Release patterns of pregnancy associated plasma protein A (PAPP-A) in patients with acute coronary syndromes

Roles of Toll-Like Receptors in Nitroxidative Stress in Mammals

Free radicals are important antimicrobial effectors that cause damage to DNA, membrane lipids, and proteins. Professional phagocytes produce reactive oxygen species (ROS) and reactive nitrogen species (RNS) that contribute towards the destruction of pathogens. Toll-like receptors (TLRs) play a fundamental role in the innate immune response and respond to conserved microbial products and endogenous molecules resulting from cellular damage to elicit an effective defense against invading pathogens, tissue injury, or cancer. In recent years, several studies have focused on how the TLR-mediated activation of innate immune cells leads to the production of pro-inflammatory factors upon pathogen invasion. Here, we review recent findings that indicate that TLRs trigger a signaling cascade that induces the production of reactive oxygen and nitrogen species.

Pregnancy-associated plasma protein-a is associated with subclinical atherosclerosis in men with HIV infection

The pathophysiology of an early and accelerated atherosclerotic process is complex and multifactorial in HIV-infected men compared with HIV-non-infected men. Several biomarkers have been well studied in the detection of the early stage of atherosclerosis, but studies are limited in HIV-infected men. The objective of this study was to investigate the association between serum pregnancy-associated plasma protein-A (PAPP-A) and carotid intima-media wall thickness (CIMT) in asymptomatic HIV-infected men. This a case-control study group comprising 118 HIV-infected men and 60 age-matched and gender-matched HIV-non-infected men. Serum PAPP-A was measured using an ELISA kit and carotid IMT was evaluated by Doppler ultrasonography in all subjects. Statistical analysis included receiver-operating characteristic (ROC) analysis, Pearson correlation and logistic regression analysis. Serum PAPP-A level was significantly higher in HIV +CIMT+ group compared with HIV +CIMT group and HIV-CIMT- group. We found a positive correlation between PAPP-A and increased CIMT (r=0.737, p<0.0001), and a negative correlation between nadir CD4 T cell counts and increased CIMT (r=-0.526, p<0.001). In multivariate logistic regression analyses, PAPP-A, nadir CD4 T cell count and age were significantly associated with subclinical atherosclerosis (p<0.001, p=0.006 and p=0.032, respectively). In ROC analysis, PAPP-A levels of >3.70 µg/mL were associated with subclinical atherosclerosis in HIV+ men with a specificity of 100% and a sensitivity of 71% (area under the curve: 0.949, 95% CI 0.875 to 1.000, p<0.001). Serum PAPP-A level was strongly correlated with increased CIMT in HIV-infected men. PAPP-A might be used as an early biomarker to identify atherosclerosis in asymptomatic HIV-infected men.

Pregnancy-Associated Plasma Protein a during Hemodialysis with Polyamide and Diacetate Cellulosic Membranes

Pregnancy-associated plasma protein A (PAPP-A) is a new prognostic factor of acute coronary syndrome in the general population. It is elevated in hemodialysis (HD) patients and at baseline, it was shown to be related to inflammation and oxidative stress. The aim of the study was to examine the relationship of PAPP-A and oxidative stress and inflammatory markers to HD treatment. Studied parameters were determined in 10 chronic HD patients treated with low flux polyamide (1st session) and diacetate cellulosic membranes (2nd session) at the beginning, after 15 minutes and at the end of the dialysis session. TRACE method (Time Resolved Amplified Cryptate Emission) was used for PAPP-A assessment. Results were evaluated with ANOVA.

PAPP-A levels did not depend on the type of HD membrane but changed significantly with the time of the HD session. They increased significantly from the beginning of HD to 15 min and then decreased to the end of the HD session – p<0.05 15 min of HD vs start, p<0.01 end vs start, p<0.0001 end vs 15 min of HD for polyamide membrane and p=0.05 15 min of HD vs start, p<0.01 end vs start, p<0.0001 end vs 15 min of HD for diacetate cellulosic membrane. Changes in other parameters and differences between membranes were only minimal.

We can conclude that PAPP-A as a marker of cardiovascular damage shows significant changes during the HD session. Its initial increase might be ascribed to its release from complexes or storage. During dialysis, it might be destroyed or cleaved and removed as free fragments. Its levels both before and after the HD session are higher than in healthy subjects.

Pregnancy associated plasma protein-A as a prognostic biomarker of all-cause mortality and cardiovascular events in patients presenting with chest pain: a systematic review

AIM

Novel biomarkers have been proposed for identification of patients at greater risk of future adverse events among those presenting with chest pain. In this review, we aim to elucidate the ability of pregnancy associated plasma protein-A (PAPP-A) to predict mortality and other cardiovascular events in this patient population.

METHODS

A literature search of the electronic databases Medline, Scopus, Cochrane Library and ClinicalTrials.gov was performed in order to identify studies investigating the utility of PAPP-A to predict mortality and adverse cardiovascular events in patients with chest pain.

RESULTS

Eight studies met our inclusion criteria. Five of these studies pertained to patients with confirmed ischemic chest pain, while the rest included patients presenting with chest pain possibly due to acute coronary syndrome, irrespectively of the underlying cause. Although the results for long-term events were inconclusive in both groups of patients, higher PAPP-A concentrations were found to be a significant predictor of short-term adverse events in patients with confirmed ischemic chest pain.

CONCLUSIONS

PAPP-A appears to be a potentially useful biomarker for short-term risk stratification of patients presenting with chest pain of ischemic origin. However, there is an eminent need for more standardized clinical studies investigating the prognostic value of this biomarker.

