Expansion of circulating Toll-like receptor 4-positive monocytes in patients with acute coronary syndrome

Systemic administration of propentofylline, ibudilast, and (+)-naltrexone each reverses mechanical allodynia in a novel rat model of central neuropathic pain

Central neuropathic pain (CNP) is a debilitating consequence of central nervous system damage for which current treatments are ineffective. To explore mechanisms underlying CNP, we developed a rat model involving T13/L1 dorsal root avulsion. The resultant dorsal horn damage creates bilateral below-level (L4-L6) mechanical allodynia. This allodynia, termed spinal neuropathic avulsion pain, occurs in the absence of confounding paralysis. To characterize this model, we undertook a series of studies aimed at defining whether spinal neuropathic avulsion pain could be reversed by any of 3 putative glial activation inhibitors, each with distinct mechanisms of action. Indeed, the phosphodiesterase inhibitor propentofylline, the macrophage migration inhibitory factor inhibitor ibudilast, and the toll-like receptor 4 antagonist (+)-naltrexone each reversed below-level allodynia bilaterally. Strikingly, none of these impacted spinal neuropathic avulsion pain upon first administration but required 1 to 2 weeks of daily administration before pain reversal was obtained. Given reversal of CNP by each of these glial modulatory agents, these results suggest that glia contribute to the maintenance of such pain and enduring release of macrophage migration inhibitory factor and endogenous agonists of toll-like receptor 4 is important for sustaining CNP. The markedly delayed efficacy of all 3 glial modulatory drugs may prove instructive for interpretation of apparent drug failures after shorter dosing regimens.

PERSPECTIVE

CNP that develops after trauma is often described by patients as severe and intolerable. Unfortunately, current treatments are not effective. This work suggests that using pharmacologic treatments that target glial cells could be an effective clinical treatment for CNP.

Systemic toll-like receptor and interleukin-18 pathway activation in patients with acute ST elevation myocardial infarction

Acute myocardial infarction (AMI) is accompanied by increased expression of Toll like receptors (TLR)-2 and TLR4 on circulating monocytes. In animal models, blocking TLR2/4 signaling reduces inflammatory cell influx and infarct size. The clinical consequences of TLR activation during AMI in humans are unknown, including its role in long-term cardiac functional outcome Therefore, we analyzed gene expression in whole blood samples from 28 patients with an acute ST elevation myocardial infarction (STEMI), enrolled in the EXenatide trial for AMI patients (EXAMI), both at admission and after 4-month follow-up, by whole genome expression profiling and real-time PCR. Cardiac function was determined by cardiac magnetic resonance (CMR) imaging at baseline and after 4-month follow-up. TLR pathway activation was shown by increased expression of TLR4 and its downstream genes, including IL-18R1, IL-18R2, IL-8, MMP9, HIF1A, and NFKBIA. In contrast, expression of the classical TLR-induced genes, TNF, was reduced. Bioinformatics analysis and in vitro experiments explained this noncanonical TLR response by identification of a pivotal role for HIF-1α. The extent of TLR activation and IL-18R1/2 expression in circulating cells preceded massive troponin-T release and correlated with the CMR-measured ischemic area (R=0.48, p=0.01). In conclusion, we identified a novel HIF-1-dependent noncanonical TLR activation pathway in circulating leukocytes leading to enhanced IL-18R expression which correlated with the magnitude of the ischemic area. This knowledge may contribute to our mechanistic understanding of the involvement of the innate immune system during STEMI and may yield diagnostic and prognostic value for patients with myocardial infarction.

Activation of toll-like receptors and inflammasome complexes in the diabetic cardiomyopathy-associated inflammation

Diabetic cardiomyopathy is defined as a ventricular dysfunction initiated by alterations in cardiac energy substrates in the absence of coronary artery disease and hypertension. Hyperglycemia, hyperlipidemia, and insulin resistance are major inducers of the chronic low-grade inflammatory state that characterizes the diabetic heart. Cardiac Toll-like receptors and inflammasome complexes may be key inducers for inflammation probably through NF-κB activation and ROS overproduction. However, metabolic dysregulated factors such as peroxisome proliferator-activated receptors and sirtuins may serve as therapeutic targets to control this response by mitigating both Toll-like receptors and inflammasome signaling.

Polyoxygenated cholesterol ester hydroperoxide activates TLR4 and SYK dependent signaling in macrophages

Oxidation of low-density lipoprotein (LDL) is one of the major causative mechanisms in the development of atherosclerosis. In previous studies, we showed that minimally oxidized LDL (mmLDL) induced inflammatory responses in macrophages, macropinocytosis and intracellular lipid accumulation and that oxidized cholesterol esters (OxCEs) were biologically active components of mmLDL. Here we identified a specific OxCE molecule responsible for the biological activity of mmLDL and characterized signaling pathways in macrophages in response to this OxCE. Using liquid chromatography – tandem mass spectrometry and biological assays, we identified an oxidized cholesteryl arachidonate with bicyclic endoperoxide and hydroperoxide groups (BEP-CE) as a specific OxCE that activates macrophages in a TLR4/MD-2-dependent manner. BEP-CE induced TLR4/MD-2 binding and TLR4 dimerization, phosphorylation of SYK, ERK1/2, JNK and c-Jun, cell spreading and uptake of dextran and native LDL by macrophages. The enhanced macropinocytosis resulted in intracellular lipid accumulation and macrophage foam cell formation. Bone marrow-derived macrophages isolated from TLR4 and SYK knockout mice did not respond to BEP-CE. The presence of BEP-CE was demonstrated in human plasma and in the human plaque material captured in distal protection devices during percutaneous intervention. Our results suggest that BEP-CE is an endogenous ligand that activates the TLR4/SYK signaling pathway. Because BEP-CE is present in human plasma and human atherosclerotic lesions, BEP-CE-induced and TLR4/SYK-mediated macrophage responses may contribute to chronic inflammation in human atherosclerosis.

Increased cytokine response after toll-like receptor stimulation in patients with stable coronary artery disease

OBJECTIVE

Atherosclerosis is associated with increased levels of plasma cytokines and expression of Toll-like receptors (TLRs). Yet, little is known about the potential use of TLR ligand induced cytokine release as a biomarker of coronary artery disease (CAD). In this study, we investigated whether TLR ligand induced cytokine release is associated with atherosclerotic disease severity and its predictive value for future cardiovascular events.

METHODS

Blood samples were obtained from 260 patients with stable angina and 15 healthy controls. Cytokine levels of TNFα, IL-8 and IL-6 were measured after 2 h of whole blood stimulation with 10 ng/ml lipopolysaccharide (LPS, TLR4 ligand) and P3C 500 ng/ml (TLR2 ligand). In a subgroup, dose-response curves were created using additional LPS concentrations.

RESULTS

LPS induced whole blood release of TNFα and IL-6, but not IL-8, was significantly higher in patients compared to healthy controls. Among CAD patients, TLR responses did hardly differ when associated with the presence of traditional risk factors and atherosclerotic disease severity (number of diseased vessels and coronary stenosis degree). Patients with secondary events during follow-up showed a trend towards an increased TLR response. Furthermore, positive associations were found between CRP levels and TLR-induced TNFα (CRP<2: 2055 pg/ml; CRP>2: 2364 pg/ml) and IL-6 production (CRP<2: 1742 pg/ml; CRP>2: 2250 pg/ml).

CONCLUSION

In conclusion, TLR-induced whole blood cytokine release in patients with stable angina indicates the presence of coronary atherosclerosis but does not reflect its severity.

