Interleukin 6 gene transcripts are expressed in atherosclerotic lesions of genetically hyperlipidemic rabbits

Mast cell-mediated immune regulation in health and disease

Mast cells are important components of the immune system, and they perform pro-inflammatory as well as anti-inflammatory roles in the complex process of immune regulation in health and disease. Because of their strategic perivascular localization, sensitivity and adaptability to the microenvironment, and ability to release a variety of preformed and newly synthesized effector molecules, mast cells perform unique functions in almost all organs. Additionally, Mast cells express a wide range of surface and cytoplasmic receptors which enable them to respond to a variety of cytokines, chemicals, and pathogens. The mast cell's role as a cellular interface between external and internal environments as well as between vasculature and tissues is critical for protection and repair. Mast cell interactions with different immune and nonimmune cells through secreted inflammatory mediators may also turn in favor of disease promoting agents. First and forefront, mast cells are well recognized for their multifaceted functions in allergic diseases. Reciprocal communication between mast cells and endothelial cells in the presence of bacterial toxins in chronic/sub-clinical infections induce persistent vascular inflammation. We have shown that mast cell proteases and histamine induce endothelial inflammatory responses that are synergistically amplified by bacterial toxins. Mast cells have been shown to exacerbate vascular changes in normal states as well as in chronic or subclinical infections, particularly among cigarette smokers. Furthermore, a potential role of mast cells in SARS-CoV-2-induced dysfunction of the capillary-alveolar interface adds to the growing understanding of mast cells in viral infections. The interaction between mast cells and microglial cells in the brain further highlights their significance in neuroinflammation. This review highlights the significant role of mast cells as the interface that acts as sensor and early responder through interactions with cells in systemic organs and the nervous system.

Physical Activity and Natural Products and Minerals in the SARS-CoV-2 Pandemic: An Update

Coronavirus-disease 19 (COVID-19) has rapidly become a global public health issue, and there is a desperate need for strategies of prevention, reduction, and treatment to halt the epidemic. The coronavirus affects the immune system, and individuals with a compromised immune system, such as those with diabetes, hypertension, obesity, are more susceptible to this virus. Lifestyle-related variables such as physical activity and nutritional supplements can decrease inflammatory markers, increase anti-inflammatory and antioxidant status, and improve the immune system. Lifesty-lerelated variables play preventive roles against various infectious diseases including COVID-19. This review highlights the effects of physical activity and nutrients supplements on the immune system and their possible benefits in combating the harms caused by infection with the COVID-19 virus.

Nkx-2.5 Regulates MDR1 Expression via Its Upstream Promoter in Breast Cancer Cells

BACKGROUND

Increased expression of MDR1 gene is one of the major mechanisms responsible for multidrug resistance in cancer cells. Two alternative promoters, upstream and downstream, are responsible for transcription of MDR1 gene in the human. However, the molecular mechanism regarding the transactivation of MDR1 upstream promoter (USP) has not been determined.

METHODS

Dual-luciferase reporter gene assays were used to assess the effect of Nkx-2.5 on MDR1 USP activity using reporter plasmids for human MDR1 USP and its mutants. MDR1 mRNA level was examined by quantitative real-time PCR. The direct binding of Nkx-2.5 to the USP of MDR1 was evaluated by promoter enzyme immunoassays and chromatin immunoprecipitation assays.

RESULTS

Nkx-2.5 significantly stimulates the transactivation of MDR1 USP and increases MDR1 mRNA expression in MCF7 breast cancer cells. Reporter gene assays with deleted MDR1 USPs showed that the Nkx-2.5-binding site is located between positions -71 and +12. Mutation of the Nkx-2.5-binding site at nucleotide +4 to +10 markedly reduced the Nkx-2.5-mediated activation of MDR1 USP activity. A promoter binding immunoassay and a chromatin immunoprecipitation assay revealed that Nkx-2.5 binds directly to the region +4/+10 of human MDR1 USP.

CONCLUSION

The results in the present study show Nkx-2.5 is a positive regulator for the transactivation of MDR1 USP in MCF7 breast cancer cells. Our findings will help elucidate the regulatory mechanism responsible for the multidrug resistant cancer phenotype.

C1q and TNF related protein 1 regulates expression of inflammatory genes in vascular smooth muscle cells

BACKGROUND

C1q and TNF related protein 1 (C1QTNF1) is known to be associated with coronary artery diseases. However, the molecular function of C1QTNF1 on the vascular smooth muscles remains to be investigated.

OBJECTIVE

This study was therefore undertaken to investigate the effect of C1QTNF1 on gene expression of human smooth muscle cells and to reveal potential molecular mechanisms mediated by C1QTNF1.

METHODS

Vascular smooth muscle cells were incubated with recombinant C1QTNF1 for 16 h, followed by determining any change in mRNA expressions by Affymetrix genechip. Gene ontology (GO), KEGG pathway, and protein-protein interaction (PPI) network were analyzed in differentially expressed genes. In addition, validation of microarray data was performed using quantitative real-time PCR.

RESULTS

The mRNA expressions of annotated 74 genes were significantly altered after incubation with recombinant C1QTNF1; 41 genes were up-regulated and 33 down-regulated. The differentially expressed genes were enriched in biological processes and KEGG pathways associated with inflammatory responses. In the PPI network analysis, IL-6, CCL2, and ICAM1 were identified as potential key genes with relatively high degree. The cluster analysis in the PPI network identified a significant module composed of upregulated genes, such as IL-6, CCL2, NFKBIA, SOD2, and ICAM1. The quantitative real-time PCR results of potential key genes were consistent with microarray data.

CONCLUSION

The results in the present study provide insights on the effects of C1QTNF1 on gene expression of smooth muscle cells. We believe our findings will help to elucidate the molecular mechanisms regarding the functions of C1QTNF1 on smooth muscle cells in inflammatory diseases.

Association between plasma fatty acids and inflammatory markers in patients with and without insulin resistance and in secondary prevention of cardiovascular disease, a cross-sectional study

BACKGROUND

Proinflammatory biomarkers levels are increased among patients with cardiovascular disease, and it is known that both the presence of insulin resistance and diet may influence those levels. However, these associations are not well studied among patients with established cardiovascular disease. Our objective is to compare inflammatory biomarker levels among cardiovascular disease secondary prevention patients with and without insulin resistance, and to evaluate if there is any association between plasma fatty acid levels and inflammatory biomarker levels among them.

METHODS

In this cross-sectional sub-study from the BALANCE Program Trial, we collected data from 359 patients with established cardiovascular disease. Plasma fatty acids and inflammatory biomarkers (interleukin (IL)-1β, IL-6, IL-8, IL-10, IL-12, high sensitive C-reactive protein (hs-CRP), adiponectin, and tumor necrosis factor (TNF)-alpha) were measured. Biomarkers and plasma fatty acid levels of subjects across insulin resistant and not insulin resistant groups were compared, and general linear models were used to examine the association between plasma fatty acids and inflammatory biomarkers.

RESULTS

Subjects with insulin resistance had a higher concentration of hs-CRP (p = 0.002) and IL-6 (p = 0.002) than subjects without insulin resistance. Among subjects without insulin resistance there was a positive association between stearic fatty acid and IL-6 (p = 0.032), and a negative association between alpha-linolenic fatty acid and pro-inflammatory biomarkers (p < 0.05). Among those with insulin resistance there was a positive association between monounsaturated fatty acids and arachidonic fatty acid and adiponectin (p < 0.05), and a negative association between monounsaturated and polyunsaturated fatty acids and pro-inflammatory biomarkers (p < 0.05), as well as a negative association between polyunsaturated fatty acids and adiponectin (p < 0.05). Our study has not found any association between hs-CRP and plasma fatty acids.

CONCLUSIONS

Subjects in secondary prevention for cardiovascular disease with insulin resistance have a higher concentration of hs-CRP and IL-6 than individuals without insulin resistance, and these inflammatory biomarkers are positively associated with saturated fatty acids and negatively associated with unsaturated fatty acids.

New Insights into the Role of Inflammation in the Pathogenesis of Atherosclerosis

Atherosclerosis is a chronic inflammatory disease characterized by the accumulation of lipids, smooth muscle cell proliferation, cell apoptosis, necrosis, fibrosis, and local inflammation. Immune and inflammatory responses have significant effects on every phase of atherosclerosis, and increasing evidence shows that immunity plays a more important role in atherosclerosis by tightly regulating its progression. Therefore, understanding the relationship between immune responses and the atherosclerotic microenvironment is extremely important. This article reviews existing knowledge regarding the pathogenesis of immune responses in the atherosclerotic microenvironment, and the immune mechanisms involved in atherosclerosis formation and activation.