The utility of pregnancy-associated plasma protein A for determination of prognosis in a cohort of patients with coronary artery disease

Background: Pregnancy-associated plasma protein-A (PAPP-A) is discussed as a biomarker representing unstable plaques in coronary artery disease (CAD). Methods: In this study 927 patients with CAD (534 with stable angina and 393 with acute coronary syndrome [ACS]) and 217 patients without CAD and measured PAPP-A levels were included. Follow-up for a median of 5 years was documented. Results: Rising quartiles of PAPP-A concentration had a higher cardiovascular mortality in the overall cohort of patients with CAD (p = 0.002) and the cohort with ACS (p = 0.01). Patients with suspected ACS below the LOD for troponin I but elevated PAPP-A levels had an increased cardiovascular mortality. A cut-off of 11.4 IU/l identified patients with a higher mortality during follow-up. Conclusion: Rising PAPP-A levels are prognostic in patients with CAD. PAPP-A levels were especially predictive in ACS patients with troponin below 10% CV of the 99th percentile for cardiovascular mortality.

PAPP-A and IGFBP-4 fragment levels in patients with ST-elevation myocardial infarction treated with heparin and PCI

OBJECTIVES

Circulating levels of pregnancy-associated plasma protein-A (PAPP-A) predict outcome in patients with acute coronary syndrome (ACS). Unfortunately, administration of heparin to patients with ACS increases circulating PAPP-A, probably by a detachment of PAPP-A from cell surfaces, inducing a considerable bias when using PAPP-A as a biomarker. It remains unknown whether PAPP-A-derived N- and C-terminal fragments of insulin-like growth factor binding protein-4 (NT-IGFBP-4/CT-IGFBP-4) are acutely affected by the increase in PAPP-A.

METHODS

We prospectively included 78 patients with ST-segment elevation myocardial infarction (STEMI) treated with percutaneous coronary intervention (PCI). Prior to PCI, patients were injected with 10,000IU of unfractionated heparin (UFH). Blood samples were collected immediately before PCI, but after UFH-injection, immediately after PCI and on day 1 and day 2. Plasma IGFBP-4, CT-IGFBP-4 and NT-IGFBP-4 levels were determined by specific, novel immunoassays, and PAPP-A and IGF-I by commercial immunoassays.

RESULTS

Plasma PAPP-A was strongly elevated upon STEMI, UFH-administration and PCI with mean concentrations (95%-confidence interval) pre-PCI, post-PCI, day 1, and day 2 of 13.0 (11.2;15.2), 14.8 (13.1;16.8), 1.03 (0.90;1.18), and 1.08 (0.92;1.28) μg/L, respectively (p<0.0001). Pre-PCI concentrations of IGFBP-4, CT-IGFBP-4 and NT-IGFBP-4 were 154 (142;166), 53 (47;60) and 136 (122;150) μg/L, and levels were unaltered post-PCI. Concentrations increased on day 1 by 63 (43;87)%, 69 (36;110)%, and 47 (21;79)%, respectively (p<0.0001), i.e. at a time point when PAPP-A levels had normalized.

CONCLUSION

Plasma IGFBP-4-fragment levels are not acutely altered in patients with STEMI treated with UFH and PCI. Thus, they possess potentials as prognostic markers in ACS patients.

Examination of serum pregnancy-associated plasma protein A clinical value in acute coronary syndrome prediction and monitoring

INTRODUCTION

Chronic vascular inflammatory process promotes and intensifies all atherogenic events. The aim of this research was to estimate the clinical value of pregnancy-associated plasma protein A (PAPP-A) measurement associated with plaque destabilization and rupture in prediction and monitoring of acute coronary syndromes (ACS) as well as to assess the predictive value of this biomarker in comparison to traditional myocardial infarction (MI) risk markers.

MATERIAL AND METHODS

The study included 119 patients in 2 investigated groups and one control group. PAPP-A assay was performed using manual ELISA kit, DRG. All other parameters were determined using automatic analyzers: Olympus and Dade Behring.

RESULTS

A statistically significant difference between PAPP-A concentration median value was found in the investigated group MI individuals' serum and control group individuals' serum (11.42 ng/ml and 7.22 ng/ml respectively, p = 0.003). PAPP-A assay had the highest specificity (83.3%) and sensitivity (53.8%), and therefore the highest clinical value. In patients with clinically and laboratory confirmed MI we proved that PAPP-A serum level is a clinically useful biomarker in ACS prediction, better than C-reactive protein (hsCRP) and fibrinogen (FBG) level.

CONCLUSIONS

The highest diagnostic efficiency for ACS prediction was proved for simultaneous panel assays consisting of 2-3 parameters (PAPP-A - hsCRP, PAPP-A - FBG, PAPP-A - hsCRP - FBG), while PAPP-A itself does not show characteristics necessary for it to be used as a biomarker for MI dynamic monitoring. It is possible that prothrombotic component is mainly responsible for repeated major adverse cardiac events, more than inflammatory process.

Effects of over-expression of TLR2 in transgenic goats on pathogen clearance and role of up-regulation of lysozyme secretion and infiltration of inflammatory cells

Background

Toll-like receptor 2 (TLR2) is important to host recognition of invading gram-positive microbes. In goats, these microbes can cause serious mastitis, anthrax, tetanus, and other problems. Transgenic goats constitutively over-expressing TLR2 in many tissues serve as a suitable model for the study of the role of TLR2 over-expression in bacterial clearance.

Results

Capra hircus TLR2 over-expression vector (p3S-LoxP-TLR2) was used to generate transgenic goats by egg microinjection. The integration efficiency was 8.57%. Real-time PCR and immunohistochemical results confirmed that the goats over-expressing the TLR2 gene (Tg) expressed more TLR2 than wild-type goats (WT). Monocyte-macrophages from the bloodstreams of transgenic goats were stimulated with synthetic bacterial lipoprotein (Pam3CSK4) and by the promotion of interleukin-6 (IL-6) and IL-10 expression in vitro. The oxidative damage was significantly reduced, and lysozyme (LZM) secretion was found to be up-regulated. Ear tissue samples from transgenic goats that had been stimulated with Pam3CSK4 via hypodermic injection showed that transgenic individuals can undergo the inflammation response very quickly.