Polymorphism -2604G>A variants in TLR4 promoter are associated with different gene expression level in peripheral blood of atherosclerotic patients

Toll-like receptor-4 (TLR4) is a primary receptor of the innate immune reaction and compelling evidence demonstrates its involvement in the pathogenesis of atherosclerosis and stroke. TLR4 is constitutively expressed on monocytes and endothelial cells; it is highly expressed in atherosclerotic plaques and in peripheral blood of patients after ischemic stroke. Polymorphisms in the promoter region that alter the transcriptional regulation of this gene may represent genetic risk factors involved in the predisposition to atherosclerotic disease. In this study we investigated the effect on TLR4 gene expression of three polymorphisms in the upstream regulatory region at positions -1607T>C/rs10759932, -2026A>G/rs1927914 and -2604G>A/rs10759931 in peripheral blood of atherosclerotic patients. RNA from individuals homozygous for the -2604A allele showed a lower expression of the gene when compared to patients carrying the counterparts GG+GA. Electrophoretic mobility shift assays showed differences in the electrophoretic mobility of the DNA-nuclear protein complexes formed by the G>A variants, suggesting that the two alleles differ in their binding affinity to transcriptional factors.

Hyperlipidemia, tissue factor, coagulation, and simvastatin

Hyperlipidemia affects millions of people worldwide and is a major risk factor for cardiovascular disease. People with hyperlipidemia have elevated levels of serum cholesterol and an increased risk of thrombosis. Studies have suggested that oxidized lipoproteins, such as oxidized low-density lipoprotein (oxLDL), contribute to the development of a pro-thrombotic state. In this review, we discuss our recent studies demonstrating a role for hematopoietic cell-derived tissue factor (TF) expression in the activation of coagulation and increased thrombosis associated with hyperlipidemia. In addition, we investigated the effect of simvastatin on TF expression and coagulation. We found that simvastatin reduced leukocyte TF expression, TF⁺ microparticles, and coagulation. These results and earlier studies suggest that the anti-coagulant activity of statins is due, in part, to their ability to reduce monocyte TF expression in patients with cardiovascular disease.

Circulating cells as predictors of secondary manifestations of cardiovascular disease: design of the CIRCULATING CELLS study

Biomarkers for primary or secondary risk prediction of cardiovascular disease (CVD) are urgently needed to improve individual treatment and clinical trial design. The vast majority of biomarker discovery studies has concentrated on plasma/serum as an easily accessible source. Although numerous markers have been identified, their added predictive value on top of traditional risk factors has been limited, as the biological specimen does not specifically reflect expression profiles related with CVD progression and because the signal is often diluted by marker release from other organs. In contrast to serum markers, circulating cells serve as indicators of the actual disease state due to their active role in the pathogenesis of CVD and are responsible for the majority of secreted biomarkers. Therefore, the CIRCULATING CELLS study was initiated, focusing on the cellular effectors of atherosclerosis in the circulation. In total, 714 patients with coronary artery disease (CAD) symptoms were included. Blood cell fractions (monocytes, T-lymphocytes, platelets, granulocytes, PBMC) of all individual patients were isolated and stored for analysis. Concomitantly, extensive flow cytometric characterization of these populations was performed. From each patient, a detailed clinical profile together with extensive questionnaires about medical history and life style was obtained. Various high-throughput -omics approaches (protein, mRNA, miRNA) are currently being undertaken. Data will be integrated with advanced bioinformatics for discovery and validation of secondary risk markers for adverse events. Overall, the CIRCULATING CELLS study grants the interesting possibility that it will both identify novel biomarkers and provide useful insights into the pathophysiology of CAD in patients.

Monocyte gene expression and coronary artery disease

PURPOSE OF REVIEW

Despite current therapy, coronary artery disease (CAD) remains the major cause of morbidity and mortality worldwide. CAD is the consequence of a complex array of deranged metabolic processes including the immune system. In this context, monocytes and macrophages are indisputable players. Thus, monocyte gene expression analysis could be a powerful tool to provide new insights in the pathophysiology of CAD and improve identification of individuals at risk. We discuss current literature assessing monocyte gene expression and its association with CAD.

RECENT FINDINGS

Monocyte surface markers CD14 ⁺⁺and CD16⁺ have been established as biomarkers for increased cardiovascular disease risk in a large number of studies. More in-depth gene expression analysis identified several interesting genes, such as ABCA1, CD36 and MSR1 with an increased expression in circulating monocytes from patients with CAD. The results for CD36 were replicated in one other study. For ABCA1 and MSR1 conflicting data are published.

SUMMARY

Recent findings indicate that genetic differences exist in circulating monocytes of patients suffering from CAD, giving us more insights into the underlying mechanisms. However, larger studies are required to prove that monocytes' expression signature could serve as a marker for diagnostic purposes in the future.

Fosinoprilat alleviates lipopolysaccharide (LPS)-induced inflammation by inhibiting TLR4/NF-κB signaling in monocytes

OBJECTIVE

To evaluate the effect of the fosinoprilat on lipopolysacharides (LPS) induced inflammation in monocytes in vitro.

METHODS

Human mononuclear THP1 cells were cultured in complete medium, treated with or without LPS and different concentrations (0,0.25,0.5,1,5,and 10μmol/L) of fosinoprilat. Toll-like receptor (TLR4) mRNA expression was detected by real-time RT-PCR and TLR4 protein level on the surface of monocyte was determined by flow cytometry. Nuclear factor-kappa B (NF-κB) protein level was detected by Western blotting. Cultured supernatant of the THP1 cells in different groups were analyzed by ELISA to detect the levels of interleukin (IL)-1β, IL-6 and tumor necrosis factor (TNF-α).

RESULTS

Both the mRNA and surface protein level of the TLR4 in the THP1 cells were enhanced by the LPS treatment and down-regulated by pretreatment of the fosinoprilat. Accordingly, LPS-induced NF-κB protein was decreased by the fosinoprilat treatment. The increasing secretion of IL-1β, IL-6 and TNF-α induced by LPS could also be attenuated by the fosinoprilat treatment.

CONCLUSION

The inhibitory effect of the fosinoprilat on the TRL4/NF-κB signaling pathway reveals a potential anti-inflammatory and anti-atherosclerosis target.

Interaction of NADPH oxidase 1 with Toll-like receptor 2 induces migration of smooth muscle cells

AIMS

NADPH oxidase (Nox) isozymes that generate intracellular reactive oxygen species (ROS) and Toll-like receptor 2 (TLR2), an inflammatory mediator, are both involved in the development of atherosclerotic lesions. To identify the molecular connection between TLR2 and Nox isozymes in vascular remodelling, we analysed generation of ROS and pro-inflammatory cytokines in aortic smooth muscle cells from Nox1-deficient mice in response to the synthetic triacylated lipoprotein Pam3CSK, a TLR2 agonist.

METHODS AND RESULTS

We showed that TLR2 signalling stimulates progression of the pro-inflammatory phenotype in mouse aortic smooth muscle cells (MASMCs) through activation of Nox1. We demonstrated the interaction of TLR2 with Nox1 using yeast two-hybrid and co-immunoprecipitation assays. MASMCs from Nox1-deficient mice failed to generate of ROS in response to Pam3CSK4, indicating that Nox1 is essential for TLR2-dependent production of ROS. We also found that Pam3CSK4 stimulated migration of MASMCs from wild-type mice in a Transwell system, but MASMCs from Nox1-deficient mice failed to show this response. Wild-type MASMCs produced matrix metalloprotease 2 in response to Pam3CSK4, whereas Nox1-deficient MASMCs failed to generate this protease. Moreover, stimulation of MASMCs with Pam3CSK4 resulted in increased expression of the pro-inflammatory cytokine macrophage inflammatory protein 2 in a Nox1-dependent manner, leading to enhanced monocyte-endothelial cell adhesion and trans-endothelial migration of U937 cells.

