Evelin Katona

The involvement of blood coagulation factor XIII in fibrinolysis and thrombosis.

It has been known for a long time that blood coagulation factor XIII (FXIII) is essential for maintaining haemostasis, its deficiency leads to severe bleeding complication. Biochemical studies have revealed that FXIII is a key regulator of fibrinolysis and, in addition to its role in haemostasis, it has also been implicated in the pathology of arterial and venous thrombosis. Most recently, the polymorphisms in the FXIII subunit genes and their influence on the risk of thrombotic diseases have stirred a lot of interest. This review, besides including the basic biochemistry of FXIII, mainly concentrates on the biochemical and clinical aspects of the involvement of FXIII in fibrinolysis and thrombosis. Biochemical aspects: Basics on the structure and activation of plasma and cellular FXIII. The enzymological features of activated FXIII and its main substrates. The interaction of FXIIIa with fibrinogen/fibrin and with components of the fibrinolytic system. The impact of cross-linked fibrin clot formation on the fibrinolytic processes. The down-regulation of FXIIIa within the fibrin clot. FXIII polymorphisms and their biochemical consequences. Clinical Aspects: FXIII level and the risk of arterial thrombosis (coronary artery disease, peripheral artery disease, ischemic stroke). The effect of FXIII subunit polymorphisms on the risk of arterial thrombotic diseases. The interplay between FXIII polymorphisms and other factors influencing the risk of arterial thrombosis. FXIII and venous thromboembolism.

Serum paraoxonase activity changes in patients with Alzheimer's disease and vascular dementia

Abstract The prevalence of Alzheimers disease (AD) and vascular dementia (VAD) increases with aging of the population. The role of lipoproteins in the pathogenesis of AD is unclear: apoE2 offers protection and apoE3 is neutral, while apoE4 promotes the development of the disease.Recently, several studies have confirmed the role of oxidative stress in the pathogenesis of AD and VAD. HDL-associated paraoxonase is one of the antioxidative enzymes that may reduce LDL oxidation. In our study, we investigated the lipid parameters of the sera and the serum paraoxonase activity in patients with AD and VAD.Lipid parameters were determined by an autoanalyzer in 30 AD patients, 40 VAD patients and 40 healthy, age-matched control (C) subjects. Paraoxonase activity was measured spectrophotometrically using paraoxon as the substrate. The phenotypic distribution of paraoxonase was determined by the dual substrate method, using paraoxon and phenylacetate as substrates.In our results, we found that most of the patients with AD had the apoE4 isoform, consistent with other studies. In the VAD and AD patients we found significantly higher total-cholesterol compared to the control group (C: 4.71 ± 0.89, VAD: 6.3 ± 0.8, AD: 6.52 ± 0.7 mmol/l; p < 0.01) and LDL-cholesterol levels (C: 2.6 ± 0.6, VAD: 3.96 ± 0.8, AD: 3.84 ± 0.6 mmol/l; p < 0.001). The HDL-associated antioxidant, paraoxonase activity did not differ significantly in the patient groups, but compared to the healthy control subjects, paraoxonase activity was significantly lower in both of the patient groups (C: 188 ± 55 U/l; AD: 131 ± 37, VAD: 151 ± 50 l; p < 0.05).Our results suggest that the defect in HDL-associated antioxidant capacity plays a role in the pathogenesis of Alzheimers disease and vascular dementia.

Serum paraoxonase activity changes in uremic and kidney-transplanted patients

Serum paraoxonase (PON) is a high-density lipoprotein (HDL)-associated hydrolase, which inhibits low-density lipoprotein oxidation. Uremic and kidney-transplanted patients have an increased risk of atherosclerosis, to which an increased lipoprotein oxidation may contribute. The aim of our study was to determine whether the PON activity or phenotype is altered in uremic and kidney-transplanted patients, and to compare the values with those of healthy controls. 117 uremic patients on long-term hemodialysis treatment, 115 renal-transplanted patients, and 110 healthy controls were involved in the study. The PON activity was significantly reduced in the uremic patients compared to controls (PON 101.36±30.12 vs. control 188.05±58.96 U/ml; p < 0.001), while in kidney-transplanted patients the values were almost identical to those of controls (PON 161.5±35.39 U/ml). The different immunosuppressive drug combinations did not influence PON activity. To assess whether the altered PON activity was due to a decrease HDL level, we standardized the enzyme activity for the HDL concentration (PON/HDL ratio). We found that the standardized enzyme activity was lower in the uremic (102.7±54.8) and kidney-transplanted patients (144.5±32.7) when compared to controls (194.5±94.5; p < 0.001). The phenotypic distribution of PON in uremic, renal transplant and control patients are as follows: AA 66.67, 56.48 and 66.67%; AB 31.62, 33.3 and 26.67%; BB 1.71, 10.19 and 6.67%. We conclude that the decreased PON/HDL and PON/apoA-1 ratios may lead to a reduction in the antioxidant capacity of HDL, which might contribute to the accelerated development of atherosclerosis in uremic and kidney-transplanted patients.