Association between local interleukin-6 levels and slow flow/microvascular dysfunction

We aimed to investigate the association between local interleukin-6 (IL-6) levels at the infarct-related artery and the risk of slow flow/microvascular dysfunction after PCI in ST-elevation acute myocardial infarction (AMI) patients treated by successful primary PCI. 56 eligible ST-elevation AMI patients (34 male/22 female, mean age: 63.5 ± 10.3 years), undergoing successful primary PCI, were included in the current study. Blood samples were obtained from the extraction catheter placed distal to the lesion before PCI. Plasma IL-6 levels were determined by immunoassay method. Slow flow/microvascular dysfunction was observed in 21 patients (37.5%). Using multiple logistic regression analysis, local IL-6 levels (OR 1.592, CI 1.135-2.268; P = 0.007) were found to be a significant risk factor of slow flow/microvascular dysfunction together with diabetes mellitus (OR = 8.065, CI 1.244-52.632; P = 0.029) and thrombus score (OR = 12.500, CI 1.100-142.857; P = 0.042). Receiver operating characteristic (ROC) curve analysis revealed that local IL-6 (ROC area 0.824, OR 1.704, CI 1.274-2.281, P < 0.001; optimal threshold ≥11.3 pg/ml) had a predictive value of slow flow/microvascular dysfunction with sensitivity of 73% and specificity of 71%. Our study indicated that inflammatory response as presented by local IL-6 levels was associated with slow flow/microvascular dysfunction in patients with ST-elevation AMI after successful primary PCI.

PPARγ and IL-6 - 174G>C gene variants in Croatian patients with ischemic stroke

AIM

Etiology of ischemic stroke (IS) is multifactorial and includes interaction of genetic and environmental factors. Different genes, their polymorphisms, host susceptibility, and inflammation processes play a role in IS development. The aim of this study was to evaluate the effect of PPAR-γ and IL-6 gene variants on IS onset.

MATERIAL AND METHODS

A total of 301 subjects (144 males, 157 females) participated in the study, 114 patients with IS and 187 healthy controls.

RESULTS

Statistically significant predictors of IS were male gender (OR 7.13, 95% CI 2.92-17.39, p<0.001), hypertension (OR 7.82. 95% CI 2.53-24.19, p<0.001), lowered HDL cholesterol (OR 8.20, 95% CI 2.41-27.94, p=0.001), elevated C-reactive protein (OR 5.26, 95% CI 1.92-14.41) and IL-6 -174 GC (OR 2.44 95% CI 1.01-5.91, p=0.0048) genotype. Males, compared to females, had 7 times higher odds for stroke. IL6 -174G/C genotype increased the odds for IS for 2.4 times. PPARγ was not statistically significantly associated with stroke.

CONCLUSION

We can point to the IL-6 -174G>C polymorphisms as candidate gene marker and risk factor for the prediction of ischemic stroke.

Plasma metabolomics identifies lipid abnormalities linked to markers of inflammation, microbial translocation, and hepatic function in HIV patients receiving protease inhibitors

Background

Metabolic abnormalities are common in HIV-infected individuals on antiretroviral therapy (ART), but the biochemical details and underlying mechanisms of these disorders have not been defined.

Methods

Untargeted metabolomic profiling of plasma was performed for 32 HIV patients with low nadir CD4 counts (<300 cells/ul) on protease inhibitor (PI)-based ART and 20 healthy controls using liquid or gas chromatography and mass spectrometry. Effects of Hepatitis C (HCV) co-infection and relationships between altered lipid metabolites and markers of inflammation, microbial translocation, and hepatic function were examined. Unsupervised hierarchical clustering, principal component analysis (PCA), partial least squares discriminant analysis (PLS-DA), Random forest, pathway mapping, and metabolite set enrichment analysis (MSEA) were performed using dChip, Metaboanalyst, and MSEA software.

Results

A 35-metabolite signature mapping to lipid, amino acid, and nucleotide metabolism distinguished HIV patients with advanced disease on PI-based ART from controls regardless of HCV serostatus (p<0.05, false discovery rate (FDR)<0.1). Many altered lipids, including bile acids, sulfated steroids, polyunsaturated fatty acids, and eicosanoids, were ligands of nuclear receptors that regulate metabolism and inflammation. Distinct clusters of altered lipids correlated with markers of inflammation (interferon-α and interleukin-6), microbial translocation (lipopolysaccharide (LPS) and LPS-binding protein), and hepatic function (bilirubin) (p<0.05). Lipid alterations showed substantial overlap with those reported in non-alcoholic fatty liver disease (NALFD). Increased bile acids were associated with noninvasive markers of hepatic fibrosis (FIB-4, APRI, and YKL-40) and correlated with acylcarnitines, a marker of mitochondrial dysfunction.

Conclusions

Lipid alterations in HIV patients receiving PI-based ART are linked to markers of inflammation, microbial translocation, and hepatic function, suggesting that therapeutic strategies attenuating dysregulated innate immune activation and hepatic dysfunction may be beneficial for prevention and treatment of metabolic disorders in HIV patients.

Effects of Thyme Extract Oils (from Thymus vulgaris, Thymus zygis, and Thymus hyemalis) on Cytokine Production and Gene Expression of oxLDL-Stimulated THP-1-Macrophages

Properties of thyme extracts from three different species (Thymus vulgaris, Thymus zygis, and Thymus hyemalis) were examined. Two oil fractions from each species were obtained by CO(2) supercritical fluid extraction. Main compounds presented in the supercritical extracts of the three thyme varieties were 1,8 cineole, thymol, camphor, borneol, and carvacrol. As a cellular model of inflammation/atherogenesis, we use human macrophages derived from THP-1 monocytes and activated by oxidized LDLs. These cells were incubated with the thyme fraction oils, and the productions and gene expressions of the inflammatory mediators TNF-α, IL-1B, IL-6, and IL-10 were determined. Thyme extracts significantly reduced production and gene expression of the proinflammatory mediators TNF-α, IL-1B, and IL-6 and highly increased these parameters on the anti-inflammatory IL-10 cytokine. Changes on production and gene expressions were dose dependent and according to the thyme content of each species. Taken together, these results may suggest that thyme extracts could have anti-inflammatory effects.

Vascular effects of glycoprotein130 ligands--part I: pathophysiological role

The vessel wall is no longer considered as only an anatomical barrier for blood cells but is recognized as an active endocrine organ. Dysfunction of the vessel wall occurs in various disease processes including atherosclerosis, hypertension, peripheral artery disease, aneurysms, and transplant and diabetic vasculopathies. Different cytokines were shown to modulate the behavior of the cells, which constitute the vessel wall such as immune cells, endothelial cells and smooth muscle cells. Glycoprotein 130 (gp130) is a common cytokine receptor that controls the activity of a group of cytokines, namely, interleukin (IL)-6, oncostatin M (OSM), IL-11, ciliary neurotrophic factor (CNTF), leukemia inhibitory factor (LIF), cardiotrophin-1 (CT-1), cardiotrophin-like cytokine (CLC), IL-27, and neuropoietin (NP). Gp130 and associated cytokines have abundantly diverse functions. Part I of this review focuses on the pathophysiological functions of gp130 ligands. We specifically describe vascular effects of these molecules and discuss the respective underlying molecular and cellular mechanisms.

Activation of monocytes and cytokine production in patients with peripheral atherosclerosis obliterans

Background

Arterial peripheral disease is a condition caused by the blocked blood flow resulting from arterial cholesterol deposits within the arms, legs and aorta. Studies have shown that macrophages in atherosclerotic plaque are highly activated, which makes these cells important antigen-presenting cells that develop a specific immune response, in which LDLox is the inducing antigen. As functional changes of cells which participate in the atherogenesis process may occur in the peripheral blood, the objectives of the present study were to evaluate plasma levels of anti-inflammatory and inflammatory cytokines including TNF-α, IFN-γ, interleukin-6 (IL-6), IL-10 and TGF-β in patients with peripheral arteriosclerosis obliterans, to assess the monocyte activation level in peripheral blood through the ability of these cells to release hydrogen peroxide (H₂O₂) and to develop fungicidal activity against Candida albicans (C. albicans) in vitro.

Methods

TNF-α, IFN-γ, IL-6, IL-10 and TGF-β from plasma of patients were detected by ELISA. Monocyte cultures activated in vitro with TNF-alpha and IFN-gamma were evaluated by fungicidal activity against C. albicans by culture plating and Colony Forming Unit (CFU) recovery, and by H₂O₂ production.

Results

Plasma levels of all cytokines were significantly higher in patients compared to those detected in control subjects. Control group monocytes did not release substantial levels of H₂O₂ in vitro, but these levels were significantly increased after activation with IFN-γ and TNF-α. Monocytes of patients, before and after activation, responded less than those of control subjects. Similar results were found when fungicidal activity was evaluated. The results seen in patients were always significantly smaller than among control subjects. Conclusions: The results revealed an unresponsiveness of patient monocytes in vitro probably due to the high activation process occurring in vivo as corroborated by high plasma cytokine levels.

