Plasma protein C inhibitor is elevated in survivors of myocardial infarction

The host genetics affects gut microbiome diversity in Chinese depressed patients

The gut microbiome and host genetics are both associated with major depressive disorder (MDD); however, the molecular mechanisms among the associations are poorly understood, especially in the Asian, Chinese group. Our study applied linear discriminant analysis (LDA) effect size (LEfSe) and genome-wide association analysis in the cohort with both gut sequencing data and genomics data. We reported the different gut microbiota characteristics between MDD and control groups in the Chinese group and further constructed the association between host genetics and the gut microbiome. Actinobacteria and Pseudomonades were found more in the MDD group. We found significant differences in the ACE and Chao indexes of alpha diversity while no discrepancy in beta diversity. We found three associations between host genetics with microbiome features: beta diversity and rs6108 (p = 8.65 × 10-9), Actinobacteria and rs77379751 (p = 8.56 × 10-9), and PWY-5913 and rs1775633082 (p = 4.54 × 10-8). A species of the Romboutsia genus was co-associated with the species of Ruminococcus gnavus in an internetwork through four genes: METTL8, ITGB2, OTULIN, and PROSER3, with a strict threshold (p < 5 × 10-4). Furthermore, our findings suggested that the gut microbiome diversity might affect microRNA expression in the brain and influenced SERPINA5 and other spatially close genes afterward. These findings suggest new linkages between depression and gut microbiome in Asian, Chinese people, which might be mediated by genes and microRNA regulation in space distance.

Heart failure in obesity: insights from proteomics in patients treated with or without weight-loss surgery

BACKGROUND

Obesity is associated with incident heart failure (HF), but the underlying mechanisms are unclear.

METHODS

We performed a nested case-control study within the Swedish-Obese-Subjects study, by identifying 411 cases who developed HF and matched them with respect to age, sex, weight-loss-surgery and length of follow-up with 410 controls who did not develop HF. In analyses corrected for multiple testing, we studied 182 plasma proteins known to be related to cardiovascular disease to investigate whether they could add to the understanding of the processes underlying obesity-related HF.

RESULTS

A total of 821 subjects were followed for 16 ± 6 years. Multivariable analysis adjusted for matching variables revealed that 32 proteins were significantly associated with HF. Twelve proteins were related to HF ≥ 80% of the time using a bootstrap resampling approach (false-discovery-rate [FDR] < 0.05): 11 were associated with increased HF-risk: TNFRSF10A*, ST6GAL1, PRCP, MMP12, TIMP1, CCL3, QPCT, ANG, C1QTNF1, SERPINA5 and GAL-9; and one was related to reduced HF-risk: LPL. An further 20 proteins were associated with onset of HF 50-80% of the time using bootstrap resampling (FDR < 0.05). A pathway analysis including all significant 32 proteins suggested that these biomarkers were related to inflammation, matrix remodeling, cardiometabolic hormones and hemostasis. Three proteins, C1QTNF1, FGF-21 and CST3, reflecting dyslipidemia and kidney disease, displayed a higher association with HF in patients who did not undergo weight-loss-surgery and maintained with obesity.

CONCLUSION

Pathways associated with HF in obesity include inflammation, matrix remodeling, cardiometabolic hormones and hemostasis; three protein biomarkers predicting HF appeared to be obesity-specific.

Verification of a proteomic biomarker panel to diagnose minor stroke and transient ischaemic attack: phase 1 of SpecTRA, a large scale translational study

OBJECTIVE

To derive a plasma biomarker protein panel from a list of 141 candidate proteins which can differentiate transient ischaemic attack (TIA)/minor stroke from non-cerebrovascular (mimic) conditions in emergency department (ED) settings.

DESIGN

Prospective clinical study (#NCT03050099) with up to three timed blood draws no more than 36 h following symptom onset. Plasma samples analysed by multiple reaction monitoring-mass spectrometry (MRM-MS).

PARTICIPANTS

Totally 545 participants suspected of TIA enrolled in the EDs of two urban medical centres.

OUTCOMES

90-day, neurologist-adjudicated diagnosis of TIA informed by clinical and radiological investigations.

RESULTS

The final protein panel consists of 16 proteins whose patterns show differential abundance between TIA and mimic patients. Nine of the proteins were significant univariate predictors of TIA [odds ratio (95% confidence interval)]: L-selectin [0.726 (0.596-0.883)]; Insulin-like growth factor-binding protein 3 [0.727 (0.594-0.889)]; Coagulation factor X [0.740 (0.603-0.908)]; Serum paraoxonase/lactonase 3 [0.763 (0.630-0.924)]; Thrombospondin-1 [1.313 (1.081-1.595)]; Hyaluronan-binding protein 2 [0.776 (0.637-0.945)]; Heparin cofactor 2 [0.775 (0.634-0.947)]; Apolipoprotein B-100 [1.249 (1.037-1.503)]; and von Willebrand factor [1.256 (1.034-1.527)]. The scientific plausibility of the panel proteins is discussed.

