Increased platelet reactivity is associated with circulating platelet-monocyte complexes and macrophages in human atherosclerotic plaques.

OBJECTIVE: Platelet reactivity, platelet binding to monocytes and monocyte infiltration play a detrimental role in atherosclerotic plaque progression. We investigated whether platelet reactivity was associated with levels of circulating platelet-monocyte complexes (PMCs) and macrophages in human atherosclerotic carotid plaques. METHODS: Platelet reactivity was determined by measuring platelet P-selectin expression after platelet stimulation with increasing concentrations of adenosine diphosphate (ADP), in two independent cohorts: the Circulating Cells cohort (n = 244) and the Athero-Express cohort (n = 91). Levels of PMCs were assessed by flow cytometry in blood samples of patients who were scheduled for percutaneous coronary intervention (Circulating Cells cohort). Monocyte infiltration was semi-quantitatively determined by histological examination of atherosclerotic carotid plaques collected during carotid endarterectomy (Athero-Express cohort). RESULTS: We found increased platelet reactivity in patients with high PMCs as compared to patients with low PMCs (median (interquartile range): 4153 (1585-11267) area under the curve (AUC) vs. 9633 (3580-21565) AUC, P<0.001). Also, we observed increased platelet reactivity in patients with high macrophage levels in atherosclerotic plaques as compared to patients with low macrophage levels in atherosclerotic plaques (mean ± SD; 8969 ± 3485 AUC vs. 7020 ± 3442 AUC, P = 0.02). All associations remained significant after adjustment for age, sex and use of drugs against platelet activation. CONCLUSION: Platelet reactivity towards ADP is associated with levels of PMCs and macrophages in human atherosclerotic carotid plaques.

Toll-Like Receptor induced CD11b and L-selectin response in patients with coronary artery disease.

Toll-Like Receptor (TLR) -2 and -4 expression and TLR-induced cytokine response of inflammatory cells are related to atherogenesis and atherosclerotic plaque progression. We examined whether immediate TLR induced changes in CD11b and L-selectin (CD62L) expression are able to discriminate the presence and severity of atherosclerotic disease by exploring single dose whole blood TLR stimulation and detailed dose-response curves. Blood samples were obtained from 125 coronary artery disease (CAD) patients and 28 controls. CD11b and L-selectin expression on CD14+ monocytes was measured after whole blood stimulation with multiple concentrations of the TLR4 ligand LPS (0.01-10 ng/ml) and the TLR2 ligand P3C (0.5-500 ng/ml). Subsequently, dose-response curves were created and the following parameters were calculated: hillslope, EC50, area under the curve (AUC) and delta. These parameters provide information about the maximum response following activation, as well as the minimum trigger required to induce activation and the intensity of the response. CAD patients showed a significantly higher L-selectin, but not CD11b response to TLR ligation than controls after single dose stimulations as well as significant differences in the hillslope and EC50 of the dose-response curves. Within the CAD patient group, dose-response curves of L-selectin showed significant differences in the presence of hypertension, dyslipidemia, coronary occlusion and degree of stenosis, whereas CD11b expression had the strongest discriminating power after single dose stimulation. In conclusion, single dose stimulations and dose-response curves of CD11b and L-selectin expression after TLR stimulation provide diverse but limited information about atherosclerotic disease severity in stable angina patients. However, both single dose stimulation and dose-response curves of LPS-induced L-selectin expression can discriminate between controls and CAD patients.

Fractional flow reserve is not associated with inflammatory markers in patients with stable coronary artery disease.

BACKGROUND: Atherosclerosis is an inflammatory condition and increased blood levels of inflammatory biomarkers have been observed in acute coronary syndromes. In addition, high expression of inflammatory markers is associated with worse prognosis of coronary artery disease. The presence and extent of inducible ischemia in patients with stable angina has previously been shown to have strong prognostic value. We hypothesized that evidence of inducible myocardial ischemia by local lesions, as measured by fractional flow reserve (FFR), is associated with increased levels of blood based inflammatory biomarkers. METHODS: Whole blood samples of 89 patients with stable angina pectoris and 16 healthy controls were analyzed. The patients with stable angina pectoris underwent coronary angiography and FFR of all coronary lesions. We analyzed plasma levels of cytokines IL-6, IL-8 and TNF-α and membrane expression of Toll-like receptor 2 and 4, CD11b, CD62L and CD14 on monocytes and granulocytes as markers of inflammation. Furthermore, we quantified the severity of hemodynamically significant coronary artery disease by calculating Functional Syntax Score (FSS), an extension of the Syntax Score. RESULTS: For the majority of biomarkers, we observed lower levels in the healthy control group compared with patients with stable angina who underwent coronary catheterization. We found no difference for any of the selected biomarkers between patients with a positive FFR (≤ 0.75) and negative FFR (>0.80). We observed no relationship between the investigated biomarkers and FSS. CONCLUSION: The presence of local atherosclerotic lesions that result in inducible myocardial ischemia as measured by FFR in patients with stable coronary artery disease is not associated with increased plasma levels of IL-6, IL-8 and TNF-α or increased expression of TLR2 and TLR4, CD11b, CD62L and CD14 on circulating leukocytes.