C-reactive protein triggers inflammatory responses partly via TLR4/IRF3/NF-κB signaling pathway in rat vascular smooth muscle cells

AIMS

C-reactive protein (CRP) plays an important role in the inflammatory process of atherosclerosis. Toll-like receptor 4 (TLR4) participates in atherogenesis by mediating the inflammatory responses. The aim of this experiment was to investigate the pro-inflammatory effects and mechanisms of CRP in rat vascular smooth muscle cells (VSMCs), especially focusing on the effects of CRP on IL-6 and peroxisome proliferator-activated receptor γ (PPARγ), and TLR4-dependent signal pathway.

MAIN METHODS

rat VSMCs were cultured, and CRP was used as a stimulant for IL-6 and peroxisome proliferator-activated receptor γ (PPARγ). IL-6 level in the culture supernatant was measured by ELISA, and mRNA and protein expressions were assayed by quantitative real-time PCR and western blot, respectively. RNA interference was used to assess the roles of TLR4 and interferon regulatory factor 3 (IRF3) in the pro-inflammatory signal pathway of CRP.

KEY FINDINGS

CRP stimulated IL-6 secretion, and inhibited mRNA and protein expression of PPARγ in VSMCs in a concentration-dependent manner. Additionally, CRP induced TLR4 expression, promoted nuclear translocation of NF-κB (p65), and augmented IκBα phosphorylation in VSMCs. Taken together, CRP induces the inflammatory responses through increasing IL-6 generation and reducing PPARγ expression in VSMCs, which is mediated by TLR4/IRF3/NF-κB signal pathway.

SIGNIFICANCE

CRP is able to stimulate IL-6 production and to inhibit PPARγ expression in VSMCs via MyD88-independent TLR4 signaling pathway (TLR4/IRF3/NF-κB). These provide the novel evidence for the pro-inflammatory action of CRP involved in atherogenesis.

Vascular cells contribute to atherosclerosis by cytokine- and innate-immunity-related inflammatory mechanisms

Cardiovascular diseases are the human diseases with the highest death rate and atherosclerosis is one of the major underlying causes of cardiovascular diseases. Inflammatory and innate immune mechanisms, employing monocytes, innate receptors, innate cytokines, or chemokines are suggested to be involved in atherogenesis. Among the inflammatory pathways the cytokines are central players. Plasma levels of cytokines and related proteins, such as CRP, have been investigated in cardiovascular patients, tissue mRNA expression was analyzed and correlations to vascular diseases established. Consistent with these findings the generation of cytokine-deficient animals has provided direct evidence for a role of cytokines in atherosclerosis. In vitro cell culture experiments further support the suggestion that cytokines and other innate mechanisms contribute to atherogenesis. Among the initiation pathways of atherogenesis are innate mechanisms, such as toll-like-receptors (TLRs), including the endotoxin receptor TLR4. On the other hand, innate cytokines, such as IL-1 or TNF, or even autoimmune triggers may activate the cells. Cytokines potently activate multiple functions relevant to maintain or spoil homeostasis within the vessel wall. Vascular cells, not least smooth muscle cells, can actively contribute to the inflammatory cytokine-dependent network in the blood vessel wall by: (i) production of cytokines; (ii) response to these potent cell activators; and (iii) cytokine-mediated interaction with invading cells, such as monocytes, T-cells, or mast cells. Activation of these pathways results in accumulation of cells and increased LDL- and ECM-deposition which may serve as an 'immunovascular memory' resulting in an ever-growing response to subsequent invasions. Thus, vascular cells may potently contribute to the inflammatory pathways involved in development and acceleration of atherosclerosis.

Raloxifene slows down the progression of intima-media thickness in postmenopausal women

OBJECTIVE

To investigate the effect of raloxifene on atherosclerosis progression in healthy postmenopausal women.

DESIGN

In a prospective fashion, a total of 155 healthy postmenopausal women were randomly assigned to receive raloxifene 60 mg/day or a matching placebo for 18 months. Atherosclerosis progression was evaluated by B-mode ultrasonography measuring the intima-media thickness (IMT) of the carotid arteries. Plasma levels of triglycerides, low-density lipoprotein cholesterol, soluble forms of intercellular adhesion molecule-1 and vascular cell adhesion molecule-1, E-selectin, interleukin-6, tumor necrosis factor alpha, adiponectin, and the degree of insulin resistance by the homeostatic model assessment method were also determined.

RESULTS

The progression slope of carotid IMT was 0.0112 mm/18 months in the raloxifene group and 0.0857 mm/18 months in the placebo group (P<0.004). Raloxifene treatment compared with placebo produced a significant decrease in plasma triglycerides (P<0.02), low-density lipoprotein cholesterol (P<0.02), soluble forms of intercellular adhesion molecule-1 (P<0.005) and vascular cell adhesion molecule-1 (P<0.04), E-selectin (P<0.02), interleukin-6 (P<0.005), tumor necrosis factor alpha (P<0.005) levels, and homeostatic model assessment index (P<0.005) and a significant increase in plasma adiponectin levels (P<0.001). Logistic regression analysis indicated that women receiving raloxifene had a lower risk of IMT progression (odds ratio=0.41; 95% CI: 0.32-0.70).

CONCLUSION

Raloxifene treatment, possibly through an increase in plasma adiponectin levels, may slow the progression of IMT in postmenopausal women.

Interleukin-6 −174G/C Polymorphism and Ischemic Stroke

Background and Purpose— Interleukin-6 (IL-6) is associated with atherosclerotic disease and is also a key mediator in the inflammatory response to cerebral ischemia. Although the IL-6 −174G/C promoter polymorphism has been associated with carotid artery atherosclerosis and coronary heart disease, its relation to ischemic stroke is unclear. This review summarizes the current literature and discusses methodological considerations for future studies.

Methods— Electronic searches were conducted in the PubMed MEDLINE, Scopus, and ISI Web of Science databases. Two investigators independently reviewed all abstracts to identify studies examining the association between the IL-6 −174G/C polymorphism and ischemic cerebrovascular events.

Results— Twelve relevant publications were identified. Three reported on a subset of patients from a later publication, leaving 9 independent studies. Two studies found an association between ischemic stroke and the G allele or GG genotype, whereas 4 found an association with the C allele or CC genotype. One study found the CC genotype to be significantly less frequent in retinal artery occlusion patients. Two studies found no association between the −174G/C polymorphism and stroke.

Conclusions— Studies investigating stroke and the −174G/C polymorphism report conflicting results, which may reflect the complex physiology of IL-6 and true differences between stroke subtypes and populations. However, interpretation of published results is hindered by methodological limitations, and greater rigor and consistency in future studies will help unravel the relationship between the −174G/C polymorphism and stroke.

Close association of regional interleukin-6 levels in the infarct-related culprit coronary artery with restenosis in acute myocardial infarction

BACKGROUND

The involvement of interleukin (IL)-6 in restenosis of the recanalized coronary artery after the percutaneous coronary intervention (PCI) was examined.

METHODS AND RESULTS

There were 40 patients enrolled in the study who had acute myocardial infarction and whose infarct-related coronary arteries were treated by new thrombectomy devices and stenting. Blood samples were collected from the culprit coronary artery before and immediately after the maneuver of the PCI. Restenosis was defined as residual stenosis because it accounted for more than 50% at the follow-up coronary angiography. Plasma IL-6 levels in the infarct-related coronary artery were 12.8 and 13.2 pg/ml before and after the initial maneuver of the PCI, respectively, values that were significantly greater than that of 7.2 pg/ml in the peripheral vein (p<0.0001). The levels of IL-6 in the pre- and the post-stage of PCI were significantly greater in the patients with restenosis than those without restenosis. The plasma IL-6 levels in the post-stage of PCI had significant correlations with late loss and loss index.

CONCLUSIONS

The present study findings indicate that plasma IL-6 levels in the culprit coronary artery at the post-stage of PCI are closely associated with the future restenosis of the revasculized coronary artery in acute myocardial infarction.

Serum markers of vascular inflammation in dyslipemia

Atherosclerosis is widely recognized as an inflammatory disease because systemic and local inflammatory events mediate all phases of plaque development and progression. Basic and clinical studies have focused on identifying potentially useful markers of inflammation. In this article, we review the inflammatory pathogenesis of atherosclerosis, and highlight recent results of several of the more promising markers of inflammation for cardiovascular risk assessment. Of these markers, the most reliable and accessible for clinical use is currently high-sensitivity C-reactive protein (CRP). At present, most clinical guidelines do not recommend routine measurement of these inflammatory markers. However, these serum markers of vascular inflammation may be useful as an adjunct to lipid screening, especially for patients whose lipid values may not be severely elevated, but who are at intermediate risk according to scoring systems that take into account multiple established risk factors. In addition, since the pleiotropic effects of statins include the inhibition of inflammatory response, serum inflammatory markers could also be useful for monitoring this action. Nevertheless, several issues have to be evaluated before the measurements of inflammatory markers can be used for cardiovascular risk prediction in either clinical practice or in clinical trials evaluating anti-atherosclerotic drugs.

