admission. However, whole-exome sequencing revealed a thrombotic risk variant (T630I) in the PROS1 gene encoding protein S. This missense variant is often reported in patients with thrombosis or protein S deficiency, and may result in a thrombotic predisposition in some situations, such as nephrotic syndrome. Conclusions: Arterial thrombosis is a rare complication; however, it must be considered, especially in patients with new-onset nephrotic syndrome. Early recognition is important for early intervention and prevention of serious sequelae.

Ile73Asn mutation in protein C introduces a new N-linked glycosylation site on the first EGF-domain of protein C and causes thrombosis

Activated protein C exerts its anticoagulant activity by protein S-dependent inactivation of factors Va and VIIIa by limited proteolysis. We identified a venous thrombosis patient who has plasma protein C antigen level of 63% and activity levels of 44% and 23%, as monitored by chromogenic and clotting assays. Genetic analysis revealed the proband carries compound heterozygous mutations (c.344T>A, p.I73N and c.1181G>A, p.R352Q) in PROC. We individually expressed protein C mutations and discovered that thrombin-thrombomodulin activates both variants normally and the resulting activated protein C mutants exhibit normal amidolytic and proteolytic activities. However, while protein S-dependent catalytic activity of activated protein C-R352Q toward factor Va was normal, it was significantly impaired for activated protein C-I73N. These results suggest that the Ile to Asn substitution impairs interaction of activated protein C-I73N with protein S. This conclusion was supported by a normal anticoagulant activity for activated protein C-I73N in protein S-deficient but not in normal plasma. Further analysis revealed Ile to Asn substitution introduces a new glycosylation site on first EGF-like domain of protein C, thereby adversely affecting interaction of activated protein C with protein S. Activated protein C-R352Q only exhibited reduced activity in sub-physiological concentrations of Na⁺ and Ca²⁺, suggesting that this residue contributes to metal ion-binding affinity of the protease, with no apparent adverse effect on its function in the presence of physiological levels of metal ions. These results provide insight into the mechanism by which I73N/R352Q mutations in activated protein C cause thrombosis in proband carrying this compound heterozygous mutation.

A Study of Congenital Protein C Deficiency With Infancy Onset of CADASIL in a Chinese Baby

OBJECTIVE

The main objectives of this article were to study a severe congenital protein C deficiency (PCD) in a patient with cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL) and analyze the cause of this case.

MATERIALS AND METHODS

We had recorded clinical manifestations of the patient, laboratory tests, imaging studies, and gene sequencing of the PROC gene and NOTCH3 gene to study the disease in this family. We checked the change of NOTCH3 protein by immunohistochemistry.

RESULTS

Laboratory studies of the patient had revealed that his PC activity was 3%. Magnetic resonance imaging results showed hyperintense lesions in the cerebral white matter of the patient. PROC gene and NOTCH3 gene sequencing was performed among the family members. The patient was confirmed as homozygous for the (A-G)-12 at the transcription initiation site in the promoter region of the PROC gene and heterozygous mutation of the NOTCH3 gene. Immunohistochemical results showed that NOTCH3 protein was positive in the skin vascular smooth muscle of the patient.

CONCLUSIONS

We studied a rare case of an infat boy diagnosed with both congenital PCD and CADASIL; congenital PCD was attributable to a compound that was homozygous for (A-G)-12 at the transcription initiation site in the promoter region of the PROC gene, and CADASIL was caused by missense mutation in exon 24 of NOTCH3. He was a sporadic patient with congenital PCD and CADASIL; it maybe that the deficiency of protein C led to early onset of CADASIL. The gene sequencing of PROC gene and NOTCH3 gene may have important value for fertility guidance and prenatal diagnosis.

Protein C Deficiency

Protein C (PC) deficiency is a heritable or acquired risk factor for thrombophilia, with presentations varying from asymptomatic to venous thromboembolism to neonatal purpura fulminans, a life-threatening disorder. Hereditary PC deficiency is caused by mutation in the PC (PROC) gene located on chromosome 2q14.3. Heterozygous and acquired PC deficiencies are more common than homozygous deficiency. The recommended initial laboratory test measures PC activity using either clot-based or chromogenic methods. There are numerous potential interferences in PC activity testing that may result in either false-positive (falsely low activity) or false-negative (falsely normal or elevated activity) results. In the present review, we discuss common clinical presentations; laboratory testing, with a focus on potential assay interferences; treatment options; and prognosis in patients with PC deficiency.

