A potential role of the CXC chemokine GROalpha in atherosclerosis and plaque destabilization: downregulatory effects of statins.

OBJECTIVE: We examined the role of the CXCR2 ligand growth-related oncogene (GRO) alpha in human atherosclerosis. METHODS AND RESULTS: GROalpha levels were examined by enzyme immunoassay, real-time quantitative RT-PCR, and cDNA microarrays. The in vitro effect of statins on GROalpha was examined in endothelial cells and THP-1 macrophages. Our main findings were: (1) GROalpha was among the 10 most differentially expressed transcripts comparing peripheral blood mononuclear cells (PBMCs) from patients with coronary artery disease (CAD) and healthy controls. (2) Both patients with stable (n=41) and particularly those with unstable (n=47) angina had increased plasma levels of GROalpha comparing controls (n=20). (3) We found increased expression of GROalpha within symptomatic carotid plaques, located to macrophages and endothelial cells. (4) GROalpha enhanced the release of matrix metalloproteinases in vascular smooth muscle cells, and increased the binding of acetylated LDL in macrophages. (5) Atorvastatin downregulated GROalpha levels as shown both in vitro in endothelial cells and macrophages and in vivo in PBMCs from CAD patients. (6) The effect on GROalpha in endothelial cells involved increased storage and reduced secretion of GROalpha. CONCLUSIONS: GROalpha could be involved in atherogenesis and plaque destabilization, potentially contributing to inflammation, matrix degradation, and lipid accumulation within the atherosclerotic lesion.

Enhanced expression of the homeostatic chemokines CCL19 and CCL21 in clinical and experimental atherosclerosis: possible pathogenic role in plaque destabilization.

OBJECTIVE: Based on their role in T-cell homing into nonlymphoid tissue, we examined the role of the homeostatic chemokines CCL19 and CCL21 and their common receptor CCR7 in coronary artery disease (CAD). METHODS AND RESULTS: We performed studies in patients with stable (n=40) and unstable (n=40) angina and healthy controls (n=20), in vitro studies in T-cells and macrophages, and studies in apolipoprotein-E-deficient (ApoE-/-) mice and human atherosclerotic carotid plaques. We found increased levels of CCL19 and CCL21 within the atherosclerotic lesions of the ApoE-/- mice, in human atherosclerotic carotid plaques, and in plasma of CAD patients. Whereas strong CCR7 expression was seen in T-cells from murine and human atherosclerotic plaques, circulating T-cells from angina patients showed decreased CCR7 expression. CCL19 and CCL21 promoted an inflammatory phenotype in T-cells and macrophages and increased matrix metalloproteinase (MMP) and tissue factor levels in the latter cell type. Although aggressive statin therapy increased CCR7 and decreased CCL19/CCL21 levels in peripheral blood from CAD patients, conventional therapy did not. CONCLUSIONS: The abnormal regulation of CCL19 and CCL21 and their common receptor in atherosclerosis could contribute to disease progression by recruiting T-cells and macrophages to the atherosclerotic lesions and by promoting inflammatory responses in these cells.

Increased levels of neutrophil-activating peptide-2 in acute coronary syndromes: possible role of platelet-mediated vascular inflammation.

OBJECTIVES: We sought to investigate the role of the CXC chemokine neutrophil-activating peptide-2 (NAP-2) in atherogenesis and plaque destabilization. BACKGROUND: Chemokines are involved in atherogenesis, but the role of NAP-2 in atherosclerotic disorders is unclear. Based on its potential pro-atherogenic properties, we hypothesized a pathogenic role for NAP-2 in coronary artery disease. METHODS: We tested this hypothesis by differential experimental approaches including studies in patients with stable (n = 40) and unstable angina (n = 40) and healthy control subjects (n = 20). RESULTS: The following results were discovered: 1) patients with stable, and particularly those with unstable, angina had markedly raised plasma levels of NAP-2 compared with control subjects, accompanied by increased expression of CXC receptor 2 in monocytes; 2) platelets, but also peripheral blood mononuclear cells (PBMCs), released large amounts of NAP-2 upon stimulation, with a particularly prominent PBMC response in unstable angina; 3) NAP-2 protein was detected in macrophages and smooth muscle cells of atherosclerotic plaques and in monocytes and platelets of coronary thrombi; 4) in vitro, recombinant and platelet-derived NAP-2 increased the expression of adhesion molecules and chemokines in endothelial cells; and 5) whereas aspirin reduced plasma levels of NAP-2, statin therapy increased NAP-2 with stimulating effects both on platelets and leukocytes. CONCLUSIONS: Our findings suggest that NAP-2 has the potential to induce inflammatory responses within the atherosclerotic plaque. By its ability to promote leukocyte and endothelial cell activation, such a NAP-2-driven inflammation could promote plaque rupture and acute coronary syndromes.

