Skip Navigation



European Heart Journal Advance Access published online on September 2, 2008
European Heart Journal, doi:10.1093/eurheartj/ehn382
This Article
Right arrow Abstract Freely available
Right arrow FREE Full Text (PDF) Freely available
Right arrow All Versions of this Article:
29/22/2713    most recent
ehn382v1
Right arrow E-letters: Submit a response
Right arrow Alert me when this article is cited
Right arrow Alert me when E-letters are posted
Right arrow Alert me if a correction is posted
Services
Right arrow Email this article to a friend
Right arrow Similar articles in this journal
Right arrow Similar articles in PubMed
Right arrow Alert me to new issues of the journal
Right arrow Add to My Personal Archive
Right arrow Download to citation manager
Right arrowRequest Permissions
Right arrow Disclaimer
Google Scholar
Right arrow Articles by Tziakas, D. N.
Right arrow Articles by Boudoulas, H.
Right arrow Search for Related Content
PubMed
Right arrow PubMed Citation
Right arrow Articles by Tziakas, D. N.
Right arrow Articles by Boudoulas, H.
Social Bookmarking
Add to CiteULike   Add to Connotea   Add to Del.icio.us  
What's this?

Published on behalf of the European Society of Cardiology. All rights reserved. © The Author 2008. For permissions please email: journals.permissions@oxfordjournals.org

Interleukin-8 is increased in the membrane of circulating erythrocytes in patients with acute coronary syndrome

Dimitrios N. Tziakas1,*, Georgios K. Chalikias1, Ioannis K. Tentes2, Dimitrios Stakos1, Sofia V. Chatzikyriakou1, Konstantina Mitrousi1, Alexandros X. Kortsaris2, Juan Carlos Kaski3 and Harisios Boudoulas4

1 University Cardiology Department, Medical School, Democritus University of Thrace, Voulgaroktonou 23, 68100 Alexandroupolis, Evros, Greece
2 Biochemistry Department, Medical School, Democritus University of Thrace, Alexandroupolis, Greece
3 Cardiovascular Biology Research Centre, St George’s Hospital, University of London, London, UK
4 Clinical Research Center, Biomedical Research Foundation, Academy of Athens, Athens, Greece

Received 19 February 2008; revised 22 July 2008; accepted 25 July 2008.

* Corresponding author. Tel: +30 25510 35596 (home)/+30 25510 76205 (office), Fax: +30 25510 76245, Email: dtziakas{at}med.duth.gr


   Abstract
Top
 Abstract
Introduction
 Methods
 Results
 Discussion
 References
 
Aims: Studies have shown that erythrocyte membranes are present within necrotic cores in atherosclerotic plaques, and that circulating erythrocytes in patients with acute coronary syndrome (ACS) have increased total cholesterol content (CEM). Interleukin-8 (IL-8) binds to erythrocytes and during intraplaque haemorrhage it is released into the plaque and thus may contribute to inflammatory cascade and atherosclerotic plaque instability. The present study was undertaken to test the hypothesis that erythrocyte membrane IL-8 is elevated in patients with ACS compared with those with chronic stable angina (CSA).

Methods and results: Consecutive patients who presented with CSA (n = 120, 92 men, 62 ± 9 years), ACS (n = 118, 90 men, 62 ± 10 years) or with chest pain who had normal coronary arteries (n = 36, 26 men, 60 ± 7 years), were studied prospectively. IL-8 concentrations in erythrocyte membranes (rIL-8) and in plasma (pIL-8), C-reactive protein (CRP) and CEM were measured. rIL-8 levels [mean ± 1 SD (standard deviation)] were higher in ACS (102.9 ± 70.1 pg/mL) compared with CSA (44.7 ± 22.8 pg/mL) (P < 0.001). No difference in pIL-8 levels between the two coronary artery disease groups was observed (P = 0.280). Serum CRP levels were correlated with rIL-8 levels (r = 0.294, P < 0.001); no association was found between CRP and pIL-8 levels (r = 0.025, P = 0.706). Further, rIL-8 had an independent association with ACS, when CRP and CEM were taken into consideration.

Conclusion: This study shows for the first time that rIL-8 content was significantly higher in ACS, compared with CSA. These findings endorse results from our previous studies suggesting that erythrocytes may play an important role in the development of unstable atherosclerotic plaque.

Key Words: Erythrocyte membranes • Interleukin-8 • Cholesterol content • Acute coronary syndrome • Chronic stable angina


   Introduction
Top
 Abstract
 Introduction
Methods
 Results
 Discussion
 References
 
It has been suggested that erythrocytes could play an active role in the development of atherosclerotic plaque and in plaque instability.1,2 Studies have shown that the necrotic lipid core of atherosclerotic plaques contains erythrocyte membranes3,4 and that total cholesterol levels in the membrane of circulating erythrocytes (CEM) was increased in patients with acute coronary syndrome (ACS) compared with patients with chronic stable angina (CSA).5

It has been proposed that red blood cells (RBC) rich in cholesterol may contribute to atherosclerotic plaque expansion leading to its instability.1,6 It is also possible that RBC membranes released within the lipid core during intraplaque haemorrhage, which contain inflammatory mediators, such as interleukin-8 (IL-8) may contribute to plaque growth and instability.2,4,7–12

The present study was undertaken to investigate whether patients with ACS have higher erythrocyte IL-8 (rIL-8) concentrations compared with patients with CSA.


   Methods
Top
 Abstract
 Introduction
 Methods
Results
 Discussion
 References
 
Patients population
From November 2006 to September 2007, 312 consecutive patients who were admitted to our institution for the assessment of their coronary artery status were recruited prospectively. From those, 20 who did not meet the inclusion criteria (described later), five who refused to give their informed consent and 13 in whom data collection was not complete were excluded from further analysis. The remaining 274 patients represented the study population. Of those, 120 had CSA, and 118 ACS, 58 (49%) with ST-segment elevation myocardial infarction (STEMI), 32 (27%) with non-STEMI (NSTEMI) and 28 (24%) with unstable angina (UA). In addition, 36 patients with chest pain and angiographically normal coronary arteries (NCA) were also included in the study.

CSA was defined as typical exertional chest pain, relieved by rest and/or nitrates, without a change in frequency or severity for 3 months prior to study entry, and one of the following: a positive response (>1 mm ST-segment depression) on the exercise stress test; reversible or fixed myocardial perfusion defect(s) during myocardial perfusion scintigraphy; segmental wall motion abnormalities at rest or during stress echocardiography.13

Myocardial infarction (MI) was diagnosed in the presence of prolonged (>20 min) chest pain, with ST-segment changes suggestive of myocardial ischaemia or necrosis on the standard 12-lead electrocardiogram (ECG) associated with increased serum markers of myocardial necrosis measured on at least two occasions during the first 24 h after the index event (increase above the 99th percentile of the upper reference limit of creatine kinase-myocardial fraction and troponin-T).14

Only patients with spontaneous MI (type 1) were recruited. Patients presented with MI secondary to ischaemia due to increased oxygen demand or decreased supply (type 2), after cardiac arrest with successful resuscitation and findings consistent with myocardial ischaemia (type 3), MI associated with percutaneous coronary intervention within the first 48 h after the procedure (type 4a) or stent thrombosis, as documented by coronary angiography (type 4b), or MI associated with coronary artery bypass grafting within the first 72 h after the procedure (type 5)14 were not included in the study.