Helper T cells and atherosclerosis: the cytokine web

There is growing evidence regarding the importance of inflammation in the pathogenesis of atherosclerosis and its ultimate progression to the clinical syndromes. Recently there has been an increasing interest in the role of helper T (Th) cells in atherosclerosis. The Th cells act with the macrophages and the dendritic cells via the various cytokines in bringing about a variety of changes thus leading to the progression of atherosclerosis. Atherosclerotic lesions have been seen to have increased expression of type 1 helper T (TH1) cells together with increased levels of the Th1 related cytokines. It is mainly the cytokines involved with Th1 functioning that seem to show a prominent effect, with the whole process centred around interferon gamma, making it seem like every pathway and the cytokines involved lead to a final common pathway of interferon gamma secretion; the increase or decrease of which dictates the progression of atherosclerosis and its final manifestation as the clinical syndromes.

Interleukin-6 Polymorphism: A Genetic Risk Factor for Cardiac Transplant Related Coronary Vasculopathy?

AIMS

Interleukin- (IL-) 6 is a pleiotropic cytokine with effects on the acute phase response, inflammation, and vascular function. A G to C polymorphism has been described at position -174 in the promoter region of the IL-6 gene. We investigated the influence of this polymorphism on the development of cardiac transplant related coronary vasculopathy (CV).

METHODS

Sequence specific polymerase chain reaction identified the -174*G/C allele for 116 cardiac transplant recipients. Coronary disease was identified by routine surveillance post-transplant coronary angiography.

RESULTS

Prevalence of the -174*G/C polymorphism was different between the transplant and control cohorts; *CC 27.6%, *CG 45.7%, and *GG 26.7% vs. 13.2%, 44.1% and 42.7% respectively (p = 0.004). Median time to the first diagnosis of CV was different between the 3 alleles; *CC 2.8 years (2.0-4.0); *CG 3.9 years (2.1-4.5); *GG 5.3 years (3.2-6.1) (p = 0.05). By Kaplan-Meier survival analysis C homozygotes developed CV significantly earlier than the other cohorts (p = 0.035). At 5 years 100% of C homozygotes had evidence for CV. G homozygotes had a more gradual onset of CV with an approximate 60% prevalence at 5 years. *CC genotype was the most predictive risk factor for CV development (Hazard ratio 4.2 (95% CI 1.3-12.9); p = 0.014). Increasing donor age was also significant (Hazard ratio 1.04 (95% CI, 1.0-1.08); p = 0.023).

CONCLUSIONS

Polymorphism at position -174 within the promoter region of the IL-6 gene may be an important risk factor for cardiac transplant related coronary vasculopathy. This may improve patient selection and allow tailored immunosuppressive treatment.

Dehydroepiandrosterone can inhibit the proliferation of myeloma cells and the interleukin-6 production of bone marrow mononuclear cells from patients with myeloma

The serum levels of an adrenal sex hormone, dehydroepiandrosterone sulfate (DHEA-S), are significantly more decreased in human myelomas compared with the reduction brought by physiologic decline with age. In order to clarify the effect of DHEA on myeloma cells, we investigated whether DHEA and DHEA-S could inhibit interleukin-6 (IL-6) production of bone marrow mononuclear cells and the proliferation of myeloma cells from patients with myeloma. DHEA-S and DHEA suppressed IL-6 production from a bone marrow stromal cell line, KM-102, as well as in bone marrow mononuclear cells from patients with myeloma. Furthermore, DHEA inhibited in vitro growth of the U-266 cell line and primary myeloma cells from the patients, as well as the in vivo growth of U-266 cells implanted i.p. in severe combined immunodeficiency-hIL6 transgenic mice. DHEA up-regulated the expression of peroxisome proliferator-activated receptor (PPAR), PPAR beta, but not PPARgamma or PPARalpha, and the expression of IkappaBalpha gene in myeloma cells and bone marrow stromal cells, which could explain the suppressive effect of DHEA on IL-6 production through the down-regulation of NF-kappaB activity. Therefore, these data revealed that DHEA-S, as well as DHEA, had a direct effect on myeloma and bone marrow stromal cells to inhibit their proliferation and IL-6 production, respectively.

The role of monocyte-derived cells and inflammation in baboon ductus arteriosus remodeling

Inflammatory processes play a crucial role in the pathogenesis of atherosclerosis and other vascular disorders. We hypothesized that ischemia of the ductus arteriosus might initiate an active inflammatory response that could play a role in ductus remodeling and permanent closure. To test this hypothesis, we studied effects of postnatal ductus construction on inflammatory processes and remodeling in late-gestation fetal and newborn baboons, and preterm newborn baboons. After postnatal ductus constriction, the expression of several genes known to be essential for atherosclerotic remodeling [vascular cell adhesion molecule (VCAM)-1, E-selectin, IL-8, macrophage colony stimulating factor-1, CD154, interferon-gamma, IL-6, and tumor necrosis factor-alpha] was increased in the ductus wall. We were unable to detect intercellular adhesion molecule (ICAM)-1, ICAM-2, P-selectin, monocyte chemoattractant protein-1, or IL-1 by either real-time PCR or immunohistochemistry. VCAM-1, which is newly expressed by luminal cells of the closed ductus, is an important ligand for the mononuclear cell adhesion receptor VLA4. After postnatal constriction, VLA4+ monocytes/macrophages (CD68+ and CD14+) and, to a lesser extent, T-lymphocytes adhered to the ductus wall. Neutrophils and platelets were not observed. The extent of postnatal neointimal remodeling (both endothelial cell layering and subendothelial space thickening) was associated with the degree of mononuclear cell adhesion. Similarly, the extent of vasa vasorum ingrowth correlated with the invasion of CD68+ cells, from the adventitia into the muscle media. Based on these data, we conclude that the inflammatory response following postnatal ductus constriction may be as necessary for ductus remodeling as it is for atherosclerotic remodeling.

Role of the interleukin-6 -174 G>C gene polymorphism in retinal artery occlusion

BACKGROUND AND PURPOSE

Proinflammatory cytokines including interleukin-6 (IL-6) are supposed to play a pivotal role in the development of atherosclerosis. A common polymorphism in the promoter of the IL-6 gene (IL-6 -174G>C) affects plasma IL-6 concentrations and has been suggested as a risk factor for cardiovascular disease. The aim of the present case-control study was to investigate the role of this polymorphism for retinal artery occlusion (RAO).

METHODS

One hundred eighty-two patients with RAO and 307 control subjects were genotyped for the IL-6 -174G>C polymorphism. Genotypes were determined by fluorogenic exonuclease (TaqMan) assay.

RESULTS

The prevalence of the CC genotype was significantly lower in patients with RAO than in control subjects (10.4% versus 19.9%; P=0.006). Homozygosity for the C allele was associated with an odds ratio of 0.50 (95% CI, 0.28 to 0.89) for RAO.

CONCLUSIONS

The CC genotype of the IL-6 -174G>C polymorphism may be associated with a protective effect against RAO.

Peroxisome proliferator-activated receptor alpha agonists increase nitric oxide synthase expression in vascular endothelial cells

OBJECTIVE

There has been accumulating evidence demonstrating that activators for peroxisome proliferator-activated receptor alpha (PPARalpha) have antiinflammatory, antiatherogenic, and vasodilatory effects. We hypothesized that PPARalpha activators can modulate endothelial nitric oxide synthase (eNOS) expression and its activity in cultured vascular endothelial cells.

METHODS AND RESULTS

Bovine aortic endothelial cells were treated with the PPARalpha activator fenofibrate. The amount of eNOS activity and the expression of eNOS protein and its mRNA were determined. Our data show that treatment with fenofibrate for 48 hours resulted in an increase in eNOS activity. Fenofibrate failed to increase eNOS activity within 1 hour. Fenofibrate also increased eNOS protein as well as its mRNA levels. RU486, which has been shown to antagonize PPARalpha action, inhibited the fenofibrate-induced upregulation of eNOS protein expression. WY14643 and bezafibrate also increased eNOS protein levels, whereas rosiglitazone did not. Transient transfection experiments using human eNOS promoter construct showed that fenofibrate failed to enhance eNOS promoter activity. Actinomycin D studies demonstrated that the half-life of eNOS mRNA increased with fenofibrate treatment.

CONCLUSIONS

PPARalpha activators upregulate eNOS expression, mainly through mechanisms of stabilizing eNOS mRNA. This is a new observation to explain one of the mechanisms of PPARalpha-mediated cardiovascular protection.