CONCLUSION

These data suggest that Nox1 plays an important role in TLR2-mediated intracellular H2O2 generation, activation of matrix metalloprotease 2, and secretion of pro-inflammatory cytokines, which in turn stimulate MASMC migration and vascular remodelling.

Toll-Like Receptor induced CD11b and L-selectin response in patients with coronary artery disease

Toll-Like Receptor (TLR) -2 and -4 expression and TLR-induced cytokine response of inflammatory cells are related to atherogenesis and atherosclerotic plaque progression. We examined whether immediate TLR induced changes in CD11b and L-selectin (CD62L) expression are able to discriminate the presence and severity of atherosclerotic disease by exploring single dose whole blood TLR stimulation and detailed dose-response curves. Blood samples were obtained from 125 coronary artery disease (CAD) patients and 28 controls. CD11b and L-selectin expression on CD14+ monocytes was measured after whole blood stimulation with multiple concentrations of the TLR4 ligand LPS (0.01–10 ng/ml) and the TLR2 ligand P3C (0.5–500 ng/ml). Subsequently, dose-response curves were created and the following parameters were calculated: hillslope, EC50, area under the curve (AUC) and delta. These parameters provide information about the maximum response following activation, as well as the minimum trigger required to induce activation and the intensity of the response. CAD patients showed a significantly higher L-selectin, but not CD11b response to TLR ligation than controls after single dose stimulations as well as significant differences in the hillslope and EC50 of the dose-response curves. Within the CAD patient group, dose-response curves of L-selectin showed significant differences in the presence of hypertension, dyslipidemia, coronary occlusion and degree of stenosis, whereas CD11b expression had the strongest discriminating power after single dose stimulation. In conclusion, single dose stimulations and dose-response curves of CD11b and L-selectin expression after TLR stimulation provide diverse but limited information about atherosclerotic disease severity in stable angina patients. However, both single dose stimulation and dose-response curves of LPS-induced L-selectin expression can discriminate between controls and CAD patients.

The SYK side of TLR4: signalling mechanisms in response to LPS and minimally oxidized LDL

Spleen tyrosine kinase (SYK) is the best known for its involvement in immune receptor signalling, mediated by binding of SYK tandem Src-homology 2 domains to tandem phosphotyrosine in immunoreceptor tyrosine-based activation motifs (ITAMs). ITAM adaptors or ITAM-containing receptor tails mediate signalling from B- and T-cell receptors, Fc receptors and many C-type lectins, including dectin-1. Recent data point to constitutive binding of SYK to the cytoplasmic domain of toll-like receptor-4 (TLR4). This SYK-TLR4 binding increases upon TLR4 dimerization and phosphorylation, and SYK plays a prominent role in TLR4 signalling in response to LPS in neutrophils and monocytes. SYK also plays an important role in TLR4-mediated macrophage responses to minimally oxidized low-density lipoprotein (mmLDL), which is a form of oxidized LDL relevant to development of human atherosclerosis. Interestingly, mmLDL-induced effects in macrophages, which occur via TLR4, are predominantly MyD88 independent. This unmasks the role of the SYK branch of TLR4 signalling, which mediates modest cytokine release via activation of AP-1 transcription and robust reactive oxygen species generation and cytoskeletal rearrangements. The latter results in extensive membrane ruffling and macropinocytosis, leading to lipoprotein uptake and foam cell formation, a hallmark of atherosclerotic lesions. Because inhibitors of SYK activity, such as fostamatinib, are in advanced clinical trials for rheumatoid arthritis and other autoimmune diseases, understanding the role of SYK in signalling via TLR4 is of immediate importance. This signalling pathway seems to be particularly important in TLR4 activation by host-derived, damage-associated molecular pattern ligands, such as mmLDL, relevant to development of atherosclerosis and other chronic inflammatory diseases.

TLR4 expression on monocyte subsets in myocardial infarction

BACKGROUND

Monocyte toll-like receptor 4 (TLR4) has been implicated in the pathogenesis of atherosclerosis with increased levels in myocardial infarction. The aim of this study was to assess the numbers of TLR4(+) monocytes in each monocyte subset in MI, the expression of TLR4 and association with markers of monocyte activation, inflammation, myocardial damage and postmyocardial infarction (MI) cardiac contractility.

METHODS

Surface expression of TLR4 and numbers of TLR4-expressing monocytes were quantified by flow cytometry of venous blood in 50 patients with ST-elevation MI (STEMI), 48 with non-STEMI (NSTEMI) and 40 with stable coronary artery disease (CAD). These parameters were measured on days 1, 3, 7 and 30 post-MI in STEMI patients. Three monocyte subsets were defined as CD14(++) CD16(-) CCR2(+) (Mon1), CD14(++) CD16(+) CCR2(+) (Mon2) and CD14(+) CD16(++) CCR2(-) (Mon3). Plasma inflammatory cytokines were assessed using cytometric bead arrays.

RESULTS

There was a significant increase in counts of TLR4(+) Mon1 and Mon2 in STEMI patients and TLR4(+) Mon2 in NSTEMI patients compared with controls with CAD. Monocyte TLR4(+) expression was similar between the groups, and was not changed during follow-up in STEMI patients. Plasma interleukin-6 (IL6) levels correlated positively with TLR4(+) Mon2 count (r = 0.54, P < 0.001), but negatively with TLR4 expression on Mon2 (r = -0.33, P = 0.021).

CONCLUSION

Following treatment of acute MI, TLR4 expression by individual monocyte subsets is unchanged. An increase in TLR4(+) Mon1 and Mon2 count in patients with STEMI and TLR(+) Mon2 count in those with NSTEMI is due to an increase in monocyte subset count and not to changes in TLR4 expression. Monocyte counts but not TLR4 expression correlate positively with plasma IL6 levels. We suggest that TLR4 expression may not be a reliable marker of monocyte activation in MI.

Fractional flow reserve is not associated with inflammatory markers in patients with stable coronary artery disease

Background

Atherosclerosis is an inflammatory condition and increased blood levels of inflammatory biomarkers have been observed in acute coronary syndromes. In addition, high expression of inflammatory markers is associated with worse prognosis of coronary artery disease. The presence and extent of inducible ischemia in patients with stable angina has previously been shown to have strong prognostic value. We hypothesized that evidence of inducible myocardial ischemia by local lesions, as measured by fractional flow reserve (FFR), is associated with increased levels of blood based inflammatory biomarkers.

Methods

Whole blood samples of 89 patients with stable angina pectoris and 16 healthy controls were analyzed. The patients with stable angina pectoris underwent coronary angiography and FFR of all coronary lesions.

We analyzed plasma levels of cytokines IL-6, IL-8 and TNF-α and membrane expression of Toll-like receptor 2 and 4, CD11b, CD62L and CD14 on monocytes and granulocytes as markers of inflammation.

Furthermore, we quantified the severity of hemodynamically significant coronary artery disease by calculating Functional Syntax Score (FSS), an extension of the Syntax Score.

Results

For the majority of biomarkers, we observed lower levels in the healthy control group compared with patients with stable angina who underwent coronary catheterization.

We found no difference for any of the selected biomarkers between patients with a positive FFR (≤0.75) and negative FFR (>0.80). We observed no relationship between the investigated biomarkers and FSS.

Conclusion

The presence of local atherosclerotic lesions that result in inducible myocardial ischemia as measured by FFR in patients with stable coronary artery disease is not associated with increased plasma levels of IL-6, IL-8 and TNF-α or increased expression of TLR2 and TLR4, CD11b, CD62L and CD14 on circulating leukocytes.