MI patients were considered to have STEMI when an elevation of the ST-segment ≥0.2 mV was detected in V1 through V3 and/or an elevation ≥0.1 mV was found in two or more contiguous ECG leads.15 NSTEMI was diagnosed in the presence of new horizontal or down-sloping ST-segment depression (≥0.05 mV) and/or T-wave inversion (≥0.1 mV) in two or more contiguous leads.16 UA was defined as anginal pain at rest fulfilling Braunwald’s IIIb criteria with transient significant ischaemic ST-segment or T-wave changes, or both, without biochemical evidence for myocardial damage.17

Patients with unstable coronary artery disease (CAD) (STEMI, NSTEMI, UA) who underwent urgent cardiac catheterization were not included in the study, since the acute event may have influenced laboratory measurements.

NCA patients group comprised individuals with CAD risk factors who presented with chest pain and were found to have NCA on coronary angiography.

Patients with a history of excessive alcohol intake, haematological, renal, liver, or thyroid diseases, or malignancies were excluded. Furthermore, patients with infectious or autoimmune diseases, familial hyperlipidaemia, and those who underwent surgical procedures in the preceding 3 months were excluded from the study. None of the patients were receiving anti-inflammatory drugs or hormone replacement therapy. Patients with abnormal RBC counts (<4.7 and >5.9 x 106 per µL for men and <4.2 and >5.4 x 106 per µL for women) and/or abnormal haemoglobin levels (<13 and >18 g/dL for men and <12 and >16 g/dL for women) were also excluded. The study was approved by the Local Research Ethics Committee, and all patients gave written informed consent prior to study entry.

Angiographic analysis
Coronary arteriography was performed using the Judkins technique; images of the coronary artery tree were obtained on routine, standardized projections with the digital GE ADVANTX LC+ System (General Electric Medical Systems, S.C.S., Buc, France). Coronary arteriography was performed within 8–23 days (median 14) from the acute ischaemic episode in patients with ACS and at least 3 months after an acute episode in patients with CSA. Patients with chest pain and NCA were studied within 2 weeks from the time of their referral for coronary arteriography. Two experienced cardiologists who had no knowledge of the patients’ clinical characteristics and biochemical results visually reviewed all angiographic images to assess the extent and severity of CAD using an automated quantitative coronary artery stenosis assessment process (GE Centricity Cardiology CA 1000 Cardiac Review 1.0, General Electric Medical Systems). Vessel score was used to assess the extent of the atherosclerotic disease in the coronary artery tree. Vessel score is based on the number of diseased coronary arteries, where a coronary artery is regarded as ‘diseased’ in the presence of ≥75% reduction in lumen diameter.18,19 Interobserver variability for vessel and stenosis score was 3.1 and 4.2%, respectively.

Laboratory analysis
Peripheral blood samples were obtained from all patients after a 12 h overnight fast, at the time of coronary angiography prior to heparin infusion and to injection of any angiographic contrast material. Blood specimens for rIL-8 and CEM analysis were collected in standard vacutainer tubes containing citrate. A 3 mL aliquot of venous blood collected in citrate plasma tubes was centrifuged at 1500 r.p.m. for 10 min at 4°C; the plasma and buffy coat were carefully removed by aspiration. Aliquots of plasma were stored at –20°C for IL-8 estimation (pIL-8), and the remaining RBC were resuspended and washed twice in 154 mM NaCl isotonic solution.20

Isolation of erythrocyte membranes
Erythrocyte membranes were obtained according to the method previously reported5 ensuring minimal haemoglobin contamination. The procedure was carried out as follows: 1 mL of washed erythrocytes solution was hypotonically lysed in 30 volumes of cold haemolysis buffer (1 mM Tris–HCl, 1 mM EDTA, 10 mM NaCl, pH 7.2), mixed by vortex and allowed to stand for 15 min. Membranes were separated from the haemolysate (supernatant from haemolysed RBC) by centrifugation at 15 000 r.p.m. for 15 min at 4°C; this step was repeated three times until a white/pale pink pellet containing haemoglobin-free erythrocytes (ghosts) was obtained.21

Erythrocyte ghosts were resuspended in 1 mL of PBS (phosphate buffered saline) and stored at –20°C until further analysis. A 125 µL aliquot of membrane suspension was used to determine membrane protein concentration by the method of Bradford using bovine serum albumin as a standard.22

Red blood cell membrane lipid extraction and cholesterol estimation
Erythrocyte membrane samples (10 mg of protein), were extracted by vigorous vortexing with 200 µL of chloroform-Triton X-100 (1% Triton X-100 in pure chloroform). The extracts were centrifuged for 5 min in a microcentrifuge, at top speed. The organic phase (lower phase) was collected and air dried at 50°C to remove chloroform. The remaining dried lipids (in Triton X-100) were then processed for cholesterol determination. This extraction procedure was recommended as appropriate for the subsequent total cholesterol content of RBC membrane lipid extracts measurements; using a colorimetric assay kit by BioVision (Cholesterol/Cholesteryl Ester Quantification Kit – BioVision Research Products, Mountain View, CA, USA) with a lower detection limit of 2 µg.23 The assay kit is suitable for measuring total cholesterol by prior incubation of all samples in the presence of cholesterol esterase included in the reaction medium. Intra- and inter-assay precision were both <2%. A 6 point calibration curve was prepared by diluting the Standard Solution provided in the kit, the absorbance of each sample was measured against blank at 570 nm and the result was plotted against the calibration curve to obtain the amount of total cholesterol. All the samples were measured in duplicates and none of the duplicates had a coefficient variation (CV) >3%. We were able to measure the amount of cholesterol in all the samples assayed. Results are expressed as micrograms of membrane cholesterol (total) per milligram of membrane protein.