Increases in Interleukin-6 and Matrix Metalloproteinase-9 in the Infarct-Related Coronary Artery of Acute Myocardial Infarction

BACKGROUND

To elucidate the involvement of inflammation in coronary artery occlusion, the regional changes in cytokines and matrix metalloproteinases (MMPs) in the infarct-related coronary artery were determined in patients with acute myocardial infarction.

METHODS AND RESULTS

Cardiac catheterization was carried out within 24 h of the onset of infarction in 36 patients. Blood samples were collected from the infarct-related coronary artery, the ascending aorta and the peripheral vein. Plasma interleukin (IL)-6 concentrations were elevated in all 3 samples. Particularly, the plasma IL-6 concentrations were 14.4 pg/ml in the infarct-related coronary artery, a value significantly greater than the respective 8.0 pg/ml and 6.5 pg/ml in the ascending aorta and peripheral vein. Plasma IL-6 concentrations in the infarct-related coronary artery had positive correlation with all of the following references measured by intravascular ultrasound: external elastic membrane cross-sectional area (EEM-CSA) (r=0.47, p<0.01), lesion EEM-CSA (r=0.51, p<0.01) and plaque area (r=0.48, p<0.01). MMP-9 was increased regionally in the infarct-related coronary artery, at 11.8 ng/ml vs 8.2 ng/ml in the ascending aorta (p<0.001).

CONCLUSIONS

The present findings suggest that IL-6 at least is released from the ruptured vulnerable atherosclerotic plaque and that regional activation of macrophages is involved in the occlusive process of coronary artery in acute myocardial infarction.

IL-6 is produced by splenocytes derived from CMV-infected mice in response to CMV antigens, and induces MCP-1 production by endothelial cells: a new mechanistic paradigm for infection-induced atherogenesis

Atherosclerosis is an inflammatory disease. One of the candidate inflammatory triggers is infection. To further characterize the interaction between infection, cytokine induction, and atherosclerosis, we tested the hypothesis that cytomegalovirus (CMV) infection induces the pro-inflammatory cytokine interleukin-6 (IL-6), which in turn induces "pro-atherosclerotic" changes in vascular endothelial cells (ECs). ELISA was used to determine the levels of monocyte chemoattractant protein-1 (MCP-1) in the supernatant of mouse and human ECs incubated with IL-6, and IL-6 levels in supernatants of splenocytes, derived from CMV-infected and uninfected mice, stimulated with mice CMV antigens. IL-6 induced, in a dose response fashion, MCP-1 expression in human ECs: 0, 2, 10, and 50 pg/ml IL-6 increased MCP-1 levels in EC conditioned medium from 1120+/-65 to 1148+/-105, 1395+/-40, and 2119+/-130 pg/ml, respectively (P<0.001). IL-6 also induced MCP-1 expression in mouse ECs (P<0.002). Importantly, IL-6 concentration in the supernatants of splenocytes stimulated with CMV antigens rose from undetectable levels in uninfected mice to 14.9+/-5 pg/ml in the infected mice (P<0.04). These results suggest a previously unrecognized, but potentially important mechanism whereby CMV, and other pathogens, contribute to atherogenesis: T lymphocytes, clonally expanded in response to antigens presented by CMV infection, home to sites of vascular injury and locally release IL-6 when presented with either pathogen antigens that may be present in the plaque, or when they cross-react with host peptides homologous to the relevant pathogen antigens; IL-6 then triggers ECs to release MCP-1, which recruits more monocytes and T-cells into the vessel wall and thereby exacerbates local inflammation, and thus atherogenesis.

Atorvastatin limits the pro-inflammatory response of rat aortic smooth muscle cells to thrombin

Thrombin, a serine protease, plays an important role in the progression of atherosclerosis. How atorvastatin could limit the pro-inflammatory response to thrombin was studied in cultured rat aortic smooth muscle cells. The variations in expression of interleukin-6, heme oxygenase-1, p(22phox) and Mox-1 mRNAs were evaluated by reverse transcriptase-polymerase chain reaction (RT-PCR). Interleukin-6 release was determined using the B9 cell assay. Nuclear factor-kappa B (NF-kappaB) translocation was analysed by electrophoretic mobility shift assay (EMSA) and RhoA protein translocation by Western blot. Thrombin activated interleukin-6 secretion and mRNA expression in smooth muscle cells in a dose-dependent manner. The greatest effect on mRNA expression was obtained after 1 h of stimulation. Preincubation (72 h) of the cells with various concentrations of atorvastatin prevented this effect. Simultaneous addition of mevalonate overcame this statin effect. Thrombin was without effect on p(22phox) and heme oxygenase-1 mRNA expression but, after 3 h of stimulation, induced a two-fold increase in that of Mox-1. Preincubation with atorvastatin dose-dependently downregulated this Mox-1 mRNA expression. In addition, thrombin induced NF-kappaB translocation and membrane translocation of RhoA in smooth muscle cells which were both prevented by pre-treatment of the cells by atorvastatin. These data demonstrate the ability of atorvastatin to prevent the induction by thrombin of a pro-inflammatory phenotype in smooth muscle cells.

Interleukins in atherosclerosis: molecular pathways and therapeutic potential

Interleukins are considered to be key players in the chronic vascular inflammatory response that is typical of atherosclerosis. Thus, the expression of proinflammatory interleukins and their receptors has been demonstrated in atheromatous tissue, and the serum levels of several of these cytokines have been found to be positively correlated with (coronary) arterial disease and its sequelae. In vitro studies have confirmed the involvement of various interleukins in pro-atherogenic processes, such as the up-regulation of adhesion molecules on endothelial cells, the activation of macrophages, and smooth muscle cell proliferation. Furthermore, studies in mice deficient or transgenic for specific interleukins have demonstrated that, whereas some interleukins are indeed intrinsically pro-atherogenic, others may have anti-atherogenic qualities. As the roles of individual interleukins in atherosclerosis are being uncovered, novel anti-atherogenic therapies, aimed at the modulation of interleukin function, are being explored. Several approaches have produced promising results in this respect, including the transfer of anti-inflammatory interleukins and the administration of decoys and antibodies directed against proinflammatory interleukins. The chronic nature of the disease and the generally pleiotropic effects of interleukins, however, will demand high specificity of action and/or effective targeting to prevent the emergence of adverse side effects with such treatments. This may prove to be the real challenge for the development of interleukin-based anti-atherosclerotic therapies, once the mediators and their targets have been delineated.

Functional interplay between angiotensin II and nitric oxide: cyclic GMP as a key mediator

Angiotensin II (Ang II) and nitric oxide (NO) signaling pathways mutually regulate each other by multiple mechanisms. Ang II regulates the expression of NO synthase and NO production, whereas NO downregulates the Ang II type I (AT1) receptor. In addition, downstream effectors of Ang II and NO signaling pathways also interact with each other. A feedback mechanism between Ang II and NO is critical for normal vascular structure and function. Imbalance of Ang II and NO has been implicated in the pathophysiology of many vascular diseases. In this review, we focus on the diverse ways in which Ang II and NO interact and the importance of the balance between the signaling pathways activated by these mediators.

Nitric oxide synthesis is involved in arterial haptoglobin expression after sustained flow changes

The acute phase protein haptoglobin is highly expressed in arteries after sustained flow changes and involved in cell migration and arterial restructuring. In the liver, haptoglobin expression is mainly regulated by interleukin-6 (IL-6). In the artery, shear stress and NO influence IL-6 expression. In the present study, we demonstrate that NO synthesis is involved in the regulation of arterial haptoglobin expression after sustained flow changes. Decreased haptoglobin expression after NO inhibition coincided with decreased IL-6 levels. However, IL-6 knockout mice had normal arterial haptoglobin expression levels after sustained flow changes suggesting that other mediators may provide compensatory mechanisms for the regulation of arterial haptoglobin expression.

Increased levels of monocyte-related cytokines in patients with unstable angina

Inflammatory cytokines play important roles in coronary artery disease. We investigated the clinical significance of monocyte-related cytokine expression in patients with angina pectoris. We studied 26 patients with stable effort angina and 20 patients with unstable angina in whom stenotic lesions of the coronary arteries were confirmed by selective coronary angiography. Plasma levels of interleukin-6 (IL-6), macrophage colony stimulating factor (MCSF), and monocyte chemoattractant protein-1 (MCP-1) were measured. Plasma levels of IL-6, MCSF, and MCP-1 in patients with unstable angina were significantly higher than those in patients with stable angina or control subjects. Patients with unstable angina were further divided into sub-groups according to their clinical classification; Levels of IL-6, MCSF, and MCP-1 in patients, who had anginal attacks at rest within the 48 h prior to admission (Braunwald class IIIB) were significantly higher than those in patients, who did not have attacks at rest (class IB). Five unstable patients, who were refractory to medical therapy and were referred for emergency coronary revascularization showed marked elevation of plasma MCSF and MCP-1 levels. In conclusion, plasma levels of monocyte-related cytokines were elevated in unstable angina. These increases were marked in patients with unstable angina with recent ischemic attack at rest, suggesting that activation of monocytes is involved in vulnerability of underlying atheromatous plaque.