R147W in PROC Gene Is a Risk Factor of Thromboembolism in Thai Children

The p.R147W mutation, the c.C6152T in exon 7, causing a change in amino acid from arginine to tryptophan of the PROC gene has been reported as a common mutation in Taiwanese populations with venous thromboembolism (VTE). The present study aimed to identify the prevalence of p.R147W in the Thai population and children with TE and the risk of developing TE. Patients aged ≤18 years diagnosed with TE were enrolled. The PROC gene was amplified by polymerase chain reaction using a specific primer in exon 7. The restriction fragment length polymorphism was designed using MwoI restriction enzyme. A total of 184 patients and 690 controls were enrolled. The most common diagnosis of TE was arterial ischemic stroke (AIS), at 100 (54.3%), followed by VTE, at 38 (20.6%), and cerebral venous sinus thrombosis (CVST), at 23 (12.5%). The prevalence of heterozygous and homozygous p.R147W in patients and controls was 9.5% versus 5.8% and 2.7% versus 0.1%, respectively. Heterozygous p.R147W had odds ratios (ORs) of 1.8 (95% confidence interval [CI]: 1.0-3.2, P = .04), 3.2 (95% CI: 1.2-8.2, P = .009), and 4.5 (95% CI: 1.6-12.8, P = .002) of developing overall TE, VTE, and CVST, respectively. Homozygous p.R147W had ORs of 20.2 (95% CI: 2.3-173.7, P < .001), 21.4 (95% CI: 2.2-207.9, P < .001), and 43.3 (95% CI: 3.8-490.6, P < .001) of developing overall TE, AIS, and CVST, respectively. This study suggested that p.R147W is a common mutation and increased risk of TE in Thai children.

Gly74Ser mutation in protein C causes thrombosis due to a defect in protein S-dependent anticoagulant function

Protein C is a vitamin K-dependent serine protease zymogen in plasma which upon activation by thrombin in complex with thrombomodulin (TM) down-regulates the clotting cascade by a feedback loop inhibition mechanism. Activated protein C (APC) exerts its anticoagulant function through protein S-dependent degradation of factors Va and VIIIa. We recently identified a venous thrombosis patient whose plasma level of protein C antigen is normal, but its anticoagulant activity is only 34 % of the normal level. Genetic analysis revealed that the proband and her younger brother carry a novel heterozygous mutation c.346G>A, p.Gly74Ser (G74S) in PROC. Thrombin generation assay indicated that the TM-dependent anticoagulant activity of the proband's plasma has been significantly impaired. We expressed protein C-G74S in mammalian cells and characterised its properties in established coagulation assays. We demonstrate that the protein C variant can be normally activated by the thrombin-TM complex and the resulting APC mutant also exhibits normal amidolytic and proteolytic activities toward both FVa and FVIIIa. However, it was discovered the protein S-dependent catalytic activity of APC variant toward both procoagulant cofactors has been significantly impaired. Protein S concentration-dependence of FVa degradation revealed that the capacity of APC variant to interact with the cofactor has been markedly impaired. The same results were obtained for inactivation of FVa-Leiden suggesting that the protein S-dependent activity of APC variant toward cleavage of Arg-306 site has been adversely affected. These results provide insight into the mechanism through which G74S substitution in APC causes thrombosis in the proband carrying this mutation.

Gene analysis of six cases of congenital protein S deficiency and functional analysis of protein S mutations (A139V, C449F, R451Q, C475F, A525V and D599TfsTer13)

