Katharina M. Katsaros

The complement component C5a is present in human coronary lesions in vivo and induces the expression of MMP-1 and MMP-9 in human macrophages in vitro

The complement component C5a is formed during activation of the complement cascade and exerts chemotactic and proinflammatory effects. Macrophages, which are localized in the rupture‐prone shoulder regions of coronary plaques, are thought to play a major role in plaque destabilization and rupture through the production of matrix metalloproteinases (MMPs). When human monocyte‐derived macrophages were stimulated in vitro with C5a, MMP‐1 and MMP‐9 mRNA levels were significantly increased. Furthermore, C5a up‐regulated MMP‐1 and MMP‐9 antigens and activity, as determined by ELISA and specific activity assays. These effects were blocked by antibodies against the receptor C5aR/CD88. In addition, blocking experiments revealed that MMP‐1 expression was mediated by activation of the transcription factor AP‐1, and MMP‐9 expression was induced by activation of NF‐κB and AP‐1. Immunohistochemical analysis of human coronary plaques demonstrated the colocalization of C5a, MMP‐1, and MMP‐9 in vivo. Together, these observations indicate that activation of the complement cascade and formation of C5a may play a role in the onset of acute coronary events by induction of MMPs in atherosclerotic lesions.—Speidl, W. S., Kastl, S. P., Hutter, R., Katsaros, K. M., Kaun, C., Bauriedel, G., Maurer, G., Huber, K., Badimon, J. J., Wojta, J. The complement component C5a is present in human coronary lesions in vivo and induces the expression of MMP‐1 and MMP‐9 in human macrophages in vitro. FASEB J. 25, 35–44 (2011). www.fasebj.org

Oncostatin M-enhanced vascular endothelial growth factor expression in human vascular smooth muscle cells involves PI3K-, p38 MAPK-, Erk1/2- and STAT1/STAT3-dependent pathways and is attenuated by interferon-γ

The pleiotropic cytokine oncostatin M (OSM), a member of the glycoprotein (gp)130 ligand family, plays a key role in inflammation and cardiovascular disease. As inflammation precedes and accompanies pathological angiogenesis, we investigated the effect of OSM and other gp130 ligands on vascular endothelial growth factor (VEGF) production in human vascular smooth muscle cells (SMC). Human coronary artery SMC (HCASMC) and human aortic SMC (HASMC) were treated with different gp130 ligands. VEGF protein was determined by ELISA. Specific mRNA was detected by RT-PCR. Western blotting was performed for signal transducers and activators of transcription1 (STAT1), STAT3, Akt and p38 mitogen-activated protein kinase (p38 MAPK). OSM mRNA and VEGF mRNA expression was analyzed in human carotid endaterectomy specimens from 15 patients. OSM increased VEGF production in both HCASMC and HASMC derived from different donors. OSM upregulated VEGF and OSM receptor-specific mRNA in these cells. STAT3 inhibitor WP1066, p38 MAPK inhibitors SB-202190 and BIRB 0796, extracellular signal-regulated kinase1/2 (Erk1/2) inhibitor U0126, and phosphatidylinositol 3-kinase (PI3K) inhibitors LY-294002 and PI-103 reduced OSM-induced VEGF synthesis. We found OSM expression in human atherosclerotic lesions where OSM mRNA correlated with VEGF mRNA expression. Interferon-γ (IFN-γ), but not IL-4 or IL-10, reduced OSM-induced VEGF production in vascular SMC. Our findings that OSM, which is present in human atherosclerotic lesions and correlates with VEGF expression, stimulates production of VEGF by human coronary artery and aortic SMC indicate that OSM could contribute to plaque angiogenesis and destabilization. IFN-γ reduced OSM-induced VEGF production by vascular SMC.

Thrombin induces the expression of oncostatin M via AP-1 activation in human macrophages: a link between coagulation and inflammation.