Changes in proinflammatory cytokine activity after menopause

There is now a large body of evidence suggesting that the decline in ovarian function with menopause is associated with spontaneous increases in proinflammatory cytokines. The cytokines that have obtained the most attention are IL-1, IL-6, and TNF-alpha. The exact mechanisms by which estrogen interferes with cytokine activity are still incompletely known but may potentially include interactions of the ER with other transcription factors, modulation of nitric oxide activity, antioxidative effects, plasma membrane actions, and changes in immune cell function. Experimental and clinical studies strongly support a link between the increased state of proinflammatory cytokine activity and postmenopausal bone loss. Preliminary evidence suggests that these changes also might be relevant to vascular homeostasis and the development of atherosclerosis. Better knowledge of the mechanisms and the time course of these interactions may open new avenues for the prevention and treatment of some of the most prevalent and important disorders in postmenopausal women.

Elevated interleukin-6 predicts progressive carotid artery atherosclerosis in dialysis patients: association with Chlamydia pneumoniae seropositivity

The cardiovascular mortality rate is unacceptably high in patients with end-stage renal disease (ESRD), which suggests an accelerated atherogenic process. The cause(s) of the accelerated atherogenesis in ESRD patients are not known, though recent studies suggest that persistent infection, such as Chlamydia pneumoniae, and proinflammatory cytokines may contribute. Forty-five ESRD patients (26 men) aged 51 +/- 2 years was studied at a time-point close to start of dialysis treatment and again after about 12 months of dialysis treatment. By using noninvasive B-mode ultrasonography, we evaluated changes in a surrogate marker of atherosclerosis, calculated intima media (cIM) area, in the common carotid artery. C-reactive protein (CRP), S-albumin, and interleukin-6 (IL-6) assessed the presence of an inflammatory reaction. We also measured C pneumoniae antibodies by microimmunofluorescence, nutritional status by subjective global assessment, lipid parameters, smoking habits, and the presence of comorbidity close to the start of dialysis. No significant changes in the prevalence of carotid plaques or the mean cIM area were observed during the first 12 months of dialysis. However, because some patients showed marked increases in the cIM area during only 12 months of dialysis we divided the patients into 2 groups: 23 nonprogressors ((delta)cIM area -2.7 +/- 0.4 mm2) and 22 progressors ((delta)cIM area 3.6 +/- 0.7 mm2). Sex, age, body mass index, comorbidity, blood lipid levels, S-albumin, and CRP levels did not differ significantly between the 2 groups. On the other hand, progressors had a significantly elevated basal median level of IL-6 (5.7 versus 3.1 pg/mL; P < 0.05) and an increased prevalence of positive (> or 1/64) immunoglobulin (Ig) A antichlamydia antibodies (59% versus 17%; P < 0.01) compared with nonprogressors. A significant positive (R = 0.41; P < 0.01) correlation was found between Log IL-6 and changes in the cIM area during 12 months of dialysis. In a stepwise multiple regression model, Log IL-6 did predict, independently (P < 0.01) of traditional risk factors and C pneumoniae antibodies, changes in the cIM area. These data suggest that a persistent chlamydial infection stimulates IL-6 levels, which in turn may be involved in the pathogenesis of accelerated carotid atherosclerosis in dialysis patients.

Immune mechanisms in atherosclerosis

Atherosclerosis is an inflammatory disease. Its lesions are filled with immune cells that can orchestrate and effect inflammatory responses. In fact, the first lesions of atherosclerosis consist of macrophages and T cells. Unstable plaques are particularly rich in activated immune cells, suggesting that they may initiate plaque activation. We have seen a rapid increase in the understanding of the mechanisms that govern the recruitment, differentiation, and activation of immune cells in atherosclerosis. Experimental research has identified several candidate antigens, and there are encouraging data suggesting that immune modulation as well as immunization can reduce the progression of the disease. This review provides an overview of our current understanding of the role of immune mechanisms in atherosclerosis.

Molecular link between cholesterol, cytokines and atherosclerosis

Current investigation on the origin of atherosclerosis has initiated an intense debate over whether atherosclerosis results from hypercholesterolemia or an inappropriate immune response to vascular injury. Although the role of the immune system has been questioned, the overwhelming body of evidence clearly indicates that atherogenesis is initiated by the interplay between cholesterol and cellular secretion of cytokines (especially IL-6) and apolipoprotein 'E' within the arterial wall. Recent studies have revealed that cells possess two cholesterol-sensors: (a) Receptor-Ck which senses the extracellular cholesterol and initiates signalling pathway responsible for the regulation of genes involved in the cell cycle, cell death, cellular cholesterol homeostasis and cytokines including IL-6; (b) LxR alpha which senses intracellular oxysterols and controls genes involved in cell death, cellular cholesterol homeostasis and cytokine IL-8. These cholesterol sensors define the molecular mechanism responsible for cholesterol-depended regulation of cellular synthesis and secretion of cytokines (IL-6, IL-8) within arterial wall. On the basis of this mechanism, presence of cholesterol and its oxy-derivative in the modified LDL will result in transient activation/deactivation of Receptor-Ck-dependent genes which will give rise to repeated cycles of growth coupled with apoptosis leading to a situation where apoptotic-deficient cells in the arterial wall, would be selected resulting in their accumulation and formation of oligoclonal atherosclerotic plaque.

Nuclear factor kappa-B and the heart

Nuclear factor kappa-B (NFkappaB), a redox-sensitive transcription factor regulating a battery of inflammatory genes, has been indicated to play a role in the development of numerous pathological states. Activation of NFkappaB induces gene programs leading to transcription of factors that promote inflammation, such as leukocyte adhesion molecules, cytokines, and chemokines, although some few substances with possible anti-inflammatory effects are also NFkappaB regulated. The present article reviews basic regulation of NFkappaB and its activation, cell biological effects of NFkappaB activation and the role of NFkappaB in apoptosis. Evidence involving NFkappaB as a key factor in the pathophysiology of ischemia-reperfusion injury and heart failure is discussed. Although activation of NFkappaB induces pro-inflammatory genes, it has lately been indicated that the transcription factor is involved in the signaling of endogenous myocardial protection evoked by ischemic preconditioning. A possible role of NFkappaB in the development of atherosclerosis and unstable coronary syndromes is discussed. Nuclear factor kappa-B may be a new therapeutic target for myocardial protection.

PPARalpha and GR differentially down-regulate the expression of nuclear factor-kappaB-responsive genes in vascular endothelial cells

The antiinflammatory action of glucocorticoids is mediated partly by the inhibition of the expression of several cytokines and adhesion molecules. Some activators for nuclear receptors other than the GR have also been shown to inhibit the expression of these inflammatory molecules, although their molecular mechanisms remain unidentified. We therefore examined the effects of the PPARalpha activator fenofibrate and the GR activator dexamethasone on TNFalpha-stimulated expression of IL-6 and vascular cell adhesion molecule-1 in vascular endothelial cells. Both fenofibrate and dexamethasone reduced TNFalpha-induced IL-6 production in human vascular endothelial cells, but only fenofibrate reduced TNFalpha-stimulated vascular cell adhesion molecule-1 expression in these cells. Transient transfection of bovine aortic endothelial cells with an IL-6 promoter construct or a vascular cell adhesion molecule-1 promoter construct revealed that fenofibrate inhibited TNFalpha-induced IL-6 promoter as well as vascular cell adhesion molecule-1 promoter activities, whereas dexamethasone inhibited only the former. EMSA demonstrated that both fenofibrate and dexamethasone reduced nuclear factor-kappaB binding to its recognition site on the IL-6 promoter, but only fenofibrate reduced such binding to the vascular cell adhesion molecule-1 promoter. Thus, down-regulation of nuclear factor-kappaB activity by PPARalpha occurs in both the IL-6 and vascular cell adhesion molecule-1 genes, whereas that by GR occurs only in the IL-6 gene in vascular endothelial cells. These results strongly suggest the existence of a target gene-specific mechanism for the nuclear receptor-mediated down-regulation of nuclear factor-kappaB activity.

