Protein Z levels, protein Z G79A polymorphism, and prothrombotic conditions

Low protein Z plasma level is a risk factor for acute myocardial infarction in coronary atherosclerosis disease patients

OBJECTIVES

To examine plasma protein Z (PZ) levels in acute myocardial infarction (AMI) and chronic coronary atherosclerosis disease (CCAD) patients without history of AMI and explore its potential clinical significance.

METHODS

Plasma PZ concentrations were measured in 90 AMI patients (Group A), 87 CCAD patients without AMI history who remained free of major clinical events at least one year (Group B), and 88 clinically healthy controls (Group C).

RESULTS

PZ was found to be significantly lower (P<0.001) in Group A (1508.5±486.2ng/mL) compared with Group B (1823.0±607.8ng/mL) and C (2001.7±733.0ng/mL) and in Group A+B compared with Group C (Group A+B 1663.1±570.0 ng/mL, P<0.001). No statistically significant difference was reached between Group B and C (P=0.081). PZ level was significantly correlated with concentration of creatine kinase MB, high sensitive-cardiac troponin T, high sensitive C reactive protein, D-dimer and coagulation factor II and may be a useful predictor for AMI (OR: 1.38, 95% CI: 1.13-1.77, P=0.03). Subgroup analysis showed PZ concentration below the lowest tertile (<1398ng/mL) had a significantly increased risk for AMI and CCAD (OR: 3.39; 95% CI: 1.12-10.31; P=0.03 and OR: 7.39; 95% CI: 2.62-20.79; P<0.001 respectively).

CONCLUSIONS

PZ deficiency is found in AMI patients and could potentially reflect the myocardium injury, local coagulation activation and inflammation response during the acute phase of coronary atherosclerosis disease.

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.

Role of protein Z in stroke

Protein Z (PZ) is a vitamin K-dependent plasma glycoprotein that acts as a cofactor for PZ-dependent protease inhibitor to inhibit coagulation factor X(a). Studies in mice suggest that that decreased blood PZ levels lead to reduced inhibition of blood coagulation, thereby predisposing to thrombosis; however, clinical studies in humans have yielded conflicting results. Among patients with stroke, some epidemiologic studies have reported that reduced PZ levels increase the risk of stroke, whereas others have reported no association between PZ levels and stroke, or that elevated PZ levels increase stroke risk. Polymorphisms involving the gene for PZ can influence the PZ concentration and some polymorphisms (eg, intron G79A AA allele) may be protective against stroke, particularly among younger individuals. Although the association between PZ levels and stroke appears to be stronger in younger patients and in patients who do not have conventional vascular risk factors, it remains unclear whether the link between PZ levels and stroke is confounded or causal or whether blood levels of PZ are altered as a consequence of the acute stroke event.