Protein Z gene polymorphisms (intron F 79 G>A; -13 A>G) are not associated with acute coronary syndromes

Low Protein Z Level: A Thrombophilic Risk Biomarker for Acute Coronary Syndrome

Acute coronary syndrome (ACS) encompasses a range of thrombotic coronary artery diseases. Protein Z (PZ)/PZ-dependent protease inhibitor complex is a natural anticoagulant system with a presumptive role for PZ deficiency in the pathogenesis of ACS. We aimed to evaluate plasma PZ level and role as a risk biomarker in Egyptian patients with ACS. Hundred patients with stable ACS and 60 matched controls were enrolled. ACS patients were divided into 3 clinical subgroups (ST-segment elevation myocardial infarction, non-ST-segment elevation myocardial infarction, and unstable angina), and 2 age subgroups (group A ≤ 55 years, and group B > 55 years). Plasma PZ levels were evaluated using enzyme linked immunosorbent assay. Lower PZ levels were found in ACS patients' group and clinical subgroups compared with controls. PZ levels showed a decrease with increasing age and were lower in females versus males. Lower PZ levels were found in hypertensive ACS patients in both age subgroups. Smokers and patients with family history of ACS in group A had lower PZ levels, while group B revealed lower PZ among diabetic patients. In group A, increased number of ACS conventional risk factors was associated with lower PZ levels. PZ level 3.7 μg/mL was the best cut-off value for prediction of ACS. Logistic regression analyses approved PZ as an independent risk biomarker for ACS. PZ levels are reduced in stable ACS and are significantly and independently associated with increased susceptibility for ACS, denoting PZ deficiency as a reliable thrombophilic risk biomarker in Egyptian patients with ACS.

The protein Z/protein Z-dependent protease inhibitor complex

Protein Z (PZ) is a vitamin K-dependent factor identified in human plasma in 1984 but it has no enzymatic activity. It is a cofactor of a serpin, the protein Z-dependent protease inhibitor (ZPI), and the complex PZ/ZPI inhibits activated factor X on phospholipid surfaces. In mice, the disruption of PZ or ZPI gene is asymptomatic, but enhances the thrombotic phenotype and mortality of other thrombotic risk factors. Most of the clinical studies focused on PZ. Despite conflicting results, a recent meta-analysis indicated that PZ deficiency could be a risk for venous and arterial thrombosis and early fetal loss. However, these conclusions are drawn from case-control studies of small size, constituting an important limitation. Recently, it was shown that PZ and/or ZPI are synthesised by normal kidney and different cancer cells, suggesting that the complex PZ/ZPI could play a role in inhibiting the tissue deposition of fibrin. The physiopathological consequences of these observations remain to be established. At this time, the measurement of plasma PZ and ZPI or analysis of their gene polymorphisms should not be performed routinely for the exploration of thrombophilia.

Contribution of protein Z gene single-nucleotide polymorphism to systemic lupus erythematosus in Egyptian patients

Protein Z has been reported to exert an important role in inhibiting coagulation. Polymorphisms in the protein Z gene (PROZ) may affect protein Z levels and thus play a role in thrombosis. This study aimed to investigate the prevalence and clinical significance of protein Z gene G79A polymorphism in Egyptian patients with systemic lupus erythematosus (SLE). We studied the distribution of the protein Z gene (rs17882561) (G79A) single-nucleotide polymorphism by PCR-restriction fragment length polymorphism in 100 Egyptian patients with SLE and 100 age, sex, and ethnically matched controls. There was no statistically significant difference in the distribution of the genotypes between SLE patients and the control group in our study (P = 0.103). But a statistically significant difference in the frequency of the alleles between SLE patients and controls was observed (P = 0.024). Also a significant association was detected between protein Z genotypes (and also A allele) and thrombosis, which is one of the manifestations of SLE (P = 0.004 and P = 0.001, respectively). Moreover, we observed a significant association between the protein Z AA and GA genotypes (and also A allele) and the presence of anticardiolipin antibodies (P = 0.016 and P = 0.004, respectively). The minor A allele of the G79A polymorphism in the protein Z gene might contribute to the genetic susceptibility of SLE in Egyptian patients. Also, an influence for this polymorphism on some of the disease manifestations has been elucidated, so protein Z G79A AG/AA may be a risk factor for thrombosis.