Congenital deficiency of protein S (PS), an anticoagulant factor, leads to venous thrombosis, with onset predominantly beginning in adolescence. In the present study, gene analysis of six unrelated Japanese families diagnosed with congenital PS deficiency identified five missense mutations in the PROS1 gene - c.757C>T (Ala139Val; A139V), c.1346 G>T (Cys449Phe; C449F), c.1352G>A (Arg451Gln; R451Q), c.1424G>T (Cys475Phe; C475F) and c.1574C>T (Ala525Val; A525V) - and one frameshift mutation, c.2135delA (Asp599ThrfsTer13; D599TfsTer13). C449F, R451Q, A525V and D599TfsTer13 are novel mutations. Results from ELISA to measure PS antigen levels in culture supernatant showed that the A139V variant was similar to wild-type, but other variants showed reductions when compared with wild-type. Results from pulse-chase analysis confirmed that the A139V variant exhibited secretion equivalent to wild-type, but for the other variants, there was no extracellular secretion, and it had nearly all been degraded inside the cell within six hours. Results from pulse-chase analysis using proteasome inhibitors also showed that intracellular degradation of mutant protein was inhibited. Activity of the A139V variant was decreased to 71% of wild-type, and the phospholipid binding capacity fell to as low as 45%. These results suggest that although the A139V variant has normal secretion, it has abnormal phospholipid binding capacity, and therefore causes type II PS deficiency, in which PS activity is decreased. It is also thought that with the other variants, misfolding due to amino acid mutations causes nearly all PS to be degraded intracellularly, therefore leading to type I PS deficiency.

State-of-the-Art Review: Activated Protein C Resistance: Clinical Implications

The discovery of inherited resistance to activated protein C (APC) as a major risk factor for venous thrombosis has dramatically improved our understanding of the pathogenesis of venous thrombosis. In a majority of cases, APC resistance is associated with a single point mutation in the factor V gene (FV) that results in substitution of arginine, R, at position 506 by glutamine, Q. (FV:Q506). The mutation renders factor Va partially resistant to degradation by APC. A functional APC resistance test, which includes predilution of the patient plasma with factor V-deficient plasma, is found to be 100% sensitive and specific for the presence of FV:Q506and is useful as a screening assay. Carriers of the FV:Q506allele have increased thrombin generation, resulting in hypercoagulability and a lifelong increased risk of venous thrombosis. In Western countries, APC resistance due to the FV mutation is present in 20-60% of thrombosis patients and in 1-15% of healthy controls, whereas the mutation is virtually absent from ethnic groups other than Caucasians. This may explain the high incidence of venous thrombosis in Western countries. The thrombotic risk in APC-resistant individuals may be further increased by other genetic defects, e.g., protein C or protein S deficiency, and by exposure to circumstantial risk factors, e.g., oral contraceptives, pregnancy, immobilization, and surgery. The question is thus raised as to whether general screening for APC resistance before circumstantial risk factors occur is warranted in Western countries. Key Words: Factor V—APC resistance-Protein C-Protein S—Thrombosis—Mutation.

Different Anticoagulant Response to Activated Protein C (APC test) and to Agkistrodon Contortix Venom (ACV test) in a Family with FV-R506Q Substitution

To identify the defect(s) responsible for the thrombotic condition affecting a 55-year-old male and his family, we have utilized a new methodological approach (ProC Global®, Istituto Behring, Milan, Italy) to screen the global anticoagulant activity of the protein C pathway, a defect that accounts for the majority of inherited thrombophilias. The test is based on the activation of endogenous protein C in plasma by Protac®, derived from Agkistrodon contortix snake venom (ACV test). Nineteen members of the family were investigated, 11 showed low responsiveness to ACV (normalized ACV ratios < 0.66; normal > 1. 12); in these individuals specific assays of protein C (PC) and protein S (PS) levels and normalized activated protein C ratios (n-APC-r) were performed. A second test evaluating response to APC, using the classic commercial APC test (n-APC-r 1), detected only 10 subjects with abnormal responses : the propositus and two members of the family with n-APC-r 1 values < 0.54, indicating the homozygous state for the R506Q factor V gene mutation, and seven with values ranging 0.69-0.83, consistent with the heterozygous condition (normal > 0.85). Although only ten subjects presented with low n-APC-r 1 values, DNA analysis, in agreement with the ACV test, detected 11 individual with factor V-R506Q substitution (two homozygotes and nine heterozygotes). Thus the classical APC test failed to identify the APC resistance phenotype in two heterozygous subjects whose values were clearly normal (1.05) in the first case and homozygous (0.53) in the second. The ACV test, however, and the modified APC test with test plasma 1/5 diluted in factor V-deficient plasma (n-APC-r 2) completely matched the DNA analysis. A phenotype/genotype correlation was observed in dilutions higher than 1/3 test plasma factor V-deficient plasma. The presence of unknown mechanisms that influence plasma response to exogenous preformed APC (normal at high factor V-deficient plasma dilutions) but not endogenous ACV activated PC was suspected. The suspected low levels of proteins C and S found in several R506Q members of the family were excluded by reassaying the anticoagulant activities at higher plasma dilution ; this supports the known influence of factor V Leiden on functional PC and PS clotting activity. We conclude that the ACV test is appropriate to evaluate the APC resistance condition, but for a firm diagnosis DNA analysis together with the modified APC test are strongly advised even in the presence of unquestionable APC-r values. Key Words: APC resistance-Factor V Leiden-APC test-ACV test-Diagnosis-Inherited thrombophilia.

