Hypokalemia Promotes Arrhythmia by Distinct Mechanisms in Atrial and Ventricular Myocytes.

RATIONALE: Hypokalemia occurs in up to 20% of hospitalized patients and is associated with increased incidence of ventricular and atrial fibrillation. It is unclear whether these differing types of arrhythmia result from direct and perhaps distinct effects of hypokalemia on cardiomyocytes. OBJECTIVE: To investigate proarrhythmic mechanisms of hypokalemia in ventricular and atrial myocytes. METHODS AND RESULTS: Experiments were performed in isolated rat myocytes exposed to simulated hypokalemia conditions (reduction of extracellular [K+] from 5.0 to 2.7 mmol/L) and supported by mathematical modeling studies. Ventricular cells subjected to hypokalemia exhibited Ca2+ overload and increased generation of both spontaneous Ca2+ waves and delayed afterdepolarizations. However, similar Ca2+-dependent spontaneous activity during hypokalemia was only observed in a minority of atrial cells that were observed to contain t-tubules. This effect was attributed to close functional pairing of the Na+-K+ ATPase and Na+-Ca2+ exchanger proteins within these structures, as reduction in Na+ pump activity locally inhibited Ca2+ extrusion. Ventricular myocytes and tubulated atrial myocytes additionally exhibited early afterdepolarizations during hypokalemia, associated with Ca2+ overload. However, early afterdepolarizations also occurred in untubulated atrial cells, despite Ca2+ quiescence. These phase-3 early afterdepolarizations were rather linked to reactivation of nonequilibrium Na+ current, as they were rapidly blocked by tetrodotoxin. Na+ current-driven early afterdepolarizations in untubulated atrial cells were enabled by membrane hyperpolarization during hypokalemia and short action potential configurations. Brief action potentials were in turn maintained by ultra-rapid K+ current (IKur); a current which was found to be absent in tubulated atrial myocytes and ventricular myocytes. CONCLUSIONS: Distinct mechanisms underlie hypokalemia-induced arrhythmia in the ventricle and atrium but also vary between atrial myocytes depending on subcellular structure and electrophysiology.

Altered Levels of Fatty Acids and Inflammatory and Metabolic Mediators in Epicardial Adipose Tissue in Patients With Systolic Heart Failure.

BACKGROUND: Adipose tissue has endocrine properties, secreting a wide range of mediators into the circulation, including factors involved in cardiovascular disease. However, little is known about the potential role of adipose tissue in heart failure (HF), and the aim of this study was to investigate epicardial (EAT) and subcutaneous (SAT) adipose tissue in HF patients. METHODS AND RESULTS: Thirty patients with systolic HF and 30 patients with normal systolic function undergoing thoracic surgery were included in the study. Plasma was sampled and examined with the use of enzyme-linked immunosorbent assays, whereas SAT and EAT biopsies were collected and examined by means of reverse-transcription polymerase chain reaction and gas chromatography. Significantly higher expressions of mRNA encoding interleukin-6, adrenomedullin, peroxisome proliferator-activated receptor α, and fatty acid (FA)-binding protein 3, as well as higher levels of monounsaturated FA and palmitoleic acid, were seen in the EAT of HF patients, whereas the levels of docosahexaenoic acid were lower. Palmitoleic acid levels in EAT were correlated with 2 parameters of cardiac remodeling: increasing left ventricular end-diastolic diameter and N-terminal pro-B-type natriuretic peptide. CONCLUSIONS: Our results demonstrate adipose tissue depot-specific alterations of synthesis of FA and inflammatory and metabolic mediators in systolic HF patients. EAT may be a source of increased circulatory and myocardial levels of these mediators through endocrine actions.

A complex interaction between Rickettsia conorii and Dickkopf-1--potential role in immune evasion mechanisms in endothelial cells.