Neuropeptide Y cotransmission with norepinephrine in the sympathetic nerve-macrophage interplay

The CNS modulates immune cells by direct synaptic-like contacts in the brain and at peripheral sites, such as lymphoid organs. To study the nerve-macrophage communication, a superfusion method was used to investigate cotransmission of neuropeptide Y (NPY) with norepinephrine (NE), with interleukin (IL)-6 secretion used as the macrophage read-out parameter. Spleen tissue slices spontaneously released NE, NPY, and IL-6 leading to a superfusate concentration at 3-4 h of 1 nM:, 10 pM:, and 120 pg/ml, respectively. Under these conditions, NPY dose-dependently inhibited IL-6 secretion with a maximum effect at 10(-10) M: (p = 0.012) and 10(-9) M: (p < 0.001). Simultaneous addition of NPY at 10(-9) M: and the alpha-2-adrenergic agonist p-aminoclonidine further inhibited IL-6 secretion (p < 0.05). However, simultaneous administration of NPY at 10(-9) M: and the beta-adrenergic agonist isoproterenol at 10(-6) M: or NE at 10(-6) M: significantly increased IL-6 secretion (p < 0.005). To objectify these differential effects of NPY, electrical field stimulation of spleen slices was applied to release endogenous NPY and NE. Electrical field stimulation markedly reduced IL-6 secretion, which was attenuated by the NPY Y1 receptor antagonist BIBP 3226 (10(-7) M, p = 0.039; 10(-8) M, p = 0.035). This indicates that NPY increases the inhibitory effect of endogenous NE, which is mediated at low NE concentrations via alpha-adrenoceptors. Blockade of alpha-adrenoceptors attenuated electrically induced inhibition of IL-6 secretion (p < 0.001), which was dose-dependently abrogated by BIBP 3226. This indicates that under blockade of alpha-adrenoceptors endogenous NPY supports the stimulating effect of endogenous NE via beta-adrenoceptors. These experiments demonstrate the ambiguity of NPY, which functions as a cotransmitter of NE in the nerve-macrophage interplay.

Serotonin increases interleukin-6 synthesis in human vascular smooth muscle cells

BACKGROUND

Interleukin-6 (IL-6) is a key molecule in chronic inflammation and has been implicated in the progression of atherosclerosis. Serotonin (5-hydroxytryptamine; 5-HT) causes vascular contraction and proliferation, but its role in atherogenesis has not been clarified. We investigated the effects of 5-HT on IL-6 synthesis in human vascular smooth muscle cells (VSMCs).

METHODS AND RESULTS

IL-6 levels in the culture medium of VSMCs were determined by ELISA. IL-6 mRNA accumulation was determined by use of a Quantikine mRNA colorimetric quantification kit. NF-kappaB activation was tested by gel retardation assay. 5-HT induced IL-6 production by VSMCs in a time- and dose-dependent manner, with increased IL-6 mRNA accumulation and nuclear factor-kappaB activation. The effect of 5-HT on IL-6 production was significantly inhibited by the 5-HT(2) receptor antagonist ketanserin and the selective 5-HT(2A) receptor antagonist sarpogrelate. Conversely, the 5-HT(2) receptor agonist alpha-methyl-5-HT increased IL-6 production. The protein kinase C (PKC) inhibitor calphostin C, but not the protein kinase A inhibitor KT5720, suppressed 5-HT-induced IL-6 production. The effect of 5-HT was also abolished in PKC-depleted VSMCs after pretreatment with phorbol 12-myristate 13-acetate for 24 hours.

CONCLUSIONS

5-HT acts on 5-HT(2A) receptors and increases IL-6 synthesis in human VSMCs at least partially through a PKC-dependent pathway. These results suggested that 5-HT may contribute to inflammatory activation of the vessels during atherogenesis.

The multiple actions of angiotensin II in atherosclerosis

Angiotensin II (Ang II), the effector peptide of the renin-angiotensin system, has been implied in the pathogenesis of atherosclerosis on various levels. There is abundant experimental evidence that pharmacological antagonism of Ang II formation by angiotensin converting enzyme inhibition or blockade of the cellular effects of Ang II by angiotensin type 1 receptor blockade inhibits formation and progression of atherosclerotic lesions. Angiotensin promotes generation of oxidative stress in the vasculature, which appears to be a key mediator of Ang II-induced endothelial dysfunction, endothelial cell apoptosis, and lipoprotein peroxidation. Ang II also induces cellular adhesion molecules, chemotactic and proinflammatory cytokines, all of which participate in the induction of an inflammatory response in the vessel wall. In addition, Ang II triggers responses in vascular smooth muscle cells that lead to proliferation, migration, and a phenotypic modulation resulting in production of growth factors and extracellular matrix. While all of these effects contribute to neointima formation and development of atherosclerotic lesions, Ang II may also be involved in acute complications of atherosclerosis by promoting plaque rupture and a hyperthrombotic state. Accordingly, Ang II appears to have a central role in the pathophysiology of atherosclerosis.

Enzymatically degraded, nonoxidized LDL induces human vascular smooth muscle cell activation, foam cell transformation, and proliferation

BACKGROUND

Enzymatic, nonoxidative modification transforms LDL to an atherogenic molecule (E-LDL) that activates complement and macrophages and is present in early atherosclerotic lesions.

METHODS AND RESULTS

We report on the atherogenic effects of E-LDL on human vascular smooth muscle cells (SMC). E-LDL accumulated in these cells, and this was accompanied by selective induction of monocyte chemotactic protein-1 in the absence of effects on the expression of interleukin (IL)-8, RANTES, or monocyte inflammatory proteins-1alpha and -beta). Furthermore, E-LDL stimulated the expression of gp130, the signal-transducing chain of the IL-6 receptor (IL-6R) family, and the secretion of IL-6. E-LDL invoked mitogenic effects on SMC through 2 mechanisms. First, an autocrine mitogenic circuit involving platelet-derived growth factor and fibroblast growth factor-beta was induced. Second, upregulation of gp130 rendered SMC sensitive to transsignaling through the IL-6/sIL-6R activation pathway. Because E-LDL promoted release of both IL-6 and sIL-6R from macrophages, application of macrophage cell supernatants to prestimulated SMC provoked a pronounced and sustained proliferation of the cells.

CONCLUSIONS

E-LDL can invoke alterations in SMC that are characteristic of the evolving atherosclerotic lesion.

Hormone replacement therapy and interrelation between serum interleukin-6 and body mass index in postmenopausal women: a population-based study

Postmenopausal women are at increased risk to develop osteoporosis, coronary artery disease, heart failure, and hypertension. Interleukin-6 (IL-6) may be a pathogenetic element in these disorders. Serum IL-6 levels increase during aging and seem to be related to increased body fat mass. In the present retrospective study we aimed to investigate the role of hormone replacement therapy (HRT) on serum IL-6 levels and the interrelation of IL-6 and body fat mass. Parameters were assessed in a population-based sample of postmenopausal women (n = 302) and, for comparison, 245 men of the same age. Women with HRT (n = 92) had significantly lower serum IL-6 levels compared to subjects without HRT, which was independent of age, antihypertensive therapy, smoking habits, and blood pressure (1.5 +/- 0.1 vs. 2.9 +/- 0.6 pg/mL; P = 0.017). In women without HRT, the body mass index (BMI) was correlated with serum IL-6 levels (P < 0.001). Multivariate analysis controlling simultaneously for the effects of blood pressure and heart rate confirmed the positive correlation (P = 0.001). However, in subjects with HRT no such correlation between IL-6 and BMI was demonstrated, which was confirmed after controlling covariates. In male subjects, BMI correlated with serum IL-6 (P = 0.009), which was, however, blunted after controlling for blood pressure and heart rate, probably indicating an influence of the sympathetic nervous system on this interrelation. In conclusion, women receiving HRT display lower serum IL-6 levels and a blunted interrelation of IL-6 and BMI. As IL-6 may be a pathogenetic factor in age-related diseases, HRT-related inhibition of IL-6 secretion could be an important element for the favorable effects of HRT in postmenopausal women.

Interleukin-6 production by endothelial cells after infection with influenza virus and cytomegalovirus

Inflammation plays a role in the pathogenesis of cardiovascular diseases. Viruses may be a cause of chronic inflammation, and both influenza virus and CMV have been associated with cardiovascular diseases. IL-6, a proinflammatory cytokine with antiviral effects, has a pivotal role in the immune response, and under pathologic conditions, prohemostatic effects of IL-6 could lead to pathologic thrombosis and vascular plaque instability. To investigate this role of IL-6, we measured the production of IL-6 by human endothelial cells after infection with influenza virus and CMV. After infection with influenza virus or CMV, IL-6 release into the medium increased (1756.5+/-156.9 pg/mL vs 284.4+/-55.3 pg/mL; P < .001) for influenza-Infected compared with uninfected cells after 36 hours' incubation. Ultracentrifuged influenza virus supernatants, heat-inactivated virus, and purified hemagglutinin were not able to elicit IL-6 synthesis by human endothelial cells. These findings show that CMV and influenza virus are capable of modulating the in vitro production of IL-6, a cytokine involved in vascular inflammation, by human endothelial cells.