CONCLUSIONS

Our panel has the potential to assist ED physicians in distinguishing TIA from mimic patients.

Plasma levels of the anti-coagulation protein C and the risk of ischaemic heart disease. A Mendelian randomisation study

Protein C is an environmentally modifiable anticoagulant, which protects against venous thrombosis, whether it also protects against ischaemic heart disease is unclear, based on observational studies and relatively small genetic studies. It was our study aim to clarify the role of protein C in ischaemic heart disease. The risk of coronary artery disease/myocardial infarction (CAD/MI) was assessed according to genetically predicted protein C in very large studies. Associations with lipids and diabetes were similarly assessed to rule out effects via traditional cardiovascular disease risk factors. Separate sample instrumental variable analysis with genetic instruments (Mendelian randomisation) was used to obtain an unconfounded estimate of the association of protein C (based on (rs867186 (PROCR), rs3746429 (EDEM2), rs7580658 (inter/PROC)) with CAD/MI in an extensively genotyped case (n=64374)-control (n=130681) study, CARDIoGRAMplusC4D. Associations with lipids and diabetes were similarly assessed using the Global Lipids Genetics Consortium Results (n=196,475) and the DIAbetes Genetics Replication And Meta-analysis case (n=34,380)-control (n=114,981) study. Genetically predicted protein C was negatively associated with CAD/MI, odds ratio (OR) 0.85 µg/ml, 95 % confidence interval 0.80 to 0.90, but had no such negative association with lipids or diabetes. Results were similar for the SNP rs867186 functionally relevant to protein C, and including additional potentially pleiotropic SNPs (rs1260326 (GCKR), rs17145713 (BAZ1B) and rs4321325 (CYP27C1)). In conclusion, protein C may protect against CAD/MI. Whether environmental or dietary items that raise protein C protect against ischaemic cardiovascular disease by that mechanism should be investigated.

Elevated tissue plasminogen activator and reduced plasminogen activator inhibitor promote hyperfibrinolysis in trauma patients

Severe hyperfibrinolysis after trauma is a poorly understood phenomenon associated with profound shock, serious anatomic injuries, increased transfusions, and high mortality rates. Molecular mechanisms driving hyperfibrinolysis in trauma have not been completely delineated. The authors aimed to determine the relationship between severe hyperfibrinolysis and outcomes in trauma patients and characterize the role of the plasminogen activator (PA) system in this condition. A prospective observational study was performed in 163 adult level I trauma patients admitted between April and August 2012. Blood was collected on admission, and fibrinolysis was determined by plasmin-α2 antiplasmin (PAP) levels. Tissue-derived and urokinase PA (tPA and uPA, respectively), PA inhibitor (PAI-1), fibrinogen, and antithrombin levels were also measured. Patient demographics, vital signs, laboratory values, mechanisms and severity of injuries, transfusions, and outcomes were collected at admission or from patient records. Moderate fibrinolysis was defined as PAP level 1,500 to 20,000 μg/L and severe hyperfibrinolysis as PAP level more than 20,000 μg/L. Severe hyperfibrinolysis was observed in 10% of patients and associated with increased injury severity, greater transfusions, fewer ventilator and hospital-free days, and higher mortality. Plasmin-α2 antiplasmin level was directly correlated with tPA level and inversely correlated with PAI-1 level. Patients with both elevated tPA and reduced PAI-1 were more severely injured, received more transfusions, and experienced fewer ventilator and hospital-free days. In conclusion, Severe hyperfibrinolysis is observed in a small percentage of trauma patients and is associated with severe injuries, greater transfusions, and worse outcomes. This condition is mediated, in part, by excessive upregulation of profibrinolytic tPA in the absence of concomitant increases in antifibrinolytic PAI-1.