Low-level exposure to ambient particulate matter is associated with systemic inflammation in ischemic heart disease patients

Short-term exposure to ambient air pollution is associated with increased cardiovascular mortality and morbidity. This adverse health effect is suggested to be mediated by inflammatory processes. The purpose of this study was to determine if low levels of particulate matter, typical for smaller cities, are associated with acute systemic inflammation. Fifty-two elderly individuals with ischemic heart disease were followed for six months with biweekly clinical visits in the city of Kotka, Finland. Blood samples were collected for the determination of inflammatory markers interleukin (IL)-1β, IL-6, IL-8, IL-12, interferon (IFN)γ, C-reactive protein (CRP), fibrinogen, myeloperoxidase and white blood cell count. Particle number concentration and fine particle (particles with aerodynamic diameters <2.5 μm (PM(2.5))) as well as thoracic particle (particles with aerodynamic diameters <10 μm (PM(10))) mass concentration were measured daily at a fixed outdoor measurement site. Light-absorbance of PM(2.5) filter samples, an indicator of combustion derived particles, was measured with a smoke-stain reflectometer. In addition, personal exposure to PM(2.5) was measured with portable photometers. During the study period, wildfires in Eastern Europe led to a 12-day air pollution episode, which was excluded from the main analyses. Average ambient PM(2.5) concentration was 8.7 μg/m(3). Of the studied pollutants, PM(2.5) and absorbance were most strongly associated with increased levels of inflammatory markers; most notably with C-reactive protein and IL-12 within a few days of exposure. There was also some evidence of an effect of particulate air pollution on fibrinogen and myeloperoxidase. The concentration of IL-12 was considerably (227%) higher during than before the forest fire episode. These findings show that even low levels of particulate air pollution from urban sources are associated with acute systemic inflammation. Also particles from wildfires may exhibit pro-inflammatory effects.

Association studies of gene polymorphisms in toll-like receptors 2 and 4 in Croatian patients with acute myocardial infarction

The aim of the study was to assess the frequency of SNP896A/G in the Toll-like receptor (TLR) 4 gene and SNP1350T/C in the TLR2 gene in patients with acute myocardial infarction (AMI) and to analyse the association of these SNPs with risk factors for atherosclerosis and clinical aspects of AMI in a sample of the Croatian population. We included 240 participants in the study: 120 AMI patients and 120 sex- and age-matched healthy blood donor controls. The SNP1350T/C variant in the TLR2 gene showed a lower frequency in the AMI patient group than in the control group (P = 0.033). The frequency of SNP896A/G variants in the TLR4 gene between the patients and the controls did not differ (P = 0.286). Significantly, fewer people had SNP1350T/C in the TLR2 gene (P = 0.003) among the participants with arterial hypertension than those without it. The frequency of SNP896A/G in TLR4 was the same in hypertensive patients compared with normotensive subjects (P = 0.088). SNP1350T/C in TLR2 was less frequent in the AMI patients and in those with hypertension. Thus, SNP1350T/C in TLR2 might play a protective role against AMI and arterial hypertension. The frequency of SNP896A/G in the TLR4 gene was not associated with AMI and arterial hypertension. Other risk factors for atherosclerosis and clinical aspects of myocardial infarction were not associated with the genotype distribution of the examined genes.

Variants of Toll-like receptor 4 predict cardiac recovery in patients with dilated cardiomyopathy

The clinical course of patients with dilated cardiomyopathy (DCM) varies from cardiac recovery to end stage heart failure. The etiology of this variability is largely unknown. In this study, we investigated the impact of coding polymorphisms of the innate immune protein Toll-like receptor 4 (TLR4) on left ventricular performance in patients with DCM. Two variants of TLR4 (rs4986790, TLR4 c.1187A→G, p.299D→G and rs4986791,TLR4 c.1487C→T, p.T399I) were investigated in 158 patients with DCM. Other reasons for heart failure were excluded by coronary angiography, myocardial biopsy, and echocardiography. Risk factors, age, gender, or treatment did not differ among the groups. At the follow-up evaluation (median 4.0-5.4 months), patients carrying the TLR4 wild type gene displayed cardiac recovery under intense medical heart failure therapy indexed by reduced left ventricular dilation, improved left ventricular ejection fraction, and reduced NT-probrain natriuretic peptide blood level when compared with the initial evaluation. In contrast, patients carrying both the rs4986790 and the rs4986791 variant showed significantly reduced improvement of left ventricular ejection fraction (p = 0.006) and left ventricular dilation (p = 0.015) at the follow-up evaluation when compared with carriers of the wild type gene under the same treatment conditions. In addition, NT-probrain natriuretic peptide level in carriers of both TLR4 variants did not change significantly at the follow up when compared with the first evaluation. Among patients with DCM, the presence of the TLR4 variants rs4986790 and rs4986791 predicts impaired cardiac recovery independently of medical treatment or cardiac risk factors.

TLR2 and TLR4 gene expression in peripheral monocytes in nondiabetic hypertensive patients: the effect of intensive blood pressure-lowering

The activation of innate immune receptors, such as Toll-like receptors (TLRs), participates in the pathogenesis of cardiovascular diseases. The authors evaluated TLR2 and TLR4 gene expression in the peripheral monocytes of nondiabetic hypertensive patients compared with normotensive individuals and investigated the effect of intensive systolic blood pressure (SBP)-lowering. Included were 43 nondiabetic hypertensive patients with essential hypertension who were randomly assigned to an intensive treatment arm, with an SBP target of <130 mm Hg, or a standard arm, with an SBP target of <140 mm Hg. TLR2 and TLR4 messenger RNA (mRNA) levels in monocytes were estimated before and 12 weeks after therapy initiation. Sixteen healthy individuals were included for comparison. Hypertensives revealed significantly higher TLR4 mRNA levels compared with normotensives (985 ± 885 vs 554 ± 234, P=.005). In contrast, no statistically significant difference was found in TLR2. Compared with standard treatment, intensive treatment significantly downregulated TLR2 and TLR4 mRNAs, expressed as fold induction (0.66 ± 0.49 vs 1.38 ± 1.65 and 0.62 ± 0.3 vs 1.9 ± 1.2, respectively; P<.001 for both). In conclusion, TLR4 mRNA levels in peripheral monocytes are significantly elevated in nondiabetic hypertensive patients. Intensive control of SBP results in attenuation of TLR2 and TLR4 gene expression in those patients. Our findings suggest that a strict SBP target in nondiabetic hypertensive patients may offer additional benefits.

Mechanisms and management of doxorubicin cardiotoxicity

Doxorubicin is an effective anti-tumor agent with a cumulative dose-dependent cardiotoxicity. In addition to its principal toxic mechanisms involving iron and redox reactions, recent studies have described new mechanisms of doxorubicin-induced cell death, including abnormal protein processing, hyper-activated innate immune responses, inhibition of neuregulin-1 (NRG1)/ErbB(HER) signalling, impaired progenitor cell renewal/cardiac repair, and decreased vasculogenesis. Although multiple mechanisms involved in doxorubicin cardiotoxicity have been studied, there is presently no clinically proven treatment established for doxorubicin cardiomyopathy. Iron chelator dexrazoxane, angiotensin converting enzyme (ACE) inhibitors, and β-blockade have been proposed as potential preventive strategies for doxorubicin cardiotoxicity. Novel approaches such as anti-miR-146 or recombinant NRG1 to increase cardiomyocyte resistance to toxicity may be of interest in the future.