Low molecular weight heparin modulates maternal immune response in pregnant women and mice with thrombophilia

PROBLEM

Thrombophilia is associated with pregnancy complications. Treatment with low molecular weight heparin (LMWH) improves pregnancy outcome, but the underlying mechanisms are not clear.

METHODS OF STUDY

We analyzed Treg frequency in blood from thrombophilic pregnancies treated with LMWH (n = 32) or untreated (n = 33) and from healthy pregnancies (n = 39) at all trimesters. Additionally, we treated pregnant wild-type, heterozygous and homozygous factor-V-Leiden (FVL) mice with LMWH or PBS and determined Treg frequency, pro-/anti-inflammatory cytokine levels and Caspase-3-activity in placenta and decidua.

RESULTS

Treg frequencies were increased in second and third trimester in LMWH-treated thrombophilic pregnancies compared to controls. Treg levels were comparable to those of normal pregnancies. Homozygous FVL mice had decreased decidual Tregs compared to wild-type mice. LMWH treatment normalized Tregs and was associated with increased decidual IL-10 mRNA. LMWH diminished Caspase-3-activity in mice of all genotypes.

CONCLUSION

We demonstrated anti-apoptotic and anti-inflammatory effects of LMWH in pregnant FVL mice. LMWH increased Treg levels in mice and humans, which suggests benefits of LMWH treatment for thrombophilic women during pregnancy.

Hereditary protein C deficiency caused by compound heterozygous mutants in two independent Chinese families

We report two compound heterozygous mutants that caused severe type I protein C (PC) deficiency in two independent Chinese families.PC antigen was determined by enzyme-linked immunosorbent assay (ELISA), and PC activity was measured by chromogenic assay. Genetic mutations were screened with polymerase chain reaction (PCR) followed by direct sequencing. PC mutants were transiently expressed in COS-7 cells for the evaluation of PC secretory activity and function. The subcellular location was visualised by immunofluorescence assay. The structural analysis of mutation was performed as well.Compound heterozygous mutations of Arg178Trp and Asp255His with reduced PC activity and antigen levels were identified in Proband 1, a 28-year-old male with deep vein thrombosis (DVT) and pulmonary embolism. The other mutations of Leu-34Pro and Thr295Ile with reduced PC activity and antigen levels were identified in Proband 2, a 19-year-old male with DVT. The PC activities with Arg178Trp, Asp255His, Leu-34Pro and Thr295Ile mutations decreased significantly. Immunofluorescence assay demonstrated that only trace amount of PC with novel Thr295Ile mutation was transported to the Golgi apparatus. Subsequent structural analysis indicated severe impairments of intracellular folding and secretion.The two rare compound heterozygous mutations could cause type I PC deficiency via impairment of secretory activity of PC.