Protein C inhibitor (PCI) binds to phosphatidylserine exposing cells with implications in the phagocytosis of apoptotic cells and activated platelets

Protein C Inhibitor (PCI) is a secreted serine protease inhibitor, belonging to the family of serpins. In addition to activated protein C PCI inactivates several other proteases of the coagulation and fibrinolytic systems, suggesting a regulatory role in hemostasis. Glycosaminoglycans and certain negatively charged phospholipids, like phosphatidylserine, bind to PCI and modulate its activity. Phosphatidylerine (PS) is exposed on the surface of apoptotic cells and known as a phagocytosis marker. We hypothesized that PCI might bind to PS exposed on apoptotic cells and thereby influence their removal by phagocytosis. Using Jurkat T-lymphocytes and U937 myeloid cells, we show here that PCI binds to apoptotic cells to a similar extent at the same sites as Annexin V, but in a different manner as compared to live cells (defined spots on ∼10-30% of cells). PCI dose dependently decreased phagocytosis of apoptotic Jurkat cells by U937 macrophages. Moreover, the phagocytosis of PS exposing, activated platelets by human blood derived monocytes declined in the presence of PCI. In U937 cells the expression of PCI as well as the surface binding of PCI increased with time of phorbol ester treatment/macrophage differentiation. The results of this study suggest a role of PCI not only for the function and/or maturation of macrophages, but also as a negative regulator of apoptotic cell and activated platelets removal.

Molecular basis of thrombin recognition by protein C inhibitor revealed by the 1.6-A structure of the heparin-bridged complex

Protein C inhibitor (PCI) is a serpin with many roles in biology, including a dual role as pro- and anticoagulant in blood. The protease specificity and local function of PCI depend on its interaction with cofactors such as heparin-like glycosaminoglycans (GAGs) and thrombomodulin (TM). Both cofactors significantly increase the rate of thrombin inhibition, but GAGs serve to promote the anticoagulant activity of PCI, and TM promotes its procoagulant function. To gain insight into how PCI recognition of thrombin is aided by these cofactors, we determined a crystallographic structure of the Michaelis complex of PCI, thrombin, and heparin to 1.6 A resolution. Thrombin interacts with PCI in an unusual fashion that depends on the length of PCI's reactive center loop (RCL) to align the heparin-binding sites of the two proteins. The principal exosite contact is engendered by movement of thrombin's 60-loop in response to the unique P2 Phe of PCI. This mechanism of communication between the active site of thrombin and its recognition exosite is previously uncharacterized and may relate to other thrombin substrate-cofactor interactions. The cofactor activity of heparin thus depends on the formation of a heparin-bridged Michaelis complex and substrate-induced exosite contacts. We also investigated the cofactor effect of TM, establishing that TM bridges PCI to thrombin through additional direct interactions. A model of the PCI-thrombin-TM complex was built and evaluated by mutagenesis and suggests distinct binding sites for heparin and TM on PCI. These data significantly improve our understanding of the cofactor-dependent roles of PCI in hemostasis.

Insulin resistance is unrelated to circulating retinol binding protein and protein C inhibitor

CONTEXT

Recent data suggest that circulating retinol-binding protein (RBP) might be involved in the pathogenesis of insulin resistance. Moreover, protein C inhibitor (PCI), which specifically binds retinoic acid, was found to be increased in myocardial infarction survivors who are also insulin resistant.

OBJECTIVE

The objective of this study was to investigate the association of insulin resistance with RBP factors and PCI active antigen.

DESIGN AND SETTING

This was a clinical study.

PATIENTS

Nondiabetic humans with high (IS; n = 20, 14 females, six males, aged 47.2 +/- 1.9 yr, body mass index 26 +/- 1 kg/m(2)) and low (IR; n = 20, 14 females, six males, aged 45.5 +/- 1.7 yr, body mass index 28 +/- 1 kg/m(2)) insulin-stimulated glucose-disposal (M) participated in this study.

MAIN OUTCOME MEASURES

M was measured by 2-h hyperinsulinemic (40 mU.min(-1).m(-2))-isoglycemic clamp tests. Measurements of RBP were performed using a nephelometric method and validated using quantitative Western blotting.

RESULTS

M (80-120 min) was higher in IS (10.9 +/- 0.6 mg.min(-1).kg(-1)) than IR (4.0 +/- 0.2; P < 10(-12)). Fasting plasma RBP concentrations were comparable between IS and IR measured by both nephelometry (IS: 4.4 +/- 0.3; IR: 4.6 +/- 0.3 mg/dl, P = 0.6) and quantitative Western blot (IS 7.9 +/- 0.5, IR 8.3 +/- 0.6 mg/dl; P = 0.6). Fasting plasma PCI active antigen was similar in both groups. Plasma RBP and PCI were not significantly related to M. RBP was positively correlated with uric acid (r = 0.488, P = 0.003), triglycerides (r = 0.592, P < 0.001), prealbumin (r = 0.63, P < 0.0001), and vitamin A (r = 0.75, P < 10(-6)).