Determination of DNA damage induced by oxidative stress in hyperlipidemic patients

In the present paper, we report data on the genotoxic properties of hydrogen peroxide in polymorphonuclear neutrophils (PMNLs) separated from normolipidemic and type II/a hyperlipidemic patients. In all, 15 hyperlipidemic patients (11 female, 4 male, mean age 54.6+/-10.25 years) were involved in the study, and 7 normolipidemic patients (5 female, 2 male, mean age 53.4+/-8.07 years) served as controls. Using the comet assay, there was a significant difference in the degree of DNA damage between the two groups. The visual score characteristic of the degree of DNA damage was 350.97+/-31.31 in the hyperlipidemic group, while it was 289.5+/-29.49 in the control group (P<0.001). In the hyperlipidemic patients, a positive correlation was found between the degree of DNA damage and the basic oxidation of PMNLs (r=0.517), and the superoxide anion production of the cells stimulated with phorbolmiristate acetate (PMA) (r=0.326) and formyl-Met-Leu-Phe (FMLP) (r=0.525) as well. There was a negative correlation between DNA damage and HDL-associated antioxidant paraoxonase (PON) activity (r=-0.469), and the PON/HDL ratio (r=-0.631). No correlation was found between the degree of DNA damage and the plasma concentration of nitric oxide (NO) (r=0.098) and thiobarbituric acid-reactive substances (TBARS) (r=0.061) in hyperlipidemic patients. Our results show that in hyperlipidemic patients there is an increase in lymphocyte DNA damage caused by oxidative stress when compared to normolipidemic individuals as demonstrated by comet assay. Decreased antioxidant capacity in hyperlipidemic patients may play a significant role in this process.

Impaired cerebral vasoreactivity in white coat hypertensive adolescents

Background and purpose:  Although its incidence is not high, adolescent hypertension may predict hypertension and increased cardiovascular risk in adulthood. Therefore, the aim of the present study was to assess whether cerebrovascular reactivity is altered in adolescent white coat and sustained hypertensive patients compared to healthy teenagers.

Effects of Simvastatin on Serum Paraoxonase Activity

BackgroundHigh density lipoprotein (HDL)-associated paraoxonase activity may play an important role in the inhibition of low density lipoprotein (LDL) oxidation. Previous studies have demonstrated that serum paraoxonase activity is decreased in patients with hyperlipoproteinaemia and coronary heart disease, and a few investigators have suggested that the lipid-lowering statins may increase paraoxonase levels.ObjectiveTo examine the effect of short-term treatment with simvastatin on lipids and paraoxonase activity in patients with hyperlipoproteinaemia.DesignProspective nonblind single-group sequential study.Patients112 (52 male and 60 female) hyperlipoproteinaemic patients with Fredrickson type IIa and IIb hyperlipoproteinaemia (mean age 52.15 ± 7.99 years, mean body mass index 27.53 ± 4.30 kg/m2).MethodsSerum cholesterol, lipoproteins, triglycerides, apolipoproteins and liver function were measured, and serum paraoxonase activity was determined spectrophotometrically using paraoxon as substrate. Simvastatin 20 mg/day was administered for 1 month, and measurements were repeated.ResultsSimvastatin significantly decreased serum cholesterol [from 10.25 ± 2.73 (SD) to 8.85 ± 2.02 mmol/L], triglyceride (from 3.95 ± 2.51 to 3.15 ± 1.47 mmol/L), LDL (from 6.36 ± 1.70 to 4.94 ± 1.48 mmol/L) and apolipoprotein B100 (from 1.93 ± 0.41 to 1.56 ± 0.35 g/L) levels, whereas HDL and apo A1 levels did not change significantly (from 1.19 ± 0.34 to 1.22 ± 0.39 mmol/L, and from 1.56 ± 1.99 to 1.64 ± 0.24 g/L, respectively). HDL-associated paraoxonase activity did not change significantly (from 182.25 ± 37.21 to 166.49 ± 35.01 U/L) after simvastatin therapy.ConclusionShort-term administration of simvastatin did not increase the activity of the HDL-associated antioxidant enzyme paraoxonase.