Monocyte tissue factor-dependent activation of coagulation in hypercholesterolemic mice and monkeys is inhibited by simvastatin

Hypercholesterolemia is a major risk factor for atherosclerosis. It also is associated with platelet hyperactivity, which increases morbidity and mortality from cardiovascular disease. However, the mechanisms by which hypercholesterolemia produces a procoagulant state remain undefined. Atherosclerosis is associated with accumulation of oxidized lipoproteins within atherosclerotic lesions. Small quantities of oxidized lipoproteins are also present in the circulation of patients with coronary artery disease. We therefore hypothesized that hypercholesterolemia leads to elevated levels of oxidized LDL (oxLDL) in plasma and that this induces expression of the procoagulant protein tissue factor (TF) in monocytes. In support of this hypothesis, we report here that oxLDL induced TF expression in human monocytic cells and monocytes. In addition, patients with familial hypercholesterolemia had elevated levels of plasma microparticle (MP) TF activity. Furthermore, a high-fat diet induced a time-dependent increase in plasma MP TF activity and activation of coagulation in both LDL receptor-deficient mice and African green monkeys. Genetic deficiency of TF in bone marrow cells reduced coagulation in hypercholesterolemic mice, consistent with a major role for monocyte-derived TF in the activation of coagulation. Similarly, a deficiency of either TLR4 or TLR6 reduced levels of MP TF activity. Simvastatin treatment of hypercholesterolemic mice and monkeys reduced oxLDL, monocyte TF expression, MP TF activity, activation of coagulation, and inflammation, without affecting total cholesterol levels. Our results suggest that the prothrombotic state associated with hypercholesterolemia is caused by oxLDL-mediated induction of TF expression in monocytes via engagement of a TLR4/TLR6 complex.

Differential expression of Toll-like receptor 4 and human monocyte subsets in acute myocardial infarction

OBJECTIVE

To investigate the involvement of Toll-like receptor 4 (TLR4) expression on two monocyte subsets in the pathologic processes related to acute coronary syndrome. How monocytes, which have recently been shown to comprise two distinct subsets, mediate the process of coronary plaque rupture remains to be fully elucidated. Recent studies have shown that TLR4 is involved in monocyte activation of patients with accelerated forms of atherosclerosis.

METHODS

We enrolled 65 patients with acute myocardial infarction (AMI, n=22), unstable angina pectoris (UAP, n=16), and stable angina pectoris (SAP, n=27) who underwent coronary angiography and 15 healthy controls. The expression of TLR4 on two monocyte subsets (CD14(+)CD16(-) and CD14(+)CD16(+)) was measured by flow cytometry.

RESULTS

In patients with AMI, TLR4 was more expressed on circulating CD14(+)CD16(+) monocytes than on CD14(+)CD16(-) monocytes (p<0.001). The expression levels of TLR4 on CD14(+)CD16(+) monocytes were significantly elevated in patients with AMI compared with other 3 groups. TLR4 expression levels on CD14(+)CD16(+) monocytes were significantly elevated at the culprit site compared with the systemic level (p=0.044). The up-regulation of TLR4 on admission was remarkably decreased 12 days after AMI (p<0.001). In addition, plasma levels of tumor necrosis factor-α were positively correlated with TLR4 expression levels on monocytes in patients with AMI (r=0.47, p=0.027).

CONCLUSION

TLR overexpression on CD14(+)CD16(+) monocytes in AMI, as demonstrated both in the circulation and at the coronary culprit site, might be associated with the pathogenesis of AMI.

Akt mediates 17beta-estradiol and/or estrogen receptor-alpha inhibition of LPS-induced tumor necresis factor-alpha expression and myocardial cell apoptosis by suppressing the JNK1/2-NFkappaB pathway

Evidence shows that women have lower tumour necrosis factor-α (TNF-α) levels and lower incidences of heart dysfunction and sepsis-related morbidity and mortality. To identify the cardioprotective effects and precise cellular/molecular mechanisms behind estrogen and estrogen receptors (ERs), we investigated the effects of 17β-estradiol (E₂) and estrogen receptor α (ERα) on LPS-induced apoptosis by analyzing the activation of survival and death signalling pathways in doxycycline (Dox)-inducible Tet-On/ERα H9c2 myocardial cells and ERα-transfected primary cardiomyocytes overexpressing ERα. We found that LPS challenge activated JNK1/2, and then induced IκB degradation, NFκB activation, TNF-α up-regulation and subsequent myocardial apoptotic responses. In addition, treatments involving E₂, membrane-impermeable BSA-E₂ and/or Dox, which induces ERα overexpression, significantly inhibited LPS-induced apoptosis by suppressing LPS-up-regulated JNK1/2 activity, IκB degradation, NFκB activation and pro-apoptotic proteins (e.g. TNF-α, active caspases-8, t-Bid, Bax, released cytochrome c, active caspase-9, active caspase-3) in myocardial cells. However, the cardioprotective properties of E₂, BSA-E₂ and ERα overexpression to inhibit LPS-induced apoptosis and promote cell survival were attenuated by applying LY294002 (PI3K inhibitor) and PI3K siRNA. These findings suggest that E₂, BSA-E₂ and ERα expression exert their cardioprotective effects by inhibiting JNK1/2-mediated LPS-induced TNF-α expression and cardiomyocyte apoptosis through activation of Akt.

Novel Toll-like receptor-4 deficiency attenuates trastuzumab (Herceptin) induced cardiac injury in mice

Background

Cardiac inflammation and generation of oxidative stress are known to contribute to trastuzumab (herceptin) induced cardiac toxicity. Toll-like receptors (TLRs) are a part of the innate immune system and are involved in cardiac stress reactions. Since TLR4 might play a relevant role in cardiac inflammatory signaling, we investigated whether or not TLR4 is involved in trastuzumab induced cardiotoxicity.

Methods

Seven days after a single injection of herceptin (2 mg/kg; i.p.), left ventricular pressure volume loops were measured in HeN compotent (TLR4^+/+) and HeJ mutant (TLR4^-/-) treated with trastuzumab and control mice. Immunofluorescent staining for monocyte infiltration and analyses of plasma by (ELISAs) for different chemokines including: MCP-1and tumor necrosis factor-α (TNF-α), Western immunoblotting assay for ICAM-1, and used troponin I for cardiac injury marker.

Results

Trastuzumab injection resulted in an impairment of left ventricular function in TLR-4 competent (HeN), in contrast TLR4^-/^- trastuzumab mice showed improved left ventricular function EF%, CO; p < 0.05, attenuation of mononuclear cell infiltration in TLR4 ^-/-; p < 0.05 vs.TLR-4 competent (HeN), reduced level of cytokines TNF-α, MCP-1 and ICAM-1 expression in TLR4^-/-, marked reduction of myocardial troponin-I levels in TLR4-deficient mice. Data are presented as means ± SE; n = 8 in each group p < 0.05 vs.TLR-4 competent (HeN).

Conclusions

Treatment with trastuzumab induces an inflammatory response that contributes to myocardial tissue TLR4 mediates chemokine expression (TNF-α, MCP-1and ICAM-1), so in experimental animals TLR4 deficiency improves left ventricular function and attenuates pathophysiological key mechanisms in trastuzumab induced cardiomyopathy.

Toll-like receptor 4 stimulation initiates an inflammatory response that decreases cardiomyocyte contractility

Toll-like receptors (TLRs) have been identified as primary innate immune receptors for the recognition of pathogen-associated molecular patterns by immune cells, initiating a primary response toward invading pathogens and recruitment of the adaptive immune response. TLRs, especially Toll-like receptor 4 (TLR4), can also be stimulated by host-derived molecules and are expressed in the cardiovascular system, thus acting as a possible key link between cardiovascular diseases and the immune system. TLR4 is involved in the acute myocardial dysfunction caused by septic shock and myocardial ischemia. We used wild-type (WT) mice, TLR4-deficient (TLR4-knockout [ko]) mice, and chimeras that underwent myeloablative bone marrow transplantation to dissociate between TLR4 expression in the heart (TLR4-ko/WT) and the immunohematopoietic system (WT/TLR4-ko). Following lipopolysaccharide (LPS) challenge (septic shock model) or coronary artery ligation, myocardial ischemia (MI) model, we found WT/TLR4-ko mice challenged with LPS or MI displayed reduced cardiac function, increased myocardial levels of interleukin-1β and tumor necrosis factor-α, and upregulation of mRNA encoding TLR4 prior to myocardial leukocyte infiltration. The cardiac function of TLR4-ko or WT/TLR4-ko mice was less affected by LPS and demonstrated reduced suppression by MI compared with WT. These results suggest that TLR4 expressed in the cardiomyocytes plays a key role in this acute phenomenon.