CONCLUSIONS

Our data demonstrate that healthy, insulin-resistant humans do not show altered plasma retinol binding factors, such as RBP and PCI. Both do not significantly correlate with insulin sensitivity. Thus, our findings do not support the hypothesis of insulin sensitivity modulation by proteins involved in retinol transport.

Serpins in thrombosis, hemostasis and fibrinolysis

Hemostasis and fibrinolysis, the biological processes that maintain proper blood flow, are the consequence of a complex series of cascading enzymatic reactions. Serine proteases involved in these processes are regulated by feedback loops, local cofactor molecules, and serine protease inhibitors (serpins). The delicate balance between proteolytic and inhibitory reactions in hemostasis and fibrinolysis, described by the coagulation, protein C and fibrinolytic pathways, can be disrupted, resulting in the pathological conditions of thrombosis or abnormal bleeding. Medicine capitalizes on the importance of serpins, using therapeutics to manipulate the serpin-protease reactions for the treatment and prevention of thrombosis and hemorrhage. Therefore, investigation of serpins, their cofactors, and their structure-function relationships is imperative for the development of state-of-the-art pharmaceuticals for the selective fine-tuning of hemostasis and fibrinolysis. This review describes key serpins important in the regulation of these pathways: antithrombin, heparin cofactor II, protein Z-dependent protease inhibitor, alpha(1)-protease inhibitor, protein C inhibitor, alpha(2)-antiplasmin and plasminogen activator inhibitor-1. We focus on the biological function, the important structural elements, their known non-hemostatic roles, the pathologies related to deficiencies or dysfunction, and the therapeutic roles of specific serpins.

Regulation of protein C inhibitor (PCI) activity by specific oxidized and negatively charged phospholipids

Protein C inhibitor (PCI) is a serpin with affinity for heparin and phosphatidylethanolamine (PE). We analyzed the interaction of PCI with different phospholipids and their oxidized forms. PCI bound to oxidized PE (OxPE), and oxidized and unoxidized phosphatidylserine (PS) immobilized on microtiter plates and in aqueous suspension. Binding to OxPE and PS was competed by heparin, but not by the aminophospholipid-binding protein annexin V or the PCI-binding lipid retinoic acid. PS and OxPE stimulated the inhibition of activated protein C (aPC) by PCI in a Ca++-dependent manner, indicating that binding of both, aPC (Ca++ dependent) and PCI (Ca++ independent), to phospholipids is necessary. A peptide corresponding to the heparin-binding site of PCI abolished the stimulatory effect of PS on aPC inhibition. No stimulatory effect of phospholipids on aPC inhibition was seen with a PCI mutant lacking the heparin-binding site. A heparin-like effect of phospholipids (OxPE) was not seen with antithrombin III, another heparin-binding serpin, suggesting that it is specific for PCI. PCI and annexin V were found to be endogenously colocalized in atherosclerotic plaques, supporting the hypothesis that exposure of oxidized PE and/or PS may be important for the local regulation of PCI activity in vivo.

Premature compared with late onset of coronary artery disease: young patients show a severe defect in fibrinolytic response to venous occlusion

Inflammatory processes play a role in the onset of acute cardiovascular events associated with activation of the coagulation system whereas the fibrinolytic system may prevent local thrombus formation. We compared 25 patients with premature coronary artery disease (CAD) (first ST-elevation myocardial infarction, < 55 years old) with 25 sex-matched patients older than 55 years at their first myocardial infarction. Six months after the acute event, patients with late onset of CAD showed a significantly higher increase of tissue-type plasminogen activator activity during venous occlusion compared with patients with premature CAD (P < 0.005). Prothrombin fragment 1+2 was higher in patients with late-onset CAD (P < 0.05), whereas the inflammatory markers C-reactive protein and soluble intercellular cell adhesion molecule-1 were not different in both groups. A multivariate analysis including cardiovascular risk factors showed that the tissue-type plasminogen activator response to venous occlusion was independently associated with patient age at onset of first ST-elevation myocardial infarction. Although in our series high age was associated with a prothrombotic state, a high fibrinolytic capacity might have some beneficial effect and contribute to a delayed onset of adverse cardiovascular events in these patients.

Mild hyperhomocysteinemia is associated with a decreased fibrinolytic activity in patients after ST-elevation myocardial infarction

BACKGROUND

Elevated homocysteine (Hcy) levels have been associated with increased risk for cardiovascular disease and it has been shown that hyperhomocysteinemia is associated with increased levels of t-PA antigen in individuals without evidence for coronary artery disease (CAD). The aim of this study was to examine if Hcy plasma levels are associated with plasma levels of fibrinolytic factors in patients with CAD and a history of acute myocardial infarction.