Inducible cardiac ischaemia is related to a decrease in the whole-blood Toll-like receptor 2 and 4 response.

TLR (Toll-like receptor) activation-induced inflammatory responses are important in the progression of atherosclerosis. We previously showed that TLR-dependent leucocyte responsiveness is acutely attenuated following percutaneous coronary intervention or vascular surgery. Furthermore, cytokine release following whole-blood TLR-2 and TLR-4 stimulation is negatively correlated with fractional flow reserve, suggesting that chronic ischaemia can elicit an enhanced inflammatory response. In the present study, we assessed the association between leucocyte TLR-2 and TLR-4 responsiveness and pre-existent and inducible ischaemia in patients undergoing SPECT (single-photon emission computed tomography)-MPI (myocardial perfusion imaging). TLR-2, TLR-4 and CD11b expression on monocytes were measured in blood samples that were obtained from 100 patients with suspected coronary artery disease before and after myocardial stress testing for SPECT-MPI. IL-8 (interleukin-8) levels were determined after whole-blood stimulation with Pam3Cys (TLR-2) and LPS (lipopolysaccharide; TLR-4). On the basis of SPECT-MPI, patients were categorized into three groups: reversible defect, irreversible defect and no defect. Myocardial stress induced a reduction in TLR-4 expression (2.46±0.21 compared with 2.17±0.16 arbitrary units, P=0.001) and CD11b expression (83.2±1.73 compared with 76.0±1.89 arbitrary units, P<0.001). TLR-induced IL-8 production before myocardial stress induction was not associated with the results of SPECT-MPI. However, a significant decrease in IL-8 production following TLR stimulation was observed after stress, which was more pronounced in patients with a reversible defect. In conclusion, inducible ischaemia is associated with a decrease in whole-blood TLR-2 and TLR-4 response. These results point to a regulating role of TLRs in order to prevent excessive inflammatory events known to occur during acute ischaemia.

A comparison between the Plateletworks-assay and light transmittance aggregometry for monitoring the inhibitory effects of clopidogrel.

A simple and rapid point-of-care platelet function assay that guides antiplatelet responses to aspirin and clopidogrel may be of great clinical value for the individual tailoring of therapy. The Plateletworks assay is based on single platelet counting and has been described as a promising point-of-care assay for the monitoring of the effects of the GP IIb/IIIa antagonists. However, data about its utility and reliability in monitoring the effects of thienopyridines is limited. In the present study we assessed reproducibility of the Plateletworks assay over time. In addition, a comparison between the Plateletworks assay and optical aggregometry was performed in a large cohort of patients on maintenance therapy with aspirin and clopidogrel. The Plateletworks assay demonstrated a good agreement with optical aggregometry in measuring the response to clopidogrel. The results of Plateletworks are, however, highly time dependent which implicates that measurements should be performed within 10 min.

The influence of clinical characteristics, laboratory and inflammatory markers on 'high on-treatment platelet reactivity' as measured with different platelet function tests.

High on-clopidogrel platelet reactivity (HCPR) and high on-aspirin platelet reactivity (HAPR) are independently associated with an increased risk of atherothrombotic events. However, despite this positive correlation, the definitions of both HCPR and HAPR vary largely throughout studies and between different platelet function assays. The aim of the present study was to explore clinical and laboratory parameters that are associated with HCPR and HAPR as measured with different platelet function tests. 530 clopidogrel and aspirin pre-treated patients undergoing elective PCI (percutaneous coronary intervention) were enrolled. Platelet function measurements were performed with: optical aggregometry, the VerifyNow device and PFA-100 cartridges (including the novel INNOVANCE P2Y assay). HCPR as measured with Adenosin-Di-Phospate-induced (ADP) aggregation based tests was associated with clinical factors such as older age, female gender and Diabetes mellitus (DM). The VerifyNow P2Y12 assay was significantly influenced by haemoglobin and haematocrit levels. HAPR as measured with aggregation based tests was significantly influenced by the presence of malignancy, BMI (Body-Mass Index), older age and increased levels of hsCRP (high sensitivity c-reactive proteine). The PFA-100 COL/EPI (collagen-epinephrine) and COL/ADP (collagen-ADP) cartridges were significantly influenced by monocyte count, hs-CRP, MPV (mean platelet volume), vWF-antigen (von Willebrand factor) and vWF-activity. HCPR as measured with the novel INNOVANCE P2Y cartridge was associated with clinical determinants such as BMI, female gender, impaired LVEF (left ventricular ejection fraction), renal failure and dosing of clopidogrel. Laboratory markers that were associated with HCPR as measured with INNOVANCE P2Y were platelet count, white blood cells (WBC), hsCRP and fibrinogen. Both HCPR and HAPR are highly dependent on the type of platelet function assay. Each platelet function assay, in turn, is significantly influenced by distinct clinical and laboratory variables.