Endothelial Protein C Receptor Gene Variants and Risk of Thrombosis

Endothelial protein C receptor (EPCR) is a candidate mediator in the pathogenesis of thrombosis, as several data in the literature indicate that polymorphisms such as EPCR 4678G/C and 4600A/G are associated with either protective effect or increased risk of thrombosis, respectively. We investigated the prevalence of these polymorphisms in patients with thrombotic disorders as well as their impact on the risk of thrombosis, the age of first thrombotic episode, and recurrence. The prevalence of the rare EPCR alleles 4600G and 4678C was comparable in patients and controls. However, in a subset analysis, we observed that 4600G allele was more prevalent among patients who developed thrombosis at younger age (<35 years). Moreover, the prevalence of 4678C allele was significantly lower in younger patients compared to older patients. Neither polymorphism seemed to have an impact on recurrence regardless of age. Soluble EPCR levels were elevated in 4600AG patients compared to controls while 4678CC patients presented with lower levels of soluble form of EPCR compared to carriers of at least 1 4678G allele. Our data suggest that either the lack of the protective EPCR 4678C allele or the presence of EPCR 4600G allele may be associated with earlier development of thrombosis.

sEPCR Levels in Chronic Myeloproliferative Diseases and Their Association with Thromboembolic Events: A Case-Control Study

Objective: Venous, arterial, and microcirculatory events are frequently encountered in the clinical course of essential thrombocytosis and polycythemia vera. We aimed to investigate the levels of soluble endothelial protein C receptor (sEPCR) in myeloproliferative diseases to see whether there was a difference between the patients with and without history of thromboembolism.

Materials and Methods: The study included patients with polycythemia vera (n=12), patients with essential thrombocytosis (n=13), and controls (n=29). In all groups, we measured proteins C and S, antithrombin and sEPCR levels, and plasma concentrations of thrombin-antithrombin complex, prothrombin fragments 1+2, and D-dimer.

Results: Comparing the patients with and without history of thromboembolic attack, statistically significant differences were not observed in terms of sEPCR, D-dimer, thrombin-antithrombin complex, prothrombin fragments 1+2, and hematocrit levels (p=0.318, 0.722, 0.743, 0.324, and 0.065, respectively).

Conclusion: Significant increase in the parameters that reflect activation of coagulation, such as sEPCR, thrombin-antithrombin complex, prothrombin fragments 1+2, and D-dimer, reflects the presence of a basal condition that leads to a tendency toward thrombosis development in ET and PV when compared to healthy controls.

Clinical features and underlying causes of cerebral venous thrombosis in Japanese patients

The clinical symptoms, causative factors, and prognosis in Japanese patients with cerebral venous thrombosis have not been adequately characterized. The present study describes these features in patients in Japan. Twenty-two patients with cerebral venous thrombosis were retrospectively identified. Diagnosis was confirmed by either digital subtraction angiography, magnetic resonance venography, or contrast-enhanced computed tomography. Demographic data and clinical and radiological features were recorded and analyzed for each patient. Prognosis was evaluated by the modified Rankin scale (mRS) at the time of hospital discharge. The most frequent symptom of cerebral venous thrombosis was headache (59.1 %). Causative factors included congenital thrombophilia (31.8 %), acquired thrombophilia (27.3 %), and iron-deficiency anemia (13.6 %). Of seven patients with congenital thrombophilia, four had mutations in the protein S gene, two had mutations in the protein C gene, and one had mutations in the antithrombin gene. All patients were alive at discharge from hospital. Nineteen of the 22 patients (86.4 %) recovered completely or exhibited only mild residual symptoms (mRS 0-2). However, three patients (13.6 %) had a poor prognosis (mRS 3-5). Cerebral venous thrombosis in Japanese patients is frequently associated with congenital thrombophilia and protein S gene mutation.

Lack of Association Between Factor V Leiden and Sepsis

Some studies evaluated the association of factor V Leiden (FVL) with sepsis risk and mortality risk. However, the results were conflicting. Thus, we performed a meta-analysis to address the association between FVL and sepsis. PubMed and EMBASE databases were searched to find relevant studies. Odds ratios (ORs) and corresponding 95% confidence intervals (CIs) were estimated using random effects model. Five case–control studies and 3 cohort studies were included. Overall, no significant association between FVL and sepsis risk was observed (OR = 0.93; 95% CI 0.74-1.15; P = .49). In addition, there was no significant association between FVL and sepsis-related mortality (OR = 1.17; 95% CI 0.73-1.88; P = .52). In the subgroup analysis, no increased sepsis risk and mortality risk were found in caucasian population. This meta-analysis suggested that FVL was not a risk factor for sepsis and sepsis mortality.