METHODS

We measured in 56 patients with CAD, 1 month after their first ST-elevation myocardial infarction, plasma levels of Hcy, the fibrinolytic parameters tissue-type plasminogen activator (t-PA), plasminogen activator inhibitor-type-1 (PAI-1), and t-PA-PAI-1 complexes.

RESULTS

Hcy plasma levels inversely correlated with t-PA activity (r=-0.303, p<0.05). Patients with mild hyperhomocysteinemia (Hcy>15 micromol/L, n=8) showed significantly lower plasma levels of t-PA activity (p<0.05). Regression analysis revealed that out of cardiovascular risk factors and medical treatment only Hcy was significantly associated with t-PA activity.

CONCLUSIONS

Patients with CAD after a first myocardial infarction and hyperhomocysteinemia show a reduced t-PA activity independently from cardiovascular risk factors and medical treatment. Homocysteine lowering therapies may increase fibrinolytic activity and thereby may help to avoid atherothrombotic events in patients with CAD after a first myocardial infarction.

Predictive value of plasma plasminogen activator inhibitor-1 for coronary restenosis: dependence on stent implantation and antithrombotic medication

BACKGROUND

The plasmin activation system is involved in the development of restenosis after percutaneous coronary interventions (PCI). Conflicting data exist concerning the role of plasminogen activator inhibitor-1 (PAI-1) and its predictive value for restenosis.

OBJECTIVES

To evaluate the fibrinolytic response to injury after PCI with or without stent implantation on different antithrombotic medications and its relation to late restenosis.

PATIENTS AND METHODS

Eighty consecutive patients with successful PCI without (balloon only; n = 37) or with stent implantation (stent; n = 43) on different antithrombotic regimes (balloon only, aspirin; stent, aspirin/coumadin/dipyridamole vs. aspirin/ticlopidine). Blood samples were taken at baseline and up to 7 days after PCI and PAI-1 active antigen and tissue plasminogen activator (t-PA) antigen were determined. Restenosis was angiographically determined after 6 months.

RESULTS

PCI increased both t-PA and PAI-1 levels (P < 0.001), with a significant prolonged and pronounced increase in stent vs. balloon-only patients (P < 0.05). Restenosis (stent 26%; balloon 38%) was significantly correlated to an attenuated PAI-1 increase after 24 h in the ticlopidine group (P = 0.007; restenosis, relative Delta PAI-1 + 50 +/- 28%; non-restenosis, + 139 +/- 50%), but not in the coumadin group. In the balloon-only group late restenosis (ISR) was associated with a trend for an augmented PAI-1 increase after 24 h.

CONCLUSIONS

Coronary stent implantation significantly increases t-PA and PAI-1 plasma levels up to 1 week compared with balloon angioplasty alone. ISR in ticlopidine-treated patients was associated with an attenuated early PAI-1 active antigen increase. A less than 50% increase 24 h after stent implantation under ticlopidine treatment may identify patients at risk for the development of ISR.

Protein C inhibitor (plasminogen activator inhibitor-3) and the risk of venous thrombosis

Protein C inhibitor (PCI), also known as plasminogen activator inhibitor-3, is a serine proteinase inhibitor that can inhibit enzymes in blood coagulation, fibrinolysis and fertility. The role of PCI in regulating the blood coagulation mechanism is not known, as it can inhibit both procoagulant (thrombin, factor Xa, factor XIa) and anticoagulant (activated protein C, thrombin-thrombomodulin, urokinase) enzymes. To determine the relevance of this inhibitor in thrombosis, PCI levels were assessed in the Leiden Thrombophilia Study, a case-control study of venous thrombosis in 473 patients with a first deep-vein thrombosis and 474 age- and sex-matched control subjects. PCI levels above the 95th percentile of the controls (136.1%) increased the risk 1.6-fold compared with PCI levels below the 95th percentile (95% confidence interval 0.9-2.8). There was a gradual increase in risk of thrombosis with further increasing levels of PCI. Adjustment for a number of possible confounders led to a reduction of the risk estimates associated with PCI. However, it is unclear whether adjustment for such factors in the risk models is justified. These results indicate that high levels of PCI may constitute a mild risk factor for venous thrombosis.