Chemokines in children with heterozygous familiar hypercholesterolemia: selective upregulation of RANTES.

OBJECTIVE: Increasing data support the involvement of chemokines in atherogenesis. However, although several studies have shown increased chemokine levels in adult patients, the literature is virtually devoid of data on chemokines in children with hypercholesterolemia. METHODS AND RESULTS: We examined the gene expression of chemokines in peripheral blood mononuclear cells (PBMCs) from clinically healthy children with and without heterozygous familial hypercholesterolemia (FH). Our main findings were: (1) compared with healthy controls, PBMCs from FH children showed significantly higher mRNA levels of RANTES, but not of the other examined chemokines; (2) an opposite pattern was seen in adult FH subjects, with markedly enhanced expression of macrophage inflammatory peptide-1alpha, but not of RANTES; (3) this increased gene expression of RANTES in PBMCs from FH children seemed to reflect enhanced RANTES expression in monocytes but not in T cells; (4) FH children also had raised serum levels of neopterin, additionally suggesting monocyte/macrophage activation in these children; and (5) PBMCs from both FH children and controls showed enhanced release of interleukin 8 on RANTES stimulation in vitro. CONCLUSIONS: Our findings support a role of inflammation also in the early stages of atherogenesis possibly involving monocyte-derived RANTES as an important mediator.

Role of interleukin-10 in atherogenesis and plaque stabilization.

Considerable progress has been made in the understanding of atherogenesis and atherosclerosis is now considered to be an inflammatory disease of the vessel wall involving several cell types, such as endothelial cells, smooth muscle cells and macrophages. Progression of an atheroslerotic lesion can lead to vulnerable and rupture-prone plaques, causing thrombus formation and the development of acute coronary syndromes. The balance between inflammatory (e.g., tumor necrosis factor-alpha, interleukin-6,) and anti-inflammatory cytokines (e.g., IL-10) seems to be of critical importance in the pathogenesis of plaque formation and destabilization, and it has recently been suggested that an inflammatory imbalance in unstable disease with inadequately raised IL-10 levels is also of importance. This lack of IL-10-mediated responses could promote inflammation, enhance oxidative stress and foam cell apoptosis, leading to plaque destabilization and thrombus formation and the development of acute coronary syndromes. Based on these issues, IL-10 has been postulated as an immunological scalpel in atherosclerotic disorders. Knowledge of IL-10 as a modulator of plaque stability may provide multiple opportunities for the treatment and prevention of atherosclerotic diseases in the future.

Potential role for immunomodulatory therapy in atherosclerotic plaque stabilisation.

Our understanding of the mechanisms underlying acute coronary syndromes has evolved beyond the view that this syndrome reflects a progressive collection of lipids and cellular debris in the vascular wall. Current evidence has implicated a role for inflammation in the pathogenesis of this process. Thus, inflammatory cytokines may attenuate interstitial collagen synthesis, increase matrix degradation and promote apoptosis in several atheroma-associated cell types, and all these cellular events may enhance plaque vulnerability. Recently, a series of experimental studies have reported the plaque-stabilising effects of immunomodulatory therapy such as chemokine blockade, anti-CD40 ligand and IL-10. It is conceivable that some of these approaches will be tested clinically and, if successful, they could provide novel treatment strategies for atherosclerotic plaque stabilisation.