Conclusions

Over-expression of TLR2 was found to decrease radical damage to host cells through low-level production of NO and MDA and to promote the clearance of invasive bacteria by up-regulating lysozyme secretion and filtration of inflammatory cells to the infected site.

Pregnancy-associated plasma protein predicts outcomes of percutaneous coronary intervention in patients with non-ST-elevation acute coronary syndrome

OBJECTIVE

Pregnancy-associated plasma protein A (PAPP-A) may play an important role in the development of acute coronary syndrome. This study aimed to investigate the relationship between the levels of circulating PAPP-A and the mid-term outcomes of percutaneous coronary intervention (PCI) in patients with non-ST-elevation acute coronary syndrome.

METHODS

The circulating PAPP-A levels and high-sensitivity C-reactive protein before PCI were measured in 129 patients with single coronary artery stenosis. The end point of clinical follow-up was cardiac death, nonfatal myocardial infarction, target vessel revascularization, and rehospitalization for angina.

RESULTS

During the follow-up of an average of 20.3 ± 5.2 months, a cardiac event was recorded in 25 patients (19.4%). The levels of PAPP-A (29.85 ± 19.51 mIu/L vs 20.47 ± 14.33 mIu/L, P = .007) and high-sensitivity C-reactive protein (5.63 ± 2.13 mg/L vs 4.11 ± 1.28 mg/L, P = .014) in patients with cardiac events were higher than in those without cardiac events. PAPP-A ≥ 11.33 mIu/L has a strong predictive value for a combined end point (risk ratio = 4.1; 95% confidence interval, 1.0-16.2; P = .037). Patients with lower PAPP-A levels (<11.33 mIu/L) had higher event-free survivals than patients with higher PAPP-A levels (log rank = 9.334, P = .025).

CONCLUSION

Circulating PAPP-A levels predict the mid-term outcomes of PCI in patients with non-ST-elevation acute coronary syndrome and single-vessel stenosis.

A pilot study of the clinical relevance of the relationship between the serum level of pregnancy-associated plasma protein A and the degree of acute coronary syndrome

Serum levels of pregnancy-associated plasma protein-A (PAPP-A), high-sensitivity C-reactive protein (hs-CRP) and tumour necrosis factor-alpha (TNF-alpha) were measured in 70 patients with acute coronary syndrome (ACS), comprising 18 with unstable angina (UA), 37 with acute myocardial infarction (AMI) and 15 with stable angina (SA); 15 healthy controls were also included. Levels of PAPP-A were significantly higher in the UA and AMI groups than in the SA and control groups. Levels of PAPP-A were similar in the SA and control groups, and higher in the ACS patients who were cardiac troponin T-negative (comprising UA and AMI patients) than in the control and SA groups. Levels of hs-CRP and TNF-alpha were significantly higher in the SA group than in the control group, significantly higher in the UA group than in the SA and control groups, and significantly higher in the AMI group than in all other groups. Levels of PAPP-A in ACS patients were positively correlated with levels of hs-CRP and TNF-alpha. It would seem, therefore, that PAPP-A is associated with inflammation and might be used to detect plaque instability and rupture before an increase in cardiac troponin T is detectable.

Pregnancy-associated plasma protein-A, a marker for outcome in patients suspected for acute coronary syndrome

OBJECTIVES

To examine if pregnancy-associated plasma protein-A (PAPP-A) in patients with chest pain, could identify patients at risk for death or myocardial infarction.

DESIGN AND METHODS

Patients admitted with chest pain and both normal ECG and normal biomarkers were evaluated by serial measurement of PAPP-A. Main outcome measures were mortality and non-fatal myocardial infarction.

RESULTS

Median age of patients included (415) was 67years and 43% were women. The risk of death or non-fatal myocardial infarction after 3 months was 15% in the highest quartile of circulating PAPP-A compared with 3% in the lowest quartile (relative risk 3.7, p<0.01). Corresponding numbers after 1 year were 24% and 10% (relative risk 2.4, p=0.01).

CONCLUSION

In patients admitted with chest pain and both normal ECG and normal biomarkers PAPP-A seems to be valuable for predicting patients at high risk of death or non-fatal myocardial infarction.

Usefulness of pregnancy-associated plasma protein A in patients with acute coronary syndrome

To investigate whether pregnancy-associated plasma protein-A (PAPP-A) is a prognostic marker in patients admitted with high-risk acute coronary syndrome. In patients admitted with high-risk non-ST-segment elevation acute coronary syndrome (NSTE-ACS) and ST-segment elevation myocardial infarction (STEMI), risk stratification is primarily determined by the markers of myocardial necrosis and known demographic risk profiles. However, it has recently been proposed that the presence and extent of vulnerable plaques might influence the prognosis significantly. A marker for the vulnerable plaque could identify patients at high risk who would potentially benefit from intensive treatment and surveillance. Two populations of consecutive patients admitted with high-risk NSTE-ACS (n = 123) and STEMI (n = 314) were evaluated with serial measurements of PAPP-A. The incidence of mortality and nonfatal myocardial infarction was prospectively registered for 2.66 to 3.47 years. In the patients with high-risk NSTE-ACS, PAPP-A was related to the risk of nonfatal myocardial infarction (p = 0.02) and death (p = 0.03). This result was consistent on multivariate analysis of the combination of mortality or nonfatal myocardial infarction (odds ratio 2.65, 95% confidence interval 1.40 to 5.03) but not for mortality alone (p = NS). In patients with STEMI, PAPP-A was related to the risk of death (p = 0.01) but not the composite outcome of myocardial infarction and death. This was also true after adjustment for other univariate predictors of death (odds ratio 2.19, 95% confidence interval 1.16 to 4.16). In conclusion, PAPP-A seems to be valuable in predicting the outcomes of patients admitted with high-risk NSTE-ACS or STEMI.