Plasma and red blood cell-bound interleukin-8 estimation
IL-8 was measured in plasma obtained as described earlier. For erythrocyte-bound IL-8, 1 mL of packed erythrocytes was washed four times with 0.9% NaCl (200 g for 10 min) to eliminate the remains of plasma, leucocytes, and platelets. The RBCs were adjusted to the original whole blood volume, and were lysed by adding Triton X-100 at a final concentration of 0.1%.24 The lysates were stored at –20°C. The removal of leucocytes as well as steady IL-8 RBC-bound concentrations during the purification procedure were shown by measuring concentrations of myeloperoxidase (MPO)—a leucocyte specific peroxidase—and IL-8 at each different step. In detail, at each step after centrifugation, the buffy coat was removed and discarded together with the top layer of sedimented RBCs at a height of ~5 mm. Following, a sample of 100 µL (samples S#1, S#2, S#3, S#4) was taken from the packed RBCs, solubilized with Triton X-100 at a final concentration of 0.1% and kept for analysis. At each step during the purification procedure declining MPO levels were observed reaching non-detectable by the assay concentrations at the final separation steps (S#1 390 ± 29 ng/mL, S#2 46 ± 18 ng/mL, S#3 and S#4 non-detectable concentrations). Furthermore, steady IL-8 RBC-bound levels were shown at each separation step (S#1 79 ± 15 pg/mL, S#2 40 ± 6 pg/mL, S#3 36 ± 7 pg/mL and S#4 35 ± 4 pg/mL).

MPO concentrations were measured using an ELISA kit (Quantikine, Human MPO, R&D Systems Inc., Minneapolis, MN, USA). IL-8 concentrations in plasma and erythrocyte lysates were measured with an ELISA kit (AviBion Human IL-8 ELISA – Orgenium Laboratories, Helsinki, Finland) with a lower detection limit of <7 pg/mL. Plasma samples were treated as recommended by the manufacturers, whereas in the case of RBC lysates, 0.1% Triton X-100 was included in the supplied sample dilution buffer used in the initial incubation step, both with respect to blank, standards or samples alike.

Intra- and inter-assay precision was <5.2 and <6.4%, respectively. Briefly, an eight-point calibration curve was prepared by diluting the Standard Solution provided in the kit, the absorbance of each sample was measured against the blank at 450 nm. The result was plotted against the calibration curve to obtain the amount of IL-8. All the samples were measured in duplicates and none of the duplicates had a CV >4%. Results are expressed as picograms of IL-8 per millilitre of plasma.

Statistical analysis
Continuous variables are presented as means ± 1 standard deviation (SD) except in Figure 1 where they are presented as medians with interquartile ranges and as percentages for categorical data. Comparisons between categorical variables were performed with the {chi}2 test or Fisher’s exact test as appropriate. Unadjusted comparisons were made by the Student’s unpaired t-test, in order to evaluate differences in continuous variables between the two groups. Bonferroni’s correction was used when appropriate. The planned sample size allowed a power of 90% for the independent comparison (rIL-8 levels between ACS vs. CSA) with a type 1 error probability of 0.05, assuming a mean difference equal to one half SD, on log-transformed data. Normality was tested using the Kolmogorov–Smirnov test. CEM, CRP (C-reactive protein), triglycerides, pIL-8 and rIL-8 levels were not normally distributed and were therefore logarithmically transformed as required to approach normal distribution and to obtain equal variances. Analysis of variance with covariates (ANCOVA) was used to evaluate differences in CEM, pIL-8 and rIL-8 levels between CSA and ACS after adjustment for all the variables that were significantly different between the two groups. Similarly, ANCOVA method was used to assess differences in the under investigation variables between ACS vs. NCA and CSA vs. NCA group.


Figure 1
View larger version (7K):
[in this window]
[in a new window]
[Download PowerPoint slide]
  		Figure 1 Interleukin concentration in erythrocyte membranes, rIL-8, in patients with chronic stable angina (CSA), acute coronary syndrome (ACS), and normal coronary artery (NCA) disease. Box plots represent median, quartiles, and range values for rIL-8. Data do not reflect logarithmic transformation or covariate adjustment as assessed in the ANCOVA (analysis of variance with covariates) model. P < 0.001 ACS vs. CSA, P < 0.001 ACS vs. NCA, P = 0.796 CSA vs. NCA.

 
Simple logistic regression analysis was used to assess univariate associations among the three biochemistry indices (rIL-8, CEM, and CRP) and CAD status (stable CAD vs. ACS). Odds ratios (OR) with 95% confidence intervals (CI) were calculated. OR for standardized log-transformed continuous variables reflect the relative risk for an increase of 1 SD (of the transformed variable) in the measure.25 Multiple logistic regression analysis was also used to assess the independent adjusted relationship between these indices and CAD status with independent variables being those that were significantly different between the two groups (ACS vs. CSA). The basic assumption of linearity was assessed by plotting residuals vs. model predicted values, for all dependent variables in each model.

The independent predictive ability of rIL-8 levels for CAD clinical presentation was assessed using logistic regression models controlled for CRP and CEM in a stepwise fashion (covariates + rIL-8, covariates + rIL-8 + CRP levels, covariates +rIL-8 + CRP + CEM levels). The additive predictive ability of rIL-8 levels for CAD status was tested using logistic regression models which additionally controlled for CRP and CEM levels in an inverse stepwise fashion (covariates + CRP levels, covariates + CRP + CEM levels, covariates + CRP + CEM + rIL-8 levels); we compared the predictive ability of these logistic regression models using the likelihood ratio-test and the C-statistic.

In addition, the prognostic ability of rIL-8 in the subgroup of patients with low and high CRP levels using its median value (5 mg/L) as cut-off point (this level is considered to represent a clinically relevant concentration associated with increased cardiovascular risk26), was tested.

Correlation analysis between variables was carried out by means of Spearman’s correlation coefficient (r). Receiver-operating characteristic (ROC) curves were calculated for rIL-8, CEM, and CRP levels. A P-value <0.05 was considered to indicate statistical significance with exception of pair-wise comparisons where Bonferroni’s correction was applied [P = 0.05/n (n = number of pair-wise comparisons)]; all tests were two-sided. The SPSS 11.0 statistical software package (SPSS Inc., Chicago, IL, USA) was used for all calculations.


   Results
Top
 Abstract
 Introduction
 Methods
 Results
Discussion
 References
 
Baseline characteristics
Baseline characteristics in patients with CSA, ACS, and those with NCA are presented in Table 1. At the time of study entry, therapy with β-blockers, statins, nitrates, calcium channel blockers, and aspirin, was more common in CSA compared with other two groups. Severity of CAD as determined by angiography was similar between CSA and ACS patients.


View this table:
[in this window]
[in a new window]

  		Table 1 Demographic and clinical characteristics in patients studied

 
No differences were observed in leucocyte (P = 0.837), neutrophil (P = 0.883), lymphocyte (P = 0.662) count or neutrophils/lymphocytes ratio (P = 0.161) among the three groups.