The pathophysiological hallmark of spotted fever group rickettsioses comprises vascular inflammation. Based on the emerging importance of the wingless (Wnt) pathways in inflammation and vascular biology, we hypothesized that Dickkopf-1 (DKK-1), as a major modulator of Wnt signaling, could be involved in the pathogenesis in rickettsial infections. Our major findings were: (i) While baseline concentration of DKK-1 in patients with R. conorii infection (n = 32) were not different from levels in controls (n = 24), DKK-1 rose significantly from presentation to first follow-up sample (median 7 days after baseline). (ii) In vitro experiments in human umbilical vein endothelial cells (HUVECs) showed that while heat-inactivated R. conorii enhanced the release of interleukin-6 (IL-6) and IL-8, it down-regulated the release of endothelial-derived DKK-1 in a time- and dose-dependent manner. (iii) Silencing of DKK-1 attenuated the release of IL-6, IL-8 and growth-related oncogene (GRO)α in R. conorii-exposed HUVECs, suggesting inflammatory effects of DKK-1. (iv) Silencing of DKK-1 attenuated the expression of tissue factor and enhanced the expression of thrombomodulin in R. conorii-exposed HUVECs suggesting pro-thrombotic effects of DKK-1. The capacity of R. conorii to down-regulate endothelial-derived DKK-1 and the ability of silencing DKK-1 to attenuate R. conorii-induced inflammation in endothelial cells could potentially reflect a novel mechanism by which R. conorii escapes the immune response at the site of infection.

Increased levels of inflammatory cytokines and endothelin-1 in alveolar macrophages from patients with chronic heart failure.

BACKGROUND: Pathophysiological interactions between heart and lungs in heart failure (HF) are well recognized. We investigated whether expression of different factors known to be increased in the myocardium and/or the circulation in HF is also increased in alveolar macrophages in HF. METHODOLOGY/PRINCIPAL FINDINGS: Lung function, hemodynamic parameters, gene expression in alveolar macrophages, and plasma levels in the pulmonary and femoral arteries of HF patients (n = 20) were compared to control subjects (n = 16). Our principal findings were: (1) Lung function was significantly lower in HF patients compared to controls (P<0.05). (2) mRNA levels of ET-1, tumor necrosis factor (TNF)-α and interleukin-6 (IL-6) were increased in alveolar macrophages from HF patients. (3) Plasma levels of ET-1, TNFα, IL-6 and MCP-1 were significantly increased in HF patients, whereas our data indicate a net pulmonary release of MCP-1 into the circulation in HF. CONCLUSIONS/SIGNIFICANCE: Several important cytokines and ET-1 are induced in alveolar macrophages in human HF. Further studies should clarify whether increased synthesis of these factors affects pulmonary remodeling and, directly or indirectly, adversely affects the failing myocardium.

Intramyocardial injections of human mesenchymal stem cells following acute myocardial infarction modulate scar formation and improve left ventricular function.

Cell therapy is a promising treatment modality to improve heart function in acute myocardial infarction. However, the mechanisms of action and the most suitable cell type have not been finally determined. We performed a study to compare the effects of mesenchymal stem cells (MSCs) harvested from different tissues on LV function and explore their effects on tissue structure by morphometry and histological staining for species and lineage relationship. MSCs from skeletal muscle (SM-MSCs) and adipose tissue (ADSCs) were injected in the myocardium of nude rats 1 week after myocardial infarction. After 4 weeks of observation, LVEF was significantly improved in the SM-MSCs group (39.1%) and in the ADSC group (39.6%), compared to the placebo group (31.0%, p < 0.001 for difference in change between groups). Infarct size was smaller after cell therapy (16.3% for SM-MSCs, 15.8% for ADSCs vs. 26.0% for placebo, p < 0.001), and the amount of highly vascularized granulation tissue in the border zone was significantly increased in both groups receiving MSCs (18.3% for SM-MSCs, 22.6% for ADSCs vs. 13.1% for placebo, p = 0.001). By in situ hybridization, moderate engraftment of transplanted cells was found, but no transdifferentiation to cardiomyocytes, endothelial cells, or smooth muscle cells was observed. We conclude that MSC injections lead to improved LVEF after AMI in rats predominantly by reduction of infarct size. After 4 weeks, we observed modulation of scar formation with significant increase in granulation tissue. Transdifferentiation of MSCs to cardiomyocytes or vascular cells did not contribute significantly in this process. MSCs from skeletal muscle and adipose tissue had similar effects.