Biomarkers in Acute Coronary Syndrome

BACKGROUND: Evaluation of patients who present to the hospital with acute undifferentiated chest pain or other symptoms and signs suggestive of Acute Coronary Syndrome (ACS) is often a clinical challenge. The initial assessment, requiring a focused history (including risk factors analysis), a physical examination, an electrocardiogram (EKG) and serum cardiac marker determination, is time-consuming and troublesome. Recent investigations have indicated that increases in biomarkers of necrosis, inflammation, ischemia and myocardial stretch may provide earlier assessment of overall patient risk, help in identifying the adequate diagnostic and therapeutic management for each patient and allow for prevention of substantial numbers of new events. APPROACH AND CONTENT: The purpose of this review is to provide an overview of the characteristics of several biomarkers that may have potential clinical utility to identify ACS patients. Patho-physiology, analytical and clinical characteristics have been evaluated for each marker, underlying the properties for potential routine clinical use. SUMMARY: The biomarkers discussed in this review are promising and might lead to improved diagnosis and risk stratification of patients with ACS, however their clinical application requires further studies. It is important to define their clinical role as diagnostic markers, their predictive value and the specificity, standardization and detection limits of the assays.

Present and Future Biochemical Markers for Detection of Acute Coronary Syndrome

The use of biochemical markers in the diagnosis and management of patients with acute coronary syndrome has increased continually in recent decades. The development of highly sensitive and cardiac-specific troponin assays has changed the view on diagnosis of myocardial infarction and also extended the role of biochemical markers of necrosis into risk stratification and guidance for treatment. The consensus definition of myocardial infarction places increased emphasis on cardiac marker testing, with cardiac troponin replacing creatine kinase MB as the "gold standard" for diagnosis of myocardial infarction. Along with advances in the use of more cardiac-specific markers of myocardial necrosis, biochemical markers that are involved in the progression of atherosclerotic plaques to the vulnerable state or that signal the presence of vulnerable plaques have recently been identified. These markers have variable abilities to predict the risk of an individual for acute coronary syndrome. The aim of this review is to provide an overview of the well-established markers of myocardial necrosis, with a special focus on cardiac troponin I, together with a summary of some of the potential future markers of inflammation, plaque instability, and ischemia.

Pregnancy-associated plasma protein-A (PAPP-A) and cardiovascular risk

The search for markers to improve risk prediction for individuals at risk of developing serious cardiovascular events is ongoing. New markers of coronary artery disease progression have been identified in recent years, among which, circulating levels of pregnancy-associated plasma protein-A (PAPP-A) offer an interesting profile. PAPP-A may play a role in the development of atherosclerotic lesions and represent also a marker of atheromatous plaque instability and extent of cardiovascular disease. PAPP-A has been shown to be a marker of adverse outcome in both acute coronary syndrome and stable coronary disease patients. The present article reviews currently available evidence supporting a role for PAPP-A as a marker of cardiovascular risk and discusses some of the pitfalls that may limit its use in clinical practice.

Pregnancy associated plasma protein A, a novel, quick, and sensitive marker in ST-elevation myocardial infarction

Traditional biomarkers in acute coronary syndromes reflect myocardial necrosis but not the underlying arteriosclerotic disease. Pregnancy-associated plasma protein A (PAPP-A) is a new biomarker in acute coronary syndromes that detects vulnerable plaques in arteriosclerotic disease and identifies acute coronary syndromes earlier than traditionally used biomarkers. Information regarding circulating PAPP-A levels in patients with ST elevation myocardial infarctions (STEMIs) is limited and contradictory. The aim of the present study was to describe the presence and time-related pattern of circulating PAPP-A levels in patients with STEMIs. Consecutive patients (n = 354) referred for primary percutaneous intervention because of STEMI were included in the study. Blood samples for the analysis of PAPP-A, creatine kinase-MB (CKMB), and troponin T were drawn at admission and every 6 to 8 hours until biomarkers of myocardial necrosis were consistently decreasing. PAPP-A was measured using a newly developed sandwich enzyme-linked immunosorbent assay technique based on 2 monoclonal antibodies. In total, 1,091 PAPP-A, 1,049 troponin T, and 1,016 CKMB samples were analyzed. Mean PAPP-A values at admission were significantly higher in patients with STEMIs than in those with non-ST elevation myocardial infarctions or unstable angina pectoris (27.6 vs 12.2 mIU/L, p <0.01). In samples drawn <2 hours after admission, the sensitivity of PAPP-A was superior (93%) to that of CKMB (60%) and troponin T (61%). In conclusion, PAPP-A levels are elevated in >90% of patients presenting with STEMIs if measured <6 hours after the onset of symptoms or <2 hours of primary percutaneous coronary intervention. In the early stages of STEMI, PAPP-A seems to be a more sensitive marker of myocardial infarction than CKMB and troponin T.

Pregnancy-associated plasma protein A in non-cardiac conditions

OBJECTIVE

PAPP-A is a promising new marker in coronary heart disease. It is important to investigate its specificity in order to establish its clinical utility as a marker of coronary heart disease.

DESIGN AND METHODS

PAPP-A was measured within 24 h following hospital admission in 1448 consecutive patients admitted with diagnoses other than acute coronary syndromes.

RESULTS

PAPP-A was detectable (> or = 4.0 mIU/L) in 278 (19.2%) patients, among whom the mean level was 6.3 mIU/L (95% C.I., 6.1-6.5 mIU/L). The 95 and 99 percentiles for PAPP-A were 7.3 and 9.4 mIU/L, respectively. There was no difference in the mean PAPP-A of different diagnoses (p=0.33). None of the specific diagnoses known to influence established coronary markers appeared to influence the level of circulating PAPP-A.