Inflammation and the development of atherosclerosis

Atherosclerosis is a progressive disease causally associated with multiple cardiovascular risk factors, including dyslipidemia. Without effective intervention, atherosclerosis becomes evidenced clinically as coronary artery and cerebrovascular disease, both of which remain the leading causes of death worldwide. Multiple lines of investigation indicate a central role for inflammation in atherosclerotic plaque progression, vulnerability and thrombogenicity. Randomized clinical trials have documented the benefit of lipid-lowering therapy for both primary and secondary prevention of cardiovascular events. Statins, a class of drugs that lower cholesterol levels by inhibiting 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase, have been shown to slow the progression of the atheroma and the frequency of associated clinical events to an extent that cannot be attributed solely to LDL reduction. The non-LDL or pleiotropic effects of statins are attributed to anti-inflammatory activity, enhanced endothelial function, and inhibition of oxidative stress. In this review, we discuss the role of inflammation in atherogenesis along with the effects of statins in slowing this process through LDL-dependent and -independent mechanisms.

Expression of circulatory dendritic cells and regulatory T-cells in patients with different subsets of coronary artery disease

BACKGROUND

Dendritic cells (DCs), regulators of innate and adaptive immunity, may play an important role in atherosclerosis. DC invasion was found in early atherosclerotic lesions. We aimed to characterize circulating DC gene expression in patients with different subsets of coronary artery disease (CAD).

METHODS

Peripheral blood mononuclear cells were quantified using real-time polymerase chain reaction and fluorescence activated cell sorting in patients with acute coronary syndrome (ST-elevation myocardial infarction [STEMI], n = 35; non-ST-elevation myocardial infarction [NSTEMI], n = 30) and stable CAD (6 months after stent implantation without progression, n = 15) compared with control subjects (n = 15). DCs and T-cells (TCs) were characterized using specific primers for CD1a (immature), CD86 (mature), CD123 (plasmacytoid), BDCA1 (myeloid), CD178 (activated TCs), and FOXP3 (regulatory TCs). To evaluate whether serum of patients with STEMI induces DC differentiation, incubation of patient serum was performed.

RESULTS

CD86 was upregulated and CD1a downregulated in all patients with CAD (P < 0.05). Patients with STEMI and NSTEMI showed a downregulation of CD1a compared with patients with stable CAD (P ≤ 0.01). In contrast, stable patients with CAD had elevated CD178 levels compared with patients with STEMI and NSTEMI (P ≤ 0.04). In patients with STEMI, FOXP3 was downregulated compared with control subjects (P < 0.0001). Incubation of STEMI serum induced an upregulation of CD1a and CD86 in a human DC cell line. Coincubation with a blocking antibody for heat shock protein 60 inhibited this upregulation.

CONCLUSIONS

DCs are differentially regulated in patients with different subsets of CAD. Mature DCs are upregulated and immature DCs are downregulated in patients with CAD. Patients with STEMI show a significant downregulation of regulatory TCs. Circulating shock protein 60 induces DC differentiation in patients with STEMI.

Toll-like receptor 4/nuclear factor-kappa B pathway is involved in myocardial injury in a rat chronic stress model

Chronic stress is considered to predispose to various cardiovascular events such as coronary artery disease, hypertension, and even heart failure. In this study, rats were exposed to stress for 1 day, 1, 2, 3, and 4 weeks to establish a chronic stress model. A specific toll-like receptor 4 (TLR4) antagonist eritoran was used to block the activity of TLR4. On the second day after the last stress exposure, the animals were killed. The expression of TLR4 mRNA and nuclear factor-kappa B (NF-κB) DNA-binding activity in the myocardium were measured using reverse transcriptase polymerase chain reaction and electrophoretic mobility shift assay. The proinflammatory cytokines such as tumor necrosis factor (TNF)-α and interleukin (IL-6) in myocardium were assayed by enzyme-linked immunosorbent assay. Myocardial injury was evident after chronic stress for 2 weeks. The TLR4 mRNA expression reached a peak after stress for 1 week. It was sustained at a stable level after stress exposure for 3 weeks and was restored to a nearly normal level in the fourth week. NF-κB DNA-binding activity was significantly enhanced after the stress for 1 day and markedly enhanced again after a 2-week stress exposure. It was weakened and reached a normal level after stress exposure for 4 weeks. The levels of TNF-α and IL-6 gradually increased and reached peaks after stress for 4 weeks. Meanwhile, eritoran significantly decreased the TLR4 mRNA expression and NF-κB activity in rats from the 2-week stress group. However, it did not downregulate the levels of TNF-α and IL-6. Importantly, it significantly improved the myocardial injury induced by the chronic stress. In conclusion, TLR4/NF-κB participates in myocardial injury during chronic stress.

Expression of let-7i is associated with Toll-like receptor 4 signal in coronary artery disease: effect of statins on let-7i and Toll-like receptor 4 signal

Toll-like receptor (TLR) 4 signal plays an important role in immunity in coronary artery disease (CAD). A recent report has demonstrated that one of the let-7 family microRNAs, let-7i, directly regulates Toll-like receptor 4 (TLR4) expression and contributes to immune response. The aim of this study was to determine whether let-7i is expressed with TLR4 in patients with CAD, and whether statins (atorvastatin or rosuvastatin) might affect these levels. To determine the effects of let-7i on TLR4 expression, human THP-1 cells transfected with let-7i were analyzed for TLR4 levels. This study included 98 patients with CAD and 48 subjects without CAD (non-CAD). Patients with CAD were randomized to 12 months of treatment with atorvastatin or rosuvastatin. Monocytes were obtained from peripheral blood at baseline and after 12 months of each type of therapy. Levels of let-7i and TLR4 were measured by real-time RT-PCR and FACS. Functional approaches to let-7i showed that transfection of let-7i into human THP-1 cells resulted in regulation of TLR4 expression. Levels of let-7i were lower in the CAD group than in the non-CAD group (0.98±0.42 vs. 4.65±1.21, P<0.01). There was a negative correlation between let-7i and TLR4 levels in patients with CAD (let-7i vs. TLR4 mRNA: r=-0.60, P<0.01; let-7i vs. TLR4 MFI: r=-0.32, P<0.01). The atorvastatin group had markedly increased let-7i levels and diminished TLR4 levels (all P<0.01), whereas the rosuvastatin group showed no change in these levels. This study suggests that atorvastatin down-regulates TLR4 signal via let-7i expression in CAD patients, possibly contributing to the beneficial effects of atorvastatin on let-7i-mediated TLR4 signal in this disorder.

