Prognostic implications of cholesterol chrystals at ACS causing culprit lesions, insights from the translational OPTICO-ACS study program

Aims

Cholesterol chrystals (CC) represent a feature of advanced plaque remodeling. Optical coherence tomography (OCT) allows for detailed morphological assessment of the culprit lesion, including the presence of CCs, in vivo. Since CCs have been identified as prognostically relevant plaque feature in coronary artery disease (CAD), the present analysis aims to further characterize their impact on adverse cardiovascular outcome in a large cohort of patients, presenting with acute coronary syndrome (ACS).

Methods

Within the translational OPTICO-ACS study program, 371 consecutive ACS-patients were included into the final analysis. OCT-characteristics, including the presence of CCs, were assessed by a standardized CoreLab analysis following universal consensus standards for OCT-derived plaque features. All patients were followed up for 12 months after the index event and major adverse cardiac events (MACE) consisting of death, myocardial infarction, target vessel revascularization plus re-hospitalization due to unstable or progressive angina pectoris were documented.

Results

215 patients (58.1%) presented with cholesterol chrystals (CCs) at the culprit lesion. Plaque rupture (RFC-ACS) represented the primary ACS-causing pathophysiology (75.3%) in those patients. Further, the presence of CCs was associated with other high-risk features within the culprit lesion, i.e. the presence of thin cap fibroatheroma (77.7% vs. 63.2%; p<0.05), plaque calcification (80.5% vs. 67.1; p<0.01) and microchannels (80.1% vs. 70.1; p<0.05) as well as an increased area stenosis (0.77 vs. 0.73 mm2; p<0.01) and a greater maximum lipid arc (282.8 vs. 242.6°; p<0.01) as compared to culprit lesions free of CCs. Of note, there was a strong association among the occurrence of macrophages within the plaque and cholesterol crystals. Finally, and most importantly MACE during 12 months follow-up, consisting of cardiac death, myocardial infarction, target vessel revascularization and re-hospitalization due to progressive or unstable angina pectoris, occurred with nearly twice the frequency in CC-patients (20.3% vs. 10.6%; p<0.01) as compared to patients without CCs at the culprit site.

Conclusion

The present analysis introduces cholesterol chrystals as a novel prognostically relevant high-risk plaque feature allowing individual risk stratification for patients after ACS.

Funding Acknowledgement

Type of funding sources: None.

TLR2 signalling orchestrates neutrophil activation in acute coronary syndrome with intact fibrous cap – results from the OPTICO-ACS study

Background

Neutrophil granulocytes are key players of the innate immunity, participating in the initiation and progression of atherosclerosis. However, the exact mechanisms of neutrophil activation after acute coronary syndrome (ACS) are poorly understood, especially in the context of the two predominant ACS-causing pathophysiologies - ACS with intact fibrous cap (IFC-ACS) and ACS with ruptured fibrous cap (RFC-ACS). Therefore, the current study focuses on immunophenotyping and ex-vivo functional characterization of neutrophils with regard to the molecular differences between IFC-ACS and RFC-ACS.

Methods

Using high-resolution optical coherence tomography (OCT) of the ACS-causing culprit lesion and re-evaluation by a second OCT-core lab, thirty-two IFC-ACS-patients were matched to thirty-two RFC-ACS-patients by gender, age and diabetes. Local and systemic blood samples were obtained from the site of the ACS-causing culprit lesion (LOC) and from the arterial sheath (SYS), respectively. Neutrophil abundance and surface marker expression were quantified by flow cytometry. Fresh neutrophils were isolated for functional analysis and ex-vivo assessment of cell-toxicity in a co-culture with human aortic endothelial cells (HAECs). Neutrophil secretion of active MMP9 was evaluated by fluorescence-based zymography in supernatants of isolated neutrophils and in patients' plasma samples.

Results

Neutrophils of patients with IFC-ACS show significantly higher expression of the toll-like receptor 2 (TLR2) in comparison to RFC-ACS-derived neutrophils (LOC: 1991±492.8 vs. 1615±440.2; p=0.01; SYS: 2062±464.4 vs. 1670±525.1; p=0.0056). Ex-vivo TLR2-stimulation of local neutrophils in patients with IFC-ACS led to increased toxicity of their secretome and aggravated endothelial cell death in co-culture, as compared to neutrophils from RFC-ACS patients (+59% dead HAECs, IFC-LOC vs. RFC-LOC; p=0.0078). Furthermore, TLR2-stimulation using Pam3CSK4 triggered higher activity rates of MMP9 exclusively in local neutrophils of IFC-ACS-patients (+38.9%±6.1% in IFC-LOC vs. RFC-LOC; p=0.0154). This effect was reversed in IFC-ACS-derived neutrophils being pre-treated with an anti-TLR2 neutralizing antibody (−58.4% ±5.2%, IFC-LOC-anti-TLR2 vs. IFC-LOC-vehicle; p=0.0069). Additionally, MMP9 activity was higher in plasma obtained from the culprit site of IFC-ACS patients (74.1 U/ml ±4.1 vs. 70.0 U/ml ±5.1, IFC-LOC vs. RFC-LOC; p=0.01).