CONCLUSION

PAPP-A is low in patients without known coronary heart disease. PAPP-A levels seem to be a potentially highly specific marker for heart disease.

Effect of hemodiafiltration on pregnancy-associated plasma protein A (PAPP-A) and related parameters

BACKGROUND

Dialysis patients are at high risk of vascular/cardiovascular complications with multifactorial pathogenesis, and pregnancy-associated plasma protein A (PAPP-A) is one of the new markers related to cardiovascular risk. Because hemodiafiltration (HDF) is supposed to be better for cardiovascular status, the aim of this study was to describe whether it has any advantage concerning changes of PAPP-A and related molecules during the session in comparison with hemodialysis (HD).

METHODS

The studied group consisted of 20 chronic hemodialysis patients. In each patient, PAPP-A and related parameters-IGFBP-4 (insulin like growth factor binding protein), IGF-I (insulin like growth factor), and two MMPs (matrix metalloproteinases)-2 and 9-were determined both during a single online HDF session (high-flux polysulfone membrane HF80, postdilution) and during a single HD session (low-flux polysulfone membrane F6, F7) at time 0 (start), 15 min, 120 min, and 240 min (end) of the session.

RESULTS

PAPP-A, elevated at baseline in dialysis patients, changes significantly both during HDF and HD without significant differences between these two procedures (mean levels during HDF were 24.3, 53.9, 24.3, and 27.3 mIU/L). It increases more than two-fold from 0 to 15 min of the session (p < 0.001) and then decreases until the end of the session (p < 0.001). MMP-2 decreased slightly during both sessions (p < 0.001), and changes of other molecules were only minimal.

CONCLUSION

A single HDF session compared to HD has no advantage in the decrease of PAPP-A and other tested molecules, all of them related to cardiovascular risk. Studies aimed at a long-term effect of both procedures on these parameters would be needed to further evaluate these therapeutical strategies.

Optimisation of sandwich ELISA based on monoclonal antibodies for the specific measurement of pregnancy-associated plasma protein (PAPP-A) in acute coronary syndrome

OBJECTIVES

PAPP-A has become the principal biochemical serum marker in first trimester screening for Down syndrome, the original data being based on results of a radioimmunoassay (RIA). Recent observations using sandwich ELISA technology have proposed PAPP-A as a potential marker in patients with acute coronary syndrome (ACS). The aims of the present study were to demonstrate (i) the importance of antibody specificity, (ii) the potential pitfalls in changing assay technology, (iii) the importance of strict definition of technology, and (iv) the application of a well-defined assay technology on sera from patients with ACS.

DESIGN AND METHODS

Candidate monoclonal antibodies (Mab) were identified by immunohistochemistry, Western blot and the absence of positive signals (ELISA) with normal, non-pregnant serum as antigen source. The ELISA technology was standardized against the original PAPP-A RIA and the WHO reference preparation (WHO 78/610). Results different from those obtained by the original RIA led to ELISA modifications with respect to dilution buffer and enzymatic digestion of the Mab.

RESULTS

The first generation ELISA revealed serum measurements from a pool of non-pregnant (n=103) individuals which, compared to the RIA, seemed to be false positive. The false positive reaction was abolished by addition of bovine serum (BS) to the dilution buffer. Subsequent analysis of individual sera (n=103) indicated that 7/103 were still false positive. This reaction was eliminated by introduction of F(ab')(2)-fragment of the indicator antibody. This modified ELISA revealed that serum PAPP-A levels in ACS were statistically significantly higher than in controls (p<0.001). Moreover, serum PAPP-A in ACS patients with ST-segment elevation (STEMI) were higher (p<0.001) compared to patients without ST-segment elevation (NSTEMI). Immunohistochemical analysis failed to identify PAPP-A in the atherosclerotic plaques.

Measurement and clinical significance of circulating PAPP-A in ACS patients

BACKGROUND

The rupture of coronary atherosclerotic plaque and subsequent thrombus formation are major events underlying acute coronary syndromes (ACS). Pregnancy associated plasma protein A (PAPP-A), a biomarker of plaque rupture, has been studied in patients with ACS. This review aimed to provide an overview of clinical utility of PAPP-A in ACS patients and analytical issues adhering to immunological PAPP-A measurement.

METHODS

The literature relating to PAPP-A in ACS, the molecular structure and immunodetection of PAPP-A was reviewed. PubMed was used to search the relevant articles published from 1974 to 2006.

RESULTS

Higher PAPP-A concentrations have been found in patients with ACS than in patients with stable angina and subjects without coronary artery disease. Elevated PAPP-A concentrations have also been shown to associate with adverse cardiac events in ACS patients. The prognostic value of PAPP-A appears to be independent of cardiac troponins. Noteworthy, the PAPP-A form that accounts for increase in ACS is uncomplexed with the proform of eosinophil major basic protein (proMBP). However, PAPP-A assays applied in clinical studies published thus far detect total PAPP-A. Consequently, the clinical value may be non-optimal when total PAPP-A is measured in ACS patients. In addition, the clinical value can also be affected by the analytical factors that exert an effect on the performance of PAPP-A assays.

CONCLUSIONS

PAPP-A appears to be a very promising biomarker useful in the clinical management of ACS patients. However, more prospective and interventional studies with carefully established immunoassays are required to validate its clinical utility.