Erythrocyte membrane and plasma measurements
Content of rIL-8 was significantly higher (P < 0.001) in ACS (102.9 ± 70. 1 pg/mL) compared with CSA (44.7 ± 22.8 pg/mL) (Figure 1). ANCOVA showed that rIL-8 remained significantly higher (P < 0.001) in ACS after adjustment for all the variables that were significantly different between ACS and CSA patients (R2 = 0.314; for full model P < 0.001). Estimated covariate- adjusted means with 95% CI for rIL-8 levels among the two study groups assessed with the ANCOVA model were 83.2 pg/mL 95% CI 74.1–93.3 pg/mL for ACS and 39.8 pg/mL 95% CI 35.5–44.7 pg/mL for CSA.

Similarly, CEM levels were significantly higher (P < 0.001) in ACS (134.5 ± 42.7 µg/mg) compared with CSA (77.2 ± 16.2 µg/mg). CEM levels remained different (P < 0.001) in an ANCOVA model after adjustment for all the variables that were different between CSA and ACS patients (R2 = 0.512, overall P < 0.001).

As IL-8 load in erythrocyte membranes has not been extensively assessed in the general population, we assessed rIL-8 levels in an age and sex matched group of individuals with NCA as a mean of comparison. Student’s t-test (P < 0.001) and ANCOVA (P < 0.001) accounting for differences between the two groups, showed that rIL-8 values were higher in ACS compared with patients without angiographic CAD (48.2 ± 25.4 pg/mL). In contrast, rIL-8 was not significantly different between patients with NCA and those with CSA (t-test, P = 0.796 and ANCOVA, P = 0.940).

Likewise, CEM levels were significantly higher (t-test, P < 0.001 and ANCOVA, P < 0.001) in ACS compared with patients with NCA (80.2 ± 12.1 µg/mg); no difference was observed between CSA and patients with NCA (t-test, P = 0.197 and ANCOVA, P = 0.491).

No differences were noted in plasma IL-8 levels among CSA (t-test, P = 0.833 and ANCOVA, P = 0.820), ACS (t-test, P = 0.053 and ANCOVA, P = 0.528), and patients with NCA (51.3 ± 19.9 pg/mL). Likewise, plasma levels of IL-8 (pIL-8) were not different among CSA (56.5 ± 36.6 pg/mL) and ACS (64.8 ± 33.2 pg/mL) in both unadjusted (univariate Student’s t-test, P = 0.057) or adjusted (multivariable ANCOVA, P = 0.280) comparisons.

Table 2 summarizes values of rIL-8, pIL-8, and CEM in the three groups.


View this table:
[in this window]
[in a new window]

  		Table 2 Erythrocyte membrane and plasma concentrations of interleukin-8 (rIL-8, pIL-8, respectively) in chronic stable angina (CSA), acute coronary syndrome (ACS) and patients with normal coronary arteries (NCA)

 
As it was expected, CRP levels were significantly higher (P < 0.001) in patients with ACS (31.3 ± 28.2 mg/L) compared with those with CSA (4.7 ± 3.5 mg/L). Patients with NCA had lower CRP levels (2.7 ± 1.8 mg/L) compared with ACS (P < 0.001) and CSA (P < 0.001) patients.

Prediction of coronary artery disease instability
Table 3 summarizes results of simple logistic regression analysis for each of the three major biochemical indices (CEM, rIL-8, CRP) that could predict CAD instability. All the three parameters were predictive of ACS.


View this table:
[in this window]
[in a new window]

  		Table 3 Prediction of coronary instability [univariable logistic regression analysis for total cholesterol content of erythrocyte membranes, interleukin-8 content of erythrocyte membranes, C-reactive protein, in patients with chronic stable angina and acute coronary syndrome (n = 238)]

 
After adjustment for all the variables that were different between the two groups (ACS, CSA) on univariate analysis (arterial hypertension, current smoking, therapy with nitrates, statins, β-blockers, calcium channel blockers, aspirin; and log triglyceride levels), multiple logistic regression analysis showed that rIL-8, CRP, and CEM levels continued to have an independent association with ACS (Table 4). When the three biochemical indices (rIL-8, CEM, and CRP) were included in the aforementioned covariate-adjusted logistic regression model in a stepwise fashion (covariates + rIL-8 levels, covariates + rIL-8 + CRP levels, covariates + rIL-8 + CRP + CEM levels), rIL-8 continued to be a significant and an independent predictor of ACS (Table 4).


View this table:
[in this window]
[in a new window]

  		Table 4 Multivariable logistic regression analysis in patients with chronic stable angina and acute coronary syndrome (ACS) (n = 238) that could predict ACS

 
Finally, when the three under-investigation biochemical indices (rIL-8, CRP, and CEM) were included in the covariate-adjusted logistic regression model in an inverse stepwise fashion (covariates + CRP levels, covariates + CRP + CEM levels, covariates + CRP + CEM + rIL-8 levels) C-statistic and likelihood ratio test showed that rIL-8 levels added significantly to the predictive ability compared with CRP and CEM levels (Table 5).


View this table:
[in this window]
[in a new window]

  		Table 5 Predictive ability of rIL-8 (interleukin-8 content of erythrocyte membranes) on the logistic regression modelling

 
Receiver-operating characteristics curve analysis
Consistent with the previous results, ROC analysis regarding predictive accuracy for CAD status showed that for rIL-8, the area under the curve was 0.826 (0.774–0.878); P < 0.001, for CEM 0.921 (0.886–0.955); P < 0.001, and for CRP 0.831 (0.780–0.882); P < 0.001. Albeit without controlling for possible cofounders, ROC analysis indicates that rIL-8 was a good marker of CAD instability, comparable with CRP levels (Figure 2).


Figure 2
View larger version (16K):
[in this window]
[in a new window]
[Download PowerPoint slide]
  		Figure 2 Receiver-operating characteristics (ROC) curve analysis regarding predictive accuracy of acute coronary syndrome. The bold line represents ROC analysis for total cholesterol content of erythrocyte membranes. The continuous line represents ROC analysis for C-reactive protein levels The dotted line represents ROC analysis for rIL-8 (interleukin-8 content of erythrocyte membranes) levels.

 
Correlation analysis
Correlation analysis in the entire patient population (n = 238) showed a significant positive association between rIL-8 and CRP plasma levels (r = 0.294, P < 0.001) while no correlation was found between plasma IL-8 and CRP levels (r = 0.025, P = 0.706). Of interest, plasma IL-8 and rIL-8 levels were positively correlated (r = 0.283, P < 0.001). Furthermore, rIL-8 and CEM were also positively associated (r = 0.409, P < 0.001).

As it was expected,5 no association was found between CEM and: (i) serum total cholesterol concentration (r = 0.047; P = 0.472), LDL (r = 0.011; P = 0.865), (ii) HDL-cholesterol levels (r = –0.043; P = 0.512), and (iii) triglyceride levels (r = 0.063; P = 0.337) when patients with ACS and CSA were included.