Interleukin-10 enhances the oxidized LDL-induced foam cell formation of macrophages by antiapoptotic mechanisms.

Interleukin (IL)-10 may have a therapeutic potential in atherosclerosis, but its mechanisms of action have not been clarified. Foam cell formation is a key event in atherogenesis, and apoptosis of these lipid-laden cells may promote plaque destabilization. We sought to explore whether IL-10 could have plaque-stabilizing properties in acute coronary syndromes (ACS). We studied the effect of IL-10 on oxidized low density lipoprotein (oxLDL)-stimulated THP-1 cells and monocyte-derived macrophages from ACS patients and healthy controls using different experimental approaches. Our main findings were: i) IL-10 enhances lipid accumulation in oxLDL-stimulated THP-1 macrophages, at least partly by counteracting oxLDL-induced apoptosis; ii) This antiapoptotic effect of IL-10 involves increased expression of the antiapoptotic genes Bfl-1 and Mcl-1, accompanied by protective effects on mitochondria function; iii) By silencing Bfl-1 and Mcl-1 genes using siRNAs, we were able to abolish this IL-10-mediated effect on lipid accumulation; iv) IL-10 also induced lipid accumulation in oxLDL-stimulated macrophages from patients with ACS, but not in macrophages from healthy controls; v) In ACS patients, this enhancing effect of IL-10 on lipid accumulation was accompanied by enhanced Mcl-1 expression. No such antiapoptotic effect was seen in macrophages from healthy controls. These findings suggest a new mechanism for the effect of IL-10 in atherosclerosis, possibly contributing to plaque stabilization.

Effect of activated platelets on expression of cytokines in peripheral blood mononuclear cells - potential role of prostaglandin E2.

Platelets may act as inflammatory cells. To study the effects of soluble and cell-bound platelet factors on the expression of several cytokines and related mediators in leukocytes, peripheral blood mononuclear cells (PBMC) were incubated with platelet-free supernatants from SFLLRN-activated platelet-rich plasma (PRP) or SFLLRN-activated PRP in itself. Our main findings were: (i) the gene expression of several chemokines and some cytokines were markedly increased by both activated PRP and supernatants, as also confirmed at the protein level for IL-6, IL-8 and MIP-1alpha; (ii) the selective protein kinase A type I (PKAI) antagonist Rp-8-Br-cAMP reduced this platelet-induced expression of IL-6, IL-8 and MIP-1alpha in PBMC, suggesting a role of cAMP/PKAI mediated mechanisms in this interaction; (iii) PGE(2) dose-dependently increased the release of IL-6, IL-8 and MIP-1alpha from PBMC mimicking the effect of activated platelets. Furthermore, activated platelets released comparable amounts of PGE(2), suggesting that platelet-derived PGE2 could interact with PBMC in co-cultures; (iv) IL-10 inhibited the platelet-inducing effect on IL-6, IL-8 and MIP-1alpha in PBMC, and notably, the addition PGE2 totally abolished this IL-10 effect suggesting that the suppressive effect of IL-10 on the plateletinduced activation of PBMC might at least partly involve PGE(2) related mechanisms. The present study supports a view of platelets as inflammatory cells, and suggests a potential role of platelet-derived PGE(2) in platelet-induced inflammatory responses.

Potential anti-inflammatory role of activin A in acute coronary syndromes.