Pregnancy-associated plasma protein-A: an emerging cardiac biomarker

Pregnancy associated plasma protein-A (PAPP-A), originally discovered as a glycoprotein found in the serum of pregnant women, is emerging as a potential biomarker of plaque instability. It is produced by the syncytiotrophoblasts of the placenta and circulates in the form of an approximately 500 kDa heterotetramer. In addition, PAPP-A is present in the sera of men and non-pregnant women at much lower levels in the form of a homodimer, and is produced by a number of different non-placental cell types, including fibroblasts, vascular endothelial cells, and vascular smooth muscle cells. The identification of PAPP-A as a member of the metzincin metalloproteinase superfamily, its synthesis by cell types involved in atherogenesis, and its role in insulin-like growth factor-I regulation has led to the hypothesis that PAPP-A is involved in atherosclerotic plaque progression and instability. Serum PAPP-A may be a biomarker for the detection of vulnerable, unstable plaque. Although early reports appear to validate this hypothesis, adoption of PAPP-A as a clinical cardiac biomarker will need assay standardization and further clinical validation. The clinical validation will require a large and diverse patient population, a clearly defined and uniform diagnostic strategy, incorporation of multiple biomarkers in addition to PAPP-A, and measurement of outcomes data.

Increased pregnancy-associated plasma protein-A as a marker for peripheral atherosclerosis: results from the Linz Peripheral Arterial Disease Study

BACKGROUND

The aim of the present investigation was to test the hypothesis that pregnancy-associated plasma protein-A (PAPP-A), a zinc-binding metalloproteinase implicated in acute coronary syndrome, is associated with atherosclerotic peripheral arterial disease (PAD).

METHODS

The study comprised 433 patients with symptomatic atherosclerotic PAD (i.e., chronic limb ischemia) and 433 controls matched to the patients with PAD in a 1:1 design by sex, age (+/-2 years), and diabetes mellitus status. Serum PAPP-A concentrations were measured with an enzymatically amplified 2-step sandwich-type immunoassay.

RESULTS

The entire study sample included 612 male and 254 female patients with a median age of 68 years. The median PAPP-A value was higher in the patients with PAD than in the referents (0.81 vs 0.64 mU/L; P <0.001). After we adjusted for several possible confounding variables with multivariable logistic regression, odds ratios for PAD were 1.59 (95% confidence interval, 1.00-2.52; P = 0.049), 2.28 (1.45-3.61; P <0.001), and 2.86 (1.78-4.59; P <0.001) in the 2nd, 3rd, and 4th quartiles of serum PAPP-A concentrations compared with the first quartile. In the present study, PAPP-A added to the predictive value of other markers commonly in use.

CONCLUSIONS

PAPP-A was associated with atherosclerotic PAD in the elderly sample studied. Because atherosclerotic PAD is considered an indicator of systemic atherosclerotic disease in elderly patients, the present results indicate that circulating PAPP-A may be a marker for systemic atherosclerotic disease.

Immunoassays Developed for Pregnancy-Associated Plasma Protein-A (PAPP-A) in Pregnancy May Not Recognize PAPP-A in Acute Coronary Syndromes

Background: Pregnancy-associated plasma protein-A (PAPP-A) concentrations are increased in the circulation of patients with acute coronary syndromes (ACS) and are associated with future adverse cardiac events. PAPP-A in ACS differs from PAPP-A in pregnancy in that PAPP-A in ACS is not complexed with the proform of eosinophil major basic protein (proMBP). We investigated the effect of antibody selection on the utility of PAPP-A assays for measurement of PAPP-A in pregnancy and/or ACS, and whether immunoassays for PAPP-A in pregnancy are suitable for PAPP-A in ACS.

Methods: We constructed 2-site sandwich time-resolved immunofluorometric assays using 22 monoclonal antibodies raised against pregnancy serum PAPP-A. All antibodies were studied in pairs, with each antibody used as either capture or tracer. We compared the reactivity of each antibody combination with PAPP-A/proMBP complex derived from pregnancy sera or with uncomplexed PAPP-A extracted from atherosclerotic plaques. Recombinant human PAPP-A and proMBP were also used to determine the specificity of the antibodies. We confirmed all major findings with serum samples collected from patients with myocardial infarction.

Results: Six monoclonal antibodies reacted with the proMBP subunit of the PAPP-A/proMBP complex. Epitopes of 3 proMBP-reactive antibodies largely overlapped, but were well separated from those of another group of 3 proMBP-reactive antibodies. Assays using any of the 6 proMBP-reactive antibodies failed to detect PAPP-A in ACS. In addition, some 2-site assays capable of detecting PAPP-A in pregnancy were almost incapable of detecting PAPP-A in ACS, although the individual epitopes remained detectable in PAPP-A in ACS.

Conclusions: Immunoassays developed for PAPP-A in pregnancy may not be suitable for PAPP-A in ACS. Assays for PAPP-A in ACS should be based on careful antibody selection and subjected to extensive testing with clinical ACS samples.

Pregnancy-associated plasma protein A: a biomarker in acute ST-elevation myocardial infarction (STEMI)

BACKGROUND

Elevated circulating levels of pregnancy-associated plasma protein A (PAPP-A), a novel marker of atherosclerotic plaque instability, are associated with increased risk of future cardiac events in patients with acute coronary syndromes (ACS). However, little is known of the kinetics or clinical significance of circulating PAPP-A after plaque rupture in acute ST-elevation myocardial infarction (STEMI).

AIM

To evaluate the 48-hour release of pregnancy-associated plasma protein A (PAPP-A) and its association with 12-month outcome in patients with acute ST-elevation myocardial infarction (STEMI).

METHODS

Sixty-two consecutive STEMI patients were included (40 men and 22 women, median age 67.5 years (range 34-84)), of whom 54 (87.1%) received reperfusion therapy. PAPP-A was measured at admission and 6-12, 24 and 48 hours thereafter. In 14 patients, samples were obtained also at 1, 2 and 4 hours.

RESULTS

There was an early peak of circulating PAPP-A during the first 12 hours from symptom onset, followed by rapid normalization. A second, late PAPP-A elevation was noticed in 20/62 patients (32.3%). Admission PAPP-A >10.0 mIU/L (highest tertile) was associated (P = 0.049) with increased 12-month risk of cardiovascular death or non-fatal myocardial infarction. Moreover, the combination of failed early reperfusion together with late PAPP-A elevation was strongly (7/13 versus 10/49 patients, P = 0.016) associated with adverse outcome. Admission PAPP-A did not correlate with admission C-reactive protein or cardiac troponin I.