CEM levels were not correlated with number of diseased vessels (r = –0.007, P = 0.881) or with stenosis score (r = 0.031, P = 0.596). This was also the case for rIL-8 levels (for number of diseased vessels: r = –0.028, P = 0.579, and for stenosis score: r = 0.017, P = 0.746).

Subgroup analysis
The incidence of ACS in patients with CAD in relation to rIL-8 and CRP is shown in Figure 3. It was observed that among CAD patients with low CRP levels (n = 126, CRP <5 mg/L), rIL-8 was significantly associated with the presence of ACS (OR log rIL-8/SD 18.6 95% CI 5.2–66.6, P < 0.001). Even among patients with CAD with high CRP levels (n = 112, CRP ≥5 mg/L), rIL-8 was still predictive of ACS (OR log rIL-8/SD 4.7 95% CI 2.3–9.6, P < 0.001). Furthermore, rIL-8 was a significant predictor of CAD instability across all quartiles of CRP, albeit stronger in the lower spectrum (Figure 4).


Figure 3
View larger version (23K):
[in this window]
[in a new window]
[Download PowerPoint slide]
  		Figure 3 Number of patients with acute coronary syndrome in a cross-tabulation of rIL-8 (interleukin-8 content of erythrocyte membranes) by C-reactive protein (CRP) values. High rIL-8 levels: ≥59.5 pg/mL; low rIL-8 levels: <59.5 pg/mL; high CRP levels: ≥5 mg/L; low CRP levels: <5 mg/L.

 

Figure 4
View larger version (16K):
[in this window]
[in a new window]
[Download PowerPoint slide]
  		Figure 4 Predictive ability of rIL-8 (interleukin-8 content of erythrocyte membranes) in relation to C-reactive protein (CRP) quartiles. Range of CRP quartiles and number of patients with chronic stable angina (CSA) and acute coronary syndrome (ACS) within each quartile. Quartile 1: ≤2 mg/L, 62 patients, 52 with CSA, 12 with ACS; quartile 2: >2 and ≤5 mg/L, 64 patients, 44 with CSA, 20 with ACS; quartile 3: >5 and ≤19 mg/L, 52 patients, 18 with CSA, 34 with ACS; quartile 4: >19 mg/L, 60 patients, 8 with ACS, 52 with CSA.

 
The use of statins was associated with lower rIL-8 values (n = 82, 60.4 ± 53.4 pg/mL, P = 0.001) compared with patients not receiving statins (n = 156, 80.6 ± 61.5 pg/mL). In view of the association observed between statin use and rIL-8 levels we compared the predictive ability for ACS of rIL-8 in both patients with and without statin treatment. In the subgroup of patients receiving statin treatment, rIL-8 levels were predictive of ACS (OR log rIL-8/SD 11.1 95% CI 3.6–34.2, P < 0.001). Furthermore, rIL-8 levels were also associated with ACS (OR log rIL-8/SD 3.9 95% CI 2.3–6.5, P < 0.001) in the subgroup of patients not receiving statins.

The previous occurrence of an acute coronary event in some patients in the CSA group may obscure the designation of CAD clinical presentation as stable. We therefore, assessed the ability of rIL-8 to predict clinical instability in the subgroup of CSA patients without a history of ACS (n = 166). We found that rIL-8 levels were associated with the occurrence of ACS (OR log rIL-8/SD 6.9 95% CI 3.6–13.1, P < 0.001) in the subgroup of patients without a previous history of ACS.


   Discussion
Top
 Abstract
 Introduction
 Methods
 Results
 Discussion
References
 
The present study is the first to report that IL-8 content in circulating erythrocyte membranes is higher in ACS compared with CSA patients. These results endorse and expand our previous findings5 according to which high CEM levels were present in ACS patients. In the present study, rIL-8 was a marker of ACS independent of CRP and CEM concentrations.27 Further, these findings were independent of leucocyte and lymphocyte count.28 It was also found that rIL-8 content in the erythrocyte membranes was associated with circulating levels of CRP.

That erythrocytes could play a role in plaque instability is biologically plausible.1 Recent studies have shown that neovascularization is important in the development of atherosclerotic plaque and in its instability.29–31 The newly formed vessels may lead to the extravasation of erythrocytes within the atherosclerotic plaque.7 Red cells rich in cholesterol may contribute to an abrupt volume expansion and to a change in the lipid composition of the plaque, thus the lipid core becomes rich in free cholesterol,1,2,5 an important determinant of plaque vulnerability.4,6,32,33

Further, it is quite plausible that extravasated erythrocytes may initiate and propagate an inflammatory cascade2,4,7,8 within the atherosclerotic plaque, which may play a pathogenic role in CAD progression and plaque rupture.9,10,34,35

This inflammation cascade may be promoted by receptors present on erythrocyte membranes, which bind to a wide array of chemokines including IL-8 and monocyte chemotactic peptide-1.4,12,36,37

IL-8 is a C–X–C chemokine that has the potential of modulating atherosclerosis progression.11 A number of studies have shown that IL-8 is present in human atherosclerotic plaques in patients with UA.38–44 IL-8 has been shown to be a potent chemotactic factor for T-lymphocytes45 and monocytes.46 In addition to its chemoattractant properties, it also possesses other plaque destabilizing effects. IL-8 contributes to smooth muscle cell migration and proliferation,47 a possible source of matrix metalloproteinases,48 and additionally down-regulates the action of inhibitors of metalloproteinases.49 Further, IL-8 is a signal for angiogenesis,43 an important mechanism of atherosclerotic plaque instability.29–31 Finally, it has been suggested that IL-8 is a key participant in the cross talk between coagulation activation and cytokine cascades.50 C–X–C chemokines may have also atheroprotective effects.

Keratinocyte-derived chemokine (KC) the mouse ortholog of human growth-related oncogene (GRO-a)—a C–X–C chemokine—has been shown to exert a protective effect on plaque formation after endothelial denudation (endothelial wound injury) presumably by accelerated re-endothelialization. This implies that KC may exert a protective role in neointima formation especially in the setting of restenosis by accelerating endothelial recovery.51

Our results are in agreement with that of de Winter et al.24 who have shown that IL-8 is mainly bound to erythrocytes in patients suffering from an acute MI and their levels of rIL-8 were significantly higher compared with those in healthy controls. In contrast, other studies reported that plasma levels of IL-8 were significantly higher in ACS compared with CSA.52,53 An explanation for this disparity may be the timing of blood sampling in the ACS patient group. In the aforementioned studies52,53 blood samples were obtained during the acute phase of the event, whereas in our study blood was obtained ~15 days after the acute event. It is known that circulating levels of IL-8 in ACS return to normal values within a few days from the onset of symptoms.24 Thus, pIL-8 and rIL-8 levels are changing constantly for a few days after the acute event and steady-state condition is reached several days after the acute ischaemic syndrome. The present study was designed to assess the diagnostic ability of the aforementioned markers at steady-state condition.