Serum Cholesterols Have a More Important Role Than Triglycerides in Determining Intima-Media Thickness of the Common Carotid Artery in Subjects Younger Than 55 Years of Age

Objective. The role of serum cholesterol and triglycerides in carotid artery atherosclerosis is controversial. We measured carotid artery intima‐media thickness (IMT), a marker of atherosclerosis in subjects younger than 55 years of age with a 6‐fold range of serum cholesterol levels (3.93–25.03 mmol/L) and a 200‐fold range of triglyceride levels (0.36–75.97 mmol/L). Methods. Eighty‐six patients with increased serum lipid values and 30 subjects with normal lipid values were included. Serum lipids were measured after an overnight fast. High‐resolution sonographic investigations of the carotid arteries of all patients were videotaped. Intima‐media thickness was measured offline at 1‐mm increments in the distal 10‐mm segments of both common carotid arteries by a reader blinded to patient characteristics. First, IMT was compared among groups defined by their cholesterol and triglyceride levels with the use of traditional cutoff values. Next, all subjects were pooled, and general regression analysis was performed to identify significant predictors of IMT with age, body mass index, lipid values, sex, diabetes, hypertension, and smoking status as independent variables. Results. Intima‐media thickness was larger in patient groups with high cholesterol levels (ie, the hypercholesterolemic and combined hyperlipidemic groups) than in the control, borderline, and isolated hypertriglyceridemic groups (P < .01). In the general multiple regression model, IMT correlated positively with total cholesterol level (β = 0.343; P = .002) and age (β = 0.3; P = .006) but not with triglyceride level. Conclusions. Both the group comparisons and the general regression analysis of the pooled data suggest that hypercholesterolemia has an important role in early onset IMT changes in the common carotid artery, whereas hypertriglyceridemia does not have an appreciable role.

Alloantibody developed in a factor XIII A subunit deficient patient during substitution therapy; characterization of the antibody.

In factor XIII A subunit (FXIIIA) deficiency, the development of alloantibodies is extremely rare. Only four reports have been published and the antibodies were not characterized.

The use of recombinant factor XIII in a major bleeding episode of a patient with congenital factor XIII deficiency - the first experience

U. Clinical utility gene card for: Glanzmann thrombasthenia. Eur J Hum Genet 2012; 20: 1102. 5 Fiore M, Firah N, Pillois X, Nurden P, Heilig R, Nurden AT. Natural history of platelet antibody formation against alphaIIbbeta3 in a French cohort of Glanzmann thrombasthenia patients. Haemophilia 2012; 18: e201–9. 6 Seligsohn U. Treatment of inherited platelet disorders. Haemophilia 2012; 18(Suppl. 4): 161–5. 7 Hedner U, Erhardtsen E. Potential role of recombinant factor VIIa as a hemostatic agent. Clin Adv Hematol Oncol 2003; 1: 112–9.

Factor XIII deficiency: complete phenotypic characterization of two cases with novel causative mutations

Coagulation factor XIII (FXIII) exists as heterotetramer (FXIII‐A2B2) in the plasma and as dimer (FXIII‐A2) in cells. Activated FXIII mechanically stabilizes fibrin and protects it from fibrinolysis by cross‐linking fibrin chains and α2‐plasmin inhibitor to fibrin. FXIII is essential to maintaining haemostasis, and its deficiency causes severe bleeding diathesis. Due to improper laboratory practices, FXIII deficiency is considered the most under‐diagnosed bleeding disorder. The aim of this study was to demonstrate in two cases how FXIII deficiency is properly diagnosed and classified, and to compare results of laboratory analysis and clinical symptoms. FXIII activity from plasma and platelets was measured by a modified ammonia release assay, while FXIII‐A2B2, FXIII‐A and FXIII‐B antigens were determined by ELISA. The exon–intron boundaries and the promoter region of F13A1 gene were amplified by PCR and the amplified products were analysed by direct fluorescent sequencing. FXIII‐A mRNA in platelets was determined by RT‐qPCR. Two children with severe bleeding symptoms were investigated. In both cases FXIII activity and FXIII‐A antigen were undetectable in the plasma and platelet lysate. In the plasma no FXIII‐A2B2 antigen was found, while FXIII‐B antigen was >30% in both cases. Proband1 was a compound heterozygote possessing a known missense mutation (c.980G>A, p.Arg326Gln) and a novel splice–site mutation (c.1112+2T>C). Proband2 was homozygote for a novel single nucleotide deletion (c.212delA) leading to early stop codon. The discovered mutations explain the severity of clinical symptoms and the laboratory data. Methods precise in the low activity/antigen range are required to draw valid conclusion on phenotype–genotype relationship.