Macrophages as inflammatory cells are involved in the pathogenesis of atherosclerosis that today is recognized as an inflammatory disease. Activation of coagulation leads to the late complication of atherosclerosis, namely atherothrombosis with its clinical manifestations stroke, unstable angina, myocardial infarction, and sudden cardiac death. Thus inflammation and coagulation play fundamental roles in the pathogenesis of atherosclerosis. We show that the coagulation enzyme thrombin up-regulates oncostatin M (OSM), a pleiotropic cytokine implicated in the pathophysiology of vascular disease, in human monocyte-derived macrophages (MDMs) up to 16.8-fold. A similar effect was seen in human peripheral blood monocytes and human plaque macrophages. In MDMs, the effect of thrombin on OSM was abolished by PPACK and mimicked by a PAR-1-specific peptide. Thrombin induced phosphorylation of ERK1/2 and p38 in MDMs. The ERK1/2 inhibitor PD98059 blocked the effect of thrombin on OSM production in MDMs, whereas the p38 inhibitor SB202190 had no effect. Thrombin induced translocation of c-fos and c-jun to the nucleus of MDMs. Using OSM promoter-luciferase reporter constructs transfected into MDMs, we show that a functional AP-1 site is required for promoter activation by thrombin. We present another link between coagulation and inflammation, which could impact on the pathogenesis of atherosclerosis.

In Human Macrophages the Complement Component C5a Induces the Expression of Oncostatin M via AP-1 Activation

Objective—Macrophages produce the cytokine oncostatin M (OSM), which beside other functions is also involved in inflammation. The complement component C5a mobilizes and activates these cells at inflammatory sites. We examined the effect of C5a on OSM production in human monocytes and in human monocyte-derived macrophages. Methods and Results—For macrophage transformation peripheral blood monocytes were cultivated for 8 to 10 days in the presence of human serum. C5a significantly increased in these cells OSM antigen as determined by specific ELISA and mRNA as quantitated by real-time polymerase chain reaction in these cells as well as in plaque macrophages. This effect was blocked by antibodies against the receptor C5aR/CD88 and by pertussis toxin. The C5a-induced phosphorylation of p38 and JNK and the C5a-induced increase in OSM production in macrophages was abolished by 2 p38 inhibitors and by a JNK inhibitor. Furthermore C5a increased the nuclear translocation of c-fos and c-jun. Using different OSM promoter deletion mutant constructs we show that the putative AP-1 element is responsible for activation of OSM promoter activity by C5a. Conclusion—Our data establish a link between the complement system and the gp130 receptor cytokine family with possible implications for the pathology of inflammatory diseases.

Coronary late lumen loss of drug eluting stents is associated with increased serum levels of the complement components C3a and C5a

OBJECTIVE Drug eluting stents (DES) reduce recurrent luminal narrowing through anti-migratory and anti-proliferative effects. However, recent concerns arose that DES may also induce significant chronic inflammatory responses that may impair vascular healing and lead to in-stent restenosis (ISR). As the complement components C3a and C5a exert particularly strong chemotactic and proinflammatory effects, we examined the association of serum levels of C3a and C5a and ISR after implantation of DES. METHODS We included 82 patients that were treated with 151 DES. Blood samples were taken directly before and 24h after PCI. Serum levels of C3a and C5a were measured by specific ELISA and restenosis was evaluated at 6-8 months by coronary angiography. RESULTS C5a but not C3a increased after implantation of DES (p<0.05). During the follow-up period, two patients (2.4%) died of cardiovascular causes and 12 patients (7.9% of stents, 15% of patients) developed ISR. Serum levels of C3a before and 24h after PCI as well as C5a levels at baseline were significantly higher in patients that developed ISR at follow-up. C3a and C5a at baseline were significantly associated to angiographic late lumen loss independent from clinical and procedural risk factors. CONCLUSION Increased complement activation as measured by higher levels of C3a and C5a before PCI is significantly associated with late lumen loss. Inhibition of the complement cascade to prevent ISR warrants further investigation.