It should be emphasized that the present study demonstrated that erythrocyte membranes IL-8 level is increased in patients with ACS compared with CSA. At present, there is not sufficient information to suggest that rIL-8 is involved in the pathogenetic mechanisms related to unstable atherosclerotic plaque. Thus, the concept that erythrocytes—entrapped within the atherosclerotic plaque—propagating an inflammatory response and interfering with plaque instability at present is speculative.54 This, however, does not detract from the fact that rIL-8 is at least a marker of CAD instability.

In summary, this study showed that IL-8 contained in erythrocyte membranes is associated with the presence of ACS. It is quite plausible that intraplaque haemorrhage and consequently extravasated erythrocytes may contribute to plaque instability via inflammatory mechanisms, in addition to the enlargement of the necrotic lipid core. Thus—as suggested in previous studies from our group—erythrocytes may play an active role in the atherosclerotic plaque progression and in plaque instability.

Funding
The study was funded jointly by a) Democritus University of Thrace, Medical School, Dragana, Alexandroupolis, 68100, Greece and b) Hellenic Cardiological Society, Potamianou 6, Athens, 11528, Greece.

Conflict of interest: none declared.


   References
Top
 Abstract
 Introduction
 Methods
 Results
 Discussion
 References
 

  1. Arbustini E. Total erythrocyte membrane cholesterol. An innocent new marker or an active player in acute coronary syndromes ? J Am Coll Cardiol (2007) 49:2090–2092.[Free Full Text]
  2. Pasterkamp G, Virmani R. The erythrocyte: a new player in atheromatous core formation. Heart (2002) 88:115–116.[Free Full Text]
  3. Arbustini E, Morbini P, D’Armini AM, Repetto A, Minzioni G, Piovella F, Viganó M, Tavazzi L. Plaque composition in plexogenic and thromboembolic pulmonary hypertension: the critical role of thrombotic material in pultaceous core formation. Heart (2002) 88:177–182.[Abstract/Free Full Text]
  4. Kolodgie FD, Herman KG, Burke AP, Fowler DR, Kruth HS, Weber DK, Farb A, Guerrero LJ, Hayase M, Kutys R, Narula J, Finn AV, Virmani R. Intraplaque hemorrhage and progression of coronary atheroma. N Engl J Med (2003) 349:2316–2325.[Abstract/Free Full Text]
  5. Tziakas D, Kaski JC, Chalikias GK, Romero C, Fredericks S, Tentes IK, Kortasris AX, Hatseras DI, Holt DW. Total cholesterol content of erythrocyte membranes is increased in patients with acute coronary syndrome. J Am Coll Cardiol (2007) 49:2081–2089.[Abstract/Free Full Text]
  6. Davies MJ. Stability and instability: two faces of coronary atherosclerosis. The Paul Dudley White lecture 1995. Circulation (1996) 94:2013–2020.[Free Full Text]
  7. Herrmann J, Lerman A. Atherosclerosis in the back yard. J Am Coll Cardiol (2007) 49:2102–2104.[Abstract/Free Full Text]
  8. Moreno PR, Purushothaman KR, Sirol M, Levy AP, Fuster V. Neovascularization in human atherosclerosis. Circulation (2006) 113:2245–2252.[Free Full Text]
  9. Bursill CA, Channon KM, Greaves DR. The role of chemokines in atherosclerosis: recent evidence from experimental models and population genetics. Curr Opin Lipidiol (2004) 15:145–149.[CrossRef][Web of Science][Medline]
  10. Weber C, Schober A, Zernecke A. Chemokines: key regulators of mononuclear cell recruitment in atherosclerotic vascular disease. Arterioscler Thromb Vasc Biol (2004) 24:1997–2008.[Abstract/Free Full Text]
  11. Shin WS, Szuba A, Rockson SG. The role of chemokines in human cardiovascular pathology: enhanced biological insights. Atherosclerosis (2002) 160:91–102.[CrossRef][Web of Science][Medline]
  12. Darbonne WC, Rice GC, Mohler MA, Hebert CA, Valente AJ, Baker JB. Red blood cells are a sink for interleukin-8, a leukocyte chemotaxin. J Clin Invest (1991) 88:1362–1369.[Web of Science][Medline]
  13. Fox K, Garcia MA, Ardissino D, Buszman P, Camici PG, Crea F, Daly C, De Backer G, Hjemdahl P, Lopez-Sendon J, Marco J, Morais J, Pepper J, Sechtem U, Simoons M, Thygesen K, Priori SG, Blanc JJ, Budaj A, Camm J, Dean V, Deckers J, Dickstein K, Lekakis J, McGregor K, Metra M, Morais J, Osterspey A, Tamargo J, Zamorano JL, Task Force on the Management of Stable Angina Pectoris of the European Society of Cardiology; ESC Committee for Practice Guidelines (CPG). Guidelines on the management of stable angina pectoris: executive summary: the Task Force on the Management of Stable Angina Pectoris of the European Society of Cardiology. Eur Heart J (2006) 27:1341–1381.[Free Full Text]
  14. Thygesen K, Alpert JS, White HD. Joint ESC/ACCF/AHA/WHF Task Force for the Redefinition of Myocardial Infarction. Eur Heart J (2007) 28:2525–2538.[Free Full Text]
  15. Van de Werf F, Ardissino D, Betriu A, Cokkinos DV, Falk E, Fox KA, Julian D, Lengyel M, Neumann FJ, Ruzyllo W, Thygesen C, Underwood SR, Vahanian A, Verheugt FW, Wijns W, Task Force on the Management of Acute Myocardial Infarction of the European Society of Cardiology. Management of acute myocardial infarction in patients presenting with ST-segment elevation The Task Force on the Management of Acute Myocardial Infarction of the European Society of Cardiology. Eur Heart J (2003) 24:28–66.[Free Full Text]
  16. Bassand JP, Hamm CW, Ardissino D, Boersma E, Budaj A, Fernández-Avilés F, Fox KA, Hasdai D, Ohman EM, Wallentin L, Wijns W, Task Force for Diagnosis Treatment of Non-ST-Segment Elevation Acute Coronary Syndromes of European Society of Cardiology. Guidelines for the diagnosis and treatment of non-ST-segment elevation acute coronary syndromes The Task Force for the Diagnosis and Treatment of Non-ST-Segment Elevation Acute Coronary Syndromes of the European Society of Cardiology. Eur Heart J (2007) 28:1598–1660.[Free Full Text]
  17. Braunwald E. Unstable angina: a classification. Circulation (1989) 80:410–414.[Free Full Text]
  18. Scanlon PJ, Faxon DP, Audet AM, Carabello B, Dehmer GJ, Eagle KA, Legako RD, Leon DF, Murray JA, Nissen SE, Pepine CJ, Watson RM, Ritchie JL, Gibbons RJ, Cheitlin MD, Gardner TJ, Garson A Jr, Russell RO Jr, Ryan TJ, Smith SC Jr. ACC/AHA guidelines for coronary angiography. A report of the American College of Cardiology/American Heart Association Task Force on practice guidelines (Committee on Coronary Angiography). Developed in collaboration with the Society for Cardiac Angiography and Interventions. J Am Coll Cardiol (1999) 33:1756–1824.[Free Full Text]
  19. Kaski JC, Chester MR, Chen L, Katritsis D. Rapid angiographic progression of coronary artery disease in patients with angina pectoris. The role of complex stenosis morphology. Circulation (1995) 92:2058–2065.[Abstract/Free Full Text]
  20. Cazzola R, Rondanelli M, Russo-Volpe S, Ferrari E, Cestaro B. Decreased membrane fluidity and altered susceptibility to peroxidation and lipid composition in overweight and obese female erythrocytes. J Lipid Res (2004) 45:1846–1851.[Abstract/Free Full Text]
  21. Miwa S, Inouye M, Ohmura C, Mitsuhashi N, Onuma T, Kawamori R. Relationship between carotid atherosclerosis and erythrocyte membrane cholesterol oxidation products in type 2 diabetic patients. Diabetes Res Clin Pract (2003) 61:81–88.[CrossRef][Web of Science][Medline]
  22. Bradford MM. A rapid and sensitive method for the quantitation of microgram quantities of protein uitilizing the principle of protein-dye binding. Anal Biochem (1976) 72:248–254.[CrossRef][Web of Science][Medline]
  23. Allain CC, Poon LS, Chan CSG, Richmond W, Fu PC. Enzymatic determination of total serum cholesterol. Clin Chem (1974) 20:470–475.[Abstract]