Krill oil attenuates left ventricular dilatation after myocardial infarction in rats.

BACKGROUND: In the western world, heart failure (HF) is one of the most important causes of cardiovascular mortality. Supplement with n-3 polyunsaturated fatty acids (PUFA) has been shown to improve cardiac function in HF and to decrease mortality after myocardial infarction (MI). The molecular structure and composition of n-3 PUFA varies between different marine sources and this may be of importance for their biological effects. Krill oil, unlike fish oil supplements, contains the major part of the n-3 PUFA in the form of phospholipids. This study investigated effects of krill oil on cardiac remodeling after experimental MI. Rats were randomised to pre-treatment with krill oil or control feed 14 days before induction of MI. Seven days post-MI, the rats were examined with echocardiography and rats in the control group were further randomised to continued control feed or krill oil feed for 7 weeks before re-examination with echocardiography and euthanization. RESULTS: The echocardiographic evaluation showed significant attenuation of LV dilatation in the group pretreated with krill oil compared to controls. Attenuated heart weight, lung weight, and levels of mRNA encoding classical markers of LV stress, matrix remodeling and inflammation reflected these findings. The total composition of fatty acids were examined in the left ventricular (LV) tissue and all rats treated with krill oil showed a significantly higher proportion of n-3 PUFA in the LV tissue, although no difference was seen between the two krill oil groups. CONCLUSIONS: Supplement with krill oil leads to a proportional increase of n-3 PUFA in myocardial tissue and supplement given before induction of MI attenuates LV remodeling.

Elevated serum osteoprotegerin levels measured early after acute ST-elevation myocardial infarction predict final infarct size.

BACKGROUND: Increased serum osteoprotegerin has been shown to be associated with increased mortality and heart failure development in patients with acute coronary syndromes. The aim of the present study was to elucidate a possible association between serum osteoprotegerin measured acutely in patients with ST-elevation myocardial infarction (STEMI) and final infarct size. METHODS Serum osteoprotegerin was measured in fasting blood samples from 199 patients with acute STEMI, sampled at a median time of 16 h after primary percutaneous coronary intervention (PCI). After 3 months, final infarct size (in percentage of left ventricular mass; LVM) was assessed by single-photon emission CT. The outcome variable final infarct size was dichotomised using the 75th percentile as the cutoff value (large infarct size ≥ 29.0%). A multivariable analysis was performed adjusting for multiple clinical and biochemical covariates. RESULTS: Median (IQR) osteoprotegerin concentration was 1.4 (1.0, 2.1) ng ml⁻¹ and patients with high osteoprotegerin level (> median) at baseline had larger infarct size at 3 months compared with patients with low osteoprotegerin levels (< median) (25 (8, 40) vs 6 (0, 19)% of LVM, respectively, p < 0.0001). A high osteoprotegerin level was also associated with an approximately sevenfold increase in the odds of developing a large myocardial infarct (OR 7.0; 3.2, 15.5, p < 0.001). After adjustment for potential confounders including peak troponin T, the adjusted OR was 5.2 (2.0, 13.1) p < 0.001. CONCLUSION: High levels of circulating osteoprotegerin measured the first morning after a PCI-treated acute STEMI were strongly associated with final infarct size.

Mechanisms of novel cardioprotective functions of CCN2/CTGF in myocardial ischemia-reperfusion injury.