[Protein Z, polymorphisms in the protein Z gene and thrombosis]

Protein Z (PZ) is a vitamin K dependent protein acting as the cofactor of the protein Z dependent inhibitor (ZPI), in the inhibition of activated factor X bound on the phospholipids. Normal plasma protein Z concentrations have wide variations among individuals, partly explained by a genetic control. Several protein Z gene polymorphisms influence plasma concentration, separately and in combination. The role of PZ in blood coagulation regulation has been demonstrated in vitro. The responsibility of low PZ level in the occurrence of thrombosis has been questioned. However, the roles of PZ plasma level and PZ gene polymorphisms remain debated with conflicting results in arterial, venous, or placental thrombosis. These discrepancies can be explained by the heterogeneity of populations chosen as control, by the PZ interindividual variability, by the small size of the cohorts in mainly retrospective studies and perhaps by the lack of real important influence of this protein on coagulation. PZ measurement is not actually considered as a biological marker of thrombophilia. Large prospective studies remain to be done to investigate its possible role in thrombosis.

Association of the protein Z ATG haplotype with symptomatic nonvascular stroke or thromboembolism in white children: a family-based cohort study

To clarify the role of protein Z (PZ) in children with stroke/thromboembolism (TE), the present haplotype (HT)–based family study was performed. We genotyped 365 pediatric stroke/TE families (stroke n = 216; TE n = 149) for 4 single nucleotide polymorphisms (SNPs; rs3024718, rs3024731, rs3024772, and rs3024778) to assess the association between genetic variation within a conserved block of linkage disequilibrium harboring the PZ gene and pediatric TE. Association was assessed with use of the transmission disequilibrium test (TDT), corrected for multiple testing (permutation testing: HAPLOVIEW). In addition, PZ antigen was determined and correlated with carriership of PZ haplotypes and the FV G1691A mutation. Rs3024718, rs3024731, and rs3024772 are in tight linkage disequilibrium (LD) and define 4 haplotypes, capturing 97% of the genetic variation for this LD block. HT1 (ATG) was significantly overtransmitted from parents to affected offspring (HT frequency 73.5%, T:U 122:80, χ2 = 8.791, P = .003). The ATG risk haplotype was significantly correlated with greater PZ antigen levels. Multivariate analysis adjusted for age, sex, established thrombophilias, smoking, fibrinogen, and PZ levels revealed a significant association of the ATG haplotype and TE in children (odds ratio [OR] 1.4; 95% confidence interval [95% CI] 1.08-1.93). Our results suggest that the ATG haplotype of the PZ gene is a genetic marker for symptomatic TE in white German children.

Protein Z/Z-dependent protease inhibitor (PZ/ZPI) anticoagulant system and thrombosis

A new anticoagulant system involving a serpin has been recently characterised. The protein Z/Z-dependent protease inhibitor (PZ/ZPI) system inhibits activated factors X, XI and IX by different mechanisms. By homology with other anticoagulant systems (antithrombin or the protein C/protein S), deficiency of the serpin (ZPI) or its cofactor (PZ) might imbalance the haemostatic system with thrombotic consequences. Evidence supports the in vivo anticoagulant role of this complex and the thrombotic consequences of its deficiency. Non-sense variations of the ZPI (W303X and R67X) have been associated with increased risk of venous thrombosis. Moreover, PZ deficient mice carrying the FV Leiden have a thrombotic phenotype. Finally, some reports suggest that PZ deficiency might increase the risk of thrombosis. However, other studies question the thrombotic relevance of both ZPI and PZ deficiencies. This system could play a redundant role in haemostasis that explains the conflicting results on its thrombotic potential, which might be exacerbated in combination with other prothrombotic factors.