Monocyte and macrophage dynamics during atherogenesis

Vascular inflammation is associated with and in large part driven by changes in the leukocyte compartment of the vessel wall. Here, we focus on monocyte influx during atherosclerosis, the most common form of vascular inflammation. Although the arterial wall contains a large number of resident macrophages and some resident dendritic cells, atherosclerosis drives a rapid influx of inflammatory monocytes (Ly-6C(+) in mice) and other monocytes (Ly-6C(-) in mice, also known as patrolling monocytes). Once in the vessel wall, Ly-6C(+) monocytes differentiate to a phenotype consistent with inflammatory macrophages and inflammatory dendritic cells. The phenotype of these cells is modulated by lipid uptake, Toll-like receptor ligands, hematopoietic growth factors, cytokines, and chemokines. In addition to newly recruited macrophages, it is likely that resident macrophages also change their phenotype. Monocyte-derived inflammatory macrophages have a short half-life. After undergoing apoptosis, they may be taken up by surrounding macrophages or, if the phagocytic capacity is overwhelmed, can undergo secondary necrosis, a key event in forming the necrotic core of atherosclerotic lesions. In this review, we discuss these and other processes associated with monocytic cell dynamics in the vascular wall and their role in the initiation and progression of atherosclerosis.

Activated TLR signaling in atherosclerosis among women with lower Framingham risk score: the multi-ethnic study of atherosclerosis

Background

Atherosclerosis is the leading cause of cardiovascular disease (CVD). Traditional risk factors can be used to identify individuals at high risk for developing CVD and are generally associated with the extent of atherosclerosis; however, substantial numbers of individuals at low or intermediate risk still develop atherosclerosis.

Results

A case-control study was performed using microarray gene expression profiling of peripheral blood from 119 healthy women in the Multi-Ethnic Study of Atherosclerosis cohort aged 50 or above. All participants had low (<10%) to intermediate (10% to 20%) predicted Framingham risk; cases (N = 48) had coronary artery calcium (CAC) score >100 and carotid intima-media thickness (IMT) >1.0 mm, whereas controls (N = 71) had CAC<10 and IMT <0.65 mm. We identified two major expression profiles significantly associated with significant atherosclerosis (odds ratio 4.85; P<0.001); among those with Framingham risk score <10%, the odds ratio was 5.30 (P<0.001). Ontology analysis of the gene signature reveals activation of a major innate immune pathway, toll-like receptors and IL-1R signaling, in individuals with significant atherosclerosis.

Conclusion

Gene expression profiles of peripheral blood may be a useful tool to identify individuals with significant burden of atherosclerosis, even among those with low predicted risk by clinical factors. Furthermore, our data suggest an intimate connection between atherosclerosis and the innate immune system and inflammation via TLR signaling in lower risk individuals.

Role of toll-like receptors in cardiovascular diseases

The discovery and characterization of the TLR (Toll-like receptor) family has led to a better understanding of the innate immune system. The strategy of innate immune recognition is based on the detection of constitutive and conserved products of micro-organisms. However, host molecules that are released during injury can also activate TLRs. Engagement of TLRs by microbial or host-derived molecules induces the expression of pro-inflammatory cytokines, which may have both beneficial and detrimental effects on the host. In addition to being expressed in immune cells, TLRs are expressed in other tissues such as those of the cardiovascular system. In the present review, the role of TLRs in septic cardiomyopathy, viral myocarditis, atherosclerosis, ischaemia/reperfusion injury and cardiac remodelling after myocardial infarction are outlined, with attention paid to genetically modified murine models. Although much has been learned about stress-induced TLR activation in the tissues of the cardiovascular system, the role of individual TLRs in initiating and integrating homoeostatic responses within the heart remains to be defined. Accumulating evidence indicates that TLRs may play an important role in the pathogenesis of atherosclerosis, viral myocarditis, dilated cardiomyopathy, cardiac allograft rejection and sepsis-induced left ventricular dysfunction. Moreover, heart failure of diverse aetiology is also now recognized to have an important immune component, with TLR signalling influencing the process of cardiac remodelling and prognosis. In the present review, we outline the biology of TLRs as well as the current experimental and clinical evidence for the role of TLRs in cardiovascular diseases.

Toll-like receptors 2 and 4 in ischemic stroke: outcome and therapeutic values

Stroke triggers an intense inflammatory response that could be a consequence of Toll-like receptors (TLRs) activation. However, the clinical significance and the therapeutic possibilities of TLR in stroke is not completely clear. In this study, we analyze the association between the expression of TLR2 and TLR4, inflammatory molecules and endogenous ligands, and clinical outcome of ischemic stroke patients, and we test the potential of TLR2/TLR4 and their endogenous ligands as therapeutic targets. For this purpose, we included 110 patients with ischemic stroke finding that TLR2 and TLR4 are independently associated to poor outcome and correlated with higher serum levels of interleukin (IL)1β, IL6, tumor necrosis factor α, and VCAM1, and that TLR4 was independently associated to lesion volume. In addition, we have developed an in vitro model to test the potential therapeutic value of blocking TLR2/TLR4 or their endogenous ligands. Cultured cells (monocytes and human umbilical vein endothelial cells) were treated with serum from ischemic stroke patients, showing a strong inflammatory response that was blocked when TLR2/4 or cellular fibronectin (cFN) or HSP60 were blocked. In conclusion, TLR2 and TLR4 are associated to outcome in stroke patients and TLR2/4 or their endogenous ligands, cFN/HSP60 could be new therapeutic targets for ischemic stroke.

Genetic variants in TLR2 and TLR4 are associated with markers of monocyte activation: the Atherosclerosis Risk in Communities MRI Study

Markers of monocyte activation play a critical role in atherosclerosis, but little is known about the genetic influences on cellular levels. Therefore, we investigated the influence of genetic variants in monocyte differentiation antigen (CD14), toll-like receptor-4 (TLR4), toll-like receptor-2 (TLR2), and myeloperoxidase (MPO) on monocyte surface receptor levels. The study sample consisted of 1,817 members of a biracial cohort of adults from the Atherosclerosis Risk in Communities Carotid MRI Study. Monocyte receptors were measured using flow cytometry on fasting whole blood samples. TLR2 rs1816702 genotype was significantly associated with CD14+/TLR2+ percent of positive cells (%) and median fluorescence intensity (MFI) in whites but not in blacks (p < 0.001). Specifically, the presence of the minor T-allele was associated with increased receptor levels. In blacks, TLR4 rs5030719 was significantly associated with CD14+/TLR4+ monocytes (MFI) with mean ± SE intensities of 16.7 ± 0.05 and 16.0 ± 0.14 for GG and GT/TT genotypes, respectively (p < 0.001). Variants in TLR2 and TLR4 were associated with monocyte receptor levels of TLR2 and TLR4, respectively, in a biracial cohort of adults. To our knowledge, this is the first study to look at associations between variants in the toll-like receptor family and toll-like receptor levels on monocytes.

Toll-like receptor 2 and 4 stimulation elicits an enhanced inflammatory response in human obese patients with atherosclerosis

The innate immune response elicited by activation of TLRs (Toll-like receptors) plays an important role in the pathogenesis of atherosclerosis. We hypothesized that cardiovascular risk factors are associated with the activation status of the innate immune system. We therefore assessed the responsiveness of TLRs on circulating cells in two groups of patients with established atherosclerosis and related this to the presence of cardiovascular risk factors. TNF (tumour necrosis factor)-α release induced by TLR2 and TLR4 activation was measured in patients with established coronary [PCI (percutaneous coronary intervention) study, n=78] or carotid artery disease [CEA (carotid endarterectomy) study, n=104], by stimulating whole blood samples with lipopolysaccharide (TLR4 ligand) and Pam3CSK4 [tripalmitoylcysteinylseryl-(lysyl)4; TLR2 ligand]. As an early activation marker, CD11b expression was measured by flow cytometry on CD14+ cells. Obesity was the ‘only’ risk factor that correlated with the TLR response. In both studies, obese patients had significantly higher TNF-α levels after stimulation of TLR2 compared with non-obese patients [16.9 (7.7–49.4) compared with 7.5 (1.5–19.2) pg/ml (P=0.008) in coronary artery disease and 14.6 (8.1–28.4) compared with 9.5 (6.1–15.7) pg/ml (P=0.015) in carotid artery disease; values are medians (interquartile range)]. Similar results were obtained following TLR4 stimulation. The enhanced inflammatory state in obese patients was also confirmed by a significant increased expression of the activation marker CD11b on circulating monocytes. In conclusion, obesity is associated with an enhanced TLR response in patients suffering from established atherosclerotic disease.