CCN2/connective tissue growth factor (CTGF), a CCN family matricellular protein repressed in healthy hearts after birth, is induced in heart failure of various etiologies. Multiple cellular and biological functions have been assigned to CCN2/CTGF depending on cellular context. However, the functions and mechanisms of action of CCN2/CTGF in the heart as well as its roles in cardiac physiology and pathophysiology remain unknown. Transgenic mice with cardiac-restricted overexpression of CTGF (Tg-CTGF) were generated and compared with nontransgenic littermate control (NLC) mice. Tg-CTGF mice displayed slightly lower cardiac mass and inconspicuous increase of myocardial collagen compared with NLC mice but no evidence of contractile dysfunction. Analysis of the myocardial transcriptome by DNA microarray revealed activation of several distinct gene programs in Tg-CTGF hearts involved in cardioprotection and growth inhibition. Indeed, Tg-CTGF mice subjected to ischemia-reperfusion injury by in situ transient occlusion of the left anterior descending coronary artery in vivo displayed reduced vulnerability with markedly diminished infarct size. These findings were recapitulated in isolated hearts perfused with recombinant human (h)CTGF before the ischemia-reperfusion procedure. Consistently, Tg-CTGF hearts, as well as isolated adult cardiac myocytes exposed to recombinant hCTGF, displayed enhanced phosphorylation and activity of the Akt/p70S6 kinase/GSK-3ß salvage kinase pathway and induction of several genes with reported cardioprotective functions. Inhibition of Akt activities also prevented the cardioprotective phenotype of hearts from Tg-CTGF mice. This report provides novel evidence that CTGF confers cardioprotection by salvage phosphokinase signaling leading to inhibition of GSK-3ß activities, activation of phospho-SMAD2, and reprogramming of gene expression.

Activin A in carcinoid heart disease: a possible role in diagnosis and pathogenesis.

BACKGROUND/AIMS: Carcinoid heart disease (CHD), a complication of neuroendocrine tumors (NETs), is characterized by right heart fibrotic lesions. Though serotonin is likely involved, the pathogenesis of CHD remains unclear. Cytokines and growth factors with fibrogenic properties may play a role. We sought to examine the relationship between plasma levels of fibrogenic cytokines and growth factors and CHD, both to provide further insight into possible biomarkers of CHD as well as into the possible pathogenesis of CHD. METHODS: Plasma samples obtained from 71 patients with NETs and 18 controls were analyzed using enzyme immunoassays. All patients underwent echocardiography. RESULTS: 15 patients (21%) had CHD, all of whom had carcinoid syndrome compared to 82% of those without CHD. CHD patients were older (p = 0.01), had larger (p = 0.007) and more numerous liver metastases (p = 0.04), and had elevated 24-hour urinary 5-hydroxyindoleacetic acid (U-5HIAA) (p = 0.03) and serum chromogranin A levels (p = 0.02). CHD patients had higher plasma levels of C-reactive protein (p = 0.03), osteoprotegerin (p = 0.005), and activin A (p = 0.005) than patients without CHD. A significant direct correlation between activin A and U-5HIAA levels was observed in the total patient group (r = 0.30, p = 0.02). Activin A ≥0.34 ng/ml (odds ratio (OR) 5.35 [1.01; 28.17], p = 0.048) and age ≥69.5 (OR 6.10 [1.60; 23.24], p = 0.008) were independent predictors of CHD. Activin A levels were elevated to the same degree in both early and advanced CHD. Activin A ≥0.34 ng/ml had 87% sensitivity and 57% specificity for detecting CHD (p = 0.006). CONCLUSION: Elevated plasma activin A levels are associated with the presence of CHD.

Increased YKL-40 expression in patients with carotid atherosclerosis.

OBJECTIVE: We hypothesized a role for the inflammatory protein YKL-40 in atherogenesis and plaque destabilization based on its role in macrophage activation, tissue remodeling, and angiogenesis. METHODS: Serum YKL-40 levels were measured by enzyme immunoassay in 89 patients with carotid atherosclerosis and 20 healthy controls. Carotid expression of YKL-40 was examined by real time RT-PCR in 57 of the patients. Regulation and effect of YKL-40 were examined in THP-1 monocytes. RESULTS: Our main findings were: (1) serum YKL-40 levels were significantly elevated in patients with carotid atherosclerosis, with particularly high levels in those with symptomatic disease; (2) patients with recent ischemic symptoms (within 2 months) had higher YKL-40 mRNA levels in carotid plaque than other patients; (3) in vitro, the beta-adrenergic receptor agonist isoproterenol, toll-like receptor (TLR) 2 and TLR4 agonists, and in particular releasate from activated platelets significantly increased the expression of YKL-40 in THP-1 monocytes and (4) in vitro, YKL-40 increased matrix metalloproteinase-9 expression and activity in THP-1 monocytes, involving activation of p38 mitogen-activated protein kinase. CONCLUSIONS: Our findings suggest that YKL-40 might be a marker of plaque instability, potentially reflecting macrophage activation and matrix degradation within the atherosclerotic lesion.