Expression and functional characterisation of natural R147W and K150del variants of protein C in the Chinese population

Protein C is a vitamin K-dependent serine protease zymogen in plasma which upon activation to activated protein C (APC) by thrombin down-regulates the clotting cascade by limited proteolysis of the procoagulant cofactors Va and VIIIa. In addition to its anticoagulant activity, APC also exhibits potent cytoprotective and anti-inflammatory activities. While the anticoagulant activity of APC is enhanced by the cofactor function of protein S on membrane phospholipids, the cytoprotective intracellular signalling activity of APC requires complex formation with endothelial protein C receptor (EPCR) expressed on the vascular endothelium. Two natural variants of APC [Arg-147 to Trp substitution (R147W) and Lys-150 deletion (K150del)] have been identified in the Chinese population as hotspot mutants occurring with high frequencies of 27.8% and 13.9%, respectively, among 36 protein C-deficient subjects. The affected individuals exhibit variable thrombotic tendencies. To understand the underlying cause of the thrombotic phenotype in these patients, we expressed these two protein C variants in mammalian cells and characterised their anticoagulant and anti-inflammatory properties using established in vitro and cellular assays. Our results suggest that both R147W and K150del variants have normal amidolytic and proteolytic activities in the absence of cofactors. However, the R147W mutant exhibits ~3 times lower affinity for binding to EPCR and the K150del variant has ~2-3-fold impaired anticoagulant activity in the presence of protein S. These results provide some insight into the possible pathogenic mechanism of protein C deficiency in Chinese patients carrying these mutations.

Thrombin generation

Generation of thrombin has been established as the critical process leading to coagulation in vivo. Indeed, ex vivo markers of thrombin generation in patients have been useful in detecting thrombosis, while many standard global clot-time tests of haemostasis in blood or plasma samples are simple endpoint measures of the potential to generate thrombin. Thus, there has been a recent surge towards direct measurement of thrombin generation potential in plasma/blood samples as a refined methodology for more precisely assessing procoagulant/anticoagulant/hemorrhagic parameters of the haemostatic status. Presently, however, there is no consensus method for thrombin generation determination. The present treatise gives detailed procedures for available thrombin generation tests, with emphasis on the preferred technology.

The coagulation system in humans

Complex, interrelated systems exist to maintain the fluidity of the blood in the vascular system while allowing for the rapid formation of a solid blood clot to prevent hemorrhaging subsequent to blood vessel injury. These interrelated systems are collectively referred to as haemostasis. The components involved in the haemostatic mechanism consist of vessel walls, platelets, coagulation factors, inhibitors, and the fibrinolytic system. In the broadest sense, a series of cascades involving coagulation proteins and enzymes, as well as cell surfaces (platelets and endothelial cells), work together to generate thrombin, the key enzyme in coagulation, subsequently leading to the formation of a fibrin clot. However, there also exist direct and indirect inhibitors of thrombin to ensure that clot formation does not go uncontrolled. Once the fibrin clot is formed, the fibrinolytic system ensures that the clot is lysed so that it does not become a pathological complication. Taken together, the systems exist to balance each other and maintain order. The balance of coagulation and fibrinolysis keeps the haemostatic system functioning efficiently.

Anaesthetic significance and management of a child with neonatal purpura fulminans

Protein C deficiency is a rare autosomal-dominant disorder of varying severity. Patients with homozygous and compound heterozygous protein C deficiency present with neonatal purpura fulminans (NPF). Other presentations usually include disseminated intravascular coagulation and venous thromboembolism. This disorder usually poses a unique anaesthetic challenge to the anaesthesiologist, requiring special precautions to prevent various intra- and post-operative complications. We hereby report the successful anaesthetic management of a 1-month-old infant who presented with NPF.

Homozygous protein C deficiency with late onset venous thrombosis: identification and in vitro expression study of a novel Pro275Ser mutation

AIMS

To identify the mutation and study the molecular mechanism of inherited protein C (PC) deficiency in a Chinese pedigree.