OBJECTIVES: We sought to investigate whether activin A could be involved in the immunopathogenesis of acute coronary syndromes. BACKGROUND: Inflammatory mechanisms seem to play a pathogenic role in atherosclerosis and acute coronary syndromes, but the actual mediators have not been fully identified. Activin A, a pleiotropic member of the transforming growth factor-beta cytokine family, has recently been suggested to play a role in inflammation. METHODS: We examined the role of activin A and its endogenous inhibitor follistatin in patients with stable (n = 26) and unstable angina (n = 20) and healthy control subjects (n = 20) by different experimental approaches. RESULTS: 1) Patients with stable angina had raised activin A concentrations, as assessed by protein levels in serum and messenger ribonucleic acid levels in peripheral blood mononuclear cells (PBMCs). 2) Although several activin A-related mediators were upregulated in PBMCs from patients with stable angina compared with controls (i.e., activin A and Smad3), no changes or even downregulation (i.e., Smad2) were seen in unstable disease. 3) The activin type II receptors, representing the primary ligand-binding proteins, were downregulated in unstable compared with stable angina. 4) Percutaneous coronary intervention induced a decrease in the activin A/follistatin ratio, suggesting downregulatory effects on activin A activity. 5) Although activin A dose-dependently suppressed the release of inflammatory cytokines from PBMCs in angina patients, an opposite effect was found in healthy controls. CONCLUSIONS: Our findings suggest an anti-inflammatory potential of activin A in angina patients, and such effects may be of particular relevance in unstable angina in which several of the activin parameters were downregulated.

Increased expression of interleukin-1 in coronary artery disease with downregulatory effects of HMG-CoA reductase inhibitors.

BACKGROUND: Inflammation is important in atherogenesis. Interleukin (IL)-1 is the prototypic inflammatory cytokine. We hypothesized a dysbalance between inflammatory and anti-inflammatory mediators in the IL-1 family in coronary artery disease (CAD) and a possible modulation of these mediators by HMG-CoA inhibitors (statins). METHODS AND RESULTS: In a microarray screening experiment examining peripheral blood mononuclear cells (PBMCs) from 6 CAD patients and 4 healthy control subjects, IL-1beta was identified as 1 of 25 genes whose expression were upregulated in CAD and downregulated by statins. In the following, we studied the role of IL-1beta and related mediators in CAD. Our major findings were as follows. (1) Although mRNA levels of IL-1alpha and IL-1beta were markedly reduced in PBMCs from CAD patients after 6 months of simvastatin (20 mg/d, n=15) and atorvastatin (80 mg/d, n=15) therapy, the reduction in IL-1 receptor antagonist (IL-1Ra) was more modest. Statins also reduced the spontaneous release of IL-1beta and IL-1Ra from PBMCs in CAD patients. (2) mRNA levels of IL-1alpha, IL-1beta, and IL-1Ra were increased in PBMCs from patients with stable (n=20) and unstable (n=20) angina compared with healthy control subjects (n=15). Although the unstable patients had particularly high levels of IL-1beta and IL-1alpha, IL-1Ra was not correspondingly increased. (3) IL-1beta induced release of proatherogenic cytokines from PBMCs, whereas atorvastatin partly abolished this effect. CONCLUSIONS: Our findings suggest that cytokines in the IL-1 family may represent therapeutic targets in CAD. The ability of statins to modulate these cytokines in an anti-inflammatory direction underscores their immunomodulatory potential.

8-isoprostane increases expression of interleukin-8 in human macrophages through activation of mitogen-activated protein kinases.

BACKGROUND AND OBJECTIVES: 8-isoprostane is a marker of oxidative stress in vivo and increased plasma and urine levels are found in patients with vascular disease and in atherosclerotic plaques. Inflammatory chemokines such as interleukin (IL)-8 seem to play an important pathogenic role in atherogenesis. We therefore investigated the effects of 8-isoprostane on the expression of inflammatory chemokines with consciousness on IL-8 (mRNA and protein) in human macrophages. In addition, we studied the involvement of mitogen-activated protein kinases (ERK 1/2 and p38 MAPK) and nuclear factor-kappaB (NF-kappaB) in this process. METHODS AND RESULTS: 8-isoprostane (10 microM) induced IL-8 expression (mRNA and protein), measured by real-time quantitative RT-PCR and enzyme immunoassay, respectively, in both THP-1 macrophages and human monocyte-derived macrophages. Moreover, 8-isoprostane increased mRNA expression of macrophage inflammatory protein-1alpha as determined by RNase protection assay. In this process, 8-isoprostane induced the activation of two major MAP-kinases; ERK 1/2 and p38 MAPK. Furthermore, the ERK 1/2 inhibitor, PD98059, and the p38 MAPK inhibitor, SB203580, markedly reduced 8-isoprostane-induced IL-8 expression (mRNA and protein), while inhibition of NF-kappaB activation and translocation had no significant effect on IL-8 expression. CONCLUSIONS: We show that 8-isoprostane increases IL-8 expression in human macrophages involving both ERK 1/2 and p38 MAPK, but not NF-kappaB signaling pathway. These findings further support a link between oxidative stress/lipid peroxidation and inflammation in human macrophages and suggest a role for 8-isoprostane in this process. This 8-isoprostane-induced chemokine expression might be involved in the pathogenesis of atherosclerosis as well as other inflammatory disorders.