CONCLUSIONS

PAPP-A is elevated early in STEMI and then declines rapidly, a pattern consistent with release from the ruptured plaque. The variability of PAPP-A kinetics at 48 hours reflects the success of reperfusion. This study also shows that PAPP-A may have prognostic value in STEMI.

Pregnancy-associated plasma protein-a is involved in matrix mineralization of human adult mesenchymal stem cells and angiogenesis in the chick chorioallontoic membrane

Pregnancy-associated plasma protein A (PAPP-A) is an IGF binding protein 4 protease that can function to increase local IGF-I bioavailability. Aside from its assumed role during pregnancy, in vitro and in vivo studies have indicated roles for PAPP-A in IGF-I-mediated wound healing, vascular repair, and bone formation. Because bone morphogenetic protein 2 (BMP-2) is known to up-regulate Igf-I gene expression, we hypothesized that PAPP-A may be involved in BMP-2 mechanisms in bone formation. To test this hypothesis, we quantified gene expression of Papp-A in response to BMP-2 treatment and runt-related transcription factor 2, Osterix, and Igf-I in response to PAPP-A protein treatment in human adult mesenchymal stem cells. Our results demonstrate that BMP-2 directly up-regulated Papp-A gene and protein expression. Purified PAPP-A protein directly up-regulated runt-related transcription factor 2 and Igf-I gene expression but not Osterix. When added in combination with recombinant human BMP-2, PAPP-A increased matrix mineralization in the absence of dexamethasone. PAPP-A further demonstrated an angiogenic effect in the chick chorioallontoic membrane, which implicates a critical developmental role and possible therapeutic potential. Our findings suggest that PAPP-A functions in the formation of mineralized tissues through direct up-regulation of key genes. Furthermore, PAPP-A is involved in the formation of new blood vessels, which is essential for proper bone regeneration.

Relationship among pregnancy associated plasma protein-A levels, clinical characteristics, and coronary artery disease extent in patients with chronic stable angina pectoris

AIMS

To assess, in chronic stable angina (CSA) patients, the relationship among clinical characteristics and cardiovascular risk factors, extent of coronary artery disease (CAD), and pregnancy-associated plasma protein-A (PAPP-A) levels.

METHODS AND RESULTS

We studied 643 CSA patients (63+/-10 years, 482 men) undergoing diagnostic coronary angiography; 97 with angiographically normal coronary arteries or <50% stenosis, 127 with single vessel disease (VD), and 419 with multi-VD. Patients' age, gender, cardiovascular risk factors, body mass index, history of previous myocardial infarction, angina class, left ventricular ejection fraction (LVEF), and treatment were assessed at study entry. PAPP-A levels (mIU/L) were higher in men than in women (6.2+/-2.4 vs. 5.2+/-1.8; P<0.001) and in hypertensive vs. normotensive patients (6.4+/-2.8 vs. 5.8+/-2.1; P=0.01). PAPP-A correlated directly with age (r=0.19, P<0.001) and inversely with LVEF (r=-0.11, P=0.01). Patients with multivessel disease (VD) had higher PAPP-A levels (6.45+/-2.58) than those with single-VD (5.49+/-1.54, P<0.001) or normal coronaries (4.62+/-1.17, P<0.001). Male gender, age, history of a previous MI, hypercholesterolaemia, and PAPP-A levels were independent predictors for the presence of CAD.

CONCLUSION

In CSA patients PAPP-A levels correlate with age, male gender, hypertension, and CAD extent. In the present study, PAPP-A was an independent predictor for the presence and extent of CAD.

PAPP-A: a marker of plaque instability. Is it ready for prime time?

Pregnancy-associated plasma protein-A (PAPP-A) is a zinc-binding metalloproteinase that was first identified circulating in the serum of pregnant women, but has recently been suggested to be a predictor of risk for cardiovascular events. Publications on PAPP-A, primarily from the last 4-5 years, were reviewed extensively. A special emphasis was placed on those that address the development of methods for the detection of PAPP-A in human serum/plasma and those that study the diagnostic/prognostic accuracy of PAPP-A in patients with acute coronary syndrome. This review shall focus on the possible mechanism of action of PAPP-A, clinical studies involving PAPP-A, PAPP-A assays and its molecular structure. All clinical studies to date related to the diagnostic/prognostic accuracy of PAPP-A (a total of eight studies) were included. They suggest that elevations in PAPP-A correlate with higher risk for the development of cardiovascular adverse events. However, there are conflicting data as to whether PAPP-A levels correlate with cardiac troponins or C-reactive protein. Thus, there is room for speculation as to whether PAPP-A is involved in inflammatory processes, and as to what its role is in plaque rupture and subsequent cardiac ischemic events. Furthermore, new insights into the molecular structure of PAPP-A could aid in the development of more specific assays that may help unravel the clinical utility of PAPP-A.

Circulating pregnancy-associated plasma protein A is not an early marker of acute myocardial infarction

OBJECTIVE

The purpose of this study was to assess whether serum levels of pregnancy-associated plasma protein A (PAPP-A) are elevated early in patients with acute myocardial infarction (AMI).

DESIGN AND METHODS

We measured serum levels of PAPP-A in 80 patients with AMI and in 80 age-matched healthy control subjects. The mean (+/-SEM) time from onset of symptoms to blood sampling was 6.3 +/- 2.8 h in the group with AMI.

RESULTS

The PAPP-A levels did not differ between the control group and the AMI group (1.24 +/- 0.07 vs. 1.29 +/- 0.02 mIU/l; P = 0.54).

CONCLUSIONS

Measurement of serum PAPP-A does not seem to be a useful early marker for AMI.