Raised MCP-4 levels in symptomatic carotid atherosclerosis: an inflammatory link between platelet and monocyte activation.

AIMS: Several studies suggest a pro-atherogenic role for the CC chemokine receptor 2 (CCR2), thought to reflect interaction with monocyte chemoattractant protein (MCP)-1. Based on its ability to attract leucocytes into inflamed tissue, we hypothesized a pro-atherogenic role for MCP-4, another CCR2 ligand. METHODS AND RESULTS: Our main findings were: (i) patients with symptomatic carotid stenosis (n = 29), but not those with asymptomatic plaques (n = 31), had significantly raised plasma levels of MCP-4 compared with healthy controls (n = 20); (ii) in vitro, releasate from activated platelets markedly increased the expression of MCP-4 and CCR2 in THP-1 monocytes, and enhanced the MCP-4-mediated effect on interleukin-8 secretion in these cells, involving the platelet-derived chemokine RANTES; (iii) while MCP-1 had no effect on the release of RANTES and interferon-inducible protein of 10 kDa in tumour necrosis factor alpha-pre-activated THP-1 monocytes, MCP-4 profoundly enhanced the release of these pro-atherogenic chemokines; and (iv) the data indicate an inflammatory interaction between RANTES and MCP-4, involving CCR2, and mRNA levels of these mediators were markedly up-regulated within symptomatic atherosclerotic carotid plaque (n = 81). CONCLUSION: Our findings suggest that the pro-atherogenic effects of CCR2 may not be restricted to interaction with MCP-1, but could also involve activation by MCP-4, being an inflammatory link between platelet and monocyte activation.

Plasma CCN2/connective tissue growth factor is associated with right ventricular dysfunction in patients with neuroendocrine tumors.

BACKGROUND: Carcinoid heart disease, a known complication of neuroendocrine tumors, is characterized by right heart fibrotic lesions. Carcinoid heart disease has traditionally been defined by the degree of valvular involvement. Right ventricular (RV) dysfunction due to mural involvement may also be a manifestation. Connective tissue growth factor (CCN2) is elevated in many fibrotic disorders. Its role in carcinoid heart disease is unknown. We sought to investigate the relationship between plasma CCN2 and valvular and mural involvement in carcinoid heart disease. METHODS: Echocardiography was performed in 69 patients with neuroendocrine tumors. RV function was assessed using tissue Doppler analysis of myocardial systolic strain. Plasma CCN2 was analyzed using an enzyme-linked immunosorbent assay. Mann-Whitney U, Kruskal-Wallis, Chi-squared and Fisher's exact tests were used to compare groups where appropriate. Linear regression was used to evaluate correlation. RESULTS: Mean strain was -21% +/- 5. Thirty-three patients had reduced RV function (strain > -20%, mean -16% +/- 3). Of these, 8 had no or minimal tricuspid and/or pulmonary regurgitation (TR/PR). Thirty-six patients had normal or mildly reduced RV function (strain < or = -20%, mean -25% +/- 3). There was a significant inverse correlation between RV function and plasma CCN2 levels (r = 0.47, p < 0.001). Patients with reduced RV function had higher plasma CCN2 levels than those with normal or mildly reduced RV function (p < 0.001). Plasma CCN2 > or = 77 microg/L was an independent predictor of reduced RV function (odds ratio 15.36 [95% CI 4.15;56.86]) and had 88% sensitivity and 69% specificity for its detection (p < 0.001). Plasma CCN2 was elevated in patients with mild or greater TR/PR compared to those with no or minimal TR/PR (p = 0.008), with the highest levels seen in moderate to severe TR/PR (p = 0.03). CONCLUSIONS: Elevated plasma CCN2 levels are associated with RV dysfunction and valvular regurgitation in NET patients. CCN2 may play a role in neuroendocrine tumor-related cardiac fibrosis and may serve as a marker of its earliest stages.