Raised serum levels of soluble CD40 ligand in patients with familial hypercholesterolemia: downregulatory effect of statin therapy.

OBJECTIVES: In the present study, we investigated the effects of statins on serum levels of soluble CD40 ligand (sCD40L) in patients with familial hypercholesterolemia (FH). BACKGROUND: Atherosclerotic disease seems to involve inflammatory and immunologic mechanisms, and sCD40L has recently been identified as one of the key players in the atherosclerotic process. HMG-Co A reductase inhibitors, statins, have been recognized as immunomodulators and reduce cardiovascular events and mortality, but the effects of statins on sCD40L has not been clarified. METHODS: In a randomized, double-blind, clinical trial, as part of the Atorvastatin versus Simvastatin on Atherosclerosis Progression (ASAP) trial, 110 patients with FH were given atorvastatin 80 mg/daily (n = 57) or simvastatin 40 mg/daily (n = 53) for two years. RESULTS: Our main findings were: 1) at baseline patients with FH had significantly higher (approximately 27-fold) serum levels of sCD40L than healthy controls; 2) statin therapy markedly decreased serum levels of sCD40L (approximately 40% reduction); 3) this decrease in sCD40L was found during both "aggressive" (i.e., atorvastatin) and "conventional" (i.e., simvastatin) statin therapy and was not correlated with the degree of reduction in cholesterol levels. CONCLUSIONS: Our findings may suggest enhanced CD40L-CD40 interaction in FH and that this inflammatory response may be downregulated by statins.

Stromal cell-derived factor-1alpha in unstable angina: potential antiinflammatory and matrix-stabilizing effects.

BACKGROUND: Chemokines play a pathogenic role in atherogenesis and plaque destabilization by activating and directing leukocytes into the atherosclerotic plaque. However, stromal cell-derived factor (SDF)-1 was recently found to have antiinflammatory effects, and we hypothesized that this chemokine could play a beneficial role in coronary artery disease. METHODS AND RESULTS: Plasma levels of SDF-1alpha were significantly decreased in patients with stable (n=30) and unstable angina (n=30) compared with healthy control subjects (n=20), particularly in those with unstable disease. By flow cytometry and RNase protection assay, we found decreased surface expression but increased gene expression of the SDF-1alpha receptor CXCR-4 in peripheral blood mononuclear cells (PBMC) from patients with stable angina and patients with unstable angina. In vitro, SDF-1alpha (500 ng/mL) reduced both unstimulated and endotoxin/mitogen-stimulated mRNA and protein levels of monocyte chemoattractant protein-1, interleukin-8, matrix metalloproteinase-9, and tissue factor while increasing tissue inhibitor of metalloproteinases-1 in PBMC from patients with unstable angina. The SDF-1alpha-mediated suppression of monocyte chemoattractant protein-1 and interleukin-8 appears to involve cAMP/protein kinase A type I-dependent pathways. Finally, although SDF-1alpha suppressed the spontaneous release of these inflammatory mediators in unstable angina, enhancing effects were seen in unstimulated PBMC from healthy control subjects, possibly reflecting that PBMC in unstable angina are preactivated in vivo. CONCLUSIONS: In contrast to several other chemokines, our findings suggest that SDF-1alpha, at least in high concentrations, may mediate antiinflammatory and matrix-stabilizing effects in unstable angina. These effects may promote plaque stabilization, and therapeutic intervention that enhances SDF-1alpha activity could potentially be beneficial in acute coronary syndromes.