  24. de Winter RJ, Manten A, de Jong YP, Adams R, van Deventer SJH, Lie KI. Interleukin-8 released after acute myocardial infarction is mainly bound to erythrocytes. Heart (1997) 78:598–602.[Abstract/Free Full Text]
  25. Olsen MH, Hansen TW, Christensen MK, Gustafsson F, Rasmussen S, Wachtell K, Ibsen H, Torp-Pedersen C, Hildebrandt PR. N-terminal pro-brain natriuretic peptide, but not high sensitivity C-reactive protein, improves cardiovascular risk prediction in the general population. Eur Heart J (2007) 28:1374–1381.[Abstract/Free Full Text]
  26. De Backer G, Ambrosioni E, Borch-Johnsen K, Brotons C, Cifkova R, Dallongeville J, Ebrahim S, Faergeman O, Graham I, Mancia G, Manger Cats V, Orth-Gomér K, Perk J, Pyörälä K, Rodicio JL, Sans S, Sansoy V, Sechtem U, Silber S, Thomsen T, Wood D, Third Joint Task Force of European Other Societies on Cardiovascular Disease Prevention in Clinical Practice. European guidelines on cardiovascular disease prevention in clinical practice. Third Joint Task Force of European and Other Societies on Cardiovascular Disease Prevention in Clinical Practice. Eur Heart J (2003) 24:1601–1610.[Free Full Text]
  27. Arroyo-Espliguero R, Avanzas P, Cosin-Sales J, Aldama G, Pizzi C, Kaski JC. C- reactive protein elevation and disease activity in patients with coronary artery disease. Eur Heart J (2004) 25:401–408.[Abstract/Free Full Text]
  28. Madjid M, Awan I, Willerson JT, Casscells SW. Leukocyte count and coronary heart disease: implications for risk assessment. J Am Coll Cardiol (2004) 44:1945–1956.[Abstract/Free Full Text]
  29. Purushothaman KR, Fuster V, O’Connor WN, Moreno PR. Neovascularization is the most powerful independent predictor for progression to disruption in high risk atherosclerotic plaques. J Am Coll Cardiol (2003) 41(Suppl. B):352–353.
  30. Moreno PR, Purushothaman KR, Fuster V, Echeverri D, Truszczynska H, Sharma SK, Badimon JJ, O’Connor WN. Plaque neovascularization is increased in ruptured atherosclerotic lesions of human aorta. Implications for plaque vulnerability. Circulation (2004) 110:2032–2038.[Abstract/Free Full Text]
  31. Virmani R, Kolodgie FD, Burke AP, Finn AV, Gold HK, Tulenko TN, Wrenn SP, Narula J. Atherosclerotic plaque progression and vulnerability to rupture: angiogenesis as a source of intraplaque hemorrhage. Arterioscler Thromb Vasc Biol (2005) 25:2054–2061.[Abstract/Free Full Text]
  32. Felton CV, Crook D, Davies MJ, Oliver MF. Relation of plaque lipid composition and morphology to the stability of human aortic plaques. Arterioscler Thromb Vasc Biol (1997) 17:1337–1345.[Abstract/Free Full Text]
  33. Virmani R, Kolodgie FD, Burke AP, Farb A, Schwartz SM. Lessons from sudden coronary death. A comprehensive morphological classification scheme for atherosclerotic lesions. Arterioscler Thromb Vasc Biol (2000) 20:1262–1275.[Free Full Text]
  34. Ross R. Atherosclerosis – an inflammatory disease. N Engl J Med (1999) 340:115–126.[Free Full Text]
  35. Libby P. Inflammation in atherosclerosis. Nature (2002) 420:868–874.[CrossRef][Web of Science][Medline]
  36. Neote K, Darbonne W, Ogez J, Horuk R, Schall TJ. Identification of a promiscuous inflammatory peptide receptor on the surface of red blood cells. J Biol Chem (1993) 268:12247–12249.[Abstract/Free Full Text]
  37. Neote K, Malk JY, Kolakowski LF, Schall TJ. Functional and biochemical analysis of the cloned Duffy antigen: identity with the red blood cell chemokine receptor. Blood (1994) 84:44–52.[Abstract/Free Full Text]
  38. Apostolopoulos J, Davenport P, Tipping PG. Interleukin-8 production by macrophages from atheromatous plaques. Arterioscler Thromb Vasc Biol (1996) 16:1007–1012.[Abstract/Free Full Text]
  39. Boisvert WA, Santiago R, Curtiss LK, Terkeltaub RA. A leukocyte homologue of the IL-8 receptor CXCR-2 mediates the accumulation of macrophages in atherosclerotic lesions of LDL receptor-deficient mice. J Clin Invest (1998) 101:353–363.[Web of Science][Medline]
  40. Koch AE, Kunkel SL, Pearce WH, Sha MR, Parikh D, Evanoff HL, Haines GK, Burdick MD, Strieter RM. Enhanced production of the chemotactic cytokines interleukin-8 and monocyte chemoattractant protein-1 in human abdominal aortic aneurysms. Am J Pathol (1993) 142:1423–1431.[Abstract]
  41. Rus HG, Vlaicu R, Niculescu F. Interleukin-6 and interleukin-8 protein and gene expression in human arterial atherosclerotic wall. Atherosclerosis (1996) 127:263–271.[CrossRef][Web of Science][Medline]
  42. Wang N, Tabas I, Winchester R, Ravalli S, Rabbani LE, Tall A. Interleukin 8 is induced by cholesterol loading of macrophages and expressed by macrophage foam cells in human atheroma. J Biol Chem (1996) 271:8837–8842.[Abstract/Free Full Text]
  43. Simonini A, Moscucci M, Muller DWM, Bates ER, Pagani FD, Brudick MD, Strieter RM. Interleukin-8 is an angiogenic factor in human coronary atherectomy tissue. Circulation (2000) 101:1519–1526.[Abstract/Free Full Text]
  44. Gimbrone MA, Obin MS, Brock AB, Luis EA, Hass PE, Hebert CA, Yip YK, Leung DW, Lowe DG, Kohr WJ, Darbonne KB, Bechtol KB, Baker JB. Endothelial interleukin-8: a novel inhibitor of leukocyte-endothelial interactions. Science (1989) 246:1601–1602.[Abstract/Free Full Text]
  45. Xu L, Kelvin DJ, Ye GO, Taub DD, Ben-Baruch A, Oppenheim JJ, Wang JM. Modulation of IL-8 receptor expression on purified human lymphocytes is associated with changed chemotactic responses to IL-8. J Leukocyte Biol (1995) 57:335–342.[Abstract]
  46. Gerszten RE, Garcia-Zepeda EA, Lim YC, Yoshida M, Ding HA, Gimbrone MA Jr, Luster AD, Luscinskas FW, Rosenzweig A. MCP-1 and IL-8 trigger firm adhesion of monocytes to vascular endothelium under flow conditions. Nature (1999) 398:718–723.[CrossRef][Web of Science][Medline]
  47. Yue TL, Wang X, Sung CP, Olson B, McKenna PJ, Gu JL, Feuerstein GZ. IL-8. A mitogen and chemoattractant for smooth muscle cells. Circ Res (1994) 75:1–7.[Abstract/Free Full Text]
  48. Segers D, Helderman F, Cheng C, van Damme LC, Tempel D, Boersma E, Serruys PW, de Crom R, van der Steen AF, Holvoet P, Krams R. Gelatinolytic activity in atherosclerotic plaques is highly localized and is associated with both macrophages and smooth muscle cells in vivo. Criculation (2007) 115:609–616.[CrossRef]
  49. Moreau M, Brocheriou I, Petit L, Ninio E, Chapman MJ, Rouis M. IL-8 mediates downregulation of tissue inhibitor of metalloproteinase-1 expression in cholesterol-loaded human macrophages: relevance to stability of atherosclerotic plaque. Circulation (1999) 99:420–426.[Abstract/Free Full Text]
  50. Johnson K, Aarden LA, Choi Y, De Groot E, Creasey A. The proinflammatory cytokine response to coagulation and endotoxin in whole blood. Blood (1996) 12:5051–5060.
  51. Liehn EA, Schober A, Weber C. Blockade of keratinocyte-derived chemokine inhibits endothelial recovery and enhances plaque formation after arterial injury in ApoE-deficient mice. Arterioscler Thromb Vasc Biol (2004) 24:1891–1896.[Abstract/Free Full Text]
  52. Aukrust P, Berge RK, Ueland T, De Groot E, Creasey A. Interaction between chemokines and oxidative stress: possible pathogenic role in acute coronary syndromes. J Am Coll Cardiol (2001) 37:485–491.[Abstract/Free Full Text]
  53. Romuk E, Skrzep-Poloczek B, Wojciechowska C, Tomasik A, Birkner E, Wodniecki J, Gabrylewicz B, Ochala A, Tendera M. Selectin P and interleukin-8 plasma levels in coronary heart disease patients. Eur J Clin Invest (2002) 32:657–661.[CrossRef][Web of Science][Medline]
  54. Hoch RC, Schraufstatter IU, Cochrane CG. In vivo, in vitro, and molecular aspects of interleukin-8 and the interleukin-8 receptors. J Lab Clin Med (1996) 128:134–145.[CrossRef][Web of Science][Medline]