Soluble ST2 and Interleukin-33 Levels in Coronary Artery Disease: Relation to Disease Activity and Adverse Outcome

Objectives ST2 is a receptor for interleukin (IL)-33. We investigated an association of soluble ST2 (sST2) and IL-33 serum levels with different clinical stages of coronary artery disease. We assessed the predictive value of sST2 and IL-33 in patients with stable angina, non-ST elevation myocardial infarction (NSTEMI) and ST elevation myocardial infarction (STEMI). Methods We included 373 patients of whom 178 had stable angina, 97 had NSTEMI, and 98 had STEMI. Patients were followed for a mean of 43 months. The control group consisted of 65 individuals without significant stenosis on coronary angiography. Serum levels of sST2 and IL-33 were measured by ELISAs. Results sST2 levels were significantly increased in patients with STEMI as compared to patients with NSTEMI and stable angina as well as with controls. IL-33 levels did not differ between the four groups. During follow-up, 37 (10%) patients died and the combined endpoint (all cause death, MI and rehospitalisation for cardiac causes) occurred in 66 (17.6%) patients. sST2 serum levels significantly predicted mortality in the total cohort. When patients were stratified according to their clinical presentation, the highest quintile of sST2 significantly predicted mortality in patients with STEMI, but not with NSTEMI or stable coronary artery disease. sST2 was a significant predictor for the combined endpoint in STEMI patients and in patients with stable angina. Serum levels of IL-33 were not associated with clinical outcome in the total cohort, but the highest quintile of IL-33 predicted mortality in patients with STEMI. Conclusions Serum levels of sST2 are increased in patients with acute coronary syndromes as compared to levels in patients with stable coronary artery disease and in individuals without coronary artery disease. sST2 and IL-33 were associated with mortality in patients with STEMI but not in patients with NSTEMI or stable angina.

Increased Restenosis Rate After Implantation of Drug-Eluting Stents in Patients With Elevated Serum Activity of Matrix Metalloproteinase-2 and -9

OBJECTIVES Our aim was to test whether serum levels of matrix metalloproteinase (MMP)-2 and -9 are associated with the development of in-stent restenosis (ISR) after implantation of drug-eluting stents (DES). BACKGROUND With the introduction of DES coronary ISR could be reduced dramatically. However, it still plays a significant role, particularly after treatment of multiple, complex lesions. METHODS We studied 85 patients who were treated with 159 DES. Blood samples for measurement of MMP-2 and -9 antigen and activity were taken directly before and 24 h after percutaneous coronary intervention (PCI). Restenosis was evaluated at 6 to 8 months by coronary angiography. RESULTS During the follow-up period, 2 patients (2.4%) died of cardiovascular causes, and 12 patients developed angiographic ISR. Patients with ISR showed significantly higher serum activity of MMP-9 at baseline (p = 0.017) and of MMP-2 (p < 0.0001) and MMP-9 (p < 0.0001) after the procedure. The PCI increased serum activity of MMP-2 (p = 0.005) and MMP-9 (p = 0.008) only in patients with ISR. The restenosis rates of patients in the highest quartile of MMP-2 after and MMP-9 before and after PCI were 40.0%, 38.9%, and 42.9% compared with 6.3%, 7.7%, and 4.0% in the lower quartiles, respectively. This was independent of clinical and procedural characteristics. CONCLUSIONS Elevated serum activities of MMP-2 and -9 are associated with dramatically increased restenosis rates after PCI with implantation of DES. Determination of MMP levels might be useful for identification of patients who are at high risk for ISR despite implantation of DES.

Premature myocardial infarction is associated with low serum levels of Wnt-1.

OBJECTIVE Besides its effects on glucose and lipid metabolism, the Wnt pathway has been increasingly implicated in the regulation of proliferation, migration and survival of vascular cells. In addition, defective Wnt signaling has been identified in a family with autosomal dominant early coronary artery disease. The aim of this study was to investigate whether premature coronary artery disease is associated with features of decreased Wnt signaling. METHODS AND RESULTS We prospectively enrolled 100 consecutive young survivors of myocardial infarction (MI≤40 years of age) from two high-volume cardiac catheterization centers and 100 sex and age matched hospital controls. We determined serum levels of Wnt-1 and its antagonist Dkk-1 by ELISA. MI patients showed significantly lower Wnt-1 levels as compared to controls (151 ng/mL, IQR 38-473 ng/mL vs. 233 ng/mL, IQR 62-1756; p<0.005) whereas Dkk-1 was not different at baseline. Wnt-1 levels remained stable over time, whereas Dkk-1 significantly increased at one-year follow-up from 3557, IQR 2306-5810 pg/mL to 4973, IQR 3293-7093 pg/mL (p<0.001). In the stable phase of the disease, Wnt-1 levels were lower (p<0.005) and Dkk-1 levels were significantly higher (p<0.001) as compared to controls. Wnt-1 at follow-up was associated with glucose, HbA1c, non-HDL-, HDL-cholesterol and triglyceride levels but no other features of the metabolic syndrome. CONCLUSION This study establishes an association between low Wnt-1 and high Dkk-1 serum levels and premature myocardial infarction. Wnt-1 is associated with markers of glucose and lipid metabolism. Further research elucidating the role of Wnt pathways in premature coronary artery disease and metabolic syndrome is warranted.