Differential coagulation inhibitory effect of fondaparinux, enoxaparin and unfractionated heparin in cell models of thrombin generation

Anticoagulants, including unfractionated heparin (UFH), enoxaparin and fondaparinux, are approved drugs in acute coronary syndrome (ACS). Monocytes and monocyte-derived microparticles (MMPs) play an important procoagulant role in ACS by expressing high tissue factor (TF) levels, which in turn triggers thrombin generation. The objective of our study is to compare the in-vitro inhibitory effect of UFH, enoxaparin and fondaparinux in monocytes and MMP models. Human-elutriated monocytes were activated for 5 and 18 h by lipopolysaccharide to obtain activated monocytes (ac-M) or MMPs, respectively. Thrombin generation inhibition was assessed using ac-M or MMPs mixed with platelet-poor plasma containing increased concentrations of anticoagulants. Thrombin generation inhibition was dose-dependent with a differential effect according to the drug: the highest for UFH, the lowest for fondaparinux. Rate index was the most sensitive parameter. For fondaparinux, its IC50 values (anti-Xa IU/ml) were 0.59±0.05 for ac-M and 0.17±0.03 for MMPs. For enoxaparin, rate index IC50 values were 0.27±0.03 for ac-M and 0.19±0.02 for MMPs. Our data support the notion that cell-induced thrombin generation assay may be a reliable alternative to anti-Xa assessment in determining patient anticoagulation level.

Atorvastatin suppresses LPS-induced rapid upregulation of Toll-like receptor 4 and its signaling pathway in endothelial cells

In the present study, we tested our hypothesis that atorvastatin exerts its anti-inflammation effect via suppressing LPS-induced rapid upregulation of Toll-like receptor 4 (TLR4) mRNA and its downstream p38, ERK, and NF-κB signaling pathways in human umbilical-vein endothelial cells (HUVECs) and human aortic endothelial cells (HAECs). TLR4 mRNA expression and its downstream kinase activities induced by LPS alone or atorvastatin + LPS in endothelial cells were quantified using quantitative real-time PCR and enzyme-linked immunosorbent assay. Preincubation of LPS-stimulated endothelial cells with TLR4 siRNA was conducted to identify the target of the anti-inflammatory effects of atorvastatin. Atorvastatin incubation resulted in the reduction of LPS-induced TLR4 mRNA expression, ERK1/2 and P38 MAPK phosphorylation, and NF-κB binding activity. Pretreatment with MEK/ERK1/2 inhibitor PD98059 attenuated atorvastatin + LPS-induced NF-κB activity but had no effect on P38 MAPK phosphorylation. In contrast, pretreatment with P38 MAPK inhibitor SB203580 resulted in upregulation of atorvastatin + LPS-induced ERK1/2 phosphorylation but had no significant effects on NF-κB activity. On the other hand, blocking NF-κB with SN50 produced no effects on atorvastatin + LPS-induced ERK1/2 and P38 MAPK phosphorylation. Moreover, TLR4 gene silencing produced the same effects as the atorvastatin treatment. In conclusion, atorvastatin downregulated TLR4 mRNA expression by two distinct signaling pathways. First, atorvastatin stabilized Iκ-Bα, which directly inhibited NF-κB activation. Second, atorvastatin inactivated ERK phosphorylation, which indirectly inhibited NF-κB activation. Suppression of p38 MAPK by atorvastatin upregulates ERK but exerts no effect on NF-κB.

Innate immunity and monocyte-macrophage activation in atherosclerosis

Innate inflammation is a hallmark of both experimental and human atherosclerosis. The predominant innate immune cell in the atherosclerotic plaque is the monocyte-macrophage. The behaviour of this cell type within the plaque is heterogeneous and depends on the recruitment of diverse monocyte subsets. Furthermore, the plaque microenvironment offers polarisation and activation signals which impact on phenotype. Microenvironmental signals are sensed through pattern recognition receptors, including toll-like and NOD-like receptors - the latter of which are components of the inflammasome - thus dictating macrophage behaviour and outcome in atherosclerosis. Recently cholesterol crystals and modified lipoproteins have been recognised as able to directly engage these pattern recognition receptors. The convergent role of such pathways in terms of macrophage activation is discussed in this review.

Expression of toll-like receptor 4, tumor necrosis factor- alpha, matrix metalloproteinase-9 and effects of benazepril in patients with acute coronary syndromes

OBJECTIVES

The study aims to explore the relationship between expressions of toll-like receptor 4 (TLR4) on peripheral blood monocytes, serum tumor necrosis factor-alpha (TNF-α) and matrix metalloproteinase-9 (MMP-9) in patients with acute coronary syndromes(ACS), and to investigate the possible mechanisms of Benazepril stabilizing atherosclerosis plaques.

METHODS

70 patients selected were randomly divided into Benazepril treatment group (35 patients) and regular treatment group (35 patients). Meanwhile, Stable angina pectoris (SAP) group of 32 patients and control group of 22 patients were also set up. With the help of flow-cytometry, expressions of TLR4 on peripheral blood monocytes of the four groups were analyzed and compared to show differences, correlations and changes of the above mentioned indicators. The concentration of TNF-α and MMP-9 in serum were measured by enzyme linked immunosorbent assay (ELISA).

RESULTS

(1) Expressions of TLR4, levels of TNF-α and MMP-9 were increased and the rate was rising from the control group, to SAP group and then to ACS group. All these indicators in ACS group are significantly higher than those in other groups (P < 0.05). (ACS versus SAP, control; all (P < 0.05). (2) Multi-linear regression analysis indicates that there was a positive correlation between the expression level of TLR4 and serum levels of TNF-α and MMP-9 in patients with ACS (P < 0.01). (3) There is no significant differences between the expression level of TLR4 and serum levels of TNF-α and MMP-9 in Benazepril treatment group and regular treatment group before treatment (P > 0.05) while they all fell after treatment (P < 0.05). In addition, all the indicators decreased more greatly than the regular treatment group.

CONCLUSIONS

TLR4 on peripheral blood monocytes and serum TNF-α and MMP-9 in patients with coronary arteriosclerosis disease may be effective markers of the vulnerable plaque. Benazepril can inhibit over-expression of TLR4 and reduce serum levels of TNF-α and MMP-9, thus stabilize the vulnerable plaques and improve the condition of the patients with ACS.

The role of monocytes in atherosclerotic coronary artery disease

Inflammation plays a key role in the pathogenesis of atherosclerosis. The more we discover about the molecular pathways involved in atherosclerosis, the more we perceive the importance of monocytes in this process. Circulating monocytes are components of innate immunity, and many pro-inflammatory cytokines and adhesion molecules facilitate their adhesion and migration to the vascular endothelial wall. In addition to the accumulation of lipids and formation of atherogenic 'foam' cells, monocytes may promote atherosclerotic plaque growth by production of inflammatory cytokines, matrix metalloproteinases, and reactive oxidative species. However, the contribution of monocytes to atherogenesis is not only limited to tissue destruction. Monocyte subsets are also involved in intraplaque angiogenesis and tissue reparative processes. The aim of this overview is to discuss the mechanisms of monocyte activation, the pivotal role and importance of activated monocytes in atherosclerotic coronary artery disease, their implication in the development of acute coronary events, and their potential in cardiovascular reparative processes such angiogenesis.