The tumour necrosis factor superfamily ligand APRIL (TNFSF13) is released upon platelet activation and expressed in atherosclerosis.

Activated platelets release a wide range of inflammatory mediators, including members of the tumour necrosis factor (TNF) superfamily (e.g. CD40 ligand [CD40L] and LIGHT). Such platelet-mediated inflammation could be involved in atherogenesis and plaque destabilisation. In the present study we investigated whether APRIL, another member of the TNF superfamily that has been detected in megakaryocytes, could be released from platelets upon activation. The release of APRIL was studied in thrombin receptor (SFLLRN) activated platelets, and the expression of APRIL was examined in plasma and within the atherosclerotic lesion in patients with carotid and coronary atherosclerosis. Upon SFLLRN activation, there was a gradual release of APRIL, reaching maximum after 90 minutes. While this pattern is similar to that of CD40L and LIGHT, the release of APRIL was quite differently regulated. Thus, prostaglandin E1, but not inhibitors of metal-dependent proteases and actin polymerisation or the lack of GP IIb/IIIa, blocks APRIL release in activated platelets. With relevance to atherogenesis, we found that patients with coronary artery disease (n=80) had raised plasma levels of APRIL as compared with controls (n=20), and APRIL immunoreactivity was detected in aggregated platelets within the ruptured plaque in patients with myocardial infarction and within macrophages in symptomatic carotid plaques. In conclusion, activated platelets release significant amounts of APRIL in a long-lasting manner, differently regulated than the gradual release of other platelet-derived TNF superfamily ligands. The enhanced expression of APRIL in atherosclerotic disorders, both systemically and within the lesion, may suggest a potential involvement of APRIL in atherogenesis.

Increased systemic and myocardial expression of neutrophil gelatinase-associated lipocalin in clinical and experimental heart failure.

AIMS: Neutrophil gelatinase-associated lipocalin (NGAL or lipocalin-2) is a glycoprotein with bacteriostatic properties. Growing evidence suggests that NGAL may also be involved in cell survival, inflammation, and matrix degradation. We therefore aimed to investigate the role of NGAL in heart failure (HF). METHODS AND RESULTS: Our main findings were (i) patients with acute post-myocardial infarction (MI) HF (n = 236) and chronic HF (n = 150) had elevated serum levels of NGAL (determined by enzyme immunoassay), significantly correlated with clinical and neurohormonal deterioration, (ii) in patients with HF following acute MI, elevated NGAL levels of at baseline were associated with adverse outcomes (median of 27 months follow-up), (iii) in a rat model of post-MI HF, NGAL/lipocalin-2 gene expression was increased in the non-ischaemic part of the left ventricle primarily located to cardiomyocytes, (iv) strong NGAL immunostaining was found in cardiomyocytes within the failing myocardium both in experimental and clinical HF, (v) interleukin-1beta and agonists for toll-like receptors 2 and 4, representing components of the innate immune system, were potent inducers of NGAL/lipocalin-2 in isolated neonatal cardiomyocytes. CONCLUSION: Our demonstration of enhanced systemic and myocardial NGAL expression in clinical and experimental HF further support a role for innate immune responses in the pathogenesis of HF.

Inflammatory interaction between LIGHT and proteinase-activated receptor-2 in endothelial cells: potential role in atherogenesis.