C5a stimulates production of plasminogen activator inhibitor-1 in human mast cells and basophils

We have recently shown that resting human mast cells (MCs) produce tissue-type plasminogen activator (t-PA) without simultaneously expressing plasminogen activator inhibitor 1 (PAI-1). In the present study we have identified the anaphylatoxin rhC5a as a potent inducer of PAI-1 expression in human MCs and basophils. In primary human skin MCs and primary blood basophils, exposure to rhC5a was followed by an increase from undetectable to significant levels of PAI-1. In addition, rhC5a induced a concentration- and time-dependent increase in PAI-1 antigen in the MC line HMC-1 and the basophil cell line KU-812 and increased the expression of PAI-1 mRNA in HMC-1. In conditioned media of HMC-1 treated with rhC5a, active PAI-1 could be detected. A simultaneous loss of t-PA activity in conditioned media from the same cells indicated that rhC5a-induced PAI-1 was capable of inhibiting the enzymatic activity of coproduced t-PA. Correspondingly, the levels of t-PA-PAI-1 complexes increased in rhC5a-treated cells. When HMC-1 cells were incubated with pertussis toxin or anti-C5a receptor antibodies, the effect of rhC5a on PAI-1 production was completely abolished. Treatment of C5a with plasmin resulted in loss of its ability to induce PAI-1 production in MCs. Considering the suggested role for MCs and components of the complement system in the development of cardiovascular diseases, we hypothesize that MCs, by producing t-PA in a resting state and by expressing PAI-1 when activated by C5a, might participate in the modulation of the balance between proteases and protease inhibitors regulating tissue injury and repair in such disease processes.

Haemochromatosis mutations and ferritin in myocardial infarction: a case-control study

BACKGROUND

Iron accumulation may contribute to coronary heart disease by catalysing free radical formation and promoting oxidation of low-density lipoprotein cholesterol. Epidemiological studies of iron status and coronary heart disease are conflicting.

DESIGN

To test whether genetic haemochromatosis is associated with myocardial infarction, we determined the prevalence of three mutations in the HFE gene (Cys282Tyr, His63Asp and Ser65Cys) in a 2 : 1 case-control study including 177 patients who survived an acute myocardial infarction and 89 controls. Genotypes were determined by PCR amplification of genomic DNA followed by restriction enzyme digestion. We also studied the relationship between plasma ferritin and myocardial infarction.

RESULTS

The carrier frequencies of these three mutations were not statistically different among patients and controls (Cys282Tyr: 1.4 vs. 10.1%; His63Asp: 26.5 vs. 31.5%; Ser65Cys: 2.8 vs. 1.1%). Mean ferritin levels were elevated among patients (176 +/- 155 microg L(-1)) compared with controls (131 +/- 106 microg L(-1), P = 0.015). Subjects with plasma ferritin concentrations of 300 microg L(-1) or more had a 2.9-fold (95% CI: 1.2-7.3, P = 0.02) unadjusted risk for a myocardial infarction compared with those with normal levels. In a univariate analysis, ferritin was significantly associated with myocardial infarction. Upon multiple regression analysis adjusting for smoking, hypertension, diabetes, body-mass index and total cholesterol, significance was no longer present.

CONCLUSIONS

No direct association was found between genetic haemochromatosis and myocardial infarction among Swiss whites. Raised ferritin levels among patients suggest a role of increased iron stores in myocardial infarction, but iron overload was not an independent risk factor for Swiss coronary heart disease patients.

Hemostatic and fibrinolytic parameters in survivors of myocardial infarction: a low plasma level of plasmin-alpha2-antiplasmin complex is an independent predictor of coronary re-events

Abnormalities of coagulation or fibrinolysis play a role in the pathogenesis of coronary artery disease (CAD). Elevated plasma levels of fibrinogen, von Willebrand factor antigen, plasminogen activator inhibitor-1 and tissue-type plasminogen activator were reported to be predictive for reinfarction and death in patients with CAD. We investigated the risk for coronary re-events associated with 18 hemostatic and fibrinolytic parameters in a prospective study including 200 survivors of myocardial infarction (MI). During a 2-year follow-up, 37 patients suffered one of the following predefined re-events: fatal MI (n = 2), non-fatal MI (n = 5), percutaneous transluminal coronary angioplasty (n = 17) or coronary artery bypass grafting (n = 13). Low plasmin-alpha2-antiplasmin complex (PAP) plasma levels were associated with an up to fivefold (95% confidence interval, 1.6-15.3) increase in relative risk. The association between decreasing PAP levels and coronary re-events remained significant (P = 0.004) after correction for possible confounders using multiple logistic regression analysis. Our data indicate low PAP plasma levels to be associated with subsequent coronary events in patients with a history of MI.