METHODS

The plasma levels of PC activity (PC:A) and antigen (PC:Ag) were measured by chromogenic assay and ELISA, respectively. The PROC gene was amplified and sequenced for mutational screening. Wild type and Pro275Ser mutant PC cDNA expression plasmids were constructed and transfected into HEK 293T cells and COS 7 cells, respectively. The expression and transcription of PC were investigated by ELISA, Western blot and real time RT-PCR. Immunofluorescence staining was utilised to analyse the intracellular distribution of PC, and pulse-chase experiments were used to detect the intracellular stability of the mutant PC.

RESULTS

The proband's plasma PC:A and PC:Ag were 5% and 13.9%, respectively. A missense mutation (p.Pro275Ser) was identified in exon 9 of PROC gene. In vitro expression study showed that Pro275Ser variant was present at 22.6% and 78.9% of wild type levels in culture supernatants and cell lysates, respectively. No significant differences in the molecular weights, mRNA levels or intracellular stability were observed between the mutant and wild type PC. Immunofluorescence staining revealed that the mutant protein was mainly located in the endoplasmic reticulum.

CONCLUSIONS

A homozygous Pro275Ser mutation was identified in a Chinese pedigree of PC deficiency. Impaired secretion of the mutant PC might be the molecular mechanism of PC deficiency caused by Pro275Ser mutation.

The Effects of Endothelial Protein C Receptor Gene Polymorphisms on the Plasma sEPCR Level in Venous Thrombosis Patients

OBJECTIVE

The aim of this study was to investigate variations in the endothelial cell protein C receptor gene (EPCRgene) that may play a role in thrombosis and the effects of these variations on the plasma soluble endothelial cell proteinC receptor (sEPCR) level in Turkish patients with venous thrombosis.

MATERIAL AND METHODS

This study included 111 thrombosis patients and 73 healthy controls. Following DNAextraction, PCR, SSCP, and DNA sequencing analysis of 4 exons of the EPCR gene was performed. Plasma sEPCR wasmeasured via enzyme-linked immunosorbent assay (ELISA).

RESULTS

In all, 3 polymorphisms were detected in exons 1-4. C3998T (SNP no: rs2069952) polymorphism was detectedin intron 2 and C4678G (A1 haplotype) (SNP no: rs9574) in the 3' untranslated region (3'UTR). There weren't anysignificant differences in C3998T polymorphism between the control and patient groups. There wasn't a significantdifference in plasma sEPCR levels between both controls and patients that carried the A1 allele. A4600G substitution (A3haplotype) (SNP no: rs867186) was observed in exon 4 and was associated with a 2.04-fold higher risk of thrombosis.A3 allele carriers had higher sEPCR levels than those without the allele. Mean sEPCR level in the patients with thehomozygous A3 allele was 289 ng μL-1, versus 113.42 ng μL-1 in those with the homozygous A1 allele.

CONCLUSION

The A1 haplotype might offer protection against thrombosis and the A3 haplotype might be associatedboth with elevated plasma sEPCR and elevated risk of venous thrombosis in the Turkish population. Plasma sEPCRlevels were significantly higher in those that carried the A3 allele (4600A>G) (both patients and controls). Among theparticipants that carried the A1 allele (4678C>G), plasma sEPCR did not differ significantly.

The association of protein S Tokushima-K196E with a risk of deep vein thrombosis

Deep vein thrombosis (DVT) is a multifactorial disease caused by acquired risk factors such as a bed rest, surgery and malignancies. Although the factor V Leiden and the prothrombin-20210G>A mutation do not exist in Japanese populations, a mutation in protein S (PS) Tokushima (K196E) has been attracting attention in Japan. In this study, the genetic contribution of PS Tokushima (K196E) was evaluated in 60 Japanese patients with thrombosis in comparison to 234 healthy volunteers and 88 patients without thrombosis. Genes associated with the response to warfarin, cytochrome P450 2C9 (CYP2C9), vitamin K epoxide reductase complex subunit 1 (VKORC1), and γ-glutamyl carboxylase (GGCX) were also investigated simultaneously. PS Tokushima (K196E) was detected in 6 patients with thrombosis, in 3 without thrombosis and in 3 healthy volunteers, indicating that there is a high frequency of the PS Tokushima (K196E). There were no significant differences of CYP2C9, VKORC1 or GGCX between the patients with and without DVT. Therefore, PS Tokushima (K196E) is an important genetic risk factor for DVT in the Japanese population.