Small high-density lipoprotein is associated with monocyte subsets in stable coronary artery disease

Objective: High-density lipoprotein (HDL) particles are heterogeneous in structure and function and the role of HDL subfractions in atherogenesis is not well understood. It has been suggested that small HDL may be dysfunctional in patients with coronary artery disease (CAD). Monocytes are considered to play a key role in atherosclerotic diseases. Circulating monocytes can be divided into three subtypes according to their surface expression of CD14 and CD16. Our aim was to examine whether monocyte subsets are associated with HDL subfractions in patients with atherosclerosis. Methods: We included 90 patients with angiographically stable CAD. Monocyte subsets were defined as classical monocytes (CD14++CD16-; CM), intermediate monocytes (CD14++CD16+; IM) and non-classical monocytes (CD14+CD16++; NCM). HDL subfractions were measured by electrophoresis on polyacrylamide gel. Results: Serum levels of small HDL correlated with circulating pro-inflammatory NCM and showed an inverse relationship to circulating CM independently from other lipid parameters, risk factors, inflammatory parameters or statin treatment regime, respectively. IM were not associated with small HDL. In particular, patients with small HDL levels in the highest tertile showed dramatically increased levels of NCM (14.7 ± 7% vs. 10.7 ± 5% and 10.8 ± 5%; p = 0.006) and a decreased proportion of CM (79.3 ± 7% vs. 83.7 ± 6% and 83.9 ± 6%; p = 0.004) compared to patients in the two lower tertiles. In contrast, intermediate HDL, large HDL and total HDL were not associated with monocyte subset distribution. Conclusion: Small HDL levels are associated with pro-inflammatory NCM and inversely correlated with CM. This may suggest that small HDL could have dysfunctional anti-inflammatory properties in patients with established CAD.

Plasminogen activator inhibitor-1 predicts coronary in-stent restenosis of drug-eluting stents.

Background: We tested the hypothesis that plasma levels of plasminogen activator inhibitor‐1 (PAI‐1) are influenced by percutaneous coronary intervention (PCI) with the implantation of drug eluting stents (DES) and are able to predict the occurrence of in‐stent restenosis (ISR). Methods and results: PAI‐1 active antigen plasma levels were determined in 75 patients before and 24 h after PCI with DES implantation. Patients with ISR after six to eight months (16%) showed significantly lower PAI‐1 plasma levels before PCI (ISR, 11.7 ± 8.1 ng mL−1; non‐ISR, 22.8 ± 18.8 ng mL−1; P <0.05). PAI‐1 levels in the lowest tertile were associated with a 9.5‐fold increased risk of ISR, independent of clinical risk factors, angiographic or procedural characteristics, compared to the highest tertile (P < 0.05). The induced change of PAI‐1 active antigen 24 h after PCI was significantly higher in patients with ISR (ISR, +5.6 ± 8.0 ng mL−1; non‐ISR, −3.2 ± 12.1 ng mL−1; P < 0.05) with positive correlation to late lumen loss (r = 0.30; P < 0.05).Conclusions: ISR after DES implantation is significantly related to plasma levels of PAI‐1 active antigen before and after PCI. If confirmed by larger multicenter studies, the determination of PAI‐1 plasma levels might be clinically helpful in the identification of patients at high risk of developing of ISR, even after DES implantation.