Synthesis and Ultrastructural Localization of Protein C Inhibitor in Human Platelets and Megakaryocytes

The occurrence of protein C inhibitor (PCI) in human platelets and megakaryocytes was analyzed. As judged from enzyme-linked immunosorbent assays (ELISAs), PCI was present in platelets at a concentration of 160 ng/2 × 109 cells. Its specific activity was 5 times higher than that of plasma PCI. Consistently, mainly the 57-kD form (active PCI) and some high molecular weight (Mr) forms, but no bands corresponding to cleaved PCI, were detected when platelet lysates were immunoprecipitated with monoclonal anti-PCI-IgG and analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and Western blotting. The localization of PCI in platelets was studied by immunofluorescence histochemistry and immunotransmission electron microscopy: PCI was detected in  granules, in the open canalicular system, and on the plasma membrane. At these sites, colocalization with plasminogen activator inhibitor-1 was seen. Studies were performed to clarify whether platelet PCI is endogenously synthesized or taken up from plasma. Internalization of biotinylated-PCI was analyzed using platelets in suspension and gold-labeled streptavidin for visualization of incorporated biotin. Dose- and time-dependent uptake of PCI was found. PCI mRNA was detected in platelets by reverse transcriptase-polymerase chain reaction (RT-PCR) and Southern blotting, as well as in megakaryocytes by in situ hybridization of human bone marrow cryosections. We therefore conclude that platelets contain a functionally active PCI pool that is derived from both endogenous synthesis as well as internalization.

Synthesis and Ultrastructural Localization of Protein C Inhibitor in Human Platelets and Megakaryocytes

The occurrence of protein C inhibitor (PCI) in human platelets and megakaryocytes was analyzed. As judged from enzyme-linked immunosorbent assays (ELISAs), PCI was present in platelets at a concentration of 160 ng/2 × 109 cells. Its specific activity was 5 times higher than that of plasma PCI. Consistently, mainly the 57-kD form (active PCI) and some high molecular weight (Mr) forms, but no bands corresponding to cleaved PCI, were detected when platelet lysates were immunoprecipitated with monoclonal anti-PCI-IgG and analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and Western blotting. The localization of PCI in platelets was studied by immunofluorescence histochemistry and immunotransmission electron microscopy: PCI was detected in  granules, in the open canalicular system, and on the plasma membrane. At these sites, colocalization with plasminogen activator inhibitor-1 was seen. Studies were performed to clarify whether platelet PCI is endogenously synthesized or taken up from plasma. Internalization of biotinylated-PCI was analyzed using platelets in suspension and gold-labeled streptavidin for visualization of incorporated biotin. Dose- and time-dependent uptake of PCI was found. PCI mRNA was detected in platelets by reverse transcriptase-polymerase chain reaction (RT-PCR) and Southern blotting, as well as in megakaryocytes by in situ hybridization of human bone marrow cryosections. We therefore conclude that platelets contain a functionally active PCI pool that is derived from both endogenous synthesis as well as internalization.

Protein C inhibitor is expressed in keratinocytes of human skin

Protein C inhibitor is a member of the serpin family that inhibits a variety of serine proteases. Protein C inhibitor is present in numerous body fluids and is produced in the liver and by various epithelial cells. To determine if this epithelial serpin is present in skin, immunohistochemical studies were performed that showed strong staining for protein C inhibitor antigen in the epidermis. Protein C inhibitor mRNA was detected in the keratinocyte cell line HaCaT and the epidermoid carcinoma cell line A431 using reverse transcription-polymerase chain reaction suggesting that also in normal skin protein C inhibitor is derived from keratinocytes. Conditioned media from these cell lines were analyzed on immunoblots, which revealed a protein C inhibitor-antigen band that comigrated with protein C inhibitor derived from the hepatoma cell line HepG2. Using an enzyme-linked immunosorbent assay specific for total protein C inhibitor antigen the accumulation of protein C inhibitor in the cell culture supernatants of HaCaT keratinocytes was found to be 0.3 ng per h per 1 million cells. This is similar to the amount of plasminogen activator inhibitor-1 produced by these cells, which also produce tissue plasminogen activator and urokinase. Fluorescence-activated cell sorter analysis revealed similar expression of intracellular protein C inhibitor antigen in proliferating and confluent HaCaT cells. These findings demonstrate that protein C inhibitor antigen is present in the normal epidermis and that protein C inhibitor is constitutively expressed by keratinocytes in culture. Therefore, protein C inhibitor may provide protease inhibitory activity not only to internal, but also to the external surface of the body. Additionally, protein C inhibitor could contribute to the regulation of retinoid supply in the epidermis, as we have shown recently that retinoic acid binds specifically to protein C inhibitor.