Peroxisome proliferator-activated receptor alpha negatively regulates the vascular inflammatory gene response by negative cross-talk with transcription factors NF-kappaB and AP-1

Interleukin-6 (IL-6) is a pleiotropic cytokine, whose plasma levels are elevated in inflammatory diseases such as atherosclerosis. We have previously reported that peroxisome proliferator-activated receptor alpha (PPARalpha) ligands (fibrates) lower elevated plasma concentrations of IL-6 in patients with atherosclerosis and inhibit IL-1-stimulated IL-6 secretion by human aortic smooth muscle cells (SMC). Here, we show that aortic explants isolated from PPARalpha-null mice display an exacerbated response to inflammatory stimuli, such as lipopolysaccharide (LPS), as demonstrated by increased IL-6 secretion. Furthermore, fibrate treatment represses IL-6 mRNA levels in LPS-stimulated aortas of PPARalpha wild-type, but not of PPARalpha-null mice, demonstrating a role for PPARalpha in this fibrate action. In human aortic SMC, fibrates inhibit IL-1-induced IL-6 gene expression. Furthermore, activation of PPARalpha represses both c-Jun- and p65-induced transcription of the human IL-6 promoter. Transcriptional interference between PPARalpha and both c-Jun and p65 occurs reciprocally, since c-Jun and p65 also inhibit PPARalpha-mediated activation of a PPAR response element-driven promoter. This transcriptional interference occurs independent of the promoter context as demonstrated by cotransfection experiments using PPARalpha, p65, and c-Jun Gal4 chimeras. Overexpression of the transcriptional coactivator cAMP-responsive element-binding protein-binding protein (CBP) does not relieve PPARalpha-mediated transcriptional repression of p65 and c-Jun. Finally, glutathione S-transferase pull-down experiments demonstrate that PPARalpha physically interacts with c-Jun, p65, and CBP. Altogether these data indicate that fibrates inhibit the vascular inflammatory response via PPARalpha by interfering with the NF-kappaB and AP-1 transactivation capacity involving direct protein-protein interaction with p65 and c-Jun.

The influence of age and gender on serum dehydroepiandrosterone sulphate (DHEA-S), IL-6, IL-6 soluble receptor (IL-6 sR) and transforming growth factor beta 1 (TGF-beta1) levels in normal healthy blood donors

Dysregulation of IL-6 synthesis is thought to play a role in the development of a number of age-related conditions, such as rheumatoid arthritis, osteoporosis, atherosclerosis, Alzheimer's disease and B cell malignancies. Recently it has been suggested that the production of IL-6 is influenced by the adrenal hormone dehydroepiandrosterone (DHEA) and its sulphated derivative DHEA-S. In humans we investigated the relationship between DHEA-S, IL-6, IL-6 sR and TGF-beta1 in the serum of normal healthy male and female blood donors. Using immunoassay techniques we found that the serum levels of DHEA-S significantly (P = 0.0001) decreased with age in both males and females. Furthermore, mean DHEA-S levels in all age groups were significantly (P = 0.0001) higher in males. Such correlations were not apparent for IL-6 using a standard assay, but a high sensitivity assay revealed that serum IL-6 was significantly (P = 0.0018) positively correlated with age in males only. In addition, serum levels of DHEA-S were significantly (P = 0.048) negatively correlated with serum IL-6, again in male subjects only. In contrast, serum IL-6 sR and TGF-beta1 levels were not correlated with age in either males or females and were not significantly different between the sexes. However, a significant (P = 0.024) negative correlation between DHEA-S and IL-6 sR was found in males. These studies clearly highlight the complex nature of the relationship between these molecules in the ageing process in normal healthy blood donors and demonstrate the need to use high sensitivity assays when measuring IL-6 in apparently healthy individuals under the age of 70 years.

Transcriptional inhibition by interleukin-6 of the class A macrophage scavenger receptor in macrophages derived from human peripheral monocytes and the THP-1 monocytic cell line

Expression of the class A macrophage scavenger receptor (MSR) contributes to the uptake of modified low density lipoproteins (LDL) by macrophages and transformation of these cells into lipid-laden foam cells, which characterize atherosclerosis. Many environmental factors, in particular, proinflammatory cytokines and growth factors, can exert regulatory effects on MSR expression, whereas intracellular accumulation of cholesterol itself does not influence MSR levels to any considerable extent. In the present study, by using an in vitro model, we examined whether stimulation with interleukin-6 (IL-6), an immunoregulatory, multipotential cytokine, modulates the expression and activities of the MSR in macrophages. When treated with IL-6, macrophages derived from peripheral monocytes and phorbol 12-myristate 13-acetate (PMA)-differentiated THP-1 monocytic cells showed significantly reduced uptake and/or binding of the MSR ligand, acetylated LDL. This effect was paralleled by a reduction in the expression of MSR protein and mRNA. Analysis of MSR promoter activity in THP-1 cells transfected with an MSR promoter-reporter gene construct demonstrated decreased activity of the MSR promoter in IL-6-treated THP-1 macrophages. Electrophoretic mobility gel shift assay also showed a reduction in the binding of a transcription factor to the MSR promoter AP-1/ets elements in IL-6-treated cells. Thus, exposure to IL-6 may inhibit expression of the class A MSR in differentiated macrophages at transcriptional levels. This result suggests that this cytokine may modulate foam cell formation during atherogenesis.

Induction of interleukin-6 expression by angiotensin II in rat vascular smooth muscle cells

Recent studies suggest that atherosclerosis is a kind of inflammatory process and that cytokine plays important roles in this process. Although it is generally accepted that angiotensin II (Ang II) plays an important role in atherogenesis, the role of Ang II in cytokine production has not been explored. In this report, we investigated the effect of Ang II on the production of interleukin-6 (IL-6), which is a multifunctional proinflammatory cytokine in rat vascular smooth muscle cells. Ang II significantly increased the expression of IL-6 mRNA and protein in a dose-dependent manner (10(-10) to 10(-6) mol/L). The expression of IL-6 mRNA induced by Ang II showed 2 peaks at 30 minutes and 12 to 24 hours after stimulation. The effect of Ang II on IL-6 release and mRNA expression was completely blocked by an Ang II type 1 receptor antagonist, CV11974; however, an Ang II type 2 receptor antagonist, PD123319, showed no effect. Chelating of intracellular Ca(2+) with BAPTA-AM, inhibition of tyrosine kinase with genistein, and inhibition of mitogen-activated protein kinase kinase with PD98059 completely abolished the effect of Ang II. However, downregulation of protein kinase C by pretreatment with a phorbol ester for 24 hours or a specific protein kinase C inhibitor, calphostin C, did not affect the Ang II-induced expression of IL-6 mRNA. Deletion and mutational analysis of IL-6 gene promoter showed that cAMP-responsive element was important for Ang II-induced IL-6 gene expression. Gel mobility shift assay showed an increase of cAMP-responsive element binding protein by Ang II. These results provide new insights into Ang II signaling and the role of Ang II in the progression of inflammatory changes of blood vessels.

Expression of the interleukin-6 gene is constitutive and not regulated by estrogen in rat vascular smooth muscle cells in culture

Vascular smooth muscle cells (SMC) are major constituents of the medial layer of blood vessels and are involved in the development of atherosclerotic plaque. SMC secrete copious IL-6 under basal conditions that can be increased by cytokines such as tumor necrosis factor-alpha and interleukin-1beta (IL-1beta). The goal of our studies was to define the role of estrogen in IL-6 production by SMC. In a first series of experiments, the expression of specific messenger RNAs as well as the production of IL-6 bioactivity by rat SMC in culture could be demonstrated in basal and IL-1-stimulated conditions, but was unaffected by estrogen treatment. Different constructs containing deleted or mutated fragments of the human IL-6 promoter driving luciferase or chloramphenicol acetyltransferase reporter gene were then transiently transfected in these cells. A significant basal activity that was increased 2- to 4-fold after IL-1beta stimulation was observed with the total IL-6 promoter. Deletion analysis indicated that the -158/+11 region containing activator protein-1 and cAMP response element sites was apparently the minimal region of IL-6 promoter to confer both constitutive and IL-1-inducible activities. Site-directed mutagenesis experiments suggest that basal activity is dependent upon the promoter sequence -158 to -112 containing the nuclear factor (NF)-IL6(-153) and Sp1 sites, whereas IL-1beta stimulation would depend on the residual -112 nucleotides containing NF-IL6(-75) and NF-kappaB sites. In contrast to the down-regulation of IL-6 expression by estrogen described in osteoblasts, ethinyl estradiol as well as 17beta-estradiol did not influence stimulated IL-6 activity in our experimental conditions whatever the construct tested, even when either estrogen receptor alpha or beta was overexpressed. Thus, the atheroprotective properties of estrogen are probably not mediated through the regulation of IL-6 production by SMC.