Molecular Distinction of Circulating Pregnancy-Associated Plasma Protein A in Myocardial Infarction and Pregnancy

Background: In the blood of pregnant women, pregnancy-associated plasma protein A (PAPP-A) is present as a covalent complex with the proform of eosinophil major basic protein (proMBP). Recently, increased serum concentrations of PAPP-A have been found in acute coronary syndromes (ACS). The aim of this study was to investigate whether the circulating PAPP-A in ACS is the same as that in pregnancy.

Methods: We developed two time-resolved immunofluorometric assays based on a relative epitope map constructed by the use of 17 monoclonal antibodies. One assay, which measured total PAPP-A, used two PAPP-A subunit-specific antibodies. The other assay, which measured PAPP-A/proMBP complex, used one proMBP subunit-specific antibody and one PAPP-A subunit-specific antibody. Serum samples from four patients with myocardial infarction (MI), three pregnant women in their first trimester, and one in her third trimester were fractionated by gel filtration on a Superose™ 6 precision column. The two assays were used to analyze fractions obtained by gel filtration as well as serum samples serially collected from four other MI patients.

Results: Pregnancy-related PAPP-A was eluted as a single peak with a molecular mass of ∼700 kDa, whereas ACS-related PAPP-A was also eluted as a single peak but with a molecular mass of ∼530 kDa. Pregnancy-related PAPP-A was detected equally by the two assays, whereas increased ACS-related PAPP-A was detected only by the assay for total PAPP-A.

Conclusions: Our results provide the first evidence that circulating ACS-related PAPP-A is different from circulating pregnancy-related PAPP-A in that it is not complexed with proMBP. These findings provide a solid foundation for the design of immunoassays to accurately measure atherosclerosis-associated plasma protein A in the circulation.

Pregnancy-Associated Plasma Protein A and Its Endogenous Inhibitor, the Proform of Eosinophil Major Basic Protein (proMBP), Are Related to Complex Stenosis Morphology in Patients With Stable Angina Pectoris

Background— The metalloproteinase pregnancy-associated plasma protein-A (PAPP-A) has been implicated in coronary plaque disruption. Its endogenous inhibitor, the proform of eosinophil major basic protein (proMBP), may also play a role in this process. Atheromatous plaque disruption often presents as complex angiographic lesions. We sought to assess whether PAPP-A, proMBP, and PAPP-A/ProMBP ratio are markers of angiographic plaque complexity in patients with chronic stable angina.

Methods and Results— We studied 396 stable angina patients (age 63±10 years, 230 men) of whom 289 had angiographically documented coronary artery disease (≥75% stenosis). All coronary stenoses ≥30% diameter reduction (n =531 in 322 patients) were assessed and classified as complex (n =228) or smooth (n =303) by previously validated criteria. PAPP-A, proMBP, and C-reactive protein (hs-CRP) serum levels were measured by ELISA. Patients with complex coronary stenoses had a significantly ( P <0.001) higher PAPP-A/proMBP ratio (3.1±1.2 versus 2.7±0.8×10 −3 ) and PAPP-A levels (5.9±1.6 versus 5.1±1.4 mIU/L) than those without. On univariate analysis, male gender ( P <0.001), age ( P <0.001), previous history of myocardial infarction ( P =0.013), reduced ejection fraction ( P <0.001), severe coronary artery disease ( P <0.001), aspirin treatment ( P <0.001), PAPP-A levels ( P <0.001), and PAPP-A/proMBP ratio ( P <0.001) were correlated with the number of complex stenoses. Multiple regression analysis showed that male gender, age, severe coronary artery disease, and PAPP-A/proMBP ratio were independent predictors of the number of angiographically complex stenoses.

Conclusions— In patients with stable angina, PAPP-A and PAPP-A/proMBP ratio are associated with angiographic plaque complexity.

Biochemical markers of cardiac diseases

This article reviews the current contribution of the determination of biochemical markers to clinical cardiology and discusses some important developments in this field. Biochemical markers play a pivotal role in the diagnosis and management of patients with acute coronary syndrome (ACS), as witnessed by the incorporation of cardiac troponins into new international guidelines for patients with ACS and in the redefinition of myocardial infarction. Despite the success of cardiac troponins, there is still a need for development of early markers that can reliably rule out ACS from the emergency room at presentation and detect myocardial ischemia also in the absence of irreversible myocyte injury. Under investigation are two classes of indicators: markers of early injury/ischemia and markers of coronary plaque instability and disruption. Finally, with the characterization of the cardiac natriuretic peptides, Laboratory Medicine is also assuming part in the assessment of cardiac function.

Circulating pregnancy-associated plasma protein a predicts outcome in patients with acute coronary syndrome but no troponin I elevation

BACKGROUND

Risk stratification in troponin (cTn)-negative acute coronary syndrome (ACS) remains a clinical challenge. We investigated the predictive value of circulating pregnancy-associated plasma protein A (PAPP-A), a novel marker of atherosclerotic plaque activity, in these patients.

METHODS AND RESULTS

Two hundred consecutive hospitalized ACS patients were included, of whom 136 (69 men and 67 women; mean+/-SD age, 66+/-16 years) remained cTnI-negative for up to 24 hours. PAPP-A was measured at admission, 6 to 12 hours, and 24 hours. During 6-month follow-up, 26 (19.1%) of the cTnI-negative patients reached a primary end point (cardiovascular death, myocardial infarction, or revascularization). At a cutoff level of 2.9 mIU/L, elevated PAPP-A was an independent predictor of adverse outcome (adjusted risk ratio [RR], 4.6; 95% confidence interval, 1.8 to 11.8; P=0.002). Another independent predictor was admission CRP >2.0 mg/L (RR, 2.6; P=0.03).

CONCLUSIONS

Measurement of plasma PAPP-A, a zinc-binding matrix metalloproteinase, is a strong independent predictor of ischemic cardiac events and need of revascularization in patients who present with suspected myocardial infarction but remain troponin negative.