Changes in the fibrinolytic system in patients with peripheral arterial occlusive disease undergoing percutaneous transluminal angioplasty

We have investigated fibrinolytic parameters in 33 patients with peripheral arterial occlusive disease (PAOD) before and 6, 24, and 48 hours after percutaneous transluminal angioplasty (PTA) as well as in 35 gender-matched healthy controls, whose mean age was not significantly different from the mean age of the patients. PAOD patients had significantly higher plasma levels of t-PA antigen (12.0+/-4.9 vs. 9.2+/-5.5 ng/ml), PAI-1 antigen (34.8+/-22.1 vs. 27.2+/-23.6 ng/ml), PAI-1 activity (10.0+/-6.5 vs. 8.0+/-8.0 U/ml), PCI (188.2+/-55.6 vs. 134.1+/-75.5% as compared with normal human plasma), and fibrinogen (420.2+/-92.6 vs. 261.9+/-32.7 mg/dl) as compared with controls. After angioplasty, fibrinolytic parameters and fibrinogen levels increased, reaching higher than preintervention levels 24 and 48 hours after the intervention. Six months after initially successful PTA, restenosis was demonstrated in 14 out of 33 patients (42%). Patients with late restenosis had significantly higher levels of PAI-1 activity 24 and 48 hours after PTA, as compared with patients with late patency (24 hours: 16.1+/-8.0 vs. 10.0+/-7.4; 48 hours: 16.5+/-7.9 vs. 12.0+/-7.0; p<0.05 for both time points). The results suggest that impaired fibrinolysis early after PTA might be a cause or marker of a disturbed repair process of vascular injury, leading to restenosis.

Association of two silent polymorphisms of platelet glycoprotein Ia/IIa receptor with risk of myocardial infarction: a case-control study

BACKGROUND

The platelet membrane glycoprotein Ia/IIa plays a major part in platelet function as a primary receptor for collagen. A previous report showed a variation of glycoprotein Ia/IIa receptor density and function associated with two silent and linked polymorphisms (807C/T and 873G/A) within the glycoprotein Ia gene. Because platelet thrombus formation is implicated in the pathogenesis of acute myocardial infarction, we investigated these polymorphisms among patients who had had a myocardial infarction.

METHODS

We did a 2/1 case-control study including 177 patients (median age 57.0 [range 32-72] years) and 89 controls with same age and sex. Distributions of the 807C/T and 873G/A polymorphisms were investigated by genotyping DNA by PCR, single-strand conformation polymorphism analysis, and sequencing.

FINDINGS

The prevalence of the homozygous 807T/873A genotype was 2.9 times higher among patients with myocardial infarction than among controls (16.4% vs 5.6%, p=0.022). There was an association between patients homozygous for the 807T/873A allele and myocardial infarction (odds ratio 3.3 [95% CI 1.2-8.8]), which was strongest in a subgroup of smokers. The homozygous 807T/873A genotype remained an independent risk factor for myocardial infarction (p=0.005) when age, sex, smoking, hypertension, diabetes, body-mass index, LDL-cholesterol and HDL-cholesterol, and fibrinogen were adjusted for by logistic regression.

INTERPRETATION

The 807T/873A homozygosity of the platelet glycoprotein Ia/IIa gene polymorphism, associated with differences in surface collagen receptor density and activity, appears to be an independent risk factor for acute myocardial infarction. Our findings need to be confirmed in a larger, prospective study that includes patients from different populations and cardiovascular risk groups.

The Mast Cell as Site of Tissue-Type Plasminogen Activator Expression and Fibrinolysis

Recent data suggest that mast cells (MC) and their products (heparin, proteases) are involved in the regulation of coagulation and fibrino(geno)lysis. The key enzyme of fibrinolysis, plasmin, derives from its inactive progenitor, plasminogen, through catalytic action of plasminogen activators (PAs). In most cell systems, however, PAs are neutralized by plasminogen activator inhibitors (PAIs). We report that human tissue MC as well as the MC line HMC-1 constitutively produce, express, and release tissue-type plasminogen activator (tPA) without producing inhibitory PAIs. As assessed by Northern blotting, highly enriched lung MC (&gt;98% pure) as well as HMC-1 expressed tPA mRNA, but did not express mRNA for PAI-1, PAI-2, or PAI-3. The tPA protein was detectable in MC-conditioned medium by Western blotting and immunoassay, and the MC agonist stem cell factor (c-Kit ligand) was found to promote the release of tPA from MC. In addition, MC-conditioned medium induced fibrin-independent plasmin generation as well as clot lysis in vitro. These observations raise the possibility that MC play an important role in endogenous fibrinolysis.