The interaction between inflammatory cytokines and endothelial cells is a critical step in atherogenesis leading to endothelial dysfunction and inflammation. We have previously reported that the tumor necrosis factor superfamily member LIGHT could be involved in atherogenesis through its ability to promote vascular inflammation. In the present study we identified proteinase-activated receptor (PAR)-2 as an inflammatory mediator that was markedly enhanced by LIGHT in endothelial cells. We also found that LIGHT acted synergistically with PAR-2 activation to promote enhanced release of the proatherogenic chemokines interleukin-8 and monocyte chemoattractant protein-1, underscoring that the interaction between LIGHT and PAR-2 is biologically active, promoting potent inflammatory effects. We showed that the LIGHT-mediated upregulation of PAR-2 in endothelial cells is mediated through the HVEM receptor, involving Jun N-terminal kinase signaling pathways. A LIGHT-mediated upregulation of PAR-2 mRNA levels was also found in human monocytes when these cells were preactivated by tumor necrosis factor alpha. We have previously demonstrated increased plasma levels of LIGHT in unstable angina patients, and here we show a similar pattern for PAR-2 expression in peripheral blood monocytes. We also found that LIGHT, LIGHT receptors, and PAR-2 showed enhanced expression, and, to some degree, colocalization in endothelial cells and macrophages, in the atherosclerotic plaques of ApoE(-/-) mice, suggesting that the inflammatory interaction between LIGHT and PAR-2 also may be operating in vivo within an atherosclerotic lesion. Our findings suggest that LIGHT/PAR-2-driven inflammation could be a pathogenic loop in atherogenesis potentially representing a target for therapy in this disorder.

Atherosclerotic plaque stability--what determines the fate of a plaque?

Although the understanding of the underlying pathology of atherosclerosis has improved in recent years, the disease is still the main cause of death globally. Current evidence has implicated the role of inflammation in atherogenesis and plaque destabilization. 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. Several cell types found within the lesion (ie, monocyte/macrophages, T cells, mast cells, platelets) contribute to this immune-mediated plaque destabilization, and a better understanding of these processes is a prerequisite for the development of new treatment strategies in these individuals. Such knowledge could also facilitate a better identification of high-risk individuals. In the present study, these issues will be discussed in more detail, particularly focusing on the interactions between matrix degradation, apoptotic, and inflammatory processes in plaque destabilization.

The complex role of T-cell-based immunity in atherosclerosis.

Although the pathogenic role of T cells in atherogenesis is well established, the function of the various T-cell subsets is far from clear. Whereas activation of the T-helper type 1 (Th1) subset promotes inflammatory and proatherogenic responses and activation of Th2 cells mediates both proatherogenic and antiatherogenic effects, the newly discovered regulatory T-cell subset seems to attenuate atherogenesis. However, the dynamics of T-cell response within the plaque are still poorly understood, and both antigen-dependent and antigen-independent stimuli may be involved in the expansion of T cells in atherosclerotic plaques. Nevertheless, the different nature of the various T-cell subsets and their complex role in atherogenesis underscore the need for future research in this field of atheroimmunology. This research is not only of interest for the basic research field, but may also have relevance for clinical cardiology, potentially leading to new targets for therapy in atherosclerotic disorders.

Increased expression of LIGHT/TNFSF14 and its receptors in experimental and clinical heart failure.

BACKGROUND: Clinical and experimental studies suggest a pathogenic role for inflammation in chronic heart failure (HF). LIGHT is a member of the tumour necrosis factor superfamily involved in innate and adaptive immune responses. AIMS: We sought to investigate a potential pathogenic role of LIGHT in chronic HF. METHODS: We used various clinical and experimental approaches including studies in post-infarction HF rats and in vitro studies of endothelial cells and peripheral blood mononuclear cells (PBMC). RESULTS: Our main findings were: (i) LIGHT and its receptors (i.e., HVEM and lymphotoxin-beta receptor) were regulated during experimental HF, with strong expression in the infarcted area accompanied by up-regulation of HVEM in cardiomyocytes and endothelial cells also in the non-ischaemic part of the left ventricle. (ii) Patients with chronic HF had significantly increased expression of LIGHT on CD3(+) T-cells accompanied by increased expression of HVEM on monocytes and within the failing myocardium. (iii) LIGHT induced interleukin (IL)-6 expression in endothelial cells. In HF patients, but not in healthy controls, such an IL-6-inducing effect was also seen in LIGHT activated PBMC. CONCLUSION: Our findings in both clinical and experimental HF may suggest a role for LIGHT signalling pathways in the progression of chronic HF involving IL-6-related mechanisms.

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.