Conclusion

The current study demonstrates novel TLR2-dependant neutrophil activation patterns at the coronary culprit lesion of IFC-ACS, leading to higher endothelial cell toxicity and MMP9 activity. Further studies need to assess whether a temporary blockade of TLR2 activation could be a possible therapeutic target in the era of personalized medicine.

Funding Acknowledgement

Type of funding source: Public Institution(s). Main funding source(s): Berlin Institute of Health (BIH), German Center for Cardiovascular Research

P6394Neutrophil activation patterns in acute coronary syndrome with intact fibrous cap - results from the OPTICO-ACS study

Background

In up to one third of all cases, acute coronary syndrome occurs without signs of plaque rupture. Instead endothelial cell erosion is considered to be the hallmark of acute coronary syndrome with intact fibrous cap (IFC-ACS), with matrix metalloproteinase 9 (MMP9) directly linked to this pathology. The main source of MMP9 immediately after ACS are the neutrophil granulocytes. Therefore, their molecular activation patterns and subsequent MMP9 production are the objectives of the ongoing, translational OPTICO-ACS-Study, aiming to compare the mechanisms and prognosis of IFC-ACS and ACS with ruptured fibrous cap (RFC-ACS).

Methods

Local and systemic blood samples were simultaneously obtained from the site of the ACS-causing culprit lesion (LOC) using an aspiration catheter and from the systemic circulation (SYS). Using optical coherence tomography (OCT) the ACS-causing culprit lesion was characterized and two patient groups, patients with ACS caused by intact (IFC-ACS) and by ruptured fibrous cap (RFC-ACS) were compared. Each group consists of twenty patients (n=20) matched by age, gender and diabetes. Neutrophil counts and expression of activation markers were immediately quantified by whole-blood flow cytometry. Release of active MMP9 into the plasma was assessed by fluorescence-based zymography. Activation profiles of freshly isolated neutrophils, including MMP9 activity and effect on endothelial cell death, in response to toll-like receptor 2 (TLR2) stimulation was studied.

Results

Local neutrophils of patients with IFC-ACS show significantly higher expression of TLR2 in comparison to RFC-ACS neutrophils (LOC: 1866±382.1 vs. 1498±426.9; IFC-ACS vs. RFC-ACS, p=0.03). MMP9 activity is significant higher (p=0.01) in plasma obtained from the culprit site of IFC-ACS (74.1 U/ml±4.1) compared to those of RFC-ACS patients (70.0 U/ml±5.1) indicating secretion and activation of the enzyme during IFC-ACS. Importantly, in patients with IFC-ACS, TLR2-stimulation using Pam3CSK4 triggers higher activity rates of MMP9 only in neutrophils isolated directly from the culprit site (LOC), but not systemically (+27%±17.2% IFC-LOC vs. IFC-SYS; p=0.003). This effect was not observed in RFC-derived neutrophils. Inhibiting TLR2 by a monoclonal antibody, strongly reduced secretion of activated MMP9 only in the local neutrophils from IFC-ACS-patients (−54.6%±6.5% in IFC-LOC-anti-TLR2 vs. IFC-LOC-vehicle; p=0.008), but not from systemic IFC-neutrophils, nor from RFC-neutrophils. Furthermore, LOC IFC-ACS neutrophils aggravate endothelial cell death upon TLR2-activation in comparison to LOC RFC-ACS neutrophils (58.4±4.96% vs. 20±1.89%, IFC-ACS vs. RFC-ACS; p=0.0023).

Conclusion

We newly describe differential kinetics of MMP9 release by neutrophils in ACS patients with IFC versus RFC. Our data support a role of a TLR-2 activated and neutrophil-MMP9-mediated mechanism leading to endothelial cell erosion in patients with IFC-ACS.

Acknowledgement/Funding

DZHK (German Centre for Cardiovascular Research); BIH (Berlin Institute of Health)