Add to CiteULike CiteULike   Add to Connotea Connotea   Add to Del.icio.us Del.icio.us    What's this?


This article has been cited by other articles:


Home page
 Cardiovasc ResHome page
S. Apostolakis, K. Vogiatzi, V. Amanatidou, and D. A. Spandidos
Interleukin 8 and cardiovascular disease
Cardiovasc Res, December 1, 2009; 84(3): 353 - 360.
[Abstract] [Full Text] [PDF]

Home page
 HypertensionHome page
F. Barcelo, J. S. Perona, J. Prades, S. S. Funari, E. Gomez-Gracia, M. Conde, R. Estruch, and V. Ruiz-Gutierrez
Mediterranean-Style Diet Effect on the Structural Properties of the Erythrocyte Cell Membrane of Hypertensive Patients: The Prevencion con Dieta Mediterranea Study
Hypertension, November 1, 2009; 54(5): 1143 - 1150.
[Abstract] [Full Text] [PDF]

Home page
 J Am Coll CardiolHome page
R. P. Giugliano and E. Braunwald
The Year in Non-ST-Segment Elevation Acute Coronary Syndrome.
J. Am. Coll. Cardiol., October 13, 2009; 54(16): 1544 - 1555.
[Full Text] [PDF]

Home page
 Eur Heart JHome page
G. Pasterkamp and M. Daemen
Circulating cells: the biofactory for markers of atherosclerotic disease
Eur. Heart J., November 2, 2008; 29(22): 2701 - 2702.
[Full Text] [PDF]

This Article
Right arrow Abstract Freely available
Right arrow FREE Full Text (PDF) Freely available
Right arrow All Versions of this Article:
29/22/2713    most recent
ehn382v1
Right arrow E-letters: Submit a response
Right arrow Alert me when this article is cited
Right arrow Alert me when E-letters are posted
Right arrow Alert me if a correction is posted
Services
Right arrow Email this article to a friend
Right arrow Similar articles in this journal
Right arrow Similar articles in PubMed
Right arrow Alert me to new issues of the journal
Right arrow Add to My Personal Archive
Right arrow Download to citation manager
Right arrowRequest Permissions
Right arrow Disclaimer
Google Scholar
Right arrow Articles by Tziakas, D. N.
Right arrow Articles by Boudoulas, H.
Right arrow Search for Related Content
PubMed
Right arrow PubMed Citation
Right arrow Articles by Tziakas, D. N.
Right arrow Articles by Boudoulas, H.
Social Bookmarking
Add to CiteULike   Add to Connotea   Add to Del.icio.us  
What's this?